Note: Descriptions are shown in the official language in which they were submitted.
-- 2
Tl-IIS INVENTION relates to an in~proved fLuid operated
hammer.
In deep bore drilling it is usual to use a fluid operated
percussive hammer to provide necessary drive for the bor-
ing operation. However a difficulty which is encountered
with hammers which are currently in use is that the
manufacture of the components for such ha~mers involves
considerable amount o~ precise machining which not only
increases the manufacturing cost of such units but also
reduces the service life of the components. Some of the
typical hammers in use generally comprise an outer cylind-
r~cal casing with a feed tube positioned concentrically
within the casing and a piston slidably mounted within the
casing and over the feed tube to reciprocate therein and
impact on a drill bit mounted in and retained at the
bottom of the casing. In order to effect the reciprocating
action of the piston fluid passage ways are provided in
the feed tube and/or the casing which periodically communi-
cate with ports provided in the piston to periodically
admit fluid to the chambers above and below the piston to
either lift it away from the drill bit or drive it so as
to impact onto the drill bit.
In such hammers, it has been known for such hammers to
prematurely fail due to excessive wear of the casing
and/or feed tube and/or piston. One rnajor cause of such
excessive wear has been the misalignment of the feed tube
within the bore of the casing. It is current practice in
at least one form of hammer to mount the feed tube of the
hammer into the top sub of the hammer which is then
threadably mounted into the casing~ Alternatively it is
cornmon practice to locate the feed tube in a counterbored
portion at one end of the casing. In such circurnstances,
to ensure that the feed tube is aligned concentrically
within the bore of the casing on assembly of the hammer,
involves precise machining of the feed tube, casing~
counter-bore, casing thread, top sub and top sub thread
2~
-- 3 --
and very stringent quality control.
It is an object of this invention to reduce the degree of
p~ecise machinery of components of fluid operated hammers.
In one form the invention resides in a fluid operated
hammer comprising a cylindrical casing having a bore for
slidably receiving a piston, a top sub mounted at one end,
a drill bit mounted to the other end by me~"s of a chuck,
a feed tube concentrically mounted within the upper end of
the bore of the casing and extending downwardly into the
casing, said feed tube being connectable to a fluid source
through said top sub, a piston slidably mounted within the
bore of said casing over said feed tube, to reciprocate
within the casing and periodically impact on the drill bit.
According to a preferred feature of the invention the feed
tube is mounted to and located in the upper end of the
bore of the casing and is isolated from the top sub.
According to a further preferred feature of the invention
the feed tube is mounted to the casing via an annular
centralising ring concentrically located within the bore
of said casing and wherein said ring is capable of being
replaced by a ring of differing dimensions so as to ~ary
thP volume of the chamber formed between the piston and
the centralising ring.
According to a preferred feature of the invention the
internal walls of said casing are substantially uncon-
toured and the external walls of said feed tube are
substantially uncontoured.
It is a preferred object of this invention to provide a
fluid operated hammer which can be operated with fluids of
varying pressures and/or can have variable characteristics
of performance by the exchange of substantially minor
internal components.
2'~
-- 4 --
According to a further preferred feature of the invention
the feed tube can be replaced with another of differing
characteristics to vary the periodicity of communication
of the fluid to the ends of the piston.
According to a further preferred-feature of the invention
there are two sets of apertures provided in the feed tube
spaced longitudinally rom each other, one set communica-
ting with the port provided in one end of the piston
adjacent the one end of said casing when said one end is
adjacent the top sub and the other set of apertures
communicating with the port in the other end of the piston
adjacent the other end of said casing when said other end
is in contact with the drill bit.
A urther preferred feature of the last mentioned pref-
erred feature resides in said one set of apertures compri-
sing at least two longitudinally spaced apertures which
communicate with said one end of said piston during its
movement towards said drill bit to provide 3 sequential
thrust towards the drill bit.
According to a preferred feature of the last two mentioned
features, said other set of apertures have a total dimen-
sion around the circumference of the feed tube greater
than their axial dimension.
According to a further preferred feature of the invention
said drill bit has an enlarged innermost end and is
capable of limited axial movement in the chuck and bears
on a bit retaining ring located in the chuck when the
drill bit is in its outermost pOSitiOII in the chuck
wherein a resilient ar.nular member is mounted in the chuck
to absorb some of the shocks exerted on the bit ring by
the enlargement.
In provid;ng the passage ways in the casing and ports in
the piston of prior art fluid operated hammers, and to
facilitate periodic communication between either end of
-- 5 --
the piston, it has been deemed necessary to contour the
external surface of the feed tube and the internal surface
of tl-e cas;ng. It is also being found necessary to machine
the external and/or internal faces of the piston in order
to facilitate the communication between the passage ways
and ports. The provision of such passage ways in the
casing and feed tube and ports and complicated machining
in the piston has not only increased the manufacturing
cost of hammer components and assemblies but has also
decreased the service life of hammers. Where a casing is
provided with passage ways drilled holes or undercuts in
its wall the degree of wear which can be tolerated on the
wall before leakage occurs from the passage ways to the
exterior of the hammer is reduced. In addition, by con-
touring the external face of the feed tube the cost of the
feed tube is not only increased but the number of edges
which can be abrasively engaged by the piston are also
increased as the piston cycles up and down in the casingO
It is an object of this invention to provide a fluid
operated hammer which does not require any ports or
passage ways in the casing of the hammer or machining of
the internal face of the casing and the external face of
the feed tube.
In another form the invention resides in a fluid operated
hammer comprising a cylindrical casing having a bore for
slidably receiving a piston, a top sub mounted at one end,
a drill bit mounted to the other end by means of a chuck,
a feed tube concentrically mounted within the upper end of
the bore of the casing and extending downwardly into the
casing, said feed tube being connectable to a fluid source
through said top sub, a piston slidably mounted within the
bore of said casing over said feed tube, the internal
walls of said casing are substantially uncontoured and the
external walls of the feed tube being substantially uncon-
toured, at least one aperture provided in the walls of
said feed tube, at least one port provided at each end of
2~3
-- 6
the piston, each port opening at spaced locations into the
bore of the piston to periodically communicate with said
aperture as a result oF slidable movement of the piston
over the feed tube to alternately drive the piston towards
the drill bit to impact thereon and to drive the piston
away from the drill bit towards the one end of the casing.
