US715740A - Draw-bench. - Google Patents

Description

Pat'ented Dec. I6, |902.

no. 715,74d.

G. BAEHR.

DRAW BENCH. Abblicaemn medreh. 14, 1902i Lgf-Zit Nrn-3D STATES V'PFATENT OFFICE.

GEORGE BAEHR, OFYMOKEESPORT, PENNSYLVANIA, ASSIGNORTO NATIONAL TUBE COMPANY, OF PITTSBURG, PENNSYLVANIA, A CORPORATION OF NEW JERSEY.

SPECIFICATION forming part of Letters Patent N o. 715,740, dated December 16, 1902- Application filed February 14,1902. Serial No. 94,123. (No model.)

To all whom t may concern:

Be it known that I, GEORGE BAEHR, a resident of McKeesport, in the county of Allegheny and State of Pennsylvania., have in- 5 vented a new and useful Improvement in Draw-Benches; and I do hereby declare the following to be a full, clear, and exact description thereof.

My invention relates to apparatus for the 1o manufacture of tubing, and more especially to drawing apparatus for use in connection with that method of butt-welding wherein cold blanks are charged into the .rear of a furnace and when properly heated are drawn by suitable tongs out of the front end of the furnace into and through a welding-bell.

In the manufacture of butt-Weld tubing the most approved present practice is to charge the blanks, in the form of flat plates,

zo into the furnace at a speed somewhat greater than that at which they are withdrawn.

It is the object of the present-invention to provide apparatus for increasing the speed of withdrawal, so that said speed will closely z5 approximate the charging speed. To this end I provide apparatus whereby the heated plates are drawn out ofthe furnaceand into the welding-bell at a comparatively slow speed, and whereby said speed is then automatically increased, so as to draw the remainder of the plate through the bell at a higher rate of speed.

One of the difficulties in the way of greatly increasing the speed of withdrawal is the danger that the jaws of the tongs may lose their hold on the blank or pull a piece thereof out when subjected to thejerkincident to the engagement of the tongs with the drawing apparatus. When such engagement takes place, the tongs are compelled to overcome the static inertia of the blank lying in the furnace, and with large blanks, and especially wide and thick plates,'this inertia is considerable. Furthermore, when the forward end of the blank strikes the weldingbell the shock of impact if the speed of drawing is very high may result in the disengagement of the tongs from the blank. Another difficulty in the way of greatly increasing the speed of drawing where' a continuously-running draw-chain or the like is employed arises from the fact that the connection of the pulling-hook with the continuously-running drawchain is effected manually, and when the speed is very high this is difficult to do. In view of these difculties the permissible speed of drawing in actual practice has been limited to a maximum of about four hundred feet per minute when butt-welding smallsized pipe and threel hundred feet perv min- 6o nte when butt-welding larger-sized pipe. Itl has been proposed, however, to actuate such drawing mechanism by variable-speed mechanism, the speed of which is adapted to be varied manually. This variable-speed mechanism is arranged to be operated at the desired moderate speed while the blank is being withdrawn from the furnace and until the front end thereof has entered the welding-bell, at which stage the mechanism of 7o higher speed is broughtinto action manually and the remainder of the pipe is drawn and butt-welded at the higher speed. One of the advantages of this arrangement is that it permits the continuous welding at a single operation of blanks long enough to make two or more pipes of standard length, thereby diminishing the cost of making the pipe by reducing the amount of scrap and increasing the output of the furnace, because the opera- 8o tions of charging and heating such doublelength blanks are practically the same as for a single-length blank, and the double-length pipe can be drawn in very little more time than that occupied in drawing the singlelength pipe. This arrangementis very effective for the purpose intended; but there is a likelihood of not getting the greatest output of the furnace due vto the slowness or neglect of the operator inthrowing in the higher- 9o speed mechanism. There is also danger of breakage should the operator fail yto throw out the higher-speed mechanism.

