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(11) | EP 0 644 131 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Waste disposal system |
| (57) As shown in Figure 1, the invention provides a cost-effective system for the transport
and disposal of potentially hazardous waste. Waste is loaded into tough, durable re-usable
containers (11) at a waste production site such as a hospital ward (10). These are
transported locally on wheeled trolleys (14) to a pick-up site where they are loaded
on to special purpose vehicles (15) fitted with special purpose hoist devices. The
vehicles (15) transport the containers to a waste disposal site where the containers
are emptied into an incinerator feed hopper. The containers are then cleaned and sanitized
before being returned on the vehicles to the waste production sites for re-use. |
[0001] This invention relates to a method of and apparatus for use in the transport and disposal of potentially hazardous waste such as the waste from hospitals.
[0002] Conventionally, each ward in a hospital has a number of waste stations where waste matter is inserted into polythene or other bags formed of thin synthetic film material. These bags are sealed and tagged when full and taken to a local collection point, where they are placed in a transportable container, which may itself be lined with a large size bag of thin plastic film. These containers are usually taken at set times (or when they are full) to a main collection station when they are removed for disposal by a collection service.
[0003] The use of thin plastic film bags is, however, unsatisfactory as sharp objects, such as scalpels or hypodermic needles, placed in them in without being enclosed in a protective container, can cause injury to anybody handling the bags and can also damage the bags so that the contents leak out. Each successive person handling damaged bags will be at risk from any contaminated articles contained in the bags.
[0004] It is an object of the present invention to provide a cost-effective system in which handling of the thin plastic film bags is reduced to a minimum, so as to reduce risks to persons involved in the transport and disposal of the waste.
[0005] In accordance with the invention there is provided a system for the transport and disposal of potentially hazardous waste, in which the waste is loaded at the waste production site into durable re-usable containers formed of material which is substantially impenetrable by the waste, and transported to a disposal site, where the containers are sanitized before return to the waste production site for re-use.
[0006] Preferably the containers are in the form of substantially rigid boxes with fastenable hinged lids which are stackable. Preferably the boxes are formed of a synthetic resin material such as polyethylene.
[0007] The invention also resides in a vehicle mounted hoist device for transporting the containers. The hoist device includes an overhead track extending longitudinally of the vehicle above a load platform thereof, a main carriage movable along such overhead track, a cross-track mounted on said main carriage and extending transversely to said overhead track, a hoist carriage movable along said cross-track, a cable hoist on said hoist carriage, a lifting device suspended on the hoist cable, and a linkage connecting the lifting device to the hoist carriage to constrain the lifting device to move up and down under the influence of the hoist.
[0008] Preferably, the linkage is in the form of a "lazy tongs" linkage comprising a plurality of pairs of main links pivotally connected to one another and two pairs of connecting links connecting the endmost main links to the hoist carriage and the lifting device.
[0009] For added stability, a toothed gear arrangement may be provided to interconnect the ends of at least one of said pairs of connecting links, such that these links are constrained to remain symmetrically disposed relative to the part they are connected to so as to maintain the lifting device in a fixed orientation relative to the hoist carriage.
[0010] Preferably, to enable the hoist to be used on both sides of the vehicle the cross-track includes a support means fixed to the main carriage and an intermediate track supported by said support means and movable longitudinally so as to be positionable in either of two extreme positions projecting from opposite sides of the vehicle, the hoist carriage being longitudinally movable on said intermediate track.
[0011] Preferably, the lifting device comprises a frame having a plurality of vacuum pads thereon, the frame also carrying an exhaust pump and controlling means therefor, for applying a lifting force to a box lid.
[0012] In the accompanying drawings:-
Figure 1 is a diagram of an example of a waste disposal system in accordance with the invention;
Figure 2 is a perspective view of a container used in the system of Figure 1;
Figure 3 is a view showing a vehicle mounted hoist used in the system; and
Figure 4 is a diagrammatic end view of the hoist of Figure 3.
[0013] The system shown in the drawings is intended specifically for the disposal of hospital waste which may include contaminated needles and other sharp objects, as well as used dressings and other infected or contaminated articles. The intention of the system is to ensure as far as possible that the waste is transported from the hospital to a disposal site without risk to the persons involved in its transport and disposal.
[0014] In Figure 1 reference numeral 10 indicates a waste disposal room attached to one or more hospital wards which it serves. The waste is brought to this room in conventional colour coded thin plastic bags which are widely utilized for this purpose. Within the room one or more special purpose containers is or are disposed.
