Patent ID: 6994172

Claim:
An automatic drilling system for regulating the release of a drill string of drilling rig during the drilling of a borehole, comprising: a drill stem having a drill bit at one end; drawworks coupled to said drill system; a prime mover engaged to said drawworks to cause said drawworks to alternatively move said stem upward and downward; a bit weight sensor configured for measuring bit weight through direct interface with bit support means which, at least in part, supports the weight of said drill bit, and which is electrically coupled to a electronic bit weight comparison means, where said bit weight comparison mens compares actual bit weight indicated by said bit weight sensor against a user-selected, bit weight value set into said electronic bit weight comparison means, and generates a signal proportionate to any difference between said actual bit weight and said pre-selected bit weight value; programmable control means operatively coupled to a variable drive electric motor which is interfaced with drill stem braking means to proportionately effect movement of said drill string in said upward or downward direction upon receipt of signals from said electronic bit weight comparison means according to the value of said signal.