Description

The present invention relates to a device for comminuting material of organic product flows such as waste, comprising a frame, a cylindrical drum of which at least a part of the surface is embodied with screen openings, a shaft member with a number of striking members extending radially relative to the shaft member, wherein the shaft member with associated striking members extends concentrically at least partially within the cylindrical drum, drive means for rotatable driving of the shaft member about the central axis of the shaft member, wherein a feed opening is provided at one outer end of the drum for feeding material for comminuting to the striking members, and further drive means for rotatable driving of the cylindrical drum about the central axis of the cylindrical drum.

Such a device is specified in the American publication US 4076177 and is also referred to by the term "hammer mill". Product flows, such as waste flows in particular, are processed using hammer mills, wherein an organic fraction is separated from a solid fraction. This may be packaging material which is broken up in the hammer mill using the striking members embodied as hammers, so that the organic content can escape. To the extent this is wholly or partially liquid material or material with dimensions which are so small (or have become so because of the comminuting action of the hammers) that it can pass through the screen openings, this material leaves the drum via the screen openings largely due to the influence of gravitational force and the rotation of the striking members. Outside the drum this fraction is collected and discharged for further processing, for instance for the purpose of producing biogas, animal feed or fertilizers. In addition to separating materials, a device according to the preamble can also be embodied to comminute materials. In such devices all the material fed to the drum via the feed opening will in principle leave the drum via the screen openings thereof.

The present invention has for its object to provide a device according to the preamble which can be utilized with increased efficiency for processing packaged food products, but without precluding processing of other types of material or product. The processing of packaged food products may for instance be required in the case of waste from supermarkets, such as products left over because they have not been sold within their sell-by date, residual products or rejected products from production processes. The device according to the preamble is characterized for this purpose in that the screen openings differ from each other in respect of their size, shape and/or mutual spacing. In a device according to the invention the possibility of rotating the cylindrical drum about the central axis thereof provides the advantage that a larger filtering surface area can be effectively created. Positive use can be made hereof during operation of the device according to the invention with a stationary cylindrical drum, wherein by prearranging the cylindrical drum in a desired rotational position screen openings with characteristics desirable for a determined batch of material can be placed on the underside of the drum. This has a positive effect on the change-over time, and the device according to the invention can be utilized more efficiently. On the other hand, the device according to the invention also provides the possibility of operating the device with a rotating drum, whereby separation of material can also take place with increased efficiency. This is because rotation of the cylindrical drum is found to limit the chance of the occurrence of (semi-permanent) clogging of the screen openings since the material which may block the screen openings runs out of the screen openings under the influence of the gravitational force. The use of screen openings differing from each other in respect of their size, shape and/or mutual spacing provides the option of adapting the size, shape and/or mutual spacing of the screen openings to the characteristics of the material. These characteristics do after all change during displacement of the material inside the cylindrical drum because of the action of the device.

An easy way to embody a cylindrical drum with screen openings at desired positions and with desired dimensions/shapes is obtained when the cylindrical drum comprises a cylindrical framework with framework openings, wherein exchangeable, preferably curved closing bodies are provided in at least some of the framework openings which close the associated framework openings to at least significant extent, and wherein at least some of the closing bodies are screen bodies comprising screen openings. By exchanging screen bodies for screen bodies with different characteristics, more specifically screen openings with a determined size, shape and/or mutual spacing, the screening characteristics of the cylindrical drum as a whole can in principle be easily optimized for a specific waste flow for processing.

A number of framework openings are preferably provided adjacently of each other in axial direction so that, if desired, the screening characteristics can be modified in the direction of transport of waste inside the cylindrical drum. It will be apparent that waste situated on the upstream side of the cylindrical drum will still be of coarser structure than waste situated on the downstream side of the drum. This imposes differing requirements for the screening characteristics.

