US3044441A - Spray coating apparatus - Google Patents

Description

July 17, 1962 H. N. BLAKESLEE ET AL SPRAY COATING APPARATUS Filed May 6, 1960 ff 55 jf j; ff ff j;

INVENTORS United States Patent Oce i s,s44,441 Patented July 17, 1,962.

Jersey Filed May 6, 1960, Ser. No. 27,341 11 Claims. (Cl. 118-317) The present invention pertains to an apparatus for spray coating the interior surfaces of hollow articles and more particularly to a spin sprayer having a novel feeding and valving arrangement for precisely controlling the flow of coating material.

One type of apparatus commonly used for coating the interior surfaces of hollow articles is the air atomizing 360 cone spray type. A disadvantage of this type of sprayer is the diculty sometimes encountered of producing an even coating, since the slightest imperfection or lack of alignment of the material discharge lips causes -unevenness in the finished coating. A further disadvantage is the diiiiculty of turning the spray on and off in such a way as to leave a sharp line of demarcation between the coated and uncoated areas, due to the expansion and cloud effect of the atomizing air.

Using the air atomizing cone spray apparatus, it is possible to rapidly rotate the article to be coated during the spraying operation to produce more uniform coating, However, this method has limited applicability since it requires complex mechanisms for gripping and rotating the article to be coated, and presents handling problems when the article is heavy and cumbersome, or conversely, light and exible. Furthermore, the difficulty of starting and stopping the spray so as to produce a sharp line of demarcation between the coated and uncoated areas is not improved.

Another type of apparatus utilizes a rapidly revolving perforated spray nozzle into which` coating material is admitted in controlled quantities. The nozzle breaks up the coating material into ne particles which are thrown out radially and deposited on the cavity surfaces. Where the cavity is relatively large and the amount of coating material to be deposited is not important, so that some build up or dripping is permissible, this can be accomplished with apparatus of a comparatively simple design. In the past, the apparatus used for such purposes has consisted of a sprayer having two concentric members forming an annular passage for the flow of the coating material. One of the members which has a spray head axed to the dispensing end is rapidly rotated by a power source while the other member remains stationary. The

coating material which flows to the rapidly rotating spray head is converted into `a radial spray of ne droplets and deposited on the walls of the cavity. A disadvantage of such an apparatus Ais that the valving arrangement usually involves a rotating member seating on a stationary member. Such a valving means is subject to excessive heat formation and -wear due to the friction between the moving parts and therefore is not adapted to precise control of the flow of the coating material. This may become a serious problem where it is desirable to have a uniform coating with no local build-up due to dripping or leakage.

Particularly where it is necessary to coat only a predetermined axial length of the cavity leaving the otherV This agitation may be undesirable with many coating materials because of the frictional heating which results and the possibility of foaming of the coating material within the annular passage. Also to coat all or a preselected length of the thin cavity with a uniform coating requires that the flow to the spray head be controllable almost instantaneously. Such precise control can be best achieved where the valve members have no relative movement which may produce friction and wear, yand necessitate continual adjustment of the unit to effect proper sealing. l

A further problem encountered in the use ofspin sprayer y"type apparatus is that resulting from the entry of coating material into the bearing clearance spaces where it ultimately hardens and binds the rotating parts rendering the unit inoperative. This is particularly `acute in the case of two-component coating materials which harden vary rapidly upon mixing of the two components to form a tenacious bond between the mating parts. Amine cured epoxy resins are an example of this type of material.

An object of the present invention is to provide an apparatusfor spray coating the interior surfaces of hollow articles which will overcome the problems hereinbefore, pointed out.

Another object is to provide such an apparatus which is especially adaptable for coating al1 or only a preselected axial length of the interior surfaces of long thin hollow articles.

Another object is to provide such an `apparatus wherein the ow of coating material to the spray head can be started and stopped without hesitation.

Another object is to provide such an -apparatus wherein the flow passage for the coatingmaterial is formed by stationary members.

Another object is to provide such an apparatus whereby a pressurized uid is used to lubricate and cool the spray head drive shaft and prevent the coating material from entering into and fouling or binding the rotating n members of the apparatus.

A further object is to provide such an Iapparatus which .is simply constructed land easily maintained.

Numerous other objects and advantages of the present invention will be apparent as it is better understood from the following description, which, taken in connection with the accompanying drawing, discloses a preferred embodiment thereof.

