EP2745015B1 - Roots pump - Google Patents

Description

The invention relates to a Roots pump.

Roots pumps usually have two-toothed rotary lobes arranged in a pump chamber. The two rotary lobes are driven in opposite directions, so that gas is sucked in through a main inlet through the individual chambers and expelled again via a main outlet. The main inlet and the main outlet run in the radial direction and are arranged opposite one another. Furthermore, rotary pistons with multiple teeth, in particular three or four teeth, are known. Here, too, the gas is essentially pumped radially from a radially arranged main inlet to a radially arranged main outlet.

Multistage Roots pumps are also known for achieving low pressures. Roots pumps of this type have a pair of rotary lobes per stage. Here, the gas to be pumped is conveyed from an outlet of one pumping stage to the inlet of an adjacent pumping stage. This is done via connection channels. The connection channels can, as for example in US 2010/0158728 described, be arranged in the housing of the Roots pump, the connecting channels that surround the pump chambers in which the rotary lobes are arranged or are arranged radially outside the pump chambers. This is necessary to get gas from an im to convey the outlet of a pump stage arranged in the lower region of the Roots pump to an inlet of the adjacent pump stage arranged in the opposite, for example upper region of a Roots pump. Roots pumps of this type have the disadvantage that the design of the channels in the housing is technically complex. Furthermore, the housing for receiving the connecting channels must be designed with a large volume. This not only leads to large external dimensions of the Roots pump but also, in particular, to high costs. In addition to the complex manufacturing process, the high costs are also caused by the large amount of metal used.

the end US 2005/0089424 a Roots pump with a plurality of multi-toothed rotary lobe pairs each forming a pump stage is known. The rotary lobes are each designed as three-tooth rotary lobes. Adjacent pump stages are connected to one another via connecting channels, the connecting channels being arranged in a z-shape in the partition walls.

It is the object of the invention to create a Roots pump which has a technically simple structure, the installation space required and the costs preferably also being reduced.

The object is achieved according to the invention by the features of claim 1.

The Roots pump according to the invention has several pairs of multi-toothed rotary lobes, each forming a pump stage. Here, two rotary lobes with more than two teeth are provided for each pumping stage, it being preferred that the rotary lobes have at least four, in particular at least six teeth. The two rotary lobes of a pump stage rotate in opposite directions to transport the gas. There is preferably one per rotary piston pair of the two rotary lobes arranged on a common shaft, so that the Roots pump has two shafts running parallel to one another, each shaft carrying one of the two rotary lobes per pump stage. The two shafts can be connected to one another via gears, so that only one of the two shafts has to be driven.

Adjacent pump stages are connected to one another via connecting channels. Here, adjacent pump stages can each have one or several connection channels can be connected to one another. According to the invention, the connecting channels are arranged in partition walls which separate adjacent pump stages from one another. The partition walls are thus provided between the piston chambers of adjacent pump stages. By arranging the connecting channels according to the invention in the partition walls, the external dimensions of the Roots pump according to the invention can be considerably reduced compared to the prior art. This has the advantage that a reduction in costs can be achieved due to the lower use of material. Furthermore, the connecting channels provided in the partition walls can be produced more cost-effectively, since it is possible to form the connecting channels by straight, in particular circular-cylindrical channels or bores. A technically difficult production of curved connecting channels provided radially outside the piston chambers is therefore not necessary according to the invention. The very compact Roots pump according to the invention also has the advantage that a weight reduction and a reduction in the number of parts can be achieved. Since Roots pumps can be designed as dry-running pumps without oil lubrication, Roots pumps also have the advantage that the maintenance requirements are lower.

Another advantage of the arrangement according to the invention of the connecting channels in partition walls is that, due to the shortness of the connecting channels, lower pressure losses occur.

At least some of the connecting channels are preferably connected to the piston chambers in which the rotary piston pairs are arranged in such a way that a channel inlet opening and / or a channel outlet opening is swept over by a side wall of a rotary piston during operation. The channel inlet and / or channel outlet opening of at least one connecting channel is therefore not arranged radially in relation to a piston chamber, but axially. The opening is painted over not via a radially formed end face but via a side wall of a rotary piston.

