EP4081714B1 - Working cylinder with cushioned end-stroke - Google Patents

Description

The invention relates to a working cylinder with end position damping.

Various variants of solutions are known from the prior art which constantly or progressively delay the movement of a piston within a hydraulic working cylinder in a defined area. The movement is usually decelerated by throttling the outflow of hydraulic fluid using a damping element. This attenuator reduces the cross section through which the hydraulic fluid can flow.

For example, this is off EP 0 949 422 B1 a solution is known in which an annular gap of a damping ring, which rests resiliently on the inner cylinder wall, serves as a flow-limiting constriction. The damping area of the cylinder is conical for progressive damping. Thus, as the movement in the damping region progresses, the damping ring is compressed and the annular gap of the damping ring is progressively reduced. This is a proven solution that makes an important contribution to the state of the art, but on the other hand is technologically very demanding due to the required precision of the gap dimensions of the piston and the inner cylinder wall in production. A similar solution of damping using a piston ring gap is also available US 4,207,800 A known.

A problem according to the prior art arises with buckling loads, since these lead to deformations in the guides of the guide closure part and in the guide bands of the piston and require a relatively large gap between the piston and the inner cylinder wall in order to ensure that the piston does not touch the cylinder inner wall grinds. This then stands in the way of the most precise damping possible.

The object of the invention is to provide a damping system for a working cylinder with end position damping, which provides high precision and easy adjustability of the damping, is also suitable for high bending stresses on the piston unit and for different types of cylinders, has a high level of robustness and operational reliability and is also simple and inexpensive can be produced.

The task is solved by the features listed in claim 1. Preferred further developments result from the subclaims.

According to the invention, the end-position-damped working cylinder has a cylinder and a piston unit.

According to the invention, the cylinder has a cylinder tube, a first and a second closure part.

According to the invention, the first closure part is arranged on the first cylinder tube end and the second closure part on the second cylinder tube end of the cylinder tube. The arrangement of the two closure parts is designed such that they are connected to the respective cylinder tube ends in a pressure-tight manner. To connect, the two closure parts are preferably welded to the cylinder tube along the circumferential common contact surface. Other connections, such as screwing, are also possible.

According to the invention, the cylinder tube and the closure parts form a cylinder interior. The cylinder interior is to be understood as the interior of the cylinder formed by the closure parts and the cylinder tube, in which the pressure medium is located when used as intended. Furthermore, the piston is arranged in the cylinder interior.

According to the invention, the cylinder has a damping zone in at least one end region. The damping zone is the area of the cylinder interior in which damping occurs when the piston unit runs in.

Damping is understood as a force effect that delays the movement of the piston unit.

The damping zone is located at at least one end region of the cylinder tube and includes the part of the cylinder interior between a pressure medium connection and an axial boundary through the closure part arranged at this end region.

According to the invention, the cylinder has a laterally arranged pressure medium connection, the pressure medium connection being assigned to the damping zone and axially spaced from the axial boundary of the cylinder interior.

The damping zone extends between the pressure medium connection and the axial boundary. The axial limitation physically blocks further movement of the piston unit and thus defines the maximum movement path of the piston unit on one side.

The axial limitation is preferably formed by the closure part. For this purpose, the closure part has a corresponding stop surface against which the piston unit can rest so that it assumes its end position.

With special designs, the end position of the piston unit during operation can also be before the axial limit is reached.

According to the invention, the piston unit has a piston base body and an annular body. The piston unit is preferably composed of a piston rod and a piston, the piston then having the piston base body and the ring body. The piston base body and the ring body are collectively referred to below as the piston.

Depending on the type of working cylinder, the piston base body can be designed differently. The piston rod can be guided completely through or only partially into the piston base body. Furthermore, the piston unit can be designed to be monolithic and then have only one piston rod and one piston section.

According to the invention, the piston unit slides through the first closure part and forms at least one working space in the cylinder interior.

The first closure part is designed to slidably accommodate the piston unit and has sealing and guide elements for this purpose.

According to the invention, the piston base body is guided in an axially displaceable manner by means of a guide in the cylinder interior.

For this purpose, the piston base body has at least one receptacle for a guide. The receptacle is preferably designed as a groove into which a guide ring is inserted as a guide.

According to the invention, the ring body has a circumferential inner ring groove on a radial outer surface. A piston ring is arranged in this inner ring groove.

