Press belts and shoe press device using the belts
A press belt employed for pressurizing a zonal material, endlessly formed by an elastic material with the thickness progressively reduced from a central pressurizing portion toward end pressurizing portions. A shoe press comprising at least the aforementioned press belt, a pressure shoe applying pressure to the aforementioned press belt and pressure regulation means regulating the pressure of the pressure shoe. Thus, the pressure can be uniformly applied to a zonal material to be pressurized.
The present invention relates to a press belt employed for pressurizing a zonal material in various industries such as the paper industry, the magnetic recording medium manufacturing industry, the textile industry and the like and a shoe press employing the same.
BACKGROUNDA press belt is employed for pressurizing a zonal material in various industries. For example, the so-called shoe press is widely used in a dehydrating press in the paper industry. Briefly stated, the shoe press is a device pressing a first surface of a zonal material (wet web) to be pressurized with a press roll or the like while pressurizing a second surface with a pressure shoe having a prescribed width in the running direction through a press belt thereby pressurizing (dehydrating) the zonal material (wet web). While a roll press performing pressing with two rolls applies linear pressure to an object to be pressurized, the shoe press provided with the pressure shoe having the prescribed width in the running direction can apply area pressure to the object to be pressurized. When performing dehydration pressing with the shoe press, therefore, a nip width can be increased for advantageously improving dehydration efficiency. The press belt is endlessly formed by an elastic material such as thermosetting polyurethane. Also in relation to a calendering step of smoothing the surface of a zonal material and setting a gloss thereon in the paper industry or the magnetic recording medium manufacturing industry, calendering employing a press belt such as a belting press or a shoe press similar to the above in place of or along with a roll press has recently been studied in order to improve the quality of a product such as paper or a magnetic recording medium. In the paper industry, further, particularly when machining paper at a high speed, employment of a similar press belt is studied for a transfer belt preventing web break before or after nip press, and stably transporting wet web.
However, the aforementioned shoe press 100 has such a problem that the pressure is not uniformly applied to the overall wet web 103. In other words, the own weight of the large-sized support 108 of metal as well as depression of the press roll 104 deflect a portion close to a central pressurizing portion C as in a support 108a shown in
In consideration of the aforementioned circumstances, an object of the present invention is to provide a press belt capable of uniformly applying pressure to a zonal material to be pressurized and a shoe press employing the same. Another object of the present invention is to provide a press belt capable of improving durability of the press belt by preventing the press belt from nonuniform wearing for reducing the cost for a pressing step by reducing the frequency for exchanging the press belt and a shoe press employing the same.
DISCLOSURE OF THE INVENTIONIn order to attain the aforementioned objects, the press belt according to the present invention, employed for pressurizing a zonal material, is endlessly formed by an elastic material with the thickness progressively reduced from a central pressurizing portion toward end pressurizing portions.
In the press belt according to the present invention, the thickness is preferably progressively reduced from the aforementioned central pressurizing portion toward the aforementioned end pressurizing portions by at least one type of technique selected from a group of a crown curve technique, a linear technique, a stepped technique and a trapezoidal technique.
The press belt according to the present invention preferably includes a cylindrical endless reinforcing base, a first elastic layer located on the outer peripheral surface of the reinforcing base and a second elastic layer located on the inner peripheral surface of the reinforcing base, and the thickness of the first elastic layer is preferably progressively reduced from the central pressurizing portion toward the end pressurizing portions.
Alternatively, the press belt according to the present invention preferably includes a cylindrical endless reinforcing base, a first elastic layer located on the outer peripheral surface of the reinforcing base and a second elastic layer located on the inner peripheral surface of the reinforcing base, and the thickness of the second elastic layer is preferably progressively reduced from the central pressurizing portion toward the end pressurizing portions.
In the press belt according to the present invention, the difference between the thickness of the aforementioned central pressurizing portion and the thickness of the aforementioned end pressurizing portions is preferably 2 to 30% of the thickness of the aforementioned central pressurizing portion.
The press belt according to the present invention is preferably a papermaking press belt.
Alternatively, the press belt according to the present invention is preferably a shoe press belt.
The present invention also provides a shoe press comprising at least the aforementioned press belt, a pressure shoe applying pressure to the aforementioned press belt and pressure regulation means regulating the pressure of the pressure shoe.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the press belt according to the present invention are now described.
FIRST EMBODIMENT
As shown in
The difference (hereinafter referred to as “thickness difference”) between the thickness C1C1′ of the central pressurizing portion of the aforementioned press belt 11 and the thickness A1B1 of the end pressurizing portions is preferably 2 to 30%, more preferably 2 to 20% and further preferably 4 to 10% of the thickness C1C1′ of the central pressurizing portion. Uniformity of the pressure applied to a zonal material to be pressurized is further improved when the thickness difference is within this range.
