Two-piece seal

#This invention relates generally to seals for sealing a moving piston rod, cylinder or the like. It is specifically directed to a new and improved, composite, two-piece seal for sealing a reciprocating member, such as a piston rod, from a stationary member.

#Various types of seals, including two-piece seals, have been developed for hydraulic and pneumatic sealing applications. Such two-piece seals have generally included a first, relatively soft, resilient sealing ring (made of rubber, for example) and a second less resilient and harder sealing ring (made of a low-friction material). Typically, the sealing rings are disposed one atop the other and seated in an annular sealing groove so that at least one ring is in sealing contact with a reciprocating member. Some such seals provide substantial seal contact areas on both the softer and the harder seal rings to insure that an effective seal is available for high pressure applications. However, such a seal, by virtue of its substantial seal contact area, introduces an undesirable amount of friction in low pressure applications where less seal contact area is preferable.

#In some cases, the degree of contact between the sealing rings and the cylinder rod is made to vary substantially with the applied pressure. Even with seals of this type, the harder seal ring often has a greater degree of contact with the cylinder rod than is necessary at low pressures. In one particular two-piece seal of the variable contact type, both the softer ring and the harder ring contact the cylinder rod at low pressures, the harder ring particularly having a large (and undesirable) contact area. As pressure increases, the softer ring presses against the harder ring and the softer ring is cammed away from the rod and loads the higher pressure ring to seal more tightly against the rod. While increasing the sealing ability of the harder ring is desirable at high pressures, camming the softer ring away from the rod may be disadvantageous since the softer ring is the better sealer.

#These and other objects of the invention are more particularly set forth in the following detailed description and in the accompanying drawings of which:

#FIG. 1 is a perspective view of one embodiment of a two-piece seal constructed in accordance with this invention with a portion thereof broken away to show the seal in section;

#FIG. 2 is an enlarged cross-sectional view of the sealing ring shown in FIG. 1;

#An embodiment of this invention which effectively seals a reciprocating member from a stationary member in accordance with the above stated objectives generally includes two annular sealing rings, a first softer ring and a second harder and lower friction ring. The first softer ring sits atop the second harder ring and is interlocked with it by means of a locking groove in one of the rings and a mating locking projection in the other ring. The first softer ring has an annular sealing lip for engagement with the reciprocating member. The lip has an edge which faces the high pressure side of the seal and which is inclined toward the reciprocating member. Increasing pressure forces the lip more firmly against the reciprocating member to improve its sealing effect. For sealing with the stationary member to seal flow from around the seal, the softer ring has an axially extending side wall extending substantially the length of the seal in engagement with the stationary member and also a bottom wall abutting the stationary member.

#A second harder annular sealing ring is made of a low friction material and has an annular lip which extends generally axially for engagement with the reciprocating member. Both lips have their respective diameters so related to the diameter of the reciprocating member that each lip becomes radially compressed by the reciprocating member when the seal is seated in a sealing groove so that, even at low pressures, a seal interference fit is formed between the softer member and the stationary member.

#Referring now to FIG. 1, there is shown a composite, two-piece, annular sealing ring, generally indicated at 10. Sealing ring 10 comprises two annular, discrete sealing rings, 12 and 14, which are interlocked to form a composite seal. A first soft ring 12 sits atop ring 14 as shown and is made of a relatively soft material. A second harder ring 14 is relatively harder, though flexible, and is made of a low friction material. This particular embodiment is designed to seal an inner reciprocating member which may fit in inner aperture 15 of the seal from a stationary member which may surround the outer circumferential surface of the seal.