JP2009039271A - Cloth cutting device of sewing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve cutting quality while preventing damage of knives. <P>SOLUTION: When a position of an upper knife 1 detected by a position detection means is in a position retreated from a lower knife 3, an upper knife base 10 is moved so as to separate a cutting edge of the upper knife from a cutting edge of the lower knife. When the tip of the upper knife is in a position where the tip starts to slide toward the lower knife, the upper knife base is moved so that the cutting edge of the upper knife can press the cutting edge of the lower knife with a first pressing force. When the cutting edge of the upper knife is in a position where the cutting edge of the upper knife starts to slide toward the cutting edge of the lower knife, the upper knife base is moved so that the cutting edge of the upper knife can press the cutting edge of the lower knife with a second pressing force greater than the first pressing force. When the cutting edge of the upper knife is in a position where cutting of cloth is completed, the upper knife base is moved so that the cutting edge of the upper knife can press the cutting edge of the lower knife with the first pressing force. A cloth cutting device 100 of a sewing machine has a movement control means which drives a base moving means 15 so as to perform the above movement. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cloth cutting device for a sewing machine.

There is known a sewing machine including a cloth cutting device capable of cutting cloth on a needle plate simultaneously with sewing by vertical movement of a needle (see, for example, Patent Document 1).
As shown in FIG. 8, in the cloth cutting device for a sewing machine, an eccentric cam fixed to a main shaft (not shown) is inserted into the rod 101. The pin 102 is fixed to a frame (not shown). The arm 103 is fixed to a shaft 104 that is rotatably inserted into the frame, and an arm 105 is fixed to the other end of the shaft 104. The arm 105 is urged by a spring 106, and its position is regulated in a state where it hits the tip of a screw 108 inserted into a base 107 fixed to the frame. A base unit 112 for fixing the upper knife 111 is attached to the tip of the shaft 110 inserted into the bearing 109 fixed to the frame. The upper knife 111 is welded to the needle plate 113. 114 is adjusted to mesh.

When the cloth is cut, the links 115 and 116 are positioned so as to form a straight line in the vertical direction, and the movement of the eccentric cam from the rod 101 is transmitted to the shaft 110 and is moved up and down to move the upper knife and the lower knife. Cut the cloth with a knife. The sharpness of cutting is obtained by adjusting the base 117 to adjust the force for pressing the upper knife 111 against the lower knife 114.
When the cloth cutting is not used, when the lever 118 is moved upward (A direction), the arm 105 rotates in the B direction, and the arm 103 at the other end of the shaft 104 rotates in the C direction. The fulcrum Z of the links 115 and 116 is made to coincide with the fulcrum Y via the link 119. The adjustment can be performed by adjusting the screw 108. When the fulcrum Z and Y coincide with each other, the shaft 110 is first lifted to the upper position, and the motion generated from the eccentric cam acts only as a swinging motion of the fulcrum Y and is not transmitted as the vertical motion of the shaft 110. As a result, the upper knife 111 stops at a predetermined upper position regardless of the movement of the main shaft.
Japanese Examined Patent Publication No. 63-50036

By the way, in order to improve the cutting quality of the cloth by the cloth cutting device, it is necessary to increase the pressure with which the upper knife is pressed against the lower knife. Therefore, it is necessary to bring the position of the upper knife toward the lower knife. However, although the sharpness is improved, when the upper knife is moved to the upper retracted position, the upper knife moves out of engagement with the lower knife, and the pressing force moves. For this reason, when the upper knife is lowered again to try to mesh with the lower knife, there is a problem that the upper knife hits the upper surface of the lower knife and breaks.
On the other hand, there is a problem that the sharpness cannot be improved unless the upper knife is pressed against the lower knife for fear of interference between the upper knife and the lower knife.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a sewing machine cloth cutting device that can prevent the knife from being damaged while improving the sharpness. .

The invention according to claim 1 is provided with an upper knife that operates in the vertical direction of the sewing machine and a lower knife fixed to a needle plate, and the needle moves as the upper knife descends and slides on the lower knife. In a sewing machine cloth cutting device for cutting cloth on a board,
An upper knife drive means for moving the upper knife up and down and making its vertical movement speed variable;
An upper knife base for holding the upper knife in a vertically movable manner;
Base driving means for moving the upper knife base in a direction in which the upper knife comes into contact with and separates from the lower knife;
Position detecting means for detecting the position of the upper knife in the vertical movement direction;
When the position of the upper knife detected by the position detecting means is a position retracted from the lower knife, the upper knife base is moved so that the upper knife cutting blade and the lower knife cutting blade are separated from each other. And the upper knife base so that the cutting blade of the upper knife presses the cutting blade of the lower knife with a first pressing force when the tip of the upper knife is in a position where it begins to slide on the lower knife. When the upper knife cutting blade is in a position where the upper knife cutting blade starts to slide on the lower knife cutting blade, the upper knife cutting blade pushes the lower knife cutting blade beyond the first pressing force. The upper knife base is moved so as to be pressed with a large second pressing force, and when the upper knife cutting blade is in a position where the cloth has been cut, the upper knife cutting blade is the lower knife cutting blade. The upper knife base is moved so as to be pressed with the first pressing force. And movement control means for controlling driving of the base drive means,
It is characterized by providing.

