US3770322A

US3770322A - Apparatus for fracture of material in situ with stored inertial energy

Info

Publication number: US3770322A
Application number: US00133262A
Authority: US
Inventors: Delwin E Cobb; Carl L Kepner; Albert L Woody; Wayne E Roberts
Original assignee: Caterpillar Tractor Co
Current assignee: Caterpillar Inc
Priority date: 1971-04-12
Filing date: 1971-04-12
Publication date: 1973-11-06
Anticipated expiration: 1990-11-06
Also published as: CA962837A; DE2216656C2; IT952574B; JPS5759375B1; DE2216656A1; AR207541A1; SE418207B

Abstract

An earth working apparatus employs large amounts of stored energy which is cyclically delivered on demand to the work tool. The energy is stored in a large flywheel and delivered by suitable transmission means to the work tool.

Description

United States Patent 1 Cobb et al.

[ APPARATUS FOR FRACTURE OF MATERIAL IN SlTU WITH STORED lNERTlAL ENERGY [75] Inventors: Delwin E. Cobb; Carl L. Kepner;

Wayne E. Roberts; Albert L. Woody, all of Peoria, 111.

[73] Assignee: Caterpillar Tractor Co., Peoria, 111.

[22] Filed: Apr. 12, 1971 [21] Appl. No.: 133,262

[52] US. Cl 299/37, 37/DlG. 18, 172/40,

299/14 [51]' Int. Cl A01b 35/00 [.58] Field of Search 172/40; 37/D1G. 18, 37/141 R, 141 T; 299/14, 37, 67; 198/10; 173/122 [56] References Cited UNITED STATES PATENTS 3,238,646 3/1966 Oldenburg ..37/141R 1 1 Nov. 6, 1973 3,293,778 12/1966 McAuliff 172/40 X 3,645,021 2/1972 Sonerud 37/141 T 3,367,716 2/1968 Bodinc 299/14 3,437,381 4/1969 Bodinc.. 299/14 X 3,443,327 5/1969 Martin 172/40 X 3,633,683 1/1972 Shatto 299/14 X Primary Examiner-Ernest R. Purser Attorney-Charles M. Fryer et al.

[57] i ABSTRACT An earth working apparatus employs large amounts of stored energy which is cyclically delivered on demand- ,to the work tool. The energy is stored in a large flywheel and delivered by suitable transmission means to the work tool.

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SHEET 1,70? 17 ENTORS DELWIN .COBB

- CARL KEPNER WAYNE ROBERTS BY ALBER WOODY I TORNEYS APPARATUS FOR FRACTURE OF MATERIAL IN SITU WITH STORED INERTIAL ENERGY BACKGROUND OF THE INVENTION This invention relates to earth moving and fracturing implements and pertains more particularly to a high energy mechanical apparatus for the storage and instantaneous delivery of high levels of energy to an implement for the fracturing or separation in situ of hard rock and other earth materials or the like.

A considerable amount of hard rock must be fractured yearly for the construction and mining industries. Most of this rock today'is fractured by drilling with percussion o'r rotary drills and blasting with dynamite or ammonium nitrate. This technique is expensive, slow, noisy and dangerous.

Mechanical tractor drawn rippers have been developed which will operate efficiently in relatively soft, weathered, flssured, layered or previously blasted rock. However, such rippers will not operate in hard rocks.

One of the major problems with theuse of rippers is the high forces that must be induced in rock and similar hard material to cause it to fracture. This necessitates the delivery of very high force and energy to the face of the rock or other material to be fractured or separated. Vehicles capable of delivering such forces statically would of necessity be enormous in size and cost and would thus be impractical.

Many exotic techniques have been proposed for fracturing earth formations. Such proposed techniques include sonic energy, electrical spark, water cannon, and others. Such techniques have shown the ability to fracture rock formations but have proven in most cases inefficient for commercial application. g

One such sonic technique is the employment of a resonant vibratory system. This system stores vibratory energy in a spring which may take many forms. The energy is thencyclically delivered to a vibrating tool at the resonant frequency of the system. The major problem with this system is that a spring large enough to store adequate energy would be too large to be practical. Another problem is that frequency is critical and varies with load such that there is a majorproblem of control.

