Abstract
A nipple device for electronically measuring flow of milk drawn by an infant through its feeding orifices. The device measures milk flow from the differential pressure generated by the milk flow through a fluid flow resistor. The resistor may be located in the peripheral region of the base of the nipple device, and milk conveyed to and from the resistor by means of passageways in the base unit. The differential pressure generated across the resistor is measured using pressure sensors located at the periphery. The pressure sensors and associated electronic circuits may be incorporated into a flow measuring head, attachable to the base unit of the device through a standard pair of fluid ports, to which can be attached heads for other measurements of the milk properties. Other implementations provide increased accuracy for nipple devices using the pressure difference across the feeding orifices for the flow measurement.
Claims
1. A nipple device for monitoring flow of milk drawn by an infant during feeding, the device comprising: a base layer with a domed protrusion having an inner surface defining an inner volume of the domed protrusion and an outer surface, the domed protrusion being adapted for insertion into the mouth of the infant; a first at least one passageway from the inner volume of the domed protrusion to a region of the base layer remote from the domed protrusion; and a second at least one passageway from the region of the base layer remote from the domed protrusion to at least one position in the outer surface of the domed protrusion, wherein the first at least one passageway and the second at least one passageway are fluidly connected at the region of the base layer remote from the domed protrusion, by a section of passageway having a first pressure sensor and a second pressure sensor, such that the differential pressure between the first pressure sensor and a second pressure sensor can be determined.
2. The nipple device according to claim 1, wherein the differential pressure between the first pressure sensor and the second pressure sensor enables determination of the flow of milk from within the inner volume of the domed protrusion to the at least one position in the outer surface of the domed protrusion.
3. The nipple device according to either of claims 1 and 2, wherein the first and second sensors are incorporated in a differential pressure module.
4. The nipple device according to any of the previous claims, wherein the differential pressure module comprises a subtraction circuit operating between the outputs of the pressure sensors.
5. The nipple device according to any of the previous claims, wherein the connection between the first at least one passageway and the second at least one passageway has a constricted bore to generate increased fluid flow resistance to the flow of milk therethrough.
6. The nipple device according to any of the previous claims, wherein the milk flow to the infant is determined from the differential pressure measured between the pressure sensors, using a known relationship.
7. The nipple device according any of the previous claims, wherein the base layer of the nipple device is shaped to be mounted on the breast of a mother providing milk to the infant.
8. The nipple device according any of claims 1 to 6, wherein the base layer of the nipple device is adapted to be mounted on a feeding bottle.
9. The nipple device according to any of the previous claims, wherein the region of the base layer remote from the domed protrusion is a peripheral region of the base layer of the nipple device.
10. The nipple device according to any of claims 1 to 8, wherein the pressure sensors or the differential pressure module are located in a separate head adapted to be attached to the periphery of the nipple device through fluid flow ports.
11. The nipple device according to claim 10, wherein the separate head comprises either a display for showing the level of the flow of milk, or a wireless facility for transmitting the flow rate to a remote receiver.
12. The nipple device according to any of the previous claims, wherein each of the first and the second at least one passageway is connected to a chamber having a flexible diaphragm dividing its internal volume into two hermetically closed compartments, and wherein the pressure transfer between each of the first and the second at least one passageway and its associated pressure sensor, is performed across the flexible diaphragm.
13. The nipple device according to claim 12, wherein the first at least one passageway is connected to a first of its two hermetically closed compartments, and the first pressure sensor is connected to the second of the two hermetically closed compartments.
14. The nipple device according to either of claims 11 and 12, wherein the second of the two hermetically closed compartments is filled with a liquid.
15. The nipple device according to any of the previous claims, wherein the diameter of the passageways is selected to be sufficiently small that milk entering the passageway at the pressure generated in the device, does not mix with air already in the passageway.
16. The nipple device according to claim 14, wherein the passageway has an internal diameter not exceeding 4 mm.
17. The nipple device according to any of the previous claims, wherein the output of the pressure measuring devices enables the pattern of the infant's ingestion of milk to be determined.
18. A nipple device to feed an infant, comprising: a flexible layer having a domed protrusion region; at least one orifice in the domed protrusion region of the flexible layer, such that at least one passage is formed connecting an inner volume within the domed protrusion region with an outer surface, enabling a flow of milk from the inner volume of the domed protrusion region outward through the at least one orifice; and at least one higher flexibility area of the domed protrusion region having a flexibility selected to be higher than that of a material of the remaining area of the domed protrusion region, the area being disposed in a location of the domed protrusion region adapted to fit within the mouth of the infant during feeding.
19. The nipple device according to claim 18, wherein the at least one higher flexibility area flexes inwards or outwards of the domed protrusion region in accordance with a differential pressure between the two opposite sides of the at least one higher flexibility area.
20. The nipple device according to either of claim 18 or 19, wherein the at least one higher flexibility area is located within an area which is adapted to be within the infant's mouth when feeding.
21. The nipple device according to claim 20, wherein the at least one higher flexibility area is located either in the region of the at least one orifice, or in a position in the wall of the domed protrusion region of the nipple device.
22. The nipple device according to any of claims 19 to 21, wherein the flexing of the at least one higher flexibility area is adapted to reduce a change in the differential pressure between the opposite sides of the at least one higher flexibility area, by reducing the volume of that side of the flexible membrane having the lower pressure and increasing the volume of that side of the flexible membrane having the higher pressure.
23. The nipple device according to any of claims 19 to 22, wherein the inward flexing of the flexible membrane when the infant relaxes a sucking action, is adapted to reduce the extent of reverse flow of milk from the mouth of the infant to the inner space of the domed nipple protrusion by enlarging the volume available to the infant for keeping milk within his/her mouth.
24. The nipple device according to any of claims 19 to 22, wherein the outward flexing of the flexible membrane when the infant begins a sucking action, is adapted to increase the extent of flow of milk from the inner space of the domed nipple protrusion to the mouth of the infant, by enlarging the volume of the inner space of the domed nipple protrusion.
25. The nipple device according to claim 19, wherein the differential pressure sensor unit is pre-calibrated, such that the differential pressure measured is related to the milk flow through the at least one orifice of the nipple device.
26. The nipple device according to either of claim 18 or 19, wherein the differential pressure sensor unit comprises at least one of: a single differential pressure sensor; or a pressure sensor for each set of passageways respectively from the inner surface and the outer surface of the domed protrusion, with a subtraction circuit operating between the outputs of the pressure sensors.
27. The nipple device according any of claims 18 to 26, wherein the base layer of the nipple device is adapted to be mounted on a breast of a mother providing milk to the infant.
28. The nipple device according any of claims 18 to 26, wherein the base layer of the nipple device is adapted to be mounted on a feeding bottle.
29. The nipple device according to any of claims 18 to 26 wherein the at least one differential pressure sensor unit is located in a peripheral region of the base layer of the nipple device.
