US3410351A - Sonic earth ripper bar with temperature gradient control - Google Patents

Description

Nov. 12, 1968 A. ca. BODINE 3,410,351

SONIC EARTH RIPPER BAR WITH TEMPERATURE GRADIENT CQNTROL 4 Sheets-Sheet 1 Filed June 2, 1965 Nov. 12, 1968 BQDINE 3,410,351

SONIC EARTH RIPPER BAR WITH TEMPERATURE GRADIENT CONTROL A. G. BODINE Nov. 12, 1968 SONIC EARTH RIPPBR BAR WITH TEMPERATURE GRADIENT CONTROL 4 Sheets-Sheet 5 Filed June 1965 A. G- BODINE NOV. 12, 1968 SONIC EARTH RIPPER BAR WITH TEMPERATURE GRADIENT CONTROL 4 Sheets-Sheet 4 Filed June 2, 1965 INVENTOR. 56 (2/ 2 613 odf/ze United States Patent 3,410,351 SONIC EARTH RIPPER BAR WITH TEMPERATURE GRADIENT CONTROL Albert G. Bodine, Los Angeles, Calif. (7877 Woodley Ave., Van Nuys, Calif. 91406) Continuation-impart of application Ser. No. 326,419, Nov. 27, 1963. This application June 2, 1965, Ser. No. 460,628

2 Claims. (Cl. 172-40) ABSTRACT OF THE DISCLOSURE An earth ripping device which has an elongated bar like tool ending in a digging point. Fluid driven vibration producing means is coupled to the tool and vibrations of a frequency equal to the resonant frequency of the tool are imparted thereto. Part of the driving fluid is used for cooling the tool and is entrained in a conduct formed in the tool and allowed to exit at the digger point or along the front side of the tool.

This application is a continuation-in-part of my prior applications Ser. No. 326,419, filed Nov. 27, 1963, now Patent No. 3,269,039 which patent is a continuation in part of application Ser. No. 163,802, filed Jan. 2, 1962, now abandoned.

This invention is concerned with sonic rock rippers, notably sonic devices for ripping rock in place in the earth, as is encountered in earth moving and rock cutting operations. This invention is concerned with a solution to serious temperature gradient problem which is unique to this particular kind of apparatus, and to an improvement which aids and facilitate the rock fracturing action.

Referring to the apparatus in its typical form, it employs a powered vehicle moving along the ground surface, Mounted on this vehicle is an acoustically resonant vibratory bar, driven by an acoustic wave generator. Typically this resonant bar has mounted on its lower extremity a penetration point, whose function is to apply high-density sonic energy to the earth and rock as the vehicle moves forward. The forward thrust of the vehicle holds the point forcibly or in a bias engagement against the rock. The penetration point has a very special function in that it acoustically couples the resonant bar, at a high level of energy density or concentration, into the earth and rock. A very special function here is a characteristic whereby this coupling point can be engaged against the rock with such force so to acoustically couple a large volume of the rock into a resonant system which includes the above mentioned resonant bar.

The type of acoustic coupling here is quite unique in that the acoustic coupling force is normally practically parallel to the surface of the ground. Moreover, this coupling effect is accomplished very near to the surface of the ground, usually progressing parallel to the surface of the ground, and only a few feet therebelow. The result is that the acoustic coupling results in a radiation of sonic energy into the rock and along a direction line somewhat parallel to the surface of the rock. In other words, in the forms of this invention where the acoustic energy is more or less longitudinal relative to the forward progression of the vehicle and relative to the top surface of the rock, we have an acoustic coupling condition wherein the sonic energy is being primarily transmitted along a path which tends to be parallel to the surface of the rock. This type of transmission of longitudinal sonic energy is very conscious of the fact that the surface of the rock behaves like a pressure release region.

By pressure release region I mean a condition wherein the forward and back elastic vibration of the point 3,410,351 Patented Nov. 12, 1968 results in an up and down vibration of the rock immediately in front of the point. In other words, when the point vibrates forward on each vibratory cycle, the rock tends to bulge up elastically momentarily on the forward half cycle at the surface a short distance ahead of the point. Conversely, when the point is pulled back on the succeeding half cycle, the upper surface of the rock tends to elastically spring down. The result is that this point then is conscious of a mechanical imepdance which is somewhat less than the acoustic imepdlance of the rock if it were a large infinite body into which the point is acoustically coupled. It is therefore important to note that this type of acoustic coupling is quite different from that in, say, an acoustic oil well drill, where the elastic bar is completely surrounded by rock deep down in the earth.

