The present invention is related to a modular-designed hammer mill and to a method for revamping a hammer mill.

Hammer mills are well-known from the prior art. Hammer mills are used for coarse comminuting of materials in large quantities.

The typical hammer mill has a grinding chamber with a motor- driven rotor on which a plurality of discs is arranged. In the circumferential area of the discs, hammer pins are suspended on which hammers are pivotably arranged. When the rotor rotates, these hammers move outwardly in response to centrifugal force, where they break up the material impacting against them. To pre- vent hammers lined up axially in the direction of the rotor from hitting each other, they are spaced apart by spacers. At the same time, adjacent hammers must be prevented from colliding in the circumferential direction. The spacers between the hammers are therefore typically different for adjacent axes.

Typically, a door closing the grinding chamber is provided. Around the rotor, one or more screens are provided through which comminuted material may enter into an outlet zone, whereas coarser material is held back and preferably further processed. On top of the grinding chamber, a material inlet is provided through material to be processed enters the grinding chamber. In the region of the material inlet, impact plates may be provided.

Hammer mills are used in various business fields. Accordingly, there is a wide range of requirements hammer mills have to ful- fill, depending on the application in which a hammer mill is used. These requirements are usually addressed with different variants of hammer mills. Accordingly, different hammer mills are built and offered on the market for various applications in different business fields.

This approach comes with the disadvantage of having to provide large machine portfolios, in order to be able to have a suitable hammer mill for each different required application.

In addition, this approach does not allow the processing of dif- ferent products by one hammer mill, or the use of one hammer mill for different applications in different business areas, as the machine is only designed for one specific application.

In addition, this approach of providing different types of ma- chine designs for different applications drives up the variety of spare parts. A manufacturing company with different hammer mills needs separate spare parts for each machine and according- ly needs to maintain a warehouse of a certain size, with associ- ated significant life-cycle costs.

It was the problem of the present invention to overcome the dis- advantages of the prior art. In particular, a hammer mill is to be provided which is suitable for use in different applications.

This problem is solved by the subject-matter described in the claims of the present invention.

In detail, the present invention is related to a hammer mill, comprising a platform with a base frame, characterized in that said platform is interchangeably connected with a motor and fix- edly and/or interchangeably connected with at least one grinding chamber containing a rotor with hammers provided thereon. According to the present invention, a modular-designed hammer mill is provided. The hammer mill according to the present in- vention provides the possibility of replacing and/or adding com- ponents, so as to revamp a hammer mill if it is to be used in a different application, Moreover, by adding grinding chambers of different designs, it is possible to process different kinds of materials in one hammer mill. Moreover, by adding grinding cham- bers of the same or different designs and/or by using a larger motor, it is possible to increase the throughput of the hammer mill. As a result, the hammer mill according to the present in- vention can be used for a wide variety of applications.

The hammer mill according to the present invention has a modular design on different levels. Basic elements of the hammer mill such as machine structure, base frame, doors, etc. always remain the same. In one embodiment, at least one grinding chamber is fixedly connected (e.g. by welding) with the basic machine structure. Said fixedly connected grinding chamber (s) can be pre-configured as desired. In another embodiment, all provided grinding chambers are interchangeably (i.e. releasably) attached to the basic machine structure.

In all embodiments, said basic machine structure (hereinafter referred to as platform) can be combined with additional compo- nents such as additional grinding chambers. Further up scaling can be achieved by replacing smaller motors with larger motors that provide more power.

On another level, the grinding chambers that can be combined with said platform can be freely configured, for example with respect to the kind and number of hammers, or with respect to the number and kind of plates to be used therein. The hammer mill according to the present invention is designed according to the principle of a construction kit. All components to be replaced at and/or added to the platform have adequate size to be used with said platform, allowing their easy replace- ment and/or addition. This allows free scaling from a technical point of view, but also from a throughput perspective, without having to switch to another machine type.

The hammer mill according to the present invention comprises a platform with a base frame. This can be any base frame conven- tionally used for a hammer mill.

