METHOD AND APPARATUS FOR THERMALLY COMPACTING EXPANDED POLYSTYRENE ARTICLES

The present invention relates to an apparatus for thermally compacting boxes formed of expanded polystyrene, particularly but not solely such boxes used for containing fish. It is common to use boxes of expanded polystyrene for the transport and storage of fish: these boxes are disposed of after the fish has been removed from them. The discarded boxes take up a substantial volume of space and also give off strong odours, arising from the fish which they had contained. We have now devised an apparatus for thermally compacting such fish boxes, but which may also be used for thermally compacting other articles of expanded polystyrene.

Thus, in accordance with the present invention there is provided an apparatus for thermally compacting boxes or other articles of expanded polystyrene, the apparatus comprising a housing having an entry opening, and means forming first and second electrically-heated surfaces inclined downwardly towards each other and provided with a passage, at their lower ends, through which melted polymer may drain. In use, one or more boxes of expanded polystyrene may be introduced into the apparatus through the entry opening, to slide down the first electrically-heated surface and into contact with the second electrically-heated surface: heat from these surfaces serves to melt the expanded polystyrene, the melted polymer draining through the gap passage at the lower ends of the two heated surfaces.

Preferably the entry opening is provided with a door which seals the housing when closed. Preferably an extraction fan is provided, which maintains a negative pressure within the housing and extracts the styrene and fish or other odours: such odours are not hazardous but are undesirable. Preferably the extraction fan is arranged to increase its airflow rate upon opening of the entry door, to minimise the heat and odour to

which the operator is subjected through this door.

Preferably the apparatus comprises a chute, extending from the entry opening to the upper end of the first electrically heated surface, down which each box slides when introduced into the apparatus. The arrangement serves to minimise the risk of the operator touching the heated surface.

Preferably at least one of the heated surfaces is provided with fins or grooves (e.g. extending in the downwardly-inclined direction of the surface) to increase the surface area and enhance the speed of melting.

Preferably the two electrically-heated surfaces are inclined at 45°to the horizontal. Preferably the second such surface is shorter, between its upper and lower ends, than the first. Preferably the apparatus includes a control system for thermostatically controlling the temperature of the electrically-heated surfaces.

Preferably the electrically-heated surfaces are formed by two plates. Preferably these plates are formed of metal, preferably aluminium. The passage for the melted polymer to drain through may comprise a gap between the lower ends of the two plates .

Preferably the electrically-heated surfaces are provided with a coating, preferably of Teflon or other plastic material, to prevent or inhibit the expanded polystyrene boxes, or other articles, adhering to the heated surfaces.

In a preferred embodiment which will be described herein, the melted polymer drains into a tray or other receptacle disposed under the passage provided at the lower ends of the two electrically-heated surfaces, in which tray the melted polymer solidifies.

Preferably the apparatus includes means for detecting or predicting when the receptacle, which receives the melted polymer, is full. Preferably the apparatus is arranged to allow the receptacle of melted polymer to cool down, either by

monitoring its temperature or effecting a time delay, before enabling a door to be opened for removing the receptacle.

Also in accordance with the present invention, there is provided a method of thermally compacting boxes or other articles of polystyrene, the method comprising the steps of introducing at least one box or other article of polystyrene into a housing through an entry opening thereof, for said box or other article to slide down a first electrically-heated surface and into contact with a second electrically-heated surface, said first and second electrically-heated surfaces being inclined downwardly towards each other and provided with a passage, at their lower ends, through which melted polymer drains .

An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawing, the single figure of which is a diagrammatic longitudinal section through an apparatus in accordance with the invention.

Referring to the drawing, there is shown an apparatus for thermally compacting boxes of expanded polystyrene, particularly but not solely boxes of expanded polystyrene used to contain fish: the apparatus which is shown comprises a housing 10 having an opening 11 in its front, provided with a door 12, and first and second electrically-heated aluminium plates 14, 16 mounted within the housing 10. The first electrically-heated plate 14 is inclined downwardly from the inner end of an entry chute 13 which is inclined downwardly from the opening 11, the opening 11 serving for the entry of boxes e.g. B into the apparatus. The second electrically- heated plate 16 is inclined upwardly from the lower end of the first plate 14 and a narrow gap 15 is provided between the lower ends of the two plates 14, 16.