In order to allow the Roots pump according to the invention to have a construction that is as compact as possible and therefore inexpensive, all the connecting channels are preferably arranged in intermediate walls that separate the pump stages from one another. Only one main inlet and / or one main outlet is not arranged in partition walls. The main inlet and / or the main outlet can be arranged axially or radially. The main inlet is preferably arranged radially opposite the main outlet. If, for example, gas is sucked in through a main inlet arranged on an upper side of the pump, in a preferred embodiment the gas is expelled at the radially opposite lower side of the pump. Of course, the main inlet is axially offset with respect to the main outlet, since the individual pump stages are arranged axially one behind the other, starting from the main inlet to the main outlet.

In particular in the case of rotary pistons with three or more teeth, provision is made according to the invention to provide connecting channels running axially in the intermediate walls. This can be achieved in that a chamber arranged between two adjacent teeth does not only expel the gas after the rotary pistons have rotated by approx. 180 °, but rather already at a smaller angle of rotation. In such a preferred embodiment of the Roots pump according to the invention, the gas does not have to be transported between two stages from a chamber on the main inlet side to a chamber on the main outlet side. For example, in the case of three-tooth rotary lobes, the gas is sucked in through a main inlet on an upper side of the pump. The gas is transported from the first to the second stage through a connecting channel which is arranged in the center at a rotation angle of approx. 90 ° for the rotary lobes. This connecting channel can run axially so that the gas enters a central chamber of the adjacent rotary lobes. In this pumping stage, the gas is then further in the direction of the outlet side conveyed and from this area reaches an inlet-side chamber of the next pumping stage through a channel arranged in particular at an angle or diagonally in the partition wall. In particular in the case of rotary lobes with more than three teeth, multiple axially extending channels can be arranged between adjacent pump stages. The provision of axial channels has the particular advantage that the channels are technically simple to manufacture. These can be axial, in particular circular-cylindrical bores.

In order to be able to design the connection channels running obliquely or diagonally in the partition walls in a technically simple manner, partition walls in which such connection channels are arranged are preferably thicker in the axial direction than partition walls in which axial connection channels are provided. This makes it possible to design the connecting channels running at an angle without any curvature.

In order to keep the power consumption of the pump as low as possible, the connecting channels have the largest possible cross-section. It is also possible to provide a plurality of channels running essentially parallel to one another in order to enlarge the cross section. Particularly in the case of the channels running obliquely in the partition walls, it must also be taken into account that they are designed to be as short as possible.

To increase the compression, the rotary lobes preferably have axially different widths, the width of the rotary lobes in particular decreasing in steps in the pumping direction. This reduces the volume of the individual chambers formed between the teeth of the rotary pistons.

In a preferred embodiment, the two intermeshing rotary pistons have the same diameter and the same shape. However, it is also possible to use rotary lobes with different diameters and Provide different number of teeth, the rotary lobes then have different speeds of rotation. Rotary pistons that mesh with one another can also have different tooth shapes.

The design of the Roots pump according to the invention in particular results in an equalization of the load peaks over the rotation of the rotor and also an equalization of the heat of compression.

The invention is explained in more detail below on the basis of preferred embodiments with reference to the accompanying drawings.

Fig. 1

eine schematische Ansicht eines dreizähnigen Druckkolbenpaars einer ersten Pumpstufe,

Fig. 2

eine schematische Ansicht eines dreizähnigen Druckkolbenpaars einer zweiten benachbarten Pumpstufe,

Fig. 3

eine schematische Ansicht eines sechszähnigen Drehkolbenpaars einer ersten Stufe,

Fig. 4

eine schematische Ansicht eines sechszähnigen Drehkolbenpaars einer zweiten Stufe,

Fig. 5

eine schematische Ansicht eines sechszähnigen Drehkolbenpaars einer dritten Stufe,

Fig. 6

eine schematische Schnittansicht einer sechsstufigen Wälzkolbenpumpe, die entsprechend den Fig. 3 - 5 schematisch dargestellte, sechszähnige Drehkolben aufweist, und

Fig. 7

eine schematische Draufsicht einer alternativen Ausführungsform eines Drehkolbenpaares.

Show it:

Fig. 1

a schematic view of a three-toothed pressure piston pair of a first pump stage,

Fig. 2

a schematic view of a three-toothed pressure piston pair of a second adjacent pump stage,

Fig. 3

a schematic view of a six-tooth rotary piston pair of a first stage,

Fig. 4

a schematic view of a six-tooth rotary piston pair of a second stage,

Fig. 5

a schematic view of a six-tooth rotary piston pair of a third stage,

Fig. 6

a schematic sectional view of a six-stage Roots pump, which corresponds to the Fig. 3-5 having six-toothed rotary lobes shown schematically, and

Fig. 7

a schematic plan view of an alternative embodiment of a rotary piston pair.

