DE102009036929A1 - Transport system for transporting flat article or substrate in continuous fluid treatment plant, has holding device to hold flat articles and comprising shaft that includes bristles for exclusive transmission of force that holds articles - Google Patents

Abstract

The system has a holding device (1) for holding flat articles and comprising a rotatably supported shaft (2). The shaft has bristles (3) for exclusive transmission of force that holds the articles. Another holding device holds a lockable slot hole, where the shaft is supported in the slot hole. The shaft is driven in a transport direction. The bristles are arranged completely on an outer surface (4) of the shaft. The bristles comprise a material e.g. polypropylene, polyvinylidene fluoride, polybutylene terephthalate, rubber and natural fibers. The shaft has a cover made of PVC. An independent claim is also included for a method for transporting a flat article.

Description

The invention relates to a transport system for transporting flat objects resting on at least one transport means in a fluid treatment system, with a device for holding down the flat objects. Furthermore, the invention relates to a method for transporting flat objects using the aforementioned transport system.

In the context of many manufacturing processes in the field of semiconductor technology, a so-called fluid treatment of the most fracture-sensitive, flat objects or substrates takes place. This fluid treatment can serve, for example, for the purification of the substrates, but also include a wet-chemical treatment. In order to achieve high throughputs and a consistent quality, the treatment of these objects is preferably carried out in a so-called continuous or inline system. Both continuous systems for one as well as for two-sided treatment of the substrates are known. Essential components of such a system are a liquid tank and a transport system with which the substrates to be treated are preferably transported horizontally through the liquid tank. The transport system has, for example, a driven belt or a plurality of rollers and rollers arranged one behind the other and at least partially driven, on which or the substrates are transported forward.

A device for one-sided treatment is for example from the document DE 10 313 127 known. In this case, the transport of the substrates takes place in such a way that only the underside to be treated comes into contact with the treatment liquid.

The publication PCT / EP 03/03739 shows a continuous flow system in which the substrates are completely surrounded by a liquid during the passage.

The large surface of the objects on the one hand and their low mass on the other hand often lead to an unwanted floating them during transport on the liquid bath. This may result in unregulated transport and even damage to the items. This effect is enhanced by the formation of bubbles, which is often observed during wet-chemical treatment. These problems are more pronounced when the substrates are to be completely immersed in the treatment liquid during transport.

In order to ensure a safe, if necessary. Spontaneous guiding of the substrates, it is therefore advantageous to additionally secure them from above against floating or leaving the desired track. For this purpose, for example, from the prior art DE 12 56 963 B and the DE 31 40 546 A known. These documents disclose hold-down, which are made in two parts of an axis and a sleeve, wherein the inner diameter of the sleeve is greater than the outer diameter of the axis and between the axis and sleeve is an elastic coupling. From the US 5,711,806 is a transport system for transporting flat cargo through chemical baths known, which is provided with transport rollers and holders and in which the hold-down are resiliently mounted. Finally, the document discloses PCT / EP 03/03739 Hold-down rollers, in which the coupling between the inner shaft and the outer sleeve takes place via positively mounted pins, so that deflections of the often very long shaft do not affect the geometric shape of the sleeve. As a result, at any time a uniform distribution of the pressure force can be achieved. However, the contact pressure in this as well as in other, sleeve-based solutions is determined solely by the weight of the sleeves, so that an adjustment of the contact pressure is possible only by replacing the sleeves.

While the latter document takes account of both weight and temperature-related changes in geometry of the shaft, in particular the passage of differently thick flat objects can lead to damage of the same. Also, said two-part construction is disadvantageous. On the one hand, such a hold-down is relatively complex and constructed to mount. On the other hand, at least the outer sleeve must be of uniform geometry and very good surface quality in order to avoid damage to the substrates. Therefore, such hold-downs are also expensive.

