Mechanical locking device for a hydraulic cylinder and hydraulic cylinder with such a device

Abstract

The invention relates to a mechanical locking device, which is designed for installation in or attachment on a hydraulic cylinder, comprising: at least one locking element which, in a locking position, interacts with a projection or a recess on a piston or a piston rod of the hydraulic cylinder, in order to lock the piston or the piston rod in a form-fitting manner; an activation element, which is adjustable relative to the locking element between an activation position and at least one deactivation position, and in the activation position holds the locking element in its locking position and / or in the deactivation provision releases the locking element; and, a hydraulic or pneumatic actuator that can be pressurised for the purpose of locking or unlocking for adjusting the activation element between the activation position and the deactivation position. According to the invention the locking element, activation element and actuator are designed as a preassembled assembly, for installation in or attachment on the hydraulic cylinder, and the assembly is rigidly connected to the hydraulic cylinder, at least in the longitudinal direction thereof, during assembly.

Description

[0001] Mechanical locking device for a hydraulic cylinder and hydraulic cylinder with such a

[0002] Description

[0003] The present invention relates to a mechanical locking device for installation in or attachment to a hydraulic cylinder, comprising at least one locking element which, in a locking position, interacts with a projection or recess on a piston or piston rod of the hydraulic cylinder to positively lock the piston or piston rod, an activation element which is adjustable relative to the locking element between an activation position and at least one deactivation position and, in the activation position, holds the locking element in its locking position and / or releases the locking element in the deactivation position, and a hydraulic or pneumatic actuator which can be independently pressurized for locking or unlocking purposes and which is used to adjust the activation element between the activation position and the deactivation position. The invention also relates to a hydraulic cylinder with such a locking device.

[0004] In safety-relevant applications, hydraulic cylinders are often designed so that the position of the piston rod is secured mechanically or hydraulically in the event of a fault, i.e., via positive or non-positive locking. This can be secured in the area of ​​the cylinder's end position (fully retracted or fully extended) or in the area, for example, of the center position. A simple positive locking mechanism can be used here, which positively prevents any movement of the cylinder after actuation.

[0005] A hydraulic cylinder with a mechanical locking device is described, for example, in DE 10 2020 119 237 B3 or DE 10 2020 127 621 A1. The locking device has various movable components that enable locking with movable locking elements. These can be balls, wedges, collet elements, etc. Because the locking device is located within the hydraulic cylinder, the assembly of such a hydraulic cylinder is complicated, time-consuming, and prone to assembly errors.

[0006] An object of the invention is therefore to provide a mechanical locking device for installation in or attachment to a hydraulic cylinder, which can be mounted easily and safely and enables reliable locking of the hydraulic cylinder.

[0007] The object is achieved by a mechanical locking device having the features of claim 1. Advantageous embodiments can be found in the dependent claims. The object is further achieved by a hydraulic cylinder having the features of patent claim 14.

[0008] In a locking device of the type mentioned at the outset, the invention provides that the locking element, activation element and actuator are designed as a pre-assembled assembly, as a so-called cartridge, for installation in or attachment to the hydraulic cylinder, and the assembly is rigidly connected to the hydraulic cylinder at least in its longitudinal direction during assembly.

[0009] The pre-assembled module can be installed into an existing hydraulic cylinder, e.g., plugged, screwed, or flanged. Only through this installation, when the piston rod is in the locked position, does a frictional connection between the piston rod and the end piece of the hydraulic cylinder occur via the locking element in its locked position. Another advantage is that the complexity of the actual hydraulic cylinder can be at least partially shifted to the locking device designed as a pre-assembled module, thus simplifying integration into an existing cylinder space. Furthermore, the locking position of the piston rod within the hydraulic cylinder can be defined simply by adjusting the length of the locking device.

[0010] In an advantageous embodiment, the assembly is designed to be inserted into the hydraulic cylinder and is attached adjacent to an end piece of the hydraulic cylinder. The assembly is thus located entirely within the hydraulic cylinder and is thus protected from damage, contamination, and tampering. The assembly is preferably secured within the hydraulic cylinder by means of a screw connection.

