Mixer silo for wooden chips

Abstract

 A mixer silo for wooden chips, characterised by consisting of at least one container (1) of substantially parallelepiped form provided with:
- members (18, 13) for receiving the chips from a chipping machine and members (19) for distributing them over the entire inner surface of said container (1),
- a mobile base (4),
- a wall (17) arranged transversely to the direction of movement of said base (4) and comprising a plurality of members (20) for loosening the chipped material conveyed by said base, and
- a conveyor member (22) disposed downstream of said wall (17) to convey said chipped material towards the size reduction line.

Description

[0001] This invention relates to a mixer silo for wooden chips.

[0002] The woodworking industry is familiar with chipboard and the more recent MDF (medium density fibreboard) panels, produced by pressing mixtures of wooden chips and glue (in the case of chipboard) and wood fibre and glue (in the case of MDF panels).

[0003] Wooden chips and fibres generally derive from the machining of wood of various types, the quality of the produced panel being higher the greater the care taken in mixing the chips of these various types. In this respect, the various wood types have very different characteristics in terms of mechanical strength, colour, bahaviour under temperature etc., and only by mixing the chips together it is possible to prevent non-uniform colour, non-uniform mechanical strength and deformation of the panel during its use after the glue has dried, these drawbacks being those which have to be given the greatest consideration in using such panels in industry for the production of furniture.

[0004] The mixing of the different types of chips is therefore a very important problem, involving very large quantities of such material, in that a chipboard manufacturing plant can easily have a capacity of 500 m³ per day, this capacity requiring a chip availability of more than 300 t per day.

[0005] These very large chip quantities, which for obvious working requirements are produced by machining successive batches of material of different types, are currently mixed by forming large heaps of the different chip types in the open air and then approximately mixing them by withdrawing them from the different heaps with a mechanical shovel and dropping them into an appropriate collection hole, from which they are then withdrawn for feeding to the panel production plant.

[0006] This known mixing system has however numerous drawbacks, and in particular:
- it is very approximate in that it is left to the judgement of the operator, and does not allow effective mixing of the various types of chips;
- it is irregular and non-homogeneous;
- it requires considerable labour in terms both of personnel for feeding the various chips into the collection hole, and of personnel for withdrawing the chips from the hole and conveying them to the size reduction line;
- it requires considerable available surface areas, which are very difficult to cover and involve the risk of pollution, especially if situated in windy zones.

[0007] An object of the invention is to provide a silo able to automatically and continuously mix the various types of chips.

[0008] A further object of the invention is to provide a silo in which the mixing can be implemented automatically without the use of labour.

[0009] A further object of the invention is to provide a silo in which large quantities of chips can be processed in a closed space of small size without the risk of environmetal pollution.

[0010] All these and further objects which will be more apparent from the description given hereinafter are attained according to the invention by a mixer silo for wooden chips, as described in claim 1.

[0011] A preferred embodiment of the present invention is described in detail hereinafter with reference to the accompanying drawings in which:

Figure 1 is a partial longitudinal section through a double mixer silo according to the invention;

Figure 2 is a plan view thereof; and

Figure 3 is a vertical cross-section therethrough on the line III-III od Figure 2.

[0012] As can be seen from the figures the silo according to the invention comprises two containers 1 of substantially parallellepiped form, with their side walls 2 aligned and of masonry construction, as is the outer end wall 3.

[0013] The base 4 of each container consists substantially of a plurality of metal longitudinal members 5 of perfectly smooth surface. They rest on an underlying concrete bed 6, from which they are separated by a layer 7 of antifriction material.

[0014] As the reason for providing two containers 1 is essentially to double the capacity and operating potential of the silo, for which they are substantially identical, the present description will relate to only one of these, it being understood that it is also valid for the other.

[0015] Extending between the upper edges of the two side walls 2 of the container 1 there are provided a plurality of metal beams 8 on which there rest two longitudinal rails 9 which extend along the entire length of the two aligned containers 1, their purpose being to support and guide a feed-in device indicated overall by 10.

[0016] The feed-in device 10 comprises essentially a metal framework 11 mounted on wheels 12, which run on the longitudinal rails 9 and are in part idle and in part motorized. There is also provided on the framework 11 a conveyor belt 13 which extends between deviation rollers 14 and is supported on support rollers 15. An electric motor 16 rotates one of the two deviation rollers 14, to thus drive the conveyor belt 13 in one or other direction according to the command received.

[0017] The length of the conveyor belt 13 is slightly greater than the length of each container 1 so that even when in the two end positions, a part of it lies in the central region of the silo, ie between the two inner end walls 17, in a position below a fixed central feed hopper (not shown on the drawings) for the chips.

[0018] Two transverse screw conveyors 19 comprising two opposite-handed portions are also mounted on the framework 11, one at each end of the conveyor belt 13, to extend substantially from one side wall 2 to the other of the containers 1.

[0019] The inner end wall 17 of the container 1, ie the wall close to the corresponding wall of the adjacent container, is slightly inclined with its top closer to the opposite wall 3, and comprises a plurality of impellers 20 of horizontal axis, rotated by electric motors 18.

[0020] Each impeller 20 consists of a tubular body from which a plurality of arms extend radially, to exert a loosening action on the facing load of chips, as described hereinafter.

[0021] Outside the end wall 17 at a level below the base 4 of the container 1 there are provided in a suitable transverse channel 21 two transverse screw conveyors 22 for conveying the chip material to the subsequent processing station.

[0022] As stated, the base 4 of the container 1 is formed from a plurality of metal longitudinal members 5. These extend from the inner end wall 17, from a position below the lower impeller 20, to beyond the outer end wall 3, which for this purpose has a lower transverse aperture to allow passage of said longitudinal members 4.

