GB2278642A

GB2278642A - Piston and cylinder device

Info

Publication number: GB2278642A
Application number: GB9410592A
Authority: GB
Inventors: Norbert Fortmann; Helmut Goettling; Horst Janetzko; Hans F Meyer; Rudolf Moller
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1993-06-03
Filing date: 1994-05-26
Publication date: 1994-12-07
Anticipated expiration: 2014-05-26
Also published as: ITMI941058A0; FR2705999A1; GB9410592D0; DE4318932A1; GB2278642B; FR2705999B1; DE4318932C2; IT1269836B; ITMI941058A1

Description

1 2278642 PISTON AND CYLINDER DEVICE The present invention relates to

piston and cylinder assemblies, and is particularly concerned with a piston and cylinder device having an end position damper.

It is known for a piston and cylinder device to be designed with a reciprocating piston assembly which in at least one end position cooPerates with an end position damper. the damper or dampers each having a non-metallic stop disc absorbing the kinetic energy of the piston assembly, and a damping seal disposed slidingly in an internal space of the stop disc on a damping piston of the piston assembly. Such an arrangement is described, for example, in DE-Al 40 39 172.

Conventionally, a compression volume is connected to a venting opening of a cylinder cover on which a damping stop is disposed on the cylinder space side. In order to permit the attachment and fixing of the damping stop in the simplest and most convenient manner for assembly with a working cylinder with end position damping, provision is made for the cylinder cover to have a recess on its side facing the interior of the cylinder and extending in the longitudinal direction, the cross-sectional outline of which recess projects at least partially beyond the cross- sectional outline of the interior of the cylinder, for the damping stop to be in one piece and divided into two adjacent portions such that one portion has the cross-sectional outline of the recess and is disposed inside the recess, and the other portion has the cross-sectional outline of the interior of the cylinder, and projects into the interior of the cylinder.

Although this known end position damper has proved itself in practice and has technical manufacturing advantages, regulation of the damping effect is not possible without special means. In addition, the damping effect can be further improved.

2 The underlying object of the present invention is to improve the damping effect of such damping devices, and in particular to obtain compression damping in addition to the impact damping.

According to the present invention, there is provided a piston and cylinder device, in particular a piston and cylinder device without a piston rod, with a reciprocating piston assembly which in at least one end position co-operates with an end position damper having a non- metallic stop disc absorbing the kinematic energy of the piston assembly and a damping seal disposed slidingly in an internal space of the stop disc on a damping piston of the piston assembly, wherein a sealed liner is provided which is secured axially in the cylinder barrel and carries the elastic stop disc on a hub projection facing the piston assembly, and in that an internal space is formed in the liner from which the medium compressed by damping can be removed through venting channels.

The advantages obtained with the invention are in particular that the attachment of the stop disc produces improved impact damping and that the ability to regulate the damping effect is improved by making the venting channels an appropriate size.

The ability to regulate the impact damping is achieved through the elasticity of different elastic materials and the compression regulation is obtained according to further features of the invention in that the damping effect is adjustable by means of a throttle screw disposed in a venting channel of the liner.

A simple assembly for the impact damping is also obtained in that the damping seal is disposed between the hub projection of the liner and a shoulder of an internal space of the stop disc. Thus, the damping seal is held in its position during forward and backward movements of the piston assembly.

According to further features of the invention it is proposed that the cylinder barrel, the liner. the stop disc and the piston flange are formed with an oval or elliptical cross-sectional shape, and that the damping piston and the damping seal have a circular cross-section. In both oval or round configurations of the 3 cylinder barrel, the liner, the stop disc and the piston flange. the damping seal and the damping piston have a circular cross-section.

While the piston flange serves as an impact device in relation to the stop disc, it can be advantageous if a recess is provided adjoining the piston flange for a groove sealing ring which forms the seal for the piston assembly.

A further improvement of the invention is that the liner bears with a flange against the end face of the cylinder barrel and a guide pulley housing carrying a guide pulley also bears against this end face and is attached to a cylinder barrel housing.

In a further development, the provision of a damping piston on the piston assembly can advantageously be exploited if a hollow damping piston is formed on the piston assembly, adjoining the piston flange, and inside it preloading means are disposed for a traction band passed sealingly through the tip of the damping piston. In such an arrangement, the damping piston internally accommodates essential components for attachment of the traction band.

It is also advantageous for guidance and sealing of the traction band that a tip of the hollow damping piston faces, but does not touch, a tapered ring in the hub projection of the liner, and that the tapered ring serves as an axial retainer for a traction band seal which is disposed in the hub projection.

An embodiment of the invention will now be described in detail, with reference to the accompanying drawings, in which:

Figure 1 shows a partial longitudinal vertical section through a piston and cylinder device without a piston rod.

Figure 2 shows, to an enlarged scale, a horizontal crosssection through the left-hand end of the piston and cylinder device according to 1, with the piston in its end position.

Figure 3 shows a horizontal longitudinal section through the liner according to Figure 1 and in the position shown therein.

Figure 4 shows an outline of an oval piston of the piston assembly.

