Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTION ` . `
This invention relates to an improved pneumatic
percussion hammer. --
The general object of the invention is to provide an
air operated percussion hammer, particularly for use in down-
the-hole rock drilling, and usable on standard rotary drilling
rigs, the hammer being particularly simple and economical to
manufacture, capable of being made to smaller sizes than is
generally practical with conventional percussion hammers, and
efficient, sturdy, durable and trouble-free operation.
SU~MARY OF THE INVENTION
In accordance with the above object, the present
in~ention is a pneumatic percussion hammer for rock drilling
which includes a tubular housing having, at its top, a top sub
adapted to be connected to, and to receive air pressure from,
a drill rod. A cylindrical air feed passage extends from this
top sub coaxially into the housing, being formed with holes
adjacent its bottom; the tube apart from the holes serving no
valving function. A bit having a shank is mounted for limited
slidable movement in the lower end of the housing; there being
an anvil on the bit shank and a bit air passage through the
anvil, shank and bit. A sliding seal tube extends axially into
the housing from the bit air passage. A piston reciprocally
slides in the housing, being adapted to strike the anvil on its
down-stroke. The housing has a top pressure chamber about and
above the top of the piston; a bottom chamber about and below
the piston, and a central pxessure chamber about an intermediate
part of the piston. There are also provided an upper cylindrical,
axial passage in the piston, slidably engaged with the air feed
tube and a lower axial passage in the piston adapted, when the
piston is on its down-stroke, to engage slidably with the
sliding seal tube. The piston has pressure ports extending
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therethrough, communicating with the upper and lower axial
passages, these ports being adapted to direct air under pressure
from t:he upper axial passage of the piston to the top pressure
chamber when the piston is in raised position, and to the
bottom pressure chamber when the piston is in lower position.
Finally, the piston has exhaust ports adapted to conduct air
under pressure between the central chamber and the lower axial
passage of the piston and to conduct air, when the piston is
lowered, from the central chamber to the top pressure chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
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In order that a preferred embodiment of the invention
may be readily understood and carried into practical effect,
reference is now made to the accompanying drawings, wherein:-
Fig. 1 is a sectional view of a pneumatic percussionhammer for rock drilling made according to the invention, its
piston being in fully raised position,
Fig. 2 is a sectional view of the hammer, its piston
being brought down on the anvil of the hammer, and
i Fig. 3 is a sectional view of the hammer, the housing
being raised relative to the bit to bring the parts to by-pass
position.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The pneumatic hammer includes a cylindrical tubular
housing 10, the bore of which is formed with enlarged-diameter
parts and threaded parts which are arranged symmetrically so
that the housing is reversible. An enlargement of the
diameter of each end portiQn of the bore is threaded, as
indicated at 11. Two further enlargements of the bore ______
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diameter define a top pressure chamber 12 and a bottom
pressure chamber 12, and a central bore enlargement defines
a central chamber 14. The annular sections of lesser
internal diameter between these enlargements comprise a top
shoulder 15, a bottom shoulder 16, and top~ and bottom piston
bearings indicated at 17 and 18 respectively.
