WO2010026461A2

WO2010026461A2 - Apparatus for producing pellets

Info

Publication number: WO2010026461A2
Application number: PCT/IB2009/006690
Authority: WO
Inventors: Guido Rota
Original assignee: Caeb International S.R.L.
Priority date: 2008-09-04
Filing date: 2009-08-31
Publication date: 2010-03-11
Also published as: WO2010026461A3; IT1391567B1; ITMI20081587A1

Abstract

An apparatus for producing pellets comprises a pelletizing chamber (3) with an inlet. The chamber (3) includes a die (7) having a wall with holes (8) for extruding pellets and presser means operably associated with said die (7) for pressing the bulk material to be pelletized out of said pelletizing chamber (3) through the holes (8) of said die (7). Advantageously, the presser means include a drum (9) which fits into the die (7) with a certain clearance to move towards/away from the holes (8), with drive means operating on the drum (9) to cause it to move within and relative to the die (7).

Description

Apparatus for producing pellets

The present invention relates to an apparatus for producing pellets from chipped material according to the preamble of claim 1.

Pellets, i.e. small cylinders of pressed milled/chipped material, are widely used at present as a fuel for stoves, fired boilers and the like.

Pellets are generally made from raw fuel material, such as wood or woodworking waste' as well as from crop and/or forest waste materials, particularly baled prunings or other types of residues.

^Pellet compaction provides a high-yield fuel suitable for heating applications. It shall be further noted that the binding power of lignin, which is contained in wood and wood waste as well as in prunings, provides a compact product without using foreign additives and chemicals, as well as wholly natural, high-yield fuel. Nonetheless, pelletization can also find application in industries that are not necessarily associated with the production of heating fuel.

At present, pelletization, i.e. production of pellets from milled/chipped or very fine-size bulk material, occurs in apparatus having large pelletizing chambers, which are rotatably driven to force the material to be pelletized out of the holes of a die, upon contact with one or more fixed scrapers within the chamber . While this arrangement is suitable for pellet production, it still requires large machines, having bulky and heavy moving parts, and consuming a considerable power for operation.

In view of the above, the need is strongly felt for a pelletizing apparatus whose construction is compatible with a small apparatus size, and requires no large moving parts, thereby reducing the required operating power under the same throughput conditions, and which has highly compact and simplified moving parts, to avoid any structural failure during use.

This invention is based on the problem of providing an apparatus for producing pellets which has such structural and functional features as to fulfill the above need, while obviating the above prior art drawbacks.

This problem is solved by an apparatus for producing pellets as defined in claim 1.

Further features and advantages of the apparatus for producing pellets according to the present invention, will be apparent from the following description of one preferred embodiment thereof, which is given by way of illustration and without limitation with reference to the accompanying figures, in which:

- Figure 1 is a perspective view of the apparatus according to the present invention;

- Figure 2 is a perspective view of the apparatus of Figure 1, from different point of view;

Figure 3 is a lateral view of the apparatus according to the present invention; - Figures 4 and 5 are plan and perspective sectional views respectively of the apparatus according to the present invention, as taken along the section line A-A of Figure 3;

- Figure 6 is a perspective view of the apparatus of Figure 1, with some parts omitted;

- Figure 7 is a lateral view of the part of the apparatus of Figure 1 corresponding to the pelletizing chamber;

- Figure 8 is a top view of the detail of Figure 7;

- Figure 9 is a perspective cross sectional view of the pelletizing chamber of Figure 7 ;

- Figure 10 is a plan cross sectional view of the pelletizing chamber of Figure 7; - Figure 11 is a top plan view of the die of the pelletizing chamber of Figure 7 ;

Figures 12 and 13 are plan and perspective sectional views respectively of the die of Figure 11, as taken along the section line C-C; - Figure 14 is a perspective view of the shaft of the pelletizing chamber of Figure 7;

- Figure 15 is a perspective view of the eccentric sleeve of the pelletizing chamber of Figure 7 ;

- Figure 16 is a perspective view of the drum of the pelletizing chamber of Figure 7 ;

- Figures 17, 18, 19 and 20 are each a top view of the pelletizing chamber in four distinct successive instants of their operation;

- Figure 21 is a perspective cross sectional view of the pelletizing chamber of the apparatus according to the present invention, according a different embodiment^';

- Figure 22 is a plan cross sectional view of the pelletizing chamber of Figure 21; - Figure 23 is a perspective cross sectional view of shaft and eccentric sleeve of the pelletizing chamber of Figure 21;

- Figure 24 is an exploded perspective view of the details of Figure 23. Referring to the accompanying figures, numeral 1 generally designates an apparatus for producing pellets .

