The present invention relates generally to two-speed drives using computer technology for adaptive control of the unit. More particularly, the present invention relates to a main motor, a clutch and gear set between the main motor and a secondary motor, the secondary motor having a brake.
The present invention has application on a wide variety of machinery requiring either high-speed, precision indexing or feed drives requiring high speed approach to a work piece and then adjustable slow speed to perform an operation on the work piece with a precision stop. Typical applications for the present invention operating in the precision index mode include index tables, transfer bars, positioning drives, index type conveyors, rotary sheet feeders and linear sheet feeders. A typical application for the present invention operating in the high speed approach with a slow speed work cycle is the feed drive for the machining heads used in automated transfer machining lines.
Various two-speed drive units have been developed for the above applications but all require the use of multiple limit switches to control the various sequences of the cycle. These units have two major drawbacks. The first drawback is that the productivity and accuracy of the driven machine depends upon the skill of the setup man and/or operator in the setting of the limit switches. The second drawback is the positioning accuracy of the various elements of the complete system. In essence, limit switches determine when a certain function will start. The resulting position at which the function is completed is thus variable due to small changes such as frictional load on the driven machine and the effects of ambient, machine and drive temperatures. With the present invention, the position where a function is to be completed is given to the computer and the computer determines on a cycle-to-cycle basis when each function of a multi-function cycle is to start.
Prior art two speed drive systems have been used in indexing applications only when absolutely necessary in order to achieve better positioning accuracy than is possible with a single speed system. The reason for this is the loss of productivity when using a two speed drive system due to the system operating at the slower speed for a portion of its cycle. Accordingly, it is one object of the present invention to increase the productivity of the driven machine using a two speed drive system to nearly the same productivity as with a single speed system by minimizing the time the system operates at the slower speed. Another object of the present invention is to increase the final positioning accuracy.
Two speed drives are also commonly used for the feed drive of machining heads in automated lines. Another object of the present invention is to more accurately position the machining head at high speed to a position just before the work piece is contacted thus increasing productivity. In order to achieve depth control of the tools machining the work piece, it is often necessary to build stops into the machine. The necessity to do this causes additional problems due to the sudden stopping of the machine and the machine's inertia. Another object of the present invention is to increase the accuracy of depth control of the tools so the stops are no longer necessary thus eliminating the sudden stopping of the machine.
Another object of the present invention is to provide a two speed drive that can also be used as a single speed drive unit without mechanical modifications. Another object of the present invention is to use the same mechanical control equipment in a wide variety of applications without user programming. This is achieved by inserting a different preprogrammed EPROM into the control board.
Another object of the present invention is to eliminate the use of compressed air that is used on many other prior art two speed drives. Experience shows that 4014 60 percent of all maintenance problems are caused by dirty or improper air supplies.
Further objects of the present invention are to provide an improved two speed drive system that is simple and compact in design, economical to produce and extremely rugged and maintenance free during operation.
Further objects, features and advantages of the present invention will become apparent from the analysis of the following written specification, the accompanying drawings and the appended claims.