NZ216091A - Conveyor for can lids: u-shaped section supports lids by edges - Google Patents

Description

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Patents Form No. 5 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION "IMPROVED OVEN" S/WE, THE BROKEN HILL PROPRIETARY COMPANY LIMITED, a company incorporated under the laws of the State of Victoria, of 140 William Street, Melbourne, in the State of Victoria, Australia, hereby declare the invention, for which <?/we pray that a patent may be granted to Re/us, and the method by which it is to be performed, to be particularly described in and by the following statement:- \"'7~ ,jH 21609 2.

Title: Ijnp roved Oven Background of the Invention This invention relates to improvements in ovens and transporting systems for ovens for the curing of sealants and baking cf lacquers applied to ends fox containers such as cans .

Easy-opening can ends of the push-in type, such as those described in New Zealand Patent Specifications Nos. 164S76, 187328 and 192045 require discrete areas of sealant to be applied in the region oi the edges of the push-in tabs 10 to hermetically seal the can end. Sealant is usually applied to discrete areas covering the cut edges of the tabs and openings, for example by the system described in New Zealand Patent Specification No. 174140.

In the case of so-called "ring-pull ends", 15 it is sometimes necessary to apply repair lacquer to the can end in the region of the score defining the tab and this lacquer is usually subsequently baked to drive off volatiles.

Where easy-opening can ends of the push-in 20 type are manufactured from steel, it is desirable to protect the shorn edges of the opening (s) formed by the end conversion process and this nay be done by spraying repair lacquer or some other form of repair coating onto the can end in that region of the end. This 14/5/84 216091 protective material must similarly be baked to drive off volatiles and to ensure that the lacquer is substantially dry before the can ends are stored or packaged for future use.

Until the present invention, ovens used in the can manufacturing industry have been extremely large, inefficient and not particularly suited to the efficient curing of sealant applied to push-in tab ends or to the efficient baking of repair lacquer applied to such ends. Known ovens not only occupy much valuable floor space in a can manufacturing plant but also cause the surrounding areas of the plant to be undesirably heated making it uncomfortable for the plant operators► SUMMARY OF THE INVENTION Xt is the object of the present invention to provide several distinct and desirable improvements to ovens suitable for heating can ends for the above described and other purposes.

The present invention provides a method of heating can ends in an oven having a generally elongate heating chamber, comprising presenting said can ends to a conveying means operable within said chamber with the curled edge of each, can end directed downwardly, and supporting each can end at two narrow regions of its curled edge by relatively narrow upstanding edges of said conveying means, and moving said can ends through, said oven on said conveying means to heat said can ends.

By conveying the can ends through the heating chamber in the above manner, heat is applied principally to the upper surface of the end and the metal is heated to ensure that the sealant applied to the opposite surface is heated by a conduction process through the * metal and then outwardly through the sealant rather than from the outside surface of the sealant inwardly. Thus, the non-critical outside surface of the end is heated and the likelihood of a cured skin forming over the surface of any 5 repair lacquer on the end is reduced whereby the proper curing of the sealant and the proper escape of volatiles is enhanced.

Furthermore, since the sealant is directed downwardly, it tends to retain its discrete 'printed' shape and profile and has less tendency to spread as it is 10 heated.

The heat source is preferably a radiant heat source located within the elongate heating chamber and incorporating means for directing radiant heat onto the upwardly directed surface of the can ends as they pass 15 through the heating charaler. More preferably, the heat source is an infra-red heat source having a high density short-wave length emanation which is selected to penetrate any repair lacquer applied to the upwardly directed surface of the can end so as to directly heat the metal of the end. 20 The vave length of the emanation is preferably of the order of 1 micron and the temperature of the heat source is preferably of the order of 2120°C.

It will be appreciated that contact with the curled edge of a can end is relatively non-critical 2 16091 . since it is turned in when the end is applied to a can body. Therefore the contact between the conveyor and the end is in a region which will rot be exposed in the final product.

The supporting of the can ends in the above described manner also ensures that the countersink portion of the end is not in contact with the conveyor so that any protective lacquer coating applied to the underside of the can end will remain undamaged. Further-10 more, the sealant applied to the downwardly directed surface of the end is similarly untouched by the conveyor during its passage through the oven.

The conveyor is preferably constructed from a plurality of interconnected slat-like elements having 15 upturned edges so that each link is in the form of a shallow U-profile. As described above the spacing betveen the upturned edges is selected so that the edges engage only narrow portions of the curled edge of each can end. This arrangement ensures that any protective coat-20 ings on critical portions of the end which are exposed to the contents of the can in use are less likely to be damaged during the heating and cooling processes.

