Patent GB-644822-A (GB)
Abstract: 644,822. Sifting and separating solid materials. ROBERTS & SCHAEFER CO. Feb. 13, 1948, No. 4341. Convention date, Feb. 13, 1947. [Class 117] An apparatus for separating raw coal of small size, e.g. within a range of # inch down to 0 inch, and dustlike particles, comprises a longitudinally extending air pervious deck 60 disposed above a resistance pack 62 which forms an operating unit therewith and having means, such as a hopper 165, for feeding raw coal on to the deck at one end, means. such as the framework 11, 12, 13, 14, 15 and the flexible suspension rods 20, 21, 22, for mounting the operating unit 60, 62 at an incline of, e.g. from 8 degrees to 15 degrees. with the feed end disposed at a higher level than the opposite end or discharge end 66. An arm 30 is disposed at the feed end of the unit 60, 62 and logitudinally rearwardly extends therefrom under the hopper 165, and an unbalanced weight vibrator 31 is supported solely on the arm 30 at the free end thereof, balancing means 46 coacting with the arm 30 for longitudinally resiliently balaning the inclined unit 60, 62 in predetermined position in which the feed end thereof is disposed in predetermined normal position relative to the hopper 165. The vibrator 31 in operation vibrates the unit 60, 62 at a frequency of from 800 to 1,400 p.p.m. and an amplitude of # inch to impart mechanical mobility and buoyant fluidity to the material particles on the deck 60 and so cause the particles of intermediate and higher specific gravities to move downwardly through the air pervious deck plate and resistance pack 62 for discharge therefrom, in counter current to air impulses, e.g. at a pressure lying within the range 1.25 inch to 2.00 inch water gauge produced in air duct 150 by flutter valve 152 and injected underneath the deck. whereby clogging of the resistance pack 62 is prevented so as to maintain the air resistance characteristics of the pack substantially constant. The balancing means comprises a pair of spaced relatively stationary supports 36, 37 (see Fig. 3), a shaft 38 extending between the supports 36. 37, a floating bushing 45 disposed on the shaft 38 and a bracket member 46 for rigidly connecting the bushing 45 and the arm 30, springs 49, 50 disposed on the shaft 38 on either side of the bushing 45, and means such as nuts 47, 48 disposed on the shaft 38 for compressing each spring against the bushing 45. The deck consists of a plurality of longitudinally serially related deck sections separated by downwardy directed discharge passages 61, 63, 64. 65, Fig. 1, so that in operation the coarse heavy material particles sink to the bottom of the bed and are discharged through the passages 61, 63, 64, 65. Each deck section comprises a deck plate 60 on top of a resistance pack 62, e.g. of clay members, or glass marbles, and underneath are disposed transversely extending valve slides 67, 68 between guide members 69 and are adjustable to regulate the air supply into and through the pack 62 for escape through the plate 60. Each discharge passage 61. 63, 64, 65 terminates in a discharge mechanism comprising a transversely extending casing 73 containing an arcuate tray 70 and oscillating scraper 71 operated from eccentric 85 through arm 105 and adjustable arm 97 to adjust the stroke of oscillation and a transversely disposed discharge screw 72 to feed the heavy materials to shoots such as 115. An airtight seal is formed between the casing 73 and transverse plates of the discharge passage 61 and between the lower end of the casing and the floor of the air tunnel is disposed a valve plate 140 extending transversely across the deck to form a transverse partition within the air tunnel. The valve plate has a series of openings adjustable in size by valve slides adjustable from outside. the apparatus. Such an arrangement is provided between each discharge passage 61, 63, 64 and 65 so that the air supply to each section can be individually controlled to suit the mixture of material on the bed. Pairs of right and left feed screws such as 128, 129 feed the particles passing through the deck and bed into the shoot 130 which has disposed therein an air seal comprising star wheel 131. A dust hood 180 extends upwardly from the machine and terminates in an exhaust duct. U.S.A. Specifications 2,374,865, 2,334,337, 2,245,942 and Reissue 21,682 are referred to.