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High Contact Force MSE Spring

IP.com Disclosure Number: IPCOM000237881D
Publication Date: 2014-Jul-17
Document File: 2 page(s) / 424K

Publishing Venue

The IP.com Prior Art Database

Abstract

The performance of a conventional MSE sealing element is enhanced by employing new geometry in the lip spring to increase the contact force between the seal lip and the sealing surface in order to improve gas sealing performance. A conventional Mechanical Spring Energized (MSE) seal consists of, at a minimum, a “jacket” of plastic or elastomeric material and a spring contained within the jacket which provides a force in a direction normal to the sealing surface. Our current interest is in dynamic piston seals, where the I.D. surface of the MSE seal is essentially static, with the seal contained within a gland on a piston, and the O.D. surface of the MSE seal engages and seals movably in a honed bore. Other supporting elements of a complete sealing system may include back-up rings, chevron rings, and “hat” rings. These elements do not directly engage the gland O.D. or bore I.D. in a sealing manner, but provide supporting structure for the MSE seal. The MSE jacket material is generally quite soft compared to the material of the piston and bore. By itself, when assembled in a piston and bore, the jacket alone does not provide enough contact force to form a good seal between the jacket lip and the honed bore when the pressure differential across the seal is low. The mechanical spring energizer is designed to provide the radial force to effect a seal at low differential pressures. Single finger-spring arrangements rely on the force available from the single bend in the spring to provide the sealing force. Increasing the radial force provided by the mechanical spring is one method of enhancing low-pressure differential sealing performance. Current methods of increasing the spring force have some disadvantages. Coil springs are subject to crushing deformation in the event of reverse loading. Dual finger springs designs generally separate the springs with a small spacer, which is subject to distortion and buckling in the event of reverse loading. Dual finger springs without spacers have a pronounced tendency to “nest” in use, resulting in the shortening of the overall seal system stack and allowing the elements to float axially in the gland, negatively affecting the support and stability of the sealing system. In order to increase the sealing force on the dynamic lip of the MSE seal, a bi-fold finger spring arrangement is proposed. The “hat” ring is made of metal and becomes a surface against which the folded, internal edge of the bi-fold finger spring can push, providing increased force against the seal lip. While the original concept was envisioned with the second bend oriented to the O.D. of the seal, the configuration could easily be reversed with the second bend towards the I.D. of the seal. The development is not limited to dynamic sealing applications. Static seal applications would benefit from increased sealability at low differentials, especially where load reversals can have a crushing effect on conventional coil-spring MSE systems, or “nesting” and instability effects on dual lip-spring designs. The new geometry avoids the drawbacks of coiled, flat springs and nested-dual spring arrangements for MSE seals.

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High Contact Force MSE Spring

The performance of a conventional MSE sealing element is enhanced by employing new geometry in the lip spring to increase the contact force between the seal lip and the sealing surface in order to improve gas sealing performance.

A conventional Mechanical Spring Energized (MSE) seal consists of, at a minimum, a “jacket” of plastic or elastomeric material and a spring contained within the jacket which provides a force in a direction normal to the sealing surface. Our current interest is in dynamic piston seals, where the I.D. surface of the MSE seal is essentially static, with the seal contained within a gland on a piston, and the O.D. surface of the MSE seal engages and seals movably in a honed bore. Other supporting elements of a complete sealing system may include back-up rings, chevron rings, and “hat” rings. These elements do not directly engage the gland O.D. or bore I.D. in a sealing manner, but provide supporting structure for the MSE seal. The MSE jacket material is generally quite soft compared to the material of the piston and bore. By itself, when assembled in a piston and bore, the jacket alone does not provide enough contact force to form a good seal between the jacket lip and the honed bore when the pressure differential across the seal is low. The mechanical spring energizer is designed to provide the radial force to effect a seal at low differential pressures. Single finger-spring arrangements rely on the force available from the single bend in the spring to provide the sealing force.

Increasing the radial force provided by the mechanical spring is one method of enhancing low-pressure differential sealing performance. Current methods of increasing the spring force have some disadvantages. Coil springs are subject to crushing defo...