US3521598A - Spray coating control apparatus - Google Patents

Description

July 21, 1970 D. w. STRAW 3, 8

SPRAY COATING CONTROL APPARATUS Filed June '2. 1968 2 Sheets-Sheet 1 7 11:21:). 7 40 I y, E51;

45 44 E; mvzrvron ATTORNEYS July 21, 1970 D. w. STRAW 3,521,598

SPRAY COATING CONTROL APPARATUS Filed June '2, 1968 I 2 Sheets-Sheet 2 72 74 "4 f I RF'F 98 9 66 52 ,uo 7a 82 86 I so I e4 94 Z NAND "a I I TIMER 35 us NAND NOR m I00 I08 68 R I -ss OFF 40 FF 88 90 J -H8 I ,.s I02 I06) MANUAL l LINEIIGO N I LINEIOBO LINE I04!) I SPRAY -INES sa-Ido LINES 90-92 LINE 84 LINE 80 LINE4O LINES IlO-Il4 LINE 78 LINE 32 CYCLE TIME I TO I 2 a 4 3 1 a 9 I0 II I2 l3 l4 l5 I6 I [MENTOR Dorsey Wayne Straw F|G.4. BY W ATTORNEYS United States Patent 3,521,598 SPRAY COATING CONTROL APPARATUS Dorsey Wayne Straw, Richmond, Va., assignor to Reynolds Metals Company, Richmond, Va., a corporation of Delaware Filed June 7, 1968, Ser. No. 735,306 Int. Cl. Bc 11/00 US. Cl. 1l82 22 Claims ABSTRACT OF THE DISCLOSURE A device for spray-coating cans wherein a spray control valve is turned on by a first solenoid and turned off by a second solenoid. Each can is passed through a cycle of operation which includes precoating and coating steps. A first signal is generated when a given can is in the proper portion of its cycle to be coated; and a second signal is generated to indicate that a can is in fact in the coating position. A gating means is operative response to the simultaneous occurrence of the first and second signals to both actuate the ON solenoid so as to begin the spraying operation and turn on a timer which generates a timing signal at the end of a selected time for the can to be sprayed. The timing signal then actuates the OFF solenoid so as to terminate that cans spraying operation. The time at which the timing pulse is generated is selectively variable without requring the spraying machine to be shut down; and the spray duration is accurately controlled by means of the dual solenoids.

This invention relates to apparatus for spray-coating articles and particularly to an apparatus for spraying the insides of rapidly spinning cans with a thermoplastic or other plastic material dissolved in an organic solvent.

The Food and Drug Administration requires the insides of certain types of cans to be coated with various types of materials to prevent the contents of the cans from being contaminated. In this respect, the acceptability of a given cans interior coating is tested by filling the can with water; inserting a probe therein; and measuring the electrical conductivity between the probe and the outside of the can. As a result of these tests, it has been determined that various types of cans must have various coating weights depending upon the type of material to be contained therein. One such requirement calls for each can to have its interior coated with a minimum of 175 milligrams of thermoplastic material. Some of the presently available spraying systems, however, are unable to stay within the allowable tolerances so that cans are presently being sprayed with a median of 230 milligrams of coatingabout 55 milligrams of overspray. Consequently, it is an object of this invention to provide a spraying mechanism for more accurately controlling the amount of coating that is sprayed at any given time.

Presently available coating mechanisms have the spray durations thereof controlled by devices which sense the location of certain spray machine mechanisms, such as cams, which travel through defined paths during a given indexing cycle of the spray machines operation. Generally speaking, therefore, it is necessary to terminate the operation of a spray machine in order to adjust the duration of its spraying time. It is another object of this invention, therefore, to provide a spray duration control means whereby the spray duration can be selectively varied without requiring the spray mechanism to be shut down.

