1. Field of the Invention
This invention relates to conveyor systems of the type having a conveying belt trained around spaced rollers for movement in a predetermined travel path. More particularly, the invention is directed to a support system for underside rollers which bear against the moving conveying belt.
2. Background Art
Conveyor systems are used in a wide range of applications in many diverse environments. In a typical conveyor system, a conveying belt is trained around spaced head and tail pulleys for continuous movement in a predetermined travel path. In a portion of the travel path, the conveying belt defines an upwardly facing supporting surface upon which material can be placed to transport the same from one location to another as dictated by the system configuration. A significant expanse may exist between the head and tail pulleys. The unsupported belt traveling in the underside path portion is commonly supported by one, or a plurality of, rollers, commonly designated “idler rollers”.
Often conveyor systems are constructed so that there is sufficient space beneath the conveying belt for individuals to pass. This presents two potentially dangerous situations. First of all, the conveying belt moving in the underside path portion at each idler pulley creates a potentially dangerous pinch point. Inadvertent contact by anyone with the conveying belt at the underside path portion upstream of an idler pulley could draw a contacting limb dangerously into the pinch point. The converging structural shape defined by the conveying belt at each idler roller is aggravated by the fact that both the conveying belt and idler roller are moving in a direction that tends to draw objects to the pinch point. The industry has long been aware of the above problem. A number of guards have been designed to reduce the risk of injury at the idler roller location. One such guard system blocks the converging geometry upstream of the pinch point.
While a guard of this type addresses potential injury, it also introduces another operating problem. The guard system defines an obstruction which intercepts material that has not been cleaned from the conveying belt as it passes through its underside path portion. This condition may eventually lead to the impairment of the system operation. Often, the conveyed material may be a particulate that has a tendency to bind. This condition may be aggravated by severe conditions in which the conveyor system operates which dampen the conveyed material and may increase the tenacity of the bond to the conveying belt. This type of material may follow the belt into its return path portion whereby it progressively accumulates at the guard location to the point that conveying belt movement and/or idler roller operation may be impaired. This accumulation of material may also be sufficient that the idler roller may be forced to separate from its mounting.
Conventional idler rollers have had a tendency to separate from their mounts in conveyor systems. These rollers have a significant weight that could inflict injury upon anyone who is contacted by them. There is an increasing awareness of this problem. This has lead to the development of certain guards which are designed to prevent potentially dangerous, unrestricted downward travel of idler rollers that have separated from their supports. One example of such a guard is shown in U.S. Pat. No. 6,318,545 (Ross, II). Ross II has a trough-shaped element placed over each idler roller. In the event of separation, the idler roller will be “caught” and confined by the trough-shaped element.
Ross II also discloses structure for wiping the underside of the blade on both the upstream and downstream ends of the guard. This avoids the migration of foreign matter carried on the conveying belt into the chamber defined by the trough-shaped element. However, it is inevitable that there will be some material that does find its way past the upstream wiper and into the roller receptacle bounded by the trough-shaped element. This progressive accumulation could ultimately fill the receptacle which could block the movement of the idler roller and also potentially accumulate a mass sufficient to disengage the entire roller mechanism, including the guard, from its support.
There is currently underway a campaign from governing bodies in this industry to require guards to prevent personal injury in the vicinity of the idler rollers resulting from the above situations. Designers in this industry continue to seek ways to address safety issues without impairing the basic operation of the conveyor systems.