EP0427995B1 - Device for spreading pre-wetted granular material - Google Patents

Abstract

In spreading devices with a spreading plate (1) as spreading member, which is motor-driven to rotate about an essentially vertical shaft (8) and provided with a number of essentially radially running casting shovels (15) which end at a central guide member (9), granular material to be spread is selectively supplied via a granular-material chute (11) to the guide member (9) and in this region mixed with moistening liquid. For better mixing of the media to be spread and guarantee of more uniform distribution of material to be spread, the spreading plate (1) is provided along the casing surface of the cylindrical or frustoconical guide member (9) with more than twelve impact surfaces (10) which are formed by tooth profiles of the guide member (9) or by the inner end sections of the casting shovels (15) and which, in the respective point of intersection (13) with the apex line (12) of the granular-material chute (11), form with the radial running through this point of intersection (13) an angle of incidence of approximately 40 DEG to 60 DEG . These impact surfaces are adjoined by the casting shovels (15) in such a manner that they run in the same direction as the impact surfaces (10) at least in the inner third of the spreading plate radius. (Fig. 2) <IMAGE>

Description

The invention relates to a spreading device.

In a known spreading device (DE-A 35 44 060), eight throwing vanes designed in the manner of an angle rail are mounted in a radial direction on the top of the spreading plate in such a way that they are at a radial distance from the spreading plate shaft which corresponds to approximately half the spreading plate radius. A cylindrical tube with a much smaller diameter, together with a frustoconical housing wall arranged concentrically around it and an annular bottom, forms an intermediate container for the dampening liquid. Over a triangular shape The outlet opening of the housing wall is at a small radial distance from a baffle that runs parallel to it and completely covers the outlet opening, which is arranged together with the baffle so that the center of its circumferential length is at the point where the grit is inclined to the axis of rotation of the Scatter plates and eccentrically arranged chute hits granular grit. On the top of the spreader plate, a toothed ring, which is provided with sawtooth-like teeth on its periphery, is attached concentrically to its shaft, the tooth backs of which form throwing surfaces, which have the task of throwing liquid running radially inwards again outwards. The diameter of the toothed ring is, however, considerably smaller than that of the lower edge of the frustoconical housing wall. The axial height of the toothed ring is greater than the axial distance of approximately 3 cm between the lower edge of the frustoconical housing wall and the top of the spreading disc.

During operation, the dampening liquid runs out of the outlet opening over a more or less wide range, depending on the dosage, and thereby flows over the outer surface of the housing wall underneath, where the granulated scattering material bouncing off the baffle wall partially strikes. At the latest on the surface of the spreading disc, the liquid comes with the granulated one Grit in contact. Due to the low tangential acceleration in the area of the point of impact and the small centrifugal forces in the inner area of the throwing blades, the throwing blades temporarily and in an uncontrolled manner accumulate and accumulate in the granules, which in large part experience vertical deflection and thus further mixing with liquid are withdrawn.

The mixing and moistening of the granulate is therefore inadequate, and there is an inconsistent spread pattern with different throwing distances and uneven distribution of the spreading material on the area to be treated.

In a further known spreading device (DE-A 30 50 355), supply channels are provided for the separate supply of the granulated, dry thawing material and a dampening liquid onto the surface of a spreading plate, which are formed by two downpipes of different widths arranged coaxially to the axis of rotation of the spreading plate. The downspouts each end below the plane formed by the upper edges of the throwing blades. The spreader plate has two radially offset groups of straight throwing blades, which are essentially in run radial direction and of which the one group between the two downpipes and the other group is arranged radially outside the outer downpipe. While the inner throwing blades run exactly radially, the separated outer throwing blades are arranged slightly obliquely.

There is an approximately semicircular ring wall between the inner throwing vane group and the outer throwing vane group, so that only in the angular area where this ring wall is missing can spreading material escape into the area of the outer throwing vane group. The granulated grit is fed through the annular channel between the outer down pipe and the inner down pipe, while the dampening liquid reaches the spreading plate through the inner down pipe and is already mixed with the granulated grit in the area of the inner throwing blades.

In this known spreading device, the granules and the dampening liquid are not specifically supplied in a narrowly limited area of the spreading plate surface, which leads in particular to inadequate moistening of the granulated spreading material when small amounts of dampening liquid are to be supplied. Here too, the arrangement of the throwing blades means that the danger is more uncontrolled Pellet accumulations are not removed and therefore a uniformly intensive mixing and a uniform spreading of the spreading material cannot be guaranteed.

