US3212312A

US3212312A - Apparatus utilizing vibratory energy

Info

Publication number: US3212312A
Application number: US289558A
Authority: US
Inventors: Charles A Boyd; Jr Harold L Mckaig
Original assignee: Aeroprojects Inc
Current assignee: Aeroprojects Inc
Priority date: 1963-06-21
Filing date: 1963-06-21
Publication date: 1965-10-19
Anticipated expiration: 1982-10-19

Description

1965 c. A. BOYD ETAL APPARATUS UTILIZING VIBRATORY ENERGY Filed June 21, 1963 l/Vl/E/VTOPS. CHARLES A. 5070 JAMES BYRON JONES HEREERT KA/PTL U/(E HAROLD L. Mc/fA/G g n Ill/1 NE 51% 4 mm mwvfm $5158 6% 9w un ATTORNEY United States Patent APPARATUS UTILIZING VIBRATORY ENERGY Charles A. Boyd, James Byron Jones, Herbert Kartluke, and Harold L. McKaig, .lr., West Chester, Pa., assignors to Aeroprojects Incorporated, West Qhester, Pa., a corporation of Pennsylvania Filed June 21, 1963, Ser. No. 289,558 18 Claims. (Cl. 72-60) This invention relates to an apparatus utilizing vibratory energy, and more particularly to a method and apparatus for drawing articles including tubes through a die.

Drawing is a well-known manufacturing process for forming materials, and it can be performed wet or dry, single stage or multi-stage, and with or without applying heat to the material before it is drawn through a die. In some materials, hardness may be increased by the drawing operation so that annealing is required before further drawing. In drawing of tubes, a plug (such as a back-supported plug) may be disposed within the tube so that the tube is drawn between the plug and the die. Drawing stresses the material above its elastic limit to permit plastic flow.

It has been proposed heretofore to apply vibratory energy when drawing material, as in United States Patents 2,393,13l, 2,568,303, and 2,638,207 which apparently have not been commercialized.

According to the present invention, a method and an apparatus has been provided wherein the plug is coupled to a source of vibratory energy, preferably by a resonant member, as disclosed in co-pending United States patent application Serial No. 289,694, filed June 21, 1963, entitled Method and Apparatus Employing Vibratory Energy. Also, in accordance with the present invention, the die is coupled to a source of vibratory energy, preferably by a resonant member. The objects of the present invention are accomplished by method and apparatus involving utilizing the die and plug in combination according to a selected one of a plurality of relationships. With the present invention, results are achievable which cannot be obtained by vibratory activation of the die alone or of the plug alone.

With the present invention, there is obtainable greater reduction in cross-sectional area per pass, increased drawing speed, and/or less drawing force than has been possible previously, as well as better surface finish and the ability to draw materials and/or articles heretofore difficult or impossible to draw with known apparatus and methods. Additional advantages of the present invention are that dies and plugs are easy to change, that the electrical equipment can be located remote from the die and the lubricant applicator, and that maintenance and set-up of the equipment is simplified.

It is an object of the present invention to provide a novel apparatus for drawing tubes and other articles having wall structure formed about an axis.

It is another object of the present invention to reduce the tension force necessary to draw materials.

It is another object of the present invention to facilitate the drawing of articles made from metals or other materials which are diflicult or impossible to draw by conventional equipment and methods.

It is another object of the present invention to facilitate drawing articles with a greater reduction in wall thickness than can be accomplished on conventional equipment.

It is a further object of this invention to provide a novel apparatus for producing a tube of superior surface finish.

Other objects will appear hereinafter.

For the purpose of illustrating the invention, there is shown in the drawings forms which are presently pre- 3,212,312 Patented 0st. 19, 1965 ice ferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIGURE 1 is an elevational view of apparatus embodying the present invention, partly in section and partly in diagrammatic form.

FIGURE 1A is an enlarged sectional view of a fragment of the apparatus illustrated in FIGURE 1.

FIGURE 2 is an enlarged view of still another fragment of the apparatus shown in FIGURE 1, with some parts being broken away and some other parts shown in section.

Referring to the drawings in detail, wherein like numerals indicate like elements, there is shown in FIGURE 1 a vibratory tube drawing apparatus designated generally as 11).

The apparatus 10 is in the nature of a draw bench and includes a die 12 having an orifice 14 (see FIGURE 1A). A tapered plug 16 (see FIGURE 1A) extends into or through the orifice 14 and defines with the die 12 a restricted passageway through which the tube material 18 is drawn.

The rear end of the plug 16 is preferably removably connected (as by cooperating threads) to one end of an acoustical transmission or coupler element 20; Where it is not necessary to provide a readily removable connection, the plug 16 and the element 20 may be metallurgically connected as by brazing. As shown in FIGURE 1A, a washer 28 of a soft material such as aluminum may be disposed between the juxtaposed end faces of the plug 16 and element 20. The washer 28 is compressed or deformed when the plug 16 is threaded to the element 20 to assure a good acoustic coupling if a screw connection is employed.

