Abstract:
A waste treatment device includes a sealable chamber having an inlet for receiving waste to be treated and an outlet through which the treated waste is discharged. A cutting mechanism within the sealable chamber shreds the waste and delivers the shredded waste to the chamber outlet. The cutting mechanism includes a planetary gearbox carrying two or more rotating cutting heads which are in close proximity to one another.

Description:
FIELD OF INVENTION 
     The present invention relates to waste treatment apparatus and more particularly to waste treatment apparatus for use in the sterilisation of infectious and/or quarantined waste. However, it will be appreciated that the invention is not limited to that particular use and will find application in treating other types of waste which require sterilisation. 
     BACKGROUND 
     Hospitals produce a large amount of infectious and/or quarantined waste. Generally, most hospitals have a number of infectious waste collection bins dispersed throughout the various wards and departments. These waste bins are periodically collected and removed to an off-site waste treatment facility for chemical sterilisation or high-temperature incineration of the waste, followed by sterilisation of the bin itself. This is an expensive process which suffers from many disadvantages. 
     One such disadvantage is the risk of environmental damage during the transport of infectious waste over public roads. In addition, the building and operation of an off-site chemical or incineration treatment centre represents a high capital cost outlay and requires expensive chemicals and/or fuels for operation. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the present invention, at least in its preferred embodiment, to overcome or at least ameliorate one or more of the above prior art disadvantages. 
     Accordingly to one aspect of the invention there is provided a waste treatment apparatus comprising: 
     a first sealable chamber for containing untreated waste, the chamber having therein a cutting mechanism and vents through which steam may be introduced under pressure. 
     In other preferred embodiment, the device further comprises a grate adjacent to the cutting mechanism through which treated waste is ejected from the first chamber. 
     In another embodiment of the invention, the first chamber further includes an advance mechanism for urging the waste against the cutting mechanism. 
     In other embodiments there is provided a pivoting hopper for depositing untreated waste into the first chamber. There is concurrently provided a transport for inverting a bin over the hopper. 
     In some embodiments there is also provided a bin cleaning mechanism located beneath the hopper. 
     In some preferred embodiments a second sealable chamber in which waste deposited from the first chamber is treated. 
     In other embodiments of the invention, a third chamber is interposed between the first and second chambers and comprises an isolation gate valve for separating the first and second chambers. 
     In other embodiments of the invention, either the first or the second chambers are provided with external jackets carrying steam to heat the respective chambers. 
     There is also disclosed means for collecting both the liquid and vapour discharges of the treatment chambers. 
     In particular embodiments, the cutting mechanism comprises a gearbox carrying two or more rotating cutting heads. 
     In some preferred embodiments, the gearbox is a planetary gearbox and the gearbox rotates within the first chamber. 
     In one form of the invention, the apparatus is mounted on the back of a truck or trailer to facilitate transporting from site to site. The truck or trailer can supply all the power requirements of the device, including electric, hydraulic, gas and/or pressurised steam. 
     In another form of the invention, the apparatus is produced as an on-site plant. 
     According to another aspect of the invention there is provide a method of treating waste comprising the steps of: 
     (i) introducing untreated waste into a sealable chamber, 
     (ii) shredding the waste in the chamber and simultaneously applying steam to the waste to thereby sterilise the waste, and 
     (iii) discharging the shredded, sterilised waste from the chamber. 
     In some preferred methods of the invention, the shredded, sterilised waste is discharged into a second sealable chamber where the waste is subjected to further treatment. 
     In preferred embodiments of the invention, the waste in the second chamber is subjected to further steam treatment. 
     In other preferred embodiments of the invention, the method further comprises the steps of collecting liquid waste discharged during the process and sterilising it separately prior to disposal. 
     In one embodiment, the method also includes evacuating all air and/or gas from the chamber prior to steps (ii) and (iii) and decontaminated through a multi-stage active carbon filter or the like. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic side view of a waste treatment device according to a first embodiment of the invention; 
     FIG. 2 is a front elevational view of the cutting head depicted in FIG. 1; 
     FIG. 3 is a side elevational view of the cutting head and gear box of the device shown in FIG. 2; 
     FIG. 4 is a perspective view of the cutting head and gear box of the device shown in FIG. 2; 
     FIG. 5 is a schematic side view of a waste treatment device according to a second embodiment of the invention; 
     FIG. 6 is a view similar to FIG. 5 showing the waste being loaded; 
     FIG. 7 is a view similar to FIG. 5 showing the waste material having been introduced into a first treatment chamber and the waste bin being cleaned. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in FIG. 1 an on-site waste treatment apparatus  100  includes a primary treatment chamber  101  into which waste  102  is fed through a chute  103  The primary chamber  101  includes an advance mechanism in the form of, for example, a hydraulic ram  104 . The shaft of the ram  105  may include a central bore  107  through which steam is fed. The steam emerges through the head of the ram  106 . The head  106  includes an elongated skirt  106   a  which serves to seal the chamber  101  from the chute  103  when the ram is sufficiently advanced. 
