Patent GB-991892-A (GB)
Title: Improvements in or relating to earth-working equipment
IPC: G01C15/00
Filed: 1961-05-19
Abstract: 991,892. Earth graders. HONEYWELL Inc. May 19, 1961 [May 23, 1960], No. 18407/61. Heading E1F. [Also in Division H4D] A control arrangement for an earth-working tool comprises a servo-mechanism for adjusting the position of the tool in relation to the ground, a beam guidance system having a source emitting radiant energy, for example, light energy, towards a co-operating device situated at a remote location therefrom to establish a reference datum; said guidance system including an element which is arranged to take up a normal aligned position in the system, and which moves in accordance with the movements of the tool relative to the reference datum, and sets up a control signal indicating when it has moved out of alignment, and operating means responsive to that control signal to adjust the tool position to return said element into alignment. In the diagrammatic arrangement, Fig. 3, light from a frequency modulated source 31 on a disc 30 rotated about an axis 35 connected on the tool or on the propelling vehicle impinges on a reflector 22 of a datum reference number 20 provided with a shadow board 21 having its top edge at the datum level. During part of a revolution of the disc 30 the projected beam 33 is returned from the mirror 22 as a beam 34 incident on a photo-electric member 32, and with the axis 35 at the same height as the top of the board 21, the period of oscillatory output of the cell is equal to that when the beam is obstructed to provide an output indicated by 52, Fig. 4. With the axis 35 below and above the datum level the relative durations of oscillatory output and obstructed reflection are as indicated at 50, 51 respectively. As shown in Fig. 5, the output of the photo-cell 32 is passed to an amplifier 61, limiter 63 and demodulator 65, removing the frequency at which the beam is modulated, to an integrator 67 producing a pulse of amplitude dependent on the duration of the oscillatory output of the cell 32, and which is fed to a comparator device 73 having from a regulated power supply 71 a second input corresponding to the "on datum" voltage. The difference voltage in magnitude and sense is passed to an indicator 76, and also to a controlled device 77 which through a servo-system changes the position of the operating blade to restore alignment of the axis 35 with the datum level prescribed by the top of the shadow board 21. In the control system, Fig. 7, the disc 30, driven by a motor 38 is mounted by a journal 39 carried by a shaft 91 mounted in a gimbal 90 and having a gear wheel 92 meshing with a gear 93 driven by a motor 94 and with a gear 95 connected to a follow-up potentiometer 220, Fig. 13. The gimbal 90 also carries a gear 117 rotatable about the ram 125 of an hydraulic cylinder 123 and driven by a gear 116 connected to the output shaft of a motor 115. A follow-up potentiometer 239 is also operated by a gear 381 driven from the gear 117. The motors 94, 115 and the follow-up potentiometers 220, 239 are driven from the outputs of a two-axis gyro control 110, Fig. 8 (not shown) controlled by light sensitive detectors to sense the deviation of the position of the shaft 91 from the horizontal and to maintain the axis 35 parallel to and directed towards the datum device. The position detecting signals are fed to a control unit 100 operating a valve 120 to control the flow through conduits 121, 122 to the cylinder 123 to move the ram 125 and to adjust the vertical position of the gimbal 90 carrying the rotating disc 30. The pivoted blade 11 of the excavator or grader is connected through a ram 170 to an hydraulic cylinder 168 to which fluid is supplied from a pump 163 by a valve 160 controlled by a unit 130 having at its input two control potentiometer arrangements. The slider 144 of a first potentiometer 142 is connected to the ram 125, and a first slider of the second potentiometer assembly is set by a knob 137. The slider controlling the input to the unit 130 is moved in accordance with the position of the ram 170. In a modified datum sensing arrangement, Figs. 9 to 12 (not shown), the output from a rotated detector is fed to two semi-circular commutator rings connected to individual demodulator and integrator circuits having their outputs fed in opposition to a unit for controlling a valve for an hydraulic ram operating to position the axis of the member carrying the detector. In modified arrangements, Figs. 14, 15, 16 (not shown), for the datum sensing device, the shadow board is carried by the excavating blade with the reflecting device and rotating detector set at a predetermined level on fixed supporting members. The control signal may be sent by a radio transmitter to a tuned receiver controlling the hydraulic system to reposition the excavating blade. A control system generally similar to that shown in Figs. 3 and 4, with the shadow board disposed at ninety degrees may be included to maintain the vehicle on a predetermined course.