SE468426B - SET FOR MANUFACTURING A CONTAINER OF THERMOPLASTIC MATERIAL AND CONTAINER MANUFACTURED AS SET - Google Patents

Abstract

A thermoplastics container comprises a body portion 1 formed from a flat sheet by bending the sheet to produce a tube and welding together the ends of the sheet by hot- plate welding. The sheet ends are preferably butt-welded. End portions 2, 3 are attached to the body portion 1 by welding or adhesive; one end portion may be injection-moulded directly onto the body portion. The body portion can be ribbed or laminated, and the end portions may have configurations which facilitate stacking.

Description

468 426 2 der, which exceeds six months.

However, customers often prefer stacking designs of 6, 9 or 12 in height and for longer periods with products with a specific gravity exceeding 1.0 g / cma, which at present can not be achieved with a blow-molded container of commercially attractive weight and with fixed even wall thickness.

Many blow-molded containers are also susceptible to fatigue cracks when they are filled with an alkaline product or a product of a cleaning composition and when they are subjected to overload loads in stacking piles.

Another technique used provides a barrel with a main body extruded to a desired section and injection molded end sections which are butt welded to the main body. The use of extrusion for the main part entails high costs for large spray matrices and this means that the technology is economical only for long production series of a certain shape and thickness.

END OF THE INVENTION AND MOST IMPORTANT CHARACTERISTICS In accordance with the invention, there is provided a simplified method of manufacturing a container according to the preamble of claim 1, characterized in that the longitudinal joint of the cylindrical body is provided by welding the cylindrical portions of the preformed ends are butt-welded to the main part by hot plate welding.

By hot plate welding is meant a process for welding surfaces of thermoplastic material together by heating the surfaces in contact with a hot or heated plate, then removing the plate and pressing the heated surfaces together and allowing them to cool and bond together at a pre-468 4.26 3 determined pressure for a predetermined time.

The flat sheets can be produced by extrusion, compression molding or by other suitable processes. The ends of the divided length of the sheet material are preferably joined by butt welding, but under certain circumstances an overlapping weld may be preferred. The main body may have any suitable cross section, such as a circular cylinder, it may be substantially square or rectangular with rounded corners or even triangular, hexagonal or octagonal in cross section.

The prefabricated end portions can be formed by injection molding, thermoforming, blow molding or rotational molding or by any other suitable process and they can be attached to the main body in any suitable manner. They are preferably butt welded to the main part by hot plate welding, but friction welding, ultrasonic welding and other connecting operations can also be used, e.g. suitable glue or the like. The injection molded end portions can be made in accordance with normal technology by molding the top and bottom sections to the container in flat form with the top section provided with a filling neck. Alternatively, a technology can be used where the bottom and top ends have the same geometry, with the filling neck (s) closed by a partition. In this case, the filler necks can be cast without threads. Since the part is to be the bottom end section, the neck can simply be machined away, which results in a flat surface. Since the part is to be the top end section, a thread can, if desired, be cut inside or on the outside of the straight filling neck and a hole can be worked up through the partition. The body and end portions may be of the same or different thermoplastic materials, and any suitable material may be used such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene, etc. The disc forming the main body can, however, be co-injected in sandwich form, so that it comprises a material in the middle section of the side wall and an inner and an outer layer which gives the extruded disc a sandwich structure. The combination of materials can be selected to give the side wall of the barrel predetermined mechanical or physical properties.

The prefabricated end portions and the main portion are normally assembled by means of hot plate welding or the like after having been manufactured in advance by suitable processes (eg injection molding for the end portions and extrusion and hot plate butt welding for the tubular main part).

This means that the three objects have cooled down and reached their preferred shapes when the shrinkage process of the thermoplastic material is completed. However, it may be preferable to keep the main portion in a fixed position and to injection mold one of the end portions directly on one side of the main portion, thereby avoiding a welding line formed during hot plate welding.

