Spring devices – Bendable along flat surface – Ring or annular spider
Reexamination Certificate
1999-12-20
2001-07-03
Butler, Douglas C. (Department: 3613)
Spring devices
Bendable along flat surface
Ring or annular spider
C267S158000, C267S162000, C267S166000
Reexamination Certificate
active
06254071
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to wave springs, and more particularly, to single-turn, round wire wave springs of circular cross-section that offer a variety of advantages over current flat wire wave springs.
Springs take many forms in the art. Some compression springs are made in a conventional manner in which a metal wire is wrapped around a mandrel in a spiral fashion to form a plurality of spring turns to form a spring of a desired length. These ordinary compression springs were not suitable for all purposes. Flat wire wave springs were developed in response for the need for specialty springs and were designed using flat wire to reduce the free height and operating height of a spring that was necessary to generate an appropriate spring force for a given application. Many such flat wire wave springs were developed for specialized applications. One example of such a wave spring is described in U.S. Pat. No. 4,901,987 issued Feb. 20, 1990 to the assignee of the present invention, in which a crest-to-crest wave spring is provided with circular flat end portions. The flat end portions permit the spring to seat better in its applications and the crest-to-crest arrangement provides for a softer and more precise spring rate.
Although the use of crest-to-crest wave springs in applications dictating higher force and deflection over the single turn flat wire wave spring, such springs are somewhat complicated and expensive to produce. Moreover, such springs require both greater free heights and operating heights which often negate their use in certain work applications. Additionally, the edge winding process has a tendency to possibly introduce an overall irregular, trapezoidal cross-sectional configuration shape that is difficult to maintain in its work position.
Other problems that may occur in flat wire, edge-wound wave springs involve the occasional production of deformed wave springs. Edge-winding of wave springs is a complex process that requires bending a flat wire about its longest cross-sectional axis, that is the full length of the flat wire is wound around a mandrel. This bending may sometimes cause compressive buckling along the interior edge of the flat wire, which is closest to the surface of the mandrel. Likewise, the exterior edge of the flat wire undergoes tension and often the exterior edge experiences a tensioning weakening along its exterior edge.
As such, a need currently exists for an improved wave spring that is more easily formed without buckling and which is less expensive to produce than a flat wire wave spring.
The present invention is directed to an improved wave spring that overcomes the aforementioned disadvantages.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide an improved wave spring that is formed from a circular cross-section round wire having a lower material and production cost.
It is another object of the present invention to provide a round wire wave spring having only a single turn and including at least two full waves formed therein, each of the waves having a defined crest portion and a trough portion, the round wire cross-section increasing the mechanical reliability and lowering the operating stress of the spring.
It is another object of the present invention to provide a round wire wave spring with a single turn and having a plurality of waves formed therein, each wave having a crest portion and a trough portion, the waves having the same amplitude and frequency, the wave spring further having a generally circular extent with two free ends to thereby prevent the wave spring from expanding when compressed under load.
It is yet another object of the present invention to provide a wave spring formed from a single turn of round wire, and a plurality of waves formed therein, each of the waves having distinct crest and trough portions, the single turn having a generally circular extent and the spring turn being defined between two free ends of the spring, the round wire cross-section resulting in higher spring force per cross-sectional area units.
These and other objects of the present invention are achieved by the structure of the present invention in which a wave spring is provided having only a single turn formed from an extent of round wire. The round wire has a plurality of waves formed therein, with each of the waves having distinct crest and trough portions. The peaks of these crest and trough portions form bearing, or work surfaces, that lie along opposite operational working faces of the wave spring.
In the preferred embodiment, the spring has a discontinuous extent, having a gap between two free ends of the spring. This gap permits the spring to move under loading and prevents the spring from binding on a work element or creeping out of its groove.
Also in the preferred embodiment, at least three complete waves are formed, with each having a distinct crest and trough portion. In this manner, the peaks of the crests face and lie adjacent to an opposing first surface of a work element, while the peaks of the troughs face and lie adjacent to an opposing second surface of a work element. The three waves are spaced approximately equally around the circular extent of the wave spring so that the peaks thereof evenly support and bear against their opposing work elements. These waves may define wave patterns that are substantially sinusoidal and/or clothoidal in appearance.
In one application of the present invention, wave springs of the invention may be used in conjunction with a work element having a semi-circular groove formed therein. The groove receives the wave spring and the radius of the groove preferably matches or approximates that of the wire used to form the wave spring. The semi-circular groove is easier to cut than a completely flat groove as is needed with a flat wire spring, so that the ultimate cost of preparing work elements for use with such a spring is reduced. The walls of the groove and the curvature of the spring somewhat match in their configuration so that the spring is more positively supported in the groove, leading to lower operating stresses that occur during operation.
These and other objects, features, and advantages of the present invention will be clearly understood through a consideration of the following detailed description.
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Butler Douglas C.
Smalley Steel Ring Company
Vedder Price Kaufman & Kammholz
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