According to the first aspect of the present invention, the movement control means controls the drive of the base driving means so that the upper knife is separated from the lower knife when the upper knife is in a position retracted from the lower knife. Next, when the upper knife is lowered, it does not contact the lower knife. Further, when the tip of the upper knife is in a position where it begins to slide on the lower knife, the cutting blade of the upper knife presses the cutting blade of the lower knife with the first pressing force, so that the tip of the upper knife is the cloth. Can be easily pierced, and a gap between the upper knife and the lower knife can be eliminated to prevent entry of foreign matter. When the cutting blade of the upper knife is in a position where it begins to slide on the cutting blade of the lower knife, the cutting blade of the upper knife presses the cutting blade of the lower knife with the second pressing force. At the time of cutting, the cutting can be performed with the sharpness improved. After cutting the cloth, when the cutting blade of the upper knife is in the position where the cutting of the cloth is finished, the cutting blade of the upper knife presses the cutting blade of the lower knife with the first pressing force. Since the pressing force is reduced, wear of the knife can be suppressed, and a gap between the upper knife and the lower knife can be eliminated to prevent entry of foreign matter.
Therefore, it is possible to prevent the knife from being damaged while improving the sharpness of the cloth.

The invention according to claim 2 is the cloth cutting device for sewing machine according to claim 1,
Torque detecting means for detecting torque applied to the base driving means;
A speed control means for controlling the drive of the upper knife drive means so as to decelerate the vertical movement speed of the upper knife when the torque detected by the torque detection means exceeds a predetermined value;
It is characterized by providing.
Here, the predetermined value is a value arbitrarily set by the user, and varies depending on the thickness and type of the cloth to be cut.

According to a second aspect of the present invention, the speed control means drives the upper knife so as to decelerate the vertical movement speed of the upper knife when the torque detected by the torque detection means exceeds a predetermined value. Control the drive of the means.
That is, the increase in torque means that the cloth cannot be cut smoothly. In such a case, the cloth can be cut by reducing the vertical movement speed of the upper knife.

According to the first aspect of the present invention, when the upper knife is in a position retracted from the lower knife, the upper knife is separated from the lower knife, so that the next time the upper knife is lowered, it comes into contact with the lower knife. There is nothing. Further, when the tip of the upper knife is in a position where it begins to slide on the lower knife, the cutting blade of the upper knife presses the cutting blade of the lower knife with the first pressing force, so that the tip of the upper knife is the cloth. Can be easily pierced, and a gap between the upper knife and the lower knife can be eliminated to prevent entry of foreign matter. When the cutting blade of the upper knife is in a position where it begins to slide on the cutting blade of the lower knife, the cutting blade of the upper knife presses the cutting blade of the lower knife with the second pressing force. At the time of cutting, the cutting can be performed with the sharpness improved. After cutting the cloth, when the cutting blade of the upper knife is in the position where the cutting of the cloth is finished, the cutting blade of the upper knife presses the cutting blade of the lower knife with the first pressing force. Since the pressing force is reduced, wear of the knife can be suppressed, and a gap between the upper knife and the lower knife can be eliminated to prevent entry of foreign matter.
Therefore, it is possible to prevent the knife from being damaged while improving the sharpness of the cloth.

According to a second aspect of the present invention, the speed control means drives the upper knife so as to decelerate the vertical movement speed of the upper knife when the torque detected by the torque detection means exceeds a predetermined value. Control the drive of the means.
That is, the increase in torque means that the cloth cannot be cut smoothly. In such a case, the cloth can be cut by reducing the vertical movement speed of the upper knife.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a best embodiment of a cloth cutting device for a sewing machine according to the invention will be described in detail with reference to the drawings.
<Configuration of sewing machine cloth cutting device>
As shown in FIG. 1, a sewing machine cloth cutting device 100 (hereinafter referred to as a cloth cutting device 100) includes an upper knife 1 that operates in the vertical direction of the sewing machine, and a lower knife 3 that is fixed to a needle plate 2. I have. And the cloth cutting device 100 cut | disconnects the cloth on the needle plate 2 when the upper knife 1 descends and slides on the lower knife 3.

