US3719164A

US3719164A - Dip coating apparatus including fluid doctor means

Info

Publication number: US3719164A
Application number: US00141941A
Authority: US
Inventors: G Hoffman; J Tench
Original assignee: Sun Oil Co
Current assignee: Sunoco Inc
Priority date: 1971-05-10
Filing date: 1971-05-10
Publication date: 1973-03-06
Anticipated expiration: 1990-03-06

Abstract

In the coating of sheet articles such as corrugated cardboard container blanks by immersing the articles in a bath of molten coating material, air is blown over the articles while they are being withdrawn from the bath, the air flow being in the same direction as the flow of coating material as it drains from the articles. Means correlate article immersion and actuation of the air flow.

Description

United States Patent Hoffman et a1.

[ 51 March 6, 1973 [54] DIP COATING APPARATUS 2,267,597 12/1941 Neville et a1 ..117/113 X INCLUDING FLUID DOCTOR MEANS ,330,124 9/1943 2,415,644 2 1947 [75] Inventors: George E. Hoffman, Media; John D. 3,232,680 241966 TEIICII, Springfield, both Of Pa. 3 312 5 4 19 7 73 A u f P 3,499,418 3 1970 1 Sslgnee izz' g fig gzf' o ennsylvama 3,681,118 8/1972 Ohama et a1. ..118/63 x 22 i May 10 1971 FOREIGN PATENTS OR APPLICATIONS [21] App1.N0.: 141,941 78,732 10/1919 Germany ..118/63 Related Applicafilm Data Primary Examiner-Morris Kaplan [631 Continuation of Ser. No. 826,431, May 21, 1969, Attorney-Frank Rechf abandoned.

[57] ABSTRACT [52] US. Cl. ..118/6, 118/63, ll318/425, In the coating of sheet articles such as corrugated l B 4 cardboard container blanks by immersing the articles 2; 4 in a bath of molten coating material, air is blown over 1 0 l 1 /6 7 1/ the articles while they are being withdrawn from the bath, the air flow being in the same direction as the flow of coating material as it drains from the articles. [56] References C'ted Means correlate article immersion and actuation of UNITED STATES PATENTS thew 1,692,286 11/1928 Brogden ..117/102 R X 4 Claims, 7 Drawing Figures l 1 20 26 (a-i; "& A 1 I M I w 4 2/ I I L .1,: I: T ,i iii-:1

PATENTED 6W5 3,719,164

SHEET 10F 5 FIG]. 56

a 26 57 I 4.4 23 X 24 I INVENTORS GEORGE E. HOFFMAN JOHN D. TENCH sowem ATTY.

PATENTEB R 6 73 SHEET 2 OF 5 FIGZ.

FIGS

a Mm mm EC- VF m0 H E E G R O E G JOHN D. TENCH ATTV.

PATENTEDHAR ems 3.719.164

SHEET 30F 5 FIGB.

OIOOOOOOOOOOOOOD ofiobooaafiuooooa INVE NTORS GEORGE E.HOFFMAN JOHN D- TENCH BYQLnA-AMKI PATENTEUHAR 61m 3,719,164

SHEET NF 5 FIGA.

INVEN OR SI GEORGE E. HOFFMAN JOHN D. TENCH PATENTED 61975 3,719,164

sum 50F 5 FIG.7.

FROM

AC. SUPPL TIME DELAY TIME DELAY FAN F'A N INVE NTORS.

GEORGE E. HOFFMAN JOHN ENCH

DIP COATING APPARATUS INCLUDING FLUID DOCTOR MEANS This application is a continuation of Ser. No. 826,431 filed May 2 l 1969 now abandoned.

This invention relates to apparatus for coating sheet articles of extensive surface area, such as corrugated cardboard container blanks, with a material such as wax.

Wax-coated containers formed from corrugated cardboard are useful for various purposes, such as the transportation of perishable commodities, packed in ice, from farms or processing plants to market. According to prior practice, the corrugated cardboard container manufacturer generally impregnated or coated the container blanks or flats with wax, and then shipped them in the flat or unformed condition to the container user (such as a farmer or food processor). The latter, at some later time, formed the blanks or flats into containers (securing them in this form by stapling, for example), and then packed them with the perishable commodity to be transported, packed in ice.

The prior practice has several disadvantages or drawbacks. Pre-waxing by the corrugated cardboard manufacturer usually requires the use of high-melt, brittle waxes, in order to avoid blocking of the blanks (sticking together when stacked) in shipment and storage. However, when blanks coated with brittle wax are formed into cartons, the surface coating often cracks, such as along the score lines, allowing moisture to enter at such cracks and reducing the wet strength of the carton; this can cause box failure.

The above-mentioned disadvantages or drawbacks may be alleviated by on-site wax coating (that is, by wax-coating or wax-impregnating the corrugated cardboard container blanks or flats at the point of use, im-

mediately prior to the forming of these blanks into containers). In the chilled edible commodity business, this would mean that the wax-coating of the flats would be done by the farmer or food processor. If this procedure is followed, the sticking of the blanks in storage is eliminated, and low-melt flexible waxes can be used, thereby avoiding any danger of cracking of the coating when the containers are formed; the containers,

ideally, can be formed while the wax coating is still warm, which is highly desirable.

An object of this invention is to provide a novel coating apparatus.

A further object is to provide a wax-coating apparatus which is relatively inexpensive and simple to operate, and is therefore particularly suitable for the on-site wax coating of corrugated cardboard containers.

