Patent GB-1046961-A (GB)
Title: Device for controlling the speed of reciprocating motors driven by a medium under pressure
IPC: A61C1/00
Filed: 1963-03-19
Abstract: 1,046,961. Fluid pressure motors. REDERI SOYA A.B. March 19, 1963 [April 6, 1962], No. 10859/63. Headings F1A and F1S. The invention relates to motors, suitable for dental purposes, including an inlet valve for medium under pressure, an inlet valve operating member, pistons movable in cylinder spaces in a rotor rotatable about a pintle and an eccentrically mounted driven member or ring co-operating with the pistons. According to the invention the motor comprises a restricted outlet duct, means for discharging a medium through the duct at a mass-flow rate dependent on the speed of the motor and a speed control device including actuating means adapted to actuate the inlet valve in response to the pressure exerted in the outlet duct by the discharged medium, the actuating means being adapted to actuate the inlet valve always in the sense tending to restore the speed of the motor to a selected value. The motor may be driven by gaseous medium under pressure or by liquid. Fig. 3 is a longitudinal sectional view of an air driven motor suitable for dental purposes. After expansion in the cylinder space the air is discharged through the outlet duct 28 and the passage formed by the holes 66, 68 and 70. If the air discharged is throttled by adjustment of the rotary valve 72, 76 a corresponding pressure will be set up the magnitude of which is proportional to the speed. This pressure is transmitted through the axial duct 80 to the chamber 82 bounded on the further side by the diaphragm 84 which will tend by means of the flange 90 to displace the tubular slide 44 to the right as viewed in Fig. 3. The displacement comes to an end when the force exerted by the diaphragm 84 is balanced by the spring force of spring 96. The motor now rotates at a speed which is determined by the counter pressure on the outlet side of the motor which is controlled by the setting of the rotary valve 74, 76. After the rotary valve has been set in position for the desired idling speed this speed is maintained substantially constant by the control device. The device acts in a manner such that any change in the adjusted speed will immediately be followed by a corresponding change in the quantity of motive air supplied to the motor by means of the tubular slide 44 which moves in the appropriate sense to tend to prevent continued change in the speed of the motor. A completely balanced slide valve having a short working stroke may be employed. Care should be taken to eliminate frictional forces as far as possible. Instead of adjusting the idling speed by means of a controllable restriction in the outlet duct the same effect may be attained by controlling the force exerted by the spring 96 as shown in Fig. 5. If the sleeve 112 is adjusted by turning the ring 106 will be axially displaced so as to change the counter force exerted by the spring 96. The diaphragm 84 may be replaced by a piston. In Fig. 7 the throttle valve consists of an annular piston 114. If the pressure in the hose connection 122 is increased by manipulation of an operating member (not shown) the piston 114 will be displaced toward the left to gradually cut off the annular groove 69 from the atmosphere. Other modifications of the control are described. The control may be a separate unit suitably connected to the ducts of the motor In one embodiment the motor has a plurality of cavities which are not connected to any of the cylinders of the motor. A duct connects each cavity to the bearing surface of the rotor on the pintle. The pintle has an opening in communication with an axial duct which communicates with a source of air under pressure.