US2476839A - Control system - Google Patents

Description

W. G. COOK CONTROL SYSTEM July 19, 1949.

, Filed June 14, 1944 2 Sheets-Sheet l ww um &

uuuuuu II uuuuuuu'l INVENTOR Wfl/ara. 600K.

ATTORN WITNESSES:

July 19, 1949. w. a. cow 2,476,839

CONTROL SYSTEM Filed June 14, 1944 2 Sheets-Sheet 2 07 we we WITNESSES: INVENTOR a? %7 MY/qrc/ & COOK.

n V I I Y a w 1 I, A ORNEY Patented July 19, 1949 UNITED STATES PATENT OFFICE CONTROL SYSTEM Application June 14, 1944, Serial No. 540,237

14 Claims.

M invention relates, generally, to control systems, and it has reference, in particular, to automatic screwdown control systems such as used for controlling the relative movements of rolls in steel rolling mills.

Generally stated, it is an object of my invention to provide an automatic screwdown control system which is simple and inexpensive to manufacture and is easy to install and operate.

More specifically, it is an object of my invention to provide an automatic screwdown control system which affords automatic acceleration and deceleration of the screwdown motor with a minimum of plugs in the limit switch plug board.

An important object of my invention is to provide for reducing the number of control circuits necessary to effect automatic control of the screwdown motor of a rolling mill.

Another object of my invention is to provide for reducing the number of contact members required in a limit switch for controlling a screwdown motor without reducing the effectiveness of the limit switch.

Yet another object of my invention is to provide for incorporating a short-cirouiting device in each of the receptacles of the limit switch plug board so as to eliminate the requirement for dummy plugs between pass plugs in order to complete an operating circuit.

Still another object of my invention is to provide an improved screwdown control system wherein a single limit switch may be used in conjunction with a plurality of plug boards for setting up a plurality of different roling schedules independently of each other, and while rolling or otherwise.

Another important object of my invention is to provide for incorporating a reliable short-circuiting switch in each of the plug receptacles of the limit switch so as to preclude the necessity of using dummy plugs between the pass plugs.

A further object of my invention is to provide a compact and reliable push button switch for each plug receptacle which has a definite wiping action so as to prevent the occurrence of an accidental open circuit.

A still further object of my invention is to provide a plug and receptacle arrangement wherein contacts of the receptacle are normally short circuited and the short-circuitin means is actuated by the insertion of a plug in the receptacle to remove the short circuit only after the contact members of the receptacle are engaged by contact members of the plug.

Still another important object of my invention is to provide for stopping a screwdown motor when it is operating in the direction to bring the rolls together and provide a remotely operable vernier adjustment for attaining the desired final position of the rolls.

Yet another important object of my invention is to provide for using a differential drive for operatively connecting the limit switch of a screwdown control system to the screwdown motor and provide for adjusting the differential drive to obtain Vernier adjustments between the relative positions of the screwdown motor and the limit switch.

It is also an important object of my invention to provide for operating an adjustable limit switch in response to movement of an object whose position is to be controlled thereby, by means of a synchrotie system and a differential mechanism having a driven element operated from the synchrotie system, a driving element operating the limit switch and a rotatable control element which may be remotely actuated to cumulatively or differentially vary the position of the object from the position indicated by the limit switch.

Other objects will in part be obvious, and will in part be explained hereinafter.

In accordance with one embodiment of my invention, the operation of a screwdown motor actuating one of a pair of relatively movable rolls is controlled by directional relays and speed control means. A limit switch is provided havin a movable contact arm for engaging a plurality of spaced contact segments which are arranged in spaced apart tracks for determining energizing circuits for the directional relays and speed control means, respectively. A plurality of pass control relays selectively controlled by a pass selector switch are connected to the segments of the limit switch by means of plugs and receptacles for controlling the operation of the screwdown motor. The receptacles are provided with shortcircuiting devices which normally provide an energizing circuit for one or another of the directional relays depending on the position of the contact arm and which of the pass control relays has been operated. The contact arm of the limit switch is operatively connected to the screwdown motor by means of a synchrotie system and a differential drive which has a control element remotely operable to vary the position of the screwdown motor from that indicated by the position of the contact arm. By reason of the short-circuiting means in the receptacles a plurality of groups of receptacles may be connected to the contact segments of the limit switch independently of each other so that a plurality of different rolling schedules may be set up independently of each other without effecting an actual rolling operation.

For a more complete understanding of the nature and scope of my invention reference may be made to the accompanying drawings in which:

Figure l is a diagrammatic view of an automatic screwdown control system embodying the invention in one of its forms;

Fig. 2 is a front elevational view of a receptacle in one of the plug boards embodying the features of the invention;

Fig. 3 is a sectional View taken along line 111-111 of Fig. 2;

Fig. 4 is a front elevational view of a plug which is disposed to be positioned in the receptacle shown in Figs. 2 and 3;

Fig. is a sectional View of the plug taken along the line V-V of Fig. 4; and

Fig. 6 is an enlarged sectional view of the shortcircuiting device shown in Fig. 3 in a partially operated position so as to illustrate the operating action of the switch member.

