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ENHANCED PERFORMANCE, LOW COST INDEXING WRAP SPRING CLUTCH

IP.com Disclosure Number: IPCOM000027656D
Original Publication Date: 1998-Aug-31
Included in the Prior Art Database: 2004-Apr-08
Document File: 6 page(s) / 240K

Publishing Venue

Xerox Disclosure Journal

Abstract

Most indexing type spring clutches used in copiers and printers are solenoid actuated. The 156 XEROX DISCLOSURE JOURNAL - Vol. 23, NO. 4 July/August 1998 ENHANCED PERFORMANCE, LOW COST INDEXING WRAP SPRING CLUTCH (CONT'D)

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XEROX DISCLOSURE JOURNAL

ENHANCED PERFORMANCE, LOW COST INDEXING WRAP SPRING CLUTCH Philip A. Billings

Proposed Classification
U. S. C1. 335/209 Int. C1. HOlf 1/00

20 - 10-

22

-

I I I I

FIG. IA

P-( - 24

26 - 10-

16 22

I I I

FIG. IB

XEROX DISCLOSURE JOURNAL - Vol. 23, NO. 4 July/August 1998 155

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ENHANCED PERFORMANCE, LOW COST INDEXING WRAP SPRING CLUTCH (CONT'D)

I

I

FIG. 2A

I

19'

19' '

FIG. 2B

FIG. 3

Most indexing type spring clutches used in copiers and printers are solenoid actuated. The

156 XEROX DISCLOSURE JOURNAL - Vol. 23, NO. 4 July/August 1998

[This page contains 1 picture or other non-text object]

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ENHANCED PERFORMANCE, LOW COST INDEXING WRAP SPRING CLUTCH (CONT'D)

more robust of these devices are also the most expensive, using plunger type solenoids to achieve the pull forces and strokes necessary to initiate indexing of the clutch. Lower cost clapper type solenoids are sometimes employed, but in less robust applications. The clapper develops far less force than a plunger type solenoid at an equivalent stroke. This tradeoff always restricts the latitude of the clutch, either in its torque transmissive capability, life, or susceptibility to piece part and assembly tolerances. This disclosure discloses the alteration of the clapper type solenoid in a way to equal or surpass plunger solenoid performance in indexing spring clutch applications, and to do so at little or no cost increase.

Clapper type solenoids have been applied to two types of indexing spring clutches. The first mounts the clutch and clapper solenoid on a bracket. When the solenoid is energized, the clapper or armature disengages from the clutch, allowing the spring to wrap onto the clutch hub, engaging the hub, and causing the clutch to rotate. The solenoid is de-energized allowing the armature to return to its original position. The detent on the clutch then rotates into contact with the armature causing the spring to unwrap, and causing the clutch to stop its rotation.

The drawback in using a low cost clapper solenoid for such an application is its forcehtroke characteristic. The clapper provides a very low force at maximum stroke, or air gap. This is exactly the place where the clutch presents its greatest force requirement -

disengagement of the clapper from the clutch detent. If the force required to pull the clapper away from the detent either increases over time, or is greater than a specification calls for, the solenoid may have insufficient pull to actuate the clutch. This is a very common failure mode. Putting more energy into the coil of the solenoid may increase the initial pull force, but may result in residual magnetism with the clapper pulled in which prevents the clapper from releasing. In this mode the clutch remains energized all the time. Putting a stronger return spring on the clapper may solve the residual magnetism problem, but increases the required force at t...