US2578778A

US2578778A - Control system for billet cutting machines

Info

Publication number: US2578778A
Application number: US39930A
Authority: US
Inventors: John L Biach
Original assignee: Air Reduction Co Inc
Current assignee: Airco Inc
Priority date: 1948-07-21
Filing date: 1948-07-21
Publication date: 1951-12-18
Anticipated expiration: 1968-12-18

Description

Dec. 18, 1951 J. L. BIACH CONTROL SYSTEM FOR BILLET CUTTING MACHINES Filed July 21, 1948 5 Sheets- Sheet l 5 5 5 '5 6 6 b lmv 2 m 2 3 b H 3 21d 3. 2 0 I 0 "d 0 I L in M #32 L 1 no" 1 8 1 1| 8 M m fl/f .M 1 )1 11\/.QI-1 1 Q a 0 I a: 3 H V F r 3 2 5 i g m 6 1 4 V 2 0 1 n r fie 1 E E. n u 1i H]. m W 6 6 n 1 1 I: 7 7 7 7 I 1.: \ill INVENTOR JOHN L. BIACH ATTOR N EYS 1951 .1. L. BIACH 2,578,778

CONTROL SYSTEM FOR BILLET CUTTING MACHINES Filed July 21, 1948 5 Sheets-Sheet 2 Fig.2

INVENTOR JOHN L. BIACH ATTORNEYS Dec. 18, 1951 J. L. BIACH 2,578,778

CONTROL SYSTEM FOR BILLET CUTTING MACHINES Filed July 21, 1948 5 Sheets-Sheet 5 INVENTOR JOHN L. BIACH BY MM/dM/lgz M ATTORNEYS Patentecl Dec. 18, 1951 CONTROL SYSTEM FOR BILLET CUTTING MACHINES John L. Biach, Cranford, N. 1., aslignor to Air Reduction Company, Incorporated, a corporation of New York Application July 21, 1948, Serial No. 39,930

18 Claims. 1

This invention relates to machines for the multiple cutting of billets with gas torches, and especially to the automatic control of the movement of the torches.

Various machines have heretofore been proposed for cutting into short lengths, billets or other elongated pieces of metal of generally uniform cross-section. For reasons well understood in the art it has frequently been desirable to employ cutters of the gas torch variety, but because of certain inherent characteristics of gas torches it has heretofore proved difilcult, if not impossible, to control such torches so that the entire cutting operation is automatic. One condition which has heretofore greatly interfered with the success of the automatic control has been that, although the billet or length of work to be out has been of generally uniform cross-section, the piece has not been straight, viz., it has been warped or bent. As a result, if the gang of torches spaced apart in accordance with the short lengths to be out are advanced as a unit toward the billet, certain torches will reach the edge of the billet before other torches. In such case the proper instants for starting the preheating flame and then the cutting flame would differ with different torches. Heretofore, the problem resulting from this variable condition has not been met satisfactorily in the automatic control of multiple cutting torches.

In accordance with the present invention it is possible to cut a billet into any desired number of shorter lengths automatically, even though the billet is considerably warped or bent. As soon as the operation of the machine is begun, all of the cutting torches advance toward the edge of the billet and each torch individually comes to rest at the starting point where the preheating is to commence, and waits there until all of the remaining torches have advanced to their respective preheating positions. As soon as the last torch reaches its starting position, all of the torches are caused simultaneously to preheat the work. If no preheating is required the torches may commence the cutting operation immediately after the last torch is in starting position. Thereafter the master control circuit is actuated to move the torches through their cutting paths, following the contour of the billet, the speed at which the torches advance along their cutting paths being automatically controlled.

When the cuts are all completed, and the gases are cut off, the torches move upward or away from the billets so as to clear the same and are returned to their original starting positions ready 2 to respond to a repetition of the cycle as soon as a fresh billet is placed in cutting position.

A better understanding of the invention and the manner in which it operates can best be had from the following description considered in connection with the accompanying drawings, in which: I

Fig. 1 is a plan view of a simplified cutting machine in accordance with the invention showing a portion of its length;

Fig. 2 is an elevational view partly in section through line 2-2 of Fig. 1:

Fig. 3 is an electrical wiring diagram of the control connections for one torch with the apparatus in its inactive or at rest position; and

Fig. 4 comprises schematic diagrams of acrossthe-line or function circuits segregated from the complete circuit of Fig. 1; indicating also a repetition of elements for the control of additional torches, and function" circuits for automatic control of the gases.

The mechanism in accordance with the invention is illustrated in Figs. 1 and 2 which show it in plan and elevational views, respectively. The cutting torches III are of the type commonly used in torch cutting machines and are provided with the usual hose connections [3, l4 and ii for delivering thereto the necessary gases. The preheating gases comprising oxygen and acetylene are provided separately through two hoses l3 and M (Fig. 2) and the cutting gas, such as commercially pure oxygen, is delivered through hose 15. The control of the supply of these gases may be eilected manually but it is preferred to achieve such control by means of valves automatically responsive to the control circuits later to be described. Such valves, which may be e1ectrically controlled, are known in the art and form no part of the present invention. However, one manner in which the operation of such valves can be controlled in response to the control system of the present invention, is described hereinafter. In Fig. 1, five cutting torches are shown by way of example, but it will be understood that any number of torches, either more or less, may be controlled by the system of the invention.

ported as on rollers ll which are mounted on a frame-work it of sturdy and rigid construction.

If desired, the uprights on which the rollers are supported may be made to be adjustable lengthwise of the work-piece to permit greater flexibility of support with respect to the spacing of the cutting torches. Any suitable type of workpiece support may be used depending upon the nature and shape of the piece to be cut.