30. A nipple device to feed an infant, comprising: a flexible layer having a domed protrusion region; and at least one orifice in the domed protrusion region of the flexible layer, such that at least one passage is formed connecting an inner volume within the domed protrusion region with an outer surface, enabling a flow of milk from the inner volume of the domed protrusion region outward through the at least one orifice; and wherein the material of at least the domed protrusion has a hardness of less than 40 Shore A.
31. The nipple device according to claim 30, wherein changes in pressure on either side of the domed protrusion generate a larger change in volume on the opposite sides of the nipple protrusion, than would be obtained using a material having a higher hardness.
32. The nipple device according to either of claim 30 or 31, wherein the material of at least the domed protrusion has a hardness of less than 35 Shore A.
33. The nipple device according to any of claims 30 to 32, wherein the entire flexible layer comprises material having a hardness of less than 40 Shore A.
34. The nipple device according to any of claims 30 to 32, wherein the entire flexible layer comprises material having a hardness of less than 35 Shore A.
35. A device to monitor a flow of milk drawn by an infant during feeding, the device comprising: a flexible layer having a domed nipple region adapted to be disposed in the mouth of the infant, and having at least one orifice connecting an inner surface of the domed nipple region with its outer surface, enabling flow of milk from within the domed nipple region to the mouth of the infant; a first chamber formed within the layer in the domed nipple region straddled by a first wall and a second wall opposed to the first wall, in a location that is adapted to be disposed within the mouth of the infant when the infant is feeding on the device, the first wall of increased flexibility disposed adjacent to the outer surface of the domed nipple region, and the second wall disposed adjacent to the inner surface of the domed nipple region; a second chamber formed within the layer in the domed nipple region straddled by another first wall and another second wall opposed to the other first wall, having the other first wall of increased flexibility disposed adjacent to the inner surface of the domed nipple region, and the other second wall disposed adjacent to the outer surface of the domed nipple region; and passageways connect the first chamber and the second chamber to inputs of a differential pressure measurement unit, such that a differential pressure between a first pressure within the first chamber and a second pressure within the second chamber is determined.
36. The device according to claim 35, wherein the increased flexibility is a thinner first wall than the opposing second wall of its respective chamber.
37. The device according to claim 35, wherein at least one of the first walls has increased flexibility by being formed of a more flexible material than the opposing second wall of its respective chamber.
38. The device according to any of claims 35 to 37, wherein the differential pressure measurement unit is pre-calibrated such that the differential pressure measured is related to the milk flow through the at least one orifice of the device.
39. The device according to claim 38, wherein the differential pressure measured determines the milk flow in real time.
40. The device according to claim 38, wherein the differential pressure measured determines the feeding pattern of the infant as a function of time.
41. The device according to any of claims 35 to 40, wherein the first and the second chambers are disposed at different circumferential positions in the domed nipple region of the device.
42. The device according to any of claims 35 to 41, wherein at least one of the first walls having increased flexibility is in the form of a thin membrane.
43. The device according to any of claims 35 to 42, wherein at least one of the chambers is disposed in a region of the domed nipple region having higher rigidity than other regions of the domed nipple region, such that the at least one chamber is more resistant to physical disturbance by the infant.
44. The device according to claim 43, wherein the higher rigidity of the region of the domed nipple device results from the at least one chamber being formed in a material having stiffer properties than other regions of the domed nipple device.
45. The device according to any of claims 35 to 44, wherein the differential pressure measurement unit comprises two pressure sensors with a subtraction circuit operating on the outputs of the two pressure sensors.
46. The device according to any of claims 35 to 45, wherein the differential pressure measurement unit comprises a microelectronic chip mounted on the device.
47. The device according to any of claims 35 to 46, further comprising a control unit adapted to convert the output of the differential pressure measurement unit to a measure of the milk flow through the device to the infant.
48. The device according to any of claims 35 to 47, further comprising a control unit adapted to convert the output of the differential pressure measurement unit to determine the feeding pattern of the infant.
49. The device according to any of the claims 35 to 48, having a base layer connected to the flexible layer that is adapted to be mounted on the breast of a mother providing milk to the infant.
50. The device according to claim 38, wherein the differential pressure measurement unit is transferred to a remote system to be displayed or analyzed.
51. The device according to any of claims 35 to 50, wherein the first chamber may comprise multiple first chambers and the second chamber may comprise multiple second chambers, the device further comprising multiple passageways to connect the multiple first chamber to a first input of the differential pressure measurement unit, and multiple passageways to connect the multiple second chamber to a second input of the differential pressure measurement unit.
52. The nipple device according any of claims 35 to 51, wherein the flexible layer of the nipple device is adapted to be mounted on a feeding bottle.
53. A nipple shield device to determine milk flow drawn by an infant during feeding, the nipple shield device comprising: a base layer; and a domed protrusion having a dome layer having an inner surface and an outer surface, the domed protrusion extends from the base layer and has at least one orifice disposed through the domed protrusion, the domed protrusion further comprising: a first chamber formed within the dome layer straddled by a first wall disposed at an outer surface with increased flexibility, and a second wall disposed at an inner surface; and a second chamber formed within the dome layer straddled by another first wall disposed at the inner surface with increased flexibility, and another second wall disposed at an outer surface, wherein a differential pressure between a first pressure within the first chamber and a second pressure within the second chamber is determined.
54. The nipple shield device of claim 53, wherein the nipple shield device further comprises a pressure measurement unit that determines the differential pressure.
55. The nipple shield device of claim 54, wherein the nipple shield device further comprises: a first passageway extending from the first chamber to a first output in the pressure measurement unit; and a second passageway extending from the second chamber to a second output in the pressure measurement unit, wherein the differential pressure is measured between a first pressure within the first chamber, and a second pressure within the second chamber.
56. The nipple device according any of claims 53 to 55, wherein the base layer of the nipple device is adapted to be mounted on a feeding bottle.
57. A nipple device to feed an infant, comprising: a flexible layer having a domed protrusion region; at least one orifice in the domed protrusion region of the flexible layer, such that at least one passage is formed connecting an inner volume within the domed protrusion region with an outer surface, enabling a flow of milk through the at least one orifice, outward from the inner volume of the domed protrusion region; and fluid connections of the end regions of the at least one passage to a differential pressure measurement module, wherein the region of at least one orifice comprises at least one structure for reducing changes in fluid resistance of the at least one passage induced during feeding.
58. The nipple device according to claim 57, wherein the region of the domed protrusion region surrounding the at least one orifice has a higher flexibility than remaining regions of the domed protrusion region.
59. The nipple device according to claim 58, wherein the domed protrusion region surrounding the at least one orifice has either a thinner thickness or different elastic properties from the remaining regions of the domed protrusion region.
