GB744662A - Improvements in or connected with balance centreing apparatus associated with means for drilling centreing holes on rotating bodies - Google Patents

Abstract

744,662. Electric indicating systems. AVERY, Ltd., W. & T. (Schenk Maschinenfabrik, Ges., C.). Jan. 20, 1953 [Jan. 23, 1952], No. 1823/52. Class 40(1) [Also in Group XXII] In a balance centring apparatus of the kind described in Specification 715,764 for drilling centring holes on the inertial axis of a rotating 'body to locate subsequent machining operations, wherein the body is carried on adjustable bearers of a rotating cage within which it may be adjusted for dynamical balance about an axis normally coincident with the axis of the cage and the centring drills, means are provided for displacing, prior to balance centring, the inertia, axis of the rotating body by a pre-determined distance relative to the rotational axis, to compensate for asymmetry introduced by subsequent machining operations, whereby the finished body is substantially dynamically balanced. Figs. 1, 2 show a workpiece 16 (e.g. a crankshaft) mounted for balancing between positioning devices 17, 18 and spring- loaded pins 19, 20 of a cage structure comprising end discs 3, 4 connected by rods 5. 6, 7 and rotatable on hollow axially aligned shafts 8, 9 surrounding drills 10, 11 driven by motors 12, 13, which shafts are carried in oscillating journals 14, 15 so that the workpiece is adjustable to a dynamic balance position within the cage for centring holes to be drilled as set forth in the Specification above referred to. Each end disc carries weights 21, 22 in quadrature positions as shown at 22, 22a, in Fig. 3, capable of radial adjustment by screws 23, 24, 26 having pointers movable relative to calibrated scales, whereby the inertia axis 33 of the rotor may be displaced relatively to the axis of rotation prior to the balance centring operation so that the centres are drilled in positions offset from true balance. In operation, a number of rough sample workpieces are taken from a series production run, balance centred on their inertia axes as set forth in the Specification referred to, fully machine finished, and re-balanced to determine the magnitude and position of the residual unbalance when finished. The average value of unbalance is then determined, and compensated by adjustment of weights 21, 22 of the balance centring machine as described with reference to the calibrated scales, so that the machine may be used to accurately centre each rough workpiece of the production run for apparent coincidence between the inertia axis and the rotational axis of the cage and workpiece assembly, but with an inherent unbalance moment such as to compensate for unbalances introduced by further machining, whereby the final product is substantially balanced. A weight 34 may be added to each end disc to compensate for the intrinsic unbalance of an asymmetrical workpiece (e.g. an eccentric) which is to be processed.