Carriage reciprocator and positioner with continuously moving chain

A carriage reciprocator comprising:

• a housing;
• a carriage movably mounted on said housing;
• a chain movably mounted on said housing and arranged to continuously present a first chain portion, moving in a first direction, to a first portion of said carriage and to present a second chain portion, moving in a second direction, to a second portion of said carriage;
• means, secured to the housing, for moving said chain;
• a first chain sprocket rotatably mounted on said carriage, and arranged to operatively engage said first chain portion and arranged to normally idly spin with chain motion;
• a second chain sprocket rotatably mounted on said carriage, and arranged to operatively engage said second chain portion and arranged to normally idly spin with chain motion;
• a first air brake secured to said carriage and arranged to permit the spinning of said first chain sprocket when in a first state and to prevent the spinning of said first chain sprocket when in a second state;
• a second air brake secured to said carriage and arranged to permit the spinning of said second chain sprocket when in a first state and to prevent the spinning of said second chain sprocket when in a second state;
• an air control valve secured to said carriage, operatively connected to said first and second air brakes, and arranged to shift between first and second control states wherein said first air brake is in its first state and said second air brake is in its second state when said air control valve is in said first control state and wherein said first air brake is in its second state and said second air brake is in its first state when said air control valve is in said second control state;
• and
• means movably mounted on said housing for shifting said air control valve between said first and second control states.