Multi-stage rotary lobe pump

Abstract

A multistage Roots pump comprise a plurality of pump chambers in a pump housing. They constitute respective pump stages, wherein each pump stage comprises two two-toothed rotary pistons. The pump stages are separated from each other by partition walls. In the partition walls essentially radially extending connecting ducts are arranged. The connecting ducts are connected with an inflow chamber whose inflow opening has a larger cross-section than the connecting ducts.

Claims

1. A multistage Roots pump, comprising: a first pump chamber and a second pump chamber defined by a pump housing, two two-toothed rotary pistons defining a pump longitudinal axis and being arranged in the first and second pump chambers to define a first pump stage adjacent to a second pump stage, a partition wall separating the first and second pump stages from each other, and a connecting duct arranged in the partition wall, wherein the connecting duct is connected with an axial inflow chamber into which a delivered medium flows from the first pump chamber through an inflow opening, and wherein said inflow opening has a larger cross-section than the connecting duct, wherein the pump housing comprises: an outlet cover which constitutes a sidewall of the axial inflow chamber and a sidewall of a prechamber of the first pump chamber, and an inlet cover which constitutes a sidewall of an outlet chamber and a sidewall of a postchamber of the second pump chamber.

2. The multistage Roots pump according to claim 1, wherein the connecting duct is radially arranged with respect to the pump longitudinal axis.

3. The multistage Roots pump according to claim 2, wherein the connecting duct is directly connected with the inflow chamber.

4. The multistage Roots pump according to claim 1, wherein all edges of the inflow opening are rounded.

5. The multistage Roots pump according to claim 1, wherein the prechamber is arranged upstream of the inflow chamber as seen in a direction of flow.

6. The multistage Roots pump according to claim 5, wherein the prechamber is arranged radially with respect to the two two-toothed rotary pistons.

7. The multistage Roots pump according to claim 5, wherein the prechamber is a portion of the first pump chamber into which the two two-toothed rotary pistons do not project.

8. The multistage Roots pump according to claim 1, wherein the connecting duct is directly connected with the outflow chamber.

9. The multistage Roots pump according to claim 8, wherein an outflow opening of the outflow chamber, through which the delivered medium flows out into the second pump chamber, has a larger cross-section than the connecting duct.

10. The multistage Roots pump according to claim 9, wherein all edges of the outflow opening are rounded.

11. The multistage Roots pump according to claim 8, wherein the postchamber is arranged downstream of the outflow chamber as seen in a direction of flow.

12. The multistage Roots pump according to claim 11, wherein the postchamber is arranged radially with respect to the two two-toothed rotary pistons.

13. The multistage Roots pump according to claim 11, wherein the postchamber is a portion of the second pump chamber into which the two two-toothed rotary pistons do not project.

14. The multistage Roots pump according to claim 1, wherein the inlet cover extends across the first and second pump stages.

15. The multistage Roots pump according to claim 14, wherein the outlet cover extends across the first and second pump stages.

16. The multistage Roots pump according to claim 1, wherein the outlet cover extends across the first and second pump stages.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Hereunder the disclosure is explained in detail on the basis of a preferred embodiment with reference to the accompanying drawings in which:

(2) FIG. 1 shows a cross-section of schematic diagrams of a two-stage Roots pump according to the disclosure in different rotational positions of the pair of rotary pistons,

(3) FIG. 2 shows a schematic perspective longitudinal section of the multistage Roots pump according to the disclosure, and

(4) FIG. 3 shows a top view schematically showing an inlet area of the inflow chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(5) Each pump stage of the multistage Roots pump according to the disclosure comprises a pair of rolling pistons. The pair of rolling pistons comprises two two-toothed rotary pistons 10. They are each arranged on a shaft 12 and are rotated in opposite directions for delivering the medium. The individual rolling pistons of the successively arranged pump stages are each disposed on a common shaft such that the Roots pump comprises two shafts 12. The rolling pistons 10 of a respective pair of rolling pistons are arranged in a pump chamber 14 constituting a pump stage. The pump chamber is formed by a bipartite housing 16, 18. Here, a partition 20 of the housing is provided in the center of the two shafts 12 such that a simple assembly is possible. In addition, the housing is provided with an inlet cover 22 and an outlet cover 24.

(6) From the schematic longitudinal section along a line II-II of FIG. 1 illustrated in FIG. 2 it can be seen that the Roots pump according to the disclosure is configured as a multistage Roots pump, wherein, in an axial direction, a plurality pump stages 26, 28, 30, 32, 34 are provided. The chamber volumes of the individual pump stages decrease starting from the pump stage 26 towards the pump stage 34. The first pump stage 26 is connected with a main inlet 36. The main inlet 36 is connected with a chamber to be evacuated or the like. The medium to be delivered thus radially flows into the pump chamber 14 of the first pump stage 26 through the main inlet 36.

(7) In the radial direction, opposite the main inlet 36, a prechamber 38 is formed. The prechamber 38 extends across the overall axial width of the pump stage 26 and thus has essentially the same width as the rolling pistons 10 of the first pump stage 26.

(8) In addition, an inflow chamber 40 is provided. The inflow chamber 40 is arranged adjacent to the prechamber 38 on the one hand and further comprises an inflow opening 42 directly connected with the pump chamber 14 in the illustrated exemplary embodiment.

(9) A connecting duct 48 arranged inside a partition wall 44 is disposed adjacent to the inflow chamber 40. In FIG. 2 the medium to be delivered flows from top to bottom in the connecting duct 48.

(10) Adjacent to the connecting duct 48, which exclusively radially extends in the illustrated exemplary embodiment, an outflow chamber 50 configured such that it corresponds to the inflow chamber 40 is arranged, and adjacent to the latter a postchamber 52 configured such that it corresponds to the prechamber 38 is arranged. The outflow chamber 50 comprises an outflow opening 54 whose contour and configuration match those of the inflow opening 42 in the illustrated exemplary embodiment.

(11) In the illustrated exemplary embodiment, all pump stages are configured such that they correspond to each other, wherein the pump stages are respectively separated from each other by partition walls 44, and in each partition wall 44 a radially extending connecting duct 48 is arranged in the illustrated exemplary embodiment. Each connecting duct 48 is respectively connected with an inflow chamber 40 and an outflow chamber 50 as well as a prechamber 38 and a postchamber 52.

(12) In particular for reducing the flow resistances, the inlet openings 42 of the inflow chambers 40 as well as preferably also the outflow openings 54 of the outflow chambers 50 are configured such that they have a larger cross-section than the connecting ducts 48.

(13) Further, both the inflow chambers 40 and the prechambers 38 are connected with a common inlet cover 24. Correspondingly, the outflow chambers 50 as well as the postchambers 52 are connected with a common outlet cover 22.

(14) The final pump stage 34 is further connected with a main outlet not illustrated through which the medium to be delivered is discharged.

(15) In FIG. 3 a schematic top view of an inlet chamber 40 is illustrated which is connected with a prechamber 38 on the one hand and with a connecting duct 48 on the other hand. In the illustrated exemplary embodiment, the inlet opening 42 is formed by the curved edge 54. Thus the inlet opening has the cross-section shown by the dashed line 56.

(16) As can further be seen, the inflow chamber 40 is directly connected with the corresponding pump chamber 14 on the one hand and with the prechamber 38 on the other hand. The same applies to the outflow opening 54.