Cylinder / piston assembly with eccentric piston rod

Abstract

In a piston / cylinder assembly with a hydraulic cylinder and a longitudinally displaceable piston which is mounted sealingly within the hydraulic cylinder and supports a piston rod at least on one side, wherein the hydraulic cylinder has a cylinder tube which has a circular cross section and is closed on both of the two sides with an end piece, and the piston rod runs along an axis which is eccentric with respect to the cylinder tube, a cylindrical element is provided which is anchored on the two end pieces and extends through the piston along a second axis which is eccentric with respect to the cylinder tube and is parallel to the first axis.

Description

[0001] Cylinder / piston aqqreqat with eccentric piston rod

[0002] Description

[0003] Cylinder / piston unit with a hydraulic cylinder and a longitudinally displaceable piston which is sealed within the hydraulic cylinder and carries a piston rod on at least one side, wherein the hydraulic cylinder has a cylinder tube with a circular cross-section which is closed on both sides with an end piece, and the piston rod runs along an axis which is eccentric with respect to the cylinder tube.

[0004] A differential cylinder with an eccentric piston rod is known, for example, from CN 1053954 A. The eccentric arrangement of the piston rod is intended to provide anti-rotation protection. However, when an external torque is applied, transverse forces act on the piston rod bearings on the guide pieces, which can lead to wear on the seals and leaks.

[0005] One object of the invention is to provide a cylinder / piston unit with improved anti-twist protection.

[0006] The problem is solved by the features of claim 1. Advantageous embodiments can be found in the dependent claims.

[0007] In a cylinder / piston unit of the type mentioned above, according to the invention, a cylindrical element is provided that is anchored at both end pieces and extends through the piston along a second axis that is eccentric with respect to the cylinder tube and parallel to the first axis. The cylindrical element can be, for example, a rod or a tube. By anchoring the cylindrical element at the end pieces and by sliding, displacement-tight mounting of the cylindrical element in a corresponding bore of the piston, torque support for the piston relative to the hydraulic cylinder is achieved. In particular, with a tubular design of the cylindrical element, this can serve alternatively or cumulatively for other purposes.For example, the cylindrical element can be designed as a pipe that leads to a hydraulic connection at one of the two end pieces and has an opening for hydraulic fluid within the hydraulic cylinder in the area of ​​the opposite end piece. This allows the hydraulic connections of the cylinder / piston unit to be arranged on the same end piece without external lines, which can be advantageous in installation situations with limited space.

[0008] In a preferred embodiment, the cylinder / piston unit is designed as a double-action cylinder in which the piston rod extends on both sides of the piston and in which the two end pieces are designed as guide pieces to which the piston rod is each sealed.

[0009] In principle, the piston and piston rod(s) can be formed as a single piece or rigidly connected. However, a further advantage arises when the piston rod is mounted on the piston so that it can rotate, since in this case, no torque is transferred from the piston rod to the piston. This leads to a more even force distribution and force transmission between the piston and cylinder.

[0010] In the case of hydraulic cylinders, there is also often a desire for a position measuring system with which the position of the piston can be determined.

[0011] Internal position measuring systems arranged within a centrally running, hollow piston rod are well known on the market. The space required for this leads to a larger diameter of the piston rod and cylinder, which in turn causes higher forces in the system. If the piston rod and position measuring system were arranged centrally, any rotation of the piston rod would also result in the maximum torque being introduced into the inner tube containing the position measuring system. An external position measuring system is complex in terms of its mechanical design, sensitive to environmental influences, and its accuracy depends on external forces, since bending of the piston rod can cause an error in the measurement. Here, the arrangement according to the invention with a tubular cylindrical element offers the possibility of integrating an internal position measuring device whose accuracy is not dependent on external forces.The displacement measuring device can preferably be designed as a magnetostrictive or Hall sensor-based displacement measuring system, although the invention is not limited thereto.

[0012] Conveniently, at least one of the end pieces can be connected to the cylinder tube via a flange connection, for example in the form of a coupling ring engaging over a collar. This takes into account the fact that, due to the cylindrical element anchored in both end pieces, the end pieces cannot be rotated independently of each other or against each other.

[0013] However, the other end piece can be screwed onto or into the cylinder tube in the conventional manner using a threaded connection. During assembly, the screwed-on or screwed-in end piece can be installed first, then the piston and cylindrical element can be inserted, and then the open end of the cylinder tube can be closed with the flanged end piece.

