Abstract
A fluid pump includes a pump body having a pump inlet and a pump outlet, and a spring valve combination provided within the pump body. The spring valve combination includes a spring body having a first end portion, a second end portion and a spring section therebetween, which spring section is compressible in an axial direction from an initial condition to a compressed condition and is subsequently expandable to its initial condition; a first valve element provided at the first end portion of the spring body; and a second valve element provided at the second end portion of the spring body, wherein the spring body and the first and second valve elements are integrally formed. The first and second valve elements interact with an interior of the pump body to define a one-way inlet valve and a one-way outlet valve, respectively.
Claims
1: A fluid pump comprising: a pump body of plastomer material, defining an axis and having a pump inlet and a pump outlet; and a spring valve combination provided within the pump body, the spring valve combination comprising: a spring body having a first end portion, a second end portion and a spring section therebetween, which spring section is compressible in an axial direction from an initial condition to a compressed condition and is subsequently expandable to its initial condition, a first valve element provided at the first end portion of the spring body, and a second valve element provided at the second end portion of the spring body, wherein the spring body and the first and second valve elements are integrally formed, and wherein the first and second valve elements interact with an interior of the pump body to define a one-way inlet valve and a one-way outlet valve, respectively, wherein the second end portion of the spring body comprises an engaging member that interacts with the pump outlet to maintain the spring in position.
2: The fluid pump according to claim 1, wherein the second valve element is formed as a circumferential element projecting outwardly.
3: The fluid pump according to claim 1, wherein the first valve element is formed as a circumferential element projecting outwardly.
4: The fluid pump according to claim 1, wherein the second valve element has a relatively smaller outer diameter than the first valve element.
5: The fluid pump according to claim 1, wherein the spring section tapers from the first end portion towards the second end portion.
6: The fluid pump according to claim 1, wherein the spring body comprises two or more open spring sections joined together in series and aligned with each other in the axial direction to connect the first end portion to the second end portion.
7: The fluid pump according to claim 1, wherein the first end portions of the spring body comprises a further engaging member for engaging the spring valve combination to the pump inlet and retaining such engagement during compression of the pump body with the spring body.
8: The fluid pump according to claim 1, wherein the first and second end portions each comprise at least one flow passage for allowing fluid to flow through or around the respective portion.
9: The fluid pump according to claim 1, wherein the spring body, first valve element and second valve element are injection molded in a single piece from plastomer material.
10: The fluid pump according to claim 6, wherein each spring section comprises four flat leaves joined together along hinge lines that are parallel to each other and perpendicular to the axial direction.
11: The fluid pump according to claim 10, wherein the leaves are feathered from a relatively thicker mid-line to relatively thinner edges.
12: The fluid pump according to claim 6, wherein the spring sections are arranged to compress from an open configuration to a substantially flat configuration.
13: The fluid pump according to claim 6, wherein the spring body comprises at least three spring sections.
14: The fluid pump according to claim 1, wherein the pump outlet, the pump inlet, or both have a smaller inner diameter than an outer diameter of the respective first and second valve elements, such that the respective valve element is compressed in a radial direction and an interior of the pump body adjacent the respective valve element forms a valve seat.
15: The fluid pump according to claim 1, wherein the pump body comprises an elongate pump chamber surrounding the spring valve combination and extending from the pump inlet adjacent to the first end portion to the pump outlet adjacent to the second end portion, wherein the pump chamber is collapsible on compression of the spring.
16: The fluid pump according to claim 15, wherein the pump chamber comprises a flexible wall that inverts during collapse of the pump chamber.
17: The fluid pump according to claim 1, consisting of only two components, namely the pump body and the spring valve combination, wherein the spring body and the first and second valve element are integrally formed.
18: The fluid pump according to claim 1, wherein a length of the spring valve combination is such that, in the initial condition, the spring body is retained within the pump body in a slightly compressed state.
