Tractor type vehicle including engine and load control therefor and provided with rotary working implement

Claim 1

A tractor type vehicle including an engine and a load control therefor, said vehicle being provided with a rotary working implement pivotally attached to a body of the vehicle, said engine including a speed setter for giving an output signal (A) corresponding to setting a suitable value of rotation of the engine, an engine speed sensor for sensing actual rotation of the engine and for giving an output signal (E) corresponding thereto, first operational means for comparing the actual engine speed signal output (E) of the speed sensor with the said set value signal output (A) of the speed setter and for giving an output signal (A-E) indicating which of these two values is larger and by what difference, control means for automatically raising and lowering the rotary working implement with respect to the vehicle body in response to the output signal (A-E) of said first operational means so that the rotary working implement is lowered when the actual engine speed sensed by the speed sensor is higher than the said set value of the engine rotation and that the rotary working implement is raised when the actual speed is lower than the set value, the improvement comprising: a working depth setter for giving an output signal (H) corresponding to setting any desired working depth of said rotary working implement, a depth sensor for sensing actual working depth and for giving an output signal (L) corresponding thereto, second operational means provided in between the said first operational means and the said control means, for receiving the output signals (A-E, H, L) of the first operational means, of the working depth setter and the depth sensor, and for performing operation of these input signals and giving an output signal (A-E+H-L) to be furnished as an input signal for the said control means, in such manner that the actual working depth sensed by the depth sensor as deeper than the said desired working depth will contribute to raising the rotary working implement and that the actual depth sensed as shallower than the desired depth will contribute to lowering the rotary working implement, further means for prohibiting lowering the said rotary working implement, to be actuated only when the sensed speed signal output (E) of the speed sensor falls beneath a value set in a predetermined interlocking relation with the set engine speed, and forced raising means for raising said rotary working implement, said forced raising means receiving information (A-E) from the first operational means and being actuated only when the actual engine speed sensed by the speed sensor falls below a predetermined value, namely when the speed of the engine is below the predetermined forced-raising-rotation-speed (c).