My invention comprises an improvement of and a simplification of the screwdown control system described and claimed in Patent Nm 1,764,312 which issued on June 17, 1930, to Harold C. Jenks and is assigned to the assignor of the present invention.

Referring to Fig. l, the reference numeral II] may denote generally a roll stand such as used in steel rolling mills wherein relatively movable rolls I I and I2 are rotatably supported in a frame structure I3. Relative movement of the rolls to change the distance between them may be obtained in any suitable manner, such as by means of a screwdown motor I5 which may be operatively connected to the journals of the roll I2 through'screw mechanisms I6 so as to provide for raising and lowering the roll I2 relative to the roll II. The driving means for the rolls is not shown but may be connected, for example, to the roll II through the shaft I8.

Operation of the screwdown motor I5 may be effected by connecting the armature thereof to the armature of a generator 2| which may be driven by any suitable prime mover (not shown) and provided with a field winding 22. The field "winding 23 of the screwdown motor may be connected to any suitable source indicated by the plus and minus terminal connections.

The direction of operation of the motor I5 may be controlled by means of raise and lower directional relays 25 and 26 which may be operable to change the connections of the generator field winding 22 and a source of excitation indicated by plus and minus terminals so as to provide for operation of the motor to raise and lower the movable roll I2, respectively. Means such as the interlock relay 2! may be provided for preventing operation of the raise relay 25 in the event that the screwdown motor I5 overshoots when operating in the downward direction.

form of a regulator 28 having an operating winding 29 for actuating a plurality of contact members 28a, 28b, 28c, etc., to progressively insert steps of a control resistor 30 in the field circuit of the generator 2| in a well known manner. A pilot generator 3| may be utilized in connection with the speed control relay 28, being connected to the screwdown motor so as to provide a retarding force proportional to the' speed of the screwdown motor.

In order to control the operation of the directional relays 25 and 26 and the speed control relay 28 in accordance with the direction and distance of the movable roll l2 from the desired operating position, the limit switch denoted generally by the numeral 32, may be provided.

The limit switch 32 may comprise a pair of tracks 33 and 34 positioned in spaced relation upon a suitable insulating support and disposed atively connected to the screwdown motor I5. The tracks may comprise a plurality of contact segments 33a, 33b through 33p, 33g and 331, and segments 34a, 34b through 34p, 34g and 341', respectively.

Only a few of the contact segments, which may actually number on the order of I38 in each track, are shown, in order to simplify the drawings, but it will be understood that the segments actually shown are intended for the purpose of illustration only and the invention is not limited to any particular number thereof. The segments in the tracks 33 and 34 are preferably provided with overlapping end portions by having the adjacent ends thereof inclined in parallel relation so as to provide a substantially continuous supporting and contact surface for the movable contact arm 35 which is disposed to move along the tracks in bridging relation therebetween.

Resistance means 36 comprising a plurality of control resistors 36a, 361) through 3620 and 3Bq may be connected in bridging relation between adjacent segments of the track 34 in order to provide a variable impedance control circuit for the regulator 28 in a manner which hereinafter will be described in detail. By connecting the resistance means 36 intermediate the ends of the segments of track 34, and positioning the segments thereof in staggered relation to the segments of track 33, it is possible to reduce the number of connections hitherto required, and still maintain uniform relations between the resistance means and the control segments 33 regardless of the direction of movement of the arm 35. Electrical connection may be made to the contact arm 35 in any suitable manner, such as by means of the operating shaft 31 and a collector 38.

In order to provide operating circuits for the directional relays 25 and 26 from the contact arm 35 through predetermined portions of the limit switch track 33 depending on the position of the movable roll I2 from the desired operating position, and hence provide for adjusting the roll I2 to a predetermined number of predetermined pass positions in a #1 schedule, a plurality of pass control relays 40, 4| and 42 may be provided in one group, having operating windings 43, 44 and 45, respectively. These pass control relays may be controlled by means of a pass selector switch 41 having a movable contact arm 48 for engaging anyone of a plurality of stationary contact members 47a, band 470, to selectively provide predetermined circuits through the tracks 33 and 34 for determining the operation of the motor I5. An additional contact member 41d may be provided for controlling the operation of a special pass control relay 50 which may be used to determine the minimum spacing between the rolls II and I2.

In order to provide for setting up a plurality of different rolling schedules, additional groups of pass control relays may be provided such as may be represented by the group of additional pass control relays 52, 53 and 54, and which may be used for setting up a diiferent rolling schedule designated as schedule #2 as distinct from schedule #1 which is provided by the pass control relays 43 through 45. Selection of a desired group of pass control relays to be effective may be made by means of a schedule selector switch 58 which provides for selectively connecting the operating windings of either the schedule #1 or schedwe #2 pass control relays to the positive terminal of the source.

