US3606818A - Fluid-operated reciprocating motors - Google Patents

Abstract

A RECIPROCATING FLUID OPERATED MOTOR INCLUDING TWO INTERCONNECTED SPACED CO-AXIAL PISTONS OF DIFFERENT DIAMETERS LYING IN TWO CORRESPONDING SPACED CYLINDERS SEPARATED BY AN INTERMEDIATE WALL, MEANS FOR INTRODUCING PRESSURE FLUID ON ONE SIDE OF THE WALL AND FOR EXHAUSTING FLUID FROM THE OTHER SIDE OF THE WALL AND AUTOMATIC VALVE MEANS CONTROLLING THE FLOW OF FLUID THROUGH PASSAGES IN THE WALL INCLUDING TWO VALVE PLATES INTERCONNECTED BY SPACERS OF GREATER EFFECTIVE LENGTH THAT THE THICKNESS OF THE WALL. ONE VALVE PLATE IS ARRANGED TO CLOSE THE THROUGH PASSAGES AND THE OTHER PLATE HAS ALIGNED OPENINGS BUT IS ARRANGED TO CLOSE THE OUTLET DUCT. THE MOTOR MAY ALSO INCLUDE AUTOMATIC VALVE MECHANISM TO HOLD THE RECIPROCATING PISTONS STATIONARY AT ONE END OF THEIR TRAVEL.

Description

Sept. 21, 1971 H. HIRN 3,606,818

FLUID-OPERATED RECIPROCATING MOTORS Filed June 27. 1969 2 Sheets-Sheet 1 FIG INVENTOR 1 /5 Mur hm/v BY W raj ATTORNEYS Sept. 21, 1971 H, R 3,606,818

FLUID-OPERATED RECIPROCATING MOTORS Filed June 27, 1969 2 Slxeets-Sheet 8 INVENTOR MEL Ml/Tfl/k/V BY tax/r ATTORNEYS United States Patent U.S. Cl. 91-329 13 Claims ABSTRACT OF THE DISCLOSURE A reciprocating fluid operated motor including two interconnected spaced co-axial pistons of different diameters lying in two corresponding spaced cylinders separated by an intermediate wall, means for introducing pressure fluid on one side of the wall and for exhausting fluid from the other side of the wall and automatic valve means controlling the flow of fluid through passages in the wall including two valve plates interconnected by spacers of greater effective length than the thickness of the wall. One valve plate is arranged to close the through passages and the other plate has aligned openings but is arranged to close the outlet duct. The motor may also include automatic valve mechanism to hold the reciprocating pistons stationary at one end of their travel.

The invention relates to a pressure fluid-operated device for generating a reciprocating movement and comprising a piston-cylinder unit with a fluid inlet and outlet. Such devices are suitable for many types of machine, in which a tool or machine part has to perform a reciprocating movement, e.g. stamping and pressing machines, rams, saws, riddling machines, conveyor apparatus and the like.

In previous devices of this type, incorporating a cylinder enclosing a differential piston which can be subjected to pressure fluid on both sides, the pressure fluid supply and discharge to and from the two cylinder spaces separated by the differential piston has been controlled by valves actuated by the piston rod in the extreme positions of the piston, so as to connect one cylinder space with the pressure source and at the same time connect the other cylinder space with a discharge pipe or, if compressed air is used as the operating medium, to atmosphere. This means that reversing valves are necessary, the adjustment of which presents considerable difficulty and which make the device undesirably expensive.

It is an object of the present invention to provide a device of the type mentioned above, which is of simple and robust construction and which is therefore capable of being manufactured economically and reliable in operation.

Broadly the invention consists in a pressure fluid-operated device for producing a reciprocating movement, comprising a housing having two coaxial cylinder spaces of different diameters and an intermediate wall, a pair of pistons movable in the spaces and connected to each other by a piston rod passing through the intermediate wall, the wall also having a through passage opening into opposite faces of the wall, and including two plate valves positioned on opposite sides of the intermediate wall to control the openings of the through passage, the plate valves being held apart at a fixed distance from each other in excess of the thickness of the intermediate wall by means of a spacer passing through the wall, and arranged to be operated by relative movement between the pistons and the housing, a discharge duct emerging into the face of the intermediate wall adjacent the larger cylinder space, to be controlled by the respective valve plate, and an inlet duct communicating with the smaller cylinder space.

