EP1538343B1 - Locking cylinder - Google Patents

Abstract

The locking cylinder (20) has two load-holding descent brake devices (150.1, 150.2) in fluid connection with two working chambers (45, 33), so that when the first side (46) of the piston (22) is put under pressure, the piston is displaced in one direction. When it is subject to a counter-pressure lower than the working pressure, this acts on the other side (44) of the piston, displacing it in the opposite direction.

Description

The invention relates to a locking cylinder with a cylinder and a piston which is movable by means of a fluid pressure medium parallel to the longitudinal axis of the cylinder, and which is provided with a piston thread which engages to form a non-self-locking thread with a spindle thread of a spindle which is rotatable about a rotational axis arranged parallel to the longitudinal axis of the cylinder and which has at least one outwardly open locking recess into which at least one locking body acted upon by spring force of a spring can engage, which is secured against rotation about the axis of rotation of the spindle and movable relative to the cylinder is mounted and which is translatable by means of the spring force of the spring in a locking position in which it engages in the locking recess of the spindle, so that then rotation of the spindle is blocked about its axis of rotation, and wherein the locking body using a it is fluid working against the spring force of the spring from the locking position into an unlocking position is transferred, in which the spindle is rotatable about its axis of rotation, to allow movement of the piston along the cylinder.

Such a locking cylinder has become known from JP 083 034 10 A. There is provided as a locking body a large-volume locking piston, through the central passage opening, a shaft of a ball screw extends and which is integrally connected to a plurality of concentric with the spindle and arranged upstanding along the spindle teeth. In the locking position, the teeth of the locking piston are in engagement with opposite teeth of a gear which is rotatably connected to this concentric receiving spindle. As a result, a kind of toothed coupling is formed. The locking piston has on its side facing away from the teeth side a hollow portion with an internal toothing, and the tooth flanks of the teeth of the internal toothing extend parallel to the axis of rotation of the spindle. The internal gear is engaged with a matching external toothing of a pinion, which is fixedly connected to a cover plate of the cylinder. In this way, the locking piston is displaceable parallel to the axis of rotation of the ball screw, but stored blocked against rotation about the spindle axis.

On the outer circumference of the locking piston, a circumferential seal is provided which seals a pressure medium acted upon pressure medium space to the end cap of the cylinder.

This construction of a locking unit is complicated and takes up comparatively much space. For unlocking or locking the design-related large and compact and therefore important locking piston comparatively large forces are needed and / or it must comparatively long locking or locking times are accepted, which also means a corresponding security risk. The locking piston must be sealed at its outer periphery with a circumferential seal, which leads to corresponding frictional forces when moving the locking piston for the purpose of locking or unlocking, whereby the efficiency of this locking cylinder is limited.

The ball screw is clamped to the cylinder via a ball bearing and arranged at the free end of the spindle shaft slide bearing clamped that a movement of the spindle in the longitudinal direction of the cylinder is not possible, while a rotation of the spindle about its longitudinal axis is possible. For this purpose, the free end of the spindle shaft slidably supported on an inner surface of the end cap of the cylinder and the ball bearing is fixed by means of a screwed onto an external thread of the ball screw nut against a transverse to the cylinder paragraph.

This design is limited to applications where only relatively small loads can be lifted. For larger loads, however, it can lead to wear up to the feeding of the plain bearing. This can lead to the formation and detachment of metal chips or particles, which may affect the function of the locking unit, up to a blockade of the locking piston. This means an unacceptable security risk.

The control of the locking piston having the locking unit and the control of the movement of the piston take place in this construction via mechanically coupled directional control valves such that it can come in the raising or lowering of the load to an undesirable advance of the piston. This means a piston movement that is difficult to control. Particularly at elevated pressures or piston speeds, cavitation may occur at the piston seal and the piston rod, which means a safety risk and correspondingly limits the service life.

From EP-A-1 106 841 a locking cylinder having the features of the preamble of claim 1 has become known. In this design, however, it is inevitable that in certain applications, especially when the piston is to be retracted or extended at an increased rate, cavitation effects occur in the area of the piston seal and / or piston rod, in conjunction with a sequential one Jerking or rattling of the piston. As a result, the use of this construction is limited to relatively low piston speeds. Otherwise, the above-mentioned effects may occur, which involves a considerable safety risk.

It is therefore an object of the invention to provide a locking cylinder which allows in particular a higher reliability.

This object is achieved by a locking cylinder having the following features:

The locking cylinder comprises a cylinder and a piston, which uses one of two sides of the piston in a first working chamber and fluid pressure means feedable into a second working chamber is movable parallel to the longitudinal axis of the cylinder and provided with a piston thread engaging a spindle thread of a spindle forming a parallel thread to a longitudinal axis of the spindle to form a non - self - locking thread Cylinder arranged axis of rotation is rotatable and which has at least one outwardly open locking recess into which at least one acted upon by spring force of a spring locking body can be secured against rotation about the axis of rotation of the spindle and fixedly connected to the cylinder, but relative to this movable is mounted, and which is transferred by means of the spring force of the spring in a locking position in which it engages in the locking recess of the spindle, so that then rotation of the spindle is blocked about its axis of rotation, and wherein the locking body using a s fluid working means against the spring force of the spring from the locking position into an unlocking position can be transferred, in which the spindle is rotatable about its axis of rotation to allow movement of the piston along the cylinder, and wherein control means for controlling the movement of the piston and the locking body and the locking body are provided, and wherein at least a first load-holding Senkbrems means is fluidly connected to the first working chamber and that at least a second load-holding Senkbrems means is fluidly connected to the second working chamber, wherein the at least two load-holding Senkbrems means effect in that when the piston is acted upon on its first side by the pressure medium present in the first working chamber, a working pressure is generated which causes a displacement of the piston in a first direction, at the same time in the second working chamber on the second side of the piston acting through the located in the second working chamber pressure medium counter-pressure acts, which is smaller than the working pressure in the first working chamber, so that an uncontrolled advance of the piston in the first Direction is avoided, and that conversely when acting on the piston on its second side with the pressure medium in the second working chamber to form a working pressure, which causes a displacement of the piston in a second direction opposite to the first direction, simultaneously in the first working chamber acting on the first side of the piston by a counterpressure exerted by the pressure medium located in the first working chamber, which is smaller than the working pressure in the second working chamber, so that an uncontrolled advance of the piston is avoided in the second direction, and wherein the load-holding Senkbrems- Mitt el at a desired pressure relief for the purpose of holding the piston in a desired stroke position lock a return flow of the pressure medium from both working chambers, so that the piston is held by the pressure medium located in the working chambers in the desired stroke position, and wherein the of the load-holding Senkbrems Controlled counter-pressure dependent on the respective, a movement of the piston along the cylinder causing working pressure is controlled.

As a result, the piston during its movement along the cylinder between the acting in the working chambers pressures quasi "clamp" so that an uncontrolled advance or uncontrolled movements of the piston can be avoided with certainty. Furthermore, both high and highest piston speeds can thereby be driven be, without causing cavitation effects in the area of the piston seal and / or the piston rod, as well as small to very small piston speeds, ie it can be advantageous in "creep" driven.

In this way, therefore, a locking cylinder can be provided, which allows for increased application and possible applications and longer life a higher reliability.

According to a preferred embodiment it can be provided that the counterpressure controlled by the load-holding lowering brake means is controlled in dependence on the respective working pressure causing the piston to move along the cylinder so that the simultaneously acting back pressure decreases with increasing working pressure.

According to a preferred embodiment, it may be provided that the backpressure is controlled inversely proportional to the working pressure.

