US3184938A

US3184938A - Methods and apparatus for automatical- ly threading strip rolling mills

Info

Publication number: US3184938A
Authority: US
Publication date: 1965-05-25
Anticipated expiration: 1982-05-25

Description

May 25, 1965 G. E. TERWILLIGER METHODS AND APPARATUS FOR AUTOMATICALLY THREADING STRIP ROLLING MILLS 3 Sheets-Sheet 1 Filed NOV. 28, 1961 George A: Emu/Wager fi/ls Attorney fr? ven or May 25, 1965 5. E. TERWILLlGER METHODS AND APPARATUS FOR AUTOMATICALLY THREADING STRIP ROLLING MILLS Sheets-Sheet 2 Filed Nov. 28, 1961 fr) vent'or' Gear M y 1965 s. E. TERWILLIGER 3,134,933

METHODS AND APPARATUS FOR AUTUMATICALLY THREADING STRIP ROLLING MILLS Filed Nov. 28, 1961 3 Sheets-Sheet 3 In en 60/" 6e or gfe ETrW/VQ'gJeP by 1 AM 4 M /7/.'s Attorney United States Patent Ofi Fice 3,184,938 Patented May 25, 1965 3,184,938 METHGDS AND APPARATUS FOR AUTOMATICAL- LY THREADING STRIP ROLLING MILLS George E. Terwiiiiger, Schenectady, N.Y., assignor to General Electric Company, a corporation of New York Filed Nov. 28, 1961, Ser. No. 155,408 18 Claims. (CI. 72-11) My invention relates to rolling mills of the type in which a strip of material is reduced in thickness by subjecting it to pressure at displaced points as the strip passes through the mill and, in particular, to methods and apparatus for rapidly and automatically threading material through such a mill.

It is customary in reducing the size of material such as strip steel, for example, to pass it through a cold rolling mill which comprises a series of rolls or pressure points arranged in tandem. At the present time it is customary to manually insert the front end of the strip into the first roll and guide it as it proceeds through the successive rolls until it reaches the final toll. Thereafter, the speed of rolling may be increased. Such a procedure is both time consuming and also requires unwanted handling of the material. It would be extremely desirable instead to have a system in which the strip can be physical transported between adjacent stands or rolls by means of tables or guides and for automatically steering the head end of the strip so that it enters each successive stand or roll on the center line thereof. One of the problems encountered in such a tandem rolling mill is the production of horizontal curvature in the strip caused by unequal percent reduction across the width of the strip which, in turn, may be caused by, for example, improper leveling of the mill, unequal pressures across the width of the rolls, improper lubrication, or unequal thickness of the strip material itself. Also, difiiculty is encountered during the final portion of the rolling operation when the strip becomes thin and flexible to provide vertical support for the strip and still prevent buckling of the strip as it is pushed along such support.

It is a prinpieal object of my invention to provide new and improved methods and apparatus for automatically threading a strip of material into a tandem cold mill.

it is still another object of my invention to provide new and improved methods and apparatus which permit rapid and automatic threading of strip material through a rolling mill while still preventing buckling of the material.

It is still another object of my invention to provide new and improved apparatus for automatically threading strip material through a tandem rolling mill in which the naterial is automatically centered between successive pressure points so that it advances substantially along the center line of the mill.

One of the features of my invention consists in sensing the position of the edge of a strip of material relative to the center line of the rolls of a tandem mill after it passes through a stand or pressure point and controlling the pressure on the edge of the strip at such a pressure point to produce centering of the strip so that it advances along the center line of the mill. In one embodiment, a plurality of sensors engage the edges of such a strip of material to produce voltages or signals which are added algebraically to provide means for controlling the pressure applied to the strip at a previous point in travel. In accordance with another feature of the invention, increased stiffness to the materialbeing reduced in thickness to inhibit its dropping below a desired horizontal plane is pro vided by exerting vertical forces on the strip material to produce a curvature of the material in a vertical plane through the material. As used herein, the term threading" means to pass the initial portion of strip material being reduced in thickness through or past the successive pressure points of a rolling mill from its entry end to its exit.

