US3068817A - Zig-zag sewing machine - Google Patents

Description

Dec. 18, 1962 s. J. HAMLETT 3,068,817

ZIG-ZAG SEWING MACHINE Filed April 26, 1960 5 Sheets-Sheet l INVENTOR. S/D/VEY \T IVA V1577" BY iP/CHE' Y, MF/VE/V/V Kg F4 Eli/N670 A 7' 7' DRIVE Y5 Dec. 18, 1962 s. J. HAMLETT ZIG-ZAG SEWING MACHINE 5 Sheets-Sheet 2 Filed April 26, .1960

INVENTOR. SIDNEY \7 HAMLETT MSNENN Ya? FA IER/NGTON R/CHE Y,

4 7'7'OENEYS Dec. 18, 1962 s. J. HAMLETT ZIG-ZAG SEWING MACHINE 5 Sheets-Sheet 3 Filed April 26, 1960 INVENTOR. SIDNEY J. HAML 77 R/cHEY, Mf/VF/WR/NGTON ATTORNEYS.

Dec. 18, 1962 s. J. HAMLETT 3,068,817

ZIG-ZAG SEWING MACHINE Filed April 26, 1960 5 Sheets-Sheet 4 IN VEN TOR. SIDNEY I HAMLETT BY 2/6/15); MEA/ENNYJFARRM/a 701v Dec. 18, 1962 8. J. HAMLETT ZIG-ZAG SEWING MACHINE 5 Sheets-Sheet 5 Filed April 26, 1960 m m m m SIDNEY J: HAMLETT BY E/cmsx SNf/VNYJFA/YR/NGTON WTTORNEYS United States Patent 3,068,817 ZIG-ZAG SEWING MACHINE Sidney J. Hamlett, Parma, Ohio, assignor to White Sewing Machine Corporation, Cleveland, Ohio, at corporation of Delaware Filed Apr. 26, 1960, Ser. No. 24,774 2 Claims. (Cl. 112-158) This invention relates to household sewing machines in general, and more particularly to Zig-zag stitch sewing machines having an oscillating needle bar guide whose motion may be controlled by a cam disc which is readily removable and replaceable with other discs to select the desired stitch pattern.

The principal object of this invention is to simplify the operation of removing and replacing interchangeable cam discs by eliminating the necessity of manually pull ing the cam follower radially away from the cam to permit removal or replacement.

Another object of this invention is to simplify and improve the operation of selecting and engaging a cam follower with one of a plurality of axially aligned cams, one or more of which may be permanently installed in the machine and at least one of which is removable and replaceablei Another object of this invention is to provide a zigzag sewing machine in which interchangeable pattern cam discs can be readily removed and replaced by other cam discs without making any adjustments in the cam follower and the needle bar guide oscillating mechanism.

Another object of the present invention is to provide a zig-zag sewing machine employing interchangeable pattern cam discs in which the discs can be removed and replaced at any time regardless of the rotational position of the cam shaft.

Another object of the present invention is to provide a zig-zag sewing machine in which interchangeable cam discs can be removed and replaced on the cam shaft without disengaging the needle bar guide actuating mechanism and without shifting or releasing the cam follower from its engaged position on the periphery of the cam disc.

Yet another object of the present invention is to provide a zig-zag sewing machine in which the cam follower is continually spring loaded into contact with the interchangeable cam disc and in which the inward movement of the cam follower is limited by a stop. All of the cam discs regardless of the pattern are arranged to have a low point in the pattern corresponding to the position of the cam follower when engaged with the stop in which the periphery of the cam disc is cut away at that point to form a notch which is slightly deeper than the remainder of the periphery to allow clearance between the notch and the cam follower so that the cam disc can be removed and replaced in this position without interference from the cam follower.

Still another object of the present invention is to provide a. zig-zag sewing machine in which the motion of the needle bar guide is controlled selectively by either a fixed pattern cam or one of a set of interchangeable pattern earns, the motion being transmitted through a single cam follower which is shifted axially of the stack of cams along the cam shaft to allow the needle bar guide to be oscillated by the selected cam and in which the cam follower may be moved between the removable cam and the fixed cam at any time and without disengaging the cam follower radially away from the surface of the cams.

