US2517049A - Apparatus for heating and spraying lacquer or the like - Google Patents

Description

Aug. 1, A, L STEVENS APPARATUS FOR HEATING AND SPRAYING LACQUER OR THE LIKE Filed March 10, 1948 i A A 1/0 you; 54 LAMP 35 I INVENTOR r/4rt/zur 1.. 5561/6/75 a W M! ATTORNEYJ forgetting the apparatus into optimum Patented Aug. 1, 1950 APPARATUS FOR HEATING AND SPRAYING LACQUER OR THE Arthur L. Stevens, Buffalo, N. Y.

Application March 10, 1948, Serial No. 14,116

8 Claims.

This invention relates to apparatus for heating and spraying coating materials such as lacquer, varnish, aircraft dopes, paints, or other chemical compositions wherever it is advantageous to spray the coating materials while in heated condition. For example, it is known that nitrocellulose type lacquers may be more efllciently and perfectly applied in furniture finishing operations and the like if the lacquer is heated before it goes to the spray gun, and that such heating temporarily lowers the viscosity of the material and thereby reduces the chemical thinner content requirement with a resulting saving in cost. However, in the handling of lacquers or like compositions comprising volatile solvents and thinners, it is of prime importance to avoid heating of the lacquer supply except as it is about to be sprayed, and to avoid dangerous overheating and/or pressurizing of the lacquer handling apparatus. It is also of prime importance in such work to avoid unnecessary heating of the entire lacquer supply prior to its being drawn into the active spray supply portion of the system; and in any case to arrange to heat only a small quantity of lacquer at a time, so that the required starting-up? period is minimized.

Therefore, it is an object of the present invention to provide an improved apparatus for drawing upon a supply of cold lacquer or the like for the purpose of heating the lacquer and delivering it to a spray gun; the apparatus including improved temperature and pressure regulating means and lacquer over-supply return means from the gun arranged so as to prevent return of hot lacquer to the cold lacquer supply tank.

Another object of the invention is to provide an improved heating and pressuring apparatus 2 temperature, irrespective of the rate of use of the material.

Another object of the invention is to provide an apparatus wherein the features and advantages aforesaid are attained in an inexpensively fabricated unit of compact and readily portable form.

Another object of the invention is to provide an apparatus as aforesaid comprising a novel combination of structurally simple and rugged operative and control elements.

Other objects and advantages of the invention will appear from the specification hereinafter.

In the drawing:

Fig. 1 is a diagrammatic illustration of the mechanical features of an apparatus of the invention; and

Fig. 2 is a diagram of the electrical mechanism thereof.

The invention is illustrated in the drawing as being employed for the purpose of drawing a supply of lacquer or the like from a tank or drum I0, and heating and feeding the lacquer to a spray gun as indicated at I2. The apparatus of the invention includes a positive displacement type fluid pump which is indicated at I4, and which is arranged to be driven by a compressed air motor I5. The intake port of the pump I4 is coupled to a conduit Iii-which leads to the lacquer supply tank III, and a check valve I8 is preferably disposed in the line of the con-.

The discharge port of the pump II is connected to a conduit I9 which is coiled as indicated at 20 and thence leads into communication with the inlet port of the spray gun as indicated at 22. A thermostat switch as indicated at 24 is disposed of the type aforesaid, which is characterized by brought rapidly up from cold condition to the desired temperature for spraying; thereby greatly reducing the starting.-up-time required sprayingcondition- Another object of the invention isto provide an improved coating material heating and sprayin apparatus whereinthe heated material is furnished to the spray headportion of the apparatus at substantiallyficonstant pressure and in the line of the conduit 20-22, for purposes which will be explained hereinafter.

The fluid over-supply return port of the spray gun I2 is indicatedat 26, and is connected through a conduit 28 to the high pressure inlet of a relief valve 30. The valve 39 is of the,diaphragm type including manually adjustable spring means biasing the diaphragm, and the low pressure port of thevalve 39 connects to a returnfcon'duit 32 I which leadslback into the pumpintak'e conduit atfa position between the pump and the check valve I8. Apr'essure'responsive electrical switch 34 is arranged with its pressure inlet turnconduit 32.

conduit "coupled into the "re- Thecoiled portion 2 of the rn Y i vhei conduitis nested within" a tank 35 con taining water and a heating element which is shown to be in the form of an immersion electrical resistance heater element designated 38 is also disposed within the tank to heat the water therein.

