The present invention is related to a plansi fter that comprises an increased sieve area .

Sieves find widespread application in industrial applications where a separation or sorting of materials according to their particle si ze is required . As an example , plansi fters may be mentioned .

Plansi fters for si fting floury or granular products in mills , especially in grain mills , are widely used . An example is the plansi fter Sirius MPAK from Buhler . Plansi fters have a lockable sieve module ( also called compartment herein) with at least one stack of sieve trays arranged one above the other, the mesh si ze of which can be selected variably throughout the sieve stack in order to sort the product in the desired particle si ze ranges .

To carry out the sieve movement , the plansi fter is set in a uniformly oscillating motion by means of an unbalanced drive . Conventionally, said drive is provided in a separate drive module that is arranged in the vicinity of the compartment .

The individual fractions of sieved material that have been separated from each other in the stack of sieve trays are subsequently led into an outlet frame . Said outlet frame is located in the lower part of the inner region of the respective compartment and guides the individual fractions into an appropriate outlet of the sieve module . Said outlet frame is typically made of plastic material such as polyurethane .

In known plansi fters , several compartments are usually arranged in an even number in two rows , with a drive module arranged between the two rows , as described for example in DE-2 256 307 Al . Furthermore , arrangements of two blocks of four sieve modules ( compartments ) with a drive module in between are known from EP- A- l 396 289 Al .

The plansi fters from the state of the art described above are not yet optimal .

The outlet frame in the lower part of the inner region of each compartment consumes valuable space that is thus not available for the provision of additional sieve trays . The design of the outlet frame as a plastic component involves the risk of introducing plastic material into the product stream, which is undesirable . The plastic outlet frame does also not contribute to the structural integrity of the plansi fter, since it does not provide necessary mechanical support .

It was the problem of the present invention to provide a plansi fter which overcomes the disadvantages of the state of the art described above .

The above problem is solved by the plansi fter according to claim 1 .

In detail , the present invention is related to a plansi fter comprising at least one compartment and a drive module for putting the compartment into a vibrational and/or oscillating movement , wherein said at least one compartment has a framework of outer walls forming a top region, an inner region and a bottom region, wherein in said top region there is provided at least one inlet and in the bottom region there is provided at least one outlet , wherein in the inner region there is provided a sieve stack comprising at least one sieve , preferably 2-32 sieves , more preferably 10 to 32 sieves , especially preferred 20 to 32 sieves , characteri zed in that the compartment has one outlet frame that is provided in the bottom region .

The present invention is based on the idea to provide the outlet frame not in the inner region of a compartment of the plansi fter, but rather in the bottom region thereof . This enables the provision of additional sieves in the inner region of said compartment and advantageously makes use of the bottom region of the compartment .

In the prior art , the top region, inner region and bottom region of a plansi fter are distinct regions . The inner region is a hollow space in the compartment , which is separated from the top region and the bottom region by separating walls . In said separating walls , there are openings that lead from the top region into the inner region, and from the inner region into the bottom region . In the hollow space of the inner region, there were provided both a sieve stack and an outlet frame .

The plansi fter according to the present invention di f fers from a conventional plansi fter only with respect to the outlet frame . Thus , the plansi fter according to the present invention is basically designed as described above . However, the outlet frame is not provided in the hollow space of the inner region, but in the bottom region . According to the present invention, there is preferably no longer a separating wall between the inner region and the bottom region . It is to be understood, however, that the bottom region is still outside the hollow space of the inner region and not a part of the inner space .

The plansi fter according to the present invention comprises compartments which act as sieve modules , and in which sieves stacks composed of sieves are provided . According to the present invention, any sieve that is used in a conventional plansi fter may be used in the plansi fter of the present invention .

The sieve stack is provided in the inner region of each compartment of the plansi fter . Said sieve stack comprises at least one sieve , preferably 2-32 sieves , more preferably 10 to 32 sieves , especially preferred 20 to 32 sieves . The design and operation of said sieves is known and is not discussed here in detail .

According to a preferred embodiment of the present invention, the plansi fter comprises two rows of compartments , each row consisting of at least one compartment , preferably 2 to 10 compartments . However, other arrangements of the compartments are also possible . According to said preferred embodiment of the present invention, a drive module is arranged between said two rows .

Said drive module serves to put the compartment ( s ) into a vibrational and/or oscillating movement . Preferably, said drive module is composed of at least one drive unit . Preferably, one drive unit is arranged between two compartments and can put these two compartment ( s ) into a vibrational and/or oscillating movement .

As conventionally known, the plansi fter is provided on rods which may be connected, for example to a ceiling of a hall in which the plansi fter is arranged . The plansi fter is thus cantilevered, which allows the vibrational and/or oscillating movement of the compartment ( s ) .

