US3390583A

US3390583A - Indexing-cam mechanism

Info

Publication number: US3390583A
Application number: US512485A
Authority: US
Inventors: Jack A English
Original assignee: CTS Corp
Current assignee: CTS Corp
Priority date: 1965-12-08
Filing date: 1965-12-08
Publication date: 1968-07-02
Anticipated expiration: 1985-07-02
Also published as: GB1166639A

Description

July 2, 1968 J. A. ENGLISH 3,390,583

INDEXING-CAM MECHANISM Filed Dec. 5 1965 I 2 Sheets-Sheet 1 INVENTOR JACK A. ENGLISH FIGURE-6A July 2, 1968 J. A. ENGLISH INDEXING-CAM MECHANISM 2 Sheets-Sheet 2 Filed Dec. 8, 1965 FIGURE-8 INVENTOR JACK A. ENGLISH 3,390,583 INDEXING-CAM MECHANISM .lack A. English, Elkhart, Ind assignor to CTS Corporation, Eikhart, Ind, a corporation of Indiana Filed Dec. 8, 1965, Ser. No. 512,485 12 Claims. (CI. 7484) ABSTRACT OF THE DISCLGSURE A rotatable and axially oscillatable indexing-cam mechanism rotatable at a uniform speed for indexing a dial having a plurality of equally spaced roller followers mounted on one side of the dial and equally spaced from the rotatable axis of the dial comprises a double tier cam having a cylindrical member and a driving member. As the cam rotates through one revolution, an oscillatory member axially shifts the driving member of the cam into and out of the plane defined by the roller followers. The dial is indexed a predetermined angle while the driving member of the cam is rotating and in engagement with one of the roller followers. After the dial is indexed, it is locked in position by the cylindrical member engaging a pair of the roller followers. In one of the preferred forms of the embodiment, the cam is provided with a constraining member to prevent acceleration of the dial ahead of the driving member of the cam.

The present invention relates to an indexing-cam mechanism and, more particularly, to a rotatable and axially oscillatable indexing-cam mechanism.

Indexing-cam mechanisms are employed in various types of mechanical equipment such as automatic screw machines, turret lathes, and the like. One particular use for an indexing-cam mechanism is to index the rotatable table of a transfer machine during assembly of electronic components, e.g., variable resistors and switches. The table, usually of circular configuration, is generally referred to as a dial and varies in diameter from approximately one to twelve feet. Such dials are generally driven at a slow, uniform speed or indexed a predetermined number of degrees by a chain, gear or cam mechanism located centrally below the dial. A plurality of equally spaced nests are secured at the top outer periphery of the dial and, as a nest moves past a certain station, an operator performs a certain function such as placing one of the parts of the component into each of the nests. Before the components are removed from the nests, the parts must be secured together with fastening equipment. When the operator controls the fastening equipment, accurate alignment between the fastening equipment and each of the nests is not necessary. But when it is desirable to actuate the fastening equipment automatically, it is necessary that complicated locating means be employed to align the equipment with each of the nests or else that precise indexing be effected for each of the nests carried by the dial. It would be desirable, therefore, to index a dial with a greater degree of accuracy of index, especially a large diameter dial; i.e., having a diameter in excess of two feet.

When a dial is combined with automatically operated equipment, it is preferable that the dial advance rapidly through a small angle with accurate control of acceleration and deceleration from one station to another station and then remain locked until the automatic operation is performed. In current indexing-cam mechanisms, the drive angle of the cam decreases as the number of roller followers increases since the cam always rotates between a pair of adjacently disposed roller followers. It would, therefore, also be desirable to provide an indexing-cam mechanism where at least one roller follower is between a States Patent driven roller follower and a constraining roller follower when the dial is being indexed.

