Patent GB-715764-A (GB)
Title: An improved apparatus for drilling centring holes on the inertial axis of rotating bodies
IPC: G01M1/24
Filed: 1951-09-20
Abstract: 715,764. Electric control systems. AVERY, Ltd., W. & T. (Schenck Maschinenfabrik Ges., C.). Sept. 22, 1952 [Sept. 20, 1951], No. 22035/51 Class 40 (1). [Also in Group XXII] Apparatus for drilling centring holes in a rotatable body, e.g. a crankshaft, comprises a dynamically balanced rotatable cage in which the body to be drilled is mounted, the dynamic unbalance of the combined body and cage being determined vectorially, and the body then moved radially within the cage whilst it is being rotated to reduce the respective unbalance components to zero. Four measurements only are required, corresponding to which two radial quadrature adjustments are made at each end of the body. When balance is achieved the cage is stopped and drills coaxial with the cage moved to drill the centring holes. As shown, Figs. 1, 2, 3, a crankshaft 1 is mounted within a cage consisting of end discs 2 and connecting bars 3. Each end 11, Fig. 3, of the crank shaft is mounted between four rollers 12, 12'. The rollers 12 are carried at the ends of radially disposed sleeves 13, mounted at right angles to each other on the associated disc 2, and the rollers 12' are carried by scissor arms 19 pivoted at 20 to a rocking arm 22 which is rockable about one of the bars 3 to permit mounting of the shaft 1 and is locked in the position shown by a spring plunger 23 on a complementary locking lever 22<SP>1</SP>. A tension spring 21 causes the frictional grip of the rollers on the shaft ends 11 to prevent relative rotation between the shaft 1 and cage. Axial play of the shaft within the cage is prevented by means (not shown). The cage bearings 4 are carried on bridges 5 capable of lateral vibration and actuate moving coil pick-offs 35. An electric motor 24 rotates the cage through a belt 26, counter shaft 27, and chain 30. A two phase generator 28 is driven by the counter shaft, its outputs together with the outputs of the pick-offs 35 being used to determine separately the "vertical" and "horizontal" unbalance components LV, LH, RV, RH at the two ends of the shaft as disclosed in Specification 642,916, the unbalance being indicated on a centre-zero wattmeter 40. As each unbalance component is being measured, a switch 101, Fig. 4, moved with associated switches 38, 43 in the unbalance measuring device, according to the component being measured, selects the corresponding motor 50. The switch 102 is moved in one sense or the other according to the sense of the wattmeter reading, to drive the selected motor 50, in the corrective sense, until the out-of-balance component in question and hence the wattmeter reading is reduced to zero. The motor 50 through gearing 18, 17, 16 rotates a sleeve 15 which has internal and external threads of different pitch. The sleeve 15 is threaded in a fixed sleeve 14 and internally engages the screw 13 carrying the roller 12. Consequently, the roller 12 is adjusted radically inwards or outwards by the motor 50 and at the same time the sleeve 15 is moved in the opposite direction so that the dynamic balance of the cage is not upset as the shaft 1 is adjusted therein. When all four unbalance components have been reduced to zero in this manner, the motor 24 is stopped, and an arm 48, Fig. 2, moved anticlockwise. This switches on the drilling motors 44, and through pinion 47 and rack mechanism causes both drills 45 mounted coaxially with the cage to drill the centring holes. In Fig. 4 the direction of rotation of each motor 50 is determined by the switch 102 energising one or the other of two fields. In a modification Fig. 5 (not shown), single separately excited fields are used and the armature current direction determines the direction of motor rotation. Safety circuits, Fig. 6.-A lamp 202a lights when the power is swiched on. A further lamp 202b lights over series contacts 203, 204 closed only when the spring plungers 23 locking the shaft in the cage are operative, and a contact 205 closed only when the drills 45 are in retracted position. A fourth contact 206 is closed only when an arresting lever (not shown), normally locking the cage against rotation, is moved to release the cage whereupon a relay 207 i;; energised to close a switch 208 after which the starting lever 32 is moved to close the switch 210 which locks the lever 32 at 211 and at 212 starts the drive motor 24.