Electricity: circuit makers and breakers – Special application – Change of inclination or of rate of motion responsive
Reexamination Certificate
2000-02-04
2001-10-02
Walczak, David J. (Department: 3754)
Electricity: circuit makers and breakers
Special application
Change of inclination or of rate of motion responsive
C200S061530
Reexamination Certificate
active
06297463
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to fluid level detectors and, more particularly, to detectors for determining when a supply of fluid being pumped by a pump has become depleted.
BACKGROUND OF THE INVENTION
Reciprocating pumps are frequently used in a variety of industrial applications for pumping liquids from storage containers. For example, pneumatic piston pumps are often used for pumping liquids from drums, barrels, plastic containers, or the like. In many applications, it is undesirable to allow the pumps to run dry for any significant length of time. For instance, unless an out-of-fluid condition is detected and the downstream process or operation employing the pumped liquid is interrupted, faulty downstream operations will be performed, or the downstream operations will be rendered impossible, because the required liquid will not be supplied. Thus, it is desirable to detect an out-of-fluid condition so that the pumps may be stopped as soon as possible and the pump connected to a new liquid supply to continue the downstream operations.
U.S. Pat. No. 4,269,223 discloses a detector for detecting an out-of-fluid condition in an air pump by sensing an increased rate of air flow to the pump which occurs when the pump runs dry. The device is installed in the line that supplies pressurized air to the air pump. The device shuts off the air flow when the increased air flow is detected. A disadvantage of the device is that if the air supply pressure to the pump changes, the device must be adjusted or it will either close prematurely or fail to close at all.
SUMMARY OF THE INVENTION
The present invention overcomes the drawback noted above by detecting an increased amplitude of pump motion indicating an out-of-fluid condition. In accordance with the invention, the pump is supported on or adjacent the container so that the pump is free to move in the direction of its pump axis along which the internal piston of the pump moves. When the liquid in the container falls below the level of the pump's intake opening, the pump begins to pump air rather than liquid. As a result, the entire pump begins to reciprocate with an increased amplitude along the pump axis direction. The magnitude of this reciprocating motion of the pump is substantially larger than the normal pump motion that occurs when the pump is pumping liquid.
The apparatus and method of the invention depend on detecting this increased-amplitude pump motion. Specifically, the invention in one embodiment provides a liquid delivery system including a pump supported as described above, and further including a detector mounted on the pump for movement therewith. The detector is operable to detect an increase in amplitude of the pump motion and to provide a signal indicating an out-of-fluid condition upon detecting the increased amplitude motion.
In a preferred embodiment of the invention, the detector comprises a mass supported within a housing in a predetermined static position with respect thereto and movable away from the static position along a defined axis. The mass is constrained against movement except along the defined axis. A sensor is located in the detector and is operable to change state (i.e., to close, or to open, or to otherwise change the state existing on an electrical line connected to the sensor) when the mass is displaced away from its static position along the defined axis by a predetermined distance. A spring is connected between the mass and the housing for applying a restoring force to the mass tending to move the mass toward the static position upon displacement of the mass away therefrom. An output line is connected to the sensor.
In use, the detector is attached to the pump with the defined axis of the device aligned along or parallel to the pump axis. During normal movement of the pump that occurs when liquid is being pumped, the movement of the mass along the defined axis is not of sufficient amplitude to cause a state change of the sensor. However, when the pump begins to pump air and move with an increased amplitude, the amplitude of the mass's movement increases and causes the mass to trigger the state change of the sensor. The state change may be used to activate a signal telling an operator to shut off the pump, or alternatively or additionally may be used to automatically shut off the pump.
In a preferred embodiment of the invention, the detector includes a stop which the mass abuts in the static position. The stop defines the static position for the mass. The stop substantially constrains the mass to movement in only one direction away from the static position during oscillation of the mass. Advantageously, the spring is preloaded in tension in the static position of the mass, so that the mass is urged against the stop in the static condition. The stop advantageously comprises a shock-absorbing member for limiting bounce of the mass upon being returned to the static position by the restoring force of the spring.
In accordance with another preferred embodiment of the invention, the sensor comprises a first contact supported on the mass and a second contact supported on the housing spaced from the first contact in the static condition of the mass. The sensor is triggered by displacement of the mass which causes the first contact to come into contact with the second contact.
In accordance with a further embodiment of the invention, the sensor comprises a magnetically operated proximity sensor mounted to the housing. The detector further includes a magnet affixed to the mass. The sensor is triggered by displacement of the mass which causes the magnet to be carried into proximity with the proximity sensor.
In a still further embodiment of the invention, the detector has a pair of proximity sensors mounted to the housing at different axial distances from the mass. Thus, the sensor nearer the mass can be used when a greater sensitivity of the detector is desired (i.e., the nearer sensor is triggered by smaller amplitude displacement of the mass), and the sensor farther away from the mass can be used when a lesser sensitivity is desired.
REFERENCES:
patent: 1868923 (1932-04-01), Semon
patent: 3414853 (1968-12-01), Motis
patent: 3781496 (1973-12-01), Jones, Jr.
patent: 3909569 (1975-09-01), Jones
patent: 4155067 (1979-05-01), Gleeson
patent: 4176390 (1979-11-01), Galbert
patent: 4257747 (1981-03-01), Goldman
patent: 4269223 (1981-05-01), Carter et al.
patent: 4547771 (1985-10-01), Rockwood et al.
patent: 4665393 (1987-05-01), Wilder et al.
patent: 4746774 (1988-05-01), Tetrault et al.
patent: 4789762 (1988-12-01), Miller et al.
patent: 4789769 (1988-12-01), Warner
patent: 4873401 (1989-10-01), Ireland
patent: 4916266 (1990-04-01), Tetrault
patent: 5174722 (1992-12-01), Lybecker
patent: 5440084 (1995-08-01), Fuse et al.
patent: 5483225 (1996-01-01), Hwang
patent: 5601413 (1997-02-01), Langley et al.
patent: 5706911 (1998-01-01), Maiwald et al.
patent: 5726403 (1998-03-01), Sondergold et al.
patent: 6087951 (2000-07-01), Ramsden et al.
Alston & Bird LLP
Huynh Khoa D.
Sealed Air Corporation (U.S.)
Walczak David J.
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