The energizing circuits for the directional relays 25 and 2B and the speed control relays 28 may be determined by means of a group of pass plugs represented by the plugs 60, 6| and 62 which are disposed to be positioned in different ones of a group of receptacles represented by the receptacles 64, 65, 66, 61 or 68. In this instance each of the receptacles is provided with a plurality of contact members and a short-circuiting device. Thus, receptacle 64, for example, is provided with contact members 64a, 64b and 640, and a short-circuiting device 64d connecting contact members 6412 and Mc. The plugs may be also. provided with corresponding contact members and operating means for the short-circuiting devices of the receptacles. Thus the plug 68, for example, is provided with contact members 60a, 60b and 680, and operating means End for operating the short-circuiting device 64d of the receptacle B4.

The contact means of the plugs and receptacles cooperate to provide connections between the pass control relays 40 through 42 and difierent ones of the segments of the tracks 33 and 34 of the limit switch 32. These plugs and receptacles are designated as schedule #1 plugs and receptacles on the drawing. Additional plugs I0, II and I2 may be provided for positioning in additional receptacles I4 through I8 in order to complete the #2 schedule connections. These plugs and receptacles are designated as schedule #2 plugs and receptacles on the drawing.

As shown, any one of the schedule #1 plugs may be positioned in any one of the schedule #1 receptacles to provide control circuits for the directional relays 25 and 26 through the contact members of the associated control relay and the segments of track 33, as well as a control circuit for the speed control relay 28 through the contact segments of track 34 and one or more of the control resistors 36c through 36g. For example, the plug 60 for schedule #1 may be positioned in receptacle 3 so that a contact member 68a, of the plug 68 engages contact member 84a of the receptacle 64. Contact members 601) and 660 of the plug 60 likewise engage contact members 64b and 640 of the receptacle 64. The shortcircuiting device 6411 which normally connects contact members 842) and 640 of the receptacle 64 is actuated by means of the actuator or insulated projection 60d of the plug 68 after the contact members 60a, 50c and 66b, 64c engage. Accordingly, an energizin circuit for one or another of the directional relays 25 and 26 will be provided through the limit switch track 33, and movable arm 35, depending on in which receptacle the plug of an operated pass control relay is positioned, since this determines Where the break in the track 33 occurs, and which of the directional relays 25 and 26 will be energized. The speed of the screwdown motor I 5 also depends upon in which receptacle the plug of an operated relay is positioned, since this determines how much of the control resistance 36 is included in the circuit of the speed control relay 28.

Operation of the movable contact arm 35 to control the energizing circuits for the directional relays 25 and 26 and the speed control relay 28 may be effected in any suitable manner such as by operatively connectin the operating shaft 31 to the screwdown motor I5 by means of a synchrotie system 80. This system may comprise a transmitter BI having a rotor 82 connected to the shaft of the screwdown motor I5 and a stator 83, and a receiver 84 having a rotor 85 electrically connected to the rotor of the transmitter 8I through conductors 86 and a stator 81. The stators 83 and 81 are connected for energy at or from a suitable source of alternating current represented by conductors 88.

In order to provide for making fine adjustmerits of the roll position, a differential drive 89 may be interposed between the operating shaft 31 and the receiver 84 to effect Vernier variations between the relative positions of the contact arm 35 and the screwdown motor I5. The differential drive 89 may comprise a pair of bevel gears 90 and 9| having a rotatable cage mounted therebetween with intermeshing bevel gears 92 mounted thereon. The cage may be connected to the rotor 85 of the receiver 84 through shaft 93 so as to be operated in accordance with the operation of the screwdown motor I5 and position of the roll I2. The bevel gear 98 may be connected to the operating shaft 3'! of the contact arm 35, while the bevel gear 9I may be provided with control means such as the control motor 94 which is controlled by push button switches 95 and 96 to raise or lower the roll I2 relative to the position normally corresponding to the position of the contact arm 35.

With the limit switch in the position shown, if the movable contact arm 48 of the pass selector switch 41 is actuated to the special pass position engaging contact member 41d, an obvious energizin circuit is established for the operating winding 5| of the special pass relay 58. Upon operation of relay 58 the contact arm 35 is connected to the negative terminal of the source through contact members 5011, conductor 91 and collector 38. This provides an energizing circuit for the lower directional relay 26 extending from the negative terminal through contact members 50a, conductor 91, collector 38, operating shaft 31, contact arm 35, contact segment 33p of track 33, conductor 98, conductor 99 which is shown as dotted since there may be a plurality of receptacles connected between those actually shown, short-circuiting device 6Bd, short-circuiting device Hid, conductor I08 which also is shown dotted since a plurality of other receptacles may be positioned between the receptacles actually shown, short-circuiting device 6511, short-circuiting device 15d, short-circuiting device 6401, short-circuitin device 14d, contact segment 33a, conductor I OI, operating winding I02 of the lower relay 26, and contact members 250 of the raise relay 25 to the positive terminal.

The operation of the lower directional relay 26 connects the field winding 22 of the generator 2! to the source with such polarity as to cause the screwdown motor I5 to operate in the direction to lower the movable roll I2. The speed of operation of motor I5 which is determined by the speed control relay 28 and. the pilot generator 3| will be at almost a minimum since the energizing circuit for the operatin windin 29 of the speed control relay 28 will be completed from the contact arm 35 through segment 34q, resistor 36g, conductor I03, contact members 50b, conductor I04 through the pilot generator 3I, operating winding 29 and conductor 91 back to the arm 35.

