DE202013001260U1 - Working cylinder with pressure medium overflow - Google Patents

Abstract

Working cylinder, comprising a cylinder tube (1) with connections for supplying and discharging a pressure medium, a bottom closure part (4), a guide closure part (5), two working spaces, a piston rod (6) which is guided in the guide closure part (5), one Piston (9) with seals, which is connected to the piston rod (6) and is guided in the cylinder tube (1) and separates the working spaces in the cylinder tube (1), characterized in that the piston (1) has a first side plate (10) and a has a second side window (11) and a central section (12), arranged between the first and second side windows (10; 11), and a first and a second annular elastic seal (13; 14), the first annular elastic seal (13) the first side window (10) is arranged axially in the direction of the second side window (11) and is supported on one side by the first side window (10), the second annular elastic seal (14) on de r second side window (11) is arranged axially in the direction of the first side window (10) and is supported on one side by the second side window (11), each of the annular elastic seals (13; 14) can be elastically deformed when pressure is applied in the direction of the central section (12) to form a gap to the inner wall of the cylinder tube (15), and when pressure is applied in the opposite direction, the elastic deformability of the annular elastic seal (13; 14) by the respective side window ( 10; 11) and the annular elastic seal (13; 14) is sealing that the cylinder tube (1) has a first and a second recess (20; 21), the first recess (20) being arranged axially in such a way that only the first annular elastic seal (13) is positioned in a first end position of the piston (9) above the first recess (20) and is located between the first annular elastic seal (13) and the cylinder tube (1) by means of the first recess (20) ) opens a first overflow cross section, the second recess (21) being arranged axially so that only the z wide annular elastic seal (14) is positioned in a second end position of the piston (9) above the second recess (21) and is located between the second annular elastic seal (14) and the cylinder tube (1) by means of the second recess (21) second cross-section opens.

Description

The invention relates to a double-acting hydraulic working cylinder with a pressure medium overflow between the working spaces, preferably in the end positions of the piston.

In certain applications of working cylinders, such as master-slave systems, hydraulically actuated switches or in conjunction with hydraulic accumulators, it is necessary to allow an end position or two end positions of the piston pressure equalization between the working spaces, or from one pressure chamber in the other Pressure chamber to transfer pressure medium. This should be compensated, for example, leakage.

In this way it is achieved that the piston of the working cylinder can always go to the end position and that its function and the function of the connected means, such as a hydraulic accumulator is ensured.

From the prior art valve systems are arranged for pressure equalization between the working spaces in the end positions in pistons or piston rods of working cylinders, which usually have biased with springs valve body with a plunger. In the respective end position of the piston, the corresponding valve is opened by the plunger in contact with the inside of a closure part of the cylinder tube opens the valve and the pressure medium flows from one to the other working space.

A generic working piston-cylinder unit is from the document DE 30 13 380 C2 out. In the working piston in this case two operable by plunger valves are arranged, which are opened in each case shortly before the respective end stop of the piston on a closure part of the cylinder tube to connect the working space with the return port to prevent damage to the components.

From the publication DE 83 24 442 U1 is the arrangement of a check valve in the piston and an inner connecting line in the piston and the piston rod of a double-acting piston-cylinder unit for pressure equalization with a hydraulic accumulator out. The hydraulic accumulator charge and the pressure medium loss compensation between the piston and piston rod chamber takes place in the retracted end position of the piston when subjected to a pressure medium via the main port of the working cylinder.

In the publication DE 12 79 908 A is a double-acting hydraulic lifting cylinder with both sides of the piston protruding valve spindles known. The valve spindles are unequal in length, whereby upon reaching the respective end position of the piston, a two-stage pressure equalization between the working spaces takes place.

Another arrangement of a controlled by plunger valve in the piston of a working cylinder is in the document DE 2 245 129 A disclosed. In the vicinity of the end positions of the piston of the respective plunger opens in contact with the inner wall of the closure part, the valve, both working chambers of the working cylinder are connected to each other, whereby the overflow of the pressure medium, the pressure equalization takes place.

