Actuating cylinder with cushioned end stroke

Abstract

The present invention relates to an actuating cylinder with a cushioned end stroke, in which a piston unit includes a piston main portion and a ring body. The exterior of the ring body receives a piston ring having a piston ring gap, and a ring opening of the ring body receives a guide pin of the piston main portion, the ring gap being formed between the ring body and the guide pin, and the ring body has axial and radial play relative to the piston main portion. The ring body has an axial ring surface on the piston main portion side, and the piston main portion has an axially opposing ring surface on the ring body side opposite the axial ring surface. The piston unit is designed so that during its inward movement into the cushion region, the piston ring passes axially through the pressure medium connection and the piston unit seals the damping pressure medium volume, the piston unit is in a first operating state during its inward movement and in a second operating state during its outward movement, in which in the first operating state the axial ring surface on the piston main part side and the axially opposing ring surface on the ring body side seat against each other and form a sealing surface, the piston ring gap is configured to throttle the outflow of the damping pressure medium volume, and in the second operating state the axial ring surface on the piston main part side and the axially opposing ring surface on the ring body side have an axial gap for the inflow of pressure medium.

Description

[Technical field]

[0001] The present invention relates to an actuating cylinder having a cushioned end stroke.

[0002] Various variant solutions are known from the prior art for constantly or progressively slowing down the movement of a piston in a hydraulic working cylinder within defined limits. Usually, the movement is slowed down by throttling the outflow of the hydraulic fluid using a damping element, which reduces the cross section through which the hydraulic fluid can exit. [Background technology]

[0003] For example, EP 0949422 discloses a solution in which the ring gap of a damping ring, which is elastically seated against the inner cylinder wall, serves as a flow-limiting constriction. The damping area of ​​the cylinder has a conical design for a progressive damping effect. The damping ring is thus compressed and the ring gap of the damping ring is progressively reduced with its progressive movement in the damping area. On the one hand, this is a proven solution that makes an important contribution to the state of the art, but on the other hand, its manufacture is technically very demanding due to the required precision of the gap dimensions of the piston and the inner cylinder wall.

[0004] One problem with the state of the art is caused by buckling loads, which result in deformations in the guides of the guide closure and in the guide bands of the piston, and require a relatively large gap size between the piston and the inner cylinder wall to ensure that the piston does not rub against the inner cylinder wall, which is inconsistent with providing the most accurate damping effect. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] European Patent No. 0949422 Summary of the Invention

[0006] The object of the present invention is to disclose a damping system for an actuating cylinder with a cushioned end stroke, which provides high precision and easy adjustment of the damping, is suitable for high bending stresses on the piston unit and different cylinder designs, has a high level of robustness and operational reliability, and can be manufactured in a simple and cost-effective manner.

[0007] This problem is solved by the features of claim 1. Preferred further embodiments result from the dependent claims.

[0008] According to the present invention, an actuating cylinder having a cushioned end stroke comprises a cylinder and a piston unit.

[0009] The cylinder according to the invention comprises a cylinder tube, a first closure part and a second closure part.

[0010] According to the invention, a first closure is arranged at a first cylinder tube end and a second closure is arranged at a second cylinder tube end of the cylinder tube. The two closures are arranged so as to be pressure-tightly connected to the respective cylinder tube ends. To provide such a connection, each of the two closures is preferably welded to the cylinder tube along a common circumferential contact surface. Other connections, for example threaded joints, are also possible.

[0011] The cylinder tube and the closure form a cylinder interior according to the invention, which is to be understood as the internal space of the cylinder formed by the closure and the cylinder tube and in which the pressure medium is placed when the system is used as intended. Furthermore, the piston is arranged in the cylinder interior.

[0012] According to the invention, the cylinder has a damping region in at least one end region, which is an area inside the cylinder in which damping (cushioning effect) occurs when the piston unit moves.

[0013] Damping should be understood to be the force that slows down the movement of the piston unit.

[0014] The damping area is arranged in at least one end region of the cylinder tube and comprises a portion of the cylinder interior between the pressure medium connection and the axial boundary achieved by the closure arranged in this end region.

[0015] According to the invention, the cylinder has a laterally arranged pressure medium connection which is assigned to the damping region and which is axially spaced from the axial boundary of the cylinder interior.

[0016] The damping region extends between the pressure medium connection and the axial boundary, which physically blocks further movement of the piston unit and thus defines on one side the maximum path of movement of the piston unit in the axial direction.

[0017] The axial boundary is preferably formed by a closure part, which for this purpose has a suitable stop surface against which the piston unit can seat so that the piston unit assumes its end position.