The transmission element 20 is preferably a resonant length of metal, such as steel (Max-El. 3 /2 free machining steel, for example), aluminum-bronze, or Monel. By this is meant that element 20 will preferably have a length equal to a whole number multiple of one-half wavelength, or an even number of one-quarter wavelengths, in the material of which the rod is made at the frequency of operation. The combined length of plug 16 and element 20 preferably is dimensioned so that a loop or antinode area of the vibratory energy is juxtaposed to the die orifice 14.

The end of the acoustical element 2%) remote from the plug 16 is joined, as by a threaded connection and lock nut 51, to one end of another acoustical coupler 22; the other end of coupler 22 is fixedly joined to a transducer 26, preferably by brazing or some other type of metallurgical joint.

Elements

16, 20, 22, and 26 comprise a transducer-coupling system 24, which is dimensioned so as to operate at a given frequency, which is a resonant frequency. The purpose of the threaded connection and lock nut 51 between

members

20 and 22 is to permit minor adjustments in the free length of coupler 20 to insure resonance at the frequency of operation. This is desirable because changes in the plug 16 to accommodate different diameters and wall thicknesses of tubing will affect the resonance of member 20. By shortening or lengthening element 20 via the threaded connection into element 22 and locking it in position with the lock nut 51, the effect of modestly differing masses and lengths of plug element 16 can be accommodated.

Acoustical coupler 22 is essentially a mechanical transformer and is of conventional single or multiple halfwavelength-long construction which is contoured for purposes of increasing amplitude of vibration. It may comprise a single member or, for purposes of manufacturing convenience, it may comprise a cylindrical portion metallurgically bonded or screw-connected in end-to-end contact with a tapered portion, the tapered portion by means of its increasingly smaller cross section affording the increased amplitude. The tapered portion may be shaped so as to have a taper that is an exponential function of its length and satisfies the following equation:

sla

where S is the reduced area at any section of the tapered portion, S is the area of the cylindrical portion, T is a constant describing the taper, and l is the length of the tapered coupler. This equation and the boundary conditions for resonance of a coupler such as coupler 22 are set forth at page 163 of Piezoelectric Crystals and Ultrasonics by Warren P. Mason, published in 1950 by D. Van Nostrand Company.

The transducer 26 may be of the magnetostrictive type and of conventional construction comprising a halfwavelength-long laminated core of nickel, nickel-iron alloy, or other magnetostrictive material, properly dimensioned to insure axial resonance with the frequency of alternating current applied thereto by coil 72 so as to cause it to increase or decrease in length according to its coefiicient of magnetostriction. The detailed construction of a suitable magnetostrictive transducer is well known to those skilled in the art and does not form a part of the present invention and, accordingly, no description of its construction will be made herein. It will be appreciated by those skilled in the art that in place of the magnetostrictive transducer 26 shown in the drawing, other known types of transducers may be substituted; for example, electrostrictive or piezoelectric transducers made of barium titanate, quartz crystals, lead titanate-lead zirconate, etc. may be utilized. Coil 72 is connected to a power supply incorporating an oscillator 80 and amplifier 86 suitable for powering the transducer 26; such equipment is well known to the art. The transducer 26 is also provided with a polarizing coil 74, the desirability of magnetically polarizing the transducer 26 by means of polarizing coil 74, in order for the metal laminations in transducer 26 to efficiently convert the applied energy from excitation coil 72 into elastic vibratory energy, being readily understood by those skilled in the art. Low voltage direct current can be supplied to coil 74 bya battery as shown, or by a generator such as is used on an automobile, by a rectifier, etc.; such sources and their use in this connection are well known.

Preferably, and as shown more clearly in FIGURE 2, for support purposes and to minimize frequency shift of the vibratory apparatus and loss of vibratory energy to the associated supporting members, a force-insensitive mount 30 is attached to coupler 22. Such force-insensitive mount 30 may comprise a sleeve 32, one-half wavelength long at the operating frequency and made from steel or other low hysteresis material such as nickel, aluminum-bronze, beryllium-copper, or Monel. One end of the sleeve 32 is metallurgically bonded to the coupler 22, preferably at an antinode or loop region on the cylindrical portion of the latter, and the other end of the sleeve 32 is free from attachment. Sleeve 32 is provided with a radially outwardly extending flange 34 located one quarter wavelength from the attached end 48, and a true node will develop at flange 34. Reference is made to United States Patents Nos. 2,891,178; 2,891,179; and 2,891,180, each of which issued in the name of William C. Elmore and is entitled Support for Vibratory Devices. Flange 34 is removably secured to a support 35 on a draw bench 36, as by a clamping ring 37 and suitable bolts. Instead of the said arrangement, and as shown to the left of FIGURE 1, support 35 may be adjustably connected to the draw bench 36 via adjusting means such as by hydraulic cylinder means or by a way slide 49 (as shown) adjustable fore and aft in the direction of the action of the draw bench as indicated by arrow 90 and arrows 100 for longitudinal positioning of transducer-coupling system 24.

A second transducer coupling system 38 includes die 12, acoustical coupler 40 (which includes a plurality of horns 44a, 44b and also 440 (and 44d not shown), and a plurality of transducers designated a, 50b, 50c, and 50d (the last not shown), respectively. System 38, like system 24, is designed to operate at a given frequency, which is preferably a resonant frequency.

