US3382692A - Sonic method and apparatus for closed-die forging - Google Patents

Description

May 14, 1968 A. G. BODINE 3,382,692

SONIC METHOD AND APPARATUS FOR CLOSED-DIE FORGNG Filed June 7, 1965 4 Sheets-Sheet l ff/// N ill n. l

ALBERT G. BODINE INVENTOR.

ATTRNY A. G. BODINE May 14, 1968 I SONIC METHOD AND APPARTUS FOR CLOSED-DIE FORGING vFiled June v, 1965 4 Sheets-Sheet 2 FIG 7 l|| lill ER mm D N Ow Bm G T R E E` L A ATTORNEY A. G. BODINE May 14, 1968 SONIC METHOD AND APPARATUS FOR CLOSED-DIE FORGING v Filed Junev 7, 1965 4 Sheets-Sheet 5 FIG 4 ALBERT G. BOBINE INVENTOR.

ATTORNEY SONIC METHOD AND APPARATUS FOR CLOSED-DIE FORGING Filed June 7, 1965 A' G- BOBINE May 14,

4 Sheets- Sheet 4 ALBERT G. BoDlNE INVEN TOR.

BY fgfwf# ATTORNEY United States Patent O 3,382,692 SONIC METHOD AND APPARATUS FOR CLOSED-DIE FORGING Albert G. Bodine, 7877 Woodley Ave., Van Nuys, Calif. 91406 Filed June 7, 1965, Ser. No. 461,835 20 Claims. (Cl. 72-60) ABSTRACT OF THE DISCLOSURE A closed-die forging machine is provided in which the billet is located at the termination region of a resonant acoustic circuit to which intense sonic energy is applied. The frequency of the applied sonic energy is adjusted to accommodate impedance changes naturally occurring in the resonant circuit during the forging process. The resulting sonic standing wave established in the work piece while it is being forged, greatly enhances its grain structure, freedom from porosity, and numerous other properties.

This invention relates to the production of closed-die forgings and more particularly to the utilization of sonics in forging processes, wherein sonic energy is delivered to the process during the time the forging is being subjected to normal die pressure, thereby improving the production rate and quality of the forging.

Forging comprises the plastic deformation of metal, generally at elevated temperatures, using compressive forces exerted through a die. The design of forgings is more restrictive than that of castings, due to the inability of solid metal to flow under pressure to the same degree as liquid metal fiows in filling a mold cavity. In conventional forging processes, forging deforms the metal at temperatures and strain rates such that no strain-hardening results. That is, the deformation is carried out above the metals recrystallization temperature. As a result of the hot-working, nonmetallic inclusions are elongated in the direction of working, producing a fiber-like structure variously called grain flow, flow lines, forging fiber, or fiber structure. This fiber-like structure causes the forging to be anisotropic with respect to mechanical properties, particularly with reference to ductility and toughness, which are considerably greater in a direction parallel to the fiow lines. The degree of anisotropy developed depends on the amount of reduction effected during forging.

There are various classifications of forging processes well known to those versed in the art. The present invention is particularly applicable to those forging processes referred to as impact forging and press forging, either of which employ closed dies. In a typical construction the forging equipment comprises a stationary die to which an impact blow is delivered by a ram which holds a moving die or punch. The ram may be mechanically or hydraulically driven, and the equipment is usually constructed to operate vertically.

-In the usual case, the material to be forged is in the form of a bar or billet. The heated metal comprising the billet is forced to fill the die cavity by the impact of the ram driven punch.

In another type of equipment, two rams are driven towards each other at high velocity by fiuid pressure. The billet is positioned at the plane of impact of the rams. Thus, the energy of the rams is almost entirely absorbed by the metal and very little energy is lost by transmission to the machine foundation.

In addition to the usual vertical rams, presses may be equipped with horizontally operating rams permitting simultaneous forging in several directions. In many inassaaz- Patented May 14, 1968 ice stances the desired shape of the part precludes the forging being done in a single operation. However, in most cases this restriction is due primarily to the frictional effect and the cooling action of the die on the hot metal. As a result, a series of performing operations have been required, heretofore, which moves the metal in steps towards the finished shape. For extremely large forgings, the hydraulic press is the only type of equipment which can provide the necessary forces (typically up to 50,000 tons).

The present invention provides a number of advantages as compared with prior forging processes, some of these advantages being the control of heat dissipation in the billet during forging, control of grain flow, explusion of nonmetallic inclusions, and increased uniformity of grain structure. The invention is based upon the discovery that a resonant member, closely coupled acoustically to the metal billet being formed in the die, may be used to create a sonic standing wave or resonant phenomenon in which the heated metal, located in a partially reflective region of the resonant area, functions as a resistive impedance. The resonant member from which acoustic energy is obtained may be associated with either the die cavity or the punch member or both parts of a two-part die as determined by the particular type of forging equipment being employed. In some instances the resonant member may comprise the die itself, or in some cases the resonant member may comprise the punch member. Also, both elements may each comprise a separate resonant element, or a part of a separate resonant circuit.

