Submersible pump with integrated liquid level sensing and control system

Abstract

In accordance with one embodiment of the present invention, there is provided a submersible pump that includes a pump housing forming a main compartment for receiving a pump impeller and having liquid entrance and exit openings in said main compartment, and an impeller mounted in the main compartment. The pump housing is adapted for submersion in a body of liquid whose level is to be controlled, and a sealed auxiliary compartment is formed as an integral part of the housing and located to be at least partially submerged in the liquid body. A drive motor is coupled to the impeller for rotating the impeller to eject liquid from the main compartment through the exit opening. An electric-field sensor is mounted in the sealed auxiliary compartment for detecting the elevation of the surface of the liquid body adjacent the sealed auxiliary compartment. At least one controllable switch is connected in the power supply line for controlling the supply of power to the drive motor, and the electric-field sensor is connected to the controllable switch for opening and closing the switch in response to changes in the detected elevation of the surface of the liquid body adjacent the outer surface of the sealed auxiliary compartment.

1 . A submersible pump comprising:
 a pump body forming a main compartment having liquid intake and discharge openings, wherein said pump body is configured to be at least partially submerged in a body of liquid whose level is to be controlled;   a drive motor housed in said main compartment;   an impeller coupled to said drive motor to selectively eject liquid through said discharge opening when said impeller is rotated by said drive motor;   a sealed liquid-tight auxiliary compartment formed as an integral part of said pump body and located to be at least partially submerged in said liquid body;   at least one electric-field sensor mounted on a circuit board, said circuit board being enclosed entirely within said sealed auxiliary compartment and attached to an inner surface of an outer wall of said sealed auxiliary compartment, said circuit board being configured to produce an electric field that extends through said outer wall into space adjacent the outer surface of said outer wall and thereby detect changes in the electric field of said sensor caused by a change in elevation of the surface of said liquid body adjacent a portion of the outer surface of said sealed auxiliary compartment directly adjacent said sensor;   a pair of electrical conductors coupling said electric-field sensor and said drive motor to a power supply; and   a controllable switch coupled to at least one of said pair of electrical conductors and configured to control the supply of electrical power to said drive motor, said electric-field sensor being connected to said controllable switch to turn said drive motor on and off in response to changes in the detected elevation of the surface of said liquid body adjacent the outer surface of said sealed auxiliary compartment.   
   
   
       2 . The submersible pump of  claim 1 , wherein said at least one electric-field sensor comprises upper and lower electric-field sensors located at different elevations with respect to said pump body, the upper electric-field sensor producing a signal for turning said drive motor on after the surface of said liquid body rises to a first predetermined elevation, and the lower electric-field sensor producing a signal for turning said drive motor off when the surface of said liquid body drops to a second predetermined elevation. 
   
   
       3 . The submersible pump of  claim 2 , wherein said second predetermined elevation is less than about 0.7 inch (1.8 cm) above the lowermost surface of said pump. 
   
   
       4 . The submersible pump of  claim 1 , further comprising a manual override switch connecting said drive motor directly to the power supply, bypassing said controllable switch. 
   
   
       5 . The submersible pump of  claim 1 , further comprising a detachable volute attachable to the lower end of said main compartment to facilitate access to said impeller. 
   
   
       6 . The submersible pump of  claim 5 , further comprising mechanical connectors formed as integral parts of said pump body and said volute for detachably attaching said volute to said pump body, said connectors including cam surfaces for drawing said volute tightly against said pump body as said volute is attached to said pump body. 
   
   
       7 . The submersible pump of  claim 6 , wherein said connectors are flanged tabs extending upwardly from the top edge of said volute, and cooperating lugs on said pump body for engaging said flanged tabs as said volute is rotated relative to said pump body, at least one of the engaging surfaces of said flanged tabs and lugs forming said cam surfaces. 
   
   
       8 . The submersible pump of  claim 7 , wherein said drive motor is contained in a motor housing surrounded by an O-ring that engages an opposed surface of said main compartment to form a liquid-tight seal between upper and lower regions of said main compartment. 
   
   
       9 . The submersible pump of  claim 8 , wherein said upper portion of said main compartment above said O-ring is sealed against the entry of liquid. 
   
