Multipurpose shredder

Abstract

A crusher (1) comprising at least one frame (2), crushing bodies, and, supported by said frame (2), a crushing chamber (4) with a longitudinal axis (XX'), an agitator comprising a rotating finger shaft coaxial with the longitudinal axis (XX') of the crushing chamber (4), a motor with a rotating part coupling to the finger shaft, and a heating system for the crushing chamber (4). The crushing chamber (4) comprising at least one first (11), second (12), and third closable inlet (13) and one outlet (14).The grinding chamber (4), the agitator, and at least the rotating part of the motor form a movable assembly that rotates about an axis (ZZ') orthogonal to the longitudinal axis (XX') of the grinding chamber (4) for moving the grinding chamber (4) between a first position in which the finger shaft extends horizontally and a second position in which the finger shaft extends vertically. The fingers of the finger shaft are removably mounted on the shaft to allow variation in the number and / or position of the fingers. Figure for the abbreviation: Fig. 1.

Description

Title of the invention: Multipurpose crusher

[0001] The present invention relates to a multi-purpose grinder with grinder and reactor function.

[0002] It relates in particular to a grinder comprising at least one frame, grinding bodies preferably in the form of balls and, carried by said frame, at least one grinding chamber delimited at least by a wall of generally cylindrical shape surrounding an axis forming the longitudinal axis of the grinding chamber, an agitator arranged at least partially inside the grinding chamber and comprising a rotary finger-carrying shaft extending coaxially with the longitudinal axis of the grinding chamber, a motor having at least one rotary part and a system for heating the grinding chamber, the grinding chamber intended to be filled at least partially with the grinding bodies being equipped with at least one inlet, called the first inlet, and an outlet, and the rotary part of the motor being couplable to the finger-carrying shaft for rotational driving of said finger-carrying shaft.

[0003] Such a mill is known for carrying out depolymerization reactions and synthesis of mineral or organic chemistry or for grinding, fractionating and functionalizing a starting compound. The designers of such mills are looking for solutions that make it easy to adapt to extremely different compositions in order to increase the spectrum of applications of such a mill.

[0004] An aim of the invention is to propose a grinder whose design makes it possible to simply adapt the grinder to different compositions or to obtain different reactions for the same starting product.

[0005] Another object of the invention is to propose a crusher whose design allows several operations to be carried out in parallel in the same chamber to simplify the production and / or treatment processes.

[0006] To this end, the invention relates to a grinder comprising at least one frame, grinding bodies preferably in the form of balls and, carried by said frame, at least one grinding chamber delimited at least by a wall of generally cylindrical shape surrounding an axis forming the longitudinal axis of the grinding chamber, an agitator arranged at least partially inside the grinding chamber and comprising a rotary finger-carrying shaft extending coaxially with the longitudinal axis of the grinding chamber, a motor having at least one rotary part couplable to the finger-carrying shaft for rotational driving of said finger-carrying shaft and a system for heating the grinding chamber, the grinding chamber intended to be filled at least partially with the grinding bodies being equipped with at least one inlet, called the first inlet, and at least one outlet, characterized in that the grinding chamber comprises at least a second inlet and a third inlet, in that said first, second and third inlets are closable inlets each equipped with at least one closing member, in that the grinding chamber, the agitator and at least the rotary part of the motor form an assembly mounted to rotate about an axis orthogonal to the longitudinal axis of the grinding chamber for movement of the grinding chamber between a first position, called horizontal, in which the finger-carrying shaft extends substantially horizontally and a second position, called vertical, in which the finger-carrying shaft extends substantially vertically and in that the fingers of the finger-carrying shaft are removably mounted on the finger-carrying shaft to be able to vary the number and / or the position of the fingers on the shaft as a function at least of the position occupied by said assembly.

[0007] The presence of at least three inlets at the grinding chamber allows the introduction into said chamber, in addition to the starting product, of liquid and / or gas allowing, if necessary, the carrying out of chemical, biochemical and physical reactions within the chamber and / or the pressurization of said chamber. The combination of removable fingers with a rotating, orientable finger-carrying shaft allows easy adaptation of the grinding to diverse and varied compositions in a short time. Such a grinder can be considered as a universal grinder adaptable to numerous situations. It should be noted that by "substantially vertical", or respectively "substantially horizontal", it is meant that the finger-carrying shaft extends vertically, or respectively horizontally, to within plus or minus 30°.

