WO2025021786A1

WO2025021786A1 - Claw pump

Info

Publication number: WO2025021786A1
Application number: PCT/EP2024/070810
Authority: WO
Inventors: Hannah BOHLEM-SPANG; Simon Manfred HAPPEL; Jens VERSCHOREN
Original assignee: Leybold Gmbh
Priority date: 2023-07-25
Filing date: 2024-07-23
Publication date: 2025-01-30
Also published as: GB202311399D0; GB2632398A

Abstract

Claw pump (10) for generating a vacuum comprising a housing having an inlet and an outlet; at least one pump stage (12) built as claw pump stage in the housing driven by an electromotor to convey a gaseous medium from the inlet to the outlet; a temperature sensor (18) connected to the outlet to detect a temperature of the claw pump (10); and a controller (20) connected to the temperature sensor (18), wherein the controller (20) is configured to generate a first control signal, if the temperature of the claw pump (10) exceeds a first temperature threshold.

Description

CLAW PUMP

The present invention relates to a claw pump for generating a vacuum and a method for operation of such a claw pump.

Common claw pumps comprise a housing having an inlet and an outlet. The housing defines a pump chamber, wherein a claw pump stage is arranged in the pump chamber. The claw pump stage comprises usually two rotors each having a pump element as claws interacting with each other when the rotors are rotated by an electromotor. Hence, by the interaction of the claws a gaseous medium is conveyed from the inlet of the claw pump towards the outlet. Therein, operation of the claw pump is mainly contact-free, i. e. there is no or only little contact between the individual claws of the claw pump stage and the claws with the housing to reduce seizure and prevent damage of the claw pump. If the temperature of the claw pump exceeds a certain threshold due to thermal expansion, the rotating parts of the claw pump come into contact with the housing or each other causing increased seizure or damage of the vacuum pump. This in particular takes place if the claw pump approaches its ultimate pressure/highest vacuum since less amount of gaseous medium is pumped and less heat can be dissipated by the pumped gaseous medium itself.

In order to avoid damage of the claw pump it is known to implement a vacuum relief valve which are usually built as biased return valve that opens against the bias if the vacuum at the inlet is above a certain threshold (i.e. pressure is below the threshold), such that ambient air is introduced into the inlet of the claw pump. This additional ambient air cools the claw pump stage by dissipating heat and avoids damage or increased seizure of the claw pump stage. However, implementing a vacuum relief valve limits the ultimate pressure that can be reached by the claw pump. At the same time, the extra gas flow through the vacuum relief valve causes a decrease in flow rate which leads to a decrease in pump efficiency. It is an object of the present invention to provide a claw pump and a method for operation providing an improved efficiency while preventing the claw pump from increased seizure or damage.

The object is solved by a claw pump according to claim 1 and a method for operating a claw pump according to claim 8.

The claw pump for generating a vacuum according to the present invention comprises a housing having an inlet and an outlet. Further, at least one pump stage is disposed in the housing, wherein the at least the pump stage is built as claw pump stage and is driven by an electromotor to convey a gaseous medium from the inlet to the outlet. Of course, the claw pump may comprise additional pump stages, which might be built as claw pump stage as well or may include a different pumping mechanism such as a screw pump stage, a rotary vane pump stage or the like. Further, according to the present invention, a temperature sensor is connected to the housing to detect the temperature of the claw pump. Therein, the temperature sensor is connected to the outlet. Usually at the outlet the highest temperatures of a claw pump are detected providing a good indication of the temperature of the claw pump stage itself.

According to the present invention the claw pump comprises a controller, which is connected to the temperature sensor and receives the temperature detected by the temperature sensor. Therein, the controller is configured to generate a first control signal if the temperature of the claw pump exceeds a first temperature threshold.

In particular, the claw pump does not comprise a vacuum relief valve. Thus, there is no vacuum relief valve limiting the ultimate pressure of the claw pump. In addition, no extra or additional gas flow through the vacuum relief valve is present which would otherwise reduce the efficiency of the claw pump in particular near its ultimate pressure. However, at the same time due to directly measuring the temperature of the claw pump by the temperature sensor indication of the temperature of the claw pump is provided such that damage or increased seizure of the claw pump can be prevented.

Preferably, by the first control signal a warning signal is generated providing indication information to a user or operator of the claw pump. Thus, the first control signal may cause a warning signal that can be an optical signal, an acoustic signal or any other kind of warning signal indicating an increased temperature of the claw pump. Therein, the warning signal can be generated by the controller itself or can be transmitted via any type of data connection to another device providing the indication information to the user.

