Sewing – Elements – Thread cutting – severing or breaking
Reexamination Certificate
1999-10-18
2001-03-27
Izaguirre, Ismael (Department: 3765)
Sewing
Elements
Thread cutting, severing or breaking
Reexamination Certificate
active
06205941
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a chain stitch sewing machine, more particularly to a chain stitch sewing machine, which includes a needle-thread pushing member that moves between a presser foot and stitching needles along a curved path.
2. Description of the Related Art
Referring to
FIG. 1
, a conventional chain stitch sewing machine
1
is shown to include a machine bed
10
, a machine frame
11
fixed relative to the machine bed
10
, a presser foot
12
, a needle seat
13
, a thread pushing device
2
and a thread cutting device
6
. The presser foot
12
is adapted to press a fabric
14
on a top surface of the machine bed
10
. The needle seat
13
is mounted vertically and movably on the machine bed
10
, and carries a row of three vertical stitching needles
131
,
131
′,
131
″ thereon. The middle needle
131
′ is shorter than the front needle
131
, and is longer than the rear needle
131
″. As such, the lower end of the middle needle
131
′ is located above that of the front needle
131
, and below that of the rear needle
131
″. The thread pushing device
2
includes two bolts
21
, a mounting member
22
, a power source
23
, a swing arm
24
, an upper rotating element
25
, a lower rotating element
26
, a connecting rod
27
and a needle-thread pushing member
28
. The bolts
21
extend respectively through two side slots
221
in the mounting body
22
, thereby locking the mounting body
22
on the machine frame
11
. The swing arm
24
is mounted rotatably on the mounting body
22
, and can be swung by the power source
23
. The upper and lower rotating elements
25
,
26
are journalled respectively on the mounting body
22
and the swing arm
26
. Each of the rotating elements
25
,
26
can rotate about a horizontal axis. The connecting rod
27
is fixed to the rotating elements
25
,
26
. When the power source
23
is driven, the swing arm
24
activates the connecting rod
27
to move the needle-thread pushing member
28
forward from the position shown by the solid lines to that shown by the phantom lines, thereby moving the same between the presser foot
12
and the needles
131
,
131
′,
131
″ forward along a generally horizontal path. The aforementioned conventional sewing machine
1
suffers from the following drawbacks:
(1) When the thickness of the fabric
14
or the lengths of the needles
131
,
131
′,
131
″ are changed, it is necessary to adjust the positions of the bolts
21
relative to the slide slots
221
in the mounting body
22
. This adjustment is relatively difficult to conduct.
(2) When the needle-thread pushing member
28
is moved to the generally horizontal position shown by the phantom lines, it is spaced apart from the rear needle
131
″ by a relatively large distance. As such, it is difficult for the pushing member
28
to push a needle thread, which is suspended from the needle
131
″, away from the presser foot
12
just before the presser foot
12
moves downward toward the fabric
14
. As a result, the suspended needle threads may be clamped between the presser foot
12
and the fabric
14
. Furthermore, in a case where the pushing member
28
is adjusted to an excessively low position, it may strike the presser foot
12
during forward movement thereof.
SUMMARY OF THE INVENTION
The object of this invention is to provide a chain stitch sewing machine with a needle-thread pushing member that moves between a presser foot and stitching needles along a curved path, thereby pushing suspended needle threads effectively away from the presser foot.
According to this invention, a sewing machine includes a machine bed, a presser foot and a needle seat. The presser foot and the needle seat are disposed vertically and movably on the machine bed. A row of vertical stitching needles of different lengths are mounted fixedly on the needle seat, and are arranged one behind another. A front one of each adjacent pair of the stitching needles has a lower end, which is located below that of the rear one. A thread pushing device is disposed on the machine bed behind the needle seat, and includes a needle-thread pushing member that can be driven by a power source and that is adapted to move gradually forward and downward between the presser foot and the stitching needles along a curved path so as to be adapted to push suspended needle threads away from the presser foot just before the presser foot moves downward toward a fabric to be stitched on the machine bed.
Preferably, a linkage is disposed between the power source and the needle-thread pushing member, and includes a driving crank, a follower crank and an inclined coupler. The driving crank and the follower crank are mounted rotatably on the machine bed, and are connected pivotally to the coupler. The driving crank can be driven by the power source. The coupler has a lower end that is connected fixedly to the needle-thread pushing member. Accordingly, the power source can drive the linkage to move the needle-thread pushing member along the curved path.
REFERENCES:
patent: 2251676 (1941-08-01), Gunther
patent: 3498243 (1970-03-01), Aoyama
patent: 3960098 (1976-06-01), Papajewski et al.
patent: 5044290 (1991-09-01), Sato et al.
patent: 5469798 (1995-11-01), Gauch
patent: 5481994 (1996-01-01), Ku
patent: 5887535 (1999-03-01), Yu
patent: 6021727 (2000-02-01), Ku
Izaguirre Ismael
Ladas and Parry
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