Dispensing valve assembly and system

A dispensing valve assembly adapted to be connected in communication with a source of material to dispense a selected quantity thereof, comprising:

• a valve casing having an interior chamber, a dispensing port in communication with the chamber, a longitudinal valve passageway communicating with the chamber at a first opening and having a second opening opposite the first opening, an inlet port extending from an exterior inlet opening in said valve casing to an interior inlet opening communicating with the valve passageway, and a metering port extending from an exterior metering opening to an interior metering opening communicating with the valve passageway whereby a flow path for material to be dispensed is defined through said valve casing from an upstream location at the exterior inlet opening to a downstream location at the dispensing port, the inlet port adapted to be connected in fluid communication with the source of material to be dispensed;
• a metering cylinder in communication with the metering port whereby material may flow into and out of said metering cylinder;
• a valve element slideably mounted in the valve passageway for reciprocal longitudinal movement therein between a fully open position and a fully closed position, said valve element including a drive shaft portion, a piston head portion having a piston head length and a waisted portion interconnecting the drive shaft and piston head portions, said drive shaft portion connectable through the second opening to a drive means for reciprocally driving said valve element between the fully open and fully closed positions;
• a first sealing means located between the interior metering opening and the first opening for sealing against the piston head portion during reciprocal movement thereof to establish a first seal between the metering port and the chamber;
• a second sealing means located between the inlet port and the second opening for sealing against said drive shaft portion during reciprocal movement thereof to establish a second seal between the second opening and the inlet port;
• and
• a third sealing means located between the inlet port and the metering port for sealing against said drive shaft portion during reciprocal movement thereof to establish a third seal between the metering port and the inlet port;
• said waisted portion having a longitudinal length greater than a first longitudinal distance between the inlet port and the third sealing means and greater than a second longitudinal distance between the metering port and the first sealing means;
• said valve element operative during a cycle of reciprocal movement from the fully closed position through the fully open position and back to the fully closed position to dispense material by first positioning said waisted portion in said valve passageway between the interior inlet opening and the interior metering opening to interrupt the third seal whereby the selected quantity of material flows from the source connected to the inlet port, alongside the waisted portion and into said metering cylinder, advancing the valve element so that the third seal is re-established, advancing the valve element to the fully open position whereby said waisted portion is positioned in the valve passageway between the interior metering opening and the first opening to interrupt the first seal whereby the selected quantity of material in said metering cylinder flows into the chamber and out of said dispensing port after which the valve element is retracted to again establish the first seal and continuing to retract said valve element until said valve element is in the fully closed position, such that retraction of the piston head portion away from the chamber after re-establishing the first seal creates a negative pressure whereby material in the dispensing port is drawn back toward the chamber.

A dispensing apparatus connectable to a source of viscous material to be dispensed and operative to dispense a selected quantity of said material, comprising:

• a metering cylinder having an interior operative to receive the selected quantity of said material and including a piston member for discharging the selected quantity of said material;
• a valve assembly including a valve casing, a valve element, a first sealing means, a second sealing means and a third sealing means;
• said valve casing having an interior chamber, a dispensing port in communication with the chamber, a longitudinal valve passageway communicating with the chamber at a first opening and having a second opening opposite the first opening, an inlet port extending from an exterior inlet opening in said valve casing to an interior inlet opening communicating with the valve passageway, and a metering port extending from an exterior metering opening to an interior metering opening communicating with the valve passageway whereby a flow path for material to be dispensed is defined through said valve casing from an upstream location at the exterior inlet opening to a downstream location at the dispensing port, the inlet port adapted to be connected in fluid communication with the source of material to be dispensed, said metering cylinder in communication with the metering port exterior opening whereby material may flow into and out of said metering cylinder;
• said valve element slideably mounted in the valve passageway for reciprocal longitudinal movement therein between a fully open position and a fully closed position, said valve element including a drive shaft portion, a piston head portion having a piston head length and a waisted portion interconnecting the drive shaft and piston head portions;
• said first sealing means located between the interior metering opening and first opening for sealing against the piston head portion during reciprocal movement thereof to establish a first seal between the metering port and the chamber;
• said second sealing means located between the interior inlet opening and the second opening for sealing against said drive shaft portion during reciprocal movement thereof to establish a second seal between the second opening and the inlet port;
• said third sealing means located between the interior inlet opening and the interior metering opening for sealing against said drive shaft portion during reciprocal movement thereof the establish a third seal between the metering port and the inlet port;
• said waisted portion having a longitudinal length greater than a first longitudinal distance between the inlet port and the third sealing means and greater than a second longitudinal distance between the metering port and the first sealing means;
• said valve element operative during a cycle of reciprocal movement from the fully closed position through the fully open position and back to the fully closed position to dispense material by first positioning said waisted portion in said valve passageway between the interior inlet opening and the interior metering opening to interrupt the third seal whereby the selected quantity of material flows from the source connected to the inlet port, alongside the waisted portion and into said metering cylinder, advancing the valve element so that the third seal is re-established, advancing the valve element to the fully open position whereby said waisted portion is positioned in the valve passageway between the interior metering opening and the first opening to interrupt the first seal whereby the selected quantity of material in said metering cylinder flows into the chamber and out of said dispensing port after which the valve element is retracted to again establish the first seal and continuing to retract said valve element until said valve element is in the fully closed position, such that retraction of the piston head portion away from the chamber after re-establishing the first seal creates a negative pressure whereby material in the dispensing port is drawn back toward the chamber;
• a first drive means connected to said drive shaft for reciprocally driving said valve element between said fully open and fully closed position;
• and
• a second drive means associated with said metering cylinder for driving said piston therethrough to discharge the selected quantity of material through the metering port, into the chamber and out of the dispensing port.