Accordingly, the energization of the operating windin 29 will be almost a maximum, and the contact members 28a, 281), etc., of the speed control relay 28 will be separated, inserting most of the sections of the speed control resistor 38 in the providing almost minimum field on the generator 2|. The motor l5 operates to move the roll I2 in the downward direction.

As soon as the rolls approach the minimum position, the speed of the motor I5 is reduced since the amount of the resistance 36 in the energizing circuit for the operating winding 29 of the speed control relay 28 is reduced when the arm 35 engages the segment 3411. while it is still engaging the segment 33m. The operating winding 29 is thereupon energized at a maximum and functions to overcome the biasing force sprin 30, and the contact members of the speed control relay are separated a maximum, inserting all of the steps of the control resistor 30 in the circuit of the field winding 22 so as to reduce the voltage applied to the armature of the motor 15 to a minimum.

When the contact arm 35 leaves the contact segment 33!], the screwdown motor stops, since the contact member 56c of the special pass control relay 5!] is open and the contact segment 33q is disconnected from the conductor HH and the operating winding I02 of the lower relay 26 thereby. Accordingly, the circuit through the contact arm 35 is interrupted and the lower directional relay 26 is deenergized, removing the field from the generator 2| and causing the screwdown motor 15 to stop. A brake (not shown) may be applied in any well known manner for insuring rapid stopping of the screwdown motor.

In order to set up a desired operating sequence, different ones of the pass plugs may be positioned in dilTerent ones of the receptacles, depending upon what roll spacing is desired for the particular pass. For example, the plug 66 may be positioned in the receptacle 64, while the plug 6| may be positioned in the receptacle 66 to provide for two difierent passes during the operation of schedule #1. 7

It will be apparent, however, that any particular schedule may comprise any particular number of passes, and that the passes may be for any of a number of difierent roll spacings. Likewise, any of the plugs 10 through 12 may be positioned in different ones of the receptacles 74 through 18 to set up schedule #2. For purposes of illustration it may be assumed plug number 16 may be positioned in receptacle while plug H is positioned in receptacle l1. These connections are shown by dotted lines connecting the respective plugs and receptacles.

The schedule selector switch 58 may now be operated to the #1 schedule position so as to connect the terminals of the operating windings 43 through 45 of the pass control relays 40 through 42 to the positive terminal of the source. When the contact arm of the pass selector switch 41 1s positioned in engagement with the #1 pass contact 41a, a circuit for the operating winding 43 of the #1 pass control relay 40 isprovided, extending from the negative terminal through contact arm 48, conductor H15, operating winding 43, contact segment I06 of the schedule selector switch 58 to the positive terminal of the source.

The control relay 40 operates, closing its contact members 4012 to connect the contact arm 35 of the limit switch to the negative terminal through conductor 91, collector 38 and operating shaft 31. Since the short-circuiting device 64d is operated to the open position by the actuator 60d of the plug 60, the energizing circuit for the lower directional'rela'y 26 is interrupted. An

energizing circuit for the raise directional relay 25 is provided from the positive terminal through contact members 260, operating winding I68, conductor I69, contact members 21a of the interlocking relay 21, conductors H6 and H2, segments 331*, contact arm 35, shaft 31, conductor 9i and contact members 40a to the negative terminal.

The raise relay 25 operates, connecting the field Winding 22 of the generator to the source through contact members 25a and 25b so that the screwdown motor l5 operates to raise the roll l2. The speed of operation of the screwdown motor I5 is determined by the amount of the control resistance 36 which is contained in the circuit of the operating winding 29 of the speed control relay 28 and the armature of the pilot generator 3!, as well as the speed of the pilot generator.

Since all of the resistance between the contact segment 34r and 34a is connected in closed circuit relation with the pilot generator 3| and the operating winding 29 through the circuit extending from contact members 4% of the pass control relay 40, through contact member a of plug 60, contact member 64a of the receptacle 64, resistance 36, segment 341', contact arm 35, conductor 9i,- Winding 29, pilot generator 3| and conductor I04 to contact member 401;, the speed of the screwdown motor will be almost a. maximum. As the contact arm 35 progresses towards the left-hand end of the limit switch, the amount of the control resistance 36 contained in the speed control circuit is reduced, thus reducing the speed of the screwdown motor. Since the output of the pilot generator 3| is proportional to the speed of the screwdown motor, this factor tends to balance or steady the speed at a predetermined desirable value.

Since contact members 400 of the control relay 40 are open, the energizing circuit for the raise relay 25 will be interrupted as soon as the contact arm 35 passes to the left of the contact segment 33b, which is the last of the segments in the track 33 connected to the conductor H2 and hence to the operating winding I68 of the raise relay 25 through the short-circuiting contact devices of the receptacles. The motor l5 stops and the roll I2 is in the desired position corresponding to the receptacle 64 in which the pass plug 60 was positioned.

