Looptaker driving arrangement and method for zig-zag sewing machines

A looptaker driving arrangement in a zig-zag sewing machine includes: a rotatable drive shaft driving rotation of the looptaker of the sewing machine; a main drive member rotatably supported on the drive shaft; a secondary drive member fixed on the drive shaft for concurrent rotation therewith; a bushing rotatably mounted on the drive shaft with an eccentric outer periphery; and a coupling member rotatably mounted on the periphery of the bushing in eccentric relation to the drive shaft and engaging the main drive member and the secondary drive member. Rotation of the main drive member about the drive shaft axis combined with rotation of the bushing about the drive shaft axis relative to the main drive member angularly accelerates and decelerates the secondary drive member with respect to the main drive member and, in turn, angularly accelerates and decelerates the drive shaft. A gear arrangement provided for driving rotation of the bushing about the drive shaft axis relative to the main drive member includes: a first gear fixed to the drive shaft; a pair of connected gears rotatably mounted to the sewing machine; and a second gear fixedly connected to the bushing and rotatably supported on the drive shaft in coaxial relation thereto. The first gear meshingly engages a first one of the pair of gears and the second gear meshingly engages a second one of the pair of gears, whereby rotation of the drive shaft rotates the bushing about the drive shaft axis relative to the main drive member.

BACKGROUND OF THE PRESENT INVENTION 
The present invention relates generally to sewing machines of the type 
wherein a thread-carrying needle is laterally shifted to form sewn 
stitches in a zig-zag pattern and, more particularly, relates to an 
arrangement for optimally positioning a hook of a looptaker of the sewing 
machine relative to laterally shifted loop-forming positions of the 
needle. 
Sewing machines capable of forming an ornamental chain of lock stitches in 
laterally-shifting, zig-zag pattern are well known and in widespread 
commercial use. In a typical commercial zig-zag sewing machine, the 
thread-carrying needle is driven from a main drive shaft of the machine 
through intermediary eccentric cam mechanisms to reciprocate vertically 
upwardly and downwardly through a throat plate in a stitching bed of the 
machine frame while the needle is laterally shifted leftwardly and 
rightwardly in alteration in timed relation to the vertical reciprocatory 
movements of the needle. A looptaker having a peripheral hooked beak 
portion, commonly referred to as a hook, is rotatably driven beneath the 
throat plate in parallel relation to the laterally shifting movements of 
the needle by a secondary drive shaft driven from the main drive shaft in 
timed relation to the needle reciprocating vertical and laterally shifting 
movements. A thread-carrying bobbin is mounted stationarily alongside the 
looptaker. In operation, upon the completion of each downward stroke of 
the needle, a loop of the thread carried by the needle is formed as the 
needle begins its upward stroke, the timing of the rotation of the 
looptaker in relation to the needle being such that the hook of the 
looptaker seizes the loop and carries it around the bobbin to lock stitch 
the threads of the needle and bobbin together. 
A long-standing and widely recognized problem in the operation of zig-zag 
sewing machines of the aforementioned type is that, since the looptaker is 
conventionally rotated at a constant angular speed about a fixed axis, the 
looptaker cannot present the hook in an optimal disposition with respect 
to the needle at both the laterally shifted leftward and rightward 
positions of the needle. Accordingly, it is conventional practice to 
coordinate the rotation of the looptaker with respect to the needle 
reciprocation as though the needle were being reciprocated in a 
non-shifting straight stitch position equidistant the leftward and 
rightward shifted needle positions for the zig-zag stitch. In this manner, 
the hook is equally out of optimal timed relationship with the needle at 
each of the needle's leftwardly and rightwardly shifted positions, whereby 
the hook prematurely takes the thread loop when the needle is shifted 
rightwardly in the direction towards the approaching hook and likewise is 
delayed in taking the loop when the needle is shifted leftwardly in the 
opposite direction away from the approaching hook. While the sewing 
machine is "acceptably" operable in this manner, missed stitches, broken 
needles, and prematurely worn hooks do occur. 
