EP2107169A1 - Hydraulic cylinder - Google Patents

Abstract

The cylinder (10) has a piston (16) arranged in a cylinder housing (12), and a piston rod (14) connected with the piston. A bypass line is provided with a valve. The bypass line has a set of valve parts provided with a set of control units, where one of the valve parts controls hydraulic flow through the bypass line into a chamber (20) of the piston. The control unit of the other valve part is operated in dependence of hydraulic pressure in a rod-sided chamber (18), and the control unit of the former valve part is operated as a function of an end position of the piston.

Description

The invention relates to a hydraulic cylinder for a charger device, comprising a cylinder housing, a piston guided in the cylinder housing, a piston connected to the piston rod, a piston side and a rod side chamber, wherein at least one of the chambers is hydraulically pressurizable, and a bypass line through which the two Chambers are connectable.

Hydraulic arrangements for hydraulically actuated cylinders are often designed such that hydraulic supply to the cylinder is maintained even when the piston moved in the cylinder has reached one of its end positions. This can cause the hydraulic pressure to continue to increase, although the piston can not perform any further movements. This can cause a cylinder housing, piston rings and piston seals to be subjected to excessive pressure, which can lead to damage and high wear. In such hydraulic arrangements, therefore, a pressure limiting device is often provided which is intended to prevent the cylinder from being exposed to an excessive hydraulic pressure in an end position in which it is fully extended or retracted.

A hydraulic cylinder with such a pressure limiting device is for example in the FR 2542298 A2 disclosed. The FR 2542298 A2 discloses a loader device which provides a hydraulic arrangement for operating or tilting a loader tool coupled to the loader device. The hydraulic cylinders used as tilting cylinders are designed in such a way that a pressure built-up in the rod-side chamber can be reduced by a pressure-limiting device as soon as possible the hydraulic cylinder has been moved to its end position. The pressure limiting device is in this case integrated in the piston and designed due to the limited space in the piston only to low flow rates.

Other hydraulic arrangements provide hydraulic cylinders with integral pressure relief devices in which pressure relief lines are formed by means of bores in the cylinder wall, often an increased piston ring wear is noted, since the holes are in the range of movement of the piston.

The object underlying the invention is seen to provide a hydraulic cylinder of the type mentioned, by which the aforementioned problems are overcome.

The object is achieved by the teaching of claim 1. Further advantageous embodiments and modifications of the invention will become apparent from the dependent claims.

According to the invention, a hydraulic cylinder of the type mentioned is formed with a bypass line which extends through a region of the piston rod and the piston-side chamber defining region of the piston, wherein the bypass line is provided with at least one valve which is disposed within the piston rod. The at least one valve comprises first and second valve parts provided with a respective control element, wherein a hydraulic flow through the bypass line out of the rod-side chamber through the first valve part and through the second valve part through a hydraulic flow the bypass line is controllable into the piston-side chamber. Here, the control of the first valve member in response to a hydraulic pressure in the rod-side chamber and the control of the second valve member in response to an end position of the piston is actuated. The arrangement of the valve within a partially formed in the piston rod bypass line, a pressure limiting device is provided, on the one hand at a final position of the piston allows a sufficiently high flow rate to achieve a rapid pressure reduction in the rod-side chamber and on the other is designed such that no holes in the range of movement of the piston are settled and thus no additional piston ring wear is effected.

Preferably, the valve parts on a hollow cylindrical housing with an open and provided with a bottom end face. Preferably, the hollow cylindrical housing are formed as sleeves, wherein in the bottom of the respective hollow cylindrical housing a bore is formed. These hollow cylindrical housings or sleeves can be fitted in a simple manner into a housing bore formed in the piston rod in the region of the bypass line. Advantageously, these hollow cylindrical housings or sleeves can be subjected to a hardening treatment, so that the region of the piston rod which receives these sleeves and in which the bypass line extends does not itself have to be hardened. As a result, manufacturing costs are minimized and maintenance options improved, since when worn the valve body only the hollow cylindrical housing or sleeves and not the piston rod itself must be replaced. This will ensures a particularly production-friendly design of a hydraulic cylinder with pressure relief device. This entails that, on the one hand, a piston which is usually surface-refined or surface-hardened due to its property and which is difficult to machine, does not have to be subjected to additional post-processing steps in which a bypass line is to be inserted. On the other hand, a usually not surface-finished piston rod itself does not have to be processed or surface-refined or tempered, since the wear-sensitive for the bypass line relevant components, such as the valve parts or hollow cylindrical housing or sleeves are separately finished and placeable in the piston rod. Advantageously, these can then be replaced for maintenance purposes also easier and cheaper. As a result, overall manufacturing processes for a hydraulic cylinder with pressure limiting device are simplified and manufacturing costs, maintenance costs and maintenance costs are reduced.

