Thread handling

A thread handling device is disclosed in a type 301 lockstitch rotary hook loop taker sewing machine having a three-to-one hook to arm shaft ratio for controlling and metering slack needle thread prior to needle penetration to prevent the thread from wrapping around the point of the needle, which could prevent loop seizure, break the thread, or interfere with correct stitch formation. The thread is guided between two stationary members, with the controller between the members, the controller comprising an edge attached to the needle bar drive connecting link, moving with it, and only engaging the thread as the take-up and needle bar descend, providing a lengthened thread path prior to needle penetration.

DESCRIPTION 
Field of the Invention: 
This invention relates to sewing machines, and more particularly, to thread 
handling therein and finds particular utility for controlling and metering 
needle thread slack prior to needle penetration in a two-thread type 301 
lockstitch sewing machine and especially such machine having a rotary hook 
driven at a three to one ratio relative the arm shaft rotation. 
BACKGROUND OF THE INVENTION 
In a conventional type 301 lockstitch sewing machine, one of the major 
difficulties is in the timing relationships existent between the needle 
thread take-up, the loop taker operation for stitch concatenation and the 
feed timing and duration, each of which take time in the machine cycle. 
Needle thread take-up, loop formation, loop expansion, loop extraction and 
feed each require separate and distinct portions of the machine cycle, 
with preferably no overlap. For this reason, loop seizure by the loop 
taker has to be coordinated with the needle bar and the take-up and loop 
extraction has to be coordinated with cast off of the loop from the loop 
taker. The feed time must also be related to the take-up, it must start at 
a time when the feed dog is up and must continue beyond the time the 
take-up is up. The handling of the needle thread is also critical in that 
the thread demand for loop formation and for expansion by the loop taker 
must be coordinated with the thread supply from the take-up. 
Most current commercial rotary hook lockstitch sewing machines use a two to 
one ratio of loop taker to arm shaft rotation so that the loop taker 
revolves twice for every complete cycle of the needle bar. Cast off of the 
needle thread from the loop taker following concatenation of the needle 
thread around the bobbin thread occurs after almost 270 degrees of machine 
arm shaft rotation from the "needle up" position. The time from loop 
seizure to cast off takes about 110 degrees of arm shaft rotation. A ratio 
of loop taker to arm shaft rotation of three to one, however, enables the 
machine to approach cast off in only 70 degrees of machine arm shaft 
rotation after loop seizure instead of 110 degrees, a gain of 35 degrees 
that can be used, for example, to complete feeding earlier in a machine 
cycle. Since the feed time is related to the needle timing, the net effect 
is a gain in capacity to sew heavy materials, the difference being from a 
capacity of about 1/16 inch material in a conventional consumer type 
sewing machine having a two-to-one hook to arm shaft ratio, to a capacity 
of about 1/4 inch thick material using a three-to-one ratio. That is, 
before the needle reaches the material, even if the material is 1/4 inch 
thick, in a three to one ratio machine the feed is completed. This 
potential for increase has been previously recognized and is discussed, 
for example, in Hemleb, U.S. Pat. No. 1,583,925 dated May 11, 1926. 
In advancing the feed, needle bar drive and take-up relative the loop 
taker, however, the take-up also starts its descent earlier and pays out 
needle thread faster than the needle bar demand, providing slack thread. 
If this slack thread is not controlled prior to needle penetration, the 
thread can wrap around the needle point, prevent loop siezure, break the 
thread, or interfere with correct stitch formation. Following needle 
penetration, however, substantial needle thread needs to be subsequently 
metered out for loop seizure and expansion to pass around the bobbin. 
Various prior art 3 to 1 machines used various methods to control the 
needle thread, such as complex rotary take-ups or lengthened needle bars, 
each of which required substantial changes from the currently prefered 
crank driven take-up design. 
OBJECTS OF THE INVENTION 
Bearing in mind the foregoing, it is a primary object of the present 
invention to provide novel and improved methods of and apparatus for 
thread handling, particularly for controlling and metering slack needle 
thread in a lockstitch sewing machine prior to needle penetration. 
Another primary object of the present invention, in addition to the 
foregoing objects, is the provision of novel and improved thread metering 
and slack control for the needle thread of a lockstitch sewing machine 
which is economical to manufacture and durable and effective in use. 
Yet another primary object of the present invention, in addition to each of 
the foregoing objects, is the provision of a novel and improved needle 
thread metering and slack control device for use with a crank operated 
needle thread take-up operative for taking up excess slack prior to needle 
penetration and metering out additional thread to the needle subsequent 
thereto. 
Yet another primary object of the present invention, in addition to each of 
the foregoing objects, is the provision of novel and improved methods of 
and apparatus for thread handling in a sewing machine, particularly a 
sewing machine having a hook to arm shaft rotation ratio of three-to-one. 
Another and yet still further primary object of the present invention, in 
addition to each of the foregoing objects, is the provision of a novel and 
improved needle thread slack control and metering device for a sewing 
machine, carried by the needle bar drive connecting link. 
Yet still another and further primary object of the present invention, in 
addition to each of the foregoing objects, is the provision, in a 
lockstitch sewing machine, of a thread control cam or device carried by 
the needle bar connecting link cooperating with a pair of fixed needle 
thread guides on the machine bracket arm for needle thread slack control 
and metering. 
Yet another and still further primary object of the present invention, in 
addition to each of the foregoing objects, is the provision of novel and 
improved methods of and apparatus for thread control providing finely 
controlled and minimal needle thread tension throughout the machine cycle. 
A yet further primary object of the present invention, in addition to each 
of the foregoing objects, is the provision of novel and improved sewing 
machines having capacity for increased thicknesses of material, without 
any lengthening of the needle bar stroke and using a crank operated 
take-up. 
It is a feature of the present invention that the novel and improved thread 
controller and metering device hereof is driven in common with the needle 
bar while yet being active only during needle bar descent. 
The invention resides in the combination, construction, arrangement and 
disposition of the various component parts and elements incorporated in 
improved lock-stitch sewing machines and thread handling methods and 
apparatus in accordance with the principles of this invention. The present 
invention will be better understood and objects and important features 
other than those specifically enumerated above will become apparant when 
consideration is given to the following details and description which, 
when taken in conjunction with the annexed drawing describes, discloses, 
illustrates and shows a preferred embodiment or modification of the 
present invention and what is presently considered and believed to be the 
best mode of practicing the principles thereof. Other embodiments or 
modifications may be suggested to those having the benefit of the 
teachings herein, and such other embodiments or modifications are intended 
to be reserved, especially as they fall within the scope and spirit of the 
subjoined claims. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a thread handling device is 
provided in a type 301 lockstitch rotary hook loop taker sewing machine 
having a three-to-one hook to arm shaft ratio for controlling and metering 
slack needle thread prior to needle penetration. If this slack thread is 
not properly controlled and metered, the thread can wrap around the point 
of the needle, prevent loop seizure, break the thread, or interfere with 
correct stitch formation. In accordance with the present invention the 
thread is guided between two stationary members, with the controller 
between the members engaging the thread during needle descent to lengthen 
the thread path prior to needle penetration, taking up slack thread 
thereby, and subsequently retracting to meter thread out to the needle. 
The controller is attached to the needle bar drive connecting link, moves 
with it, and only engages the thread as the take-up and needle bar descend 
.

DETAILED DESCRIPTION OF THE INVENTION 
With reference now to the drawing, there is shown and illustrated the head 
end portion 6 of a Federal stitch type 301, two thread lockstitch sewing 
machine constructed and arranged and incorporating means for thread 
handling in accordance with the principles of the present invention and 
comprising a cast rear casing section 8 to which various modular 
sub-assemblies may be mounted and covered by one or more front panel cover 
members, not shown, as set forth in my co-pending application Ser. No. 
971,962 filed Dec. 21, 1978, now U.S. Pat. No. 4,193,361 dated Mar. 18, 
1980 assigned to the assignee of the present application and hereby 
incorporated herein by reference as fully and completely as if reproduced 
hereat. 