While the method of progressively reducing the thickness of the first elastic layer 13 is not restricted, this thickness is preferably so progressively reduced as to crown a curve connecting the portions A1, C1 and A1′ with each other. In this case, the applied pressure is locally changed on no portion, whereby the uniformity of the pressure applied to the zonal material to be pressurized is further improved.
The aforementioned press belt 11 may be manufactured by a method of impregnating the reinforcing layer 12 consisting of an endless reinforcing base with an elastic material, hardening this elastic material thereby forming the first elastic layer 13 and the second elastic layer 14 and thereafter performing cutting, polishing or the like for progressively reducing the thickness of the first elastic layer 13 from the central pressurizing portion C1 toward the end pressurizing portions A1 and A1′ of the first elastic layer 13, for example.
The reinforcing base impregnated with the elastic material can be prepared from woven fabric or nonwoven fabric, for example. While generally known woven fabric can be employed as the woven fabric, for example, multiple cloth such as warp triple cloth, warp quadruple cloth or the like is preferably employed, for example. In this case, the woven fabric includes such a large number of voids that the degree of impregnation with the elastic material can be improved for attaining a sufficient anchor effect between the elastic material and the reinforcing base, whereby delamination between the elastic material and the reinforcing base can be prevented. The nonwoven fabric can be formed by dry nonwoven fabric prepared by a method such as thermal bonding, chemical bonding or air layering, wet nonwoven fabric prepared by bonding fiber with a binder or the like or nonwoven fabric prepared by a method such as spun lacing, spun bonding, melt blowing, needle punching or stitch bonding.
At least one type of natural fiber and/or at least one type of synthetic fiber can be employed as the material(s) for the aforementioned woven or nonwoven fabric. The natural fiber includes fiber such as cotton, hemp, silk or wool, for example. The synthetic fiber includes fiber such as rayon, polyester, acrylic, polypropylene, polyethylene, ultrahigh-molecular polyethylene, polyvinyl alcohol, polyurethane, polyamide, total aromatic polyamide, carbon, glass, metal or fluorine, for example.
At least one type of rubber and/or at least one type of thermoplastic elastomer can be employed as the elastic material. The rubber includes butyl rubber, natural rubber, butadiene rubber, isoprene rubber, chloroprene rubber, ethylene-propylene rubber, styrene-butadiene rubber, styrene-butadiene-styrene rubber, nitrile rubber, polynorbornene rubber, acrylic rubber, urethane rubber, silicone rubber or epichlorohydrin rubber, for example. The thermoplastic elastomer includes styrene-based, olefin-based, ester-based, polyamide-based, vinyl chloride-based or urethane-based thermoplastic elastomer, for example.
Reinforcing filamentous bodies can be arranged in the first elastic layer 13 and the second elastic layer 14. In this case, the mechanical strength of the press belt 11 can be improved. The aforementioned at least one type of natural fiber and/or at least one type of synthetic fiber can be employed for the reinforcing filamentous bodies, for example. The reinforcing filamentous bodies are preferably prepared from at least one type of fiber selected from inorganic fiber such as carbon fiber, glass fiber, boron fiber, alumina fiber, potassium titanate fiber, silica fiber or zirconia fiber or organic fiber such as total aromatic polyamide fiber, total aromatic polyester fiber, ultrahigh-molecular polyethylene fiber, high-strength vinylon fiber or high-strength acrylic fiber. In this case, the strength of the press belt 11 according to the present invention can be further improved.
The aforementioned reinforcing filamentous bodies can be used in the form of bundles of filaments, thread, roving or cords. Further, the reinforcing filamentous bodies can be arranged in unidirectional or multidirectional combination selected from the peripheral direction, the width direction and the oblique direction of the press belt 11.
SECOND EMBODIMENT
In the press belt 21 according to the second embodiment, a curve connecting the portions B2, C2′ and B2′ in the second elastic layer 24 with each other is also preferably crowned as described above. The remaining points of the second embodiment are similar to those of the first embodiment.
THIRD EMBODIMENT
In the press belt 31 according to the third embodiment, a curve connecting the portions B3, C3′ and B3′ in the second elastic layer 34 with each other is preferably crowned as described above. The remaining points of the third embodiment are similar to those of the first and second embodiments.
FOURTH EMBODIMENT
In the press belt according to each of the first to seventh embodiments, methods of progressively reducing the thicknesses of the portions of the belt located on the right and left sides of the central pressing portion C-C′ are preferably identical to each other, while the same may be different from each other.