   
       10 . The submersible pump of  claim 1 , further comprising a strainer detachably attached to the lower end of said pump body, wherein said strainer is configured to prevent solid material of a predetermined size from entering said main compartment. 
   
   
       11 . The submersible pump of  claim 10 , wherein the lower portion of said strainer is tapered inwardly to reduce the footprint of said strainer. 
   
   
       12 . The submersible pump of  claim 2 , wherein said electric-field sensors are mounted on a printed circuit board attached to the inside surface of an outer wall of said auxiliary compartment. 
   
   
       13 . The submersible pump of  claim 12 , wherein at least one of said pair of electrical conductors passes through a sealed aperture in a wall of said auxiliary compartment and is electrically connected to a conductor on said printed circuit board. 
   
   
       14 . The submersible pump of  claim 12 , wherein said controllable switch is mounted on said printed circuit board, wherein electrical conductors connect said controllable switch to the upper end of said drive motor. 
   
   
       15 . The submersible pump of  claim 1 , further comprising a spout extending outwardly from said discharge opening, and a check valve mounted on said spout. 
   
   
       16 . A method of pumping liquid from a liquid body with a pump, the method comprising:
 placing a pump body in said body of liquid whose level is to be controlled, said pump body forming a main compartment defining liquid intake and discharge openings, said main compartment containing a drive motor operatively connected to an impeller and configured to eject liquid from said body of liquid outwardly through said discharge opening by selectively rotating said impeller;   detecting the elevation of the surface of said liquid body with at least one electric-field sensor mounted on a circuit board, said circuit board being enclosed entirely within a sealed liquid-tight auxiliary compartment formed as an integral part of said pump body and located to be at least partially submerged in said liquid body, said circuit board being attached to an inner surface of an outer wall of said sealed auxiliary compartment to produce an electric field that extends through said outer wall into space adjacent the outer surface of said outer wall so that the electric field of said at least one electric-field sensor is altered by the presence or absence of liquid adjacent a portion of the outer surface of said outer wall of said auxiliary compartment adjacent said at least one electric-field sensor and thereby producing an output signal that changes with the presence or absence of liquid along the outer surface of said auxiliary compartment adjacent said at least one electric-field sensor; and   controlling the supply of electrical power to said drive motor in response to changes in said output signal from said at least one electric-field sensor.   
   
   
       17 . The method of  claim 16 , wherein said at least one electric-field sensor includes upper and lower electric-field sensors respectively located at first and second predetermined elevations, said upper sensor producing an on signal turning said drive motor on when the surface of said liquid body rises to said first predetermined elevation, and said lower sensor producing an off signal turning said drive motor off when the surface of said liquid body drops to said second predetermined elevation. 
   
   
       18 . The method of  claim 17 , wherein the turning on of said drive motor is delayed by a predetermined delay interval following the detection of the rising of the surface of said liquid body to said first predetermined elevation. 
   
   
       19 . A method of pumping liquid from a liquid body with a pump at least partially disposed in said liquid body whose level is to be controlled, the method comprising
 placing a pump body in said body of liquid, said pump body forming a main compartment defining liquid intake and discharge openings, said main compartment containing a drive motor connected to an impeller and configured to eject liquid from said body of liquid outwardly through said discharge opening by selectively rotating said impeller;   detecting the elevation of the surface of said liquid body with at least one electric-field sensor mounted on a circuit board, said circuit board being enclosed entirely within a sealed liquid-tight auxiliary compartment formed as an integral part of said pump body and located to be at least partially submerged in said liquid body, said circuit board being attached to an inner surface of an outer wall of said sealed auxiliary compartment such that said at least one electric-field sensor senses a difference in a dielectric constant in the space adjacent the outer surface of said outer wall due to the presence or absence of liquid adjacent a portion of the outer surface of said outer wall of said auxiliary compartment adjacent said at least one electric-field sensor and thereby producing an output signal that changes with the presence or absence of liquid along the outer surface of said auxiliary compartment adjacent said at least one electric-field sensor; and   controlling the supply of electrical power to said drive motor in response to changes in said output signal from said at least one electric-field sensor to trigger a pump to begin pumping said liquid.