GB2024365A - Piston packing - Google Patents

Abstract

Packing 13 in a groove 14 of a piston 12 comprises a first sealing ring 15 of a plastics material in contact with the surface 10' to be sealed, an O-ring 16 which presses the sealing ring 15 against the sealing surface with pretension, and a second sealing ring 17 embedded in the first sealing ring 15 and likewise in contact with the surface 10' to be sealed. <IMAGE>

Description

SPECIFICATION A sealing arrangement for pressure mediuminfluenced parts movable relatively to each other The invention originates from a sealing arrangement according to the type set forth in the main claim. Such a sealing arrangement has the disadvantage that the pre-tension force exerted by the O-ring acts on the sealing ring in such a manner that, during pressure influencing, its two external sealing edges can be lifted to some extent due to the considerable distance of the effective direction of the force from the surface to be sealed, whereupon leakage results.

ADVANTAGES OF THE INVENTION As opposed to this, the sealing arrangement in.

accordance with the invention comprising the characterising features of the main claim has the advantage that, due to the embedding of the second sealing ring in the first sealing ring, there are a plurality of sealing edges, wherein the inside sealing edges lie relatively close to the effective line of the force.

Advantageous further developments and improvements of the features set forth in the main claim are made possible by the measures set forth in the sub-claims.

DRAWING An embodiment of the invention is illustrated in the drawing by way of example and is described in more detail in the following specification. The drawing shows a partial longitudinal section through a working cylinder.

DESCRIPTION OF THE INVENTION The working cylinder consists of a cylindrical tube 10 in which a piston 11 is sealingly slidingly guided and which is fixed to a piston rod 12.

Sealing with respect to the cylinder wall 10' is produced by a sealing arrangement 1 3 which consists of a plurality of sealing rings two of which are arranged in annular groove 14 provided in the outer surface of the piston.

The true sealing ring 1 5 has a rectangular cross-section and preferably consists of a plastics material. Radially inwards of the sealing ring 15 is a pretensioned O-ring 1 6 which exerts a pretension force F on the sealing ring 1 5. If no special measures were employed, then the sealing edges a and b would be lifted to some extent away from the cylindrical tube 10 during pressure influencing due to the considerable distance of the effective line F of the pre-tension force, whereupon leakage would take place.

However, in accordance with the invention, a sealing ring 17, which likewise has a rectangular cross-section, is embedded in the sealing ring 1 5.

It contacts the cylindrical tube and is moreover embedded symmetrically in the sealing ring 1 5 on ali sides. In so doing, there are two further sealing edges c, d. These lie substantially nearer to the effective line of the force F whereby they are urged against the cylinder wall in a better manner. Thus, there are altogether four sealing edges provided a to d. The sealing effect is substantially improved thereby.

The sealing ring 17 can consist of the same material as the sealing ring 15, that is to say of a plastics material -- preferably a polytetrafluorethylene compound material - or even consist of a soft material whereby the sealing effect is further improved. The sealing ring 1 5 must have a sufficiently high rigidity in order to bridge the gap s between the outer diameter of the piston and the inner wall of the cylinder, that is to say to protect the sealing ring 1 7 against immigration into the gap.

Preferably the O-ring consist of a rubber elastic material.

1. A sealing arrangement for pressure mediuminfluenced parts longitudinally movable relatively to one another, for example working cylinders, which consists of a plastics sealing ring in contact with the part to be sealed and an O-ring which is arranged radially of the plastics sealing ring and which urges the latter against the part to be sealed with pre-tension, characterised in that, at least one second sealing ring, which is likewise in contact with the part to be sealed, is arranged in the plastics sealing ring.

2. A sealing arrangement according to claim 1 characterised in that the second sealing ring is made substantially rectangular in cross-section and is embedded in the centre of the plastics sealing ring.

3. A sealing arrangement according to claim 1 and/or 2 characterised in that the plastics sealing ring also has a rectangular cross-section.

4. A sealing arrangement according to one of claims 1 to 3 characterised in that the plastics sealing ring consists of a polytetra fluorethylene compound material.

5. A sealing arrangement according to one of claims 1 to 4 characterised in that the second sealing ring embedded in the plastics sealing ring consists of polytetrafluorethylene or a polytetra fluorethylene compound material.

