DE102013102167A1 - Hydraulic cylinder with redundant safety valve system - Google Patents

Abstract

The invention relates to a hydraulic cylinder (1) having a cylinder housing (2) in which a piston (3) connected to a piston rod (4) is guided in an axially displaceable manner, which in the cylinder housing (2) has a first pressure chamber (10) which is variable in size ), wherein a with the pressure chamber (10) connected controllable obturator (9) in the cylinder housing (2) is integrated, through which the pressure chamber (10) can be shut off and which is adjustable in a release position in which a connection between the pressure chamber (10) and a pressure medium connection (7) of the hydraulic cylinder (1), wherein in the hydraulic cylinder (1) a second pressure chamber (13) is formed by moving the piston (2) and the piston rod (4) in the same direction with the first Pressure chamber (10) is variable in size, and wherein a second controllable with the second pressure chamber (13) connected second controllable obturator (14) in the cylinder housing (2) through which the second Dru Back space (13) can be shut off and is adjustable in a release position in which a connection between the second pressure chamber (13) and a pressure medium connection (19) of the hydraulic cylinder (1).

Description

The present invention relates to a hydraulic cylinder according to the preamble of claim 1. It comprises, in a manner known per se, a cylinder housing in which a piston connected to a piston rod is guided in and out in the axial direction. Within the cylinder housing, the piston defines a variable in size first pressure chamber which is connected via a line to a first pressure medium connection of the hydraulic cylinder. By supplying pressurized hydraulic fluid, the piston is moved, thereby axially extending the piston rod led out of the cylinder housing on the head side to perform mechanical work. The volume of the pressure chamber increases accordingly.

In order to prevent inadvertent retraction of the standing under the action of an external load piston and the piston rod in the event of a break or leak in a connected to the pressure medium connection hydraulic line or hose, it is known to integrate a controllable obturator in the cylinder housing, that it in the line between the pressure medium connection and the pressure chamber is located. If this internal obturator is in a blocking position, the pressure chamber is shut off and the piston and the piston rod can not retract further into the cylinder. Only when the obturator serving as a safety valve is actuated such that it is adjusted to a release position, is a connection established again between the pressure chamber and the pressure medium connection of the hydraulic cylinder, so that the hydraulic fluid can intentionally flow out of the pressure chamber. The control of the obturator can be done in particular via an electrical or hydraulic control line. It is also conceivable to control the obturator manually.

Constructively differently designed safety devices for hydraulic cylinders are for example from the DE 20 2007 015 781 U1 or from the DE 10 2005 016 090 A1 known, which also serve to block or lock the cylinder, but are relatively expensive.

Furthermore, from the DE 199 34 480 B4 a double-acting hydraulic cylinder with two pressure medium connections and two pressure chambers associated therewith, in which the piston can be moved by supplying hydraulic fluid in one or the other pressure medium connection in one or the other direction. In this case, each pressure chamber is provided with its own shut-off valve, by which the hydraulic fluid is shut off separately in both pressure chambers and the piston can thus be blocked in both directions. Only if one of the two shut-off valves, which are designed here as hydraulically releasable check valves, is actuated hydraulically to open, hydraulic fluid can flow out of the so-unlocked pressure chamber and the piston can be moved by supplying liquid in the other pressure chamber in the appropriate direction. In this way, an in both directions (retraction and extension) effective safety device of the hydraulic cylinder is achieved. However, this shut-off system is in each case only effective in each direction.

In principle, a failure of the aforementioned safety systems, such as wear or contamination of the shut-off devices is possible, so that the intended backup function can then no longer be performed, which can lead to major damage or danger to life and limb depending on the application. Therefore, often mechanically acting security elements are also attached, but this is associated with increased effort.

Object of the present invention is therefore to provide a structurally simple hydraulic cylinder of the type mentioned, which provides greater security and can perform its locking function even at the failure of the obturator still reliable.

This object is achieved by a hydraulic cylinder according to claim 1. Advantageous embodiments and modifications of the invention will become apparent from the dependent claims.

It is essential in the inventive solution that in the hydraulic cylinder, a second pressure chamber is provided, which is variable in size in the same direction with the first pressure chamber by moving the piston and the piston rod, and that connected to the second pressure chamber second controllable shut-off in the Is integrated cylinder housing, through which the second pressure chamber is shut off at a locking position of the second obturator, wherein the second obturator can be placed in a release position in which a line connection between the second pressure chamber and a pressure medium connection of the hydraulic cylinder and hydraulic fluid thus from the second pressure chamber can flow out.