The objects of this invention are accomplished, briefly, in the following manner: The corrugated container blanks or flats to be wax-coated are loaded into a supporting rack which is lowered into a vat containing molten wax and then, after a timed immersion, is raised upwardly, out of the vat. Fans are mounted above the rack, these fans being turned on preferably while the rack with its load is being raised upwardly, to blow a (cooling) stream of air over the blanks or flats in the same direction as the wax flows in draining from the blanks back into the vat.

A detailed description of the invention follows, taken in conjunction with the accompanying drawings, wherein:

FIG. I is a front elevation (partially broken away to show interior details) of a coating apparatus according to this invention;

FIG. 2 is a horizontal section taken along line 2-2 of FIG. 1;

FIG. 3 is a top or plan view of the apparatus of FIG.

FIG. 4 is a side view (partially broken away) of the apparatus of FIG. 1;

FIG. 5 is a section taken along line 5-5 of FIG. 1; FIG. 6 is a section taken along line 66 of FIG. 5; and

FIG. 7 isa schematic of electrical circuitry used in the apparatus of this invention.

Referring now to the drawings, an open-topped vat l of rectangular prismoidal configuration, is suitably formed from structural steel framing members welded together, to which are welded steel wall plates to form the side and bottom walls of the vat, the whole being welded together in a water-tight manner. This vat is adapted to contain a molten bath of a coating material such as wax, of sufficient depth to allow the complete immersion therein of the sheet articles (corrugated cardboard container blanks ro flats) which are to be wax-coated. The wall plates are preferably covered with a layer of heat-insulating material (not shown), over the outside of which is a thin sheet metal jacket.

At one end of the vat, a relatively narrow portion of the same is divided off by means of a vertically extending rectangular plate 2 which extends across the entire width of the vat but has a height less than that of the vat, leaving spaces at the top and bottom of the vat. Plate 2 is welded along its side edges to the vat. The spaces at the top and bottom of the vat are filled in by rectangular sheets 48 and 49, respectively, of expanded metal which are welded to the adjacent (upper and lower) ends of plate 2. Plate 2, and the sheets 48 and 49, partition off a melt section 3 at one end of the vat, which section communicates with the remainder of the vat by way of the expanded metal sheets 48 and 49. A so-called plate coil 4 is mounted in the melt section 3, as by means of suitable hangers secured to plate 2. Plate coil 4 is a commercially available item based on pipes, and is intended for the steam heating of fluids. Plate coil 4 is supplied with steam by means of an inlet pipe 5 which is connected by way of a pipe union 13 to one end of coil 4 and which is sealed through a side wall of the vat l, at the melt section end. The opposite end of coil 4 is connected through a pipe union 14 to a short piece of pipe 6 which passes through the lower expanded metal sheet 49 to the other, and larger, portion of the vat.

When the coating apparatus of the invention is in use, the steam supplied to coil 4 provides heat for melting slabs of wax which are dropped into the melt section 3 via the open upper end thereof. These slabs are added by the operator to the vat l as necessary, to maintain the level of the wax in the vat at an appropriate height.

A pipe, schematically illustrated at 7, may extend through the end wall of the vat l at the melt section end, near the top of the vat proper, to enable molten wax to be supplied to the vat automatically, when desired, instead of manually adding slab wax to the vat. When this bulk supply arrangement is not being used,

the outer end of pipe 7 is closed off by means of a suitable cap.

The remainder and larger section of the vat l proper may be termed the holding section 8, wherein the wax is held in a hot, liquid state, and wherein the said articles to be coated (e.g., corrugated cardboard container blanks or flats) are dipped or immersed. Within the holding section 8, a plate coil 9 is mounted slightly above the bottom wall of the vat. Plate coil 9 is similar in construction to plate coil 4, though different in size. The pipe 6 (which is supplied with steam by way of the coil 4) is connected by way of a pipe union 10 to the inlet end of plate coil 9, and the outlet end of this coil is connected by way of a pipe union 1 l to a small-diameter condensate discharge pipe 12 which passes through the sheet 49 andis sealed through the end wall of the vat at the melt section end thereof. Pipe 12 may lead to a sewer, or it may lead to the steam boiler feed water pump. When the coating apparatus of this invention is in use, the steam supplied to plate coil 9 provides heat for maintaining the wax in vat l in a liquid condition, the coil 9 being located within the holding section of the vat, in direct thermal contact with the wax.

A holder for a temperature sensor (e.g., a bimetallic I thermostatic element) is provided in the melt section 3 of the vat, in the form of a pipe nipple schematically illustrated at 50 (FIG. 4). A temperature sensor (not shown) is connected to a valve operator for a-valve in the steam supply line, the operation being such that the steam valve is made temperature-responsive; in this way, the temperature of theliquid wax in vat 1 is maintained substantially constant. A similar holder (not shown) is provided in the holding section 8 of the vat, so that the temperature sensor may be placed in this section if desired, instead of in the melt section 3.

A standard pipe sump 15 is provided in the bottom wall of vat l, and the inner end of a drain pipe l6is connected to the sump; pipe 16 is sealed through the end wall of the vat. A valve (not shown) may be provided on the outer end of drain pipe 16; this valve may be opened periodically to check for the presence of extraneous (and undesired) water in the sump 15.

A rectangular sheet 17 of expanded metal is laid on top of the plate coil 9, for protective purposes. This sheet 17 covers substantially the entire cross-sectional area of the holding section 8, inside the vat.

