Accumulator return stroke cylinder

Abstract

The invention relates to an accumulator return stroke cylinder having a cylinder, a piston unit (8) with a piston (8.1), having a pressure accumulator (7), a pressure medium port (5.1) and a pressure medium channel (6.1), wherein the pressure medium channel (6.1) connects a rod working space (6) to the pressure accumulator (7), wherein the piston (8.1) has an encircling central inner annular groove (9) with a seal (10) which bears against the inside of the cylinder tube (1.1) and separates the rod working space (6) from a head working space (5), wherein the cylinder tube (1.1) has a recess (11) which is arranged opposite the central inner annular groove (9) in a guide-side end position of the piston (8.1), characterised in that the piston (8.1) has respective encircling inner annular grooves (12.1, 13.1) which are spaced apart axially on both sides of the seal (10) and in each of which a piston ring (12.2, 13.2) is arranged, which bears resiliently against the cylinder inner wall (1.1) and has, in each case, a piston ring gap (12.3, 13.3), in that, between the seal (10) and in each case one of the piston rings (12.2, 13.2) a head-side annular space (12.4, 13.4) is formed in each case, in that the accumulator return stroke cylinder is designed for an overflow operating state and a lifting operating state, and in that, in the overflow operating state, the piston ring gaps (12.3, 13.3) form throttled portions of an overflow channel from the head working space (5) into the rod working space (6).

Description

[0001] Accumulator return stroke cylinder

[0002] The invention relates to a storage return stroke cylinder which enables a return movement of the piston unit without external force.

[0003] Accumulator return stroke cylinders are known from the state of the art. The design and operation of accumulator return stroke cylinders poses the problem that leakage losses cannot be completely avoided. As a result, the volume or pressure of the pressure medium stored in the accumulator may no longer be sufficient to reliably perform a return stroke. To achieve this, it is known to refill the accumulator cylinder at appropriate intervals, but this is very complex and can only be considered a suitable solution in special cases.

[0004] Furthermore, it is known to provide an overflow, i.e., a limited transfer of pressure medium between the working chambers, particularly in a stroke end position, so that the pressure accumulator is completely refilled. For example, it is known to arrange an overflow valve in the piston. The disadvantage of this is the high manufacturing cost. Furthermore, it is known to set up an overflow in such a way that a small flow of pressure medium can pass through the seal. The disadvantage of this is that the seal is subject to considerable stress due to diesel effects, which reduces its service life.

[0005] The object of the invention is to provide an accumulator return stroke cylinder which automatically establishes and maintains its operational readiness for a return stroke and has a long service life, is cost-effective to manufacture and can be easily adapted to different operating requirements.

[0006] The problem is solved by the features listed in claim 1. Preferred developments emerge from the subclaims. The accumulator return stroke cylinder according to the invention offers an advantageous solution, particularly in cases where, after the piston unit has extended, a return movement is not already initiated by the forces of the device to be actuated. The hydraulic lines, valves, and other components required for active hydraulic control of the piston return movement can be eliminated.

[0007] The accumulator return stroke cylinder according to the present invention is characterized in particular by an advantageous solution for a pressure medium flow in the stroke end position after completion of the working stroke, which always ensures a complete filling of the pressure accumulator.

[0008] The accumulator return stroke cylinder according to the invention comprises, in a manner known per se, the cylinder and the pressure accumulator as basic structural components.

[0009] The cylinder consists of a cylinder tube, a base closure part, and a guide closure part. The base closure part and the guide closure part are collectively referred to below as the closure parts. The closure parts are connected to the cylinder tube at both cylinder ends, thus forming an interior space. Within this interior space—divided by a piston of a piston unit—are a base working chamber and a rod working chamber, collectively referred to below as the working chambers. The piston unit further comprises a piston rod that slides through the guide closure part.