The invention comes closest to the spreading device known from AT-B-369 076, in which a truncated cone-like cladding arranged concentrically with the spreading plate shaft is firmly connected as a guide body to the six straight, exactly radially extending throwing vanes, so that it also rotates of the spreading disc. The dampening fluid flows from a plurality of feed bores, which are arranged stationary above the cladding near the axis, from above onto the lateral surface of this cladding, specifically in an angular range in which the granulate arriving through the granular slide hits the lower half of the lateral surface. The liquid located on the upper half of the lateral surface of the guide body is continuously rotated by the rotation of the guide body from the point below which the dry granulate hits, so that only a small part of the dampening liquid comes into direct contact with the dry incoming granulate. Since the dampening liquid is more strongly on the outer surface of the The guiding body adheres as the heavier granulate and because the dampening liquid is distributed over the entire surface of the guiding body before it comes into contact with the granulated grit, mixing and moistening cannot be achieved with the desired intensity. In addition, there is the risk that the dry granulate, in particular salt, coming from the granule slide or the feed chute will adhere to the moist surface and build up to a growing crust. Furthermore, due to the radial arrangement of the throwing vanes, uncontrolled accumulations of granules form in the inner area, which cannot be moistened or mixed with liquid and lead to an uneven throwing distance and distribution of material.

In most known spreading devices, which are suitable for moistening the granulate which is supplied dry, neither a uniformly intensive mixing nor a steady, controlled, uniform flow of the mixture of dampening liquid and granulated spreading material by guiding the throwing vanes on the spreading plate is in the desired range Kind guaranteed. Rather, especially in the radially inner area of the throwing vanes, the centrifugal forces that are only present to a small extent form uncontrolled accumulations and agglomerations that lead to congestion of the granules along the throwing blades and thus can cause deflection of the spreading material in the vertical direction. Particularly when the spreading material is moistened, which can additionally clump, the sudden detachment of the clusters from a throwing blade leads to an inconsistent and uneven spreading pattern with regard to both the spreading density and the throwing range.

The invention is therefore based on the object of providing a spreading device in which, on the one hand through the safe avoidance of uncontrolled accumulation of granules on the throwing vanes, better mixing of the two spreading media, i.e. to achieve a more even and intensive moistening of the granulated spreading material emerging from the spreading disc and, on the other hand, a more uniform spreading material distribution on the road, and thus to ensure more effective and economical use of spreading material.

This object is achieved according to the invention by the features specified in claim 1, in particular in that the spreading plate is provided along the lateral surface of the frustoconical or cylindrical guide body with more than twelve baffles, the tooth flanks of the guide body or from the inner end portions of the same number existing throwing blades are formed and which form an angle of attack α of approximately 40 ° to 60 ° at the respective intersection with the apex line.

The angle of attack α, which the throwing blades form with the radial, creates a force component acting radially on the spreading material, which the granulated spreading material and the supplied dampening fluid after bouncing off the impact surfaces and striking the surface of the spreading plate after reaching the inner root line of a throwing blade outside along the foot line accelerates. These acceleration forces cause a uniform distribution of the spreading material along the throwing blades, so that the spreading material is guided to the spreading plate edge in a steady, steady flow. This homogeneous, steady flow along the throwing blades results in better mixing and moistening of the granulated grit with the dampening liquid, and the mixture leaves the throwing blades in the form of a homogeneous, steady jet in an approximately horizontal direction. This effectively prevents temporarily uncontrolled accumulations and thus deflection of the granules upwards.

The larger number of throwing blades reduces the exposure of the individual throwing blades to the spreading material, so that the flow cross-section of the spreading material is reduced and thus a further improvement in the mixing and moisture penetration along the throwing blades from the detection point of the spreading material and liquid through the throwing blades inside the spreading plate to to the edge of the spreading plate. Further advantageous embodiments of the invention can be found in claims 2 to 11 inclusive.