[0008] According to one embodiment of the invention, the grinder comprises a system for supplying product to the grinding chamber connectable to the first inlet of the grinding chamber, this supply system comprising a product storage container equipped with at least one outlet and a product transfer device interposed between the outlet of the storage container and the first inlet of the grinding chamber, said container being, at its outlet, coupled to the transfer device by a movable mechanical connection to be able to vary the relative positioning of the container and the transfer device according to the position occupied by said assembly. The design of the supply system allows the use of said system regardless of the orientation of said assembly.

[0009] According to one embodiment of the invention, the transfer device comprises a tubular casing having one end connectable to the first inlet of the grinding chamber, a rotating worm screw arranged coaxially inside the casing, and the mechanical connection coupling the transfer device to the outlet of the storage container extends between the outlet of the product storage container and an opening provided in said casing.

[0010] According to one embodiment of the invention, the mechanical connection has the form of a conduit capable of rotating on itself over at least part of its length.

[0011] According to one embodiment of the invention, the transfer device is equipped with at least one heating member. Preheating of the starting product can be carried out before introduction into the grinding chamber.

[0012] According to one embodiment of the invention, the or at least one of the heating members of the transfer device is an electrical resistor surrounding the casing of the worm screw.

[0013] According to one embodiment of the invention, the transfer device is equipped with at least one gaseous fluid injection orifice. Preferably, this gaseous fluid injection orifice is arranged at the level of the tubular casing.

[0014] According to one embodiment of the invention, the member for closing the first, second and third inlets of the grinding chamber is a pneumatic closing member.

[0015] According to one embodiment of the invention, the grinding chamber heating system comprises at least one electrical resistor configured to surround the generally cylindrical wall of said grinding chamber, said electrical resistor being removably mounted on said wall. The removable mounting of the grinding chamber heating system makes it possible to produce a grinding chamber that is lighter, easier to clean and easily sterilized.

[0016] According to one embodiment of the invention, the mill comprises a steam explosion unit called a “steam explosion unit” connectable to the outlet of the grinding chamber, said unit comprising at least one reactor, a steam generator capable of supplying steam to the reactor, and a reactor depressurization system. The presence of a “steam explosion” unit makes it possible to depressurize the contents of the grinding chamber and limit the risk of burning. The explosions thus take place inside the reactor of the “steam explosion” unit. The “steam explosion” process has two distinct phases: steam cracking and explosive decompression. Steam cracking consists of causing high-pressure steam to penetrate by diffusion into the structure of the treated material.Explosive decompression is caused by a sudden drop (rapid expansion) in pressure which causes the re-evaporation of some of the condensation water penetrating the material.

[0017] According to one embodiment of the invention, the grinding chamber is equipped with at least one pressure sensor and at least one exhaust member.

[0018] According to one embodiment of the invention, at least one of the fingers is, for its removably coupling to the finger-carrying shaft, equipped with at least one threaded portion for screw coupling to said shaft.

[0019] The invention also relates to a treatment method, in particular to the destruct processing and / or fractionation and / or depolymerization of a material, such as biomass or a lignocellulosic material, in particular with a view to obtaining sugars, in particular oligosaccharides and / or amino acids, in particular peptides, comprising at least one step of grinding the material in a grinder, characterized in that the grinder is of the aforementioned type. Brief description of the drawings

[0020] The invention will be better understood on reading the following description of exemplary embodiments, with reference to the appended drawings in which:

[0021] [Fig-1] represents a perspective view of a grinder according to the invention in the first horizontal position of the grinding chamber;

[0022] [Fig.2] represents a partially sectional view of a crusher according to the invention in the first horizontal position of the grinding chamber;

[0023] [Fig.3] represents a partial view of a crusher taken at the level of the axis around which the crushing chamber rotates;

[0024] [Fig.4] represents a perspective view of a crusher according to the invention in second vertical position of the grinding chamber;

[0025] [Fig.5] represents a perspective view of a grinder according to the invention in the second vertical position of the grinding chamber;

[0026] [Fig.6] represents a sectional view in the first horizontal position of the grinding chamber;

[0027] [Fig.7] represents a sectional view in the second vertical position of the chamber of grinding.

