JPH031898A - Needle thread feeder for sewing machine - Google Patents

Abstract

PURPOSE:To prevent thread from breaking due to slacking, entangling or over- tensioning of thread by a method wherein existence and absence of fabric are detected, and the feed rate of needle thread is controlled according to the detected result. CONSTITUTION:Information is read from a memory 1 which outputs the basic pattern data on a sewing pattern selected from two or more sewing patterns, a pitch designating element 2 which designates a pitch for every stitch and a machine main shaft detector 3, and input to an arithmetic element 4 for every stitch to calculate the needle thread feed rate corresponding to the information and control a needle thread feeding unit 5 so as to optimize the needle thread feed rate. In addition, a fabric detector 6 is provided to detect existence or absence of the fabric, and the fabric existence-absence detected signal energizes a needle thread reducing signal arithmetic element 7. The arithmetic element 7 reads out a speed reduction ratio previously set in the arithmetic element 7 and performs calculation. A driving roller control motor 8 of the needle thread feeder unit 5 is controlled according to the output signal calculated to reduce the needle thread feed rate.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a needle thread supply device for a sewing machine.

[Conventional technology]

In a conventionally known sewing machine, as shown in FIG. 3, there is a storage means 1 for outputting basic pattern data of a negative sewing pattern by selecting one of a plurality of sewing patterns, a pitch specifying means 2 for each stitch, and a main shaft of the sewing machine. The information from the detection means 3 etc. is read, and if necessary, the heavy data is sent to the heavy detection means (
(not shown), and adds this to the calculation means 4 for each stitch to calculate the corresponding upper thread supply amount for each stitch, and based on this calculation result, the upper thread payout device 5 to optimize the yarn supply amount.

C Problems to be Solved by the Invention] In the conventional needle thread supply device of a sewing machine, the needle thread is supplied in the same way during dry sewing when there is no fabric as when there is fabric.

However, during dry sewing when there is no fabric, only the upper and lower threads are used for stitching, and there is little or no stitch feeding due to double feed, so the upper and lower threads are hardly consumed. This has the disadvantage of causing problems such as baggage, tangles, and thread breakage caused by the needle.

The present invention is designed to eliminate these drawbacks.

[Means to solve the problem]

The needle thread supply device of the sewing machine of the present invention includes means for setting the needle thread supply amount for each stitch according to sewing information, and needle thread pulling-out means that is controlled by the set value of the needle thread supply amount setting means. It is characterized by comprising means for detecting the presence or absence of cloth during sewing, and means for adjusting the value set by the needle thread supply amount setting means depending on the presence or absence of the cloth.

[For production]

In the needle thread supply device of the sewing machine of the present invention, the presence or absence of cloth is detected, and the amount of needle thread supplied is controlled in accordance with the detection result.

〔Example〕

The present invention will be explained in detail below with reference to the drawings.

In the present invention, as shown in FIG. 1, a storage means 1 outputs basic pattern data of one sewing pattern by selecting one of a plurality of sewing patterns, a pitch designation means 2 for each stitch,
Reads information from main shaft detection means 3 of the sewing machine, etc., and if necessary, sends heavy data to frost thickness detection means (not shown)
This is read from the computer and added to the calculating means 4 for each stitch to calculate the corresponding upper thread supply amount for each stitch, and based on this calculation result, the upper thread pay-out device 5
In addition to controlling the amount of thread supplied to an optimum amount, a cloth non-detection means 6 is provided, and the needle thread reduction signal calculation means 7 is energized by the cloth no-detection signal from the cloth presence/absence detection means 6. The reduction ratio set in advance in the thread reduction signal calculation means 7 or manually set from the outside with a variable volume or the like is read out and calculated, and the needle thread reduction signal calculation means 7 calculates the reduction ratio based on this output signal. Due to the small needle thread supply amount, the drive roller control motor 8 in the needle thread pay-out device 5 is controlled to reduce the needle thread supply amount.

The cloth presence/absence detecting means 6 may be implemented by providing a through hole 12 in the cloth presser foot 10 located above the throat plate 9 at a position immediately before the needle drop portion 11, as shown in FIG. 2, for example. The light from the light emitting element 14 is projected toward the throat plate 9 through a transparent vi 13 such as glass or acrylic plate that is closed, and the reflected light is received by the light receiving sensor 15, and the cloth 16 is placed on the throat plate 9. If there is, the state of light reflection changes, that is, the light reflected from the throat plate 9 becomes much stronger than from the cloth 16. Therefore, the configuration is such that the presence or absence of the cloth 16 is detected.

C Effects of the Invention] As described above, in the needle thread supply device of the sewing machine of the present invention, the cloth presence/absence detecting means 6 detects the cloth 1 at the needle drop point 11.
If it is determined that 6 continues to exist, the needle thread supply device is allowed to function as is, and if it is determined that there is no more fabric 16 in the needle drop area 11, the needle thread decrease signal calculation means 7 calculates By reducing the amount of needle thread supplied at the specified value, it is possible to prevent thread breakage due to looseness, tangles, and tension of the thread, and because the loop during dry sewing is stabilized, skipped stitches due to poor loop formation can be prevented. There are great benefits such as being able to prevent thread breakage due to half-hanging of loops and round stitching, and stabilizing seams and loops during idle sewing.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the needle thread supply device of the sewing machine of the present invention;
FIG. 2 is a sectional view of the cloth presence/absence detecting means, and FIG. 3 is a block diagram of a needle thread supply device of a conventional sewing machine.

Claims (2)

[Claims] (1) A means for setting the needle thread supply amount for each stitch according to sewing information, a needle thread feeding means controlled by the set value of the needle thread supply amount setting means, and a means for detecting the presence or absence of cloth during sewing. and means for adjusting the value set by the needle thread supply amount setting means depending on the presence or absence of the cloth. (2) The sewing machine according to claim 1, wherein the set value adjusting means reads out a preset reduction ratio based on the cloth absence detection signal from the cloth presence/absence detection means and decelerates the needle thread feeding means. Needle thread supply device.