US2161065A - Apparatus for reducing tubular blanks - Google Patents

Description

June 6, 1939. F. R. KRAUSE I APPARATUS FOR REDUCING TUBULAR BLANKS Filed.Dec. '2, 1956 7 Sheet-Sheet INVENTOR.

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June 6, 1939. F. R. KRAUSE 4 APPARATUS FOR REDUCING TUBULAR BLANKS Filed Dec. 2, 1936 7 SheetsSheet 2 m5 *1 I j I I i a I g w a j, I I

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June 6, 1939, F. R. KRAUSE APPARATUS FOR REDUCING TUBULAR BLANKS' Filed Dec. 2, 1956 7 Sheets-Sheet 3 INVENTQR.

WITNESSES ATTORNEYS.

June 6, 1939. F. R. KRAUSE APPARATUS FOR REDUCING TUBULAR BLANKS 2, 1936 Sheets-Sheet 4 INVENTOR.

Filed Dec.

VITA/Z5555 ATTORNEYS.

June 6, 1939. F. R. KR A USE APPARATUS FOR REDUCING TUBULAR. ,BLANKS 5 & M 5 m m r W m m \k 3 A ,m M S n v 4 6 n1- W u I'llllul'Il-IllllllllI-lllll B MIA/[Hi5 Jim 6, 1939.

F. RQKRAUSE V APPARATUS FOR REDUCING TUBULAR BLANKS Filed Dec. 2, 1936 INVENTOR.

' ATTORNEYS.

June 6, 1939. F. R. KRAUSE 2,161,055

' I APPARATUS FOR REDUCING TUBULAR BLANKS Filed Dec. 2, 1956 7 Sheets-Sheet 7 i 105 1'03 I A 101 i Q wlruassm INVENTOR. i M R. M w-d. v. 4, w, v I BY W,/ %wv 4 ATTORNEYS.

Patented June 6, 1939 UNITED STATES APPARATUS Foa REDUCING TUBULAR BLANKS Frank R. Krause, Ellwood City, Pa.

. Application December 2, 1936, Serial No. 113,839

16 Claims.

This invention relates to a method and apparatus for reducing and elongating metal blanks. and relates more particularly to the rolling'of seamless tubes. 1 v

In tube reducing and elongating by longitudinal rolling on a mandrel as now practiced, a tubular blank is reduced a relatively small amount ineach of a series of independent full-length roll passes until it finally acquires the desired size. The blank is fed into the rolls which roll it from front end to rear whereby the rolls continuously roll against the portion of the blank having the greatest diameter and the draft therefore remains uniform throughout. The reduction that can be made in any one pass is limited both by the tendency of the rolls to slip against the blank if too great a reduction is attempted, and by tearing of the metal when the reduction becomes too great.

It is among the objects of this invention to provide a method and apparatus for rolling seamless tubes from tubular blanks in which only one. mill is necessary, in which there is substantially no limit to the reduction that can be made while a blank is passing through the mill only once, in which the character of the metal of the blank is improved, and in which the life and capacity of the mill is increased.

In accordance with this invention a tubular blank mounted on a mandrel is reduced to a tube of desired dimensions by passing it only once through a mill havingv grooved rolls which are caused to periodically roll simultaneously toward the front end of the blank and the axis thereof, and then parallel to the axis. The movement of the rolls is brought about by relative reciprocable movement between the blank and track surfaces which the rolls engage. During the return strokes of the rolls between working strokes, unrolled increments of the blank are successively brought into position for reduction by the rolls. The tracks are preferably so formed that they cause the rolls to approach each other gradually during the first part of each working stroke, then toapproach each other quite rapidly followed by in section, of my tube-rolling mill; Fig. 2 is a central vertical section thereof; Fig. 3 is a view of the delivery end-of the mill; Fig. 4 is a plan view,

partly in section, of apparatus for feeding and v turning a blank in the mill; Figs. 5 and 6 are side and end views, respectively, of that apparatus; Fig. 7 is a view showing diagrammatically the I relative positions of tracks and rolls at diiferent points in the rolling operation; Fig. 8 is a fragmentary vertical section showing a modification, of this invention; Fig. 9 is an enlarged vertical section taken on the line IX-IX of Fig. 8; and Fig. 10 is a vertical section through the rolls taken on the line X-X of Fig. 9.

