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  Pump deviceUSPTO Application #: 20060198743Title: Pump device Abstract: A pump device has an impeller rotatable in a pump space, a rotational shaft interconnecting a rotational drive source and the impeller, a rotational shaft casing having a bearing assembly and/or a seal assembly, a first blocking flow mechanism, having a discharge section for discharging a portion of a main delivery liquid introduced from the pump space as a first blocking flow, for preventing a second blocking flow containing fine particles produced by the bearing assembly and/or the seal assembly from being entrained into the main delivery liquid, and a second blocking flow mechanism for combining the second blocking flow with the first blocking flow and discharging the second blocking flow from the discharge section while preventing the first blocking flow from being introduced. (end of abstract)
Agent: Wenderoth, Lind & Ponack, L.L.P. - Washington, DC, US Inventor: Jun Taga USPTO Applicaton #: 20060198743 - Class: 417423100 (USPTO) Related Patent Categories: Pumps, Motor Driven, Electric Or Magnetic Motor, Rotary Motor And Rotary Nonexpansible Chamber Pump The Patent Description & Claims data below is from USPTO Patent Application 20060198743. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a rotary pump device for transporting a very highly-purity active liquid for use in a process of fabricating semiconductor devices, liquid crystals, etc., and more particularly to a pump device which is capable of preventing metal ions and other fine particles from being produced by isolating an active liquid, such as ultrapure water or the like, and a metallic part of a pump mechanism from each other. [0003] 2. Description of the Related Art [0004] For achieving a high level of integration of semiconductor devices, it is necessary to increase the purity of various liquids used in the fabrication process and, in particular, to achieve extremely lower content of impurities in those liquids. With regard to ultrapure water that is used in a cleaning process for semiconductor fabrication, the content of fine particles having a size of 0.1 micron poses a problem and greatly affects the yield of products. Particularly, it was a challenging task for pumps for transporting ultrapure water to prevent fine particles from being produced by the wear of rotary sliding components. The task has been achieved by the inventor of the present application as disclosed in Japanese patent No. 1807169, U.S. Pat. No. 5131806, or Japanese laid-open patent publication No. H3-26897. [0005] As the level of integration of semiconductor devices and the performance of liquid crystals further increase, however, the concentration of metal ions, which remain in ultrapure water, poses a large problem. Today, the content of metal ions is required to be 1 PPT (Part Per Trillion) or less. Metal ions are caused to occur when ultrapure water dissolves a metal in liquid-contacting regions of devices including pumps, pipes, valves, etc. in a wet process. It is understood that ultrapure water of highest purity having a resistance of 18.20 M.OMEGA. or higher tends to elute highly active ions of metal or the like. SUMMARY OF THE INVENTION [0006] In order to solve the above disadvantage, it has been customary to apply a surface treatment, such as a lining or coating of tetrafluororesin, to regions of devices, such as pumps, that are brought into contact with ultrapure water. However, it is generally difficult to apply a surface treatment, such as a lining of tetrafluororesin, to rotary sliding components and seals of pumps. Even if very chemically stable, highly hard SiC (silicon carbide) is used for rotary sliding components and seals of pumps, it cannot fully prevent ultrapure water from dissolving the metal. At present, it has been attempted to use functional ultrapure water containing a small amount of ozone (O.sub.3) or hydrogen fluoride (HF). Use of functional ultrapure water, however, is problematic in that metal and ceramics are exposed to a chemical attack, causing the liquid-contacting regions in rotary sliding components of pumps, i.e., bearings and seals, to suffer erosion due to elution of metal and ceramics. [0007] A pump device according to the present invention has an impeller rotatable in a pump space, a rotational shaft interconnecting a rotational drive source and the impeller, a rotational shaft casing having a bearing assembly and/or a seal assembly, a first blocking flow mechanism, having a discharge section for discharging a portion of a main delivery liquid introduced from the pump space as a first blocking flow, for preventing a second blocking flow containing fine particles produced by the bearing assembly and/or the seal assembly from being entrained into the main delivery liquid, and a second blocking flow mechanism for combining the second blocking flow with the first blocking flow and discharging the second blocking flow from the discharge section while preventing the first blocking flow from being introduced. [0008] In a preferred aspect of the present invention, the first blocking flow mechanism has a first blocking flow passage defined between the rotational shaft and an inner circumferential surface of the rotational shaft casing, and the second blocking flow mechanism has a second blocking flow passage defined between the rotational shaft and an inner circumferential surface of the rotational shaft casing, the first blocking flow passage and the second blocking flow passage being disposed in respective positioned on both sides of the discharge section, the second blocking flow passage being supplied with an inactive liquid as the second blocking flow from a second blocking flow supply port which is open into the second blocking flow passage. [0009] Preferably, the discharge section comprises a blocking disk mounted on the rotational shaft and a disk chamber defined in the rotational shaft casing and housing the blocking disk therein. Further preferably, a labyrinth is provided in the disk chamber between an inner circumferential surface of the disk chamber and the blocking disk. [0010] The second blocking flow preferably has a higher liquid