According to a preferred embodiment, it may be provided that the load-holding lowering brake means each have a first inlet for the pressure medium, an outlet for the pressure medium and a control port for the pressure medium, wherein the inlet of the first load-holding Senkbrems means with the first working chamber fluidly connected and the inlet of the second load-holding lowering brake fluid is fluidly connected to the second working chamber, and wherein the outlet of the first load-holding Senkbrems agent is fluidly connected to the control port of the second load-holding Senkbrems means and the outlet of the second load-holding Senkbrems -Mittel with the control terminal the first load-holding lowering brake fluid is fluidly connected, and wherein each of the inlet and the outlet of the respective load-holding lowering brake fluid communication is a Rückströmsperrmittel, each having a flow of the pressure medium from the outlet to the inlet of the respective load-holding lowering brake means allows, but blocks an opposite direction, and that either the outlet of the first load-holding lowering brake means and thus the control terminal of the second load-holding lowering brake means or the outlet of the second load-holding lowering brake means and thus the. Control connection of the first load-holding lowering brake means are acted upon with pressure medium to a movement of the piston in the first direction or in the second direction due to the respective working pressure and with simultaneous formation of the respective back pressure, via the second load-holding Senkbrems-means or via the first load-holding lowering brake means depending on the pressure acting on the respective control port pressure to effect.

According to a preferred embodiment, it can be provided that either the outlet of the first load-holding lowering brake means or the outlet of the second load-holding lowering brake means in fluid communication with the locking body or the locking bodies can be brought, so that upon application of the outlet of the first Load-holding lowering brake means or the outlet of the second load-holding Senkbrems means with pressure medium, this is supplied to the locking body or the locking bodies to convert this or this in his or her unlocked position.

According to a preferred embodiment it can be provided that between the outlet of the first load-holding lowering brake means and the outlet of the second load-holding lowering brake means at least one Rückströmsperrmittel is arranged, which upon application of the outlet of the first load-holding Senkbrems means with pressure medium prevents pressure fluid flow to the outlet of the second load-holding Senkbrems agent and vice versa upon application of pressure to the outlet of the second load-holding Senkbrems means prevents pressure fluid flow to the outlet of the first load-holding Senkbrems agent, and in both cases a Supply of the pressure medium to the locking body or the locking bodies permits, so that this or this is transferred to its unlocking position or will be.

According to a preferred embodiment, it may be provided that the non-return valve comprises a first inlet for the pressure medium, a second inlet for the pressure medium and an outlet for the pressure medium, wherein the first inlet of the Rückströmsperrmittels is fluidly connected to the outlet of the first load-holding lowering brake means and wherein the second inlet of the non-return valve is in fluid communication with the outlet of the second load-holding counter-brake fluid, and wherein the first inlet of the non-return valve and the second inlet of the non-return valve are interconnected via a fluid passage into which one connected to the outlet of the non-return valve Fluid channel opens at an orifice, so that branches off from the discharge point, a first channel part of the fluid channel and a second channel part of the fluid channel, and wherein a locking member for shutting off the first channel part or the second channel part is provided, and wherein in the shut-off state of the second passage member, the first inlet of the Rückströmsperrmittels, the first channel part and the outlet of Rückströmsperrmittels are fluidly connected, so that a pressure fluid flow from both the first inlet of the Rückströmsperrmittels to the outlet of the Rückströmsperrmittels and the outlet of the Rückströmsperrmittels to the first inlet and, conversely, in the shut-off state of the first passage member, the second inlet of the non-return means, the second passage and the outlet of the non-return means are fluidly connected, such that pressurized fluid flows from both the second inlet of the non-return means to the outlet of the non-return means and the outlet of the Rückströmsperrmittels is admitted to the second inlet of the Rückströmsperrmittels.

According to a preferred embodiment, it may be provided that the non-return valve comprises a first inlet for the pressure medium, a second inlet for the pressure medium and an outlet for the pressure medium, wherein the first inlet of the Rückströmsperrmittels is fluidly connected to the outlet of the first load-holding lowering brake means and wherein the second inlet of the non-return valve is in fluid communication with the outlet of the second load-holding counter-brake fluid, and wherein the first inlet of the non-return valve and the second inlet of the non-return valve are interconnected via a fluid passage into which one connected to the outlet of the non-return valve Fluid channel opens at an orifice, so that branches off from the orifice a first channel part of the fluid channel and a second channel part of the fluid channel, and wherein a first locking member for shutting off the the first channel part and a second locking member for shutting off the second channel part is provided, which shut off the first channel part and the second channel part in terms of a pressure fluid flow from the outlet of the Rückströmsperrmittels to the first inlet of the Rückströmsperrmittels and the second inlet of the Rückströmsperrmittels and the one Druckmittelströmung from the first inlet of the Rückströmsperrmittels to the outlet of the Rückströmsperrmittels and from the second inlet of the Rückströmsperrmittels to the outlet of the Rückströmsperrmittels.

According to a preferred embodiment, it can be provided that the working means or the pressure means is supplied to the locking body or the locking bodies in order to transfer this or these in its unlocking position and that at the same time the pressure medium selectively supplied to the first working chamber or the second working chamber is to cause movement of the piston in the first direction or in the second direction.

According to a preferred embodiment it can be provided that the working means or the pressure means is first supplied to the locking body or the locking bodies in order to transfer this or these in his or her unlocking position and then that the pressure medium optionally the first working chamber or the second working chamber is supplied to cause movement of the piston in the first direction or in the second direction.

According to a preferred embodiment it can be provided that the respective backflow blocking means A blocking member for preventing a flow of pressure medium from the inlet to the outlet of the respective load-holding lowering brake means, which is acted upon by spring forces of a spring, so that an opening of the Rückströmsperrmittels and thus a pressure medium flow from the outlet to the inlet of the respective load-holding Senkbrems- Means is only possible from above a limit pressure of the pressure medium, the value of which depends on a spring characteristic of the respective spring.

It is understood that the above measures can be combined as desired in the feasibility of a locking cylinder of the type mentioned in order to provide a locking cylinder with correspondingly combined advantages.

Further aspects, features and advantages of the invention can be taken from the following description part, in which two preferred embodiments of the invention are described in more detail with reference to the figures:

Fig. 1

einen Längs-Querschnitt durch einen erfindungsgemäßen Verriegelungszylinder;

Fig. 2

einen vergrößerten Ausschnitt des Querschnitts gemäß Figur 1 im Bereich des dort rechts dargestellten Verriegelungsbolzens;

Fig. 3

einen Teilquerschnitt des Verriegelungszylinders längs der Schnittlinie 3-3 in Figur 1 zur Verdeutlichung der Zahl und Anordnung der Verriegelungsausnehmungen;

Fig. 4

einen vergrößerten Längs-Querschnitt im Bereich eines alternativen Ausführungsbeispiels eines Verriegelungsbolzens;

Fig. 5

einen hydraulischen Schaltplan gemäß einer ersten Ausführungsvariante der Erfindung;

Fig. 6

einen hydraulischen Schaltplan gemäß einer zweiten Ausführungsvariante der Erfindung.

Show it:

Fig. 1

a longitudinal cross section through a locking cylinder according to the invention;

Fig. 2

an enlarged section of the cross section of Figure 1 in the region of the locking bolt shown there on the right;

Fig. 3

a partial cross section of the locking cylinder along the section line 3-3 in Figure 1 for clarity the number and arrangement of the locking recesses;

Fig. 4

an enlarged longitudinal cross section in the range of an alternative embodiment of a locking bolt;

Fig. 5

a hydraulic circuit diagram according to a first embodiment of the invention;

Fig. 6

a hydraulic circuit diagram according to a second embodiment of the invention.