According to a preferred embodiment of the present invention, the plansi fter is designed such that each row has a modular design, so that compartments can be added to or removed from a row . Each compartment of the plansi fter of the present invention has a framework of outer walls forming a top region, an inner region and a bottom region . Preferably, each compartment has a cuboid structure in which said above three regions are provided .

In said top region, there is provided at least one inlet . Said inlet serves for introducing material to be sieved into the compartment . According to the present invention, the number of inlets provided on each compartment is only limited by the available space . Typically, 1 to 5 inlets , preferably 2 to 4 inlets are provided . These inlets may be connected to feed lines through which material can be transported to said compartment . From said top region, the material entering the compartment through the inlets falls into the inner region provided underneath said top region, by gravitational force . In said inner region, the sieve stack described above is provided .

According to a preferred embodiment of the present invention, the compartment ( s ) comprise a door in the front wall , allowing access to the inner region of the plansi fter . This allows inserting and/or replacing sieves into the inner region of the compartment . The door should have such a dimension that when opened suf ficient access to the inner region of the compartment is enabled .

In said bottom region, there is provided at least one outlet . Said outlet serves for removing sieved and sorted material out of the compartment . According to the present invention, the number of outlets provided on each compartment is only limited by the available space . Typically, 1 to 10 outlets , preferably 2 to 8 , more preferably 3 to 6 outlets are provided . These outlets may be connected to feed lines , such as conveying lines , through which material can be transported away from said compartment . In a plansi fter according to the prior art , the outlet frame is an area in the lower part of the inner region of a compartment in which there are arranged openings which lead to the outlets , as well as channel ramps for guiding the sieved material to the openings . In addition, there are provided (non-inclined) side walls which separate the area into pockets . These components are separate and independent from each other .

In contrast thereto , according to the present invention the outlet frame is arranged in the bottom region of the compartment , i . e . into a region that is separate from the inner region . This gives more space in the inner region of the compartment , which can be used for providing additional sieves (which would otherwise only be possible by increasing the dimensions of the plansi fter, which is not desirable ) . Accordingly, the sieving ef ficiency of the plansi fter of the present invention is improved, as compared to a conventional plansi fter .

According to a preferred embodiment of the present invention an outlet frame is provided which consists of one piece in which at least one pocket is provided, said pocket comprising a bottom surface with openings and inclined side walls .

Thus , the present invention is also related to an outlet frame for a plansi fter, said outlet frame consisting of one piece , preferably made of a metallic material , wherein said one piece comprises at least one pocket , preferably 2 to 10 pockets , more preferably 3 to 6 pockets , wherein each pocket comprises inclined side walls and an opening in the bottom surface of the pocket , the side walls being inclined towards the opening so that material may be moved over the side walls into the opening . Preferably, the outlet frame is made of a metallic material , preferably stainless steel . This avoids the use of plastic parts in the plansi fter and thus eliminates the risk of any introduction of plastic material into the product stream, thus increasing the hygiene properties of the plansi fter of the present invention . Moreover, an outlet frame of a metallic material typically has a longer service-li fe than an outlet frame of a plastic material . Finally, the metallic outlet frame of the present invention provides for an improved recyclability .

Furthermore , by providing an outlet frame of a solid and rigid material in the bottom region of the compartment , the structural support of the compartment is increased . With said outlet frame of preferably stainless steel in place , the bottom region of the compartment becomes more rigid .

According to a preferred embodiment of the present invention, the outlet frame is a deep-drawn part , preferably a deep-drawn metal sheet .

Deep-drawing is a known technique for preparing metal parts of a desired shape and does not have to be discussed here in detail . With deep-drawing, preparation of a one-piece outlet frame according to the present invention with pockets is ef ficiently possible .

According to another preferred embodiment of the present invention, the outlet frame is made by additive manufacturing . In additive manufacturing, data computer-aided-design ( CAD) software or 3D obj ect scanners are used to direct hardware to deposit material , preferably layer upon layer, in precise geometric shapes . A preferred variant of additive manufacturing is 3D printing . Additive manufacturing and the materials used in additive manufacturing are known .