The object of my invention is to improve upon this arrangement and render the same 95 more reliable and efficient by making the mechanism entirely automatic and preferably by having the variable-speed mechanism controlleddirectly by the load on the drawing mechanism, so that when the load roo is thrown upon said drawing mechanism it will be speeded up and continue at this increased speed until the load is thrown off, when it will automatically return to its lower speed. Preferably the arrangement comprises the driving of the drawing mechanism by means of an electric motor and providing a generator and booster system for said motor, whereby it will be speeded up when the load is thrown upon the same.

In the accompanying drawings, Figure lis a diagrammatic plan View of thc furnace and my improved drawing mechanism, and Fig. 2 is a diagrammatic view of one form of electrical driving system that may be employed.

I employ any suitable welding-furnace of the necessary length, depending upon the length of tubing to be formed, and for the purpose of making double-length pipe a furnace practically double the length of the ordinary furnace will be used, such furnace being shown at 1 and being in the neighborhood of forty feet in length and havinga hearth 2 of sufficient width to receive six or more tube plates or blanks. The furnace is preferably heated by gas and of the regenerative type, and it has a charging-opening 3 at the rear end and a withdrawing-opening 4at the forward end. The blanks may be charged into the furnace either by hand or by any suitable mechanical charging means. In front of the furnace is located any suitable drawing apparatus, that illustrated being a draw-bench 5 which preferably is arranged to move laterally in front of the furnace so it can be brought into line with any one of the plates or blanks lying on the hearth thereof, that illustrated being a draw-bench 5 pivoted at o', and mounted on suitable rollers, (not shown,) so that it can be swung into line with the blanks in the furnace. This drawbench is preferably provided with a continuously-running draw-chain 7, and as my invention can be as well illustrated in connection with such continuously-running chain as with a reciprocating or other drawing mechanism I will describe that form as illustrating means suitable for carrying out the invention. This draw-bench has at its forward end the bell-holder 8 for receiving the welding-bell 9, as is com mou in the art, and the continuously running draw-chain 7 passes over a sprocket-wheel (not shown) at the forward end of the bench and a sprocket'- wheel 1l upon the driving-shaft 12. This driving-shaft is preferably located at the rear end of the bench and is driven by means of variable-speed mechanism, which will automatically impart variable speeds thereto. This may be accomplished by connecting to said shaft an electric motor 14, which is driven automatically at a variable speed by a boost-er system, one arrangement of which isdiagrammatically shown in Fig. 2. In this figure the main generator is shown at 15, and this may be of any of the well-known types, preferably a constant-current generator. To

the terminals of this generator are connected the power-mains 16 and 17. The armature of the motor 14 is shown at 18, and this will be connected to the driving-shaft 12 by any suitable gearing or other connection. The eld of the motor 14 is preferably compound wound, although this is not absolutely essential, as a shunt-wound motor would answer for some purposes. The shunt-winding is shown at 19, and this is connected across the power-mains, as shown, and the series winding of the fleld'is shown at 2O and has one terminal connected to one of the armaturebrushes while the other terminal is connected to the motor generator or booster, as will be hereinafter described. The motor 14 is connected to the power-mains by any suitable switch or starting device, one suitable for this purpose being shown at 21, the same comprising a switch arm or blade 22, electrically connected to the power-main 17 and adapted to pass onto a contact-strip 23, connected to the shunt-field 19, and also to pass over contact-pieces 24, which are separated by a resistance agency, such as the coils of fine wire 25, and connected to the armature 1S of the motor. The strip 23 is of such length that when the switclrarm 22 is moved to close the circuit the field 19 will be first energized and brought to its full strength before the circuit to the armature is closed, and as the switch-arm 22 is moved along the resistance 25 is gradually cut out, thus gradually increasing the current through the armature and avoiding injury to the same.