Fig. 1

eine Streuvorrichtung in Seitenansicht;

Fig. 2

einen vertikalen Teilschnitt aus Fig. 1;

Fig. 3

einen Schnitt III-III aus Fig. 2;

Fig. 4

einen vertikalen Teilschnitt einer Ausführungsform mit einem anderen Leitkörper;

Fig. 5

einen Schnitt V-V aus Fig. 4;

Fig. 6

einen Schnitt V-V aus Fig. 4 mit geschwenkter Granultrutsche;

Fig. 7

den Flüssigkeitsbehälter mit Deckblech in Seitenansicht;

Fig. 8

einen Schnitt VIII-VIII aus Fig. 7;

Fig. 9

einen Teilschnitt IX-IX aus Fig. 5;

Fig. 10

einen Teilschnitt X-X aus Fig. 5 mit schräg gestellten Wurfschaufeln

Fig. 11, 12, 13

die Streuvorrichtung der Fig. 1 mit unterschiedlichen Flüssigkeitszuführeinrichtungen.

Based on the drawing, the invention will be described in more detail below explained. It shows:

Fig. 1

a spreader in side view;

Fig. 2

a vertical partial section of Fig. 1;

Fig. 3

a section III-III of Fig. 2;

Fig. 4

a vertical partial section of an embodiment with another guide body;

Fig. 5

a section VV of Fig. 4;

Fig. 6

a section VV of Figure 4 with pivoted Granultrutsche.

Fig. 7

the liquid container with cover plate in side view;

Fig. 8

a section VIII-VIII of Fig. 7;

Fig. 9

a partial section IX-IX of Fig. 5;

Fig. 10

a partial section XX of FIG. 5 with inclined throwing blades

11, 12, 13

1 with different liquid supply devices.

The spreading device shown in the drawing has a spreading disc 1 which is fastened to a vertical shaft 3 by means of a cylindrical hub 2 (FIG. 2) and is rotatably driven by a controllable hydraulic motor 4 in the direction of arrow 5 (FIG. 2). The spreading disc 1 has a flat inner section 6, which extends over approximately one third of the entire diameter, and an outer ring section 7, which rises outwards at a cone angle (α1) of approximately 10 °. On the upper side of the spreading plate 1, a frustoconical guide body 9, which rotates with the spreading plate 1, is fastened in the area of the inner section 6 concentrically to the axis of rotation 8. The guide body 9 is provided on its periphery with fifteen baffles 10, which are formed by the tooth flanks sawtooth-like teeth 10 'which rotate in the direction of rotation and which taper in the radial direction from the inside outwards and in the axial direction from the bottom up.

As can be seen from FIGS. 1 and 2, above the spreading plate 1 there is a granular slide 11 approximately U-shaped or V-shaped in cross section at a small axial distance, the apex line 12 along which the granulate is essentially guided onto the spreading plate , the outer surface of the guide body 9 intersects at an intersection or point of impact 13 and which has an angle of inclination of about 30 ° to the axis of rotation 8. In the embodiment of FIGS. 1, 2 and 3, the arrangement of the granule slide 11 is the further made such that the apex line 12 runs exactly radially, ie that it intersects the axis of rotation 8.

The above-mentioned impact surfaces 10 of the guide body 9 are, as can best be seen from FIG. 3, essentially designed as flat surfaces and arranged in their radial course in such a way that they form an angle of attack α with a radial 14 extending through the point of impact 13, which can be between 40 ° and 60 °, preferably 45 °, and that their inner ends are each in the direction of rotation in front.

Each impact surface 10 is followed in the same direction by a throwing blade 15, which extends to the outer edge 16 of the spreading plate 1 and is seated without gaps on the top of the spreading plate. In the embodiment of FIGS. 1, 2 and 3, these throwing blades run approximately up to half the radius of the spreading disc in exactly the same direction as the baffles 12, ie also at the angle of attack α. The remaining part of the throwing blades 15, as can best be seen from FIG. 3, has a curved course, in such a way that the straight inner section 17 is followed by a curvature 18 which is directed backwards in the direction of rotation and which has a somewhat stronger shape, continues in the direction of rotation forward curvature 19 to the scatter plate edge 16.

In addition, the throwing blades 15 are each provided with a triangular cutout 20 in the area where the granules impact the impact surfaces 10 or where the granules come from the granule slide into the plane of their upper edges, which unimpeded impact of the granules in the lower third the baffles 10 favored. For this purpose, the recesses 20 are so deep that their tips lie below the horizontal plane of the point of impact 13.