The ones in the Figs. 1 and 2 three-toothed rotary lobes 10 shown schematically are in a first pumping stage ( Fig. 1 ) arranged in a pump chamber 12. The two rotary pistons 10 are each rotatably supported by a shaft (not shown) and are rotated in opposite directions in the direction of arrows 14 and 16, respectively. Gas is fed to a chamber 20 via a main inlet 18. By rotating the in Fig. 1 On the left rotary piston, the gas is enclosed in the chamber 20, which is closed off by the curved region 22 of an outer wall. If you continue to rotate the in Fig. 1 left rotary piston in the direction of arrow 14, the chamber 20 is opened corresponding to the chamber designated 24 in this position. The chamber 24 encloses the entire lower area of the two rotary pistons, so that the areas 24, 26, 28 have the same pressure level. As a result, the gas originally located in the chamber 20 is pressed out through a connecting channel 30 running axially, ie parallel to the rotating shafts of the rotary pistons.

Accordingly, the in Fig. 1 right rotary piston gas enclosed in a chamber 32 by rotating the rotary piston 10 in the direction of arrow 16 in FIG Fig. 1 moved downwards and then ejected through the connecting channel 34, which is also shown in dashed lines and also runs axially.

At the next pumping stage ( Fig. 2 ), which in relation to the first pumping stage ( Fig. 1 ) is arranged axially behind this, for example, gas enters through the connecting channel 30 into a chamber 36 which has the same pressure level as the areas 38, 40. By turning the in Fig. 2 left Rotary piston, a self-contained chamber is formed in connection with the curved wall 42, so that the gas enclosed therein is conveyed in the direction of a main outlet 44. The in Fig. 2 right rotary piston, gas entering the chamber 40 through the connecting channel 34 as soon as the right piston 10 is rotated further in the direction of the arrow. The gas then enclosed in a chamber 46 is also transported in the direction of the main outlet 44.

To form a third stage, the gas from the in Fig. 2 outlet 44 designated as the main outlet can be conveyed upwards again in the direction of a main inlet. According to the invention, this takes place through channels, which are not shown in this embodiment, and run diagonally or obliquely in an intermediate wall.

In the Fig. 3-5 are six-tooth rotary piston pairs 48, 49 together with the first stage ( Fig. 3 ), a second stage ( Fig. 4 ) and a third stage ( Fig. 5 ) relevant connection channels are shown. For example, with a six-stage Roots pump ( Fig. 6 ) corresponds to the representation of Fig. 3 a first stage 50, the representation in Fig. 4 a second stage 52 and the representation in Fig. 5 a third stage 54. The fourth stage 56 essentially corresponds to the first stage ( Fig. 3 ), although the inlet does not take place radially but via an inclined or diagonal connecting channel 57. The fifth stage 58 corresponds to the second stage 52 or Fig. 4 and the sixth stage 60 corresponds to the third stage 54 or that in FIG Fig. 5 illustrated stage, the outlet taking place here through a main outlet 62 in the radial direction. The individual rotary pistons 48, the width of which decreases in the axial direction or in the pumping direction 64, are carried by a common shaft 66. Correspondingly, the rotary pistons 49 are carried by a common shaft 68. The two shafts 66, 68 are rotatably mounted in an upper housing half 70 and a lower housing half 72 and can be via not shown Gear wheels are connected to one another, so that only one of the two shafts 66, 68 has to be driven by a motor.

Partition walls 74, 76, 78, 80, 82 are provided between adjacent pumping stages. In the illustrated embodiment, at least one connecting channel 84, 86, 88, 90, 57 is arranged in each partition wall. In addition, connection channels are also possible which are arranged at least partially in an outer area, as is known from the prior art. In the illustrated embodiment, the gas is sucked in through the main inlet 51.Instead of a radially arranged main inlet 51, this can also be used axially as an inlet 53 ( Fig. 3 ) be trained. Of course, an inclined inlet or a combination of different inlets is also possible, whereby the inlet merely feeds gas into the chamber 55 ( Fig. 3 ) must be done.

