Patent GB-718154-A (GB)
Title: Improvements in or relating to material handling mechanisms
IPC: B01D21/06
Filed: 1952-08-07
Abstract: 718,154. Gravity-separation apparatus. HARDINGE, H. Aug 7, 1952 [Aug. 23, 1951], No. 19906/52. Class 46. [Also in Groups XXIV and XXIX] A tank (e.g. a settling tank) comprising a scraping apparatus rotated by a shaft is characterized by a power supplying means including a hydraulic pump and cylinder and a piston mechanism actuated thereby, the piston mechanism in turn actuating a pawl-driving system which engages with a ratchet wheel substantially continuously to rotate the ratchet wheel, shaft and scraping apparatus in one direction. A ratchet wheel 30, Fig. 3, secured to a shaft (not shown) carrying two curved scrapers which operate over the bottom of a conventional settling tank is rotated by a pulling pawl 88 engaging alternate teeth 96 and by a pushing pawl 90 engaging the remaining teeth 98. Both pawls are linked to a rod 58 connected to the piston rod 56 of a piston which is reciprocated m a cylinder 46 by hydraulic fluid supplied through pipes 72 and 74. The fluid is alternately fed to, and discharged from, each end of the cylinder 46 under the control of a valve 70 connected to a motor-driven pump 62 by pipes 66 and 68. The valve is solenoid-operated and governed alternately by one-way switches 76 and 78 each movement of which reverses the position of the valve. Each switch is actuated by a detent 106 on its respective pawl arm when the pawl drops radially (urged by springs 100) into the notch between two teeth, such actuation initiating a driving movement for that pawl. Each driving movement moves the wheel periphery through a distance of one tooth, but during the return movement of one pawl the other pawl is driving the wheel a further tooth distance. The returning pawl is prevented from dropping into the next adjacent tooth notch by engagement of a roller (92 or 94) on the pawl arm with the outside of one of a series of lugs 102. To ensure continuous movement of the ratchet wheel the outer half of the working face of each tooth is set at a small angle to the radial direction of movement of the pawl so that at the time when each pawl is moving radially into a tooth notch just prior to its next driving movement it rotates the wheel by cam action. In the embodiment of Fig. 10 push pawls 116 and 118 drive the ratchet wheel 30 alternately. A detent 162 on a rod 138 has just actuated a switch 156 causing a valve 130 to feed hydraulic fluid to the rear end of a cylinder. 120, so that pawl 116 moves forward. The pawl is returned when detent 164 actuates switch 158, thus reversing valves 130. The pawl is maintained in contact with the wheel 30 by a spring 150. Just before the driving movement of pawl 116 is completed pawl 118 begins its driving stroke, thus ensuring that movement of the wheel 30 is continuous. This overlapping is rendered possible by the fact that the return stroke of each pawl is much quicker than the driving stroke. In this embodiment separate motor-driven pumps 124 and 126 are provided. In the embodiment of Fig. 14 diametrically-opposed pulling pawls 204, 206 are hydraulically operated by cylinders 120, 122 respectively fed from a single pump 208 through valves 130 and 132 respectively. To enable overlapping of driving strokes and thus bring about continuous rotation of the wheel, flow-control valves 222, 226, 224 and 228 are included in the lines from main valves to cylinders, these flowcontrol valves ensuring that the return strokes of the pawls are quicker than their driving strokes. Valve 130 is operated upon actuation of one or other of switches 232, 234 by a detent 240 on the arm of pawl 204. Valve 132 is operated similarly. With the embodiment of Fig. 3 is incorporated a mechanism 18, Fig. 9, for elevating shaft 34 and its associated scraping apparatus automatically on undue resistance to rotary motion being encountered. A pressure-responsive valve 198 which may be adjustably set is arranged in a pipe 196 between the pump outlet pipe 66 and the lower end of a hydraulic cylinder 182 incorporating a piston connected through cross-heads and bars to the shaft 34. A return line 194 between the upper end of the cylinder 182 and the pump inlet communicates with the line 196 by a bleed valve 202. In operation the pump pressure causes valve 198 to open when the scraping mechanism is stopped (or nearly so), the scraping mechanism thereupon rising until the obstruction to rotation is no longer effective. Rotation is then resumed, the resulting lowering of pressure in the hydraulic system permitting valve 198 to close. The only means of escape of hydraulic fluid from the lower end of cylinder 182 is then through the bleed valve 202 whereby the shaft 34 is slowly lowered. An audible signal and cut-off switch may be incorporated to obviate breakdown if the obstruction is not overcome when the scraping mechanism is elevated to the fullest extent. Fig. 16 shows elevating mechanism incorporated in the apparatus of Fig. 14. A pressure relief valve 250 in the line 214, Fig. 14, leading from valve 130 to the inner (driving) end of cylinder 120 is connected by a line 256 to the lower end of a cylinder 182, Fig. 16. A similar valve 252 near cylinder 122 is also connected by line 254 to cylinder 182. Check valves 262 ensure that hydraulic liquid flows only from valves 250 and 252 to the cylinder 182 and not in the reverse direction. Also the arrangement is such that the scraping mechanism will be elevated if either valve 250 or valve 252 is open, or if both are open. A bleed valve 260 is'provided, as before.