Present can spraying devices actuate a spray control valve by means of a solenoid which, in turn, is turned on and off by signals received from proximity sensors located on relatively adjustable probes adjacent a suitably 3,521,598 Patented July 21, 1970 lobed timing cam or the like. In accordance with principles of the instant invention, on the other hand, a spray control valve is placed in its ON position by a first solenoid which is operative in response to signals indicating that the appartus is in a proper portion of its cycle for a can to be sprayed and that a can is, in fact, in the spray position. The spray control valve is placed in its OFF position by means of a second solenoid which is operative in response to a signal from an independent timer which generates an OFF signal at a selected time after the ON solenoid has been actuated. In this manner, the median over-spray has been reduced to 5 milligrams which, at present prices represents a savings of approximately onehalf million dollars per year per 5 billion cans. Moreover, because the timing means is independent of the spray mechanisms indexing system, the spray time duration can be selectively varied without turning otf the entire spraying machine.

The foregoing and other objects, features, and advantages of this invention will be apparent from the following more particular description of preferred embodiments thereof as illustrated in the accompanying drawings wherein the same reference numerals refer to the same parts throughout the various views. The drawings are not necessarily intended to be to scale, but rather are presented so as to illustrate the principles of the invention in clear form.

In the drawings:

FIG. 1 is a schematic illustration of an indexing mechanism for positioning and rapidly spinning a can to be coated at a spraying position;

FIG. 2 is a schematic illustration of a spinning can being sprayed by a mechanism having a main valve thereof controlled by two separate ON and OFF solenoids.

FIG. 3 is a schematic diagram of a logic circuit including an independent timer mechanism for controlling the ON and OFF solenoids of FIG. 2;

FIG. 4 is a timing diagram for the apparatus illustrated in FIG. 3.

In FIG. 1, cans to be coated travel down a shoot 10 to an indexing wheel '12 which picks up the cans in recesses thereof. The indexing member is rotatable on a shaft 16 which is schematically illustrated as being extended through a dwell mechanism, not shown, to a cam 18'.

In a known conventional spray mechanism, the cam 18 has a variably sized portion 20 thereof located so as to rotate under relatively adjustable sensors 22 and 24. In the past, these sensors have been either of the magnetic proximity type or micro switches operative in response to variably located lobe on the cam 18 or other such devices. In these respects, the probes 22 and 24 have been relatively adjustable back and forth in a slot 26 by means of suitable fasteners 28. In the instant apparatus, the probes 22 and 24 are eliminated in favor of a single proximity sensor 30. This sensor produces an output signal on line 32 when the leading edge 34 of a metallic strip 35 passes thereunder. This signal from the proximity sensor 30 terminates when trailing edge 36 on the metal strip 35 passes under the sensor. In this respect, although not illustrated, the speed of the timing cam 18 is suitably reduced with respect to the indexing element 12 so that the timing cam makes a complete revolution for each can that passes down the shoot 10 and into a pocket on the indexing member 12. Between the time a can such as 36 leaves a path position corresponding to location 14a in FIG. 1, until it is about to leave a position corresponding to location 1417, the cam 18 makes one complete revolution. In thusly moving from location 14a to location 1417, each can passes under a second proximity sensor 3-8 which provides a signal on line 40 in response to the passage of a can thereunder. AS each can arrives at sta- 3 tion 14b, it engages with and is rapidly spun by a friction wheel 42. As each can is spun by the wheel 42, it is sprayed with a suitable thermoplastic material 44 (FIG. 2) forced through a nozzle 46 under control of a valve mechanism 48: which will now be described.

The valve mechanism 48 is schematically illustrated in FIG. 2 and includes a main valve 50 in a housing 52 for directing the flow of air and epoxy or the like entering in lines 56 and 58, respectively, and being passed to the nozzle 46 through line 60. In this regard, the thermoplastic material is delivered to the valve mechanism at a controlled temperature and pressure so that the amount of spray leaving the valve 46 is controlled by the duration that air flows from line 56 to valve 50'. I

The main valve 50 is controlled by pilot valves 62 and 64 which, in turn, are controlled by solenoids 66 and 68, respectively. That is, when solenoid 66 is energized, it causes pilot valve 62 to move an amount sufficient to cause the main valve 50 to permit air to flow through line 56 and out line 60 so that the outfiowing air carries with it a metered amount of thermoplastic material from line 58. Similarly, when solenoid 68 is energized, the pilot valve 64 is moved sufliciently so as to cause the main valve 50 to close so that the flow of thermoplastic material from the nozzle 46 terminates. The main valve 50 is structured so that it remains in its last position even though the solenoids 66 and 68 are deenergized. After each can is sprayed, the indexing wheel 12 is again moved so as to bring another can into position at pocket 14b and so :ona coated can being delivered to an exit shoot 70 at the termination of each of the above described machine cycles.

