Patent GB-409501-A (GB)
Title: Electro magnetic gears
IPC: H02K51/00
Filed: 1933-04-05
Abstract: 409,501. Systems for transmitting mechanical power. CLEAVER, W. F., 701, Notre Dame Street, West, Montreal, Canada. April 5, 1933, No. 10168. [Class 38 (iv).] An electromagnetic device for transmitting mechanical power particularly applicable to motor vehicles comprises an inner armature unit A fixed to a driving shaft D, an outer rotor unit C coupled to the load shaft at E<1> and rotatably mounted on the shaft D, and an intermediate unit B in inductive relation with both inner and outer units and releasably clutched to the outer unit, provision being made whereby in the event of the torque exceeding a predetermined amount the intermediate unit is automatically released and the drive is then transmitted through two stages of electromagnetic coupling. The inner unit has a ring or drum winding 8 associated with a commutator 10 at one end and slip rings 11 at the other end. The intermediate unit has an inner field winding 24 co-operating with the winding on the inner unit, and an outer 3-phase winding 25 connected to three brushes 28 adapted to co-operate with the slip rings 11. The outer unit has a short circuited squirrel cage winding 43 co-operating with the field set up by the 3-phase winding on the intermediate unit. The latter is provided with a clutch element 18 and is urged in an axial direction by a spring 23 so as normally to be clutched to the outer unit. Under conditions of heavy torque, however, the coupling E1, which is connected with the outer unit C through springs 62 becomes angularly displaced with respect to the unit C and by reason of cam elements on its inner face causes axial movement of a member E which through thrust pins 72 displaces the intermediate unit to free it from the outer unit. To enable the device to be used for engine starting when applied to motor vehicles, provision is made for maintaining the intermediate unit stationary such provision comprising (1) bars 85 pivoted to the end plate of the outer unit and adapted on energization of a coil 84 to engage notched plates 39, 86 on the intermediate and outer units respectively, and (2) a pivoted lever R adapted on energization of a coil 104 to engage a notched ring 103 on the outer unit. Connections from the brushes 31 associated with armature winding on the inner unit and from the field winding on the intermediate unit are brought out through brushes 35, 36 and slip rings 56, 57 to a further set of slip rings 90-94 on the outer face of the outer unit. Connections from the coil 84 are also brought to these slip rings which co-operate with brushes a-e associated with a battery and with a control circuit, Fig. 13 (not shown). In operation, starting is effected by closing a starter switch which operates on the control circuit in such manner as to cause connections to be established as indicated in Fig. 9, i.e. the armature and field windings 8, 24 and the coil 84 controlling the locking bars 85 are connected in series across the battery circuit 115. The coil 104 controlling the locking lever R is also energized so that the intermediate unit is restrained and the inner unit is rotated to start the engine. The starter switch is then opened and a control switch is operated to cause the control circuit to establish the connections indicated in Fig. 10, i.e. the armature and field windings 8, 24 are connected in parallel to the battery circuit 115, and the coils 84 and 104 are de-energized to free the intermediate and outer units. Under this condition the armature being driven by the engine feeds current to the battery circuit 115 and imparts rotation to the intermediate unit. Up to a predetermined torque, the latter carries with it the outer unit through the clutch coupling 18, 51, and beyond that torque the clutch is decoupled as previously described and at the same time due to axial displacement of the intermediate unit the brushes 28 are brought into engagement with the slip rings 11 so that slip current from the armature 8 is fed to the 3-phase winding 25 on the intermediate unit. Thus a field is produced which cooperates with the squirrel cage winding 43 on the outer unit and torque is then transmitted electromagnetically from the intermediate unit to the outer unit. Braking is effected by a further setting of the control circuit which establishes connections as indicated in Fig. 11, i.e. the armature and field windings 8, 24 are again connected in series across the battery circuit but in such manner that regenerative current due to armature over-run is fed to the battery, the locking coils 84, 104 being deenergized.