Each of

transducers

50a, 50b, 50c, and 50d is provided with an excitation coil 68 and a polarizing coil 70, and the description given hereinbefore as to transducer 26 is applicable to each of

magnetostrictive transducers

50a, 50b, 50c, and 50d, including the fact that other types of transducers may be substituted in system 38.

As with excitation coil 72 of transducer 26, excitation coils 68 of

transducers

50a, 50b, 50c and 50d are connected to a power supply incorporating an amplifier (such as amplifier 90) and oscillator (such as oscillator 80), suitable for powering the

transducers

50a, 50b, 50c, and 50d.

The die 12 has, for purposes of ease of attachment to coupler 40, an axially extending portion 42 (see FIGURE 1A) to whose outer surface one end of coupler 40 is secured by means of cooperating threads. The other end of coupler 40 which is remote from the die, namely, each of the horn ends 44a, 44b, 44c, and 44d, is fixedly secured to a transducer; that is, horn end 44a is joined to transducer 50a, horn end 44b is joined to

transducer

50b, 440 is joined to 500, and 44d is joined to 50d, preferably by brazing or some other type of metallurgical joint.

Acoustical coupler 40 is essentially a mechanical transformer and is of contoured construction for purposes including the increasing of the amplitude of vibration. Reference is made to United States patent application Serial No. 114,932, filed June 5, 1961, now Patent No. 3,148,293, in the names of James Byron Jones et al., entitled Tree Limb Vibratory Device, for details concerning construction of a coupler such as coupler 40 and its associated plurality of transducers such as transducers 50.

The horn-type construction of system 38 is particularly suitable for application of relatively high levels of vibratory energy at a given frequency, and for avoiding undesirable modes of vibration in connection with both the powering and the operation of a relatively large single coupler, as well as for appropriate access and attachment to a member such as the die in order to vibrate it in the longitudinal mode.

For support purposes and to minimize frequency shift of the vibratory apparatus and loss of vibratory energy to the associated supporting members, the die 12 is supported by a force-insensitive mount 52, similar to forceinsensitive mount 30 hereinabove described. The mount 52 in the drawing comprises a conical tubular member (a form which is not necessarily preferred), one or more one-half wavelengths long, which is free of attachment at one end and joined at its other end to coupler 40. Mount 52 further includes flange 58 (like flange 34 of mount 30) for connecting the mount 52 to a support 60, as by a clamping ring 61 and suitable bolts. Support 60 is rigidly secured to the draw bench 36.

It will be appreciated that, instead of being formed and positioned as shown, mount 52 may comprise a plurality of more or less rodlike members, all having flanges and some being attached to each of the straight portions of horns 44a, 44b, 44c, and 44d. This may be desirable, as, for example, in associating mount 52 with coupler 40 in the section not representing an increase in amplitude of vibration, thereby minimizing the subjection of mount 52 to the increased stresses associated with the maximum amplitude implicit to the contoured portion. If this latter configuration is used, the position of the support members relative to the draw bench will also be adjusted accordingly.

In operation a tube 18 is telescoped over the plug 16 and element 20. The tube 18, in accordance with standard practice, is provided with a reduced outside diameter end portion, which may be accomplished in a variety of ways including swaging. Such reduced portion is fed in the direction of arrow 90 through the die orifice 14. The jaws 64a and 64b of a pulling device 62 are clamped to the reduced end portion of the tube 18. Pulling device 62 is movably mounted on draw bench 36 for pulling the tube 18 through the passageway defined by die 12 and plug 16. The pulling device 62 is first actuated in the direction of arrow 90 to seat the plug 16. That is, the tube 18 is pulled in the direction of arrow 90 until the tube 18 is locked between the die orifice 14 and the outer peripheral surface of the plug 16.

The tube 18 can be translated by the pulling means for a short distance, so that the plug will seat properly and drawing can be readily accomplished; however, the invention is not limited to any particular sequence of steps in seating the plug, although certain sequences are far more favorable. As is readily evident, various lengths of tubing may be accommodated in accordance with the present invention.

After the plug 16 is properly seated and positioned, as, for example, by means of the way slide system and supporting transducer-coupling system 24, and vibratory energy is applied to the plug and the die, the pulling device 62 will move the jaws 64a and 64b in the direction of arrow 90. A wide variety of devices may, of course, be ulilized to pull the jaws 64a and 64b, such as a hydraulic cylinder, a cable windup device, a rack and pinion trolley device, etc. It will be appreciated that the jaws 64a and 64b will be provided with means for selectively opening and closing the same, so that the reduced end portion of the tube 18 may be inserted and gripped therebetween.

A lubricant may be applied to the inner and/or outer surfaces of the tube 18 may means well known in the art.

As aforesaid, oscillator or frequency converter 80 is part of the power supply system and, in a typical example, is capable of producing electrical signals in the range of between about 60 cycles per second and about 300,000 cycles per second. This frequency range is suitable for purposes of the present invention, including as it does frequencies in both the audible range (such as up to about 15,000 cycles per second) and the ultrasonic range (generally about 15,000 to 300,000 cycles per second). A preferred frequency would be in the range of from about 3,000 to about 50,000 cycles per second with the optimum being between about 14,000 to about 35,000 cycles per second.

