US3587495A

US3587495A - Sewing machines

Info

Publication number: US3587495A
Application number: US8257A
Authority: US
Inventors: Ralph E Johnson
Original assignee: Singer Co
Current assignee: SSMC Inc
Priority date: 1970-02-03
Filing date: 1970-02-03
Publication date: 1971-06-28
Anticipated expiration: 1988-06-28
Also published as: FR2080440A5; GB1317712A

Abstract

A LOCKSTITCH SEWING MACHINE WITH A LOOP TAKER WHICH IS DRIVEN IN A UNTIMED RELATION WITH THE COMPLEMENTAL STITCH FORMING INSTRUMENTALITIES IS PROVIDED WITH A COMMON DRIVING SOURCE FOR A NEEDLE RECIPROCATING MECHANISM AND A NEEDLE THREAD TAKEUP MECHANISM WHICH COOPERATE TO PROVIDE NEEDLE THREAD MANIPULATION AND THREAD CONTROL IDEALLY SUITED FOR ACCOOMODATION OF THE WIDE VARIATION IN TIME OF LOOP SEIZURE, EXPANSION, AND RELEASE WHICH IS EXPERIENCED USING AN UNTIMED LOOP TAKER.

Description

United States Patent Inventor Ralph E. Johnson Boonton, NJ.

Feb. 3, 1970 June 28, 1971 The Singer Company New York, N.Y.

Appl. No. Filed Patented Assignee SEWING MACHINES 6 Claims, 7 Drawing Figs.

US. Cl

I 112/220, 112/241 Int. Cl D05b 57/14 Field of Search 1 12/220,

[56] References Cited UNITED STATES PATENTS 1,402,930 1/1922 Herr 1 12/241 3,382,826 5/1968 Johnson 112/184 3,386,401 6/1968 Johnson 112/184 Primary Examiner-H. Hampton Hunter AuorneysMarshall J. Breen, Chester A. Williams, Jr. and

Robert E. Smith ABSTRACT: A lockstitch sewing machine with a loop taker which is driven in an untimed relation with the complemental stitch forming instrumentalities is provided with a common driving source for a needle reciprocating mechanism and a needle thread takeup mechanism which cooperate. to provide needle thread manipulation and thread control ideally suited for accommodation of the wide variation in time of loop seizure, expansion, and release which is experienced using an untimed loop taker.

PATENTEDJUNZ8IHYI 3,587,495

SHEET 1 BF 3 Fig.l

JNVENTOR. Ralph E. Johnson WITNESS: W

d/aca Jazzwza ATT RNEY PATENTEUJUH28IB7I 3581495 SHEET 3 0F 3 INVENTOR.

Ralph E. Johnson WITNESS: @141...

$1M MOM TTORNEY SEWING MACHINES SUMMARY'OF THE INVENTION The present invention includes drive means in a sewing machine for imparting both the needle reciprocation and the movement of needle thread takeup arm in a sewing machine in which the loop taker is operated in untimed relation thereto. An arrangement is provided whereby the needle bar and the thread takeup arm are simultaneously driven from the same driving source, which source includes a rotary drive member upon which is fast a crank pin offset from the center of rotation and a driven member formed with a groove in which is tracked the crank pin. The driven member is caused to reciprocate and to transmit reciprocating movement simultaneously to the needle bar and thread takeup arm. The groove is so formed as to effect a dwell simultaneously in-the movement of the needle thread takeup arm and in the needle reciprocation during the upstroke of the needle bar when the eye of the needle is still beneath the path of the loop taker. The described embodiment of the present invention assures that the needle thread loop formed during reciprocation ofthe needle will be seized by a one of the beaks of the loop taker since the dwell effected by the particular configuration of the groove in the driven member occurs when the eye of the needle is below the path of the loop taking beaks thereby maintaining the needle thread loop in position for engagement by the loop taker for an 'added period of time.

It is an object of this invention to provide in a sewing machine having a loop taker operated in untimed relation with the endwise reciprocation of the needle means for providing a dwell in the movement of the needle thread takeup arm during the time when the eye of the needle is below the path of the rotary loop taker.

