Release assembly and method of forming drilling tool

Abstract

A release assembly and a method of forming a drilling tool for rock or overburden drilling is provided. The release assembly is arranged axially between two drilling tool components. The release assembly includes a release mechanism allowing an initial axial length to shorten when a joint of the drilling tool components provided with connecting threads is turned in an opening direction. The release assembly has a decreased second axial length and friction forces in the joint decrease.

1 . A release assembly of a drilling tool for rock and overburden drilling, the release assembly arranged to be axially located between two drilling tool components connectable together at a joint by connecting threads; the release assembly comprising:
 a first counter element and a second counter element, the first counter element and the second counter element being counter surfaces, which are facing each other, at least one of the first and second counter elements arranged in an intermediate component separate from the drilling tool components, the intermediate component having a contact surface facing the drilling component; and   a release mechanism formed between the first counter element and the second counter element, the release mechanism allowing an axial length of the release assembly to be shortened in response to turning the connecting threads of the joint in an opening direction, wherein the connecting threads of the joint have a first handedness; and   at least one inclined flank surface on the first counter surface and second counter surface, the at least one inclined flank surface having a second handedness opposite to the first handedness of the connecting threads, whereby the release assembly is arranged to be lengthened when the first counter surface and the second counter surface are turned relative to each other in a closing direction of the first handedness, and arranged to be shortened when turned in an opening direction of the first handedness.   
     
     
         2 . The release assembly as claimed in  claim 1 , further comprising at least one first intermediate component and at least one second intermediate component, both including counter surfaces facing each other and contact surfaces facing the drilling components of the joint. 
     
     
         3 . The release assembly as claimed in  claim 1 , further comprising one single intermediate component, wherein the intermediate component is provided with the counter surfaces and one of the connectable drilling components of the joint being provided with the second counter surface, whereby the second counter surface is an integrated part of the drilling component. 
     
     
         4 . The release assembly as claimed in  claim 1 , wherein the connecting threads have a first pitch angle, the inclined flank surfaces have a second pitch angle, and the second pitch angle is greater than the first pitch angle. 
     
     
         5 . The release assembly as claimed in  claim 1 , wherein the first counter surface is provided with at least one first transverse surface and the second counter surface is provided with at least one second transverse surface, which are transverse to the inclined flank surfaces the at least one first transverse surface facing the at least one second transverse surface, the at least one flexible member being between the at least one first transverse surface and the at least one second transverse surface and occupying a distance between the transverse surfaces. 
     
     
         6 . The release assembly as claimed in  claim 5 , wherein the at least one flexible member is at least one separate resilient element. 
     
     
         7 . The release assembly as claimed in  claim 5 , at least one of the transverse surfaces is covered by a resilient material comprising the flexible member. 
     
     
         8 . The release assembly as claimed in  claim 1 , wherein the at least one contact surface is provided with at least one friction zone having intentionally increased surface roughness. 
     
     
         9 . The release assembly as claimed in  claim 1 , wherein the at least one contact surface is tapered. 
     
     
         10 . The use of the release assembly as claimed in  claim 16 , wherein the drilling operation is down-the-hole drilling, the release assembly being arranged between a drill bit assembly and a down-the-hole percussion device, and wherein the drill bit assembly comprises a drill bit and fastening members for fastening the drill bit. 
     
     
         11 . The use according to  claim 10 , wherein the release assembly is arranged between a locking nut of the drill bit assembly and the down-the-hole percussion device. 
     
     
         12 . The use of the release assembly as claimed in  claim 16 , wherein the drilling operation is extension drilling, the release assembly being arranged between two successive drilling components. 
     
     
         13 . The use of the release assembly as claimed in  claim 16 , wherein the drilling operation is rotary drilling, the release assembly being arranged between a rotating unit and a drill bit. 
     
     
         14 . A method of forming a drilling tool for rock or overburden drilling; the method comprising:
 connecting and detaching at least two drilling tool components to each other by means of a thread joint having connecting threads;   turning the drilling tool components relative to each during the connection and detaching;   ensuring opening of the thread joint by arranging a release assembly to the joint between the successive drilling tool components, the release assembly comprising a first counter element and a second counter element, the first counter element and the second counter element being counter surfaces facing each other, at least one of the first and second counter elements being arranged in an intermediate component separate from the drilling tool components, the intermediate component having a contact surface facing the drilling components, and a release mechanism formed between the first counter element and the second counter element, the release mechanism allowing an axial length of the release assembly to be shortened in response to turning connecting threads of the joint in an opening, wherein the connecting threads of the joint have a first handedness; and at least one inclined flank surface on the first counter surface and second counter surface, the at least one inclined flank surface having a second handedness opposite to the first handedness of the connecting threads, whereby the release assembly is arranged to be lengthened when the first counter surface and the second counter surface are turned relative to each other in a closing direction of the first handedness, and arranged to be shortened when turned in an opening direction of the first handedness; and   rotating the thread joint in an opening direction and allowing simultaneously an axial length of the release assembly to shorten, whereby frictional forces in the thread joint decrease.   
     
     
         15 . The release assembly as claimed in  claim 1 , wherein the at least one contact surface is covered with a material having a greater friction coefficient than a material of the intermediate component. 
     
     
         16 . A use of a release assembly in a drilling operation for connecting and detaching at least two drilling tool components to each other by a joint having connecting threads, comprising the steps of:
 providing the release assembly, the release assembly comprising a first counter element and a second counter element, the first counter element and the second counter element being counter surfaces facing each other, at least one of the first and second counter elements being arranged in an intermediate component separate from the drilling tool components, the intermediate component having a contact surface facing the drilling components, and a release mechanism formed between the first counter element and the second counter element, the release mechanism allowing an axial length of the release assembly to be shortened in response to turning connecting threads of the joint in an opening, wherein the connecting threads of the joint have a first handedness, and at least one inclined flank surface on the first counter surface and second counter surface, the at least one inclined flank surface having a second handedness opposite to the first handedness of the connecting threads, whereby the release assembly is arranged to be lengthened when the first counter surface and the second counter surface are turned relative to each other in a closing direction of the first handedness, and arranged to be shortened when turned in an opening direction of the first handedness; and   arranging the release assembly between two successive drilling components.