US2569264A

US2569264A - Strip tensioning apparatus

Info

Publication number: US2569264A
Application number: US31818A
Authority: US
Inventors: Morris D Stone; Joseph I Greenberger
Original assignee: United Engineering and Foundry Co
Current assignee: United Engineering and Foundry Co
Priority date: 1948-06-08
Filing date: 1948-06-08
Publication date: 1951-09-25
Anticipated expiration: 1968-09-25
Also published as: FR987151A

Description

INVENTORS Sept. 25, 1951 M. D. STONE ET AL STRIP TENSIONING APPARATUS Filed June 8, 1948 patented Sept. 25, 1951 STRIP TENSIONIN G APPARATUS Morris D. Stone and Joseph I. Greenberger, Pittsburgh, Pa., assignors to United Engineering & Foundry Company, Pittsburgh, Pa., a corporation of Pennsylvania Application June 8, 1948, Serial No. 31,818

. 3 Claims.

The invention relates to apparatus for tensioning strip metal by deflecting it upwardly into a loop as it passes between the rolls of adjacent stands of a tandem or a continuous strip-rolling mill.

It is known that in the continuous rolling of strip metal the length of the strip between the bites of adjacent pairs of rolls may vary, due, among other things, to the relative peripheral speeds of the rolls, and to variations in the thickness, heat and other factors and properties of the strip from its leading to its trailing end. Because of this, it is desirable to maintain the strip under tension between the bites of adjacent pairs of rolls, which has beendone by various forms of apparatus, known as tensiometers, that exert controlled upward pressure on strip metal to deflect it upwardly.

The object of the invention is to provide an improved tensiometer that is simple in construction, and in the operation of which it effectively maintains a substantially constant tension on the strip when deflected upwardly in a loop that varies materially in height.

The apparatus provided according to this invention comprises a pair of struts that may be either single members or frame-like structures, the adjacent ends of which are pivotally connected to an idle roller that lies below strip metal as it passes from one to another of adjacent pairs of rolls, and that extends transversely of the strip. The roller is preferably positioned substantially midway between the adjacent pairs of rolls, and the struts extend laterally and downwardly from it, 'one towards one pair of rolls and the other towards the other. The lower ends of the struts are pivotally supported in fixed positions proximateto the points of upward deflection of the strip, the arrangement being such that each strut lies substantially parallel to the strip when it is variably deflected upwardly by the roller.

Preferably only one of the two roller-supporting struts is extensible, but both may be. The extensible strut, or each of the two if both are extensible, includes means for applying a constant force to its extensible parts acting in a line passing through the pivoted ends of the strut.

The invention is diagrammatically illustrated in the accompanying drawings of which Fig. 1 is an elevation of the apparatus showing strip metal being deflected or looped upwardly as it passes from one to another roll, in which the fixed pivot axis of the outer endof each strut is below the point of upward deflection of the strip and in substantially vertical alignment with it, and in only one strut is extensible; Fig. 2 a force diagram of the apparatus shown in Fig. l; and Fig. 3 a force diagram of apparatus similar to that shown in Fig. 1, but in which the fixed pivot axis of the outer end of each strut is at one side of the point of upward deflection of the strip.

Having reference first to Fig. 1, strip metal I is shown as being looped or deflected upwardly by an idle roller 2 that is positioned substantially midway between two rolls 3 and 4, which may be the upper working rolls of two stands of striprolling mills, or may be idle rolls positioned between two such mills. Roller 2 is supported by two struts 5 and 6 whose adjacent ends are pivotally connected to the roller or to a frame that supports it. Strut 5 preferably comprises a pressure cylinder 1 and a pistonrod 8 provided with a piston 9 within the cylinder, pressure fluid being applied to the rear of the piston through a pipe I4 that is provided with a control valve l0 and a pressure indicator H. The lower end of strut 5 is pivotally supported by a horizontal trunnion [2 attached to cylinder 1, the axis of the trunnion being vertically below the axis of roll 3 and substantially vertically below the point of upward deflection of strip l as it passes below roll 3. The lower outer end of rigid strut 6 is similarly pivotally supported at 13 in a fixed position below roll 4, and the vertical distance between points of upward deflection of strip I and the pivot points [2 and I3 of struts 5 and 6 is equal to the radius'of idle roller 2.

