Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1990-06-28
1992-06-09
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
112306, H01J 4014
Patent
active
051209527
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a device for ascertaining the actual feed transmitted by a feed device of an industrial sewing machine to the material to be sewn, in which warp and weft threads located subsequent to each other in the direction of sewing are detected and counted during the feed of the material to be sewn by means of an optical sensor device having a light source and a photo cell, a signal corresponding to the actual feed being formed from this signal and from the predetermined thread density of the specific material to be sewn.
STATE OF THE ART
When sewing one or several layers of material on an industrial sewing machine, a difference between the set and actual feed occurs with each stitch, which is the result of the slippage between the feed device and the material, and which accumulates until the end of the seam. The result is an undefinable result of the sewing, which makes the production of high-quality seams more difficult.
Accordingly, it has already been tried, as described in German Patent DE-PS 23 61 375, to determine the actual feed with the aid of sensing wheels, in which case it is also possible that an error in the form of slippage between the respective layer of work and the sensing wheel may occur.
According to German Published, Non-examined Application DE-OS 35 25 028 a method is known in which marks, either already present or placed at random places of the respective work pieces, are scanned by means of contact-free sensor devices and where the sum of the pulses between the successive scans of each mark is compared with a set number of pulses corresponding to the length of the stitch and the distance between the scanned locations.
Thus this known method requires that corresponding marks or markings, e.g. in the form of a fabric design usable for this, be already present, which applies only to some materials to be worked. Otherwise, markings have to be applied, the application of markings to the individual layers of material to be sewn being laborious and time-consuming and thus economically hardly justifiable, while the application of usable markings on stacks of material to be sewn, in a way that would allow dependable recognition, leads to considerable technological problems.
Furthermore, it should be borne in mind that because of the requirements of modern sewing technology relatively strict standards must be applied to the quality of the method of measuring to be used, where consideration should be given to the fact that the material may be stretched or bunched in the course of the process steps and that warping or material stretching might occur during sewing because of the elasticity of the material. With high-quality materials, maximum material speeds up to 1,200 mm/s, maximum number of stitches up to 10,000 stitches/min. and a maximum shift of 0.3% of the sewn length of material are the goal.
A device according to the species is known from WO 86/00347. However, in connection with this known device it is an important prerequisite for the correct detection of the shift that the threads to be counted extend at exactly right angles to the direction of feed; during actual sewing operations, this prerequisite is virtually unattainable, because of the high speeds and in the light of the material-specific differences of the individual threads in regard to their intended orientation.
DESCRIPTION OF THE INVENTION
Based on the foregoing it is an object of the invention to design a device of the type mentioned above in such a way that a very exact detection of the feed becomes possible in connection with the major portion of commercially available materials used in sewing, to a large degree regardless of the orientation of the warp and weft threads of the material to be sewn.
In accordance with the invention this object is attained in that a rotating slit diaphragm having at least one radially extending and parallel limited slit is placed in front of the receiver cell, the rpm of the slit diaphragm being at least high enough so that during a feed corresponding t
REFERENCES:
patent: 3633037 (1972-01-01), Langenbeck
patent: 4964352 (1990-10-01), Yokoe et al.
patent: 4999488 (1991-08-01), Sollars
Frank Manfred
Geisselmann Heribert
Durkopp Adler Aktiengesellschaft and PFAFF Industriemaschinen Gm
Le Que T.
Nelms David C.
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