The valve parts or the valve parts designed as hollow cylindrical housings or sleeves are arranged side by side in the piston rod such that the bore in the first valve part is connected to the bypass line in the direction of the rod-side chamber, that the bore in the second valve part with the bypass line in the direction of the piston side Chamber is connected and that the open sides of the hollow cylindrical housing facing each other, so that a cavity is provided by the valve parts, which is connected through the bores in each case with the bypass line. The as sleeves or hollow cylindrical housing formed valve parts are essentially two identical components, which are arranged mirror-symmetrically to each other or fitted into the housing bore formed in the piston rod, wherein the bottom sides each face the openings of the bypass line. Within the hollow cylindrical housing or sleeves, a corresponding cavity or space is created, in which the valve parts associated controls are arranged. The two valve parts or hollow cylindrical housing or sleeves are arranged in the housing bore such that their open sides are aligned with each other and the annular surfaces formed on the open sides abut each other. The outer diameter of the valve parts is substantially equal to the inner diameter of the housing bore formed in the piston rod. The valve members may be provided at their outer periphery with a ring seal to seal the outer surface of the valve members against the inner surface of the housing bore.

Preferably, the controls are each slidably mounted in the hollow cylindrical housing, wherein in a closed position, the respective bore is closable and the controls are biased by a spring arranged in the valve parts in the closed position. The controls are actuated such that by moving the controls into the interior of the valve parts, an open position can be achieved, in which an opening cross-section of the respective bore is formed. Depending on the extent to which the respective control is moved out of its closed position, the opening cross-section can vary accordingly. The controls may be formed as cylindrical bodies or plungers, which by a spring in Be biased closed position. In this case, a part of the cylindrical body or plunger may be hollow to provide a space for receiving the spring. Further, this cavity may also constitute a part of the bypass line, through which the hydraulic fluid is passed when the controls have taken an open position. The outer diameter of a respective control element is matched to the inner diameter of the hollow cylindrical housing. The bore of the hollow cylindrical housing facing side of the control or the bore and thus the bypass line occlusive side of the control is designed such that a closing of the opening of the bore connected to the bypass line is ensured in the closed position. This can be ensured in the case of a circular opening of the cylindrical bore, for example by means of a truncated cone formed on the control or by means of a stump which is of spherical design on the control element. Instead of the hollow cylindrical body or plunger ball-shaped body may be provided as a control, which are guided within the hollow cylindrical housing and biased by a spring in a closed position.

Preferably, the control of the second valve member is provided with a shaft which extends through the bore of the second valve member and engageable with the cylinder housing such that upon reaching the end position of the piston, the control of the second valve member moves through the cylinder housing in an open position becomes. The shaft thus constitutes a control means formed on the control element of the second valve part, in that the control element moves from its closed position into its Opening position is moved. On the one hand, the shaft has a smaller diameter than the bore formed in the second valve part and, on the other hand, its length is dimensioned such that it projects through the bore into the piston-side chamber of the cylinder housing. As soon as the piston now reaches its end position together with the valve parts fitted in the housing bore of the piston rod, the shaft of the control element of the second valve part is moved into the interior of the hollow cylindrical housing of the second valve part and the control element is brought into an open position. At the same time, with continued pressurization of the hydraulic cylinder, the hydraulic pressure in the rod-side chamber increases until the control located in the first valve part moves out of its preloaded closed position into an open position and the bypass line is now open on both sides. The hydraulic fluid can now flow through the holes of the hollow cylindrical housing and enter the piston-side chamber of the hydraulic cylinder and drain there, so that the piston is not pressurized beyond a presettable extent.

