Compaction methods and apparatus

Information

  • Patent Grant
  • 6505550
  • Patent Number
    6,505,550
  • Date Filed
    Wednesday, May 9, 2001
    23 years ago
  • Date Issued
    Tuesday, January 14, 2003
    21 years ago
  • Inventors
  • Examiners
    • Rosenbaum; Mark
    Agents
    • Adams, Schwartz & Evans, P.A.
Abstract
Waste compaction apparatus has a screw conveyor which conveys material along a passage toward an exit nozzle which constricts the flow, to cause compaction. The screw conveyor is slidably mounted on a shaft, biased toward the nozzle. This allows the screw conveyor to move axially during compaction to help remove or avoid blockages within the apparatus.
Description




The present invention relates to compaction methods and compaction apparatus and in particular but not exclusively to methods and apparatus for compacting (i.e. compressing) waste material. Other applications for the invention include the compaction of waste materials used in farming and the food industry, but not necessarily waste materials.




Compacting apparatus is described in International Patent Application No. WO 94/07688. That apparatus uses a hopper to supply material to a screw conveyor which conveys material through a passage to cause compaction. The compacted material then leaves through an exit nozzle. A control circuit is provided to sense when the compacting apparatus becomes blocked. When this happens, the screw conveyor is reversed to draw compacted material back to the hopper, with a view to clearing the blockage. It has been found that even if this technique for clearing blockages is effective, its reliance on a potentially complex and expensive control arrangement can prevent its use for certain commercial applications, particularly with relatively small, cheap compacting apparatus. The present inventor has therefore sought to provide improved compacting apparatus.




SUMMARY OF THE INVENTION




The present invention provides compacting apparatus comprising a screw conveyor for axial rotation to convey material through a passage and compact it therein, and an exit nozzle communicating with the passage, the screw conveyor being supported for axial movement relative to the passage during use, whereby the screw conveyor may move axially in the event of a blockage.




The screw conveyor is preferably resiliently biased in the axial direction relative to the passage. The screw conveyor may be biased to move relative to the passage in the conveying direction. At least part of the screw conveyor is preferably located within a tapering part of the passage and has a diameter which tapers in the same sense, whereby axial movement of the screw conveyor relative to the passage varies the gap between the tapering part of the screw and the tapering part of the passage. The tapering parts of the screw conveyor and passage may have substantially the same degree of taper.




Preferably fixed blade means are located adjacent the screw conveyor, and cooperating blade means are carried by the screw conveyor, whereby material located between the said blade means is subjected to a cutting action by continued rotation of the screw conveyor. The cooperating blade means may be located along the outer edge of the flight of the screw conveyor. The cooperating blade means may extend over a greater axial length of the screw conveyor than the fixed blade means, whereby the blade means remain in cooperation over a range of positions of the screw conveyor relative to the passage. Preferably at least part of the cooperating blade means are located along a tapering portion of the screw conveyor.




In a second aspect, the invention provides compacting apparatus comprising a screw conveyor for conveying waste material through a passage and compacting it therein, and an exit nozzle communicating with the passage, the nozzle defining an internal transverse cross-sectional area which enlarges and reduces respectively in response to increasing and decreasing material pressure, and wherein the nozzle comprises at least one resilient member which causes the nozzle to be biased toward a position of minimum cross-sectional area, the or at least one resilient member comprising an inflatable portion which provides an adjustable degree of resilience dependent upon the degree of inflation of the resilient portion.




Preferably the nozzle has a plurality of wall portions which are movable relative to each other to vary the cross-sectional area of the nozzle, the resilient member cooperating with the wall portions to bias the nozzle toward a position of minimum cross-sectional area.




