US1858788A - Rolling mill - Google Patents

Description

y 1932' w. J. P. RQHN ROLLING MILL Filed June 21, 1928 '7' Sheets-Sheet 1 Fig.

May 17, 1932. w. J.VP.'ROHN ROLLING MILL 7 Sheets-Sheet- 2 Filed June 21, 1928 Fig. 2

May 17, 1932.

w. .1. P. ROHN ROLLING MILL Filed June 21, 1928 7 Sheets-Sheet 3 I 432mg y 1932- w: J. PLROHN 1,858,788

' ROLLING MILL Filed June 21. 1928 7 Sheets-Shegt I 4 Q l g Q i i g g y Fig. 4

May 17, 1932. w. J. P. ROHN 1,858,788

ROLLING MILL Filed June 21, 1928 7 Sheets-Sheet 5 May 17, 1932. w. J. P. ROHN 8 ROLLING MILL Filed June 21. 1928 7 Sheets-Sheet e fnzr'a rurfor:

- May 17, 1932 w. J. P. @m

ROLLING MILL 7 sheets -sheqt Filed June 21, 1928 Fig. 40

[nvan 50/3:

Patented May 17, 19 32 UNITED srA'rEs PATENT O C wrmmmr JULIUS mun. norm, or mau-on-rnn-uam, emm

. ROLLING m;

Application. fled June 21, 1928, Serisil No. 287,226, and in Germany August 8, 1925 This invention relates to improvements in the construction and working of rollingmllls, more especiallyof rolling-mills of the tube reduction type, in which the individual mills are arranged in alignment, but the shafts of each individual mill are inclined at an an le of 90 to those of the following or pre'ce ing individual mill.

The main object of my invention isto pro- .cure a rolling mill which permits of eflectively and economically rolling hardcompact materials to great lengths with a minimum of attendance. For this purpose I have chosen the type of the tube reduction rolling mills in which hitherto the individual mills were jointly driven by one or two shafts arranged in' the length direction of the mill, and I have adapted this type for the purpose in question by providing a separate electric drive for each individual mill.

Other objects of my invention are: to at-' tain an exact consonance of the speeds of the individual mills; to avoid the formation of loops in the bar or otherpiece under treatment between each two individual mills; to exclude an overloading of one or more single mills caused by upsetting or excessively drawing the material under treatment; to permit of an exact adjustment of the whole series of mills; to ermit of rolling back an entangled bar; to o tain abnormal'diameters of the rolled material; to permit of a succinct arrangement of the whole mill, and therewith a reduction of the area required for the plant and of the losses during the passage of the material under treatment through the whole mill.

, These further objects are realized by employing compound motors as prime movers;

by finest subdivision of the shunt regulation;

.by feeding all single motors from a Leonard distributing dynamo; by providing each individual mill with an ammeter, a maximum relay and twotriggers for makvn or breaking the circuit of the whole mill; y providing deflecting guides to be inserted at any desired point between the individual mills; by adjusting the rolls by means of wedges; by automatic lubrication; by lnclining the axes upwards and downwards instead of forwards and backwards, as heretofore; 1) providing scrapers for removing edges; ally by arranging closed. guides between the individual mills.

Although I have described and illustrated my invention substantially in connection with mills of the tube reduction type, Lwish it to be understood that certain features of the invention may be advantageously used in connection with other types of mills.

In order to permit a clear understanding of my invention I will now describe the same in detail with reference to the annexed drawings, of which I Fig. 1 is a plan view showing four individual mills driven by single motors.

Fig. 2 shows, in side view part of a plant. comprising three individual mills, three compound motors for driving the same, conduits coming from a Leonard dynamo, ammeters and triggers.

-Fig. 3 shows the Leonard converter and one individual mill.

Fig. 4 is a section along line IV-IV of Fig. 5. b

Fig. 5 shows in section along the line V--V of Fig. 1 on an enlarged scale the one pair of rolls with their bearings,

Fig. 6 is a vertical section along the line VI--VI of Fig. 1 showing the automatic lubricatin system. y

Figs. 8 and 9 indicate the closed guides an (1ll deflecting guides between the individual m1 s.

