US2220048A - Apparatus for drawing wire - Google Patents

Description

Oct. 29; 1940. P, M, MUELLER 2,220,048 I APPARATUS FOR DRAWING WIRE Filed March 2, 1952 2 Sheets-Sheet 1 W% INVEYNTOR Oct. 29, 1940. P. M. MUELLER 2,220,048

7 APPARATUS FOR DRAWING WIRE Filed March 2, 1932 2 Sheets-Sheet 2 F1 Q. :J'

2; i Z3 27 I 1 25 5: if 2; '25 43:?2 I in 2%.? I 722G327 I Z INVENTOR I ATTQRNEY Patented Oct. 29, 1940 PATENT OFFICE APPARATUS FOR DRAWING WIRE Paul M. Mueller, Rome, N. Y., assignor to General Cable Corporation, New York, N. Y., a corporation of New Jersey Application March 2, 1932, Serial No. 596,214

3 Claims.

This invention relates to apparatus for drawing metal, and pertains particularly to wire drawins minimize or to entirely eliminate back pull.-

conditions, instead of being detrimental, back pull used, instead of increasing the horse power required for the draft, the horse power can be decreased sufliciently to effect substantial savings in the wire drawing operation. In order to take advantage of this eflect, however, the back pull must be applied in such manner that its force is applied to some member connected, either mechanically, electrically, or otherwise, with the source of power so that power may be returned to the system without substantial dissipation by frictional or other losses. Preferably the back pull applied should be substantial, and much greater than the ordinary or accidental back pulls which are warned against in the literature because the saving in power increases as the amount of back pull increases. The ideal condition would be that in which the back pull was substantially equal to the tensile strength of the metal, but this is impractical in operation because of lack of any safety factor. In general, therefore, it may be said that best results are obtained when the back pull applied approaches the tensile strength of the metal as nearly as possible, havingregard for a proper factor of safety. A back pullof 30,000 pounds per square inch of exit area of the die has been found to give good results in drawing copper, but this figure may vary widely under varying conditions and with different metals. It has been found that if back pull is applied as described herein, the surface friction of the metal as it passes through the die is reduced substantially, and this of course, provides a logical explanation of the saving in power, for power is consumed I have discovered, however, that under certain in overcoming surface friction and internal friction, and even though the internal friction may be unchanged, any saving in surface friction will result in a saving in the power required for the draft.

' A preferred embodiment of the invention selected for purposes of illustration is shown in the accompanying drawings, in which:

Figure l. is a top plan view in semi-diagrammatic form of an apparatus embodying the invention and adapted for a single draft.

Fi e 2 is a side elevation of the same.

Figure 3 is a similar top plan view of apparatus adapted for multiple draft work.

Figure 4 is a side elevation also in semi-diagrammatic form. In this figure the numerals and arrows above'the figure indicate the tensions and die seat pressures applied at various points in accordance with the illustrative table given here-- inafter.

Figure 5 is an enlarged view of one of the capstan shafts, the clutch mechanism being shown in section.

Figure 6 is a section of one of the dies.

Referring to the drawings, the apparatus illustrated in Figures 1 and 2 is a simple form of apparatus embodying the invention in which the wire being drawn is first wound around capstan I, then passed through die 2, and then wound around capstan 3. The capstans are driven by a motor 4 through capstan shafts 5 and 8 which are connected to the main shaft 1 through properly graduated bevel gears 8 and 9, the capstan 3 being driven at a higher speed that the capstan 2. In the preferred embodiment illustrated cap- '5 stan 3 is connected to its shaft through a compensating clutch which may take the form illustrated in-Figure 5 showing a spring loaded friction clutch in which the sliding sleeve 28 is pressed against the web 29 of the capstan by means of the spring '30. The clutch on shaft 6 is adjusted so as to limit the torque applied to the capstan I to a predetermined amount determined as hereinafter set forth. In makingthis determination the back pull to be applied is first decided. This -back pull is multiplied by the exit area of the die in order to obtain the actual value of the back pull in pounds. For example, if it is decided to inch, and the exit area of the die is .0064! square inch, the back pull or tension on'the wire between the capstan i and die 2 would be 194 pounds. The amount of resistance to passage of the wire through the die or die seat pressure is determined next by actual test, and by adding this amount to the back pull, a value is obtained which represents the amount of forwardtpull which is required. Thus in the aboveexample, the die seat pressure is found to be 92 pounds, which, added to the back pull gives the sum of 2 86 pounds which is the required forward pull. The torque applied to the capstan is therefore limited to this amount, and the clutch is adjusted accordingly.

