US1878117A - Method of and apparatus for metal rolling - Google Patents

Description

W 1932- s. E. mEscHER 1,378,117

METHUD @F APPAMTUS MB METAL BQLLlNfi Filed April 15, 1925 5 Sheets-Sheet 1 Elm 'Sept. 20, 1932. s. E. DIESCHER ET AL 1,873,117

METHOLI' OF AND APPARATUS FOR METALROLLING 5 Sheets-Sheet 2 INVENTORS Filed April 15, 1925 pt. 20, 932- s. E. DIESCHER ET AL 1,873,117

METHOD OF AND APPARATUS FOR METAL ROLLING Filed April 1925 5 Sheets-Sheet 3 W (f /MM ATTORNEY Sept. 20, 1932. s. E. DIESCHER ET AL METHOD OF AND ARPARKTUS FOR METAL ROLLING Filed April 15, 1925 5 Sheets-Sheet 4 INVENTORS 5/01 1054 52 5 cHEe and ATTORNEY 5 Sheets-Sheet 5 INVENTOR5 JHMUEL [II/5.501152 ATTORNEY Filed April 15, 1925 p 20, 2- s. E DIESCHER ET AL METHOD OF AND APPARATUS FOR METAL ROLLING Patented Sept. 20, 1932 UNITED STATES PATENT OFFICE SAMUEL E. DIESCHER, F WILKINSBURG, AND CARL W. A. KOELKEBECK, OF MOUNT LEBANON, PENNSYLVANIA, ASSIGNORS TO FOSTER WHEELER CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK METHOD OF AND APPARATUS FOR METAL ROLLING Application filed April 15, 1925. Serial N0. 23,219.

The general object ofthe present invention is to provide a practical and effective method of, and mechanism for rolling a helical groove into a tubular metal body. The invention was primarily devised for the production of tubular heat exchange elements for use in superheaters, eeonomizers. water tube boilers, and like apparatus. and having externally ribbed surfaces to provide an external heat absorbing surface greatly increased in proportion to the internal surface of the element, in comparison with the external and internal surfaces of tubular elements having cylindrical inner and outer walls.

In thepreferred practical method which we have devised for producing such a helically grooved element we subject a pierced steel billet, or analogous tubular blank, to the action of a pair of disk rolls, the plane of each of which is inclined at a small angle which depends on the pitch of the helical groove formed, to a plane transverse to the axis of the blank. The two rolls are located at opposite sides of the blank axis, thus forming a roll pass the axis of which is slightly inclined to the axis of the blank and through which the blank is in effect threaded, by the action on the blank of the two rolls which turn in the same direction, and consequently rotate the blank in the opposite direction. In practice to form a groove of the depth and configuration ordinarily desired, we pass the blank through the roll pass two or more times, reversing the direction of rotation of the rolls at the end of each movement of the I work through the pass in one direction, and

at the same time feeding the rolls inward toward the work axis, so that in the subsequent or return passage of the work through the pass, the groove will be made deeper than it was made during the previous passage of the work through the roll pass.

In practice we preserve the form of the blank and facilitate its proper rolling, by placing a snugly fitting mandrel in the blank and maintaining it therein until the rolling operation is completed. In accordance with our present invention we carry out the rolling operation so as toavoid any appreciable or significant change in the internal or maximum external diameter of the Work. The metal displaced by the rolls is displaced longitudinally of the work axis rather than radially, and the length of the work progressively increases as the rolling operation proceeds. In consequence, the rolling operation gives but little twist to the fibre of the metal.

The mechanism which we have devised for carrying out our invention comprises various novel features of construction and arrangement devised with the general idea of providing effective means for attaining our general purposes, and with specific objects in mind of permitting the rolling operation on each blank to be carried out with precision, and to be expeditiously concluded so that each blank may be finished without objectionable cooling and without requiring reheating.