Each torch in is supported by a torch carriage 2 which moves the torch vertically and horizontally. The top of vertical column I8 is secured to a plate H, and the bottom of column I3 is supported by a foot flange 19. The slide piece 20, through which column l8 passes, is arranged to be slid vertically on the column by means of a lead screw 2| which is threaded in a hole in piece 20. The upper end of screw 2| is journalled in plate II, and the lower end thereof is rotated by a reversible electric motor 22 which in turn is secured to the foot flange I9.

An extension of slide piece 29 forms a bracket 8 to which is attached a horizontal column 23. At the end of column 23 is attached an end-plate 1 corresponding to plate II on the vertical column. As before, the end-plate supportsone end of a lead screw 25 which is rotated by a reversible electric motor 26, which in turn is secured to the bracket 8 so that the lead screw 25 is parallel to the column 23. Sliding on column 231s a slide piece 24 in which lead screw 25 is threaded, so that rotation of this screw in either direction causes piece 24 to slide horizontally in either direction. The cutting torch I is mounted in piece 24 so as to be vertically adjustable therein.

Slide pieces

20 and 24 carry adjustable arms 2! and 28 on which are mounted photo-

electric cells

29 and 30, respectively. These photo-electric cells are arranged with suitable shields or lenses, or both, so as to be sensitive only to light rays projected to them in definite limited directions. Thus, photo-cell 29 receives only a narrow beam of light reaching it in a horizontal direction, as represented by dash-dot line 31a, and similarly, photo-cell 30 is sensitive only to a narrow beam of light received in a vertical direction, as represented by dash-dot line 3|. These two lines are here represented as being marginal or tangential lines to the piece 9. Thus, if the work-piece gives oil light rays because of its high temperature, for example, the photo-cell will respond when the cell moves with respect to the work from a line just tangent to the work to a parallel line which does not pass through the work, and vice verse. I! the work is not at a temperature suchas to emanate radiations to which the photo-cells are sensitive, the same result may be achieved by placing behind the work suitable sources of light, preferably polarized, and arranged so that the work casts a shadow along each of lines ilo and 3|.

Motor 22, in addition to driving screw 2| also drives apotentiometer 35 coupled thereto by an electrically controlled clutch 36. A so-called magnetic clutch would be suitable. Motor 29 is similarly arranged to drive another potentiometer 33 through electrically controlled clutch 34. The drives for these two potentiometers are so geared as to cause the potentiometers to extend to their full range when the

slide pieces

20 and 24 are at their lowest and outermost positions, respectiveb. Motor 26 is also coupled to a small elec-- tric generator 31 of such nature that the output voltage is proportional to its speed.

A limit switch 38 is adjustably positioned on bracket 8 so as to be actuatedby striker on slide piece 24 at any desired extreme inward position of the piece resulting from the longitudinal adjustment of switch 38. A similar limit switch be actuated by striker 5 attached to slide piece 23. By longitudinal adjustment of switch 39 on the column iii the uppermost point in the travel of slide piece 20 may be predetermined. The apparatus above described is all supported on a platform 3 which may be arranged to form the top of a'chamber 50. Each torch carriage 2 may be adjusted longitudinally of the work-piece 3 by sliding the foot flange along rail I2 which is secured to platform 3. Thus, the lengths into which the work-piece is out can be predetermined by the spacing of the foot flanges.

Within chamber it is located a master control mechanism where it is enclosed for protection against slag particles and dirt. It is, however, not necessary that this master control mechanism be located in the base of the cutting apparatus because it may be located at any convenient place inasmuch as it is connected to the apparatus only electrically. This mechanism controls all of the torches during the cutting operation and is actuated when, and not until, the last of the individual torches has been moved to its starting point. The mechanism is operated by a reversible master motor 42 (Fig. 2) which translates a carriage 43 along a slide bar 44 by rotating a lead screw 45. An arm 46 secured to carriage 43 carries at the lower end thereof a sliding contact on a potentiometer 41. The carriage 43, in addition, carries

cams

48 and 49 which cooperate with

cam followers

50 and 5|, respectively, tomove the sliders on

potentiometers

52 and 53, respectively. The cams are removable and are correlated as to shape and size with the shape, size and other characteristics of the workpiece to be cut. Cam 48, which controls the vertical movement of the torch, may be of the same or similar shape as the work-piece, and cam 49 is shaped so that the particular billet will be out according to the horizontal cutting speeds required. For convenience in illustration, the carriage 43 is shown in the center of its travel path, whereas the torch III is shown at the beginning of its travel path. Actually, with the cams at the positions shown, the torch tip would normally be directly over the center of the work.

To the motor 42 is coupled an electric generator 54 of a type such that the output voltage 0! the generator is proportional to the motor speed.

Strikers

4 and 4a are attached to carriage 43 in such a position as to actuate

limit switches

55 and 56. At the ends of the travel of this carriage, switches 55 and 56 may be adjusted longitudinally, viz., in the direction of movement of the carriage so as to be actuated at any desired limit point of movement.

Operation The operation of the control system in accordance with the invention will be described in connection with the circuit diagrams. Fig. 3 is a complete circuit diagram of a control system for one torch and includes the circuit elements and their connections. However, the operation of the system and the functions of the elements'will more readily be understood by reference to Fig. 4 which comprises a series of across-the-line or functionfdiagrams, together corresponding to the diagram of Fig. 3. From these diagrams it will be noted. that the circuits as shown are intended to be operated from a direct-current source. Those skilled in the art will, however, appreciate that at least some of the circuits 3! is adjustably mounted on column l9 so as to may readily be operated from alternating ourrent provided appropriate type of equipment be substituted where required. Assuming, therefore, that for present purposes direct current is employed, the three driving motors herein referred to, may conveniently comprise split series reversible motors, and

motors

22 and 26 should have slightly greater acceleration than motor 42.

