US3820689A

US3820689A - Elastomeric pump

Info

Publication number: US3820689A
Application number: US00350622A
Authority: US
Inventors: A Cocita
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-04-21
Filing date: 1973-04-12
Publication date: 1974-06-28
Anticipated expiration: 1991-06-28

Abstract

An elastomeric pump comprises a rigid base member and an elastomeric upper member having a dome-shaped part and an elongated lip or flat member extending from a region of the periphery thereof and spaced a small distance above the base. An inlet pipe enters through the base member under the dome and is normally covered by a flat valve. An outlet opening enters under the flat member and is surrounded by an annulus extending into contact with the flat part of the upper member. Pumping is effected by repeated depression of the dome-like part of the upper member. In an alternative drip-free embodiment the elongated lip is secured to the base about its periphery except for its tip which is pre-stressed to abut the base. When the dome is depressed liquid in the pump forces the tip of the lip upward to provide an egress for the liquid along the upper surface of the base.

Description

United States Patent [191 Cocita June 28, 1974 ELASTOMERIC PUMP Primary Examiner-Stanley H. Tollberg [76] Inventor: Arliene N. Cocita, 11506 Newport Atmmey Mill Rd., Wheaton, Md. 20902 22 Filed: Apr. 12, 1973 [57] 1 pp o 350 622 An elastomeric pump comprises a rigid base member Related US. Application Data Humphrey 222/207 and an elastomeric upper member having a dome shaped part and an elongated lip or flat member extending from a region of the periphery thereof and spaced a small distance above the base. An inlet pipe enters through the base member under the dome and is normally covered by a flat valve. An outlet opening enters under the flat member and is surrounded by an annulus extending into contact with the flat part of the upper member. Pumping is effected by repeated depression of the dome-like part of the upper member. In an alternative drip-free embodiment the elongated lip is secured to the base about its periphery except for its tip which is pre-stressedto abut the base. When the dome is depressed liquid in the pump forces the tip of the lip upward to provide an egress for the liquid along the upper surface of the base.

12 Claims, 8 Drawing Figures mum m4 SHEET 1 (If 2 ELASTOMERIC PUMP CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of my U.S. Pat. application Ser. No. 246,176, filed Apr. 21. 1972, and entitled Elastomeric Pump now abandoned.

BACKGROUND OF THE INVENTION The present invention relates generally to fluid pumps and more particularly to fluid pumps of the type which are mounted on the top of bottles from which liquids are to be dispensed by a user.

There is disclosed in US. Pat. No. 3,486,663, a fluid pump or check valve which consists of an elastomeric member adapted to fit for instance on the end of a bottle for the purpose of pumping fluid from the bottle. A series of chambers are defined by the pump which chambers are isolated from one another by flexible barriers constituting one way valves. When the elastomeric member is depressed repeatedly by a user fluid is caused to flow from chamber to chamber and eventually out through an exit port. As stated in the aforesaid patent, many advantages arise from the use of this general approach to pumping liquids and more specifically the device is considerably simpler and therefore less expensive than the prior art mechanical pumps and less subject to corrosion, etc.

Although the device of the aforesaid US. Pat. is a great improvement over the prior art mechanical pumps, the configurations employed are far from optimum and require different devices for a simple check valve on the one hand and a pump and check valve combination on the other. The device of the prior patent in its simplest form, that is, the check valve, requires a two chamber device in which the input channel opens into one chamber and the output channel opens into the other chamber. The two chambers are separated by an elongated flexible member which'must be able to maintain a long line contact with the rigid plastic base to provide proper operation. When the apparatus is intended to be employed as a pump a three chamber device is required with the three chambers arranged in seratum and the inlet pipe entering into the chamber at one end of the series and the outlet pipe entering into the chamber at the other end of the series. Two flexible members define the partitions between the three chambers and are required again to maintain isolation between the chambers over an elongated line surface. As a result of the above arrangement, the prior art devices set forth in the patent mentioned above are relatively complex requiring considerably more of the plastic material than might otherwise be necessary and requiring relatively expensive molds for formation of the devices from the raw plastic material. Further the inlet and outlet pipes are always in communication with their respective chambers and contamination particu larly through the outlet pipe may be a problem.

It is an object of the present invention to provide an elastomeric pump and/or check valve in which a single device serves both purposes and in which elongated line contacts between multiple chamber dividers are eliminated and wherein there is only one chamber.