The billet is placed at a termination region of a resonant circuit wherein the acoustical impedance of the billet will have a very pronounced effect upon the characteristics of the circuit. While the forged part cools or hardens, and sets up, as it forms into the die, the reactive impedance increases. This increase in reactive impedance causes a shift in the resonant frequency of the circuit so that the part remains intimately coupled thereto. This intimate acoustic coupling of the part into the acoustic circuit causes an enhanced degree of fiuidization of the grain structure within the part as it is setting up during the forging operation. The result is an unusually uniform grain structure and also an increased fluidity of the metal which helps expel the gas and other impurities within the part or work piece being formed. Furthermore, the intense sonie energy imparted to the billet during the forging operation maintains a high degree of mobility within the workpiece. This serves to maintain uniform temperature conditions throughout the work piece so that as it cools it is not subject to large, locked up, internal stresses, as is common with ordinary forging operations. The work piece functions as a resistive impedance in a region of refiection. This results in substantial mobility at the interface of the work piece and the die cavity, thereby reducing friction and adhesion so that the die need have less draft for forming and removal of the parts. This reduced draft in the die permits the parts to have more nearly finished dimensions.

It is therefore an object of the invention to provide novel and improved means for imparting intense sonic energy to a work piece during a forging operation.

Another object of the invention is to provide novel and improved forging apparatus for establishing a sonic standing wave in a work piece While it is being forged.

Still another object of the invention is to provide novel and improved forging apparatus employing resonant members, having as a part of the termination region of a resonant circuit which includes said resonant members, a part which is to be formed during a forging process.

Yet another object of the invention is to provide novel and improved methods and apparatus employing sonic energy to enhance the degree of fluidization, and to im- 3 prove the grain structure, wit-hin a part during a forging operation.

t is an object of the invention to provide a novel and improved method of forging which requires less draft in the die, thereby producing forgings having ymore nearly finished dimensions.

It is yet another object of the invention to provide novel and improved apparatus which utilizes sonic energy to forge parts so as to `have a very uniform grain structure and which are relatively free of porosity as compared with forgings produced by prior processes.

A general object of this invention is the improvement of closed-die forging processes.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

Additional advantages and features of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheets of drawings in which various structural embodiments, incorporating the principles of the present invention, are shown by way of illustrative examples.

In the drawings:

FIGURE 1 is a front elevational view of a vertical forging press incorporating the principles of the invention;

FIGURE 2 is a side elevational view of the apparatus of FIGURE l;

FIGURE 3 is a cross sectional view taken along line 3-3 of FIGURES l and 2;

FIGURE 4 is a cross sectional view taken along line 4 4 of FIGURE 1 and illustrates one form of an orbiting mass oscillator which may be used in the practice of the invention;

FIGURE 5 is a perspective view partially in section and partially broken away, w-hich illustrates an alternative embodiment of an orbiting mass oscillator which may be used in the practice of the invention;

FIGURE 6 is a plan cross sectional view of the apparatus of FIGURE 5;

FIGURE 7 is a front elevational View of an alternative embodiment of the invention, in which sonic energy is imparted to the hollow die member;

FIGURE 8 is a cross sectional view taken along line 8 8 of FIGURE 7;

FIGURE 9 is a front elevational view illustrating a third embodiment of the invention wherein the sonic oscillator is asymmetrically disposed relative to the termination region of the die;

FIGURE l0 is a cross sectional view taken along line 10-10 of FIGURE 9 and illustrates the manner in which the orbiting mass oscillator is coupled to the punch member.

Inasmuch as the art relating to forging methods and apparatus, and the art relating to acoustics are not coextensive the latter may be outside the experience of those skilled in the former and in order to aid in the full understanding of the invention, the following general discussion is deemed to be useful. As used throughout this specification the term sonic vibration is intended to mean elastic vibrations, i.e., cyclic elastic deformations, which travel through a medium with a characteristic velocity of propagation. If these vibrations travel longitudinally, or create a longitudinal wave pattern in a medium or structure having uniformly distributed constants of elasticity or modulus, and rrnass, they comprise sound wave transmission. Regardless of the vibratory frequency of such sound wave transmission, the same mathematical formulae apply, and the science pertaining thereto is called Sonics In addition, there can be elastic vibratory systems wherein the essential features of mass appear as a localized influence or parameter, referred to hereinafter as a lumped constant. Also, a lumped constant can `be a localized or concentrated elastically deformable element, affording a local effect referred to variously as elasticity, modulus, modulus of elasticity, stiffness, stiffness modulus, or compliance (which is the reciprocal of the stiffness modulus). Fortunately, these constants, when functioning in an elastically vibratory system, as herein under consideration, have cooperating and mutually intluencing effects for which there are equivalent factors in alternating current electrical networks. In fact, in both distributed and lumped constant systems, mass is mathematically equivalent to inductance; elastic compliance is mathematically equivalent to capacitance; and, friction or other pure energy dissipation is mathematically equivalent to resistance.