Still another object'of the present invention is to provide a zig-zag sewing machine employing interchangeable pattern cam discs-in which the interchangeable cam discs can be removed and replaced while the machine is running and while the cam follower is inv position to engage the 3,068,817 Patented Dec. 18, 1962 ptezrlifphery of a cam disc in operating position on the cam S t.

The above and other and additional objects and advantages of the present invention have been accomplished according to the preferred embodiment of the invention by providing a cam shaft which extends horizontally from front to back in the sewing machine frame and which is rotatably driven through a worm and worm gear drive from the machine main drive shaft. A fixed zig-zag cam is secured near the front end of the cam shaftand a space is provided in front of the fixed zig-zag cam for installing any one of a number of interchangeable pattern cams. A cam follower has been provided which is mounted for both pivotal and axially slidable movement along a pivot shaft by a selector mechanism. The cam follower is spring loaded into contact with the periphery of the cams, and the motion of this cam follower 'is transferred through a lever arm secured to a rocker shaft and a variable stroke length mechanism directly to the needle oar guide.

The periphery of each of the pattern cam discs has a low point, which, on installation, is arranged to be aligned with the cam follower in accordance with suitable indicia provided on the machine frame and on the cam disc. A stop is provided to limitthe inward travel of the cam follower and hold it out of engagement'with the alignment notch, but without limiting the normal travel of the cam follower and \the cam pattern. The cam disc is easily installed by aligning the indicia marks and moving the cam disc axially toward the fixed cam, after which the cam disc is rotated relative to the cam shaft until a projecting pin on the side of the fixed zigzag cam engages a notch on the side of the cam disc to provide a locking and driving connection with the machine cam shaft. A spring-loaded lost motion linkage is interposed between the selector lever and the cam follower so that the selector lever may be moved directly to the desired position and a spring load is placed on the cam follower to move axially of the cam shaft in the selected direction. Whenever the relative positions of the cams allow the cam follower to move from the fixed cam to the removable cam disc, or vice versa, the applied spring load will irnmediately move the cam follower into the desired position without need of disengaging the cam follower and moving it radially away from the cam discs.

Funther details and features of the invention are shown in the accompanying drawings of a preferred embodiment of the invention whose constructimrand operation are described in the following detailed specification.

In the drawings:

FIG. 1 is a front elevational view of a sewing machine incorporating the present invention;

FIG. 2 is a front elevational view with parts broken away to show the pattern control mechanism arranged for maximum width;

FIG. 3 is a top plan view of a machine with removed;

FIG. 4 is a fragmentary front elevational view with parts broken away to show the pattern control mechanism arranged for straight stitching;

FIG. 5 is a fragmentary cross-sectional view through the pattern cam shaft and its mounting bracket;

FIG. 6 is a fragmentary cross-sectional view taken on line 66 of FIG. 3 to show the width adjustment;

FIG. 7 is a cross-sectional view taken on line 7-.7 of FIG. 2 showing the cam follower shifted to engage the fixed zig-zag cam;

FIG. 8 is a cross-sectional view similar to FIG. 7 but showing the cam follower shifted to engage the removable pattern cam; and

FIG. 9 is a fragmentary perspective view of the lost the cover motion linkage in the selector for shifting the cam follower.

Referring now to the embodiment of the invention shown in the drawingsin greater detail, the sewing machine shown generally in FIG. 1 includes a bed plate a head portion 13. As shown more particularly in FIGS.

2 and the machine has a main drive shaft 14 which extends horizontally through the interior of the hollow arm 12 and is journaled in a pair of bearing blocks 15 and 16. A pulley wheel and clutch mechanism 17 is secured on the one end of drive shaft 14 extending outward of the column 11 to allow the drive shaft 14 to be rotatably driven in' the usual manner by belt connection to an electric motor (not shown).

On the opposite end of the drive shaft 14 outboard of the'outer bearing block 16 is located the crank mechanism 18 which serves to oscillate the needle bar (not shown) in the manner well known in the art. The needle bar is mounted for reciprocating sliding movement in the usual manner on the needle bar guide 19 which in turn is pivotally mounted at its upper end on head 13 by pivot bolt 20 for oscillating movement about a horizontal axis, laterally across the bed plate 10. It will be understood that by oscillating the needle bar guide 19 in timed relationship with the cyclic operation of the needle bar and the remainder of the stitch-forming mechanism, that various stitch patterns can be obtained. The present invention is concerned'with the pattern mechanism for oscillating the needle bar guide, and the remaining portions of the complete sewing machine will not be described in further detail.