6. A sealing arrangement according to one of claims 1 to 4 in which the second sealing ring embedded in the plastics sealing ring consists of a rubber elastic material.

7. A sealing arrangement for relatively longitudinally movable pressure medium influenced parts, substantially as herein described with reference to the accompanying drawing.

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

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A sealing arrangement for pressure mediuminfluenced parts movable relatively to each other The invention originates from a sealing arrangement according to the type set forth in the main claim. Such a sealing arrangement has the disadvantage that the pre-tension force exerted by the O-ring acts on the sealing ring in such a manner that, during pressure influencing, its two external sealing edges can be lifted to some extent due to the considerable distance of the effective direction of the force from the surface to be sealed, whereupon leakage results. ADVANTAGES OF THE INVENTION As opposed to this, the sealing arrangement in. accordance with the invention comprising the characterising features of the main claim has the advantage that, due to the embedding of the second sealing ring in the first sealing ring, there are a plurality of sealing edges, wherein the inside sealing edges lie relatively close to the effective line of the force. Advantageous further developments and improvements of the features set forth in the main claim are made possible by the measures set forth in the sub-claims. DRAWING An embodiment of the invention is illustrated in the drawing by way of example and is described in more detail in the following specification. The drawing shows a partial longitudinal section through a working cylinder. DESCRIPTION OF THE INVENTION The working cylinder consists of a cylindrical tube 10 in which a piston 11 is sealingly slidingly guided and which is fixed to a piston rod 12. Sealing with respect to the cylinder wall 10' is produced by a sealing arrangement 1 3 which consists of a plurality of sealing rings two of which are arranged in annular groove 14 provided in the outer surface of the piston. The true sealing ring 1 5 has a rectangular cross-section and preferably consists of a plastics material. Radially inwards of the sealing ring 15 is a pretensioned O-ring 1 6 which exerts a pretension force F on the sealing ring 1 5. If no special measures were employed, then the sealing edges a and b would be lifted to some extent away from the cylindrical tube 10 during pressure influencing due to the considerable distance of the effective line F of the pre-tension force, whereupon leakage would take place. However, in accordance with the invention, a sealing ring 17, which likewise has a rectangular cross-section, is embedded in the sealing ring 1 5. It contacts the cylindrical tube and is moreover embedded symmetrically in the sealing ring 1 5 on ali sides. In so doing, there are two further sealing edges c, d. These lie substantially nearer to the effective line of the force F whereby they are urged against the cylinder wall in a better manner. Thus, there are altogether four sealing edges provided a to d. The sealing effect is substantially improved thereby. The sealing ring 17 can consist of the same material as the sealing ring 15, that is to say of a plastics material -- preferably a polytetrafluorethylene compound material - or even consist of a soft material whereby the sealing effect is further improved. The sealing ring 1 5 must have a sufficiently high rigidity in order to bridge the gap s between the outer diameter of the piston and the inner wall of the cylinder, that is to say to protect the sealing ring 1 7 against immigration into the gap. Preferably the O-ring consist of a rubber elastic material. CLAIMS

1. A sealing arrangement for pressure mediuminfluenced parts longitudinally movable relatively to one another, for example working cylinders, which consists of a plastics sealing ring in contact with the part to be sealed and an O-ring which is arranged radially of the plastics sealing ring and which urges the latter against the part to be sealed with pre-tension, characterised in that, at least one second sealing ring, which is likewise in contact with the part to be sealed, is arranged in the plastics sealing ring.

2. A sealing arrangement according to claim 1 characterised in that the second sealing ring is made substantially rectangular in cross-section and is embedded in the centre of the plastics sealing ring.

3. A sealing arrangement according to claim 1 and/or 2 characterised in that the plastics sealing ring also has a rectangular cross-section.

4. A sealing arrangement according to one of claims 1 to 3 characterised in that the plastics sealing ring consists of a polytetra fluorethylene compound material.

5. A sealing arrangement according to one of claims 1 to 4 characterised in that the second sealing ring embedded in the plastics sealing ring consists of polytetrafluorethylene or a polytetra fluorethylene compound material.

6. A sealing arrangement according to one of claims 1 to 4 in which the second sealing ring embedded in the plastics sealing ring consists of a rubber elastic material.

7. A sealing arrangement for relatively longitudinally movable pressure medium influenced parts, substantially as herein described with reference to the accompanying drawing.