US2250541A

US2250541A - Tensioning device

Info

Publication number: US2250541A
Application number: US237456A
Authority: US
Inventors: Gerhard P Lessmann
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1938-10-28
Filing date: 1938-10-28
Publication date: 1941-07-29
Anticipated expiration: 1958-07-29

Description

y 29, 1941- G. P. LESSMANN 2,250,541

TENSIONING DEVICE Filed Oct. 28, 1958 7 Sheets-Sheet l WITNESSES: I INVENTOR 0%;1. 6 M. Gerhard P Lemma/m July 29,-194 1. G. P. LEssMANN TENSIONING DEVICE Filed Oct. 28, 1938 7 Sheets-Sheet 2 INVENTOR Gerhard Bless/7mm.

w ATTOR EY July 29, 1941. G. P. LESSMAVNN TENSIONING- DEVICE Filed Oct. 28, 1958 '7 Sheets-Sheet 3 INVENTOR Gerhard/ Z ass/77am.

ATTOR EY y 1941- G. P. LESSMANN 2,250,541

' TENSIONING DEVICE Fil ed- Oct. 2a, 1938 7 Sheets-Sheet 4 INVENTOR Gerhard Bless/270x711.

WITNESSES:

July 29, 1941. G. P. LESSMANN 2,250,541

TENSIONING DEVICE Filed Oct. 28, .1938 7 Sheets-Sheet 6 ATT July 29, 1941.

G. P. LESSMANN TENSIONING DEVICE Filed Oct. 2a, 1938 7 Sheet-Sheet 7 \l 0 Mg INVENTOR Gerhard/Plessmam AT ORN WITNESSES:

%v WM Patented July 29, 1941 TENSIONIN G DEVICE Gerhard P. Lessmann, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 28, 1938, Serial No. 237,456

12 Claims.

My invention relates, generally, to tensioning devices, and, more particularly, to tensioning devices that may be employed to apply tension to a strip of material as it passes through a rolling mill.

It has become common practice in the operation of steel strip rolling mills to subject the strip to front and back tensions at each roll stand and to maintain tension on the strip as it is wound upon and unwound from the winding reel and unwinding reel, respectively. Until recently these tensions-have been under the control of the mill operators, who adjusted the mill and reel motors to apply whatever torque they judged would produce the desired tension in the strip.

As the practice of subjecting steel strip to tension was developed, the strip tensions were increased and these tensions have become so high that at the present time the reduction of the strip due to the front and back tensions applied at each roll stand is a large proportion of the total reduction at the roll stand. With the strip tension playing such an important part in the rolling operation, and since the amount of reduction depends largely upon the amount of tension, it became necessary that the amount of tension applied to the strip be accurately controlled in order to produce a strip of uniform thickness.

A very successful device for subjecting the strip in a strip rolling mill to tension andautomatically maintaining a predetermined amount of tension on the strip is shown and described in my copending application Serial No, 133,419, filed March 27, 1937, now Patent No. 2,189,609, issued February 6, 1940.

Many of the existing strip rolling mills whose operation it is desired to improve by the addition of automatic tensioning devices have their several roll stands and winding reel stands very closely spaced and have other apparatus mounted at and near the mill stands, leaving very little space for the tensioning devices and causing considerable crowding of machinery if indeed there is suflicient space for the tension devices.

In building new strip rolling mills where plenty of space for the tensioning devices could be provided in laying out the mill, it is desirable that the mill be not spread out over too great a floor space and that a minimum of equipment he located at or near the pass line where it may obstruct the operator's access'to the rolling equipment.

It is an object of my invention, therefore, to

provide an automatic strip tensioning device for a strip rolling mill which shall occupy a minimum mill.

A more specific object of the invention is to provide a strip tensioning device for a strip' rolling mill which may be readily adapted to and installed upon existing mills without interfering with the operation or accessibility of the operating parts of the mill.

A further object of my invention is to provide a strip tensioning device which may be readily adapted to and installed upon any of the several types of strip rolling mills and which shall function to subject the strip to and regulate front and back tensions at each roll stand and/or to provide automatically regulated winding reel and unwinding reel tensions.

Another object of my invention is to provide a strip tensioning device which shall be simple and eflicient in operation and inexpensive to manufacture, install and maintain.

