Sewing – Elements – Thread cutting – severing or breaking
Reexamination Certificate
2002-12-16
2004-02-24
Nerbun, Peter (Department: 3765)
Sewing
Elements
Thread cutting, severing or breaking
Reexamination Certificate
active
06694903
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to a knife track adjustment structure of thread cutter of a sewing machine. A front guide board of a swing arm is up and down adjustably displaceable on the base board, whereby the position of a thread cutter composed of a knife arm and a hook rod arm can be drivingly adjusted so as to rectify the movement track of the thread cutter. A spring is compressed between the swing arm and the base board to help in restoring the thread cutter.
2. Description of the Prior Arts
U.S. Pat. No. 6,234,097 discloses a thread cutter of sewing machine. The thread cutter includes a fixed plate
1
, a knife arm
2
, a hook rod arm
3
, a cantilever assembly
4
and cooperative conventional securing member
63
, cutting knife
64
, hook rod
66
and swing arm
67
. The periphery of the fixed plate
1
is formed with locating holes for mounting the fixed plate
1
on the sewing machine. The fixed plate
1
is formed with a mounting recess
12
in which one end of the knife arm
2
is placed. The other end of the knife arm
2
is formed with perforations
23
and thread holes
24
for mounting the securing member
63
and the cutting knife
64
. The hook rod arm
3
is formed with left and right slots
31
,
32
and a notch
33
. One end of the swing arm
67
is placed in the notch
33
for driving the hook rod arm
3
to displace. The tail end of the hook rod arm
3
is assembled with the hook rod
66
. In cooperation with the securing member
63
and the cutting knife
64
, the thread cutter can perform thread cutting operation.
The thread cutter is characterized in that the cantilever assembly
14
is composed of a left and a right cantilevers
41
,
42
and fixed with the fixed plate
1
. The left cantilever
42
has a downward directed projecting post
423
placed in the left slot
32
of the hook rod arm
3
. The projecting post
413
of the right cantilever
41
is inserted in the perforation
26
of the lug
25
of the knife arm
2
. The projecting post
413
serves as a fulcrum about which the knife arm
2
swings so as to greatly reduce the swinging torque of the hook rod arm
3
and knife arm
2
. The tail end of the knife arm
2
is formed with a slot
22
. The projecting post
35
under the tail end of the hook rod arm
3
is placed in the slot
22
, whereby the hook rod arm
3
can more stably operate to enhance the quality of the thread cutting operation.
However, the above thread cutter structure has some shortcomings as follows:
1. The left cantilever
42
is substantially N-shaped. One leg of the left cantilever
42
is locked on the fixed plate
1
, while the other leg is cantilevered. The bottom end of the cantilevered leg has a projecting post
423
placed in the left slot
32
of the hook rod arm
3
. When the hook rod arm
3
or the knife arm
2
slides, due to rubbing, the cantilevered leg of the left cantilever
42
often co-vibrates. This makes it impossible for the hook rod arm
3
or knife arm
2
to operate in a smooth move track or even a noise is produced.
2. When the swing arm
67
restores the knife arm
2
and hook rod arm
3
, due to the gap between the respective components, such as the gap between the swing arm
67
and the notch
33
of the hook rod arm
3
, the knife arm
2
and the hook rod arm
3
often cannot be accurately restored. This results in inaccurate thread cutting operation.
3. The bending section
321
of the left slot
32
of the hook rod arm
3
is continuously rubbed by the projecting post
423
of the left cantilever
42
and is widened. This leads to enlarged gap between the projecting post
423
and the bending section
321
. Accordingly, the thread cutting operation can be hardly accurately performed.
4. The projecting post
413
of the left cantilever
42
placed in the left slot
32
of the hook rod arm
3
is spaced from the fixing point where the left cantilever
42
is fixed on the fixed plate
1
. That is, a force arm exists. When the hook rod arm
3
reciprocally slides, the bending section
321
of the left slot
32
will collide the projecting post
413
. The action force multiplies the force arm to produce a bending torque onto the fixing point where the left cantilever
42
is fixed on the fixed plate
1
. As a result, the left cantilever
42
is very easy to loosen and detach.
In addition, U.S. Pat. Nos. 5,469,798, 5,481,994, 5,870,962, 5,887,535, 6,021,727, 6,205,941 and 6,378,448 disclose other thread cutter structures.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to provide a knife track adjustment structure of thread cutter of sewing machine. By means of up and down adjusting the guide seat or the swing arm on the lower shaft inner cover, the positions of the thread cutter composed of the fixed knife seat and movable knife seat can be drivingly adjusted so as to rectify the movement track of the thread cutter.
It is a further object of the present invention to provide the above knife track adjustment structure of thread cutter of sewing machine in which the guide seat is a straight plate and upper and lower ends of the guide seat are firmly fixed on the lower shaft inner cover. When the thread cutter operates, the guide seat will not vibrate or co-vibrate as the conventional cantilever structure. Therefore, the movement track is smoothened and no noise or vibration will be produced.
It is still a further object of the present invention to provide the above knife track adjustment structure of thread cutter of sewing machine in which a spring is mounted between the lower shaft inner cover and the swing arm to restore the thread cutter to predetermined position so as to avoid inaccurate thread cutting operation.
According to the above objects, the thread cutter of sewing machine of the present invention includes a lower shaft inner cover over which a fixed knife seat is bridged. A movable knife seat is bridged over the fixed knife seat. The movable knife seat is driven by a driving arm to stably axially slide on the fixed knife seat. The knife track adjustment structure includes: a guide seat bridged over the lower shaft inner cover, an upper and a lower ends of the guide seat being locked on the lower shaft inner cover, the guide seat being up and down adjustably displaceable on the lower shaft inner cover, whereby the fixed knife seat and a middle section of the movable knife seat bridged over the fixed knife seat are permitted to slide between the guide seat and the lower shaft inner cover, a guide spacer ring being disposed under the middle section of the guide seat, the guide spacer ring being sequentially passed through a first guide slot of the movable knife seat and a guide slot of the fixed knife seat; and a swing arm, a first end of the swing arm being pivotally connected with the lower shaft inner cover, a spacer ring being disposed under the bottom of the second end of the swing arm, the spacer ring being sequentially passed through a second guide slot of the movable knife seat and pivotally connected on the fixed knife seat, a spring being compressed between the swing arm and the lower shaft inner cover to help in restoring the fixed knife seat and movable knife seat.
REFERENCES:
patent: 5469798 (1995-11-01), Gauch
patent: 5481994 (1996-01-01), Ku
patent: 5775246 (1998-07-01), Lin
patent: 5870962 (1999-02-01), Ku
patent: 5887535 (1999-03-01), Yu
patent: 6021727 (2000-02-01), Ku
patent: 6205941 (2001-03-01), Yu
patent: 6234097 (2001-05-01), Ku
patent: 6378448 (2002-04-01), Huang
Ching Chi Machine Co., Ltd.
Rosenberg , Klein & Lee
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