U.S. Pat. No. 5,209,705 to Gregg ostensibly discloses a synchronous drive belt with oblique and offset teeth.
U.S. Pat. No. 3,078,206 to Skura ostensibly discloses a method of forming belt teeth and reinforced positive drive belts.
U.S. Pat. No. 2,600,775 ostensibly discloses a method and apparatus for making and curing power transmission belts.
Finally, Japanese Patent No. 59-133,034 is also directed to a method of manufacturing a synchronous drive belt.
Synchronous drive belts generally comprise a resilient elastomer reinforced with a longitudinal tensile member made up of a plurality of cords of a high elastic modulus. The cords may be made from glass fiber, carbon fiber, steel, polyester, high tenacity rayon or preferably, polyamide.
The tooth surface of the belt may be reinforced with an abrasion resistant fabric, one example of which is nylon.
The elastomers may be any one of those known to be suitable for use in such belts, including polychloroprene, polyurethane, NBR, IIR, IR, SBR, CSM, EPDM, other thermosets, thermoplastic elastomers and other polymer alloys.
Typically, synchronous drive belts are manufactured by winding layers of fabric, unvulcanized elastomer and cord on a drum. The drum functions as an internal mold and may have a periphery consisting of axially oriented evenly pitched grooves. During vulcanization, the belt slab is molded by pressure exerted by an external diaphragm or autoclave which forces the slab radially inwardly against the drum periphery. After vulcanization, the belt sleeve is slid axially off the drum or mold. The sleeve is then slit transversely into individual belts in a separate operation.
The synchronous belts so formed normally have a single track of teeth extending from the belt at right angles to the belt circumference, the teeth having dimensions compatible with the grooves on the drum periphery. A simple grooved drum is utilized in the manufacture of such belts.
It is known in the art to provide synchronous belts having at least two transversely adjacent rows of teeth which are at oppositely balanced oblique angles to the direction of the belt. One such belt structure is disclosed in U.S. Pat. No. 5,209,705 the disclosure of which is incorporated herein by reference. The belt structure disclosed therein provides certain advantages, especially relating to noise, which offer improvements over belts having a single track of teeth which extend at right angles to the belt circumference.
A problem encountered in the art, however, is the ability to manufacture the improved belts by a method that allows the building and vulcanization of a band having more than one belt section on an internal drum mold. The presence of the two or more tracks of teeth extending at oppositely balanced oblique angles on each belt section bars the cured belt sleeve from being slid axially off the drum mold, as is done in the prior art manufacturing method described above. Heretofore there has not been a viable method of manufacture of the improved belts.
The inventive process described herein provides a method whereby a synchronous belt having two or more tracks of teeth extending at oppositely balanced oblique angles may be advantageously manufactured in a way that is simple and effective.