Thus, transducer-

coupling system

24 and 38 may be each constructed to operate at 15,000 cycles per second, for example.

As shown in FIGURE 1, excitation coils 68 for

transducers

50a and 50b (and also 50c and 50d) of system 38 are connected in parallel to the output of 90. Excitation coil 72 for transducer 26 of system 24 is connected to the output of amplifier 86. The polarizing coils 70 and 74 (of

systems

24 and 38 respectively) are connected to a low voltage source of direct current. Thus, it can be seen that the power applied to the two

systems

24 and 38 can be independently controlled at a common frequency, such as 15 kc. Frequency differentiating means are known to the art.

The output 85 of oscillator 80 is connected directly to the input of amplifier 86 by means of conductor 82 and via phase shifting device 88, to the input of amplifier 90 by means of conductor 84.

By means of oscillator 80, the electrical frequency of the alternating current power supply (such as 60 cycles per second) is changed to match the mechanical or elastic vibratory frequency of the transducers (15,000 cycles per second in this example, as aforesaid). In accordance with 6 standard practice, the output waveform of oscillator and amplifiers 86 and 90 is sinusoidal.

It is to be noted that the source of high frequency alternating current may be a motor alternator having suitable frequency control, and that such a motor alternator source is particularly appropriate for drawing applications requiring large amouts of power. The output of the motor alternator may be divided between the two acoustic systems and an appropriate phase shifting network of proper power handling capability, can be inserted between the motor alternator and one of the acoustic systems, thus achieving the same result as described above for the oscillater-amplifier system.

The oscillator 80, the phase shifting device 88, and the amplifiers 86 and 90 are not described in detail, inasmuch as they are of conventional and well known construction, being described, for example, in such publications of McGraw-Hill Book Company, Inc., as Vacuum Tube Amplifiers (1948), Waveforms (1949), and Electronic and Radio Engineering (4th edition, 1955); in D. Van Nostrand Company Inc.s International Dictionary of Physics and Electronics (1956); and in Radiotron Designers Handbook (4th edition, 1952), distributed by the RCA Victor Division of the Radio Corporation of America.

It is the function of the phase-shifting network of device 88 to serve as means for selectively adjusting the phase relationship of the electrical energy supplied to transducer 26 and to

transducers

50a, 50b, 50c, 50d, respectively. When the device 88 is set to establish an inphase relationship between the signals, maximum values of these signals will occur simultaneously.

When the device 88 is set otherwise, there will be an out-of-phase relationship of the signals, namely, a difference between the times of the maxima of the respective signals, the time difference being the phase difference, which can be expressed in angular measure (degrees or radians) or in periods. For example, if one cycle or period of 360 degrees or 211- radians is taken as the unit, and if the phase difference between two signals is degrees, the maximum magnitude of signals to transducer 26 will occur before and/ or later than the maximum magnitude of signals to transducers 50a50b50c-50d, by a time difference of one-half of one cycle or period.

For purposes of describing one of the relationships in accordance with the invention, which relationship involves no fixed or built-in difference in relationship between the two systems the relationship between the vibration of .plug 16 and the vibration of die 12 is considered, for the sake of illustration, to correspond to an electrical in-phase relationship between the two series of signals delivered to the transducers respectively associated with plug -16 and die 12. For example, the knob 93 of the phase-shifting device 88 .may be set to establish the desired electrical in-phase relationship. Thus, in accordance with the present invention and this particular embodiment having the aforesaid electrical relationship (and when the pulling device 62 is moving the tube 18 at the same time that transducer-

coupling systems

24 and 38 are being energized), the respective vibratory movements of the plug 16 and the die 12 will also be in phase, reaching points of maximum vibratory amplitude or excursion in the same direction simultaneously.

In connection with the above described embodiment, as aforesaid, there should be no fixed or built-in difference between the transducer-coupling system.

For example, in this embodiment each of the two

systems

24 and 38 must resonate at a frequency which is as close as possible to the resonant frequency of the other system. However, in the present state of the acoustics art (identical performance of any two systems being difficult to achieve), if both systems are constructed to operate at 15,000 cycles per second, it is probable that this will be but a nominal frequency. Thus, one system may actually resonate at 15,125 cycles per second when driven alone, while the other (also when driven ing within about :two-tenths of one percent of the frequency of the former. This would be considered a sulficient (though not necessarily optimum) mutuality of resonant frequencies for purposes of this embodiment, an identical frequency being the optimum.

In addition to strict control of the design and construction of the various components of

systems

24 and 38, certain steps may be taken during assembly of the components for purposes of suitably adjusting the factors that effect the resonant frequency of a system. Thus, if the components are brazed together, the braze metal masses must be taken into account. Also, during or after assembly, one or more of the system components may be cropped for frequency adjustment purposes.