Under these condition the rock thus presents a somewhat lower acoustic impedance, and therefore it is able to accept very substantial acoustic energy from the point of the cutter tooth above mentioned. The result is that the rock around the region of the cutter tooth undergoes very substantial elastic vibration, with constant high energy elastic hysteresis. Moreover, in the normal practice of this invention, .the point as above described is made very sharp in relation to the cross-section of the elastic system into which it is coupled. Accordingly, the point itself is also a high-concentration region of sonic energy, in relation to the sonic energy being transmitted along the elastic member. The result is that the point itself and the rock immediately therearound are both undergoing very substantial elastic hysteresis action in response to the sonic vibration energy. This then causes a very considerable heating in the point, to the ultimate destruction of the point unless proper cooling is accomplished.

A further and more important disadvantage of this localized heating is that this results in a very extreme temperature gradient along the resonant bar. In this connection it should be noted that a substantial portion of the resonant bar is located above ground, which of course is quite different from the sonic drill above mentioned. Accordingly, with this rock ripper type of device, the sonic bar is conscious of an extreme temperature gradient. In other words, the upper portion of the bar runs very much cooler than the point region. This temperature gradient is very bad for the acoustic resonance characteristic, and also causes considerable trouble with the fatigue life of the bar.

This invention then consists, in combination with a sonic ripper bar (with its bad temperature gradient conditions), of a fluid path running along the bar, normally a passage drilled therethrough, for the purpose of flowing a cooling fluid down to the above mentioned point.

In a preferred form of the invention, the coolant fluid is discharged from the point, which is embedded in the rock, and a second benefit of very material importance accrues from this uuid injection. The type of vibration applied to a rock shoulder or ledge in the operation of the invention, in combination with the application of a forward bias force, results in the rapid development of cracks or fractures which go forward in the rock and turn up towards the surface of the rock a short distance ahead of the point. These upwardly inclined cracks become good paths for the flow fluid injected from the vibratory penetration point. As will be discussed in more particular hereinafter, the result is a rapid dissemination of fluid through the rock in the region where heating and cracking are taking place at a very high rate. The final consequence of the fluid injection is a promotion of the rock fracturing and cracking action that is desired, as to be set forth in more detail below.

The present invention is concerned with or makes use of certain phenomena in the field of acoustics, and a more complete understanding of the acoustic phenomena involved in the apparatus in which the invention is incorporated with be gained from a consideration of the following discussion.

Acoustic discussion Certain acoustic phenomena disclosed in the foregoing and hereinafter are, generally speaking, outside the experience of those skilled in the acoustics art. To aid in a full understanding of these phenomena by those skilled in the acoustics art, and by others, the following general discussion, including definition of terms, is deemed to be of importance.

By the expression sonic vibration I means 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 mass, this is sound wave transmission. Regardless of the vibratory frequency of such sound wave trans mission, the same mathematical formulae apply, and the science is called sonics. In addition, there can be elastically vibratory systems wherein the essential features of mass appear as a localized influence or parameter, known as a lumped constant; and another such lumped constant can be a localized or concentrated elastically deformable element, affording a local effect referred to various 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 such as mine, have cooperating and mutually influencing effects like equivalent factors in alternating-current electrical systems. In fact, in both distributed and lumped constant systems, mass is mathematically equivalent to inductance (a coil); elastic compliance is mathematically equivalent to capacitance (a condensor); and friction or other pure energy dissipation is mathematically equivalent to resistance (a resistor).

Because of these equivalents, my elastic vibratory systems with their mass and stiffness and energy consumption, and their sonic energy transmission properties, can be viewed as equivalent electrical circuits, where the functions can be expressed, considered, changed and quantitatively analyzed by using Well proven electrical formulae.

It is important to recognize that the transmission of sonic energy into the interface or work area between two parts to be moved against one another requires the above mentioned elastic vibration pheomena in order to ac complish the benefits of my invention. There have been other proposals involving exclusively simple bodily vibration of some part. However, these latter do not result in the benefits of my sonic or elastically vibratory action.