A superstructure, denoted generally by numeral 18, is mounted on the upper end walls of vat 1, above the upper open end of the vat. The superstructure 18 has the general form of a horizontal, substantially planar framework 19 of rectangular configuration, to the four cornersof which are secured respective downwardlyextending legs whose lower ends are in turn secured to the respective upper corners-of vat 1. Near one end of the framework 19, a transversely extending shaft 20 is supported and journaled for rotation by a pair of pillow blocks (bearings) 21 which are secured to respective opposite sides of the framework 19, and also by another pillow block 51 secured to the framework near the center thereof. Shaft 20 is journaled in the pillow blocks 21 and 51. A pair of

guide wheels

22 and 22 are fastened to shaft 20 near the respective opposite ends thereof, within framework 19:

Near. the other end of framework 19, a transversely extendingshaft 23 is supported and journaled for rotation by a pair of pillow blocks (bearings) 24 which are similar to blocks 21 and which are similarly secured to respective opposite sides of the framework 19. The two ends of shaft 23 are journaled in the respective pillow blocks 24. Shaft 23 is further supported by another pair of pillow blocks (bearings) 25 similar to

blocks

21, 24, and 51 secured to framework 19 near the longitudinal center line of the framework. A two-section wire rope (cable) drum 26 is fastened to shaft 23 near one end thereof, one section of this drum being in alignment with guide wheel 22, which latter is at the other end of the framework 19. A similar two-section wire rope (cable) drum 26' is fastened to shaft 23 near the other end thereof, one section of this latter drum being in alignment with guide wheel 22', which latter is at the other end of the framework 19.

One end of a length of wire rope (3/l6-inch steel cable) 27 is secured to drum 26, this cable being wound around one section of drum 26 and then extending to the opposite end of the framework 19, where it passes over guide wheel 22 and extends vertically downwardly to provide a first hoisting connection at its free end 28. Similarly, one end of a length of wire rope 29 is secured to drum 26', this rope being wound around one section of drum 26' and then extending to the opposite end of the framework 19, where it passes over guide wheel 22' and extends vertically downwardly to provide a second hoisting connection at its free end 30.

One end of a shorter length of wire rope 31 is secured to drum 26, this rope being wound around the other section of drum 26 and then extending directly downwardly from this drum to provide a third hoisting connection at its free end 32. Similarly, one end of a length of wire rope 33 is secured to drum 26', this rope being wound around the other section of drum 26' and then extending directly downwardly from this drum to provide a fourth hoisting connection at its free end (not shown).

The reeling arrangement of the

wire ropes

27, 29, 31 and 33 is such that rotation of shaft 23 in one direction causes the freeends of all four of these ropes to move upwardly at the same rate as one another, and rotation of shaft 23 in the opposite direction causes the free ends of all four of these ropes to move downwardly at the same rate as one another.

Shaft 23 is rotatably driven by means of a reversible electric motor 34, which is mounted on framework 19 and which drives a sprocket 35 through a worm gear reducer 36 also mounted on framework 19. The sprocket 35 is coupled through a drive chain 37 to a sprocket 38 which is fastened to shaft 23, between the bearings 25.

A hoisting rack and carton loading assembly, denoted generally by numeral 39, is utilized for immersing the sheet articles to be wax-coated in the liquid wax and for withdrawing or removing them therefrom. The rack portion of assembly 39 essentially comprises a substantially planar horizontal rack formed by crossmembers welded or otherwise rigidly secured. together to provide a grill-like structure having a rectangular configuration, and four small apertured plate members 40, one secured to each respective corner of the planar rack and extending outwardly with respect thereto. The rack is so dimensioned as to permit immersion thereof in the holding section 8 of vat l. The four members 40 are vertically aligned respectively with the downwardly depending free ends of the

wire ropes

27, 29, 31, and 33, and the free ends of these cables are attached to the respective members 40, the ends of these cables looping through holes provided in the respective members 40. Thus, the assembly 39 is arranged to be lifted or lowered as a unit by the hoist motor 34, acting through the wire rope reeling arrangement previously described.

The carton holding portion of the assembly 39 includes two rows of separator members 41. The members 41 have the shape of inverted Vs, and the free ends of the Vs are welded to horizontally extending supporting members, so as to maintain these separator members fixed in position. The supporting members are bolted or otherwise suitably secured to the grill-like structure or rack or assembly 39. One row of members 41 comprises a plurality of spaced, parallel members (spaced 96-inch apart, by way of example) which are aligned to form a row in the direction of the length of the assembly 39 (and in the direction of the length of the vat 1), on one side of the longitudinal center line of this assembly and of the vat, and the other row of members 41 is similar but is on the other side of the longitudinal center line of assembly 39 and of the vat (see FIG. 4, wherein the ends of the two rows may be seen). Thus, two carton holders are provided; each carton holder provides space for a large number of carton blanks or flats, each flat being inserted into the space between two adjacent members 41, in the same row.

In operation, the raw or uncoated sheet articles to be wax-coated (corrugated cardboard container blanks or flats) are loaded into the slots between adjacent separator members 41, with the flutes up. Then the assembly 39 is lowered as a unit into the vat l (as will be further described hereinafter), to immerse the blanks completely in the liquid wax contained in vat 1. After a preset time interval, the assembly 39 with its load of dip-coated blanks is raised upwardly out of the vat, to permit the articles to drain. Normally, only one of the rows (of separator members 41) is active at a time, for dip-coating. Thus, while the row of blanks which has been dip-coated is draining and cooling (after having been raised out of the vat), blanks to be coated are loaded into the other (then empty) row; following this, the coated blanks are removed from their row, emptying this latter row. The assembly 39 is then lowered into the vat with one empty row and one loaded row, for dip-coating of the blanks in the latter row, and so on.

The assembly 39 is constrained to move vertically upwardly and downwardly, and thus into and out of vat l, by means of a pair of vertically extending guide bars 56 and 57, guide bar 56 being secured to one side wall of the vat, inside the same, and guide bar 57 being secured to sheet 49, plate 2, and sheet 48, on the holding section side of the latter.