While the above embodiment enables results to be achieved which in many instances are not possible with use of either an activated plug system alone or an activated die system alone, including provision of a better surface finish on both the inside and outside surfaces of the tubing, this embodiment is particularly suitable for relatively greater reductions per pass of a given material, including the reduction of materials otherwise difficult or impossible to draw (such as materials having high yield strength). Thus, it has been found that, when utilizing both of

systems

24 and 38 in accordance with the above embodiment, there is a tendency for the plug system to chatter at relatively smaller area reductions for a given material, whereas there is not such chatter tendency at greater area reductions. Moreover, inasmuch as the displacements imparted to the tubing during drawing by this embodiment are applied in the same direction at any given time, there is provided, especially in the case of relatively thin-walled tubing, a minimization of the likelihood of the displacement toward the center of the thickness of the material having a gradient such as to approach zero and therefore remain unaffected. Thereby, vibrationally-induced plasticity of the tubing material during drawing is fully implemented, rather than merely a reduction of friction between the contacting inner surface of the die and the outer surface of the tube and/or a limitedvibrationally-induced plasticity of the tubing material during drawing.

Instead of the embodiment above described, but still in accordance with the present invention and also in accordance with FIGURE 1, there may be provided tube drawing performed under substantially opposed or differing conditions, such conditions being provided electrically and/ or vibration-ally, for example.

Examples of results achieved with the above described embodiment of the present invention are the following:

Example 1 A series of draws was made at increasing area reductions using a drawing speed of 35 feet per minute and 1100 aluminum alloy tubing having initial dimensions of 0.250-inch OD. and 0.065-inch wall thickness, using an in-phase relationship both electrically and vibrationally in an apparatus wherein transducer-

coupling systems

24 and 38 each had a nominal resonant frequency of 15,000 cycles per second sufficient within the limitations above described. Using progressively smaller dies, up to 56 percent reduction could be obtained with a total electrical power input of 1400 watts (power input to the transducer 26 of system 24 was 200 watts and power input to the transducers of system 38 was 1200 watts). Reductions of up to 49.2 percent were obtained when the total input power was 2350 watts (350 watts to the plug system; 2000 watts to the die system). A light oil was used as a lubricant. Significant is the fact that operation of neither system 24 alone nor of system 38 alone enabled a successful draw at this area reduction of this size and kind of tubing.

Example 2 The one-half wavelength dimensioning of each component of each of the

plug systems

24 and 38 described is critical with respect to the in-phase embodiment of the present invention. The plug is, of course, considered as part of the element 20 in connection with its dimensioning, and the die is considered as part of element 40 in connection with its dimensioning. Thus, if, for example, a one-half wavelength portion of element 20 is removed, as for purposes of accommodations a different size of plug or for shortening element 20 to accommodate different tubing or other different draw bench situation, system 24 will be 180 degrees out-of-phase with system 38, because of a fixed or built-in phase difference associated with the change in direction of amplitude in each succeeding onehalf wavelength. Since, as aforesaid, in the above embodiment the maxima of both signals and vibratory amplitude must be simultaneous in time and direction, this phase difference must be adjusted, as, for example, by reversing the electrical phase of one of the

systems

24 and 38.

Thus, in connection with the drawing of 1100 aluminum alloy tubing under the same conditions as in Example 1 above, but after a one-half wavelength portion of element 20 had been removed, it was impossible to draw satisfactorily. However, after the electrical phase of system 24 had been reversed, as by reversing the windings, drawing at the same area reduction and under the same conditions was successfully accomplished.

Example 3 Using the same relationship as was used in connection with Example 1, together with a special lubricant used by the industry for drawing stainless steel, stainless steel tubing was successfully drawn at wall area reductions of about 35 percent. The drawing rate was 35 feet per minute, and the total electrical power input was 2450 watts (450 watts to plug system; 2000 watts to die system).

Especially significant was the fact that the drawn tubing thus drawn was of commercially acceptable quality and had a surface finish which was better, whereas that obtained without vibratory activation with identical conditions was not commercially acceptable, the wall thickness being uneven because of the chattering encountered during drawing. Present commercial practice in connection with the drawing of steel involves the use of special lubricants, of special tubing having a conversion coating thereon, and generally of a solid rod corresponding in CD. to the intended ID. of the drawn tubing. This rod must be removed by means of expanding of the tubing after the drawing operation, and such expanding may change the properties, size, and surface finish of the steel. Utilization of die activation in addition to plug activation enables a better surface finish on the outer surface of the tubing as well as on the inner surface.

Example 4 In connection with the attempted drawing of 1010 steel tubing at a 40 percent area reduction, using a drawing speed of 25 inches per minute, this drawing could be accomplished without utilization of the present invention, utilizing a drawing force of 360 pounds, but there was severe chatter during the drawing and the drawn product was not of acceptable quality because of the defects produced in the tubing as a result of the chatter. When the drawing die was vibratorily activated, using 1000 electrical watts of power input to the transducer portion of the system, this reduction could be accomplished with an average drawing tension of only 245 pounds, and with reduced chatter, but the drawn product was still of unacceptable quality because of the tubing defects resulting from chatter. When the drawing plug was vibratorily activated, using a power input to the transducer of electrical watts, the same average force of 245 pounds could be used to accomplish the reduction, and there was less chatter than with an unactivated system, but again the tubing was of unacceptable quality because of the chatter results. When both drawing die and drawing plug were activated (with a total of 1,100 electrical watts power input), the reduction could be accomplished at a lesser average drawing force (210 pounds) with no chatter, so that drawn tubing of acceptable quality was produced.

