Endless belt power transmission systems or components – Friction drive belt – Including plural interconnected members each having a drive...
Reexamination Certificate
1999-10-08
2001-09-25
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Friction drive belt
Including plural interconnected members each having a drive...
C474S245000, C474S237000
Reexamination Certificate
active
06293886
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a heavy-duty power transmission V-belt.
A heavy-duty power transmission V-belt comprising a large number of blocks and a tension member including tension cords and hard rubber is conventionally well known and used in the field of stepless transmission. In this V-belt, power is transmitted between the tension member and the blocks through engagement between convex parts of the blocks and concave parts of the tension member. The respective blocks are fixed on the tension member not through adhesion but through physical engagement in order to secure flexibility of the V-belt.
In this conventional heavy-duty power transmission V-belt, each of the blocks is made form a hard resin material in which a reinforcing member for reinforcing the block is embedded in a manner that at least parts to be engaged with the tension member and parts to be in contact with a groove face of a pulley are made from the resin material. The reinforcing member includes upper and lower beam parts respectively located above and below the tension member and a pillar part for connecting the bases of the upper and lower beam parts.
In heavy-duty power transmission using this belt, however, when stress is repeatedly applied to the base of the upper beam part of the reinforcing member within the block located above the tension member (i.e., on the outer side in a radial direction of the pulley), the upper beam part can be broken at the base thereof. This makes impossible the power transmission by using the belt.
Therefore, as is disclosed in Japanese Laid-Open Utility Model Publication No. 5-3692, the upper beam part of the reinforcing member of the block is proposed to be bent into an arcuate shape so that the center portion thereof can be higher than right and left portions thereof extending in a widthwise direction of the belt. In the proposed reinforcing member, stress applied to the base of the upper beam part can be reduced by the bent of the upper beam part, thereby preventing the breakage thereof.
In the proposed reinforcing member, however, it is necessary to increase the size of the entire reinforcing member when further heavier-duty power transmission is desired. In this case, the block is increased in its weight, and hence, centrifugal tension is increased in drive of the belt around a pulley. Accordingly, there is a fear of early breakage of the tension member.
An object of the invention is reducing stress applied to the base of the upper beam part by appropriately modifying the shape of the reinforcing member embedded in each block, so as to further increase transmission load of the belt without largely increasing the weight of the block.
SUMMARY OF THE INVENTION
In order to achieve the aforementioned object, a beam angle between an upper beam part of a reinforcing member and a groove face of a pulley is set to be larger than a right angle in this invention, so as to suppress bending moment caused by a reaction force from the groove face pushing the tip of the upper beam part upward.
Specifically, the heavy-duty power transmission V-belt of this invention comprises two tension members each including a large number of upper engaged parts and lower engaged parts respectively correspondingly formed on upper and lower faces thereof and arranged in a lengthwise direction of the belt; and a large number of blocks each including a fitting groove on each side face thereof in a widthwise direction of the belt and upper and lower contact parts formed on upper and lower sides of the fitting groove to be brought into contact with a pulley groove face, and the fitting groove includes an upper engaging part formed on an upper face thereof to be engaged with each of the upper engaged parts of the tension members and a lower engaging part formed on a lower face thereof to be engaged with each of the lower engaged parts of the tension members. The blocks are fixedly engaged with the tension members by fitting the tension members in the fitting grooves of the blocks. Also, each of the blocks includes a reinforcing member embedded in a resin part in a manner that at least the upper and lower engaging parts and the contact parts are made from the resin part, and the reinforcing member includes upper and lower beam parts located above and below the fitting groove and a pillar part for connecting bases of the upper and lower beam parts.
Furthermore, a beam angle between a vertical center line of the upper beam part of the reinforcing member and a pulley groove face closer to a center of a pulley than a portion of the pulley in contact with the upper contact part on the side face of the block is 90° or more.
In this manner, the following effects can be attained: In a power transmission state between the belt and the pulley, a three-dimensional force is applied between each block and each tension member. This force is caused from a shearing force in the lengthwise direction working between the engaged part of the tension member and the engaging part of the block and also from a pushing force of the tension member for pushing the lower engaging part of the block toward the center of the pulley. On the other hand, in a state where the belt is not wound around the pulley, the above-described forces are not applied. Therefore, tensile stress is applied to the base of the upper beam part of each block due to repeated stress application between these two states. Furthermore, due to the shearing force, tensile stress is applied to one side portion of the reinforcing member in the lengthwise direction and compressive stress is applied to the other side portion of the reinforcing member. When the block is pushed against the groove face of the pulley by the pushing force from the tension member, the block receives a reaction force in a direction perpendicular to the groove face at the upper contact part disposed on the upper side of the tension member. In a conventional structure, a beam angle between a vertical center line of the upper beam part of the reinforcing member and the groove face of the pulley in a position closer to the center of the pulley than a portion thereof in contact with the contact part of the block is smaller than 90°. Therefore, upward bending moment for bending the tip of the upper beam part upward is applied to the upper beam part due to a component force of the reaction force from the groove face. This upward bending moment causes tensile stress at the base of the upper beam part. As a result, not only the tensile stress derived from the shearing force but also the tensile stress derived from the upward bending moment are applied to the base of the upper beam part, resulting in synergistically increasing the tensile stress. The thus increased tensile stress causes fatigue failure at the base of the upper beam part.
In contrast, the beam angle between the vertical center line of the upper beam part of the reinforcing member and the groove face of the pulley in a position closer to the center of the pulley than a portion thereof in contact with the upper contact part of the block is 90° or more in this invention. When the beam angle is 90°, the upward bending moment is not caused. Alternatively, when the beam angle is larger than 90°, downward bending moment for reversely bending the tip of the upper beam part downward is caused due to a component force of the reaction force from the groove face of the pulley, so as to cause compressive stress at the base of the upper beam part. Accordingly, the tensile stress derived from the shearing force or tensile stress reduced correspondingly to the compressive stress derived from the downward bending moment is applied to the base of the upper beam part. As a result, large tensile stress can be suppressed from being applied to the base of the upper beam part, so as to prevent the fatigue failure due to the tensile stress from occurring at the base of the upper beam. In this manner, the transmission load of the belt can be further increased without increasing the weight of each block.
In a similar heavy-dut
Ohkawa Hirokazu
Takahashi Mitsuhiko
Bando Chemical Industries Ltd.
Bucci David A.
Charles Marcus
Cole Thomas W.
Nixon & Peabody LLP
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