Case Study: Safety and Usability impaired by a heavy lid
Peko Precision Products, working for a well-known maker of imaging equipment, asked Weber Knapp to design hinges to support a 147 lb. lid for a thermal printing plate maker machine, which was too heavy for unaided operators to lift safely.
Unlike most units, this has a door on the front that hangs straight down throughout the opening motion of the lid. Perhaps most significant was the heavy lid weight, combined with the horizontal component of the center of gravity. This required substantial output torque from the support, within a very limited space.
The solution demanded large spring forces, difficult to achieve within the limited height and width provided for the counterbalance. It was necessary to calculate torque inputs for both components separately, then combined, and finally matched with the output torque of the counterbalance.
Weber Knapp’s engineers employed custom in-house software to efficiently use the available space, “stacking” the springs so they work in parallel, rather than in series, giving the plate processor stability when opening and closing. It also offsets the weight, making the heavy lid easier for operators to open and close.