PLASTIC SPRING

• US 3,815,887 A
• Filed: 03/21/1972
• Issued: 06/11/1974
• Est. Priority Date: 03/21/1972
• Status: Expired due to Term

• Current Assignee: David C. Trimble, William R. Curtis
• Original Assignee: David C. Trimble, William R. Curtis
• Inventors: Curtis, William R., Trimble, David C.
• Primary Examiner(s): Marbert, James B.
• Application Number:
  US05/236,621
• Time in Patent Office: 812 Days
• Field of Search: 267/153,181,182,91 5/351,353
• US Class Current: 267/91
• CPC Class Codes: A47C 23/002 with separate resilient support elements, e.g. elastomeric springs arranged in a two-dimensional matrix pattern
• CPC Class Codes: A47C 27/065 of special shape
• CPC Class Codes: A47C 7/34 with springs in compression, e.g. coiled
• CPC Class Codes: F16F 1/025 characterised by having a particular shape F16F1/04, F16F1/14, F16F1/18, F16F1/32, F16F1/34 take precedence
• CPC Class Codes: F16F 1/424 of membrane-type springs
• CPC Class Codes: F16F 2236/022 of membrane-type springs
• CPC Class Codes: F16F 9/0409 characterised by the wall structure
• CPC Class Codes: Y10S 297/08 Inflatable bellows

Abstract

A thin wall hollow, corrugated plastic spring is provided which has a plurality of annular peaks, each separated by a respective one of a plurality of annular valleys. A first group of bottoms of respective valleys are spaced a first distance from the longitudinal axis of the spring and a second group of valley bottoms, each of which alternate with a bottom of the first group, are spaced a second distance from the longitudinal axis of the spring. The peaks are arranged in the manner as the valley bottoms thereby providing a telescopic effect of the valley bottoms and a telescopic effect of the peaks when the spring is fully compressed. As modifications, all of the peaks may be at the same distance from the longitudinal axis while the distances of the valley bottoms vary as above described or vice versa. This provides for a telescoping effect of either the peaks or the valley bottoms. The spring rate is non-linear. The spring is preferably made of polypropylene and has primary utility in seating and reclining applications such as chairs, sofas, and bedding.

Claims

1. A biaxially stretched spring comprising a hollow, corrugated shell having a plurality of annular peaks and annular valleys separating each of said peaks, a first group of valley bottoms being arranged to be a first distance from the longitudinal axis of the spring and a second group of valley bottoms being arranged to be a second distance from the longitudinal axis of the spring, said groups of valley bottoms being arranged so that a bottom of one group alternates with a bottom of the other group, said first distance being greater than said second distance by at least the wall thickness of the spring at the valley bottoms, said first valley bottoms being dimensionally greater than said second valley bottoms, a plurality of side walls for each valley, each said side wall being generally frusto-conical in shape with the smaller diametered edge thereof being integral with one edge of a respective valley bottom and the larger diametered edge thereof being integral with one edge of a respective peak, the side walls integral with a common peak diverging from each other, the thickness of any portion of said spring shell not exceeding about 90 mils.

2. A spring as recited in claim 1 wherein a first group of peaks are arranged to be a third distance from the longitudinal axis of said spring, a second group of peaks are arranged to be at a fourth distance from the longitudinal axis of said spring, said first and second groups of said peaks being arranged that one peak of one group alternates with a peak of the other group, said third distance being greater than said fourth distance.

3. A spring as recited in claim 1 wherein all of the peaks are arranged to be equal distance from the longitudinal axis of the spring.

4. A spring as recited in claim 1 wherein said side walls are slanted between 60* and 85* with the longitudinal axis of the spring.

5. A spring as recited in claim 4 wherein the radius of circumscription of the peak farthest from the spring axis is no more than 3 times the radius of circumscription of the valley bottom closest to said axis, the thickness of the valley bottom wall closest to said axis is no greater than 18 times the thickness of the peak farthest from said axis.

6. A spring as recited in claim 2 wherein said side walls are slanted between 60* and 85* with the longitudinal axis of the spring.

7. A spring as recited in claim 6 wherein the radius of circumscription of the peak farthest from the spring axis is no more than 3 times the radius of circumscription of the valley bottom closest to said axis, the thickness of the valley bottom wall closest to said axis is no greater than 18 times the thickness of the peak farthest from said axis.

8. A spring as recited in claim 7 wherein the ratio of the different radii of circumscription of the valley bottoms is no greater than 1 1/2 :

1 and the ratio of the different radii of circumscription of the peaks is no greater than 1 1/2 ;

1.

9. A spring as recited in claim 8 wherein the side walls are generally planar in cross section.

10. A spring as recited in claim 8 wherein the side walls are generally concavo-convex in cross section, the pair of side walls connected to a common peak having the concave surfaces thereof facing each other.

11. A spring as recited in claim 8 wherein the valley bottoms and the peaks are planar in cross section and generally parallel to the Longitudinal axis of the spring.

12. A spring as recited in claim 8 wherein the valley bottoms and the peaks are U-shaped in cross section with the open ends thereof merging into a respective one of said side walls.

13. A spring as recited in claim 8 wherein the spring is made of polypropylene.

14. A biaxially stretched spring comprising a hollow, corrugated shell having a plurality of annular peaks and annular valleys separating each of said peaks, a first group of peaks being arranged to be a first distance from the longitudinal axis of the spring and a second group of peaks being arranged to be a second distance from the longitudinal axis of the spring, said groups of peaks being arranged so that a peak of one group alternates with a peak of the other group, said first distance being greater than said second distance by at least the wall thickness of the spring at the peaks, said first peaks being dimensionally greater than said second peaks, a plurality of side walls for each valley, each said side wall being generally frusto-conical in shape with the smaller diametered edge thereof being integral with one edge of a respective valley bottom and the larger diametered edge thereof being integral with one edge of a respective peak, the side walls integral with a common peak diverging from each other, the thickness of any portion of said spring shell not exceeding about 90 mils.

15. A spring as recited in claim 14 wherein all of the bottoms of the valleys are arranged to be equal distance from the longitudinal axis of the spring.

16. A spring as recited in claim 14 wherein said side walls are slanted between 60* and 85* with the longitudinal axis of the spring.

17. A spring as recited in claim 16 wherein the radius of circumscription of the peak farthest from the spring axis is no more than three times the radius of circumscription of the valley bottom closest to said axis, the thickness of the valley bottom wall closest to said axis is no greater than 18 times the thickness of the peak farthest from said axis.

18. A spring as recited in claim 14 wherein the annular peaks and the annular valleys are u-shaped in cross-section with the open ends thereof merging into a respective one of said side walls.