US2029552A

US2029552A - Method and machine for making tapered tubes

Info

Publication number: US2029552A
Application number: US693112A
Authority: US
Inventors: George E Barnhart
Original assignee: Individual
Current assignee: Individual
Priority date: 1933-10-11
Filing date: 1933-10-11
Publication date: 1936-02-04
Anticipated expiration: 1953-02-04

Description

Feb. 4, 1936. N G E, BARNHART 2,029,552

METHOD AND MACHINE FOR MAKING TAPERED TUBES Filed Oct. 11, 1933 Sheets-Sheet l INVENTOR GEORGE E. BAANHAPT ATITORNEY Feb. 4, 1936. G. E. BARNHART 2,029,552

METHOD AND MACHINE FOR MAKING TAPERED TUBES Filed Oct. 11, 1933 2 Sheets-Sheet 2 84 85 1 1g INVENTOR 65020: E. DAQNHART wag/M ATTORNEY Patented Feb. 4, 1 936 UNITED STATES PATENT OFFICE George E. Barnhart, Pasadena, Calif.

Application October 11, 1933, Serial No. 693,112

22 Claims.

This invention has to do in a general way with the art of working metal, and is more particularly related to the production of tapered metal tubes of either welded or seamless construction.

It is one object of this invention to produce a method and apparatus for drawing a tapered metal tube in which the wall is of uniform structure throughout its circumference, or, more specifically, to produce a tube in which the possibility of scratches, flaws, or blemishes in or on the wall thereof is entirely eliminated.

" It is a further object of this invention to provide a method and apparatus wherein a tapered tube can be produced and fibers drawn in the 5 metal, such fibers being uniformly distributed throughout the circumference and'parallel to the axis of the tube.

. It is a primary object of this invention to provide a method and apparatus of the class de- 39 scribed whereby I am able to produce a tapered tube having one or more steps therein. In other words, this invention contemplates the produclcn of a tapered tube embodying two or more sections interconnected by means of steps, the

3.", different sections having parallel or tapered walls which may be of different or the same taper.

It is still a further object of this invention to provide a method of the class described where.- by the wall thickness of a tapered tube may be :1.) varied at different points throughout its length.

It is a further object of this invention to provide a machine and a die unit for accomplishing the various objects enumerated above.

The details of my invention will be best underii.) stood from the following description of the method and the accompanying drawings which are chosen for illustrative purposes only, and in which I v Fig. 1 is an elevational view partly broken away 1 showing one form of machine contemplated by this invention;

Fig. 2 is a plan view of the machine shown in Fig. 1;

Fig. 3 is an end elevation partly in section 3 showing a preferred form of die unit contemplated by this invention;

Fig. 4 is an enlarged fragmentary view partly in section showing further details in the construction of the die unit and a preferred form 5 i of die opening;

Fig. 5 is a sectional elevation taken through a die unit of the type shown in Fig. 3 and may be considered as having been taken on the plane 55 of Fig. 3;

Fig. 6 is a diagrammatic elevation il ustrating one procedure in drawing a stepped tapered tube of the type contemplated by this invention;

Fig. 7 is a diagrammatic plan view showing one form of mechanism for operating the die unit in the formation of a stepped tapered tube;

Fig. 8 is a diagrammatic elevation showing a tapered tube and illustrating another method of forming the same;

Fig. 9 is an elevational view showing a modified form of die element which may be employed in the production of a stepped tapered tube;

Fig. 10 is a sectional view showing a modified form of tapered tube which may be drawn by the process contemplated by this invention;

Figs. 11, 12 and 13 illustrate various other forms of tubes which may be drawn by the meth- 0d. and apparatus contemplated by this invention; and

Fig. 14 is an elevational view showing a modified form of die element and illustrating the manner in which tube configurations may be obtained through changes in the shape or configuration of the die surface.

The method contemplated by this invention consists in a general way of drawing a. tube through a contractible die opening and contract ing the die opening in accurately timed relation with the longitudinal movement of the tube therethrough.

