WO1992009489A1

WO1992009489A1 - Metallic pressure container

Info

Publication number: WO1992009489A1
Application number: PCT/AU1991/000546
Authority: WO
Inventors: Robert Norman Smith; Roland David South
Original assignee: Rheem Australia Pty Ltd
Current assignee: Rheem Australia Pty Ltd
Priority date: 1990-11-27
Filing date: 1991-11-27
Publication date: 1992-06-11
Anticipated expiration: 1993-05-27

Abstract

A container (10) for holding fluid under pressure, particularly suitable as a non-returnable beer keg having a capacity between 20 and 80 litres approximately, comprising a sheet metal cylindrical body (12) and two curved sheet metal ends (18, 21), at least one end including a filling and dispensing opening (23), each end comprising a curved circular central portion, a knuckle radius (19) adjoining the outer periphery of the central portion and a generally cylindrical portion (20) adjoining the knuckle radius. Each end is connected to the body to form the container by a bond (22) formed solely by an organic adhesive interposed between at least the cylindrical portion of each end and a fully circumferentially extending portion of the inside surface of the body. In addition there may be inwardly formed circumferential beads (13, 14) in the body wall to locate and abut the ends. The preferred adhesive is a toughened epoxy type applied in paste or gel form to the joint regions.

Description

METALLIC PRESSURE CONTAINER.

BACKGROUND.

This invention relates to serially produced metallic pressure vessels. One exemplary application although not a limitation is such a vessel for use as a single-trip non-returnable beer keg.

Serially produced pressure vessels are manufactured under codes such as Australian Standard 2971. Under this code such vessels need to be capable of specified ability under burst and fragmentation type tests. In such containers when used as beer kegs, pressure is liable to be built up due to carbonation of the beer as delivered. In addition to this, in the dispensing of beer, carbon dioxide gas under pressure is introduced to the keg to cause the beer to be displaced from the keg through pipes or tubes to the point of dispensing.

In the past metallic beer kegs, which have come into widespread use since the demise of wooden barrels for this purpose, have been typically manufactured from stainless steel in a relatively heavy gauge of about 1.4 to about 1.6mm thickness. Typical capacities of such beer kegs are 5 gallons, 9 gallons and 18 gallons (i.e. Imperial gallons) or respectively, 20 through to 80 litres approximately. Such heavy gauge kegs or barrels are used in a returnable circuit and are cleaned and refilled on each return.

For some markets it is desirable to have a single trip beer barrel which is of low enough cost to enable it to be sent to a point of use and not returned for cleaning and refilling. For acceptable economy this requires a significant reduction in the use of expensive stainless steel in particular and generally requires use of the minimum quantity of metal. Attempting to achieve such an end by the use of reduced thickness of steel or stainless steel leads to welding difficulties using the conventional beer keg assembly techniques. This is particularly so in the absence of expensive special purpose welding machines. The type of equipment satisfactory for manufacture of 1.4mm stainless steel beer kegs, namely mechanised positioning and manipulating equipment coupled with inert gas shielded mechanised and hand-held welding torches, is not adaptable to substantially lighter weight constructions of kegs. With these requirements and with the limitations of existing manufacturing processes in mind, the present invention has as an objective to enable the production of a lightweight one-way non-returnable beer keg which is sufficiently economical in the use of steel and/or stainless steel as to be feasible for this type of application and similar ones and to be of a construction able to be manufactured reliably in the face of known welding difficulties with relatively large light gauge containers.

SUMMARY OF THE INVENTION.

Accordingly, the present invention consists of a sheet metal container comprising a sheet metal cylindrical body and two curved sheet metal ends, at least one end including a filling and dispensing opening means, each end comprising a curved circular central portion, a knuckle radius adjoining the periphery. of said central portion and a generally cylindrical portion adjoining said knuckle radius; and each end is connected to the body to form the container by a bond formed solely by an organic adhesive, said adhesive being interposed between at least said cylindrical portion of said end and a fully circumferentially extending portion of the inside surface of the said body.

in a preferred form, the container in addition is provided with a bead extending inwardly and circumferentially in the body wall as a step in the vicinity of one end against which a peripheral portion of the said central portion of the curved end abuts.

In a further preferred form the body in addition is provided with two closely spaced inwardly directed circumferentially extending beads formed in the vicinity of each of its ends to house the cylindrical portion of each end.

As further preferred features the container in addition is provided with a bead extending inwardly and circumferentially in the body wall as a step in the vicinity of one end against which a peripheral portion of the said central portion of the curved end abuts. Also, the adhesive bond may be extended to include contact with at least a portion of the bead bearing against the said peripheral portion. Also in which the body in addition may be provided with two closely spaced inwardly directed circumferentially extending beads formed in the vicinity of each of its ends to house the cylindrical portion of each end. Also, the body in addition may be provided with a rounded portion at at least one end, the rounded portion extending circumferentially that the rounded portion may be formed from the material of the body wall .

In one particularly preferred form the curved ends are located with respect to the body such that each has a convex surface facing the exterior of the container.

