Image Number 5 for United States Patent #5700186.
A spindle, comprised of a spindle body and an indexing fixture, is configured to retain, and rotatingly drive, a crankshaft relative to a grinding tool, so that each pin on the crankshaft is ground with a high degree of precision. A locking mechanism, such as a pair of jaws with complementarily shaped teeth, is interposed between the spindle body and the indexing fixture. Pressure is applied to one side of the locking mechanism so that the jaws are normally engaged and the spindle body and the indexing fixture rotate as a unit. Motive power for such fixture is supplied by a single servomotor secured to a primary drive shaft, which is joined to a secondary drive shaft, through an offset coupling, to define a motorized spindle.The indexing fixture is bolted, or otherwise secured, to the free end of the secondary drive shaft. A bearing block in the indexing fixture receives and retains, the main shaft of the crankshaft; clamping arms with clamp shoes press the shaft downwardly into the bearing block. To place a pin on the crankshaft in position to be ground, pressure is supplied intermediate the jaws of the locking mechanism to force same apart. The secondary drive shaft then rotates the uncoupled indexing fixture relative to the spindle body to place an unground pin in a position to be ground by a grinding tool operatively associated with the motorized spindle.Keys and keyways are formed between the spindle body and the indexing fixture. A threaded bolt, and the cooperating nut, allow limited movement between such components to adjust the throw for pins located at different elevations along the crankshaft to be ground. A zero angle reference point is established by milling a reference pad on a crank pin web situated between the main bearing shaft and the first pin on the crankshaft.