US1856546A - Shear for use in rolling mills, etc. - Google Patents

Description

May 3, 1932.

I J. GASSEN snmm FoR'usE m ROLLING MILLS,

ETC

Filed June 27, 1930 ILJ LJ] HRH Patented May 3, 1932 UNITED STA JOSE]? GASSEN, F 'DUSSELDOBF, GERMANY, ASSIGNOR T0 SOHLOEMAN'N' AKTIEN- v GESELLSCHAFT, 0F DUSSELDORF, GERMANY, .A CORPORATION O]? GERMANY SHEAR FOR USE IN ROLLING MILLS, ETC.

Application filed June 27, 1930, Serial No.

My invention relates to'rolling mills or the like and more especially to means for severing rolled material e. g. bars, while in motion.

For this purpose, cutting edges or knives are used, which during the cutting operation, have the speed of the moving bars. There are many different types of shears which opcrate on that principle:

Shears provided with continuously operating, rotating knives, produce a rectangular cut, but the adjustment of the cutting length ofi'ers considerable difliculties and in particular, depends on the diameter of the knife circle, inasmuch as only a multiple of the circumference of the knife circle is available as a cutting length.

Shears provided with continuously operating, rotating disks or saws, which are disposed at an angle to the longitudinal axis of the'bars, produce an oblique cut involving great waste, while the sharp ends of the bars are dangerous and frequently cause disturbances during conveyance of the bars. But 1n shears of this type, the cutting length may readily be adjusted as desired.

The so-called flying shears comprising re ciprocating knives, mounted on a lever and which by means of steam or gas pressure are quickly accelerated from a; position ofrest to the speed of the moving bar, produce a rectangular cut and, at the same time. the'cutting length can be readily varied. But, since these shears mustalways operate underfull pressure without utilization of the expansive force and since the moving masses for each cut must be accelerated during successive reciprocating strokes, an excessive amount of power is consumed and the operation is uneconomical. In case of fluctuations in the steam or air pressure, as they will always occur in a smelting plant, the cutting length will automatically vary, because the cutting knives reach the moving bar alternately sooner or later. Such irregularities escape attention until the bars, thus cut to different lengths, are placed neirt to each other for shipment.

Some of the principal objects of this invention are to replace the cumbersome reciprocating motion by an improved rotary motion in one direction; to use electricity for 464,221, and in Germany August 10, 1929.

accelerating the shears from a position of rest. to the cutting speed, that source of power pressure fluctuations, so that the pieces cut with a particular adjustment are practically even in length, there being only a difference of small increments caused by shrinkage or expansion due to temperature variations; and to drlve a pair of co-operating cutting means by independent, substantially synchronized motors, while reducing the gearing opera-- tively connecting co-operating cutting means to a minimum, using such gearing only for balancing fractional difi'erences in speed of rotation, but not using it for theactual transmission of power, in this way being able to overcome excessive inertia which would be caused by strong gearing.

To attain these and other objects, the improvements are arranged as follows :-The rotation of the knives starts from a position of rest; the start of rotation of the knives being adjusted in respect to the position of the end of the moving bar, auy desired lengths may be produced by cuts disposed at right-angles to the longitudinal axis of the bars. The knife shafts are severally and directly driven by electric motors, which are compelled to synchronize by means of a gear coupling. The end an electrical contactor, as known to those of the bar actuates acquainted with the respective art, thus simultaneously closing the electric circuits of the motors on the knife shafts. For the purpose of cutting larger profiles, the induction motors, which are directly coupled with the knife shafts, are supplied with current from a polyphase generator, and the heavy operating currents may be rapidly switched on, and correspondingly heavy work may be performed in rapid repetition by the exciting current of the generator being controlled instead of the heavy operating current flowing between the generator and the motors being connected and disconnected.

Immediately after the cut-tin operation, the induction motors on the kni e shafts are retarded by means of direct current brakes, which are incorporated in said motors, and the knives are brought to a stop in a predetermined starting position of the cutting operation. The motors on the knife shafts are of the induction type provided with rotors of the squirrel cage, or any short-circuit type, and equipped with direct currentbrake means which are reliable in operation even under the strain of frequently interrupted, intermittent operation of the motors. It has been. experimentally determined that such motors, when started from a position of rest of the knife shaft, can attain, while moving through the angle between said position and the cutting position, a speed of rotation which corresponds to the speed of movement of the bars.

When shears are to operate in connect-ion with bars moving at different speeds, the current supply for the induction motors is drawn from a polyphase generator, the speed of which may be adjusted according to the speeds of movement of the bars.

Since the contactor, which is actuated by the end of the bar closes the circuit of the two knife motors at a predetermined fixed starting position, and since the time intervals between the start and the cutting are fixed and remain the same for a specific ad justment, the bars are cut at substantially equal length.

