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A powder pumping apparatus including a pump body formed with a pumping chamber having a venturi passageway, a suction tube intersecting the pumping chamber and an air nozzle including a valve mechanism which discharges pressurized air directly into the venturi passageway of the pumping chamber to cr

A powder pumping apparatus including a pump body formed with a pumping chamber having a venturi passageway, a suction tube intersecting the pumping chamber and an air nozzle including a valve mechanism which discharges pressurized air directly into the venturi passageway of the pumping chamber to create a vacuum within the pumping chamber and suction tube to withdraw particulate powder material from a powder feed hopper. The air nozzle is carried within the interior of the pump body and has a discharge outlet located within the pumping chamber which discharges a substantially constant pressure pulse of air directly into the venturi passageway of the pumping chamber. In turn, a sharp, well-defined powder pulse is produced having a substantially homogeneous powder-to-air density throughout the duration of the pulse.

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1. Apparatus for pumping powder material from a powder source, comprising: a pump body formed with a pumping chamber having a powder inlet adapted to communicate with the powder source, and a powder outlet; nozzle means adapted to be connected to a source of pressurized air for ejecting pressuri

1. Apparatus for pumping powder material from a powder source, comprising: a pump body formed with a pumping chamber having a powder inlet adapted to communicate with the powder source, and a powder outlet; nozzle means adapted to be connected to a source of pressurized air for ejecting pressurized air into said pumping chamber; means for periodically interrupting the passage of pressurized air through said nozzle means into said pumping chamber of said pump body to form intermittent pulses of pressurized air each having a substantially constant pressure for the duration of a pulse, said intermittent pulses of pressurized air being effective to withdraw powder material from the powder source through said powder inlet and to form pulses of air-entrained powder material having a substantially homogeneous air-to-powder density. 2. Apparatus for pumping powder material from a powder source, comprising: a pump body formed with a pumping chamber having a powder inlet adapted to communicate with the powder source, and a powder outlet; a nozzle formed with an air chamber adapted to receive pressurized air, said air chamber being formed with a discharge outlet; said nozzle being carried by said pump body so that said discharge outlet is positioned to eject pressurized air from said air chamber in said nozzle into said pumping chamber of said pump body which creates a suction in said pumping chamber to draw particulate powder material from the powder source into said powder inlet of said pumping chamber and through said powder outlet thereof; said nozzle including means for periodically interrupting the passage of pressurized air through said discharge outlet in said nozzle into said pumping chamber of said pump body to form intermittent pulses of pressurized air each having a substantially constant pressure for the duration of a pulse, said intermittent pulses of pressurized air being effective to withdraw powder material from the powder source through said powder inlet and to form pulses of air-entrained powder material having a substantially homogeneous air-to-powder density. 3. The apparatus of claim 2 in which said pump body is formed with a throughbore, a portion of said throughbore defining at least a portion of said pumping chamber, said nozzle comprising: a nozzle body formed with said air chamber and said discharge outlet, said nozzle body being insertable within said throughbore in said pump body so that said discharge outlet thereof is located at said pumping chamber; a seat mounted within said air chamber of said nozzle body at said discharge outlet therein; a plunger having a tip, said plunger being movable between an open position wherein said tip is spaced from said seat and a closed position wherein said tip contacts said seat to seal said discharge outlet; means for moving said plunger between said open and closed positions. 4. The apparatus of claim 3 in which said means for moving said plunger comprises: an armature slidably mounted within said nozzle body, said armature being engagable with said plunger; a solenoid operative to move said armature in a first direction, said armature being effective in the course of moving in said first direction to move said plunger to said open position; a return spring connected to said plunger, said return spring being effective to move said plunger in a second direction to said closed position. 5. The apparatus of claim 4 in which said armature is formed with an annular shoulder and said plunger is formed with a ring, said annular shoulder being effective to engage said ring to move said plunger to said open position. 6. The apparatus of claim 5 in which said nozzle body includes a spring for biasing said armature to a first position when said plunger is in said closed position, said annular shoulder of said armature being spaced from said ring of said plunger with said armature in said first position. 7. Apparatus for pumping powder material from a powder source, comprising: a pump body, said pump body being formed with a powder pumping chamber having a venturi outlet; a nozzle formed with an air chamber adapted to receive pressurized air, said air chamber being formed with a discharge outlet which is positioned within said pump body in alignment with said venturi outlet of said powder pumping chamber; an inlet tube adapted to connect to the powder source, said inlet tube intersecting said powder pumping chamber at a location between said venturi outlet of said powder pumping chamber and said discharge outlet of said air chamber in said nozzle; valve means located at said discharge outlet of said air chamber in said nozzle and movable between an open and closed position relative thereto for for periodically interrupting the passage of pressurized air through said discharge outlet in said nozzle into said powder pumping chamber to create intermittent pulses of pressurized air each having a substantially constant pressure for the duration of the pulse, said intermittent pulses being effective to withdraw powder material from the powder source through said inlet tube and into said powder pumping chamber to form pulses of air-entrained powder material having a substantially homogeneous air-to-powder density. 8. The apparatus of claim 7 in which said valve means comprises: a seat mounted within said air chamber of said nozzle at said discharge outlet therein; a plunger having a tip, said plunger being movable between an open position wherein said tip is spaced from said seat to permit the passage of pressurized air through said discharge outlet, and a closed position wherein said tip contacts said seat to seal said discharge outlet; means for moving said plunger between said open and closed positions. 