These and other objects and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings, in which like reference characters denote similar elements of structure, and in which:

Figure 1 is a diagrammatic side elevation view. partly broken away, of a portion of a roll stand and strip reel of a strip rolling mill embodying the principal features of, the invention;

Fig. 2 is a plan view of the apparatus of Fig.

Figs. 3 and 4 are perspective views of portions of the strip tensioning device operating mechanisms and the mountings therefor shown in Figs. 1 and 2;

Fig. 5 is a diagrammatic representation of a single stand temper pass mill embodying the principal electrical control features of my invention;

Figs. 6 and '7 are a diagrammatic side elevation view and a simplified control diagram. respectively, of a two stand temper pass strip mill embodying the principal features of my invention; and,

Figs. 8 and 9 are a diagrammatic side elevation and a simplified control'diagram, respectively, of a single stand reversible strip mill embodying the principal features of my invention.

In carrying out my invention, a tensioning device Ill, best shown in Figs. 1, 2 and 4, is mounted upon the mill housing l2 and positioned to subiect the strip It to a tension as it passes between of space at and near the pass line of the the mill.

by the

upright members

26 and 28 of the mill housing l2. The tensioning device 26 has its operating mechanism supported on a beam member 36 which in turn is supported by

bracket members

32, 34 and 35 secured to the

uprights

26 and 28, respectively. The operating mechanisms of the tensioning devices l6 and 26 are supported sufiiciently high above the pass line of the mill to preclude their occupying space in the area about the pass line where space is at a member 26 in any suitable manner.

made to abut against a bracket member 66 and are secured thereto in any suitable. manner.

The outwardly extending end of the beam section 54 may be secured to the mill housing The outwardly extending end of the beam member i2 is mounted upon a bracket 62, which is secured to the mill housing 26. The total length of the

beam sections

62 and 64 is less than the distance between the

mill housings

26 and 26, and this total length is such as to permit the beam to be mounted on mill stands having a minimum spacing between the opposing mill housings. The bracket 62 extends from the housing 26 a distance such as to permit the mounting of the beam 24 on mill stands having different spacings between the opposing mill housings so that the premium, and where considerable space is needed to insure freedom of access of the operator to-

Spaced linkage rods

36 and 36 extend downwardly from the operating mechanism of the tensioning device If and support a tensioning roll 46. Similarly, spaced linkage rods 42 and extend downwardly from the operating mechanism of the tensioning device 26 to support a tensioning roll 46.

The simplified control diagram for a single stand mill is shown in Fig. 5. In this figure there are shown a single set of rolls iii, a winding reel 22, an-unwinding reel 22', and strip pullers i8 and I6 disposed between the rolls and the winding and unwinding reels, respectively.

The tensioning device 26 controls the tension exerted on the strip as it is wound on the winding v reel 22 by means of a regulator which controls the field excitation of the winding reel drive motor. In a similar manner, the tensioning device l6 controls the front tension exerted on the strip by the strip puller l6gby field control of the puller drive motor. The unwinding reel 22 and the strip puller I6" are each connected t6 dynamic braking generators, and the tensioning devices I6 and 26' control the back tension and the reeling tension on the strip by field control of the generators associated with the strip puller l8 and the unwinding reel 22', respectively.

The system of Fig. 6 comprises two roll stands 48 and 56 with the strip tension between the stands controlled by a tensioning device 52. The winding reel tension, the unwinding reel tension, the front tension on the strip at the roll stand- 48, and the back tension at the roll stand 66 are controlled by tensioning devices 26, 26', i6 and i6, respectively, in the manner described in the discussion of Fig. 5. These controls are shown in Fig. '7.

In Figs. 8 and 9, the tensioning devices l6 and i6 are shown employed to regulate the tension on the strip between the reels and the rolls of a reversible strip mill. The tensioning devices are connectedto control the torque applied to the winding and unwinding reels by field control of the dynamo-electric machines associated with the reels.

Referring to Figs. 1 .to 4 for a more detailed description of the preferred embodiment of my inventionfthe crossbear'n 24 is made up of two

sections

66 and 64. A plate 66 is secured to the end of the section 62 of the beam in anysuitable manner, such as by welding, and the plate 66 is secured tome and of the beam section 64 in a similar manner.. The-

plates

66 and 66 are 7 tensioning device may be employed with. mill stands having a considerable range of spacing between the opposing mill housings.