According to a preferred feature of the invention the feed
tube is mounted to and located in the upper end of the
bore of the casing and is isolated from said top sub.
According to a further preferred feature of the invention
there are two sets of apertures provided in the feed tube
spaced longitudinally from each other, one set communi-
cating with the port provided in one end of the piston
adjacent the one end of said casing when said one end is
adjacent the top sub and the other set of apertures
communicating with the port in the other end of the piston
adjacent the other end of said casing when said other end
is in contact with the drill bit.
According to a further preferred feature of the last
mentioned preferred feature, said one set of apertures
comprises at least two longitudinally spaced apertures
which communicate with said one end of said piston during
its movement towards said drill bit to provide a sequen~
tial thrust towards the drill bit.
.
According to a further preferred feature of the last two
mentioned features, said other set of apertures have a
combined dimension around the circumference of the feed
tube greater than their axial dimension.
According to a further preferred feature of the invention,
said drill bit has an enlarged innermost end and is
capable of limited axial movement in the chuck and which
bears on a bit retaining ring located in the chuck when
the drill bit is in its outermost axial position in the
_ 7 --
chuck wherein a resilient annular member is mounted in the
chuck to absorb some of the shock forces exerted on the
bit retaining ring by the enlargement.
Fluid operated hammers currently in use are capable of
operating at a variety of pressures only after a number of
components of fairly complex design are exchanged for
similar components of differing dimensions and mass to
vary the length of movement and/or periodicity of movement
of the piston.
It is a preferred object of this invention to provide a
fluid operated hammer which can be operated with fluids of
varying pressures and/or can have variable characteristics
of performance by the exchange of substantially minor
internal components.
According to a further preferred feature of the invention
the feed tube can be replaced with another of differing
characteristics to vary the periodicity of communication
of the fluid to the ends of the piston.
According to a further preferred feature of the invention
the feed tube is mounted to the casing via an annular
centralising ring concentrically located within the bore
of said casing and wherein said ring is capable of being
replaced by a ring of differing dimensions so as to vary
the volume of the chamber formed be~ween the piston and
the centralising ring.
In addition with fluid operated hammers in use when the
hammer is placed in the "blow-down'l position in which the
hammer is inoperative and the anvil of the drill bit is in
contact with the bit retaining ring there can often be
failure of the bit retaining ring or the portion of the
drill bit engaged by the bit retaining ring. This is due
to the anvil being impacted by the piston of the hammer
when the drill bit first moves to the "blow-down" position
-- 8 --
or due to "back ha~mering" occuring, when the hammer is in
the "blow-down" position. In some cases, it has been known
for hammers to fail regularly when such hamrners are
involved in normal operational use. Such failure not only
causes consider~b]e delay in drilling operations but is
expensive and requires an operator to maintain a large
supply of spare parts for such hammers and can in some
instances results in the abandonment of the drill hole
when the failed components cannot be retrieved or with-
drawn from said drill hole.
It is an object of this invention to absorb some of the
shock forces exerted on the bit retaining ring when the
hammer is in the "blow-down" position caused by the drill
bit being impacted by the piston to reduce the possibility
oE failure of the drill bit or bit retaining ring in the
course of normal operations.
In another form the invention resides in a fluid operated
hammer comprising a cylindrical casing having a bore for
slidably receiving a piston, a top sub mounted at one end,
a drill bit mounted to the other end by means of a chuck,
a feed tube concentrically mounted within the upper end of
the bore of the casing and extending downwardly into the
casing, said feed tube being connectable to a fluid source
through said top sub, a piston slidably mounted within the
bore of said casing over said feed tube, to reciprocate
within the casing periodically impact on the drill bit,
said drill bit being capable of limited slidable axial
movement in the chuck and has an enlarged ;nnermost end
which bears on a bit ring located in the chuck when the
drill bit is in its axially outermost position in the
chuck, wherein a resilient annular member is mounted in
the chuck to absorb some of the shock forces exerted on
the bit ring by the enlargement.
According to a preferred feature of the invention the feed
tube is moùnted to and located in the upper end of the
bore of the casing and is isolated from said top sub.
29~
g
According to a preferred feature of the invention the
internal walls of said casing are substantially uncon-
toured and the external walls of said feed tube are
substantially uncontoured.
According to a further preferred feature of the invention
there are two sets of apertures provided in the feed tube
spaced longitudinally From each other, one set communi-
cating with the port provided in one end of the piston
adjacent the one end of said casing when said one end is
adjacent the top sub and the other set of apertures
communicating with the portion the other end of the piston
adjacent the other end of said casing when said other end
is in contact with the drill bit.
According to a further preferred feature of the last
mentioned preferred feature said one set of apertures
comprises at least two longitudinally spaced apertures
which communicate with said one end of said piston during
its movement towards said drill bit to provide a sequen-
tial thrust towards the drill bit.
According to a preferred feature of the last two mentioned
features, said other set of apertures have a combined
dimension around the circumference of the feed tube
greater than their axial dimension.
Fluid operated hammers currently in use are capable of
operating at a variety of pressures only after a number of
components of fairly complex design are exchanged for
similar components of differing dimensions and mass to
vary the length of movement and/or periodicity of the
movement of the piston.
It is a preferred object of this invention to provide a
fluid operated hammer which can be opera~ed with fluids of
varying pressures and/or can have variable chacteristics
of performance by the exchange of substantially minor
`
- 10 --
internal compo~ents.
According to a further preferred feature of the invention
the feed tube can be replaced with another of differing
characteristics to vary the periodicity of communication
of the fluid to the ends of the piston.
According to a further preferred feature of the invention
the feed tube is mounted in the casing via an annular
centralising ring concentrically located within the bore
of said casing and wherein said ring is capable of being
replaced by a ring of differing dimensions so as to vary
the volume of the chamber formed between the piston and
the centralising ring.
In most fluid operated hammers currently in use, the
piston is effected by the introduction of pressurised
fluid to the space between the piston and the top sub or
other assembly parts located below the top sub. However
this introduction of pressurised fluid is usually for a
fixed interval of time which is only a portion of the time
taken for the piston to complete its downward movement.
Therefore the degree of thrust that can be`applied to the
piston is limited to effect its impact on the drill bit.
In cases where holes are to be bored upwards, as occurs in
underground mines the effect of gravity can result in
deterioration of the performance of the hammer.
Xt is an object of this invention to increase the period
of time normally available in fluid operated hammers in
which a thrust may be applied to the piston to effect its
impact on the drill bit.
