Seal for a joint or juncture – Seal between relatively movable parts – Relatively rotatable radially extending sealing face member
Patent
1979-10-29
1982-08-24
Ward, Jr., Robert S.
Seal for a joint or juncture
Seal between relatively movable parts
Relatively rotatable radially extending sealing face member
277 15, 277 17, 277 33, 277212F, 92 99, 74 18, F01B 1902, F04B 4504, F16J 1556
Patent
active
043457681
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
A self pumping seal assembly for a reciprocating member provides lubricant and cooling fluid to the reciprocating member and seal assembly. Degradation of the relatively long life elastomeric seal is reduced by a relatively rigid seal separating the hot portions of the machinery from heat sensitive elastomeric seal.
2. Background Art
In reciprocating machinery, and particularly rock breakers, there is a requirement for a seal on the reciprocating shank of the rock breaker to isolate the reciprocating mechanism, usually an eccentric, from the abrasive atmosphere inherent in rock breaking operations. The normal procedure has been to provide a boot seal between the machinery frame and the reciprocating member. The commonly used boot seal has, in part, been dictated by the displacement of the shank which, in some cases, may be as much as 81/2 to 9 centimeters. Recent developments in the rock breaking art have provided high velocity short stroke intermediate impact links with displacements of the link of approximately 11/2 centimeters. In either type of rock breaker the operating temperature of the lubricating fluid surrounding the eccentric is high enough to influence the fatigue life of elastomeric seals.
The limited displacement type intermediate impact link permits a dual seal assembly consisting of a shear type seal of an elastomeric material that is affixed to the housing or machine frame and also to the reciprocating member and a stationary, more rigid, seal affixed to the housing and sliding relative to the reciprocating member. Because of the high frequencies and velocities experienced by the intermediate impact link, the fatigue life of the elastomeric seal is of prime importance. Natural rubber has the best fatigue properties of any elastomeric material, however natural rubber is particularly susceptible to attack by petroleum products. Synthetic elastomers, such as "Neoprene," have a lower susceptibility to attack by oil, but also have a shorter fatigue life. In either case the temperature of the oil and the surrounding machinery is also a limiting factor since temperature decreases the fatigue life of any elastomer conservatively by a factor of 1/100th per 37.8.degree. C.
It thus becomes advantageous to separate the elastomeric seal member from a temperature source. Further it is appropriate to separate the elastomeric seal from hot lubricant or petroleum particularly if natural rubber is used for a seal. As set forth above, any reduction in operating temperature of the seal will increase the life of the various seal members.
DISCLOSURE OF INVENTION
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of this invention a seal arrangement is provided for an impact device which includes a housing and a reciprocating member mounted in the housing. The seal arrangement comprises a relatively rigid seal member sealingly associating the reciprocating member with the housing and a flexible seal member also sealingly associating the reciprocating member with the housing. The flexible seal member forms a variable volume cavity with the rigid seal member so that a source of cooling fluid may be communicated to the variable volume cavity.
This invention permits the use of an elastomeric seal on a high-speed relatively short displacement impact link of a reciprocating device such as a rock breaker. The use of the rigid seal and the flexible seal allows the reciprocating action to vary the volume of the variable volume cavity to draw cooling fluid into the variable volume cavity thus serving the purpose of increasing the fatigue life of the various seal members by providing the necessary cooling to the seal arrangement.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is an embodiment of this invention shown partly in section and partly schematically with the reciprocating member in the "at rest" position.
FIG. 2 is the same embodiment depicted in FIG. 1 with the reciprocating member in the fully extended position.
BEST MODE FO
REFERENCES:
patent: 2387066 (1945-10-01), Harding
patent: 2725078 (1955-11-01), Glancy
patent: 2824759 (1958-02-01), Tracy
patent: 3039399 (1962-06-01), Everett
patent: 3884482 (1975-05-01), Ball et al.
patent: 3912045 (1975-10-01), Morris
patent: 3922017 (1975-11-01), Cobb
patent: 4049366 (1977-09-01), Becker
Caterpillar Tractor Co.
Ward, Jr. Robert S.
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