[0028] As mentioned above, the subject of the invention is a grinder 1 of the type shown in [Fig.l]. This grinder 1 comprises at least one frame 2 produced here in the form of a mechanically welded base on casters. This frame 2 can be equipped with a control unit to ensure the operation of the elements described below. This frame 2 can also be equipped with a human / machine interface such as a touch screen. This frame 2 carries at least one grinding chamber 4. This grinding chamber 4 is intended to contain at least grinding bodies 3. The grinding bodies 3 are generally balls. These balls can be, for example, made of steel, ceramic, zirconium or agate. These balls can have a diameter of between 1 mm and 20 mm. To allow efficient grinding, it is known to organize the grinding chamber with one third balls, one third product to be ground and one third vacuum.

[0029] In the example shown, this grinding chamber 4 is a cylindrical chamber delimited by a wall 5 of generally cylindrical shape surrounding an axis. This axis forms the longitudinal axis XX' of the grinding chamber 4.

[0030] The grinder 1 also comprises an agitator 6 arranged at least partially at inside the grinding chamber 4. This agitator 6 comprises a shaft 7 carrying fingers 8 extending around said shaft 7.

[0031] The shaft 7 extends coaxially with the longitudinal axis XX' of the grinding chamber 4. The fingers 8 of the finger-carrying shaft 7 are removably mounted on the finger-carrying shaft 7 8. At least one of the fingers 8, preferably each finger 8, is, for its removably coupling to the finger-carrying shaft 7 8, equipped with at least one threaded portion, such as a helical thread, for screw coupling.

[0032] The fingers may be arranged in a helix around the shaft. These fingers may also be arranged radially around the shaft 7 to form one or more series of radial fingers.

[0033] The crusher 1 also comprises a motor 9 for driving the rotation of the shaft 7 holding the fingers 8 around the longitudinal axis XX' of the crushing chamber 4. For this purpose, the motor 9 has a rotating part 91 configured to rotate around an axis YY' of rotation, this rotating part forming the motor shaft of said motor 9.

[0034] In the examples shown, the rotary part 91 of the motor 9 is coupled to the finger-carrying shaft 7 8 at least by an angle transmission and by a magnetic drive, so that the longitudinal axis XX' of the grinding chamber 4 and the axis YY' of rotation of the rotary part of the motor are orthogonal to each other.

[0035] This results in a smaller size of the crusher compared to a solution where the longitudinal axis XX' of the crushing chamber and the axis YY' of rotation of the rotating part of the motor would be aligned.

[0036] The grinder 1 further comprises a system 10 for heating the grinding chamber 4. In the example shown, the system 10 for heating the grinding chamber 4 comprises an electrical resistor 100 configured to surround the generally cylindrical wall 5 of the grinding chamber 4. This electrical resistor 100 is removably mounted on the wall 5. The control unit of the grinder 1 is configured to control the supply of electricity to the resistor 100 of the heating system 10 according to the desired heating. The removable mounting of the electrical resistor 100 makes it easier to clean and possibly autoclave the grinding chamber 4.

[0037] The grinding chamber 4 comprises several inlets and at least one outlet 14. The first inlet 11 is shown in [Fig. 2] in the form of a radial inlet opening into the cylindrical wall 5 of the grinding chamber 4. This first inlet 11 is generally intended for feeding the starting compound. This first inlet 11 can be connected to a product feeding system 16, more particularly visible in FIGS. 1, 2 and 5. This feeding system 16 comprises a product storage container 17, produced here in the form of a conical container in the manner of a funnel. The large base of the cone constitutes the inlet of the container 17 while the top of the cone forms the outlet 18 of the storage container 17.

[0038] The feed system 16 also comprises a product transfer device 19 interposed between the outlet 18 of the storage container 17 and the first inlet 11 of the grinding chamber 4. The container 17 is, at its outlet 18, coupled to the transfer device 19 by a mechanical connection 20 whose role will be described below. This mechanical connection 20 is a so-called mobile connection.

[0039] The transfer device 19 comprises a tubular, in particular cylindrical, casing 21. This tubular casing 21 has a closed end and an opposite end, shown at 210, connectable to the first inlet 11 of the grinding chamber 4, so that the longitudinal axis of the casing 21 and the longitudinal axis XX' of the grinding chamber 4 are orthogonal to each other.

