Sewing – Stitch forming – Multiple needle
Reexamination Certificate
2002-05-22
2003-11-18
Izaguirre, Ismael (Department: 3765)
Sewing
Stitch forming
Multiple needle
C112S260000
Reexamination Certificate
active
06647906
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a loop forming device for a chainstitch sewing, and more particularly to a loop forming device for successively forming the empty rings of yarn by a plurality of needle threads and a looper thread.
2. Description of the Related Art
A well known technique is disclosed in Japanese patent laid-open No. 2000-93671. This technique will be described with reference to
FIGS. 8 and 9
.
FIG. 8
is a perspective view showing a cloth holding device and a throat plate, and reference numeral
20
designates a support member detachably mounted on the lower end of the presser bar (not shown). Reference numeral
21
designates a cloth holder part, which is rotatably supported at the lower end of the support member
20
by its horizontal shaft
22
. Reference numeral
23
indicates a loop holder, which is rotatably supported by a shaft
23
A oriented horizontal to the cloth holder part
21
.
Reference numeral
24
indicates a throat plate claw plate. Needle location holes
24
A, as needle location parts, for three needles N, a gate-shaped slit
24
B formed in front of the needle location holes
24
A as viewed in the cloth feeding direction, and an edge sewing-up pawl
24
C are provided on the throat plate claw plate
24
, and its base end is fastened to a throat plate
25
.
Three arcuate hollow parts
25
A to
25
C shown in
FIG. 9
are provided at a location under the needle location holes
24
A of the throat plate claw plate
24
of the throat plate
25
. A thread setter
25
F having two engaging claws
25
D and
25
E which are slanted upward in the cloth feeding direction and provided among the arcuate hollow parts
25
A to
25
C, is further provided on the throat plate
25
. A cloth feed dog
27
through which an auxiliary feed dog
26
appears and disappears and a main feed gear hole
30
through which a main feed dog
29
including a center loop feed dog
28
appears and disappears, are formed in the throat plate
25
. Reference numeral
31
is a looper. The width of the loop feed dog
28
in a direction perpendicular to the cloth feeding direction is narrower than the width of an array of the three needles N. Operation of the conventional technique described above will briefly be described.
When the sewing machine is driven, the three needles N vertically moves interlocking with the main shaft (not shown). A looper
31
swings around the needles on a planar shape, while drawing an elliptical locus, and the main feed dog
29
and the auxiliary feed dog
26
perform four movements of cloth feeding.
Motion relationship of those needles N, the looper
31
and the feed dog will be described. The description will start from a state that the needles N are at the bottom dead point, the looper
31
is at the most retracted position, and the feed dog is under the throat plate.
The needles N starts to slightly lift from the bottom dead point. Then the looper
31
starts to advance, the needle threads NT of the three needles N are looped, and those needle threads looped are successively caught by the point of a sword of the looper
31
.
The needle thread loop caught by the looper
31
is pulled in the advancing direction of the looper
31
. The needle thread loop is retained at the retaining claws
25
D and
25
E provided among the arcuate hollow parts
25
A to
25
C as shown in
FIG. 9
, are set at the arcuate hollow parts
25
A to
25
C.
The needles N further lift and the looper
31
also proceeds, and the needle threads NT are taken up by a thread take-up lever (not shown).
The needles N further lift and reach the top dead point, and then starts to descend. The looper
31
advances while moving in the direction opposite to the cloth feeding direction, and after it reaches the most advanced position, and then start to retract.
The three needles N having descended, as shown in
FIG. 10
, are caught by the looper
31
, and reaches the lower most point in a state that it is placed in a called triangle of the needle threads NT extending in the cloth feeding direction.
The up and down movement of the needles N and the reciprocal motion of the looper
31
are repeated, and loops
32
as a chain-off thread are formed, as shown in
FIG. 9
, in the cloth feeding direction by the three needles N and a single looper thread LT. The loops
32
are fed in the cloth feeding direction by a loop feed dog
28
of the main feed dog
29
and the loop holder
23
.
The conventional technique, however, involves the following problems.
The loops
32
, which is formed in the cloth feeding direction by the three needles N and the single looper thread LT, is swung to the front and rear, and to the right and left by the up/down motion of the needles N and the reciprocating motion of the looper thread L. The needle threads NT that are retained at the retaining claws
25
D and
25
E as indicated by solid lines in
FIG. 9
climb over the retaining claw
25
E as indicated by a two-dot chain line, and are retained at the retaining claw
25
D. And those threads are unable to return to their original positions, and the subsequent formation of loops is impossible.
The loops
32
fed in the cloth feeding direction are pulled out in the cloth feeding direction by the loop feed dog
28
of the main feed dog
29
and the loop holder
23
, and the fore ends of the loops
32
are pulled to the center to be narrow as shown in
FIG. 9. A
called triangle of the needle threads NT, which are caught by the looper
31
and extend in the cloth feeding direction, becomes small as indicated by a two-dot chain line FIG.
10
. The needle does not fall to within the triangle and the stitch skipping occurs, and the loop cannot be formed.
The width of the loop feed dog
28
in a direction orthogonal to the cloth feeding direction is narrow than the width of the needle location part of the three needles N. The fore ends of the loops
32
, which are pulled out in the cloth feeding direction to be narrow, are deviated sideways from the loop feed dog
28
as shown in
FIG. 11
, and loops cannot be fed in the cloth direction, and it is impossible to form the loops.
SUMMARY OF THE INVENTION
To achieve the above object, there is provided a chainstitch sewing machine having a plurality of needles having needle threads which are moved up and down through needle holes of a throat plate, a looper having a looper thread, which is reciprocatively moved in a direction orthogonal to a cloth feeding direction under the throat plate, guide holes provided in the throat plate for guiding loops formed by the needle threads and a looper thread by the cooperation of the needles and the looper, to a rear part in a cloth feeding direction, and a main feed dog, disposed at a part closer to a rear than the guide hole, for feeding the loops in the cloth feeding direction,
the improvement being characterized in that
the upper end edge of the needle hole located at a rear part as viewed in the cloth feeding direction, takes a planar shape configured such that a part thereof located closer to the forward movement end of the looper is gradually varied toward the needles with respect to a straight line orthogonal to a cloth feed direction, and a thread guide surface, which is chamfered off to become thin in the forward direction of the looper and toward the lower surface of the throat plate, is provided on the upper edge of the guide hole.
In the chainstitch sewing machine mentioned above, the loops are fed out by a loop holder and a loop feed dog, the loops are expanded, so that the needle threads being in contact with the thread guide surface move along the guide surface and in a direction that the needle threads separate from each other. As a result, the needle threads are caught by the looper, a called triangle of a needle thread NT extending in the cloth feeding direction becomes large. The needle reliably drops into the triangle, and no stitch skipping occurs. Accordingly, the loops are formed reliably.
In the chainstitch sewing machine, the planar shape is arcuate.
With this feature, the e
Izaguirre Ismael
Juki Corporation
Merchant & Gould P.C.
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