Accordingly, it is an object of the present invention to provide an improved indexing-cam mechanism. Another object of the present invention is to provide an improved indexing-cam mechanism having a single cam engageable with a plurality of roller followers disposed near the outer periphery of a rotatable dial and on the same side thereof. An additional object of the present invention is to provide an improved indexing-cam mechanism having a rotatable cam with an axially oscillatory motion during a portion of the cycle to prevent the cam from interfering with a roller follower disposed intermediate a driven roller follower and a constraining roller follower. A further object of the present invention is to provide an indexing-cam mechanism with a double tier cam having a cylindrical member for maintaining a dial in locked position when the cam is in a first position of oscillation and a driving member having a small and a large circu lar dwell portion and an accelerating and a decelerating portion. Still another object of the present invention is to provide an improved indexing-cam mechanism having a cam with a cut-out portion to avoid interference with an intermediate roller follower disposed between a driven and a constraining roller follower. Yet another object of the present invention is to provide a rotatable and axially oscillatable indexing-cam mechanism with a positivedrive condition for eliminating backlash and effectively constraining the follower under high speed and high dynamic or shock loads. Yet an additional object of the present invention is to provide an indexing-cam mechanism with a cam having a cylindrical member and a driving member with congruent sections. Further objects and advantages of the present invention will become apparent as the following description proceeds, and the features of novelty characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Briefly the present invention comprises a rotatable and axially oscillatable indexing-cam mechanism having a simple double tier cam rotatable at a uniform speed for rapidly controlling indexing of a dial from one station to another. The cam comprises a cylindrical member and a driving member. As the cam rotates through one revolution, an oscillatory member axially shifts the cam, more particularly, the driving member of the cam into and out of a plane defined by the roller followers. The roller followers are equally spaced circumferentially along one side of the dial, and the cam is disposed near the periphery of the dial where increased accuracy is obtained. The cylindrical member of the cam maintains the dial in a locked position during a portion of the revolution of the cam. Immediately prior to indexing of the dial, the locking action is transferred from the cylindrical member to the driving member of the cam. The cylindrical member is provided with a cut-out portion to avoid interference with one of the roller followers prior to angular movement of the dial, and the dial becomes unlocked when the accelerating portion of the driving member meshes with one of the roller followers. In another embodiment of the present invention, a positive-drive condition is obtained by providing the driving member of the cam with congruent sections for engaging a driven and a constraining roller follower during angular movement of the dial from one station to another.

For a better understanding of the present invention, reference may be had to the accompanying drawings wherein identical reference numerals have been applied to like parts and wherein: FIGURE 1 is a fragmentary top plan view of an indexing-cam mechanism showing a double tier cam immediately after the dial has been indexed; FIGURE 2 is a fragmentary side elevational view of the indexing-cam mechanism of FIGURE 1 showing an oscillatory member prior to downward movement of the cam shaft; FIGURE 3 is an enlarged fragmentary section of the indexing-cam mechanism shown in FIG- URE 1 with the dial in a locked position; FIGURE 4 is an enlarged view similar to FIGURE 3 showing the cam immediately prior to accelerating the dial; FIGURE 5 is a side view of the cam taken along line VV of FIGURE 3; FIGURE 6 is an isometric view of the cam of FIGURE 5; FIGURE 6A is a top plan view of the cam; FIGURE 7 is a fragmentary section of another embodiment of an indexing-cam mechanism immediately after the cam has indexed the dial; FIGURE 8 is a fragmentary section similar to FIGURE 7 with the dial in the locked position; FIGURE 9 is a fragmentary section similar to FIGURE 8 with the cam immediately prior to accelerating the dial; and FIGURE 10 is a side view of the cam shown in FIGURES 7, 8 and 9.

Referring now to the drawings and preferably to FIG- URES 1 and 2 thereof, there is illustrated a multiposition indexing-cam mechanism generally indicated at 10, comprising a rotatable dial 111 indexed by a rotatable and oscillatable cam mechanism 20. Considering first the dial 1 1, it is generally of circular configuration supported by suitable means such as a not-shown rotatable shaft or radially disposed bearings. For the purpose of indexing the dial 11 from one station to another, a plurality of roller followers 12 is fixedly secured to one side of the dial near the outer periphery. The roller followers 12 can extend in any direction depending upon the application of the dial. Preferably, and as shown in the drawings, the roller followers depend downwardly from the bottom face of the dial to permit complete use of the top surface as a work area by an operator. A plurality of nests 13 employed for receiving and supporting the various parts of a component before assembly thereof are suitably secured to the outer edge of the top surface and a stationary not-shown cover supported above the dial carries a plurality of bins or boxes for storing component parts. The angle between adjacent followers is determined by dividing 360 by the number of followers utilized. The number of roller followers chosen depends upon the number of stops that the dial 11 is to make during one rotation thereof and the number of stops depend upon the number of nests. Practically the number of nests for a specific diameter dial depends upon the size and the number of parts placed into a nest and the complexity of the component. Each of the followers 12 comprises a stub shaft 1'4 (see FIGURE 2) fixedly secured to the dial, and a cylindrical casing 15 rotatably mounted on the stub shaft 14 minimizes friction between the cylindrical casing and the stub shaft. The end of each of the stub shafts is provided with suitable means =16, e.g., a shoulder, to support the cylindrical casing. One of the dials made in accord with the present invention is forty-eight inches in diameter and carries thirty nests and thirty roll-er followers. Dials having a diameter of one to twelve feet can readily be indexed with the cam mechanism of the present invention.

