A PLASTIC CONTAINER OR CRATE, AN INJECTION MOULD AND METHOD FOR MANUFACTURING SAID PLASTIC CONTAINER OR CRATE

Abstract: A plastic container or crate comprises upright side walls (3) provided with a step (4) extending in the circumferential direction of the container. Wall portions above the steps are under an angle with respect to the bottom (2) of the container or crate and differ from a similar angle of wall portion beneath said step. The container or crate is made in an injection mould comprising a core (9) provided with a plurality of circum­ ferential steps in a spaced manner, while sets of side slides (11) of the mould of different height are being used in dependence on the height of a container or crate to be manufactured.

Description: A plastic container or crate, an injection mould and method for manufacturing said plastic container or crate. This invention relates to a plastic container or crate, com- prising upright side walls extending between reinforced outwardly directed upper edges and a bottom. Said plastic containers, also called crates in case their walls are provided with openings, are generally known. In practice, containers are provided, which can be stacked upon one another and are embodied in an almost identical manner but with a different height. Low and high plastic containers are used for different purposes, containers having a height thereinbetween being used for yet another purpose. Series of similar containers may advantageously be injectionmoulded by one and the same mould, only the "side slides" of the mould having to be exchanged in case another height is desired. Said known technique is e.g. disclosed in Netherlands patent application 7908265. In this known technique the disadvantage arises that at the inner sides of containers being lower than the highest ones a "sharp" upper edge is provided. The latter is caused in that during operation the side slides are being pressed against the core of the mould, so realizing the upper boundory of the container; exactly at the inner edge of the container the mould division will be visible and undesired sharp edges will be effected at an acute square transition between the inner walls and the upper edge after the plastic material has been injected into the mould, Said transition causes burrs. The present invention aims to provide series of plastic containers or crates manufactured by one and the same injection mould, and having various different heights, without the aforementioned disadvantage arising of sharp edges in containers or crates having a height lower than the highest ones. This object is attained in accordance with the invention in a plastic container or crate of the type as described above, which is characterized in that at least at the inner side of the container or crate, the walls or portions thereof are provided with a step extending into the circumferential direction of the container or crate and up to the corners of same, at which step - as seen in the upright direction of the walls - those portions at the upper edge above the step are under an angle with respect to the bottom, differing from the similar angle of the wall portions beneath said step at the bottom of the container. In this manner the advantage arises that the containers or crates will always remain stackable independent of their height, because the highest container or crate possesses an upper edge which remains adapted to the circumference of the bottom, so that sagging or nesting of a stack of combiners, crates respectively is no longer possible. It is observed that plastic containers or crates the walls of which comprise one or more steps extending into the circumferential direction, are known in the art. Said known steps then exclusively serve to reinforce the substantially flat walls of the respective products. The wall portions beneath and above the steps hereby always have one and the same "release" angle with respect to the bottom. The circumference of the bottom is so adapted to the inner circumference of the upper edge of the container or crate that a stacking operation can be effected. These known containers or crates do, however, not allow for an employment of lower ones, as stacking them would be impossible, due to the fact that the circumferential dimension of the bottom would no longer fit into the inner circumference of a lower container because of the identical extension of the wall portions below and beneath the steps. In a plastic container or crate according to the invention, however, the wall portions above a lower step - as seen in upright direction - preferably extend in a counterwise direction to the wall portions beneath the lower step. The plastic container or crate according to the invention is therefore so embodied that, with respect to the "release" position of the wall portions between a step and the bottom of the container or crate respectively, the wall portions above this step possess an "anti-release" position. The particular conception of the present invention is therefore also based upon the insight that a container or crate having an "anti-release" portion may also be disengaged from the respective mould core without any damages occurring. The invention in another respect relates to an injection mould for manufacturing a plastic container or crate in accordance with the invention. Use is thereby made of an injection-mould, comprising a base plate for forming the bottom of the container, a core cooperating with said base plate for forming the inside of the container or crate and side slides co-operating with said core for forming the side walls of the container, crate respectively. In accordance with the invention said injection mould is characterised in that the mould core is provided in circumferential direction, with a plurality of steps extending in a spaced manner, the mould division always being situated above the respective step between the core and the top portion of the side slides which are adapted for that purpose. One and the same mould core provided with steps for manufacturing a series of containers or crates with differing heights, therefore comprises a plurality of sets of side slides having mutually differing heights, the height of each set of side slides at a respective step being adapted to the mould division above said step. This results in the fact that, notwithstanding the height of a container or crate of a series, said series no longer comprises any container or crate having a sharp inner edge. The invention also relates to a method for manufacturing a plastic container or crate according to the invention while employing an injection-mould in accordance with the invention. Said novel method consists in that, independent of a given height of a container or crate to be manufactured, always one and the same mould core is used, whilst dependent on the height of the container or crate to be manufactured, side slides adapted for that purpose are used with the said mould core. Depending upon the desired height a given and siected set of side slides is employed. The invention is illustrated with the aid of the accompanying drawing, wherein: Fig. 1 is a vertical section of the side wall of a container or crate with a great height; Fig. 2 is a section of part of a mould comprising a vertical section of a side wall of a container or crate having a height lesser than that of Fig. 1; and Fig. 3 is a section corresponding to Fig. 2 but illustrating the lowest container or crate of a series. Fig. 1 is a vertical section of a side wall of a plastic container or crate at the zone of the grip. Part of the adjoining side wall is as yet visible in an outer view. The plastic container or crate comprises upright side walls 3 extending between the reinforced outwardly directed upper edges 1 and a bottom 2. The walls or portions thereof are at least at the inner side of the container or crate provided with a step extending into the circumferential direction of the container. Two steps referenced 4 are shown in section in fig. 1. A similar step 4a is provided near the upper edge of the container or crate, mostly in the form of a rounding to prevent a sharp edge directed towards the interior of the container or crate of being provided at the upper edge of the same. The use of such a step or rounding 4a is known per se. As is further apparent from the section of fig. 1, the portions above the steps 4, so the portions at the upper edge, are - as seen in the upright direction of the walls - disposed with respect to bottom 2, under an angle differing from the angle of the wall portions beneath those steps and the bottom of the container, for a purpose to be described hereinafter. The dot-dash lines 5 in fig. 1 illustrate the supplementary planes. Said planes extend parallel to the plane of bottom 2. The wall portion between bottom 2 and the first step 4 is a release portion, that is to say that this portion can be drawn from a mould core without any problems, due to the inclination of the wall on a shrinkage of the injected material. It has been found that the angle of this wall portion with respect to the plane of bottom 2 or the plane as depicted by lines 5, is approximately 900 + 3 . The wall portion at the upper edge towards the step disposed therebeneath has a different angle, for example 900 - O The same feature applies to the wall portion between the two steps. Wall portions above a lower step in the container wall consequently extend in the upright direction counterwise to wall portions beneath a lower step 4. It will be obvious from the angles as described, that the opposite walls of the container with their portions situated above the lower step 4 converge with respect to one another in a direction towards the upper edge 1 of said container. The wall portions between one step 4 and the bottom 2 of the container extend in a "releasing" manner, whilst the wall portions above said step extend in an "anti-releasing" manner. As is clearly visible in fig. 1, the step at the inner side of the container extends in a manner curved or inclined with respect to the plane of the wall, as is depicted by angle a. Preferably the steps 4 in the walls 3 at the inner side of the container also extend at the outer side of the container and merge into a rib 6 projecting from the wall. A container or crate com- prising walls or wall portions, as illustrated in fig. 1, is particularly suitable to be manufactured inalower embodiment also, by one and the same mould. The measures as described hereinbefore, therefore apply in particular to containers or crates to be mutually stacked and having different heights but also to containers or crates to be stacked and having other heights. For, in case a low container or crate is manufactured comprising wall portions with steps, all the said wall portions extending in a "releasing" manner, - the respective container or crate, for example, having a height extending from the bottom towards the first lower steps - it will be obvious that no problems will occur when stacking said containers or crates. At the event, however, that containers or crates according to fig. 2 are being manufactured, the use of the steps 4 could cause the top opening of the same-to be too wide to suitably adjoin the bottom and the edge 7 of another container or crate to be stacked. An incorrect fitting into one another might even cause superimposed containers to get lowered into the subjacent ones, as independent of the height of the manufactured product, the dimensions of the bottom 2 always remain constant. This is the reason why given portions are embodied in an anti-releasable manner, thus allowing the opening of the container at the upper edge 1, to always have the same dimension; this in comparison with a low container the upper edge of which is e.g. positoned at the lower step 4. In the figures the upper edges of lower containers or crates are depicted by dotted lines 8. Lower containers therefore no longer have a sharp edge because of the use of steps 4, the more so because the same circumstances are attained as at step 4a at upper edge 1 of the container, which will be illustrated with reference to fig. 2. Fig. 2 illustrates the same wall section analogous to fig. 1, and provided immediately after having injection-moulded plastic material into a mould. The steps 4 are provided in the mould core 9. Said mould core 9 have a height such, that a container of fig. 1 can also be produced by means of the former. Fig. 2 only illustrates a vertical section of part of the lower portion of the mould core 9. Mould core 9, in conjunction with a base plate 10, co-operates with a side slide 11, the height of which is adapted to manufacture a container, of which the upper edge la is situated at the upper step 4. Use is therefore made of an injection-mould with a base plate 10 for forming