FLUID-PESSURE OPERATED MOTORS

Abstract: An air motor comprising a piston and cylinder unit and control means mounted wholly within a housing secured to the unit. The housing comprises two parts (11, 12) at the ends of the cylinder (10) and a manifold assembly (28, 30) extending alongside the cylinder (10) and these end parts. The control means comprises a changeover valve (25) in the manifold assembly and two control valves (26, 27) in the respective end parts (11, 12) which are operated by mechanical actuators (K 1, K2) engaged by the piston (13) when it reaches the ends of its stroke and thereupon cause the changeover valve to change over the supply of compressed air from an inlet (60) in the manifold assembly, from one end of the cylinder to the other thereby to reverse the movement of the piston so that the piston reciprocates in the cylinder. The piston may comprise two parts (51, 52) which are adjustable to vary its effective length and hence its strocke.

Description: Title: "Fluid-pressure operated motors" Description of Invention This invention relates to fluid-pressure operated motors. In particular, the invention is concerned with a fluid-pressure operated motor of the kind, hereinafter referred to as the kind specified, comprising a piston and cylinder unit and control means operable to connect a supply of fluid under pressure alternately to opposite ends of the cylinder thereby to cause relative reciproca¬ tion between the piston and cylinder. The invention has been devised, primarily in connection with pneumatic motors but there is no limitation in this regard as the invention is also applicable to hydraulic motors. The object of the invention is to provide a motor of the kind specified which is more compact and neater than conventional motors. According to the invention, there is provided a fluid-pressure operated motor of the kind specified wherein the control means are mounted wholly within a housing incorporating or secured to the piston and cylinder unit, the housing has an inlet connected or connectible to a source of fluid under pressure and the control means comprises a valve operable to connect the inlet alternately to opposite ends of the cylinder via passages provided within the housing. The control means may include two control units for operating the valve, one of these units being operable by the piston or the cylinder when it approaches or reaches the end of one stroke, and the other unit being operable by the piston or cylinder when It approaches or reaches the end of the other ' stroke (depending on whether the piston reciprocates and the cylinder is fixed, or vice versa), each control unit being arranged, when operated, to cause the valve to change over the supply of fluid under pressure from one end of the cylinder to the other thereby to reverse the movement of the piston or cylinder. Another form of control means may have only one such control unit operable by the piston or the cylinder when it approaches or reaches the end of one stroke, and means operable by an external signal when the piston or the cylinder approaches or is at the end of the other stroke, the control unit sand said means being arranged, when operated, to cause the valve to change over the supply of fluid under pressure from one end of the cylinder to the other thereby to reverse the movement Of the piston or cylinder. Preferably, the changeover valve of the control means is operable by fluid-pressure and the or each control unit comprises a valve operable to control the supply of fluid under pressure from the inlet to the changeover valve for the purpose of operating the latter, via passages provided within the housing.. The valve constituting the or each control unit is preferably operable by a mechanical actuator arranged to be acted upon directly by the piston or the cylinder. Conveniently, the housing comprises two parts disposed at the respective ends of the cylinder and a manifold assembly which extends alongside the cylinder and these end parts, the changeover valve being mounted in the manifold assembly, the control valve or valves being mounted in one of the end parts or the respective end part, and the passages formed in the manifold assembly connecting the control valve or valves to the - 3 - changeover valve and the latter to the inlet which is provided in the manifold assembly. Means may be provided for cushioning the movement of the piston or cylinder when it reaches the end of each stroke. Preferably, each end of the cylinder is provided with a cavity which opens into the chamber of the cylinder and is arranged to be closed by the piston when the piston or cylinder approaches the end of the stroke concerned whereby fluid is trapped in the cavity, this fluid being compressed as the piston or cylinder moves to the end of its said stroke, whereby such movement is cushioned. Each cavity may have a restricted