Backhead assembly for DTH hammer

Abstract

A backhead assembly system for a Down The Hole (DTH) hammer operated by a supply of compressed fluid, that comprises mainly a backhead, said backhead having a central hole capable of transporting the pressurized air to the hammer and an inner cylinder, coaxially disposed and coupled with releasable holding mediums to the backhead, were said backhead has an interior frontal cavity and said releasable holding mediums are in the mentioned frontal cavity. The hammer also comprises a wear sleeve, coaxially disposed to the backhead and inner cylinder, in which the backhead is coupled to the rear side of the wear sleeve. In both embodiments of the present invention, the inner sleeve has a rear section of less diameter and a front side of larger diameter; both sections joined through a portion of generally increasing diameter.

Claims

1. A Down-the-Hole hammer, comprising: a cylindrical casing having a rear and front side; an axial axis, longitudinal to the Down-the-Hole hammer and cylindrical casing; a backhead coupled to the rear side of said casing, said backhead having a frontal interior cavity and a central bore to transport a compressed fluid flow from a supply to the Down-the-Hole hammer, an inner cylinder coaxially disposed inside said casing, said inner cylinder having a front and a rear side of different diameters, fastening means that allow a releasable coupling of the rear side of the inner cylinder to the frontal interior cavity of the backhead; a piston co-axially disposed inside the cylindrical casing, where the rear side of said piston is disposed at an interior of the inner cylinder, the piston capable of reciprocating slidable movement; wherein the fastening means includes: a plurality of longitudinal grooves in a rear portion of the inner cylinder; a plurality of fins, formed between the longitudinal grooves of the inner cylinder, one or more ledges in the rear portion of the inner cylinder, one or more grooves in the frontal interior cavity of the backhead, where the one or more ledges of the inner cylinder can fit into the one or more grooves of the backhead when the fins are being deflected; and radial retention means to avoid an inward deflection of the fins of the inner cylinder.

2. The Down-the-Hole hammer as claimed in claim 1, wherein: the backhead with the inner cylinder and the fastening means form a subassembly that can be removed from the Down-the-Hole hammer as a whole, allowing direct access to the piston.

3. The Down-the-Hole hammer as claimed in claim 1, wherein the inner cylinder has a rear section of less diameter than a frontal section, and a variable diameter section that joins previous sections, this way the rear section of less diameter can be inserted into the frontal interior cavity of the backhead.

4. The Down-the-Hole hammer as claimed in claim 3 wherein the inner cylinder is fastened to the backhead through releasable fastening means.

5. The Down-the-Hole hammer as claimed in claim 1, wherein the one or more ledges of the inner cylinder form a conical profile, wherein the one or more ledges increase in height from the front to the rear side, being shorter at the front ledge and taller at the rear ledge.

6. The Down-the-Hole hammer as claimed in claim 1, wherein the inner cylinder has a rear section of less diameter than a frontal section, and a variable diameter section that joins previous sections together.

7. The Down-the-Hole hammer as claimed in claim 6, wherein the inner cylinder ports have a total or partially tilted exit.

8. The Down-the-Hole hammer as claimed in claim 1, wherein the inner cylinder has ports on a frontal side of the one or more grooves to allow the compressed fluid flow.

9. The Down-the-Hole hammer as claimed in claim 1, wherein the radial retention means consist of a part which contains an opening or channel capable of letting the air flow through the opening, where this part is held to the backhead through a pin.

10. The Down-the-Hole hammer as claimed in claim 1, wherein the backhead, inner cylinder, fastening means and radial retention means form a subassembly that can be removed from the Down-the-Hole hammer, allowing direct access to the piston.

11. The Down-the-Hole hammer as claimed in claim 1, wherein the inner cylinder is releasably fastened to the backhead through a pin.

12. The Down-the-Hole hammer as claimed in claim 1, wherein the radial retention means includes a part located inside the rear portion of the inner cylinder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1-A is a sectioned view of the rear side hammer assembly of a first embodiment. In this view, a backhead, wear sleeve, fastened means, inner cylinder and piston are presented.

(2) FIG. 1-B is a sectioned view of a second embodiment.

(3) FIG. 2 is an isometric view of the inner cylinder defined in the first embodiment.