7 In accord' with the usual sewing machine construction, the column 11, transverse arm 12, and head 13 are preferably formed together as a unit in a casting of a suitable metal such as cast iron or, for purposes of light weight, aluminum. By virtue of this construction, the casting has relatively thick walls which serve both as the frame on which the various portions of the mechanism'are mounted as well as a protective cover and shield enclosing the various moving parts. The casting is open at the top and is fitted with a suitable protective cover 23 formed of sheet metal or other suitable material.

The front and rear side walls 21 and 22, respectively, of the frame casting are each provided with an inwardly extending boss 24, and these bosses are drilled to receive a horizontally extending support shaft 25 which is secured in place within the bosses by suitable set screws 26 The support shaft 25 serves as a mounting for the cam shaft bracket 27 which has a tubular section 28 bored to fit on'thesupport shaft 25. The cam shaft bracket 27 is locked against rotation about support shaft 25 by apair of set screws 29 which are threaded in the tubular section 28 to lock the bracket securely in position on shaft 25.

Extending horizontally outward from the tubular section 28 are a pair of arms 30 and 31 which terminate at their outer ends in enlarged bosses 32 and 33. These bosses 32 and 33 are drilled to provide hearings to journal the cam shaft 35, as shown in greater detail in FIG. 5. Cam shaft 35 is rotatably driven in timed relationship with the main drive shaft 14, and to that end is provided with a worm gear 36 which is secured on the cam shaft between the bosses 32 and 33. Worm gear 36 serves to drive the cam shaft 35 by making driving engagement with a worm 37 secured on the main drive shaft 14 adjacent the inner bearing block 15. To position cam shaft 35 against axial movement, the worm gear 36 is secured 'on the cam shaft adjacent the front boss 32,

- formed radial cam disc 40 whose outer periphery is formed with a series of regularly spaced notches. The disc 40 may be a single cam or a series of fixed cams.

The notches are spaced uniformly around the axis of' the cam to divide the outer periphery of the cam into crest portions 41 and valley portions 42 spaced apart by sloping connecting surfaces. The number of these crests and valleys is chosen to correspond to the gear ratio between worm 37 and worm gear 36, so that for each revolution of main drive shaft 14, and hence one complete reciprocation of the needle, the cam disc 40 is rotated through an angular distance corresponding to the distance between an adjacent crest and valley, and vice versa.

' In front ofthe integral cam disc 40, the cam shaft has a reduced shaft portion 45 on which the interchangeable cam discs 46 are mounted. These cam discs 46 are made of a suitable material such ashard plastic or metal, and are provided with an outer periphery 47 having a shape corresponding to the desired pattern of movement for the needle bar carrier. The cam disc 46 is rotatably driven by means of a radially extending slot 48 in the web of the disc which fits over a projecting pin 49 on the side of the integral cam disc 40. In order to hold the interchangeable cam disc 46 in place on the reduced shaft portion 45 adjacent the integral cam disc 40, the cam disc 46 is provided with an enlarged recess 51 inits hub or shank portion 52 to make engagement with a detent spring 53 fitted within an axially extending bore 54 in reduced shaft portion 45.

A pivot shaft 56 is mounted on the frame casting below the main drive shaft 14 to extend parallel to the cam shaft 35. This pivot shaft 56 is mounted at each end within projecting bosses 57 on the front and rear side walls 21 and 22 and is secured in place by set screws 58 in the usual manner. Pivot shaft 56 serves as a supporting mount for the cam follower member indicated generally at 59. Cam follower member 59 has a tubular section 60 provided with an axially extending bore to fit on pivot shaft 56 so that the cam follower member is journaled thereon for both pivotal and axially slidable movement. A cam follower arm 61 is secured at its one end to the front portion of tubular section 60 and extends upward adjacent the cam discs 40 and 46 where it is provided with a contacting tip 62 which projects inwardly toward the cam shaft 35 to make contact with the periphery of the cam discs 40 and 46.