On the other hand, these recesses 20 of the throwing blades 15 are only so deep that in the lower quarter of the throwing blade height there is a gapless connection between the throwing blades 15 and the baffle surfaces 10 and thus a continuous guidance of the spreading material from the baffle surfaces 10 to the edge of the spreading plate 16.

These recesses 20 have the advantage that the granules falling from above are not already grasped at the upper edge of the throwing vanes 15 and at least partially kept away from the baffles 10, but that it actually reaches the baffles 10 in order to be the shortest from there Ways to be directed to the spreading disc surface between the throwing blades 15. This results in a more uniform, controlled distribution of the granulate between the individual throwing blades 15.

The above-described curved shape of the individual throwing blades 15 results in an additional and increased radial acceleration of the spreading material along the front throwing blade surface to the outside in the region of the trailing curvature 18. By the subsequent end curvature 19 directed in the forward direction, on the other hand, a certain delay in the flow of grit along the throwing vane surface is again effected, which enables a somewhat tighter bundling of the grit jet and thus a more targeted spreading. This also results in a certain shift of the spreading fan in the direction of rotation of the spreading disc. The two curvatures also result in an extension of the guide surface along the individual throwing blades 15 and thus also an extension of the mixing zone in which the liquid is forcibly kept in contact with the granules.

The dampening liquid is supplied from an intermediate container 21, which consists of a housing arranged above the guide body 9 with a frustoconical housing wall 22 and a housing base 23, both of which are tightly attached to a central fixed tube 24. The moistening liquid is supplied through a hose connection piece 25, which is connected via a hose 26 to a storage container (not shown) or a metering pump is connected. On the side facing the granule chute 11, the housing wall 22 is provided with an essentially triangular outlet opening 27, which extends over a larger circumferential section and lies approximately halfway up the intermediate container 21. Below this outlet opening 27, an extended wall section is arranged as an apron 28, via which the liquid emerging from the outlet opening 27 and flowing downward along the outer surface of the housing wall 22 is conducted at a small distance above the point of impact 13 onto the baffle surfaces 10. As can best be seen from FIG. 7, the outlet opening 27 has the shape of an isosceles triangle standing on its tip, the equally long legs 27 'of which form an obtuse angle with one another and merge into one another in a curve.

Both the outlet opening 27 and the section of the housing wall 22 which extends over the width of this outlet opening and serves as a liquid guide surface 28 are covered by a cover plate 29 which runs partly at an angle and partly vertically, so that both are protected against the impact of granules.

As can be seen from FIG. 7, the lower boundary edge 30 of the apron 28 has an oblique course in such a way that its front end in the direction of rotation extends further downward than the opposite end of this boundary edge 30. The cover plate 29 is adapted to the curvature of the housing wall 22 and is provided on the side with bent connecting webs 31 and 32 which sit tightly on the housing wall 22 and thus laterally limit the liquid guide surface 28 'of the housing wall 22. This also ensures a targeted supply of liquid to the point at which the granulate impinges on the impact surfaces 10 or on the outer surface of the guide body 9.

In addition, the outlet opening 27 with the cover plate 29 covering it is arranged in such a way that its common plane of symmetry 33 has an offset of approximately 10 mm in the direction of rotation with respect to the point of impact 13, where the granulated grit coming from the granule chute 11 comes in in a targeted manner. It can also be seen from FIGS. 3, 5 and 6 that the width of the liquid guide surface 28, which is delimited by the lateral webs 31 and 32, extends over a circumferential length which corresponds to approximately 1.5 times the division of the baffle surfaces 10 .

Due to the oblique course of the lower boundary edge 30 of the extension apron 28 ', the liquid arriving at this edge is preferably in the circumferential direction continued so that the majority of the dampening liquid strikes the impact surfaces 10 behind the point of impact 13 of the granules. It is also important that the liquid is guided as far down as possible on the liquid guide surface 28 formed by a section of the housing wall 22 and the apron 28 ', so that when the spreader plate 1 is rotating rapidly, it is passed through the baffles 10 and throwing blades 15 on its surface caused air vortex is not atomized.

