US2525182A - Extensometer - Google Patents

Description

Oct. 10, 1950 T. F. REED EXTENSOMETER Filed June 2a, 1946 m, w m w m mfifi E K m w W Patented Oct. 10, 1950 UNITED STATES PATENT OFFICE EXTENSOMETER Thomas F. Reed, Mount Lebanon, Pa., assignor to United States Steel Corporation of Delaware, a corporation of Delaware Application June 28, 1946, Serial No. 679,916

. 3 Claims.

This invention relates to an extensometer and more particularly for an extensometer used to measure the percent extension in temper rolling. In temper rolling sheet steel it is desirable to cold reduce the strip sufilciently to knock out the yield point, but the extension for this purpose should be kept as low as possible in order to minimize work hardening. In order to exceed the minimum extension as little as possible, it is necessary to provide means for accurately measuring the extension so that it can be controlled. Many devices have been proposed for this purpose, but none have proved entirely satisfactory for various reasons.

It is a object of my invention to provide an extensometer which is simple and accurate.

This and other objects will be more apparent after referring to the followin specification and attached drawing, in which the single figure is a schematic view of the extensometer of my invention as applied to a temper rolling mill.

Referring more particularly to the drawing, the reference numeral 2 indicates an uncoiler from which the strip S is uncoiled. The uncoiled strip passes over an idler or "bi1ly roll 4 into the work rolls 6 of a temper rolling mill which is provided with back up rolls 8 for the Work rolls 6. After passing through the work rolls 6 the strip S passes over "billy roll l and is coiled on the coiler l2. The peripheral speed of rolls 4 and II] are substantially the same as the speed of the strip over these rolls so that the peripheral speed of the roll [0 will be greater than that of roll 4 by an amount directly proportional to the extension. Two identical generators l4 and [6 are connected to be driven by rolls 4 and I0, respectively. The characteristics of generators l4 and I6 are such that their voltage output increases directly in proportion to their speed so that they have a straight line speed voltage characteristic. The voltage V2 from generator I6 is applied across the fixed side of a potentiometer and the voltage V1 from generator I4 is applied across the variable side of the potentiometer. The potentiometer has a fixed resistance R1 and a variable resistance R2. The ratio of R1/R2 can vary from 0 to any predetermined value. In other words, the resistance R1 may be omitted, but it is not desirable to do so since the Working range would then take up only a small percentage of the indicating scale. A selfbalancing device I8 is arranged in the variable side of the potentiometer for actuating a slider 20.

I6 also varies. This causes the self-balancing device l8 to move the slider 20 in the proper direction to balance Vi against some fraction of V2. The self-balancing device l8 may be of any standard make such as the Brown Electronik or the Leads Northrup Micromax. An indicator (not shown) is associated with the self-balancing device I8 and will be calibrated as follows:

Let Y1=strip speed on entering side of work rolls. Y2=strip speed on exit side of work rolls. D1=diameter of roll 4. Dz=diameter of roll [0. S1=angular speed of roll 4. S2=angular speed of roll 10. X=fraction of R2 to right of slider contact. E=per cent extension of strip in temper rolling. K=constant If the roll diameters are made equal, Equation 12 becomes:

For example, if the percent extension E varies from 0 to 10% as X varies from 0 to 1.00, the values of X=1.00 and E=10% may be substituted in Equation 13 to obtain:

Substituting this value of B in Equation 13, the scale calibration is found to be While one embodiment of my invention has been shown and described it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim:

1. An extensometer for determining the elongation of strip passing through a reducing machine which comprises a generator driven at a speed proportional to entering strip speed, an identical generator driven at a speed proportional to exit strip speed, a resistance in series with the second named generator, a slider in series with the first named generator and part of the said resistance for varying the amount of said resistance in series with the first named generator, and a self-balancing device in series with the slider for moving said slider to balance the voltage output of the first generator against a fraction of the voltage output of the second generator to determine the percent elongation.

2. An extensometer for determining the elongation of strip passing through a reducing maancing device in series with the slider for moving said slider to balance the voltage output of the first generator against a fraction of the voltage output of the second generator to determine the percent elongation.

3. An extensometer for determining the elongation of strip passing through a reducing machine which comprises a generator driven at a speed proportional to entering strip speed, an identical generator driven at a speed proportional to exit strip speed, a potentiometer, the second named generator being connected across the fixed side of the potentiometer and the first named generator being connected across the variable side of the potentiometer, a slider, a selfbalancing device in the variable side of the potentiometer for moving said slider to balance the voltage output of the first generator against a fraction of the voltage output of the second generator to determine the percent elongation. THOMAS F. REED.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,039,914 McBane May 5, 1936 2,051,018 Umansky Aug. 11, 1936 2,248,504 Kenny July 8, 1941 2,447,208 Rendel Apr. 17, 1948 2,447,209 Rendel et a1 Apr. 17, 1948

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