It is another object to'provide means simultaneously for driving the needle bar and the needle thread takeup arm ina manner which is particularly advantageous when used in cooperation with a loop taker which is driven in untimed relation thereto.

It is another object to provide takeup means for assuring that a sufficient yet controlled quantity of thread slackis available instantly as demanded by the stitch forming instrumentalities throughout the entire range of time during which seizure and expansion of the thread loop is possible by a loop taker having multiple beaks and operated in untimed relation with the needle and takeup means.

Having in mind the above and other objects that will be evident from an understanding of this invention, the invention comprises the devices, combinations and arrangements of parts as illustrated in a preferred embodiment of the invention which is hereinafter set forth in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a front elevational view of the sewing machine incorporating the subject matter of the present invention, with portions of the sewing machine illustrated in vertical cross sectlon,

FIG. 2 is a perspective view of the stitch forming instrumentalities and actuating mechanism therefor of the sewing machine illustrated'in FIG. 1,

FIG. 3 is a right endelevational view of the sewing machine illustrated in FIG. 1,

FIG. 4 is a right end elevational view, partly in cross section, of portions of the sewing machine shown in FIG. 3 with the movable parts of the needle and takeup mechanisms illustrated in one position in solid lines and in a different position in dot and dashed lines,

FIG. 5 is a graph illustrating, in solid line, the path of travel of the eye of the needle and illustrating, in dotted line, the amount of needle thread which is made availablcto the stitch forming instrumentalities by the takeup mechanism,

FIG. 6 is an enlarged right end elcvational vicw ofthe head end portion of the sewing machines illustrated in FIG. 3 in which the needlethread has been included from a source of supply through the needle eye, and

FIG. 7 is a perspective view of the takeup arm and the cam blade with which it cooperates shown at the top of the takeup stroke in a position in which threading of the takeup is facilitated.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, particularly FIG. I, there is shown a sewing machine having a frame 10 including a bed 12, and a standard 14 supporting an arm 16 which terminates in a head unit 18.

Mounted in the bed 12 is an electric motor 20 which drives a toothed pulley 22. A notched timing belt 24 is carried in mesh with the pulley 22 and also meshes with a toothed pulley 26 fast on a feed drive shaft 28 which is journaled in and extends lengthwise of the bed 12. Because they do not relate to the present invention, the connections with the shaft 28, which impart work feeding movement to the feed dog 30, are not shown on the drawings. Secured fast on the shaft 28 adjacent to the pulley 26 is a toothed pulley 32. A notched timing belt 34 meshes with the toothed pulley 32 and meshes with a toothed pulley 36 fast on a shaft 38 which is journaled in the bed I2. Also mounted fast on the shaft 28 adjacent to the pulley 32 is a pulley 40 and a conventional handwheel 42. An idler pulley 44 is carried on a shaft 46 journaled in the bed 12 beneath the pulley 40, which shaft 46 extends transversely of the shaft 28. Mounted on the

pulleys

40 and 44 is a smooth belt 48, which also engages on a grooved pulley 50 located at the other end of the bed beneath the stitch forming instrumentalities. The pulley 50 is fast on a vertically disposed loop taker shaft 52, to the top end of which is secured a loop taker 54. The loop taker 54 is a lock stitch forming loop taker which operates in accordance with the principles set forth in my U.S. Pat No. 3,386,401 of June 1, 1968 and U.S. Pat. No. 3,382,826 of May 14, I968, to which reference may be had. The principles of loop taker operation as set forth in the above referenced patents do not require that the loop taker be driven in a predetermined timed relationship with the needle reciprocation. The top section of the loop taker 54 is a flat annular ring 56 formed with a plurality of inwardly extending needle thread loop seizing beaks 58. The provision of a plurality of beaks 58 serves to increase the probability that each thread loop formed will be seized by the loop taker.