SUMMARY OF THE INVENTION The pump and check valve of the present invention comprise a single chamber device comprising a rigid base member and an upper member comprising a flexible hollow generally semispherical (dome-like) plastic member having an elongated flat flexible part extending therefrom over about a angle thereof. The dome-like part of the upper member is sealed about approximately 270 of its periphery directly to the rigid base. The elongated flat flexible member extends outwardly from the 90 unsecured region over but spaced from a similarly shaped part of the base and contacting a raised annulus disposed about the outlet pipe and extending upwardly from the floor of the otherwise flat rigid base member. The interior wall of the dome-like member has a tongue or flap formed integrally therewith and extending downwardly and over an inlet orifice from the inlet pipe. Small protuberances may extend downwardly from the flap to hold it off the base and permit unimpeded flow through this region.

When pressure is applied to the top of the elastic dome and it is collapsed, the interior of the dome, the chamber, is pressurized and the fliap is forced securely against the rigid base member to seal the opening into the chamber. Concurrently the pressure in the chamber forces the elongated flat flexible part of the upper member upwardly against ambient air pressure and i permits air or other fluid in the: chamber to escape through the outlet tube. When the dome is released, its natural resilience returns to its normal position, fluid is sucked through the inlet tube into the partial vacuum created thereby and the partial vacuum now existing under the flat elongated part of the upper member causes the plastic to be forced downwardly against the annulus formed around the outlet tube thereby sealing the outlet tube, preventing air from entering the chamber. When the plastic or flexible dome end is again depressed, the fluid that was sucked up into the chamber during the prior expansion cycle is expelled through the outlet tube.

It is thus seen that a single chamber member may be employed to provide the pumping action that multiple chamber extended line contact flap valve arrangements now provide and that the internal structure of the device is such as to reduce mold and material costs. Also the inlet and outlet tubes are always covered when the device is not in use and problems with contamination are reduced.

In a drip-free alternative embodiment the pump includes the dome and lip but eliminates the outlet pipe extending through the base member and the raised annulus surrounding that outlet pipe. Instead the lip edge is secured to the base except at its tip which is prestressed to normally abut the base in sealing relation. When the dome is collapsed, liquid in the pump forces the tip of the lip away from the base and flows out of the pump along the base surface. lUpon release of pressure from the dome, the tip of the lip returns to the base, sealing the pump against liquid egress.

It is therefore an object of the present invention to provide an elastomeric pump which comprises a single chamber member of relatively simple configuration and in which such a member may serve both as a pump and a one way check valve in its simplest form.

It is another object of the present invention to provide an elastomeric pump in which the interior of the device is isolated from the inlet and outlet pipe during periods of non-use.

It is another object of the present invention to provide a single chamber device having two inlet passages; one of which is sealed and the other of which is opened when pressure is produced in the chamber and in which the above condition is reversed when a partial vacuum is created in the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein: FIG. 1 is a three dimensional view in perspective of one embodiment of the present invention fitted to the top of a bottle;

FIG. 2 is a sectional view of the pump of the present invention secured to the top of a bottle or similar container taken along line 2--2 of FIG. 1;

FIG. 3 is a sectional view along line 33 of FIG. 2;

FIG. 4 is a longitudinal sectional view similar to FIG. 2 showing the apparatus of the present invention with the dome substantially fully depressed and rising or expanding back to its normal position;

FIG. 5 is a view similar to FIG. 4 showing the operation of the device when the dome of the flexible elastomer is being depressed;

FIG. 6 is a sectional view of an alternative embodiment of the present invention;

FIG. 7 is a top view in plan of the pump of FIG. 6; and

FIG. 8 is a sectional view similar to FIG. 6 showing the pump of FIG. 6 with the dome substantially fully depressed.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now specifically to the figures of the accompanying drawings, the pump of the present invention comprises a base member 1 and an elastomeric upper member 2, the terms upper and lower referring to the position of these members during normal use of the device. The base member 1 is fabricated from a rigid material preferably in this particular instance a rigid plastic and is adapted to be attached to a source of the fluid to be pumped. In the particular environment which has been selected for purposes of illustrating the present invention, the fluid to be pumped is a liquid and it is contained in a bottle 3 having an externally threaded neck 4 to which the base member is secured. Specifically in this particular situation the base member has a hollow cylindrical wall 6 having internal threads 7 adapted to mate with external threads 8 formed on the neck 4 of the bottle. The hollow cylindrical wall 4 terminates in an end wall 9 having a centrally located passage 11 communicating internally with a tube 12 adapted to extend to adjacent the bottom of the bottle 3 for purposes of having the liquid pumped therethrough.

