Patent Description:
Such a drying device is known, for example, from United States patent publication <CIT>. The drying device is configured for drying moist solid material, and is of the type utilizing disc heat exchange elements into which a heating fluid is introduced and cooled fluid is withdrawn, the material being dried through contact with a plurality of discs in its passage through the drying device. The disc heat exchange elements are torus discs formed from relatively thin-walled circular metal plates for good heat transfer to the material and having a plurality of concentric rings of convex arcuate cross section for strength. The disc heat exchange element encloses a plurality of interconnected concentric generally toroidal chambers through which heating fluid, such as steam, is circulated successively and from the outermost of which cooled fluid, such as condensate, is withdrawn.

The drying device also has a housing with a drying chamber including a material inlet at one end and a material discharge at the other end. The material is agitated and moved through the housing by means of the disc heat exchange elements, through which the heating fluid circulates, wherein the material is contacted to remove moisture from the same.

<CIT> and <CIT> disclose drying devices according to the prior art.

The inventor has found that during use of the known disc dryer for drying small amounts of product, the product is not moved through the drying device and, therefore, remains on the bottom. A disadvantage of the known disc dryer is that the disc dryer is inefficient at drying small amounts of product.

It is an object of the present invention to ameliorate or to eliminate one or more disadvantages of the known drying device, or to at least provide an alternative drying device.

The invention is a drying device according to claim <NUM> and a method for drying according to claim <NUM>.

According to a first aspect, the invention provides a drying device for drying a product, wherein the drying device comprises:.

During use of the drying device according to the invention, a product to be dried is introduced into the drying chamber via the product inlet. Subsequently, the product is moved through the drying chamber by means of the rotating drying rotor and the rotating screw. During movement of the product through the drying chamber, thermal energy is provided to the drying chamber in order to heat the product within the drying chamber. By heating the product within the drying chamber, moisture is removed from the product such that the product is dried or substantially dried when it reaches the product outlet. The product within the drying chamber is at least agitated within the drying chamber by the multiple helical grooves of the drying rotor. The inventor has found that such drying rotor with the plurality of helical grooves is capable of agitating and moving a small amount of product within the drying chamber. By agitating and moving the product within the drying chamber, a dried or at least substantially dried product will be discharged at the product outlet. The drying device according to the invention, thus, is capable of drying small amounts of product.

Additionally, by providing the drying rotor with the plurality of helical grooves, the drying rotor has an increased outer surface for contacting the product.

It is noted that in the context of the present patent application, product has to be understood as relating to filter cakes, powders, viscous materials and/or granules. Additionally, product to be dried has to be understood as any kind of product, such as a pharmaceutical product or food product.

Moreover, during drying of the product, wet product can stick to the outer surface of the drying rotor. Product stuck to the drying rotor may cause clumping of the product or may reduce the efficiency of the drying device. Due the screw being engaged into the multiple helical grooves, rotational movement of the screw causes the screw to scrape over the surface of the multiple helical grooves, or at least a part thereof. Product stuck to the outer surface, of the plurality of helical grooves, is thereby removed from the outer surface, such that clumping is reduced or in the ideal case eliminated. Additionally, the efficiency of the drying device is improved.

In an embodiment the screw and the drying rotor are configured such that the drying rotor is driven in rotation by the screw when the screw is driven in rotation. During use, the screw is driven in rotation by means of the driving mechanism operatively connected thereto. Because of the screw being engaged into the multiple helical grooves, rotational movement of the screw will be transmitted to the drying rotor. The drying rotor, therefore, can be driven in rotation by the screw, such that only the screw has to be operatively connected to the driving mechanism. This is advantageous as only one driving mechanism is needed for driving both the drying rotor and the screw.

In an embodiment the drying rotor is configured to move the product in rotation around a rotor axis parallel to the screw axis, and wherein the screw is configured to push the product in a direction from the first end to the second end. During use, the product is moved, at least, in rotation by the drying rotor within the drying chamber. During rotation, the product passes the screw arranged substantially parallel or parallel to the drying rotor. Due to the screw being engaged into the multiple helical grooves, the product contacts the flight, preferably the pushing flight, of the screw. Upon contact, the flight of the screw pushes the product towards the second end. After being pushed forward, the product can make a next rotational movement through the drying chamber, after which the product contacts the screw again and can be pushed towards the second end again. By moving the product through the drying chamber in this manner, the stay of the product within the drying device can be extended, therewith increasing the efficiency of the drying device.

In an embodiment the plurality of helical grooves has a groove depth, and the screw has a channel depth, wherein the groove depth is substantially equal to the channel depth. As the groove depth is substantially equal to the channel depth of the screw, the screw is enabled to reach the bottom of the groove. Therefore, the groove can be contacted by the screw at substantially the complete surface thereof, such that during use, for example, all product present within the groove can be scraped from the surface at the location where the screw contacts the drying rotor. This is advantageous since it is prevented that product remains stuck to the drying rotor.