The publication DE 10 2005 008 070 A1 has a hydraulic cylinder for the object whose piston has a valve arrangement for pressure equalization between the working spaces. The valves are also opened in the vicinity of the end positions of the piston by means of plungers, so that pressure medium can flow over between the working spaces of the hydraulic cylinder.

All said valve assemblies in the piston of a working cylinder have symmetrically designed valve assemblies that lift with the help of plungers shortly before reaching the respective end position of the piston biased with springs valve body from the seat, a connection between the work spaces is made and pressure equalization overflow of the pressure medium he follows.

The design-related effort and the relatively small cross-section to the overflow of the pressure medium as well as existing by the spatial conditions in the piston installation space of the valve components limit the potential application of the solutions described.

The object of the invention is to develop a structurally favorable solution for a definable pressure medium overflow between the working spaces of a double-acting hydraulic working cylinder in definable positions, in particular in the end positions of the piston.

The problem is solved by a working cylinder with the features listed in the protection claim 1 and alternatively by a working cylinder with the features listed in the protection claim 2. Preferred developments emerge from the subclaims.

An inventive cylinder according to claim 1 allows a pressure medium flow between the working spaces in both directions.

An inventive cylinder according to claim 2 with Druckmediumüberströmung between the working spaces has a cylinder tube with connections for supplying and discharging a pressure medium, a bottom closure part, a guide closure part, two working spaces, a piston rod which is guided in the guide closure part, a piston which is connected to the piston rod connected and guided in the cylinder tube and separates by means of seals two working spaces in the cylinder tube.

The working cylinder according to the invention is characterized in that the piston has a first side plate and a second side plate and a central portion between the first and second side plate and a first and a second annular elastic seal, wherein the first seal on the first side plate axially in the direction of the second side window is arranged and is supported on one side of the first side window, while the second seal is disposed on the second side plate axially in the direction of the first side plate and is supported on one side by the second side plate. The annular space enclosed axially between the two seals and radially between the middle section of the piston and the cylinder tube wall is referred to below as the piston center space.

Each of the seals is deformed differently depending on the direction of the pressurization and thus has a different sealing behavior depending on the direction of the pressure gradient.

When pressure is applied from the middle section, that is, when there is a higher pressure of the pressure medium in the piston middle space than in the working space separated by the respective seal, the elastic deformability of the seal is limited by the respective side window. The side plate facing axial edge of the elastic annular seal is supported by the side window. The seal behaves sealingly even at high pressure drops in this direction.

When pressurizing in the direction of the central portion, ie at a higher pressure in the working space than in the piston center space, the seal deforms by the pressure-related force application to the axial edge of the elastic annular seal towards the central portion. In this case, a gap is formed between the cylinder surface facing the radial surface of the seal and the Zylinderrohrinnenwandung. About this gap a cross section is opened, which allows a pressure medium transfer on the working space in the piston central space and thus a pressure compensation. The height of the pressure gradient between the working space and the piston center space, from which a pressure fluid transfer occurs, can be adjusted by the geometry and the material properties of the relevant elastic seal application.

Each of the seals thus behaves like a valve, the opening direction and closing direction of both seals being opposite to each other. If, for example, a higher pressure prevails in the first working space than in the second working space, the seal facing the first working space allows pressure medium to pass into the piston center space, while the seal facing the second working space is supported by the second side disk and behaves in a sealing manner and no pressure medium passage between the piston central space and the second working space permits. As a result, there is no pressure medium transfer from the first working space into the second working space.

The cylinder tube has a first and a second recess, wherein the first recess is arranged axially so that the first seal is positioned in a first end position of the piston above the first recess and by means of the first recess between the first seal and cylinder tube, a first overflow cross section opens. Similarly, the second recess is axially arranged so that the second seal is positioned in a second end position of the piston over the second recess and opens a second overflow cross section by means of the second recess between the second seal and cylinder tube. Such an overflow cross section can preferably be provided by an annular groove-like depression of the cylinder tube inner wall or a conical expansion; However, other shapes are also possible in which the cylinder tube inner wall at least in sections springs back so far that the relevant sealing ring and, if appropriate, the side window assigned to this sealing ring no longer bears completely against the cylinder tube inner wall.

