US3695724A

US3695724A - Rotary impact rock breaking equipment

Info

Publication number: US3695724A
Application number: US70309A
Authority: US
Inventors: Richard Francis Taylor
Original assignee: Anglo Transvaal Consolidated Investment Co Ltd
Current assignee: Anglo Transvaal Consolidated Investment Co Ltd
Priority date: 1970-09-08
Filing date: 1970-09-08
Publication date: 1972-10-03
Anticipated expiration: 1989-10-03

Abstract

Rock breaking equipment wherein a power driven rotor has hammers pivotally secured thereto with each hammer carrying a striking tip. The hammers are designed as compound pendulums with the striking tip on the major axis of symmetry for the pendulum. The hammers are also made to ensure that they are also capable of a combination of radial and rotational movement relative to the axis of rotation of the rotor. As a result of the unique construction of the hammers and rotor, the operational impact loading applied to the hammer pivot is only a minor proportion of that applied to the hammer striking tip.

Description

D United States Patent [151 3,695,724 Taylor [451 Oct. 3, 1972 [54] ROTARY IMPACT ROCK BREAKING 2,537,702 1/1951 Putnam ..l73/99 X EQUIPMENT 2,691,511 10/1954 Lundquist ..173/99 X Fm 2512.23 $412.22 3433;; burg, Transvaal Province, Republic of South Afnqar- Primary Examiner-Emest R. Purser 73 Assignee; g ud g d 1 Attomey-Shoemaker and Mattare vestment Company Limited, Johannesburg, Republic of South Africa [57] ABSTRACT 22 Filed; Sept, 1970 Rock breaking equipment wherein a power driven rotor has hammers pivotally secured thereto with each [2]] Appl- N05 70,309 hammer carrying a striking tip. The hammers are designed as compound pendulums with the striking tip Related Applicahon Dat. on the major axis of symmetry for the pendulum. The [63] Continuation-impart of Ser. No. 774,061, Nov. mm r are also m de o ensure tha hey are also 7, 1968, abandon d, capable of a combination of radial and rotational movement relative to the axis of rotation of the rotor. 52 US. Cl. ..299/69, 173/99, 299/85, AS a result of the unique construction of the hammers 299/94 and rotor, the operational impact loading applied to [51] Int. Cl ..E21c 25/02 hammer pivot is only a minor proportion of that 58 Field of Search ..299/37, 62, 69, 7o, 81, 85, 31 3 9 9??? ?{}FP ffF kR P [56] References Cited .1f .f.f P g res UNITED STATES PATENTS 1,195,396 8/ 1916 Recen.... ..299/

1 ROTARY IMPACT ROCK BREAKING EQUIPMENT BACKGROUND OF THE INVENTION This application is a continuation-in-part of application Ser. No. 774,061 filed Nov. 7, 1968, now abandoned, and relates to rock breaking equipment and more particularly to equipment which may be used for mining or tunnelling operations.

Where hard rock is to be mined or tunnelled into there is no efficient machine to effect this operation. The tunnelling machines available require high pressures against the rock face and excessive wear and damage to these machines occur with hard rock conditions. Even with rock which is of a softer nature, these machines are expensive because of their weight and auxilliary equipment necessary to provide the pressures against the rock faces.

OBJECTS OF THE INVENTION It is an object of the present invention to provide rock breaking equipment which will be less expensive to manufacture than that presently available, and which will be useful for operations in both hard and soft rock, when incorporated in a rock breaking machine.

It is a further object of this invention to provide a rock breaker wherein a series of swinging hammers is provided on a rotor with each hammer carrying a suitable rock breaking tip.

Another object of this invention is to provide for the hammers to be designed as compound pendulums each with the striking tip substantially on the line of major symmetry of the hammer.

A still further object is to provide a rock-breaking hammer wherein substantially no shock load is transmitted to the hammer pivot.

SUMMARY OF THE INVENTION According to this invention there is provided rock breaking equipment including a rotor carrying at least one hammer pivotally secured thereto with the pivot axis eccentric to but substantially parallel to the axis of rotation of the rotor and with the center of gravity of the hammer eccentric to the pivot and in a manner allowing a combination of both radial and rotational movement of the hammer striking tip relative to the axis of rotation of the rotor under normal operating conditions for the equipment.