For this purpose, the circumferential inner ring groove is designed to accommodate the piston ring and to fix it in its axial position. Furthermore, the circumferential inner ring groove is designed to allow a radial movement of the piston ring at least to the extent that it can deform resiliently. This is achieved by a sufficient depth of the circumferential inner ring groove.

According to the invention, the piston ring rests resiliently on the inner wall of the cylinder and has a piston ring gap.

For this purpose, the piston ring is designed to be resilient, in particular radially elastic, and in a relaxed state has an outer diameter which is larger than the inner diameter of the cylinder tube.

If the piston unit is inserted into the cylinder tube, the piston ring assumes a state of tension in the circumferential inner ring groove and lies against the inner cylinder wall. In this state of tension, the piston ring deforms elastically and reduces its outer diameter and the size of the piston ring gap.

According to the invention, the ring body receives a guide pin of the piston base body in a ring opening and forms an annular gap between a radial inner surface of the ring body and the guide pin. The ring opening is a preferably hollow cylindrical recess. However, it can also have a different geometry as long as it is designed to be guided by the guide pin. The ring body is designed in such a way that its ring opening can be arranged on the guide pin of the piston base body.

The guide pin is part of the piston base body. The guide pin is preferably a tapered section of the piston base body. But it can also be a connected component. The guide pin is arranged at the end of the piston unit which faces the end position to be damped. The guide pin is preferably cylindrical. The outside diameter of the guide pin is then smaller than the inside diameter of the ring opening. However, the guide pin can also have any other geometry that is suitable for guiding the ring body.

The solution according to the invention is particularly characterized in that the ring body has an axial movement play and a radial movement play relative to the piston base body. Due to the radial movement play, the ring body is also referred to below as a floating ring body.

The ring body is limited in its position on the guide pin in its axial mobility by means of a locking body. The locking body is preferably designed as a circlip, which is inserted into an annular groove arranged accordingly on the guide pin. Other locking body shapes are also possible, which can be arranged on the piston base body and axially limit the range of movement of the ring body.

According to the invention, the ring body has an axial annular surface on the piston base body side and the piston base body has an axial counter-ring surface on the ring body side on the opposite side.

According to the invention, the piston unit is designed to axially move over the pressure medium connection with the piston ring during an entry movement into the damping zone and to enclose a damping pressure medium volume in a damping zone space in the damping zone.

If the piston ring passes over the pressure medium connection during the retraction movement, it reaches the damping zone. At the same time, a volume of damping pressure medium is included. The pressure medium can now no longer flow out of the working space directly via the pressure medium connection.

The damping zone space refers to the part of the cylinder interior that is delimited by the piston unit, the closure part and the cylinder tube after the piston ring has passed over the pressure medium connection. As the piston unit progresses axially in the direction of the axial end position, the damping zone space becomes smaller.

The part of the pressure medium that is enclosed in the damping zone space and flows out of it is referred to as the damping pressure medium volume.

According to the invention, the piston unit is designed to have a first operating state during a retraction movement within the damping zone and a second operating state during an extension movement within the damping zone. The first operating state is also referred to below as the damping operating state. The second operating state is also referred to below as the exit operating state.

According to the invention, in the first operating state, the axial annular surface on the piston base body side and the axial counter-ring surface on the annular body side lie against one another and form a sealing plane.

During the retraction movement, the damping pressure medium volume is enclosed by the piston unit, which also increases the pressure in the damping zone space compared to the pressure at the pressure medium connection.

According to the invention, in the damping operating state there is therefore an excess pressure of the damping pressure medium volume compared to the pressure at the pressure medium connection. Furthermore, according to the invention, the piston ring gap is designed for a throttled outflow of the damping pressure medium volume.

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 rest of the working space, so that the ring body with its axial ring surface on the piston base body side is pressed against the axial counter ring surface on the ring body side and forms a sealing plane there. The operating pressure is understood to mean the pressure of the pressure medium applied to the pressure medium connection, which corresponds to the pressure in the remaining working space.

In the damping operating state, the pressure medium can only flow out through the piston ring gap. By delaying the outflow of the damping pressure medium volume, a force effect is generated which counteracts the retraction movement of the piston unit.

In the second operating state, according to the invention, an axial gap is formed between the axial annular surface on the piston base body side and the axial counter-ring surface on the annular body side. This axial gap between the axial annular surface on the piston base body side and the axial counter-ring surface on the ring body side is also referred to below as the axial gap. The reason for this is that in the exit operating state the operating pressure is higher than the pressure of the damping pressure medium volume in the damping zone space. The ring body moves away from the axial counter-ring surface of the piston base body on the ring body side and an axial gap is formed between the piston base body and the ring body.