Having described the mechanical aspects of the inventions structure, its electrical control aspects will now be described. In this respect, FIG. 3 is a schematic illustration of a logic diagram that is suitable for use with the invention. NOR logic has been found to be preferable and will be used in describing the invention. But it will be appreciated by those skilled in the art that positive. logic can also be used. In this regard, it should be appreciated that negative or NOR logic is based upon the premise that a logical 1 input to any one or more of the inputs of a given NOR logic block produces a logical output.

With reference to the FIG. 3 circuit, a signal from the proximity sensor (FIG. 1) is delivered on line 32 to both an inverter 72 and the set position of a conventional bistable flip-flop (FF) 74. The output from the sensor 38 on line for indicating the entry of a can into the spraying pocket 14b, on the other hand, is delivered to the set side of a second bistable flip-flop 76. Olutputs on lines 78 and 80 from the bistable FFs 74 and 76, respectively, are delivered to a NAND gate 82 which is adapted to produce an output on line 84 to a NOR gate '86.

The output from the proximity sensor 38 on line 40 indicates that a can 36 has passed into position at location 14b so as to be spun by the friction wheel 42. A signal on line 32 indicates that the cam 18 and the indexing mechanism are in a proper position to be sprayed. Consequently, logical ls appear at the set sides of the FFs 74 and 76; and because NOR logic is employed, logical Os appear on lines 78 and 80 so as to produce a logical 1 output on line 84 from NAND gate 82. Hence, when the machine is at the proper portion of its cycle and a can is, in fact, positioned so as to be sprayed, simultaneous signals are delivered on lines 32 and 40 to result in an output on line 84 to NOR gate 86. The NOR gate also has a provision for a manual input on line 88 which can be used to initiate a test spraying operation in connection with an independent timing means which will not be described.

When NOR gate 86 receives an input on either of lines 84 or 88, it produces a logical 0 output on lines 90 and 92 to an independent timer 94 and a second NAND gate 96, respectively. The timer is operative upon receipt of the 0 signal on line 90 to prepare to produce subsequent 1 outputs on lines 98- and 100 at a selected, predetermined time after receipt of the 0 pulse on line 90. In this respect, the timer 94 is preferably of the unijunction type and is adapted to have the time of its output independently varied by means of a suitable potentiometer 102, or the like. Without regard to the period of the timer 94, however, its output on line 98 is a logical 0 at the time it receives its 0 input on line 90*. Consequently, when the timer is placed into operation, the inputs on lines 92 and 98 to the NAND gate 96 are both 0 whereby, by virtue of the preferred embodiments NOR logic, the NAND gate 96 produces a 1" output on line 104 to the spray valves ON solenoid 66. This actuates pilot valve 62 which, in turn, actuates the main valve 50 and the can 36s spraying step is initiated.

Depending upon the timers period, as determined by the setting of the potentiometer 102, the timer subsequently produces l timing pulses on lines 98 and 100 for delivery to the NAND gate 96 and a single shot multivibrator (SS) 106. As soon as the NAND gate 96 receives the 1 pulse, its output on line 104 is terminated and the solenoid 66 is deenergized. At the same time, SS 106 is operative in response to receipt of its 1 pulse to generate a signal on line 108 for energizing the OFF solenoid 68 which, in turn, actuates the pilot valve 64 to close the main valve 50 and terminate the spraying operation wholly independently of the present position of the cam 18.