[0014] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the figures. It shows:

[0015] Figure 1 shows a first embodiment of a cylinder / piston unit designed as a double-action cylinder with an eccentric piston rod and a rod running parallel to the piston rod as a torque support,

[0016] Figure 2 shows a second embodiment of a cylinder / piston unit with an eccentric piston rod and a hydraulic oil pipe running parallel to the piston rod, Figure 3 shows a third embodiment of a cylinder / piston unit with an eccentric piston rod and a position measuring system arranged in a pipe running parallel to the piston rod,

[0017] Figure 4 shows a fourth embodiment of a cylinder / piston unit with an eccentric piston rod, in which a pipe running parallel to the piston rod serves both as an oil line and for accommodating a position measuring system,

[0018] Figure 5 shows an embodiment corresponding to that shown in Figure 1 with an additional piston rod rotatably mounted in the piston,

[0019] Figure 6 shows an embodiment corresponding to that shown in Figure 2 with an additional piston rod rotatably mounted in the piston,

[0020] Figure 7 shows an embodiment corresponding to that shown in Figure 3 with an additional piston rod rotatably mounted in the piston and

[0021] Figure 8 shows an embodiment corresponding to that shown in Figure 4 with an additional piston rod rotatably mounted in the piston.

[0022] The cylinder / piston unit 1 shown in Figure 1 comprises a hydraulic cylinder 2 with a cylinder tube 3, which is closed on both sides by an end piece 4, 5. Inside the hydraulic cylinder 2 there is a longitudinally movable piston 6, which is mounted in a sealing and sliding manner against the inner cylinder wall by means of corresponding piston seals (not shown) of a conventional design. A piston rod 7 extends on both sides of the piston 6, so that the cylinder / piston unit 1 acts as a double-stroke cylinder. Accordingly, the two end pieces 4, 5 are designed as guide pieces and each have a through-bore 8, 9 for the piston rod 7, which through-bore is provided with a rod seal (not shown) of a conventional design. What is important here is that the piston rod 7 and the two through-bores 8, 9 for the piston rod 7 are guided in the guide pieces 4, 5 along a path which is parallel to the cylinder tube 3 and the piston rod 7.whose central axis is arranged on an eccentric axis 14.

[0023] By arranging the piston rod 7 offset within the existing circular cross-section of the cylinder tube 3, a second bore 10 can be accommodated in the piston 6 in the area of ​​eccentricity, which is closed off with a cylindrical element 11. In the first exemplary embodiment, a rod 11 is shown as the cylindrical element, which extends through the piston 6 along a second axis 15 that is eccentric with respect to the cylinder tube 3 and parallel to the first axis 14. The rod 11 is inserted into blind holes 12, 13 arranged along the second axis 15 on the inner sides of the guide pieces 4, 5 and is thus anchored in the cylinder tube 3 in a rotationally fixed manner with respect to any rotation of the piston 6. The rod 11 is sealingly mounted in the associated bore 10 in the piston 6 using a conventional rod seal (not shown), so that the piston 6 can be moved longitudinally along the rod 11.The rod 11 thus serves as an anti-twist device and torque support for the piston 6.

[0024] The two cylinder chambers separated from each other by the piston 6 can be supplied with hydraulic oil via lateral bores 17, 18 in the cylinder tube 3, which serve as hydraulic connections P1, P2 and can be provided for this purpose, for example, with a threaded connection (not shown), in order to move the piston 6 within the cylinder tube.

[0025] A further improvement in the force introduction via the piston rod 7 results from the fact that the piston rod 7 is mounted rigidly in the direction of displacement relative to the piston 6 via a pivot bearing 16, but freely rotatable in the direction of rotation. This is shown as an example in Figure 5. The rotatable mounting of the piston rod relative to the piston 6 improves the decoupling of a torque introduced from the outside via the piston rod 7 onto the components of the hydraulic cylinder 2, such as the cylinder tube 3, piston 6, guide bands and piston seal. In Figure 2, a tube 11' is inserted into the hydraulic cylinder 2 as a cylindrical element instead of a rod, which runs along the axis 15 through the bore 10 in the piston 6. The tube 11' also provides torque support, but can also serve as an oil line for hydraulic oil to the left-hand cylinder chamber closed by the guide piece 5.For this purpose, the bore 12' in the guide piece 4 is designed as a through-bore instead of a blind hole, the outward-facing opening 19 of which serves as the hydraulic connection P1 and can be provided for this purpose, for example, with a threaded connection (not shown). In the area just before the pipe 11' ends in the blind hole 13 of the guide piece 5, a transverse bore 20 is provided in the pipe 11', through which hydraulic oil can flow via the connection P1 and the pipe 11' from and to the cylinder chamber on the left in the drawing. The second hydraulic connection P2 of the hydraulic cylinder 2 is formed, as in Figure 1, by a lateral bore 18 in the cylinder wall.