According to a further preferred embodiment, a number of framework openings are provided adjacently of each other in peripheral direction. This achieves first of all that exchange of closing bodies, such as screen bodies in particular, can take place in simple manner, while furthermore it is thus easily possible, as seen in peripheral direction, to apply screen bodies with differing screening characteristics, which may be particularly useful when the device according to the invention is applied for the processing of different batches of waste imposing different requirements in terms of desired screening characteristics.

In the above stated context it is recommended that the screen openings of closing bodies which close framework openings provided adjacently of each other differ from each other in respect of their size, shape and/or mutual spacing.

In order to enable effective comminution of waste it is advantageous when at least some of the closing bodies are provided on the inner side with at least one breaking body for co-action with rotating striking bodies. The co-action between the at least one breaking body and the rotating striking bodies could be characterized as a cutting co-action, whereby the waste can be comminuted rapidly particularly on the upstream side of the drum.

The at least one breaking body is preferably strip-like and/or preferably extends spirally. The spiral orientation of the breaking body can enhance displacement of waste in the transport direction inside the drum.

It is further recommended that the breaking bodies are provided at the same axial positions as the axial positions of the striking bodies. The full length of the drum, at least to the extent striking bodies are present inside it, can in principle thus be utilized for the cutting co-action between the striking bodies and associated breaking bodies. The path which the striking bodies follows lies on the inner side of the breaking bodies.

The invention has particular advantages, particularly in the processing of packaged food products, when the size of screen openings at a downstream outer end of the screen drum is greater than the size of screen openings at an upstream outer end of the screen drum. Applying relatively small screen openings at the upstream outer end achieves that food products which have an associated packaging which is immediately opened at the upstream outer end because of the action of the striking members and which leave the packaging via the openings in the packaging , as will particularly be the case with for instance liquid-like food products, can leave the screen drum directly via the screen openings without the risk, or at least with only a very limited risk, of the packaging material also leaving the screen drum via these relatively small screen openings. Separate collection of this screened material prevents this material being mixed with broken up pieces of packaging material. The screened material will not usually require any further treatment, such as a filtering, so as to enable further processing, for instance as raw material for the production of biogas.

More specifically recommended here is that the surface area of individual screen openings at the downstream outer end of the screen drum is at least 12.5 mm ² and more preferably a maximum of 100 mm ² , and still more specifically that the surface area of individual screen openings at the downstream outer end of the screen drum is at least 40 mm ² and more preferably a maximum of 75 mm ² . It is more specifically the case in respect of the dimensions of screen openings at the upstream outer end of screen drum that the surface area of individual screen openings at the upstream outer end of the screen drum is a maximum of 2000 mm ² and is more preferably at least 500 mm ² , and still more specifically that the surface area of individual screen openings at the upstream outer end of the screen drum is a maximum of 1500 mm ² and is more preferably at least 1000 mm ² .

In particular, though not exclusively, in combination with the above specified preferred embodiment, wherein the size of screen openings at a downstream outer end of the screen drum is greater than the size of screen openings at an upstream outer end of the screen drum, it can be advantageous for the device to comprise a first collecting member for collecting a first part of material leaving the screen drum via screen openings at the upstream outer end of the screen drum, and a second collecting member for collecting a second part of material leaving the screen drum via screen openings at the downstream outer end of the screen drum. The present preferred embodiment does not preclude even more than two collecting members being provided distributed over the axial length of the screen drum. Making use of different collecting members enables the screened material to be separated into groups of screened material which must for instance optionally undergo a further treatment such as filtering, or groups which must be further treated in different ways.

A structurally favourable embodiment is obtained when the frame or the cylindrical drum comprises at least one group of a number of guide rollers disposed in a circle, and the other of the frame or the cylindrical drum comprises a circular running surface per group of guide rollers, wherein the guide rollers forming part of a group and the associated running surface co-act in guiding manner during rotation of the cylindrical drum, wherein two groups of a number of guide rollers disposed in a circle are more preferably provided at opposite outer ends of the cylindrical drum.

