NL8400951A - METHOD FOR MANUFACTURING A CONTAINER OF THERMOPLASTIC MATERIAL AND SO MANUFACTURED CONTAINER - 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. <IMAGE>

Description

NL / 31-956 — tM / f.

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Method for manufacturing a container of thermoplastic material and container thus manufactured.

The invention relates to a method for manufacturing a container of thermoplastic material and container thus manufactured.

In recent years, the use of steel 5 in the manufacture of drums for storing and transporting chemicals has gradually been replaced by thermoplastic plastics materials.

A commonly used technique has been blow molding. This technique is well understood / leads to difficulties. One problem is that in the areas opposite the mold dividing line, the material becomes thin due to the stretching of the preform. This leads to thin corners on the top and bottom of the holders.

Also, a blow-molded product always shrinks relative to its proper dimensions, which are indicated in the product drawing, and zones of greater wall thickness have a different shrink factor than zones of smaller wall thickness. For example, a container with a square body section shrinks less along the shape separation line compared to the cross section at an angle of 90 ° relative to it.

Most blow molded containers can only be stacked four high when. they are filled with the product to be packed and when exposed to the weather for periods longer than six months.

However, it is often the case that customers prefer a stacking option of six high, nine high or twelve high for longer periods of products with a specific weight greater than 1.0 gm / cm, which cannot be achieved with a blow molded container of commercially attractive weight and with a certain uniform wall thickness distribution.

In addition, many designs of hail molded containers are susceptible to stress cracking when filled with an alkaline product or doped with a detergent composition and when subjected to a detergent composition. superimposed loads in stacks.

Another technique used provides a barrel with a web that has been extruded into a desired section, wherein injection molded end sections are butt welded to the web. The use of extrusion for the body leads to the cost of large extrusion dies and this means that this is economical only for long-term production of a certain shape and thickness.

According to the invention, the method for manufacturing a holder of thermoplastic material, consisting of a body part and two preformed end parts of thermoplastic material, which are welded to the body part, is provided, characterized in that the body part 15 is formed from a flat sheet by forming a predetermined length of the flat sheet into a tube of the desired cross-section and welding the ends of this length together by welding with a hot sheet.

Hot plate welding means 2Ό a method of welding surfaces of thermoplastic material by heating the surfaces in contact with a hot or heated plate, removing the plate and assembling and compacting the heated surfaces and allow them to cool and adhere to each other under a predetermined pressure for one. predetermined time.

The flat plates can be made by extrusion, compression molding or other suitable methods.

The ends of the length of the sheet material are preferably butt welded together, but in certain cases it may be preferable to form an overlapping weld. The body portion can have any suitable cross section, such as a circular cylinder, generally square or rectangular with rounded corners or even triangular, hexagonal or octagonal in cross section. The preformed end parts can be formed by injection molding, hot forming, blow molding or rotary casting or any other suitable process and they can be attached to the body part in any suitable manner. They are preferably butt welded to the 84 0 0 9 5 i

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Body by hot plate welding, but spin welding / ultrasonic welding or other bonding operations using a suitable adhesive or the like can be used. The injection molded ends can be produced according to the normal technology of casting top and bottom sections of the flat shape container, the top section having a filler neck. Otherwise, a technology may be used where the top and bottom ends have the same geometry and the filler neck (filler necks) is (are) closed by a membrane. In this case

the filler necks can be formed without a screw thread. I

When the part is to be the bottom end section, the neck is simply machined to obtain a flat surface. If the part is to be the top end section 15, a thread can be cut on the inside or outside of the straight fill neck if desired, and a hole can be machined through the membrane.

The body part and the end parts can consist of the same or different thermoplastic materials and any suitable material can be used such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene etc. However, the sheet forming the body can be co-extruded in sandwich form so that a material is in the center section of the side wall with an inner and an outer layer, whereby the extruded plate has a sandwich construction. The combination of materials can be selected to impart predetermined mechanical or physical properties to the side wall of the vessel.

The preformed end portions and the body portion 30 are normally assembled by hot plate welding or the like after they have been prefabricated by the appropriate processes (e.g. injection molding for the end portions and plate extrusion and butt welding with a hot plate for the tubular body portion).

This means that the three parts have cooled and obtained their preferred shape, since the shrinkage of the thermoplastic material has been completed.

However, it may be preferable to hold the body portion in a fixed position and injection mold an end portion 40 directly on one side thereof, thereby producing hot plate welding. welding line caused is avoided.

The flat plate for forming the body! part can also be formed with reinforcing ribs, which can be placed on the inside or outside of the container, or it can have a kind of honeycomb construction within its wall thickness, which promotes the mechanical properties of the body part.

The reinforcing ribs can be placed in the horizontal or vertical direction of the body part and perform different functions depending on their location.

Horizontal ribs can be used as: a) vessel holding devices; B) roller hoops and / or c) aids to prevent the side walls of the drum from collapsing under the influence of a superimposed load (when stacking) or under the influence of a partial vacuum, which is created due to temperature differences of fillers with

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significant partial vapor pressure.