Preferably, the controller is configured to reduce a motor speed of the electro motor in response to the first control signal. Thus, upon detection of a temperature above the first temperature threshold, the motor speed of the electromotor is reduced in order to reduce heat generation in the claw pump stage and in order to prevent a further increase of the temperature. In this configuration, the first control signal is a used by the controller to control the electromotor of the claw pump. Therein, in particular the controller is configured to reduce the motor speed of the electromotor in dependence on an increase of temperature. In particular, a continued reduction of the motor speed of the electromotor may be applied upon increase of the temperature. Thus, a correspondence between the temperature and the motor speed can be provided by the controller. This relationship may be a linear relation or may be any other kind of relation between the motor speed of the electromotor and the temperature.

Preferably, the controller is configured to generate a second control signal to shut down the claw pump if the motor speed of the claw pump is equal to or below a motor speed threshold. In particular, a claw pump requires a minimum motor speed in particular to maintain lubrication of gears and other moving elements within the claw pump. Thus, if the motor speed of the claw pump falls below the motor speed threshold damage to these moving parts could occur. In order to prevent damage, the claw pump is shut down.

Preferably, the controller is configured to generate a second control signal to shutdown the claw pump if the temperature of the claw pump exceeds a second temperature threshold. Therein, the second temperature threshold is larger than the first temperature threshold. Hence, if the temperature of the claw pump exceeds the second temperature threshold a risk of severe damage occurs. Consequently, the claw pump is shutdown to prevent any damage. In particular, in combination with the reduction of the motor speed, if the temperature still increases despite reduction of the motor speed as described before, the claw pump is shut down when exceeding the second temperature threshold in order to prevent damage to the claw pump.

Preferably, by the second control signal a warning signal is generated providing indication information to a user or operator of the claw pump. Thus, the second control signal may cause a warning signal that can be an optical signal, an acoustic signal or any other kind of warning signal indicating an increased temperature of the claw pump. In particular, by the waring signal it is indicated to the user that shutdown of the claw pump is caused by an increased temperature reaching or exceeding the second temperature threshold Therein, the warning signal can be generated by the controller itself or can be transmitted via any type of data connection to another device providing the indication information to the user.

In another aspect of the present invention, a method for operating a claw pump is provided. The claw pump comprises a housing having an inlet and outlet. Further, the claw pump comprises at least one pump stage built as claw pump stage disposed in the housing and driven by an electromotor to convey a gaseous medium from the inlet to the outlet. The method includes: During operation detecting the temperature of the claw pump and If the temperature exceeds a first temperature threshold, generating a first control signal.

Hence, the temperature of the claw pump is directly measured and used in order to generate the first control signal. Therein, the first control signal may cause a warning signal that is indicative of an increased temperature. Thus, increased seizure or damage of the claw pump due to the increased temperature above the first temperature threshold can be prevented.

In particular, the claw pump of the present method can be further built along the features of the claw pump described before.

Preferably, in response to the first control signal the motor speed of the electromotor is reduced. Hence, heat generation of the claw pump is reduced by reducing the motor speed of the electromotor if the temperature of the claw pump exceeds the first temperature threshold. Therein, preferably the motor speed is reduced in dependence on increase of the temperature.

Preferably, the claw pump is shut down if the motor speed is equal to or below the motor speed threshold.

Preferably, the claw pump is shut down if the temperature exceeds a second temperature threshold. Therein, the second temperature threshold is larger than the first temperature threshold.

In the following the present invention is described in more detail with reference to the accompanying figures.

The figures show:

Figure 1 a claw pump in a schematic representation according to the present invention, Figure 2 a diagram regarding operation or the claw pump according to the present invention and

Figure 3 a flow diagram of the method according to the present invention.

Referring to Figure 1 showing a claw pump 10 according to the present invention. The claw pump 10 comprises at least one pump stage 12 built as claw pump stage having an inlet 14 and an outlet 16. The claw pump stage 12 is driven by an electromotor, which is connected to controller 20. Therein, the controller might integrate the motor controller or an external motor controller might be situated between the electromotor of the claw pump 10 and the controller 20 such that control signals of the controller 20 may be further processed by the motor controller and transmitted to the electromotor. Further, the claw pump 10 comprises a temperature sensor 18 which is connected to the outlet 16. Other positions may also be possible. Therein, by the temperature sensor 18 a temperature of the claw pump stage 12 is detected. The controller 20 receives the temperature detected by the temperature sensor 18 and is configured to generate a first control signal if the temperature detected by the temperature sensor 18 exceeds a first temperature threshold. The first control signal may generate a warning signal indicative of an increased temperature of the claw pump 10, which can be used in order to prevent increased seizure and/or damage of the claw pump 10.