The nozzle may comprise a number of spaced apart, longitudinally extending fingers. Preferably there are no gaps between the fingers and the nozzle tapers towards its outlet when the nozzle cross-sectional area is at its minimum. The nozzle may comprise two members each of which has a number of spaced apart, longitudinally extending fingers, one member being arranged inside the other. The resilient member may be located to surround the outer of the two members to provide resilient bias thereto. Preferably the two members are arranged such that a finger of one member overlaps two fingers of the other member whereby there are substantially no gaps between the fingers.




In another aspect, the invention provides material handling apparatus comprising compacting means operable to compact material and to deliver compacted material to collection means, the collection means providing a plurality of locations at which compacted material may be received, and being movable to allow one location to move to an emptying position while another is moving to a position for receiving material from the compacting means.




The collection means may comprise a rotatable carousel. Each location may be adapted to removably receive a receptacle which can be removed when full for replacement by an empty receptacle. The receptacle may be a bag or bin liner.




Preferably the apparatus comprises means operable to detect the weight of material received at a location and to cause the collection means to move when the received weight exceeds a threshold value.




Preferably the compacting means comprises a screw conveyor which has a substantially vertical orientation to drive compacted material up to a position from which the material may fall to the collection means.











BRIEF DESCRIPTION OF THE DRAWINGS




Embodiments of the present invention will now be described in more detail, by way of example only, and with reference to the accompanying drawings, in which:





FIG. 1

shows a longitudinal cross-sectional view of a compactor;





FIG. 1



a


shows an enlarged view of pat of the compactor of

FIG. 1

;





FIG. 2

shows a longitudinal cross-sectional view of the compactor of

FIG. 1

when filled with waste material;





FIG. 3

shows a cross-section of the compactor of

FIG. 1

along line III—III;





FIG. 4

shows a perspective view of the nozzle of

FIG. 1

which has been partially cut away for clarity;





FIG. 5

shows a cross-sectional view of the output end of the compactor of

FIG. 1

, with the screw conveyor packaged for transportation;





FIG. 6

shows a cross-section view of the output end of the compactor of

FIG. 1

, when filled with waste material;





FIG. 7

shows a cross-sectional view of the screw conveyor of the compactor of

FIG. 1

; and





FIG. 8

is a highly schematic perspective view indicating one application of apparatus according to the present invention.











DESCRIPTION OF THE PREFERRED EMBODIMENT AND BEST MODE




As can be seen from

FIGS. 1

to


7


, the waste compaction apparatus


2


has a screw conveyor


4


which conveys as well as compacts material along a passage


6


from an inlet


8


to an exit nozzle


10


.




The passage


6


is generally cylindrical and has a first part


12


of generally uniform cross-section. The first part


12


of the passage has a longitudinally extending opening


14


through which uncompacted waste material is fed from the hopper


16


. The size of the hopper


16


is selected so as to prevent over-filling of the apparatus. In practice, this first part


12


is in the form of a trough having a rounded bottom


18


(see FIG.


3


), the sides of which also define the hopper


16


. The trough opening defines the longitudinally extending opening


14


.




The passage


6


also has a second part


20


which is tapered in the direction towards the exit nozzle. This second part


20


thus has a generally frusto-conical shape.




The inner walls of the passage


6


, both in the first part


12


and the second part


20


are provided with longitudinally extending ribs


22


which project inwardly into the passage. These ribs


22


prevent partially compacted material from rotating with the screw conveyor


4


.




The inner walls of the first part


12


of the passage are provided with two projections


230


(see

FIG. 3

) which extend along its length. These two projections


230


are arranged to contact the outer periphery of the screw conveyor to cut up elongate waste material such as plastics bin liners and the like. This prevents such material from wrapping itself around the screw conveyor and causing it to jam. The projections


230


are provided with a cutting edge for this purpose. The outer periphery of the screw conveyor may also be provided with a sharpened edge to cut up the material. Where appropriate the ribs


22


are also able to provide a cutting surface or anvil against which the flight


24


of the screw conveyor


4


can act to break the waste material down into smaller pieces which are more easily compacted.




