JPH07114869B2 - Sewing machine thread trimming cam - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread cutting cam for driving a thread cutting knife in a sewing machine.

[0002]

2. Description of the Related Art The thread cutting device shown in FIG. 6 has been widely known before this application. The thread driving cam 10 fixed to the lower shaft 1 of the sewing machine operates the knife drive link 6 swingably supported by the support shaft 8, and is connected to the knife drive link 6 via another link. It drives the existing thread trimming knife. As shown in this figure, the knife driving roller 7
Is normally received by the roller receiver 11 which is a stopper and floats above the end surface of the thread cutting cam 10. The roller receiver 11 is rotatably supported by a shaft 12 and is urged in a counterclockwise direction by a female cutting spring 13 having a very strong spring pressure. When performing thread trimming, first, in a domestic sewing machine, by rotating an operating lever by hand, in an industrial sewing machine, by operating a solenoid,
After rotating the roller receiver 11 clockwise against the strong spring pressure of the knife cutting spring 13, the knife driving roller 7 is moved from the knife cutting roller 9 to the thread cutting cam 10 side. Done. From this state, the lower shaft 1 is rotated to move the knife driving roller 7 rightward along the thread cutting cam surface 10a, and then pushed back leftward to perform thread cutting. After the knife driving roller 7 is pushed back to the end surface of the thread trimming cam 10, if the hand is removed from the operation lever or the operation of the solenoid is stopped, the roller receiver 11 is moved counterclockwise by the strong spring pressure of the knife cutting spring 13. While rotating, the knife cutting roller 9 is pushed away, and the knife driving roller 7 is cut off from the thread cutting cam 10 to
It is held in a state of being floated from the end surface of.

[0003]

SUMMARY OF THE INVENTION The above thread trimming device is
By rotating the roller receiver 11 by the strong spring pressure of the knife disconnecting spring 13 to engage the knife disconnecting roller 9,
Since the knife driving roller 7 is floated from the end surface of the thread trimming cam 10, when the thread trimming is started, in the case of a domestic sewing machine, the roller is manually received against the strong spring pressure of the knife cutting spring 13. You have to move 11. Further, in the case of an industrial sewing machine, the solenoid for rotating the roller receiver 11 must be a large one having a large force. Further, the knife driving roller 7 may not be lifted from the end surface of the thread cutting cam 10 due to variations in the spring pressure of the knife removing spring 13 and the slide of the roller receiver 11.

An object of the present invention is to provide a thread trimming cam of a sewing machine which enables a stopper of a knife driving link to be operated by a small and inexpensive actuator suitable for a domestic sewing machine.

[0005]

To achieve the above object, a thread cutting cam of a sewing machine according to the present invention comprises a cylindrical outer cam fixed to a lower shaft and a lower shaft rotatably housed therein. And a cylindrical inner cam having a spiral spring provided between the inner cam and the inner cam that rotates under the pressure of the knife driving roller, so that the cam surface partially projects from the cam surface of the outer cam. It is a thing.

[0006]

[Operation] In the thread trimming cam of the sewing machine configured as described above, the knife driving roller hits the inner cam during thread trimming,
When the inner cam rotates under the pressure against the helical spring, the inner cam is pushed out and its cam surface partially projects from the cam surface of the outer cam. As a result, at the final stage, the knife driving roller moves to the outside by the protruding amount of the inner cam, and the gap into which the stopper enters is opened.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a thread cutting cam of a sewing machine according to the present invention will be described with reference to FIGS. The thread trimming device adopting the thread trimming cam of the present invention is a conventional example except that the structure of the thread trimming cam and the spring pressure of the female cutting spring (denoted by reference numeral 13 in FIG. 6) are weak. The thread cutting device shown in FIG.