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The supply and discharge of pressure fluid to and from the two cylinder spaces is thus controlled by the reversing valve formed by the plate valves disposed within the housing between the two cylinder spaces, and the pistons and piston rod may therefore be dimensioned without regard to the accommodation or actuation of the valves. As a result the valves do not require any special expensive seals, since they are totally enclosed. The .actuation of the plate valves results from the relative movement between the connected pistons and the housing, the housing normally being stationary while the pistons perform the reciprocating movement so as to reverse the plate valves when they reach their respective extreme positions. -It is also possible for the pistons to remain stationary while the cylinder performs the reciprocating movement, in which case the tool or machine part to be moved is connected to the cylinder.

By virtue of the fact that the pistons seal off the cylinder spaces, the outer ends of the cylinder spaces may be open, so that the provision of cylinder covers is unnecessary.

In order to keep the diameters of the pistons as small as possible, as is expedient when high pressures are being used, and which also assists in reducing the overall size of the device, the inner ends of the cylinder spaces adjacent the intermediate Wall may each have a relatively large diameter recess to accommodate the respective plate valve.

The plate valves are conveniently operated by the associated pistons through spring means, in order to cause an abrupt reversal and to prevent the pressure medium from escaping directly into the discharge duct from the supply duct during the reversal process. The spring means are preferably braced on the housing when in the inoperative state, and preferably the spring means associated with the two plate valves have different degrees of initial stress, so that when the device is put into operation, one plate valve will be resting on its valve seat, and the device can start up in any position of the pistons.

In order to diminish the pressure loading on the plate valves, the facing surfaces of the plate valves which cooperate with the mouths of the through passage in the intermediate wall may be locally raised so that partial balancing of the pressure on both sides of the plate valves occurs.

The supply duct may be positioned in an outwardly extending piston rod or directly in the housing.

In order to halt the device in an inoperative position at one extreme position of the pistons, the smaller diameter cylinder space may be provided with a pressure relief valve. 'In the case of a substantially vertically disposed apparatus, after this valve has been opened, the desired inoperative position will be achieved by the force of gravity, or for example by a spring.

Another possible method of providing an inoperative position in one extreme position of the pistons consists in disposing a shut-off valve in the discharge duct or in the discharge pipe. If the shut-off valve is closed, while pressure medium is being supplied to the larger diameter cylinder space, then the pistons, after the extreme position has been reached, cannot travel back in the opposite direction since the closed shut-off valve prevents the pressure medium escaping out of the larger-diameter cylinder space. In order to provide an inoperative position in an extreme position independently of the direction in which the pistons happen to be travelling at the time, the shutoff valve may be operated automatically by the pressure in the larger-diameter cylinder space.

By way of example, two embodiments of the invention will now be described in greater detail with reference to the accompanying drawings, in which:

FIG. 1 is a longitudinal section through a first embodiment of the invention, and

FIG. 2 is a longitudinal section through a second embodiment, similar parts being indicated by the same reference numerals.

Referring firstly to FIG. 1, this shows a housing 1 having two coaxial cylinder spaces 2 and 3 of different diameter, the spaces being positioned on opposite sides of an intermediate wall 4. Movably enclosed in the cylinder spaces 2 and 3 are pistons 5 and 6 respectively. The pistons 5 and 6 each have a diameter corresponding to the diameter of their cylinder spaces 2 and 3 respectively, and are connected rigidly to each other by a piston rod 7 which extends through the intermediate wall 4. The pistons 5 and 6 and the piston rod 7 are guided in the housing by packings 8 which also act as fluid seals. Secured to an extension 9 at one end of the piston rod 7 is a tool, not shown, for example the stamping plate of a soil consolidating device.

The annular wall faces 10 and 11 of the intermediate wall 4 have valve seats for plate valves 12 and 13 which are held by spacers 15 at a fixed distance from each other, in excess of the thickness of the intermediate wall 4, so that only one or other plate valve 12, 13 can rest on the corresponding wall face 10 or 11 respectively. The intermediate wall 4 is also formed with through passages or ducts 16, having openings on both sides of the wall. The openings in the wall face 11 are capable of being closed by the plate valve 13, but the plate valve 12 has apertures 17 in line with the openings into the face 10. Into the wall face 10 facing the cylinder space 2 of larger diameter, also emerges a discharge duct 18 which can be closed by the plate valve 12. The smaller diameter cylinder space 3 communicates with a pressure medium supply duct 19 formed in the housing 1.

At their ends adjacent the intermediate wall 4, the cylinder spaces 2 and 3 have recesses 20, 21 of larger diameter to accommodate the plate valves 12, 13, so that the diameters of the pistons 5, 6 can be kept small. The plate valves 12, 13 are engaged by springs 22, 23 in the form of pairs of radially corrugated annular plates which are located in and abut against the housing 1 through spring plates 24, 25. The spring plates 24, 25 are guided on the piston rod 7 but allow fluid to flow into and out of the spaces 2, 3, and act in the manner described below in conjunction with the pistons 5, 6 in order to operate the plate valves 12, 13.