9. Apparatus for intermittently pumping powder material from a powder source, comprising: a pump body formed with a pumping chamber having a powder inlet adapted to communicate with the powder source and a powder outlet; a nozzle formed with an air chamber adapted to receive pressurized air, said air chamber being formed with a discharge outlet; said nozzle being carried by said pump body so that said discharge outlet in said nozzle is positioned to eject pressurized air from said air chamber of said nozzle directly into said pumping chamber of said pump body which creates a suction in said pump body to draw particulate powder material from the powder source into said powder inlet of said pumping chamber and through said powder outlet thereof; a seat mounted within said air chamber at said discharge outlet therein; a plunger movable between an open and closed position with respect to said seat, said plunger disengaging said seat in said open position to permit the passage of pressurized air through said discharge outlet of said nozzle into said pumping chamber of said pump body, said plunger engaging said seat in said closed position to prevent the passage of pressurized air through said discharge outlet of said nozzle; means for intermittently moving said plunger between said open and closed positions to form intermittent pulses of pressurized air which are discharged from said discharge outlet of said air chamber into said pumping chamber, each of said intermittent pulses of pressurized air having a substantially constant pressure for the duration of the pulse which forms intermittent pulses of air-entrained powder material having a substantially homogeneous air-to-powder density. 10. The apparatus of claim 9 in which said means for intermittently moving said plunger comprises: an armature slidably mounted within said nozzle body, said armature being engagable with said plunger; a solenoid operative to move said armature in a first direction, said armature being effective in the course of moving in said first direction to move said plunger to said open position; a return spring connected to said plunger, said return spring being effective to move said plunger in a second direction to said closed position. 11. The apparatus of claim 10 in which said armature is formed with an annular shoulder and said plunger is formed with a ring, said annular shoulder being effective to engage said ring to move said plunger to said open position. 12. The apparatus of claim 11 in which said nozzle body includes a spring for biasing said armature to a first position when said plunger is in said closed position, said annular shoulder of said armature being spaced from said ring of said plunger with said armature in said first position. 13. A powder pump comprising: a pump body having a cavity defining a venturi pumping chamber; an air supply nozzle mounted within said body for supplying air to said venturi pumping chamber, said air supply nozzle having a discharge orifice in axial alignment with said venturi pumping chamber; a powder supply conduit communicating with said venturi pumping chamber such that air-entrained powder may be drawn into said venturi pumping chamber by air flow through said chamber; and an air flow control valve mounted in said air supply nozzle closely adjacent to said discharge orifice of said nozzle, said air flow control valve including means for periodically interrupting the flow of pressurized air through said air supply nozzle to produce intermittent pulses of pressurized air within said venturi pumping chamber which draw powder material through said powder supply conduit and form pulses of air-entrained powder material within said venturi pumping chamber having a substantially homogeneous air-to-powder density. 14. The method of intermittently pumping powder material from a powder source, comprising: supplying pressurized air into the air chamber of a nozzle communicating with the pump body of a powder pump; ejecting pressurized air from a discharge outlet formed in the air chamber of the nozzle into a pumping chamber formed in said pump body to create a suction within said pumping chamber and within a suction tube extending between said pumping chamber and the powder source; periodically interrupting the flow of pressurized air from said discharge outlet in said nozzle into said pumping chamber of said pump body to form intermittent pulses of pressurized air having a substantially constant pressure throughout the duration of the pulse, said intermittent pulses of pressurized air forming pulses of air-entrained powder material having a substantially homogeneous air-to-powder density. 15. The method of claim 14 in which said step of periodically interrupting the flow of pressurized air comprises intermittently moving a valve member between a closed position relative to said discharge outlet in said air chamber and an open position relative to said discharge outlet. 16. The method of intermittently pumping powder material from a powder source, comprising: supplying pressurized air into the air chamber of a nozzle communicating with the pump body of a powder pump; unseating a valve member from a seat located at the discharge outlet of said air chamber in said nozzle; ejecting pressurized air from said discharge outlet of said nozzle into a pumping chamber formed in said pump body to create a suction within said pumping chamber and within a suction tube extending between said pumping chamber and the powder source; and intermittently returning said valve member into contact with said seat to terminate the flow of pressurized air from said discharge outlet of said air chamber in said nozzle into said pumping chamber in said pump body to form intermittent pulses of pressurized air each having a substantially constant pressure throughout the duration of the pulse, said intermittent pulses of pressurized air forming pulses of air-entrained powder material having a substantially homogeneous air-to-powder density. 17. The method of intermittently pumping powder material from a powder source, comprising: maintaining substantially constant air pressure within an air chamber formed in a nozzle which is carried by the pump body of a powder pump; intermittently ejecting pressurized air through a discharge outlet in the air chamber of the nozzle into a pumping chamber formed in the pump body to form intermittent pulses of pressurized air within the pumping chamber each having a substantially constant pressure throughout the duration of the pulse, the intermittent pulses of pressurized air each creating a suction force within the pumping chamber which is effective to withdraw powder material from the powder source into the pumping chamber of the powder pump to form pulses of air-entrained powder material having a substantially homogeneous air-to-powder density. 18. A method of intermittently pumping powder material from a powder source, comprising: supplying pressurized air into the air chamber of a nozzle carried in the pump body of a powder pump; ejecting pressurized air from a discharge outlet formed in the air chamber of the nozzle into a pumping chamber formed in the pump body; intermittently withdrawing pulses of air-entrained powder material from the powder source into the pumping chamber each having a substantially homogeneous air-to-powder density by periodically interrupting the flow of pressurized air from the discharge outlet of the nozzle into the pumping chamber of the pump body. 19. The method of claim 18 in which said step of intermittently withdrawing pulses of powder material from the powder source includes periodically interrupting the flow of pressurized air from the discharge outlet of the nozzle into the pumping chamber to form intermittent pulses of pressurized air within the pumping chamber each having a substantially constant pressure throughout the duration of the pulse.