WO1990015265A1

WO1990015265A1 - Friction clutch mechanism

Info

Publication number: WO1990015265A1
Application number: PCT/US1990/003277
Authority: WO
Inventors: Howard W. Selby, Iii
Original assignee: Selsys Corporation
Priority date: 1989-06-09
Filing date: 1990-06-08
Publication date: 1990-12-13
Also published as: AU5923190A

Abstract

A friction clutch includes a pivot pin (10) and a capture element (12) that tightly encircles a portion of the pivot pin (10). The material characteristics of the capture element (12) enable it to hold the pivot pin (10) in place when no external force is applied to either the pivot pin (10) or the capture element (12), but allow relative movement to occur between the pivot pin (10) and the capture element (12) when a sufficient external force is applied to the pivot pin (10) or the capture element (12). The pivot pin (10) is formed of a metal, and the capture element (12) is formed of an ultra-high molecular weight polyethylene.

Description

Friction Clutch Mechanism

Technical Field

This invention relates to a friction clutch mechanism, and specifically to a simplified friction clutch mechanism in which the material characteristics of the clutch components provide friction clutch action.

Background Art

The friction clutch mechanism of this invention can be used to normally non-movably hold the relative position between two objects, which position can however be changed upon the application of a given external force to the one or both of the two objects. Once the position is changed by the application of such a force, a new position is non-movably held by clutch friction, until such time as the relative position is again changed by the application of an external force.

Prior art for such a device includes elements that operate to hold a preset position, but which elements are in addition to the elements that provided for the variable preset positions. The position holding elements used in the prior art include springs, clamps, levers and the like, which elements serve as the friction member that holds the position of two connected objects.

Disclosure of the Invention

It would be desirable to provide a friction clutch mechanism in which the friction means is an integral part of the clutch mechanism, thus cutting down on the number of parts and the weight of the mechanism, simplifying construction of the mechanism, and providing for a variety of possible movements between the objects that are connected by the clutch mechanism. It is an object of the invention to use the material characteristics of the components of the clutch mechanism to provide for a variety of movements or positions for the objects that are connected to and that use the clutch mechanism.

It is a further object of the invention to use the material characteristics of the components of the clutch mechanism to provide the friction for clutch action.

These and other objects of the invention are accomplished in accordance with the invention by employing a material in the clutch mechanism which is used not only to connect two objects, such as the leaves of a hinge, but which material also has the intrinsic properties which provide for friction clutch action.

The invention consists of two elements, herein called a pivot pin and a capture element, but without limitation thereto. The capture element encircles a portion of the pivot pin. The pivot pin is held in place by the capture element by virtue of the friction that exists between the capture element and the pivot pin. This friction is a function of the nature of the material of which the capture element is made, i.e. the capture element "grasps" the pivot pin with a given friction force.

When either the pivot pin or the capture element is moved by the application of an external force of a given magnitude, axially or laterally in relation to one another, the force of friction is overcome, allowing relative movement to occur between the pivot pin and the capture element. Break-away, or the release of grasp, by the capture element is a function of the material of which the capture element is made. When the external force ceases to be applied, or is reduced in magnitude, the frictional force between the pivot pin and capture element again takes over, and the pivot pin is non-movably held in place once again.

Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the invention. Brief Description of the Drawing

FIG. 1 is a perspective view showing the pivot pin and the capture element of the invention.

Detailed Description of the Preferred Embodiment

Referring now to the drawing, there is shown in FIG. 1 a perspective view of the friction clutch mechanism of the invention, comprising a metal pivot pin 10 and a plastic capture element 12. Any material will work as pivot pin 10, for example a plastic. However, metal, for example a metal rod or a metal tube, is preferred for pivot pin 10 because of its strength.

In the use of the invention, pivot pin 10 and capture element 14 can be attached to, or can be integrated with, other objects which utilize the friction clutch action that is provided by the .invention, Such other objects are not included in the invention, and are not described herein.

Capture element 12 is made of an ultra-high molecular weight polyethylene (UHMWPE) having a weight-average molecular weight of about 4 X 10 . Reference may be made to the publication ENGINEERING MATERIALS HANDBOOK, Vol. 2, Engineering Plastics, ASM International, Metals, 1988, for a description of UHMWPE materials, incorporated herein by reference.

Capture element 12 operates to tightly encircle a portion of pivot pin 10. In this way, capture element 12 firmly holds pivot pin 10 by virtue of the friction that exists between these two clutch members. Due to the nature of the ultra-high molecular weight polyethylene material, when an external force is applied to produce relative movement between pivot pin 10 and capture element 12, capture element 12 "gives", allowing the external force to overcome the force of friction between elements 10,12. This in turn results in relative movement between elements 10,12. When the external force is no longer applied, or is reduced in magnitude, capture element 12 resumes its original grasp on pivot pin 10, and the force of friction between capture element 12 and pivot pin 10 reestablishes these two clutch members as relatively non-movable.

When capture element 12 is made of an ultra-high molecular weight polyethylene, capture element 12 exhibits the following characteristics which are advantageous for use in a friction clutch mechanism: it has a high resistance to wear (i.e. it is abrasion resistant); it has a natural lubricity (i.e. no additional lubricant such as oil is needed in the clutch mechanism) ; it has a low creep factor in that after movement of pivot pin 10, capture element 12 returns to its original shape, thereby reestablishing the friction that holds pivot pin 10 in place; the frictional force along the length of pivot pin 10, where the pivot pin is in contact with capture element 12, is uniform and has a predictably low break-away force, thus providing smooth and consistent clutch operation.

Movement between pivot pin 10 and capture element 12 can be any of the following, depending on the application of the invention: rotation of pivot pin 10 (the movement shown in FIG. 1 as 14); rotation of capture element 12 around pivot pin 10 (the movement shown in FIG. 1 as 16) ; lateral movement of pivot pin 10 relative to capture element 12 (the movement shown in FIG. 1 as 18) ; lateral movement of capture element 12 relative to pivot pin 10 (the movement shown in FIG. 1 as 20) ; and any combination of these movements.

The manner of mounting capture element 12 relative to pivot pin 10 is not critical to the invention. For example, a hole may be drilled in capture element 12 to receive pivot pin 10, this hole being somewhat smaller in diameter than cylindrical pivot pin 10, so as to provide an interference fit of, for example, an interference of 0.001 inch. As another example, an elongated slot may be formed in capture element parallel to the axis of pivot pin 10, and threaded fasteners may be used to close this slot down upon pivot pin 10, thus capturing or holding pivot pin 10 with a force whose magnitude is adjustably determined by the extent of movement of the threaded fasteners. As will be apparent to those skilled in the art, the invention may be incorporated into a variety of devices, taking advantage of the position holding (i.e. friction clutch) characteristics of the invention, as well as the variety of above described movements that are available through use of the invention. Two typical uses are a position holding hinge and a torque limiter.

Claims

, „ O 90/1526 Claims

1. A friction clutch mechanism comprising: a pivot pin; a capture element tightly encircling a portion of said pivot pin, the material characteristics of said capture element enabling said capture element to hold said pivot pin in place when only a relatively low external force is applied to either said pivot pin or said capture element, but allowing relative movement to occur between said pivot pin and said capture element when a sufficient external force is applied to said pivot pin or said capture element.

2. The friction clutch mechanism of claim 1 wherein said capture element is made of ultra-high molecular weight polyeth lene.

3. The friction clutch mechanism of claim 1 wherein said capture element holds said pivot pin with a force that is adjustable.

4. The friction clutch mechanism of claim 4 wherein said pivot pin is made of a metal.