US3499404A - Buttonhole sewing machine with improved stopping mechanism - Google Patents

Description

K. NICOLAY 3,499,404

BUTTONHOLE SEWING MACHINE WITH IMPROVED STOPPING MECHANISM March 10, 1970 5 Sheets-Sheet 1 Filed Sept. 25, 1968 Karl Nicolay INVENTOR 6 4mm N 1: 9 HH l Y March 10, 1970 K. NICOLAY 3,499,404

BUTTONHOLE SEWING MACHINE WITH IMPROVED STOPPING MECHANISM Filed Sept. 25, 1968 5 Sheets-Sheet 2' 22 K 73a G o a 75 23' FIG.2 30a F 26 Hi 71 H 48a 48 72 47 52 68 3 30 52a 2 I 54 0 68a I l G 1 44b 53 4311 INVENTOR.

Attorney Karl Nicolay March 10, 1970 K. hue 0L1 3,499,404

BUTTONHOLE SEWING MACHINE WITH IMPROVED STOPPING MECHANISM Filed Sept. 25, 1968 5 Sheets-Sheet 5 Karl Nicolag INVENTOR.

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Attorney March 10, 1970 1Com 3,499,404

BUTTONHOLE SEWING MACHINE WITH IMPROVED STOPPING MECHANISM Filed Sept. 25, 1968 5 Sheets-Sheet 4 Karl Nicol INVENTO March 10, 1970 K. NICOLAY 3,499,404

BUTTONHOLE SEWING MACHINE WITH IMPROVEDSTOPPING MECHANISM Filed Sept. 25, 1968 5 Sheets-Sheet 5 Attorney United States Patent 3 499 404 BUTTONHOLE snwn ro MACHINE wrTH IMPROVED STOPPING MECHANISM Karl Nicolay, Bielefetd, Germany, assignor to Durkoppwerke G.m.b.H., Bielefeld, Germany, a corporation of Germany Filed Sept. 25, 1968, Ser. No. 762,387

Claims priority, application Germany, Sept. 26, 1967,

1,660,841 Int. Cl. D05b 3/00 US. Cl. 11267 Claims ABSTRACT OF THE DISCLOSURE A high-speed buttonhole sewing machine having a beltshifting mechanism for bringing the main shaft of the sewing machine to a low-speed condition after completion of the buttonhole-stitching cycle and prior to the commencement of the next cycle. The main control cam triggers a lever which initiates the shift from high-speed to low-speed by a belt-control fork and simultaneously triggers a follower lever riding in a worm carried by the main drive shaft so that the latter, after a predetermined number of revolutions independent of the stitching speed of the machine, operates a latch adapted to lock the main control shaft, a clutch de-coupling the latter from the twospeed belt-shifting transmission, and the belt-shifting fork to return the transmission to its high-speed condition preparatorily for the next cycle.

My present invention relates to buttonhole-sewing machines and, more particularly, to a buttonhole-stitch sewing machine adapted to form part of a battery of such machines for the high-speed production of buttonholes, especially straight buttonholes for bed linen, etc.

It has already been proposed to provide a battery of such sewing machines for the high-speed production of buttonholes in pieces of fabric displaceable across the sewing-machine tables and under the control of a programmer or other system designed to operate the machines at high rates and with a minimum of operator attention. The formation of buttonholes, however, has involved difiiculties in this regard since the buttonholestitching assembly is relatively complicated and it is desirable to provide greater or lesser stitch number (i.e. number of stitches per unit of length) as well as higher or lower stitching rates (number of stitches per unit of time).

It has already been proposed to provide speed-changing mechanisms adapted to operate the rotary shaft of the sewing machine at a slower speed, for example, so that a high stitching rate can be followed by a low machineoperating rate prior to stopping the machine. It may be noted that such mechanisms have been proposed and operated with a cam formation on the main control cam to shift a belt or the like between high and low speed pulleys. It has been found in such systems, however, that the transition between high speed (stitching) and low speed (stopping), resulted in undesirable poor stitch formation of the transition points. Consequently, a precise delineation is not obtained between the highand low-speed cycle portions and defective buttonholes result. The earlier systerns have also been incapable of effectively and quietly bringing the machine to a standstill and has required complex mechanisms which were prone to breakdown.