The base member 1 further comprises an elongated tapered part 13 terminating in a downward drooping member 14 which is not at all essential to the invention but is employed for purposes of convenience only. The base member 1 has an upper wall 16 defined by recessing the upper surface of the member such as to define an upstanding wall or lip 17 extending about the periphery of the upper surface 16 as defined by the

parts

9 and 13 of the base member 1. The drooping portion 14 of the base member is not so recessed. A passage 18 extends through the drooping member 14 of the base 1 and terminates in a vertical passage 19 within the region 13 of the base member 1 and somewhat remote from the wall 9 of the base member. The passage 19 is surrounded in this area by a narrow raised annulus 21 which extends upwardly from the wall 16 at a distance from the wall 17 at all locations.

The upper member 2 comprises a hollow semispherical elastomeric dome-like member 22 generally symmetrical with the axis of the hollow cylindrical mem bers of the base member 1. The hollow spherical or dome-shaped member 22 of the upper member 1 has extending therefrom a lip-like or flat tapered part 23 which is positioned to overlie the region 13 of the base member 1. The flat part 23 of the upper member 2 has a downwardly depending peripheral wall 24 of such a height that a lower surface, as viewed in FIG. 2, of the part 23 lies flat against the top of the annulus 21 when the device is assembled.

. Assembly of the upper part 2 to the lower part 1 is by bonding by appropriate cements or other materials interiorly of the wall 17 at all locations; the specific regions of bonding being illustrated by the thickened black wall regions 26 in the drawings. At the junction of the spherical part 22 and the flat part 23 there may be provided on the lower surface of the elastomeric member a series of small protrusions 27 for causing the upper member to maintain specific spacing above the surface 16 of the base member 1. These projections are spaced from one another so as not to interfere with the free flow of fluid through the device. In many instances the projections 27 may be eliminated.

To complete the structure of the upper member 2 there is provided a flap 28 formed integrally with and extending downwardly from the inner surface of the dome-shaped member 22. The flap 28 overlies the passage 11.

In the operation of the device, initially, the flap 28 is intended to seal the opening 11 whereas the flat part 23 of the upper member 22 is in contact with the upper surface of the hollow annulus 21 and seals the passage 18. Thus the interior of the upper member 22 is isolated from both inlet and outlet openings when not in use. If now the dome-shaped member 22 is depressed as illustrated in FIG. 4, the pressure thus created internally of the dome 22 forces the flap 28 securely against the surface 16 in the region of the orifice l1 and prevents air or other fluid in the chamber from entering the passage 11, tube 12 and thus the bottle 3. Concurrently the increased pressure formed between the member 2 and the base member 1 causes the flat part 23 of the upper member 2 to be forced upwardly away from the annulus 21 thereby opening the passage 19 to the pressurized fluid lying between the

members

1 and 2. The pressurized fluid is thus expelled through the passage 18-19.

Upon releasing the dome 22 as illustrated in FIG. 5 its natural resiliency causes it to return to the position illustrated in FIGS. 1 and 2 thus creating a low pressure in the region between the

members

1 and 2. The low pressure thus created causes fluid to rise in the tube 12 and enter the interior of the dome region 22. The passage 18 at this point is sealed since the reduced pressure between the

regions

13 and 23 of the

members

1 and 2, respectively, causes the member 23 to be forced downwardly against the upper surface of the annulus 21. Thus it can be seen that the pressure created when the dome-shaped member is depressed seals the inlet pipe 11 and the reduced pressure created when the dome-shaped member 22 is released and returns to its normal position causes the outlet passage 18-19 to be sealed.

When the dome-shaped member 22 is again depressed the fluid previously pumped into the interior of the member during the previous cycle of operation is expelled through the outlet passage 18-19 again by the creation of the pressure interiorly of the domeshaped member 22 and thus the pumping cycle is completed.

The annulus 21 may be eliminated if the flat part 23 of the upper member normally contacts wall 16. In such an arrangement pumping pressures are greater than in the illustrated embodiment.