The structure and operation of the invention will now be described in connection with the timing diagram of FIG. 4. As can 36 moves down the shoot 10, it was engaged by the indexing wheel 12. As the can approaches location 14b, the proximity sensor 38 generates a pulse (T on line 40 indicating the presence of a can at loca tion 14b. Inasmuch as this signal is delivered to the set side of PF 76, therefore, the output thereof on line drops from a 1 to a 0 at T Thereafter, the leading edge 34 of metallic strip 35 on the cam 18 passes under the proximity sensor 32 to produce a 1 pulse at time 3 (T as illustrated in FIG. 4. Inasmuch as this signal is delivered to the set side of PF 74, therefore, the output from the FF on line 78 drops to a 0 level at T and the output from inverter 72 on line 110 also drops to 0,

but has no affect upon a SS 112 to which it is delivered. At T therefore, NAND gate 82 is provided with two 0 inputs and, by virtue of the preferred embodiments use of NOR logic, the NAND gate 82 provides a 1 output on line 84 at T which causes NOR gate 86 to provide a 0 output on lines and 92, also at T The pulse on line 90 at T causes the timer 94 to start running in preparation for the subsequent generating of a timing signal on lines 98 and at a time to be determined by the setting of rheostat 102. Until such time as that timing signal is generated, however, the output on line 98 remains a 0. Hence, at T NAND gate 96 receives two 0 inputs so as to produce one output on line 104 which energizes the ON solenoid 66 in FIG. 3.

When the solenoid 66 is energized, the pilot valve 62 (FIG. 2) is actuated causing the main valve 50 to be opened to air pressure from line 56 which draws thermoplastic coating from line 58 and forces it through line 60 and nozzle 46 so as to coat the inside of the can 36 which is being spun by friction roller 42. This spray operation is accomplished quite irrespective of inaccuracies in the signals coming from the proximity sensors 30 or 38. This is due, at least in part, to the fact that the proximity signals are used only for a starting point of operation. The timing network controls the length of the period of spraying. Once the main valve 50 is actuated into the spray position by the ON solenoid 66, it can only be returned to its OFF position in response to actuation of the OFF solenoid 68 whose operation, as will now be described, relies only upon an output from the timer for its energization.

At the selected time, as determined by the setting of rheostat 102 (T (in the illustrated embodiment), the timer 94 generates a pulse on lines 98 and 100 causing the line 104 signal to drop to 0 and SS 106 to produce a 1 pulse on line 108 so as to energize the OFF solenoid 68. At T therefore, energization of the OFF solenoid actuates pilot valve 64 which, in turn, causes the main valve to close olf the air inlet 66 and thereby terminate the spray of thermoplastic material from the nozzle 46. At some suitable time thereafter, in a conventional manner, the indexing means 12 moves the can 36 onwardly toward the exit shoot 70 and positions the next can at the spraying pocket 14b.

If inspection of the can 36 indicates that more or less than the desired amount of thermoplastic spray was deposited on the cans interior, it is merely necessary to adjust the rheostat 102 without requiring the machine to be shut down so as to permit changes in the relative loca tion of probes 22 and 24 and lobes such as might occur on cam 18 (FIG. 1). Moreover, by using a dual solenoid operated valve such as 50, the inaccuracies of a single spring returned solenoid or valve are avoided. In these respects, it should be noted that the instant device permits a reduction of over 90% in the amount of overspray that has previously been required on the interiors of cans with which the invention has been employed.

