EP2719899B1 - Screw vacuum pump - Google Patents

Description

The invention relates to a screw vacuum pump, preferably with a compression of a medium, usually from gas to atmosphere takes place.

Screw vacuum pumps have a pump chamber in a pump chamber. In the pump chamber two screw rotors are arranged. The screw rotors have on their outer side in each case a helical thread, wherein for conveying and compression of the medium, the two threads of the screw rotors mesh with each other. Within the pump chamber takes place from the suction side, ie the pump inlet in the direction of the pressure side, ie the pump outlet, a compression of the pumped medium. Conventional compression ratios of screw vacuum pumps are in the range of 1 to 10 ⁶ . Depending on the pressure applied to the pump inlet, over-compression can take place within the screw vacuum pump. Such over-compression, ie when pumping against atmospheric pressure, a pressure which is above the atmospheric pressure, leads to a sharp increase in the energy consumption of the screw vacuum pump. This leads to power losses, since an unnecessary compression, ie an over-compression of the medium to be delivered takes place.

For example, to avoid overcompressions in screw vacuum pumps DE 100 46 768 known to provide a pressure relief. The overpressure outlet has an overpressure opening arranged in a side wall of the pumping chamber. Within the overpressure outlet, a pressure relief valve is arranged.

Furthermore, it is off WO 2006/099104 a screw vacuum pump are known in which are provided at different pressure levels overpressure outlets. The individual outlets are each closed with separate spring-loaded valves. The provision of similar spring-loaded valves in screw vacuum pumps for closing pressure relief outlets is also out DE 198 00 711 and the JP 61065087 known.

The object of the invention is to design the overpressure outlet in such a way that the risk of over-compression within the screw vacuum pump is reduced and the pumping power as well as the energy efficiency and the reliability of the screw vacuum pump are improved.

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

The screw vacuum pump according to the invention has a plurality of overpressure openings, each of which is arranged in a side wall of the pump chamber and connected to a pressure outlet. In the pressure relief valves overpressure valves are arranged. These are inventively designed as weight-loaded valves.

The preferred pressure relief valves have valve bodies with a convex outside. In particular, the valve bodies are balls. The use of such valve body has the advantage that they can move when actuated in the valve seat, in particular can rotate and thus an automatic cleaning of the valve seat and the ball takes place. The valve seat itself is correspondingly complementary to the voltage applied to the valve seat Outside of the valve body formed. In particular, it is a frusto-conical bore.

To determine the pressure at which the pressure relief valve opens, it is possible to provide a spring-loaded valve body. For ease of construction, it is preferable to provide weight-loaded valves. Such valves are then preferably arranged within the pump housing such that the valve body abut due to their weight in the valve seat.

Suitable materials for the valve body and the valve seat are in particular material pairings of elastomer and metal. For example, an elastomeric ball may be arranged in a valve seat formed of a metallic material or else a metal ball in a valve seat formed from an elastomer. It is also possible to provide elastomer-coated metal balls, which are then arranged in a metallic valve seat. Also, a combination of hard and soft metallic materials or ceramic materials is possible. By suitably selected material pairing a good seal in the closed state of the pressure relief valve can be ensured. Furthermore, the choice of material based on the process medium to be pumped and the temperatures occurring and the required weight for weight-loaded valves.

In conventional screw vacuum pumps with a suction volume of 50 to 1000 m ³ / h are used as a valve body balls with a diameter in the range of 20 to 30 mm. The bore of the valve seat in this case has a diameter of 16 to 20 mm.

For positional definition of the valve body, it is advantageous for weight-loaded valve bodies to provide holding elements which are arranged in a particularly preferred embodiment within the channel. It is preferred in this case to provide pin-shaped holders, wherein a valve body formed in particular as a ball is held by preferably three or four correspondingly arranged pins. This has the particular advantage that the holder for the valve body can be easily formed. For example, it is possible for different pump types and different application areas of the pumps to provide the same housing with one or more longitudinal channels. The position of the overpressure openings is then defined by subsequent introduction of corresponding holes. Accordingly, the holding elements can be easily inserted into the channel. It is thus possible to provide a pump housing for different pump types or different areas of application, in which then the desired position of the overpressure openings and the valves can be realized in a simple manner.

Preferably, a plurality of overpressure openings are provided, which are preferably arranged at the same pressure level. By providing a plurality of overpressure openings, the effective cross section of the entire overpressure opening can be increased in a simple manner in order to ensure rapid media removal.

