GB2125907A - Fluid pumps - Google Patents

Abstract

A fluid pump for manual or foot operation has a base (1) and a treadle (2) pivoted to it. A piston-and-cylinder unit (4) is connected between the treadle and base and comprises a cylinder (5) with a composite piston (24, 25) on a piston rod (23). The cylinder has an outlet (14) with a one- way valve (13) and has an inlet, extending through the hollow interior of the piston rod (23), with a one-way valve (27) housed in the piston. The cylinder also has a secondary inlet (16), adjacent to the outlet (14), with a one-way valve (15). When the treadle (2) is depressed, fluid from the front part (34) of the cylinder is discharged through the outlet (14) with while fluid is sucked into the rear part (29) through the piston rod inlet. When the treadle is released a spring (31) raises the treadle while fluid flows around and through the piston from the rear (29) to the front (34). Fluid may also be sucked in through the secondary inlet (16). <IMAGE>

Description

SPECIFICATION Fluid pumps This invention relates to fluid pumps. The invention is applicable to pumps for use in pumping liquids and to pumps for use in pumping gases and to pumps for use in pumping both liquids and gases.

According to the present invention there is provided a fluid pump comprising a piston-andcylinder unit incorporating a cylinder and a reciprocable piston inside the cylinder, operating means for the unit comprising a base and a pivotally mounted operating lever capable of being depressed from a raised position to a lower postion by the exertion of the user and thus to cause relative movement of the piston along the cylinder in one direction for a forward stroke, spring means being provided to return the operative lever to its raised position and thus to cause relative movement of the piston along the cylinder in the other direction for a reverse stroke, the cylinder having a fluid inlet communicating with the rear of the cylinder, that is a part of the interior of the cylinder, to one side of the piston, and a fluid outlet communicating with the front of the cylinder, that is a part of the interior of the cylinder, to the other side of the piston, a one-way inlet valve for fluid entering the cylinder through the inlet and a one-way outlet valve for fluid leaving the cylinder through the outlet, the piston being such as to prevent the transfer of fluid inside the cylinder from one part to the other during a forward stroke but permitting such transfer of fluid during a return stroke, the arrangement being such that during a forward stroke fluid is drawn through the inlet into the rear of the cylinder and fluid is discharged from the front of the cylinder through the outlet, and that during a return stroke fluid inside the cylinder is transferred from the rear of the cylinder to the front of the cylinder.

The operating lever of a fluid pump in accordance with the invention may be depressed by the user's hand or by the user's foot or otherwise. The fluid pump may resemble in overall appearance a foot-pump of the conventional type such as is widely marketed for the inflation of vehicle tyres. The fluid pump in accordance with the invention, however, differs significantly from such a conventional foot-pump in that it serves in use to draw fluid into the cylinder through a oneway valve and then to discharge it through another one-way valve.

As the forward stroke is effected by depression of the operating member and the reverse stroke is effected by the spring means, the spring means need not be particularly strong as all the energy required to draw fluid into the cylinder and to discharge it from the cylinder is derived from the exertions of the user, while the spring means serves solely to raise the operating member and to cause the transfer of the fluid in the cylinder from one side of the piston to the other side thereof.

In a preferred form of fluid pump the inlet or the outlet comprises a duct extending through the interior of the piston rod. This arrangement can have several advantages. Suppose that it is the inlet which comprises the duct through the piston rod (and this is the preferred arrangement) then there is no need to provide a separate inlet elsewhere in the cylinder. Similarly if it is the outlet that comprises the duct through the piston rod there is no need to provide a separate outlet elsewhere in the cylinder. The one-way valve associated with the duct in the piston rod is preferably disposed inside the cylinder at or adjacent to the place where the piston rod meets the piston.The interior of the piston rod preferably communicates with that part of the interior of the cylinder through which the piston rod extends, so that where, as is preferred, the interior of the piston rod constitutes the inlet, then the piston rod extends through the rear of the cylinder.

That end of the piston rod remote from the piston is preferably pivotally connected to the base or to the operating member; in a particularly preferred arrangement it is pivotally connected to the base. In use this end of the piston rod moves relatively little during reciprocation of the piston in the cylinder and may do no more than rock about the axis of the pivotal connection. Flexible piping may be connected to this end of the piston rod.

If desired, a secondary inlet may be provided, communicating with the front of the cylinder, this secondary inlet being provided with a non-return valve which prevents the egress of fluid through the secondary inlet. When the pump is being used to pump air, the secondary inlet can operate in the following manner. The principal inlet (referred to above merely as the inlet) is connected by suitable ducting and/or piping to a vessel to be evacuated.