19. (canceled)
20: A pump assembly comprising: the pump according to claim 1; and a pair of sleeves, arranged to slidably interact to guide the pump during a pumping stroke, including a stationary sleeve engaged with the pump inlet and a sliding sleeve engaged with the pump outlet.
21: A method of dispensing a fluid from the fluid pump according to claim 1, the method comprising: exerting an axial force on the pump body between the pump inlet and the pump outlet to cause axial compression of the spring body and a reduction in volume of the pump body; allowing the second valve element to open, such that fluid from the pump body flows through the pump outlet, while the first valve remains closed; releasing the axial force on the pump body to cause expansion of the spring body and an increase in volume of the pump body; and allowing the first valve element to open, such that fluid is allowed to flow into the pump body, while the second valve remains closed.
22: The method of claim 21, wherein the pump comprises a pump chamber, in which the spring body is located and the axial force exerted on the pump body causes the pump chamber to collapse.
23. (canceled)
24: A disposable fluid dispensing package, comprising the fluid pump according to claim 1 sealingly connected to a collapsible product container.
25. (canceled)
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] The features and advantages of the present disclosure will be appreciated upon reference to the following drawings of a number of exemplary embodiments, in which:
[0051] FIG. 1 shows a perspective view of a dispensing system;
[0052] FIG. 2 shows the dispensing system of FIG. 1 in an open configuration;
[0053] FIG. 3 shows a disposable container and pump assembly in side view;
[0054] FIGS. 4A and 4B show partial cross-sectional views of the pump of FIG. 1 in operation;
[0055] FIG. 5 shows the pump assembly of FIG. 3 in exploded perspective view;
[0056] FIG. 6 shows the spring of FIG. 5 in perspective view;
[0057] FIG. 7 shows the spring of FIG. 6 in front view;
[0058] FIG. 8 shows the spring of FIG. 6 in side view;
[0059] FIG. 9 shows the spring of FIG. 6 in top view;
[0060] FIG. 10 shows the spring of FIG. 6 in bottom view;
[0061] FIG. 11 shows a cross-sectional view through the spring of FIG. 8 along line XI-XI;
[0062] FIG. 12 shows the pump chamber of FIG. 5 in front view;
[0063] FIG. 13 shows a bottom view of the pump body directed onto the pump outlet;
[0064] FIG. 14 is a longitudinal cross-sectional view of the pump body taken in direction XIV-XIV in FIG. 13;
[0065] FIGS. 15-18 are cross-sectional views through the pump of FIG. 3 in various stages of operation;
[0066] FIG. 17A is a detail in perspective of the pump outlet of FIG. 17; and
[0067] FIG. 18A is a detail in perspective of the pump inlet of FIG. 18.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0068] FIG. 1 shows a perspective view of a dispensing system 1. The dispensing system 1 includes a reusable dispenser 100 of the type used in washrooms and the like and available under the name Tork from ESSITY HYGIENE AND HEALTH AKTIEBOLAG. The dispenser 100 is described in greater detail in WO2011/133085, the contents of which are incorporated herein by reference in their entirety. It will be understood that this embodiment is merely exemplary and that the present invention may also be implemented in other dispensing systems.
[0069] The dispenser 100 includes a rear shell 110 and a front shell 112 that engage together to form a closed housing 116 that can be secured using a lock 118. The housing 116 is affixed to a wall or other surface by a bracket portion 120. At a lower side of the housing 116 is an actuator 124, by which the dispensing system 1 may be manually operated to dispense a dose of cleaning fluid or the like. The operation, as will be further described below, is described in the context of a manual actuator but the invention is equally applicable to automatic actuation e.g. using a motor and sensor.
[0070] FIG. 2 shows in perspective view the dispenser 100 with the housing 116 in the open configuration and with a disposable container 200 and pump assembly 300 contained therein. The container 200 is a 1000 ml collapsible container of the type described in WO2011/133085 and also in WO2009/104992, the contents of which are also incorporated herein by reference in their entirety. The container 200 is of generally cylindrical form and is made of polyethylene. The skilled person will understand that other volumes, shapes and materials are equally applicable and that the container 200 may be adapted according to the shape of the dispenser 100 and according to the fluid to be dispensed.
