Method and device for gravimetric dosing bulk material
In order to increase the dosing accuracy of a dosing device, the bulk material is temporarily stored upstream from a reservoir ( 1 ) in an intermediate storage container ( 6 ) and is transferred only when a compensating pressure value is reached. The invention also relates to a corresponding device with a valve lock ( 4,5 ) on the intermediate container ( 6 ).
1. A method for gravimetric dosing of bulk material which is supplied from a storage container to a reservoir, is weighed there by determining a weighing signal for forwarding to an electronic weighing system and is discharged from the reservoir to a gravimetric dosing apparatus, wherein the bulk material is intermediately stored in an intermediate container prior to being weighed in the reservoir and is only released from the intermediate container upon reaching a compensation pressure value, and wherein a pressure in the intermediate container and in the reservoir is measured continually, and wherein a pneumatic charging/discharging of the bulk material with negative or excess pressure, a pressure in a conveying conduit is measured in addition and is compared with the pressure in the intermediate container for determining the compensation pressure value.
2. A method as claimed in claim 1 , wherein the intermediate container and/or the reservoir is vented from a certain pressure increase rate.
3. A method as claimed in claim 1 , wherein the compensation pressure value is fixed to a pressure difference of approximately zero.
4. A method as claimed in claim 1 , wherein the pressure measured in the intermediate container and/or the reservoir, and their differential pressure value, is guided to a dosing control unit or electronic weighing system for the purpose of controlling a dosing apparatus.
5. A method as claimed in claim 4 , wherein the intermediate container and/or reservoir can be pressurized by a pump.
6. An apparatus for gravimetric dosing bulk material with a reservoir which rests on at least one weighing cell connected to an electronic weighing system and is connected via flexible connections with a bulk material supply line and a gravimetric dosing apparatus, wherein a valve lock is formed by an upper flap and a lower flap at an intermediate container arranged upstream of the reservoir, and wherein a pressure sensor is provided each in the intermediate container and in the reservoir for detecting a pressure in the intermediate container and in the reservoir and means for measuring a pressure in a conveying conduit, wherein a pneumatic charging/discharging of the bulk material with negative or excess pressure, the pressure in the conveying conduit is compared with the pressure in the intermediate container for determining a compensation pressure value.
7. An apparatus as claimed in claim 6 , wherein at least one filling level probe is provided on the intermediate container.