[0018] In a special design, the end position of the piston unit during operation can be located before the axial boundary is reached.

[0019] According to the present invention, the piston unit has a piston main part and a ring body. Preferably, the piston unit is composed of a piston rod and a piston, and the piston includes the piston main part and the ring body. Hereinafter, the piston main part and the ring body are collectively referred to as the piston.

[0020] Depending on the type of working cylinder, the piston body can have different designs. For example, the piston rod can be guided completely through the piston body or only partially in it. Furthermore, the piston unit can be designed as a monolithic part and then only have a piston rod part and a piston part.

[0021] According to the invention, the piston unit slidably passes through the first closure portion and defines at least one working chamber inside the cylinder.

[0022] The first closure part is designed to slidingly receive the piston unit and has sealing elements and guides for this purpose.

[0023] According to the invention, the piston main portion is guided by a guide inside the cylinder so as to be axially displaceable.

[0024] In this design, the piston body has at least one receiving part for the guide, which is preferably designed as a groove into which a guide ring is inserted as a guide.

[0025] The ring body according to the invention has a circumferential inner ring groove on its radially outer surface, in which a piston ring is arranged.

[0026] For this purpose, the circumferential inner ring groove is designed to receive the piston ring and fix it in its axial position, and furthermore, to allow radial movement of the piston ring at least to the extent that it can elastically deform itself, which is achieved by a sufficient depth of the circumferential inner ring groove.

[0027] In accordance with the present invention, the piston ring is resiliently seated against the inner cylinder wall and has a piston ring gap.

[0028] For this purpose, the piston ring is provided with an elastic, in particular radially elastic, design which in its relaxed state has an outside diameter which is greater than the inside diameter of the cylinder tube.

[0029] When the piston unit is inserted into the cylinder tube, the piston ring is stressed in the circumferential inner ring groove and seats against the inner cylinder wall. In this stressed state, the piston ring elastically deforms, reducing its outside diameter and the size of the piston ring gap.

[0030] According to the invention, the ring body receives the guide pin of the piston main part in the ring opening and forms a ring gap between the radially inner side surface of the ring body and the guide pin. The ring opening is preferably a hollow cylindrical recess. However, it can also have a different geometric shape, provided that it is designed to be guided by the guide pin. The ring body is designed so that its ring opening can be placed on the guide pin of the piston main part.

[0031] The guide pin is a component of the piston body. It is preferably a tapered part of the piston body. However, it can also be a connected component. The guide pin is arranged at the end of the piston unit facing the end stroke to be damped. The guide pin is preferably cylindrical. And the outer diameter of the guide pin is smaller than the inner diameter of the ring opening. However, the guide pin can also have any other shape suitable for guiding the ring body.

[0032] The solution according to the invention is particularly characterized in that the ring body has an axial play and a radial play relative to the piston main part, in the following due to the radial play the ring body is also called floating ring body.

[0033] In its position on the guide pin, the axial movement of the ring body is limited by a blocking element, which is preferably designed as a Seger circlip ring, which is inserted into a corresponding ring groove arranged on the guide pin. Other designs of the blocking element are also possible, which can be arranged on the piston body and which can limit the play of the ring body in the axial direction.

[0034] The ring body according to the present invention has an axial ring surface on the piston main portion side, and the piston main portion has an axially opposing ring surface facing the ring body side.

[0035] According to the invention, the piston unit is designed in such a way that during its inward movement into the damping area, the piston unit with the piston ring passes axially through the pressure medium connection and seals in the damping area the damping pressure medium volume in the damping area space.

[0036] When the piston ring passes the pressure medium connection during its inward movement, it reaches the damping area. At the same time, the damping pressure medium volume is enclosed. Now, pressure medium can no longer flow directly from the working chamber via the pressure medium connection.

[0037] The damping zone space defines the portion of the cylinder interior that is limited by the piston unit, the closure and the cylinder tube when the piston ring has passed the pressure medium connection, and the size of the damping zone space decreases as the piston unit continues its axial movement towards the axial end position.

[0038] The portion of pressure medium enclosed within the damping region space and flowing therefrom is referred to as the damping pressure medium volume.

[0039] The piston unit according to the invention is designed to have a first operating state in the damping region during the inward movement and a second operating state in the damping region during the outward movement, hereinafter the first operating state is also referred to as the damping operating state, hereinafter the second operating state is also referred to as the outward movement operating state.

[0040] According to the present invention, in the first operating state, the axial ring surface on the piston main portion side and the axially opposing ring surface on the ring body side come into contact with each other to form a sealing surface.

