The invention concerns a portable container for liquefied gases under pressure with a valve which is mounted in the top of the container.

Even at common temperatures gases, such as oxygen, hydro¬ gen, carbon dioxide and propane/butane, change phase to liquid form at a pressure above a certain limit which is characteristic of the gas concerned. In this phase the gas has a greatly reduced volume, and this is utilized to a considerable extent for storing and distributing liquefied gases in portable pressure containers, which are commonly called gas cylinders.

Examples of such gas cylinders include propane/butane cy¬ linders which are used in large numbers i.a. in the home, in industry, agriculture and horticulture, where the gas is used as a source of heat.

When a cylinder is empty, it is replaced by a new filled cylinder, while the empty cylinder is returned via the distribution network to a filling station to be filled again. This entails that in addition to the costs of the actual gas, considerable costs are incurred with respect to handling and transport of the cylinders.

To reduce these transport costs as much as possible, the cylinders are stacked in transit in several layers on the trucks, and to save space a corresponding stacking takes place at the filling stations, the depots which, as inter¬ mediate stores, supply a specific district with cylinders, and frequently also at consumption sites where many cylin¬ ders are used.

The cylinder valve, which extends upwardly from the top of the cylinder, frequently has no form of protection, and in that case it greatly impedes stacking, because the cylin¬ ders cannot stand stably directly on top of the valves, which would moreover be liable to be damaged by this.

It has been attempted to solve this problem in practice by placing loose boards between the individual layers in the stack of cylinders, but, of course, this measure involves extra work for the stacking and also expenses for the boards used, and to this should be added that the valves are not completely protected against being damaged, be¬ cause the overall weight from the overlying layers of cy¬ linders of course continues to be transferred through the valves.

With a view to remedying the above-mentioned drawbacks there have been developed cylinder types which are pro¬ vided with a cylinder collar welded firmly onto the cylin- der around the valve. By means of this structure the cy¬ linders can now be stacked on top of each other without loading the valves and without it being necessary to use loading boards. However, experience gained in the course of time has revealed that these collars do not give the valve satisfactory protection during handling and stack¬ ing. The reason is that the thickness of the collar must necessarily be kept within certain limits to avoid in¬ creasing the cylinder weight so much that the number of cylinders which may lawfully be loaded on a truck is re- duced, thereby increasing the overall transport costs correspondingly. Furthermore, the structure results in a not insignificant increase in the production costs because of the considerable extra work involved in manufacturing and welding the collar on the cylinder.

The US Patent Specification 2 015 904 discloses a con¬ tainer for liquefied gases under pressure with a container collar in the form of a fold which is provided by the wall of the container. In this case a seamless container is in- volved, and the fold is formed by first necking the top of the container in a conventional manner and then pressing the top into the container in several heats. The fold will hereby extend all the way along the periphery of the con¬ tainer and thus leaves a closed cavity upwardly in the container where rainwater may collect when the container is left to stand in the open, as is frequently the case. The container can hereby be subjected to corrosion, which may cause dangerous bursts that may involve loss of life, because the pressure in the container can be very great. Furthermore, the valve can be destroyed when the water gradually rises around it. Containers of this type are portable, but the containers known from the above-men¬ tioned US patent are difficult to handle since it is not possible, within the outer boundary of the container, to mount handles anywhere on it for carrying the container.

Accordingly, there is a great need for a portable con¬ tainer or gas cylinder of the type mentioned in the ope¬ ning paragraph which, without increasing the manufacturing costs and reducing the number of the cylinders that may be loaded on a truck in transit, gives the cylinder valve efficient protection during handling and permits the cy¬ linders to be stacked on top of each other without using loading boards and without loading the valve, without the top of the container and the valve being thereby subjected to corrosion and damage from e.g. collected rainwater, and which also has a structure such that a handle for carrying the container can be mounted easily and conveniently.