The locking cylinder 20 shown in Figure 1 comprises a cylinder 21 and a longitudinally slidably mounted therein piston 22. The piston 22 is sealed relative to the cylinder inner wall by a ring seal 68 and is on its in the direction of the longitudinal axis 29 of the cylinder 21 facing away from each other pages 44, 46 by a fluid pressure medium, preferably oil, acted upon to allow a pressure-medium-assisted movement of the piston 22 in a direction of unlocking referred to as the second direction or unlocking direction 27 or in a direction also referred to as the first direction of extension 28.

The piston 22 is fixedly connected to a piston rod 23, which extends from its end face 44 coaxial with the cylinder longitudinal axis 29. The cylinder 20 is closed at its the free end 67 of the spindle 35 side by a piston rod 23 receiving cover 30. On its other side, the cylinder 21 is fixedly connected to a step-shaped projection 66. This is in turn completed by a cylinder base 53 forming lid or head 31.

The piston 22 forms a projection 32 which is non-rotatably connected to the piston rod 23. The piston 22 is designed as a tubular hollow body and has an internal thread 34, also referred to as a piston thread. This is engaged with an external thread 36, also referred to as a spindle thread, of a spindle 35 on which the piston 22 is guided. The internal thread 34 of the piston 22 and the external thread 36 of the spindle 35 are preferably designed as achtgängige trapezoidal coarse thread, which together form a non-self-locking thread 37.

For attachment of the locking cylinder 20, the piston rod 23 at its free end a here designed with an eyelet fastener 25, and a correspondingly shaped fastener 26 is mounted opposite to the head 31 of the cylinder 21.

The pressure medium can be fed via the channels 48 and 49 on both sides 44 and 46 of the piston 22 into a first working chamber 45 and into a second working chamber 33 in order to achieve a movement of the piston 22 along the cylinder 21 in the retraction direction 27 or in the extension direction 28 can. In this case, the first working chamber 45 is sealed relative to the second working chamber 33 via the annular seal 68 of the piston 22.

In the area of the free end 67 of the spindle 35 facing away end 77 of the spindle 35, this is rotatably connected to a flange-shaped projection 65. This has a transversely in the region of its cylinder bottom end or at right angles to the axis of rotation 43 of the spindle 35 extending, here annular wall portion 79. This is mounted on the free end 67 of the spindle 35 side facing by a first thrust bearing 120, here in the form of a first ring bearing 127, which is designed here as a needle bearing 138, at a support and investment level of the cylinder extension 66. This designed as a rolling bearing 137 ring bearing 127 serves to absorb the force acting on the spindle 35 in the extension direction 28 axial forces. In order to be able to absorb the axial forces acting on the spindle 35 in the retraction direction 27 in the opposite direction to the extension direction 28, two measures are taken:

For receiving the operating axial forces acting on the spindle 35 during normal operation of the locking cylinder 20 in the first direction 28, a second thrust bearing 121 is provided in the form of a second annular bearing 130 arranged at the head end 77 of the spindle 35. This thrust bearing 121 is also designed as a roller bearing 122 in the form of a needle bearing 123. It is on a coaxial with the axis of rotation 43 of the spindle 35 fixedly connected to the spindle 35 supporting body 124 received in the form of a cylinder pin 125 which extends in the direction of the cylinder bottom or head 31 of the cylinder 21 and the coaxial with the axis of rotation 43 spindle 35 is arranged ,

Adjoining the needle bearing 123 in the retraction direction 27 is a disc spring package 135, which consists of a plurality of disc springs 134, 136. In the embodiment shown, five disc springs 134 and five disc springs 136 are provided. In this case, the disc springs 134 and the disc springs 136th each alternately successively preferably arranged such that in each case the spring travel of each plate spring 134, 136 for a resilient mounting of the spindle 35 is available. The plate springs 134, 136 are selected with regard to their spring characteristics and arrangement such that in the regular driving operation, when the piston 22 is moved in the retraction direction 27, the thereby transmitted via the non-self-locking thread 37 and the spindle 35 dynamic resulting forces are absorbed, that is compensated , so that the support body 124 is always lifted from the head 31 of the cylinder bottom of the cylinder 21.

However, if the piston 22 in the opposite direction, d. H. extended in the extension direction 28 acts on the spindle 35, a resultant axial force in the extension direction 28, so that even with this piston movement of the support body 124 is always lifted from the head 31.

Nothing else applies in the case of holding the piston 22 in a desired stroke position. Because then, as will be explained in more detail below, the piston 22 of pressure medium, which is located in the two working chambers 33 and 45 and with these fluid-connected channels 49 and 48, held "clamped", so that even under permissible high static loads, which are to be held or moved by the locking cylinder 20, the support body 124 is always lifted from the head 31 of the cylinder 21. In this case, therefore, the static load to be retained by means of the locking cylinder 20 and the axial forces transmitted thereto to the spindle 35 are substantially transmitted via the pistons 22 and taken up this pressurizing pressure medium and on the adjacent cylinder walls.

However, if a claim occurs, so z. B. leakage occurs in the area or a fraction of a pressure medium line, 27 acting overload axial forces can occur in the retraction direction, which can no longer be received by the small needle bearing 123 without destruction. Because this second needle bearing 123 has a relation to the carrying capacity or the supporting diameter of the first needle bearing 138 smaller capacity or smaller load-bearing diameter to meet the requirements for a space-saving design of the locking cylinder 20 in the locking and storage area. The wear the used disc springs 134 and 136, so that upon application of the overload axial forces a displacement of the spindle 35 in the retraction 27 with simultaneous compression of the disc springs 134, 136 occurs until the support body 124 with the present at its free end support surface 129 the opposite support surface 131 of the head 31 of the cylinder rests. The support body 124 is then supported there so that the acting overload axial forces are then transferred from the spindle 35 via the support body 124 on the head 131 of the cylinder 21 without the needle bearing 123 would be damaged.

By the arrangement and the selected spring characteristics of the disc springs 134, 136 so a certain force is given, which corresponds to a certain limit axial force at which falls below the support body 124 is lifted and upon reaching or exceeding a displacement of the spindle 35 together with the Support body 124 in the retraction 27 occurs until the support body 124 bears against the head 31 of the cylinder 21.

The flange-shaped projection 65 is provided on the transverse to the axis of rotation 43 of the spindle 35 extending wall portion 79 with here a total of eight locking recesses 38.1 to 38.8, which are open to the cylinder bottom 53 out to the outside. The locking recesses 38.1 to 38.8 are arranged at equal angular distances from each other on an imaginary circumferential circle such that two locking recesses are arranged diametrically opposite one another and are therefore arranged on a line containing the axis of rotation 43 of the spindle 35. Each locking recess 38 is configured with conically inwardly tapering wall portions 70 and serves to receive outwardly conically tapered wall portions 72 of locking bolts 40, 140. Here, the tapered wall portions 72 having free end 57 of the respective locking bolt 40, 150 is preferably designed in such a manner on the locking recesses 38 in the region of their conically tapered wall parts 70, that a Durchströmspalt 71 is formed for the pressure medium. This Durchströmspalt 71 is in fluid communication with a gap 91 which is arranged in the region of the radial edges of both the flange-shaped projection 65 and the opposite part of the head 31 of the cylinder 21. This gap 91 is in fluid communication with a switching channel 47, which in turn can be brought into fluid communication with channels 48 and 49, via which the piston 22 can be acted upon by pressure medium on its respective sides 44 and 46.