The invention, both as to its organization and operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in which FIGURE 1 is a schematic vertical view of a tandem rolling mill embodying my invention;

FiGURE 2 is a plan view of the mill of FIGURE 1 taken along the lines 2-2;

FIGURE 3 is a circuit diagram illustrating certain features of the invention;

FIGURE 4 illustrates one of the sensors used in the mill of FIGURE 1;

FIGURE 5 is a cross-section view of the material stiffening device employed in apparatus embodying my invention;

FIGURE 6 is a perspective view of an alternative material stiffening device;

FIGURES 7-9 are schematic drawings illustrating certain features of my invention; and

FIGURE 10 is a schematic drawing of a modification of the mill of FIGURE 1.

In FIGURE 1 there is shown a typical tandem rolling mill illustrated in this instance as comprising six stands, l d. Each stand conventionally comprises a frame 7 in which is supported a pair of working rolls 8 and 9 which exert pressure on a strip of material 10 whose thickness is to be reduced. The pressure upon the strip 10 is exerted by rolls 8 and 9 through backup rolls 11, 12 and a pressure exerting device, such as the screw 13, whose position is controlled by means of a motor 14.

In a typical mill of the type illustrated in FIGURES l and 2, the thickness of a strip of material 10 as it passes through the stands 1-6 is reduced each time it passes through a pressure point created by the opposed rolls 8, 9 of each stand. The amount of reduction in each stand is determined by the spacing between each pair of rolls 8, 9, these spacings being preset so that the strip of material 10 as it emerges from the mill after passing through the rolls of stand 6 is of a desired final thickness. In a mill of this type, it has been customary heretofore to initiate operation of the mill by manually threading or guiding the strip of material 10 through each of the successive stands. Such an operation is limited to relatively low threading speeds and is time consuming. In accordance with my invention, I provide means for performing this function automatically, allowing higher threading speeds and increased production.

In order to automatically guide a strip of material through the mill illustrated, I provide means for sensing the position of the edge of a strip relative to the center line of the mill after it has passed through a pressure point. Such a means is illustrated in FIGURES 1 and 2 as including three sets of two closely spaced pairs of rollers and carrying

arms

15, 16 and 17, 18 positioned at points spaced along the path of travel of the strip 10 and arranged to engage and be rotated by the opposite sides of the strip after it emerges from the engagement with the work rolls 8, 9 of each of the

stands

1, 2 and 3. As will be explained later in connection with the diagram shown in FIGURE 3, rotation of arms 15-18 is operative to sense the position of the edge of the strip relative to the center line of the mill and control subsequent lateral movement of the strip by controlling the pressure exerted by the work rolls 8, 9 of the preceding stand to produce a horizontal bending of the strip in a direction to guide it along the center line of the mill. Such bending is in a .1 direction to correct any horizontal curvature of the strip which may e caused, as it passes through the first several rolls of the mill, by either improper leveling of the mill, unequal pressures across the width of the rolls, or unequal thickness in the cross section of the entering strip material itself.

After the sensing means -18 have produced a corrective curvature in the horizontal position of the strip of material 10, the need for any additional corrective bend ing is determined by an additional pair of sensing means comprising rotatable arms 19, displaced from arms 15-18 along the path of travel of the strip 10. Through circuit arrangements to be described later, sensing means 19, 20 provide an additional corrective adjustment of the pressure across the width of the strip exerted by rolls 8, 9 of the preceding stand.