In order to limit the contact of the blank holder with the substrate or object to a necessary minimum and at the same time to minimize the area covered by the blank holder, contact elements are fixed on the outside of the sleeve whose diameter defined by them is larger than the largest diameter of the blank holder. For this purpose, O-rings are used in particular. Due to the point or line contact, the contact area between the O-rings and the substrates is low. Accordingly, the surface pressure to be transmitted to achieve a sufficiently high holding force is correspondingly high. Damage up to wafer break due to local overload is the result. In addition, a substrate can gradually leave its predetermined track with a longer passage.

In order to keep the substrates in a desired track, according to the prior art additionally annular track elements are provided, which have a distance from each other, which exceeds the width of the substrates slightly. However, in the case of substrates of different widths or already too far from a track, the described solution is not applicable. In addition, in the worst case, a mechanical tilting of the substrate can occur, which in turn can lead to a fracture of the same.

Finally, hold-downs according to the prior art are often composed of several components and partially complex. Depending on the design, the often long hold-down shafts must be manufactured with high precision in order to produce the same contact force at each point along their axis. The often massive construction leads to relatively high costs. Likewise, a change in damage to the hold-down, in the case of a changed substrate geometry, or to change the contact pressure often only with greater loss of time to realize.

The object of the invention is therefore to provide a transport system with a device for holding down (hold-down), with which the described disadvantages of the prior art are overcome. In particular, the hold-down should be inexpensive to manufacture, and regardless of temperature and quality fluctuations ensure a safe function in terms of holding down the substrates as well as the tracking or Spurfindung the same.

The object is achieved by providing the transport system according to the main claim. Further advantages and embodiments of the invention are described in the subclaims and emerge from the description and the accompanying drawings. To solve the problem, the method is also proposed according to the independent claim. All features explained are not only in the particular combination specified, but also in other combinations or alone, without departing from the scope of the invention.

The present invention therefore relates to a transport system for transporting flat objects resting on at least one lower transport means such as, in particular, silicon semiconductor substrates in a fluid treatment system, with a device for holding down the flat objects. Such substrates are often susceptible to breakage and therefore require particularly gentle handling, for example in the context of a fluid treatment throughflow system, wherein the fluid treatment may relate to a cleaning, but also to a wet chemical treatment of the objects or substrates. The fluid treatment can consist, for example, in a one- or two-sided spray treatment. Also, the removal of liquid with, for example, gas streams directed at the substrates is by definition subject to fluid treatment. In particular, however, the transport system according to the invention is suitable for use within the scope of a fluid treatment, which is referred to below by way of example as "wet treatment", in which the articles are disposed within or above, i. H. are arranged resting on a treatment liquid. In particular, in such treatments is to be expected with an undesirable floating of the substrates, which counteracts the device according to the invention for holding down. For this purpose, it is provided that the device for holding down comprises a rotatably storable shaft, which in the present case is also called "hold-down shaft". Preferably, this wave is arranged above the object to be treated. Also preferably, several of these waves are arranged one behind the other in the direction of passage, wherein the distance between the shaft centers relative to one another is preferably no more than the length of the flat objects, also viewed in the direction of passage. In this way, it is ensured that a flat object is always in contact with at least one of the devices according to the invention for holding down even in the case of relatively long passages within the transport system according to the invention. In some cases, however, a larger spacing of the waves may be possible. In addition, the device for holding down a transport system according to the invention may also comprise only a single shaft.

The transport system further comprises at least one lower transport means on which or which the objects rest and are preferably transported substantially horizontally through or over the treatment fluid. Such a lower transport means may consist in particular of a band, or of rollers or rollers arranged one behind the other in the transport direction. Full rollers are preferred, whose axes are particularly preferably arranged at such a distance from each other that they are at least slightly less than the length of a substrate. These solid rollers are structured on the surface to improve the contact between the roller and the object to be transported. Preferably, here is a groove which is applied with a certain slope.

According to the invention, it is provided that a hold-down shaft according to the invention comprises bristles. These bristles serve to transmit the forces with which the objects are held down become. In addition, it is provided that these forces are exerted exclusively by the bristles.