60. The nipple device according to claim 57, wherein the inner side of the domed protrusion region surrounding at least one orifice comprises a region of thickness greater than that of the remaining area, the region having a number of channels within the thickness of that region, these channels leading to the region around the inner orifice opening.
61. The nipple device according to claim 57, wherein at least one orifice has a first inner opening whose ends are fluidly connected to the differential pressure measurement module, and a second outer opening having a larger diameter.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0095] The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which:
[0096] FIG. 1A shows a schematic representation of the manner in which the nipple devices of the type shown in the present disclosure operate; FIG. 1B shows a cross section of on exemplary implementation of the nipple device shown schematically in FIG. 1A; while FIG. 1C shows a schematic isotopic skeleton drawing of a specific exemplary implementation of nipple device of the type shown in FIG. 1A;
[0097] FIG. 2 shows a cross-sectional view of the dome region of the nipple device of FIG. 1C;
[0098] FIGS. 3A and 3B are temporal plots of the variation of pressure related to the sinusoidal type of sucking action which the infant performs, FIG. 3A shows the negative pressures inside and outside of the nipple, while FIG. 3B shows the differential pressure across the nipple orifice;
[0099] FIGS. 4A and 4B schematically illustrate the functionality of the flexible membrane embodiment of the nipples of this disclosure, to reduce the return flow of milk from the infant towards the mother's side of the nipple;
[0100] FIGS. 5A and 5B graphically illustrate the effect of the use of a nipple with a flexible membrane on the pressure cycle shown in the real-life plots of FIG. 3A, while FIGS. 5C and 5D show respectively plots against time of the differential pressure for a conventional nipple device of the present disclosure without the flexible membrane, and for a novel nipple device of the present disclosure with the flexible membrane;
[0101] FIGS. 6A and 6B illustrate schematically alternative nipple structures using a flexible membrane to reduce the level of backward flow of milk in the nipple, FIG. 6A showing the flexible membrane in the domed region of the nipple device, and FIG. 6B showing the flexible membrane in a side wall of the nipple device;
[0102] FIGS. 7A and 7B illustrate schematically two practical implementations of novel orifice structures, which can be used to avoid effects of external forces, such as from the mouth or tongue motions of the infant, from interfering with the shape or form of the feeding orifice, and hence with the magnitude of the flow resistance of the orifice or orifices;
[0103] FIGS. 8A and 8B illustrate schematically a novel structure which can be incorporated on the inner side of the domed nipple protrusion around the feeding orifice, in order to prevent its blocking or partial blocking, by the tip of the mother's nipple;
[0104] FIG. 9 shows an implementation of the presently described milk flow measurement devices, in which the components and features required for the measurement of the flow, namely the fluid flow resistor and the pressure sensors, are incorporated into a plug-in head;
[0105] FIG. 10 shows a method of ensuring that the pressure sensors are not exposed to contact with the milk flow, by use of a pressure transfer chamber unit in which a flexible diaphragm is used for transferring the pressure within the milk in each flow channel to their respective pressure sensors, without allowing any of the milk to touch the pressure sensors; and
[0106] FIG. 11 illustrates an exemplary replaceable flow resistor, suitable for use as part of the orifice through which the infant sucks, the flow resistor being cleanable by virtue of its external flow path.
DETAILED DESCRIPTION
[0107] Reference is first made to FIG. 1A, which illustrates a schematic representation of the general manner in which the nipple devices of the type shown in the present disclosure operate. In FIG. 1A, the flow of milk from the mother's breast, represented by region 1, to the infant's mouth, represented by region 2, occurs through the orifice or orifices in the nipple device, which are shown in FIG. 1A as a resistive section 3 of the flow path. Because of the restriction of flow through the resistive section 3, a pressure drop is generated in the flow path between the volume of the mother's side 1 of the device, and that of the infant's side 2 of the device. This pressure difference AP can be measured by two separate pressure sensors 6,7, each connected by means of ports 4, 5, to both sides of the resistive section 3 of the flow path, or by use of a differential pressure sensor (not shown in FIG. 1A). Port 4 measures the pressure P2 on the mother's side, and port 5, the pressure P1 on the infant's side. So long as the resistance of the orifice(s) remains constant, the measured pressure difference AP thus provides an indication of the fluid flow rate of the milk from the mother to the infant. Specific implementations of this model are shown hereinbelow.
[0108] In its simplest implementation, the method shown in the schematic device of FIG. 1A, has a particularly useful form, with significant advantages from the point of reusability of the device. The differential pressure sensor, or the two separate pressure sensors, are connected hermetically by means of their respective conduits 4, 5, to the milk flow regions 1, 2 respectively, such that no pressure leakage occurs in the ports or the connecting conduits, thereby impairing the accuracy of the pressure measurements. However, the effect of this is that since the pressure measurement ends of the conduits are closed volumes, the milk only enters the conduits by a very limited amount, conveying the pressure within the conduits to the sensor by means of the trapped air in the conduit. The end of the conduits connected to the differential pressure sensor or the separate pressure sensors 6, 7, and the pressure sensor or sensors themselves, remain free of milk, which is limited to possible small incursions into the conduits close to the milk flow regions. Consequently, the pressure measurement section of the device remains essentially clean of milk, and can be reused without the need to clean it, or with a minimal cleaning procedure which will not cause any damage to the sensitive sensors themselves. The rest of the device, namely the flexible nipple section with the orifice(s) and the conduits conveying the pressures to the connected pressure sensor(s), can then be cleaned by any method deemed sufficiently thorough to provide a nipple safe to use again, including for instance, cleaning in hot or boiling soapy water. The apparatus schematically shown in FIG. 1A, and its method of use, thus enable a milk flow device which is completely reusable, rather than some of the prior art devices, which have to be disposable.
[0109] Reference is now made to FIG. 1B, which is a schematic cross section of one exemplary implementation of the nipple device 10 using the concepts shown schematically in FIG. 1A. In FIG. 1B, there is shown a nipple device 10 having an orifice 13 or a number of orifices (not shown in FIG. 1B), in the top region of the domed nipple protrusion of the nipple device. The nipple device is shown as mounted on nipple region of the mother's breast 8, such that the mother's milk collects in the volume 1 between the mother's breast and the inside surface of the domed nipple protrusion. The infant sucks on the outside surface of the domed nipple protrusion, such that the mother's milk flows through the orifice(s) 13 to the infant's mouth 2. Two passages or conduits 4, 5, are formed within the thickness of the flexible material of the domed nipple protrusion 10, one of which 4 opens to the inside volume of the nipple device, where it is in fluid contact with the accumulated mother's milk, and the other of which opens to the external space around the nipple domed structure 10, such that it is positioned within the mouth of the sucking infant when feeding. The passageways lead to connection ports (not shown in FIG. 1B) to locations on the outer edge of the base layer of the nipple device where they can be connected to a differential pressure sensor, or to individual pressure sensors. Though the passageways 4, 5, are shown in FIG. 1B on diametrically opposite sides of the nipple dome, it is to be understood that this is done merely to clearly show both of the passageway in a single cross sectional drawing, and the passageways could advantageously be located in close proximity to each other on one side of the nipple domed protrusion, such that a single differential pressure sensor device could conveniently be connected to their remote ends. It is also to be understood that one or both of the passageways could comprise multiple passageways.