[0011] In particular, the assembly may be provided with one or more seals or sealing surfaces, with which it forms a sealing contact with an inner circumferential surface of the hydraulic cylinder after installation. Thus, part of the cylinder chamber can be used as the hydraulic chamber of the hydraulic actuator.

[0012] Regardless of whether the actuator utilizes part of the cylinder chamber, its hydraulic chamber is sealed against the working chamber(s) of the hydraulic cylinder and can be pressurized independently. Accordingly, the pressure required to deflect the hydraulic actuator is applied via control ports that are separate from the hydraulic ports of the hydraulic cylinder into which the assembly is installed.

[0013] The actuator is preferably hydraulically actuated. In principle, however, pneumatic actuation of the actuator can also be provided and is encompassed within the scope of the present invention. Therefore, if reference is made below to a hydraulic actuator by way of example, this can also be replaced by a pneumatic actuator with the same mode of operation. In this case, not only is the pneumatic actuator actuated independently of the pressurization of the hydraulic cylinder, but the pneumatic pressure supply must also be provided by a pneumatic pressure generator separate from the hydraulic pressure supply of the hydraulic cylinder.

[0014] Preferably, the activation element is axially adjustable, and the locking element is radially movable and held in its locking position radially against the piston or piston rod of the hydraulic cylinder. This results in a structurally compact, simple, and reliable device. The locking device can be designed in particular such that it engages with the locking element in a cavity formed in the piston and piston rod of the hydraulic cylinder, e.g., an axial bore, and the locking element is moved radially outward within the cavity in its locking position. Thus, the locking element locks inside the piston rod. This results in a particularly compact design.

[0015] In a preferred embodiment, the locking device comprises a sleeve-shaped component that protrudes from an end piece of the hydraulic cylinder into its cylinder chamber and extends into the cavity of the piston rod. The sleeve-shaped component can be used, in particular, to support the locking elements at its end.

[0016] The activation element can be designed as an inner tube or a mandrel that is longitudinally movable within the sleeve-shaped component and that carries an annular bead that serves as a locking catch in one end region and that holds the at least one blocking element in the blocking position in the activation position.

[0017] In principle, different types of locking bodies can be used as locking elements, such as pawls, catches, rollers, segment bodies, wedges, etc., and are encompassed within the scope of the present invention. In a preferred embodiment, a plurality of circumferentially distributed spring tongues are provided as the locking element, each of which has a locking lug at its end, which engages in a recess, in particular an annular groove, on the inside of the cavity of the piston rod.

[0018] The actuator is preloaded toward both the activated and deactivated positions by a return spring, so that it returns to the respective position when depressurized. Particularly in a single-acting hydraulic actuator unit, a return spring can be installed in the piston chamber facing away from the pressure. This spring chamber can conveniently be connected to a tank line / oil container. With the double-acting actuator unit, there is generally no preferred direction; instead, the unit behaves bistable and always remains in the position it was previously placed in by pressurization.

[0019] The hydraulic activator can preferably comprise a cylindrical housing part to be installed in the hydraulic cylinder, which, if appropriate, forms a hydraulic chamber together with the hydraulic cylinder, in which a control piston is mounted in a displacement-tight manner, and the control piston is connected to the activation element. When installed in the hydraulic cylinder, the housing part can preferably be sealed around its circumference against the cylinder to form the hydraulic chamber.

[0020] If the activation element is tubular and the control piston is annular with an open inner diameter, which is guided and sealed on its inside against a sleeve projecting into the tubular activation element and connected to the housing component, an axial inner space advantageously remains free through the locking device into the cavity of the piston rod, which can be used, for example, for the installation of a position measuring system.

[0021] The cylindrical housing part can in particular be provided with an external thread with which it can be screwed into a corresponding internal thread in the cylinder tube of the hydraulic cylinder in order to connect the locking device to the cylinder tube.

[0022] A hydraulic cylinder according to the invention has a cylinder chamber with a piston which is mounted therein in an axially displaceable, sealing manner and which carries a piston rod, and a locking device of the type mentioned above which is arranged at least partially within the hydraulic cylinder and which positively locks the piston or the piston rod in a locking position.