The bristles are made of a flexible material. They can be limp or preferably elastic and, for example, in the form of fibers. Furthermore, the bristles may be present individually or as a tuft. Preferably, all bristles have the same length; However, it may be advantageous that the bristles are longer in certain areas, for example, to prevent lateral drift of the object to be held down or at least complicate.

According to a preferred embodiment, the device for holding down the transport system according to the invention further comprises at least one bearing, in which the shaft can be used without any special tool or from which it can be removed. Thus, an exchange of the shaft can be done in a short time and without much effort. For this purpose, it is particularly preferably provided that at least one of the bearings preferably to be provided on both sides of the shaft comprises a closable slot. In this slot, the shaft end of the shaft is storable. Particularly preferably, the slot is open at the top. To store the shaft whose shaft end is inserted from above into the camp until it rests on the actual bearing point. Subsequently, the shaft is secured by the slot being closed, preferably by means of a suitable quick-release closure. Thus, the altitude of the wave is fixed. The second bearing to be provided at the other end of the shaft may preferably also be constructed as described. Alternatively, this second bearing may also have a hole-like recess into which the corresponding second end of the shaft is inserted before the first end is inserted from above as described above.

An advantage of a storage with a fixed altitude is that the contact pressure of the device for holding down does not depend on the weight of the same, so that a precise regulation and adjustment of the contact pressure is possible.

Even in the case of additional bearings, which are particularly advantageous for longer shafts, those with upwardly open slots are to be preferred in order to allow a quick and easy replacement of the shaft according to the invention.

In addition to simple plain bearings and ball bearings are suitable, the entire body of the ball bearing is preferably attached to the shaft.

According to the invention, a drivability of the shaft is not necessarily provided. Thus, in one embodiment, the shaft is only passively rotated and only rotated by the interaction between the objects and the bristles.

Preferably, however, it is provided that the shaft can be driven at least on one side. This means that the shaft is connected to a drive which causes it to rotate. This drive can be provided both exclusively for the shaft according to the invention, as well as be derived from other existing in a treatment plant or the transport system according to the invention waves.

According to one embodiment, the rotational movement and thus the feed rate are matched to that of the at least one lower transport means, so that act on both sides of a substrate identical feed rates.

According to a further embodiment, the feed rate generated by the shaft according to the invention is higher than that of the lower transport means. In this way and in conjunction with certain bristle arrangements to be described, an article can be particularly effectively kept in its track or centered on it during its transport.

In addition to individual active drives (motors) provided for a shaft or shaft group, such drives can also be used for the drive, which serve to divert already existing movements, which are usually already present in the context of a treatment plant or the transport system according to the invention. The transmission of these movements can be done for example by means of toothed belts, chains, gears or universal joints. The transmission to the shaft by means of a gear is preferred because a height compensation is given at the appropriate tooth height. Therefore, the transport system according to the invention can be easily adapted to different substrate thicknesses, without a readjustment of the shaft of the invention driving component is required, as would be necessary, for example, in the case of a belt or chain drive.

According to a preferred embodiment it is provided that the shaft can be driven in the transport direction. This means that the forces transmitted to the substrate by means of the bristles have a component which acts on the substrate in the transport direction. In this way, the friction between the substrate and hold-down can be reduced, namely, when the speed of the bristles just corresponds to the conveying speed. Otherwise, either the substrate would have to take the bristles or it would be the same slow down, which would be associated with increased friction.

According to another embodiment, it is provided that the shaft can be driven counter to the transport direction.

The arrangement of the bristles on the surface of the shaft is of great importance for the precise properties of the transmission of force to the objects to be held down. The bristles are first arranged in one or more rows, wherein the distance between the bristles or tufts of bristles preferably remains the same along a row. For the preferred case that a plurality of parallel tracks of substrates are to be held down by means of a shaft, one or more rows of bristles may be combined to form corresponding tracks on the lateral surface of the shaft. This means that a bristle track on the shaft is just assigned to a substrate track of the treatment plant.