Various proposals have been made to regulate the depth of needle 
penetration through the throat plate with respect to the hook to 
compensate for the shifted positions of the needle to improve the timing 
of the needle with respect to the hook, as representatively disclosed in 
U.S. Pat. Nos. 1,159,523; 2,932,268; and 3,779,187. However, none of these 
arrangements are known to have met with any significant degree of 
commercial acceptance and success. In other types of zig-zag sewing 
machines, the looptaker or other looper device is arranged for lateral 
shifting in timed relation to the lateral shifting of the needle to 
achieve proper relative timing, as representatively disclosed in U.S. Pat. 
Nos. 2,690,723; 3,490,401; and 3,783,810. It is also known in another type 
of zig-zag sewing machine to provide a cam-controlled mechanism for 
intentionally producing a pattern of missed stitches by selectively 
advancing or retarding rotation of the looptaker out of timed relationship 
with respect to the needle, as disclosed in U.S. Pat. No. 3,804,042. 
Finally, it is also known to angularly accelerate and decelerate the 
looptaker in timed relation to the shifting movements of the needle to 
position the hook of the looptaker in optimal relationship to the needle 
at each shifted position thereof, as disclosed in U.S. Pat. No. 4,924,788. 
While this latter technique is considered superior to the aforementioned 
proposals, there still remains a potential for further improvement over 
the angular acceleration and deceleration arrangements disclosed in this 
particular patent. 
BRIEF SUMMARY OF THE PRESENT INVENTION 
It is accordingly an object of the present invention to provide an improved 
looptaker driving arrangement and method for use in a zig-zag sewing 
machine of the above-described type to drive rotation of the looptaker in 
timed relation to shifting movements of the needle to position the hook of 
the looptaker in optimal relationship to the needle at each laterally 
shifted position thereof 
The present invention is basically adapted for incorporation in essentially 
any zig-zag sewing machine having a thread-carrying needle, a needle 
manipulating mechanism for reciprocating the needle longitudinally to form 
thread loops and for shifting the needle laterally between spaced first 
and second loop-forming positions to distribute the thread loops in 
zig-zag pattern, a looptaker rotatable about a fixed axis and having a 
hook for cooperating with the needle to seize the thread loops, and a 
drive shaft for rotating the looptaker. 
Briefly summarized, the present invention includes: a drive shaft supported 
underneath the sewing machine for rotation about a longitudinal axis 
thereof, with rotation of the drive shaft driving rotation of the 
looptaker of the sewing machine; a main drive member supported on the 
drive shaft in movable relation thereto and rotatable about the drive 
shaft axis; a secondary drive member mounted to the drive shaft in fixed 
relation and rotatable therewith about the drive shaft axis; and a 
coupling member supported by the drive shaft in movable relation thereto 
and rotatable about the drive shaft axis and about an axis parallel to the 
drive shaft axis, with the coupling member engaging through abutment the 
main drive member and engaging through abutment the secondary drive member 
for coupling movement of the main drive member with the secondary drive 
member. Rotation of the main drive member about the drive shaft axis 
causes rotation of the secondary drive member and the drive shaft about 
the drive shaft axis thereby driving rotation of the looptaker. 
In the preferred embodiment, the main drive member includes a drive rod 
which is mounted to a drive pulley, and the secondary drive member 
includes a drive rod which is mounted to an anchor member secured to the 
drive shaft. 
In a further feature of the present invention, the bushing is supported on 
the drive shaft in eccentric axial relation thereto and rotatable about 
the drive shaft axis, with the coupling member being rotatably supported 
on the bushing. 
