US2151832A

US2151832A - Cam motion transmitting device

Info

Publication number: US2151832A
Application number: US40831A
Authority: US
Inventors: Bugatti Ettore
Original assignee: Individual
Current assignee: Individual
Priority date: 1934-09-21
Filing date: 1935-09-16
Publication date: 1939-03-28
Anticipated expiration: 1956-03-28
Also published as: BE411242A; DE640898C; FR791847A

Description

March 28, 1939. I E BUGATTl 2,151,832

' CAM MOTION TRANSMITTING DEVICE Filed Sept 16, 1955 Patented Mar. 28, I939 Q'UN ITED STATES "PATENT OFFICE 7 2,151,832 CAM MOTION TRANSMITTING DEVICE Ettore Bugatti, Molsheim, France Application September 16, 1935, Serial No. 40,831 In France September 21, 1934 7- Claims.

' exists, between said roller and its spindle, a certain play a, due to wear, and tear, the distance between the axis of the cam and the axis of the spindle'is modified and varies according to the relative position of the cam. Consequently, the law of displacements of the controlled member as a function of the angular position of the cam is modified and greatly perturbed. This drawback becomes extremely important if the alterations thus brought about in the displacements of the member controlled by the cam result in magnified alterations caused in the operation of devices which are actuated or operated by said member. This is the case when the cam controls the upward movement of a valve through which takes place the inflow of a fiuid under pressure.

The object of the present invention is to provide an improved mechanical transmission through a cam which obviates or at least reduces the disadvantages above stated. The essential feature of the present invention consists in doing away with the spindle of the roller and in arranging said roller in such manner that it rests through its periphery on other rollers, these last mentioned rollers being mounted in the usual manner on the driven member.

Owing to this arrangement, the play that may occur between the supplementary rollers and their spindles modifies the displacements of the driven member only by an amount which does not vary or does not vary substantially throughout a revolutionof the cam; owing to the use of two or more auxiliary rollers, each auxiliary roller is less subjected to wear so that the above named amount is generally small and in any case can be easily taken up by reason of its being constant throughout a revolution of the cam. Furthermore, the forces that are transmitted to the rollers added according to the present invention act on each of them in a fixed direction, their only variations being variations of amplitude.

Other features of the present invention will result from the following description of some specific embodiments thereof.

Preferred embodiments of the present invention will be hereinafter described, with reference 'to the accompanying drawing, given merely by way of example, and in which: i 1 Fig. 1 diagrammatically shows a known transmission applied to the vertical reciprocating displacement of a member;

Fig. 2 shows a transmission ensuring the same movement according to the present invention;

Figs. 3 and 4 diagrammatically show two rocker arms, according to the invention, respectively, together with the cams through which they are" 5 actuated;

Figs. 5 and. 6 are sectional views, on an enlarged scale, of two other embodiments of the invention.

With a view to simplifying the description of 10 the invention, I have shown, in Figs. 1 and 2, a

- member I, which may be any member whatever of a mechanical structure, said member I being actuated by a cam 2, through a roller 3, in such manner as to have a vertical reciprocating dis- 15 placement.

Fig. 1 shows the usual arrangement, in which roller 3 is carried by a pivot or spindle. 4 provided on member i. Supposing that said spindle 4 has been worn uniformly over its periphery,'so that 20 the reduction of its diameter is 2a, this value -being shown with a considerable exaggeration on the drawing, the upward displacement of member l is reduced by an amount which depends upon the angle a, if a is the angle made by a line 25 passing through the center of pivot 4 and through the point of contact of roller 3 and cam 2 with a line passing through the respective centers C and C1 of cam 2 and pivot 4. This angle varies, in the course of a revolution of the cam, between 30 'zero and one or several maxima. Consequently,

it is not possible, by means of a packing piece of determined thickness or any other mechanically equivalent means, to take up the existing play, and if, for instance, member I serves to .35 cause the opening of a valve, the adjustment of the flow of fluid past said valve is wholly destroyed, without any possibility of restoring said I adjustment.

In its simplest form, the device according to 40 the invention consists, as shown in Fig. 2, in the provision of at leasttwo rollers 5, '6, preferably disposed symmetrically with. respect tothe line of the respective centers of the main roller and the cam, said

rollers

5, 6 being supported by pivots 45 I, 8 and replacing the pivot of roller 3. Said roller 3 is attached to member I through any suitable means. 7

As there. are two rollers, 5 and 6, for guiding roller 3, their wear is obviously smaller than that, 50 of spindle 4 in Fig. 1. Although the effort of cam 2 on roller 3 is always exerted at a point more or less remote from line C 01, roller 3 remains constantly applied against

rollers

5, 6 if said last mentioned rollers have been placed sufficiently Wide apart from each other, so that only the magnitude of the components of this effort along lines C102 and C103 varies. Consequently, if p is the angle of ClCZ of C103 with C C1, the modification of the position of members depends upon the angle 13, but is the same for all the positions of said member since the angle 3 does not vary during a revolution of the cam 2. Generally, the angle ,8 can be given a relatively high value. Thus, owing to the arrangement according to the present invention, the variation of position of the member driven by the cam for a play equal to 2a between the auxiliary rollers and their support is uniform.

When the driven member is a pivoting one such as a rocker arm 9 actuating a valve stem, for instance in the vertical direction, the modification in the position of center Cl, other things being equal, has a uniform value, it being still supposed that both rollers are identical. Due to the fact that angle 13 is relatively large and that the wear of the rollers is reduced since the effort exerted by the cam is divided between them, the displacement of the center C1 of the roller is always very small and as this roller is generally,

located at a relatively great distance from the axis Ill of the rocker arm, the alteration produced in the rocking displacements of the arm 9 is small and therefore easy to remedy.

Of course, the distance between the

auxiliary rollers

5, 6 and their diameter must be chosen in such manner that roller 3 has no tendency to lose contact with them as a consequence of the obliquity of the thrust of the cam, and, on the other hand, that there is no risk of wedging.

In order to connect roller 3 with the rocker arm or any other driven element, I may make use of any device capable of ensuring the required freedom of movement of said roller while preventing it from dropping or otherwise escaping when the rocker arm is assembled or removed. Such a device may consist of a setting arrangement, a plate ll provided with an aperture of suitable size, an elastic connection, etc. I may even leave a pivot or spindle for the roller, provided that said spindle serves only to prevent the roller from dropping when no longer in contact with the cam. In other words, and according as the case may be, the pivot or spindle extends, with a considerable play, through a central hole of the roller, or, if it is rigid with the roller, through holes provided in the driven element.

Owing to the fact that roller 3 is no longer guided by a pivot or spindle, it is possible to reduce to a minimum the diameter of this roller, in which case it is easier than with an ordinary roller to make use of cams the outline of which includes concave portions, such as cam l2 of Fig. 4. If a larger roller were employed, it might bridge the edges of the depression in the cam.

The roller may be replaced by'a ball 13, as shown in Fig. 5, in which case the auxiliary rollers I4 have an outline corresponding to that of the ball, as shown by the drawing.

The roller may also have a conical shape, as shown at IS in Fig. 6. In this figure, one of the auxiliary rollers with which roller [5 cooperates is visible at l6.

The cams I! that are shown in Figs. 5 and 6 are shaped in such manner as to permit an adjustment of the lift of the valves which are driven by the device by moving the cams in the direction of their geometrical axis of revolution.

In a general manner, while I have, in the above description, disclosed what I deem to be practical and eflicient embodiments of the present invention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

What I claim is:

1. In a mechanical motion transmitting device having a cam controlled movable member and an actuating cam therefor, the combination of at least two spaced apart rollers, means for pivotally mounting said rollers on the movable member about substantially parallel, spaced apart axes, a floating, rolling element interposed between the cam and the rollers, adapted in operation to have tangential rolling contact with said rollers, and means for retaining the rolling element in a floating position on the movable member in abutting relationship with said rollers, the said cam cooperating with said floating element.

2. In a mechanical motion transmitting device having a cam controlled member movable along a predetermined path and a cam for actuating said member, the combination of two spaced apart rollers, means for pivotally mounting said rollers on the cam controlled member about substantially parallel axes spaced apart in a plane substantially at right angles to said path, a floating, rolling element interposed between the cam and the rollers, adapted in operation to have tangential rolling contact with said rollers, and means for retaining the rolling element in a floating position on the movable member in abutting relationship with said rollers, the said cam cooperating with said floating element.

3. In a mechanical motion transmitting device having a cam controlled member movable along a predetermined path and a cam for actuating said member, the combination of two substantially parallel, spaced apart pivot pins mounted on the cam controlled member in a plane substantially at right angles to said path, a roller on each pivot pin, a floating, rolling element held on the cam controlled member adapted, in operation, to have tangential rolling contact both with the two rollers and the cam, and means for retaining the rolling element in a floating position on the movable member in abutting relationship with said rollers, the said cam cooperating with said floating element.

4. In a mechanical motion transmitting device having a cam controlled movable member and an actuating cam therefor, the combination of at A least two spaced apart rollers; means for pivotally mounting said rollers on the movable member about substantially parallel, spaced apart axes; a rolling, floating cam-engaging element interposed between the cam and the rollers to have tangential rolling contact with said rollers; and means on said movable member for positively limiting the displacement of the rolling element away from the rollers.

5. In a mechanical motion transmitting device having a cam controlled movable member and an actuating cam therefor, the combination of at least two spaced apart rollers; means for pivotally mounting said rollers on the movable member about substantially parallel spaced apart axes; a rolling element having a noncylindrical periphery, interposed between the cam and the rollers, the latter having noncyclindrical peripheries complementarily shaped with respect to that of the rolling element for engagement in.

tangential rolling contact therewith; and means for retaining the rolling element in a floating position on the movable member in abutting relationship with said rollers, the said cam cooperating With said floating element.

6. In a mechanical motion transmitting device having a cam'controlled movable member and an actuating cam therefor, the combination of two grooved, spaced apartrollers; means for pivotally mounting said rollers on the movable member about substantially parallel, spaced apart, axes a ball interposed between the cam and the grooved rollers, adapted in operation to fit in both rollers simultaneously, in tangential rolling contact therewith, and means for retaining the ball in a floating position on the movable member in abutting relationship with said grooved rollers, the said cam cooperating with said floating element.

'7. A mechanical motion transmitting device which comprises a movable member, at least two spaced apart rollers; means for pivotally mounting said rollers on said movable member about substantially parallel, spaced apart axes, a control cam the cross section of which varies gradually along its axis, a floating rolling element interposed between the cam and the rollers for imparting motion from said cam to said member, adapted in operation to have tangential rolling contact with said rollers, and means for retaining the rolling element in a floating position on the movable member in abutting relationship with said'rollers, the said cam cooperating with said floating element.

ET'I'ORE BUGATTI,