Proportioning pump for introducing an additive in a fluid stream

Abstract

The invention concerns a device for varying the dosage of an additive (A) in a main flow (P) of liquid, the proportioning being provided by a pump ( 1 ) driven by the main flow, the pump comprising a first intake ( 2 ) for the main flow, a second intake ( 3 ) for the additive and an outlet for the dosed mixture. A branch pipe ( 5 ) of the main flow is provided between a zone ( 6 ) located upstream of the first intake ( 2 ) and a zone ( 7 ) located downstream of the outlet ( 4 ), so as to enable a parallel flow not comprising the additive. Periodic control means (C) for the branch pipe ( 5 ) and the first intake ( 2 ) of the pump are also provided so that each control period comprises at least a phase (Ud 1 ) for which the branch pipe ( 5 ) is open and the first intake ( 2 ) is closed, and another phase (Ud 2 ) for which the branch pipe ( 5 ) is closed while the first intake ( 2 ) is open.

1 . A device for varying the metering of an additive (A) to a main flow (P) of liquid, the metering being carried out by a pump ( 1 ) driven by the main flow of liquid, the pump comprising a first inlet ( 2 ) for the main flow with a branch leading from a region ( 6 ) lying upstream of the inlet ( 2 ) and control means on this branch, a second inlet ( 3 ) for the additive, and an outlet ( 4 ) for the metered mixture, characterized in that: 
 the branching-off ( 5 ) of the main flow is performed between the region ( 6 ) lying upstream of the first inlet ( 2 ) and a region ( 7 ) lying downstream of the outlet ( 4 ) on a length ( 10 ) of pipe that can be connected to the outlet ( 4 ) so as to allow a parallel flow that does not contain the additive;    and the control means on the branch are means (C) of periodically controlling the branch ( 5 ) of the first inlet ( 2 ) of the pump, these control means (C) being designed so that each control period comprises at least one phase (Ud 1 ) for which the branch ( 5 ) is open and the first inlet ( 2 ) is closed, and another phase (Ud 2 ) for which the branch ( 5 ) is closed while the first inlet ( 2 ) is open.    
     
     
         2 . The device as claimed in  claim 1 , characterized in that the periodic control means (C) are designed to allow the duration of each phase (Ud 1 , Ud 2 ) to be adjusted.  
     
     
         3 . The device as claimed in  claim 1  or  2 , characterized in that the periodic control frequency (N) is chosen to be high enough to ensure homogeneous mixing of the additive at the outlet.  
     
     
         4 . The device as claimed in  claim 1  or  2 , characterized in that the periodic control frequency (N) is at least 10 Hz, particularly of the order of 50 Hz.  
     
     
         5 . The device as claimed in one of the preceding claims, characterized in that the periodic control means (C) comprise: 
 a first valve means ( 12 ) for closing or opening the branch ( 5 );    a second valve means ( 13 ) for closing or opening the first inlet ( 2 ) of the pump;    and control means ( 14 ) for, on the one hand, opening the first valve means ( 12 ) and at the same time closing the second valve means ( 13 ) and, on the other hand, closing the first valve means ( 12 ) and at the same time opening the second valve means ( 13 ) using pulses, the frequency (N) and duration (Ud 1 , Ud 2 ) of which are adjustable.    
     
     
         6 . The device as claimed in  claim 5 , characterized in that each valve means ( 12 ,  13 ) consists of a solenoid valve and the control means comprise an electric pulse generator ( 14 ) controlling the solenoid valves.  
     
     
         7 . The device as claimed in  claim 6 , characterized in that the first and second valve means are combined into a single three-way solenoid valve ( 12   a ).  
     
     
         8 . The device as claimed in one of the preceding claims, characterized in that it comprises, downstream of the region ( 7 ) lying downstream of the outlet ( 4 ), a flow regulator ( 17 ), possibly adjustable.  
     
     
         9 . A metering pump, particularly with a fixed metering setting, for metering an additive (A) into a main flow (P) of liquid, the pump ( 1 ) being driven by the main flow of liquid and comprising a first inlet ( 2 ) for the main flow, a second inlet ( 3 ) for the additive and an outlet ( 4 ) for the metered mixture, which pump is equipped with a device as claimed in one of  claims 1  to  8  for varying the metered proportions.  
     
     
         10 . An installation for metering an additive (A) into a main flow (P) of liquid, comprising a metering pump, particularly with a fixed metering setting, the pump ( 1 ) being driven by the main flow of liquid and comprising a first inlet ( 2 ) for the main flow, a second inlet ( 3 ) for the additive and an outlet ( 4 ) for the metered mixture, which pump is equipped with a device as claimed in one of  claims 1  to  8  for varying the metered proportions.