According to one embodiment, it is therefore provided that the bristles are arranged over the entire surface of the lateral surface of the shaft. Possibly. excluded herefrom are areas of the lateral surface which are not provided anyway for contact with the objects, such as in particular the edge and of course the storage areas. Even if several parallel tracks of objects are to be held down by a wave, it is advisable to leave the spaces between the tracks bristle-free; in particular if the treatment system comprises further means which serve to maintain the tracking of the substrates.

According to another embodiment, the bristles are arranged in at least two tracks parallel to each other and to the shaft end face, wherein the tracks have a distance from each other and from the shaft end face. The shaft end face lies parallel to a plane whose normal is collinear with the shaft axis. A track may consist of one or more, preferably likewise concentrically arranged rows on the shaft surface. The distance between two rows, which bound a substrate track on both sides, can be dimensioned so that it corresponds to the width of an object. In this way, a simultaneous hold down and tracking of the substrates can be achieved in an advantageous manner. Preferably, however, the pitch of the rows is sized to be slightly less than the width of an article. In this way, a rolling movement of the substrates is particularly effectively prevented. The distance between adjacent tracks, however, can be chosen so small that as many tracks as possible can be arranged next to each other. In this way, the available space is optimally utilized without the fact that laterally adjacent substrates can collide.

According to another embodiment of the device according to the invention for holding down is provided that a track comprises at least two rows of bristles, which are arranged at an angle to each other. This means that in a plan view of the lateral surface of the shaft, the bristle rows of a track are not linear, but have a kink, which is preferably symmetrical to the track center. This kink is arranged so that it is just in the middle of each track. The angle enclosed by the two legs of the bend is preferably in the range of 10 to 170 degrees, and more preferably 80 degrees. Also particularly preferably, each track not only one, but a plurality of mutually parallel rows of bristles.

For the production of the shaft according to the invention, in particular those materials are preferred which are insensitive to all fluids coming into contact with them. Preference is given to plastics. Particularly preferably, the bristles are made of a material selected from the group consisting of polypropylene (PP), polyvinylidene fluoride (PVDF), polybutylene terephthalate (PBT), rubber and natural fibers. The shaft, on the other hand, preferably comprises at least one shell of polyvinyl chloride (PVC), or it is made of a corresponding solid material. Alternatively, it may comprise a core of metallic material, which may result in less deflection in view of longer lengths.

Preferably, the bristles are attached directly to the shell of the shaft and may, if desired, consist of the same material. According to an alternative embodiment, the bristles may also be attached to another component such as a cylindrical foil or an elastic hollow body, which is then pulled over the jacket.

Accordingly, the hold-down shaft can be constructed in one piece as a whole as well as a plurality of subcomponents. In particular, suitable subcomponents are the actual shaft (core) and the at least one sheath with bristles arranged thereon. Preferably, a plurality of spaced coats are pushed or plugged onto a core. It must be ensured that the axial arrangement is maintained during operation. For example, press fits between sheaths and core may be provided for this purpose, or additional mechanical safeguards (for example, split pins, Screws). Furthermore, the shells may be sized so that their end faces touch each other, and bear against the end of the core on a correspondingly provided shaft shoulder. At the other end of the shaft, for example, a shaft nut for play-free fixation of the structure can be used.

Further embodiments relate to the arrangement and geometry of the bristles. According to one embodiment, the bristles are arranged radially on the lateral surface of the shaft. This means that the bristles or the directions of action of the bristle tufts are substantially perpendicular to the lateral surface of the shaft. The effective direction of a bristle tuft is justified by the fact that with a tuft of thin fibers, although never all the individual fibers have exactly the same orientation, however, due to the proximity of the individual fibers of a tuft, it can be said that the effects of the individual fibers are superimposed.