Example Using the arrangement of FIGURE 1, with phase-shifting device 88 capable of varying the phase angle between system 24 and system 38 from 0 degrees to l80 degrees (negative values indicating system 38 lagging behind system 24), copper tubing (0.250-in. OD. x 0.200-in. ID.) was drawn at 50-53 percent one-pass area reductions utilizing 250 electrical watts power input to system 24 and 1000 electrical watts power input to system 38. The resonant frequencies of the two

systems

24 and 38 were as nearly identical as possible, as was the acoustical wavelength dimensioning of each of the two systems (for purposes of providing simultaneity of amplitude direction at any given time).

When a phase difference was provided between the two systems inan electrical manner (by device 88) so as to provide an angle equal to 180 degrees (out-of-phase), the reduction could be accomplished with a lower average drawing tension than is necessary wit-h conventional drawing, but a somewhat wavy surface finish. However, a still lower average drawing tension was obtained at 0 degree (in-phase), and the in-pl1ase condition pnovided an improved surf-ace finish over that obtainable with either conventional drawing or ou-t-of-phase drawing in accordance with the present invention in this drawing application.

While the phase difference was provided electrically in this instance, it will be appreciated that it could also have been provided vibrationally, as by shortening, lengthening, or otherwise adjusting the acoustical length of one of the systems with respect to that of the other.

As indicated by the above examples, the natural limits imposed upon drawing operations by the physical properties of a given material (such as tensile or yield strength and hardness) are circumvented to some extent by the present invention. Thus, the present invention enables greater reductions than have been possible heretofore and/or the use of a lesser drawing tension and/or a greater drawing speed, the systems relationships herein described being of particular utility with respect to the degree of achievement of vibrationally-induced plasticity in the material during drawing, especially with regard to the thickness of the tubing wall. It has also been observed, in connection with the present invention that there is a lesser temperature increase in the tubing material under the influence of the present invention than occurs in conventional drawing, a factor of some importance for purposes of avoiding undesirable temperature-induced property changes in materials such as high carbon steel, for example. Ordinarily, it would be expected that the acoustical vibrations would appear in the form of a temperature rise in the tubing material, which rise would be in addition to the rise occasioned by the drawing operations per se.

It will be appreciated that the wattage indicated in the above examples is exemplary only, and that power input may be varied according to the operating conditions utilized, including the material being drawn, and also according to the transducer-coupling system employed.

As is well known to those skilled in the art, power output (to the work) of acoustical vibration devices is not readily ascertainable directly, and indirect determination thereof often involves the use of liquids and other aspects not suitable for ready adjustment to differing industrial applications. Moreover, permissible power input is variable according to the type of transducer utilized and the acoustical coupler geometries and materials used, as well as such factors as the efficiencies of joints between the various members of the transducercoupling system. For example, a magnetostrictive transducer is far more rugged and trouble-free than a ceramic transducer, but it has a lesser efficiency in converting electrical power into mechanical vibration, and steel is a more readily machinable and joinable coupler material than Monel or beryllium-copper but it has a lesser acoustical transmission efficiency.

For those desiring to insure continued transmission efficiency of a given system (in order to obtain warning of malfunction, for example), or for those desiring to compare the relative transmission efficiencies of a plurality of systems, means may be used such as are described in co-pend'ing patent application Serial No. 66,642, filed November 1, 1960, for Method and Apparatus for Measurement of Acoustic Power Transmission and Impedance, by Dennison Bancroft et al.

For purposes of insuring a sufficient level of acoustical energy for purposes of the present invention, it is to be noted that provision has been made, in addition to a sufficient level of electrical power input to the transducer, for acoustical amplitude transformation. Also, this acoustical amplitude transformation should preferably involve, when a magnetostrictive transducer is used, a total transformer ratio (from the driving face of the transducer to the point of energy utilization) in the range of about 3.0 to 7.5; when an electrostrictive transducer (such as one of lead zirconate titanate) is used, such transformer ratio should preferably be in the range of about 1.5 to 5. This ratio depends in part upon the material or materials of which the coupling system member or members is made.

The transformer ratio is of particular importance for purposes of most efficient (and most economical) utilization of the present invention in any of its embodiments, and especially with regard to clear differentiation between embodiments so as to obtain the benefits of each in an appropriate application thereof. Thus, and particularly in embodiments essentially the same or essentially opposed as to other characteristics there should preferably be a mutuality of transformer ratios. That is, with like transducer materials, the effective acoustical transformer ratio of transducer-coupling system 24 should equal or reasonably approximate the effective acoustical transformer ratio of transducer-coupling system 38, considering the different masses (because of dimensions) of the die 12 and the plug 16, which difference may necessitate a greater supporting coupler cross section (with resultant effect on transducer requirements) for the die 12 on coupler 40 than for the plug 16 on coupler 20.

Different acoustical transformer ratios may be used, and the systems utilized in connection with the above examples had such differing ratios, the ratio for system 24 having been about twice that of system 38, but these are not preferable as hereinabove indicated.

