Pump unit

Abstract

The present invention relates to a pump unit (1) comprising at least a first main vacuum pump (3) and a second vacuum pump (5) connected in series, with the outlet of the second vacuum pump (5) fluidly connected to the inlet of the first main vacuum pump (3). Each vacuum pump (3, 5) comprises a stator (30, 50) having at least one pumping chamber, two rotors configured to rotate within the pumping chamber about respective axes of rotation (I, II), and at least one motor (33, 53) for rotating the rotor shafts (31, 32, 51, 52). The pump unit (1) comprises at least one common casing (7) between the two vacuum pumps (3, 5), which at least partially houses the rotor shafts (31, 32, 51, 52) of each vacuum pump (3, 5).

Description

[Technical Field]

[0001] The present invention relates to a pumping unit having at least two vacuum pumps fluidly connected in series, i.e., the outlet of one vacuum pump is fluidly connected to the inlet of the other vacuum pump, each vacuum pump having two rotor shafts for pumping a gas. [Background technology]

[0002] A vacuum pump may comprise one pumping stage or multiple pumping stages in series, with the gas to be pumped flowing between an inlet and an outlet. Known vacuum pumps include rotary lobe pumps with two or more lobes, or nozzle pumps, also called "claw" pumps, or screw pumps. Compressor-type vacuum pumps, also known as "Roots" (or "Roots blowers"), are used especially upstream of a primary vacuum pump, and can increase pumping capacity compared to the primary vacuum pump alone, for example in situations where gas flow rates are high.

[0003] These vacuum pumps are called "dry" because, in operation, the two rotors rotate within the stator without any mechanical contact with each other or the stator, and no oil is used in the pumping stage. The two rotors are supported for rotation by bearings that can be lubricated with grease or oil, and are typically synchronized by gearing that is also lubricated. Unlike a solution using a single vacuum pump, when multiple vacuum pumps are used, multiple components are required to operate and control each vacuum pump, resulting in the vacuum pumps taking up more space.

[0004] Horizontal vacuum pumps are known and are generally arranged one above the other, but particularly if the first vacuum pump is multi-stage and relatively long, sufficient floor space is required to install the pump unit, for example in a customer's clean room. Summary of the Invention [Problem to be solved by the invention]

[0005] Vertically-configured vacuum pumps are known to reduce the footprint of the pump unit. However, the overall height of the pump unit can be relatively high, making it difficult to install at a customer's site to replace an existing pump. Furthermore, this vertical configuration poses a higher risk of tipping over than a horizontally configured vacuum pump.

[0006] One object of the present invention is to reduce the size of the pump unit while reducing costs. SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved pump unit that at least partially overcomes one or more of the above-mentioned drawbacks. [Means for solving the problem]

[0007] To this end, the subject of the present invention is a pump unit comprising at least one first vacuum pump and at least one second vacuum pump arranged in series, said second vacuum pump having an outlet fluidly connected to the inlet of said first vacuum pump, each said vacuum pump comprising a stator having at least one pumping chamber, two rotors arranged to rotate within said pumping chambers about their respective axes of rotation, and at least one motor arranged to drive the rotor shafts in rotation.

[0008] According to the invention, the pump unit comprises at least one common casing for the first vacuum pump and the second vacuum pump, the common casing being arranged between the two vacuum pumps and at least partially accommodating the rotor shaft of each of the vacuum pumps. According to the invention, the common casing allows one or more of the vacuum pump's operating functions to be collectively shared, such as motor drive, synchronization, cooling, etc. This integration reduces the size of the pump unit. Furthermore, the common casing also contributes to cost savings compared to conventional solutions.

[0009] The pump unit of the present invention may also include one or more of the features described below, either individually or in combination. The at least one vacuum pump may be of the dry type. The first vacuum pump may be, for example, of the "Roots" type, or of the "claw" type, or of the scroll or screw type. The second vacuum pump is, for example, a Roots type vacuum pump. The axis of rotation of the rotor shaft of the first vacuum pump may be vertical. The axis of rotation of the rotor shaft of the second vacuum pump may be vertical. When the vacuum pump is vertical, the single common casing reduces the height of the pump unit.

[0010] Alternatively, the axis of rotation of the rotor shaft of the first vacuum pump or the second vacuum pump may be horizontal. For example, several motors may be arranged in a common casing, and the rotational speeds of these motors may be different. The pump assembly may include at least two gears, each gear mounted around a rotor shaft of a corresponding vacuum pump and configured to synchronize rotation of the rotors. The two gears may be arranged in a common casing. The two gears may be located on the same side of the motor in a common casing. The pump unit may include at least eight bearings. At least two bearings may be located around each rotor shaft.

