US3132038A - Method and means for dry enameling - Google Patents

Description

y 1964 J. A. WARD 3,132,038

METHOD AND MEANS FOR DRY ENAMELING Filed Jan. 29, 1960 '7 Sheets-Sheet 1 JOHN A. WARD ,4 T TOP/V 7 y 1964 J. A. WARD METHOD AND MEANS FOR DRY ENAMELING D R Y e r m am .A r S9 MW A m w mm 7 N m w.

Filed Jan. 29, 1960 y 5, 1964 J. A. WARD 3,132,038

METHOD AND MEANS FOR DRY ENAMELING A TTORNEY May 5, 1964 J. A. WARD METHOD AND MEANS FOR DRY ENAMELING '7 Sheets-Sheet 4 Filed Jan. 29, 1960 INVENTOR JOHN A. WARD lllll lllllli llllllllll ATI'OAV/VEY 7 Sheets-Sheet 5 INVENTOR.

JOHN A. WARD May 5, 1964 J. A. WARD;

METHOD AND MEANS FOR DRY ENAMELING Filed Jan. 29, 1960 May 5, 1964 J. A. WARD METHOD AND MEANS FOR DRY ENAMELING 7 Sheets-Sheet 6 Filed Jail. 29, 1960 JOHN A. WARD May 5, 1964 J. A. WARD METHOD AND MEANS FOR DRY ENAMELING Filed Jan. 29, 1960 7 Sheets-Sheet 7 INVENTOR JOHN A. WAKD rray/vs) United States Patent METHOD AND MEANS FOR DRY ENAIWELING John A. Ward, Leorninster, Mass, assignor, by mesne assignments to American Radiator & Standard Sanitary Corporation, New York, -N.Y., a corporation of Delaware Filed Jan. 29, 1960, Ser. No. 5,405

14 Claims. (Cl. Mi -1%) piece is first heated to a temperature above the fusing point of the enamel in powdered form referred to herein as powder and of thereafter applying the powder to the heated 'work piece so that the powder fuses thereon to form the enamel coating.

' In present practice the workpiece, such as a metal bathtub or sink, is first placed in a furnace where its temperature is raised above the fusing point of the powder. Thereafter, the work piece is removed from the furnace, and workmen manually apply the powder to the heated work piece in such a manner that an even coating of powder is appliedand bonded to the work piece before it cools below the melting point of the powder. This present method has two serious disadvantages, one of which is the necessity for the workmen to apply the powder in a room having'a relatively high temperature and also of their working in close relation to the heated work piece which has a very high initial temperature of the order of 1100 F. to 1600 F. This requires the workmen to wear suitable asbestos aprons, mittens and arm protectors and other protective gear which hinders their movements and which also prevents them from working for more than a few minutes at a time on the dry enameling process. V i

In addition it is often necessary to return the metal work piece to the furnace several times during the dry enameling process to re-heat it above the melting point of the glass powder since the work piece cools rapidly at the powder applying station even though the room may be at a temperature as high as 130 'F.

- The reheating slows down increases its cost. r The applicationof powder to the work pieces by the present 'manual operation is done by specialized workthe enameling process and 'men who become highly skilled in the enameling operation; The production rate for'the enameled articles" thus is entirely dependent upon the supply of such skilled labor and this dependence uponthe labor supply tends to limit increases in output as the training of new workers is a.

long process. a

Accordingly, it is an object of the present invention to provide a method and means of automatically "applying powder to the heated workpiece. This will permit the powder to be applied in an antechamber to the main heating furnace which antechamber may be maintained at a temperature considerably above that which could be-main- ,tained where the powder was manually applied. Thus,

the methodand means of the present invention alsoprovides an antechamber adjacent to and communicating with the main heating furnace to which the heated work piece may be moved when it has been heated to a proper dry enameling temperature and in which it may be kept during the entire dry enameling operation. This antecham:

her, for example, may be maintained at a temperature'of' ice about 800 F., and this significantly reduces the cooling rate of the heated Work piece and thus provides a considerably longer period during'which the dry enameling operation may be carried out.

Another object of the present invention is to provide a dry enameling operation which is almost entirely automatic and which requires a minimum of supervision.

Another object of the present invention is to provide a method and means for dry enameling which is more rapid than the present manual methods. g

Another object of the present invention is to provide an automatic dry enameling method and means suitable for irregularly shaped articles. 7

Another object of the present invention is to provide an automatic method and means which is easily adjustable for use with a wide range of article shapes and sizes.