For balancing the weight of the roller and strut apparatus and also, if desired, the weight of the strip passing over roller 2, such roller is pivotally connected to the upper end of a vertically disposed piston rod l5 whose lower end is connected to a piston l6 in a vertically disposed pressure cylinder I! which is pivotally supported in a fixed position by a horizontal trunnion l8. Pressure is supplied to the lower end of piston [6 through a pipe 19 that is provided with a control valve 20 and a pressure indicator 2|. By applying a predetermined constant pressure to the rear of the piston IS in cylinder ll, the dead weight of the strut and roller apparatus and of the strip passing over the roller may be balanced.

-As has been stated, by applying a constant uniform pressure to the back of piston 9 in extensible strut 5, a substantially constant tension is maintained in strip I throughout a wide range of upward looping or deflection of the strip. This appears from a consideration of the force diagram of the Fig. 1 apparatus shown in Fig. 2, in which strip I has a tension T effected by a pressure P applied to roller 2 by the extensible strut 5, resulting in a vertical upward pressure R on roller 2. With negligible variations within the practical range of vertical movement of roller 2, the vertical distance it between the axis of roller '2 and a horizontal line 25 passing through the lower pivots I2 and I3 of struts and 6 is the same as the vertical distance h between the line of tangency of the strip with roller 2 and a horizontal line 26 passing through the lines of tangency of the strip with rollers 3 and 4. Similarly, angle a. between line 25 and the longitudinal axial line of strut 5 is the same asangle a between line 2'6 and the plane of the inclined portion of strip I.

Under these conditions, and taking into consideration the fact that-the tension in the strip pulls Vertically downward and the struts push vertically upward on both sides of roller 2, the vertical pressure R. exerted on roller 2 by the struts, and by roller 2 to the strip, is equal to 2P sin .a, and the like pressure R exerted by the strip is 2T sin a. Since the angles a and a are the same for all practical positions of roller 2, it follows that T equals P. Hence, the amount of constant pressure P that is required may be determined by. multiplying the cross-sectional area of a given strip by the pounds per square inch of tension desired to be maintained in the strip as it passes between adjacent roll stands.

If in the tensioning apparatus shown in Fig. 1 the rolls 3 and 4 are the upper working rolls of two adjacent roll stands, instead of being idle rolls positioned between the working rolls in the line of pass between them, it is necessary to pivotally support the lower ends of struts 5 and 6 at the outsides of the roll stands to avoid interference with the lower rolls of the mill. Because in such an arrangement the tensioning apparatus interferes with free access to the mills, in most cases it is undesirable thus to support the struts.

In the force diagram shown in Fig. 3, the fixed pivot point of the lower end of each of the struts 5' and 6 is positioned proximate to the upper working roll at a side of it, and when so positioned it can conveniently be supported at the inside of the roll stands. this arrangement of the tensioning apparatus the total tension in the strip equals the pressure in the strut multiplied by a constant, or in other words T equals KP, in which K is a constant. This can best be shown by assuming a. practical spacing of 20 feet between adjacent 4-,high stands .of a tandem or continuous mill, and by assuming that the pivot .axes l2 andl3' of the outer ends of the struts are spaced 2 feet from vertical planes passing through the axes of the rolls. When so spaced from the rolls of the mill stands, the pivot axes l2 and I3 of the struts can readily be supported at the insides of the roll stands free from interference with the mills, and can be so positioned belowthe inclined planes of the looped or upwardly deflected strip I that the axes of the struts are, within the practical range of vertical movement of pressure roller 2', substantially parallel with the inclined planes of the strip at each side of roller 2'. The assumed spacing of 20.feet between the roll stands and 2 feet betweenthe rolls of each stand and As will be shown, in

the pivot axes of the struts are conveniently given in inches in Fig. 3.

Using the nomenclature explained with reference to Fig. 2, the following equations are apparent:

2T sin a =R 2P sin a=R sin a sin a If sin-a. divided by sin a is held constant for all values of the height h of the axis of roller 2 above the horizontal line 25, as it substantially is for all values of the angles a and a within the practical range of the height h, then T is equal to KP, in which K is a constant. From the geometry of the mechanism the following equations are apparent, in which the amounts expressed in numerals are those shown on Fig. 3 under the assumption that the roll stands are spaced 20 feetapart, and on the further assumption that the horizontal distances, 96 inches, be-v tween the pivot axes l2 and I3 and a vertical. line passing through the axes ofroller 2' remain.

constant, which they substantially do within the practical range of vertical movement of roller 2:

/l20 (squared) +h' (squared) sin 11:

126 (squared)+h (squared) V 96 (squared)+h (squared) 14400-l-h. (squared) \l9216+h (squared) Solving the last equation'on the assumption.

