Piston-cylinder assembly

Abstract

A piston-cylinder assembly includes a cylinder having a cylinder interior filled with a fluid and divided by a piston, which is axially displaceable in cylinder, into a first working space and a second working space. A piston rod is arranged on piston and is guided through second working space and through an end-side second closure in a manner sealed off to the outside at the second end of the cylinder. The retraction stroke of piston and piston rod is restricted by a stop which is arranged in cylinder and against which piston comes to bear directly or indirectly, wherein the axial position of the stop in cylinder is variably adjustable by an adjustment device.

Claims

1. A piston-cylinder assembly, comprising: a cylinder having a first end and a second end and defining a cylinder interior, the cylinder having an end-side first closure at the first end and an end-side second closure at the second end; a piston axially displaceably disposed in the cylinder and dividing the cylinder interior into a first working space and a second working space; a piston rod arranged on the piston and guided through the second working space and through the end-side second closure in a manner sealed off to the outside at the second end of the cylinder; a stop arranged at a fixed position in the cylinder against which the piston can come to bear directly or indirectly at an end position of a retraction stroke of the piston and the piston rod into the cylinder so that the fixed position of the stop defines the end position of the retraction stroke of the piston and the piston rod into the cylinder; and an adjustment device actuatable to allow an axial adjustment of the fixed position of the stop in the cylinder and thereby allow adjustment of the end position of the retraction stroke, wherein the stop is a stop piston arranged displaceably in a sealed off manner in the cylinder, the stop piston dividing the first working space from a stop space between the stop piston and the end-side first closure at the first end of the cylinder, and the stop piston including a valve device adjustable by an actuating device from a closed position into an open position, the valve device connecting the first working space to the stop space in the open position of the valve device, and the stop piston can be guided towards the piston in the open position of the valve device.

2. The piston-cylinder assembly according to claim 1, wherein the valve device is a slide valve with a valve slide or a seat valve with a seat closing element, and wherein the actuating device is actuatable to move the valve slide or the seat closing element from the closed position into the open position.

3. The piston-cylinder assembly according to claim 2, further comprising an actuating rod protruding axially from the outside into the interior of the cylinder, the actuating device acting on the actuating rod, wherein the valve slide or the seat closing element can be moved from the closed position into the open position by the actuating rod.

4. The piston-cylinder assembly according to claim 3, wherein the piston has a projection rod, which protrudes into the first working space, the projection rod having a continuous coaxial through-bore and is enclosed by a telescopic sleeve which is telescopically displaceable relative to the projection rod, wherein the telescopic sleeve is selectively couplable in a force-fitting manner to the projection rod, the valve slide or the seat closing element of the valve device can be acted upon movably in its opening direction by an end of the telescopic sleeve facing the stop piston.

5. The piston-cylinder assembly according to claim 4, wherein a free end of the actuating rod protruding out of the projection rod into the interior of the telescopic sleeve has an expansion element protruding into a central opening of a ring-like friction element, wherein, upon actuation of the actuating rod by the actuating device, the friction element can be radially expanded and pressed against the inner wall of the telescopic sleeve.

6. The piston-cylinder assembly according to claim 3, wherein the piston rod has a continuous axial bore in which the actuating rod, which can be acted upon at its outer end with an actuating force, is guided in a sealed off and axial moveable manner.

7. The piston-cylinder assembly according to claim 3, wherein the actuating rod can be acted upon manually at its outer end with an actuating force through the actuating device.

8. The piston-cylinder assembly according to claim 3, wherein the actuating device includes an expansion material element with an expansion material piston configured to act on the outer end of the actuating rod with an actuating force.

9. The piston-cylinder assembly according to claim 1, further comprising an actuating device disposed on the piston rod that is operable to actuate the adjustment device when the piston is in the end position of the retraction stroke.

10. The piston-cylinder assembly according to claim 9, further comprising an actuating rod that protruding axially from the outside into the interior of the cylinder, the actuating device acting on the actuating rod.

11. The piston-cylinder assembly according to claim 10, wherein the adjustment device is adjustable by the actuating device via the actuating rod from a first position preventing the axial adjustment to a second position allowing the axial adjustment.