Referring to Figs. 1, 2 and 3 of the drawings, a track housing I, provided with an opening 2 extending from end to end thereof and having parallel horizontal and vertical side walls, is slidably mounted in a bed plate 3. Preferably, the housing is reciprocated in the frame by a crank arm 4 pivoted to the base of the housing and to a disc 5 rotated by a drive shaft 6. Mounted in any suitable manner, adjustably' if desired, in the rear portions of the horizontal walls of opening 2 is a pair of hardened track plates 1. Another pair of track plates 8 is mounted in the vertical side walls of opening 2 midway between tracks I. Disposed one behind the other in the housing opening are roll housings 9 and I l the rear housing 9 having side flanges I2 slidable along the top and bottom surfaces of tracks 8, and the front housing H having similar flanges l3 for the same purpose.

A pair of horizontal reducing rolls I4 is journaled in bearing blocks l6 slidable inrecesses in the side walls of housing 9, and a pair of vertical finishing rolls I8 is journaled in like manner in blocks l9 disposed in recesses 2| in the top and bottom walls of housing H. The front and rear pairs of rolls are each provided centrally with annular grooves 22 and 23, respectively, the two sets of grooves forming roll passes through which a cylindrical mandrel 24 extends. The grooves in the reducing rolls are larger than those in the finishing pair because the former must engage unreduced portions of the tubular blank 26 mounted on the mandrel, while the latter engage only portions of the blank that have already been reduced by the other rolls. The side walls of the grooves in the reducing rolls are substantially flat and flare outwardly at a tangent to the unreduced portion of the blank, as shown in Fig. 1, but the grooves in the finishing rolls are semi-circular in cross section because they form the pass in which axis of the mandrel, and thereby, by a combined rolling and sinking operation, reduce and elongate the blank. During the latter part of the working stroke the rolls travel parallel to the axis of the mandrel to form a reduced cylindrical tube. Accordingly, as shown in Fig". 2, tracks I are provided adjacent their rear ends with parallel areas 27 merging into areas 28 inclined away from each other toward the front of the track housing. Likewise, as shown in Fig. 1, tracks 8 have parallel areas 29 terminating in outwardly inclined areas 3| at their front ends.

Consequently, as the track housing starts to move forward from the position shown in Fig. 2 in which horizontal rolls M loosely engage an unreduced increment of the blank a portion of which has already been reduced during preceding working strokes of the mill, the inclined areas of tracks I move into frictional engagement with the adjoining rolls and force them tightly against the blank. Continued movement of the tracks causes these rolls to roll forward and inwardly at the same time. This reduces the previously unrolled cylindrical increment to tapered form and further reduces the blanks previously tapered portion the smaller end of which is thus reduced to an unfinished tube by the rolls when the parallel areas of the tracks'reach them and move them in parallel paths. During the same working stroke vertical rolls I8 are moved forward and inwardly along the reduced unfinished-portion of the blank by track plates 8 until the parallel areas of the tracks reach the rolls, whereupon they travel parallel to the axis of the tube and finish it. s

It will be noted in Fig. 2 that the front end of the tube has been allowed to upset by sinking over the tapered front end of the mandrelat the start of rolling. The reason for this is to increase its wall thickness to prevent the front end from spreading and splitting open while it is being reduced. The remaining increments of the blank that are successively reduced are supported at both ends of their zone of contact with the rolls by portions of the blank not under rolling pressure and therefore do not spreadout and split open.