Because of these equivalents the elastic vibratory systerms of the apparatus of the present invention with their mass stiffness and energy consumption, and their sonic energy transmission properties, can be viewed as equivalent electrical circuits, where the functions can be eX- pressed, considered, changed, and quantitatively analyzed by using well proven electrical formulae.

In analyzing resonant phenomenon of an acoustic circuit it is important to note that resonance includes capacitance, inductance, and usually in any practical system it also employs resistance. However, the main factors determining the resonant frequency in the present system is the inductance and capacitance combination of the circuit. Therefore, in a practical application of the invention it is preferred to set up the arrangement of the apparatus in such a way that either the die or the punch functions as a major portion of either the capacitance or the inductance of the resonant circuit. On the other hand, this invention can also be accomplished =by using a separate resonant circuit in coupling either the punch or die member thereto so as to form a termination thereof. It is also important to understand that the billet or part being forged is an essential part of the termination region of the acoustic circuit. The resonant member, whether it`be the punch, the die, or both, places the work piece at a boundary at each resonant circuit, thereby permitting the work piece to function as a resistive impedance termination.

As was mentioned hereinabove, as the part cools, hardens, and sets up during its formation in the die, the reactive impedance of the termination region increases. This causes a shift in the resonant frequency so that the part remains intimately coupled into the acoustic circuit. This requires the frequency of the driving oscillator to also shift. To accomplish this change in frequency it is preferred that an oscillator of the type shown and described in my Patent No. 2,960,314, entitled Method and Apparatus for Generating and T ransmitting Sonic Vibrations, be employed. This oscillator comprises a sonic gyrating or orbiting mass which is selfadjusting to generate an output frequency coinciding with the resonant frequency of the member to which it is coupled. In other words, a sonic oscillator of this type is not resonant in and of itself, but rather is responsive to the natural frequency of the system to which it is coupled. Therefore, by designing the apparatus of the present invention so that the die member or the punch member is an intimate part of the system, then the combination employing an orbiting mass oscillator, of the type referred to in the foregoing patent, will cause the die or punch to be involved to a major degree in the resonant phenomenon.

It is to be understood that inasmuch as the orbiting mass oscillator does not constitute a necessary part of the present invention, only so much of the structural details and operational features thereof considered to be essential for a complete understanding of this invention are described herein. Any suitable means for irnparting sonic energy of the required frequency and amplitude may -be employed.

It is important to recognize that the transmission of sonic energy onto the interface or work area between two parts to be moved against one another requires the above-mentioned elastic vibration phenomena in order to accomplish the benefits of the present invention. There have been other proposals involving exclusively simple bodily vibration of some parts; however, these simple bodily vibrations do not result in the benefit of sonic or elastically vibratory action as is inherent in the present invention. This is particularly noteworthy, for example, where the die or punch is the major part of the resonant acoustic circuit.

Since sonic or elastic vibration results in the mass and elastic compliance elements of the system taking on these special properties akin to the parameters of inductance and capacitance in alternating current phenomena, wholely new performances can be made 4to take place in the mechanical art. Mo-re particularly, the concept of acoustic impedance becomes of paramount importance in understanding the operation of the present invention. Here impedance is the ratio of cyclic force or pressure acting in the media to resulting cyclic velocity or motion, and is analogous to the ratio of voltage to current in an alternating current network. In this sonic adaptation, impedance is also equal to media density times the speed of propagation of the elastic vibration. In this invention impedance is important to the transfer of sonic energy to the billet through the die and/or punch interface. A sonic vibration transmitted across an interface -between two media or two structures may undergo some reflection, depending upon differences of impedance. This can cause large relative motion, if desired, at the interface. Impedance is also important to consider if optimized energization of system is desired. If the impedances are adjusted to be closely matched, energy transmission is made very effective.

Resonating the die, as provided by the present invention, facilitates removal of the finished part. This permits substantial reduction or elimination of the need for sloping walls in the die, which is the normal expedient for part removal. These sloping walls give an undesirable shape to the part, requiring extra machine work for finishing. The present invention permits no-drift forging.

Of particular importance in the present invention is the fact that sonic energy at fairly high frequency can have energy effects on molecular or crystalline systems. Also, these fairly high frequencies can result in very high periodic acceleration values, typically of the order of hundreds of thousands of times the acceleration of gravity. This is because, from a mathematical point of view, acceleration -varies with the square of frequency. Accordingly, by taking advantage of this square function, very high forces can be accomplished by the sonic system of the present invention.