In connection with shears used to sever bars of larger profiles, such as billets oringots, I do not control the current of the knife motors b correspondingly larger circuit breakers, but the considerably smaller exciting current of the polyphase generator is controlled so that only comparatively small currents have to be controlled, which require considerably smaller circuit-breakers. As an additional safeguard and guarantee for frequent circuit-making and breaking, a number of circuit-breakers or a number, of the component parts which are subject to wear are connected in parallel, so that one of said parts may be substituted for the other without any interruption of the continuity of the operation. By means of suitable connections, such a change can be brought about automatically.

The breaking of the current operating the knife motors and the stopping of the rotation of the knives by a direct current brake, take place, as soon as the knives open up, after having cut the bar and after having moved away from it. The braking distance may be adjusted with such accuracy that the knives always come to a stop at the same predetermined starting positions.

In the drawings, in which I have, by way of illustration, shown an embodiment of my invention more or less diagrammatically, Fig. 1 shows a longitudinal, partially sectioned side view of the shears, Fig. 2 a front view of the same, the knives being shown in the cutting position, and Fig. 3 a wiring diagram illustrating an arrangement of the electric circuits.

The knives l of the shears are mounted upon arms 20 radially extending from the shafts 2. These shafts are directly driven by the electric motors 3 which are connected to the ends of said shafts by couplings 16. The motors 3 are equipped with direct-current brake means and are mounted upon the housing 17 in concentricity with the journals 18 and 19, supporting the shafts 2 in the front and in the back of the housings, respectively. In Fig. 2, alternative positions of the knives are shown in dotted lines respectively at 5, 6 and 7. The knives 1 do not rotate continuously, but they start their rotation for successive cuts from a starting position 5, in

which they are at rest. After the motors 3 have been started, the knives reach at the position 6 a peripheral speed substantially equal to the linear speed of movement of the bars and this speed is maintained until the bar has been cut and until the knives have reached the position 7 in which they clear the moving bar. At this point of -.he operation, the current supply of the motor is interru ted and the rotation of the knives is retar ed to such an extent that they will be again at rest when they reach the starting position 5. The length 8, which has been cut off the bar 21, is brought out of thelreach of the switch lever 9 by movement in a longitudinal or lateral direction, or the switch lever may be of a collapsible design that it is released after the cutting operat on, and returns to an operative position before the approach of the end of the bar 21. The various ways in which the switch lever may be returned to c an operative position are quite familiar to those acquainted with the respective art, and the arrangement and operation of the circuitbreaker 10, which is operatively connected with the switch lever 9, are also well known. The common fulcrum 22 of the switch lever 9 and of the circuit breaker 10 is longitudinally adjustable in the direction of travel of the bar in an exemplarily indicated slot 23, which preferably forms part of the trough in which the bars move. When the end of the bar 21 strikes the switch lever 9, the same is swung in a counter-clockwise direction, and the circuit-breaker 10 is closed thereby. That circuit-breaker is connected in the circuit of the motors 3, which are started thereby to effect a new severing of the bar 21.

The motors 3 are polyphase motors with short-circuit rotors and direct current brakes.

In said figure are shown at 3-3 the two operating motors which, as will appear from Fig. 1, are secured by flanges to the supports of the shears. These motors are provided with short circuit rotors. The stator windings 16 and 17 respectively are interconnected in the manner of a star or in any other suitable manner and the windings of the two motors are connected by the conductors 18 and 19 respectively with the unconnected stator windings 20 of the three-phase generator 11 in series. This generator is operated by a belt from the rolling mill 21, from which the bars to be out are ejected. The frequency of the current produced by the generator and thus also the speed of the operating motors correspond to the speed of the bars to be cut. The exciter winding of the generator 11 is connected with the collector rings 22 and is fed by the direct current generator 15 which is operated by a motor indicated at-14.. In the connecting conductors between the direct current generator and the collecting rings 22 is included the magnetic contactor 13 and the regulating resistance 23, whereby the amount of voltage of the current can be adjusted at will. The coil of the contactor 13 is fed by the direct current generator 15. In the same circuit with said coil there is connected in series the switch 10, which is operated by the end of the bar 8' to be cut, and furthermore, there are connected in series the contacts 24, which by means of a cam disk 25 mounted on the extended end of the shaft of one of the motors 3 are bridged or interrupted according to the position of the motor rotor.

The stator windings 16 and 17 of the motors 3 are permanently connected with the stator winding 22 of the generator 11. Two of the phases of these motors are connected by the terminal contactor 12 with the direct current generator, the connection being so arranged that between the ends of each single phase winding of the generator 11 there does not occur any difference in voltage, as shown by the polarity marks on the drawings.

Therefore, the direct current does not flow through the windings of the generator, but through two of the phase windings of each motor. The coil of the contactor 12 is also fed by the direct current generator 15. Connected in series with said coil are the two contacts 26, which by a cam 27 mounted on the extended end of the shaft of the other operating motor 3, according to the position of the motor rotor, are bridged or interrupted in a similar manner as with the contacts of the first mentioned operating motor.