According to the invention, the axial gap and the annular gap form a pressure medium inflow channel. The pressure medium inflow channel is designed for an inflow of pressure medium into the damping zone space.

An inflow of pressure medium is also possible via the cross section remaining through the piston ring gap. However, particularly in the case of progressive damping with a conical cross section in the damping zone, the cross section of the piston ring gap can be so small that an active exit would then only be possible with a very long delay and the considerable pressure loss across the piston ring gap would also have to be overcome.

The axial gap between the axial annular surface of the annular body on the piston base body side and the axial counter-annular surface of the piston base body on the annular body side and the radial annular gap between the radial inner circumferential surface of the annular body and the guide pin form a pressure medium channel with a structurally designable cross section, which provides an inflow of pressure medium independently of the cross section of the piston ring gap into the damping zone space.

In this way, the piston unit is moved out of its end position and the damping zone without undesirable damping. The piston unit thus carries out the extension movement.

In addition, it was surprisingly found that the extension movement can be initiated practically without delay by means of the ring body and its axial movement play. The reason for this is that when pressure is applied to the pressure medium connection, the ring body is actively moved axially away from the piston base body. The force that causes this results from the area of the annular surface on the piston base body side and the pressure difference between the pressure at the pressure medium connection and the pressure of the damping pressure medium in the damping zone space. During its axial movement, the ring body is designed as a solid body and is therefore designed to displace a partial volume of the damping pressure medium in the damping zone space, whereby the pressure medium presses onto the piston base body and the piston unit is displaced from the end position without delay. This initial phase of the exit operating state is only provided until the piston ring body reaches the end play position of its axial movement play on the locking ring. In this state, however, the axial gap is advantageously completely opened, so that the pressure medium can flow into the damping zone space via the pressure medium inflow channel and so an uninterrupted exit can be continued without disadvantageous delay.

The end-position-damped working cylinder according to the invention has the following advantages in particular:
With the floating ring body, a surprisingly simple solution was found to solve several technical problems at the same time.

Firstly, the ring body is decoupled from the exact radial position of the piston base body due to its floating bearing. The ring body always follows the inner cylinder wall exactly in its radial position for self-adjustment by means of the radially elastic piston ring. This also applies in particular if the piston base body is negatively influenced in its radial position, particularly as a result of deformations of the piston rod during buckling loads.

There is also the advantage that the ring body does not have to transmit any radial forces to the inner wall of the cylinder.

This can also advantageously provide a particularly small gap between the outer surface of the ring body and the inner cylinder wall without the risk of grinding on the cylinder inner wall, as would not be possible according to the prior art.

It is also advantageous that particularly precise end position damping can be provided by means of the ring body and thus with one and the same component. The special precision is due to the fact that the ring body is in its position Radial position also follows the respective shape of the cylinder inner wall in the damping zone, which here can in particular be conical.

In addition, the floating ring body can advantageously be provided with an axial play at the same time with particularly little design effort, and two different operating states can be provided with a damping operating state and an exit operating state, which on the one hand provide a precise damping effect during a retraction movement and, on the other hand, bypassing the damping enable an active extension movement.

The cross section of the annular gap is also advantageously always constant, regardless of the relative radial positional relationship of the ring body and guide pin within the radial movement play, and can be easily determined by the difference between the inner diameter of the ring body and the outer diameter of the guide pin.

It is also advantageous that the damping characteristics and the extension characteristics can be adapted to the respective requirements using simple design means such as the choice of the axial distance of the pressure medium connection, the shape of the cylinder inner wall in the damping zone, the width of the piston ring gap or the width of the radial gap and the annular gap . If provided, this can also be done separately for each end position.

Furthermore, it is advantageous that a delay-free extension movement can be provided by means of the ring body and its axial movement play in its design as a solid body.

Furthermore, it is advantageous that the end position damping can be provided in just one end position as well as in both end positions.

In addition, the solution can be used in different types of cylinders, such as differential working cylinders, synchronous cylinders, pull cylinders or plunger cylinders.

The elastic piston ring, which is tensioned against the inner wall of the cylinder, can advantageously compensate for production-related deviations in the cylinder tube and thus enable high precision of the damping.

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

Ultimately, a particular advantage is the high robustness, the high operational reliability and the technologically good manufacturability.