A further disadvantage of conventional systems is that the restoration of the system to its initial position for each cycle often led to damage of the setting and latching members, the development of inordinate amounts of play and the generation of vibratory and impact noises. Additionally, the prior art belt-shifting mechanism led to early deterioration of the belts or shifting mechanisms.

It is, therefore, the principal object of the present invention to provide an improved speed-changing mechanism for a sewing machine of the character described, ie a mechanism which is capable of operating the sewing machine at more than 3,000 stitches per minute at high speed and can have a ratio between high and low stitching speeds of 10:1 or more but yet is able to bring the machine to standstill without any of the aforementioned difficulties.

Still another object of this invention is to provide an improved mechanism for effecting an improved transition between high and low speed in a sewing machine of the class described.

These objects and others which will become apparent hereinafter are attained, in accordance with the present invention, by the provision of a belt-shifting mechanism having a high-speed and a low-speed pulley engageable by the shiftable belt and adapted to drive a releasable clutch member cooperating with the driven clutch member carried by the machine shaft of the sewing machine. In addition to the speed-changing belt-shifting means, therefore, I provide the buttonhole-sewing machines with a clutch mechanism or means between the belt-shifting means and the main drive shaft, and cam-operated control means for initiating the operation of the belt-shifting means in accordance with a cycle predetermined by the main control cam. An auxiliary mechanism is connected with the main shaft of the sewing machine and serves to de-couple the clutch, lock the drive shaft and reverse the belt-shifting operation upon the lapse of a predetermined number of turns of the main shaft from the initiation of the belt-shifting operation.

The predetermined number of revolutions at the main shift or stitches is established by a worm arrangement carried by the main shaft such that simultaneously with the actuation of the belt-shifting mechanism from the highspeed to the low-speed pulley, as triggered by a cam formation on the main control cam, the auxiliary mechanism is trapped and establishes the aforementioned predetermined number of revolutions prior to release of a locking device adapted to block the main drive shaft.

The auxiliary mechanism can include, according to a further feature of this invention, a worm mounted on the main drive shaft and an auxiliary shaft parallel to this worm and upon which a lever is axially shiftable. The lever is engageable with the worm and is urged in one direction by a spring such that, when a shifting operation is initiated, it engages the Worm and is drawn thereby in the opposite direction to release a slide engageable with the shaft and also releases the clutch. To this end, the slide may be shiftable into locking engagement with the main drive shaft by a spring and is retained in its disengaged position against the force of this spring by a latch which is released by the worm-driven slide.

From the foregoing, it will be apparent that the arrangement of the present invention provides for precise preparation of the high-speed sewing machine for each cycle without endangering the belt-shifting mechanism or varying the belt-shifting operations in dependency upon the stitching speed. The sequence initiated by the main control cam at the end of the buttonhole stitching cycle, which is particularly satisfactory for the straight buttonhole provided on bed linen or the like, is: (a) displacement of the belt-shifting lever to bring the belt from the high-speed pulley to the low-speed pulley and simultaneously to engage the follower lever which is shifted against its spring by the worm of the auxiliary mechanism (now rotated at slow speed); and (b) after a predetermined number of revolutions of the main shaft (as determined by the number of turns of the worm and its pitch),

release of the latch to lock the main shaft and substantially simultaneously de-coupling the clutch and returning the belt-shifting lever from the low-speed pulley to the high-speed pulley.

