Information
-
Patent Grant
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6234097
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Patent Number
6,234,097
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Date Filed
Wednesday, September 20, 200023 years ago
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Date Issued
Tuesday, May 22, 200123 years ago
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Inventors
-
-
Examiners
Agents
-
CPC
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US Classifications
Field of Search
US
- 112 298
- 112 296
- 112 297
- 112 291
- 112 292
- 112 285
- 112 288
- 112 199
- 112 286
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International Classifications
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Abstract
A thread cutting device of a sewing machine has a fixed plate, first and a second adjustable arms, a cutting arm with a front end knife, a swing arm pivoted to the fixed plate and a hook arm with two hooks. The adjustable arms are relocatably fitted on the fixed plate. The cutting arm is pivoted to the first adjustable arm. The hook arm is movably fitted to the cutting arm with two long holes connecting a bolt of the cutting arm, and the second adjustable arm respectively, and has a gap receiving one end of the swing arm such that the hook arm is moved back and forth to hook and retreat threads for the knife to cut off when the swing arm is swung.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a thread cutting machine, and particularly to one which has a hook arm movable to hook and retreat threads for a cutting knife to cut off; the hook rod is fitted to a hook rod arm which can be adjusted in respect of position relative to a swing arm for adjusting the moving path of the hook rod.
Related prior arts of the thread cutting device for a sewing machine of the present invention include U.S. Pat. Nos. 4,098,209 and 2, 892,012; 5,481,994 was also devised by the inventor of the present invention, aimed at improving U.S. Pat. No. 4,098,209.
Referring to
FIG. 10
, a conventional thread cutting device of a sewing machine has fixed plate
61
, a cutting knife arm
62
, a securing member
63
, a cutting knife
64
, a hook rod arm
65
, a hook rod
66
and a swing arm
67
.
The fixed plate
61
has several fixing holes
611
, and is fixed to the sewing machine by means of screws
6111
passed through the fixing holes
611
. The fixed plate
61
further has a receiving recess
612
and screw holes
613
,
6121
.
The cutting knife arm
62
has a through hole
621
, a guide slot
622
, screw holes
623
,
623
at an intermediate portion, and a screw hole
624
at a front end portion. The cutting knife arm
62
is pivoted to the fixed plate
61
by a screw
6212
and an axle cap
6211
; the screw
6212
being passed through the through hole
621
and the a-de cap
6211
, and connected to the screw hole
6121
on the receiving recess
612
; the rear end portion of the cutting knife arm
62
being received in the receiving recess
612
.
The cutting knife
64
is fixed to the front end portion of the cutting knife arm
64
with a screw
642
screwed into the screw hole
624
; a pad
643
is disposed between the cutting knife
64
and the cutting knife arm
62
.
The securing member
63
is also fixed to the front end portion of the cutting knife arm
62
by screws
632
with a fixing plate
633
connected to a bottom.
The hook rod arm
65
has a gap at a rear end portion, two elongated guide holes
652
and screw holes
653
at a front end portion. The hook rod arm
65
is movably connected to the cutting knife arm
62
by means of two screws
6522
each passed through an axle cap
6521
, a respective one of the elongated guide holes
652
, and screwed into a respective one of the screw holes
623
of the cutting knife arm
62
.
The hook rod
66
is connected to the front end portion of the hook rod arm
65
by screws
662
screwed into the screw holes
653
. The hook rod
66
has a front hook
663
at a front end, and a rear hook
664
behind the front hook
663
.
The swing arm
67
has a pivotal hole
671
, a through hole
674
and a head
673
. The swing arm
67
is pivoted to the fixed plate
61
by means of a screw
6721
passed through an axle cap
672
, the pivotal hole
671
and the screw hole
613
of the fixed plate
61
in sequence. The head
673
of the swing arm
67
is movably received in the gap
651
of the hook rod arm
65
such that the hook rod arm
65
can be moved back and forth relative to the cutting knife arm
62
when the swing arm
67
is swung. Moreover, a screw pin
6751
is connected to the through hole
674
of the swing arm
67
and nuts
676
,
677
from two ends. The nut
677
is movably received in the guide slot
622
of the cutting knife arm
62
.
In using the thread cutting device, referring to
FIG. 11
, firstly, the swing arm
67
is swung for the head
673
to move forwards with the nut
677
moving from the curved rear end position to a straight front portion; thus, the cutting knife arm
62
will be pivoted on the screw
6212
to a position substantially parallel to lateral sides of the fixed plate
61
. Meanwhile, the hook rod arm
65
is also moved to the parallel position.
Secondly, referring to
FIG. 12
, the swing arm
67
is swung further forwards, forcing the hook rod arm
65
to move forwards relative to the cutting knife arm
62
. Thus, hook rod
66
projects from the cutting knife
64
, and hook threads from the hooks
663
,
664
. Then, the swing arm
67
is swung back to retreat the hook rod arm
65
; thus, the threads are cut by the cutting knife
64
and the hooks
663
,
664
when the hooks
663
,
664
move past the cutting knife
64
; the hook rod
66
abutting the cutting knife
64
for the threads to be cut easily because of the securing member
63
.
