Patent GB-974224-A (GB)
Title: Improvements relating to rotary machines incorporating electrical brush devices
IPC: H02K31/04
Filed: 1960-02-05
Abstract: 974,224. Couplings between relatively movable conducting parts; dynamo-electric machines. J. SAYERS. Feb. 3, 1961 [Feb. 5, 1960], No. 4098/60. Headings H2A and H2E. In a rotary machine incorporating a plurality of liquid brush devices, two or more brush devices are connected with each other by a passageway to form a circuit along which the conductive liquid travels such that each brush device has a sufficient quantity of liquid during operation of the machine. Fig. 1 shows one embodiment incorporated in a torque transmission device which operates as described in Specification 927,394. The device comprises two homopolar machines with a common stator structure 18, completion of the electrical circuit 29 between the relatively rotatable armature parts 23, 24 of input rotor 21 and output rotor 22 respectively and the associated parts of the stator structure being effected by outer brush devices 32, 33 and inner brush device 34. The conductive liquid circulates from brush device 32 to the brush 34 via a bore 71 through the stator plate 10, an external tube 72, bore 73 and one or more bores 74 through the rotor 21, returning to the brush device 33 via bore 76. The brush devices 32 and 33 are connected by bore 77. The outer brushes 32, 33, each include outer and inner copper conductor members, the inner members being united to the armature parts 23, 24. The inner brush 34, Fig. 2, comprises outer copper conductor member 35 and inner copper conductor member 36, united to armature parts 23, 24, respectively, the conductive liquid e.g. mercury being retained therein against centrifugal force during operation of the machine by the surrounding structure in combination with a retaining ring 39 in chamber 47. The ring is held in position by a screw ring 46 co-operating with a flange 46a of member 35 and is thus loosely disposed in the chamber, the side walls 48 of which diverge in the same direction as the sides of the ring. During operation, the mercury in the gap 37 urges face 49 of the ring 39 into contact with sealing face 50 of the other member 36, thus damming the mercury in the gap. The ring 39 may be of synthetic rubber or may be a split metallic ring. In a further embodiment, Fig. 4, the ring 55 is of disclike form having a frusto-conical inner part 63 which engages a sealing face 66 on the inner conductor member 51. The outer part of ring 55 is clamped between a ring 67 and the outer conductor member 52. During operation of the machine mercury in the gap 60 presses ring 55 further into contact with sealing face 66, the ring being of synthetic rubber or flexible plastics material. The sealing ring forms the subject of Specification 974,222. Parts of the machine which come into contact with the mercury, other than the conductor members, have a nickel barrier layer with an extra layer of metal unreactive with mercury, e.g. chromium. The current communicating members have a nickel layer as described in Specification 927,395, with an outer layer of rhodium. Palladium or another metal of Group VIII of the Periodic Table (except rhodium) is used as a " wetting agent," and may be plated on the rhodium layer or alternatively brought into contact with the mercury before its enclosure in the machine or during its circulation such that a certain amount of palladium is dissolved. The provision of the rhodium layer forms the subject of Specification 974,221. A chamber 81 may be provided on the stator plate 11, the said chamber containing a dehumidifying substance and communicating with the interior space of the machine by two ducts 82, 83 extending through plate 11. The pressure difference between these ducts, due to the entrainment of air or gas adjacent to the face of the rotor 22 presented towards these ducts, causes the gas to circulate into chamber 81 via duct 83 and out therefrom via duct 82. Extension 82a of duct 82 then communicates with space 78 between rotors 21, 22. The dehumidifying substance may be silica gel or anhydrous phosphorous pentoxide which may be in the form of capsules. Also chamber 81 may contain a substance such as finely divided copper which absorbs oxygen, the copper being heated by an electrical resistor (not shown) and being contained in a porous container. The interior space of the machine may be pressurized to inhibit leakage of damp air into the machine. The dehumidifying chamber forms the subject of Specification 974,223. The mercury may be cooled by way of annular chambers 84, 85 which communicate via holes 86, 87 with inlet and outlet headers 88 connected to a cooling fluid such as air or water, the chambers having flanges 89, 90 ribbed to promote extensive thermal communication between themselves and the cooling fluid. The stator structure 18 may include inwardly radially extending bores for the cooling fluid. In an alternative construction of machine (Fig. 3, not shown) the rotors are of substantially cylindrical form instead of being L-shape in cross-section, and the passageway system along which mercury can circulate from brush device 32 to the brush 34 and thence back to the brush device 33 is formed wholly by bores in the stator plates and passageways defined between stator and rotors, instead of employing an external tube. Also the passageway 82a is inclined the opposite way to encourage mercury to enter the inlet to the brush device rather than the passageway 82a.