US1888401A - Tube drawing process - Google Patents

Description

Nov. 22, 1932. H. VON FORSTER YTUBE DRAWING PROCESS 4 SheetsSheet l in Filed May 13, 1950 w- W W E! I: I: i w 1' I I ll I 1 I l F'l I l l II I I: i 1 1' I! H H I "1' i I l "N l l I I 1' 1* l I l l i I In venfpn:

Nov. 22, 1932. H. VON FORSTER TUBE DRAWING PROCESS Filed May 13. 1930 4 Sheets-Sheet 2 ill ulli'lnunllnm lll ihlllllllllz NOV. 22, VQN FORSTER TUBE DRAWING PROCESS Filed May 13, 1950 4 Sheets-Sheet 3 /n venfor': W W

1932 H. VON FORSTER TUBE DRAWING PROCESS 4 Sheets-Sheet 4 Filed May 13. 1950 Patented Nov.. 22. 1932 UNITED STATES PATENT OFFICE HERMANN VON FORS'IEB, OF NIEDERURSEL, NEAR FRANKFORT-ON-THE-MMN, GER- MANY, ASSIGNOR '10 AMERICAN LURGI CORPORATION, OF NEW YORK, N. Y., A COB- IPORATION OF NEW YORK TUBE DRAWING PROCESS Application filed May 13, 1930, Serial No. 452,093, and in Germany December 21, 1927.

stages during the operation.

In drawing hollow bodies over a mandrel according to the present invention, the hollow body is loosened from the mandrel, after each draw, or after a small number of draws, in order to be further drawn on the same mandrel. Several loosening and drawing operations can be performed in succession on the same mandrel.

The invention prevents the risk of tension cracks due to the tube seizing on the mandrel. The hollow body can now also be drawn to such extent, on the same mandrel,

that the limit of elongation of the metal is attained. The several degrees of draught can also be substantially increased, as compared with the known processes, since the material elongates more readily in consequence of being loosened on the mandrel. For example, in the lmreindescribed process, copper-tube billets prepared in the Mannesmann mill and having a thickness of 6 mm. of metal and any convenient internal diameter, such as mm., can be drawn to tubes with a thickness of 1 mm. of metal, in 7 passes, without intermediate annealing and change of mandrel. In the case of other metals and alloys, such as iron and ferro-alloys, similar conditions exist.

The invention has the further advantage that the work of inserting the mandrel in the tube, and its withdrawal therefrom, has only to be performed once, or at least more rarely than in the known processes. .At the same time, the risk of damaging the smooth surface of the tube is reduced. Moreover,

considerable saving in time is effected, since the intervals for changing the mandrel are e:1tirelyor at least partiallydispensed with, and the wear on the mandrels is substantially reduced. I

In rolling tubes on a mandrel, it is known to employ, alternately with the actual rolling apparatus, other rolling-means which loosen the tube on the mandrel. This process, however, is suitable only for the production of tube billets of thick metal and inaccurate dimensions by hot rolling. In comparison with this known process, the invention presents the advantage that tubes, or similar hollow bodies, of any thickness of metal, even the however, is especially advantageous when performed in the following manner In order to prevent the movemenat of the work with the mandrel, and therefore avoid the risk of injury to the mandrel by the movements, and also to.shorten the working period considerabl the operation is per-- formed by fixing t e hollow body and mandrel in the drawing machinefor example,

the chain draw benchand drawing the die over the same by means of a tool carriage travelling to and fro.

