Tractor with improved valve system

A tractor for moving a component through a borehole, comprising:

• an elongate body;
• aft and forward gripper assemblies longitudinally movably engaged with said body, said aft and forward gripper assemblies each being hydraulically actuated and defining engagement surfaces configured to selectively engage an inner surface of the borehole;
• aft and forward propulsion assemblies configured to advance said body through the borehole relative to said aft and forward gripper assemblies, respectively;
• a gripper control valve having a first position in which said gripper control valve directs pressurized fluid to said aft gripper assembly and a second position in which said gripper control valve directs pressurized fluid to said forward gripper assembly;
• a propulsion control valve having a first position in which said propulsion control valve directs pressurized fluid to said aft propulsion assembly and a second position in which said propulsion control valve directs pressurized fluid to said forward propulsion assembly;
• a supply line for providing pressurized fluid from a supply source at a location on the surface to said gripper control valve and said propulsion control valve;
• and
• a pressure relief valve disposed within said body of the tractor for limiting fluid pressure in said supply line.

A tractor for moving a component through a borehole, comprising:

• an elongate body formed with an internal passage extending longitudinally therethrough, said internal passage being adapted for receiving pressurized operating fluid from a supply line;
• aft and forward gripper assemblies longitudinally movably engaged with said body, said aft and forward gripper assemblies each being hydraulically actuated and defining engagement surfaces configured to selectively engage an inner surface of the borehole;
• aft and forward propulsion assemblies configured to advance said body through the borehole relative to said aft and forward gripper assemblies, respectively;
• a hydraulic valve system housed within said elongate body, said valve system being configured for directing a portion of the pressurized fluid from said internal passage to said aft or forward gripper assembly in a desired sequence for effecting movement of the tractor through the borehole;
• a pressure relief valve for limiting fluid pressure within said supply line, said pressure relief valve being adapted to vent a portion of the fluid from said internal passage to an annulus when the fluid pressure in said supply line exceeds a pre-selected threshold pressure;
• a first fluid path extending from said internal passage to said hydraulic valve system;
• and
• a second fluid path extending from said internal passage to said pressure relief valve.

An apparatus for moving through a borehole, comprising:

• an elongate body formed with an internal passage extending longitudinally therethrough, said internal passage being adapted for passing pressurized operating fluid through said elongate body;
• aft and forward gripper assemblies longitudinally movably engaged with said body, said aft and forward gripper assemblies being hydraulically actuated for selectively engaging an inner surface of the borehole;
• aft and forward propulsion assemblies adapted for advancing said body through the borehole relative to said aft and forward gripper assemblies, respectively;
• a hydraulic valve system housed within said elongate body, said valve system being configured for receiving a portion of the pressurized fluid from said internal passage and directing the fluid to said aft or forward gripper assembly in a desired sequence for effecting movement of the tractor through the borehole;
• a pressure relief valve for limiting fluid pressure within said internal passage, said pressure relief valve being adapted to vent fluid from said internal passage to an annulus when the fluid pressure in said internal passage exceeds a pre-selected threshold;
• a first fluid path extending from said internal passage to said hydraulic valve system;
• and
• a second fluid path extending from said internal passage to said pressure relief valve.

A tractor for moving a component through a borehole, comprising:

• an elongate body;
• aft and forward gripper assemblies longitudinally movably engaged with said body, said aft and forward gripper assemblies being hydraulically actuated for selectively engaging an inner surface of the borehole;
• aft and forward propulsion assemblies adapted for advancing said body through the borehole relative to said aft and forward gripper assemblies, respectively;
• a gripper control valve having a first position for directing pressurized fluid to said aft gripper assembly and a second position for directing pressurized fluid to said forward gripper assembly;
• a propulsion control valve having first and second end surfaces, said propulsion control valve having a first position for directing pressurized fluid to said aft propulsion assembly and a second position for directing pressurized fluid to said forward propulsion assembly;
• a first flow path between said aft gripper assembly and said first end surface for piloting said propulsion control valve;
• a second flow path between said forward gripper assembly and said second end surface for piloting said propulsion control valve;
• and
• a first sequence valve disposed along said first flow path and adapted to open only when fluid pressure in said first flow path exceeds a pre-selected threshold;
• and
• a second sequence valve disposed along said second flow path and adapted to open only when fluid pressure in said second flow path exceeds a pre-selected threshold.

