The present invention is the result of diligent and successful work in eliminating periods of water in the basement. In past years there would be surprise and dismay to find several inches of water over the basement floor. Frantic effort would be required to undo the damage.
Conventionally a pump is placed in a cavity ("sump") or well cut into the floor in or below the gravel/rock bed which is found under basement floors. A float attached to the sump pump, or a separate float switch, moves a mechanical switch to activate the pump whenever the water level in the sump rises far enough. A direct float-actuated switch arrangement can cause frequent cycling of the pump motor, shortening its life, so precautions need to be made to ensure the pump runs for a moderate amount of time after actuation.
Float control is prone to problems due to mechanical interference with the float mechanism. Hoses or debris in the water can hold the float under water, preventing it from turning on the pump, or such objects can slip under the float, causing the pump motor to run continuously. Corrosion on the float hinge or slip rod can cause the float to hang up. The float itself requires clear space around the float, especially for a hinged float, increasing the required sump size. In addition, the water level is not well controlled, and the process of floatation requires a certain amount of water to physically support the float sufficiently to activate a switch. In short, float switches are subject to jamming, require much space, and need wide water height variations.
The drawbacks of float usage have been addressed in the past, with the use of direct sensing of water level by electrodes dating back as far as 1906 in other applications (filling of steam vessels or batteries, for example)--see U.S. Pat. No. 820,429 "APPARATUS FOR ASCERTAINING THE LEVEL OF LIQUIDS", issued to Charles May or U.S. Pat. No. 821,623 "STORAGE BATTERY FILLING APPARATUS", issued to Thomas Edison. Not long after, electrode-sensing was applied to emptying of sumps. The following U.S. Patents use an electrode-controlled sump pump:
U.S. Pat. No. 1,979,127 "ELECTRICAL CONTROL DEVICE" issued to Charles Warrick in 1934. This purely electromechanical equivalent of control system of invention, shown in a sump pump-like application has three probes driving a special two-coil relay. The use of relays requires relatively high current, which results in accelerated corrosion, and the custom mechanical relay is both expensive and troublesome by today's standards. PA1 U.S. Pat. No. 2,202,197 "GAUGE AND CONTROL APPARATUS FOR LIQUID CONTAINERS", issued to Gordon Ewertz in 1940 uses five probes (including a ground probe), with switches to control either filling or emptying of tank. The control element is a vacuum tube. PA1 U.S. Pat. No. 3,337,778 "RELAY APPARATUS" issued to Lester Becker in 1967 is a general patent on the use of thyratrons to control relays. The embodiment of FIGS. 5-8 uses the thyratron circuit with three probes in a sump to control a sump pump. PA1 U.S. Pat. No. 3,787,733 "LIQUID LEVEL CONTROL SYSTEM" issued to Tony Peters in 1974 is a sump pump control using two active electrodes (high and low level), with the sump lining being the ground. A Triac is used as the control element. PA1 U.S. Pat. No. 3,894,240 "CONTROL CIRCUIT FOR MAINTAINING A MOVABLE MEDIUM BETWEEN LIMITS" issued to Ronald Rose Simer Pump Co! in 1975 is a sump pump control using two probes (again, the ground is the sump lining). This patent uses a neon lamp and photosensor to provide high on/low off function. PA1 U.S. Pat. No. 4,061,442 "SYSTEM AND METHOD FOR MAINTAINING A LIQUID LEVEL" issued to Anthony Clark Beckett Corp! in 1977 is a sump pump or air conditioner condensate tank pump control. Four probes are used--ground plus three active probes--high, low and alarm (shuts off a/c or heating system). This patent uses a low voltage high frequency signal on probes. PA1 U.S. Pat. No. 4,182,363 "LIQUID LEVEL CONTROLLER" issued to Mark Fuller in 1980, uses four probes (ground, high, low, alarm) and CMOS logic circuitry to control a pump for filling (rather than emptying) a vessel. The design of the probes is such as to minimize false returns due to waves or splashing (not a concern in the present invention). PA1 U.S. Pat. No. 4,600,844 "LIQUID LEVEL CONTROL APPARATUS" issued to Donald Atkins Marley-Wylain Co! in 1986 is a two probe (high/low) sump pump system, referenced to earth ground. Two comparators are used to sense probe current, with an IC OR gate driving a photoisolator to control the pump. PA1 U.S. Pat. No. 4,742,244 "ELECTRONIC FLOAT SWITCH APPARATUS" issued to Charles Koerner ITT Avionics! in 1988 uses two (high/low) probes. An oscillator applies an AC signal to each probe, and the AC signal is detected and used to drive the controller logic. When the probe is submerged, the oscillator stops oscillating. PA1 U.S. Pat. No. 5,216,288 WATER LEVEL CONTROL CIRCUIT FOR SUMP PUMPS AND THE LIKE issued to James Greene Marley co.! in 1993 uses comparator sensors connected to high/low probes. The comparators drive an SCR to operate the pump motor in a sump pump application. PA1 U.S. Pat. No. 5,408,223 "DEVICE FOR DETECTING TWO LEVELS OF A LIQUID HAVING HIGH AND LOW ELECTRODES OF METALS OF DIFFERENT ELECTRODE POTENTIALS WHICH ARE CONNECTED BY CONDUCTORS SO AS TO FORM AN ELECTRICAL PRIMARY CELL" issued to Gilbert Guillemot in 1995, uses two probes but just one wire--differing metals between the two probes produce differing voltages, which are sensed to control a sump pump.
U.S. Pat. No. 3,916,213 "LIQUID LEVEL CONTROLLER" issued to Frank Luteran in 1975 is another sump pump using two probes, plus power-line ground, for high on/low off control. The control element is an SCR. AC current is used in the probes.
A major concern with electric probe water sensing is corrosion and contamination, which, from literature on the subject and from testing, has two origins: (a) ordinary environmental corrosion and deposition of contamination such as algae, lime and the like; and (b) electrolysis corrosion due to the sensing current.
The use of a sump, in general, introduces a relatively large pit which is usually partially filled with water, which adds to the humidity problems already present in the basement. This is eliminated through the use of the present invention.
Some additional advantages of the invention over commonly used methods are simplicity of installation, overall cost reduction, less disruption of basement floor space and better control of sub-floor water levels.