The various features of novelty Which characterize our invention are pointed out with particularity in the claims annexed to and forming a part of this specification; but for a better understanding of the invention, however, its advantages and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which we have illustrated and described preferred embodiments of the invention.

Of the drawings:

Fig. 1 is a plan;

Fig. 2 is a transverse section on the line 2-2 of Fig. 1;

Fig. 3 is a section on the broken line 33 of Fig. 2 with parts broken away and in section;

Fig. 4 is an elevation partly in section of a portion of the machine;

Fig. 5 is an elevation taken similarly to Fig. 4 of the portion of the machine not shown in Fig. 4;

fIIPig. 6 is a partial section on the line 66 0 ig. 1; 7

Fig.7 is a side elevation of a portion of the apparatus with parts omitted;

Fig. 8 is a diagrammatic plan illustrating one stage of the rolling operation;

Fig. 9 is a section on the line 99 of Fig. 8; Fig. 10 is a view similar to Fig. 8 illustrating a subsequent stage of the rolling operation; Fig. 11 is a section on the line 11-11 of Fi 10;

ig. 12 is a view taken similarly to Fig. 2 illustrating a modification; and

Fig. 13 is a section on the line '1313 of Fi 12.

he machine shown in Figs. 1 to 6 comprises a work guide B fixed on a stationary ed A and provided with a work receiving trough or channel along the length of which are work supporting rollers B. In operation the Work piece X is moved back and forth in the work guide through the pass between a pair of co-operating rolls D and d mounted in a supporting frame C. The frame C is mounted on a base or bed plate A as by means of the pivot C, so as to permit of the angular adjustment of the frame about a vertical axis intersecting the center line of the work as it passes through the roll pass. This angular adjustment is effected in the apparatus shown, by means'of a worm gear segment C secured to the frame C and in mesh with a worm E journalled on the bed plate A and manually rotated by means of a crank shaft E. The latter is provided with a crank arm E and rotates the worm E through spur gears E and E. Clamping bolts C passing through apertured lugs carried by the frame C and arc-shaped slots A in the bed plate A, form means for rigidly clamping the frame C to the bed plate A in any desired angular adjustment of the frame 0. An index pointer C carried by the frame C, and a scale A on the bed plate accurately indicate the angular position of the frame C.

The rolls D and d are mounted in the frame member C in such manner as to permit of an adjustment of each roll toward and away from the Work, and to permit of an angular adjustment of each roll about an axis intersecting the point of intersection of the work axis with the vertical axis about which the frame C is angularly adjusted. The common axis about which each roll is thus angularly adjustable with respect to the frame C passes through the point in the crown D or (1 of the working surface of each roll which is closest to the work axis.

The mounting for the roll D providing for the described adjustments comprises a roll supporting member F having a cylindrical body angularly and axially adjustable in a spring H cylindrical chamber C formed for the purpose in the frame member 0 and forked at one end to provide arms F for carrying suitable bearings for the ends of the roll spindle. The roll supporting member F is provided adjacent the roll D with an arm F provided with a gear sector in mesh with a worm gear G journalled in the frame C and provided with a hand wheel G by which the worm G may be rotated.

The axial adjustment of the roll supporting member F in the chamber C is effected by means comprising a tubular abutment H mounted in the frame 0, and against which the outer end of the roll support F is held by the reaction of the work, and by means of a bolt H passing axially through the body of the support F, and through the abutment H with its head bearing against the yoke of the forked portion of the bearing F, and a compression spring H surrounding the external end of the bolt and interposed between a nut on the bolt and the portion of the frame C through which the bolt extends. The inner end of the abutment H is threaded and passes through a nut H mounted in the outer end of the chamber C Splined on the cylindrical body of the abutment H is a worm gear H in mesh with a worm H by rotation of which the abutment is axially advanced. and retract" ed. When advanced it forces the roll support F and thereby the roll D toward the work, and when retracted it permits the roll support and roll to be drawn away from the work by the The worm H, as shown, is mounted on the shaft I of a roll adjusting motor I mounted on the frame C. I represents a hand wheel for the manual rotation of tlge worm H when this is necessary or desira le.