To limit pivotal movement of the cam follower arm 61 and contacting tip 62 in the direction of cam shaft 35, a stop plate 64 is secured to the front side wall 21 of the frame casting to extend inwardly and make abutting cngagement with the cam follower arm 61 as the latter pivots toward cam shaft 35. A depending lug 65 is formed on the stop plate 64 and serves as the fixed support for a coil tension spring 66 extending between the lug 65 and the midpoint of cam follower arm 61. Tension spring 66 provides a spring bias for the cam follower 59 tending to rotate the follower about the'pivot shaft 56 so that the arm 61 is normally positioned in contact with the stop plate 64 unless moved outward as a result of contact between the contacting tip 62 and a raised portion on one of the cam discs 40 and 46.

The mechanism whereby the motion of the cam follower 59 is transferred to the needle bar guide 19 is shown in FIGS. 2, 3, 4, and 6. As ,is shown most clearly in FIG. 3, the frame side walls 21 and-22 are provided with anotherset of lugs or bosses 69 which support a mounting plate 70 which is fastened to the lugsby screws 71. 7 At its one end adjacent the cam shaft 35, mounting plate 70 is provided with a suitable transversely extending bore to, journal a rocker shaft 72. 'On the front end of rocker shaft 72 outward of the mounting plate 70 there is secured a lever arm 73 locked in place on the shaft by means of a set screw 74. Lever arm 73 extends angularly downward adjacent the outer end of cam follower arm 61 Where it terminates in a contacting tip 75 adapted to bear against the follower arm and receive the movement imparted to the cam follower and transfer such motion into oscillatory rotation of rocker shaft 72. The rear end of rocker shaft 72 is formed into an integral lever arm 76 which forms part of an adjustable, variable length lever arm mechanism. To allow for this length adjustment, lever arm 76 is provided with a rectangular channel 77 cut into its rearwardly facing surface and extending axially along the lever arm with the axis of the channel intersecting the axis of rocker shaft 72. At the lower end of integral lever arm 76, there is located a small depending lug 78 to which is secured a coil tension spring 79. The other end of tension spring 79 is fastened to a lug 80 formed integrally with the rear side wall 22 and serves to bias the rocker shaft72 in the rotational direction wherein the contacting tip 75 of the front lever arm 73 is adjacent cam follower arm 61 and the needle bar guide 19 is in the right hand position, as will be explained in greater detail hereinafter.

To limit the rotation of rocker shaft 72 under the biasing action of tension spring 79, a bracket plate 82 is fastened on the upper end of the integral rear lever arm 76 and carries a stop screw 83 threaded in the bracket plate and locked in position by lock nut 84. Stop screw 83 is adjusted to come into abutting contact with the upper surface of mounting plate 70 and thereby prevent further rotation of lever arm 76 under the bias of tension spring 79 to provide a limiting position for the needle bar guide 19 in the direction toward hollow standard 11 when the width control mechanism is set for maximum width, all as will be described in greater detail hereinafter.

At the opposite end of mounting plate 70 from rocker shaft 72, a second transverse bore is provided to journal the control shaft 86. On the front end of control shaft 86 in front of mounting plate 70 there is secured a stop arm 87 which serves to limit the rotation of the control shaft 86 in both directions. When control shaft 86 is rotated in the counterclockwise direction as seen in FIG. 4, the stop arm 87 moves into abutting contact with the adjacent mounting lug 85 of the mounting plates 70 to prevent further rotation of control shaft 86 in that direction. When the control shaft 86 is rotated in the clockwise direction, a stop screw 88 threadedly engaged on the outer end of stop arm 87 makes abutting contact with the beveled surface of a projecting lug 89 also formed as a part of the mounting plate 70.

Rearwardly of the mounting plate 70, a release arm 90 is secured on the control shaft 86 and carries a contacting tip 91 which is positioned to contact the under side of a projecting tab 92 on bracket plate 82. When the control shaft 86 is rotated in the counterclockwise direction, tip 91 engages the projecting tab 92 to rotate the lever arm 76 and hence rocker shaft 72 to a position where the front lever arm 73 is moved away from the cam follower arm 61. Rearwardly of release arm 90 another lever arm 94 (see FIG. 6) is secured on the end of control shaft 86 and at its outer end is pivotally connected to a connecting link 95 by a suitable pivot screw 96. The lower end of connecting link 95 is pivotally connected to a connecting rod 99 by another pivot screw 97.