The die opening in the mechanism which I propose to employ is formed by a plurality of rotatable die elements, preferably four, which are mounted in a. suitable die head in tangent relation with each other, and are geared or otherwise interconnected so that all of the elements rotate in synchronism.

Each of the die elements is provided on its periphery with a tapered groove, such grooves cooperating at their region of tangency to form the die opening. This die head is associated with means for drawing work through the die opening, and such means are in turn associated with additional means whereby the die elements are rotated in timed relation with the movement of work therethrough;

In order to produce the maximum drawing action in the operation of a machine of the class described, I consider it preferable to actuate the die elements so that their peripheral surfaces are rotated in a direction which is opposite to the direction of the movement of the work through the die opening, but under certain circumstances the operation may be reversed. In the production of a tapered tube, it is important that the die elements be arranged so that the grooves in their peripheries are rotated from the large radius to the small radius during the movement of the work through the openings, but under certain circumstances this operation may also be reversed.

I have discovered that, in the operation of drawing tapered tubes of the class described, there is a tendency for the metal of the tube, as the tube is being reduced in cross section by the contracting die, to flow outwardly into the angular spaces which diverge from the points of tangency between the die elements. It will thus be seen, assuming a circular die opening, that the tube as it enters such opening is deformed by this flowing action, and as such a tube is drawn through the confined die opening the metal which has been squeezed outwardly in this manner is either compressed inwardly to distort the wall of the tube or increase its thickness or is sheared from the tube wall, forming scratches on the wall of the tube. In any event, this action produces a flaw in the wall of the tube and it therefore becomes another object of this invention to provide a die and a method of operation wherein this feature is eliminated.

This object of my invention is accomplished by recessing the edges of the grooves to conform to the flow of the metal in the various die elements so as to form confined segmental areas within the die opening into which the distorted areas of the tube described above may be drawn into beads on the wall. After a tube has passed through a (lie of this character, it is again passed through the same die or a similar die with the beads thereon in angular spaced relation with the relieved or recessed segments in the die opening so that these beads are drawn or ironed out, and at the same time drawing again takes place and additional beads are placed in the tube in the regions of the relieved portions. This procedure is repeated with progressive increases in length of the tube or progressive increases in the relative rate of die rotations until the desired taper is obtained. The tapered tube is then drawn through a contracting die opening having no relieved areas or through a relieved die opening with the beads spaced angularly from the relieved areas.

In this last mentioned pass, in either event, the die is operated so as to contract in direct ratio with the taper of the tube so that no drawing takes place, thereby ironing out the beads of the last pass and producing a tube which is tapered in form and has a smooth exterior surface without distortions or flaws of any character in its wall.

It was pointed out above as one object of this invention to provide a method and apparatus for producing a stepped tapered tube. This object is accomplished in a general way by drawing the tube through a contracting die opening and at a predetermined point expanding or contracting the die opening. The expansion of the die opening may be obtained by momentarily reversing the direction of rotation in a die unit of the general character referred to above, or it may be obtained by forming the die elements with an expanded portion in the grooves, such portion either terminating the pressure engagement of the dies with the tube or being formed so as to continue the pressure engagement with the same or different taper.

In connection with the actual drawing of a tapered tube, my invention contemplates the ut lization of a plurality of separate passes or drawing operations in the production of a finished tube. This procedure does not subject the metal of the tube to such an excessive strain as would be occasioned if the taper were made in one pass, and it is particularly valuable in working tubes of relatively large cross section and wall thickness. This procedure may also be used where an alloy steel, having a relative high carbon content, is used. In working such steel, care must be taken not to exert too great a pressure at any time, and the steel must not be overworked.

One procedure followed in this connection, is to start operations by drawing a short section of the tube through a contracting die opening which is contracted in timed relation with the movement of the tube and increasing the length of the section drawn through the die opening, or, more specifically, starting the drawing operation at a point farther back on the tube for each successive pass.