Journaled in the head 18 of the sewing machine 10 above the bed 12, as shown in FIG. 3, is a conventional presser bar 60 that supports a presser foot 61 above the feed dog 30. Fast on the top of the presser bar is a bracket 62 which engages beneath a projecting arm 63 of a torsion spring which is secured on the sewing machine frame arm 16 and serves to bias the presser foot downwardly. Also mounted in the head 18 is a needle bar unit indicated generally at 64 including a plastic block 6.6 formed with a lower elongate rib 68 captured by and slidingly keyed in a vertical slot 70 formed in the lower portion of the head 18. The block 66 also includes a series of

collars

72, 74 and 76 all slidingly embracing the presser bar 60. Formed in the block 66 in an upper section 78 between the

collars

74, 76, is a slot 80. Secured to the front face of the lower rib 68 is an elongate metallic needle bar 82 which is formed lengthwise with a slot 84 that receives the shank 85 of a thread carrying needle 86. The needle 86 is held in place in the slot 84 by a leaf spring 88 that is secured at one end section to the metallic needle carrying bar 82. The free end 87 of the leaf spring 88 engages the shank of the needle with sufficient force to hold the needle securely in place during operation of the machine.

The mechanism for driving the needle bar unit 64 and therefore the needle 86 in endwise reciprocation includes a rock shaft 90 journaled longitudinally of the arm 16 of the sewing machine frame substantially parallel with the bed 12. Each end face ofthc rock shaft 90 is formed with a conical recess 92 and each reccssaccommodatcs the conical end portion of a pintle 94 secured in each end of the arm 16. Mounted fast on the rock shaft 90 near the head end thereof is a rock arm 96 on one end of which a driving crank stud 98 is secured. Pivotally mounted on the crank stud 98 is a drive lever indicated generally at 100 on one end of which is secured a thread engaging arm 102 of a needle thread takeup device. The other end of the drive-lever 100 is bifurcated as at 106 to define an open ended slot 107 that slidably receives an anchor stud 108 affixed to the sidewall of the head 18. Pivotally mounted on the dive lever 100 is a block 110 slidably accommodated in the slot 80 formed in the plastic block 66. Thus, as the rock shaft 90 and the rock arm 96 are oscillated, the needle bar unit 64 is driven in endwise reciprocation along the presser bar 60 through the intermediacy of the drive lever 100 and the slide block 110.

The thread engaging" arm 102 of the takeup device is preferably formed in a U-shaped fashion with spaced identically shaped limbs secured by screws 112 to the drive lever 100. The takeup device 102 straddles a thread camming blade 114 which is fixed on the sewing head 18, and is formed with a thread engaging cam lobe 115. The thread engaging arm 102 which straddles the thread camming blade 114 is formed with an aperture 116 at the base of its U-shape so that the spaced limbs of the thread engaging arm 102 are joined by an upper connection piece 117 and a lower connection piece 118. As the drive lever 100 is oscillated, the upper and

lower connection pieces

117 and 118 traverse paths closely adjacent to the front edge of the camming blade 114, and at the top of the stroke as shown in FIGS. 6 and 7, the upper connection piece 117 is elevated above the'level of the camming blade 114.

As best shown in FIG. 6, the needle thread is directed from a supply spool 119, which may be carried on any conventional thread spool holder 120, to a conventional thread tensioning device 121 supported on the sewing machine head unit 18. From the tensioning device, the thread is directed to a wire thread guide 122 fixed near the bottom of the head unit 18. The thread guide 122 preferably takes the form of a downturned loop of which a free extremity 123 extends beneath a leaf spring 124. The thread when introduced over the free extremity 123 of the thread guide 122 will thus extend beneath the leaf spring 124 which will then act as a check spring to cushion shock loading of the thread during the operation of the machine. From the thread guide 122;, the thread is directed upwardly in a loop into the aperture 116 between the upper and lower connecting

pieces

117 and 118 of the takeup thread engaging arm 102 and about the cam lobe 115 of the camming blade 114. The thread then extends downwardly, through a wire thread guide 125 at the bottom of the head unit 18 and to the needle. As the takeup device 102 oscillates, the thread is not only drawn upwardly into a varying size loop relatively to the thread guides 122 and 125, but the thread is simultaneously drawn rearwardly into a varying size loop from the aperture 116 of the takeup arm 102 about the cam lobe 115 ofthe stationary cam blade 114.

As shown in FIG. 7 the insertion of thread into the aperture 116 of the takeup arm is facilitated at the top of the takeup stroke when the upper connection piece 117 clears the top of the stationary cam'blade.