Vertical ribs can be used as reinforcing ribs on the inside or outside of a container with a square, round or rectangular cross section. The above ribs are applied to improve the vertical compression resistance.

To form the body from a flat sheet of material, the costs of a large number of extrusion dies, one for each required cross-section, are avoided.

By starting from a flat plate an additional advantage arises, because the plate can be pre-printed in a flat state according to a suitable printing method and printing of higher quality is possible compared to printing on cylindrical or rounded rectangular or square body sections.

The invention will be further described with reference to the accompanying drawings, in which Fig. 1 is a side view of a vessel, which

84 0 0 9 5 T

-5- '* is formed according to the invention.

Fig. 2 is a top view of the vessel of FIG. 1.

Fig. 3 is a bottom view of the yat of FIG. 1.

Fig. 4 is a sectional view, on a larger scale, taken along line A-A of FIG. 2.

Fig. 5 is an enlarged sectional view taken along line B-B of FIG. 3 and additionally shows stacking of two vessels.

Fig. 6 is a side view showing an embodiment of sheet material from which the body can be formed.

Fig. 7 is a side view of a vessel body 15 formed from the sheet material sheared in FIG. 6.

Fig. 7a is a side view of another embodiment of the vessel body.

Fig. 7b is a horizontal sectional view of the body of FIG. 7a.

Fig. 8 is a perspective view showing another embodiment of the sheet material.

Fig. 9 shows an embodiment of a casting that can be used as a base for the top or bottom of a vessel.

Fig. 10 is a section through a modified embodiment of the bottom end casting.

Fig. 11 is a sectional view through a top end casting and also shows a bottom end casting of FIG. 10 in a stacked condition.

Fig. 12 is a plan view of the top end casting of FIG. 11.

Fig. 13 is a side view of a larger vessel.

As shown in Figs. 1-5, the vessel consists of a body part 1, an upper end part 2 and a lower end part 3. The body part 1 has the shape of a circular cylinder and is formed by bending a flat plate of material using a suitable molding and 40 weld the ends * · butt together with a hot plate.

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The top and part 2 and 3 are preformed separately from the body part 1 by injection molding or otherwise.

From the drawings it can be seen that the end parts 52 and 3 have central push-throughs for reinforcement and the upper part 2 is provided with a filling neck 5, which has screw thread for receiving a closure cap 6 (with dashed points shown only in Fig. 4).

The top part 2 is provided with an upright circumferential wall or edge 7 to enable stacking despite the presence of the filling neck and the closing cap 6 and the press-throughs 4. This wall is provided with an interruption 8 in the area of the filler neck 5 to facilitate pouring from the vessel and also to prevent rainwater or other liquids from collecting on the vessel. The wall 7 is integrally formed with the upper end portion 2 and is connected to the generally flat closing section of the end portion 2 by multiple spaced reinforcement corner brackets 9, 5

The upper part 2 is butt welded to the upper end of the body part 1 by welding with a hot plate along the line indicated by 11 in fig. 4.

The lower part 3 is provided with spaced downwardly facing circumferential edges 12 and 13, between which a recess 14 is formed, which will lie over the upright wall 7 of the underlying vessel when the vessels are stacked on top of each other turn into.

The edge 13 is reinforced by a row of spaced apart corner supports 15.

The lower part 3 is butt welded to the lower end of the wall 1 by welding with a hot plate along the line, indicated by 16 in fig. 5.

In particular, it is intended that 35 barrels of this construction will be used in sizes such as 15 liters, 20 liters and 25 liters. However, the manufacturing technique can be applied over a wide range of dimensions, for example from 15 liters to 250 liters.

When using the technique of 40 hot plate welding, it may be necessary to weld 1400951

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-7- zone to be widened slightly by compression of the material and these widenings can be finished smooth after welding if necessary-

The upper part 2 may have a provision for attaching a suitable carrying handle.

Although the top part 2 is inclined with an upright wall 7, which cooperates with the recess 14 when stacking, other stacking systems can be used. The top portion may be convex, while the bottom portion 3 is concave to ensure nesting when stacked for a significantly increased strength of the end portions 2 and 3. In such. In an embodiment, a filling spout can be fitted in a recess in the dome.

Also, the filler neck may be internally threaded to receive a threaded spigot externally threaded to accommodate a threaded cap or be smooth to accommodate a crimped closure.

Pig. 6 shows a plate 21 of plastic material, such as polyethylene, which is extruded with a pair of ribs 22. The plate has side edges 23 and 25 end edges 24. A plate of suitable length is formed into a vessel body by butt welding the end edges 24 together. as shown in Fig. 7, where the weld line is indicated at 25. The ribs 22 then extend horizontally on the body and partially act as roll hoops 30 and also as reinforcement. In another embodiment, the side edges 23 of a suitably width extruded sheet can be butt welded together with a hot sheet, so that the ribs 22 then run vertically, thus parallel to the welding line 25, as shown in Fig. 7a. In any event, the ribs 22 can be folded to lie on the inside (as in Figure 7a) or on the outside (as in Figure 7) of the finished vessel body. The embodiment of Figs. 7a and 7b begins with a four-rib plate 22 and Fig. 7b shows how it can be used to measure the corners of a vessel body of generally square cross section 8400951 -8-. to reinforce.

