Pumps – One fluid pumped by contact or entrainment with another – Jet
Patent
1994-11-28
1997-11-04
Thorpe, Timothy
Pumps
One fluid pumped by contact or entrainment with another
Jet
417187, F04F 520
Patent
active
056832273
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Art
This invention relates to a multistage ejector assembly which is provided with a plural number of nozzles in series for the purpose of increasing the intake air quantity or the suction force of the ejector.
2. Description of the Prior Art
Multistage ejector assemblies incorporating a plural number of nozzles in multiple stages for augmentation of the amount of intake air or suction force have been known in the art, for example, from Japanese Patent Publication No. 59-24280 (U.S. Pat. No. 3,959,864) and Japanese Patent Publication No. 63-29120 (U.S. Pat. No. 4,466,778). The multistage ejector of this sort has an inherent problem in that a slight degree of misalignment of the axes of the nozzles which are arranged in series could result in considerable degradations in its suctional performance quality. For instance, the desired performance quality cannot be expected unless the concentricity of the respective nozzles is less than a few hundredths of one millimeter.
In this regard, according to the prior art multistage ejector assemblies proposed in the above-mentioned patent publications, a plural number of separately shaped nozzles are assembled into an ejector casing in series in the axial direction of the casing. It follows that high precision work is required not only in the machining operations on the ejector casing but also in the nozzle assembling operations, making these machining and assembling operations troublesome and resulting in a high production cost.
With a view to providing a multistage ejector assembly at low cost, attempts have thus far been made to form the whole ejector into one integral structure by plastic molding, as disclosed in Japanese Laid-Open Patent Application H2-37200 (U.S. Pat. No. 4,960,364). However, in this case it is extremely difficult to enhance the accuracy of molding to such a degree as to completely eliminate partial irregularities in thickness which normally exist in plastic moldings, and to maintain the original accuracy of molded structural shapes over an extended period of time.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a multistage ejector assembly which can be assembled very easily without involving a high precision work in assembling a plural number of nozzles of the multistage ejector and which can be fabricated at a low cost.
It is another object of the present invention to provide a multistage ejector assembly which has a number of its major high precision components such as nozzles and diffusers of the multistage ejector formed into an integral structure by molding to preclude the necessity for aligning the center axes of the respective nozzles and diffusers in the ejector assembling stage, facilitating the operation of assembling a multistage ejector into a casing body and its replacement.
It is still another object of the present invention to provide a multistage ejector assembly employing an integral multistage ejector structure which can be easily fitted into a bore on a casing body or which can be fixed on a flat ejector mounting surface on a casing body by the use of extremely simple means, thereby permitting to simplify machining operations on the casing body.
It is a further object of the present invention to provide a multistage ejector assembly which is arranged in such a way that a vacuum generating chamber is defined within a casing body upon assembling a multistage ejector structure into the casing body, thereby simplifying the construction of the casing body as well as the construction of the multistage ejector structure to be assembled into the casing body.
It is a further object of the present invention to provide a multistage ejector assembly which is arranged in such a way that a check valve or check valves to be incorporated into the multistage ejector for blocking air flows into a suction passage or passages can be mounted in position upon assembling a multistage ejector structure into a casing body, thereby facilitating the check valve assembli
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Matsushima Hiroshi
Nagai Shigekazu
Kim Ted
SMC Corporation
Thorpe Timothy
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