The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is an elevational view, partly in a section and with parts broken away of a high-speed sewing machine for the formation of buttonholes (e.g. in bed linen) according to the present invention;

FIG. 2 is an end view in the direction of arrow II of FIG. 1;

FIG. 3 is a cross-sectional view taken along the line IIIIII of FIG. 1 showing the drive system for the machine shaft in phantom lines;

FIG. 4 is a front view of the auxiliary mechanism of the sewing machine; and

FIG. 5 is a detailed view thereof from above.

GENERAL DESCRIPTION (FIGS. 1 and 2) The zig-zag buttonhole-sewing machine of the present invention comprises an upwardly open socket-forming base 1 which is mounted upon a sewing-machine stand for support (not shown) in the usual manner and which receives the base plate 2 of a sewing machine having an upright post 3 upon which the arm 4 is cantilevered to overhang the stitch plate 2a of the machine. The plate 2 is hingedly mounted on the base plate by a pair of pintles 2 (not shown in FIG. 1) carried in the wall 1a of the base 1 and permitting the overhanging arm 4, the post 3 and the base 2 to swing outwardly (clockwise in FIG. 2) to allow access to the underside of the machine for cleaning, adjustment or replacement of parts. The arm 4 has a head 4 in which the needle holder 6, replaceably carrying the needle 7, is vertically reciprocable and may swing from side to side for zig-zag stitching operations.

Within the post 3, which is broken away in FIG. 1 to show the drive and control elements of the mechanism, I have provided the usual machine control disk or cam 9 seen in broken lines and adapted to control the working cycle of the machine. The cam 9 is rotatable on its shaft 29 and is driven, in turn, by a main shaft 5 extending horizontally at the top of the machine. The shaft 5 has an extremity 5a projecting rearwardly from the post 3. The drive connection between shaft 5 and cam 9- is conventional and, in the usual manner, determines the stitch number (i.e. the number of stitches per unit length) in accordance with the setting of the cam 9 and the speed of shaft 5. The contours of cam 9 determine the number of stitches per revolution of shaft 5 while the rate of rotation of shaft 5 establishes the number of stitches formed per unit of time.

To hold the fabric, I provide a clamping foot 11 which is conventional in such buttonhole-sewing machines and is driven by the main cam 9 via a second control cam, not illustrated, to impart the back-and-forth movement to the fabric which is necessary to complete a closed buttonhole pattern. Within the arm 4, moreover, the usual control mechanism with vertical displacement of needle bar 6 and needle 7 and lateral movement thereof is provided, this mechanism being also conventional and being driven by the shaft 5. The needle 7 co-operates with a gripper systems (not seen in FIG. 1) below the plate 2a for forming the buttonhole stitch. The gripper system may be driven from the shaft 5 as described in my recently issued Patent No. 3,376,837 of Apr. 9, 1968, which also shows the gripper arrangement as Well as the mechanism for imparting a zig-zag motion to the needle 5.

TWO-SPEED TRANSMISSION MEANS (FIGS. 1 and 3) As earlier described, the shaft 5 may be driven at high or low speed by a continuously operating variable-speed motor (drive means) not shown. The two-speed transmission of this invention comprises the unillustrated motor having two drive pulleys of the same diameter connected by respective V-belts to a small-diameter driven pulley 13 and a large diameter driven pulley 15, respectively, so that these pulleys are rotated at high and low angular velocities, respectively, about a common axis on a common shaft.

The pulleys 13 and 15 are axially spaced and in the gap between them are rigid with smooth cylindrical pulleys 12 and 14, respectively. The pulleys 12 and 14 are coaxial and of the same diameter to enable a belt 16 to slide axially from one pulley to the other. The belt 16 is shown in FIG. 1 to be driven by the pulley 12 (high speed for stitching) and to be shiftable (arrow A) to engage pulley 14; pulley 14 is rotated at relatively low speed for immobilization of the machine.

The fiat-section belt 16 passes around a pulley 19 which is formed with a channel 19 which prevents undesired lateral movement of the belt and forms part of a clutch connecting the driving systems 12 through 16 with the driven shaft 5.