In an overflow position, shown on the example of a first end position, so that the sealing of the first seal between the piston central space and the first working space, so the working space with the lower pressure, repealed. The pressure medium can flow from the piston center space via the first overflow cross section into the first working space. Thus, the pressure in the piston central space drops to the pressure of the first working space. As a result, elastic deformation of the second seal toward the center portion occurs; the second seal opens and a resulting overflow from the second working space forms over the gap between the second seal and the cylinder tube inner wall into the piston middle space and from there over the first Overflow cross section in the first working space. The overcurrent can take place until, for example, leakage losses from the pressure medium system assigned to the first working space are compensated for and pressure equalization is again established. The operation in the second end position is corresponding. The end position in the sense of an overflow position can also be understood to be a different position than corresponds to the stroke end position predetermined by the cylinder. This may be the case, for example, when the means driven by the working cylinder do not permit movement of the piston all the way in the cylinder tube or require overflow at another position.

The simple design of the piston has a particularly advantageous effect, since it has no additional mechanically moving components which require special machining of the piston and assembly work. It is achieved an overflow in both directions between the working spaces, wherein the overflow direction is determined by the piston position.

With the elastic annular seals the function of pressure equalization between the work spaces is realized in a simple and reliable manner. In addition, a cylinder according to the invention operated as a particular advantage trouble-prone and easy to maintain. Furthermore, by choosing the geometry and the material properties of the seals, a desired pressure gradient, from which a pressure medium occurs, can also be adjusted without problems for each of the two overflow layers.

An alternative inventive working cylinder according to claim 2 allows a pressure medium flow between the work spaces in only one direction. Such a working cylinder initially has the same features and the same operation as a working cylinder according to claim 1, so that here the description to claim 1 applies, with the following differences exist. The cylinder tube need only have a recess, referred to as the second recess. Furthermore, only one of the two seals must be designed as a first annular elastic seal, which is supported on one side by a first side window. The positioning of the second recess defines an overflow position. In the overflow position, the second seal is in height of the recess, so that over an overflow cross section, referred to as the second overflow cross section, pressure medium from the piston central space can pass into the separated by the second seal working space, which at the same time a pressure equalization takes place. This creates a pressure gradient between the working space, which is separated by the first elastic annular seal of the piston central space and the piston central space, whereby the elastic annular seal is deformed to form a gap, and pressure medium from this working space in the piston central space and from there via the overflow cross section into the other workspace.

The overflow layer is preferably positioned in an end position, but can also be positioned in other cases at a different axial location, if on the way of the piston stroke, for example, depending on a particular piston position, an overflow possible, but excluded in an end position.

Since an overflow in the alternative solution according to claim 2 should be possible only in one direction, the second seal can be formed without the special features of the elastic deformability in connection with the one-sided support and the valve effect achieved thereby.

In an advantageous development, the pressure medium overflow in an overflow position is limited by at least one additional throttle. In a particularly advantageous manner, the throttle is provided with very simple and interference-insensitive means that an annular gap is provided with a desired cross-section by a suitable adjustment of the diameter of a side window to the inner diameter of the cylinder tube inner wall of the cylinder tube. The width of the annular gap is dimensioned according to the required overflow of the pressure medium between the work spaces for the particular application. If the piston is in an overflow position, an overflow limitation is brought about by the annular gap between the cylinder tube inner wall and the side window, which is not positioned above the recess, even at pressure drops caused by the elastic deformation of the elastic annular seal associated with this side disc with a larger cross-section and thus would lead to a larger Druckmediumübertritt per unit time. In addition to the regulation of the overflow volume, as a further advantage, the elastic annular seals are also protected against high loads.

Preferably, both side windows are formed so that each a throttle is provided. Thus, one throttle in each end position becomes active. Depending on the requirements, different throttle values in the two end positions can be defined as a particular advantage in this way.

In an advantageous development related to a working cylinder according to claim 2 with unidirectional overflow, the development described above according to claim 3, a throttle, which is formed by an annular gap between the first side window and the cylinder tube inner wall.