However, the above thread cutting device of a sewing machine is found to have disadvantages as follows.
1. The arm of force A, i.e. the distance between the fulcrum screw
6212
and the nut
677
, is much shorter than B, i.e. the distance between the nut
677
and the hook rod
66
. Consequently, relatively much force has to be applied to swing the swing arm
67
, resulting in waste of power.
2. Using the screw
6212
as a fulcrum, the front and the rear hooks
663
,
664
of the hook rod
66
has relatively large range of oscillation, and cannot move very smoothly. Consequently, the service life of related parts can be shortened.
3. Using the screw
6212
as a fulcrum, the cutting knife arm
62
and other parts associated with it cannot be adjusted to an optimum position.
SUMMARY OF THE INVENTION
Therefore, it is a main object of the present invention to provide a thread cutting device of a sewing machine which can be operated with less power and more smoothly, and of which the parts can be adjusted to an optimum position.
The thread cutting device of a sewing machine of the present invention has a fixed plate, an adjustable arm member, a cutting knife arm with a front end cutting knife, a swing arm and a hook rod arm with two front end portion hooks.
The fixed plate is fixed to the sewing machine.
The adjustable arm member has a first and a second adjustable arms relocatably fitted on the fixed plate; the adjustable arm each having a connecting protrusion on an outer end.
The cutting knife arm is pivoted to the connecting protrusion of the first adjustable arm from a pivotal hole at a distance from the inner end.
The swing arm is pivoted to the fixed plate from an intermediate portion, and has a head at an end facing the knife arm.
The hook rod arm has a gap receiving the head of the swing arm, and a first and a second elongated holes receiving a bolt on the knife arm and the connecting protrusion of the second adjustable arm respectively for confining a moving path of the hook rod arm. The second elongated hole has a curved end portion at a front end.
The hook rod arm is moved back and froth by the swing arm when the swing arm is swung, hooking and retreating threads for the cutting knife to cut off.
The curved end portion of the second elongated hole permits the hook rod arm to be adjusted in respect of the direction when the curved end portion of the hook rod arm separates from the connecting protrusion.
Because the adjustable arms are relocatable, the cutting path of the thread cutting device can be adjusted.
BRIEF DESCRIPTION OF THE DRAWINGS
This invention will be better understood by referring to the accompanying drawings, wherein:
FIG. 1
is an exploded perspective view of the thread cutting device of a sewing machine of the present invention.
FIG. 2
is a top view of the thread cutting device of a sewing machine of the present invention.
FIG. 3
is another top of the thread cutting device of a sewing machine of the present invention.
FIG. 4
is a third top view of the thread cutting device of a sewing machine of the present invention.
FIG. 5
is a fourth top view of the thread cutting device of a sewing machine of the present invention.
FIG. 6
is a cross-sectional view of the thread cutting device of a sewing machine of the present invention.
FIG. 7
is another cross-sectional view of the thread cutting device of a sewing machine of the present invention.
FIG. 8
is a fragmentary cross-sectional view of the thread cutting device of a sewing machine of the present invention.
FIG. 9
is a top view of the thread cutting device of a sewing machine of the present invention under operation.
FIG. 10
is an exploded perspective view of the conventional thread cutting device in the Background.
FIG. 11
is a top view of the conventional thread cutting device in the Background.
FIG. 12
is another top view of the conventional thread cutting device in the Background.
FIG. 13
is a top view of the thread cutting device of
FIG. 11
under operation.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to
FIGS. 1 and 2
, a thread cutting device of a sewing machine of the present invention has a fixed plate
1
, a cutting knife arm
2
, a hook rod arm
3
, an adjustable arm member
4
, a securing member
63
, a cutting knife
64
, a hook rod
66
and a swing arm
67
.
The fixed plate
1
is fixed to the sewing machine, and has a receiving recess
12
, a first and a second holding recesses
13
,
13
′ having a screw hole
131
,
131
′ respectively.
The cutting knife arm
2
has a through hole
21
, a side protrusion
25
formed a distance from the rear end, a lengthwise elongated hole
22
on an intermediate portion, holes
23
and screw holes
24
on a front end portion. A connecting bolt
210
is connected to the through hole
21
. A through hole
26
is formed on the side protrusion
25
.
The adjustable arm member
4
includes a first adjustable arm
41
and a second adjustable arm
42
having an inner end portion
411
,
421
respectively; the inner end portion
411
,
421
having a long hole
412
,
422
respectively. The arms
41
,
42
further have a connecting protrusion
413
,
423
on an outer end respectively. The arms
41
,
42
are connected to the holding recesses
13
,
13
′ from inner end portions
411
,
421
respectively by means of screws passed through the long hole
412
,
422
and the screw holes
131
,
131
′. Thus, the first and the arms
41
,
42
can be adjusted in respect of position relative to the holding recesses
13
,
13
′.
The cutting knife arm
2
is pivoted to the first adjustable arm
41
with the connecting protrusion
413
of the arm
41
passed into the through hole
26
of the cutting knife arm
2
.
