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The present invention relates to a comminution device; more specifically a hammer mill for breaking up glass bottles and containers to reduce the storage and transport volume.
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Glass bottles and containers once empty can create a storage and/or disposal problem. Though glass is recyclable only so much is needed for this purpose and the rest needs to be disposed of. Landfill disposal of the waste glass is problematic, unless broken down and disposed of properly it occupies a large volume and can be a safety hazard.
The safe storage and transport of spent glass containers can be especially difficult for businesses that operate in the food and beverages industry. Bars, cafes, restaurants, casinos and hotels regularly empty large numbers of glass containers, as do large sports and entertainment events, all of which need to be disposed of. The most common method of disposing of the glass containers at present is by throwing them into a bin for collection (often recycling). As a percentage of the containers break in use, or as they are thrown into the bins, care needs to be taken. Those throwing the containers away, or handling the bins need to be careful or injuries can result.
Glass containers, even with a proportion broken, occupy a large volume relative to their weight so businesses face the expense of storing and disposing of the bins which are largely air. For this reason a number of onsite bottle crushers have been developed. Some of the onsite bottle crushers succeed in reducing the volume but result in glass fragments, shards and pieces, often with razor sharp edges, sometimes with very fine pieces and dust present. This material can be useful as cullet (waste glass for the use in producing new glass), but often needs further processing for other purposes.
Many of the glass crushers currently available produce cullet (approximately serving spoon size) which is useful for recycling. Without careful sorting (colour and type) it is difficult to use all of this material, and even if sorted the transport costs to ship this to a remanufacturing plant can make it uneconomical to re process, in this case the cullet often ends up in landfill sites.
Any discussion of the prior art throughout the specification is not an admission that such prior art is widely known or forms part of the common general knowledge in the field.
It would be advantageous if the invention could overcome one or more of the deficiencies in present bottle crushing devices.
Where the term bottle, or bottles, is used it is intended to include glass containers of all shapes and sizes, for example jars, vases, etc. Most likely the bottles are used in bars, cafes, restaurants, hotels, casinos or similar.
DISCLOSURE OF INVENTION
The present invention provides a bottle crusher that includes a feed section, a crushing section, a collection section and a venting section.
Preferably the crushing section is essentially a hammer mill with a crushing assembly inside a drum; such that:—
the crushing assembly includes a plurality of hammers, an assembly shaft and at least two hammer shafts;
each hammer shaft lies essentially parallel to, and is spaced equidistantly from, the assembly shaft to which it is attached;
each hammer includes a hammer tail and a hammer head at opposite distal ends of said hammer, such that each hammer tail is hingedly connected to one hammer shaft; and the drum and crushing assembly have essentially coincident centrelines.
Preferably the drum includes a void section which is an indentation in the inner surface of the drum, when viewed in cross-section across the drum, configured to create a reduced pressure in the feed section, when the crushing section is in use.
Preferably the void section is an indentation in an inner surface of the drum extending, when viewed in cross-section across the drum, from approximately the 9 o\'clock position to the 12 o\'clock position on an analogue clock. In a highly preferred form the void section smoothly curves away from the centre of the drum to a point located at between about the 11:00 o\'clock position and 11:45 o\'clock position on an analogue clock, then smoothly transitions back to a point on the edge of the circle the same diameter as the drum.
Preferably for a drum with a radius of 104 cm the maximum void section depth, at close to about the 11:30 o\'clock position on an analogue clock, is between 20 mm and 60 mm. In a more preferred form the depth is between about 30 mm and 50 mm.
Preferably the crushing assembly includes at least two assembly plates, such that each hammer shaft is attached to the assembly shaft by the assembly plates, said assembly plates are spaced along the length of the of the assembly shaft, wherein each hammer is located between two immediately adjacent assembly plates. In a highly preferred form each of the hammer shafts is equispaced around the periphery of the assembly plates. In a further preferred form each assembly plate is shaped like an equilateral triangle with rounded vertices with a hammer shaft located close to each vertex.
Preferably each hammer is, when viewed from the front, “I” shaped, with one cross bar longer than the other, the longer cross bar corresponding to the hammer head and the shorter cross bar corresponding to the hammer tail.
Preferably the bottle crusher is a substantially sealed unit configured to operate with a slightly reduced pressure in the feed section and vent essentially all air exiting through the venting section.
Preferably the collection section includes a container configured to collect the crushed glass from the crushing section. Preferably the venting section is configured to reduce the particulate load of air flowing out of the bottle crusher via the venting section. Preferably the venting section includes one or more of the following: a filter, a cyclone, an electrostatic precipitator and an oil bath, configured to reduce the particulate loading.
Preferably the drum includes a crusher screen, said crusher screen being a fully or partially perforated plate configured to co-operate with each hammer to break down a bottle being processed. Preferably the crusher screen extends, when viewed in cross-section across the drum, from approximately the 3 o\'clock position to the 9 o\'clock position on an analogue clock. Preferably the perforations in the plate extend essentially the full length of the crusher screen. Preferably, where perforated, the crusher screen is between about 30% and 50% void. In a highly preferred form each perforation is a hole between 7 mm and 12 mm in diameter. In a still more preferred form the crusher plate is about 6 mm thick has about 40% void and each hole is between 9 mm to 10 mm in diameter.
In one preferred form the minimum clearance between a leading edge of each hammer head, where the leading edge is the part of each hammer configured to first impact a bottle being processed, and an inner surface of the crusher screen is configured to decrease when the bottle is impacted. Preferably the minimum clearance, in the unloaded position i.e. prior to the hammer impacting the bottle, is between 5 mm and 7 mm. In a preferred form the minimum clearance, in the loaded position i.e. after the hammer has impacted the bottle, is between 2 mm and 4 mm. In a highly preferred form the unloaded clearance is about 6 mm and the loaded clearance is about 2.7 mm. It should be noted that all clearances are given in the as new condition, and wear or impact damage may change this.
Preferably the crushing assembly is driven, directly or indirectly, by a driving means.
In a highly preferred form the driving means is an electric motor configured to directly rotate the crushing assembly at about 2800 rpm. An alternative preferred form the electric motor indirectly (e.g. belt, chain, gearbox, etc) drives the crushing assembly.
Preferably the bottle crusher is configured to produce a crushed glass with 90% less than 4 mm. In a highly preferred form 65% of the crushed glass is 2 mm or less in size.
Preferably the feed section includes an inlet with at least one valve, the or each valve being configured to allow a bottle to be fed into the crushing section and assist in maintaining a reduced pressure inside the feed section. In a highly preferred form the or one valve is a resilient material, such as rubber, with a cross cut.