This preference maximises the container capacity for a given consumption of sheet metal.

The organic adhesive may be applied in a paste or gel form and cured with the application of heat to form the bond. One particularly preferred form of the organic adhesive is a thermosetting toughened epoxy type.

In one preferred form the body and ends may be mild steel having protective thin organic coatings over at least all interior surfaces of the container. In other preferred forms the cylindrical body may be mild steel to which is applied a protective thin organic coating and the ends are stainless steel.

Alternatively the body and ends may be stainless steel.

When the container is all mild steel sheet metal, it is preferred that the thicknesses of the body wall is in the range of O.θmm to 1 mm, the thickness of the ends is in the range 0.6 to 0.8 mm and the diameter of the body is about 380mm and the capacity is at least 50 litres.

When the container is all stainless steel sheet metal, it is preferred that the thickness of the body and ends is in the range 0.6 to 0.8 mm, the diameter of the body is about 380mm and the capacity is at least 50 litres.

In one further preferred version, at least one end may be concave to the container exterior and the rounded portion of the body adjacent the end or ends is inwardly rolled to enclose an outer edge of the cylindrical portion of the respective end.

BRIEF DESCRIPTION OF THE DRAWINGS.

The invention is further described by reference to a particularly preferred example and variations thereof as illustrated in the accompanying figures in which: Figure 1 is a part cross section, part elevation view of a container embodiment according to the invention.

Figure 2 is an enlarged detail in cross section of the container as illustrated in Figure 1, showing in detail how the bottom is attached to the body.

Figure 3 is a series of schematic fragmental cross sections depicting alternative embodiments of containers having adhesive bonded joint arrangements according to the invention.

DETAILED DESCRIPTION.

With reference to Figure 1 a container according to the invention (10) comprises a sheet metal cylindrical body portion (12) with circumferentially extending inwardly directed beads (13) and (14) positioned in two adjacent pairs generally close to either end of the body. Either end of the cylindrical body has a rounded end (16), that may be rolled from the body material and outwardly directed, as illustrated, or may be inwardly directed.

The container further comprises a bottom end (18) and a top end (21) both formed of sheet metal. Each end comprises a curved central portion, a knuckle radius (19) and a short generally cylindrical portion (20). The top end has provision for an opening fitting to be attached that may be of conventional type such as a Barnes- - Bush, well known in the trade. The top opening need not necessarily be centrally located although this is a convenient location. The top end opening (23) may alternatively be fitted with a threaded type opening such as a Colsh Cap or a flange of the type used for steel drums that require no welding. A flange of two inch (nominal 50mm) size is preferred, made from aluminium, organically coated steel or stainless steel. The beads, (13) and (1 ) may be of differing depths as illustrated. The outermost bead (14) on either end may preferably be more deeply formed than the innermost bead (13). Although a container according to the present invention could be made without any beads, the reason for their preference is that the innermost beads (13) can provide an assembly location stop for the ends during manufacture whilst the outermost beads (1 ) can provide for a more positive attachment of the ends to the body and a greater resistance to leakage.

With reference to Figure 2, the bottom end (18) is attached to the body wall between an outer (14) and inner bead (13). Between the periphery of the bottom (18) and the adjacent inside wall of the body a layer of adhesive (22) is positioned to attach the end to the body in a pressure-tight sealing manner. The position of application of the adhesive (22) may extend, as illustrated, to increase the area of bonding to include an outer part of the curved bottom adjacent the one flank of the bead (14). Suitable adhesives for use in the bonding process include toughened epoxies which are applied as a single part and then heat cured. Suitable types are designated as "Permabond 110" which is in a paste form or

"Permabond 108", in a gel form. Permabond is a trade mark and the adhesives are made by Permabond Adhesives Limited, Woodside Road, East Leigh, Hartsfordshire S05 4EX, UK.

The sheet metal of the body is preferably mild steel with a thin protective lining of an organic material such as based on an epoxy phenolic. For a nominal 18 gallon (80 litre) keg, a preferred overall diameter for the body cylinder is 380mm approximately. In this case the body thickness in mild steel is preferably in the range 0.8 to 1.00 mm and more preferably is 0.9mm. The ends (18) and (21) may be of organically coated mild steel but preferably are formed from stainless steel. Again, where the diameter of the keg is nominally 380mm the thickness of the stainless steel ends is preferably in the range 0.6 to 0.8 mm and more preferably is 0.7mm for both body and ends.