[0010] A pressure medium connection is assigned to the base working chamber, via which the pressure medium at the respective operating pressure can be introduced into the base working chamber, thus causing an extension movement of the piston unit, hereinafter also referred to as the working stroke. The piston rod slides through the guide closure part, whereby the volume of the rod working chamber is reduced and the pressure medium located there is forced out. For this purpose, a pressure medium channel is provided, which is assigned to the rod working chamber and leads to the pressure accumulator. The pressure accumulator has a fluid chamber in a manner known per se and can, for example, be designed as a bladder accumulator or diaphragm accumulator. The diaphragm accumulator is preferably filled with nitrogen, the pressure of which is matched to the operating pressure and can, for example, be 180 bar.The pressure medium channel connects the rod working chamber with the fluid chamber, so that pressure medium displaced from the rod working chamber is led into the fluid chamber and stored there under pressure.

[0011] According to the invention, the piston of the piston unit has a central inner ring groove in which a preferably elastomeric seal is arranged and which rests against the inner cylinder wall and separates the working chambers from one another. The cylinder tube has a recess on the inner cylinder wall. The recess is arranged axially such that the central inner ring groove is positioned opposite the recess when the piston unit is in a stroke end position at the end of a working stroke, hereinafter also referred to as the guide-side end position due to the position of the piston on the guide closure part. The recess is preferably formed as a concave curvature by cold forming and is thus completely burr-free.

[0012] According to the invention, the accumulator return stroke cylinder is further characterized in particular in that the piston has two further inner ring grooves on both sides of the central inner ring groove, each axially spaced apart, in each of which a piston ring with a piston ring gap is arranged.

[0013] Here, the inner ring groove arranged towards the base closure part is referred to as the base-side inner ring groove and the inner ring groove arranged towards the guide closure part is referred to as the guide-side inner ring groove. The base-side and guide-side inner ring grooves are collectively referred to below as the piston ring inner grooves. In each of the piston ring inner grooves, a piston ring with a piston ring gap is arranged so as to rest against the inner cylinder wall. Both piston rings can preferably be of identical design. Here, too, the designations base-side piston ring with base-side piston ring gap and guide-side piston ring with guide-side piston ring gap are used, depending on the positional orientation relative to the respective closure parts.

[0014] Viewed axially, a bottom-side annular space is formed between the sealing ring and the piston ring on the bottom side, between the piston and the cylinder barrel. Similarly, a guide-side annular space is formed between the sealing ring and the piston ring on the guide side.

[0015] According to the invention, the accumulator return stroke cylinder is also designed for an overflow operating state and a stroke operating state.

[0016] In the overflow operating state, the piston is in the guide-side end position and thus rests against the guide closure part. The base working chamber has its maximum volume, and the rod working chamber has its minimum volume.

[0017] This positions the sealing ring opposite the recess. In the overflow operating state, an overflow cross-section is opened between the sealing ring and the recess. The cross-sectional size of the overflow cross-section can be advantageously and easily adjusted by the size of the recess. At the same time, an overflow channel is opened. The overflow channel leads from the pressure medium connection, via the base working chamber, via the base-side piston ring gap, via the base-side annular space, via the overflow cross-section, via the guide-side annular space, via the guide-side piston ring gap, via the rod working chamber, and finally via the pressure medium channel to the fluid chamber of the pressure accumulator. In this way, any leakage losses are compensated, thus ensuring that the pressure accumulator is always fully filled.Advantageously, the overflow cross-section, at which the elastomer sealing ring is subject to the effect of the overflowing pressure medium, is located in the overflow channel, protected between the bottom-side annular space and the guide-side annular space. The pressure medium is throttled both when passing from the bottom working space into the bottom-side annular space by the bottom-side piston ring gap of the bottom-side piston ring, and when passing from the guide-side annular space into the rod chamber by the guide-side piston ring gap of the guide-side piston ring. The piston rings are preferably made of steel. They are very robust and are not subject to any risk of damage from diesel effects, pressure peaks, or similar. Furthermore, the desired cross-section at the piston ring gaps can be adjusted very simply by selecting suitable piston rings.Such piston rings are also advantageously available as standard parts and are available at low cost. The cross-section at the piston ring gaps is usually selected to be significantly smaller than the overflow cross-section, so that the elastomer sealing ring is reliably protected from any diesel effects, pressure peaks, or similar. This can advantageously significantly extend the service life and the required maintenance cycles of the accumulator return stroke cylinder. The cross-section at the piston ring gaps can preferably be set the same for both piston rings. However, different cross-sections are also possible depending on the application.