After a strip of material has been reduced in thickness by passing through several of the stands, it may become sutficiently thin that it exhibits a tendency to either droop below a desired horizontal position or buckle as it passes across supporting tables, not illustrated, conventionally employed to support the strip of material between successive later stands in the mill, such as, for example, stands 4, 5 and 5, 6. In order to PTcVCIli such undesired buckling of the strip, I provide means for exerting a vertical force on the strip to produce a curvature of the strip in a vertical plane and increase its stiffness in its direction of travel. The strip stiifening means in the case of the mill illustrated in FIGURES 1 and 2 comprises two sets of

retractable rollers

21, 22, 23.

Rollers

21, 22 positioned below the strip along opposite edges thereof and roller 23 positioned above the center of the strip, are movable in converging directions to engage the moving strip of material and cause it to bend to an arcuate shape in a vertical plane.

The schematic drawing of FIGURE 3 illustrates the operative connections between the sensing means 15-20 and the electrical circuits through which pressure is exerted on the moving strip. Each of the sensing means may comprise a pivoted arm which is connected through a pair of

gears

24, 25 to a variable rheostat. Rheostats 26. 27 associated with

arms

15, 16, respectively, are connected to a first amplifier 28. Rheostats 26, 27 are connected across a source of unidirectional voltage illustrated by conductors 29, 3t) and a grounded conductor 31. Thus, rheostat 26 is connected between

conductors

30, 31 to supply to amplifier 28 a voltage whose magnitude varies with the position of the left hand edge of strip 10 from the center line of the mill. Similarly, rheostat 27 supplies to the amplifier a voltage whose magnitude varies with variation of the right hand edge of strip 10 from the center line of the mill. A typical form of rheostat 26 is shown in FIGURE 4 in which one end of the rheostat is connected to ground and the other end connected to a point of supply voltage while the variable arm thereof provides an intermediate value of voltage which is supplied to amplifier 28.

With reference again to FIGURE 3, the

rotatable arms

17, 18 associated with the second set of sensors are connected through

similar gears

24, 25 to variable rheostats 32, 33. Rheostats 32, 33, in a manner similar to rheostats 26, 27, likewise supply to amplifier 28 a pair of voltages whose magnitudes vary respectively with the position of the left and right hand edges of strip 10 from the center line of the mill. Movement of arm 18 and, likewise, of arm 17 if desired, is etlective to close a pair of contacts 34, connected in the energizing circuit of relay 36 whose operation effects closure of

contacts

37, 38 connccted in circuit between the output of amplifier 28 and an amplifier 39. Energization of relay 36, likewise, closes

contacts

40, 41 connected between amplifier 39 and a control device 42. Device 42 may be, for example, a silicon controlled rectifier circuit or an amplidyne circuit which supplies excitation voltage to the

field windings

43, 44 ot a pair of direct current generators 45, 46. Generators 45,

46, in turn, supply operating potential to motors 14, 14' which control the rotation of screws 13, 13' and the pressure exerted through rolls 8 and 9 on strip material 10. As illustrated, motors 14, 14' effect rotation of worm drives 47, 47 which engage cooperating gears attached to the upper ends of

screws

13, 13.

Energization of relay 36 is effective also to open normally closed contacts 43, 49 connected in the circuit of a screw down control 50 in circuit between

conductors

29, 30, 31 and amplidyne control 42. Control 50 is adjusted at the beginning of each run of strip material to supply predetermined voltages to control 42 to obtain a desired pressure on strip 10 between rolls 8 and 9.

Associated with

arms

19 and 20 are a pair of

variable rheostats

51, 52 which supply, respectively, to an amplifier 53 voltages varying with the positions of the left hand and right hand edges of strip 10 from the center line of the mill at this point of its travel. The output of amplifier 53 is supplied through a peak holding circuit 54 to amplifier 39 to provide a voltage which is combined with the voltage supplied thereto from amplifier 28.