the bottom of the container, said base plate 10, in conjunction with a core 9, forming the inner side of the container, side slides cooperating with said core and being laterally removed from the core after the injection-moulding operation so engaging the side walls, that the manufactured container can be drawn from the core after having drawn core 9 and base plate 10 from one another. In the embodiment of the injection mould according to the invention the mould core 9 is provided, in its circumferential direction, with a plurality of steps 4 extending at distance from one another, the mould division referenced 12, between the core 9 and the top part of the side slides 11 being as a result, always positoned above the respective step, for which purpose the slides 11 are adapted. One and the same mould core 9 provided with steps therefore comprises a plurality of sets of side slides 11 having mutually differing heights, the height of each set of side slides being adapted to a respective step 4 with the mould division 12 positioned above said step. Fig. 3 only illustrates the lower part of the mould core 9 and a side slide 11 the division 12 of which being positoned just above the lower step 4. From this it follows that the mould core is in this case adapted to manufacture a very low container or crate the upper edge 1 of which is positioned relatively near the bottom 2. The possibility exists that the side slides in the upright direction be built up from a number of sections, a certain combination of this sections determining the position of the mould division at a step of the core. In case the upper edge la is situated at one of the steps 4, obviously the same situation is attained as at step 4a in fig. 1, eliminating the occurrence of a sharp edge at the upper edge of the container or crate. In case the wall is provided with an opening 13 for a grip bounded by a flange 14 (fig. 1), a filler 15 can be screwed upon the mould core at said opening 13. Said filler 15 has a chamfered top side 16 to obtain an inclined edge 17, so also eliminating the presence of a sharp edge caused by the mould division. A method for manufacturing a plastic container or crate of the type as described hereinbefore, while using the mould as described, therefore consists in that independent of a given height of a container or crate to be manufactured, always one and the some mould core is used, whilst dependent on the height of the container or crate to be manufactured, side slides, adapted for that purpose, are used with the said mould core. It is observed that the reference numerals in the claims are not intended to restrict the scope thereof, but are only denoted for clarification.

Claims: Claims: 1. A plastic container or crate, comprising upright side walls (3) extending between reinforced outwardly directed upper edges (1) and a bottom (2), characterised in that at least at the inner side of the container or crate, the walls (3) or portions thereof are provided with a step (4) extending into the circumferential direction of the container or crate and up to the corners of same, at which step - as seen in the upright direction of the walls - those portions at the upper edge (4a) above the step are under an angle with respect to the bottom (2) differing from the similar angle of the wall portions beneath said step (4) at the bottom of the container. 2. A plastic container or crate as claimed in claim 1, characterised in that the wall portions above a lower step (4) - as seen in upright direction - preferably extend in counterwise direction to the wall portions beneath said lower step. 3. A plastic container or crate as claimed in claims 1 and 2, characterised in that the portions of the opposite walls (3) situated above the lower step (4) converge with respect to one another in a direction towards the upper edge (1) of the container. 4. A plastic container or crate as claimed in claims 1 - 3, characterised in that with respect to the "release" position of the wall portions between a step (4) and the bottom (2) of the container, the wall portions above the step possess an "anti-release" position. 5. A plastic container or crate as claimed in any one or more of claims 1 - 4, characteri#ed in that the step (4) in the walls (3) at the inner side also extend at the outer side of the container. 6. A plastic container as claimed in claim 5, characterised in that the step (4) in the wall (3) at the outer side thereof, merges into a rib (6) projecting from said wall. 7. An injection-mould for manufacturing a plastic container or crate as claimed in any one or more of claims 1 - 6, comprising a base plate 10 for forming the bottom (2) of the container or crate, a core (9) co-operating with said base plate for forming the inside of the container or crate and side slides (11) cooperating with said core for forming the side walls (3), characterised in that the mould core (9) is provided in circumferential direction, with a plurality of steps (4) extending in a spaced manner, the mould division (12) always being situated above the respective step between the core (9) and the top portion of the side slides (11) which are adapted for that purpose. 8. An injection-mould as claimed in claim 7, characterised in that one and the same mould core (9) provided with steps (4) for manufacturing a series of containers or crates with differing heights, comprises a plurality of sets of side slides (11) having mutually differing heights the height of each set of side slides at a respective step (4), being adapted to the mould division (12) above said step. 9. An injection-mould as claimed in claim 7 or 8, characterised in that the side slides (11) are, in the upright direction, built up from a number of sections, a certain combination of this sections determining the position of the mould division (12) at a step (4) of the core (9). 10. A method for manufacturing a plastic container or crate as claimed in any one or more of claims 7 - 9, characterised in that independent of a given height of a container or crate to be manufactured, always one and the same mould core is used, whilst dependent on the height of the container or crate to be manufactured side slides (11), adapted for that purpose, are used with the said mould core.

Inventors: BENRAAD, COENRAAD JOHANNES B. M., ETTEMA, ERNST
Applicants: WAVIN B.V.
Application year: 1983
Main classification: B65D21
IPC codes: B65D21, B29C45