[0110] Reference is now made to FIG. 1C, which is a schematic isometric see-through drawing of an exemplary nipple device using the general methods of the basic device described in FIG. 1A, but in which the pressure measurements are performed in a manner completely free of direct contact with the milk. FIG. 1C illustrates the dome region 10 of the nipple device, showing the pressure conveyance passageways which are used to implement the operation of the device. As applied in its simplest implementation, as in FIG. 1B, the pressure conveyance passageways, 16, 17, lead from the upper region of the dome nipple protrusion, one from within the domed nipple protrusion, and one from outside of the protrusion, as shown in FIG. 1B, (where they are denoted by passageways 4 and 5) to a miniature differential pressure measurement control module 31, disposed remotely from the domed nipple protrusion, advantageously at a peripheral region of the device. The module 31 includes a differential pressure sensor 30, which may have a direct read-out display 32 on the module 30 itself, or could send the data to a remote display. The module is configured to use a previous calibration measurement performed on the device to indicate the rate of flow of milk from the mother to the infant.
[0111] More complex controllers could be used for outputting a real-time signal proportional to the flow rate such that information can be collected regarding the nature of the infant's feeding habits, the change in feeding action during a feeding session, and, by integrating the signal, the total amount of milk taken by the infant during the whole feeding session. Alternatively, and advantageously, the pressure measurement chip or the control unit can be adapted to transmit its measurements to a remote smart device, such as a mobile phone, where the data can be analyzed and presented. This has the advantage that the control unit 31 can be made much more compact and simpler, since its only function is to export the differential pressure readings to an external control system, where all of the calculations can be executed relating to the milk flow rate, milk quantity or the nature of the feeding process. Furthermore, it has the advantage that the mother or another party can readily read the results of the measurement in real time on a device separate from the nipple device itself. Furthermore, the chip or the control unit or both can be manufactured such that they are transferable from nipple device to nipple device, so that the user only needs one chip or control unit with its electronics, which can be used for many successive nipples.
[0112] The nipple device is advantageously formed of a thin layer of flexible material 12, such as a silicone compound, or another suitable flexible polymer, and has a base section 11 from which the dome region 10 extends. The example device shown in FIG. 1C is adapted for use by a nursing mother, who would fit the device over the nipple of her breast, like a conventional nipple shield. A device for use on a feeding bottle (not shown) would typically have a flexible elastically equipped cover section matching the bottle top, instead of the base section 11 of the device shown in FIG. 1C. In common with a conventional nipple shield, the present nipple device has one or more orifices 13 at or around the tip of the domed region of the nipple device, enabling a nursing infant with the domed region located in his/her mouth, to suck the mother's milk from the internal space of the device between the mother's breast and the internal volume of the domed region.
[0113] The device shown in FIG. 1C differs from a conventional nipple shield in that it includes two internal chambers 14, 15 formed within the material of the domed protrusion region of the device in its upper region, each connected separately by means of narrow passageways 16, 17, to the pressure measurement control module 31, preferably disposed at an outer part of the base 11 of the device, with each chamber and its narrow passageway being filled with air, and each constituting a closed volume. The chambers are formed close to the tip of the domed region, such that their position is intended to be located within the infant's mouth when the infant is sucking the milk. An advantageous configuration of the chambers is in the form of oppositely positioned chambers around the circumference of the nipple dome. However, the device will be operational with any other suitably positioned chambers.
[0114] The chambers differ from each other in that they are not equally positioned relative to the centerline of the thickness of the flexible layer in the dome region, as will be more clearly shown in the cross-sectional view of FIG. 2 hereinbelow. The first chamber 14 is positioned closer to the outer surface of the flexible layer than is the second chamber 15, which is positioned closer to the inner volume of the nipple device dome. As a result of this placement within the thickness of the wall of the nipple dome region, the first chamber 14 has a significantly thinner wall with the outside surface of the nipple dome, than the wall with the inner volume of the nipple dome. The second chamber 15, on the other hand, has a significantly thinner wall with the inside surface of the dome than the wall with the outer surface of the nipple dome. The two thin walls may thus be considered as pressure sensitive membranes, which move perpendicularly to the surface of the nipple dome, the extent of the movement being proportional to the pressure applied across the membrane. The thicker walls may be regarded as being essentially stiff static walls compared to the ease of movement of the thin membrane-like walls, such that when the infant sucks on the dome structure in order to obtain milk, the thin-walled membrane of the first chamber 14 moves outward from the dome surface, the extent of the outward movement being proportional to the level of the negative pressure generated by the sucking force of the infant. As the thin-walled membrane moves outwards, since the first chamber is a closed pneumatic system, the pressure of the air inside that system will decrease in a manner proportional to the extent of output motion of the membrane-like wall. The negative pressure generated within the first chamber is thus proportional to the negative pressure generated by the infant's sucking, which is equal to the negative pressure generated at the outer end of the nipple orifice or orifices. In a similar fashion, the thin-walled membrane of the second chamber 15 moves inwards or outwards from the dome surface, the extent and direction of the movement being proportional to the level of the pressure generated within the volume of the nipple. Consequently, that motion of the membrane wall will generate a corresponding pressure within the second chamber 15, such that the pressure within the second chamber reflects the pressure within the inner volume of the nipple, and hence at the inner end of the nipple orifice or orifices. Therefore, the difference in the pressures between the air in the first chamber 14 and the second chamber 15, is a measure of the difference in pressure along the milk orifice or orifices. Since the orifice or orifices have a fixed flow resistance, that difference of pressure along the milk orifice or orifices is directly proportional to the rate of flow of the milk to the infant. As explained hereinabove, the difference in pressures between the two chambers can be readily measured by attaching a differential pressure sensor at the ends of the narrow passageways 16, 17, which convey the pressure levels within the chambers 14, 15, for measurement by the differential pressure sensor 30. Alternatively, separate pressure sensors (not shown in FIG. 1C) may be used to measure each passageway pressure separately, and the difference in reading subtracted to obtain the differential pressure measurement. The volume of the narrow passageways 16, 17, are sufficiently small that they do not significantly affect the level of the pressures measured by the chambers.
