Rotary kinetic fluid motors or pumps – With means for re-entry of working fluid to blade set – Pump priming means
Patent
1999-01-22
2000-11-28
Look, Edward K.
Rotary kinetic fluid motors or pumps
With means for re-entry of working fluid to blade set
Pump priming means
415 556, 415 581, 415143, 4151691, 4171992, F04D 1708
Patent
active
061526894
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a self-priming type centrifugal pump capable of pumping up even a highly-viscous liquid containing a large amount of bubbles, and muddy substances or solid foreign matters. More particularly, the present invention is intended to provide a high-performance, economical, self-priming centrifugal pump capable of perfectly automatic operation and not requiring troublesome work for maintenance.
BACKGROUND ART
Generally, a muddy substance having a high viscosity and containing a large amount of bubbles is difficult to pump by a centrifugal pump. Simple, safe means for pumping and transporting such a muddy substance further containing solid foreign matters has generally been desired. A conventional centrifugal pump cannot be simply used for the foregoing purpose even if the centrifugal pump is used in combination with a vacuum device because cavities formed in a region near the central part of the impeller by centrifugal separation cannot be easily replaced with a liquid having the foregoing properties.
Such a problem was solved clearly by an invention disclosed in JP-B-40-3655 relating to a centrifugal pump. As is apparent from JP-B-40-3655, this prior art centrifugal pump comprises, in combination, a main pump unit for pumping a liquid, and an auxiliary pump unit for removing cavities, having a suction opening which opens in the vicinity of a central part of the main impeller of the main pump unit and is disposed in parallel to the main pump unit, in which the suction opening of the auxiliary pump unit is formed in a small sectional area relative to the discharge ability of the auxiliary pump unit. The discharge opening of the auxiliary pump unit is opened into the suction side of the main pump unit. An exhaust passage is formed between a position near a central part of the auxiliary impeller of the auxiliary pump unit to a vacuum pump to remove forcibly cavities formed in the vicinity of the central part of the main impeller of the main pump unit so that the liquid can always be continuously pumped. A self-priming centrifugal pump disclosed in JP-B-42-3145 is an improvement of the invention disclosed in JP-B-40-3655. As shown in FIGS. 15 and 16, this prior art self-priming centrifugal pump is provided in its exhaust passage with a safety valve 6 to be operated by an actuator which is displaced by a negative pressure to prevent a vacuum (exhaust) pump 12 from failure in operation due to the flow of a liquid into the exhaust passage while the self-priming centrifugal pump is stopped. (Hereinafter, those invention will be referred to as "original inventions".)
This prior art device of the original inventions is capable of pumping up muddy substances which have been difficult to pump and has prevalently been used. However, the prior art device still has the following unsolved problems.
First, the prior art self-priming centrifugal pump relies on negative pressure produced by the vacuum pump to provide power to open the safety valve. Therefore, the negative pressure decreases when the safety valve is opened and the safety valve starts closing, and the negative pressure increases when the safety valve is closed and the safety valve starts opening. Thus, the safety valve repeats closing and opening operations to generate vibration and noise. It is possible that such a flapping action of the safety valve makes the operation of the safety valve unstable.
Secondly, any problem cannot arise because the discharge ability of the gas-liquid separating auxiliary pump unit surpassing the negative pressure produced by the vacuum pump isolates an exhaust system from the liquid while the self-priming centrifugal pump is in operation, and the safety valve is closed to isolate the exhaust system from the liquid while the pump is stopped. However, the discharge ability of the auxiliary pump unit becomes insufficient and the negative pressure produced by the vacuum pump overcomes the discharge ability of the auxiliary pump unit at a transient moment when the auxiliary pump unit ope
REFERENCES:
patent: 3230890 (1966-01-01), Yokota
patent: 5536147 (1996-07-01), Lang
patent: 5772394 (1998-06-01), Yokota et al.
Yokota Hiroshi
Yokota Shingo
Kabushiki Kaisha Yokota Seisakusho
Look Edward K.
McDowell Liam
Yokota Hiroshi
Yokota Shingo
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