Another procedure followed is to draw the full length of the tube through a contractable die opening which, on the first pass, is contracted very slowly in timed relation with the movement of the tube therethrough and thenincreasing the rate in which the die opening is contracted for each successive pass of the tube.-

The two general procedures outlined above may be combined to produce an improved product in a more eiiicient manner than the use of either step individually by first tapering one end of the tube with the first method and then bringing the entire tube down to the desired taper with the second method.

More particularly describing the invention as herein illustrated, reference numeral ll indicates one form of tube-drawing machine which is shown as comprising a die head I2 mounted on a suitable support I3 and associated with a reciprocating mechanism for drawing work through the die opening, such mechanism in this form of my invention comprising a pair of cylinders H and H which are closed at both ends and contain pistons l5 and I5. The pistons l5 and I5 are mounted on piston rods i6 and I6 which extend through packing glands I1 and I1 and which have their outer extending ends attached to a cross member IS.

A pull bar or a come-along bar 20 is attached to the cross member as indicated at 21, such bar being supported at its free end by a beam mem ber 22 which has

rollers

23 and 23 on its ends, such rollers traveling on the tops of the respective cylinders 14 and H. The front end of the come-along bar 20 is provided with a suitable grip 20' which engages the work such as the tube 24.

In the operation of the device, the tube 24 may or may not be provided with a mandrel. As shown in Figs. 1 and 2, the tube contains a man-. drel, one end of which extends from the tube as indicated at 25.

For the purpose of reciprocating the pistons and the come-along bar, I deliver a suitable pressure fluid alternately into opposite ends of the pistons through a conduit system, generally indicated by reference numeral 26. This conduit system comprises an inlet connection 21 which is connected with a suitable source of pressure fluid by a T 28 from which conduits 29 and 30 extend through suitable connections to opposite ends of the respective cylinders. The

conduits

29 and 30 are provided with three-way valves 3| and 32 respectively, the valve 3| having an exhaust connection 3! and the valve 32 having an exhaust connection 32.

aoaasea The valves 3| and 32 are actuated in timed re lationwith each other by means of levers 33 and 33' which are connected together by an extended link'34. The link 34 has

arms

35 and 36 adjustably mounted upon its opposite ends, such arms The adjustable feature in the

bars

35 and 36 per- Reference numeral 33 indicates a compression spring mits varying the length of the stroke.

mechanism which holds the valve units in their proper position and carries the valve past dead center.

The construction and operation of the die unit can be best understood by referring to Fig. 3 in connection with Figs. 1 and 2. In Fig. 3, it will be observed that the die head l2 comprises a block 4| which in this form has a cross-shaped opening 42.

Reference numerals

43, 44, 45, and indicate rotatable die elements mounted on shafts or

pinions

43', 44, 45 and 46' in the sections of the cross-shaped opening 42. These die elements have beveled faces on their peripheries and are positioned and formed so that they constantly have lines of tangency indicated generally by reference numeral 41. Between the beveled edges, the die elements are provided with tapered groovesor channels indicated at 48 so that a die opening 49 is formed between the various die elements at their region of tangency, the shape of such opening depending, of course, upon the shape of the grooves. In the form shown, the grooves form a segment of a circle so that the general configuration of the die opening is circular in form.

In the event a tapered tube of circular section is to be obtained, the grooves are formed so that the length of their chords are always equal at their region of tangency, and the die elements are geared together so as to have uniform or synchronous rotation as indicated at 53 and 50'. In addition to the gears 50 and 50', which connect the die elements in sets of two, this particular arrangement necessitates that

die elements

43 and 45, for example, also be geared together, and this is eifected by extending the shafts 43' and 45 and providing their lower extending ends with meshed pinions 5| and 5|.

