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With Intent to Improve.

15th February 1917
Page 22
Page 22, 15th February 1917 — With Intent to Improve.
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Which of the following most accurately describes the problem?

A Weekly Summary of Recent Patents, of Interest to the Maker and User of Commercial Motor Vehicles.

Selected and Abridged by H. S. Hall, A.M.I.A.E.

Sparking Plug Construction.

One would think, in such a small item as a sparking plug, and also considering its importinCe, that finality would by now have been readied. As a matter of fact, a week seldom goes by without a record appearing of some effort to improve upon this small but significant part of the anatomy of a petrol engine. Specification No. 103,179, of 1916, which forms the subject of one of our illustrations this week, is a patent of Crosbee and .Sons, Ltd., Apollo ,Works, Moseley Street, Birmingham, and another. It is in the main an improvement on a design previously patented by the same company, and the intention is, in the main, to provide a sparking plug of simple design which nevertheless lends itself readily to being dismantled for cleaning purposes.' '

The previous specification (No. 4808, of 1915) describes a method of utilizing pulverized mica for insulation purposes. Tho present" one incorporates the same principle in a plug which is in. two parts ; an'outer one • which screws into the cylinder, and which is screwed internally to receive the other .portion; the latter is the plug proper, and carries the central electrode" and the whole of the insulation. % It is in fact, a plug within a plug. The formation of. the is,

part is very similar to that of a screwed packing-box ; the joint between the two is made by means of a copper-andasbestos washer. Reference to our illustration will supple'. ment the text almost to completion, but, it may be as well to state that the layers of material round tho central electrode are : a wrapping of sheet mica, mica washer,pulverized mica, and, _finally, mica washers. with the metal carrier of the inner portion of the plug carried between.

A portion 'of the specification concerns the method of assembly.' The principal, claim is for a plug made' in two parts, one of Which carries the central electrode and is scsewed into the other. Reference is also made to the previous specification.

Strengthening Silent Chains.

. A weakness of silent chains as heretofore manufactured, in that they were liable to breakdown .under shocks or sudclenly-aprolied stresses, was due to the shape of the links, unavoidable in view of the purpose for which they were made,

which was not one that was favourable to the withstanding of such stresses. To overcome this difficulty it has been hitherto found necessary to leave the_linke soft in the main parts, hardening them only 'on the teeth. They Alex° bushed -in the eyes so that the wearing surface on the rivets mild be hardened. This construction, besides' causing difficulties in the heat-treatingprocesses also added'con.siderably to the weight for a. given strengths of chain.. Further, in the event of one link being somewhat short in pitch; the effect was to throw the whole load on to that link, with the risk of breakdown.

Specification No. 103,247, of 1916, by' A. E.Carter and Hans Renold,•Ltd., of Burnage Works, Didsbury, Manchester, describes an improvement in the construction of chains of this type whereby the objections enumerated above are overcome. The innovation consists of the Addition, to th., chain, of reinforcing links, which do!not bear upon the teeth of the sprocket wheel, their duty being that of .transmi.tting the Major part of the transmission load, in this way relieving the chain links proper of most of the stresses which they ordinarily bear. Owing to the fact that these links .do -ncit require to mesh with the wheel teeth, they can be made substantially different in form to the chain links, and this property has been taken advantage of in order to-afford the de: sired additional strength: Reference to our illustration will show the form adopted, and it, will be seen that the aOhshaped gap, necessary in the standard links, is avoided in the reinforcing links, which are nearly rectangular. in shape. Owing to this accession of metal in the Cross-section, these links can be made thinner than the ordinary links.'

The additional strength afforded by the adoption of this constructi,in is such that all the links, of both kinds, maybe hardened,' thus dispensing with the need for bushes, allowing of larger-sized rivets for a given pitch of chain, and ,provid. in increased bearing surface. La consequence a reduction in width can be made, the chain is lighter and .ai the noise made by ouch a chain is in proportion to its weight, a nearer approach to silence is possible.

• A Magneto Coupling. '

The manufacturing firm of Saurer, of Arbon, Switzerland, discloses in specification No. 100,005, a new design of coupling for driving a mageeto. For purposes of accessibility, this component is always arranged so that, by the uncoupling Of one hole or strap holding the magneto in place, it can be immediately lifted clear of the engine. This necessitates a loose coupling Which must have; therefore, a small amount of clearance between its driving and driven portions. This 'clearance would not matter if the resistance to driving was fairly Constant, so that there was no likelihood of the driven, portion trying to over-run the driving part. With a magneto this favourable condition does not hold, and couplings of this type have in the past been subject to rattle and rapid Wear.

The subject of this invention is an anti-rattle jaw coupling. It is shown on the drawing which we reproduce, and in its simplest form, with one projecting tongue on one shaft engaging with a corresponding slot or jaw in the other. • One face of the jaw is bored to receive a spring and steel.ball.' The spring is of such tension normally that it causes the ball to press upon the tongue portion of the coupling with, a force greater than the tendency of the magneto to over-rim; this

prevents back-lash and tendency to rapid-wear. • •

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Locations: Birmingham, Manchester, Arbon

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