As shown in Fig. 2, the thermostat switch 24 and the pressure switch 34 are connected in series with the heater element 38 by means of conductors 40--4I which in turn connect into any suitable power supply source, and a signal lamp is shunted across the conductors to indicate whether or not the heater is energized. The entire mechanical and electrical organization of the apparatus of the invention is preferably mounted upon a single baseboard, with the pump and coil and conduit parts relatively arranged as compactly as possible so that the entire fluid circulating system defined by the conduits i9- 2ll28,32 is of minimized volumetric capacity. Thus, preparatory to a spraying operation a spray gun will be attached to the conduit connections 22-26 and a drum of lacquer or the like will be set in position relative to the intake conduit l6, as illustrated in Fig. l of the drawing. The control device governing operation of the motor 15 will then be set to cause the motor to operate, thereby drawing cold lacquer from the drama l through the check valve and thence into the coil 20 and filling the conduit system i9--20--28-32 with lacquer; the closed spray gun valve being operable at this time to shunt the lacquer from the conduit head 22 to the conduit head 26.

The machine attendant will simultaneously operate a switch or the like to close the conductors 40--4l with their power source, and inasmuch as the lacquer in the region of the thermostat switch 24 is cold this switch will be closed. As soon as the pressure within the circulating conduit system equals the setting of the pressure responsive switch 34, the latter will be pressureoperated to complete the closing of the electrical circuit to the heater 38 and the signal lamp. Thus, the relatively small quantity of lacquer within the closed conduit system will be thereby circulated over and over again and through the coil 20, whereby heat from the element 38 will be transferred through the tank of water and into the circulating lacquer as it moves through the coil. Consequently, in a relatively short time the lacquer within the closed circulating system will be brought up to the desired spraying temperature, whereupon the operator may commence the spraying operation after only a minimum "starting-up" loss of time.

Whenever the spray gun is operated the heated lacquer passes directly from the conduit coil 20 through the gun and onto the work, and whenever the gun trigger pressure is relaxed the heated lacquer is shunted into the return conduit 28. The valve 30 operates to maintain the pressure at the spray gun approximately constant for optimum performance of the gun, but inasmuch as the demand for lacquer rate of discharge from the gun fluctuates widely in accord with the spraying operation requirements, the output load on the pump l4 will similarly vary. .Since the pump I4 is preferably of the positive displacement type, for efiicient operation under high pressure conditions, it is therefore preferred to employ a compressed air type motor as indicated at I for driving the pump. By supplying air to the motor l5 at constant pressure, the motorpump unit will operate at correspondingly varying speeds so as to deliver the required fluctuating volumes of lacquer under a constant pressure. The valve 30 alone would be incapable of furnishing the required volume-to-pressure control under such widely fluctuating output demand conditions, and thus it is the combination and whenever the pump I4 is stopped, or in event of a mechanical failure resulting in loss of operating pressure within the conduit system, the pressure responsive switch 34 will operate automatically to de-energize the heater. A small "pin hole is preferably drilled through the disc of the check valve l8 as indicated at 45, so as to permit a gradual bleeding oif of the operative pressure within the conduit system whenever the apparatus is shut down. This insures opening of the pressure switch 34 and de-energization of the heating element when the apparatus is inactive, and therefore eliminates the possibility of accidental and dangerous overheating incidental to shut downs. Also, the opening through the check valve operates at all times in the manner of a safety outlet, permitting escape of excessive pressures from the system.

Thus, it will be appreciated that the apparatus of the invention comprises a mechanically and electrically simple operative and control organization which maintains the spraying lacquer at constant temperature and pressure;- and which is characterized particularly in that only a small quantity of lacquer is required to fill the starting-up circulating and heating system of the apparatus, whereby it may be brought into full operation within a minimum of time after a cold" start. It will also be appreciated that by reason of the arrangement of the over supply return conduit system, return of "hot lacquer to the cold" lacquer supply tank is avoided. This avoids heating of large quantities of lacquers and minimizes evaporation losses of the volatile solvents in the material being handled.

It will also be appreciated that although one specific form of the apparatus of the invention has been shown and described in detail herein, it will be apparent to those skilled in the art that the invention is not so limited but that various changes may be made therein without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. In a liquid heating and spray system, in combination, a spray gun, a liquid supply source under atmospheric pressure, a continuously operated positive displacement pump, liquid intake conduit means connecting said source to the intake of said pump, a discharge conduit connected to the discharge port of said pump and to the intake connection of said spray gun, a heater arranged in heat exchange relation with said discharge conduit, a return conduit connected to the return connection of said spray gun and to the intake port of said pump, a pressure regulator in said return conduit to maintain a constant pressure at said spray gun, means responsive to the temperature of the fluid within said discharge conduit for regulating operation of said heater, and a check valve in said intake conduit.