Loosening can be'efiected, after each pass or a few passes, by known means, such as rotary reeling or hammering machines, which preferably move in conjunction with the tool carriage and revolve round the mandrel. They come into operation during the forward or return travel of the tool carriage, or simultaneously with the drawing operation. In carrying out the invention, the mandrel may also be rotatably mounted, so that the loosening devices effect the rotation of the mandrel by means of their loosening movements, or the mandrel may be rotated by special actuating means. Greater advantage, however, is presented by' the new loosening process, which is distinguished by the use of very simple devices which, being small, are easily disposed in the drawing machine, and by particular reliability in operation and protective treatment of the work material and 'the surface of the work. This new loosening process is performed by working the hollow body on the mandrel on only a portion of its periphery, in such a way that any substantial elongation of the hollow body is avoided and that the flow set up in the material by the treatment takes a direction substantially tangential to the axis of the hollow body. It has been found that the elasticity of thehollow body loosens the unworked portion from the mandrel during the working treatment, and loosens it all round afterwards, to an extent sufficient to allow a further drawing operation to be performed, or for the hollow body to be stripped from the mandrel. Particularly elastic conditions are produced when the treatment performed with tools set at an angle causing a powerful flow of the material. In this manner, stresses which loosen the structural cohesion of the material at the parts subjected to work are avoided, and the orientation imparted to the crystallites by the drawing operation is substantially unaltered. The angle of setting means the angle formed by the axis of the hollow body with the tan gent at which the longitudinal-profile curve of the tool is applied at the foremost point of contact (in the operative direction) between the tool and the material.

The ratio between the worked and unworked portions of the cross section will vary according to the material and the thickness of metal of the hollow body, but must always be such that the total strength of the unworked portion of the cross section is greater than the resistance to deformation set up by the working of the worked portion, in order that no substantial elongation of the hollow body ma be produced by the loosening treatment. ince, in the loosening operation according to the invention, the material of the hollow body is deformed by tools operating in the direction of its length, and therefore in the same direction as that-in which it flows when being drawn, and since excessive stresses are revented by the flow permeating the thic ess of the material, this method of loosening is naturally far more favourable to the material properties of the hollow body than the known methods, because, in the latter, the flow pressure producing the loosening effect is applied at a larger or smaller angle to the direction of flow of the drawn hollow body, which, in the case. of oblique rolls, amounts to about 90. In such case, and particularly when the loosening is several times repeated, the same loss of quality occurs as-is observed when apiece of work, which has been deformed in one direcconfined to the surface of the hollow body,

whereby powerful injurious stresses are set up in the material and, in some cases, lead to the hollow body tearing after stripping or during further drawing. Hence, the invention has the additional advantage of preventing the waste hitherto resulting from the loosening treatment.

The new loosening process is performed, with particular advantage by means of tools which slide over the work, in the same manner as the die, since such tools can be set with the greatestaccurac and at a small angle, and finally because, y reason of their small dimensions, such tools can be very easily accommodated in any machine.

For example, loosening discs-with elliptical bore can be employed, which set up a deforming action on only a small portion of the periphery of the hollow body, by means of the narrower parts of the bore. Such loosening dies are drawn over the hollow body, 7

by the tool carriage, in the same way as the ordinary dies. They may be brought into action when the machine is running idly, or inorder to reduce the working time, concurrently with the die. also be designed in such a way as to possess adjustable working jaws, which can be set, by fine adjustment means, so as to produce the degree of. loosening required in such case. A particularly advantageous practice is to construct the tool which carries the jaws in sections and fit them in that condition into the tool carriage.

The stripping of the hollow body from the mandrel can be effected by means of the known devices, but, in carrying out the invention, it is preferable to employ a divided disc or bush having a bore of the same, or approximately the same diameter as the mandrel. This divided disc is mounted on the rear end of the mandrel and-after opening the front clamp of the mandrelpushed over the mandrel by the retreating tool carriage, so that the hollow body is ejected from the machine in one operation with the drawing and loosening operation, and with the mandrel always in the same position in the machine. As compared, for exam 1e, with the undivided stripper this divide pattern offers the advantage that it can be mounted in any convenient position on the mandrel without having to loosen the clamps of the mandrel and slide away the drawing tools which have already been drawn over the work. The divided stripper according to the invention is preferably designed as a door, gate and the like, suitably connected with and moved by the tool carriage and, being set in These new tools can ward, return or stop motion.

the open position during the drawing operation, assures free passage to the die.

The invention can be carried out with advantage by means of existing types of drawing machines, such as chain drawbenches, drawing presses or the like, the die being, for example, in a fixed position and the mandrel, with the hollow body disposed thereon, drawn or pushed through the die. Still greater advantages, however, are obtained in respect of time saving, simplicity of management, accuracy of work and the like in carrying out the invention by means of the drawing machine hereinafter described with reference to the accompanying drawings in which Fig. 1 shows, by Way of example, a diagrammatic plan of a tube-drawing machine constructed and operating in accordance with the invention;

Fig. 2 is the corresponding side elevation of the machine shown in Fig. 1;

Figs. 3 and 4 represent another embodiment in the same way.