In order to simplify the description of the operation of the invention the circuits elements in the diagrams have been designated by letters and numbers in accordance with their functions. To this end, the letter H has been employed in connection with circuit elements employed in circuits operating to drive the torch along its horizontal path, and the letter V for circuit elements operating to drive the torch along its vertical path. The letter M is used to designate elements in the master control circuit. The letter R designates a relay, and the letter P designates a polarized relay. Thus relay No. 1 in the master control circuit is represented as RMI, and the first one of its contacts by RMI-l." Similarly a polarized relay connected in the circuit which operates the horizontal drive mechanism is designated as RHPI, and contacts on that relay are designated by the same number followed by l, 2, etc. A number prefixed to letters, as in IRHI, designates an element identified with a torch of that number, viz., here torch #l, indicating that there are as many more duplicate elements in duplicate circuits as there are torches. In the diagrams of Fig. 4 elements and circuit connections thereto enclosed with dotted lines would be duplicated for each additional torch. The letter enclosed in a parenthesis following the designation of a circuit element, such as RMI-J (a) is a reference to the diagram (a) in which that element appears.

The operation of the system of the invention will now be described in connection with the function diagrams of Fig. 4. Assuming that the mechanism is in its inactive position whereat all of the equipment is deenergized, carriage 43 of the master control (Fig. 2) will be fully retracted and striker do will be against limit switch 56 causing the switch to be actuated. Likewise all individual torches will be fully retracted back, viz., nearest the post i 8 and up, nearest plate II; and

slide pieces

24 and 20 will be in position to open

limit switches

38 and 39. In this condition the control circuits for the electrically operated gas valves will be open so that no gas flows. It may be further assumed that the work-piece 9 is in place on the supporting rollers 11.

The automatic cycle of operations is initiated by pressing the start button I, Fig. 4(a) which completes a circuit through master relay RMI (Fig. 4a), which, as shown, is connected across the line in series with the starting button I and normally closed contacts I of relay RM Energization of relay RMI causes the closing of all of its contacts including contacts RMl-l (a) which provides an electric lock-in circuit for that relay so that it remains energized after the button i is released. Actuation of relay RMI also closes the other contacts thereof which cause all the horizontal-drive motors to move the torches forward and all the vertical-drive motors to move the torches down. This is achieved by closure of contacts RMI-2(1) which feeds power to the forward coils of all horizontal-drive motors, and by closure of contacts RMI-3 (f) which energize relay IRV3 through normally closed contact iRVl-Z, which in turn closes contacts IRVI-l (d) to energize the down coils to the vertical-drive motor 22.

The horizontaland vertical-drive motors continue to operate until all the torches are in their proper positions to start the cuts. The cutting position is also the preheating position, and it is, incidentally, substantially the position of the torch I0 with respect to the work-piece 9 illustrated in Fig. 2. Whether preheating is required, and if so the duration of the preheating period is, of course, a variable depending on the nature, dimensions and temperature of the material. It the temperature of the work is as high as its ignition temperature no preheating would be required, it merely being necessary, in order to start the cut, to open the cutting oxygen valve. 0n the other hand, it is usually necessary to provide preheating, and this step is commenced at the mentioned position. Suitable control of the period of preheating is provided, and may be either manual or automatic.

Energization of relay RMI also closes contacts RMI-4(0) which permits the closing of the circuits including the photo-electric cells through normally closed contacts lRHI-l and lRVI-l. If the billet is hot enough to emit radiations to which the photo-cells are sensitive they will respond when the slide pieces on which they are supported move so that the photo-cells first in tercept such radiations, as represented by lines 3| and 3|(a), Fig. 2. If the billet is not hot enough to emit activating radiations a suitable source or sources of light may be located beyond and beneath the billet, and by suitable optical, or other, means arranged to emit light beams tangential to the work-piece. In this event the dash-dot lines 3! and 3Ia would represent the marginal line between such light beams and the shadow of the work-piece. Control apparatus responsive to photo-electric cells can in a manner well known in the art be caused to respond in either sense desired, so that the control circuit is actuated either when the photo-cell moves from an illuminated area into an unilluminated area, or vice versa.

Assuming that the billet is of sufficiently high temperature to emit light radiations, the photoelectric cells will be activated as soon as they intercept the light rays on

lines

31a, 3!. Activation of these cells is correlated with a desired torch position by suitable adjustment of

arms

21 and 28. When the preselected position is reached by each photo-electric cell, the light from the billet shining into the cells reduces their resistance permitting current to flow through them to energize relays IR.V|(c) and IRHI. Actuation of these relays is not likely to occur at the same instance because the amount of time required by each torch to reach its proper vertical position is likely to differ from that taken to reach its proper horizontal position. However, as each cell in turn is energized the respective relay is actuated to stop movement of the horizontalor vertical-drive motor as the case may be, and when both motors have stopped, the torch will be in the preselected preheating or cutting position.

Actuation of relays IRVHc) and IRHI when photo-

cells

29 and 30 have become conducting, closes contacts lRVl-l and |RH|-|, respectively, to lock in the corresponding relays, after the photo-cells have become deenergized. Relays IRHI and IRVI are so constructed that the lower contacts (as shown in the drawing) close before the upper, normally closed contacts, open. 81-- multaneously, contacts iRVi-IG) and mm- 2(i) are reversed, thus respectively interrupting current through relay iRV3(f) to deenergize the downward driving coils of the vertical-drive motor, and to deenergize the forward driving coils of the horizontal-drive motor. Electric control clutches 34(b) and 36 which are, respectively, connected in parallel with relays iRHI and IRVi,

clutch potentiometers

33 and 35, respectively, Figs. 2 and 3, to the horizontaland vertical-

drive motors

26 and 22.

The actual preheating or the cutting cannot proceed until all of the torches have been properly positioned, both horizontally and vertically.

