Rotary kinetic fluid motors or pumps – Runner has spirally arranged blade or fluid passage – Extending along runner axis
Reexamination Certificate
2001-06-28
2003-02-04
Ryznic, John E. (Department: 3745)
Rotary kinetic fluid motors or pumps
Runner has spirally arranged blade or fluid passage
Extending along runner axis
C416S176000, C415S143000
Reexamination Certificate
active
06514035
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a pump capable of performing an ideal air removal action in pressure zones from atomospheric pressure zones to high vacuum zones, and in particular relates to a multiple-type pump that possesses the function of a turbo-molecular pump which transfers air in high vacuum zones in a highly efficient manner, and the function of a screw type pump which compresses air and transfers it in atmospheric pressure zone.
Uses for this multiple-type pump invention include the emptying of the vacuum chamber of CVD equipment used in the manufacture of semiconductors. Further, the multiple-type pump, according to this invention, is used for compressing air in the atmosphere and transferring the compressed air to an air intake system of an engine or a fuel cell.
2. Background Art
(The Screw Type Pump)
The screw type vacuum pump is one which is well-known among the conventional vacuum pumps. For example, a known one, described in the Japanese Laid-open Publication No. Sho 60-216089, is a kind of screw type pump used from low vacuum zones, known as sliding flow zones, to high vacuum zones, known as free molecule zones, and has superior air evacuation capabilities in low vacuum zones.
In other words, screw type pumps are highly efficient in the evacuation of air in low vacuum zones and are capable of high-speed air evacuation, but experience a decrease in air intake volume and a lowered air evacuation efficiency in high vacuum zones. However, in the vacuum pumps used as air evacuation units in the CVD equipment used in the manufacture of semiconductors, they are required to possess superior air evacuation characteristics not only in low vacuum zones, but also in high vacuum zones.
(The Technology of (J01) Described in Japanese Examined Patent Publication No. Hei-6-92799)
The following is a known prior art (J01) that is described in Japanese Examined Patent Publication No. Hei-6-92799 which aims to fulfill the above-mentioned requirement. Described in this publication is a screw type vacuum pump whose air intake volume in high vacuum zones was increased for the purpose of improving its air evacuation efficiency in high vacuum zones.
The screw type vacuum pump mentioned in this publication has a groove width correlation {groove width/(thread width+groove width)} of 0.8-0.95 in its upstream edge portion in the direction of the air conveyance, and attempts to increase the air intake volume at its upstream edge by increasing the groove depth as it goes toward the upstream edge.
(Problems Relating to the Above-mentioned Prior Art (J01))
The air evacuation efficiency of the above-mentioned prior art did not actually increase in the high vacuum zones to the degree anticipated. The reasons for this are not clear, but probable causes such as the following can be assumed:
(1) When speaking of a screw type pump which has inferior air evacuation capacity in high vacuum zones, a reason for which its air intake volume in high vacuum zones does not increase can be explained by the design for vacuum pumps which originally came from screw type pump theories relating to direction of air transfer, from the upstream edge to the downstream edge. In other words, in turbo-molecular pumps, which have a high air transfer capacity in high vacuum zones, vanes are used for air transfer that, if strong, the thinner they are, the more volume of air they can take in, and the greater the air evacuation capacity. In screw type pump theory, however, no matter how the screw grooves and screw threads of the upstream edge portion were to be designed, the air intake capacity in high vacuum zones would not increase.
(The Turbo-Molecular Pump)
In contrast to the above-mentioned screw type pumps, turbo-molecular pumps, like those disclosed in patent publications and the like, such as in Japanese Examined Patent Publication No. Sho 50-27204, have superior air transfer characteristics in high vacuum zones.
That is, turbo-molecular pumps have a casing with a cylindrical inner surface, wherein lies a rotor which rotates around the rotary shaft of the shaft of the above-mentioned casing. On the inner surface of the above-mentioned casing, multiple fixed vanes (static vanes), arranged along the circumference, are arranged in a multi-level fashion at prescribed intervals in the direction of the shaft. On the outer surface of the above-mentioned rotor, multiple dynamic vanes, arranged along the circumference, are arranged in a multi-level fashion in the direction of the shaft. The above-mentioned static vanes and dynamic vanes are slanted in relation to the above-mentioned rotary shaft, and the tilt angle (vane angle) decreases from the upstream side to the downstream side.
Each level of each of the static vanes and dynamic vanes, which are placed in multi-level fashion at intervals in the direction of the above-mentioned shaft, is placed alternately in the direction of the shaft and organized in such a way as to take the air brought from the upstream edge going in the direction of air transfer and transfer it to the downstream side by virtue of the rotation of the above-mentioned dynamic vanes.
The air evacuation efficiency of a turbo-molecular pump such as this is high in high vacuum zones, but the problem with it is that its air evacuation efficiency in low vacuum zones is low.
Another problem is the use of large numbers of static vanes and dynamic vanes, which means a large number of parts, and a construction that is complex and costly. Still another problem is the ease with which the above-mentioned static vanes and dynamic vanes become dirty.
(The Multiple-Type Vacuum Pump)
Conventionally, multiple-type vacuum pumps that are a combination of the screw type pump and the turbo-molecular pump have been known, and it was hoped that a vacuum pump would be created capable of achieving a highly efficient air evacuation rate in low to high vacuum zones by bringing together the advantages of the above-mentioned screw type and turbo-molecular pumps. The technology for such multiple-type vacuum pumps, as in the following (J02), for example, are well known in the art.
(J02) is “An Easy to Understand Vacuum Technology (Compiled and written by the Japan Vacuum Association, Kansai Branch; Published by the Japan Vacuum Association, Kansai Branch, pg. 91~99, published Jun. 23, 1995)
This (J02) prior art relates to a multiple-type vacuum pump that combines a screw type pump with a turbo-molecular pump, by placing the turbo-molecular pump on the upstream side of the screw type pump. The air taken in by the turbo-molecular pump on the upstream side is compressed and transferred to the screw type pump on the downstream side. For this reason, the screw type pump, which performs air evacuation with low efficiency in high vacuum zones, is able to take the air which has been compressed by the turbo-molecular pump on the upstream side and transfer it to the downstream side with great efficiency.
(Problems Associated with the Aforementioned Prior Art (J02))
The foregoing prior art (J02) requires that numerous static vanes and dynamic vanes be manufactured and placed at many levels in the direction of the shaft of the turbo-molecular pump and installed at prescribed locations. This results in high manufacturing costs.
Moreover, the structure of the turbo-molecular pump portion is complex, so that when it is used in CVD equipment as an air evacuation device, or when it expels a large quantity of reactive air which has not reacted with anything, it provides many places where side reaction product can easily stick and build up. Side reaction product sticks and builds up easily on the static vanes of turbo-molecular pumps, for example. The result is a multiple-type vacuum pump whose durability may be greatly deteriorated.
The applicants of the present invention learned from the problems associated with the above-mentioned conventional multiple-type vacuum pump, and have developed the following technology (J03) which has already been on the market for some time.
Iwane Matsumi
Jou Rong-Yuan
Armstrong Westerman & Hattori, LLP
Kashiyama Kougyou Industry Co., Ltd.
Ryznic John E.
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