A first embodiment of a Verriegelungsbolzens.40 is shown in Figures 1 and 2 and a second embodiment of a locking bolt 140 is illustrated in Figure 4. In contrast to the locking bolt 140, the locking bolt 40 is designed to be cross-sectionally closed in the region of its free end 57, while the locking bolt 140 is provided as a perforated nozzle 90 with a through-channel 54 which is open towards its free end 57 and concentric with its longitudinal axis 74. Except for this passage 54, however, the locking bolts 40 and 140 are identical, wherein like reference numerals refer to like elements.

Each locking bolt 40, 140 is designed as a preferably elongated cylinder pin 69 rotationally symmetrical to its longitudinal axis 74. Each locking bolt 40, 140 has a circular cylindrical outer contour 50 and a circular cylindrical inner contour, is thus designed as a rotary hollow body. Each locking bolt 40, 140 also has a circular cylindrical recess 92 which is formed with parallel to the longitudinal axis 74 of the respective locking bolt 40, 140 delimiting wall parts and which is open to the head 31 of the cylinder 21 opposite end 56 to the outside. This recess 92 serves to receive and lateral support of a designed as a compression spring spring 39. This is received in the mounted state with a spring portion 93 in the recess 92. In this case, the spring 39 is supported with one of its ends 95 on an inner surface 94 of a radially inwardly extending support and conditioning stage 60 of the locking bolt 40, 140 from. The other end 96 of the spring 39 is supported on an inner surface of a corresponding one Support and conditioning stage 76 of the head 31 of the cylinder 21 from.

Offset at an axial distance from the inner surface of the supporting and contact stage 76 and in the extension direction 28, a radially outwardly extending abutment and counter-sealing surface 98 for the locking pin 40, 140 is provided, which is arranged perpendicular to the wall portions bounding the bearing recess 75 , Each locking bolt 40, 140 has at its head or spring-side end 59 a ring end edge 99, which is designed with a circumferential annular sealing surface 97 and in the unlocking 27 of the respective locking bolt 40, 140 has. This ring-sealing surface 97 is sealingly against the likewise circumferential abutment and counter-sealing surface 98 of the head 31 of the cylinder 21, when the respective locking pin 40, 140 has been transferred into its unlocked position after being subjected to the pressing forces exerted by the pressure medium in unlocking 27 , Under the then effective pressure forces a seal is achieved there, so that no leakage of pressure fluid along the outer surfaces of the respective locking bolt 40, 140 occurs. In addition, the abutment and Abdichtgegenfläche 96 advantageously limits the respective Entriegelungshub the locking pins 40, 140th

Each locking bolt 40, 140 is slidably mounted parallel to the axis of rotation 43 of the spindle 35 with little clearance in the bore or bearing recess 75 having a cylindrical inner contour 98, that is, starting from the locking position 41 shown in FIGS. 1, 2 and 4. or unlocking direction 27 using the pressure medium against the spring forces of the spring 39 are moved to its unlocked position, or vice versa after pressure relief in the region of its free locking end 57 of its unlocked position automatically, ie by the force exerted by the respective spring 39 on the respective locking pin 40, 140 return spring forces be transferred back to its locking position 41. The bearing recess 75 thus has an inner diameter which is slightly larger than the outer diameter of the locking bolt 40, 140.

In contrast to the locking bolts 40 shown in FIGS. 1 and 2, the locking bolt 140 illustrated in FIG. 4 is configured as a hole nozzle 90 and has a free end 57 which protrudes into the locking recess 38 in the locking position 41 shown in FIG central passageway 54. This through-passage 54 is arranged coaxially with the longitudinal axis 74 of the locking bolt 140. The through-passage 54 has a comparatively small through-flow cross-section and, in the direction of its other end 59, merges into a likewise with cylindrical wall parts designed channel part 78, which has a larger flow area. The channel part 78 in turn, forming the support and contact surface 60 in a recess 92 of the larger channel diameter 61, which is slightly larger than the outer diameter 62 of the spring 39 received in said recess 92. The compression spring is at one end to the support And investment level 60 of the locking bolt 140 and is supported at the other end of the support and investment stage 76 of the lid or head 31 of the cylinder 21 from.

The locking bolt 140 has at its free end 57 a perpendicular to its longitudinal axis 74 arranged active surface 58 to which the fluid pressure medium can act to transfer the locking bolt 140, starting from the locking position 41 shown in Figure 4 in an unlocking position, in which he out of engagement with the locking recesses 38.1 to 38.8, so no rotation of the spindle 35 in a rotational direction 51 or an opposite direction of rotation 52 is no longer blocked. The active surface 58 is much larger than the flow cross-section of the through-channel 54 in the region of the free end 57 of the locking bolt 40, 140. This enables a secure unlocking of the locking bolt 40, 140. In addition, it can be at a pressure relief in the locking recesses 38, it is intended, for the purpose of fixing the piston 22 with its piston rod 23 in a certain stroke position, or be it unintentionally, for example in the event of leakage or a total failure of the hydraulic system, the locking bolt 40, 140 are moved due to the forces exerted by the spring 39 forces in its locking position 41. In this case, in the case of the locking bolts 140, the pressure medium located in the associated locking recess 38 can flow through the through-passage 54 of the locking bolt 140 into the channel 55 serving as the relief channel. In contrast, when using the locking bolt 40 in its movement from its unlocking position into the locking position 41 located in the associated locking recesses 38 oil displaced via the switching channel 47 and the Rückströmsperrmittel 160 either in the flow channel 86 or in the return channel 87, depending after, in which position the locking member 171 of is arranged as a shuttle valve designed Rückströmsperrmittels 160.

In the figures 5 and 6 hydraulic circuit diagrams are illustrated in which particularly advantageous control means and paths are used. The circuit according to the circuit diagram shown in Figure 5 can be advantageously used for the operation and operation of a equipped with locking pin 40 locking cylinder 20. It is understood, however, that the switching or control elements resulting from the circuit diagram according to FIG. 5 can also be advantageously used in conjunction with the locking bolts 140 shown in FIG.

A particularly advantageous control of the locking cylinder 20 can be achieved with the circuit of Figure 5, because this circuit and the control means used there make it possible that the pressure medium is first supplied to the locking bodies 42 in order to convert them into their unlocked position and then the pressure medium either the first working chamber 33 or the second working chamber 45 is supplied to cause a movement of the piston 22 in the first direction 28 or in the second direction 27. As a result, the wear in the area of the locking bolts 40 and in the area of the locking recesses 38 can be minimized and the locking bolts 40 can not become jammed, in particular at low switching pressures.

In contrast, it is provided in the circuit according to FIG. 6 that the working medium or the pressure medium is supplied to the locking bodies 142 in order to place them in their position Unlock unlocking position and that at the same time the pressure medium is optionally the first working chamber 33 or the second working chamber 45 is supplied to cause a movement of the piston 22 in the first direction 28 or in the second direction 27.

Certain essential to the invention switching or control elements, which are advantageously used in conjunction with both circuit variants are described in more detail below:

There are two designated as a load-holding Senkbrems means 150.1, 150.2 load holding Senkbrems valves are provided which cause when pressurizing the piston 22 on its first side 46 with the in the first chamber 33 pressure medium to form a working pressure, the causing a displacement of the piston 22 in a first direction 28, at the same time in the second working chamber 45 on the second side 44 of the piston 22, a counter pressure exerted by the pressure medium in the second working chamber 45 acts, which is smaller than the working pressure in the first working chamber 33, so that an uncontrolled advance of the piston 22 in the first direction 28 is avoided, and that conversely upon application of the piston 22 on its second side 44 with the pressure medium in the second working chamber 45 to form a working pressure, the displacement of the piston 22 in a second direction 27 opposite to the first direction 28 causes, at the same time in the first working chamber 33 on the first side 46 of the piston 22, a pressure exerted by the pressure medium in the first working chamber 33 acts counterpressure, which is smaller than the working pressure in the second working chamber 45, so that an uncontrolled advance of the piston 22 in the second direction 27 is avoided, and wherein the load-holding Senkbrems means 150.1, 150.2 at a desired pressure relief for the purpose of holding the piston 22 in a desired stroke position, a backflow of the Locking pressure medium from both working chambers 33, 45, so that the piston 22 is held securely in the desired stroke position by the pressure medium in the working chamber 33, 45.

