Measuring and testing – Dynamometers – Responsive to force
Patent
1987-03-24
1989-01-03
Ruehl, Charles A.
Measuring and testing
Dynamometers
Responsive to force
G01L 510, G01B 1700
Patent
active
047948027
DESCRIPTION:
BRIEF SUMMARY
Measurement of the warp tension in looms and the like is an essential factor for keeping the tension constant by means of warp tension regulators. A constant warp tension is essential for the production of a perfect weave. Processes and apparatus have therefore always been in use for measuring this warp tension and using the measurements as a basis for control parameters with which to activate devices for controlling the warp tension.
The earliest method of measuring the warp tension and converting it into a measuring signal uses a deflecting device operated by the force exerted by the whole warp, for example on the back rest. The disadvantage of measuring the whole warp tension lies mainly in the large masses which have to be moved but only produce a relatively small deflection of the spring mounted back rest. Another disadvantage is that the force measurement is produced by all the warp threads so that variations in the warp tension across the width of the warp are not detected.
Other processes and apparatus have been proposed in which the whole warp is deflected between two fixed points by means of a loaded roller or the like and the magnitude of the deflection is taken as a measure of the warp tension. Although such devices could in principle be used over separate portions of the warp, they invariably constitute an obstruction, especially for servicing and operating the loom. Moreover, none of the processes mentioned above has solved the problem of the so called zero point constancy.
Processes and apparatus recently proposed are based on setting the warp, preferably partially, into localized resonance vibrations, either by bringing an auxiliary mass into contact with a portion of the warp threads and causing this system to vibrate or by setting only the warp threads into vibration. In either case, the thread tension can be determined from the resulting resonance frequency and the known mass of the warp threads in accordance with the principle of the vibrating cord. The problem of zero point constancy is solved in this process.
Even these systems, however, are not free from disadvantages, at least with regard to the complicated structure and therefore high cost of such vibrating systems. The process fails when attempts are made to use if for measurements in the whole fabric since the weft threads are liable to vary in density.
The present invention relates to a process for measuring the warp tension either on the warp itself and/or in the fabric in textile machines and the like, characterised by the features given in claim 1.
The invention also covers an apparatus having the features given in claim 10 for carrying out the process.
Exemplary embodiments of the invention will now be explained with the aid of the description and drawings, in which
FIG. 1 is a first schematic representation of the principle of measurement,
FIG. 2 shows the arrangment of the vibrating device and the warp,
FIG. 3 is a schematic representation of a vibrating device with associated drive means,
FIG. 4 shows schematically a vibrating device in relation to parts of the loom,
FIG. 5 shows the geometrical relationships between the widths of cloth and the vibrating device,
FIG. 6 is another representation of the geometric relationships,
FIG. 7 represents a variation of the vibrating device, FIG. 8 shows schematically a vibrating device with sensor,
FIG. 9 shows a vibrating device with selfexcitation and FIG. 10 shows a vibrating device with counter weight.
In the arrangement shown schematically in FIG. 1, the warp 10 whose tension is required to be measured or the woven cloth 11 is normally gripped between conveyor devices such as, for example, rear cylindrical rollers 1, 2 and front cylindrical rollers 3, 4. A vibrating device 20 is introduced between these two lines. This device executes a rotational vibration about its axis. It is capable of rotating about its axis but when there is a deflection from the straight line it produces a restoring force which is proportional to the deflection and to the tension.
The vibrating device 20
REFERENCES:
patent: 2923150 (1960-02-01), Imboden et al.
patent: 3040565 (1962-06-01), Church et al.
patent: 3802467 (1974-04-01), Steverlynck
patent: 3916687 (1975-11-01), Loepfe et al.
Ruehl Charles A.
Zellweger Uster Ltd.
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