[0015] As shown in Figure 2, the container is a substantially cuboidal box 11, which has a hinged lid 12. The walls of the box are ribbed or otherwise reinforced, the box and its lid being formed of a relatively light synthetic resin material such as medium density polyethylene. The lid 12 of the box, which can be fastened in its closed position by means of locks or latches 13, has a raised central area 12a and a correspondingly shaped and dimensioned recess is provided in the bottom of the box so that the boxes can be stacked stably.
[0016] The boxes 11 are transported locally on castor-wheel trolleys 14 shaped to receive the base of a box.
[0017] Longer distance transportation is effected by means of specially adapted lorries 15 which are each provided with a built in hoist mechanism to simplify handling of the containers. As shown in Figure 1, a container from the hospital waste disposal room, having first being latched or locked shut, is loaded onto a lorry and carried to a final disposal site, where it is unloaded onto a wheeled trolley and taken to an incinerator 16 where it is lifted by suitable lift device and emptied into the hopper of the incinerator. It is then wheeled on its trolley to a cleaning and decontamination apparatus 17 where it is lifted, inverted and thoroughly sprayed internally with a suitable disinfectant. The container is then ready to be returned to the hospital for re-use.
[0018] Turning now to Figures 3 and 4, the hoist device used in the special purpose lorries 15, includes longitudinal bearers 20 fitted intermediately under the roof 20 of the load carrying area of the lorry (the load platform of which is not shown in Figures 3 and 4). Attached to these bearers 20 are two tracks 22 which are in the form of inverted channel section members having interned flanges thereon. A main carriage 23 is suspended from roller bogeys 24 which run in the tracks 22. An endless belt or chain drive arrangement driven by an hydraulic motor (not shown) is used to propel the main carriage 23 along the tracks 21.
[0019] As will be seen in Figures 2 and 3 the main carriage 23 extends across the vehicle width within the doors or curtains 25 on each side of the lorry load carrying area. A hoist carriage 26 is mounted on this main carriage for transverse movement. In fact, an intermediate track 27 is employed (see Figure 4) which has outwardly facing channels 28 which are supported on rollers 29 rotatably mounted on the main carriage 23. The intermediate track 27 extends over substantially the whole width of the vehicle and can be moved in either direction from a central stowed position to project from either side of the vehicle. To this end there are several sets of rollers 29 at spaced positions along the main carriage. In the stowed position the channels 28 on the intermediate track are positioned to receive all of the rollers 29, but as the intermediate track is displaced in either direction it is supported by fewer and fewer of the rollers. There may, for example, be five sets of rollers 29 equally spaced along the main carriage. At the extremes of its travel, the channels 28 intermediate track 27 receives and is supported by only three of the sets of rollers 29.
[0020] An hydraulic motor (not shown) mounted on the main carriage drives the intermediate track through an endless belt or chain drive (not shown).
[0021] The intermediate carriage 27 is also provided with two mutually inwardly facing channels 30 in which rollers 31 on the hoist carriage 26 run. There is an hydraulic motor (not shown) for driving the hoist carriage through the intermediary of another endless belt or chain drive (not shown).
[0022] Mounted on the hoist carriage is a hoist drum 32 which is driven by an hydraulic hoist motor 33. A cable 34 wound on the hoist drum 32 is attached at its lower end to a lifting device in the form of a rectangular frame 35 fitted with vacuum lifting pads 36 at its corners. These pads are connected to a self contained exhaust pump/motor unit (not shown) mounted on the frame 35 and various remote controls (not shown) are provided for this unit.
[0023] To stabilize the lifting frame 35, a pair of guide linkages 37 are provided and these are disposed respectively in front of and behind the lifting frame 35 in the longitudinal direction of the vehicle. In the example shown, each linkage 37 is in the general form of a "lazy tongs" linkage comprising several pairs of crossed identical links 38. The links of each pair are connected to one another at their centres and each has one end connected to one end of one of the links in the pair above and at the other end to one end of one of the links in the pair below. The top-most and bottom-most link pairs are connected to the hoist carriage 26 and the lifting frame 35 respectively by connecting links 39 and 40. The links 39 and 40 are, in fact, provided at the ends which are connected to the hoist carriage 26 and lifting frame 35 respectively with gear teeth, which mesh with respective ones of a pair of meshed idler gears 41 rotatably mounted on the lifting frame 35 and the hoist carriage 26. These ensure that the links 40 are always symmetrically arranged relative to the hoist carriage 26. It should be noted that the gear arrangement may be provided on the hoist carriage or the lifting frame only.