Figs. 5 to 13 represent technical details of these machines.

In the embodiment shown in Figs. 1 and 2, the bedof ordinary pattern-of the drawbench carries, between guide rails 17, a tool carriage 8, designed as a tool rest and adapted to be moved to and fro by the rotation of two or more threaded spindles 9. On the bench head is a divided clamping device 4 (which will hereinafter be described), which is adapted to be opened and closed, and serves to grip the end' of the piece which is to be worked. Power is transmitted to the spindles 9, which actuate the tool carriage 8, from a clutch 10which may be electrically reversiblethrough pinions 11. The travel of the tool carriage from forward to return movement is preferably reversed by means of a switch 12, disposed at the head of the bench and serving to set the clutch for for- The cool carriage 8 contains a locking device 13 which looks the die 3 when closed, but, on being opened, leaves a sufiicient free space, for the die to be drawn out of the carriage and replaced, if desired, by another die, loosening tool or the like.

The piece 2 to be treated is gripped, by means of its end, in the clamp 4, after the dies have been threaded on said end, and the dies 3 are then drawn, singly or in groups, over the work by means of the reciprocating tool carriage 8.

If the machine according to the invention is used for drawing hollow bodies over a mandrel, the mandrel 1with the hollow body (such as the tube 2) to be treated thereon, and the dies, (and, if necessary, loosening tools) 3is gripped at. the end by the clamp 4. The other end of the mandrel is gripped by a similar clamping device 6, connected with a freely movable cross head 5 in the machine, the movement of said cross head being limited, in the direction of drawing, by suitable devices, such as stops 7, in order that the mandrel may remain stationary while the tube is being stripped oif. The stripper 14, which is preferably connected to the tool carriage 8, is opened during the drawing operation and leaves a free passage for the die, but is adapted to be closed, for the purpose of stripping the tube, when drawing is terminated. If the loosening is not effected by means of elliptical loosening tools-which are threaded, alternately with the dies, on the one end of the mandrel before commencing to draw-the loosening device 16 may be preferably attached to the tool carriage. 15 is an auxiliary mandrel, which is adapted to swing on the pivot 15' and to slide in' the axial direction of the mandrel, and on which the dies and loosening tools can be threaded, after the ejection of the tube, in order to facilitate threading a fresh tube on the mandrel.

The method of operating is, for example, as follows v The forwardly tapered tube blank 2 is passed through the opened clamp 4 and-telescoped on the mandrel until the tapered tip of thetube bears against the stop 1a formed by turning down the tip of the mandrel. The dies 3, which are arranged in proper succession on the swinging holder 15 are threaded on to the tip of the mandrel. The clamp 4 is then closed, and the machine is ready for drawing. On operating the electric switch 12, which sets the known electric double-disc clutch 10 for forward or reverse running, as desired, by simple reversal, the tool carriage 8 is caused to advance and return by means of the actuating mechanism 11 and the spindles 9, and the drawing operation proceeds in that, by means of the locking device 13 on the tool carriage, one or more dies (for example 2) are engaged, each time, and drawn over the tube. Since the movable cross head 5, which guides the mandrel accurately at the rear and by means of the clamp 6, and is fixed-by means of the stops 7only in the direction of the head end of the bench, slight changes in the length of the mandrel, due to bending or to the elastic elongation resulting from the drawing operation, can be balanced by slight movements of the cross head 5 away from the stops 7 and towards the driving end of the machine. This longitudinal balancing can, of course, also be effected in any other convenient way, for example by sliding the mandrel in the clamp 6.

That loosening of the tube from the mandrel, which is necessary for the drawing process, is efi'ectedaccording to the inventi0nfor example by setting the loosening device 16 to suit the desired degree of loosening, and drawing it over the tube. This loosening is performed in a separate working operation, during the forward or return travel of the tool carriage, or in the same operat on as the drawing stroke. When the loosening has been effected, the loosening device is opened, to allow free passage to the oncoming dies and enable them to be inserted in the tool carriage.

