Validation Device for the Stiffness of Cylindrical Coiled Pressure Springs

Abstract

This work presents a structural design as well as a created 3D model used for subsequent physical implementation of a validation device that allows for measuring the force as well as the shortening of a coiled pressure spring during laboratory experiments. The described device was created in order to verify and determine the stiffness of cylindrical coiled springs which are used, e.g., for tension equalizers in lift carrying ropes and handling unit fixation mechanisms. The device is located in the Laboratory of Research and Testing at the Institute of Transport, Faculty of Mechanical Engineering of VSB - Technical University of Ostrava, and is used for presentation events focusing on engineering intended for elementary and high school students as well as for teaching Bachelor and Master courses at the FME. This work presents (using tables) the pressure forces and shortening of two types of pressure cylindrical springs obtained experimentally using the validation device. The figures describe the lines obtained by purchased sensors, the sizes of immediate forces and immediate compression of the specific examined spring. These experimentally obtained values can be used to calculate the stiffness of the given spring (i.e., the actual stiffness of the spring) via the formulas specified herein, and to compare these to the stiffness values listed in the spring manufacturer's catalogue. Since there is no standard or general guideline, it may be possible to measure a stiffness value that is up to an order higher than the data listed on the product packaging for most spring manufacturers. This may logically lead to problems after the assembly of the intended machine, whereas its configuration may assume a certain stress that differs from the reality, leading to greater and unexpected stress on parts and possibly greater wear and tear.