Patent Document

TECHNICAL FIELD 
   This invention relates to a unit for compacting waste prior to disposal. The unit is particularly useful but not limited to use in a domestic environment, for example in the home or in hotels and catering establishments. 
   BACKGROUND INFORMATION 
   Disposal of domestic waste is becoming more difficult in today&#39;s society, as more and more waste is produced, and the capacity of existing landfill sites is rapidly exhausted. Present methods of disposal of domestic waste are extremely inefficient due to the fact that the waste generally takes up so much volume in comparison to its weight. In general domestic waste is transported by waste disposal vehicles which carry between 10% and 20% of their potential capacity by weight, the total capacity being limited by the volume of the waste material. Some waste compaction is carried out by these waste disposal vehicles. In general the waste is subjected to compression during the journey, although due to the fact that most materials exhibit ‘shape memory’, once the waste material is emptied from the vehicle some expansion takes place and the waste material returns towards its original shape and therefore volume. Therefore landfill sites are filled up more quickly by this large volume waste than is strictly necessary. 
   SUMMARY 
   Waste processing systems are known which crush or pulverise waste prior to disposal. However, such systems are generally large and cumbersome and use a large amount of power to achieve the desired result. Use of excessive energy is contrary to the objective of providing a more environmentally friendly waste disposal system. 
   Known waste compacting systems intended for use in the domestic environment such as that described in U.S. Pat. No. 3,736,863 suffer from a number of drawbacks. If waste is compressed inside a bin liner, then the liner will tend to snag and tear against the compression member. Furthermore, the compressing apparatus will tend tilt and to compress unevenly due to different type of waste being present in the apparatus. If there is no locking mechanism then the apparatus can be unsafe. If an electrical locking mechanism is used it can be prone to failure, and will not necessarily be fail-safe. 
   The present invention seeks to alleviate such problems. 
   According to the invention there is provided a waste compaction unit for fitting into a housing comprising a lid and an interior for collecting waste, the compaction unit comprising
         a plunger comprising bellows housed in said lid;   a pneumatic locking mechanism housed in said lid; and   a pump connected to the plunger via said locking mechanism
 
wherein the pump is arranged in operation to activate the locking mechanism prior to inflating the bellows to extend the plunger axially towards the bin interior such that any waste collected therein is compacted.
       

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
       FIG. 1  illustrates a partially cut away three dimensional view of a waste compaction unit in accordance with the present invention; 
       FIG. 2  illustrates part of a compactor tube assembly; 
       FIG. 3  illustrates a pair of locking rings; 
       FIG. 4  illustrates a compactor tube; 
       FIG. 5  illustrates a pair of locking rings attached to an outer bin; 
       FIGS. 6   a  to  6   e  show various parts of a plunger assembly; 
       FIG. 7  illustrates deflated bellows; 
       FIG. 8  is a close up partial cross section of part of a waste compaction unit; 
       FIG. 9  illustrates a topside view of a lid moulding; 
       FIG. 10  illustrates locking pistons housed in the lid moulding of  FIG. 9 ; 
       FIGS. 11   a  and  11   b  illustrates parts of a locking mechanism; 
       FIGS. 12   a  and  12   b  illustrate a piston detail; 
       FIGS. 13   a  and  13   b  illustrate a locking hook detail; 
       FIG. 14  is a perspective cross section of part of the bottom of a waste compaction unit; 
       FIG. 15  is a close up view of a hinge detail; and 
       FIGS. 16   a  to  16   d  illustrates bellows in partially and fully extended configurations. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  illustrates a partially cut away three dimensional view of a waste compaction unit  1  in accordance with the present invention. A conventional flip top bin assembly has a hinged lid  3 , an outer bin  2  and an inner bin  4 . The compaction unit  1  comprises a pump assembly  5 , a compactor tube assembly  6  and a plunger assembly  7 . 
   A pump housed in the pump assembly  5  is used to activate a plunger, which comprises bellows, housed in the plunger assembly  7 . The plunger travels axially inside the compactor tube assembly  6  and compresses any waste in the unit. 
   Referring to  FIGS. 2 to 5  the compactor tube assembly will now be described in more detail. 
   Referring firstly to  FIG. 2 , the compactor tube assembly comprises an upper locking ring  8 , a lower locking ring  9  and a compactor tube  10 .  FIG. 3  illustrates the locking rings  9 ,  10  which are assembled to provide a bayonet fitting  11  for the compactor tube  10 .  FIG. 4  illustrates the compactor tube  10 , which has tabs  12  to fit into corresponding bayonet fittings  11 . The compactor tube  10  has bag locator tabs  13 , of which only one is shown in  FIG. 4 , which are used for attaching conventional bin liner (not shown) to the outside of the compaction tube  10 . Hand holds  16  are provided for ease of insertion and removal of the compaction tube  10  from the bayonet fittings  11  formed in the locking rings  8 ,  9 . Ideally the compactor tube extends between one half and two thirds of the total bin height. 