The belt 16 is shiftable between the pulleys 12 and 14 by a belt-shifting fork 17 (FIGS. 1 and 3) by a control assembly represented at 18 and described in greater detail herein below.

CLUTCH MEANS (FIGS. 1 and 2) The clutch mechanism between the transmission 12 through 16 and the shaft 5 includes the pulley 19 which forms one clutch half and has a frustoconical concave clutch surface 19a adapted to engage a friction lining 21a on the frustoconical male clutch half 21. The pulley 19 has a hub 1% which is rotatably journaled on the shaft extension 5a in needle bearings 20 and is axially shiftable along the shaft as well. The needle bearings 20 abut an internal shoulder of the hub 19b and can be displaced to the left (to engage the clutch) by a lever 32, a pin 37,v a bearing plate 38, a thrust bearing 39 and a ring 40. The nonrotatable pin 37 is bifurcated to receive the end 32a of the lever 32 and is articulated to the latter by a pin 43- so that the swinging movement of lever 32 can shift the pin 37 to the left (arrow B) or to the right (arrow C) and thereby bring the clutch into or out of engagement as. viewed in FIG. 1. The pin 37 is riveted at 38a to the disk 38 which bears upon the axial ball thrust bearing but which engages the hub 1% at a cap 41 which performs a func-- tion similar to that of shoulder 190 for movement of the pulley 19 in the direction of arrow C. The ring 40 has a. diameter exceeding that of the shaft extension 5a and. bears against the outer race of the needle bearing 20,. the outer race acting in turn against the shoulder 19s.. In its movement to the right '(arrow C in FIG. 1), the disk 38 can bear against the inwardly turned flange 41a: of the cap '41 clamped onto the base 19d of hub 19b.

The other clutch half 21 is afiixed by the screws 22 to a cam 23 shown in elevation in FIG. 2 and rotatably ell-- trained with the shaft extension 5 by spring key 24 (FIG. 1). Thus rotation of the clutch half 21 Will entrain both the cam 23 and the shaft 5, 5a, in the same sense.

A lever 31 controls the clutch 19, 21 and is fulcrumed by a bolt 27 on an arm 25 extending rearwardly (FIG. 1) from a plate 26 secured to the post of the machine. The lever 31 is aflixed to previously described lever 32 by screws 43 and 44 which allow relative movement of the levers 31 and 32 for the purpose of adjustment.

Clutch-actuating means for swinging the lever 31 to actuate the clutch 19, 21 is provided at the lower end of the lever 31 in the form of a sleeve 54 (FIGS. 1 and 2) which slidably received a pin 55 having a bifurcated head 55a articulated by a pin 58 to a lever 57. A cylindrical shoulder 55b of the pin 55 constitutes a seat for spring 56 which urges the pin 55 to the left (arrow D in FIG. 1) and which is seated against the right-hand wall of the sleeve 54. The lever 57 has an inclined edge 57a (FIG. 1)

which bears against a roller 60 journaled on a bolt 60a affixed to the rear wall of the post 3. A further roller 64 (broken lines in FIG. 1) is journaled on a pin affixed to the lever 57 and is embraced by a fork 63 carried by a slide 30 (broken lines in FIG. 3 and in FIG. 2).

When the slide 30 is shifted downwardly (FIGS. 1 and 2), when the machine is started, the lever 57 is swung by the fork 63 and the roller 64 about its pivot 58 to bring its inclined edge 57a into engagement With the roller 60, thereby permitting the pin 55 of levers 31, 32 to swing about the bolt 27 in the counterclockwise sense (FIG. 1); clutch half 19 is thus shifted to the left (arrow B in FIG. 1) into engagement with the stationary clutch half 21 for a rotary entrainment of the latter and the shaft 5a.

SHAFT-LOCKING MEANS (FIGS. 1 and 2) The previously described support 36 provides a guide for the slide 30 and, to this end, defines with the back Wall of post 3 a groove-like channel in which the slide 30 is held by a spring-load cushion 41 (FIG. 2) and is linked at 42 with a lever 43 swingable about the fulcrum 45.

