US1175687A - Cam. - Google Patents

Description

v m zfzze's M. BIRKIGT.

CAM.

APPLICATION FILED JUNE 21, ms.

1, 1 175,? Patented Mar. 14,1916.

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MARC-BIRKIGT, 0F BOIS-COLOMBES, FRANCE.

CAM.

Specification of Letters Patent.

Patented Mar. 14, 1916.

Application filed June 21, 1915. Serial No. 35,384.

is a specification.

This-invention relates to cams such as are used for operating the valves of explosion engines.

The invention has for its object to enable cams to be built so that they should be free from the serious defect which it was impossible to avoid up to now, of suddenly engaging with the part to be driven, and of releasing it in an equally sudden-manner, which is a source of noise. This defect occurred owing to the fact that the boss or projection of the said parts was connected tangentially to their circular operative surface, while the track was given a smallerdiameter than that given by calculation for the purpose of providing play in order to enable the part to be driven to return 1n a reliable manner to its position of rest. From this it followed that the boss of said parts struck and released'the part to be driven with'one of its points, more or less distant from. its point of contact and the more heavily the greater the speed.

The invention consists, in making cams exactly as determined by calculation without taking the play into account, then the circular portion is subsequently machined so as to reduce its diameter by a given quantity; and then the new operative surface thus produced is connectd to the boss by a rounded off portion constltutlng a comparatively short incline.

The invention further comprises other arrangements more explicitly described hereinafter.

A construction of cam according to this invention is shown in the accompanying drawing in which Figure 1 shows the cam in side elevation. Fig. 2 is a diagram of the respective action on a valve spindle of an ordinary cam and of a cam according to the invention.

The cam is first manufactured, having exactly the shape determined by calculation, in order that when the valve rests on its seat, it is supported by its spindle or an intermediate part, without the least play, on

the operative surface a of the cam. In that Way the engagement of the boss I) of the cam the corrections for lifting the valve and returning it to its seat takes place theoretically in a noiseless nlilanner, slnce the engagement takes place at t e tangentially to the operative surface, that is to say, with a speed equal to zero, and since the valve returns to ts seat at the exact moment when the spindle or the'intermediate part engages withthe point 6 of the cam where the boss is connected tangentially to the operative surface, that is to say, with a speed equal to zero. As, however, in practwo it is impossible to obtain reliably the return of the valve to its seat if, during the period of closing, it rests without play on the circular operative surface of the cam,

the operative surface a is lowered by a milling machine, by grinding or by any other means, so as to obtain a new operative surface a of a smaller diameter than that of the theoretical operative surface a, and care is ,taken to connect the said operative surface a to the boss Z) at the points of contact b and b by rounded off portions or curves 0 and c'- constituting inclines of a comparatively small length.

The difference of diameter that must exist between the operative surfaces of a and a is determined in a suitable manner, the said difference, in the case of an engine inwhich the parts are exposed to different expansions, is preferably made equal to double the play to be provided for the valve gear, owing to the change from the cold state to the hot state of normal running. In order to enable the adjustment to be effected when the engine is cold, a packing piece is made so that when it is applied to the operative surface a it is only necessary to bring the valve spindle or intermediate part into contact with the said packing piece in order that, in normal running, the engagement with the valve and its release by the boss I) should take place exactly at the points of contact. To that end, a packing piece is taken, of which is equal to half the difference between the diameters of the tracks a and a, a first adjustment is effected cold, and afterward, when the engine is running normally,

to be made to the packing piece are determined. With such a cam, instead of the engagement taking place, as with ordinary cams, at a point far away from the point of contact as shown by the diagram Fig. 2) at A. which is the point of meeting of the boss of an ordinary cam (shown in point I) where the boss is connected the thickness.

7 the points of engagement or release, which full lines) with the end of the valve spindle I (shown dotted) will take place at the exact point of contact, as shown by the diagram at B. The engagement or release will take' 5 place, in these conditions, at the moment when the speed of ascent or descent of the valve is zero, and consequently in a noiseless manner. As the curves 0 and c are of very small length, the errors of regulation will not materially modify the position of and in what manner thesame is to be per- 20 formed, I declare that what I claim is A cam for actuating a reciprocatory element havlng a raised operative portion, a concentr1c portion having a radius less than that calculated to allow a full stroke of said element in one direction and forming a clear ance space between it and said element, and

a curved surface constituting a relatively short incline connecting said concentric and raised portions.

2. A valve actuating cam having a raised operative portion, a concentric portion of a radius less than the radius calculated to insure seating of the valve without taking intoaccount play. in the valve actuating connections, and surfaces constituting relatively short inclines connecting the ends of said concentric portion to said raised operative portion.

In testimony whereof I have hereunto set my hand in presence of two subscribing wit-.

IIBSSGS.

MARC BIRKIGT.

Witnesses: I

MATEO GRAU, G. INGERSALL.

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