Endless belt power transmission systems or components – Friction drive pulley or guide roll
Patent
1987-06-22
1989-03-07
Bui, Thuy M.
Endless belt power transmission systems or components
Friction drive pulley or guide roll
474189, F16H 5536
Patent
active
048102377
DESCRIPTION:
BRIEF SUMMARY
The invention relates to V-belt drives, which includes two or more pulleys and a die cut type V-belt. The most typical adaptations are such drives and variators, where a reliable function and suitability to variable circumstances are preferred to a long wearing life of the belt. The invention will improve the function of the V-belt drive in particular at low running speeds of the belt, but besides the speed range can as well grow upwards.
The basic idea of the invention is to make low grooves with round bottom onto the contact surfaces of pulleys. The teeth between the grooves can be sharp or rounded. The principal advantage gained by groovings is to improve efficiency and safety of the function. The characteristic features of the invention are presented more in detail in the enclosed patent claims.
In itself it is not a new idea to make grooves onto contact surfaces of a pulley. In the variators type PIV with laminated toothed chains it is known already since the year 1924, German Pat. Nos. 430252 and 435554.
The aforementioned grooves in PIV-variators have round profiles and they are straight, accurately radial and in the opposite sheaves so staggered located that they form teeth into the chain, reducing the slide effectively.
This same idea has been applied also to rope winches for example in the German patent application No. 2328474. The object of teeth is to bend the rope into crosswise curves and thus to prevent it from sliding on the pulley.
The Swedish patent application No. 302545 and the U.S. Pat. Nos. 3,730,483 and 4,093,185 include compared with the former an additional insight, that the straight grooves can be inclined and it is possible to strengthen or reduce the sinking of the rope between the cones of pulley through selection of the direction of skewness.
The Swedish patent application No. 428677 (Uno Ekman 1982) and the U.S. Pat. No. 4,151,980 include further such a feature, that the teeth added or formed on the pulley cones can be shaped like a circle. The object of the arched form is however only to improve the grip of the cone surfaces on a rope, chain or round rod running between them. If these groovings were applied to V-belt pulleys, the function would despite of the arched form not be better compared with radially grooved cone pulleys.
There are also prior known V-belt pulleys, where contact surfaces have grooves or teeth arched in shape. The document DEPS No. 224180 from year 1910 includes a V-belt pulley, where identical halves are cut in such a manner, that they screw into one other. The boundary surfaces of the teeth are perpendicular closed screw surfaces, whose intersections on symmetrical cones are spirals, which are identical but inclined to opposite directions.
This opposite direction of inclination causes, that the form of spirals does neither improve the efficiency of drive nor reduce the wear on the flanks of the V-belt. This fact is valid also for the V-belt pulley described in the document DEPS No. 821743, which pulley deviates from the afore mentioned only so that the contact cone surfaces consist of fingers, which are connected to the wheel only at the outer ring. According to the description the form of the fingers can be for example a spiral of Archimedes.
A V-belt pulley, where the contact surfaces are equipped with grooves having an exact form of the spiral of Archimedes, is introduced in the document DEPS No. 2324998. This invention is characterized by a small pitch of the spiral, pro round only ca a half of the height of the V-belt running on the pulley, The belief of the inventor, that a grooving like this would reduce vibrations of the belt, is based on the supposition, that the sliding of the belt on the contact surfaces of pulleys would take place evenly in the whole contact sector. According to the newest investigations this theory is not valid.
The spiral grooves according to the present invention deviate from the afore described by such a manner that the spiral form is an involute or approaching it. The deviations from the involute forms are needful, be
REFERENCES:
patent: 740258 (1903-09-01), Ensign
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