US3666900A - Push button switch operating means with improved joystick and cam structure - Google Patents

Abstract

An operating arm pivotably movable selectively in opposite directions along two mutually-perpendicular paths of movement about an intermediate pivot point drives a sliding cam for operating linear reciprocative operators of a plurality of selfrestoring switches by means of translating pins.

Description

United States atent Rothweiler et al. 51 May 30, 1972 s41 PUSH BUTTON SWITCH OPERATING [56] References Cited MEANS WITH IMPROVED JOYSTICK UNITED STATES PATENTS AND CAM STRUCTURE 2,589,025 3/1952 Phelps et a]. ..200/6 A UX [72] Inventors: Richard C. Rothweiler, Asheville, NC; 2,679,678 6/1954 Stephan ..200/6 A Carl g sh Bay; John A. 2,841,659 7/1958 Eitel ..l..2oo/6 A x Washbum, Mllwaukeei both of 2,941,048 6/1960 Lybrook et al ..200/6 A 73 Assignee: Square 1) Company, Park Ridge, 111. 3,027,807 4/ Barcus 200/6 A X I 3,030,459 4/1962 Elliott et al. 200/6 A [221 Flled= 1971 3,235,679 2/1966 Schaad et al ..200/6 A x 21 App] 113,645 3,385,942 5/1968 Mc Cann ..200/6 A X Related Application Data Primary Examiner-J. R. Scott [63] Continuation of Ser. No. 886,290, Dec. 18, 1969,

abandoned. 1 [57] ABSTRACT An operating arm pivotably movable selectively in opposite "200/6 200/17 lgg directions along two mutually-perpendicular paths of move- [58] Field of Search ..200/6 A abut a shdmg cam for operating linear reciprocative operators of a plurality of self-restoring switches by means of translating pins.

8 Claims, 10 Drawing Figures Patented May 30, 1972 3 Sheets-Sheet 2 INVENTORS GALE- 1m A TTOAA/E Vs Patented May 30,1972

3 Shuts-Sheet; 3

INVENTOR5 f uwai Hm 7 mm M FIG IO W 4. MW FM-- 1 Arron/ens PUSH BUTTON SWITCH OPERATING MEANS WITH IMPROVED JOYSTICK AND CAM STRUCTURE This application is a continuation of Ser. No. 886,290, filed Dec. 18, 1969, now abandoned.

This invention relates to improvements in operating means for electric switches, and more particularly to a switch operator mechanism having an operating arm or joy stick constrained for selective pivotal movement from a central position in opposite directions along two paths of movement at right angles to each other for selective operation of a plurality of self-contained, self-restoring switches of the push button YP- In prioroperators of this type, a sliding cam which operates the switches has been exposed permitting accumulation of dirt to adversely affect the operation. In accordance with the present invention, improved means are provided for guiding the cam, and the cam is completely enclosed. Further any desired number of switches may be operated. Standard switches may be used and a base member of the operator is so dimensioned that a modular construction is provided as will be described.

. An object of the invention is to provide an improved switch operator of the joy stick type.

Another object is to provide an improved joy stick switch operator capable of operating any desired number of push button type switches arranged with pairs of the switches in tandem.

A further object is to provide an improved joy stick switch operator including a sliding cam arranged to cause operation of self-contained switches by means of translating pins interposed between the cam and the switch push buttons.

Further objects and advantages of this invention will become apparent from the following description wherein reference is made to the drawings, in which:

FIG. 1 is a sectional view of a switch operator in accordance FIG. 5 is an exploded view of the switch operator of FIGS. l

and 2, including a pair of switches, but with some parts and details of some parts omitted for clarity of illustration;

FIGS. 6, 7, 8, and 9 are perspective views of the uppersides of various guide plates that can be used in the switch operator of FIGS. 1 and 2; FIG. 6 being a momentary-contact, fiveposition guide plate; FIG. 7 being a maintained-contact, fiveposition guide plate; FIG. 8 being a momentary-contact, fiveposition guide plate; and FIG. 9 being a maintained-contact, three-position guide plate; and

FIG. 10 is a sectional view of a portion of a modified switch operator including an OFF-point latch mechanism, the section being taken along the longitudinal axis of the switch operator as in FIG. 1, but with the cutting plane for-the section rotated about that axis so as to intersect a body member of the switch operator as indicated by the line 10-10 in FIG. 5.