Moreover, there should preferably be a mutuality of acoustical power (expressed in electrical watts input to the transducer, in accordance with the present state of the art) activating the die and the plug systems, particularly in connection with an embodiment in which the systems are otherwise substantially the same as to other characteristics, although this may also be important in an embodiment in which the two systems are substantially opposed in operation, such as systems degrees out of phase. Some slight departure from identity as to power may be necessitated by reason of the fact that the plug 16 may be in actual contact with a smaller (inside) area of the tube 18 being drawn than is the die 12 (which contacts the outside of the tube). Thus, somewhat less power may be supplied to coils 72 of system 24, the supply of power being controllable, for example, by adjustment of the respective amplifiers 86 and/or 90.

It is to be noted that the apparatus described herein is arranged to be isolation-mounted so as to avoid undesirable transfer of acoustic energy from the transducer-coupling system to the drawbench per se and/or from the drawbench (because of inherent resonances therein) to the work and/or transducer-coupling system.

In connection with the examples above provided, a tapered tungsten carbide plug was used, although other geometries and materials may be suitable for the purpose. A beryllium copper acoustical element (%2-lIlCh in diameter at 15 kc.; t/2=4.9 inches in length) attached to the plug was more etficacious than a steel element for reasons of more efficient acoustical power delivery also; although having (in conjunction with the plug) the same acoustical wavelength (57 one-half wavelengths in a typical instance), it was physically somewhat shorter than the steel element.

As aforesaid, this invention is not limited to any particular sequence of steps in seating the plug, and the order of seating in the operation is not critical to the present invention. For example, and as may be particularly desirable in applications contemplating relatively higher area reductions per pass for a given material, the plug and die systems may first be energized, the reduced cross section end of the tubing may be threaded through the die orifice (with or without assistance of the pulling device, which device may aid in a desirable amount of sinking of the reduced cross section end of the tubing), and the plug may then be advanced into the tubing and seated as desired. Advance activation of the plug and/ or die systems before seating of the plug may serve to simplify production operations. It may also minimize likelihood of undesirable tubing metal pickup by the unenergized plug and/or die during seating, such as may be encountered with certain materials, or with relatively high area reductions for a given material.

For efficient operation, the pulling device (including the jaws 46 and 48) should be acoustically non-compliant. That is, the pulling device should not resonate in any mode at the frequency of operation, or at any frequency related thereto, but should be essentially acoustically non-responsive, a condition attainable by various known means including appropriate adjustment of mass.

It was found that an infrared radiometer could be used to scan the surface of the tubing before and/ or after drawing by means of the present invention, the tubing being held at constant temperature during such scanning and the variation in radiometer reading bearing a relationship to the surface finish.

Although the invention is shown and described herein in connection with the drawing of tubes, it is to be understood that the invention is applicable generally to the drawing of elongated articles having wall structure formed at least partly about a longitudinal axis thereof.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing description as indicating the scope of the invention.

It is claimed:

1. Article forming apparatus comprising first and second elements defining therebetween a passageway, means for moving an article through said passageway, first and second means operative to oscillate the respective first and second elements with the same mode of vibration, and means coupled to said elements for establishing a selected phase relationship between the oscillations of said first and second elements.

2. Article forming apparatus according to claim 1 wherein a phase relationship of is established between the oscillations of said first and second elements so that the elements vibrate in phase with one another.

3. Article forming apparatus comprising first and second elements defining therebetween an annular passageway, means for moving an article through said passageway, first and second vibratory means operably connected to said first and second elements, respectively, and vibratorily responsive to a vibratory signal for vibrating the respective first and second elements, means for supplying a vibratory signal to the respective first and second vibratory means, and electro-mechanical means for selectively adjusting the phase difference between the vibrations of said first and second vibratory means whereby the relative vibrational movements of said first and second elements can be selectively controlled.

4. Article forming apparatus comprising first and second elements defining a passageway, means for moving an article to be formed through said passageway, first and second vibratory means each operable in response to a vibratory signal for vibrating respective first and second elements independently of one another, means for supplying sides of vibratory signals, a first series to said first vibratory means and a second series to said second vibratory means, and mean coupled to said first and second vibratory means for selectively adjusting the phase relationship between said first and second series of vibratory signals, whereby the phase relationship between vibrational movements of said first and second elements can be selectively controlled so that said elements vibrate in phase with one another.

5. Article forming apparatus according to claim 3 wherein the first element is a die including an orifice and the second element is a plug which is smaller in crosssectional area than said orifice.

6. Article forming apparatus according to claim 3 wherein said signal supplying means is constructed and arranged so that said first series of vibratory signals and said second series of vibratory signals are of like frequency.

7. Article forming apparatus according to claim 3 wherein the phase relationship adjusting means is selectively adjustable in the range of between 0 and 8. Article forming apparatus comprising first and second elements defining a passageway therebetween, said passageway being formed at least partly about and axis thereof, first and second means for oscillating the respective first and second elements independently of each other in axial direction, each of said oscillating means being operable in response to vibratory signals, means for moving an article through said passageway whereby the cross section of said article assumes substantially the cross-sectional configuration of said passageway, means for supplying a series of vibratory signals of like frequency to each of said first and second oscillating means, means for amplifying each of said plural series of signals, and means associated with said supply means for selectively adjusting the phase relationship between the respective series of vibratory signals supplied to said first and second oscillating means whereby the axial oscillatory movement of said first and second elements relative to each other can be selectively controlled.