The operation of my apparatus for automatically threading a strip rolling mill may best be explained by reference to FIGURE 3 and FIGURES 79. As the strip material 10 emerges from one of the stands 1- 3, it first encounters the

rotatable arms

15, 16 which supply to amplifier 28 two voltages whose algebraic sum is indicative of the variation of the center line of the strip front the center line of the mill. The edges of the strip 19 next engage

arms

17, 18 whose rotation, likewise, supplies to amplifier 28 a second set of voltages whose algerbraic sum is indicative of the variation of the center line of the strip from the center line of the mill. Amplifier 28 is eflective to resolve the four voltages supplied thereto and provide through amplifier 39 to amplidyne 42 a control voltage varying with the distance between the center line of the strip and the center line of the mill. If the sum of the voltage supplied by rheostats 26, 27 is exactly equal in magnitude but of opposite polarity to the sum of the voltages supplied by

rheostats

32, 33, this condition indicates that while the center line of the strip is not exactly along the center line of the mill, nonetheless, there is no curvature in the horizontal direction of the head end of the strip. On the other hand, if these two voltages are not exactly equal, their algebraic sum varies in magnitude with the curvature of the front end of the strip. Accordingly, such a voltage is supplied to control device 42 to vary the excitation of the

fields

43, 44 of generators 45, 46. Preferably, these fields are poled in opposite directions so that the effect is to produce opposing changes in the output voltages of generators 45, 46. Supplying such opposite voltages to motors 14, 14 is effective to increase the pressure on one side of strip 10 and, simultaneously, decrease the pressure on the opposite side. The over-all effect is to produce a rapid variation in the pressure applied across the width of the pressure point defined by rolls 8, 9 and produce a decrease in thickness of one side of strip 10 and an increase in the opposite side so that the strip is elongated on one side to produce a strip that has no horizontal curvature and is travelling parallel to the mill center line.

The foregoing result is illustrated in FIGURES 7 and S in which strip 10, in emerging from the stand, has a horizontal curvature which directs it toward the bottom of the drawing as illustrated; i.e., toward the right of the center line of the mill. Contacting rolls 1548 produces a change in the pressure between the rolls 8, 9 of the preceding stand such that the strip cmerging from the rolls travels parallel to the mill center line. The strip emerging from the stand will continue to have no horizontal curvature until the head end of the strip engages

rolls

19, 20 as illustrated in FIGURE 8. Since the strip at this point has an initial section having horizontal curvature which is now directed to the right hand side of the center line of the mill, rotation of arms 19, by strip 10 is effective to operate

rheostats

51, 52 and amplifier 53 to provide to amplifier 39 a voltage which, when algebraically added to the voltage supplied from amplifier 28, provides a corrective voltage to control device 42 to again adjust the voltages across motors 14, 14'. The pressure across the rolls 8, 9 of the preceding stand is now readjusted to produce a horizontal curvature of the strip in a direction to direct the head end of the strip toward the center line of the mill so that by the time the head end of the strip reaches rolls 8, 9 of the next succeeding stand, its center line is substantially along the center line of the mill.

After the head end of the strip has entered the gap between the rolls 8, 9 of the next succeeding stand, I provide means for disabling the control circuits operating to vary the pressure on the strip at the preceding stand and to return that pressure to a desired preset value. This means comprises a pair of

contacts

55, 56 operating from a pressure responsive device 57 positioned below the bearing block 58 of the stand (not shown in FIG- URE 3) which the strip is now entering.

Contacts

55, 56 are connected in the circuit of relay 36 and when opened by entry of the strip into the gap between rolls 8, 9 of the next succeeding stand are effective to deenergize relay 36, thus opening

contacts

40, 41 and closing contacts 48, 49 and connecting the predetermined screw down control voltage supplied by control to control device 42 and reset the pressure on strip 10 to a desired value.

