U.S. patent number 3,695,724 [Application Number 05/070,309] was granted by the patent office on 1972-10-03 for rotary impact rock breaking equipment.
Invention is credited to Richard Francis Taylor.
United States Patent |
3,695,724 |
Taylor |
October 3, 1972 |
ROTARY IMPACT ROCK BREAKING EQUIPMENT
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.
Inventors: |
Taylor; Richard Francis
(Johannesburg, Transvaal Province, ZA) |
Family
ID: |
22094521 |
Appl.
No.: |
05/070,309 |
Filed: |
September 8, 1970 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
774061 |
Nov 7, 1968 |
|
|
|
|
Current U.S.
Class: |
299/69;
173/99 |
Current CPC
Class: |
B28D
1/181 (20130101); E21C 27/12 (20130101) |
Current International
Class: |
B28D
1/18 (20060101); E21C 27/12 (20060101); E21C
27/00 (20060101); E21c 025/02 () |
Field of
Search: |
;299/37,62,69,70,81,85,94,86 ;175/91 ;173/99 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Purser; Ernest R.
Parent Case Text
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.
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.
Description
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 hammers remain
substantially rigid under centrifugal force. Furthermore, the
effect of speed must be taken into consideration particularly where
a hammer construction including a resilient web (as described
below) is used.
It is essential for a rock breaking machine of the type generally
set out above that at the moment of impact of the hammer tip this
tip immediately moves out of its normal striking path so that it
may clear any rock remaining unbroken by the hammer blow.
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 difficult 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 1 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 hammer's center of gravity is at
D.sub.1. 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:
(B C).sup.2 = B D .times. B E
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.sub.1. This movement towards A is measured by A D minus
A D.sub.1.
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 provided 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 S.sub.1. 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 following
formula:
(Q R).sup.2 = Q T .times. Q S
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 S.sub.1,
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 above-mentioned 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.
* * * * *