As the track housing returns to its starting position at the conclusion of each working stroke the roll housingsare retarded in their backward movement relative to bed plate 3 after the rolls have rolled back tothe inclined areas of the track plates to permit them to spread apart and release the blank for an increment of feed. This retarding of the roll housings is preferably accomplished by a fluid pressure cylinder 32 mounted on the rear end of the bed plate with its piston 33 connected 'to rear roll housing 9. Suficient pressure .is maintained behind the piston to retard the roll housings until a stop 34, attached to the front end of the track housing, engages roll housing H and pushes both housings back to their starting positions, as shown in Fig. 2. At the conclusion of the return stroke the fluid under pressure is reversed to the front end of cylinder 32 to hold the roll housings stationary at the start of the working stroke until the rolls are in firm frictional engagement with the tracks and blank. The two roll housings are connected together, but it is a spring connection 36 to allow their separation for a short distance during rolling to accommodate differences in roll speed.

Although the inclined area of each rear track I may be flat lengthwise when relatively small reductions are being made, for making large reductions'with the same length working stroke each inclined area is preferably in the form of a reverse curve with its ends nearly horizontal and its central portion more steeply inclined to the horizontal, as best shown in Fig. 7. The principal reason for this shape of track is to prevent the rolls.

from slipping on the track or blank. The likelihood of roll slippage is greatest when they first move into contact with the'blank, and also when they approach the smaller end of the tapered portion of the blank that has already been reduced a material extent and has a thin unyielding wall.

With tracks of the shape just referred to, the draft is gradually increased during the beginning and gradually decreased during the ending of the working stroke of the mill so that there will be no roll slippage at those times. I

With track plates of either shape each successive draft starts at zero on the periphery of the unrolled increment and gradually increases to its maximum amount. This gradual increase of the draft with its accompanying reduction orientates the crystals in the metal before subjecting them to more severe elongations, and thereby improves the character of the metal, and this improved portion ofthe metal is not affected adversely during most sudden and the crystals are therefore caused to fracturewhen elongated under heavy drafts.

The shape of the rear tracks and the outline of a blank rolled between them is best shown in the diagram of Fig. 7 where the relation of the different members to one another when in three different positions is also illustrated. The full lines show the shape of a portion of a blank 26 in the process of being reduced, and also the positions of the tracks I and rolls M at the start of a work-' ing stroke after the blank has first been advanced a step to subject an unrolled increment A--B to the action of the rolls. As the tracks advance to the position indicated by broken lines they roll the rolls into their broken line position wherein increment A-B and the adjoining portion of the partly reduced blank are further reduced an amount also shown'by broken lines. It will be seen that'at this stage the increment AB has been reduced but slightly, the reduction increasing as the front of the increment isapproached. On the other hand, the previously reduced portion near line C is reduced materially during this working stroke. As the tracks continue to advance to the dotted line position in which their parallel areas reach the rolls, also dotted, the blank is reduced to the shape indicated by both broken and dotted lines. The portion C-D of the blank is materially reduced, but as line D is approached the draft starts to diminish, and by the time the rear ends of the tracks reach the rolls another portion of tubing of substantially uniform Wall thickness has been added to the preceding portion.

With this type of mill in which the rolls roll a tubular blank step by step towards its front end while they bodily approach each other, blanks can be reduced in a single pass through the mill an amount heretofore thought impossible, because the same draft can be taken in making a large reduction that is used in making a small one. This is because the amount of reduction does not depend upon the draft which is governed by the amount of feed, but upon the shape of the tracks and the length of the working strokes. The track plates can be so shaped that large reductions can be made with short working strokes, because roll slippage is prevented by the shape of the ends of the track'plates, and also by the fact that the apex of the contact angle F (Fig. 'l) is at the junction of the rolls and tracks instead of at the axes of the rolls so that the angle is smaller for any given area of contact between the rolls and blank. Also with the hardened track plates backing up the rolls, the rolls are supported on substantially flatsurfaces throughout their length and, the rolls can therefore be of relatively small diameter.

Another factor that differentiates this mill from 1 naturally flow in opposite directions therefrom,

as indicated by the arrows, whereby the metal in the pass is under tension as well as compression as it is being displaced and therefore spreads very little. In fact, the spreading of the metal is very much less with this mill than in any other rolling making its return'stroke, i. e., returning to its,

starting point during each cycle, and while the rolls are released from the blank due to their backward movement being retarded by piston 33, the blank and mandrel are fed or advanced a step to subject the next succeeding unrolled or unreduced increment of the blank to the action of the rolls.