Also, the second controllable obturator is thus in the line between the associated pressure medium connection and the associated second pressure chamber. It can be controlled as well as the first obturator in particular via an electrical or hydraulic control line. A Coincidental change in size of the two pressure chambers means that the second pressure chamber is larger, although the first pressure chamber is larger, and that it is smaller, even if the first pressure chamber is smaller, although the volume changes of the two pressure chambers can also vary in size.

The main advantage of the embodiment according to the invention is that two redundant safety systems are integrated in the hydraulic cylinder. Even if a shut-off should fail, the cylinder via the other obturator can still fulfill its locking or blocking function. In this way, a significantly increased security can be achieved without additional mechanical securing means to be attached, so that the effort in the operation of the hydraulic cylinder or a device equipped therewith does not increase.

Another significant advantage is that the hydraulic cylinder according to the invention is designed to be particularly compact due to the integrated security systems and because of this compact design requires no additional space for external security systems. At the same time it is relatively inexpensive to produce with a simple design.

Advantageously, the two shut-off valves of the two pressure chambers of the cylinder according to the invention can be controlled so that both shut-off valves are adjusted together or simultaneously in their respective release position.

The second pressure chamber acts during the filling with a hydraulic fluid advantageously parallel to the filled with a hydraulic fluid first pressure chamber on the piston and the piston rod. Thus, the piston and the piston rod can be extended with parallel pressurization of both pressure chambers with correspondingly high pressure forces.

According to a particularly preferred embodiment of the invention, it is provided that the piston and the piston rod are provided with a central axial bore into which a cylinder base fixed and axially projecting tube engages with the interposition of a seal, wherein the trained in the pipe for conducting hydraulic fluid Channel is conductively connected to the second obturator.

The piston rod is closed at its outgoing from the cylinder housing free end so that it forms in its interior a closed-end cavity, which forms at least part of the second pressure chamber of the hydraulic cylinder according to the invention.

Thus, the piston rod is tubular or hollow at least over a portion facing the cylinder bottom, wherein the second pressure chamber extends at least partially in the cavity of the piston rod and is limited in the axial direction by the closed end of the piston rod. The tube forms a separating element between the two pressure chambers.

It is particularly advantageous if the channel formed in the channel is so wide that it forms not only a line to the second pressure chamber, but itself a part of the second pressure chamber of the hydraulic cylinder.

The first pressure chamber is advantageously formed annularly around the tube, so that it adapts to the shape of the annular piston.

A particularly compact and stable design can be achieved if the two controllable shut-off valves are integrated in the opposite side of the head of the hydraulic cylinder.

It is particularly favorable if the two controllable shut-off valves are each formed by a pilot-operated check valve, in particular with a respective spring-loaded blocking body, such as a ball, and can be hydraulically unlocked.

It is also particularly advantageous if the two, in particular hydraulically controllable shut-off valves are connected to a common control line, so that they can be unlocked by supplying a corresponding control signal, such as a hydraulic control pressure together and simultaneously.

According to a further preferred embodiment of the invention, it is provided that the hydraulic cylinder is designed to be double-acting, wherein the piston rod by supplying hydraulic fluid through a second pressure medium connection in a third pressure chamber annularly surrounding the piston rod, which is located on the side facing away from the first pressure chamber side of the piston , can be retracted. On the inventive arrangement of the first and second separate pressure chamber of the third pressure chamber has no influence.

It is particularly advantageous if the control line of the two shut-off valves is connected to the third pressure chamber or to the pressure medium connection for the third pressure chamber, so that by supplying a hydraulic fluid through the Pressure medium connection for the third pressure chamber not only the piston rod is retracted, but also the two check valves are controlled. The supplied hydraulic fluid means at the same time also the application of a hydraulic control pressure to unlock the two shut-off valves, which is a prerequisite for the retraction of the piston.

According to a particularly preferred embodiment of the invention it is further provided that in each case a pressure sensor is arranged in the first and in the second pressure chamber, through which the pressure prevailing in the respective pressure chamber of the hydraulic fluid can be monitored. In this way, a possible partial failure of one of the two redundant security systems can be detected at an early stage so that it can be remedied in a timely and safe manner before it even comes to a failure of the other security system. The safety of the hydraulic system according to the invention is thereby significantly increased again.

