Gear Changing Made Easy.
Page 5
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Within the past week our attention has been directed to a 'simple and compact form of change-speed gearbox, the invention of Mr. F. A. Oddie, of 13, Essendene Road, Maida Vale, and we illustrate the device herewith by means of two line drawings. An examination of thee views will show that Mr. Oddie's gearbox may be adapted for almost any purpose that demands the provision of a number of changes of gear ratio, any one of which is required to be brought into operation without noise or shock. For motor vehicles or machine tools it is equally suitable, and an experimental gearbox has been tested with very satisfactory results while under load from a 30 h.p. electric motor.
It is not suggested that, in this gen t•box, as here illustrated, finality of design has been attained, hut, on account of its simplicity and the feet that it has been carried beyond the " paper stage, it should commend itself to the consideration of anyone who may be searching for a new form of gearbox. Tf well made, this gearbox should he very silent in operation, as its shafts are exceptionally short and of unusually-large diameter. The box illustrated shows three sets of change-speed gears, all for running in the same direction, but provision may be made for any number of speeds.
The three driving pinions are securely keyed to the .main shaft, and they mesh with three gear wheels (A, B and C), each of which is independently and freely mounted on the layshaft (D). The layshaft, it will be noted, is of tubular formation, and holes are drilled through it at diametrically-opposite points, at a right angle to the axis of the shaft, in order to admit the clutch plungers
(El) liv which the clutch shoes are applied. The outer ends of the plungers are forked, and to each of then' is hinged is sector (E), whose periphery is turned to a radius which is greater than the distance from the periphery to the centre of the pin on • which the sector is hinged. As a matter of fact, the radius is struck from a point midway between the sector pivot pin and the centre of the lay shaft (D).
In order to increase the bearing surface. and to obviate the possibility of damage to the internal surfaces of the clutch drums—the latter, by the way, form integral parts of the gear rings, the loose cast-iron shoes (E2) are provided, the only driving connection between these gimes and their respective sectors being the transverse bars that are east solid with the shoes, and between which bars the sectors are made to register. In order to pre vent any one pair' of shoes from being thrown outwards by centrifugal force, and engaging with a drum when not required, a pair of helical springs (R) of suitable resistance is provided. One pair each of plungers, sectors, shoes and springs are necessary for
each change of gear ratio, and each of these sets of clutch units may be brought into operation independently by means of a double-ended turned wedge (C), which may be given an endwise movement within the tunnel of the layshaft (D) by means of a rod (F) and a change-speed lever.
When it is desired to render operative a particular pair of gears, the turned wedge piece (C) is caused to move along the bore of the hollow shaft (D) until it engages with the inner ends of the required pair of plungers (El); the plungers are forced outwards by means of the wedge piece, and the movement is transmitted to the sectors (E). The result of this outward movement is that the periphery of each sector is forced against its respective clutch shoe, and the latter is forced into engagement with the clutch drum. The sector then has a tendency to cant over in the direction of rotation to that in which the wheel is being driven round, by reason of the wheel's engagement with its respective pinion on the driving shaft ; this canting of the sector has the effect of jamming the shoe into closer frictional contact. with the surface of the clutch drum. • Immediately the turned wedge piece is moved out of engagement with the plungers, the shoes (El) are withdrawn from contact with the clutch drum, and the sectors (F) resume their disengaged positions.