[0041] During the inward movement the damping pressure medium volume is enclosed by the piston unit such that the pressure in the damping area space also increases compared to the pressure at the pressure medium connection.

[0042] According to the invention, therefore, in the damping operating state, there is an overpressure in the damping pressure medium volume compared to the pressure in the pressure medium connection. Furthermore, the piston ring gap according to the invention is configured for throttling the outflow of the damping pressure medium volume.

[0043] In the damping operating state, the pressure of the enclosed pressure medium, i.e. the damping pressure medium volume, exceeds the operating pressure present in the remainder of the working chamber, so that the ring body is pressed with its axial ring surface on the piston body side against the axially opposing ring surface on the ring body side, forming a sealing surface there. The operating pressure is to be understood as the pressure of the pressure medium applied to the pressure medium connection, which corresponds to the pressure in the remainder of the working chamber.

[0044] In the damping operating state, the pressure medium can only flow out through the piston ring gap. The slowdown of the outflow of the damping pressure medium volume creates a force effect which counteracts the inward movement of the piston unit.

[0045] According to the present invention, in the second operating state, an axial gap is formed between the axial ring surface on the piston main part side and the axially opposing ring surface on the ring body side. Hereinafter, the axial gap between the axial ring surface on the piston main part side and the axially opposing ring surface on the ring body side is also simply referred to as the axial gap.

[0046] This is based on the fact that in the outward moving operating state, the operating pressure is higher than the pressure of the damping pressure medium volume in the damping area space, the ring body is separated from the axially facing ring surface of the piston main part on the ring body side, and an axial gap is formed between the piston main part and the ring body.

[0047] According to the invention, the axial gap and the annular gap form a pressure medium inlet channel, which is designed for the inflow of pressure medium into the damping area space.

[0048] In fact, the inflow of the pressure medium is also possible via the remaining cross section defined by the piston ring gap, but especially in the case of progressive damping with a conical cross section in the damping region, the cross section of the piston ring gap is so small that active outward movement is then only possible with a very long delay and, in addition, considerable pressure losses across the piston ring gap must be overcome for this purpose.

[0049] The axial gap between the axial ring surface of the ring body on the piston main part side and the axially opposing ring surface of the piston main part on the ring body side, as well as the radial ring gap between the radially inner side surface of the ring body and the guide pin, form a pressure medium channel with a structurally designable cross-section which allows the pressure medium to flow into the damping area space, regardless of the cross-section of the piston ring gap.

[0050] In this way, the piston unit is moved out of its end positions and damping regions without undesired damping, whereby the piston unit performs its outward movement.

[0051] In addition, it was surprisingly found that the outward movement can be started practically without delay due to the ring body and its axial play. This is based on the fact that when pressure is applied to the pressure medium connection, the ring body is actively moved axially away from the piston main part. The force that causes this movement is due to the surface area of ​​the ring surface on the side of the piston main part and the pressure difference between the pressure at the pressure medium connection and the pressure of the damping pressure medium in the damping area space. In its axial movement, the ring body is designed as a solid body, so that it displaces a partial volume of the damping pressure medium in the damping area space, so that the pressure medium presses against the piston main part and the piston unit is displaced from the end position without delay. This initial phase of the operating state of the outward movement is in fact only provided until the piston ring body reaches the end position of its axial play with the circlip. However, in this state, the axial gap is advantageously completely open, so that the pressure medium can flow into the damping area space via the pressure medium inlet channel and therefore the uninterrupted outward movement can be continued without undesirable delay.

[0052] The actuating cylinder with cushioned end stroke according to the invention has the following advantages in particular:

[0053] A surprisingly simple solution has been found which simultaneously solves several technical problems by providing a floating ring body.

[0054] First, the ring body is decoupled from the exact radial position of the piston main part due to its floating bearing. In the self-adjusting manner, the ring body always follows the inner cylinder wall exactly in its radial position due to the radially elastic piston ring. This is especially true even if the piston main part is adversely affected in its radial position, especially as a result of deformation of the piston rod under buckling loads.

[0055] Another advantage is that the ring body does not need to transmit any radial forces to the inner cylinder wall.

[0056] This also advantageously makes it possible to provide a particularly small gap size between the outer surface of the ring body and the inner cylinder wall without the risk of rubbing with the inner cylinder wall, which is not possible according to the prior art.

[0057] It is also advantageous that a particularly precise cushioned end stroke can be provided by the ring body and thus by one and the same component. The particular precision is based on the fact that the ring body in its radial position also follows the respective shape of the inner cylinder wall of the damping region, which in this case can in particular be cone-shaped.

