FLOWMETER AND CASSETTE MODULE FOR A FLOWMETER

Abstract

A cassette module (19, 29, 319, 419, 59, 69) for a differential flowmeter is disclosed, wherein the cassette module (19, 29, 319, 419, 59, 69) forms a first fluid-carrying channel (16, 216, 316, 611, 615) and the second fluid-carrying channel (17, 217, 317, 610, 616) during operation of the differential flowmeter. The cassette module is specific in the regard that a geometric deformation of the channels due to a temperature difference between the channels (16, 216, 316, 611, 615, 17, 217, 317, 610, 616) is minimized or prevented. In addition a differential flowmeter containing the cassette module (19, 29, 319, 419, 59, 69) disclosed here is also described.

Claims

1. A cassette module (19, 29, 319, 419, 59, 69) for a differential flowmeter, wherein the cassette module (19, 29, 319, 419, 59, 69) forms a first fluid-carrying channel (16, 216, 316, 611, 615) and a second fluid-carrying channel (17, 217, 317, 610, 616) during operation of the differential flowmeter, characterized in that the cassette model is designed so that a geometric deformation of the channel due to a temperature difference between the channels (16, 216, 316, 611, 615, 17, 217, 317, 610, 616) is minimized or prevented.

2. The cassette module according to claim 1, having a base body (12, 414) on which the channels (16, 17) are attached, wherein the geometric deformation is minimized or prevented by a reinforcing structure of the base body (12, 414).

3. The cassette module (29, 59) according to claim 1, wherein an insulation layer (214) for thermal insulation of the channels (216, 217) is provided between the first channel (216) and the second channel (217).

4. The cassette module (319) according to claim 1, wherein the geometric deformation is minimized or prevented by the fact that a contact zone between the first channel (316) and the second channel (317) is minimized.

5. The cassette module (319) according to claim 4, wherein the contact zone is minimized or prevented by the fact that the first channel (316) and the second channel (317) are disposed essentially at right angles to one another.

6. The cassette module (319) according to claim 1, wherein at least two first channels (611, 615) and at least two second channels (610, 616) are provided and wherein the channels are disposed so that mechanical stresses due to a temperature difference between the first channels (611, 615) and the second channels (610, 616) are equalized.

7. The cassette module (319) according to claim 6, wherein the at least two first channels (611, 615) and the at least two second channels (610, 616) are each disposed in mirror symmetry to one another.

8. The cassette module (19, 29, 319, 419, 59, 69) according to claim 1, wherein the change in measured value attributable to deformation of the channels amounts to less than 0.05 percent per degree Kelvin.

9. The cassette module (19, 29, 319, 419, 59, 69) according to claim 1, for use as a disposable article.

10. A differential flowmeter (105) for balancing between fluid flows, comprising: a cassette module (19, 29, 319, 419, 59, 69) according to claim 1, a magnet for generating a magnetic field in the first channel (16, 216, 316, 611, 615) and in the second channel (17, 217, 317, 610, 616) of the cassette module, each having an electrode pair (101, 102) for tapping an electric voltage at the first channel (16, 216, 316, 611, 615) and at the second channel (17, 217, 317, 610, 616), when the fluid flows through the first and/or the second channel so that a difference between the tapped voltages is indicative of a difference between a fluid flow through the first channel (16, 216, 316, 611, 615) and through the second channel (17, 217, 317, 610, 616).

11. The differential flowmeter (105) according to claim 10, comprising an evaluation unit (103) for determining the difference between the voltage tapped at the first fluid-carrying channel (16, 216, 316, 611, 615) and the voltage tapped at the second fluid-carrying channel (17, 217, 317, 610, 616) and for determining the difference in the fluid flows based on the certain voltage difference.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIGS. 1-6 show different embodiments of a cassette module for a differential flowmeter.