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, wholly new performances can be made to take place in the mechanical arts. The concept of acoustic impedance becomes of paramount importance in understanding performances. Here impedance is the ratio of cyclic force or pressure acting in the media to resulting cycle velocity or motion, just like the ratio of voltage to current. 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 accomplishment of desired ends, such as Where there is an interface. A sonic vibration transmitted across an interface between two media or two structures can experience 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 a system is desired. If the impedance are adjusted to be matched somewhat, energy transmission is made very effective.

Sonic enengy 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 or thousands of times the acceleration of gravity. This is because mathematically acceleration varies with the square of frequency. Accordingly, by taking advantage of this square function, I can accomplish very high forces with my sonic systems. My sonic systems preferably accomplish such high forces, and high total energy, by using a type of sonic vibration generator taught in my Patent No. 2,960,- 314, which is a simple mechanical device. The use of this type of sonic vibration generator in the sonic system of the present invention affords an especially simple, reliable, and commercially feasible system.

An additional important feature of these sonic circuits is the fact that they can be made very active, so as to handle substantial power, by providing a high Q factor. Here this 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. Circuit-wise, 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.

Certain definitions should now be given:

Impedance, in an elastically vibratory system, is, mathematically, the complex quotient of applied alternating force and linear velocity. It is analogous to electrical impedance. The concise mathematical expression for this impedance is Where M is vibratory mass, C is elastic compliance (the reciprocal of the stiffness, or of modulus of elasticity) and f is the vibration frequency.

Resistance is the real part R of the impedance, and represents energy dissipation, as by friction.

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

Mass reactance is the positive imaginary part of the impedance, given by 21rfM. It is analogous to electrical inductive reactance, just as mass is analogous to inductance.

Elastic compliance reactance is the negative imaginary part of impedance, given by l/21rfC. Elastic compliance reactance is analogous to electrical capacitative 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) becomes 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.

A valuable feature of my sonic circuit is the provision of enough extra elastic compliance reactance so that the mass or inertia of various necessary bodies in the system does not cause the system to depart so far from resonance that a large proportion of the driving force is consumed and Wasted in vibrating this mass. For example, a mechanical oscillator or vibration generator of the type normally used in my inventions always has a body, or carrying structure, for containing the cyclic force generating means. This supporting structure, even when minimal, still has mass, or "inertia. This inertia could be a forcewasting detriment, acting as a blocking impedance using up part of the periodic force output just to accelerate and decelerate this supporting structure. However, by use of elastically vibratory structure in the system, the elfect 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 the resistive component of the impedance.

Sometimes it is especially beneficial to couple the sonic oscillator at a low-impedance (high-velocity vibration) region, for optimum power input, and then have high impedance (high-force vibration) at the work point. The sonic circuit is then functioning additionally as a transformer, or acoustic lever, to optimize the effectiveness of both the oscillator region and the work delivering region.

For very high-impedance systems having high Q at high frequency, I sometimes prefer that the resonant elastic system be a bar of solid material such as steel. For lower frequency or lower impedance, especially where large amplitude vibration is desired, I use a fluid resonator. One desirable specie of my invention employs, as the source of sonic power, a sonic resonant system comprising an elastic member in combination with an orbiting mass oscillator or vibration generator, as above mentioned. This combination has many unique and desirable features. For example, this orbiting mass oscillator has the ability to adjust its input power and phase to the resonant system so as to accommodate changes in the work load, including changes in either or both the reactive impedance and the resistive impedance. This is a very desirable feature in that the oscillator hangs on to the load even as the load changes.

It is important to note that this unique advantage of the orbiting mass oscillator accrues from the combina tion thereof with the acoustic resonant circuit, so as to comprise a complete acoustic system. In other words, the orbiting mass oscillator is matched up to the resonant part of its system, and the combined system is matched up to the acoustic load, or the job to be accomplished. One manifestation of this proper matching is a characteristic whereby the orbiting mass oscillator tends to lock in to the resonant frequency of the resonant part of the system.

The combined system has a unique performance which is exhibited in the form of a greater effectiveness and particularly greater persistence in a sustained sonic action as the work process proceeds or goes through phases and changes of conditions. The orbiting mass oscillator, in this matched-up arrangement, is able to hang on to the load and continue to develop power as the sonic energy absorbing environment changes with the variations in sonic energy absorption by the load. The onbiting mass oscillator automatically changes its phase angle, and therefore its power factor, with these changes in the resistive impedance of the load.

A further important characteristic which tends to make the orbiting mass oscillator hang on to the load and continue the development of effective power, is that it also accommodates for changes in the reactive impedance of the acoustic environment while the work process continues. For example, if the load tends to add either inductance or capacitance to the sonic system, then the orbiting mass oscillator will accommodate accordingly. Very often this is accommodated by an automatic shift in frequency of operation of the orbiting mass oscillator by virtue of an automatic feedback of torque to the energy source which drives the orbiting mass oscillator. In other words, if the reactive impedance of the load changes this automatically causes a shift in the resonant response of the resonant circuit portion of the complete sonic systern. This in turn causes a shift in the frequency of the orbiting mass oscillator for a given torque load provided by the power source which drives the orbiting mass oscillator.

All of the above mentioned characteristics of the orbiting mass oscillator are provided to a unique degree by this oscillator in combination with the resonant circuit. As explained elsewhere in this discussion the kinds of acoustic environment presented to the sonic source by this invention are uniquely accommodated by the combination of the orbiting mass oscillator and the resonant system. Accordingly, this combination is an important specie. As will be noted, this invention involves the application of sonic power which brings forth some special problems unique to this invention, which problems are primarily a matter of delivering effective sonic energy to the particular work process involved in this invention. The work process, as explained elsewhere herein, presents a special combination of resistive and reactive impedances. These circuit values must be properly met by a resonant system in order that the invention be practiced effectively.

The invention will be better understood from the following detailed descritpion of a number of representative and illustrative embodiments thereof, reference for this purpose being had to the accompanying drawings, in which:

FIG. 1 is a perspective view of a dozer equipped with improvements in accordance with the invention;

FIG. 2 is a vertical longitudinal section taken transversely through the dozer blade of the apparatus of FIG. 1 and showing a vibratory bar in side elevation;

FIG. 3 is a sectional view of the vibration generator of FIGS. 1 and 2, taken on broken line 33 of FIG. 4;

FIG. 4 is a sectional view taken on broken line 4-4 of FIG. 3;

FIG. 5 is a view similar to a portion of FIG. 2, with mounting arrangements for the vibratory bar shown in section;

FIG. 6 is a diagrammatic view showing a representative action of the vibratory bar of the apparatus on a shoulder or ledge of rock engaged thereby;

FIG. 7 is a perspective view of a ripper bar machine incorporating improvements in accordance with the invention;

FIG. 7a is a longitudinal medial sectional view of a ripper bar;

FIG. 8 is a longitudinal sectional view through the upper, rearward extremity of a bar of the machine of FIG. 7, showing the generator in elevation and the generator casing in section;

FIG. 9 is a diagrammatic side elevational view of a modified type of vibratory bar of the invention, in typical engagement with a shoulder of bedrock during the ripping operation, and including a standing wave diagram representing the vibratory lateral wave pattern in the bar; and

FIG. 10 is a fragmentary and partially sectioned enlarged detailed view of a portion of FIG. 9.

In FIGS. 1-6, I have shown a dozer equipped with improvements in accordance with the invention. The dozer, generally indicated by the numeral 40, may be entirely of a conventional type excepting for addition of sonic vibration means in accordance with the invention. Thus it may comprise a two-wheeled transport vehicle 41, equipped in the usual manner with push arms 42 projetcing forwardly of the vehicle and carrying at their forward ends a concave dozer blade 43.. The frameworksupporting blade 43 includes upright end walls 44 secured to the forward ends of push arms 42, as shown. Halfwavelength vibratory bars 45 project downwardly and forwardly through suitable apertures in blade 43, being mounted at their midpoints in a mounting fixture 46 secured to the rearward side of the blade. In the illustrative design, the rearward half portions of the bars 45 are tubular in form, while the forward half portions thereof are of square cross-section, as illustrated. The juncture between the two may be at a shoulder 47, seen best in FIG. 5. The forward extremities or points 48 of the bars are beveled to an edge 49. The rearward ends of the bars carry vibration generators 50, details of an illustrative form of which will be presently described. The bars are clamped at their midpoints by means of split, tapered collets 52, fitting in a tapered opening 53 in a mounting ring 54, screws 55 serving to draw the collet toward the ring 54 and thereby contract the collet to tightly engage the cylindrical portion 45a of the bar. Mounting ring 54 has a flange 56 abutting the rearward wall 57 of mounting fixture 46, and screws 58 passing through flange 56 and threaded into wall 57 complete the mounting of the bar.

