Pumps – With signal – indicator – or inspection means
Reexamination Certificate
1999-10-28
2001-08-28
Freay, Charles G. (Department: 3746)
Pumps
With signal, indicator, or inspection means
C417S395000
Reexamination Certificate
active
06280149
ABSTRACT:
This invention relates to active feedback devices for diaphragm pumps, and more particularly for air operated diaphragm pumps.
Air operated diaphragm pumps use compressed air to operate diaphragms which alternately draw in and discharge a material to be pumped. Such diaphragm pumps are known in the art and are widely used in pumping a wide variety of materials. Examples are shown in U.S. Pat. Nos. 4,854,832; 4,936,753; and 5,391,060, the disclosures of which are incorporated herein by reference. The diaphragm pumps disclosed in these patents have a first diaphragm coupled to a first end of an axially reciprocating shaft, and a second diaphragm coupled to a second end of the shaft. Each diaphragm constitutes a flexible wall that separates a liquid chamber from an air chamber. The liquid chambers are connected to a common intake manifold and a common discharge manifold, and check valves are positioned at the fluid inlets and outlets of the fluid chambers.
In operation, the axially reciprocating shaft is reciprocated by pressurizing the first air chamber while venting the second air chamber, and then venting the first air chamber while pressurizing the second air chamber. As the shaft moves in one direction, the first diaphragm pushes the fluid out of its fluid chamber into the discharge manifold, while the second diaphragm draws fluid into its fluid chamber from the intake manifold. When the diaphragms and connecting rod have traveled a predetermined distance, a mechanical switch is tripped. This mechanical switch in turn shifts a main valve that reverses the pneumatic action to pressurize the second air chamber and reverse the direction of the shaft. As the shaft begins to move in the other direction, the first diaphragm draws fluid into its chamber from the intake manifold, and the second diaphragm pushes the fluid out of its chamber into the discharge manifold. The pump continues this reciprocation until the air supply is stopped.
Various factors including the dynamics of the fluid being pumped affect the rate of reciprocation of the connecting rod. In the case of more viscous fluids, for a given air supply pressure, the connecting rod will be caused to reciprocate more slowly thus reducing the output rate of the pump. In attempting to compensate for inequalities between the desired output and the actual output of the pump, passive control systems have been used to measure the pump output and perform some function to increase or decrease the rate of reciprocation of the connecting shaft. One problem with conventional diaphragm pumps having such passive control systems is that they are not readily controllable except by the introduction of external flow measuring devices which add to the complexity and expense of the pump.
The foregoing illustrates limitations known to exist in present diaphragm pumps. Thus it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly an alternative diaphragm pump having active feedback monitoring is provided including the features more fully disclosed hereinafter.
SUMMARY OF THE INVENTION
According to the present invention, diaphragm pumps having active feedback systems are provided. In a first embodiment, the diaphragm pump includes a diaphragm pump having a housing including a pumping cavity. The pump cavity having at least one diaphragm dividing the pumping cavity into a first pumping chamber and a first pump actuating chamber. A rod is attached to and reciprocally movable along an axis with the at least one diaphragm with the rod including a ferromagnetic material. An induction coil disposed around the rod wherein relative axial movement between the inductance coil and the ferromagnetic material of the rod varies the inductance of the induction coil.
In a second embodiment, a diaphragm pump is provided having an active feedback system in which the rod has an electrically conductive, diametrically tapered portion. A linear displacement sensor is disposed next to the tapered portion which induces a current in the tapered portion and generates an output voltage proportional to a relative position between the linear displacement sensor and the tapered portion.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with accompanying drawing figures.
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Able Stephen D.
Meloche Joseph L.
Freay Charles G.
Ingersoll-Rand Company
Nigohosian, Jr. Leon
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