[0023] The outer end of each longitudinal member is connected to the rod of a hydraulic cylinder-piston unit 23 fixed to the bed 6 of the container 1. The various cylinder-piston units 23 are connected to a distributor (not shown on the drawings) which feeds them simultaneously or individually on the basis of the silo operating cycle.

[0024] The side walls of the container 1 slightly converge from the outer end wall 3 to the inner end wall 17, and also slightly diverge in a downward direction in their lower part.

[0025] The operation of the silo according to the invention is as follows:
using conventional means, the various types of chip material are fed via the upper fixed loading hopper onto the conveyor belt 13, which is driven so that its upper portion moves in the direction of the container 1 to be loaded. The material therefore advances with the conveyor belt 13 and on reaching the end transverse screw conveyor 19 is distributed along the entire width of the container 1 and made to fall into it. At the same time, the framework 11 is driven along the longitudinal rails 9 so that the chips fall over the entire surface of the container 1 for their homogeneous distribution.

[0026] When one batch of chips has been loaded, the next batch is loaded and so on, so that the final result is a container 1 filled with very thin layers of different types.

[0027] To extract the chips, which because of their nature and weight are of considerable overall compactness, the impellers 20 are operated, as at the same time are the hydraulic cylinder-piston units 23, according to a predetermined sequence. This sequence provides for them to be fed simultaneously during elongation so as to uniformly advance the base 4 of the container 1, and the chip material carried on it, towards the wall 17. Here, the rotating impellers 20 exert a loosening effect on said material, operating at different heights and therefore with uniform distribution of the withdrawn material. This material is made to fall onto the transverse screw conveyors 22, from which it is transferred to subsequent operations.

[0028] When the cylinder-piston units 23 have reached the end of their elongation stroke, an automatic command provided by their distributor causes them to move in the opposite direction.

[0029] However, not all the cylinder-piston units are operated in this manner at the same time, as they were during the outward stroke, but instead only one longitudinal member 5 is made to move at a time so that as it slides backwards the chip material, which as stated forms a compact mass resting on all the longitudinal members, is not also dragged backwards. When all the longitudinal members have returned one by one to their rear limiting position, a command is given to cause them to simultaneously move forwards to repeat the operating cycle.

[0030] During this chip withdrawal stage, other chip material can be loaded into the container 1 or, if the operating conditions require it, into the other container so that the two containers undergo loading and withdrawal alternately.

[0031] From the aforegoing it is apparent that the silo according to the invention in either its single or double container version has numerous advantages over the conventional art, and in particular:
- it allows continuous mixing of chips of different types,
- it enables this mixing to be effected automatically without any use of labour,
- it enables large quantities of chips to be treated in a closed space of small size,
- there is no risk of polluting the environment.

Claims

1. A mixer silo for wooden chips, characterised by consisting of at least one container (1) of substantially parallelepiped form provided with:
- members (18, 13) for receiving the chips from a chipping machine and members (19) for distributing them over the entire inner surface of said container (1),
- a mobile base (4),
- a wall (17) arranged transversely to the direction of movement of said base (4) and comprising a plurality of members (20) for loosening the chipped material conveyed by said base, and
- a conveyor member (22) disposed downstream of said wall (17) to convey said chipped material towards the size reduction line.

2. A mixer silo as claimed in claim 1, characterised in that the container (1) comprises two vertical side walls (2) and one vertical end wall (3) all of masonry construction.

3. A mixer silo as claimed in claim 2, characterised by being provided upperly with at least one longitudinal guide (9) for a metal framework (11) for supporting and guiding a longitudinal (17) and transverse (19) conveying member for the entering chips.

4. A mixer silo as claimed in claim 3, characterised in that the metal framework (11) supports a conveyor belt (13) extending betweeen motorized rollers (14), and a transverse screw conveyor (19) disposed in a position corresponding with the exit end of said conveyor belt (13), the length of which is such that as its position along the framework (11) varies, a part of it is always below a fixed loading hopper, the end provided with the transverse screw conveyor (19) moving from one end wall (3) to the other (17).

5. A mixer silo as claimed in claim 1, characterised in that the mobile base (4) of the container (1) consists of a plurality of side-by-side longitudinal members (5) each driven in an axial direction by an activator (23).

6. A mixer silo as claimed in claim 5, characterised in that the activators (23) are located externally to the container (1), the longitudinal members (5) passing below an end wall (3) thereof.

7. A mixer silo as claimed in claim 5, charcaterised in that the longitudinal members (5) rest on an underlying bed (6) via a layer of antifriction material (7).

8. A mixer silo as claimed in claim 5, characterised in that the longitudinal members (5) have a smooth upper surface.

9. A mixer silo as claimed in claim 1, characterised in that the wall (17) is inclined, with downward divergence.

10. A mixer silo as claimed in claim 1, characterised in that the wall (17) comprises a plurality of impellers (20) of horizontal axis acting at different heights on the chips contained within the container (1).

11. A mixer silo as claimed in claim 10, characterised in that each impeller (20) comprises a tubular body and a plurality of loosening arms branching radially from said tubular body.

12. A mixer silo as claimed in claim 1, characterised in that the conveyor member (22) consists of at least one screw conveyor arranged transversely to the direction of movement of the base (4) of the container (1) and housed in a corresponding channel (21) provided at a lower level than said base.

13. A mixer silo as claimed in claim 1, characterised in that the side walls (2) of the container (1) converge towards the wall (17) provided with loosening members (20).

14. A mixer silo as claimed in claim 1, characterised in that the side walls (2) diverge downwards, at least in their lower part.

Drawing