The connecting rod 99 serves to transfer the motion of the cam follower 59 and rocker shaft 72 to the needle bar guide 19. As shown in FIGS. 2 and 3, connecting rod 99 extends lengthwise through the hollow transverse arm 12 and into the head 13. Within head 13, the connecting rod 99 has an offset end 100 which is secured by a suitable pivot bolt 101 to a projecting lug or ear 102 on the lower end of needle bar guide 19. At the other end of the connecting rod 99, a pivotally mounted guide block 104 is secured to the connecting rod end and positioned to ride within the rectangular channel 77 on variable length lever arm 76. Since the lower end of the needle bar guide 19 is rigidly connected through connecting rod '99 to lever arm 76 and hence rocker shaft 72, the oscillating movement of the rocker shaft is translated directly into oscillating or vibratory movement of the needle bar guide 19, the amplitude of movement of the latter being determined by the position of guide block 104 along channel 77. Thus, movement of the needle bar guide toward the right as seen from the front of the machine occurs under the action of tension spring 79, while movement to the left results from the movement of the cam follower 59 away from camshaft 35 being transmitted to rocker shaft 72 through the front lever arm 73.

To allow the control shaft 86 to be readily rotated by hand, the control shaft extends toward the front of the machine and passes through an opening 186 in the front side wall 21. On the outer end of control shaft 86 on the front side of wall 21, there is mounted a control lever 107. Control lever 107 is provided with an attached indicia plate 108 on which are printed suitable indicia marks in the form of numbers visible to the operator through a small window 109 formed in the cover 110 which extends over the front of the transverse arm portion of the machine. The marks or numbers on indicia plate 108 serve to indicate to the user of the machine the relative position of control lever '187 and hence the rotary position of control shaft 86. In order that the control shaft 86 may not rotate too freely and thus move out of the desired position of adjustment as a result of the vibration of the machine, an adjustable drag is provided. A block 135 is secured by screws 136 on mounting plate 70 above the control shaft 86. A screw 137 held in position by locknut 138 is threaded in block 135 and applies downward pressure on a plunger or drag shoe (not shown) within mounting plate 70 which in turn bears against the surface of the control shaft. By adjusting screw 137, this drag may be made great enough to hold the shaft in position, yet allows it to be turned without excessive efiort by the operator of the machine.

It will be seen that rotation of control shaft 86, through the motion of lower arm 94 and connecting link 95, will raise and lower the inner end of connecting rod 99 and hence slide the guide block 104 along the axis ofrectangular channel 77. When the control lever 107 is moved to the position of FIG. 4, so that-stop arm 87 is in contact with mounting lug 85, the pivot axis of the guide block 104 is in alignment with the axis of rocker shaft 72 so that any oscillatory motion imparted to the rocker shaft 72 will not impart any movement to the connecting rod 99 and the needle bar guide 19. In addition, connecting rod 99 is made of such a length that in this position the needle bar guide 19 is positioned at the center of its path of oscillation for straight stitch sewing. As the control lever 107 is rotated in a clockwise direction toward the position of FIG. 2, the guide block 104 is moved down the rectangular channel 77 to provide an increasingly effective length for the variable length lever arm 76. When the control lever '107 is moved into the full clockwise position of FIG. 2, contact between stop screw 88 and beveled surface 89 serves to limit further rotation of the control shaft 86 and hence further movement of guide block 104 within rectangular channel 77 to define the maximum length of lever arm 76 and in turn the maximum possible amplitude for the zigzag oscillation of the needle bar guide 19.

The selector mechanism for shifting the cam follower 59 axially along pivot shaft 56 to choose between operation by the integral cam disc 40, or a particular part thereof, or one of the interchangeable cam discs 46, is best shown in FIGS. 2, 7, 8, and 9. A boss projects outwardly from the portion of the inner Wall of column 11 which is beneath the transverse arm portion 12. This boss is drilled axially to receive the threaded end of a pivot shaft or bolt 116 having an enlarged slotted head 117 at its other end. An elongated actuating lever 118 having an upper end 119 and a lower end 120 is pivotally mounted at its midpoint on pivot shaft 116 adjacent the end of the boss 115. Upper end 119 carriesa projecting pin 121 to make engagement within a vertical slot 122 cut in the end of tubular section 60 of the cam follower member 59. It will be seen therefore that pivotal movement of the actuating lever 118 about pivot shaft 116 will cause pin 121 to move the tubular section 60 axially along the pivot shaft 56 to shift the contacting tip 62 of the cam follower between the integral cam 40 and the interchangeable cam disc'46.

