The invention concerns an improved rotor for fibrous suspension strainers.
In particular, the rotor object of the invention can be applied to any strainer used in the papermaking industry to clean fibrous suspensions, especially those deriving from recycled paper and cardboard, in which contaminants of the type with filaments are present.
It is known that to remove the contaminants present in the fibrous suspensions used in the papermaking industry special strainers are used, comprising a filtering basket provided with a rotor with wing-shaped blades that force the suspension through the holes present in the filtering basket.
The filtered suspension that passes through the holes of the filtering basket is commonly indicated as “accepted”, while the part of the suspension that still contains contaminants is called “rejected” and is further processed in order to recover the fibre that is still present in it.
When the fibrous suspensions to be filtered derive from recycled maceration paper constituted, for example, by cardboard, they contain contaminants of the type with filaments that stick to the rotor blades, where they accumulate, thus affecting the correct operation of the strainer.
In fact, in the rotors of the known type the blades have profiles and shapes that facilitate the accumulation of these polluting substances with filaments, which must be periodically removed through suitable maintenance operations.
Since these maintenance operations must necessarily be carried out with the machine at rest, this involves, in addition to the cost of the maintenance operation, the cost related to the production stop due to system down time.
The present invention aims to overcome the drawbacks listed above.
In particular, it is a first aim of the invention to achieve an improved rotor for fibrous suspension strainers that compared to the known rotors has a reduced tendency to retain the contaminants with filaments.
It is a further aim of the invention to achieve a rotor that can be applied to any strainer with filtering basket of the known type.
The last but equally important aim is to construct the rotor object of the invention so that the service time required for its cleaning is reduced.
The aims mentioned above are achieved by a rotor for fibrous suspension strainers that, in accordance with the main claim, comprises:
and wherein in each one of said blades the direction defined by at least one of the front edges is inclined in the opposite direction with respect to the direction of rotation of said rotor and forms an acute angle with any other coplanar direction that intersects it, defined by the intersection of said blade and any vertical sectioning plane passing through said vertical rotation axis.
According to a favourite embodiment of the invention, each shaped blade has a wing-shaped surface that develops parallel to the vertical axis of the central body to which it is applied on the outer lateral surface by means of a connection element.
The front edges of the wing-shaped surface and of the connection element, also called “connection edges” because they are the first to make contact with the suspension to be treated, are inclined in the direction opposite the direction of rotation of the rotor.
In this way it is possible to avoid the creation of undercut areas or corners that provide grip for any contaminants with filaments, since the profile of the front edge of the blades, being receding with respect to the direction of rotation of the rotor, facilitates their detachment and allows them to slide towards the end of the blade.
Advantageously, the rotor object of the invention requires less maintenance than the known rotors.
Still to advantage, the rotor object of the invention makes the strainer to which it is applied more efficient.
Advantageously, since the profile of the blades of the rotor object of the invention is such that the detachment of the polluting substances is easier, the latter remain inside the strainer for a shorter time than it would be required in case of use of rotors of the known type.
Consequently, the wear of all the parts of the strainer that make contact with such polluting substances during processing is also reduced.
It is equally advantageous that the rotor object of the invention can be applied to strainers with filtering basket of any type.
The aims and advantages described above will be explained in greater detail in the description of a favourite embodiment of the invention given as an example without limitation with reference to the attached drawings, wherein:
The rotor object of the invention is represented with an overall axonometric view in
It can be observed that it comprises a tubular central body 2 with substantially circular cross section, in which it is possible to identify a top base 3, a bottom base 4 and a vertical rotation axis K.
The lateral surface 5 of the central body 2 is provided with a plurality of protruding shaped blades, indicated as a whole by 6.
The rotor object of the invention can be applied to any fibrous suspension strainer, in particular of the type provided with filtering basket, where the rotor object of the invention is set rotating around the already mentioned vertical axis K according to the clockwise direction of rotation ω indicated by the arrow.
In each one of the blades 6 the front edges 7, 8, 9, alternatively called also connection edges, are constituted by all the points that during the rotation of the rotor are the first to make contact with the fibrous suspension to be cleaned.