     After waste is introduced into the chamber, it may be sealed and evacuated prior to any introduction of steam to promote uniform penetration of steam into the mass of waste  102 . 
     Owing to the action of the ram, waste matter  102  is forced under pressure against a shredding or cutting mechanism  108  located within the primary chamber  101 . The cutting mechanism includes a hydraulic motor  111  which drives a planetary gear box  110 , the planet gears of which are coupled to two or more rotating cutting heads  109 . 
     Pressurised or super-heated steam (“steam”) may be provided directly into the chamber  101  before and during the operation of the cutting mechanism in various ways. Additionally steam may be piped or otherwise provided to the chamber, either by vents  270  along the length of the chamber or by vents  271  in the area of the cutting heads  109 . These vents, like others depicted in these examples are supplied by jackets or pipes  276  suggested in FIG. 1, but not shown for clarity. 
     In preferred embodiments of the invention, the temperature is monitored in the chamber  101  overtime. Waste is maintained in the chamber  101  at a specified temperature, for a specified time before the advance mechanism, and cutting mechanism  109  are activated. This may be done with automated process control equipment. 
     Waste material  102  which is forced by the ram into contact with the cutting heads  109  is thoroughly macerated and ejected from the chamber  101  through a grate  112  when the cycle is completed. The entire process may be auto recorded for record keeping purposes. The grate is replaceable and interchangeable with other grates so that the size of the grate openings can be varied to suit different types of waste or replaced for maintenance purposes. The narrow gap “g” between the cutting heads and the interior o the chamber helps control the site of the ejector. 
     The shredding mechanism  108  is shown in greater detail in FIGS. 2 to  4 . As shown in these Figs., the cutting heads  109  are mounted on the shafts of the rotating planet gears of a planetary gear box  110 . They are disposed around the gear box so that the clearance between the outside diameter of the cutting circle of the heads  109  and the inside diameter of the primary chamber  101  creates a narrow gap which limits the size of the waste which is ejected through the grate  112 . The preferred number of cutting heads  109  is between two and four although more cutting heads  109  may be mounted on an appropriately designed planetary gear box, as required. Each of the cutting heads  109  is fashioned from a hardened steel to provide maximum durability and service life. Each cutting head  109  includes cutting edges  120  which run the full length of each head  109 . A cutting head  109  may also include cutting edges  121  on a face or a portion of the face of the head  109 . A small clearance is provided between adjacent heads. Owing to the action of the planetary gear box, the gear box itself  110  rotates in the same direction as the cutting heads but at a different speed to the cutters  109 . 
     The clearance  275  between the chamber wall  276  an the cutting head  109  is kept small so that the waste is broken down by the heads  109  into small pieces. Waste leaving the primary chamber  101  enters an optional secondary processing chamber  118 . Additional steam can be provided by vents  280  into this secondary chamber  118  which is sealable with a isolation gate valve  113  located beneath the grating  112 . Shredded and steamed waste collects on the gate valve  113  after it passes through the grate  112 . The grate valve is kept closed during the secondary steaming process and is opened after the secondary steaming process has been completed. 
     A discharge chamber  114  is located directly beneath the isolation gate valve  113  and receives the shredded and steam treated waste when the gate valve  113  is opened. Within the discharge chamber  114  there is an agitator or auger  115  that is driven by a motor  116  to tumble the waste which is again steamed during this step of the process which takes places as the primary main process is being repeated on the next batch of waste in the primary chamber  102  with the gate valve  113  closed. 
     The tertiary process in the discharge chamber  114  ensures that the waste material is thoroughly treated. When this cycle is complete, the discharge door  117  is opened and the shredded and sterilised material is ejected by the agitator  115  into a waste container for disposal. 