The outlet frame according to a preferred embodiment of the present invention comprises at least one pocket , preferably 2 to 10 pockets , more preferably 3 to 6 pockets . These pockets are intended for taking up fractions of the material that is sieved in the sieve stack of the respective compartment of the plansi fter of the present invention . As is known, a sieve stack of a plansi fter is composed of vertically arranged sieves having di f ferent mesh si zes , wherein typically the mesh si ze of the sieves decreases from the top to the bottom of a sieve stack . Material having a particle si ze that is smaller than the mesh si ze of a respective sieve falls through the sieve onto a collecting tray from which it is conveyed by the vibrational and/or oscillatory movement of the sieve during operation with support of the oscillatory movement of sieve cleaners in between the sieve and the collecting tray to an outlet at a side of the sieve , from which it is led to a pocket of the outlet frame or back inside the sieve stack at a later point , whereas particles having a particle si ze that is larger than the mesh si ze of a respective sieve is conveyed by the vibrational and/or oscillatory movement of the sieve during operation to a sieve outlet at a side of the sieve , from which it is led to a pocket of the outlet frame or back inside the sieve stack at a later point . By repeated separation of the material on di f ferent sieves , di f ferent material fractions are obtained which are led to separate pockets of the outlet frame of the present invention, for example with the aid of lines arranged in the plansi fter .

In a preferred embodiment of the outlet frame of the present invention, each pocket comprises inclined side walls and an opening in the bottom surface of the pocket , the side walls being inclined towards the opening so that material may be moved over the side walls into the opening . Material entering the pocket from above is therewith trans ferred to the opening in the bottom surface of the pocket . Each opening in a pocket of the outlet frame , when installed in a plansi fter of the present invention, is fluidly connected to an outlet in the bottom region of the plansi fter . Thus , the material is reliably trans ferred through the openings in the outlet frame and the outlets of the compartment out of the plansi fter . Outside the compartment , the material may be transported away from the plansi fter, for example by known conveying means .

According to a preferred embodiment of the present invention, an insulation is provided outside , preferably glued to , the bottom surface and/or the inclined side walls of the outlet frame . Any material capable of insulating the outlet frame from environmental conditions such as temperature of humidity may be used for this purpose . Preferably, the insulation is provided in the form of a layer, more preferably an inj ection-molded layer .

According to a preferred embodiment of the present invention, the outlet frame is mechanically fixed, preferably releasably fixed, in the bottom region of the compartment . More preferably, said mechanical fixation is provided by screw j oints , preferably by eight screw j oints arranged in the four corners of the bottom region . Preferably, said bottom region is made from a metal such as cast iron .

Especially when the one-piece outlet frame described above is used, this fixation provides for an increased structural support in the bottom region of the compartment . The bottom region has an increased sti f fness , wherein the mechanically fixed outlet frame is mechanically loaded . This leads also to a reduction of the weight of the plansifter, since the mechanically fixed outlet frame replaces other portions that would otherwise be required for taking up mechanical load.

With the plansifter according to the present invention, different types of materials can be sieved. For example, floury or granular products such as grains may be mentioned. However, also sugars or chemical substances can be well sieved in the plansifter according to the present invention.

The present invention is also related to a method for sieving material in a plansifter described above, comprising the steps: a) Introducing material to be sieved into an inlet of a compartment of the plansifter, b) Sieving the material using a sieve stack provided in the inner region of said compartment, c) Removing the sieved material through an outlet frame provided in the bottom region of said compartment and an outlet of said compartment.

Details of said method have already been explained above.

There is a difference between sieving and sifting. In a sieving process, particles are separated from one another strictly due to their different particle sizes, allowing smaller particles to protrude through sieve openings of a certain size, whereas larger particles are held back by the sieve. In a sifting process, particles are separated from one another based on their size, shape and density, using the stratification on the sieve mesh due to the circular movement of the sieve and the product flow . Preferably, the material is removed in step c) by moving downward over inclined side walls of at least one pocket of said outlet frame to an opening in the bottom surface of the pocket of the outlet frame, the side walls being inclined towards the opening so that material is moved over the side walls into the opening .

The present invention will hereinafter be explained in more detail by reference to non-limiting examples and drawings.

Fig. 1 shows a perspective view of a plansifter according to the prior art

Fig. 2 shows the lower part of a compartment of a plansifter according to the prior art

Fig. 3 shows a perspective view of an embodiment of a plansifter according to the present invention

Fig. 4 shows an embodiment of an outlet frame according to the present invention in a plansifter.

In the drawings, the same reference numbers denote the same components .

In Figure 1, an embodiment of a plansifter 1 from the prior art is shown. The plansifter 1 comprises compartments 2, 2' acting as sieve modules. In the embodiment of Fig. 1, two rows of compartments 2, 2' are provided, wherein each row is composed of three compartments 2, 2' . Between these rows of compartments 2, 2' , there is arranged a drive module 3. In the embodiment of Fig. 1, two compartments 2, 2' can be put into vibrational or oscillatory movement by means of a drive unit arranged between them. Each compartment 2, 2' comprises a top region 2a, an inner region 2b and a bottom region 2c, which are separate from one another, and is equipped with a door 4, 4' . In Fig. 1, for illustration purposes one door 4 is removed from a compartment 2’ , so that an entire sieve stack 5 arranged in the inner region 2b of said compartment 2’ is visible.