The device shown in FIG. 1 functions in the following manner In the illustrated position of the plate valves 12, 13, the pistons 5, -6 will move downwardly under the action of the pressure medium supplied through the duct 19, since the ducts 16 are covered by the plate valve 13 and the discharge duct 18 is open. The pressure therefore acts above the piston 6, while the fluid medium in the cylinder space 2 can escape through the duct 18. Upon further movement of the pistons 5, 6 downwardly, the piston 5 engages the spring plate 24, thus compressing the spring 22. When the reaction of the spring 22 is sucient to overcome the upward force exerted on the plate valve 13 by the pressure in the recess 21 and by the spring 23, the plate valve 12 is abruptly pressed downwards onto the wall face 10, shutting off the discharge duct 18, and the plate valve 13 is simultaneously lifted off the wall face 11 by the spacers 15. The pressure medium supply through the duct 19 can now pass through the ducts 16 into the cylinder space 2 and since this latter has a greater diameter than the cylinder space 3, the pistons 5, 6 in the drawing move upwardly. In the upper extreme position of the pistons 5-, 6, the plate valve 13 is again pressed onto its seating and the process described is repeated.

In order to achieve a definite location of one of the plate valves 12, 13 in the inoperative position, the plate springs 22, 23 are provided with differing initial com- 4 pressions. This ensures that the device starts to operate with the supply of pressure medium, since the plate valves 12, 13 cannot be located in an intermediate position in which the pressure medium could flow through the ducts 16 directly into the discharge duct 18.

In order to permit the device to be held stationary in one extreme position of the pistons 5, 6, a shut-off valve 27 is disposed in the discharge pipe 26. Thus when the shut-off valve 27 is closed, while the pistons 5, 6 are moving upwardly in the drawing, in other words while the plate valve 12 has closed the discharge duct 18, the pistons cannot any longer move downwardly after reaching the upper extreme position, since the pressure medium cannot escape from the cylinder space 2.

The embodiment illustrated in FIG. 2 differs initially from that shown in FIG. 1, in that the supply duct 19' is disposed in the extension 9 of the piston rod and discharges into the cylinder space 3 immediately above the smaller diameter piston 6. Another difference is the construction of the plate valves 12' and 13', which have facing surfaces 28 and 29 to co-operate with the mouths of the ducts 16 and 18, the surfaces being raised locally in order to achieve partial balancing of the pressures on both sides of the plate valves 12 and 13, in order to reduce the resultant hydraulic of pneumatic pressure holding these plate valves against the wall faces 10, 11.

In addition, the embodiment shown in FIG. 2 is provided with a pressure relief valve 30 through which the cylinder space 3 can communicate with the atmosphere or, in the case of hydraulic operation, with a return pipe. When the valve 30 is opened, the pressure medium supplied through the duct 19' is exhausted immediately without performing any work and the pistons 5, 6, move under gravity into an extreme position when the device is substantially vertical in operation. When the piston rod extension 9' is braced on the ground, as is the case with soil stamping devices, the housing 1 falls under its own weight until the spring plate 25 rests on the piston 6. If the device is arranged on an essentially horizontal longitudinal axis, than the extreme position can be achieved upon opening of the valve 30 by an appropriate spring loading of the pistons 5, 6.