In accordance with a still further aspect of the invention, the SS 106 is included in the timing circuit so as to prevent objectionable and wasteful blow-by of air past the pilot valve 64 when the OF solenoid 68 is energized. That is, many conventional solenoid actauted pilot valves such as '64 permit high pressure air (such as from a bleed line illustrated in phantom between inlet line 56 and pilot valve 64) to blow past the pilot valve so as to actuate the main valve. Consequently, any time the OFF solenoid 68 is energized, high pressure air blows by the pilot valve 64. For this reason, and inasmuch as the main valve automatically retains the position to which it was last set, the OFF solenoid 68 is energized by SS 106 rather than being merely energized whenever the ON solenoid is deenergized. This is illustrated in FIG. 4 where the SSs output on line 108 drops to its 0 level at T Looking back now to T in FIG. 4, it can be seen that the signal on line 40 from the proximity sensor 38 dropped shortly after the can 36 passed. Inasmuch as no subsequent significant signal was received by the PF 76, however, its output on line 80 remained at its 0 level. But at T the trailing edge 36 on the cam 18s metal strip (FIG. 1) passed under the proximity sensor 30 so as to drop the signal on line 32. This causes the inverter 72s output on lines 110 and 114 to rise so that FF 74 is reset placing a 1 signal on line 78; and causing SS 112 to produce an output on line 116 for resetting FF 76 so as to return line 80 to its 1 level at T The NAND gate 82s output on line 84 also drops to O at T which causes the output of NOR gate 86 on lines 90 and 92 to return to the 1 level. The timer 94 is also reset by a suitable pulse on line 118 at T The timer reset pulse on line 118 can be derived from any suitable source such as from NOR 86, for example.

By T the output from SS 112 on line 116 has returned to its 0 level and the entire circuit has returned to its starting point so as to be prepared for the next cycle of operation which is initiated by the next cycletime pulse from the proximity sensor 30 on line 32 as illustrated in FIG. 4 at T It will be appreciated by those skilled in the art that the above structure provides a spray mechanism for accurately selecting the duration that a given article is to be sprayed so that the weight of sprayed material can be accurately controlled and the amount of over-spray reduced to a more practical minimum. Moreover, it will be appreciated that the spray duration can be selectively 6 varied without requiring the entire spray apparatus to be shut down; and still further, it should be noted that the use of a separate energization means such as SS 106 for the OFF solenoid 68 permits a reduction in the amount of objectional blow-by from the pilot valve associated with the OFF solenoid.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. For example, although the operating circuit was described in connection with NOR logic, it should be clear that positive logic could also be used. Similarly, although the invention has been described in connection with the spraying of can interiors, the structure of the invention can be used for spraying other articles such as might be required in the refinishing of integrally riveted can ends, for example.

The embodiments of the invention in which an exclusive property or privileges claimed are defined as follows:

1. In an apparatus for spray-coating articles wherein each such article to be spray-coated is sequentially moved in a cycle from a precoating position to a coating position and then to a postcoating position, the combination comprising:

means for producing a first signal when said apparatus begins the coating portion of said cycle;

means for generating a second signal in response to the presence of an article in said coating position;

selectively operable spraying means for selectively spray-coating said article;

timing means;

gating means operative in response to said first and second signals for generating a gating signal to initiate operation of said spraying means and said timing means, said timing means being operative to generate a timing signal a selected time after being turned on; and

means operative in response to said timing signal for turning off said spraying means.

2. The apparatus of claim 1 wherein said spraying means is comprised of:

a nozzle having the flow of coating material therethrough controlled by a main valve having an ON position and an OFF position;

first and second pilot valves operative upon actuation to place said main valve in said ON and said OFF positions, respectively;

a first pilot valve actuating means for actuating said first pilot valve and a second pilot valve actuating means for actuating said second pilot valve;

means for delivering said gating signal to said first actuating means and means for delivering said timing signal to said second actuating means, said first actuating means being operative in receipt of said gating signal to actuate said first pilot valve so that said main valve is placed in said ON position; and

said second actuating means being operative in response to said timing signal to actuate said second pilot valve for placing said main valve in said OFF position.

3. The apparatus of claim 2 including a means for delivering said timing signal to said first actuating means, said first actuating means being operative in response to receipt of said timing signal to deactuate said first pilot valve.

4. The apparatus of claim 2 wherein said first and second actuating means are comprised of solenoids.

5. The apparatus of claim 2 wherein said second actuat ing means includes a solenoid and energizing means operative in response to receipt of said timing signal for energizing said solenoid.

6. The apparatus of claim 5 wherein said energizing means is comprised of a single shot multivibrator.

7. The apparatus of claim 1 wherein said timing means includes means for selectively varying the time duration between the initiation of the operation thereof and the generation of said timing signal.