In an embodiment the drying rotor has an upper part and a lower part and the drying chamber is substantially trough-shaped. Preferably the lower and/or upper part of the drying rotor is tightly enclosed by the drying chamber. In an embodiment thereof the screw is arranged adjacent to the upper part of the drying rotor. The lower and/or upper part of the drying rotor being tightly enclosed by the trough-shaped drying chamber has to be understood as a gap between the outer surface of the drying rotor, at least the lower and/or upper part thereof, and walls of the drying chamber is kept to a minimum. During use, the grooves scrape over the surface of the walls thereby removing material optionally stuck to the walls of the drying chamber or laying at the bottom of the drying chamber. It is thus prevented advantageously that material remains stuck to the wall(s) of the drying chamber.

In an embodiment the drying device comprises an additional screw having an additional flight with an additional flight channel there between, wherein the additional screw is arranged rotatable within the drying chamber and substantially parallel to the drying rotor. In an embodiment thereof the additional screw is arranged adjacent to the upper part of the drying rotor. Preferably the additional screw is arranged remote from the screw. The additional screw can perform the same or another function as the screw arranged within the drying chamber. An advantage of providing the additional screw is that the load on the screw can be alleviated or the function of the screw can be complemented.

In an embodiment the screw and/or the additional screw are selected from the group comprising a screw with full pitch segments, a screw with half pitch segments, and a screw with three quarter pitch segments. In an embodiment thereof the screw and the additional screw are both a screw with three quarter pitch segments. By providing a screw with partially open pitch segments, the product or at least a part thereof is enabled to pass (through) the screw, in particular in a direction transversal to the longitudinal direction of the screw, substantially without being moved towards the product outlet by the screw. The ratio between the open area and the closed area of the pitch segments, at least partially, relates to a duration of stay of the product within the drying chamber. An advantage of this embodiment is that the stay of the product within the drying device can be extended or shortened in order to sufficiently dry the product. An extended stay has as an advantage that an extended period of time is available for drying the product.

In an embodiment the flight of the screw and/or the additional flight of the additional screw have a helix angle, wherein the helix angle is an acute angle. The helix angle being an acute angle has as an advantage that the product is pushed from the first end to the second end over a larger or smaller distance, which among others is determined by the helix angle. Thus, by varying the helix angle of the screw, the distance over which the product is moved by the screw or the additional screw, every time the product passes the screw or the additional screw, can be adjusted.

In the context of the present patent application, an acute angle has to be understood as an angle larger than <NUM> degrees and smaller than <NUM> degrees.

It is noted that the plurality of helical grooves of the drying rotor are under a rotor angle with respect to a longitudinal axis of the drying rotor. In an embodiment, the rotor angle is larger than the helix angle. An advantage of this embodiment is that the screw can be used for driving the drying rotor in rotation, when the screw is driven in rotation by the driving mechanism.

In an embodiment the drying device comprises at least one rotary valve provided at the product inlet and/or the product outlet of the drying device. An advantage of providing a rotary valve at the product inlet and the product outlet is that the drying device can operate in vacuum, or at least a vacuum can be applied within the drying chamber.

In an embodiment thereof the rotary valve comprises a valve housing with a product inlet, wherein the housing has a substantially cylindrical chamber defined therein, and a valve rotor arranged rotatable within the substantially cylindrical chamber, wherein the valve rotor is provided with a plurality of helical grooves at the outer surface thereof. In an embodiment thereof, when the rotary valve is placed at the inlet of the drying device, the rotary valve is positioned such that the screw engages into at least one of the helical grooves of the valve rotor. As the screw engages into at least one of the helical grooves of the valve rotor, the screw can be used for driving the valve rotor in rotation and/or for removing product within the at least one helical groove from the rotary valve. An advantage of this embodiment is that one screw, for example, can be used for driving the drying rotor and the valve rotor. The drying device is therewith kept mechanically simple.

In an embodiment, when the rotary valve is placed at the product outlet of the drying device, the rotary valve further comprises a valve screw having a valve flight with a valve flight channel there between, and a valve driving mechanism operatively connected to the valve screw and configured for driving the valve screw in rotation, wherein the valve screw is arranged rotatable within the valve housing and substantially parallel to the valve rotor, wherein the valve screw and the valve rotor are configured such that the valve flight of the valve screw engages into at least one helical groove of the valve rotor. According to this embodiment, the valve rotor can be driven in rotation by means of the valve screw while the valve screw scrapes product from at least one of the helical grooves of the valve rotor. An advantageous of this embodiment is that driving the valve rotor and scraping the helical grooves of the valve rotor is accomplished by the valve screw, whereby the rotary valve has a relatively simple mechanical construction.

Optionally, the valve screw can be positioned such that the valve screw engages into at least one helical groove of the valve rotor, and is in engagement with the at least one helical groove of the drying rotor. The valve screw, then, can be used for scraping the, in particular dried, product from the drying rotor, such that the product, in particular the dried product, is prevented from remaining stuck to the drying rotor when it has been moved through the drying chamber.