Other proposals have been made to apply vibratory energy to an earth working implement. Such proposals have generally met with failure for one reason or another.

Air and hydraulic hammers are impractical because of their low efficiency. Such large amounts of energy are required to vibrate a tool for breaking rock that unreasonably large amounts of input power would be required.

The present invention is based on the application of the theory that a dynamic system is desirable for cutting and breaki'ngrock and other materials since large forces can be produced with a small average thrust. This is an important feature when the average thrust is limited by tractive effort and weight of a vehicle.

The average force will be proportional to the time the force is applied. For example, if 100,000 lb is applied for 1/10 of a second every second, the needed average force will be only 10,000 lb. The basic idea then is to put the desired force on and unload again as quickly as possible so that during most of the cycle the force is zero or small. If this can be done the average force, compared to the peak force, will be small. If it is as sumed that the work done in breakng rock does not depend on the rate of loading, then the total work and average power will not be affected by this pulse type of loading.

The peak power requirements, however, will belarge if the work is done in short pulses. This means that large amounts of energy have to be available to be released quickly when needed. For a flywheel-crank system most of the energy is stored as kinetic energy in the flywheel. For a vibrating mass-spring system, the energy cycles back and forth from potential energy in the spring to kinetic energy of the mass. In either case the force that can be developed by the tool is limited by the stored energy.

Large amounts of energy have to be available to produce large forces quickly. The reason for this is that the tool has to penetrate into the rock or soil before the needed force can be developed. If the rock or soil were rigid, little energy would be required. But since they act much like a spring, energy has to be released in order to develop the required force. As an example, assume that a tool in rock has a spring rate of 6 X 10*lb/in. and

the breaking force is 6 X 10 pounds. In this case, 30,000 in-lb of energy will be needed to break out a chip. If this is done at a frequency of 20 times a second then 91 horsepower will be required.

In the subject invention as applied to a ripper, the work that the ripper performs is of an intermittent nature, taking place only during a small part of the time required for the driving shaft of the ripper to make a complete revolution. Since the material being fractured is extremely hard, the instantaneous demand of the rippers exceeds that of the drive motors. Therefore, a flywheel or flywheels are placed on the drive shaft to store sufficient'energy to meet peak demands. During a greater part of the revolution of the driving shaft, the

motor power is used to accelerate the speed of the flywheel. During the part of the revolution when the work is done, the energy thus stored up in the flywheel is given out at the expense of its velocity. As the velocity of the flywheel changes, the energy it will absorb or give up is proportional to the difference between the squares of its initial and final speeds and is equal to the difference between the energy which it would give out if brought to'a full stop and that which is still stored in it at the reduced velocity. Hence E A I ("1 "2 n (21rN,/60) (1r N,/30) n 'n' N /30 I W Klg E A (W Klg) (11 /30 (N, N E (W K /5873) (N N,) E Energy release (ft. lbs) I Movement of inertia of rotating mass in lb. ft.

sec. W Weight (lbs) G Gravity 32.2 ft./sec./sec. at seal level K Radius of gyration in feet N,'= Revolutions per minute (RPM) before any energy has been given out N Revolutions per minute (RPM) at end of period during which energy has been given out n,= Angular velocity radian/sec. before any energy is given out n Angular velocity radian/sec. at end of period during which energy has been given out W K is a measure of the energy potential of a flywheel system in lb.-ft. at a given RPM and can be determined by the formula This formula is a derivative of the above formula for energy.

Extensive computer and soil bin model tests have been conducted on the subject concept as applied to a ripper. A model impact ripper has been built and tested in various rock materials to determine the feasibility of fracturing hard rock with an impact device constructed in accordance with the present invention. The performance criterion for the model was specific energy, and is defined as the amount of energy (in.-1bs.) required to fracture a unit volume (in?) of rock. Specific energy permits one to determine the amount of power necessary to obtain a given production (yd. /hr.) in a certain rock material. The specific energy of rocks vary.- The specific energy is calculated according to the following equation:

SE. N E D/W where SE. Specific energy (in.-lb./in.

N Number of impacts during a run D Density of rock (I ./in.')