According to another preferred embodiment, the bristles are arranged tangentially on the lateral surface of the shaft, or are at least at an angle to the lateral surface, which is significantly smaller than 90 degrees. The bristles are preferably arranged so that their tips on contact of the substrate against the transport or feed direction show. This means that the substrates are not touched with the tips but with the lateral surfaces of the bristles. This is advantageous since penetration of the bristle tips into the gap, which may possibly form between the rear edge of a substrate and the lower transport means, is not possible. Furthermore, different orientations can be combined with each other to achieve the best possible centering effect on the substrates. Thus, for example, it is preferred that in an arrangement of the rows with a bend described above, the bristles located at the edge of a respective track are arranged radially, and the bristles located in the center of this track are arranged tangentially in the direction of rotation of the lateral surface.

In another embodiment, the angle at which the bristles exit the sheath is a value other than 0 degrees (radial direction) or 90 degrees (tangential direction).

The bristles can have different shapes. You can run linear or curved, for example, be bent in a circle. Depending on the bristle shape, different holding and friction forces are transmitted to the substrates.

The geometry of the tip of a bristle can also be of different types. Thus, the bristle end can run at right angles, beveled or sharpened. Of course, it is also possible to combine differently shaped or provided with different ends bristles together. For example, bristles that tend to contact the central area of a substrate may have a curved shape and thus be more elastic, whereas bristles that are more likely to contact the edge area of a substrate may have a linear shape and thus be less elastic.

The diameter of a single bristle may be, for example, in the range of 0.01 to several millimeters. Of course, differently sized bristles in the context of a single blank holder according to the invention can be combined.

The length of a bristle is preferably in the range of 5 to 25 mm. In the event that the bristle does not exit the jacket radially, it is preferred that the distance of the lateral surface to an imaginary envelope bounded by the bristle tips is between 5 and 25 mm.

According to the invention it is provided in any case that the shape and the material of the bristles and thus their spring force has a significant influence on the contact pressure with which the substrates are held down. By combining a plurality of bristle sorts, quite different pressure force profiles can accordingly be realized along a hold-down device according to the invention.

The invention further relates to a method of transporting flat objects using the aforementioned transport system.

• – Positionieren der Vorrichtung zum Niederhalten, so dass zwischen den Borsten der Vorrichtung und den Oberseiten der zu transportierenden flachen Gegenstände ein Spalt entsteht, der kleiner ist als die Dicke der flachen Gegenstände;
• – Antreiben des mindestens einen unteren Transportmittels und/oder der Vorrichtung zum Niederhalten, so dass die auf dem mindestens einen unteren Transportmittel aufliegenden flachen Gegenstände in Transportrichtung gefördert werden.

Accordingly, this method comprises the following steps:

• - Positioning the device to hold down, so that between the bristles of the device and the tops of the flat objects to be transported, a gap is formed, which is smaller than the thickness of the flat objects;
• - Driving the at least one lower transport means and / or the device for holding down, so that the resting on the at least one lower transport means flat objects are conveyed in the transport direction.

In other words, the positioning device is first of all positioned in such a way that in fact pressure forces can also be transmitted from it to the flat objects. The gap to be provided for this purpose must be smaller than the thickness of the flat objects, but may also be equal to zero, namely when the bristles of the device according to the invention come into direct contact with the at least one lower transport means, if no substrate between the device and the transport means is arranged. By adjusting the gap height or the distance of the axes of a lower transport means and a hold-down shaft according to the invention, the contact pressure can be adjusted to the substrates.

In the following step, then driving either of the at least one lower conveyor, and / or the device according to the invention for holding down. Preferably, both components are driven simultaneously, so that their peripheral speeds are the same at the lower and upper substrate surface. In this way, friction forces, which could lead to damage of the most sensitive substrate surfaces, effectively avoided.

Furthermore, it is provided according to the invention that the method comprises a cleaning step, for example between two transport operations. This cleaning step serves, in particular, to remove any encrustations from the bristles. Such incrustations can be produced, for example, by drying treatment liquid on the bristles if corresponding components remaining as solids are present in the treatment liquid. The cleaning step is thus carried out in such a way that the shaft of the device for holding down on the at least one transport means arranged underneath and is driven without a substrate between the shaft and the means of transport is located.