[0024] The hoist arrangement described above is of particular utility in the waste disposal system described herein as it enables the boxes to be handled very easily and takes up very little space in the vehicle load space. The hoist design is also suitable for use in many other applications in which lifting devices other than the frame/vacuum pad arrangement may be employed.
[0025] In another example of the invention not shown the boxes are replaced by lining bags which are transported within the hospital in wheeled containers. The lining bags are formed of a flexible tough material with good resistance to being cut by a scalpel or pierced by a needle. The material used may be a rubber/fabric laminate. Each lining bag has around its mouth a lip which can be turned back around the sides of a wheeled transportation container. It is provided with clips to secure the lip to the container so as to hold the lining bag open. The mouth of the bag is further provided with a hermetically sealing sliding clasp type fastener, which extends around three sides of a rectangle, allowing the rectangle to be opened along a fold line at the fourth side to form a lid.
[0026] Each bag also has a receptacle on the fastener or on the body of the bag for a bar-coded or other identification label.
[0027] The bag has a lifting ring at its top by means of which it can be lifted by a suitable hoist and it also has a plurality of eyeletted or otherwise reinforced tabs at its bottom to enable it to be attached to other handling equipment to be mentioned hereinafter.
[0028] Lining bags as described above are fitted into wheeled transportable containers at the local collection points. The lip on the bag is engaged with the container to ensure that loose material does not enter the container outside the lining bag. Periodically the wheeled containers from different parts of an establishment are brought to a main collection point, where the bags are sealed up and lids on the containers are closed and locked pending collection.
[0029] Special purpose vehicles are used for the transportation of the lining bags to a disposal site. Each such vehicle has a box shaped back which is fitted with a lining box. The lining box is supported on rollers in the box back so that it can readily be rolled in and out. The vehicle is also fitted with special purpose bag handling equipment specifically intended to be used in transferring sealed lining bags from the wheeled containers to the interior of the lining box. Such equipment may either lift the entire wheeled container and tip its lining bag into the lining box, or it may include a lifting device for lifting the bag from the wheeled container and transferring it into the interior of the lining box.
[0030] The vehicle operator has the tasks of unlocking and opening the wheeled containers, attaching bar-coded labels to the lining bags and releasing the clips which hold the lip of the bag on the container, before actuating the mechanical handling equipment to pack the bags into the lining box. The operator then relines the wheeled containers with fresh lining bags which are stowed for transport in a special compartment of the vehicle.
[0031] On arrival at the disposal site, the vehicle operator attends to the removal of the complete lining box from the box back of the vehicle. This operation is carried out very rapidly by using a winch to pull the lining box on to a special purpose wheeled bogey. The bogey can be raised and lowered using a built in scissors lift. Having unloaded a full lining box, the vehicle operator can load an empty lining box, obtain a supply of fresh lining bags and depart from the disposal site.
[0032] When it is required to dispose of the contents of the lining bags, the wheeled bogey is taken, with the intact lining box still carried by it, to the loading area of an incinerator plant. The lining box has a tail gate with side cheeks designed to ensure that lining bags do not fall off the tailgate sideways when the tailgate is lowered. The disposal site operator uses a lifting crane or the like to remove the bags one by one from the lining box using the lifting ring on each bag for this purpose. The crane includes a weigher for weighing the bags and the operator reads the bar code label of each bag when it is weighed for accounting purposes. Each bag is transferred by the crane to a lifting cradle, having hooks or the like for engaging in the eyeletted tabs at the bottom of the bag. The operator opens the bag and clips the lip referred to above to the cradle to hold the mouth of the bag open. The cradle then lifts the bag and inverts it over the feed hopper of the incinerator.
[0033] Each bag is next transported on its cradle to a washing station, where it is inverted, washed, sanitized and dried inside and out ready for re-use. Clean bags removed from the cradles are rolled and packed for recycling.
[0034] It will be appreciated that the above described system ensures that nobody involved with the transportation or disposal of the waste has to handle the original thin plastic bags within the lining bags. The risk of contamination and personal injury is thus minimized. The use of removable lining boxes in the vehicles ensures safe rapid unloading of the bags from the vehicle at the disposal site and maximises vehicle utilization. All the resources of the whole system are used in an efficient manner enabling disposal cost to be kept low whilst the operators are exposed to minimal risk.
[0035] In an alternative arrangement, the lining bags may have drawstrings instead of the clips mentioned for fastening the lip on each liner to its wheeled container. Instead of a lifting hook the rectangular lid of the lining bag may have a steel plate attached to it for lifting by a hoist with a magnetic clamp.
