This application is generally directed to the art of pulling elongated workpieces and, more particularly to draw benches or drawing devices for peeling machines.
Draw benches and the like for drawing materials through a drawing die are known to include two clamping devices arranged in tandem to act alternately for continually drawing material through a drawing die. In one known arrangement, one clamping device travels on one half the length of the draw bench bed while the other clamping device travels on the other half of the length of the draw bench bed. The clamping devices are reciprocatingly driven by a roller cone projecting downward from each clamping device into engagement with a curve on the circumference of a large diameter shaft rotatably mounted under the clamping devices in the machine frame. Each clamping carriage is assigned an approximately eliptical curve on the surface of the large diameter shaft.
In drawing devices of the type described, the speed and drawing force are limited by the curve in the large diameter shaft. Where the same curve is used for movement of a carriage in both the pulling and return directions, the type of curve capable of being used is very limited. If the curve is relatively flat and has a high pitch, rapid return of a clamping device is achieved but such a flat curve causes very high transverse forces when the clamping device is moved in the pulling direction. The transverse forces can be reduced by increasing the diameter of the shaft but limitations of the machine frame usually prevents use of extremely large shaft diameters. With each clamping device travelling over only one half of the length of the machine bed, the change-over frequency of the two clamping devices must be quite high.