GB2192433A - &cirf& Double acting pump - Google Patents

Abstract

A double acting pump comprises first (11) and second (41) parts, the first part (11) comprising a fluid-driven motor in which a piston (13) reciprocates, under the influence of fluid supplied to first (20) and second (22) inlet ports, through valve means directing the first fluid either to one (20) or to the other (22). As the piston (13) reaches the end of its stroke in each direction it comes into contact with an actuator (17, 47) of a microswitch (18, 48) which signals the actuator to change over the valve means. The second part (41) comprises a pump with piston (67) connected to the rod 26 of piston (13) to pump fluid supplied through non-return valves V, one in the fluid-tight divider 14 and one in end-plate 35, to outlet valves 64. Divider 14 has clamped seals at each end surrounding rod 26 so that driving fluid and pumped fluid do not mix; a drain is formed between these seals to carry away fluid passing them. <IMAGE>

Description

SPECIFICATION Double acting pump Description if lnvention This invention relates to a double acting pump, that is a pump having a reciprocating piston which is operative to pump in both directiòris of reciprocation.

One such pump is shown in British specification 1276591 which comprises first and second ends, hydraulic fluid fed under pressure to one side ofthe piston atthefirst end ofthe pump to cause the piston to reciprocate, the piston being rigidly connected via a rod to a further piston at the second end ofthe pump, to one or other side ofwhich water is fed, water being expelled from the opposite side of the piston at the second end, under pressure, and the piston atthefirst end changing direction, as hydraulicfluid is fed to the other side ofthe piston.

In order to cause the hydraulicfluid to be alternativelyfedto one orothersidesofthe piston atthefirst end, a lost motion sensing rod is used, which is moved longitudinallywith the piston, only as the piston at the first end ofthe rod reaches the end of its stroke, the position ofthe lost motion sensing rod dictating a valve position and hence the side of the piston at the firstendto which hydraulicfluidis directed.

This arrangement has been in production for about sixteen years and for all of that time, has suffered from the problem that due to the close tolerances which are necessary in orderthatthe lost motion sensing rod will work adequately, the sensing rods tend to break, either because the pump is wrongly adjusted, or becomes maladjusted in use.

It is an object of the present invention to provide a new or improved double acting pump which overcom esorreducesthis problem.

According to the inVention we provide apu m p comprising firstand second parts, the first part comprising a-chamber in which a piston in use, reciprocates, first and second inlet ports, thefirstport being arranged aiways to lie at one side ofthe piston and the second inlet port being arranged always to lie at the second, opposite side of the piston, the first and second inlet ports each being connected to a valve means to which a firstfluid is fed under pressure, the valve means directing the first flu id either to the first inlet port to cause the piston to move in first direction of reciprocation, orto the second inlet portto cause the piston to move in a second direction reciprocation depending on the position of an electrically controlled actuator thereof, the piston, or a part which moves rigidlywiththepiston, as the piston reaches the end of its stroke in each direction of reciprocation, coming into contactwith an actuatorof a microswitch which signals the actuator of the valve means to cause the first fluid to be directed to the opposite side ofthe piston, whereby the piston recjprocates, the second part of the pump comprising an actuator connected to the piston of thtirst pair, movemen-toftite actuator acting on a second fluid to pump the second fluid.

Thus no lost motion sensing rod carried by the piston, as described in British specification 1276591 is required, and so the problem involved with such sensing rods is entirely overcome.

The actuator ofthe valve means is simply switched when the piston reaches the end of its stroke, as the piston at the first end contacts the actuator ofthe microswitch attheend of its stroke.

Preferably the actuator ofthe second end of the pump comprises a second piston connected by a piston rod to the first mentioned piston of the first part, the second piston being slidable in a chamber ofthe second part. The second part ofthe pump may have first and second inlet ports, the first inlet port being arranged always to lie at one side ofthe piston and the second inlet port being arranged always to lie at a second, opposite side of the piston, each inlet port being connected to a supply of second fluid,'there being a valve associated with each inletto ensure that fluid is onlyfed into the chambervia either inlet port as the second piston moves away from the respective inlet port.