The flat plate for forming the main portion can also be formed with stiffening flanges, which can be placed on the inside of the container or it can have a kind of honeycomb pattern inside its wall thickness, which improves the mechanical properties of the main part.

The stiffening flanges can be placed in a horizontal or vertical direction on the main part and can fulfill different functions depending on their position.

Horizontal ribs can be used as: a) aids for lifting a barrel; b) conveyor belts; and / or c) means for protecting the side walls of the barrel from collapsing under the influence of a load standing thereon (stacking performance) or under the influence of a partial 468 426 s vacuum arising from temperature differences of the products filled in the barrel with considerable partial vapor pressure .

Vertical flanges can be used as stiffening flanges on the inside or outside of a container with a square, round or rectangular cross section. The aforementioned flanges are intended to improve the resistance to vertical compression.

By forming the main part of a flat sheet of material, the cost of a large number of spray matrices, one for each required cross section, is avoided.

By starting from a flat disc, an additional advantage is achieved in that the disc while it is flat can be pre-printed by means of a suitable printing method and thereby a better quality of the printing can be achieved compared to printing on cylindrical or rounded rectangular or square main body sections.

DESCRIPTION OF THE DRAWINGS The invention will be described in more detail below with reference to the accompanying drawings.

Figure 1 shows a view of a typical shape of a barrel shaped in accordance with the invention.

Figure 2 is a top plan view of the dish of Figure 1.

Figure 3 is a plan bottom view of the barrel of Figure 1.

Figure 4 is an enlarged section along the line A-A in Figure 2.

Figure 5 is an enlarged section along the line B-B in Figure 3, and also showing the stacking of two barrels. 468 426 6 Figure 6 is a view showing a form of sheet material from which the main part can be formed.

Figure 7 is a view of a barrel body formed from the disc material shown in Figure 6.

Figure 7a shows an alternative shape of a barrel body part.

Figure 7b is a horizontal view of the main part according to Figure 7a.

Figure 8 is a perspective view showing an alternative form of sheet material.

Figure 9 shows a form of casting product that can be used as a starting material for the top or bottom of a barrel.

Figure 10 is a section through a casting detail for a bottom end of modified shape.

Figure 11 shows a section through a casting part for an upper part, and also a casting part of a bottom part according to figure 10 in stacking position.

Figure 12 is a plan view of the casting part for the upper part according to Figure 11, and Figure 13 shows a drum of larger size.

DESCRIPTION OF EMBODIMENTS As shown in Figures 1 - 5, a barrel consists of a main part 1, an upper end part 2 and a lower end part 3. The main part 1 is shown with a circular cylindrical shape, and it is formed by bending a flat sheet of material by means of of a suitable forming tool and butt welding of the ends by means of hot plate welding. The upper and lower portions 2 and 3 are manufactured separately by injection molding or otherwise. 468 426 It can be seen from the drawing figures that the end portions 2 and 3 may have central recesses 4 for reinforcement purposes and the upper portion 2 is provided with a filling neck 5, which is shown with thread intended to receive a closing cap 6 (shown only with dashed lines in Fig. 4).

The upper part 2 is provided with an upright peripheral wall or edge 7 to provide stackability despite the filling neck, the closing lid 6 and the recesses 4.

This wall is provided with an opening 8 in the area of the filling neck 5 to simplify the pouring from the barrel and also to ensure that rainwater or other liquids do not collect on top of the barrel. The wall 7 is formed integrally with the upper end portion 2 and is joined to the generally planar closing section of the end portion 2 by means of a plurality of circumferentially distributed reinforcing angle supports 9. The upper portion 2 is butt welded to the upper end of the main portion 1 by hot plate welding along the line II in Figure 4.

The lower portion 3 is provided with mutually spaced, downwardly facing peripheral flanges 12 and 13, which between them form a recess 14, which fits over the upright wall 7 on the next barrel when the barrels are stacked on top of each other. The flange 13 is stiffened by means of a series of angular flanges 15 arranged at a distance from each other.

