| 摘要 |
<p>1. An air-vacuum cleaner for domestic or professional use, comprising a suction fan (11) driven by an electric motor (21) and a measurement device for measuring the reduced pressure in the stream of working air, which measurement device influences electrical control means (20) for the electric motor (21) and comprises a light emitter (18) which emits a light beam towards a light receiver (19), which light beam can be intercepted by a movable shutter device (17) whose movement is governed by the pressure difference between the atmospheric pressure PA and the pressure of the stream of working air PT, the shutter device (17) being moved in one direction under the influence of the force produced by the pressure difference which is opposed to the action of a return force (16) which acts in the opposite direction, characterized in that the movable shutter device comprises a movable shutter (17) which is fixedly connected to a piston (13) which is movable in a housing (15) which communicates with the stream of working air and with the atmosphere and, when the operating pressure PT is close to the smallest value Pm attainable by the vacuum cleaner, the movable shutter (17) influences the luminous flux emitted towards the receiver (19) in such a way that the measurement device influences the electrical means (20) to reduce the suction rate of the vacuum cleaner.</p> |