To bring the slide 30, which constitutes a locking element, into engagement with the notch 23 in the cam 23 in the de-energized condition of the machine, I provide a tension spring 44 (FIG. 2) which is anchored to the pin 44a on the base plate 2 and draws a pin 44b on the lever 43 in the counterclockwise direction about the pivot 45. The lever 43 thus has three arms which are represented at 43a, 43b and 430, the latter being formed with the pin 44b. Arm 43a carries the hinge-pin 42 which connects the lever 43 with the slide 30. counterclockwise rotation of the lever 43 drives the slide 30 upwardly (arrow E in FIG. 2) in the direction of cam 23.

For withdrawal of the slide 30, which is deflectable in the direction of arrow F against the cushion 41 (FIG. 2), from the notch 23' in the cam 23 and for the simultaneous engagement of the clutch half 19 with the clutch half 21, I provide an actuating member which is represented at 150 in FIG. 2 and has a finger 150a adapted to drive a rod 46 upwardly in a guide sleeve 46a of the support 41 until the head 46b of this rod engages an abutment 50 carried by the arm 43b of lever 43 to swing the latter in the clockwise sense (arrow G) and thereby shift the slide 30 in the direction opposite that represented by arrow E.

A latching mechanism L is provided to retain the clutch 19, 21 in its engaged position.

LATCHING '(DETENT) MEANS (FIGS. 1 and 2) The latching mechanism L (see FIGS. 1 and 2) comprises a lever 47 (FIG. 1) which is swingable on a bolt 48 carried by the lever 31 and is urged in the clockwise direction by a torsion spring 52 (arrow H in FIG. 1). The torsion spring is anchored at one end in the head 48a of the bolt (FIG. 2) and has a finger 52a resting beneath the lever 47. The edge of the lever '47 is receivable in the notch 49 provided in slide 30. When the machine is started, the lever 47 is withdrawn from the notch 49 and springs against support 26 to prevent counterclockwise rotation of the lever 31, 32, thereby preventing disengagement of the clutch.

A latching mechanism also retains the slide 30 in its ineffective position (downwards) while the machine is operated. The slide 30 thus is formed with a notch 66 (FIG. 2) in which a tooth 67 of a pawl 68 is engageable. The tooth 67 is afiixed to the pawl 68 by screws 68a while a pivot 70 allows swinging movement of the pawl relative to the post 30 in which the screw 70 is seated. A torsion spring 71 has one end bearing against a stop 72 on the post 3 and another end engaging the pawl 68 to urge the latter yieldably in the clockwise sense (arrow H).

When the machine is started, the latching pawl 68 renders the slide 30 ineffective, the pawl 68 being controlled by arm 73 which is aflixed to the pawl 68 by a screw 74. The arm 73 has its free end 73a in the path of a tripper represented in phantom lines at 75 in FIG. 2 but shown in elevation in FIG. 5. The tripper 75 is described as a part of the auxiliary mechanism discussed in greater detail below.

AUXILIARY MECHANISM (FIGS. 1, 2, 4 and 5) The main shaft 5 is provided, according to this invention, with a worm (see FIGS. 1, 4 and 5) as well as a cam 81 which is located at a predetermined distance from the worm. An auxiiary shaft 83 extends parallel to the main drive shaft 5 and carries a tilting lever 82 which is axially shiftable on the shaft 83 and is constituted as a bell-crank lever with arms 82' and 82". The arm 82' is formed with a tooth 84 urged by a spring 84 into the Worm groove and between the lands so that rotation of the worm axially displaces the lever 82 along its shaft 83. The other arm 82" carries a pin 82a" to which a tension spring 87 is anchored. The spring 87 draws the lever 82 against a spring cushion 98 (FIG. 1) which has its axial mobility limited by an adjustable stop ring 91 carried by the shaft 83. The spring 87 is anchored to the sewing-machine housing. Toward the end of the sewing cycle, the lever 82, as is shown in FIG. 4, is shifted to bring its tooth 84 into the groove of the worm 80 against the force of the tension spring 87, the lever 82 being held at this time by the spring 87 against the cushion (i.e. in its extreme left-hand position as represented in FIG. 1) corresponding to the extreme forward position of the lever 82 on the shaft 83.