12. The piston-cylinder assembly according to claim 9, wherein the adjustment device is adjustable by the actuating device from a first position preventing the axial adjustment to a second position allowing the axial adjustment.

13. The piston-cylinder assembly according to claim 9, wherein the actuating device is disposed on a portion of the piston rod that is outside of the cylinder.

14. The piston-cylinder assembly according to claim 1, wherein the cylinder is filled with a pressurized gas.

15. The piston-cylinder assembly according to claim 1, further comprising a pretensioned spring acting on the stop piston and urging the stop piston towards the piston.

16. The piston-cylinder assembly according to claim 1, further comprising a magnet arranged on the stop piston, wherein the piston is composed of a ferromagnetic material or has a ferromagnetic part, the piston is coupled in a force-fitting manner by the magnetic field of the magnet to the stop piston when the piston bears against the stop piston.

17. The piston-cylinder assembly according to claim 1, wherein the valve device includes a closing element which can be axially moved by the actuating device.

18. The piston-cylinder assembly according to claim 1, wherein the adjustment device is an electromagnetically or electromechanically actuable valve device.

19. The piston-cylinder assembly according to claim 1, wherein the pretensioned spring which acts upon the stop piston is a helical compression spring supported with one end on the end-side first closure at the first end of the cylinder and with its other end on the stop piston.

20. A piston-cylinder assembly, comprising: a cylinder having a first end and a second end and defining a cylinder interior, the cylinder having an end-side first closure at the first end and an end-side second closure at the second end; a piston axially displaceably disposed in the cylinder and dividing the cylinder interior into a first working space and a second working space; a piston rod arranged on the piston and guided through the second working space and through the end-side second closure in a manner sealed off to the outside at the second end of the cylinder; a stop arranged at a fixed position in the cylinder against which the piston can come to bear directly or indirectly at an end position of a retraction stroke of the piston and the piston rod into the cylinder so that the fixed position of the stop defines the end position of the retraction stroke of the piston and the piston rod into the cylinder; and an adjustment device actuatable to allow an axial adjustment of the fixed position of the stop in the cylinder and thereby allow adjustment of the end position of the retraction stroke, wherein the adjustment device is an electromagnetically or electromechanically actuable valve device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention are represented in the drawing and are explained in greater detail below. In the drawings:

(2) FIG. 1 is a longitudinal sectional view of a first exemplary embodiment of a piston-cylinder assembly according to the present invention;

(3) FIG. 1a is an enlarged cut-out of the piston-cylinder assembly according to FIG. 1;

(4) FIG. 2 is a longitudinal sectional view of a second exemplary embodiment of a piston-cylinder assembly according to the present invention;

(5) FIG. 2a is an enlarged cut-out of the piston-cylinder assembly according to FIG. 2;

(6) FIG. 3 is a longitudinal sectional view of a third exemplary embodiment of a piston-cylinder assembly according to the present invention;

(7) FIG. 4 is a longitudinal sectional view of a fourth exemplary embodiment of a piston-cylinder assembly according to the present invention;

(8) FIG. 4a is an enlarged cut-out of the piston-cylinder assembly according to FIG. 4;

(9) FIG. 5 is a longitudinal sectional view of a fifth exemplary embodiment of a piston-cylinder assembly according to the present invention; and

(10) FIG. 5a is an enlarged cut-out of the piston-cylinder assembly according to FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(11) The piston-cylinder assemblies represented in the Figures have a cylinder 1 which is closed off at its ends by a first closure 14 and a second closure 15 and in which a piston 2 is arranged axially displaceably. Piston 2 divides the inner space of cylinder 1 filled with a fluid into a first working space 3 and a second working space 4.

(12) A piston rod 5 arranged on one side of piston 2 extends coaxially through second working space 4 and is guided to the outside through a guide and sealing unit 6 and second closure 15.

(13) Piston rod 5 has a continuous axial bore 7 in which an actuating rod 8 is guided axially displaceably. An actuating device 9 is arranged on the piston rod 5. The actuating device 9 acts on the end of actuating rod 8 protruding to the outside from piston rod 5 to drive the actuating rod 8 directly or indirectly in an axially moveable manner.