  The upper knife 1 is attached to the upper knife mounting plate 5 by a set screw 4. The upper knife mounting plate 5 is provided on the upper knife mounting base 6 so as to be movable in a direction orthogonal to the vertical movement direction of the upper knife 1. As a moving mechanism, a projection 5a is provided on the upper knife mounting plate 5, and the projection 5a is fitted into a guide groove 6a formed on the upper knife mounting base 6, thereby guiding the movement of the upper knife mounting plate 5. . The upper knife mounting base 6 is partly fitted to the rotation stopper 7 so that its rotation is restricted so that the position of the upper knife 1 does not change due to its own rotation. Two bearings 8 and 9 are inserted through the upper knife mounting base 6, and an upper knife base 10 is provided so as to be sandwiched between the bearings 8 and 9.

  On the side surface of the upper knife base 10, one end of a link 11 arranged so as to extend in a direction orthogonal to the vertical movement direction of the upper knife 1 (direction in which the upper knife 1 contacts and separates from the lower knife 3) is stepped. The screw 12 is rotatably connected. One end of the link arm 13 is rotatably connected to the other end of the link 11 by a step screw 14. At the other end of the link arm 13, an output shaft 15 a of a pulse motor 15 as a base driving means for moving the upper knife base 10 in a direction in which the upper knife 1 contacts and separates from the lower knife 3 is set screws 16, 16. Are connected by The pulse motor 15 is provided with an encoder 17 as torque detection means for detecting torque applied to the pulse motor 15.

An upper knife shaft 20 is inserted through the upper knife mounting base 6, the bearings 8 and 9, and the upper knife base 10. The upper knife shaft 20 is arranged such that its axis extends in the vertical movement direction of the upper knife 1. A rack 21 extending along the axial direction of the upper knife shaft 20 is formed near the upper end of the upper knife shaft 20. The rack 21 is provided with a pinion gear 22 in mesh.
An output shaft 23a of a pulse motor 23 as an upper knife driving means for moving the upper knife 1 up and down and making its vertical movement speed variable is connected to the pinion gear 22 by a set screw 24.

As shown in FIG. 2, the cloth cutting device 100 includes a control device 30 that controls driving of the pulse motors 15 and 23.
The control device 20 includes a known CPU and memory, and the control device 30 serves as position detection means for detecting the positions of the pulse motors 15 and 23, the encoder 17, and the upper knife 1 in the vertical movement direction. A position sensor 31 is connected.
When the position of the upper knife 1 detected by the position sensor 31 is the retreat position retracted upward from the lower knife 3, the control device 30 causes the cutting blade of the upper knife 1 and the cutting blade of the lower knife 3 to be separated from each other. When the upper knife base 10 is moved to the position where the tip of the upper knife 1 starts to slide on the lower knife 3, the cutting blade of the upper knife 1 presses the cutting blade of the lower knife 3 with the first pressing force. When the upper knife base 10 is moved so that the cutting blade of the upper knife 1 starts to slide on the cutting blade of the lower knife 3, the cutting blade of the upper knife 1 moves the cutting blade of the lower knife 3 first. When the upper knife base 10 is moved so as to be pressed with a second pressing force larger than the pressing force of 1, and the cutting blade of the upper knife 1 is in the position where the cutting of the cloth is finished, the cutting blade of the upper knife 1 is The pulse mode is used to move the upper knife base 10 so as to press the cutting blade of the lower knife 3 with the first pressing force. Functions as movement controlling means for controlling the drive of 15.

Here, the first pressing force is such a force that the upper knife 1 contacts the lower knife 3 and presses the lower knife 3 with a relatively weak force, and the setting of the force is arbitrary.
The second pressing force is a force capable of exerting a sharpness capable of sufficiently cutting the cloth by pressing the lower knife 3 with a relatively strong force while the upper knife 1 is in contact with the lower knife 3, and setting of the force is set. Is optional.
The second pressing force is larger than the first pressing force, and any pressing force is determined by the amount of movement of the upper knife base 10.

