Patent Application
20210033086
The present disclosure relates to scientific instruments and other apparatuses that incorporate vacuum systems and/or evacuated chambers.
Scientific instruments that use an internal pump to achieve vacuum in the measurement volume must be cooled in order to achieve best operation. The continual pump operation in an enclosed housing generates heat that must be exhausted for the instrument to function properly. Generally, vacuum pumps are air cooled with cooling fans typically being used to continuously cool the pump motor. Unfortunately, such air cooling limits overall instrument design as managing the heat load effectively is a balancing act between fan volume, air ducting space and system efficiency. Large vacuum pumps shorten the time required to achieve a target low pressure but disadvantageously require large or multiple fans to cool the pump and other surrounding components of the apparatus. The level of sound and vibrations produced by the apparatus' fans are generally considered undesirable. These effects may be especially severe when operating multiple apparatuses in the same laboratory space.
As an example,
The charged particles generated at the source 12 may be subsequently transported into a partitioned vacuum chamber 3 through either an aperture or an ion transfer tube 16 that passes through a first partition element or wall 11 into an intermediate-vacuum compartment 18. Although only a single intermediate-vacuum compartment is illustrated in the drawings, there may be additional intermediate-vacuum compartments between the illustrated compartment 18 and the high-vacuum compartment 26 within which a mass analyzer 28 is disposed.
In the illustrated example, in which the ion source 12 is an electrospray source, evaporation of solvent within the ionization chamber 14 and, if present, the ion transfer tube 16 liberates free ions into the intermediate-pressure chamber 18. The ion transfer tube 16, if present, may be physically coupled to a heating element or block 23 that provides heat to the gas and entrained particles in the ion transfer tube so as to aid in the desolvation of charged droplets so as to thereby release free ions. At least one ion optical assembly or ion lens 20 provides an electric field or electric fields that guide and focus the ion stream leaving ion transfer tube 16 through an aperture 22 in a second partition element or wall 15 that may be an aperture of a skimmer 21. Ions passing through the aperture 22 enter the high vacuum compartment 26 within which the internal pressure is typically maintained at about 10−5 Torr. A second ion optical assembly or lens 24 may be provided within the high-vacuum compartment 26 so as to transfer or guide ions to the mass analyzer 28. The mass analyzer 28 comprises one or more detectors 30 whose output can be displayed as a mass spectrum.
As ions travel downstream from the ionization chamber 14 to the high-vacuum compartment 26, they pass through a series of compartments of the vacuum chamber 3 having progressively reduced internal pressures. The pressure gradient across the chambers is maintained by differential vacuum pumping through a series of vacuum ports, with one vacuum port per chamber. Two such vacuum ports are illustrated in
Performance of an analytical scientific instrument, such as a mass spectrometer or electron microscope, is heavily influenced by the operating pressure inside the vacuum chamber. Thus, instruments having improved evacuation efficiency yield greater analytical efficiency. Accordingly, heated vacuum chambers have been used to improve the attainment of low pressures within the various vacuum compartments and to reduce the time required for evacuation. Such heating requires provision of heat sources that are thermally coupled to the vacuum chamber. Yet, as noted above, much heat generated by the various required vacuum pumps is wasted by conventional air cooling configurations, thereby causing the expenditure of additional electrical energy and generating excess laboratory noise and vibrations. Accordingly, alternative systems and methods for cooling a vacuum pump are desired.