   Locking rings  8 ,  9  form a circumferential recess  14 , which serves to attach the locking rings  8 ,  9  around an inner rim  17  of the outer bin  2  as illustrated in  FIG. 5 . 
   The locking rings are affixed to each other by conventional fixings; six bolts are inserted through the lower ring  9 , and are screwed into the upper ring  8 . 
   The compactor tube  10  helps to prevent tilting of the plunger and helps to prevent non uniform expansion caused by different types of waste having different compression characteristics. The compactor tube  10  also helps to prevent contact between the plunger and any bin liner, which is placed attached to the outside of the compactor tube, between the compactor tube and the inner bin. Conventional compactors with no compaction tube also have the problem that the bellows start deform and tilt axially as they expand. The gap between the compactor tube  10  is very small, in this embodiment of the invention it is 1 mm. The gap must be small to maintain the cylindricity, and prevent the plunger from tilting when compressing material of non-uniform density of the bellows. 
   Referring now to  FIGS. 6 to 13  the plunger assembly  7  will be described in more detail. 
     FIGS. 6   a  to  6   e  show various parts of the plunger assembly comprising a lid moulding  18  and a plunger comprising a plunger casing  19  together with bellows  20 . 
     FIG. 7  illustrates deflated bellows  20  showing connector  22  which is connected to the pump via an aperture  21  in the lid moulding  18 . The plunger casing  19  is attachable to the bellows  20  by Velcro, or similar reattachable fixing to facilitate easy removal for cleaning. Furthermore, if a waste item gets trapped during decompression the plunger casing can disengage from bellows, allowing the bellows to retract fully into the lid and the locks  29  to disengage. The casing serves to protect the bellows  20  from damage. The casing in the embodiment described is cylindrical but protection could equally well be provided by a substantially flat plate. The depression in the centre of the plunger casing serves to push the waste material inwards and prevents it being pushed outwards towards the walls and locking the plunger. 
   The lid moulding houses a locking mechanism, and tubes for attaching the pump to the bellows  20 . 
   The bellows  20  are substantially cylindrical when inflated and includes concertinaed side and a rigid plate at each end of the bellows. The rigid plates prevent bulging of the ends of the bellows during inflation. 
   Referring now to  FIG. 8 , the lid moulding also houses a sensor  23 . The sensor  23  uses an infra red beam to sense whether the plunger casing  19  is present. Any other suitable sensor may be used. The sensor  23  is connected to the pump, and pump will not operate to inflate the bellows  20  if the plunger casing  19  is not detected. If an attempt is made to activate without the plunger casing  19  the pump will not activate until the plunger casing  19  is replaced. This is to prevent damage to the bellows if the casing  19  has been removed, for example for cleaning in a dishwasher. An alarm  45 , is provided, in this case a buzzer, which sounds when the pump is activated 
     FIG. 9  illustrates a topside view of the lid moulding  18 . Aperture  24  allows electrical connection to the sensor  23  and switch panel  33 . Aperture  25  provides access for a tube connecting the pump to the bellows  20  via aperture  21 . Fixings  40 , 41  are provided for the sensor  23  together with the alarm  45  The lid moulding  18  is attached to the lid  3  by snap fit locking tabs  27 . 
   The lid moulding  18  houses a novel pneumatic locking mechanism, partially illustrated in  FIG. 10 . Four pistons  28   a - 28   d  are provided. The pistons  28  are connected to operate corresponding hooks  29   a - 29   d . The pistons together with the hooks may be seen more clearly in  FIG. 11   a , which includes a partially cut away view of the upper locking ring  8 . When the pistons are extended, hooks  29  engage apertures  15  in the locking ring to lock the lid  3  shut prior to inflation of the bellows. 
   A tube from the pump enters through aperture  25  and along channel  42  in the lid moulding  18 . The pump is connected to the pistons via ports  35 ,  FIG. 11   a  at the rear of the pistons. The pistons may be connected to the pump, either in series or in parallel. One of the pistons  28   b  has a side port  32  which is then connected to a tube feeding the bellows  20 .  FIG. 11   b  illustrates the connected tubes in a preferred embodiment of the invention. 
   Detail of the piston  28   b  may be seen in  FIGS. 12   a  and  12   b , which show a cross section of the piston  28   b  in which the port  36  is in an open ( FIG. 12   a ) and a closed ( FIG. 12   b ) position. 
