Tool driving or impacting – Drive controlled by relative axial movement of tool – Drive motor controlled
Patent
1989-04-24
1990-03-27
Yost, Frank T.
Tool driving or impacting
Drive controlled by relative axial movement of tool
Drive motor controlled
173136, 173 73, B23Q 500
Patent
active
049112503
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
(1) Field of the Invention
THIS INVENTION relates to a pneumatic percussion hammer.
(2) Prior Art
Pneumatic percussion hammers are well-known and widely used in rock drilling, such a hammer being described and illustrated in the specification of my Australian Patent No. 493847. Although hammers according to this Patent have been found to be very efficient in operation, they are not able to provide uncontaminated core samples as the rock fragments carried by the flow of air up the bore hold, outside the hammer and the drill tube onto which the hammer is screwed, will be likely to detach fragments from the sides of the bore hole and the air flow will carry these as well as fragments from the bottom of the hole.
SUMMARY OF THE PRESENT INVENTION
The general object of the present invention is to provide a pneumatic percussion hammer which will overcome this disadvantage.
The invention resides broadly in a pneumatic percussion hammer for rock drilling including:
a tubular casing;
a top sub at the top of the casing for connection to, and to receive air under pressure from, the outer tube of a double tube drill stem;
an air feed pipe from the top sub extending co-axially into the casing
an air outflow pipe for connection at the top to the inner tube of the drill stem and passing co-axially through the air feed pipe;
a bit, its shank mounted for limited slidable movement in the lower end of the casing;
an anvil on the bit shank;
a bit air passage through the anvil, shank and bit, and ducted to the exterior of the bit, the lower end of the air outflow pipe being slidably engaged in the lower part of this passage and communicating, through ducts, to the bottom of the bit;
a sliding seal tube, its lower end secured in the upper part of the bit air passage, and extending above the anvil and co-axially about the air outflow pipe;
a piston disposed co-axially about the air outflow tube and slidable in the casing to strike the anvil on its down-stroke, the bore of the piston being restricted at an intermediate position for close slidable engagement with the air outflow tube and to divide the axial passage of the piston into an upper axial passage which is slidably engaged with the air feed tube and a lower axial passage for sliable engagement, when the piston is on its downstroke, with the sliding seal tube;
a top pressure chamber in the casing about and above the top of the piston;
a bottom pressure chamber in the casing about and below the piston;
a central chamber in the casing about an intermediate part of the piston; and
pressure ports in the piston for directing air under pressure from the 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 lowered position, and exhaust ports in the piston for conducting air, when the piston is lowered, from the central chamber to the top pressure chamber.
Other features of the invention will become apparent from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
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 percussion hammer according to the invention, its piston in fully raised position;
FIG. 2 shows in section the hammer with its piston driven down anvil; into the and
FIG. 3 is a similar view of the hammer lifted from the work face.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
This percussion hammer includes a cylindrical tubular casing 10, of which each end part of the bore is enlarged and threaded. Two further enlargements of the bore define a top pressure chamber 11 and a bottom pressure chamber 12, and a central bore enlargement defines a central chamber 13. The lesser diameter parts between these chambers define a top shoulder 14, a bottom shoulder 15 and top and bottom piston bearings 16 and 17.
A piston stop ring 18 engaged with the top shoulder 14 has a seat
REFERENCES:
patent: 3524511 (1970-08-01), Klemm
patent: 3527239 (1970-09-01), Boom
patent: 3599730 (1971-08-01), Luthman et al.
patent: 4321974 (1982-03-01), Klemm
patent: 4446929 (1984-05-01), Pillow
patent: 4753302 (1988-06-01), Gien et al.
patent: 4790390 (1988-12-01), Sweeny
Fridie Jr. Willmon
Yost Frank T.
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