[0018] In the stroke operating state, however, the overflow cross-section and thus the overflow channel are closed. The sealing ring rests circumferentially and sealingly against the inner cylinder wall. For the purposes of the present application, a stroke operating state is understood to mean any operating state that is not an overflow operating state. The stroke operating state includes the operating state during the working stroke, the return stroke, and the end position at the base. In the stroke operating state, the working stroke, caused by a pressure medium inflow via the pressure medium connection into the base working chamber, and the return stroke, caused by a pressure medium inflow from the pressure accumulator via the pressure medium channel into the rod working chamber, can thus advantageously take place without undesired pressure medium overflow between the working chambers.

[0019] According to an advantageous development, the accumulator return stroke cylinder is characterized in that the seal in the central inner ring groove has an axial movement play, that the seal in the overflow operating state is in a guide-side end position of its axial movement play by means of a pressurization of the bottom working chamber and there releases the overflow cross-section and that the seal in a return stroke operating state is in a bottom-side end position of its axial movement play by means of a pressurization of the rod working chamber from the pressure accumulator and there closes the overflow cross-section.

[0020] This advantageous development is based on the sealing ring having axial play and the recess being positioned axially precisely so that an overflow cross-section is only open when the sealing ring is in a guide-side position. To provide the axial play, the central inner ring groove is wider than the sealing ring. The axial position of the sealing ring within the central inner ring groove is determined by the ratio of the pressures in the crown-side and guide-side annular space and, ultimately, due to the pressure connection via the piston ring gaps, by the ratio of the pressures in the crown working space and the rod working space.

[0021] If the pressure in the base working chamber during the working stroke and in the guide-side end position is higher than in the rod working chamber, the sealing ring rests against the guide-side groove side wall of the middle inner ring groove. When the guide-side end position is reached, the sealing ring and the piston move into a position opposite the recess and the overflow cross-section is opened. When the pressure is reversed to effect the return stroke, the sealing ring is moved to the opposite axial end position and thus to the base-side groove side wall of the middle inner ring groove. In this position, the sealing ring is no longer opposite the recess and the overflow cross-section is closed. The overflow cross-section can therefore advantageously be closed before the piston unit begins its return stroke, minimizing unwanted pressure medium overflow from the rod working chamber into the base working chamber.The sealing ring is also advantageously protected during movements within the movement clearance by means of the throttling effect of the piston ring gaps.

[0022] According to a further advantageous development, the accumulator return stroke cylinder is characterized in that the piston ring gap on the base side and the piston ring gap on the guide side have the same cross section.

[0023] With training in accordance with this advanced training, the sealing ring can be particularly effectively protected against diesel effects, pressure peaks or similar.

[0024] The invention is illustrated by way of example with reference to

[0025] Fig. 1 Sectional view in bottom-side end position

[0026] Fig. 2 Sectional view in guide-side end position

[0027] Fig. 3 Enlarged section in bottom-side end position

[0028] Fig. 4 Enlarged section in guide-side end position

[0029] Fig. 5 shows the piston ring in more detail. The same reference numerals in the various figures refer to the same features or components. These reference numerals are used in the description even if they are not shown in the respective figure.

[0030] Fig. 1 shows an embodiment of a storage return stroke cylinder in a bottom-side end position.

[0031] The basic structure of the cylinder 1 comprises a cylinder tube 1.1, the bottom closure part 3 at one end of the cylinder tube, and the guide closure part 4 at the axially opposite end of the cylinder tube. This forms an interior space 2. Furthermore, there is the piston unit 8, consisting of the piston rod 8.1 and the piston 8.2 attached to the piston rod 8.1. The piston divides the interior space 2 into a rod working chamber 6 and a bottom working chamber 5.

[0032] The pressure accumulator 7 is located on the guide side and, schematically shown, has a fluid chamber 7.1 and an air chamber 7.2, which here is designed as a nitrogen-filled bladder. The pressure medium channel 6.1 connects the rod chamber 6 with the fluid chamber 7.1 of the pressure accumulator 7.

[0033] In the bottom end position shown in Fig. 1, the piston unit 8 is retracted and the piston 8.2 rests against the bottom closure part 3.