The apparatus 1 comprises a support structure that supports : - a pelletizing chamber 3 having an inlet for the bulk material to be pelletized,

- a milling/chipping unit 4 having an inlet for the material to be milled/chipped and an outlet for the milled/chipped material and - conveyor means 5 for connecting the outlet of said milling/chipping unit with the inlet for the bulk material to be pelletized in the pelletizing chamber 3.

According to the embodiment of the figures, the milling/chipping unit 4 is placed at a higher level than the pelletizing chamber 2, for ensuring a gravity feed into said inlet of the pelletizing chamber 3. Preferably, the milling/chipping unit 4 is located exactly above the pelletizing chamber 3.

The milling/chipping unit 4 includes at least two counter- rotating milling/chipping cutters 24 which, in the illustrated embodiment, are cylindrical helical- tooth cutters accommodated in a box- like body with parallel axes of rotation substantially horizontal to the surface upon which the apparatus 1 lies . In the illustrated embodiment, the conveyor means^' 5 are in the form of a funnel which is adapted to collect the milled/chipped material from the outlet of the milling/chipping unit 4 into the inlet for the bulk material to be pelletized in the pelletizing chamber 3. Otherwise, the milled/chipped material to be pelletized can be forced into the pelletizing chamber by motor- driven conveyor means, such as an auger, a belt conveyor or the like. This solution is particularly suitable when the pelletizing chamber cannot be fed from the top by gravity.

Concerning the pelletizing chamber 3, it shall be noted that :

- it has a substantially cylindrical shape,

- it extends along a vertical axis X-X between a bottom 6 and an opposed open end that provides the above mentioned inlet for the bulk material to be pelletized into the pelletizing chamber 3 and

- it is delimited by a substantially cylindrical side wall. More in detail, the pelletizing chamber 3 includes a die 7 having a wall with holes 8 for extruding pellets and presser means operably associated with the die 7 for pressing the bulk material to be pelletized out of the pelletizing chamber 3 through the holes 7 of said die 7. The die has a substantially circular closed-ring shape with radial holes 8. Such die 7 forms at least one axial section (extending along the axis X-X) of the above mentioned side wall that delimits the pelletizing chamber 3.

Advantageously, the die 7 has channels 25 for a cooling fluid. Obviously, these channels shall be connected to a cooling circuit of the apparatus 1. This allows the die to be maintained within such a temperature range as to prevent deterioration of the pelletized material due to overheating.

In the illustrated embodiment, such presser means include a substantially circular drum 9, which fits into the die 7 with a certain clearance. More in detail, the outside diameter of the drum 9 is much smaller than the inside diameter of the die 7 in which it fits, wherefore it can be moved within the die 7 towards/away from the radial holes 8 of the die.

Also, the apparatus 1 has drive means operating on the drum 9 to cause it to move in the die towards/awayfrom the holes 8.

As explained hereinafter, for efficient extrusion of the material to be pelletized contained in the pelletizing chamber 3 through the radial holes 8 of the die 7, the drum 9 should contact the inner wall of the die 7 at its perforated portions . It should be noted here that the shape of the die 7 and/or the drum 9 may^¬ be also other than the substantially circular cylindrical shape as described above, and that such elements may be also formed with different shapes, although the shapes of the side wall of the drum and the inner wall of the perforated die should match as much as possible.

In an advantageous aspect, the drum 9 is eccentrically supported in the die 7. According to the illustrated embodiment, the drum 9 is eccentrically supported by a shaft 10 extending through the die 7 coaxial with the axis X-X of the pelletizing chamber 3. The bottom 6 of the pelletizing chamber 3 has a calibrated opening for the shaft 10 to fit into the chamber by a top portion 10a thereof.

As a result of the above mentioned eccentricity, any rotation of the shaft 10 causes a displacement of the drum 9 relative to the holes 8 of the die 7. According to a preferred embodiment, the drum 9 is mounted eccentrically to the shaft 10 by causing the drum 9 to be supported by the upper axial section 10a of the shaft 10. Such upper section 10a does not extend along the axis X-X of rotation of the shaft 10, but parallel to the axis X-X and is offset from the axis X- X by a predetermined eccentricity value (see Figures 7 and 14) .

Therefore, the drum 9 is supported by an eccentric portion 10a of the shaft 10. It shall be noted that in order to allow an adjustment of the eccentricity value, depending on which during the rotation of the shaft 10 the drum 9 move to a greater/smaller extent within the die 7, the drum 9 is mounted on said eccentric portion 10a of the shaft 10 with interposition of an eccentric sleeve 11 coaxially mounted to said eccentric portion 10a of the shaft 10 (see fig. 9, 10,15) . In particular, as results from figure 15, the axis of the inner trough opening of the sleeve 11, where the eccentric portion 10a of the shaft " 10 is inserted, is both parallel and eccentric with respect to the axis of the external wall of the sleeve 11 where the drum 9 is mounted. As a result, by controlling the angular position of the eccentric sleeve 11 relative to the eccentric portion 10a of the shaft, the eccentricity of the drum 9 relative to the axis X-X of the shaft 10 and the pelletizing chamber 3 may be increased or decreased, depending on whether the eccentricity of the sleeve 11 is added to or subtracted from the eccentricity E of the eccentric portion 10a of the shaft 10. Advantageously, this allows an accurate adjustment of the eccentricity of the drum 9 in the pelletizing chamber 3 to ensure proper contact between the side wall of the drum 9 and the side wall of the die 7 with the holes 8, not only according to the characteristics of the particular milled/chipped material to be pelletized but also and especially to allow recovery of any clearance due to inaccurate processing of mechanical parts or occurring in the apparatus due to wear after extensive use.

According to a preferred embodiment, the drum 9 is supported by the shaft 10 through interposed bearings 12, allowing it to be idly mounted to the shaft 10. In this case, due to the presence of the above mentioned eccentric sleeve 11 mounted to the portion 10a of the shaft 10, the rolling bearings 12 are interposed between the hub of the drum 9 and the outer side wall of the sleeve 11, as shown in Figure 10.

Advantageously, the bearings 12 are thrust rolling bearings capable of sustaining and opposing any axial loads transmitted by the drum 9 to the shaft 10 during normal operation of the apparatus 1. In the illustrated embodiment, a pair of inclined roller bearings are interposed between the drum 9 and the sleeve 11, and are arranged one behind the other along the axis of the eccentric sleeve 11 so that the inclination of the two rollers converges at the facing ends of the two bearings 12. This allows the bearings 12 to effectively oppose loads in both directions . It shall be noted that the lower portion of the shaft 10 is also rotatably supported by the structure of the apparatus 1, namely relative to the pelletizing chamber 3,_ by interposed rolling bearings. These are also rolling thrust bearings with inclined rollers arranged exactly as described above for the bearings 12.

In order to prevent losses of material to be pelletized from the opening at the bottom 6 of the pelletizing chamber 3 through which the shaft 10 fits into the pelletizing chamber 3 by its eccentric portion 10a, the drum 9 advantageously has sealing means 13 in sliding contact with the wall of the pelletizing chamber 3 that defines the bottom 6.

Here, these sealing means 13 are embodied by an O- ring accommodated in a corresponding annular groove formed in the end wall of the drum 9 facing towards and substantially contacting the bottom 6. Furthermore, elastic means 14, in this embodiment one or more helical springs, are received in this annular groove and exert a predetermined load on the 0-ring to press ^

it out of the annular groove to contact with the bottom 6 of the pelletizing chamber 3.

The end of the eccentric portion 10a of the shaft 10 is formed with threads and a threaded ring 15 is screwed thereon to act as an axial stop, allowing both the eccentric sleeve 11 and the drum 9 to hold their proper position, and preventing them to come out of the upper end of the shaft 10.

A gear wheel 23 is keyed to the lower end of the shaft 10, i.e. the outer non-eccentric end external to the pelletizing chamber 3, and is adapted to be rotatably driven by motor means through motion- transferring means which are embodied in this case by a chain 18. As an alternative, a belt, a gear train or other functionally equivalent drive means may be used.