The supporting and adjusting provisions for the roll d are generally similar to those provided for the roll D 'and comprise elements 0', f, f, F, g, g, h, h, 72. and b similar respectively, to the parts C, F, F, F G, G, H, H, H and H previously described. The abutment h is rotated by means of a motor 2' similar to the motor I, and like the latter mounted on the frame'C at the front of the machine. The shaft of the motor 2' carries 4 a worm in'm'esh witha worm gear h carried by a shaft It. The latter is ournalled in the frame C, and passes beneath the rolls D and d, and at the rear of the machine carries a spur gear h which meshes with a gear 7L splined on the adjustable abutment member it.

Since, as hereinafter explained, the movements of the rolls D and d towards and away from the work must be made accurately as Well as rapidly, we have provided the apparatus shown in Figs. 1 to 6 with indicating provisions readily visible from the front of the machine for showing the roll adjustments. The provisions for thus indicating the d1stance of the roll D from the work axis comprises a dial J mounted on the frame 0 at the front of the machine and an indicating pointer J co-operating with the dial and carried by a shaft on WhlCh is mounted a spur gear H connected b an idler gear H" to a spur gear H spline on the adjustable abutment member H. As hereinafter explained, in the j 6 operation of the apparatus shown, the move- 1 ment of the roll 03 toward and away from the work which must be made as the rolling operation is carried out, is greater than the corresponding movement of the roll D. In consequence, we have provided indicating provisions for showing the distance between the work axis and the roll somewhat different for the roll d, from those provided in the case of the roll D. The indicating mechanism thus provided for the roll at comprises a stationary dial 7', and two co-operating indicating pointers j and 7'". The indicating pointer j is arranged to make one rotation around the dial for each rotation of the adjustment member H, while the pointer 7' makes three complete turns for each rotation of the abutment member H. For this purpose in the arran gement shown, the pointer 7' is carried by a hollow shaft h which also carries a spur ear h driven through an idler k by a gear i splined on the abutment member h. The pointer 1' is carried by a shaft h extending through the hollow shaft h and carrying at its rear end a spur gear it which is in mesh with a gear 7L secured to a counter shaft which also carries a spur gear h in mesh with the adjusting gear h splined on the member h. The gear it has a third as many teeth as the gear h.

To prevent any possibility of the accidental lifting of the work out of its normal position between the rolls D and at, we have provided an upper work guide K which extends longitudinally of the work above the latter adjacent the rolls and is carriedby a lever K, the pivot K of which is pivoted to the frame C of oneside of the machine. To provide for the quick and easy removal of the guide K to permit the work to be lifted out of its normal position between the rolls, we advantageously provide the lever K with a counter weight K tending to swing the guide K into an inoperative position. In operation the guide K is normally locked in place as by means of a locking bolt K controlled by a latch lever K at the front of the machine. When the bolt K is retracted the counter weight K swings the upper work guide K in the position shown in dotted lines in Fig. 2. In this position, the counter weight K 69 engages a stop C on the supporting frame C.

The driving means for the rolls comprise floating shafts L and Z connected to the rolls D and 03, respectively, and driven from a lay or main driving shaft P through gear boxes N and 11., respectively. As shown, the

shaft L is connected at one end to one end of the roll D by a suitable universal coupling M, and at the opposite end is connected by a similar coupling M, to a counter shaft N in the gear box N. The latter, as shown, has mounted in it the shaft N, one end of the drive shaft P and a vertical shaft 0 connected to the shaft N by bevel gears O, and O, and connected to the shaft P by bevel gears O and O. The shaft L is elongated to minimize the angular displacement of the axis of the shaft L relative to the axis of the roll D produced by the adjustment of the latter, and to permit the gear box N to be displaced from the line of the work sufiiciently to permit the introduction of the latter into the machine from a feed table S comprising work supporting rolls S arranged in line with the guide rolls B of the machine proper. The use of bevel gearing in the gear box N enables the latter to be made compact and thus facilitates the provisions of the clearance needed for the work table S. The