Fig. 10 is a vertical section showing 'a li ht rolling 111311, the individual mills being mounted upon a vertical supporting lateand alternately directed downwards an upwards at an angle of Figs. 11, 12 and 13 are details showing rollers provided with exchangeable grooves.

The same reference letters are used for the corresponding parts throughout all the figures.

In rolling mills more and more socalled continuous trains are employed, artly for increasing the production, partly or reducing to a minimum the cooling-down of the material under treatment between two passes and obtaining a maximum of lengthening 1n c adapted for rolling tubes, but are less suitable for rolling compact material which is pliable at rolling temperature, and are unsuitable for rolling material which is hard at rolling temperature. Moreover such mills are less suitable or unsuitable for producing strips, rods, or wires of considerable length.

When rolling or reducing tubes it is not necessary to accomplish an exact consonance of the speeds of the individual mills even though the roll passes are not adjusted strictly in accordance with the gradations of the cross-sections, because tube-like material is capable, owing to its hollow character, of

being extended or upset" between the individual mills even in the case of incorrect gradation of the speeds of the separate consecutive mills. This applies even to compact material to be rolled, which is soft and pliable at the rolling temperature, only to a considerably smaller extent: if the roll passes and the speeds of the consecutive individual mills are not in strictly correct consonance stresses and compressions take place 1n the material to be rolled between the single mills.

cold rolling1 A soft and greatly pliable material will give way to stresses by extension, to compressions by contraction, whereas with a material which is hard at the rolling temperature loops will be formed or unallowable stresses and pressures will be transferred from one individual mill to the other. With compact material of high strength, and especially in the stresses and compressions exerted by t e incorrectly adjusted mills upon the preceding or subsequent ones may become so important that either a rapid wear of several parts or breakage is produced.

This wear may affect the calibers, tooth wheels, gears or bearings, whereas the parts subjected to breaking may be the armatures, frames or parts of the gear. These difiiculties are avoided by driving each single mill of a plant similar in arrangement to the reduction roll mills bya single motor. Especially when electric motors are used for this'purpose the relative speed of each individual mill may-be adjusted with the desired exactness even though the passes are not quite correctly adjusted. Furthermore with single drive it is possible to continuously control the load of each individual mill by a simple ammeter. Such an arrangement "affords great advantages. When, for instance, 20 individual mills arran ed in alignment are jointly driven, one of t e mills may have eaten bearings or any other dama e whereby its load may be increased by 100 o. For the whole power consumption of the plant this would amount on] to 5% of the total energy consumed and therefore would escape observation. With single electric drive and ammeters before each single individual mill the conditions of the latter may be controlled with perfect exactness. Furthermore such an'arrangement permits of an extraordinarily simple adjustment of the plant. Assuming that the roll passes are a proximately adjusted, but with relative y great deviations from the theoretical amounts, then even though in this case the speed of the individual mills strictly corresponds to the theoretical values tension or compression stresses are transferred by the material to be rolled from one individual mill to the preceding or subsequent one, which stresses will become the greater, the harder the material and the lon er the vein to be rolled to one strap. Wit the arrangement described any active pushing or drawing of an individual mill makes itself conspicuous at once by an excessive deflection of the ammeter, whereas the deflection is. less than normal when the individual mill is pushed or drawn.

A simple grip on a shunt regulator (preferably arranged near to the respective ammeter) permits at onceadjusting the load of the corresponding mill to its exact calculated amount. With joint drive defects of this kind are not recognizable at all without further ado; if they were recognized they could only be removed by exactly adjusting the roll pass whereby a good deal of trouble would be caused, and ge erally speaking, this adjustment would no he possi le at all as long as abar is pas d through the plant. Consequently with ha material to be rolled in some cases the brea ing would have been effected before the defecgcould be redressed.

The advantages of the arrangement described appeared with the first working of a rolling mill constructed according to the foregoing deliberations. Whereas the men skilled in the art had prognosticated that several days were needed for satisfactorily adjusting the plant when not yet put right inorder to permit a faultless working w1th a material of singular hardness, it appeared that the above described arrangement allowed an adjustment of the whole plant within less than one hour. It was even possible to roll cold veins of any desired lengths in continuous closely standing mills. Even with a length of several miles the plant can be attended by a single man who may keep the plant going absolutely without fault for many hours. I a

Preferably the structural details may be conformed to those of the usual tube reduc tion rollin mills. For instance, the rolls are given t e form of freely flying rin s in product of the corresponding train.

reduction rolling mills.