In order to enable rapid replacement of a cylindrical drum with another cylindrical drum it is extremely favourable for a part of the outermost guide rollers of a group of a number of guide rollers disposed in a circle and of the associated running surface to form part of a bracket for opening, wherein the cylindrical drum can be taken from the frame in radial direction when the bracket is opened.

The device advantageously comprises a hydraulic cylinder for holding the bracket in closed position.

When such a hydraulic cylinder is applied, the device more preferably comprises detecting means for detecting the pressure in the hydraulic cylinder, or at least the pressure in a hydraulic circuit incorporating the hydraulic cylinder, and for generating detection signals. If the pressure changes, this may be an indication that the bearing- mounting applied to enable rotation of the screen drum/or of the shaft member is worn and requires maintenance or replacement. A sudden change in the pressure can indicate a calamity, on the basis of which the device could be fully shut down automatically.

An extremely effective embodiment of the further drive means is obtained when the further drive means comprise a drive motor, a first toothed wheel provided in rigidly concentric manner with the cylindrical drum and a second toothed wheel rotatably drivable by the drive motor, wherein the first toothed wheel and the second toothed wheel are in mutual engagement.

If the device according to the invention is intended for the purpose of separating materials, it is preferably characterized in that a discharge opening is provided at an outer end of the drum lying opposite the feed opening for the purpose of discharging relatively large parts of material, such as packaging material may be, that has been subjected to the action of the rotating striking members and has not left the drum via the screen openings.

The occurrence of (semi-permanent) blockage of the screen openings can be further limited when the device is provided with at least one blow nozzle for blowing a fluid toward the screen openings. If for instance air is blown at the screen openings with the at least one blow nozzle, they are less likely to become clogged or, if they are clogged , they will be opened up again more quickly by the blow nozzles.

The at least one blow nozzle is preferably provided on the outer side of the drum. The at least one blow nozzle is more preferably stationary, or provided rigidly relative to the frame. Because of the rotation of the drum, screen openings will here pass through the operative range of the at least one blow nozzle.

In order to subject all screen openings of the drum to the action of the at least one blow nozzle it is recommended that a number of blow nozzles are provided distributed along the length of the drum.

Displacing means can alternatively also be provided for this purpose for moving the at least one blow nozzle reciprocally in the lengthwise direction of the drum.

The present invention further relates to a method for applying a device according to the invention as specified above. The invention is characterized in the first instance in that the drive means and the further drive means for comminuting material operate simultaneously.

Favourable results, i.e. an effective separation of waste, are obtained particularly when the rotation speed of the cylindrical drum is a maximum of 100 revolutions per minute.

More specifically it will usually be sufficient in practice for the rotation speed of the cylindrical drum to lie between 0.5 and 10 revolutions per minute. The invention further provides an alternative method for applying a device according to the invention as already specified in the foregoing. This alternative method comprises the steps of:

processing a first batch of material using the device with stationary cylindrical drum,

subsequently processing a second batch of material using the device with stationary cylindrical drum,

rotating the cylindrical drum between processing of the first batch and second batch.

As already stated above, the invention is particularly, though not necessarily exclusively, advantageous in the processing of packaged food products. A preferred embodiment of the method according to the invention is therefore characterized in that the device is applied for the purpose of processing packaged food products.

The invention will be elucidated hereinbelow on the basis of the description of a preferred embodiment of the present invention with reference to the following figures:

Figure 1 shows a perspective view of a separating device according to the invention;

Figure 2 shows one of the closing bodies as can be applied in a device according to figure 1 .