In an embodiment the drying rotor has a rotor diameter and the screw has a screw diameter, wherein the rotor diameter is larger than the screw diameter. In an embodiment thereof the heater is provided at least partially within the drying rotor. Preferably the heater comprises fluid conduits provided within the drying rotor and configured for being connected to a heat exchange fluid source. During use, the product within the drying device is dried by thermal energy provided by the heater. As the heater is provided within the drying rotor which has a larger diameter compared to the screw, a large heat exchange surface is provided within the drying device. A large heat exchange surface is advantageous for the efficiency of the drying device.

It is noted that in the context of the present patent application, any suitable heater, for example an electric heating spiral or an inductive heater, can be used.

According to the invention the drying rotor comprises a plurality of helical grooves arranged at the outer surface thereof and adjacent to each other. The plurality of helical grooves at the outer surface of the drying rotor increases the outer surface of the drying rotor. In the case that the heater is provided within the drying rotor, a large heat exchange surface is provided by the drying rotor. This is advantageous for the efficiency of the drying device.

In an embodiment the heater is provided at least partially around the drying chamber.

In an embodiment the drying device comprises an additional driving mechanism operatively connected to the drying rotor, wherein the additional driving mechanism is configured for driving the drying rotor in rotation. An advantage of this embodiment is that the screw is prevented from physically contacting the drying rotor, or vice versa, therewith preventing that the product within the drying chamber becomes damaged by being trapped between the screw and the drying rotor. Further, since the screw is prevented from physically contacting the drying rotor, or vice versa, substantially no friction will occur between the screw and the drying rotor, therewith preventing particles from loosening from the screw/drying rotor due to frictional contact there between. After all, such loosened particles are a contamination for the product within the drying device.

This disclosure also describes a rotary valve comprising:.

During use of the rotary valve, wet product can stick to the outer surface of the valve rotor. Product stuck to the valve rotor may cause clumping of the product or may reduce the efficiency of the rotary valve. Due the valve screw being engaged into the at least one helical groove, rotational movement of the valve screw causes the valve screw to scrape over the surface the at least one helical groove, or at least a part thereof. Product stuck to the outer surface, of the at least one helical groove, of the valve rotor is thereby removed from the outer surface, such that clumping is reduced or in the ideal case eliminated. Additionally, the efficiency of the valve rotor is improved.

In an embodiment the valve screw and the valve rotor are configured such that the valve rotor is driven in rotation by the valve screw when the valve screw is driven in rotation. Thus, the valve rotor can be driven in rotation by means of the valve screw while the valve screw scrapes product from at least one of the helical grooves of the valve rotor. An advantage of this embodiment is that driving the valve rotor and scraping the helical grooves of the valve rotor is accomplished by the single valve screw, whereby the rotary valve has a relatively simple mechanical construction.

In an embodiment the valve screw is arranged between the valve rotor and the product outlet.

In an embodiment the rotary valve comprises an additional valve driving mechanism operatively connected to the valve rotor, wherein the additional valve driving mechanism is configured for driving the valve rotor in rotation.

According to a second aspect, the invention provides a method for drying a product by means of a drying device according to the first aspect of the invention, wherein the method comprises the steps of:.

wherein the step of moving and agitating the product within the drying chamber comprises the step of scraping over the surface of the multiple helical grooves by means of the screw.

The method according to the invention has at least the same advantages as mentioned in relation to the drying device according to the first aspect of the invention.

In an embodiment the step of moving and agitating the product within the drying chamber comprises the step of driving the screw in rotation.

In an embodiment the step of moving and agitating the product within the drying chamber comprises the step of forcing the product in a direction from the first end to the second end by means of the screw.

The invention will be elucidated on the basis of exemplary embodiments shown in the attached drawings, in which:.

A drying device <NUM> according to an embodiment of the invention is shown in <FIG> and <FIG>. The drying device <NUM> comprises a housing <NUM> in which a drying chamber <NUM> is defined. The housing <NUM> is provided with an inlet <NUM> at a first end <NUM> of the housing, wherein the inlet <NUM> is configured for introducing product to be dried into the drying chamber <NUM> of the housing <NUM>. The housing <NUM> is also provided with an outlet <NUM> at a second end <NUM> opposite to the first end <NUM> of the housing <NUM>. The outlet <NUM> is configured for discharging dried product from the drying chamber <NUM>. The housing <NUM> has a first closing lid <NUM> at the first side <NUM> and a second closing lid <NUM> at the second side <NUM> of the housing <NUM> in order to close off the drying chamber <NUM>. The drying chamber <NUM> is trough-shaped as shown in <FIG> and <FIG>.

A support bracket <NUM> is attached to the housing <NUM>, which support bracket <NUM> is provided with two sliding rails <NUM> extending from the support bracket <NUM> towards and beyond the first side <NUM> of the housing <NUM>. The first closing lid <NUM>, and the parts connected thereto, is connected slidable to the sliding rails <NUM>. The first closing lid <NUM> can be slid along the sliding rails <NUM> in order to get access to the drying chamber <NUM>, as is shown in <FIG>.