Reference characters 10 and 12 designate, respectively, the head end 
portion of the bracket arm and the work supporting or bed portion of the 
machine. The head end portion 10 of the bracket arm includes a fixed 
support bracket 14 having an upper extending arm 16 and a lower extending 
arm 18 which support a needle bar bracket 20. 
A needle bar 22 is supported in the bracket 20 for endwise reciprocation by 
an arm shaft 24 journalled for rotation in the bracket arm 10; acting 
through a counterbalanced crank 26, a connecting drive link 28, and a 
needle bar collar 30. The crank 26 drives one end of the needle bar 
connecting drive link 28 through an actuating crank pin 32. The needle bar 
connecting drive link 28 carries a raceway member 34 which slidably 
carries a compensating needle bar operating crank 36 operatively connected 
with the needle bar collar 30. Further details of the needle bar drive and 
the compensating needle bar operating crank 36 are disclosed in further 
detail in my co-pending application Ser. No. 49,679, filed concurrently 
herewith, assigned to the assignee of the present application, and 
incorporated herein by reference as fully and completely as if reproduced 
hereat. An eye pointed needle 38 is carried by the lower end portion of 
the needle bar 22 and cooperates with a rotary hook loop taker 23 
journalled in the bed portion 12 and driven by means, not shown, in timed 
relationship to the arm shaft 24 and at a three-to-one ratio relative 
thereto for concatenating the needle thread, around a bobbin thread, not 
shown, for stitch formation. 
A presser foot 40, affixed to a presser bar 42, is utilized to urge fabric 
into contact with the feeding mechanism (not shown) in the bed portion 12 
of the machine. The needle bar 22 extends through an eliptical opening 44 
in the arm 18 of the fixed bracket 14, which opening is of sufficient size 
to permit zig-zag movements of the needle bar 22 in response to 
reciprocatory actuation of the needle bar supporting bracket 20 by needle 
bight control means causing the bracket to pivot at its upper end on a 
shaft 46. Substantially any desired needle bight control means may be 
utilized but preferably a needle bight control means similar to that 
disclosed in my co-pending application Ser. No. 971,963 filed Dec. 21, 
1978, now U.S. Pat. No. 4,188,895, assigned to the assignee of the instant 
application, and incorporated herein by reference as fully and completely 
as if reproduced hereat may be used which, as shown, includes an actuating 
link 48 shown pivotally connected to the needle bar bracket 20 by a 
fulcrum screw 50, and a return spring 52 having one end restrained by a 
screw 54 and an intermediate portion partially wrapped about the shaft 46, 
the screw 56 and shaft 46 defining fixed locations in the bracket arm head 
end portion 10 fixedly positioning the spring relative thereto. The other 
end of the spring 52 is in engagement with an abutment 56 on the needle 
bar bracket 20 urging the bracket to the right as viewed in FIG. 1. 
The needle bar 22 is supported between the lower end of the needle bar 
bracket 20 and the arm 18 of the fixed bracket 14, in the sleeve 58 of a 
spherical bearing 51 (see FIGS. 2 and 3). Further details of the needle 
bar suspension means are disclosed in my co-pending application Ser. No. 
915,084 filed June 12, 1978, assigned to the assignee of the present 
application, and hereby incorporated by reference herein as fully and 
completely as if reproduced hereat. 
The crank pin 32 is also embraced by one arm 62 of a take-up lever 64 and 
the other arm 66 of the take-up lever 64 is provided with a thread eyelet 
68. The take-up lever 64 is pivoted, as at the juncture of the arm 62 and 
66 on a fulcrum pin 70 to an anchor link 72 fulcrumed on a pin 74 carried 
by the fixed support bracket 14. 
As heretofore pointed out, the sewing machine of the present invention 
preferably comprises a plurality of sub-assemblies mounted with the 
casting 8 in a manner set forth in my co-pending application Ser. No. 
971,962. The presser and needle bar sub-assembly includes a flat rigid 
plate 76 mounted with the machine cast rear casing section 8 by the screw 
54 and a further screw 78. The flat rigid plate 76 is also mounted with 
the fixed support bracket 14 by means of screws 80 and 82. Carried on the 
flat rigid plate 76 is a thread guide 84 having a thread guiding portion 
86 of generally inverted U-shaped configuration and a mounting portion 88 
enabling the thread guide 84 to be rigidly mounted with the flat rigid 
plate 76 as by means of a clamp member 90 secured by screws 92. The guide 
84 may, as shown, be fabricated of formed wire. 
A further flat rigid plate 94, which is also part of the presser and needle 
bar sub-assembly, is secured, as by a screw 96 to the rear casing section 
8 and by a screw 98 to the fixed support bracket 14. Mounted on the 
further rigid plate 94 is a rotatably adjustable thread tensioning device 
102 of conventional construction and including a check spring 104, also of 
conventional design. The further rigid plate 94, generally adjacent the 
tensioning device 102 is provided with a thread guide 106 of generally 
U-shaped configuration which is curved, as shown in FIG. 1, so as to be 
generally concentric with the thread tensioning device 102 and which 
passes through a loop or bight portion 108 of the check spring 104 to 
guide a needle thread 110 about (i.e., to the right as viewed in FIG. 1) 
the loop portion 108 of the check spring 104, as shown. 
Further, the flat rigid plate 94 carries a generally planar downwardly 
depending thread supporting surface 112 upon which is mounted an 
additional thread guide 114 of generally inverted U-shape configuration 
generally parallel and spaced apart from the thread guiding portion 86 of 
the thread guide 84. The guide 114 may, as shown, be fabricated of formed 
wire. A gap exists between the thread guides 84 and 114, as shown, into 
which a thread controlling and metering means, such as a cam or device 116 
is adapted to be cyclically moved for controlling and metering slack in 
the needle thread 110 as the take-up lever 64, and particularly the eyelet 
68 carried on the arm 66 thereof, initially descends, so as to prevent the 
needle thread 110 from wrapping around the point of the needle 38 prior to 
needle penetration. The cam or device 116 may be fabricated, for example, 
of sheet like material such as sheet steel or may, preferably, as shown, 
be fabricated of formed wire. 
The thread control and metering cam or device 116 is cyclically advanced 
between the two stationary thread guides 84 and 114 and retracted 
therefrom, to vary the length of the thread path, by being mounted to and 
for movement with, the needle bar connecting link 28, as by means of a 
screw 118, so as to only engage the thread 110 as the take-up 64 and 
needle bar 22 descend. 
In normal sewing, the path of the thread to the needle 38 occurs from a 
supply spool, not shown, to the thread tensioning device 102, behind the 
bight 108 of the check spring 104 and between the legs of the thread guide 
106, thence to the stationary thread guide 114, across the gap in line 
with the thread control and metering cam or device 116, thence around the 
thread guiding portion 86 of the thread guide 84 to the eyelet 68 of the 
thread take-up lever 64 and then to the needle eye, as by being passed 
through a further thread guide 120 at the lower end portion of the bracket 
arm head end portion 10. 
Yet further, there may be provided a protective guard 122 of transparent 
plastic, or the like, in front of the stationary thread handling guides 
114 and 84, thread control and metering cam 116, and check spring 104. 
Referring now particularly to FIGS. 1 and 2, wherein the needle bar 22 and 
the thread take-up lever 64 are shown in their uppermost positions, it 
will be seen that at the start of the machine cycle, as the needle bar 22 
and take-up lever 64 start their descent (the arm shaft 24 rotating in the 
clockwise direction as seen in FIGS. 2-4) the thread path is from the 
tensioning device 102 substantially directly to the stationary thread 
guide 114 and the check spring 104 is stressed and has rotated the bight 
or loop 108 thereof counterclockwise so as to pay out needle thread 110 
under some tension since the take-up has just set the preceding stitch. 
From the stationary guide 114 the needle thread 110 passes directly to the 
thread guide portion 86 of the other stationary thread guide 84 around 
which the thread is capstaned upwardly to the eyelet 68 of the thread 
take-up 110 where it is again capstaned through almost 360 degrees and 
thence downwardly to the needle 38. As shown most clearly in FIG. 2, in 
this position the thread controller and metering cam or device 116 does 
not contact the needle thread 110 and is therefore inactive. As the arm 
shaft 24 rotates (clockwise in FIGS. 2 and 3), the needle bar connecting 
link 28 is progressively tilted toward the right (in FIGS. 2 and 3) as the 
crank pin 32 of the counterbalanced crank 26 sweeps downwardly and to the 
right until the thread controlling and metering cam 116 passes outwardly 
of the thread supporting surface 112 and between the stationary thread 
guides 114 and 84, a condition which commences after about 30 degrees of 
arm shaft rotation. As the arm shaft and counterbalanced crank 26 continue 
to rotate, the take-up lever 64 continues to descend paying off needle 
thread 110 at a rate faster than the needle bar 22 is descending creating 
slack in the needle thread 110. Simultaneously, however, the thread 
controlling and metering cam or device 116 progressively projects further 
and further past the thread supporting surface 112 and outwardly of the 
stationary thread guides 114 and 84, pushing the needle thread 110 further 
and further outwardly until a maximum amount of slack thread has been 
absorbed in the elongated path from the stationary guide 114 over the 
projecting thread controlling and metering cam 116 to the other of the 
stationary thread guides 84 after about 75 degrees of arm shaft rotation. 
The thread controller and metering cam or device 116 comprises a generally 
linear portion or surface 124 which remains in engagement with the needle 
thread 110 for about 15 degrees of arm shaft rotation so as to hold the 
maximum amount of thread during this part of the cycle, as shown in FIG. 
3. Simultaneously, additional slack is taken up by the check spring 104, 
the loop or bight 108 of the check spring 104 moving towards the right (as 
viewed in FIG. 1). The position shown in FIG. 3 is the position just 
before needle penetration. 
After the needle penetrates the fabric, the continued rotation of the arm 
shaft 24 and counterbalanced crank 26 progressively withdraws the thread 
controlling and metering cam 116 from between the fixed guides 114 and 84 
and this withdrawal of the thread control and metering cam 116 accordingly 
meters out needle thread to the needle 38 so as to provide sufficient 
thread for formation of a loop for seizure and loop expansion by the 
rotary hook loop taker 23. Once the arm shaft 24 and counterbalanced crank 
32 have rotated sufficiently to withdraw the thread controlling and 
metering cam 116 from between the stationary guides 114 and 84, a 
condition that exists after approximately 120 degrees of arm shaft 
rotation, for the remainder of the arm shaft cycle the thread control and 
metering cam 116 is inactive. During the inactive period it is merely 
moving with the needle bar connecting link within the bracket arm, moving 
even further in as the crank pin 32 of the counterbalanced crank 26 passes 
the bottom dead center position of maximum needle penetration and starts 
raising the needle, while the take-up lever 64 continues to pay out needle 
thread to the loop taker for loop expansion as the rotary hook loop taker 
23 carries the loop around the bobbin case (not shown) for stitch 
concatenation around the bobbin thread as the loop approaches cast off 
from the loop taker, which occurs at approximately 255 degrees of arm 
shaft rotation, the take-up lever 64 and, particularly, the eyelet 68 
carried on the distal end of the arm 66 is at its lowest most point in its 
orbital travel, and ready to commence thread take-up for loop extraction 
following cast off from the loop taker to pull up and set the stitch. 
As the loop taker approaches cast off, the take-up lever 64 with the thread 
eyelet 68 is in its lowermost position and the eyelet 68 and the 
stationary thread guides 114 and 84 are in substantially a straight line 
with the needle thread 110 falling generally freely therethrough, 
generally downwardly and to the left side, as shown, the stationary guide 
114 being higher than stationary guide portion 86 and in line between the 
guide 86 and the check spring 104. The take-up eyelet 68, on the other 
hand, is generally below the stationary thread guide portion 86 and in 
line therewith so that a needle thread 102 at this point in time descends 
generally linerally through the guides 114, 86 and the eyelet 68 towards 
the needle with minimal capstaning or wrapping of thread around either the 
stationary guides 114 or 86 or around the take-up lever eyelet 68. Hence, 
at this point in time, that is, as the loop approaches cast off from the 
loop taker and when it is drawn between the bobbin case stop and the case 
positioning plate, the thread is under minimal tension, being in a 
straight line from the check spring downwardly through the guides and 
eyelet so as to reflect little distortion to the stitch concatenation 
process. 