Referring to FIGS. 6-8 of the accompanying drawings, there is illustrated an alternative, drip-free embodiment of the present invention. The rigid base member 31 includes an upper surface 32 on which the elastomeric member 33 is secured. The elastomeric member includes a dome 34 and a radially extending lip 36, similar to dome 22 and lip 23 in FIG. 2. Likewise a flap 37, similar to flap 28, normally overlies inlet passage 38 which in turn communicates with the interior of a bottle or the like from which liquid is to be pumped. At the junction of lip 36 and dome 34 a series of small spaced protrustions 35 project from the elastomeric member and are similar to protrusions 27 in FIG. 2. These protrusions continuously abut surface 32 to maintain the junction between the lip and dome spaced by a specific distance from surface 32. In this manner, liquid is free to flow along surface 32 and around protrusions 35 from the dome-covered portion to the lip-covered portion. I

Surface 32 is contoured such that its apex or highest point 39 resides under lip 36. From apex 39 toward the dome region the surface 32 exhibits a gradual downward taper or slope; in the other direction (i.e., toward the outlet end of lip 36) surface 32 exhibits a somewhat more severe downward slope.

Except for its forward. tip, the periphery of lip 36 is firmly secured, by adhesive or the like, to surface 32, as generally indicated at 40. The forward tip 41 of lip is not secured but is pre-stressed to normally abut surface 32 in liquid-sealing relation. When the pressure inside the pump exceeds ambient pressure, however, tip 41 is forced upward and away from surface 32 to permit liquid outflow from the pump.

With the exception of the outflow from the pump, operation is substantially the same as described above for the pump of FIGS. 1-5. More particularly, liquid is introduced into the initially empty single pump chamber by depressing dome 34 and then releasing. Upon release, the dome returns to its unflexed position due to its natural resiliency, thus creating a low pressure region in the pump chamber. The low pressure causes fluid to rise in passage 38and enter the chamber. Upon depressing the dome again, as illustrated in FIG. 8, the liquid in the chamber is forced along surface 32, be-' neath lip 36, where it forces tip 41 away from the surface and flows out of the chamber. When the liquid in the chamber is depleted, or when the dome is released again, tip 41, by its own resiliency, returns to sealing relation with surface 32 and prevents further liquid outflow from the pump chamber.

It is preferable that more than simply the periphery of tip 41 be contoured to normally abut surface 32. Specifically, and as best illustrated in FIG. 6, a substantial length of the interior portion of lip 36 abuts surface 32 when the pressure in the chamber is less than and equal to ambient pressure. This provides a seal of relatively long length which improves the drip-free characteristic of the pump. Preferably this seal should begin proximate apex 39 and extends all the way to tip 41. This forces substantially all of the residual liquid in the pump to flow down the gradual slope and back into the dome-covered portion of the pump chamber, further assuring dripless steady state condition of the pump.

The pump illustrated in FIGS. 6-8 has its base 31 contoured to provide particular utility for dispensing hand cream or other liquid which is normally dispensed directly onto the palm of the user. Specifically, the under-surface of base 31 is contoured to include an arcuate portion 42 adapted to receive the side of the forefinger of. theuser while the thumb is used to depress dome 24. In this position which is illustrated in FIG. 8, the palm of the users hand is positioned to catch liquid outflow from beneath tip 41.

An important feature of the embodiment of FIGS. 6-8 resides in the fact that lip 36 is fixedly secured to surface 32 along the entirety of both of its longitudinal sides but is merely resiliently biased against surface 32 at outlet tip 41 and along part of its interior region upstream of outlet tip 41.

Another important feature of the embodiment of FIGS. 68 resides in the fact that liquid outflow proceeds along the upper surface 32 beneath tip 41 and does not require that a specific outlet passage be defined in the base member.

It1will be noted that in the structure of the present invention only a single chambered device is provided and that the necessary valving actions are effected by alternately blocking flow through the inlet and outlet passages, respectively, and not by the expedient of isolating these passages from one. another through various intermediate chambers and valve walls.

