US2195009A

US2195009A - Tensioning device

Info

Publication number: US2195009A
Application number: US210194A
Authority: US
Inventors: Gerhard P Lessmann; Glenn E Stoltz; Alonzo F Kenyon
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1938-05-26
Filing date: 1938-05-26
Publication date: 1940-03-26
Anticipated expiration: 1957-03-26

Description

TENS IONING DEVICE Filed May 26, 1958 4 Sheets-Sheet 1' r EL f -32%;: Raga/afar? fiom Mill WlfNESSES: INVENTORS Gerhard PLessma/m, G/e/m E. Jfo/fz M and Alonzo I. 19/1 00.

Mar h 26,1940. G. P. LESSMANNf ml. 2,195 009 mnnslonm DEVICE Filed may 2a, 1938 4 Sheets-Sheet 2 WITNESSES: INVENTORS 5 If f 54 Ger/mrdPLessmann, lennEJfo/fz,

' and 14/020 E/fenyon.

March 26, 1940. P, LESSMANN AL 2,195,009

TENSIONING DEVICE File d May 26, 1938 4 Sheets-Sheet Z6 Reserm/k J.

Raga/afar:

Air Reservoir:

Confrol/er. Confro/len Confro/lex WITNESSES: INVENTORS Ger/rardPLessmarm, Glen/1f. Sfolfz,

arch 26, 1940. s. P. LESSMANN El AL, 2'195'009 TENSIONING DEVICE Filed May 26, 1938 4 Sheets-Sheet 4 Regulalor anfml/ek (on/reflex Camm/len I v I v j WITNESSES: I INVENTORS Gerhard I? Lemma/m, Glenn 5. Jfa/fz,

%f A I and 14/0/7205 heny.

Patented Mar. 26, 1940 TEN SIONING DEVICE Gerhard P. Lessmann, Forest Hills, Glenn E. Stoltz, Pittsburgh, and Alonzo F. Kenyon, Wilkinsburg, Pa., assignors to Westinghouse Electric & Manufacturing Company, East Pitts burgh, Pa., a. corporation of Pennsylvania Application May 26, 1938, Serial No. 210,194 16 Claims. (Cl. 80-32) Our invention relates, generally, to tensioning devices, and more particularly toa device and system for maintaining predetermined tension on a strip of material as it passes through a work device.

It has been found desirable to keep both a front and a backv tension on strip material as it is passing through a reducing mill and systems have been provided for producing such strip tensions. In order to produce the desired results it is necessary that these tensions be under control and known -at all times. It is also necessary that there be some relation between these front and back tensions and the thickness, width and general physical characteristics of the strip material and degree of reduction of the strip at the roll stand where the tension is being applied.

The application of front tension on the strip at the last roll stand and back tension on the strip at the first roll stand by means of load regulation of the winding and unwinding reel motors has not been entirely satisfactory because of the diificulty of maintaining uniform tensions by this method and because of the necessity of maintaining much higher tensions at the reducing rolls than is desirable on the winding and unwinding reels.

The object of our invention is to provide a tensioning device for a strip rolling mill which shall function to produce a predetermined controlled and known tension on a strip of material as it is passed through the-reducing rolls and which shall function to permit a difference in the tension on the strip as it enters and leaves the tensioning device.

A further object of the invention is to provide a system of tension regulation which shall act upon a strip of material while it is between a roll stand and the winding or'unwinding reel and which shall function to maintain a much higher tension on the strip as it is engaged by the reducing rolls than. is maintained by the winding or unwinding reels.

These and other objects and advantages of 5 the invention will be apparent from the following detailed description taken in connection with the accompanying drawings, in which:

Figure 1 is a view, in side elevation, ofthe preferred embodiment of our invention,

Fig. 2 is a sectional view taken along line II-II of Fig. 1,

Fig. 3 is a diagrammatic illustration of a tensioning control system showing the operation of the device of our invention in providing controlled and known tension on a strip of material at a roll stand and controlled and known tension on the strip as it is wound on a reel, and

Fig. 4 is a diagrammatic illustration of a modification of the system shown in Fig. 3, in which the tensioning motors are controlled in response to the tensions on the strip.