Analysis of the action of a rotor carrying a series of hammers pivotally secured thereto shows that if the inter-relationship of the eccentricity of the pivots and the center of gravity of the hammers and the center of rotation of the rotor is not calculated and not made to meet certain requirements the result is excessive wear of parts or ineffectual operation or a construction which operates in the manner of a hammer mill where The invention also provides for the rotor to carry a pair of stops for each hammer to limit the swinging movement thereof if required.

Yet another feature of this invention provides for the hammer striking tip to be carried on the outer periphery of a web or webs of resilient material including means for limiting the radial extension of the web under the centrifugal force occurring during operation of the equipment.

The preferred design of the rotor and swing hammers is such that when the hammer strikes the rock surface to be broken, no shock load is thrown back onto the hammer pivot. It is also desirable that all the energy given up by the hammer in striking the rock is restored to the hammer by the centrifugal force applied thereto during the remaining portion of the revolution of the rotor in order to bring the hammer back into the striking position at the appropriate time.

This is difiicult to achieve in practice with a free swinging compound pendulum hammer mounted eccentrically to the axis of rotation of the rotor although the first preferred design feature is fairly simply arranged.

Practical considerations may make it desirable to have resilient stops positioned to prevent over swinging of each hammer in either direction about its pivot.

If the hammer construction includes the feature mentioned above involving a web or webs of resilient material, it will be realized that these webs help substantially in restoring the speed of the hammer tip.

In essence, the hammer acts as a compound pendulum to obtain a balance controlling the operational impact loading applied to the hammer pivot to a minor proportion of that applied to the hammer striking tip. The eccentricity of the center of gravity of the hammer relative to its pivot, the spacing of the striking tip from the hammer pivot, and the polar radius of gyration of the hammer all cooperate to result in very little shock load being transmitted to the hammer pivot.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention are illustrated in the accompanying diagrammatic drawings in which:

FIGS. 1 and 2 illustrate a solid hammer arrangement on a rotor.

FIG. 3 shows a more detailed view of one hammer and stop block of the type shown in FIGS. 1 and 2.

FIG. 4 shows a preferred shape of cutting tool, and

FIGS. 5 and 6 illustrate hammers having resilient web portions.

DETAILED DESCRIPTION OF THE INVENTION Referring firstly to FIGS. 1 and 2, wherein like reference numerals refer to like parts throughout the several views, a rotor comprising a plurality of spaced side plates 2 is mounted on a rotatable axle l for rotation therewith. A plurality of hammers 4 are mounted between the spaced side plates 2 about a hammer pivot pin 3 carried by the plates for pivotal movement of the hammers 4 relative to the rotor. A suitably sealed and lubricated bush or bearing 5 is disposed about the hammer pivot pin 3. A tungsten carbide tipped tool 7 is inserted into the hammer for striking rock to be broken. The hammer is shown in FIG. 1 in solid lines in position ready for striking rock, and in dashed lines at 6 in position after striking the rock and against a back resilient stop G. A front resilient stop F is disposed on the rotor in a position to limit forward movement of the hammers 4. Still referring to FIG. 1, the hammer has a pivotal axis B spaced from the axis of rotation A of the rotor. The distance from C to B is equal to the radius of gyration of the hammers about their pivot B. The center of gravity of the hammer when it is about to strike the rock is indicated at D, and after the hammer has struck the rock and just before striking the back stop G, the hammers center of gravity is at D,. The point relative to the rotor at which the insert strikes the rock is indicated at E.

From the above construction, it will be appreciated that a second pivot pin would usually be placed symmetrically to the pin 3 on the opposite side of the rotor axle 1. With such an arrangement, two hammers operate on a single path but, depending on the overall design, one, three, four or more hammers could be used per path.

Furthermore, sufficient paths would be incorporated on the rotor (only three are shown in FIG. 2) to cut a swathe of the desired width.

Ideally the dimensions should accord with the following formula:

also as far as possible B F should equal B E and B G should equal B E, but this is not so necessary as these stops are resilient and would not give sharp shock loads to the hammer.

Furthermore, the energy lost by the hammer when hitting the rock should equal the energy required to move the hammer towards A against the centrifugal force, until its center of gravity reaches position D,. This movement towards A is measured by A D minus A D This latter requirement may be more difficult to accomplish bearing in mind the wear on the inserts which tends to be high at high tip striking speeds. The stop G is, therefore, used to prevent excessive back swing.