[0058] Furthermore, with little, particularly design effort, the floating ring body can advantageously be provided with axial play and thus two different operating states can be provided in the form of a damped operating state and an outward operating state, on the one hand allowing a precise damping effect during the inward movement and, on the other hand, avoiding damping during the active outward movement.

[0059] Furthermore, the cross section of the ring gap is advantageously always constant regardless of the radial positional relationship of the ring body and the guide pin within the radial play and can be defined in a simple manner by the difference between the inner diameter of the ring body and the outer diameter of the guide pin.

[0060] It is also advantageous that the damping and outward displacement characteristics can be adapted to specific requirements by simple constructional measures, such as the axial spacing of the pressure medium connections, the shape of the inner cylinder wall in the damping area, the selection of the width of the piston ring gap or the width of the radial and ring gaps, etc. Furthermore, this can be done separately for each end stroke, if applicable.

[0061] Furthermore, if the ring body is designed as a solid body, it is advantageous that the ring body and its axial play can provide for an outward movement without delay.

[0062] Furthermore, it may be advantageous to provide a cushioned end stroke at only one end position, as well as at both end positions.

[0063] In addition, this solution can be used with different cylinder types, such as differentially actuated cylinders, synchronous cylinders, pull cylinders or plunger cylinders in particular.

[0064] The elastic piston ring is tensioned against the inner cylinder wall and can also advantageously compensate for deviations in the cylinder tube caused by manufacturing, thus allowing for precise damping.

[0065] The constant distance between the ring body and the inner cylinder wall provides the advantage that magnetic position sensors can be used very reliably and provide accurate axial position data of the piston unit.

[0066] Finally, particular advantages are high robustness, high operational reliability and technically good manufacturability.

[0067] According to an advantageous further development, the axial play of the ring body is limited axially distal from the piston centre by a circlip.

[0068] For this purpose, the circlip is inserted into a groove in the guide pin, but the circlip is not completely received by the groove. The circlip can in particular be a Seeger circlip ring, which is not expensive and is available as a standard component.

[0069] Thus, the axial play of the ring body is limited in one direction by the axially opposing ring surface of the piston main portion and in the other direction by the circlip.

[0070] The advantage is that by means of a constructionally very simple and at the same time reliable measure, namely the axial distance of the circlip relative to the ring body, the axial play of the ring body and therefore the possible width of the axial gap between the axial ring surface on the piston body side and the axially opposing ring surface on the ring body side can be defined as part of the pressure medium inlet channel. In this way, the possible speed of the outward movement in the second operating state can also be specifically influenced.

[0071] According to a further developed embodiment, the guide pin has an axial groove, which here is formed as part of the pressure medium inlet channel.

[0072] The axial groove is at least one groove that extends axially with the guide pin. The axial groove can also be formed by several grooves.

[0073] By means of the axial grooves, the cross section of the ring gap can be easily widened and thus, in conjunction with the axial gap, can be advantageously used for selective adjustment of the pressure medium inflow in the second operating state. In this way, the achievable speed of the outward movement in the damping area can be determined. The cross section of the pressure medium inlet channel can be advantageously widened by the axial grooves, independently of the radial play of the ring body.

[0074] According to an advantageous further development, the cylinder has a position sensor, which is designed to register the position of the ring body.

[0075] Position sensors detect the position of the piston unit by measurement methods that record and evaluate capacitive, magnetic, mechanical or electromagnetic changes in properties during piston movement. Various position sensors for determining the piston position are known from the prior art. For example, in the case of a magnetic design, a reed switch can be used for detection purposes.

[0076] This further development is particularly advantageous, since an extremely accurate position detection can be provided. This accuracy is based on the fact that the ring body is mounted with radial play relative to the piston main part, i.e. in a floating design. The exact radial position of the ring body relative to the cylinder tube remains unaffected by inaccuracies in the radial position of the piston body, which may occur in particular as a result of buckling loads, dynamic loads or uneven wear of the guides, since the ring body is guided directly by the inner cylinder tube wall via the piston ring. This means that there is always an exact gap size between the ring body and the inner cylinder wall, and furthermore, the gap size can be provided in a design that is considerably smaller compared to the prior art. The position sensor is arranged in a fixed position relative to the cylinder tube. It has been found that a reliable radial distance between the ring body and the position sensor can significantly increase the accuracy of the axial position detection.

[0077] According to another additional development, the inner cylinder wall is tapered in the damping region and in the first operating state the piston rings are designed to narrow the piston ring gap by a gradual inward movement.