In this case, according to one embodiment, it is preferable to arrange a plurality of overpressure openings at the same pressure level. Such overpressure openings are thus arranged on a line corresponding to the gradient of the screw rotor. Furthermore, it is also possible to arrange a plurality of overpressure openings, possibly designed as elongated holes, at different pressure levels, such overpressure openings then being spaced apart from one another in the longitudinal direction of the screw rotor. Of course, the arrangement of several overpressure openings can be combined at the same pressure level with the arrangement of several overpressure openings at different pressure levels.

When providing a plurality of overpressure openings, these are preferably at least partially connected to the same overpressure outlet. As a result, the construction of the vacuum pump, in particular the vacuum pump housing, is simplified.

Preferably, the at least one overpressure outlet has a channel which is connected to the pump outlet of the screw vacuum pump, wherein preferably atmospheric pressure is present at the pump outlet. The channel preferably extends in the longitudinal direction of the screw rotors. In such, extending in the longitudinal direction of the screw rotors channel several overpressure openings open, which are then arranged at different pressure levels. Possibly. the overpressure ports are connected to the channel via transverse bores. Furthermore, it is possible for a plurality of preferably longitudinally extending channels to be provided in the pump housing, with the individual channels in turn being connected to a plurality of overpressure openings, which may then at least partially be at the same pressure level. The provision of at least one channel in turn constitutes an independent invention which is independent of the width of the overpressure ports, but preferably combined with this invention.

In a further preferred embodiment of the above inventions, a plurality of overpressure openings are connected in particular via individual feed channels to a common overpressure valve. As a result, with a magnification of the effective cross section of the overpressure openings, a simple, cost-effective design can continue to be realized, since a separate overpressure valve does not have to be provided for each overpressure opening.

In a further preferred embodiment, the channel of the overpressure outlet is closed by a housing cover. Possibly. a plurality of provided channels, which are integrated in particular in the pump housing, be closed with a common cover. Here, the housing cover is preferably designed such that it extends over the entire length of the channel, so that the housing cover forms or closes a longitudinal side of the channel. This makes it possible in a simple manner, the channel or the channels of the pressure relief and the preferably arranged herein valves to clean and maintain. Furthermore, it is possible in a simple manner during assembly of the screw vacuum pump with the housing cover removed to provide the corresponding valve holes at the desired location for the corresponding pump in a simple manner, since the channel is open on one side and thus easily accessible. Also, the mounting of the retaining elements for the valve body and the mounting of the other components in the valve is thereby possible in a simple manner.

Furthermore, it is preferable to arrange the at least one channel of the overpressure outlet in the pump housing in such a way that it is easily accessible even when the pump housing is connected to an attachment such as a further pump.

In a further preferred embodiment, the at least one channel of the overpressure outlet extends over the entire length of the screw vacuum pump, ie from the pump inlet to the pump outlet. Here, a pressure relief valve is also arranged in the inlet area. This has the advantage that, if the desired pressure is already present at the pump inlet, the medium can be discharged directly through the channel and thus an unnecessary power consumption of the screw vacuum pump is avoided. If, for example, with two pumps connected in series, the medium is pumped against the atmosphere and atmospheric pressure is already present at the inlet of the second pump, this opens corresponding pressure relief valve, so that the medium flows at least partially at the pump inlet of the second pump directly into the channel of the pressure relief.

It is particularly preferred, in particular when providing a plurality of overpressure openings and possibly several pressure relief valves, to arrange a plurality of valve bodies essentially within a common channel. It is preferred that the valve seat is formed in a channel wall.

In a further preferred embodiment of the invention, the width of the overpressure opening in the longitudinal direction of the screw pump or in the conveying direction is selected such that it is less than or equal to the tooth width of Screw rotor is. In this case, the position of the overpressure opening is preferably taken into account, since the tooth width of the screw rotor can vary in the longitudinal direction. By reducing the maximum width of the overpressure opening in the longitudinal direction according to the invention, an overflow via the tooth of the screw rotor in the region of the overpressure opening is reduced. This reduces the occurrence of backflows, ie the occurrence of flows counter to the conveying direction, so that the pumping capacity is not or only slightly reduced by the provision of an overpressure opening. This is particularly relevant for the operating state in which the pressure relief valve is closed and thus the maximum capacity of the screw vacuum pump is to be achieved. In this case, the width of the overpressure opening in the longitudinal direction of the screw rotor is preferably less than or equal to 90%, in particular less than or equal to 80% of the tooth width in this area.

