Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-10-22
2001-05-22
Yao, Sam Chuan (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S137000, C156S309600, C428S306600, C428S308400, C428S319300
Reexamination Certificate
active
06235133
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a conveyor belt and a method of making the same, and more particularly such a conveyor belt and method utilizing, as a parting material, polymeric material which becomes part of the finished surface of the conveyor belt.
b) Background Art
A common method of manufacturing a conveyor belt is to provide a body of material in an elongate belt configuration having upper and lower surfaces with the material of the conveyor belt comprising at least in large part rubber and/or synthetic rubber. The conveyor belt body is positioned between upper and lower heated platens, which are then pressed against the conveyor belt body to cause vulcanization of the rubber and/or synthetic rubber (hereinafter to be referred to as “rubber”). Quite commonly, reinforcing material is provided between layers of the rubber material that is to form the body, such as steel cables, fabric or other material. Further, the layers of the belt body can differ in composition, such as an inner layer or layers being made of a cushioned rubber material, and the outer layers being of a cover rubber material.
It is usually necessary to provide some sort of parting agent at the upper and lower surfaces of the body which is positioned between and pressed by the platens, so that upon completion of the application of heat and pressure to cause vulcanization of the rubber material, the platens can be properly separated from the belt section that has just been formed. One common method of doing this is using a chemical or a fabric like material to provide a release and prevent sticking. Chemical releases can be in the form of a powder (e.g. talc), a liquid (e.g. silicone spray) or a solid (paraffin waxes). These are applied to the top and bottom surfaces of the belt. Also, as a parting agent, fabric materials can be utilized (e.g. a fine strand square woven polyester cloth). The cloth is removed after vulcanizing. Also, light random wisps of synthetic or natural material (e.g. nylon or cotton-like “angel hair”) is used. One type of such material is manufactured under the trademark “CEREX”. This material which is very thin is vulcanized into the belt surface and becomes part of the belt).
There are a number of significant considerations relating to the character of the upper and lower surface portions of the belt. One such consideration is the appearance of these upper and lower surfaces. It often happens that during the vulcanizing process where the platens are applied against the belt section, the color, shading or texture of the belt surface may become non-uniform so that there are “splotches” of a differing shade and/or color that degrade the appearance of the belt. Also, if the belt has a highly reflective surface (i.e. a mirror-like surface) the splotches become substantially more noticeable than if there is a reflectively soft textured surface.
Another consideration regarding the character of the surface of the belt is its elastomeric qualities. As a loaded belt passes over the support rollers, there is an indentation of the belt surface portion in contact with the rollers. If the surface portion of the belt has poorer elastomeric qualities, then more energy is required to move the belt over the rollers, thus requiring more powerful motors. On the other hand, if the surface portion of the belt recovers from the compression more resiliently, the energy required to move the belt is diminished.
A search of the U.S. patent literature has revealed a number of patents, these being the following:
U.S. Pat. No. 4,744,843 (Lewis) discloses the use of a releasing agent for a conveyor belt. In column 1, line 35 and following the invention is described as follows:
“I have discovered that a polymeric monomer nonwoven fabric made preferably directly from molten polymer as preferably continuous filaments that are entangled and may or may not be bonded at each crossover point can be used as a very satisfactory mold release in molding belts and related materials and the nonwoven fabric becomes a part of the molded article. The resulting molded article has an improved appearance of the article due to the elimination of trapped air or gases and the elimination of mold release build-up with its effect on appearance of the molded article.”
U.S. Pat. No. 4,411,947 (Haynhold) shows a conveyor belt having a body of rubber or synthetic materials with steel cable reinforcing. The belt is formed with an elastically deformable cushioning insert which contains air pockets and is embedded in either the upper and/or lower cover layer. The problem toward which this is directed is that the conveyor belt is stressed at the loading location since the material being loaded is usually dropped onto the belt. Accordingly, these air pockets cushion the belt to withstand these impacts. There is a double weave cloth 5 comprising two fabric layers 15 and these are interconnected by the threads 25 to keep them in parallel relationship.
U.S. Pat. No. 2,841,515 (Runton et al) shows a belt made of canvas layers having between the layers a synthetic foam which bonds the canvas layers together. A layer of the foam is also placed on the face of the belt when required for a protective coating to prevent cutting or tearing the belt when hard objects fall on it.
U.S. Pat. No. 2,515,778 (Knowland et al) discloses a belt which is adapted for use in the canning and food handling industry. The body of the belt is made of “rubberized multiple plys vulcanized into a unit and covered with synthetic plastic composition bonded and vulcanized thereto.” The layer is of a light color, odorless and resistant to solvents, oils, fats, etc. The plastic composition and a fabric sheet are bonded under pressure and heat to soften the plastic so that it permeates and bonds to the fabric sheets.
SUMMARY OF THE INVENTION
In the method of the present invention, there is first provided an elongate body having upper and lower surfaces. The body comprises a material which is uncured rubber, synthetic rubber, or combinations thereof, and this body material has a vulcanizing temperature.
A parting material is placed adjacent to at least one of the upper and lower surfaces of the body. The parting material comprises a polymeric material having interstitial open spaces and a melting or degradation temperature higher than the vulcanizing temperature.
Heated platen means are applied to the upper and lower surfaces of the body to at least soften surface portions of the body adjacent to the parting material and causing at least part of the body portion to flow into the interstitial open spaces of the parting material, and also cause the body material to vulcanize to form a conveyor belt section.
The platen means are then withdrawn from the conveyor belt section.
The conveyor belt section which is made by the process is characterized in that the parting material and the adjacent belt surface portion become combined with the parting material being embedded in the adjacent surface portion of the body to provide a substantially uniform and reflectively soft surface texture.
In the method of the present invention, the parting material is an open cell foam with a maximum pore size of between about 0.5 and 4 millimeters, and desirably between about 0.5 and 2 millimeters.
In the preferred form, the parting material is a cured elastomer. Also, in the preferred form, the parting material has a tan &dgr; of no greater than 0.1, and more desirably no greater than about 0.03.
The preferred parting material comprises at least one polymer which ia a polyethylene, polypropylene, polybutene, polyhexane, polyurethane, polyamide, polyamid 6, polyamid 66, polycarbonate, polyacetal, polyacrylate, polybutylene telephthelate, polyphenylene oxide, polyurea, silicone, polyester terephthalate, polyheptene or cross linked polyolefin.
The belt made in accordance with the process of the present invention comprises the elongate body of a material which is uncured rubber, synthetic rubber or combinations thereof. The parting material is a material
Bridgestone Corp.
Ostrolenk Faber Gerb & Soffen, LLP
Yao Sam Chuan
LandOfFree
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