Each load-holding lowering brake valve 150.1, 150.2 has an inlet 153.1, 153.2, an outlet 154.1, 154.2 and a control connection 155.1, 155.2 for the pressure medium, wherein the inlet 153.1 of the first load-holding lowering valve 150.1 fluidly connected to the first working chamber 33 and wherein the inlet 153.2 of the second load-holding lowering valve 150.2 is fluidly connected to the second working chamber 45, and wherein the outlet 154.1 of the first load-holding lowering valve 150.1 is fluidically connected to the control port 155.2 of the second load-holding lowering valve 150.2 and wherein the outlet 154.1 of the second load-holding lowering brake valve 150.2 is fluidically connected to the control port 155.1 of the first load-holding lowering valve 150.1, and wherein with the inlet 153.1, 153.2 and the outlet 154.1, 154.2 of the respective load-holding lowering valve 150.1, 150.2 each a backpressure blocking means 156.1, 156.2 is fluidly connected, each having a flow of the pressure medium of the Outlet 154.1, 154.2 to the inlet 153.1, 153.2 of the respective load-holding lowering valve 150.1, 150.2 allows, but in the opposite direction respectively blocks, and that optionally the outlet 154.1 of the first load-holding lowering valve 150.1 and thus the control terminal 155.2 of second load-holding lowering brake valve 150.2 or the outlet 154.2 of the second load-holding Senkbrems valve 150.2 and thus the control port 155.1 of the first load-holding Senkbrems valve 150.1 are acted upon with pressure medium to a movement of the piston 22 in the first direction 28 or in the second direction 27 due to the respective working pressure and with simultaneous formation of the respective back pressure acting on the second load-holding Senkbrems valve 150.2 or via the first load-holding Senkbrems valve 150.1, preferably depending on the at the respective control port 155.1, 155.2 To effect pressure.

In each case between the outlet 154.1 of the first load-holding lowering brake valve 150.1 and the outlet 154.2 of the second load-holding lowering valve 150.2 at least one Rückströmsperrmittel 160, 161 is arranged, which upon exposure of the outlet 154.1 of the first load-holding Senkbrems valve 150.1 with Pressure medium prevents a pressure fluid flow to the outlet 154.2 of the second load-holding lowering valve 150.2 out and vice versa upon application of the outlet 154.2 of the second load-holding lowering valve 150.2 with pressure medium, a pressure fluid flow to the outlet 154.1 of the first load-holding Senkbrems valve 150.1 out prevented and that in both cases allows a supply of the pressure medium to the locking body 42, 142, so that they can be transferred to their unlocked position.

It is further provided that the non-return valve means 160, 161 has a first inlet 164 for the pressure medium, a second inlet 165 for the pressure medium and an outlet 166 for the pressure medium, wherein the first inlet 164 of the respective Rückströmsperrmittels 160, 161 fluidly connected to the outlet 154.1 of the first load-holding Senkbrems valve 150.1, and wherein the second inlet 165 of the respective Rückströmsperrmittels 160, 161 fluidly connected to the outlet 154.2 of the second load-holding Senkbrems valve 150.2, and wherein the first inlet 164 of the respective Rückströmsperrmittels 160, 161 and the second inlet 165 of the respective Rückströmsperrmittels 160, 161 are interconnected via a fluid passage 167, in which a connected to the outlet 166 of the respective Rückströmsperrmittels 160, 161 fluid channel 167 at an orifice 168th opens, so that a first channel portion 169 of the fluid channel 167 and a second channel portion 170 of the fluid channel 167 branches off from the confluence point 168.

In the circuit according to FIG. 5, a blocking element 171 is furthermore provided for shutting off the first channel part 169 or the second channel part 170, and in the shut-off state of the second channel part 170 the first inlet 164 of the non-return means 160, the first channel part 169 and the outlet 166 of FIG Backflow blocking means 160 are fluidly connected, so that a pressure medium flow from both the first inlet 164 of the Rückströmsperrmittel 160 to the outlet 166 of Rückströmsperrmittel 160 and the outlet 166 of the Rückströmsperrmittel 160 to the first inlet 164 of the Rückströmsperrmittel 160 is allowed, and vice versa, in the locked state of the first Portion 169, the second inlet 165 of the Rückströmsperrmittels 160, the second channel portion 170 and the outlet 166 of the Rückströmsperrmittels 160 fluidly connected, so that a pressure fluid flow from both the second inlet 165 of the Rückströmsperrmittel 160 to the outlet 166 of Rückströmsperrmittels 160 as well as the inlet 164 of the Rückströmsperrmittels 160 to the second inlet 165 of the Rückströmsperrmittel 160 is allowed.

In the circuit according to FIG. 5, it is further provided that the respective nonreturn blocking means 156.1, 156.2 has a blocking member 173.1, 173.2 for preventing a pressure medium flow from the inlet 153.1, 153.2 to the outlet 154.1, 154.2 of the respective load-holding lowering brake means 150.1, 150.2, which is acted upon by spring forces of a spring 174.1, 174.2, so that an opening of the Rückströmsperrmittels 156.1, 156.2 and consequently a flow of pressure medium from the outlet 154.1, 154.2 to the inlet 153.1, 153.2 of the respective load-holding lowering brake means 150.1, 150.2 only from above Limit pressure of the pressure medium is possible, the value of a spring characteristic of the respective spring 174.1, 174.2 depends. These springs 174.1 and 174.2 are also well visible in Figure 1 at the lower ends of the two load-holding lowering valves 150.1, 150.2 there.

In contrast to the circuit according to FIG. 5, according to a circuit according to FIG. 6 it can be provided that a first blocking element 172.1 is provided for shutting off the first channel part 169 and a second blocking element 172.2 is provided for shutting off the second channel part 170 which comprises the first channel part 169 and the first channel part 169 second passage portion 170 with respect to a flow of pressurized fluid from the outlet 166 of the Rückströmsperrmittels 161 to the first inlet 164 of the Rückströmsperrmittels 161 and the second inlet 165 of the Rückströmsperrmittels 161 shut off and the one Druckmittelströmung from the first inlet 164 of the Rückströmsperrmittels 161 to the outlet 166 of Rückströmsperrmittels 161 and from the second inlet 165 of the Rückströmsperrmittels 161 to the outlet 166 of the Rückströmsperrmittels 161.

The operation of the locking cylinder 20 is described in more detail below:

In the rest position of the locking cylinder 20 shown by way of example in FIG. 1, that is to say holding the piston 22 and the piston rod 23 in a desired stroke position, this is already hydraulically secured by the use of the load-holding lowering brake valves 150.1, 150.2. These are fluidly connected via the channel 48 and the channel 49 with the pressure medium working chambers 45 and 33 of the cylinder 21, the pressurization of the piston 22 on its side facing the piston rod end 44 and / or on its side facing the cylinder bottom 53 side 46th enable.