A tractor for moving a component through a borehole, comprising:

• an elongate body;
• aft and forward gripper assemblies longitudinally movably engaged with said body, said aft and forward gripper assemblies being hydraulically actuated for selectively engaging an inner surface of the borehole;
• aft and forward propulsion assemblies adapted for advancing said body through the borehole relative to said aft and forward gripper assemblies, respectively;
• a gripper control valve, said gripper control valve having a first position in which said gripper control valve directs pressurized fluid to said aft gripper assembly and a second position in which said gripper control valve directs pressurized fluid to said forward gripper assembly;
• and
• a means for detecting advancement of said body relative to said aft or forward gripper assembly;
• wherein said means for detecting advancement of said body causes said gripper control valve to change positions after said body has completed an advancement stroke through the borehole relative to said aft or forward gripper assembly.

A tractor for moving a component through a borehole, comprising:

• an elongate body;
• aft and forward gripper assemblies longitudinally movably engaged with said body, said aft and forward gripper assemblies being hydraulically actuated for selectively engaging an inner surface of the borehole;
• aft and forward propulsion assemblies adapted for advancing said body through the borehole relative to said aft and forward gripper assemblies, respectively;
• a gripper control valve, said gripper control valve having a first position for directing pressurized fluid to said aft gripper assembly and a second position for directing pressurized fluid to said forward gripper assembly;
• a propulsion control valve disposed within said body, said propulsion control valve having a first position for directing pressurized fluid to said aft propulsion assembly and a second position for directing pressurized fluid to said forward propulsion assembly;
• a supply line for providing pressurized fluid from a supply source at a location on the surface to said gripper control valve and said propulsion control valve;
• and
• a means for regulating the fluid pressure in said supply line.

A method of moving a component through a borehole, comprising:

• providing a tractor having an elongate body, aft and forward gripper assemblies longitudinally movably engaged with said body, said aft and forward gripper assemblies being hydraulically actuated for selectively engaging an inner surface of the borehole, and aft and forward propulsion assemblies adapted for advancing said body through the borehole relative to said aft and forward gripper assemblies, respectively;
• attaching the component to the elongate body;
• conveying a pressurized fluid through a supply line to said elongate body for powering movement of the tractor;
• conveying pressurized fluid through said elongate body to the component;
• directing a portion of the pressurized fluid through a valve system in the elongate body for selectively supplying fluid to said aft and forward gripper assemblies and said aft and forward propulsion assemblies for producing movement of the tractor;
• regulating the pressure of the pressurized fluid in the supply line for limiting the pressure of the fluid supplied to the component and said valve system.

A method of moving a component through a borehole, comprising:

• providing a tractor having an elongate body, aft and forward gripper assemblies longitudinally movably engaged with said body, said aft and forward gripper assemblies being hydraulically actuated for selectively engaging an inner surface of the borehole, and aft and forward propulsion cylinders adapted for advancing said body through the borehole relative to said aft and forward gripper assemblies, respectively;
• attaching the component to the elongate body;
• conveying a pressurized fluid through a supply line to said elongate body for powering movement of the tractor;
• conveying pressurized fluid through said elongate body to the component;
• directing a portion of the pressurized fluid through a valve system in the elongate body for selectively supplying fluid to said aft and forward gripper assemblies and said aft and forward propulsion assemblies for producing movement of the tractor;
• and
• mechanically detecting the completion of an advancement of said elongate body relative to said aft and forward propulsion cylinders for causing said aft and forward gripper assemblies to alternately engage the inner surface in a desired operational sequence.

A tractor for moving a component through a borehole, comprising:

• an elongate body defining an internal passage, said internal passage being adapted for receiving pressurized fluid from a supply line;
• aft and forward gripper assemblies longitudinally movably engaged with said body, said aft and forward gripper assemblies each being hydraulically actuated and delivering engagement surfaces configured to selectively engage an inner surface of the borehole;
• aft and forward propulsion assemblies configured to advance said body through the borehole relative to said aft and forward gripper assemblies, respectively;
• a gripper control valve, said gripper control valve having a first position in which said gripper control valve directs pressurized fluid to said aft gripper assembly along a first flow path and a second position in which said gripper control valve directs pressurized fluid to said forward gripper assembly along a second flow path;
• a propulsion control valve disposed within said body, said propulsion control valve having a first position in which said propulsion control valve directs pressurized fluid to said aft propulsion assembly and a second position in which said propulsion control valve directs pressurized fluid to said forward propulsion assembly;
• a pressure relief valve disposed within said body of the tractor for limiting fluid pressure within said internal passage;
• and
• a reverser valve adapted for reversing said first and second flow paths for causing the tractor to move in the reverse direction.