A bell crank 64 is secured to a shaft 66 which in turn is rotatably mounted on a bearing member 68, and which extends to, and is suitably supported upon, a corresponding bearing member (not shown) upon the opposite end of the beam 24 adjacent the mill housing 26. A roller is rotatably mounted on one end'of the bell crank 64, and this roller forms the contact member between the bell crank 64 and a pressure fluid operated actuator 12 therefor. The pressure fluid actuator I2. may be any suitable pressure fluid operated piston and cylinder arrangement, such as that shown diagrammatically in my above-referred-to Patent No. 2,189,609. A rod 14 connects the actuator 12 with

plate members

16 and 16 which engage the roller 16 on Opposite sides.

A bearing member in the form of a knife edge 66 is mounted upon the opposite end of the bell crank 64 to engage the link member 36, hereinbefore referred to, through a supportable hearing member upon the link member 66, as shown in Fig. 1. A suitable dashpot 62 may be provided to damp the motion of the bell crank 64 under the'infiuence of the actuator 12.

A crank having a bearing member similar to the bearing member 66 is suitably mounted for rotation with the shaft 66 on the opposite end of the shaft and cooperates with the link member 66 shown in Fig. 2 to support the other end of the tension roller 46.

In Fig. 3 there is shown the corresponding elements of the tension device 26 for actuating the tension roller 46. and similar reference characters have been applied to similar elements in Fig. 3 and in Figs. 1, 2 and 4. The tension device 26 is also shown in elevation and in plan view in Figs. 1 and 2. In Fig. 2, it may be seen that the shaft 66' is rotatably mounted on a suitable bearing support 64 on the opposite end of the beam 26 from the supporting bearing 66, and

64 rotatably mounted upon supporting brackets.

66 and 66, which in turn are suitably supported upon' the mill housings '26 and 26; respectively.

The roll 94 is rotated through its shaft I by a suitable dynamo-electric machine I02 shown in Fig. 5. The roll 92 may be an idling 'roll or may be driven by the machine I02 also by suitable gearing connecting the

rolls

92 and 84.

Referring now to Fig. 5 for a description of the controls for a single stand mill embodying'the the reel 22 is connected by means of the shaft I04 to a suitable dynamo-electric machine I06. An idling roller I08 is suitably mounted between the puller I8 and the reel 22, so that the strip I4 may always be held in a predetermined relation with the tension roll 46. Tensioning devices I0 and 20 similar to tensioning devices I0 and 20 are situated on the other side of the roll stand I6 and actuate tensioning rolls 40' and 46', respectively. A puller I8 operably connected with a dynamo-electric machine I02 is mounted in a position corresponding to the position of the puller I8 on the other side of the mill stand. A reel 22 operably connected with a dynamo-electric machine I06 is provided, and an idling or guide roll I08 is suitably mounted in a position similar to that of the guide roll I08. The machines I02, I02, I06 and I06 and the motor driving the reducing rolls are all connected by suitable controllers to a suitable source of power indicated by the conductors marked plus and minus The field winding of the machine I06 is suitably connected to a regulator,

. as indicated in Fig. 5, to be controlled in accordance with the degree of deflection of the strip I4 by the tensioning device 20 in a manner described in detail in my above-named patent. In a like manner, the motor I02 is controlled by the regulator actuated by the tensioning device I0, and the motors I02 and I06 are controlled by the regulators connected to be actuated by the tensioning devices I0 and 20', respectively.

In the operation of the, mill shown in Fig. 5, assuming that the reel 22 is acting as a winding reel and that the reel 22' is acting as the unwinding reel for the strip I4, and the rolls of the mill are being driven in a direction indicated by the arrows, then the machines I02 and I06 will be acting as motors, and the machines I02 and I06 will be acting as generators to provide regenerative braking for the reel 22' and the puller I8. As the strip passes from the reel 22', the tension on the strip as it leaves the reel will be regulated by the tensioning device 20' through the regulator actuated by the-tensioning device 20 and acting upon the field winding of the dynamo-electric machine I06. At the same time, the back tension on the strip I4 at the roll stand will be maintained at a constant desired amount by the puller I8 through the control of the dynamo-electric machine I02 acting asa elements of structure shown in Figs. 1 through 4,

