WO1989002987A1

WO1989002987A1 - Lockable hydraulic cylinder

Info

Publication number: WO1989002987A1
Application number: PCT/EP1988/000835
Authority: WO
Inventors: Gerhard Reuber; Reinhard Nowack; Jürgen LINKE; Rainer Jesse; Uwe Nerger; Eugen Fleisch; Peter Thiele; Gerhard NÜSSLE
Original assignee: Alfred Teves Gmbh & Co Ohg; Daimler Benz Aktiengesellschaft
Priority date: 1987-09-26
Filing date: 1988-09-13
Publication date: 1989-04-06
Also published as: DE3872222D1; EP0334924A1; DE3732561C2; EP0334924B1; JPH02501403A; DE3732561A1; JP2701906B2

Abstract

A lockable hydraulic cylinder comprises a cylindrical tube (1) with at least one discharge connection (7), a working piston (3) sealed in the cylindrical tube (1) in which it slides, and a hydraulically operated closure element which engages with blocking elements (10). In order to achieve a compact locking unit which can also be incorporated in the cylinder and which has a small number of relatively moving parts of simple, compact design, the closure element is a differential piston (6) which travels in a sealed manner in a blind bore in the piston (3) and which is prestressed against the pressure in the direction of the locked position with an inlet space (8) adjoining the discharge connection (7). The diameter of the differential piston decreases near the inlet space (8) and the prestressed differential piston (6) exerts an outward radial force on the blocking elements (10). Radial recesses (11, 15) in which the blocking elements (10) engage are provided in the cylindrical tube (1) or in a component rigidly mounted on the latter, and in the piston (3).

Description

Lockable hydraulic cylinder

The invention relates to a lockable hydraulic cylinder according to the preamble of claim 1.

Hydraulic cylinders of this type are used universally in technology and are distinguished, inter alia, by the fact that they can hold larger forces securely in the locking position even without pressure medium. Such a piston-cylinder unit is known from DE-OS 31 43 040, a locking piston movable perpendicular to the direction of movement of the working piston being provided which can be displaced into a recess in the piston rod. This locking device requires a large amount of space and requires an additional pressure medium connection between the working piston and the locking piston. From DE-OS 35 40 277 a self-locking double-acting working cylinder is known in which a differential piston is axially displaceable on the one hand on its outer diameter in the housing and on the other hand with its inner channel is mounted on a housing-fixed socket, with a locking piston which on the one hand in the differential piston and on the other hand is mounted in the socket, the locking balls actuated. at this working cylinder three components move relative to each other within the housing, which is a relatively complicated structure; on the other hand, a complex pressure medium connection within the differential piston is required.

The invention is therefore based on the object of creating a generic hydraulic cylinder which is distinguished by a compact structure which can be integrated in the working cylinder, and which has a small number of relatively movable parts with a simple structure; the use of very small piston rods and piston diameters (6 to 16 mm) with very long strokes should be made possible.

This object is achieved by the characterizing features of claim 1.

A further solution to the problem is achieved in that a stepped piston, which is guided in a sealed manner in a blind bore of a cylinder base or a component rigidly connected to it, is provided as the closure element, which against the pressure in a working space connected to the pressure connection in the direction of

Locked position is biased, the portion of the cylinder bottom, in which the stepped piston is guided, protrudes into a recess in the front side of the working piston facing the input space, which has a radial undercut, into which the locking parts can be latched. A particularly favorable embodiment of the invention provides that the locking parts are designed as balls.

In order to create a working cylinder which can be locked in both end positions, it is particularly advantageous that a locking unit, in particular symmetrical to the radial plane, is provided on both end faces of the working piston and cylinder tube.

If the stepped piston is provided in a blind bore in the cylinder base or a component connected to it, it is advantageous if the section of the cylinder base into which the stepped piston is guided is surrounded radially by a return ring which is preloaded to a limited extent by a spring , because in this way the locking balls are secured against falling out.

An advantageous embodiment of the invention provides that the locking parts moving with the working piston have no contact with the cylinder tube in the unlocked position. It is therefore provided that the end of the stepped piston protruding into the entrance space projects in the locking position into a deflection bushing which is provided with a bevel which acts radially outward on the locking parts. This makes it possible for the stepped piston to clamp the locking parts in the unlocked position and for the latter to be moved outwards again only when the locking position is reached by the deflection bushing. Allow it Material or the quality of the cylinder tube that the locking parts act on the cylinder tube during the piston movement, so it is useful with the simultaneous elimination of the deflection bushing that the stepped piston is equipped with at least one conical section.