[0011] At least four of the bearings around each rotor shaft may be located within a common casing. All bearings may be located in one common casing. Gear and / or bearing lubricants may be pooled. A common casing may contain at least one thermal control device, allowing for shared thermal control functions, such as motor and bearing cooling.

[0012] The pump unit may include at least one pipe fluidly connecting the outlet of the second vacuum pump with the inlet of the first main vacuum pump, and such pipe may be at least partially located within a common casing, or may be located external to the common casing. Other advantages and features of the invention will become more apparent on reading the following description and drawings, given as illustrative and non-limiting examples. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram of a vertically structured pump unit according to a first embodiment of the present invention; [Figure 2] FIG. 5 is a schematic view of a pump unit with a vertical structure according to a second embodiment of the present invention. [Figure 3] FIG. 10 is a schematic view of a pump unit having a vertical structure according to a third embodiment of the present invention. [Figure 4] FIG. 10 is a schematic view of a pump unit having a vertical structure according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The following embodiments are illustrative. Although one or more embodiments are referred to in this specification, this does not necessarily mean that each embodiment refers to the same embodiment, nor does it mean that each feature applies only to one embodiment. Simple features of different embodiments can be combined or interchanged to form further embodiments. In this specification, an index may be assigned to a particular element, such as a first element or a second element. In this case, the index alone allows similar but not identical elements to be distinguished and named. This index does not imply a priority of one element over another, and these names may be easily interchanged without departing from the scope of the present invention. Furthermore, this index does not imply a chronological order. The term "upstream" refers to an element that is located before another element with respect to the direction of flow of the gas or gas stream being pumped. Conversely, "downstream" refers to an element that is located after another element with respect to the direction of flow of the gas or gas stream being pumped.

[0015] 1 to 4 show various embodiments of the pump unit 1 of the present invention. The pump unit 1 is connected to, for example, a process chamber for pumping gases. The process chamber may be a chamber in which deposition or etching processes are performed, such as those used in the manufacture of microelectronic devices on silicon wafers. The pump unit 1 includes a first vacuum pump 3 and a second vacuum pump 5 connected in series. The pump unit 1 also includes at least one common casing 7 that is common to the first vacuum pump 3 and the second vacuum pump 5. One or both of the two vacuum pumps 3, 5 may be of the dry type.

[0016] The first vacuum pump 3 is a primary vacuum pump. This primary vacuum pump is a positive displacement vacuum pump that uses two rotors to suck in, transport and discharge the gas to be pumped at above atmospheric pressure. The first primary vacuum pump 3 is, for example, a vacuum pump with rotating lobes of the same shape, for example of the "Roots" type, or "claw" type, spiral type, screw type or similar positive displacement vacuum pump principle. The discharge pressure of the first primary vacuum pump 3 is above atmospheric pressure. The first vacuum pump 3 is in particular a multi-stage vacuum pump with several stages (at least two stages). The first vacuum pump 3 has a stator 30 that divides a number of pump stages connected in series between an inlet and a discharge port, and the gas to be pumped circulates through a pump chamber within the stator 30. The stator 30 is typically made of cast iron.

[0017] The two rotors are supported by two shafts 31, 32 and are driven to rotate about their respective axes of rotation I by one motor 33 of the first primary vacuum pump 3. The two axes of rotation I are parallel. The motor 33 is arranged, for example, at one end of the first vacuum pump 3 . Each rotor shaft 31, 32 is rotationally guided by at least two bearings 9a, 9b. Therefore, the first vacuum pump 3 has at least four bearings 9a, 9b. Specifically, a pair of first bearings 9a and a pair of second bearings 9b are provided. Each bearing 9a, 9b is, for example, made up of multiple bearings.

[0018] The first vacuum pump 3 is equipped with one gear 11 for synchronizing the rotation of the rotor shafts 31, 32. This gear 11 consists of two toothed wheels attached to the respective shafts 31, 32 of the rotors of the first vacuum pump 3. A second vacuum pump 5 is placed upstream of the first vacuum pump 3 in the direction of flow of the gas to be pumped. The second vacuum pump 5 may be a positive displacement vacuum pump. This second vacuum pump 5 is, for example, a Roots type vacuum pump. A Roots type vacuum pump is a positive displacement vacuum pump that uses a Roots type rotor to suck, transport, and discharge the gas to be pumped. The second vacuum pump 5 includes a stator 50 that defines one to three pump stages between the suction and discharge stages, and the gas to be transported circulates within the stator 50. The outlet of the second vacuum pump 5 is fluidly connected to the inlet of the first vacuum pump 3. The stator 50 is typically made of cast iron.