In order to ensure a fast removal of media in the case of an over-compression in relation to the tooth width, relatively small width of the overpressure opening, the overpressure opening can be formed as a slot with, for example, oval or rectangular cross section. Here, the slot is arranged such that the longitudinal extent of the slot corresponds to the gradient of the thread of the screw rotor. Furthermore, it is possible to provide a plurality of overpressure openings, which may also be designed as elongated holes, in order to increase the effective cross section of the overpressure opening for rapid media removal.

The invention will be explained in more detail below with reference to preferred embodiments with reference to the accompanying drawings.

Fig. 1

eine schematische Längs-Schnittansicht einer Schraubenvakuumpumpe gemäß einer ersten Ausführungsform,

Fig. 2

eine schematische Quer-Schnittansicht einer Schraubenvakuumpumpe gemäß einer weiteren bevorzugten Ausführungsform,

Fig. 3

eine schematische Draufsicht eines Schraubenrotors mit mehreren angedeuteten Überdrucköffnungen,

Fig. 4, 5

schematische Darstellungen möglicher Ausgestaltungsformen von Kanälen des Überdruckauslasses mit hierin angeordneten Überdruckventilen, und

Fig. 6

eine schematische Seitenansicht einer mit einer Roots-Pumpe verbundenen erfindungsgemäßen Schraubenvakuumpumpe.

Show it:

Fig. 1

FIG. 2 is a schematic longitudinal sectional view of a screw vacuum pump according to a first embodiment; FIG.

Fig. 2

a schematic cross-sectional view of a screw vacuum pump according to another preferred embodiment,

Fig. 3

a schematic plan view of a screw rotor with several indicated overpressure openings,

Fig. 4, 5

schematic representations of possible embodiments of channels of the pressure relief with arranged therein relief valves, and

Fig. 6

a schematic side view of an associated with a Roots pump according to the invention screw vacuum pump.

According to a first embodiment ( Fig. 1 ) is formed in a pump housing 10, a pump chamber. In this are related to Fig. 1 , one behind the other two screw rotors 14 are arranged. The screw rotors each have threads 16 on their outer sides, so that through opposite rotation of the two screw rotors 14 medium is sucked through an inlet 18 and conveyed in the direction of an arrow 20 to the outlet 22.

To avoid over-compression within the pump chamber, a positive pressure outlet 26 is provided in a side wall 24 of the pump housing 10. In the embodiment shown, the overpressure outlet 26 has two overpressure openings 28 connected to the pumping chamber 12. The overpressure openings 28 are connected via connecting channels 30 with a channel 32 extending in the longitudinal direction 20. The connecting channels 30 are closed by weight-loaded pressure relief valves 34, wherein each pressure relief valve has a valve body 36 designed as a ball. The two valve bodies are in the illustrated embodiment, respectively a valve seat 39 at. Depending on the configuration of the pressure relief valve 34, ie in particular the weight of the spherical valve body 36, when a limit pressure in the connecting channel 30 is exceeded, the valve body 36 is pushed upwards, so that medium flows into the channel 32.

In the illustrated embodiment, the channel 32 of the overpressure outlet 26 is connected to the pump outlet 22 through the channel 33. At the pump outlet 22 is preferably at atmospheric pressure.

The width b ( Fig. 3 ) of the overpressure openings 28 in the flow direction 20 is less than the tooth width B of a corresponding portion of the helical tooth 38 of the screw rotor 14.

In the area of the pump inlet 18, a further connecting channel 41 is connected to the suction chamber 12. This is also closed with a pressure relief valve 34. The valve 34 closing the connecting channel 41 serves to ensure that, in special operating states, the desired final pressure, usually atmospheric pressure, may already prevail at the inlet 18. In this operating state, the medium would unnecessarily be further compressed by the screw vacuum pump. Due to the provision according to the invention of the overpressure valve 34 in the region of the pump inlet, the already sufficiently compressed medium can flow directly into the channel 32 of the overpressure outlet and exit therefrom through the outlet 22 of the pump.

The channel 32 of the overpressure outlet 26 is closed by a housing cover 40, which is fastened to the housing 10 by screws 42, for example. This makes it possible to clean the channel 32 and the valves 34 by removing the housing cover 40 in a simple manner.

In a further preferred embodiment of the invention ( Fig. 2 ) are identical or similar components with the same reference numerals characterized. In the in Fig. 2 illustrated embodiment, the two screw rotors 14 are not shown for reasons of clarity in the pump chamber 12. With the pumping chamber 12 a plurality of connecting channels 30 are connected. These in turn lead into channels 32, in each of which relief valves 34 are arranged. According to the first embodiment ( Fig. 1 ) is also at the in Fig. 2 illustrated embodiment, a housing cover 40 is provided. In this embodiment, all channels 32 shown are closed with a common housing cover 40.