The screw conveyor


4


, which is illustrated in detail in

FIG. 7

has a first part


26


where the flight is of uniform diameter. The length of this first part


26


corresponds substantially to the length of the first part


12


of the passage


6


. The flight diameter of the second part


28


of the conveyor


4


decreases in a manner which corresponds generally to the degree of taper of part


20


of the passage


6


. The diameter of the flight


24


of the screw conveyor is selected such that there is usually a few millimeters clearance between the screw conveyor


4


and the projecting ribs


22


. Typically this clearance is in the range of 2 to 3 mm.




The screw conveyor


4


has a third part


30


in the form of a shank with no flight which extends into the nozzle


10


. When the apparatus


2


is in use, the annulus of moving compacted waste material


65


in the compaction chamber


200


of the nozzle


10


acts as a bearing and supports the third part


20


i.e. the threadless axial shank of the screw conveyor


4


. It has been found that the screw conveyor


4


is centered as well as supported by the waste material in the compaction chamber


200


so that the flight


24


no longer contacts the bottom


63


of the passage


6


.




The pitch of the screw conveyor


4


also varies along its length. In particular the pitch of flight


24


decreases in the direction towards the second tapered part


28


. The decrease in pitch of the screw conveyor


4


as well as the tapered of passage


6


enhances the degree of compaction achieved by the waste compaction apparatus


2


. The pitch of the screw conveyor is of course selected depending on the material usually to be compacted as well as the degree of compaction required.




The thickness of the flight


24


changes along the length of the screw conveyor


4


and, in particular increases as the pitch decreases. Thus, the part of the flight which is subjected to the greatest force as a result of the tapering passage and reduced pitch, has the greatest thickness to withstand that increased force and the resulting increase in wear. The life of the screw conveyor


4


is thus increased. Likewise, those parts of the conveyor which are subjected to least force have the smallest flight thickness. This results in a useful reduction in the weight of screw conveyor especially since the part


34


of the flight


24


having the least thickness has the largest diameter. In practice, the thickness preferably begins to increase slightly upstream of the tapering part


28


, although this is not appreciable from the drawings. The dimensions for pitch, flight thickness and flight diameter can all be varied in accordance with the application and size of the apparatus.




The screw conveyor


4


is made from any suitable material which has the desired strength, rigidity and resistance to wear for the particular application in question. For example the screw conveyor


4


may be of mild steel.




In accordance with the invention, the screw conveyor


4


is mounted to allow some degree of axial movement relative to the rest of the apparatus, while rotating. More specifically, the conveyor


4


is slidably mounted on a shaft


300


, either by splines


301


as shown or by the shaft


300


having a non-circular cross-section, or similar. The shaft


300


extends out from the upstream end of the conveyor


4


, by means of an extension


60


, to a gearbox/bearing


69


through which the conveyor is driven by a drive motor


66


. The shaft


300


therefore drives the conveyor


4


to rotate, while being able to move axially.




The screw conveyor


4


has a collar


225


against which a resilient bias means


302


acts. The bias means


302


is shown schematically as a compression spring acting between the collar


225


and the housing of the bearing


69


but it will be appreciated that many alternatives are possible, including compression or extension springs, hydraulic or other pressure arrangements to push on the screw conveyor


4


, and others. Alternatively, the conveyor


4


could be fixed to the shaft


300


, with the entire shaft and conveyor being movable axially relative to the hopper


16


.




The spring


302


acts to push the conveyor


4


forwards, i.e. toward the nozzle


10


. This causes the tapering part


36


,


38


to come into closest adjacency with the tapering second part


20


of the passage but if the conveyor


4


moves axially away from the nozzle


10


, the separation between the flight


24


and the second part


20


would increase by virtue of the tapers of both. This allows blockages to be simply removed or avoided, in a manner which will be described in more detail below. It can be seen from the drawings that in this example, both tapers are substantially to the same degree but could be different.




