Sewing – Elements – Thread cutting – severing or breaking
Reexamination Certificate
2000-09-20
2001-05-22
Nerbun, Peter (Department: 3741)
Sewing
Elements
Thread cutting, severing or breaking
Reexamination Certificate
active
06234097
ABSTRACT:
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.
REFERENCES:
patent: 5870962 (1999-02-01), Ku
patent: 5887535 (1999-03-01), Yu
Nerbun Peter
Rosenberg , Klein & Lee
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