In a particularly preferred embodiment of the invention, the control elements guided in the valve parts or hollow-cylindrical housings are designed as poppet valve plungers, so that the valve embedded or arranged in the bypass line within the piston rod dartits a double-plate valve.

With reference to the drawing, which shows an embodiment of the invention, the invention and further advantages are below and advantageous developments and refinements of the invention described and explained in detail.

It shows:

Fig. 1

a cross-sectional view of a hydraulic cylinder according to the invention with a formed in a piston rod bypass line,

Fig. 2

an enlarged cross-sectional view of the bypass line FIG. 1 and

Fig. 3

a schematic side view of a charger device with a hydraulic cylinder according to FIG. 1 ,

FIG. 1 1 shows a hydraulic cylinder 10, as used, for example, for actuating or tilting a loading tool (not shown) of a loading device 11 (FIG. FIG. 3 ) can be used. However, it is also conceivable to use such hydraulic cylinders for lifting and lowering the charger device 11. Such superchargers 11 are, for example, front loaders for tractors. Furthermore, it is conceivable to provide such hydraulic cylinders also on other lifting devices, for example on three-point hydraulic hitch devices. Furthermore, such hydraulic cylinders 10 are also suitable for use on other hydraulic devices of agricultural or forestry machines and construction machines. The hydraulic cylinder 10 has a cylinder housing 12, in which a connected to a piston rod 14 piston 16 is guided.

The cylinder housing 12 has a rod-side chamber 18 and a piston-side chamber 20, wherein the two chambers 18, 20 are separated from each other by the piston 16. Both chambers have a hydraulic connection 22, 24 via which the chambers 18, 20 are supplied with hydraulic fluid for hydraulic pressurization. The cylinder housing 12 comprises a cylinder bottom 26 on the piston side and a cylinder cover 28 on the rod side and is thereby closed, with the piston rod correspondingly being guided through the cylinder cover 28. Thus, the rod-side chamber 18 is bounded by the wall of the cylinder housing 12, by the piston 16 and by the cylinder cover 28. Accordingly, the piston-side chamber 20 is bounded by the cylinder housing 12, by the piston 16 and by the cylinder bottom 26. On the cylinder base 26 and the cylinder cover 28 each pivot bearing 30 are formed, with which the hydraulic cylinder 10 pivotally to a moving device, such as to the charger device 11 from FIG. 3 , can be coupled.

In FIG. 2 is the area off FIG. 1 shown enlarged, in which the piston 16 is positioned within the cylinder housing 12, wherein the piston 16 is almost in an end position (cylinder bottom end position) in which it is fully retracted. Only a small part of the piston-side chamber 20 is still formed. The cylinder bottom end position is reached when a region of the piston head 32 has reached the cylinder bottom 26 and a retraction movement of the piston 16 is limited by the cylinder bottom 26.

The piston 16 is received by a piston ring 34 which is received on the outer periphery of the piston 16 in an annular groove 36 is guided in the cylinder housing 12. The piston 16 is cylindrical and pot-shaped and has a concentric threaded bore 38 into which the piston rod 14 is screwed by means of a thread 40 formed at one end 40.

A concentric bore 44 is arranged in the piston head 32 so that the bore 44 extends through a region of the piston 16 delimiting the piston-side chamber. The cylindrical piston rod 14 also has a concentric bore 46 formed at its end 40. The bore 46 has a first portion 48 with a larger and a second portion 50 of smaller diameter, wherein the second portion 50 is formed at the end of the bore 46 and opens into a further bore 52 which is arranged radially to the piston rod 14 and of the Outside surface of the piston rod 14 leads to the center of the piston rod 14. The radially aligned bore 52 opens into a formed on the piston 16 at the opening of the threaded bore 38 inner shoulder 54th

The bore 44, the bore 46, with their areas 48 and 50, and the bore 52 thus form a bypass line which connects the rod-side chamber 18 with the piston-side chamber 20 hydraulically.