After a pass is completed with the roll l2 in the setting determined by the pass plug 60 and pass control relay 46, the roll position may be changed for pass #2 in schedule #1 by operating the contact arm 48 of the pass selector switch to the #2 pass position on contact 471). As soon as the contact arm 48 leaves contact member 41a, the pass control relay 46 is deenergized. When the arm 48 engages contact member 41b, an energizing circuit for the operating winding 44 of the #2 pass control relay M is provided. Relay 4| operates to connect the contact arm 35 to the negative terminal through contact members 4Ia. With the pass plug 6| positioned in the receptacle 66, the actuator 6|d operates the short-circuiting device 66a to interrupt the circuit between the contact segments 33f and 33g.

Since the contact arm 35 had been previously moved to a position engaging contact segment 33a of the limit switch, no energizing circuit is provided for the raise relay 25, and instead a control circuit is provided for the lower relay 26. This circuit extends from the positive terminal through contact members 250 of the raise relay, operating winding I02, conductor IOI, seg-- ment 33a, contact arm 35, operating shaft 31, conductor 91, and contact members 4Ia to the negative terminal of the source. At the same time the operating circuit for the speed control relay 28 is completed from the contact arm 35 through operating shaft 31, conductor 91, operating winding 29, pilot generator 3|, conductor I04, contact members Mb, contact member 6Ia, contact member 58a, conductor II8, control resistors 36d through 36a and segment 34a to the contact arm 35.

Accordingly, the screwdown motor I operates at a moderate speed since the amount of resistance included in the speed control circuit is fairly low. The speed is reduced gradually until the contact arm 35 engages the contact segment 34c when the speed is reduced to a minimum, since all of the resistance 36 is then cut out and the maximum amount of the speed control resistor 30 will then be inserted in the generator field circuit. As'soon as the contact arm 35 leaves the contact segment 33e,the energizing circuit for the lower relay 26 is interrupted, since the contact members 4Icbridging the short-circuiting device 66a are open.

Should the screwdown motor I5 tend to overtravel, it cannot reverse since the interlocking relay 2?, which is energized through contact members 26d of the lower relay 26, interrupts the energizing circuit for the "raise control relay 25 by opening contact members 21b. The interlocking relay 2'I seals itself in through contact members 21a, preventing operation of the raise relay until the pass selector switch 4! is operated to a different position, during which operation the holding circuit for the interlocking relay 21 is interrupted.

Upon the completion of the #2 pass operation hereinbefore described, operations may be begun on the #2 schedule of operations by operating the schedule selector switch 58 to the #2 schedule position, thereby connecting the operating windings 55, 55v and 51 of the #2 schedule pass control relays 52, 53 and 54 to the positive terminal of the source through contact member I20 of the schedule selector switch. It will be apparent, of course, that more than the two pass operations hereinbefore described may be made during operations on schedule #1 and the number of control relays, plugs and receptacles may be much greater than actually shown since the actual number has been reduced in order to simplify the circuit and facilitate explanation. Actually there may be a hundred or more receptaclesand as many as eleven pass plugs and control relays for each schedule.

With the schedule selector switch in the #2 position, the pass selector switch 41 may be operated to the #1 pass schedule #2 position engaging contact member 4Ia, whereupon an energizing circuit is provided for the operating winding 55 of the #2 schedule control relay 52. This circuit extends from the negative terminal, through contact arm 48, contact member 41a, conductor I05, operating winding 55, conductor H9, contact segment I20 to the positive terminal of the source. Control relay 52 operates, connecting the contact arm 35 to the negative terminal through contact members 52a, and providing an operating circuit for the speed control relay 28 through a circuit extending from the contact arm 35 engaging contact segments 33f and 34a, through control resistors 36d to 36b, conducto'r I22, to contact member 150. of receptacle 15, contact member 10a of plug I0, contact members 52b to conductor I04 through the pilot generator 31, operating winding 29 of the speed control relay 28, conductor 91 to the operating shaft 3"! and contact arm 35. At the same time an energizing circuit is provided for the raise relay 25 extending from the positive terminal through contact members 260 of the lower relay 26, operating winding I08, conductor I09, contact members 27a, conductor IIO, conductor II2, contact members 500, conductor H4 and the short-circuiting devices of the receptacles 68, i8, 61, I1 through 68 and I5, segment 33] and contact arm 35, to the negative terminal of the source through contact members 52a of the pass control relay 52.

Accordingly, the screwdown motor I'll operates to raise the roll I2 and actuate the contact arm 35 from right to left until it leaves the contact member 336. Since the short-circuiting device 75d is open-circuited, and the contact members 520 shunting the short-circuiting device are also open, the contact segment 33b is disconnected from the circuit to the right of the segment 33b, and the raise relay 25 becomes de-energized as soon as the contact arm 35 of the limit switch reaches this segment. During the period of travel from the contact segment 33] to the contact segment 331), the amount of the control resistance 35 included in the speed control circuit of the speed control relay 28 is gradually reduced so that the screwdown motor I5 is gradually slowed down to the stopping point. Successive passes may be made in a manner previously described by operating the pass selector switch 41 to successively engage contact members 41b, 0, etc., for as many pass plugs as may be positioned in the receptacles of the particular schedule.