An additional feature of sonic circuits as employed in the present invention is the fact that they can be made very active, so as to handle substantial power, by

providing a high Q factor. As considered hereinafter, g

the factor Q is the ratio of energy stored to energy dissipated per cycle. In other words, with a high Q factor, the sonic system can store a high level of sonic energy, to which a constant input and output of energy is respectively added and subtracted. From a network circuit point of View this Q factor is numerically the ratio of inductive reactance to resistance. Moreover, a high Q system is dynamically active, giving considerable cyclic motion Where such motion is needed.

To facilitate an understanding of the invention the following definitions are set forth:

Impedance-The complex quotient of applied alternating force and linear velocity, in an elastically vibratory system. It is analogous to electrical impedance.

Resistance- The real part of the impedance, and represents energy dissipation, as by friction.

Reactance.-The imaginary part of the impedance, and is the difference of mass reactance and compliance reactance.

Elastic compliance reactance.-Elastic compliance reactance is analogous to electrical capacitance reactance, just as compliance is analogous to capacitance.

Resonance in the vibratory circuit is obtained at the operating frequency at which the reactance (the algebraic sum of mass and compliance reactances) vbecomes zero. Vibration -amplitude is limited under this condition to resistance alone, and is maximized. The inertia of the mass elements necessary to be Vibrated does not under this condition consume any of the driving force.

Referring now to FIGURE l there is shown a first embodiment comprising a Vertical forging press of the type in which both the die and the punch Jare hydraulically driven towards each other during the forging operation. This press comprises a pair of vertical frame members 1 and 2 which extend upward from base 3 and support the apparatus. A bottom platform 4 extends between frame members 1 and 2, and a top platform 5 extends between the opposite or upper ends of frame members 1 and 2. Lateral bar 6 is supported by means of two upwardly extending support members 7 and 8, and is secured thereto by means of a pair of cross pins 9 and 10. Bar 6 is caused to vibrate along its major axis in a manner to be described hereinafter. Pins 9 and 10 extend through the neutral axes or nodes of bar 6 as it vibrates in its resonant mode. Saddle 12 extends lupwardly from, and is secured to, lateral bar 6 by means of a pair of cross pins 13 and 14 which extend transversely thereof. Saddle 12 is attached to die member 15 by means of bolts 16 and 17 or other suitable fastening means. Die member 15 is provided with a cavity 18 into which billet 19 is placed for forging.

A sonic oscillator, indicated generally at 21, is coupled to lateral bar 6 by means of a pair of transverse pins 22 and 23, located in proximity to the nodal point of bar 6 in its resonant mode.

Top platform 5 is provided with a pair of downwardly extending hanger projections 24 and 25 from which hydraulic cylinders 26 and 27 are supported. Cylinders 26 and 27 are secured to projections 24 an-d 25 by means of transverse pins 28 and 29.

Guide rails 31 and 32 are attached to frame members 1 and 2, respectively, and to top platform 5. These rails serve to guide frame 33 which is slidably supported therein. Piston rods 34 and 35 extending from hydraulic cylinders 26 and 27, respectively, are attached to frame 33 by means of pins 36 and 37, and upon the application of fluid pressure to cylinders 26 and 27, frame 33 will be driven downwardly carrying punch 38 into the cavity 18 of die member 15.

Shaft 39 is secured to frame 33 by means of collar 41 and has its lower end acoustically coupled to punch 38; its upper end is acoustically coupled to sonic oscillator 42. Bushing 43 serves to attach punch 38 to frame 33 and to support the lower end of shaft 39. Sonic oscillator 42 is supported by rib member 44 extending upwardly from frame 33. A central opening 45 is provided in top platform 5 through which shaft 39 and rib member 44 may pass while the punch 38 is in the retracted position.

As can be seen in FIGURES 2 and 3, motor 46 is drivingly coupled to sonic oscillator 42, by means of drive shaft 47. Oscillator 21 is coupled to motor 48 by means of drive shaft 49. Motor 46 is mounted on rib member 44 and motor 48 is mounted on bottom platform 4. It is preferred, though not required, that motors 46 and 48 be rotary fluid motors since this will permit them to be driven from the same source of fluid pressure used to operate hydraulic cylinders 26 and 27. The source 0f fluid pressure is not shown since any such source of suitable and well-known construction may be employed, as will be obvious to those versed in the art.

During the forging operation hydraulic pressure is applied to cylinders 26 and 27 causing piston rods 34 and 35 to move downwardly, thereby extending frame 33 towards die member 15 and urging punch 38 into the cavity 13 of the die. Simultaneously, sonic oscillator 42 transmits a high intensity sonic wave through shaft 39 which is acoustically coupled, at a low impedance region at its upper end to oscillator 42. The die 38 is coupled to a low impedance region at the lower end of shaft 39. Shaft 39 is resiliently supported by means of collar 41. Collar 41 is held in place by resilient washer 51 and plate member 52 which is threadably secured to frame 33.