Preferably said generally elongate heating chamber closely surrounds the conveyor to reduce the sur-25 face area of the chamber exposed to "said heat source.

The walls of the chamber and the upper surface of the conveyor are preferably reflective to ensure that the heat source is concentrated on the can ends.

The heat source is preferably a radiant 30 heat source incorporating a reflector which concentrates the heat energy in a generally narrow band which corresponds generally in width to the width of the region of -the can end to which the sealant and/or repair lacquer has been applied. The heat source preferably 35 has a parabolic reflector and is an infra-red heat 21/5/84 ?I*>091 i w " j source. j The oven preferably has a cooling chamber following the heating chamber and of similar dimensions to the heating chamber, said cooling chamber including means for directing a stream of cool gas onto a central region of the can end as it is conveyed through the oven.

In a preferred embodiment of the in-vention, any combination of the described -——— — preferments may be incorporated into the oven. Preferably all of the features described above are incorporated in the oven.

Brief Description of the Drawings One presently preferred embodiment of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional end elevation of the oven embodying the invention through part of the heating zone of the oven; Figure 2 is a similar sectional end elevation through part of the cooling region of the oven, and Figure 3 shows details of the slats of the conveyor assembly.

Description of Preferred Embodiment Referring firstly to Figure 1 of the drawings, the apparatus will be seen to comprise a central supporting stajid 1 supporting two identical oven assemblies 2 only one of which is shown and only one of which will be described in further detail. - The oven assemblies 2 are provided to acoept can ends from the /.jVT N / ' Prospective lanes of a two lane end conversion press of known 'V -s*\\ ;.z Construction with the can ends having the surface thereof to which I 2 5FEB 1987 1 V sealant has been applied directed downwardly.

T^e oven assembly 2 comprises a base tube 4 216091 7. mounted or supporting arms 5 extending from the central stand 1 and to the upper portions of the sides of which parallel side elements 6, 7 are secured as shown to define an elongate oven zone 8 of rectangular cross-section. The upper edges of the side walls 6, 7 have seals 9 fitted thereto and the top of the oven zone 8 is closed by means of a closure lid 10 which is held in position on the side walls 6, 7 by releasable clamping mechanisms 10a as shown.

At a plurality of positions along an initial portion of the length of the oven, the cover 10 is formed with an opening 11 over which infra-red radiation lamps 12 are mounted to direct infra-red radiant heat into the heating zone 8. In the present embodiment, four Phillips parabolic reflector infra-red heaters having a type IGR-P790 body and 13230X lamps are arranged substantially end to end over the opening 11. The number of lamps selected in the present case was to ensure that the oven performed adequately in a cold climate and it may be possible to reduce the number of lamps in a warmer climate.

The upper surface of the support tube 4 has spaced pairs of mounting blocks 13 secured thereto as shown. Stepped wear strips 14 are mounted on the support blocks 13 as shown and are engaged by wear pieces 15 secured to conveyor slats 16 and to a roller chain 17 driven by suitable sprockets (not shown) to move the conveyor through the oven.

As is shown in more detail in Figure 3 of the drawings, each slat 16 is of shallow U configuration providing narrow upstanding edges 18 by means of which can ends are supported by means of engagement with short and narrow areas of their curled edges. The slats 16 are spaced apart by a short distance along the length of the conveyor to give the conveyor the 2 1 6091 8 . necessary flexibility to pass around its endless path.

Referring now to Figure 2 of the drawings, a second portion of the oven following the heating zone 8 provides a cooling zone 19. In this zone 19 the cover 10 is modified to support an elongate tube 20 having slots 21 in its lowermost portion overlying wider slots 22 in the cover 10. Cooling air is delivered to the tube 2 0 through a conduit 23 and passes through the slots 21 and 22 onto the upper surface of the can ends (not shown) supported by the conveyor. The cooling air impinges onto the top surface of the can ends and thence downwardly through apertures in the support tube 4 at either side of the conveyor and also between the can ends and through the spaces between the slat and wear pieces and through holes 26 in the top of the support tube 4. An air evacuation duct 24 is connected to the support tube 4 to draw the cooling air therefrom. Following the cooling zone, the conveyor delivers the can ends to a collection chute or the like (not shown).

