Plate spring with adjustable support cam

[0001] The present invention pertains to the field of constrained path plate-spring spring systems, or suspensions, in which a sprung portion of a mass is connected to an un-sprung portion of the said mass, by means of a resilient flat wide spring mechanism. This invention will find application in constrained path mechanical shock and vibration isolation spring mechanisms and suspensions.

[0002] Edbert E. L. Dittmar the inventor, applied for a patent in the year 2000, showing a suspension system with rigidly mounted plate-springs. Failures of the plate-springs in testing caused Dittmar to abandon this initial filing effort. Continued development work and testing has led to additional discoveries, which has made his invention viable. Thus, Dittmar is filing this new patent application.

[0003] No prior art, other than the inventor's previous development, relating to a bifurcated compliant spring systems was found.

[0004] It is the objective of this invention to provide for a simple, functional, plate-spring spring system, rigidly mounted on both ends, providing an inherent unidirectional, prescribed suspension path, and an adjustable, progressive and adaptive spring rate.

[0005] This object is achieved with a bifurcated plate-spring system with strain control. Bifurcated, meaning that the flex of each plate-spring is divided into two equal but opposite flexing radii as the plate-springs are flexed into the shape of a serpentine. Strain Control is achieved by strain-control cams, mounted adjacent to the plate-springs rigid mounting lines, to progressively support loads placed on the spring system and distribute the strain over the length of the plate-springs.

[0006] In the said bifurcated spring systems, perpendicularly spaced or stacked flat plate-springs, under load, inherently flex into the shape of a serpentine with two equal but opposing radii. Flex-shear movement between plate-spring layers of the first radius is canceled by the opposing flex-shear movement in the second and opposing radius, resulting in equalization of shear to occur within the length of the two radii of the serpentine. With the shear movement equalized within the serpentine, the not flexed ends of these stacked plate-springs can be rigidly mounted to the un-sprung portion of a mass on one end, and to the sprung portion of the said mass on the opposite end.

[0007] Strain control cams or surfaces, mounted perpendicular, adjacent to the rigid mounting line, and spaced progressively apart from the plate-spring planes, control the strain exerted on the plate-springs under load, by distributing the load induced strain over the full length of each plate-spring controlled by the location and shape of the said cam.

[0008] The said plate-springs, being rigidly mounted on two ends, are flexible in a direction perpendicular to the surface of the plate-springs, but rigid in parallel directions to the said plate-springs. Thus, under load, the plate-springs flex, bifurcated, into a serpentine shape, inherently providing for a constrained unidirectional suspension travel path.

[0009] This invention further teaches a progressive spring rate. Strain control cams are mounted adjacent to the rigid mounting line, perpendicular and spaced progressively apart from the plate-spring surface, in such a way that, under a progressive load, said strain-control cams come progressively in contact with the plate-springs, and progressively support a portion of the load. Spring rate and the progression of the spring rate are thus determined by the position and shape of the said strain-control cams. The limiting of the deflection and thus the strain in the plate-springs, by the strain-control cams, inherently provides for a progressive spring rate.

[0010] This invention further teaches an adjustable, variably progressive, spring rate. This is achieved by providing a mechanism to change the relative positions and, or, the contours of the said strain-control cams. Varying the position and, or, contour of the said cams, varies the proportion of load the strain-control cams carry, which, in turn, varies the spring rate and spring rate progression.

[0011] This invention further teaches of an active adaptive spring rate control. This is achieved by outfitting the bifurcated spring system with sensors in communication with a control module. The said module converts input from sensors into a positioning command. The positioning command actuates a strain-control cam positioning mechanism, changing the relative positions and, or, contours of the said strain-control cams, and thus actively adapting the spring rate and spring rate progression of the spring system.

[0015] It is the objective of this invention to provide a simple, flat plate-spring suspension system, with a constrained unidirectional suspension travel path, progressive spring rate, adjustable spring rate, and adaptive spring rate control. This objective is achieved by a bifurcated spring system of plate-springs, coupled with fixed or movable strain-control cams.

[0016] Flexing members of the spring system are made of flat wide plates of any type of resilient spring material referred to as plate-springs (1). The bifurcated spring system plate-springs (1), under load, flex into the shape of a serpentine of two separate and opposing radii (2 and 3). Shearing action (4 and 5) between plate-springs under load, are of opposing directions and are canceled within the two opposing radii (2 and 3). No shear action is propagated beyond the two opposing radii (2 and 3), allowing for rigid mounting of the plate-springs (1) on two opposing ends (8 and 9), with the first end mounted rigidly to the un-sprung portion of a mass (10) and the opposing end, rigidly mounted to the sprung portion of a mass (11).

[0017] With the ends mounted rigidly, the spring system inherently travels in a constrained, unidirectional path (12).

[0018] This invention further teaches that undesirable stress concentrations most dominant at each rigid mounting line (13) are eliminated by the use of strain control surfaces, or cams, (15 and 14) mounted adjacent to the mounting area (13), perpendicular, and spaced progressively apart from the plate-springs (1). Strain-control surfaces, or cams (14), mounted adjacent to the negative travel side of the said plate-springs (1), determine the strain distribution and thus the spring-rate in the negative flex direction, while strain-control cams (15), mounted adjacent to the opposite surface of the said plate-springs, determine the strain distribution and thus the spring-rate for the positive flex direction of the plate-springs.

[0019] This invention further teaches an adjustable, variably progressive, spring rate. This is achieved by providing movable strain-control surfaces (18), which change the relative contact positions between the plate-spring (1) and the strain-control surfaces (18). Varying the position and or contour of said strain-control cam segment (18), varies the proportion of load the support surfaces carry, which in turn varies the spring rate and spring rate progression.

[0020] This invention further teaches an active adaptive spring rate control. This is achieved by outfitting the bifurcated spring system (FIG. 2) with sensors (19) in communication with a control module (20). The said module (20) converts input from sensors (19) into a positioning command. The positioning command actuates a support cam positioning mechanism (21), which changes the relative positions and, or contours of said strain-control surfaces (18), thus actively changing the spring rate and spring rate progression of the spring system.

[0021] With specific reference to FIG. 2, a first plate spring (1b) is disposed between unsprung mass (10) and sprung mass (11). A second plate spring (1a) is also disposed between unsprung mass (10) and sprung mass (11) and above the first plate spring (1b). A first cam (15b) is disposed on a top surface (7) of the first plate spring (1b) and a second cam (15a) is disposed on a top surface (6) of the second plate spring (1a). A third cam (15d) is disposed about a bottom surface of the first plate spring (1b). A fourth cam (15c) is disposed about a bottom surface of the second plate spring (1a). A fifth cam (14a) is disposed about the bottom surface of the second plate spring (1a). A sixth cam (14b) is disposed about the bottom surface of the first plate spring (1b). A seventh cam (14c) is disposed about a top surface (7) of the first plate spring (1b). Finally, an eighth cam (14d) is disposed about a top surface (6) of the second plate spring (1a).

[0022] With specific reference to FIG. 3, cam (14) comprises a moveable portion (18) and a non-movable portion (14e). Moveable portion (18) comprises a tab member (22) configured to mate with groove (23) of the non-moveable portion (14e) of cam (14).