7 has tensioning equipment similar to that described in connection with Figs. 1 through 5. In

this system, the tensioning devices I0 and andthe puller -I8 are'mounted on one side of one roll stand 48, and corresponding tension devices I 0' and 20 and puller-I8 are mounted onthe opposite side of the roll stand 50. Front and back tensions are maintained on the strip I4 by a tensioning device 52, which is similar to the tensioning devices I0 and 20, and employs the principles described in detail in my above-mentioned patent. The tensioning device 52 comprises a shaft 66' with one of its ends pivotally mounted on a suitable bearing 68' which in turn is mounted on a crossbeam 30, these elements having similar reference characters as in Figs. 1 through 4. The actuator 12' for the tensioning device 52 is mounted upon a plate member I09 which may be suitably mounted upon the outside generator by the regulator operated by the tensioning device I0. Front tension on the strip I4 as it leaves the rolls of the roll stand I6 will be provided by'the puller I8, and this tension will be maintained at the substantially constant desired amount by means of the field control of the dynamo-electric machine I02 acting as a motor through the regulator operatively con- The two stand temper pass mill of Figs. Band of the mill housing of the roll stand 50. The actuator I2 operates through a roller I0 to actuate a crank IIO which is suitably secured to the shaft 66'. A tensioning roller H2 is suitably mounted upon crank member H4 and a similar crank member cooperating with the other end of the tension roll II2, both of the crank members being secured for rotation with the shaft 66. The tensioning device 52 controls the field current of the driving motor for the rolls of the roll stand 48, as indicated in Fig. 7, in a'mannersimilar to that described in connection with the control diagram of Fig. 5.

In the operation of the system of Fig. 7, assuming that the strip I4 is'passing throughthe mill from reel 22 to reel'22, the tensioning devices 20 and I0 will operate through the dynamo-electric machines I08 and I02, respectively, to maintain reeling tension and back tension on the strip I4, as described in connection with the system of Fig. 5. Front tension at the roll stand 50 and back tension at the roll stand 48 will be controlled by the tensioning device 52 which will act through its associated regulator upon the driving motor for the rolls of the roll stand 48 as indicated. The tensioning devices I0 and 20 and the puller I8 will cooperate as described in the discussion of the system of Fig. 5 to maintain a predetermined front tension upon the strip I4 at the roll stand'48 and a predetermined rolling tension on the strip at the reel 22.

In Figs. 8 and 9 are shown the adaptation of the tensioning device I0 to a reversible mill wherein the tensioning device I0 and a similar tensioning device I0 are employed to provide reeling and unreeling tensions on the strip I4 and corresponding front and back tensions on the strip as it passes between the rolls of roll stand II6. upon the mill housings in the manner described in detail in connection with Figs. 1, 2 and 4, and cooperate in the manner indicated in Fig. 1 with the dynamo-electric machines I06 and I06 through the regulators associated with thetensioning devices to so control the power supplied to the reels by the dynamo-electric machines I06 and I06 as to maintain the desired tension upon the strip I 4.

In connection with this control system, it is to be understood that the

reels

22 and 22 mayact as either winding or unwinding reels as the mill is reversed and the strip is run through the mill in the art to operate the dynamo-electric chines I06 and I 06' either as motors or gen- The tension devices I0 and I0 are mountederators depending upon the direction of travel of the strip through the mill, and, therefore, upon whether or not the strip is to be subjected to a pull or a drag by the

reels

22 and 22'. l

' It will be noted that in each of these types of mills to which the tensioning devices Ill and are applied, the instrumentalities already existing on the mill, such as the reels 2! and 22' and the pullers l8 and i8 and the guide rolls H8 and H8, are so situated as to leave little room for the tensioning devices. The novel construction of the tensioning devices I0 and 20, whereby the operating members of the devices may be mounted well above the pass line of the mills where they will not obstruct movements of the mill operator, permits the installation of tensioning devices upon already existing strip rolling mills which have such instrumentalities as the pullers and reels closely spaced, without undue crowding of the equipment at the pass line. is particularlyto be noted that only the tensioning rolls and the two supporting links for each of the rolls extend into the pass line area,-and that these are of such dimensions as to require very little space, thus leaving the pass line area practically unobstructed.

It is to be understood that any of the systems discussed hereinbefore may be operated as re 'versible mills by suitable control of the dynamoelectric machines connected with the reels, the 0 mill rolls, and the pullers to operate them as .either motors or generators as the direction of pass of the strip through the mill requires.

