JPH0354696Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of application) This invention is used to prevent engagement between the cloth frame and the needle in an automatic sewing machine that has a cloth frame that holds and moves the cloth and forms a predetermined seam shape. Regarding safety equipment.

(Disadvantages of the prior art) The cloth frame is moved by operating a drive means such as a pulse motor based on sewing data stored in advance in a microcomputer etc. so as to form a predetermined stitch on the cloth held in the cloth frame. As sewing machines to be controlled, automatic embroidery sewing machines, automatic bar-tack sewing machines, etc. are known. In this type of sewing machine, in order to prevent the fabric from lifting up when the needle moves up and down in the fabric frame, the fabric near the needle drop point when the needle descends is moved to the fabric that follows the needle bar and is separated above the throat plate when the needle rises. A pressing body (intermediate presser) is provided. For example, in FIGS. 3 to 5, reference numeral 1 denotes a fabric frame consisting of an inner frame 1a and an outer frame 1b, which is a well-known fabric frame that can be moved over a sewing machine bed 2 in conjunction with a pulse motor or the like.

3 is an engaging portion 3 which moves up and down in conjunction with the main shaft of the sewing machine (not shown) and is vertically spaced apart in the axially intermediate portion.
4 is a needle that is fixed to the lower end of the needle bar 3; 5 is a needle that slides the upper end and middle bent portions 5a, 5b between the engaging portions 3a, 3b of the needle bar 3 and the lower end; A cloth pressing member 6 is an engaging portion 3 of the needle bar 3 that can be fitted into the pressing portion 5c at the lower end thereof and has a hole 5d through which the needle 4 passes.
This is a wound spring wound between a and 3b. As a result, when the needle bar 3 descends, the cloth pressing body 5 follows and descends, and after the pressing part 5c engages with the upper surface of the throat plate 2, the coil spring 6 is compressed and the following of the needle bar 3 is stopped. When the needle bar rises, the upper end bent portion 5a engages with the engaging portion 3b and begins to follow. The cloth frame can be selected and replaced with one of various sizes depending on the type and size of the sewing shape, but if the operator selects it by mistake or the sewing data is enlarged or reduced in order to change the size of the sewing shape. If you do not replace the fabric frame despite this, there is a risk that the stitches will not fit within the frame of the fabric frame and will protrude, causing the fabric frame and needle to engage at the protruding part, causing damage to both. occured.

(Means for solving the problem) The amount of current supplied to the DC motor that drives the sewing machine is reduced to a predetermined standard due to an increase in motor load due to an increase in the motor load caused by preventing the needle bar from descending when the cloth pressing body engages with the cloth frame. When the value increases, the current to the motor is cut off and the sewing machine is stopped.

(Example) Since the mechanical configuration is the same as the conventional one, the same reference numerals will be used and the explanation will be omitted.

In FIG. 1, 10 is an adder, the (+) side inputs the voltage corresponding to the motor speed command from the computer, the (-) side inputs the feedback voltage from the converter 11, which will be described later. The feedback voltage compensates the motor 12 so that it rotates at a speed corresponding to the speed command.

Reference numeral 13 denotes a pulse width modulator, which changes the output pulse width depending on the voltage from the adder 10.

14 is a motor driver, which drives the motor 1 with an amount of current that is proportional to the pulse width from the pulse width modulator 13.
Supply to 2.

Reference numeral 15 denotes an oscillation circuit which is arranged in relation to the motor shaft or the main shaft of the sewing machine and which generates pulses at a frequency that is proportional to the number of revolutions.

The converter 11 performs F/V conversion to convert the pulse (frequency) of the oscillation circuit 15 into a voltage.

16 is an amplifier that amplifies the current flowing through the motor 12; 17 is a comparator that compares the output of the amplifier 16 with a reference value obtained experimentally;
6, that is, when the current flowing through the motor 12 exceeds a reference value, an output (detection signal) is generated.

18 is a CPU inside the computer;
Performs various sewing machine controls including the flowchart shown in the figure.

Regarding the flow shown in Fig. 2, a rotation command is output to the motor 12 (step 1), and a position detection signal from a well-known needle position detection means (not shown) that detects the rotation angle of the main shaft corresponding to the up and down positions of the needle is sent to the CPU.
It is counted by an internal counter (not shown) (step 2), and it is determined whether or not a detection signal is generated from the comparator 17 (step 3). If the detection signal is generated, it is determined whether the count value has reached the count value for two stitches. Judgment (Step 4), Steps 3 and 4
When the result is NO, return to step 2, and when 2 stitches have been counted at step 4, turn off the rotation command (step 5).