The inventors have realized that a fluid cooling loop can be routed inside the housing of an apparatus that has a vacuum chamber in order to continuously cool the vacuum pump(s) that generate(s) the vacuum. The fluid line may send coolant liquid through channels that are thermally coupled to the vacuum pump motor(s) in order to extract heat. The heated coolant liquid that exits the channels at the pump motor(s) is then routed to an external heat exchanger at which the heat is extracted. A liquid pump completes the fluid circuit. Alternatively, prior to entering the heat exchanger, the heated coolant liquid can be routed through one or more channels in a wall (or walls) of the vacuum chamber walls or through a tube that is in thermal contact with the wall(s) in order to raise the temperature of the chamber without requiring additional energy to generate the heat. The higher temperature of the chamber walls increases molecular energy in the internal chamber volume that is evacuated by the pump, thereby reducing the time required to reach the desired chamber pressure(s). In addition, the transfer of heat energy to the chamber wall surfaces naturally displace molecules that are adhered to the walls, thus further reducing the time required to reach an appropriate operating pressure. These heated chamber wall channels could also benefit instruments that have a large thermal gradient along the length of the vacuum chamber (i.e., hot on one end, cold on the other). Creatively placing the entrance and exit points for the flowing coolant along the chamber walls could provide a method to normalize the chamber wall temperature throughout the assembly.
According to a first embodiment of an apparatus for cooling a vacuum pump that is disposed within the housing of a scientific instrument or other industrial apparatus in accordance with the present teachings, a liquid cooling system is integrated into the instrument. This involves routing a fluid tubing line inside the instrument housing to fittings on the pump motor. The coolant liquid in this line is routed through channels or other conduits that are either in the pump motor assembly or in thermal contact with the pump motor assembly, such as being affixed to a housing portion of the pump motor assembly. The coolant may be then routed back out of the instrument housing to a heat exchanger that may be external to the apparatus. This closed-loop system cycles cool coolant liquid to the pump motor and brings warm coolant liquid out of the instrument where it can be cooled externally. According to a second embodiment of an apparatus in accordance with the present teachings, the path of the coolant liquid can be designed such that, after absorbing heat from the vacuum pump, the heated coolant liquid is routed through channels in the vacuum chamber's walls before it exits the system. The metal chamber walls absorb this heat and produce an environment that is more conducive to evacuation due to higher molecular energy within the chamber.
Using a liquid cooled system to cool the pump motor instead of fans provides opportunities to use the heat in other areas of the housing where it is beneficial to overall instrument operation. The beneficial feature of improving the ability to cool the pump is achieved through liquid cooling of the pump's motor or housing (or pumps' motors or housings) is augmented by the secondary benefit of a more efficient vacuum pumping environment inside the vacuum chamber as a result of the additional heat introduced into the chamber's walls. Using the exhaust heat from the pump allows for this secondary benefit without requiring additional energy or components to heat the vacuum chamber. This approach can be extended by configuring the fluid circuit that transports the coolant liquid to also come into thermal contact with either additional vacuum pumps or other heat-generating components inside the housing, such as other motors or electronic components, in order to off-load heat to the cooling fluid circuit. The net effect is improved cooling of the instrument with fewer noise-generating fans and increased heat generation for the vacuum chamber's walls.
According to a method in accordance with the present teachings, the overall temperature of the vacuum chamber can be controlled by opening and closing a diverter valve in the fluid cooling loop. The method can include monitoring the chamber's temperature and controlling the flow rate of heated coolant liquid coming into thermal contact with the chamber walls as the chamber temperature increases. This method may be employed to control the operating temperature of the chamber and avoid overheating in this area of the instrument. Once the desired chamber temperature is reached, the diverter valve can be used to send more of the heated coolant liquid to the external heat exchanger through an alternate path that does not come into direct thermal contact with the chamber walls. This technique could be used to produce instruments that generate less noise and vibration than do conventional instruments. For instruments with varying temperatures inside the vacuum chamber, this technique could produce a more temperature-uniform environment inside the vacuum chamber.
The above noted and various other aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings, not necessarily drawn to scale, in which:
The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the described embodiments will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. Thus, the present invention is not intended to be limited to the embodiments and examples shown but is to be accorded the widest possible scope in accordance with the features and principles shown and described. To fully appreciate the features of the present invention in greater detail, please refer to
In the description of the invention herein, it is understood that a word appearing in the singular encompasses its plural counterpart, and a word appearing in the plural encompasses its singular counterpart, unless implicitly or explicitly understood or stated otherwise. Furthermore, it is understood that, for any given component or embodiment described herein, any of the possible candidates or alternatives listed for that component may generally be used individually or in combination with one another, unless implicitly or explicitly understood or stated otherwise. Moreover, it is to be appreciated that the figures, as shown herein, are not necessarily drawn to scale, wherein some of the elements may be drawn merely for clarity of the invention. Also, reference numerals may be repeated among the various figures to show corresponding or analogous elements. Additionally, it will be understood that any list of such candidates or alternatives is merely illustrative, not limiting, unless implicitly or explicitly understood or stated otherwise.