In practicing our invention we provide a movable or floating frame which may be mounted on rollers for horizontal movement in a fixed main frame and supporting substantially vertically spaced tensioning rolls. The tensioning rolls are geared to a motor which is also mounted on the floating frame or which may be flexibly coupled to the rolls to permit movement of the .from the mill reducing rolls on a substantially horizontal line, and the other functions to guide the, strip off of the lower roller on a substantially horizontal line as the strip passes to the winding reel. Controlled and known forces are applied to the floating frame along the horizontal lines on which the stripenters and leaves the pair of tensioning rolls, by means of fluid pressure operated pistons acting through levers and controlled by fluid pressure.regulators, and the" desired tensions on the strip are maintained by means of regulators which "govern'the reel. motor and tensioning roll motor in response to the. horizontal movement or displacement of the floating frame which carries the tensioning rolls.

In a modification of the system, the reel motor and the tension roll motor are controlled in response to the tensions on the strip in the two directions.

Referring to Figs. 1 and 2 of the drawings, the tensioning device may comprise a fixed frame 6 provided with end openings so that a strip of material 8 may pass therethrough and with a central cavity in which a movable or floating frame I 0 may be mounted on rollers l2 which roll upon tracks M on the fixed frame 6. Any other suitable mounting may be utilized for the frame l0.

.A pair of tensioning rollers l6 and I8 are rotatably mounted in the frame I 0, as shown, and are geared together by

gear wheels

20 and 22. The tensioning roller I6 is driven by a motor 24 through pinion 26 and gear wheel 28. Apair of

idling rollers

30 and 32 are rotatably mounted in the fixed frame 6 and are so positioned as to guide the strip 8 onto the tensioning roller l6 and off the tensioning roller lax-in such manner as to maintain a constant angular relation of the strip 8 with these tensioning rollers. To maintain this angle, the guide roll 36 is positioned above the line from the top of tensioning roll IE to the pass line of the rolls of the mill and the guide roll 32 is positioned below the line from the lower side of the tensioning roll l8 to the largest diameter of the winding reel, so that the strip 8 will always engage the

guide rollers

30 and 32.

A pair of vertically disposed lever arms 34 is pivoted on the fixed frame 6 on one side of the tensioning rolls, as shown, and these arms are connected together at their upper ends by a bar or rod 38 above the frame 6. A pair of similar lever arms 46 is also pivoted on the main frame on the opposite side of the tensioning rolls and interconnected below the frame 6 by a bar 42. A pair of lugs 44 is secured to and extends laterally beyond the movable frame l0 and each have a bearing edge, as shown,- engaging the pair of levers 34. A similar pair of lugs 46 is secured to the opposite side of the movable frame l6 and extends laterally beyond the frame to engage the pair of lever arms 40. The points of engagement of these pairs of lugs with their associated levers lie in the plane of the strip as the strip passes between the guide roll 30 and the tensioning roll I6 and between the tensioning roll I 8 and the guide roll 32, respectively, so that the reactions on the frame l0 caused by the tension applied to the strip by the tension rolls l6 and I8 as they are driven by motor 24 and the tension on the strip as it is wound by the reel will be transmitted to the lever systems in the, line. of these tensions through the sets of

lugs

44 and 46.

An air' cylinder 48 is mounted at the top of the frame 6 and has a piston 50 movable therein to actuate a piston rod 52 which is pivotally connected to the cross bar 38. A similar cylinder 54 is mounted at the bottom of the fixed frame 6 and has a piston 56 which is connected to the cross bar 42 through the piston rod 58. Compressed air is conducted to the

cylinders

48 and 54 by

fluid conducting pipes

68 and 62, respectively. A regulator 63, the details of which will be described hereinafter, is positioned to be operated by the movement of the piston rod 52 on top i of the fixed frame 6 and a similar regulator 65 is positioned below the frame 6 to be actuated by the piston rod 58.

