The present invention relates to a roller assembly for use in a turn chain assembly of a towveyor system of the type manufactured and sold by S.I. Handling Systems of Easton, Pennsylvania.
In a so-called low profile towveyor system made by S.I. Handling Systems, a continuous tow chain is supported just beneath the floor in a warehouse. The tow chain is positioned for continuous movement through a closed circuit horizontal path beneath a slot in the warehouse floor and has spaced apart recessed dogs thereon. The dogs are typically spaced 101/2 feet apart and each dog is adapted to engage a lug depending from a cart or carriage utilized by the system.
In operation, a warehouse employee loads an order onto a cart and then positions that cart above the floor slot with the lug extending into the slot. The cart will have means such as electrical or mechanical probes which can be placed in different positions for indicating where the cart should go and a dog on the continuously moving tow chain eventually engages the lug and starts moving the cart on its journey to its designated destination, such as a specified terminal or bay at the warehouse loading dock. Typically, the drive mechanism for each tow chain has a variable speed control so that the tow chain can be driven at a speed of between 80 feet and 120 feet per minute.
In a typical section of a towveyor system a continuous tow chain is arranged to travel in an elongate loop with a 180.degree. degree turn at each end of the loop. Of course, other sections will have paths of different configurations which may have other types of turns such as 45.degree., 90.degree. and 120.degree. turns. Each turn has some form of means for bearing and guiding the tow chain around the turn, one such means being a turn chain assembly. The turn chain assembly includes a continuous turn chain comprising a plurality of bearing rollers rotatably journaled between links of the turn chain, an arcuate bearing guide plate having a concave front bearing surface, an arcuate return guide plate situated behind the bearing guide plate and stationary turn posts mounted at each end of the turn in so-called clean out boxes. The bearing guide plate and the return guide plate are generally parallel spaced and extend between the two clean out boxes. A section of the turn chain is situated between the tow chain and the front surface of the bearing guide plate to provide a means for bearing the tow chain around the turn while the remainder of the turn chain is trained around each of the turn posts and onto the surface of the return guide plate facing the bearing guide plate.
Typically each of the turn posts is defined by a short section of 4 inch pipe with one post being rigidly fixed in position and the other post being adjustably mounted so that its position can be adjusted to take up slack in the turn chain and to facilitate installation and removal of the turn chain.
From time to time during the operation of the towveyor system, bearing rollers of the turn chain become jammed and flats are worn onto them. These flats wear grooves into the turn posts. After five or six flats have developed on the rollers, the turn chain, and frequently the turn posts also, must be replaced. As a result the present average life of a turn chain and turn posts is approximately one to three years depending on how well they are maintained (e.g., lubricated and kept clean).
It will be understood that in a typical towveyor system there are numerous turns and that each time a turn chain needs to be replaced the whole system has to be shut down. This results in a work stoppage in the warehouse. It has been estimated that this work stoppage or down time in a warehouse each time a turn chain needs to be replaced presently costs between $1000.00 and $5000.00 per hour in addition to the cost of the replacement chain. A turn chain has a length from 8 to 40 feet and presently costs about $38.00 per foot. Depending on the length of the turn, the down time is typically between 3 and 10 hours. Thus, turn chain replacements are very costly; and it is a primary object of the present invention to reduce the frequency of turn chain replacements and increase the life of each turn chain in a towveyor system.