Sewing – Elements – Starting or stopping
Reexamination Certificate
2000-05-05
2001-10-30
Nerbun, Peter (Department: 3741)
Sewing
Elements
Starting or stopping
C112S140000, C112S475020
Reexamination Certificate
active
06308647
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an interlock stitch sewing machine for blindstitch hemming with a slippage preventing device. More particularly, the invention relates to an interlock stitch sewing machine for blindstitch hemming with a slippage preventing device which is constructed so as to prevent such slippage that is liable to occur in the blindstitch hemming of a tubular article such as T-shirts or underwear. Specifically, of fabric portions stacked by a top-stitching at the fabric end, a lower fabric portion slips, or a locally deformed portion due to a cutting error is present at the edge of the lower fabric portion.
2. Description of the Prior Art
FIG. 11
illustrates a construction of a major part of a three-needle interlock stitch sewing machine for blindstitch hemming which has conventionally being in general use. In this sewing machine, paired front and rear feed dogs (which are not shown because this is known) which feed a tubular article W in a sewing direction indicated by the arrow Y, are disposed underneath a throat plate
2
provided on the upper surface of a sewing machine bed
1
. A pressure foot
3
that presses the article W against the upper surface of the throat plate
2
, and three needles
4
that are movable vertically reciprocally are supported on an arm
5
disposed above the throat plate
2
. In front of the pressure foot
3
and a needle location
6
formed in the throat plate
2
, a top-stitching width guide
7
and a fabric edge guide
8
are oppositely disposed in a direction orthogonal to the sewing direction Y. The top-stitching width guide
7
defines a top-stitching width h toward the back of the edge of the article W, and makes contact with a bent portion W
2
a
formed by a lower fabric portion W
1
and an upper fabric portion W
2
overlying thereon, to guidedly feed the bent portion W
2
a
in the sewing direction Y. The fabric edge guide
8
makes contact with an edge W
1
a
of the lower fabric portion W
1
to guidedly feed the edge W
1
a
in the sewing direction Y.
In the three-needle interlock stitch sewing machine for blindstitch hemming so constructed, the rotation of the sewing machine is started when the operator sets the article W on the surfaces of the bed
1
and throat plate
2
, while the end of the article W is folded downwardly through the top-stitching width guide
7
, so as to obtain an approximately constant top-stitching width h. As the sewing machine is rotated, the fabric portions W
2
and W
1
which are stacked at the top-stitching are subsequently fed in the sewing direction Y along the upper surface of the throat plate
2
, by up and down movements of the paired feed dogs and by the pressure foot
3
cooperating with the movements of the feed dogs. Then, when the fabric portions W
2
and W
1
reach the needle location
6
, the three needles
4
and a looper (not shown) cooperate to form a stitch Wa that is wide in the direction in which the fabric portions W
2
and W
1
cross at a right angle to the sewing direction Y, as shown in
FIG. 12
, thereby performing a predetermined interlock stitch sewing.
In such a blindstitch hemming sewing, as indicated by virtual line in
FIG. 11
, the bent portion W
2
a
of the upper fabric portion W
2
and the edge W
1
a
of the lower fabric portion W
1
make contact with the top-stitching width guide
7
and fabric edge guide
8
, respectively, thereby to be guidedly fed in the sewing direction Y. That is, the conventional interlock stitch sewing machine for blindstitch hemming is so constructed that a blindstitch hemming while retaining a constant top-stitching width h of the lower fabric portion W
1
, is carried out only by slidingly guiding the ends of the upper and lower fabric portions (i.e., the bent portion W
2
a
and the edge W
1
a
), by the top-stitching width guide
7
and fabric edge guide
8
oppositely disposed in front of the needle location
6
.
In the above sewing machine, however, of the fabric portions W
2
and W
1
stacked at the top-stitching, the lower fabric portion W
1
is extremely hard to see by the operator's eye. It is therefore difficult that the top-stitching toward the back of the fabric end is always kept constant only by the top-stitching width guide
7
and fabric edge guide
8
. It is also very difficult to adjust the top-stitching width in the course of the fabric feed. Thus, the stacked fabric portions tend to be guidedly fed to the needle location
6
in the state that the edge W
1
a
of the lower fabric portion W
1
has a position error, thereby causing slippage. In addition, even if a locally deformed portion is present at the edge W
1
a
of the lower fabric portion W
1
, it is difficult to observe the deformed portion by the eye during the sewing operation. Therefore, when the deformed portion is large in the sewing direction, a faulty sewing such as slippage is liable to occur. Hence, it has conventionally been indispensable to conduct, after sewing operation, a product inspection to visually inspect for faulty sewing such as slippage.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an interlock stitch sewing machine for blindstitch hemming equipped with a slippage preventing device which can reliably prevent the occurrence of a faulty sewing such as slippage, by previously detecting the cause of the faulty sewing due to the position error of a lower fabric portion or a cutting error.
According to the present invention, in an interlock stitch sewing machine for blindstitch hemming which comprises a top-stitching width guide that defines the width of a top-stitching toward the back of a fabric and makes contact with a bent portion of a lower fabric portion and an upper fabric portion overlying thereon in the top-stitching, to guidedly feed the bent portion in a sewing direction, and a fabric edge guide that makes contact with an edge of the lower fabric portion to guidedly feed the edge in the sewing direction, the top-stitching width guide and the fabric edge guide being oppositely disposed in front of a needle location in a direction orthogonal to the sewing direction, is characterized in having a slippage preventing device comprising: a slippage detecting sensor attached to the fabric edge guide, the sensor detecting slippage of the upper and lower fabric portions by detecting the position of an edge of the lower fabric portion to be guidedly fed by the guide; and an informing means that compares a slippage quantity detected by the slippage detecting sensor and a preset permissible slippage quantity, and, when the slippage quantity exceeds the permissible slippage quantity, determines the possibility of slippage and performs an informing operation.
With this construction, in a predetermined blindstitch hemming sewing, when the setting of the edge of the lower fabric portion which is extremely hard to be seen from the operator is so shifted as to cause slippage, when such a position error as to cause slippage during feed in a sewing direction is created, or when a large locally deformed portion due to a cutting error is present at the edge of the lower fabric portion, the slippage detecting sensor detects these factors of causing a faulty sewing, and the informing means is operated to inform the operator of the possibility of slippage before sewing. That is, the factor of causing a faulty sewing is removed before the stacked upper and lower fabric portions reach the needle location, and these fabric portions is subjected to sewing while a predetermined width overlap allowance is ensured. This enables to reliably prevent the occurrence of a faulty sewing such as slippage, increase yield and achieve labor saving by omitting a visual product inspection after sewing.
Preferably, the above sewing machine is provided with a translucent plate that slidingly guides the lower fabric portion in the sewing direction is disposed in front of the fabric edge guide; and a light source that applies an upward light to the back of the translucent plate to illu
Kurata Hiromichi
Masaoka Takayoshi
Nakata Norio
Okabe Masato
Sakai Itsuo
Hochberg D. Peter
Holt William H.
Nerbun Peter
Vieyra Katherine R.
Yamato Sewing Machine Seizo Co., Ltd.
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