[0034] Fig. 2 shows the same embodiment in a guide-side end position. The guide-side end position occurs when the piston unit 8 is extended after executing a working stroke and the piston 8.2 rests against the guide closure part 4. To execute a working stroke, a hydraulic oil is introduced as a pressure medium into the base working chamber 5 via the pressure medium connection 5.1, subjected to an operating pressure. As a result of the working stroke, the volume of the rod working chamber 6 decreases, and the hydraulic oil located there is pressed into the fluid chamber 7.1 of the pressure accumulator 7 via the pressure medium channel 6.1, overcoming the counterpressure from the air chamber 7.2 and compressing it.

[0035] Fig. 3 shows an enlarged section of the structure of the piston 8.2, which is here in the bottom-side end position.

[0036] The piston 8.2 has a central inner ring groove 9 in which the elastomer sealing ring 10 is arranged. By sealingly abutting the inner cylinder wall 1.2 of the cylinder barrel 1.1, it separates the crown working chamber and the rod working chamber from each other in a fluid-tight manner in this operating state. Axially positioned in the direction of the crown closure part 3, the piston 8.2 also has a crown-side inner ring groove 12.1 in which the crown-side piston ring 12.2 with the crown-side piston ring gap 12.3 is arranged. Between the outer wall of the piston 8.2 and the inner cylinder wall 1.2 there is a circumferential annular gap, which in the section axially located between the sealing ring 10 and the crown-side piston ring 12.2 is the crown-side annular space 12.4.

[0037] In the present embodiment, the guide-side inner ring groove 13.1 with the guide-side piston ring 13.2, with the guide-side piston ring gap 13.3 and forming the guide-side annular space 13.4 is arranged in the direction of the guide closure part 4, essentially mirror-symmetrically to the central inner ring groove 11.

[0038] Fig. 4 shows an enlarged section of the overflow operating state in the guide-side end position. As shown in Fig. 4, a recess 11 in the form of a cold-formed concave bulge is provided in the cylinder tube 1.1. The sealing ring 10 is axially opposite the recess 11, thus opening an overflow cross-section 14 at this point. By means of continued pressurization of the hydraulic oil, hydraulic oil is fed from the bottom working chamber 5, throttled by the bottom-side piston ring gap 12.3, via the bottom-side annular chamber 12.4, the overflow cross-section 14, the guide-side annular chamber 13.4, throttled again by the guide-side piston ring gap 13.3, the rod working chamber 6 and the pressure medium channel 6.1 into the fluid chamber 7.1 of the pressure accumulator until a pressure equalization to the counterpressure provided by the air chamber 7.2 is achieved.

[0039] If the pressure is now released at the pressure medium connection 5.2, the piston unit 8 moves back on the piston rod 8.1 as a return stroke, even without external force acting on it, by introducing the pressurized hydraulic oil located in the fluid chamber 7.1 into the rod chamber 6 via the pressure medium channel 6.1 and acting on the annular surface of the piston 8.2. During this return stroke, the seal is again located outside the area of ​​the recess 11, so that there is a complete pressure medium separation between the working chambers 5, 6.

[0040] Fig. 5 additionally shows the piston rings 12.2, 13.2, which are of the same design, with their respective piston ring gaps 12.3, 13.3.