In Fig.3 there is shown diagrammatically a system by which the tensioning device shown in Figs. 1 and 2 maybe made to provide constant or controlled and known tensions'upon a strip of material as it is received from a rolling mill and as it is wound on a winding reel. The parts of the tensioning device are shown diagrammatically in Fig. 3, the parts having the same operative relation and being designated by the same reference characters as in Figs. 1 and 2. The rolling mill is shown at 68 and is driven by a motor 10 energized from a suitable source of direct current power, as shown. A winding reel 12 is shown receiving the strip 8- from the tensioning rolls and is driven by a motor I4which is energized from any suitable source of power, as shown. The field winding 16 of the reel motor is connected through the regulator 65, as indicated,

which functions to so govern the current in the field winding 16 as to increase the speed of the motor 14 and to, therefore, increase the torque exerted on the strip 8 by the winding reel 12 when the reaction of the frame l6 through the lug 46 on the lever 40, decreases below a predee termined amount and to decrease the speed of the motor 14 when this reaction increases above a predetermined amount. The regulator 63 governed by the positioning of the piston 56 and actuated by the piston rod 52 controls the current in the field winding" 18 of the tensioning motor 24 whenever the reaction on the frame ID by the tension between the tensioning device and the mill varies from a predetermined amount. The action of the

regulators

63 and 65 to govern the speeds of the motors 24 and 14' as described, and the action of the

pressure regulating valves

64 and 66 to maintain controlled air pressure on the

pistons

56 and 56, as discussed, is fully explained in the copending application of Mr. G. P. Lessmann, Serial No. 133,419, filed March 27, 1937, now Patent No. 2,189,609 issued February 6, 1940, and reference is made to that patent for the detailed description of these devices.v The cylinder 54 is connected by a fluid conductor 62 to a pressure regulating valve 64 which functions to provide a predetermined adjustable constant air pressure in the cylinder 54 and a similar valve 66 functions to provide a controlled predetermined pressure in the cylinder 48.

In the operation of the system shown in Fig. 3, with a constant pressure on the piston 50, it will be seen that the motor 24 will be so controlled by the regulator 63 as to maintain such a tension on the strip 8 as it leaves the mill 68 as will maintain the lever 34 in a substantially fixed position. If now for any reason some slack should occur between the tensioning roll l6 and the mill 68, the constant pressure behind the piston 50 will, cause the piston to move the frame which, in turn, will so actuate the regulator 63 as to increase the speed of the motor 24 and this increase will regain the desired tension on the strip 8. The regulator 65 connected with the field winding I6 of the reel motor 14 will function in a similar manner to maintain a constant tension on the strip 8 between the reel 12 and the tensioning roll I 8. The rheostats 61 and 69 shown .connected in circuit with the adjusting solenoidsof the regulating

valves

64 and 66, and the adjustable rheostats H and I3 shown in circuit with the

field windings

16 and 18 of the reel motor 14 and the tensioning'motor 24, may be adjusted to provide any desired normal tension on the strip as it enters the tensioning device and as it is wound on the reel. In Fig. 4 of the drawings there is shown a diagrammatic illustration of a tensioning device having most of the elements of the tensioning device shown in Figs. 1, 2'and 3 but having a different form of regulator operated thereby. In this tensioning device, instead of governing the speeds of the tensioning motor 24 and the winding reel motor 14 as described in connection with Figs. 1, 2 and 3, the lugs.44 and 46 are disposed to -ngagestrain gages and 82, respectively. These strain gages may be of any suitable type which will accurately measure the force applied to them and which will govern a circuit in accordance with the force applied to them through 'the

lugs

44 and 46 on the movable frame I. The gages 80 and 82 may be spring gages controlling the resistance in a circuit including the

conductors

84 and 86 and 88 and 98, respectively, and 'may take the form of magnetostrictive strain gages. These gages are connected through any suitable regulator as indicated to control the flow of current in the field windings l6 and 18 of the reel motor 14 and the tensioning motors 24, respectively. These regulators may take the form of the regulators indicated in Fig. 3 of the drawings, the strain gauge actuating the contact supporting arms of the regulators shown as actuated by the

piston rods

52 and 58 in Fig. 3.

