Pumps – One fluid pumped by contact or entrainment with another – Diverse pumps
Reexamination Certificate
2000-01-24
2001-06-26
Walberg, Teresa (Department: 3742)
Pumps
One fluid pumped by contact or entrainment with another
Diverse pumps
Reexamination Certificate
active
06250889
ABSTRACT:
This invention relates to pumps, particularly the priming thereof, and represents an improvement to the pump described and shown in U.K. Patent No. 1,157,767.
In the embodiment described in that patent specification, the pump has an inlet duct having a chamber immediately upstream of an impeller. A port in an upper wall of the chamber leads to a vent passage for the withdrawal of air from said chamber. The vent passage, which has a venturi section, extends between the inlet duct chamber and a further chamber, a top wall of which has a vent port for the escape of air from the vent passage. The further chamber also has a liquid port communicating with the inlet duct, for returning to the inlet duct any liquid which reaches the further chamber. A float is disposed in said further chamber to control flow through the liquid port.
Compressed air is forced through the venturi section, and as a result of the suction caused by such action, air in the inlet duct will be entrained through the vent passage. This will continue until the inlet end of the inlet duct is surrounded by liquid, whereupon the liquid will be sucked up the inlet duct into said inlet duct chamber and then will fall into the inlet of the pump impeller.
When all the air has been removed from the inlet duct, some liquid will pass through the vent passage and into said further chamber. When a sufficient volume of liquid has accumulated in the further chamber, the float will rise and will permit the liquid which has been drawn through the vent passage to be returned to the inlet duct.
This float is simply operated on an on-off basis in an attempt to isolate the compressed air operated ejector from the pumped liquid, once priming has been achieved. It takes no account of how the arrangement would operate on a continuous dynamic pumping operation where a pumping machine could be regularly handling air/water mixture due to a regular re-priming demand (or ‘snore’ condition). The above mentioned patent specification merely addresses the initial prime and isolation cycle.
An object of the present invention is to provide a pump assembly which takes account of the abovementioned continuous dynamic pumping operation.
According to the invention there is provided a pump assembly comprising a pump having an inlet duct and an outlet duct between which liquid may be pumped, a vent communicable with the inlet duct and to which air may be drawn from the inlet duct, a non-return valve in the outlet duct to prevent air from being drawn therethrough in a direction towards the pump, means for passing air under pressure through the vent so as to cause air from the inlet duct to be entrained therewith whereby to effect withdrawal of air from the inlet duct and consequent priming or re-priming of the pump, and valve means which operate to prevent liquid entering said vent, the arrangement being such that once the pump is primed or re-primed said vent is communicated to an increased pressure, and remains so until air is again to be withdrawn from the inlet duct, whereupon the valve means operate again to allow passage of air to the vent from the inlet duct and to return said vent to negative pressure, so that air from said inlet duct is again caused to be entrained with said air under pressure to re-prime the pump, such automatic re-priming occurring repeatedly as required.
As referred to herein ‘air’ includes any gas (or mixture thereof and is not to be considered limited to atmosphere. Also as referred to herein, the air from the ‘inlet duct’ may simply be air initially drawn into the inlet duct from outside the pump, air from within the pump, or may be air extracted from liquid in which it was suspended, or any combination thereof. ‘Primed’ refers to the state reached when the priming process is complete, i.e. when pumping of liquid is taking place without withdrawl of air from the inlet duct.
Preferably the valve means includes a buoyancy member, and is, for example, a float valve assembly. Desirably the inlet duct has an inlet chamber and said vent is in the form of an ejector head communicable with said inlet chamber. Conveniently the ejector head receives said air under pressure which entrains said air from the inlet duct, via said inlet chamber. Advantageously said float valve assembly has a float within said inlet chamber, the float being on a shaft which extends into the ejector head and carries a first valve member, engageable with a valve seat between the inlet chamber and the ejector head, and a second valve member engageable with a valve seat between the ejector head and a source of said increased pressure, for example atmosphere.
REFERENCES:
patent: 1551362 (1925-08-01), Barton
patent: 5536147 (1996-07-01), Lang
patent: 5772394 (1998-06-01), Yokota
patent: 6152689 (2000-11-01), Yokota
patent: 1 157 767 (1968-02-01), None
patent: 1 210 058 (1969-03-01), None
Andrus Sceales, Starke & Sawall
Godwin Pumps Limited
Patel Vinod
Walberg Teresa
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