This invention pertains to the art of electrically powered machinery. The invention finds particular application in conjunction with binding and stitching apparatus and will be described with particular reference thereto. It is to be appreciated, however, that the invention is also applicable to other electrically powered machines, particularly those which experience relatively high inertial forces during start-up from eccentric mass distributions, or the like.
Of the many prior binding apparatus and machines heretofore made available, one has found particularly significant commercial success. This apparatus is shown and described in U.S. Pat. No. 3,554,531 to Heigle et al., issued June 12, 1971. Briefly stated, the apparatus includes means for sequentially placing printed sheets into ordered stacks at spaced intervals along a workpath. A continuously moving conveyor feeds the stacks to a reciprocating shuttle mechanism which removes each stack from the conveyor to a stationary stitcher assembly. Following stitching, the stacks are moved to further processing stations along the workpath as required to complete a particular work requirement. Such additional processing stations may accommodate folding, trimming, sorting, collating, and the like. An electric motor is mechanically connected with the continuous moving conveyor, the reciprocating shuttle, and the stitcher for providing motive power thereto. The motor has sufficient speed and power characteristics for driving the stitching mechanism at a fixed rate, which is adequate to process about a forty-five hundred (4,500) stacks per hour.
Although the foregoing binding apparatus has found commerical success, it does have certain practical drawbacks. For example, the AC motor is controlled by an electrical control circuit which is only able to supply full power or no power to the motor. This causes the motor to drive the binding apparatus rapidly to its full operating speed at apparatus start-up. Such rapid acceleration tends to cause excessive wear, particularly on eccentric and reciprocating parts as well as to the electric motor itself. The high torques required for the rapid start-up may necessitate the use of an electric motor which is larger and more power consumptive than necessary for steady state operating conditions.
The present invention contemplates a new and improved start-up circuit for automated binding apparatus and the like which overcomes the above referenced problems and others. The invention provides a start-up apparatus which causes less wear, requires less power, is more economical to manufacture, and is simplier to maintain and adjust.