In Figs. 2 and 3, enlarged front elevational and sectional views of one of the receptacles, for example the receptacle 64, are shown for the purpose of describing in detail the construction and arrangement of the short-circuiting device contained therein. As shown, the receptacle may comprise an insulating support I24 positioned within a tubular casing I25 which may be mounted on a suitable base member I26. The support may have a plurality of terminals 64a, 64b and 640 mounted therein by means of the terminal studs I27. The contact members 6401. through 640 may be of any construction, comprising, for example, tubular members I28 having cutaway portions I30 on one side for receiving the inturned end portions of a spring contact member I32.

The short-circuiting device 64d may comprise a pair of contact strips I33 each having one end securely fastened between the tubular members of the contact members 64b and 640, respectively, and the insulating support. The other ends thereof may be provided with upwardly inclined portions I34 to provide inclined contact surfaces I35 on the lower side positioned in spaced relation to each other. A movable contact member I36 may be provided, having a rounded end portion I31 for engaging the contact surfaces, and being provided with means such as the spring I38 for resiliently biasing it against the contact surfaces.

In order to ensure positive contact between the short-circuiting member I36 and the adjacent contact surfaces I35 of the contact strips I33, the spring I38 may be disposed to actuate the short-circuiting member I36 in a direction which is inclined toward the contact surfaces. Thus, by providing a recess I40 in the insulating support member intermediate the contact strips I33, and which is inclined, toward the outer ends of the contact strips, and making the recess I40 of slightly larger cross-sectional dimensions than the short circuiting member I36, it is possible to provide for some lateral movement of the shortcircuiting contact member I36 along the contact surface of the contact strips I34 both during engagement and disengagement of the short-circuiting contact member and the contact strips.

Figs. 4 and 5 illustrate enlarged front end and sectional views of one of the plugs such as, for example the plug 60, which it will be seen may comprise a plurality of contact members or prongs 66a, 60b and 600 mounted on an insulating support member I42. The insulating support member I42 may be positioned within a casing or housing comprising a substantially tubular body portion I44 having a headed projection I46 at one end to provide a handle for gripping the plug, and an opening I41 for receiving a plug cable I48 for making connections to the contact members.

In order to provide for operation of the shortcircuiting device 64d, means such as the actuator 60d may be provided comprising, for example, a rod of insulating material mounted in the insulating support I42 and projecting slightly beyond the contact members 60a through 600. The outer end of the actuator 60d may be provided with a reduced section I50 disposed to be positioned between adjacent end portions of the contact strips I33 of the receptacle, and having a bevel or inclined contact surface I5I for engaging the rounded end surface of the shortcircuiting contact member I31 in order to separate the contact member I31 from the contact portions I34.

In order to provide a wiping or sliding action between the movable short-circuiting contact member I36 and the contact portions I34 of the strips 133, the relationship of the actuator slid to the movable contact member I36 may be substantially as shown in the enlarged fragmentary view in Fig. 6. From this view it will be clear that the inclined surface I SI of the actuator 80d engages the rounded end portion of the movable short-circuiting contact member I36 on the outer portion thereof on the side more remote from the contact strips I33, thus supplying an actuating force which is inclined to the longitudinal axis of the short-circuiting member from the side which is more remote from the contact strips I33.

Thus when the actuator 60d first engages the rounded end portion I3I of the movable shortcircuiting contact member I36, the short-circuiting member is moved from its free or normal position against the outer wall of the recess I40 as shown by the dot-dash line I53 and slides along the contact surface of the contact strip I34 until it strikes the inner wall portion of the recess I40. By this time the contact members a, 63b and 600 have already engaged the contact members 64a, 64b, 640 of the receptacle. Further movement of the plug into the receptacle actuates the short-circuiting contact member away from the contact strips I33, thus opening the circuit therebetween. When the plug is removed this wiping action is repeated in reverse, and the spring slides the movable contact member along the sloping contact surfaces I35 to a position against the outer wall of the recess I40 as shown in Fig. 3.

By providing a plug and receptacle arrangement such as hereinbefore described, it is possible to connect a plurality of the receptacles between each of the contact segments of the limit switch and thus provide for a plurality of rolling schedules. Since each of the plugs is connected to a control relay having normally closed contact members bridging the short-circuiting device, it will be apparent that different schedules may be changed or set upon different groups of receptacles during the time that one schedule of rolling operations is being performed without interfering with the connections preset in said one schedule.

In addition, by positioning the contact segments of one track in staggered relation to the contact segments ofthe other track, it is possible to connect to the control resistors 36 intermediate the ends of the segments 34a through 34n and still provide for cutting out the last step of resistance in order to effect operation of the screwdown motor at'the minimum speed, as it approaches the predetermined stopping position from either direction, at the same time reducing the number of connections and contact members required in each of the plugs and receptacles.

Because the reversing operation of the screw down motor is prevented in the event that the limit switch should slightly overshoot the desired position in the downward direction, further simplification of the circuit is made possible so that the additional dead contact buttons originally required with such limit switches may be dispensed with, together with the additional contact members required in each of the plugs and receptacles for making connections thereto.

