Patent GB-1023670-A (GB)
Title: A device for compensating unbalance in rotatable bodies
IPC: G01M1/22
Filed: 1962-12-06
Abstract: 1,023,670. Grinding; balancing by machinery. W. & T. AVERY Ltd. Dec. 6, 1962 [Dec. 14, 1961], No. 46070/62. Headings B3B, B3C, B3D and B3K. [Also in Division G1] A device for compensating unbalance in rotatable bodies in which unbalance compensation can only be carried out at specific compensation points symmetrically distributed around the body has at least two machining tools which are simultaneously drivable and are so adjustable together relative to the body, or are so adjustable relative to one another, in dependence on the observed angular position of the unbalance in relation to the compensation points, that to correctly locate the unbalance compensation on the body they in general each remove the same or a different amount of material from the body at a corresponding compensation point. A device, Fig. 1 (not shown), for correcting unbalance in an electrical rotor 8, e.g. a motor armature having windings disposed in grooves between the rotor teeth, comprises a table 4 in which the rotor 8 is supported. The table 4 is supported on the bed 1 by rollers 2, 3 so that it is rotatably adjustable about a point 11; the table carries a side 9 and the bed or index mark 10. Grinding discs 14, 15 milling cutters or similar rotary cutters are secured to the shaft of a motor 17 attached to a tool holder 18 rotatable about a bolt 19 by a handle 20. The tool holder carries a scale 22 and the bolt an index mark 21 for indicating the depth of cut. In use the table 4 is adjusted in accordance with the reading on the dial of a vector meter upon which unbalance is indicated in a dynamic balance machine, the dial having divisions corresponding to the scale 9; this adjustment determines how much material is removed from the teeth 12, 13 of the rotor, by the cutters 14, 15. The adjustment of the table 4 may be effected by the handle 2D. In an alternative mode of use, the table 4 is fixed and the bolt 19 is moved along the curve 23 having its centre at 11. In another device, Fig. 3 (not shown), material is removed from the mid-points of the teeth 12, 13 of the armature 8 by drills 33, 34 or the like, the shafts 40, 41 of which are driven by a motor. The drills are rotatably mounted in cylinders 35, 36 axially movable in a housing 42. Racks 37, 38 on the cylinders mesh with a pinion 39 connected to a disc 44 and operated manually or automatically by a lever 48. The disc 44 has a scale 45 and the housing 42 has an index 46. The housing 42, which has an index 49, is displaceable towards the work on a base 51, which has a scale 50. The body may be tested in a dynamic balancing machine, the unbalance being measured by a vector meter 60, Fig. 4 (not shown), comprising an instrument 60a, having fixed field coil 62a and rotary coil 64a and an instrument 60b having fixed field coil 62b and rotary coil 64b. During measurement the field coils are connected with a phase indicator having a rotor rotating in synchronism with the body to provide reference alternating voltages with a mutual phase relationship of 90 degrees; the rotary coils are connected with two windings of the moving coil of a transducer providing signals corresponding to the vibrations of the body due to its unbalance. The rotary coils are held, by coils 61a, 61b, in their positions indicating the components of unbalance; the body is placed in the compensation device in the same position as it was in the dynamic balance machine. The field coils are now fed with alternating voltages embodying the same phase difference as those from the phase generator; the rotary coils 64a, 64b are connected respectively with windings 66, 68 in the rotor of a rotary transformer 67, the windings being disposed at right angles to each other. The stator of the rotary transformer 67 has windings 71, 72 at right angles to each other. .Winding 71 is connected with a device 95 to indicate zero position so that when the body is set in the zero position, i.e. the unbalance is in the machining position, a motor 73 is disconnected by a switch 96. The motor shaft 74 carries the rotor 69 of the rotary transformer, a gear 75 and a coupling 77 connected through shaft 78 with means 79 for rotating the body. The gear 75 meshes with a gear 81, the ratio of the gearing being the reciprocal of the number of teeth on the body; the gear 81 operates the lever 48 to set the drills 33,34. Precise positioning of the body relation to the drills is effected by pressing a roller 86 against a part 80 mounted on the shaft 78 and having as many teeth as the body. The signal induced in the winding 72 indicates the depth to be drilled; drilling may be automatically discontinued after the required depth has been drilled.