AN ENDEAVOUR TO SECURE SILENT GEARING.
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A Résumé of Recently Published Patent Specifications.
HAD the specification No. 284,955 not borne the wellknown name of Panhard and Levassor we should have hardly thought it worth while to mention it and, had no mention been made of its suitability for use in the gearboxes of motor vehicles, we should have considered it unsuitable for that purpose on account of the necessarily great width of the gearwheels.
As the specification is an unusually short one we give it in
its entirety. We notice, however, that no mention is made of how the great end-thrust, which is inseparable from the use of such gears, is to be dealt with :—
, The present invention relates ' to helical gearing and chiefly to gearing employed in change-speed devices for motor
vehicles. In such gearing the miurger of. teeth is always Considerable, by reason of the use of the standard fates of teeth in wkich the thickness of the teeth depends uponthe pitch employed.
Such teeth are of a noisy. character, the noise being produced by the contact between the teeth, and hence the noise becomes greater as the, number of teeth is larger, so that it is desirable, employ gearing which has the minimum number of eeth.' . However, with the use of the known method by which the height of the teeth'is made greater than the thickness, there is no room left in the hub to allow the gearing to be mounted on the shaft.
The present invention obviates all such defects, and one ii
enabled to construct gearing which comprises a very small number of teeth, for instance, three, whilst leaving as much material at the centre as in the known forms of gearing.
Li „the said invention the ' teeth are of the usual kind, but a certain number of them, and the corresponding recesses, are combined-in one, thus forming teeth and recesses of equal size the thickness of which depends upon the number of teeth which is thus combined in one.• This arrangement may be carried out with helical gearing by selecting the width of the
gearing in such manner that one tooth will always be in engagement, -that is, say, notwithstanding its unusually small height in proportion to its degree of thickness. A
In the drawings which are given by way of example, Fig. 1 shows the form of a wheel with three normal teeth (a), and it is observed that there is too little material left at the central part (b) to allow it to be mounted on a shaft. Fig. 2 shows in dotted lines a wheel with 15 teeth (c), and in the full lines, an example of a grouping of teeth (d) so as to form a three-teeth wheel. Fig. 3 is a cross-section of the said three-teeth wheel. ,Figs. 4 and 5 show respectively. in •side elevation audio perspectite a pair of wheels consisting of a three-teeth wheel (e) and a five-teeth wheel (f) provided with teeth according to the specification of the invention.