Other and further objects of the invention Will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for purposes of illustration and description and is shown in the accompanying drawings, forminga part of the specification, wherein:

FIG. 1 is a side elevational view partially in section of the dry enameling means in accordance with the present invention; I

4 FIG. 2 is a horizontal sectional view of thedry enamel- 7 ing means taken alongline 22 of FIG. 1;

FIG. 3 is a vertical sectional view of the dry enameling means taken along line 33 of FIG. 2;

. FIG. 4 is a side elevational view of the work piece tilting and rotating jig;

FIG. 5 is a front elevational view of the jig of FIG. 4; FIG. 6 isa top plan view of the jig of FIG. 4;

FIG. 7 is a fragmentary top plan view. of an auxiliary powder feeder;

FIG. 8 is an enlarged sectional viewiof the powder feeder of FIG. 7 taken along line 8-8 of FIG. 7; T

FIG. 9 is a fragmentary top plan view of the main powder feeder;

FIG. 10 is an enlarged sectional viewtaken along line 101il of FIG. 9; p

FIG. 11 is an enlarged fragmentary perspective View of a portion of a powder feeding comb;

FIG. 12 is a diagrammatioperspective view partially in section illustrating the feeding of powder on an irregularly shaped work piece in accordance with the present invention;

FIG. 13 is a diagrammatic perspective view of another powder to an irregucation of powder to the irregularly shaped work piece.

General Description The dry enameling method and means of the present invention will first be described generally with particular reference to FIGS. 1-3. a

As illustrated in FIGS. l-3, thedry enameling apparatus 1 comprises afurnace 2 in which the coatedwork piece 3 which is to be enameled is initially heated to a temperature above the melting point of the dry powdered vitrifiable enamel. The work piece illustrated in these figures is a lavatory or basin but any article requiring enameling may be similarly handled. The coatedwork piece 3 is initially positioned in thefurnace 2, having a slidingdoor 4 and is heated therein to a temperature above the melting point of the powder which typically is between 1100 F. and 1600" F.

An enclosure orantechamber 5 is provided adjacent thefurnace 2 in which the automatic dry enameling operation is carried out after thefurnace 2 has heated thework piece 3 to a suitable dry enameling temperature. When the temperature of thework piece 3 has been raised to the enameling temperature, thework piece 3 is moved from thefurnace 2 into theantechamber 5. Theantechamber 5 is heated by a suitable means so that its temperature is kept well abovethat of the surrounding room to reduce the cooling rate of thework piece 3 and to cause it to remain above the melting point of the glass powder for an appreciable period during which the automatic dry enameling operation is carried out.

As illustrated in FIGS. 1-3, thework piece 3, when positioned in the heatedantechamber 5, is mounted on a movable work piece holder indicated generally at 6. As will be more fully described below, the holder 6 provides for rotation of thework piece 3 about a horizontal axis and an axis perpendicular to the horizontal axis which permits thework piece 3 to be moved in a desired predetermined pattern during the application of the powder. The powder is applied to the 'work piece 3 by amain powder feeder 7 and an auxiliary powder feeder 8. Thepowder feeders 7 and 8 supply a continuous and controlled sheet of falling powder to predetermined surfaces of thework piece 3 to cause thework piece 3 to be enameled with an enamel coating of predetermined area and thickness. The rate and pattern of fall of the powder from both themain feeder 7 and the auxiliary feeder 8 are controlled as also is the movement of thework piece 3 by the holder 6 to provide for an even coating of enamel over the irregular surfaces of thework piece 3 during the enameling operation as will be described below. As the powder from thefeeders 7 and 8 strikes the surfaces of thehot work piece 3, the powder melts and forms a smooth enamel coating of predetermined thickness.

Thereafter, thework piece 3 is removed from thehot antechamber 5 and is permitted to cool causing the enamel to harden.

A rail mounted fork lift 9 is preferably provided to move thework piece 3 into and out offurnace 2 and theantechamber 5.

Work Piece Holder The work piece holder6 is illustrated in detail in FIGS.

4-6 and comprises ajig 11 adapted to mount the particular work piece being enameled. In order to expose all of the surfaces of the work piece which are to be enameled to the powder which is being applied by thefeeders 7 and 8, thejig 11 is mounted for a simultaneous rotational and tilting movement.