In the operation of the system of Fig. 4, when the tension on the strip 8 between the mill 68 and the tensioning roller l6 increases for any reason, the strain gage 80 will respond to this increase in the reaction on the movable frame l0 and will act through the regulator 'l'! to increase the current 'fiow in the field winding 18 of motor 24 to thus tend to decrease the speed of the motor 24 and to decrease the torque transmitted to the tensioning roll l6, and, in like manner, a

, decrease in the tension on the strip 8 will tend to increase the speed of the motor 24 to thus again restore the tension on the strip 8. In a like manner the field current of the winding reel motor 14 is governed through the regulator 19 by the reaction of the frame 10 upon the strain gage 82 to maintain a constant tension on the strip 8 between the reel 12 and the tensioning roll l8.

It will be seen that the systems shown in Figs. 3 and 4 will also operate to maintain the desired tension on the strip 8 when the strip is moving in the opposite direction, that is, when the strip is being unwound from reel 12 and is being fed to the mill 68. With the strip moving in this direction, the reel motor 14 and the tensioning motor 24 will act as a regenerative brake and the amount of braking provided by these motors and, therefore, the tension on the two parts of the strip 8'will be governed through the regulating systems described which will control the field excitation of these motors. It is also to be understood that this tensioning device may be used between two adjacent roll stands of a tandem strip rolling mill where it is desired to subject the strip to one predetermined tension as it leaves one roll stand and to another predetermined tension as it enters the other. With the systems used in this manner the driving motor for one of the reducing roll stands may be controlled by the regulating devices shown and described in Figs. 3 and 4 in the same manner as the winding reel motor is controlled to maintain a constant tension on the strip between the tensioning roll I8 and the reducing roll stand which is ahead of the tensioning device. Where the tensioning device is used between two adjacent roll stands, the tensioning motor 24 may be used as a driving motor for the two rolls I6 and I8 or as a braking generator for these tensioning rolls depending upon which side of the tensioning device the greater tension on the strip 8 is desired.

It is to be understood that any equivalent elements may be substituted for the regulators herein described. It will be seen that wehave provided a tensioning device and a control system therefor which will act to maintain any desired predetermined tensions on a strip of material as it passes through the device and which will maintain diiferent tensions on the material on the two sides of the device and which is simple in construction and inexpensive to install, operate and maintain.

In compliance with the requirements of the patent statutes, we have shown and described herein the preferred embodiments of our invention. It is to be understood, however, that the "invention'is not limited to the precise constructions shown and described but is capable of modification by one skilled in the art, the embodiments herein shown being merely illustrative of the principles of our invention.

We claim as our invention:

1. In a tensioning device for producing tension on a strip of material as it passes between a first work device and a second work device, a frame mounted for free movement and positioned between the work devices, a plurality of rolls mounted on said frame including a first roll so mounted as to permit the strip to pass over it as the strip extends between the first work device and said first roll and a second roll so mounted as to permit the strip to pass over it as the strip extends between said second roll and the second work device, a first dynamo-electric machine connected in driving relation with said plurality of rolls, a second dynamo-electric machine connected in driving relation with the second work device, means for maintaining a first predetermined adjustable constant force on said frame in the tangential plane of the strip as it passes over said first roll and extends between the first work device and said first roll, means for maintaining a second predetermined adjustable constant force on said frame in the tangential plane of the strip as it passes over said second roll and extends between said second roll and the second work device, means responsive to the displacement of said frame in the line of said first-force for controlling the transfer of energy between said first dynamo-electric machine and said plurality of rolls, and means responsive to the displacement of said frame in the line of said second force for controlling the transfer of energy between said second dynamo-electric machine and. said second work device.

