Rotary vacuum blower

1. An improved rotary vacuum blower machine, comprising an impeller, provided with a hub keyed on a shaft adapted to be set in rotation by a motor, further provided with blades and closed in a casing which defines a circumferential annular conduit in which the blades turn, the annular conduit having a radially inward peripheral slot through which said impeller passes, the annular conduit exhibiting two openings, one of the two openings being an induction mouth for aspirating fluid from outside the machine, and a delivery mouth from which the fluid exits from the machine; comprising at least two further openings which are neither the induction mouth nor the delivery mouth, afforded on opposite sides of the casing with respect to the impeller and defining passages which place an inside of the casing in communication with an outside environment, wherein the further openings are afforded on the casing in a zone thereof which is radially inward of the annular conduit in a central part of the casing adjacent and in fluid communication with said hub, through holes being afforded on a central body of the impeller which through holes place the at least two further openings located on opposite sides of the impeller in direct reciprocal communication.

2. The machine of claim 1 , wherein a size of the passage of one said further opening is regulated by means for regulating.

3. The machine of claim 2 , wherein the size of the passage of the one said further opening is regulated by one or more heat-activated valves.

4. The machine of claim 1 , wherein one said further opening is composed of a plurality of through holes made on a circumference arranged on the casing adjacent the hub of the impeller.

5. The machine of claim 1 , in combination with the motor which sets the shaft in rotation and which comprises an electric motor powered by an inverter.