[0023] Further advantages and embodiments of the invention will become apparent from the following description of exemplary embodiments with reference to the figures. It shows:

[0024] Figure 1 shows a first embodiment of a hydraulic cylinder with a locking device in the form of a pre-assembled module, Figure 2 shows a second embodiment of a hydraulic cylinder with a locking device in the form of a pre-assembled module,

[0025] Figure 3a shows an actuator unit for a locking device with a return spring pre-tensioned in the direction of the deactivation position,

[0026] Figure 3b shows an actuator unit for a locking device with a return spring pre-tensioned in the direction of the activation position and

[0027] Figure 3c shows a double-acting actuator unit without return spring.

[0028] In the following described figures 1, 2 and 3a to c, a hydraulic cylinder or an actuator unit is shown in axial section, wherein the upper half of the sectional drawing shows the hydraulic cylinder or the actuator unit in the deactivation position with unlocked locking device and the lower half of the respective figure shows the hydraulic cylinder or the actuator unit in the activation position with mechanically locked piston rod.

[0029] The hydraulic cylinder 100 shown in Figure 1 comprises a cylinder tube 110 and a piston 111 mounted therein in a displacement-tight manner, which carries a piston rod 112. The piston 111 divides the interior of the cylinder tube 110 into two working spaces, namely the piston chamber 110a on the side of the piston 111 facing away from the piston rod 112 and the annular chamber 110b on the side of the piston rod 112. The piston 111 and the piston rod 112 are provided with a cavity 113 in the form of an axially extending bore. The annular chamber 110b and the piston chamber 110a can be alternately pressurized with hydraulic fluid via two hydraulic connections 114, 115 in order to displace the piston 111 within the cylinder tube 110. The piston rod 112 protrudes from the cylinder tube 110 at an end guide piece 116 and is sealed there by means of known piston rod seals (not shown).The opposite side of the cylinder tube 110 is fluid-tightly closed with an end piece 117 in the form of a cylinder base.

[0030] A special technical feature of the hydraulic cylinder is a mechanical locking device 120, which is mounted within the cylinder tube 110 and engages the cavity 113 in the piston 111 and piston rod 112. The locking device 120 cooperates with a recess 118 in the form of an annular groove formed in the inner peripheral surface of the cavity 113 to positively lock the piston 111 and piston rod 112 in the locking position predetermined by the position of the annular groove 118.

[0031] The locking device 120 comprises a hydraulic actuator 121 with a housing part 122 and a locking element 123 rigidly connected to the housing part 122 in the form of a clamping sleeve with multiple longitudinal slots. Due to the longitudinal slots, this clamping sleeve forms spring tongues towards its end, at the end of which an annular bead 124 is formed, serving as locking lugs. The clamping sleeve 123 is designed to extend slightly conically inward in the axial direction, whereby the spring tongues formed by the longitudinal slots can be moved resiliently outward when the piston 111 is in its locking position. The locking lugs 124 then engage in the annular groove 118 formed in the cavity 113 of the piston 111 and lock the piston 111 and piston rod 112 in a form-fitting manner.

[0032] In order to move the spring tongues of the clamping sleeve 123 outwards, a movable punch or mandrel 125, whose head 126 widens conically towards the end, runs within the clamping sleeve and serves as an activation element. If the punch 125 is adjusted to the left, as shown in the upper part of the drawing, it is in its deactivation position and releases the spring tongues acting as locking elements, so that they can move inwards into their unlocked position. If the punch 125 is adjusted to the right, as shown in the lower part of the drawing, its conically widened head 126 radially expands the clamping sleeve 123 and the locking lugs 124 engage in the annular groove 118 of the piston 111. The punch 125 thus serves as an activation element, which holds the locking element 123 in its locked position in the activation position and releases it in the deactivation position of the locking element 123.

[0033] A control piston 128, which supports the piston 125, serves to adjust the piston 125. For this purpose, a hydraulic chamber 127 is formed in the housing part 122 of the hydraulic activator 125, in which the control piston 128 is mounted in a displacement-tight manner. The hydraulic chamber 127, divided by the control piston 128, can be selectively pressurized with hydraulic fluid pressure via control connections 129, 129'. A return spring 130, which mechanically preloads the control piston 128 toward the activated position of the piston 127, ensures that the locking element 123, with its detent lugs 124, engages in the annular groove 118 of the piston 111 in the depressurized state, mechanically locking the piston. By applying pressure to the control connection 129', the control piston and with it the plunger 125 can be moved into the deactivation position in which it releases the locking element 123.