pressure than the first blocking flow at the second blocking flow supply port. [0011] The second blocking flow passage is preferably filled at all times with the inactive liquid supplied from the second blocking flow supply port. [0012] The first blocking flow is preferably discharged from the discharge section at a rate higher than the second blocking flow, the rate of the second blocking flow being at least 1.5 when the rate of the first blocking flow is 1. BRIEF DESCRIPTION OF THE DRAWINGS [0013] FIG. 1 is a cross-sectional view of a pump device according to an embodiment of the present invention; and [0014] FIG. 2 is a cross-sectional view of a pump device according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0015] A pump device according to an embodiment of the present invention has regions, other than rotary sliding components, such as a bearing assembly and a seal assembly in a rotational shaft casing, which are brought into contact with a main delivery liquid (ultrapure water) and which have surfaces treated for erosion resistance by a lining of tetrafluororesin or the like. In a first blocking flow mechanism, a first blocking flow as a portion of a main delivery liquid (ultrapure water) flowing from a pump space into the rotational shaft casing is discharged out of the rotational shaft casing through a first blocking flow passage defined between a rotational shaft and an inner circumferential surface of the rotational shaft casing, a discharge section contiguous to the first blocking flow passage and disposed in the rotational shaft casing closely to an impeller, and a discharge passage communicated with the discharge section. Therefore, a second blocking flow containing fine particles produced from the rotary sliding components, such as the bearing assembly and the seal assembly, as they are worn is blocked by the first blocking flow against entry from the rotational shaft casing into the pump space. [0016] Specifically, in a second blocking flow mechanism, an inactive liquid, such as ordinary tap water, which exhibits an excellent lubricity to ultrapure water, flows as the second blocking flow from a supply source into the rotational shaft casing, and then flows through a second blocking flow passage defined between the rotational shaft and an inner circumferential surface of the rotational shaft into the discharge section of the first blocking flow mechanism. Therefore, the first blocking flow is prevented from entering into the rotary sliding components, such as the bearing assembly and the seal assembly. In the rotational shaft casing, the inactive liquid (water) delivered as the second blocking flow into the rotational shaft casing flows along the rotational shaft away from the first blocking flow mechanism, i.e., toward the rotary sliding components, such as the bearing assembly and the seal assembly. Since a terminal end of the rotational shaft casing, i.e., the end thereof close to a rotational drive source, is sealed by a seal mechanism, the inactive liquid (water) fills the rotational shaft casing including the rotary sliding components, such as the bearing assembly and the seal assembly, isolating the first blocking flow (ultrapure water) and the rotary sliding components from each other. [0017] The pressure of the second blocking flow of the inactive liquid at a second blocking flow supply port is higher than the pressure of the first blocking flow. However, the rate of the second blocking flow may be lower than the rate of the first blocking flow at all times, primarily at a level for allowing the second blocking flow to operate as lubricating oil and exhibit a cooling effect. Since the rate of the second blocking flow after it has flowed into the rotational shaft casing is much lower than the rate of the first blocking flow, the pressure of the second blocking flow is gradually lowered toward the pressure of the first blocking flow, and becomes equal to the pressure of the first blocking flow when the second blocking flow is discharged in combination with the first blocking flow. Consequently, the second blocking flow does not flow toward and into the pump space on the impeller side. [0018] The inactive liquid (water), which forms the second blocking flow, is supplied by a diaphragm that is actuatable pneumatically, hydraulically or electrically, or a metering pump comprising a plunger pump that is actuatable by an air cylinder. Tap water having a suitable pressure may also be used as the inactive liquid. If necessary, a supply passage interconnecting the supply source and the rotational shaft casing may have a pressure regulating valve, a flow regulating valve, an on-off valve, and the like. [0019] Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a cross-sectional view of a pump device according to an embodiment of the present invention. [0020] As shown in FIG. 1, the pump device has an impeller 2 rotatable in a pump space 1, a rotational shaft 3 interconnecting a rotational drive source M and the impeller 2, and a rotational shaft casing 4 having a bearing assembly B and a mechanical seal assembly S. The mechanical seal assembly S has a fixed ring S1 and a rotary ring S2. Regions of the various components, other than the bearing assembly B and the mechanical seal assembly S, which are brought into contact with ultrapure water as a main delivery liquid, are treated for erosion resistance by a lining of tetrafluororesin or the like. The regions, which are treated for erosion resistance, are indicated by bold solid lines in FIG. 1. Continue reading... Full patent description for Pump device Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Pump device patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Pump device or other areas of interest. ### Previous Patent Application: Downhole uses of piezoelectric motors Next Patent Application: Skipping frequencies for variable speed controls Industry Class: Pumps ### FreshPatents.com Support Thank you for viewing the Pump device patent info. IP-related news and info Results in 0.16036 seconds Other interesting Feshpatents.com categories: Software: Finance , AI , Databases , Development , Document , Navigation , Error |
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