As the arm shaft continues rotation, the take-up lever 64 rises, extracting 
the loop and enabling the stitch to be pulled up and set. 
FIG. 4 graphically illustrates the coordination of thread demand by the 
needle and loop taker with the thread supply from the take-up and check 
spring and how the thread control and metering device of the present 
invention modifies the thread supply so as to coordinate the thread supply 
closely with the thread needs or demand of the needle and loop taker. in 
FIG. 4 the time, in degrees of arm shaft rotation from top dead center at 
the left of the graph for a full 360 degrees of arm shaft rotation back to 
top dead center again at the right of the graph, are indicated along the 
horizontal axis, in degrees of arm shaft rotation, while the amount of 
thread, in inches, supplied or demanded is indicated along the vertical 
axis. 
The lowermost curve, designated generally by the reference character 126 
shows the supply of thread from the take-up 64 as modified by the thread 
control and metering device or cam 116. Starting at the upper lefthand 
corner of the graph, at 0 degrees arm shaft rotation (top dead center), 
the thread supply also, by definition starts at zero. For the first 30 
degrees of arm shaft rotation, as indicated by the line segment 128, the 
thread take-up starts to descend, supplying thread. From 30 to about 115 
degrees, the thread controller and metering device or cam 116 becomes 
active and the supply from the thread take-up 64 is indicated by the 
dashed line segment 130 while the actual thread supply provided by the 
take-up 64 combined with the thread control and metering device or cam 116 
is indicated by the solid line segment 132. The thread taken up by the 
thread controller and metering device or cam 116 is indicated by the space 
between the dotted line segment 130 and the solid line segment 132, as 
indicated by the reference character 134. 
The next curve, designated generally by the reference character 136 
indicates the actual thread supply with the check spring being added to 
the system to provide automatic coordination of the thread supply to the 
thread demand as needed for proper stitch formation. From 0 to about 80 
degrees of crank shaft rotation, as indicated by the line segment 136, the 
check spring 104 takes all slack out of the system, as the check spring 
expands and the bight or loop 108 thereof moves to the right lengthening 
the path between the tensioning device 102 and the fixed thread guide 114. 
At this point, penetration occurs and the check spring being fully 
relaxed, the thread supply, indicated by the line segment 140 generally 
parallels the line 126 until after about 315 degrees of arm shaft 
rotation, the check spring commences taking up thread, as indicated by the 
line segment 142. 
The space between the curves 126 and 136, designated by the reference 
character 144, corresponds to the amount of slack taken by the check 
spring 104. 
The final curve, designated generally by the reference character 146 
indicates the needle bar and loop taker demand. The line segment 148 
indicates the needle bar demand, starting from eye penetration at about 
97-98 degrees after the needle bar reaches its lowermost position, and 
starts to rise, the upcurve indicates loop formation, followed by loop 
seizure at about 190 degrees and the line segment 150 indicates the loop 
taker demand until cast off at about 260 degrees rotation, as indicated by 
the line segment 152. The area between curves 136 and 146 indicates the 
presence of slack in the system which is taken up by loop expansion prior 
to cast off and loop extraction following cast off. 
Point penetration is indicated on the graph, in FIG. 4 by the reference 
character 154, eye penetration is indicated by the reference character 
156, needle bar down by the reference character 158, loop seizure by the 
reference character 160, feed beginning by the reference character 162 and 
feed ending by the reference character 164. 
Accordingly, in accordance with the present invention the needle thread is 
controlled to prevent slack which might foul the needle prior to needle 
penetration, following needle penetration the needle thread is payed out 
by the thread controlling and metering device to meet the needle thread 
demand. Moreover, as loop cast off approaches, the tension applied to the 
needle thread is minimal.