In another form the invention resides in a fluid operated
hammer comprising a cylindrical casing having a bore for
slidably supporting a piston a top sub mounted at one end,
a drill bit mounted to the other end by means of a chuck,
a feed tube concentrically mounted within the upper end of
f4. ~2'~
the bore of the casing and extending downwardly into the
casing, said feed tube being connectable to a fluid source
through said top sub, a piston slidably mounted within the
bore of said casing over said tube two sets of apertures
provided in the feed tube spaced longitudinally from each
other, one set communicating with one port provided in one
end of the piston adjacent the one end of said casing when
said one end is adjacent the top sub and the other set of
apertures communicating with another port in the other end
of the piston adjacent the other end of said casing when
said other end is in contact with the drill bit to
alternately drive the piston towards the drill bit to
impact thereon and to drive the piston away from the drill
bit towards the one end of the casing wherein said one set
of apertures comprises at least two axially spaced aper-
tures which communicate with said one end of said piston
during its movement towards said drill bit to provide a
sequentially applied thrust to the piston towards the
drill bit.
According to a preferred feature of the invention said
other set of apertures have a combined dimension around
the circumference of the feed tube which is greater than
their axial dimension.
~ '
According to a preferred feature of the invention the feed
tube is mounted to and located in the u~per end of the
bore of the casing and is isolated from said top sub.
According to a preferred feature of the invention the
internal walls of said casing are substantially uncon-
toured and the external walls of said feed tube are
; substantially uncontoured.
Fluid operated hammers currently in use are capable of
operating at a variety of pressures only after a number of
components of fairly complex design are exchanged for
similar components of differing dimensions and mass to
'f~ 3'~
- 12 -
vary the length of movement and/or periodicity of the
piston.
It is a preferred object of this invention to provide a
fluid operated hammer which can be operated with fluids of
varying pressures and/or can have-variable characteristics
of performance by the exchange of substantially minor
internal components.
According to a further preferred feature of the invention
the feed tube can be replaced with another of differing
characteristics to vary the periodicity of communication
of the fluid to the ends of the piston.
According to a further preferred feature of the invention
the feed tube is mounted in the casing via an annular
centralising ring concentrically located within the bore
of the casing and wherein said ring is capable of being
replaced by a ring of differing dimensions so as 'to vary
the volume of the chamber formed between the piston and
the centralising ring.
According to a further preferred feature of the invention
said drill bit has an enlarged innermost end and is
capable of limited axial movement in the chuck and bears
on a bit retaining ring located in the chuck when the
drill bit is in its outermost position in the chuck
wherein a resilient annular member is mounted in the chuck
to absorb some of the shocks exerted on the bit ring by
the enlargement.
In addition, fluid operated hammers currently in use
suffer from "back hammer1' when the hammer is in the
"blow-down" position. Such back hammer is the continued
reciprocation of the piston in the hammer when the drill
bit is in its outermost position in the chuck and if such
back hammer persists, it can lead to failure of parts of
the hammer assembly or drill bit. This problem can be
S:~
- 13 -
caused by use of apertures in the feed tube which supply fluid
to the drill bit end of the piston, being too large in the
axial dimension in relation to the piston whereby only a small
degree of movement is required by the piston for fluid to be
directed from the "blow-down" flow path, to cause movement of
the piston from the drill blt or even to effect both functions
together. It has been a feature of some of the prior art
hammers that the ports in the feed tube that pass fluid to the
space between the piston and the drill bit to cause the
piston to move away from the drill bit have an axial dimension
equal or greater than their combined circumferential dimension
around the feed tubeO
According to a preferred feature of the invention said
other set of apertures have a combined dimension around the
circumference of the feed tube which is greater than their
axial dimension.
3'~
- 14 -
Accordiny to a preferred feature o the invention, the other
set of apertures comprise one aperture.
According to a preferred feature of the invention the other
set of apertures comprise a plurality of apertures
circumferentially spaced around the feed tube.
Fluid operated hammers currently in use are capable of
operating at a variety of pressures only after a large number
of components of fairly complex design are exchanged for
similar components of difering dimensions and mass to vary
the length of movement and/or periodicity of movement of the
piston.
It is a preferred object of this invention to provide a fluid
operated hammer which can be operated with fluids of varying
pressures and/or can have variable characteristics of
performance by the exchange of substantially minor internal
components.
~0
According to a further preferred feature of the invention.
- 15 -
the feed tube can be replaced with another of differing
characteristics to vary the periodicity of communication
of the fluid to the ends of the piston.
According to a further preferred-feature of the invention
the feed tube is mounted to the casing via an annular
centralising ring concentrically located within the bore
of said casing and wherein said ring is capable of being
replaced by a ring of differing dimensions so as to vary
the volume of the chamber formed between the piston and
the centralising ring.
According to a further preferred form of the invention the
drill bit has an enlarged innermost end wherein said
enlargement is capable of limited axial movement in the
chuck and bears on a bit retaining ring located in the
chuck when the drill bit is in its outermost axial posi-
tion within the chuck wherein a resilient annular member
is mounted in the chuck to absorb some of the shock forces
exerted on said bit retaining ring by the enlargement.
The invention will be more fully understood in the light
of the following description of several specific embodi-
ments. The description is made with reference to the
accompanying drawings of which:
Figure 1 is a sectional side elevation of a fluid
operated hammer according to the first embodiment in the
"blow-down" position;
Figure 2 is a sectional side elevation of the fluid
operated hammer of Figure 1 in the "impact77 position;
Figure 3 is a sectional side elevation of the fluid
operated hammer of Figures 1 and 2 with the hammer in
the "raised" position;
Figure 4 is a sectional side eleva~ion of a fluid
operated hammer according to the second embodiment in
the "blow-down" position;
- 16 -
Figure 5 is a sectional side elevation of the fluid
operated harnmer of figure 4 in the "impact" position;
Figure 6 is a sectional side elevation of the fluid
operated hammer of Figures 4 and 5 with the hammer in
the "raised" position;
Figure 7 is a sectional side elevation of a fluid
operated hammer according to the third emhodiment in the
"blow-down" position;
Figure 8 is a sectional side elevation of the fluid
operated hammer of Figure 7 in the "impact" position;
Figure 9 is a sectional side elevation of the fluid
operated hammer of Figures 7 and 8 with the hammer in
the "raised" position;
Figure 10 is a part sectional elevation of a fluid
operated hammer showing the mounting of the drill bit in
the chuck; and
Figure 11 is a part sectional elevation of a fluid
operated hammer showing the mounting of the feed tube in
the hammer.
