Boring or penetrating the earth – With below-ground tool drive prime mover
Patent
1991-03-22
1992-08-18
Dang, Hoang C.
Boring or penetrating the earth
With below-ground tool drive prime mover
173 78, 173 80, 175215, 175296, E21B 414
Patent
active
051390965
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to improvements in pneumatic percussion hammers.
(2) Prior Art
The specification of my Australian Patent Application No. 81767/87 describes and illustrates a pneumatic percussion hammer having a tubular casing with a top sub to receive air under pressure from the outer tube of a double tube drill stem, and with a bit having an anvil head slidable in a bottom sub of the casing. An axial air feed tube directs air under pressure through the bit and air passages therethrough and a piston slidable on a central air outflow tube is caused to reciprocate by air under pressure directed through an arrangement of air passages and chambers to strike the anvil in a rapid succession of blows which are transmitted to the bit for rock drilling. These hammers have proved to be very successful, and the present invention has been devised with the general object of adding certain improvements which will broaden the versatility and range of applications of the hammer, as well as facilitating its repair and maintenance.
SUMMARY OF THE PRESENT INVENTION
Accordingly, the invention resides broadly in a pneumatic percussion hammer including:
a tubular casing,
a top sub connected to the top of the casing and adapted to receive air under pressure from the outer tube of a double tube drill stem,
a bottom sub connected to the housing,
an air feed tube disposed coaxially in the casing to conduct air under pressure by way of non-return valve means from the top sub into the casing,
an air outflow tube disposed coaxially within the casing and through the air feed tube means for connecting the air outflow tube to the inner tube of the double tube drill stem,
a bit slidable in the bottom sub, having a shank axially apertured for slidable engagement on the air outflow tube and with an anvil at its head,
an axially apertured piston slidable on the air outflow tube and at its upper part slidable on the air feed tube, and
air passages and ports in the piston and chambers in the inner wall of the casing so to direct air under pressure from the air feed tube as to cause the piston to reciprocate to strike the anvil on its downstroke and to exhaust through passages in the bit leading to the bottom of the air outflow tube,
the air outflow tube being slidably removable through the top sub.
Other features of the invention will become apparent from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the invention is shown in the accompanying drawings, wherein:
FIG. 1 is a sectional view of the upper part of a pneumatic percussion hammer according to the invention,
FIG. 1a is a sectional view of the lower part of a pneumatic percussion hammer according to the invention,
FIG. 2 is a sectional view, to larger scale, of the upper part of the pneumatic percussion hammer shown in FIG. 1, with its adaptor unscrewed and with its air outflow tube partly withdrawn,
FIG. 3 is a sectioned view to the same scale as FIG. 2 of the upper part of the pneumatic percussion hammer, the air outflow tube shown in FIGS. 1, 1a, and 2 being replaced with one of modified type, and
FIG. 4 is a sectioned view to the same scale as FIGS. 2 and 3 of the upper part of the hammer fitted with a modified replacement for the air outflow tubes of the other figures,
FIG. 4a is a sectional view to the same scale as FIGS. 2 and 3 of the lower part of the hammer fitted with a modified replacement for the air outflow tubes of the other figures.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The percussion hammer illustrated in FIGS. 1, 1a, and 2, to which reference is initially made, 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 comprise a top shoulder 14, a bottom shoulder 15 and top and bottom piston be
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patent: 3941196 (1976-03-01), Curington et al.
patent: 3991834 (1976-11-01), Curington
patent: 4084647 (1978-04-01), Lister
patent: 4321974 (1982-03-01), Klemm
patent: 4705118 (1987-11-01), Ennis
patent: 4819746 (1989-04-01), Brown et al.
patent: 4921052 (1990-05-01), Rear
patent: 4921056 (1990-05-01), Ennis
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