Tool for transporting cutting means to and from a ground drill

Details Tool for transporting cutting means to and from a ground drill Tool for transporting cutting means to and from a ground drill

1998-02-27

2001-03-27

Lillis, Eileen D. (Department: 3673)

Boring or penetrating the earth

Tool removable or insertable through or around driving or...

Laterally shiftable cutter element movable through shaft

C175S257000, C175S259000, C175S260000, C175S273000, C175S289000

Reexamination Certificate

active

06206114

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a tool and, in particular, but not exclusively, to a tool for use in a system for in situ replacement of cutting means for a ground drill.
BACKGROUND OF THE INVENTION
A system for in situ replacement of cutting means for a ground drill is described in Applicant's International application no. PCT/AU94/00322 (WO 94/29567), the contents of which are incorporated herein by way of reference. The system in WO 94/29567 comprises a drive sub which is adapted for connection to a lower end of a core barrel attached to a drill pipe; a tool for installing and retracting drill bit segments from the drive sub; and, an insert or bit locking sleeve for selectively locking the bit segments into seats provided about the inner circumferential surface of an end of the drive sub and subsequently releasing the bit segments for those seats. The tool includes a main body portion and a sleeve slidably mounted thereon. Installation latch dogs provided in the tool extend from apertures or slots cut in the sleeve so as to engage the bit locking sleeve and force it into an installation position in which it locks the bit segments in a cutting position about the drive sub. The tool further includes retrieval latch dogs which can extend from different slots provided in the sleeve for engaging the bit locking sleeve and pulling it upwardly into a retrieval position in which the bit segments can be retrieved from the drive sub.
A slidable cradle extends from a lower end of the tool for carrying the bit segments to and from the drive sub. When installing the bit segments, the cradle is extended from the lower end or head of the tool against the bias of a spring. Bit segments are held by rubber bands about the cradle with one end abutting a stop provided at one of the cradle and an opposite end bearing against the head of the tool. When the tool is lowered into the ground drill (comprising the combination of the drill tube, core barrel and drive sub) and reaches a predetermined position within the drive sub (that being the point of engagement with the bit locking sleeve), the sleeve is caused to move relative to the main body of the tool which in turn releases a set of pins holding the spring about the cradle in compression. This fires the cradle so that the spring is able to expand, retracting the cradle into the main body of the tool which causes an upper end of the bit segment to slide along the head of the tool so as to extend laterally of the outer periphery of the tool. The bit locking sleeve is simultaneously pushed by the tool so as to catch the ends of and move inside the drill bit segments thereby expanding the drill bit segments to the inner diameter of the drive sub and locking the drill bit segments in the cutting position.
When lowering the tool into the ground drill the tool is initially placed within a transport sleeve which acts to compress the installation latch dogs to prevent catching on internal surfaces of the drill tube prior to entering a core barrel and the drive sub. A landing ring is provided between the core barrel and drill tube of a diameter which prevents further progress of the transport sleeve but allows the tool to pass therethrough. The transport sleeve sits on the landing ring and, after installation or retrieval of the cutting means again carries the tool once pulled from beneath the landing ring to the surface.
Field trials of the above system have proved very successful. Nevertheless, it is thought that there is a potential for various problems to arise under extreme operational conditions.
One potential problem with the above system of WO 94/29567 is that due to the relative lengths and configurations of the tool and the bit locking sleeve, when the tool bottoms out, that is, reaches the very end of its travel within the ground drill and stops, the bit locking sleeve may sit several millimetres above an abutment surface formed on the radially inner surface of the bit segments against which, ideally the bit locking sleeve should contact. When this contact is achieved, the maximum clamping force of the bit locking sleeve and bit segments against the inner surface of the drive sub is obtained. It is thought that there is a possibility of the bit locking sleeve effectively working its way loose under the influence of severe and sustained vibration when not disposed in direct contact with the abutment surface of the bit segments.
SUMMARY OF THE INVENTION
It is an object of the present invention to improve the tool of the above system which can push the bit locking sleeve further down into the drive sub.
According to the present invention there is provided a tool for transporting bit segments to and from a drive sub of a ground drill and for moving a bit locking sleeve held within the drive sub to an installation position in which the bit locking sleeve can lock the bit segments against an inner surface of the drive sub, said tool further adapted to cooperate with stopping means disposed within said drive sub for stopping the travel of said tool in a first direction, the tool comprising:
a first portion;
a second portion retractably coupled to a lower end of said first portion; and,
means carried by said first part for engaging said bit locking sleeve;
whereby, in use, when said tool travels in said first direction, said means initially engages said sleeve to move said sleeve toward said installation position and on further travel in said first direction a leading end of said tool engages said stopping means to halt travel of said leading end causing one portion to retract into the other portion enabling further movement of the first portion in the first direction so that said engaging means can move said bit locking sleeve fully into said installation position.
Preferably said first and second portions are resiliently coupled together so that after initial retraction of one of said portions into the other, said portions tend to move away from each other to restore said tool to an equilibrium state.
Preferably an upper end of said second portion is connected to a lower end of said first portion to allow relative movement of said first and second portions in the direction of the length of said tool.
Preferably said first and second portions are provided with respective abutment surfaces adapted to abut each other when said tool hits said stopping means and said one portion retracts into said other portion by a predetermined distance thereby limiting the further movement of said first portion in said first direction.
Preferably said tool further comprises a resilient element retained between said first and second portions acting so as to push said first and second portions away from each other.
Preferably said first portion at said lower end is provided with a first member and said second portion at said upper end is provided with a second member, said members being relatively dimensioned so that one of said members can fit and slide with the other member so as to allow one of said portion to retract into the other portion.
Preferably one of said members is provided with at least one slot which is elongated in the first direction and further comprising means which is coupled to the other member and extends into said at least one slot thereby coupling said first and second portions together.
Preferably said resilient means is retained in a recess formed between said first and second members.
Preferably said first member is tubular in form and said second member slidingly fits within said first member.
Preferably a portion of the length of an interior surface of said first member and/or an exterior surface of said second member is cut out to form said recess for retaining said resilient means.
Preferably said tool is adapted for transporting cutting means to and from a ground drill, said ground drill defining said conduit, said tool further adapted to travel through said ground drill and to corporate with a cutting means locking sleeve disposed in said ground drill, said locking sleeve movable into an installation positi

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