DETAILED DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 shows one embodiment of a cassette module 19 for a differential flowmeter. The cassette module 19 has a solid base body 12 in which channels 16, 17 are formed, carrying fluid when the differential flowmeter is operated. Fluid-carrying lines 10, 11 are connected to the fluid-carrying channels 16, 17. In one embodiment the differential flowmeter is part of a balancing unit 105 for balancing dialysis fluid in a dialysis fluid circulation. In this case the lines 10, 11 as well as the channels 16, 17 are part of a dialysis fluid circulation.

[0031] The channels 16, 17 are penetrated by a magnetic field 13 which is generated by a magnet (not shown). The magnetic field is essentially perpendicular to the direction of flow in the channels 16, 17. Electrodes 101, 102 are disposed on the channels 16, 17, essentially perpendicular to the magnetic field 13 and to the direction of flow in the channels 16, 17, tap a voltage transversely to the respective direction of flow. The electrodes are connected to an evaluation unit 103 which determines a difference in the fluid flows in the channels and thus a fluid balance between the fluid-carrying lines based on the tapped voltages, in particular based on a difference in the derived voltages.

[0032] Due to the solid design of the base body 12, a reinforcing structure is provided, minimizing the geometric deformation of the base body due to a temperature difference between the lines 10, 11. In an alternative embodiment, a reinforcing structure may also be formed by reinforcing ribs.

[0033] FIG. 2 shows an alternative embodiment of a cassette module 29 for a differential flowmeter. The cassette module 29 has a base body 212 in which channels 216, 217 which are fluid-carrying are formed when the differential flowmeter is operated. Fluid-carrying lines 210, 211 are connected to the fluid-carrying channels 216, 217. The channels 216, 217 are permeated by a magnetic field 213. Voltages tapped at electrodes that are not shown in greater detail here are induced by the magnetic field 213 and permit the determination of a fluid balance corresponding to the configuration already described with regard to FIG. 1.

[0034] The base body forms a recess 214 between the fluid-carrying channels 216 and 217 which forms an insulation layer for thermal insulation of the channels. The recess may be filled with a thermal insulation material such as ceramic or a foam. In an alternative embodiment, insulation of the channels is provided by the fact that the air layer situated between the channels has an insulating effect. The insulation between channel 216 and channel 217 results in minimization of any geometric deformation of the base body due to a temperature difference between the lines 216 and 217.

[0035] FIG. 3 shows another alternative embodiment of a cassette model 319 for a differential flowmeter. The cassette module 319 has a base body 312 in which channels 316, 317, which are fluid-carrying when the differential flowmeter is being operated, are formed. Fluid-carrying lines 310, 311 are connected to the fluid-carrying channels 316, 317. A magnetic field generated by magnets (not shown) permeates the first and second channels in a contact zone. Electrons for diverting voltages induced on the electrons are also disposed in this region. Voltages derived at the electrodes make it possible to determine a fluid balance corresponding to the configuration already described in conjunction with FIG. 1.

[0036] The contact zone between the first and second channels is minimized or prevented in an advantageous embodiment by the fact that the first and second channels are disposed essentially at right angles to one another.

[0037] The minimized contact zone between the channel 316 and the channel 317 has the result that any geometric deformation of the base body due to a temperature difference between the lines 216 and 217 is minimized.

[0038] FIG. 4 shows an alternative design of a cassette module 414 for a differential flowmeter. The cassette module 414 has a base body in which a first channel and a second channel, which are fluid-carrying when the differential flowmeter is in operation, are formed. These channels are part of the fluid-carrying lines 411, 412 and are permeated by a magnetic field 413 which is generated by a magnet (not shown). The magnetic field is essentially perpendicular to the direction of flow in the channels.

[0039] Voltages induced by the magnetic field 413 and tapped at electrodes (not shown in detail here) make it possible to determine a fluid balance according to the configuration already described in conjunction with FIG. 1.

[0040] A certain magnetic field line permeates both the first and second channels. Therefore, essentially the same magnetic field prevails in the first channel as in the second channel. This permits a particularly accurate determination of the fluid balance.