W Weight of rock removed during a run (lbs) E Average Energy per blow (in.-lbs.)

It should be noted that the parameters must be considered collectively with a unique relationship existing between one another. The specific energy of the material being fractured is a significant factor.

With a steel spring of the type needed in a resonant system (a ripper shank, bar, spring), the maximum amount of potential energy that can be stored in a cubic inch of spring material is:

where S is the maximum axial stress that the material can endure and E is the modulus of elasticity. For a working stress of 40,000 psi of a spring material then, the stored energy will be (4 X lO) /(2) (30 X 80/3 26.7 in.lb./in. In a vibrating system using a column of uniform cross section for example, the maximum stored energy will be one-half of this value since the column will not be uniformly fully stressed throughout its length.

In contrast, a flywheel, can store much more energy than this'per cubic inch of steel. Use a thin annular ring rotating about its polar axis as an example. The tangential stress in the rotating ring is given by the equation:

In this case, w is the mass density of the ring, r is the radius, and n is the angular velocity. The kinetic energy in the ring'due to its velocity will be:

Where V is volume of ring. V l in. I(.E. A S 20,000 in.lb. for S 40,000 psi The ratio between flywheel and spring energies is, therefore at least: 20,000/13.35 or 1500 to 1. In other words, 1500 times more energy can be stored in the flywheel than in an equivalent amount of steel spring for a given stress level. In addition, the stress in the spring is fully reversed each cycle, while the stress in theflywheel at most goes from zero to the maximum cycle. Reversing thestress in the spring energy cycle can adversely affect the fatigue life of the spring.

In order to work the above ring at 40,000 psi, the flywheel would have to be quite largeor else rotate at a high speed. If the speed is limited to 1200 rpm with a wheel radius of 15 in. and a resulting stress of only 2600 psi, the energy in a cubic inch of the steel ring will be 1300 in.-lb. for an energy ratio of about I00. This is less than the 1500 ratio, but it is still a substantially significant advantage.

For breaking rock in situ in quantity, large forces and power are required. This means large energies per blow and many blows per minute. The prior art systems have been unable to meet these requirements.

The primary object of the present invention is to provide an earth working implement that is rugged and efficient and overcomes the above disadvantages of the prior art.-

Another object of the present invention is to provide an'earth working apparatus that is capable of storing large amounts of energy and selectively applying it to an earth working implement.

A further object of the present invention is to provide a dynamic system that is capable of delivering sufficient energy to a tool for earth working to be practical.

A still further object of the present invention is to provide a mechanical dynamic system that is capable of efficiently delivering high energy pulses to an earth working tool.

In accordance with the present invention large amounts of inertial energy is stored in a massive flywheel to be cyclically delivered to an earth working implement at peak power demand. Suitable transmission means including a crank and connecting rod is used to transmit the energy to an earth working implement such as a ripper.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects and advantages of the present invention will become apparent from the following description when read in conjunction with the accompanying drawings in which:

FIG. 1 is an elevational view partially in section of a rock ripper incorporating a preferred embodiment of the present invention;

FIG. 2 is a plan view partially in section of the embodiment of FIG. 1;

FIG. 2a is a section taken along lines IIa-IIa of FIG. 1;

FIG. 3 is a sectional view taken along lines III-III of FIG. 1;

FIG. 4 is a sectional view taken along lines IV-IV of FIG. 2;

FIG. 5 is a sectional view taken along lines V-V of FIG. 2;

FIG. 6 is a sectional view taken along lines VI--VI of FIG. 2;

FIG. 7 is a sectional view taken along lines VII-VII of FIG. 2;

FIG. 8 is a sectional view taken along lines VIIIVIII of FIG. 2;

Claims

1. A mechanical system for imparting energy intermittently to an earth working implement, said system comprising: an implement for separating portions from an earth formation; means for supporting and manipulating said implement; inertial energy storage means including a massive balanced flywheel system mounted on rotatable eccentric shaft means for storing high levels of inertial energy sufficient to meet the peak demands of said systems; a prime mover for continuously delivering energy to said energy storage means; and transmission means including an impact device and a substantially rigid element establishing a positive connection of said eccentric shaft means To said impact device for converting and intermittently transmitting said stored inertial energy to said earth working implement on demand.