In the area 48 of the bore 46, a valve 56 is arranged. The valve 56 comprises a first and a second valve part 58, 60, the valve parts 58, 60 having a hollow cylindrical housing 62, 64 and in each case a guided in the housing 62, 64 control element 66, 68. The hollow cylindrical housing 62, 64 of the valve parts 58, 60 are sleeve-shaped or cup-shaped and each form a hollow cylindrical body, with an outer diameter which substantially corresponds to an inner diameter of the bore 46 in the region 48. The hollow cylindrical housings 62, 64 have an open side 70, 72 and a side 74, 76 provided with a bottom. In the floors 74, 76 each have a concentric bore 78, 80 is formed. The hollow cylindrical housings 62, 64 are fitted in the bore 46 such that their bottoms 74, 76 are aligned with their bores 78, 80 respectively to the bores 50 and 44 and with their open sides 70, 72 facing each other. The hollow cylindrical housings 62, 64 thus form a cavity 82, in which the control elements 66, 68 are movably arranged or guided and which is connected via the bores 78, 80 to the bypass line or to the bores 50 and 44.

The control elements 66, 68 are likewise designed as hollow-cylindrical bodies and have an outer diameter which substantially corresponds to an inner diameter of the hollow-cylindrical housings 62, 64. The controls 66, 68 thus represent piston-like or pot-like body, which are slidably mounted in the hollow cylindrical housings 62, 64. The control elements 66, 68 in turn have a concentric blind bore 84, 86 which is provided with a shoulder 88, 90 and opens into a radially aligned bore 92, 94. The control elements 66, 68 have a control head region 96, 98 which each has a conical region and in a closed position (as in FIG FIG. 1 and 2 shown), the opening of the holes 78, 80 closes. The control head portion 96, 98 has a smaller diameter than the outer diameter of the remaining part of the controls 66, 68, wherein the radially arranged bores 92, 94 from the center of the control elements 66, 68 to the outer surface of the Control head portion 96, 98 lead into the cavity 82. The controls 66, 68 are thus similar to the hollow cylindrical housings 62, 64 with their open sides 100, 102 arranged facing each other in the cavity 82 slidably. In order to provide a preloaded closed position, a spring 104 is arranged in the cavity 82, which is guided with their ends in each case in the bores 84, 86, wherein the paragraphs 88, 90 serve as an abutment for the spring 104. By the biasing force of the spring 104, the controls 66, 68 are held in the closed position. The control head region 96 formed on the control element 66 of the first valve part 58 is designed as a truncated cone. In contrast, the control head region 98 formed on the control element 68 of the second valve part 60 has an extended region in which a cylindrical shaft 106 is formed, which extends through the bores 80 and 44 and projects into the piston-side chamber 20. The length of the shaft 106 is dimensioned such that upon reaching the end position of the piston 16, the shaft 106 engages the cylinder bottom 26 and is pressed through the cylinder bottom 26 into the cavity 82, so that when reached the end position, the control 68 of the second Valve member 60 is moved to an open position in which the opening of the bore 80 is released.

The controls 66, 68 shown here are designed as conical poppet valves. However, it is also conceivable to choose other shapes, such as spherical shapes, such as a ball or a ball stump.

The operating principle of the arrangement shown above is such that upon reaching the end position of the piston 16, the bore 80 is opened counter to a biasing force caused by the spring 104 by moving the control element 68 via the shaft 106. At a subsequent pressure increase in the rod-side chamber 18, or at there sufficiently high pressure, the control element 66 is moved into the cavity 82 and the opening of the bore 78 is released against the spring 104 caused by the biasing force. If both openings of the bores 78, 80 are released, all areas of the bypass line, namely the bore 44, the bore 46, with their areas 48 and 50, and the bore 52 via the cavity 82 and formed in the controls 66, 68 holes 78, 80, 84, 86, 92, 94 connected to each other, so that the hydraulic fluid located in the rod-side chamber 18 via the bypass line or via the cavity 82 and said holes 78, 80, 84, 86, 92, 94 of the rod-side chamber 18 can flow into the piston-side chamber 20 and from there via the hydraulic port 24.