[0041] The cassette module corresponds to the cassette module described in conjunction with FIG. 1 inasmuch as the base body has a solid design. Due to the solid design of the base body, a reinforcing structure is provided, minimizing any geometric deformation of the base body due to a temperature difference between the lines 411, 412.

[0042] FIG. 5 shows another alternative embodiment of cassette module 59 for a differential flowmeter. The cassette module has a base body 512 which forms a first and a second channel, each being part of the fluid-carrying lines 510, 511.

[0043] The channels are permeated by a magnetic field 513, which is generated by a magnet (not shown). The magnetic field is essentially at a right angle to the direction of flow in the channels.

[0044] Voltages induced by the magnetic field 513 and tapped at electrodes, which are not shown in detail, permit determination of a fluid balance corresponding to the configuration already described in relation to FIG. 1.

[0045] A certain magnetic field line passes through both the first and the second channels. Therefore, essentially the same magnetic field prevails in the first channel as in the second channel. This permits a particularly accurate determination of the fluid balance.

[0046] The cassette module has a recess 514 in the base body 512 for thermal insulation of the channels. The recess can be filled with a thermal insulation material such as ceramic or a foam. In an alternative embodiment, insulation of the channels is provided by the fact that the air layer situated between the channels has an insulating effect.

[0047] The insulation between the first channel and the second channel causes a geometric deformation of the base body due to a temperature difference between the lines 510 and 511 to be minimized.

[0048] FIG. 6 shows an alternative embodiment of a cassette module 612 for a differential flowmeter. The cassette module 69 has a base body 612 in which first channels 611 and 615 and second channels 610, 616 are formed; these are fluid-carrying channels when the differential flowmeter is in operation. The first channels are part of a first line which is a fluid-carrying line during operation of the differential flowmeter, such that the line splits into the two first channels, and the second channels are part of a second line which is fluid-carrying during operation of the differential flowmeter and splits into the two second channels.

[0049] In other words, the directions of flow in the two first channels correspond to one another, and the directions of flow in the two second channels correspond to one another. The fluid flows in the same direction through opposing channels.

[0050] The configuration of channels has the result that mechanical stresses caused by a prevailing temperature difference between the first line and the second line corresponding to a temperature difference between the two first channels and the two second channels are equalized.

[0051] The channels 611, 610, 616, 615 are permeated by a magnetic field 613 which is generated by a magnet (not shown). The magnetic field is essentially perpendicular to the direction of flow in the channels 611, 610, 616, 615.

[0052] Electrodes (not shown) are disposed on the channels 611, 610, 616, 615 so that they are essentially perpendicular to the magnetic field 613 and to the direction of flow in the channels 611, 610, 616, 615 in order to tap a voltage transversely to the respective direction of flow.

[0053] The electrodes are connected to an evaluation unit (not shown) which indicates a difference between the fluid flow in the first line and the fluid flow in the second line and thus in the case of fluid balance between the first and second lines based on the voltages thereby tapped.

[0054] Voltages tapped at the electrodes of the first channels are each added to obtain a total voltage at the two first channels, and voltages tapped at the electrodes of the second channels are added to obtain a total voltage at the two second channels. The two total voltages are then subtracted one from the other.

[0055] In an alternative embodiment, electrode pairs are provided at only one of the first channels and one of the second channels.

[0056] Such a configuration then also leads to little or no deformation when no particular reinforcing structure is provided. Therefore, such a configuration is particularly sparing of materials.

[0057] In an advantageous embodiment of the cassette module, the change in measured value attributed to the deformation of the channels amounts to less than 0.05 percent per degree Kelvin.

[0058] The following rule also holds for all embodiments: Due to the fact that geometric deformation of the channels is prevented or minimized, the position relationships between the electrodes and the magnetic field are preserved when a temperature difference prevails between the first and second lines. A constant position relationship between electrodes and the magnetic field contributes toward an improved measurement accuracy of the differential flowmeter.