4 m Referring now to the drawings, a cylinder barrel housing I accommodates a cylinder barrel 2, and parallel to the axis of the cylinder barrel 2 a power take-off 3 which is connected to a piston assembly 7 by means of a traction means 4, in this example a traction band 4a. The traction band 4, 4a passes over guide pulleys 5 disposed in guide pulley housings 6 at the ends of the cylinder barrel housing 1. A movement of the piston assembly 7 causes a corresponding movement of the power take-off 3, but in the opposite direction. The power take-off 3 also moves an elastic cover 8. The piston assembly 7 may be circular in cross-section or may be elliptical or oval as shown in Figure 4. Moreover, although the embodiment illustrated is based on a piston and cylinder assembly without a piston rod, the invention can also be applied to piston and cylinder assemblies wherein the traction band is replaced by one or two piston rods.

In Figure 1, an end position damper 9 is provided consisting of a liner 10 fixed axially in the cylinder barrel 2, with an elastic, non-metallic stop disc 11, made for example of plastics or other suitable resilient material, facing the piston assembly 7. At each end of the piston assembly 7, an axially projecting damping piston 14 extends from the piston assembly 7. A damping seal 15, which slides and seals on a cylindrical skirt surface 17 of the damping piston 14 in front of a piston flange 16, is disposed in an internal space 12 inside the stop disc 11.

In operation, as the piston approaches the end of its travel, the leading end of damping piston 14 engages and seals with the damping seal 15. Continued movement of thE piston 7 causes damping piston 14 to enter the internal cavity 10b of the liner 10, and to displace the fluid therefrom.

The fluid displaced by the piston assembly 7 flows along a passage 18 (visible in Figure 4) which runs equidistant to an ellipse 19, and away through a venting channel 20 of the liner 10 and through a throttle screw 21 into the open. Here, the damping effect can be regulated by adjusting the throttle screw 21.

W The damping seal 15 is disposed between the axial end of a hub projection 22 of the liner 10, and an undercut shoulder 23 at the axial end of the internal space 12 of the stop disc 11, so that the axial position of the damping seal 15 is maintained.

Depending on the chosen shape of piston (round or oval or elliptical), the cylinder barrel 2, the liner 10, the stop disc 11 and the piston flange 16 are formed with a round or oval or elliptical cross-sectional shape, but the damping piston 14 and the damping seal 15 always have a circular cross-sectional shape for ease of manufacture. This also eliminates problems of misalignment between the damping piston 14 and the damping seal 15 caused by rotation of the damping piston 14 relative to the damping seal 15.

The piston 7 has a flange 16 with a recess 24 for a sealing ring 25.

The liner 10 bears with a flange 10a against an end face 26 of the cylinder barrel 2, and the guide pulley housing 6 carrying the guide pulley 5 also bears against this end face 26 and is attached to the cylinder barrel housing 1.

A hollow damping piston 14 is formed on the piston assembly 7, adjoining the piston flange 16, and inside it pre-loading means 27 are disposed for the traction band 4a passed sealingly through a tip 14a of the damping piston 14.

In the damping position shown in Figure 2 the tip 14a of the hollow damping piston 14 faces, but does not touch, a tapered ring 28 in a hub 10c of the liner 10. and the tapered ring 28 serves as an axial retainer for a traction band seal 29 which runs through the hub 10c.

Figure 3 is an illustration similar to Figure 1 but in a plane perpendicular thereto, of the liner 10 showing the traction band seal 29 in its second dimension and a greatly enlarged stop disc 11 of thinner cross-section and a damping seal 15 matched to the enlarged internal space 12.

6 W In front of the traction band seal 29, facing the piston assembly 7, there is the tapered ring 28 which retains the traction band seal 29 axially so that this is in a precise position and can provide the full sealing effect in relation to the traction band 4a.

i 7 W

Claims

1. A piston and cylinder device wherein a reciprocating piston assembly moves axially in a cylinder barrel between two end positins, and co-operates in at least one end position with an end position damper, the end position damper having a non-metallic stop disc capable of absorbing the kinematic energy of the piston assembly and including a sealed liner secured axially in the cylinder barrel and carrying the elastic stop disc on a hub projection facing the piston assembly, an internal cavity being formed in the liner in fluid communication with the cylinder barrel via an opening in the stop disc and venting channels being provided to allow egress of fluid from the internal cavity through throttling means, and the end position damper further having a damping seal disposed in an internal space of the stop disc and adapted to close the opening in the stop disc to fluid by forming a sliding seal on a damping piston extending axially of the piston assembly..

2. A device according to claim 1, wherein the damping effect is adjustable by means of a throttle screw disposed in a venting channel of the liner.

3. A device according to claim 1 or claim 2, wherein the damping seal is disposed between the hub projection of the liner and a shoulder of an internal space of the stop disc.

4. A device according to any preceding claim. wherein the cylinder barrel, the liner, the stop disc and the piston flange are oval or elliptical in cross-sectional shape, and the damping piston and the damping seal have a circular cross-section.

5. A device according to any preceding claim, wherein a recess is provided adjoining the piston flange for a groove sealing ring.

6. A device according to any preceding claim, wherein the liner bears with a flange against the end face of the cylinder barrel and a guide pulley housing carrying a guide pulley also bears against this end face and is attached to a cylinder barrel housing.

8 W

7. A device according to any preceding claim, wherein a hollow damping piston is formed on the piston assembly. adjoining the piston flange, and inside it pre-loading means are disposed for a traction band passed sealingly through the tip of the damping piston.

8. A device according to any preceding claim, wherein in the damping position the tip of the hollow damping piston faces a tapered ring in the hub projection of the liner and in that the tapered ring serves as an axial retainer for a traction band seal which is disposed in the hub projection.

9. A piston and cylinder device, substantially as described herein with reference to Figures 1, 2, 3, or 4 of the accompanying drawings.

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