TRANSMISSION-CONTROL MEANS The return movement is triggered by a camming projection 92 of the main cam 9 which simultaneously shifts the drive belt 16 from the high-speed pulley 12 to the low-speed pulley 14. To this end, a lever 94 is swingably mounted in the post 3 about the fulcrum 93 and has in the path of the camming projection 92 a cam follower 95 which is urged by the tension spring 96 in the direction of the cam. The tension spring 96 tends to urge the lever 94 in the clockwise sense (FIG. 1) about its fulcrum 93. Lever 94 is of the double-arm type and bears with its arm 94 against the plate 2.

Above its fulcrum 93 the lever 94 carries on its other arm a wing 97 upon which a single-arm lever 98 is articulated. The post 3 also is provided with a pivotal axis 1100 upon which a lever 101 is journaled, the lever having a follower roller 102 at its lower end. The roller 102 cooperates with the abovementioned control mechanism 18 for the belt-shifting fork 17 to actuate the latter. Lever 101 is urged by tension spring 103 in the clockwise sense about the fulcrum to bring an abutment projection 101a of the lever 101 into engagement with a stop 104 depending from the base plate 2.

A double arm lever 105 is also swingable about the fulcrum 100 and is connected with lever 101 by screw 1%. Lever 105 carries on its open arm a crank 107 via a pin 187a (FIG. 3) thereof while the other pin 1071) (FIG. 3) of this crank is received in an elongated opening 98a of the aforementioned single-arm lever 98. Torsion spring 188 (FIG. 3) acts upon the crank 107 in a sense tending to swing the crank or lever 98 in the clockwise direction (FIG. 1).

A third bell-crank lever 109 is pivotally mounted upon the axis 100 and is connected with the lever 105 by screw 110. On the free arm of the lever 109, I have provided a pin 111 on which a traction lever or bar 112 is mounted, as is best seen in FIGS. 3 and 4. The traction bar or lever 112 has a finger 112 on its upper end which cooperates with a rod 113 extending parallel to the shafts 5 and 83 and is mounted in the arm 82 of the tilting lever 82. The finger 112 is thus able to draw the rod 113 downwardly to carry the tooth 84 into engagement with the worm groove.

As is best seen in FIGS. 1 and 3, the belt-shifting control means includes an upstanding shaft 116 upon which a lever 117 is mounted for swinging movement of the fork 17 connected with the lever 117. The shaft 116 is rotatable in a sleeve 116a formed in the base 1 and is provided at its upper end with a lever 114 (FIGS. 1 and 3) adapted to engage the roller 102 from below so that the lever 101, which is connected with lever 105 by screw 106, can camrningly engage the lever 114 and entrain the latter against the force of torsion spring 115 bearing against a stop 115a. The lever 114 is provided with a ramp 114a upon which the roller 102 can ride.

A pawl 118 is swingable on a pin 119 (FIGS. 4 and 5) laterally of the arm 82 of the tilting lever 82 and is held by a torsion spring 120 in the counterclockwise sense (as seen in FIG. 4). The torsion spring thus holds the pawl 118 normally against a stop screw 121 which lies in the region of the cam 81 of the worm 80.