If loosening tools with elliptical bores be employed in place of the loosening device 16 travelling to and fro with the tool carria e, said tools are threaded, together with the d1es in proper succession, on the tip of the mandrel, and, like the dies, are drawn over the tube b means of the tool carriage. By suitably esigning the tool carriage, the loosening tool can be drawn over the tube after, and in the same operation with, the die, which it follows immediately or with a small intervening space, so that no s ecial loosening stroke of the machine is nee ed and a saving of time is effected.

The reciprocating tool carriage is also rovided with a known lubricating device Fnot shown), which moistens the work with lubricant after the manner of a drip lubricator. The lubrication is preferably combined with a circulating device, in which the lubricant escaping into the drawbench is led into a co] lector and pumped back into the lubricator. The time-wasting lubrication by hand is done away with and better lubrication is obtained.

In order to strip the drawn tube from the mandrel the clamp 4 is opened, the divided stripper 14 is closed and the tubewhich, is previously loosened from the mandrelis ejected through the opened clamp 4 by the return stroke of the tool carriage. The dies, which have been assembled, near the clamp 6, on the rear end of the mandrel, after the drawing operation, are slipped over the mandrel back into position at the head end of the latter, after the devices on the tool carrier have been set so as to allow the dies a free passage. The dies can then be threaded, in exactly the same order and without any trouble, through the opening in the clamp 4 and on to the holder 16, which has been swung into position and reaches to the end of the man-- drel. The several operations are thenrepeated in the manner hereinbefore described. 7

Instead of being secured on the tool carriage, the loosening and stripping devices of the invention may, of course, be disposed in the machine in such a manner that they can be independently actuatedby the spindles 9. If loosening is necessary, for the purpose of stripping, after the termination of the drawing process, and if special stress is laid on surface quality and accurate gauge of the 3 tube, the latter must be trued up after being stripped from the mandrel. In carrying out the invention, however, this finishing process can also be performed in the machine itself, prior to stripping, by employing, after the mandrel without difiiculty.

Figs. 5, 6 and 7 show, in elevation and Elan, a particularly suitable embodiment o the reciprocating tool carriage 8 of Fig. 1. This carriage, which is designed after the manner of a slide rest, is provided with two bores housing the two spindle nuts 19 and 20 by means of which the tool carriage is moved to and fro by the rotation of the driving spind1es. In order to prevent the relatively long driving spindles from bending under the weight of the carriage, the latter travels, like a slide rest, on ledges 21 and 22, which are screwed onto the bed of the bench and provide accurate guidance to the tool carriage. The carriage is provided with a central opening 23 of such width that the tools employed, such as the die (or loosening tool) 3 can pass through it without trouble. The mandrel clamps are disposed, both in the vertical and lateral directions, in such a way that the mandrel 1 lies, unsupported, in the centre of said opening 23. In the middle of the tool carriage is the locking device, in the form of a gate 13, adapted to be raised by means of a lever 25. This gate is provided, on the under side, with a downwardly opening gap 26, the width of which is onl a little larger than the external diameter 0 the tube 2 carried on the mandrel. For the drawing operation, this gateas is shown in the Fig. 7is raised by means of the lever 25 far enou h to leave the opening 23 perfectly free, the ie or loosening tool 3 being pushed through the opening and the gate lowered again. During the forward travel of the tool carriage, the die 3 bears against the wall of the lowered gate and is drawn over the tube.

Figs. 8 and 9 show, in elevation and plan, a particularly suitable form of construction of divided stripper in accordance with the invention. 27 is a frame having an opening 28 of the same width as the passage in the tool carriage, so that the die can be passed through it unhindered. This frame 27 is provided with four projecting lugs 29, between which, two door leaves 31 and 32 are adapted to swing on pivots 30. Said door leaves are provided with gaps 33 in which can be inserted interchangeable dividedbushes 34 having a bore equal to the diameter of the mandrel for the time being When the leaves 31 and 32 are closed (Fig; 8) the bushes enclose the mandrel with a sufiicient tightness for effecting the stripping of the hollow body, and slide the tube off the fixed mandrel during the travel of the tool carriage. The opening and closing of the two leaves 31 and 32 simultaneously-is effected by means of two interengaging toothed quadleaves are closed, whereas, during the whole of the drawing operation, they are kept in the open position as shown in Fig. 8, so as not to hinder said operation. This divided stripper may, of course, also be designed in any other convenient manner, for example in such way that the two halves can be caused to converge and diverge by means of sliding keys or screw spindles.