[0071] The pump assembly 300 has an outer configuration that corresponds substantially to that described in WO2011/133085. This allows the pump assembly 300 to be used interchangeably with existing dispensers 100. Nevertheless, the interior configuration of the pump assembly 300 is distinct from both the pump of WO2011/133085 and that of WO2009/104992, as will be further described below.
[0072] FIG. 3, shows the disposable container 200 and pump assembly 300 in side view. As can be seen, the container 200 includes two portions, namely a hard, rear portion 210 and a soft, front portion 212. Both portions 210, 212 are made of the same material but having different thicknesses. As the container 200 empties, the front portion 210 collapses into the rear portion as fluid is dispensed by the pump assembly 300. This construction avoids the problem with a build-up of vacuum within the container 200. The skilled person will understand that although this can be a preferred form of container, other types of reservoir may also be used in the context of the invention including but not limited to bags, pouches, cylinders and the like, both closed and open to the atmosphere. The container may be filled with soap, detergent, disinfectant, skin-care fluid, moisturizers or any other appropriate fluid and even medicaments. In most cases, the fluid will be aqueous although the skilled person will understand that other substances may be used where appropriate, including oils, solvents, alcohols and the like. Furthermore, although reference will be made in the following to fluids, the dispenser 1 may also dispense fluids such as dispersions, suspensions or particulates
[0073] At the lower side of the container 200, there is provided a rigid neck 214 provided with a connecting flange 216. The connecting flange 216 engages with a stationary sleeve 310 of the pump assembly 300. The pump assembly 300 also includes a sliding sleeve 312, which terminates at an orifice 318. The sliding sleeve 312 carries an actuating flange 314 and the stationary sleeve has a locating flange 316. Both the sleeves 310, 312 are injection moulded of polycarbonate although the skilled person will be well aware that other relatively rigid, mouldable materials may be used. In use, as will be described in further detail below, the sliding sleeve 312 is displaceable by a distance D with respect to the stationary sleeve 310 in order to perform a single pumping action.
[0074] FIGS. 4A and 4B show partial cross-sectional views through the dispenser 100 of FIG. 1, illustrating the pump assembly 300 in operation. According to FIG. 4A, the locating flange 316 is engaged by a locating groove 130 on the rear shell 110. The actuator 124 is pivoted at pivot 132 to the front shell 112 and includes an engagement portion 134 that engages beneath the actuating flange 314.
[0075] FIG. 4B shows the position of the pump assembly 300 once a user has exerted a force P on actuator 124. In this view, the actuator 124 has rotated anti-clockwise about the pivot 132, causing the engagement portion 134 to act against the actuating flange 314 with a force F, causing it to move upwards. Thus far, the dispensing system 1 and its operation is essentially the same as that of the existing system known from WO2011/133085.
[0076] FIG. 5 shows the pump assembly 300 of FIG. 3 in exploded perspective view illustrating the stationary sleeve 310, the sliding sleeve 312, spring 400 and pump body 500 axially aligned along axis A. The stationary sleeve 310 is provided on its outer surface with three axially extending guides 340, each having a detent surface 342. The sliding sleeve 312 is provided with three axially extending slots 344 through its outer surface, the functions of which will be described further below.
[0077] FIG. 6 shows an enlarged perspective view of the spring 400, which is injection moulded in a single piece from ethylene octene copolymer material available from ExxonMobil Chemical Co. Spring 400 includes a first end portion 402 and a second end portion 404 aligned with each other along the axis A and joined together by a plurality of rhombus shaped spring sections 406. In this embodiment, five spring sections 406 are shown although the skilled person will understand that more or less such sections may be present according to the spring constant required. Each spring section 406 includes four flat leaves 408, joined together along hinge lines 410 that are parallel to each other and perpendicular to the axis A. The leaves 408 have curved edges 428 and the spring sections 406 join at adjacent corners 412.