The term “coolant liquid”, as used herein, refers to the liquid that is caused to flow within the fluid tubing lines, channels or other conduits that are portions of liquid circuits described herein. Depending upon the environment of any particular portion of such a liquid circuit, the coolant liquid within the portion may either absorb heat from the local environment, release heat to the local environment or possibly neither absorb nor release heat. For consistency, however, the liquid is referred to as a “coolant liquid” throughout. Unless otherwise defined, all other technical and scientific terms used herein have the meaning commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control. It will be appreciated that there is an implied “about” prior to the quantitative terms mentioned in the present description, such that slight and insubstantial deviations are within the scope of the present teachings. In this application, the use of the singular includes the plural unless specifically stated otherwise. Also, the use of “comprise”, “comprises”, “comprising”, “contain”, “contains”, “containing”, “include”, “includes”, and “including” are not intended to be limiting. As used herein, “a” or “an” also may refer to “at least one” or “one or more.” Also, the use of “or” is inclusive, such that the phrase “A or B” is true when “A” is true, “B” is true, or both “A” and “B” are true.
The system 40 of
Many types of heat exchangers are known in the art and may be used within the system 40. If the heat exchanger 46 is in thermal contact with an air bath (either at ambient temperature or chilled), then a fan may be employed so as to maintain a constant flow of air over about or through the heat exchanger. In contrast to conventional fan-based methods of cooling a vacuum pump, the provision of the fluid tubing lines, channels or conduits 47a, 47b and 47c enables the fan to be located remotely from the vacuum pump and its associated apparatus or even remotely from the laboratory environment. The remote placement of the fan may prevent noise and vibrations from interfering with apparatus or laboratory operations.
Preferably, the tubing, channel or conduit 47b comprises one or more fluid channels or other conduits within the body of the motor housing 5. Alternatively, the tubing, channel or conduit 47b may comprise a metal tube of high thermal conductivity, such as a copper or aluminum that is affixed to the outer surface of the motor housing 5, such as by solder. Such a tubing configuration is schematically illustrated in
Although
Having acquired heat energy from the vacuum pump 10, any so-heated coolant liquid that subsequently passes through fluid tubing line 47c and that is diverted into the one or more channels, conduits or fluid tubing lines 41 then releases all or a portion of this heat energy to the vacuum chamber 3. As a consequence, a portion of the heat energy is imparted to the compartments 18, 26 therein (assuming that the chamber and compartments are at a lower temperature than the heated coolant). The heating of gas within the compartments improves pumping efficiency and enables the attainment of lower pressures than would otherwise be achieved. Although flow through the one or more channels, conduits or fluid tubing lines 41 is depicted as being unidirectional through a single wall of the vacuum chamber 3 in
The temperature of the vacuum chamber interior or of one or more of its compartments may be measured by one or more temperature sensors 48a and regulated by a control system to maintain a set temperature (or temperature range) within the vacuum chamber 3. Non-limiting examples of suitable temperature sensors include thermocouple and thermistor sensors. The one or more temperature sensors 48a may be in electronic communication with a computer or other electronic controller 49 whereby a signal from the temperature sensor may be digitized, if the signal was previously in analog form. Similarly, the heat exchanger 46 may comprise one or more temperature sensors 48b that measure the temperature(s) of one or more of the air or liquid bath, the ambient environment, the coolant liquid at the inlet 33 and the coolant liquid at the outlet 34. The one or more temperature sensors 48b may be in electronic communication with the computer or other electronic controller 49 and analog signals, if any, from the one or more temperature sensors 48b may be digitized by the computer or other electronic controller. Further one or both of the diversion valve 44 and the liquid pump 43 may be in electronic communication with the computer or other electronic controller 49. Other temperature sensors (not shown) may be disposed so as to measure temperatures elsewhere in the system, such as at various locations within the fluid tubing lines, channels or conduits 47a, 47b and 47c.
