Seal for a joint or juncture – Seal between relatively movable parts – Relatively rotatable radially extending sealing face member
Patent
1992-05-26
1992-12-22
Cuchlinski, Jr., William A.
Seal for a joint or juncture
Seal between relatively movable parts
Relatively rotatable radially extending sealing face member
277138, 277165, 277236, F16J 1500
Patent
active
051729210
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a sealing device for providing a seal between two members which are movable relative to each other and have cylindrical contacting surfaces between which there is play. One of the members to be sealed is provided with a sealing groove in which is positioned a sealing ring. The sealing ring is circumferentially pre-stressed against the cylindrical surface of the other member for dynamic sealing against such surface. The sealing groove also includes a gap positioned on at least one side of the sealing ring and at least one element is arranged in the sealing groove and pre-stressed against the sealing ring.
BACKGROUND OF THE INVENTION
Sealing at high pressures in, for instance, hydraulic cylinders and similar components, is critical regarding function and reliability for most mobile working machines and heavy mechanized and automatized equipment. In spite of intensive efforts to develop more adequate dynamic seals, these wearing sealing members must still be exchanged one or more times during the life of the cylinder. Inadequate sealing function is also one of the most usual and the most serious cause for breakdowns in hydraulic systems. Current sealing techniques and the inadequacies of seals in meeting the desired function not only result in a short lifetime but also result in several other disadvantages which, in varying degrees, depending on application type, adversely impact upon the function of the product and also limit its use in hydraulic applications. In addition, there are other serious disadvantages such as the influence of high and low temperatures and friction and stic-slip limitations.
Because of the importance of proper sealing and also because of the difficulties incurred in achieving proper sealing, it is common in both relatively demanding, and also in relatively simple, applications to attain the best possible result by requiring close diameter tolerances and very smooth surface finishes on the sealing surface, both for cylindrical tubes and piston rods. The prior art seals, usually made of polymeric materials, involve a small part of the total cost of the component, but the demands imposed on cooperating surfaces to be sealed involve substantial cost as compared to the material costs. Thus, the total cost for sealing a component represents a significant cost item while the cost of the sealing ring itself generally is very low.
The problem of short lifetime for the seals arises from three main causes. Seal fatigue can occur due to pressure and pressure changes, resulting in cracks which result in leakage and breakdown. As a result of pressure forces, the seal can be forced into the gap between the two members to be sealed, with cracks, leakage and breakdown occurring as a consequence. Also, in order to reach low dynamic leakage, the sealing body is usually formed with sealing lips or surface projections which will pierce the liquid film. If this part of the seal becomes worn, the desired pressure peak is not obtained, resulting in increased dynamic leakage.
Prior art seals are accordingly designed to take into account fatigue, and to provide adequate wear resistance for the wearing surfaces of the seal. No significant improvements in seals have, however, been developed during the last 20 to 30 years. However, some new optimized configurations of the sealing ring and the introduction of new materials have improved the fatigue and wear characteristics. Nevertheless, the problem of short seal lifetime still exists, mainly due to the wear of the contacting surface of the seal members.
Even with use of the best wear-resistant materials now available, wear is nevertheless, in most cases, unacceptably great. The reason for this is that the principal function of conventional present-day sealing members is dependent upon providing a very high contact pressure at the lip, to provide the required sealing function. But the effectiveness of such a seal presupposes that the sealing lip is not worn or deformed. The required pressure exerted on the mate
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Cuchlinski Jr. William A.
DePumpo Daniel G.
Flutron AB
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