Metal working – Method of mechanical manufacture – Roller making
Reexamination Certificate
2002-05-06
2003-07-01
Vidovich, Gregory (Department: 3726)
Metal working
Method of mechanical manufacture
Roller making
C029S895300, C264S327000, C264S328160, C492S048000, C492S050000
Reexamination Certificate
active
06584688
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a cylindrical press jacket made of a castable elastomeric material for use on a press device which treats materials in the form of a web. The press device is particularly used for dewatering or smoothing a fibrous material web. The jacket will also have reinforcement threads and/or reinforcement fabric embedded in the elastomeric material and is made with the hardness of the material in the area of the interior side being different from the exterior side of the press jacket. A process for manufacturing the press jacket is also disclosed.
2. Discussion of Background Information
Press jackets are generally known, for example, from DE-OS 196 54 194 and DE-OS 196 54 751; in particular, which use reinforcement threads and cast the press jacket from a homogeneous material. They use relatively large distances between the reinforcement threads to facilitate their manufacture which allows the material to sufficient penetration the spaces formed between these distances.
The manufacturing the jacket in a single casting process also has the advantages of being simpler to manufacturing and producing a jacket with improved strength.
However, depending on the application, it may be necessary to make the jacket with different hardness characteristics between interior and exterior sides. For example, a harder exterior side has advantage with regard to improved abrasion resistance. This characteristic is especially desired when the press jacket is to have grooves or blind holes for receiving the pressed-out water. In contrast, a harder interior side allows for less oil absorption and improves the running properties of hydraulically supported press jackets.
SUMMARY OF THE INVENTION
The invention provides for a press jacket and a manufacturing process in which the press jacket has different hardness characteristics between its interior and exterior sides. Moreover, the jacket is made from an elastomeric material which contains at least one component which causes stronger crystallization in the area of the casting mold during casting on a relatively cold casting mold.
The jacket ideally cast against a mold which is colder than the jacket material being cast. The surface formed against the colder mold generally experiences stronger crystallization, and the result is a generally higher proportion of hard segments being formed on this surface. Thus the surface which is formed against the mold will be harder than the other parts of the jacket.
The elastomer material may be, for example, polyurethane and made include polymers or prepolymers, such as diphenylmethan—diisozyanate (MDI) with polyester, since they are appropriate as components for strengthen crystallization. In addition, the elastomeric material should also contain a cross-linker.
The differences in the hardness between the interior and exterior sides should be in the range of approximately 2 to 7 Shore A. For example, one side may have a hardness in the range of approximately 92 to 96 shore A, while the other side has a hardness of approximately 94 to 98 shore A. However, each surface may also be as low as approximately 85 shore A is desired.
By manipulating the manufacturing process, it is therefore possible to influence which side is to be made harder. Thus in order to manufacture a harder interior side, the elastomeric material is applied to the exterior side of a cylindrical casting mold, since a surface which is formed against a mold surface will be made harder. If it is desired to make the exterior side harder, then the elastomeric material is applied to the interior side of a hollow cylindrical casting mold, again since a surface which is formed against a mold surface will be made harder. Preferably the jacket is cast using conventional centrifugal or hot-casting techniques such as those discussed in U.S. Pat. No. 5,766,421. Moreover, the particulars of such conventional molding are identified in each of U.S. Pat. Nos. 5,118,391 and 5,134,010, which are fully incorporated by reference. These conventional techniques being modified by the use of a mold which is colder than the casting material as described herein.
In either case the temperature of the casting mold should be controlled between approximately 10 and 100° C., and preferably between approximately 20 and 80° C., colder than the temperature of the elastomeric material being cast. For it is this cold mold effect which causes a elastomer material formed against it to become harder. Preferably, the mold is preheated to the desired temperature. For this purpose, a heavy steel mold is preferred since it can maintain the desired temperature for a relatively long period of time.
Even more control over the formation of the various degrees of hardness is improved by the use of reinforcement threads or the reinforcement fabric, because this acts as an insulating layer and therefore limits the temperature effect of the cold casting mold to the area between the contact or forming surface and the reinforcement threads or reinforcement fabric. The reinforcing fibers made be those which are conventionally and can include polyester, polyamid, and/or aramid.
According to one aspect of the invention, there is provided a cylindrical press jacket for treating a material web which includes a hollow cylindrical sleeve made of an castable elastomeric material containing at least one crystallization component, wherein the sleeve has an interior cylindrical surface and an exterior cylindrical surface, and one of reinforcement threads and reinforcement fabric embedded in the elastomeric material, such that the hardness of the elastomeric material in an area of the interior surface differs from a hardness of the exterior surface. The jacket may be made using a casting mold which is colder than the elastomeric material being cast. The cold casting mold may be positioned against the interior surface so as to cause a greater crystallization to occur in on the interior surface relative to the exterior surface. Alternatively, the cold casting mold may also be positioned against the exterior surface so as to cause a greater crystallization to occur in on the exterior surface relative to the interior surface. Moreover, the jacket may be used for one of dewatering and smoothing a fibrous material web. The greater crystallization may correspond to greater hardness.
The invention also provides that the crystallization component includes a polymer. The polymer may be a prepolymer. The difference between the hardness of the interior surface and the exterior surface may be in a range of approximately 2 to 7 Shore A.
According to another aspect of the invention, there is provided a process for manufacturing a press jacket which includes using a cylindrical casting mold having an exterior surface, setting a temperature of the cylindrical casting mold which is colder than an elastomeric material being cast, casting a hollow cylindrical sleeve from the elastomeric material on the casting mold, such that the elastomeric material contains at least one crystallization component, embedding one of reinforcement threads and reinforcement fabric in the elastomeric material, providing the sleeve with an interior cylindrical surface and an exterior cylindrical surface, such that the internal surface is formed against the external surface of the cylindrical casting mold, wherein the internal surface of the sleeve is harder than the external surface of the jacket.
According to still another aspect of the invention, there is provided a process for manufacturing a press jacket which includes providing a cylindrical casting mold having a hollow internal surface, such that the casting mold has a temperature which is colder than an elastomeric material being cast, casting a hollow cylindrical sleeve from the elastomeric material on the casting mold, such that the elastomeric material contains at least one crystallization component, embedding one of reinforcement threads and reinforcement fabric in the elastomeric material, providing the sleeve with an int
Compton Eric
Greenblum & Bernstein P.L.C.
Vidovich Gregory
Voith Sulzer Papiertechnik Patent GmbH
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