US3007452A

US3007452A - Fluid operated reciprocating devices

Info

Publication number: US3007452A
Application number: US859904A
Authority: US
Inventors: Lee Norman
Original assignee: Keelavite Co Ltd
Current assignee: Keelavite Co Ltd
Priority date: 1958-12-19
Filing date: 1959-12-16
Publication date: 1961-11-07
Anticipated expiration: 1978-11-07

Description

Nov. 7, 1961 N. LEE 3,007,452

FLUID OPERATED RECIPROCATING DEVICES Filed Dec. 16. 1959 Fla. 3.

lNVENTOR Nokmau LEE States Unite 1 This invention relates to fluid-operated reciprocating devices of the kind comprising a working piston operating within a working cylinder relatively to which it can reciprocate and having oppositely directed working faces on which fluid pressure in chambers respectively at the two ends of the working cylinder can act, and reciprocating control valve apparatus controlling the'flow of working fluid through inlet and outlet ports at at least one end of the cylinder to cause such relative reciprocating movement.

In a fluid operated reciprocating device of the above kind according to the present invention the control valve apparatus comprises parts which are disposed respectively at the two ends of the working cylinder and are capable of being reciprocated by fluid pressure acting on faces (hereinafter called operating faces) of said parts, the arrangement being such that as the piston approaches each end of the working cylinder a part which moves with the piston co-operates with a part at the adjacent end of the working cylinder to restrict or prevent the fluid flow from such end of the cylinder and thereby causes fluid pressure to be built up between the adjacent face of the working piston and the operating face on the adjacent part of the valve apparatus, to move such part of the valve apparatus and thereby control one or more of the inlet and/or outlet ports to cause reversal of the working piston movement.

For convenience herein it will be assumed that the working cylinder is stationary and the working piston reciprocates but it will be understood that the working piston may be stationary and the working cylinder may reciprocate for both the working piston and the working cylinder may move in opposite directions during the relative reciprocating movement.

The valve apparatus may be constructed and arranged in various ways but inone preferred arrangement the valve apparatus comprises separate reciprocating valve members disposed respectively at the ends of the working cylinder and each having a port through which outflow of working fluid from its end of the cylinder takes place as the working piston moves towards it, and the working piston is provided with parts which, towards the ends of its working strokes partially or wholly close such ports respectively in the two valve members to restrict the outflow of fluid through each of such ports at the required time to cause pressure to be built up between the adjacent piston face and the operating face of the adjacent valve member to cause the latter to be moved into a position in which it causes reversal of the direction of movement of the working piston.

In most cases the working piston will be provided with a rod part which passes in a fluid tight manner through a gland or the equivalent at one end of the working cylinder and in this case the valve member at that end of the working cylinder through which the piston rod passes is con veniently of tubular form with a bore which constitutes a fluid inlet and outlet passage through which the piston rod passes and which is of substantially greater diameter than that of the piston rod, and the piston carries a shoulder of slightly smaller diameter than the said bore of the valve member which shoulder enters said bore in the valve mematenrO her during the latter part of the working piston movement towards it to cause the required restriction in the outflow of fluid and hence the required pressure build-up in the adjacent end of the cylinder to move the valve member. In this arrangement the part of the valve apparatus at the other end of the working cylinder conveniently comprises a valve member of the piston type having a bore opening into the cylinder and constituting an inlet and outlet port, the adjacent face of the piston carrying a cylindrical projection of slightly smaller diameter than that of such bore so that, when the projection enters the bore it effects the required restriction of outflow of fluid. In such a case the valve member through which the piston rod passes may control the connection respectively to the source of working pressure and to a relief passage of a chamber the pressure in which acts on a face of the valve member at the other end of the working chamber so that the valve member through which the piston rod passes acts as a pilot valve controlling movement of the valve at the other end of the working chamber, which latter valve controls the flow of working fluid to and from the working chamber for causing reciprocation of the working piston.