[0078] The first end portion 402 includes a ring element 414 and a cross-shaped support element 416. An opening 418 is formed through the ring element 414. The cross-shaped support element 416 is interrupted intermediate its ends by an integrally formed first valve element 420 that surrounds the first end portion 402 at this point.
[0079] The second end portion 404 has a rib 430 and a frusto-conical shaped body 432 that narrows in a direction away from the first end portion 402. On its exterior surface the frusto-conical shaped body 432 is formed with two diametrically opposed flow passages 434. At its extremity it is provided with an integrally formed second valve element 436 projecting outwardly and extending away from the first end portion.
[0080] FIGS. 7-10 are respective front, side and first and second end elevations of the spring 400.
[0081] Starting with FIG. 7, the ring element 414 and cross-shaped support element 416 can be seen, together with the first valve element 420. In this view it may be noted that the first valve element 420 is part spherical in shape and extends to an outer edge 440 that is slightly wider than the cross-shaped support element 416. Also in this view, the rhombus shape of the spring sections 406 can be clearly seen. The spring 400 is depicted in its unstressed condition and the corners 412 define an internal angle of around 115 degrees. The skilled person will recognise that this angle may be adjusted to modify the spring properties and may vary from 60 to 160 degrees, from 100 to 130 degrees, or between 90 and 120 degrees. Also visible is the frusto-conical shaped body 432 of the second end portion 404 with rib 430, flow passages 434 and second valve element 436.
[0082] FIG. 8 depicts the spring 400 in side view, viewed in the plane of the rhombus-shape of the spring sections 406. In this view, the hinge lines 410 can be seen, as can be the curved edges 428. It will be noted that the hinge lines 410 at the corners 412, where adjacent spring sections 406 join, are significantly longer than the hinge lines 410 where adjacent flat leaves 408 join.
[0083] FIG. 9 is a view onto the first end portion 402 showing the ring element 414 with the cross-shaped support element 416 viewed through opening 418. FIG. 10 shows the spring 400 viewed from the opposite end to FIG. 9, with the second valve element 436 at the centre and the frusto-conical shaped body 432 of the second end portion 404 behind it, interrupted by flow passages 434. Behind the second end portion 404, the curved edges 428 of the adjacent spring section 406 can be seen, which in this view define a substantially circular shape. In the shown embodiment, the ring element 414 is the widest portion of the spring 400.
[0084] FIG. 11, is a cross-sectional view along line XI-XI in FIG. 8 showing the variation in thickness through the flat leaves 408 at the hinge line 410. As can be seen, each leaf 408 is thickest at its mid-line at location Y-Y and is feathered towards the curved edges 428, which are thinner. This tapering shape concentrates the material strength of the spring towards the mid-line and concentrates the force about the axis A.
[0085] FIG. 12 shows the pump body 500 of FIG. 5 in front elevation in greater detail. In this embodiment, pump body 500 is also manufactured of the same plastomer material as the spring 400. This is advantageous both in the context of manufacturing and disposal, although the skilled person will understand that different materials may be used for the respective parts. Pump body 500 includes a pump chamber 510, which extends from a pump inlet 502 to a pump outlet 504. The pump outlet 504 is of a smaller diameter than the pump chamber 510 and terminates in a nozzle 512, which is initially closed by a twist-off closure 514. Set back from the nozzle 512 is an annular protrusion 516. The pump inlet 502 includes a boot portion 518 that is rolled over on itself and terminates in a thickened rim 520.
[0086] FIG. 13 shows an end view of the pump body 500 directed onto the pump outlet 504. The pump body 500 is rotationally symmetrical, with the exception of the twist-off closure 514, which is rectangular. The variation in diameter between the pump outlet 504, the pump chamber 510 and the thickened rim 520 can be seen.
