GB2195149A - Tubular diaphragm pumps - Google Patents

Abstract

A fluid pump has a tubular housing (2), containing a flexible hose (4) capable of expanding to conform to the inner walls of said housing. The housing (2) has an inlet port (24) and an outlet port (18) communicating with said hose (4). A first one-way valve (28) is provided to allow fluid to pass from the inlet port (24) to the hose (4). A second one-way valve (20) is provided to allow fluid to pass from the hose (4) to the outlet port (18). The space between the housing (2) and the hose is coupled to an alternating pressure source whereby upon the application of a relatively high pressure the hose (4) is caused to contract, to expel any fluid therein through the outlet port (18), and upon the application of a relatively low pressure the hose (4) is caused to expand to draw in fluid through said inlet port (24). <IMAGE>

Description

SPECIFICATION Fluid pumps The present invention relates to fluid pumps.

Peristaltic pumps for pumping liquids are known. In such pumps liquid is moved along flexible tube in discrete quantities by the action of a cam on the tube. The tube is thus not only subject to flexure but also to the frictional forces produced when a cam is caused to contact and slide along the tube.

The life of the tube in such cases is limited. In addition, the flexible tube is subject to stretching and so there is no control on the amount of liquid in each discrete quantity displaced along the tube.

It is an object of the invention to provide an improved pump.

According to the present invention there is provided a fluid pump comprising a housing, a flexible enclosure capable of expanding to conform to the inner walls of said housing, an inlet port and an outlet port communicating with said enclosure, a first one-way valve for allowing fluid to pass from said inlet port to the enclo ure, a second one-way valve for allowing fluid to pass from said enclosure to said outlet port, and means for coupling the space between the housing and the flexible enclosure to an alternating pressure source whereby upon the application of a relatively high pressure the enclosure is caused to contract, to expel any fluid therein through the outlet port, and upon the application of a relatively low pressure,the enclosure is caused to expand to draw in fluid through said inlet port.

Advantageously the housing comprises a cylindrical tube and the enclosure comprises a length of hose lining the inner wall of the tube and having its opposite ends secured to respective ones of the opposite ends of the tube.

Preferably the hose is of rubber or plastics.

The first and second ports are defined by end caps which act to clamp the ends of the hose to the ends of the tube.

Each end cap is rigidly secured to a clamp plate and the two clamp plates are locked together by tie rods.

Advantageously each said one-way valve comprises a ball valve. The ball valve of the first one-way valve is normally urged against its valve seat by a spring. The ball valve of the second one-way valve is normally urged against its valve seat by gravity.

A fluid pump embodying the present invention will now be described by way of example with reference to the accompanying diagrammatic drawing which shows a longitudinal section through the pump.

As shown in the sole Figure the pump comprises a cylindrical housing or tube 2 which is lined with a flexible rubber hose 4. Opposite ends of the hose 4a and 4b are bent back around the adjacent extremeties of the tube 2.

A pair of end caps 6 and 8 each having an annular recess for accomodating the opposite ends of the tube 2 act to clamp the hose ends 4a and 4b to the tube 2. Each end cap 6 and 8 is rigid with a corresponding clamping plate 10 and 12 and the two clamping plates 10 and 12 are drawn together by tie rods 14 (shown only as an axis).

Each end cap 6 and 8 defines a cylindrical channel which is partly internally screwthreaded.

A member 16 defining an inlet port 18 has an externally screw-threaded cylindrical portion which is in screw-threaded engagement with the end cap 6. A sealant (not shown) is provided to form a fluid tight seal between the member 16 and the end cap 6. A ball 20 is imprisioned in the cylindrical channel defined by the end cap 6. A coiled spring 26 partly housed in an enlarged diameter portion of the member 16 urges the ball towards a valve seat in the cap 6 at the downstream end of the channel.

A member 22 defining an outlet port 24 has an externally screw-threaded cylindrical portion which is in screw-threaded engagement with the internal screw-thread of the end cap 8. A sealant (not shown) is provided to form a fluid tight seal between the member 16 and the end cap 8. A ball 28 is imprisioned in the cylindrical channel defined by the end cap 8. The ball 28 is normally drawn by gravity against a valve seat defined by the member 22. An apertured plate 30 in the channel of the end cap 8 limits the movement of the ball along the channel away from the valve seat.