[0115] The chambers have been described (as will be shown more clearly in FIG. 2 below) as having respectively, a thinner wall towards one of the surfaces of the nipple domed protrusion structure, and a thinner wall towards the other surface of the domed protrusion structure. As explained in the previous paragraph, this structure provides a higher flexibility to the thinner wall than to the opposing wall of the chamber being considered, such that one of the chambers provides an indication of the pressure on one surface of the domed structure, and the other chamber provides an indication of the pressure on the other surface of the domed structure. This method of constructing the chambers is advantageous, since the different walls can be produced simultaneously of the same material as the rest of the nipple device, in a single molding process. However, it is to be understood that the same effect could be provided by making one of the walls of each chamber of a material having a higher flexibility than the material of the opposing wall, such that the essential property of the chambers of this nipple structure, namely having one wall more flexible than the opposing wall, can be achieved thuswise. The important feature of the chambers is that they each have one wall having greater flexibility than the opposing wall, and that one of the chambers has its more flexible wall on the inner surface of the nipple protrusion structure, and the other chamber has its more flexible wall on the outer surface of the nipple protrusion structure.
[0116] The device operation has been explained with the chambers 14 close to the orifice or orifices, such that they are located within the mouth of the infant during the feeding session. Since the infant may distort the flexible layer of the dome structure by physical squeezing or pushing of the flexible layer, and this may distort the motion of the membrane-like wall, and hence the pressure level generated within the chamber, the chambers should be located in a region having a higher rigidity than other parts of the nipple dome, so that they are less disturbed by physical forces. As previously stated, the position in the curved upper part of the dome of the nipple has more resistance to distortion than the lower parts of the dome. An increased resistance to distortion can also be achieved by making the material in the upper part of the nipple dome with a higher rigidity than elsewhere on the dome, either by using a stiffer material in that region, or by making the flexible layer thicker in that region. It is of course to be understood that this increased rigidity relates to the thicker wall of the chamber and not to the membrane-like wall, which should maintain the desired flexibility to respond sufficiently to the variable pressure applied to it.
[0117] Reference is now made to FIG. 2 which shows a cross-sectional view of the dome region 10 of the nipple device of FIG. 1C, in order to show more clearly, the location of the first pressure measurement chamber 14, and of the second pressure measurement chamber 15, relative to the thickness of the material of the nipple, and a position of the orifice or orifices 13. The narrow passageways 16, 17, shown in FIG. 1C, which convey the pressure levels within the chambers, for measurement by the differential pressure sensor at the edge of the nipple base, are not shown in FIG. 2 to avoid detracting from the purpose of FIG. 2 to show the measurement chamber positions. As is observed, the first chamber 14 is located closer to the outer surface of the dome nipple structure than to the inner surface, such that the wall 20 between the first chamber 14 and the outer surface of the nipple dome structure is significantly thinner than the wall 21 between the first chamber 14 and the inner surface of the nipple dome structure. Consequently, the application of a pressure outside of the thinner wall 20 causes the thinner wall 20 to bulge either outwards or inwards according to the pressure difference applied, while the inner thicker wall 21 is regarded in a first order approximation, to maintain its position without moving. Therefore, the first chamber 14 can be regarded as a measurement device of the externally applied pressure. Conversely, because of the reversed positions of the thinner and thicker walls of the second chamber 15, the second chamber can be regarded as a measurement device of the internal pressure within the nipple dome volume. Therefore, the difference in pressure between the first 14 and second 15 chambers can be used as a measure of the pressure difference across the orifice 13, and hence of the milk flow through the orifice 13.
[0118] As previously stated, the forward and backward flow of milk through the nipple orifice, caused by the pulsating nature of the infant's sucking, generates a noise level which renders the differential pressure measurement more difficult to perform accurately, and also increases the effort required by the infant to feed from the mother. Reference is now made to FIGS. 3A and 3B, which are plots of the variation with time of the pressure resulting from the sinusoidal, pulsating type of sucking action which the infant performs, on the infant's side of the orifice, and on the mother's side of the feeding orifice. FIG. 3A shows the pressure P1 generated by the infant during the sucking routine, together with the resulting pressure P2 generated on the accumulated milk on the mother's side of the orifice, as a result of the sucking action of the infant on the outside of the nipple. As is observed, the sub-pressures generated on the accumulated milk on the mother's side of the orifice follow the sub-pressures generated by the infant, but over a smaller range, since passage of the milk through the nipple orifice produces a pressure drop. The difference P2P1, between the two plots shown in FIG. 3A represents the differential pressure which is generated across the orifice, and it is this which determines the flow of the milk through the orifice. At any point of time, the milk flows from the higher absolute pressure to the lower absolute pressure, meaning from points having the lower extent of negative pressure, to points having the higher extent of negative pressure. Thus, on the graph of FIG. 3A, at the bottom of the pressure dips, the milk flows from the mother's side, which is at a higher pressure, to the infant's side, while at the top peaks of the curves, the milk flows back from the infant's side to the mother's side. It is noted that the difference in absolute pressures P2P1 at the bottom dips of the infant's sinusoidal pressure cycle show a larger difference than the difference in absolute pressures P2P1 at the top peaks of the infant's pressure cycle. This means that the flow of milk from the inside of the nipple to the infant's mouth is larger than the reverse flow of milk from the infant's mouth back to the accumulated milk within the nipple volume, as is expected from the real-life situation of the feeding process.
[0119] Reference is now made to FIG. 3B, where the differential pressure P2P1, between the infant's side and the mother's side of the nipple, is plotted as a function of time, with the central horizontal line of the graph representing the zero level of differential pressure. As is observed from an inspection of the graph of FIG. 3A, it is clear that the difference P2P1 is larger at the bottom dips of the curve, representing the point of maximum suction of the infant, than at the peaks of the curves, representing the point of maximum relaxation of the infant's suction. Since the differential pressure, P2P1 is the driving force for the flow of the milk through the orifice, areas above the zero differential pressure level represent times when there is a forward flow of milk, i.e. from the mother to the infant, while areas below the zero line represent times when there is a reverse flow from the infant back towards the mother's side of the nipple. Therefore, when the integrated area above the zero line is larger than that below the zero line, there is a net flow from the mother to the infant. That is the situation in FIG. 3B, where it is noted that the area within the differential pressure curve above the zero line is larger than the area within the differential pressure curve beneath the zero line, correctly corresponding to the situation that the net flow of milk is from the mother to the infant. It is an object of the additional implementation of the nipple devices of the present disclosure to increase the flow of milk from the mother to the infant as much as possible, and to reduce the reverse flow of milk from the infant towards the mother's side of the nipple as much as possible. This would be represented in FIG. 3B, by a reduction of the area beneath the zero differential pressure line as much as possible.