The hammer, after swinging back (and possibly hitting G), will swing forward and will tend to swing past the desired striking point E unless prevented from so doing by the stop F.

Referring now to FIGS. 3 and 4 which give a practical example of the hammer and stop construction for use in a rock breaking machine, a stop block 21 and hammer 22 are each mounted between backing discs one of which is indicated at 23 and it will be understood that only one stop block and hammer is shown in FIG. 3. A plurality of such assemblies will preferably be pro vided for each width of cutting tool as well as a series of similar arrangements along the length of the rotor to give the required width of cut.

The block 21 is mounted between the discs 23 by means of pin 24 and circlips will be preferred for this purpose. The block 21 is held against the rotor shaft 25 along an arcuate section 26 and fluid passages 27 are provided through the shaft and stop block 21 to terminate inside the stops 28 themselves which are made as cylindrical, metal reinforced, hollow rubber bulbs similar to the commercially available Oscillith bush construction. The passages 27 also open through apertures 29 so that fluid forced through the passages can also be ejected onto the rock face being cut. In minning operations, for example, this fluid will preferably be water.

The stops 28 absorb the energy of the hammers 22 as they are brought to rest against them and the resilience in the construction returns this energy, less the inherent losses to the system.

The hammer 22 is mounted to swing freely on pin 30 and is constructed according to the principles described above. Resilient blocks 31 are provided on the hammers also and positioned to strike against stops 28 on stop blocks 21 on each side of the hammer as indicated in the drawings.

The outer end of the hammer has a socket 32 to receive the cutting tool 33 and this socket has a tapered surface to correspond to the tool which is illustrated in FIG. 4. The socket is also radiused at 34 to provide space for the shoulder 35 on the tool 33.

The tool is shaped to prevent excessive stresses occurring on the tool during use and the tapered shank 36 terminates at the narrow end in a parallel screw threaded portion 37 which has a suitable nut associated therewith to enable the tool to be secured in the socket 32 of the hammer 22.

The wider end of the shank terminates in the rounded shoulder 35 of the head portion 38 which head is slotted at 39 to carry the tunsten carbide striking tip 40. This insert is secured in accordance with usual practice but it will be appreciated from FIG. 4 that the striking tip is symmetrically curved along the width of the head 38 and bounded by

sides

41 and 42 which are approximately at right angles to each other. Side 41 is made to be at a very much larger angle to the axis of the tool than is side 42.

It has been found that the construction indicated above results in an effective operation of rock breaking without involving heavy machinery.

Referring now to FIGS. 5 and 6 of the drawings, a hammer 16 is shown mounted on two resilient webs 15. The resilient webs 15 are made in the form of annular discs with the thickness inversely proportional to the radius at that point, and the hammer 16 is in the form of a ring heavily weighted in the zone contained by a circle of diameter QT and highly constructed elsewhere. The webs 15 are clamped between a drive boss 13 and a pair of clamps 14. The drive boss 13 is attached to a drive shaft 11 for the rotor, the drive boss being eccentrically mounted in such a manner that when the hammer swings back relative to the boss, the center of gravity of the rotating portion of the hammer approaches a point P which corresponds to the axis of rotation of the drive shaft of the rotor. A water channel 12 is formed down the center of the drive shaft 11. A pair of clamping rings 17 are disposed in clamping relationship on the outer edge of the webs for holding the webs to hammer 16. A water channel 18 is formed in the hammer 16 for conveying water in front of the striking point of the hammer. The water also acts as a coolant for the webs 15. A plastic-impregnated wire rope restrainer 19 or the like is disposed over the drive boss 13 to prevent undue distortion of the webs 15 when subjected to the centrifugal forces of the hammer. When the hammer is stationary, this restrainer is not in contact with the boss 13. A tungsten carbide tipped tool 20 is inserted into the hammer for striking rock to be broken. A water channel (not shown) is also formed in the drive boss 13 to enable water from channel 12 to flow in the space between webs 15. The pivot center of the device is indicated at Q and this center may vary slightly relative to the body of the hammer due to the resilient web distorting under the centrifugal force of the hammer, which as mentioned previously is limited by the restrainer 19. The center of gravity of the rotating portion of the hammer in striking position is indicated at S, and the center of gravity of the rotating portion of the hammer in a position after striking rock is indicated at 8,. The point relative to the rotation at which the hammer insert strikes rock is indicated at T. The distance from R to Q is equal to the radius of gyration of the rotating portion of the hammer about Q.