As shown in <FIG>, the drying device <NUM> further comprises a particulate filter <NUM> attached to an exhaust port <NUM> of the housing <NUM>, which particulate filter may be connected to non-shown gas extraction equipment, such as a vacuum pomp. The particulate filter <NUM> is in fluid communication with the drying chamber <NUM> via the exhaust port <NUM> and is configured for preventing particles from leaving the drying device <NUM>, at least during creating a vacuum within the drying chamber <NUM>.

The drying device <NUM> further comprises a drying rotor <NUM> having a plurality of helical grooves <NUM>. In the context of the present application, helical has to be understood as spiraling around the longitudinal axis thereof. The drying rotor <NUM> is arranged rotatable within the drying chamber <NUM> of the housing <NUM> about a rotation axis K and attached rotatable to the first closing lid <NUM> of the housing <NUM>. The helical grooves <NUM> of the drying rotor <NUM> are extending over the outer surface of the drying rotor <NUM>, thereby forming a toothed outer surface of the drying rotor <NUM> with a plurality of teeth <NUM>. Each of the helical grooves <NUM> does extend over a partial revolution in the circumferential direction of the drying rotor <NUM>. The outer surface of the drying rotor <NUM> is increased by providing the helical grooves <NUM> in comparison with a non-shown drying rotor with a smooth outer surface.

As shown in <FIG>, a fluid chamber <NUM> is defined within the drying rotor <NUM>. The fluid chamber <NUM> is adapted for holding a heat exchange fluid which is in thermal contact with the outer surface of the drying rotor <NUM>. At a side face <NUM>, the fluid chamber <NUM> has a fluid opening <NUM> for introducing the heat exchange fluid into the fluid chamber <NUM> or to enable the heat exchange fluid to exit the fluid chamber <NUM>. A rotating fluid connector <NUM> is coupled to the side of the side face <NUM> facing away from the fluid chamber <NUM>. The rotating fluid connector <NUM> comprises a rotating part <NUM> connected to the drying rotor <NUM> and a stationary part <NUM> connected to the first closing lid <NUM> of the housing <NUM>. Because of the rotating fluid connector <NUM>, the drying rotor <NUM> is enabled to rotate with respect to the first closing lid <NUM>. A first fluid channel <NUM> is provided within the rotating part <NUM>, which is in fluid communication with a first fluid port <NUM> within the stationary part <NUM>. A second fluid channel <NUM> is provided within the rotating part <NUM>, which is in fluid communication with a second fluid port <NUM> within the stationary part <NUM>. The first fluid port <NUM> and the second fluid port <NUM> are configured for supplying heat exchange fluid to the fluid chamber <NUM> and to remove heat exchange fluid from the fluid chamber <NUM>, respectively. The first and second fluid ports <NUM>, <NUM> can be connected to a non-shown heat exchange system.

As shown in <FIG> the drying chamber <NUM> has a substantially trough-shaped cross-section, wherein the drying rotor <NUM> is positioned in the lower part of the drying chamber <NUM>. The drying rotor <NUM> has an outer diameter DR and the drying chamber <NUM> is dimensioned, such that the teeth <NUM> of the drying rotor <NUM> are enabled to scrape the inner wall <NUM>, in particular the inner bottom wall <NUM>, of the drying chamber <NUM> when the drying rotor <NUM> is arranged within the drying chamber <NUM>. By scraping the inner wall <NUM>, in particular the inner bottom wall <NUM>, a product to be dried inserted into the drying device <NUM> is prevented from staying behind or staying stuck to the inner wall <NUM> or the inner bottom wall <NUM>.

As shown in <FIG> the drying device <NUM> further comprises a screw <NUM> having a shaft <NUM> and a flight <NUM> provided spiraling around and at an outer surface of the shaft <NUM>. The shaft <NUM> is provided with a first connecting end <NUM> at a first side thereof, wherein the first connecting end <NUM> is adapted to be rotatable received within a first connecting channel <NUM> arranged at the first closing lid <NUM> of the housing <NUM>, in particular at the side of the first closing lid <NUM> facing the drying chamber <NUM>. The first connecting end <NUM> of the screw <NUM> is operatively connected to a magnetic drive <NUM> which is partially shown in <FIG>. The magnetic drive <NUM> is configured for driving the screw <NUM> in rotation. By providing the magnetic drive <NUM> for driving the screw <NUM>, the screw <NUM> can be driven without the need for providing a physical linkage between the magnetic drive <NUM> and the screw <NUM>. Any leakage problems which may arise with such a physical linkage are thereby avoided. The screw <NUM> further includes a second connecting end <NUM> configured for being received rotatable within a second connecting channel <NUM> provided at the second closing lid <NUM> of the housing, in particular at the side thereof facing the drying chamber <NUM>. The screw <NUM>, thus, is rotatable received within the first and second connecting channels <NUM>, <NUM> and enclosed between the first closing lid <NUM> and the second closing lid <NUM> of the housing <NUM>.