6 shows a top view of a spreading plate 1/1, the throwing blades 15/1 of which there are also fifteen-fold designs and have a continuous straight course from the inside to the outside. In addition, this embodiment also shows that the granule slide 11 can also be arranged such that its apex line 12 does not run through the axis of rotation 8 of the spreading plate 1, but that it forms an angle β with a radial 14 passing through the point of impact 13. In order to obtain the above-described effects of the baffles 10 in at least approximately the same quality, this angle β should be chosen so large that the apex line 12 can form a baffle angle δ of a maximum of 90 ° with a baffle 10 at the point of impact 13 of the guide body 9 . The impact angle δ is composed of the Angle β and the angle of attack α, which the baffles 10 form to a radial 14 leading through the point of impact 13.

By pivoting the granulate chute 11 relative to the position shown in FIGS. 3 and 5, the impact angle δ, at which the granulate strikes the impact surfaces 10, can be dimensioned such that the granulate strikes as far as possible on the inside of the spreading disc surface and thus approximately the entire length of the throwing blades 15 is used as a mixing zone for the two scattering media. This condition is best guaranteed in the arrangement of the granule slide 11 according to FIGS. 3 and 5, because there β = 0.

While the throwing blades 15 and 15/1 can also be formed without the recesses 20, that is to say with straight upper edges which extend right up to the edge of the guide body, FIGS. 4 and 5 show an exemplary embodiment in which a central cylindrical guide body 9/1 is provided, on the lateral surface 34, the inner end edges 35 of throwing blades 15/2 are fixed without a gap, such that the straight inner portions 17/1, which extend to about half the spreading disc radius R, extend at the same angle of attack α as that of the tooth flanks of the Teeth 10 ' 3 and 6. In this embodiment, the inner end sections 17/1 form the baffles, which in the embodiments of FIGS. 3 and 6 are formed by the leading tooth flanks 10 '. In the outer half of the spreading disc radius, the throwing blades 15/2 have the same course as the throwing blades 15 in the exemplary embodiment in FIG. 3. It is also possible to provide these throwing blades 15/2 with a straight course running from the inside to the outside, as is the case with the throwing blades 15/1 of FIG. 6. An inclined position of the granule chute 11, for example shown in FIG. 6, can also be provided in the embodiment of FIG. 5.

In Fig. 9 it can be seen that in the embodiment of Fig. 5, the throwing blades 15/2 are perpendicular to the top of the spreader plate and thus run parallel to the spreader plate axis.

In Fig. 10 a variant is shown, which shows that the throwing blades 15/2 and by the way also the throwing blades 15 and 15/1 or the baffles 10 with respect to the axis of rotation 8 or with respect to the perpendicular 36 to the spreading plate surface at an inclination angle γ , which can be about 4 ° to 10 °, so inclined can be that their top edges each advance in the direction of rotation of the spreading plate 1. As a result of this inclination, the spreading material that rebounds from an impact surface 10 strikes the spreading plate surface over a smaller radius. The spreading material is thereby detected more quickly by the lower edge of the impact surface 10 or the throwing blade 15, 15/1 or 15/2 and is guided along the throwing blade 15, 15/1 over a longer distance.

But also in this embodiment it is expedient to provide the throwing blades 15/2 with recesses 20 so that the same advantageous effects can be achieved with these throwing blades 15/2 as are given with the throwing blades 15 and 15/1.

Instead of the frustoconical guide body 9, which is provided on its outer surface with wedge-shaped teeth from top to bottom, a cylindrical guide body with teeth running straight through from top to bottom could also be provided, the leading edges of which in turn form the baffle surfaces 10. In this case too, saw tooth-like tooth profiles should be involved.

Correspondingly, the cylindrical guide body 9/1 of the embodiment of FIG. 5 could also be provided with teeth on its circumferential surface, on which the throwing blades 15/2 end in an analogous manner. The guide body or 9/1 expediently consist of an abrasion-resistant hard material, for example of metal or a suitable plastic. It can be designed both as a compact and as a hollow body. It goes without saying that the material from which the throwing blades, the spreading plate as a whole and also the baffle surfaces 10 are made should be corrosion-resistant.

While in the exemplary embodiments described so far, the liquid supply in the form described occurs from an intermediate container, there is also the possibility that the liquid supply according to FIG. 11 by means of a flat nozzle 37 arranged on the underside of the granule slide 11 or by means of a flat nozzle 38 arranged vertically above the point of impact is fed. With such flat nozzles 37, 38 it is also possible to carry out the above-described manner of supplying liquid to the baffle surfaces 10.

