The Latest C.A.V.-Bosch Starter
Page 45
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ARECENT introduction. of C.A.V.-Bosch, Ltd., of Acton, London, W.3, consists of a new starter of the axial type. This designation is applied because the armature with its shaft is free to move endwise into engagement with the teeth on the flywheel rim. The general .construction can be gathered iirom the partly sectioned view which we reproduce.
Inside the shaft, at the commutator end, is a spring; this normally keeps the armature out of complete register -with the pole shoes, and the pinion away from the flywheel.
The field winding of this machine is divided into the main series winding, the auxiliary series winding and a shunt winding. When the starter switch is operated a small current passes through the shunt and auxiliary windings, causing the armature to commence slowly to rotate. Simultaneously, the magnetic field set up pulls the armature forwards, which brings the pinion gently into mesh with the flywheel teeth. This movement of the armature also causes the tripping disc to operate the tripping lever, attached to the contacts of a solenoid switch, which completes the main circuit. The full current from the battery then flows through the armature and series winding and the motor exerts its full torque on the engine. Directly the engine gets under way the motor current is greatly reduced, the magnetic field is decreased in power, the tension of the spring overcomes the force exerted by the magnetic field and the pinion automatically disengages. An important feature of the C.A.V.-Bosdb axial starter is that even by keeping the starter switch pressed, the starter will not again engage with the teeth on the flywheel rim. It will continue to run free, however, but will come to rest immediately the switch is released.
'Another special feature of this starter is a unique over
ver
load device, preventing damage occurring due to an engine backfire. This device is a positive safeguard against the teeth of the pinion being sheared due to excessive load.
One other feature worthy of note is that the pinion is made of a phosphor-bronze alloy, which allows the wear tot take place on the pinion in preference to the teeth on the flywheel rim.