Pneumatic system for combine header height control

Claim 1

In a combine having a mobile frame adapted for movement across a field; a transverse header supported from said frame for movement in a generally vertical direction relative to the ground and said mobile frame, said header being operable to collect crop material from the field and initiate the crop harvesting process, said header being generally vertically movable relative to said frame to follow longitudinal ground contours; sensing means mounted on said header to sense the location of the ground rleative to said header; and header lift means interconnecting said header and said frame to power the generally vertical movement of said header relative to said frame, the improvement comprising: pneumatic control means operatively connected to said sensing means and to said header lift means to effect the operation of said header lift means to move said header in a generally vertical direction in response to the sensing of a change in the position of the ground relative to said header by said sensing means such that the position of said header relative to said frame is varied to maintain a generally constant positional relationship between the ground and said header; and means for selectively actuating a movement of said combine in a reverse direction operatively connected to said pneumatic control means such that an actuation of said actuating means causes said pneumatic control means to effect a raising of said header so that said header is raised in response to the selective movement of said combine in a reverse direction.