Concerning the above mentioned milling/chipping unit 4, it can be noted that the two cylindrical cutters 24 are also rotatably driven by motor means through a drive including a chain 19 or other functionally and/or structurally equivalent drive means .

In this respect, it shall be noted that the motion for driving the milling/chipping unit 4 may be ensured by independent motor means or derived, via a special kinematic chain, from the motor means that transfer motion to the shaft 10, while possibly providing clutch or friction means to stop the rotation of the cutters 24 only.

The apparatus 1 also comprises scraper means 16 within the pelletizing chamber 3 for removing the material from the portions of the walls of the pelletizing chamber 3 above the holes 8 of the die 7 and convey such material between the drum 9 and the die 7. The scraper means 16 are directly supported and rotatably driven by the shaft 10, namely by its upper portion 10a.

The support structure 2 of the apparatus 1 namely comprises a frame 20 having connections for removably mounting it to an agricultural machine, such as a tractor. In this case, the shaft 10 and the cutters 24 of the milling/chipping unit 4 may be advantageously rotatably driven by the motor means of the agricultural machine or its hydraulic system.

Furthermore, the apparatus 1 has feeder means (not shown) for automatically feeding bales of bulk material to be milled/chipped to the above mentioned milling/chipping unit 4, after withdrawing such bales from a bale storage house.

During operation of the apparatus 1, the motor means rotatably drive the shaft 10 and the two cutters 24 of the mi11ing/chipping unit 4. Then, the bulk mateπal that is fed to the inlet of the milling/chipping unit 4 is milled/chipped by the teeth of the counter- rotating cutters 24 and falls by gravity through the funnel 5 into the pelletizing chamber 3.

In the pelletizing chamber 4, as the shaft 10 rotates, the drum 9 is forced to an eccentric, e.g. counterclockwise motion, according to the sequence of Figures 17, 18, 19 and 20. The shaft 10 may be obviously also rotated clockwise instead of counterclockwise .

The motion of the drum 9 within the pelletizing chamber 3 causes the outer side wall of the drum 10 to increasingly adhere against successive points of the side wall of the die 7 with the radial holes 8. As the drum 9 moves towards a given portion of the side wall of the die 7 with the holes 8 , it causes the milled/chipped material held in the chamber in the vicinity of such portion of the wall to be compressed, wherefore such material is pressed and forced out of the pelletizing chamber 3 through the holes 8 of the die 7.

Once the material falls from the die, it is collected by an additional funnel 21 and conveyed to a collection bag 22. It shall be noted that by idly mounting the drum 9 to the shaft 10 the sliding contact of the side wall of the drum 9 against the side wall of the die 7 with the holes 8 is considerably reduced. By controlling the angular position of the eccentric sleeve 11 with relative to the eccentric portion 10a of the shaft 10 it is so possible to adjust the eccentricity of the drum 9 inside the pelletizing chamber 3, as previously explained. Figures 21 to 24 show a different embodiment of the apparatus 1 according to the present invention. The parts of the apparatus according to this second embodiment which correspond structurally and (or functionally the corresponding parts of the apparatus already described are indicated with the same referral numbers used for the corresponding parts already described e will not further described in detail.

More particularly, this second embodiment refers to a preferred embodiment where the eccentric sleeve 11 is fixed on the eccentric portion 10a of the shaft 10 by means and with interpositions of an elastic sleeve 26 which is coaxially inserted on the eccentric portion 10a of the shaft 10. As shown in figure 24, the elastic sleeve 26 has a longitudinal opening which is extended throughout its axial length, said longitudinal opening allowing the elastic sleeve 26 to extend or to contract circumferentially and to act as a clamping pincer.

The elastic sleeve 26 has a first cylindrical portion 26a which is smoothly connected to a second conical portion 26b with outer conical shape which increases towards the conical end of the elastic sleeve

26.

The elastic sleeve 26 is inserted on the eccentric portion 10a of the shaft 10 starting from its conical end 26b, so that the conical portion 26b of the elastic sleeve 26 is more inserted into the pelletizing chamber than the cylindrical portion 26a.

In order to have a right axial positioning of the elastic sleeve 26 on the eccentric portion 10a of the shaft 10, the eccentric portion 10a of the shaft 10 has a circumpherential stop 28 which act as axial stop against which a corresponding internal axial projection of the elastic sleeve 26 abuts. As shown in figure 24, the circumpherential stop 28 of the eccentric portion 10a of the shaft 10 is obtained by an increasing of the diameter of the eccentric portion 10a to a prefixed distance from the free end of the eccentric portion

10a.

