Patent Description:
The present invention relates to liquid dispensing systems, and more particularly, to liquid dispensing systems having nozzles for dispensing small controlled quantities of highly viscous liquids. See for example <CIT>.

In many industries there is a need for dispensing small, controlled quantities of highly viscous liquids. In the food industry, by way of example, in the commercial production of pizzas, it is required to dispense small droplet sized quantities of sauces onto the pizza dough. Because of the thick nature of the sauce, it is difficult to rapidly dispense closely controlled small liquid droplets as desired. Moreover, if the sauce contains solids that can clog the nozzle passages, the flow passages must be sized larger making it even more difficult to control the dispensing of small droplets and often resulting in undesirable splattering of discharging sauce. Furthermore, when the dispensing device uses an air operated liquid control piston, rapid operation of the piston is limited by the compressibility of the controlling air. Additionally, when air operated devices are spring returned, the springs return force can be limited up to roughly half of the air pressure's force used to open the device, which resists rapid piston closure.

It is an object of the invention to provide a liquid dispensing system having spray nozzles effective for dispensing precisely controlled small droplet sized quantities of highly viscous liquids.

Another object is to provide a liquid dispensing system as characterized above that is effective for rapidly depositing precisely controlled pixel sized droplets without undesirable splattering of the liquid.

A further object is to provide a liquid dispensing system of the above kind in which the spray nozzles are operable with larger inlet passages less susceptible to clogging from the solids content in the liquid.

Yet another object is to provide such a liquid dispensing system which can be selectively operated for dispensing different sized precisely controlled small droplets.

Another object is to provide such a liquid dispensing system that can be operated more rapidly.

A further object is to provide a liquid dispensing system of such type that have air actuated pistons with return springs the function of which is less resistant to air pressures used in operating the system.

Still another object is to provide a liquid dispensing system of the foregoing type that is relatively simple in design and lends itself to economical manufacture and efficient usage.

Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings.

Referring now more particularly to <FIG> of the drawings, there is shown an illustrative liquid dispensing system <NUM> in accordance with the invention. The illustrated liquid dispensing system <NUM> is in the form of a modular valve manifold <NUM> comprising a plurality of individual liquid dispensing modules <NUM> supported and retained in sealed side by side stacked relation between end blocks <NUM> and <NUM> at opposite ends secured together by tie rods <NUM> and nuts <NUM>. Each module <NUM> includes a module nozzle support body <NUM> formed with a liquid supply port <NUM> disposed in aligned relation with liquid supply ports <NUM> of the adjacent modules <NUM> for defining a common liquid supply passage <NUM> communicating between a liquid inlet port <NUM> in the upstream end block <NUM> and a liquid outlet port <NUM> in the downstream end block <NUM>. Hence, liquid directed to the inlet <NUM> communicates through each of the stacked modules <NUM>.

Each illustrated module <NUM> has a respective spray nozzle <NUM> mounted in depending relation to an underside of the module nozzle support body <NUM> having an upstream liquid inlet <NUM> in an upper side communicating with the liquid supply passage <NUM>. For controlling liquid from the common liquid supply passage <NUM> to the spray nozzle inlet <NUM> of the module <NUM> a piston <NUM> is supported in each module body <NUM> above the spray nozzle inlet <NUM> for reciprocating movement between a raised inlet open position and a lowered inlet closed position.

Each piston <NUM> in this case is supported for selective relative movement in a carrier <NUM> mounted in sealed relation within a vertical opening <NUM> of the respective module body <NUM> with a downstream end of the piston <NUM> extending through the liquid supply passage <NUM> for engagement with the spray nozzle inlet <NUM>. For biasing the piston <NUM> in a lowered position closing the spray nozzle inlet <NUM>, a return spring <NUM> is disposed within a spring chamber <NUM> of the module body <NUM> in interposed relation between a head 32a of the piston <NUM> and a retention sleeve <NUM> secured within an upper end of the body opening <NUM> and retained by a retention cap <NUM> threadedly engaged within an upper end of the body opening <NUM>. The retention sleeve <NUM> in this case extends downwardly about the return spring <NUM> and the piston head 32a, as best depicted in <FIG> and <FIG>. The spring retention sleeve <NUM> and opening <NUM> of the module body <NUM> in this case define an annular air flow passage <NUM> (<FIG>) about the retention sleeve <NUM> which communicates to and through the spring chamber <NUM> by circumferentially offset holes <NUM> in the spring retention sleeve <NUM>. A sealed piston chamber <NUM> is defined between opposing axel ends of the piston head 32a and the carrier <NUM> (<FIG>).