A desirable feeding apparatus for this purpose is illustrated in Figs. 4, 5 and 6 wherein a carriage 5i is slidable on a table 52 toward and away from the mill which is not shown in these figures but which would be disposed at the right of the apparatus as viewed in Figs. 4 and 5. Journaled in one side of the carriage is a hollow spindle 53 in which the rear ends of the blank and mandrel are clamped by means of a chuck 54 mounted on the front end of the spindle. The carriage is constantly biased toward the mill by a fluid pressure cylinder 56 and a piston rod 51, but its movement is obstructed by a stop 58 projecting up through a slot 59 in the table from a screw 6| on which it is threaded. This screw is shown disposed beneath one side of the table for the sake of clearness, but if desired it can be located in the center of the table. The screw is constantly rotated through a belt 62 and any suitable adjustable speed drive, such as a Reeves drive 63, y

from a shaft 64 geared to drive shaft 6 of Fig. 1.

At periodic intervals, that is, during each working stroke of the mill, the tube and mandrel are clamped in fixed position by an automatic clamp comprising'a downwardly opening fluid pressure cylinder 65 "mounted in the table directly beneath the blank and containing a piston 66 provided at its lower end with a cross-head 61 which is connected by tie rods 68 to a clamping bar 69 above the blank. The cylinder should be disposed as close to the mill as possible, and may even be mounted in a separate support between the table and mill. When fluid pressure is introduced into the upper end of this cylinder the piston is forced downwardly, which draws the clamping bar down against the blank and clamps it against the upper end of the cylinder. Fluid pressure is automatically supplied to the cylinder and released therefrom by any well-known automatic control which may be actuated by the reciprocating track housing l. While the blank and an increment of it is being elongated in the mill, stop 58 continues to move forward on screw 6| whose speed'and pitch determine the amount the stop can move during the interval that the blank is held by the clamp. At the moment the blank is released, which is during the return stroke of the mill when the rolls are free of the blank,

cylinder 56 connected to the carriage forces the carriage ahead until it strikes stop 58, whereupon the clamp again grips the blank and holds it stationary for the next reducing and elongating step. Consequently, the stop determines the amount the blank is fed forward each time, and this feed is variable by the Reeves drive.

To rotate the mandrel any desired number of degrees while it is being fed forward, so that the blank will be properly rolled on all sides, a pinion H having an axial passage therethrough is jouris thus clamped in position 1 naled in the carriage where it meshes with a gear l2 keyed on the carriage spindle. The passage through the pinion is preferably square for receiving a square shaft 13 to produce a splined connection that permits the carriage to move forward on the square shaft without interfering with rotation of the pinion. To turn shaft 13 a predeterminated amount every time the blank is released from the automatic clamp, the shaft is connected to a cylindrical shaft 14 journaled in suitable spaced pedestals 16 mounted on a supDOrt TI. Keyed on shaft 14 between the pedestals is a ratchet 18 (Fig. 6) which is turned by a pawl 19 mounted in a suitable clutch, such as a housing 6| surrounding the ratchet and having a radial arm 82 provided with holes 83. Pivotally suspended from any desired hole in this arm is a link 84 pivotally connected at its lower end to one end of a substantially horizontal beam 86 adapted to rock vertically on its opposite end.

In order to oscillate housing 8|, beam 66 is rocked by a cam 81 fixed on a shaft 86 journaled in pedestal bearings 89' on support 71. As the cam is rotated by a chain and sprocket drive 9| from shaft 64, it engages a roller 92 journaled in beam 86, the roller being held in contact with the cam at all times byzja coilspring 93 compressed and normally spaced from the bottom of the bore F :the beam connected to the plunger compresses the spring under it and that end of the. beam oscillates instead of the other end..