use of bevel gears also makes it readily possible to set the shaft N out of parallelism with the shaft P and thus minimize the maximum angular displacement of the axis of the shaft L relative to the axis of the shaft N. The gear box 0 is conveniently enclosed so that the gears therein may run in oil.

Advantageously, the shaft L is provided With a floating bearing Q, midway between its ends arranged to take the weight of the shaft L wholly or largely off the universal couplings M at its ends. The floating bearing Q, as shown, is carried by a vertically movable plunger Q mounted in a cylindrical guide Q and formed with a pivotal support for a lever Q the inner end of which engages the plunger Q while its outer end carries a counter weight Q balancing the weight of the shaft L and bearing parts Q and Q. The guide Q is mounted on a stationary support A with freedom to move horizontally in a direction transverse to the axis of the shaft L. The shaft Z is connected at one end to the roll (Z by a universal coupling M, and at its outer end is connected by a similar coupling to the shaft n in a gear box n which may be similar to the gear box N and comprises a shaft 0 and gears O, O, and O and 0 connecting the shaft '11. to the lay shaft P as in the gear box N.

The driving means for. the shaft P may advantageously comprise an electric motor R having its shaft directly connected to one end of the shaft P through a leading spindle R, which need not be described as it-may be of the type commonly employed in rolling mills. The motor R may be energized and controlled by provisions not shown such as are ordinarily employed in operating reversing mills. As shown, the shaft P is formed in sections coupled by standard flange couplings P, and advantageously the shaft sections are made relatively large in diameter to avoid torsional deflection, the diameter of the sections being reduced for practical reasons where connected to the coupling flanges P and where the shaft is supported in bearings. The shaft P in the machine shown,

' comprises in addition to the hearings in the gear boxes N and 11., a hearing A in the bed plate A. and an intermediate bearing A between the central bearing and each gear box. As shown. the bearings A are mounted on foundation pedestals which also support the floating bearings for the floating shafts L and 7.

In the ordinarily contemplated mode of operation of the apparatus shown in Figs. 17, a hot pierced billet or other tubular blank first has passed through it a snugly fitting cold mandrel U and is then moved into place over the work table rolls S and guide rolls B, to bring its tapered forward end between the rolls D and d which have previously been started into rotation. \Vith the roll arrangement illustrated, and the method of introducing the work described, the two rolls D and d are initially rotated in the counterclockwise direction, as viewed from the left hand end of Figs. 1 and 8, with the result that the work piece X is rotated in the clock-wise direction, and the helical groove produced, is in the form of a right handed screw thread. Figs. 8 and'9 illustrate the initial disposition of the rolls, and the form of the work after the Work has been given a few initial revolutions. The roll d produces a shallow helical groove X, and the roll D deepens and widens the groove X longitudinally of the work axis to form the groove X lVhen the full length of the work piece, except for a short rear end portion, is thus threaded through the roll pass, the rotation of the rolls is stopped, and the roll D is fed into the work a certain distance, and the roll (Z is fed into the work piece a greater distance, and the rolls are then started into rotation in the clockwise direction. This threads the work piece back through the roll pass. As the roll passes back through the roll pass, the roll D deepens and enlarges the groove X to form the groove X and the roll d further deepens and Widens the groove X to produce the final groove form X. The left hand end of the work X, as shown in the section in Fig. 1-0 is thus the completed form. It will be understood, of course, that in some instances the helical groove produced, may be completely formed by a single passage of the work through the roll pass, while in other cases more than two movements of the work through the roll pass will be required, or at least will be advantageous to form a groove of the full depth. In general, to form a helical grooved element of the configuration of the left hand end of the work piece X shown in Fig. 10, with the diameter of the blank and the diameter of the grooved element produced, approximately 4% inches, we consider it desirable to pass the work through the roll pass twice as described above.