Referring now to the cam structure 20 (see FIGURE 2), it comprises a simple double tier cam 21 engageable with the roller followers 12. The cam 21 is keyed to a cam shaft 22 and rotatably supported by a frame 23. The shaft 22 is movable toward and away from the center of the dial 11 to control the contact pressure between the roller followers 12 and the cam 21, As will be later described, it is necessary that the cam clear an intermediate roller follower during an indexing cycle, preferably by oscillating the cam 21 axially to avoid interference with the intermediate follower 12a. To oscillate the cam 21 from a first position to a second position during an indexing cycle, i.e., one revolution, a cylindrical cam 24 rotatably mounted on a shaft 24a fixedly secured to the frame 23 engages an oscillatory follower 25 attached to the cam shaft 22. Rotation of the cam shaft 22 provides oscillatory motion to the cam 21 and, for every revolution of the cam 21, the cylindrical cam 24 completes one oscillation. The cam shaft 22 is preferably rotated at a uniform speed by suitable power means, e.g., an electric motor.

As best shown in FIGURES 5 and 6 of the drawings, the cam 21 preferably comprises a cylindrical member 26 defining the first or top tier of the cam 21 and a driving member 27 defining the second or bottom tier of the cam 21 extends from the cylindrical member. The cylindrical member 26 has a diameter slightly larger than the distance between the outer edges of a pair of adjacent cylindrical casings 15 to maintain the dial 11 in a locked position during the part of the revolution when the cam shaft 22 is in the first position of oscillation. The cylindrical member 26 is provided with a cut-out portion 26a and, when one of the roller followers 12, hereinafter referred to as the intermediate roller follower 12a, enters the cut-out portion, the dial becomes free to rotate. When high speed indexing is desired, the driving member 27 of the cam 21 is provided with a pair of arcuate notches or slots 27a sloping toward the bottom edge of the cut-out portion 26a to assure that the intermediate roller follower '12a does not hit the edge of the cut-out portion 26a as the cam 21 is shifted upwardly to position the driving member 27 into mesh with a first and a third roller follower, hereinafter referred to as a driven roller follower 12b and a constraining roller follower 120. The driving member 27 of the cam 21 is provided with a pair of different diameter circular dwell portions 27b and 270 (see FIGURES 5 and 6) to maintain the dial in a locked position immediately after the cam 21 is shifted upwardly (such cam position being shown in dashed lines in FIGURE 4), and with accelerating and decelerating

portions

27d and 27a. The different diameter circular dwell portions are necessary since the driving member 27 of the cam 21 is not centered between the driven and constraining roller followers 12b and 120. The small diameter circular dwell portion 27c is of the same diameter as the cylindrical member 26 to permit transfer of the locking action of the cam 21 when the cam 21 is shifted axially by the oscillatory follower 25 from one position to another. The driving member 27 is also provided with

portions

27b, 27d and 27e' congruent to the circular dwell portion 2717, the accelerating portion 27d, and the decelerating portion 27@ respectively for constraining rotation of the dial.

