US2362634A - Spraying apparatus - Google Patents

Description

NOV. 14, 1944. w, HQUGHTON 2,362,634

SPRAYING APPARATUS Filed Aug. 20, 1942 66 //\/l/EN TU/Fi y 3;,

Patented Nov. 14, 1944 UNITED STATES PATENT OFFICE SPBAYING APPARATUS William M. Heighten, Marblehead, Masa, assignor to United Shoe Machinery Corporation, Fiemington, hi. 1., a corporation of New Jersey Application August, 1942, Serial No. 455 ,4155

4 Claims. (Cl. 299-140) This invention pertains to apparatus for ap plying a coating to articles and more especially to means for spraying shoe parts with coatin material.

The apparatus illustrated herein for sprayins coating material comprises, in part, a conventional spray gun upon the barrel of which is placed a heating coil for heating the coating material as it passes through the spray gun. Under normal conditions the spray gun is used intermittently. That is, between each spraying operation there may be a considerable period of time and consequently it the same amount of heat is supplied to the spray gun when it is idle as is supplied to it when it is in operation to liquefy the coating material during its passage through the spray gun the temperature will build up to such an extent that during thesucceeding spraying operation the coating material may be overheated and thus spoiled, or, the gun may be damaged.

It is an object of the present invention to provide means for maintaining the spraying apparatus at a substantially constant predetermined temperature irrespective of whether it is in operation or is idle.

In the illustrated apparatus, coating material is forced through a heating chamber to a spray nozzle by a fluid under pressure and is heated during its passage through the chamber by heatin means associated with the chamber. A valve is provided for controlling the flow of the coating material and, in accordance with a feature of the invention, the valve is operable to cause the heating means to maintain a substantially ing coil is placed about the barrel of the spray gun to heat the coating material which is forced therethrough, as will appear hereinafter.

In shoe manufacturing, the application of the coating material to shoe parts is not a continuous operation. That is, after each part is coated there is an appreciable interval before the next part is coated. andbetween one rack of shoe parts and the next there may be a considerable period of time. During the intervals when the spray gun is not being used and when no coating material is passing through it, the temperature builds up and, consequently, when the next coating operation is performed the coating material may be overheated to such an extent as to spoil its properties as a covering agent. Furthermore, there is also the danger of overheating the spray gun itself. To prevent this, the motivating means for driving the coating material through the spray gun and a pressure-operated switch controlling the electric circuit for heating the spray gun are interconnected in a manner to maintain 1 the spray gun at a substantially uniform temuniform temperature in the chamber irrespective of whether the valve is open or closed.

The details of the apparatus will now be de scribed with reference to the accompanying drawing, in which Fig. 1 shows the spray n. in section;

Fig. 2 shows an end elevation of the spray gun as seen from the right side 0! Fig. 1;

Fig. 3 shows a diagrammatic view of the spray gun, the air conduits connected thereto, and the heating circuit; and 1 Fig. 4 shows the details of the pressure-operated switch.

Most coating materials are quite viscous at room temperature and, accordingly, when applied to articles by a spray gun, means must be provided for heating the material before it reaches the spray gun or during its passage through the spray gun to make it liquidenoush perature regardless of whether the coating material is or is not passing through it.

Referring to Fig. l, the spray gun G is shown as comprising a barrel ill having a nozzle l2 at one end, interior passages It, It for delivering air and It for delivering coating material to the nozzle, and a needle valve It in the passage It for controlling the passage of the coating material through the nozzle. The needle valve ll passes through a packing gland 20 at the rear of the barrel l0 and has fixed thereto at its end a piston 22. A cylinder 24 closed at one end is threaded on the rear end of the barrel and provides a chamber 26 for the piston 22. A compression spring 28 is interposed between thepiston 22 and the closed end of the cylinder 24 to urge the needle valv toward a position to close the fluid passage it near the nozzle l2. A passage 2. in the body of the spray gun permits access of air under pressure to the chamber 2| and thus to the front side of the piston 22, thereby providing means to open the needle valve ll against the opposition of the compression spring 2!. A part of the air which gains access to the chamber 2! passes through the passages is to the nozzle I! of the spray gun, thereby providing means for atomizing the coating material delivered to the nozzle through the passage II. A nipple 32 (Fig. 2) is threaded into the barrel ll of the spray gun and provides a connection between the barrel 0! the spray gun and an air tobeatomised. Inthepresentapparatusaheat- 56 conduit 34 (Fig. 3) by which'air under pressure ,cuit 62 by leads 64 and 56.

is delivered through the passage 30 to the chamber 26. A second nipple 36 provides a connection between the fluid passage I in the barrel of the spray gun and a conduit 38 by which the coating material is delivered to that passage. To heat the spray gun, a heating coil 40 in the form of a sleeve is slipped over the barrel of the spray gun and held in place by a nut 42.

The coating material in a liquid or semisolid state is contained in a closed receptacle 44 (Fig. 8) which may be remote from the spray gun and may be of any desired capacity, preferably such that an operator may operate the spray gun for an entire day without refllling the receptacle. The coating material is conducted from the receptacle 44 to the spray gun through the conduit 33 which is connected to the bottom of the receptacle. An air conduit 46 is connected to the top of the receptacle and is connected to a source of air pressure, indicated generally by the reference character 41, whereby air under pressure may be delivered to the receptacle to force the coating material from the receptacle through the conduit 38 to the .spray gun. The conduit 34 through which air is delivered to the chamber 26 of the spray gun is connected to the air conduit 46 by way of a valve 48 and a branch conduit 00. Thus, by manipulation of the valve 40, air may be permitted to enter the chamber 26 through the conduit 34 and passage 30, thereby opening the needle valve I8 and admitting the coating material to the nozzle. As soon as the valve 48 is closed, the air under pressure will be out oif and the spring 28 in the cylinder 24 will close the needle valve I8.

The heating coil 40 surrounding the barrel of the spray gun is connected in an electric cir- The circuit consists of two variable resistances 62 and 66 connected in series to an outside power line by a knife switch 68. As illustrated, current from the knife switch 58 passes through a cut-out 60, the

variable resistance 62, the variable resistance 66,

,and via the leads 54 and 66 to the coil 40. It

is to be observed that the second resistance 66 is connected across the terminals 68 of a pressure switch 64 and may be short-circuited by it when fluid under pressure is admitted to operate it.

In Fig. 3 the pressure switch 64 is shown in a' purely diagrammatic fashion, thereby to illustrate clearly the electric circuit. The pressure switch 64 is of a commercial type and is shown indetail in Fig. 4. The switch comprises a pair of dished disks I0 and I2 fastened together face to face by screws 14 threaded through the peripheral portions thereof, and between the disks is clamped a flexible diaphragm 16. The upper disk I2 is fastened by screws -'I8 to the base plate of a box 80 forming the body of the switch. A

aseaaas I00 projects upwardly from one side of the cup 00, and an arm H0 is pivotally attached thereto at II2, the arm also being pivotally attached at II4 to one of a pair of upstanding legs I00 fastened at their lower ends to the base 80. Accordingly, upward movement of the cup causes the arm III to tilt counterclockwise about the pivot II4. At one end of the arm IIO there is formed a projection II6, to the end of which is pivotally attached a rod III. A bar I20 is pivoted at I22 upon one wall of the box 80, one end of the bar having a depending leg I24 which is adapted to rest upon the base of the box 00 and the other end of which carries an upright I20 having a contact I28 thereon operable to bridge the terminals 68. The terminals 68 are mounted on a strut I3I extending between and fastened to the opposite sides of the box 80. The contact I28 is snapped into and out of engagement with the terminals 66 by a spring I32 which is fastened at one end to the rod H8 and at its other end to the leg I24. As illustrated, when the arm H0 is caused to tilt about the pivot H4 in a counterclockwise direction, the end of the rod I I8 fastened to the projection I I6 is brought down below the pivot point I22, and the spring I32, which is now exerting an upward pull, causes the bar I20 to tilt in a clockwise direction about its pivot I22, thereby to snap the contact I20 into engagement with the terminals 68. Thus, the resistance 66 is short-circuited. When the air pressure is cut off, the diaphragm I6 is collapsed, that is, returned to its lowermost position by a spring 94. To this end, the sprin 94 is seated at one end in the cup 90 and is held under compression by an adjustable nut 86 threaded on a screw 98, thereby urging the diaphragm downwardly. The upper end of the screw is provided with a flanged head I00 which projects through an aperture I02 formed in a horizontal plate I04 joining the upper ends of the upstanding legs I06. Clockwise movement of the arm IIO causes the rod II8 to rise above the pivot I22, as shown in Fig. 4. The spring I32 thus exerts a downward pull and causes the bar I20 to tilt in a counterclockwise direction to break engagement between the contact and terminals, thereby to cause the current to pass through the resistances 62 and 66 in series. A strap I34 fastened to the base 80 limits the upward movement of the rod H8. The clockwise conduit 82 is connected at one end to the lower disk I0 and at its opposite end to the valve 48. Thus, air under pressure may be delivered through the conduit 82 to the underside of the the plate 06 by the aforesaid screw 02. A finger movement of the arm H0 is limited by a screw I36 threaded through the end of the arm H0 and adjustably secured therein by a lock nut I38.