Moreover, in this case the chamber at the end of the cylinder through which the piston rod passes may be open at all times to the working fluid pressure while the valve apparatus is arranged to connect the chamber at the other end of the working cylinder alternately to working fluid pressure and to a relief passage.

In all cases the arrangement may be such that during movement of the working piston in each direction under fluid pressure in one end of the cylinder, that pressure by acting on a face of the valve apparatus maintains this, apparatus in the appropriate position for entry of working fluid under pressure to that end of the cylinder and escape of working fluid from the other end of the working cylinder, until the build up of pressure in such other end of the working cylinder due to restriction of outflow therefrom operates the valve apparatus to cause reversal of the direction of movement of the working piston.

Moreover the arrangement may in any event be such that. at low speeds the working piston will operate the valve apparatus by direct mechanical engagement, that is to say until the speed is suflicient for the operation of the valve apparatus by the building up of pressures in the manner described.

Three constructions according to the, invention, in each of which the valve apparatus is coaxial with the piston, are shown by way of example in the accompanying drawings, in which:

FIGURE 1 is a cross-section of one construction in a plane containing the common axis of the piston and the valve apparatus and in which the valve apparatus comprises two separately movable valve members,

FIGURE 2 is a similar view to FIGURE 1 of an alternative construction in which the valve apparatus comprises a single movable Valve member, and

FIGURE 3 is a similar view to FIGURES 1 and 2 of a still further construction in which the valve apparatus comprises a single movable valve member.

In the construction shown in FIGURE 1, the device comprises a casing 1 formed in four parts as shown bolted together at In and lb. The casing is formed to provide a working cylinder 2 in which is mounted to reciprocate a piston 3 having a piston rod 4 which extends in a fluid-tight manner through a gland provided by a sealing ring 4a at one end of the casing. 'Disposed at one end of the working cylinder 2 is a reciprocating control valve 5 of the piston type having a bore 6 therein opening through one end thereof into the adjacent end of the working cylinder 2 and provided with two lands 7 and 8 separated by an annulus 9 which communicates with the bore 6 through ports 6a.

The end of the valve 5 remote from the working cylinder 2 is arranged to be subject to the Pressure within a cylindrical pressure chamber while the bore in which the body of the valve 5 lies and moves is provided with two annular recesses 11 and 12.

Arranged within a bore 2a at the opposite end of the working cylinder 2 from the valve 5 and slightly larger diameter than that of the working cylinder 2, is a tubular pilot valve 13 having lands 14 and 15 arranged to control communication between two annular recesses 16 and 17 and between the recess 17 and the adjacent end of the working cylinder 2.

The annulus 11 and the end of the working cylinder 2 adjacent to the valve 13 are in permanent communication with a working fluid delivery passage 18 communicating with a source of fluid pressure, the annuli 12 and 16 are in permanent communication with a relief passage 18a, and the chamber 10 communicates through a passage 10a continuously with the annular recess 17.

The cross-sectional area of the piston 3 is substantially greater than that of the piston rod 4, for example approximately twice that of the piston rod 4.

During operation pressure from the source of fluid pressure 18 tends always to maintain the relay valve 13 in the position shown due to the fact that its righthand end 14 is of slightly larger effective diameter than its lefthand end, so that under these conditions the chamber 10 is connected through the passage 1% and the annuli 17 and 16 to the relief passage 18a. Under these conditions also since the annulus 12 is connected to the relief passage 18a, the bore 6 and hence the adjacent end of the working cylinder 2 will be connected to the relief passage 1811, the valve 5 being maintained in the position indicated by the fluid pressure from the passage 18 acting on the annular face 21.

With the valve 5 in the position shown, therefore, the working piston 3 will be moved to the left under the fiuid pressure acting on its annular face, while fluid escapes from the lefthand end of the working cylinder through the bore 6, ports 6a, annulus 12 and passage 18a.

When the piston 3 approaches the end of its movement to the left, a cylindrical projection 19 thereon of slightly smaller diameter than the bore 6 enters this bore and thus restricts the outward flow of working fluid from the lefthand end of the working cylinder through the bore 6, the ports 6a, the annulus 12 and the relief passage 18a, and this causes fluid pressure to build up in the lefthand end of the cylinder 2.