[0040] This tubular casing 21 houses a worm screw 22 visible in [Fig.2]. This worm screw 22 is a rotary screw driven in rotation by a coaxial motor extending in the extension of the closed end of the tubular casing 21.

[0041] The mechanical connection 20 for coupling the transfer device 19 to the outlet 18 of the storage container 17 extends between the outlet 18 of the product storage container 17 and an opening 23 provided in said casing 21. This opening 23 opens into the casing 21 at the end of the worm screw 22 furthest from the first inlet 11 of the grinding chamber 4.

[0042] The mechanical connection 20 for coupling the transfer device 19 to the outlet 18 of the storage container 17 has the form of a conduit capable of rotating on itself, over at least part of its length.

[0043] Ideally, the transfer device 19 is equipped with at least one heating member 24. This or these heating members 24 of the transfer device 19 may each be formed by an electrical resistor surrounding the casing 21 of the worm screw 22. Thus, the product may be preheated before its introduction into the grinding chamber 4. Similarly, to assist in the decompaction of the material when it enters the transfer device 19, the transfer device 19 is equipped with at least one orifice 25 for injecting gaseous fluid arranged at the level of the tubular casing 21, in particular at the level of the end of the worm screw 22 furthest from the first inlet 11 of the grinding chamber 4.

[0044] The second inlet of the grinding chamber 4, shown at 12 in the figures, opens into the grinding chamber 4 through one end of the grinding chamber 4 as illustrated in [Fig.2]. This end of the grinding chamber 4 is also the end of the grinding chamber 4 which is provided with the outlet 14 of the grinding chamber 4. This second inlet 12 of the grinding chamber 4 is preferably an inlet for liquids.

[0045] The third inlet, shown at 13 in the figures, is preferably an inlet for gaseous fluids.

[0046] The first, second and third inlets are each provided with a closing member represented at 151 for the first inlet 11, at 152 for the second inlet 12 and at 153 for the third inlet 13.

[0047] The closure member of each inlet of the grinding chamber is a pneumatic mechanical closure member allowing intervention in environments with an explosive atmosphere.

[0048] To complete the grinding chamber 4, the latter can be equipped with at least one pressure sensor 27 and at least one exhaust member 28, such as a vent.

[0049] To give the grinder 1 increased versatility, the grinding chamber 4, the agitator 6 and at least the rotary part 91 of the motor 9 form an assembly mounted to rotate about an axis ZZ', orthogonal to the longitudinal axis XX' of the grinding chamber 4, for movement of the grinding chamber 4 between a first position, called horizontal, in which the shaft 7 holding the fingers 8 extends substantially horizontally, and a second position, called vertical, in which the shaft 7 holding the fingers 8 extends substantially vertically.

[0050] Thanks to the fact that the fingers 8 of the finger-carrying shaft 8 are removably mounted on the finger-carrying shaft 7, it is possible to vary the number and / or the position of the fingers 8 on the finger-carrying shaft 7 as a function at least of the position occupied by said assembly.

[0051] To allow such rotation of said assembly and its passage from one position to another, said assembly has an arm insertable inside bearings arranged in the frame 2, as illustrated in [Fig. 3]. This arm can be held in said bearings in at least two distinct angular positions using locking members 29 in the form of jaws capable of immobilizing the arm in each of the two angular positions corresponding, one, to the first horizontal position of the grinding chamber 4, the other, to the second vertical position of the grinding chamber 4.

[0052] A lever mounted on the arm makes it easier to move the arm from one angular position to another in the open position of the jaws.

[0053] Thanks to the fact that the mechanical connection 20 has the form of a conduit capable of rotating on itself over at least part of its length, the storage container 17 can occupy a variable position relative to the transfer device 19 by simple rotation of said mechanical connection 20. This is the case between figures 1 and 5.

[0054] Figures 1, 2 and 6 illustrate the grinding chamber in the first horizontal position. This first position is more particularly suitable in the case of starting products containing little liquid or powder. In this first position horizontal, the fingers 8 are ideally distributed over the entire length of the finger-carrying shaft 7 as illustrated in [Fig.6]. Similarly, the grinding bodies 3 which are here in the form of balls are arranged along the entire length of the grinding chamber 4.

[0055] The second vertical position, as shown in Figures 4, 5 and 7, is more particularly intended to be used in the case of starting products tending to contain a significant quantity of liquid or in certain cases solids. In this second vertical position, the fingers 8 tend to be grouped at the lower end of the finger-carrying shaft 7, as illustrated in [Fig.7], leaving the upper part of the grinding chamber 4 free of fingers.