As shown in <FIG> and <FIG> the screw <NUM> is arranged substantially parallel to the drying rotor <NUM>. The screw <NUM> and the drying rotor <NUM> are arranged, such that the flight <NUM> of the screw <NUM> engages into multiple helical grooves <NUM> of the drying rotor <NUM>. The flight outside diameter, the shaft outer diameter and the depth of the helical grooves <NUM> are chosen such that the circumference of the flight <NUM> of the screw <NUM> is directly adjacent to or into contact with at least the bottom of the multiple helical grooves <NUM>.

The screw <NUM> extends beyond the drying rotor <NUM> in a drying direction P extending from the first end <NUM> of the housing <NUM> to the second end <NUM> of the housing <NUM>. A space is defined between the end of the drying rotor <NUM> facing the second closing lid <NUM> of the housing <NUM> and the second closing lid <NUM>. Dried product is removed from the drying rotor <NUM> and transported into the space at the end of the drying rotor <NUM> facing the second closing lid <NUM> of the housing <NUM> by means of the screw <NUM>. Optionally, at least one tooth <NUM> of the drying rotor <NUM> also extends beyond the drying rotor <NUM> in the drying direction P and into the space at the end of the drying rotor <NUM> facing the second closing lid <NUM> of the housing <NUM> by means of the screw <NUM>. By means of the extending tooth <NUM>, product within the space is prevented from sticking to the walls of the drying chamber, defining the space. During use, the screw <NUM> is driven in rotation by means of the magnetic drive <NUM>. Because of the screw <NUM> being engaged into multiple helical grooves <NUM>, a rotating movement of the screw <NUM> can be transferred to the drying rotor <NUM>. The drying rotor <NUM> is then also driven in rotation by means of the magnetic drive <NUM> via the screw <NUM>.

It is possible that, during use, product to be dried gets stuck at the surface of the helical grooves <NUM>. As the circumference of the flight <NUM> of the screw <NUM> is directly adjacent to or into contact with at least the bottom of the engaged helical grooves <NUM>, any product stuck within the respective helical groove <NUM> is scraped from the respective groove <NUM> by the flight <NUM> of the screw <NUM> when the screw is driven in rotation.

Additionally, as the flight <NUM> of the screw <NUM>, during use, moves through the helical grooves <NUM> of the drying rotor <NUM>, the product present within the helical grooves <NUM> of the drying rotor <NUM> is pushed forward within the respective helical groove <NUM> in the drying direction P extending between the first side <NUM> and the second side <NUM> of the housing. After being pushed forward, the product to be dried makes at least one revolution around the rotation axis K of the drying rotor <NUM> while remaining in the respective helical groove <NUM>. After the at least one revolution, the product to be dried abuts against the screw <NUM> and is pushed forward again. These steps are repeated until the product to be dried reaches the outlet <NUM> of the housing <NUM>. The product to be dried is basically moved through the drying chamber <NUM> step-by-step, therewith enabling to extend the length of stay of the product within the drying chamber <NUM>.

As shown in <FIG>, a rotary valve <NUM> is provided at the inlet <NUM> of the drying device <NUM>. The rotary valve <NUM> comprises a circular housing <NUM> with an upper part <NUM> and a lower part <NUM>. The upper part <NUM> is provided with an inlet duct <NUM> with an inlet opening <NUM> for inserting product to be dried into the circular housing <NUM> of the rotary valve <NUM>. The lower part <NUM> is provided with an outlet opening <NUM> for enabling product to be dried to exit the rotary valve <NUM> and to enter the drying chamber <NUM>. A valve rotor <NUM> is arranged rotatable around a first valve rotation axis <NUM> within the circular housing <NUM>. As shown in <FIG> the valve rotor <NUM> comprises a plurality of helical grooves <NUM> at the outer surface thereof. The plurality of helical grooves <NUM> forms a plurality of teeth <NUM> between the helical grooves <NUM>. The rotary valve <NUM> is shaped, such that the tops <NUM> of the teeth <NUM> are directly adjacent to an inner wall <NUM> of the circular housing <NUM>, wherein the inner wall <NUM> defines a valve chamber <NUM> in which the valve rotor <NUM> is arranged. The inlet duct <NUM> ends at the circumference of the valve rotor <NUM>, therewith preventing that air can flow freely into the drying chamber <NUM>.