The thread trimming cam includes a cylindrical outer cam 2 fixed to the sewing machine lower shaft 1 and a cylindrical inner cam 4 rotatably supported in the outer cam 2 about the lower shaft 1. It is composed of

The outer cam 2 is fixed to the sewing machine lower shaft 1 by a fixing screw 3, and four convex portions 2b are formed inside the bottom surface of the outer cam 2 as shown in FIG. As shown in FIG. 3, the convex portion 2b has an inclined surface on one side.

The inner cam 4 is housed in the outer cam 2 and is loosely supported by the sewing machine lower shaft 1. And
Spring receiver 1a fixed to the inner cam 4 and the sewing machine lower shaft 1.
A helical spring 5 is provided between and. Also,
A concave portion 4b having a shape (see FIG. 3) corresponding to the convex portion 2b of the outer cam 2 is formed outside the bottom surface of the inner cam 4.

The respective phases of the cam surface 2a of the outer cam 2 and the cam surface 4a of the inner cam 4 are shifted in a normal state as shown in FIG. That is, the cam surface 4a of the inner cam 4 is usually
The positional relationship shown by the dotted line is with respect to the cam surface 2a of the outer cam 2.

At the time of thread cutting, the knife driving roller 7 enters the thread cutting cam and hits the inner cam 4, receives the pressure thereof, and the cam surfaces 2a, 4a are out of phase, so that the inner cam 4 is suspended. It rotates against the spiral spring 5. At that time, the sloped surface of the concave portion 4b of the outer cam 4 slides up the sloped surface of the convex portion 2b of the inner cam 2, and the inner cam 4 is pushed out to form the cam surface 4a.
Moves to the position indicated by the thick solid line in FIG. That is, the cam surface 4a moves L1 in the axial direction and L2 in the circumferential direction. Then, the knife driving roller 7 thereafter moves along with the rotation of the sewing machine lower shaft 1 along the cam surface 4a of the extruded inner cam 4 and is extruded to the apex of the protrusion of the inner cam surface 4a at the final stage. Therefore, since the knife cutting roller 9 shown in FIG. 6 is also located at a position far away from the thread cutting cam end surface, even if the spring pressure of the knife cutting spring 13 is weak, the roller receiver 11 serving as the stopper is provided with the thread cutting cam end surface. It is possible to easily enter between the knife cutting-off roller 9 and. In other words, by adopting the above-mentioned configuration, the spring pressure of the female cutting-off spring 13 can be reduced, and the actuator for operating the roller receiver 11 which is a stopper can be a small one with low output. can do. Further, when the roller receiver 11 receives the roller 9, the inner cam 4 moves the spiral spring 5
The power of returns to the original.

[0013]

Since the present invention is configured as described above, it has the following effects.

That is, the spring pressure of the female cutting spring can be weakened, and the stopper can be operated with a small output and small actuator. Further, the operation of the stopper does not depend on the spring pressure, so that the operation is reliable.

[Brief description of drawings]

FIG. 1 is a sectional view of a thread cutting cam of a sewing machine according to the present invention.

FIG. 2 is a view of the inside of the bottom surface of the outer cam.

FIG. 3 is a cross-sectional view taken along the line AA of the convex portion of the outer cam and the concave portion of the inner cam.

FIG. 4 is a cross-sectional view of a protrusion of the outer cam and a recess of the inner cam when the inner cam rotates with respect to the outer cam.

FIG. 5 is a development view of respective cam surfaces of an outer cam and an inner cam.

FIG. 6 is a cross-sectional view of a thread cutting cam of a conventional sewing machine.

[Explanation of symbols]

 1 Lower shaft 2 Outer cam 4 Inner cam 5 Coil winding spring 6 Female driving link 7 Female driving roller 9 Female cutting roller 11 Roller receiving 13 Female cutting spring

Claims (1)

[Claims] 1. A knife drive comprising a cylindrical outer cam fixed to a lower shaft and a cylindrical inner cam rotatably housed therein and provided with a spiral spring between the lower cam and the lower cam. A thread trimming cam of a sewing machine, whose cam surface partially projects from the cam surface of the outer cam when the inner cam rotates under the pressure of the roller.