US20080145243A1

US20080145243A1 - Vacuum pump with a hood

Info

Publication number: US20080145243A1
Application number: US12/001,908
Authority: US
Inventors: Gernot Bernhardt; Juergen Wagner
Original assignee: Pfeiffer Vacuum GmbH
Current assignee: Pfeiffer Vacuum GmbH
Priority date: 2006-12-13
Filing date: 2007-12-12
Publication date: 2008-06-19
Also published as: JP2008151125A; DE102006058840A1; DE102006058840B4; EP1936202A3; EP1936202A2; EP1936202B1

Abstract

A vacuum pump includes a pumping system (30) located in a pump housing (1) and a hood (1) at least partially surrounding the pump housing at least in the region of the pumping system to provide for at least partial dissipation of heat generated in the pumping system.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a vacuum pump having a housing which has inlet and outlet and in which a pumping system and a motor for driving the pumping system are located.
2. Description of the Prior Art
Vacuum pumps generate heat in their interior as a result of compression therein of pumped gases. However, the gas compression is not the only source of heat in the vacuum pumps. In most cases, the vacuum pumps includes movable parts driven by respective drives. These drives have all a certain efficiency level so that a power dissipation takes place which, as a rule, is converted into heat. Heat is also generated as result of friction in the bearings and by other sources. The generated heat is released into the environment and presents a source of danger for a pump user.
Therefore, there is a need to protect the vacuum pump user. In state of the art, the pumps are provided with handles which can be used by a pump user for displacing a pump shortly after start of the pump operation, i.e., in a heated condition. However, the handles do not provide protection against a contact with the pump and are, therefore, not satisfactory. Another solution is suggested in European Publication EP-A 1 696 132. This solution consists in enclosing the entire vacuum pump in an external housing that surrounds the pump housing. This solution is associated with high costs and presents a problem from the point of view of access to the operational elements of the pump. Further, there is a danger of the pump being overheated.
Accordingly, an object of the present invention is to provide a vacuum pump with heat insulation means that would not unfavorably influence the heat balance of the pump.

SUMMARY OF THE INVENTION

This and other objects of the present invention which will become apparent hereinafter, are achieved by providing a hood that at least partially surrounds the pump housing. The hood prevents contact with heat conducting components of the pump, providing protection for the pump user. In the region of hot parts of the pump, there are provided surfaces which can be contacted without danger to the user. Therefore, the increased costs which are associated with an unnecessary large hood, are eliminated. The hood is a simple part, and the access to all of the operational elements can be insured by forming in the hood recesses and/or openings which can be economically produced.
According to one modification of the present invention, an intermediate member is arranged between the hood and the pump housing, so that the housing and the hood are not in a surface contact with each other. This reduces heat transmission to the hood. In addition, the intermediate member provides spacing between the pump housing and the hood, providing an intermediate space filled with air that functions as an isolating air cushion in the absence of a forced aeration that causes an air exchange.
According to a further modification of the present invention, the intermediate member contains material components that damps mechanical vibrations imparted to the intermediate member. This prevents transmission of the vibrations to the hood, which provides for a generally silent operation of the vacuum pump. Little noise is transmitted to the environment, which is advantageous for use of the inventive vacuum pump in a laboratory environment in which operational personnel is always present.
According to an advantageous embodiment of the present invention, the intermediate member has material components having heat insulating properties, so that the intermediate member functions also as a thermal barrier. This further reduces heat transmission to the housing.
The advantages of the provision of the intermediate member, which were discussed above, are further increased when the intermediate member includes elastomeric components as they have both vibration damping properties and heat insulating properties, which provides for functioning of the intermediate member as both vibration damping means and a thermal barrier.
According to a further advantageous embodiment of the present invention, the hood is so formed and arranged that it guides the cooling gas flow, which is generated by a fan, at least to a portion of cooling ribs provided on the housing. This insures an efficient cooling of the housing, with the hood being also cooled from inside.
With the above-mentioned arrangement of the hood, the aeration of channels between the cooling ribs and the hood is increased when the fan is located behind the hood.
According to a still further development of the present invention, the hood has an opening through which air is aspirated by the fan to be subsequently delivered in the cooling channels. The opening provides for an effective suction of air and; at the same time, provides for freedom in selection of the location of the fan. E.g., the fan can be arranged very close to the cooling ribs and needs not to be necessarily located at the hood end.
The advantages of providing a hood significantly increase with the vacuum pump the housing of which is formed of several housing sections, with the pumping system and control electronics being located in different housing sections. This improves the heat balance of the pump because the pumping system represents a source of heat while the control electronics has electronic components which should be protected from heat, as they aged very rapidly under heat.
The advantages of the present invention are particularly apparent when the pumping system is adapted for compressing gas in low or high vacuum range and for discharging the compressed gas against atmosphere.
The novel features of the present invention which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiment, when read with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings show:

FIG. 1 a a side view of a vacuum pump equipped with a hood according to the present invention in a disassembled condition;

FIG. 1 b a side view of the vacuum pump with a hood shown in FIG. 1 a in an assembled condition;

FIG. 2 a cross-sectional view through the intermediate section and the control section of the inventive vacuum pump;

FIG. 3 a horizontal cross-sectional view along III-III in FIG. 2;

FIG. 4 a vertical cross-sectional view of through the pump-section and the peripheral section; and

FIG. 5 a cross-sectional view along line V-V in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a vacuum pump that is formed of four sections and is surrounded by a hood 1. The hood 1 is shown in FIG. 1 a in a disassembled or dismounted condition. In FIG. 1 b, the hood 1 is shown in a mounted condition on the vacuum pump and surrounds a portion of the vacuum pump housing 1′. The vacuum pump itself rests on a stand 10.
The sections of the vacuum pump include different functional units. The control section 2 includes the control electronics that controls feeding of current from a network to the coils of the pump drive. In the intermediate section 3, a fan 6 is arranged. The fan 6 aspirates air and delivers it in the space between cooling ribs 8 provided on the housing, whereby cooling of the pump takes place. The suction and the delivery of air by the fan 6 is shown with the arrows. The peripheral section 4 includes gas connections, i.e., gas inlet 9 and gas outlet. The stand 10 also is arranged at the peripheral section 10. The stand 10 includes means, e.g., an elastomeric body which reduces transmission of vibrations between the vacuum pump and the floor. In the pumping section 5, those components of the pump are located with which the gas is compressed to such an extent that it can be discharged against the atmosphere. These four sections are arranged axially one after another, with the intermediate section being located between the peripheral and control sections. The pumping section 5 is provided on a side of the peripheral section 4 remote from the intermediate section 3.
The sections of the vacuum pump are at least partially surrounded by the hood 1. In the embodiment shown in the drawings, the hood 1 is so formed that it covers the lower portion of the vacuum pump. Lower portion means a portion of the vacuum pump adjacent to the stand 10, i.e., in the direction of the floor. The shape of the hood 1 is such that the control and intermediate sections 2 and 3 are completely covered by the hood 1. The hood is somewhat short in the region of the pumping section, covering only the lower part of the pumping section. The cooling ribs 8 are provided in the lower part of the pumping section 5. However, the cooling ribs can also be formed in the upper part of the pumping section 5. The hood 1 covers at least a portion of the cooling ribs 8, forming channels that are limited by the hood 1, the pump housing, and the cooling ribs 8. For the purpose of protection, it can be sufficient to cover only the lower portion of the pump because it is in the lower portions of the pumping and peripheral sections 4 and 5 that the heat-carrying elements such as lubricant and coils are provided. When shaping a hood, design consideration can naturally play a certain role. The hood 1 also covers the fan 6.
In order for the fan to be able to aspirate the air and to deliver it into the channels, the hood has an opening. In the shown embodiment, the opening is formed as a plurality of aeration slots 7. The number and the shape of the slots 7 can vary for different pumps and are dependent on the requirements to the cooling gas flow.
FIG. 2 shows the design of the control and intermediate sections 2 and 3. The control section 2 has a closed housing with cooling ribs 11. The cooling ribs 11 insure cooling by a free convection. Within the control section 2, there are located electronic components which form control electronics and are mounted on a printed circuit board. The electronic components convert a supply voltage in such a way that feeding of voltage and current in a suitable form to the drive coils to provide for rotation of the drive shaft is insured. The supply voltage source can be a conventional network voltage of 220 V and 50 Hz or any contemporary industrial voltage such as 48V. Those components of the control electronics, which generate a certain amount of heat, can be so arranged that they would contact the inner wall of the housing of the control electronics. Advantageously, the contact takes place in the region of the cooling ribs 11. Likewise, it is possible to embed the control electronics in a filling compound partially or completely. This would also insure a high mechanical stability.
