BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
FIG. 1 is a partial, top perspective view of a first exemplary embodiment of a hydrofoil according to the invention;
FIGS. 2-4 are similar views of three variations of the first exemplary embodiment shown in FIG. 1;
FIG. 5 is a partial, top perspective view of a second exemplary embodiment of the hydrofoil according to the invention; and
FIGS. 6-8 are similar views of three variations of the second exemplary embodiment of the hydrofoil shown in FIG. 5.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a hydrofoil, which may also be referred to as a wiper strip, a wiper, a screen foil, or simply a scraper, or even a wire foil. A carrier strip 1 is manufactured, for example, from glass fiber-reinforced plastic and is provided on its side which is assigned to the wire of a paper production installation with a wear strip 2. The wear strip 2 comprises a multiplicity of plates 21 which are built up on top of one another and are made from a ceramic material. The plates 21 are fastened to the surface of the hydrofoil 1 and to one another by way of adhesive layers 3.
In the embodiment which is shown, the wear strip 2 is formed by three layers of plates 21, the plates 21 of the layers which lie directly on one another being offset with respect to one another.
Due to the fact that, firstly, the plates 21 have a very low thickness (from about 0.5 mm to 1 mm or of up to a maximum of 3 mm) and, secondly, the adhesive layers 3 are situated between the plates 21, there is provided a hydrofoil 1 with a wear strip 2 that is substantially more elastic and therefore far less susceptible to fracture than prior art wear strips which have only a single layer of substantially thicker plates. As a result, the novel wear strip is damaged substantially less often than is the case for previously known wear strips. This is achieved in that firstly only small thermal stresses occur in the individual plates 21 on account of their very low thickness, and in that secondly the wear strip 2 has a substantially greater elasticity on account of the layered construction and the adhesive layers 3 which are situated between the individual plates 21, than is the case for known wear strips which comprise individual substantially thicker plates which lie next to one another and are made from a ceramic material.
The hydrofoil carrier strip 1 according to FIG. 1 is configured, on its side which faces away from the plates 21, over its entire length with an undercut groove 11, by means of which it can be fastened releasably to a carrying strip which is provided in the paper production installation, as a result of which it can be replaced at any time by a new hydrofoil.
The hydrofoil 1a according to FIG. 2 differs from the hydrofoil 1 according to FIG. 1 only in that, on its side which faces away from the plates 21, it is configured over its entire length with a base 12 which is undercut on both sides, as a result of which it can be pushed into an associated groove of a carrying strip and can be fastened in this way to the latter.
The hydrofoil 1a according to FIG. 3 differs from the hydrofoil 1a according to FIG. 2 in that the individual plates 21a of the wear strip 2a are configured in their central region on their upper side in each case with a groove 22 and on their lower side in each case with a protruding strip 23 which is diametrically opposed to the groove 22, the strips 23 protruding into the grooves 22 of the plates 21a which in each case lie underneath. In addition, the hydrofoil 1a is likewise configured on its upper side with a groove 13, into which the strip 23 of the adjacent plate 21a protrudes. As a result, in addition to the adhesive layers 3 which are situated between the individual layers of the plates 21a, mechanical locking of the individual plates 21a to one another is brought about.
The hydrofoil 1b according to FIG. 4 differs from the design variants according to FIG. 1 to FIG. 3 in that the plates 21 and 21b of the wear strip 2b have different cross sections to the extent that the uppermost plates 21b have a trapezoidal cross section transversely with respect to the longitudinal extent of the wear strip 2b, the thickness of the plates 21b being reduced in the movement direction of the wire, whereas the other plates 21 have a uniform cross section over their entire surface area. This hydrofoil 1b is also configured with a fastening groove 11.
The second embodiment which is shown in FIG. 5 of a hydrofoil 1c according to the invention differs from the first embodiment of a hydrofoil according to FIG. 1 to FIG. 4 in that the surfaces of the plates 21c of the wear strip 2c are not arranged approximately parallel to the wire, but rather are oriented transversely with respect to the wire, with the result that the latter comes into contact with the end faces of the plates 21c. Here, the plates 21c are also connected to one another by means of adhesive layers 3 which are situated between them.
Here, this wear strip 2c is fastened to the hydrofoil 1c in that the hydrofoil 1c is configured on its upper side which faces the wire with an undercut groove 13′, into which a strip 24 which protrudes from the wear strip 2c protrudes. In order to fasten it to a carrying strip, the hydrofoil 1c is configured with a base 12 which is undercut on both sides.
The design variants according to FIG. 6 and FIG. 7 differ from the embodiment according to FIG. 5 in the type of fastening of the wear strips 2d to the hydrofoil 1c. For this purpose, the hydrofoil 1c is configured on its side which is assigned to the wire with a stop strip 14 and, furthermore, a clamping strip 15 is provided which is fastened releasably to the hydrofoil 1c, it being possible for the wear strip 2d to be clamped between the stop strip 14 and the clamping strip 15. As a result, the wear strip 2d can be removed from the hydrofoil 1c in a very simple manner and can be replaced by a new wear strip 2d.
Here, the wear strip 2d differs from the wear strip 2c according to FIG. 5 in that it is formed by plates 21d of trapezoidal cross section which lie on the outside and by at least one layer of plates 21 of rectangular cross section which are situated between the plates 21d. Here, the plates 21 and 21d are also connected to one another by means of adhesive layers 3.
The design variant according to FIG. 8 differs from the design variants according to FIG. 6 and FIG. 7 in that the hydrofoil 1d which is configured with a groove 11, with a stop strip 14 and with a clamping strip 15 is provided with a wear strip 2e which comprises a plurality of layers of plates 21c which are adhesively bonded to one another and all have rectangular cross sections.
This second embodiment which is shown in FIG. 5 to FIG. 8 of a hydrofoil according to the invention firstly ensures the advantages of the first embodiment, namely reduced brittleness of the wear strip, as a result of which the risk of damage to the latter is reduced. Since the individual plates of the wear strip are offset with respect to one another in the longitudinal direction of the strip, they secondly do not have any continuous joint gaps in the movement direction of the wire on the face which bears against the wire, as a result of which the hydrofoil has the same effect over its entire length.
The individual plates 21, 21a, 21b and 21c can be manufactured from silicon carbide or aluminum oxide, zirconium oxide or silicon nitride. Here, silicon carbide represents the hardest and most brittle ceramic material. Aluminum oxide is somewhat less hard and brittle, and zirconium oxide and silicon nitride are somewhat less hard and brittle than aluminum oxide. Here, the individual layers of the wear strip can be manufactured from different ceramic materials. The plates which come into contact with the wire or those plates, on which the wire runs, are preferably manufactured from a very hard ceramic material, whereas the plates which lie underneath or the plates which follow in the movement direction of the wire are manufactured from a somewhat less hard ceramic material. As a result, the wear strip has very high wear strength and, in addition, high elasticity.
Patent Application
20080087398