The booster or motor generator is shown at 27, and this may be of any approved type of motorgenerator, preferably having the motor and generator directly coupled,as by means of the shaft 2S. The motor-armature is shown at 29 and the motor-field at 30. This motor is connected across the power mains, as shown, and in the circuit is placed a suitable switch or starting device 31, which. may be of any approved form and is shown of the same construction as the starting device 2l in the circuit of motor 14.

The generator-armature of the booster is shown'at 32, and the field is preferably of a differential type composed of two windings 33 and 34. The former is of large Wire and large cu rient-carrying capacity and is in series with the generator-armature 32 and with the series winding 2O and armature 18 of the motor 14. The other field-winding 34 is of small Wire and correspondingly small current-carrying capacity and wound in a direction opposite to the winding of the field 33, and it is connected across the power-mains, as shown. Suitable means will be provided for regulating the strength of each 0f these fields, and this is most conveniently accomplished by putting in the field-circuits variable-resistance devices, as shown diagrammatically at 36 and 37. The variable-resistance device 36 in the circuit of the shunt or differential field 34 is in series therewith, as shown, while the IOO IIO

variable resistance 37 in the circuit of the series field 33 is in parallel therewith, as shown, although these arrangements may be varied, if desired or necessary. A variable-resistance device is also preferably put in the circuit of the shunt-winding 19 of the motor 14, as shown at 38, so that the strength of the field of said motor can be varied. Should it be desired to increase the speed of the motor 14 above thatV given by the booster, this resistance device will be adjusted to weaken the field 19, thus giving the increased speed to the armature 18. The operation of this electrical system is as follows: We will assume that the main generator 15 is operating in the usual manner and that the circuits through both the motor 14 and the booster 27 have been closed by the switches 21 and 31. Current from the power-main 16 will then fiow through both the shunt and series windings 19 and 20 of the motor 14 and cause rotation of the armature 18 thereofin the wellunderstood manner. The current fiowing through the armature 18 and series field 20 also fiows through the series field 33 and armature 32 of the generator of the booster, as will be seen by tracing the circuits. Current will also be flowing through the motor of the booster, thereby rotating said motor and the armature 32 of the generator. Current will also be fiowing through the shunt-winding 34 of this generator; but the variableresistancesV 36 and 37 will have been so adjusted that when the motor 14 is running idle or merely under a friction-load, or, more strictly speaking, at its desired lower speed, the ampereturns of the two field-windings 33 and 34 will be equal, and as they work in opposition they will neutralize each other. As a cousequence no magnetismy will manifest itself at the ends of the pole-pieces, and no current will be generated by the armature 32; but said armature will merely rotate idly and will not interfere with the flow of the current through the same and to the series field 20 of the motor 14. As soon as the load or the additional load, as the case may be, is thrown on the motor 14 it will tend to decrease the torque of the armature, thereby decreasing the counter electromotive force and permitting more current to fiow through said armature, which current must necessarily come by way of the series field 33 ofthe motorgenerator, so that said field 33 is increased in strength, while the oppositely-wound field 34 remains of the same strength. As a consequence the field becomes overbalanced, or, more strictly speaking, a magnetic field is established, so that the rotation of the armature 32 in this field will generate additional current, and this current with the connections shown must flow through the series field 2O and armature 18 of the motor 14, thus increasing both the voltage and the amperage flowing through said field and armature and correspondingly increasing the torque Vand speed of said motor. As long as this load or additional load remains o'n the motor 14 the extracurrent will be generated by the booster and transmitted to strengthen the field and armature of the motor 14, thereby maintaining the higher speed of this,` motor during the continuance of this load. As soon, however, as the load is taken off this motor the current flowing through the motor furnishes an excess of torque which momentarily causes the speed to increase, thus increasing thev counter electromotive force and decreasing the current flowing through the armature 18 and the series field 33 of the booster. As a consequence the fields of `this generator will again neutralize each other and stop the generation of current thereby, and the motor 14 will drop back to its normal or slow speed. The shunt-winding 19 of this motor prevents the armature 18 from racing when the load is taken off, as would be the case if only the series winding 2O were used. This is well understood by those skilled in the art and need not be further described.