A generally annular body 32 envelops a central portion of the tube 2 and defines a passage 34 which communicates with the space between the tube 2 and the flexible hose 4. The passage 34 is arranged to be alternatively coupled to a source of pressure and a source of vacuum (neither of which is shown).

In operation the inlet port 24 is coupled to a supply of liquid to be pumped. The passage 34 is coupled to a source of relatively high pressure air which then fills the space between the tube 2 and the hose 4 and compresses the hose 4 to the profile 4' shown in broken lines. This action expels any air or residual fluid within the hose 4 through the oneway valve in the end cap 6 by urging the ball 20 against the bias of the spring 28. The pressure within the hose 4 causes the oneway valve in the end cap 8 to close by urging the ball 28 against its valve seat.

The passage 34 is then connected to a source of relatively low pressure, for example a vacuum. The vacuum created in the space between the tube 2 and the hose 4 will cause the hose 4 to expand into its former profile as shown in solid lines 4. This in turn will create a vacuum within the hose 4 which will cause the one-way valve in the end cap 6 to close, assisted by the action of the spring 26 and the one-way valve in the end cap 8 to open.

Liquid in the inlet port 24 will then be drawn up past the one-way valve into the hose 4 until the hose 4 is filled. At this time the passage 34 is connected again to a source of air pressure which acts on the hose 4 to expel the liquid from the hose 4 through the one-way valve in the end cap 6 into the outlet port 18. The cycle is repeated and liquid is therefore pumped in discrete quantities from the inlet port 24 to the outlet port 18.

It will be appreciated that because the tube 2 forms a rigid housing which limits the maximum extent to which the hose can expand, the discrefe quantities of liquid pumped are constant in volume. Furthermore since the force applied to the hose 4 is one of uniform air pressure, the frictional action to which the hose is subjected to is minimal.

The mannner in which the passage 34 is switched alternately between a source of pressure and a source of vacuum may be effected using a standard change over fluid valve, either of the linear reciprocatry or the rotary type. The valve is operated in such a manner as to maintain communication with each source for a period sufficient to allow the hose alternately to fill with liquid and to evacuate the liquid.

In a modification, sensing means can be provided to sense when the tube is filled with liquid and empty of liquid to trigger the operation of the change-over valve: Such means may take the form of means responsive to the weight of the pump and contents or magnetic means for sensing the movement of the spherical balls 20 and 28 into this normally biassed closed positions following the comple- tion of the filling or emptying of the hose 4.

In yet another modification the tube 2 and the hose 4 may be translucent and the sensing means be optical means for sensing the opacity of the contents of the hose which would be different when the hose 4 is full of liquid and when the hose is empty of liquid.

The hose may be of plastics or other material instead of rubber.

Claims (7)

1. A fluid pump cpmprising a housing, a flexible enclosure capable of expanding to conform to the inner walls of said housing, an inlet port and an outlet port communicating with said enclosure, a first one-way valve for allowing fluid to pass from said inlet port to the enclosure, a second one-way valve for allowing fluid to pass from said enclosure to said outlet port, and means for coupling the space between the housing and the flexible enclosure to an alternating pressure source whereby upon the application of a relatively high pressure the enclosure is caused to contract, to expel any fluid therein through the outlet port, and upon the application of a relatively low pressure the enclosure is caused to expand to draw in fluid through said inlet port.

2. A pump according to Claim 1 wherein the housing comprises a cylindrical tube and the enclosure comprises a length of hose lining the inner wall of the tube and having its opposite ends secured to respective ones of the opposite ends of the tube.

3. A pump according to Claim 2 wherein the hose is of rubber or plastics material.

4. A pump according to any one of Claims 1 to 3 wherein the first and second ports are defined by end caps which act to clamp the ends of the hose to the ends of the tube.

5. A pump according to Claim 4 wherein each end cap is rigidly secured to a clamp plate and the two clamp plates are locked together by tie rods.

6. A pump according to any preceding claim wherein each said one-way valve comprises a ball valve, the ball valve of the first one-way valve being normally urged against its valve seat by a spring and the ball valve of the second one-way valve being normally urged against its valve seat by gravity.

7. A fluid pump substantially as hereinbefore described with reference to the accompanying diagrammatic drawing.