As explained previously, the circuits and controls described are duplicated between each set of

stands

1, 2, 2, 3, and 3, 4. Through operation of these circuits and controls, the strip 10 is automatically threaded through the first four stands of the mill. By the time it advances to this position in its travel through the mill, the strip is substantially aligned along the center line of the mill, and the pressures exerted on the strip through the first three stands are of a predetermined value established to provide uniform reduction of the thickness of the strip so that the strip is of a desired uniform thickness by the time it enters stand 4. At this point, however, the strip usually is sutficiently thin that it shows a tendency to droop if unsupported or buckle if it is slid along the supporting tables conventionally used between

stands

4, 5 and 5, 6. In order to prevent such buckling, the strip is curved in a vertical plane to increase its stillness in its direction of travel, Such stiffness in the case of the mill shown in FIGURES l and 2 is provided through operation of rollers 21-23 illustrated in FIGURE 5. Each of the rollers 2123 is carried on a rod 59 movable by means of a control 60. Preferably, the rods 59 of the respective rollers 21-23 move in converging direc tions so that roller 23 exerts a force vertically downward at the center of the strip 10 while

rollers

21, 22 engage the outer portions of the strip to bend these outer portions in an upward direction. Controls 60 may comprise either conventional hydraulic controls or may comprise solenoids operating through a contact arm 61 engaged by the strip 1i]. After the strip has advanced, for example, through the distance between

stands

4, 5 and enters stand 6, pressure switch 58 on stand 6 is operative to disable the stillness increasing apparatus between

stands

4 and 5. Similarly, operation of the strip stiffening means between

rolls

5 and 6 is effected when the strip engages contact 61 between

stands

5 and 6 and is discontinued when the strip enters stand 6.

Many well known alternative arrangements. for bending or bowing strip 10 to increase its stifiness are apparent. One such alternative form of strip stiffening means is illustrated in FIGURE 6 and comprises a supporting table 62 formed of a suitable material which will not scratch the strip, such, as, for example, a pair of separable maple blocks, and having an entry 63 therein which is adapted to receive the strip 1t] upon its emergence from the pressure point of the preceding stand and bend the strip slightly so that its stiffness is increased until it enters the gap of the rolls 8, 9 of the next succeeding stand. As illustrated in FIGURE 6, the entry point of slot 63 has sufiicient height to it to facilitiate receiving the head end of the strip. The slot 63, however, narrows slightly laterally and deepens vertically toward the right hand or exit end of the slot and also is arcuate shaped so that the strip has an arcuate shape when it emerges from slot 63, which shape it retain until it enters the gap between the rolls of the next succeeding stand.

In FIGURE 10, I have shown an alternative arrangement for controlling the horizontal curvature of a strip of material being reduced in thickness to facilitate threading of a rolling mill. In this arrangement, the contact arms 17', 13 are eliminated and the voltage produced by adding algebraically the voltages supplied by movement of

arms

15, 16 is used to control the pressure across the width of the strip in the preceding stand. A second pair of arms 64, 65 is positioned further along the travel of the strip than the

arms

17, 18 of the mill of FIGURES 1 and 2 and in a position which is intermediate the position of the

arms

17, 18 and 19, 20. Arm 64, 65 are operative through variable rheostats of the type shown in FIGURE 3 to produce a control voltage which is algebraically added to the control voltage supplied by

arms

15, 16 to alter any adjustment of the pressure across the rolls of the preceding stand produced through operation of

arms

15, 16. The combined voltages produced by the two sets of arms l5, l6 and 64, 65 are thus effective to provide corrective bending of the head end of the strip sufficient to cause its entry into the next stand along the center line of the mill. In many instances, contacting the edges of the advancing strip at only two points and in some cases at only one point in its path of travel will suihce to control threading of the mill. In either case, whether the arrangement of FIGURES l and 2 or of FIGURE 10 is employed, by my invention a tandem rolling mill can be successfully automatically threaded to facilitate operation of the mill. By combining the feature of directing the path of the head end of the advancing strip utilizing the arrangements shown in FIGURES 79 or in FIGURE 10 and the arrangement for producing stiffness in the strip during the later of its travel through the mill using the arrangements of either FIGURE 5 or FIGURE 6, I am able to provide a tandem mill which can be automatically threaded rapidly and safely.

