US 2081390 A
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Description (OCR text may contain errors)
G. J. TRAPP CAM FOLLOWER May 25, 1937;
. Filed Feb. 17, 1936 ZA VEA/Ta/e G. e]. Trap Q.
Patented May 25, 1937 PATENT oFFicE CAM FOLLOWER George Joseph Tram), Merton Park, England, assignor to Automotive Products Company Limited, London,
England Application February 17, 1936, Serial No. 64,377
In Great Britain 3 Claims.
This invention relates to cam and like followers for reciprocating parts and it has for its primary object to provide an improved form and construc- L tion of follower which is particularly strong and which is therefore capable of resisting satisfactorily the comparatively heavy loads usually encountered in reciprocating parts such as the cam followers of fuel injection pumps. A form of cam-follower is known comprising a housing and a substantially cylindrical roll supported on a pair of spaced circumferential rows of rollers, the roll and the rows of rollers being contained within the housing. According to the invention a cam-follower of this form is arranged so that the cam or equivalent coacts with the outer curved surface of the roll between the rows of rollers. As an example, the invention thus provides a cam-follower comprising a block rectilinearly slidable between guides and bored transversely for the accommodation of a roll which is mounted upon a pair of axially spaced circumferential rows of rollers, said blockbeing cut away between the rows of rollers for permitting the curved surface of the roll between said rows to cooperate with a cam or equivalent. Alternatively, the housing may be carried by a pivoted arm, the cam or equivalent being arranged to coact with the outer curved surface of the roll between the rows of rollers. The block may conveniently be mounted between guiding surfaces for reciprocation relatively thereto without rotation, the axis of the roll being arranged during substantially the whole travel of the block to lie within the lengthof the guide sur- 35 faces, measured parallel with the direction of reciprocation.
With the cubic or rectangular form of block, the two opposite faces parallel to the axis of the roll cooperate with the corresponding faces of the guide to provide large contact areas for resisting the lateral thrusts produced by the cam, while any twisting of the block within the guide is prevented by the contact of all the sliding surfaces. Any end thrust upon the follower will be taken by one of its end faces against the adjacent wall of the guide. The portion cut away from the bottom of the block to expose the roll for cam-operation may be out straight across the block in the shape of a rectangular notch, or may be cut on a curve corresponding to the path of the operating cam, soas to maintain the full contact area at the opposite sides of the block. It will be obvious that any shape of block may be employed, means usually being provided for preventing its rotation in the guides.
October 31, 1934 Figure 6 is a diagrammatic side elevation show- T ing the application of the invention to a vehicle brake; and
Figure 7 is a perspective view showing a further modification of the invention.
In the embodiment shown in Figures 1 and 2, a cam-shaft I has an integrally formed cam 2 engaging a follower comprising a roll 3 to cause vertical movement of a push rod 4, such as the plunger of a fuel injection pump.
The present invention is concerned with the cam-follower, consisting of a roll 3 mounted for rotation in a rectangular block 5, which latter in this particular'example, slides within a guide 6, the roll 3 being arranged to reduce friction between the block 5 and the cam 2 which execute a sliding movement relative to one another. The rectangular block 5 has a cylindrical bore 7, extending transversely with respect to its direction of movement, while the face adjacent the cam 2 is cut away by means of a rectangular groove 8 to expose the bore 1. The roll 3 is approximately the same length as the block and has a diameter only slightly less than that of the bore 1, so that when the follower is assembled the roll 3 substantially fills the bore 1.
The diameter of the roll, however, adjacent its ends is reduced to provide races 9 for two spaced circumferential rows of bearing rollers or pins 10, thus leaving for engagement with the cam a central portion having a length substan tially equal to the width of the groove 8 in the block 5. At their outer ends the rollers H] are prevented from bearing against the guide 6 by the provision of radial flanges ll.
The upper face of the block co-operates with U the foot I I of the push rod 4, which is prevented from rotating by a pin l2 while a radially split washer 13 provides a bearing surface for a conventional helical compression spring (not shown) surrounding the rod 4. Preferably the guide 6 is of such length that during reciprocation of the block 5, the axis of the roll 3 does not travel beyond the extent of said guide 6, measured in the direction of reciprocation.