The piston valve 5 is thus forced by this buildup of fluid pressure to the left since it will overcome the force due to the pressure on the small annular face 21. The annulus 11 will thus be connection through the ports 6a and the bore 6 to the lefthand end of the working cylinder 2 so that fluid pressure now passes from the passage 18 to the lefthand end of the cylinder 2 through the ports 6a and the bore 6. The piston 3 will therefore be moved to the right, in view of the fact that the eifective area of its lefthand working face is considerably greater than that of its righthand annular face, although both these faces are now subject to working fluid pressure from the passage 18, working fluid simultaneously being expelled from the righthand end of the working cylinder 2 through the bore of the pilot valve 13.

As the piston 3 approaches the end of its movement to the right, an annular shoulder 20 on the piston, of slightly smaller diameter than the bore of the pilot valve 13 enters this bore to restrict the flow of fluid out through this bore and thus cause pressure to be built up between the annular face of the piston 3 and the annular face at the lefthand end of the pilot valve 13. The pilot valve 13 is therefore moved to the right, thus cutting otI communication between the chamber 10 and the relief passage 18a, the passage 10a and the annuli 17 and 16, and bringing the chamber 10 into communication 4 through the annulus 17 with the righthand end of the working cylinder 2 and hence with working fluid pressure from the passage 18.

The valve 5 is thus moved by the pressure thus created in the chamber 10 to the right i.e. again into the position shown, thereby connecting the lefthand end of the working cylinder 2 through the ports 6a and the annulus 12 to the relief passage 18a. The piston 3 therefore now moves again to the left, as does the pilot valve 13, due to the fact that the righthand end 'of the valve 13 is of larger diameter than its lefthand end, the valve 5 being maintained in the position shown by the pressure in the annulus 11 acting on the small annular area 21. When the projection 19 again enters the bore 6 towards the end of the travel of the piston 3 to the left, the pressure thus built up in the left hand end of the cylinder 2 again moves the valve 5 to the left to bring about the return movement of the piston 3 to the right in the manner above described and so on.

At low speeds, that is to say, for example, when starting up the apparatus, the operation of the

valves

5 and 13 may be effected by direct mechanical engagement with the appropriate parts of the working piston 3, since under these conditions the piston 3 may be moving so slowly that towards the end of its movement in the appropriate directions the rate of escape of fluid between the part 20 and the bore of the valve 13 on the one hand, and/or between the part 19 and the bore 6 on the other hand, may be such that the requisite pressures to cause the movements of these valves are not built up.

In the construction shown in FIGURE 2 the apparatus comprises a three-part casing 21 formed to provide a cylindrical bore in which is arranged for limited reciprocation a sleeve 22 within which is arranged to reciprocate a working piston 23 having a piston rod 24 passing through a sealing gland indicated at 25 at one end of the casing. The lefthand end 21a of the casing 21 is formed with an inwardly extending plug-like projection having a part 26 of larger external diameter and a part 27a of smaller external diameter, and these parts make sliding working fits respectively with an end portion 22a of the sleeve 22 and with a bore in an internal partition or diaphragm 22b formed on the sleeve 22 as shown.

Formed in the bore of the casing 21 within which the sleeve is mounted to reciprocate are two annular chambers 27, 28 communicating with one another and with a relief passage 29, while formed in the end 21a of the casing is a supply passage 30 communicating with a source of working fluid pressure and leading to ports 31 communicating with an annular space 32 between the diaphragm 22b and the end of the part 26, and to

ports

32 and 33 in the part 27a. The supply passage 30 also communicates continuously through a passage 34 with the righthand end of the bore in which the sleeve 22 lies. The righthand end of the sleeve 22 is provided with an internal flange 220.

An annular projection 2311 on the lefthand end of the piston 23 is arranged to enter the bore of an internal rib 22d on the sleeve 22 when the piston 23 approaches the end of its travel to the left, while a shoulder 23b on the righthand side of the piston 23 is arranged to enter the bore of the internal flange 220 on the sleeve 22 when the piston approaches the end of its travel to the right.

