GB1481083A - Cutting height control for combine harvester - Google Patents

Abstract

1481083 Controlling combine harvesters MASCHINENFABRIK FAHR AG 4 Oct 1974 [5 Oct 1973 17 Oct 19731 43152/74 Addition to 1396078 Heading A1F The, or each, preferably hydraulic jack which raises or lowers the pivoted cutting platform of a combine harvester is actuated in response to movement of at least one resiliently bendable ear raiser rigidly fixed at one end to the cutting platform and engaging near its other end the ground. The bending of the, or each, ear raiser in response to ground irregularities is converted either; (a) by a senser to an electric signal directly controlling the jack or jacks without amplification, or (b) into an electric signal by a magnetically-operating senser the electric signal controlling the jack or jacks directly or indirectly. Each ear raiser 7 is attached to the cutting platform at 18 and is provided with a stop 20 which is rivetted thereto. Welded to the stop 20 is an angleplate 27. A limit scanner 28 which acts as a changeover switch, is secured interchangeably by two screws to the angleplate 27, the switch plunger 29 resting against a screw 30 the position of which, relative to a deflector 31, is adjustable by a lock nut 32. The deflector 31 can abut the angleplate 27 subsequent to a predetermined bending of the ear raiser, thereby preventing damage to the limit scanner 28. A lifting bar 19 is carried by the forward end of each ear raiser and is provided with a safety bar 35 which contacts the stop 20 should the bar 19 be pressed down by wet harvest material &c. As the ear raiser 7 bends due to ground surface irregularities the screw 30 moves relative to the plunger 29 thereby issuing 'raise' or 'lower' commands, as appropriate, to the cutting platform adjustment system. The command is given directly to a corresponding valve in the hydraulic system of the harvester and does not pass through any electronic amplification system. Preferably a 3-point limit scanner is used wherein, when the harvester is travelling on flat ground the 'neutral' position is set on the valve. The embodiments of Figures 2a and 2b, 3a and 3b and 4a and 4b (not shown) illustrate other arrangements of a limit scanner 28 with respect to the ear raisers 7. A contact-free switching system may be used to convert the bending of the ear raisers to an electric signal. In the embodiment of Figure 5 an inductive pick-up comprises a coil 30a rigidly fixed to a finger 21 and hence the cutting platform and a sensing pin 31a which clips into the coil and is held in contact with the ear raiser 7. In the embodiment of Figure 6 (not shown) a magnetic switch is rigidly fixed to the finger 21 and an actuating magnet therefor is secured to the ear raiser. In a further embodiment (Fig. 7, not shown) an electronic switch which makes use of the Hall effect is fixed to the ear raiser and an actuating magnet therefor is secured to the finger 21.