GB1588113A

GB1588113A - Shock absorber for motor vehicles

Info

Publication number: GB1588113A
Application number: GB934378A
Authority: GB
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1977-03-22
Filing date: 1978-03-09
Publication date: 1981-04-15
Also published as: DE7708863U1; FR2384998A1; FR2384998B1

Description

(54) SHOCK ABSORBER FOR MOTOR VEHICLES (71) We, FICHTEL 6t SACHS AG, a German Body Corporate, of 62 Ernst-Sachs Strasse, Schweinfurt am Main, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to a shock absorber for motor vehicles having a seal for the piston rod thereof which seal is located at the piston rod exit-sided end of the shock absorber, in a hollow space which is partly defined by a piston rod guide, and seals the inner space outwardly, where the seal in axial direction is constructed so as to be shorter than the hollow space and is pressed with the outwardly pointing front surface against a counter-surface.

Seals of this type are usually held by their outer diameter in a shock-absorber-fixed component and cannot expand radially, so that with any errors in centring the seal is loaded on one side. Similarly, it is known for piston rod seals to be located in a groove, in which case the former rest with their front surfaces against the groove on both sides and thus have great resistance to radial movability.

According to the present invention we provide a shock absorber for motor vehicles, comprising a shock absorber cylinder, a piston which is displaceable in the shock absorber cylinder and whose piston rod is axially displaceably guided in a guide at one end of the shock absorber cylinder, a cover which closes the shock absorber cylinder for the formation of a hollow space at an axial distance from the guide on the side that is directed away from the piston, a first sealing ring which is held on the cover and which seals the piston rod from the cover and a second sealing ring which is clamped between the guide and the cover in an axially resilient manner and embraces the piston rod, and a supporting ring arranged in a radially movable manner in the hollow space between the cover and the guide, wherein the second sealing ring bears against the inner circumference of the supporting ring in the radial direction and is arranged between two ring-shaped supporting discs in the axial direction, a compression spring being clamped between the guide and the adjacent supporting disc, the surfaces of the cover and the guide which are axially directed towards one another forming stop faces for the supporting ring or the guide having a stop face for the cover forming the hollow space for said supporting ring.

If merely the centring of the seal is desired during assembly of the shock absorber, the annular component can be a thrust collar, where the shock absorber closing disc is constructed as the one stop surface and the piston rod guide as the other stop surface for the front faces of the thrust collar, whilst the outside diameter of the thrust collar is smaller than the inside diameter of the shock absorber pipe. During assembly, this thrust collar consequently transmits the force which is introduced in axial direction, from the shock absorber closing disc to the piston rod guide and therefore also to the shock absorber cylinder.

In order to ensure a satisfactory centring of the sealing unit, the thrust collar possesses in the area of its outwardly pointing front face an inner groove into which an intermediate ring engages, whereby the diameter of the inner groove is larger than the outside diameter of the intermediate ring and this intermediate ring forms the stop surface for the seal. This construction of the thrust collar and intermediate ring permits movement of the intermediate ring towards the thrust collar in radial direction and therefore satisfactory centring, without narrow tolerances for these components being necessary.

In order to make easy sliding of the seal on the intermediate ring possible, a layer of material which is advantageous to sliding is located between the intermediate ring and the seal.

A further advantageous embodiment, in which the thrust collar is constructed as one piece with the piston rod guide, is obtained by the fact that the annular component is a supporting ring which merely rests against a component with the outwardly pointing front face, whilst the seal comes into abutment against the inner surface and there is an annular space in radial direction between the outside diameter and the piston rod guide.

Such a specific embodiment permits not only a satisfactory centring of the sealing element during assembly of the shock absorber, but also a re-centring during great radial motion play of the piston rod. The supporting ring also prevents flowing of material in radial direction in the case of seals which are axially prestressed, because the seal rests against the cylindrical inner surface of this supporting ring, whereby the annular space permits a radial movability of the supporting ring and therefore also of the seal.

In a further embodiment the supporting ring is provided over its outer surface with flexible tongues which come into abutment against a stop surface on the piston rod guide and fix the supporting ring in axial direction, whilst the supporting disc is led with its outside diameter against the cylindrical inner surface of the supporting ring. Simple assembly is thereby achieved, besides the possibility of very good centring.

Further details of the invention can be seen from the specification and the drawings: Fig. 1 shows a shock absorber in longitudinal section, where a thrust collar is located between the shock absorber closing disc and the piston rod guide; Fig. 2 shows the seal and guide arrangement as in Fig. 1 in enlarged representation; Fig. 3 shows a specific embodiment of the guide and seal unit, where the seal is provided with a supporting ring; Fig. 4 shows a piston rod seal which is constructed as a disc seal, and Fig. 5 shows a specific embodiment in which the supporting ring carries flexible tongues.