Note that the reference value of the comparator 17 is larger than the value corresponding to the amount of current supplied to the motor due to an increase in the motor load when the needle penetrates when sewing thick fabric, and is due to an increase in the motor load due to the cloth pressing body 5 not descending. In particular, in this embodiment, the reference value is set to a value that corresponds to the amount of current supplied to the motor due to an increase in motor load when the needle bar 3 compresses the coiled spring 6 more than necessary. Value is set.

Next, the action will be explained.

When the sewing machine is started, the motor load increases greatly, but the detection signal is cut off in step 4 until the first two stitches are formed, and the motor continues to rotate.

When the needle drop point is within the fabric frame 1, the penetration resistance of the needle into the fabric becomes the main motor load.

When the fabric frame 5 is moved and the needle drop point approaches the fabric frame 5, the pressing part 5C of the fabric pressing body 5 that follows the needle bar 3 when it descends engages with the upper surface of the fabric frame 5, and the needle bar 3 is further moved. As the needle bar 3 descends, the coiled spring 6 is compressed more than usual between the engaging portion 3a and the bent portion 5a, and as a result, as the needle bar 3 descends, the motor load gradually increases and is fed back via the converter 11. The feedback signal increases the amount of current supplied to the motor 12, and the input via the amplifier 16 is input to the comparator 17.
A detection signal is generated when the reference value is exceeded.

Upon generation of the detection signal, the rotation command is turned off (step 5), and the sewing machine is immediately stopped.

(Effects) When the needle drop point overlaps with the fabric frame, the sewing machine motor can be stopped before the needle drop occurs, so the needle and fabric frame are not damaged, extending the life of the device and improving the sewing machine's user experience. Make work safer and improve work efficiency. Since a mechanical detection means for detecting the overlapping of the fabric frame and the needle is not required, and detection can be performed using an electric circuit, the apparatus becomes simple.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit of this embodiment, Fig. 2 is a flow chart, Fig. 3 is a front partial sectional view of the head of the embroidery sewing machine, Fig. 4 is a perspective view of the fabric frame at the sewing position, and Fig. 5
The figure is a partially sectional side view of a state in which the cloth frame and the pressing part are engaged. DESCRIPTION OF SYMBOLS 1... Cloth frame, 3... Needle bar, 4... Needle, 5... Cloth pressing body, 12... DC motor, 11... Converter (feedback circuit), 17... Comparator (comparison circuit), 18... ...CPU (control circuit).

Claims (1)

[Scope of Claim for Utility Model Registration] A needle bar that supports the needle at the lower end and moves up and down in conjunction with the main shaft of the sewing machine, and a pressing part that faces the upper surface of the throat plate near the needle drop point, The fitted and supported cloth pressing body is connected so that the cloth pressing body follows the vertical movement of the needle bar while the needle moves up and down above the throat plate, and has elasticity that allows the connection to be released when the needle descends below the throat plate. A connecting means arranged between the two, a cloth frame that holds the cloth inside the frame and is movable on a plane along the upper surface of the throat plate, and A drive means that controls the movement of the cloth frame to form the seam shape, a DC motor that is connected to the main shaft of the sewing machine and rotates or stops at a speed that corresponds to the amount of current supplied, and a DC motor that corresponds to the speed at which the DC motor should rotate. A drive circuit that increases or decreases the amount of current supplied to the DC motor, and a drive circuit that increases or decreases the amount of current supplied to the DC motor in order to achieve the set speed in response to the difference between the set speed and the actual speed of the DC motor. A feedback circuit that acts on the circuit, a reference signal of the quantity of electricity set in advance corresponding to the specific amount of current supplied to the DC motor, and a detected signal of the quantity of electricity corresponding to the actual amount of current supplied to the DC motor. A comparison circuit that generates a detection signal when the detected signal becomes larger than the reference signal after comparison, and a control circuit that acts on the drive circuit to cut off the supply current to the DC motor in response to the detection signal. A safety device for an automatic sewing machine, wherein the specified amount of supplied current corresponds to a motor load larger than a motor load when the needle penetrates the cloth.