Design of a stacker/lifter to handle bales of straw

Abstract

At the Government Experimental Farm, at Għammieri (limits of Luqa), a material handling problem is encountered in the stacking of bales of straw in an open barn. In this barn, more than 14,000 bales are stacked every season. The present method of stacking these bales is a totally manual operation. Bales of straw are brought by containers to the farm. The bales are thrown onto the ground from the container and transported to the stack by another operator. If the stacking had to be at ground level only, the bales are put in place immediately, and up to the height to which the stacker can lift, no problems would arise. When this height is reached, the stacker gets onto the stack and now, the bales are tied one by one, by the worker on the ground and lifted by the one on the stack, and then stacked. When the highest level is reached, the bales have to be pulled up a height of up to 5m, by the worker at the top of the stack. During this whole operation there is the danger that either the bale or the operator at the top of the stack, or both, could fall on top of the man at ground level. Another difficulty encountered is that the season for stacking and storing the bales is mid-summer, and with the outside temperature rising up to 35°C, or more, the temperature inside the barn reaches even 40°C. These temperatures certainly would not allow the workers to work at their maximum efficiency, and productivity would be at its lowest rate. Together with these difficulties another disadvantage of this present method is that due to much needed relaxation and time lost whilst the bale is being tied, pulled up and untied, before it is stacked, a lot of working man hours are lost. This leads to loss of productivity and time and thus money. In actual fact the management as well as the workers are totally unsatisfied with this method and have shown a great desire for this system to be changed to a mechanised method. In the following chapters, a mechanised system, to eliminate the above-mentioned problems, will be described.