The load-holding lowering brake valves 150.1 and 150.2 thus already make it possible to secure the respective stroke position of the piston 22 with the piston rod 23 relative to the cylinder 21, both when using the locking cylinder 20 for the transmission of compressive forces and for the transmission of tensile forces ,

In addition to the hydraulic securing by means of the load-holding lowering brake valves 150.1, 150.2, a mechanical securing of the locking cylinder 20 via the locking unit 56 is possible. This additional mechanical protection is particularly effective when leakage or failure or similar damage to the hydraulic system occurs. Because then grab the locking pin 40, 140 in the locking recesses 38, so that a positive and bidirectional locking of the spindle 35 and thus of the piston 22 is given in the given stroke position. This engagement or blocking position of the cylinder bolts 40, 140 is reached at the moment in which an unwanted, in the channels 48 or 49 and thus also in the switching channel 47 impacting pressure relief occurs. Because then the respective locking bolt 40.1, 40.2; 140.1, 140.2 pushed by the mechanical force of the compression springs 39 against the previously rotating flange-shaped projection 65 until the respective locking pin 40.1 and 40.2 or 140.1 and 140.2 in the next possible locking recess 38 engages and thereby blocks the further rotational movement of the spindle 35.

The operation of the lock cylinder 20 will be described below using the circuit shown in FIG. 5.

In order to achieve, for example, a movement of the piston 22 and thus of the piston rod 23 relative to the cylinder 22 in the extension direction 28, the channel designated here with feed channel 86 is subjected to pressure medium, ie. H. it is supplied by means of a pump not shown in the figures through the flow channel 86, the pressure medium.

Up to a certain pressure, which depends on the spring characteristic of the spring 174.1 of the non-return valve 156.1, the pressure medium can not initially enter the channel 49 and thus not in the working space 33, but first passes through the first inlet 164 in the first channel part 169 of as a shuttle valve designed Rückströmsperrmittels 160, whereby its blocking means 171 is moved into the fluid channel 167 via the outlet point 166 and from there via the outlet 166 into the switching channel 47 with substantially simultaneous closing of the second channel part 165 into the blocking position shown on the left in FIG. 5, opening a flow path.

At the same time, the channel 88.1 leading to the control connection 155 of the second load-holding lowering brake valve 150.2 is subjected to pressure medium. However, the pending pressure medium pressure still causes no opening of the second load-holding lowering valve 150.2. For an opening of the load-holding lowering brake means 150.1 and 150.2 takes place against adjustable spring forces of a respective spring 80.1 or 80.2. Consequently, the respective load-holding lowering brake means 150.1 and 150.2 opens only from a certain, prevailing at the respective control port 155.1 or 155.2 pressure medium pressure, depending on the set on the springs 80.1 and 80.2 spring forces or spring characteristics. These spring forces or spring characteristics are preferably adjusted so that the load-holding lowering brake means 150.1, 150.2 respectively open only when the Rückströmsperrmittel 156.2 or 156.1 opens, d. H. Here, when the respective Rückströmsperrventil against the spring force of the respective spring 174.2 or 174.1 opens to cause movement of the piston 22 in the extension direction 28 and in the retraction 27.

The pressure medium then flows first through the switching channel 47 to the pressure medium spaces in the region of the free ends 57 of the locking bolt 40 and causes them to be transferred from the locking position 41 shown in the direction 27 in its unlocked position become. As soon as the sealing surfaces 97 of the locking bolts 40 bear against the counter-sealing surfaces 98, a further supply of pressure medium into the flow channel 86 causes a further increase in pressure, which causes the spring-loaded backflow barrier 156.1 to open. Then, the pressure medium can flow via the channel 49 into the first working chamber 49 in order to effect a movement of the piston 22 and thus of the piston rod 23 in the extension direction 28.

At the same time leading to the control port 155.2 of the second load-holding lowering valve 150.2 channel 88.1 pressure medium of a corresponding pressure is applied, whereby, depending on the pressure currently acting in the flow channel 86, the load-holding Senkbrems valve 150.2 opens more or less wide to allow a pressure fluid flow from the second working chamber 45 via the channel 48 and the second load-holding lowering brake valve 150.2 in the direction of arrow shown in Figure 5 in the return passage 87.

The control takes place in such a way that the counterpressure set here by the load-holding lowering brake means 150.2 is controlled in the supply channel 86 as a function of the working pressure in the supply channel 86 causing the piston 22 to move along the cylinder 21, the counterpressure acting simultaneously decreasing as the working pressure increases, and preferably inversely proportional to the working pressure. In this way, it is always achieved during driving that the piston 22 is "clamped" in a force acting counter to its current direction of movement, thereby preventing an uncontrolled advance of the piston 22.

If the piston is then to be stopped in a desired stroke position, preferably both the flow channel 86 and the return channel 87 are pressure-relieved. As a result, both the two return valves 156.1 and 156.2 as well as - due to the pressure relief then occurring in the control channels 88.1 and 88.2 - close the two load-holding lowering valves 150.1 and 150.2 so that the pressure medium located in the working chambers 33 and 45 does not escape therefrom can. The piston 22 is then clamped between the pressure columns present on its two sides 44 and 46 and fixed in its current stroke position.

A pressure relief at the channels 86 and 87 also has an effect in the switching channel 47, so that the locking bolts 40 can be transferred from their unlocking position into the locking position 41 shown in the figures by the spring forces of the springs 39 acting on them , Here, the located in the pressure medium spaces in front of the free locking ends 57 of the locking bolt 40 pressure fluid via the channel 47 and the shuttle valve 160 here flow back into the flow channel 86.

Depending on in which current rotational position, the spindle 35 and thus the locking recesses 38 are at a current holding stroke position of the piston 22, the locking bolts 40 then engage either in the locking recesses 38 or are these at the head 31 of the cylinder 21 indicative end face of the locking recesses 38 containing ring lug 65, which is located between two immediately adjacent Locking recesses 38 are located. In such, any holding stroke position of the piston 22, it is not relevant in the normal case, whether the locking pin 40 or 140 engage in the locking recesses 38. Of course, something else applies in the event of leakage or damage in the pressure medium system. Then the approach containing the locking recesses 38 still continues to rotate slightly until the locking pins 40, 140 engage in the next-reaching locking recess 38. In the embodiments shown and described, however, it can only come to a very small stroke of the piston 22, which is in the millimeter range and which is completely sufficient in terms of safety.

If the piston 22 and thus the piston rod 23, starting from the stroke position shown schematically in Figure 5 relative to the cylinder 21 in the opposite direction, d. H. are moved in the retraction 27, the return passage 87 is acted upon by pressure medium. Then, the blocking member 171 of the shuttle valve 160 is displaced by the inflowing pressure medium in the locking direction shown on the right in Figure 5, so that then the inflowing via the second inlet 165 in the second channel part 170 pressure medium via the discharge point 168 again in the fluid channel 167 and from there from flowing into the switching channel 47, in which case the first channel part 169 of the fluid channel 159 is shut off by the blocking means 171.

After unlocking the locking pin 140 or after they are transferred to their unlocked position, opens spring-loaded Rückströmsperre 156.2, so that then pressure medium can flow into the working chamber 45 to move the piston 22 in the retraction 27. simultaneously is, in turn, depending on the current working pressure, now in the flow channel 87, the first load-lowering valve 150.1 controlled via the fluidically connected to the control port 155.1 control channel 88.2 so that in the working chamber 33, a back pressure is formed which is smaller than the operating pressure in the working chamber 45, so that the movement of the piston 22 in the retraction direction 27 without an undesirable advance of the same takes place.

The operation of the locking cylinder 20 will now be described in more detail using the circuit shown in FIG. 6.