It will be seen that I have provided an automatic strip tensioning system for strip rolling mills which may be readily adapted to, and installed upon, any of the several types of strip rolling mills which shall function to subject the tion. It is to be understood, however, that the invention is not limited to the precise construc tions shown and described, but is capable of modiiicationby one skilled in the art, the embodiments herein shown being merely illustrative of the principles of my invention.

I claim as my invention:

1. In a tensioning device for a strip rolling mill, a tensioning roller disposed to bear against the strip as it passes through the mill to deflect the strip, from its normal pass line and thus subject the strip to tension, an operating mechanism for causing said roller to bear against the strip, means mounting said operating mechanism on the mill housing above and substantially spaced from the strip, and link means operatively connecting said operating mechanism with said tensioning roller.

2. In.a tensioning device for a strip rolling mill, a tensioning roller disposed to bear against the strip as it passes through the mill to deflect the strip from its normal pass line and thus subject the strip to tension, an operating mechanism for causing said roller to bear against the strip,

a cross-member extendingbetween and mounted operatively connecting said operating mechanism with said tensioning roller.

3. In a tensioning device for a strip rolling mill, a tensioning roller disposed to bear against the strip as it passes through the mill to deflect the strip from its normal pass line and thus subject thestrip to tension, 9, cross-member extending between and mounted upon the housings of the mill above and substantially spaced from r the strip 'as it passes through the mill, an operating mechanism for causing said roller to bear against the strip comprising a shaft extending substantially parallel to said cross-member,

means pivotally mounting said shaft for rotation about its axis on said cross-member, crank means securedto said shaft for rotation therewith, link means operatively connecting said crank means with said tensioning roller, and means for actusaid tensioning roller, and means for causing pivotal movement of said crank means to thereby cause said tensioning roller to bear against the strip.

5. In a tensioning device for a strip rolling mill, bracket means mounted upon the adjacent mill housings above and substantially spaced from the normal strip pass line, a cross-member extending between and mounted upon said bracket means, a shaft member, means pivotally mounting said shaft member parallel to and upon said cross-member, a bell crank secured to said shaft whereby the shaft serves as a pivot for the bell crank, aforce applying means, means mounting said force applying means on one ofthe mill housings in operative relation with one arm of said bell crank, alever mounted on the shaft for rotation therewith, a tensioning roller disposed to bear against the strip as it passes throlmh the mill to deflect the strip from its normal pass line and thus subject the strip to tension, and

link means operatively connecting said tensioning roller with said lever and said bell crank.

6. In a tensioning device for a strip rolling mill, bracket means mounted upon the adjacent mill housings above and substantially spaced from the normal strip pass line, a cross-member extending between and mounted upon said bracket means, a shaft member, means pivotally mounting said shaft member parallel to and upon said cross-member, a bell crank secured to said shaft whereby the shaft serves as a pivot for the bell 'crank, a force applying means, means mounting said force applying means on said cross-member in operative relation with one arm of said bell crank, a lever mounted on .the shaft for rotation therewith, a tensioning roller disposed to bear against the strip as it passes through the mill to deflect the strip from its normal pass line and thus subject the strip to tension, and link means operatively connecting said tensioning roller with said lever and said bell crank.

7. In a strip tensioning device for a strip rolling mill, a tensioning roller disposed to bear against and transmit a transverse force to the strip as it passes through the mill and thus subject the strip to tension, an operating mechanism disposed above and substantially spaced from the normal pass line of the strip and operatively connected with said tensioning roller to cause the roller .to bear against the strip, and mounting means for said operating mechanism comprising a bracket member, a beam member secured to and extending outwardly from each of the opposite sides of the bracket member, and means mounting the outwardly extending ends of said beam members on the housings of the mill.

8. In a strip tensioning device for a strip rolling mill, a tensioning roller disposed to bear against and subject the strip to a transverse force as it passes through the mill and thus subject the strip to tension, an operating mechanism disposed above and substantially spaced from the normal pass line of the strip and operatively connected with said tensioning roller to cause the roller to bear against the strip, and mounting means for said operating mechanism comprising a bracket extending from each of the opposing sides of the mill housings toward the opposite mill housing, a beam member extending between said brackets, and means for adjustably securing said beam member to said brackets, the length of said beam member and the degree of the extent of the brackets from their respective mill housings toward the other mill housings being such as to enable said operating mechanism mounting means to be applied to roll stands of different spacings between mill housings.

