Endless belt power transmission systems or components – Friction drive pulley or guide roll – Including nonmetallic belt-engaging surface portion
Reexamination Certificate
2001-01-02
2004-02-17
Hannon, Thomas R. (Department: 3682)
Endless belt power transmission systems or components
Friction drive pulley or guide roll
Including nonmetallic belt-engaging surface portion
C474S184000
Reexamination Certificate
active
06692392
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a lagging system for conveyor belt pulleys and, more particularly, to lagging members having lagging material for providing traction between the face of pulleys and conveyor belts driven thereabout.
BACKGROUND OF THE INVENTION
Conveyor belt lagging systems are known for providing improved traction between the underside of the conveyor belt and the outer surfaces of the pulleys about which they travel. The belt lagging materials, which can include belt engaging raised rubber nodules or ceramic tiles for example, transmit the drive force from the drive pulley to the underside of the conveyor belt. Accordingly, the resistance to slippage under their applied drive loading is a primary consideration in the performance of conveyor belt lagging systems. The load carrying capability of belt lagging is affected by the operating conditions of the conveyor, such as moisture and/or the combination thereof with loose material that can generate mud or sludge-like materials at the lagging/belt interface. In addition, the type of belt, e.g. rubber plied or PVC, can affect the load carrying capability of lagging systems.
Another factor affecting the load carrying capacity is the application for which the lagging is used. In heavy duty applications in particular, the amount of drive force differential that is generated in the interface area between the conveyor belt and lagging material can become great enough to cause slippage of the conveyor belt. Specifically, the drive force change between the positions where the belt is incoming to and outgoing from the pulley is an important consideration as with lower coverages of lagging material about the pulley, it is generally assumed that such a differential will be larger potentially causing problems for the lagging system. A conveyor belt typically will undergo some contraction as it is driven around the drive pulley at the discharge end of the conveyor belt and loading thereon is progressively reduced. If the coverage of lagging is too low and/or poorly distributed on the pulley face, then the belt contraction can cause belt slippage which increases the loading on the pulley lagging. Increased loading if sufficiently high in terms of friction and sheer forces can damage the lagging material, and if enough heat is generated by excessive loading, can cause breakdown and degradation of the pulley lagging.
Applicant's assignee herein has a product called Flex-Lag® which utilizes strips of elastomeric material to serve as a rubber backing for ceramic tiles that are molded therein. The strips are generally in elongate form with a long length and a relatively narrow width such that when attached to the pulley drive surface, the length of the strip extends axially across the pulley surface. Herein, it will be understood that the direction straight across the pulley surface will be referred to as the axial or lateral direction extending between the lateral ends of the pulley which is also commonly referred to as the width of the pulley. When discussing elongate lagging strips, the length of the strips is intended to be run in the lateral direction when attached to the pulley surface; hence, reference can be made to the strips and other features thereof as extending in the axial or lateral directions which is along the length of the strip, or corresponding in most instances to the strip's longitudinal direction. Similarly, the direction about or around the pulley surface will be referenced as the circumferential direction which with elongate strips attached as intended to the pulley surface will run across the narrow width of the strips between the long sides thereof. In all instances, these reference directions/dimensions are intended to be consistent with standard industry uses and are otherwise consistent with normal understanding, and do not establish any significant variation therefrom. However, because a pulley's width is perpendicular to that of the attached lagging in elongate strip form, any inconsistencies that may be generated thereby should be readily clarified by the surrounding description and figures provided herein.
The ceramic tiles for Flex-Lag® extend continuously along the length of the strip. The ceramic tiles include small raised round-shaped nibs so that under normal belt compression, there are numerous nibs that embed themselves into the underside belt cover to virtually eliminate belt slippage even in the most extreme operating conditions. Generally, the higher the ratio of belt engaging ceramic tiles to the area on the pulley face about which the belt travels, the greater the load carrying capacity of the lagging material. However, the cost of the ceramic tiles is the most expensive component in the total cost for ceramic lagging products. A cost effective ceramic lagging product is needed that maintains acceptable load carrying characteristics despite the presence of harsh operating conditions.
The strips of the Flex-lag® product are installed by bonding them to the pulley face. To insure a proper fit about the pulley, longitudinally extending cutting sipes are provided between rows of the ceramic tiles to allow for the width of the strips to vary in a predetermined manner around the circumference of the pulley. As is apparent, the Flex-Lag® product can require significant pre-planning to obtain a proper fit of the strips about the circumference of the pulley. In addition, cutting the strips to a desired width is labor intensive. Despite the provision of the longitudinal cutting sipes, it is still possible for a worker to install the strips so that there is a gap left between the first attached strip and the last attached strip that is too small for a strip to be fit therebetween but larger than desirable for operation of the belt.
In this instance, the installation of the strips must be reworked, or otherwise the gap that is left between the strips causes several problems during the operation of the belt. If there is a long extended axial area across the face of the pulley having such a gap spacing so that the pulley surface is devoid of ceramic tiles therein, the belt will not be supported in this gap area increasing the likelihood of belt slippage under heavy loading. Further, as the pulley rotates and belt scrapers for cleaning the belt engage the unsupported belt as it travels past the laterally long, circumferentially wide gap in lagging material on the pulley face, the scraper, which is typically biased toward the belt and pulley, will push inward on the belt and engage hard against the trailing strip of lagging on the other side of the gap. This can cause bouncing of the scraper so that there is uneven cleaning of the belt and can be hard on belt splices as they traverse the gap on the pulley such as either where there are mechanical belt fasteners in place or where the belts are attached by a vulcanized splice. Chattering of the scraper or cleaner caused by long, wide gaps free of lagging material can create damaging impacts to the belt cover, and possibly to belt carcass as well.
Accordingly, a more general definition for when such an undesirable long lateral gap is present is when the belt is not rigid enough across the gap to resist inward deflection caused when the biased scraper blade is engaged therewith. Of course, where the blade is thicker than the gap, it will straddle the adjacent lagging strips and thus not cause the problems if it were of a thickness that allowed it to project into the gap. As a specific example, such gaps are generally understood as occurring where there is a circumferential spacing of greater than approximately ⅝ inch between lagging material on adjacent strips as between a trailing or rear edge of lagging material on a forward or leading strip and a leading or forward edge of material on a rearward or trailing strip.
Another lagging product is known that utilizes strips of lagging material tightly fit between laterally extending retainers that are bolted or welded to the pulley face circumferentially spaced thereabout.
Finnegan Robert K.
Gayford Michael J.
Ramsey Peter M.
Fitch Even Tabin & Flannery
Flexible Steel Lacing Company
Hannon Thomas R.
McAnulty Timothy
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