Boring or penetrating the earth – Below-ground impact members – Fluid-operated
Patent
1996-03-20
1998-03-03
Neuder, William P.
Boring or penetrating the earth
Below-ground impact members
Fluid-operated
175417, E21B 406
Patent
active
057224951
DESCRIPTION:
BRIEF SUMMARY
THIS INVENTION relates to the make-up system of down the hole hammers for supporting components such as the valving system, check valve, control rods, cylinders or like fixed internal components within the hammer casing.
Down the hole hammers (hereinafter referred to "of the type specified) to which the invention relates comprises a hammer casing which has a top sub mounted to one end and supports a drill bit chuck at the other end, the casing accommodates a piston between the top sub and the drill bit chuck which is caused to reciprocate within the hammer casing. The reciprocation of the piston is effected by the delivery of high pressure air to the hammer. Such high pressure air can be delivered to the space within the hammer casing by a variety of valving systems which can comprise; a valve body and assembly with moving components; or an internal cylinder incorporating porting; or a central axial control rod and a check valve assembly; which are each removably supported at the one end of the hammer casing between the top sub and a shoulder or flange formed in the hammer casing or a retainer ring which is snugly received in a recess formed in the wall of the hammer casing. Throughout the specification the term "valving system" shall be taken to include any form of fluid delivery system including that described above which are utilised in down the hole hammers.
It has been found that in the past, the manufacture of down the hole hammers of the type specified, significant costs are incurred in machining the hammer casing, internal cylinders, and components of the valve system to very close tolerances such that they are suitably located and adequately supported and accommodated within the hammer assembly over the life of the hammer to be able to withstand the cyclic forces, inertial forces and stresses which are incurred as a result of the normal operation of the hammer. In addition, such machining can result in a significant reduction in the wall thickness at the ends of the hammer casing in comparison to the wall thickness of the central portion of the hammer casing which accommodates the piston. The system of supporting the above components is hereafter referred to as the "make-up system".
It is an object of this invention to reduce the fabrication costs of a down the hole hammer through a modification of the make up system and the method of retention of the valving system and to maximise the internal bore of the hammer casing in the portion which accommodates the piston in order to maximise the diameter of the piston for a given hammer casing outside diameter. In addition, this support needs to be provided over the life of the hammer.
In one form the invention resides in a make up system of a down the hole hammer of the type specified comprising an air flow delivery or valving assembly to be supported at said one end of the hammer casing having an annular flange thereon where the annular flange is capable of being slidably received within the hammer casing, an annular recess formed in the wall of the hammer casing, a retainer ring supported from said recess and extending inwardly beyond the inner face of the hammer casing, said flange being formed with an annular rebate around its perimeter adjacent the inner axial face to define a space between the retainer ring, the flange and the side wall of the hammer casing, a compressible ring also received in the recess and located in the space; said compressible ring being compressed to fill the space as a result of the clamping forces applied by the fixing of the top sub to the hammer casing.
According to a preferred feature of the invention the retainer ring is formed of a plurality of segments. In addition, the recess may be formed of two axially spaced annular portions separated by an intermediate rib portion and wherein the outer circumferential face of the retainer ring is formed of a complementary configuration to be received in the recess to both sides of the rib portion.
According to a further preferred feature of the invention the recess has a width c
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