JPH0217575Y2 - - Google Patents

Description

[Detailed description of the invention] This invention makes it possible to detect the edge of the fabric of a workpiece or the edge of one of the two fabrics of a double-layered workpiece in order to operate a sewing machine control device such as a fixed position stop device of the sewing machine. , relates to a fabric edge detection device for a sewing machine that uses ultrasonic waves as a detection medium.

[Conventional technology]

As a conventional example, a layout diagram of a cloth edge sensor that can see through the object to be sewn will be explained based on FIG. 3.

A is a transmitter having an ultrasonic transducer, B is a receiver for receiving ultrasonic waves from the transmitter A,
They are arranged facing each other on a perpendicular line to the surface of the sewing object with the object W being sewn in the middle. When transmitter A is driven to emit ultrasonic waves vertically downward, the ultrasonic waves are attenuated by the presence or absence of the sewing material or its thickness, etc., and reach receiver B.
The edge of the cloth is detected from the change in the received signal output from the receiver B.

[Problem that the invention attempts to solve]

However, when the ultrasonic waves are emitted vertically downward to the material to be sewn, the ultrasonic waves hit the material to be sewn and a standing wave is generated. This device could not be used as a cloth edge detection device because it was disturbed by waves and the S/N ratio of the ultrasonic waves reaching the receiver B was lowered.

For this reason, it is possible to prevent the influence of standing waves by causing the transmitter to oscillate intermittently to create an intermittent wave, but in this case, a dead time occurs during the period when the oscillation is stopped, resulting in an error when detecting the edge of the material. There was a problem that occurred.

The present invention was developed to solve these problems, and by attaching the transmitter at an angle to the material to be sewn, even if the ultrasonic waves are continuously oscillated, the ultrasonic waves from the material to be sewn are not emitted. The object of the present invention is to provide a cloth edge detection device that is free from reflection and can prevent the influence of standing waves.

[Means for solving problems]

For this reason, the present invention includes a transmitter that is arranged at a distance above the throat plate of the sewing machine and is fixed to the sewing machine so that the incident axis that reaches the throat plate generates ultrasonic waves at an incident angle θ with the perpendicular to the throat plate surface. A fabric edge detection device including a receiver disposed on the throat plate, capable of receiving ultrasonic waves from a transmitter by passing through the sewing material on the throat plate, and generating a reception signal in connection with the reception, The transmitter is fixed so that the reflection axis, which passes through a position where the axis of incidence intersects the object to be sewn and has an inclination angle of reflection angle θ symmetrical to the axis of incidence, does not intersect with the transmitting part of the transmitter. The present invention provides a fabric edge detection device for a sewing machine.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

1 and 2, an upper cloth 4 and a lower cloth 5 are pressed against the upper surface of the throat plate by a presser foot 3 elastically biased downward on the upper surface of the throat plate 2 of the sewing machine bed 1.
Place the workpiece W consisting of
It is located further forward in the cloth feeding direction (to the left in the figure) than that of . Reference numeral 7 denotes a transmitter having an ultrasonic transducer, which has a tip transmitter 7a with a radius r, and is disposed facing above the workpiece W at a distance H apart from the needle 6 in the fabric feeding direction. It is fixed to the sewing machine head 14 so that the incident axis I of the ultrasonic wave is inclined at an incident angle θ with respect to a perpendicular line intersecting the object to be sewn. Further, the needle plate 2 includes
A throat plate hole 8 is formed at a position intersecting the incidence axis I so that the ultrasonic waves emitted by the transmitter 7 pass downward, and a receiver 9 is further arranged on the incidence axis I below the throat plate 2. The configuration is such that the ultrasonic waves emitted from the transmitter 7 pass through the object W to be sewn while attenuating and are received.

10 is a driver circuit that generates ultrasonic waves from the transmitter 7, and is driven by a drive signal from the CPU 11.
Turns ON and OFF. Reference numeral 12 denotes an amplifier for an electric signal outputted from the receiver of the receiver 9 in response to the ultrasonic signal, and outputs a detection signal for the CPU 11 .
13 is an I/O device that inputs and outputs signals to and from the CPU 11;

With the cloth edge detection device configured in this way, when the incident axis I of the ultrasonic waves is made to strike the sewing material W from the transmitter 7a of the transmitter 7 at an incident angle θ,
A part of the ultrasonic waves hitting the upper surface of the workpiece W is reflected and diverges upward. The reflection of this ultrasonic wave is centered on a reflection axis that passes through a point P where the axis of incidence intersects the object to be sewn and has an inclination angle of reflection angle θ symmetrical to the axis of incidence. The transmitter of the present invention is fixed to the sewing machine so that the incident axis does not intersect at least the transmitter, and is arranged so that the following equation is satisfied, assuming that the radius of the transmitter is r.

2H tan θ＞r ...(1) By arranging the transmitter at this angle, it is possible to use ultrasonic waves without being affected by reflection from the cloth, allowing continuous cloth edge detection. It is capable of operating in real time.

[Effect of idea]

In this invention, the ultrasonic transmitter is tilted and fixed so that the reflection of ultrasonic waves does not have a negative effect on the transmitter, which prevents the generation of standing waves and allows for stable and continuous detection of fabric edges. Now I can do it.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an ultrasonic transmitter fixed to the head of a sewing machine, FIG. 2 is a diagram illustrating an embodiment of the present invention, and FIG. 3 is a layout diagram of a conventional transmitter and receiver. 7...Transmitter, 9...Receiver.

Claims (1)

[Claims for Utility Model Registration] A transmitter that is placed at a distance above the throat plate of the sewing machine and is fixed to the sewing machine so that the incident axis that reaches the throat plate generates ultrasonic waves at an incident angle θ with the perpendicular to the throat plate surface. and a receiver disposed on the throat plate that allows ultrasonic waves from the transmitter to pass through the sewing material on the throat plate so that they can be received, and generates a reception signal in connection with the reception. In the device, the transmitter is fixed such that the axis of incidence passes through the position where it intersects the object to be sewn, and the reflection axis, which has an inclination angle of reflection angle θ symmetrical to the axis of incidence, does not intersect with the transmitting part of the transmitter. A fabric edge detection device for sewing machines featuring: