Low backlash-high-torque power transmission system and toothed belt used therein

A flexible power transmission belt having a plurality of teeth separated from each other by a plurality of alternating belt land areas, each tooth having a center line and comprising a pair of opposed flanks each of which in longitudinal cross-section has a generally convex arcuate contour, each flank being joined to the adjacent belt land area by a root having an arcuate contour approximating an arc of a circle having a given first radius and having a tooth tip portion connecting said pair of flanks at a location spaced from said root, each tooth having a longitudinal width dimension measured between the points where said root arcs intersect the opposing flanks of the belt tooth and a height dimension measured from the belt land line representing an extension in longitudinal cross-section of the belt land area to the outermost surface portion of the tooth tip, said height dimension being in the range 0.50 to 0.67 of said tooth width dimension, each of the arcuate flanks approximating an arc of a circle and being formed such that a line drawn tangent thereto at a point spaced a distance equal to 0.3 times the said width dimension from the belt land line will intersect the tooth center line at an angle in the range of 18.degree. to 23.degree., and said belt land area joining the root of adjacent teeth, having a length dimension in longitudinal cross-section in the range 0.2 to 0.66 of said tooth width dimension.

A power transmission system comprising the combination of (A) an endless flexible power transmission belt having a succession of identical teeth uniformly spaced apart, said belt having land areas between consecutive teeth and the outer surfaces of said land areas, in cross-section, defining a belt land line L, each tooth having substantially identical fore and aft convex flank surfaces with at least part of said fore and aft flank surfaces shaped in cross-section as a curve approximating the arc of a circle centered on the line L, each said belt tooth having a root portion connecting said flank curves to the respective land areas and havng a tip portion connecting the opposite ends of said flank curves to each other, said tooth having a height H measured from said line L to the extremity of said tip portion, said tooth having a width W measured between the end points of said flank curves where said flank curves meet said root portions, the curvature of said arcuate flanks being such that a tangent line drawn thereto at a point which is spaced from the belt line L a distance equal to 0.3 times the width dimension W will make an angle alpha with the vertical center line of the belt tooth, said belt tooth having a height-to-width relation within a first predetermined range and an angle alpha within a second predetermined range, said first predetermined range being 0.50 to 0.67 and said second predetermined range being 18.degree. to 23.degree. and (B) a pulley having a plurality of identical peripheral belt-engaging teeth defining between them pulley cavities, wherein each pulley cavity possesses substantially identical fore and aft flank surfaces, at least part of each said flank surfaces being shaped in cross-section as a curve approximating the arc of a circle and said pulley teeth having pulley land surfaces at the tips thereof, said land surfaces defining in longitudinal cross-section portion of a pulley land line L.sub.p approximating a circle concentric with the center of the pulley and said pulley cavity having a cavity bottom portion connecting the opposite arcuate flanks thereof at points on said flanks furthest spaced from said pulley land line L.sub.p, each said pulley tooth tip having arcuate portions adjacent the pulley land line L.sub.p and joining the respective arcuate flank portions to the adjacent pulley land areas and said cavity having a width dimension W.sub.p measured between corresponding points of said arcuate flank portions where said arcuate portions of said pulley tooth tip connect with the respective arcuate flank surfaces, said cavity having a depth Hp measured between said pulley land line L.sub.p and the portion of the cavity bottom portion which is spaced furthest from said pulley land line L.sub.p, the curvature of said cavity flank surfaces being such that they are substantially concave with respect to the body of the pulley and that a line drawn tangent thereto at a point thereon spaced from said pulley land line L.sub.p a distance 0.3 times said width dimension W.sub.p makes an angle .alpha.p with the center line of said pulley cavity, said pulley cavity having a dept-to-width relation within a third predetermined range and said angle .alpha.p being within a fourth predetermined range, wherein said third predetermined range is from 0.74 to 0.64 and said fourth predetermined range is from 18.5.degree. to 23.5.degree..

The combination of (A) an endless flexible power transmission belt having a succession of identical teeth uniformly spaced apart, said belt having land areas between consecutive teeth and the outer surfaces of said land areas, in longitudinal cross-section, defining a belt land line L, each tooth having substantially identical fore and aft convex flank surfaces with at least part of said fore and aft flank surfaces shaped in longitudinal cross-section as a curve approximating the arc of a circle centered substantially on the line L, each said belt tooth having a root portion connecting said flank curves to the respective land areas and having a tip portion connecting the opposite ends of said flank curves, said tooth having a height H measured from said line L to the extremity of said tip portion, a width W measured between the end points of said flank curves where said flank curves meet said root portions, the curvature of said arcuate flanks being such that a tangent line drawn thereto at a point which is spaced from the belt land line L a distance equal to 0.3 times the width dimension W will make an angle alpha with the vertical center line of the belt tooth, said belt tooth having a height-to-width relation within a first predetermined range and an angle alpha within a second predetermined range, said first predetermined range being 0.50 to 0.67 and said second predetermined range being 18.degree. to 23.degree. and (B) a pulley having a plurality of identical peripheral belt-engaging teeth defining between them pulley cavities, wherein each pulley cavity is substantially the conjugate of one said belt tooth.

A power transmission system comprising the combination of (A) an endless flexible power transmission belt having a succession of identical teeth uniformly speaced apart, said belt having land areas between consecutive teeth and the outer surfaces of said land areas, in cross-section, defining a belt land line L, each tooth having substantially identical fore and aft convex flank surfaces with at least part of said fore and aft flank surfaces shaped in cross-section as a curve approximating the arc of a circle centered on the line L, each said belt tooth having a root portion connecting said flank curves to the respective land areas and having a tip portion connecting the opposite ends of said flank curves to each other, said tooth having a height H measured from said line L to the extremity of said tip portion, said tooth having a width W measured between the end points of said flank curves where said flank curves meet said root portions, the curvature of said arcuate flanks being such that a tangent line drawn thereto at a point which is spaced from the belt line L a distance equal to 0.3 times the width dimension W will make an angle alpha with the vertical center line of the belt tooth, said belt tooth having a height H equal to 0.60W and an angle alpha equal to 21.5.degree., said root portion having a pair of arcuate portions at opposite ends of said land area and said land area between said arcuate portions being equal to 0.2W in length, said curved portion of said arcuate flanks being the arc of a circle of radius equal to 0.85W and centered belt land line L, said belt tooth tip comprising in longitudinal cross-section a pair of non-intersecting arcs having radii equal to 0.19W and a substantially straight line of length equal to 0.36W connecting said non-intersecting arcs and (B) a pulley having a plurality of identical peripheral belt-engaging teeth defining between them pulley cavities, wherein each pulley cavity possesses substantially identical fore and aft flank surfaces, at least part of each said flank surface being shaped in cross-section as a curve approximating the arc of a circle and said pulley teeth having pulley land surfaces at the tips thereof, said land surfaces defining in longitudinal cross-section a portion of a pulley land line L.sub.p approximating a circle concentric with the center of said pulley and said pulley cavity having a cavity bottom portion connecting the opposite arcuate flanks thereof at points on said flanks furthest spaced from said pulley land line L.sub.p, each said pulley tooth tip having arcuate portions adjacent the pulley land line L.sub.p and joining the respective arcuate flank portions to the adjacent pulley land areas and said cavity having a width dimension W.sub.p measured between corresponding points of said arcuate flank portions where said arcuate portions of said pulley tooth tip connect with the respective arcuate flank surfaces, said cavity having a depth Hp measured between said pulley land line L.sub.p and the portion of the cavity bottom portion which is spaced furthest from said pulley land line L.sub.p, the curvature of said cavity flank surfaces being such that they are substantially concave with respect to the body of the pulley and that a line drawn tangent thereto at a point thereon spaced from said pulley land line L.sub.p a distance 0.3 times said width dimension W.sub.p makes an angle .alpha.p with the center line of said pulley cavity, said pulley cavity having a depth-to-width relation within a third predetermined range and said angle .alpha.p being within a fourth predetermined range, wherein said third predetermined range is from 0.47 to 0.64 and said fourth predetermined range is from 18.5.degree. to 23.5.degree..

A power transmission system comprising the combination of (A) an endless flexible power transmission belt having a succession of identical teeth uniformly spaced apart, said belt having land areas between consecutive teeth and the outer surfaces of said land areas, in cross-section, defining a belt land line L, each tooth having substantially identical fore and aft convex flank surfaces with at least part of said fore and aft flank surfaces shaped in cross-section as a curve approximating the arc of a circle centered on the line L, each said belt tooth having a root portion connecting said flank curves to the respective land areas and having a tip portion connecting the opposite ends of said flank curves to each other, said tooth having a height H measured from said line L to the extremity of said tip portion, said tooth having a width W measured between the end points of said flank curves where said flank curves meet said root portions, the curvature of said arcuate flanks being such that a tangent line drawn thereto at a point which is spaced from the belt line L a distance equal to 0.3 times the width dimension W will make an angle alpha with the vertical center line of the belt tooth, said belt tooth having a height H equal to 0.63W and an angle alpha equal to 21.5.degree., said root portion having a pair of arcuate portions at opposite ends of said land area and said land area between said arcuate portions being equal to 0.49W in length, said curved portion of said arcuate flanks being the arc of a circle of radius equal to 0.85W and centered on belt land line L, said belt tooth tip comprising in longitudinal cross-section a pair of non-intersecting arcs having radii equal to 0.19W and a curved line of radius equal to 0.63W connecting said non-intersecting arcs and centered on said belt land line L and (B) a pulley having a plurality of identical peripheral belt-engaging teeth defining between them pulley cavities, wherein each pulley cavity possesses substantially identical fore and aft flank surfaces, at least part of each said flank surfaces being shaped in cross-section as a curve approximating the arc of a circle and said pulley teeth having pulley land surfaces at the tips thereof, said land surfaces defining in longitudinal cross-section a portion of a pulley land line L.sub.p approximating a circle concentric with the center of the pulley and said pulley cavity having a cavity bottom portion connecting the opposite arcuate flanks thereof at points on said flanks furthest spaced from said pulley land line L.sub.p, each said pulley tooth tip having arcuate portions adjacent the pulley land line L.sub.p and joining the respective arcuate flank portions to the adjacent pulley land areas and said cavity having a width dimension W.sub.p measured between corresponding points of said arcuate flank portions where said arcuate portions of said pulley tooth tip connect with the respective arcuate flank surfaces, said cavity having a depth Hp measured between said pulley land line L.sub.p and the portion of the cavity bottom portion which is spaced furthest from said pulley land line L.sub.p, the curvature of said cavity flank surfaces being such that they are substantially concave with respect to the body of the pulley and that a line drawn tangent thereto at a point thereon spaced from said pulley land line L.sub.p a distance 0.3 times said width dimension W.sub.p makes an angle .alpha.p with the center line of said pulley cavity, said pulley cavity having a depth-to-width relation within a third predetermined range and said angle .alpha.p being with a fourth predetermined range, wherein said third predetermined range is from 0.47 to 0.64 and said fourth predetermined range is from 18.5.degree. to 23.5.degree..