GB1347941A - Centrifuge with safety device for controlling excessive rotor oscillations - Google Patents

Abstract

1347941 Safety device for controlling rotor oscillations BECKMAN INSTRUMENTS Inc 7 Jan 1972 [28 April 1971] 742/72 Heading B2P [Also in Division H1] In a centrifuge including a rotor 10 and driving means 51, 52 for spinning the rotor at selected rotational speeds, a safety control device for interrupting power to the driving means in the event of excessive rotor oscillations comprises an actuating means 20 carried solely by the rotor 10 at its lower peripheral portion and switch means 40 disposed in spaced relation to the lower peripheral portion of the rotor adjacent the normal path of travel of the actuating means and connected in electrical circuit with the driving means 51 52, the switch means 40 being engageable by the actuating means 20 to open the electrical circuit and interrupt power to the driving means when the rotor undergoes excessive oscillations. The rotor 10 is drivingly connected by interengaging pins 16, 17 to a shaft 12 journalled in a mounting 13 and driven through gearing 52 by a variable speed electric motor 51. The rotor may be enclosed within a refrigerated liner 18 of a vacuum chamber 19. A resilient vacuum sealing member 22 expanded by a spring 23 extends between the chamber 19 and the mounting 13. The switch means 40 may include a movable pin 41 which normally presses against a U-shaped spring metal strip 42 which is in contact with a terminal bolt 48. The actuating means 20 may comprise a tubular housing 21 threadably secured in a radial bore in the rotor and an an adjustable set screw 25 threadably secured to the outer end of the housing and adapted to trip the pin 41 and open the control circuit associated with a magnetic starter 53 for the motor 51 to de-energize the latter when the rotor undergoes excessive vibrations. The set screw 25 may include a cylindrical bore in which a pin is located and is caused to break under shear forces upon the rotor exceeding a predetermined speed and to travel along the bore to engage the pin 41 and interrupt power to the drive motor 51. In a modification, Fig. 4 (not shown), the switching means consists of a turret assembly which may be indexed four times before requiring replacement of snap wires associated therewith and adapted to be snapped by the set screw 25. Reference has been directed by the comptroller to Specification 903,209.