To make itfunnecessary to provide a hardened through which it extends.

and tempered mandrel as long as the tube to be formed, mandrel 24 is made in two parts with its vrelatively short and hardened front part projecting but a relatively short distance through the roll pass. This mandrel is connected at its rear end to a cylinder 99 by which it is pulled back- 26 is mounted on mandrel 24 and is clamped to carriage 5| by chuck 54. The front end'o-f the blank encircles the tapered end of the mandrel and is disposed in the pass of reducing rolls 14 when the track housing is at the rear end of the bed plate 3. With the blank held in fixed position by clamp 69, disc 3 is rotated whereby the track housing is moved forward and rolls M taper the end of the blank before running off the end of it. During the return stroke of the mill clamp 69 releases the blank which is fed forward an increment by carriage 54 that is pushed ahead by cylinder 56 until it strikes constantly moving stop 58 on screw GI. At this time the blank is again clamped in place by clamp 69 and the horizontal rolls taper an unreduced increment and further reduce the tapered end of the blank, However, during the first few cycles of operation of the mill the front end of the blank is sunk upon the tapered front end of the mandrel instead of having its Wall thickness reduced, whereby the end of the tube is upset to maintain a thick wall that prevents splitting open.

This tapering alone continues until a sufilcient length of the blank extends through the rear roll pass to be engaged by rolls M throughout the working stroke, whereupon the foremost portion of the blank is engaged by the rolls while they are moving parallel to its axis and a tube of uniform wall thickness is produced, with the exception of the upset end. By this time the blank on the exit side of the rear roll pass is also, long enough to extend into the front pass'where it is smoothed and shaped by finishing rolls l8. The

mandrel and blank continue to be fed ahead step by step, and between each step a portion of the blank is reduced by the mill rolls. During each feeding step the blank is also turned a predetermined number of degrees by spindle 53 At intervals the mandrel is pulled back through the blank by cylinder 99 which also serves to strip the mandrel from the finished tube.

This invention is particularly applicable to the.

cold rolling of tubes, and some of the advantages mentioned, such as improvement of the grain structure of the blank and substantially unlimited reduction in 'one pass through the mill, refer to cold rolling. Nevertheless, it will be understood that the invention can likewise be practiced to advantage in the hot rolling of tubular blanks.

Although the invention has been described as contemplating holding the blank stationary while the mill is reciprocated to reduce it, it will be understood that the mill can be stationary and the blank reciprocated in it as it is fed through the previous pass and loosen the tube from the v mandrel.

In the modification shown in Figs. 8, 9 and 10 the-roll-engaging areas of the track plates llll are similar to track plates 1 of Fig. 2, and there is only oneroll housing H12 and one pair of rolls I03 disposed in the track housing I M. The shape of the grooves 105 in this single pair of rolls is relied upon to reduce and shape the blank into a cylindrical tube. Accordingly, as best shown in Figs. 9 and 10, each roll groove I05 is of the tapering type, that is, it is semi-cylindrical in cross section' and gradually decreases in width and depth as theroll is encircled, the smaller endof the groove being of uniform size for a short distance so that it will not taper the smaller end portion of each increment of the tubular blank rolled. Consequently, each time crank I06 moves the track housing from its left hand position on bed plate I01, as viewed in Fig. 8, to the position shown, the track plates cause the rolls to roll forwardly, and inwardly for part of the distance, along a portion of the blank III].

In the starting position of the rolls the deep endsof their grooves are opposite each other for receiving an unreduced increment of theblank, but as they roll toward the front end of the blank the surfaces'of the two grooves gradually approach each other and reduce the increment of the blank to tapered form. Near the end of the working stroke the groove surfaces cease to approach each other and a cylindrical increment of a tube is thereby produced: During each working stroke this operation is repeated until the entire blankhas been fed between the rolls and has been reduced to a tube. The shape of the tracks and roll grooves thus effect sinking of the blank in two different ways; that is, as the rolls move bodily toward each other their grooves become shallower.