The cutting operation is as follows:

In the state of rest of the motors 3 the contacts of the switch 10 are open. The rotors of the two operating motors are ready for the cutting operation. The cam 25 is so positioned that the contacts 2a are connected. The cam 27 of the other motor, however, is so positioned that the contacts 26'are interrupted. Both contactors 13 and 12 therefore are in inoperative position, and therefore, no direct current flows through the exciterfwinding of the generator 11, and therefore, no voltage is produced in its stator windings. Also no three-phase current flows through the stator windings oi the operating motors 3. \Vhen the contactor 12 is in inoperative position, no direct current flows through these windings.

Now, when the roller bar 8 approaches the shears, the end of the bar closes the switch 10 in front of the shears 10 so that across the closed contacts 24 current flows through the coil of the contactor 13, closing said contactor, with the result that direct current now flows across the regulating resistance 23 through the excitcr winding of the generator 11. The voltage now produced in itsstator winding forces three-phase current inseries connection through the two operating motors and these will start to run with increasing speed. W'hen the rotors have made a rotation of about 160l70, the cam 25 interrupts the contacts 24. Therefore, no more current passes through the coil of the contactor and the exciter winding of the generator is again interrupted. Thus also disappears the three-phase current in the windings of the three-phase generator and the operating motors, which meanwhile have reached their greatest speed corresponding to the speed of the bar to be cut. As the rotors' of the operating motors continue to rotate after the bar has been cut the cam 27 connects the contacts 26. Thus the coil of the contactor 12 is fed by current, and this contactor connects direct current to two'of the windings of the two operating motors. This direct current flows in parallel connection between the windings of the two motors and in their stators produces-astationary field whereby the two rotors are braked, strong braking currents flowing through the short circuit windings of the same, which because of the self-induction of these windings, disappear only after the motors have come to rest. The amount of the -braki11g current is so determined thatthe rotors of the operating motors come to rest exactly in the normal position of the cutters. Shortly before this position is reached, the cam 27 interrupts the contacts 26 whereby the contactor 12 again interrupts the direct current, and the cutters are now ready for the next cutting operation.

While I have described my invention and the manner of operation in detail, I do not, of course, limit myself to such disclosure, because changes may be made without a departure from the principles involved.

I claim: I

1. Means for severing a moving bar comprising a pair of electric motors, a pair of cooperating shear elements operatively connected with said motors for operation by the switch to start the motors, me

the cutting. operation, and me operation of the motors also efie in ink tor windings.

exciter winding and stator windings discon nected with -respect to each other, means for driving said generator at a rate pro to movement of the bar, conductors connecting the stator windings of the generator in series with the stator windings of the motors, respectively, a source of direct current, a circuit between the source of direct current and the exciter winding of the generator, a normally open magnetic switch in said circuit.. a normally open switch adapted to be closed by movement of the bar, a direct current circuit inclusive of said bar operable switch and said magnetic switch, said last mentioned circuit being inclusive ofa switch operable by one of the motors and closed when the motor is in a state of rest and adapted to be opened following a predetermined amount of operation of the motor, said last mentioned c rcuit also being inclusive of a second switch operable by the other motor and open when the motor is in a state of rest and adapted to be closed following a predetermined 4o amount of operation 'of the motor," normally open direct current circuits between two of the stator windings of each motor, and means whereby said last mentioned circu ts are closed by closing of the second mentioned motor operable switch, whereby a braking flow of direct current is supplied to said mo Means for severing a moving bar com prising a pair of cooperating shears, a pair of three-phase asynchronous electric shearoperat ng motors each inclusive of a circuit rotor and interconnected stator ings, a three-phase genera-tor inclusiveexciter winding and field windings discon- 5 nected with respect to each other and connected in series with the motor windings, respectively, means for driving said generator at a rate proportionate to movement of the bar, a source of direct current, a normally open circuit between said source of direct current and the exciter winding of the generator, means whereby movement of the bar closes said circuit to initiate operation of the motors, 'means whereby said circuit isopened by operation of the motors following same, a switch controlling the flow of operthe cutting operation, normally open direct ating current to said motors, means whereby current circuits between two of the windings movement of the bar effects actuation of said ans whereby operation of the motors cuts off the flow of operat'ng current to the motors following ans whereby cts a braking current flow through the stator coils of the motors following the cutting operation.

2. Means for severing a moving bar comprising a pair of cooperating shears, a pair of three-phase asynchronous electric shearoperatingmotors each inclusive of a short circuit rotor and interconnected stator Wind- .ings, a three-phase generator inclusive of an of each motor, and means whereby the last mentioned circuits are closed following opening of said first mentioned direct current circult whereby a braking flow of direct current is supplied to said motor windings.

4. Means for severing a moving bar comprising a air of cooperating shears, a pair of three-p ase asynchronous electric shearoperating motors, a three-phase generator means for driving said generator at a. speed proportionate to the movement of the bar,

means whereby movement of the bar causes a How of operating current between the generator and the motors, a source of direct current, andmeans whereby operation of the motors cuts off the supply of operating current following the cutting operation and v subsequently eifects a braking supply of direct current to the motors. y

In testimony whereof I aflix my signature.

' JOSEF GASSEN.

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