It will be apparent to the skilled man that as the conveyor


4


slides along the shaft


300


, some provision may be required to prevent waste material being compacted into gaps formed as the conveyor moves, which might prevent the conveyor moving back again. Appropriate sheaths or gaskets could be used, or the various components could comprise telescoping shields which ride over each other and deflect waste material away from the central axis, to prevent fouling.





FIGS. 1 and 2

also show an adjustable cutting plate


220


having a cutting edge adjacent the screw at the beginning of its tapering portion. A cooperating cutting edge is formed along the outer edge of the conveyor flight in the tapering part


36


,


38


of the conveyor, as indicated at


304


, which shows a serrated edge extending around substantially one complete turn of the screw. The blades


220


,


304


cooperate together to cut up long items such as wooden poles and the like as they pass through the apparatus and also to serrate large, bulky or incompressible items, to help prevent blockages. The provision of the edge


304


along a significant length of the screw


4


ensures that the blades


220


,


304


can cooperate over substantially the whole range of axial positions likely to be occupied by the screw conveyor


4


during use. However, it will be apparent that by virtue of the taper on the conveyor


4


, the separation of the blades


220


,


304


will vary as the conveyor


4


moves backward and forward along the shaft


300


.




The nozzle


10


will now be described in more detail with particular reference to

FIGS. 4

,


5


and


6


. The nozzle


10


is coupled to the outlet end of passage


6


at the end of section


20


and is surrounded by chamber


41


which allows any material leaking from the nozzle


10


to be collected in the chamber


41


. The nozzle is made up of two main parts


42


and


44


. The first part


42


is formed from a sheet of material such as a sheet steel with a thickness of 2 to 3 mm which has been rolled up to form a cylinder and welded to maintain that shape. The base portion


46


of the first part


42


, which is connected to the passageway


6


, is circular, of substantially constant cross-section and of unbroken sheet material. This defines a compaction chamber


200


in which further substantial compaction of the waste material takes place upstream of the tapering portion of the nozzle. From this base portion


46


a plurality of e.g. twelve fingers


48


extend, the axis of each finger initially being generally parallel to the longitudinal axis


50


of the nozzle


10


. The width of each finger


48


decreases in the direction towards the outlet


52


of the nozzle


10


to thereby define V-shaped gaps (not shown) between adjacent fingers


48


.




The second part


44


is constructed in a similar manner to the first part


42


, the two parts differing only in dimensions. In particular the second part


44


is slightly longer than the first part


42


and has a slightly larger diameter. The first part


42


is arranged inside the second with the base portions


46


of the first and second parts


44


and


44


being welded together. The two parts


42


and


44


are arranged so that the fingers


48


of tone part overlap the gaps between the fingers of the other part i.e. each finger of one part overlaps two fingers of the other part.




On the outer surface of the ends


54


of each of the fingers


48


of the second outer part


44


, a lug


56


is provided. These lugs


56


extend in a generally outward direction. An inflatable member


306


of rubber, rubberised or other inflatable material surrounds the outer part


44


over at least part of the length of the fingers. The lugs


56


help retain the inflatable “spring”


306


in position around the nozzle. The inflatable spring


306


fills a gap between the fingers and the walls of the chamber


41


, and provides resilient bias to the fingers of the first and second parts, to bias them to their smallest position (i.e. the position in which they define the smallest nozzle aperture). However, as the pressure and/or volume of waste material passing through the nozzle


10


increases, the cross-sectional area of the nozzle


10


can increase, for example as shown in

FIG. 6

, against the resilience of the spring


306


. In this instance, the inward force exerted by the spring


306


(reacting on the walls


41


) is exceeded by the outward force exerted by the fingers


48


as a result of the waste material, and a new equilibrium position is therefore established. Thus, the tapering portion of the nozzle


10


regulates its size in response to variations in the pressure and volume of material passing through the nozzle and other operating conditions, and an appropriate back pressure can be provided for satisfactory compaction over a range of operating conditions. The equilibrium position which is occupied will be determined in part by the resilience of the spring


306


, which in turn is set by the degree of inflation. As the spring


306


is further inflated, it becomes harder and therefore more strongly resilient, tending to hold the nozzle more tightly with the fingers closer together. As the degree of inflation is reduced, the fingers are held more softly and the nozzle will tend to be wider for a given set of operating conditions.