It should be further noted that the member 22 does not have to be dome-shaped as such and that the member 23 does not have to be absolutely flat, lie precisely parallel to the base member nor must it be elongated to the extent illustrated in the accompanying figures of the present invention. The area of the surface of the member 23 is somewhat exagerated in these figures so that the operation of this portion of the invention will be readily apparent to one skilled in the art, that is,

when a reduced pressure is created interiorly of the region between the

numbers

1 and 2, atmospheric pressure operating onthe outer surface of the member 23 causes the member 23 to seal the: passage 19.

The upper member is described as bonded to the base member and the base member is described as rigid. Securing of the upper to the lower member may be by mechanical means as well as bonding. Also the term rigid is used in the sense of a base member that does not materially deform under the pressures normally in this type of pump. Further although the flap 28 is illustrated as integral with the upper member, this is not essential to the invention and the flap may be secured to the base member.

The materials which may be employed in the fabrication of the members of the present invention are well known in the art and for details reference is made to the aforesaid patent.

While I have described and illustrated one specific embodiment of my invention, it will be clear that variations of the details of construction which are specifically illustrated and described may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

I claim:

1. An elastomeric pump comprising a base member having an upper surface and an integral resilient upper member overlying and secured generally about its periphery to said upper surface to define a fluid-tight chamber between the base and upper members, said upper member having an enlarged section and a lip-like section extending outwardly from an edge of said enlarged section with the periphery of said lip-like section secured to said upper surface, the interior portion of said lip-like section being spaced from said upper surface, an inlet port entering said chamber, a movable flap overlying said inlet port in said chamber, an exit port extending through said base member under the interior portion of said lip-like section and means causing said lip-like section when in its unflexed position to seal said exit port.

2. The combination according to claim 1 wherein said movable flap is integral with the interior surface of said upper section.

3. The combination according to claim 1 wherein said means is an annular projection disposed about said outlet port and extending from said upper surface of said base member into said chamber and into contact with a region of said lip-like section in its unflexed position.

4. The combination according to claim 1 wherein said enlarged section is generally a semisphere.

5. The combination according to claim 1 wherein said lip-like sectionhas projections extending from its interior portion toward said upper surface of said base member to maintain said interior portion spaced from said upper surface.

6. A single-chambered elastomeric pump comprising:

a base member having an upper surface;

an integral elastomeric member secured to said upper surface of said base member in fluid-tight relation to define a single dome-shaped pump chamber between said elastomeric member and said upper surface of said base member;

said upper surface of said base member having an inlet flow passage defined therethrough and terminating in an inlet opening to said pump chamber;

flap valve member disposed within said pump chamber and positioned to block said inlet opening when the pressure in said pump chamber is substantially equal to and greater than the pressure in said inlet passage, said flap valve member being adapted to unblock said inlet opening when the pressure in said pump chamber is substantially below the pressure in said inlet passage; and

wherein said elastomeric member includes a flexible lip-like projection extending radially outward from said dome-shaped chamber and overlying said upper surface of said base member and defining an outflow region between said projection and said upper surface, said dome-shaped chamber and said projection intersecting at a junction which is raised from said upper surface such that said outflow region is in constant flow communication with said chamber, said projection being adhesively secured at least along its sides to said upper surface and arranged to block flow communication between said outflow region and ambient when the pressure in said chamber is substantially equal to and less than ambient pressure, said projection being adapted to be flexed away from said upper surface of said base member to expand said outflow region and unblock flow communication between said outflow region and ambient when the pressure in said pump chamber substantially exceeds ambient pressure.

7. The pump according to claim 6 wherein said liplike projection includes a tip at its end remote from said junction, said tip being resiliently biased to abut said upper surface when the pressure in said chamber is less than and substantially equal to ambient pressure, said tip being otherwise unconstrained to permit flexure of i said tip away from said upper surface when the pressure in said chamber substantially exceeds ambient pressure to thereby permit outflow of pump liquid between said tip and said upper surface.

8. The pump according to claim 7 wherein said upper surface is contoured to provide an apex located beneath said projection, said upper surface being sloped downward from said apex toward both said tip and said chamber.

9. The pump according to claim 8 wherein the interior portion of said projection is resiliently biased to abut said upper surface along a substantial portion but not all of its length when the pressure in said chamber is less than and substantially equal to ambient pressure.