According to an advantageous development, the axial movement play of the ring body is limited axially against the center of the piston by a locking ring. For this purpose, the locking ring is inserted into a groove in the guide pin, whereby the locking ring is not completely received by the groove. The retaining ring can in particular be a circlip ring that is inexpensive and available as a standard component.

The axial movement play of the ring body is limited in one direction by the axial counter-ring surface of the piston base body and in the other direction by the locking ring.

The advantage is that the axial movement play of the ring body and thus the possible width of the axial gap between the axial annular surface on the piston base body side and the axial counter-ring surface on the ring body side as a section by means of a structurally very simple and at the same time reliable means by means of the axial distance of the locking ring from the ring body of the pressure medium inflow channel can be determined. The possible extension speed in the second operating state can therefore also be influenced in a targeted manner. According to a further development, the guide pin has an axial groove. The axial groove is designed as part of the pressure medium inflow channel.

The axial groove is at least one groove which runs axially along the guide pin. The axial groove can also be formed by several grooves.

Through the axial groove, the cross section of the annular gap can be expanded using a simple means and can thus be used advantageously in conjunction with the axial gap for targeted adjustment of the pressure medium inflow in the second operating state. The achievable speed of the extension movement in the damping zone can thus be determined. By means of the axial groove, the cross section of the pressure medium inflow channel can advantageously be expanded independently of the radial movement play of the ring body.

According to an advantageous development, the cylinder has a position sensor. The position transmitter is designed to record a position of the ring body.

The position transmitter detects the position of the piston unit using a measuring method that registers and evaluates a capacitive, magnetic, mechanical or electromagnetic property change during the piston movement. Different position sensors for determining the piston position are known from the prior art. For example, with a magnetic design, detection can take place using a reed switch.

This development is particularly advantageous because a particularly precise position detection can be provided. The reason for this is that the ring body is mounted with a radial play, i.e. floating, relative to the piston base body. The exact radial position of the ring body relative to the cylinder tube remains unaffected by radial position inaccuracies of the piston base body, which can occur in particular as a result of buckling loads, dynamic loads or uneven wear of the guide, since the ring body is guided via the piston ring directly from the inner wall of the cylinder tube. This means there is always an exact gap dimension between the ring body and the inner cylinder wall, whereby the gap dimension can also be designed to be significantly smaller than in the prior art. The position sensor is arranged in a fixed position relative to the cylinder tube. It was found that the accuracy of the axial position detection can be significantly increased due to the reliable radial distance between the ring body and the position transmitter.

According to another development, the cylinder inner wall has a conicity in the damping zone and in the first operating state the piston ring is designed to narrow the piston ring gap as the retraction movement progresses.

If the inner cylinder wall has a conicity in the damping zone, the piston ring is tensioned more and more during the retraction movement because its outer diameter has to adapt to the ever-shrinking inner diameter of the inner cylinder wall. This means that the piston ring gap also progressively decreases and the cross section for the outflow of the damping pressure medium volume decreases.

The damping effect of the damping zone thus increases to a maximum. The strength of the conicity determines the increase in the damping effect depending on the entry distance covered.

The inner cylinder wall can also initially have a conical section and then a cylindrical section in the damping zone along the retraction movement. Here, the damping effect is increased to a maximum in the conical area, while in the subsequent cylindrical section of the damping zone, the maximum damping effect achieved continues to work until the end position is reached. This means that the course of the damping effect can also be adapted to specific requirements.

According to an advantageous development, the cylinder has a further damping zone in a further end region axially opposite the end region.

According to this advantageous development, the cylinder has a further laterally arranged pressure medium connection, the further pressure medium connection being assigned to the further damping zone and axially spaced from a further axial boundary of the cylinder interior opposite the axial boundary.

The further pressure medium connection, the further damping zone and the further axial limitation basically correspond in function and design to the pressure medium connection, the damping zone and the axial limitation.

The further damping zone and the further pressure medium connection are arranged in spatial proximity to the second closure part at the second cylinder tube end.

According to the advantageous development, the piston unit has a further ring body axially opposite the ring body and the piston base body has a further guide pin axially opposite the guide pin.

The further ring body is designed analogously to the ring body and is arranged on the opposite side of the piston unit. The further guide pin also has at least one further locking body, which limits the axial freedom of movement of the further ring body. Preferably, this further locking body is also designed as a further locking ring, which is inserted into a further groove in the further guide pin.