Of course, when rolling compact and very hard material the strength of the mills must be correspondingly increased, so as to be considerably stronger than with the usual faultless working of such rolling trains is warranted even for compact and very hard material, whereas when rolling com act material of high strength whilst rigidly riving the individual mills breaking could not be avoided.

In order to simultaneously allow a fine adjustment of the roll passes, this adjustment is preferably eifectuated not in the common way by screw-bolts, but by means of wedges,

which method of adjusting is advantageously employed in rolling mills of other types. In view of the outwardly placed rolls (rolling 1 rings), in the bearing adjacent to the rolls the wedge adjustment is arranged above the upper roll, whereas in the bearing of the opposite upright it is arranged between both rolls. Preferably both wedge adjustments are coupled one with another. In order to obtain a maximum eifect with such rolling mills, it is to be recommended to provide the bushing with cooling devices according to the German Gebrauchsinuster No. 930,474. The operation of such rolling plants is considera ly simplified byproviding an automatic universal oiler for all lubricating points. Preferably different kinds of oil may be se lected for gear bearings and roll-bearings as,

- for instance, castor-oil for the roll-bearings.

, Continuous rolling plants of the kind described may be used to advantage for still another important manufacture. It is well known that tubes are reduced by rolling in reduction rolling mills not only when whole, so as to reduce their inner diameter whilst approximately maintaining the thickness of the walls, but also tubes are rolled on a core running along with the tube so'that the inner diameter remains constant and only the thickness of the walls is reduced. However the latter method of working continuous rolling trains has not proved satisfactory. Inside the tubes there is a cold core running along with the tube and consisting of a very hard material. Only the relatively thin layer between the core and the roll-pass forming the wall of the hot tube is subjected to preferably exchangeable ished Nevertheless a 1 stretchin In this case it is most important to keep t e speeds of the individual mills in strictest consonance with each other. When i providing a common drive for all individual mills the relation of the speeds is determined I of such plants has not been attained. It is self-explanatory, that the plant here described is especially suitable for the purposes in question.

The invention is particularly applicable to the rolling of bars, rods or wires of chromium-nickel-alloys such as used as heating elements for electric stoves and as stainless metal in the chemical; industry. These alloys have an extremely high strength at a temperature of 1000 to 1100 degrees C. in which condition such materials are usually subjected to the rolling process. When heated to such a de ee their tensile strength is 5 to 7 times as high as thatof steel. has originally been developed with a view to solving the problems encountered in forming such material, but experience has shown that the invention although primarily designed for that purpose is just as useful for the production of rods or wires of nickel,

The invention motors of that type, c. g. electric motors of the shunt winding type, involves serious disadvantages. In case of very hard material which is not capable of yielding to pulling or compressing stresses in axial direction, any deviation in the adjustment of the width of the rolling throatfrom the theoretical value must result in a departure from the theoretical speed for which the electro-motor is de- 1 signed. If, for instance, a certain pair of rolls confines a narrower throat than calculated and if the adjacent. mills feed the material with a predetermined speed, a higher speed than that calculated will be imposed upon that air of rolls through action of axial forces transmitted by'the passing stock. The pair of rollsis, as it were, forced by the material to rotate at a higher speed, but tends to counteract such action whereby an additional loadis imposed upon the two adjacent mills.

'In case of a motor of the shunt winding type a departure from the theoretical speed, for which it is designed, results in an excessive change in the torque produced. A very small decrease in speed results in a multiplication of the torque, while an increase in speed may reduce the torque to zero or may even produce a negative torque. In case of a relatively soft material a certain pair of rolls may maintain its predetermined speed in spite of an incorrect adjustment of its throat, because the axial stress caused thereby in the material will not be transmitted to the other mills as the material is capable of yielding. It follows that hard material cannot be economically operated upon by means of independent rolling units driven by electric motors of the shunt winding type.