'When each torch is in place to start its out (viz.,

at its starting point), relays iRHi(c) and lRVi are actuated to close contacts iRHl--3(b) and lRVI-3 which are connected in series with relay RMZ and also with normally closed contacts RM3-2. The broken line in the diagram of Fig. 4, b represents the connection in that series circuit of the RHI-3 and RVl-3 contacts of the corresponding relays of all of the torches. Consequently this circuit cannot be completed until the RHI and RV! relays of all torches as controlled by the respective photo-electric cells, have been actuated, in other words, until all torches are in starting position. Thus, when all the torches have arrived at their respective starting points the master relay RMZ is energized.

Actuation of relay RMZ closes contacts RM2- 2(b) which locks in" all of the series contacts RHI3 and RVi-3 through the shunt circuit,

- shown, and places all of the motor driving circuits in responsive condition to move in paths determined by the master control, as will be explained.

Actuation of relay RM2(b) closes contact RM2-i(h) completing the circuit through potentiometer 53 from which the tapped voltage determines the horizontal speed control. This speed will at all times be proportional to the potentiometer tap voltage as will later be described, and, therefore, is correlated with the cam 49 (Fig. 2) by means of which the position of the potentiometer slider is determined. Energization of potentiometer 53 by closure of contacts RM2- i, in turn, energizes the coils of the sensitive master relay RM(h) which closes RM5l(g) and thus energizes the forward driving coils of master motor 42 (see also Fig. 2) through the contact RM2-4 which has already been closed by actuation of relay RM2. This relay operation results in driving motor 42 forward. Simultaneously, parallel circuits also supplied through potentiometer 53 energize the relay IRH2 permitting a, circuit to be completed through closed contacts RM2-5(i), lRH2-i and iRHl-2 which energizes the forward driving coils of the horizontal-drive motor 26 causing it to move its torch forward. Corresponding relays and contacts duplicated in the other horizontal-drive motor circuits cause similar movement of all of the other torches.

The actuation of relay IRVZU) or of IRV3 to energize the vertical-drive motor and consequently to drive the torch carriage respectively pendent upcn the shape of c 48 as will later be described in more detail.

As the master motor '32 increases its speed it drives its coupled generator $601.) which generates a rising voltage of polarity opposite to that across potentiometer 53. A speed will be reached at which the generated voltage equals the tapped potentiometer voltage at which point the relay RM5(h) will drop out because no current will pass through it. Since the current to the master motor 42 is supplied through contacts RM5i (g) of relay RME. the opening of these contacts causes the motor to slow down until the generator voltage drops sufficiently to permit relay RMS to pull in again. A balance point will, therefore, be reached when relay RME flutters in and out, just maintaining the proper motor speed. Therefore, the contacts RMd-i of relay RME may be considered as controlling the speed of the master motor. For convenience, this circuit in which relay RM5 is connected may be called a balance circuit. This relay and generator 645 thus together function as a governor automatically allowing motor 52 to operate at speeds corresponding to the voltages tapped oif potentiometer 53 by its slider. As the master motor moves its carriage 43 (Fig. 2), the cam follower 5i will automatically readjust the setting of potentiometer 53 in accordance with the shape of cam 49, and consequently the speed of the master motor will follow these automatic adjustments. Since cam 49 is shaped for the particular billet that is being cut, the master motor will move at horizontal cutting speeds which are predetermined for the various vertical dimensions of the work-piece. Y

The horizontal-drive motor is coupled to and drives its own generator 310:.) which is connected in a circuit similar to that of the master motor generator 54. As shown in the diagram (Fig. 4, h) generator 31 is connected in series with relay IRH2 so that the output voltage of the generator 31 is also compared with the tapped voltage from potentiometer 53. Thus each torch-driving motor will operate at a speed corresponding to that of the master motor, and all motors will follow the speed pattern established up or down, is dependent, once the torch is in 1 in the. master control system. Although the speeds of the horizontal-drive motors and the master motor will be closely matched they will not coincide. One or the other will be slightly greater causing the motors gradually to become out of step and the torches to assume incorrect positions, tending to result in a loss of the out. A supervisory or position control is, therefore, provided which efiectively makes a continuous check on the position of each torch and causes it to move in fixed relation to the master control carriage, and, therefore, to move in the same speed pattern. This result is achieved by increasing or decreasing the speed of any errant motor until the torch has regained its proper relation to the master control position. Although speed changes of almost any degree are possible in accordance with this invention, it is preferable to design the components so that the change of speed of any given motor will not exceed approximately 10%.

The supervisory or position control just referred to includes the potentiometer 41 (Fig. 2, Fig. 4, d) of which the slider always indicates the position of the cam-supporting carriage 43, and the potentiometer 33 of which indicates the horizontal position of the torch 10. Since all horizontal-drive motor potentiometers were clutched to their respective motors when the proper starting point was reached, via, when the photo-cell 30 etc., (Fig. 4, were energized, each potentiometer 33 assumes a position corresponding to that of the slider 46 on master potentiometer 41. If the motor speeds matched exactly, the sliders on potentiometer 33 and master potentiometer 41 would always be in the same relative positions and in balanced relation. However, when the motors get out of step and the cutting torch consequently out of position, the balance between these potentiometers is upset. For instance when the horizontal-drive motor 26 (Fig. 2) is running slightlytoo fast, the upset of the potentiometer balance energizes polarized relay IRHPU) which shifts its contact lRI-IPi from neutral position to the upper contact so as to energize relay IRH3. This relay closes contact iRH3l(h) shunting relay IRHZ through resistance R1. At other times when the relative horizontal position of a torch lags that of the master carriage, relay i RHPQi) moves its contacts lRHP-l to the lower position, actuating relay IRHl which in turn closes contact IRHl-Hh), shunting generator 31 through resistance R2. The application of the shunt resistances R1 and R2 in this manner controls the relation between the horizontal positions of the torch and the master control carriage 43 as follows:

As above stated, the horizontal-drive motors, of which motor 25 is one, are calibrated for a slightly greater acceleration than the master motor 42. During normal operation of the torch driving motors, the potentiometer 53(h) provides a voltage which actuates relay IRH2 and permits power tobe supplied to the motor driving coils through contact iRHZ-i (i). The connected generator 31 provides a voltage in opposition to the potential tapped from the potentiometer 53 which, when the motors are rumiing, creates a differential voltage in each circuit that does not affect the relay IRHZ as long as this differential exceeds a predetermined minimum. The motor 26 moves the torch forward at a slightly greater acceleration than that of the master motor, until the positions of-the torch and the master motor carriage are out of synchronism, and consequently the differential between the voltages tapped from potentiometers33(;i) and 41 is of sufiicient magnitude to actuate relay IRHP which interconnects the sliders of those two potentiometers. Each torch control circuit is independent oi the others and responds only when its torch is out of position with the master control.

' As above described, relay contacts IRHP| (7) which actuate relay IRH3 when the torch position leads that of the master carriage, connects resistance R1 (h) in shunt with relay IRH2 by closure of relay contact IRH3-i. The shunting of resistance R1 across relay IRH2 reduces the voltage across that relay to a value below the necessary minimum energizing voltage, causing the relay to drop out and open its contacts iRH2-l (i). Forward acceleration of the corresponding motor 26 is thereby temporarily stopped. Acceleration is resumed when the torch has subsequently fallen behind the carriage position during the idling interval, resulting in a reversed relative potential of

potentiometers

33 and 41 causing the relay IRHPU) to swing its moving contact iRHPI to the lower fixed contact where it completes a circuit through relay lRHl. The resistance R: shunted across generator 31 by closure of contacts IRH4i(h) decreases the output voltage of the generator to a value corresponding to a speed lower than the actual speed of the generator, this decreased voltage being sufficiently small to create a potential across relay IRH2 to close contacts iRHl-Hi) and re-energize the forward drive coils of motor 26. As the motor has a slightly greater acceleration its torch will rapidly catch up with the master carriage, causing relay IRHP to be returned to its neutral position and subsequently to its upper position, again completing the circuit through relay IRH3 as the torch position once more leads that of the master carriage.

The cycle just described is repeated in this and th other of the torch control circuits to maintain a fine degree of position control by virtue oi the rapidity of .the cycle of operations which permits the torches to lead or lag the position of the master carriage 43 by but a minute amount. Each torch continuously varies its position by this minute amount either side of the exact corresponding position of the master carriage, but never gets out of position by any greater amount. In this manner the control circuits act as a governor maintaining the position 01' each 01 the torches in proper relation to the master carriage, and permitting all of the torches to follow the pattern of cutting speed in accordance with the contour of cam 49. While the horizontaldrive motors have constant speed variation the change of speed is never great. These motors are so controlled that they do not stop, nor are they driven at high speed, because abrupt changes of speed are undesirable if the cutting operation is to be satisfactorily maintained.

Similarly, the vertical movement of the torches is also correlated with the displacement of the master carriage. As has previously been shown, the vertical control of each torch includes a camactuated potentiometer bridge circuit such as is shown in diagrams Fig. 4(e) and (1) together. Upward or downward movement of the torches depends on the polarity of the potential impressed across the relay lRVP(e), which in turn is dependent on the comparative settings of the

potentiometers

52 and 35. The speeds at which the torches move in either direction are generally faster than the movement of the master speed control mechanism. The torch position will therefore tend to be in advance of the control mechanism positions and will, by the action of the control circuits, be retarded to follow a series of controlled vertical positions which correspond to simultaneous horizontal displacements and thereiore to the shape of the work-piece. The polarized relay lRVP(e), when actuated so as to close the upper contact iRVPl(f), in turn actuates relay I RVZ( f), or when actuated to close the lower contact lRVP-i, actuates relay iRV3. Depending on the direction in which the connection between

potentiometers

52 and 35 is unbalanced, relay IRV2 closes contacts IRV2I (d) to energize the upward'driving coils of the motor 22, or relay IRV3 closes contacts |RV3i(d) to energize the downward driving coils of the same motor. Of course, only one set of motor driving coils can be energized at a time because relay contacts IRVP-l are closed either up or down.

The setting of potentiometer 52 is determined by the position of cam 48 and therefore by the position of the master control carriage. The setting of potentiometer 35 is determined by the actual vertical displacement of the torch as translated into the displacem t of potentiometer 35 through electric clutch 3 (c). This clutch couples the potentiometer 35 to the torch carriage at the beginning of the cutting cycle so that the potentiometer voltage indicates the actual 11, vertical displacement of the torch for all its positions duringthe cutting cycle.

The to'flih is' caused to move upward at the beginning of a cutting operation when cam 46 elevates cam follower 50, together with its potentiometer contact arm, to impress an initial differential voltage across the relay lRVP(e). With the polarity in this ,direction, contact IRVP-Hf) energizes relay IRV2 which energizes the upward driving coils of the motor 22 through the contacts lRV2-l(d). The torch carriage is thus driven upwardly at a rate cor- 12 disconnects the speed control phase of the torch control. Simultaneously, contacts EMS-3(a) are reversed, opening the upper contact and responding to the speed of the driving motor until its position gets ahead of the corresponding position of the master control carriage. In

reaching this position the potentiometer 35 will have "matched" potentiometer 52, so that no current will flow through IRVP. Upward acceleration of the torch carriage is therefore stopped until further displacement of cam 48 and readjustment of potentiometer 52 reestablishes a sufllcient potential across IBVP to actuate it, whereupon the driving co of the motor will again be energized. The ac al operational sequence of these torch circuits, being extremely rapid, causes the torch to follow a predetermined pattern of upward vertical movement as indicated or determined by the shape of cam 46.