Thus the second fluid is drawn into the chamber at the second end of the pump as the piston moves away from the respective inlet port.

The second part of the pump may also comprise first and second outlet ports, thefirstoutletport being arranged always to lie at one side ofthe piston and the second outlet port being arranged always to lie at a second side ofthe piston, each outlet port being connected to a delivery conduit along which the pressurised fluid is fed from the pump to its intended location of use, a valve being associated with each outlet portto ensure that fluid cannot pass from the cham ber of the second part of the pump via either outlet portwhen the second piston is moving away from the outlet respective port.

Thus fluid is continuously pumped from one-or other of the outlet-ports as the second piston reciprocates in its respective chamber, to provide a continuous supply of pressurised fluid to the delivery conduit.

The valves associated with the inlet andlor outlet ports atthe second end ofthe pump may comprise simple non return valves each having sealing memberwhich may be biased into sealing rela tionship with a seat, via a resilient means such as a spring.

Preferably, the sizes of the inlet ports are greater than the sizes ofthe outlet ports so that the pressure of fluid supplied to the delivery conduit is@high.

Preferably, at the first end of the pump, only inlet ports are provided, but when the piston nioves towards a respective inlet port, the port acts as an outlet port permitting fluid to leave the chamber through the port to pass to the valve means, wh ich directsthefluid back to tank.

Preferably, the first and second pistons are can nected via a righid piston rod and are thus a line, - although other arrangements are possible.

-One inlet portafthefrstend ofthe pump may be provided in an end closure plate thereof, and the other inlet port may be provided in an intermediate connec torbetweenthefirstandsecond parts of the pump, at the opposite end ofthe chamber ofthe first partto the ciosure plate.

One inletportatthesecond end ofthe pump may be provide in an end closure plate atthe second end of the pump, opposite to thefirstclosure plate, and another inlet port may be provided in the intermediate connector between the first and second pump parts.

However, the inlet ports ofthe first and second parts are preferably separated sothatfirstfluid does not mix with the second fluid.

An outlet port at the second end ofthe pump may also be provided in the end closure plate, and another outlet port m-ay be-provided in the intermediate connector.

One microswitch the actuatorofwhich maybe contacted at the first end ofthe pump aslhepiston moves towards the end closure-plate, may be mounted in the closure plate, the actuator thereof extending from the closure plate and being operated bythe piston or a part moving rigidly and integrally with the piston, such as the piston rod, where provided.

Another midroswitch may be provided in the end- closure plate atthe opposite end ofthe pump, and be operated bythe second piston, which moves inte'gral- ly and rigidly with the first piston, orthe piston rod, where provided, or a part provided on the piston rod, which again moves integrally and rigidly with the piston at the first end of the pump.

However, the first afldfdr second microswitch may be provided at other positions if required.

In a preferred embod ent, the firstflu(d which is used to drive the piston atthefirst end ofthe pump, preferably comprises a hydrau lic fluid. Any second fluid may be pumped at the second end ofthe pump, for example, the~second fluid may comprise water.

The invention will now be described with reference to the accompanying drawings in which: FIGURE lisa side cross section through a first part of the pump in accordance with the invention.

FIGURE 2 is a cross section of a second part of the pump of Figure 1 rotated through 90 .

FIGURE 2a is a detailed view of part of the pump of Figure 2 shown in the orientation of Figure 1.

Referring fi rst to Figure 1, a pump 10 comprises a first part 11 having a chamber 2 in which a piston 13 is disposed to reciprocate. One end of the chamber 12 is closed by an intermediate connector 14 which connects the part 11 of the pump to the second part 41 shown in Figure 2.

The opposite end of chamber 12 is closed by an end closure plate 15 which has a generally centrally positioned stepped bore 16 which receives an actuator 17 of a microswitch 18 for a purpose hereinafter described.