Pursuant to an important feature of this embodiment, each module body has a pressurized air passage system controlled by a respective valve such that pressurized air that moves the piston to an open position also augments rapid movement of the piston to closure. In the illustrated embodiment, operation of the piston <NUM> of each module <NUM> between open and closed positions is controlled by a respective solenoid valve <NUM>, as best depicted in <FIG> and <FIG>. Each module solenoid valve <NUM> is attached to its respective module body <NUM> with a solenoid mounting block <NUM> mounted in sealed relation to its respective module body <NUM> by screws <NUM>. The module bodies <NUM> each have an air supply port <NUM> aligned with the air supply port <NUM> of each adjacent module body to define a common air inlet passage communicating with a system air inlet port <NUM> in the end block <NUM>. The module bodies <NUM> further each have an air outlet port <NUM> aligned to define a common outlet air passage communicating with a system exhaust outlet port <NUM> in the end block <NUM>. The air supply port <NUM> of the module body <NUM> communicates through inlet air passages <NUM>, 63a in the module body <NUM> and solenoid mounting block <NUM> to an air inlet port <NUM>a of the solenoid valve <NUM>. The air outlet port <NUM> of the module body <NUM> communicates through outlet passage <NUM> with the return spring chamber <NUM> via holes <NUM> in the retention sleeve <NUM> and the annular passage <NUM> about the sleeve <NUM>, and outlet passages <NUM>, <NUM>a in the module body <NUM> and solenoid mounting block <NUM> with an exhaust port <NUM>b of the solenoid valve <NUM>. The piston chamber <NUM> communicates via work passages <NUM>, 62a in the module body <NUM> and solenoid mounting block <NUM> with a work port <NUM>c of the solenoid control valve <NUM>.

When the solenoid valve <NUM> in this case is in its natural or non-energized state, inlet pressure at solenoid valve port air inlet <NUM>a is blocked by a mechanism <NUM>a, in this case in the form of a stem, of the solenoid valve <NUM> (<FIG>) preventing pressurized air at the air supply port <NUM> of the module body <NUM> from communicating with the piston chamber <NUM> via passages <NUM>a, <NUM> in the solenoid mounting block <NUM> and module body <NUM>. Additional passage routing when the solenoid valve <NUM> is in its natural or non-energized state connects ports <NUM>c, <NUM>b of solenoid valve <NUM>, allowing communication of air between piston chamber <NUM> and outlet port <NUM> in the module body <NUM> via passages <NUM>, <NUM>a in the module body <NUM> and solenoid mounting block <NUM>, outlet passages 61a, <NUM> in the solenoid mounting block <NUM> and module body <NUM>, the annular passage <NUM> about through the spring <NUM> via holes <NUM>, and outlet passage <NUM>.

When the solenoid valve <NUM> is energized, the solenoid shifts actuating mechanism 43a to close exhaust port 55b removing the connection of port 55c to atmosphere and connecting solenoid valve ports <NUM>a, 55c. Pressurized air at the air supply port <NUM> of module body <NUM> then communicates with pressure chamber <NUM> via passages <NUM>, 63a in the module body <NUM> and solenoid mounting block <NUM>, solenoid valve ports 55a, 55c and passages <NUM>a, <NUM> causing the piston <NUM> to stroke upwardly, opening the nozzle inlet <NUM> and compressing the return spring <NUM>. The upward stroke of the piston head <NUM>a imparts a positive air displacement within the spring chamber <NUM> resulting in a slight pressure increase. The pressure increase in the spring cavity <NUM> drains through holes <NUM> in the spring retention sleeve <NUM>, annular passage <NUM>, outlet passage <NUM>, and air outlet port <NUM> to atmosphere pressure (<FIG> and <FIG>). The nozzle inlet <NUM> remains open, allowing liquid flow, from the common liquid supply passage <NUM> through the spray nozzle <NUM> to atmosphere while the solenoid is energized.