In an advantageous development, the central portion of the piston parallel to the vertical center axis of two spaced-apart annular grooves, between which a circumferential collar is arranged with shoulders on both sides.

In this way, elastic annular seals are held securely and significantly reduces notch stresses during deformation of the seals for pressure equalization, whereby their long service life is guaranteed.

In an advantageous variant, an annular collar is integrally formed on the side windows in the outer region. This collar allows reliable reception of the annular elastic seals without the need for additional fasteners.

According to a further advantageous development, the elastic annular seals have a T-shaped cross-section.

With the T-shaped cross-section of the elastic annular seals secure capture between the annular grooves in the central portion and the annular collar of the respective side window is guaranteed, so that their position in the deformation and the lifting of the inner shell of the working cylinder to overflow the pressure medium during pressure equalization between the workspaces can not change.

Relative to a working cylinder according to claim 2 with unidirectional overflow, the first annular seal on a T-shaped cross-section with the advantages described above.

The invention will be described as an embodiment with reference to

1 Cut a working cylinder

2 Section of a middle section of the piston

3 Section of an elastic annular seal explained in more detail.

To 1 a double-acting cylinder has a cylinder tube 1 with a first connection 2 and second connection 3 for supplying and removing a pressure medium, a bottom closure part 4 , a guide closure part 5 , a piston rod 6 , guided in a hole 7 with seals 8th in the guide closure part 5 and a piston 9 , picked up by the piston rod 6 in the cylinder tube 1 is guided and the work spaces in the cylinder tube 1 separates.

The piston 9 consists of a first side window 10 and a second side window 11 and a middle section 12 ,

Between the middle section 12 and the side windows 10 ; 11 is in each case a first annular elastic seal 13 and a second annular elastic seal 14 added.

The side windows 10 ; 11 have a diameter that is opposite to the inner diameter of the cylinder tube 1 is reduced so far that between a Zylinderrohrinnenwandung 15 of the cylinder tube 1 and the circumference of the side windows 10 ; 11 an annular gap 16 is formed, whose width corresponding to the required overflow of the pressure medium for pressure equalization between the working spaces, between the respective pressure-carrying piston chamber 17 or piston rod space 18 and the piston rod space 18 or the piston chamber 17 , dimensioned for the particular application.

The maximum outside diameter of the middle section 12 is at most equal to that of the side windows 10 ; 11 ,

At the side windows 10 ; 11 is in the outer area an annular collar 19.1 ; 19.2 formed.

In the cylinder tube 1 are in the range of the end positions of the piston 9 a first recess 20 and second recess 21 , in cooperation with the respective side window 10 ; 11 , the respective annular elastic seal 13 ; 14 and the middle section 12 an overflow cross section for overflow of the pressure medium from the respective pressurized working space in the other working space in the end position of the piston 9 form.

The in 2 sectioned middle section 12 of the piston 9 points parallel to its vertical central axis 22 a wraparound collar 23 with double-sided shoulder 24 and a first annular groove 25 and a second annular groove 26 on. The annular elastic seals 13 ; 14 are like in 3 shown enlarged in section, T-shaped.

Between the first side window 10 and the middle section 12 becomes the first annular one elastic seal 13 as well as between the middle section 12 and the second side window 11 the second annular elastic seal 14 with the help of the respective annular collar 19.1 ; 19.2 on the side windows 10 ; 11 in cooperation with the respective annular groove 25 ; 26 at the middle section 12 held securely due to the T-shaped design.

When deforming the annular elastic seals 13 ; 14 Notch stresses occurring in the region of the middle section for pressure equalization 12 be by means of the respectively associated side of the two-sided shoulder 24 significantly reduced, so that their long service life is guaranteed.

When pressure is applied to the piston rod chamber 18 with the pressure medium to the piston 1 the in the 1 shown end position, such as that of a master cylinder in a master-slave system reach.

This was previously in the piston chamber 17 located pressure medium previously flowed through the second port 3 in the slave cylinder from. Due to leakage during operation of the system, the slave cylinder is not fully extended, so that pressure fluid must track and pressure equalization must be done.