With particular reference to FIGURES 2 and 3 there is shown the manner in which die member is sonically coupled into an acoustical circuit. As mentioned hereinabove, die member 15 is supported on lateral bar 6 by means of saddle 12 and cross pins 13-14 which extend through the neutral axis of bar 6, in its resonant mode. It is preferred that cross pins 13 and 14 be located at a region of optimum impedance in the resonant bar 6 so as to obtain the best acoustical matching to the die mem ber 15. The die member 15 functions primarily as a mass inductance. However, it is still part of the resonant circuit. Sonic oscillator 21 is acoustically coupled to bar 6 at a fairly low impedance region so as to maintain a strong standing wave or resonant wave pattern therein. The wave pattern is graphically indicated by dotted lines 53 and 54. As can be seen, this wave action will cyclically drive die member 15 up and down in a direction toward and away from. punch 38. This vibratory or sonic energy is obtained from oscillator 21 and typically may have a frequency in the range of l to 2 kilocycles per second. The displacement amplitude of bar 6 typically may be of the order of 5 either side of the horizontal centerline, as measured in terms of angular rotation about the axes of cross pins 9 and 10.

As can be seen in FIGURES 2 and 3 hydraulic pres sure is supplied to uid motor 48 which in turn drives sonic oscillator 21. Sonic oscillator 21 is of similar construction to oscillator 42 which transmits sonic energy to the punch 38 from the top of the apparatus.

There is shown in FIGURES 4-6 two examples of sonic oscillators which may be employed in the apparatus of FIGURES 1-3. The operating principle of the gyratory type sonic oscillator is shown in FIGURE 4 and comprises, in part, an eccentric outer cylinder 61 and an inner cylinder 62. The inner cylinder 62 is provided with a plurality of jet orifices or turbine nozzles 63-66. By applying uid under pressure to the interior of cylinder 62 and withdrawing it from the interior of cylinder 61, the (outer) cylinder 61, which acts as an orbiting mass, will be caused to follow an epicyclic or gyratory path as it moves about the exterior surface of the (inner) cylinder 62. This will generate a substantially sine wave vibration which will be imparted to the structure supporting outer cylinder 61.

There is shown in FIGURES 5 and 6 an alternative construction of a sonic oscillator of the orbiting mass type in which rotary kinetic energy, rather than hydraulic fluid pressure, is employed to drive the eccentric mass.

The orbiting mass oscillator comprises an outer cylinder 67 which may be press-fit into, or otherwise supported by, a frame 68 or other structure to which sonic energy is to be imparted. Cylinder 67 is closed on one end by plate 69 and gear ring 71 and on the other end by frusto-conical shell 72 and gear ring 73. Plate 69 is provided with a circularly grooved track 74. Stationary tube 75 is secured to shell 72 and extends therefrom. The orbiting mass comprises a cylindrical weight 76 coaxially mounted on gear member 77, for rotation therewith. Boss 78 extends from gear member 77 and mates with or engages circular track 74 in plate 69. The teeth of gear member 77 mesh with gear ring 71. The opposite end of steam 83, which runs through cylindrical weight 76, is secured to Igear wheel 79, the peripheral gear teeth of which mesh with the interior gear teeth of gear ring 73. Gear wheel 79 is provided with a frusto-conical boss 81 which travels in mating circular groove 82 in drive member 86. Drive shaft 84 is driven from a rotary prime mover (not shown). Splined end 35 enga-ges the interior mating spline of drive member 86, which is rotatably supported by ball bearings l87 and 88. Rotary motion is imparted to drive member `86 which in turn causes gear wheel 79 to rotate by toothed engagement therewith. This in turn `will impart motion to the cylindrical weight 76 or orbiting mass causing it to revolve and follow an orbital path about the interior surface of outer cylinder 67.

As shown in FIGURE 6 spring bias means 89 and 91 may be employed to resist end play of stern 83.

A valuable feature of the sonic circuit of the present invention is the provision of an extra elastic compliance reactance so that the inherent mass or inertia of various bodies in the system does not cause the system to depart so far from resonance that a lange proportion of the driving force is dissipated in vibrating this mass. For example, in any practical construction, the mechanical oscillator or vibration generator will require a body or supporting structure for carrying the cyclic force ygenerating means. This supporting structure, even when minimal, will have some finite mass or inertia. This inertia could be a force-wasting detriment, acting as a blocking impedance using up part of the periodic force output just to accelerate and decelerate the supporting structure. However, by use of elastically vibratory structure in the system, the effect of this mass, or the mass reactance resulting therefrom, is counteracted at the frequency for resonance; and, when a resonant acoustic circuit is thus used, with adequate capacitance (elastic compliance reactance), these blocking impedances are tuned out of existence, at resonance, and the periodic force generating means can thus deliver its full impulse to the work which is a resistive component of the impedance. In the embodiment of FIGURES l-3 this extra elastic compliance is provided by shaft 39 in the acoustic circuit of the punch 38 and by bar 6 in the acoustic circuit of the die member 15.

