US2121404A - Method of coating sheet metal cans - Google Patents

Description

June 21, 1938). J. H. ONEIL METHOD OF COATING SHEET METAL CANS Filed Aug. 1'7, 1936 3 Sheets-:Sheer. l.

J; H. ONEIL METHOD OE COATING SHEET METAL CANS June 21, 1938.

3 Sheets-Sheet 2 Fixed Aug. 1'7, 1936 4 m, 193a. J NE L 2,121,404

METHOD OF COATING SHEET METAL CANS Filed Aug? 1?, 193a s SheetsL-Sheet 3 Patented June 21 1938 2,121,4q4 METHOD or COATING SHEET METAL cANs James H. 'ONeil, Syracuse, N. Continental Can Company,

Y., asslgnor to Inc., New York,

N. Y., a corporation of New York Application August 17, 1936, Serial No. 96,502.

3 Claims. (01. '91 ss) The invention relates to new and useful im-- provements in a method for coating sheet metal cans.

An object of the invention is. to provide a method of coating sheet metalcans on the-interior thereof with a thermo-plastic material whereby a coating of substantially uniform thickness completely covering the interior of the can may be provided.

A further object of the invention is to provide a method of coating a can having a neck portion terminating in a sealing lip wherein a vacuum creating means may be? utilized for drawing air from the can in such a way as to remove, excess coating material accumulating on the inner and outer faces of the sealing lip during the draining thereof.

In the drawings-- Figure 1 is a vertical sectional view showing a 20 can in inverted position, for draining the excess coating from the can;

Fig. 2 is a vertical sectional view of a can having a coating applied to the inner surface thereof by the method embodying the invention;

Fig. 3 is a view in vertical section showing a portion of an apparatus for carrying out the improved method; r

Fig. 4 is a view showing a can after draining and prior to the subjecting of the same to the suction means for drawing the air from the can, and

Fig. 5 is a view similar to Fig. 4, but showing the air drawn from the can and the excess wax accumulating at the inner and outer surfaces of the sealing lip removed by the flow of airfrom the can.

In the patent granted Alfred L. Kronquest, June 15, 1937, No. 2,084,093, there is shown a machine for coating cans with a thermo-plastic sealing material. The can coated is of the type wherein the top end is provided with a raised cone-shaped portion terminating in a neck having a sealing lip and a shoulder so that a crown cap can be used for closing the can. The can is coated with a thermo-plastic material, preferably of petroleum wax, which has a melting point of 160 F. or above. The wax is reduced to a fluid form by heating and is then discharged through the can has a dome-shaped bottom, the draining of the wax will cause a drop of wax to form at the center of the inverted dome. If the can is inverted quickly while the wax is in fluid form, 60 this drop of wax will flow so as to form a suba nozzle into the can while it is inverted, and

stantially uniform layer on the inner surface of the dome. During the draining, wax will accumulate at the inner surface of the sealing lip forming a thickened coating which is likely to be thrown from, the can on to the outer face of the lip when the can is quickly inverted.

The present invention has to do particularly with the removing of this excess wax accumulating on the inner and outer surfaces of the sealing lip of the can. It is believed that the in vention will be better understood by a detail description of the can and the apparatus for carrying out the improved method of coating the interior of the can.

In Fig. 1 of the drawings, a can is shown in vertical section which has been coated and is in draining position. The can consists of a body portion I which is, as shown, cylindrical in cross section. The bottom end 2 is secured to the body by a double seam 3. This bottom end is domeshaped as indicated at 4. At the top end of the can body is a closure end 5 which is doubleseamed to the can body at 6. This top end has a cone-shaped portion extending above the double seam and terminating in a neck I. The neck is inturned to form a sealing lip 8 and a locking shoulder 9, so that a crown cap'may be applied to the sealing lip and the flange thereof crimped underneath the shoulder 9 for sealing the can. In carrying out the invention, the thermoplastic material is reduced to fluid form by heating and is then flooded over the inner surface of the can through a nozzle which is projected into the can as shown in the Kronquest patent above referred to. As the surplus material drains from the can, a thin film or lining of the thermoplastic material will adhere to the inner surface of the can. The lining is indicated at II] on Fig. 1 of the drawings. During this draining of the petroleum wax from the can, a drop of wax will form as indicated at H. The sealing lip 8 of the can extends inwardly substantially horizontally,

and the inner edge is preferably rolled back upon the inner surface of the sealing lip. This forms moreor lessv of a trap so that the wax draining from the can will accumulate as indicated at l2 in Fig. 4, and thus form an excess of wax which is objectionable. Some excess wax may adhere to the outer surface of the lip 8 during draining which is also objectionable. It is found that if the can while the wax is still in a semi-fluid condition, is turned back to an upright position, the drop of wax accumulating at the center of the dome will distribute itself evenly over the domeshaped bottom. When. however, the can is turned from an inverted position to an upright position quickly, this accumulation of wax at the inner surface of the sealing lip which is indicated at l2 in the drawings, is likely to be thrown from the can mouth and lodge on the outer side of the lip. It is very, objectionable to have wax on the outer face of the sealing lip, for the reason that when the crown cap is forced into contact with the sealing lip, it will prevent an efficient seal.

The purpose of the present invention is to provide a method whereby this excess wax on the inner surface of the sealing lip may be removed so as to leave a thin lining in the region of the sealing lip which will not be thrown from the can when it is turned to a righted position. The apparatus as shown in the drawings includes a standard 13 around which a turret I4 is mounted for rotation. This turret has an outwardly projecting portion I5 on which is mounted a series of nozzles 15. These nozzles are all of similar construction and a description of one will answer for the others. The nozzle is mounted on a sleeve shank 11 which fits within a recess formed in the member IS. A set screw I8 clamps the nozzle firmly in the recess. This member I5 is provided with a port l9 and the sleeve shank of the nozzle has an opening 20 therein connected to the port IS. The nozzle 15 is tapered and the can indicated at C in the drawings, is inverted over this nozzle and rests on the nozzle. The can is fed into a pocket 2| in the turret and is held in the pocket by a guide rail 22. The shoulder 23 is so dimensioned relative to the nozzle that the can body normally rests on the nozzle with the tapered portion thereof extending into the mouth of the can. The inner edge of the sealing lip contacts with the nozzle and this contact is maintained by the weight of the can body.

The nozzle has an annular recess 24 extending around the upper end thereof. A cap 25 extending into the nozzle overhangs this recess so as to form an annular channel. The nozzle l6 has a series of ports 26 which open into the sleeve l1 at their lower ends and into the channel 24 at their upper ends. It will be noted that when a can rests 'on the nozzle, the inner surface of the sealing lip at the inner edge thereof contacts with the nozzle just below the channel 24. The port 19 is adapted to be connected to a suction creating means, and this will cause the air in the can to flow out through the ports 26. As the air flows out through the ports 26, it will follow the direction of the arrows indicated in Fig. 4, that is, the air current will sweep down against the thickened layer of wax on the inner surface of the sealing lip, and the wax will be gradually taken up with the flowing air current until the layer of wax is thinned as indicated in Fig. 5 of the drawings. The suction force can be adjusted so that the excess wax is removed and a thin layer of wax remains covering the inner surface of the sealing lip and the parts adjacent thereto when all of the air has been drawn from the can. A continuation of the suction pull will cause air to press against the under face of the sealing lip as indicated by the arrows in Fig. 5, and this will raise the lip sufliciently from the nozzle to permit air to pass into the mouth and out through the ports. This shifting of the air current to the outside of the sealing lip will remove any feather edge of sealing material extending around on to the outer face of the sealing lip so that there is only a thin even layer of wax adhering to the inner edge of the sealing lip and the outer face thereof.-

Inasmuch as the excess wax accumulating on the inner surface of the sealing lip has been removed, the can can now be quickly righted to the position shown in Fig. 2, and the drop of wax which accumulated on the center of the dome during draining, will as above noted, distribute itself evenly over the dome-shaped bottom.

Associated with the turret is a ring member 21 which is stationary and which has a chamber 28 therein. A port 29 at a certain section of this ring member 21 registers with a port 30 connecting with the port l9. This ring member 21 is connected to a pipe 3| which in turn is connected to a suitable vacuum creating means. The wax taken up by the air current passes into the vacuum creating means and may be separated therefrom by a suitable strainer. There, are a plurality of nozzles, and these nozzles, one after another, receive cans and are brought into operative connection with the vacuum creating means for carrying out the method above described.

The novel method consists in the closing of the can while in inverted position and the drawing of the air from the can by the suction means which causes the air current to flow over the excess wax on the inner surface of the sealing lip so as to remove the same. The method also includes the step of drawing air across the outer face of the sealing lip after the air has been exhausted from the can.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent is:

l. The method of coating a sheet metal can having a neck portion terminating in a sealing lip with a thermo-plastic material, consisting in flowing the material while in fluid condition over the entire inner surface of the can, draining the surplus material from the can, subjecting the can to a vacuum creating means for drawing air from the can, and directing the flow of the air from the can so that it passes across the material accumulating on the inner surface of the sealing lip during draining for reducing the coating thereon to a thin adhering covering.

2. The method of coating a sheet metal can having a neck portion terminating in a sealing lip with a thermo-plastic material, consisting in flowing the material while in fluid condition over the entire inner surface of the can, draining the surplus material from the can, subjecting the can to a vacuum creating means for drawing air from the can, and directing the flow of the air from the can so that it passes across the material accumulating on the inner surface of the sealing lip during draining for reducing the coating .thereon to a thin adhering covering, and then causing air to flow across the outer face of said sealing lip for removing coating material therefrom.

3. Themethod of coating a sheet metal can having an inwardly curved dome-shaped bottom end and an outwardly extending cone-shaped top end, terminating in a neck portion provided with a sealing lip, consisting in flowing the material in fluid condition over the entire inner surface of the can while held in an inverted position, permitting the material to drain from the can, subjecting the can to a vacuum creating means for drawing air from the can and directing the flow of the air so that it passes across the material accumulating on the inner surface of the sealing lip during draining for reducing the coating thereon to a thin adhering covering, and subsequently placing the can in an upright position while the coating material is suiiiciently fluid to permit excess material gathering at the center of the dome to be distributed over the dome.

JAMES H. O'NEIL.

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