Roots pump connection channels separating adjacent pump stages

1. A Roots pump comprising:

a plurality of multi-toothed rotary pumps, each forming a Roots-type pump stage, and

connection channels connecting respective adjacent Roots-type pump stages,

wherein the connection channels are arranged in partitioning walls separating the adjacent Roots-type pump stages, and

wherein said multi-toothed rotary pistons comprises at least 3 teeth and at least some of the connection channels extend only axially between the adjacent Roots-type pump stages.

2. The Roots pump of claim 1 , further comprising, in operation, a channel inlet opening and/or a channel outlet opening of at least one connection channel is swept over by a side wall of a rotary piston.

3. The Roots pump of claim 1 , wherein all said connection channels are arranged in said partitioning walls separating the Roots-type pump stages.

4. The Roots pump of claim 1 , further comprising a main inlet arranged radially opposite a main outlet.

5. The Roots pump of claim 4 , wherein at least one said connection channel that connects said Roots-type pump stage with said adjacent Roots-type pump stage extends obliquely in the corresponding partitioning wall and transversely to the plane formed by the two shaft axes.

6. The Roots pump of claim 5 , wherein said partitioning walls including oblique connection channels are thicker than said partitioning walls including axial connection channels.

7. The Roots pump of claim 1 , wherein one of the two rotary pistons of each rotary piston pair is arranged on a common shaft.

8. The Roots pump of claim 1 , wherein the axial width of the rotary pistons of individual Roots-type pump stages decreases in particular in the pumping direction.

9. A Roots pump comprising:

a plurality of rotary pumps forming a Roots-type pump stage, each rotary pump comprising at least 3 teeth;

a partitioning wall separating a first Roots-type pump stage from a second Roots-type pump stage; and

a connection channel defined through the partitioning wall so as to connect the first Roots-type pump stage to the second Roots-type pump stage, the connection channel consisting of a straight cylindrical bore between the first and second Roots-type pump stages.

10. A Roots pump comprising:

a plurality of rotary pumps forming a Roots-type pump stage, each rotary pump comprising at least 3 teeth;

a partitioning wall separating adjacent Roots-type pump stages; and

a connection channel defined through the partitioning wall so as to connect the adjacent Roots-type pump stages, wherein the Roots-type pump stage and connection channel are configured to expel gas only after a rotation of the rotary pumps by an angle of rotation of less than 180°.