There is shown in FIGURE 7 an yalternate embodiment of the invention in which sonic energy is imparted only to the die member 92. In this embodiment the apparatus is supported by side frame members 93 and 94 which extend vertically from base platform 95. Support members 96 and 97 are carried on platform 95 and serve to support lateral bar 98. As in the case of the embodiment of FIGURES 1-3, bar 98 is secured to support members 96 and 97 by a pair of cross pins 99 and 101. Saddle 102 is attached to bar 98 by means of cross pins 103 and 104, and serves to support die member 92. Sonic oscillator 105, which may be either of the types shown in FIGURES 4 and 5, is drivingly coupled to bar 98 via link 106 and cross pins 107-108. This arrangement results in the sonic oscillator being coupled to bar 98 at a low impedance (high velocity vibration) region, for optimum power input. Also, die member 92 is coupled to bar'98 at a low impedance region in order to impart a high'velocity to the billet 109 during the forgin-g process.

Hydraulic cylinder 111 is mounted on upper platform 112, which in turn is supported between frame members 93 and 94. The application of uid pressure into cylinder 111 will cause ram 113 to drive punch 114 downward and thereby cause billet 109 to till the die cavity.

There is shown in FIGURES 8-10 still another embodiment of the invention in which sonic energy is imparted to both the punch andthe die; however, in this instance the sonic oscillators are offset or asymmetrically placed with respect to the central axis of the apparatus, in contrast with the arrangement of the embodiments shown in FIGURES 1-3 and 7.

The main supporting structure of this embodiment comprises frame members `115 and 116, and platforms 117 and 118. Base 119 rests upon platform 118. Posts 126 and 127 extend upwardly from base 119 and serve to support lateral bar 123. In this instance the die cavity 128 is formed directly in the lateral bar 123.

9 As shown in FIGURE 9 there are two cavities 121 and 122 cut up into lateral bar 123 up to its neutral 'axis in its resonant mode), so that a pair of fulcrum points 124 and 125 can be maintained at a region of minimum motion, so that energy is not dissipated from the resonant die member (bar 123) into the base 119 of the press. For example, these two support points 124 and 12S can be located at a nodal region. Moreover, if there is a complex pattern in the die providing'a number of nodes, there can be more than two such points. The sonic oscillator 129 for driving bar 123 into resonance is coupled to a point near one end of the bar and due to the relatively high Q of the laucoustical circuit, is as effective in driving the bar 123 as if it were coupled in the manner shown in the embodiments of FIGURES 1-3 and 7. Fluid motor 130, shown in FIGURE 10, is drivingly coupled to oscillator 129. The resulting wave pattern is indicated by dotted lines 131 and 132.

The punch '1133 is attached to ram 134, which is driven by hydraulic cylinder 135. Platform 117 supports cylinder 135.

Sonic energy is imparted to punch 133 by a sonic oscillator assembly which is secured thereto by means of cross pin 136. This sonic oscillator assembly comprises a pair of gyratory sonic oscillators 137 and `138 of .the type shown in lFIGURE 4. Fluid under pressure is supplied to oscilla-tors'137 and 138 through high pressure hoses 139 and 141, respectively. Cross members `142-2 .and '143 carry oscillators 137 and 138, and are in turn attac-hed to punch 134 by pin 136. Oscillators 137 and y138 are acoustically coupled to a low impedance region of cross members 142 and 143. Cross pin I136 is also coupled to cross members 14'2 and 143 at a low impedance region. This results in a system having a high Q and provides an optimum transfer of sonic energy from the oscillators (137-138) to the termination region at punch 133.

In the embodiment of FIGURES 9 and 10 sonic energy is imparted to both the die (123) and the punch 133; however, it should be lunderstood that the resonant frequency of the acoustic circuit which includes the die need not be the same as the resonant frequency of the lacoustic circuit which includes 'the punch.

While the exemplary embodiments have been described in terms of a punch member and a die member, such terminology is also intended to embrace so-called twopart dies and should not be construed as limited to a simple male punch and female -die combination.

summarizing, in each of the embodiments describe-d above the billet is placed at 'the termination region of a sonically driven resonant circuit wherein it may function primarily as a resistive impedance. Inasmuch a-s reflection of sonic energy .may occur at an interface between sonic energy transmitting members when there is a difference in impedance therebetween, such effect may be utilized in accordance with the present invention wherein the billet is placed in the region of reflection in order to take advantage of the relative motion between the billet and the structure defining the die cavity. Since Ithe reactive impedance of the billet tends to increase during the forging process, means are provided to maint-ain resonance in the acou-stic circuit during this change. The required variable frequency sonic energy is obtained from a sonic oscillator which may be either symmetrically or asymmetrically disposed relative to the termination region of the die structure, so long as i"t is coupled thereto at a low impedance region of the acoustic circuit. A lumped constant, which for example may comprise a metal bar or shaft inserted in the acoustic circuit between the sonic oscillator and the mass inductance of the die, provides extra elastic compliance reactance or capacitance which tunes out undesirable blocking impedances which might otherwise exist in the apparatus.