In the case of the heating zone, each heating lamp 12 has an air duct 25 located centrally thereof to deliver air for cooling each lamp 12 and for purging undesirable gases and volatiles from the heating zone 8. It will be noted from Jigure 1 that the air circulates around the back of the lamp through apertures in the lamp body into a cavity behind the lamp reflector and also circulates down the sides of the lamp through holes (not shown) in the portions of the lid 10 supporting the lamps 12 across the top of the can end (not shown) down the sides of the conveyor between the supports 13 and through openings in the top of the support tube 4 near the sides thereof and also between the can ends and between the slats and wear pieces under the conveyor and through central openings 26 in the top of the 2 1 6091 9. support tube 4. A suitable fan or fans (not shown) drive the air through the irxlet tubes 25 and draw the air through the outlet duct. 24 via a central duct 27 which services both ovens 2.

Each heater 12 is arranged to direct a relatively coherent narrow beam of radiant energy onto the upwardly directed surface of each can end supported by the conveyor. For this reason, the orientation of the can ends as they enter the oven should be arranged such that the closure tabs, for example, in the form shown in any one of the previously described Australian patents, is aligned with the direction of travel of the conveyor so that the sealant applied to the downwardly directed side of the can end and any repair lacquer applied to the upwardly directed side of the can end in the region of the tahs is appropriately heated. Where it is necessary to apply repair Lacquer, a suitable spray nozzle may be arranged near the entry to the oven to spray a band of repair lacquer across the panel portion of each can end including the region in which the tabs are formed.

Since the can ends are supported by the conveyor with the sealant applied thereto directed downwardly, the radiant energy applied to the upwardly directed surface of the can end will heat the can end so that the sealant is heated by the metal surface outwardly rather than from the outer surface of the sealant inwardly. This arrangement is advantageous for several reasons: 1) the heat is applied to the less critical side of the end, 2) any lacquer applied to the end is also heated before the sealant is heated to promote adhesion between the sealant, usually a pvc plastisol, and the lacquer, . 10 - 216091

Claims (14)

WHAT WE CLAIM IS:

1. A method of heating can ends in an oven having a generally elongate heating chamber, comprising presenting said can ends to a conveying means operable within said chamber with the curled edge of each can end directed downwardly, and supporting each can end at two narrow regions of its curled edge by relatively narrow upstanding edges of said conveying means, and moving said can ends through said oven on said conveying means to heat said can ends.

2. An oven when used for carrying out the method of Claim 1, comprising a generally elongate heating chamber, means for applying heat to tlie chamber, conveying means for supporting said can ends as they are conveyed through said heating chamber, said conveying means being characterised by relatively narrow upstanding edges which are spaced so as to support each can end at two narrow regions of its curled edge.

3. The oven of claim 2, wherein said conveyor comprises a plurality of interconnected slat-like elements having upturned edges so that each link is in the form of a shallow U-profile, the spacing- between said upturned edges being selected so that said edges engage only narrow portions of the curled edge of each can end.

4. The oven of Claim 2 or Claim 3, wherein said elongate heating chamber closely surrounds said conveyor to reduce the surface area of the chamber exposed to said heat source. r, * /- r\ x O U J;- 11 -;

5. The oven of Claim 4, wherein the walls of said chamber and the upper surface of said conveyor is reflective to ensure that said heat source is concentrated on said can ends.;

6. The oven of any one of Claims 2 to 5, wherein said heat source is a radiant heat source incorporating a reflector which concentrates the heat energy in a generally narrow band which corresponds generally in width to the width of the region of the can end to which the sealant and/or repair lacquer has been applied.;

7. The oven of Claim 6, wherein said heat source has a parabolic reflector.;

8. The oven of Claim 6, wherein said heat source is an infra-red heat source having a wavelength;emanation which is selected to penetrate any repair lacquer applied to the upwardly directed surface of the can end so as to directly heat the metal of the end.;

9. The oven of Claim 8, wherein the peak intensity of the emanation occurs at a wave length of about 1 micron and the temperature of the heat source is about 2120°C.;

10. The oven of any one of Claims 2 to 9 further comprising a cooling chamber following said heating chamber and o£ similar dimensions to the heating chamber, said cooling chamber including means for directing a stream of cool gas onto a central region of the can end as it is conveyed through the oven.;

11. The oven of any one of Claims 2 to 10, wherein said conveyor has slat-like elements substantially as described with reference to the accompanying drawings.;216091;- 12 -;

12. The oven of Claim 10, wherein the cooling chamber is substantially as described with reference to Figure 2 of the accompanying drawings.;

13. The oven of any one of Claims 2 to 12, wherein;5 the heat source is constructed and arranged substantially;T;as described with reference to Figure 1 of the accompanying drawings.;

14. A can end heating oven as claimed in Claim 2 substantially as described -with reference to the accompanying drawings. THE BROKEN HILL PROPRIETARY COMPANY LIMITED;A- ^ i 1SSBpr>87£,;ft;\ * Jj