Bars

56 and 57 are in alignment with each other, in the length direction of the vat, and these bars fit rather closely (but slidably) within respective outwardly facing exterior notches provided on the hoisting rack portion of assembly 39. By this arrangement, sidewise movement of the assembly 39, as it travels up and down, is prevented.

A lower limit switch 42 is mounted on framework 19, near guide wheel 22, the actuator 43 of this switch being located closely adjacent the wire rope 27, in such a position that switch 42 can be actuated or tripped by a tripper 44 clamped on this rope and moving therewith. Tripper 44 is adapted to come into engagement with switch actuator 43, thereby to actuate switch 42, when the assembly 39 reaches the desired lower limit of its travel, which signifies the complete immersion in the vat l of the sheet articles (carton blanks), when the bottom of assembly 39 is just above the protecting sheet 17 in the vat.

An upper limit switch 45 is mounted on framework 19, near drum 26', the actuator 46 of this switch being located closely adjacent the wire rope 29, in such a position that switch 45 can be actuated or tripped by a tripper 47 clamped on this rope and moving therewith. Tripper 47 is adapted to come into engagement with switch actuator 46, thereby to actuate switch 45, when the assembly 39 reaches the desired upper limit of its travel, which signifies the compete withdrawal from the vat l of the sheet articles. In this limiting position, the blanks may be removed from the carton holding portion of the assembly 39.

In connection with the operation of the switches 42 and 45, it is pointed out that the

wire ropes

27 and 29 move toward the right in FIG. 3 when the assembly 39 moves downwardly, and these wire ropes move toward the left in FIG. 3 when the assembly 39 moves upwardly.

The method of this invention includes the blowing of air over the coated articles, in the same direction as that in which the coating material (wax) drains off the articles back into the vat, preferably during the lifting of the dip-coated articles out of the coating vat. This air flow enhances greatly the uniformity of the coating of the articles (corrugated cardboard container blanks), from top to bottom of such articles; in addition, this air flow produces an additional cooling effect on the blanks, thus decreasing the time required for cooling and hasteningthe drying of the wax coating.

The air flow just referred to is provided by one set 52 of three blower means (fans) which are mounted in a side-by-side array (parallel to the longitudinal center line of the vat) above one row of separator members 41, and by another set 53 of three similar fans which are mounted in a similar array (also parallel to the longitudinal center line of the vat) above the other row of separator members 41. The fans 52 are mounted in a suitable frame 54 which is fastened to framework 19 on one side of the longitudinal center line of this framework, and the fans 53 are mounted in a similar frame 55 fastened to framework 19 on the other side of the longitudinal center line of this framework. Hoist motor 34 and gear reducer 36 are centered on the framework longitudinal centerline, and the drive chain 37 is close to this center line; thus, there is no inter- .ference between the fans 52-53 and the carton raising vertically aligned with the carton raising and lowering mechanism. To overcome this, and to provide a substantially uniform flow of air from the fans over the cross-sectional area of the blanks being wax-coated,

each of the

frames

54 and 55 is provided with a slotted arrangement (not shown) at each end, whereby each set of three fans (52 or 53) may be adjustably and independently tilted toward the longitudinal center line of the framework 19, so that air will be blown by the fans into the region below the carton raising and lowering mechanism. The fans, once adjusted, may be secured in this tilted position.

Each of the fans 52-53 is of conventional design, and each is driven by its own electric motor located above the respective fan and directly mechanically coupled thereto. The fans 52-53 are preferably energized while the coated articles (corrugated cardboard container blanks) are being drawn upwardly, out of the vat.

As has been stated, the fans 52-53 are preferably turned on during the period of raising the sheet articles (container blanks) out of the liquid wax which is contained in the holding section 8 of vat 1. When the blanks are raised out of the vat, the wax flows downwardly, as it drains off the blanks back into the vat. The fans are arranged to blow air downwardly over the blanks, from their positions in the superstructure 18, above the vat proper; thus, the fans blow cooling air over the blanks in the same direction as the wax flow (that-is, in the drainage direction of the wax).

What is desired, in the wax coating of corrugated cardboard container blanks or similar sheet articles, is to obtain a uniform distribution of wax throughout the blank, and specifically from top to bottom of the blank, the terms top and bottom in this context referring to the blank as it is positioned in the carton holding portion of assembly 39, in the space or slot between two adjacent ones of members 41.

It has been found that, by utilizing an air flow over the blanks according to this invention, an essentially constantdistribution of wax, from top to bottom of the blank, can be obtained, the wax distribution being much more uniform than what it would be if this air flow were not used. This is shown by actual test results, set forth in Table I following.

Referring to the above table, Percent Wax Pickup is the ratio (expressed in percent) of the final (coated) weight of a blank minus the original (uncoated) weight thereof, to the original weight. The values for the final weights of the blank were obtained by cutting a coated blank into equal thirds, from top to bottom, and weighing the pieces separately (it being assumed that the original weights of these pieces were each equal to one-third of the total weight of the uncoated blank, which is a quite valid assumption).

The improved uniformity of the wax coating, from top to bottom of the blank, obtained by the use of fans, as compared to the wax coating distribution obtained by the same method without the use of fans, is strikingly demonstrated by the above table. For example, at 183 F. the difference in the percentage of wax pickup from top to bottom of the blank, without fans, was 12.5 (55.0 42.5), while with fans, this difference was only 3.7 (56.2 52.5). A similar improvement obtained by the use of fans may be noted at 179 F.

In connection with Table I above, it is pointed out that the With .Fans values were measured using a setup wherein the fans were blowing air down over the blanks, that is, in the same direction as the wax flow. Poor results (as to uniformity of the coating) were obtained when the air flow was in other directions, such as upwardly rather than downwardly, and sideways instead of downwardly. Thus, the downward direction of air flow is quite important and significant.