Referring principally to FIGS. 1, 2, and 5, the switch operator comprises a hollow metal supporting body member 10 having a generally cylindrical upper portion 1 1 and a lower rectangular flange portion 12. The body member 10 is shown as mounted on a panel 14 by insertion from the lower side of the panel through an opening therein. Different numbers of rubber-like gaskets 15 may be placed between-the flange portion 12 and the lower face of the panel 14 to compensate for panels of different thicknesses. The body member 10 is held in position on the panel 14 by a ring nut 16 which threads over the upper portion 11 of the body member 10. A conventional locating ring 17 may be interposed between the upper face of the panel 14 and the bottom of the ring nut 16 to secure the body member 10 against rotation with respect to the panel 14. Two cylindrical locating nibs 18 FIG. 5 depend from the bottom of the flange portion 12 and have tapped openings for receiving screws 19 which maintain the parts of the switch operator in assembled relation as will be described.

An upper wall portion 20 of the body member 10 has a clover-leaf shaped opening 21 defining four recesses arranged in quadrature for guiding an elongated operating member or operator arm 24 for movement selectively along two mutuallyperpendicular paths of movement. A flexible dustproofing boot 25 has a lower lip portion 26 received in an annular groove in the upper portion 11 of the body member 10 and an upper lip portion 28 received in an annular groove in an enlarged upper portion of the operator arm 24.

Intermediate of its length, the operator arm 24 has a generally spherical bearing portion 29 received within a journal defined by aligned openings in two identical face-to-face positioned bearing members 30 and 31, the upper bearing member 30 being held, in a manner to be described, against an annular downwardly-facing shoulder 32 formed on an inner wall of the upper portion 11 of the body member 10. A generally spherical lower end portion 34 of the operator arm 24 is received in a cylindrical socket 35 formed in the upper surface of an operating cam 36, and an indexing collar 38, preferably formed of oil-impregnated sintered iron material for a reason to be described, is slidably mounted along the operator arm 24 above a selected one of a group of guide plates such as guide plate 39 shown in FIGS. 1, 2, 4, 5, and 7. A spring 40 is interposed between the indexing collar 38 and the bearing portion 29 and a conical spring 41 surrounds the spring 40 and is interposed between the lower bearing member 31 and an annular shoulder on the indexing collar 38.

In addition to biasing the indexing collar 38 against the guide plate 39, the springs 40 and 41 serve to hold the upper bearing member 30 against the shoulder 32 and, when certain guide plates are used, also serve as return springs for the operator arm 24 as will be described.

The operating cam 36, which is positioned below the guide plate 39, is slidably mounted in a cruciform-shaped recess 42 in a molded upper base portion 43 having a pair of openings 44 through which a pair of translating pins 45 extends. Four spaced guide pins 46 (FIG. 4) depend from the guide plate 39. The cam 36 is guided for movement along one axis by reception of the guide pins 46 in parallel-spaced slots 47 formed in the upper surface of the cam 36, and is guided for movement along the other axis by engagement of the guide pins 46 with opposing side walls 48 of the cam 36. The inner walls of the recess 42 assist in guiding the cam 36 along both axes of movement.

The translating pins 45 are slidably received, respectively, in the openings 44 in the upper base portion 43 and in openings 50 in a molded lower base portion 51, the base portions 43 and 51 together constituting a base member of the switch operator. As best illustrated in FIG. 1, the openings 44 and 50 are preferably circular and are axially aligned, and the openings 50 are of a greater diameter than the openings 44. A semi-circular shoulder 50a at the lower end of each of the openings 50 prevents the associated translating pin 45 from dropping out of its opening 50, and a lower enlarged portion of the pins 45,cooperating with the narrowed diameter of the openings 44, limits the extent to which the pins can extend into the recess 42 in the upper molded base portion 43 thereby to prevent the pins 45 from interfering with the sliding movement of the cam 36. The translating pins 45 engage respective self-restoring reciprocable push buttons 52 of a pair of selfcontained switches 54 arranged by side-by-side relation as best illustrated in FIG. 5.

The switches 54 are preferably of the general type disclosed in Tumbull US. Pat. No. 3,336,455 issued Aug. 15, 1967. Each comprises a hollow housing 55 enclosing a bridging contact (not shown) which moves, in response to movement of its associated push button 52, to engage or disengage from upper and lower pairs of stationary contacts electrically connected to respective pairs of terminals 56. Although the switches as heretofore described are double pole double throw switches, they could, as will be apparent to those skilled in the art, also be made in a single pole configuration merely by omitting one of the pairs of stationary contacts.