[0034] The mechanical locking device 120 is designed as a pre-assembled unit, a so-called cartridge, and is mechanically connected to the cylinder tube 110. For this purpose, an internal thread 119 is cut into the inner wall of the cylinder tube 110 in the area of ​​the end piece 117, into which the housing part 122 of the pre-assembled locking device 120 is screwed with a corresponding external thread. A tangential pin 133 driven through a corresponding bore serves as an assembly aid and prevents the pre-assembled locking device 120, which is spring-loaded by the return spring 130, from springing apart.

[0035] Grooves 131, 132 are formed on the outer circumference of the housing part 122 on both sides of the radially outgoing control connection 129, into which seals are inserted, by means of which the housing part 122 is sealed within the cylinder tube 110 with respect to the piston chamber 110a.

[0036] A second embodiment of a hydraulic cylinder with a mechanical locking device 220 is shown in Figure 2. The hydraulic cylinder 200 again has a cylinder tube 210, with a piston 211 and piston rod 212 mounted therein in a sealed manner for longitudinal displacement. The annular chamber 210b and piston chamber 210a can be pressurized with hydraulic fluid via hydraulic connections 214, 215 in order to displace the piston 211 within the cylinder tube 210. The piston rod 212 protruding from the cylinder tube 210 is mounted on the guide piece 216 in a sealed manner.

[0037] Piston 211 and piston rod 212 are provided with an axially extending cavity 213, which in this case is, however, considerably larger than in the first embodiment. On the inside of the cavity 213, an annular groove 218 is formed at the level of the piston 211, into which a locking lug is inserted for the mechanical locking of the piston 211 and the piston rod 212.

[0038] 224 provided locking element 223 engages. The locking element 223 is formed, as in the previous embodiment, by elastic spring tongues as part of a clamping sleeve with multiple slots in the longitudinal direction. In the relaxed state, the spring tongues are inclined slightly inward so that they do not rest against the inner wall of the cavity 213 of the piston 211 and piston rod 212. By means of an inner tube 225 serving as an activation element, which has a conically widening annular bead 226 at its end, the clamping sleeve can be expanded and the spring tongues with the locking lugs 224 can be pushed outwards. For this purpose, the inner tube 225 is hydraulically adjustable via a control piston 228. The control piston 228 is a component of a hydraulically operated actuator 221 and is mounted for longitudinal movement in a hydraulic chamber 227 in the housing part 222 of the actuator 221. The control piston 228 can be adjusted by applying pressure to control ports 229, 229'.A return spring 230 biases the control piston 228 toward the activation position of the locking device 220. The activation element is not a solid piston as in the first embodiment, but an inner tube.

[0039] 225 is used, the control piston 228 is annular with a corresponding inner diameter and is guided and sealed on its inner side against a sleeve 234 that projects into the inner tube 225 and is connected to the housing component 222. Thus, an axial interior space remains free through the locking device 220 into the cavity 213 of the piston rod 212, which can be used, for example, for installing a position measuring system.

[0040] The locking device 220 is again realized as a preassembled module in the form of a cartridge, which is installed as a complete unit in the cylinder tube 210 and connected to it. The connection of the locking device 220 to the cylinder tube 210 is again made via an external thread provided on the housing part 222, which interacts with a corresponding internal thread 219 on the inner circumferential surface of the cylinder tube 210. A tangential pin 233 secures the preassembled locking device 210 before and during installation to prevent it from springing apart under the spring preload of the return spring 230. The assembly of the locking device 220 is sealed within the cylinder tube 210 by seals inserted in grooves 231, 232.

[0041] In the illustrated embodiments, the locking position of the piston 211 is selected in the central position. However, the invention is not limited to this. The locking position essentially depends on the length or installation position of the device and can thus be determined as desired by appropriately selecting the locking device and its installation location. It would also be possible to provide multiple locking positions.

[0042] In the exemplary embodiment, locking in the locking position takes place without pressure by the force of the return spring 230. The hydraulic actuator 221 therefore only needs to be designed to be single-acting, i.e. adjustable to the deactivation position by applying pressure via the control connection 229'.