It is pointed out that the temperature of the air (at ambient temperature) which is blown downwardly by the fans 52-53 over the coated blanks (from top to bottom of the latter) is lower than the temperature of the liquid wax in vat 1. This flow of cooling air over the blanks, preferably as they are being raised out of the vat, hastens the cooling or setting of the coating. This greatly decreases the time required for cooling, and thus permits an increased rate of production of wax-coated blanks. This increased rate of cooling of the dip-coated blanks is an additional advantage (additional to the increased uniformity of coating) obtained by blowing air over the blanks as they are being lifted out of the dipping vat. i'

A cabinet 60, containing various electrical components such as starters, relays, fuses, etc. (which will be described in more detail hereinafter, in connection with FIG. 7) is mounted on the superstructure 18 near the upper framework 19, at the end of the vat opposite to melt section 3 (see FIGS. 1 and 3). Preferably, the entire end area of the superstructure 18, at this end of the vat, is closed, the area not occupied by the imperforate cabinet 60 being closed by means of sheet metal panels or closures (not shown). This prevents air driven by the fans 52-53 from passing out this end of the superstructure, and from thus being diverted outwardly, away from the container blanks or flats being coated. At the opposite end of the superstructure, adjacent the melt section 3, the end area of the superstructure 18 above a cross bar 61 is closed by similar sheet metal panels or closures (not shown), to prevent undesired diversion of the fan-driven air. At this latter end, the area of the superstructure 18 below bar 61 is left open, to permit wax slabs to be added as necessary to the melt section 3 of the vat.

A pair of

pushbutton control boxes

58 and 59 are provided for the control of the wax-coating apparatus, one control box being mounted at each respective side of the apparatus, where it can easily be reached after a corresponding row of the carton holding portion of assembly 39 has been loaded or unloaded, as the case may be. The

boxes

58 and 59 are mounted on respective corner legs of the superstructure 18, at the melt section end of the vat.

Each of the

control boxes

58 and 59 has a total of three pushbuttons,

pushbuttons

62, 63, and 64 being mounted in box 58 and

pushbuttons

65, 66, and 67 being mounted in box 59.

Refer now to FIG. 7. The hoist motor 34 is energized from a three-phase a.c. power supply or source (230 volts) through a reversing starter illustrated as a pair of

relays

68 and 69. When relay 68 is energized to close its three pairs of

power contacts

70, 71, and 72, the feed from the power source is straight through and the motor 34 is energized to rotate shaft 23 in a predetermined direction, such as to raise the assembly 39. Conversely, when relay 69 is energized to close its three pairs of

power contacts

73, 74, and 75, the phase of the power fed to two of the three motor terminals is reversed, and the motor 34 is energized to rotate shaft 23 in the opposite direction, such as to lower the array 39. The

relays

68 and 69 are mechanically interlocked in a conventional manner (not shown), such that only one of these relays can be energized at a time, and are also electrically interlocked by providing relay 68 with a pair of normally closed contacts 76 which are connected in series with the winding of relay 69, and by providing relay 69 with a pair of normally closed contacts 77 which are connected in series with the winding of relay 68.

A stepdown transformer 78, whose primary is connected across one of the phases of the three-phase supply, provides power in its secondary for control purposes. The two

Stop pushbuttons

64 and 67, one of which is in box 58 and the other of which is in box 59, are connected in series between one end of the secondary of transformer 78 and a circuit point 79; these pushbuttons are of the normally closed, push-to-open type.

The two Lower or Automatic Start"

pushbuttons

63 and 66, one of which is in box 58 and the other of which is in box 59, are connected in parallel between point 79 and one terminal of the normally-closed switch arrangement 42' of lower limit switch 42; switch arrangement 42' is normally closed, but opens when switch 42 is tripped or actuated by tripper 44 (FIG. 3). The other terminal of arrangement 42' is connected through the normally closed contacts 76 of raise relay 68 and the operating winding of lower relay 69 to the opposite terminal 80 (i.e., opposite to point 79) of the control power source (secondary of transformer 78). The normally open contacts 81 of relay 69 are connected across the

pushbuttons

63 and 66, and serve to lock in relay 69 when this relay is energized.

The two

Raise pushbuttons

62 and 65, one of which is in box 58 and the other of which is in box 59, are connected in parallel between point 79 and one terminal of the normally closed switch arrangement 45' of upper limit switch 45; switch arrangement 45' is normally closed, but opens when switch 45 is tripped or actuated by tripper 47. The other terminal of arrangement 45' is connected through the normally closed contacts 77 of lower relay 69 and the operating winding of raise relay 68 to terminal 80. The normally open contacts 82 of relay 68 are connected across the

pushbuttons

62 and 65, and serve to lock in relay 68 when the latter is energized.

From one terminal of the secondary of transformer 78, a connection extends through the switch arrangement 42" of lower limit switch 42 and the operating winding of a dipping time delay relay 83 to the opposite secondary terminal 80. Switch arrangement 42" is normally open, but closes when switch 42 is tripped or actuated by its tripper 44. The series combination of a manual-automatic" selector switch 84 and the normally open contacts of relay 83 is connected across the

Raise pushbuttons

62 and 65. Selector switch 84 is located, physically, on the cover of cabinet 60 and, once the apparatus has been properly set up and is operating, is normally in the automatic or closed position illustrated.

A brake 86, which is more or less conventional, is mechanically coupled to motor 34 and is electrically operated in such a way that it is actuated or rendered operative when this motor is deenergized, being ineffective when this motor is energized.