The end closure plate 15 has an annular, first, inlet port 20 towhich a first fluid, in the present example hydraulic fluid, may befed via-a passage 21 connected to a valve means (notshown).

The connector 14 similarly has an annular,second, inlet port 22 to which hydraulicfluid may be fed via a further passage 23 which is also connected to the valve means.

The piston 13 is sealed relative to the chamber 12 by means of a sealing member 24 received in a groove 25 in a sidewall ofthe piston 13.

In the present example, the chamber 12 and piston 13 are cylindrical, the sealing member 24 being thus annular, although a chamber and piston of other configuration may be provided, thereby requiring a sealing member of another configuration.

The sealing member 24 comprises five separate parts which, when assembled together as shown, provide very efficient sealing againstthe egress of hydraulic fluid from a first side A ofthe piston 13 to a second other side B.

The piston 13 is connected to the stepped end of a piston rod 26 which moves integrally and rigidly with the piston 13. The rod 26 is sealed relative to the piston 13 by virtue of an O ring seal 27.End 28 of the rod 26 extends entirely through piston 13 and is flush with one surface 29 thereof.

The first end 11 is held rigid by a plurality of tie rods, only one of which can be seen in Figure 1,at30,which rods are secured to the end closure plate 15 by nuts 31.

Each can be tensioned via meansofthe nuts31.The rods 30 each extend throughout the entire length of the pump, to an end closure plate 35 at the opposite end (see Figure 2). In practice, at leastthree such tie rods 30 are provided, although preferablyfour are provided as in the present example.

The connector 14 is thus simply retained in-engage- ment with the chamber 12 bythetension in the rods 30. Sealing is effected between the connector 14 and the chamber 12 by an 0 ring 33 and between end plate 15 and chamber 12 by another O ring 34.

In use, hydraulic fluid is fed under pressure to the valve means, which-diverts the fluid alternatively to the first inlet port 20 to cause the piston 13 to move from left to right as seen in the drawings, orto the second inlet port 22 to cause the piston 13 to move from right to left as seen in the drawings.

To achieve this, the valve means has an electrically operated actuator which is controlled in response to signals receivedfrom microswitch 18, or a further microswitch 38 attheopposite end ofthe pump (see Figure 2) as hereinafter described.

Of course when the piston 13 moves from left to right for example, fluid from side B of the chamber 12 will be ejected by the piston 13 through the port 22 which acts as an outlet port; and the valve means diverts the fluid backtotank.

Conversefy when the piston 13 moves from right to left, fluid is ejected from side B of the chamber bythe piston 13 via port 20, and again the valve means re-directsthis back to tank for reuse.

Valve means to achieve this function arewell known in the art and~operate as described in G.B. patent 1276591. One suitable valve is a solenoid double acting type directional valve sold by Vickers Systems, model DG4V-3, 30 design, although other types of valve could be used.

Referring now also to Figure 2, a second end part41 ofthe pump loins shown, which in this example also comprises a chamber42 in which a piston 43 is disposed to reciprocate. One end ofthe chamber 42 is closed by connector 14, a different aspect ofwhich is seen in Figure 2, and as mentioned above, the opposite end of chamber 42 is closed by an end closure plate 35. The end closure plate 35, like plate 15, has a stepped bore 46 in which an actuator 47 of a microswitch 38 is disposed.

The end closure plate 35 has at one position (shown in Figure 2a) a first inlet port 50 to which a second fluid, in the present example water to be pumped under high pressure, isfed via a passage 51-which is connected to a branch coduit 49 (see Figure 1) as hereinafter described.

The connector 14 also has an inlet port 52 which is also shown in Figure 1 to which water is fed via a passage 53 from further branch conduit 48,the conduits 48 and 49 being connected together and to a supply conduit S which extends to a water supply.