[0056] The grinding bodies 3 are, in this case, also grouped in the lower part.

[0057] To perfect the crusher, the latter can include an explosion unit 26 at the steam, called “steam explosion”, connectable to the outlet 14 of the grinding chamber. This unit 26 comprises at least one reactor 261, a steam generator 262 containing chemical reagents capable of supplying steam to the reactor 261, and a depressurization system 263 for the reactor 261.

[0058] Example 1 below illustrates the case of an application of the grinder 1 to a composition comprising, as starting product, for the first inlet 11, a poplar wood ground from 0.5 to 2 mm, as aqueous composition for the second inlet 12 water containing, expressed as a percentage by weight relative to the total weight of the starting product, 5% of phosphoric acid, the quantity of water being equal by weight to the quantity of starting product, and as gas for the third inlet 13, pressurized air.

[0059] The crusher is in the first horizontal position of the crushing chamber. The fingers are 6 or 8 in number. The fingers are arranged in a helix or other manner. The balls forming the crushing bodies are steel balls with dimensions between 5 mm and 20 mm.

[0060] The operating conditions are, for example, as follows: the finger-carrying shaft is driven at a rotation speed of between 200 and 300 revolutions per minute for 1 hour.

[0061] The outlet 14 of the grinding chamber is connected to the steam explosion unit 26. Thus, at the outlet of the grinding chamber 4, an aqueous solution is obtained which contains lignin in solid form (insoluble in water) and an aqueous phase containing oligosaccharides. The two fractions can be separated by filtration or centrifugation after being extracted from the steam explosion unit 26.

[0062] Example 2 below illustrates the case of an application of the grinder 1 to a composition comprising, as starting product, for the first input 11, a ground poplar wood of 0.5 to 2 mm, as aqueous composition for the second input 12 water containing, expressed as a percentage by weight relative to the total weight of the starting product, 5% phosphoric acid, the quantity of water being equal by weight to 4 times the quantity of starting product, and as gas for the third inlet 13, pressurized air. The grinder is in the second vertical position of the grinding chamber. The fingers are arranged in a helix and their number is between 4 and 6. These fingers are arranged in the lower part of the grinding chamber as illustrated in [Fig.7]. The balls forming the grinding bodies are made of steel with dimensions varying between 5 and 20 mm. The outlet 14 of the grinding chamber is connected to the steam explosion unit 26. Thus, at the outlet of the grinding chamber 4, an aqueous solution is obtained which contains lignin in solid form (insoluble in water) and an aqueous phase containing oligosaccharides.The two fractions can be separated by filtration or centrifugation after being extracted from the steam explosion unit 26. In Example 2, compared to Example 1, it is found that the hemicellulose is not degraded although the starting product is similar to that of Example 1. The second vertical position of the grinding chamber allows a larger quantity of water to be used than when the grinding chamber is in the first horizontal position. The operating conditions of Example 2 can be identical to those of Example 1.

[0063] It is noted that, for the passage from the position of the crusher to another, it is sufficient: - to open the locking members 29, as shown in [Fig.3], - to modify the angular position of the arm using the lever equipping this arm for the passage of the grinding chamber 4 for example from the horizontal position, as shown in [Fig.l], to the vertical position, as shown in [Fig.4].

[0064] Once this angular movement has been carried out, it is then necessary to close the locking members to maintain the arm in the new angular position.

[0065] It is also appropriate to modify the angular position of the storage container 17 by rotation around its mechanical connection 20 to the transfer device 19, to adapt the position of this storage container 17 and allow a supply from this storage container 17 to the transfer device 19.

[0066] The above-mentioned operations and their simplicity confirm the ease of use of the crusher without compromising its versatility. If necessary, the fingers of the finger-carrying shaft can be removed or changed in position during this transition from one position to another. Similarly, fingers 8 can be added.