outlet for the compressed fluid. Each cavity may have a circular mouth facing the piston and provided with an annular seal arranged to be engaged by a tapered part of the piston to close the cavity. The piston may -comprise two parts which- are connected together so as to be adjustable towards and awa-y from one another ' to vary the effective length of the piston and hence the stroke of the piston or the cylinder. Thus, where the control means has two control units as described above, the two parts of the piston act on the respective units at the ends of the cylinder. Reducing the effective length of the piston and hence increasing the distance it has to travel to operate both control units increases the stroke, and increasing the length so as to decrease said distance reduces the stroke.The two parts of the piston are preferably connected together by adjusting means enabling the stroke to be infinitely varied. The motor according to the invention may be used with a reciprocating type pump. The pump may be operated as a metering pump providing a continuous flow rate which can be infinitely varied, or as a pump dispensing single or multiple shots, one cycle of the motor producing one shot. In the latter case, the control means will have only one control unit and means operable by an external signal as described above so that the air motor would perform only one cycle until reactuated by an external signal. The invention will now be described by way of example, with reference-to the accompanying drawings, in which:- FIGURE 1 is a side view, mainly in section, of one form of air motor embodying the invention; FIGURE 2 is a scrap section taken on the line II-II of Figure 1 showing the changeover valve with its spool omitted; FIGURE 3 is a section on the line III-III of Figure 1 showing the manifold; FIGURE 4 is a section on the line 17-17 of Figure 1 showing the manifold gasket and, behind it the manifold plate; , • FIGURE 5 i? a section on the line 7-7 of Figure 1 showing the top end gasket; FIGURE δ is a section on the line 71-71 of Figure 1 showing the bottom end cap gasket; and FIGURE 7 is a side view, partly in section, of another form of air motor embodying the invention. The two forms of air motor illustrated in the drawings each comprises a piston and cylinder unit, the cylinder 10 of which is fixed and closed at its ends by a top end cap 11 and a bottom end cap 12, the piston 13 being reciprocable in the cylinder. In the embodiment shown in Figures 1 to 6, the piston 13 comprises one part having a piston rod 14 connected to it and extending through the bottom end cap 12. The piston has a circumferential groove containing an 0-ring 15 in sealing engagement with the wall of the cylinder 10. The inner end of the piston roc 14 is of a reduced diameter and extends through a central aperture in the piston, and two cushioning sleeves 16 at opposite - - ends of the piston, being secured to the piston by a nut 17. * In the embodiment shown in Figure 7, the piston 13 comprises two parts 51 and 52 which are secured together so as to reciprocate as one in the cylinder but which are adjustable towards and away from one another to vary the effective length of the piston and hence its stroke. The part 51 of the piston has a piston rod 53 connected to it and extending through the bottom end cap 12. The part 52 has a hollo internally screw-threaded sleeve 54 which extends through the top end cap 11, and a screw-threaded stem 55 connected to the part 51 extends through the hollow sleeve, being engaged with its screw thread. The projecting end of the stem carries a locknut 56 which abuts the free end of the sleeve. The two parts 51 and 52 of the piston each has a circumferential groove containing an 0-ring 57 in sealing engagement with the wall of the cylinder. Two cushioning sleeves 65 are provided at the respective ends of the piston. In both embodiments, the piston rod 14, 53 extends through a seal assembly 18 carried by the bottom end cap 12 and the outer end of the piston rod is formed for connection to an apparatus required to be driven by the air motor. In the embodiment of Figure 7, the sleeve 54 extends through a similar seal assembly 58 carried by the top end cap 11. The ' top and bottom end caps 11 and 12 are formed respectively with recesses 19 and 20 which communicate with the parts of the cylinder chamber 21 and 22 at respectively opposite ends of the piston. The recess in the bottom end cap has the piston rod extending through it, the bottom of the recess being closed by the seal assembly 18. In the embodiment shown in Figure 7, the recess in the top end cap has the sleeve 54 extending through it, the top of the recess similarly being closed by the seal assembly 58. The recesses are provided at - 6 - their mouths with annular cushioning seals 23 and 24, the piston rod 14, 53 extending through the seal 24 and, in