[0078] If the inner cylinder wall is tapered in the damping region, the piston ring is increasingly tensioned during its inward movement because its outer diameter must fit into the increasingly smaller inner diameter of the inner cylinder wall. This also progressively reduces the piston ring clearance, decreasing the cross-sectional area for the outflow of the damping pressure medium volume.

[0079] Thus, the damping effect of the damping region is increased to a maximum, and the level of taper determines the increase in damping effect along the inward travel path that is covered.

[0080] However, the inner cylinder wall can also have a conical section at the beginning and then, moving inwards, a cylindrical section again in the damping region, in which case the damping effect increases to a maximum in the conical section, but in the next cylindrical section of the damping region the maximum damping effect achieved remains effective until an end position is reached. The course of the damping effect can therefore also be adapted to the specific requirements.

[0081] According to an advantageous further development, the cylinder has an additional damping region in an additional end region axially opposite the end region.

[0082] According to this advantageous further development, the cylinder has a laterally arranged additional pressure medium connection which is assigned to an additional damping region and is axially spaced away from an additional axial boundary inside the cylinder opposite the axial boundary.

[0083] The function and the design of the additional pressure medium connection, the additional damping area and the additional axial boundary essentially correspond to the function and the design of the pressure medium connection, the damping area and the axial boundary.

[0084] The additional damping area and the additional pressure medium connection are arranged spatially close to the second closure part at the second cylinder tube end.

[0085] According to an advantageous further development, the piston unit has an additional ring body arranged axially opposite the ring body, and the piston main body has an additional guide pin arranged axially opposite the guide pin.

[0086] The additional ring body is designed similarly to the ring body and is arranged on the opposite side of the piston unit. The additional guide pin also has at least one additional blocking element which limits the axial play of the additional ring body.

[0087] Preferably, this additional blocking element is also designed as an additional circlip which is inserted into an additional groove of an additional guide pin.

[0088] The dimensions of the additional ring body and the additional guide pin may differ from the dimensions of the ring body and the guide pin, despite their essentially identical design. For example, different damping characteristics may be realized at the two end positions of the piston unit. This is particularly useful for actuating cylinders that are subject to strong asymmetric loads.

[0089] According to an advantageous further development, the piston unit is designed to have a third operating state during the inward movement in the additional damping area and a fourth operating state during the outward movement in the additional damping area. Hereinafter, the third operating state is also called the additional damping operating state. Hereinafter, the fourth operating state is also called the operating state of the additional outward movement.

[0090] The third operating state is also referred to as the additional damping operating state and correspondingly exhibits characteristics of the first operating state for the additional damping region. The fourth operating state is also referred to as the additional extension operating state and correspondingly exhibits characteristics of the second operating state for the additional damping region.

[0091] Characteristics of the operating state are to be understood as being, inter alia, the pressure ratio, the position of the ring body and the additional ring body relative to the piston main body and the positional relationship of the piston unit to the pressure medium connection and the additional pressure medium connection.

[0092] A particular advantage of the above-specified further development is that a cushioned end stroke which is effective at both end positions is also provided for double-acting actuating cylinders.

[0093] In addition, the damping characteristics at each of the two cushioned end strokes can advantageously be adjusted independently of the damping characteristics at each other cushioned end stroke.

[0094] The invention is explained in more detail by way of exemplary embodiments with the aid of the following figures, in which: [Brief description of the drawings]

[0095] [Figure 1] FIG. 1 is a cross-sectional view of an actuating cylinder with a cushioned end stroke as a differential cylinder with a cushioned end stroke on one side. [Diagram 2] FIG. 1 is an enlarged detailed cross-sectional view of an actuating cylinder with a cushioned end stroke as a differential cylinder with a cushioned end stroke on one side. [Diagram 3] FIG. 1 is a cross-sectional view of an actuating cylinder with cushioned end stroke as a differential cylinder with cushioned end strokes on both sides. [Figure 4] FIG. 13 is a cross-sectional view of an actuating cylinder with a cushioned end stroke as a synchronous cylinder with cushioned end strokes on both sides. [Diagram 5] FIG. 1 is an enlarged detailed cross-sectional view of an actuating cylinder with cushioned end strokes as a differential cylinder with cushioned end strokes on either side of a first operating state; [Figure 6] FIG. 13 is an enlarged detailed cross-sectional view of an actuating cylinder with cushioned end strokes as a differential cylinder with cushioned end strokes on either side of a second operating state. [Figure 7] FIG. 2 is an isometric view of the piston unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0096] Figure 1 is a schematic diagram of a first embodiment of a differential actuation cylinder with a cushioned end stroke. In this embodiment, it is a differential actuation cylinder with a cushioned end stroke on one side. In this embodiment, the cushioned end stroke is provided at the end position associated with the second closure 5. This is a cushioned end stroke at the piston crown that damps the inward movement.