The operation of the apparatus is as follows: Assuming the working piston 23 and the sleeve 22 to be in the position shown, it will be seen that the righthand end of the working chamber represented by the bore of the sleeve is in permanent communication through the passage 34 with the supply passage 30, while the lefthand end of the working chamber is in communication with the supply passage 30 through the ports 33. The working piston 23 will thus move to the right and expel working fluid through the bore of the internal flange 220 as it does so. As the working piston approaches the end of its travel to the right the shoulder 23b enters the bore of the internal flange 22c and thus restricts the outflow of fluid piston 23 is now moved to the left by the working pressure acting on its righthand annular face, and expels working fluid through the ports 22e and relief passage 29. As the working piston 23 approaches the end of its travel to the left, the annular projection 23a enters the bore of the internal rib 22d to restrict outflow of fluid from the lefthand end of the working chamber through the ports 22e so that fluid pressure is built up on the lefthand end of the working chamber and, by acting on the righthand face of the diaphragm 22b causes the sleeve 22 to move to the left, thus reestablishing communication between the left hand end of the working chamber and the inlet passage 30 through the ports 33 and thereby causing the return movement of the piston to the right in the manner described above.

In the alternative construction shown in FIGURE 3, the arrangement is similar in many respects to that shown in FIGURE 2 and comprises a casing 34 formed to provide a bore in which is mounted for limited reciprocation a sleeve 35. In this construction the sleeve 35 has an internal flange 35a at its righthand end and is formed at its lefthand end with a part 35b having a bore of substantially smaller diameter than the remaining part of the bore of the sleeve, the part 35b being provided with an external rib 35c constituting a stop while an internal rib 35d with radial ports 35a is formed on the part of the sleeve immediately adjacent to the part 3512. Formed in the bore in which the sleeve 35 lies are an annulus 36 communicating with a relief passage 37 and an annulus 38a communicating with a supply passage 39a for working fluid under pressure. The supply passage 39 also communicates through a passage 40a with the righthand end of the bore while the space in which the left hand end face of the part 35b lies communicates with the relief passage 37. The piston 38 in this construction is generally similar to the piston 23 in the construction shown in FIGURE 2 and is provided with a piston rod 39 passing through a gland 40 in one end of the casing as shown. Thus the piston 38 has an annular projection 41 on its lefthand face similar to the projection 23a in the construction shown in FIGURE 2, and is provided with a shoulder 42 similar to the shoulder 23b in the construction shown in FIGURE 2. The projection 41 is arranged to enter the bore of the internal rib 35d as the piston approaches the end of its movement to the left, while the shoulder 42 is arranged to enter the bore of theinternal flange 35a when the piston approaches the end of its travel to the right.

The operation of the apparatus shown in FIGURE 3 is as follows:

Assuming that the sleeve 35 is in the position shown, it will be seen that the righthand end of the working chamber is in permanent communication with the supply passage 39. and that the lefthand end of the working chamber is in communication with the supply passage through the ports 35e'" so that the piston 38 will move to the right. As the piston approaches the end of its travel to the right, the shoulder 42 will enter the bore of the flange 35a and thus restrict the outflow of working fluid from the righthand end of the sleeve 35 and cause pressure to be built up between the annual righthand face of the piston and the lefthand face of the flange 35a. 'lnis pressure will thus move the sleeve 35 to the right. This movement, the extent of which will be determined by the rib 35c meeting a shoulder indicated at 43 on the casing, will move the ports 35e out of communication with the '6 supply passage 3% and into communication through'the annulus 36 with the relief passage 37 so that the lefthand end of the working chamber is now open to the relief passage 37 and the piston therefore now moves to theleft. Towards the end of its travel to the left the annular projection 41 on the piston enters the bore of the internal rib 35d and thus restricts the outflow of working fluid from the lefthand end of the working chamber and causes a pressure to be built up between the lefthand face of the piston and the annular face on the sleeve represented by the face of the rib 35d and the adjacent face of the part 3511 so that the sleeve 35 is moved by this pressure to the left to bring the lefthand end of the working chamber again into communication with the supply passage 39a and cut off communication between such lefthand end of the working chamber and the relief passage 37, thus causing the return movement of the piston to the right in the manner above described, and so on.