The container of the invention is novel and unique in that the upper wall of the container, along part of the peri-

phery, is drawn up into at least one inwardly open and outwardly closed fold with a substantially horizontally extending fold edge which is positioned at the same level as or above the upper boundary of the valve, and that each fold at both ends is closed outwardly with an end edge ex¬ tending downwardly from the fold edge to the base of the fold on the upper end bottom. By means of this dual use of the container or cylinder wall it is now possible to manu¬ facture a cylinder which efficiently and securely protects the cylinder wall during handling and transport, and this is achieved without simultaneously increasing the trans¬ port and manufacturing costs. The fact that the fold or folds only extend along part of the periphery of the con¬ tainer entails that openings are left for drainage of water, which, e.g. in the open, might otherwise inexpe¬ diently collect in the space within a completely closed fold. Furthermore, handles for carrying the container may be mounted between the end edges of the fold or the folds.

To impart sufficient stability to the fold edge against the impacts from the inner positive pressure in the cylin¬ der, the fold edge may substantially extend in a curve be¬ tween its innermost and outermost walls. When the fold is corrugated at the same time, it is strengthened additio- nally to a considerably degree.

A particularly strong and stable structure is obtained by connecting the lowermost part of the innermost one of the two upstanding walls of each fold with the opposed con- tainer wall by means of preferably obliquely outwardly and downwardly extending stays.

When the pressure in the cylinder exceeds a certain per¬ missible size, the cylinder begins to expand until it finally bursts. During this expansion an even and uniform stretching of the cylinder wall is intended to avoid dan-

gerous stress peaks that may cause premature burst. Ac¬ cordingly, it is of great importance that the stays are so arranged as to be capable of following the expansion. This is advantageously obtained by providing the stays in the form of narrow ties which are positioned in juxtaposed mu¬ tually spaced relationship, so that these ties may have the form of triangles which are secured in star shape to a plate ring, which is in turn secured to the lowermost part of the innermost one of the two upstanding walls of each fold.

Many cylinders, e.g. 11 kg propane/butane cylinders, are carried in a handle which is secured to the top of the cylinder. Such a handle, which also serves to stiffen the fold, may advantageously be mounted such as to connect two adjacent end edges on the fold or the folds, so that the distance between these end edges is so great as to provide sufficient space for a hand to grip the handle.

For the fold to be deformed as evenly and uniformly as possible during the expansion of the cylinder, the inner wall of the fold may substantially have the shape of a surface of revolution which is concentric with the con¬ tainer wall and which is moreover to have a greater dia- meter than the greatest transverse dimension of the valve, such as to leave sufficient space for it in the fold.

The invention will be explained more fully by the follow¬ ing description of embodiments, which just serve as ex- amples, with reference to the drawing, in which

fig. 1 is a perspective view of a portable pressure con¬ tainer or cylinder with a single fold to protect the valve,

fig. 2 is an axial section across the fold in the cylinder shown in fig. 1 standing on top of a corresponding cylin¬ der, of which only the uppermost portion is shown,

fig. 3 is a fragment of an axial section through the ope¬ ning in the fold in the cylinder shown in fig. 1,

fig. 4 is a fraction of an axial section across a corru¬ gated fold stiffened by means of a stay,

fig. 5 is a section along the line V-V in fig. 4,

fig. 6 is a top view of a fraction of a cylinder with a corrugated fold, and

fig. 7 is a side view of the same.

Fig. 1 shows a container, which may e.g. be an 11 kg pro¬ pane/butane cylinder, which ordinarily consists of two deep-drawn metal end bottoms welded together by means of a central seam. This detail is not shown in the drawing, be¬ cause the cylinder may be manufactured in any other suit¬ able manner without departing from the idea of the inven¬ tion.

The cylinder, which is moreover shown in figs. 2 and 3 in section, has a container wall 2 defining a closed space 3 for the gas, which is present in liquefied form in the cylinder under pressure. The container wall must therefore be sufficiently strong to be able to withstand the pres¬ sure from the liquefied gas under ordinary conditions of operation, as well as the prescribed greater test pressure to which the cylinders are subjected before being approved for use. The contents of the cylinder, which are propane/ butane in this case, are not shown in the drawing.