In another feature, the present invention includes a gear arrangement for 
driving rotation of the bushing relative to the drive shaft about the 
drive shaft axis. In particular, the gear arrangement preferably includes: 
a first gear fixedly supported on the drive shaft in coaxial relation 
thereto and rotatable therewith about the rotational axis thereof; a pair 
of gears mounted to a frame of the sewing machine; and a second gear 
fixedly mounted to the bushing in coaxial relation to the drive shaft and 
rotatable about the drive shaft axis. The first gear meshingly engages a 
first one of the pair of gears and the second gear meshingly engages a 
second one of the pair of gears, with the pair of gears being fixedly 
joined together for simultaneous rotation. Furthermore, four complete 
revolutions of the first gear about the drive shaft axis with respect to 
the sewing machine preferably results in three complete revolutions of the 
second gear about the drive shaft axis with respect to the sewing machine. 
In yet a further feature of the present invention, the coupling member is 
H-shaped having two opposing channels. The main drive member is received 
in engaging abutment in a first one of the channels and the secondary 
drive member is received in engaging abutment in a second one of the 
channels. Furthermore, the coupling member is disposed in slidable and 
pivotable engagement with both the main drive member and the secondary 
drive member. 
In operation, rotation of the bushing about the drive shaft axis relative 
to the drive shaft causes the coupling member to pivot in oscillating 
manner about the main drive member thereby causing the secondary drive 
member to oscillate in an arcuate path about the drive shaft axis. The 
looptaker is thus angularly accelerated and decelerated about a constant 
angular speed of the main drive member by this pivoting of the H-shaped 
coupling member. The method of the present invention includes rotating the 
bushing about the drive shaft axis relative to the drive shaft and 
rotating the main drive member about the drive shaft axis, whereby the 
bushing is rotated three times about the drive shaft axis relative to 
frame of the sewing machine each time the main drive member is rotated 
four times about the drive shaft axis relative to the frame of the sewing 
machine.

DETAILED DESCRIPTION OF THE PREFERRED METHOD AND APATUS 
With reference initially to FIG. 1, the preferred embodiment of the 
looptaker driving arrangement of the present invention is indicated 
generally at 10 as preferably embodied in an otherwise conventional sewing 
machine of the zig-zag lock stitch type, indicated generally at 12. By way 
of example and without limitation, the illustrated zig-zag sewing machine 
is representative of the SINGER brand sewing machine Model No. 107W3 
manufactured by The Singer Company of New York, N.Y., or the YAMATO brand 
machine Model No. DP3 manufactured by Yamato Sewing Machine Manufacturing 
Co. Ltd. of Japan. Of course, as those persons skilled in the art will 
recognize, the present invention may be equally well adapted for use in 
other types of zig-zag sewing machines. Inasmuch as the construction and 
operation of the SINGER and YAMATO machines are well known within the art, 
the sewing machine 12 is illustrated and described herein only to the 
extent necessary to facilitate understanding of the present invention. 
As seen in FIG. 1, the sewing machine 12 has a substantially hollow 
structural frame 14, shown only in phantom, which includes a horizontal 
machine bed 16, an upstanding arm 18 extending from the rightward end of 
the bed 16, and a horizontal arm 20 extending from the upright arm 18 and 
terminating in a sewing head 22 spaced directly above the bed 16. A needle 
bar frame 24 is pivotally supported within the sewing head 22 for relative 
swinging movement leftwardly and rightwardly, as viewed in FIG. 1, and a 
needle bar 26 having a sewing needle 28 affixed to its depending end is 
slidably supported by the needle bar frame 24 for vertical movement 
upwardly and downwardly relative thereto. 
A main drive shaft 30 is rotatably supported by bearings 32 to extend 
horizontally through the hollow horizontal arm 20 of the machine frame 14. 