In the constructions shown in FIGURES 2 and 3, ports are provided in the

projection

23a and 41 while ports are also shown leading radially through the

sleeve

22 or 35 adjacent to the flanges 22c and35a. The purpose of these ports is to provide leakage paths for the flow or working fluid from the ends of the working chamber, during the last part of the movement of the piston in each direction, having the appropriate characteristics to cause the required build-up of pressures to move the sleeve 22 without undue shock and in accordance with the speed range of the apparatus. In each case it will be appre ciated that part of the leakage path will normally be constituted by the clearance between the appropriate parts on the piston and the bores in the sleeve which such parts enter towards the ends of the travel of the piston, but in many cases it may be convenient to provide a predetermined comparatively small clearance between the parts on the piston and the bores which they enter and to increase the leakage path to some predetermined extent by means of ports such as those indicated. I

It will be appreciated that in the construction shown in FIGURES 2 and 3, during slow operation of the ape paratus as, for example when start-ing, the movements of the

sleeves

22 and 35 may be caused by direct engagement of parts on the piston with parts on the sleeve, that is to say under conditions when the rate of movement of the piston is so slow as not to build up the appropriate fluid pressures for moving the sleeve.

What I claim as my invention and desire to secure by Letters Patent is:

1. A fluid-operated reciprocating device comprising a working cylinder, a working piston arranged within and for reciprocation relatively to the working cylinder and forming with the working cylinder pressure chambers at the two ends of the working cylinder in which fluid pressure will act respectively on oppositely directed working faces of the working piston, and control valve apparatus comprising parts disposed at opposite ends of and arranged for limited reciprocation relatively to the working cylinder and having operating faces on which fluid pressure can act to cause said limited reciprocation the working piston carrying parts which as the piston approaches the end of its movement in each direction relatively to the working cylinder restrict the fluid flow from such end of the working cylinder and thereby cause fluid pressure to be built up between the adjacent face of the working piston and the operating face on the adjacent part of the valve apparatus to move such part of the valve apparatus in the same direction as the piston is moving to cause reversal of the working piston movement.

2. A fluid-operated reciprocating device as claimed in claim 1, in which the said valve apparatus comprises separate reciprocating valve members disposed respectively at opposite ends of the Working cylinder and each having an outflow port through which outflow of the working fluid from its end of the working cylinder takes place as the working piston moves towards it, and in which the said parts carried by the working piston partially or wholly close said outflow ports respectively in the two valve members to restrict the outflow of fluid through each of such outflow ports to cause the said pressure build-up between the adjacent piston face and the said operating face of the adjacent valve member and cause the latter to be moved to cause reversal of the direction of movement of the working piston.

3. A fluid-operated reciprocating device as claimed in claim 2 including a piston rod rigid with the working piston, a sea] at one end of the working cylinder through which the piston rod passes and slides and in which the valve member at the end of the working cylinder adjacent to said gland is of tubular form with a bore which constitutes said fluid outflow port at said end of the working cylinder and also constitutes a fluid inlet port, through which bore the piston rod passes with substantial clearance, and wherein the piston carries a shoulder of slightly smaller diameter than the said bore which shoulder en ters the said bore during the latter part of the movement of the working piston towards said valve member to constitute the part which restricts the outflow of fluid and hence causes the said pressure buildup in the adjacent end of the working cylinder to move the valve member.

4. A fluid-operated reciprocating device as claimed in claim 3, in which the valve member at the end of the Working cylinder remote from the piston rod is of the piston type having a bore opening into the working cylinder and constituting an inlet and an outlet port, and in which the adjacent face of the piston carries a. cylindrical projection of somewhat smaller diameter than that of said bore which projection enters said bore towards the end of the travel of the working piston towards the adjacent end of the working cylinder and constitutes the part which eflects the said restriction or outflow of fluid and build-up of pressure to cause movement of the said valve member.