Downward motion of'the torch takes place when the cam follower is displaced in the opposite direction to that which'causes upward motion. A reversed polarity having been established across relay IRVP(e) the downward driving coils of motor 22 become energized through contacts lRVi-Hd) of relay IRVSU). Here again, the torch will tend to lead the cam position and will be held in check by the intermittent operation of the motor imposed by the balance requirements of the control circuit. It should be noted that as long as follower 50 of cam 46 is made to move in the-same direction. the potential established across relay IRVP will be in the same direction, because uninterrupted movement of the-torch carriage 2 is prevented when the potential across IRVP is zero or in any event less than that required to operate that relay. Subsequent movement of the cam follower will always reestablish the relay-actuating potential according to the direction in which the cam follower has been displaced. It should also be noted that all of the "vertical control circuits are so connected as to permit them to act independently of one another, each functioning as its corresponding torch position warrants. For this purpose contacts lRVl-4(j) are inserted in each circuit between contacts iRVP-l and the remaining parallel circuit connections associated with the other motors. Contacts lRVl-4 are normally closed, but are opened during the cutting operation when the photoelectric cell 26 has been energized and the relay IRVI has been actuated. Actuation of relay IRVP to close the upper one of the contacts lRVP-Hf) so as to energize relay IRV2 does not result in energizing all such relays in the remaining motor circuits because of the open circuit at contacts IRVI4(!).

- When the end of the cutting cycle is reached, the striker 4 (Fig. 2) on carriage 43 closes limit switch 55. This energizes a master relay RM3(a) which is locked in by contacts HMS-4 connected across switch 55. Relay RM2(b) which is deenergized by the opening of the normally closed contact EMS- 2, opens the circuit of potentiometer 530i) through contacts RM2-l and thus .closing the lower contact, as shown in the drawing, reversing the connections to the master motor 42 and connecting the coils for reversed operation. The master motor then drives carriage 43 rapidly back to its inactive position at which striker 4a on carriage 43 actuates switch 56, closing contacts 56-2(g) and opening contacts 56l (o) and holding them open until they automatically close again when the carriage is next moved forward. The opening of contacts 56-! opens the reverse drive circuit of the master motor 42. The controls for the verticaland horizontal-drive motor circuits remain in circuit because contacts RM34(e) and EMS-411(1) connected in parallel with contacts RM2-3 and RM2-3a, respectively, which are now open, close to continue operation of these circuits. When the follower 50 of cam 48 is retracted, the potential across relay IRVP is reversed, causing the contacts of that relay to reverse thus energizing relay IRV2; andclosing contact lRV2-l(d), which causes motor 22 to operate in high reverse speed corresponding to the speed of the master motor, driving the torch carriage to its uppermost or inactive position. Upward vertical movement of the torch carriage is stopped when the slide piece 20 contacts adjustable limit switch 39 (Fig. 4, f and Fig. 2) which opens the circuit to the upward driving coils of motor 22 by deenergizing relay IRV2(f).

The retum" coils of the horizontal-drive motor 26 are energized through the closing of contacts RM35(g), as above described, and lRH3-2. Whenever the torch lags behind the position of the carriage 43, as previously mentioned, the resulting unbalance between

potentiometers

41 and 33 energizes relay IRHP so as to operate relay IRH3(9') which then closes contacts lRH3-2(i) connecting the return coils of motor 26 to the line. Motor 26 then drives the torch carriage horizontally back to the starting point.

As each horizontal and vertical-drive motor operates to bring its respective torch back to the inactive position, the normallyvclosed contacts IRV3-2(a), IRV-2 and iRH3-3 etc., will be closed after the polarized relays of the control circuits (e) and (i) have been restored to neutral position by return of the respective potentiometers to their initial positions. The completion of these contacts vin series with contacts 56-2, which were closed by actuation of switch 56, establishes a circuit through the master. relay RM4 (a). Normally closed contact RM4-l (a) is thereby opened and all the master relays are deenergized. When relay RMI is deenergized electric clutches 34 and 36 (Fig. 4, c) are deenergized so as to uncouple

potentiometers

33 and 35 from

motors

26 and 22, respectively. Contacts RMl--6(,f and RMl--5(i) are returned to their normally closed positions as the master relay RMI is deenergized. Under the conditions Just described all of the torches are in their most receded and uppermost positions, and the cycle commencing at this inactive position, passing through the starting point and the cutting operation and returning to the initial inactive position will have been completed.

Gas control apparatus by which the preheating and cutting gases may be automatically turned on and fed to the torches at the proper times may take any of several forms. but may be as follows:

It maybe assumed that the preheating gas comprising oxygen and acetylene may be controlled, respectively, by two electrically operated valves of known type, sometimes called "solenoid valves, and that the cutting gas comprising oxygen may be controlled by another electrically controlled valve of similar type. These electrically operated valves are represented Ming; 4, k, I and m, and are actuated in response to the closing of relay contacts.