The first embodiment of figures 1, 2 and 3 is a fluid
operated hammer which comprises a cylindrical casing 11
having a substantially uncontoured inner face with a top
sub 12 mounted at one end and a drill bit 13 mounted at
the other end. The drill bit is mounted within a drill
chuck which is ~hreadably engaged in the other end of the
casing such that it is longitudinally slidable for a
limited degree within the end of the chuck. Such limited
slidable movement of the drill bit is facilitated by a bit
ring 14 mounted in the inner end of the chuck and which is
received within a waisted portion 15 at the innermost end
of the drill bit. The innermost end of the drill bit 13
which extends beyond the bit ring 14 is formed with an
enlarged portion which serves as the anvil 16 for the
drill bit 13.
3'~
-- 17 -
As shown at Figure 10, the bit retaining ring 14 is
retained in the chuck between a shoulder 40 formed on the
inner face of the chucks outer casing and a sleeve 41
received within the chuck. An 0-ring seal 42 is located
between the bit retaining ring and the outer casing of the
chuck. The bit ring 14 is separated from the inner end of
the sleeve 41 by a resilient ring 43O The resilient ring
43 is intended to absorb some of the shocks that may be
imparted to the bit retaining ring when the anvil 16 of
the drill bit is in contact therewith and is impacted by
the piston of the hammer.
The top sub 12 is threadably enaged in the one end of the
casing 11 and is provided with a fluid inlet port 17 which
communicates with a spring loaded check valve 1~ located
within the top sub to prevent any reverse fluid flow and
provided at the innermost end of the top sub 12.
The bore of the casing 11 supports a feed tube 20 which is
concentrically mounted at the one end of the bore of the
casing 11 in abutting relation with the inner end of the
top sub 12. The feed tube 20 extends from the one end of
the casing for a portion of the length of the casing~ As
shown at Figure 11 the mounting of the feed tube comprises
a centralising ring 21 which is accurately closely and
concentrically retained in the one end of the bore of the
casing 11. The centralising ring is also formed with a
flange 21a which is loosel~ received in a counter-bored
portion of the casing and which serves to limit axial
movement of the ring 21 and feed tube 20. The centralising
ring 21 receives the one end of the feed tube and
accurately retains the feed tube such that it is
concentrically located within the casing 11. A flange 22
at the one end of the feed tube overlies the outer axial
face of the centralising ring 21 to be located within a
suitably shaped recess formed w;thin the top sub 12.
- 18 -
Suitable tolerances are provided between the top sub 12
and the flanged end of the feed tube 22 in order that any
mis-alignment of the top sub will not effect the alignment
of the feed tube 20 within the casing as established by
the spacer ring 21. Suitable sealing resilient and
accommodating means in the form of O-rings are provided in
the centralising space between the centralising ring 21
and the flanged 22 of the feed tube and the top sub 12 and
the flanged 22 of the feed tube to prevent any loss of
fluid from the junctions therebetween and to allow some
movement of the feed tube. The centralising ring 21 prov-
ides a means of supporting and centralising the feed tube
concentrically within the bore of the casing 11 and thus
the piston 26.
Previous means of locating the feed tube in a hammer
having included threadably engaging the feed tube into the
top sub and then threadably engaging the top sub onto the
casing, or engaging the feed tube in a counter-bored
portion of the casing which also threadably receives the
top sub. As a result very careful quality control had to
be maintained in the machining of the top sub, feed tube
and casing in order for the feed tube to be located
centrally within the bore of the casing on assembly of the
hammer. If due to poor quality control the feed tube was
no~ located cen~rally in the bore of the casing there can
be accelerated wear of the feed tube, piston and casing
which will result in pFemature failure of the hammer.
The centralising ring 21 may be readily exchan~ed with
other rings of differing thickness in order that the
volume of the space between the upper end of the piston 26
and the top sub may be varied. The free end of the feed
tube is provided with a suitably dimensioned choke 23
which permits a controlled continuous flow of fluid down
through the drill bit 13. The walls of the feed tube are
uncontoured and are formed with two sets of apertures. One
æ~
set 24 comprises a single aperture which extends for a
considerable portion of the circumference of the feed tube
but which has a relatively small dimension in the
longitudinal axis of the feed tube. Alternatively the nne
set ~ay comprise a series of circumferentially spaced
apertures in the walls of the feed tube which have a
relatively small axial dimension. The other set of
apertures comprise a pair of longitudinally spaced
apertures 25a and 25b located towards the free end of the
feed tube from the one set of apertures 24. One aperture
25a of the other set of apertures which is located closest
to said one set of apertures 24 is greater in size than
the other of said apertures 25b and has a greater axial
dimension than the other aperture 25b.
The hammer further supports within the casing 11 a piston
26 which is longitudinally slidable within said casing 11
and over said feed tube 20. Each end of said piston is
provided with a port 27 and 29 which communicate with a
passage way 28 or 30 respectively extending from the
respective port to the internal bore of said piston. The
passage ways 28 and 30 are formed by obliquely boring a
hole from the respective end of said p;ston to the bore of
said piston. In addition the end of the piston adjacent
the top sub 12 is counterbored to provide an expanded
portion 31 in the bore of the piston which extends for a
small portion of the length of the bore.
As shown at figure 1 to place the hammer in the "blow-
down" position the hammer is moved axially away from the
base of the drill hole in order that the drill bit moves
to its outermost position in the chuck and the bit ring 14
is engaged with the anvil 16 of the drill bit. When in the
"blow-down" mode the piston 26 is retained in contact with
the anvil 16. The maintenance of this position is a result
of the counter-bored portion 31 at the one end of the
hammer 26 being in communication with the one set of
- 20 -
apertures 24 to provide fluid communication between the
source of fluid pressure and the space located between the
one end of the piston 26 and the top sub 12. Since no
equivalent pressure or greater pressure is applied to the
other end of the piston through the passage-way 30 the
piston 26 is positively retained in contact with the
anvil. Fluid from the top sub end of the piston escapes to
the drill bit via port 27 and the one passage way 28.