According to a preferred embodiment of the present invention, the base frame has a variable length. The length of the base frame may have to be elongated depending on the number and kinds of components to be provided thereon. For example, a larger mo- tor typically has a larger size, and it may be preferable to ac- cordingly adjust the length of the base frame in order to secure reliable operation of the hammer mill.

According to the present invention, by "the base frame has a variable length" it is meant that the base frame itself can be elongated, for example by providing an additional frame section in the base frame that can be pulled out of the base frame or shifted back again into the base frame, thus extending or short- ening the length of the base frame. However, the term also com- prises embodiments where an additional frame section is connect- ed to or removed from the base frame, thus extending or shorten- ing the length of the base frame and obtaining a pre-configured base frame. Said additional frame section is releasably connect- able or welded to the base frame. According to the present invention, by "releasably connected" or

"interchangeably connected" it is meant that a respective compo- nent is connected to the base frame (or to another component of the hammer mill) by releasable connections (as compared to con- nections which cannot be released without destruction, such as welding connections). As an example, screw connections may be mentioned .

According to the present invention, said platform is inter- changeably connected with a motor. According to the present in- vention, any type of motor conventionally used for hammer mills can be used. The hammer mill according to the present invention is designed such that motors of different size and power may be connected to the base frame. According to a preferred embodiment of the present invention, motors having a power in the range from 37 kW to 450 kW may be used.

According to the construction kit principle employed by the pre- sent invention, all motors to be connected to the base frame preferably have the same arrangement of releasable connections, so that they fit to the same base frame without the need for any modification. Alternatively, flexible base frames are capable of being connected to motors of different sizes. In more detail, if at the base frame there are provided, for example screw connec- tions at a distance of 50 cm from each other, each motor to be connected therewith has the respective counter connections at the same distance of 50 cm from each other. Replacement of one motor by another is thus easily possible by removing a first mo- tor, by releasing the connections to the base frame and moving it away e.g. with the aid of a crane, and putting a second motor on the base frame e.g. with the aid of a crane, and connecting it with the base frame by securing the releasable connections. According to one embodiment of the present invention, said plat- form is furthermore fixedly connected with at least one grinding chamber, preferably by welding said at least one grinding cham- ber and said base frame together. It is possibly to fixedly con- nect one grinding chamber or more than one grinding chambers with the base frame. According to another embodiment, all pro- vided grinding chambers are interchangeably (i.e. releasably) attached to the basic machine structure.

Grinding chambers for hammer mills are known. A grinding chamber for a hammer mill contains a rotor with hammers provided there- on. Said rotor is rotated by a rotor axis that is connected with a motor described above. The connection between the rotor axis and the motor is releasably designed, so as to allow engagement and detachment of said components. For example, the rotor axis may be releasably inserted into a sleeve of a motor. Alterna- tively, a portion of the axis may be fixedly arranged at the mo- tor and releasably connected, for example by a flexible coupling system, with the rotor axis of the grinding axis via a suitable connection, for example a sleeve.

According to a preferred embodiment of the present invention, said platform is connected with 1-10 grinding chambers, prefera- bly 1-5 grinding chambers, especially preferred 1-4 grinding chambers. Said grinding chambers may be connected to said plat- form in series, i.e. a first grinding chamber is connected to a motor arranged on said platform, a second platform is connected to said first grinding chamber, a third grinding chamber is con- nected to said second grinding chamber, and so forth.

According to the construction kit principle employed by the pre- sent invention, all grinding chambers to be connected to the base frame preferably have the same arrangement of releasable connections, so that they can be easily replaced by one another or added to each other. In more detail, if at the base frame there are provided, for example screw connections at a distance of 20 cm from each other, each grinding chamber to be connected therewith has the respective counter connections at the same distance of 20 cm from each other, at both sides. In this way, each grinding chamber can be attached to the base frame or to another grinding chamber, respectively. Replacement of one grinding chamber by another is thus easily possible by removing a first grinding chamber, by releasing the connections to the base frame and moving it away e.g. with the aid of a crane, and putting a second grinding chamber on the base frame e.g. with the aid of a crane, and connecting it with the base frame by se- curing the releasable connections.

Likewise, an additional grinding chamber may be provided by put- ting a second grinding chamber on the base frame e.g. with the aid of a crane, and connecting it with a first grinding chamber already provided on the base frame by securing the respective releasable connections.

According to the construction kit principle employed by the pre- sent invention, all grinding chambers to be connected to the base frame preferably have the same outer dimensions.

According to the present invention, each grinding chamber pref- erably comprises a door in order to enable access to the interi- or of the grinding chamber. Such doors are known. Alternatively, one door may be provided for all grinding chambers that are pro- vided.

According to the present invention, each grinding chamber com- prises an inlet for allowing material to be processed to enter the grinding chamber. Said inlet is arranged on the top of the grinding chamber.

According to a preferred embodiment of the present invention, it is possible to provide a single inlet for all grinding chambers arranged at the hammer mill. Said single inlet can be arranged on top of the series of grinding chambers arranged at the hammer mill. Said single inlet accordingly has a larger size than an inlet for an individual grinding chamber and allows parallel feeding of all arranged grinding chambers.

In each grinding chamber, impact plates may be arranged below said inlet of said grinding chamber. Preferably, two impact plates are provided below said inlet, at each side of the path from the inlet into the grinding chamber. Preferably, said im- pact plates are arranged in an inclined manner, at angle from 15-75°, preferably 30-60°, with respect to a perpendicular line through the grinding chamber when arranged at the platform of the hammer mill.

According to a preferred embodiment of the present invention, the impact plates provided below said inlet may be selected from the group consisting of a flat plate or an impact plate with a (varying) pattern of different surface areas having different impact properties, or a combination thereof. Depending on the selected impact plate (s), the grinding power provided by the first impact of the material fed into the grinding chamber can be adjusted. In particular, by selecting a specific pattern of different surface areas having different impact properties (e.g. areas of different thickness and/or height and/or coatings ap- plied thereon), the grinding power can be selectively adjusted. Impact plates are known and preferably made from a suitable me- tallic material such as steel.

According to the construction kit principle employed by the pre- sent invention, all impact plates to be provided below the inlet preferably have the same outer dimensions and the same arrange- ment of releasable connections, so that they can be easily re- placed by one another or added to each other. The above discus- sion for motors and grinding chambers also applies here.

In each grinding chamber, there is arranged a rotor on which a plurality of discs is arranged. Alternatively, one rotor for all grinding chambers may be used. As described above, said rotor is provided on a rotor axis which is connected with said motor for rotationally driving the rotor in said grinding chamber. As will be discussed below in more detail, on said rotor hammers are provided. The speed at which those hammers (specifically their tips) are rotated through the grinding chamber plays a signifi- cant role with respect to the kind of grinding that is performed in said grinding chamber, i.e. coarse grinding or fine grinding. Said speed can be adjusted by modifying the diameter of the ro- tor in the grinding chamber. Rotors with different diameters (respectively radii) rotate with a different speed when operated by the same motor. The rotor typically comprises a plurality of rotor discs, which divide the rotor into a plurality of seg- ments. The rotor discs can be arranged on the rotor axis at uni- form or variable distances from one another. For example, the individual rotor discs can be fixed on the rotor axis by a screwed connection. The rotor has a plurality of hammer pins for receiving one or more hammers. The individual hammer pins pref- erably do not extend over all segments. The hammer pins may also be rotationally symmetrical and can be fastened releasably on both sides to opposite rotor discs defining an individual seg- ment.

One or more segment disks may be arranged between each two adja- cent rotor discs. Such a segment disk, which likewise has open- ings, through which the hammer pin passes or is passed, is used in particular to provide additional support for the hammer pin. In particular at high rotational speeds, the hammer pins are highly stressed by the weight of the hammers and by the rotation of the rotor. The hammer pins can be made accordingly smaller due to the use of segment disks. The segment disks can be con- nected to the rotor discs by means of support pins. Such a con- nection of the segment disks to the rotor discs results in addi- tional stability of the rotor. The support pins may be continu- ous over all rotor discs. A simple construction is possible as a result of such support pins extending over all rotor discs.