The control device 30 functions as a speed control unit that controls the driving of the pulse motor 23 so as to decelerate the vertical movement speed of the upper knife 1 when the torque detected by the encoder 17 exceeds a predetermined value.
As shown in FIG. 3, in the control of the vertical movement speed of the upper knife 1 by the control device 30, when the load applied to the pulse motor 15 increases due to the cloth cutting resistance, the torque increases and the torque phase shifts. The control device 30 acquires the torque phase shift and controls the driving speed (rotational speed) of the pulse motor 23 in accordance with the torque phase shift.
Specifically, if the load applied to the pulse motor 15 increases, the cloth cannot be cut. Therefore, the driving speed of the pulse motor 23 is reduced according to the torque phase shift at that time. The reason for decelerating is that, even if the force with which the upper knife 1 presses the lower knife 3 does not change, the sharpness is improved if the vertical movement speed of the upper knife 1 is reduced.

<Upper knife movement control>
As shown in FIG. 4, the control device 30 determines whether the position of the tip 1 a of the upper knife 1 is above the lower knife 3 based on the position of the upper knife 1 detected by the position sensor 31. Judgment is made (step S1). In the determination of the position of the upper knife 1 in the present process, the position of the lower knife 3 where the position of the tip 1a of the upper knife 1 detected by the position sensor 31 is 0 is used.
Here, when the control device 30 determines that the position of the distal end portion 1a of the upper knife 1 is above the lower knife 3 (step S1: YES), the control device 30 determines whether the position of the tip 1a is higher than that of the lower knife 3 as shown in FIGS. As shown in (a), the upper knife base 10 is moved by driving the pulse motor 15 so that the upper knife 1 and the lower knife 3 are not in contact with each other when the upper knife 1 is lowered. (Step S2). In addition, when the upper knife 1 is already arrange | positioned in the position where the upper knife 1 and the lower knife 3 do not contact | abut, the state is maintained.
On the other hand, when the control device 30 determines that the position of the tip 1a of the upper knife 1 is not above the lower knife 3 (step S1: NO), the controller 30 determines that the tip 1a of the upper knife 1 is lower knife. 3 is determined (step S3).

In step S3, when the control device 30 determines that the tip 1a of the upper knife 1 is in contact with the lower knife 3 (step S3: YES), as shown in FIGS. 5B and 6B. Furthermore, the control device 30 drives the pulse motor 15 to move the upper knife base 10 to a position where the upper knife 1 can press the lower knife 3 with the first pressing force (step S4).
Next, the control device 30 determines whether or not the cutting blade 1c for cutting the cloth in the upper knife 1 is in contact with the lower knife 3 (step S5).

In step S5, when the control device 30 determines that the cutting blade 1c of the upper knife 1 is in contact with the lower knife 3 (step S5: YES), as shown in FIGS. 5 (c) and 6 (c). Furthermore, the control device 30 drives the pulse motor 15 to move the upper knife base 10 to a position where the upper knife 1 can press the lower knife 3 with the second pressing force (step S6).
Next, the control device 30 determines whether or not the cutting blade 1c of the upper knife 1 is in a position when the cutting of the cloth is completed (step S7).

In step S7, when it is judged that the control apparatus 30 exists in the position when the cutting blade 1c of the upper knife 1 completed the cutting | disconnection of a cloth (step S7: YES), FIG.5 (d) and FIG.6 (d) As shown in FIG. 4, the control device 30 drives the pulse motor 15 to move the upper knife base 10 to a position where the upper knife 1 can press the lower knife 3 with the first pressing force (step S8). . That is, the pressing force of the upper knife 1 is weakened so that the pressing force of the upper knife 1 that has been pressed by the second pressing force can be pressed by the first pressing force that is weaker than the second pressing force.
When the process of step S2 or step S8 ends, the control device 30 returns to step S1 again.

<Upper knife vertical speed control>
As shown in FIG. 7, the control device 30 detects torque (torque phase shift) applied from the encoder 17 to the pulse motor 15 (step S11).
Next, the control device 30 determines whether or not the torque value (torque phase shift amount) is equal to or greater than a predetermined value (step S12).
Here, when the control device 30 determines that the detected torque value is equal to or greater than the predetermined value (step S12: YES), the control device 30 moves the upper knife 1 up and down according to the detected torque value. The drive speed of the pulse motor 23 is decelerated (step S13).
On the other hand, when the control device 30 determines that the detected torque value is less than the predetermined value (step S12: NO), the control device 30 maintains the driving speed of the pulse motor 23 or has already been decelerated. It returns to the set drive speed (step S14).