(14) A stop piston 10 in cylinder 1 is arranged axially displaceably in the end region of first working chamber 3 opposite piston rod 5, which stop piston 10 separates first working space 3 from a stop space 13 between first working space 3 and first closure 14 of cylinder 1. The push-in stroke of piston 2 and piston rod 5 can be restricted by stop piston 10 in that piston 2 or a component connected to piston 2 comes to hear against stop piston 10.

(15) There is arranged in stop piston 10 a slide valve 11 which has a valve slide 12 which is axially displaceable in a coaxial bore in stop piston 10 and which, in its unactuated position, blocks a connection from first working space 3 to stop space 13 and thus fixes stop piston 10 in its assumed position.

(16) In the embodiments of FIGS. 1-4a, to open the slide valve 11, piston rod 5 moves with piston 2 until piston 2 bears against stop piston 10. If actuating rod 8 is now displaced towards stop piston 10 by actuating device 9 so that the free end of actuating rod 8 projecting into cylinder 1 comes to bear at the end side against valve slide 12 and, in the case of further displacement, displaces it counter to the force of a spring 16 towards stop space 13, the slide valve 11 can be opened.

(17) As a result of opened slide valve 11, the fixing of stop piston 10 is released and fluid can flow out of stop space 13 into first working space 3 and vice versa.

(18) To achieve a larger stroke, stop piston 13 is displaced from piston 2 towards first closure 14 by further retraction of piston rod 5 into the cylinder 1.

(19) In the embodiment of FIGS. 1 and 1a, a smaller stroke can be achieved by allowing a pretensioned helical compression spring 17 arranged in stop space 13 and supported with one end on first closure 14 to act on the stop piston. If, in the case of opened slide valve 11, piston rod 5 is moved with piston 2 in the extension direction, stop piston 10 follows piston 2 because of the action by helical compression spring 17. In the now desired new end position of stop piston 10, actuating rod 8 is retracted again into axial bore 7 of piston rod 5 by actuating device 9, as a result of which valve slide 12 again moves into its end position as a result of it being acted upon by a valve spring 16 and the connection between stop space 13 and first working space 3 is closed. Stop piston 10 is thus fixed again.

(20) In the case of the exemplary embodiment of FIGS. 2 and 2a, the structure and the function are the same as in the case of the exemplary embodiments of FIGS. 1 and 1a except for the fact that no helical compression spring 17 is present. Instead, a magnet formed as a magnetic ring 18 is present on stop piston 10. In this embodiment, the piston 2 comprises a ferromagnetic material. If piston 2 comprising the ferromagnetic material moves towards stop piston 10, stop piston 10 is thus coupled to piston 2 by the magnetic field of magnetic ring 18.

(21) During opening of slide valve 11 in the manner described in relation to FIGS. 1 and 1a, piston rod 5 can thus be displaced with piston 2 and stop piston 10 coupled thereto into stop space 13 or into first working space 3 in order then to be fixed again in the new end position by closing slide valve 11.

(22) The structure of stop piston 10 with slide valve 11 and its actuation by actuating rod 8 of the embodiments of FIGS. 3 and 4 correspond to the embodiment of FIGS. 2 and 2a.

(23) In the case of the embodiment of FIGS. 5 and 5a, the structure of stop piston 10, which is acted upon by helical compression spring 17, with slide valve 11 and its function correspond to the structure and the function of the exemplary embodiment of FIGS. 1 and 1a.

(24) In the embodiment of FIGS. 5 and 5a, piston 2 possesses a projection rod 19, which protrudes into first working space 3 and includes a continuous coaxial through-bore 22. The projection rod 19 is enclosed by a telescopic sleeve 20 which is telescopically displaceable relative thereto. The end of telescopic sleeve 20 that faces stop piston 10 and projects beyond the free end of projection rod 19 includes a coaxial actuating pin 21, which projects towards stop piston 143. Actuating pin 21 projects through a coaxial pin opening 35 into a chamber 34 which is open with respect to first working space 3. A free end of actuating pin 21 has a radial expansion 36 of greater radial extent than pin opening 35, with the result that actuating pin 21 is movably arranged on stop piston 10 so that the actuating pin 21 can move axially through a length of an axial clearance 37.