Accordingly, in a preferred embodiment of the present invention more than one grinding chamber is provided, wherein said grind- ing chambers each contain a rotor and said rotors in said grind- ing chambers have different diameters. With this embodiment, it is possible to realize different speeds in different grinding chambers without the use of a frequency converter. According to a very preferred embodiment, the rotor diameters in the differ- ent grinding chambers are selected such that either a frequency of 50 Hz or a frequency of 60 Hz is realized in all provided grinding chambers when operating the hammer mill. It is possible to have different grinding speeds for one frequency. This allows material to be processed to different grinding grades, in the same hammer mill. Preferred rotor diameters according to the present invention are in a range from 300 to 1400 mm, preferably 1100 to 1350 mm, for a width of the grinding chamber of 2000- 2200 mm, preferably 2050-2150 mm. The width of the grinding chamber is preferably not variable, as discussed above with re- spect to the construction kit principle of the present inven- tion.

In each of said grinding chambers that are provided at the plat- form of the hammer mill of the present invention, preferably there are interchangeably provided elements surrounding the cir- cumference of said rotor. Said elements are preferably releasa- bly arranged at the inner surface of the grinding chamber.

According to a preferred embodiment of the present invention, four such elements are interchangeably provided in each grinding chamber around a rotor, so that essentially the entire circum- ference of the rotor is surrounded by said elements. Said four elements preferably have the same dimensions and the same ar- rangement of releasable connections, so that they can be easily replaced by one another. These elements typically have a curved shape, so that they can be conveniently be arranged in a typi- cally cylindrical grinding chamber.

As in a known arrangement in a hammer mill, said elements may be screen plates through which comminuted material may enter into an outlet zone, whereas coarser material is held back and pref- erably further processed. According to a preferred embodiment of the present invention, screen plates with different mesh sizes may be installed in a grinding chamber or in different grinding chambers .

According to a preferred embodiment said elements are selected from the group consisting of a screen and an impact plate. In other words, any variation of screen plates and impact plates may be arranged around the rotor in a grinding chamber, for mod- ifying the quality of grinding to be performed in said grinding chamber (finer or coarser).

According to a very preferred embodiment of the present inven- tion, four such elements are interchangeably provided in each grinding chamber around a rotor, wherein the two elements ar- ranged around the lower half of the circumference of the rotor in the grinding chamber are screens, preferably screens with different mesh sizes, and the two elements arranged around the upper half of the circumference of the rotor in the grinding chamber are impact plates.

According to a preferred embodiment of the present invention, there is not a single one-piece element provided that surrounds the circumference of a rotor, but rather separate elements, preferably four separate elements. This allows a flexible ap- proach as to the replacement and arrangement of said elements in said grinding chamber.

According to a preferred embodiment of the present invention, between the elements surrounding said rotor there are arranged regrind chambers, preferably three regrind chambers. Preferably, three regrind chambers are provided at a distance of about 90° to each other. In other words, two of the above elements (screen plates or impact plates) are connected to each other via a re- grind chamber. In the upper portion of the grinding chamber where the inlet is provided, no regrind chamber is arranged (since otherwise material fed through the inlet would enter into a regrind chamber without having been comminuted beforehand).

The connection of the elements surrounding said rotor to a re- spective regrind chamber are also releasable, preferably using a quick mounting system, so as to allow their easy replaceability. The regrind chambers preferably are releasably attached to the grinding chamber, preferably by screw connections. Also here, preferably the regrind chambers have the same dimensions and the same arrangement of releasable connections, so that they can be easily replaced by one another.

The purpose of the regrind chambers is to reject particles that have not been sufficiently comminuted after their first impact. As discussed above, on each rotor there are provided hammers. The hammers are the components that provide for the actual com- minuting of the material in said grinding chamber.

