Flat element spring
United States Patent Dillard Apr. 22, 1975 1 FLAT ELEMENT SPRING 3,408,061 12/196718 267/162 3.578.305 19 l .67 I6. [75] memo Paul Limemh&#39; 3.589.703 6l97l 6,111 631: 2675162 [73] Assignee: The United States of America as represented by the Secretary of the Primary Examiner-James B. Marbert Army. s ington. C. Attorney. Agent. or Firm-Lawrence A. Neureither; [22] Filed: Nov. 6 I973 Joseph H. Beumer; Harold W. Hilton 21 A I. N 413,420 1 PP 57] ABSTRACT 52 US. Cl. 267/165 A w which P [51] InL Cl. n 6f 1/18 storage. The sprmg 1s formed of a pan of heat treated [58] Field O1&#34;,;;;J1;&#39;IIII1111111355715s&#34;156. 160. 161. meta Ships Pmvided with suhsmhially 7 figuration. The strips are secured together at one of 267/16... I63. I64, 165, I3.  
  the1r ends with the other of then ends free for sprmg 1561 :2:a;12&amp;22 1i111152312.3:2113x3133 UNITED STATES PATENTS ments. 379,502 3/1888 Brinkcrhoff 267/164 3.390.873 7/1968 Wullcrstein 267/165 4 Claims, 6 Drawing Figures PATENTED Z 3.879325 sum 2 115 g FLAT ELEMENT SPRING BACKGROUND OF THE INVENTION Many attempts have been made to design a long travel spring with a very low spring constant and which takes up small volume in storage. One such spring is the coiled wire torsion spring which is comprised of a plurality of coaxial, parallel coils intermediate the free ends of the spring. The free ends are in substantially parallel planes and extend transversely to the longitudinal axis of the coils. The spring is loaded by exerting a lateral force on the ends in opposite directions about the longitudinal axis. This type of spring has the ability to reduce the spring constant by adding coils. However, the more coils added. the more space required. The addition of more coils contribute eccentricities and misalignment because the coils when loaded become misaligned.  
  Another approach to a spring having long travel with a low spring constant, and one which takes up small volume in storage, is the bent strip spring. This spring is comprised of a single leaf which is bent in the middle so that the ends of the leaf are extended in the same direction at a predetermined angle between the extending portions of the leaf (30-60. for example), in its free position. The extending portions are disposed in substantially parallel relation in the loaded position. While eccentric loading problems are solved by this approach, the small radius, formed at the bend, during manufacture causes stress concentration at the bend. The small radius also adds to the height in the loaded position. Other attempts, such as the thin gage coil spring, the flat coiled spring element. etc., have been resorted to, but for various reasons fail to provide a long travel spring having desired features such as a very low spring constant and small volume in storage.  
 SUMMARY OF THE INVENTION The invention described herein has the desirable characteristics mentioned above. The invention is a flat element spring formed by joining two formed heattreated metal strips together at corresponding ends thereof. Each strip includes a pair of substantially horizontally extending end portions disposed in parallel planes and an intermediate portion in angular relation to the end portions. The spring element is formed by joining corresponding ends of each leaf together so that the intermediate portion of each leaf extends in the same direction away from the joined ends in predetermined angular relation between the intermediate portions. The free ends of each leaf are positioned in parallel relation. The spring element may be combined with a plurality of other similarly formed spring elements to obtain many different configurations for different applications.  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a pictorial view of the spring element of the present invention in free position.  
  FIG. 2 is a view of the spring element of FIG. 1 in loaded position.  
  FIG. 3 is a pictorial view of a pair of spring elements in stacked relation.  
  FIG. 4 is a view of another combination utilizing four of the spring elements.  
  FIG. 5 is a pictorial view of another combination utilizing six of the spring elements.  
  FIG. 6 is a pictorial view showing a combination of spring elements which will yield both axial and rotational motion.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. I, a flat element spring 10 is comprised of a pair of formed heat-treated metal strips 12 and 14. Each strip includes an intermediate portion 16 disposed in angular relation with a pair of end portions 18 and 20. End portions 18 and 20 are disposed in parallel relation. A small radius r is formed at the juncture of the end portions with the intermediate portion. The spring element 10 is formed by joining each strip at corresponding ends 20, as by welding. etc. Intermediate portions I6 of each strip is disposed in angular relation with respect to one another, and end portions 18 of each strip are in parallel relation when the spring element is in the free position (FIG. 1).  
  FIG. 2 illustrates the spring element in its loaded position wherein the intermediate portions 16 and end portions 18 are in substantially parallel relation.  