The rightward end of the drive shaft 30 extends outwardly from the frame 
14 and has a drive pulley arrangement 34 fixed to the exposed end of the 
drive shaft 30 to facilitate driven operation thereof from any suitable 
power source. A hand wheel 36 is also fixed to the exposed extent of the 
drive shaft 30 for manual operation thereof The opposite end of the drive 
shaft 30 carries a counterweight 38, one end of a crank arm 40 being 
pivotally mounted eccentrically to the counterweight 38 with its opposite 
end being affixed by a connecting bracket 42 to the needle bar 26 for 
reciprocating the needle bar 26 vertically upwardly and downwardly with 
respect to the needle bar frame 24. A spiral pinion gear 44 is affixed to 
the main drive shaft 30 at an intermediate location in meshing engagement 
with another spiral gear 46 mounted on a perpendicular shaft 48 supported 
by the machine frame 14 immediately below the pinion gear 44. A drive bar 
50 is mounted eccentrically at one end to the spiral gear 46 and is 
connected at the opposite end to the needle bar frame 24 to drive 
reciprocating leftward and rightward swinging movement of the needle bar 
frame 24 (as viewed in FIG. 1). In this manner the main drive shaft 30 
controls vertical reciprocating movement and lateral shifting movement of 
the needle 28 for stitch formation in conventional fashion. 
The bed 16 of the machine frame 14 includes a throat plate (not shown) 
immediately beneath the assembly of the needle bar frame 24 and the needle 
bar 26 to define a stitching work area through which the needle 28 is 
permitted to penetrate the bed 16. Immediately beneath the throat plate, a 
looptaker 52 having a beaked hook portion 54 at its outer periphery, such 
unit sometimes being commonly referred to in its entirety as a hook, is 
fixed in conventional manner to a shaft 56 rotatably supported by the bed 
16 for rotational movement of the looptaker 52. A bevel gear 58 is mounted 
coaxially on the shaft 56 in meshing engagement with another bevel gear 60 
mounted at the leftward end of a secondary drive shaft 62 rotatably 
supported by bearings 64 horizontally along the underside of the bed 16. 
Conventionally, the secondary drive shaft 62 is belt-driven from the main 
drive shaft 30 in timed relation therewith via appropriate speed-change 
pulleys fixed respectively to the main and secondary drive shafts 30, 62, 
whereby the secondary drive shaft 62 and, in turn, the looptaker 52 are 
driven at a constant angular speed. Furthermore, as is conventional, the 
drive train of the looptaker 52 is provided with appropriate gearing to 
drive rotation of the looptaker 52 to perform two full revolutions for 
each downward stitching reciprocation of the needle 28 to lock-stitch each 
loop of the needle-carried thread with respect to the bobbin-carried 
thread in a known manner. As aforementioned, however, timing problems 
arise with this arrangement because the laterally shifting movements of 
the needle 28 cause the needle to be alternatively disposed upon 
completing its downward reciprocation at spaced loop-forming stitch 
positions at opposite lateral sides of the rotational axis of the 
looptaker 52, while in contrast the hook 54 of the looptaker 52 is at the 
same angular disposition in its path of rotational movement when the 
needle 28 is at each of its loop-forming stitch positions because the 
looptaker 52 is rotated at a constant angular speed about a fixed axis 
defined by the shaft 56. This inherent mistiming of the hook 54 and the 
needle 28 is illustrated in FIGS. 3A and 3B, wherein only the needle 28 
and looptaker 52 are shown from the same front elevation as in FIG. 1. In 
FIG. 3A, the needle 28 is illustrated at its leftwardly shifted 
loop-forming stitch position, while in FIG. 3B the needle 28 is 
illustrated at its rightwardly shifted loop-forming stitch position. In 
each case, the looptaker 52 is shown at the identical rotational 
disposition with its hook 54 passing through the uppermost extent of its 
counter-clockwise rotational path of movement immediately beneath the 
throat plate (not shown). Thus, in the leftwardly shifted stitch position 
of the needle 28, the needle 28 has been shifted generally in the same 
direction as the counter-clockwise rotational path of the hook 54 and, 
therefore, the hook 54 is delayed in reaching a loop-seizing disposition 
passing the needle 28, as seen in FIG. 3A. Similarly, as seen in FIG. 3B, 
at the rightwardly shifted stitch position of the needle 28, the needle 28 
has been shifted in a direction essentially opposite the rotational path 
of the hook 54 and, therefore, the hook 54 passes prematurely through a 
loop-seizing position adjacent the needle 28. Conventionally, as also 
aforementioned, the looptaker 52 is timed with respect to the needle 28 to 
orient the hook 54 in proper loop-seizing disposition with respect to an 
imaginary "neutral" needle reciprocating path 55 which the needle 28 would 
follow if it were not shifted laterally, shown in phantom lines in each of 
FIGS. 3A and 3B, which causes the needle 28 and the hook 54 to be equally 
out of time at each stitch position of the needle. So long as the extent 
of laterally shifting movement of the needle 28 is not too great, the 
sewing machine will still perform a zig-zag lock stitching operation, but 
the mistiming between the needle 28 and the hook 54 produces an 
undesirable amount of contact between these components causing premature 
wear and frequent needle breakage and additionally causing a greater than 
desirable frequency of missed stitches. 