The cylindrical half portion 45a of each bar, together with its vibration generator 50, are enclosed by a cylindrical case 59, the forward end of which may have a flange 60 secured to the flange of mounting ring 54, as shown. Casing 59 is pressure-tight, and carries air under pressure for operating of generator 50. Air under pressure is introduced to the casing via a conduit 62 coupled into the head of casing 59 as at 63. The air pressure in casing 59 is moderate, not being over the order of 100 pounds per square inch. The splits 52a in collet 52 are narrow, and effectively closed against leakage of air pressure when the collet is clamped tightly in place. However, to guard against possible leakage, a sealing O-ring 64 may be placed in the bottom of ring 54 below the lower end of the collet.

Air supply condiuts 62 lead from a header 65 (FIG. 1), supplied with air under suitable pressure from an air compressor plant generally indicated by the numeral 66.

The vibration generator 50, in a preferred illustrative form, is shown in detail in FIGS. 3 and 4. A cylindrical casing 68, having an inturned head flange 69 at the top over which is a cover 69a, snugly receives a body 70 having a circular head wall 71 at the top and a circular bottom wall 72 at the bottom, the peripheries of these walls being sealed to casing 68 as by O-ring seals as shown. Body 70 extends the full width of the casing 68 as seen in FIG. 4, but in the aspect of FIG. 3 is narrowed to form a bridge-like intermediate Wall 73, affording air chambers 74 on each side thereof as shown.

Bridge wall 73 is formed with a pair of horizontally spaced horizontal bores 82 and side plates 83, secured to wall 73 as by screws 84, have cylindrical plugs 85 extending into bores 82 and pressure sealed therein as by means of O-ring seals, as shown. The inner ends of opposed plugs 85 are spaced, as shown, and disposed in the bores 82 with a close fit between the plugs 85 are race rings 87. The cylindric chamber inside each ring 87 contains a cylindrical inertia rotor 91, of a diameter preferably somewhat greater than the radius of the inner diameter of the ring 87, and of slightly less width than the distance between opposed plugs 85. A plurality of air channels or grooves 92 are cut in opposite sides of each of rings 87, and these are directed tangentially to the chambers 90. These grooves act as air nozzles, introducing air under pressure to chamber 90 in tangential directions in a manner to drive rotor 91 orbitally about the inner periphery of ring 87.

The outer ends of nozzle grooves 92 are in communication with channels 95 formed in wall 73 around plugs 85. Pressure air is introduced to channels 95 via bores 96 extending upwardly therefrom through the upper end of body 70 to the space 97 inside casing flange 69. Air under pressure enters the latter chamber through slots 98 formed in casing flange 69. It will be recalled that the space around the generator contains pressure air, and this pressure air enters via the slots 98, and is led to and through the nozzle groove 92 into rotor chamber 90 as already described. Spent air leaves chamber 90 via ports 99 centrally located in plugs 85. This air thus passes to chambers 74, and thence flows through a transverse passage 100 in the bottom portion of wall 73 to a vertical passage 101 formed in a tubular stem 102 extending downwardly from body 70.

Stem 102 is tightly mounted in the upper end of cylindrical bar portion 45a, as shown. The lower portion of stem 102 has a taper-threaded portion 103 which is engaged with taper threads 104 formed in member 45a. Above threaded section 103 is a portion 105 of reduced diameter, at the top of which is a portion 106 of increased diameter snugly fitting in the entrance opening to tubular member 45a. In addition, the upper end of member 45a engages firmly under generator body 70. The juncture as thus described is firm and secure notwithstanding the vibratory action which it must undergo in service.