[0019] Each rotor is supported by two shafts 51, 52 and is driven to rotate about its own axis of rotation II by a motor 53 of the second vacuum pump 5. The two axes of rotation II are parallel. The motor 53 is disposed, for example, at one end of the second vacuum pump 5 . Each rotor shaft 51, 52 is rotationally guided by at least two bearings 13a, 13b. Therefore, the second vacuum pump 5 has at least four bearings 13a, 13b. Specifically, a first pair of bearings 13a and a second pair of bearings 13b may be provided. The bearings 13a, 13b may be, for example, rolling bearings.

[0020] Each vacuum pump 3, 5 has its own motor for driving two rotor shafts 31, 32, 51, 52 respectively. The second vacuum pump 5 is provided with one gear 15 for synchronizing the rotation of the rotor shafts 51, 52. This gear 15 consists of two toothed wheels respectively attached to each shaft 51, 52 of the rotors of the second vacuum pump 5. The two vacuum pumps 3, 5 are said to be "dry" because during operation, each rotor rotates within its respective stator 30, 50 without any mechanical contact with each other or with the stator 30, 50, meaning that no oil is used in the pumping stage.

[0021] The second vacuum pump 5 is arranged spatially above the first vacuum pump 3, for example, according to the arrangement of the elements in the figure, which corresponds to the arrangement after the pump unit 1 is installed. The vacuum pumps 3, 5 are arranged, for example, in the frame of one of the pump units 1. The pump unit 1 can be configured to be placed, i.e., installed, for example, on the ground or on a frame, with the axes of rotation I, II extending vertically. This vertical direction corresponds to the direction of gravity when the first vacuum pump 3 is installed on the ground or on a frame. The vertical arrangement of the pump unit 1 significantly reduces the installation area. The axes of rotation I, II of the vacuum pumps 3, 5 are vertical as shown in the example of Figures 1 to 4.

[0022] In the remainder of this specification, the terms "upper", "lower", "top", "lower", "upper side" and "lower side" are defined according to the vertical or gravitational direction relative to the orientation of the pump unit 1 on the ground or chassis. Alternatively, the axes I, II of rotation of the vacuum pumps 3, 5 may be horizontal.

[0023] Furthermore, it may be necessary to lubricate one or more elements of the vacuum pumps 3, 5. For this purpose, the pump unit 1 may comprise at least one pump (not shown), such as an oil pump, for circulating a liquid lubricant towards the elements to be lubricated, such as at least one bearing 9a, 9b, 13a, 13b, at least one gear 11, 15, etc. By way of example, lubrication can be provided by a lubrication device, in particular an oil pump 17, which can be located externally or internally on the chassis of the pump unit 1.

[0024] The oil pump 17 can be selected from a positive displacement oil pump, a centrifugal pump, or a vane pump. During operation, the oil pump 17 circulates liquid lubricant towards the parts to be lubricated via at least one lubrication duct. For this purpose, the casting of the pump unit 1 can be provided with at least one liquid lubricant inlet 19. Furthermore, it may be necessary to thermally regulate, in particular heat or cool, one or more elements of the vacuum pumps 3, 5. This regulation makes it possible to avoid breakdowns, in particular by avoiding that the gas species to be conveyed exceed certain temperature thresholds that could cause condensation in one of the vacuum pumps 3, 5 and cause seizure.

[0025] This function can be realized by at least one thermal control device 21. This thermal control device 21 may comprise a hydraulic circuit, in which a heat transfer fluid, such as water, may circulate. The thermal control device 21 may comprise one or more thermal blocks through which the hydraulic circuit passes, the thermal blocks being arranged in thermal contact with at least one element of the pump unit 1. Alternatively or additionally, air cooling may be provided by one or more fans and / or cooling fins. One common casing 7 is interposed between the two vacuum pumps 3, 5. More specifically, one common casing 7 is interposed between the stators 30, 50 of the vacuum pumps 3, 5. Like the stators 30, 50, the common casing 7 can be made from cast iron.

