Rock drill bit and a drilling assembly for percussive rock drilling

Abstract

A rock drill bit for percussive drilling includes a bit head attached at an end of a drill element of a drilling assembly. The bit head has a diameter larger than that of the drill element. The bit head has at a front end as seen in the intended drilling direction a plurality of buttons distributed thereon to engage material to be crushed. At least one of the buttons is allowed to rotate about its own symmetry axis.

1 . A rock drill bit for percussive drilling comprising a bit head attached at an end of a drill element of a drilling assembly and having a diameter larger than a diameter of said drill element, said bit head having a front end and as seen in the intended drilling direction a plurality of buttons at the front end and distributed over said bit head and configured to engage material to be crushed wherein at least one of said buttons is allowed to rotate about its own symmetry axis. 
     
     
         2 . A rock drill bit according to  claim 1 , wherein said plurality of buttons include gauge buttons distributed along the circumference of said bit head and configured to determine the diameter of a hole to be drilled by the rock drill bit, wherein at least one of said gauge buttons is allowed to rotate about its own symmetry axis. 
     
     
         3 . A rock drill bit according to  claim 2 , further comprising a first member having a substantially circumferential ring surface defining a substantially frusto-conical shape as seen in the intended drilling direction, and wherein said at least one gauge button has a base portion resting on said ring surface configured to transfer impact forces to the at least one gauge button and to allow said base portion to move thereon when rotating. 
     
     
         4 . A rock drill bit according to  claim 3 , further comprising a second member defining said front end of said bit head and having said plurality of gauge buttons extending out thereof, and wherein said at least one rotating gauge button is arranged in a hole in said second member and allowed to move with respect to walls defining said hole when rotating. 
     
     
         5 . A rock drill bit according to  claim 4 , wherein said at least one rotating gauge button has a base portion with a larger cross-section than the rest of the plurality of gauge buttons, and wherein at least a part of said hole in said second member has a cross-sectional area being smaller than that of said base portion so as to maintain the gauge button received in said second member. 
     
     
         6 . A rock drill bit according to  claim 5 , wherein said hole is a through hole, and said gauge button is arranged with the base portion thereof on a rear side of said hole as seen in the intended drilling direction. 
     
     
         7 . A rock drill bit according to  claim 3 , wherein said first member has means configured to secure said first member to said drill element. 
     
     
         8 . A rock drill bit according to  claims 4 , further comprising means configured to secure said second member to said first member. 
     
     
         9 . A rock drill bit according to  claim 8 , wherein said means configured to secure said second member to said first member is configured to releasably secure the members to each other. 
     
     
         10 . A rock drill bit according to  claim 3 , wherein said first member is a ring configured to be supported on and/or secured to an end of a said drill element. 
     
     
         11 . A rock drill bit according to  claim 4 , further comprising means for securing said second member and said rock drill bit to a said drill element. 
     
     
         12 . A rock drill bit according to  claim 2 , wherein a majority of said gauge buttons are is allowed to rotate about their respective symmetry axes. 
     
     
         13 . A rock drill bit according to  claim 2 , wherein all of said gauge buttons of the rock drill bit are allowed to rotate about their respective symmetry axes. 
     
     
         14 . A rock drill bit according to  claim 1 , wherein said bit head has a front surface provided with a plurality of front buttons configured to engage material to be crushed. 
     
     
         15 . A rock drill bit according to  claim 14 , wherein at least one of said plurality of front buttons is allowed to rotate about its respective symmetry axis. 
     
     
         16 . A rock drill bit according to  claim 15 , wherein said at least one front button has a design similar to that of said at least one gauge button, said second member being configured to receive said at least one front button similarly to said at least one gauge button. 
     
     
         17 . A rock drill bit according to  claim 15 , wherein a majority of said front buttons or all said front buttons are allowed to rotate about their respective symmetry axis. 
     
     
         18 . A rock drill bit according to  claim 1 , further comprising a flush channel extending through said bit head and having at least one flushing hole opening at said front end and passing the circumference of at least one of said buttons and being allowed to rotate about its respective symmetry axis. 
     
     
         19 . A rock drill bit according to  claim 1 , wherein said at least one rotating button is arranged in a hole in said bit head and allowed to move with respect to walls defining said hole when rotating, said at least one button being provided with a circumferential annular groove and said walls defining said hole having a female member, wherein the rock drill bit includes means configured to engage said groove and said female member so as to lock said button in said hole while allowing it to rotate. 
     
     
         20 . A rock drill bit according to  claim 19 , wherein said female member is an annular groove located in said hole walls, and said engaging means comprises a ring of elastic material. 
     
     
         21 . A rock drill bit according to  claim 19 , wherein said engaging means comprise a pin configured to be pushed into said groove and said female member for being fixed with respect to said bit head and to lock said button in said hole while allowing it to rotate. 
     
     
         22 . A drilling assembly for percussive rock drilling comprising:
 a rock drill bit;   power means configured to act upon said rock drill bit to rotate the drill bit and carry out impacts for engaging material to be crushed; and   a control arrangement to control the operation of said power means.   
     
     
         23 . A drilling assembly according to  claim 22 , wherein the control arrangement controls said power means to obtain a frequency of said impacts exceeding 250 Hz, exceeding 350 Hz or being in the range of 350 Hz-1000 Hz. 
     
     
         24 . (canceled)