The free end of the cylindrical portion 26a is provided with an external thread on which a female screw of a flanged ring 29 is screwed.

In this embodiment, during the assembling of the apparatus the elastic sleeve 26 is inserted on the eccentric portion 10a of the shaft 10, as far as the internal axial projection of the elastic sleeve 26 abuts against the circumpherential stop 28 of the eccentric portion 10a. Afterwards, the eccentric sleeve 11 is inserted on the elastic sleeve 26. When the bearings and the drum 9 are mounted, it is necessary to rotate angularly the eccentric sleeve llwith respect to the eccentric portion 10a, so as to have an adjustment of the eccentricity value of the drum 9 with respect to the pelletizing chamber. Afterwards, the flanged ring 29 is fastened on the threaded portion of the elastic sleeve 26. Finally, the above threaded ring 15 is tightly screwed on the threaded end portion of the eccentric portion 10a of the shaft 10.

As can be appreciated from the above description, the apparatus for producing pellets of the invention fulfills the above mentioned need and also obviates prior art drawbacks as set out in the introduction of this disclosure.

Thus, in the particular structure of the inventive apparatus, the presence of a movable drum in the chamber allows pellets to be produced with a lower operating power, under identical throughput conditions, as compared with prior art apparatus, in which the presser means are stationary and the pelletizing chamber is movable, being possible to adjust within a professed range the eccentricity of the drum, so as to recovery of any clearance due to friction wear of the drum against the die 7 or for optimizing the eccentricity of the drum depending on the kind of material to be pelletized. Furthermore, it should be stressed that the possibility to adjust the eccentricity value of the drum within the pelletizing chamber 3 is very useful also during the assembling of the apparatus for producing pellets. In fact, the insertion of the drum 9 within the pelletizing chamber 3 is easier when the eccentric sleeve 11 is rotated so as its eccentricity is subtracted from the eccentricity E of the eccentric portion 10a of the shaft 10. This allows to have an easy housing of the drum 9 within the pelletizing chamber 3 also when this chamber is provided with an inner rim projecting from the inner wall of the die 7, which forms an undercut underneath which an circumferentially end portion of the drum 9is positioned.

One advantage of the apparatus for producing pellets of the invention is the simplicity of its construction, which ensures proper operation with no costly maintenance requirements.

Another advantage of the apparatus for producing pellets of the invention consists in that the arrangement for driving the drum inside the chamber is simple and sturdy, to prevent any undesired failure of the mechanical parts as long as the parts are correctly sized, especially in terms of the diameter of the shaft, the bearings and the drum. A further advantage of the apparatus for producing pellets of the invention consists in the possibility of adjusting the eccentricity of the drum relative to the shaft that supports it, to control the displacement of the drum within the chamber. Yet another advantage of the apparatus for producing pellets of the invention consists in that the die 7 can be cooled during pelletization due to the presence of channels for the cooling liquid. Considering that the pelletization chamber is stationary relative to the bearing structure of the apparatus, the channels may be easily sealingly connected to a cooling circuit of the apparatus, or external to the latter.

Those skilled in the art will obviously appreciate that a number of changes and variants may be made to ^ _Q

the apparatus for producing pellets as described hereinbefore, in response to specific requirements, without departure from the scope of the invention, as defined in the following claims. Thus, for example, as an alternative to the above, an ordinary crank gear, a link or other functionally- equivalent structures may be provided, to cause the drum to eccentrically move within the pelletizing chamber . Otherwise, in view of fulfilling particular requirements, the drum may be arranged to be movable as described above, while allowing the pelletizing chamber to be also movable and not stationary.

