EP4638967A1

EP4638967A1 - Vacuum pump

Info

Publication number: EP4638967A1
Application number: EP23833675.4A
Authority: EP
Inventors: Roland Albert MUELLER; Dennis GELDERMANN; Hannah BOHLEM-SPANG; Daniel Weaver
Original assignee: Leybold GmbH
Current assignee: Leybold GmbH
Priority date: 2022-12-21
Filing date: 2023-12-15
Publication date: 2025-10-29
Also published as: GB2625582A; WO2024132911A1; KR20250124114A; CN120380255A; GB202219372D0; TW202441075A; US20260210360A1; GB2625582B

Abstract

Vacuum pump, in particular 2-shaft rotor pump, comprising a housing defining a pump chamber, an inlet and an outlet; two rotor shafts arranged in in the pump chamber, wherein each pump shaft comprises at least one pump element interacting with each other, wherein each rotor shaft comprises a first end and a second end; a front cover connected to the housing at the second end of the rotor shaft; wherein the front cover comprises at least one cooling element with a radial symmetry.

Description

VACUUM PUMP It is an object of the present invention to provide a vacuum pump and in par- ticular a two-shaft vacuum pump. Conventional vacuum pumps comprise a housing defining one or more pump chambers, an inlet and an outlet. A rotor is rotatably disposed in the pump chamber and comprises at least one pump element. The rotor is rotated by an electromotor. The at least one pump element is interacting either with a stator or a pump element of another rotor in the case of a two-shaft rotor pump in order to convey a gaseous medium from the inlet to the outlet. Different vacuum pumps exist such as claw pumps, root pumps or screw pumps. In particular, for claw pumps the gas is compressed before entering the outlet, releasing a lot of heat, and making the exhaust the hottest part. This causes an uneven temper- ature distribution and deformation of that part. The front cover seals the pump- ing chamber axially and determines the clearance between the claws and the font cover (=axial clearance). This clearance should be as small as possible for best performance and as big as needed for safe operation. An uneven axial clearance through a high thermal deformation of the front cover would make a bigger clearance necessary to avoid a contact of claw and front cover and thus reduce performance. Even though described in connection with a claw pump, different vacuum pumps from the prior art suffer a similar problem. Hence, it is an object of the present invention to provide a vacuum pump which is operated more reliable with an increased pump performance. The problem is solved by a vacuum pump according to claim 1. The vacuum pump according to the present invention is in particular a two shaft- rotor pump such as a claw pump, a roots pump, a screw pump or the like. The vacuum pump according to the present invention comprises a housing defining a pump chamber, an inlet and an outlet. Two rotor assemblies are arranged in the pump chamber and rotatably supported, wherein the rotor assemblies are rotated by an electric motor. Each rotor assembly comprises a rotor shaft and at least one pump element connected to the rotor shaft and interacting with each other in order to convey a gaseous medium from the inlet to the outlet. Therein the rotor shaft comprises a first end and an opposite second end. In particular, the first end is directed towards the electromotor or a gear of the vacuum pump, wherein the second end is directed towards or in the region of the exhaust or outlet of the vacuum pump, i. e. a region of low vacuum/high pressures. Further, the vacuum pump according to the present invention provides a front cover connected to the housing and arranged at the second end of the rotor assembly. Thus, by the front cover the axial end of the rotor assembly is cov- ered, wherein the front cover may be part of the housing, i. e. integrally built with the housing, or releasably connected to the housing. The front cover thus covers the axial end of the rotor assemblies. Therein, in particular the front cover covers the whole cross-sectional area of the pump chamber and thus has the size of the area which the pump elements of the first shaft and the second shaft create as surface of revolution, i.e. the combined diameters of the pump elements. Preferably, the front cover is larger than this area. The front cover comprises at least one cooling element with a radial symmetry. It has been shown that the radial symmetry provides on one hand sufficient heat dissipation and distribution, and at the same time provides increased stiffness of the front cover. Thus, uneven temperature distribution in the front cover and deformation caused by this uneven temperature distribution can be minimized, therein at the same time deformation of the front cover is further minimized by the in- creased stiffness. Thus, the axial clearance can be decreased without the risk of contact between the rotor assemblies, and in particular the pump elements, and the front cover, thereby increasing the pump performance of the vacuum pump. Preferably, the cooling element is radially symmetric around the axis of rotation of one of the rotor assemblies. Thus, the center of the radial symmetry is defined by the axis of rotation of the rotor shaft of the respective rotor assembly. Alter- natively, two cooling elements are arranged at the front cover, wherein each cooling element is radially symmetric around a respective axis of rotation of each rotor assembly. Therein, by arranging the cooling element with respect to the axis of rotation, sufficient temperature distribution in the front cover is achieved to reduce thermal stress and deformation of the front cover. Preferably, the two cooling elements are overlapping with each other. In partic- ular, if the cooling elements comprise one or more cooling ribs, the cooling ribs may be entangled with each other in order to provide sufficient heat dissipation and sufficiently even temperature distribution across the front cover. Preferably, the two cooling elements cover the rotor diameter of the pump ele- ments (cross-sectional area of the pump elements). Alternatively, the area of the cooling elements is smaller than the respective area of the pump elements. Alternatively, the area of the cooling elements is larger than the respective area of the pump elements. Preferably, the two cooling elements are shaped differently or identically. By shaping the cooling elements differently, specific and tailored temperature dis- tribution in the front cover can be achieved. In particular, uneven temperature distribution due to uneven heat generation in the vacuum pump can be mini- mized. Preferably, the at least one cooling element comprises one or more cooling ribs. In particular, for two cooling elements both cooling elements may comprise one or more cooling ribs. Preferably, the at least one cooling element comprises one or more circular ribs. In particular, the circular ribs are arranged concentric around the respective axis of rotation of each rotor assembly. Preferably, the cooling element comprises two or more nested circular ribs. Preferably, the diameter of the circular ribs is between 2 cm and 15 cm and preferably between 