A New Balanced Full-drop Window
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FOLLOWING the success of its P.Y.P. winding half-drop window for buses and coaches, Rawlings Manufacturing Co., Ltd., Larch Road, Balham, London, SW. 12, has now developed a winding full-drop window. Designated the P.Y.P. Full-drop, the design is based upon that of the halfdrop pattern, and, in adapting the mechanism to a full-drop window, a number of important features has been incorporated. •
Of primary importance is the fact that the entire winding mechanism is carried on top of the waist rail, so that maintenance is simplified. Moreover. by removing the fillets, the window can be wound right out of its frame without in any ' way disturbing the mechanism. A broken window can, therefore, be quickly replaced. To return the window to its frame, all that is necessary is to rest it on the pinions and wind it back into position.
The winding mechanism comprises a worm gear which rotates a shaft having on each end a pinion that engages with racks formed on the vertical frames of the window. The winding handle is situated in a central position on the waist rail; it can, however, be offset if desired.
Surrounding the driving shaft is a coil spring, the characteristics of which are calculated to suit the size of window, and this is attached at one end to the shaft and at the other to a boss on the worm-box casing.
Reference to the accompanying illustration will show that the spring main
tains a constant balance. In consequence, it renders unnecessary the use of a large worm and wheel, the load on the winding mechanism being greatly reduced. Within the winding handle is contained a spring-loaded dog clutch which prevents damage o4turring from accidental overwinding in either direction.
The operating shaft is carried in two bushed brackets and oil-saturated felts are provided on each of the brackets; thus the maintenance operations are reduced to the minimum. Care has been taken to make simple the work of fitting the window and the angle forming the rack carries a distance bracket into which the shaft and pinion fit. It acts, therefore, as a template and ensures correct meshing between the pinion and rack. A pointed boss is also. incorporated in the top face of the worm-gear casing and on the bearing caps, so that the fillet can be correctly marked for the screw positions. To prevent rattle, phosphor-bronze spring bearing blocks are provided behind the runner.
The absence of any mechanism below the waist rail is a big advantage, for every working part is easily accessible without removing upholstery, seats, etc. We were impressed with the easy action of the mechanism, the balance being so arranged that the window could be raised or lowered by the application of one finger to the operating handle.
Moreover, a careful inspection of the components showed them to be sturdily built, so that the easy operation should be maintained over long periods without attention. The design lends itself admirably to windows with sloping pillars.