Pumps – With signal – indicator – or inspection means
Reexamination Certificate
1999-08-30
2001-02-20
Thorpe, Timothy S. (Department: 3746)
Pumps
With signal, indicator, or inspection means
C417S395000, C073S040000, C073S046000
Reexamination Certificate
active
06190136
ABSTRACT:
This invention relates to failure sensors for diaphragm pumps, and more particularly for air operated diaphragm pumps.
Air operated double diaphragm pumps use compressed air to operate diaphragms which alternately draw in and discharge a liquid. Such double 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 useful life of a diaphragm is limited, however, such that under conditions of wear the diaphragm will slowly lose its elasticity and eventually rupture. Because the motive air used to drive these pumps and the fluid being transferred are separated only by the diaphragm, failure of the diaphragm can result in the contamination and/or damage of the pump equipment by the material being pumped. When a diaphragm failure occurs, the liquid being transferred can leak through the tear and gradually fill the air side of the diaphragm. If the pump is not stopped by the operator, the fluid will eventually invade the valve mechanism of the pump. Such failures can require considerable time and expense for cleaning, repair, or both. Moreover, diaphragm failures permit chemicals being pumped to be ejected into the atmosphere via the exhaust thereby releasing them into the environment where they may result in further damage or injury.
The use of leak detection apparatus for sensing the presence of unwanted fluids in double diaphragm pumps is known in the art. An example is shown in U.S. Pat. No. 5,062,770 issued to Story et al., the disclosure of which is incorporated herein by reference. In the '770 patent, two leak trace detection probes are provided in containment chambers which are formed by spaced apart dual diaphragm pumping components.
ARO® Fluid Products, a wholly owned subsidiary of Ingersoll-Rand Company, also presently manufactures large diaphragm pumps equipped with leak detection sensors in the air chambers of the pump that give an output signal when a fluid is present in the air chamber. Shown in
FIG. 1
is an ARO® double diaphragm pump
52
having two pumping cavities formed between an air cap
54
and a fluid cap
56
. The pumps provided with these leak detection sensors are larger size pumps, i.e., those having inlet and outlet National Pipe Thread (NPT) sizes of one inch or greater. Because of their larger size and shape, these large pumps permit the insertion of a sensor
40
through the air cap
54
and directly into each air chamber. Thus, for a double diaphragm pump, two sensors are used to detect leaks in the pump. Because the cost of the sensors is relatively low compared with the overall cost of the pump, the use of multiple sensors is not cost prohibitive.
Pumps having inlet and outlet thread sizes that are smaller than 1″ NPT, however, typically do not provide the geometry or space required to readily accommodate the insertion of sensors in the air caps as described above. Additionally, because the cost of smaller pumps (i.e., pumps having inlet and outlet thread sizes less than one inch) is proportionally less than for larger pumps (i.e., pumps having inlet and outlet thread sizes of one inch or greater) and, typically, is less than the cost of two sensors, the use of multiple leak detection sensors in smaller diaphragm pumps is generally cost prohibitive. Although smaller pumps suffer from the same diaphragm failure problems as larger pumps, diaphragm failure detection sensors have not been readily incorporated into smaller pumps for the reasons stated above.
The foregoing illustrates limitations known to exist in present diaphragm failure detection devices. Thus it is apparent that it would be advantageous to provide diaphragm failure detection devices which can reduce the number of sensors needed. Accordingly a diaphragm failure sensing apparatus and diaphragm pumps incorporating the same are provided including the features more fully disclosed hereinafter.
SUMMARY OF THE INVENTION
According to the present invention, a diaphragm failure sensing apparatus is provided for use in a diaphragm pump having at least two pumping cavities, each pumping cavity having a fluid chamber and a motive gas chamber separated by a pumping diaphragm. The diaphragm failure sensing apparatus includes a fluid conduit for connection with each of the motive gas chambers of the diaphragm pump, a sensor chamber connected to the fluid conduit, and a check valve located in the fluid conduit for alternately connecting the sensor chamber to the motive gas chambers.
Also provided is a diaphragm pump having at least two pumping cavities, each pumping cavity having a fluid chamber and a motive gas chamber separated by a pumping diaphragm. A fluid conduit is disposed between and connected individually to each of the motive gas chambers and a sensor chamber is connected to the fluid conduit which is alternately connected to the motive gas chambers by a check valve located in the fluid conduit.
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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Meloche Joseph L.
Stuart Kevin C.
Gray Michael K.
Ingersoll-Rand Company
Nigohosian, Jr. Leon
Thorpe Timothy S.
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