A description of one of the double pole switches 54 will suffice for all. The push button 52 is biased outwardly to its extended position by a return spring (not shown) contained within the housing 55. In the extended or released position of the push button 52, the bridging contact completes the circuit between the upper pair of stationary contacts. When the push button 52 is in its fully depressed position, the bridging contact completes the circuit between the lower pair of stationary contacts. At an intermediate position of the reciprocable push button, neither pair of the stationary contacts is engaged by the bridging contact. Thus three distinct contact conditions corresponding to three positions of the reciprocable push button 52 exist for each of the switches 54, as follows: a released position in which the circuit is closed between the upper pair of stationary contacts, an intermediate position in which the circuit is open; and a depressed position in which the circuit is completed between the lower pair of stationary contacts. As will later be described, the operating cam 36 effects movement of the push buttons 52 selectively between each of the three aforementioned positions.

The versatility of the joy stick operator is enhanced in that the push buttons 52 of the switches 54 are exposed for access through the bottom of their respective housing 55 thereby permitting, as described in the Turnbull patent and as shown in FIG. 2, additional switches 57, which are like the switches 54, to be mounted in tandem below the switches 54 for concurrent operation therewith. Additionally, one or more of the switches 54 or 57 may be provided with means whereby its contacts open or close either early or late with respect to the operation of a standard one of the switches. As will be apparent to those skilled in the art, this may be accomplished by altering the length of the push button 52 or by changing the effective spacing between the stationary and bridging, contacts within the switch.

Although the operator arm 24 may be made in one piece, it is preferably an assembly, as best shown in FIG. 5, having an upper sleeve portion 240 press-fitted onto a lower stem portion 24b on which the bearing portion 29 is secured by soldering. The operator arm 24 has an axial bore 24c and an intersecting transverse bore 24d for a purpose to be described. The sleeve portion 24a is threaded to receive a knob 58, and the rounded lower end portion 34 is formed on the stem portion 24b.

As shown best in FIG. 3, four projecting portions 60,61,62, and 63 extend from a bottom face 36a of the cam 36. The projecting portions 60 and 61 are at one pair of diagonally opposite corners of the cam 36 and the projecting portions 62 and 63 are at the other pair of diagonally opposite corners. The projecting portions 60 and 61 have inwardly-facing camming surfaces 64 and 65, and opposite end walls 66 and 67 of the cam 36 have outwardly facing camming surfaces 69 and 70, the surface 69 being between the projections 61 and 63, and the surface 70 being between the projections 60 and 62. Thus, the cam 36 provides three camming elevations for operation of the translating pins 45, one being on the bottom surface of the projecting portions 60 and 61, a second being at the bottom face 36a, and a third being at the outer edge of the camming surfaces 69 and 70. Accordingly, the cam 36 is operable to move each of the push buttons 52 of the switches 54 and 57 by means of the translating pins 45 selectively into the three distinct positions mentioned above.

As previously described, the translating pins 45 are free to slide within the confines of the openings 44 and 50. As illustrated in FIG. 1, the lower end portion of each translating pin 45 terminates in a flat surface against which the push button 52 of the switches 54 bear, the outward bias of the self-restoring push buttons 52 urging the translating pins into engagement at their upper ends with the under surface of the operating cam 36. Thus, in effect, the translating pins 45 act as extensions of the push buttons 52, thereby causing the push buttons to be operated by the camming surfaces 64, 65, 69, and 70 of the cam 36. But for the operating cam 36, the push buttons 52 would assume their respective fully-extended or released positions.

In the central or OFF position of the switch operator illustrated in FIG. 1, both push buttons 52 engage the face 36a of the operating cam 36 and thus are depressed to their intermediate position so that all circuits of the switches 54 are open. By way of illustrating the operation of the cam 36, it will be observed that as the cam 36 is slidingly moved to the left from the position shown in FIG. 1, the right hand one of the translating pins 45 will, under the self-restoring bias of its as sociated push button 52, follow the camming surface 69 so as to permit the right hand push button 52 to assume its released or extended position. Similarly, as the operating cam 36 is moved to the right from the position shown in FIG. 1, the left hand one of the translating pins 45 will follow the camming surface 70, thereby permitting the left hand push button 52 to assume a released position.