In many instances it is desirable to control the rate of adjustment of pressure and in some instances to vary that rate with the speed of the strip moving through the mill. To effect such control, I have provided in the apparatus illustrated in FIGURE 3 means responsive to the rate of change of position of adjusting screw 13 which may comprise, for example, a tachometer or alternative speed responsive device 66 arranged to provide a signal varying in polarity and magnitude with direction and speed of rotation of screw 47. The output signal of device 66 is supplied through a time constant circuit comprising resistance 67 and capacitance 68 and contacts 69. 70 to amplifier 3?. The signal thus supplied to control device 42 is etlcctive to provide a faster adjustment of pressure in accordance with the magnitude of the signal provided by sensors 15-13. In this circuit, resistance 67 and capacitance 63 may be varied as the speed of strip 10 varies to obtain a fast response of pressure adjustment for all speeds of the strip. To effect this result, I provide means for varying the values of resistance 67 and enpacitance 68 with the speed of roll 8 comprising a speed responsive device 71 which may be, for example, a tachometer and which is connected to vary the values of circuit elements 67, 63. Such connection may be any conventional mechanical or equivalent electrical linkage, such as motor 72, between device 71 and circuits elements 67, 68.

While I have shown my arrangements for sensing lateral movement of a strip positioned between each of stands 1, 2, 2, 3, and 3, 4, in many instances such an arrangemeat may be needed between only the first pairs of stands or the first two pairs of stands. Also, it may be found that the arrangement for stiffening the strip is required only between

stands

5 and 6. Again, while I have shown the use of pressure sensitive switches 53 to disable the control apparatus between the preceding sets of glands, it is obvious that a photoelectric relay or similar device could be employed for this purpose.

While in the foregoing particular embodiment of my invention have been shown, it will, of course, be undc stood that the invention is not limited to these emb ments since many modifications in the arrangements and in the instrumentalities employed may be made. It is contemplated by the appended claims to cover all such modifications which fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. The method of automatically tlrcading a rolling mill in which a strip of material is subjected to pressure at displaced points in its travel through the mill con prising:

measuring the curvature of the head end of the by contacting an edge of the strip adjacent the end at a pair of predetermined points after head end has passed a pressure point and using such measurement to vary the pressure across the width of the strip at the pressure point to produce a horizontal bending of the head end in a direction to guide it toward the center line of the mill.

2. The method of automatically threading a rolling mill in which a strip of material is subjected to pressure at displaced points in its travel through the mill comprising:

measuring the curvature of an edge of the head end of a strip at a plurality of predetermined points after it has passed a pressure point, using such measurement to vary the pressure across the strip as it passes through the point to produce a horizontal bending of the head end in a direction to guide it to the center line of the mill at the next pressure point, and after passage of the strip through a subsequent pressure point exerting a vertical force. on the head end to produce a curvature of the strip in a vertical plane to increase the stiffness of the strip in its direction of travel. 3. Apparatus for automatically threading a rolling mill cf the type in which a strip of material is subjected to pressure at successive points as the material passes through the mill comprising:

means for measuring the displacement from a desired position of the edge of the head end of. a strip of material at a plurality of points after it has travelled a predetermined distance past a pressure point, and

means responsive to said measuring means for vary the pressure on the material at the point to control the horizontal position of the head end of the material.

4. Apparatus for automatically threading a rolling mill of the type in which a strip of material is subjected to pressure at successive points as it passes through the mill comprising:

means for contacting the edge of the head end of the material at a plurality of spaced points after it has travelled a predetermined distance past a pressure point to sense the position of the edge at each of such points relative to the ceutcr line of the mill, and means responsive to said edge contacting means for controlling the distribution of pressure across the width of the material at the pressure point to control the horizontal movement of the head end of the nuterial after it passes the pressure point so that the material advances along the center line or" the mill.