To keep like areas of grooves I05 opposite each other atall times, the roll necks are provided with sprockets I98 that mesh with chains I09 anchored at their ends. Preferably, the rear ends of the chains are connected to any suitable rigid support H I at the rear of the bed plate, while their front ends are connected to rods H2 slidably mounted in plates E E3 aflixed to the rear ,of the track housing. The rods are biased rearwardly by coil springs l M which permit the chains to move away from plates l l3 far enough to compensate for the change in effeotive'diameter of the rollsas different points in the roll grooves come into contact with the blank. 1

According to the provisions of the patent statutes, I have explained the principle and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that,.within the scope of the appended claims, the invention may be practiced otherwise stantially parallel areas merging into areas in- I clined away from each other toward the exit end of the housing, a roll housing disposed in said track housing and blank to cause said rolls'to blank to the action of said rolls whereby to periodically roll successive portions of the blank.

2. A tube rolling mill comprising a track housing open from end to end and provided interiorly with a pair of spaced t.ack surfaces having substantially parallel areas merging into areas inclined away from each other toward the exit end of the housing, a roll housing disposed in said track housing between said tracks, a pair of grooved rolls rotatably mounted in said roll housing in frictional engagement with said tracks, a mandrel extending through the roll pass formed by the roll grooves and adapted to support a tubular blank, means for reciprocating said track housing longitudinally of the mandrel to cause said rolls to periodically roll simultaneously on the blank toward the entering end of .the blank and toward each other to elongate a portion of the blank, said rolling movement of the rolls being caused solely by their frictional engagement with said tracks and blank, means'for holding the unrolled portion of the blank'in fixed position during each blank-reducing step, and means for periodically advancing successive unrolled increments of said blank into the roll pass whereby to periodi cally roll successive portions of the blank.

3. A tube rolling mill comprising a track housing open from end to end and provided interiorly with a pair of spaced track surfaces having substantially parallel areas merging into areas inclined away from each other toward the front of the housing, a roll housing disposed in said track housing between said tracks, a pair of grooved rolls rotatably mounted in said roll housing in frictional engagement with said tracks, a mandrel extending through the roll pass formed by the roll grooves and adapted to support a tubular blank,

means for effecting relative reciprocable movement between said track-housing and blank to cause said rolls to periodically roll simultaneously toward the front end of the blank and toward each other to elongate a portion of the blank, and means for periodically subjecting successive unrolled increments of said blank to the action of said rolls, said inclined areas of the tracks being formed to cause the rolls to approach each other angles to said first pair and likewise having substantially parallel areas merging into areas inclined away from eachother-toward the exit end of the housing, a roll housing disposed in said track housing between each pair of tracks, a pair of grooved rolls rotatably mounted in each roll housing in frictional engagement with the adjoining pair of tracks, a mandrel extending through the roll pass formed by the roll grooves and adapted to support a tubular blank, means for effecting relative reciprocable movement between said track housing and blank torcause each pair of rolls to roll simultaneously on the blank toward the entering end of the blank and toward each other to elongate a portion of the blank, the rotation of the rolls being controlled principally by their frictional engagement with the tracks and blank, means for holding said track housing and the unrolled portion of the blank against movement in the same direction during the blankreducing steps, and means for periodically subjecting successive unrolled increments of said blank to the action of said rolls whereby to periodically roll successive portions of the blank.

5. A tube rolling mill comprising a track housing open from end to end and provided interiorly with a pair of spaced track surfaces having substantially parallel areas merging into areas inclined away from each other toward the exit end of the housing, said housing being provided with a second pair of spaced track surfaces at right angles to said first pair and likewise having substantially parallel areas merging into areas inclined away from each other toward the exit end of the housing, a roll housing disposed in said track housing between each pair of tracks, a pair of grooved rolls rotatably mounted in each roll housing in frictional engagement with the adjoining pair of tracks, a mandrel extending through the roll pass formed by the roll grooves and adapted to support a tubular blank, means for effecting relative reciprocable movement between said track housing and blank to cause each pair of rolls to roll simultaneously on the blank toward. the entering end of the blank and toward each other toelongate a portion of the blank, the rotation of the rolls being controlled principally by their frictional engagement with the tracks and blank, means for holding said track housing and the unrolled portion of the blank against movement in the same direction during the blankreducing steps, means for periodically subjecting successive unrolled increments of said blank to the action of said rolls,'and means for turning the blank on its axis between working strokes.