If relay RM2 is furnished with a sixth pair of contacts connected across the line in series with the oxygen (02) and acetylene (CzHz) valves, as shown in Fig. 4, k, the preheating gas will be automatically fed to the torches as soon as the relay RM2 is actuated. It will be recalled that relay RM2 is actuated as soon as the last of the photo-electric cells has been actuated, viz., when all of the torches have reached their starting points or positions. Inasmuch as a time delay is I frequently required to permit preheating before the torches begin to move on their cutting paths, the relay contacts RM2-l, in this case, instead of being connected in circuit to energize potentiometer 5301) would be omitted, and contacts RTD-l, of a suitable time-delay relay would be substituted therefor, as indicated in Fig. 4, h. Also, contacts RMZ-Mg) of relay RM2, instead of being connected to the forward moving coils of master motor '42 would be omitted, and contacts RTD-4 of the same time-delay relay would be substituted therefor, as shown in Fig. 4, g. This time-delay relay should be of a type permitting the period of delay to be adjustable, and it would be connected across the line by closure of a seventh pair of contacts RM2-1(l) of relay 3M2. Hence, when relay contacts RMZ-l close, relay RTD will be energized, but the closing of the contacts of relay RTD will be delayed depending upon the time delay adjustment. Relay RTD carries seven sets of contacts, six of them replacing, and having the same function as, those of relay RM2 as follows: RDTI for RM2-l (h), EDT-2 for RM2,2(b), RTD-3 for RM2-3(e),

Mg) and RTD5 for RM2 -5(i). If this timedelay relay is initially adjusted for a time period equal to that required for preheating; the particular work-piece to be cut, the cutting gas will likewise be automatically controlled as follows:

When relay RM2 is energized as above mentioned, contacts RM2-|(l) will close, energizing relay RTD. After expiration of the preselected delay period for which relay RTD has been set, contacts RTD-6(m) will close, opening the cutting-gas valve which is connected in series therewith across the line. Contacts RTDl and RTD-2 also close upon operation of relay RTD and in so doing initiate operation of the master motor 42 and at the same time energize the master motor control circuit of Fig. 4, h, thus automatically initiating the cutting movement of the various torches simultaneously with the application of cutting gas to the workpiece. The remaining contacts of rela RTD have the same functions'as the corresponding contacts of relay RMZ. If necessary, a suitable control may be provided to discontinue the preheating gas after the cutting gas has been ignited, but ordinarily this would not be required because it is customary not to cut off the preheating gas during the cutting operation. At the end of the cutting cycle, as previously explained, the relay RM2 is deenergized by the opening of relay contacts EMS-2 which occurs upon actuation of limit switch 55 when master control carriage 43 reaches the end of its travel. By this means all of the gases are automatically cut off by the closing of the gas control valves when the relay RM2 is deenergized.

What is claimed is:

1. In combination with a billet cutting machine including a plurality of supporting standards, cutting torches supported by torch-carriages movable on said standards vertically and horizontally, drive means for moving said carriages in each of said directions, unitary control means actuating all of, said drive means simultaneously and billet support means for holding a billet in cutting relation to said torches, an automatic control system which includes photoelectric cells movable with said carriages and arranged so that one cell receives light from said billet only in a vertical direction and another cell receives light from said billet only in horizontal direction, control circuits actuated in response to said photoelectric cells for automatically stopping the movement of each torch-carriage when the tip of its torch arrives at a preselected position with, respect to said billet, and control means causing automatic resumption of movement of all of said torches after the last thereof has arrived at its said preselected position.

2. A control system according to claim 1, in which said control includes a master circuit in which there are connected a plurality of separate circuit elements actuated respectively in response to said photoelectric cells, a master element connected in said master circuit which is actuated only as a result of the actuation of all of said circuit elements, and connections for energizing all of said drive means upon actuation of said master element.

3. A system according to claim 2 wherein said master element comprises a time delay device arranged to effect energization of said drive means at a predetermined time after said master element is actuated.

4. In an automatic billet cutting machine adapted to operate in a cutting cycle, a cutting torch supported on a carriage movable vertically and horizontally, vertical-drive and horizontaldrive means for said carriage, first and second potentiometers having sliders mechanically coupled to each of said drive means, respectively, a master control circuit for controlling operation of both said drive means, said master control circuit including third and fourth potentiometers electrically connected, respectively, to said first and second potentiometers to form two balance circuits, and a control element connected in each balance circuit to control the operation of each of said drive means, separately in response to the balance between said potentiometers in each of said balance circuits.

5. In a machine according to claim 4, a clutch serving to couple and uncouple each of said drive means to and from the potentiometer associated therewith, and means automatically actuating said clutches at the beginning and end of the cutting cycle.

6. In an automatic billet cutting machine adapted to operate in a cutting cycle, a cutting torch supported on a carriage movable vertically and horizontally, vertical-drive and horizontal drive means for said carriage, a master control circuit, a drive-control circuit for each of said drive means, two balance circuits each including a master circuit control element and a drive circuit control element, a polarized control element connected in each balance circuit, and connections from each polarized control element to control the operation of one of said drive means.

7. In a cutting machine suitable for automatically cutting a bent billet into a plurality of shorter lengths, a plurality of cutting torches each supported on a separate movable torch carriage, drive means for each of said carriages, a support for holding a billet in cutting relation to said torches, control means actuating all of said drive means simultaneously to move each torch individually into a predetermined cutting position uniformly spaced from the billet irrespective of its contour at the point where such torch is to start its cut, means for automatically stopping each carriage when the torch which it supports arrives at said position, and means for initiating cutting movement of all of the torch carriages simultaneously after all of said torches have reached said predetermined cutting positions.

8. A cutting machines according to claim 7 wherein said last mentioned means includes a master control system coupled to said control means so as to effectively control the speed of said drive means, said drive means including horizontal and vertical drive means, and cam means in said system shaped to predetermine the speeds of said horizontal and vertical drive means in accordance with the cross-sectional shape of said billet.

9. In a cutting machine according to claim '7. a first control element which is actuated only when all of said torches have arrived at their respective starting points, and a second control element actuated by said first control element so as to start said torches on their cutting paths.