The tilting movement is provided by having thejig 11 mounted upon anarbor 12 which is mounted for rotation about a horizontal axis by thepivotal mountings 13 and 14 on thestationary frame 15. The angle of tilt of thearbor 12 is controlled by a reversible tilting motor 16 (FIG. 1) through the intermediation ofsuitable sprockets 17 and 18 and a connectingchain 19. The suitable controls are provided to change both the speed and direction of the tiltingdrive motor 16 so that thearbor 12 and the work piece on thejig 11 may be tilted to the desired working angle or may be continuously moved through a 4 predetermined path by suitable automatic controls as the powder is applied to the work piece.

In general it is desirable that the surface of the work piece being enameled be positioned as nearly perpendicularly as possible to the direction of powder fall to facilitate the even distribution of the fluxed powder on the hot metal surface. Thearbor 12 is positioned by the tiltingmotor 16 to accomplish this result for the particular work piece being enameled. Since the work pieces generally have irregular shapes, the entire surface being enameled cannot be horizontally positioned; however, a compromise position is determined which places the surfaces which are being enameled as nearly horizontal as possible. I

In order to provide for an even distribution of the powder, it is desirable to provide for the movement of thework piece 3 beneath the falling powder. This is done by having thejig 11 rotatably mounted on thearbor 12 on asuitable shaft 20. Theshaft 20 is driven by ajig rotating motor 21 through the intermediation of a suitable connecting means. Inthe preferred embodiment illustrated in FIGS. 1 and 4-6, the drive connection comprises adrive gear 22 attached to the bottom of therotatable shaft 20 which is driven from the motor through the intermediation ofpinion gear 23,bevel gears 24 and 25,

shaft 26, and connectinggears 27 and 28. Connectinggear 28 is mounted on acommon shaft 29 with thesprocket 30 which is driven from thejig rotating motor 21 through the intermediation of sprocket 31 andchain 32.

When a work piece such as thesink 3 is being enameled, certain surfaces will be more steeply inclined with respect to the direction of powder fall than others and will thus require an additional flow of powder if a uniform depth is to be obtained on these surfaces. This may be accomplished conveniently by reducing the speed of the rotation of the drive for thejig 11 when these surfaces are passing beneath the powder fall. In the preferred embodiment of FIGS. 4-6, anon-uniform drive gear 22 is mounted at the bottom of thejig rotating shaft 20 to accomplish this result. The portion A of this gear is formed with an increased diameter to cause theshaft 20 to rotate more slowly when thepinion 23 is engaged with this portion of the gear. In FIGS. 4-6 the enameling position for thesink 3 is shown in dash-dot lines. Thegear 22 is so positioned that thejig 11 is carrying the steeply inclined backportions 3 of the sink orwork piece 3 beneath thearea 36 of powder fall when portion A of the gear is in engagement withpinion 23 and so that the more horizontally positionedbowl portion 3" of the sink is moved beneath the powder fall for the remaining smaller diameter portion ofgear 22. In order to compensate for the varying diameter of thedrive gear 22, thepinion 23 is slidably mounted on areciprocable support 37 which is slidably mounted on the bracket member 38 and which is connected to thedrive gear 22 by means of the slottedcam 39 in thedrive gear 22 and thecam follower pin 40 on the end of thesupport 37. Thebevel gear 25 is slidably mounted on its mountingshaft 26 by a suitable spline to cause the bevel gears 24 and 25 to remain in engagement during the movement of thepinion 23.

Other suitably shaped gears may be used in place of thedrive gear 22 to provide for the desired rotational speed changes for any particular work piece so that the work piece is slowed down as its more steeply inclined portions pass under the powder fall.

The same result may be also obtained by varying the speed of the jig-rotatingmotor 21 manually or by a suitable automatic control such as a cam operated speed control.

Powder Feeders As best illustrated in FIGS. 2 and 3, amain powder feeder 7 is provided to apply the powder to the principal areas of thework piece 3 and an auxiliary powder feeder 8 is also provided which is adapted to apply powder to powder feeders, depending upon the number of differently sloped surfaces on the work piece which must be enameled.

As is best illustrated in FIG. 3, the main powder feeder comprises aU-shaped trough 41 having apowder hopper 42 positioned at one end and apowder feeding edge 43 at its opposite end. When thetrough 41 is in use, it is mounted with a slight downward incline towards thepowder feeding edge 43 to facilitate the travel of the powder from thehopper 42. In addition, amechanical vibrator 45 is mechanically attachedto-the trough so that the movement of the powder is further facilitated by the vibration of the trough. Thepowder hopper 42 also has a suitablemechanical vibrator 46 mounted thereon. In order to provide for movement of thetrough 41 into a suitable powder delivery position, a roller-type mounting is provided on thehorizontal rails 47 which support theupper frame 48 and therail engaging rollers 49. Thetrough 41 is attached to theupper frame 48 by thehangers 50 which havesuitable length adjustors 51 to permit the trough to be positioned at a suitable incline to provide the rate of powder feed desired for a particular work piece.

