Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Reexamination Certificate
2001-01-30
2003-02-18
Allen, Stephone B (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
C250S559400, C250S559440, C250S559460, C356S429000, C356S430000, C356S238100, C356S238200, C356S238300
Reexamination Certificate
active
06521906
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable
REFERENCE TO A “MICROFICHE APPENDIX”
Not applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of measuring the distortion angle of the weft threads or rows of stitches in a strip of textile, and to an apparatus for implementing this method.
2. Description of Related Art
In view of the fact that the distortion angle of a woven or knitted strip of textile must be measured so that the result of the measurement can be used in machines for the automatic correction of textile strips (tentering or straightening machines), such measurement is a technical problem that has existed for decades and has already been solved in a more or less costly and reliable way.
The German patent DE-PS 674 750 describes a control mechanism for the automatic straightening of woven, light-transmitting cloth strips for web-tentering or similar machines, which derives its input signals from an arrangement of photoelectric cells that are illuminated by light passing through narrow slits, which are oriented at an angle to the transport direction of the cloth strip, and then through the moving web. By comparison of the signals from photocells associated with two slits that are perpendicular to one another, as a function of time, a control signal is obtained for tentering chains that have a straightening action on the web, although this arrangement does not explicitly measure the distortion angle.
In the patent DE-OS 1 635 266 a method of determining the weft-thread position of moving strips of woven material is described, along with an apparatus for implementing this method, in which a photoelectric detection device is likewise employed. The apparatus described here also, in one embodiment, comprises slots arranged in a V shape, with each of which are associated two photocells that are illuminated through the web. In another embodiment the measurement device comprises one photocell and one slot which, together with the photocell, can be moved back and forth like a pendulum, so that when the time-dependence of the photocell signal is evaluated in synchrony with a signal indicating position of the slot, information comparable to that obtained with the two-slot arrangement is provided. Disadvantages in a certain sense are the inertia of the mechanically moved arrangement and its mechanical wear and tear.
In the patent EP-B 0 291 729 another method and an apparatus for measuring the weft-thread or stitch-row position of strips of textile are described, in which by means of a photoelectric transducer a slit-like section is observed; in this case the transducer is formed by an arrangement of CCD arrays with a plurality of sensor fields (to be read out in series). In this printed specification several variants of concrete arrangements having one or two such CCD-sensor arrays are described, as well as a number of variants for evaluating the sensor signals. The evaluation principle is that as the textile strip moves past, the weft threads (which appear as dark fields) and the intervening spaces (which appear light) continuously illuminate the individual sensor elements of the CCD array(s) more or less strongly in alternation, and the corresponding light-dark signal sequence is analyzed digitally by a threshold-value discrimination. The algorithm for this analysis is of course chosen in accordance with whether one or two sensor arrays are employed and how these are positioned relative to the transport direction. In this solution the information obtainable from the results of the evaluation depends substantially on the specific design of the sensor arrays chosen, and is to some extent satisfactory only if two sensor arrays are used; however, there is need for improvement with respect to the accuracy of the results and the flexibility of the arrangement for differentiated evaluations.
BRIEF SUMMARY OF THE INVENTION
It is thus the object of the invention to disclose a method of this generic kind and an apparatus for implementing this method that is distinguished by high accuracy and reliability as well as versatility with respect to various evaluation tasks.
This object is achieved in regard to its methodological aspect by a method briefly described as follows. A method of measuring a distortion angle between the longitudinal extent of the weft threads or rows of stitches in a textile strip (T) that is being continuously transported in a transporting apparatus (M) and the perpendicular to the transport direction, by means of a lighting arrangement (
100
A,
200
A), a photoelectric sensor arrangement (
FIG. 1
;
FIG. 2
;
107
) with a plurality of sensor elements that are interrogated individually to obtain discrete light-dark sampling values, and an evaluation device (
115
) for processing the values sampled from the sensor fields in order to obtain the distortion angle is performed by using as a sensor arrangement an arrangement (
FIG. 1
;
FIG. 2
) of sensor elements with a plurality of rows and columns in which individual elements can be accessed as desired. In a sequence of scanning steps different predetermined groups of sensor elements are interrogated, each of which is situated substantially on a sensor-field line (
FIG. 1
; FIG.
2
). The groups involved in each scanning step are determined such that the scanned sensor-field lines, which in particular have one sensor field in common, are positioned at progressively altered angles with respect to the transport direction. With regard to the implementation aspect, the invention is achieved by an apparatus briefly described as follows. The apparatus comprises a lighting arrangement (
100
A,
200
A), a photoelectric sensor arrangement (
FIG. 1
;
FIG. 2
;
107
) composed of sensor elements, each accessible individually as desired, disposed in a plurality of rows and columns, a scanning-control device (
113
) to define the predetermined sensor-field line at each scanning step, and an evaluation device (
115
) connected to the sensor arrangement for processing the values sampled from the sensor elements in order to determine the distortion angle.
The invention includes the essential idea of producing an electronically moved slot, so to speak, linked to the fundamentally well-established principle of the moving slot and the use of a photoelectric sensor arrangement with a plurality of sensor fields. It further includes the idea of using for this purpose a field arrangement, driven in a suitable manner, that consists of optionally selectable photoelectric sensor elements with a plurality of arrays and slots. The field arrangement is controlled in such a way that in each detection step of the measurement procedure a linear array of sensor elements (in the following termed briefly “sensor-field line”) is scanned and in each detection step the scanning configuration is changed in such a way that in comparison to the preceding step a (virtual) rotation of the sensor-field line occurs.
By this means, in one scanning cycle over a predetermined angular range a “rotating sensor array” is realized, which imitates a swingable detection slot but has no inertia and is not subject to wear; furthermore, depending on the number of sensor elements in the arrangement and the resulting resolution of the apparatus, it allows extensive additional possibilities for analysis. The electronically achieved range of rotation angles covered in a scanning and analysis cycle is selected in dependence on the particular conditions for a specific form of use, as is the (virtual) rotation-angle increment between the individual scanning steps, and is maximally 180°.
The above-mentioned (virtual) rotation of a sensor-field line, which is realized by suitable choice of the sensor elements within a two-dimensional sensor array that are to be scanned in consecutive steps, can also take the form of “oscillating” about an intermediate orientation of the sensor-field line formed by the selected sensor fields. In this case, in particular
Abelen Gunter
Beying Karl-Heinz
Klaehsen Helmut
Allen Stephone B
Glass Christopher W.
Mahlo GmbH & Co. KG
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