The lower part 3 is butt welded to the lower end of the wall 1 by means of hot plate welding along the line 16 in Figure 5.

It will be appreciated that barrels of this construction can be used especially in sizes such as 15 liters, 20 liters and 25 liters.

However, the manufacturing technique can be used over a large size range, e.g. from 15 liters up to 250 liters. 468 426 8 When using the hot plate welding technique, it may be necessary to provide some kind of enlargement of the surface to be welded by compaction of the material, and such enlargements may conveniently be planarized after welding.

The upper portion 2 may have means for attaching a suitable carrying handle.

In addition, although the upper portion 2 is shown with a raised wall 7 which cooperates with the recess 15 for stacking, other stacking systems can be used. The upper portion 2 may also be convex, while the lower portion 3 is concave to offer their fit into each other during stacking and considerable additional strength of the end portions 2 and 3. In such a cupped arrangement, a filling neck may be included in a recess. in the coup.

The filler neck can either be threaded on the inside to receive a threaded pin, or on the outside to receive a threaded lid, or it can be smooth to receive a crimped lid. Figure 6 shows an extruded sheet 21 of plastic material, such as polyethylene and provided with a pair of flanges 22. The sheet is shown provided with side edges 23 and end edges 24. A sheet of suitable length is formed into a barrel body by butt welding the end edges 24, as shown in Figure 6. 7, where the welding line is indicated at 25. It appears that the flanges 22 then extend horizontally on the main part and serve partly as conveyor belts and partly as reinforcements. In an alternative arrangement, the side edges 23 of a sufficiently wide, sprayed disc can be butt welded together by means of hot plate welding so that the flanges 22 run vertically, i.e. parallel to the welding line 25 shown in Figure 7a. In both cases, the flanges 22 can be folded so that they are on the inside (shown in figure 7a) or on the outside shown in figure 7 on the finished barrel body part. The arrangement according to Figures 7a and 7b starts h 468 426 9 with a disc having four flanges 22 and Figure 7b shows how these can be used to stiffen the corners of a barrel part with a substantially square section.

Figure 8 shows an alternative form of disc material 26, which is slightly thicker than the disc 21 and is formed with an inner arrangement of cavities 27, which gives a simple shape of honeycomb structure. Flanges, e.g. such similar flanges 22 may be used in such an arrangement if necessary.

Figure 9 shows a simple form of injection molded part that can be used for either the top end portion or the bottom end portion. A central area 31, which may be cupped or otherwise designed for integral reinforcement, is provided at its periphery with flanges 32 and 33, which extend upwards resp. down. In addition, the central surface 31 is provided with two upright grooves 34 and 35. If the part is to be used as the lower end element, the necks 34 and 35 will probably be removed by cutting and grinding, and the flange 33 can then be used to attach the part to the lower end of the main part. If the portion is to be used as the upper end portion, the central one is pierced in the area of one or both necks 34, 35, as shown by the dotted line 36. If only one filling neck is needed, obviously only one hole will be made and the other neck may removed if desired. The neck or necks that are retained can then be provided with either internal or external threads if necessary to receive a pin or a closure cap.

When a bottom end portion 3 of the type shown in Figure 5 is used and the barrels are stacked, it may be that the flange 12, which is to transfer the entire weight of the stack to a pallet or another support surface, may be damaged or distorted. In order to improve the stackability, an arrangement as shown in Figs. 10-12 can be used. In this arrangement, the flange or skirt 12 is aided in its supporting task by a series of spaced apart annular flanges 41, 42 and 43, which are centered about the center axis of the barrel. These flanges abut against the surface of the pallet. and reduces the load on the skirt or flange 12. Figure 11 shows how a corresponding upper end has a filling neck 44, which is placed in a recess 45, and it is also shown how the upper end is provided with a shoulder 46, which cooperates with the flange. or the skirt 12 to absorb portions of the weight, while the upright wall 7 still fits in the flange 12 to provide additional support for overlying barrels.

