Tool height control

Claim 1

A177(46)/5 12 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: A ground working machine having a ground working tool mounted thereon and being adjistable in height for varying tool penetration into the ground, a radiation signal transmitting and receiving means mounted on the ground working machine in spaced relationship with the ground surface and for directing the signal towards the ground surface generally in the direction towards the ground working tool so that the signal is reflected from the ground surface and back to said transmitting and receiving means, first means for generating a first timing signal proportional to the time for the radiation signal to be transmitted and reflected back from the ground surface to be received by the radiation transmitting and receiving means, oe second means for generating a reference timing signal representative of the time it would take for a radiation o signal transmitted by the transmitting and receiving means I to be reflected from a horizontal surface level with the oe, lowermost portion of the ground working tool and to be received by the transmitting and receiving means, third means for generating a signal representative of the desired working depth of the tool below tha ground surface, and :o signal processing means arranged to respond to the signals generated by said first means, second means, and third means and for generating a control signal representative of departure of the tool from the desired working depth. DATED this 25th day of July 1985 a AGTRONICS PTY. LIMITED By their Patent Attorneys GRIFFITH HASSEL FRAZER S'3513S If0 0909 Rse 310 33 9q L I oo to* 09ee h/7 gqrd *7 0O 171 o 000to 0007 91e De eP1 a 099f9~y isly rV/77t Enah/e. MI01705tefle COL117 0 77.6 /0 *0.0 0 0 0 0 000000 0 0 0 0 0 0 0 0 0 000 0 40 00 0 00 00 0 0 0 0 0 0 0 *0 0 00 000 0 V