Due to the small axial dimension of the one set of
apertures if the piston should for some reason be moved
from engagement with the anvil a considerable degree of
movement of the piston is required for the one set of
apertures to communicate with the drill bit end of the
piston through the passage way 30 and port 29. The small
axial dimension of the one set of apertures ensures that
there can be no overlap between the counter-bored portion
and the passage way 28 by the one set of apertures.
Thereforeg the possibility of back hammer is considerably
reduced. In addition, due to the absence of restriction
between the one set of apertures and the drill bit other
than the counterbored portion 31 and the passage way 28
connecting the drill bit end of the piston wi~h the bore
of the piston the flow of air to the drill bit during
"blow-down" is relatively unrestricted ensuring clearing
of drill cuttings.
When the fluid operated hammer is moved axially towards
the base of the drill hole such that the drill bit engages
with the base of the bore hole the drill bit 13 moves into
the fluid hammer. As a result ~as shown in figure 2) the
counter-bored portion 31 in the one end of the hammer 26
is isolated from the source of fluid pressure and the one
passage way 28 connecting the top sub end port 27 of the
piston 26 with the bore of the pîston is isolated from the
source of fluid pressure while the other passage way 30
2~3
- 21 -
connecting the drill bit port 29 of the piston 26 with the
internal bore of the piston is in communication with the
one set of apertures 24 in the feed tube 20, as a result
fluid pressure from the fluid source is applied to the
space between the drill bit end-29 of the piston 26 and
the chuck 14. The resultant pressure differential produces
a movement of the piston 26 from the drill bit.
The use of an aperture 24 of relatively small axial
dimensions is a departure from previous practice and
allows a greater control over the introduction of fluid at
a precise point in the travel of .he piston 26 and
similarly causes the fluid flow to the piston to be shut
off rapidly rather than having a gradual decrease as would
occur if a longitudinally larger port ~ere used.
If desired the one set of apertures 24 can be positioned
to communicate fully with the drill bit end of the piston
when the piston is raised a small distance from the anvil
in order to make use of the reactive rebound of the piston
after striking the anvil 16 in returning the piston to its
position adjacent the centralising ring 21.
.
When the piston 26 is in its position adjacent the
centralising ring 21 (as shown at figure 3) ~he other
passage way 30 between the drill bit port 29 of the piston
26 and the bore of the piston is not in communication with
any source of fluid pressure while the one passage way 28
providing communication between the top sub port 27 of the
piston 26 and the bore is in communication with the one
aperture 25a o the other set of apertures 25. The
resultant increased pressure in the space between the top
sub 12 and the corresponding end of the piston produces a
thrust on the piston 26 to cause it to move towards the
drill bit. The pressure producing the thrust on the piston
25 is reduced once the opening of the one passage way 28
- 22 -
into the bore of the piston 26 passes the one aperture 25a
but is further reinforced when the opening of the one
passage way 28 communicates with the other aperture 25b of
the other set of apertures 25 during the movement of the
piston 26 toward the drill bit.
The location of the spaced apertures 25a and 25b allows
greater control over the distance that the piston 26 moves
over previous methods which utilised one aperture only.
The greater control stems from the fact that by variation
of the spacing between the apertures 25a and 25b the
frequency and force of impact of the piston 26 on the
drill bit can be varied according to the geological
conditions in which the hammer is being used or the
pressure of the fluid being used. To effect such variation
requires the replacement of the feed tube 20 only, whereas
previous hammers have required the replacement of
completely different assemblies to effect the same
variation. In addition, by varying th~ spacer ring 21
simultaneously or independently with the feed tube the
nerformance characteristics can be optimised to suit the
conditions or specifications of the holes being drilled.
In existing hammers when the apertures required to effect
the thrust on the piston to drive it onto the drill bit,
are raised in position on the feed tube in order to
lengthen the strike of the piston there is little increase
in the impact force of the piston on the drill bit. By
introducing a second aperture 25b additional pressure is
introduced into the space above the piston to provide an
additional thrust on the piston during its movement
towards the drill bit. It will be appreciated that the use
of the two apertures 25a and 25b also serves to introduce
further fluid into the space above the piston during the
movement of the piston from the drill bito However since
such fluid is introduced into a space previously evacuated
- 23 -
of pressurised fluid in a precise and limited manner due
to the reduced size of the second apertures 25b and since
at the time of such introduction the piston has almost
attained its maximum velocity such introduction does not
greatly effect the pistons movement from the drill bit.
In addition the fluid input into the space between the top
sub 12 and the piston 26 during the movement of the piston
26 from the drill bit serves to prevent the impact of the
piston 26 with the centralising ring 21.
As a result of the embodiment a fluid operated hammer is
produced which utilises a casing not having any passage
ways formed in its wall and not having any contours formed
on its internal surface to effect fluid communicating with
the respective ends of the piston. In addition the hammer
utilises a feed tube which is not contoured on its
external surface and which only involve in its manufacture
the location of the respective apertures. In addition, the
feed tube 20 is accurately and centrally located within the
casing 11 and is independant of any misalignment which may
exist between the top sub 12 and the casing 11 due to
inaccurate machining or tolerance variations in the machin-
ing of either component. Furthermore the piston 26 is
provided with a minimum amount of machining which not only
reduces the manufacturing cost 3f the piston 26 but also
serves to maximise the mass of ~he piston. Similarlyg
because the external surface of the feed tube 20 is
uncontoured, it can be of a reduced diameter from that
currently in use and therefore the mass of the piston 26
can be further maximised.
In order that the operating characteristics of the hammer,
such as stroke, the volumes of spaces within the hammer
and the frequency of reciprocation of the piston 26 can be
varied, the components of the hammer may be readily
changed to provide substitute components of differing dim-
ension, to effect such a change in performance as may be
desirable when operating with compressors which provide
,,p~^~
~ q3
- 24 -
Eluids with greater or lesser pressures than a particular
optimum pressure or in differing bore hole conditions.
Furthermore by use of an aperture having a large area but
a small axial dimensions as the supply aperture to return
the piston to the position adjacent the centralising ring
21 the admission of fluid to effect the raising of the
piston is controlled and the incidence of back hammer is
considerably red~lced. In addition, the use of a set of
longitudinally spaced apertures to effect a thrust on the
piston to produce movement towards the drill bit provides
a greater downward impact-force by the piston on the
anvil. Finally the incorporation of a resilient annular
member between the bit retaining ring in the chuck and the
anvil of the drill bit serves in absorbing at least some
of the impact forces exerted on the an~il by the piston on
the drill bit moving to the "blow-down" position or in the
event of back hammer ~hen in the "blow-down" position.
