US2721651A - Adjustable floating plug for tube drawing - Google Patents

Description

E. ROTH 2,721,651

2 Sheets-Sheet l M m v f Y IN VEN TOR. v

EUGENE ROTH FLOATING PLUG FOR TUBE DRAWIN"`- Oct. 25, 1955 ADJUSTABLE Filed June 26, 1955 A MY. NN WN mN E. ROTH Oct. 25, 1955 ADJUSTABLE FLOATING PLUG FOR TUBE DRAWING Filed June 26, 1953 2 Sheets-Sheet 2 EUGEN: ROTH IN VEN TOR;

United States Patent O ADJUSTABLE FLOATNG PLUG FOR TUBE DRAWING Eugene Roth, New York, N. Y.

Application June 26, 19535 Serial No. 364,465

13 Claims. (Cl. 20S- 7) This invention relates to improvements in means for drawing tubes and more particularly for drawing tubes with dies and fioating plugs.

The basic process in the manufacture of non-ferrous seamless tubing involves simultaneous reductions in the size of both the outside diameter and wall thickness. In this manner, tubes of base or starting sizes can be worked down by one or more draws into finished tubes of pre-determined dimensions. This process involves drawing or pulling the tube by suitable mechanical means through a circular ring or die of steel or carbide thus forming and sizing the outside diameter. This die is securely held in a fixed position in the die head of the machine. At the samc time, a suitable steel or carbide tool inside the tube forms and sizes the inside diameter. It is apparent that proper control of the size of both the outside and inside diameters produces the desired wall thickness. The tool which forms the inside diameter can vary in design.

In some plants a long red or mandrel of uniform diameter is placed in the tube before drawing and travels with the tube through the die during the drawing operation. This is known as drawing with mandrels. After one or more draws, the tube is stripped from the mandrel and a separate operation is completed. This method is useful when heavy reductions of wall thickness are desired or when proper lubrication of the inside of the tube is difficult. However, its use on non-ferrous metals is limited because the stripping operation is an added expense and also distorts the tube. ln addition, only relatively short tubes can be drawn since the mandrels must be longer than the drawn tube.

ln most plants drawing non-ferrous seamless tubing in straight lengths the inside diameter is formed by a cylindrical plug The plug is firmly attached to a rod which extends through the back end of the tube and which in turn is securely attached to the frame of the machine (drawbench) by means of a threaded rod, which also allows changes in the position of the plug relative to the die which forms the outside of the tube. The nose of the plug, over which tht-I drawing actually takes place may be uniform in diameter (a straight plug) or may be tapered, usually about 0.015 in diameter per inch of length. In actual drawing the inside diameter of the tube is formed by a relatively short portion of the nose, of the plug. Wear occurs on this area of the nose, resulting in a smaller inside diameter and heavier wall thickness. By means of the threaded connection between the plug rod and the drawbench frame, the position of the plug can be changed periodically to bring a new portion of the plug nose into use, thus restoring the desired size of the inside diameter. In this manner, wear can be distributed over the entire nose of a non-tapered or straight plug thus greatly increasing its life. When completely worn a straight plug may be machined to a smaller size or may be restored to its original size by chome plating.

With a plug having a tapered nose, distribution of wear 2,721,651 Patented Oct. 25, 1955 ICC is also possible but the chief advantage of the tapered nose is that small variations in the size of the inside diameter can be produced by altering the position of the plug by means of the threaded connection on the plug rod. The relative positions of die and plug control the inside diameter and wall thickness of the tube. The ability to control the wall thickness is a very important advantage not only in meeting dimensional tolerances for wall thickness for finished tubes (that is during the last draw) but also in maintaining specified wall thicknesses during draws previous to the last draw.

In these so-called breakdown draws the greatest possible reduction of the crossl sectional area of the tube in each draw is sought in order to minimize the total number of draws required to produce a finished tube from a given starting size.

Wear occurs in the die which forms the outside diameter, thereby allowing an increase in both the outside diameter and wall thickness. By changing the position of the tapered plug so that a corresponding greater inside diameter is produced, the wall thickness is brought back to its specified value thereby assuring the proper reductions in cross sectional area.

Because the tapered nose allows not only distribution of wear of the plug itself but also compensation for die wear, the use of the tapered plug is very widespread in the non-ferrous tube field. The straight or non-tapered plug finds much less frequent application being used mostly in finish draws, in which compensation for die wear is not a factor. Added life for both types of plugs can be obtained by using tungsten carbide for the nose.