Areas of application of the hydraulic cylinder according to the invention can be any type of fixed or mobile installations in which larger holding forces must be exerted or larger loads must be supported. Thus, the hydraulic cylinder according to the invention can be used for example in lifting platforms, jacks or cranes.

Further advantages and features of the invention will become apparent from the following description of the embodiment shown in the drawing.

The drawing shows a cross section through a hydraulic cylinder according to the invention, which is designed with a redundant safety valve system.

The double acting hydraulic cylinder 1 includes an outer cylinder housing 2 , in which a piston acted upon by hydraulic fluid on both sides 3 with a tubular piston rod 4 axially guided in and out. In the illustrated embodiment, the hydraulic cylinder 1 designed as a support cylinder for a motor vehicle. This is at the free end of the piston rod 4 a support plate 5 provided, which can be brought into contact with the ground when supporting the vehicle.

In the area of the soil 6 of the cylinder housing 2 is a first pressure medium connection 7 Arranged over in the ground 6 running lines 8th via a first hydraulically operated check valve 9 with the first pressure chamber 10 connected, which is on the ground 6 facing side of the piston 3 located. This first pressure room 10 is just like the piston 3 ring-shaped, as it is from a central tube 11 is crossed, which at the cylinder bottom 6 is attached and coaxial through a central bore of the piston 3 through into the interior of the piston rod 4 extends. The end of this tube is approximately at the level of the outside surface of the lid 12 with which the cylinder housing 2 closed at the top.

Inside the piston rod 4 and inside the tube 11 is the inventively provided second pressure chamber 13 which axially on the one hand through the housing bottom 6 and on the other hand by the end-side closure of the piston rod 4 who is here by the support plate 5 is formed, is limited. One of the pipe runs through the floor 8th branched line 8a , which has a second hydraulically operated check valve 14 with the second pressure chamber 13 connected is. Both check valves 9 and 14 are arranged here parallel next to each other, with the blocking body 9a and 14a the two check valves 9 and 14 each in the same direction from its locking seat out into the respective release position are movable. The first and second check valves 9 . 14 form together with the first and second pressure chamber 10 . 13 the double security system of the hydraulic cylinder according to the invention 1 ,

The piston 3 slides with the interposition of a ring seal 15 on the outer wall of the pipe 11 along, leaving the second pressure chamber 13 is sealed. Further, between the peripheral wall of the piston 3 and the inner wall of the cylinder housing 2 a ring seal 16 and between the passage opening of the lid 12 and the outer wall of the piston rod 4 a ring seal 17 arranged, creating a third pressure chamber 18 is sealed, the piston rod 4 on the first pressure room 10 opposite side of the piston 3 surrounds annularly. The third pressure chamber 18 is with a second pressure medium connection 19 connected, through which hydraulic fluid can be supplied to the piston 3 and the piston rod 4 retract.

Via a hydraulic control line 20 coming from the to the second pressure medium connection 19 connected supply line branches, is the third pressure chamber 18 with the two check valves 9 and 14 connected. By supplying pressurized hydraulic fluid into the fluid port 19 so can both check valves simultaneously 9 and 14 unlocked and thus the piston 3 and the piston rod 4 be retracted.

Through this hydraulic control of the two check valves 9 and 14 will the as redundant backup system executed parallel blocking of the two pressure chambers 10 and 13 lifted together, leaving the piston 3 and the piston rod 4 conscious and controlled can be retracted. An unintentional retraction is without such a targeted control by two parallel and independently acting safety valves 9 and 14 , the two parallel pressure chambers 10 and 13 the hydraulic cylinder according to the invention 1 are assigned twice, which results in a double security against unwanted movements of the piston in case of failure of the hydraulic system. As a result, external loads acting on the piston can be kept particularly reliable and secure.

If, due to a leak or other defect, the pressure in one of the two pressure chambers 10 or 13 should fall off, it can early by one of the two pressure sensors arranged there 21 be recognized so that appropriate repair work can be done in time to restore the double safety of the redundant safety valve system.