* * * * * *

Claims

1. An apparatus for producing pellets comprising a support structure (2) and a pelletizing chamber (3) having an inlet for the bulk material to be pelletized, said pelletizing chamber (3) comprising: v. a die (7) having a wall with holes (8) for extruding pellets and

- presser means operably associated with said die (7) for pressing the bulk material to be pelletized out of said pelletizing chamber (3) through the holes (8) of said die (7) , wherein:

- said presser means include a drum (9) which fits into said die (7) with a certain clearance, - said drum (9) is movable relative to said die (7) towards/away from the holes (8) of said die (7) ; said pelletizing chamber (3) comprises drive means operating on said drum (9) to move said drum (9) to move within said die (7) towards/away from the holes (8) of said die (7) ;

- said drum (9) is eccentrically supported in said die (7) by an eccentric portion (10a) of said shaft (10) , by a shaft (10) that extends through said die (7), whereby any rotation of said shaft (10) causes a displacement of said drum (9) relative to the holes (8) of said die (7) , characterized in that: said drum (9) is supported by said eccentric portion (10a) of said shaft (10) by means and with interposition of an eccentric sleeve (11) , whereby by adjusting the angular position of said eccentric sleeve

(11) relative to said eccentric portion (10a) of said shaft (10) , the eccentricity (E) of the drum (9) may be adjusted relative to the axis of rotation (X-X) of the shaft (10) and hence relative to the die (7) .

2. An apparatus according to claim 1, wherein the eccentric sleeve (11) is mounted on the eccentric portion (10a) of said shaft (10) by means and with interpositions of an elastic sleeve (26) having a longitudinal opening (27) which extends throughout its axial length.

3. An apparatus according to claim 2, wherein the elastic sleeve (26) comprises a first cylindrical portion (26a) which is smoothly connected to a second conical portion (26b) with outer conical shape increasing towards the conical end of the elastic sleeve (26) , said elastic sleeve (26)being mounted on the eccentric portion (10a) of said shaft (10) from its conical end (26b) , the free end of said first cylindrical portion (26a) of the elastic sleeve (26) being provided with a thread on which a female screw of a flanged ring (29) is screwed.

4. An apparatus according to claim 3, wherein said eccentric portion (10a) of said shaft (10) is provided with a circumpherential stop (28) which act as axial stop against which a corresponding internal axial projection of the elastic sleeve (26) abuts to assure a right axial positioning of the elastic sleeve with respect to the shaft (10) .

5. An apparatus in any one of claims 1 to 4, wherein said drum (9) is supported by said shaft (10) through interposed bearings (12) , allowing it to be idly mounted to said shaft (10) .

6. An apparatus as claimed in any one of claims 1 to 5, wherein said die (7) has channels (25) for a cooling liquid.

7. An apparatus as claimed in any one of claims 1 to 6, wherein said die (7) has a circular shape, said holes (8) being formed in a radial arrangement' at the circular side wall of said die.

8. An apparatus as claimed in any one of claims 1 to 6, wherein: said pelletizing chamber (3) extends axially between a first end closed by a bottom (6) and an opposed open end, - said die (7) forming a lateral portion of said pelletizing chamber (3) .

9. An apparatus as claimed in any one of claims 1 to 8, wherein said shaft (10) extends along the axis (X-X) of said pelletizing chamber, between said first end (6) and said second open end.

10. An apparatus as claimed in claim 8 or 9, wherein said drum (9) comprises sealing means (13) in sliding contact with the bottom (6) of said pelletizing chamber (3) .

11. An apparatus as claimed in any one of claims 1 to 10, wherein said shaft (10) extends in a substantially vertical direction (X-X) .

12. An apparatus as claimed in any one of claims 1 to 11, comprising:

- a milling/chipping unit (4) having an inlet for the material to be milled/chipped and an outlet for the milled/chipped material and

- conveyor means (5) for connecting the outlet of said milling/chipping unit (4) with the inlet for the bulk material to be pelletized in said pelletizing chamber (3 ) .

13. An apparatus as claimed in claim 12, wherein said milling/chipping unit (4) is placed above said pelletizing chamber (3) , for ensuring a gravity feed ^

into said inlet of said pelletizing chamber (3) .

14. An apparatus as claimed in claim 12 or 13, wherein said milling/chipping unit (4) comprises at least two counter- rotating milling/chipping cutters.

15. An apparatus as claimed in claim 14, wherein said cutters (24) are cylindrical helical- tooth cutters accommodated within a box- like body with parallel axes of rotation.

16. An apparatus as claimed in any one of claims 1 to 15, wherein: said support structure comprises a frame (20) having connections for removable mounting thereof to an agricultural machine and

- said drive means are adapted to be driven by the motor means of the agricultural machine to which it is mounted.