GB425704A - Improvements in or relating to washer boxes for treating coal or other granular substances - Google Patents

Abstract

425,704. Washing granular materials. HIRST, A. A., 3, Sherbourne Road, Acocks Green, Birmingham. Oct. 21, 1933, No. 29184. [Class 82 (ii)] A washer box of the compressed air or Baum type in which the heavy material is discharged mainly through an outlet gate or gates is provided with a float which is suspended in the bed of material on the screen and which regulates the supply of air effecting the pulsations, the arrangement being that when the bed becomes too tight the strength of the pulsations is increased and when the bed becomes too loose the strength of the pulsations is diminished. In the form shown, the washer box comprises two compartments having screens 7 and separated by a partition 6, a shoot 5 for feeding the material to the screen, and means for discharging the heavy material comprising a discharge conduit 8 controlled by an adjustable gate 10 and a star valve 9. The pulsations are effected by compressed air supplied to and exhausted from the air compartments of the box by means of sliding valves mounted in valve casings 11 and worked by eccentrics 14. The supply pipe for the compressed air for the valve casings 11 is provided with one or more blow-off valves and means are provided, controlled by a float suspended in the working bed, to permit or prevent the opening of the blow-off valve or valves. A float 15, which preferably projects above the bed and is provided with a tapered or rounded lower part and, as shown, comprises a central cylindrical portion with upper and lower conical portions 18, 17, is suspended in the bed by a rod 16 guided by rollers 17<a> and connected at the top to a chain 19 which passes over a sprocket 20 on a spindle 22 and carries a counterweight 21 on its free end. On the spindle 22 a plurality of cams 24 is mounted, the inclined steps of the cams being in staggered relationship. Each cam actuates a control valve through a roller 31 which travels on the cam and is connected to a valve spindle 30 carrying closure members 33, 32 which coact with seats formed respectively in a partition 27 and the bottom wall 34 of a box 26. The lower compartment of the box 26 is connected by a pipe 29 provided with a tap 43 to a relay associated with a blow-off valve in the main air-supply pipe, and the upper compartment of the box 26 is connected by a pipe 28 to an air supply. Each relay comprises a casing 35 containing a slidable piston rod 36 and piston 37, the latter being normally forced to the top of the casing by a spring 42. When the float rises, the spindle 22 rotates and the roller 31 is forced upwards by the inclined step of one of the cams. This movement forces the closure member 33 off its seating and allows compressed air to pass from the pipe 28 to the pipe 29 and relay 35. The piston 37 is forced downwards and the rod 36 coacts with the spindle 38 of the associated blow-off valve and prevents its opening, and the strength of the pulsations is consequently increased. A number of blow-off valves, weighted for different pressures, may be provided in the air supply, a corresponding number of cams, control valves, and relays being provided. A cam with a step 25d inclined in a direction opposite to that of the steps of the other cams may be mounted on the spindle 22, the cam being effective when the bed becomes very loose. The pipe 29 attached to the control valve associated with this cam is connected to a warning signal, e.g. an alarm whistle, horn, bell, or signal lamp. The float may also control the discharge of the heavy material from the bed and may also control the quantity of water supplied below the screen. A combination of floats may be used if desired, for example, one float may be used for increasing the strength of the pulsations and a different float for decreasing the strength. Also instead of or in addition to the float control of the main air supply a plurality of floats may be provided to regulate the supply of air to individual compartments of the washer box.