However, both the straight and tapered plugs have two main disadvantages. First, because the plugs are positioned by rods, they obviously cannot be used for drawing of tubes in coil form. This precludes their use in the small tube field in which coils are the usual form. Second, the drawing of relatively long tubes in straight lengths tends to produce surface defects known as chatters. A long rod will stretch more under a given tension than a short rod. Unless the friction between the tube and the plug is quite uniform (which is unusual in actual drawing) the changes in friction cause variations in rod tension which in turn produces varying amounts of stretch in the plug rod. This variation in stretch causes slight changes in the position of the plug (an oscillation) producing a series of visible circumferential rings of variable wall thickness in the tube. This has become a serious problem particularly in the drawing of long copper tubes (up to l2() feet) for radiation heating.

The defects of chatters in drawing bars, steel, aluminum and other metals can also be avoided by the use of floating plugs.

Tube drawing may be done by conventional floating plugs having a straight nose of uniform diameter and a tapered shoulder which makes the plug self-positioning and eliminates the need for a plug rod. The friction between the tube, and nose tends to carry the plug along with the tube but is balanced by the bearing of the shoulder against the inside surface of the tube. Floating plugs are particularly adaptable to the drawing of tubes in coil form and have been used in this field for a number of years. More recent applications have been made on the drawing of tubes in long straight lengths, principally to eliminate chatter and to reduce machine set-up time. Floating plugs will eliminate chatter since the self-positioning effect of the plug eliminates tension of the plug rod and consequent chatten When used to draw straight lengths, floating plugs are usually attached to plug rods to facilitate the insertion of the plug in the tube. The rod is loosely attached to the drawbench and has no positioning effect.

The conventional floating plug has one major disadvantage. Since the plug is of one-piece construction and the shoulder of the plug determines its position, only a limited area of the nose can be utilized. Therefore, distribution of wear overY thenose and the use of a tapered nose to produce dimensional changes and to compensate for die wear are impossible. This results in short service life for both plugs and dies. Present attempts to counteract this disadvantage consist of the use of solid tungsten carbide plugs and the grinding back of the shoulder in successive steps to produce additional nose area. This remedy is costly both in time and material.

Another disadvantage is that dies and plugs must be matched for successful drawing. The shape of the mouth of the die must be such that the tube in following the contour of the die forms a suitable inside surface against which the shoulder of the plug bears. Unless the die contour and shoulder contour follow a definite relationship, breaking of the tube occurs.

In spite of these serious disadvantages tube manufacturers are forced to use conventional oating plugs because they are the only type that can be used for coil drawing and because, at present, they are the only consistent remedy for chatter in long straight lengths.

It is accordingly a principal object of the present invention to provide an adjustable floating plug which eliminates the disadvantages connected with conventional floating plugs and which also incorporates most of the advantages of both conventional floating plugs and cornmon drawing plugs.

It is another object of the present invention to provide an adjustable lloating plug wherein the shoulder portion can be easily and accurately moved relative to the nose of the plug and can be positively locked in the desired position.

It is another object of the present invention to provide an adjustable floating plug of the type having a nose of uniform diameter wherein wear can be distributed over the entire nose.

It is another object of the present invention to provide an adjustable floating plug o-f the type having a tapered nose wherein distribution of wear, adjustment for dimensional tolerances and compensation for die Wear can be achieved.

lt is still another object of the present invention to provide an adjustable lloating plug wherein a proper combination of thread pitch and nose taper allows rapid and accurate adjustment of the adjustable floating plug.

lt is still another object of the present invention to provide an adjustable iioating plug wherein a nose of wear resisting tungsten carbide can be inserted to increase plug life.

It is still another object of the present invention to provide an adjustable floating plug having a shoulder which makes the plug self-positioning, making it adaptable for drawing of tubes in coil form.

It is still another object of the present invention to provide an adjustable floating plug wherein the selfpositioning effect of the shoulder eliminates chatter in the drawing of tubes in straight lengths and wherein the self-positioning effect reduces materially machine set-up time.

It is still another object of the present invention to provide an adjustable floating plug which can be easily attached to drawbench plug rods to facilitate the insertion of the plugs into the tube before drawing, although the rod is not needed for positioning the plug during drawing.

It is still another object of the present invention to provide an adjustable floating plug including an interchangeable assembly of shoulder sleeves and plug bodies which allows maximum exibility in matching dies and plugs, reduces machine time lost in reconditioning of plugs and reduces overall tool maintenance costs.