6. A tube rolling mill comprising a track housing open from end to end and provided interiorly with a pair of spaced track surfaces having substantially parallel areas merging into areas inclined away from each other toward the front of the housing, said housing being provided with a second pair of spaced track surfaces at right angles to said first pair and likewise having substantially parallel areas merging into areas inclined away from each other toward the front of the housing, a roll housing disposed in said track housing between each pair of tracks, a pair of grooved rolls rotatably mounted in each rollhousing in frictional engagement with the adjoining pair of tracks, the grooves in the rolls between said first-mentioned tracks having outwardly flaring flat side walls, and the grooves in the other pair of rolls being substantially semi-circular in roll pass formed by the roll grooves and adapted to support a tubular blank, means for effecting relative reciprocable movement between said track housing and blank to cause each pair of rolls to roll simultaneously toward,the front end of the blank and toward each p th er to elongate a portion of the blank, means for periodically subjecting successive unrolled increments of said blank to the action of said rolls, and means for periodically turning the blank on its axis.

7. A tube rolling mill comprising a track housing open from end to end and provided interiorly with a pair of spaced track surfaces having substantially parallel areas merging into areas inclined away from each other toward the front of the housing, a roll housing disposed in said track housing between said tracks, a pair of grooved rolls rotatably mounted in said roll housing in frictional engagement with said tracks, a mandrel extending through the roll pass formed by the roll grooves and adapted to support a tubular blank, means for reciprocating said track housing to cause said rolls to periodically roll simultaneously toward the frontend of the blank and toward each other to elongate a portion of the blank, means for returning said rolls to their starting position after each working stroke, means for delaying said return of the rolls during the return stroke of said track housing, and means for periodically advancing successive unrolled increments of said blank into the roll pass.

8. A tube rolling mill comprising a track housing open from end to end and provided interiorly with a pair of spaced track surfaces having substantially parallel areas merging into areas inclined away from each other toward the front of the housing, a roll housing disposed in said track housing between said tracks, a pair of grooved rolls rotatably mounted in said roll housing in frictional engagement with said tracks, a mandrel extending through the roll pass formed by the roll grooves and adapted to support a tubular blank, means for reciprocating said track housing longitudinally of the mandrel to cause said rolls to periodically roll simultaneously toward the front end of the blank and toward each other to elongate a portion of the blank, means associated with said track housing for engaging said roll housing to return it to starting position after each working stroke, fluid pressure means for delaying the return of said roll housing during the return stroke of said track housing, and means for periodically advancing successive unrolled increments of said blank into the roll pass.

9. A tube rolling mill comprising a track housing open from end to end'and provided interiorly with a pair of spaced track surfaces having substantially parallel areas merging into areas inclined away from each other toward the front of the housing, a roll housing disposed in said track housing between said tracks, a pair of grooved rolls rotatably mounted in said roll housing in frictional engagement with said tracks, a mandrel extending through the roll pass formed by the roll grooves and adapted to support a tubular blank, means for reciprocating said track housing longitudinally to cause said rolls to periodically roll simultaneously toward the front end of the blank and toward each other to elongate a portion of the blank, means constantly urging said blank forward, means periodically arresting said forward movement, and means for clamping said blank infixed position when its forward movement is arrested.

10. A tube rolling mill comprising a track housing open from end to end and provided interiorly with a pair of spaced track surfaces having substantially parallel areas merging into areas inclined away from each other toward the front of the housing, a roll housing disposed in said track housing between said tracks, a pair of grooved rolls rotatably mounted in said roll housing in frictional engagement with said tracks, a mandrel extending through the roll pass formed by the roll grooves and adapted to support a tubular blank, means for reciprocating said track housing longitudinally to cause said rolls to periodically roll simultaneously toward the front end of the blank and toward each other to elongate a portion of the blank, means constantly urging said blank forward, means periodically arresting said forward movement, means for clamping said blank in fixed position when its forward movement is arrested, and means for periodically drawing said mandrel backwardly in said blank.