In the example shown, the plates 14, 16 are inclined at 45° to the vertical, the second plate 16 being short (between its upper end and its lower end) compared with the first plate

14, and the gap 15 is in the range of 5mm to 20mm. The upper surfaces of the two plates 14, 16 are coated with Teflon. A removable tray 18 is supported below the gap 15 between the lower ends of the two plates 14, 16 in order to collect melted material: a door 19 is provided in the side of the housing 10, to enable the tray 18 to be removed, when full, and replaced by an empty tray.

The apparatus includes a control system having a control panel 20 on the front of the housing 10 and serving to control the electrical supply to the heating elements with which the plates 14, 16 are provided, and to control an extraction fan 22, which is provided with a filter 23. The apparatus may be powered by a single-phase or by a three-phase electrical supply. The apparatus is preferably arranged so that it may operate out of doors: the apparatus will usually be situated close to food retailers, although may be situated within premises where food is sold. The housing 10 is preferably formed of stainless steel, plastics-powder coated steel, plastics or fibreglass, in order to withstand the heat, humidity and salt usually found in its typical operating environment .

The interior of the housing 10 is sealed when the doors 12, 19 are closed, and the extraction fan 22 serves to create a small negative pressure within the housing. The control system is arranged to sense when the entry door 12 is opened, to increase the airflow rate of the fan 22 and so minimise the flow of styrene and fish odours out through the entry opening 11. When the operator opens the entry door 12, he introduces one or more fish boxes e.g. B into the apparatus, for these to slide down the entry chute 13 and then onto the first electrically-heated plate 14. The arrangement restricts the risk of the operator touching the heated plate 14. The operator then closes the entry door 12. Thereafter, the first

fish box slides down the heated plate 14, for its forward end to come into contact with the second heated plate 16: the heat which is conducted into the fish box from the two plates 14, 16 serves to melt the box progressively, the melted polymer draining into the tray 18 through the gap 15 between the two plates: the tray 18 acts as a mould, in which the polymer which it collects will solidify.

The control system is arranged to detect when the tray 18 is full, for example by the provision of a weight sensor or proximity sensor, or the control system may calculate, from elapsed time and temperature, when the tray is full: in either event, the control system provides a visual indication, on the control panel 20, that the tray is full, and interrupts or reduces the electrical supply to the heated plates 14, 16. The control system acts to lock the tray-removal door 19 until the tray 18 is cooled, preferably by providing a time-delay (e.g. of 30 minutes) before releasing the lock of door 19.

The heated plates 14, 16 are thermostatically controlled, in order to maintain a preset temperature, typically in the range of 180 ⁰ C to 250 ⁰ C: at such temperatures, any animal by-products such as blood or bacteria are sterilised, rendering the waste material safe for disposal or recycling. The apparatus serves to reduce the volume of the expanded polystyrene material by up to 95%. The control system comprises a programmable logic controller (PLC) or an electrically programmable read only memory (EPROM) and may be arranged for remote interrogation.

The operator is restricted to loading boxes into the apparatus, switching the apparatus on and off and removing the tray of solidified polymer, when required. The control panel 20 includes a "start" button which serves as a mains contactor, supplementing a wall-mounted contactor via which the mains is supplied to the apparatus. The control panel 20 includes only three indicator lights, namely "load", "empty" and "fault". It will be appreciated that the apparatus will accept

a fish box without difficulty and can contain more than one box at a time for processing. The apparatus has no moving parts, other than the entry door 12 for boxes and the door 19 for the removal of the tray 18 of solidified polymer. The housing 10 is provided with a removable panel (not shown) to provide access for removing any blockages. The control system is arranged to sense removal of this panel to interrupt the electrical power and adopt a mode in which a service engineer is required to reset the system. The housing 10 is arranged for bolting to the ground to prevent theft or the machine toppling over. The entry door 12 has a manual key lock (not shown) to secure this door when the apparatus is not in use.