8. The apparatus of claim 7 wherein said spraying means is comprised of a nozzle having the flow of coating material therethrough controlled by a main valve having an ON position and an OFF position;

first and second pilot valves operative upon actuation to place said main valve in said ON and said OFF positions, respectively;

a first pilot valve actuating means for actuating said first pilot valve; and a second pilot valve actuating means for actuating said second pilot valve;

means for delivering said gating signal to said first actuating means and means for delivering said timing signal to said second actuating means, said first actuating means being operative on receipt of said gating signal to actuate said first pilot valve so that said main valve is placed in said ON position; and

said second actuating means being operative in response to said timing signal to actuate said second pilot valve for placing said main valve in said OFF position.

9. The apparatus of claim 8 including a means for delivering said timing signal to said first actuating means, said first actuating means being operative in response to receipt of said timing signal to deactuate said first pilot valve.

10. The apparatus of claim 8 wherein said first and second actuating means are comprised of solenoids.

11. The apparatus of claim 8 wherein said second actuating means includes a solenoid and energizing means operative in response to receipt of said timing signal for energizing said solenoid.

12. The apparatus of claim 11 wherein said energizing means is comprised of a single shot multivibrator.

13. The apparatus of claim 1 wherein said means for producing said second signal includes a proximity sensor and a bistable flip-flop, said proximity sensor being operative in response to the proximity of an article to be coated for generating a SET signal to said flip-flop, and said flip-flop being operative in response to receipt of said SET signal for generating said second signal.

14. The apparatus of claim 13 wherein said first signal producing means includes a means for generating a cycletime signal when said apparatus is adapted to position an article at said coating position;

a second flip-flop and means for delivering said cycletime signal to a SET input on said second flip-flop to produce said first signal at an output of said flip-flop.

15. The apparatus of claim 14 including a means for resetting the first and second flip-flops.

16. The apparatus of claim 15 wherein said reset means is comprised of:

an inverter;

a single shot multivibrator;

means for delivering said cycle-time signal to said inverter; means for delivering the output of said inverter to:

(i) a reset input on said second flip-flop; and (ii) said single shot multivibrator; and

means for delivering an output signal from said single shot multivibrator to a reset input on said flip-flop. 17. The apparatus of claim 16 wherein said timing means includes a means for varying the time duration between receipt of said signal from said gating means and the generation of said timing signal;

a reset means; and

means for delivering said output signal from said single shot multivibrator to said timer reset means for resetting said timer.

18. The apparatus of claim 14 wherein said spraying means is comprised of:

a nozzle having the flow of coating material therethrough controlled by a main valve having an ON position and an OFF position;

first and second pilot valves operative upon actuation to place said main valve in said ON and said OFF positions, respectively;

a first pilot valve actuating means for actuating said first pilot valve; and a second pilot valve actuating means for actuating said second pilot valve;

means for delivering said gating signal to said first actuating means and means for delivering said timing signal to said second actuating means, said first actuating means being operative in response to receipt of said gating signal to actuate said first pilot valve so that said main valve is placed in said ON position; and

said second actuating means being operative in response to said timing signal to actuate said second pilot valve for placing said main valve in said OFF position.

19. The apparatus of claim 18 including a means for delivering said timing signal to said first actuating means, said first actuating means being operative in response to receipt of said timing signal to deactuate said first pilot valve.

20. The apparatus of claim 18 wherein said first and second actuating means are comprised of solenoids.

21. The apparatus of claim 18 wherein said second actuating means includes a solenoid and energizing means operative in response to receipt of said timing signal for energizing said solenoid.

22. The apparatus of claim 21 wherein said energizing means is comprised of a single shot multivibrator.

References Cited UNITED STATES PATENTS 2,103,270 12/1937 Murch 11s 31s X 3,356,061 12/1967 Wiggins 118-2 JOHN P. McINTOSH, Primary Examiner US. 01. X.R. 00 11s 9, 31s

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