The elements of the present invention consist of tubular inner and outer members disposed one within the other to form a flow passage for the coating material, an inlet in the upper portion of the outer member to admit coating material to the/ow passage, a valve formed by the engagement ofthe inner and outer members at their lower extremities to open and close the flow passage, means for moving the inner and outer members longitudinally relative to one another to open and close the valve, a drive shaft extending through the inner member and hav-ing a spray head attached to the lower end adjacent the.valve, means for rapidly rotating the shaft and spray head, and an inlet for admitting pressurized fluids to the annular clearance space between the drive shaft and the inner member.

Referring to the drawings:

FIGURE 1 is a sectional View of a spin sprayer embodying features of the present invention;

FIG. 2 is a fragmentary view showing the spray head in position for coating the interior surfaces of a hollow article; i

FIG. 3 is an elevational view of a spin sprayer apparatus adapted for automatic operation;

FIG. 4 is a sectional view taken substantially along line 4 4 of FIG. 3.

As a preferred or exemplary embodiment of the instant invention, FIG. 1 shows a spin sprayer assembly generally designated 11 comprised of a tubular inner member 12 rigidly attached to a mounting plate 13 and extending vertically downwardly therefrom. The inner member is circular in cross-section and disposed within a tubular outer member 14 which is also circular in cross-section. The upper portion of the inner member 12 has an outside diameter substantially equal to the inside diameter of the is supplied to the 'passage 15. The flow of coating material y into the hose 13 is controlled by a suitable valve such as a gate valve (not shown). The pressurized coating material is prevented from escaping from the upper end of z.

the sprayer 11 by an O-ring seal 19 of the type well known in the art located between the inside diameter of the outer member 14 and the outside diameter of the upper portion ofthe inner member 12. v

The lower end ofthe outer member 14 is turned inwardly to form a flange 2i). The inside surface 23 of the flange is conical shaped, sloping inwardly and downwardly from the inside diameter' of the outer member 14 to form one member or the seat of a valve 24. A mating conical surface on the lower end of the inner member 12 forms the second member of the valve 24, the valve being closed to seal the passage 15 when the conical end 25 abuts against the ange surface 23. Reciprocating movement of the outer member 14 relative to the inner member 12 disengages the flange surface 23 from the conical end 25 thereby permitting the coating material to flow from the passage 1,5 through the outlet opening thus formed. It is understood'that the outer member 14 may` be fixed with the inner member 12 movable upwardly relative thereto to open the valve 24, or conversely the inner member -1,2 may be fixed with the outer member 14 movable downwardly to accomplish the same result.

An arm 26 is attached to thefupper end of the outer member 14 extending outwardly therefrom in a radial direction. A stop bracket 27 is comprised of a vertical portion ZS attached at one end to the mounting plate 13 and extending downwardly therefrom, and a horizontal portion 29 integral with and extending at right angles from the lower end of the vertical portion 28. The horizontal portion 29 is positioned beneath the arm 26 to limit the reciprocating motion of the outer member 14 relative to the inner member 12 by engaging the arrn 26 when the valve 24 is opened sufficiently to permit unrestricted ow of the coating material. Y

An elongated drive shaft 30 extends downwardly through a hole 33 in the plate 13 and through a centrally located bore 34 in the inner member 12, the hole 33 and bore 34 being in alignment. The drive shaft 30 is rigidly attached at its upper end to any suitable means for producing high speed rotation of the shaft, for example the air motor 35 shown in FIG. 3. A cylindrical cup shaped spray head 36 attached to the lower end of the drive shaft 3i) is comprised otra disc portion 37 andA an upwardly appending skirt portion 33 integral with the disc portion 37 and having a plurality of thin axially oriented slots 39 uniformly spaced around its periphery. The disc portion 37 has a centrally located upwardly projecting boss 49. The drive shaft 30 is reduced in diameter andrthreaded on its lower end 43,'with the threaded reduced end 43 extending through a centrally, located hole in the boss 40 and being secured thereto by a nut 44. Y t j The spray head 36 is positioned on the drive shaft 3i) so that the upper edge of the skirt portion 3S is slightly above the bottom'surface of the flange 20 when the inside surface 23 of the flange is seated on the conical end 25 of the inner member 12 to close the valve 24, as shown in FIG. 1. The lower portion of the outer member 14 adjacent the spray head 36 has a reduced outside diameter to allow the outer member to enter the skirt portion 38 of the spray head 36 when the outer member is moved longitudinally relative to the inner member 12 to open the valve 24, as shown in FlG. 2.