If, however, compound wound motors are used, the co-operation of the successive roll ing units may easily be controlled and does not result in an excessive increase or decrease of the load of the individual electro-motors should the rolling throats not be exactly adjusted in accordance with the calculated speed ratio. In event of a cross-sectional reduction in thestock of 10 percent in each unit, every mill must rofatate at a speed which is about 10 per cent in excess of the speed of the preceding unit. In order to prevent an overload exceeding 100 per cent of the nominal load the compound winding may be so calculated that the speed of the motor is varied by 10 per cent only, in case of a change in the load by 100 per cent. This value of the compound winding represents an upper limit for a practical construction in accordance with the invention while the lower limit approaches the ordinary shunt winding condition of the field, I-have found that the most favorable results are obtained 'by dimensioning the compound winding in such a manner that its I ratio lies approximately in the middle of the aforementioned upper and lower limit. In this event, axial stresses are exerted on the passing stock to the smallest extent only,

and consequently, wear and tear are greatly reduced and the dimensions of the frames and the driving gear may be kept within economic limits. Another advantage resides in the relatively low speed of the units when they are running idle. This low speed greatly facilitates the introduction of the tip of a new stock in the various throats.

The difliculties which have been met with prior to my invention are the more of serious moment the higher the strength and rigidity of the material at the rolling temperature are, and the longer the entire stock is which is to be rolledin one operation. My invention permits stocks of a length of many miles to be rolled from the hardest material in one operation by means of plants comprising 20 to 40 mills. In order to avoid the necessity of adjusting the rolling throats'of any one of the mills to the theoretical value with an exactness which can hardly be attained under the condition prevailing inthe work shop, I prefer to make provisions for an easy regulation of each motor, for instance in the manner described in which the field resistor 97 permits a sensitive adjustment of the motor field. By means of the resistor handle every electro-motor can easily be adjusted to produce at its actual speedthe desired torque which equals those produced by the other electro-motors and, consequently, the load can very uniformly be distributed over all mills. Theammeter 87 permits aneasy supervision of various loads. By comparing the ammeters of three successive mills it may be perceived at a glance whether one of the mills is running with a higher or lower load than the other mills. A re-adjustment can easily be performed either by regulating the field of the driving motor or by adjusting the rolling throat of the mill which departs from the average .load of the other mills. The latter adjustment, however, has proved not to be necessary under ordinary conditions, as the wedge arrangement makes it possible to adjust the throats prior to the introduction of the stock very exactly to their theoretical values. The first stock, consequently, may beintroduced without particular precautions and any irregularity may subsequently be eliminated by adjusting the motor fields. l f

While the compound wound motors may be supplied from any suitable source,particular advantages result from the arrangement shown in which the source of current 1s provided by a Leonard set. This creates the possibilty of economically operating plants comprising a very high number of mills without the wellknown disadvantage that the first units run too-slow when the stock is'introduced in which case the material would excessively cool down. Another advantage achieved by the arrangement of the Leonard set consists in the possibilty to regulate the basic speed of the Whole plant by delivering thereto an adjustable energy. In "starting the whole plant is driven at a high speed when the stock is introduced and, then, it is slowed down incidentally with the progress of the stock. If the compound winding of the field is so designed that it keeps the middle between a shunt winding characteristic and such a characteristic in which an increase in load by 100 per cent would cause the speed to decrease by 6 per cent. the speed ratio of the units remains sufficiently constant at all basic speeds of the plant, provided, that the throats are so adjusted to cause a theoretical increase, step by step. by 3 per cent at any unit. If the theoretical speed increase would amount to 10 per cent in each unit, the electric motors would have to be designed to keep the middle between the characteristic of the shunt windingt pe and a characteristic in which an overloa of 100 per cent would cause a drop in speed by 10 er cent.

nthe production of wire the Leonard set offers particular advantages. During the rather difficult introduction of the first wire the whole plant may be driven very slowly and may then be accelerated as soon as the front .end of the' wire issuing from the last unit has been attached to the spool.

Furthermore, a Leonard set provides a possibility of reversing the drive of the entire plant whereby in case the stock should get clogged it may be rearwardly driven out. The speed ratio of the various units remains practically unafl'ectedby changes in the electric energy delivered to plant by the Leonard set.