According to the invention, in each one of the above mentioned blades 6 the direction X, Y, Z defined by at least one of the front edges 7, 8, 9 is inclined in the direction opposite the direction of rotation ω of the rotor 1 and forms an acute angle α′, β′, γ′ with any other coplanar direction X′, Y′, Z′ that intersects it, defined by the intersection of the blade 6 and any other vertical sectioning plane α, β, γ passing through the vertical rotation axis K.
Such inclination of the front edges 7, 8, 9, opposite the direction of rotation w of the rotor 1, facilitates the detachment of the contaminants from the rotor blades during rotation.
Each shaped blade 6, as shown in
In particular, with reference to
The curved surface δ and the plane ε intersect each other defining, on a vertical plane, the substantially right angles δ′ that can be observed in
In particular in
It is obvious that in different embodiments the arrangement of the series of blades, as well as the number and shape of the blades present in each series, may also be different from the solution proposed and illustrated.
As regards the shaped blades, it can be observed, with reference to the FIGs. from 4 to 8, that in each upper shaped blade 16 the wing-shaped surface, indicated as a whole by 21, develops parallel to the vertical rotation axis K on one side only of the connection element 22 towards the bottom base 4 and comprises a lower wing-shaped surface 21′.
Each lower shaped blade 18 or intermediate shaped blade 20, instead, has its wing-shaped surface 23 and 25, respectively, that develops parallel to the vertical rotation axis K on opposite sides of the respective connection element 24 and 26 and comprises a lower wing-shaped surface 23′ and 25′ that develops on the side where there is the bottom base 4 and an upper wing-shaped surface 23″ and 25″ that develops on the side where there is the top base 3.
It can be observed, therefore, that most wing-shaped surfaces forming the blades develop towards the bottom base 4, so that the contaminants with filaments present in the fibrous suspension tend to slide preferably towards the bottom base 4 of the central body 2 and therefore towards the bottom of the strainer, where the contaminant outlet is generally positioned.
In this way the polluting substances with filaments remain inside the strainer for a shorter time than the fibre.
This also offers another advantage, constituted by the fact that there is less rubbing of the polluting substances against the walls with which they make contact during the cleaning process, with consequent reduced wear of the strainer.
Again with reference to
This construction characteristic, together with the convergence of the directions Y and Z of the front edges 8 and 9 in the same direction of rotation w of the rotor, gives the respective wing-shaped surface 23 and 25 a receding profile in the direction opposite the direction of rotation ω of the rotor 1, which allows the polluting substances with filaments to slide away and facilitates their detachment from the rotor.
As regards the rear edges 8′, 9′ of the wing-shaped surfaces, it can be observed that they are parallel to the corresponding front edges 8, 9 and that they also converge in the direction of rotation ω of the rotor 1.
It can also be observed that the rear edge 8′ is positioned backward with respect to the rear edge 9′ in the direction opposite the direction of rotation w of the rotor 1.
As regards each connection element 11, representative of any connection element 22, 24 and 26 of the shaped blades 16, 18, 20, respectively, it can be observed that it has a triangular profile 11′, 22′, 24′, 26′, visible in detail in the figures, converging according to the direction of rotation ω of the rotor and having the vertex positioned in correspondence with the front edge 7.
Furthermore, the front edge 7 defines an obtuse angle θ with the half line λ tangential to the outer lateral surface 5 of the central body 2 drawn in the intersection point 5′ of the outer lateral surface 5 and the front edge 7.
Each connection element 11, as it can be observed in particular in
Obviously, also the connection elements 22, 24 and 25 have the same configuration described regarding the connection element 11 that represents all of them.
This facilitates the installation and removal of the blades 6 when maintenance operations or repairs are necessary.
The above shows that the rotor object of the invention achieves all the goals set.
In particular, the profile of the front edges of the blades that is receding with respect to the direction of rotation of the rotor facilitates the discharge of the contaminants with filaments.
In this way greater cleanliness of the rotor and less wear of the parts of the strainer adjacent to it are obtained.
Upon implementation changes may be made in the construction of the rotor object of the invention that are neither represented, nor described and are aimed to improve the performance of the rotor or to make its construction easier and more economical.
If said changes fall within the protection scope of the following claims, they must certainly be considered covered by the present patent.
Number | Date | Country | Kind |
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VI2004A000208 | Sep 2004 | IT | national |