[0120] Reference is now made to FIGS. 4A and 4B, which schematically illustrate the functions of a flexible membrane embodiment of the nipples of this disclosure, as described in the Summary section of this disclosure. The drawings show a representation of the flexible membrane 40 dividing the milk regime into two virtual chambers, the left hand chamber 41 representing the mother's side of the nipple, where the mother's milk accumulates, and the right hand chamber 42 representing the infant's mouth cavity, as bounded by the lips of the infant around the nipple. The flexible membrane can be located in the region of the feeding orifice or orifices 43, as shown in the flexible membrane of FIGS. 4A and 4B, but this location is only schematically indicated. In practice, the membrane 40 could be located in any other upper region of the domed nipple protrusion of the device, as a closed flexible partition, dividing the representation of the space between the mother's breast and the inside of the nipple 41, from the infant's mouth cavity 42, and the feeding orifice or orifices can 43 be shown at their conventional location, but other than in the membrane 40. In FIG. 4A, the infant is shown during a sucking phase, and milk is drawn from the mother's side 41 of the nipple through the feeding orifice 43 and to the infant's mouth cavity 42. The more negative pressure in the infant's mouth 42 causes the flexible membrane 40 to bend outwards from the surface of the nipple thereby assisting the passage of milk from the mother's side 41 through the orifice 43. In FIG. 4B, on the other hand, when the infant relaxes his/her sucking action, and the negative pressure in the infant's mouth 42 rises towards atmospheric pressure, there is no longer the pressure pulling the membrane 40 out towards the infant's mouth cavity 41, and the negative pressure still existent on the mother's side 41 of the nipple, causes the membrane 42 reverse direction and to bend into the mother's side 41. This enlarges the available space for the excess milk in the infant's mouth side 42 of the nipple, such that it has less tendency to flow back into the mother's side 41, and at the same time raises the absolute pressure on the mother's side 41 of the nipple, also reducing the fluid tendency of the milk to flow back into the mother's side 41. The results of these functions of the flexible membrane 40 are twofoldfirstly that the flow from the mother to the infant when the infant is in the sucking phase of his/her sucking cycle is not impeded, other than the inherent fluid impedance of the limited orifice openings, and secondly, that when the infant stops the sucking phase and relaxes its negative pressure, there is a lower tendency of milk to flow back into the mother's side of the nipple.
[0121] Reference is now made to FIGS. 5A and 5B, which illustrates graphically the effect of the use of a nipple with a flexible membrane on the pressure cycle shown in the real-life plots of FIG. 3A. Firstly, in FIG. 5A, there is shown a plot of the absolute pressures on the infant's side and on the mother's side, resulting from the pulsating sucking action of an infant feeding using a conventional nipple, without the membrane feature of the present disclosure. Each horizontal graduation of the plots represents 1 second. The pressure on the infant's side of the nipple, P1 of FIG. 3A, is denoted by the curve made up of small circles, while the pressure on the mother's side, within the nipple, P2 of FIG. 3A, is shown by the solid curve. As is observed, the infant is sucking at a pulsating rate of 2 Hz. The pressure P1 on the infant's side of the nipple ranges from close to atmospheric pressure, 20 mm of Hg, when the infant has fully relaxed his/her sucking, to a pressure of approximately 170 mm of mercury at the peak of the infant's suction. The resulting pressure range on the mother's side, inside the nipple, ranges from approximately 40 mm Hg, down to 130 mm Hg. Two conclusions can be drawn from these results: [0122] (i) Firstly that the fluid resistance of the orifice(s) to the flow of milk through the orifice(s) connecting the mother's side with the infant's side is sufficiently high that the pressure changes on the mother's side are significantly lower than the pressure changes generated by the infant. In the case of the pressure measurement nipples of the present application, this resistance level has been intentionally selected, rather than a resistance as low as possible, in order to provide sufficient differences in pressure to enable an accurate measurement of the pressure differential, so that the milk flow rate can be accurately measured. [0123] (ii) Secondly, as previously mentioned, it is clear that the large pressure difference between the maximum negative pressure generated by the infant, 170 mm of Hg, and the maximum level of negative pressure, 110 mm of Hg, occurring within the mother's side of the nipple, is indicative of a large flow of milk from the less negative pressure, which is on the mother's side, to the more negative pressure on the infant's side. This difference of pressure is somewhat larger than the difference occurring when the infant is in the relaxation mode, when the flow is from the infant to the mother's side, such that a comparatively small net flow of milk from mother to infant occurs.
[0124] FIG. 5B now shows the situation that arises in a nipple which does have the flexible membrane feature of the present disclosure. A significant feature is that the use of the flexible membrane has enabled the pressure within the mother's side to more closely follow that generated by the infant on the infant's side. Thus for instance at the point of maximum sucking relaxation, the pressure on the mother's side goes up to 20 mm. of Hg, which is very close to the pressure of relaxation on the infant's side. Likewise, at the point of maximum suction of the infant, 165 mm of Hg, the negative pressure on the mother's side, 130 mm of Hg, comes much closer than in the nipple without the flexible membrane shown in FIG. 5A. The net result of these two findings is that a significantly smaller proportion of the milk flow through the nipple is returned to the mother's side when the infant relaxes its sucking action. The above described functionality of the flexible membrane can be illustrated by reviewing graphical plots of the differential pressure generated across the milk flow orifice, between the infant's side of the nipple, and the mother's side of the nipple. As previously stated, the differential pressure is defined as the difference between the pressure P1 on the infant's side, and the pressure P2 on the mother's side, i.e. P2P1. Such graphical plots are now shown in FIGS. 5C and 5D.
[0125] FIG. 5C shows a plot against time of the differential pressure for a conventional nipple device without the flexible membrane of the present disclosure. As is observed, the differential pressure ranges from approximately 70 mm of Hg, implying a flow from the mother's side to the infant's side, down to 30 mm of Hg, implying the flow from the infant's side to the mother's side of the nipple, but the important feature of the plot is that a significant part of the integrated pressure plot falls below the zero level of the differential pressure, meaning that there is a significant flow of milk from the infant back to the mother's side of the nipple.
[0126] Reference to FIG. 5D, which shows a plot against time of the differential pressure for a nipple device with the novel flexible membrane of the present disclosure, shows that the differential pressure now varies between two much closer pressure levels, over a range of only 40 mm of Hg, which implies that the sub-pressure on the mother's side follows the sub-pressure on the infant's side, which is the driving force for the sub pressure on the mother's side, more closely than in the nipple device without a flexible membrane of FIG. 5C. This immediately suggests that the feeding resistance for the infant is less using the nipple device shown in FIG. 5D with the flexible membrane. However, more important is that the differential pressure, defined as P2P1, is zero at the maximum relaxation level of the infant, and only moves into positive values as the infant begins the negative pressure of the sucking action. This means that the back flow of milk from the infant back to the mother's side of the nipple has been drastically reduced by use of the flexible membrane of the present application. This feature is also apparent from the plots in FIG. 5B, where it is observed that when the infant is at the peak of the relaxation period, the pressure in the mother's side is essentially equal to the pressure on the infant's side. This result is the reason for the previously mentioned outcome that the feeding resistance for the infant using the nipple with the flexible membrane is less than when nursing from a conventional nipple device of the present disclosure, without the flexible membrane.