Following "through the above example and calculating the horsepower required if the capstans i and 3 are geared to run at 1390 feet per minute and 1750 feet per minute respectively, we find:

Ft. lbs. per minute Work applied at capstan 3- 286 1750:500000 Work applied at capstan l 194 1390=269,000

' Difierential work supplied by motor 231,000

191x1750=334,000 ft. lbs. per minute Thus the horsepower required in the second case is more than 40% greater than that required in the first case where back pull is applied.

must be applied by the capstan It. The back pull from the next succeeding die 13 is applying a forward pull of 194' pounds to the capstan. Therefore, it is only necessary to apply a torque through the capstan shaft equivalent to a pull of 144 pounds, and the clutch is adjusted in such manner that this amount shall not be exceeded. Thus, the torque applied to each capstan shaft except the last is less than suflicient to pull the wire through the preceding die, and the back pull of the next succeeding die is relied upon to make up the deficiency. If for any reason the torque applied tends to increase above the predetermined amount, the clutch will slip, of course. It will be understood, of course, that in place of a common drive from a single source of power, each capstan shaft might be driven by a separate constant torque motor.

It will also be understood that in practice, one of the capstans in the series, as for example capstan I1, may be locked to its shaft by setting up on the clutch or in any other convenient manner. This is advisable in order to provide proper wire speed control.

; As an example of i the saving which may be made in multiple draft work by utilizing back pull in the manner described, an actual comparison between the practice described herein and old wire drawing practice will be given.

The example used is a reduction of annealed wire from size .128 to size .064 in one continuous draft in six dies. The following table illustrates the determination of power required in a case where back pull is used in accordance with the The same principles may be applied with compresent method:

Dib Resultant Velocity Exit Back Forward Power in Size area of pull in $2; p ll 355??? 3 foot pounds pounds sure pounds pounds minute per mmute turns are taken around capstans 11, then the wire is passed through a-die L2 and around capstan l8 and so on through the entire series of dies. As illustrated, the capstans are all driven by a motor 23 which is connected to a main shaft 24 having mounted thereon bevel gears 25 of properly graduated sizes which mesh with bevel gears 26 on the capstan shafts 21. Each of the capstans is connected to its drive shaft 21 through a compensating clutch such as that illustrated in Figure 5 and in each case, the clutch is adjusted in such manner that the torque applied to the capstan by its shaft is equal to the required forward pull, less the back.

In the above table, as in the single draft example, the back pull applied is 30,000 pounds per square inch of exit areaof each die. Thus the Back pull in pounds is obtained by multiplying 30,000 pounds by the exit area of each die. The values for Die seat pressure" are determined experimentally, and the values for Forward pull in pounds are obtained by adding the back pull to the die seat pressure. ,The Resultant forward pull in pounds is the difference between the forward pull and the back pull for the next succeeding die. This value, as previously explained, determines the torque which must be applied to each capstan shaft. The power is obtained by multiplying the resultant forward pull by the velocity.

In the above table, and in the machine illustrated in Figures 3 and 4 it will be noted that no back pull is applied at die Hi. It will be understood, of course, that if desired, an additional capstan could be placed ahead of the die E0 in the same manner that the capstan i is placed ahead of the die 2 in Figures 1 and 2, with a further saving in power.' But whereas in the single draft machine this capstan is essential, in the multiple draft machine its use is optional, and in many installations the saving from its use in proportion to the total saving may not be suiflcient to warrant the extra complication. The

above table, however, in comparison with the.

table about to be given, shows the large saving to be had even without the use of the extra cap- M stan.

For purposes of comparison, the next table gives the comparable figures for the same reduction, but without utilizing the back pull effect.

Velocity Exit area Die seat Forward ln'feet Power In Size of die ressm pull in per foot pounds p pounds minute per minute In the above table the die seat pressures are also determined experimentally, but since back pull is eliminated, the forward pull is equal to the die seat pressure in each case. The power required is again calculated by multiplying forward pull by the velocity. As will he observed, the total power required in the second table is 33%% greater than the power required in the first table where back pullis usedin accordance with the principles of the invention.

It will be understood, of course, that the above tables are merely illustrative of the results obtainable under the conditions assumed. With other conditions the results will vary, but a saving in power will result uniformly 'if the back pull applied is utilized in accordance with the principles described herein. Wear on the dies is also materially reduced by this method.

It has been observed. that wire drawn in accordance with the above described invention possesses a somewhat greater tensile strength than wire drawn by ordinary methods.

It will be understood that the invention may be variously modified and embodied within the the wire through the preceding die.

2. A wire drawing machine comprising, in combination, a plurality of dies. a plurality of capstans located between said dies, a common shaft for driving said capstans, and means for limiting the torque applied by said drive shaft to each capstan to anarnount less than suificient to draw the wire through the die immediately preceding the capstan.

3. A wire drawing machine comprising a die, a capstan for pulling wire through the die, a second capstan for exerting a back pull on the wire as it is drawn through the die, common means for driving said capstans, and means for limiting the torque applied to the first mentioned capstan to an amount less than suflicient to draw the wire through the die in the absence of back pull on the wire.

PAUL-M. MUELLER.

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