Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – With casting – plastic molding – or extruding means
Reexamination Certificate
1999-01-18
2001-06-05
Yao, Sam Chuan (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
With casting, plastic molding, or extruding means
C425S028100, C425S034200
Reexamination Certificate
active
06240993
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to power transmission belts and, more particularly, to a method and apparatus for producing a power transmission belt having cogs/teeth on opposite sides thereof.
2. Background Art
There are two methods commonly practiced to form raw-edge, double-cogged belts; a pre-form method and a spun cog method.
In the pre-form method, a sheet material made up of at least a reinforcing fabric and an unvulcanized rubber layer is placed against a flat mold having alternating grooves and projections on the surface thereof. The sheet material is pressed against the mold surface to cause a complementary groove and projection pattern to be formed on the sheet material. The resulting product is commonly referred to as a “cog pad”. The cog pad is then fitted around a cylindrical inner mother die that is part of an inner mold assembly. The butt ends of the cog pad are joined to form an endless sleeve around the inner mother die. Load carrying cords are then spirally wound around the sleeve followed by uncontoured canvas fabric and unvulcanized rubber sheet layers. This entire assembly is then fit within a cylindrical outer mother die/mold assembly having alternating grooves and projections forming cogs on its radially inwardly facing surface. The outer mother die is used to form cogs on the outer surface of the sleeve, which is then vulcanized. This method is capable of producing accurate cogs by reason of the preforming of the sheet material. However, because of the pre-forming step, this method may be relatively expensive to practice.
In the spun cog method, an uncontoured reinforcing fabric and unvulcanized rubber sheet are wound around a cylindrical inner mother die/mold assembly having a cog pattern defined by alternating grooves and projections. The inner mother die is disposed on a support. Load carrying cords are wound spirally around the fabric and rubber sheet under high tension. Thereafter, another uncontoured reinforcing fabric layer and uncontoured unvulcanized rubber layer are wound therearound. The inner mother die with the various layers built up thereon is then fitted within a cylindrical outer mother die having alternating grooves and projections defining a cog pattern. The built up layers on the inner mother die are shaped into a sleeve with a cog-like pattern on oppositely facing surfaces. This sleeve is then vulcanized.
While the spun cog method can be performed relatively inexpensively, often an inaccurate cog formation results by reason of the reinforcing fabrics and unvulcanized rubber sheets not being preformed. Accurate cog formation requires winding of the load carrying cords under tension that is high enough to cause the unvulcanized rubber sheet to fully penetrate into the grooves of the inner mother die.
In both of the above methods, the alignment between the teeth/cogs on the oppositely facing surfaces of the sleeve depends upon the accurate alignment of the inner and outer mother dies, as dictated by the belt specification. A common problem is a misalignment between the dies, resulting in misalignment of the teeth/cogs on the oppositely facing sleeve surfaces.
This is particularly a problem in environments such as driving mechanisms on snowmobiles and the like using variable speed belts. These belts are required to have high side pressure resistance and good flexibility for long belt life. Precise, predetermined positioning between the inner and outer cogs in such environments is critical.
SUMMARY OF THE INVENTION
In one form, the invention contemplates a method of making a power transmission belt/belt sleeve, which method includes the step of providing a first mold assembly having a central axis and a circumference, providing a sheet material having first and second oppositely facing surfaces, placing the sheet material around the first mold assembly and causing a contoured portion of the first surface to be keyed to the first mold assembly so that the sheet material is in a predetermined circumferential position relative to the first mold assembly, providing a second mold assembly having a contoured surface, placing the contoured surface of the second mold assembly against the second surface of the sheet material, providing a guide element, operatively connecting the guide element between the first and second mold assemblies so that the guide element maintains the second mold assembly in a predetermined circumferential position relative to the first mold assembly, and forming the second surface of the sheet material through the contoured surface of the second mold assembly with the first and second mold assemblies and sheet material in an operative relationship. The contoured portion of the first surface of the sheet material can be preformed or formed in place on the first mold assembly.
Using the inventive method, the mold assemblies can be accurately positioned relative to each other to cause the teeth/cogs formed thereby on the opposite surfaces of the sheet material to be consistently aligned in a predetermined relative position.
The first mold assembly may have grooves and projections alternating around the circumference thereof. A contoured portion of the first surface of the sheet material may likewise have grooves and projections that are complementary to the grooves and projections on the first mold assembly. By placing the sheet material around the first mold assembly, the grooves and projections on the first mold assembly and first surface of the sheet material can be meshed.
The sheet material may have first and second spaced, butt ends. The sheet material can be placed around the mold assembly by wrapping the sheet material around the first mold assembly and joining the butt ends to each other to maintain the sheet material in a cylindrical shape on the first mold assembly.
The sheet material may have a body with at least one rubber layer and an elongate load carrying cord embedded in the body and extending around the central axis of the first mold assembly with the sheet material placed around the first mold assembly.
The second mold assembly may have alternating grooves and projections defining the contoured surface of the second mold assembly.
The second mold assembly may be formed to define a continuous cylindrical shape.
The guide element may be separated from the second mold assembly before forming the second surface of the sheet material.
The guide element may be operatively connected by directing a part of the guide element into one of the grooves on the second mold assembly.
The part of the guide element can be repositioned so that the guide element part does not reside in the one groove with the first and second mold assemblies and sheet material in the operative relationship. The sheet material may be vulcanized after the part of the guide element has been repositioned.
The method may further include the step of cutting the sheet material to define a plurality of endless belts.
The invention also contemplates the combination of: a first mold assembly having a central axis, a circumference, and a plurality of keying elements; a sheet material having first and second oppositely facing surfaces with a plurality of alternating grooves and projections on each of the first and second oppositely facing surfaces of the sheet material, wherein with the sheet material and first mold assembly in operative relationship the sheet material extends around the first mold assembly and the keying elements and grooves and projections on the sheet material cooperate to maintain the sheet material and first mold assembly in a predetermined circumferential position relative to each other; a second mold assembly having a surface with a plurality of alternating grooves and projections thereon; and a guide element operatively connecting between the first and second mold assemblies to maintain the first and second mold assemblies in a predetermined circumferential position relative to each other.
The keying elements may be defined by alternating grooves and projections.
In one form, the g
Ito Takehiko
Onaka Yoshiaki
Ueda Toshihiro
Yamamoto Yuji
Mitsuboshi Belting Ltd.
Wood Phillips VanSanten Clark & Mortimer
Yao Sam Chuan
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