A further possibility of supplying liquid is shown in FIG. 13 in the form of a smaller intermediate container 39, which is arranged on the side of the tube 24 facing the granule slide 11 and conducts the dampening liquid onto the baffles 10 of the guide body 9 in the same way as that in FIG the 2 and 4 shown device.

Claims (11)

1. Gritting device, comprising a gritting disc (1), rotationally driven by a motor about a vertical axis (8) as the gritting member, which disc is provided with a plurality of casting blades (15, 15/1) extending substantially radially, which terminate at a central, cylindrical or truncated-conical guide block (9, 9/1), and which is provided with more than twelve impact surfaces (10), formed of tooth flanks of the guide block (9, 9/1) or of inner end portions of the casting blades (15/1), wherein the impact surfaces are disposed along the generated surface of the guide block (9, 9/1) and at each intersection point (13) with the invert line (12) of a dish-shaped or tubular grit chute (11) make an angle of attack (α) of approximately 40° to 60° in the direction opposite to rotation (arrow 5) with the radial line (14) passing through this intersection point (13), and the casting blades (15, 15/1) of which, at least in the inner third of the gritting disc radius, run in the same direction as the impact surfaces (10) and each form, at least in the lower quarter of their height, an uninterrupted connection with the associated impact surface (10), wherein granulated road grit, e.g. de-icing salt, is directed to the gritting disc (1) via the grit chute (11), which is disposed eccentrically and obliquely to the gritting disc axis (8), in a substantially dry state and in metered quantities in such a manner that it strikes the generated surface in the lower half of the guide block (9, 9/1), and wherein substantially unpressurized humidifying liquid is guided by a liquid feed device in the peripheral region onto the generated surface of the guide block (9, 9/1), in which the grit strikes the guide block (9, 9/1).
2. Gritting device according to Claim 1, characterized in that the impact surfaces (10) and/or the casting blades (15, 15/1) are each provided, in the attachment region to the impact surfaces (10), with apertures (20), which extend at least approximately to the intersection point (13) of the invert line of the grit chute with the generated surface of the guide block (9, 9/1).
3. Gritting device according to Claim 2, characterized in that the apertures (20) have a width at the upper edge of a casting blade (15, 15/1), which is at least approximately as large as the radius of the guide block (9).
4. Gritting device according to Claim 2 or 3, characterized in that the apertures (20) have an at least approximately triangular form, the lower corner of which lies below the horizontal plane in which the invert line (12) of the grit chute (11) meets the revolving impact surfaces (10), in which the granulate strikes the revolving impact surfaces (10).
5. Gritting device according to one of Claims 1 to 4, characterized in that the casting blades (15, 15/2) have a curved form, commencing approximately in the inner third of the gritting disc radius with a curvature (18) directed backwards from the direction of rotation and terminating outwardly in a curvature (19) directed forwards in the direction of rotation.
6. Gritting device according to Claim 1, characterized in that the impact surfaces (10) are inclined downwards at an angle of attack (γ) of approximately 4° to 10° relative to the gritting disc axis (8), so that their upper edge is leading in the direction of rotation.
7. Gritting device according to one of Claims 1 to 6, characterized in that the guide block (9) consists of a truncated conical plastics or metal block, which possesses on its generated surface sawtooth-shaped teeth (10'), tapering axially upwards and radially from the inside outwards, the tooth flanks of which, leading in the rotational direction, are at least approximately flat-surfaced and form the impact surfaces (10).
8. Gritting device according to one of Claims 1 to 6, characterized in that the guide block (9/1) consists of a cylindrical or slightly downwardly, truncated-conically tapering hollow block, to the generated surface of which the end portions (17/1) of the casting blades (15/2), forming the impact surfaces, are uninterruptedly fixed.
9. Gritting device according to one of Claims 1 to 8, characterized in that the liquid feed device comprises a covered liquid guide surface (28') or flat nozzle (37, 38), directed from above onto the impact surface (10), which extends in the circumferential direction of the guide block through at least one impact surface spacing.
10. Gritting device according to Claim 9, characterized in that the liquid guide surface (28') penetrates into the apertures (20) of the revolving casting blades (15, 15/1) and terminates in the axial region of the impact surfaces (10) immediately at the radial boundary edges of the impact surfaces (10).
11. Gritting device according to Claim 10, characterized in that the liquid guide surface (28') is provided with a boundary edge (30), extending obliquely downwards in the direction of rotation of the gritting disc, i.e. towards the gritting disc.

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