[0041] Reference symbols used

[0042] 1 cylinder

[0043] 1.1 Cylinder barrel

[0044] 1.2 Cylinder tube inner wall

[0045] 2 Interior

[0046] 3 Bottom closure part

[0047] 4 Guide closure part

[0048] 5 Floor workroom

[0049] 5.1 Pressure medium connection

[0050] 6 bar work area

[0051] 6.1 Pressure medium channel

[0052] 7 pressure accumulators

[0053] 7.1 Fluid space

[0054] 7.2 Air chamber

[0055] 8 Piston unit

[0056] 8.1 Piston rod

[0057] 8.2 Piston

[0058] 9 middle inner ring groove

[0059] 10 Seal

[0060] 11 Recess

[0061] 12.1 bottom inner ring groove

[0062] 12.2 bottom piston ring

[0063] 12.3 Bottom-side piston ring gap

[0064] 12.4 bottom annular space

[0065] 13.1 guide-side inner ring groove

[0066] 13.2 guide-side piston ring

[0067] 13.3 Guide-side piston ring gap

[0068] 13.4 guide-side annular space

[0069] 14 Overflow cross-section

Claims

Patent claims 1 . Accumulator return stroke cylinder, comprising a cylinder (1), a piston unit (8), a pressure accumulator (7), a pressure medium connection (5.1) and a pressure medium channel (6.1), wherein the cylinder (1) has a cylinder tube (1.1), a bottom closure part (3), a guide closure part (4), an interior space (2), a bottom working space (5) and a rod working space (6), wherein the closure parts (3, 4) are each connected to the cylinder tube (1.1) at the cylinder tube end, wherein the interior space (2) is formed by the cylinder tube (1) and the closure parts (3, 4) and accommodates the bottom working space (5) and the rod working space (6), wherein the pressure accumulator (7) has a fluid chamber (7.1) and a pressure-deformable air chamber (7.2) separated from the fluid chamber (7.1) by a membrane, wherein the pressure medium connection (5.1) is assigned to the bottom working space (5), wherein the pressure medium channel (6.1) the rod working chamber (6) with the fluid chamber (7.1) of the pressure accumulator (7), wherein the piston unit (8) has a piston rod (8.1) which slides through the guide closure part (4), and a piston (8.2), wherein the piston (8.2) is arranged in the interior (2) and divides the latter into the base working chamber (5) and the rod working chamber (6), wherein the piston has a circumferential central inner ring groove (9) and a seal (10) arranged in the central inner ring groove (9), which seal rests on an inner cylinder wall (1.2) of the cylinder tube (1.1) and separates the base working chamber (5) and the rod working chamber (6) from one another, wherein the cylinder tube (1.1) has a recess (11) on the inner cylinder wall (1.2) which, in a guide-side end position of the. Piston (8.1) is arranged opposite the central inner ring groove (9), characterized in that the piston (8.1) has a circumferential bottom-side inner ring groove (12.1) spaced axially from the seal (10), in which a bottom-side piston ring (12.2) is arranged, which resiliently rests against the cylinder inner wall (1.1) and has a bottom-side piston ring gap (12.3), and that a bottom-side annular space (12.4) is formed between the bottom-side piston ring (12.2) and the seal (10), that the piston (8.1) further has a circumferential guide-side inner ring groove (13.1) spaced axially from the seal (10), in which a guide-side piston ring (13.2) is arranged, which resiliently rests against the cylinder inner wall (1.1) and has a guide-side piston ring gap (13.3), and that between the guide-side piston ring (13.2) and the seal (10) there is a guide-side annular space (13.4) and that the accumulator return stroke cylinder is designed for an overflow operating state and a stroke operating state, that in the overflow operating state the piston (8.1) is in the guide-side end position on the guide closure part (4) and forms an overflow cross-section (14) between a radial boundary of the seal (10) and the recess (11) and an overflow channel is open from the pressure medium connection (5.1), via the base working chamber (5), via the base-side annular chamber (12.4), via the overflow cross-section (14), via the guide-side annular chamber (13.4), via the guide-side piston ring gap (13.3), via the rod working chamber (6) and via the pressure medium channel (6.1) to the fluid chamber (7.1), that in the stroke operating state the piston (8.1) is in a position other than the guide-side end position and the Overflow cross-section (14) and the overflow channel are closed.

2. Storage return stroke cylinder according to claim 1, characterized in that that the seal (10) has an axial play in the central inner ring groove (9), that the seal (10) in the overflow operating state is in a guide-side end position of its axial play by means of a pressurization of the base working chamber (5) and there releases the overflow cross-section (14) and that the seal (10) in a return stroke operating state is in a base-side end position of play by means of a pressurization of the rod working chamber (6) from the pressure accumulator (7) and there closes the overflow cross-section (14).

3. Accumulator return stroke cylinder according to one of the preceding claims, characterized in that the bottom-side piston ring gap (12.3) and the guide-side piston ring gap (13.3) have the same cross-section. THREE PAGES OF DRAWINGS

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