10. In a cutting machine for automatically,

cutting a billet, a cutting torch mounted on a movable carriage, a drive motor for driving said carriage, a speed control circuit for said motor, and a master control system linked to said speed control circuit so as to control the speed of said drive motor, said master control system including a master motor, a source of voltage generated in proportion to the speed of said master motor, a master carriage driven by said master motor, a first cam element moved by said master carriage, a potentiometer having a fixed voltage connected thereacross, a second cam element mechanically coupled to move the slider 01 said potentiometer, a balance circuit including said source of voltage and the slider of said potentiometer and a control element, whereby the eflective voltage impressed on said element is a function of the speed of said master motor and of the position of said cam, and connections from said control element to control the speed of said master motor.

11. In a cutting machine for automatically cutting a billet, a cutting torch mounted on a movable carriage, a drive motor for driving said carriage, a first potentiometer having a slider driven by said drive motor in proportion to the displacement of said carriage, a speed control circuit for said motor, a master control system including a master motor, a master carriage driven by said motor and a master potentiometer having a slider moved by said carriage, a source of efiectively fixed voltage connected across each of said potentiometers, a polarized control element connected in circuit between the sliders of said potentiometers, and connections between said control element and said speed control cir- 16 cuit whereby to control the speed of said drive motor as a function of the relative positions of said carriages.

12. In acutting machine for automatically cutting a billet, a plurality of cutting torches arranged to be drivn in individually different paths, a plurality of torch-'drivingmotors including a horizontal-drive motor and a verticaldrive motor operatively coupled to each torch to control the path and speed of movement of said torch, means for independently controlling the horizontal-drive motors and the vertical-drive motors, respectively, a master motor, means actuated by said master motor for regulating the cutting speed of all said torch-driving motors in response to that of the master motor, a master control system including a master control circuit for controlling the speed of said master motor and a mechanism having a speed pattern pre-= selected in accordance with a cross-sectional dimension of the billet, and connections from said speed pattern mechanism to said master motor control circuit'for automatically controlling the speed of said master motor and hence the relative speeds of ,said horizontal driving motors and of said verticaldriving motors, respectively, in accordance with said speed pattern.

13. A system for automatically controlling the position of a moving element, including in combination, an electric motor coupled to said element for moving the same, a generator driven by said motor and having an output voltage substantially proportional to the speed of said motor, a constant voltage source, a first potentiometer connected across said voltage source, a first balance circuit comprising said generator and a first relay connected in series between the slider oi said first potentiometer and one side of said voltage source so that the voltages of said generator and of said source are in opposition, second and third potentiometers connected in parallel across said voltage source, a second balance circuit comprising a polarized relay connected between the sliders of said second and third potentiometers, second and third relays, contacts on said polarized relay including two fixed contacts and a moving contact which is connected to one side of an electric power source, said second and third relays being connected respectively between said ,fixed contacts and the other side of said last mentioned power source, first and second resistors, said second relay having contacts connecting said first resistor in shunt to said first relay, said third relay having contacts connectin said second resistor in shunt to said generator, coupling means coupling the slider of said second potentiometer and said element whereby the position of the slider of second potentiometer is determined by the position of said element, and contacts on said first relay operable upon closure to connect said motor to a power line.

14. In a system according to claim 13, a movable master position control element, and linking means interconnecting said master control element and the slider of said third potentiometer whereby the position of the slider of said third potentiometer is determined by the position of said master control element.

15. In a, system for automatically controlling the speed of an electric driving motor operated from a power line, the combination which includes, a generator driven by said motor and having an output voltage substantially proportional to the speed of said motor, a source of constant voltage, a balance circuit including in series a first relay and said generator connected across said voltage source with the output voltage of said generator in opposition to that of said source with respect to said relay, a master control circuit, second and third relays actuated by said master control circuit, a resistor connectible by closure of contacts of said second relay effectively to reduce the voltage on said first relay, a second resistor connectible by closure of a contact of said third relay effectively to reduce the voltage output of said generator, and contacts on said first relay operable upon closure to connect said motor to said line.

16. A system according to claim 15 in which said master control circuit includes a master control motor, the normal rate of acceleration of said master motor being less than that of said driving motor.

17. In combination with a billet cutting machine including a plurality of supporting standards, cutting torches supported by torch-carriages movable on said standards vertically and horizontally, drive means for moving said carriages in each of said directions, unitary control means actuating all of said drive means simultaneously and billet support means for holding a billet in cutting relation to said torches, an automatic control system which includes photo-electric cells movable with said carriages and arranged so that one cell receives light from said billet only in a vertical direction and another cell receives light from said billet only in a horizontal direction, and control circuits actuated in response to said photoelectric cells for automatically stopping the movement of each torch-carriage when the tip of its torch arrives at a preselected position with respect to said billet.

18;. In a cutting machine suitable for automatically cutting a bent billet into a plurality of 18 shorter lengths, a, plurality of cutting torches each supported on a separate movable torch carriage independently controllable, a support for holding a billet in cutting relation to said torches, said carriages and torches being spaced apart longitudinally of said support, drive means for each of said carriages, individual control means for independently controlling each of said drive means, unitary control means actuating all of said individual control means simultaneously to move each torch individually into a predetermined cutting position uniformly spaced from the billet irrespective of its contour at the point where such torch is to start its cut, and means for automatically stoppin each carriage when the torch which it supports arrives at said position.

JOHN L. BIACl I.

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

UNITED STATES PATENTS Number Name Date 2,021,196 Oldham Nov. 19, 1935 2,116,593 Bouvier et a1. May 10, 1938 2,143,969 Biggert, Jr Jan. 17, 1939 2,177,276 Bucknam Oct. 24, 1939 2,229,448 Garman Jan. 21, 1941 2,269,643 Bechtle et a1 Jan. 13, 1942 2,277,054 Anderson Mar. 24, 1942 2,281,844 Jones May 5, 1942 2,404,600 Scovill, Jr a- July 23, 1946 2,504,171 Anderson Apr. 18, 1950 FOREIGN PATENTS Number Country Date 84,276 Sweden Sept. 11, 1935