The further ring body and the further guide pin can differ in their dimensions from the ring body and the guide pin despite the basically identical structure. For example, different damping characteristics can be implemented at the two end positions of the piston unit become. This is particularly useful for a working cylinder that is heavily asymmetrically loaded.

According to the advantageous development, the piston unit is designed to have a third operating state during a retraction movement within the further damping zone and a fourth operating state during an extension movement within the further damping zone. The third operating state is also referred to below as a further damping operating state. The fourth operating state is also referred to below as a further extended operating state.

The third operating state is also referred to as a further damping operating state and, in relation to the further damping zone, has the features of the first operating state in a corresponding manner. The fourth operating state is also referred to as a further extended operating state and, in relation to the further damping zone, has the features of the second operating state in a corresponding manner.

The characteristics of the operating states include, in particular, the pressure conditions, the positions of the ring body and the further ring body relative to the piston base body and the positional relationships of the piston unit to the pressure medium connection and the further pressure medium connection.

The particular advantage of the above development is that end position damping that is effective in both end positions is also provided for double-acting working cylinders.

In addition, it is advantageous that the damping characteristic in each of the two end position dampings can be adjusted independently of that of the other end position damping.

Fig. 1

Endlagengedämpfter Arbeitszylinder als Differenzialzylinder mit einseitiger Endlagendämpfung (Schnittansicht)

Fig. 2

Endlagengedämpfter Arbeitszylinder als Differenzialzylinder mit einseitiger Endlagendämpfung (vergrößerter Ausschnitt in Schnittansicht)

Fig. 3

Endlagengedämpfter Arbeitszylinder als Differenzialzylinder mit beidseitiger Endlagendämpfung (Schnittansicht)

Fig. 4

Endlagengedämpfter Arbeitszylinder als Gleichgangzylinder mit beidseitiger Endlagendämpfung (Schnittansicht)

Fig. 5

Endlagengedämpfter Arbeitszylinder als Differenzialzylinder mit beidseitiger Endlagendämpfung im ersten Betriebszustand (vergrößerter Ausschnitt in Schnittansicht)

Fig. 6

Endlagengedämpfter Arbeitszylinder als Differenzialzylinder mit beidseitiger Endlagendämpfung im zweiten Betriebszustand (vergrößerter Ausschnitt in Schnittansicht)

Fig. 7

Kolbeneinheit (isometrische Ansicht)

näher erläutert.The invention is illustrated as an exemplary embodiment using

Fig. 1

End-position-damped working cylinder as a differential cylinder with one-sided end-position damping (sectional view)

Fig. 2

End position-damped working cylinder as a differential cylinder with one-sided end position damping (enlarged detail in sectional view)

Fig. 3

End position dampened working cylinder as a differential cylinder with end position damping on both sides (sectional view)

Fig. 4

End-position-damped working cylinder as a synchronous cylinder with end-position damping on both sides (sectional view)

Fig. 5

End position dampened working cylinder as a differential cylinder with end position damping on both sides in the first operating state (enlarged detail in sectional view)

Fig. 6

End position dampened working cylinder as a differential cylinder with end position damping on both sides in the second operating state (enlarged detail in sectional view)

Fig. 7

Piston unit (isometric view)

explained in more detail.

Fig. 1 shows an overview view of a first exemplary embodiment of the end-position-damped differential working cylinder. This exemplary embodiment involves a differential working cylinder with end position damping on one side. In this exemplary embodiment, the end position damping is arranged at the end position assigned to the second closure part 5. This is an end position cushioning on the piston crown, which dampens the retraction movement.

The end-position-damped working cylinder has a cylinder 1 and a piston unit 2.

The cylinder 1 is composed of the cylinder tube 3, the first closure part 4 and the second closure part 5. The cylinder tube 3 and the two closure parts 4, 5 are connected to one another in such a way that they enclose a cylinder interior 8. The first closure part 4 is assigned to the first cylinder tube end 6 and the second closure part 5 to 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 a further axial boundary 27, which limits the axial movement space of the piston unit 2 arranged in the cylinder interior 8. The axial boundaries 11, 27 are designed as stop surfaces for the piston unit 2, which moves axially during operation.

On the cylinder tube 3, the pressure medium connection 10 is arranged on the second cylinder tube end 7 and the further pressure medium connection 26 is arranged on the first cylinder tube end 6.

The piston unit 2 has a piston base body 12 and an annular body 13. In the exemplary embodiment, the piston unit 2 is composed of a piston rod and a piston, which are firmly connected to one another. In the exemplary embodiment, the piston base body and the ring body together form the piston.