It will be seen from the construction so far described that the die elements are arranged and constructed so as to rotate in synchronism, and, that when the die elements are rotated in the general direction of the arrow A in Fig. 3, the die opening between the region of tangency of these elements is contracted. It was pointed out above as one feature of the invention, that the die opening must be contracted in accurately timed relation with longitudinal movement of the shaft therethrough, and for the purpose of carry ing out this operation it is advisable that the die unit be operated by the same mechanism which draws the shaft through the die opening. The mechanism for operating the dies must be positive in operation and can have no slack elements such as rope or cable drives. Instead of using the piston mechanism for moving the work 1 and rotating the dies, other accurately timed mechanism may be employed. For example, I may use electric motors and suitable driving means assoc iated'therewith. In the form of my invention shown in Figs. 1 ,to 3' inclusive, this mechanism is,shown as comprising a'pinion-52 mounted on the upper end of the shaft 45', such pinion being in mesh with an idle .gear 53 which engages a gear 54. The gear 541s engaged by a rack 55 which is attached to the beam member 22 as indicated at 58. It will be seen, therefore, that during the movement of the come-along in either direction the dies are rotated and the die opening is opened and closed, depending upon the direction of movement.

It 'was pointed out hereinabove that one feature attending the operation of a unit of this character in which the die opening was formed by a plurality of die elements having grooves in their periphery and arranged so as to have lines of tangency in the plane of the die opening was that the operation of the die is attended by a distortion of the tube resulting from the flow of metal into the angular opening extending from the lines of tangency, which will result in the scratching and distortion of the tube. This feature can perhaps be best illustrated by reference to the view shown in Fig. 5 which shows the

die elements

44, 45, and 45 with the work 24 indicated in broken lines as having been drawn almost completely through the die opening. The work is traveling in the direction of the arrow B and the die elements are rotating in the direction v of the arrow C. From this view, it will be seen that as the tube is compressed by passing through the contracting restriction or die opening, it forms a drawn and bent region in the wall which rides against the inclined surfaces of the die elements leading to the die opening. Inasmuch as the die elements are tangent along one line only, it will be seen that there are in this form of the invention four open corners indicated generally at X into which the metal of the tube as it is being drawn will flow to form ridges or beads thereon. If the grooves in the peripheries of the die elements are formed so that their edges are tangent with or fit tightly against each other to provide a complete circle, for example, these beads, formed in the manner pointed out above,

will either be out or sheared as they are drawn through this circular opening by'the engaging corners of the die elements, or, they will be compressed inwardly to distort the wall of the tube.

In order to avoid this action, I form the grooves of the die elements so as to provide relieved or recessed segmental areas within the die opening at the lines of tangency of the die elements. This arrangement is best illustrated in Fig. 4 where the die elements are shown as having recesses and 60' at edges of the grooves. These recesses are positioned so as to form relieved segmental areas 6| within the die opening into which the metal of the tube will flow in ridges or beads, indicated at 62. After the tube has passed through a die of this character, it is rotated through, say, 45 and again passed through the same die or a similar die so that the ridges are ironed out and the tube may be drawn into a substantially circular cross section. In actual practice, the tube may be subjected to a plurality of drawing steps before the final taper is obtained. In which case. one set of beads is formed on the tube and another set is ironed out for each pass. After the final taper is obtained, the tube is drawn a last time through the same die or another die which is similar in all respects to the one shown in Fig. 4 except that the edges of the grooves are not recessed, and in this last pass the die is operated so that no drawing action takes place. other words, this last die which may have an opening which comprises a perfect circle is used merely to shape. the tube and perfect the wall structure therein.

It was pointed out above as one object of the invention to provide a method for tapering metal tubes in which the tube is gradually worked into the desired configuration so as to avoid subjecting the machine and the tube to undue stresses. One form of practicing this operation is illustrated in Fig. 6 where reference numeral 64 indicates a tapered tube and the lines F-F to GG indicate the various forms taken by the tube in the different drawing passes. In other words, in forming a tube of this character, assuming that the tube is substantially cylindrical in shape to begin with as indicated by the lines F-F, it is drawn through a contracting die opening of the general construction described above and the mechanism for rotating the die in timed relation with the movement of the tube is set or adjusted so that the die is rotated very slowly compared with the movement of the tube. This first pass then draws the tube down to a shape indicated by the lines FF and the tube is repeatedly passed throughout its entire length through the same die or through a series of different dies in which the die operating mechanism is set or adjusted for each pass so as to slightly increase the rate of rotation of the die and consequently the rate of contraction of the die opening until the final taper is obtained.