The time delay afforded by relay 83 (between the energization of its coil or winding and the closing of its contacts 85) is mechanically adjustable or settable over a certain range, such as from 6 to 106 seconds; a typical setting may be 30 seconds.

Assume that the wax-coating apparatus of this invention has been properly adjusted and set up for automatic operation; switch 84 is then closed as illustrated. When the assembly 39 is in its raised position, ready for loading, the upper limit switch 45 is tripped or actuated, so that switch arrangement 45' is open.

When one or the other of the two rows of separator members 41 has been properly loaded with raw or uncoated blanks, one or the other of the two Lower or Automatic Start pushbuttons 63 or 66 (whichever one is then more convenient) is operated. Closure of either pushbutton 63 or pushbutton 66 completes an energization circuit for the lower relay 69, as follows: lefthand end of the transformer 78 secondary,

closed pushbuttons

64 and 67, pushbutton 63 (or 66), switch arrangement 42' (now closed), closed contacts 76 of relay 68, coil or relay 69, to terminal 80. Relay 69 then operates to close its

power contacts

73, 74, and 75, energizing motor 34 in the sense to lower the assembly 39. Once energized, relay 69 locks itself in through its closed contacts 81, which maintain the energization circuit for relay 69 closed even though the

pushbutton

63 or 66 is released.

The motor 34 continues to lower the assembly 39 into the vat until such assembly reaches the desired lower limit of its travel, at which time the lower limit switch 42 is tripped, opening the switch arrangement 42' and deenergizing relay 69, which stops the motor. The tripping of lower limit switch 42 also closes the switch arrangement 42", which energizes the coil of time delay relay 83, through an obvious circuit.

After the time delay set into relay 83 has elapsed, its contacts 85 close, completing an energization circuit for the raise relay 68, as follows: point 79 (

pushbuttons

64 and 67 remaining closed), relay contacts 85, closed switch 84, switch arrangement 45' (now closed, since upper limit switch 45 reverts to its untripped position soon after the assembly 39 starts downwardly), closed contacts 77 of relay 69, coil of relay 68, to terminal 80. Relay 68 then operates to close its

power contacts

70, 71, and 72, energizing motor 34 in the sense to raise the assembly 39. Once energized, relay 68 locks itself in through its closed contacts 82, which maintain the energization circuit for relay 68 closed even though the lower switch arrangement 42" opens (releasing relay 83) when the lower limit switch 42 reverts to its untripped position, soon after the assembly 39 starts upwardly.

The motor 34 continues to raise the assembly 39 out of the vat until such assembly reaches the desired upper limit of its travel, at which time the upper limit switch 45 is tripped, opening the switch arrangement 45' and deenergizing relay 68, which stops the motor. When this upper limit of travel of the assembly 39 is reached, the coated blanks have been raised to aposition such that they can be removed from the separator members 41.

The foregoing has described the circuit operation of merely the carton raising and lowering portion of the apparatus, and has not included the fans of this invention. The operation of the latter will now be described.

As previously mentioned, the carton holding portion of the assembly 39 is provided with two parallel rows of separator members 41, one row being adjacent to and accessible (for article loading and unloading purposes) from each side of the vat. Also, it will be recalled that one such row of separator members 41 is located below the array or set of three fans 52, and the other row is located below the array or set of three fans 53. For convenience in the following description, the set of fans 52 may be thought of as located adjacent the A Side of the apparatus, and the set of fans 53 located adjacent the B Side of the apparatus.

Refer again to FIG. 7. The two opposite terminals for the control power (115 volts) may be circuit point 87, which is at one end of the secondary of transformer 78, and circuit point 80, which is at the other end of this transformer secondary and is grounded. Point 87 is connected through a pair of parallel-connected switches 88 and 89 to a bus 90. Switches 88 and 89 form part of a fan selector switch which is mounted on the cover of cabinet 60 and will later be referred to in more detail; one or the other of the switches 88, 89 is closed at all times, except when the fans are turned off by this selector switch, so bus 90 can be considered to be energized whenever the fans are operative. A bus 91 is connected to the grounded terminal 80 and provides the other bus for the control power.

The time delay relay 83, in addition to its contacts 85, has another pair of normally open contacts 92 which are closed when relay 83 operates. in this connection, it will be recalled that relay 83 is the dipping time delay relay, and when its contacts 85 close the hoist motor 34 is energized to begin raising the assembly 39 (and the sheet articles carried thereby) out of the vat 1. Thus, contacts 92 close at the time the assembly 39 begins to move upwardly.

The closing of contacts 92 connects a coil (clutch) 92 across buses 90 and 91, energizing this coil. The energization of coil 93 causes. instantaneous closure of a pair of movable arms 94 and 95 on their fixed

contacts

96 and 97, respectively; the arms 94 and 95 are both connected to bus 90.

The closing of arm 95 on contact 97 provides a shunt across contacts 92 by way of a movable arm 98, which is closed at this time on its fixed contact 99, and a lead 100; this circuit maintains coil 93 energized as long as arm 98 remains on contact 99 (independently of contacts 92, which open when relay 83 is deenergized as a result of the opening of the lower-limit-switch contact 42" when assembly 39 moves upwardly). The closing of arm 95 on contact 97 also energizes a delay timing motor 101 (which determines the running time of the fans), by way of arm 98, contact 99, and a lead 102. In

this connection, it will be noted that one end of coil 93, and also one terminal of motor 101, are connected to bus 91. The motor 101, after a preset time delay (settable over a range of thirty seconds to 6 minutes), moves arm 98 away from its contact 99, and also moves an arm 103 away from its fixed contact 104; arm 103 is normally closed on contact 104, as is arm 98 on contact 99.