Secured to and depending from the standard extremity of the rock shaft 90 is a driving arm 132 which is secured at its lower end to a cam plate 134 as by two bolts 136. The cam plate 134 is substantially rectangular and is formed with a curvalinear slot 138 extending completely through the cam plate 134. The slot 138 is formed with

extremities

140 and 142 which diverge substantially tangentially from a circular central portion 144. A crank pin 146 which protrudes through the slot 138 is carried by'a counterweighted driving plate 150 fast on the shaft 38 and driven by the belt 34. A roller 152 journaled on the crank pin 138 is accommodated in a shallow recess 154 formed in one side of the cam plate 134 along the slot 138.

Turning now to the operation of the hereinabove described mechanism, when the motor is actuated the belt 24 drives the shaft 28 through the intermediacy of the toothed pulley 26 thereby driving the feed dog mechanism (not shown) and also the loop taker 54 through the intermediacy of the grooved pulley 40, the smooth belt 48, the grooved pulley 50 and the vertical shaft 52. Since a smooth belt rather than a timing belt is utilized for driving the loop taker 54, it will be understood that the loop taker 54 is not driven in timed relationship with the endwise reciprocation of the needle 86. The rotation of the shaft 28 serves to drive the notched belt 34 thereby to rotate the toothed pulley 36 and the counterweighted crank driving plate 150. As the driving plate 150 is rotated, the crank pin 146 and roller 152 are driven in a circular path. During a portion of each rotation of the crank pin and roller, they will track the circular portion 144 of the slot 138 and recess 154 which will be disposed substantially in the path of travel of the crank and roller so that a dwell will occur in the motion of the needle reciprocating and takeup mechanisms. At all other portions of the crank travel the crank pin and roller will oscillate the cam plate 134, driving arm 132, and

rock shaft and rock arm 96. As the arm 96 is rocked, the drive lever pivoted about the stud 108 moves through a short arcuate path. The arcuate motion of the drive lever 100 is utilized to drive the needle bar unit 64 in a vertical direction through the cooperation of the block 110, which is pivotally connected to the drive lever 100, and the sliding connection between the block and the block 66. The thread engaging arm 102 is secured to the drive lever 100 at an angle relatively to the drive lever 100 such that the arcuate motion of the drive lever provides the requisite thread takeup motion along the camming blade 114. inasmuch as the movement imparted to both the needle bar unit 64 and the thread engaging arm 102 is initiated and effected by the cooperation of the driving plate 150, the crank pin 138, the roller 152, and the cam plate 134 formed with the curvalinear slot 138, recess 154, it should be apparent that the movement ofthe thread engaging arm 102 is correlated with substantially the movement of the needle bar unit 64.

The curve marked Needle" as shown in the graph illustruted in solid line in FIG. 5 depicts the path of the eye of the needle as it moves through one complete cycle. The graph abscissa measures the needle cycle in units of degrees while the graph ordinate defines the vertical position of the needle eye, at any particular point in the cycle. The circles A, B, and C, on the curve represent the positions of the needle eye as shown in FIG. 3, HO. 4 solid lines, and FIG. 4 dotted lines, respectively. The horizontal lines D, E, and F represent the position of the needle eye at the very top of the stroke, at the level of the loop taker beaks and at the very bottom of the vertical reciprocation, respectively.

As indicated above, it is important when utilizing an untimed hook, to provide a period of dwell when the eye of the needle is on the upstroke but beneath the level of the hook beaks to assure prolonged presentation of a needle thread loop into position to be seized by one of the beaks. Such a dwell period is indicated on the graph between points G and H. It is in that segment ofminimal needle travel that the roller 152 moves downwardly as seen in FIG. 4 through the curved portion 144 of the slot and recess. The curvature of this slot corresponds to the curvature of the circle traversed by the crank pin 138 and roller 152 thus providing for the aforementioned dwell period since there is an absence ofa driving force exerted by the crank pin and roller on the cam plate.

Also shown in FIG. 5 is a needle thread takeup curve, of dashed line, approximating the manner by which the needle thread is metered by the thread engaging arm 102 cooperatively with the camming blade 114. The ordinate is generally indicative of thread length which is drawn up between the

guides

121 and 124 by the arm 102 of the takeup and the abscissa as indicative of the cycle of movement of the thread engaging arm 100 measured in units of degrees.