Th inclusion of the short-circuiting device in the receptacle itself eliminates the necessity for positioning dummy plugs in all of the receptacles between passes in order to complete the necessary control circuits between adjacent segments for operating the screw-down motor. The elimination of these plugs greatly reduces the time required in making any one setup or in changing from one operating schedule to another.

From the above description and the accompanying drawing, it will be apparent that I have provided a simple and effective manner for simplifying and improving the control system for a screwdown or positioning motor. The number of contact segments and amount of wiring, as Well as the number of contact points in the different plugs and receptacles and the number of plugs required have been greatly reduced.

Accordingly, the limit switch may be made more compact, and the service and maintenance on the control apparatus are greatly reduced. By incorporating the short-circuiting devices in the receptacles in the manner described, a plurality of schedules may be either preset or subsequent schedules may be set up while rolling operations are proceeding on a previous setup schedule without any interference therebetween, and the need for dummy plugs to provide control circuits between pass plugs is eliminated.

Since certain changes may be made in the above described construction, and different embodiments may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the above description and shown in the accompanying drawings shall be considered as illustrative and not in a limited sense.

I claim as my invention:

1. In a control system for a plurality of relatively movable -rolls, a reversible motor operable to adjust the position of one roll relative to the other, control means selectively operable to effect operation of the motor in opposite directions, a limit'switch operable to determin the sense of operation of the control means and comprising a contact device having an external circuit connection thereto and movable along a predetermined path in response to operation of the motor for engaging only a pair of spaced apart tracks of contact segments positioned in end-to-end and spaced relation along said path, and a plurality of control devices selectively arranged for connection to predetermined ones of said segments tor providing an operating circuit for selectively operating the control means to operate the screwdown motor to actuate one of the rolls to a predetermined position.

2. A control system for apair of relatively movable members comprising, a motor operativel'y connected to one of the members for moving it relative to the other, control means selectively operable to effect operation of the motor in opposite directions, a limit switch having a contact device movable along a predetermined path in response to movement of said one member for engaging a pair of spaced apart tracks of spaced contact segments arranged in staggered relation, a plurality of control devices disposed for connection to different ones of the segments for providing a control circuit through a portion of one of said tracks for selectively providing for operation of the control means, and means including a plurality of resistors connected in series relation with and having a connection from between each resistor to an adjacent segment of the other of said tracks for providing a control circuit for controlling the speed of the motor dependent on the distance of the one member from the desired position.

3. A control system for a movable member comprising, a motor operable to move the member to any of a plurality of positions, control means determining the direction of operation or the motor, a limit switch having a contact member operatively connected to the motor for engaging a plurality of spaced segments forming spaced apart and substantially parallel tracks for controlling the operation of the control means, a plurality of control relays, a master control switch for selectively operating said relays, and circuit means connecting the control relays to predetermined ones of said segments for providing predetermined control circuits for the control means including a plurality of receptacles having short-clrcuiting devices for normally connecting the segments of one track to each other and a plug associated with each control relay cooperative therewith to provide shunt circuits for the short-circuiting devices.

4. A control system for a pair of relatively movable rolls having a reversible motor for moving one of the rolls relative to the other comprising, a limit switch having a pair of spaced tracks of segments disposed in spaced and end-to-end relation with the segments of one track staggered relative to the segments in the other and having a contact member movable in response to movement of the movable roll, a pair of control relays operable to effect operation of the motor in opposite directions, circuit means including a plurality of receptacles for providing circuits for operating the motor to position the movable roll in different predetermined positions, each of said receptacles having contact members connected to adjacent ends of segments of one track and to the segment of the other track opposite the ad-' jacent ends, a plurality resistor means connected between adjacent segments of the other track, a master switch operable to a plurality of positions, control means operable to vary the speed of the motor, a plurality of control relays selectively op erable in accordance with different positions of the master switch, and a plug device associated with each control relay disposed to be positioned in one of the receptacles for controlling the connections between the segments of the one track and providing a variable resistance circuit for the control means through a portion of said resistors depending on th distance of the movable roll from the desired position as determined by the plug device.

5. In a control system for a reversible positioning motor, control means operable to determine the direction or" operation of the motor, additional control means operable to determine the speed of the motor, a limit switch having a pair of spaced tracks of contact segments arranged in staggered relation and a movable contact member positionable in accordance with the position of the motor for engaging one track of spaced segments to provide a preselected operating circuit for the control means and for engaging the other track to provide a variable impedance cir cuit for the additional control means, and a plurality of control relays selectively operable to determine said circuits.

6. A limit switch for an automatic screwdown control system comprising, a movable contact member, a pair of tracks of spaced contact segments positioned in side-by-side relation so as to be bridged by the movable contact member, each of the segments in each track overlapping the adjacent segment to provide a substantially continuous conducting path for the contact member and the segments of the one track being so positioned as to have the adjacent ends thereof substantially intermediate the ends of the segments of the other track, resistance means bridged between the segments of the one track, and switch means connecting adjacent segments of the other track operable to interrupt the connection therebetween.