Movement of the push buttons 52 between their intermediate and depressed positions is effected by movement of the operating cam 36 along a path normal to that which moves the push buttons 52 between their intermediate and released positions. As viewed in FIG. 1, this path of movement is into and out of the plane of the sheet of drawing. Movement of the operating cam 36 normal to the plane of the drawing and toward the viewer causes the camming surface 65 to urge the right hand one of the translating pins 45 downwardly so as to urge the associated push button 52 against its self-restoring bias to its depressed position. In like fashion, sliding movement of the operating cam 36 into the plane'of the drawing and away from the viewer causes the camming surface 64 (See (FIG. 3) to urge the left hand one of the push buttons 52 against its self-restoring bias to its depressed position. In this manner, selective movement. of the operating cam 36 from its central position to four positions within the cruciform shaped recess 42 (FIG. 5) effects selective operation of the switches 54 and the switches 57, if used.

Movement of the operating cam 36 in the recess 42 is caused by movement of the lower end portion 34 of the operator arm 24. The operator arm 24 may be selectively manipulated from its central or OFF position, as illustrated in FIG. I, to any of four distinct positions determined by the clover-leaf shaped opening 21. The lower end portion of the operator arm 24 is similarly guided in complementary fashion by the interaction of the indexing collar 38 with a clover-leaf shaped opening 39b in the guide plate 39, the lower end portion of the indexing collar being urged into abutting relationship with the edges of the opening 39b by the bias of the springs 40 and 41.

By the use of the interchangeable guide plates illustrated in FIGS. 6 9, the switch operator mechanism can be assembled to ,provide four different modes of operation, selectively. Three position or five position operation may be provided with either maintained or momentary operation of the switches 54. Each of the guide plates of FIGS. 6 9 is proved with a pair of holes like the holes 390 of the guide plate 39 which cooperate with the locating nibs 18 of the flange portion 12 to insure proper orientation of each guide plate with respect to the remainder of the switch operator mechanism. The function and operation of each of the guide plates will now be described.

FIG. 6 illustrates a guide plate 71 that provides momentary contact, three-position operation. The guide plate 71 is provided with a raised boss 72 having a curved recess 73 therein with an elongated indexing slot 74 within the recess 73. When the guide plate 71 is assembled in the switch operator mechanism intermediate the flange portion 12 and the upper base portion 43, the lower portion of the indexing collar 38 is guidingly positioned in the slot 74. As is evident from FIG. 6, the indexing slot 74 limits movement of the operator arm 24 to a single path of movement even though the clover-leaf shaped opening 21' in the body member would otherwise permit movement of the operator arm in two mutually perpendicular paths. When the operator arm 24 is in its central or OFF position, the indexing collar 38 is disposed at the bottom of the recess 73 intermediate the ends of the slot 74. As the operator arm 24 is moved in its path of movement to either side of the OFF position, the indexing collar 38 is caused to slide along the surface of the curved recess 73 in a path defined by the slot 74. The recess 73 is concave upwardly so that as the indexing collar 38 moves in either direction from the OFF position, it is caused to slide axially along the operator arm 24 in a direction to further compress the spring 40. The bias of the spring 40 and the cooperation of the indexing collar 38 with the curved recess 73 cause the operator arm 24 to return to its central position if the operator arm 24 is moved in either of its two directions from the OFF position and then released. The conical spring 41 also assists in restoring the operator arm to its OFF position. To minimize sliding friction between the indexing collar 38 and the guide plate 71, the collar 38, as previously mentioned, is preferably formed of oil-impregnated sintered iron material. Thus, the guide plate 71 provides threeposition momentary contact operation for the switch operator mechanism.

The guide plate 39 of FIGS. 1, 2, 4, 5 and 7 provides fiveposition maintained-contact operation for the switch operating mechanism. For this purpose, the guide plate 39 is provided with the generally quatrefoil shaped opening 39b defin ing four indexing slots 76-79 which are aligned with the recesses'of the opening 21 in the upper wall portion of the body member 10. In operation, the indexing collar 38 may be moved selectively into any one of the four slots 76-79 where it will remain because of interaction between the indexing collar 38 and the guide plate, until forcibly returned to the central or OFF position. This is accomplished in the following manner. Because the indexing slots 76-79 are generallycoplanar, the indexing collar is urged, by the spring 40, to slide downwardly along the operator arm 24 in a direction to permit the spring 40 to expand as the operator arm is moved from its OFF position. Conversely, in order to return the arm 24 to its central or OFF position, the indexing collar must slide along the arm 24 in a direction to compress the spring 40. Hence, if the operator arm 24 is moved from its central position to any one of the four positions corresponding to the slots 76-79, positive force is required to return the operator arm to the OFF position. In the OFF position, the indexing collar 38 is seated at the center of the opening 39b against the cusps defining the slots 76-79 where it is resiliently retained by the springs 40 and 41.