[0026] The single common casing 7 accommodates at least a portion of the rotor shafts 31, 32, 51, 52 of each vacuum pump 3, 5. In particular, first ends of the rotor shafts 31, 32, 51, 52 may be accommodated within the single common casing 7. Furthermore, the single common casing 7 may incorporate, as shown very diagrammatically in the figure, at least one pipe 23 which provides a fluid connection between the outlet of the second vacuum pump 5 and the inlet of the first vacuum pump 3. This pipe may be at least partially cast into the single common casing 7, or it may be located outside the single common casing 7. The single common casing 7 allows for the sharing of one or more functions in the operation of the vacuum pump, i.e., one or more components for motor drive, synchronization, lubrication or temperature regulation, for example, can be mounted in this single common casing 7. This commonality reduces the overall dimensions of the pump unit 1.

[0027] (First Example) In a first embodiment of the invention shown in Figure 1, the two motors 33 and 53 are arranged in a common casing 7. Each vacuum pump 3, 5 has its own dedicated motor 33, 53. The rotor shafts 31, 32, 51, 52 are driven by separate motors 33, 53 and may therefore have different rotational speeds. This arrangement makes it possible to reduce the overall dimensions of the pump unit 1, in particular its height when the axes of rotation I and II are vertical, compared to conventional solutions in which each motor had to be located at one end of the pump unit 1, for example at the bottom for the first vacuum pump 3 and at the top for the second vacuum pump 5, as shown in FIG. 1.

[0028] Also, in the first vacuum pump 3, a first pair of bearings 9a can be mounted on a first upper end of the rotor shafts 31, 32, and a second pair of bearings 9b can be mounted on an opposite second end of the rotor shafts 31, 32. Similarly, in the second vacuum pump 5, a first pair of bearings 13a can be mounted on a first lower end of the rotor shafts 51, 52, and a second pair of bearings 13b can be mounted on an opposite second end of the rotor shafts 51, 52. For example, the first bearing pairs 9 a , 13 a at each end of the shafts 31 , 32 , 51 , 52 are arranged in one common casing 7 .

[0029] The remaining four bearings 9b, 13b can be arranged on both sides of the two vacuum pumps 3, 5. Thus, the second bearing 9b of the first vacuum pump 3 can be arranged at the lower end of the pump unit 1 (the bottom in FIG. 1). Conversely, the second bearing 13b of the second vacuum pump 5 can be arranged at the upper end of the pump unit 1 (the top in FIG. 1). The gears 11, 15 of the respective vacuum pumps 3, 5 are on the same side as the second bearing pair 9b, 13b, and therefore each gear 11, 15 is arranged on the opposite side along the axis of rotation I, II to the corresponding motor 33, 53 of the first vacuum pump 3 or second vacuum pump 5.

[0030] The lubrication of the first bearing pair 9a, 13a may be shared. More specifically, one oil pump 17 may be common to both vacuum pumps 3, 5 and one common liquid lubricant inlet 19 may be provided in one common casing 7. In operation, the one oil pump 17 circulates liquid lubricant towards, for example, the first bearing pair 9a, 13a. One thermal control device 21 may be at least partially integrated into one common casing 7. In this way, one thermal control device 21 may be common to one or more elements of the two vacuum pumps 3, 5. The thermal control device 21 may be configured, for example, to cool the motors 33, 53 and / or the first bearing pair 9a, 13a.

[0031] For this purpose, the hydraulic circuits of one thermal control device 21 can be integrally molded or stamped into the casting of one common casing 7. One or more thermal blocks through which the hydraulic circuits pass can be fixed to one common casing 7. Alternatively or additionally, the thermal control device 21 can be provided with one or more fans and / or cooling fins on the casting of one common casing 7.

[0032] (Second Example) A second embodiment of the present invention is shown in Figure 2. It differs from the first embodiment in that the two gears 11, 15 are also arranged in one common casing 7. Therefore, each gear 11, 15 is arranged on the same side as the corresponding motor 33, 53 of the first vacuum pump 3 or the second vacuum pump 5. For this purpose, gears 11 and 15, as well as first bearing pairs 9a and 13a, are arranged around first ends of rotor shafts 31, 32, 51 and 52. Gears 11 and 15 are arranged at the ends of shafts 31, 32, 51 and 52. First bearing pair 9a of first vacuum pump 3 is arranged below gear 11 along axis of rotation I. First bearing pair 13a of second vacuum pump 5 is arranged above gear 15 along axis of rotation II. The gears 11, 15 and / or the first bearing pair 9a, 13a may share lubrication. Other features are the same as those of the first embodiment, so a repeated description will be omitted.

