A Change-speed Unit Without Gearwheels
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V -pulleys and Belt Drive Used in New Form of Variable-speed Transmission Device THERE have been many forms 01 variable-speed device_ in which belts and pulleys have been used , to 'eliminate the more customary gearwheels. The most recent of these is the N. and B., which is• shown in an accompanying illustration. As will be seen, the unit is small and compact, -the . actual dimensions being 21i ins. by 10i• ins. by 8 ins. This invention is claimed to provide the solution of the short-centre belt-drive problem, combined with a system for giving a range of six speeds, the change being carried out by moving the change-speed, lever.
There are two sets of V-pulleys, each formed as an integral unit, arranged one above the other, within a suitable supporting structure. The pulleys differ from the usual type in having transverse inter-connecting grooves formed in the pulley faces, so that, when the belt is pushed sideways in either direction. it slides through the transverse grooves, from one pulley to another. The respective diameters of the engaging pulleys are such as to maintain belt tension on all speeds, although there is a spring! loaded jockey pulley provided in the, design,
A change of gear,is carried out by moving the handle shown on top of the unit, This, in its turn, moves a guide plate assembly through the acrency of a chain running over a sprocket and guide pulleys,;,
The normal arrangement is for the driving, or input shaft, to he at the bottom, and at 1,000 r.p.m. the top shaft can be arranged to give variations of 2,000, 1,538, 1,129, 886, 750 and 500 r.p.m. This is the arrangement with the six-step unit under discussion, but different pulley assemblies could be arranged to give any range of speedi deSired.
All moving parts are carried on ball bearings, so that there should be little trduble irons the lubrication aspect. Two features worthy of mention in connection with this device are that it is quiet in action and, in the case of the piece of machinery being driven coming to an involuntary stop as the result of a dig in or obstruction, belt slip would be experiented—a distinct advantage as compared with any form of positive drive.
The model shown covers power transmission from hp, to 2 h.p., and we understand that other sizes are to be made available up' to 7 h.p. The N. and B. change-speed evice has been put on the market by the Newey Engineering Co., Ltd., Brook Street. Nottingham.