The general operation of the apparatus will now be described with particular reference to

FIGS. 2

to


6


. First, material is inserted into the hopper


16


. The operator then starts the motor


66


to rotate the screw conveyor


4


. Initial compaction takes place in the tapering portion of the screw, as described above. More substantial compaction will then take place in the compaction chamber


200


, downstream of the end of the screw conveyor flight, between the flight and nozzle


10


. This is due to the back pressure established by the nozzle


10


, under the variable influence of the inflatable spring


306


. The action of the screw is to force material from a lower pressure upstream region under the hopper, to a higher pressure region in the chamber


200


. It does this by sweeping out a void space trailing a blunt free end of the screw, which space is then filled by new material moving from the hopper to fill the void. Material in the high pressure region eventually collapses (is compacted) to become stable.




In the event that the compaction process becomes blocked for any reason, such as an incompressible or oversized object, the torque required to continue turning the conveyor will increase and the thrust required to maintain the conveyor at a particular axial position will also increase. However, the sliding mounting arrangement of the conveyor


4


allows the conveyor


4


to move back from the nozzle when the back thrust is sufficient to exceed the bias provided by the spring


302


. As that happens, the gap between the conveyor and the tapering section


20


increases, as has bene described. Eventually, a new equilibrium position will be reached, in balance between the spring thrust and the back thrust. This may be sufficient to allow the cause of the blockage to pass through to the final compaction chamber


200


, thereby clearing the blockage. Similarly, if the blades


220


,


304


are cutting or chopping material while the conveyor is in the forward position, but an oversize element cannot fit between the cutting blades, the conveyor can be forced back against the spring


302


until either the article is accommodated between the blades, so clearing the blockage, or the cutting force between the blades increases (by virtue of the spring bias) to a degree at which the article is finally cut.




This ability of the conveyor to be interactive to react to blockages and move to help clear them results in a compaction apparatus which can work more reliably with a wide range of materials and in a wide range of operating conditions, without requiring other, more complex arrangements for clearing blockages. The apparatus operates in a different manner to the earlier apparatus described in the above-mentioned PCT application, in that the present apparatus will reset itself to allow blocking material to pass through (at least on some occasions), rather than withdrawing the blocking material and repeatedly presenting it until it is compacted or chopped in the intended fashion.





FIG. 8

shows an application for a compactor of the type described, particularly a small version having a hopper volume of approximately 0.1 and 0.4 mm


3


. In

FIG. 8

, a compactor


500


generally as described above is arranged within an aesthetically pleasing housing


502


and with the axis inclined upwardly, perhaps even vertical. A door


504


may swing down to allow material to be introduced into the hopper through an opening


506


. The compactor then forces this material up, compacting it as it does so, into a pipe


508


which connects the compactor


500


to a collection arrangement at


510


.




The collection arrangement, which may be housed in a second aesthetic housing (not shown) which matches the housing


502


, incorporates a carousel having three collection locations


512


in the example shown. These locations


512


are equally spaced around a vertical central axis


514


and each consists of a basket which can hold a refuse bag or sack. Each basket


516


is supported on the axis


514


by an arm


520


. A sensor


522


associated with each arm


520


monitors the weight of the basket


516


and its contents. When the weight exceeds a threshold, an instruction is sent to a drive arrangements


524


to rotate the axis


514


to bring a second, empty basket


516


to the collection position underneath the outlet of the pipe


508


. Having moved away from the collection position, the full basket can then be emptied while the fresh, empty basket is still receiving material through the pipe


508


. It may be desirable to allow all except one of the baskets to be accessed for emptying, or to provide a single emptying location from which baskets may be emptied as they move to that location.