10. A single-chambered elastomeric pump comprisa rigid base member having an inlet passage defined therethrough and including an upper surface at which said inlet passage terminates in an inlet opening;

an elastomeric member secured to said upper surface above said inlet opening to define a single chamber between said elastomeric member and said upper surface, said elastomeric member comprising:

a dome portion;

a resilient flap valve member disposed within said dome portion and positioned to flexibly block said inlet opening when the pressure in said chamber is substantially equal to and greater than the pressure in said inlet passage, said flap valve member being sufficiently resilient to unblock said inlet opening when the pressure in said pump chamber is below the pressure in said inlet passage;

an elongated projection extending substantially radially outward from the periphery of said dome portion along said upper surface;

said dome portion and said projection intersecting at a junction which is maintained raised above said upper surface to permit liquid flow along said upper surface from said dome portion to said projection;

said projection being fixedly secured to said upper surface along its radially extending edges, and having a tip at its radially outermost end which is resilbeneath said projection, said upper surface being sloped downward from said apex toward both said tip and said chamber.

12. The pump according to claim 10 wherein the interior portion of said projection is resiliently biased to abut said upper surface along a substantial portion but not all of its length when the pressure in said chamber is less than and substantially equal to ambient pressure.

Claims

5. The combination according to claim 1 wherein said lip-like section has projections extending from its interior portion toward said upper surface of said base member to maintain said interior portion spaced from said upper surface.

6. A single-chambered elastomeric pump comprising: a base member having an upper surface; an integral elastomeric member secured to said upper surface of said base member in fluid-tight relation to define a single dome-shaped pump chamber between said elastomeric member and said upper surface of said base member; said upper surface of said base member having an inlet flow passage defined therethrough and terminating in an inlet opening To said pump chamber; a flap valve member disposed within said pump chamber and positioned to block said inlet opening when the pressure in said pump chamber is substantially equal to and greater than the pressure in said inlet passage, said flap valve member being adapted to unblock said inlet opening when the pressure in said pump chamber is substantially below the pressure in said inlet passage; and wherein said elastomeric member includes a flexible lip-like projection extending radially outward from said dome-shaped chamber and overlying said upper surface of said base member and defining an outflow region between said projection and said upper surface, said dome-shaped chamber and said projection intersecting at a junction which is raised from said upper surface such that said outflow region is in constant flow communication with said chamber, said projection being adhesively secured at least along its sides to said upper surface and arranged to block flow communication between said outflow region and ambient when the pressure in said chamber is substantially equal to and less than ambient pressure, said projection being adapted to be flexed away from said upper surface of said base member to expand said outflow region and unblock flow communication between said outflow region and ambient when the pressure in said pump chamber substantially exceeds ambient pressure.

7. The pump according to claim 6 wherein said lip-like projection includes a tip at its end remote from said junction, said tip being resiliently biased to abut said upper surface when the pressure in said chamber is less than and substantially equal to ambient pressure, said tip being otherwise unconstrained to permit flexure of said tip away from said upper surface when the pressure in said chamber substantially exceeds ambient pressure to thereby permit outflow of pump liquid between said tip and said upper surface.

10. A single-chambered elastomeric pump comprising: a rigid base member having an inlet passage defined therethrough and including an upper surface at which said inlet passage terminates in an inlet opening; an elastomeric member secured to said upper surface above said inlet opening to define a single chamber between said elastomeric member and said upper surface, said elastomeric member comprising: a dome portion; a resilient flap valve member disposed within said dome portion and positioned to flexibly block said inlet opening when the pressure in said chamber is substantially equal to and greater than the pressure in said inlet passage, said flap valve member being sufficiently resilient to unblock said inlet opening when the pressure in said pump chamber is below the pressure in said inlet passage; an elongated projection extending substantially radially outward from the periphery of said dome portion along said upper surface; said dome portion and said projection intersecting at a junction which is maintained raised above said upper surface to permit liquid flow along said upper surface from said dome portion to said projection; said projection being fixedly secured to said upper surface along its radially extending edges, and having a tip at its radially outermost end which is resiliently biased to abut said upper surface in liquid sealing relation when the pressure in said chamber is substantially equal to and less than ambient pressure, said tip being sufficiently resilient to be flexed away from said upper surface when the pressure in said Chamber exceeds ambient pressure to thereby permit liquid to egress from said chamber along said upper surface and beneath said tip.

11. The pump according to claim 10 wherein said upper surface is contoured to provide an apex located beneath said projection, said upper surface being sloped downward from said apex toward both said tip and said chamber.