It will be observed that by the use of the booster system the motor 14 will run at one speed when under a friction or light load and at an increased speed when under a heavier load, and this regulation takes place automatically and without any manual manipulation. It will be understood, of course, that all the details of arrangement shown are not necessary; but these may be varied within limits without disturbing the effect produced. For instance, a single source of current, such as the generator 15, need not be employed, as separate sources of current might'be used for the motor 14 and for the booster-motor, -if desired. Furthermore, this booster need not be of the motor-generator type, as shown, as an engine-driven generator whose elds are eX- cited from an outside source of current would give the same effect. So, too, the series winding 20 is not absolutely necessary, as a shuntwound motor can be used. In that case the series field 33 of the booster will'be connected directly to the armature 18 of the motor 14. For convenience and efficiency, however, the

arrangement shown in the drawings is preferred. The main generator 15 will of course be located at any desired point, and the booster 27 will preferably be located in proximity to the drawing mechanism or just outside the mill in which the latter is located. The motor 14 will of course \be located as close as convenient to the draw-bench.

By means of the booster system illustrated and described the motor 14 is designed to be normally driven at such a relatively slow speed that it will prevent undue shock in overcoming the static inertia of the tubeblank in the furnace and when the front end of the blank strikes the welding-bell and that will permit the convenient attachment by the buggy-boy of the hook to the draw-chain. The entrance of the front .end of the tubeblankV into the bell, however,.imposes avery large additional load on the motor, and by IOG IIO

the booster described the speed and torque of said motor will be automatically increased, and the draw-chain will thus be driven at the increased speed and draw the remainder of the blank through the welding-bell at the higher speed. The motor may be designed so as to be driven at its normal orslow speedsay at two hundred and iifty revolutions per minute-the power-mains 16 and 17 being designed to carry twenty-five amperes and two hundred and twenty volts. Then the load is thrown upon the motor, the current through the motor will be increased to ninetyfive amperes and the voltage raised to three hundred, and said mot-or will be given approximately three hundred and forty revolutions per minute.

In practicing the invention with the apparatus described the usu-al mode of procedure is followed, and as this is well understood in the art description thereof is unnecessary.

The invention is applicable to the welding of U-shaped or like blanks, as well as to the welding of dat plates, although it is especially advantageous in the welding of the flat plates, because of the greater friction in the welding-bell caused by the turning up of the dat plate into tubular form.

In the preferred use of the invention, and especially where it is employed in the making of double-length pipe, the blanks are fed to the furnace preferably at a speed greater than the normal or slow speed of the drawchain, and generally about double this speed. The withdrawing of this plate when properly heated is, as above stated, first at the slow or normal speed and then at the higher or more rapid speed, thereby causing the time of withdrawal to very closely approximate the time of charging. The increase of speed, however, takes place gradually, so that there is little shock in passing from the slow speed to the higher, and consequently little or no liability of pulling the tongs or other drawing-tool off the pipe. By drawing the pipe at the higher speed the output of the furnace is considerably increased, because of the quicker travel of the heated blank through the welding-bell, making it possible to more quickly introduce another blank into its place in the furnace, the fresh blank being, if desired, charged before the heated blank is entirely withdrawn. By making the time of charging and the time of withdrawal practically the same it gives almost the ideal conditions for heating the plates. Furthermore, the increased speed of drawing in making double-length pipe overcomes in great measure the liability of the stretching` or sagging of the pipe during the drawing operation. Also all the other advantages relative to the drawing of pipe at variable speeds are secured by my apparatus.

While the invention is of advantage when used in connection with the butt-welding of tubing from flat plates, it can be used with any other form of skelp, such as tubular, or,

in fact, for the drawing of seamless tubes or vpipes or rods of any description.

The specific booster system shown and described is not claimed by itself in this application, but is claimed in my application of even date herewith, Serial No. 94,122.