Figure 12 shows how the shoulder 46 is interrupted at two zones 47 for connecting a conventional wire handle 48 and the figure also shows that the shoulder 46 decreases in width in the area of an opening 49 in the wall 7 in the vicinity of the filling neck 44. Figure 12 also shows flanged zones 51 on the wall 7 leading down into the opening 49.

Although the neck ring is shown provided with an outer thread and a screw cap is shown in position thereon, it must again be pointed out that it is understood that the neck ring may be provided with internal threads to receive a rigid pin, or can be left unthreaded to receive a shrunk or another form of closure.

While the invention has hitherto been described with respect to drums suitable for manual handling and stacking, e.g. within a capacity range of 15 or 30 liters, it is understood that the same manufacturing technology can be used on barrels with larger capacity, e.g. 50 liters to 250 liters. Such barrels may be provided with or lack the arrangement for fitting together when stacked, but may have flanges or skirts with flat upper surfaces facing each other.

Figure 13 shows such an arrangement in which a barrel has a main part provided with conveyor belts 61 formed of integral flanges. The upper and lower end portions are each provided with flanges 62, which form brittle or projecting edges. 468 426 ll Figure 13 also shows the upper end portion provided with two necks 63 of different sizes. These can of course be of the same size or a neck can be dropped if desired. It is also possible that the main part itself is provided with a tap fixture 64 and in this case one or both necks 63 can be eliminated. For the smaller sizes, the skirt 62 may preferably be provided with drainage holes for discharging rainwater. The top of the drum can be designed to facilitate mechanical handling.

Various modifications may be made within the scope of the invention.

Claims (6)

10 15 20 25 30 35 468 426 12 PATENT CLAIMS A method of manufacturing a container of thermoplastic material comprising a cylindrical main part (1) and two preformed end portions (2,3) of thermoplastic material welded to the main part, the main part being formed from a flat piece of material (21, 26) by forming a predetermined length of the flat piece of material to form a cylindrical tube of the desired cross-section and welding the edges (23,24) of said length and where the end portions are preformed by casting technique and have cylindrical portions, characterized in that that the longitudinal joint (25) of the cylindrical main part is produced by welding the edges (23,24) of the material piece together towards each other by means of a hot plate, and that the cylindrical portions of the preformed ends (2,3) are butt welded to the main part (1) by hot plate welding. 2. A method according to claim 1, characterized in that the edges (23, 24) of the length (21, 26) are welded together by butt welding. Container of thermoplastic material comprising a cylindrical main part (1) and two preformed end portions (2,3) of thermoplastic material welded to the main part, the main part being formed from a flat piece of material (21,26) of predetermined length into a cylindrical tube of desired cross-section welded together at the ends of said length and where the end portions are preformed by casting technique and have cylindrical portions, characterized in that the longitudinal joint (25) of the cylindrical body is formed as a weld joint between. the edges (23,24) of the material piece made against each other by means of hot plate, and that the cylindrical portions of the preformed ends (2,3) are butt welded to the main part (1) by hot plate welding. 10 15 20 J; CN CO J; h.) Ch I3 Container according to claim 3, wherein the end portions have stacking means adapted to fit into the corresponding stacking means in an adjacent, similar container, which stacking means are in the form of circumferential edges (7; 13, 14; 32,33), which protrudes from a generally flat closing portion (31), characterized in that the circumferential edges (7; 13) are connected to the end closure by means of a number of stiffening corner reinforcements (9, 15). d ä r'a v, Container according to claim 3, characterized in that the end portions (2,3) are formed from one and the same casting part. d ä r a v, U Container according to claim 3, 4 or 5, characterized in that the lower end portion (3) is provided with a series of annular flanges (41,42,43) substantially in the same plane as the lower plane of the lower end part.