In contrast, the improved looptaker driving arrangement 10 of the present 
invention provides drive arrangement by which the secondary drive shaft 62 
and, in turn, the looptaker 52 are accelerated when the needle 28 is 
shifted to its leftward loop-forming stitch position so as to advance the 
hook 54 of the looptaker 52 into a loop-seizing disposition in optimal 
relation with respect to the needle 28, as shown in FIG. 4A. Likewise, the 
secondary drive shaft 62 and the looptaker 52 are decelerated when the 
needle 28 is in its rightward loop-forming stitch position to retard the 
hook 54 of the looptaker 52 into a loop-seizing disposition also optimally 
related with respect to the needle 28, as shown in FIG. 4B. This optimal 
positioning of the hook 54 with respect to the laterally shifted needle 
positions as shown in FIGS. 4A and 4B will now be described in detail. 
As best seen in FIG. 1, a first drive pulley 66 is fixed to the main drive 
shaft 30 and a speed-change second drive pulley 68 is rotatably mounted on 
the secondary drive shaft 62, with an endless drive belt 71 being trained 
about the pulleys 66, 68. The drive pulleys 66,68 are identical to the 
drive pulleys utilized in a conventional sewing machine as described above 
except that the drive pulley 68 is supported in movable relation to the 
secondary drive shaft 62 for rotation about the drive shaft axis 72 rather 
than being fixed to the drive shaft 62. For instance, the pulleys 66, 68 
are sized to accomplish the aforementioned speed change to produce four 
revolutions of the looptaker 52 for every pair of stitch-forming 
reciprocations of the needle 28, as is conventional. 
As best seen in FIG. 2, the second drive pulley 68 includes a main drive 
rod 70 fixedly mounted to the second drive pulley 68 and extending 
therefrom parallel to the secondary drive shaft 62 for orbital movement of 
the the main drive rod 70 about the longitudinal axis 72 of the secondary 
drive shaft 62 upon rotation of the secondary drive pulley 68. Disposed 
adjacent the second drive pulley 68 and fixed to the secondary drive shaft 
62 is an anchor member 74 with a secondary drive rod 76 fixedly mounted 
thereto and extending therefrom parallel to the secondary drive shaft 62 
for similar orbital movement by the secondary drive rod 76 about the 
rotational axis 72 of the secondary drive shaft 62. 
An H-shaped coupling member 78 is supported by secondary drive shaft 62 
adjacent the anchor member 74 and, in particular, is rotatably mounted on 
a bushing 80 which itself is rotatably mounted on the secondary drive 
shaft 62 adjacent the anchor member 74. The H-shaped coupling member 78 
includes two diametrically opposed channels 82, 84 each for receiving in 
engaging abutment main drive rod 70 and secondary drive rod 76, 
respectively. Furthermore, the H-shaped coupling member 78 slidably and 
pivotally engages the drive rods 70, 76 for movement relative thereto as 
will be explained presently. 
