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Spring Assist Cam Profile Drive

IP.com Disclosure Number: IPCOM000249633D
Publication Date: 2017-Mar-09
Document File: 3 page(s) / 278K

Publishing Venue

The IP.com Prior Art Database

Related People

Paul Weber: AUTHOR [+3]

Abstract

A servo driven cam profile is often limited in speed since the torque required for the oscillating motion exceeds motor torque capacity. Use of a spring to assist in the rotation can significantly reduce the maximum torque required from the motor.

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Spring Assist Cam Profile Drive

December 21, 2016

Inventors:           Adam Schoultz

Paul Weber

Joe Coenen

Abstract

A servo driven cam profile is often limited in speed since the torque required for the oscillating motion exceeds motor torque capacity.  Use of a spring to assist in the rotation can significantly reduce the maximum torque required from the motor.

Background

There are many motion control applications that require cam profile motion control for production equipment and processes.  An example is in the making of disposable diapers for operations such as water-cut leg openings, turn and repitch modules for application of elastic components, and folding methods such as is described in US9132982. 

Most oscillating rolls are driven by a mechanical cambox.  Although the mechanical solution can operate at high speeds, its profile is inflexible, so grade changing can be intense.  Alternatively, a servo motor can be direct coupled to the roll, and although the cam profile can be readily modified, the accelerations and therefore operational speeds are limited based on the roll and motor rotational inertias.  In such applications for high speed machines the motion profile needed often exceeds the torque available from commercial servo motors at the cyclical speeds. 

Methodology

A solution was devised to increase the speed capability of the servo motor driven roll.  A mechanical spring was installed to act in parallel with the servo motor.  This could be a torsional spring or a linear spring with a crank slider as shown in Figure 1.  The result is that the peak torque requirement of the motor are reduced.  This is illustrated in Figure 2.  The red inertial line represents the required torque to accelerate the roll to the prescribed acceleration.  The blue line shows the springs contribution.  Note that the spring geometry was tuned to provide near plateaus during the periods where constant torque was required.  The green line represents the required motor torque which is the difference between the total inertial requirement and the torque...