US2941726A - Booster-action airless spray unit - Google Patents

Description

BOOSTER-ACTION AIRLESS SPRAY UNIT Filed Nov. 19, 1954 2 Sheets-Sheet 1 Il` 54 ,wu

= l 22 l A 7 f4/M50 l I g |4 /IQ /l' /IO la /BI [I6 28 j 22 3' 32 @g g /l/ 'I 24 30 ff M25 IV 2| l/ I| Y INVENTOR. I/ IJ-L- HagrY-v Szczepansy H. SZCZEPANSKI BOOSTER-ACTION AIRLESS SPRAY UNIT Filed Nov. 19, 1954 2 Sheets-Sheet 2 F/'gn Harry Szggg ki ffomey United States PatentV4 BOOSTER-ACTIN AIRLESS SPRAY UNIT Harry Szczepanski, 407 Henry Ave. SE.,

Grand Rapids, Mich.

Filed Nov. 19, 1954, Ser. No. 470,058

5 Claims. (Cl. 239-139) This invention has been developed for the direct spray ing of a liquid without the use of a high-velocity stream of air for transporting the particles of material from the spray orifice over to the target. It is conventional for paints and other coating materials to contain a volatile solvent, or a mixture of them, and the breakup of the stream of-material into a mist (in the type of equipment to which this invention is related) is induced through a preliminary heating of the spray material to a point above the temperature at which one of the solvents will Iboil under atmospheric pressure (or the chamber pressure within whichthe spraying operation is conducted). Prior to the ejection of the sprayed material from the nozzle of the spray unit, it is maintained under sufficient pressure to prevent boiling. As the liquid emerges from the spray orifice, the sudden tendency for the `solvent to vaporize generates an almost explosive action within the spray stream causing it to` disperse into the fine mist necessary for proper uniformV coverage of articles being coated. i

-Stated in these terms, the procedure outlined above is not new. It is commonly referred to as ,airless spraying, and several types of equipment have been devised which make -use of it. Patent Numbers 1,457,634; 2,176,128; and 2,481,813 describe the use of this principle, and this invention is intended primarily to provide a compact and simplified mechanism for utilizing this system of operation. `Previous developments have centered their Aattention around the maintenance of the liquid` to be sprayed at a high temperature and pressure throughout theliquidsupply system. General `practice has been simply to supply the spray unit with `heated spray material under pressure, with a valve arrangement disposed to control the flow through the supply line. The cost of maintaining an entire supply system (including tanks, pumps, conduits, and so forth) at an elevated pressure and temperature has created such practical diiiiculties as to interfere with the utilization of this type of operation. A very important feature of this invention is the elimination of-the necessity of maintaining the supply system up to the gun at either an elevated temperature or pressure. The spray material, therefore, exhibits no tendency to break down into its components, nor to be converted under the effects of long-sustained heat. `In the preferred form of this invention, spray material is'admitted to a chamber under aninitially low pressure (sufficient to prevent boiling of the material while in the gun), with the supply system provided with a check valvepreve'nting outow from this chamber. A spray nozzle communicates with the chamber, and a piston rod operated by an air cylinder is disposed so that reciprocation of the piston causes the` rod to be projected and withdrawn from the spraying chamher.A The projection of the piston rod into the chamber causes a sufiicient displacement of material to generate a veryhigh pressure, which is sutiicient to force the spray material out through the nozzle orifice at the requisite velocity. i zzAn' auxiliary valve is provided in the neighborhood of 2,941,726 Patented June 21, 1960 icel the nozzle, and which controls the ow from the spray chamber to the nozzle. This valve is operative to permit ow only during the operation of the air cylinder. The preferred form of this valve involves a piston and cylinder actuator in which air is admitted from the main air cylinder to withdraw the valve into open position. The return of the main driving piston, accompanied by the lling of the spraying chamber with a new charge of liquid, may therefore take place within a heated chamber without volatilizing the included solvent, since the auxiliary valve will at that moment be in closed position. As an alter-` native to the piston-operated auxiliary valve, an independent pressure-limiting valve may be used which requires the generation of a given level of pressure within the spraychamber before uid is permitted to pass out through the nozzle. The admission of the spraying liquid into the chamber need therefore only be under a pressure suiicient to maintain the liquid state of the solvent, which is ordinarily far less than that required for the spraying operation.

In contrast to the heating of the entire paint-supply system, this invention provides for the application of heat to a small quantity of spray material immediately prior to the ejection thereof through the spray nozzle. One modification of this invention provides for a jacket for the circulation of heating fluid around the spray chamber, and a second modification delivers heat directly to the nozzle `unit itself, preferably through the use of electrical resistive elements controlled by suitable thermocouple equipment. With` the heated nozzle unit,l temperature of the spray material is raised as it passes through the nozzle itself. To facilitate the heat exchange, the nozzle may be provided with inwardly-extending tins so as to increaseV the net amount of surface contact between the liquid and nozzle conduit.