The gas is then conveyed from the first pump stage 50 into the second pump stage 52 through a connecting channel 84 running axially, ie parallel to the shafts 66, 68. The connecting channel 84 is arranged in the intermediate wall 74. The gas is here based on the Figs. 1 and 2 The principle described is conveyed via an intermediate chamber 57 into a chamber 59 connected to the connecting channels 84.

The gas is then conveyed further ( Fig. 4 ) and flows from the second pumping stage 52 into the third pumping stage 54 through a connecting channel 86, which likewise runs axially. The connecting channel 86 is arranged in the intermediate wall 76.

If the gas is transported further ( Fig. 5 ) it is then necessary to convey the gas from the main outlet side in the direction of the main inlet side. For this purpose, a diagonal or inclined channel 77 is provided in the intermediate wall 78, which is thicker in the axial direction than the other intermediate walls 74, 76, 80, 82.

The gas is conveyed from the fourth pump stage 56 into the fifth pump stage 58 through a channel 88 running axially in the partition 80. Since the sixth pumping stage 60 is the last pumping stage in the exemplary embodiment shown, it is connected to the essentially radially extending main outlet 62.

Since, as in particular from the Fig. 3-5 It can be seen that only a part of the chambers is used for gas delivery, a surface treatment of the chambers in which the rotary pistons are arranged, which is kept within small tolerances, is only necessary in the area of the active, ie relevant for the delivery chambers. As a result, the manufacturing costs can be further reduced.

Instead of identically designed rotary lobes, rotary lobes with different diameters and, in particular, different numbers of teeth can also be provided. A combination of rotary lobes with different tooth shapes is also possible. An example of this is shown in plan view in Figure 7 shown. Here, a left rotary piston 92 has teeth which interact with five separately designed teeth of a right rotary piston 94.

Claims (8)

1. A Roots pump comprising

   a plurality of pairs of multi-toothed rotary pistons (10; 48, 49), each forming a pump stage (50, 52, 54, 56, 58),

   wherein each rotary piston (10; 48, 49) is formed as an at least three-toothed rotary piston (10; 48, 49), and

   connection channels (30, 34, 77, 84, 86, 88, 90) connecting respective adjacent pump stages (52, 54, 56, 58, 60),

   wherein at least one of the connection channels (30, 34, 77, 84, 86, 88, 90) is arranged in partitioning walls (74, 76, 78, 80, 82) separating the pump stages (50, 52, 54, 56, 58, 60),

   characterized in that

   at least one of the connection channels (30, 34, 77, 84, 86, 88, 90) arranged in partitioning walls (74, 76, 78, 80, 82) separating the adjacent pump stages (50, 52, 54, 56, 58, 60) extends exclusively in an axial direction..
2. The Roots pump of claim 1, characterized in that, in operation, a channel inlet opening and/or a channel outlet opening of at least one connection channel (30, 34, 77, 84, 86, 88, 90) is swept over by a side wall of a rotary piston (10, 48, 49).
3. The Roots pump of claim 1 or 2, characterized in that all connection channels (30, 34, 77, 84, 86, 88, 90) are arranged in partitioning walls (74, 76, 78, 80, 82) separating the adjacent pump stages (50, 52, 54, 56, 58, 60).
4. The Roots pump of one of claims 1-3, characterized in that a main inlet (51) is arranged radially opposite a main outlet (62).
5. The Roots pump of claim 4, characterized in that with more than two pump stages (50, 52, 54, 56, 58, 60), a connection channel (77) connecting a pump stage (54) with an adjacent pump stage (56) extends obliquely in the corresponding partitioning wall (78) and substantially transversely to the plane formed by the two shaft axes (66, 68).
6. The Roots pump of claim 5, characterized in that partitioning walls (78) including oblique connection channels (77) are thicker than partitioning walls (74, 76, 80, 82) including axial connection channels (84, 86, 88, 90).
7. The Roots pump of one of claims 1-6, characterized in that one of the two rotary pistons (10; 48, 49) of each rotary piston pair (10; 48, 49) is arranged on a common shaft (66, 68).
8. The Roots pump of one of claims 1-7, characterized in that the axial width of the rotary pistons (10; 48, 49) of individual pump stages (50, 52, 54, 56, 58, 60) decreases in particular in the pumping direction.

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