[0043] Figures 3a to 3c show various possible alternatives for the hydraulic actuator. Figures 3a to 3c again show the two possible switching positions of the respective actuator in the upper and lower halves of the drawings.

[0044] Figure 3a shows a hydraulic actuator 321, which is pressurized via the control connection 329' in order to move the piston 326 to the left. A return spring 330 is installed in the piston chamber facing away from the pressure, which moves the piston 326 to the right in the depressurized state. Connected to the piston is a piston rod 322 serving as an activation element, which interacts with the blocking element (not shown here) of the blocking device according to the invention. The piston chamber facing away from the pressure is usually connected to a tank line via the control connection 329. As in the previous exemplary embodiments, it is assumed that the upper switching position of the piston 326, adjusted to the left, corresponds to the deactivation position of the associated blocking element, and that the switching position of the control piston 326 shown in the lower half of the figure and assumed by the force of the return spring 330 corresponds to the activation position.

[0045] Figure 3b shows the reverse case. The hydraulic actuator 421 is pressurized via the control port 429 and moved to the right against the force of the return spring 430 installed in the piston chamber facing away from the pressure. The control port 429' is connected to a tank line. In the depressurized state, the control rod 422, which serves as the activation element, assumes the deactivation position shown in the upper half of the figure. In the pressurized state, it assumes the activation position shown in the lower half of the figure against the force of the return spring 430.

[0046] Finally, Figure 3c shows an embodiment with a double-acting actuator 521. The piston chambers on either side of the control piston 526 can be alternately pressurized via the control ports 529, 529' to move the control piston 526 into the left switching position shown in the upper half of the figure, or the right switching position shown in the lower half of the figure. In this case, there is no preferred direction; rather, the actuator behaves bistable and always remains in the position to which it was previously pressurized.

[0047] The pre-assembled mechanical locking device assembly can be installed (inserted, screwed, or flanged) into an existing hydraulic cylinder. In particular, the assembly can be housed entirely within the hydraulic cylinder. Alternatively, it would also be possible to replace the rear cylinder base of the hydraulic cylinder with the assembly and use it to pressure-tightly seal the cylinder barrel, with the rear housing section of the assembly extending beyond the cylinder barrel.

[0048] To ensure the force is transmitted between the piston of the hydraulic cylinder and the cylinder barrel via the locking device, it must be ensured that the assembly is rigidly connected to the cylinder barrel, at least in the longitudinal direction. This can be achieved using a screw connection, as shown in the example. This allows the axial forces that occur to be absorbed well. Alternatively, a flange connection would also be possible, for example, by flange-mounting the pre-assembled assembly to the cylinder barrel. The pre-assembled assembly significantly simplifies the final assembly of the hydraulic cylinder with locking device. The pre-assembled assembly itself can be easily assembled outside the hydraulic cylinder and tested before final assembly.In the exemplary embodiments, the activation element has two switching positions: an activated position in which it holds the locking elements in the locking position, and a deactivated position in which it releases the locking elements. However, it is also possible and encompassed within the scope of the present invention for the activation element to be adjustable between two deactivated (end) positions, with the activated position being located in the middle position between the deactivated positions. In this case, return springs can be provided that preload the activation element from both end positions toward the middle position, so that it assumes the activated middle position when depressurized.

Claims

Claims 1. Mechanical locking device (110, 220) for installation in or on a hydraulic cylinder (100, 200), with - at least one locking element (124, 224) which, in a locking position, cooperates with a projection or a recess (118, 218) on a piston (111, 211) or a piston rod (112, 212) of the hydraulic cylinder (100, 200) in order to positively lock the piston (111, 211) or the piston rod (112, 212), - an activation element (125, 225) which is adjustable relative to the blocking element (124, 224) between an activation position and at least one deactivation position and, in the activation position, holds the blocking element (124, 224) in its blocking position and / or releases the blocking element (124, 224) in the deactivation position, and - a hydraulic or pneumatic actuator (121, 221) which can be pressurized for locking or unlocking purposes and which adjusts the activation element (125, 225) between the activation position and the deactivation position, characterized in that The locking element (124, 224), the activation element (125, 225) and the actuator (121, 221) are designed as a pre-assembled module for installation in or attachment to the hydraulic cylinder (100, 200) and the module is rigidly connected to the hydraulic cylinder (100, 200) at least in its longitudinal direction during assembly.