The bushing 80 includes an outer circular surface 86 concentric about an 
axial centerline 88 which is offset from but parallel to the axial 
centerline 72 of the secondary drive shaft 62 when mounted thereon. Thus, 
the bushing 80 is rotatably supported on the secondary drive shaft 62 in 
eccentric axial relation thereto. The H-shaped coupling member 78, 
rotatably mounted on the circular surface 86 of the bushing 80, is thus 
rotatable with the bushing 80 about the rotational axis 72 of the 
secondary drive shaft 62 as well as rotatable about the axis 88 of the 
circular surface 86 eccentric to the rotational axis 72 of the secondary 
drive shaft 62. 
The bushing 80 is continuously driven to rotate about the secondary drive 
shaft axis 72 relative to the secondary drive shaft 62, as more fully 
described hereinafter. By virtue of such rotation of the bushing 80 and 
the driven rotation of the drive pulley 68, the drive pulley 68 and the 
anchor member 74 with their respective drive rods 70, 76, and the bushing 
80, each move relative to one another during ongoing operation of the 
sewing machine. In particular, four representative positions I-IV in the 
relative rotation of the drive pulley 68 and its drive rod 70, the anchor 
member 74 and its drive rod 76, and the bushing 80 about the rotational 
axis 72 are schematically shown in FIGS. 5A-5D. In position I of FIG. 5A, 
the axial centerline 88 of the circular surface 86 of the bushing 80 is 
located vertically below the rotational axis 72 of the secondary drive 
shaft 62. In this position, the main drive rod 70, the secondary drive rod 
76, and the rotational axis 72 of the secondary drive shaft 62 vertically 
align. In position II of FIG. 5B, the axial centerline 88 of the circular 
surface 86 of the bushing 80 is located horizontally to the left from the 
rotational axis 72 of the secondary drive shaft 62. In this position, the 
main drive rod 70 and the secondary drive rod 76 do not align with the 
rotational axis 72 of the secondary drive shaft 62. In position III of 
FIG. 5C, the axial centerline 88 of the circular surface 86 of the bushing 
80 is located vertically above the rotational axis 72 of the secondary 
drive shaft 62. In this position, the main drive rod 70, the secondary 
drive rod 76, and the rotational axis 72 of the secondary drive shaft 62 
again vertically align. Finally, in position IV of FIG. 5D, the axial 
centerline 88 of the circular surface 86 of the brushing 80 is located 
horizontally to the right from the rotational axis 72 of the secondary 
drive shaft 62. In this position, the main drive rod 70 and the secondary 
drive rod 76 do not align with the rotational axis 72 of the secondary 
drive shaft 62. 
In each of the positions I-IV of the bushing 80 shown in FIGS. 5A-5D, the 
orbital movement of the centerline 88 of the circular surface 86 of the 
bushing 80 relative to the rotational axis 72 of the secondary drive shaft 
62 has both vertical and horizontal components of movement as indicated by 
the arrows V, H in FIG. 5A-5D. Moreover, because the H-shaped coupling 
member 78 is mounted on the circular surface 86 of the bushing 80, it too 
undergoes the same vertical and horizontal movement shown by arrows V, H 
as schematically shown in FIGS. 6A-6D. 
Thus, in position I of the H-shaped coupling member 78 as schematically 
shown in FIG. 6A, the channels 82, 84 are vertically aligned with the 
axial centerline 88 of the circular surface 86, with the main drive rod 70 
disposed in channel 82 of the H-shaped coupling member at its greatest 
radial spacing outwardly from the axial centerline 88 of the circular 
surface 86, and with the secondary drive rod 76 disposed in channel 84 at 
its closest radial spacing inwardly to the axial centerline 88 of the 
circular surface 86. 