[0097] The working cylinder with cushioned end stroke comprises a cylinder 1 and a piston unit 2 .

[0098] The cylinder 1 consists of a cylinder tube 3, a first closure part 4 and a second closure part 5. The cylinder tube 3 and the two closure parts 4, 5 are connected to each other such that they enclose the cylinder interior 8. The first closure part 4 is associated with the first cylinder tube end 6 and the second closure part 5 is associated with the second cylinder tube end 7. In this embodiment, the inside of the second closure part 5 forms an axial boundary 11, and the inside of the first closure part 5 forms an additional axial boundary 27 that limits the axial movement space of the piston unit 2 arranged in the cylinder interior space 8. The axial boundaries 11, 27 are designed as stop surfaces for the piston unit 2 moving axially during operation.

[0099] On the cylinder tube 3 a pressure medium connection 10 is arranged at the second cylinder tube end 7 and an additional pressure medium connection 26 is arranged at the first cylinder tube end 6 .

[0100] The piston unit 2 has a piston main part 12 and a ring body 13. In an exemplary embodiment, the piston unit 2 is composed of a piston rod and a piston that are rigidly connected to each other. In this embodiment, the piston main part and the ring body together constitute the piston.

[0101] In this embodiment, the piston rod of the piston unit 2 is guided through the first closure part 4 and is slidably mounted therein.

[0102] The ring body 13 is pressed onto a guide pin 18 designed as a taper on the piston main part 12 .

[0103] The piston main portion 12 is guided within the cylinder tube 3 by a guide 14 .

[0104] 2 shows an enlarged detail of FIG. 1 in the region of the second closure 5. Furthermore, the piston body 12 is in an end position such that it seats with its guide pin 18 on the axial boundary 11.

[0105] In this figure the arrangement and design of the ring body 13 is shown in more detail. In this embodiment the ring body 13 is designed as a metal ring with an inner ring groove 15 on its outer surface 13c, into which the piston ring 16 is inserted. The inner ring groove 15 is designed with a large radial play so that the piston ring 16 can elastically deform in the radial direction. The elastic piston ring has a piston ring gap 16a (see in particular FIG. 7) and is tensioned against the inner cylinder wall 17.

[0106] The ring body 13 is pressed onto the guide pin 18 and seats with its axial ring surface on the piston body side 13d against the opposing ring surface on the ring body side 12a of the piston main part 12. On the opposite axial side, the axial play of the ring body 13 is limited by a circlip 22.

[0107] Furthermore, the ring opening 13 a in the ring body is designed to exceed the diameter of the guide pin 18 so that the ring body has radial play relative to the guide pin 18 .

[0108] The damping area 9 is an axial section, which extends from the pressure medium connection 10 to the end position of the piston ring 16 in front of the second closure part 5. When the piston unit 2 moves inwards, a damping effect is generated in the damping area 9, which is directed against the inward movement of the piston unit 2 and slows down the piston unit 2. This will be explained in more detail with reference to FIG.

[0109] Figure 3 shows a second embodiment. This is a differential working cylinder with cushioned end strokes at both ends. For this purpose, an additional ring body 28 is provided. The additional ring body 28 has an identical design to that of the ring body 13, is pressed onto an additional guide pin 29 and is fixed there by an additional circlip 30. Both ring bodies 13, 28 and both guide pins 18, 29 are arranged axially opposite each other on the piston main part 12.

[0110] The additional ring body provides a further damping effect in an additional damping area 25 corresponding to the damping area 9. The additional damping area 25 extends between the additional pressure medium connection 26 and the end position of the additional piston ring 31 in front of the additional axial boundary 27 at the first closure 4.

[0111] Furthermore, the differential actuation cylinders of Figures 1 and 3 have the same basic design.

[0112] Figure 4 shows a synchronous working cylinder, which also has a cushioned end stroke on both sides. The difference to the differential working piston of Figure 3 is that the piston rod part of the piston main part 12 is guided through both closure parts 4, 5 and is slidably mounted. Therefore, in this embodiment, the second closure part 5 is also designed as a guide closure part. The piston main part 12 is designed similarly to Figure 3, but differs in that the piston rod passes through it. Here too, both parts of the piston unit 2 are rigidly connected to each other.

[0113] In figure 5 a first operating state, which is a damping operating state, is shown, and in figure 6 a second operating state, which is an outward moving operating state, is shown during operation of the working cylinder with a cushioned end stroke. These figures are used to explain the method of damping function.

