Torque stabilization for a rig mast

Abstract

A rig mast torque stabilization system has a racking board extending rearward from a middle portion of a vertical mast. Right and left braces are movable from a transport position to an operating position extending laterally outward from the mast. Right and left mast tethers are each connected to the corresponding brace, and to the mast above the brace. Right and left board tethers are each connected to the corresponding brace, and to the racking board. Right and left vehicle tethers are each connected to the corresponding brace, and to a forward location on the vehicle supporting the mast. The mast tethers, board tethers, and vehicle tethers are configured to be in tension when the racking board is in the board operating position, the mast is in the mast operating position, and the braces are in the brace operating position.

1 . A rig mast torque stabilization system comprising:
 a mast pivotally mounted on a vehicle for transport, the mast movable from a substantially horizontal mast transport position to a substantially vertical mast operating position extending upward from a rear end of the vehicle;   a racking board extending, when in a board operating position, rearward from a vertical location in a middle portion of the mast when the mast is in the mast operating position;   right and left elongated braces movably attached to corresponding right and left sides of the middle portion of the mast, the braces movable from a brace transport position where outer ends of the braces are in proximity to the mast, to a brace operating position where the braces extend laterally outward from corresponding right and left sides of the mast to the outer ends of the braces;   right and left mast tethers, each mast tether connected at a lower end thereof to the corresponding right and left brace, and each mast tether connected at an upper end thereof to the mast at a location above the corresponding right and left brace, the mast tethers configured to be in tension when the racking board is in the board operating position, the mast is in the mast operating position, and the braces are in the brace operating position;   right and left board tethers, each board tether connected at an outer end thereof to an outer end of the corresponding right and left brace, and each board tether connected at an inner end thereof to the racking board, the board tethers configured to be in tension when the racking board is in the board operating position, the mast is in the mast operating position, and the braces are in the brace operating position;   right and left vehicle tethers, each vehicle tether connected at an upper end thereof to the corresponding right and left brace, and each vehicle tether connected at a lower end thereof to a forward location on the vehicle, the vehicle tethers configured to be in tension when the racking board is in the board operating position, the mast is in the mast operating position, and the braces are in the brace operating position.   
     
     
         2 . The system of  claim 1  wherein the mast is extendable, and wherein the mast is retracted when in the mast transport position, and wherein when moving from the mast transport position to the mast operating position the mast is moved from the horizontal transport position to a vertical retracted position with a lower mast section extending upward from the rear end of the vehicle, and then an upper mast section is moved upward with respect to the lower mast section to extend the mast vertically to the mast operating position. 
     
     
         3 . The system of  claim 2  wherein the braces are attached to an upper portion of the lower mast section and the racking board is attached to a lower portion of the upper mast section, such that the racking board moves upward with the upper mast section to a vertical position in proximity to the braces when the mast moves to the mast operating position. 
     
     
         4 . The system of  claim 3  wherein the right and left board tethers and right and left vehicle tethers are provided by corresponding right and left main tethers, each main tether comprising a board section between an upper end thereof connected to the racking board and a stop member attached to the main tether at a distance from the racking board that corresponds to a length of the board tether, and a vehicle section between the stop member and a lower end thereof attached to the forward location on the vehicle. 
     
     
         5 . The system of  claim 4  wherein the vehicle section of each main tether passes through a hole in a stop plate attached to the outer end of the corresponding brace and then over a pulley attached to the corresponding brace, and then downward and forward to the forward location on the vehicle, where in operation the lower end of the main tether is pulled downward as the upper mast section moves upward, and when the mast is in the mast operating position the lower end of the main tether is connected to a tensioning device operative to exert tension on the main tether such that the stop members on the right and left main tethers bear against the stop plates on the corresponding right and left braces and exert a forward force on the stop plates. 
     
     
         6 . The system of  claim 4  wherein the stop member is releasably clamped to the main tether. 
     
     
         7 . The system of  claim 5  wherein the racking board is pivotally attached to the upper mast section about a substantially horizontal board pivot axis and wherein the racking board pivots upward to a board transport position lying against the upper mast section, and downward to the board operating position extending rearward from the mast. 
     
     
         8 . The system of  claim 7  wherein the outer ends of the braces are below the board pivot axis when the racking board is in the board operating position, the mast is in the mast operating position, and the braces are in the brace operating position. 
     
     
         9 . The system of  claim 8  wherein the right and left braces are pivotally attached to corresponding right and left sides of the mast, and pivot from the transport position folded substantially into alignment with the mast, to the operating position extending substantially perpendicularly outward from the mast. 
     
     
         10 . The system of  claim 1  wherein the right and left braces are telescopically attached to corresponding right and left sides of the mast, and telescope outward from the brace transport position to the brace operating position.