' It will be apparent from the takeup and needle curves shown in FIG. 5 that during the entire period in which the eye of the needle is situated below the level of the loop taker beaks as indicated by line E, substantially all of the thread is given up by should seize the needle thread near point A or point H on the curves shown in FlG. 5.'

It will be noted here that the roller 152 may be constructed from resilient urethane material to absorb the vibration and impact produced when the roller rapidly traverses its arcuate path and engages the wallsof the recess l54JBy reducing this impact, there is effecteda considerable reduction in noise and wear of the parts. ln addition, the cam plate 134 may be constructed with a glass fiber' material. The coefficient of friction between the urethane roller 152 and the glass fiber material utilized to constructthe cam plate 134 is relatively high, thus assuring that the roller will roll and not slide as it moves along the recess 154.

Having thus set forth the nature of this invention, what I claim herein is:

lclaim:

1. in a lockstitch sewing machine having an eye pointed thread carrying needle, mechanism for imparting endwise work penetrating and withdrawing reciprocation to said needle, a takeup mechanism for alternately drawing in and paying out the thread carried by said needle, and a loop taker cooperating in the formation of lockstitches with said needle in an untimed relation with an endwise reciprocation thereof, a drive mechanism common to both said needle reciprocating and takeup mechanisms, and means in said drive mechanism for providing a concomitant dwell in said needle reciprocation and in the operation of said takeup mechanism, means for causing said dwell in said. needle reciprocation to occur during the withdrawal stroke of reciprocation and while said needle eye occupies a position capable of presenting a needle thread for seizure by said loop taker, and means for causing said dwell in the operation of said takeup mechanism to occur while the thread manipulated thereby is substantially completely paid out.

2. In a lockstitch sewing machine as set forth in claim I in which said drive mechanism includes an oscillatory rock shaft, a lever fulcrumed on said sewing machine and oscillatable in response to movement of said rock shaft, a thread takeup arm carried by said lever, and an operative connection between said lever and said thread carrying needle and in which said means for providing concomitant dwell in said needle reciprocation and takeup mechanism comprises mechanism for inducing a pause in the oscillatory motion of said rock shaft in one direction ofoscillation.

3. In a lock stitch sewing machine as set forth in claim 1 wherein said drive mechanism comprises a rock shaft operably connected to both said needle reciprocating and takeup mechanisms, a crank driven by said sewing machine, a rock arm fast on said rock shaft, means carried on said rock arm and formed with a crank abutting surface of which only a portion is of curvalinear configuration and substantially corresponds to a portion of the circular path described by said crank, said curvalinear surface portion, when in abutting relation with said crank during said portion of the circular path of motion of said crank providing sad concomitant dwell in said needle reciprocating and takeup mechanisms.

4. in a lock stitch sewing machine as set forth in claim 3 wherein said crank abutting surface formed on said rock arm is provided by a curvalinear slot formed in a plate affixed to said rock arm and wherein said curvalinear slot embraces a crank pin associated with said crank driven by said sewing machine.

5. In a lock stitch sewing machine as set forth in claim 2 wherein said takeup arm is formed with thread engaging means and is arranged to move toward and away from a pair of thread guides, for drawing in and paying out a thread loop of which said thread en aging means on said takeup arm, and wherein said thread ta eup arm IS arranged to move relatively to a stationary camming blade formed with a thread engaging cam surface which varies in distance from the path of motion of said thread engaging means on said takeup arm.

6. ln a lock stitch sewing machine as set forth in claim 1 wherein said sewing machine includes a presser bar carrying a presser foot for engaging work fabrics adjacent the path of reciprocation of said needle, a needle carrier slidably supported on said presser bar, said needle carrier being formed with a slot substantially perpendicular to said presser bar, wherein said takeup mechanism includes a lever fulcrumed in said sewing machine on an axis substantially perpendicular to said presser bar and a thread engaging element carried on said lever, wherein said drive mechanism is operatively connected to said lever, and wherein said lever carries a driving element in spaced relation along said lever from said fulcrum axis and in sliding engagement with said needle carrier slot.