The shock absorber represented in Fig. 1 is constructed as a double cylinder shock absorber, i.e. the cylinder 2 is located concentrically in the shock absorber cylinder 1, where these two cylinders together form an annular space which is in communication with the inner space of the cylinder 2 via valves at the bottom of the cylinder 2. The piston 4, which carries damping valves, slides on the inner wall of the cylinder 2 and is sealed against the latter, is fixedly connected to the piston rod 3. The piston rod guide 5, which also forms the abutment surface for the compression spring 6, is provided to guide the piston rod 3 and to centre the cylinder 2. Between the piston rod guide 5 and the shock absorber closing disc 11 there is a thrust collar 12, which is provided with an inner groove 13 to accept the intermediate ring 9. In radial direction the seal 8 is placed against the cylindrical inner surface of the thrust collar 12, and in axial direction against the intermediate ring 9. Via the supporting disc 7, the compression spring 6 acts in axial direction on the seal 8. Between the outside diameter of the thrust collar 12 and the inside diameter of the shock absorber cylinder 1 there is the hollow space 14, which extends inwardly to the seal space via penetration passages in the piston rod guide 5. The pre-seal 10, which rests in axial direction against the intermediate ring 9, is retained in a groove of the shock absorber closing disc.

As the mode of operation of such double cylinder shock absorbers is sufficiently known, only the operation of the guide and seal unit is examined in the description hereafter. As is shown in Figures 1 and 2, the thrust collar 12 is jammed between the piston rod guide 5 and the shock absorber closing disc 11. During assembly, the piston rod guide 5 is firstly inserted from above and then the compression spring 6, which ensures the axial prestress of the seal 8, is inserted.

The supporting disc 7 and the seal 8 are then pushed along, as far as permitted by the released spring. Then the thrust collar 12 is led via the seal 8 and the supporting disc 7, which collar can be moved in radial direction and so placed against the front surface of the piston rod guide 5, that a uniform pressure distribution over the periphery of the piston rod 3 exists on the sealing edge of the seal 8.

Now is inserted the intermediate ring 9, which engages in the inner groove 13 of the thrust collar 12, and forms in axial direction the stop surface for the seal 8, on the one hand, and for the pre-seal 10, on the other.

After pushing-in of the pre-seal 10, the shock absorber closing disc 11 is also introduced, which is pressed with a tool in axial direction against the force of the compression spring 6 and clamps the thrust collar 12 in the position between the front surfaces of the piston rod guide 5 and the shock absorber closing disc 11 which it has adopted during assembly. This axial force on the shock absorber closing disc 11 is maintained until the shock absorber is closed, which can occur by welding or flanging. Since during assembly, the seal 8 and the thrust collar 12 can move radially in the hollow space 14, a good centring of the seal 8 during assembly is achieved.

In the specific embodiment of Fig. 3, the piston rod guide 5 has an upwardly aligned shoulder and rests with its front surface against the shock absorber closing disc 11.

The hollow space is consequently formed by the inside diameter of the cylindrical part of the piston rod guide 5, and accepts the compression spring 6, the supporting disc 7 and the seal together with the supporting ring 17. This supporting ring 17 with its cylindrical inner surface serves an an abutment for the seal 8 and prevents an increase in diameter as a result of the flow of material in radial direction. Between the supporting ring 17 and the inside diameter of the piston rod guide 5 there is the annular space 18, which permits a radial adjustment of the seal 8 together with the supporting ring 17. In order to facilitate re-centring during operation, in this specific embodiment, a layer 15 of material which is advantageous to sliding is located between the seal 8 and the intermediate ring 9. In the hollow space 14 also located the compression spring 6 and the supporting disc 7, whereby these parts exert on the seal 8 a pressing force running in axial direction.

The specific embodiment as in Fig. 4 differs from that of Fig. 3 essentially by the fact that a sealing washer 16 is used as a seal.

Between this sealing washer 16 and the intermediate ring 9 is provided the layer 15 of material advantageous to sliding. The axially acting force is exerted on the sealing washer 16 via the compression spring 6 and the supporting disc 7. The location of a supporting ring 17 on the outside diameter of the sealing washer 16 is also advantageous in such a specific embodiment.