The closing of arm 94 on contact 96 (which occurs when assembly 39 begins to move upwardly, as previously described) completes an energization circuit for the coil of a fan start time delay relay 105, through arm 103, closed on contact 104. After a short time delay, on the order of 2 second, for example, relay 105 closes its normally open contacts 106, which completes a circuit to one of the two fan motor starters (illustrated as relays 107 and 108), the particular fan motor starter energized being determined by the position of a movable switch arm 109 which will be later referred to. In FIG. 7, arm 109 is on its contact 110, so that a circuit is completed to the A Side fan motor starter 107, as follows: bus 90, arm 94, contact 96, arm 103, contact 104, closed contacts 106, arm 109, contact 110, winding of relay 107, bus 91.

The energization of starter-relay 107 causes closure of its three pairs of normally open power contacts 111,- 112, and 113, thereby to supply power from the threephase power source to the

conductors

114, 115, and- 116' which are connected in single-phase fashion to feed power through the respective hi-off-

lo switches

117, 118, and 119 to the

individual fans

52,, 52,, and 52, of Side A. Thus, assuming the switches 117-119 are all in either their hi or 10 positions, the

fans

52,, 52,, and52 are all started when relay'105 closes its contacts 106.

If arm 109 is on its other contact 120 when relay contacts 106 close, a circuit is completed to the B Side fan motor starter 108, as follows: bus 90, arm 94, contact 96, arm 103, contact 104, closed contacts 106, arm 109, contact 120, winding of relay 108, bus 91. In this case, the energization of starter-relay 108 causes closure of its three pairs of normally

open power contacts

121, 122, and 123, thereby to supply power from the three-phase power source to the

conductors

124, 125, and 126 which are connected in single-phase fashion to feed power through the respective hi-off-

lo switches

127, 128, and 129 to the

individual fans

53,, 53,, and 53;, of Side B. Assuming the switches 127-129 are all in either their hi or 10 positions, the

fans

53,, 53,, and 53;, would in this case all be started when relay 105 closes its contacts 106.

Whichever group of fans has been started as a result of the previously described operation, which is to say either the A Side fans 52 or the B Side fans 53, remains on for a preset (and adjustable) length of time established by motor 101. This timing motor operates, at the end of the preset time interval (after initial energization thereof), to move arm 103 away from its fixed contact 104 and to move arm 98 away from its fixed contact 99. The opening of contact 104 breaks the circuit to relay 105 and also to whichever one of the starter-

relays

107 or 108 has been operated or energized, resetting these relays and opening the fan power circuits, turning off the fans. Thus, the motor 101 is the fan running time" relay.

The opening of contact 99 open-circuits the motor 101 causing this timing motor to reset; it also open-circuits the coil 93, releasing the arms 94 and 95 so that they return to the positions illustrated in FIG. 7.

As previously stated, each of the fans has a hi-off-lo switch connected thereto, which means that the fans may be set to operate at one or the other of two speeds, a high speed or a low speed. This provision of a fan speed selection is advantageous, since in general blanks of different sizes may call for different rates of air flow, for most effective coating. In general, larger blanks may call for a lower rate of air flow than smaller blanks, possibly because the upper ends of such larger blanks are closer to the fans. The hi-off-lo switches 117, 118, and l 19 are grouped together and mounted on one side of the cabinet 60, at location 130 (FIG. 3), adjacent the A Side. The hi-off-

lo switches

127, 128, and 129 are grouped together and mounted on the other side of cabinet 60, at location 131, adjacent the B Side.

It has been stated previously that the supporting members which carry the separator members 41 are bolted to the rack of assembly 39. Various subassemblies (each subassembly including separator members and the supporting members therefor) can be made up for bolting to a single rack, for ready replacement of an installed subassembly. In order to accommodate blanks of various sizes, each subassembly would be made up with separator members of an appropriate, individual size.

As previously stated, it is contemplated that, in operation, only one row of separator members 41 will be utilized at a time for the actual dip-coating. It is important that the appropriate set, and only the appropriate set, of fans be turned on as the coated articles are being raised out of the vat. Thus, if the row of separator members 41 at Side A of the vat is the loaded side emerging from the vat, only the Side A fans 52 should be turned on; if the row of separator members at Side B of the vat is the loaded side emerging from the vat, only the Side B fans 53 should be turned on. In some cases, it may be desired to use Side A AND Side B in sequence for dip-coating, while in other cases it may be desired to use only Side A or only Side B. The circuit arrangements for appropriate operation of the fans will now be described.

Assume first that sequential operation of Side A and Side B is desired. For this, the fan selector switch previously referred to is operated to the A or B sequential position. In this switch position, switch 88 is closed and switch 89 open, energizing bus 90. Also, a switch 132, which is connected in series with relay contacts 92 and one end of the coil 133 of a flip-flop or sequencing relay, is closed; the other end of coil 133 is connected to the grounded bus 91. Switch 134, which is con nected between the switch 132 end of coil 133 and bus 90, is open for this mode of operation. The coil 133 is mechanically coupled to switch arm 109, and moves this arm back and forth between its

contacts

110 and 120. That is to say, each time that coil 133 is energized from bus 90 through relay contacts 92 and closed switch 132, it flips arm 109 to its other contact. (In this connection, it will be recalled that relay contacts 92 close at the end of each dipping interval, to start movement of the assembly 39 upwardly.) For example, if arm 109 is on contact 110 as illustrated, then, at the end of the next succeeding dipping interval arm 109 would be flipped to its contact 120, which would result in turning on the Side B fans 53 upon operation of the time delay relay 105. Later, at the end of the next succeeding dipping interval (when relay contacts 92 again close), coil 133 would be again energized to flip arm 109 back to contact 110, resulting in turning on the Side A fans 52 when relay again operates.