Fig. 8 shows another form of sheet material 26 which is somewhat thicker than the sheet 21 and is formed with an internal configuration of cavities 27 which provide a simple shape of a honeycomb construction. Ribs, for example ribs similar to ribs 22, can be provided in such an embodiment if desired.

Fig. 9 shows a simple injection molding shape which can be used as the top or bottom end portion. A central zone 31, which may be domed or otherwise formed for reinforcement, is provided with upwardly and downwardly extending flanges 32 and 32, respectively.

33 on its perimeter. Furthermore, the central zone 31 is provided with two upright necks 34 and 35. If the part 15 is to be used as bottom end, the necks 34 and 35 will likely be removed by cutting and grinding and the flange 33 can then be used to cut the part attach to the lower end of the body. If the part is to be used as the top end, the central zone 31 will be pierced in the region of one or both necks 34, 35, as indicated by the dashed lines 36. If only one filler neck is required, only one piercing will of course be made and the other neck can be removed if desired. The neck or necks that remain can then, if desired, be provided with internal or external threads for receiving a bung or cap.

When a bottom end portion 3, as shown in Fig. 5, is used and the barrels are stacked, the edge 12, which must transfer the entire weight of the stack to a pallet or other support surface, may be , is damaged or deformed. To improve stackability, an embodiment as shown in Fig. Fig 2 can be used. In this embodiment, the rim or jacket 12 is assisted in its support roll by a series of spaced annular ribs 41, 42, 43 centered on the axis of the vessel. These ribs rest on the palette surface and lighten the load on the jacket or rim 12 '. Fig. 11 shows a corresponding top end that has a filler neck 44, which enters a local 40 blister 45 and also how the top end is provided with a $ 400951-9 -7.

Shoulder 46, which cooperates with the rim or jacket 12 to support a portion of the weight, while the upright wall 7 still passes within the rim 12 to provide further support for the overlying vessel.

FIG. 12 shows how the shoulder 46 is broken in the region of a pair of bonding zones 47 for a conventional wire handle 48 and also shows a reduction in the width of the shoulder 46 in the region of a break 49 in the wall 7 at the filler neck 44. Also fig. 12 shows tapered zones 51 on the wall 7, which lead down to the break 49.

Although the neck ring is shown with external threads and a screw cap is shown in place, it will be understood that the neck ring may be internally threaded to accommodate a spigot or may be left unthreaded to accommodate a crimped or otherwise shaped closure.

Although the invention has been described so far in connection with drums suitable for human handling and stacking, for example in the capacity of 15 or 30 liters, it will be understood that the same manufacturing technology can be applied to drums of greater capacity for example 50 - 250 liters. Such vessels may or may not be designed to nest when stacked and may have flat-topped flanges or jackets abutting each other.

Fig. 13 shows such an embodiment, in which a vessel has a body, which is provided with rollers 61, which are formed <RTI ID = 0.0> 3 </RTI> fully formed ribs.

The top and bottom end portions each include flanges 62 which form sheaths or raised edges. Fig.

13 also shows that the upper end portion has two necks 63 of different sizes. These may, of course, be the same size or one neck may be omitted if desired. It is even possible that the body itself is provided with a rebate set 64 and in this case one or both necks 63 can be omitted.

With regard to the smaller dimensions, the jacket 62 is preferably provided with drainage holes for draining rainwater 40. The top of the vessel may be designed to facilitate mechanical handling.

Various changes are possible within the scope of the invention.

\ 8400951

Claims (9)

1. Method for manufacturing a vessel of thermoplastic material, consisting of a body part and two preformed end parts of thermoplastic material, which are welded to the body part, characterized in that the body part is formed from a flat plate by a shape the predetermined length of the flat sheet into a tube of a desired cross section and weld the ends of this length together with a hot sheet. 2. Method according to claim 1, characterized in that the ends of the length are welded together butt-welded. 3. Method according to claim 1 or 2, characterized in that the preformed end parts are butt welded to the body part. 4. A method according to claim 3, characterized in that the end parts are welded butt to the body part with a hot plate. c I Method according to claim 1 or 2, 20, characterized in that at least one end part is formed directly on the body part by injection molding. 6. Container manufactured by the method according to any one of claims 1-5, characterized in that the end parts are provided with stacking members which can nest with the stacking member of an adjacent similar container, the stacking member being in the form of circumferential edges protrude from a generally flat closing part. 7. Holder according to claim 6, characterized in that the edges are connected to the closing part by a row of reinforcement angle supports. 8. Container manufactured by the method according to any one of claims 1-5, characterized in that the end parts are formed from a common molding. Holder as claimed in claim 6 or 7, characterized in that the bottom end part is provided with a row of annular ribs, which are at least substantially in the same plane as the bottom plane of 8 4 0 Q 0 5 1 s ν -12- Μ. the bottom end part. 8400951