2. In a tensioning device for producing tension on a strip of material as it passes between a first work device and a second work device, a frame mounted for free movement and positioned between the work devices, a plurality of rolls mounted on said frame including a first roll so mounted as to permit the strip to pass over it as the strip extends between the first work device and said first roll and a second roll so mounted as to permit the strip to pass over it as the strip extends between said second roll and the second work device, a first dynamo-electric machine connected in driving relation with said plurality of rolls, a second dynamo-electric machine connected in driving relation with the second work a second predetermined constant force on said frame in the tangential plane of the strip as it passes over said second roll and extends between said second roll and the second work device, means responsive to the displacement of said frame in the line of said first force for controlling the transfer of energy between said first dynamoelectric machine and said plurality of rolls, and means responsive to the displacement of said frame in the line of said second force for controlling the transfer of energy between said second dynamo-electric machine and said second work device, each of said force maintaining means" comprising a fiuid pressure operated piston and means for maintaining an adjustable constant fluid pressure on said piston.

' 3. In a tensioning device for producing tension on a strip of material as it passes between .av

first work device and a ,second work device, a frame mounted for free movement and positioned between the work devices, a plurality of rolls mounted on said, frame including a first roll so mounted as to permit the strip to pass over it as the stripextends between-the first work device and said first roll and a second roll so mounted as to permit the strip topass over it as the strip extends between said second roll and the second work device, a first dynamo-electric machine connected in driving relation with said plurality of rolls, a second dynamo-electric machine connected in driving relation with the second work device, means for maintaining a first predetermined constant force on said frame in the tangential plane of the strip as it passes over said first roll and extends between the first work device and said first roll, means for maintaining a second predetermined constant force on said frame in the tangential plane of the strip as it passes over said second roll and extends between said second roll and the second work device, means responsive to the displacement of said frame in the lineof said first force for controlling the transfer of energy between said first dynamo-electric machine and said plurality of rolls, and means responsive to the displacement of said frame in the line of said second force for controlling the transfer of energy between said second dynamo-electric machine and said second work device, each of said energy transfer controlling means comprising a regulator connected to control the excitation of a separate one of said dynamo-electric machines.'

4. In a tensioning device for producing a predetermined tension on a strip of material as it passes through a work device which engages the strip, a frame mounted for free movement, roll means over which the strip passes in a partial wrap to apply a force to the strip by frictional engagement therewith as the strip moves between said roll means and the work device, a dynamoelectric machine connected in driving relation with said roll means, means for applying a substantially constant force to said frame in opposition to the force between said roll means and said strip and in the tangential plane of the strip as it engages said roll means and extends between the work device and said roll means, and means responsive to movement of said frame in the line of said forces for controlling the transfer of energy between said dynamo-electric machine and said roll means.

5. In a tensioning device for producing a predetermined tension on a strip of material as it passes through a work device which engages the strip, a frame mounted for free movement, roll means over which the strip passes in a partial wrap to apply a force to the strip by frictional engagement therewith as the strip moves between said roll means and the work device, a dynamoelectric machine connected in driving relation with said roll means, means for applying a substantially constant force to said frame in opposition to the force between said roll means and said strip and in the tangential plane of the strip as it engages said roll means and extends between the work device and said roll means, and means responsive to movement of said frame in the line of said forces for controlling the transfer of energy between said dynamo-electric machine and said roll means, said means for applying said opposition force comprising a fluid pressure operated piston and means for maintaining a substantially constant fluid pressure on said piston.