the embodiment of Figure 7, the sleeve 54 extending through the seal 23- In operation, the piston 13 is reciprocated in the cylinder 10 by supplying compressed air alternately to the parts of the cylinder chamber 21 and 22 at opposite sides of the piston. This supply of air is controlled by a changeover valve 25 and two control valves 26 and 27. The changeover valve 25 is housed in a manifold 28 which is secured to the end caps 11 and 12, and the control valves 26 and 27 are mounted in the top and bottom end caps 11 and 12 respectively. Interposed between the manifold 28 and the end caps are a manifold gasket 29 and a manifold plate 30, both of which extend the full length of the manifold, and two end cap gaskets 31, 32 which extend only over the respective end caps 11 and 12. - ' The changeover valve 25 is shown in detail in Figure 2 and com-prises a spool (omitted frcm Figure 2 in the interests of clarity) which is slidable in a sleeve 33 fixed in a bore formed in the manifold, the ends of the bore being closed by plugs 3 secured by screws to the manifold. Resilient end stops 35 are provided at the ends of the bore in the sleeve 33 to cushion the spool when it reaches the end of its movement in the sleeve. The sleeve Is formed with a number of ports 101, 102, 103, 104 and 105 which communicate with passages in the manifold, and the spool has a number of circumferential grooves arranged to place different ports in communi¬ cation with one another in different axial positions of the spool. The upper end of the spool, as viewed in. Figure 2, is of reduced diameter and extends into a detent device 36, the reduced diameter portion having a circumferential groove and the detent device having two balls 37 which, when the spool is in its normal position, - 7 - are urged by springs 38 into this groove. 0-ring seals are .provided around the sleeve 33 and the end plug 34. The control valves 26 and 27, shown in detail in Figure 1 , each comprise a spool 39 which is slidable in a sleeve 40 fixed in a bore formed in the end cap - concerned. One end of the spool is acted upon by an actuator pin K1, K2 extending through an end plug 41 and a bore in the end cap and projecting into the adjacent part of the cylinder chamber 21, 22. The other end of the spool is acted upon by a spring assembly UI , U2. The sleeve 40 has a number of ports 201, 202 and 203 in the case of the valve 27, and 301, 302 and 303 in the case of the valve 26. The manifold 28 has an inlet port 60 which is connected to a source of compressed air, which may be from 15 to 100 p.s.i., and an exhaust port 61. The manifold 28, the manifold gasket 29, the manifold plate 30, the end cap gaskets 31, 32 and the end caps 11, 12 are formed with passages or recesses defining passages, and the arrangement of these passages will be evident from the following description of the manner of operation of the air motor. Compressed air from the inlet port 60 is supplied at all times to port 101 of the changeover valve 25 via passage B in the manifold, and to ports 201 and 301 of the control valves 27 and 26 respectively, via passage B in the manifold, passage D in the manifold gasket, passages F1 and F2 in the manifold plate, passages G1 and G2 in the end cap gaskets and passages E1 and E2 in the end caps. Commencing with the piston performing a downstroke (as viewed in Figure 1), as it approaches the end of its stroke, the piston (i.e. its part 51 in the embodiment of Figure 7) engages the actuator pin 1 of the control valve 27 and moves its spool 39 to a position in which port 202 is closed and port 201 is placed in communi- cation with port 203, so that air from passage E1 flows through passage M1 in the end cap 12, passage N1 in the bottom end cap gasket 32, passage P1 in the manifold plate, slot Q1 in the manifold gasket and passage Rl in the manifold to the changeover valve 25. The air enters the valve at the upper end of the spool and moves the latter against the action of the detent device 36 to a position in which port 101 is placed in communication with port 102, so that air from passage 3 flows to passage S1 in the manifold. This air flows from passage SI through passages T10, T11 and T12 in the manifold gasket, the manifold plate and the bottom end cap gasket respectively to an inlet/exhaust port in the top end cap which opens into the recess 20 of the cylinder chamber at the lower side of the piston 13- As a result, the piston is moved upwardly. As the piston performs its upstroke, the spring ass.erably UI of the control valve 27 returns its s ' pool 39 to its original position. Port 202 is therefore opened and air from the valve is exhausted through passage L1 in the end cap and passage 71 in the bottom end cap gasket which opens to atmosphere. Also, the air in the upper part 21 of the cyliinder chamber above the piston 13 is exhausted through an inlet/exhaust port in the top