Figs. 10 and 11 show, in elevation and plan, a particularly suitable form of the mandrel clamp 4 of Fig. 1. Two sliding members 41 and 42 are slidably mounted and accurately guided in two guide ledges 39 and 40. These sliders are provided with gaps 43 and 44 housing the half bushes 45 and 46. On the sliders being pushed together, the head of the mandrel is firmly ipped by the bush, as indicated by the otted lines in Fig- 10. For stripping, inserting'and removing the dies, &c., on the other hand, the sliders occupy the position shown, so as to leave a sufficient passage open between them and the ledges 39 and 40. The synchronous displacement of the sliders is effected by means of two threaded spindles 47 and 48 which are displaced in the axial direction by the rotation of the threaded bushes 49 and 50, each of which is actuated, through a pair of pinions 51, 52

and 53, 54, from a common shaft .55, which is mounted in the cross frames56 and 57 supporting the guide ledges, and are caused to close and open, as desired, by turning the hand wheel 58 to right or left.

Fig. 12 shows the manner in which the loosening action is effected accordingtothe invention. 59 is a loosening tool provided with an elliptical bore, and 1 is the mandrel carrying the tube 2 which is to be loosened. The tube 2 is now engaged and worked by the die solely at 60 and 61, in the narrow part of the elliptical bore'in thatas is shown on an exaggerated scale in the drawingthe thickness of the tube wall is reduced by .a certain percentage at this place. The cross section of the elliptical bore is so calculated thatthe unworked portion of the tube, indicated by 62 and 63 in the drawing, prevents any longitudinal elongation of the tube, so that the material displaced at the points 60 and 61 merely widens the tube, thereby increasing its diameter and producing the desired looseningefi'ect. A loosening tool of this kind is needed for each loosening within the series of the drawing passes prescribed in accordance with the invention. Thus ,if the treatment comprises 5 drawing passes and 5 loosenings,

5 dies and 5 loosenin tools accordin to Fig. 12 are employed, an are disposed a ternate- 1y on the mandrel in corresponding gradation.

Particular advantages attaches to the employment of the twoart loosening tool ac cording to Fig. 13. n this tool, the elliptical loosening bores, such as 64, 65, 66, 67 are machined in such a way that the separating joint lies along the major diameter of the ellipse, Where no deforming action takes place. This tool is preferably mounted in the tool holder and is vertically and laterally adjustable, for example by means of wedges, in sucha Way that ,when open, it allowsthedie to pass between its operative surfaces, whilst, when closed, it allows the desired loosening bore to be brought into operation. If this divided loosening tool be provided with another bore 68 adapted to the diameter of the mandrel, the same tool can also be emplo ed for stripping the tube off the mandrel, t us rendering a separate stripping tool superfluous.

