Passive variable stiffness device for vibration isolation

Patent metadata

Field	Value
Publication number	US-11434973-B2
Application number	US-202017601945-A
Country	US
Kind code	B2
Filing date	Apr 10, 2020
Priority date	Apr 10, 2019
Publication date	Sep 6, 2022
Grant date	Sep 6, 2022

Abstract

Described and shown are passive variable stiffness devices, which are of compact design and configured to produce a restoring force that varies optimally with the isolator displacement when subjected to vibration-inducing loading.

First claim

What is claimed is:

1. A passive variable stiffness device, comprising:
a base plate;
a pair of parallel variable diameter cylinders having first ends and second ends, each variable diameter cylinder mounted to the base plate so as to be restrained against linear movement and constrained to allow rotation only about its longitudinal axis;
a linearly displaceable but rotationally restrained spring assembly comprising a pair of constant force springs located in a space between the variable diameter cylinders;
a lead screw extending parallel to the longitudinal axes of the variable diameter cylinders, the lead screw coupled to the spring assembly such that rotation of the lead screw will produce a linear displacement of the spring assembly along the length of the lead screw;
a lead screw gear train located near the first ends of the variable diameter cylinders and configured to rotate the lead screw upon rotation of the lead screw gear train;
a lead screw gear rack residing above the lead screw gear train and in toothed engagement therewith;
a cylinder gear train located near the second ends of the variable diameter cylinders and configured to rotate a first one of the variable diameter cylinders upon rotation of the cylinder gear train;
a cylinder gear rack residing above the cylinder gear train and in toothed engagement therewith;
a pulley attached to the first end of each variable diameter cylinder, and a belt coupling one pulley to the other;
a top plate residing above the lead screw gear rack and the cylinder gear rack and connected to both, the top plate constrained to linear movement in a direction substantially perpendicular to the longitudinal axes of the variable diameter cylinders; and
a cable coupled to a first one of the constant force springs and extending to and winding partially around a first one of the variable diameter cylinders in a helical fashion, and a cable coupled to a second one of the constant force springs and extending to and winding partially around a second one of the variable diameter cylinders in a helical fashion;
wherein, linear movement of the top plate upon application of a sufficient force thereto will be resisted by a restoring force that varies optimally with the displacement of the top plate.

2. The device of claim 1 , wherein each variable diameter cylinder includes, along the length thereof, a constant diameter portion and a variable diameter portion.

3. The device of claim 2 , wherein the variable diameter cylinders are arranged such that the constant diameter portion of one variable diameter cylinder is across from the variable diameter portion of the other variable diameter cylinder, and the points of transition between a constant diameter and a variable diameter on both cylinders are aligned.

4. The device of claim 1 , wherein an outer surface of each variable diameter cylinder includes a helical groove that spans substantially the length of the variable diameter cylinder, and the portions of the cables wound around the cylinders reside in the helical grooves.

5. The device of claim 1 , wherein the cables are wound around the variable diameter cylinders starting from aligned ends thereof.

6. The device of claim 1 , wherein the pulleys are of like diameter, such that the ratio of the angular displacements between the variable diameter cylinders will be 1:1 when the variable diameter cylinders are caused to be rotated by linear displacement of the top plate.

7. The device of claim 1 , wherein the lead screw, the lead screw gear train and the constant force spring assembly are collectively configured to maintain a longitudinal axis of each cable at a substantially perpendicular angle to the longitudinal axis of the variable diameter cylinder around which the cable is wound.

8. The device of claim 1 , wherein linear movement of the top plate will result in:
a clockwise rotation of one of the variable diameter cylinders and a counterclockwise rotation of the other variable diameter cylinder; and
a winding/unwinding up the variable diameter portion of one of the variable diameter cylinders and a corresponding increase its resistive torque, and a winding/unwinding along a constant diameter portion of the other variable diameter cylinder with no change in its resistive torque.

9. The device of claim 1 , wherein one of the cables is wound around its associated variable diameter cylinder in a clockwise direction and the other cable is wound around its corresponding variable diameter cylinder in a counterclockwise direction.

10. The device of claim 1 , wherein the lead screw gear train and the cylinder gear train cooperatively control the rotation of the variable diameter cylinders relative to rotation of the lead screw, which in turn controls the position of the constant force springs relative to the position of the cables that extend therefrom and are wound around the variable diameter cylinders.

11. The device of claim 1 , wherein the lead screw gear train and the cylinder gear train cooperatively amplify the resistive restoring force that is imparted to the top plate.

12. The device of claim 1 , wherein the resistive force exerted on the top plate by the device as a function of the displacement of the top plate is represented by the equation:

F
plate

=

f
·

F
s

r

p
⁢
i
⁢
n

·

[

(

r
1

-

r
2

)

+

(

∑
1
i

⁢

(

m
1

i
-
1

-

m
2

i
-
1

)

·

Assignees

• Univ Ohio

Inventors

• Walsh Kenneth K

Classifications

• F16F2228/001

  Specific functional characteristics in numerical form or in the form of equations · CPC title

• F16F2232/06

  Translation-to-rotary conversion · CPC title

• F16F15/04 Primary

  using elastic means (single elements or their attachment F16F1/00 - F16F13/00); {(F16F15/023, F16F15/03 take precedence)} · CPC title

• F16F2228/066

  Variable stiffness · CPC title

• E04B1/98

  against vibrations or shocks (on foundations E02D31/08); against mechanical destruction, e.g. by air-raids (against incendiary damage only E04B1/94; finishing work therefor E04F; buildings withstanding earthquake or the like, shelters, arrangements of splintercatching walls E04H9/00) · CPC title