Vhat I claim as my invention, and desire to secure by Letters Patent, is-

l. In apparatus forforming tubing,the combination of drawing mechanism, and means for actuating said drawing mechanism and automatically increasing the speed thereof by the drawing strain when the latter is thrown thereon.

2. In apparatus for forming tubing,the combination of drawing mechanism, and means for actuating said drawing mechanism and atomatically increasing the speed by the drawing strain when the latter is thrown thereon and automatically decreasing the speed thereof when itis relieved of the drawing strain.

3. In apparatusforforming tubing,the combination with drawing mechanism, of means for actuating said drawing mechanism, and means controlled by the drawing strain for increasing the speed of said drawing mechanism as the strain increases.

4C. In apparatus for forming tubing,the combination with a furnace for heating the tubeblanks, of drawing mechanism in front of the same, and means for actuating said drawing mechanism and automaticallyincreasing the speed thereof by the drawing strain when the latter is thrown thereon.

5. In apparatus for forming tubing,tl1e combination with drawing mechanism, of an electric motor for actuating said drawing mechanism, and automatic means for increasing the speed of said motor by the drawing strain when the latter is thrown on the drawing mechanism.

6. In apparatus forformingtubing,the combination withdrawing mechanism, of an electric motor for actuating said drawing mechanism, and means controlled by the drawing strain for varying the speed of said motor in proportion to the drawing strain.

7. Inapparatus for formingtubing,thecombination of drawing mechanism, an electric motor for actuating said drawing mechanism, a source of current therefor, and automatic means for varying the amperage and voltage of the current at the motor-terminals in proportion to the drawing strain.

S. In apparatus for forming tubing,the combination of drawing mechanism, an electric motor having a shunt-winding for actuating said drawing mechanism, a generator supplying current for said motor, and a source of current for exciting the field of said generator, said field being in series with the armature of the motor, whereby variations in the drawing strain will cause similar variations in strength of the generator-field.

9. Inapparatusforformingtubing,thecom bination of drawing mechanism, an electric IOO IOS

IIC

and a source of current for exciting said gen-V erator-iield.

lO. In apparatus for forming tubing, thel combination of drawing mechanism, an electric motor for actuating said drawing mechanism, a generator having two field-windings of diierent carrying capacities and wound in opposite directions, the larger of said fieldwindings being connected in series with the armature of the motor, said windings being so proportioned as to neutralize each other when the motor is running under a friction or lightload anda source of current for exciting said generator-fields.

l1. In apparatus for forming tubing, the combination of drawing mechanism, an electric motor for actuating said drawing mechanism, a generator having two field-windings oppositely wound and of different carrying capacities, the smaller of said windings being in shunt with the generator-armato re and the larger of said windings being in series with the generator-armature said windings being so proportioned as to neutralize each other when the motor is running under a friction or light load and with the motor-armature, and a source of current for exciting said generator-fields.

12. In apparatus for forming tubing, the combination of drawing mechanism, a compound-wound electric motor for actuating said drawing mechanism, a source of current for the shunt-winding of said motor, a variable resistance in the circuit of said shunt-winding, a generator having two field-windings oppositely'wound, one 'of said windings being in series with the series winding and armature of the motor, and a source of current for exciting said generator-tields.

13. In apparatus for forming tubing, the combination of drawing mechanism, electricpower mains, a compound-wound motor for actuating said drawing mechanism,the shuntwinding of which is connected across said mains, of a booster having two field-windings of different carrying capacities and wound in opposite directions, the smaller of said windings being connected across said mains and the larger of said eld-windings being conf nected in series with the generator-armature and with the series winding and armature of the motor.

14;. In apparatus for forming tubing, the combination of drawing mechanism, electricpower mains, a compound-wound motor for actuatingsaiddrawing mechanism,the shuntwinding of which is connected across said mains, of a motor-generator having its motor connected across said mains and having two l

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