Both passageways 53 and 51 have, where they join conduits 48 and 49 respectively, non return valves V, although the valve V;sonlyshown in position in passageway 53, the valves being omitted from passageway 51 forclarity.

The valves V each comprise a sealing member 54 which is larger than a valve seat 55 and is spring biased into sealing relation with the seat 55, by a coil spring 56.

Thus water may pass from conduits48,49, into passageways 53,51, the flowingwater lifting the respective sealing member 54 by overcoming the force exerted by the spring 56, but anywater cannot flow past members 54 in the opposite direction as this will forcethe valve member 54 into increasingly tight engagement with their seat55.

The connector 14 and end closure plate 35 also have outlet ports 57 and 58 respectively, in addition to inlet ports 50 from which water may passfrom the chamber 42 by passageways 59 and 60 into respective branch conduits 61 and 62 and henceto a delivery conduit 63.

Non-return valves 64 simailar to valves Vat the inlets, are provided between the passageways 59 and 60, and the respective branch conduits 62, although sealing members 65 of the valves 64 are lifted from their seats by water passing from the chamberA2, and returned to their seats to preventwater passing back through intochamber42.- The piston 43 is secured to the piston rod 26 at the opposite end to piston 13, and thus moves rigidly and integrally therewith Again, the end ofthe rod 26 is stepped but an integral projection 66 extends forwardly ofthe one end 67 of the piston 43.

Although notshown on piston 43, the piston 43 preferably has asealing member similar to sealing member 24 of piston 13, to effect a seal between the piston 43 and the chamber 42 as the piston slides.

The piston 43 is sealed relative to rod26 by means of an O ring 68 and the chamber 42 sealed relative to the connector 14by another ring seal 69.

The closure plate 35 is sealed relative to chamber 42 by an 0 ring seal 70.

The actuators 17,47, of the microswitches 1 8,38, are sealed relative to their respective chambers 12,42, by sealing members 71,72 respectively, which. permit the actuators 17,47, to slide. The actuators each have a shoulder 73 and a stack of spring washers 74, which normally urge the actuators 17,47, outwardly of their bores 16,46.

As the piston 13 reaches the end of its stroke (rightto left in Figure 1) the end 28 ofthe rod 26 will engagethe projecting actuator 17,to movetheectuator 17 against the force of the spring washers 74 until the actuator operates the microswitch 18 to close the microswitch 18 momentarily.

This will cause the microswitch 1 to signal the actuator ofthe valve means to dicontinue the supply of hydraulic fluid to port 22, and to commence the supply of fluid to port 20. Thus the piston 13 will then move from left to right During movementofthe piston 13from rightto left, at the second end 41 of the pump; the piston 43will move away from the end closure plate 35, drawing water in through port 50 via the valve V between passageway 57 and branch conduit 49, which valve V will be open,to a first side C ofthe piston 43.At the same time, water will be expelled from a second side D ofthe piston 43 in camber 42, vis outlet port 57 into branch conduit 61, due to the decreasing volume of chamber 42 atthat side D of piston 43. At the same time, valve 64 between branch conduit 62 and passageway 60 will be closed, as will valve V between branch conduit 48 and passageway 53.

When the direction of movement of the pistons13, 43, reverses, due to hydrauliofluid acting on face 29 of piston 13, valve 64 between branch conduit 61 and passageway 59 will then be closed-as-will the will valve V between branch conduit49 and passageway 51.

However, the valve V between the branch conduit48 and the passageway 53 will be openedto permit water to be drawn into piston side-D ofthechamber42.

At the same time, waterwhich was previously drawn into the chamber 42 at side C ofthe piston, will be expelled from the chamber 42 through thevalve 64 between the branch conduit 62 and the passageway 60.

When the piston 13 reaches the end of its stroke from leftto right, the piston 43 will be close to end closure plate 35. The projecting end 66 ofthe rod 26 will thus engage the actuator 47 of microswitch 38, to move the actuator 47 in its bore 46 against the force of the stack of spring washers 74to momentarily close the microswitch 38.