The sequence of operation of the indexing-cam mechanism of the present invention is best illustrate-d in FIG- URES 1, 3 and 4 of the drawings where FIGURE 1 shows the dial 11 at the end of travel in a clockwise direction of an indexing cycle and the start of the dwell period of the cam, in other words, that period of rotation of the cam where the dial remains locked, since the driven roller follower 12b and the constraining roller follower 12c engage the circular dwell portions 27b and 27c respectively. Although counterclockwise rotation of the cam 21 is assumed in the drawings, the cam can rotate in either direction. To avoid interference between the intermediate follower 12a and the driving member 27 as the cam 21 continues to rotate in the counterclockwise direction, it is necessary that the cam shift downwardly or back to the first position. Since the cam maintains the dial in the locked position during downward movement of the cam 21, the locking action of the cam 21 is transferred from the followers 12c and 12b to followers 12a and (see FIG- URE 1). The cam 21, therefore, not only shifts downwardly as the cam 21 rotates from the position shown in FIGURE 1 to the position shown in FIGURE 3 but the locking action is also transferred from the driving member 27 to the cylindrical member 26'. After the cam 21 is in the first position, the cylindrical member 26 engages a pair of adjacent roller followers, i.e., the intermediate roller follower 12a and the driven roller follower 12/)( see FIGURE 3), maintaining the dial in a locked position. The cam 21 continues to rotate in a counterclockwise direction with the cylindrical member 2.6 maintaining the dial in a locked position until the intermediate roller follower 12a again is in alignment with the cut-out portion 26a. The oscillatory follower 25 then shifts the cam 21 upwardly until the circular dwell portions 27b and 27c of the driving member 27 of the cam 21 lie in the same plane as occupied by the roller followers 12. As the cam rnoves upwardly from the first position to the second position, the locking action of the cam is transferred from the intermediate roller follower 12a and the driven roller follower 12b to the constraining roller follower 12c. FIGURE 4 shows the cam in a dashed line just prior to upward movement of the cam 21 and in a solid line after the cam 21 has shifted into the second position and rotated through a small angle. After transfer of the locking action occurs, the accelerating portion 27d of the driving member 27 of the cam 21 begins to mesh with the driven roller follower 12b (see FIGURE 4). Further rotation of the cam 21 causes the accelerating portion 27d of the cam to shift the driven roller follower 12b and the dial from one station to another, i.e., the distance between a pair of adjacent followers. In accord with one embodirnent of the present invention as shown in FIGURES 1-6 of the drawings, the cam is in positive control of the dial at all times since one section of the driving member of the cam meshing with the driven roller follower 12b is congruent to the other section of the driving member meshing with the constraining roller follower 120.

In the embodiment shown in FIGURES 7-10, a double tier cam 121 is substantially identical to the cam 21 shown in FIGURES 1-6 of the drawings except that a driving member 127 of the cam 121 is not provided with a congruent section to cons-train movement of the dial 111 to movement of the cam 121 during deceleration of the dial 111. The cam 121 shown in FIGURES 7-10 is suitable for indexing dials at speeds up to approximately thirty-five indexes per minute. A larger number of indexes are possible where the moment of inertia of the dial is decreased or drag of the dial is increased to overcome advancing of the dial ahead of the decelerating portion of the driving member 127 of the cam 121.

In other respects, the cam 121 is identical to the cam shown in FIGURES 1-6 of the drawings and comprises a cylindrical member 126, having a cut-out portion 126a. the driving member 127 of the cam is provided with a large diameter circular dwell portion 127b and a small diameter circular dwell portion 127e, an accelerating portion 127d and a decelerating portion 1272. FIGURE 7 shows the cam after the dial has been indexed from one station to another and just prior to downward shifting of the cam to transfer the locking action from first and third roller followers 112b and 112c to a pair of adjacent roller followers. The cylindrical member 126 of the cam 121 maintains the dial 111 in the locked position during the dwell period. When an intermediate roller follower 112a is in alignment with the cut-out portion, the cam is shifted upwardly to move the driving member 12.7 of the cam 121 into mesh with the driven roller follower.

While there has been illustrated and described what is at present considered to be a preferred embodiment of the present invention, and a single modification thereof, it will be appreciated that numerous changes and modifications are likely to occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications which fall within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A method of indexing a dial having a plurality of roller followers including a driven roller follower, a constraining roller follower, and an intermediate roller follower engageable by a rotatable cam having a cut-out portion, a dwell portion and an accelerating portion, said method comprising the steps of: rotating the cam during a dwell period to maintain the dial in a locked position until the intermediate roller is adjacent to the cut-out portion provided in the cam, shifting the cam axially in one direction to move the accelerating portion of the cam into a plane defined and occupied by the roller followers, rotating the cam further in the same direction until the accelerating portion meshes with the driven roller follower, advancing the dial a predetermined angle by continuing rotation of the cam in the same direction, constraining movement of the dial in the direction of index to prevent advancing of the dial ahead of the accelerating portion of the cam, and shifting the cam axially in the other direction to prevent a part of the cam from interfering with the intermediate roller follower as the cam continues to rotate in the same direction while maintaining the dial in the locked position.