A tubular element of a maximum diameter of four and one-half inches, and of the relative proportions indicated by the left hand end of Fig. 10, is of a form and dimensions well adapted for use in a superheater element and for other purposes, which may advantageously be produced by the apparatus and with the method disclosed herein, but it is to be understood, of course, that the present invention may advantageously be used in producing elements of quite diflerent diameters and configurations.

In producing a helically grooved element in accordance with the present invention, the maximum diameter of the blank is not changed, and the metal is not radially displaced by the rolls, but is displaced in such manner as to elongate the blank in the operation. In producing an element of the configuration shown in the left hand portion of Fig. 10, the blank is elongated about two times, In the operation, the mandrel U serves as a sort of floating, normally inactive third roll, to preserve the original internal diameter and smooth inner surface of the blank. Any tendency of an exter.- nal roll to crowd the wall of the blank inward against the mandrel converts the latter from a normally inactive or idle roll into an active roll, between which and the external roll the blank is then rolled to enlarge the blank circumferentially sufliciently to eliminate radial pressure between the Work and the mandrel, whereupon the latter again becomes .a passive or idle roll.

The axial elongation and peripheral grooving of the element is accomplished with a desirably small amount of helical twist in the fibres of the work piece, owing to the fact that the displacement of the metal is very largely confined to displacement in the longitudinal or axial direction as distinguished from displacement in a circumferential direction. In practice, it is impossible to avoid some helical twist of the material, as there is inevitably some displacement of the metal in a circumferential direction, and such displacement produces fibre twist. The ratio of the circumferential displacement to the longitudinal displacement of the metal depends upon the configuration of the area of contact between the rolls and the work piece, and is diminished by increasing the circumferential dimension of the figure of contact relative to the longitudinal dimension of that figure. In consequence, the twist given to the metal may be diminished within limits by increasing the diameters, and by decreasing the thickness of the working portions of the disk-shaped rolls D and d.

Avi,

As soon as the rolling operation is completed, the finished work piece is removed, and the mandrel is Withdrawn, preferably before appreciable further cooling of the work may occur, as such cooling might result in shrinking the work on the mandrel. The practical utility of the described mode of forming helically groovel elements depends, of course, upon the speed and accuracy with which the operations may be conducted. lt is especially desirable, to carrying on the rolling operation with suflicient expedition to avoid any necessity for re-heating the work during or at the end of the operation when possible. The production of work pieces of uniform dimensions and form obviously requires predetermined and accuate adjustments of the rolls radially toward the work axis at the beginning of each passage of the work through the roll pass. The mechanism disclosed in Figs. 1 to 7 is well adapted to secure such results. The mechanism shown in Figs. 1 to 7 is of desirable form because of its comparative mechanical simplicity, strength and rigidity, and the facility withwhich it may be adjusted to produce work of different dimensions and groove configuration and pitch. Ample power and strength is provided to force the rolls into the work preparatory to each movement of the latter through the roll pass, notwithstanding the unusually large force required for this purpose.

A desirable modification of the means shown in Figs. 1 to 7 for feeding the rolls radially into the work, is illustrated in Figs. 12 and 13.