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 202007015781 U1 [0003]
• DE 102005016090 A1 [0003]
• DE 19934480 B4 [0004]

Claims (12)

Hydraulic cylinder ( 1 ) with a cylinder housing ( 2 ), in which one with a piston rod ( 4 ) connected piston ( 3 ) is guided axially displaceably, in the cylinder housing ( 2 ) a variable in size first pressure chamber ( 10 ), one with the pressure chamber ( 10 ) connected controllable obturator ( 9 ) in the cylinder housing ( 2 ) is integrated, through which the pressure chamber ( 10 ) is shut off and that is adjustable in a release position in which a connection between the pressure chamber ( 10 ) and a pressure medium connection ( 7 ) of the hydraulic cylinder ( 1 ), characterized in that in the hydraulic cylinder ( 1 ) a second pressure chamber ( 13 ) is formed by displacing the piston ( 2 ) and the piston rod ( 4 ) in the same direction as the first pressure chamber ( 10 ) is variable in size, and that one with the second pressure chamber ( 13 ) connected second controllable shut-off ( 14 ) in the cylinder housing ( 2 ) is integrated, through which the second pressure chamber ( 13 ) is shut off and that is adjustable in a release position in which a connection between the second pressure chamber ( 13 ) and a pressure medium connection ( 19 ) of the hydraulic cylinder ( 1 ) consists. Hydraulic cylinder ( 1 ) according to claim 1, characterized in that the second controllable obturator ( 14 ) together with the first controllable shut-off device ( 9 ) is adjustable in a release position. Hydraulic cylinder ( 1 ) according to claim 1 or 2, characterized in that the second pressure chamber ( 10 ) parallel to the first pressure chamber ( 13 ) on the piston ( 3 ) and the piston rod ( 4 ) acts. Hydraulic cylinder ( 1 ) according to one of claims 1 to 3, characterized in that the piston ( 3 ) and the piston rod ( 4 ) are provided with an axial bore into which a cylinder bottom ( 6 ) fixed and axially projecting tube ( 11 ) with the interposition of a seal ( 15 protruding in the tube ( 11 ) trained channel ( 11a ) with the second obturator ( 14 ), and that the piston rod ( 4 ) at its out of the cylinder housing ( 2 ) is guided closed free end, so that it has in its interior a closed-end cavity, the at least a portion of the second pressure chamber ( 13 ) of the hydraulic cylinder ( 1 ). Hydraulic cylinder ( 1 ) according to claim 4, characterized in that in the tube ( 11 ) trained channel ( 11a ) a part of the second pressure space ( 13 ) of the hydraulic cylinder ( 1 ). Hydraulic cylinder ( 1 ) according to claim 4 or 5, characterized in that the first pressure chamber ( 10 ) annularly around the tube ( 11 ) is formed around. Hydraulic cylinder ( 1 ) according to one of the preceding claims, characterized in that the two controllable shut-off devices ( 9 . 14 ) in the ground ( 6 ) of the hydraulic cylinder ( 1 ) are arranged. Hydraulic cylinder ( 1 ) according to one of the preceding claims, characterized in that the two controllable shut-off devices ( 9 . 14 ) are formed by pilot operated check valves, which are hydraulically unlocked. Hydraulic cylinder ( 1 ) according to one of the preceding claims, characterized in that the two controllable shut-off devices ( 9 . 14 ) with a common control line ( 20 ) are connected so that they are simultaneously unlocked by supplying a control signal. Hydraulic cylinder ( 1 ) according to one of the preceding claims, characterized in that it is designed double-acting, so that the piston rod ( 4 ) by supplying hydraulic fluid through a pressure medium connection ( 19 ) into a piston rod ( 4 ) annularly surrounding third pressure chamber ( 18 ) is retractable. Hydraulic cylinder ( 1 ) according to a combination of claims 8 to 10, characterized in that the control line ( 20 ) of the two check valves ( 9 . 14 ) with the third pressure chamber ( 18 ) or with the pressure medium connection ( 19 ) for the third pressure chamber ( 18 ) is connected, so that by supplying a hydraulic fluid, the piston rod ( 4 ) retractable and the two check valves ( 9 . 14 ) are unlocked. Hydraulic cylinder ( 1 ) according to one of the preceding claims, characterized in that in the first pressure chamber ( 10 ) and in the second pressure chamber ( 13 ) each a pressure sensor ( 21 ) is arranged through which the in the respective pressure chamber ( 10 . 13 ) prevailing pressure of the hydraulic fluid can be determined.

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