A selector lever 123 is also pivotally mounted on the pivot shaft 116 between actuating lever 118 and the slotted head 117. ,To allow manipulation of the selector lever 123, the lever is provided with a handle 124 which projects outwardly toward the front of the machine through opening 125 formed in the wall of the hollow column 11. A slotted cover plat-e113 fits over opening 125 to receive and, guide the movement of handle 124. Three detent notches 126, 127 and 128 are provided at the bottom, width and top, respectively of the slot in cover plate 113 to receive the handle 124 and hold selector lever 123 and cam follower 59 in the three operating positions, as described in detail hereinafter.

The selector lever 123 is provided with upper and lower arms 129 and 130, respectively, to extend outwardly from pivot shaft 116 adjacent the upper and lower arms 1'19 and 120 of actuating lever 118. A coil torsion spring 131 has its body portion wound about the pivot shaft 116 between slotted head 117 and selector lever 123. Torsion spring 131 is also provided with projecting upper and lower ends 132 and 133, respectively, which extend outward and are formed into hooks extending over the front edges of the arms of both the actuating lever 118 and selector lever 123. Thus upper end 132 of the torsion spring is hooked over the front edge of arms 119 and 129, while the lower end 133 of the torsion spring is hooked over the lower arms 120 and 130.

It will be seen therefore that the actuating lever 118, the selector lever 123, and torsion spring 131 serve to form a resilient lost motion linkage to allow the selector handle 124 to be moved positively into one of the detent notches 126, 127 and 128 while providing only a resiliently limited force upon the cam follower 59 urging it to slide axially toward its corresponding position. For example, if it is desired to move the selector handle 124 from its position indetent notch 127 as shown in FIG. 7 to a position in detent notch 126, as shown in FIG. 8, to shift the cam follower from engagement with the front portion integral cam disc 40 into engagement with the interchangeable cam disc 46, the shape of the cam surfaces on the two cam discs may be such as to interfere with motion of the cam follower in that direction. If the interchangeable cam disc has a profile such as that of cam disc 139 shown in FIG. 4, there will occur rotary positions of the cam shaft in which the adjacentsection of the interchangeable carn disc has agreater radius than the portion of the integral cam disc 40 in which the contacting tip 62 is in engagement. Under these conditions, axial force applied to the cam follower to movetoward the front of the machine will cause the contacting tip 62 to move into abutting engagement with the end surface of cam disc 46, and if suflicient force is applied to the cam follower the interchangeable cam disc will be forced off the end of cam shaft 35.

However, the use of the selector linkage just described results in the axial force applied to the cam follower 59 being limited to that of the tension within the coil torsion will remain in contact with the lower actuating lever from upper actuating lever arm 119' and thereby further] compress the spring. Whenever the cam discs are rotated into an aligned position so that the cont-acting tip 62 can slide axially without resistance, the force of torsion spring 131 acting through its lower end 1330!] the lower actuating lever arm 126 will bias the actuating lever 118 in a counterclockwise direction and slide tubular section 60 toward the front of the machine until the actuating lever 118 and selector lever 123 are again in alignment. If the selector lever is moved in the clockwise direction to shift the cam follower 59 toward the rear of the machine and interference occurs, the'linkage will perform in exactly the reverse manner, so that only the force of the torsion spring 131 is actually applied to slide the cam follower 59 in either direction. As a result -0f-this lost motion linkage, the operator of the machine need not be concerned about the relative positions of'the cam discs or possible interference between them, inasmuch as the selector lever can be moved at any time and the actual shifting of the cam follower will take place only when there is no interference against axial movement between the cams. The three positions of the selector lever handle 124 in the detents 126, 127, and 128 are employed in'the sewing of buttonholes. Utilizing this arrangement, the complete buttonhole can be made simply by moving the selector handle 124 without adjustment of-the width control as determined by the position of control lever 107. When the selector lever handle 124 is in the middle detent 127, the cam follower contacting tip 62 rides on the front portion of the integral cam disc 40 to oscillate the needle bar guide 19 through the full amplitude of oscillation as determined by the position of control leve'r107. The selector lever handle 124 is placed in this positionto make the bar tack stitches at each end of the button hole.

