Sewing – Elements – Take-ups
Reexamination Certificate
2002-11-26
2003-12-30
Izaguirre, Ismael (Department: 3765)
Sewing
Elements
Take-ups
Reexamination Certificate
active
06668739
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to an improved sewing machine, and more particularly to an improved looper thread take-up structure of a sewing machine.
2. Description of the Prior Art
In sewing operation of a sewing machine, the take-up mechanism loosens the looper thread once in each stitch so as to automatically feed the thread and adjust the tension of the looper thread.
FIGS. 11
to
16
show a first type of conventional looper thread take-up structure
78
including a thread guide
79
and a take-up cam
84
both hidden in a lower housing
72
of the sewing machine. A first lower rotary shaft
73
is disposed in the lower housing
72
which is directly driven to further drive a second lower rotary shaft
74
via a shaft coupler
75
. The take-up cam
84
is fitted on the second lower rotary shaft
74
and rotatable along with the first lower rotary shaft
73
.
Referring to
FIGS. 11
,
15
and
16
, the thread guide
79
has a guide plate
80
formed with a slot
81
and two eyelets
82
,
83
respectively disposed on two sides of the slot
81
. Two guide members
86
,
87
are respectively locked on two sides of the slot
81
by screws
88
. Via a screw
94
, L-shaped coupling seat
105
, screw
106
, fixing seat
104
and screw
98
, the guide plate
80
is locked in the lower housing
72
. Each guide member
86
,
87
has an eyelet
82
,
83
. The thread guide
79
includes a guide bar
85
. One end of the guide bar
85
is locked on one end of the guide plate
80
via a screw
95
, coupling seat
103
and screw
97
. The other end of the guide bar
85
is extended into a fissure
91
between two cam plates
89
,
90
of the take-up cam
84
and bridged over the other end of the guide plate
80
. The guide bar
85
has a guide slot
92
for guiding the looper thread
93
to pass therethrough (also referring to FIG.
14
).
Please refer to
FIGS. 11
,
15
and
16
. The take-up cam
84
is composed of two cam plates
89
&
90
which have identical shape and are welded into one piece. The two cam plates
89
,
90
are spaced by a small diameter spacer wheel to define the fissure
91
. The end of the guide bar
85
is extended into the fissure
91
.
Referring to
FIG. 14
, after the looper thread
93
is passed through the eyelet
83
, the looper thread
93
is further passed through the lower knotting hook
101
as shown in FIG.
14
. The lower knotting hook
101
cooperates with an upper stitching needle
77
and an upper knotting hook
100
in sewing operation.
Referring to
FIGS. 11
,
12
,
14
,
15
and
16
, when the take-up cam
84
is rotated along with the second lower rotary shaft
74
, by means of the outer circumference of the take-up cam
84
, the thread is loosened in sewing operation.
Referring to
FIGS. 11
to
16
, the first type of conventional looper thread take-up structure
78
is fixed on the second lower rotary shaft
74
. Accordingly, once the thread breaks, the take-up cam
84
in the looper thread take-up structure
78
will continuously rotate to make the thread head tangle between the cam plates
89
,
90
welded together. The take-up cam
84
is fixed in the lower housing
72
and is undetachable. Moreover, there is no room between the looper thread take-up structure
78
and the shaft coupler
75
. Therefore, it is necessary to use a very thin artistic knife to clear up the tangling thread in a very narrow space. This is a task.
FIGS. 17
to
19
show a second type of conventional looper thread take-up structure
78
for solving the above problem. The looper thread take-up structure
78
is mounted beside the column
76
of the upper housing
71
of the sewing machine
70
. This makes it easier to detach the take-up cam
84
from the sewing machine. However, the two cam plates
89
,
90
are still welded into one single piece. After the take-up cam
84
is detached, it is still difficult to clear up the tangling thread from the very narrow fissure of the take-up cam
84
. (The width of the fissure is only 2 mm.) A very thin artistic knife can be extended into the very narrow fissure to cut off the tangling thread. However, when cutting off the tangling thread, the sharp blade often incautiously cuts the polished outer circumference of the take-up cam to form a notch. After the take-up cam is reassembled, such notch tends to cut off the thread. Therefore, it is unsafe to use the artistic knife to clear up the tangling thread.
In addition, no matter what tool is used, it is time-consuming to clear up the tangling thread. (It often takes half day or even one day to clear up the tangling thread.) During this period, the work must be stopped. This greatly affects the production. Therefore, it is necessary to solve the above problem.
U.S. Pat. No. 6,263,812 of this applicant discloses a looper thread take-up mechanism for solving the problem existing in the first type of conventional looper thread take-up structure shown by
FIGS. 11 and 16
. In the above Patent, the take-up cam is composed of a first cam plate and a second cam plate which are separable and detachable from the rotary shaft. In case the thread tangles, the first and second cam plates can be separated to quickly and easily clear up the tangling thread.
With respect to the second type of conventional looper thread take-up structure
78
shown by
FIGS. 17
to
19
, the take-up section starts from the looper thread take-up structure
78
and ends at the stroke position of the lower crochet needle. This take-up section is too long. That is because the looper thread take-up structure
78
is mounted on inner side of the column
76
and spaced from the stroke position of the lower crochet needle by a too long distance. It is known that the increased length of the looper thread in each take-up travel of the looper thread take-up structure
78
is limited. The longer the take-up section is, the less the looper thread is loosened. The take-up section of the second type of conventional looper thread take-up structure
78
is much longer than the take-up section of the first type of conventional looper thread take-up structure
78
. In addition, the stitching thread is extensible. Therefore, the second type of conventional looper thread take-up structure
78
shown by
FIGS. 17
to
19
has a take-up effect poorer than that of the first type of conventional looper thread take-up structure
78
shown by
FIGS. 11
to
16
.
The looper thread take-up mechanism of U.S. Pat. No. 6,263,812 of this applicant provides a measure for solving the problems existing in both the first and second types of conventional looper thread take-up structures
78
. In the above Patent, the looper thread take-up mechanism is mounted on the lower driving shaft of the sewing machine without intervening with the sewing operation, while it is still easy to clear up the thread tangling between the two cam plates of the take-up cam.
Besides, referring to
FIGS. 15 and 16
, before released, the relative phase between the take-up cam
84
and the second lower rotary shaft
74
has been well adjusted by the manufacturer, that is, the timing of the take-up cam
84
has been set. However, the preset timing is not suitable for different kinds of sewing materials and stitching threads. Too early or too late take-up operation will affect the seam on the sewing material. The take-up cam
84
has been well adjusted by specialists before released from the factory. In the case that the garment manufacturers want to re-adjust the take-up cam
84
themselves, as shown in
FIGS. 15 and 16
, it is necessary to unscrew the screws
96
and
99
.
However, referring to
FIGS. 15 and 16
, the problem is that the take-up cam
84
is fitted on the second lower rotary shaft
74
and locked thereon by screws
96
and
99
. By means of unscrewing the screws
96
and
99
, the take-up cam
84
can be turned relative to the second lower rotary shaft
74
so as to change the phase of the take-up cam
84
relative to the second lower rotary shaft
74
. However, there is no reference for the turni
Ching Chi Machine Co., Ltd.
Izaguirre Ismael
Rosenberg , Klein & Lee
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