Patent GB-590598-A (GB)
Title: Agricultural machines for hoeing, weeding or thinning
IPC: A01B41/06
Filed: 1944-05-09
Abstract: 590,598. Photo-electrically controlled hoeing-machines. MARIHART, L. A. May 9, 1944, No. 8814. Convention date, April 12, 1943. [Class 6 (i)] [Also in Group XL] Mechanically-driven hoes are automatically controlled by light-responsive means serving to discriminate between plants in differing stages of growth, or of differing kind. Coarse and fine rotary-hoes 81, 82 are carried on shafts 47 arranged longitudinally in a frame 32 which is supported on a wheel 39 and capable of vertical movement between rollers 36 in the main frame 10. As shown in Fig. 2, the main frame 10 carries two frames 32, and each of the latter has two shafts 47 which are driven from the engine 26 through gearing and a shaft 107. Universal joints 109, 108 connect the shaft 107 with the sets of gearing between it and the engine and the shafts 47 respectively. The coarse hoes 81 are fixed to the shafts 47 and sweep, say, 9 inch gaps between residual 3 inch groups of plants. These pass through a lightresponsive device 136, termed a huddler, which selects a plant in a desired condition of growth and controls the fine hoe 82 to remove the remainder. The fine hoe may consist of three pairs of blades mounted on arms projecting radially from a hub loose on the shaft 47. It receives its movement from the shaft 107 through gearing 103, a shaft 98, gearing 129a, a one-revolution clutch 129, gearing 128a and chain gearing 127. The clutch 129 is tripped by an arm 131, connected to the armature of a solenoid 133, in response to an impulse from the huddler. This consists of a tapered hood 142, Fig. 4, in front of a housing 145 containing an illuminating device 146 and the photo-electric unit 147 which is connected with the solenoid 133 through the circuit shown in Fig. 6. The unit 147 may include one or two stages of amplification and is connected with a second amplifier 153, and thence to a relay 154 with normally open contacts. Closure energizes a further relay 156 in the circuit of a battery 155. Through a solenoid 177 a clutch 173 is then closed and operates a switch arm 157, the clutch-shaft being driven synchronously with the toolactuating gearing. As the arm 157 commences to rotate the circuit 183 is broken and the circuit of the amplifier 153 disrupted. Further rotation of the arm 157 closes contacts 181, after a predetermined time interval, and energizes the solenoid 133. Thereafter the contacts 182 are opened, the circuit of the relay 156 broken, then that of the solenoid 177. The clutch 173 disengages and the spring 171 brings the arm 157 back to the position shown, where it re-establishes that of the amplifier 153. As the solenoid 133 is energized the clutch 129 is tripped and the fine hoe 82 rotated through one-third of a revolution, removing all but the selected plant. The huddler of Fig. 4 is shown with a light-excluding rear plate 130 and sharpened hard-steel side edges 151 to penetrate the ground surface. The lower end of the tapered front is designed to bend over the plants and expose their stems to the devices 146, 147. In other constructions this is effected by the radial arms of a rotating spider, and by compressed air. The plant-tops may also be bunched together by passage between travelling belts. In a further form the hood is of rubber with a central slit and internal converging plates. Plant pressure against the plates separates them and opens the slit for exposure to the light and light-sensitive units. Both stems and plant tops may be exposed to illuminating and light-sensitive units. Airsuction may be applied to keep the units dustfree. Light filters may be fitted. The fine hoes of each pair, Fig. 3, are driven in opposite directions. Hoe blades are fixed to pairs of radial arms, the timing being such that one blade 88 of a pair passes in front of the selected plant and the other blade behind it. Coarse and fine hoe-blades may be combined in a single tool. As shown in Figs. 8 and 9, fine hoe-blades 191 ... 197 are distributed along the hub 203 on the shaft 47, each blade being pivoted to a radial arm 202 and held within lugs 206 by a spring 207., The much wider coarse hoe 198 is fixed to the hub. From each pivoted hoe a spindle 208 projects through a disc 208 and terminates in a roller 211. If a solenoid 218 receives an impulse from one of the light sensitive devices the pivoted arm 213 with its shoepiece 212 is projected and moves one of the spindles 208. The corresponding hoe 194 is then bent to the left against the action of a spring 207, out of the path of the plant to be retained.