In the plansifter 1, the sieve stack 5 comprises sieve frames equipped with insert frames, as conventionally known. The number of sieves that can be provided over the height of the inner region of the plansifter 1 is limited due to the presence of an outlet frame 9 in the lower part of the inner region 2b of the compartment 2, 2’ .

The plansifter 1 has a swing drive (not shown) in the drive module 3 which imposes a circular motion on all the sieves in the compartments 2, 2’ . For this purpose, the plansifter 1 is suspended as a cantilever on rods 8.

The material is fed to the sieve stacks 5 in the compartments 2, 2’ via inlets 6, 6' , 6' ’ provided in the top region 2a of each compartment 2, 2’ , and the sorted material is discharged via outlets 7, 7' , 2’ ’ provided in the bottom region 2c of each compartment 2, 2’ . In the embodiment of Fig. 1, one inlet 6, 6' , 6' ’ and two outlets 7, 7' , 2’ ’ are attributed to each compartment 2, 2’ . It is understood, however, that the number of inlet ports and outlet ports attributed to each compartment 2, 2’ may be adjusted if desired or necessary.

Fig. 2 shows the lower part of two compartment 2, 2' of the plansifter 1 from the prior art according to Fig. 1. In the left compartment 2, there is arranged a sieve stack 5 in the inner region of the compartment 2. Moreover, in the inner region 4 of the compartment 2, there is also arranged an outlet frame 9, below the sieve stack 5. Said outlet frame 9 comprises pockets 9a, which open into the openings 9c, which are connected to outlets 7, 7 ’ , 7' ' (not shown in Fig. 2) . Furthermore, as can be best seen in the right compartment 2’ (where no sieve stack 5 and no outlet frame 9 is inserted into the inner region 2b of said compartment 2' ) , channel ramps 9b are provided which serve for guiding the sieved material into the openings 9c. As can be seen in Fig. 2, the bottom region 2c of each compartment 2, 2’ only provides the openings 9c. The bottom region 2c is separate from the inner region 2b (which provides a hollow space for insertion of the sieve stack 5) .

Fig. 3 shows an embodiment of a plansifter 1 according to the present invention. As compared to the plansifter from the prior art according to Fig. 1, the outlet frame 9 is now provided in the bottom region 2c of each compartment 2, 2’ , instead of being provided in the inner region 2b thereof. Also here, the bottom region 2c is separate from the inner region 2b. In the bottom region 2c, no sieves can be provided. However, since the hollow space of the inner region 2b no longer has to take up the outlet frame 9, there is free space for inserting additional sieves into the inner region 2b.

Fig. 4 shows the bottom region 2c of the plansifter 1 according to the present invention (as shown in Fig. 3) in more detail. The outlet frame 9 is provided in the bottom region 2c of the compartment 2. Thus, the inner region 2b does not comprise said outlet frame 9 and can house more sieves.

Preferably, the outlet frame 9 is made of a metallic material such as stainless steel, so as to provide structural support to the plansifter. The outlet frame 9 comprises pockets 9a into which sieved material is introduced. The pockets 9a each comprise an opening 9c in their bottom surfaces. Said openings 9c are in communicating connection with outlets 7, 7', 7' ’ (shown in Fig. 3) of the compartment 2, so that sieved and sorted material exits the compartment 2 through said openings 9c and outlets 7, 7', 2’ ’ (shown in Fig. 3) .

Each pocket 9a comprises inclined side walls 9d that guide sieved material entering a pocket 9a to the respective opening 9c in the bottom surface of the pocket 9a.

In the embodiment of Fig. 4, an insulation 9e is provided underneath the bottom surface and/or the inclined side walls 9d. Preferably, said insulation to glued to the outlet frame 9.

In the embodiment of Fig. 4, the outlet frame 9 consists of one piece, preferably of a metallic material, more preferably stainless steel. Especially preferred, the one-piece outlet frame (9) is a deep-drawn part, preferably a deep-drawn metal sheet.

As shown in Fig. 4, the outlet frame 9 is provided with screws 9f for securing the side walls 9d to the bottom region 2c of the compartment 2, 2' . Furthermore, but not displayed in Fig. 4, said outlet frame 9 is mechanically fixed, preferably releasably fixed, to the bottom region 2c of the compartment 2, 2' by screw joints, preferably by eight screw joints arranged in the four corners of the bottom region 2c of the compartment 2, 2' .