The second embodiment of figures 4~ 5 and 6 is a fluid
operated hammer which comprises a cylindrical casing 111
having a substantially uncontoured inner face with a top
sub 112 mounted at one end and a drill bit 113 mounted at
the other end in the same manner and having the same
features as the hammer of the first embodiment including
the resilient ring located in the chuck and associated
with the bit retaining ring 114 which was described in the
description of the first embodiment.
The casing 111 further supports a feed tube l~0 which is
concentrically mounted at the one end of the casing 111 in
abutting relation with the inner end of the sub 112. The
feed tube120 extends from the one end of the casing for a
portion of the length of the casing. The mounting of the
feed tube is of the same form as that shown and described
in the first embodiment.
As in the first embodiment the centralising ring 121 may
be readily exchanged with other rings of differing thick-
~.
- 25 ~ 3~
ness in order that the volume of the space between the
upper end of the piston 126 and the top sub may be varied.
The free end of the feed tube is provided with a suitably
dimensioned choke 123 which permits a controlled contin-
uous flow of fluid down through the drill bit 113. The
walls of the feed tube are uncontoured and are formed with
two sets of apertures. One set 124 comprises a single
aperture which extends for a considerable portion of the
circumference of the feed tube but which has a relatively
small dimension in the longitudinal axis of the feed tube~
Alternatively the one set may comprise a series of circum-
ferentially spaced apertures in the walls of the feed tube
which have a relatively small axial dimension. The other
set of apertures comprise a pair of longitudinally spaced
apertures 125a and 125b located towards the free end of
the feed tube from the one set of apertures 124. One
aperture 125a of the other set of apertures which is
loc~ted closest to said one set of apertures 124 is
greater in size than the other of said apertures 125b and
has a greater axial dimension than the other aperture 125b.
The hammer further supports within the oasing 111 a piston
126which is longitudinally slidable within said casing 111
and over said feed tube 1200 One end of said piston i5
provided with a port 127 while another port 129 is located
at an intermediate position on the piston. Said ports
communicate with a passage-way 128 and 130 respectively
extending from the respective port to the internal bore of
said piston. The passage-ways 128 and 130 are formed by
obliquely boring a hole from the position of the respec-
tive port of said piston to the bore of said piston. In
addition the end of the piston adjacent the top sub 112 is
counterbored to provide an expanded portion 131 in the
bore of the piston which extends for a small portion of
the length of the bore.
The circumferential face of the piston 126 between the
position of the other port 129 and the other end of the
- 2G iL~ 3~
piston which is adjacent the drill bit is machined to
reduced diameter and the outer end of that reduced diam-
eter porticn 132 is formed with a rib 133. In addition the
drill bit end of the casing supports a sleeve 134 which
extends a small distance beyond the innermost position of
the anvil 116 of the drill bit 113. The inner most end of
the sleeve 134 is formed with a rib 135 dimensioned such
that the rib 133 at the other end of the piston 126
sealingly engages with the rib 135 on the sleeve when they
are adjacent each other.
As shown at figure 4 to place the hammer in the "blow-
down" position the hammer is moved axially away from the
base of the drill hole in order that the drill bit moves
to its outermost position in the chuck and the bit ring
114 is engaged with the anvil 116 of the drill bit. When
in the "blow-down" mode the piston 16 is retained in
contact with the anvil 116. The maintenance of this posi-
tion is a result of the counter-bored portion 131 at the
one end of the hammer 126 being in communication with the
one set of apertures 124 to provide fluid communication
between the source of fluid pressure and the space located
between the one end of the piston 126 and the top s~b 11~
Since no equivalent pressure or greater pressure is
applied to the other end of the piston through the pass-
age-way 130 the piston 126 is positively retained in
contact with the anvil. Fluid from the top sub end of the
piston escapes to the drill bit via one port 127 and the
one passage 128.
Due to the small axial dimension of the one set o
apertures if the piston should for some reason be moved
from engagement with the anvil a fair degree of movement
of the piston is required for the one set of apertures to
communicate with the drill bit end of the piston through
the passage-way 130 and port 129. The small axial dimen-
sion of the one set of apertures ensures that there can be
no overlap between the counter-bored portion and the pass-
i~ ~
..3
27 ~ Z~3~
age way 128 by the one set of apertures. Therefore 3 thepossibility of back hammer is considerably reduced. In
addition9 due to the absence of restriction between the
one set of apertures and the drill bit other than the
counter-bored portion 131 and the passage-way 128 connec-
ting the drill bit end of the piston with the bore of the
piston, the flow of air to the drill bit during "blow-
down" is relatively unrestricted ensuring clearing of
drill cuttings.
When the fluid operated ham~er is moved axially towards
the base of the drill hole such that the drill bit engages
with the base of the bore hole the drill bit 113 moves
into the fluid hammer. As a result (as shown in figure 5)
the counter-bored portion 131 in the one end of the hammer
126 is isolated from the so~lrce of fluid pressure and the
one passage way 128 connecting the top sub end port 127 of
the piston 126 with the bore of the piston is isolated
from the source of fluid pressure while the other passage
way 130 connecting the drill bie port 129 of the piston 126
with the internal bore o the piston is in communication
with the one set of apertures 124 in the feed tube 120. As
a result fluid pressure from the fluid source is applied
to the space between the reduced diameter portion 132 of
the piston 126, the inner end of the sleeve 134 and the
casing 111 due to the sealing engagement between the ribs
133 and 135 on the piston lZ6 and sleeve 134 respectively.
The resultant pressure differential produces a movement of
the piston 1~6 from the drill bit.
The use of an apPrture124 of relatively small axial
dimensions is a departure from previous practice and
allows a greater control over the introduction of fluid at
a precise point in the travel of the piston126 and
similarly causes the fluid flow to the piston to be shut
off rapidly rather than having a gradual decrease as would
occur i a longitudinally larger port were used.
If desired the one set of apertures 124 can be positioned
- 28 h~
to communicate fully with the drill bit end of the piston
when the piston is raised a small distance from the anvil
in order to make use of the reactive rebound of the piston
after striking the anvil 116 in returning the piston to its
position adjacent the centralising ring 121.
The use of the sleeve 134 in the drill bit end of the
casing reduces the volume of the space into which the
other port 129 delivers fluid to effect movement of the
piston from the drill bit. This reduces the volume of
fluid required to return the piston to its position adjac-
ent the centralising ring 121.