During the operation of the plant the ammeters are to be checked and supervised by the operator. The ammeters give an immediate response to a change in the load imposed upon the units and indicate thereby whether the airs of rolls perform their theoretical function or whether the latter is in- V fluenced by objectionable axial stresses in the stock. If the handle of the field resistor of every unit is arranged in the immediate neighbourhoqd of the frame of the unit and of the coordinated ammeter, any correction of the load may easily be carried out by a simple manipulation. In this manner every unit may be easily adjusted in such a manner that it does neither push the stock towards the next lmit nor set up a pull.

Another feature of the plant in which each.

unit is independent from the other units in mechanical respect and correlated to the same by ,electric conditions is the possibility of arranging overload relays capable of stopping the entire plant. These overload relays could be replaced by a current-controlled mech anism actin upon the field resistor to automatically just the field. Owing to the arrangement of such overload relays the plant is protected against injuries which otherwise .would easily result from new overloads on the individual units. The arrangement of the units in symmetrical position relative to a horizontal plane in combination with the arrangement of the ammeter in the immediate neighbourhood of the frame of each unit creates the possibility of simultaneously observing the material operated upon and theload. In case of emergency the entire plant may immediately be stopped without the necessity for the operator to leave his observation place. As the current supplied to all units is cut oif at the same moment, all

-motors come to rest simultaneously. In this regard my invention is distinguished from other known arrangements in which every motor has its own overload relay. In this other for simultaneously operating upon successive portions of an advancing bar, strip or wire 10 fed from one of the mills to the subsequent one. Each of the four rolling mills or units comprises a pair of rolls, such as 28,

29, cooperatively connected with an electromotor 12 to be driven thereby. The axes of successive pairs of rolls are alternately inclined by 45 degrees to an imaginary vertical plane through the passing stock 10,-or in other words, successive units are alternately disposed to the right or to the left of said vertical plane and in symmetrical disposition to the latter. The various units are so correlated to each other that their rolling throats are in registration with each other to accommodate the straight stock passing through the plant and being reduced in diameter step by step. Each unit is, in mechanical respect, independent from the adjacent units, apart from the mutual influence which is due to the operation upon the common stock 10 and the stresses'transmitted thereby from the one unit to the other. The cooperation of the various units in the desired manner is ensured by electric connections between the various electromotors 12 as willbe described hereinafter.

A preferred constructional form of the rolling units is illustrated in Figs; 4, 5 and 6. As successive units equal each other, apart from their symmetric construction, it will be sufficient to describe one of the same. In Fig.- 6, 13 indicates a frame having suitable fitting surfaces for supporting an auxiliary frame 14 and a gear housing 15. In the latter two paralle shafts 16 and 17 are journaled and in driving connection with each other through the intermediary of meshing gears 18 and 19. The shaft 16 is arranged to be driven by the electromotor 12. Housing'15 is formed with bearings'20 and 21 to accommodate a spindle 22 arranged'at an angle of 45 degrees to the vertical. A bevel gear 23'keyed to said spindie is in driving engagement with a second bevel gear 24 attached to gear 18. 4

The construction of the auxiliary frame 14 and the parts mounted therein is shown on -alarger scale in Fi s. 4 and 5. The front suitable manner not shown in the drawings.