     Another embodiment of the invention which may utilise the same cutting mechanism  108  is shown in FIGS. 5 to  7 . This waste treatment device  200  includes an optional sealed enclosure or housing  201  that includes a sealed loading chamber  202  which is partitioned (dotted lines  203 ) from the remainder of the device. The loading chamber  202  includes a sealable door  204  through which bins  205  may be introduced. The bins  205  are lifted and inverted by a gripper and arm  206  which follows a guide, rail or track  207 . The gripper or arm may include a load cell  280  so that the weight of the bin  205  may be measured, recorded and accounted for. 
     The loading chamber has a bin cleaning device  230 , 231  which is mounted below a pivoting transfer hopper  209 . 
     As shown in FIG. 6, once the bin  205  is inverted, the lid  208  opens allowing the waste contents of the bin  205  to fall into the hopper  209 . To assist with the ejection of waste from the hopper, the hopper may be equipped with cavity walls  210  so that steam my be forced into the cavity and then into the working volume  211  of the hopper through vents (not shown) formed in the inner wall  212 . 
     After the contents of the bin  205  have been discharged into the working volume  211  of the hopper, the bin is momentarily withdrawn or retracted along the guide  207  so that the hopper may deliver its contents to the primary processing chamber  220 . 
     As shown in FIG. 7, the hopper  209  pivots around one edge  221  to deliver its contents into the primary processing chamber  220 . The curved guide wall  222  assists in delivering the contents of the hopper into the processing chamber  220 . 
     With the hopper  209  now pivoted out of the way, the inverted bin  205  can be advanced once again along the guide  207  into contact with a cleaning mechanism  230 . The bin cleaning mechanism  230  comprises a rotating brush  231  which is raised along guide rails  232  into engagement with the bin  205 . The rotating brush  231  may be assisted with the provision of steam, then lowered prior to the return of the hopper  209  to its original position as depicted in FIG.  5 . 
     If required, the air from the loading chamber  202  may be evacuated after bin cleaning. The exhaust air is preferably drawn over a steam line to kill air-borne micro-organisms prior to venting to the atmosphere. 
     The primary processing chamber  220  comprises a generally cylindrical chamber  235  which can accommodate the entire contents of the hopper  209 . The primary chamber  220  is analogous to and may be constructed similarly to the chamber  101  depicted in FIG.  1 . It is sealed either with a separate door or by the action of a hydraulic ram. The chamber  235  may be evacuated prior to the introduction of steam. Waste material in the chamber  220  is then advanced either by a hydraulic ram or auger into contact with a cutting mechanism located at the top of the chamber  220  which mechanism is like the one depicted in FIGS. 2 to  4 . External steam lines  236  may be provided along the length of the primary chamber so that steam may be delivered to its contents through vents located periodically along the jacket  236 . Like the device depicted in FIG. 1, the embodiment depicted in FIG. 7 includes a grate  237  located near the cutting heads and a isolation valve  239  located between the primary chamber  220  and a tertiary processing chamber  240 . Thus a secondary steam processing chamber is defined between the grate  237  and the isolation vale  239 . 
     The tertiary processing chamber  240  may serve either or both of two distinct functions. One function of the secondary processing chamber is to further treat the shredded waste produced by the primary chamber  220  by treating it with additional steam provided through a steam jacket  241 . In the alternative, the secondary processing chamber  240  may be used to dry the waste prior to discharge through heating of the auger blades internally with steam. The secondary chamber  240  is preferably provided with a ram, screw feeder or auger which moves the waste within the secondary chamber  240  toward a discharge chute  245  which discharges when the exit seal  290  is opened to a removable bin  246 . 
     Both the first and third processing chambers  220 ,  240  may be provided with a facility for collecting the liquid runoff of the waste  250 . In this way, accumulated liquids can be separated from the waste and treated, sterilised or vaporised separately, if required, prior to disposal. 
     Where the secondary chamber is used to dry waste, a vent  252  is provided to carry away water vapour and other vapours so that they can be treated, for example, with carbon filters  253  or other means of removing waste material from the vapour discharge. 
     Pressurised steam for the device  200  is provided by water held in a tank  260  which supplies its contents to a steam generator  261 . The steam generator  261  derives its energy from a power source such as an LPG burner  262 . The water tank  260  may be supplied with fresh water or water originating from the liquid trap  250  or vapour condensation and treatment device  253 . 
     While the invention has been described with reference to particular details and methods of construction, these should be appreciated as having been provided by way of example and not as limitations to the scope or spirit of the invention.