When the piston 126 is in its position adjacent the
c~n~ralising ring 121 (as shown at figure 6) the other
passage way 130 between the other port 129 of the piston
126 and the bore of the piston is not in communication
with any source of fluid pressure while the one passage
way 128 providing communication between the one port 127
of the piston 126 and the bore is in communication with
the one aperture 125a of the other set of aperturees 125.
The resultant increased pressure in the space between the
top sub 112 and the one end of the piston produces a
thrust on the piston 126 towards the drill bit.
The pressure producing the thrust on the piston 126 is
reduced once the opening of the one passage ~ay 128 into
the bore of the piston 125 passes the one aperture 125a
but is further reinforced when the opening of the one
passage way 128 communicates with the other aperture 125b
of the other set of apertures 125 during the movement of
the piston 126 toward the drill bit.
The location of the spaced apertures 125a and 125b allows
greater ~ontrol over the distance that the piston 126
moves over previous methods which utilise one aperture
only. The greater control stems from the fact that by
variation of the spacing between the apertures 125a and
~ 3
- 29 -
1225b the frequency and force of impact of the piston 26
on the drill bit can be varied according to the geological
conditions in which the hammer is being used or the
pressure of the fluid being used. To effect such variation
requires the replacement of the feed tube 120 only, where-
as previous hammers have required the replacement of com-
pletely different assemblies to effect the same variation.
In addition, by varying the centralising ring 121 simultan-
eously or independently with the feed tube the performance
characteristics can be optimised to suit the conditions or
specifications of the holes being drilled.
In existing hammers when the apertures required to effect
the thrust on the piston to drive it on the drill bit are
raised in position on the feed tube in order to lengthen
the strike of the piston there is little increase in the
impact force of the piston on the drill bit. By intro-
ducing a second aperture 125b additional pressure is intro-
duced into the space above the piston to provide an
additional thrust on the piston during its movement tow-
ards the drill bit. It will be appreciated that the use of
the two apertures 125a and 125b also serves to introduce
further fl~id into the space above the piston during the
movement of the piston from the drill bit. However since
such fluid is introduced into a space previously evacuated
of pressurised fluid in a precise and limited manner due
to the reduced size of the second apertures 125b and since
at the time of such introduction the piston has almost
attained its maximum velocity such introduction does not
greatly effect the pistons movement from the drill bit.
In addition the fluid input into the space between the top
sub 112 and the piston 12~ during the movement of the
piston 126 from the drill bit serves to prevent the impact
of the piston 126 with the centralising ring 121.
As a result of the second embodiment a fluid operated
hammer is produced having the same advantages as the first
em~odiment together with the advantage that a smaller
- 30 - ~
vo]ume of pressurised fluid is required to return the
piston to the "raised" position.
The third embodiment of figures 7, 8 and 9 is a fluid
operated hammer which comprises a cylindrical casing 211
having a substantially uncontoured inner face with a top
sub 212 mounted at one end and a drill bit 213 mounted at
the other end in the same manner and having the same
features as the hammer of the first embodiment including
the resilient ring located in the chuck and associated
with the bit retaining ring 214 which is described and
shown in the description of the first embodiment.
The casing 211 further supports a feed tube 220 which is
concentrically mounted at the one end of the casing 211 in
abutting relation with the inner end of the top sub 212.
The feed tube 220 extends from the one end of the casing
for substantially the full length of the casing 211 such
that its free end is received in the bore of the drill bit
213 when the drill bit 213 is in its innermost position in
the casing but it is free of the drill bit when the drill
bit is in its outer most position within the casing 211.
The mounting of the feed tube to the top sub 212 is of the
same form as that shown and described in relation to the
first embodiment.
As in the first embodiment, the centralising ring 221 may
be readily exchanged with other rings of differing thick-
ness in order that the volume of the space between the
upper end of the piston 226 and the top sub may be varied.
The walls of the feed tube are uncontoured and are formed
with two sets of apertures. One set 2~4 comprises a single
aperture which e~tends for a considerable porticn of the
circumference of the feed tube but which has a relatively
small dimension in the longitudinal axis of the feed tube.
Alternatively the one set may comprise a series of circum-
ferentially spaced apertures in the walls of the feed tube
which have a relatively small axial dimension. The other
set of apertures comprise a pair of longitudînally spaced
2~3:L
- 31 -
apertures 225a and 225b located towards the free end of
the feed tube Erom the one set of apertures 224. One
aperture 225a of the other set of apertures which is
located closest to said one set of apertures 224 is
greater in size than the other of said apertures 225b and
has a greater axial dimension than the other aperture 225b.
Towards the free end of the feed tube 220 the walls
thereof are formed with a further aperture or set of
apertures 236 having relatively large dimsen;ons. A choke
223 is located in the feed tube between the two sets of
apertures 224 and 225 and the further set of apertures 236
to provide a controlled continuous flow of fluid down
through the drill bit 213.
The hammer further supports within the casing 211 a piston
226 which is longitudinally slidable within said casing
211 and over said feed tube 220. One end of said piston is
provided with a port 227 while another port 229 is located
at an intermediate position on the piston said ports
communicate with a passage way 228 or 230 respectively
extending from the respective port to the internal bore of
said piston. The passage ways 228 and 230 are formed by
obliquely boring a passage-way from the position of the
respective port on the exterior of said piston to the bore
of said piston. In addition the end of the piston adjacent
the top sub 212 is counterbored to provide an expanded
portion 231 in the bore of the piston which extends for a
small portion of the length of the bore.
The circumferential face of the piston 226 between the
int~rmediate position of the other port 229 and the other
end of the piston 226 which is adjacent the drill bit is
machined to provide a reduced diameter portion wherein the
other end portion of that reduced diameter portion 232 is
formed with a rib 233. In addition, the drill bit end of
the casing supports a sleeve 234 which extends a small
distance beyond the innermost position of the anvil 216 of
the drill bit 213. The inner~ost end of the sleeve ~34 is
2~
- 32 -
formed with a rib 235 dimensioned such that in the rib 233
at the other end of the piston 226 sealingly engages with
the rib 235 on the sleeve when adjacent each other.
As shown at figure 7 to place the hammer in the "blow-
down" position the hammer is moved axially away from the
base of the drill hole in order that the drill bit 213
moves to its outermost position in the chuck and the bit
ring 214 is engaged with the anvil 216 of the drill bit.