The microswitch 38thus sends a signal to the actuator ofthe valve means to cause the actuator of thevalve means to discontinue the supply of hydraulic fluid to port 20, and to again supply hydrnulic-fJuidto port 22 to thus again reversethe directon of move- ment ofthe piston 13.

Thus each of the pistons 13 and 43 will reciprocate in their respective chambers 12,42, and water will be pumped under pressure into the deliveryconduit63 for use.

Hydrauliefluid will be continuously recycled be tween the chamber 12 and tank, by-thevalve means as described.

It will be appreciated that it is essential that the first fluid and the second fluid do not mix. Hence the intermediate connector 14 through which the rod 26 slides, hastwo further 0 ring seals 76,77, which are compressed into close engagement with rod 26, by clamps 78, 79 rigidly. Any first or second fluid which does flow past seals 76,77, is vented via vent 80 without being allowed two cross from thefirst or second parttothe other.

Various modifications may be made withoutdepart- ing from the scope ofthe invention.

Particularly, in place ofthe-non-return valves V, any other type of non-return valve may be provided.

Similarly,the non-return valves 64atthe outlets from chamber 42 may be replaced by othertype of non-return valve.

Although itis convenientforthe inlet port20 to be provided in the end closure plate 15, this may be otherwise provided if required. Similarly, although it is convenientforthe inletport22to chamber 12, and the inlet port 52 to chamber 42 and outlet port 57 from chamber 42 to be provided in the connector 14rother arrangements are no doubt possible. Similarly, the inlet port 50 and outlet port58 provided in end closure plate 55 could otherwise be provided if required.

In place ofthe 0 ring seals described, and the sealing members 24 between pistons 13,43, and the chambers 12,42, any other appropriate sealing means may be provided.

Although as described, it isthe end 28 ofthe rod 26 which contacts the actuator 17 a nd the projecting end 66 ofthe rod 26 which contacts actuator 74, if desired, the pistons themselves may be provided with microswitch engaging parts.

Although it is preferred forthe microswitches 18 and 38to be positioned at opposite ends ofthe pump as described, if desired, one or both ofthe microswitches may be provided atother positions along the length ofthe pump, in whichtasethe or each ofthe microswitches may be otherwise operated-by other means which move integrally and rig idly with piston 13, but only contact the microswitch actuator, as the piston 13 reaches the respective end of its strokes.

For exam ple, microswitch 38 could be positioned in connector 14 and contacted by an abutment carried own rod 26.

In another arrangement (notshown) the second end part 41 of the pump-may be of an entirely different construction, the second-end having an actuator -which may be a piston like piston 43 bran entirely different componentto pump a second fluid such as water as the piston 13 in thefirstpump part 11 reciprocates in bothdirections in its chamber 12.

The features disclosed in the foregoing description, orthe accompanying drawings expressed in their specifi-cforms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, ora class or group of substances orcompositions, as appropriate, may, separately or in any combination of such features, be utilised for realising the-invention in diverse forms thereof.

Claims (19)

1. A pump comprising first~and second parts, the first part comprising a chamber in which a piston in use, reciprocates, first and second inlet ports, the first port being arranged always to lie at one side ofthe piston a nd th-e second inlet portbeing arranged alwaysto lie at the secorid, opposite side of the piston, the first and second inlet ports each being connected to a valve means to wh ich a first fluid is fed under pressure, the valve means directing the firstfluid eitherto the first inlet port to cause the piston to move in a first direction of reciprocation, orto the second inlet portto cause the piston to move in a second direction of reciprocation depending on the position of an electrically controlled actuatorthereof, the piston, ora part which moves rigidly with the piston, as the piston reaches the end of its stroke in each direction of reciprocation, coming into contact with an actuator of a microswitch which signals the actuator ofthe valve means to cause the first fluid to be directed to the opposite side ofthe piston, whereby the piston reciprocates, the second part of the pump comprising an actuator connected to the piston ofthefirst part, movement ofthe actuator acting on a second fluid to pump the second fluid

2. A pump according to claim 1 wherein the actuator ofthe second end of the pump comprises a second piston connected by a piston rod to the first mentioned piston ofthefirstpart,thesecond piston being slidable in a chamber ofthe second part.

