US Patent 7195547 Dual plate sander

The present invention relates to a dual plate sander comprising a housing, a motor mounted in the housing, first and second transmission devices driven by the motor and eccentric shafts each rotating about a main drive shaft connected to the transmission device. Twin sanding assemblies terminating in sanding plates are mounted on respective eccentric shafts. A guiding element serves to translate the eccentric rotary motion of the eccentric shafts into opposite reciprocating movement of the sanding assemblies. The opposed reciprocating movement serves to balance the inertial forces generated by the sander and reduce oscillations.