Figure 1 shows a hammer mill 1 which can be deemed a possible embodiment of a device according to the invention and which is configured to separate waste. The hammer mill 1 comprises a frame 2 with legs 3 and, on the upper outer ends of legs 3, two parallel longitudinal beams 4 and two parallel cross beams 5. The hammer mill 1 further comprises a cylindrical drum 6, the central axis of which extends horizontally in the longitudinal direction of the frame 2. The hammer mill 1 is further provided with a horizontally oriented shaft body (not shown in the figures), the central axis of which runs parallel to, and in this example coincides with, that of the cylindrical drum 6 and which is mounted at both outer ends for rotation in the bearing housings 7, 8 mounted on the cross beams 5. On the side of the bearing housing 8 the shaft body is coupled via the transmission 9 to the electric motor 10. Another type of drive, such as a hydraulic motor, could alternatively be applied and/or the shaft body could be provided eccentrically inside the drum 6.

The shaft member is provided with a number of strip-like hammer bodies 1 1 which extend radially at least during operation and which extend in the present example at an angle of 90 degrees relative to each other. As alternative to strip-like hammer bodies 1 1 , use could also be made of elongate hammer bodies of another shape, for instance with a square or round cross-section along the length of the hammer body, or of chains such as link chains. Provided in this example at each longitudinal position of the shaft member are four strip-like hammer bodies 1 1 , although this number could also be different, for instance only one, or no hammer body at all could be provided at determined longitudinal positions, this depending on the nature of the waste for processing. The hammer bodies 4 are provided on the shaft member not only inside the cylindrical drum 6 but also on the upstream side thereof where a feed opening 12 is present for supply of waste for separating via this feed opening 12 to the rotating hammer bodies 1 1 . With suitable actuation of the electric motor 10 the hammer bodies 1 1 will rotate about the central axis of the shaft member and break up the waste. The content of packagings forming part of the waste is hereby released. The waste will displace from the feed opening 12 in the direction of the bearing housing 7. This displacement can be enhanced by providing the hammer bodies 1 1 with for instance an inclining flank, by disposing the hammer bodies in spiral manner or by making use of breaking bodies, still to be discussed, inside the cylindrical drum 6. The drum 6 is open at the outer end opposite the feed opening. This open outer end can be deemed a discharge opening for material which moves along the full length inside the cylindrical drum 6 without leaving the drum 6 via the round screen openings of the drum 6 still to be discussed. Upstream of said open outer end this "unscreened" and normally speaking coarse material is collected under cover 29 and discharged therefrom, for instance using a conveyor belt. In the processing of packaged food products this will for the greater part be packaging material.

The cylindrical drum 6 is rotatable or at least pivotable about the central axis of the cylindrical drum 6. On the side of the bearing housing 8 the cylindrical drum 6 is provided for this purpose with a toothed wheel 13 which is concentric with the central axis of the cylindrical drum 6. The toothed wheel 13 is in engagement with the toothed wheel 14 which is mounted rotatably relative to the frame 2 and coupled via the coupling shaft 15 and the transmission 16 to the electric motor 17. Actuation of the electric motor 17 causes the cylindrical drum 6 to rotate about the central axis thereof. For the purpose of this rotation the cylindrical drum 6 is provided at the outer ends thereof with circular running surfaces 18, 1 9. Provided on the periphery of the respective running surfaces 18, 1 9 are groups of three guide rollers 20a, 20b, 20c and 21 a, 21 b, 21 c. The guide rollers 20a-20c and 21 a-21 c are disposed at equal distances from each other in a circular form, or at least fit within a circular form. The two lower guide rollers 20b, 20c and 21 b, 21 c are not visible in the figures. The cylindrical drum 6 rests on these guide rollers 20b, 20c and 21 b, 21 c. The upper guide rollers 20a and 21 a form part of respective brackets 22, 23 which are connected for pivoting about pivot shafts 24, 25 to the frame 3. Opposite the respective pivot shafts 24, 25 the brackets 22, 23 are provided with hydraulic cylinders 26, 27 which hook releasably at an outer end onto the respective brackets 22, 23 and which are connected at an opposite outer end to the frame 3 for pivoting about pivot shafts similar to the pivot shafts 24, 25. The pivot shafts 24, 25 on the one hand and the latter pivot shafts for the hydraulic cylinders 26, 27 on the other are provided diametrically opposite each other in relation to the cylindrical drum 6. Pivoting open the brackets 22, 23 and the hydraulic cylinders 26, 27 following mutual uncoupling creates on the upper side of the cylindrical drum 6 an opening via which the cylindrical drum 6, together with the associated bearing housings 7, 8, can be released from the frame 3.

