Conveyors: power-driven – Conveyor section – Endless conveyor
Reexamination Certificate
2000-09-12
2002-12-10
Walsh, Donald P. (Department: 3651)
Conveyors: power-driven
Conveyor section
Endless conveyor
C198S837000, C198S838000
Reexamination Certificate
active
06491156
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus for supporting a conveyor belt. More specifically, the apparatus of the present invention relates to a fluid plenum trough conveyor support that provides a near frictionless fluid film bearing to support a conveyor belt. The apparatus of the present invention may be used as a discrete conveyor belt support element. The discrete elements formed by the method of the present invention may also be sealingly joined to form a continuous trough conveyor path for a conveyor system. An improved particulate collection system is provided at termination points of the conveyor system for eliminating particulate emissions as the bulk materials transported by the conveyor are unloaded or transferred to receiving points.
BACKGROUND OF THE INVENTION
Conveyor belt systems have been known and used in many industries for many years. Many of these systems utilize a continuous loop belt to transport bulk materials from one point to another. Traditionally the belt is supported by idler rollers, or troughing rollers which define a conveyor path. The drive means that translate the belt along the conveyor path must be capable of moving the weight of the materials as well as overcoming the frictional forces developed between the belt and the above described support means.
The conveyor systems described above have many drawbacks. First, each of the support rollers is subject to wear and mechanical failure. These failures can damage a belt or cause premature wear of the belt. Second, the rollers require routine maintenance. Often the location of these rollers within the conveyor system will pose significant hazards to maintenance personnel assigned to service these components. Other times, the location of these components will merely be an inconvenience. In either case these difficulties can lead to significant delays or equipment downtime while maintenance personnel service the equipment. Finally, each roller introduces a component of friction into the system, which must be overcome by the belt drive mechanism. These frictional components tend to increase as the rollers and their associated bearings wear, requiring additional energy consumption by the drive mechanism. In turn, the belt drive mechanism is subjected to additional wear, potentially causing premature mechanical failure.
Fluid plenum conveyor belt support elements have been introduced to overcome these limitations. They function by the introduction of a pressurized fluid source between the belt and a trough formed in the plenum to contain and guide the belt. The pressurized fluid forms a fluid film layer between the trough and the conveyor belt. The fluid film supports the weight of the belt and the materials transported thereon, while providing a near frictionless bearing surface between the belt and the trough. This concept provides distinct improvements over earlier roller methods. First, maintenance of the bearings is virtually eliminated by the elimination of the moving components of the earlier roller systems. Second, the fluid film bearing significantly reduces the amount of friction between the belt and supporting conveyor path. Finally, the reduction of frictional forces encountered by the belt permits operation of the conveyor drive mechanism at reduced power levels resulting in reduced energy costs and reduced wear and tear on the belt drive mechanism.
While fluid plenum conveyor systems have many advantages over troughing roller systems, fluid plenum systems in the art demonstrate significant inefficiencies. First, the shape of these fluid plenum troughs inhibits efficient fluid film layer propagation. Second, the fabrication techniques used to form the troughs introduce surface irregularities which become more pronounced in response to operational and environmental factors. These surface irregularities further inhibit efficient propagation of the fluid film layer. Third, the prior art methods used to join discrete trough elements to form a continuous fluid plenum conveyor system introduce further surface irregularities at the joint between each element. Moreover, these junctions do not sealingly join trough elements, permitting the inefficient escape of pressurized fluid from the plenum. Fourth, the fluid plenum troughs of the prior art demonstrate the undesired characteristic of belt float, wherein an unloaded portion of the conveyor belt lifts uncontrollably from the trough. Finally, in applications that transport bulk materials containing or developing significant amounts of particulate matter, the pressurized fluid used to produce the fluid film surface can release the particulate into the environment, creating an environmental hazard.
Prior art versions of fluid plenum conveyors employ a cross-sectional trough shape consisting of a central radius symmetrically extending upward from each side of a vertical centerline. When the central radius reaches a desired angle, the trough is further extended with straight sides extending upward from a point of tangency with the central curve to create a trough of the desired cross section. The intent of the prior art designs was to create a trough with the same cross-sectional profile as prior art troughing rollers in accordance with Conveyor Equipment Manufactures Association, (CEMA) standards. It was thought that a fluid film conveyor trough of the described profile would best permit the intermittent use of standard CEMA troughing rollers in cooperation with fluid plenum troughs to form a continuous conveyor path. While this design more accurately replicates the conventional roller profile, it is not the optimum shape to create a supporting fluid film. Uniform contact of the belt with the trough surface is critical to allow the pressurized fluid to equally react against the entire surface of the belt. The flat tangential sections of the prior art design prevent uniform contact of the belt with trough surface. As a result, fluid flow separation occurring near the boundary of the tangentially flat portions and the curved portion disrupting the propagation of the fluid film layer.
Prior art troughs with tangential sides also exhibit surface irregularities which become more pronounced in response to operational and environmental factors. The surface irregularities primarily manifest themselves along the length of the tangential portions of the trough, and are defined by convex and concave portions interspersed throughout the trough surface. However, the techniques used to join the flat tangential portions to the central radius portion can also distort the surface of the central radius portion. The surface variations cause corresponding variations in the fluid pressure between these portions of the trough and the belt. The concave areas impose a lower pressure against the belt due to the belt bridging across the concave areas. The increased fluid flow across the concave portions further disrupts the propagation of the fluid film layer. Conversely, the convex areas impose higher pressures against the belt. When the pressure between the belt and the convex portions of the trough exceeds the pressure of the fluid film, the belt will come into frictional contact with the trough. In response to operational and environmental stresses, these surface irregularities become more pronounced, further reducing the efficiency of the fluid plenum conveyor system. In an application using air as the supporting fluid, a relatively low operating pressure of 1. PSI is typical. This seemingly low pressure exerts substantial total pressure within the plenum. For example: a trough supporting a 54″ wide conveyor belt has over 15,000. pounds of upward lift on a typical 20. foot long section. When combined with the effects of thermal expansion, these pressures will further distort the surface irregularities in the trough, seriously degrading the efficiency of the system. The resultant effect of all these inefficiencies is an increased power demand from the conveyor drive and blower mechanisms with corresponding wear on the belt, trough, and
Hudco Industial Products, Inc.
Sharma Rashmi
Walsh Donald P.
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