OPERATION When the cycle-controlling cam is rotated to bring its camming projection 92 into engagement with the follower 95, the lever 94, as the follower 95 rides upon the cam 92, is urged against the force of spring 96 in the clockwise direction about its fulcrum 93. The lever 98, which is coupled by the fulcrum 97 with lever 94, is thus shifted to the right and is drawn at its free right-hand end downwards by the spring-biased crank 107. The levers 98 and 105 thus are shifted clockwise into a dead-center position in which the pins 107a and 1071) of the crank 107 lie in a horizontal plane and in which, consequently, the lever 98 or lever 105 are rigidly connected. Upon further rotation of the cam 9, the cam follower 95 is swung further out by the carnming portion 92, the lever 105 is swung in the clockwise direction about the fulcrum 100. The bellcrank lever 109, coupled with lever 105, is entrained in the same sense (FIG. 1) and draws the traction lever 112 downward. The finger 112 of this lever swings the arm 82 of the tilting lever 82 (via the rod 113) in the clockwise sense as shown in FIG. 4, against the force of spring 86 to bring the tooth 82 into the groove of the worm 80.

At the same time, the lever 101 is swung in the counterclockwise direction since it is connected with the lever 105 by the screw 106. The roller 102 at the lower end of lever 101 engages the arm 114 (FIG. 3) of the control mechanism 18 for the belt 16 and swings this lever 114 against the force of the torsion spring 115. Lever 114, in turn, rotates the shaft 116 (FIGS. 1 and 3) and its arm 117 which carries the belt-shifting fork 17.

The main shaft 5 can thus be operated at an elevated or a reduced speed and, with the shifting of belt 16 in the direction of arrow A (FIG. 1) is rotated at its reduced speed of about 400 rpm. The tilting lever 82, the nose 84 of which has engaged the work 80, is thus shifted to the right against the tension of spring 87 until this lever engages the wall of post 3. After several revolutions, e.g. about 5, the detent or pawl 118, which is swingable on the side of the tilting lever 82 at its arm 82' on the pivot 119, is engaged by the camming projection 81 of the worm 80. The cam 81 swings the pawl 118 in the clockwise sense (FIG. 4) against the torsion spring 120 which normally holds this pawl against the stop screw 121. The pawl 118 is thereby shifted with respect to the guide plate 88, which, as previously indicated, serves to maintain the tooth 84 of the tilting lever 82 in engagement with the worm 80 as previously noted. The tilting lever 82 is thereby freed and is swung by the spring 86 in the counterclockwise sense (FIG. 4) to lift it to 84 from the worm 80.

The entraining rod 75 (FIG. 1 and 5) carried by the arm 82" of the tilting lever 82 is brought into the region of lever 72 (FIGS. 2 and 3) during the axial movement of the lever 82 along the worm. When the tilting lever 82 is swung under the action of spring 86 out of engagement with the worm, its rod 75 carries the lever 73 in the counterclockwise direction (FIG. 2) so that the tooth 67 at the lower end of lever 73 is withdrawn from the notch 66 to release the slide 30. The latching slide 30 is consequently freed and is shifted upwardly via the lever 73 and the tension spring 44 until the forward edge 30a of the slide engages in the notch 23' of the cam 23 to lock the shaft 5 against further rotation.

During the upward movement of the slide 30, a lever 122 (FIG. 1 and FIG. 3) which is pivoted on the pin 123 to the rear wall of the post 3, is displaceable in the clockwise direction (FIG. 3) until its downwardly bent edge 122 engages a notch 124 of the slide 30 (FIG. 1). The lever 122 also presses against the free end of lever 98 to swing the latter in the counterclockwise sense (FIG. 1) about its pivot 97 whereby the toggle linkage formed between members 98 and by the crank 107 is returned to the position shown in FIG. 1 as the tension spring 103 again becomes effective and the lever 101 is swung with its roller 102 against the stop 104. The torsion spring is thereby rendered effective to swing the lever 114 and its shaft 116 in the opposite sense and carry the arm 117 with the belt-shafting fork 17 in the opposite direction. The belt 16 is thereby returned from the slowly rotating pulley 12 and the machine set up for high-speed operation with the triggering of the next cycle.