An inlet port 45 -through the plate 13 communicates with the hole 33 through which the drive shaft 30 extends. The bore 34 and the portion of the hole 63 below the inlet port 45 have a diameter slightly larger than the diameter of the `drive shaft 30 forming a thin annular clearance space 46 around the drive shaft. A tube 47 attached to the inlet port 45 is connected to a hose 43 whereby a pressurized fluid is conducted to the clearance space 46. The pressurized iiuid may be a gas, such as air, but is preferably a liquid solvent for the particular coating material being used. The flow of this uid into the hose 4S is controlled by a suitable valve 35 described more fully hereinafter. The uid admitted to theV clearance space 46 flows downwardly along the drive shaft 30 and escapes at the lower end of the inner member 12 adjacent the spray head 36. This fluid, 'admitted in small quantities so as not to change the characteristics of the coating material appreciably, serves the dual function of lubricating and cooling the rapidly rotating drive shaft 30 and also preventing the entry of coating material into the clearance space 46 to preclude fouling of the drive shaft 30 and consequent binding of the drive shaft to the rbore 34. The fluid is prevented from escaping upwardly between the hole 33 and drive shaft 30 by an O-ring seal 49 of the type well known in the art positioned between the inlet port 45 and the upper surface of the plate 14.

The pressurized fluid may also consist wholly or in part of one component of a two component coating material, `such as the amine component of an lamine-epoxy resin coating. With this type of operation all or part of the amine component, either by itself or mixed with a gas such as air ows through the clearance space 46 to the spray head 36 where it is intimately mixed with the epoxy or epoxy-amine mixture iiowing into the spray head 36 from the ow passage 15. Since these coating materials generally harden rapidly when the two components are mixed, keeping them separated up to the time they are sprayed eliminates the possibility that the material will harden in the sprayer passages during a shut down period yand ruin the apparatus. When only a portion of the amine component is initially added to the epoxy and the remainder of the taminercomponent is contained in the pressurized fluid,4 the time required for hardening is increased so that the possibility of premature hardening in thesprayer passages is greatly minimized.

The spin sprayer assembly 11 may be used manually or as part of an automated spray coating apparatus, `as shown in FIG. 3, adapted to coat the interior surfaces of a hol- 1 low `article 5G in a predetermined time sequence. ltis to be understood that other suitable arrangements can be used to accomplish the same result. vThe exemplary embodiment of the spray coating apparatus is comprised of a base 53 and an upright supporting structure 54 integral therewith. A s shown in FIG.` 4, the supporting structure 54 isrcomprised of two rectangular channel members 55 with the openings 56 in the channel members being inline with and facing each other.

A reciprocating support lbracket 57 is comprised of a vertical guide member 58 having the mounting plate 113 integral with and extending at yright angles from the upper edge thereof. The guide member 58 is rectangular in cross-section having a thickness substantially equal to the width of the openings 56, in the channel members 55 and having a width substantially equal to the distance between the end surfaces 59 of the openings 56. The guide guide member 58 is positioned within the channel members 55 being adapted to move vertically therein. A shaft l position by the spring 75.

I 60 integral with the guide member 58 extends outwardly A solenoid actuator 67 mounted on the upper surfacek of the mounting plate 13 has a plunger 68 which extends downwardly through an opening in the mounting plate and is connected to the arm 26 by means of a pin 69. The actuator 67 is connected 'to a source of electrical power through la switch 70u The switch 70 is secured to a frame member 73 and is operated by a disc cam 74 which is rigidly attached to the shaft 66 and therefore rotates in unison -with the cam 65. Consequently, the energizing of the actuator 67 by the action of the cam 74 occurs in `a timed relationship with the up and down movement of the support bracket 57 and attached spin sprayer assembly 11 under the impetus of the cam 65. The plunger 68 is spring biased upwardly by a spring 75 so that when the actuator 67 is de-energized the arm 26 and the integrally connected outer member 14 are maintained in a raised position with the ange surface 23 of the outer member abutting against the conical end 25 of the inner member 12 thereby closing the valve 24. When the switch 70 is closed by the cam 74 to energize the actuator 67 the plunger 68 is depressed against the action of the spring 75 therelby depressing the arm 26 to move the outer member 14 downwardly which disengages the -iiange surt face 23 from the conical end 25 opening the valve 24.

The air motor is mounted on the upper surface of the mounting plate 13 with the drive shaft 30 being rigidly connected to the output shaft of the air motor 35. An a-ir supply tube 76 having a two position solenoid valve 77 is connected to the air motor inlet port. The valve 77 is spring biased to the open position so that when the solenoid valve is de-energized, motiv-ating air is admitted to the air motor 35 to drive the motor and rotate the drive shaft 36 and attached spray head 36. The air motor exhaust is carried away by an exhaust tube 7,8 connected to the air motor outlet port.