While there have been shown and described and pointed out the fundamental novel features `of the invention as applied to preferred methods and embodiments, it will be understood that various omissions Iand substitutions and changes in lthe method of the invention, and in the form .and details of lthe devices illustrated, may be made by those skilled in the art, without departing from the spirit o-f theinvention; therefore, it is inten-ded that the invention be limited only as indicated by the scope of the following claims.

What is claimed is:

1. In a method of forging Ia work piece in which a billet is caused to Ifill a closed die cavity in a die by the force of a movin-g ram, t'he improvement comprising:

imparting sonic energy to said billet land said die at a frequency and at an intensity sufficient to e'stablish a resonant vibration in the acoustic circuit comprising said billet .and said die, concurrently with the application of said force by said ram, and thereby modify the interface surface ow and the grain flow of said billet as it fills ysaid -die -cavity to form said work piece.

2. In a method of forging a work piece inA which a billet is caused to fill a cavity in a die by the force of a moving ram, the improvement comprising:

imparting high intensity sonic energy to said ram; and

adjusting the frequency of the sonic energy imparted to said ram, concurrently with the application of said force, so as to establish a resonant vibration in the acoustic circuit compri-sing said die and said billet, and thereby enhance the flow of 'said billet as it fills said cavity to form said work piece.

3. In a method of forging a work piece in which a billet is caused to ill a closed die cavity by means of an impact force imparted to a moving member supporting a die defining said cavity, the improvement comprising:

imparting high intensity sonic energy to said die; and

adjusting the frequency of `the sonic energy imparted to said die, concurrently with the application of said impact force, so as to establish a resonant vibration in the acoustic circuit comprising said die and said billet, and thereby enhance the ow of -said billet as it fills .said cavity to form said work piece.

4. In a method of forging .a work piece, in which a billet is subjected to the impact force of a pair of members moving vtowards each other, thereby causing said billet to i'ill a die cavity therebetween, the improvement comprising:

imparting high intensity Isonic energy to one of said members from a rst source; imparting high intensity sonic energy to the other of -said members from a second source; and

adjusting the frequencies `of the sonic energies from said sources, concurrently with the .application of said impact force on 'said billet, so as to establish a resonant vibration in the acoustic termination region of said cavity and .said lbillet, and thereby control the flow of said billet as it iills said cavity to form said work pie-ce.

S. In a method of forging a work piece in which a billet is caused to fi'll a closed die cavity by means of an impact force imparted thereto, the improvement comprising:

generating high intensity sonic energy of a selectively adjustable frequency;

transmitting said energy to an acoustical termination region .substantially defined by said die cavity and said billet; and lthereafter adjusting the frequency -of said sonic energy, concur-l ren'tly with the application of said impact force to said billet, so as to establish a resonant vibration in said termination region, thereby enhancing the flow of lsaid billet into the contines of said cavity.

6. The method of forging a part from a billet comprising the steps of c forcing said billet into the cavity defined by a closed die in response to the impact of a rectilinearly directed moving member; and concurrently imparting high intensity sonic energy to said billet at a frequency which will establish a resonant vibration therein, thereby enhancing the ow of said billet into said cavity to form said part.

7. The method of forging a part from a billet comprising the steps of:

providing a die cavity adapted to be closed by means of the relative movement of a die member and a punch member;

placing said billet in the region between said die member and said punch member whereby said billet may be caused to iill said die cavity in response to said relative movement; thereafter closing said die cavity and thereby force said billet to fill said cavity; and concurrently imparting high intensity sonic energy to said billet at a frequency which will establish a resonant vibration therein, thereby enhancing the flow of said billet into said cavity to form said part.

8. In a method of forging a work piece in which a billet is caused to fill a closed die cavity in a die by au impact force imparted thereto, the improvement comprising:

generating high intensity sonic energy;

transmitting said sonic energy to an acoustic termination region substantially defined by said die and said billet; thereafter adjusting the frequency of said sonic energy to establish resonant vibration in said termination region; and thereafter withdrawing said work piece from said die cavity while continuing the transmission of said sonic energy at resonance, thereby enhancing the interface mobility of said die and said work piece and thus facilitate the withdrawal of said work piece from said die cavity.

9. The method of forging a part from a billet comprising the steps of:

forcing said billet into the cavity defined by a closed die, in response to the impact force of a moving ram; concurrently imparting high intensity sonic energy to said ram and to said billet at a frequency which will establish resonant vibration in the acoustic circuit comprising said ram and said billet; and

extracting said part from said cavity while continuing the impartation of said high intensity sonic energy at said resonant vibration frequency thereby facilitating the release of said part from said cavity as a result of the interface mobility therebetween caused by said sonic energy.

