Gas spring fastener driving tool with fill valve located in an end cap

A fastener driving tool, comprising:

• a working cylinder that includes a movable piston having a reciprocating direction of movement within the cylinder, said cylinder including a variable displacement volume on a first side of said piston, and said cylinder including a variable venting volume on a second, opposite side of said piston;
• a storage chamber;
• an end cap that is attached to at least one of said cylinder and said storage chamber at an end portion of said fastener driving tool, said end cap including at least one first gas passageway that is in fluidic communication with said cylinder and with said storage chamber;
• a movable driver that is in mechanical communication with said piston;
• a guide body that guides movements of said driver;
• and
• a fill valve subassembly that is mounted at a side portion of said end cap, the fill valve subassembly including a fill valve that is partially enclosed by a fill valve pocket that contains the fill valve, the fill valve pocket being positioned at a sufficient distance from a centerline of the working cylinder so that it entirely clears the working cylinder even though the fill valve pocket is positioned in a direction that is parallel to the direction of movement of the movable piston, said end cap including a second gas passageway that travels between an inner end of the fill valve and said at least one first gas passageway of the end cap;
• wherein:
• the end cap is positioned at the very distal end from the guide body of the fastener driving tool such that an outer end of said fill valve is directly accessible from an angle that is directly above the end cap;
• said variable displacement volume of the cylinder, said storage chamber, and said at least one first gas passageway of the end cap all contain pressurized gases when said fastener driving tool is in use;
• and
• said pressurized gases are not vented to atmosphere after a drive stroke, but instead said pressurized gases are re-used for a plurality of operating cycles.