3. A pump according to claim 2 wherein the second part ofthe pump has first and second inlet ports, thefirst inlet port being arranged always to lie at one side ofthe piston and the second inlet port being arranged always to lie at a second, opposite side of the piston, each inlet port being connected to a supply of second fluid, there being a valve associated with each inletto ensurethatfluid is oniy fed into the chamber via either inlet portasthe second piston moves away from the respective inlet port.

4. A pump according to claim 3 wherein the second part of the pump also comprises first and second outlet ports, the first outlet port being arranged always to lie at one side of the piston and the second outlet port being arranged to lieat a second side of the piston, each outlet port being-connected to a delivery conduit along which the pressurised fluid is fed from the pump to its intended location of use, a valve being associated with each outlet port to ensure thatfluid cannot pass from the chamber of the second part ofthe pump via either outlet port when the second piston is moving away from the respective outlet port.

5. A pump according to claim 3 or claim 4wherein the valves associated with the inlet-and/or outlet ports at the second end ofthe pump comprise simple non-return valves each having a sealing member, which is biased into sealing relationship with a seat, bya resilient means.

6. A pump according to-claim 4 or claim 5 where appendantto claim 4 wherein the sizes of the inlet ports are greated than the sizes oftheoutlet ports so thatthe pressure of fluid supplied to the delivery conduit is high.

7. A pump according to any one of the preceding claims wherein atthefirst end of the pump, only inlet ports are provided, and when the piston moves towards a respective inlet port, the ports acts as an outlet port permitting fluid to leave the chamber through the portto pass to the vaive means.

8. A pump according to anyone ofclaims2to7 whereappendantto claim 2wherein the first and second pistons are connected via a rigid piston rod.

9. A pump according to any one ofthe preceding claims wherein one inlet port atthe first end of the pump is provided in an end closure plate thereof and the other inlet port is provided in an intermediate connector between the first and second pump parts of the pump atthe oppposite end ofthe chamberofthe firstparttotheclosure plate

10. A pump according to any one of claims 3to 9 where appendantto claim 3 wherein one inlet port of the second end of the pump is provided in an end closure plate atthe second end ofthe pump, and another inlet port is provided in an intermediate connector between the first and second pump parts.

11. A pump according to claim 10 wherein an outlet port at the second end ofthe pump is provided in the end closure plate, and another outlet port is provided in the intermediate connector.

12. Apumpaccordingto anyoneofthe preceding claimswherein the actuator ofthe microswitch which is contacted atthe first end of the pump as the piston.

moves towards an end closure plate, is mounted in the closure plate, the actuator extending from the closure plate and being operated by the piston ora part moving rigidly and integrally with the piston.

13. A pump according to claim 12 wherein the other microswitch is provided in an end closure plate at the second end of the pump, and is operated by a piston rod which moves integrally and rigidly with the first piston.

14. A pump according to any one of the preceding claims wherein the first fluid which is used to drive the piston atthe first end ofthe pump, comprises a hydraulicfluid.

15. Apumpaccordingto anyoneofthe preceding claims wherein the second fluid pumped at the second end ofthe pump, comprises water.

16. A pump substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

17. Acombination of a pump according to any one ofthe preceding claims and a valve means to which a firstfluid is fed under pressure, the valve means directingthefirstfluid eithertothefirstinletportorthe second inlet port of the pump depending on the position of an electrically controlled actuator.

18. A combination as hereinbefore described with reference to the accompanying drawings.

19. Any novel feature or novel combination of features as herein defined and/or shown in the accompanying drawings.