The applied pressure in the piston rod space of the pressure medium deforms the first annular elastic seal 13 in the direction of the facing side of the two-sided shoulder 24 at the middle section 12 so that the first annular elastic seal 13 from the cylinder tube inner wall 15 of the cylinder tube 1 lifts and forms a gap, and the pressure medium through the annular gap 16 between the first side window 10 and the cylinder tube inner wall 15 of the cylinder tube 1 , the said gap, the piston central space 27 in the middle section 12 and the overflow cross section at the second recess 21 in the piston chamber 17 and continue over the second port 3 flows to the slave cylinder and this extends completely.

The second annular elastic seal 14 and the second side window 11 of the piston 9 are located in a position in the region of the second recess 21 so that a free space for overflow of the pressure medium is formed.

An analogous operation of the device for pressure equalization between the working chambers of the working cylinder is also on pressurization of the piston chamber 17 in front.

In the end position of the piston 9 is located in the direction of movement leading elastic annular seal 13 ; 14 in the region of the recess 20 ; 21 in the cylinder tube 1 , whereby there is a free passage in this area. The pressure equalization between the working chambers of the working cylinder is then carried out by the in the closed area of the Zylinderrohrinnenwandung 15 of the cylinder tube 1 located elastic annular seal 13 ; 14 is deformed elastically on the circumference by the pressure of the pressure medium in the pressurized working space in the direction of the non-pressurized working space, whereby these from the inner shell 14 is lifted and the pressure medium, as described above, flows over.

In another embodiment, as it corresponds to claim 2, a working cylinder has a Überströmungsmöglichkeit only in one direction. Such a cylinder corresponds essentially to the first in 1 shown embodiment, although only the second recess 21 is trained. The piston is in the end position on the bottom closure part 4 , the pressure medium from the piston rod space 18 the first annular elastic seal 13 deform, so that this a gap to Zylinderrohrinnenwandung 15 forms, bringing the pressure medium into the piston middle space 27 can transgress. From the piston middle space 27 occurs the pressure medium over the overflow cross section between the second seal, which in the 1 as the second annular elastic seal 14 is shown, but deviating from the illustration, as a normal seal without special deformation properties may be formed, and the cylinder tube 1 in the region of the second recess 21 in the piston chamber 17 above. In the reverse direction, that is from the piston chamber 17 in the piston rod space 18 can no pressure medium transfer occur.

LIST OF REFERENCE NUMBERS

1

cylinder tube

2

first connection

3

second connection

4

Bottom seal section

5

Guide closure part

6

piston rod

7

drilling

8th

seals

9

piston

10

first side window

11

second side window

12

midsection

13

first annular elastic seal

14

second annular elastic seal

15

Zylinderrohrinnenwandung

16

annular gap

17

piston chamber

18

Piston rod space

19

circular collar ( 19.1 ; 19.2 )

20

first recess

21

second recess

22

vertical center axis

23

circumferential collar

24

double-sided shoulder

25

first ring groove

26

second annular groove

27

Piston means space

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3013380 C2 [0005]
• DE 8324442 U1 [0006]
• DE 1279908 A [0007]
• DE 2245129 A [0008]
• DE 102005008070 A1 [0009]

Claims (8)