On each forward stroke of the pump air is withdrawn from the vessel and drawn into the rear of the cylinder. On the succeeding reverse stroke air from the rear of the cylinder is transferred to the front of the cylinder. On the next forward stroke air in the front of the cylinder is discharged.

As the pressure in the vessel becomes less and less, the quantity of air drawn into the cylinder on each forward stroke becomes less and less, with the result that less and less air from the vessel is discharged from the outlet on each forward stroke.

If it is desired to provide a source of compressed air at the same time as the vessel is being evacuated, this can be effected with the aid of the secondary inlet, for on each reverse stroke of the pump air is drawn into the front of the cylinder through the secondary inlet to maintain the air pressure in the front of the cylinder at substantially atmospheric pressure. The air which entered through the two inlets is then discharged through the outlet on the following forward stroke.

The use of the secondary inlet may not be required, and may be unsuitable when a liquid or a gas other than air is being pumped. Closure means is therefore preferably provided to close the secondary inlet when it is not required. The closure means may comprise a removable and replaceable cap, or it may be such as to prevent the opening of the non-return valve, associated with the secondary inlet.

A pump in accordance with the invention may be used for any of a wide range of purposes. The pump may be used to pump water or other liquids from one place to another. For instance it may be used to pump water from the bilges of a boat or to empty water from a flooded cellar. It may be used to empty a fish tank, in which case the inlet end of the flexible piping connected to the inlet of the pump may be provided with a scraper for detaching algae and the iike from the walls of a tank. The pump may also be used in the supply of drinking water. Brackish or unclean water may be caused by the pump to flow through a series of filters of progressively increasing fineness and possibly through a mass of activated carbon or the like.There may, for example, be three filters, the finest of which will not permit the passage of particles of a size greater than 1 micron across.

The pump may also be used to pump air. There are for example a number of medical applications for the pump. For instance the pump may be used in aspiration. For this purpose the inlet would be connected by a flexible pipe to the upper part of a closed vessel into which would also extend an extraction tube. In use the pump would extract air from the vessel, and the reduced pressure in the vessel would draw liquid matter etc.

through the extraction tube. Thus the device could be used as a stomach pump. In a somewhat similar manner the device could be used as breast pump, the pump being used to extract air from the upper part of a closed vessel which is also connected to an extraction device in the shape of a flared tube for application to the breast. Milk can then be extracted with the aid of the device. In order to avoid the application of continuous or excessive suction, a bleed hole may be provided to allow air slowly to enter the vessel or the pipe leading from the pump. In addition or alternatively, the length of the stroke of the pump may be reduced.

The pump may also be used to pressurize air for any of various purposes. For example it may be used to pressurize air for medical purposes. For instance it may be used to operate a nebulizer, as described in patent application No. 8312737 (dated 9th May 1983). It may also be used as a ventilator or in the supply of liquid as for example in the supply of water for washing out a patient's stomach. For this latter application, the outlet of the pump would be connected to an upper part of a vessel containing the water or other liquid to be employed, there being a liquid outlet tube extending into a lower part of the vessel. In use compressed air driven by the pump into the vessel displaces the liquid through the liquid outlet tube.

The pump conveniently forms part of a kit for use in carrying out two or more of these functions.

The kit includes one or more vessels of the kind outlined above, and appropriate ducting connected to the pump by way of user-operable valve means forming part of the kit. By suitable manipulation of the valves, any one of the possible functions can be carried out without the necessity for the user to connect or disconnect piping. The kit, comprising the pump, ducting, vessel or vessels and valve gear can conveniently be mounted in a case resembling an attach8, case that it can readily be carried from place to place as required. The arrangement is preferably such that the pump can be normally operated without the need to remove it from the case.

Thus, from another aspect the present invention consists in a fluid pump of the kind outlined above in combination with at least one vessel for containing fluids and having an inlet and an outlet, ducting enabling the inlet or the outlet of the pump to be connected to the outlet or inlet respectively of the vessel or at least one of the vessels, and user-operable valve means enabling the connections of the ducting between the pump and the vessel or vessels to be varied at will.

An embodiment of the present invention will now be described in more detail, by way of example, with reference to the accompanying drawing which is a side view of a fluid pump in accordance with the present invention, the pump incorporating a piston-and-cylinder unit which is shown in section to reveal its interior.

The pump comprises a base 1 with a treadle 2, which constitutes an operating member pivoted to it at 3. It also comprises a piston-and-cylinder unit 4. These components are generally similar to those of the pumps described and illustrated in patents Nos. 1 603 302 and 1 603 303 of E. J.

Price (Developments) Limited. The base 1 and treadle 2 will therefore not be further described herein.