Fig. 6 indicates a tube which has been provided with what I may term a reverse step 65. In other words, it shows a tube having two tapered sections which are connected by a reverse step. The general procedure in obtaining this construction is to draw the tube through a contracting die opening to a predetermined point at which the reverse step is to be formed and then relieve the tube from pressure engagement with the die opening either by employing die elements which are cut away entirely from that point on; by providing die openings which are cut away at the mentioned point and then continue with the desired taper; or by momentarily reversing the rotation of the die to expand the die opening and then continuing the rotation so as to form the next tapered section. For example, the tube 64 with the reverse step 65 may be formed by first drawing the tube, in the manner first referred to above, to the desired taper. The tube is then drawn through. a die opening in which the rate of contraction, relative to the speed of travel of the tube through the die opening, is substantially greater than that of the die opening inwhich the original taper was formed. At a predetermined point, this die is cut away or relieved so as to form the step 65, the remaining section of the tube having the taper of the original tube. Such a die is indicated by reference numeral 66 in Fig. 9.

Another manner of obtaining a reverse step in a tube such as is shown in 64 is to employ a mechanism of the type shown in Fig. 7 which momentarily reverses the rotation of the die elements and then continues the rotation to contract the die opening. In Fig. 7, reference numeral 55' indicates a rack having the function of the rack 55, such rack having teeth 55a which engage a gear 54, such gear being engaged with an idle gear 53' which in turn drives the die-rotating pinion 52. At a predetermined point on the rack, indicated by reference numeral 55b, the

teeth are cut away or removed, and the opposite side of the rack is provided with a. series of smaller teeth 86 which engage a pinion 61. This pinion 61 is keyed to or formed rigidly with anothr pinion 68 which engages an idle gear 69, such idle gear being engaged in turn witha pinion III which is keyed to or formed integrally with the gear From this construction it will be seen that when the rack is moved to the point at which the cutaway portion 55b occurs, the rotation of the dies in their normal direction stops at the same time or immediately thereafter the first tooth on the section 66 engages the pinion 68 which is effective to momentarily reverse the rotation of the die actuating mechanism thereby expanding the die openings to form a reverse step. Immediately after this step is formed, however, the teeth in the set 55a are again engaged with the gear 54' and continue the contracting rotation of the dies.

Another manner of, forming a tapered tube with a pluralityof passes is indicated in Fig. 8 where reference numeral indicates a tapered tube and the lines HH to I--I indicate the form of the tube after the successive passes. In following this process, a portion of the tube only is inserted into the die opening for the first pass, and this portion of the tube is drawn through the opening which is at the same time contracted to form a tapered end indicated at H1. The starting point of this pass is indicated by reference numeral IP and the tube is passed repeatedly through the die, increasing the length of the tube which passes therethrough or, in other words, decreasing the distance from the large end of the tube to the point at which the drawing operation is started for each pass. The lengths of the successive passes' are indicated by

reference numerals

2P, 3P, 4P, 5P, 6P, IP, and 8P, and may be continued for any desired length of tube.

As pointed out hereinabove, I consider it preferable in the production of perfect results with maximum efficiency to combine the process illustrated in Fig. 8 with that illustrated in Fig. 6. In effecting this combination, the tube is first subjected to the method of Fig. 8 to taper the end thereof back to say the point 4P. Then the tube is drawn in accordance with the method of Fig. 6 to obtain a finished article. This reduces the number and length of the long passes and consequently reduces the time and labor consumed in the production of a finished tube.

In Fig. 10, I show a stepped tapered tube having a series of steps of different types and different wall thicknesses, and having one end portion tapered in a direction which is opposite to the remainder of the tube. Such a tube may be conveniently formed by the process contemplated by this invention, and the procedure followed is preferably to first form the tapered section 12 in any of the manners pointed out above, and then turn the tube around and draw the remainder of the tube through a special die to form the stepped configuration. The various steps are formed by providing stepped tapered sections on the die surface, the general configuration of the die for producing one type of tube being illustrated in Fig. 14.

It will be observed that the section 12 of the tube H decreases in wall thickness as the diameter of the tube increases. It will be also observed that the section 13 is of uniform wall thickness; that the section ll increases in wall thickness as the diameter of the tube decreases; that the section I5 is of uniform wall thickness; and the section 16 decreases in wall thickness as Y 2,029, the. diameter'of the tube decreases. I obtain these variations iri wall thickness by controlling or varying the movement or changing the radius of the die surfaces as the tube passes therethrough, thereby changing the drawing effect.

In Figs. 11, 12, and 13, I show variousforms of tapered tubes which are preferably obtained by one drawing procedure in the opposite direction, Different dies are employed for both drawing procedures, and the desired'configuration is formed preferably in the die. j

The tube shown in Fig. 11 has a tapered section 18 which is followed by' a cylindrical section 19, and another tapered section 80, after which the configuration continues in"a reverse tapered section 8| having a reverse step 82 therein.

The tube shown in Fig. 12 starts out with a substantially cylindrical section 83 which is followed by a stepped tapered section 84 and then a stepped tapered section in the reverse direction indicated at 85.

The tube shown in Fig. 13 has a. tapered section 86 followed by a necked section 81 which terminates in a reverse tapered section 88 having a reverse step 89. 1

These various types of tubes are merely examples of what may be obtained with the apparatus contemplated by this invention, and the die shown in Fig. 14 is merely an example of one form of die which may be employed in producing one of these types of tubes.

Although I have described the dies as being operated in a direction opposite to the movement of the work therethrough to obtain a full drawing action, it should be pointed out that the dies may be rotated with the work to obtain a combined drawing and rolling action. Under such circumstances, the circumference of the dies be ing less than the length of the work, it is important that the dies be driven in timed relation with the work at a speed which is slower than that of the work, the relative speeds of the work and the die being proportioned to the length of the work and the circumference of the die respectively,

It is to be understood that, while I have herein described and illustrated certain preferred methods of procedure contemplated by this invention and certain preferred mechanisms for effecting such procedures, the invention is not limited to the precise construction described above, but includes within its scope whatever changes fairly come within the spirit of the appended claims.

I claim as my invention:

1. The method of tapering a metal tube which includes the steps of first tapering one end portion by repeatedly passing increasing lengths of said end through a contractable die opening and contracting said die opening in timed relation with the movement of said tube for each successive pass; and then repeatedly passing the entire length of-said tube. through a contracting die opening, contracting said die opening in timed relation with the movement of said tube during each pass and increasing the rate of contraction of said last mentioned die opening relative to the speed of travel of said tube for each successive pass.

2. The method of drawing a tapered metal tube having a reverse step therein which includes: drawing a tube which is unsupported internally through a contractable die opening and in pressure drawing engagement therewith; contracting said die opening in timed relation with the speed of travel of said tube during the passage of said tube therethrough;. and relieving said tube from I pressure drawing engagement withthe surface of said die opening at a predetermined point in its travel. i 3. The method of drawing a tapered metal tube having a reverse step therein which includes: drawing saidtube through a contractable die opening; contracting said die opening in timed relatLon .with the speed of travel of said tube during the passage of said tube therethrough so as to form a tapered tube; then passing said tube again through a contractable die opening; contracting said die opening during the second pass in timed relation. with the speed of travel of the tube but at a rate greater than the rate at which the die opening was contracted during the first pass; and fully relieving said tuberfrom pressure engagement with said die opening at a predetermined point and for the remainder of its travel thereby forming two tapered sections in said tube, said sections being connected by a reverse step.

4. The method of drawing a tapered metal tube having a reverse step therein which includes: drawing said tube through a contractable die opening; contracting said die opening in timed relation with the speed of travel of said tube during the passage of said tube therethrough; opening said die opening a predetermined amount when said tube has reached a" predetermined point therein; and then continuings the contraction of said die opening in timed relation with the speed of travel of said tube.

5. A machine for drawing tapered tubes embodying: a die formed of four rotatable die elements arranged in tangent relation with each other to form a cross and geared together for simultaneous unidirectional rotation, said die elements having tapered grooves in their peripheries the longitudinal movement of work through said die opening said relieved portions being joined to said grooves through rounded corners and the v depth of said relieved portions being less than their width.

6. A machine for drawing tapered tubes embodying: a die formed of four rotatable die elements arranged in tangent relation with each other to form a cross and geared together for simultaneous unidirectional rotation, said die elements having tapered grooves in their peripheries which cooperate to form a die opening at their region of tangency and the edges of said grooves being recessed and the corners between the recesses and the grooves being rounded to relieve said die opening at the points of tangency of said die elements the depth of said relieved portions being less than their width; power means for drawing work through said die openings; and means actuated by said power means for rotating said die elements in timed relation with the longitudinal movement of work through said die opening and in a direction opposite to the direction of movement of said work.

7. A machine for drawing tapered tubes embodying: a die formed of four rotatable die elements arranged in tangent relation with each other to form a cross and geared together for region of tangency and the edges of said grooves being recessed and the corners" between the recessesand the, grooves being rounded to relieve said die openin'g at the points of tangency of said die elementsthe depth of .said relieved portions beingless than their width; power means for drawing work through ,said die opening; gear means for driving said dies; and a rack operated by said power means for driving said gears in timed relation withthe movement of said tube.

8. A machine for drawing tapered tubes embodying: a die formed of four rotatable die elements arranged in tangent relation with each other to form a cross and geared together for simultaneous unidirectional rotation, said die elements having tapered grooves in their peripheries which cooperate to form a die opening at their region of tangency and the edges of said grooves being recessed to relieve said die opening at the points of tangency of said die elements; power means for drawing work through said die opening; gear means for driving said dies; and a rack operated by said power means for driving said gears in timed relation with the movement of said tube, said gear means including an idle gear for operating said dies in a direction opposite to the direction of movement of said rack and said work.

9. A machine for drawing tapered tubes embodying: a die formed of a plurality of rotatable die elements arranged in tangent relation with each other to form a cross and geared together for simultaneous unidirectional rotation, said die elements having tapered grooves in their peripheries which cooperate to form a die opening at their region of tangency and the edges of said grooves being recessed to relieve said die opening at the points of tangency of said die elements; power means for drawing work through said die opening; gear means for driving said dies; a rack operated by said power means for driving said gears in one direction and in timed relation with the movement of said tube; and additional gear means for momentarily reversing the rotation of said dies at a predetermined point.

10. A machine for drawing tapered tubes embodying: a die formed of four rotatable die elements arranged in tangent relation with each other to form a cross and geared together for simultaneous unidirectional rotation, said die elements having tapered grooves in their peripheries which cooperate to form a die opening at their region of tangency and the edges of said grooves being recessed to relieve said die opening at the points of tangency of said die elements; power means for drawing work through said die opening; means actuated by said power means for rotating said die elements in timed relation with the longitudinal movement of work through said die opening and in a direction opposite to the direction of movement of said work; and additional means operated by said power means for momentarily reversing the rotation of said dies at a predetermined point.

11. For use in a machine of the class described a die mechanism embodying: a plurality of rotatable die elements arranged in tangent relation with each other and geared together for synchronous rotation, said die elements being provided with correspondingly tapered grooves on their peripheries which cooperate at their region of tangency to form a completely enclosed die passage, and said die elements being recessed at the edges of said grooves and said recesses being con- I which cooperate to form a die opening at their ,nected to said grooves by rounded corners so as 13. The method of, drawing a metal tube having a step therein which includes drawing said tube through a contractible die opening; contracting said die opening in timed relation with the speed 01 travel of said tube during the passage of said tube therethrough so as to form a tapered tube; then drawing one end portion of 4 said tapered tube into a second die opening in pressure drawing engagement therewith over a predetermined distance; and during said second drawing operation maintaining a spaced relation between the drawing surfaces and the axis of the tube diiferent from that which was maintained over the same section of the tube in the first drawing operation, whereby a step is formed in said tube at the end of the second drawing operation.