(25) An axially conical expansion element 23 is arranged on the free end of actuating rod 8 projecting out of projection rod 19, which expansion element 23 protrudes into a correspondingly axial conical recess 38 of a radially elastically deformable carrier ring 39 which is connected to projection rod 19. Carrier ring 39 is in turn enclosed by a ring-like friction element 24. Upon actuation of release lever 26, expansion element 23 is pushed deeper into conical recess 38 of carrier ring 39 by actuating rod 8, as a result of which carrier ring 39 and ring-type friction element 24 enclosing it are radially expanded. As a result, friction element 24 is pressed against an inner wall of telescopic sleeve 20. Projection rod 19 connected to piston 2 and piston rod 5 is thus coupled to telescopic sleeve 20. By displacing piston rod 5, actuating pin 21 can thus overcome clearance 37 until actuating pin 21 bears against valve slide 12 and displaces valve slide 12 into the open position in which the connection between stop space 13 and first working space 3 is opened.

(26) Stop piston 10 is thus moved into the desired new end position by moving piston rod 5 and telescopic sleeve 20 coupled thereto. By moving back actuating rod 8, the coupling of telescopic sleeve 20 is released by piston rod 5, with the result that telescopic sleeve 20 is freely displaceable and spring 16 can displace valve slide 12 back into its closed position. As a result, the occupied end position of stop piston 10 is fixed.

(27) In order to avoid an opening of slide valve 11 if no opening actuation by actuating rod 8 is present, a spacer sleeve 32 which encloses telescopic sleeve 20 with a spacing is arranged on piston 2. In the event of an unactuated actuating rod 8 and retracted piston rod 5, spacer sleeve 32 comes to bear against stop piston 10, while telescopic sleeve 20 is freely displaceable on projection rod 19.

(28) In the embodiments of FIGS. 1, 1a and 5, 5a, actuating device 9 comprises a release lever 26 which extends radially with respect to piston rod 5 and projects with one end into a recess 27 directed transversely to the longitudinal extent of piston rod 5 in a connection piece 33 of piston rod 5 and is tiltable therein. Tilting is carried out by manual exertion of force on the free end of release lever 26 transverse to its longitudinal extent. As a result of the tilting, actuating rod 8 is displaced in the opening direction of slide valve 11.

(29) In FIG. 3, actuating device 9 is an electromechanical drive 28, by which actuating rod 8 can be displaceably driven, which is arranged at the outer end of piston rod 5.

(30) In the embodiment of FIGS. 4 and 4a, actuating device 9 includes an expansion material element 29 arranged on the outer end of piston rod 5. A piston of expansion material element 29 can be movably acted upon by expansion material 31. In the present case, a diaphragm 30 acts on actuating rod 8 and thus drives actuating rod 8 in a displaceable manner. Stop piston 10 is thus adjusted in a temperature-dependent manner by expansion material 31 which changes its volume in a temperature-dependent manner.

(31) Of course, the actuating device 9 may alternatively include any other suitable device arranged on the outer end of piston rod 5 to adjust actuating rod 8.

LIST OF REFERENCE NUMBERS

(32) 1 Cylinder 2 Piston 3 First working space 4 Second working space 5 Piston rod 6 Guide and sealing unit 7 Axial bore 8 Actuating rod 9 Actuating device 10 Stop piston 11 Slide valve 12 Valve slide 13 Stop space 14 First closure 15 Second closure 16 Valve spring 17 Helical compression spring 18 Magnetic ring 19 Projection rod 20 Telescopic sleeve 21 Actuating pin 22 Through-bore 23 Expansion element 24 Friction element 26 Release lever 27 Recess 28 Drive 29 Expansion material element 30 Diaphragm 31 Expansion material 32 Spacer sleeve 33 Connecting piece 34 Chamber 35 Pin opening 36 Radial expansion 37 Clearance 38 Conus recess 39 Carrier ring