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

The ring body 13 is pushed onto the guide pin 18, which is designed as a taper on the piston base body 12.

The piston base body 12 is guided in the cylinder tube 3 by means of a guide 14.

Fig. 2 shows an enlargement of Fig. 1 in the area of the second closure part 5. Furthermore, the piston base body 12 is in an end position, whereby the piston base body 12 rests with its guide pin 18 on the axial boundary 11.

In this figure, the arrangement and design of the ring body 13 is shown in more detail. In the exemplary embodiment, the ring body 13 is designed as a metal ring, which has an inner ring groove 15 on its outer surface 13c, in which the piston ring 16 is inserted. The inner ring groove 15 is designed so that the piston ring 16 has a larger range of movement in the radial direction, so that it can deform radially elastically. The elastic piston ring has a piston ring gap 16a (see in particular Fig. 7 ) and is stretched against the inner cylinder wall 17.

The annular body 13 is pushed onto the guide pin 18 and rests with an axial annular surface 13d on the piston base body side against the counter-annular surface 12a of the piston base body 12 on the annular body side. Axially opposite, the axial range of movement of the ring body 13 is limited by a locking ring 22.

Furthermore, the ring opening 13a of the ring body is designed such that it exceeds the diameter of the guide pin 18, so that the ring body has a radial freedom of movement relative to the guide pin 18.

The damping zone 9 represents an axial section and extends from the pressure medium connection 10 to the end position of the piston ring 16 in front of the second closure part 5. In damping zone 9, when the piston unit 2 retracts, there is a damping effect which is opposite to the retraction movement of the piston unit 2 and brakes it . This will be further discussed in Fig. 5 described in detail.

In Fig. 3 a second exemplary embodiment is shown. This is a differential working cylinder with damping in both end positions. For this purpose, another ring body 28 is present. The further ring body 28 is identical to the ring body 13 and is pushed onto a further guide pin 29 and fixed there by a further locking ring 30. Both ring bodies 13, 28 and both guide pins 18, 29 lie axially opposite one another on the piston base body 12.

The further ring body additionally effects a damping effect in the further damping zone 25 in a corresponding manner to that in the damping zone 9. The further damping zone 25 extends between the further pressure medium connection 26 and the end position of the further piston ring 31 in front of the further axial boundary 27 on the first closure part 4.

Otherwise, the differential working cylinders are out Fig. 1 and Fig. 3 identical in their basic structure.

In Fig. 4 A synchronous working cylinder is shown, which is also end position damped on both sides. The difference to the differential working pistons Fig. 3 lies in the fact that the piston rod section of the piston base body 12 is guided through both closure parts 4, 5 and is slidably mounted. Therefore, the second closure part 5 is also designed as a guide closure part in this exemplary embodiment. The piston base body 12 is similar to that from Fig. 3 designed, but it differs in that the piston rod extends through it. Both sections of the piston unit 2 are also firmly connected to one another here.

In Fig. 5 is the first operating state, which is the damping operating state, and in Fig. 6 the second operating state, which is the exit operating state, represents during operation of the end-position-damped working cylinder. These figures serve to illustrate how the damping works.

In Fig. 5 the piston unit is in the retraction movement and the piston ring 16 in the inner ring groove 15 of the ring body 13 has just passed over the pressure medium connection 10 and encloses a damping pressure medium volume in the damping zone space 20. The pressure in the damping pressure medium volume is greater than the pressure at the pressure medium connection 10. The ring body 13 is therefore pressed with its axial annular surface 13d on the piston base body side against the axial counter-ring surface 12a on the ring body side, whereby an annular sealing plane is formed there.

The pressure medium from the damping pressure medium volume can now only flow back to the pressure medium connection 10 via the piston ring gap 16a in the piston ring 16, whereby the retraction movement of the piston unit 2 is counteracted by a damping force effect. The retraction movement is delayed until the piston unit 2 reaches the axial limit 11.

In Fig. 6 the second operating state is displayed.

In this second operating state, the piston unit 2 performs an extension movement. This is caused by the pressure medium flowing from the pressure medium connection 10 into the damping zone space 20 (as soon as the pressure at the pressure medium connection 10 is greater than that in the damping pressure medium volume).

As soon as the pressure at the pressure medium connection 10 is greater than that in the damping pressure medium volume, the ring body 13 is displaced axially and pressed against the locking ring 22. This opens an axial gap 21 between the axial counter-ring surface 12a on the ring body side and the axial annular surface 13d on the piston base body side.