2. Locking device (120, 220) according to claim 1, wherein the assembly is designed to be installed in the hydraulic cylinder (100, 200) and is attached adjacent to an end piece (117, 217) of the hydraulic cylinder (100, 200).

3. Locking device (120, 220) according to claim 2, wherein the assembly comprises one or more seals or sealing surfaces (131, 132, 231, 232), with which it rests sealingly against an inner circumferential surface of the hydraulic cylinder (100, 200) after installation.

4. Locking device (120, 220) according to one of the preceding claims, in which the activation element (125, 225) is adjustable in the axial direction and the locking element (124, 224) is pressed in its locking position in the radial direction against the piston (111, 211) or piston rod (112, 212) of the hydraulic cylinder (100, 200).

5. Locking device (120, 220) according to one of the preceding claims, in which the locking device (120, 220) is designed to engage with the locking element (124, 224) in a cavity (113, 213) formed in the piston (111, 211) and piston rod (112, 212) of the hydraulic cylinder (100, 200) and the locking element (124, 224) is moved radially outwards within the cavity (113, 213) in its locking position.

6. Locking device (120, 220) according to claim 5 with a sleeve-shaped component (123, 223) projecting from an end piece (117, 217) of the hydraulic cylinder (100, 200) into its cylinder chamber, which extends into the cavity (113, 213) of the piston rod (112, 212).

7. Locking device (120, 220) according to claim 6, wherein the activation element (125, 225) is designed as an inner tube or mandrel which is longitudinally movable within the sleeve-shaped component (123, 223) and which carries in an end region an annular bead (126, 226) serving as a locking detent, which in the activation position holds the at least one locking element (124, 224) in the locking position.

8. Locking device (120, 220) according to claims 5 to 7, in which a plurality of circumferentially distributed spring tongues are provided as the locking element (124, 224), each of which has a locking lug at its end, which engages in a recess, in particular an annular groove (118, 218) on the inside of the cavity (117, 217) of the piston (111, 211) or the piston rod (112, 212). 14 REVISED SHEET (RULE 91) ISA / EP 9. Locking device (120, 220) according to one of the preceding claims, wherein the actuator (121, 221) is biased in the direction of the activation position or in the direction of the deactivation position by means of a return spring (130, 230, 330, 430) so that it returns to the respective position in the pressureless state.

10. Locking device (120, 220) according to one of the preceding claims, in which the hydraulic or pneumatic activator (121, 221) comprises a cylindrical housing part (122, 222) to be installed in the hydraulic cylinder (100, 200), which, if appropriate, together with the hydraulic cylinder (100, 200) forms a hydraulic chamber (127, 227) in which a control piston (128, 228) is mounted in a displacement-tight manner and the control piston (128, 228) is connected to the activation element (125, 225).

11. Locking device (120, 220) according to claim 10, wherein the housing part (122, 222) is sealed circumferentially against the hydraulic cylinder (100, 200) when installed in the latter in order to form the hydraulic chamber (127, 227).

12. Locking device (120, 220) according to claim 10 or 11, in which the activation element (225) is tubular and the control piston (228) is annular with an open inner diameter, which is guided and sealed on its inner side against a sleeve (234) which projects into the tubular activation element (225) and is connected to the housing part (222), so that an axial inner space remains free through the locking device (220) into the cavity (213) of the piston rod (212).

13. Locking device (120, 220) according to one of claims 10 to 12, wherein the housing part (122, 222) is provided with an external thread with which it can be screwed into a corresponding internal thread (119, 219) of the hydraulic cylinder (100, 200).

14. Hydraulic cylinder (100, 200) with a cylinder tube (120, 210) with an axially displaceable, sealingly mounted piston (111, 211) which carries a piston rod (112, 212), and a piston rod (112, 212) arranged at least partially within the hydraulic A locking device (120, 220) according to one of the preceding claims, which is arranged on the hydraulic cylinder (100, 200) and which positively locks the piston (111, 211) or the piston rod (112, 212) in a locking position.

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