The guide plate 80 of FIG. 8 provides five-position momentary contact operation for the switch operator mechanism. The manner of cooperation of the indexing collar 38 with the guide plate 80 is similar to that described in connection with the guide plate 71 of FIG. 6 in that the collar 38 is caused to follow a curved recess 81, thereby to permit the springs 40 and 41 to return the operator arm 24 to its central position from any of its four operating positions. In the guide plate 80, however, there is provided a quatrefoil-shaped opening 82 having four indexing slots 83-86, thereby to permit operation of the operator arm 24 to five operating positions rather than the three positions of the guide plate 71.

The guide plate 870! FIG. 9 provides maintained contact operation in a fashion similar to the guide plate 39 of FIGS. 1, 2, 4, 5 and 7, but when the guide plate 87 is used the operator arm 24 is restricted to bi-directional operation from the OFF position in a single path of movement. As illustrated in FIG. 9, a slot 88 has a number of protrusions 88a over which the indexing collar 38 passes as it moves from its central position to either of its operating positions. The protrusions 88a define a seating portion intermediate the ends of the slot 88 where the indexing collar 38 is resiliently retained when the arm 24 is in the OFF position.

As previously mentioned, the screws 19 maintain the switch operator mechanism in assembled relationship. The screws 19 pass through aligned openings in the lower base portion 51,

the upper base portion 43, and the selected 51, the upper of the guide plates and are threadedly received in the tapped openings in the locating nibs 18, the heads of the screws being recessed in the base portion 51.

Referring now to FIG. 10, there is illustrated a modified operating mechanism which includes an OFF-point latch assembly. In this assembly, the hollow upper sleeve portion 24a and the bore 24c in the lower stem portion 24b of the operator arm 24 accommodate a releasing mechanism including a release pin or shaft 89 having a larger diameter head 89a projecting into a recessed portion of a knob 90 and an undercut lower portion surrounded by a helical spring 91. A cross pin 92, slidable axially of the stem portion 24b within the confines of the transverse bore 24d, rigidly couples a bearing sleeve 93 to the release pin 89 and the release pin 89 is normally biased by the spring 91 to position the side of the bearing sleeve 93 centrally within the opening 21. With the release pin 89 and bearing sleeve 93 in the position shown in FIG. 10, the operator arm 24 is prevented from movement out of its central portion, however, upon depressing the release pin 89 against the bias of the coil spring 91, the release pin and bearing sleeve 93 are moved downwardly, whereby the operator arm 24 may be moved as determined by the indexing slots of the selected one of the guide plates 39, 71, and 87.

Referring now to FIG. 2, it will be observed that the combined thickness or height (measured vertically in FIG. 2) of the base portions 43 and 51 is approximately equal to the height of one of the switches 54. Such sizing of the base portions was purposefully accomplished to enable users of this joy stick operator mechanism to employ a modular approach in designing and building control stations incorporating the mechanism.

We claim:

1. A switch operating mechanism and switch combination comprising a supporting body, an elongated operating member pivotally mounted intermediate its ends on said body and having an upper end portion extending outwardly from said body, means on said body for constraining said operating member for pivotal movement along two mutually-perpendicular paths, a guide plate on said body positioned at a lower end portion of said operating member for restricting said pivotal movement of said operating member in one or both of said paths, a base member positioned below the guide plate, a slidable cam member slidably carried by the base member between the base member and the guide plate and engaged by said other end portion of said operating member for sliding thereby, means for guiding the cam member for sliding movement along two mutually-perpendicular paths corresponding to the paths of movement of the operating member, a pair of pin-receiving openings extending vertically through said base member, translating pins loosely received in said pin-receiving openings and each engaged at their upper end face by said cam, and a pair of switches positioned below the base member and having self-restoring, reciprocable push buttons respectively engaged by the lower end faces of the translating pins.

2. A combination as in claim 1 wherein the means for guiding the cam member comprises a pair of parallel-spaced slots in an upper wall of the cam member and a plurality of spaced guide pins depending from the guide plate, said guide pins being received in said slots for guiding the cam member in one of its paths of movement and engaging opposite side faces of the cam member for guiding the cam member in its other path of movement.

3. A combination as in claim 1 wherein the means for guiding the cam member comprises a cruciform-shaped recess in an upper wall of the base member and the cam member is received in the recess.

