US2366150A - Spraying apparatus - Google Patents

Description

De.26, 1944. QBYOUNT 2,366,150

SPRAYING APPARATUS Filed MarchBO; 1942 2 Sheets-Sheet 1 INVENTOR. @aww 4 Dec. ze, 1944.

Filed March 30, 1942 c. B. YoUNT 2,366,150

SPRAYING APPARATUS 2 Sheets-Sheet 2 Patented Dec. 26, 1.944

UNITED STATES .PATENT OFFICE;

SPRAYING APPARATUS Clarence B. Yount, Dayton, Ohio, asslgnor to The Sherwin-Williams Company, Cleveland, Ohio,

a corporation of Ohio Application March 30, 1942, Serial No. 436,800 (c1. :a1- 45) Claims. This invention relates to a device for applying liquid spray materials and more particularly to vwhile cold.

An object'of this invention is to provide a device for applying coating materials while hot.

Another objeei-l of this invention is to provide a spray gun wherein the coating material at the spray gun is maintained within apredeterf mined temperature range so as to have available for use in spraying` a liquid or semi-liquid at a predetermined temperature.

Another object of this invention is to provide a manual control for opening a by-pass permit- Aof Figure 3 with parts shown in elevation.

ting some of the coating material to be returnedl tothe source of supply when the spray gun is not in use, to thereby maintain a, substantially uniform temperature of the spray material at the Spray gun. i

Another object of this invention is to provide a thermostatically controlled by-pass circuit or passage that by-passes the uid when the tem'- perature drops below a predeterminedvtemperature range, vso as to maintain circulation of hot fluid.

Another object of this invention is to provide a release circuit responsive to manipulation of a the spray gun for releasing the now of the coating material during certain periods of time.

Another object of this invention is to provide a dual control for by-passing the hot uid supplied to the spray gun, which dual control is responsive to movementsof the trigger of the spray gun and to temperature variations.

Another object of this invention is to provide a by-pass circuit for a spray gun wherein the hot fluid supplied to the spray gun is permitted to be by-passed under predetermined conditions in response to the manipulation of the spray gun.

Another object of this invention is to provide a spraying device for spraying hot materials, which spraying device maintains a predetermined temperature at the spray gun, is cheap, economical to produce andai; the same time dependable and eillcient.

Other objects and advantages reside in the construction of parts, the combination thereof and the mode of operation, as will become more apparent from the following description.

In the drawings,

Figure 1 is a schematic elevational view of a system for applying hot coating materials and 'other hot materials by means of a spray gun,

with parts shown in section. Y

Figure 2 is a cross sectional view of the thermostatic valve, taken substantially on the line 2-2 Figure 3 is a side elevational view of a spray gun with manually controlled by-pass valve shown vin section.

Numerous attempts have been made vtospray coating' materials, sometimes referred to as plastic coating materials, while hot, so as to'econof mize upon the use of solvents. However, in the past, diiliculties have been encountered in 4so spraying hot coating materials, in that it is very diiiicult to maintain a uniform viscosity of the coating material entering the spray gun. The

temperature may remain substantially constant when the spray gun discharges a predetermined amount of coating material continuously; but as soon as the spraying operation ceases, the coating material between the source where the heat is applied and the spray gun may cool and thicken to such an extent that it is practically impossible 1 to reestablish the flow of coating material through the spray gun.

In the embodiment disclosed herein a dual control for by-passing the hot fluid under predetermined conditions has been provided. This dual control may include a thermostatically controlled valve for by-passing the fluid when the temperature drops below a predetermined value, at which time the fluid is by-passed, so as to supply hot iiuid to the spray gun to maintain the proper fluid temperature. The other control may be responsive to operations of the valve of the spray gun to permit the by-passage of fluid only when the spray gun valve is inoperative.` These two controls may be used simultaneously, so that the thermostatic valve can only by-pass fluid when the spray gun valve is closed. Furthermore, the thermostatic valve prevents the bypasage of iiuid'by the valve mechanism responding to the closing of the main valve in theV spray gun until the temperature of the uid in the vicinity of the spray gun drops below a predetermined value. Instead of using both of these control means, only one may be used. For example, the thermostatic valve may be used to release the uid when the temperature drops below a predetermined value, without the use of the second-control mechanism responsive to movements of the trigger. When the thermostatic valve is used without thesecond control mechanism, the iiuid may continue to by-pass for some time after starting the operation of the spray gun. It may take some time'for suillcient fluid to pass the thermostatic valve to close it.

On the other hand, if only the by-pass responsive to the operation of the spray gun is used, without, the use of the thermostatic valve, fluid will be by-passed irrespective of the temperature whenever the spray gun valve is closed. This means that in the event the operator interrupts the operation of the spray gun temporarily to change articles, change position of the articles to be sprayed, or for any other reason closes the spray gun temporarily, fluid will begin to be bypassed immediately upon the closing of the spray gun valve. This means that fluid will continue to by-pas whenever the spray gun valve is closed, irrespective of whether or not the temperature of the fluid justifies some of the uid being bypassed, so as to maintain the proper temperature at the spray gun.

Referring to the drawings, this system for sup- 1 plying hot fluid, such as coating materials and other sprayable liquids or semi-liquids, to spray guns, includes a reservoir I0, having a supply of dissolved coating material. This coating material is pumped from the reservoir I0 by means of an electric pump I2 having an outlet I4 connected to a release valve I8, which maintains a constant pressure on the iuid in the outlet pipe or conduit I4. 'I'he fluid flows through the conduit I4, through one or more heating coils I8 mounted in suitable tanks 20. The opposite ter- ;minals of the heating coils I8 are connected by iiexble hose 22 to a spray gun mechanism 24. This spray gun mechanism 24 will be described more fully later.

Hot water,` or any other suitable heat transfer medium, is supplied to the tanks 20 from a suitable boiler 30, where the water or other heat transfer medium is heated and maintained at a predetermined temperature in any suitable manner. The heat transfer medium ows through .conduits 32 into the tanks 2D.. Suitable valves 34 are vmounted in the conduits so as to shut off the heat transfer medium from any selected tank 20. In the event a plurality of tanks are connected in the system andy only one or more of the tanks are needed, the fluid medium is shut oi from the remaining tanks. Return conduits 38 provide a return passage from the tanks 20 to the heater or boiler 30, Suitable valves 38 are used to close the return conduits -whenever the tanks are not in use.

The fluid to be sprayed is forced by the pump I2 through the heating coils I8, where the fluid to be sprayed is heated to the desired temperature. For example, if the temperature of the spray fluid should be within a temperature range of from 150 to 170 F., the heat transfer medium in the tanks 2IJ'is lpreferably maintained at a temperature of approximately 170. As the spray fluid flows through the coils I8, it is heated to the desired temperature. The coils I8 are selected to have sufllcient capacity to transfer the necessary heat from the fluid transfer medium to the spray fluid to maintain the desired temperature of the spray fluid during the maximum flow of spray fluid from the spray gun. In the event the system is used without operating all of the spray guns, valves 40 and 42, connecting the spray guns that are not in use, are preferably closed. A

The number of spray guns inthe system is a matter of choice. Instead of operating one spray gun from each heating coil I8, the heating coils may be selected so as to have sulcient capacity to take care of two or more spray guns. This is a matter of choice, depending entirely upon the system used and the particular requirements thereof.

In spraying articles lt is not feasible at all times f become too thick for operation through the spray gun. That being the case, it is necessary to provide means for maintaining the temperature of the spray iluid throughout the length of the hose and in the spray gun.

'I'his has been accomplishedv by providing a bypass spray fluid circuit or a return passage from the spray gun to the reservoir I0. The by-pass circuit is closely associated with the spray gun 24. Thatbeing the case, a brief description of the s-pray gun will now be made.

The spray gun 24 includes a main body por. tion 50 having a handle-like portion 52 that forms' a passage for the air intake. The air supply and the hose for supplying air to the spray gun has not been shown, as this is well known to those skilled in the art. Suiiice. to say, that the hose is connected to the intake terminal 54. The forward end of the main body portion `50 of the spray gun includes a nozzle B0. The amount of iluid supplied to the nozzle is controlled by a valve terminating in a valve stem 62 adjusted by a trigger 64 pivoted at 66 to the main body portion 5I). The trigger 64 is provided with a slot 64a in which is positioned a pin 62a rigidly secured to the valve stem 62, so that the trigger 64 and the valve stem 32 travel together. As the trigger 64 is pulled, it opens the valve 62 to the nozzle 60 and it opens the air valve 68 positioned in the upper portion of the handle-like portion 52. `'I'he valve stem 82 projects into a cylindrical cavity 52a in the upper end of the handle-like portion 50. The valve stem 62 has xedly secured thereto a collar B2b mounted within the cavity 52a. A helical coil spring 62e is mounted in compression between the collar 62h in the end wall of the cavity 52e. Whenever the operator releases the trigger 64, the spring 62e actuates the valve stem 62 to the left, as viewed in Figure 3, and rotates the trigger 64 in a clockwise direction, as viewed in this figure. A suitable adjustment for the trigger pull includes a knurled screw head 10. The

portion of the spray gun device that has been disclosed thus far is conventional and any suitable spray gun mechanism may be used.

A tubular projection or extension connects the chamber of the spray gun with a suitable' fluid compartment, 82, that is preferably cylindrical and housing a suitable thermostatic valve the hose 22 through a conduit B6 `through the reservo r compartment 82, through the extension 80 to t e spray gun valve. As it passes around the thermostatic valve 84, this valve expands or contracts in response to increase or decrease of the temperature of the fluid. If the temperature increases, it expands, so as to cause the needle valve 90 to be seated in and seal a passage 92 connected to a return passage 94, having its lower end connected to a hose 96 connected to a return pipe 90, permitting the spray fluid to be returned to the reservoir whenever itis bypassed. In order to permit expansion of the Sylphon or bellows after the seating of the needle valve, the Sylphon is adjustably mounted on a resilient support. i

The lower end of the bellows or Sylphon member 84 is attached to a screw threaded stud |00 merging into a shank |02 provided with a knurled head |04. The screw threaded stud |00 threadedly engages a bridging member |06, resiliently mounted upon a pair of springsl |00 surrounding suitable bolts or guide members ||0. This provides a yieldable support for the bellows or Sylphon 84, so that in the event this bellows or Sylphon expands after the .needle valve 90 engages its seat, the lower end of the Sylphon, as viewed in Figure 2, will cause the bridging member |06 to move downwardly by compressing the springs |08. By adjusting the knurled head |04, the needle valve 90 may be adjusted to open the by-pass passage at any predetermined temperature, as for example, a temperature of 160.