. The several features of thisinvention will be discussed in detailby an analysis of the particular embodiments i1- lustrated in the accompany drawings. Inthe drawings:

. Figure 1 presents a view in elevation, partially in section, of a spray gun embodying this invention, with the mechanism in the position corresponding to Vthe inactive condition.

Figure 2 presents a view of the same device shown in Figure l, with the mechanism at the extreme end of the spraying operation. l Figure 3 presents a modiied form of this invention which utilizes a different ysystem for the application of heat to the sprayed material. t

Figure 4 presents a section showing the details of the heated nozzle and outlet valve utilized in 'the modification shown on Figures 1 and 2. A

Figure 5 presents a section taken on a plane 5--5 of Figure 2.

Figure 6 is a section taken on a plane 6 6 of Figure 3.

Figure 7 is a section taken on the plane 7 7 of Figure 4.

Figure 8 presents a form of Anozzle which may be utilized with the present invention.

Referring to Figures l, 2, 4, 5, 6, and 7, a spray gun having a body 10 is provided with a main driving cylinder 11 with the end-Wall 12 separating the driving cylinderl it to project into the spray chamber 13 creates spraying pressure therein.

The body of the spray gun is provided with a handle 21 and a trigger 22. The trigger is pivotally mounted on the pin 23, and a clockwise movement of the trigger about the pin induces'movement to the left of the control valve 24. An air conduit 25V is machined in the handle 21, and is provided with a suitable connection fitting 26 as shown. The conduit 2S communicates with the cylinder 11, and the depression of the trigger positions the cut-away portion 27 of the valve 24 to permit flow of air into the cylinder. A spring 28 operates against the handle structure to bias the valve member 24 to the right to the closed position; and in this position the cut-away 29 provides an exhaust passage for the escape of air from the cylinder through the upper portion of the conduit 25, the chamber containing the spring 28, and outwardly through the exhaust passage 30.

On the return of the piston rod from the position shown in Figure 2 to that shown in Figure 1, a new supply of spray material is taken in an inlet fitting 31 to which is connected a suitable hose (not shown) communicating with a supply of liquid under appropriate pressure. The ball valve 32 restricts the direction of flow through the fitting 3l to prevent outflow from the chamber 13.

The application of heat to the spray material may be accomplished either through the system illustrated in Figure 3 or that illustrated in Figure 4. The unit shown in Figures l and 2 is With the mechanism shown in Figure 4, which includes an electric heating element 33 wound around a portion of a nozzle unit 34 of thermally conductive material. The heating element 33 is preferably separated from the surrounding structure by the transverse insulating discs 35 and 36, and the assembly of discs, coil, and nozzle unit is held in position by the retaining -cap 37. A hole 38 is provided in the housing 10 to accommodate the leads (not shown) which supply the electrical energy to the heating element 33.V The spray material is heated as it passes through the conduit portion 39 of the nozzle 34, and the exchange of heat from the nozzle to the uid may be facilitated through the use of tins 40 which are parallel to the axis of the conduit 39 and extend radially inward to increase the total amount of surface to which the sprayed material is exposed. Preferably, a thermocouple unit (not shown) is incorporated in the heating element 33 for the control 'of the temperature, since the flow of material at ahigh velocity will rapidly withdraw the heat from the nozzle unit. Continued application of su-flicient electricity to maintain the temperature will result in an excessive heat after the ow of paint material has ceased, unless the current is reduced in response thereto.

Referring to Figure 3, a spraying unit is illustrated which has a body 41 provided with a handle 42, a driving cylinder 43, a spraying chamber 44, and an inlet tting 45. This fitting is part of a conduit communicating with the supply system. An outer cylindrical Wall 46 is formed around the structure establishing the chamber 44, which provides a jacket 47 within which heated liquid may be circulated to maintain an elevated temperature within the chamber 44. Inlet and outlet connections 48 and 49, respectively, communicate with the jacket, and are formed to receive conventional hose fittings (not shown). The structure ofthe driving cylinder, the piston, and the asso- .ciated members shown in Figure 3 are similar to that illustrated in Figures 1 and 2.

The elevation of the temperature Within the chamber 44 through circulating heated liquid in the jacket 47 renders it advisable to provide the outlet valve construction which is positioned immediately adjacent the nozzle. This same valve system may also be utilized in conjunction with the nozzle-heating system provided in the devices illustrated in Figures 1, 2, and 4 for added convenience. Since the entire spray chamber 13 vis not subjected to elevated temperature, the problem of preventing premature outow of fluid under the vapor pressure of vthe solvent does not occur to as great an extent in the nozzleheater modification. However, since it is advisable to supply paint to the spray chamber under suicient pressure to assure rapid filling of the chamber, it follows that the outlet through the nozzle should be blocked so that such pressure does not cause the paint material to ow prior to the operation of the piston. A valve member 50 (refer to Figure 4) is slideably mounted in the hous ing 10, and is disposed to block the conduit 51 leading from the chamber 13 (or chamber 44) outwardly through the nozzle. A spring 52 biases the valve member 50 to the closed position, and a piston 53 is acted upon by air pressure admitted through the conduit S4 within the cylinder 55 to withdraw the valve member 50 from obstructing position. The conduit 54 is preferably connected so that it receives pressure at approximately the same time as does the driving cylinder, resulting in the opening of the conduit 51 during periods in which pressure is maintained in the spray chamber 44. The cap 56 maintains the valve components in assembled relationship, and the spring 52 returns the 'valve to closed position on the release of the pressure from the driving cylinder (and on the consequent release of spraying pressure from within the spraying chamber 44).V It may be noted that a high-pass pressure-responsive valve may be substituted for the valve structure just described, with a valve adjusted to retain suicient pressure within the chamber 44 to maintain the Vsolvents ofthe spray material in the liquid condition at the temperatures used. excess of such pressures generated by the action of the piston rod will open the valve and permit ow through the nozzle.

Referring to Figure 8, a nozzleunit is illustrated which may be used in conjunction with either of the illustrated modifications, with appropriate changesbeing made `,for the mounting structure. The body portion 57 contains a bore 58 providing a conduit for the ow'of spray material. A pair of opposite outlet channels 59 and 60 are preferably formed with their axes intersecting the axis 61 of the bore 58. This configuration will result in the creation of a fan-type spray due to the interaction of ,the streams owing from the outlets 59 and 60. it may be noted ,that a time factor is involved between a) the moment of emergence of the spray material from the orifices, and b) the breakup of the liquid into a line mist as a result of the vaporization of the particular solvents. The axes of the openings 59 and 60 may be directed to intersect at a point which is reached by the liquid prior to substantial volatilization, resulting in the interactionof two relatively solid streams. The axes may also be voriented so Vthat `intersection ofA the two streams occurs at-a point after a selected degree of volatilization has been completed. The particular embodiments of this invention which have been illustrated and described herein are for illustrative purposes only and are not to be considered as a limination upon the scope of the appended claims. In these claims, it is my intent to claim the entire invention disclosed herein except as I am limited by the prior art.

I claim: l 1. A spraying device, comprising: a body having'a driving cylinder and means forming walls deiinm' g the oppositev ends of said driving cylinder,one of said walls having an opening therein, said body also having a chamber communicating with said opening and coaxially `disposed with said cylinder opening; piston means disposed in said driving cylinder for axial movement therein and including piston rod means slideably received in said opening; rst biasing means, said rst biasing meansfincluding a coil spring acting between said piston means-and said body urging said vpiston means in a 'direction towithdraw said rod means from said chamber, saidfrodmeans having a length selected to prevent disengagementfrom Said opening-within the normal stroke of {said `piston vto project said rod means into said chamber, said second biasing means including air pressure supply means having intake and outlet conduits `communicating with said driving cylinder, and valve means for said conduits; spray nozzle means having a conduit communicating with said chamber; liquid-supply means communicating with said chamber and including a one-way valve preventing backtdow from said chamber via said liquid-supply means; heating means including a jacket in heat-conducting relationship with said chamber and provided with inlet and outlet conduits; and outlet valve means controlling the llow of liquid between said chamber and said nozzle means, said outlet valve means including a piston actuator acting in a cylinder and operative to open said outlet valve means in response to pressure in said driving cylinder, and also including a spring in said cylinder operative to bias said valve to closed position.