As already mentioned above, the mode of operation and function of the load-holding lowering brake means 150.1, 150.2 is the same as explained with reference to the example of the circuit according to FIG. 5, so that reference may be made to the above description parts.

If the locking cylinder 20 is acted upon via the flow channel 86 or the return channel 87 with pressure medium, this now leads simultaneously to a loading of the switching channel 47 with pressure medium. As a result, the fluid pressure medium passes through the switching channel 47, the gap 91 and the Durchströmspalt 71 in the locking recesses 38, so that the locking bolt 140 against the spring force of the respective spring 39 from the locking position shown in FIG be pressed in the figures not shown unlocking position. At the same time there is a controlled leakage through the flow passage 54 of each locking bolt 40. If so For example, the flow channel 86 is acted upon by a pressure medium flow, pressure medium via the parallel to the load-holding Senkbrems valve 150.1 switched backflow 156.1 into the channel 49 and from there into the first working chamber 33 and can at the same time via the first check valve 84 of the Rückströmsperrmittels 161 get into the switching channel 47. The pressure medium then flows via the first inlet 164 of the Rückströmsperrmittels 161 in the first channel portion 169 of the fluid channel 159 and from there via the discharge point 168 in the branched fluid channel 167 and again from there into the switching channel 47. Here, the second check valve 85 of the Rückströmsperrmittels 161 closed, ie their locking member 172.2 blocks the second channel part 170th

As soon as the locking bolts 140.1 and 140.2 are transferred to their unlocking position upon further supply of oil, the piston 22 can move in the extension direction 28 due to a simultaneous application of pressure medium on its side facing the cylinder bottom 53. As soon as the pressure medium flow in the flow channel 86 preferably drops to zero, both the two backflow shutters 156.1 and 156.2 and both load hold lowering brake valves 150.1 and 150.2 close. Almost at the same time, the locking bolts 140 are displaced by the springs 39 in the extension direction 28, so that they can latch 38 depending on the current position of the locking recesses 38, so that locked in the locking position 41, the spindle 35 and thus the piston 22 both hydraulically and mechanically are.

Should be moved from the above reached stroke position of the piston 22 back in the retraction direction be, the return passage 87 can be acted upon with pressure medium, that is, the pressure medium can be supplied there. The pressure medium can then pass through the check valve 156.2 in the channel 48 and from there into the working chamber 45, so that the side facing the piston rod end side 44 of the piston 42 can be acted upon with pressure medium. At the same time, a branched-off pressure medium flow from the return passage 87 via the second check valve 85 of the return flow blocking means 161 again reaches the switching passage 47, while the first check valve 84 is closed. This leads in the same way, as already explained above, to the fact that the locking pins 140 are automatically, ie transferred without additional switching operation in their unlocked position. Then, the piston 22 and thus the piston rod 23 moves in the retraction direction 27, wherein also, as explained above in connection with the circuit of Figure 5, in the working chamber 33, a back pressure acts, which is smaller than the working pressure in the working chamber 45, so that, in turn, no uncontrolled advance of the piston 22 in the retraction direction 27 can occur.

It is thus a characteristic feature of the method according to the circuit shown in Figure 6 that the pressure means for the purpose of retraction and / or for the purpose of extending the piston 22 at least one side 44 or 46 of the piston 22 and at the same time the locking pin 40 is supplied, wherein the Locking pin 40 is transferred against the spring force of the spring 39 from the locking position 41 in the unlocked position, so that then the spindle 35 can rotate in a rotational direction 51 or in an opposite direction of rotation 52 with the result that the piston 22 is moved in the extension direction 28 or in the retraction direction 27 in accordance with the direction of rotation 51 or 52.

The pressure medium flowing back through the channel 55 can be returned to the channel 86 or the channel 87 either via the check valve 82 or via the check valve 83, depending on which of the channels 86 or 87 is pressurized.

Claims (11)