The intermediate section 3 contains several components in its housing. A switch 15 serves for turning the vacuum pump on and off. Further switches can be also arranged in the intermediate section housing. The further switches can include, e.g., a standby switch or a speed selection switch. Here, likewise, a socket 16, to which the power supply is connected, is arranged. This power is transmitted to the control electronics, on one hand, and on the other hand, it is transmitted to a small panel that is connected by suitable conductors with an auxiliary electronics 18, supplying it with power. The auxiliary electronics serves for converting the switching condition of the switch 15 in a control signal that is transmitted over suitable conductors to the control electronics. The auxiliary electronics has also means that insures feeding voltage to the fan motor 6 a and that controls switching the fan motor 6 a on and off. A seal 14 is provided between the housings of the intermediate section 3 and the control section 2. The seal 14 serves, on one hand, for sealing the inner space against the moisture and dust. On the other hand, the seal 14 functions as a thermal barrier, making the transmission of heat from the intermediate section to the control section more difficult. A similar seal is also provided between the intermediate section 3 and the peripheral section 4, making the transmission of heat therebetween also more difficult. In a portion of the intermediate section 3, a support 19 supports the fan 6 that includes the motor 6 a and a fan blade 6 b. The dash arrows show the cooling gas flow that is aspirated by the fan 6. The air is aspirated and flows between the cooling ribs 8.
FIG. 3 shows a cross-sectional view of the control and intermediate sections 2 and 3 and a portion of the peripheral sections 4. In this view, cooling ribs 11, which are provided on a control section-side, end side of the vacuum pump, are shown in cross-section. The longitudinal axis of the ribs 11 is oriented in direction of the gravity force in order to optimize the free convection. Advantageously, the cooling ribs of the control section are not covered by the hood 1 in order not to obstruct the air flow of the free convection. The feeding electrical conductors from the control section 2 pass to the peripheral section 4 through a cable channel provided in the intermediate section 3. Two channel seals 21 and 22 protect the cable channel from moisture and dust. In particular, on a side of the motor control, a cable leadthrough 27 is provided. Inside the peripheral section 4, there are provided coils 26 of the pump drive.
The control electronics 12 provides for feeding power to the coils 26. A rotationally symmetrical separation member 23 is arranged between the coils 26 hermetically separating them from the inner space of the separation member 23. An end of a shaft 24, on which permanent magnets 25 are secured, projects into the inner space of the separation member 23. The cooling gas flow, which is generated by the fan 6, is again shown with dash arrows. The suction is effected through the aeration slots 7, and the air is delivered in the direction of the peripheral section 4. According to a further modification of the vacuum pump, such aeration slots are formed in the pump bottom. The stand then needs to be sufficiently spaced from the pump bottom in order to provide a clearance through which the air can be aspirated.
FIG. 4 shows a cross-sectional view of the peripheral and pumping section 4 and 5. The embodiment of the vacuum pump shown in the drawings represents a one-stage, lubricant-tight vane rotary vacuum pump. The vacuum pump shown in FIG. 4 has a pumping system 30 located in the pumping section 5. The pumping system 30 has its end side connected with the peripheral section 4 along a large surface, whereby a good heat transmission is insured.
The housing of the pumping section 5 has good heat-conducting characteristics, so that the heat of the peripheral section 4 is transmitted to a large-surface body. The shaft 24 eccentrically extends through a cylindrical bore formed in the pumping section 5. The shaft 24 can be formed of one or several pieces and is supported by first and second slide bearings 31 and 32 which are lubricated by a lubricant. The lubricant is supplied from a lubricant reservoir 35 that surrounds the pumping system 30. A vane 33 is rotatably supported in the cylindrical bore of the pumping section 5, with a compression chamber 34 being formed between the wall of the cylindrical bore and the vane 33. The permanent magnets 25 are secured, as it has already been discussed above, on the end of the shaft 24 that projects into the peripheral section 4 in which the coils 26 are located. Cooperation of the magnets 25 with coils 26 provides for ration of the shaft 24, with the coils 26 and permanent magnets 26 forming an electric motor. Here, there is provided a brushless D.C. motor. Though the advantages of the present invention are particularly apparent with this type of an electric motor, the invention is not limited to this type of a drive motor. The lubricant, primarily oil, serves, in addition to lubrication of the bearings, also for lubrication and sealing of the vane 33.
