Concentric Arc Spline Rotational Spring

Abstract

A planar torsion spring where the spring comprises a first outer ring and a second inner ring. The inner ring is positioned within the first outer ring and possesses a same axis of rotation. The outer ring is connected to the inner ring with one or more splines. Each spline extends in one or more concentric arc segments to a maximum circumference relative to the position of the next concentric arc between the outer ring and the inner ring. The outer ring, the inner ring and the spline concentric arcs segments are positioned in the same plane. At least one spline connects the outer ring to the inner ring. The spline is positioned in a plurality of concentric arcs segments and sequentially positioning each arc to a maximum circumferential length relative to its position between the outer ring and inner ring.

What we claim is: 
     
         1 . A rotational torsion spring comprising:
 a) an inner ring;   b) an outer ring;   c) one or more splines connecting the inner ring with the outer ring wherein each spline comprises a plurality of concentric arc segments which store energy when either the inner or outer ring is rotated in relation to the complementary inner or outer ring.   
     
     
         2 . The rotational torsion spring of  claim 1  comprising concentric arc segments that create an extended spline length wherein spline stress concentrations are decreased. 
     
     
         3 . The rotational torsion spring of  claim 2  wherein the extended spline length creates increased tolerance of the inner ring to radial misalignment of the outer ring. 
     
     
         4 . A planar rotational torsion spring comprising an inner ring nested within an outer ring and the rotational torsion spring further comprises at least one spline connecting the outer ring to the inner ring and the spline forms concentric arc segments between the outer ring and the inner ring. 
     
     
         5 . The planar rotational torsion spring of  claim 4  further comprising the concentric arc segments each encircling at least 90 percent of the length of circumference existing along each arc segment. 
     
     
         6 . The planar rotational torsion spring of  claim 5  wherein at least one concentric arc segment is circumferentially oriented about an axis of rotation of the inner ring. 
     
     
         7 . The planar rotational torsion spring of  claim 5  wherein at least one concentric arc segment is substantially circumferentially oriented about an axis of rotation of the inner ring. 
     
     
         8 . The planar rotational torsion spring of  claim 4  comprising a single spline connecting the outer ring to the inner ring and the spline forms a plurality of concentric arc segments between the outer ring and the inner ring and the single spline achieves deflection of either ring relative to the other ring with higher stress at the same load of the spring than a planar rotational torsion spring comprising a plurality of splines. 
     
     
         9 . A first planar rotational torsion spring comprising a number of n splines and achieving deflection of the arc segments with more stress than a second planar rotation torsion spring of the same load, material thickness and torsion spring diameter of the first torsion spring wherein the second torsion spring comprises n+1 splines. 
     
     
         10 . A first planar rotational torsion spring comprising a number of n+1 splines and the first planar rotational torsion spring achieves a greater stiffness than a second rotational torsion spring comprising n splines and comprising the same material, material thickness and torsion spring diameter as the first planar rotational spring wherein more splines achieve greater stiffness than a spring with fewer splines. 
     
     
         11 . The planar rotational torsion spring of  claim 4  wherein the concentric arc segments form an extended load path. 
     
     
         12 . The planar rotational torsion spring of  claim 4  wherein the extended spline length created from the concentric shape decreases stress concentration in the spline. 
     
     
         13 . A planar rotational torsion spring comprising an inner ring nested within an outer ring and the rotational torsion spring further comprises a plurality of splines wherein each spline comprises multiple arc segments wherein one arc segment of a first spline is fixed to the outer diameter of the inner ring and a different arc segment of the first spline is attached to the inner diameter of the outer ring. 
     
     
         14 . The planar rotational torsion spring of  claim 13  wherein each of the plurality of splines comprise a plurality of circumferential arc segments. 
     
     
         15 . The planar rotational torsion spring of  claim 14  wherein the arc segments are joined by curved segments and the arc segments are attached to the inner and outer rings by L shaped structures where the circumferential arc segments turn approximately 50 degrees into the inner or outer ring 
     
     
         16 . The rotational torsion spring of  claim 4  comprises a spring achieving a preselected stiffness with a computed spline thickness and known spring constant. 
     
     
         17 . The rotational torsion spring of  claim 4  wherein the design is selected based upon desired stiffness and strength and known spring constant. 
     
     
         18 . A planar rotational torsion spring comprising an inner ring nested within an outer ring wherein the rotational torsion spring further comprises at least one spline connecting the outer ring to the inner ring and a spline forms concentric arc segments between the outer ring and the inner ring. 
     
     
         19 . A planar torsion spring wherein the spring comprises a first outer ring, a second inner ring which is positioned within the first outer ring and possessing a same axis of rotation, the first outer ring connected to the second inner ring with one or more splines each extended in one or more concentric arcs to a maximum circumference relative to the position of the concentric arc between the first outer ring and the second inner ring and positioning the first outer ring, the second inner ring and the spline concentric arcs in the same plane. 
     
     
         20 . A method of constructing a planar torsion spring wherein the spring comprises fabricating a first outer ring, fabricating a second inner ring which is positioned within the first outer ring and possessing a same axis of rotation, further connecting the first outer ring to the second inner ring with one or more splines, extending the spline in a plurality of concentric arcs, sequentially positioning each arc to a maximum circumferential length relative to its position between the first outer ring and second inner ring, fabricating the spline with the maximum number concentric arcs between the inner circumference of the first outer ring and the outer circumference of the second inner ring and positioning the first outer ring, the second inner ring and the concentric arcs of the spline in the same plane.