1. Locking cylinder (20) with a cylinder (21) and a piston (22), which is movable parallel to the longitudinal axis (29) of the cylinder (21) with the help of a fluid pressure medium able to be fed on both sides of the piston (22) to a first working chamber (33) and to a second working chamber (45) and which is provided with a piston thread (34), which with formation of a non-self-locking thread (37) is disposed in engagement with a spindle thread (36) of a spindle (35), which is rotatable about an axis (43) of rotation arranged parallel to the longitudinal axis (29) of the cylinder (21) and which has at least one outwardly open locking recess (38), in which at least one locking body (42, 142) loaded by means of spring force of a spring can engage, the locking body being secured against rotation about the axis (43) of rotation of the spindle (35) and fixedly connected with the cylinder (21), but mounted to be movable relative thereto, and being transferrable with the help of the spring force of the spring (39) to a locking setting (41) in which it engages in the locking recess (38) of the spindle (35) so that rotation of the spindle (35) about its axis (43) of rotation is then blocked, and wherein the locking body (42, 142) is transferrable with the help of a fluid working medium against the spring force of the spring (35) from the locking setting (41) to an unlocking setting in which the spindle (35) is rotatable about its axis (43) of rotation so as to enable movement of the piston (22) longitudinally of the cylinder (21), and wherein control means for control of the movement of the piston (22) and of the locking body (42, 142) or bodies (42, 142) are provided, wherein at least one first load-holding sink-brake means (150.1) is in fluid connection with the first working chamber (33) and that at least one second load-holding sink-brake means (150.2) is in fluid connection with the second working chamber (45), wherein the at least two load-holding sink-brake means (150.1, 150.2) have the effect that on loading of the piston (22) on its first side (46) with the pressure medium, which is disposed in the first working chamber (33), with formation of a first working pressure which causes displacement of the piston (22) in a first direction (28) a counter-pressure which is exerted by the pressure medium disposed in the second working chamber (45) and which is lower than the working pressure in the first working chamber (33) simultaneously acts in the second working chamber (45) at the second side (45) of the piston (22) so that an uncontrolled advance of the piston (22) in the first direction (28) is avoided and that conversely on loading of the piston (22) on its second side (44) with the pressure medium, which is disposed in the second working chamber (45), with formation of a working pressure which causes a displacement of the piston (22) in a second direction (27) opposite to the first direction (28) a counter-pressure which is exerted by the pressure medium disposed in the first working chamber (33) and which is lower than the working pressure in the second working chamber (45) simultaneously acts in the first working chamber (33) at the first side (46) of the piston (22) so that an uncontrolled advance of the piston (22) in the second direction (27) is avoided, and wherein the load-holding sink-brake means (150.1, 150.2) when an intended pressure relief for the purpose of holding the piston (22) in a desired stroke setting is carried out blocks return flow of the pressure medium from the two working chambers (33, 45) so that the piston (32) is held in the desired stroke setting by the pressure medium disposed in the working chambers (35, 45), characterised in that the counter-pressure controlled by the load-holding sink-brake means (150.1, 150.2) is controlled in dependence on the respective working pressure causing movement of the piston (22) longitudinally of the cylinder (21).
2. Locking cylinder according to claim 1, characterised in that the counter-pressure controlled by the load-holding sink-brake means (150.1. 150.2) is controlled in dependence on the respective working pressure, which causes a movement of the piston (22) longitudinally of the cylinder (21), so that with increasing working pressure the simultaneously produced counter-pressure decreases.
3. Locking cylinder according to claim 2, characterised in that the counter-pressure is controlled in inverse proportion to the working pressure.
4. Locking cylinder according to one of claims 1 to 3, characterised in that the load-holding sink-brake means (150.1, 150.2) each have a first inlet (153.1, 153.2) for the pressure medium, an outlet (154.1, 154.2) for the pressure medium and a control connection (155.1, 155.2) for the pressure medium, wherein the inlet (153.1) of the first load-holding sink-brake means (150.1) is in fluid connection with the first working chamber (33) and the inlet (153.2) of the second load-holding sink-brake means (150.2) is in fluid connection with the second working chamber (45) and wherein the outlet (154.1) of the first load-holding sink-brake means (150.1) is in fluid connection with the control connection (155.2) of the second load-holding sink-brake means (150.2) and the outlet (154.2) of the second load-holding sink-brake means (150.2) is in fluid connection with the control connection (155.1) of the first load-holding sink-brake means (150.1) and wherein disposed in fluid connection with the inlet (153.1, 153.2) and the outlet (154.1, 154.2) of each load-holding sink-brake means (150.1, 150.2) is a respective return flow blocking which respectively permits flow of the pressure medium from the outlet (154.1, 154.2) to the inlet (153.1, 153.2) of the respective load-holding sink-brake means (150.1, 150.2), but respectively blocks an opposite direction, and that selectably the outlet (154.1) of the first load-holding sink-brake means (150.1) and thus the control connection (155.2) of the second load-holding sink-brake means (150.2) or the outlet (154.2) of the second load-holding sink-brake means (150.2) and thus the control connection (155.1) of the first load-holding sink-brake means (150.1) can be loaded with pressure medium so as to produce a movement of the piston (22) in the first direction (28) or the second direction (27) by way of the respective working pressure and with simultaneous formation of the respective counter-pressure, being by way of the second load-holding sink-brake means (150.2) or by way of the first load-holding sink-brake means (150.1) depending on the pressure acting at the respective control connection (155.1, 155.2).
5. Locking cylinder according to claim 4, characterised in that selectably the outlet (154.1) of the first load-holding sink-brake means (150.1) or the outlet (154.2) of the second load-holding sink-brake means (150.2) can be brought into fluid connection with the locking body (42, 142) or bodies (42, 142) so that on loading of the outlet (154.1) of the first load-holding sink-brake means (150.1) or the outlet (154.2) of the second load-holding sink-brake means (150.2) with pressure medium this is fed to the locking body (42, 142) or bodies (42, 142) so as to transfer this or these to its or their locking setting.
6. Locking cylinder according to claim 4 or 5, characterised in that arranged between the outlet (154.1) of the first load-holding sink-brake means (150.1) and the outlet (154.2) of the second load-holding sink-brake means (150.2) is at least one return flow blocking means (160, 161) which on loading of the outlet (154.1) of the first load-holding sink-brake means (150.1) with pressure medium prevents pressure medium flow towards the outlet (154.2) of the second load-holding sink-brake means (150.2) and that conversely on loading of the outlet (154.2) of the second load-holding sink-brake means (150.2) with pressure medium prevents pressure medium flow towards the outlet (154.1) of the first load-holding sink brake means (150.1) and which in both cases permits feed of the pressure medium to the locking body or bodies (42, 142) so that this or these is or are transferred to its or their unlocking setting.
7. Locking cylinder according to claim 6, characterised in that the return flow blocking means (160) has a first inlet (164) for the pressure medium, a second inlet (165) for the pressure medium and an outlet (166) for the pressure medium, wherein the first inlet (164) of the return flow blocking means (160) is in fluid connection with the outlet (154.1) of the first load-holding sink brake means (150.1), and wherein the second inlet (165) of the return flow blocking means (160) is in fluid connection with the outlet (154.2) of the second load-holding sink brake means (150.2), and wherein the first inlet (164) of the return flow blocking means (160) and the second inlet (165) of the return flow blocking means (160) are connected together by way of a fluid channel (167), into which a fluid channel (167) connected with the outlet (166) of the return flow blocking means (160) opens so that a first channel part (169) of the fluid channel (167) and a second channel part (170) of the fluid channel (167) branch off from the opening point (168), and wherein a blocking element (171) for blocking the first channel part (169) or the second channel part (170) is provided, and wherein in the blocked state of the second channel part (170) the first inlet (164) of the return flow blocking means (160), the first channel part (169) and the outlet (166) of the return flow blocking means (160) are in fluid connection so that a pressure medium flow is permitted not only from the first inlet (164) of the return flow blocking means (160) to the outlet (166) of the return flow blocking means (160), but also from the outlet (166) of the return flow blocking means (160) to the first inlet (164) of the return flow blocking means (160), and wherein conversely in the blocked state of the first channel part (169) the second inlet (165) of the return flow blocking means (160), the second channel part (170) and the outlet (166) of the return flow blocking means (160) are in fluid connection so that a pressure medium flow is permitted not only from the second inlet (165) of the return flow blocking means (160) to the outlet (166) of the return flow blocking means (160), but also from the outlet (166) of the return flow blocking means (160) to the second inlet (165) of the return flow blocking means (160).
8. Locking cylinder according to claim 6, characterised in that the return flow blocking means (161) has a first inlet (164) for the pressure medium, a second inlet (165) for the pressure medium and an outlet (166) for the pressure medium, wherein the first inlet (164) of the return flow blocking means (161) is in fluid connection with the outlet (154.1) of the first load-holding sink brake means (150.1), and wherein the second inlet (165) of the return flow blocking means (161) is in fluid connection with the outlet (154.2) of the second load-holding sink brake means (150.2), and wherein the first inlet (164) of the return flow blocking means (161) and the second inlet (165) of the return flow blocking means (161) are connected together by way of a fluid channel (167), into which a fluid channel (167) connected with the outlet (166) of the return flow blocking means (161) opens at an opening point (168) so that a first channel part (169) of the fluid channel (167) and a second channel part (170) of the fluid channel (167) branch off from the opening point (168), and wherein a first blocking element (172.1) for blocking the first channel part (169) and a second blocking element (172.2) for blocking the second channel part (170) are provided, which block the first channel part (169) and the second channel part (170) with respect to a pressure medium flow from the outlet (166) of the return flow blocking means (161) to the first inlet (164) of the return flow blocking means (161) and to the second inlet (165) of the return flow blocking means (161) and which permit a pressure medium flow from the first inlet (164) of the return flow blocking means (161) to the outlet (166) of the return flow blocking means (161) and from the second inlet (165) of the return flow blocking means (161) to the outlet (166) of the return flow blocking means (161).
9. Locking cylinder according to claim 4, characterised in that the working medium or the pressure medium is fed to the locking body (142) or bodies (142) so as to transfer this or these into its or their unlocking setting and that simultaneously the pressure medium is selectably fed to the first working chamber (33) or the second working chamber (45) so as to produce movement of the piston (22) in the first direction (28) or in the second direction (27).
10. Locking cylinder according to claim 4, characterised in that the working medium or the pressure medium is initially fed to the locking body (42) or bodies (42) so as to transfer this or these into its or their unlocking setting and that then the pressure medium is selectably fed to the first working chamber (33) or the second working chamber (45) so as to produce a movement of the piston (22) in the first direction (28) or in the second direction (27).
11. Locking cylinder according to claim 10, characterised in that the respective return flow blocking means (156.1, 156.2) comprises a blocking element (173.1, 173.2) for preventing a pressure medium flow from the inlet (153.1, 153.2) to the outlet (154.1, 154.2) of the respective load-holding sink-brake means (150.1, 150.2), which is loaded by spring forces of a spring (174.1, 174.2), so that an opening of the return flow blocking means (156.1, 156.2) and consequently a pressure medium flow from the outlet (154.1, 154.2) to the inlet (153.1, 153.2) of the respective load-holding sink-brake means (150.1, 150.2) is made possible only after exceeding a limit pressure of the pressure medium, the value of which depends on a spring characteristic of the respective spring (174.1, 174.2).

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