US2052788A - Automatic tensioning or braking of unwinding rolls, etc. - Google Patents

Description

p 1936- L. MILLER 2,052,788

AUTOMATIC TENSIONING 0R BRAKING OF UNWINDING ROLLS, ETC

Filed May 16, 1934 Pecrv ZCQI INVENTOR.

Ll ya 6. km! BY ATTORNEYS.

Patented Sept. 1, 1936 UNITED STATES PATENT OFFICE AUTOMATIC TENSIONING R BRAKING 0F UNWINDING ROLLS, ETC.

Lloyd E. Miller, Cleveland, Ohio, assignor to The Reliance Electric & Engineering Company, Cleveland, Ohio, a corporation of Ohio Application May 16,1934, Serial No. 725,948

3 Claims. (Cl. 242-45) means involving making physical changes in the efiort to introduce a control to maintain the tension more uniform. In accordance with the present invention however, tension on material from an unwinding roll or reel, or the control of a variably rotating shaft of analogous variability may be attained without manual adjustment by an operator or recourse to physical changes by corrective devices or electrical or mechanical relays, etc.

To the accomplishment of the foregoing and'related ends, the invention, then, comprises the features hereinafter fully described, and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail certain illustrative embodiments of the invention, these being indicative however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawing:-

Fig. l is a semi-diagrammatic view of an embodiment of the invention; and Fig. 2 is a similar view of a modification.

A roll or other shaft S to be controlled, for instance a roll from which material is being unwound, is connected, direct or through suitable gearing, in accordance with individual circumstances, with a generator G whose output consists of an electrical load compensating wattage to frequency variation. The generator for instance, may be an alternating current generator, single phase or polyphase, and in the form illustrated in Fig. 1 is a polyphase machine whose three leads Cl, C2, 03 from its terminals Tl, T2, T3

'40 are provided respectively with a resistance RI and inductance LI, and resistance R2 and inductance L2, and resistance R3 and inductance L3, connected together in Y or delta, as desired. The generator may be excited in usual manner from a direct current source, as line D, and the detail of the machine's design may of course vary somewhat depending upon the particular duty involved. The generator works into a circuit of resistance and inductance of such value as to keep the current in any and all of the phases approximately constant. The amount of retarding effort exerted on the reel S or the braking action provided is proportional to the watts power produced by the generator. If the power be main- 66 talned constant and the lineal speed of the material being unwound is constant, then the tension on the material must be constant. As well known, the power delivered to an electric circuit is equal to PR where I is the effective current and R is the resistance of the circuit. That is, 5

W equals PR The current in an alternating circuit is equal to the voltage divided by the square root of the square of the resistance plus the square of the 10 inductance multiplied by the frequency. That is,

E I I equals Then, 15

P equals Accordingly,

R15 W equals 20 Corresponding, as an example in the case of a paper unwinding reel having connected thereto a three-phase 460 volt four-pole generator operating at a speed of ,3600 R. P. M. to 600 25 R. P. M., a resistance value per phase may be 0.397

ohms, and inductance per phase 0.0794. Then R equals 0.1575, and L equals 0.0063, and-such an installation is capable of maintaining approxi mate uniformity of power for any speed within It will be seen from the above tabulation that the variation in power supplied does not exceed 6 per cent over the entire range of speed varia- 50 tion.

In some instances, it is desirable to take account of certain losses occurring in the generator, although ordinarily these are not large. Such losses are for instance those due to windage and friction and iron loss, and these increase somewhat as the speed increases. As a further refinement of the invention then, I may provide for the elimination, or rather for the compensation of inequalities due to such losses. As illustrated in Fig. 2, in relation with the shaft 8 from which the sheet-material w is being unbetween C2 and C3 is low, but it increases as the speed increases, and by such increment it tends to prevent the voltage in the generator from increasing in direct proportion to the speed. The field F and its rectifier may thus eifect a reduction in voltage proportionally with increase in speed, such that the sum of the direct power produced at high speed and losses at high speed is equal to the sum of the direct power produced at low speed and the losses at low speed. Close adjustment of initial setting voltagesmay be facilitated by a rheostat r in the field circuit and a rheostat r in the bucking circuit. The connections of the terminals of the generator, and the inclusion therein of the respective resistance and inductance components may be as already described foregoing. The particular values in the bucking circuit in a given case will depend upon the design of the generator, but as an example, in a case where the direct power produced is 8'79 watts at low speed and the losses in windage etc. '71 watts, and at high speed the direct power 930 watts and the losses 170 watts, the sum at low speed would be 879+71=950 watts, and the sum at high speed would be 930+170=1100 watts.

.The direct power produced at high speed must or must be reduced to 91.6 per cent of the value it would have had at this speed if the gneto motive-force remained unchanged.

spears It will thus be seen that an electric load.- may be applied to a shaft to be controlled, in a manner particularly advantageous from equipment and operating standpoint. since there is no requirement of supervision by an operator, nomanual control means whatsoever, nor even any relay switches to be depended upon, with their proneness to inopportunely sticking or getting out of order. Instead, the entire unit is salt contained, the electrical load of the generator constituting the electrical regulator, and installations may be correspondingly made available in situations now handicapped by lack of space or other conditions which have heretofore militated against extensive application of control means.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described-provided the features stated in any of the following claims, or the equivalent of such, be employed.

I therefore particularly point out and distinctly claim as my invention:-

1. In combination, a roll for material to be unwound, an alternating current generator connected thereto, means including resistance and inductance of selected value in circuit with said generator for automatically controlling. to substantial uniformity the tension of material being delivered from the roll, and a bucking field winding on said generator and a rectifier in series therewith connected with one phase of the output circuit of the generator.

2. In combination, a rotated shaft, means for controlling the same to produce a substantially uniform tension on material being unwound from the shaft and including an alternating current generator connected to the shaft and resistance and inductance means of selected value constituting a circuit for said generator, and means'for supplying in the field of said generator a rectified bucking component taken from the generator output.

3. Winding and reeling apparatus, comprising a rotated shaft and a piece of material in treatment passing therefrom, means for controlling said shaft to produce substantially uniform tension on the material through various speeds of rotation, said means embodying an alternating current generator having its terminals connected across a resistance and inductance of value to control the wattage substantially uniformly through a range 6f frequency-change, and means for compensating said generator for inequalities due to the group of loss-factors including windage, iron loss, and friction.

LLOYD E. MILLER.

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