When un-energized, the solenoid valve <NUM> shifts back to the natural state. Inlet air pressure at solenoid port 55a is again blocked preventing pressurized air from entering the device. Rapid decompression of the pressurized air in piston chamber <NUM> causes a migration of elevated pressure within passages <NUM>, 62a in the module body <NUM> and solenoid mounting block <NUM>, ports <NUM>c and <NUM>b of solenoid valve <NUM>, outlet passage 61a and <NUM> in the solenoid mounting block <NUM> and module body <NUM>, spring chamber <NUM>, outlet passage <NUM>, and outlet port <NUM> as the system pressure in piston chamber <NUM> is released and equalizes with the atmosphere. Migrating pressure in the annular passage <NUM> communicates through holes <NUM> in spring retention sleeve <NUM> causing elevated pressure within spring chamber <NUM> and acting on the surface area of piston head <NUM>a within the spring chamber <NUM> resulting in a momentary downward force supplementing the constant downward force from return spring <NUM> opposing the decompressing pressure in the piston chamber <NUM>, returning piston <NUM> to its natural state, closing passage <NUM> and stopping liquid flow through spray nozzle <NUM>, from common liquid supply passage <NUM>. An appreciable decrease in time required to return the piston <NUM> to its natural state is attributed to the momentary increase in pressure within the spring chamber <NUM>. All passages and cavities downstream of solenoid valve <NUM> including spring chamber <NUM> intrinsically return to atmospheric pressure through an outlet port <NUM> effectively removing the supplemental force the transient pressure applied to piston head <NUM>a.

Further operation of the liquid dispensing module <NUM> by again energizing solenoid <NUM> is unaffected by the previous cycles increased pressure in the spring chamber <NUM> as the increased pressure is transient and quickly returns to atmosphere pressure allowing the increased pressure to have the desired effect on piston's <NUM> opening stroke without effecting the piston's <NUM> closing stroke. As it will become apparent, the solenoid valve <NUM> can be cycled at predetermined rates for the particular dispensing operation with the piston's <NUM> variable open time providing a varying pixel volume.

In accordance with a further aspect of the present embodiment, each spray nozzle module <NUM> is operative for dispensing controlled small round pixel sized droplets of highly viscous liquid as an incident to cycling of the piston <NUM> even when the liquid has an appreciable solids content. Each spray nozzle <NUM> with particular reference to <FIG>, <FIG>, and <FIG>, in this case comprises a nozzle body <NUM>, a nozzle seat <NUM> and an internal nozzle core <NUM>. The nozzle seat <NUM> in this instance has an externally threaded cylindrical downstream end <NUM> that is threadedly engaged within an upstream cylindrical end <NUM> of the nozzle body <NUM> to secure the nozzle core <NUM> within the nozzle body <NUM>. An upstream end <NUM> of the nozzle seat <NUM> defines the predetermined size liquid inlet <NUM>, which is at the upstream end of the assembly. The nozzle core <NUM> in this instance has an upstream cylindrical mounting flange <NUM> positioned on an annular ledge <NUM> within the nozzle body <NUM> and retained in place by the nozzle seat <NUM>, although it will be appreciated that other methods may be used to secure the nozzle core <NUM> within the nozzle body <NUM>.

The cylindrical mounting flange <NUM> of the core <NUM> has a concavely configured (relative to the direction of fluid flow) downstream end wall <NUM> formed with a plurality of circumferentially spaced axially oriented liquid orifices <NUM>. These liquid orifices that communicate between an expansion cavity <NUM> of the nozzle seat <NUM> and an annularly configured liquid discharge passage defined between the nozzle core <NUM> and the nozzle body <NUM> for directing liquid in a controlled fashion for optimum dispensing in small droplet form as will become apparent. It will be understood that while the illustrated nozzle <NUM> comprises a multi-part assembly, alternatively, it could have a one-piece construction or fewer or greater assembled parts.

In carrying out this aspect of the present embodiment, the nozzle core <NUM> has a teardrop shaped pintle <NUM> which together with the internal circumferential surface of the surrounding nozzle body <NUM> defines an expanding discharge passage <NUM> that reduces exit velocity of the dispensed liquid for maintaining a desired flow rate and consistent droplet size of the highly viscous discharging liquid. To that end, the illustrated pintle <NUM> (see <FIG>, <FIG>, and <FIG>) has a relatively small diameter upstream end section <NUM> extending centrally from the mounting flange <NUM>, a radially outwardly extending curved section <NUM> adjacent to the upstream end, and an inwardly tapered, relatively long conical terminal end section <NUM>. As noted, the nozzle body <NUM> has a generally hollow cylindrical configuration with the internal circumferential surface of the nozzle body <NUM> defining the outer wall of the annular discharge passage <NUM> about the core section <NUM>. The inner wall of the discharge passage <NUM> is defined by the outer surface of the pintle <NUM>. In this case, the internal circumferential surface of the nozzle body <NUM> includes a radially outwardly directed section <NUM> that extends in surrounding relation to the outwardly curved section <NUM> of the nozzle core <NUM> and a uniform diameter section <NUM> that then extends downstream substantially the remaining length of the pintle <NUM>. The design is unique in that flow through the annular discharge passage effects inward expansion of viscous liquid during travel through the nozzle body. The geometry of the pintle defines the inner diametric wall of the annular flow path while providing a structure against which a vacuum due to the flow expansion can be formed. The deceleration of the liquid within the expanding annular discharge passage is a function of the surface tension and the capillary forces' ability to draw a vacuum and resist flow.

In operation, with continued reference to <FIG>, when the piston <NUM> is in a raised inlet open position, liquid is permitted to pass through the nozzle inlet <NUM> in a controlled fashion into the expansion cavity <NUM> defined within the cylindrical downstream end of the nozzle seat <NUM>. Liquid passing through the nozzle inlet <NUM> is directed against an impingement surface defined by the concave downstream end wall <NUM> of the expansion cavity <NUM>. This causes liquid to fill the expansion cavity <NUM> and then subsequently extrude from the expansion cavity through the series of circumferentially spaced orifices <NUM> into the discharge passage <NUM>. Moreover, the size of each of the orifices <NUM> is at least as large as the nozzle inlet <NUM> to allow solid particles in the liquid to flow from the expansion cavity <NUM> to the fluid discharge passage <NUM> without clogging. The collective area of the circumferentially spaced orifices <NUM> is greater than the area of the nozzle inlet <NUM> such that the velocity of the liquid passing through the orifices <NUM> is inversely proportional to the ratio of the size of the orifices <NUM> to the size of the nozzle inlet <NUM>.

More specifically, the circumferential orifices <NUM> at the downstream end of the expansion cavity <NUM> communicate with an inlet section <NUM> of the discharge passage <NUM> that is defined between the outwardly directed wall section <NUM> of the nozzle body <NUM> and the pintle <NUM> of the nozzle core <NUM>. The cross-sectional area of the annular inlet section <NUM> may increase as the section extends in the downstream direction such that the velocity of the fluid in this region continues to be reduced as the cross-sectional area of the discharge passage expands. A slight reduction in the cross-sectional area of the discharge passage <NUM> in a subsequent stabilizing section <NUM> of the discharge passage <NUM> (again defined by the outer surface of the pintle <NUM> and the inner circumferential surface of the nozzle body <NUM>) immediately downstream of the inlet section <NUM> can provide a slight increase in pressure. This increase in pressure stabilizes and balances the flow removing individual jet streams caused by the fluid entering the inlet section <NUM> of the discharge passage <NUM> through the series of orifices <NUM> and allows uniform flow along the internal wall surface of the nozzle body <NUM>. The cross-sectional area of the stabilizing section <NUM> remains constant through this region as the fluid gains stability.

Downstream of the stabilizing section <NUM>, the liquid enters a final expansion section <NUM> defined by the inwardly tapered terminal end section <NUM> of the nozzle core <NUM> that extends downstream to a nozzle mouth <NUM> defined at the downstream end of the nozzle body <NUM>. The progressively increasing cross-sectional area of the final expansion section <NUM> is achieved through the reducing conical diameter of the pintle <NUM> in the terminal end section <NUM> while the inner circumferential surface of the nozzle body <NUM> is maintained at a consistent diameter. The pintle <NUM> helps stabilize the fluid and enables greater expansion of the liquid than could be achieved with nozzle core having a simple uniform diameter. Sustained contact of the liquid with inner and outer wall surfaces of the discharge passage is a function of the surface tension of the liquid.

The cross-sectional area of the final expansion section <NUM> at the nozzle mouth <NUM> defines the exit velocity of the liquid, which is inversely proportional to the cross-sectional area at the nozzle mouth <NUM> in relation to the area of nozzle inlet <NUM>. The terminal end section <NUM> of the nozzle core <NUM> preferably extends slightly beyond the nozzle mouth <NUM> to assist in breaking the surface tension of the liquid with the inner circumferential surface of the nozzle body <NUM> without impacting the outer diameter of the discharging liquid stream. Having the inner circumferential surface of the nozzle body <NUM> at a constant diameter helps establish a consistent diameter of the boundary layer of the liquid when it exits the nozzle, which assists in maintaining the desired droplet diameter independent of the distance of the nozzle from the target.

It has been found that a dramatic reduction in the velocity of the liquid can be achieved through progressively increasing the cross-sectional area of the discharge passage <NUM>. The inward expansion of the discharge passage <NUM> is achieved by progressively reducing the diameter of the pintle <NUM> while maintaining the inner circumferential surface of the nozzle body <NUM>. This helps produce discharging liquid with a consistent stream diameter. The reduced velocity of the liquid allows it to be dispensed without splattering. This further allows the utilization of larger nozzle inlet orifices <NUM> for enabling the dispensing of liquids with larger solids content. Once the discharge passage of the nozzle is initially filled with viscous fluid, the surface tension of the liquid will keep the nozzle <NUM> charged with liquid ready to be dispensed upon opening of the nozzle inlet <NUM>. Because the liquid can be substantially incompressible, an exact relationship can be maintained between the liquid volume entering the nozzle <NUM> through the inlet <NUM> and the liquid exiting the nozzle mouth <NUM>. Cycling the piston <NUM> to open and close the inlet orifice <NUM> at a rapid rate, such as <NUM> milliseconds, has been found to produce small, consistent droplets of liquid that are discharged at a reduced exit velocity. This allows the discharging droplets to be deposited on a target, such as a target about <NUM> inches from the nozzle, without splattering.

Claim 1:
A spray nozzle comprising:
a nozzle seat (<NUM>) having a liquid inlet and an expansion cavity (<NUM>) in fluid communication with the liquid inlet (<NUM>), the expansion cavity terminating at a downstream end wall (<NUM>);
a nozzle body (<NUM>) having a generally hollow cylindrical configuration defining an internal circumferential surface; and
an internal nozzle core (<NUM>) arranged within the nozzle body (<NUM>), said nozzle core (<NUM>) including a teardrop shaped pintle (<NUM>) having an upstream end section (<NUM>) adjacent to the upstream end wall of the expansion cavity, a radially outward curved section (<NUM>) adjacent to the upstream end section (<NUM>) and a radially inwardly tapered conical terminal end section (<NUM>), an annular discharge passage (<NUM>) being defined between an outer surface of the pintle (<NUM>) and the internal circumferential surface of the nozzle body (<NUM>) that is in fluid communication with the expansion cavity of the nozzle seat; characterized by the annular discharge passage (<NUM>) including an expansion section (<NUM>) defined by the radially inwardly tapered conical terminal end section (<NUM>), wherein the expansion section (<NUM>) has a cross-sectional area that progressively increases as the expansion section extends in the downstream direction.