In the movement of the slide 30 to its elevated position, the clutch lever 31, 32. is actuated as previously discussed to de-couple the belt-driven clutch half 19 from the clutch half 21 so that the clutch of shaft 5 is released at the time that the belt 16 is shifted to the highspeed pulley 12. The lever 82 and the remainder of the auxiliary mechanism is carried back to its left-hand position (FIG. 1) and the device thus restored to its initial state for a repeated cycle in the manner described.

The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the invention.

I claim:

1. In a sewing machine having drive means, a main shaft operatively connected to said drive means and a main cam driven by said shaft and establishing a sewing cycle for said machine, the improvement which comprises a two-speed transmission connected to said drive means and shiftable between a high-speed and a low-speed position; clutch means between said transmission and said shaft having a first position wherein said transmission is coupled with said shaft and a second position wherein said transmission is decoupled from said shaft;

transmission-control means triggered by said cam for shifting said transmission between said high-speed position and said low-speed position at the completion of a stitching cycle; and

mechanism operable by said cam simultaneously with said transmission-control means for shifting said clutch means from said first position to said second position after a predetermined degree of rotation of said shaft and for operating said transmission-control means to shift said transmission from said low-speed position to said high-speed position.

2. The improvement defined in claim 1, further comprising locking means operable by said mechanism after said predetermined degree of rotation of said shaft for releasably immobilizing the same.

3. The improvement defined in claim 2, wherein said machine is a buttonhole-sewing machine and sand mechanism includes:

a worm rotatable with said shaft;

worm-follower means shiftable along said worm and engageable therewith for establishing said predetermined degree of rotation of said shaft prior to the operation of said locking means; and

lever means connecting said transmission-control means with said worm-follower means for bringing the latter into engagement with said worm.

4. The improvement defined in claim 3 wherein said worm is mounted on said shaft and said mechanism ineludes:

an auxiliary shaft parallel to said main shaft, said worm-follower means including a lever swingably mounted on said auxiliary shaft and having means for engagment with and disengagement from said worm and is axially shiftable along said auxiliary shaft;

first spring means bearing axially upon said lever for biasing same into one extreme axial position along said worm,

second spring means for disengaging said lever from said worm; and

traction means between said transmission-control means and said lever for drawing same into engagement with said worm whereby said lever is entrained axially by said worm into a second extreme axial position.

5. The improvement defined in claim 4 further comprising means tri erable by said lever in said second extreme axial position thereof for operating said clutch means and said locking means.

6. The improvement defined in claim 5 whereby said locking means includes:

a cam carried by said main shaft and formed with a notch;

a slide having a locking position whereby it engages said notch and an unlocking position wherein it is withdrawn from said notch;

means biasing said slide from said unlocking position toward said locking position, and

latch means for releasably retaining said slide in said unlocking position.

7. The improvement defined in claim 6 whereby said latching means includes a pawl swingable by said lever for releasing said slide.

8. The improvement defined in claim 7 wherein said clutch means includes:

a first clutch member coupled with said main shaft and a second clutch member axially shiftable relatively to said first clutch member and frictionably engageable therewith in said first position of said clutch means for retraction therefrom in said second position of said clutch means; and

further lever means connected between said slide and said two clutch members for shifting said second clutch member between said positions.

9. The improvement defined in claim 8 wherein said transmission includes:

a low-speed pulley and a high-speed pulley;

a belt shiftable between said pulleys and connected with said second clutch member for driving same; and

a belt-shifting fork operable by said transmission-control means for displacing said belt.

10. The improvement defined in claim 9 wherein said lever is provided with a swingable tooth shiftable into and out of engagement with said worm, said mechanism further comprising means co-operating with said tooth for retaining it in engagement with said worm over a predetermind axial displacement of said lever.

References Cited UNITED STATES PATENTS 1,878,091 9/1932 Allen et al. 1]267 3,216,381 11/1965 Bono ll267 H. HAMPTON HUNTER, Primary Examiner

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