Rock drill
AssigneeSantrade Ltd.
InventorLars E. Larsson
Life of this patent
Estimating the term…
Abstract
A drilling assembly for use in percussion drilling comprising a drill bit and a drill rod having cooperating conical surfaces, one of said surfaces being provided with a helically extending thread. For purposes of ensuring a reliable connection the thread meets certain geometrical demands and is designed as a left hand thread. Further, the conical surface being provided with the thread is harder than the other conical surface.
Claims13
In a percussion rock drilling assembly of the type comprising:
- a drill bit mounted on a drill rod such that a first conical surface on said drill bit engages a second conical surface on said drill rod, the improvement wherein:
- one of said first and second conical surfaces is harder than the other and includes a helically extending left-hand thread, and
- said other conical surface is generally smooth and sized to receive said one surface by a frictonal sliding fit so that a corresponding helical thread is formed in said other surface in response to shock waves generated during a percussion drilling operation.
A drill rod for carrying a drill bit in a percussion rock drilling assembly, said drill rod having a first conical surface adapted to be frictionally slidingly received in a second smooth conical surface of the drill bit, said drill rod including a helically extending left-hand thread, the depth of said thread being at least equal to the small leg of a right triangle having a large leg coinciding with a generatrix of said conical surfaces, a hypotenuse parallel to a longitudinal axis of said drill rod, and a smallest angle formed by the generatrix and hypotenuse, the triangle being inscribed within the profile of the thread.
A method of forming a threaded connection between a drill bit member and a drill rod member of a percussion rock drilling assembly, comprising the steps of:
- providing one of said members with a first conical surface having a first helically extending left-hand thread,
- joining said one member with the other of said members such that said first surface engages a generally smooth second conical surface of said other member and which second surface is softer than said first surface, and
- performing a percussion drilling operation so that the generated shock waves form in said second surface a second helical thread which corresponds to said first thread.
Dependencies are inferred from the claim text.