As soon as the pressure in the rod-side chamber 18 is reduced, due to the biasing force caused by the spring 104, the control element 66 closes the opening of the bore 78 and interrupts the connection to the bypass line, so that in the piston-side chamber 20, a hydraulic pressure can be built up moves the piston 16 in the cylinder housing 12 in the direction of the rod-side chamber 18, so that the shaft 106 is released from engagement with the cylinder bottom 26 and the opening of the bore 80 is closed by the biasing force of the spring 104. Thus, in the rod-side chamber 18, a hydraulic pressure build-up is possible up to the point where the shaft 106 engages the cylinder bottom 26 and the connections to the bypass line are manufactured, wherein the fine tuning of the pressure conditions by the biasing force of the spring 104 and the associated control behavior of the controls 66, 68 are variable or presettable. Dadaurch a pressure relief device is created by the hydraulic cylinder can be spared and signs of wear can be reduced. Furthermore, a production-friendly device is provided by the above-described construction of the valve parts 58, 60, which is characterized by parts with simple geometric shapes, avoids reworking of already surface-treated components and allows separate material treatment of control-relevant valve parts.

Although the invention has been described by way of example only, in light of the foregoing description and the drawings, those skilled in the art will recognize many different alternatives, modifications and variations which are within the scope of the present invention.

Claims (6)

Hydraulic cylinder (10) for a loading device (11), comprising a cylinder housing (12), a piston (16) guided in the cylinder housing (12), a piston rod (14) connected to the piston (16), a rod-side and a piston-side chamber ( 18, 20), wherein at least one of the chambers (18, 20) is hydraulically pressurizable, and a bypass line through which the two chambers (18, 20) are connectable, characterized in that the bypass line extending through an area (48, 50, 52) of the piston rod (14) and extending through a piston side chamber (20) defining region (44) of the piston (16), wherein the bypass line is provided with at least one valve (56) which is disposed within the piston rod (14) and a first and second valve member (58, 60) each having a control member (66, 68), hydraulic flow through the bypass conduit out of the rod side chamber (18) through the first valve member (58) and by the second valve member (60), a hydraulic flow through the bypass line in the piston-side chamber (20) into controllable, wherein the control element (66) of the first valve member (58) in response to a hydraulic pressure in the rod-side chamber (18) and the control element (68) of the second valve part (60) can be actuated as a function of an end position of the piston (16). Hydraulic cylinder (10) according to claim 1, characterized in that the valve parts (58, 60) comprise a hollow cylindrical housing (62, 64) with an open and a bottomed side (70, 72, 74, 76), wherein the bottom (74, 76) of the respective hollow cylindrical housing (62, 64) has a bore (78, 80) is formed. Hydraulic cylinder (10) according to claim 2, characterized in that the valve parts (58, 60) in the piston rod (14) are arranged side by side, that the bore (78) in the first valve member (58) with the bypass line in the direction of the rod-side chamber (18) that the bore (80) in the second valve part (60) is connected to the bypass line in the direction of the piston side chamber (20) and that the open sides (70, 72) of the hollow cylindrical housing (62, 64) to each other have, so that through the valve parts (58, 60), a cavity (82) is provided, which is connected through the bores (78, 80) in each case with the bypass line. Hydraulic cylinder (10) according to claim 2 or 3, characterized in that the control elements (66, 68) in each case in the hollow cylindrical housing (62, 64) are displaceably mounted, wherein in a closed position, the respective bore (78, 80) is closable, wherein the control elements (66, 68) are biased by a in the valve parts (58, 60) arranged spring (104) in the closed position and the control elements (66, 68) are actuated such that by moving the control elements (66, 68) into Interior of the valve parts (58, 60), an opening position can be achieved, in which an opening cross-section of the respective bore (78, 80) is formed. Hydraulic cylinder (10) according to one of claims 2 to 4, characterized in that the control element (68) of the second valve member (60) has a shaft (106) extending through the bore (80) of the second valve member (60) and through in that the piston-side chamber (20) delimits the region (44) of the piston (16) and can be brought into engagement with the cylinder housing (12) such that when the end position of the piston (16) reaches the control element (68) of the second valve part ( 60) is moved by the cylinder housing (12) in an open position. Hydraulic cylinder according to one of claims 1 to 5, characterized in that the control elements (66, 68) are designed as poppet valves tappet.

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