In particular, in response to the first control signal generated by the controller 20 the motor speed of the claw pump stage 12 is reduced. This is exemplified in Figure 2 showing the motor speed "rpm" of the claw pump stage 12. Below a first temperature threshold Ti the claw pump stage 12 is allowed to be operated at full motor speed indicated as RPMi. When the temperature increases and exceeds the first temperature threshold Ti a decrease of the motor speed is applied by the controller 20. Therein, there is a decrease of the motor speed "rpm" in dependence on the temperature of the claw pump 10. In the example of Figure 2 the relationship between the temperature T and the motor speed "rpm" is shown as a linear relation. However, other relationships between the temperature T "rpm" are also possible. If the temperature T further increases and reaches the second temperature threshold T₂, the claw pump 10 is shut down in order to prevent damage and the motor speed is reduced to 0. In particular, the second temperature threshold T₂ may correspond to a minimum motor speed RPM₂. In particular, claw pump 10 requires a minimum motor speed in order to maintain lubrication of moving parts such as the gear of the claw pump. If the temperature T would exceed the second temperature threshold T2 the motor speed of the electromotor would need to be controlled to be below the minimum motor speed RPM₂ of the claw pump 10, which could lead to damage of the moving parts. Consequently, the claw pump 10 is shut down.

In the following it is referred to Figure 3 showing a schematic flow diagram of the method according to the present invention. The method shown in Figure 3 includes:

In step SOI, a temperature of the claw pump is detected during operation.

In step S02, if the temperature exceeds a first temperature threshold a first control signal is generated.

In particular, the method is further built along the features of the claw pump described before. In particular, the first control signal is used in order to reduce the motor speed of the electromotor and a second control signal is generated to shut down the claw pump if the temperature exceeds a second temperature threshold.

Thus, by the present invention a claw pump and a method for operating a claw pump is provided, wherein an improved ultimate pressure can be achieved in a more efficient way than in the prior art and preventing the need of any vacuum relief valve. At the same time due to detecting the temperature of the claw pump, damage to the claw pump caused by overheating can be prevented.

List of reference

10 claw pump

12 claw pump stage

14 inlet

16 outlet

18 temperature sensor

20 controller

Claims

1. Claw pump for generating a vacuum comprising a housing having an inlet and an outlet; at least one pump stage built as claw pump stage in the housing driven by an electromotor to convey a gaseous medium from the inlet to the outlet; a temperature sensor connected to the outlet to detect a temperature of the claw pump; and a controller connected to the temperature sensor, wherein the controller is configured to generate a first control signal, if the temperature of the claw pump exceeds a first temperature threshold.

2. Claw pump according to claim 1, wherein the first control signal causes a warning signal providing an indication information to a user.

3. Claw pump according to claims 1 or 2, wherein the controller is configured to reduce a motor speed of the electromotor in response to the first control signal.

4. Claw pump according to any of claim 3, wherein the controller is configured to reduce the motor speed of the electromotor in dependence on an increase of the temperature.

5. Claw pump according to claims 3 or 4, wherein the controller is configured to generate a second control signal to shut down the claw pump if the motor speed of the claw pump is equal to or below a motor speed threshold.

6. Claw pump according to any of claims 1 to 5, wherein the controller is configured to generate a second control signal to shut down the claw pump if the temperature of the claw pump exceeds a second temperature threshold.

7. Claw pump according to any of claims 1 to 6, wherein the claw pump does not comprise a vacuum relief valve.

8. Method for operating a claw pump comprising a housing having an inlet and an outlet, and at least one pump stage built as claw pump stage in the housing driven by an electromotor to convey a gaseous medium from the inlet to the outlet; the method includes:

During operation detecting a temperature of the claw pump; and

If the temperature exceeds a first temperature threshold, generating a first control signal.

9. Method according to claim 8, wherein in response to the first control signal, a motor speed of the electromotor is reduced.

10. Method according to claim 9, wherein the motor speed is reduced in dependence on increase of the temperature.

11. Method according to claims 8 or 10, wherein a second control signal is generated to shut down the claw pump, if the motor speed is equal to or below a motor speed threshold.

12. Method according to any of claims 8 to 11, wherein a second control signal is generated to shut down the claw pump, if the temperature exceeds a second temperature threshold.

13. Method according to any of claims 8 to 12, wherein the claw pump is built according to any of claims 1 to 7.