The powderfeeder 8 comprises aU-shaped trough 52 adjustably mounted on aframe 53 which supports it by means of the rollers 54 onrails 55.Arhopper 56 supplies powder to the auxiliary feeder 8, and the powder is moved to a powder feeding slot therein by means of a suitable tilt in thetrough 52 in cooperation with the vibratory motion provided by avibrator 57 ontrough 52 and avibrator 58 onhopper 56.

The details of thepowder feeding edge 43 of themain powder feeder 7 are illustrated in FIGS. 9-11. Powder 59 moving down theinclined feed trough 41 under the influence of thevibrator 45 will fall in a radially disposed sheet onto the heated surface of thework piece 3, moving therebelow. Inorderto retain a uniform distribution of the fallingpowder 62 and in order to prevent bunches or lumps of powder from falling onto theWork piece 3, a sieve-like means is mounted below theopen edge 43 of thetrough 41. In the preferred embodiment illustrated, this sieve-like means comprises the comb 60 having a plurality of parallel wires or metal tines 61 positioned in the path of the falling powder62. These wires or tines 61, are preferably proportioned so that they vibrate sympathetically with the vibratory action of thefeeder trough 41. Lumps or bunches'63 of powder '62 falling onto these fivibrating tines 61 are broken up by'their vibratory movement to a suitable degree for the enameling action.

The tines 61 are sloped upwardly towards theirfree end 64 so that anylumps 63' which are not broken up by the vibratory motionwill be retained on the tines 61 until they can be removed between enameling operations.

FIGS. 7 and 8 illustrate the powder feeding end of the auxiliary feeder 8 and illustrateanother embodiment of a powder applying edge in slot form. The auxiliary powpositioned adjacent to the free end of thetines 69 prevents the passage of any lumps or powder balls 71 over the ends of the vibratingtines 69. Thesetines 69 also are prefer ably sloped upwardly towards thebaffie 70 to cause the I Depth Control of the Applied Powder As described above, the powder flows downwardly through the vibrating feeder combs or 67 in a generally vertical stream radially directed with relation to the rotating work piece. If the trough of the feeder is level, the powder will fall with a uniform density towards the surface of the work piece. As is described above, a con venient method of spreading the powder over'the surface of the work piece is to rotate the work piece in a jig having a rotatable mounting shaft. When the work piece is thus rotated, it is obvious that the portions of the work piece closer to the rotating shaft are moving at a slower speed than are the portions remote from the shaft. It is therefore desirable to compensate for this difference in speed, as the faster moving outer portions of the work piece will receive lesser amounts of powder than will the slower moving central portions of the work piece.

In FIG. 12 a generallyrectangular basin 74 is shown positioned in a jig 75. The jig 75 is rotatably mounted on a suitable work piece holder similar to the abovedescribed work piece holder 6 comprising a central rotatable shaft 76 driven by thegears 77 and 78.

One preferred means of compensating for the difference in surface speed at the outer portions of thebasin 74 is illustrated in FIG. 12 and it comprises the tilting of thepowder applying trough 85 whereby a relatively shallow portion ofthepowder stream 86 in the tilted trough drops onto the morecentral portion 82 of the rotating basin '74 and whereby an increasing amount of powder corresponding to the increasing depth of thepowder stream 86 in the tiltedtrough 85 is dropped towards theouter edge 84 of the rotatingbasin 74. Thus, the gradually increasing depth of thepowder 86 in the tiltedtrough 85 provides an increasing density of powder fall towards the outer edges of the rotatingbasin 74 to correct for the increasing rotational speed of these portions which are more remote from the axis of rotation of the jig 75. i

This correction will be somewhat approximate fora workpiece such as thebasin 74, as there are a number of changes in the slope of the basin surface being enameled. Thus the changes in rotational speed across the generallyhorizontal portion 87 will be relatively large as compared to the morevertical side portion 88 which is generally parallel to the axis of the rotating shaft 76.

