DE2216524C2 - Plastic canister - Google Patents

Description

1. The canisters must be sufficiently diffusion-tight. This means that during a certain period of time and within a certain temperature range diffuse only a certain amount of fuel out of the canisters (permeate). Otherwise an explosive mixture will be created with the air, which will result in handling can ignite with the canisters. The amount of diffusion may be according to German safety regulations Do not exceed a certain level per canister, regardless of whether the Canister is large or small. The diffusion rate is independent of the wall thickness and size the container surface. Since smaller canisters have a smaller surface area, they diffuse less than is permitted For larger canisters, especially for the 20 L and 30 L canisters However, the surface area is so large that normal low-pressure polyethylene increases a lot of filling material can diffuse when the container is filled with carburetor fuel.

2. Canisters rub against each other during transport. This creates electrostatic charges. If the surface resistance of the canister material is too great, this can create charging potentials cannot be derived. The charge can then not equalize quickly enough and at Sparks can be poured out, e.g. B. from the tank to the canister. These flashover sparks can, like ignition sparks, explosions initiate.

3. The canisters must be able to withstand large temperature differences. Only canisters made of plastic, which are modeled on the known three-handle canister made of sheet metal, inflate ^{like a balloon at an ambient temperature of about 70 °} C. because an overpressure builds up inside.

4. The canisters must be designed in such a way that they can be opened with their three handles, e.g. B. on the parachute hanging, can be dropped and the jerk of the parachute opening does not damage the canister.

5. The canisters must be designed in such a way that they will not burst at any point when you use them drops from a height of a few meters onto a concrete slab at a considerable minus temperature.

6. The shape of the canister has to take into account that there are already a lot of brackets There are lifting pallets, storage rooms and the like, in which the 20 L Wehrmacht canister made of sheet metal fits and into which the plastic canisters also have to fit.

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The invention relates to a plastic canister for volatile fuels according to the preamble of claim 1 specified features.

So far it has still not been possible to pull out the well-known 20 L three-handle Wehrmacht canister The list of these requirements can be extended.

Although it is known that plastic canisters can be made much more easily than Metal canister, there is still no suitable L-plastic canister with three handles. It is also known that you do not have to paint the plastic canister inside or outside after a few years, so that these costs do not apply. The costs involved in regeneration are a considerable fraction the new price of a metal canister. The ratio of regeneration costs to the purchase price is

crackle about 1: 4.

It is also known that the plastic canister could be made considerably cheaper. This would are particularly important for a mass-produced item.

There have been very many efforts and attempts to provide diffusion tightness with antistatic properties to unite and to achieve sufficient dimensional stability. All of these attempts, however, are stuck stayed because it was not possible to control all the essential parameters at the same time.

So is z. B. from US-PS 33 38 020 a plastic canister with the generic features has become known, which already has reinforcing elements adhering to individual wall areas Stiffening it does not meet the requirements set out at the beginning, so that it is not used as a storage canister for non-volatile fuels can be.

From US-PS 35 96 794 a plastic tank for a car is known in which approximately in the center opposite wall parts have mutually symmetrical frustoconical indentations, in the bottom of which the wall parts are fused together. This training serves as a bracket, to which the tank is attached in the vehicle. To better the dynamic forces in the support area support elements are inserted into the conical indentations, which are made of plastic, wood, Metal or the like can exist, and in turn by a clamping element with high pretension are drawn against each other. The point here is the "bracket" opposite the wall parts of the tank. A vehicle tank does not need to meet most of the requirements mentioned at the beginning fulfill. A vehicle tank is protected against overpressure and electrostatic problems through the tank ventilation Charges as well as the easy removal from the mounts do not need to be taken into account to name just a few examples. The absorption of dynamic loads in the area of the Bracket is important for vehicle tanks, the capacity of which is mostly over 60 liters, however completely irrelevant for canisters that are never to be attached anywhere in this way and that in addition, should hold a maximum of 30 liters. 4 ~>

From US-PS 35 52 599 a motor vehicle tank has become known in which for stiffening opposite wall parts have mutually symmetrical frustoconical indentations, in the base of which the wall parts are fused together. Any additional external wall elements are not available. The tank is attached to the vehicle in a conventional manner by means of a strap. Here, too, several of the requirements that are made of a canister are not asked. i ^r i

From DE-GM 18 52 986 a method has become known, according to which in economic Way in the blow molding hollow body made of thermoplastic prefabricated reinforcement parts are to be attached. The problem of fuel storage containers is not addressed here and the reinforcements shown are also not intended to solve the requirements mentioned at the beginning suitable.