To be able to absorb the pressure from the gas in the cy¬ linder in the best possible way, the wall 2 of the cylin¬ der is downwardly vaulted outwardly, and at this location there is moreover provided a foot ring 4, on which the cy- under can stand, and which is in this case additionally provided with an elastomeric ring 5 of e.g. rubber. This ring serves to reduce the noise during handling of the cylinders and to protect their paint during stacking.

A flange 6 is welded in the top of the cylinder, said flange threadingly accommodating a valve 7 in airtight manner. The container wall 2 in the cylinder top is more¬ over drawn up into a fold 8 surrounding the valve, but leaving an opening 9 between the end edges 10 of the fold. Rainwater, which in conventional structures with a com¬ pletely closed fold collects in the space within the fold when the container is left to stand in the open, can here¬ by readily escape through the opening/openings so that the container does not corrode and the valve is not damaged by the water. Upwardly, the end edges 10 are stiffened by a pipe 11 which also serves as a handle for the cylinder. For the last-mentioned reasons the distance between the end edges 10 is selected to be so great as to leave suffi¬ cient space for a hand to grip the handle 11.

The upper fold edge 19 of _^ fehe fold is arranged so high above the valve 7 that the valve is effectively protected against external mechanical impacts during handling, and that the cylinders, as shown best in fig. 2, can be stacked on top of each other without the bottom of the uppermost cylinder contacting the valve of the lowermost cylinder.

As will appear, the fold, which serves as a protection collar for the valve, is made directly from the wall of the cylinder without involving additional welding work

like in the conventional structures with a protection collar and without a corresponding increase in the weight of the cylinder. Moreover, according to the invention, the protection collar in the form of the fold is extremely strong and completely eliminates the necessity of using separate loading boards in connection with transport and storage.

Upwardly and along the end edges 10 the wall of the fold 8 extends in a curve which is the optimum shape to absorb the internal positive pressure in the cylinder. When the cylinder is made of deep-drawn end bottoms of e.g. steel, it is advantageous that the curve between the innermost and outermost walls 13, 14 of the fold has a radius of curvature which is greater than three times the thickness of the end bottom so that the material is not overloaded during the actual deep-drawing process. As shown in figs. 4, 6 and 7, the fold 8 may moreover be stiffened by corru¬ gations or waves 12, which are pressed into the material of the container wall or provided in another manner in it.

Additional stiffening of the fold 8 is obtained by means of the stay 15 which is shown in fig. 4 and which connects the lowermost portion of the innermost wall 13 of the fold with the container wall 2, said stay extending obliquely downwardly toward the container wall to absorb at least part of the vertically upwardly directed pressure load on the fold in the best possible manner. The ends of the stay 15 may e.g. be secured on the container by means of weld- ing.

If the stay 15 is provided as a continuous truncated cone face, it will tend to lock the container wall 2 in the area where the wall is connected with the stay, during the expansion of the cylinder. Owing to this locking, depend¬ ing upon the structure of the cylinder, very dangerous

stress peaks may occur in precisely this area, which may entail that the cylinder bursts at a too low pressure and without obtaining a sufficiently great expansion in vol¬ ume. Such a great expansion in volume is desired especi- ally when the cylinders are used for propane/butane, which has a very great thermal coefficient of expansion. If the cylinder should be heated in case of e.g. fire, it is very important of course that the cylinder can follow the ex¬ pansion of the gas without being burst by a pure liquid pressure.

Fig. 5 shows a flexible stay 16 which is divided into a large number of narrow, triangular branches 17 which ra¬ diate from a plate ring 16. The upwardly directed pressure impact of the gas on the fold 8 is transferred completely or partly via the branches 17 to the container wall 2, which can now unobstructedly extend between the points where the branches 17 are secured to the container wall, during expansion of the cylinder. The possibilily of stress peaks in this area is hereby eliminated.