Browse Prior Art Database

Differential Bias Mechanism for Leadscrew Drives

IP.com Disclosure Number: IPCOM000049746D
Original Publication Date: 1982-Jul-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 4 page(s) / 69K

Publishing Venue

IBM

Related People

Denny, CM: AUTHOR

Abstract

Disclosed is apparatus for allowing the transfer of rotary screw motion to linear carrier motion with high and equal efficiency in either direction. This is accomplished without backlash, during steady state operation and without transfer of transfer screw motion to the carrier, which normally would be generated by leadscrew eccentricity or runout. The differential bias mechanism hereinafter disclosed, and as shown schematically in the drawing, permits the leadscrew followers or nuts to float and seek their own engagement with the screw, thereby eliminating imposed constraints and eccentric loading upon the screw.

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Differential Bias Mechanism for Leadscrew Drives

Disclosed is apparatus for allowing the transfer of rotary screw motion to linear carrier motion with high and equal efficiency in either direction. This is accomplished without backlash, during steady state operation and without transfer of transfer screw motion to the carrier, which normally would be generated by leadscrew eccentricity or runout. The differential bias mechanism hereinafter disclosed, and as shown schematically in the drawing, permits the leadscrew followers or nuts to float and seek their own engagement with the screw, thereby eliminating imposed constraints and eccentric loading upon the screw.

It is important in transport drive systems, especially those that are a part of a servo system with feedback which controls transport velocity bidirectionally, that frictional characteristics are the same in both directions. Otherwise, bidirectional velocity control becomes difficult. With the added benefit of high efficiency, power supply size may be reduced, an important consideration where available space, in, for example a business machine, is limited.

Frictional characteristics are also important in velocity and position sensitive machines, such as ink jet printers and the like. It is important in this type of machine that backlash between the leadscrew and carrier be minimized. This is especially true if a leadscrew angular position and velocity are required to determine carrier position and velocity. Inasmuch as no leadscrew is perfect, either in its axial extent or in lead consistency along its length, any mechanism for coupling a carrier to a leadscrew should contain compensation for the inaccuracies in both straightness and lead consistency. Moreover, the followers of such a leadscrew system should conform to the screw without constraining the screw and without introducing backlash at any point especially under steady- state driving conditions.

These conditions are particularly important when a printer, for example, is to be operated bidirectionally.

Referring now to Fig. 1, a fragmentary sectional side elevational and schematic view of a differential biasing mechanism is illustrated therein. In the drawing, a pair of follower nuts 10 and 12 are positioned to circumscribe a leadscrew 14, the followers 10 and 12 engaging respectively the inner thread flanks 14a and 14b of the leadscrew 14 such that when the leadscrew 14 rotates, the follower nuts tend to move in the direction of the thread. A carrier 13 having a depending portion 13a contains a pivot pin 17 which is connected through a pair of differential links 15 and 16. The opposite ends of links 15 and 16, as at 15e, 16a, are biased as by the bias spring 18 such that the terminal ends of the links engage the innerfaces 1Oa, 12a of the follower nuts 10 and 12. The spring 18 applies a force B on the differential links 15 and 16, rotating them against the followers 10 and 12 and bringing the followers into engage...