end cap, passages T20, T22 and T23 in the top end cap gasket, the manifold plate and the manifold gasket respectively, passage S2 in the manifold and port 103 in the changeover valve 25 which, by virtue of the position of the spool of the valve, is in communication with port 105 connected via a passage 2 in the manifold to the exhaust port 61. As the piston 13 approaches the end of its upstroke, the piston (i.e. its part 52 in the embodiment of Figure 7) engages the actuator pin 2 of the control valve 26 and moves its spool to a position in which port 302 is closed and port 301 is placed in communication with port * 303 so that air .from passage E2 flows through passage M2 - 9 - in the end cap 11, passage 2 in the top end cap gasket 31, passage P2 in the manifold plate, passage Q2 in the manifold gasket and passage R2 in the manifold to the changeover valve 25. The air enters the valve at the lower end of the spool and moves the latter to a position in which port 101 is placed in communication with port 103 so that air from passage B flows to passage S2 in the manifold. This air flows from passage S2 through passages T10, T11 and T20 in the manifold gasket, the manifold plate and the top end cap gasket respectively to the inlet/exhaust port in the top end cap which opens into the recess 19 of the cylinder chamber at the upper side of the piston 13. As a result, the piston is moved downwardly. As the piston performs its downstroke, the spring assembly U2 of the control valve 26 returns its spool 39 to its original postion. Port 302 is therefore opened and air from the valve is exhausted through- the passage L2 in the end cap and passage 72 in the top end cap gasket which opens to atmosphere. Also, the air in the lower part 22 of the cylinder chamber below the piston 13 is exhausted through the inlet/exhaust port in the bottom end cap, passages T12, T11 and T10 in the bottom end cap gasket, the manifold plate and the manifold gasket respectively, passage S1 in the manifold and port 103 in the changeover valve 25 which, by virtue of the position of the spool of the valve, is in communication with a port 104 connected via a passage 1 in the manifold to the exhaust port 61. The piston of the air motor is therefore reciprocated continuously to drive the apparatus connected to the piston rod. When the piston 13 approaches the end of each stroke, the leading one of its two cushioning sleeves 16, 65 engages the opposed annular cushioning seal 23 or 24 and closes the mouth of the associated recess 19 or 20 - 10 - respectively. The sleeve 16, 65 has a tapered outer portion to produce a sealing engagement with the seal. The air trapped in the recess is compressed by the piston but allowed to escape slowly to atmosphere through a small outlet opening in the end cap concerned into the part 21 or 22 of the cylinder chamber above or below the piston, with the resultant effect of cushioning the piston as it moves to the end of its stroke. It will be observed that the changeover valve 25 and the control valves 26 and 27 are mounted wholly within the housing formed by the top and bottom end caps 11, 12 and the manifold assembly comprising the manifold 28, and the manifold plate 30♦ There are no external valves, pipework or mechanical devices as in conventional motors and the motor is therefore more compact and neater. The valves are readily accessible and the whole assembly is smoothly contoured and easier to clean In sanitary conditions, ' The motor may be used to operate a reciprocating pump, the piston rod 14, 53 being connected to the pump, and the pump being operated either as a continuous metering pump or as a one shot multiple shot dispensing pump. In the latter case, one shot is delivered for each cycle, i.e. two strokes, of the motor and one of the control units 26 or 27 is omitted and replaced by means operable by an external signal so that the motor would perform only one cycle until reactuated by such a signal. The operation of the air motor may be controlled by a counting device providing said signal, the motor, pump and device forming the basis for a filling machine which may be used, for example, in the food and pharmaceutical industries. To adjust the stroke of the piston, in the embodiment shown in Figure 7 the locknut 56 is released and then the sleeve 54 and the part 52 of the piston are turned relative to the stem 55 and the part 51. If the stroke is to be increased, the sleeve 54 and the part 52 are turned in a clockwise direction (viewed from the top of the air motor) so that the distance between the two parts of the piston is decreased. This increases the distance the piston must travel to strike the pins K1 and 2. If the stroke is to be reduced, the sleeve 54 and the part 52 are turned in an anti-clockwise direction. This increases the spacing between the two parts of the piston and thereby reduces the distance it must travel to operate the pins K1 and K2. After adjustment of the pistons, the locknut 56 is re-tightened. The adjusting means for the pistons are disposed outside the motor in a conveniently accessible position and are a simple to operate. The sleeve 54 may be provided with a scale comprising a series of gradations marked along the sleeve to facilitate adjustcent of the effective length of the piston. '