Claims

Claims

1. Grinder (1) comprising at least one frame (2), grinding bodies (3) preferably in the form of balls and, carried by said frame (2), at least one grinding chamber (4) delimited at least by a wall (5) of generally cylindrical shape surrounding an axis forming the longitudinal axis (XX') of the grinding chamber (4), an agitator (6) arranged at least partially inside the grinding chamber (4) and comprising a rotary finger-carrying shaft (7) extending coaxially with the longitudinal axis (XX') of the grinding chamber (4), a motor (9) having at least one rotary part (91) coupleable to the finger-carrying shaft (7) for rotating said finger-carrying shaft (7) (8) and a system (10) for heating the grinding chamber (4), the grinding chamber (4) grinding intended to be filled at least partially with the grinding bodies (3) being equipped with at least one inlet, called first inlet (11), and at least one outlet (14),characterized in that the grinding chamber (4) comprises at least a second inlet (12) and a third inlet (13), in that said first, second and third inlets (11, 12, 13) are closable inlets each equipped with at least one closing member (151, 152, 153), in that the grinding chamber (4), the agitator (6) and at least the rotary part (91) of the motor (9) form an assembly mounted to rotate about an axis (ZZ') orthogonal to the longitudinal axis (XX') of the grinding chamber (4) for movement of the grinding chamber (4) between a first position, called horizontal, in which the finger-carrying shaft (7) (8) extends substantially horizontally and a second position, called vertical,in which the finger-carrying shaft (7) (8) extends substantially vertically and in that the fingers (8) of the finger-carrying shaft (7) (8) are removably mounted on the finger-carrying shaft (7) (8) in order to be able to vary the number and / or the position of the fingers (8) on the shaft as a function at least of the position occupied by said assembly.,

2. Grinder (1) according to claim 1, characterized in that the grinder (1) comprises a system (16) for supplying product to the grinding chamber (4) connectable to the first inlet (11) of the grinding chamber (4), this supply system (16) comprising a product storage container (17) equipped with at least one outlet (18) and a product transfer device (19) interposed between the outlet (18) of the container (17) for storage and the first inlet (11) of the grinding chamber (4), said container (17) being, at its outlet (18), coupled to the transfer device (19) by a movable mechanical connection (20) to be able to vary the relative positioning of the container (17) and the transfer device (19) depending on the position occupied by said assembly.

3. Grinder (1) according to claim 2, characterized in that the transfer device (19) comprises a tubular casing (21) having an end (210) connectable to the first inlet (11) of the grinding chamber (4), a rotating worm screw (22) arranged coaxially inside the casing (21), and in that the mechanical connection (20) for coupling the transfer device (19) to the outlet (18) of the storage container (17) extends between the outlet (18) of the product storage container (17) and an opening (23) provided in said casing (21).

4. Crusher (1) according to one of claims 2 or 3, characterized in that the mechanical connection (20) has the form of a conduit capable of rotating on itself over at least part of its length.

5. Grinder (1) according to one of claims 2 to 4, characterized in that the transfer device (19) is equipped with at least one heating member (24).

6. Grinder (1) according to claim 5 taken in combination with claim 3, characterized in that the or at least one of the heating members (24) of the transfer device (19) is an electrical resistor surrounding the casing (21) of the worm screw (22).

7. Grinder (1) according to one of claims 2 to 6, characterized in that the transfer device (19) is equipped with at least one orifice (25) for injecting gaseous fluid.

8. Grinder (1) according to one of claims 1 to 7, characterized in that the member (151, 152, 153) for closing the first, second and third inlets (11, 12, 13) of the grinding chamber (4) is a pneumatic closing member.

9. Grinder (1) according to one of claims 1 to 8, characterized in that the system (10) for heating the grinding chamber (4) comprises at least one electrical resistor (100) configured to surround the wall (5) of generally cylindrical shape of said grinding chamber (4), said electrical resistor (100) being removably mounted on said wall (5).

10. Crusher (1) according to one of claims 1 to 9, characterized in that the crusher (1) comprises a steam explosion unit (26) called “steam explosion unit (26)” connectable to the outlet (14) of the grinding chamber (4), said unit (26) comprising at least one reactor (261), a steam generator (262) capable of supplying steam to the reactor (261) and a depressurization system (263) of the reactor (261).

11. Grinder (1) according to one of claims 1 to 10, characterized in that the grinding chamber (4) is equipped with at least one pressure sensor (27) and at least one exhaust member (28).

12. Crusher (1) according to one of claims 1 to 11, characterized in that at least one of the fingers (8) is for its coupling in a removable manner to the shaft (7) finger holder (8) equipped with at least one threaded part for coupling by screwing to said shaft.

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