[0127] FIGS. 5A to 5D thus show how the use of the flexible membrane of the present application significantly improves the ease with which the infant can feed, and also sufficiently reduces the back flow of milk from the infant towards the mother's side of the nipple, such that a more accurate measurement of the sensitive differential pressure measurement can be achieved.
[0128] Reference is now made to FIGS. 6A and 6B, which illustrate schematically two practical implementations of the novel use of a flexible membrane in a nipple structure, to achieve the above described advantageous effects. The flexible membrane is shown in FIGS. 6A and 6B, installed on a nipple such as that shown in FIG. 1C and FIG. 2, for measurement of the milk flow by measurement of the differential pressure in the two pressure detection chambers, as explained in connection with FIG. 2. It is to be understood that the flexible membrane feature of the present disclosure, with its concomitant advantages, can also be applied to a conventional prior art nipple without any flow measurement features, but such use may be unnecessary, since in such nipples, the size of the feeding orifice or orifices for can be enlarged to provide as high a fluid conductance path for the infant as is commensurate with a reasonably controlled feeding rate. On the other hand, in the pressure measurement nipple structures of the present disclosure, where the orifice fluid conductance must be limited to ensure that there is a sufficiently large differential pressure across the nipple orifice or orifices, to enable an accurate differential pressure measurement to be obtained, the use of the flexible membrane is very advantageous.
[0129] The difference between FIG. 6A and FIG. 6B is only in the location of the flexible membrane in the nipple structure, but the method of operation is the same in the two examples shown. In FIGS. 6A and 6B, the flexible membrane is incorporated into a nipple of the type shown in FIG. 2, and the features of that nipple device are generally labelled as in FIG. 2. In FIG. 6A, the flexible membrane 61 is incorporated into the side wall of the material of the nipple protrusion. It should cover as large a part of the circumference of the nipple protrusion, as possible, to provide maximum change in the volume of the space into which it protrudes, but that area should not be so large that the physical strength of the nipple device is reduced unnecessarily. Furthermore, it should be in a region of the wall that is intended to be within the extent of the inclusion of the infant's mouth when feeding on the nipple, so that it is regarded as being within the infant's mouth cavity. In other words, it must be within the area over which the lips of the infant grip the nipple. This flexible region can be most readily formed by making the area of thinner material or of more pliable material than the rest of the nipple area. Such a thinner region can be readily formed in the molding process of the whole nipple. In FIG. 6B, the flexible membrane 62 is incorporated into the material at the tip of the nipple dome, surrounding the feeding orifice or orifices.
[0130] It is to be emphasized that even though the flexible membrane have been shown applied in FIGS. 6A and 6B, to implementations in which the pressure measurements are made using thin-walled chambers, as shown in FIG. 2, this is only one illustration of applications of the flexible membrane in nipple devices, and that the flexible membrane can be installed in nipple devices having any other form of pressure measurement, such as the simple direct measurement embodiment, as shown in FIG. 1B.
[0131] Reference is now made to FIGS. 7A and 7B, which illustrate schematically two practical implementations of novel orifice structures, which can be used to avoid effects of external forces, such as from the mouth or tongue motions of the infant, from interfering with the shape or form of the orifice or orifices, and hence with the magnitude of the flow resistance of the orifice or orifices. In FIG. 7A, there is shown an enlarged cross-section of the tip extremity of the nipple device, with the orifice 71 formed in the nipple device material having its normal thickness, that thickness also being shown down the side 70 of the nipple domed protrusion. The orifice region of the domed nipple protrusion device is connected to the remainder of the device by means of a thinner region 72 of the flexible material, such that the orifice region is flexibly attached to the rest of the device, so that forces applied to the orifice region will cause it to move or change its orientation, but will essentially not deform or compress its shape, thus maintaining the accuracy of the fluid flow resistance through the orifice. A single orifice is shown in FIG. 7A, though it is to be understood that more than one orifice may also be used to provide milk to the infant, and the same requirements that the orifices should not be deformed or compressed apply also to such multiple orifices.
[0132] FIG. 7B now shows an alternative or additional method for preventing the tongue of the feeding infant from blocking the orifice of the domed nipple structure. In FIG. 7B, the orifice 75, which acts as the flow resistance for generating the differential pressure for the flow measurement, is shown located at the base of a deeper and slightly wider hole 76. This hole 76 ensures a safe distance between the infant's tongue and the feeding orifice 75, by preventing the tongue from reaching the feeding orifice and possibly blocking it. FIG. 7B also shows the passageway 78 used to convey the pressure of the milk in the infant's mouth, to the pressure sensor for determining the pressure on the infant's side of the flow resistor 75. The passageway 78 should be made comparatively narrow, a typical internal diameter being no more than 4 mm., so that the milk from the baby cannot readily pass down the passageway, mix with the air already trapped within the passageway, and thus prevent the air layer from acting as a gaseous buffer or cushion which is intended to prevent the milk, as far as is possible, from reaching the pressure sensor, which may not take kindly to contact with the milk.
[0133] In the same way that the infant's tongue may block the feeding orifice from its outer end, the tip of the mother's nipple may inadvertently block the feeding orifice from its inner end. Reference is now made to FIGS. 8A and 8B, which illustrate schematically a novel structure which can be incorporated on the inner side of the domed nipple protrusion 80, around the feeding orifice 81, in order to prevent its blocking or partial blocking, by the tip of the mother's nipple. On the inner side of the domed nipple protrusion, and surrounding the feeding orifice 81 or orifices, the device is formed with a region of increased thickness 83, having a number of channels 86 within the thickness of that region, these channels leading to the region around the inner orifice opening 81. Consequently, even if one or two of the channels are blocked by the mother's nipple, other channels are open to freely deliver milk from the mother's nipple to the feeding orifice. The increased thickness layer 83 can either be formed in the device material itself, or it can be added as a separately manufactured insert. FIG. 8A also shows the passageway 84 conveying the pressure of the milk 85 on the mother's side of the nipple structure towards the pressure sensor for determining the pressure on the mother's side of the feeding orifice, which acts as the flow resistor.