6. In a tensioning device forproducing a predetermined tension on a strip of material as it passes through a work devce which engages the strip, a frame mounted for free movement, roll means over which the strip passes in a partial wrap to apply a force to the strip by frictional engagement therewith as the strip moves between said roll means and the work device, a dynamoelectric machine connected in driving relation with said roll means, means for applying a substantially constant force to said frame in opposition to the force between said roll means and said strip and in the tangential plane of the strip as it engages said roll means and extends between the work device and said roll means, and means responsive to movement of said frame in the line of said forces for controlling the transfer of energy between said dynamo-electric machine and said roll means, said energy transfer controlling means comprising a regulator for controlling the excitation of said dynamo-electric machine in accordance with the displacement of said frame from a predetermined position.

7. In a tensioning device for producing tension on a strip of material as it passes from a work device to a winding reel, a frame mounted for free movement and positioned between the work device and the winding reel, a pair of spaced rolls mounted on said frame and having the strip extending from the work device over one of said rolls and to and over the other of said rolls and to the winding reel, an electric motor connected to drive said rolls, an electric motor connected to drive said winding reel, means applying a first predetermined substantially constant force on said frame in opposition to and in the line of the force applied to the strip by the rolls as the strip engages said one roll, means responsive to the movement of said frame in the line of said first force for controlling the torque applied to the strip through said rolls by said roll driving motor, means applying a second predetermined substantially constant force on said frame in opposition to and in the line of the force applied to the strip by the winding reel as the strip passes oversaid other roll and to the winding reel, and means responsive to movement of said frame in the line of said second force for controlling the torque applied to the strip through said winding reel by said reel driving motor.

8. In a tensioning device for producing tension on a strip of material as it passes from a reel to a work device, a frame mounted for free movement and positioned between the reel and the work device, a pair of spaced rolls mounted on said frame and having the strip extending from the reel over one of said rolls and to and over the other of said rolls and to the work device, a first dynamo-electric machine connected to be driven by said rolls as a braking generator, a second dynamo-electric machine connected to be driven by the reel as a braking generator, means applying a first predetermined substantially constant force on said frame in opposition to and in the line of the force applied to the strip between the rolls and the work device as the strip travels over said one roll toward the work device, means responsive to the movement of said frame in the line of said first force for controlling the tension applied to the strip by said first dynamo-electric machine, means applying a second predetermined substantially constant force on said frame in opposition to and in the line of the force applied to the strip between the rolls and the reel as the strip travels from the reel and over said other roll, and means responsive to the movement of said frame in the line of said second force for controlling the tension applied to the strip by said second dynamo-electric machine.

9. In a strip tensioning device, a stationary frame, a second frame mounted for free movement in said stationary frame, a pair of vertically spaced rolls mounted in said second frame, guide means for maintaining a fixed tangential relation between a strip of material and the top of the upper one of said rolls, guide means for maintaining a fixed tangential relation between the strip of material and the bottom of the lower one of said rolls, energy translating means connected in driving relation with said rolls, and means restraining the motion of said second frame.

10. In a strip tensioning device, a stationary frame, a second frame mounted for free movement in said stationary frame, a pair of vertically spaced rolls mounted in said second frame, guide means for maintaining a fixed tangential relation between a strip of material and the top of the upper one of said rolls, guide means for maintaining a fixed tangential relation between the strip of material and the bottom of the lower one of said rolls, energy translating means connected in driving relation with said rolls, and means restraining the motion of said second frame, said restraining means comprising a first system of levers bearing on said second frame in the plane in which the strip is tangent to the. top of said upper roll and a second system of levers bearing on said second frame in the plane in which the strip is tangent to the bottom of the lower roll.