A rotary valve <NUM> is also provided as the outlet <NUM> of the drying device <NUM>. The rotary valve <NUM> comprises a circular housing <NUM> with an upper part <NUM> and a lower part <NUM>. The upper part <NUM> is provided with an inlet duct <NUM> with an inlet opening <NUM> for allowing dried product to enter the circular housing <NUM> of the rotary valve <NUM>. The lower part <NUM> is provided with an outlet opening <NUM> for enabling product to be dried to exit the rotary valve <NUM>. A valve rotor <NUM> is arranged rotatable around a first valve rotation axis <NUM> within the circular housing <NUM>. The valve rotor <NUM> comprises a plurality of helical grooves <NUM> at the outer surface thereof. The plurality of helical grooves <NUM> forms a plurality of teeth <NUM> between the helical grooves <NUM>. The rotary valve <NUM> is shaped, such that the tops <NUM> of the teeth <NUM> are directly adjacent to an inner wall <NUM> of the circular housing <NUM>, wherein the inner wall <NUM> defines a valve chamber <NUM> in which the valve rotor <NUM> is arranged. A valve screw <NUM> having a valve flight <NUM> is provided downstream of the valve rotor <NUM>. The valve screw <NUM> is operatively connected to a driving mechanism <NUM> for driving the valve screw <NUM> in rotation around a further valve rotation axis <NUM>. The valve screw <NUM> is arranged parallel to the valve rotor <NUM>. The valve screw <NUM> and the valve rotor <NUM> are configured, such that the valve flight <NUM> engages into one or more of the helical grooves <NUM> of the valve rotor <NUM>. The valve screw <NUM>, therefore, can be used for driving the valve rotor <NUM> in rotation and/or to scrape dried product from the one or more helical grooves <NUM> of the valve rotor <NUM>.

Because of the valve rotors <NUM>, <NUM>, it is possible to apply a vacuum within the drying chamber <NUM> which is generated by a vacuum pomp connected to the particulate filter <NUM>.

Another embodiment of the drying device <NUM> is shown in <FIG>. The drying device <NUM> comprises substantially the same features as the drying device <NUM> as shown in <FIG>, <FIG>, <FIG>, <FIG> and <FIG>, wherein to corresponding features is referred by the same reference number increased by <NUM>. For the sake of brevity, corresponding features are not introduced again.

The drying device <NUM> further comprises a second screw <NUM> with a shaft <NUM> and a flight <NUM> provided spiraling around and at an outer surface of the shaft <NUM>. The shaft <NUM> is rotatable connected to the first closing lid <NUM> of the housing <NUM>, in particular at the side of the first closing lid <NUM> facing the drying chamber <NUM>. The additional screw <NUM> is operatively connected to the magnetic drive <NUM> or to a non-shown additional magnetic drive for driving the additional screw <NUM> in rotation. The additional screw <NUM> further includes a second connecting end <NUM> configured for being received rotatable within a second connecting channel <NUM> provided at the second closing lid <NUM> of the housing, in particular at the side thereof facing the drying chamber <NUM>.

As shown in <FIG> the additional screw <NUM> is arranged substantially parallel to the drying rotor <NUM>. The additional screw <NUM> and the drying rotor <NUM> are arranged, such that the flight <NUM> of the additional screw <NUM> engages into one or more of the helical grooves <NUM> of the drying rotor <NUM>. In accordance with the screw <NUM>, the additional screw <NUM> can be used, during use, for: driving the drying rotor <NUM> in rotation by transferring the rotation movement of the additional screw <NUM> to the drying rotor <NUM>; scraping any product stuck within a respective helical groove <NUM> by the flight <NUM> of the additional screw <NUM> when the screw is driven in rotation; and/or pushing forwards product to be dried within a respective helical groove <NUM> of the drying rotor <NUM>.

The additional screw <NUM> can be used as an addition to the screw <NUM>, or to take over one of the functions of the screw <NUM>.

Another embodiment of the drying device <NUM> according to the invention is schematically shown in <FIG>. The shown drying device <NUM> has substantially the same features as the drying device <NUM> as shown in <FIG>, and re-introduction of corresponding features is omitted.

As best shown in <FIG> and <FIG> the drying device <NUM> comprises a drying rotor <NUM> with a number of helical grooves <NUM> provided at the outer surface of the drying rotor <NUM>. A screw <NUM> with a flight <NUM> is placed adjacent to the drying rotor <NUM>, such that the flight <NUM> engages into the helical grooves <NUM> of the drying rotor <NUM>. The product outlet of the drying device <NUM> comprises a rotary valve with a valve rotor <NUM>. The valve rotor <NUM> has a plurality of helical grooves <NUM> provided at the outer surface thereof. An outlet screw <NUM> with a flight <NUM> is located between the drying rotor <NUM> and the valve rotor <NUM>, such that the flight <NUM> engages into the helical grooves <NUM> of the valve rotor <NUM> and the helical grooves <NUM> of the drying rotor <NUM>. The outlet screw <NUM> extends over a part of the drying rotor <NUM> in the longitudinal direction thereof and is configured for removing the product from the helical grooves <NUM> of the drying rotor <NUM> and for introducing the product into the rotary valve.

