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172 
A NEW TOOTH FORM.
Page 130
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A Resume of Recently Published Patent Specifications.
"Cl RNEST WILDHABER, of New
ai r York, in specification No. 266,163, shows a departure from the ordinary form of tooth for gearing. The claims made for this form of tooth are that gears of this kind can withstand greater pressure without undue wear, that when wear does take place it is more evenly distributed than with ordinary, teeth, that such teeth retain their initial form longer, that they run with less possibility of noise, that they transmit true uniform motion, and that oil can be better retained between the contacting teeth under heavy pressure owing to th'e much larger surfaces in contact enabling a thicker film of lubricant. to be maintained.
The upper view shows a pair of gears with teeth of the kind described, and it will be seen that the actual tooth which is in a line drawn from axis to axis does not engage, but that those on each side of it have a much larger surface in contact than would be possible with the usual tooth form. The lower view is
• that of a rack meshing with a gear wheel, and on the left will be seen the relative positions of the teeth as the rack travels along. At first a tapering film of lubricant is present between the teeth, but in the second position this film becomes a parallel one, affording a bearing between the teeth of approximately the whole length of the teeth. In the third and fourth positions shown the film becomes of a tapering form again.
The specification claims that the form of tooth shown is mathematically correct, and that the plan can be applied to bevel gears of the usual type where the axes intersect, also with non-intersecting axes. The invention is particularly described as being applicable to helical and herringbone gears, and no mention is made of its application to worm gearing, where it would appear to be most suitable.
Anti-glare Goggles.
IN SPECIFICATION No. 266,245, Francis Henry le Sueur, of Cape Town, describes a means whereby a driver can reduce the daezling effect of bright lights that may be on art approaching car. The invention consists of special goggles of plain glass, but with a small patch of suitably coloured glass attached to, or formed in one with, each lens as shown, so that a light filter is provided, •fer the driver can, by slightly moving his head sideways and
bending forward, bring the coloured patches opposite the offending lights, and still retain a clear view of all other parts of the road. The patches of light filter are described as being on the right as seen by the driver, but the illustration shows them as being on the left. This is not important however, as they would have to be on the left for countries where the rule of the road is the reverse to that existing here. No mention of any particular kind of light filter is made in the specification.
An Aid to Electric Starters.
ANY DEVICE which will aid the
• starting of heavy commercial vehicles should be of interest to the industry, as, owing to the fact that such vehicles often have to stand out all night in all .sorts of weather, the difficulty of starting for the first time in the morning so often causes delay. The starting of a heavyvehicle entirely by means of an electric starter is a great strain on a battery, and the present invention would seem to afford a means whereby such strain could We greatly relieved and a lighter electrical equipment might be permissible.
The specification of Thomas Latham Porter and Clarence Stanley Jones, No. 264,934, describes a combined crank and 'electric starter. The invention consiete of means whereby the starter switch can be operated from a position
convenient for cranking an, engine. Various methods are described, such as a double electric switch, but the one selected for illustration is merely a Bowden wire, which operates the usual starting switch and is under the control of the person who is helping it by cranking the engine. We take it that, after comPartititelY short stops, the electric starter would be able. to do its work unaided and that the device is intended more far the first start after a long period of rest.
An Effort to Improve the Piston Ring.
THE PISTON ring, as generally fitted, is by no means a perfect device, and all who have had experience in examin ing engines that have been taken to pieces after long periods of work, will see that there is evidence of the.passage of gas between the piston and the rings.
Page Madsen, of Goteborg, Sweden, in his specifications Nos. 266,173 and 259,521, describes a piston ring which is so designed that when the groove in which it fits wears too wide for the ring, such wear can be compensated for by the fitting of a new packing ring.
It will be seen that the ring proper lies in the groove above two rings which serve merely as packing or distance pieces, which do not beer against the
walls of the cylinder. The distance pieces are both made in halves so that they can easily be introduced into the groove, and various means, are described for holding them in place. Being 'of a harder metal than aluminium, they can better resist wear than the light alloy of which the piston is composed. We do not by any means consider the plan shown here to be the last word in piston-ring design, but it may be taken as a sign that attention is being given to this somewhat neglected point in engine design. Rings, that automatically compensate for sideways wear have been described in The Commercial Motor on many occasions, and some of these we consider to be more practical than the present invention.
IK
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266 173
Novelty in Engine Design. FRANCIS DE LATITOUR, of Welling
ton, New Zealand, in his specification No. 266,144, describes an engine of the type in whin the charge is drawn into the cylinder during only part of the outward stroke, and is then attenuated by the continued movement of the piston, so that the pressure at which the exhaust is allowed to escape is reduced to nearly that of the atmosphere. The specification points out that in this class of engine it has been found that the attenuation of the mixture has resulted in a cooling of the charge, and the present invention provides a means whereby the charge is'brought into more intimate contact with the walls of the cylinder and so is enabled better to absorb heat therefrom. A pocket is formed near the inlet valve and this guides the incoming charge into the cylinder in a tangential direction, which produces a rotary movement of the charge, de indicated by the dotted lines and arrow in the diagrams.