[0087] FIG. 14 is a longitudinal cross-sectional view of the pump body 500 taken in direction XIV-XIV in FIG. 13. The pump chamber 510 includes a flexible wall 530, having a thick-walled section 532 adjacent to the pump inlet 502 and a thin-walled section 534 adjacent to the pump outlet 504. The thin-walled section 534 and the thick-walled section 532 join at a transition 536. The thin-walled section 534 tapers in thickness from the transition 536 with a decreasing wall thickness towards the pump outlet 504. The thick-walled section 532 tapers in thickness from the transition 536 with an increasing wall thickness towards the pump inlet 502. The thick-walled section 532 also includes an inlet valve seat 538 at which the internal diameter of the pump chamber 510 reduces as it transitions to the pump inlet 502. In addition to the variations in wall thickness of the pump chamber 510, there is also provided an annular groove 540 within the pump body 500 at the pump inlet 502 and sealing ridges 542 on an exterior surface of the boot portion 518.
[0088] FIG. 15 is a cross-sectional view through the pump assembly 300 of FIG. 3, showing the spring 400, the pump body 500 and the sleeves 310, 312, connected together in a position prior to use. Stationary sleeve 310 includes a socket 330 opening towards its upper side. The socket 330 has an upwardly extending male portion 332 sized to engage within the boot portion 518 of the pump body 500. The socket 330 also includes inwardly directed cams 334 on its inner surface of a size to engage with the connecting flange 216 on the rigid neck 214 of container 200 in a snap connection. The engagement of these three portions results in a fluid tight seal, due to the flexible nature of the material of the pump body 500 being gripped between the relatively more rigid material of the connecting flange 216 and the stationary sleeve 310. Additionally, the sealing ridges 542 on the exterior surface of the boot portion 518 engage within the rigid neck 214 in the manner of a stopper. In the depicted embodiment, this connection is a permanent connection but it will be understood that other e.g. releasable connections may be provided between the pump assembly 300 and the container 200.
[0089] FIG. 15 also depicts the engagement between the spring 400 and the pump body 500. The inlet portion 402 of the spring 400 is sized to fit within the pump inlet 502 with the ring element 414 engaged in the groove 540 and the cross-shaped support element 416 engaging against the interior surface of the pump inlet 502 and the adjacent pump chamber 510. The first valve element 420 rests against the inlet valve seat 538 with a slight pre-load, sufficient to maintain a fluid-tight seal in the absence of any external pressure.
[0090] At the other end of the pump body 500, the outlet portion 404 engages within the pump outlet 504. The rib 430 has a greater diameter than the pump outlet 504 and serves to position the frusto-conical shaped body 432 and the second valve element 436 within the pump outlet 504. The outside of the pump outlet 504 also engages within the orifice 318 of the sliding sleeve 312 with the nozzle 512 slightly protruding. The annular protrusion 516 is sized to be slightly larger than the orifice 318 and maintains the pump outlet 504 at the correct position within the orifice 318. The second valve element 436 has an outer diameter that is slightly larger than the inner diameter of the pump outlet 504, whereby a slight pre-load is also applied, sufficient to maintain a fluid-tight seal in the absence of any external pressure.
[0091] FIG. 15 also shows how the sleeves 310, 312 engage together in operation. The sliding sleeve 312 is slightly larger in diameter than the stationary sleeve 310 and encircles it. The three axial guides 340 on the outer surface of the stationary sleeve 310 engage within respective slots 344 in the sliding sleeve. In the position shown in FIG. 15, the spring 400 is in its initial condition being subject to a slight pre-compression and the detent surfaces 342 engage against the actuating flange 314.
[0092] In the position shown in FIG. 15, the container 200 and pump assembly 300 are permanently connected together and are supplied and disposed of as a single disposable unit. The snap connection between socket 330 and the connecting flange 216 on the container 200 prevents the stationary sleeve 310 from being separated from the container 200. The detent surfaces 342 prevent the sliding sleeve 312 from being removed from its position around the stationary sleeve 310 and the pump body 500 and spring 400 are retained within the sleeves 310, 312.