For other objects and a better understand of the invention, reference may be had to the following detailed description taken in connection with the accompanying drawin gs, in which:

Figure l is a central longitudinal sectional view portion of a drawbench construction, its die and tubing being drawn, and shows the adjustable floating plug construction in operative use therein;

Fig. 2 is a similar view of a modified form of drawing plug showing a carbide nose.

Fig. 3 is an exploded perspective view of the parts comprising the adjustable floating plug;

Fig. 4 is a transverse sectional view taken along the line 4-4 of Fig. 3; and

Fig. 5 is a view similar to Fig. 1 and showing a still further modified form of drawing plug.

Referring now more in detail to the drawing, in which similar reference numerals identify corresponding parts throughout the several views, there is shown an adjustable floating plug, referred to collectively as 10, and including a drawing plug 11 of hardened tool steel, substantially as illustrated.

In machinery that is used to draw tubing, it is generally the practice to pull the tubing 12 through an opening between the outside of the drawing plug 11 and the inside of the die 13. Since the tube drawing machinery is well known and understood by those skilled in the art, it is not believed that an elaborate discussion of the tube drawing machinery is necessary. Therefore, the drawing and description will be confined to the adjustable floating plug itself, and which comprises the present invention.

The drawing plug 11 consists of a tapered nose 14 integral with a smooth cylindrical portion 15. The intermediate portion 15 on its face remote from the tapered nose 14 is integrally formed with a smooth cylindrical portion 16 of lesser diameter and which continues in an elongated, externally threaded shank 17, substantially as illustrated.

Countersunk openings 18 and 19 are provided in opposite ends of the drawing plug 11, for a purpose which will be clear to those skilled in the art.

An adjustable shoulder sleeve, referred to collectively as Ztl, is provided at one end with a smooth internal bore 21, adapted to slidably receive the intermediate portion 15 of drawing plug 11, as shown in Fig. l. The sleeve 20 is also provided at its other end with an internally threaded bore 22, communicating with and of lesser diameter than the bore 21 and adapted to receive the externally threaded shank 17, also as shown in Fig. 1. The sleeve 20 is also provided on opposite sides with wrench flats 23 to facilitate adjusting of the sleeve 20 relative to the plug 11.

The sleeve 20 is formed of the same hardened tool steel as plug 11, and is bevelled as at 24 at the end thereof receiving the tapered nose 14. The trailing edge of sleeve 20 is circumferentially chamfered, as at 25.

A lock nut, referred to collectively as 25' is provided with an internally threaded bore 26 adapted to receive the externally threaded shank 17, as shown in Fig. 1, one face of lock nut 25 abutting the adjacent face of sleeve 20 and locking the position of the latter relative to the tapered nose 14. The lock nut 25 is provided with wrench flats 27 to facilitate locking. The opposite ends of lock nut 25 are circumferentially chamfered, as at 28 and 29.

The tapered portion 24 of above 20 is ground while the intermediate portion 15 and tapered nose 14 of plug 11 are ground and chrome plated.

Thus, the above three-piece construction allows the shoulder 24 to be moved relative to the tapered nose 14 and to be locked securely in a desired position. The threaded connection between the plug body 11 and shoulder sleeve 20, as illustrated in the drawing, is the most accurate and positive means of relative motion but other means of locking and adjusting may be used, as will be obvious to those skilled in the art.

Because the shoulder 24 is movable, the area of contact between the inside of the tube 12 and the plug nose 14 can be shifted. With the tapered nose 14, the shoulder position can be changed to produce small changes in the inside diameter in order to meet dimensional tolerances for inside diameter or wall thickness; to compensate for die 13 wear during breakdown draws, or to distribute wear on the nose 14. These will be remembered as the chief advantages of common drawing plugs.

Because of the shoulder 24, the adjustable floating plug retains the advantage of the conventional floating plug. Being self-positioning, it reduces machine set-up time and eliminates chatter in the drawing of long straight lengths and light wall tubing of any length. In addition, it can be used in the drawing of tubes in coil form.

As with conventional floating plugs the shoulder angle of the adjustable floating plug 10 and the mouth angle of die 13 must be matched for successful drawing. However, with the adjustable floating plug several shoulder sleeves of different shoulder angles can be used with one plug body 11 allowing the use of different dies 13 with the substitution of shoulder sleeves 20 until the most satisfactory shoulder angle is found. Several plug bodies 11 may also be used with only one shoulder sleeve 20 to reduce the original cost and to eliminate loss of production time when one plug body requires polishing, plating or other reconditioning. This flexibility is not found in conventional floating plugs.