The securing member
63
and the cutting knife
64
is connected to the front end portion of the cutting knife arm
2
with screws in a way same as the conventional thread cutting device of the Background; a pad
643
is disposed between the cutting knife
64
and the cutting knife arm
2
; a fixing plate
633
is used to fix the securing member
63
to the arm
2
.
The hook rod arm
3
has a gap
33
, a first and a second elongated holes
31
,
32
, holes
34
and a connecting protrusion
35
on a bottom of a front end portion; the second elongated hole
32
has a curved end portion
321
at a front end. The hook rod arm
3
is movably connected to the cutting knife arm
2
, and the second adjustable arm
42
with the connecting bolt
210
of the cutting knife arm
2
, and the connecting protrusion
423
of the second adjustable arm
42
received in the first and the second elongated holes
31
,
32
respectively. Moreover, the connecting protrusion
35
is received in the lengthwise elongated hole
22
of the cutting knife arm
2
. Thus, the hook rod arm
3
can move relative to the cutting knife arm
2
.
The hook rod
66
is connected to the front end portion of the hook rod arm
3
by means of screws screwed into the holes
34
of the hook rod arm
3
. The hook rod
66
has a front hook
663
at a front end and a rear hook
664
behind the front hook
663
.
The swing arm
67
is pivoted to the fixed plate
1
from an intermediate portion, and has a head movably received in the gap
33
of the hook rod arm
3
.
In using the thread cutting device of a sewing machine, referring to
FIGS. 2
,
3
,
4
and
5
, the swing arm
67
is swung to move the hook rod arm
3
back and forth. Firstly, the connecting protrusion
423
of the second adjustable arm
42
is located in the curved end portion
321
of the hook rod arm
3
(FIG.
2
); secondly, the hook rod arm
3
moves forwards for the connecting protrusion
423
to separate from the curved end portion
321
such that the hook rod arm
3
and the cutting knife arm
2
are disposed at a position substantially perpendicular to the front side of the fixed plate (FIG.
3
). Thirdly, the hook rod arm
3
is moved forwards for the hooks
663
,
664
of the hook rod
66
to hook the threads (FIG.
5
). Then, the hook rod arm
3
is moved back for the hooks
663
,
664
to retreat the threads for the knife
64
to cut off.
To adjust the position of the cutting knife arm
2
such that the fulcrum position, the range of oscillation of the arm
2
and the moving path of the arm
2
are adjusted to optimum ones, the first and the second adjustable arms
41
,
42
are first moved in the holding recesses
13
,
13
′ to suitable positions and fixed again.
From the above description, the thread cutting device of a sewing machine of the present invention can be known to have desirable features as follows.
1. The fulcrum of the cutting knife arm
2
, i.e. the connecting protrusion
413
of the adjustable arm
41
, is located away from the inner end of the knife arm
2
such that the distance between the fulcrum and the front ends of the knife
64
and the hook rod
66
is smaller than that of the prior art one. Consequently, it takes less power to operate the thread cutting device, and the related parts of the thread cutting device can move more smoothly.
2. Referring to
FIG. 9
, because the distance between the hook rod arm front end and the protrusion
413
, i.e. B, is not much longer than the distance between the curved end portion
321
and the protrusion
413
, i.e. A, the swing arm
67
can be swung with less power than the prior art.
3. The position of the fulcrum of the knife arm
2
can be adjusted for an optimum cutting path by means of the adjustable arms
41
,
42
.
4. The hook rod arm
3
, confined by the elongated holes
31
,
32
as well as the elongated hole
22
of the knife arm
2
, is prevented from shaking in the course of moving back and forth.
Claims
- 1. A thread cutting device of a sewing machine, comprising a fixed plate fixed to said sewing machine,an adjustable arm member having a first and a second adjustable arms relocatably fitted on said fixed plate; said adjustable arms each having a connecting protrusion on an outer end thereof,a cutting knife arm having a cutting knife on a front end, said knife arm being pivoted to said connecting protrusion of said first adjustable arm from a hole formed at least a distance from a rear end;a swing arm pivoted to said fixed plate from an intermediate portion, said swing arm being capable of being swung; said swing arm having a head at an end facing said knife arm;a hook rod arm having a hook rod at a front end, said hook rod having a plurality of hooks thereon; said hook rod arm having a gap receiving said head of said swing arm therein for permitting said swing arm to move same back and forth; said hook rod arm having first and a second elongated holes receiving a bolt on said knife arm, and said connecting protrusion of said second adjustable arm respectively for confining a moving path thereof when said swing arm is moved back and forth;said second elongated hole having a curved end portion for permitting said hook rod arm to be adjusted in respect of said moving path when said hook rod arm is moved where said curved end portion separates from said connecting protrusion of said second adjustable arm;whereby said hooks can hook and retreat threads for said knife to cut off when said swing arm is swung.
- 2. The thread cutting device of a swing machine as claimed in claim 1,wherein said cutting knife arm has a lengthwise elongated hole on an intermediate portion, and said hook rod arm has a connecting protrusion movably received in said lengthwise elongated hole for confining said moving path of said hook rod arm.
US Referenced Citations (2)