The piston-and-cylinder unit 4 comprises a cylinder 5 made as a moulding of a plastics material. One end of the cylinder is closed by an integral end plate 6. A pair of tubular bosses 7 and 8 are moulded with the end plate. Each is internally threaded and has one end part of a tubular connector 9 screwed into it. A fitting 10 incorporating a strap 11 is trapped between the connectors 9 and the bosses 7 and 8 and serves to prevent the unit being detached from a pivot rod 12 on the treadle. Boss 7 contains a resilient valve member 13 which is one end position seals an outlet 14 from the cylinder but in the other end position engages spaced projections on the associated connector 9. The valve contained in the boss 7 thus constitutes a one-way valve permitting only the egress of fluid from the cylinder. The outlet 1 4 constitutes the outlet of the cylinder referred to above. The boss 8 contains a resilient valve member 1 5. In one end position this seals against the inner end of the associated connector 9 but in the other end position rests against spaced projections around an inlet 16 into the cylinder. The valve contained in the boss 8 is therefore a one-way valve permitting only the entry of fluid into the cylinder. The inlet 16 constitutes the secondary inlet referred to above.

Its associated connector 9 is illustrated as being connected to flexible ducting 17 but this ducting may be removed to enable the connected to be provided with a removable sealing cap (not shown) to close the inlet for the purpose described above.

The opposite end of the cylinder 5 has a closure cap of composite form, comprising an inner plate 18 and an outer plate 19. An integral collar 20 on the inner plate 1 8 is a press fit in a central recess in the outer plate 1 9. During assembly two O-rings are located between the plates: an outer O-ring 21 and an inner O-ring 22. During assembly of the unit the composite closure cap is inserted into the end of the cylinder 5, the outer plate 1 9 having a circumferential rib which snaps into a complementary groove in the cylinder. The outer O-ring 21 serves to form a seal between the cylinder and the closure cap. The inner O-ring 22, unlike the outer O-ring 21, is located between the plates and is free for limited radial movement. It is made of a resilient material, such as rubber, coated with polytetrafluorethylene (pffe).It will be observed that the inner face of the closure cap is of shallow, concave, frusto-conical shape.

A tubular piston rod 23 extends axially through central holes in the inner and outer plates 1 8 and 1 9. The inner O-ring 22 seals against the outer surface of the piston rod. The inner end of the piston rod terminates in a piston of composite construction comprising a forward member 24 and a rear member 25 which is integral with the piston rod 23. The forward member 24 has an integral collar 26 which is a press fit in a central recess in the rear member 25. Integral spacing ribs on the rear face of the forward member maintain a slight gap between the members for the passage of fluid as described below.The collar 26 defines the periphery of a chamber containing a resilient valve member 27 which in one end position seals the end of the piston rod 23 and in the other end position permits the flow of fluid from the interior of the piston rod into the chamber and thence through holes 28 in the rear member 25 into that part 29 of the interior of the cylinder between the piston and the closure cap and through which the piston rod extends. This part 29 is the rear of the cylinder referred to above. It will be observed that the rear face of the rear member 25 is of convex frusto-conical shape complementary to the inner face of the closure cap. When the piston is in one of its end positions, the volume of the rear part 29 of the cylinder is consequently very small.

An O-ring seal 30 is disposed in a peripheral groove of the forward member 24 of the piston and engages the bore of the cylinder. Like the inner O-ring 22 it is made of a resilient material, such as rubber, coated with ptfe. The groove is of sufficient radial depth to prevent the O-ring seal 30 being squashed between the base of the groove and the bore of the cylinder. The width of the groove is sufficient to permit some endwise movement of the seal relative to the piston.

A stainless steel compression spring 31, constituting the spring means referred to above, acts between the end plate 6 and the forward face of the piston, being located around an annular rib 32 on the forward face of the piston.

Holes 33 in the forward member 24 of the piston permit fluid to pass from the gap between the members 24 and 25 of the piston and that part 34 of the interior of the cylinder between the piston and the end plate 6. This part 34 is the front part of the cylinder referred to above.

At that end of the piston rod 23 remote from the piston there is a tubular fitting 35 which has a spigot entering an end part of the bore of the piston rod. An O-ring seal 36 is trapped between the piston rod and the fitting 35. Trunnions (not shown) integral with the fitting 35 are disposed immediately beyond the adjacent end of the piston rod 23. The axes of the trunnions are normal to the plane of the section illustrated, so neither is visible in the drawing. The trunnions pivotally engage bearings in the base 1 as described and illustrated in the aforementioned patents Nos.

1 603 302 and 1 603 303. Beyond the trunnions the fitting 35 has an inlet spigot for insertion into one end of a length of flexible piping 37 for the inlet of fluid to the pump.