The lower wedge 33 is inserted in the recess accommodating the block 26 and thereby prevented from any displacement; Wedge 32is kept in adjustable position by means of a screw spindle 36 engaging a thread in the wedge and rotatably supported in the cover 34. The bolts 35 which are located in the vertical plane through spindle 36 are in their central part provided with hollow blocks 37 offering the spindle 36 an unobstructed passage. In this way the upwardly directed pressure exerted upon the cover 34 by the wedges 32, 33 is taken up by the bolts without causing objectionable lateral com onents. The spindles 27 and 30 which, or sake ofsimpllcity, are not shown in Fig. 4, are coupled with each other by means of meshing gears 38, 39 arranged within the box-shaped frame 14. Those ends of the spindles 27 and 30 which are opposite to the ends carrying the rolls 28, 29 are supported in bearing blocks 40 and 41, res ctively, inserted in a vertical recess of t e rear wall 42 of frame 14 and a recess in cover 34 registering therewith. Provision is made for an adjustment of the distance of the bearing blocks 40 and 41 by a wedge. arrangement resembling the aforedescribed one and comprising wedges and a screw spindle 43. The latter is coupled, for simultaneous rotation with the spindle 36 by means of gears 44 and 45 to be rotated by a hand wheel 46. For sake of clearness these gears are not'shown in Fig. 5. The vertical pressure exerted upon the roll 28 durin operation is taken up b the block 26 an transmitted through the wedges 32 and 33, the cover 34 and the bolts pressure exerted upon the lower roll 29 and directly transmitted to the frame 14. As the spindles or shafts 27 and 30 may be compared with double arm levers their other ends are pressed together, and this pressure is taken up by the wedge connection adjustable through spindle 43. The pitch of the threads 35 to the frame 14, and is counteracted by the to be turned to effect the desired adjustment, whereupon the nuts are fastened again.

The auxiliary frame 14 is so mounted on frame 13 that shaft 30 is in registration with shaft 22. Both shafts are coupled for common rotation by "means of a sleeve 47 permitting shaft 30 to be pulled out from its bearings in axial direction when securing nuts 48 have been unscrewed.

The lubrication of anyrolling unit is provided for by an automatic oil pump and dis tributor 50 capable .of delivering different kinds, of oil to various lubricating places. In the embodiment shown, the pump 50 feeds one kind of oil, for instance castor oil, to the bearings of the shafts 27 and30 through pipe lines 51, while another kind of oil for-instance ordinary machine oil is pumped to the bearings 20 and 21 through pipes 52 and to the bearings of shaft 16, not shown in the drawings, through pipes 53. The oil is collected in suitable pools provided in frame 13 and conducted through collecting pipes 54 to a tank 55 provided with. an oil filter and a cooling coil. From this tank the oil is' fed by means of an oil pump 56 driven by an electromotor 57 to the various intermeshing gears 38, 39, 23 24 and 18, 19 through a pipe 58 hav'-. ing suitable branch lines.

The rolls 28 and 29 are arranged on their shafts in a suitable mannerpermitting a simple and easy detachment. In the embodiment shown the shafts 27 and 30 have ends of reduced diameter upon which the rolls are slipped and keptin position by means of washers 59 and bolts 60." In Figs. 11 to 13 I have shown a preferred form of rolls which may be substituted for those shown in Fig. 5. Each of these is provided with a plurality of caliber grooves 61 to 64, which may have equal or different profiles and are arranged in pairs comprising grooves symmetrically disposed relatively to the central plane of the roll. This arrangement provides for a very simple way of replacing a worn caliber groove by a new bne. In Fig.

3 11 the groove 63 which is in operative position is marked with a small circle. When the groove is worn out the roll is disassembled from its shafts, turned around and u again brought into position, so that it assumes the position illustrated-in Fig. 12 in which groove 62 has the same location which groove 63 and before. In order to bring 12 groove 64 or 61 in the operative position marked with the small circle, a washer65 is placed between the frame and the roll, as shown in Fig. 13. In case of different profiles of the caliber grooves 61 to 64, different profiles may be given to the material operated upon. This arrangement ensures an unexcelled economy because a plurality of rolling profiles may be produced by means of a relatively small number-of rolls, and it takes 1 a very short time to exchange the calibers to produce a different product.

Between the rolling throats of the rolling units guides are arranged for guiding the stock from one pair of rolls to the subsequent one. In Fig. 9 such an aranlgement is diagrammatically illustrated. etween adjacent pair of rolls a closed guide 66 in form of a tube is arranged, preferably in such a manner that it may easily be detached and replaced by a diverting guide such as 67 A which is brought into position when the stock passing through the mill is not to be reduced to the full extent of which the plant is ca-' pable, but to a smaller extent only which maybe effected by a part of the pair of rolls available. Consequently, the diverting guide is positioned behind that pair of rolls which is adjusted to give the passing stock the desired diameter. In this manner'a readjustment of the plant may be dispensed with in producing a final product of larger diameterthan that for which the plant has originally been adjusted. This is particularly valuable in a case where the, plant is ordinarily in use for the production of rods or 'wires of a certain diameter and where a small number of thicker rods or wires are to be produced. To this efi'ect it is merely necessary to place the diverting guide behind that pair of rolls which corresponds with the diameter desired.