Particularly preferred are the rotational movements in opposite directions and / or carried out with different relative speed. Due to the resulting friction effective cleaning of the bristles and possibly also the means of transport is achieved.

figure description

1 shows a device according to the invention for holding down in side view with radially arranged on the shaft bristles.

2 shows a device according to the invention for holding down in side view with tangentially arranged on the shaft bristles.

3 shows the lateral surface of a device according to the invention for holding down in plan view with two parallel to each other and the shaft end face spaced rows of bristles.

4 shows the lateral surface of a device according to the invention for holding down in plan view, in which the lateral surface is covered over its entire surface with bristles.

5 shows the lateral surface of a device according to the invention for holding down in plan view, in which a plurality of bristle rows having a kink are arranged on the lateral surface.

6 shows the lateral surface of a device according to the invention for holding down as in 5 , but with only a single row of bristles arranged on the lateral surface.

In the 1 is a device according to the invention for holding down 1 in side view with radially on the shaft 2 arranged bristles 3 shown. The bristles thus close with a on the lateral surface 4 lying on imaginary plane an angle of 90 degrees, therefore, point in the direction of the lateral surface normal. The bristles are regularly spaced from each other to be able to transmit uniform compressive forces regardless of the current rotation angle of the axis.

The 2 shows a device according to the invention for holding down 1 in side view with tangential to the shaft 2 arranged bristles 3 , The angle between one on the lateral surface 4 resting imaginary plane and the bristle axes is significantly less than 90 degrees, for example, as shown here 30 degrees. The tilting direction of the bristles may be directed forward or backward as needed. Forward means that the bristles are in contact with the substrate in the transport direction. Reverse means that the bristles face the transport direction in contact with the substrate. In addition, the tilting direction of the bristles may also have a sideways-directed component, meaning that the bristles in a shell view follow the pattern of the 3 . 4 . 5 or 6 can not be up or down, but also inclined in the direction of one of the shaft ends.

In the 3 is the lateral surface 4 a device according to the invention for holding down 1 in plan view with two parallel to each other and the shaft end face 5 spaced bristle rows 6 shown. Not shown are therefore the shaft ends and possibly arranged thereon bearings. The two rows of bristles have an axial distance from each other, which is at least slightly smaller than the width of an object to be held down. This bristle arrangement is characterized by the lowest possible contact of bristles with the substrate.

In the 4 is the lateral surface 4 a device according to the invention for holding down 1 shown in plan view, wherein the lateral surface 4 full surface with bristles 3 is covered. Unlike in the 3 Although the arrangement shown here is the highest possible contact of bristles with the substrate given; in certain cases, However, for example, in the case of round substrates, this arrangement is preferable. Due to the full surface with bristles stocked surface of the lateral surface is not bound to a fixed width of a track. It is thus possible to treat substrates with different widths on the same system.

The 5 shows the lateral surface 4 a device according to the invention for holding down 1 in plan view, in which on the lateral surface a plurality of rows of bristles having a kink 6 are arranged. Due to the kink, a centering of the downheld with the device according to the invention substrates can be achieved. According to the embodiment shown in the figure, three tracks are provided, the centers of which are each in the range of the corresponding kink. The three rows of bristles run parallel to each other. The included by the bend angle is according to the 5 about 30 degrees, but may be depending on the application in a preferred range of 10 to 170 degrees, and is particularly preferably about 80 degrees. According to the illustrated embodiment, it is provided that the substrate during conveying under the lateral surface shown 4 located. The transport direction may point in or against the direction in which the respective rows are tapered. The case in which the transport direction is oriented counter to the direction of the bend is preferred in order to stabilize the orientation of the article to be transported in its transport path.