In position II of the H-shaped coupling member 78 as schematically shown in 
FIG. 6B, the channels 82, 84 out of vertical alignment with the centerline 
88 of the circular surface 86 and the main drive rod 70 and the secondary 
drive rod 76 are respectively disposed in channels 82, 84 approximately 
midway therein at essentially the same radial spacing from the centerline 
88 of the circular surface 86 and the H-shaped coupling member 78 is 
pivoted about the main drive rod 70 by an angle .omega. from the vertical, 
with such pivoting movement of the H-shaped coupling member 78 in turn 
causing clockwise movement of the secondary drive rod 76 along an arcuate 
path with respect to the rotational axis 72 of the secondary drive shaft 
62. This moving of the secondary drive rod 76 clockwise as shown in FIGS. 
5B, 6B causes the secondary drive shaft 62 to moveby a corresponding 
arcuate distance (same angle of rotation .omega.), which in turn causes 
the looptaker to move an arcuate distance. 
In position III of the H-shaped coupling member 78 as schematically shown 
in FIG. 6C, the main drive rod 70 is disposed in channel 82 at its closest 
radial spacing to the axial centerline 88 of the circular surface 86 with 
the secondary drive rod 76 disposed in channel 84 at its greatest radial 
spacing from the axial centerline 88 of the circular surface 86 as shown 
in FIG. 8; this orientation of the drive rods 70, 76 with respect to the 
channels 82, 84 is opposite that of position I. Again, the channels 82, 84 
vertically align with the axial centerline 88 of the circular surface 86. 
Thus, rotation of the bushing 80 from position II to position III causes 
the H-shaped coupling member 78 to be pivoted about main drive rod 70 back 
to the vertical position, thereby rotating secondary drive shaft 62 and 
the looptaker 52 back to their respective orientations of position I. 
In position IV of the H-shaped coupling member 78 as schematically shown in 
FIG. 6D, the main drive rod 70 and the secondary drive rod 76 are again 
disposed in channels 82, 84 respectively midway therein at corresponding 
spacings from the axial centerline 88 of the circular surface 86. The 
channels 82, 84 are again out of vertical alignment with the axial 
centerline 88 of the circular surface 86, but in this position, the 
H-shaped coupling member 78 has been pivoted about the main drive rod 70 
by rotation of the bushing 80 through a negative angle (-.omega.) opposite 
to the angle in position II, with this negative pivoting movement of the 
H-shaped coupling member 78 causing negative movement of the secondary 
drive rod 76 along an opposite, counter-clockwise arcuate path to that of 
position II. In turn, this movement of the secondary drive rod 76 causes 
the secondary drive shaft 62 to move a corresponding opposite arcuate 
distance by the same angle of rotation -.omega., which causes the 
looptaker to move an opposite arcuate distance to that moved when the 
bushing 80 is rotated from position I to position II. 
Rotation of the bushing 80 a full revolution (i.e., from starting position 
I through position IV) returns the H-shaped coupling member 78, secondary 
drive shaft 62, and looptaker 52 back to their respective orientations 
found in position I. Continued rotation of the bushing 80 results in 
oscillation of the secondary drive rod 76 along the arcuate path 
corresponding to a total angle of 2.omega. during each revolution of the 
bushing 80. 
The positioning effected by the looptaker driving arrangement 10 may thus 
be understood. During the sewing operation, the bushing 80 is rotated 
relative to the secondary drive shaft 62 about its rotational axis 72 (as 
hereinafter explained), which causes the above described movements of the 
H-shaped coupling member 78 and, in turn, which causes the secondary drive 
rod 76 to move back and forth along an arcuate path defined by the angle 
2.omega.. Thus, the looptaker 52, which otherwise would be driven at the 
constant angular speed of the main drive rod 70, is angularly accelerated 
and angularly decelerated by the movement of the secondary drive rod 76 
closer to and further from the main drive rod 70 in the clockwise 
direction, which results from rotation of the bushing 80 about the 
rotational axis 72 relative to the secondary drive rod 62. (If the bushing 
80 were to rotate about the rotational axis 72 at the same angular speed 
as the main drive rod 70, then the main drive rod 70, secondary drive rod 
76, and rotational axis 72 would be in constant alignment, the H-shaped 
coupling member 78 would not be pivoted about the main drive rod 70 and no 
angular acceleration or angular deceleration of the looptaker 52 would 
occur absent angular acceleration or angular deceleration of the main 
drive rod 70). 