The design of the adjustable floating plug 10 also permits easy and accurate adjustment. For example, the combination of a 16 pitch thread on the connection between the shoulder sleeve 20 and plug body 11 with a nose 14 taper of 0.016 on diameter per inch of length will result in a change of 0.001" in the inside diameter (and 0.005 in the wall thickness) of the drawn tube 12 when the shoulder sleeve 20 is rotated a full turn (360 degrees) around the plug body 11. This feature facilitates final adjustment of the shoulder sleeve position after the measurement of several tubes drawn with the preliminary adjustment. Other combinations of taper and standard threads are, of course, possible.

Referring now particularly to Fig. 2, there is shown a modified form of drawing plug, referred to collectively as 11a, adapted to be used in connection with the shoulder sleeve 20 described above. In this form a tungsten carbide nose piece 14a is inserted for incorporation in the drawing .plug 11a to increase wear resistance. The tapered nose 14a is provided at its inner end with a conical formation 30 which is received with a correspondingly shaped conical opening 31 provided in intermediate portion 15a, substantially as illustrated and secured therewithin by suitable bonding material. This type of insert has been used frequently in common drawing plugs and has proven an advantage in sizes up to 11/2 in diameter. In larger sizes, the economic advantage has not been determined.

In other respects the form of the invention shown in Fig. 2 is the same as that shown in Figs. l through 4, and like reference numerals identify like parts throughout the several views.

Referring now to Fig. 5, there is shown a still further modified form of drawing plug, referred to collectively as 11b, and differing from the plug 11 in the provision of a straight nose 14b coterminous with the intermediate portion 15. Because the shoulder sleeve and shoulder 24 is movable, the area of contact between the inside of the tube 12 and the nose 1411 can be shifted, distributing in the wear over the entire nose 14b by successive changes of shoulder position.

In other respects the form of the invention shown in Fig. 5 is the same as that shown in Figs. l through 4, and like reference numerals identify like parts throughout the several views.

Shoulder sleeve 20 as seen in Figure 3 may have an outer portion of carbide at a conventional brazed joint as indicated by numeral 20a.

Actual use of adjustable floating plug 10 has been made in the finish drawing of copper water tube in forty foot lengths. This draw reduced tubing of 'MU' outside diameter with 0.0045 wall thickness to a finished size of outside diameter 0.040" wall thickness (designated by the plumbing trade as 1/2 Type L copper water tube) a reduction of cross sectional area of approximately 32%. This size was chosen because it is typical of the sizes most frequently required in installations for radiant heating. The demand for long lengths for this application has led to the use of long drawbenches and the use of floating plugs to eliminate chatten The same demand for long lengths has also led to the experimental drawing of copper tubes in coil form on drawblocks similar to those used in heavy wire drawing. It has already been pointed out that only floating plugs can be used in this form of drawing.

The extension of the use of adjustable floating plugs into other size ranges is certain. In the smaller ranges the drawing of tubes in coil form is prevalent particularly in the so-called small tube mills. Conventional floating plugs are already used in these plants. In addition, the problem of chatter in the drawing of straight lengths becomes progressively more serious as the tube size decreases regardless of the length involved. In this field conventional floating plugs have had limited application as a solution because of their short life. However, the adjustable floating plug 10, which eliminates the economic disadvantages of the conventional floating plug, should receive a more favorable reception. In the direction of larger sizes, the use of adjustable floating plugs will depend upon their ability to reduce machine set-up time. The present trend for breakdown draws is to use multiple drawbenches, usually employing three dies and six plug rods, requiring six preliminary adjustments and six final adjustments of plug position, when common drawing plugs are used. The use of adjustable floating plug 10 can eliminate the preliminary adjustment time but this advantage must be balanced against the higher first cost of adjustable floating plugs as compared to common plugs.

While various changes may be made in the detail construction, it shall be understood that such changes shall be within the spirit and scope of the present invention, as defined by the appended claims.

I claim:

l. An adjustable floating plug for tube drawing cornprising a plug body, including a nose adapted to size the inside diameter of the tube, a shoulder sleeve adjustable along said body plug and including a tapered nose portion, and means for locking the position of said shoulder sleeve relative to said plug body.