2. The apparatus of claim 1 wherein said implement is a rock fracturing tool; said tool is supported on a mobile vehicle for travel with the point thereof in engagement with a rock formation beneath the surface thereof to continuously separate portions from said formation along a path of travel of said vehicle; and, said impact device is adapted to intermittently engage said tool at an angle from the surface of said formation.

3. The apparatus of claim 2 wherein said tool is supported so that the angle of attack with respect to said formation may be selectively varied.

4. The apparatus of claim 3 wherein said angle of attack is variable between 20* and 55* .

5. The apparatus as defined in claim 2 wherein said frequency of said impact is variable.

6. The apparatus as defined in claim 4 wherein said impact device is supported by a pair of links.

7. The apparatus of claim 6 wherein said links form a quadrilateral.

8. The apparatus of claim 6 wherein said implement is supported by means of a pair of links.

9. The apparatus as defined in claim 1 wherein said implement is a dozer blade.

10. The apparatus of claim 9 wherein the angle of attack of said blade is variable.

11. The invention of claim 9 wherein the vibratory energy is imparted to said blade at an angle from the surface of the formation.

12. The invention of claim 1 comprising movable reaction means including a housing pivotally supporting said flywheel and crankshaft on said frame for permitting said transmission means to move to an equilibrium position in response to load demands on said implement.

13. The invention of claim 12 wherein said reaction means is pivotable for movement of said transmission means and said energy storage means substantially along the path of stroke of said implement.

14. The invention of claim 12 including means for biasing said transmission means toward said implement.

15. The invention of claim 12 wherein the pivotal support of said housing to said frame is disposed upward and forward of the axis of said crankshaft so that said impact device swings toward said implement under the influence of the weight of said flywheel and crankshaft so that said reaction means varies automatically in response to variable load on said implement.

16. The invention of claim 15 wherein said reaction means comprises hydraulic control means.

17. The invention of claim 1 wherein said implement is supported centrally on said vehicle within boundaries defined by four main support wheels of said vehicles so that substantially the entire weight of said vehicle may be imposed on said implement.

18. The invention of claim 17 wherein said wheels are driving wheels.

19. The invention of claim 1 wherein the r.p.m. of said prime mover means and the frequency of said transmission means are variable to maintain a high velocity ratio of said implement to the forward speed of said vehicle.

20. The invention of claim 19 wherein said implement is supported for vibratory movement by means of a quadrilateral linkage such that the instantaneous center of pivoting for said implement is slightly ahead of the cutting edge thereof.

21. The invention of claim 20 wherein said implement is a rock fracturing shank.

22. The invention of claim 20 wherein said transmission means includes an impact coupling.

23. The apparatus as defined in claim 1 wherein said implement is pivotally supported to move into and out of position for engagement by said impact device under force reaction from said formation; and, stop means operative to limit the movement of said implement into engagement with said impact device so that said eccentric means rotates at least one quarter of a revolution before engagement of said impact device with said implement.

24. The apparatus as defined in claim 23 wherein said Implement is a rock ripping shank pivotally mounted on said supporting means and including a chisel shaped tip extending in a forward direction; said impact means comprises a hammer pivotally mounted directly behind said shank for intermittent engagement there-with; and, said rigid element comprises a rigid link journaled at one end on said eccentric shaft means and pivotally connected at the other end to said hammer.

25. The apparatus as defined in claim 24 wherein said hammer is pivotally mounted directly to said shank.

26. A dynamic mechanical system for applying vibratory energy to an implement for earth working, said system comprising: an implement for separating portions from an earth formation; a frame mounted on a mobile vehicle; said implement being pivotally supported to said frame and movable to a position for engaging said earth formation; stop means on said frame to engage and limit the pivotal movement of said implement away from said formation; means including a massive balanced flywheel mounted on a rotary crankshaft for storing sufficiently high levels of inertial energy to meet the peak power demand of said system; housing means pivotally mounted on said frame and rotatably mounting said flywheel and said crankshaft, said housing being pivoted to said frame on an axis above said crankshaft, and pivotal under the weight of said flywheel, said crankshaft, and said housing toward said implement to oppose bias of said tool away from said formation and thereby define reaction means; a prime mover for continuously delivering energy to said energy storing means; and transmission means including impact means operatively connected by a rigid link journaled to said crankshaft for converting and cyclically transmitting said stored energy to said earth working implement on demand to drive said implement toward said formation.