The 6 shows the lateral surface 4 a device according to the invention for holding down 1 as in 5 , but with only a single row of bristles arranged on the lateral surface 6 , Here, the bristle arrangement is similar to that in 3 illustrated embodiment by the least possible contact of bristles with the substrate, but without losing the achievable in this arrangement centering effect.

The invention described above has a number of advantages over the prior art. In particular, a hold-down device according to the invention can be produced cost-effectively, since the manufacturing accuracy can be significantly lower in comparison to prior art hold-downs, without reducing the effectiveness with regard to the task to be performed. The device is largely independent of temperature and quality fluctuations; By the use according to the invention of bristles as force-transmitting elements, corresponding fluctuations are compensated in a very wide range and a reliable function is ensured. This includes both holding down the objects as well as tracking or tracking of the same. Other components for guiding or centering are not necessary, which in turn has an advantageous effect on the cost, as well as the one-piece construction according to a particular embodiment, and the usability of a hold-down for objects of different widths. The handling is done gently, as well as differences in thickness of the substrates or erroneous arrangements of the same need not necessarily lead to breakage. The pressures desired for optimum hold down can be easily varied by selecting the bristles that transmit these pressures. Finally, the combination of the device according to the invention with a bearing having a slot favors fast and uncomplicated interchangeability, which is of great advantage, in particular with regard to the shortest possible interruption times in the context of a piece production.

Due to the simple geometry and universal applicability, a hold-down device according to the invention is suitable for supplementing or replacing many hold-downs known from the prior art.

LIST OF REFERENCE NUMBERS

1

Device for holding down (hold-down)

2

wave

3

bristles

4

lateral surface

5

Wave face

6

bristle row

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10313127 [0003]
• EP 03/03739 [0004, 0006]
• DE 1256963 B [0006]
• DE 3140546 A [0006]
• US 5711806 [0006]

Claims (14)

Transport system for transporting flat, resting on at least one lower transport items in a fluid treatment flow system, with a device for holding down the flat objects, comprising a rotatably mountable shaft, characterized in that the shaft bristles for exclusively transmitting the objects holding down forces covers. Transport system according to claim 1, wherein the device for holding down further comprises at least one closable slot in which the shaft is storable. Transport system according to claim 1 or 2, wherein the shaft is driven at least on one side. Transport system according to claim 3, wherein the shaft is drivable in the transport direction. Transport system according to one of the preceding claims, wherein the bristles are arranged over the entire surface of the lateral surface of the shaft. Transport system according to one of claims 1 to 4, wherein the bristles are part of the surface and arranged in at least one track on the shaft, each track comprises at least one row of bristles. Transport system according to claim 6, wherein the bristles are arranged in at least two tracks parallel to each other and to the shaft end face and the tracks have a distance from each other and from the shaft end face. Transport system according to claim 6, wherein a track comprises at least two rows of bristles, which are arranged at an angle to each other. Transport system according to one of the preceding claims, wherein the bristles consist of a material selected from the group consisting of polypropylene, polyvinylidene fluoride, polybutylene terephthalate, rubber and natural fibers and / or the shaft comprises or consists of at least one sheath of polyvinyl chloride. Transport system according to one of the preceding claims, wherein the bristles are arranged radially on the lateral surface of the shaft. Transport system according to one of claims 1 to 9, wherein the bristles are arranged tangentially on the lateral surface of the shaft and facing against the transport direction. Transport system according to one of the preceding claims, wherein the bristle shape is curved linear or circular curved, and wherein the bristle end is perpendicular, beveled or sharpened. A method of transporting flat objects using the transport system of claim 1, comprising the following steps: - Positioning the device to hold down, so that between the bristles of the device and the tops of the flat objects to be transported, a gap is formed, which is smaller than the thickness of the flat objects; - Driving the at least one lower transport means and / or the device for holding down, so that the resting on the at least one lower transport means flat objects are conveyed in the transport direction. The method of claim 13, further comprising a cleaning step between two transport operations, wherein the shaft of the device for holding down on the at least one transport means arranged underneath and is driven, without being an object between the shaft and the transport means.

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