The solenoid valve 85 which controls the `ilow of the pressurized iluid to the clearance space 46 around the drive shaft 30 is Spring biased to the open position so that when it is de-energized, the fluid is admitted to the clearance space 46. The valve 85 is connected in parallel with the valve 77 to a source of electrical power through a switch 83. The switch 83 is secured to the frame member 73 and is operated by a disc cam 80. The cam 80 is rigidly attached to the shaft 66 and rotates in unison with the cams 74 and 75 so that the deenergizing of the valves 77 and 85, the energizing of the actuator 67 and the up and down movement of the Spin sprayer assembly 11 all occur in a predetermined timed sequence.

An indexing turret 79 holds a plurality of hollow articles (only one shown) and positions them one at a time beneath the spin sprayer 11 in a timed relationship with the vertical movement of the sprayer under the impetus of the cam 65. As shown in FIG. 3 the roller 63 is on the high dwell portion of the cam 65 thereby mantaining the support bracket 57 and spin sprayer 11 in the raised position while the hollow article Sti is being brought into position by the turret 79. During this portion of the operating cycle the cam 74 maintains the switch 7 t) in the open position de-energizing the actuator 67; consequently the valve 24 is maintained in the closed Also, during this portion of the cycle the switch` S3 is maintained in the closed position by the cam 8). In this position the switch 83 closes the circuitenergizing the solenoid valve 77 cutting olf the ow of motivating air to the air motor 35 thereby 6. ,Y stopping the rotation of the drive lshaft 30 and spray head 36. 'I'his engaged position of the switch 83 also energizes the solenoid valve 85 thereby cutting olf the flow of pressurized iluid to the clearance space 46 around the drive shaft 30. It is to be understood, however, that rotation of the spray head 36 and the ow of iiuid to the clearance space 46 may be continuous throughout the operating cycle where the type of coating material being used or the speed of operation-makes this desirable.

In the exemplary embodiment shown in FIG. 3 after the article to be coated is positioned beneath and in axial alignment with the spin sprayer 11 by the turret 79, upon further rotation of the cam 65, the roller 63 reaches a descending portion of the cam surface 64 and consequently the support bracket 57 and arm 80 move downwardly. When the spray head 36 reaches a position slightly above the surface to be coated, the cam opens the switch `83 de-energizing the solenoid valves 77 and 85. The solenoid valves 77 and 8S being spring biased towards the open opsition `open immediately upon being tie-energized. Pressurized air then `ilows to the air motor 35 which rotates ,the drive shaft 30 and attached spray head 36; simultaneously pressurized fluid is admitted to the clearance space 46 around the drive shaft 30. The actuator 67 remains `dse-energized so that the valve 24 remains closed due to the yaction of the spring 75, preventing the flow of coating material to the spray head When the spray head 36 is adjacent to the surface to be coated the cam 74 closes the switch 70 energizing the solenoid actuator 67. Thereupon the actuator 67 depresses the plunger 68 thereby moving the arm 26 to the position shown in dotted lines in FIG. 3. Due to its integral connection therewith, the downward movement of the arm 26 forces the outer member 14 downwardly relative to the inner member `12 opening the valve 24 and allowing the coating material to owinto the spray head 36. The pressurized coating material flows into the spray head 36 in the form of an annular stream thereby uniformly introducing the coating material to the rotating spray head and insuring a uniform deposit on the cavity surfaces. The high rotative speed of the spray head 36 imparts a high rotative speed to the coating material admitted therein and the resulting centrifugal force ycauses it to be thrown radially into the slots 39 in the skirt portion 38 of the spray head 36. The slots 39 convert the coating material into 'a very ne spray which continues out in a radial direction and is deposited on the cavity surfaces. The pressurized iluid flowing through the clearance space 46 and escaping vadjacent the spray head 36 is intimately mixed with the coating material under the action of the rapidly rotating spray head.

Further rotation of the cam 65 lowers the spin sprayer to its lowermost position within the cavity. At this point the cam 74 opens the switch 70 to rie-energize the actuasprayer assembly 11 are rapidly raised. When the roller 63 reaches the high dwell portion of the cam 65 elevating the support bracket 57 Iand spin sprayer 11 to the uppermost raised position, the turret 79 is indexed to bring an uncoated article into position and the cycle repeated.