A divided tool with only a single 0 ening may also be employed for loosening. n such case, the operative surfaces of said 0 ening must be capable of adjustment to each esired degree of loosening, for which purpose knownmeans can be used. This arrangement dispenses with the expensive elliptical bores, and therefore corresponds to a considerable reduction in cost. This divided loosening tool can also be suitably attached to the reciproeating tool carriage 8 of Fig. 1, and is constructed in such a way as to allow unrestricted performance of the drawing operation when open, Whereas, when closed, the operative surfaces are brought into contact with the tube, for the purpose of loosening it. For example, use can be made with advantage, of an arrangement shown in Figs. 8 and 9 the onlymodification being that, in place of the divided bush 34, irons with elliptical or straight drawing surfaces are attached on the leaves 31 and 32, and that the pivots 30 are mounted in eccentric bushes which enable the operative surfaces to be correspondingly converged. During the drawing operatlon, the leaves 31 and 32 are opened into the position shown in Fig. 9. Before the loosening operation they are closed, that is, moved into the position shown in Fig. 8, and are then set to the requisite loosening gauge by means of the said eccentrics. Of course, the operative surfaces of the said loosening device can be for example, is drawn over the tube d (d cordance with the invention, several mandrels, instead of a single one, are arranged in the machine and drawing is effected simultaneously on these mandrels, the several parts being designed accordingly. In this "way, the return stroke of the tool carriage also can be utilized for the actual operation of drawing. Fig. 4 shows in plan, a suitable embodiment of a machine for such a process. a denotes the frame of the machine; 0, c 0 c are the mandrels over which the tubes are drawn; (1', d", d and d are the tubes which are to be drawn; f, f f 7'" are the devices for locking the dies, which are adapted to be actuated by means of the tool carriage f and the spindles b and b g'-g" are rows of dies, which are passed, in succession or 1n grou s, over each tube. The tips of the man rels 0 and c are clamped in the fixed crosshead l at k and is, their other ends being clamped, at m and m in a movable crosshead l. The mandrels c and 0 are secured in a similar manner in the movable crossheads n and 0. These last two are driven by the gearing e through the spindles p and 12 In the first working operation, a die 9 and (g) for example, is drawn over the tube d (d) and, after reversingthe machine, a die 9 (9 It is known that the work undergoes considerable elongation at each drawing pass. In order to prevent this elongation causing the machine to run idle,the procedure adopted according to the invention consists in imparting a corresponding relative displacement to the two clamps, WhlCll clip the work in a machine, during or at the end of each drawing pass. Accordingly, for example, during the forward stroke of the machine, the crossheads in which the two mandrels c and c are gripped are moved backwards, by means of the gear mechanism 6, to the same'extent as the tubes have stretched in the first pass. The reciprocating tool carriage now, by means of the diesheld by the locking devices, alternately draws the tubes d and 01 during the forward stroke, and the tubes d and d during the return stroke, until the final dies have operated and the tubes are ejected in a finished condition.

The loosening operations needed for the purpose of drawing and stripping, and the stripping operation itself, are effected in the manner previously described. I g

This process has the great advantage that, without any increase in the working staff, the output *of drawn tubes can be increased, in one and the same machine, and in a-p roximately the same time, two to fourfol (according to the number of mandrels) as compared with the output of a single-mandrel machine. This naturally implies a considerable reduction in the cost of production.

The hereindescribed process may obviously be applied to the production of other hollow blank by a drawing operation, loosening the blank from the mandrel, and repeating said drawing and loosening operations while said hollow body is continuously retained upon said mandrel, and at least, one end of said body being maintained in its original position on the mandrel.

2. The invention as set forth in claim 1, wherein two sets of hollow bodies are simultaneously formed, and the drawing operation for decreasing the diameter of one set of the hollow body blanks is effected simultaneously with the loosening of the second set of blanks, and the loosening of the first set of blanks is effected simultaneously with the drawing op erations performed upon the second set.

3. The process of manufacturing hollow bodies which comprises the steps of supporting the hollow body blank on a mandrel, drawing down the blank by repeated passes through drawing dies, and loosening the blank from the mandrel after each of a plurality of said drawing passes, said blank being retained substantially in its original position on said mandrel throughout the entire process.

4. The invention set forth in claim 3, wherein said loosening is efiected by progressively applying at successive transverse sections alon said body blank pressureexerted radially o the blank and at circumferentially spaced portions of the periphery thereof.

5. In the formation of. seamless pipe from a short thick-walled blank by a series of passes through drawing dies, the process which comprises lacin securing one end t ereo to an elongated stationary mandrel, successively moving a series of drawing dies over the entire length of said blank to reduce the external diameter of and to elongate the same, loosenin the blank from said mandrel between two 0 said drawing operations, and stripping the blank from said mandrel only at the completion of the drawing operation.

6. The process as set forth in claim 5,

the blank on and wherein a loosing operation follows each drawing operation.

7. The method of forming hollow bodies which comprises, positioning a blank upon a mandrel, subjecting said blank while substantially in its original position on said mandrel to a series of drawing operations to reduce the diameter of the blank, subjecting said blank to such loosening, intermediate the first and last drawing operations, that the creep of the blank on the mandrel during the drawing operations is sufiicient to prevent the occurrence of tension cracks in the blank during drawing, and stripping said finished body from said mandrel subsequent to the last drawing operation.

In testimony whereof I aflix my signature HERMANN VON FORSTER.

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