[0026] A further development in which the piston rod 7 is rotatably mounted relative to the piston 6 via a pivot bearing 16 is shown as an example in Figure 5.

[0027] In the embodiment shown in Figure 3, the pipe 11' does not serve as an oil line, but accommodates a displacement measuring device 21. The displacement measuring device 21 is a magnetostrictive displacement sensor that determines the position of a permanent magnet 22 arranged around the bore 10 in the piston 6. Such magnetostrictive displacement sensors are known per se. A sensor rod 23 is designed as a soft magnetic waveguide. A short current pulse is passed through an inner wire in the sensor rod 23, generating a circular magnetic field that is focused in the waveguide due to the soft magnetic properties of the waveguide. At the position of the permanent magnet 22, which serves as a position sensor, a magnetic field acts whose field lines run at right angles to the pulsed magnetic field and are also focused in the waveguide.In the region of the waveguide where both magnetic fields overlap, elastic deformation occurs due to magnetostriction, generating a mechanical wave which in turn can be converted into an electrical signal by a signal converter. The distance to the position sensor can be determined from the propagation time of the response signal, i.e. the time between sending the current pulse and receiving the magnetostrictive echo. In addition to a magnetostrictive measuring system, other measuring methods can also be used within the scope of the invention. For example, an arrangement of Hall sensors can be used to detect a magnetic position sensor arranged on the piston. Acoustic or optical distance measuring methods can also be used, for example by a permanent magnet arranged on the piston dragging a position sensor within the tube 11', from which a signal can be reflected and measured as a response signal.

[0028] The eccentric arrangement of a position measuring system in the support tube 11', which is separate from the piston rod 7, means that the piston rod and thus also the cylinder tube can be designed with a smaller diameter for the same force requirements.

[0029] A further development of the third embodiment, in which the piston rod 7 is again rotatably mounted relative to the piston 6 via a pivot bearing 16, is shown as an example in Figure 7.

[0030] Finally, in the fourth embodiment shown in Figure 4, the pipe 11' serves both as an oil line to the remote cylinder chamber and to accommodate a position measuring system 21. The hydraulic connection P1 to the pipe 11' is formed by a radially extending bore 19' in the guide piece 4, with which the pipe 11' is drilled laterally, since the opening of the bore 12 is occupied by the position measuring system 21 and its signal converter.

[0031] A further development of the fourth embodiment, in which the piston rod 7 is again rotatably mounted relative to the piston 6 via a pivot bearing 16, is shown as an example in Figure 8.

Claims

Claims 1. Cylinder / piston assembly comprising a hydraulic cylinder (2) and a longitudinally displaceable piston (6) mounted sealingly within the hydraulic cylinder (2), which carries a piston rod (7) at least on one side, wherein the hydraulic cylinder (2) has a cylinder tube (3) with a circular cross-section, which is closed at both ends by an end piece (4, 5), and the piston rod (7) extends along a first axis (14) eccentric with respect to the cylinder tube (3), characterized by a cylindrical element (11 , 11 ') anchored at both end pieces (4, 5) and extending through the piston (6) along a second axis (15) eccentric with respect to the cylinder tube (3) and parallel to the first axis (14).

2. Cylinder / piston assembly according to claim 1, which is designed as a synchronous cylinder, in which the piston rod (7) extends on both sides of the piston (6) and the two end pieces (4, 5) are designed as guide pieces on which the piston rod (7) is sealed.

3. Cylinder / piston assembly according to one of the preceding claims, wherein the piston rod (7) is rotatably mounted on the piston via a rotary bearing (16).

4. Cylinder / piston assembly according to one of the preceding claims, wherein the cylindrical element (11 , 11 ') serves as a torque support for the piston (6) relative to the hydraulic cylinder (2).

5. Cylinder / piston assembly according to one of the preceding claims, wherein the cylindrical element (11 ') is tubular in shape.

6. Cylinder / piston assembly according to claim 5, wherein the cylindrical element (11') is designed as a pipe leading to a hydraulic connection (19, 19', P1) at one of the two end pieces (4) and within the The hydraulic cylinder (2) has an opening (20) for hydraulic fluid in the region of the opposite end piece (5). A cylinder / piston assembly according to claim 5 or 6, wherein a displacement measuring device (21) is arranged within the cylindrical element (11'). A cylinder / piston assembly according to claim 7, wherein the displacement measuring device (21) is designed as a magnetostrictive or Hall sensor-based displacement measuring system. A cylinder / piston assembly according to any one of the preceding claims, wherein at least one of the end pieces (4, 5) is connected to the cylinder tube (3) via a flange connection. A cylinder / piston assembly according to claim 9, wherein the other end piece (4, 5) is screwed onto or into the cylinder tube (2) via a threaded connection.

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