4. A combination as in claim 1 wherein the lower face of the cam member is provided with two camming areas each having three camming elevations and so positioned that the camming areas respectively engage upper end faces of the translating pins to provide three operating positions for each of the pins selectively.

5. A combination as in claim 1 wherein the lower ends of the openings in the base member have shouldered areas restraining the translating pins within the openings while permitting their lengthwise movement in response to movement of the cam member and the self-restoring action of the push buttons.

6. A combination as in claim 5 wherein the base member comprises separate upper and lower base portions held in face-to-face engagement, the cruciform-shaped recess is in the upper wall of the upper base portion, and a pair of upper openings in the upper base portion are axially aligned with a pair of lower openings in the lower base portion and constitute said pair of pin-receiving openings extending through the base member, the lower openings are of larger diameter than the upper openings, the translating pins have lower enlarged portions of greater diameter than the upper openings and said lower enlarged portions are received in the lower openings.

7. A combination as in claim 1 wherein an indexing collar is slidably received on the operating member above the guide plate, the guide plate has a guiding recess in an upper wall surface thereof, and spring means are provided for biasing the collar into engagement with the recess thereby to restrict movement of the indexing collar and the operating member along one or both of said paths.

8. A combination as in claim 7 wherein the area around the guiding recess is concave upwardly so that when the guiding collar is moved selectively from an intermediate position toward the outer ends of the guiding recess by movement of the operating member, the spring means is compressed thereby to urge the indexing collar and the operating member toward the intermediate position.

Claims (8)

1. A switch operating mechanism and switch combination comprising a supporting body, an elongated operating member pivotally mounted intermediate its ends on said body and having an upper end portion extending outwardly from said body, means on said body for constraining said operating member for pivotal movement along two mutually-perpendicular paths, a guide plate on said body positioned at a lower end portion of said operating member for restricting said pivotal movement of said operating member in one or both of said paths, a base member positioned below the guide plate, a slidable cam member slidably carried by the base member between the base member and the guide plate and engaged by said other end portion of said operating member for sliding thereby, means for guiding the cam member for sliding movement along two mutually-perpendicular paths corresponding to the paths of movement of the operating member, a pair of pinreceiving openings extending vertically through said base member, translating pins loosely received in said pin-receiving openings and each engaged at their upper end face by said cam, and a pair of switches positioned below the base member and having selfrestoring, reciprocable push buttons respectively engaged by the lower end faces of the translating pins.

2. A combination as in claim 1 wherein the means for guiding the cam member comprises a pair of parallel-spaced slots in an upper wall of the cam member and a plurality of spaced guide pins depending from the guide plate, said guide pins being received in said slots for guiding the cam member in one of its paths of movement and engaging opposite side faces of the cam member for guiding the cam member in its other path of movement.

3. A combination as in claim 1 wherein the means for guiding the cam member comprises a cruciform-shaped recess in an upper wall of the base member and the cam member is received in the recess.

4. A combination as in claim 1 wherein the lower face of the cam member is provided with two camming areas each having three camming elevations and so positioned that the camming areas respectively engage upper end faces of the translating pins to provide three operating positions for each of the pins selectively.

5. A combination as in claim 1 wherein the lower ends of the openings in the base member have shouldered areas restraining the translating pins within the openings while permitting their lengthwise movement in response to movement of the cam member and the self-restoring action of the push buttons.

6. A combination as in claim 5 wherein the base member comprises separate upper and lower base portions held in face-to-face engagement, the cruciform-shaped recess is in the upper wall of the upper base portion, and a pair of upper openings in the upper base portion are axially aligned with a pair of lower openings in the lower base portion and constitute said pair of pin-receiving openings extending through the base member, the lower openings are of larger diameter than the upper openings, the translating pins have lower enlarged portions of greater diameter than the upper openings and said lower enlarged portions are received in the lower openings.

7. A combination as in claim 1 wherein an indexing collar is slidably received on the operating member above the guide plate, the guide plate has a guiding recess in an upper wall surface thereof, and spring means are provided for biasing the collar into engagement with the recess thereby to restrict movement of the indexing collar and the operating member along one or boTh of said paths.

8. A combination as in claim 7 wherein the area around the guiding recess is concave upwardly so that when the guiding collar is moved selectively from an intermediate position toward the outer ends of the guiding recess by movement of the operating member, the spring means is compressed thereby to urge the indexing collar and the operating member toward the intermediate position.

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