An aesthetic and useful device for enclosing a vacuum pump within a framed enclosure for the evacuation of air from used containers is herein disclosed. The trailer frame includes a pair of spaced, parallel wheel ramps. A single or multiple such treatments may be employed. A controlling unit is connected electrically to the strain sensor unit and the moving unit, and actuates the touching member when the strain sensor unit detects a torque that is larger than a reference torque level. Alternatively, the output movable mirrors of the optical switch are separated into a plurality of areas to be arranged, and are arranged in each area so that the path switchover between two output movable mirrors is performed without the optical signal crossing other output movable mirrors.