In a modified roll adjusting arrangement illustrated in Figs. 12 and 13, the roll D is carried by a roll supporting member FA generally like the members F of the construction first described. The roll supporting member FA passes through a cylindrical bearing C formed in the roll supporting frame CA and is retracted by a spring H engaging an adjustable abutment formed by lock nuts F on its protruding end. The member FA is provided with an arm F carrying a worm gear se ment in mesh with the corresponding gear for rotating the roll support F about its inner axis. The member FA is provided with trunnions F connected 'by levers F and shafts Y and Y to plungers Y and Y respectively. The plunger Y works in a cylindrical chamber C formed in or supported by the frame CA and is connected to the shaft Y by a stem Y having an enlarged head through which the shaft Y passes. Pressure fluid is admitted to the outer end of the chamber C to advance the plunger Y at the proper time through a supply pipe Y. The extent of movement thus imparted to the plunger Y is definitely fixed by means of an arm Y formed on the plunger Y and engaging an adjustable stop shown as comprising a nut Z adj ustably locked, as by means of a lock nut Z at any desired point along the length of a stop bolt Z carried by the frame CA.

The plunger Y is mounted in a cylinder C formed in or supported by the frame CA and is connected to the shalt Y through a stem Y having an enlarged head in which the shaft Y is mounted. The plunger Y is advanced by pressure fluid supply to the outer end. of the chamber C through a supply pipe Y. The resultant movement of the plunger 1' is definitely limited by means of an arm Y carried by the plunger Y and cooperating with a corresponding adjustable stop comprising a bolt Z nut Z*, and lock nut Z In Fig. 12 the plunger Y is shown in its advanced position, while the plunger Y is shown in its retracted position. The position of the roll D in Fig. 12 corresponds to that shown 1n Fig. 9, the roll having been forced mto this intermediate position by pressure fluid supplied to the cylinder C through the pipe Y. WVhen, thereafter, pressure fluid is supplied to the cylinder C by the pipe Y, the roll D is moved still closer to the work axis into the position corresponding to that occupied by it in Fig. 11." The adjustable stops Z and Z which limit the advancing movements of the plungers Y and Y respectively, permit of a very accurate adjustment of each feed movement of the roll and the provisions made for advancing the plungers Y and Y are simple, effective, and expeditious.

While in accordance with the provisions of the statutes, we have illustrated and described the best embodiment of our invem tion now known to us, itwill be apparent to those skilled in the art that changes may be made in the form of apparatus and method illustrated and described in detail without departing from the spirit of our invention as set forth in the appended claims, and that certain features of the invention may be used to advantage in some cases without a corresponding use of other features.

' Having now described our invention, what we claim as new and desire to secure by Letters Patent, is:

1. The method of forming la helically grooved tubular element from a hot tubular body without significant change in the maximum diameter of the latter, which consists 1n mounting said body on a mandrel and passlng the body and its contained mandrel back and forth through the roll pass between disk rolls revolving in the same direction about axes generally parallel to the axis of the roll blank but longitudinally displaced and inclined with respect thereto to give the desired pitch to the helical groove to be formed by the rolls, feeding the rolls radially inward to cause them to bite into said and the axis of the body bein body at the beginning of each movement of the blank through the roll pass, and reversing the direction of rotation of the rolls to reverse the direction of travel of the blank through the'pass.

2. In a machine for rolling a helical groove in a tubular body, co-operating reversible disk rolls defining a roll pass, means for progressively advancing each roll toward the axis of the roll pass in a plurality of definite steps and means for rotating said rolls about normally fixed axes.

3. In a machine for rolling a helical groove in a tubular body, co-operating disk rolls normally rotating about fixed axes defining a roll pass, means for adjusting the rolls to displace the rolls axially of said body and thereby change the pitch of the helical groove formed, and means for adjusting each roll to set its plane of rotation in correspondence with the pitch of the helical groove being formed.

4. In a machine for rolling a helical groove in a tubular body, a guide along which a body being operated upon is moved in an axial direction, a pair of disk rolls at opposite sides of said guide, and a supporting frame which is revoluble about an axis transverse to the length of said guide to displace said rolls lengthwise of said'guide and thereby change the pitch of the groove formed.