[0036] For handling such lining bags, the special purpose vehicles used may have removable rear bodies with telescopic or otherwise retractable legs. The body would have a number of compartments for the bags, each compartment being open at the top. The lifting hoist for lifting the bags and a container clamp mechanism for holding the wheel container as the bag is lifted therefrom would be built on to the removable body and would be used both at the collection point for loading the bags and at the disposal site where the bags are unloaded after the body has been left behind by the vehicle.
1. A system for the transport and disposal of potentially hazardous waste in which the
waste is loaded at a waste production site (10) into durable re-usable containers
(11) formed of a material which is substantially impenetrable by the waste, and transported
to a disposal site (16), where the containers are emptied and sanitized before return
to the waste production site for re-use.
2. A system as claimed in Claim 1, in which the containers are in the form of substantially
rigid boxes (11) with fastenable hinged lids (12).
3. A system as claimed in Claim 2, in which the lid of each box has a raised central
area (12a) and the base of the box has a correspondingly shaped recess so that the boxes can
be stacked stably.
4. A system as claimed in Claim 2 or Claim 3, in which the boxes are formed of a synthetic
resin material.
5. A system as claimed in any of Claims 2 to 4, further comprising wheeled trolleys used
at the two sites (10 and 16) for local transportation of the boxes.
6. A system as claimed in any of Claims 2 to 6, further comprising special purpose vehicles
for transporting the boxes between the two sites (10 and 16) such vehicles having
a load space and a hoist device mounted above said load space for loading and unloading
the boxes.
7. A system as claimed in Claim 6, in which said hoist device comprises an overhead track
extending longitudinally of the vehicle above a load platform thereof, a main carriage
movable along such overhead track, a cross-track mounted on said main carriage and
extending transversely to said overhead track, a hoist carriage movable along said
cross-track, a cable hoist on said hoist carriage, a lifting device suspended on the
hoist cable, and a linkage connecting the lifting device to the hoist carriage to
constrain the lifting device to move up and down under the influence of the hoist.
8. A system as claimed in Claim 7, in which said linkage comprises a "lazy tongs" linkage
comprising a plurality of pairs of main links (38) pivotally connected to one another
and two pairs of connecting links (39, 40) connecting the end-most main links to the
hoist carriage (26) and the lifting device (36) respectively.
9. A system as claimed in Claim 8, in which a gear arrangement (41) is provided to interconnect
the ends of at least one of said pairs of connecting links, such that these links
are constrained to remain symmetrically disposed relative to the part they are connected
to.
10. A system as claimed in any of Claims 7 to 9, in which said cross track includes a
support means fixed to the main carriage, and an intermediate track supported by said
support means and movable longitudinally so as to be positionable in either of two
extreme positions projecting from opposite sides of the vehicle, the hoist carriage
being longitudinally movable on said intermediate track.
11. A system as claimed in any of Claims 7 to 10, in which said lifting device comprises
a frame having a plurality of vacuum pads thereon, the frame also carrying an exhaust
pump and controlling means therefor, for applying a lifting force to a box lid.
12. A hoist device for use in a vehicle comprising a track supporting a hoist carriage
for movement longitudinally of the track, said track including an intermediate track
movable longitudinally relative to the track to project from the track, said hoist
carriage being mounted on the intermediate track for longitudinal movement.
13. A hoist device as claimed in Claim 12, in which said track has a plurality of pairs
of support rollers mounted on it at spaced positions along its length, the intermediate
track having a pair of mutually outwardly facing channels which receive said rollers.
14. A hoist device as claimed in Claim 13, in which the intermediate track also has a
pair of mutually inwardly facing channels for receiving rollers on the hoist carriage.
15. A hoist device for use in a vehicle comprising a track, a hoist carriage movable along
said track, a hoist drum mounted on said hoist carriage, a lifting device suspended
on a cable wound on said hoist drum, and a stabilising linkage inter-connecting the
hoist carriage and the lifting device.
16. A hoist device as claimed in Claim 15, in which said linkage comprises a "lazy tongs"
linkage comprising a plurality of pair of interconnected links and two pairs of connecting
links connecting the end-most links of said "lazy tongs" linkage to the hoist carriage
and the lifting device respectively.
17. A hoist device as claimed in Claim 16, in which each of at least one of said pairs
of connecting links has a toothed gear at its ends, the two toothed gears being interconnected
by a pair of meshed idler gears.