After the initial bar tack has been made, the operator shifts the selector lever handle 124 down to engage the lower detent 126, in which case the cam follower con tacting tip 62 is shifted by the selector linkage to engage the interchangeable buttonhole cam disc 46. This cam disc is arranged to have crest portion 43 and valley portion 44 in corresponding position with the crests and valleys on the-integral cam disc 40, except that the crest portions 43 are of a lesser radius than the crest portions 41 on cam disc 40. As a result of these lower crestportions, the needle bar guide 19 oscillates with a lesser amplitude extending-from the right-hand side to the center of the range of movement for'the bar tack stitches, thereby sewing the right-hand side of the buttonhole.-

Afterthe buttonhole has been sewed to the proper length along the right-hand side, the selector lever handle 124 is shifted back into the middle detent 127 to make the bar tack stitches at the other .end of the buttonhole. To complete the buttonhole, he selector lever handle 124 is shifted into the upper detent 128. In this posi tion,the contacting tip 62-is shifted rearwardly to engage the rear portion of the integral cam disc 40, and the entire cam follower assembly 59 is shifted to a position rearwardly of its middle position as determined by detent 127. In this position, an upwardly extending blade secured at the rearward end of tubular section 60 cam follower oscillates between the high position of crest portion 41 and a mid-position intermediate crest portion 41 and valley portion 42, these positions corresponding to the stitches to make the left-hand side of the buttonhole.

When the selector lever handle 124 is moved upward into upward detent 128, a projecting arm 154 on selector lever 123 engages and lifts a projecting arm 155 on the reverse mechanism indicated generally at 156. Reverse mechanism 156 may be of any design well known in the art, and will not be described in greater detail. By virtue of this engagement, the feeding mechanism of the cloth is reversed in direction so that as the sewing positions of the needle bar guide 19 are shifted to make the left-hand side of the buttonhole, the feed is automatically reversed to return the stitches to the initial bar tack and complete the buttonhole.

The ease with which the interchangeable cam discs can be removed and replaced at any time will be more readily appreciated when viewed in conjunction with the feature shown most clearly in FIGS. 1, 2, and 4.

, As shown in FIG. 2, each of the interchangeable cam discs, such as cam disc 46, is provided on its periphery with a notch 140 where the periphery of the cam has a lesser radius than the remaining portion. When this notch is aligned with the contacting tip 62 of the cam follower, the arm 61 will pivot about pivot shaft 56 into engagement with the stop plate 64 under the action of tension spring 66 while remaining out of contact with the surface of notch 140; Thus the presence of notch 140 allows the cam disc to be moved axially onto the reduced shaft portion 45 without interference from the cam follower contacting tip 62. It will be noted that all of the interchangeable cam discs having various different profiles, such as cam disc 139 shown in FIG. 4, are arranged to have a notch 140 at some position on their peripheries. In order to obtain engagement with the projecting pin 49 on the fixed cam disc 40 to provide the driving connection to the interchangeable cam disc 46, after the cam disc has been placed on reduced shaft portion 45 with the notch 140 in alignment with contacting tip 62, it is necessary only to rotate the cam disc in either direction until the pin 49 is aligned with slot 48, whereupon additional inward axial movement will perfect the locking action of detent spring 53 to hold the cam disc firmly in position.

In order that the operator need not search either visually or by touch to locate the position of contacting tip 62, the cam discs are each provided with an index arrow 141 which is radially aligned with the notch 40. In like manner, another index arrow 142 is provided on the cover 1 also in radial alignment with the contacting tip 62. Therefore, it is necessary only to align the index arrows 141 and 142 when the cam disc is being placed in position and then push the cam inward until movement is stopped by contact between the pin 49 and the face of the cam disc 46. Thereafter, the cam disc is rotated by turning the shank portion 52 until the pin 49 engages slot 48 in the aforedescribed manner.