The conduit 82 leading to the pressure switch 64 is connected to the main air conduits 46 and 50 through the valve 48 so that when air is admitted to the spray gun, air is also admitted to the pressure-operated switch 64 and, consequently, when the coating material is being forced through the spray gun. the contacts of the pressure-operated switch remain closed. As a result, a maximum of current passes through the heating coil 40 because of the fact that the second resistance 66 is shunted or short-circuited out of the circuit. When the valve 48 is turned to a position to cut off the flow of air to the spray gun, air is also cut-off from the pressureoperated switch so that the contacts are separated, thus cutting the second resistance 66 back into the circuit in series with the resistance 62. As a result, a minimum of current passes through the circuit and the amount of heat generated at the spray gun is reduced. It is to be observed that both the resistances 62 and 60 are variable terial to pass into the nozzle.

and by properly adjusting them the amount of current delivered to the heating coil iii of the spray gun while it is in operation and the coating material is passing therethrough and the amount of current delivered to the heating coil 40 of the-spray gun when no coating material is passing therethrough can be so balanced that the temperature of the spray gun will be uniform whether the gun is or is not in operation.

In using the apparatus, the operator throws on the main switch 58 which heats the coil 40 of the spray gun. When it is desirable to coat an article such as a shoe part, the operator directs the spray gun at the shoe part or holds the shoe part in front of the spray gun and turns the valve 48 which admits air under pressure to the piston-operated needle valve l8, thereby causing it to open and to permit the coating ma- Simultaneously, air is admitted to the underside oi the diaphragm 16, and the contact I28 and terminals 68 are closed, thereby to short-circuitthe variable resistance 68, which increases the current in the circuit so that the quantity of heat at the spray I gun increases with the flow oi the coating material through the spray gun. when the valve 48 is manipulated to cut oil the air, the p stonoperated needle valve II is closed by the spring 28. The diaphragm I8 is returned to its lowermost position by the spring II. and the contact I28 and terminals .88 are separated so that-the current again passes through both resistances 82 and 88, thus reducing the current in the circuit and consequently the amount oi! heat at the spray gun. By setting the variable resistances beforehand, a balance may be established so that the temperature of the spray gun may be maintained substantially constant. Thus the spray gun may be operated without overheating, whether it is used continuously or intermittently.

The method oi forcing an unheated spray material to a spray gun and there heating it to liqueiy it forms no part of the present invention but forms the subject matter of application Serial No. 461.435. filled October 9, 1942, in the name of John J. E p y- Having described my invention. what I claim as new and desire to secure by Letters Patent oi, the United States is:

1. Apparatus for ap lying a s ray coating to an object, said apparatus being used in connect on with a source oi fluid pressure and a source of electric power. said apparatus comprising a spray gun. a source or coating material; means for normally closing the nozzle of the spra gun. electrical means for heating the spray gun. said electrical heating meansincluding a resistance and a switch operable to short circuit a part of the resistance when the nozzle is open. means whereby said fluid under pressure effects delivery of the coating material from said source to said spray gun and simultaneously opens said firstnamed means and operates said switch, and means for cutting oi! the flow oi fluid under pressure to said first-named. means and switch without aflecting delivery or the chitin: material to the spraygun. l

2. Apparatus for applying a spray coating to an object, said apparatus being used in connection with a source of fluid pressure and a source of electric power, said apparatus comprising a spray gun, a source of coating material, means for normally closing the nozzle of the spray gun, electrical means for heating the spray gun, said electrical means including an electric circuit connecting said heating means to a source of electric power, a resistance and a switch operable to short circuit a part of the resistance when the nozzle is open, means whereby said fluid un-' der pressure efle'cts delivery the coating material from said source to the spray gun and simultaneously opens said ilrst named means and operates said switch and atomizes the coating materialas it is discharged from the nozzle, and means for cutting off the flow of fluid under pressure to said first-named means and switch without aflecting deliver of the coating material to the spray gun.

3. Apparatus for applying a spray coating to an object, comprising a spray gun having materlal and air passages therein, a source 0! coating material, a conduit connecting said source as to the material passage of the gun, a valve'in said material passage for controlling the passage of coating material therethrough, a conduit connecting the air passage to a source of compressed air, means in said air passage to ac- 80 tuate said valve, heating means surrounding the spray gun, an electric circuit connecting the heating means to a source of electric power, resistance means in the circuit, a pressure-operated switch to short-circuit a part of the resistance.

a conduit connecting. the pressure-operated switch to said source of compressed air, and a valve between said source of compressed air and said secondand third-named conduits operathe pressure-operated switch.

4. Apparatus for applying a spray coating to an'obiect, comprising a spray gun having ma-- terial and air passages therein, a container for coating material, a conduit connecting said container to the material passage of the spray gun, a conduit connecting the container to a source of compressed air to force the coating material through the first-named conduit to the material air passage to actuate said valve, heating means surrounding the spray gun, an electric circuit connecting the heating means to a source 0! electric power, resistance means in the circuit,

a pnemnatically'opcratedswitch to short-circuit apartoftheresistanceaconduitconnectinl the pneumatically operated switch to the source of compressed air, and a valve between the source of compressed air and the'third and fourthnamed conduits operable to admit air simulta neously to the pneumatically operated menu and switch.

ble to admit compressed air simultaneously to the; means for actuating said first-named valve and wnmu as. nooon'ron.

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