[0093] FIG. 16 shows a similar view to FIG. 15 with the twist-off closure 514 removed. The pump assembly 300 is now ready for use and may be installed into a dispenser 100 as shown in FIG. 2. For the sake of the following description, the pump chamber 510 is full of fluid to be dispensed although it will be understood that on first opening of the twist-off closure 514, the pump chamber 510 may be full of air. In this condition, the second valve element 436 seals against the inner diameter of the pump outlet 504, preventing any fluid from exiting through the nozzle 512.
[0094] FIG. 17 shows the pump assembly 300 of FIG. 16 as actuation of a dispensing stroke is commenced, corresponding to the action described in relation to FIGS. 4A and 4B. As previously described in relation to those figures, engagement of actuator 124 by a user causes the engagement portion 134 to act against the actuating flange 314 exerting a force F. In this view, the container 200 has been omitted for the sake of clarity.
[0095] The force F causes the actuating flange 314 to move out of engagement with the detent surfaces 342 and the sliding sleeve 312 to move upwards with respect to the stationary sleeve 310. This force is also transmitted by the orifice 318 and the annular protrusion 516 to the pump outlet 504, causing this to move upwards together with the sliding sleeve 312. The other end of the pump body 400 is prevented from moving upwards by engagement of the pump inlet 502 with the socket 330 of the stationary sleeve 310.
[0096] The movement of the sliding sleeve 312 with respect to the stationary sleeve 310 causes an axial force to be applied to the pump body 400. This force is transmitted through the flexible wall 530 of the pump chamber 510, which initially starts to collapse at its weakest point, namely the thin walled section 534 adjacent to the pump outlet 504. As the pump chamber 510 collapses, its volume is reduced and fluid is ejected through the nozzle 512. Reverse flow of fluid through the pump inlet 502 is prevented by the first valve element 420, which is pressed against the inlet valve seat 538 by the additional fluid pressure within the pump chamber 510.
[0097] Additionally, the force is transmitted through the spring 400 by virtue of the engagement between the rib 430 and the pump outlet 504 and the ring element 414 being engaged in the groove 540 at the pump inlet 502. This causes the spring 400 to compress, whereby the internal angle at the corners 412 increases.
[0098] FIG. 17A is a detail in perspective of the pump outlet 504 of FIG. 17, showing in greater detail how second valve element 436 operates. In this view, spring 400 is shown unsectioned. As can be seen, thin walled section 534 has collapsed by partially inverting on itself adjacent to the annular protrusion 516. Below the annular protrusion 516, the pump outlet 504 has a relatively thicker wall and is supported within the orifice 318, maintaining its form and preventing distortion or collapse. As can also be seen in this view, rib 430 is interrupted at flow passage 434, which extends along the outer surface of the frusto-conical shaped body 432 to the second valve element 436. This flow passage 434 allows fluid to pass from the pump chamber 510 to engage with the second valve element 436 and exert a pressure onto it. The pressure causes the material of the second valve element 436 to flex away from engagement with the inner wall of the pump outlet 504, whereby fluid can pass the second valve element 436 and reach the nozzle 512. The precise manner in which the second valve element 436 collapses, will depend upon the degree and speed of application of the force F and other factors such as the nature of the fluid, the pre-load on the second valve element 436 and its material and dimensions. These may be optimised as required.
[0099] FIG. 18 shows the pump assembly 300 of FIG. 17 in fully compressed state on completion of an actuation stroke. The sliding sleeve 312 has moved upwards a distance D with respect to the initial position of FIG. 16 and the actuating flange 314 has entered into abutment with the locating flange 316. In this position, pump chamber 310 has collapsed to its maximum extent whereby the thin walled section 534 has fully inverted. The spring 400 has also collapsed to its maximum extent with all of the rhombus-shaped spring section 406 fully collapsed to a substantially flat configuration in which the leaves 408 lie close against each other and, in fact all of the leaves 408 are almost parallel to each other. It will be noted that although reference is given to fully compressed and collapsed conditions, this need not be the case and operation of the pump assembly 300 may take place over just a portion of the full range of movement of the respective components.