; keep it more constant for the portions generally parallel to shaft 76. Thus a curved bottom 89 is provided in the trough'90 having a relativelyhorizontal portion 91 corresponding to the basin surface 92 which is parallel to the axis of shaft 76. Thebottom has more steeply slopedportions 94 and 95 which correspond to theportions 87 and 84 of thebasin 74 which'are at an angle 'to the axis of the shaft 76. The most steeplyangled portions 96 and 97 'of the bottom 89 correspond to thebasin sections 98 and 99 which are normal to shaft, 76 and which therefore have the greatest change in speed.

Theauxiliary feeder 100, which is positioned above theouter side walls 101 and 192 of the rotatingbasin 74, has a shapedbottom 104 with a slopingportion 105 to compensate for the rotational speed increase at the outer edge of theportion 102 of thebasin 74 and a generallyflat portion 106 for theportion 101 of thebasin 74 which is parallel to the axis of rotation of shaft 76 so that all portions of it which are receiving powder at a given time are moving at the same speed. 7

An additionalcorrection may also be provided in the bottom 89 for the relative angle of the basin surface with relation to the falling powder. Thus theportion 87 of thebasin 74 which is normal to the powder'fall will receive a heavier coating than section 92 which is at an angle.; The downward step 107 in bottom 89 increases the powder fall by the necessary increment entirely across the section 92 to compensate for its reduced angle to the powder fall.

FIGS. 12 and 13 are sectional views of thebasin 74 illustrating a. diagonal section taken approximately through opposite corners. Asbasin 74 rotated by the jig 75, the angular positions of the portions of the basin surface directly beneath the fallingpowder 81 will change with respect to the direction of powder fall. Thus, in thebasin 74 illustrated, the angular positions of the basin surfaces beneath the falling powder tend to decrease with respect to the direction of powder fall for the portions of thebasin 74 intermediate the basin corners as illustrated by the dash-dot showing 74 of such an intermediate section in FIG. 12 whereportions 84' and 87 are at an angle from correspondingportions 84 and 87 in the diagonal section. When the angle of the surfaces with respect to the falling powder does decrease such as forportions 84 and 87', an additional amount of powder must be applied to compensate for the change; One way of accomplishing this result is illustrated in FIGS. 12 and 13 wherein the rotational speed of the jig 75 is reduced intermediate the corner portions by the use of the generallyrectangular gear 77 having its greater diameter portions positioned to contact thepinion gear 78 while the portions of the basin intermediate thecorners pass beneath the path of the falling powder stream. This results in a reduction of the rotational speed of thebasin 74 at these points to permit a greater powder fall. The greater powder fall contacts the more steeply sloped portions 84' and 87' and provides for a uniform depth of enamel.

Another means of compensating for variations in the speed and position of the surface of the work piece being coated wherein the falling stream of powder is moved is illustrated in FIGS. 1418.

In FIG. 14 a generallyrectangular basin 110 is illustrated in the enameling position mounted on a. suitable jig 111 rotated by the drive shaft 112. Thebasin 110 has three principal portions which are being enameled,

i.e. the bottom 114, the sides 115, and the rim 116. The. powder is applied from aninclined chute 117, as illustrated in the cross sectional view FIG. 14, and portion 118 of the powder is falling on the bottom 114 of the sink,portion 119 is falling on the side walls 115, and the portion 120 is falling on the rim 116. Since thebasin 110 is rectangular, it is obvious that thecorner portions 121 of the sink will be moving at a faster rate than will be the intermediate portions of the side wall. Thus, unless a compensating means is provided, the enamel coating adjacent thecorners 121 will be thinner than the enamel coating over the remaining areas of the side wall 115. A compensating means is provided in the form of a rotatably mountedvane 122 which is positioned in, the path of the fallingpowder 119 and which is mounted for both rotational and longitudinal movement on thehorizontal shaft 124.' The compensating action of thevane 122 is provided as illustrated in FIGS. 15-18.

. In FIG. 16 thevane 122 is stationary in the titled position shown and thepowder 119 is being applied at the desired depth on anarea 125 midway between the center of the basic side walls 115 and thebasin corner 121. Thereafter, as the basin continues to rotate counterclockwise to the position illustrated in FIG. 17, the side walls 115 are positioned progressively further from the shaft 112 and therefore move with increasing speed through the falling stream ofpowder 119. In order to compensate for the increased speed of the side walls,vane 122 8 is rotated in a counterclockwise direction (FIG. 17) to cause the falling stream of powder to move in the direction of the side walls 115 and to provide a relatively constant speed between the powder and the basin side walls to thus coat the sidewall 115 to a generally constant depth even though the side wall 115 is moving at an increased speed. The rotation of thevane 122 is continued at a gradually increasing rate until thecorner 121 of the basin is reached, as is illustrated in FIG. 17 and there after the counterclockwise rotation is continued at a decreasing rate until theside wall area 126 is reached (FIG. 18) which is positioned one quarter of the distance along the sidewall 115 and which corresponds toarea 125. Thereafter, thevane 122 is rotated in the opposite direction since the side wall speed is decreasing and the powder stream is moved in the opposite direction to the rotating basin to prevent an accumulation of excess powder. Thevane 122 is rotated clockwise at an increasing rate until the basin reaches the position of FIG. 15 with thepowder 119 striking the center of side wall 115. Thereafter, the clockwise movement of thevane 122 is continued at a decreasing rate until the basin again reaches the position of FIG. 16 when the vane is stationary and ready for another cycle.