Operation of the pump will now be described as it occurs when pumping air. When the operating member of the pump is depressed, the piston moves forward towards the end plate 6. The Oring seal 30 seals against the rear member 25 of the piston and prevents air in the front part 34 of the cylinder escaping into the rear part 29 through the holes 33 and the gap between the members 24 and 25. Air in the front part 34 of the cylinder is therefore discharged from the cylinder through the outlet 14. At the same time, the volume of the rear part 29 of the cylinder increases. This tends to reduce the pressure in the rear part and to cause air to be drawn through the piston rod 23 into the chamber defined by the collar 26 and thence through the holes 28 into the rear part 29. The movement of the piston constitutes the forward stroke referred to above.

When the operating member is released, the spring 31 causes the piston to return to the rear of the cylinder. As this occurs the operating member rises. The O-ring seal 30 moves away from the rear member 25 of the piston and air in the rear part 29 of the cylinder is forced through the gap between the members 24 and 25 and through the holes 33 into the front part 34 of the cylinder. This therefore constitutes the reverse stroke referred to above. Closure of the one-way valve having the valve member 27 prevents any air escaping from the rear part 29 of the cylinder through the piston rod 23.

If, at the start of the reverse stroke, the pressure in the rear part 29 of the cylinder is below atmospheric pressure then there is a tendency for the pressure in the front part 34 of the cylinder to be below atmospheric at the end of the reverse stroke. If the secondary inlet valve is operative, however, air can enter the front part 34 through that valve.

On the next succeeding stroke which is a forward stroke, air is drawn into the rear part 29 of the cylinder through the piston rod 23, as before, while the air from the front part 34 of the cylinder is discharged through the outlet 1 4.

For many purposes the secondary inlet 1 6 is rendered inoperative by being closed with a cap.

In a modification (not illustrated) a felt or similar washer is provided to the rear of the inner O-ring 22, and spaced from that O-ring, the washer serving to wipe the outer surface of the piston rod 23 during the forward stroke and thus to prevent the inner O-ring 22 being damaged by grit or other particles that may adhere to the outside of the piston rod.

The pump illustrated is provided with a filter 38 attached to the outlet connector 9. This may be similar to those described in the aforementioned patent application No 8312737.

Claims (9)

1. A fluid pump comprising a piston-andcylinder unit incorporating a cylinder and a reciprocable piston inside the cylinder, operating means for the unit comprising a base and a pivotally mounted operating lever capable of being depressed from a raised position to a lower position by the exertion of the user and thus to cause relative movement of the piston along the cylinder in one direction for a forward stroke, spring means being provided to return the operative lever to its raised position and thus to cause relative movement of the piston along the cylinder in the other direction for a reverse stroke, the cylinder having a fluid inlet communicating with the rear of the cylinder, that is a part of the interior of the cylinder, to one side of the piston, and a fluid outlet communicating with the front of the cylinder, that is a part of the interior of the cylinder, to the other side of the piston, a one-way inlet valve for fluid entering the cylinder through the inlet and a one-way outlet valve for fluid leaving the cylinder through the outlet, the piston being such as to prevent the transfer of fluid inside the cylinder from one part to the other during a forward stroke but permitting such transfer of fluid during a return stroke, the arrangement being such that during a forward stroke fluid is drawn through the inlet into the rear of the cylinder and fluid is discharged from the front of the cylinder through the outlet, and that during a return stroke fluid inside the cylinder is transferred from the rear of the cylinder to the front of the cylinder.

2. Afluid pump according to claim 1 in which the inlet or the outlet comprises a duct extending through the interior of the piston rod.

3. A fluid pump according to claim 2 in which the one-way valve associated with the duct in the piston rod is disposed inside the cylinder at or adjacent to the place where the piston rod meets the piston.

4. A fluid pump according to either of claims 2 and 3 in which the interior of the piston rod communicates with that part of the interior of the cylinder through which the piston rod extends.

5. A fluid pump according to any one of claims 2 to 4 in which it is the inlet that comprises said duct.

6. A fluid pump according to any one of the preceding claims in which that end of the piston rod remote from the piston is pivotally connected to the base.

7. A fluid pump according to any one of the preceding claims in which there is a secondary inlet, communicating with the front of the cylinder and provided with a non-return valve which prevents the egress of fluid through the secondary inlet.

8. A fluid pump substantially as herein described with reference to the accompanying drawings.

9. A fluid pump according to any one of the preceding claims in combination with at least one vessel for containing fluids and having an inlet and an outlet, ducting enabling the inlet or the outlet of the pump to be connected to the outlet or inlet respectively of the vessel or at least one of the vessels, and user-operable valve means enabling the connections of the ducting between the pump and the vessel or vessels to be varied at will.