Bag splitter and wet separator

A bag splitting apparatus for use in splitting open bags containing solid waste having a rotatable flail structure with a plurality of flexible flails attached to a rotatable mounting, the flails being formed from a material having a Young's modulus of less than 50 GN/m 2 ; and a waste feed guide structure capable of receiving bagged solid waste and directing it towards the rotatable flail structure when the apparatus is in use.

The embodiment of the bag splitter apparatus as shown in FIG. 1 comprises a rotatable flail structure 1 having a plurality of flails 2 attached to a rotatable mounting 3 which in this embodiment is a rotor arm driven by a flail drive motor 4 and drive belt 5 . The flails are spaced apart along the length of the rotor arm, as illustrated in FIG. 3 . The flails are formed of a strong yet highly flexible material, as described above. When the device is in use the rotor arm rotates at a speed of at least 150 rpm. This high speed of rotation results in a high peripheral speed of the flails and this, combined with the flexible nature of the material from which the flails are formed, generates a ‘soft’ cutting edge which is able to tear open plastic refuse bags and the like whilst minimising the risk of damage to the contents of the bags. The bag splitting apparatus further includes a waste feed structure for receiving bagged solid waste. In the embodiment shown in FIG. 1 the waste feed structure is a feed chute comprising a top chute portion 11 and a bottom chute portion 12 . The top chute portion has fixed sides 10 and an adjustable back plate 13 which is joined to the bottom chute portion 12 via a hinged joint 14 . The hinged joint 14 permits independent movement of the entire bottom chute portion 12 relative to the top chute portion 11 and the back plate 13 of the top chute portion relative to the bottom chute portion 12 . In FIG. 1 the adjustable back plate of the top chute portion 13 is also shown in an extended position 13 ′. A balance weight 15 is affixed to the bottom portion 11 of the feed chute and functions to retain the bottom portion of the chute at a pre-determined angle to the vertical. In the embodiment illustrated in FIG. 1 the balance weight 15 maintains the bottom portion 12 at an angle of approximately 45° to the vertical. This is merely illustrative and not intended to be limiting to the invention. The angle of the bottom chute portion to the vertical may be adjusted to control the speed at which bagged solid waste passes through the apparatus. FIG. 1 also illustrates the bottom portion of the feed chute in a deflected position ( 12 ′, 15 ′) in which it is deflected away from the rotating fail structure 1 . In FIG. 1 the bottom chute portion is shown in a deflected position at 60° to the vertical but this is intended to be merely illustrative rather than limiting to the invention. The application of pressure against the balance weight results in controlled deflection of the bottom chute portion, with the angle of deflection being directly proportional to the amount of pressure applied. The ability of the bottom chute portion to move away from the rotatable flail structure for example when a larger bulky item is encountered prevents jamming of the apparatus. The rotatable flail structure may optionally be protected by a weighted flap 16 which is positioned to direct heavy items away from the flails thus preventing damage to the bag splitter. The rotatable flail structure and the waste feed chute are both attached to a supporting framework, as shown in FIG. 1 . The rotatable flail structure is covered by a removable outer cover 6 . FIG. 2 schematically illustrates the bag splitting apparatus in use in combination with a wet separator apparatus according to the invention 20 . In the embodiment shown in FIG. 2 , bagged solid waste is delivered to the feed chute of the bag splitting apparatus via a feed conveyor 40 . The wet separator apparatus 20 comprises a large separator tank 21 filled with liquid, usually water. Antimicrobial agents may be added to the liquid in order to prevent growth of bacteria. A horizontal flow of liquid within the tank is created in the direction indicated, i.e. away from the site of addition of waste to the tank. In order to create a horizontal cross-flow the separator comprises liquid inlets 22 positioned at the end of the tank at which the waste to be separated is added. At the other end of the tank, liquid flows out of outlets 25 in the side of the tank into an outlet box 26 . Overflow from the tank 21 which occurs at the surface level of the liquid in the tank also discharges into the outlet box 26 . Liquid from the outlet box 26 drains into pump box 27 and a constant return flow from the outlet box to the inlets is maintained by the action of a pump 28 . The pump box is fitted with a ball valve controlling a liquid in-feed 31 to maintain a constant level of liquid within the pump box. The outflow from the outlet box to the pump box 32 may be fitted with a screen for the removal of fine material which may otherwise cause the pump to become blocked. In an alternative arrangement, the overflow from the outlet box 26 may discharge directly into the pump for re-circulation. In this arrangment the ball valve is fitted to the outlet box. Waste material leaving the bag splitting apparatus falls into the separation tank. The heavy waste fraction above a certain density drops down towards the bottom of the tank immediately below the bag splitter and is collected on the heavy waste conveyor 23 and conveyed out of the tank. Light material above a certain density is carried laterally by the horizontal flow within the tank and is collected on a light waste conveyor 24 and conveyed out of the tank. An adjustable baffle plate 33 is provided between the heavy waste conveyor 23 and the light waste conveyor and functions to further separate the ‘heavies’ and ‘lights’ sections of the separator. The depth of separator tank is determined by the time required to achieve effective separation of the light and heavy materials, with due consideration to the input velocity of the waste, the velocity of the cross-flow within the tank and the height of the baffle plate 33 . In a typical embodiment the depth of the separation tank will be ˜7 ft. FIG. 3 schematically illustrates a cross-section of the apparatus of FIG. 2 through the bag splitting apparatus. The heavy waste conveyor 23 is clearly shown as positioned directly beneath the rotatable flail structure when the bag splitting apparatus and wet separator are used in combination. The use of separate heavy and light conveyors provides a simple and effective means for separately removing the heavy and light waste fractions from the separation tank. It also has the advantage that the two waste fractions are removed from the separation tank substantially intact. This may be important for the further processing of the waste fractions. In the arrangement illustrated in FIGS. 2 and 3 the rotatable flail structure of the bag splitting apparatus is shown positioned close to the surface of the liquid within the separator tank. This is to ensure that any bags which are not fully split as they pass through the bag splitter but which remain floating on the surface of the separator tank remain in contact with the flails to provide an additional opportunity for effective splitting of the bags. This arrangement is very effective at splitting ‘bags-within-bags’ which are commonly encountered in household waste.