While in the above described method of installing the interchangeable cam discs it has been assumed that the machine is stopped so that cam shaft 35 is not rotating, the cam discs may also be installed while the machine is running. In this case, the operator will simply place the cam disc 46 in position on reduced shaft portion 45 with the index arrows 141 and 142 in alignment. If the cam discs 46 is then held in that position while the machine continues to run, further rotation of cam shaft 35 and fixed cam disc 40 will bring the pin 49 into alignment with slot 48, whereupon the cam disc 46 will be shifted axially by detent spring 53 the short distance necessary to make engagement.

Inasmuch as the cam follower contacting tip 62 makes engagement only with the peripheral surface of the cam disc, it will be seen that if sufficient outward axial force 10 is applied to the cam disc to overcome the holding action of the detent spring 53, the cam disc can heremoved at any time regardless of the rotational position of the cam disc and regardless of whether or not the cam discs are rotating.

For purposes of safety and appearance, the cover plate is provided with a door shown in the open position in FIG. 1. Door 145 is pivoted on a hinge pin 146 and held closed by a suitable catch mechanism actuated by button .147. Thus the door 145 normally covers opening 111 in cover plate 110 when the machine is running and need be opened only when it is desirable to change one of the pattern cam discs.

While one embodiment of the invention has been shown in the drawings and described in detail in the foregoing specification, the invention is not limited to any particular form, and various arrangements and modifications may be resorted to by those skilled in the art without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

l. A sewing machine comprising a frame, a drive shaft rotatably journaled in said frame, a needle bar guide pivotally mounted on said frame for lateral swinging movement, a needle bar slidably mounted on said needle bar guide for endwise reciprocation in timed relationship with said drive shaft, a cam shaft on said frame rotatably driven in timed relationship with said drive shaft, a cam disc releasably secured to said cam shaft, said cam disc having a minimum radius portion on its periphery, said cam disc also having a portion of its periphery at greater radius than said minimum portion, a cam follower mounted on said frame for movement to and from said cam disc, said cam follower having a contacting tip adapted to engage the peripheral surface of said cam disc, means resiliently biasing said cam follower toward said cam disc, the periphery of said cam disc having a notch with a surface portion of lesser radius than said minimum radius portion, stop means engageable by said cam follower to limit movement of said cam follower toward said cam disc, said stop means being positioned to be engageable by said cam follower only when said contacting tip engages said notch, and linkage means connected to said needle bar guide and operable by movement of said cam follower to oscillate said needle bar guide in response to the pattern of said cam disc.

2. A sewing machine comprising a frame, a drive shaft rotatably journaled in said frame, a needle bar guide pivotally mounted on said frame for lateral swinging movement, a needle bar slidably mounted on said needle bar guide for endwise reciprocation in timed relationship with said drive shaft, a cam shaft on said frame rotatably driven in timed relationship with said drive shaft, a radial cam disc releasably secured on said cam shaft, said cam disc having a minimum radius portion on its periphery, said cam disc also having a portion of its periphery at greater radius than said minimum portion, a cam follower pivotally mounted at one end on said frame, the other end of said cam follower having a contacting tip engageable with the periphery of said cam disc, means resiliently biasing the other end of said cam follower toward said cam disc, the periphery of said cam disc having a notch with a surface portion of lesser radius than said minimum radius portion, stop means on said frame engageable by said cam follower to limit pivotal movement of said cam follower toward said cam disc, said stop means being positioned to be engageable by said cam follower only when said contacting tip engages said notch, a rocker shaft pivotally mounted on said frame parallel to said cam shaft, a lever arm secured to one end of said rocker shaft and having an end portion extending adjacent the other end of said cam follower to make abutting contact therewith whereby movement of said other end of said cam follower away from said cam disc rotates said rocker shaft in one direction, an adjust- 11 1'2 able lever arm secured to the other end of said rocker 2,833,233 DAmico a May 6,-1958 shaft, 'and linkage meansconnected to said needle bar 2,972,319 Moro Feb. 21, 1961 guide and operable by movement of said adjustable lever FOREIGN PATENTS arm to oscillate said needle bar guide in response to the I a oscillation of said rocker shaft. 5 517,363 Italy Feb, 28, 1955 518,288 Italy Mar. 5, 1955 References Cited in the file of this patent 1 756,403 Great Britain Sept. 5, 1956- I 1,143,022 France Apr. 8, 1957 UNITED STATES PATENTS 1,143,023 France I Apr. 8, 1957- Enos APR 958 10 219,620 Australia Jan. 14, 1959

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