FIG. 5 shows a vertical cross-sectional view of the pumping section 5. FIG. 5 illustrates in particular the eccentric position of the shaft 24 and the position of vane 33. Between the vane 33 and the shaft 24, there is provided a spring, not shown. The pumping section housing has the cooling ribs 8. The hood 1 covers the cooling ribs 8, forming flow channels 42. The cooling gas flow, which is generated by the fan 6, flows through the flow channels 42, which can be connected with each other, absorbs the heat of the housing and carries the heat away from the housing. The heat is produced in the pumping system 30 and is transmitted to the housing by the lubricant reservoir 36.
Preferably, the hood 1 is so shaped that the channels are open at their ends. This can be managed very easily as the hood 1 does not cover the pumping section-side, end side of the inventive vacuum pump. Between the hood 1 and the housing, there is provided an intermediate element 40 that, e.g., has highly elastomeric components. Preferably, the intermediate element 40 is provided at that location between the hood 1 and the housing at which the hood 1 and the housing are connected with each other. The location and material selection take care of both thermal insulation and reduction of transmission of vibration from the pumping housing to the hood 1. The hood 1 is fixed with attachment means, e.g., with screws 41.
The embodiment of the vacuum pump shown in the drawings has a favorable heat balance. A first source of an extensive heat is the heat of compression in the pumping section 5. A further source of an extensive heat is the peripheral section 4 because it is there that the drive coils, in which the power dissipation is converted into heat, are located. In addition, the heat to the peripheral section 4 is transmitted by the end side of the pumping system 30 which contact the peripheral section 4 along a large surface. These heat sources are isolated from the control section by the intermediate section. In view of the serial connection of the pump sections, this distance is maximized. Also, the thermal resistance of the seals, which are provided between the intermediate section and the adjacent sections, contributes to isolation of the heat sources from the control section 2. These passive measures provide for a very favorable heat balance. The active cooling with a fan also contributes to the favorable heat balance. By locating the fan in the intermediate section, the sections; which generate most of the heat, are subjected to the action of the cooling air. The hood serves, on one hand, as a convection protector and, on the other hand, guides the cooling air flow, which is generated by the fan, in optimal manner to the heat sources of the pumping and peripheral sections. In those regions, where no air movement takes place, under the hood, the air acts as an air cushion and isolates the environmental heat from the bottom parts, e.g., of the control section. In sum, the cooling of the inventive vacuum pump is noticeably improved in comparison with the state of the art.
Though the present invention was shown and described with references to the preferred embodiment, such is merely illustrative of the present invention and is not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is therefore not intended that the present invention be limited to the disclosed embodiment or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A vacuum pump, comprising a housing having inlet and outlet; a pumping system located in the housing; a motor for driving the pumping system and likewise located in the housing; and a hood at lest partially surrounding the pump housing.

2. A vacuum pump according to claim 1, further comprising an intermediate member located between the hood and the housing.

3. A vacuum pump according to claim 2, wherein the intermediate member is formed of a vibration-damping material.

4. A vacuum pump according to claim 3, wherein the vibration-damping material has heat insulation properties, so that the intermediate member forms a heat barrier between the pump housing and the hood.

5. A vacuum pump according to claim 2, wherein the intermediate member includes elastomeric components.

6. A vacuum pump according to claim 1, wherein the pump housing is provided with cooling ribs, wherein the vacuum pump further comprises a fan for generating a cooling blow, and wherein the hood guides the cooling flow, which is generated by the fan, at least to a portion of the cooling ribs.

7. A vacuum pump according to claim 6, wherein the fan is arranged behind the hood.

8. A vacuum pump according to claim 7, wherein the hood has at least one opening through which air is aspirated by the fan.

9. A vacuum pump, according to claim 1, wherein the pump housing is formed of a plurality of housing sections, wherein the pump further comprises control electronics, and wherein the pumping system and the control electronics are located in different housing sections.

10. A vacuum pump according to claim 1, wherein the pumping system includes means for compressing gas from at least one of low and high vacuum range and for discharging a compressed gas against atmosphere.