The c-am 74 may be ydesigned, so that the valve 24 will be opened at any desired point in the downward travel of the sprayer 11, for any desired interval, and for either or both the downward and upward travel of the sprayer 7 Within the cavity being coated. It is to be understood that the cam 80 would be correspondingly `designed so that `the spray head 36 is rotating at full speed and theL bination of desirable features, the subject invention will'` be extremely useful for the coating Vof hollow articles where precise control of the coating thickness and area to be coated is required.V By positioning the val-ving means adjacent to the spray head, essentially no residual coating material ywill be introduced to the spray head after the coating outlet is closed. Correspondingly, the coating material will be introduced almost instantaneously into the spray head when the valving means is opened. Thus it is possible to very closely control the dow of coating material to the spray head and therefore the particular portion of the cavity on which it will be deposited. Uniformity of coating thickness is achieved, without uneven thicknesses at the points of starting and stopping the flow of coating material.

Furthermore, the maintenance Vrequirements of the subject'invention will be very minimal due to the novel manner by which entry of .the coating material into the drive shaft bearing space where it may harden and jam the apparatus is precluded. Periodic cleaning of the spray head Ito keep these parts Vfree of accumulations of coating material is also facilitated Aand can be easily accomplished by momentarily passing ya solvent through the drive shaft clearance space and into the rotating spray head while the dow of coating material is stopped, using suitable shields to prevent spattering of .the other portions of the apparatus.

It is thought 'that the invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction, land arrangement of the parts'without departing from the spirit and scope of the invention or sacrificing all of its material advanltages, the form hereinbefore described being merely a preferred embodiment thereof.

We claim: Y Y

1. A spin sprayer for coating'the interior -of hollow articles comprising a tubular outer member, a tubular inner member having a circular bore extending there# through, said inner member being disposed within said outer member and forming a passage therebetween, an inlet port communicating with said passage adjacent one end thereof for ladmittingja iluid material under pressure into said passage, valve means integral with said inner yand outer members .at the end of said passage remote from said inlet port, means for reciprocating said inner yand outer members relative to one another to open and close said valve means, la circular drive shaft extending through said circular bore fand .forming an elongated annular bearing space therebetween, said drive shaft being adapted 'to rotate within said bore but having substantially no axial movement relative thereto, an inlet conduit communicating with said bearing space for introducing a pressurized liquid therein, a spray head attached to said drive shaft ladjacent said valve means, and means for rotating said drive shaft and attached spray head, the bearing surface for said rotating ldrive shaft consisting of Ithe contiguous surface of said circular bore, said valve means in the open position permitting said fluid material to how into said rotating spray head to be icentrifugally dispensed thereby, said pressurized liquid owing through said bearing space and emerging adjacent said valve means Whereby said rotating shaft is lubricated and cooled by said pressurized liquid land the entry of said fluid material into said bearing space is prevented.

2. The spin sprayer set forth in claim 1 wherein said valving means comprises a conical valve seat integral with the end of said outer member and a mating conical conguration on the end of said inner member fitting Within said valve'seat.

3. The spin spnayer set forth in claim 1 wherein said pressurized liquid is a solvent for said fluid material.

4. The spin sprayer set forth in claim l wherein said pressurized liquid comprises at least a portion of one component of a two component coating material, said fluid material comprising the balance of said coating material.

5. 'I'he spin sprayer set forth in claim 1 wherein said outer and inner tubular members are circular in cross section.

6.' The spin sprayer set xforth in claim 5 wherein said passage is an annular passage formed by the inner wall of said outer member and the outer wall of said inner member.

7. The spin sprayer set forth in claim l wherein said spray head is in the form of 'a cylindrical cup comprising an imperforate disc portion Ito which the `drive shaft is secured and a skirt portion having openings therein, said skirt portion extending towards the outer member and having an inside diameter large enough to permit the outer member Ato enter into the rotating spray head when the valve is opened without coming into contact with said rotating spray head.

8. The spin sprayer set forth in claim 7 wherein the openings in said skirt portion are a series of axial slots, said slots being regularly spaced around the periphery of said skirt.

9. The spin sprayer set forth in claim 1 reciprocatably mounted on a frame whereby it is guided into and out -of said hollow article.

10. The spin sprayer set forth in claim 9 wherein said means Vfor reciprocating said inner and outer members relative to one another is an electric solenoid.

11. The spin sprayer set forth in claim 10 wherein said solenoid is energized by means of la switch, said switch being 'actuated by the reciprocating movement of said sprayer within said frame.

References Cited in the le of this patent UNITED STATES PATENTS 2,480,663 McNab Aug. 30, 1949 2,501,736 Olsen Mar. 28, 1950 2,602,002 Schutt July 1, 1952 2,769,670 Dunn Nov. 6, 1956 Y FOREIGN PATENTS 965,119 Germany May 29, 1957

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