10. The method of forging a part having substantially finished dimensions from a billet comprising the steps of: providing a rio-draft die cavity adapted to be closed by means of relative movement between a die member and a punch member;

placing said billet in the region of said die member and said punch member whereby said billet may be caused to fill said die cavity in response to relative movement therebetween;

imparting relative movement between said die member and said punch member thus forcing said billet to till said cavity; concurrently transmitting high intensity sonic energy to said billet at a frequency which will establish a resonant vibration therein, thereby enhancing the ow of said billet into said cavity to form said part; thereafter opening said cavity by separating said die member and said punch member; and thereafter extracting said part from said cavity while maintaining the transmission of said high intensity-sonic, resonantfrequency energy thereto, thereby facilitating the release of said part from said cavity.

l1. In apparatus for forging a work piece in which a billet is caused to fill a closed die cavity in a die by thc force of a moving ram, the improvement comprising:

acoustic circuit means including said billet, fabricated from an elastically deformable medium; and

au orbiting mass oscillator having its output connected to said acoustic circuit means for continuously generating sonic vibrations at a frequency corresponding to the resonant frequency of said acoustic circuit means. 12. In apparatus for forging a work piece in which a billet is caused to lill a closed die cavity by the force of lo a moving rarn, the improvement comprising:

sonic wave transmission element connected to said ram;

and

an orbiting mass oscillator having its output connected to said transmission element for continuously generating sonic vibrations at a frequency corresponding to the resonant frequency of the acoustic circuit comprising said billet, said ram, and said transmission element.

13. In apparatus for forging a work piece in which a billet is caused to ll a closed die cavity in a die by the force of a moving ram, the improvement comprising:

a sonic wave transmission element connected to said die; and

an orbiting mass oscillator having its output connected to said transmission element for continuously generating sonic vibrations at a frequency corresponding to the resonant frequency of the acoustic circuit comprising said billet, said die, and said transmission element,

14. In apparatus for forging a work piece in which a billet is caused to fill a closed die cavity in a die by the force of a moving ram, the improvement comprising:

a rst sonic wave transmission member connected to said die;

a lirst sonic energy generator having its output connected to said lirst transmission member for establish ing a resonant vibration in said first transmission member and said die;

a second sonic wave transmission member connected to said ram; and

a second sonic energy generator having its output connected to said second transmission member for establishing a resonant vibration in said second transmission member and said ram.

1S. An apparatus for forging comprising:

a die having a die cavity therein;

a ram adapted to force said billet into said die cavity;

means for imparting relative motion between said ram and said die;

an adjustable-frequency sonic energy generator; and

a sonic energy transmission member having its input connected to said generator and its output connected to said die, and the frequency of said generator being adjusted to establish a resonant vibration in the acoustic circuit comprising said transmission member, said die, and said billet.

16. An apparatus as defined in claim 15 wherein said sonic energy generator comprises:

an orbiting mass oscillator, responsive to changes in the reactive impedance of said acoustic circuit to cause a corresponding shift in the frequency output of said oscillator and thereby maintain resonance in said circuit.

17. An apparatus as defined in claim 15 wherein said sonic energy transmission member comprises:

a metal bar having a high elastic compliance reactance as compared with the mass reactance of the remainder of said acoustic circuit,'said bar being supported at a velocity node region during resonance, and said input being at a low impedance region of said bar.

18. Apparatus for forging a part from a billet contpiising:

a stationary frame;

a part from a billet a die member defining a die cavity and adapted to be sonically vibrated;

means mounted on said frame for supporting said die member at nodal regions thereof;

ram means for forcing said billet into said die cavity;

and

variable frequency sonic energy generator means having its output connected to a low impedance region of said die member for establishing and maintaining a resonant sonic vibration in the acoustic circuit comprising said die member and said billet while said ram means forces said billet into said die cavity.

19. Apparatus for forging a part from a billet comprising:

a stationary frame;

a. die member defining a die cavity and adapted to be sonically vibrated;

means mounted on said frame for supporting said die member at nodal regions thereof;

ram means for forcing said billet into said die cavity;

a rst variable frequency sonic energy generator means having its output connected to a low impedance region of said die member for imparting a resonant sonic vibration to said die member; and

a second variable frequency sonic energy generator means having its output connected to a loW impedance region of said ram means for imparting a resonant sonic vibration thereto.

20. A sonically driven acoustic circuit for use in a closed die forging apparatus comprising:

a die member having a substantial mass inductance;

a sonic generator having a low impedance output;

a capacitive lumped constant member connected between said die member and said generator for completing a resonant acoustic circuit; and

a billet providing a resistive impedance in the termination region of said resonant acoustic circuit.

References Cited UNITED STATES PATENTS 2,382,045 8/ 1945 Flowers l--- 72--377 2,960,314 11/1960 Bodine f 74-86 X 3,002,614 10/1961 Jones 72-253 RICHARD I. HERBST, Prim'ary Examiner.

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