GB2178508A

GB2178508A - Apparatus with a piston able to move in a cylinder casing

Info

Publication number: GB2178508A
Application number: GB08615600A
Authority: GB
Inventors: Hermann Bansbach
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-07-19
Filing date: 1986-06-26
Publication date: 1987-02-11
Also published as: DE8520850U1; IT8667481A1; FR2585099A1; IT8667481A0; IT1190588B; GB2178508B; GB8615600D0

Abstract

An apparatus has a piston (5) able to move in a cylinder casing (2), the piston comprising a sealing part (6), a spacer part (7) and a guide part (8). Valve (11) is operated to allow or prevent fluid flow between chambers (26,25), the flow path including bores in the spacer part (7) and a throttle passage provided on the periphery of the guide part (8). The passage can be helical and serves to guide, centre, and lubricate the piston. <IMAGE>

Description

SPECIFICATION Apparatus with a piston able to move in a cylinder casing The invention relates to an apparatus according to the preamble of Claim 1.

In a known apparatus of the aforementioned type constructed as a gas suspension, provided in the axial projection of the piston is a sealing device for sealing the clearance between the valve body and the tappet supporting the latter on one side and the piston on the other side and a stop device, which limits the displacement of the actuating rod within the piston rod (East German Patent Specification 207 410).

In a known linkage with springing, one linkage part projects into the sleeve-shaped end of the second linkage part by a journal, on which two loosely fitted rings are pressed by an interposed helical spring against abutments of the linkage parts so that shocks occurring in both directions are absorbed by the spring.

The spring chamber is filled with a lubricant and for this specially shaped channels impeding the movement of the lubricant withdrawing behind these rings and re-appearing at the time of shocks are located towards both linkage parts in the spring-support rings (German PS 849 044).

It is the object of the present invention to provide better guidance and centering of the piston whilst avoiding solid friction. This object is achieved according to the invention by the features in the characterising part of Claim 1. The additional guide part at a distance from the sealing part of the piston provides its satisfactory guidance within the cylinder casing of the apparatus, in that tilting of the piston is counteracted. The sealing part may be constructed to be relatively short in the axial direction.Better centering of the piston is achieved due to the turbulent flow of the pressure medium from one end face of the guide part of the piston to its other end face during the movement of the piston inside the cylinder casing, due to which lubrication is also substantially improved and solid friction between the walls of the cylinder casing and of the guide part is largely avoided.

The remaining claims relate to preferred developments of the invention.

A gas suspension which can be locked is shown diagrammatically as an embodiment of the object of the invention in the drawings.

Figure 1 is a longitudinal section Figure 2 shows a part illustrated in Fig. 1, on a larger scale.

A gas suspension 1 has a cylinder casing 2, which is closed off at each of its ends by means of a sealing member 3, 4. Guided in the cylinder casing 2 is a hollow piston 5 (Fig.

2), which comprises a sealing part 6, a spac ing part 7 and a guide part 8. A hollow piston rod 9 is screwed into the hollow piston 5, passing through which piston rod 9 is an actuating rod 10. At its end adjacent the sealing member 4, the actuating rod 10 comprises a sealing cone 11. A separating piston 12 is located between the piston 5 and the sealing member 4. The gaps between the cylinder casing 2 on one side and the sealing members 3, 4 and the separating piston 12 on the other side are each sealed by means of annular seals. An annular seal also seals the gap between the piston rod 9 and the sealing member 3. The sealing part 6 of the piston 5 supports a gasket 13, which seals the gap between the piston 5 and the cylinder casing 2. The gap between the piston rod 9 and the piston 5 is also sealed by a gasket 14.

Ori its sealing part 6, the piston 5 illustrated in Fig. 2 has an annular groove 15 for receiving the gasket 13. Located in the spacing part 7 is an annular groove 16 with a substantially semi-circular cross section. Three radial bores pass through the base of the annular groove 16, of which the radial bore 17 is illustrated.

The annular groove 16 serves for receiving a gasket, due to which a valve able to be opened from the inside outwards is formed.

Located between the annular grooves 15 and 16 is a bore in the form of an outwardly enlarging restrictor 18 for the passage of pressure medium in both directions.

The guide part 8 is guided with little clearance in the cylinder casing 2. On its outer side a helical connecting groove 19 with approximately 1.5 turns is provided, which connects the two end faces of the guide part 8 to each other in a restricting manner. The cross section of the connecting groove 19 is trapezoidal and widens out radially towards the outside. It has a width of approximately 0.08 to 0.12-times, in particular 0.1 times the diameter of the guide part 8 of the piston 5 and a depth of approximately 0.015 to 0.025 times, in particular 0.02-times the diameter of the guide part 8 of the piston 5. The connecting groove 19 may comprise approximately 1 to 10, in particular 5 turns. It may be constructed not only with a single-thread, but also with a multi-thread.The clearance between the cylinder casing 2 and the guide part 8 amounts to approximately 0.001 to 0.006times, in particular 0.002-times the diameter of the guide part 8.

An annular groove 20 inside the guide part 8 serves for receiving the gasket 14 and a screw-thread 21 serves for screwing-in the piston rod 9, which rests on a shoulder 22 projecting inwards. Located at the end of the piston 5 remote from the annular groove 20 is a valve seat 23, which cooperates with the sealing cone 11 on the actuating rod 10.

