Patent GB-1323773-A (GB)
Title: Hydraulic lifting equipment for combine harvesters
IPC: A01D34/24
Filed: 1970-07-23
Abstract: 1323773 Combine harvesters ROBERT BOSCH GmbH 23 July 1970 [23 July 1969] 35663/70 Addition to 1196210 Heading A1F Hydraulic lifting equipment for a combine harvester is fitted with a device by means of which regulation of the height of cut cannot have effect when the pressure in the lifting cylinder 31 is substantially lower than the pressure necessary to fully support the weight of the cutting table 36. Construction:-The cylinder 31 is connected by a service line 32 to a control slide 127 which, via service line 78, also feeds a regulating member 64 whose length depends upon the pressure of the fluid. The control slide 127 can be pulled from its central 'neutral' position to 'lift' or 'lower' by solenoids 128, 129 respectively. Two resistors 181, 186 have sliders 182, 185 whose position depends upon the height of the table 36, slider 185 by means of the lever 184 connected to the rigid coupling arm 79, and slider 182 varying with the pressure in the member 64. The desired height of the table is set by the lever 193 on the resistor 187 having a pressure-dependent range 188 and a position-dependent range 189 and sliders 190, 191 respectively. The slider 190 is moved by the carrier 192 and spring 195, whilst slider 191 is varied through a lost-motion coupling 194. The sliders 190, 182 are connected to a relay 147 serving as a switch for the solenoids 128, 129, a second switching device 205 only being brought into the circuit when the switch 199 is closed by the member 198 due to the pressure in member 64. When the table is in its raised transport position, slider 185 is as shown in Fig. 1 and member 198 has closed the switch 199. Operation:-To lower the table 36 from its transport position to a level where its weight is borne jointly by the ground and the cylinder 31, the slider 190 is moved from its maximum position to the desired value, e.g. midway in range 188, and the slider 191 is set at its minimum position (as in Fig. 1). The sliders 182 and 190 are in different relative positions and a current flows through the coil 146 which moves the armature 149 to close the contacts 153, 154. This activates the lowering solenoid 129 and the pressure in cylinder 31 falls. The pressure in member 64 also falls, and thus the slider 182 moves away from its maximum position until it balances slider 190 when the control slide 127 returns to 'neutral'. To then raise the table to the desired height of cut, the lever 193 is moved until slider 190 is at maximum and the stop 196 is pressed up against the shoulder 197, whereupon the slider 191 is set in the desired position. The slider 185 is at minimum and slider 182 is as shown in Fig. 1. Again a current flows between sliders 182 and 190, and this time contacts 151, 152 are closed, activating solenoid 128, so raising the table 36 until the slide 182 is at maximum. At this point the switch 199 is closed and the armature 208 moves out of the coil 204 due to the voltage source 140. When the contacts 211, 212 and 213, 214 are closed, sliders 185 and 191 are connected through the coil 146 and the potential difference causes the continued activation of solenoid 128, so that the table 36 continues to be raised until the slider 185 is moved by the lever 184 into the equivalent position of slider 191, when the control slide 127 returns to 'neutral'. If then the table 36 meets an obstacle, part of the weight of the table is again borne by the ground and the pressure in cylinder 31 and member 64 drops, thus the slider 182 moves from its maximum position and the switch 199 is opened. The slider 190 is still at maximum, so the potential difference causes the solenoid 128 to effect the raising of the table 36 until the slider 182 is again at maximum. This closes the switch 199 and the potential difference between the sliders 185 and 191 sets the table at the desired height of cut once more. To minimise the effect of small obstacles, the member 198 keeps the switch 199 closed for slight displacements of the slider 182. In a further embodiment, Fig. 2 (not shown), feelers are fitted to each side of the table 36 and are connected to a further adjustable resistor (227) by levers to regulate the height of the table on meeting obstacles. The resistor 187 is replaced by a three-range resistor, comprising a pressure-dependent range and two position-dependent ranges, are as before and the other for feeler control. A modification, Fig. 3 (not shown), has the resistor (227) replaced by an adjustable resistor operating for each feeler, and diodes in the circuit only allow the raising or lowering of the table when both feelers are activated.