2. A method of indexing a dial having a plurality of roller followers including a driven roller follower, a constraining roller follower and an intermediate roller follower engageable by a cam having a cylindrical member and a driving member, said method comprising the steps of: rotating the cam during a dwell period, said cylindrical member having its circumferential edge engaging the driven roller follower and the intermediate roller follower to maintain the dial in a locked position, the circular member being provided with a cut-out portion to avoid interference between the intermediate roller follower and a portion of the cam as the driving member engages the driven and constraining roller followers; advancing the cam until the inter-mediate roller follower is in alignment with the cut-out portion, shifting the cam axially toward the dial and simultaneously advancing rotation of the cam until the driving member engages the driven and the constraining roller follower to maintain the dial in a locked position as the inter-mediate cam moves into the cut-out portion, further rotating the cam until an accelerating portion of the driving member meshes with the driven roller follower, moving the dial from one station to another with the cam, constraining movement of the dial in the direction of index to prevent advancing of the dial ahead of the driving member of the cam to maintain a positive-drive condition, and shifting the cam away from the dial to disengage the driving member from the roller followers while maintaining the dial in a locked position with the cylindrical member.

3. In an indexing mechanism, the combination of a frame, a dial rotatably mounted on the frame, a plurality of equally spaced roller followers mounted on one side of the dial near the outer periphery thereof, a cam comprising a cylindrical member having a diameter slightly larger than the distance between a pair of adjacent roller followers and a driving member having different diameter circular dwell portions for maintaining the dial in a locked position, the cam being provided with a cut-out portion for avoiding interference with an intermediate roller follower disposed between a driven roller follower and a constraining roller follower as the cam is rotated through an indexing cycle, means for reciprocating said cam to shift the driving member into and out of engagement with the driven and the constraining roller followers, and power means for rotating the cam shaft.

4. An indexing mechanism comprising a frame, a dial rotatably supported on the frame, a plurality of equally spaced roller followers carried by the dial near the outer periphery thereof, a cam meshing with the roller followers, power means for rotating the cam and indexing the dial, and means for reciprocating the cam during each revolution thereof.

5. The mechanism of claim 4, wherein the cam comprises a double tier, a first member of the tier lying in a plane occupied by the roller followers, and a second member of the tier movable toward and away from the plane occupied by the roller followers for indexing the dial a predetermined angle.

6. The mechanism of claim 5, wherein the first member is cylindrical for maintaining the dial in a locked position when the second member is out of the plane occupied by the roller followers, and the cam is provided with a cutout portion to avoid interference with one of the followers when the second member is in the plane occupied by the followers.

7. The mechanism of claim 5, wherein the first member has a diameter larger than the distance between a pair of adjacent roller followers and the second member is provided with a first circular dwell portion having a radius greater than one and onehal-f times the distance between a pair of adjacent roller followers and a second circular dwell portion having a diameter equal to the diameter of the first member to maintain the dial in a locked position as the cam is being shifted toward or away from the dial.

8. The mechanism of claim 5, wherein the second member comprises a pair of congruent sections, one section being engageable with a driven roller follower and the other section being engageable with a constraining roller follower to maintain positive control of the dial during acceleration and deceleration thereof.

9. The mechanism of claim 4, wherein all of the roller followers are carried by one side of the dial.

10. The mechanism of claim 6, wherein the first member has a diameter larger than the distance between a pair '8 of adjacent roller followers and the second member is provided with a first circular dwell portion having a radius greater than one and one-half times the distance between a pair of adjacent roller followers and a second circular dwell portion having a diameter equal to the diameter of the first member to maintain the dial in a locked position as the cam is being shifted toward or away from the dial.

11. The mechanism of claim 6, wherein the second member comprises a pair of congruent sections, one section being engageable with a driven roller follower and the other section being engageable with a constraining roller follower to maintain positive control of the dial during acceleration and deceleration thereof.

12. The mechanism of claim 7, wherein the second mem. ber comprises a pair of congruent sections, one section being engageable with a driven roller follower and the other section being engageable with a constraining roller follower to maintain positive control of the dial during acceleration and deceleration thereof.

References Cited UNITED STATES PATENTS MILTON KAUFMAN, Primary Examiner.