9. Article forming apparatus according to claim 7 wherein the phase relationship adjusting means is selectively adjustable at least in the range of between 0 and 180.

16!. Article forming apparatus according to claim 7 wherein the first element is a die including an orifice, the second element is a plug, and the passageway is of annular configuration.

11. Article forming apparatus according to claim 9, wherein extreme positions of oscillatory movement in axial direction for each element occur at substantially the same time as the maxima of its associated series of vibratory signals.

12. Tube drawing apparatus comprising a die having an orifice and a plug extending at least partly into said orifice to define with said die a restricted annular passageway therebetween, said passageway being formed about an axis, first and second vibrating means for respectively oscillating the die and plug independently of each other in axial direction, each of said first and second vibrating means being operable in response to vibratory signals, means for pulling a tube through said passageway whereby the cross section of said tube is reduced and assumes substantially the cross-sectional configuration of said passageway, means including an oscillator for supplying plural series of vibratory electrical signals of like frequency to said first and second vibrating means, respectively, amplifying means for increasing the power level of each of said plural series of signals, and phase shifting means for selectively adjusting the phase relationship of said plural series of vibratory signals prior to their being delivered to said vibrating means, whereby the phase relationship between axial oscillatory displacements of said first and second elements relative to each other can be selectively controlled.

13. Tube drawing apparatus according to claim 11 wherein extreme positions of oscillatory displacement in axial direction of each of said die and said plug occur at substantially the same time as the maxima in its associated series of vibratory signals.

14. The tube drawing apparatus according to claim 11 wherein each of said series of vibratory signals is of sinusoidal wave form.

15. Tube drawing apparatus comprising a die having an orifice therein, a plug extending at least partly into said orifice from one side of said die and defining there with a restricted passageway for a tube to be drawn, means associated with said die on a side thereof opposite said plug for pulling a tube through said passageway, first vibrating means for oscillating said plug including a first transducer, a first coupler, and an acoustic transmission element coupled at one end to said plug and at the other end to said first coupler so that said plug oscillates in axial direction and a vibratory loop occurs in a portion of said plug at said passageway, a second vibrating means for oscillating said die including a second transducer, a second coupler connected at one end to said second transducer and at the other end to said die so that said die oscillates in axial direction, each of said first and second vibrating means being vibratorily operable in response to an electrical vibratory signal, means for pro ducing an alternating current electrical signal, electrical circuitry including conductors for transmitting said signal to the respective first and second transducers, the extreme positions of oscillatory movement of said plug and said die each occurring at the time of transmission to the respective first and second transducers of the maxima in said signal, and phase shifting means in said circuit for selectively adjusting the phase relationship in the range of between 0 and between the times of transmission of said signal to the respective transducers, whereby the phase relation of the relative axial oscillatory movements of said die and said plug can be selectively controlled.

16. Tube drawing apparatus comprising a die having an orifice, a plug partially extending into said orifice and co operating therewith to define an annular passageway, an acoustically non-compliant means for pulling a tube adapted to be disposed around said plug through said passageway, a force-insensitive mount supporting said die, an elongated coupler coupled axially to said plug, first vibratory means coupled to said coupler to vibrate said coupler and plug in an axial direction thereof, second vibratory means coupled to said die for vibrating said die in an axial direction with respect to said orifice at substantially the same frequency and in phase with vibrations of said plug, with the wavelength dimensioning of said first vibratory means and the coupler and plug coupled thereto being substantially equal to the wavelength dimensioning of said second vibratory means and the die coupled thereto.

17. Apparatus in accordance with claim 16 wherein a transformer ratio of between 1.5 and 7.5 is provided between the driving face of the transducer of the vibratory means to the point of energy utilization.

18. Apparatus in accordance with claim 17 wherein the respective transformer ratios of a first system containing the first vibratory means and a second system containing the second vibratory means are substantially equal.

References Cited by the Examiner UNITED STATES PATENTS 2,393,131 l/46 Vang 11346 3,002,614 10/61 Jones 2072 FOREIGN PATENTS 955,943 1/57 Germany.

CHARLES W. LANHAM, Primary Examiner.

MICHAEL V. BRINDISI, Examiner.

Attesting Officer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,212,312 October 19, 1965 Charles A Boyd et 31.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 12, line 17, for "sides" read series Signed and sealed this 31st day of January 1967.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Commissioner of Patents

Claims

1. ARTICLE FORMING APPARATUS COMPRISING FIRST AND SECOND ELEMENTS DEFINING THEREBETWEEN A PASSAGEWAY, MEANS FOR MOVING AN ARTICLE THROUGH SAID PASSAGEWAY, FIRST AND SECOND MEANS OPERATIVE TO OSCILLATE THE RESPECTIVE FIRST AND SECOND ELEMENTS WITH THE SAME MODE OF VIBRATION, AND MEANS COUPLED TO SAID ELEMENTS FOR ESTABLISHING A