From US-PS 23 66 274 a method for the production of plastic rivet connections has become known, for example in connection with the production of a plastic canister according to the invention can be used.

The object of the invention is to develop a plastic canister of the type mentioned at the beginning so that that you get a 20- and 30-liter canister for volatile fuels, on the one hand both the previous requirements for the approval of such canisters are met, such as impermeability to diffusion, freedom from Ignition spark, drop resistance, temperature resistance and, on the other hand, independent of the filling volume of the canister retains such a shape that the for Metal canisters of the same volume will continue to fit the intended receiving spaces. Also is on one economic manufacturability and ease of use must be observed.

This object is achieved according to the invention with the characterizing features of claim 1.

Advantageous further developments of the invention are characterized in the subclaims.

The invention and its advantages are explained in more detail using preferred exemplary embodiments. In the Drawing shows

F i g. 1 the side view of a 20 L canister with screw cap,

F i g. 2 shows the top view of the canister according to FIG. 1,

F i g. 3 shows a section along the line 3-3 in FIG. 2,

F i g. 4 shows a section along the line 4-4 in FIG. 1 in another embodiment,

F i g. 5 shows a section along the line 4-4 in FIG. 1 in a further embodiment.

A 20 L canister 11 made of polyethylene has three handles 12, 13, 14 and a pouring spout 16, e.g. B. with external thread. You could also use the usual claw lock or use a ring lock. Approximately in the diagonal area of the larger side surfaces of the Canister 11 a frustoconical indentation 17 is provided which extends so far inwardly that they Opposite wall meets and can provide the basis for a fixed connection still to be described.

The canister 11 has two shells 18, 19 which are arranged symmetrically to the central plane 21 of the canister are. The handle 14 is injection-molded onto the shell 18, and the handle 12 is onto the shell 19 injected. The edges 22,23 of the shells 18,19 end shortly before the central plane 21 and even jump back a little in the area of the handle 13. The edges 22, 23 have an inwardly facing bevel 24, 26. With the inner surfaces of the shells 18, 19 is a blown Hose 27 firmly welded to its outer surface. The shells 18, 19 carry for better welding on its inside numerous pointed elevations 28 which cut open the outer surface of the tube 27, however, do not pierce the hose 27. Occurs only in the area between the edges 22, 23 the tube 27 is exposed on the outside and can nestle well because of the chamfers 24, 26 and you have no transition difficulties.

During production, the shells 18, 19 together with the handles 12, 14 and the conical indentation 17 are first injected. The injection-embossing process is used for this. In this method, one closes the Spritn ^f orm a few tenths of a millimeter not complete, injected from the cavity completely and then closes after the completed injection operation, the mold completely. As a result, the material in the mold is mechanically compressed and becomes much more dimensionally stable, dimensionally stable and diffusion-resistant than conventionally injected thermoplastic material.

rial or blown material. The injection pressure is usually 15 atii and more. The material used is a type of polyethylene with a surface resistance that is significantly below 10 ⁹ ohms. A material with a surface resistance of 10 ohms is preferably used. After spraying, heating the shells 18,19 to about 11O ⁰ C. Then, each tray is placed in one half of a blow mold. Canisters are always blown upside down, with the pouring spout 16 serving as an insertion opening for the blow pin. In the usual blowing process, the tube 27 is blown so that it lies against the shells 18, 19 from the inside when it is hot. The cones 29, 31 are enclosed by the paraffin-like skin of the hose 27 and welded to one another. The hose 27 is also made of polyethylene. However, a material is used here that is particularly diffusion-tight. The size of the shell 18, 19 can be up to half the size of a canister.

In the case of the FIG. 4, the shells 18, 19 have a hole 20 in the bottom surface 15 on. This hole 20 must be large enough so that the hose 27, which the two designed in mirror image Shells 18, 19 welded, can swell through at the location of the hole 20 and thus a rivet head-like Welding 25 of the shells 18, 19 causes. The inner surfaces of the cones 29, 31 are strong roughened, but they can also be provided with pointed elevations 28. The purpose of the indentations 17 is it, the balloon-like flatulence when exposed to temperature on the with z. B. Carburetor fuel-filled canister to prevent.