In Figure 3 the modification consists in the construction of the roller races 9, which in this case are formed in the block 5, the roll itself being ground to the same diameter for its whole length, thus simplifying the manufacture.
A still further construction is shown in Figures 4 and 5, where, in order to prevent the compo nents of the follower from falling apart when removed from the guide 5, the roll 3 is made of a length less than the length of the block and in place of the flanges H, a disc 14 is disposed at each end of the bore, the periphery of each disc l4 lying flush with the corresponding end wall of the block within an annular recess concentric with the bore and of slightly greater diameter. Each disc M has a central depression and aperture to receive the head and shank of a rivet l5 passing through the roll for maintaining the assembly. It will be noted that this construction has advantages in manufacture, since the races in the roll extend to the ends of the latter, thus facilitating turning and grinding. Moreover, in this example the roll 3 is mounted in a housing I8 formed in one or carried by an arm l9 pivoted at l9a whereby the housing l8 is constrained to move in an arcuate path when actuated by the cam or equivalent indicated at 2. It will be understood that the cam follower according to the invention can be actuated by devices other than cams, including wedge members, and in Figure 5 an alternative application is illustrated in broken lines. In this instance an arm 20 pivoted at 20a has an oscillatory movement imparted to it by any suitable means and as the roll 3 bears upon the edge of said arm 20, a derived movement is imparted to the arm IS, the whole of the sliding friction between the arms l9 and 20 being obviated by the roll 3.
A still further adaptation of the invention is shown in Figure 6 in which a pair of arcuate brake shoes 2! disposed within a brake drum 22 and pivoted at 23 are each fitted at its free end with a roll 3 as previously described, the brake shoe itself being arranged to form or carry the housing of the roll. These two rolls 3 co-operate with a wedge member 26 which is actuated by suitable means such as a hydraulic wheel cylinder unit so that when the brake is to be applied the Wedge member 24 is moved outwardly thus moving apart the shoes 2! with very little operating 55 friction.
In the further modification shown in Figure '7,
the roll 3, which again is comparatively simple to manufacture, is provided at each end with a collet l6 which is preferably forced into position, thus producing the same effect as the roll in Figures 1 and 2, although if desired the collets Hi can be larger in diameter than the roll 3 so as to maintain the latter in the block 5.
It is evident that other modifications are possible without departing from the invention; and, in particular that ball bearings may be used as the equivalent of roller bearings. Moreover, the cam-follower has a Wide application in practice, and, although it has been described with particular reference to fuel injection pumps, its use is not restricted thereto. The term cam-follower, as used in the appended claims, is thus intended to include cases where the motion obtained from a cam, wedge or equivalent is transmitted to a reciprocating member, the improved construction of follower serving to reduce the friction between the cam or equivalent and the member actuated thereby.
What I claim is:--
1. A cam follower mechanism comprising a guide, a block-like housing mounted for rectilinear reciprocating movement within said guide, a bore in said housing having its axis at right angles to the direction of said movement, a roll of shorter axial length than the bore and disposed completely therewithin, a pair of circumferential tracks around the end portions of the roll, said tracks being smaller in diameter than that part of the roll therebetween, a row of bearing rollers engaging between each of said tracks and the interior of the bore in the housing, a flange upon each end of the roll for preventing endwise displacement of the rollers, that part of the housing between the two rows of rollers being cut away for permitting the roll to engage with a cam, and the reciprocating movement of the housing being limited so that the axis of the roll is at all times within the guide.
2. A cam follower mechanism according to claim 1 in which the flanges at each end of the roll are formed separately from said roll, and said flanges overlapping the ends of the housing so as to prevent endwise displacement of the roll within the housing.
3. A cam follower mechanism according to claim 1 in which the flanges at each end of the roll are formed separately from said roll, and said flanges overlapping the ends of the housing so as to prevent endwise displacement of the roll within the housing, and means connecting the flanges.
GEORGE JOSEPH TRAPP.