5. The apparatus of claim 4 in which the e"" contacting means comprises a plurality of rollers poo tinned strip head such material and means to produce a signal varying with horizontal positions of said rollers.

5 6. The method of automatically threading a rolling mill of the type in which a ltrip of material is subjected to pressure at displace points in its travel through the mill comprising:

applying a predetermined pressure to such strip as it passes a first point; measuring any horizontal curvature in the strip after its head end has passed the first pressure point;

using such measurement to vary the pressure across the Width of the strip at the first pressure point to produce horizontal bending of the head end of the strip in a direction to guide it toward the center line of the mill, and

reverting to the predetermined pressure at the first point after the strip enters the next pressure point.

7. The method of automatically threading a rolling mill in v, icll a strip of material is subjected to pressure at dis laced points in its travel through the mill comprising:

applying a predetermined pressure to the strip at a first point as it passes through the mill,

measuring any lateral curvature in the head end of the strip after it has passed such first point,

using such measurement to vary the pressure across the strip at the first point to produce a horizontal bending of the strip in a direction to guide it to the center line of the mill,

reverting to the predetermined pressure after the strip enters the next successive pressure point,

after passage of the strip through a pressure point subsequent to the first point exerting a vertical force on the strip to produce a curvature of the strip in a vertical plane to increase the stillness of the strip in its direction of travel, and

removing such force after the strip has passed through the next succeeding pressure point.

8. Apparatus for automatically threading a rolling mill of the type in which a strip of material is subjected to pressure at successive points as the material passes through the mill comprising:

means for exerting a predetermined pressure on the strip at a first pressure point,

means for sensing any lateral curvature of the head end of the strip alter it has travelled a predetermined distance past such first pressure point,

cans controlled by said sensing means for varying the pressure across the material at the first pressure point to control the horizontal position of the material,

additional means for sensing the lateral curvature of the head end of the strip alter it has travelled a second predetermined distance past said first pressure point, and

means responsive to said additional means for adjusting said pressure varying means.

The apparatus of claim 8 including means operaatter the strip has passed the next pressure point for disabling said pressure varying means and for returning to the predetermined pressure at said first point.

10. Apparatus for automatically threading a rolling mill of the type in which a strip of material is subjected to pressure at successive points as the material passes through the mill comprisin screw means at a first of said points for exerting a predetermined pressure on a strip of material;

means responsive to the horizontal position of the head end of a strip of material after it passes through the first point for controlling the pressure applied at said point, and

means operative after passage of a strip of material through the neat succeeding pressure point for dis- 0 tive abling said control means and returning to said predetermined pressure.

11. The apparatus of claim 10 in which the screw responsive means comprises a roll and a pair of screws exerting pressure on the ends of said roll, and said pressure varying means comprises means for operating said screws in opposite directions to effect rapid change in the pressure exerted on the strip.

12. Apparatus for automatically threading a rolling mill of the type in which a strip of material is subjected to pressure at successive points as the material passes through the mill comprising:

means for exerting a vertical pressure on a strip of material after its head end passes through a pressure point to produce curvature of the head end of the strip in a vertical plane, and

means operative after the strip of material passes through the next succeeding pressure point for disabling said vertical force exerting means.

13. The apparatus of claim 12 in which the vertical force exerting means comprises a chute having an open ing curved in a vertical plane at the point in which the material leaves the chute.

14. The apparatus of claim 12 in which the vertical force exerting means comprises means for simultaneously exerting a vertically downward force at the center of a strip and vertically upward forces at points displaced laterally from the center of the strip.