The function and other features essential to the invention result from the following description of three preferred embodiments of the invention.

This shows:

Fig. 1 shows a first embodiment

Fig. 2 shows a second embodiment of the invention in the locked state

3 shows an embodiment according to FIG. 2 in the unlocked state,

Fig. 4 shows a third embodiment of the invention.

In all figures, the same reference numerals are chosen for corresponding parts.

The hydraulic cylinder shown in Fig. 1 consists of a cylinder tube 1 which is screwed to the cylinder base 2 and in which the working piston 3 is axially displaceable and is guided by the sealing rings 4 and 5 sealed. The cylinder base 2 has a pressure connection 7 which can be connected to a pressure medium source and which is connected to the input space 8 also provided in the cylinder base 2. In the end face of the working piston 3 facing the input space 8, a blind bore 13 is provided, in which the stepped piston 6 is arranged to be axially displaceable and acted upon by the spring 14 in the direction of the input space 8. For this purpose, the spring 14 is supported on the one hand on the bottom of the blind bore 13 and on the other hand on a further blind bore 16 which is provided in the stepped piston 6. The stepped piston 6 is sealed by the sealing ring 17, which is located in an annular groove in the working piston 3 or locking piston 6.

The end section of the working piston 3 facing the input space 8 is provided on its jacket side with three radial through bores 15, in each of which a locking part 10 designed as a ball is guided so as to be radially movable. In the illustrated, locked position, the locking parts 10 are pressed radially outward into an annular groove-shaped radial recess 11 in the cylinder base 2 by the force of the spring 14 in conjunction with a first conical section 19 on the stepped piston 6. The sections of the locking parts 10 protruding from the working piston 2, in cooperation with the stop 12, prevent axial movement of the working piston 2.

In contrast, the working piston 3 should

Applying pressure medium hydraulically via the pressure connection 7 and the input space 8, the locking device described above unlocks itself. The stepped piston 6 pushed against the force of the spring 14 into the blind bore 13 of the working piston 2. Characterized in that the stepped portions of the stepped piston 6 facing the entrance space are each tapered in diameter, the locking parts 10 can move radially inward and thus release the locking in the piston head 2. During the movement of the working piston 3 in the cylinder tube 1, the locking parts 10 are pressed against the inner wall of the cylinder tube 1 by the remaining excess force of the spring 14 in connection with the second conical section 20 on the stepped piston with a small radial force component.

The working piston 3 can be reset hydraulically, for example, via a working chamber opposite the input space 8 on the other side of the working piston, or else mechanically via the piston rod 21 screwed into the working piston 3.

For the embodiment shown in FIGS. 2 and 3, essentially that which has already been explained in connection with FIG. 1 applies. Only the differences from the embodiments according to FIG. 1 are described below.

To act on the locking parts, the stepped piston 6 has a piston section 25 which is either very weakly conical or cylindrical, to which a cylindrical section 26 adjoins. As a result, in the unlocked state, as shown in FIG. 3, no radial force component acts on the locking parts 10 to the outside. As a consequence, that the locking parts 10 are clamped in the unlocked state between the edges 27, 28 on the working piston 2 or on the stepped piston 6 by the force of the spring 14 and hold in the engaged position.

There is therefore no contact between the inner wall of the cylinder tube and the locking parts 10 during the movement of the working piston 2 in the cylinder tube 1, as a result of which no special measures such as hardening, nitriding or galvanizing are necessary on the inner surface of the cylinder tube 1.

In order to release the locking parts 10 from this engaged position when the locking position is reached, a deflection bushing 29 is attached to the cylinder base 2 in the region of the input space 8. This has, on its end facing the working piston 3, an oblique chamfer 30 attached to the outer lateral surface. When the locking position is reached, the cylindrical section 26 of the stepped piston 6 moves into the deflection bushing 29, the locking parts 10 are moved radially outward by the application of the oblique chamfer 30. In order to achieve an optimal pressurization of the working piston 3 from the locked position, radial passage channels 31 are provided distributed over the circumference of the deflection bushing 29.