It will be observed that the nozzle grooves 92 are so directed as to introduce pressure air into chambers 90 with opposite directions of spin. The jets of air issuing from grooves 92 spin circularly about the chambers 90, and, impinging on the rotors 91, drive them in opposite directions at a relatively high spin frequency in orbital paths guided by the inner surfaces of race rings 87. Sonic wave generators of this general class were disclosed and claimed in my prior Patent No. 2,960,314, issued Nov. 15, 1960. The operation thereof will, however, be briefly explained herein. In general, pressure fluid introduced into the two inertia rotor chambers 90 causes orbital motion of the two inertia rotors 91, each of which exerts a centrifugal force on its corresponding race ring 87. The rotating force vectors so exerted on the race rings are of course transmitted to the body 70, and thence to the longitudinal bars 45. The rotors 91 are automatically synchronized to operate in like phase, i.e., so that the rotors have their vertical components of motion in step with one another, as presently to be described. Incidentally, it will be seen that owing to opposite spin directions, the rotors, if synchronized, must move with horizontal components of motion in step with one another, but always in opposed directions, with desirable consequence that laterally exerted components of force are always equal and opposed and therefore balanced out. Synchronization of the rotors 91 results from their being connected through the generator body 70 with the longitudinally elastic vibratory bar 45. When the inertia rotors are driven by the pressure fluid at a spin frequency approaching or approximating the resonant frequency of the bar 45 for the described mode of half-wave longitudinal standing wave vibration, the bar 45, as a result of some initial force impact received from the generator, is started into its longitudinal mode of standing wave vibration. The generator 50 on the end of the bar 45 then undergoes longitudinal vibration at the standing wave frequency of the bar 45. As a result of this longitudinal vibration of the generator the rotors 91 begin to synchronize automatically with one another. As the rotors come into better and better phase correspondence as a result of this action, the standing wave in the bar 45 becomes stronger and stronger. The process builds up until bar 45 vibrates at its maximum amplitude and rotors 91 are perfectly synchronized.

Briefly summarized, therefore, the vibration generator 50 applies to the rearward end of the bar 45 an alternating force directed longitudinally thereof, and is regulated to do so at the frequency for half-wave longitudinal standing wave vibration of the bar. It is of course necessary that the air pressure delivered to the vibration generator be such as will drive the inertia rotors 91 at a spin frequency approximating a half-wavelength vibration frequency of the bars. When this has been accomplished, the rotors 91 lock in at the resonant frequency in synchronism with one another.

Exhaust air is preferably discharged from the vibration generator by being conducted through a conduit 108 in the bar 45 to a discharge orifice 109 in the beveled extremity 48 of the bar. The air jet issuing from this discharge orifice acts to stir up and blow away from the point of attack earthen material loosened by the bar. This air also cools the bar, and particularly the point thereof, which tends to heat very surprisingly during service.

It will be understood that the sonically vibrating bars 45 act to disintegrate the earthen material ahead of the scraper blade. The earthen material thus disintegrated or broken up ahead of the blade is handled by the latter with greatly increased ease.

The vibratory bars need not be synchronized with one another. However, using vibration generators of the type shown in FIGS. 3-5, they will do so automatically as a result of the intercoupling provided therebetween through the blade 43. While the vibratory motion of the blade as a consequence of vibration of bars 45 is minimal, there is enough vibration at this point to exert a synchronizing effect on the several bars.

It will be seen that, as illustrated in FIG. 2, a resonant vibratory bar 45 has a point 48 thereof oriented for forward progression against a rock ledge L as the vehicle moves forward. This forward progression keeps the point 48 in forcible or bias engagement with the rock, and actually embedded therein. Moreover, it will be noted that if a longitudinal resonant wave is established in the resonant bar 45, this will tend to deliver longitudinal vibrations at point 48 which have their vibration excursion along practically the same path as the forward travel of the bar. This keeps the bar acoustically coupled very effectively for this type of longitudinal energy, because the forward travel of the vehicle is in somewhat the same direction as the longitudinal vibration.

I have found that this type of longitudinal vibration in combination with the longitudinal biasing force results in the formation of rapidly occurring cracks or fractures c which go forward in the rock and turn up towards the surface s of the rock some short distance ahead of the point (see FIG. 6). These upwardly-sloping cracks then become very good paths for the flow of liquid which is introduced into the region of the point from the conduit or passage 108. The result is, then, a very rapid dissemination of fluid through the rock in the region where heating and cracking is taking place at a very high rate. It should be noted that this phenomenon is quite different from the sonic oil well drill, wherein these upward-sloped rock crack paths do not take place.

