Chucks or sockets – Accessory or component – Adapter
Patent
1998-11-16
2000-08-29
Pitts, Andrea L.
Chucks or sockets
Accessory or component
Adapter
2281145, 279 193, 279 194, 279 196, 279145, 408144, 408226, B23B 522
Patent
active
061096202
DESCRIPTION:
BRIEF SUMMARY
This invention relates to shank adapters for rock drilling tools, and to a method of making a shank adapter. A shank adapter is used in rock drilling to connect a drill string (ie a set of drilling rods joined end to end with a drill bit at the remote end) to the chuck of a drill hammer. Shank adapters are sometimes also called lug chuck adapters.
The invention relates to the design and manufacture of a shank adapter and has benefits for both in-service performance and ease of manufacturing.
In the past, shank adapters have been machined from a single piece of solid homogenous material. The single piece is conventionally a solid bar or billet of uniform cylindrical section. Considerable machining effort is required to convert this single piece of material to the complex form of a shank adapter. Furthermore, in such adapters, different parts of the adapter, which experience different working loads, are made from material with the same mechanical properties. A compromise therefore has to be found by way of a material which will cope with different loads, while being less than optimum for any one working load.
According to the invention, there is provided a method of making a shank adapter wherein the chuck end of the adapter is made from one piece of material, the threaded end is made from another, different, material and the chuck end and the threaded end are permanently joined to one another in one stage of manufacturing.
The chuck end and the threaded end are preferably joined to one another by friction welding.
Friction welding is a known process for connecting metal parts. In friction welding, the surfaces of the parts to be joined are first pressed together with a high compression force (typically 10 Bar) and the parts are moved over one another in a direction generally normal to the direction of the compressive force. The friction between the parts produces high local temperatures resulting in local melting of the metal. In a second stage, the pressure is increased (to say 40 Bar), flash is formed between the surfaces and there is some length reduction between the surfaces as material is forced from the centre of the interface to the edge of the interface as a consequence of (a) the material's new found ability to flow, (b) the presence of centrifugal force due to the relative motion of the surfaces and (c) the presence of the compressive force. In a third stage, relative movement between the surfaces is stopped and there is large increase in compressive force (for example to 65 Bar) and the surfaces are forged together and the parts weld together as the locally melted metal solidifies.
In this case, the relative movement between the parts (head and shank) is a relative rotation about the bit axis.
The properties of the two materials used, respectively, for the chuck end and the threaded end can then each be optimised for different in-service demands.
It is within the scope of the invention for the shank adapter to include more than two different materials.
The threaded end can be made from a length of hollow bar stock which is preformed with an axial bore. This directly avoids one machining step which would otherwise be necessary (ie the drilling out of a bore). The length of hollow bar stock can however upset forged to form an enlargement at one end, and a thread can then machined into the material of the enlargement. In this way, it may be possible to enlarge the diameter of the part of the stock where the thread will be formed, and then to avoid having to machine the part of the stock which will form the shaft of the adapter.
The adapter is preferably carburised after the chuck end and the threaded end have been permanently joined to one another.
The invention also extends to a shank adapter wherein the chuck end of the adapter is made from one piece of material, the threaded end is made from another, different, material and the chuck end and the threaded end are permanently joined to one another.
The chuck end can be made from a high nickel chromium steel and the threaded end can be made from a c
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Dillon Joseph
O'Brien John
Roberts Nigel
Boart Longyear Limited
Hochberg D. Peter
Pitts Andrea L.
Smith Monica
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