9. In a strip tensioning system for a single stand reversible strip rolling mill, in combination, a strip reel disposed on each side of the mill, a dynamo-electric machine mechanically connected in operative relation with each of said reels, a strip puller disposed between the mill and each of the reels to thereby provide both front and back rolling tension regardless of the direction of pass, a dynamo-electric machine mechanically connected in operative relation with each of said reels, a first pair of strip tensioning devices one disposed to act on the strip between each of said strip pullers and the mill rolls, con trol means whereby each of said first tensioning devices controls the dynamo-electric machine associated with its adjacent strip puller to maintain substantially constant front and back tensions on the strip at the reducing rolls of the mill, a second pair of strip tensioning devices one disposed to act on the strip between each of said strip pullers and its adjacent reel, control means whereby each of said second tensioning devices controls the dynamo-electric machine associated with its adjacent reel to maintain substantially cioristant winding and unwinding tensions on' the s r p.

10. In .a strip tensioning system for a tandem reversible'strip rolling mill, a strip reel disposed beyond each of the end stands of the mill, a dynamo-electric machine mechanically connected in operative relation with each of said reels, a strip puller disposed between each of the reels and its adjacent roll stand to thereby provide both front and back rolling tension regardless of the direction of pass, a dynamo-electric machine mechanically connected in operative relation with each of said strip pullers, a first pair of strip first strip tensioning devices controls the dynamo-electric machine associated with its adjacent reel to maintain substantially constant winding and unwinding tensions on the strip, a second pair of strip tensioning devices one disposed to act upon the strip between each of said strip pullers and the rolls of its adjacent roll stand, control means whereby each of said second strip tensioning devices controls the dynamo-electric machine associated with its adjacent strip pulller to maintain the desired back and front tensions on the strip at the rolls of the first and last roll stands respectively, a strip tensioning device disposed to act on the strip between each adjacent pair of roll stands of the mill, and control means whereby each of said last named tensioning devicescontrols the driving motor for an adjacent roll stand to maintain the desired tension on the strip between each adjacent pair of roll stands.

11. In a tension control system for a strip rolling mill, in combination, a strip reel adjacent the mill, a strip puller disposed to act on the strip between the reel and the mill rolls, first and second tensioning devices, said tensioning devices comprising a tensioning roller disposed to bear against the strip to deflect the strip from its normal pass line and thus subject the strip to tension, an operating mechanism for causing said roller to bear against the strip disposed above and substantially spaced from the strip and link means operatively connecting said operating mechanism with said tensioning roller; the tensioning roller of said first tensioning device being disposed to bear upon the strip between said reel and said puller, bracket means extending outwardly from the sides of the mill housings toward said reel above and substantially spaced from the strip,-and means mounting said operating mechanism for said first tensioning device upon said bracket; the tensioning roller of said second tensioning device being disposed to bear upon thestrip between said puller and the mill rolls, inwardly extending bracket means mounted on opposing sides of the mill housing above and substantially spaced from the strip, and means mounting said operating mechaanism on said inwardly extending bracket means.

12. In a tension control system for a strip rolling mill, in combination, a strip reel adjacent the mill, a strip puller disposed to act on the strip between the reel and the mill rolls, first and second tensioning devices, said tensioning devices comprising a tensioning roller disposed to bear against the strip to deflect the strip from its normal pass line and thus subject the strip to tension, an operating mechanism for causing said roller to bear against the strip disposed above and substantially spaced from the strip and link means operatively connecting said operating mechanism with said tensioning roller; the tensioning rollerof said first tensioning device being disposed to bear upon the strip between said reel and said puller, bracket means extending outwardly from the sides of the mill housings toward said reel above and substantially spaced electric machine nperatively connected with said reel. control means whereby said first tensioning device controls the operation of said first dynamo-electric machine thereby controlling the tension to which the strip is subjected between said reel and said puller, a second dynamo-electric machine operatively connected with said puller,

and control means whereby said second tensioning device controls the operation of said second dynamo-electric machine thereby controlling the tension to which the strip is subjected between 5 said puller and the mill rolls.

GERHARD P. LEssMANN.