[0114] In Fig. 5 the piston unit has performed an inward movement and the piston ring 16 in the inner ring groove 15 of the ring body 13 has just passed the pressure medium connection 10 and encloses a damping pressure medium volume in the damping area space 20. The pressure in the damping pressure medium volume is greater than the pressure at the pressure medium connection 10. This causes the ring body 13 to be pressed by the axial ring surface of the piston main side 13d against the axially opposing ring surface of the ring body side 12a, so that an annular sealing surface is formed there.

[0115] The pressure medium from the damping pressure medium volume can now only flow back via the piston ring gap 16a in the piston ring 16 to the pressure medium connection 10, so that the inward movement of the piston unit 2 is countered by a damping force effect. The inward movement is slowed down until the piston unit 2 reaches the axial boundary 11.

[0116] FIG. 6 shows a second operating state.

[0117] In this second operating state, the piston unit 2 performs an outward movement, which is caused by pressure medium flowing from the pressure medium connection 10 into the damping area space 20 (as soon as the pressure in the pressure medium connection 10 is greater than the pressure in the damping pressure medium volume).

[0118] As soon as the pressure in the pressure medium connection 10 becomes greater than the pressure in the damping pressure medium volume, the ring body 13 is displaced axially and pressed against the circlip 22. This opens the axial gap 21 between the axially facing ring surface on the ring body side 12a and the axial ring surface on the piston main side 13d.

[0119] Furthermore, the ring body 13 has radial play, which is provided by the ring gap 19 between the inner side surface 13b and the guide pin 18. The axial gap 21 and the ring gap 19 form a continuous pressure medium inlet channel for the pressure medium flowing into the damping area space 20. In this embodiment, the axial groove 24 of the guide pin further increases the flow cross section of the pressure medium inlet channel.

[0120] This allows the pressure medium to flow into the damping area space 20 with low pressure loss and with almost no slowing down of the outward movement.

[0121] In an embodiment having a cushioned end stroke on both sides, the operating mode shown in Figures 5 and 6 corresponds to the interaction of the third and fourth operating states in the additional damping region 25 with the additional ring body 28.

[0122] The piston unit is in a third operating state during the inward movement towards the additional damping region 25 and in a fourth operating state during the outward movement from the additional damping region 25. In a further end position, the third operating state is a damping operating state and the fourth operating state is an outward movement operating state.

[0123] Additionally, Figures 5 and 6 show a position sensor 23 disposed on the cylinder tube.

[0124] FIG. 7 shows in a perspective view the piston unit 2 of an embodiment of a differential actuating cylinder with cushioned end strokes on both sides.

[0125] Shown are the ring body 13, the piston ring 16 with the piston ring gap 16a, the circlip 22, the guide 14 and the axial groove 24. Furthermore, on the axially opposite side of the piston body 12, an additional ring body 28 and an additional piston ring 31 arranged therein with an additional piston ring gap 31a are shown. The piston rings 16, 31 and the circlip 22 are each designed as elastic metal rings. The additional circlip and the additional guide pin are hidden and therefore do not have reference numbers in FIG. 7.

[0126] The ring body 13 receives the piston ring 16 in the inner ring groove 15 and is fixed to the guide pin 18 by the circlip 22. The same applies to the additional ring body 28 and the additional piston ring 31 as well as the additional circlip and the additional guide pin.

[0127] The guide 14 is disposed in a groove in the piston body 12 . [Explanation of symbols]

[0128] 1 cylinder 2 Piston unit 3 Piston tube 4 First Closure 5 Second Closure 6 First Cylinder Tube End 7 Second Cylinder Tube End 8 Inside the cylinder 9. Attenuation Region 10 Pressure medium connection 11 Axial boundary 12 Piston main part 12a Axial facing ring surface on the ring body side 13 Ring body 13a Ring opening 13b Medial side 13c outer side 13d Axial ring surface on main piston side 14 Guide 15 Inner ring groove 16 Piston rings 16a Piston ring clearance 17 Inner Cylinder Wall 18 Guide pin 19 Ring gap 20 Attenuation Domain Space 21 Axial clearance 22 Circlip 23 Position Sensor 24 Axial groove 25 additional attenuation areas 26 Additional pressure medium connections 27 Additional Axial Boundaries 28 additional ring bodies 29 Additional guide pins 30 Extra Circlips 31 Extra piston rings 31a Additional piston ring clearance