Such hammers are known. Said hammers comprise at least one open- ing, respectively, that allows for an insertion of a hammer pin of a hammer mill through the hammers. Said hammer pin is ar- ranged at the rotor disks in a conventional way, as described for example in WO 2011/086035 A2. Preferably, said hammers may be provided in an assembly, such as described in WO 2011/086035 A2.

According to a preferred embodiment of the present invention, the same number of hammers is provided in all grinding chambers arranged at the platform of the hammer mill of the present in- vention. This embodiment is preferred if the throughput of a hammer mill is to be increased, without modification of the grinding quality over the grinding chambers.

According to another preferred embodiment of the present inven- tion, the number of hammers differs among at least two grinding chambers. This embodiment is preferred if a modification of the grinding quality over the grinding chambers is desired. More hammers in a grinding chamber provide for different granularity. According to a preferred embodiment of the present invention, in each grinding chamber the hammers (more specifically their tips) have the same distance to the elements surrounding the circum- ference of said rotor.

According to another preferred embodiment of the present inven- tion, in each grinding chamber the hammers (more specifically their tips) have a different distance to the elements surround- ing the circumference of said rotor. It is particularly pre- ferred that the distance of the hammers to the elements sur- rounding the circumference of said rotor differs among at least two grinding chambers.

The distance of the hammers (more specifically their tips) to the elements surrounding the circumference of said rotor can be adjusted depending on the desired grinding quality (finer or coarser) to be achieved in said grinding chamber.

Preferably, the varying distances of the hammers to the elements surrounding the circumference of said rotor can be realized by using hammers of different lengths. For a larger distance, a short hammer is used. For a shorter distance, a longer hammer is used. If, for example, the hammers are provided as an assembly, as discussed above, hammers of varying length can be provided in one assembly.

According to the present invention, the number of possible vari- ations of hammers in one or more grinding chambers is extremely large, due to the construction kit principle applied.

The present invention is furthermore related to a method for re- vamping a hammer mill as described herein, comprising the steps of optionally removing from said platform a component selected from the group consisting of a motor and a grinding chamber, and attaching to said platform at least one component selected from the group consisting of a motor and a grinding chamber, wherein at least one of said components has not previously been attached to said platform.

Due to the modular design of the hammer mill of the present in- vention, it is easy to detach components from the platform of the hammer mill, or to attach components to the platform of the hammer mill. This has been described above in detail. As dis- cussed above, however, in the embodiment where at least one grinding chamber is fixedly connected with the platform, it can- not be easily detached. In another embodiment where all grinding chamber are releasably attached to the platform, all those grinding chambers can be easily detached therefrom.

According to a preferred embodiment of the method of the present invention, at least one additional grinding chamber, preferably 1-3 additional grinding chambers, is/are attached to said plat- form. By this, the throughput of the hammer mill can be in- creased and/or a variability in grinding quality in the differ- ent grinding chambers of the same hammer mill can be realized, if the grinding chambers have one or more of the variations de- scribed above.

According to another preferred embodiment of the method of the present invention, a motor is replaced by a motor of different size and power. By this, the throughput of the hammer mill can be increased.

The present invention is now explained in more detail with non- limiting embodiments and drawings. Fig. 1 shows a schematic representation of the modular design of a hammer mill according to the present invention.

Fig. 2 shows a perspective view of a hammer mill according to the present invention.

Fig. 3 shows a perspective view of the interior of a grinding chamber.

Fig. 4 shows grinding chambers with rotors of different diame- ters.

Fig. 5 shows hammers having different distances to an adjacent element.

In the figures, same reference numbers denote the same compo- nents.

Fig. 1 shows a schematic representation of the modular design of a hammer mill 1 according to the present invention. The hammer mill 1 comprises a platform onto which other modular components may be attached. Said platform comprises a base frame 2. Depend- ing on the size of the other modular components to be attached thereon, the base frame 2 may have a different length. In Fig.

1, a first base frame 2 (in solid lines) and a second base frame 2' (in broken lines) are shown, wherein the second base frame 2' may be used instead of the first base frame 2 if there is a need for a longer platform.