<Effect>
As described above, according to the cloth cutting device 100 for the sewing machine, when the upper knife 1 is in the upper retracted position retracted from the lower knife 3 by the drive control of the pulse motor 15 by the control device 30, the upper knife 1 is lowered. Since it is separated from the knife 3, the upper knife 1 does not come into contact with the lower knife 3 when it is lowered. Further, when the tip of the upper knife 1 is in a position where the lower knife 3 starts to slide, the cutting blade of the upper knife 1 presses the cutting blade of the lower knife 3 with the first pressing force, so that the upper knife 1 1 is easily pierced into the cloth, and a gap is not formed between the upper knife 1 and the lower knife 3 to prevent entry of foreign matter. When the cutting blade of the upper knife 1 is in a position where the cutting blade of the lower knife 3 starts to slide, the cutting blade of the upper knife 1 presses the cutting blade of the lower knife 3 with the second pressing force. Therefore, when cutting the cloth, cutting can be performed with the sharpness improved. When the cutting blade of the upper knife 1 is in the position where the cutting of the cloth is finished after the cloth is cut, the cutting blade of the upper knife 1 presses the cutting blade of the lower knife 3 with the first pressing force. Since the pressing force is reduced after cutting, the wear of both the scalpels 1 and 3 can be suppressed, and the clearance between the upper scalpel 1 and the lower scalpel 3 can be eliminated to prevent foreign matter from entering. it can.
Therefore, it is possible to prevent breakage and wear of both the scalpels 1 and 3 while improving the sharpness of the cloth.

Further, the control device 30 controls the driving of the pulse motor 23 so as to decelerate the vertical movement speed of the upper knife 1 when the torque detected by the encoder 17 exceeds a predetermined value.
In other words, the increase in torque means that the cloth cannot be cut smoothly. In such a case, the cloth can be cut by reducing the vertical movement speed of the upper knife 1. .

<Others>
The present invention is not limited to the above embodiment. In the above embodiment, the upper knife is configured to be pressed against the lower knife. However, the upper knife can only be moved up and down, and the pulse motor adjusts the movement in the direction in which the lower knife is pressed against the upper knife. It may be possible.
Moreover, the pressing force to the lower knife of the upper knife is not limited to two steps, and the pressing force to the lower knife may be changed more finely depending on the position of the upper knife.

The disassembled perspective view which shows the cloth cutting device of a sewing machine. The block diagram which shows the structure around a control apparatus. The figure which shows the circuit structure of the speed control of the pulse motor by a control apparatus. The flowchart which shows the movement control of an upper knife base. The figure from the front of an upper knife for demonstrating the movement control for every position of an upper knife in the movement control of the upper knife table by a pulse motor. The figure from the side of an upper knife for explaining the movement control for every position of an upper knife in movement control of the upper knife stand by a pulse motor. The flowchart which shows control of the up-and-down moving speed of an upper knife shaft. The disassembled perspective view which shows the cloth cutting device of the conventional sewing machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper knife 1a Tip part 1c Cutting blade 2 Needle plate 3 Lower knife 10 Upper knife base 15 Pulse motor (base drive means)
17 Encoder (Torque detection means)
23 Pulse motor (upper knife drive means)
30 Control device (movement control means, speed control means)
31 Position sensor (position detection means)
100 Sewing machine cloth cutting device

Claims (2)

A sewing machine comprising: an upper knife operating in the vertical direction of the sewing machine; and a lower knife fixed to a needle plate, wherein the upper knife moves down and slides on the lower knife to cut the cloth on the needle plate. In the cloth cutting device,
An upper knife drive means for moving the upper knife up and down and making its vertical movement speed variable;
An upper knife base for holding the upper knife in a vertically movable manner;
Base driving means for moving the upper knife base in a direction in which the upper knife comes into contact with and separates from the lower knife;
Position detecting means for detecting the position of the upper knife in the vertical movement direction;
When the position of the upper knife detected by the position detecting means is a position retracted from the lower knife, the upper knife base is moved so that the upper knife cutting blade and the lower knife cutting blade are separated from each other. And the upper knife base so that the cutting blade of the upper knife presses the cutting blade of the lower knife with a first pressing force when the tip of the upper knife is in a position where it begins to slide on the lower knife. When the upper knife cutting blade is in a position where the upper knife cutting blade starts to slide on the lower knife cutting blade, the upper knife cutting blade pushes the lower knife cutting blade beyond the first pressing force. The upper knife base is moved so as to be pressed with a large second pressing force, and when the upper knife cutting blade is in a position where the cloth has been cut, the upper knife cutting blade is the lower knife cutting blade. The upper knife base is moved so as to be pressed with the first pressing force. And movement control means for controlling driving of the base drive means,
A sewing machine cloth cutting device comprising: Torque detecting means for detecting torque applied to the base driving means;
A speed control means for controlling the drive of the upper knife drive means so as to decelerate the vertical movement speed of the upper knife when the torque detected by the torque detection means exceeds a predetermined value;
The cloth cutting device for a sewing machine according to claim 1, further comprising:

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