Clamped between the actuating rod 10 and the piston rod 9 is a spring arrangement (not shown) so that it attempts to hold the sealing cone 11 on the valve seat 23. The radial bore 17 and the restrictor 18, which are located between the valve seat 23 and the shoulder 22, open into a chamber 24. The gap between the actuating rod 10 and the hollow piston 5 is sealed by a gasket (not shown), which is preferably located on the side of the shoulder 22 remote from the screw-thread 21 and is held by an additional shoulder (likewise not shown).

The piston 5 separates two fluid chambers 25 and 26 from each other. A gas chamber 27 is located between the separating piston 12 and the sealing member 4. The gas which is under pressure in the gas chamber 27 attempts to push the piston 5 outwards, which is prevented by the sealing cone 11 located in its closed position. If the latter is raised from the valve seat 23, then fluid may flow from the chamber 25 into the chamber 26 or viceversa, depending on the piston 5 being moved. When the piston 5 moves downwards, fluid flows into the chamber 24 and passes by way of the radial bores 17 and the annular groove 16 as well as via the restrictor 18 into the space between the spacing part 7 and the cylinder casing 2 and from here by way of the helical connecting groove 19 into the chamber 25.On flowing through the connecting groove 19, a turbulent flow is created, which leads to the formation of a film of liquid between the guide part 8 of the piston 5 and the inner wall of the cylinder casing 2. Solid friction of the guide part 8 on the inner wall of the cylinder casing 2 is thus reliably prevented. The guide part 8 allows exact guidance of the sealing part 6 of the piston 5 in the cylinder casing 2, so that in this case a relatively small clearance can be used with good sealing efficiency.

If more than one helical connecting groove (19) is provided, two connecting grooves may also be arranged cross wise (with a left-hand and right-hand thread). If two connecting grooves meet in a cross-wise manner, then at the intersection point, due to the accumulation, turbulence occurs in the medium flowing through the grooves, which acts in the radial direction on the piston. If at least three intersection points of connecting grooves are distributed uniformly on the periphery of the guide part, the piston is centered due to this.

If the connecting groove 19 has such an angle of inclination that it does not extend over the entire periphery of the guide part 8 or axis-parallel (angle of inclination of 90 ), then for centering reasons, more than one connecting groove, preferably more than two connecting grooves must be arranged on the periphery of the guide part 8 with the same angles at the center.

Instead of a connecting groove 19, a flattened area may also be provided on the guide part 8. The flattened area and the connecting groove respectively form a restrictor between the opposing end faces of the guide part 8.

In order to achieve additional centering of its guide part 8 at the time of movement of the hollow piston 5, a chamfer extending towards the end face of the guide part 8 and its center may additionally be provided on each of its end faces, which serves for the formation of a lubricating wedge. The chamfer on one end face terminates at a.sufficient distance from the other end facX or a chamfer located on the same side of the guide part 8, so that no connection exists between the two end faces of the guide part 8 by way of the chamfer or by way of two chamfers arranged one behind the other. One chamfer is preferably located on both sides of the region of the connecting point located on the end face of the guide part 8.

Whereas in the embodiment described, the piston separates two fluid chambers 25 and 26, a construction of the apparatus according to the invention is also possible such that the piston serves to separate two gas chambers.

Instead of being used in a gas suspension, the apparatus according to the invention may also be provided in a shock absorber or the like.

Claims

1. Apparatus with a piston able to move in a cylinder casing, which piston comprises a connection between its two sides and in the region of its piston rod, a projection projecting axially beyond its sealing part, provided in which projection is a bore connecting its inner side and outer side, characterised in that the projection comprises a guide part cooperating with the cylinder casing, between which guide part and the sealing part a spacer part comprising the bore is provided and that provided on the outer periphery of the guide part is at least one restricting connecting point connecting its two end faces to each other, in the region of which connecting point the guide part deviates from its circular cross section in the direction of the centre.

2. Apparatus according to claim 1, characterised in that the connecting point extends in the manner of a helix.

3. Apparatus according to claim 2, characterised in that at least two helical connecting points are arranged cross wise.

4. Apparatus according to any one of the preceding claims, characterised in that with an angle of inclination of the connecting point connecting the two end faces of the guide part to each other so that the connecting point extends solely over part of the periphery of the guide part, at least two connecting points arranged with uniform distribution on its periphery are provided.

5. Apparatus according to any one of the preceding claims, characterised in that its two end faces adjacent the connecting point, the guide part respectively comprises a chamfer producing a lubricating wedge during the movement of the piston.

6. Apparatus according to any one of the preceding claims, characterised in that the connecting point is constructed as a connecting groove.

7. Apparatus according to one of claims 1 to 3, 5 and 6, characterised in that the connecting point arranged in the manner of a helix has approximately 1 to 10, in particular 5 turns.

8. Apparatus according to any one of the preceding claims, characterised in that the connecting point arranged in the form of a helix is constructed to have multiple threads.

9. Apparatus according to any one of the preceding claims, characterised in that the connecting point constructed as a connecting groove has a width of approximately 0.08 to 0.12-times, in particular 0.1-times the diameter of the guide part and a depth of approximately 0.015 to 0.025-times, in particular 0.02-times the diameter of the guide part.

10. Apparatus according to any one of the preceding claims, characterised in that the clearance between the cylinder casing and the guide part amounts to approximately 0.001 to 0.006 times, in particular 0.002-times the diameter of the guide part.

11. Apparatus substantially as hereinbefore described with reference to the accompanying drawings.