Working cylinder, comprising a cylinder tube ( 1 ) with connections for the supply and removal of a pressure medium, a bottom closure part ( 4 ), a guide closure part ( 5 ), two work spaces, a piston rod ( 6 ), which in the guide closure part ( 5 ), a piston ( 9 ) with seals, with the piston rod ( 6 ) and in the cylinder tube ( 1 ) and the work spaces in the cylinder tube ( 1 ), characterized in that the piston ( 1 ) a first side window ( 10 ) and a second side window ( 11 ) and a middle section ( 12 ), arranged between first and second side windows ( 10 ; 11 ), and a first and a second annular elastic seal ( 13 ; 14 ), wherein the first annular elastic seal ( 13 ) on the first side window ( 10 ) axially in the direction of the second side window ( 11 ) is arranged and on one side of the first side window ( 10 ), the second annular elastic seal ( 14 ) on the second side window ( 11 ) axially in the direction of the first side window ( 10 ) is arranged and on one side of the second side window ( 11 ) is supported, wherein each of the annular elastic seals ( 13 ; 14 ) when pressurized towards the middle section ( 12 ) forming a gap to the cylinder tube inner wall ( 15 ) is elastically deformable and wherein at a pressurization in the reverse direction, the elastic deformability of the annular elastic seal ( 13 ; 14 ) through the respective side window ( 10 ; 11 ) and the annular elastic seal ( 13 ; 14 ) is sealing, that the cylinder tube ( 1 ) a first and a second recess ( 20 ; 21 ), wherein the first recess ( 20 ) is arranged axially so that only the first annular elastic seal ( 13 ) in a first end position of the piston ( 9 ) above the first recess ( 20 ) is positioned and by means of the first recess ( 20 ) between the first annular elastic seal ( 13 ) and the cylinder tube ( 1 ) opens a first overflow cross section wherein the second recess ( 21 ) is arranged axially so that only the second annular elastic seal ( 14 ) in a second end position of the piston ( 9 ) over the second recess ( 21 ) is positioned and by means of the second recess ( 21 ) between the second annular elastic seal ( 14 ) and the cylinder tube ( 1 ) opens a second overflow cross section. Working cylinder, comprising a cylinder tube ( 1 ) with connections for the supply and removal of a pressure medium, a bottom closure part ( 4 ), a guide closure part ( 5 ), two work spaces, a piston rod ( 6 ), which in the guide closure part ( 5 ), a piston ( 9 ) with seals, with the piston rod ( 6 ) and in the cylinder tube ( 1 ) and the work spaces in the cylinder tube ( 1 ), characterized in that the piston ( 1 ) a first side window ( 10 ) and a first annular elastic seal ( 13 ; 14 ), a middle section ( 12 ) and a second seal, wherein the first annular elastic seal ( 13 ) on the first side window ( 10 ) is arranged axially in the direction of the second seal and on one side of the first side window ( 10 ) and wherein the middle section is arranged between the first side window and the second seal, and wherein the first annular elastic seal 13 ; 14 ) when pressurized towards the middle section ( 12 ) forming a gap to the cylinder tube inner wall ( 15 ) is elastically deformable and wherein at a pressurization in the reverse direction, the elastic deformability of the first annular elastic seal ( 13 ; 14 ) through the first side window ( 10 ; 11 ) and the first annular elastic seal ( 13 ; 14 ) is sealing, that the cylinder tube ( 1 ) a second recess ( 21 ), wherein the second recess ( 21 ) is arranged axially so that only the second seal in an overflow position of the piston ( 9 ) over the second recess ( 21 ) is positioned and by means of the second recess ( 20 ) between the second seal and the cylinder tube ( 1 ) opens a second overflow cross section. Working cylinder according to claim 1, characterized in that the piston ( 9 ) has at least one pressure medium throttle, wherein the pressure medium throttle through an annular gap ( 16 ) between the cylinder tube inner wall ( 15 ) of the cylinder tube ( 1 ) and the circumference of one of the side windows ( 10 ; 11 ) is trained. Working cylinder according to claim 2, characterized in that the piston ( 9 ) has a pressure medium throttle, wherein the pressure medium throttle through an annular gap ( 16 ) between the cylinder tube inner wall ( 15 ) of the cylinder tube ( 1 ) and the circumference of the first side windows ( 10 ) is trained. Working cylinder according to claim 1 or 3, characterized in that the middle section ( 12 ) of the piston ( 9 ) parallel to its vertical center axis ( 22 ) two spaced annular grooves ( 25 ; 26 ) between which a circumferential collar ( 23 ) with double-sided shoulder ( 24 ) is arranged. Working cylinder according to claim 1, 3 or 5, characterized in that in the outer region of the side windows ( 10 ; 11 ) an annular collar ( 19.1 ; 19.2 ) is formed. Working cylinder according to claim 1, 3, 5 or 6, characterized in that the annular elastic seals ( 13 ; 14 ) have a T-shaped cross-section. Working cylinder according to claim 2 or 4, characterized in that the first annular elastic seal ( 13 ) has a T-shaped cross-section.

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