Since the basin illustrated in FIGS. 14-18 is rectangular, it is also clear that the portion of the side wall being struck by the vertical sheet ofpowder 119 changes its outward position with respect to the shaft 112.Vane 122 is also moved axially in a corresponding degree so that the above-described correction in the powder fall follows the side walls 115 during this irregular motion. This correction is provided by the horizontal movement of theshaft 124 under control of the crank member 128 and a suitably calibratedcam 129 coupled to the jig drive shaft 112. Thesame cam 129 may also be used to control the above-described rotation of thevane 122, since the change in position of the side walls is proportional to the change inside wall speed. Asuitable cam follower 130 connected bybevel gears 131 and 132 moves thevane 122 throughthe above-described powder position ad ustments. As is illustrated in FIG. 14, the various compensating means may be combined. In the trough 117 asloped bottom 134 is provided to provide a correction to compensate generally for the increase in speed for the outer portions of therotating basin 110 as compared to the central portions, and thevane 122 is provided to specifically compensate for the variations in speed and position of the basin side walls 115 in the above-described manner. 1

Operation The operation of the automatic dry process enameling py the above-described methodand apparatus is as folows.

The dry enameling operation is commenced by the placement of thework piece 3 having a suitable base coating into thefurnace 2 by means of the fork lift 9. The preferred base coating is a relatively thin vitreous enamel coating applied by a wet enameling process such as spraying or dipping. Access to thefurnace 2 is gained through the verticallymovable furnace door 4. Thework piece 3 such as the wash basin illustrated in FIG. 1 is now heated until its temperature is raised above the fusmg point of the powdered vitreous glass which is to be used in enameling its surface. The fusing temperatures of the enameling powders are usually between 1000 F. andl6 00 F., and the furnace and work piece are heated to a higher temperature before enameling such as about 1750" F. When thework piece 3 has reached this temperature, it is removed by the fork lift 9 from thefurnace 2 and is placed in theinsulated antechamber 5 which is kept at an elevated temperature such as 600 F. to slow down the cooling of the work piece while the powder is automatically applied to the surface of the work piece in the enameling operation. The elevated temperature of the antechamber permits theheated work piece 3 to remain above the fusing temperature of the powder during the entire time which is necessary for the automatic application of the powder to the surface to be enameled by the following operation.

As more completely described above, the work piece is mounted on a movable work piece holder 6 while positioned in the antechamber so that the work piece may be tilted to a predetermined enameling position and may also be rotated about a predetermined axis. The tilt of 10" These movements of thevane 122 are controlled by arotating cam 129 operatively coupled to thevane 122 and to the drive means for the jig 111 so that thecam 129 and the jig 111 rotate in synchronism. It will be seen that an improved method and means have been disclosed for a dry process enameling of metal the work piece and its rotation about the desired axis are controlled by the tiltingmotor 16 and thejig rotating motor 21, respectively. Thejig 11 is mountedon the work piece holder '6 so that it will support thework piece 3 in a predetermined positionwith respect to the rotational axis of thejig 11. Thus, after thework piece 3 has been properly positioned in thejig 11 by the fork lift 9, thework piece 3 may be moved to its enameling position by the tilting of thejig 11 by' the tiltingmotor 16. Y

' For each particular shape of work piece, a rotational speed pattern is worked out in accordance with the above discussed principles and the rotation gear, including thedrive gear 22, is designed to provide the proper decrease in rotational speed for the more steeply sloped surfaces of the work piece. In the preferred embodiment shown, thework piece 3 is moved in its proper enameling motion by the operation of thejig rotating motor 21 at a predetermined speed. The powder is thereafter applied to the movingwork piece 3 from, themain feeder 7 and the auxiliary feeder 8 or other feeders as is necessary. After thetroughs 41 and 52 have been moved onrails 47 and 55 into theantechamber 5 to their correct position above thework piece 3, the powder fall is initiated by energizing thehopper vibrators 46 and .58 and thetrough vibrators 45 and 57. The powder fall downwardly along theinclined troughs 7 and8 and falls in a predetermined'density through thetines 61 and 69 of thecombs 60 and 67, respectively. When the powder strikes the heated surface ofthework piece 3, it fuses and fiows into a smooth liquid coating of predetermined depth which will harden into the enameled surface when thework piece 3 cools below the fusing temperature.

