Method and apparatus for dispensing small amounts of liquid material

A method of depositing a layer of liquid or viscous material on a substrate, said method comprising the steps of:

• dispensing a stream of said liquid or viscous material through an outlet end of a nozzle with a valve;
• stopping the stream of the liquid or viscous material by closing the valve so that the stream breaks away rapidly from the nozzle to form a droplet;
• forming a plurality of the droplets of said liquid or viscous material when said stream of said liquid or viscous material breaks away from said nozzle;
• and
• depositing said plurality of droplets onto said substrate at spaced, selective locations so that said plurality of droplets flow together into a uniform coating.

A method for dispensing small amounts of liquid material, said method comprising the steps of:

• supplying liquid material to an inlet end of a first flow passage extending through a valve assembly having a valve seat disposed near an outlet end of said first flow passage and a reciprocating valve located within said first flow passage;
• filling a second flow passage extending through a nozzle assembly with said liquid material when said valve is in a first position spaced from said valve seat, said second flow passage having an inlet section to receive said liquid material from said outlet end of said first flow passage and an outlet section with an orifice extending through an elongated nozzle from which said liquid material is dispensed;
• accelerating said valve from said first position to a second position spaced closer to said valve seat than said first position whereby a majority of said liquid material in said first flow passage flows towards said inlet end of said first flow passage and the remaining liquid material in said first flow passage flows from said outlet end into said second flow passage and is dispensed from an outlet of said elongated nozzle as a stream of liquid material;
• moving said valve from said second position towards a third position in seating engagement with said valve seat whereby the flow of said liquid material is towards said inlet end of said first flow passage is decreased and the flow of liquid material through said second flow passage is increased;
• and
• moving said valve to said third position where said valve closes against said valve seat whereby the flow of said liquid material through said second flow passage is cut-off and the stream of liquid material being dispensed from said outlet of said elongated nozzle is broken from said outlet end of said nozzle orifice to a form droplet.

A method for rapidly dispensing a minute quantity of a viscous material, comprising the steps of:

• providing a chamber for receiving a continuous flow of the viscous material from a source of the viscous material;
• providing a nozzle having an exit orifice located adjacent a workpiece surface;
• rapidly accelerating the flow of viscous material into the nozzle with a valve for ejecting a stream of the viscous material from the exit orifice;
• and
• positively stopping the flow of the viscous material into the nozzle so the stream breaks away rapidly from the nozzle to form a droplet as a result of forward momentum of the stream and without any need to wet the workpiece surface.

An apparatus for dispensing small amounts of liquid or viscous material, said apparatus comprising:

• a dispenser housing having a flow bore extending therethrough, said dispenser housing having an elongated heated extension element forming an outlet end of the flow bore, an inlet of the flow bore being connected to a source of liquid or viscous material;
• a valve seat assembly mounted at the outlet end of said flow bore, said valve seat assembly having a closed lower end with an outlet opening having a valve seat disposed thereabout extending therethrough;
• a nozzle assembly mounted to the elongated heated extension element and in flow communication with said outlet opening of the valve seat assembly;
• a valve shaft extending through the flow bore having a lower end adapted for seating engagement with the valve seat;
• and
• a heating assembly including a heating element disposed about the elongated heated extension element.