GB922311A - Improvements in or relating to dental apparatus - Google Patents

Abstract

922,311. Dental engines. SIEMENSREININGER-WERKE A.G. Nov. 25, 1960 [Dec. 5, 1959], No. 40690/60. Class 81 (2). In a dental unit the controls for speed, direction and starting of a drill motor are arranged separately. Thus, in one form, a control panel 7 having a number of push-buttons for determining the speed of the motor, is detachably mounted on the head rest while a foot switch 8 has two separate pedals providing respectively separate on-off switches for the two directions of rotation. The latter (see Fig. 4, not shown) incorporates a number of micro-switches associated with the control circuits and actuated selectively by the two pedals. Thus, in Fig. 6, switches 40, 41 are closed by one pedal and switches 42, 43, 44 are closed by the other. Power is applied to the input 65 and closure of switch 40 energizes relay 55, through rectifier 53, with consequent energization of relay 56, the contact 67 of which, in conjunction with the second contact 66, completes a circuit through the motor field winding 59 and armature 60. Resistance 60 is connected in parallel with the armature 60 so that the closure of pushbuttons 12 ... 17 may determine the magnitude of this shunt and consequently the speed of the motor. The second pedal causes contacts 42, 43, 44 to be closed and, of these, the first merely replaces contact 40 for the purpose of switching on the motor, while 43 and 44 reverse the connections of the armature so that the running direction is reversed. Electromagnetically operated valves 63, 46 are energized by changeover contacts 62, actuated by the support mounting of an airdriven turbine drill. These valves control the air and water supplies respectively to this drill while the contacts 62 simultaneously interrupt the supply circuit to the motor control relay 55.