Patent GB-1093480-A (GB)
Title: Direct driving mechanism for an ultracentrifuge
IPC: B04B9/04
Filed: 1966-07-15
Abstract: 1,093,480. Driving and supporting ultracentrifuges. CANAL INDUSTRIAL CORPORATION. July 15, 1966 [Aug. 17, 1965], No.31857/66. Heading B2P. [Also in Division F2] In an ultracentrifuge for effecting sedimentation of solids in liquids, the drive shaft 10 connected to the centrifuge head 29 is directly driven by means of a synchronous electric motor comprising a cylindrical rotor 11 of high coercivity magnetic material (e.g. a ferro-cobalt alloy) integral with the shaft 10 and surrounded by a stator 12 supplied with alternating current from a high-frequency source 13, the shaft 10 being mounted in alignment bearings 15, 16 and a compressed-air thrust bearing 34 being provided below the rotor and constituting the sole vertical support for the rotor and the centrifuge head during normal operation of the centrifuge. The bearings 15, 16 are of the forced-lubrication type and are resiliently supported by polychloroprene O- rings 25, 26. The bearing 15 also serves as a seal when the centrifuge head is operated in a vacuum. Forced ventilation of the motor is provided by air passing from an inlet duct 27 through bores 11 a in the rotor 11 and leaving through an outlet duct (28), Fig. 2 (not shown). The thrust bearing 34 includes a plate 33 secured to the rotor 11 and spaced from a stationary (seat 33a having. an upturned lip and a depending annular flange 33b which cooperates with a ring 36 of vibration-damping material, e.g. cork, enclosed by a shell 35. High pressure compressed air is supplied to the annular space between the plate 33 and the seat 33a through an inlet (37), a duct (38) and an opening (38a) in a bearing cap 38b. An auxiliary, normally inactive, thrust bearing, which comes into operation should the air supply to bearing 34 fail, or when the centrifuge is at rest before the start of an operation, comprises a single bearing ball 42 seated in the upper face of a thrust block 39 supported from a post 40 by means of a thrust ball bearing 41. The post 40 extends into an air pressure chamber 43 communicating with a compressed air inlet (37) through a duct (38), Fig. 2 (not shown). A spring-biased bellows 44 in the chamber 43 is secured to the post 40 and is responsive to a predetermined low value of compressed air for fringing the auxiliary thrust bearing into action and for causing the low recessed end 47 of the post 40 to engage an actuating element 48 for switches 14, 14a. At the start of a centrifuging operation, compressed air is supplied to the thrust bearing 34 to lift the plate 33 and the connected rotor 11 and centrifuge head 29 from the seat 33a. At the same time the compressed air in chamber 43 acts on the bellows 44 causing it to move the post 40 downwards thereby lowering the auxiliary bearings 39, 41, 42 to an inactive position. At the same time, switch 14 is actuated to close the circuit between the source 13 and the motor 11, 12 which is then started upon closing of a switch 9. Should air pressure to the bearing 34 fall to an unsafe value, the bellows 44 will force the part 40 upwards to bring the auxiliary bearing 39, 41, 42 into action. At the same time switch 14 is opened and cuts off the driving power and switch 14a is closed to apply direct current from terminals 49 to the stator 12 to brake the centrifuge. If desired, the stator 12, after deenergization by opening switch 9, may be re-energized from the direct current terminals 49 through a manual switch 50 and an adjustable resistor 51 by means of which the centrifuge may be braked smoothly to a stop.