Thus the fluid issuing from the point 48 tends to flow somewhat along the same pathway as does the pressure release path of sonic energy which is going from the point and also causing flow of sonic energy upward in a direction towards the surface of the rock some distance ahead of the point. This sonic pressure release phenomenon is due to the fact that the surface of the rock is unconfined, and is a region of low acoustic impedance, large vibration amplitude, and large wave reflection. In other words, this pressure release effect is due to the fact that the longitudinal sonic energy is being transmitted into the rock, somewhat parallel to the surface thereof, and most importantly of all, up close to the surface. This close proximity of the surface of the rock then functions as a sonic force or pressure release region which tends to spring up and down in sympathy with the fore and back motion of the resonant pattern in the elastic bar. Again, as pointed out above, the important point here is that fluid is delivered into virtually the same path as the pressure release flux path of the sonic energy. The result is a very rapid fatigue of the rock because this fluid going into these cracks further increases the acoustic mismatch, so that the cracks become localized regions of high relative motion of the rocks relative to the surface on each side of the crack.

In order words, these cracks in the rock can be made a very effective stress raising region due to relative motion of the rock on each side of the crack, particularly due to the impedance mismatch encountered by a sound wave going through the rock and reaching such a crack region. The point here is that the introduction of fluid into the crack very greatly increases its acoustic impedance mismatch. This effect is very greatly increased by the fact that the phenomenon is taking place in a generally or largely horizontal path running along close to the surface of the rock.

Referring again to the figure, it will be noted that the fluid passage 108 runs for a substantial length of the resonant bar 45. The result is that the temperature of this resonant bar is held much more uniform :by virtue of the fact that there is fluid flowing rapidly therethrough. Without this provision the lower region of the bar becomes very much hotter than the upper region, because the upper region is primarily located above the ground. The lower region, of course, becomes quite hot because this is the region where the sonic energy is dissipated by virtue of delivering sonic energy into the point and on into the rock.

Without this transmission of cooling fluid through the bar, particularly to the region where the heat is generated, the elastic hysteresis of the rock and the elastic action of the tooth material both combine to generate a high local temperature at the lower end of the bar. The result is then that the bar is subjected to a very large temperature gradient, unless this lower end is cooled by virtue of transmitting fluid thereto. This temperature gradient, as above described, is very bad in that it causes thermal stresses through the bar which greatly reduce its fatigue life, so that the ability of the bar to transmit sonic energy, particularly the ability of the point to transmit such sonic energy, is very greatly reduced because of the heating effect.

In addition, this heating effect very greatly reduces the rigidity of the lower region, particularly around the point, so that this region becomes very much more a plastic and nonelastic material. The result is then that the bar itself becomes an influence which greatly reduces the Q of the resonant system, solely because of this softening of the lower end of the bar. The lower end of the bar becomes a hot, annealed, low-hardness material having high internal damping, with a very great and highly undesirable reduction in the acoustic Q of the over-all circuit.

FIGS. 7 and 8 show an illustrative application of the invention to a ripper bar machine. A two-wheeled vehicle has a fairly heavy platform 121 which includes a rearward portion 122 mounting a pair of ripper bars 123, and a forward portion 124 coupled as at 125 to the drag element 126 of a tractor machine, not shown. It will be understood that the element 126 is designed for vertical adjustment to accomplish proper engagement of the lower extremities of bars 123 with the earth, or to elevate the bars 123 sufficiently for adequate road clearance during towing when not in service.

The bars 123 are again half-wavelength standing wave vibration members, being tightly mounted at or near their midpoints in fittings 128 secured to platform 121 in positions inclined somewhat rearwardly from vertical, as clearly shown. The forward extremities or points 129 of the bars 123 are beleved, as indicated, and their rearward or upper extremities carry vibration generators 130, which may be of the same type shown in FIGS. 3 and 4. Refering to FIG. 8, generator casing 132 is snugly embraced by pressure-tight casing 133, including: dome 134 into which is coupled air supply conduit 135 leading from a suitable compressor plant, not shown. The tubular air discharge and mounting stern 136 of the generator is fitted tightly in the upper end of bar 123, and air is exhausted via passage 137 or conduit in the bar leading first down and through the point 129, and then back up to a discharge orifice 129a in the upper portion of the leading edge of the bar.

The generators will be understood to be operated to set up half-wavelength standing wave vibration of the bars 123. In operation, platform 121 is manipulated to engage the relatively sharp edges 138 on. the forward and lower extremities of the bars with the earth, causing ripping and disintegration of the earth material ahead of the bars in accordance with principles heretofore explained.