The ring body 13 also has a radial range of movement. This is provided by an annular gap 19 between the inner surface 13b and the guide pin 18. The axial gap 21 and the annular gap 19 form a continuous pressure medium inflow channel for the pressure medium flowing into the damping zone space 20. In this exemplary embodiment, an axial groove 24 in the guide pin additionally increases the flow cross section of the pressure medium inflow channel.

The pressure medium can thus flow into the damping zone space 20 with a small pressure loss and the extension movement is hardly delayed.

In the Fig. 5 and 6 In the case of an embodiment with end position damping on both sides, the mode of operation shown corresponds to the interaction of the third and fourth operating states in the further damping zone 25 by means of the further annular body 28.

The third operating state is during the retraction movement into the further damping zone 25 and the fourth operating state is during the extension movement taken from the further damping zone 25. In the further end position, the third operating state is the damping operating state and the fourth operating state is the exit operating state.

In addition, it is in Fig. 5 and Fig. 6 a position sensor 23 arranged on the cylinder tube is shown.

Fig. 7 shows the piston unit 2 of an exemplary embodiment of a differential working cylinder with end position damping on both sides in an oblique view.

The ring body 13, the piston ring 16 with its piston ring gap 16a, the locking ring 22, the guide 14 and the axial groove 24 are shown. Furthermore, the further ring body 28 and the further piston ring 31 arranged there with its further piston ring gap 31a are shown axially opposite the piston base body 12. The piston rings 16, 31 and the safety ring 22 are each formed by an elastic metal ring. The additional locking ring and the additional guide pin are covered and therefore in Fig. 7 without reference symbols.

The ring body 13 accommodates the piston ring 16 in the inner ring groove 15 and is fixed on the guide pin 18 with the safety ring 22. The same applies to the further ring body 28 and the further piston ring 31 as well as the further locking ring and the further guide pin.

The guide 14 is arranged in a groove of the piston base body 12.

Reference symbols used

1

cylinder

2

Piston unit

3

cylinder tube

4

first closure part

5

second closure part

6

first cylinder pipe end

7

second cylinder pipe end

8th

Cylinder interior

9

Damping zone

10

Pressure medium connection

11

axial limitation

12

Piston body

12a

axial counter ring surface on the ring body side

13

Ring body

13a

Ring opening

13b

Inner lateral surface

13c

outer surface

13d

Piston base body-side axial annular surface

14

guide

15

Inner ring groove

16

Piston ring

16a

Piston ring gap

17

Cylinder inner wall

18

Guide pin

19

Annular gap

20

Damping zone space

21

axial gap

22

Circlip

23

Positioner

24

axial groove

25

further damping zone

26

additional pressure medium connection

27

further axial limitation

28

another ring body

29

another guide pin

30

another locking ring

31

another piston ring

31a

further piston ring gap

Claims (6)

1. A working cylinder with end-position damping,

   comprising a cylinder (1) and a piston unit (2),

   wherein the cylinder (1) comprises a cylinder tube (3), a first closure part (4) and a second closure part (5),

   wherein the cylinder tube (3) comprises a first cylinder tube end (6) and a second cylinder tube end (7),

   wherein 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),

   wherein the cylinder tube (3) and the closure parts (4,5) form a cylinder interior (8),

   wherein the cylinder (1) comprises a damping zone (9) in at least one end region,

   wherein the cylinder (1) comprises at least one laterally arranged pressure medium connection (10), wherein the pressure medium connection (10) is assigned to the damping zone (9) and is axially spaced from an axial limitation (11) of the cylinder interior (9),

   wherein the piston unit (2) has a piston main body (12) and a ring body (13), wherein the piston unit (2) slidably passes through the first closure part (4) and forms at least one working chamber in the cylinder interior (8),

   wherein the piston main body (12) is guided in an axially displaceable manner in the cylinder interior (8) by means of a guide (14),

   wherein the ring body (13) has a circumferential inner ring groove (15) on a radial outer lateral surface (13c),

   wherein a piston ring (16) is arranged in the inner ring groove (15),

   wherein the piston ring (16) resiliently rests against an inner cylinder wall (17) and has a piston ring gap (16a),

   wherein the ring body (13) receives a guide pin (18) of the piston main body (12) in a ring opening (13a) and a ring gap (19) is formed between a radial inner surface of the ring body (13b) and the guide pin (18),