5. In a machine for rolling a helical groove in a tubular body, a guide along which a body being operated upon is moved in an axial direction, a pair of disk rolls at opposite sides of said uide, a supporting frame which is revoluble a out an axis transverse to the length of said guide to displace said rolls lengthwise of said guide and thereby change the pitch of the groove formed, and means for adjusting said rolls relative to said frame to set the plane of rotation of each roll in correspondence with the pitch of the groove being formed.

6. In a machine for rolling a helical groove in a tubular body, a guide along which a body being operated upon is moved in an axial direction, a pair of disk rolls at opposite sides of said guide, a supporting frame which is revoluble about an axis transverse to the length of said guide to displace said rolls lengthwise of said guide and thereby change the pitch of the groove formed, and means for adjusting each roll relative to said frame to vary the distance between the roll worked upon.

7. In a machine for rolling a helical groove in a tubular body, a guide along which a body being operated upon is moved in an axial direction, a pair of disk rolls at opposite sides of said guide, a supporting frame which is revoluble about an axis transverse to the length of said guide to displace said rolls lengthwise of said guide and. thereby change the pitch of the groove formed, and

means for adjusting each of said rolls about an axis generally transverse both to the first mentioned axis and to the length of said guide.

8. In a machine for rolling a helical groove in a tubular body, a guide along which a body being operated upon is moved in an axial direction, disk rolls defining a roll pass traversed by a body moving along said guide, a roll holder for each roll comprising a cylindrical body extending away from said roll pass, a roll supporting frame work formed with bearings for said cylindrical bodies, separate driving connections for rotating said rolls in said holder and means for adjusting the latter angularly and axially in said bearings.

9. In a machine for rolling a helical groove in a tubular body, the combination with means for guiding said body along an axial path of movement, of a pair of disk rolls at opposite sides of said path of movement and turning about axes oppositely inclined away from said path, a pair of roll driving gears located at opposite sides of said path and longitudinally displaced with respect thereto in opposite directions from said rolls, and each comprising a roll driving counter-shaft, a power shaft connecting said gears, and connections between each of said counter-shafts and the corresponding rolls, each such connection comprising a spindle, a flexible coupling between one end of said spindle and the corresponding counter-shaft, and a flexible coupling between the opposite end of the spindle and the roll.

10. In a machine for rolling a helical groove in a tubular body, the combination with means for guiding said body along an axial path of movement, of a pair of disk rolls at opposite sides of said path of movement, and turning about axes oppositely inclined away from said path, roll supporting means including provisions for adjusting said rolls relative to said path, a pair of roll driving gears located at opposite sides of said path and longitudinally displaced with respect thereto in opposite directions from said rolls, each of said gears including a gear member co-axial with the corresponding gear member of the other, a counter-shaft and bevelled gears connecting said countershaft to the corresponding gear member, a power shaft connecting the gear members of the two gears, and connections including flexible shaft couplings between the counter-shafts and the rolls.

11. In a machine for rolling a helical groove in a tubular body, a trough-shaped work guide, disk rolls at opposite sides of said work guide rotating about axes oppositely askew to the length of said work guide in correspondence with the pitch of the helix to be formed, and a work guide mounted above the first mentioned work guide and readily removable to permit a body in the pass between said rolls to be lifted out of the latter.

1:2. In a machine for rolling a helical groove in a tubular body, a trough-shaped work guide, disk rolls at opposite sides of said work guide rotating about axes oppositely askew to the length of said work guide in correspondence with the pitch of the helix to be formed, a support in which said rolls are mounted, and a lever pivoted at one side of said guide and adapted to be swung into and out of the position in which it extends over said work guide and prevents the work from lifting out of the latter.

13. In a machine for rolling a helical groove in a tubular body, a trough-shaped work guide, disk rolls at opposite sides of said work guide rotating about axes oppositely askew to the length of said work guide in correspondence with the pitch of the helix to be formed, a lever pivoted at one side of said guide and adapted to be swung into and out of the position in which it extends over said work guide and prevents the work from lifting out of the latter, and means for quick- 1y moving said lever out of said position to permit the work to be lifted out of said guide.