It is preferred that the compactor operates vertically or in an inclined direction as described, to minimise the floor space occupied by the apparatus. Furthermore, the collection arrangement


510


allows material to be automatically packaged into a conveniently handleable form, for instance for manual handling. The sensor arrangement ensures that safety requirements are not exceeded, by preventing baskets from becoming too heavy.




It will be apparent that very many variations and modifications from the apparatus described above can be made without departing from the scope of the present invention. In particular, the form and geometry of the hopper, conveyor and compacting chambers described can be widely varied, as can be the manner of mounting the conveyor for axial movement. Many alternative designs of carousel could be designed for the apparatus of FIG.


8


and the compactor may require some variation from the designs shown in other figures in order to operate with a vertical rotation axis.




Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.



Claims
  • 1. Compacting apparatus comprising a screw conveyor for conveying waste material through a passage and compacting it therein, an exit nozzle communicating with the passage, the nozzle defining an internal transverse cross-sectional area which enlarges and reduces and which comprises at least one selectively variable and adjustable resilient member which sets the nozzle to be biased towards and maintains a specifically desired cross-sectional area within its range of enlargement or reduction to achieve compaction substantially independent of increasing and decreasing waste material pressure.
  • 2. Apparatus according to claim 1, in which the or at least one resilient member comprises an inflatable portion which provides an adjustable degree of resilience dependent upon the degree of inflation of the resilient portion.
  • 3. Apparatus according to claim 1, in which the nozzle has a plurality of wall portions which are movable relative to each other to vary the cross-sectional area of the nozzle, the resilient member cooperating with the wall portions to bias the nozzle toward a position of minimum cross-sectional area.
  • 4. Apparatus according to claim 1, in which the nozzle comprises a number of spaced apart, longitudinally extending fingers.
  • 5. Apparatus according to claim 4, in which there are no gaps between the fingers.
  • 6. Apparatus according to claim 1, in which the nozzle tapers towards its outlet when the nozzle cross-sectional area is at its minimum.
  • 7. Apparatus according to claim 1, in which the nozzle comprises two members each of which has a number of spaced apart, longitudinally extending fingers, one member being arranged inside the other.
  • 8. Apparatus according to claim 7, in which the resilient member is located to surround an outer of the two members to provide resilient bias thereto.
  • 9. Apparatus according to claim 7, in which the two members are arranged such that a finger of one member overlaps two fingers of the other member whereby there are substantially no gaps between the fingers.
  • 10. Apparatus according to claim 1 and further comprising collection means, to which compaction material is delivered, in use, the collection means providing a plurality of locations at which compacted material may be received, and being movable to allow one location to move to an emptying position while another is moving to a position for receiving material from the compacting means.
  • 11. Apparatus according to claim 10, in which the collecting means comprises a rotatable carousel.
  • 12. Apparatus according to claim 10, in which each location is adapted to removably receive a receptacle which can be removed when full for replacement by an empty receptacle.
  • 13. Apparatus according to claim 12, in which the receptacle is a bag or bin liner.
  • 14. Apparatus according to claim 10, in which the apparatus comprises means operable to detect the weight of material received at a location and to cause the collection means to move when the received weight exceeds a threshold value.
  • 15. Apparatus according to claim 10, in which the screw conveyor has a substantially vertical orientation to drive compacted material up to a position from which the material may fall to the collection means.
Priority Claims (1)
Number Date Country Kind
9618465 Sep 1996 GB
Parent Case Info

This application is a division of patent application Ser. No. 09/254,331, which issued as U.S. Pat. No. 6,247,662 B1 on May 3, 1999. This application claims the priority date of Sep. 5, 1996 for Great Britain Patent Application No. 9618465.0.

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