On said base frame 2, 2', a motor 3, 3' is releasably attached so as to be interchangeable. The motors 3, 3' differ with re- spect to their size and power, preferably in a range from lOOkW to 450 kW. For example, motor 3 may have a power of 100 kW, and motor 3' may have a power of 450 kW. The motor 3, 3' is connect- ed to a power supply (not shown) that is provided in said plat- form. The hammer milll comprises at least one grinding chamber 4, which may be fixedly attached or releasably attached so as to be interchangeable, and containing a rotor 7, 7' with hammers Ila, 11b, 11c, lid proved thereon, as will be discussed below with respect to Fig. 4 in more detail. However, the modular-designed hammer mill 1 of the present invention may comprise more than one grinding chamber 4. In the embodiment of Fig. 1, the hammer mill 1 comprises 4 grinding chambers 4, 4', 4'’, 4'’’, that are attached in series.

Fig. 2 shows a perspective view of a hammer mill 1 according to the present invention. On the base frame 2, there is provided a motor 3 in a releasable manner so as to be interchangeable. The motor 3 is connected to a power supply (not shown) that is pro- vided.

Moreover, in the embodiment of Fig. 2 there are two grinding chambers 4, 4' releasably attached so as to be interchangeable. Each grinding chamber 4, 4' contains an inlet 5. 5' for material to be comminuted in said grinding chamber 4, 4', and a door 6, 6' for allowing access to the interior of said grinding chamber 4, 4', for example for inspection or maintenance purposes.

Fig. 3 shows a perspective view of the interior of a grinding chamber 4. The grinding chamber 4 and the inlet 5 thereof are shown in broken lines.

In said grinding chamber 4, there is provided a rotor 7 on a ro- tor axis 7a. The rotor axis 7a is connected to the motor 3, 3' of the hammer mill 1 and causes rotation of the rotor 7 in the grinding chamber 4. On said rotor 7, there are provided hammers Ila, 11b, 11c, and lid. In the embodiment of Fig. 3, the hammers Ila, 11b, 11c, lid are provided in cages or cassettes that can be releasably at- tached to the rotor 7 so as to be interchangeable.

Around the rotor 7, elements 8a, 8b, 8c, 8d are provided so as to surround the circumference of the rotor 7. Said elements 8a, 8b, 8c, 8d are releasably attached, preferably to the inner sur- face of the grinding chamber 4, so as to be interchangeable. In the embodiment of Fig. 3, 4 elements 8a, 8b, 8c, 8d are provid- ed. The elements may be screens or impact plates, and thus serve for screening comminuted material or in the case of impact plates for conveying the material back to the rotor 7.

In the embodiment of Fig. 3, the upper two elements 8a, 8b pref- erably are impact plates, whereas the lower two elements 8c, 8d preferably are screens.

In the embodiment of Fig. 3, between the elements 8a, 8b, 8c, 8d, there are provided regrind chambers 10a, 10b, 10c for taking up coarse material that requires further comminuting. In the em- bodiment of Fig. 3, three regrind chambers 10a, 10b, 10c are provided at a distance of about 90° to each other.

In the embodiment of Fig. 3, there are furthermore provided im- pact plates 9a, 9b (only one being visible in Fig. 3) below the inlet 5.

Fig. 4 shows grinding chambers 4, 4' with rotors 7, 7' of dif- ferent diameters. In grinding chamber 4 a rotor 7 is provided that has a diameter dl. In grinding chamber 4' a rotor 7' is provided that has a diameter d2 which is larger than dl. For ex- ample, dl may be 1111 mm and d2 may be 1328 mm. With rotors 7, of different diameters, finer or coarser grinding may be achieved.

Fig. 5 shows hammers Ila, 11b having different distances da, db to an adjacent element 8d. On rotor 7, there is provided a ham- mer Ila that has a distance da to an adjacent element 8d around the circumference of said rotor 7. On rotor 7’, there is provid- ed a hammer 11b that has a distance db to an adjacent element 8d around the circumference of said rotor 7’, whereas the distance db is smaller than the distance da. With such different distanc- es, finer or coarser grinding may be achieved.