[0033] (Third Example) The third embodiment of the present invention shown in FIG. 3 differs from the second embodiment in that all bearings 9 a , 9 b , 13 a , 13 b are arranged in one common casing 7 . In this case, the first pair of bearings 9a, 13a are arranged at the ends of the shafts 31, 32, 51, 52, and each motor 33, 53 is interposed between the first pair of bearings 9a, 13a on the one hand and the gears 11, 15 and the second pair of bearings 9b, 13b on the other hand. The lubrication of the gears 11, 15 and / or all bearings 9a, 9b, 13a, 13b may be shared. One thermal control device 21 is configured to cool, for example, the motors 33, 53 and / or all bearings 9a, 9b, 13a, 13b.

[0034] (Fourth Example) A fourth embodiment of the present invention is shown in Figure 4. This embodiment differs from the second embodiment described above in that the motors 33 and 53 are not housed in a single common casing 7. Instead, the motors 33, 53 are arranged on opposite sides of the pump unit 1. The motor 33 is arranged at one end of the first vacuum pump 3 opposite the one common casing 7, and the motor 53 is arranged at one end of the second vacuum pump 5 opposite the one common casing 7. Thus, each motor 33, 53 is arranged at one end of the pump unit 1, for example, at the bottom for the first vacuum pump 3 and at the top for the second vacuum pump 5, according to the orientation in FIG. Other features are the same as those of the second embodiment, so a repeated description will be omitted.

[0035] Thus, according to the invention, in one common casing 7, one or more functional elements of several vacuum pumps 3, 5, i.e. motors 33, 53 of the pump unit 1, bearings 9a, 9b, 13a, 13b, gears 11, 15, and / or common devices for, for example, temperature regulation or lubrication, for the two vacuum pumps 3, 5, can be accommodated, in any embodiment, to reduce the overall dimensions of the pump unit 1. In particular, in the case of vertical vacuum pumps 3, 5, the height of the pump unit 1 can be minimized. [Explanation of symbols]

[0036] 1 pump unit 3. No. 1 main vacuum pump 5 Second vacuum pump 7 Common casing 9a, 9b bearings 11 gears 13a, 13b bearings 15 gears 21 Thermal control device 23 Piping 30 Stator 31 rotor shaft 32 rotor shaft 33 Motor 50 Stator 51 rotor shaft 52 rotor shaft 53 Motor I Axis of rotation II. Axis of rotation

Claims

1. A pump unit (1) comprising at least one first primary vacuum pump (3) and at least one second vacuum pump (5) arranged in series, said second vacuum pump (5) having an outlet fluidly connected to an inlet of said first primary vacuum pump (3), Each of the vacuum pumps (3, 5) a stator (30, 50) having at least one pumping chamber; two rotors configured to rotate about respective axes of rotation (I, II) within the pump chamber; and at least one motor (33, 53) configured to rotate the rotor shaft (31, 32, 51, 52); the pump unit (1) comprises at least one common casing (7) for the first primary vacuum pump (3) and the second vacuum pump (5), the common casing (7) being interposed between the two vacuum pumps (3, 5); The pump unit is characterized in that the common casing (7) accommodates at least a part of the rotor shafts (31, 32, 51, 52) of the vacuum pumps (3, 5).

2. 2. Pump unit according to claim 1, characterized in that the axis of rotation (I, II) of the rotor shaft (31, 32, 51, 52) of at least one of the vacuum pumps (3, 5) is vertical.

3. 2. A pump unit according to claim 1, characterized in that the motors (33, 53) are arranged in the one common casing (7).

4. 2. The pump unit according to claim 1, characterized in that it comprises at least two gears (11, 15) arranged in one common casing (7), each gear (11, 15) being mounted around the rotor shaft (31, 32, 51, 52) of the associated vacuum pump (3, 5) and configured to synchronize the rotation of the rotor.

5. 5. A pump unit according to claim 4, characterized in that the gears (11, 15) are arranged on the same side of the common casing (7) as the motors (33, 53).

6. 2. A pump unit according to claim 1, characterized in that it comprises at least eight bearings (9a, 9b, 13a, 13b), at least two of which are arranged around each rotor shaft, and at least four of which are arranged around each rotor shaft (31, 32, 51, 52) in the single common casing (7).

7. 7. Pump unit according to claim 6, characterized in that all said bearings (9a, 9b, 13a, 13b) are arranged in said one common casing.

8. 2. A pump unit according to claim 1, characterized in that said one common casing (7) is provided with at least one thermal control device (21).

9. 2. The pump unit according to claim 1, further comprising at least one pipe (23) fluidly connecting the outlet of the second vacuum pump (5) to the inlet of the first primary vacuum pump (3), the pipe being at least partially formed within the single common casing (7).

10. 2. A pump unit according to claim 1, characterized in that at least one of said vacuum pumps (3, 5) is of the dry type.

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