Claims: CLAIMS : 1. A fluid-pressure operated motor of the kind specified wherein the control means are mounted wholly within a housing incorporating or secured to the piston and cylinder unit, the housing has an inlet connected or connectible to a source of fluid unde < pressure and the control means comprises a valve operable to connect the inlet alternately to opposite ends of the cylinder via passages provided within the housing. 2. A motor as claimed In Claim 1 wherein the control means include two control units for operating the valve, one of these units being operable by the piston or the cylinder when it approaches or reaches the end of one stroke, and the other unit being operable by the piston or cylinder when it approaches or reaches the end of the other stroke, each control unit being arranged, when operated, to cause the valve to change over the supply of fluid under pressure from one end of the cylinder to the other thereby to reverse the movement of the piston or cylinde . 3. A motor as claimed in Claim 1 wherein the control means includes a control unit operable by the piston or the cylinder when it approaches or reaches the end of one stroke and means operable by an external signal when the piston or the cylinder approaches or is at the end of the other stroke, the control unit and said means being arranged, when operated, to cause the valve to change over the supply of fluid under pressure from one end of the cylinder to the other thereby to reverse the movement of the piston or cylinder. 4. A motor as claimed in Claim 2 or Clai * 3 wherein the changeover valve of the control means is operable by fluid-pressure and the or each control unit comprises a valve operable to control the supply of fluid under pressure from the inlet to the changeover valve for the purpose of operating the latter, via passages provided within the housing. 5. A motor as claimed in Claim 4 »wherein the valve constituting the or each control unit is operable by a mechanical actuator arranged to be acted upon directly by the piston or the cylinder. 6. A motor as claimed in Claim 4 or Claim 5 wherein the housing comprises two parts disposed at the respective ends of the cylinder and a manifold assembly which extends alongside the cylinder and these end parts, the changeover valve being mounted in the manifold assembly, the control valve or valves being mounted in one of the end parts or- the respective " end parts,, and the passages formed in the manifold assembly connecting the control valve or valves to the changeover valve and the latter to the inlet which is provided in the manifold assembly. 7. A motor as claimed in any one of the preceding claims wherein means are provided for cushioning the movement of the piston or cylinder when.it reaches the end of each stroke. 8. A motor as claimed in Claim 7 wherein each end of the cylinder is provided with a cavity which opens into the chamber of the cylinder and is arranged to be closed by the piston when the piston or cylinder approaches the end of the stroke concerned whereby fluid is trapped in the cavity, this fluid being compressed as the piston or cylinder moves to the end of its said stroke, whereby such movement is cushioned. - 14 - 9. A motor as claimed in Claim 8 wherein each cavity has.a restricted outlet for the compressed fluid. 10. A motor as claimed in Claim 8 or 9 wherein each cavity has a circular mouth facing the piston and provided with an annular seal arranged to be engaged by a tapered part of the piston to close the cavity. 11. A motor as claimed in any one of the preceding claims wherein the piston comprises two parts which are connected together so as to be adjustable towards and away from one another to vary the effective length of the piston and hence the stroke of the piston or the cylinder. 12. A motor as claimed in Claim 11 wherein the two parts of the piston are connected together by adjusting " means enabling the stroke to be infinitely vafried. 13. An air motor substantially as herein described with reference to and as illustrated in Figures 1 to 6 or Figure 7 of the accompanying drawings. 14. Any novel feature or novel combination of features disclosed herein and/or illustrated in the accompanying drawings.

Inventors: EVANS ERIC GEORGE, HUDSON ANTHONY JOHN, MASON FRANK WILLIAM
Applicants: EVANS ERIC GEORGE, HUDSON ANTHONY JOHN, KINGDOM ENG CO LTD, MASON FRANK WILLIAM
Application year: 1982
Main classification: F01L25
IPC codes: F01B11, F01L25, F04B49