In the embodiment according to FIG. 4, it is provided that the locking parts 10 do not cover an axial stroke path with the working piston 3. The step piston 6 is sealed by the seal 42 and axially displaceable in an insert cylinder 41, which with the cylinder bottom

2 is clamped by the screw 43. For this purpose, a stepped, axial through bore is provided in the cylinder base 2; a sealing ring 44 is provided in an annular groove on the insert cylinder 41. In the locked state, as shown in Fig. 4, the insert cylinder 41 protrudes into an axial recess 45 which is in the working cylinder

3 is attached to the end facing the pressure connection 7. This recess 45 is provided with a radial undercut into which the locking parts 10 can be moved to lock the working piston 3. For this purpose, they are loaded radially outwards by the conical first step 46 on the step piston 6 in cooperation with the compression spring 48 acting on the step piston 6.

The working piston 3 is unlocked by introducing pressure into the pressure connection 7, which continues through the passage channels 49 in a radial expansion of the insert cylinder 41 into the working space 50 and from there through the radially extending channel 51 in the working piston 3. When the pressure is introduced, the stepped piston 6 is moved into the insert cylinder 41 against the force of the compression spring 48. Through the bevel 52 on the annular radially inward projection 53 on the working piston 3, the locking parts 10 are moved radially inward until they come to rest on the second step 47 of the step piston 6. Due to the pressurization, the working piston 3 moves away from the pressure connection 7, while at the same time the return ring 54, which radially surrounds the insert cylinder 41 and is biased by the return spring 55, the Working piston 3 is tracked until the stop 56 of the return ring 54 comes to rest on the step 57 of the insert cylinder 41. The return spring 55 is supported on the one hand on the radial extension of the insert cylinder 41, to which the passage 49 is also attached, and on the other hand on an outer step of the return ring 54. The path that the return ring 54 can travel conditionally through the return spring 55 is dimensioned such that the recesses 58, in which the locking parts 10 are guided, are passed axially. As a result, the locking parts 10 are secured against falling out of their recesses 58.

When the working piston 3 moves back in the direction of the locking position, the return ring 54 is displaced by the end face of the working piston 3 against the force of the return spring 55. If the projection 53 has passed over the recess 58 in the insert cylinder 41, the locking parts 10 are acted upon radially outwards by the prestressed stepped piston 6, which moves in the direction of the working cylinder 3. The working cylinder 3 is thus locked again.

Claims

1. Lockable hydraulic cylinder with a cylinder tube, at least one pressure connection, a displaceably arranged, displaceable working piston in the cylinder tube and with a hydraulically actuated closure element, through which locking parts can be brought into engagement, characterized in that the closure element as a in a blind bore (13) in Working piston (3) sealed step piston (6) is provided, which is biased against the pressure in an input space (8) connected to the pressure connection (7) in the direction of the locking position, that the step diameter of the step piston (6) to the input space (8 ) reduce that the stepped piston (6) is loaded by the pretension, the locking parts (10) act radially outwards and that radial recesses (11, 15.) in the cylinder tube (1) or a component rigidly connected to it and in the working piston (3) ) are provided, in which the locking parts (10) are branchable.

2. Lockable hydraulic cylinder with a cylinder tube, at least one pressure connection, a displaceably arranged, displaceable working piston in the cylinder tube and with a hydraulically actuated closure element through which locking parts can be brought into engagement, characterized in that as Closure element is provided in a blind bore of a cylinder base (2) or a rigidly connected to this component (41) stepped piston (6) which is provided against the pressure in a working space (50) connected to the pressure connection (7) in the direction of the locking position is biased, the portion of the cylinder bottom (2) in which the stepped piston (6) is guided, protrudes into a recess (45) in the pressure connection (7) facing the end of the working piston (3), which has a radial undercut, in which the locking parts (10) can be snapped into place.

3. Lockable hydraulic cylinder according to claim 1 or 2, characterized in that the locking parts (10) are designed as balls.

4. Lockable hydraulic cylinder according to one or more of the preceding claims, that a locking unit, in particular symmetrically to the radial plane, is provided on both end faces of the working piston (3) and the cylinder tube (1).

5. Lockable hydraulic cylinder according to claim 2, characterized in that the section (41) of the cylinder base (2) in which the stepped piston (6) is guided is surrounded radially by a return ring (54) which is displaceable to a limited extent by a return spring (55 ) is biased.

6. Lockable hydraulic cylinder according to one of the preceding claims, characterized in that the end of the stepped piston (6) projecting into the input space (8) in the locking position projects into a deflection bushing (29) which acts on the locking parts (10) to the outside oblique chamfer (30) is provided.

7. Lockable hydraulic cylinder according to one of the preceding claims, characterized in that the stepped piston (6) is equipped with at least one conical section (19).