It will thus be apparent to one of ordinary skill in the art that in order 
to move the looptaker 52 from a first laterally shifted loop-seizing 
position to the other laterally shifted loop-seizing position and then 
back again as discussed above, which corresponds to two revolutions of the 
main drive shaft 30 and four revolutions of the main drive rod 70, the 
bushing 80 must pass from a first position (either position II or IV) 
through all of the other positions and then back to the starting position 
relative to the main drive rod 70. 
In order to accomplish this rotation of the bushing 80 about the rotational 
axis 72 relative to the main drive rod 70, the present invention 
preferably includes a gear arrangement 90 of four gears: first and second 
gears 92, 94 supported by the secondary drive shaft 62 and a pair of gears 
98, 100 connected together and rotatably mounted on the sewing machine 
frame 14. In particular, the first gear 92 is fixedly mounted in coaxial 
relation to the secondary drive shaft 62 for concurrent rotation therewith 
about the rotational axis 72. The second gear 94 is fixedly mounted to an 
extension 95 of the bushing 80 which itself is rotatably mounted 
concentrically on the secondary drive shaft 62 in coaxial relation thereto 
for rotation about the rotational axis 72 thereof, whereby rotation of 
second gear 94 therefore rotates bushing 80 about the rotational axis 72. 
The pair of gears 98, 100 are mounted on a support shaft 102 which, in 
turn, is mounted to the sewing machine frame 14 with a conventional 
bracket mount 104, with the gear 98 in meshing engagement with the first 
gear 92 and the gear 100 in meshing engagement with the second gear 94. 
In operation of the gear arrangement 90, rotation of the drive pulley 68 
and its integral drive rod 70 effects rotation of the secondary drive 
shaft 62 and the first gear 92 fixed thereto which, in turn, acts on the 
gear pair 98, 100 to drive rotation of gear 94 and bushing 80 about 
rotational axis 72. Hence, rotation of the drive pulley 68 and the main 
drive rod 70 results in angular accelerated and decelerated rotation of 
the secondary drive member 76 about the constant angular speed of the main 
drive rod 70, which results in the desired angular acceleration and 
deceleration, and thus positioning, of the looptaker 52. In particular, 
four complete revolutions of the main drive rod 70, the first gear 92, and 
the H-shaped coupling member 78 relative to the sewing machine frame 14 
preferably results in three full revolutions of the second gear 94 and 
bushing 80 relative to the sewing machine frame 14. Thus, four complete 
revolutions of the main drive rod 70, first gear 92, secondary drive shaft 
62, and H-shaped coupling member 78 relative to the sewing machine frame 
14 results in one complete revolution of the second gear 94 and bushing 80 
relative to the main drive rod 70, first gear 92, secondary drive shaft 
62, and H-shaped coupling member 78. 
It will therefore be readily understood by those persons skilled in the art 
that the present invention is susceptible of broad utility and 
application. Many embodiments and adaptations of the present invention 
other than those herein described, as well as many variations, 
modifications and equivalent arrangements will be apparent from or 
reasonably suggested by the present invention and the foregoing 
description thereof, without departing from the substance or scope of the 
present invention. Accordingly, while the present invention has been 
described herein in detail in relation to its preferred embodiment, it is 
to be understood that this disclosure is only illustrative and exemplary 
of the present invention and is made merely for purposes of providing a 
full and enabling disclosure of the invention. The foregoing disclosure is 
not intended or to be construed to limit the present invention or 
otherwise to exclude any such other embodiments, adaptations, variations, 
modifications and equivalent arrangements, the present invention being 
limited only by the claims appended hereto and the equivalents thereof.