Different alternatives of screws to be used in a drying device according to an embodiment of the invention are shown in <FIG>, in which figures the drying rotor <NUM> is included for the sake of clarification. <FIG> shows a first alternative of a screw <NUM>. The screw <NUM> comprises a shaft <NUM> and a flight <NUM> which is arranged spiraling around the shaft <NUM>. The screw <NUM> is also called a screw <NUM> with full pitch <NUM> segments. As indicated, a helix angle α between the shaft <NUM> and the flight <NUM> is about <NUM>°.

An alternative of the screw <NUM> is shown in <FIG>. The screw <NUM> comprises a shaft <NUM> and a flight <NUM> which is arranged spiraling around the shaft <NUM>. The screw <NUM> is a screw <NUM> with an interrupted flight <NUM>, in particular a screw <NUM> with three quarter pitch <NUM> segments. This has to be understood as that the flight <NUM> extends over three quarter of a pitch <NUM> and then is absent for a quarter of the pitch <NUM>. By using the screw <NUM> with three quarter pitch <NUM> segments, the open area for the product has increased in comparison with the screw <NUM> of <FIG>. The larger the open area for the product to pass the screw, the longer the duration of stay of a product to be dried within a drying device can be increased.

A further alternative of the screw <NUM> is shown in <FIG>. The screw <NUM> comprises a shaft <NUM> and a flight <NUM> which is arranged spiraling around the shaft <NUM>. The screw <NUM> has full pitch <NUM> segments. As indicated, a helix angle α between the shaft <NUM> and the flight <NUM> is smaller than <NUM>°. Because of the smaller helix angle α, the amount of pushing forward material within a helical groove is increased.

Another alternative of a screw <NUM> is shown in <FIG>. The screw <NUM> comprises first and second connectors <NUM> for connecting the screw <NUM> rotatable to a non-shown driving mechanism and/or to a non-shown connecting channel. The screw <NUM>, further, is provided with a coreless flight <NUM> secured to the first and second connectors <NUM>. Because of the coreless flight <NUM>, the screw <NUM> has a large open area through which product can pass, and thus has an increased duration of stay.

<FIG> shows a further alternative of a screw <NUM>. The screw <NUM> includes a shaft <NUM> and a flight <NUM> which is arranged spiraling around the shaft <NUM>. The flight <NUM> has a leading edge <NUM> and a trailing edge <NUM>, wherein a wedge-shaped filler <NUM> is provided between the trailing edge <NUM> and the shaft <NUM>. Because of the wedge-shaped filler <NUM> the open area through which product can pass, is reduced in comparison with, for example, the screw <NUM> as shown in <FIG>. Due to the reduced open area, less product can pass through the screw <NUM> and, therefore, the forward movement of the product is increased. The higher the forward movement of the product, the shorter the duration of stay of the product within the housing <NUM>.

Another alternative of a screw <NUM> is shown in <FIG>. The screw <NUM> has a shaft <NUM> and a flight <NUM> arranged spiraling around the shaft <NUM>. The flight <NUM> has a leading edge <NUM> and a trailing edge <NUM>, wherein a first wedge-shaped filler <NUM> is provided between the leading edge <NUM> and the shaft <NUM> and a second wedge-shaped filler <NUM> is provided between the trailing edge <NUM> and the shaft <NUM>. Compared with the screw <NUM> shown in <FIG>, the open area of the screw is reduced, whereby the forward movement of the product is increased.

Further alternatives of screws to be used wherein aspects of the screw, such as channel width, flight diameter, channel flight, etc. can be modified, are possible within the scope of the invention.

An embodiment of a rotary valve <NUM>, not within the scope of the invention, is shown in <FIG>. The rotary valve <NUM> comprises a circular housing <NUM> with an upper housing part <NUM> and a lower housing part <NUM>. A rotor chamber <NUM> is defined within the circular housing <NUM>, which rotor chamber <NUM> is delimited by a lower chamber inner wall <NUM> of the lower housing part <NUM> and an upper chamber inner wall <NUM> of the upper housing part <NUM>. An additional housing member <NUM> is provided at the upper chamber inner wall <NUM> of the upper housing part <NUM>. The upper housing part <NUM> has an inlet channel <NUM> with an inlet opening <NUM> for inserting a material into the rotary valve <NUM> and in fluid communication with the rotor chamber <NUM>. The lower housing part <NUM> has an outlet channel <NUM> with an outlet opening <NUM> for enabling an inserted material to exit the rotary valve <NUM> and in fluid communication with the rotary chamber <NUM>.

The rotary valve <NUM> further comprises a valve rotor <NUM> having a plurality of helical grooves <NUM> at the outer surface thereof. Because of the helical grooves <NUM>, the outer surface of the valve rotor <NUM> comprises a plurality of teeth <NUM>. The valve rotor <NUM> is arranged rotatable around a first valve rotation axis <NUM> within rotor chamber <NUM>. As shown in <FIG> the rotary valve <NUM> is dimensioned, such that the tops <NUM> of the teeth <NUM> are directly adjacent to the additional housing member <NUM> and the lower chamber inner wall <NUM> op het lower housing part <NUM>. The inlet channel <NUM> ends at the circumference of the valve rotor <NUM>, therewith preventing that air or a material can flow freely through the rotary valve <NUM>.