The guides 66 are preferabl out out in their central part as shown at 6 a, to permit observation of the passing stock and the arrangement of circumferentially disposed in the rolling process. In case of plants comprising a relatively small number of rolling units it issufiicient to provide one or several v scrapers behind the last unit. Fig. 8 illustrates diagrammatically a preferred mode of mounting the guides 66 in adjustable posi tions by means of circumferentially distributed adjusting screws 69. While in Fig. 1 the guides and scrapers haye not been shown for sake of clearness, it is to be understood, of course, that the embodiment shown therein is, in. fact, equipped with these attarhments.

Figs. 2 and 3 illustrate the electrical'interconnection of the various units, Fig. 3 representing a continuation of Fig. 2 to theright. The electric energy is supplied to the plant by a so-called Leonard set comprising a prime mover such as the threebase-motor. 70, and a generator 71 coupled t erewith. The generator isof the compoundwound type having a series of field winding 71 and a'shunt field winding 72. The latter is energized from a small generator 73 of similar type, also coupled with motor 70. The electric current produced in the armature 74 ofthe' enerator 73 flows through line 75, an ad-' ustable field resistor 76 and line 77 to supply the shunt winding 72 of generator 71. The circuit. is closed through line 78 returning to the energizing generator 73. By means of the resistor 76 the electric energy produced by the generator 71 may be controlled and, by means of a switch (not shown) adapted to reverse the current flowing through the field winding of'the generator, the direction of current produced by the generator ma be reversed, as .desired to reverse the irection of rotation ofthe single electric motors. The current produced is conducted through main- lines 80 and 81 to the electric motors of the individual rolling.

. 85 and connected by wire 86 to the other main 80. Inserted in the wire 86 is an ammeter generator 73, through suitable branch lines 94 and 95 which are connected with lines 78 and 75 respectively. Hence, a current is flowing, undennormal conditions .from line 78 through lines 94 and 91, through the various overload relays 90 inserted in the latter and back to line 75 through coil 92,; whereby switch 93 is kept closed. In the moment any one of motors 12 is overloaded coils 89 will be. energized to such an extent as to throw'- open the coordinated switch 90, thereby interrupting line 91 and deenergizing'coil 92. As a conse uence, the main 81 is out off and the pl ant is rought out of operation.

In order to enable the operator to cut ofi the current supply of the lant, switches 96, pref 'erably in the form 0 press button switches, are inserted in line-91 and arranged at suitable places where they can easily be reached by the operator in case of emergency. I

In operationall of the electro-motors are bound to run at speeds being in predetermined ratio to each other because the various pairs of rolls are, as it were, coupled with each other through the intermediary of the passing stock. The ratio of rotation of subsequent pairs depends on the extent by which the stock is reduced in cross section. At any rate, every individual pair of rolls is running at a higher speed than the preceding one. On account of the fixed ratio of reduction in cross-section in subsequent units which cannot be adjusted during the operation, the speed ratio of the various units ispractically invariable during operation. It is desirable, however, that each electromotor produces just that very torque which is required inits associated pair of rolls to perform the reducing work therein. If a'higher torque were produced, the pair of rolls would tend to feed the passing stock at a higher speed and would thereby exert a pull on the portion fed to them and a pressure on the portion leaving them. The regulation and adjustment of the torque is provided for by a field resistor 97 controlling the circuit flowing through the winding 98 which is supplied from lines 94 and 95. The series wind- 'ing 84 and the independently controlled winding 98 are so designed in relation to each other that an increase in the normal load by 100 per cent is accompanied by a decrease in speed of 10 per cent.

The ammeter 87 permitting a constant su: pervision of the torque poduced, the field resistor or regulator 97 and the press button switch 96 for cutting out the current supply to the entire plant, are preferably on a common switch board 99 located on the frame of the unit.

