This invention relates to an apparatus for reducing or shredding plastics articles, particularly waste articles.

It is often desirable to reduce waste plastics articles in size to facilitate transport or subsequent processing. Hitherto use has been made of mechanical shredding machines

(employing cutting or compression devices) or of chemical reactors. These have suffered from various disadvantages.

We have now devised an apparatus which is of simple construction and easy to use, but which is effective in reducing or shredding plastics articles.

In accordance with this invention, there is provided an apparatus for reducing plastics articles, comprising a housing having a passageway extending through it, a grid disposed across the passageway, the housing having an entry opening into the passageway above the grid and an outlet from the passageway below the grid, and the grid being formed of electrically heated bars.

In use, plastics articles are fed into the apparatus through the entry opening and come to rest on top of the grid. Over their regions which come into contact with the electrically heated bars of the grid, the plastics articles are sufficiently heated that they melt, allowing the intervening portions of the plastics articles to fall through the spaces in the grid. Thus relatively large plastics articles can be introduced into the apparatus, and will be divided or reduced into smaller sizes for removal from the outlet of the apparatus.

The bars of the grid are preferably rigid. They may comprise metal tubes having an electrical resistance filament extending through a body of mineral insulating material which fills them.

Preferably the grid comprises a first set of parallel, spaced-apart bars and a second set of parallel, spaced-apart bars, the second set running perpendicular to the first set by lying in a plane parallel to but spaced from the plane in which the first set lie.

An embodiment of this invention will now be described

An embodiment of this invention will now be described by way of example only and with reference to the accompanying drawings, in which:

FIGURE 1 is a vertical section through an apparatus in accordance with this invention;

FIGURE 2 is a plan view of an electrically heated grid of the apparatus;

FIGURE 3 is a section through a terminal box which incorporates the electrically heated grid; and FIGURE 4 is a side view of the apparatus used in conjunction with a densifying apparatus.

Referring to Figures 1 to 3 of the drawings, there is shown a reducing or shredding apparatus for plastics articles, particularly plastics waste. The apparatus comprises a metal housing 10 which in the example shown is generally square in horizontal cross-section and rectangular in vertical section. The housing 10 is hollow and provides a passageway between an entry opening 12 in its front wall adjacent its top, and an outlet 14 in its back wall adjacent its bottom. Across this passageway there is mounted an electrically heated grid 16. In the example shown the grid 16 lies in a generally horizontal plane but if desired it may be inclined to the horizontal. The entry opening 12 is provided with the hatch 13 which is pivoted along its bottom edge to the housing. The electrically heated grid 16 is formed of two sets of bars, the bars of each set being parallel to each other but spaced apart and the bars of one set lying perpendicular to the bars of the other set, as shown in Figure 2. The grid thus has spaces between the bars through which articles may pass. A sloping wall 18 is provided within the housing below the grid 16, and the articles which pass through the grid slide down this wall 18 to the outlet 14 of the apparatus. The bars are spaced apart at distances corresponding to the size of the exit material required. As shown in Figure 3, the grid 16 may be incorporated in a terminal box 20, which may be removable from the housing 10. Also as shown in Figure 3, the two sets of bars 16a, 16b of which the gid 16 is formed may lie in separate planes which are spaced apart in the vertical direction.

metal (e.g. stainless steel or iconel) tubes filled with mineral insulating material (e.g. magnesium oxide) and having an electrical resistance filament extending through the body of insulating material. In use, plastics articles to be reduced in size are loaded into the apparatus through the entry opening 10 once the hatch 13 has been opened, the hatch 13 now forming a hopper. The plastics articles come to rest on the grid 16. The electrical elements are loaded to a predetermined watts-density which ensures that the plastics material will not carbonise or ignite, but those portions of the plastics articles which lie on the heated bards will be melted. The intervening portions of the articles thus break off and fall through the spaces in the grid 16. Preferably the apparatus includes an extractor fan to withdraw any fumes, preferably through a filter.

The material which is available at the outlet of the apparatus is of relatively small size and therefore more suitable than the entry material for disposal or reprocessing, or it may be used as low grade in-fill packaging.

Figure 4 shows the reducing or shredding apparatus 10 used in conjunction with a plastics densifying apparatus 30. The apparatus 30 is in accordance with International patent application PCT/GB90/01730. Material leaving the outlet 14 of the reducing apparatus 10 passes on a conveyor belt 40 to an inlet near the top of densifying apparatus 30, which melts the plastics material and then cools and resolidifies the melted material. Extraction ducts 11 and 31 extend from the top of the respective apparatus 10 to 30.