2. A spraying device, comprising: a body having a driving cylinder and means forming walls defining the opposite ends of said driving cylinder, one of said walls having an opening therein, said body also having a chamber communicating with said opening and coaxially disposed with said cylinder opening; piston means disposed in said driving cylinder for axial movement therein and including piston rod means slideably received in said opening; iirst biasing means, said first biasing means urging said piston means in a direction to withdraw said rod means from said chamber, said rod means having a length selected to prevent disengagement from said opening within the normal stroke of said piston means; second biasing means, said second biasing means being operative to urge said piston means in the direction to project said rod means into said chamber, and including air pressure supply means having intake and outlet conduits communicating with said driving cylinder, and valve means for said conduits; spray nozzle means having a conduit communicating with said chamber; liquid-supply means communicating with said chamber and including a one-way valve preventing backflow from said chamber via said liquidsupply means; heating means including a jacket in heatconducting relationship with said chamber and provided with inlet and outlet conduits; and outlet valve means controlling the ow of liquid between said chamber and said nozzle means, said outlet valve means being biased to closed position and including a piston actuator acting in a cylinder and operative to open said outlet valve means in response to pressure in said driving cylinder.

3. In combination with a liquid-supply system providing a spray liquid having a volatile component, said system maintaining said liquid at a pressure and temperature corresponding to that of the liquid condition of said component, a spraying device, comprising: a body having a driving cylinder and means forming walls deining the opposite ends of said driving cylinder, one of said walls having an opening therein, said body also having a chamber communicating with said opening and coaxially disposed with said cylinder opening; piston means disposed in said driving cylinder for axial movement therein and including piston rod means slideably received in said opening; rst biasing means, said first biasing means including a coil spring acting between said piston means and said body urging said piston means in a direction to Withdraw said rod means from said chamber, said rod means having a length selected to prevent disengagement from said opening within the normal stroke of said piston means; second biasing means being operative to urge said piston means in the direction to-project said rod means into said chamber and including air pressure supply means having intake and outlet conduits communicating with said driving cylinder, and valve means for said conduits; spray nozzle means having a conduit communicating with said chamber; conduit means communicating between said liquid supply system and with said chamber and including a one-way valve preventing backiiow from said chamber; heating means including a jacket in heatconducting relationship with said chamber and provided with inlet and outlet conduits; and outlet valve means controlling the ilow of liquid between said chamber and said nozzle means, said outlet valve means operating to prevent such ow when liquid pressure in said chamber is below a selected level.

4. In combination with a liquid-supply system providing a spray liquid having a Volatile component, said system maintaining said liquid at a pressure and temperature corresponding to that of the liquid condi-tion of said component, a spraying device, comprising: a body having a driving cylinder and means forming walls defining the opposite ends of said driving cylinder, one of said walls having an opening therein, said body also having a chamber communicating with said opening; piston means disposed in said driving cylinder for axial movement therein and including piston rod-means slideably received in said opening; rst biasing means, said rst biasing means including a coil spring acting between said piston means and said body urging said piston means in a direction to withdraw said rod means from said chamber, said rod means having a length selected to prevent disengagement from said opening within the normal stroke of said piston means; second biasing means, said second biasing means being operative to urge said piston means in the direction to project said rod means into said chamber, and including air pressure supply means having intake and outlet conduits communicating with said driving cylinder, and valve means for said conduits; spray nozzle means having a conduit communicating with said chamber; conduit means communicating between said liquid supply system and with said chamber and including a oneway valve preventing backflow from said chamber; heating means in heat-conducting relationship with the contents of said chamber; and outlet valve means controlling the ow of liquid between said chamber and said nozzle means, said outlet valve means operating to prevent such flow when liquid pressure in said chamber is below a selected level.

5. In combination with a liquid-supply system providing a spray liquid having a volatile component, said system maintaining said liquid at a pressure and temperature corresponding to that of the liquid condition of said comportent, a spraying device, comprising: a body having a driving cylinder and means forming Walls defining the opposite ends of said driving cylinder, one of said walls having an opening therein, said body also having a charnber provided with an opening; piston means disposed in said driving cylinder for axial movement therein and including piston rod means slideably received in said opening; rst biasing means, said rst biasing means urging said piston means in a direction to withdraw said rod means from said chamber, said rod means having a length selected to prevent disengagement from said openings within the normal stroke of said piston means; second biasing means, said second biasing means being operative to urge said piston means in the direction to project said rod means into said chamber, and including air pressure supply means having intake and outlet conduits communicating with said driving cylinder, and valve means for said conduits; spray nozzle means having a conduit communicating with said chamber; conduit means communicating between said liquid supply system and with said chamber and including a one-way valve preventing backow from said chamber; heating means including a jacket in heat-conducting relationship with said chamber and provided with inlet and outlet conduits; and outlet valve means controlling the Iflow of liquid between said chamber and said nozzle means, said outlet Vvalve means operating to prevent such ilow when liquid pressure in said chamber is below a selected level.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Haslett Sept. 10, 1901 Lyon Jan. 31, 1911 Schenck June 8, 1926 Allen Ian. 4, 1927 Ofeldt Sept. 5 1933 Wentzel Oct. 8, 1935 vraie c:

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