27. The invention of claim 26 wherein said energy storage means stores sufficient inertial energy to prevent more than a ten per cent variation in angular velocity of the crankshaft.

28. The apparatus of claim 26 wherein said implement is supported so that the angle of attack with respect to said formation may be selectively varied.

29. The apparatus as defined in claim 26 wherein the frequency of said impact is variable.

30. The apparatus as defined in claim 29 wherein said impact device and said implement are each supported by a pair of links.

31. The apparatus of claim 30 wherein each of said pairs links form a quadrilateral with the respective one of said impact device and said implement.

32. A mechanical system for imparting vibratory energy to an earth working implement, said system comprising: an implement for separating portions from an earth formation; means for supporting and manipulating said implement; inertial energy storage means including a massive balanced flywheel mounted on a rotatable crankshaft for storing high levels of inertial energy sufficient to meet the peak demands of said systems; a prime mover for continuously delivering energy to said energy storage means; transmission means including an impact device operatively connected to said crankshaft for converting and intermittently transmitting said stored inertial energy to said earth working implement on demand; movable reaction means including a housing pivotally supporting said flywheel and crankshaft on said frame; and a pressurized fluid circuit operatively connected to bias said housing toward said implement for permitting said transmission means to move to an equilibrium position in response to load demands on said implement.

33. The invention of claim 32 wherein said circuit includes an accumulator.

34. A mechanical system for imparting vibratory energy to an earth working implement, said system comprising: an implement for separating portions from an earth formation; means for supporting and manipulating said implement; inertial eNergy storage means including a massive balanced flywheel mounted on a rotatable crankshaft for storing high levels of inertial energy sufficient to meet the peak demands of said systems; a prime mover for continuously delivering energy to said energy storage means; transmission means including an impact device operatively connected to said crankshaft for converting and intermittently transmitting said stored inertial energy to said earth working implement on demand; and movable reaction means including a fluid circuit and a housing pivotally supporting said flywheel and crankshaft on said frame for permitting said transmission means to move substantially along the path of stroke of said implement to an equilibrium position in response to load demands on said implement.

35. The invention of claim 34 wherein said circuit includes an accumulator circuit.

36. A mechanical system for imparting vibratory energy to an earth working implement, said system comprising: an implement for separating portions from an earth formation; means for supporting and manipulating said implement; inertial energy storage means including a massive balanced flywheel mounted on a rotatable crankshaft for storing high levels of inertial energy sufficient to meet the peak demands of said systems; a prime mover for continuously delivering energy to said energy storage means; transmission means including an impact device operatively connected to said crankshaft for converting and intermittently transmitting said stored inertial energy to said earth working implement on demand; movable reaction means including a housing pivotally supporting said flywheel and crankshaft on said frame for permitting said transmission means to move to an equilibrium position in response to load demands on said implement; and means including a fluid circuit for biasing said transmission means toward said implement.

37. The invention of claim 36 wherein said circuit includes an accumulator.

38. A dynamic mechanical system for applying intermittent unidirectional energy to a rock fracturing implement, said system comprising: an elongated fracturing shank; means including a support frame for pivotally supporting said fracturing shank for vibratory movement; a rotatable shaft including eccentric means; means including a massive balanced flywheel mounted on said rotatable shaft for storing substantial amounts of rotative inertial energy; and impact means comprising a rigid link journaled to said eccentric means to directly connect said eccentric means and said impact means to intermittently engage said shank for transmitting said energy from said flywheel to said shank in the form of high energy unidirectional blows.

39. The invention of claim 38 wherein the point of impact of said energy transmitting means with said shank includes a curved surface.

40. The invention of claim 39 comprising means to shield said impact area from foreign matter.

41. The apparatus as defined in claim 40 wherein said hammer means is pivotally mounted directly on said shank.