2. In a liquid heating and spray system, in combination, a spray gun, a liquid supply source under atmospheric pressure, a continuously operated positive displacement pump, liquid intake conduit means connecting said source to the intake of said pump, a discharge conduit connected to the discharge port of said pump and to the intake connection of said spray gun and passin through a water bath, an electric heater rranged in heat exchange relation with said water bath, a return conduit connected to the return connection of said spray gun and to the intake port of said pump, a pressure regulator in said return conduit to maintain a constant pressure at said spray gun, thermostat means responsive to the temperature of the fluid within said discharge conduit for regulating operation of said heater. and a check valve in said intake con-,

duit.

3. In a liquid heating and spray system, a spray gun, a continuously operated pump, a discharge conduit connected to the discharge port of said pump and to the intake connection or said spray gun, a heater arranged in heat exchange relation with said discharge conduit, a return conduit connected to the return connection of said spray gun and to the intake port of said pump, a pressure regulator in said return conduit to maintain a constant pressure at said spray gun, means responsive to the temperature of the fluid within said discharge conduit for regulating operation of said heater, means responsive to loss of pressure in said return conduit to de-energize said heater, and a fresh fluid supply conduit having a check valve therein and connected into the intake port of said pump.

4. In a liquid heating and spray system, a spray gun,acontinuously operated positive displacement pump. a compressed air operated motor drivin said pump, a discharge conduit connected to the discharge port of said pump and to the intake connection of said spray gun, a heater arranged in heat exchange relation with said discharge conduit, a return conduit connected to the return connection or said spray gun and to the intake port of said pump, a pressure regulator in said return conduit to maintain a, constant pressure at said spray gun, means responsive to the temperature of the fluid within said discharge conduit for regulating operation of said heater, means responsive to loss of pressure in said return conduit to de-energize said heater, and a fresh fluid supply conduit having a check valve therein and connected into the intake port of said pump.

5. In a liquid heating and spray system, in combination, a spray gun, a liquid supply source under atmospheric pressure, a continuously operated positive displacement pump, liquid intake conduit means connecting said source to the intake of said pump, a discharge conduit connected to the discharge port oi said pump and to the intake connection of said spray gun and passing through a water bath, a heater arranged in heat exchange relation with said water bath, a return conduit connected to the return connection of said spray gun and to the intake port of said pump, a pressure regulator in said return conduit to maintain a constant pressure at said spray gun, means responsive to the temperature of the fluid within said discharge conduit tor regulating opcheck valve in said charge port of said pump and to the intake connection of said spray gun and passing through a water bath, a, heater arranged in heat exchange relation with said water bath, a return conduit connected to the return connection of said spray gun and to the intake port of said pump, a pressure regulator in said return conduit to maintain a constant pressure at said spray gun, thermostat means responsive to the temperature of the fluid within said discharge conduit for regulating operation of said heater, means responsive to loss of pressure in said return conduit to deenergize said heater, and a fresh fluid supply conduit leading to the intake port of said pump.

7. In a liquid heating and spray system, a spray gun, a continuously operated pump, a discharge conduit connected to the discharge port of said pump and to the intake connection of said spray gun, a, heater arranged in heat exchange relation with said discharge conduit, a return conduit connected to the refurn connection of said spray gun and to the intake port of said pump, a pressure regulator in said return conduit to maintain a constant pressure at said spray gun, means responsive to the temperature of the fluid within said discharge conduit for regulating operation of said heater, means responsive to loss of pressure in said return conduit to de-energize said heater, 8. fresh fluid supply conduit connected into the intake port of said pump. and a check valve having a small bleed of! opening therethrough in the line of said fresh fluid supply conduit.

8. In a liquid heating and spray system, a spray gun, a continuously operated positive displacement pump, a compressed air operated motor driving said pump, a discharge conduit connected to the discharge port of said pump-and to the intake connection of said spray gun, a heater arranged in heat exchange relation with said discharge conduit, a return conduit connected to the return connection of said spray gun and to the intake port of said pump, a pressure regulator in said return conduit to maintain a constant pressure at said spray gun, means responsive to the temperature or the fluid within said discharge conduit for regulating operation of said heater, means responsive to loss of pressure in said return conduit to de-energize saidheater, a fresh fluid supply conduit connected into the intake port of said pump, and an only partially closing check valve in said fresh fluid supply conduit.

ARTHUR L. STEVENS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,266,354 Christenson et a]. Dec. 16, 1941 2,366,150 Yount Dec. 26, 1944 2,378,184 Carlson June 12, 1945

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