11. A tube rolling mill comprising a track housing open from end to end and provided interiorly with a pair of spaced track surfaces having substantially parallel areas merging into areas inclined away from each other toward the front of the housing, a roll. housing disposed in said track housing between said tracks, a pair of grooved rolls rotatably mounted in said roll housing in frictional engagement with said tracks, a mandrel extending throughthe roll pass formed by the roll grooves and adapted to support a tubular blank, means for reciprocating said track housing longitudinally to cause said rolls to periodically roll simultaneously toward the front end of the blank and toward each other to elongate said forward movement, means for clamping said blank in fixed'position when its forward movement is arrested, and means for turning said blank on its axis while it is moving forward.

12. Feeding and turning apparatus for use with a tube rolling mill, comprising a carriage, means biasing the carriage toward said mill, a hollow spindle journaled in the carriage for receiving a mandrel supporting a tubular blank, means for detachably clamping the mandrel and blank in said spindle, means for periodically clamping the mandrel and blank in fixed position relative to the mill, and means for rotating said spindle a predetermined amount while the carriage is moving forward.

l3. Feeding and turning apparatus for use with a tube rolling mill, comprising a carriage, means biasing the carriage toward said mill, a. constantly rotating screw, a; stop threaded on said screw and projecting into the path of the carriage, a hollow spindle journaled in the carriage for receiving a mandrel supporting a tubular blank, means for detachably clamping the mandrel and blank in said spindle, means for periodically clamping the mandrel and blank in fixed position relative to the mill, a rotatable shaft operably connected to said spindle for turning it, pawl and ratchet members for turning said shaft, a beam operably connected at one end to one of said members for actuating it, resilient means pivotally supporting the opposite end of the beam, and means normally oscillating said firstmentioned end of the beam.

14. A tube rolling mill comprising a track housing open from end to end and provided interiorly with a pair of spaced track surfacesl'iaving substantially parallel areas, a roll housing disposed in said track housing between said tracks, a pair 1 of grooved rolls rotatably mounted in, said roll housing in frictional engagement with said tracks, the grooves in each roll being substantially semi-cylindrical in cross section and tapering from a wide and deep portion to a relatively narrow and shallow portion, a mandrel extending through the roll pass formed by the roll groove and adapted to support a tubular blank, means for effecting relative reciprocable movement between said track housing and blank, the axes of the rolls being free to accommodate themselves to the relative speeds of the tracks and blank and means for maintaining like areas of said grooves opposite to each other at all times.

15. A tube rolling mill comprising a track housing open from end to end and provided interiorly with a pair of spaced track surfaces having substantially parallel areas, a rollhousing disposed in said track housing between said tracks, a pair of grooved rolls rotatably mounted in said roll housing in frictional engagement with said tracks, the grooves in each roll being substantially semicylindrical in cross section and tapering from a wide and deep portion to a relatively narrow and shallow portion, a mandrel extending through the roll pass formed by the roll groove and adapted to support a tubular blank, means for effecting relative reciprocable movement between said track housing and blank, the axes of the rolls being free to accommodate themselves to the relative speeds of the tracks and blank sprockets mounted on the ends of said rolls, and means anchored at the rear of said track housing and meshing with said sprockets, the front ends of said means also being anchored.

16. A tube rolling mill comprising a housing open from end to end and provided interiorly with a pair of spaced track surfaces having substantially parallel areas merging into areas inclined away from each other toward the exit end of the housing, a pair of grooved rolls rotatably mounted between said track surfaces in frictional engagement therewith, a mandrel extending through the roll grooves and adapted to support a tubular blank, means for effecting relative longitudinal reciprocable movement between said housing and blank to cause said rolls to periodically roll simultaneously on the blank toward its entering end and toward each other to reduce and elongate a portion of the blank, the axes 'of the rolls being free to accommodate themselves to the relative speed of the tracks and blank, and means for periodically subjecting successive unrolled increments of said blank to the action of said rolls whereby to periodically roll successive portions of the blank.

" FRANK R. 'KRAUSE.

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