Powder flow control valve
First Claim
1. A powder flow control valve for dispensing a predetermined weight of powder in which a downwardly extending powder flow path is surrounded by a perforated boundary surface past which powder may flow under gravity, said perforated boundary surface having a first side which faces the powder flow path, the valve having first means for creating a pressure drop across the boundary surface with a higher pressure on the first side of the boundary surface to terminate flow of powder along the path and second means for creating a pressure rise across the boundary surface with a lower pressure on said first side of the surface to promote flow of powder past the surface;
- wherein the improvement comprises control means responsive to the quantity of powder delivered for selectively operating said first and second means in a sequence having a first period of time during which the first means is deactivated and the second means is activated to dispense powder with accelerated flow past the boundary surface, a second period of time during which the second means is deactivated and the first means is maintained deactivated to allow flow to continue past the boundary surface under gravity until a required quantity of powder has been dispensed by the valve as detected by the control means, and a third period of time during which the first means is activated by the control means to terminate flow of powder through the valve.
3 Assignments
0 Petitions
Accused Products
Abstract
The disclosure relates to a powder flow control valve comprising a nozzle formed from a material such as high density polythene having an upper frusto-conical section which converges towards the lower end of the nozzle and terminates in a cylindrical section. The nozzle is encircled by a plenum chamber to which sources of vacuum and air pressure are selectively connectable through a pneumatic control system. When vacuum is connected to the plenum chamber, the resulting pressure drop across the wall of the porous nozzle causes powder flowing through the nozzle to consolidate in the nozzle and terminate the flow. When air pressure is applied to the plenum chamber, the resulting pressure rise across the boundary surface accelerates powder flow through the nozzle. The control means is arranged to establish air pressure in the plenum chamber to initiate opening of the valve and flow through the valve and, after a pre-determined time, to terminate the air pressure supply and allow powder to flow under gravity through the nozzle before flow is terminated when a pre-determined quantity of powder has been delivered by the nozzle by applying vacuum to the plenum chamber.
82 Citations
11 Claims
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1. A powder flow control valve for dispensing a predetermined weight of powder in which a downwardly extending powder flow path is surrounded by a perforated boundary surface past which powder may flow under gravity, said perforated boundary surface having a first side which faces the powder flow path, the valve having first means for creating a pressure drop across the boundary surface with a higher pressure on the first side of the boundary surface to terminate flow of powder along the path and second means for creating a pressure rise across the boundary surface with a lower pressure on said first side of the surface to promote flow of powder past the surface;
wherein the improvement comprises control means responsive to the quantity of powder delivered for selectively operating said first and second means in a sequence having a first period of time during which the first means is deactivated and the second means is activated to dispense powder with accelerated flow past the boundary surface, a second period of time during which the second means is deactivated and the first means is maintained deactivated to allow flow to continue past the boundary surface under gravity until a required quantity of powder has been dispensed by the valve as detected by the control means, and a third period of time during which the first means is activated by the control means to terminate flow of powder through the valve. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
Specification