  The flat spring of the present invention overcomes most of the problems relating to other spring designs. The travel is increased and the rate reduced by increasing the span d. As the spring is flexed it puts the weld in tension. The stress concentration is low owing to the rolling action of the spring layers. The storage volume need be only large enough to house the flat stacked height of the spring elements.  
  The spring elements may be combined in many configurations to provide greater travel. Each spring leaf gives d/2 inches of travel but the stacked height spring force is the same, no matter how many elements are used.  
  One configuration using a pair of spring elements is shown in FIG. 3 wherein a pair of spring elements are arranged in stacked relation. Like numerals refer to like portions of each spring element. The second (additional) spring element is identified by the numeral 22. The first spring element 10 is joined to spring element 22 at the free ends 18 of the spring elements. Ends 20 of the spring elements extend in parallel relation in a direction opposite to the direction in which ends 18 extend.  
  FIG. 4 illustrates another configuration utilizing four spring elements identified by the numerals I0, 22, 24, and 26. Like numerals refer to like portions of each spring element. In this configuration free ends 18 of each spring elements are joined as discussed in the configuration shown in FIG. 3. However, additional spring elements 24 and 26 similar to elements 10 and 22 are joined to elements 10 and 22 at the free ends 18 and are disposed in apposition to elements 10 and 22. If desired, the free ends 18 may be a portion of spring elements l0 and 22, respectively and spring elements 22 and 26, respectively.  
  An additional configuration is shown in FIG. 5 wherein like numerals refer to like portions of each spring element. This configuration utilizes six spring elements identified by the numerals 30, 32, 34, 36, 38, 40. Spring elements 30, 34, and 38 are joined at the upper ends 18 by an annular member 46 and at the lower ends 18 by annular member 48. Lower spring elements 32, 36, and 40 are stacked beneath the upper spring elements 30, 34, and 38 and are joined at their upper ends 18 to circular member 48 and at their lower ends 18 by a circular member 50.  
  FIG. 6 discloses a combination of spring elements which yield both axial and rotational motion. Like numerals refer to like portions of each spring element. As shown in FIG. 6, a spring element 52 is formed by joining a pair of metal strips 12 and 14 together at ends 58 and 60, respectively, and having their opposite ends 62 and 64 extending in opposite directions. Ends 62 and 64 are secured to a pair of discs 54 and 56, respectively. which are in spaced parallel relation. Two other pairs of strips 66 and 68 are connected between discs 54 to complete spring element 52. These strips are identical to that strip formed by strips 12 and 14. As is obvious from a consideration of FIG. 6, discs 54 and 56 can be moved toward and away from each other and there can be relative rotation between the two discs.  
 I claim:  
  1. A spring comprising a plurality of spring elements, each element including a pair of leaves having corresponding ends secured together, each leaf having an intermediate portion and a free end, said intermediate portions disposed in angular relation with respect to one another and extending in the same direction away from the secured ends, said free ends disposed in substantially parallel relation for spring action therebetween, a first pair of said plurality of spring elements disposed in stacked relation, a first free end of the first of said first pair of spring elements secured to a first free end of the second of said first pair of spring elements, the second free ends of each said spring element disposed for spring action therebetween; and a second pair of spring elements disposed in stacked relation, the free ends of the first of said second pair of spring elements secured to the free ends of the second of said second pair of spring elements.  
  2. A spring comprising a plurality of spring elements, each element including a pair of leaves having corresponding ends secured together, each leaf having an intermediate portion and a free end, said intermediate portions disposed in angular relation with respect to one another and extending in the same direction away from the secured ends, said free ends disposed in substantially parallel relation for spring action therebetween, said spring including the first of three of said elements disposed in substantially equally spaced circular relationship, the first of said free ends of each of said first three elements secured to a first circular member, a second of three pairs of said elements disposed in substantially equally spaced circular relationship, the first of said free ends of each of said second three elements secured to said second circular element, a third circular disc having the second said free ends of each of said second three elements secured thereto, said circular members being mounted in substantially parallel relation for spring action therebetween.  
  3. A spring disposed to yield axial and rotational motion comprising a pair of discs disposed in spaced parallel relation, a first plurality of leaf spring members having first and second ends, the first end secured in substantially equally spaced relation on the edge of the first of said pair of discs, a second plurality of leaf spring members having first and second ends, the first end secured in substantially equally spaced relation on the edge of said second disc, the second end of each spring member being secured together.  
  4. A spring as in claim 3 wherein said leaf spring members include first and second ends disposed in parallel relation and an intermediate portion formed between said ends in angular relation therebetween.  
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