3 cm and 13 cm. If the cooling element comprises two cir- cular ribs, the diameter of the outer circular rib may be between 8 cm and 15 cm and preferably between 10 cm and 13 cm. The diameter of the inner circular rib may be between 2 cm and 8 cm and preferably between 3 cm and 5 cm (Here and in the following all provided intervals are understood to include the boundary values as well – “Between 2cm and 15cm” shall be understood as “between and including 2cm and 15cm”). Preferably, the ratio between the diameter of the inner circular rib and the outer circular rib is between 1:2 and 1:5 and preferably between 1:2 and 1:4. These rations have been shown to provided sufficient temperature distribution and stiffness at the same time. Preferably, the height of the cooling ribs is between 0.8 cm and 2 cm and more preferably between 1 cm and 1.6 cm. Thus, by the specific radial symmetry of the cooling elements the cooling height of the cooling ribs can be limited thereby reducing the costs of such cooling elements for manufacturing without loss of cooling functionality. Preferably, the width or thickness of the cooling ribs is between 3mm and 1cm and more preferably between 4mm and 6mm. Preferably, the cooling element comprises more than one circular rib, wherein the circular ribs are connected by one or more radial webs. Therein, the webs may be equally distributed around the circular rib. Preferably, the cooling ele- ment comprises more than 3, more preferably more than 4, and most preferably 8 webs. Preferably, the height of the webs is between 0.8 cm and 2 cm and more pref- erably between 1 cm and 1.6 cm. Preferably, the width or thickness of the webs is between 3mm and 1cm and more preferably between 4mm and 6mm. Preferably, the cooling element is integrally built with the front cover. Thus, the cooling element and the front cover can be manufactured in a single step thereby reducing complexity of manufacturing process and costs. Preferably, the cooling element and the front cover are made from the same material. Thus, thermal stress due to thermal expansion can be minimized be- tween the cooling element and the front cover. Preferably, the outlet is provided in the front cover. Thus, the front cover also forms the outlet or exhaust of the vacuum pump. Preferably, the outlet comprises an outlet cooling element, wherein the outlet cooling element may be overlapping with the one or more cooling elements of the front cover. Preferably, the outlet cooling element may comprise linear cooling fins, which may run perpendicular to a connecting line of the two axes of rotation of the two rotor assemblies. Alternatively, the cooling fins of the outlet cooling element run perpendicular to the connecting line between the two axes of rotation of the two rotor assemblies. In the following the present invention is described in more detail with reference to the accompanying drawings. The figures show: Figure 1 a schematic drawing of a claw pump according to the present invention and Figure 2 a detailed view of the front cover according to the pre- sent invention. Referring to Figure 1, the vacuum pump 10 comprises a housing 12 defining several pump chambers 14 connected by channels (not shown). The vacuum pump 10 comprises two rotor assemblies 16. Each rotor assembly 16 comprises a rotor shaft 17, wherein pump elements 18 are connected to the respective rotor shafts 17 and arranged in the respective pump chambers. The rotor as- semblies 16 are rotated by an electromotor synchronously to each other by gears 20. By rotation of the rotor assemblies 16 the respective rotor elements 18 interact with each other in order to convey a gaseous medium from an inlet (not shown) to an outlet 22. The rotor assemblies 16 comprise a first end 24 towards the gear 20 and a second end 26 towards the outlet 22, i. e. in regions of high pressure/low vacuum. At the second end 26 of the rotor assemblies 16 a front cover 28 is connected to the housing 12. Therein, the front cover 28 may be built as separate element releasably connected to the housing 12 or may be built as integral element of the housing 12. Therein, by the front cover 28 the axial clearance between the rotor assemblies 16 and the front cover 28 is min- imized in order to increase pump performance of the vacuum pump. Referring to Figure 2 showing a detailed view of the front cover 28. The outlet 22 is connected or integrally built with the front cover 28. The front cover 28 comprises a first cooling element 34 and a second cooling element 36. Each cooling element 34, 36 is radially symmetrically built around the axis of rotation 32 (see Figure 1). Therein, the area of the first cooling element 34 and the second cooling element 36 may correspond to the area defined by the combined cross-sectional area of the pump elements 18, i. e. correspond to the size of the pump chamber 14 or may overlap with the pump chamber 14. The first cooling element 34 and the second cooling element 36 are mainly identically built. Thus, in the following only the first cooling element 34 is described in more detail. However, the same description also applies to the second cooling element 36. Alternatively, the first cooling element 34 and the second cooling element 36 may be shaped differently contrary to what is shown in Figure 2. The first cooling element 34 comprises a plurality of cooling rips which are arranged with the radial symmetry. The first cooling element 34 comprises a first circular cooling rib 38 and a concentrically arranged second circular cooling rib 40. Therein, the diameter of the first circular cooling rib 38 is between 2 cm and 8 cm and pref- erably between 3 cm and 5 cm and the diameter of the second circular cooling rib 40 is between 8 cm and 15 cm and preferably between 10 cm and 13 cm. Further the first circular cooling rib 38 and the second circular cooling rib 40 are connected by webs 42, wherein in the example of Figure 2, eight webs 42 are arranged between the first circular cooling rib 38 and the second circular cooling rib 40. Additional webs are arranged outside the second circular cooling rib 40. By the cooling ribs of the cooling elements 34, 36 heat is distributed across the front cover 28 to prevent or reduce thermal stress and deformation of the front cover. By the cooling ribs sufficient heat dissipation can be achieved. At the same time, it has been shown that by the radial symmetry of the cooling ele- ments 34, 36 stiffness of the front cover 28 can be increased. Thus, contact between the front cover 28 and the rotor assemblies 16 can be avoided thereby increasing the reliability and security of operation of the vacuum pump 10. In addition, as shown in Figure 2, linear cooling fins 44 are connected to the outlet 22. Therein, the linear cooling fins 44 connected to the outlet 22 are overlapping with the cooling elements 34, 36. List of references 10 vacuum pump 12 housing 14 pump chamber 16 rotor assembly 17 rotor shaft 18 pump element 20 gear 22 outlet 24 first end 26 second end 28 front cover 32 axis of rotation 34 first cooling element 36 second cooling element 38 first circular cooling rib 40 second circular cooling rib 42 web 44 cooling fin

