A power transmission toothed belt drive having a belt tooth power transmission surface defined by an arc having a radius centered on a point approximately one-half the belt tooth pitch from the centerline of the tooth. The pulley groove has a sidewall surface which confronts the power transmission surface of the belt tooth centered on the same point when the belt tooth is fully meshed with the pulley groove in the operation of the drive. A relatively small clearance with the pulley is provided adjacent the belt tooth root and a relatively large clearance is provided between the pulley groove inner surface and the tip surface of the belt tooth. In one form of the invention, both the power transmission surface and tip surface of the belt tooth are defined by a single radius and the confronting pulley groove sidewall surface and inner surface confronting the belt tooth power transmission surface and tip surface have a constant clearance therewith and are defined by continuous circular arcs.
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1. A power transmission toothed belt comprising:
a belt body defining a longitudinal pitch line and an inner land line; and a plurality of teeth projecting inwardly from said body, each tooth defining a centerline and being symmetrical about said centerline, each side of the tooth being defined by a convex radially outer root surface, an inner tip surface, and an intermediate power transmission surface, said power transmission surface defining a circular arc having a radius centered at a point spaced from said centerline approximately one-half the pitch of the teeth, and said radius having a length less than the pitch of the teeth.
18. A power transmission toothed belt comprising:
a belt body defining a longitudinal pitch line and an inner land line; a plurality of teeth projecting inwardly from said body, each tooth defining a centerline and being symmetrical about said centerline, each side of the tooth being defined by a convex radially outer root surface, an inner tip surface, and an intermediate power transmission surface, said power transmission surface defining a circular arc having a radius centered at a point spaced from said centerline approximately one-half the pitch of the teeth, and said radius having a length less than the pitch of the teeth, said inner tip surface defining a circular arc having a radius centered at said point; and a rounded surface extending inwardly from said tip surface, said rounded surface having a radius substantially smaller than the radius of said tip surface.
10. A power transmission toothed belt drive comprising:
a belt body defining a longitudinal pitch line and an inner land line; a plurality of teeth projecting inwardly from said body, each tooth defining a centerline and being symmetrical about said centerline, each side of the tooth being defined by a convex radially outer root surface, an inner tip surface, and an intermediate power transmission surface, said power transmission surface defining a circular arc having a radius centered at a point spaced from said centerline approximately one-half the pitch of the teeth, and said radius having a length less than the pitch of the teeth; and a pulley having a plurality of circumferential radially outwardly opening grooves, each groove being symmetrical about a radial centerline, each half of each groove having a convex outer surface defined by an arc of a circle extending inwardly from a face line defined by the radially outer distal face of a land between successive pulley grooves, a concave sidewall surface extending inwardly from said outer surface and being defined by a circular arc having a radius centered at a point spaced from said centerline approximately one-half the pitch of the grooves, and a concave inner surface.
2. The power transmission toothed belt of
3. The power transmission toothed belt of
4. The power transmission toothed belt of
5. The power transmission toothed belt of
6. The power transmission toothed belt of
7. The power transmission toothed belt of
8. The power transmission toothed belt of
9. The power transmission toothed belt of
11. The power transmission toothed belt drive of
12. The power transmission toothed belt drive of
13. The power transmission toothed belt drive of
14. The power transmission toothed belt drive of
15. The power transmission toothed belt drive of
16. The power transmission toothed belt drive of
17. The power transmission tooth belt drive of
19. The power transmission toothed belt of
20. The power transmission toothed belt of
21. The power transmission toothed belt of
a belt body defining a longitudinal pitch line and an inner land line; and a plurality of teeth projecting inwardly from said body, each tooth defining a centerline and being symmetrical about said centerline, each side of the tooth being defined by a convex radially outer root surface, an inner tip surface, and an intermediate power transmission surface, the distance between each side of the tooth at the root surface defining a tooth width, said power transmission surface defining a circular arc with
a radius approximately equal to said tooth width. 23. The power transmission toothed belt of claim 22 wherein said radius is centered at a point intermediate the pitch line and the land line. 24. The power transmission toothed belt of claim 22 wherein said radius is centered at a point spaced from said centerline approximately one-half the tooth width. 25. The power transmission toothed belt of claim 22 wherein said power transmission surface extends inwardly from a junction with an outer end of said root surface, said junction being spaced inwardly from said land line no more than approximately one-fourth the height of the belt tooth from said land line. 26. The power transmission toothed belt of claim 22 wherein said tip surface extends inwardly from a junction with an outer end of said power transmission surface, said junction being spaced from inwardly said land line no more than approximately one-half the height of the belt tooth from said land line. 27. The power transmission toothed belt of claim 22 wherein said belt transmission surface extends inwardly from a first junction with an outer end of said root surface, and said tip surface extends inwardly from a second junction with an outer end of said power transmission surface, a line extending through said first and second junctions intersecting said tooth centerline at an angle in the range of approximately 10° to 18°. 28. The power transmission toothed belt of claim 22 wherein said power transmission surface and said inner tip surface together define a circular arc with a radius approximately equal to said tooth width. 29. A power transmission toothed belt drive comprising: a belt body defining a longitudinal pitch line and an inner land line; a plurality of teeth projecting inwardly from said body, each tooth defining a centerline and being symmetrical about said centerline, each side of the tooth being defined by a convex radially outer root surface, an inner tip surface, and an intermediate power transmission surface, the distance between each side of the tooth at the root surface defining a tooth width, said power transmission surface defining a circular arc with a radius approximately equal to said tooth width; and a pulley having a plurality of circumferential radially outwardly opening grooves, each groove being symmetrical about a radial centerline with there being groove halves on each side of the groove centerline, each half of each groove having a convex outer surface defined by an arc of a circle extending inwardly from a face line defined by the radially outer distal face of a land between successive pulley grooves, a concave sidewall surface extending inwardly from said outer surface and a concave inner surface. 30. The power transmission toothed belt drive of claim 29 wherein the radius of the arc defined by said power transmission surface is centered at a point spaced from said centerline approximately one-half the tooth width. 31. The power transmission toothed belt drive of claim 29 wherein the radius of the arc defined by said power transmission surface is centered at a point intermediate the pitch line and the land line. 32. The power transmission toothed belt drive of claim 29 wherein said point at which the sidewall arc radius is centered is coincident with said point at which the power transmitting surface of the belt is centered when the belt tooth is fully meshed with the pulley in the groove. 33. The power transmission toothed belt drive of claim 29 wherein said belt tooth inner tip surface is defined by an arc of a circle having a radius centered in said tooth and said inner surface of the pulley groove defines a circular arc having a radius centered at a point in the pulley groove, said inner pulley groove surface radius being shorter than said belt tooth tip surface radius. |
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As seen in FIG. 1, a line drawn through junctions 23 and 24 intersects the centerline 15 at an angle α. The invention comprehends that the angle α be in the range of approximately 9° to 18° and preferably in the range of 12° to 14°.
Junction 23 is preferably spaced from land line 13 approximately one-fourth the height H of the belt tooth from the land line, or less. Junction 24 is preferably spaced inwardly from the land line approximately two-thirds the height of the belt tooth from the land line, or less. A preferred spacing for the junction 24 is approximately one-half the height of the belt tooth from the land line.
As further shown in FIG. 1, the power transmission surfaces 18 at the opposite sides of the belt tooth define reversely similar arcs having their respective radii centered at points spaced apart a distance W. The spacing W is preferably in the range of approximately 0.95 to 1.05 the pitch of the belt teeth.
The power transmission surface radius 19 preferably has a length in the range of approximately 80% to 85% of the spacing W.
Belt 10 is adapted for cooperative use with an improved pulley 25 shown in FIG. 2. As shown, pulley 25 has a plurality of circumferentially radially outwardly opening grooves 26. Each groove is symmetrical about a radial centerline 27.
As shown in FIG. 2, each half of the groove has a convex outer surface 28 defined by an arc of a circle extending inwardly from a face line 29 defined by the radially outer distal face of the lands, or teeth, 30 between the pulley grooves 26.
The flank surface of the pulley groove further defines a concave sidewall surface 31 extending inwardly from the outer surface 28. Sidewall surface 31 is defined by a circular arc having a radius 32 centered at a point 33 spaced from the centerline of the groove approximately one-half the pitch of the pulley grooves P'. As shown in FIG. 2, the outer surface 28 is defined by a circular arc having a radius 34 centered at a point 35 in the pulley land 30.
The pulley groove further defines an inner surface 36 extending inwardly from the sidewall surface 31 and defining a circular arc having a radius 37 centered on a point 38 in the pulley groove 26.
Belt tooth tip surface 17 defines a circular arc having a radius 39 centered at a point 40 in the belt tooth, as shown in FIG. 1. Preferably, radius 37 of the pulley groove inner surface 36 has a length shorter than the length of radius 39.
Belt tooth 10 defines a distal inner surface 42 inwardly of the tip surfaces 7 and pulley groove 26 further defines a convex radially inner bottom surface 43. The height of the belt tooth from land line 13 to the distal surface 42 is preferably greater than the depth of the pulley groove from face line 29 to the bottom surface 43.