The computer or other electronic controller 49 may comprise a separate general-purpose computer that is electronically coupled to the various physical components or may comprise electronic logic components and associated circuitry within the apparatus. The computer or other electronic controller 49 may comprise computer-readable instructions, either software-based or in firmware, that are operable to read and/or record temperature-related signals from the various temperature sensors and that are further operable, in response to the temperature signals, to control the operation of the liquid pump 43, the operation of the diversion valve 44 and/or the temperature of a liquid or air bath in contact with the heat exchanger 46. The operation of the liquid pump, diversion valve and/or heat exchanger bath fluid may be performed by control signals delivered to one or more of the liquid pump, diversion valve and heat exchanger over one or more electrical wires or cables (not shown) that couple these components to the computer or other electronic controller 49. One or more of the temperature(s) may be monitored and this information may be used to control either the temperature or the rate of flow of heated coolant liquid that passes through the conduits or fluid tubing lines 41 as the chamber temperature changes. The flow rate may be controlled by either the pumping speed or by the apportioning of flow between fluid tubing lines, channels or conduits 47d and 47e. This technique provides a method to control the operating temperature of the chamber and avoid overheating in this area of the instrument. Once the desired chamber temperature is reached, either the pumping speed of the pump 43 may be reduced or the diverter valve 44 may be configured to send more of the heated coolant liquid to fluid tubing line, channel or conduit 47d and then to the external heat exchanger 46.
According to a variation of the system 50 (not shown), both the temperature sensor 48a and the controller 49 may be replaced by a simple analog thermostat, such as a thermostat of the bi-metal type. The thermostat may act as an electrical switch that is directly coupled to an actuator of the diversion valve 44. In operation, the thermostatic switch may cause the diversion valve to send coolant liquid through the one or more channels, conduits or fluid tubing lines 41 when the internal chamber temperature exceeds a pre-determined set point and to send the coolant liquid through the bypass fluid tubing line 47d otherwise. The additional one or more temperature sensors 48b may be absent from such a system.
Improved systems and methods have been herein disclosed for removing heat from a vacuum pump of an apparatus that includes a vacuum chamber. Various embodiments of the systems and methods in accordance with the present teachings make use of the heat energy that is received from the vacuum pump by transporting at least a portion of the heat to the vacuum chamber and thereby improving pumping efficiency. The discussion included in this application is intended to serve as a basic description. The present invention is not intended to be limited in scope by the specific embodiments described herein, which are intended as single illustrations of individual aspects of the invention. Functionally equivalent methods and components are within the scope of the invention. For example, although a heat exchanger 46 has been illustrated as being disposed outside of a housing 8 of an apparatus in question, some applications may require the heat exchanger to be disposed within the housing (e.g. for purposes of overall apparatus compactness or because an external heat exchanger is not available or feasible). Similarly, the liquid pump 43 may be disposed within the apparatus housing. As another example, although the present teachings are generally applicable to an apparatus that includes a vacuum pump within the apparatus housing, some applications may require the vacuum pump to be disposed on its own separate chassis and within its own separate housing (e.g., for purposes of vibration isolation or structural support of a heavy vacuum pump. In such instances, removal of heat from the vacuum pump may be necessary or required in order to avoid overheating and, in such instances, the principles and features taught herein will still apply. Various other modifications of the invention, in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description and accompanying drawings.
Any patents, patent applications, patent application publications or other literature mentioned herein are hereby incorporated by reference herein in their respective entirety as if fully set forth herein, except that, in the event of any conflict between the incorporated reference and the present specification, the language of the present specification will control.
