GB627042A - Improvements relating to apparatus for feeding powdered material suspended in air orother gas - Google Patents

Abstract

627,042. Fluid-pressure servomotor control systems. SMIDTH & CO. AKTIESELSKAB, F. L. Dec. 17, 1946, No. 37146. Convention date, June 12, 1943. [Class 135] [Also in Group XXX] In order to ensure a substantially constant rate of delivery for a given discharge aperture, from a receptacle 3 containing powdered material suspended in air, the receptacle is charged from a further receptacle 2 only so long as the material in the receptacle 3 is below a predetermined level, and the receptacle 2 is similarly charged from a storage silo 1 only when the material in the receptacle 2 is below a predetermined level. Preferably passage of material from the silo 1 to the receptacle 2 is also prevented when the material in receptacle 3 is above the predetermined level. The material passes from the silo 1 to the receptacle 2 by way of a valve chamber 4, extracting device 5, elevator 6 and a shoot 7, this passage being controlled by a valve 40 in the chamber 4. Similarly, passage of material from the receptacle 2 to receptacle 3 by way of valve chamber 8 and shoot 9 is controlled by a further valve 40. Each valve 40 is mounted on a lever 38 pivoted at 39 and operated by a pneumatic piston and cylinder 35, 34, supply of compressed air to which is controlled pneumatically according as the material in receptacles 2 and 3 does or does not reach the level of diaphragms 11 in wells 10 in the receptacles. Each diaphragm 11, when pressed by material in the receptacle, moves an arm 12 rigid with a lever 13 pivoted at 14 and carrying a balance weight 15. The arm 13 is connected at 16 to a rod 17 carrying a valve 18 in a casing 19 having a vent to atmosphere. Associated with the receptacle 3 is a valve 23 comprising a slide valve 27, 28 and a control piston 25 biassed by a spring 29 and having one side vented at 30 to atmosphere. The corresponding valve 18 is arranged to connect a pipe 26 from the right-hand side of the piston 25 to atmosphere through the vent in the valve chamber 19 or to a pipe 20, normally connected through the valve 23 to a compressed air supply 21. The slide valve 27, 28 is connected by pipes 31, 32, 33, 36 to control the piston 35 operating the valve 40 from the chamber 2 so that when the diaphragm 11 is depressed the valve 18 is operated to move the piston 25 to the right so that the valve 27, 28 admits compressed air to the upper side of the piston 35 which closes the valve 40. A further valve in a housing 45 is associated with the valve 40 controlling the flow from the silo 1 and comprises a piston valve having a piston 47, grooves 48, 49 and intermediate pistons 46. The housing 45 is formed with passages 52, 53, 54, 55 and 56 and with a vent 57. Normally the right-hand side of the piston 47 is connected to atmosphere through a pipe 43 and the valve housing 19 while the chamber 50 is connected by a pipe 51 to a source of compressed air. In this position, if the valve 27, 28 is operated as described above compressed air is admitted through pipe 42, groove 49, passage 54 and a pipe 59 to the upper end of the piston 35 to close the valve 40 from the silo, while the space below the piston 35 is vented through a pipe 58, passage 56, groove 48 and a pipe 41. If the diaphragm 11 in chamber 2 is operated the valve 18 connects the right-hand side of the large piston 47 to the compressed air supply through chamber 50, a pipe 44 and pipe 43, so that the piston valve moves to the left. The pipe 59 is thus connected to the compressed air supply through passage 52, groove 49 and passage 53, while the pipe 58 is vented to atmosphere at 57 through groove 48 and passage 55 ; the piston 35 thus closes the valve 40 from the silo 1.