   wherein the ring body (13) has an axial movement play and a radial movement play relative to the piston main body (12),

   and wherein the ring body (13) has an axial ring surface (13d) on the piston main body side and the piston main body has an opposite axial counter ring surface (12a) on the ring body side,

   wherein the piston unit (2) is designed to pass axially with the piston ring (16) over the pressure medium connection (10) during a retraction movement into the damping zone (9) and to enclose a damping pressure medium volume in a damping zone chamber (20) in the damping zone (9),

   wherein the piston unit (2) is designed such that it has a first operating state during a retraction movement and has a second operating state during an extension movement within the damping zone (9),

   wherein, in the first operating state, the axial ring surface (13d) on the piston main body side and the axial counter ring surface (12a) on the ring body side abut against each other and form a sealing plane,

   wherein the damping pressure medium volume has an overpressure relative to the pressure medium connection (10) and the piston ring gap (16a) is designed for a throttled outflow of the damping pressure medium volume, wherein, in the second operating state, an axial gap (21) is formed between the axial ring surface (13d) on the piston main body side and the axial counter ring surface (12a) on the ring body side,

   wherein the axial gap (21) and the ring gap (19) form a pressure medium inflow channel, and the pressure medium inflow channel is designed for an inflow of a pressure medium into the damping zone chamber (20).
2. The working cylinder with end position damping according to claim 1,
   characterized in
   that the axial movement play of the ring body (13) is limited axially against the piston centre by a locking ring (22).
3. The working cylinder with end position damping according to claim 1 and 2,
   characterized in
   that the guide pin (18) has an axial groove which is formed as a part of the pressure medium inflow channel.
4. The working cylinder with end position damping according to one of the preceding claims,
   characterized in
   that the cylinder comprises a position sensor (23) and the position sensor (23) is designed to record a position of the ring body (13).
5. The working cylinder with end position damping according to one of the preceding claims,
   characterized in
   that the cylinder inner wall (17) has a conicity in the damping zone (20) and, in the first operating state, the piston ring (16) is designed to narrow the piston ring gap (16a) as the retraction movement progresses.
6. The working cylinder with end position damping according to one of the preceding claims,
   characterized in

   that the cylinder (1) has a further damping zone (25) in a further end region existing axially opposite the end region,

   wherein the cylinder (1) has a further laterally arranged pressure medium connection (26), wherein the further pressure medium connection (26) is assigned to the further damping zone (25) and is axially spaced from a further axial limitation (27) of the cylinder interior opposite the axial limitation,

   wherein the piston unit (2) has a further ring body (28) axially opposite the ring body (13) and the piston main body (12) has a further guide pin (29) axially opposite the guide pin (18),

   wherein the further ring body (28) has a circumferential inner ring groove on a radial outer lateral surface, wherein a further piston ring (31) is arranged in the inner ring groove, wherein the further piston ring (31) resiliently rests against the cylinder inner wall (17) and has a piston ring gap, wherein the further ring body (28) receives the further guide pin (29) of the piston main body (12) in a ring opening and a further ring gap is formed between a radial inner lateral surface of the further ring body (28) and the further guide pin (29), wherein the further ring body (28) has an axial movement play and a radial movement play relative to the piston main body (12), and wherein the further ring body (28) has an axial ring surface on the piston main body side and the piston main body has an opposite axial further counter ring surface on the ring body side, wherein the piston unit (2) is designed to pass axially with the further piston ring (31) over the further pressure medium connection (26) during a retraction movement into the further damping zone (25), and to enclose a further damping pressure medium volume in a further damping zone chamber in the further damping zone (25),

   wherein the piston unit is designed such that it has a third operating state during a retraction movement within the further damping zone (25) and a fourth operating state during an extension movement within the further damping zone (25), wherein, in the third operating state, the axial ring surface of the further ring body (28) on the piston main body side and the axial further counter ring surface on the ring body side abut against each other and form a sealing plane, wherein the further damping pressure medium volume has an overpressure relative to the further pressure medium connection (26) and the piston ring gap of the further piston ring (31) is designed for a throttled outflow of the further damping pressure medium volume, wherein, in the fourth operating state, an axial gap is formed between the axial ring surface of the further ring body (28) on the piston main body side and the axial further counter ring surface on the ring body side, wherein the axial gap and the further ring gap form a pressure medium inflow channel, and the pressure medium inflow channel is designed for an inflow of a pressure medium into the further damping zone chamber.

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