When in the "blow-down" mode the piston 226 is retained in
contact with the an~il 215. The maintenance of this posi-
tion is a result of the counter-bored portion 231 at the
one end of the hammer 226 being in communication with the
one set of apertures 224 to provide fluid communicatior-
between the source of fluid pressure and the space located
between the one end of the piston 226 and the top sub 212.
Since no equivalent pressure or greater pressure is
applied to the other end 29 of the piston through the
passage ways 230 the piston 226 is positively retained in
contact with the anvil. Fluid from the top sub end of the
piston escapes to the drill bit via port 227 and the one
passage-way 229 and the further aperture 236 located tow-
ards the free end of the feed tube. The further aperture
236 is dimensioned such that it permits as much flow as is
possible into the drill bit to maximise the use of the
fluid when in the "blow-down" position to clear cuttings
from the bore hole.
Due to the small axial dimension of the one set of
apertures if the piston should for some reason be moved
from engagement with the anvil a fair degree of movement
of the piston is required for the one set of apertures to
communicate with the drill bit end of the piston through
the passage way 230 and port 229. The small axial dimen-
sion of the one set of apertures ensures that there can be
no overlap between the counter-bored portion and the pass-
age-way 228 by the one set of apertures. There~ore, the
possibility of back hammer is considerably reduced. In
_ 33 ~ 2~
addition, due to the lack of restriction between ttle one
set oE apertures and the drill bit other than the counter-
bored portion 231 and the passage way 228 connecting the
drill bit end of the pis~on with ~he bore of the piston,
the flow of air to the drill bit during "blow-down" is
relatively unrestricted ensuring clearing of drill
cuttings.
When the fluid operated hammer is moved axially towards
the base of the drill hole such that the drill bit engages
with the base of the bore hole the drill bit 213 moves
into the fluid hammer. As a result (as shown in figure 8~
the counter-bored portion 231 in the one end of the hammer
226 is isolated from the source of fluid pressure and the
one passage way 228 connecting the top sub end port 227 of
the piston 226 with the bore of the piston is isolated
from the source of fluid pressure while the other passage
way 230 connecting the drill bit port 229 of the piston
226 with the internal bore of the piston is in communica-
tion with the one set of apertures 224 in the feed tube
~20, as a result fluid pressure from the fluid source is
applied to the space between the reduced diameter portion
232 of the piston 226, the inner end of the sleeve 234 and
the casing 211 due to the sealing interengagement between
the ribs 233 and 235 on the piston 236 and sleeve 234
respectively. The resultant pressure differential produces
an upward ~ovement of the piston 226from the drill bit.
The use of an aperture 224 of relatively small axial
dimensions is a departure from previous practice and
allows a greater control over the introduction of fluid at
a precise point in the travel of the piston 226 and
similarly causes the fluid flow to the piston to be shut
off rapidly rather than having a gradual decrease as would
occur if a longitudinally larger port were used.
If desired the one set of apertures 224 can be positioned
to communicate fully with the drill bit end of the piston
when the piston is raised a small distance from the anvil
34 ~ 2~3~L
i~ order to make use of the reactive rebound of the piston
after striking the anvil 16 in returning the piston to its
position adjacent the centralising ring 221.
The use of the sleeve 234 in the drill bit end of the
casing 211 reduces the volume of the space into which the
other port 229 delivers fluid to effect the movement of
the piston towards the drill bit. This reduces the volume
of fluid required to return the piston to its position
adjacent the drill bit.
When the piston 226 is in its position adjacent the
centralising ring 221 (as shown at figure 3~ the other
passage way 230 between the other port 229 of the piston
226 and the bore of the piston is not in communication
with any source of fluid pressure while the one passage
way 228 providing communication between the one port 227
of the piston 226 and the bore is in communication with
the one aperture 225a of the other set of apertures 225.
The resultant increased pressure in the space between the
top sub 12 and the corresponding end of the piston prod-
uces a thrust on the piston 26 to cause it to move towards
the drill bit.
The pressure producing the thrust on the piston 226 is
reduced once the opening of the one passage way 228 into
the bore oi the piston 226 passes the edge of the one
aperture 225a but is further reinforced when the opening
of the one passage way 228 communicates with the other
aperture 225b of the other set of apertures 25 during the
movement of the piston 26 toward the drill bit.
The location of the spaced apertures 225a and 225b allows
greater control over the distance that the piston 226
moves over previous methods which utilise one aperture
only. The greater control stems from the fact that by
variation of the spacing between the apertures 225a and
225b the frequency and force of impact of the piston 26 on
3 5 ~ 29~
the drill bit can be varied according to the geological
conditions in which the hammer is being used or the
pressure of the fluid being used. To effect such variation
requires the replacement of the feed tùbe 220 only, where-
as previous hammers have required the replacement of com-
pletely different assemblies to effect the sarne variation.
In addition, by varying the spacer ring 221 simultaneously
or independently with the feed tube the performance charac-
terlstics can be optimised to suit the conditions or
specifications of the holes being drilled.
In existing hammers when the apertures required to effect
the thrust on the piston to drive it onto the drill bit
are raised in position on the feed tube in order to
lengthen the strike of the piston there is little increase
in the impact force of the piston on the drill bit. By
introducing a second aperture 225b additional pressure is
introduced into the space above the piston to provide an
additional thrust on the piston during its movement
towards the drill bit. It will be appreciated that the use
of the two apertures 225a and 225b also serves to intro-
duce further fluid into the space above the piston during
the moYement of the piston Erom the drill bit~ However
since such fluid is introduced into a space previously
evacuated of pressurised fluid in a precise and limited
manner due to the reduced size of the second apertures
225b and since at the time of such introduction the piston
has almost attained its maximum velocity such introduction
does not greatly effect the pistons movement from the
drill bit.
In addition the fluid input into the space between the top
sub 212 and the piston 226 and during the upward movement
of the piston 226 to serve to prevent the impact of the
piston 226 with the top sub 212.
As a result of the third embodim~nt a fluid operated
hammer is produced having the same advantages as the
second embodiment described above.
.3
- 36 -
It should be noted that the hammer of each embodiment may
be used for bore holes disposed at any angle from a work
station above and below the horizontal axis.
It should be appreciated that the scope of the invention
need not be restricted to the ~particular scope of the
embodiments described above.
