Load-indicating washer

Patent metadata

Field	Value
Publication number	US-10408250-B2
Application number	US-201715428114-A
Country	US
Kind code	B2
Filing date	Feb 8, 2017
Priority date	Feb 8, 2017
Publication date	Sep 10, 2019
Grant date	Sep 10, 2019

Abstract

A load-indicating washer for use with a fastener. The washer is comprised of a circular base plate, a domed cap that projects from the base plate, a cavity formed between the circular base plate and the domed cap, and a fastener hole that extends through the circular base plate and the domed cap. The domed cap is configured to collapse into the cavity upon application of a force that exceeds a threshold.

First claim

What is claimed is:

1. A load-indicating washer comprising:
a circular base plate;
a domed cap that projects from the base plate, wherein the domed cap and the circular base plate are integrally formed so that the load-indicating washer has a unibody structure;
a cavity formed between the circular base plate and the domed cap; and
a fastener hole that extends through the circular base plate and the domed cap.

2. The load-indicating washer of claim 1 wherein:
the circular base plate and the domed cap are formed from a metallic material.

3. The load-indicating washer of claim 2 wherein:
the domed cap is configured to plastically deform upon application of a clamping force by a fastener that exceeds a yield strength of the domed cap.

4. The load-indicating washer of claim 3 wherein:
the cavity has a semi-elliptical cross-section.

5. The load-indicating washer of claim 4 wherein:
the yield strength of the domed cap is determined based on:
a major axis of the semi-elliptical cross-section of the cavity;
a minor axis of the semi-elliptical cross-section of the cavity;
a thickness of the domed cap; and
the metallic material.

6. The load-indicating washer of claim 1 wherein:
a thickness of the circular base plate is greater than a thickness of the domed cap.

7. The load-indicating washer of claim 1 wherein:
a thickness of the domed cap decreases from the circular base plate to the fastener hole.

8. The load-indicating washer of claim 1 wherein:
the fastener hole is sized to be slid upon a fastener.

9. A load-indicating washer comprising:
a base plate formed from a metallic material, and that is circular along a first plane;
a convex wall that projects outward from a circumference of the base plate, and is integrally formed with the base plate from the metallic material;
a cavity between the base plate and the convex wall having a plano-convex shape along a second plane orthogonal to the first plane; and
a fastener hole that extends through the base plate and the convex wall through a center axis of the base plate.

10. The load-indicating washer of claim 9 wherein:
the convex wall is configured to collapse into the cavity and plastically deform upon application of a clamping force by a fastener that exceeds a yield strength of the convex wall.

11. The load-indicating washer of claim 9 wherein:
a thickness of the base plate is greater than a thickness of the convex wall.

12. The load-indicating washer of claim 9 wherein:
a thickness of the convex wall decreases from the base plate to the fastener hole.

13. The load-indicating washer of claim 9 wherein:
the fastener hole is sized to be slid upon a fastener.

14. A method of determining a clamp-up load at a joint of structural members, the method comprising:
acquiring a load-indicating washer that comprises a circular base plate, a domed cap that projects from the circular base plate and forms a cavity between the domed cap and the circular base plate, and a fastener hole that extends through the domed cap and the circular base plate, wherein the domed cap and the circular base plate are integrally formed so that the load-indicating washer has a unibody structure;
sliding the load-indicating washer onto a shank of a fastener via the fastener hole so that the domed cap engages the fastener;
inserting the shank of the fastener into a pass-through hole at the joint;
applying an increasing clamping force to the joint with the fastener;
inspecting the joint for a gap between the structural members; and
determining that the clamp-up load at the joint does not exceed a threshold when the gap is closed and the domed cap of the load-indicating washer has not collapsed into the cavity.

15. The method of claim 14 further comprising:
determining that the clamp-up load at the joint exceeds the threshold when the gap is not closed and the domed cap of the load-indicating washer has collapsed into the cavity.

16. The method of claim 14 wherein the fastener comprises a bolt and a nut, and further comprising:
threading the nut onto the bolt; and
applying an increasing torque to the nut to apply the increasing clamping force to the joint.

17. The method of claim 14 wherein:
the structural members comprise layers of a composite material.

Assignees

• Boeing Co

Inventors

• Webb Sean Christian

Classifications

• F16B31/028 Primary

  with a load-indicating washer or washer assembly · CPC title

• F16B31/02

  for indicating {the attainment of a particular tensile load} or limiting tensile load {(apparatus for, or method of, determining value of torque or twisting moment for tightening a nut or other member similarly stressed G01L5/24)} · CPC title

• F16B43/00 Primary

  Washers or equivalent devices; Other devices for supporting bolt-heads or nuts (circlips F16B21/18; {for indicating tensile load F16B31/02; forming a whole with the bolt or nut F16B33/00; locking bolts or nuts by means of a fixed plate or ring, or washer-like resilient plates F16B39/10, F16B39/24}) · CPC title