Whenever the temperature of the spray 4fluid d-rops below this predetermined temperature, the

needle valve will open so as to cause the fluid to return to the reservoir I0, thereby supplying hot spray uid from theheating coils I8 to raise the temperature of the spray fluid in the spray gun.

By this arrangement, it can be re-adily seen that the temperature of the spray iluid in the spray gun may be kept at a temperature' such that it 4has the proper viscosity for spraying.

In the event the needle valve 90 is in open position and the spray gun is at that time put into operation, it is very desirable that the return passage be closed instantaneously, so as to supply the entire pressure of the fluid tothe spray gun without the use of the by-pass or bleeder passage. `It will take a short period of time to heat the Sylphon suiiiciently to close the needle valve after the valve in the spray gun is open. In order to close the by-pass passage or the bleeder circuit, a manually controlled valve is preferably inserted into the bleeder circuit, which closes the bleeder circuit immediately upon the opening of the .spray gun valve. words, the valve in the bleeder circuit may be responsive to movements of the trigger 64.

As may best be seen in Figure 3, avalve |20, providedA with a frusto-conical valve head, is spring urged to the.right by a compression spring |22, urging the stem |24 Aof the valve member |20 against the trigger 64. The compression spring |22 is weaker than the compression spring 62e, so that as the operator releases the trigger 64, the compression spring 62a actuates the trigger 64 in a clockwise direction, as viewed in Figure 3. 'Ihe trigger 64, when closing the valve 62, opens the valve |20. Immediately upon the trigger 64 being manually operated in a counterclockwise direction, as viewed in Figure 3, to open the main valve 62 in the spray gun, the valve |20 is actuated into closed position, so as In other to close the `by-pass passage or bleeder circuit. By this arrangement, it can readily be seen that in spite of the fact that'the needle valve 00 is held in open position, the by-pass passage or bleeder circuit is closed whenever the main valve is open, so as to supply the entire pressure of the spray uid to the nozzle of the spray gun.

From the foregoing description it may readily Ibe seen that a dual control for the by-pass passage or bleeder circuit has been provided, wherein one valve is manually controlled and the other is thermostatically controlled. The manually controlled valve responds to movements of the main valve, so that in this respect it is automatic.

vAlthough the preferred modiiication of the device has been described, it will ,be understood that within the purview of this invention various changes may be made in the form, detalls, proportion and arrangement of parts, the combination thereof and mode of operation, which gendual controlby-pass circuit means for returningy fluid from the spray gun to the source of supply so as to maintain a predetermined temperature of the fluid supplied to the spray gun, said control means including a by-pass valve mechanism having a valve, means for opening said last mentioned valve in response to the closing of the valve in the spray gun, and a thermostatically controlled valve for preventing the by-passing of fluid whenever the temperature of the iiuid in the vicinity of the spray gun is suiilciently high to maintain the proper viscosity for spraying the iiuid.

2. In a spraying device for spraying fluids while hot, the combination including means i'or supplying hot nuid. a spray-` gun having a main valve, tubular means for interconnecting the spray gun to said first mentioned means, and by-pass circuit means, said by-pass circuit means interconnecting the spray gun to said rst mentioned means, said by-pass circuit means including a by-pass passage, a thermostatically controlled valve opening the by-pass passage in response to a predetermined drop in the temperature of the fluid in the vicinity of the spray gun, and closing the `bypass passage in response to a predeter` mined temperature of the fluid the spray gun.

3. In a spraying device for spraying fluids while hot, the combination including means for .supplying hot uid, a spray gun having a, main valve, tubular means for interconnectingthe spraygun in the vicinity of -to said first mentioned means, and by-pass cirtubular means for interconnecting the spray gun to said .flrstmentioned means, and by-pass circuit means for providing a return passage from the spray gun to said first mentioned means, said' bypass circuit means including a thermostatic valve responding to changes in the temperature oi the iiuid supplied to the spray gun, said thermostatic valve closing when the temperature is above a predetermined value and opening when the temperature drops below said predetermined value, and a manually controlled valve for opening and closing the by-pass circuit at the will o! the operator.

5. In a spraying device for spraying fluids while hot, the combination including means for supplying hot fluid, a spray gun having a main valve, tubular means for interconnecting the spray gun to said first mentioned meansL and by-pass circuit means, said 'by-pass circuit means interconnecting the spray gun to saidi'lrst mentioned means. said by-pass circuit means including a by-pass passage. a thermostatically controlled needle valve

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