For the press button switches 96 inserted in the line 91 a well known arrangement may be substituted permitting the entire plant to be put in and out of operation from any of the switch boards 99. As such arrangements are well known and do not form part of the present invention an illustration thereof has been omitted in the drawings for sake of simplicity and clearness. While in Fig. 2 only two of the electromotorswith their electrical connections are shown it is to be understood of course that every single unit is equipped and arranged in the same manner as heretofore described.

In describing the embodiment shown in Fig. 1 the assum tion has. been made that Fig. 1 represents a pan view so that the ends of the rolling shafts carrying the rolls are all upwardly directed and, consequently, symmetrically arranged relative to a vertical centralcplane of the plant. The operation takes place abovethe area covered with the heavy and voluminous parts of the units whereby an observation and supervision of the work on art of the operator is rendered extremelyd' cult and inconvenient on account of the inaccessibility of the stock. An exchange or to carry out this work the operators have to climb into the s aces between the frames.

In case of a very ong plant at least two persons are required for supervising and conducting the operation.

One object of my invention is to eliminate these disadvantages. I have found a rather simple and very efiicient remedy which resides in simply mounting the entire plant, as it were, on a vertical basis. In this case Fig. 1 would illustrate an elevation and-the right margin line would indicate the floor in crosssection. It is obvious that an operator standing on the floor can easily observe'the operation of the rolls and adjust the scrapers and guides. A single operator who is always standing on the one side of the plant only can easily reach the rolls of any unit. The details of construction as described may re main unchanged except for the lubricating system shown in Fig. 6 which must be modified to provide collecting pools for the lubricating oil at suitable portions of the casing 15 and the frame 14. This arrangement is of particular advantage for cold rolling plants for thin wires. Such a plant comprising up to 20 units may easily be operated by a single man. Another advantage obtained is the small floor area required. Plants to roll wires from. 0.4 to .2 inch can be composed of units enclosing a distance betweentheir pair of rolls of 10" only. Plants for the manufacture of wires from .2 to .4 inch may be constructed to have distances of 14" while plants for rolling rods from 5 to 4" may have distances of 3.5 to 4 feet. This construction is, obviously, compact and, consequently, the portion of the stock between the rolling points is-so short that wire issuing froma heating stove before entering the first unit is still hot when leaving the last unit.

In Fig. 10 I have shown a preferred form of a plant for rolling. thin rods or wires in which successive pairs of rolls are symmetrically arranged relatively to a horizontal plane. One pair of rolls, 100 and 101, is clearly shown, while of the next pair, only the upper one 102 is visible the lower one being located behind the structure of the pair 100 and 101. The rolls are carried by shafts 103 and 104 supported in bearing blocks 105 and 106 which are adjustable by wedge mechanism adjustable through a spindle 107. The shafts 103 and 104 are fitted with pinions 108 and 109 meshing with one another. To the shaft 104 a bevel gear 110 is attached which is in driving engagement with a pinion 111 supported on a shaft 112 rotatably held in suitable bearings of a frame113. The shaft 112 is driven by the elect-romotor 114 through the intermediary of a worm, not shown, and a worm wheel 115. In the base 116 carrying the electromotor and the frame 113 a 111- bricating oil pump is arranged to be driven by diagrammatically indicated electromotor 117.

The roll 102 is driven by the electromotor 118 through the intermediary of a driving gear which is similar in construction to that heretofore described and symmetrically arranged in relation to a horizontal plantthrough the stock 119 operated upon in the plant. The electric outfit is the same as shown in Figs. 2 and 3 and the plant may be provided with the attachments illustrated in Figs. 7 to 9.,

What I claim is A rolling plant comprising a plurality of rolling mills in tandem relation for simultaneously operating upon successive portions of an advancing rod fed from one of said mills to the subsequent one, said mills being independent from each other in mechanical respect, aplurality of electric driving motors of the compound wound type, one for each of said mills, the compound winding of said motors comprising a series field winding and a second field winding, a generator, an energizing generator coordinated therewith, electric connections to supply said .motors with current from said generator, electric connections to supply each of said secondv windings with current from said energizing generator, field resistors one for'each of said second windings, and overload relays one coordinated with each of said driving motors to be controlled by the current driving the latter, and adapted to cut off the current supply of all of said driving motors.

In testimony whereof I aifix my signature.

VVILHELM JULIUS PAUL ROHN.

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