14. In a machine for rolling a helical groove in a tubular body, a trough-shaped work guide, disk rolls at opposite sides of said work guide rotating about axes oppositely askew to, the length of said work guide in correspondence with the pitch of the helix to be formed, and a lever pivoted at one side of said guide and adapted tobe swung into and out of the position in which it extends over said work guide and prevents the work from lifting out of the latter, means tending to move said lever out of said position to permit the work to be lifted out of said guide, and means for releasably locking said member in said position.

15. In a machine for rolling a helical groove in a tubular body, a pair of disk rolls at opposite sides of the roll pass, a support in which said rolls are adjustably mounted, and separate motor means for moving each roll relative to its support toward the axis of the roll pass.

16. In a machine for rolling a helical groove in a tubular body, a pair of disk rolls at opposite sides of the roll pass, a support in which said rolls are adjustably mounted, separate motor means for moving each roll relative to its support toward the axis of the roll pass, and means for precisely determining the extent of each such movement.

17. In a machine for rolling a helical groove in a tubular body comprising a disk roll turning about an axis askew to the axis of the work, an adjustable support for said roll, and means for moving said roll toward the work axis in two successive steps comprising. a lever connected to said support, two

pressure fluid motors each comprising a piston member and a cylinder member one of which is stationary, and the other of which is connected to said lever.

18. In a machine for rolling a helical groove in a tubular body comprising a disk roll turning about an axis askew to the axis pf the work, an ad ustable support for sald no 1,

and means for lIlOVlDg said roll toward the work axis in two successive steps comprising a lever connected to said support, two

pressure fluid motors each comprising a p1ston member and a cylinder member, one of which is stationary, and the other of which is connected to said lever, and adjustable means limiting the relative movement of the piston and cylinder members of each motor when the latter is actuated.

19. In a machine for rollin a helical groove in a tubular body compr sing a pair of cooperating rolls with their axes slig tly askew to the axis of the roll pass defined by the rolls with respect to which each roll is adj ustable, and driving means for each roll comprising a power driven shaft, an elongated spindle connecting said shaft to the roll, and a floating bearing for said spindle engaging the latter intermediate the ends of the latter and adjustable to accommodate the movements of the spindle as the corresponding roll is adjusted.

20. In a machine for rolling a helical groove in a tubular body comprising a pair of cooperating rolls with their axes slightly askew to the axis of the roll pass defined by the rolls with respect to which each roll is adjustable, and driving means for each roll comprising a power driven shaft, an elongated spindle connecting said shaft to the roll, and a floating bearing for said spindle engaging the latter intermediate the ends of the latter and adjustable to accommodate the movements of the spindle as the corresponding roll is adjusted and comprising means for exerting a yielding spindle weight supporting effect in its various adjustments.

21; The method of forming a helically grooved tubular element from a hot tubular which consists in mounting said body on a v mandrel and passing the body with its contained mandrel through the roll pass between disc rolls norm ally revolving in the same direction about fixed axes generally parallel to the axis of said body but longitudinally displaced and inclined with respect thereto to give the desired pitch to the helical groove formed by the rolls.

22. The method of forming a tubular heat exchange element with an external helically ribbed surface from a tubular bod without appreciable chan e in the outer an inner diameters of the tu ular body and without imparting much helical twist to the fibres in ISO the body which consists in mounting said tubular body on a mandrel, and passing said mandrel and body through a roll pass wherein the peripheral surface of the body is progressively indented along a continuous helical path of indentation with a longitudinal displacement of the material of said body at opposite sides of the momentary point of indentation, whereby said body is 10 substantially elongated.

Signed at Pittsburgh, in the county of Allegheny, and State of Pennsylvania, this 4th day of April, A. D. 1925.

- SAMUEL E. DIESCHER. CARL W. A. KOELKEBECK.

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