CA2424194C

CA2424194C - Drill string shock absorber

Info

Publication number: CA2424194C
Application number: CA 2424194
Authority: CA
Inventors: Bernard Lionel Gien
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-04-10
Filing date: 2003-03-31
Publication date: 2007-10-09
Anticipated expiration: 2023-03-31
Also published as: AU2003203608A1; CA2424194A1

Abstract

The invention concerns a shock absorber for a borehole drilling machine to absorb axial and torsional loads having a pair of components for connection to each other in a drill string, each component having a circumferentially extending series of lobes and a plate with inwardly extending lobes between the lobes of the components, a resilient member located between the components and fastening means extending between the plates on one side of the member and the lobes on the component on the other side.

Description

DRILL STRING SHOCK ABSORBER
FIELD OF THE INVENTION
This invention relates to shock absorbers which are included in drill strings used with borehole drilling machines.
BACKGROUND TO THE INVENTION
Drilling machines utilize drill strings to transmit power down predrilled holes to a drill bit at the bottom of the hole. The drill bit may be operated by a down-the-hole hammer assembly or by a rotary action.
Whatever method is used it is highly desirable that a shock-absorber be incorporated in the drill string between the bit and the driving head. This is usually done by positioning the shock-absorber between the driving head and the first drill rod of the drill string.
Known types of shock absorbers, which must absorb axial shock loading and the torque applied to the drill string, have either cumbersome casings with two sets of rubber elements or one element with straps holding the top and bottom halves of the shock absorbers together.
Applicant's earlier South African Patent No 94/2201 discloses a shock absorber which to a large extent eliminated the problems above referred to resulted in a somewhat cumbersome construction which induced undesirable stresses in the connecting bolts during operation of the drill.

OBJECT OF THE INVENTION
It is the object of the present invention to provide a shock absorber which is more cost effective and technically more advantageous than the applicant's earlier construction.
SUMMARY OF THE INVENTION
In accordance with this invention there is provided a borehole drilling machine shock absorber comprising a pair of oppositely disposed circumferentially flanged components adapted for connection into a drill string, each flange providing a series of outwardly projecting perforated lobes symmetrically positioned with a resilient member located between the flanges, the components being relatively offset circumferentially, a pair of annular plates providing inwardly extending perforated lobes located between the lobes of the flanges and fastening means extending between the lobes of the plates on one side of the resilient member and the lobes on the flange of the component on the opposite side of the member.
2~ The invention further provides for the fastening means to be bolts and nuts and for the resilient member and the plates to have a circular shape.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of this invention will become apparent from the following description of a preferred embodiment in which:
FIG.1 shows a plan view of a shock absorber; and FIG .2 shows a longitudinal cross-section of Fig 1.

DETAILED DESCRIPTION OF THE INVENTION
As illustrated the shock absorber (1 ) for a drill string (not shown) consists of two components (2) and (3) for attachment in a drill string for a borehole drill.
The component (2) is for attachment to the drill head (not shown) and component (3) will in use be secured to the first drill rod (not shown) of the drill string.
The usual tapered threads will be used to join the components into the drill string.
The components (2) and (3) have oppositely disposed hollow central bosses which overlap axially and are sealingly engaged with each other as indicated at (4).
Component (2) has an outwardly extending flange (5) which, as can be seen in Figure 2, carries peripheral outwardly extending lobes (6) symmetrically arranged around the periphery of the flange (5). Each lobe (6) has an aperture (7) therethrough.
Similarly component (3) has a flange (8) and lobes (9) with apertures (10) therethrough.
A cylindrical resilient member (12) engages over the component (3) and is located between the flanges (5) and (8) of components (2) and (3).
When the components (2) and (3) are assembled with the resilient member (12) the lobes (5) and (8) are symmetrically circumferentially offset to extend between each other.
At each end of the resilient member (12) is an annular rigid plate (13). The interior periphery of these plates (13) are also shaped to have inwardly projecting symmetrically located lobes (14). These lobes (14) locate between the lobes (6) and (9) as can be seen in Figure 1 and the lobes (14) are also perforated as shown at (15) The resilient member (12) has passages (16) therethrough arranged to be co-axial with the apertures (7) and (10) and (15) through the lobes (6) and (9) and 5 (14).
It will be appreciated that the components (2) and (3), resilient member (12) and annular plates (13) are, in use, arranged so that bolts (17) can be passed through flange (5), resilient member (12) and annular plate (13) adjacent flange (8).
Similarly, bolts can be passed through flange (8), the resilient member (12), and the plate (13) adjacent the flange (5).
With the bolts so secured the shock absorber (1 ) can cushion axial intermittent IS loads through the resilient member (12) being under compressive loads while torsional loading is resiliently absorbed by the plates (13) and flanges (5) and (8) and the bolts.
It will be appreciated that both torsional and axial loads through the drill string are absorbed and the securing bolts are not subjected to bending loads such as, in the past, have damaged the shock absorber (1 ).
Further the overall radial dimensions of the shock absorber can be kept smaller and the unit more compact than has been possible heretofore.
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Claims

1. A borehole drilling machine shock absorber comprising a pair of oppositely disposed circumferentially flanged components adapted for connection into a drill string, each flange providing a series of outwardly projecting perforated lobes symmetrically positioned with a resilient member located between the flanges, the flanged components being relatively offset circumferentially, a pair of annular plates providing inwardly extending perforated lobes located between the lobes of the flanges and fastening means extending between the lobes of the annular plates on one side of the resilient member and the lobes on the flange of the flanged component on the opposite side of the resilient member.

2. A borehole drilling machine shock absorber as claimed in claim 1 in which the flanged components have oppositely disposed hollow central bosses which overlap axially.

3. A borehole drilling machine shock absorber as claimed in claim 2 in which the flanged components have oppositely disposed hollow central bosses which overlap axially in sealing engagement with each other.

4. A borehole drilling machine shock absorber as claimed in claim 1 in which the fastening means are nuts and bolts.