It may here be noted that the form of vibration generator shown in FIGS. 3 and 4, enclosed in a casing and filled to the ends of vibratory bars as indicated in FIG. 8, may be used for the generators 50 of FIGS. 1 and 2.

Reference is next directed to FIGS. 9 and 10 showing application of the invention to a ripper bar of a laterally vibratory type, disclosed in my prior and copending application Ser. No. 402,136, filed Oct. 7, 1964, and entitled Method and Apparatus for Ripping Rock. Said application Ser. No. 402,136 furnishes a complete disclosure of a rock ripping machine using such a laterally vibratory ripper bar, and the disclosure thereof is incorporated herein by this reference. In such a machine, a generally vertically disposed elastically vibratory bar or shank 140 is mounted on a powered vehicle, not shown, and bears at its lower end a rock-engaging point 141 which is pinned to a tooth 142 welded in the toe of the shank. The bar supports at its upper end a vibration generator 144, which generates a component of vibration laterally of the length of the bar. A suitable generator is shown in my aforesaid application Ser. No. 402,136, and in more detail in my applications Ser. Nos. 181,385 and 258,216, all incorporated herein by this reference. The frequency of the generator is such as to produce a lateral standing wave pattern such as represented at st in FIG. 8. The bar is largely diagrammatically depicted in FIG. 9, and mounting means for the bar on the vehicle is designated at 149. This mounting means supports a pin 150 which is fixed in the bar 140 substantially at the location of a node N' of the standing wave st. The draw bar pull of the vehicle on the bar 140 is also exerted through this pin 150; and a compression spring 152, mounted on the vehicle by means not here illustrated, exerts a forward spring bias force on the bar between the node N and its lower end. 3

In the set-up as illustrated, the lower node N in the bar is spaced a short distance above the point 141, and the latter therefore has a lateral (generally horizontal) direction of vibration, of high force magnitude, but relatively low amplitude, as may be seen from a consideration of the standing wave pattern. The vibratory tooth, in engagement with the rock ledge or shoulder, and with the bias force application as indicated, has a very effective rock ripping action. Cooling and fluid injection features of the present invention are in this case supplied by an external fluid conduit 160 coupled as at 161 to a fluid passage opening rearwardly through the heel of the bar 140 and extending laterally through the bar and out through the tooth 142 to fluid discharge orifices 163 leading outward through the point 141. The fluid supply conduit 16%) leads from a source of coolant, not shown, and the coolant can be either a gas or a liquid, and can be at reduced temperature for necessary cooling in cases of extreme difliculty with heating. It might be mentioned here that the generator of FIGS. 3 and 4 has been spoken of as air-driven, but it can also be liquid-driven, with improved coolant properties resulting from the use of the liquid to cool the point. The machines of FIGS. 1-6 and 7, 8 may also use separate sources of fluid for cooling the point and for fluid injection into the rock. In this connection, a separate conduit can be used, rather than any drilled passage in the resonant bar.

A number of illustrative embodiments and applications of the invention have now been illustrated and described, It will of course be understood that these are merely for illustrative purposes, and that various changes in design, structure and arrangement, as well as many additional applications to other forms of earth moving machinery, are within the spirit and scope of the invention and are intended to be included within the scope of the appended claims.

I claim:

1. In a sonic rock ripping machine, the combination of a vehicle arranged for traveling along the surface of the ground;

an elastically vibratory bar member, having a resonant frequency range, mounted on said vehicle and having a portion of its vibratory structure located above the ground surface;

a sonic oscillator acoustically coupled to said vibratory bar member and being operable in the resonant frequency range of said member, whereby said member undergoes resonant vibration;

an earth-engaging point formed on one end of said vibratory bar member and oriented for forwardly engaging the earthen formation in response to said travel of said vehicle;

said resonant vibration having a component of motion substantially parallel to the ground surface; and

a conduit being formed in said bar member and constituting a passage extending through said bar member for conducting cooling fluid to said point.

2. The subject matter of claim 1, including fluid drive means for said oscillator, with fluid inlet and exhaust connections thereto, and wherein said fluid exhaust connection leads to said passage in said bar member.

References Cited UNITED STATES PATENTS 4/1962 Bodine 37195 4/1966 Bodine l72-1 X

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