Cam follower with pivotally movable cam engagable shoe

A cam follower including an arm pivotally movable about an axis which is perpendicular to the axis of rotation of an actuating cam is provided with a shoe that pivots on the arm to maintain line contact with the cam as the cam is rotated.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to cam and cam follower arrangements, and in 
particular to such arrangements wherein a cam follower is pivotally 
movable about an axis which is perpendicular to the axis of rotation of an 
actuating cam. 
2. Description of the Prior Art 
Space limitations and other considerations imposing restrictions on the 
design of a mechanism sometimes require that a pivotally mounted cam 
follower be movable by a rotatable cam about an axis which is 
perpendicular to the axis of the rotatable cam. In such arrangements there 
is point contact between the engaging surfaces of the cam and cam follower 
as the cam follower is pivoted by the cam, and the cam follower digs into 
the actuating cam resulting in excessive wear and damage to the engaging 
parts. 
SUMMARY OF THE INVENTION 
In accordance with the invention, a cam follower including an arm pivotally 
movable about an axis which is perpendicular to the axis of rotation of an 
actuating cam is provided with a shoe to pivot on the arm of the follower 
and maintain line contact with the cam. The shoe is preferably formed of 
sheet metal or of plastic which is wear resistant, and is preferably 
configured to fit over an end portion of the cam follower arm and pivot on 
a finger depending from the arm. The arrangement of the invention has 
particular application is sewing machines, as for example, where a work 
feeding control includes a knob which is operable to rotate a disc cam and 
cause a cam follower that is pivotally mounted about an axis perpendicular 
to the axis of the disc cam, to be disposed in a position to activate cam 
controlled feed mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1 and 2 of the drawings, reference character 10 
designates the feed control knob of a sewing machine. The knob is 
rotationally fixed by a key 12 to the hollow end portion 14 of a cam hub 
16 which is mounted for rotation on a longitudinally movable shaft 18. Cam 
hub 16 includes a disc cam 20 as an integral part thereof. The cam hub 16 
and disc cam 20 can be turned in unison by knob 10. A quick reverse feed 
button 22 movable in a recess 24 in the knob 10 is attached to shaft 18 
for use in positioning the shaft longitudinally. 
A cam follower 26 pivotally mounted for movement on a shaft 28 about an 
axis 30 perpendicular to the rotational axis 32 of cam hub 16 and disc cam 
20 is positionable by the cam disc when rotated by knob 10. As shown, the 
cam follower 26 includes an arm 34 which normally extends generally 
parallel to cam hub 16 and shaft 18. Such arm 34 includes a depending 
finger 36. In accordance with the invention, a shoe 38 formed of sheet 
metal or of plastic having wear resistant characteristics, and 
substantially U-shaped in cross section (see FIG. 3) is provided on arm 34 
to engage disc cam 20. The shoe is loosely slidable over the arm where it 
is disposed for engagement on its bottom inside surface 40 with finger 36. 
A spring 42 biases the cam follower 26 counterclockwise as viewed in FIG. 
1 to maintain the finger 36 against the bottom inside surface 40 of the 
shoe and the bottom outside surface 42 of the shoe against the 
circumferential periphery 44 of disc cam 20. A stationary plate 46 and an 
abutment 48 on cam follower 26 confine the shoe 38 longitudinally on the 
arm 34. An integral tab 50 on the shoe extends over the top of arm 34. 
As shown, plate 46 includes a central opening 48 for the end portion 14 of 
cam hub 16. One side of the plate engages a ledge 50 on the hub 16 and the 
other side of the plate is engaged by a boss 52 on control knob 10. The 
plate is secured by screws 54, 56 and 58 in threaded bosses 60, 62 and 64, 
respectively, on a frame 66. A vertical slot 68 in plate 46 receives and 
guides an end portion of cam follower arm 34. 
Button 22 acting through shaft 18 and conventional mechanism (not shown) 
serves when depressed to effect a reversal in the feeding direction of 
work on a sewing machine. Knob 10, if turned to locate the top of a step 
70 on the periphery of disc cam 20 under shoe 38, causes the cam follower 
26 to activate cam controlled feed mechanism (not shown) such that work is 
fed in a predetermined manner to provide for the formation of stitch 
patterns as defined by pattern cams. Such cam controlled feed mechanism is 
well known in the sewing machine art and the specific details thereof are 
not pertinent to the present invention. 
As the disc cam 20 is turned by knob 10, the shoe 38 maintains line contact 
with the peripheral circumferential surface 44 of disc cam 20. Such line 
contact is maintained even as the shoe is moved from a low level line 
contacting position with the cam's peripheral surface to the top of step 
70 since the shoe pivots at the same time on finger 36 about an axis 
perpendicular to the said line and so compensates for angular movement of 
the cam follower arm 34 relative to the cam surface 44. A substantial 
length of the shoe and width of the disc cam engage at all times and wear 
on the contacting surfaces is therefor minimized. Gouging and grooving of 
the periphery of the disc arm is eliminated and the life of the disc is 
thereby extended especially when the disc cam is of plastic which is the 
preferable material for this part because of the ease with which it can be 
fabricated and because of cost considerations. 
It is to be understood that the present disclosure relates to a preferred 
embodiment of the invention which is for purposes of illustration only and 
that it is not to be construed as a limitation of the invention. Numerous 
alterations and modifications of the structure herein disclosed will 
suggest themselves to those skilled in the art, and all such modifications 
and alterations which do not depart from the spirit and scope of the 
invention are intended to be included within the scope of the appended 
claims.