Claims

CLAIMS 1. Vacuum pump, in particular 2-shaft rotor pump, comprising a housing defining a pump chamber, an inlet and an outlet; two rotor assemblies arranged in in the pump chamber, wherein each rotor assembly comprises at least one pump element interacting with each other, wherein each rotor assembly comprises a first end and a sec- ond end; a front cover connected to the housing at the second end of the rotor assembly; wherein the front cover comprises at least one cooling element with a radial symmetry. 2. Vacuum pump according to claim 1, wherein the cooling element is radi- ally symmetric around the axis of rotation of one of the rotor assembly. 3. Vacuum pump according to claim 1 or claim 2, wherein two cooling ele- ments are arranged at the front cover, wherein each cooling element is radially symmetric around a respective axis of rotation of each rotor as- sembly. 4. Vacuum pump according to claim 3, wherein the two cooling elements are overlapping with each other. 5. Vacuum pump according to claim 3 or 4, wherein the two cooling ele- ments are shaped differently or identically. 6. Vacuum pump according to any of claims 1 to 5, wherein the at least one cooling element comprises one or more cooling ribs. 7. Vacuum pump according to any of claims 1 to 6, wherein the at least one cooling element comprising one or more circular ribs. 8. Vacuum pump according to claim 7, wherein the cooling element com- prises more than one circular rib, wherein the circular ribs are connected by one or more radial webs. 9. Vacuum pump according to any of claims 1 to 8, wherein the outlet is provided in the front cover. 10. Vacuum pump according to claim 9, wherein the outlet comprising an outlet cooling element, wherein the outlet cooling element is overlapping with the one or more cooling elements of the front cover. 11. Vacuum pump according to any of claims 1 to 10, wherein the vacuum pump is a claw pump, a roots pump or a screw pump.