Sewing – Work manipulating – Trimmers
Reexamination Certificate
2002-06-17
2004-02-10
Izaguirre, Ismael (Department: 3765)
Sewing
Work manipulating
Trimmers
C112S319000
Reexamination Certificate
active
06688246
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a loop holding device of a chain stitch sewing machine, and more particularly to a loop engaging device of a chain stitch sewing machine which continuously forms a loop stitch by a needle thread and a looper thread.
2. Description of the Related Art
A loop holding device of a sewing machine of this type shown in
FIGS. 7 and 8
has been known.
The well-known chain stitch sewing machine can form both an over-edge chain stitch and a covering chain stitch.
FIG. 7
is a side view showing a cloth presser
10
, and
10
A denotes a support member which can be freely attached to and removed from the lower end of a presser rod which is not shown.
10
B denotes a cloth presser and a shaft
10
C in a horizontal direction thereof can be attached to and removed from the lower end of the support member
10
A by means of a lever
10
D.
10
E denotes a spring and has a base portion supported on a shaft
10
F of the support member
10
A. The tip of the spring
10
E abuts on the forward upper surface of the cloth presser
10
B and serves to energize the cloth presser
10
B in a clockwise direction around the shaft
10
C.
10
G denotes a loop presser, and is rotatably supported by a shaft
10
H in a horizontal direction with respect to the cloth presser
10
B and is energized in the clockwise direction by means of a spring
10
I. The loop presser
10
G is constituted such that a tip thereof is positioned below the lower surface of the cloth presser
10
B by the function of the spring
10
I as shown in
FIG. 7
when the presser rod which is not shown is lifted.
FIG. 8
is a plan view showing a throat plate
20
according to the conventional art, and three needle holes
20
A for needle location parts through which three needles N for a covering chain stitch penetrate are formed in a central part and a loop guide hole
20
B is formed in the forward cloth feeding direction of the needle hole
20
A, and the needle hole
20
A and the guide hole
20
B are caused to communicate through three slits
20
C which are parallel with the cloth feeding direction. Two threading pieces
20
D are formed by the slit
20
C.
Moreover, the throat plate
20
is provided with a needle hole
20
E for an over-edge chain stitch and a threading piece
20
F on the right side of a portion in which the needle hole
20
A is formed.
Furthermore, the throat plate
20
is provided with a cloth feed dog hole
20
G from which an accessory feed dog frequently appears on this side and left side in the cloth feeding direction of the needle hole
20
A, and a feed dog hole
20
J from which a loop feed dog
20
H and a main feed dog
20
I frequently appear is formed in a rear part in the cloth feeding direction of the needle hole
20
A.
Next, functions will be described.
When the sewing machine is driven, the three needles N are vertically moved interlockingly with a main spindle which is not shown, a looper which is not shown is rocked to describe an elliptic locus around the needle, and the accessory feed dog and the main feed dog
20
I carry out four motions for cloth feeding.
Consequently, when the cloth presser
10
B descends and comes in contact with the upper surface of the throat plate
20
without a cloth put on the lower surface of the cloth presser
10
B, a loop is formed between the lower surface of the cloth presser
10
B and the upper surface of the throat plate
20
by the needle thread of the needle N and the looper thread of the looper which is not shown and is pressed by the loop presser
10
G.
Moreover, when the cloth is present between the lower surface of the cloth presser
10
B and the upper surface of the throat plate
20
, it is fed by the cloth feed dog in the cloth feeding direction and a stitch is formed on the cloth by the needle thread of the needle N and the looper thread of the looper which is not shown.
However, the conventional art has the following problems.
More specifically, as shown in
FIG. 7
, when the cloth presser
10
B is lifted, the tip of the loop presser
10
G protrudes downward from the lower surface of the cloth presser
10
B by the function of the spring
10
I.
For this reason, when the cloth is to be set between the upper surface of the throat plate
20
and the lower surface of the cloth presser
10
B, the cloth abuts on the tip of the loop presser
10
G protruding downward from the lower surface of the cloth presser
10
B. Consequently, there is a problem in that a cloth setting property is poor and a sewing work efficiency is deteriorated. In particular, this problem is remarkable when a thick cloth is to be set.
Moreover, holding force for pressing and holding a loop against the upper surface of the throat plate
20
by means of the loop presser
10
G is determined by the elastic force of the spring
10
I. If the holding force of the loop by the elastic force of the spring
10
I is small, the loop is pulled in a reverse direction to the cloth feeding direction depending on thread fastening for the needle thread so that the loop cannot be formed stably and continuously.
Moreover, in the case in which a step is made between the lower surface of the loop presser
10
G and that of the cloth presser
10
B, the loop cannot be held between the lower surface of a loop pressing portion and the upper surface of the throat plate. In order to eliminate the step, a highly developed processing technique is required.
SUMMARY OF THE INVENTION
In order to solve the conventional problem, a first aspect of the invention is directed to a loop holding device of a chain stitch sewing machine comprising:
a needle for penetrating through a cloth on a throat plate to be vertically moved interlockingly with a main spindle of the sewing machine, thereby holding a needle thread;
a cloth presser provided on the throat plate and serving to press the cloth;
a looper having a looper thread for reciprocating in such a direction as to cross a cloth feeding direction below the throat plate interlockingly with the main spindle of the sewing machine;
a main feed dog for feeding a loop formed by the needle thread and the looper thread in cooperation of the needle and the looper rearward in the cloth feeding direction; and
a loop engagement member for upward protruding from an upper surface of the throat plate and engaging the loop when the main feed dog is descending from the upper surface of the throat plate.
According to the first aspect of the invention, if the loop presser is brought down from the upper surface of the loop presser when the cloth presser is lifted, nothing protrudes between the upper surface of the throat plate
30
and the lower surface of the cloth presser. Therefore, a cloth setting property between the upper surface of the throat plate
30
and the lower surface of the cloth presser can be improved and the effect of enhancing a sewing work efficiency can be obtained, and particularly, the effect of enhancing a thick cloth setting property can be obtained.
A second aspect of the invention is directed to the loop holding device of a chain stitch sewing machine according to the first aspect of the invention, wherein the loop engagement member is provided between a main feed dog and a needle location part.
According to the second aspect of the invention, it is possible to obtain such an advantage as to more enhance the effect according to the first aspect of the invention.
A third aspect of the invention is directed to the loop holding device of a chain stitch sewing machine according to the first or second aspect of the invention, wherein the loop engagement member can adjust upper and lower positions.
According to the third aspect of the invention, it is possible to regulate the holding force of the loop over the lower surface of the cloth presser by the loop engagement member, thereby corresponding to the strength of thread fastening for the needle thread. Therefore, it is possible to obtain an effect that the loop can be prevented from being pulled in a reverse direction to the cloth feeding direction and can be fo
Nishimura Satoru
Sadasue Kazuya
Izaguirre Ismael
Merchant & Gould P.C.
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