Method for pneumatically controlling discharge of particulate material

The method of dispensing particulate material comprising:

• establishing an accumulation of particulate material in a nozzle having an opening at the bottom for discharging the particulate material, said accumulation having a top surface within said nozzle,
• establishing a buffer zone in communication with said accumulation of particulate material at said top surface,
• discharging a flow of particulate material from said accumulation through said nozzle opening, and
• changing the air pressure in said buffer zone to control the flow of particulate material through said nozzle opening, the air pressure being rapidly decreased in said buffer zone in a first mode of operation to thereby generate an airflow through said nozzle opening and into said accumulation whereby the flow of particulate material through said nozzle opening is quickly stopped, said airflow being selected to maintain particulate material forming said surface of said accumulation substantially unentrained in said airflow and to maintain said particulate material in said accumulation in a substantially unfluidized state.

The method of dispensing particulate material comprising the steps of:

• establishing an accumulation of particulate material in a discharge device having a discharge opening, said accumulation having a top surface of unconstrained particulate material;
• establishing an air buffer zone which is in communication with said top surface of said accumulation of particulate material;
• discharging a flow of particulate material from said accumulation through said discharge opening, and
• changing the air pressure in said buffer zone to effect airflow along an airflow path through said accumulation which is generally coincident with a discharge flow path to thereby, in a first mode of operation, control a flow of particulate material through said discharge opening by rapidly stopping the flow of particulate material through said discharge opening without substantial entrainment of particulate material from said top surface in said airflow.

The method of dispensing particulate material comprising the steps of:

• establishing an accumulation of particulate material in a vessel having a discharge opening, said accumulation having a top surface area of unconstrained particulate material, and said accumulation forming a weight of particulate material at said discharge opening;
• establishing an air buffer zone which is in communication with said accumulation top surface area;
• discharging a flow of particulate material from said accumulation through said discharge opening, and
• rapidly changing the air pressure in said buffer zone to generate a modifying airflow having a drag force parallel to a discharge flow path followed by said particulate material as said particulate material flows through said vessel to thereby control the flow of particulate material through said discharge opening, which modifying airflow is selected in a first mode of operation to substantially prevent entrainment of particulate material forming said top surface area in said modifying airflow while substantially immediately stopping particulate material discharge through said discharge opening, said modifying airflow being selected in said first mode with a drag force sufficient to suspend said weight of particulate material.

The method of dispensing particulate material comprising the steps of:

• establishing a reservoir of particulate material in a container having a discharge opening for dispensing on a substrate;
• maintaining said reservoir at a substantially constant volume throughout dispensing by providing an uninterrupted supply of particulate material to said reservoir;
• establishing an air flow along an air path extending through said discharge opening which air flow is in contact with said particulate material in said reservoir along a discharge path defined by a flow of particulate material through said container;
• discharging a flow of particulate material from said reservoir through said discharge opening;
• and
• changing the rate of air flow through said discharge opening to thereby control said flow of particulate material through said discharge opening.

The method of dispensing particulate material comprising the steps of:

• establishing an accumulation of particulate material in a vessel having a discharge opening, which accumulation has a top surface area, and maintaining said accumulation;
• establishing an air buffer zone in communication with said top surface area;
• discharging a flow of particulate material from said accumulation through said discharge opening, and
• reducing the air pressure in said buffer zone to generate an airflow through said discharge opening and through said accumulation which mixes with said particulate material and follows an airpath generally parallel with a discharge flow path of said particulate material as said particulate material flows through said vessel and in a direction opposite to said discharge flow path to thereby control said flow of particulate material through said discharge opening, said airflow through said discharge opening being adjusted at a maximum to prevent the particulate material from flowing through said discharge opening without substantial entrainment of particulate material from said top surface area in said airflow.

A method for dispensing particulate material onto a substrate moving past the dispenser comprising the steps of:

• providing a nozzle having an elongated slot at the bottom of the nozzle for discharging the particulate material,
• establishing an accumulation of the particulate material in the nozzle, said accumulation having a top surface area of unconstrained particulate material, said accumulation forming a weight of particulate material in the bottom of said nozzle at said slot,
• providing a buffer chamber positioned in communication with said top surface area of said accumulation of particulate material, and providing a vacuum source for reducing air pressure in said buffer chamber,
• discharging a flow of particulate material from said accumulation through said slot onto said substrate, and
• rapidly stopping the flow of particulate material through said slot by controlling said vacuum means to effect an airflow through said nozzle and into said accumulation sufficient to create a fluid drag to suspend the weight of particulate material at said slot in a first mode of operation.

A method for dispensing particulate material having a fast discharge cut-off, comprising the steps of:

• providing a vessel with a discharge opening defined therein,
• supplying particulate material to said vessel to establish an accumulation of particulate material in said vessel which accumulation has a top surface area spaced from said discharge opening, with said supplying step further including maintaining said accumulation;
• providing an air buffer chamber which encloses said accumulation top surface area;
• discharging a flow of particulate material from said accumulation through said discharge opening;
• and
• rapidly generating and controlling via said buffer chamber an airflow through said accumulation which airflow follows an airpath generally parallel with a discharge flow path for said particulate material, said airflow in one mode of operation being generated by reducing air pressure in said buffer chamber to create a reverse airflow along said airpath in a direction opposite to said discharge flow path and counter to a flow of particulate material through said discharge opening, said reverse airflow through said discharge opening being controlled to rapidly stop particulate material from flowing through said discharge opening in said one mode of operation.

The method of dispensing particulate material comprising the steps of:

• providing a container for holding an accumulation of particulate material, said container having a discharge opening through which said particulate material is dispensed along a discharge path onto a substrate;
• supplying particulate material to said container to establish an accumulation of particulate material in said container, and further in response to removal of particulate material through discharge so as to substantially maintain said accumulation at a constant volume;
• discharging a flow of particulate material from said accumulation through said discharge opening;
• and
• generating and controlling an air flow through said accumulation which air flow is mixed with said particulate material and follows an air flow path extending along said discharge path, to thereby control a flow of particulate material through said discharge opening.

A method for dispensing particulate material comprising the steps of:

• providing a container for holding an accumulation of particulate material, said container having a discharge opening through which said particulate material is dispensed along a discharge path, said accumulation having a top surface defined by particulate material in said container which is spaced from said discharge opening;
• providing a housing defining an air buffer zone enclosing said top surface;
• providing means for changing air pressure in communication with said air buffer zone;
• discharging a flow of particulate material from said accumulation through said discharge opening;
• and
• generating and controlling air pressure in said air buffer zone to thereby effect a flow of air through said discharge opening and along said discharge path to control a flow of particulate material through said discharge opening, including one mode of operation wherein air pressure in said air buffer zone is rapidly reduced to create an airflow along said discharge path to draw air through said discharge opening into said container, said airflow through said discharge opening being controlled to rapidly stop particulate material from flowing through said discharge opening in said one mode of operation.