In order to compensate for changes in rotational speed between the central portions and the outer portions of rotated work pieces, thepowder feeding troughs 7 and 8 are tilted so that the powder fall increases towards the outer edgesof the falling stream, as is illustrated in FIG. 12. For work pieces such as that illustrated in FIG. 13 having a relatively non-uniform cross section, a false or curved bottom is placed in the powder feeding troughs. The depth of the powder is adjusted by means of this bottom to progressively increase the powder flow towards the outer edges of surfaces disposed generally at right angles to the axis of rotation of the work piece jig and which therefore have speed changes across their width and to keep the powder flow fairly constant over surfaces disposed parallel to the axis of rotation where there is little change in surface speed over such portions.

An additional compensating means is illustrated in FIGS. 14-18. In this means avane 122 is positioned in the stream of falling powder and the vane is moved in synchronism with the rotating jig to compensate for changes in the speed of particular portions of the work piece. Thus, as the basin illustrated is rotated beneath the falling powder, its speed past the stream of powder increases for the outer corner portions. Thevane 122 is turned to maintain a constant relative speed between the falling ware. The process and means disclosed provide for. a rapid, automatic dry process enameling which is accomplished with a single heating of the Work piece. The method and means disclosed speed up the enameling process by eliminating reheating requirements and pro vide a more rapid and less expensive enameling process by eliminating the series of manual operations heretofore required in the dry process enameling operation.

The method and means disclosed may be used for a variety of metal shapes and may be used on both uniform and non-uniform articles with relatively simple and automatically operated compensating devices which provide for a uniform enamel coating of constant depth.

'As various changes may be made in the form, construction-and arrangement of thepartsherein without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be underto a temperature above the melting point of vitreous enamel, thereafter maintaining the temperature of the atmosphere about the work piece substantially above room temperature and below the melting temperature of the enamel, moving the work piece in the atmosphere with laterally spaced surface areas of the work piece moving at different linear speeds, impinging a falling stream of 'dry powdered enameling material through said atmosphere onto said surface areas of said work piece, and supplying said material to said areas of the work piece in quantities predetermined in direct proportion to the rate of speed of the movement of said areas.

2. Apparatus for enameling a metal work piece with vitreous enamel which comprises the combination. of a furnace adapted to heat the work piece above the melting point of the enamel, an adjacent enclosure having an auxiliary heating means adapted to raise the temperature of the adjacent enclosure substantiallyabove room temperature and below the temperature of said furnace, means for applying enamel indry powdered form tofthe work piece positioned in said adjacent enclosure, means .to movably mount the Work piece in said enclosure beneath said enamel applying means, and a remotely controlled drive means for said movable mounting means.

3. The apparatus as claimed inclaim 2 in which said enamel applying means comprises'a powder; retaining hopper, a trough member connected to said hopper at one end and having its other end adapted to enter said adjacent enclosure, an elongated powder dispensing poraxis.

powder and the rotating basin as the speed of the rotating for portions of the basin of smaller diameter which move at lower speeds such as the centers of the side walls.

5. The apparatus as claimed inclaim 3 in which said powder dispensing portion comprises an elongated edge of said trough and a sieve-like member beneath said edge portion and extending co-extensively therewith.

7. Apparatus for enameling a metal work piece with vitreous enamel which comprises an enclosure having a heating means adapted to maintain the temperature of the atmosphere in the enclosure substantially above room temperature and below the melting temperature of the enamel, means mounting the work piece in said enclosure for movement with laterally spaced surface areas of the work piece moving at different linear speeds, means for impinging a falling stream of enameling material in dry powdered form onto said surface areas of said work piece including means for supplying said material to said areas of the work piece in quantities predetermined in direct proportion to the rate of speed of the movement of said areas.