Preferably, radius 21 of the belt tooth surface is longer than the radius 34 of the pulley groove outer surface. Thus, referring to FIG. 3, when the pulley tooth is fully meshed with the pulley groove, a small clearance 44 is had between the belt root surface 16 and pulley outer surface 28, a constant clearance 45 is had between the belt power transmission surface 18 and the pulley sidewall surface 31, and a relatively large clearance 46 is had between the belt tip surface 17 and the pulley groove inner surface 36.
Further as seen in FIG. 3, because the height of the belt tooth is greater than the depth of the pulley groove, an interference occurs at the distal end 42 of the belt tooth, causing the belt tooth to be compressed by the engagement thereof with the convex bottom surface 43 of the pulley groove.
The belt tooth 14 is relatively large and strong for use in transmitting high loads. A large surface area is provided between the power transmission surface 18 of the belt tooth and the sidewall surface 31 of the pulley groove, providing improved power transmission capabilities and prevention of belt jumping.
The provision of the relatively small clearance 44 at the outer end of the groove and the relatively large clearance 46 at the inner end thereof reduces the amount of movement of the belt tooth on start-up and effectively prevents interference between the belt tooth and pulley in the operation of the drive.
Referring now to the embodiment of FIGS. 4-6, a modified form of power transmission toothed belt drive generally designated 147 is shown to comprise a drive similar to drive 47 of the embodiment of FIGS. 1-3, but wherein the tip surface 117 of the pulley belt tooth 114 comprises a continuation of the circular arc defining the power transmission surface 118 thereof. Thus, the power transmission surface 118 and tip surface 117 are defined by a single radius 148 from the point 120 corresponding to point 20 of belt 10. As shown, the distance between each side of the tooth at the root surface 116 defines a tooth width or thickness T'. Tooth width T' is approximately equal to the distance W between the points 120, such that the distance between each point 120 and the centerline is equal to approximately one-half the tooth width. Moreover, it can be seen that each radius 148 is approximately equal to the tooth width T', and each center 120 is located between pitch line 112 and land line 113.
The junctions 123 and 124 with the root surface 116 and tip surface 117 of power transmission surface 118 are located similarly as junction 23 and 24 in belt 10 and, thus, define a relatively small angle α with the centerline 115 of the belt tooth. That is to say, junction 123 preferably is spaced approximately one-fourth the height H of the belt tooth from the land line, or less, and junction 124 preferably is spaced approximately one-half the height H of the belt tooth from the land line.
The distal end of the tooth is defined by a flat surface 149 joined to the outer ends of the tip surfaces 117 by rounded corners 150. The rounded corner is defined by an arc having a radius 151 centered on a point 152 in the belt tooth. Radius 151 is relatively small. Thusly, the surfaces 118 and 117 define a continuous circular arc extending substantially the entire height of the belt tooth inwardly from the root surface 116.
In all other respects, belt 110 is similar to belt 10. Elements of belt 110 which are similar to elements of belt 10 are identified by similar reference numerals but 100 higher.
As shown in FIG. 5, drive 147 includes a pulley 125 having a groove 126. Pulley groove 126 is similar to groove 26 of pulley 25 except that the inner surface 136 is defined by the radius 132 centered on point 133 corresponding to radius 32 and point 33 of pulley 25 and further defining the sidewall surface 131 of pulley 125.
Bottom surface 143 is joined to the outer ends of the outer surfaces 136 of the pulley groove 126 by rounded corner surfaces 153. The corner surfaces are defined by a radius 154 centered on a point 155.
As seen in FIG. 6, the clearance 156 between the belt tooth and pulley groove flank surface is constant between the confronting surfaces 131 and 118, and the confronting surfaces 136 and 117. As in drive 47 147, the clearance 144 between the belt tooth root surface 116 and the pulley groove outer surface 128 is relatively small, and the clearance 146 between the rounded corners 153 of the pulley groove and 150 of the belt tooth is somewhat larger.
The length of the belt tooth is preferably approximately 3% longer than the depth of the pulley groove in the respective embodiments. Such a relationship provides for low noise engagement of the belt with the pulley by minimizing noise of contact at the pulley lands by the belt root surfaces. In each of the embodiments, an improved high load transmission characteristic is provided while yet minimizing interference between the belt and pulley in the operation of the drive. By enlarging the area of engagement between the power transmission surface of the belt tooth and the pulley groove sidewall surface, increased capability of load transmission is obtained while, at the same time, minimizing the belt jumping problem discussed above.
Other than as discussed specifically above, drive 147 functions similarly to drive 47.
The foregoing disclosure of specific embodiments is illustrative of the broad inventive concepts comprehended by the invention.
Tanaka, Hiroyuki, Uto, Kuniharu, Kawai, Kazumi, Shaura, Tsuneo, Yasuhuku, Motonobu
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