(4) FIG. 3 is a backhead sectioned view, where it is possible to observe the grooves profile of the backhead interior for the first embodiment.

(5) FIG. 4 is a sectioned view of the rear side hammer assembly, in which the upper subassembly of the first embodiment is removed from the hammer.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(6) FIG. 1-A is a DTH hammer section according to a first embodiment, conformed by a cylindrical casing or wear sleeve (30), a central bored (12) backhead (10), and a frontal interior cavity (15) connected to said central bore (12). Said backhead is coaxially coupled to the cylindrical casing or wear sleeve (30) posterior side (32), and an inner cylinder (40) is coaxially disposed in the interior of said wear sleeve (30), generating an annular fluid path (33) between said inner cylinder (40) and said wear sleeve (30). The inner cylinder (40) has fins (47) and ledges (41) in the rear side and said backhead (10) has inner grooves (11) in the interior frontal cavity (15), where said inner cylinder (40) can be fixed to said backhead (10), deflecting said inner cylinder (40) fins (47) and matching said ledges (41) to the inner grooves (11) of the backhead (10). Said inner cylinder (40) can be released from the backhead (10) deflecting said fins (47) of the inner cylinder (40) and pulling the inner cylinder out of the backhead (10).

(7) In the first embodiment, a retainer element (20) is provided, located in the interior of the inner cylinder (40) to avoid the accidental inward deflection of the same; a pin (23) is provided to maintain the retainer element (20) and is at the same time fixed to the backhead (10).

(8) Inside the wear sleeve (30), there is a piston (50) that moves alternately along the axial axis (01) when the hammer is fed with pressurized fluid. The piston's (50) rear section (51) is inserted in the inner cylinder (40), while the frontal section (52) is in contact with the wear sleeve (30).

(9) To make the pressurized fluid flow move the piston (50), it is first necessary to channel the flow to the annular channel (33) formed between the wear sleeve (30) and the inner cylinder (40), to then distribute the flow alternative to the rear section (51) and to the front section (52) of the piston.

(10) For that reason the inner cylinder has ports (45) in its rear section, connecting the interior of the inner cylinder (40) to the annular channel (33), while the retainer element (20) has holes (24), that in conjunction with the inner cylinder port (45) allows the flow path from the central bore (12) of the backhead (10) to the annular channel (33).

(11) FIG. 2 shows an inner cylinder (40) that has in the posterior section (42) several longitudinal grooves (44) that generate fins (47). Next to the grooves (44), following the axial direction (01) and towards the frontal section (43) there are ports (45) ending in a total or partially inclined exit (46). In the outside surface of the fins (47) there are the ledges (41) that work as a fastening medium in this embodiment.

(12) FIG. 3 shows a section of the backhead (10), with its central bore (12) that continues in its internal frontal section (14) until a bigger diameter cavity (15). In the interior of this cavity (15), there is a groove profile (11) that allows the releasing coupling mechanism with the ledges (41) of the inner cylinder. Also, a profile (13) that connects the pressurized fluid path to the annular section (33) between the inner cylinder (40) and the cylindrical casing (30) is seen.

(13) FIG. 4 shows a rear sub-assembly of the first embodiment, which is conformed mainly of the backhead (10), the inner cylinder (40), the retainer element (20) and the pin (23).

(14) FIG. 1-B shows a DTH hammer section, according to a second embodiment, which is conformed by a cylindrical casing (30), also called wear sleeve, and in its rear side (32) is located a backhead (10). On said backhead, there is an inner cylinder (40), concentric to the wear sleeve (30) and the backhead (10); which is fixed to the latter by releasable fastenings means. In this embodiment, the fixture is done by a pin (23), resulting in a backhead sub-assembly, composed mainly by a backhead (10), an inner cylinder (40) and a pin (23)

(15) In this second embodiment, to guide the pressurized fluid flow to the annular section between the inner cylinder and the wear sleeve, the inner cylinder (40) has orifices or ports (49) in its posterior section (42) that allow the flow to go through it defining a passage that starts at the central bore (12) of the backhead (10) continuing to the frontal interior cavity (15) of the backhead (10), passing through the orifices (49) of the inner cylinder (40), to then be guided by an external surface (48) of the increasing diameter section of the inner cylinder and the backhead profile (13).