In the closed situation wherein the hydraulic cylinders 26, 27 hook onto the brackets 22, 23 the hydraulic cylinders 26, 27 are brought under pressure manually. The pressure in the cylinders 26, 27 is measured continuously via pressure gauges which are not further shown. The pressure gauges are coupled to the control of the device 1 . If the pressure gauges detect that the pressure is gradually decreasing, this is then an indication of wear to components of the device 1 , whereby the concentricity of the screen drum 6 and the shaft member on which the hammer bodies 1 1 are mounted can be lost. Maintenance or replacement may then be necessary. A sudden pressure drop can indicate a calamity. The control can then provide for automatic shutdown of the device 1 .

The cylindrical drum 6 comprises a cylindrical framework which is constructed from four annular elements 31 , 32, 33, 34 provided at equal distances from each other, and six axial elements which are likewise provided at equal distances from each other, run parallel to the central axis of the cylindrical drum 6 and connect the annular elements 31 - 34 to each other. The outer side of the outermost annular elements 31 , 34 form the above- mentioned respective running surfaces 18, 19. Between the annular elements 31 -34 and the axial elements 35 there are a total of eighteen (six times three) framework openings 36, two of which are shown open in figure 1 for the sake of clarity. In practice however, all the framework openings 36 are closed during operation using the closing bodies 37, which are available in different embodiments but all have the same curved main shape.

Figure 2 shows an embodiment of a possible closing body 37. The closing body 37 comprises a curved plate 41 which in the mounted situation is concentric with the central axis of the cylindrical drum 6. The curved plate 41 is provided on the outer side with a handle 42 and, at the position of the two opposite curved peripheral edges, with coupling strips 43, 44, with three coupling holes 45 in each of the coupling strips 43, 44. The closing bodies 37 can also be embodied as flat plates instead of as curved plates. The distance between the closing bodies and the outer ends of the hammer bodies 1 1 will then not be constant during rotation of the hammer bodies 1 1 , this not necessarily being a drawback in the context of the invention. In the mounted situation the curved plate 41 is placed in a framework opening 36, wherein it abuts with the opposite straight longitudinal sides against the undersides of mutually opposite axial elements 35, and the closing body 37 is bolted fixedly via the openings 45 to two adjacent annular elements 31 -34 which are provided for this purpose with threaded holes. The closing bodies 37 can be replaced , for instance by a closing body of another type, in simple manner by loosening/tightening the bolts. In figure 2 the closing body 37 is embodied with a closed curved plate 41 . This plate can be provided on the inner side with a spirally extending strip-like breaking body. Such breaking bodies co-act during operation with the hammer bodies 1 1 in order to break/cut up the waste. The use of such breaking bodies can be useful particularly on the upstream side of the shaft body. Frequently used in practice as an alternative to the curved (closed) plate 41 is a correspondingly curved screen plate with screen openings preferably provided in a regular pattern. The closing bodies can be embodied with different types of screen plate, wherein the screen openings of such screen plates can differ from each other in respect of for instance the mutual distance, the pattern , the size and/or the shape. It is particularly advantageous for the size of the individual screen openings in the screen plates lying on the upstream side of the screen drum 6 (on the right in figure 1 ) to be smaller than the size of the individual screen openings in the screen plates on the downstream side of the screen drum 6 (on the left in figure 1 ). It has been found for instance that the screen openings on the upstream side advantageously have a diameter of 8 mm, while the diameter of the screen openings on the downstream side is advantageously 30 mm or 40 mm. The screen openings in the central plates 41 can in turn have a differing diameter of for instance 15 mm or 20 mm. The advantage is a limited risk of packaging material exiting the screen drum 6 through the screen openings on the upstream side. The packagings will be opened here by the operation of the hammer bodies, whereby the content can flow out of the packagings. This content, particularly if it is of liquid nature, can exit the screen drum directly via the relatively small screen openings on the upstream side and be separately collected, and does not for instance need further filtering. This latter may well be the case for material leaving the screen drum 6 via screen openings at the downstream outer end. Because of the larger screen openings and because of the fact that packaging material has been divided into smaller pieces because of the continuous action of the hammer bodies 1 1 , a fraction of packaging material is also present in this screened material (or at least the risk thereof cannot be precluded) and it may be necessary or at least desirable to nevertheless perform a further filtering of the relevant material in a follow-up step, for instance using a screw press filter. The relatively large screen openings on the downstream side contribute toward larger fragments of organic material also being able to leave the screen drum 6 via these screen openings and toward a good flow of material through the screen drum 6 from the feed opening 12 in the direction of the outflow side of the screen drum 6 at the cover 29. A good throughflow is important, since there is otherwise an increased risk of the packaging material, due to a long processing time in the screen drum 6, being reduced in size such that parts of the packaging material can exit the screen drum 6 via the screen openings.

