Items of vibrating hand-held equipment, in particular grinding machines and rotary hammers, are fitted with support handles. Vibrations higher than those on the main handle often arise on these handles, which are very light, sometimes of simple design, and fixed rigidly to the machine. A test procedure with associated evaluation criteria does not exist. The vibration characteristic of these handles is determined by means of the test procedure employed for the machine. In the case of grinding machines and rotary hammers, this represents a substitute working method which fails to take into account the particularly high influence of the coupling forces for handles with damping. In addition, the single-point measurements do not take the natural vibration characteristics of the handles into consideration. The objective of this project was to develop suitable test and evaluation principles for low-vibration handles and to introduce them into the international standardization process in the form of a proposed supplement. This would enable low-vibration support handles to be evaluated more effectively. At the same time, an incentive was to be created for the further development of anti-vibration handles.
The study was to examine the transmission of vibration to the hands by handles with and without anti-vibration systems on a number of selected sample devices. The following study methods were employed: measurement of the vibration damping in accordance with the applicable standard for the item of equipment concerned and the substitute working method and under real working conditions; measurement of the damping characteristics by vibration simulation over a broadband spectrum; modal analysis for evaluation of the influence of the measurement point selected and measurement of further parameters, e.g. the elastic characteristics of energy transmission.
The modal analysis system has proved effective for the development of test and assessment methods for low-vibration handles on hand-held equipment. A suitable calibration method was developed and tested for this purpose. Angle grinders served as sample machines for testing of the method on support and supplementary handles. The results for the handles tested showed the measurement errors to be in the order of the current uncertainty of measurement. For antivibration handles supplied by the manufacturer and therefore designed for the machine in question, the measurement points specified in the measurement standards may be regarded as adequate. The results of the study can be exploited for development of a test method for handles which may be selected freely by the user of the machine.
-cross sectoral-Type of hazard:
Lärm/Vibrationen, Arbeitsbedingte Erkrankungen, Gestaltung von Arbeit und TechnikCatchwords:
Belastung, Vibration, SchutzmaßnahmeDescription, key words:
hand-arm vibration, vibration impact, grinding machines, support handles, vibration protection