8. The apparatus as claimed inclaim 7 in which said means for impinging said material comprises a trough member adapted for connection to a source of powdered enamel at one end, said trough movably mounted for the positioning of its opposite end within said enclosure, a vibrating means operatively coupled to said trough to facilitate the movement of powder toward said opposite end, and said trough having its bottom inclined from the horizontal in a direction normal to the direction of the powder movement thereon to permit a greater flow of powder to be applied to the work piece at its relatively faster moving portions and at its relatively more steeply sloped portions.

9. The apparatus as claimed inclaim 7 in which said means for impinging said material comprises a trough member, a powderdispensing portion on said trough adapted for positioning within said enclosure, a vibrating means operatively coupled to said trough to facilitate the movement of powder toward said dispensing portion, and

said trough having one or more portions inclined from v the horizontal in a direction normal to the direction of powder movement.

10. The apparatus as claimed inclaim 7 in which said means to movably mount the work piece comprises a rotatably mounted jig, and drive means for said jig comprising one or more irregularly shaped gears adapted to rotate it at a non-uniform rate. I

11. Apparatus for applying enamel in dry powdered form to a work piece heated to a temperature at which the powdered enamel will melt to form a smooth enamel surface comprising means producing a sheet-like stream of powdered enamel, a second means movably supporting said work piece for moving said work piece through said stream, and a vane movably mounted for rotary movement and for axial movement laterally of the stream of enamel to vary the position of said stream with respect to said work piece.

12. The apparatus as claimed inclaim 11 which includes additional means for coordinating the relative movements of said vane and said work piece in a pre-selected manner dependent upon the shape of said 'work piece.

13. Apparatus for enameling a metal workpiece with vitreous enamel which comprises the combination of a furnace adapted to heat the workpiece above the melting point of the enamel, an adjacent enclosure having an auxiliary heating means adapted to raise the temperature of the adjacent enclosure substantially above room temperature and below the temperature of said furnace, means for aplying enamel in dry powdered form to the workpiece positioned in said adjacent enclosure, means to movably mount the workpiece in said enclosure beneath said enamel applying means, and a drive means operatively coupled to said movable mounting means and including a speed changing means.

14. Apparatus for enameling a metal workpiece with vitreous enamel which comprises the combination of a furnace adapted ,to heat the workpiece above the melting point of the enamel, an adjacent enclosure having an auxiliary heating means adapted to raise the temperature of the adjacent enclosure substantially above room temperature and below the temperature of said furnace, means for applying enamel in dry powdered form to the workpiece positioned in said adjacent enclosure, means to movably mount the workpiece for motion about two axes in said enclosure beneath said enamel applying means, a pair of drive means each operatively coupled to said movable mounting means for providing the motion.

References Cited in the file of this patent UNITED STATES PATENTS 605,903 I Otto June 21, 1898 707,490 Zwermann Aug. 14, 1902 710,443 Dupont Oct. 7, 1902 759,351 Dawes May 10, 1904 862,285 Schmidt Aug. 6, 1907 1,361,869 Kebler Dec. 14, 1920 1,669,587 Brotz Sept. 23, 1927 2,223,476 Amstuz Dec. 3, 1940 2,360,413 Getz et al Oct. 17, 1944 2,402,183 Rowe et a1. June 18, 1946 2,513,434 Tinsley July 4, 1950 2,572,702 Davis Oct. 23, 1951 2,719,093 Voris Sept. 27, 1955 I 2,789,926 Tinholt et al Apr. 23, 1957 2,792,030 Wahl May 14, 1957 Tafel Sept. 13, 1960

Claims (1)

1. THE METHOD OF ENAMELING A METAL WORK PIECE WITH VITREROUS ENAMEL WITH COMPRISES HEATING THE WORK PIECE TO A TEMPERATURE ABOVE THE MELTING POINT OF VITREOUS ENAMEL, THEREAFTER MAINTAINING THE TEMPERATURE OF THE ATMOSPHERE ABOUT THE WORK PIECE SUBSTANTIALLY ABOVE ROOM TEMPERATURE AND BELOW THE MELTING TEMPERATURE OF THE ENAMEL, MOVING THE WORK PIECE IN THE ATMOSPHERE WITH LATERALLY SPACED SURFACE AREAS OF THE WORK PIECE MOVING AT DIFFERENT LINEAR SPEEDS, IMPINGING A FALLING STREAM OF DRY POWDERED ENAMELING MATERIAL THROUGH SAID ATMOSPHERE ONTO SAID SURFACE AREAS OF SAID WORK PIECE, AND SUPPLYING SAID MATERIAL TO SAID AREA OF THE WORK PIECE IN QUANTITIES

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