When the thicknesses of both of the first elastic layer and the second elastic layer are progressively reduced in the press belt according to each of the aforementioned second and fourth to seventh embodiments, methods of progressively reducing the thicknesses of the first elastic layer and the second elastic layer are preferably identical to each other, while the same may be different from each other. The press belt according to the seventh embodiment can be preferably employed as a papermaking press belt in particular, above all as a shoe press belt for dehydration.
Also in the press belt according to each of the first to sixth embodiments, drains may be formed on the first elastic layer when the press belt is employed as a papermaking belt, particularly as a shoe press belt for dehydration. The application of the press belt according to the present invention described with reference to each of the aforementioned first to seventh embodiments is not particularly restricted but the press belt can be preferably employed as a belt for pressing, calendering, transfer, embossing or the like in the paper industry, the magnetic recording medium manufacturing industry, the fiber industry or the like. The press belt can be preferably employed as a belt for a shoe press, in particular.
(Shoe Press)
The shoe press according to the present invention at least comprises the aforementioned press belt, a pressure shoe applying pressure to the press belt and pressure regulation means regulating the pressure of the pressure shoe. The pressure shoe can be prepared from a generally known metal plate or the like, for example. The pressure regulation means can be prepared from generally known hydraulic cylinders or the like, for example.
A zonal material (not shown) such as wet web transported to the aforementioned shoe press 80 is subjected to pressurization such as dehydration, calendering or the like due to pressure formed between the press belt 81 forced up by the pressure shoe 82 and the depressed press roll (not shown).
The shoe press 80 according to the present invention employs the press belt 81 whose thickness is progressively reduced from a central pressurizing portion toward end pressurizing portions. Also when a portion of the support 84 close to the central pressurizing portion is deflected downward due to the depression of the press roll (not shown) and the own weight of the support 84, therefore, the pressure applied to the zonal material (not shown) is uniform in the overall pressurizing region so that the quality of products to be pressurized can be improved.
The embodiments disclosed this time must be considered as illustrative in all points and not restrictive. The range of the present invention is shown not by the above description but by the scope of claim for patent, and it is intended that all modifications within the meaning and range equivalent to the scope of claim for patent are included.
Industrial Availability
As hereinabove described, the thickness of the press belt according to the present invention is progressively reduced from the central pressurizing portion toward the end pressurizing portions, whereby the press belt can be prevented from extreme wear from the central pressurizing portion toward both end pressurizing portions, and durability of the press belt can be improved. In the shoe press, the frequency for exchanging the press belt can be reduced due to the improvement of the durability of the press belt, whereby the cost for pressurization can be reduced. According to the present invention, further, the thickness of the press belt is progressively reduced from the central pressurizing portion toward the end pressurizing portions, whereby the overall zonal material to be pressurized can be uniformly pressurized, and the quality of products to be pressed can be improved.
Claims
1. A press belt employed for pressurizing a zonal material, endlessly formed by an elastic material with the thickness progressively reduced from a central pressurizing portion toward end pressurizing portions.
2. The press belt according to claim 1, wherein the thickness is progressively reduced from said central pressurizing portion toward said end pressurizing portions by at least one type of technique selected from a group of a crown curve technique, a linear technique, a stepped technique and a trapezoidal technique.
3. The press belt according to claim 1, including a cylindrical endless reinforcing base, a first elastic layer located on the outer peripheral surface of said reinforcing base and a second elastic layer located on the inner peripheral surface of said reinforcing base, wherein the thickness of said first elastic layer is progressively reduced from said central pressurizing portion toward said end pressurizing portions.
4. The press belt according to claim 1, including a cylindrical endless reinforcing base, a first elastic layer located on the outer peripheral surface of said reinforcing base and a second elastic layer located on the inner peripheral surface of said reinforcing base, wherein the thickness of said second elastic layer is progressively reduced from said central pressurizing portion toward said end pressurizing portions.
5. The press belt according to claim 1, wherein the difference between the thickness of said central pressurizing portion and the thickness of said end pressurizing portions is 2 to 30% of the thickness of said central pressurizing portion.
6. The press belt according to claim 1, wherein said press belt is a papermaking press belt.
7. The press belt according to claim 1, wherein said press belt is a shoe press belt.
8. A shoe press comprising at least the press belt according to claim 1, a pressure shoe applying pressure to said press belt and pressure regulation means regulating the pressure of said pressure shoe.
Type: Application
Filed: Apr 3, 2003
Publication Date: Jul 7, 2005
Inventor: Takahisa Hikida (Osaka)
Application Number: 10/510,517