11. In a strip tensioning device, a stationary frame, a second frame mounted for free movement in said stationary frame, a pair of vertically spaced rolls mounted in said second frame, guide means for maintaining a fixed tangential relation between a strip of material and the top of the upper one of said rolls, guide means for maintaining a fixed'tangential relation between the strip of material and the bottom of the lower one of said rolls, energy translating means connected in driving relation with said rolls, and means restraining the motion of said second frame, said restraining means comprising a first system of levers bearing on said second frame in the plane in which the strip is tangent to the top of said upper roll and a second system of levers bearing on, said second frame in the plane'in which the strip is tangent to the bottom of the lower roll, means for maintaining a constant force on said first system of-levers, and means for maintaining a constant force on said second system of levers.

12. In a tensioning device for a tandem strip rolling mill, a frame mounted for free movement and positioned between adjacent roll stands of the tandem mill, a pair of spaced tensioning rolls mounted 'on said frame and having the strip extending from one roll stand over one of said tension rolls, to and over the other of said tension rolls, and to the other adjacent roll stand, a dynamo-electric machine connected in driving relation with said pair of tensioning rolls, an electric motor connected in driving relation with the reducing rolls of one of said roll stands, means applying a first substantially constant force on said frame in opposition to and in the line of the force applied to the strip as the strip engages said one tension roll and extends to an adjacent roll stand, means responsive to the movement of said framein the line of said first force for controlling the transfer of energy between said strip and said dynamo-electric machine through said tension rolls, means applying a second substantially constant force on said frame in opposition to and in the line of the force applied to the strip as the strip engages said other tension roll and extends to the other roll adjacent stand, and means responsive to the movement of same frame in the line of said second force for controlling the transfer of energy between said reducing roll motor and said strip.

13. In a tensioning device for producing tension on a stripof material'as it passes between a first work device and a second work device, a frame mounted for free movement and positioned between the work devices, a plurality of rolls mounted on said frame including a first roll so mounted as to permit the strip to pass over it as the strip extends between the first work device and said first roll and a second roll so mounted as to permit the strip to pass over it as the strip extends between said second roll and the second work device, a first dynamo-electric machine connected in driving relation with said plurality of rolls, a second dynamo-electric machine connected in driving relation with the second work device, a first means bearing on said frame in the tangential plane of the strip as it passes over said first roll and extends between the first work device and said first roll and restraining the movement of said frame in said plane, means responsive to the force on said first movement restraining means for controlling the transfer of energy between said first dynamo-electric machine and said plurality of rolls, a second means bearing on said frame in the tangential plane of the strip as it passes over said second roll and extends between the second work device and said second roll and restraining the movement of said frame in said plane, and means responsive to the force on said second movement restraining means for controlling the transfer of energy between said second dynamo-electric machine and said second work device.

14. In a strip tensioning device, a stationary frame, a second frame mounted for free movement-in said stationary frame, a pair of vertically spaced rolls mounted in said second frame, guide means for maintaining a fixed tangential relation between a strip of material and the top of the upper one of said rolls, guide means for maintaining a fixed tangential relation between the strip of material and the bottom of the lower one of said rolls, energy translating means connected in driving relation with said rolls, means restraining the motion of said second frame, said restraining means comprising a strain gage mounted to measure the restraining force, and means responsive to said strain gage for controlling the amount of energy transmitted between said rolls and said energy translating means.

15. In a strip tensioning device, a frame mounted for free movement, a pair of spaced rolls mounted in said frame, guide means for maintaining-a fixed tangential relation between a strip of material and one side of one of the rolls, guide means for maintaining a fixed tangential relation between the strip of material and the opposite side of the other one of said rolls, energy translating means connected in driving relation with said rolls, and means restraining the motion of said frame.

16. In a strip tensioning device, a frame mounted for free movement, a pair of spaced rolls mounted in said frame, guide means for maintaining a fixed tangential relation between a strip of material and one side of one of said rolls,

guide means for maintaining a fixed tangential relation between the strip of material and the opposite side of the other of said rolls, energy translating means connected in driving relation with said rolls, and means restraining the motion of said frame, said restraining means comprising GERHARD P. LESSMANN. GLENN E. STOL'IZ. ALONZO F. KENYON.