The hammer bodies 1 1 are driven in practice at a typical rotation speed of for instance 600 revolutions per minute by appropriate actuation of the electric motor 10. The cylindrical drum 6 will in practice be driven at a considerably lower rotation speed of for instance 8 revolutions per minute. Liquid material or material smaller than the diameter of screen openings in closing bodies provided on the periphery of the cylindrical drum will exit the cylindrical drum through the screen openings on the one hand because of the gravitational force and on the other because of the effect of material being flung about by the hammer bodies 1 1 . This material is collected here in a for instance cylindrical jacket enclosing the cylindrical drum 6. This jacket is not shown in figures for the sake of clarity but is per se known to the skilled person. The jacket can be divided as seen in axial direction into different, for instance three, compartments. Each compartment can optionally be connected to a discharge conduit or conveyor for the purpose of discharging the content of the respective compartments. The content of the compartments can then be further processed in different ways, to the extent this is deemed necessary.

Due to the rotation of the cylindrical drum 6 it has been found that the screen openings in the closing bodies 37 which are embodied with a curved screen plate remain open better, or in any case tend less to become clogged, or that blockages of the screen openings are cleared autonomously due to the gravitational force and the rotation of the cylindrical drum 6, since "clogging" material runs out of the screen openings. The screen openings remaining clear can be further enhanced by making use of blow nozzles which blow a fluid such as water, air or steam in the direction of the screen openings. These blowing means can for instance be disposed stationary on the outer periphery of the drum 6. The rotation of the drum 6 ensures that, at the longitudinal position of the drum 6 where a blow nozzle is provided, all screen openings move once within the operating range of the blow nozzle during a complete rotation of the drum 6. In order that blowing can take place along the full length of the drum 6 it is possible to apply a number of blow nozzles adjacently of each other. It is also possible to envisage making use of a blow nozzle moving reciprocally in axial direction along the drum 6. Making use of the rotation of the drum, optionally supplemented with blowing means, achieves that screening of the waste, which is subjected to the action of the rotating hammer bodies 1 1 via the feed opening 12, can take place better. That is, a larger fraction of liquid or at least small (comminuted) material will leave the cylindrical drum 6 via the screen openings therein.

The above device is configured to separate material, in this case particularly to separate packaged food products. Devices according to the invention can also be configured to comminute material without separating the material. It is however also possible within the scope of the present invention for a device similar to the hammer mill 1 to be applied which is closed at the outer end opposite the feed opening so that no material can pass therethrough. All the material, as soon as it has optionally been made sufficiently small by the action of the hammer bodies 1 1 , will therefore exit the drum 6 via the screen openings. Such a device can for instance be suitable for processing unpackaged food products or (unpackaged) organic materials in general.