Ideally the dimensions should accord with the followin g formula:

Furthermore, the energy given up by the hammer in hitting the rock should be equal to that required;

a. to move the center of gravity of the hammer closer to the axis P against the centrifugal force of the hammer by the amount P S minus P 8,,

plus

b. the energy required to distort the resilient webs by twisting them substantially about their axis.

It should be noted that due to the elastic properties of the webs it will be found that there is an optimum rotational speed at which the hammer on its swing back will be in the striking position just at the correct time to strike the rock.

The optimum speed will not vary very much with variations in the energy expended per blow, for any given hammer-web combination. There is, however, an upper limit to the energy expended per blow which is the kinetic energy of the hammer rotating at the speed at moment of impact.

The speed of rotation of the hammer at moment of impact will normally be faster than the normal rotor speed due to its added pendulum like swing relative to the rotor.

From the above, it will be appreciated that the hammer and rotor design can also be adapted for more efficient operation of hammer mills than is possible with those mills of presently available constructions. Further, where the equipment is adapted for mining or tunnelling operations a wide variety of designs can be made to give useful results. For example, the rotor can be made to revolve about a second axis at an angle to the primary axis of rotation in order that a circular tunnel or shaft can be bored into the rock. This will necessitate variations in hammer arrangements along the length of the rotor to give approximately equivalent traverse across the rock per cutting blow.

Variations in the shapes and sizes of tunnels, shafts and holes generally can be obtained using this type of equipment by the controlled movement of the abovementioned second axis.

From the above it will be understood that the principle of rock breaking does not require the high pressures heretofore necessary for machines for the operations referred to, thus reducing the costs of the equipment and increasing efficiency.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within the metes and bounds of the claims or that form their functional as well as conjointly cooperative equivalents, are therefore intended to be embraced by those claims.

I claim:

1. Rock breaking equipment comprising, a power driven rotor mounted about an axis of rotation, at least one hammer freely pivotally mounted to said rotor and having a polar radius of gyration, the pivotal axis of said hammer eccentric to and substantially parallel to the axis of rotation of the rotor, the center of gravity of said hammer eccentric to its pivot by a predetermined distance, a striking tip carried by said hammer spaced from the pivot of said hammer by a predetermined distance, the product of the two predetermined distances approximating the square of the polar radius of gyration of the hammer, means mounting said hammer to said rotor for both radial and rotational movement of the hammer and its striking tip relative to the axis of rotation of the rotor, the striking tip of the hammer lying substantially on a line extending through the pivot axis and center of gravity of the hammer so that when the hammer strikes the rock surface to be broken substantially no shock load is transmitted to the hammer pivot due to the interrelationship of the eccentricity of the center of gravity of the hammer relative to its pivot, the spacing of the striking tip from the hammer pivot, and the polar radius of gyration of the hammer, and stop means operatively associated with the hammer to limit pivotal movement thereof between predetermined limits.

2. Rock breaking equipment as in claim 1, wherein a plurality of hammers are freely pivotally mounted to said rotor.

3. Rock breaking equipment as in claim 1, wherein said hammer is carried on the outer periphery of a flexible resilient web secured to said rotor.

4. Rock breaking equipment as in claim 3 wherein means are provided for limiting the radial extension of the web under centrifugal force occurring during operation of the equipment.

5. Rock breaking equipment as claimed in claim 1 in which the rotor carries a pair of stops for each hammer to limit the swinging movement thereof.

6. Rock breaking equipment as claimed in claim 5 in which each hammer carries a resilient stop positioned to cooperate with the stops carried by the rotor.

7. Rock breaking equipment as claimed in claim 5 in which each hammer and the stops therefor are mounted on pins between discs forming part of the rotor.

8. Rock breaking equipment as claimed in claim 5 in which the stops are resilient stops.

9. Rock breaking equipment as claimed in claim 8, in which the stops are formed as metal reinforced cylindrical hollow rubber bulbs.

10. Rock breaking equipment as claimed in claim 9 in which the rotor has fluid passageways therein communicating with the stops and with outlet apertures in the rotor.

11. Rock breaking equipment as claimed in claim 1 in which the striking tip is carried by a tool removably held in the hammer.

12. Rock breaking equipment as claimed in claim 11 in which the tool has a tapered shank fitted in a complementary socket in the hammer and the striking tip is a tungsten carbide insert in the tool.