   Thus it can be seen that it is not possible for the bellows to start to inflate before piston  28   b  is extended such that the port  32  is open. In this extended position the hook  29   b  has engaged the aperture  15   a  to lock the lid  3  shut. 
   It is important that the friction characteristics of the pistons are such that the pistons  28   a ,  28   c ,  28   d  open before the piston  28   b . This is achieved by providing a single “O” rings around pistons  28   a ,  28   c ,  28   d  and a double “o” rings around piston  28   b . During deflation of the bellows, the bellows will deflate due to the fact the port  36  is open. Only when all the air has been evacuated from the bellows and the bellows has been fully retracted into the lid will there be sufficient vacuum in the system to retract all four pistons and all four locking hooks. 
     FIGS. 13   a  and  13   b  illustrate the hook  29   b  in a locked ( FIG. 13   a ) and in an unlocked ( FIG. 13   b ) position. 
   Finally referring to  FIG. 14  the pump assembly  5  will be described in more detail. 
   A housing  30  houses a pump (not shown) together with electronic circuitry to operate the pump when required. The pump is a rotary vane pump which has the benefit of being reversible. 
   The pump is electrically connected to a switch panel  33  on the lid by wires which extend through the bottom of the bin and between the outer bin  2  and the inner bin  4  through an aperture (not shown) near the top of the outer bin and near a hinge connecting the outer bin  2  to the lid  3 . The wires then enter through an aperture in the lid  31  ( FIG. 6   b ) and through the aperture  24  in the lid moulding and connect to a switch panel  33  ( FIG. 13   a / 13   b ) mounted on the lid  3 . 
   The pump is pneumatically connected to the bellows by a tube which extends through the bottom of the bin and between the outer bin  2  and the inner bin  4  through an aperture (not shown) near the top of the outer bin and near a hinge connecting the outer bin  2  to the lid  3 . The tube then enters through an aperture in the lid  32  ( FIG. 6   b ), through the aperture  25  in the lid moulding and connects to the bellows via the pneumatically driven locking mechanism. 
   The housing  30  is connected to the bottom of the bin outer by bolts which are inserted through the original base and into a locking ring  34 . 
   The pump has two modes of operation. A short compression cycle, which briefly compresses any waste in the unit, in order to introduce more waste for example, and an extended compression cycle, during which the waste is compressed for a fixed amount of time (for example overnight) or until a specified pressure is reached. 
   During the extended compression cycle a compressive force is applied to the waste continually for a period of several hours during which time all plastic material lose their shape memory and remain in a compressed or flattened state with no tendency to return to their original formed shape. 
   The pump operates at three to four psi (20.7-27.6 Pa). This exerts a force of between 150-200 lbs (667-890 Newtons). 
   On activation of the pump, the pneumatically operated hooks are caused to lock the bin lid shut. Once the lid is locked, the bellows inflate, thus extending the plunger and compacting any waste in the unit for either a fixed period of time or until a predetermined pressure is reached. 
   As the pressure inside the bellows increases pressure is exerted on the lid.  FIG. 15  illustrates a modified hinge  46  which has been elongated to allow vertical lid travel when the bin is pressurised. The lid lifts slightly thus locking each hook into each corresponding aperture. 
   A pressure switch may be used to switch off the pump once the predetermined pressure has been achieved. In practice, this means that the bellows inflate to a certain pressure and the pump turn off. After the waste has been compressed for a while the pressure drops as the waste becomes compressed and the pump switches on once more. 
     FIG. 16   a  and  FIG. 16   b  are a cross section and a perspective cross section respectively showing the bellows  20  in a partially extended configuration.  FIG. 16   b  and  FIG. 16   c  are a cross section and a perspective cross section respectively showing the bellows  20  in a fully extended configuration. 
   As mentioned previously the pump will not operate if the plunger casing is not sensed by the sensor  23 . 
   After the compaction cycle is complete the pump operates in reverse, the bellows deflates and the plunger retracts into the lid. Once the plunger has retracted fully, the pneumatically operated hooks release the bin lid in order that it may be opened once more. 
   An advantage of the waste compactor is that it is easily scaleable. It can be housed in a conventional domestic waste bin, or it can housed in any hollow, sealable container. It can be made larger for commercial use, such as for disposal of packaging in a fast food outlet where large amounts of compressible waste is produced. It can also be made smaller if desired. The waste compactor uses very little power typically around 22 Watts. 
   It will be understood by those skilled in the art that a number of modification may be made to the embodiment described above without departing from the scope of the invention as defined in the appended claims.

Technology Category: b