14. The method of drawing a metal tube having a reverse step therein which includes: first drawing said tube through a contractible die opening; contracting said die opening in timed relation with the speed of travel of said tube during the passage of said tube therethrough so as to form a tapered tube; and then drawing the large end of said tube into a second die opening which has pressure engagement therewith for a predetermined distance only, said second die opening, during such pressure engagement being smaller than the engaged surface of said tube whereby a reverse step is formed at the end or said second drawing operation.

15. The method of drawing a metal tube having a reverse step therein which includes: drawing said tube through an expansible and contractible die opening and operating said opening so as to reduce the diameter of said tube; expanding said die opening a predetermined amount when said tube has reached a predetermined point therein; and then contracting said die opening in timed relation with the speed 01 travel of said tube.

16. A machine for drawing tapered tubes embodying: a die formed of a plurality of rotatable die elements arranged in tangent relation with each other, said die elements having tapered grooves in their peripheries which co-operate to form a die opening at their region of tangency; power means for drawing work through said die opening; means actuated by said power means for rotating said die elements in one direction so as to contract said die opening in timed relation with the longitudinal movement of work therethrough; and additional means operated by said power means for momentarily reversing the rotation of said dies at a predetermined point.

17. A machine for drawing tapered tubes embodying: a die formed of a plurality of rotatable die elements arranged in tangent relation with each other and provided with tapered grooves in their peripheries so as to form a die opening at their region of tangency; power means for drawing work through said die opening; gear means Ill) for driving said dies; a rack operated by said power means and having a toothed section and a cut-away section on one side for normally driving said gears in timed relation with the "movement of said tube, an idle gear associated with said gear means for operating said die in a direction opposite to the direction of movement of said rack and said work; and a toothed section on the other side of said rack opposite saidcut-away section for engaging said idle gear.

18. A machine for drawing tapered tubes embodying: a die formed of a plurality of rotatable die elements arranged in tangent relation with each other and provided with tapered grooves in their peripheries so as to form a die opening at their region of tangency; power means for drawing work through said die opening; gear means for driving said dies; a rack operated by said power means for driving said gears in one direction and in timed relation with the movement of said tube; and additional gear means for momentarily reversing the rotation of said dies at a predetermined point.

19. The method of drawing a tapered metal tube having a reverse step therein which includes: drawing said tube through a contractible die opening; contracting said die opening in timed relation with the speed of travel of said tube during the passage of said tube therethrough so as to form a tapered tube; then passing said tube again through a contractible die opening; contracting said die opening during the second pass in timed relation with the speed of travel of the tube but at a rate greater than the rate at which the die opening was contracted during the first pass; and completely relieving the tube from pressure engagement with said die opening at a predetermined point in its travel, thereby forming two tapered sections connected by a reverse step.

20. The method of forming a stepped tapered tube which comprises drawing said tube through a contractible die opening; contracting the die 1 opening in timed relation with the speed of travel of said tube therethrough; momentarily increasing the rate or contraction of said die opening to form a step in the wall of said tube; after a predetermined interval opening said die to form another step-in the wall of said tube; then contracting the die again in timed relation with the speed of travel of the tube; and after another predetermined interval opening the die'to form a reverse step.

21. The method of forming a tapered metal tube having a reverse step therein which includes: advancing said tube through a contractible die opening; contracting said die opening in timed relation with the distance of travel of said tube during the passage of said tube therethrough; and opening said die opening a predetermined amount when said tube has reached a predetermined point therein.

22. The method of forming a metal tube having a step therein which includes: advancing said tube through a contractible die opening; contracting said die opening in timed relation with the distance of travel of said tube during the passage of said tube therethrough so as to form a tapered tube; than advancing one end portion of said tapered tube into a second die opening in pressure advancing engagement therewith over a predetermined distance; and during said second advancing operation maintaining a spaced relation between the advancing surfaces and the axis of the tube different from that which was maintained over the same section of the tube in r