5. A fluid-operated reciprocating device as claimed in claim 4, in which the said valve member through which the piston rod passes controls the connection respectively to a source of working pressure and to a relief passage of a chamber the pressure in which acts on a face of the valve member at the other end of the working cylinder whereby the valve member through which the piston rod passes acts as a pilot valve controlling movement of the valve member at the other end of the working cylinder, which latter valve member controls the flow of working fluid to and from the working cylinder for causing reciprocation of the working piston.

6. A fluid-operated reciprocating device as claimed in claim 1, including a piston rod rigid with the working piston, 21 seal at one end of the working cylinder through which the piston rod passes and slides, said end of the working cylinder being formed with a fluid outlet passage, and in which the valve member at the end of the working cylinder adjacent to said seal is of tubular form with a bore which communicates with said fluid outflow passage at said end of the working cylinder and also constitutes a fluid inlet port, through which bore the piston rod passes with substantial clearance, and wherein the piston carries a shoulder of slightly smaller diameter than the said bore which shoulder enters the said bore during the latter part of the movement of the working piston towards said valve member to constitute the part which restricts the outflow of fluid and hence causes the said pressure build-up in the adjacent end of the working cylinder to move the valve member.

7. A fluid-operated reciprocating device as claimed in claim 6, in which the valve member at the end of the working cylinder remote from the piston rod is of the piston type having a bore opening into the working cylinder and constituting an inlet and an outlet port, and in which the adjacent face of the piston carries a cylindrical projection of somewhat smaller diameter than that of said bore, which projection enters said bore towards the end of the travel of the working piston towards the adjacent end of the working cylinder and constitutes the part which effects the said restriction or outflow of fluid and build-up of pressure to cause movement of the said valve member.

8. A fluid-operated reciprocating device as claimed in claim 7, in which the said valve member through which the piston rod passes controls the connection respectively to a source of working pressure and to a relief passage of a chamber the pressure in which acts on a face of the valve member at the other end of the working cylinder whereby the valve member through which the piston rod passes acts as a pilot valve controlling movement of the valve member at the other end of the working cylinder, which latter valve member controls the flow of working fluid to and from the working cylinder for causing reciprocation of the working piston.

9. A fluid-operated reciprocating device as claimed in claim 1, in which the valve apparatus comprises a sleeve disposed within the working cylinder and within which the working piston reciprocates, the sleeve having adjacent to its ends parts with bores of smaller internal diameter than the working piston, and wherein the working piston carries parts adjacent to its working faces which, towards the ends of its travel enter said bores and constitute the said parts which restrict the outflow of working fluid from the ends of the working cylinder and cause the said build-up of pressure and movement of the valve member.

10. A fluid-operated reciprocating device as claimed in claim 1, including parts on the working piston which if the valve apparatus is not moved by the build-up of the appropriate pressure towards the end of the travel of the working piston in either direction relatively to the working cylinder, directly engages a part on the valve apparatus to cause such movement of the valve apparatus by said direct engagement.

11. A fluid-operated reciprocating device as claimed in claim 1 which includes a piston rod attached to the working piston, a seal at one end of the working chamber through which the said piston rod passes and slides, and wherein the end of the working cylinder adjacent to the piston rod is continuously connected to a source of working fluid under pressure and the said valve apparatus connects the other end of the working cylinder alternately to the source of working fluid pressure and to a relief passage.

References Cited in the file of this patent UNITED STATES PATENTS 1,582,614 Kusunoki et al Apr. 27, 1926 1,843,958 Smith Feb. 9, 1932 2,406,747 Davis Sept. 3, 1946 2,720,864 Smith Oct. 18, 1955 2,804,052 Halladay et a1. Aug. 29, 1957 2,919,678 Sublett et al. Jan. 5, 1960