The overpressure openings 28 can as in Fig. 3 be arranged shown. Here are the two in Fig. 3 left overpressure openings 28 arranged at a pressure level. The two overpressure openings 28 thus lie within a range defined by a threaded area or tooth 38. In the longitudinal direction 20 successively arranged housing openings 28 are at different pressure levels.

For holding the formed in the illustrated embodiments as a ball valve body 36 holding elements are provided. This can be done according to a first embodiment ( Fig. 4 ) be realized in that the channel 32 has a substantially round in cross section bulge 44. However, this embodiment has the disadvantage that the position of the valve 34 is predetermined and the Abblasequerschnitt may be limited.

In order to be able to vary the valve openings and also be able to provide large flow cross sections, it is preferred if the channels 32 have substantially the same width over their length. As holding elements for the valve body 36 can then in a channel wall 46 attached, in particular perpendicular to this arranged, pin-shaped holding elements 48 (FIGS. Fig. 5 ) be provided.

When connecting two vacuum pumps, such as in Fig. 6 As shown, it is possible, for example, to arrange on an upper outer side 50 of the housing 10 of the screw vacuum pump, a further vacuum pump 52, such as a Roots pump. In this case, it is preferable to arrange the channels 32 of the overpressure outlets in such a way that they are arranged laterally next to the contact surface of the Roots pump 52 on the outer side 50. In the illustrated embodiment, the channels 32 are in turn closed by the housing cover 40. Due to the preferred, in Fig. 6 illustrated arrangement of the channels and the housing cover 40, it is possible to remove the housing cover 40 without having to remove the roots pump 52. As a result, a cleaning of the channels 32 and a cleaning and maintenance of the pressure relief valves 34 is possible in a simple manner.

Claims (14)

1. A screw vacuum pump, in particular for compression against atmospheric pressure, comprising
   a pump housing (10) defining a suction chamber (12),
   two meshing screw rotors (14) arranged in the suction chamber (12),
   a plurality of overpressure openings (28) arranged in a side wall (24) of the suction chamber (12) and each connected with an overpressure outlet (26), at least two overpressure openings being arranged on different pressure levels, and
   overpressure valves (34) arranged in the overpressure outlets (26),
   characterized in that
   the overpressure valves (34) are configured as weight-loaded valves.
2. The screw vacuum pump of claim 1, characterized in that the overpressure openings (28) of different pressure levels are spaced apart in the longitudinal direction of the screw rotor.
3. The screw vacuum pump of claim 1 or 2, characterized in that the overpressure openings (28) are at least partially connected with the same overpressure outlet (26).
4. The screw vacuum pump of one of claims 1 - 3, characterized in that the overpressure outlet (26) comprises a channel (32) connected with a pump outlet (22), said channel preferably extending in the longitudinal direction (20) of the screw rotors (14).
5. The screw vacuum pump of one of claims 1 - 4, characterized in that a plurality of overpressure openings (28) are connected with the same channel (32).
6. The screw vacuum pump of claim 4 or 5, characterized in that a plurality of channels (32) is provided, wherein, preferably, a plurality of overpressure openings is connected with individual channels (32).
7. The screw vacuum pump of one of claims 1 - 6, characterized in that a valve body (36) is arranged substantially within the channel (32), a valve seat (39) preferably being arranged in a channel wall (24).
8. The screw vacuum pump of one of claims 1 to 7, characterized in that a valve body (36) is held in the channel (32) by preferably pin-shaped holding elements (48).
9. The screw vacuum pump of one of claims 1 to 8, characterized by a housing cover (40) that covers the channel (32) of the overpressure outlet (26) at least partially, preferably completely.
10. The screw vacuum pump of one of claims 1 to 9, characterized in that the channel (32) is integrated in the pump housing (10).
11. The screw vacuum pump of one of claims 1 to 10, characterized in that the channel (32) extends in the longitudinal direction (20) of the screw rotors (14) from a pump inlet (18) to a pump outlet (22).
12. The screw vacuum pump of one of claims 1 to 11, characterized in that the width (b) of the overpressure opening (28) in the longitudinal direction (20) of the screw rotors (14) is smaller than or equal to a tooth width (B) of the screw rotors (14).
13. The screw vacuum pump of claim 12, characterized by a plurality of overpressure openings (28) substantially arranged on the same pressure level.
14. The screw vacuum pump of one of claims 1 to 13, characterized in that the valve body (36) are formed as a sphere.

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