An air intake member 19 is located in the upper part
of the housing 10 and has a circumferential flange bearing on
the top shoulder 15, this member being secured in place b~r a
top sub 20 screwed into the upper end of the housing, and
having an axial air passage 21. In this air passage is an
annular valve seating for a spring-loaded check valve 22
slidable in an axial aperture in the top of the air intake
member. Air entering the axial air passage 21 of the air
intake member 19 under pressure will unseat the valve 22,
p~ 5B between the enlarged lower part of the axial passage 21
and the top part of the air intake member, and pass through
radial holes 23 in the air intake member and thence through
an air feed tube 24 extending coaxially down into the housing
from the air intake memberO
A piston 25 is slidable in the top anci bottom piston
bearings 17 and 18 of the housing 10, and is formed with an
upper axial passage 26, in which the feed tube 24 is closely
but slidably engaged, and with a lower axial passage 27, a
restricted choke passage 28 interconnecting these two axial
passages of the pistonO
A bit 29 has its shank 30 slidably engaged in a
driver sub 31 screwed ixlto the threaded lower part 11 of the
;; ~ housing 10, the driver sub holding a split stop ring 32
against the bottom shoulder 16 of the housing. The enlarged
top of the bit shank constitutes an anvil 33, and thee;top
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ring 32 limits the downward movement of this anvilO The
lower part of the bit shank is of hexagonal form, as
indicated at 34, and the lower part of the bpre of the driver
sub 31 is of corresponding cross-section so that the bit is
restrained against rotation relative to the housing 10. A
slidable seal tube 35 has its lower end secured in an air
passage 36 e~tending axially through the anvil 33 and bit
shank 30 and leading to several passages passing obliquely ~;
through the bit 29, When the piston 25 is lowered to the
anvil 33, as shown in FIG. 2 the sliding seal tube 35 is
closely engaged in the lower axial passage 27 of the piston,
and when the piston is raised, as shown in FIG. 1, it is
li~ted clear o~ the sliding seal tubeO
Assuming the piston 25 is to be raised initially, as
shown in FIG. 1, when air under pressure is introduced through
the feed tube 24, as before described, it passes into the
upper axial passage 26 of the piston, and passes thence
through an oblique pressure port 37 and into the top pressure
chamber 12, and consequently the piston is driven down onto
the anvil 33, a9 shown in FIG. 20 Air under pressure in the
top pressure chamber 12 can then pass into the central chamber
14 by way of a top exhaust port 38 extending down from the top
of the piston and radially out from its side, this port being
closed by the upper bearing 17 when the piston is raisedO
From the central chamber 14, the air under pressure can pass
through an oblique central chamber exhaust port 39 in the
piston, leading to the lower axial`passage 27, of the piston
and through the sliding seal tube 35 and the axial passage 36
of the ~it, for clearing fragments from the bore hole,
When the piston 25 is brought down to the anvil 33,
as shown in FIG. 2, air introduced under pressure through the
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axial passage 21 of the top sub and entering the upper axial
passage 26 of the piston, by way of the feed tube 24, is
conducted through an oblique pressure port 40 from this axial .
passage to the bottom pressure chamber 13, and consequently
the piston 25 is driven upwards, the pressure port 40 being
quickly closed by the lower bearing 180 When the piston rises
clear of the sliding seal tube 35, air under pressure in the
bottom pressure chamber can expand into the lower axial ::.
passage 27 of the pi.~ton and thence through the oblique port
39 to the central chamber 14. With the up-stroke of the
piston~ air is compressed in the top pressure chamber to :`:
absorb shodk and to give some reaction air-thrust before the
pressure port 37 is opened to cause the piston to be driven
down again, as before described. ~ .
When the hammer is dri~ling rock, the pressure
: applied to the too~ keeps the driver sub 31 close down on to
bit 29, as shown in FIGS. 1 and 2. If the housing 10 is
lifted relative to the bit, as shown in FIG. 3, so that the
; anvil 33 is brought onto the stop ring 32, then the piston, on
its down-stroke, will descend further, relative to the housing,
than previously, uncovering radial holes 41 in the lower end
of the feed tube 24. Consequently, the air introduced under
pressure to the tool may pass through these holes into the top
pressure chamber 12, through the top exhaust port 38 to the
central chamber 14. From the central chamber 14, the air under
pressure will pass to the bottom pressure chamber 13, by way
of pressure port 37, axial passage 26 and pressure port 40, and
u~ pass also through the central chamber exhaust port 39 to
~: the lower axial passage 27 of the piston, and through the
,
: 30 sliding seal tube 35 to the passage 36 through the bit. It
wilI be seen, then, that the action of lifting the tool from
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the working face causes the air under pressure to by-pass the
piston, bringing the operation of the tool to a halt, and at
the same time allows extra air under pressure to clean out
the bore holeO
The restricted passage or choke ~8 permits extra air
to flow through the passage 36 of the bit during normal
operation of the hammer, this flow of air, however, being of
insufficient volume to interfere with the reciprocation of the
piston. -
For clarit~, the various ports of the piston have
been shown in singular, but in practice it is preferred that
a number, say three, should be provided of eachO
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