15. In a tandem cold rolling mill the combination comprising:

a plurality of stands each comprising a pair of rolls for exerting pressure on a strip of material;

means positioned along the travel of the strip after its head end passes through a first of said stands for sensing the position of an edge of the strip; means responsive to said sensing means for controlling the pressure applied at said preceding pressure point;

means operative upon passage of the head end of the strip through the next succeeding pressure point for disabling said pressure controlling means and returning the pressure at said first point to a predetermined value;

means operative after passage of the strip through a subsequent pressure point for producing a curvature of the head end of the strip in a vertical plane to produce stiifness thereof in the direction of its travel, and

means operative after passage of the head end of the strip through the next succeeding pressure point for disabling the stiffness producing means.

16. Apparatus for automatically threading a rolling mill of the type in which a strip of material is subjected to pressure at successive points as the material passes through the mill comprising:

means positioned at a first of said points for exerting a predetermined pressure on a strip of material;

means responsive to horizontal curvature in the head end of the strip of material after it passes through the first point for controlling the pressure applied at said point, and

means operative after passage of the head end of the strip of material through the next succeeding pressure point for disabling said control means and returning to said predetermined pressure.

17. Apparatus for automatically threading a rolling mill of the type in which a strip of material is subjected to pressure at successive points as the material passes through the miil comprising:

means responsive to horizontal curvature in the head end of the strip of material after it passes through such first point for varying the magnitude of the pressure applied to said point, and

means responsive to the rate of travel of a strip of material through the mill for controlling the rate of varying the pressure at said point.

18. The apparatus of claim 17 in which the said pressure magnitude varying means includes a time constant circuit and said rate varying means includes means for varying the magnitude of the components in said time constant circuit.

References Cited by the Examiner UNITED STATES PATENTS 2,261,972 11/41 Matthew 271-74 2,289,410 7/41 Dahlstrom 80--56.2 2,292,535 8/42 MacChesney 80-56.2 2,331,246 10/43 Stoltz 80-51 2,552,459 5/51 Rice 8035.l 2,909,717 10/59 Hulls et al. 8056.1 2,933,626 4/60 Giboney et al. 8056.1

FOREIGN PATENTS 607,961 11/60 Canada.

WILLIAM J. STEPHENSON, Primary Examiner.

LEON PEAR, Exmniner.

Claims

1. THE METHOD OF AUTOMATICALLY THREADING A ROLLING MILL IN WHICH A STRIP OF MATERIAL SUBJECTED TO PRESSURE AT DISPLACED POINTS IN ITS TRAVEL THROUGH THE MILL COMPRISING: MEASURING THE CURVATURE OF THE HEAD END OF THE STRIP BY CONTACTING AN EDGE OF THE STRIP ADAJCENT THE HEAD END OF A PAIR OF PREDETERMINED POINTS AFTER SUCH HEAD END HAS PASSED POINT AND USING SUCH MEASUREMENT TO VARY THE PRESSURE ACROSS THE WIDTH OF THE STRIP AT THE PRESSURE POINT TO PRODUCE A HORIZONTAL BENDING OF THE HEAD END IN A DIRECTION TO GUIDE IT TOWARD THE CENTER LINE OF THE MILL.

3. APPARATUS FOR AUTOMATICALLY THREADING A ROLLING MILL OF THE TYPE IN WHICH A STRIP OF MATERIAL IS SUBJECTED TO PRESSURE AT SUCCESSIVE POINTS AS THE MATERIAL PASSES THROUGH THE MILL COMPRISING: MEANS FOR MEASURING THE DISPLACEMENT FROM A DESIRED POSITION OF THE EDGE OF THE HEAD END OF A STRIP OF MATERIAL AT A PLURALITY OF POINTS AFTER IT HAS TRAVELLED A PREDETERMINED DISTANCE PAST A PRESSURE POINT, AND MEANS RESPONSIVE TO SAID MEASURING MEANS FOR VARYING THE PRESSURE ON THE MATERIAL AT THE POINT TO CONTROL THE HORIZONTAL POSITION OF THE HEAD END OF THE MATERIAL.