Instead of the valve 30, the device may be held stationary in one extreme position of the pistons 5, 6, by means of a shut-off valve 27' which in operation corresponds to the shut-off valve 27 shown in FIG. 1, but in this case is operated by the pressure in the cylinder space 2. For this purpose, the shut-off valve 27' has a piston 31 which is normally held by a spring 32 in the open position in which the discharge duct 18 communicates with the discharge pipe 26. The device then operates as a reciprocating pressure medium motor, so long as pressure medium is being fed through the duct 19. A manually operated rotary valve 33 is included in the connection between the piston 31 and the cylinder space 20. The valve 33 has an exhaust port 34, and in the position shown in FIG. 2 the valve is open and the port 34 is closed. If the piston 31 is depressed by the pressure obtaining in the cylinder space 2, with the rotary valve 33 in the open position as illustrated, it will move against the resistance of the spring 32 and shut off the discharge duct 18. The pressure medium supplied via duct 19' can now move the pistons 5, 6 upwardly to the extreme position. In this extreme position, the plate valves 12, 13' are reversed in the manner described above in relation to FIG. 1, i.e. the plate valve 13' comes to rest on the wall face 11 and closes off the ducts 16, while the plate valve 12' is lifted and exposes the discharge duct 18, which however remains closed by the piston 31. Thus, since the pressure medium cannot escape from the cylinder space 2, the pistons 5, 6 remain in this extreme position. The same result happens if the piston 31 is depressed by pressure admitted via the rotary valve 33, when the pistons 5, 6 moved downwardly, in other words when the plate valves 12', 13' assume the position shown in FIG. 1. In this case, the pistons first perform their downward stroke and thereafter their upward stroke, final- 1y remaining stationary at the end of the upward stroke, since the shut-off valve 27', in contrast to the shut-off valve 27 in FIG. 1, can only be operated when pressure obtains in the cylinder space 2. This embodiment has the advantage that the pistons 5, 6 will halt at a definite selected end position independently of the direction in which they happen to be moving at the moment when the rotary slide valve 33 is operated, whereas with the simple shut-off valve 27 in FIG. 1, the pistons 5, 6 would remain stationary in the position shown if the shut-off valve 27 were operated at that moment, but would run into an extreme end position if the shut-off valve 27 is operated during upward movement of the pistons 5, 6.

Under normal operation, the rotary valve 33 is pivoted leftwards through 90 so that the pressure side of the piston 31 is exhausted to atmosphere via the control aperture 34, In the case of hydraulic operation the pressure side of the piston is connected with the discharge pipe 26 or directly with a reservoir, and in either case the spring 32 can displace the piston 31 into the open position.

If the device is operated with a non-compressible working medium, e.g. oil, then it may prove expedient to incorporate into the line between the cylinder space 2 and the rotary valve 33 a non-return valve and to incorporate a pressure storage means into the line between the rotary valve 33 and the shut-off valve 27'. This will prevent the fluid which loads the piston 31 for shut-01f purposes from being dispelled when the plate valve 12' is lifted off the wall face and the discharge duct 18 is not completely filled with oil.

I claim:

1. A pressure fluid-operated device for producing a reciprocating movement, comprising a housing having two coaxial cylinder spaces of difierent diameters and an intermediate wall, a pair of pistons movable in the spaces and connected to each other by a piston rod passing through the intermediate wall, the wall also having a through passage opening into opposite faces of the wall, and including two plate valves positioned on opposite sides of the intermediate wall, the plate valve in the smaller cylinder space controlling the opening of the through passage into the said smaller cylinder space the plate valves being held apart at a fixed distance from each other in excess of the thickness of the intermediate wall by means of a spacer passing through the wall, and arranged to be operated by relative movement between the pistons and the housing, a discharge duct emerging into the face of the intermediate wall adjacent the larger cylinder space, to be controlled by the plate valve in said larger cylinder space, and an inlet duct communicating with the smaller cylinder space.

2. A device according to claim 1, in which the remote ends of the cylinder spaces are open.

3. A device according to claim 1 in which the inner ends of the cylinder spaces adjacent the intermediate wall each have a recess of larger diameter to accommodate the respective plate valve.

4. A device according to claim 1, in which the plate valves are arranged to be operated by the associated pistons through spring means.

5. A device according to claim 4, in which the inoperative condition, the spring means react on the housing.

6. A device according to claim 4, in which the spring means associated with the two plate valves have different initial stresses or strengths.

7. A device according to claim 1, in which the facing surfaces of the plate valves which co-operate with the openings at the ends of the through passage have locally raised formations to provide partial pressure balancing of each plate valve.

8. A device according to claim 1, in which the inlet duct is located in an outwardly extending piston rod connected to one of the pistons.

9. A device according to claim 1, in which the inlet duct is formed in a wall of the housing.

10. A device according to claim 1, in which the smaller cylinder space is provided with a pressure relief valve.

11. A device according to claim 1, in which a shutoff valve is provided in the discharge duct.

12. A device according to claim 11, in which the shutoff valve is adapted to be operated automatically by the pressure in the larger diameter cylinder space.

13. A device according to claim 12, including a threeway on-otf relief valve, a non-return valve, and pressure accumulator means, disposed in the line between the respective cylinder space and the shut-01f valve.

References Cited UNITED STATES PATENTS 1,243,199 10/1917 Miller 91329 1,441,017 1/1923 Mattson et al. 91-329 3,017,868 1/1962 Ginder 91--329 FOREIGN PATENTS 471,139 2/1929 Germany 91-329 PAUL E. MASLOUSKY, Primary Examiner U.S. Cl. X.R. 91-348, 468

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