[0134] Reference is now made to FIG. 9, which illustrates schematically the implementation of the multi-task milk measurement devices shown in the above mentioned International Patent Publication WO2022/175833, for electronic measurement of milk flow from the mother to the infant. The device comprises a nipple shield flexible base unit 90, and a plug in measurement unit 99, which comprises the differential pressure measurement arrangement. The plug-in measurement unit is connected to the flexible base unit 90 by means of a set of connection ports 94. A pair of passageways are provided connected to the orifices 91 in the top part of the domed protrusion. One of these passageways 93 is for conveying the mother's milk from the inner space of the domed protrusion to the standard attachment ports 94, and a second passageway 92, for conveying the milk back to the feeding orifice in the top part of the domed protrusion, after flow measurement in the plug-in unit 99. The enlarged view at the bottom of FIG. 9 shows the fluid flow resistor 95 connecting the inlet passageway 93 with the return passageway 92. Pressure sensors P.sub.H and P.sub.L, are shown connected to the inlet passageway 93 and return passageway 92, P.sub.H for measuring the pressure of the milk on the input side of the fluid flow resistor 95, and P.sub.L for measuring the pressure of the milk after passing through the fluid flow resistor 95. The measurement unit 99 is shown schematically as a circular unit, but it is to be understood that it could be of any other shape. Additionally, the pressure sensors should be connected to electronic circuits (not shown in FIG. 9), for converting the differential pressure measurement into the measured flow level, and an electronic display can also be incorporated into the measurement unit. Alternately, the unit may include a wireless connection facility for sending the measured flow rate to a remote device, such as a mobile phone.
[0135] FIG. 9 shows an implementation of the presently described milk flow measurement devices, in which the components and features required for the measurement of the flow, namely the fluid flow resistor and the pressure sensors, are incorporated into a plug-in head 99. According to a further implementation, those components can be incorporated into a self-contained milk flow nipple device, without the advantage of using different plug-in attachment heads for different milk measurement functions. In such an embodiment, the nipple device may comprise only the base unit 90, with the fluid flow resistor 95 mounted within the peripheral skirt region of the device, and not in a separate attachable measurement unit. In any of these devices, the fluid flow resistor 95, shown schematically in FIG. 9 and in FIG. 10, may be implemented as a replaceable resistor, whose function will be further explained hereinbelow in relation to FIG. 11. The replaceable resistor could be mounted either in the plug-in head 99, which is where the flow resistor 95 is shown in FIG. 9, or in the region of the fluid attachment ports 94 in the extremity of the base region of the milk flow measurement device. In either of these cases, a resistor housing may be formed in the region where the resistor is to be inserted, and the resistor can be removably mounted into the base of the device or into the plug-in head, such that the milk flows through it. It can then be removed periodically for cleaning or replacement. Further details are given in relation to FIG. 11 below.
[0136] This location of the fluid flow resistor, in the base peripheral region of the device, is an advantageous alternative to using the feeding orifice as the fluid flow resistor with the problems generated thereby, and measuring the pressure drop across the orifice by means of pressure transferring passageways leading to the outer edge of the device base layer, and measuring the differential pressure at that location.
[0137] Reference is now made to FIG. 10, which shows an alternative, and more reliable method, of ensuring that the pressure sensors P.sub.H, P.sub.L, are not exposed to contact with the milk flow. This is achieved by use of a pressure transfer chamber unit 100, in which a flexible diaphragm is used for transferring the pressure within the milk in each flow channel 93, 92, to their respective pressure sensors P.sub.H, P.sub.L, without allowing any of the milk to touch the pressure sensors. Relating to the inlet flow of the mother's milk in passageway 93, the pressure of the milk is experienced in the sub-chamber 97.sub.H, and the comparatively higher pressure of the inlet flow of the mother's milk, causes the diaphragm 96.sub.H on the inlet side of the pressure transfer chamber, to deflect outwards from the inlet sub-chamber 97.sub.H, transferring a pressure proportional to the level of the inlet pressure to the inlet sub-chamber 98.sub.H, where the pressure level is measured by pressure sensor P.sub.H. The same process takes place on the outlet side of the milk flow through the fluid flow resistor 95, where the flexible diaphragm 96.sub.L transfers a level of pressure proportional to the pressure in the outlet side to the outlet sub chamber 98.sub.L, where it is measured by the outlet pressure sensor P.sub.L. Since the pressure on the outlet side is considerably lower than that on the inlet side, the flexing of the outlet flexible diaphragm 96.sub.L is considerably less than that of the inlet flexible diaphragm, as is shown by the representation of the length of the arrows on the two flexible diaphragms. The sub-chambers 98.sub.H and 98.sub.L, to which the pressure experienced is transferred, may be advantageously filled with oil or another liquid, increasing accuracy because of the essentially non-compressible nature of liquids compared with leaving those sub-chambers air-filled. The stiffness of the flexible diaphragms should also be comparatively high, such that the flexing is limited, and any non-linear elastic effects are avoided. The use of such a pressure transfer chamber unit 100, ensures that the pressure sensors are therefore protected from contact with the milk itself, but do sense the fluid pressures of the milk flow by means of the extension of the flexible diaphragms.
[0138] Reference is now made to FIG. 11, shows another implementation of the features of the present disclosure, in the form of a reusable fluid flow resistor. The need for such a reusable resistor is because in those applications where the pressure drop across the nipple orifice is used in order to determine the flow of milk to the infant, it is important that the resistance to flow of the resistor remains at its planned value. Because the resistor is a precision part, it may be advantageous to have such a reusable fluid flow resistor, rather than a part of a disposable nipple device. Since the milk flow may leave residues of fat and other milk components on the walls of the resistor, the flow resistance will change unless the resistor is cleaned regularly. Since the bore of the previous flow resistors is so small, it is difficult to clean a resistor with an internal bore.
[0139] FIG. 11 illustrates an exemplary replaceable flow resistor 110, suitable for use as part of the orifice through which the infant sucks. The flow resistor of FIG. 11 differs from previously used flow resistors in that the flow path of the milk through the resistor is formed on the outer surface 111 of the flow resistor, rather than as an internal bore. The flow resistor is adapted to fit into a dedicated housing which could be part of the orifices 71 of FIG. 7A, or 75 of FIG. 7B or 81 of FIGS. 8A and 8B. The flow resistor 110 slides into the housing until the shoulder 115 of the resistor meets its matching seat in the housing. When properly seated, the regions 113 and 114 are located respectively opposite an input channel in which the milk from the mother flows, and an output channel from which the milk flows to the exit end of the orifice and to the sucking infant. The passageways to the pressure sensors may also be fluidly connected to the regions 113 and 114. The fluid resistor flow path itself 112 is formed on the outside surface 111 of the flow resistor 110. It has a cross section and length such that it provides the resistance to the milk flow that develops a desired pressure difference between its ends that can be readily measured by the differential pressure measurement module, or the individual pressure sensors. The advantage of the external flow resistor of FIG. 11 is that it can be removed at periodic intervals and thoroughly cleaned to maintain the accuracy of its flow resistance. Such a replaceable resistor can also be implemented in the type of plug-in device shown in FIG. 9, where the housing may be advantageously located horizontally across the direction of the fluid passageways, and the flow would be diverted to run into the resistor 95, in the same way as implemented for the removable resistor mounted at the feeding orifice.
[0140] Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details have been set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. Furthermore, it is appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of various features described hereinabove as well as variations and modifications thereto which would occur to a person of skill in the art upon reading the above description and which are not in the prior art.