Although a mild steel body is preferred because it is easier to weld the longitudinal body weld on a drum welder, stainless steel would not be precluded. For a mild steel body, the longitudinal body weld-heat affected area has an organic coating applied after welding to cover the weld. For a stainless steel body the heat affected area by the weld may be chemically treated after completion to clean and passivate it. A mild steel body may use precoated steel or, uncoated mild steel may be sprayed or powder coated with the organic coating after welding. When precoated steel is used, only the coating that may be removed or heat affected adjacent to the weld need be repaired with spray or powder applied organic coating. When mild steel ends are preferred, they are preferably coated with a protective layer such as epoxy phenolic resin particularly including the sheared edge of each end that in use is in contact with the contents of the container. Using stainless steel ends has the advantage of not requiring protection of the sheared edge. Figure 3 shows in scrap schematic cross section views a number of alternative arrangements for the disposition of the end in relation to the body, all of which are examples of embodiments of the invention. In each case an adhesive bond, similar to that described in relation to Figure 2 is interposed between the mating faces of the respective cylindrical portions of the ends and the body that abut each other. In Figure 3 (f) is shown a joint arrangement that includes a rounded end of the body formed by rolling the body inwardly to enclose the outer edge of the cylindrical portion of the end.

An example of the invention made according to the description in Figures 1 and 2 has been shown to be capable of withstanding 975 kPa internal pressure. It has been shown capable of meeting the requirements for burst and fragmentation tests according to Appendix C of Australian Standard 2971.

Suitable steps in manufacturing the container shown in Figures 1 and 2 are as follows:

1. Forming a rectangular body sheet into a cylinder and welding a longitudinal side seam (not shown), preferably using a drum body welding machine.

2. Forming the innermost beads (13) by either of the following 2 steps:

(a) expanding the remainder of the cylinder outwardly to leave the beads (13) unexpanded; or

(b) forming the cylinder at its final diameter and using a series of opposed rollers to inwardly deform the beads (13).

3. Forming the bottom and top end by pressing stainless steel sheet metal into the shapes as shown.

4. Forming an opening in the top end (21 ) to insert the closure (23). Closure (23) may be af ixed to the top end (21 ) by means of an adhesive.

5. Applying adhesive to the joint area outwardly of each inner bead (13). 6. Inserting each end in until it positively locates against bead (13).

7. Inwardly rolling the outermost beads (14) so that their shape conforms with the shape of the knuckle radius (19) of each end.

8. Heating the entire container at a temperature sufficient to rapidly cure the adhesive, typically 110°C in the case of the preferred toughened epoxy type.

9. Pressing the ends of the body between two opposed dies each having a curved cross section profile to form the curled ends (16).

10. Pressure testing the completed container.

The order of manufacturing steps need not strictly follow the order as listed above for example, the curled ends (16) could be put in place prior to step 7.

Claims

CLAIMS.

1. A container for holding fluid under pressure, comprising a sheet metal cylindrical body and two curved sheet metal ends, at least one end including a filling and dispensing opening means, each end comprising a curved circular central portion, a knuckle radius adjoining the periphery of said central portion and a generally cylindrical portion adjoining said knuckle radius; and each end is connected to the body to form the container by a bond formed solely by an organic adhesive, said adhesive being interposed between at least said cylindrical portion of said end and a fully circumferentially extending portion of the inside surface of the said body.

2. A container as claimed in claim 1 in addition provided with a bead extending inwardly and circumferentially in the body wall as a step in the vicinity of one end against which a peripheral portion of the said central portion of the curved end abuts.

3. A container as claimed in claim 2, the adhesive bond extending to include contact with at least a portion of the bead bearing against the said peripheral portion.

4. A container as claimed in claim 1 in which the body in addition is provided with two closely spaced inwardly directed circumferentially extending beads formed in the vicinity of each of its ends to house the cylindrical portion of each end.

5. A container as claimed in any one of the preceding claims in which the body in addition is provided with a rounded portion at at least one end, the rounded portion extending circumferentially.

6. A container as claimed in claim 5 in which the rounded portion is formed from the material of the body wall.

7. A container as claimed in any one of the preceding claims in which the curved ends are located with respect to the body such that each has a convex surface facing the exterior of the container.

8. A container as claimed in any one of the preceding claims in which the organic adhesive is applied in a paste or gel form and cured with the application of heat to form the said bond.

9. A container as claimed in claim 8 in which the organic adhesive is a thermosetting toughened epoxy type.

10. A container as claimed in claim 1 in which the body and ends are mild steel having protective thin organic coatings over at least all interior surfaces of the container.

11. A container as claimed in claim 1 in which the cylindrical body is mild steel to which is applied a protective thin organic coating and the ends are stainless steel.

12. A container as claimed in claim 1 in which the body and ends are stainless steel.

13. A container as claimed in claim 11 in which the thicknesses of the body wall is in the range of O.θmm to 1mm, the thickness of the ends is in the range 0.6 to 0.8 mm and the diameter of the body is about 380mm and the capacity is at least 50 litres.

14. A container as claimed in claim 12 in which the thickness of the body and ends is in the range 0.6 to 0.8 mm, the diameter of the body is about 380mm and the capacity is at least 50 litres.

15. A container as claimed in claim 6 in which at least one end is concave to the container exterior and the rounded portion of the body adjacent the said at least one end is inwardly rolled to enclose an outer edge of the cylindrical portion of said at least one end.

16. A container as claimed in any one of the preceding claims for use as a single-trip non-returnable beer keg.