Claims

1. Equipped with a cylinder (1) and a piston unit (2) An actuating cylinder having a cushioned end stroke, The cylinder (1) includes a cylinder tube (3), a first closing part (4) and a second closing part (5); The cylinder tube (3) has a first cylinder tube end (6) and a second cylinder tube end (7); the first closure part (4) is arranged at the first cylinder tube end (6) and the second closure part (5) is arranged at the second cylinder tube end (7); The cylinder tube (3) and the closure portion (4, 5) form a cylinder interior (8); The cylinder (1) has a damping region (9) in at least one end region, the cylinder (1) has at least one laterally arranged pressure medium connection (10), which is associated with the damping area (9) and is axially spaced from an axial boundary (11) of the cylinder interior (8), The piston unit (2) includes a piston main portion (12) and a ring body (13), The piston unit (2) slidably passes through the first closing portion (4) and defines at least one working chamber in the cylinder interior (8); The piston main portion (12) is guided by a guide (14) inside the cylinder (8) so as to be displaceable in the axial direction, The ring body (13) has a circumferential inner ring groove (16) on a radially outer surface (13c), and a piston ring (16) is disposed in the inner ring groove (15); The piston ring (16) is elastically seated on a cylinder inner wall (17) of the cylinder tube (3) and has a piston ring gap (16a) provided around the piston ring (16); The ring body (13) receives a guide pin (18) formed as a part protruding in the axial direction of the piston main part (12) in a ring opening (13a), and a ring gap (19a) is formed between a radially inner side surface of the ring body (13b) and the guide pin (18); The ring body (13) has axial and radial play relative to the piston main part (12), The ring body (13) has an axial ring surface (13d) directed toward the piston main part, and on the opposite side, the piston main part has an axially facing ring surface on the ring body side (12a), said piston unit (2) is designed to pass axially through said pressure medium connection (10) with said piston ring (16) during its inward movement into said damping area (9) and to enclose a damping pressure medium volume in a damping area space (20) in said damping area (9), said piston unit (2) being designed to be in a first operating state within said damping area (9) during its inward movement and in a second operating state during its outward movement, In the first operating state, the axial ring surface (13d) directed toward the piston main portion and the axially opposing ring surface on the ring body side (12a) abut against each other to form a sealing surface, the damping pressure medium volume has an overpressure compared to the pressure medium connection (10), and the piston ring gap (16a) is configured for throttling the outflow of the damping pressure medium volume, In the second operating state, an axial gap (21) exists between the axial ring surface (13d) directed toward the piston main portion and the axially opposing ring surface on the ring body side (12a), The axial gap (21) and the annular gap (19a) form a pressure medium inlet channel, the pressure medium inlet channel being designed for the inflow of pressure medium into the damping area space (20).

2. The axial play of the ring body (13) is limited axially distal from the piston center by a circlip (22).

2. An actuating cylinder having a cushioned end stroke according to claim 1 .

3. The guide pin (18) has an axial groove formed as part of the pressure medium inlet channel 3. An actuating cylinder with cushioned end stroke according to claims 1 and 2.

4. The cylinder includes a position sensor (23), the position sensor (23) being configured to record the position of the ring body (13). Characterized in that 4. An actuating cylinder having a cushioned end stroke according to any one of claims 1 to 3.

5. The cylinder inner wall (17) of the cylinder tube (3) is tapered within the damping region (20), and in the first operating state, the piston rings (16) are designed to narrow the piston ring gap (16a) as the inward movement progresses. Characterized in that 5. An actuating cylinder having a cushioned end stroke according to any one of claims 1 to 4.

6. The cylinder (1) is provided with an additional damping region (25) in an additional end region axially opposite the end region. It is characterized by: said cylinder (1) comprises a laterally arranged additional pressure medium connection (26), said additional pressure medium connection (26) being associated with said additional damping area (25) and axially spaced from an additional axial boundary (27) inside said cylinder opposite said axial boundary, the piston unit (2) includes an additional ring body (28) axially opposite the ring body (13), the piston main part (12) includes an additional guide pin (29) axially opposite the guide pin (18); during its inward movement into the additional damping area (25), the piston unit (2) passes axially over the additional pressure medium connection (26) with the additional piston ring (30) and is designed to enclose an additional damping pressure medium volume in an additional damping area space in the additional damping area (25), the piston unit is designed to have a third operating state in the additional damping area (25) during an inward movement and a fourth operating state in the additional damping area (25) during an outward movement, With respect to the additional attenuation region (25), the third operating state is characterized by the characteristics of the first operating state and the fourth operating state is characterized by the characteristics of the second operating state.

6. An actuating cylinder having a cushioned end stroke according to any one of claims 1 to 5.

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