Pumps – One fluid pumped by contact or entrainment with another – Liquid pumped by supplying or exhausting gaseous motive...
Reexamination Certificate
1998-09-22
2001-01-16
Kamen, Noah P. (Department: 3747)
Pumps
One fluid pumped by contact or entrainment with another
Liquid pumped by supplying or exhausting gaseous motive...
C417S132000
Reexamination Certificate
active
06174138
ABSTRACT:
BACKGROUND OF THE INVENTION AND PRIOR ART
This invention relates to a float operated device which operates at high pressure, such as a pressure powered pump or a condensate trap.
In the context of the present invention, the expression “high pressure” means a pressure in excess of 5 bar and refers to the internal pressure in the housing of the device, to which pressure the float is subjected.
Pressure powered pumps are used in steam systems in order to raise condensate to a condensate return system from which the condensate is reintroduced to the steam generating boiler. Such pumps comprise a chamber in which the condensate accumulates, to be periodically discharged by the periodic admission of steam and venting of the chamber under the control of a float which is responsive to the level of condensate in the chamber. Examples of such pumps are disclosed in GB 2302916 and U.S. Pat. No. 5,141,405.
In some applications, where there is an adequate pressure head at the condensate inlet, the rising float may operate an outlet valve before steam is admitted to the chamber, the condensate then being discharged through the outlet under the pressure at the inlet. If the pressure head is insufficient to discharge the condensate, the float will rise further, and steam will be admitted to the chamber to force the condensate out under pressure.
The pressure powered pump is normally situated at the lowest point in the steam system. It is usually floor-mounted. Sometimes the heat exchanger, or other component of the steam system from which condensate is supplied to the pressure powered pump, is only a small distance above the floor, and consequently the filling head for the pump is too small to produce an adequate filling rate for the pump chamber. It is therefore desirable for the pressure powered pump to operate reliably with a small change in liquid level within the chamber between the end positions of the float. However, in conventional pressure powered pumps which use a spherical float, the diameter of the float itself influences the overall height of the pump chamber. The size of the float itself is dictated by the need to provide adequate buoyancy to operate the toggle mechanism in the rising direction of the float, and adequate weight to operate the toggle mechanism in the reverse direction as the float falls. Spherical floats have conventionally been used in high pressure devices such as pressure powered pumps and condensate traps because a spherical shape is best able to withstand the high pressure to which they are subjected in use.
Another disadvantageous characteristic of known pressure powered pumps is that the toggle mechanism exerts its greatest resistance to movement of the float when the float is at its end positions. This means that substantially the entire buoyancy (or weight) of the float is utilized to overcome the resistance imposed by the toggle mechanism. Consequently, there is no surplus energy which can be utilised to perform other operations, such as the opening of an outlet valve for process fluid.
SUMMARY OF THE INVENTION
According to the present invention there is provided a float operated device comprising a float, capable of withstanding a high pressure, which is supported by a linkage for pivotable movement upwardly and downwardly within a chamber in response to the level of liquid in the chamber, the linkage being connected to actuating means which is operable by movement of the float to actuate control means for controlling the flow into and/or out of the housing, in which device the float has an aspect ratio (as defined herein) which is not less than 2.
In this specification, the expression “aspect ratio” means the ratio of the maximum dimension of the float in the horizontal direction to the maximum direction of the float in the vertical direction. A spherical float as used in the prior art consequently has an aspect ratio of 1. In a device in accordance with the present invention, the aspect ratio preferably lies in the range 2 to 3.5.
A device in accordance with the present invention consequently has a relatively low profile float occupying a small vertical space. This means that the chamber, and consequently the device itself, may be reduced in height by comparison with an equivalent device employing a spherical float.
The float may comprise a single float element having a flattened shape, for example the shape of an oblate spheroid or of a flattened cylinder disposed with its axis vertical. Alternatively, the float may be made up of a plurality of float elements disposed so that the aspect ratio of the float as a whole is not less than 2. For example, the float may comprise a plurality of spherical float elements disposed in a common horizontal plane, possibly in a circular array. In a preferred form, the float may comprise two float elements each in the form of a horizontally disposed cylinder having hemispherical ends, the two float elements lying side-by-side.
The linkage may comprise a parallelogram linkage having two levers which each interconnect the float to a fixed support, one link being connected to the top of the float and the other being connected to the bottom. Such an arrangement provides adequate guidance, orientation and stability to the float. The levers may be cranked to enable them to clear the float when the float is at its end positions.
The actuating means may comprise a toggle mechanism. It may be operatively connected to an operating valve arrangement for controlling the flow of a motive fluid into and out of the chamber. The linkage may be connected to an outlet valve for controlling the flow of liquid to be discharged from the chamber.
In a preferred embodiment, the horizontal projection of the float may have an area which is not less than 50%, and more preferably not less than 60% of the maximum horizontal cross-section of the chamber.
Another aspect of the present invention provides a float operated device having a toggle mechanism which comprises an input lever carrying a float, and an output lever, the levers being pivotably mounted at spaced locations on a common support, and resilient means which acts between a first point on the input lever and a second point on the output lever, the output lever being pivotable between limit positions and the input lever being pivotable between a first position, in which the resilient means acts to bias the output lever into one of its limit positions, a dead point in which the first and second points and the mounting location of the output lever lie on a common straight line, and a second position, in which the resilient means acts to bias the output lever into the other of its limit positions.
In a preferred embodiment constructed in accordance with this aspect of the invention, the force required to displace the input lever from either the first of second position to the dead point increases continuously as the input lever approaches the dead point.
The limit positions of the output lever are preferably defined by stops which are engageable by the output lever.
The input lever may be connected to a float so that the toggle mechanism is float-operated. The output lever may be connected to a valve mechanism.
When used in a float-operated pressure powered pump, the toggle mechanism defined above has the advantage that the initial movement of the float from either of its end positions requires little force, so that the initial movement of the float can be employed, for example, to open an outlet valve for controlling the flow of process liquid from the chamber of the pump.
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p
Duane Morris & Heckscher LLP
Gimie Mahmoud M
Kamen Noah P.
Spirax-Sargo, Limited
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