Sewing – Special machines – Pattern controlled or programmed
Reexamination Certificate
2000-10-23
2002-07-23
Nerbun, Peter (Department: 3765)
Sewing
Special machines
Pattern controlled or programmed
C112S165000, C112S199000, C112S300000
Reexamination Certificate
active
06422165
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for preventing the unraveling (also hereafter referred to as “raveling”) of a seam at the end of sewing, the apparatus being provided in a sewing machine such as a double chain stitch sewing machine or a covering chain stitch sewing machine for sewing cloth with a looper thread and needle threads.
In a double-ring-sewing sewing machine or a flat-sewing sewing machine for sewing cloth by using needle threads and a looper thread, a loop of needle threads
6
a
and
6
b
and a looper thread
7
are intertwined in a form of another thread loop on a rear surface of a sewing cloth, so that a seam shown in
FIG. 1A
is formed. Such seam has a problem in that the looper thread
7
is pulled out from the final loops
6
c
and
6
d
by pulling the looper thread
7
cut at the end of the sewn portion, so that such pulling out progresses toward the start of sewing and the seam formed as shown in the drawing is raveled from the end of sewing.
In order to prevent such raveling of the seam, conventionally two methods have been generally used: a first method allows sewing in several stitches before the end by shortening the distance between seams on the sewing cloth or reducing the tension of the needle thread, so that the needle threads and the looper thread intertwine more easily between stitches near the end of sewing. A second method allows the needle thread to be tightened by increasing the tension of the looper thread next to the sewing cloth immediately before the end of the sewing.
However, there is a problem in the first method in that the seam in the vicinity of the end of sewing has a form different from the other portion thereof, or the seams look slack as a whole, so that the external appearance of the sewn product becomes poor and besides the needle threads and the looper thread are not necessarily intertwined as desired, so that a secure effect of preventing the raveling of the thread cannot be obtained. There is also a problem in the second method as well in that a wrinkle is generated on a sewn cloth in the vicinity of the end of sewing along with the tensioning of the needle thread, so that the external appearance becomes poor and a sufficient effect of preventing the raveling of the thread cannot be obtained.
Under these circumstances, the inventors of the present invention propose in Japanese Patent Publication No. 2879399 a method and an apparatus for preventing the raveling which provide a secured effect in preventing the raveling without the deterioration in the external appearance. The method and the apparatus are such that a looper thread hanger (a looper thread hanging hook) is provided for holding the looper thread, which is allowed to pass through the loop of the needle thread with the advance of the looper, on the side of the advancing end of the looper, the sewing operation is temporarily suspended with the looper being in the state of advancing, followed by catching the looper thread on the looper thread hanging hook so that one stitch is sewn in this state and the needle thread and the looper thread are cut.
According to this method, as shown in
FIG. 1B
, the looper thread
7
caught on the looper thread hanging hook remains in the form of another thread lacing on the final loops
6
c
and
6
d
of the needle thread
6
a,
6
b
formed before the suspension of the sewing operation, and the looper thread
7
is not pulled out from the final loops
6
c
and
6
d
even when the end portion is pulled, with the result that the raveling of the seam can be prevented with certitude. Furthermore, as shown in the drawings the seam on the end portion of the sewing does to seem to be different from the other portion and the external appearance is not deteriorated.
In this manner, the method and the apparatus for preventing the raveling which are proposed in the Japanese Patent Publication No. 2879399 are excellent method and apparatus which can prevent the raveling of the thread generated on the seam at the end of the sewing in a sewing machine for sewing cloth by using a looper thread and needle threads such as the double-ring-sewing sewing machine, flat-sewing sewing machine or the like. The same method and apparatus are also disclosed in Japanese Patent Application Laid-Open No. HEI-910-225163, Japanese Patent Application Laid-Open No. HEI-11-57253, Japanese Patent Application Laid-Open No. HEI-11-57268 and Japanese Patent Application Laid-Open No. HEI-11-70281.
The apparatus conducting a method for preventing raveling of the seem as described above is constituted in such a manner that a looper thread hanging hook for catching the looper thread is arranged on the side of the advance end of the looper which advances from the right side of the needle drop point to the left side thereof, namely the rear side of the left of the needle drop point, so that an advance or retreat operation at the point or a swing operation around a vertical axis is conducted to catch the looper thread on the rear side of the looper.
However, for the arrangement of the looper thread hanging hook including a driving mechanism for the advance or retreat operation or a swing operation of the looper thread hanging hook, a large space is required on the left side of the needle drop point, namely, at the tip side of the sewing bed of the sewing machine. In particular, in a sewing machine provided with a small diameter cylinder-shaped bed for handling a cylindrically sewn product, the tip portion of the bed is extended for securing an arrangement space of the looper thread hanging hook, so that it is feared that the sewing operation is prevented.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in view of the above circumstances, and an object of the invention is to provide an apparatus for preventing the raveling of a seam, the apparatus realizing a method for preventing the raveling disclosed in the Japanese Patent Publication No. 2879399 without requiring a large arrangement space on the tip side of the sewing bed of a sewing machine by arranging a looper thread hanging hook and a driving mechanism thereof together with a cutting mechanism of the looper thread and the needle thread, on the right side of the needle drop point, the apparatus being applicable to a sewing machine provided with a cylindrical bed in which the arrangement space on the tip side is restricted.
According a first aspect of the present invention, there is provided an apparatus for preventing raveling of a seam, which is provided on a sewing machine for sewing a product by allowing a looper which advances from the right side to the left side of a needle drop point to pass through a loop of a needle thread formed at the needle drop point to force the looper thread held by the looper to twine around the needle thread, said apparatus comprising:
a loop thread hanging hook arranged on the right rear side of the needle drop point to advance or retreat and catches the looper thread in the vicinity of the advance end of the looper at the time of the advance thereof;
a needle thread cutting hook arranged on the right side of the needle drop point to advance ro retreat and catches the needle thread being inserted into the loop of the needle thread at the time of the advance thereof;
a needle thread knife slidably contacting the needle thread cutting hook at the time of the retreat of the hook, the knife cutting the needle thread which is caught at the time of the advance of the needle thread cutting hook;
a looper thread cutting hook arranged on the right side of the needle drop point to advance or retreat and catches the looper thread caught by the looper thread hanging hook at the time of the advance thereof;
a looper thread knife slidably contacting the looper thread cutting hook at the time of the retreat of the hook, the knife cutting the looper thread caught at the time of the advance of the loop thread cutting hook; and
a looper thread cutting hook arranged on the right side of the needle drop point to advance or retreat and catches the lo
Hayashida Takayuki
Tanaka Yoshiyuki
Darby & Darby
Nerbun Peter
Yamato Mishin Seizo Kabushiki Kaisha
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