In the case of the specific embodiment of Fig. 5, the supporting ring 17 is constructed slightly longer in axial direction, and the supporting disc 7 engages With its outside diameter in the cylindrical part of this supporting ring 17. This supporting ring 17 is provided over its outer surface with flexible tongues 19, which one again come into abutment against the stop surface 20 of the piston rod guide 5. These flexible tongues 19 consequently give the supporting ring 17 an axial force, whereby the collar of the supporting ring 17 rests against the intermediate ring 19. The compression spring 6 acts via the supporting disc 7 on the seal 8 and thereby presses the latter by its front face against the intermediate ring 9. With this specific embodiment, a very good self-centring of the seal unit for the piston rod 3 is achieved during assembly of the shock absorber.

WHAT WE CLAIM IS: 1. A shock absorber for motor vehicles, comprising a shock absorber cylinder, a piston which is displaceable in the shock absorber cylinder and whose piston rod is axially displaceably guided in a guide at one end of the shock absorber cylinder, a cover which closes the shock absorber cylinder for the formation of a hollow space at an axial distance from the guide on the side that is directed away from the piston, a first sealing ring which is held on the cover and which seals the piston rod from the cover and a second sealing ring which is clamped between the guide and the cover in an axially resilient manner and embraces the piston rod, and a supporting ring arranged in a radially movable manner in the hollow space between the cover and the guide, wherein the second sealing ring bears against the inner circumference of the supporting ring in the radial direction and is arranged between two ring-shaped supporting discs in the axial direction, a compression spring being clamped between the guide and the adjacent supporting disc, the surfaces of the cover and the guide which are axially directed towards on another forming stop faces for the supporting ring or the guide having a stop face for the cover forming the hollow space for said supporting ring.

2. A shock absorber as claimed in claim 1, wherein on the face of the supporting ring or the guide that is axially directed towards the cover, there is provided an inner groove, in which the supporting disc adjacent to the cover engages with radial play.

3. A shock absorber as claimed in claim 1 or 2, wherein a sliding layer is provided between the second sealing ring and the supporting disc at the cover end.

4. A shock absorber as claimed in claim 1, wherein on the outer surface of the supporting ring there are provided flexible tongues which bear against a contact surface of the guide and axially fix the supporting ring.

5. A seal substantially as described with reference to and as illustrated by any one of the embodiments shown in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. radial direction. Between the supporting ring 17 and the inside diameter of the piston rod guide 5 there is the annular space 18, which permits a radial adjustment of the seal 8 together with the supporting ring 17. In order to facilitate re-centring during operation, in this specific embodiment, a layer 15 of material which is advantageous to sliding is located between the seal 8 and the intermediate ring 9. In the hollow space 14 also located the compression spring 6 and the supporting disc 7, whereby these parts exert on the seal 8 a pressing force running in axial direction. The specific embodiment as in Fig. 4 differs from that of Fig. 3 essentially by the fact that a sealing washer 16 is used as a seal. Between this sealing washer 16 and the intermediate ring 9 is provided the layer 15 of material advantageous to sliding. The axially acting force is exerted on the sealing washer 16 via the compression spring 6 and the supporting disc 7. The location of a supporting ring 17 on the outside diameter of the sealing washer 16 is also advantageous in such a specific embodiment. In the case of the specific embodiment of Fig. 5, the supporting ring 17 is constructed slightly longer in axial direction, and the supporting disc 7 engages With its outside diameter in the cylindrical part of this supporting ring 17. This supporting ring 17 is provided over its outer surface with flexible tongues 19, which one again come into abutment against the stop surface 20 of the piston rod guide 5. These flexible tongues 19 consequently give the supporting ring 17 an axial force, whereby the collar of the supporting ring 17 rests against the intermediate ring 19. The compression spring 6 acts via the supporting disc 7 on the seal 8 and thereby presses the latter by its front face against the intermediate ring 9. With this specific embodiment, a very good self-centring of the seal unit for the piston rod 3 is achieved during assembly of the shock absorber. WHAT WE CLAIM IS:

1. A shock absorber for motor vehicles, comprising a shock absorber cylinder, a piston which is displaceable in the shock absorber cylinder and whose piston rod is axially displaceably guided in a guide at one end of the shock absorber cylinder, a cover which closes the shock absorber cylinder for the formation of a hollow space at an axial distance from the guide on the side that is directed away from the piston, a first sealing ring which is held on the cover and which seals the piston rod from the cover and a second sealing ring which is clamped between the guide and the cover in an axially resilient manner and embraces the piston rod, and a supporting ring arranged in a radially movable manner in the hollow space between the cover and the guide, wherein the second sealing ring bears against the inner circumference of the supporting ring in the radial direction and is arranged between two ring-shaped supporting discs in the axial direction, a compression spring being clamped between the guide and the adjacent supporting disc, the surfaces of the cover and the guide which are axially directed towards on another forming stop faces for the supporting ring or the guide having a stop face for the cover forming the hollow space for said supporting ring.