'7. A limit switch for controlling the operation of a motor provided with reversing means and speed control means comprising, a pair of tracks of elongated contact segments positioned in spaced and side-by-side relation with the segments of one track staggered relative to the segments of the other, a movable contact member disposed in bridging relation between said tracks, and a plurality of resistance means connected in series circuit relation with connections intermediate the resistors to adjacent segments of one track to provide a variable impedance circuit for the speed control means.

8. A limit switch for a roll screwdown motor having associated therewith a pair of directional relays for controlling the direction of operation of the motor and speed control means for controlling the speed of the motor comprising, a pair of tracks of spaced contact segments positioned in side-by-side relation, a movable contact member disposed to be operated in accordance with operation of the motor for bridging said tracks, and a plurality of receptacles for effecting connections to said segments, each receptacle having short-circuiting means for normally connecting the adjacent ends of adjacent segments in one track to provide an operating circuit in cooperation with the contact member for selectively' operating one or another of the directional relays and a contact means connected to the segment of the othertrack for providing a control circuit for the speed control means.

9. A limit switch for controlling the operation of a motor having associated therewith a pair of direction controlling relays, comprising, a plurality of elongated segments positioned in overlapping relation, a movable contact arm engaging said segments and movable in accordance with the position of the motor, and circuit means providing an operating circuit for one or another of the directional relays including a plurality of receptacles having contact members connected to adjacent segments and having movable contact means normally connecting said contact members to provide an operating circuit for one of the direction controlling relays.

10. The combination in a limit switch, of a pair of elongated tracks comprising spaced apart contact segments positioned in staggered relation with the adjacent ends of segments in one track 7 intermediate the ends of a segment in the other track, a movable contact member engaging said segments, a plurality of resistance elements connected in series circuit relation and having a connection from between each element to an adjoining segment of one track, and a plurality of receptacles for efiecting connections to the segments including one contact member connected intermediate each pair of the resistance elements and a pair of contact members normally connected by a switch element in the receptacle, said contact members being connected to the adjacent ends of the segments in the other track opposite the segments to which said one contact member is connected.

11. A limit switch comprising, a pair of tracks of elongated spaced apart segments disposed in side-by-side relation and positioned in staggered relation, resistance means bridging the segments of one track, a movable contact arm engaging said segments, and a plurality of receptacles having contact members for making external connections to the segments, said receptacles being disposed in plural relation for providing a plurality of different control circuits through the contact arm and segments with one contact member of each receptacle of each group being connected between the resistance means bridging one segment of said one track and the adjoining segments, and a pair of contact members of each receptacle of each group provided with shortcircuiting means and connected in series circuit relation between the adjacent segments of the other track which are positioned opposite said one segment.

12. A limit switch comprising, a pair of spaced apart tracks of spaced apart contact segments positioned in longitudinally. staggered relation, a movable contact arm positioned in bridging relation between said tracks, driving means-operable to actuate the contact arm along said tracks, a differential drive having a driven element connected to actuate the contact arm, a driving element operatively connected to said driving means, and an idling element operatively connecting the driving and driven elements, said idling element being adjustable to vary the position of the contact arm relative to the driving means.

13. A control system for a reversible motor operable to vary the position of a movable member comprising, directional control means operable to control the direction of operation of the ceptacles having stationary contacts and switch means cooperative therewith normally connecting adjacent ends of the segments of one track and additional stationary contacts connected to the segment of the other track opposite the adjacent ends of the segments in said one track, resistance means connected between adjacent segments of the other track, control means including a master switch and a plurality of control relays selectively operable under the control of the master switch, a plurality of plug members connected to said control relays and disposed to be positioned in said receptacles to provide difierent control circuits for the directional control means and the speed control means through the contact arm and the segments of said one and said other track for operating the motor to position the movable member to different positions depending on the operating position of the master switch and in which receptacles the plugs are positioned, and means for varying the relative position of the movable member relative to the position of the contact arm comprising a differential device having a driven member operatively connected to the motor, a driving member operatively connected to the limit switch arm, and an idler member operatively connecting the driving and driven members, said idler member being adjustable relative to the driving and driven members to vary the position of the contact arm relative to the positions of the motor and the movable member.

14. A control system for a screwdown motor operable to vary the position of a pair of rolls relative to each other comprising, directional control means operable to determine the direction of operation of the motor, speed control means operable to vary the speed of the motor, means including a limit switch with a movable contact arm operatively connected to the screwdown motor and a plurality of tracks of spaced segments for providing operating circuits for the directional control means and the speed control means for operating the contact arm and movable rolls in predetermined relation to predetermined positions, and Vernier means comprising a difierential device interposed between the motor and the limit switch, said difierential device having an adjustable control element remotely operable to change the operating connec tion between the motor and the limit switch so as to permit changing the position of the movable roll relative to the position of the limit switch.

WILLARD G. COOK.

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

UNITED STATES PATENTS Number Name Date 1,121,567 McWilliams Dec. 15, 1914 1,414,709 Reisback Ma 2, 1922 1,711,397 Rumble Apr. 30, 1929 1,919,207 Douglas July 25, 1933 2,092,051 Cook Sept. 7, 1937 2,106,965 Wright Feb. 1, 1938 2,144,033 Root Jan. 17, 1939 2,432,861 Cook Dec. 16, 1947

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