So that the operator will know which side of assembly 39 should next be loaded for proper operation, a pair of

indicator lamps

135 and 136 are provided, these lamps being mounted in respective opposite sides of cabinet 60, lamp 135 being mounted toward Side A of the apparatus and lamp 136 being mounted toward Side B of the apparatus. One terminal of each of the

lamps

135 and 136 is connected to grounded bus 91. The coil 133 of the flip-flop or sequencing relay is mechanically coupled to a switch arm 137 which is permanently connected at one end to bus 90 and which flips back and forth between two

fixed contacts

138 and 139. For the sequential" mode of operation, the fan selector switch causes closure of a switch 140 which is connected between contact 138 and lamp 135,

and also causes closure of a switch 141 which is connectedbetween contact 139 and lamp 136. For this mode, a switch 142, which is connected between contact 138 and lamp 136, remains open; the same is true of a switch 143, which is connected between contact 139 and lamp 135.

Now, if arm 137 is on contact 139 as illustrated, then at the end of the next succeeding dipping interval (when relay contacts 92 close), coil 133 is energized to flip arm 137 over to contact 138, resulting in the energization of the A lamp 135 through switch arm 137, contact 138, and the closed switch 140. This indicates that Side A should be loaded next. (From the previous description, it will be remembered that at the end of the next succeeding dipping interval after the one illustrated, it is the Side B fans 53 which are turned on.) Thereafter, at the end of the next succeeding dipping interval (when relay contacts 92 again close), coil 133 would be again energized to flip arm 137 back to contact 139, resulting in the energization of the B lamp 136 through switch arm 137, contact 139, and the closed switch 141. This indicates that Side B should be loaded next. (It will be remembered that at the end of this last-mentioned dipping interval, it is the Side A fans 52 which are turned on.)

Next, assume that operation of only Side A or only Side B is desired. The fan selector switch is operated to the A or B only position. In this switch position, switch 88 is open, switch 89 is closed, switch 132 is open, switch 134 is closed, switch 140 is open, switch 141 is open, switch 142 is closed, and switch 143 is closed. Bus 90 is again energized. In this mode of operation, coil 133 is constantly energized from bus 90 through closed switch 134, and thus no flip-flop action of the sequencing relay takes place. Arm 109 remains on whichever contact or it was last on, and arm 137 remains on whichever contact (138 or 139) it was last on. As illustrated, the operation would be on Side A only, arm 109 on contact 110 resulting in energization of the Side A fans 52 during the raising of the assembly 39. The A indicator light would be energized through switch arm 137, contact 139, and the closed switch 143.

If operation on Side B only is desired, the fan selector switch would be operated momentarily to the sequential position to open switch 134, and then back to the A or B only" position to reclose switch 134. This opening and then reclosing of switch 134 would pulse coil 133 to move arm 109 to contact 120, and to move arm 137 to contact 138. Arm 109 on contact 120 would result in energization of the Side B fans 53 during the raising of the assembly 39. The B indicator light 136 would be energized through switch arm 137, contact 138, and the closed switch 142.

In the off position of the fan selector switch, the

switches

88, 89, 132, 134, and 140-143 are all open. in this off mode, no energization of the fans or of the indicator lights can occur, since bus 90 is now deenergized.

It has been stated previously that the fans are preferably turned on while the blanks are being withdrawn from the vat of molten wax. However, this mode of operation has been described only by way of example. In some instances, it may be desired to turn the fans on, thereby to blow air over theblanks, after the blanks have been completely withdrawn from'the vat, but while the wax is still'draining from the blanks, before it has completely solidified thereon. The provision of the fan start time delay relay 105, whose time delay is adjustable, allows for this latter mode of operation. As previously described, a circuit is completed to one of the

fan motor starters

107 or 108 when the fan start time delay relay 105 closesits normally open contacts 106; the time delay between the energization of the coil of relay (by the closing of arm 94 on contact 96) and the closing of its contacts 106 is adjustable. v

The invention claimed is: I

1. Apparatus for coating sheet articles of extensiv surface area, comprising a vat, a bath of hot liquid coating material contained in said vat, means for lowering the articles to be coated into said bath, means operating upon article immersion to start the measurement of a first finite time interval and to begin the raising of said articles out of said bath at the end of said first interval, means operating upon the beginning of the raising operation to start the measurement of a second adjustable finite time interval and to establish a flow of air over said articles in the direction toward said bath at the end of said second interval.

2. Apparatus of claim 1, wherein said first interval is adjustable in length over a range of 6 to 106 seconds.

3. Apparatus according to claim 1, wherein the flow of air is produced by motor-driven blower means; said apparatus including also means operating upon the beginning of the raising operation to start 'the measurement of a third finite time interval and to deenergize the blower driving motor at the end of said third interval.

4. Apparatus of claim 3, wherein said third interval is adjustable in length over a range of 0.5 to 6 minutes.

Claims

1. Apparatus for coating sheet articles of extensive surface area, comprising a vat, a bath of hot liquid coating material contained in said vat, means for lowering the articles to be coated into said bath, means operating upon article immersion to start the measurement of a first finite time interval and to begin the raising of said articles out of said bath at the end of said first interval, means operating upon the beginning of the raising operation to start the measurement of a second adjustable finite time interval and to establish a flow of air over said articles in the direction toward said bath at the end of said second interval.

3. Apparatus according to claim 1, wherein the flow of air is produced by motor-driven blower means; said apparatus including also means operating upon the beginning of the raising operation to start the measurement of a third finite time interval and to deenergize the blower driving motor at the end of said third interval.