[0100] As a result of the spring sections 406 collapsing, the internal angle at the corners 412 approaches 180 degrees and the overall diameter of the spring 400 at this point increases. As illustrated in FIG. 18, the spring 400, which was initially slightly spaced from the flexible wall 530, engages into contact with the pump chamber. At least in the region of the thin walled section 534, the spring sections 406 exert a force on the flexible wall 530, causing it to stretch.
[0101] Once the pump has reached the position of FIG. 18, no further compression of the spring 400 takes place and fluid ceases to flow through the nozzle 512. The second valve element 436 closes again into sealing engagement with the pump outlet 504. In the illustrated embodiment, the stroke, defined by distance D is around 14 mm and the volume of fluid dispensed is about 1.1 ml. It will be understood that these distances and volumes can be adjusted according to requirements.
[0102] After the user releases the actuator 124 or the force F is otherwise discontinued, the compressed spring 400 will exert a net restoring force on the pump body 500. The spring depicted in the present embodiment exerts an axial force of 20 N in its fully compressed condition. This force, acts between the ring element 414 and the rib 430 and exerts a restoring force between the pump inlet 502 and the pump outlet 504 to cause the pump chamber 510 to revert to its original condition. The pump body 500 by its engagement with the sleeves 310, 312 also causes these elements to return towards their initial position as shown in FIG. 16.
[0103] As the spring 400 expands, the pump chamber 510 also increases in volume leading to an under pressure within the fluid contained within the pump chamber 510. The second valve element 436 is closed and any under pressure causes the second valve element 436 to engage more securely against the inner surface of the pump outlet 504.
[0104] FIG. 18A shows a perspective detail of part of the pump inlet 502 of FIG. 18. At the pump inlet 502, the first valve element 420 can flex away from the inlet valve seat 538 due to the lower pressure in the pump chamber 510 compared to that in the container 200. This causes fluid to flow into the pump chamber 510 through the rigid neck 214 of the container 200 and the opening 418 formed through the ring element 414 and over the cross-shaped support element 416.
[0105] As the skilled person appreciates, the spring may provide a major restoring force during the return stroke. However, as the spring 400 extends, its force may also be partially augmented by radial pressure acting on it from the flexible wall 530 of the pump chamber 510. The pump chamber 510 may also exert its own restoring force on the sliding sleeve 312 due to the inversion of the thin walled section 534, which attempts to revert to its original shape. Neither the restoring force of the spring 400 nor that of the pump chamber 510 is linear but the two may be adapted together to provide a desirable spring characteristic. In particular, the pump chamber 510 may exert a relatively strong restoring force at the position depicted in FIG. 17, at which the flexible wall 530 just starts to invert. The spring 400 may exert its maximum restoring force when it is fully compressed in the position according to FIG. 18.
[0106] The spring 400 of FIGS. 6 to 11 and pump body 500 of FIGS. 12 to 14 are dimensioned for pumping a volume of around 1-2 ml, e.g. around 1.1 ml. In a pump dimensioned for 1.1 ml, the flat leaves 408 have a length of around 7 mm, measured as the distance between hinge lines 410 about which they flex. They have a thickness at their mid-lines of around 1 mm. The overall length of the spring is around 58 mm. The pump body 400 has an overall length of around 70 mm, with the pump chamber 510 including around 40 mm and having an internal diameter of around 15 mm and a minimal wall thickness of around 0.5 mm. The skilled person will understand that these dimensions are exemplary.
[0107] The pump/spring may develop a maximum resistance of between 1 N and 50 N, more specifically between 20 N and 25 N on compression. Furthermore, the pump/spring bias on the reverse stroke for an empty pump may be between 1 N and 50 N, between 1 N and 30 N, between 5 N and 20 N, or between 10 N and 15 N. In general, the compression and bias forces may depend on and be proportional to the intended volume of the pump. The values given above may be appropriate for a 1 ml pump stroke.
[0108] Thus, the present disclosure has been described by reference to the embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art without departing from the spirit and scope of the invention as defined by the appended claims.