2. An adjustable floating plug for tube drawing comprising a plug body, said plug body including a nose portion adapted to size the inside diameter of the tube and an externally threaded shank, an adjustable shoulder sleeve having a smooth internal bore at one end adapted to receive said nose portion of said body plug and an internally threaded bore at the other end communicating with and of substantially less diameter than said smooth bore, said internally threaded bore being adapted to receive said externally threaded shank, and an internally threaded lock nut adjacent the end of said sleeve and adapted to be screwed on to said threaded shank.

3. An adjustable floating plug for tube drawing comprising a plug body, said plug body consisting of a smooth cylindrical intermediate portion, a substantially cylindrical nose portion adjacent said intermediate portion and an elongated, externally threaded shank adjacent the other end of said intermediate portion, said nose portion being adapted to size the inside diameter of the tube being drawn, an adjustable shoulder sleeve having a smooth cylindrical bore adapted to receive said intermediate portion at one end, said sleeve at the other end having an internally threaded bore of lesser diameter than and communicating with said smooth bore and adapted to receive said threaded shank, said sleeve at the end adjacent said nose portion being inwardly tapered and means for locking the position of said sleeve relative to said nose portion.

4. An adjustable floating plug according to claim 3, said means comprising a lock nut screwed on to said threaded portion adjacent the end of said sleeve remote from said nose portion.

5. An adjustable oating plug for tube drawing cornprising a plug body, said plug body consisting of smooth, substantially cylindrical intermediate portion, a substantially cylindrical, tapered nose integral with and adjacent one end of said intermediate portion, and an elongated externally threaded shank integral with and adjacent the other end of said intermediate portion, an adjustable shoulder sleeve having at one end the smooth internal bore adapted to slidably receive said intermediate portion and at the other end an internally threaded bore communicating with and of less diameter than said smooth bore and adapted to receive said threaded shank, and means for locking said sleeve relative to said tapered nose.

6. An adjustable floating plug, according to claim 5, said means comprising an internally threaded lock nut adapted to be screwed on to said externally threaded shank adjacent the end of said sleeve remote from said nose portion.

7. An adjustable floating plug for tube drawing comprising a plug body, said plug body consisting of smooth, substantially cylindrical intermediate portion, a tungsten carbide nose piece connected to one end of said intermediate portion and an elongated externally threaded shank integral with the other end of said intermediate portion, an adjustable shoulder sleeve having a smooth internal bore at one end adapted to slidably receive said intermediate portion and having an internally threaded bore at the other end communicating with and of less diameter than said smooth bore, and adapted to receive said threaded shank, and means for locking the position of said sleeve relative to said nose piece.

8. An adjustable floating plug according to claim 7, said means comprising a lock nut having an internally threaded bore adapted to receive said externally threaded shank.

9. An adjustable oating plug for tube drawing comprising a drawing plug of hardened tool steel, said plug consisting of a smooth, substantially cylindrical intermediate portion, a nose portion adjacent one end of said intermediate portion and integral therewith, said nose portion being adapted to size the inside diameter of the tube being drawn, and an elongated externally threaded shank integralvwith the other end of said intermediate portion and of less diameter than said intermediate portion, an adjustable shoulder sleeve of hardened tool steel having at one end a smooth internal bore adapted to slidably receive said intermediate portion and at the other end having internally threaded bore communicating with and of less diameter than said smooth bore and adapted to receive said threaded shank, said sleeve at its end adjacent said nose portion being inwardly bevelled, and means for locking said sleeve relative to said nose portion.

10. An adjustable oating plug according to claim 9, said nose portion being tapered inwardly away from said intermediate portion.

11. An adjustable oating plug according to claim 10, said nose portion being substantially cylindrical and of uniform diameter.

12. An adjustable floating plug according to claim 10, said nose portion being formed of tungsten carbide.

13. An adjustable floating plug for tube drawing according to claim 10, said means for locking said sleeve comprising a hardened tool steel lock nut adapted to be screwed on to said externally threaded shank adjacent the end of said sleeve remote from said nose portion.

References Cited in the le of this patent UNITED STATES PATENTS 1,511,091 ORourke Oct, 7, 1924 2,025,439 Brownstein Dec. 24, 1935 2,173,099 Dennis Sept. 19, 1939 2,285,539 Staples June 9, 1942 2,355,734 Katz Aug. 15, 1944 2,359,339 Wadell Oct. 3, 1944 2,473,383 Messinger June 14, 1949 FOREIGN PATENTS 458,737 Great Britain Dec. 24, 1936

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