As shown in <FIG> a valve screw <NUM> is provided within the outlet channel <NUM> downstream of the valve rotor <NUM> and upstream and upstream of the outlet opening <NUM>. The outlet channel <NUM> comprises a circular channel part <NUM> for receiving the valve screw <NUM>. The valve screw <NUM> has a valve screw shaft <NUM> and a valve screw flight <NUM> arranged helically around and at the outer surface of the valve screw shaft <NUM>. A rotation spindle <NUM> extends through the valve screw shaft <NUM>, which rotation spindle <NUM> is operatively connected to a magnetic drive <NUM> via a drive coupling <NUM>, e.g. a magnetic drive coupling <NUM>. The magnetic drive <NUM> is configured for driving the rotation spindle <NUM> in rotation and comprises a non-shown magnet for transferring a rotation movement of the magnetic drive <NUM> to the rotation spindle <NUM> via the drive coupling <NUM>.

As shown in <FIG> the valve screw <NUM> is arranged parallel to the valve rotor <NUM>. The valve screw <NUM> and the valve rotor <NUM> are configured, such that the valve screw flight <NUM> engages into one or more of the helical grooves <NUM> of the valve rotor <NUM>. When the valve screw <NUM> is driven in rotation by the magnetic drive <NUM> around the rotation spindle <NUM>, the rotational movement of the valve screw <NUM> is transferred to the valve rotor <NUM> due to the engagement between the valve screw <NUM> and the valve rotor <NUM>. The valve screw <NUM>, therefore, can be used for driving the valve rotor <NUM> in rotation.

Additionally, it can be seen in <FIG> that the valve screw flight <NUM> moves through the helical grooves <NUM> of the valve rotor <NUM> during driving of the valve rotor <NUM>. As the valve screw flight <NUM> moves through each of the helical grooves <NUM>, the valve screw <NUM> may remove and/or any material from the respective helical groove <NUM> through which it is currently moving. It is therewith prevented that any material remains stuck within the helical grooves <NUM>, therewith increasing the efficiency of the valve rotor <NUM>.

As shown in <FIG> the rotary valve <NUM> is further provided with a clamp <NUM>. The clamp <NUM> is configured for, for example, clamping a non-shown transport duct or a non-shown collecting bag to the outlet channel <NUM> of the rotary valve <NUM>. Any material exiting the rotary valve <NUM>, therefore, may be received in the transport duct for transport to a further processing device or in the collecting bag for storage of the material.

It is noted that aspects mentioned in relation to the drying device, such as variants of the screw, are also applicable in relation to the claimed, described and shown rotary valve, and vice versa.

Claim 1:
Drying device (<NUM>; <NUM>; <NUM>) for drying a product, wherein the drying device (<NUM>; <NUM>; <NUM>) comprises:
- a housing (<NUM>; <NUM>) having a drying chamber (<NUM>; <NUM>) defined therein, and having a product inlet (<NUM>; <NUM>) at a first end (<NUM>; <NUM>) and an product outlet (<NUM>; <NUM>) at a second end (<NUM>; <NUM>);
- a drying rotor (<NUM>; <NUM>; <NUM>) being arranged rotatable within the drying chamber (<NUM>; <NUM>), wherein the drying rotor (<NUM>; <NUM>; <NUM>) comprises a plurality of helical grooves (<NUM>; <NUM>; <NUM>) arranged at the outer surface thereof and adjacent to each other;
- a screw (<NUM>; <NUM>; <NUM>; <NUM>) having a flight (<NUM>; <NUM>; <NUM>) with a flight channel there between, wherein the screw is arranged rotatable within the drying chamber and substantially parallel to the drying rotor;
- a driving mechanism (<NUM>; <NUM>) operatively connected to at least the screw, which driving mechanism is configured for driving the screw in rotation around a screw axis; and
- a heater for providing thermal energy to at least a part of the drying chamber in order to dry the product present within the drying chamber,
wherein the drying rotor (<NUM>; <NUM>; <NUM>) and/or the screw (<NUM>; <NUM>; <NUM>; <NUM>) at least are configured for moving the product from the first end to the second end,
wherein the screw (<NUM>; <NUM>; <NUM>; <NUM>) and the drying rotor (<NUM>; <NUM>; <NUM>) are configured such that the flight (<NUM>; <NUM>; <NUM>) of the screw engages into multiple helical grooves (<NUM>; <NUM>; <NUM>) of the drying rotor (<NUM>; <NUM>; <NUM>),
wherein the screw (<NUM>; <NUM>; <NUM>; <NUM>) and the drying rotor (<NUM>; <NUM>; <NUM>) are configured such that, during use, the screw (<NUM>; <NUM>; <NUM>; <NUM>) scrapes over the surface of the multiple helical grooves (<NUM>; <NUM>; <NUM>).