that the height h is zero, T equals 1.25P, and

solving it on-theassumption that the. maximum.

height h is 30 inches, T equals 123?. Amaximum height of 30 inches is the practical maximum height of a loop between rollstands that are spaced 20 feet apart, it being understood that.

a tensiometermechanism of .the..type herein disclosed is equipped with mechanism, well known in the art, for so controllingthe relative periph eral speeds of the working rolls that the length of strip between two roll stands will permit looping of the strip within minimum and maximum.

limits. The solving of thelast of the. above equations shows that the tension T in a strip is constant throughout a height h of. from-0 to 30, Therefore, to obtain a constant known total tension in-.a.v strip in the arrangement shown in Fig. 3 .the'

inches to within plus orminus 0.8%.

required pressure P applied to the extensible strut may be obtained by dividing the known tension by l.24, which is the average of 1.25.and.

From the foregoing it is plainthat, for all practical spacings ofroll stands, a constant force 7 applied to the extensible strut acting in a linepassing through itspivot points will result in maintaining a constant tension in the strip ineither hot or coldrolling mills. Ifthe-spacingof roll stands is materially less than 20feet, asit. usually is in cold rol1ing;.mi1ls, themaximum. permissible height of the loop is correspondinglydiminished below 30 inches, and if the spacing of the roll stands is increased beyond 20 feet the maximum permissible height of the loop may be increased beyond 30 inches. Similarly, the spacing of the lower pivot points of the struts from the sides of the rolls may be varied within practical limits without varying the principle of operation of the tensioning mechanism or the result obtained by it.

According to the provisions of the patent statutes, we have explained the principle of our invention and have diagrammatically illustrated, and have described, practical embodiments of it. However, we desire to have it understood that, within the scope of the appended claims, the invention may be practiced with apparatus different than that diagrammatically illustrated.

We claim:

1. A tensioning device for subjecting a strip to constant tension between two zones comprising a vertically movable idle roller below the strip extending transversely thereof between the two zones and constructed to bear upon the lower face of the strip and deflect it upwardly at substantially equal inclinations to the horizontal at each side of the roller, a pair of struts, at least one of which is extensible, each pivotally connected at one of its ends to and for supporting said roller and directed laterally and downwardly therefrom, one towards one and the other towards the other zone, the lower outer ends of.

said struts being pivotally supported in fixed positions proximate to the points of upward deflection of the strip to permit said struts to maintain substantially parallel relationship with respect to said upwardly deflected strip, and means for applying a substantially constant force to said extensible strut acting between and in a line passing through the end pivots thereof to vary the distance therebetween, thereby varying the elevation of said roller.

2. A tensioning device for subjecting a strip to constant tension between two zones comprising a vertically movable idle roller below the strip extending transversely thereof between the two zone and constructed to bear upon the lower face of the strip and deflect it upwardly at substantially equal inclinations to the horizontal at each side of the roller, a pair of struts, each pivotally connected at one of its ends to and for supporting said roller and directed laterally and downwardly therefrom, one towards one and the other towards the other zone, the lower outer ends of said struts being pivotally supported in fixed positions proximate to the points of upward deflection of the strip to permit said struts to maintain substantially parallel relationship with respect to said upwardly deflected strip, one of said struts bein extensible comprising a cylinder having a piston therein and a rigid member connected to said piston, the other of said struts having the same length between its pivot points in all vertical positions of said roller, and means for applying a constant pressure to said cylinder to extend said extensible strut in a direction passing through the pivots thereof to vary the distance therebetween, thereby varying the elevation of said roller.

3. A tensioning device for subjecting a strip to constant tension between two zones comprising a vertically movable idle roller below the strip extending transversely thereof between the two zones and constructed to bear upon the lower face of the strip and deflect it upwardly at substantially equal inclinations to the horizontal at each side of the roller, a pair of struts, each pivotally connected at one end to and for supporting said roller and directed laterally and downwardly therefrom, one towards one and the other towards the other zone, the lower outer ends of said struts being pivotally supported in fixed positions proximate to the points of upward deflection of the strip to permit said struts to maintain substantially parallel relationship with respect to said upwardly deflected strip, one of said struts being extensible, means for applying a constant force to said extensible strut acting between and in a line passing through the end pivots thereof to vary the distance therebetween, thereby varying the elevation of said roller, and means for balancing the weight of said roller and struts.

MORRIS D. STONE. JOSEPH I. GREENBERGER.

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

UNITED STATES PATENTS Number Name Date 1,886,232 Sykes July 5, 1932 2,296,753 Wilton Sept. 22, 1942