In a further embodiment according to FIG. 5 the shells 18, 19 are reduced to two cones 29, 31. With a foot area 32, these merge into the outer wall of the canister like a radius and run to the edge out in a thin tip 33 in order to achieve a uniform transition. The two Bottom surfaces 34, 36 have such a distance to from each other that there is still enough between them a lot of tubing 37 is located. In this context it should be noted that the Invention nowhere about film-thick material under 1 mm. Rather, the wall thicknesses are such that they can also withstand the rough conditions. The total wall thickness for a 20 L canister is in the range from 5 to 10 mm. The wall thicknesses can be halved on the hose material and the injected one Distribute material. The cones 29,31 do not serve so much for the surface resistance and the diffusion to belittle. Rather, they serve more to keep the blown wall of the canister in that area to make it more dimensionally stable. If the indentation 17 is produced only when blowing, it can namely happen that the hose material 37 is welded, but because of the excessive stretching, d. H. Stretching of the hose material in this area becomes too thin. To prevent this from happening, they are injected Shells used. The forces to be absorbed here can be very large. For example, there is 75 "C in a petrol can an internal pressure of up to 3.5 atmospheres.

Like F i g. 5 shows, the cones 29,31 are right slim. This achieves, on the one hand, that they take away as little volume as possible from the inside of the canister. In addition, the side walls of the indentation 17 then align more with one another, so that they essentially can only be used in train. This is a type of stress that plastic can withstand well.

The bottom surfaces 34, 36 are just as large as is necessary to accommodate the rivet heads of the double-headed rivet 38 accommodate. The shaft of the double-headed rivet 38 has a large diameter in relation to this.

The indentations 17 of the two shells 18, 19 are designed the same in the first embodiment.

The middle handle 13 is made of hose material and can be produced by a method such as it is described, for example, in French patent specification 70 18 685.

With regard to the diffusion tightness it should be pointed out that the hose material is the essential Contributes to this and that the shell material only has the remaining lack of diffusion tightness has to raise. It should also be noted with regard to the material to be used that the hose 27 must be made of a thermoplastic material, while the shells 18, 19 either from one thermoplastic or thermosetting or glass fiber reinforced plastic can exist. Only one The only condition is that the material of the hose can be welded to that of the shells.

For this purpose 4 sheets of drawings

Claims (8)

Patent claims: 1. Plastic canister for volatile fuels, with a contiguous, inflated an extruding tube formed wall, which at least in individual wall areas through to the outside of the wall, also made of plastic, reinforced outer wall elements is, characterized in that with 20 and 30 liter canisters opposite Wall parts (27) have mutually symmetrical frustoconical indentations (17), in whose base the wall parts (27) are fused together that the outer wall elements of the Shape of the indentations (17) adapted, from an is surface-stabilized, low-warpage, sufficiently impermeable to diffusion and sufficiently low without Injection molded shells (18, 19) with surface resistance are in the area of their opposing bottom surfaces (15, 34, 36) have holes (20) aligned with one another, that rivet heads (25, 38) springing from the holes (20) on the bottom surfaces (15, 34, 36) rest, and that the shells (18, 19) are welded flat to the canister wall (27). 2. Plastic canister according to claim 1, characterized in that the rivet heads (25) a die Holes (20) penetrating part of the wall adjacent to the inside of the shells (18, 19) (27) are. 3. Plastic canister according to claim 1, characterized in that the wall (37) also has a the holes (20) aligned hole, and that in the holes a separate plastic rivet (38) is used. 4. Plastic canister according to one of the preceding claims, characterized in that the Trays (18,19) are injection-compression molding trays. 5. Plastic canister according to one of the preceding claims, characterized in that the Shells (18, 19) in one piece with canister handles (12, 14) are formed. 6. Plastic canister according to claim 5, characterized in that with three-handle canisters (11) each Shell (18, 19) has the outer handles (12, 14) and that the middle handle (13) from the blown Plastic wall is formed. 7. Plastic canister according to one of the preceding claims, characterized in that the The inside of the shells (18, 19) has a roughened surface. 8. Plastic canister according to one of the preceding claims, characterized in that the Inside of the shells (18, 19) has a plurality of pointed elevations (28), the height of which is less than the adjacent area (27) of the blown plastic wall and that in the adjacent Penetrates outer edge areas of this blown plastic wall. 60 Steel sheet (Jerry-Can) can be produced in plastic in the same way, although plastics have been known for a very long time. There are several reasons for this: