Electric generator protection system

A protection system for an electric generator includes a fluid sensor to measure a fluid level in a fuel tank, an indicator lamp to display the fluid level, a timer to measure a time interval beginning in response to a low fuel signal from the fluid sensor and a low fuel switch to shut off the electric generator at the end of the time interval.

FIELD OF THE INVENTION

This invention relates to electric generators and more particularly to protection systems for electric generators.

BACKGROUND

Small-scale electric generation, such as backup, standby and emergency generators, are used in many locations. The electric generators must be maintained by an operator to monitor fuel, oil and temperature levels. In some cases, alarms might alert the operator that the electric generator might be running low on fuel. However, by the time the operator becomes aware of the low fuel condition, the electric generator could run out of fuel before fuel supplies are replenished and/or may not be able to safely shut-down electrical loads before a power system disruption.

Fuel level detectors for warning an individual of a low fuel supply are well known. For example, a Hara, U.S. Pat. No. 4,175,435 discloses a liquid level detection device. As disclosed a liquid level detection device comprises an annular float adapted to float constantly on the surface of a body of liquid subjected to level detection, a barrel passing through the float to guide the motion of the float, permanent magnets disposed in the float and a magnetically operable lead switch disposed in the barrel permits the detection of the liquid level. The device works on the principle that the lead switch is magnetically turned into it's on state at the time that the float while in motion reaches the position at which the barrel incorporates the switch.

A more recent patent of Wickman et al., U.S. Pat. No. 6,253,742 discloses a method for controlling the operation of a fuel system that uses a lift pump. The system uses a lift pump to transfer fuel from a remote tank to a vapor separator tank. Only one level sensor is provided in the vapor separator tank and an engine control unit monitors the total fuel usage subsequent to the most recent filling of the tank. When the fuel usage indicates that the fuel level in the vapor separator tank has reached a predetermined lower level, a lift pump is activated to draw fuel from a remote tank and provide that fuel to the vapor separator tank.

Notwithstanding the above, it is presently believed that there is a need and a potential commercial market for a protection system for an electric generator in accordance with the present invention. There should be a demand for such systems for use with electrical generators to protect the generators from running out of fuel and shutting down prematurely.

SUMMARY

In essence, a protection system for an electric generator includes a fluid sensor to measure a fluid level in a fuel tank, an indicator lamp to display the fluid level, a timer to measure a time interval beginning in response to a low fuel signal from the fluid sensor and a low fuel switch to shut off the electric generator at the end of the time interval.

Embodiments of the invention may include one or more of the following features. For example, the fluid sensor may include a float, a conductor block, a rod to attach the float to the conductor block and spring contacts to contact the conductor block thereby causing an electric current to illuminate an indicator lamp.

As another feature, an isolation wall may have a port that receives the rod and that separates the spring contacts from the volume of the fuel tank.

The indicator lamp may also include a green lamp to indicate a nearly full fluid level, a yellow lamp to indicate an approximately half full fluid level and a red lamp to indicate an almost empty fluid level. The green, yellow and red lamps may be green, yellow and red LEDs, respectively.

The timer may also include a clock that measures a time interval and an output circuit that issues a shut-off signal at the end of the timer interval.

The protection system may also include an audible alarm to indicate a low liquid level in the fuel tanks.

A battery may provide backup electric power for the protection system to operate the indicator lamp, alarm, fuel sensor, timer and switches. In addition, a solar cell and a battery charger can be used to recharge the battery.

Additional protection features include a thermal sensor and a high temperature switch to shut of the electric generator in response to a high temperature signal from a thermal sensor.

The fuel tank may also be supplemented by a reserve fuel tank and a pump to transfer fluid from the reserve fuel tank to the fuel tank. The pump transfers the fuel to the fuel tank in response to the low fuel signal from the fluid sensor.

In another general aspect, the protection system for an electric generator includes a float to measure a fluid level in a fuel tank, a conductor block, an arm to attach the float to the conductor block and spring contacts to contact the conductor block, a set of indicator green, yellow and red LED lamps receiving signals from the fluid sensor to indicate a high fluid level, a half full fluid level and a nearly empty fluid level, respectively, a timer to measure a time interval beginning in response to a low fuel signal from the fluid sensor, a low fuel switch to shut off the electric generator at the end of the time interval and an audible alarm to indicate a nearly empty fluid level. The protection systems in accordance with the present invention may include any of the above features.

In another general aspect, a method of protecting an electric generator from a low fuel condition includes sensing a fluid level in a fuel tank of the electric generator, measuring a time interval beginning in response to a sensed low fluid level and shutting off the electric generator at the end of the measured time interval.

The method may include any of the above or following features. For example, the method may include displaying the fluid level.

The invention will now be described in connection with the accompanying drawings wherein like reference numerals have been used to designate like parts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIG. 1, an electric generator with a protection system in accordance with the present invention includes an electric generator101with a fuel tank (not shown) that incorporates a float switch102. The float switch102provides information about the amount of fuel in the fuel tank to a fuel level gauge or display104and to a relay106.

The relay106is operable to trigger a timer108which can issue a shut-off signal to the electric generator101. The relay106also triggers an audible alarm110which notifies an operator of a low fuel condition. The alarm110is connected to a battery and battery charger which is provided with an electrical charge via a solar cell114.

Referring toFIG. 2, the float switch102is located in the fuel tank202. The float switch includes a float204, a rod or pipe206, and a conductor block208. The conductor block208moves up and down inside a housing210which encloses pairs of electrical spring contacts212. The position of the conductor block208varies depending on the fuel level214causing the conductor block to complete an electrical connection through a pair of the spring contacts212. Each pair of spring contacts is connected to a lamp or light emitting diode (LED) which is lit to indicate the amount of fuel left in the tank202.

Fuel can be added to the fuel tank202through a filling port216at the top of the fuel tank202. A first fuel line218feeds a fuel pump220which pumps fuel through a second fuel line222to the electric generator101.

FIG. 3shows a fuel warning indicator which includes a series of green, yellow and red LEDs302. As the fuel level gets lower the green and then the yellow LEDs are extinguished and the red LEDs are illuminated.

FIG. 4illustrates an electrical schematic diagram of the protection circuit. Each pair of spring contacts212is connected in series with green, yellow and red LEDs302, respectively, and current limiting resistors402.

The relay106is also actuated when the fuel level is low. When the relay106is actuated, the electrical circuit is completed so that the solar/generator charged battery404energizes the audible alarm110. The relay also provides power to a transistor406which sends a signal to initiate the counter in the timer circuit. A current limiting resistor408reduces the input current to the base of the transistor406and a capacitor58reduces rapid voltage fluctuations.

Referring toFIG. 5, in the event that the fuel runs out suddenly, a reserve tank502that can be installed in a vehicle is used to provide additional fuel. The tank502has a fuel line504connected to a pump506which pumps fuel through a filler hose508. The pump is operated by an operation switch510which provides power to the pump506from the car battery. An aluminum bracket512is used to install the tank502in the car and maintains the tank in a fixed position to prevent it from tipping or spilling.

Referring toFIG. 6, the protection system may have more than one relay to protect the electric generator from malfunctioning. In addition to providing power to the relay106that triggers the fuel alarm110, the solar cell114and battery112may power a heat alarm602that is triggered by a relay604to warn the operator of a potential overheating problem. In addition, a heat timer606, which is triggered by another relay608, may issue a shut-down signal to the electric generator after a short time delay if the high heat condition is not alleviated. Referring toFIG. 7, is a solar cell702that is connected to a switch is used to drive a small motor706of a fan708.

FIG. 8shows a more detailed view of the heat alarm with a relay802which is connected to a timer804which is in turn connected to a lamp806. Source1808refers to the energy provided from an electric generator. Source2810refers to the electric power available from the charged battery. A second relay is connected to a heat alarm which in turn is connected to lamps816and a speaker818. When the generator is switched off, the circuit is powered by the charged battery.

FIG. 9is a schematic diagram of a heat lamp circuit902and a heat alarm circuit904. The heat lamp circuit is designed to extinguish a lamp910after the generator cools off. Source1906refers to a 9 volt, 0.5 ampere power supply and source2908is a 9 volt, 3 ampere power supply. L1910is a lamp connected to a transistor912in the heat lamp circuit902. C1914and R1916are a capacitor and resistor, respectively, that are connected to the base of the transistor912. Relay1918switches off the timer after one second if the generator shuts off.

Transistors920are used in the heat alarm circuit904to actuate a speaker922and a warning lamp924, in what is referred to as a “bi-stable” circuit. Capacitors C3926and C2928and resistors R3930and R2932bias the transistors920at a determined voltage and current level. SC1934is a solar cell that maintains a charge on a 6 volt, 3 ampere battery. S1is an on/off electrical switch.

Referring toFIG. 10, a lamp1002on the portable screen is used to indicate whether the generator1004is working. The portable screen,FIG. 16can be connected by cable or wireless connection so that it can be seen from inside a building or other structure. A switch1006connects the generator1004to the lamp circuit. The switch1006is also connected to a base1008, motor1010and small generator1012.

FIG. 11shows a portable display screen1from the back with a motor2and a handle4used to start the motor.

FIG. 12is a circuit connected to the main generator. A switch on the portable screen is used to switch the main generator on. The switch1202provides power to a lamp1204and a motor1206to indicate whether the generator is working.

FIG. 13is a block diagram of a screen for a window installed in a tent or other structure to use direct solar warming without the use of electric energy. It can be made of plastic or heat-resistant nylon and can allow passage of hot air and fine dust.

FIG. 14shows the window screen1402that can be installed in a window1404of tent1403or other building structure with a roof1405.

FIG. 15is a diagram of an electric distribution system which includes 240 volt electric distribution sources1502. A switch1506connects the 240 volt distribution source1502to an electric converter1508. The converter1508provides a low voltage of between 1.5 to 12 volts to an electric distribution panel1510. The distribution panel1510distributes the low voltage power to the electric devices in the main tank1512, tent1514and petrol tank1516and to the relays1518,1520.

FIG. 16is a display panel with status indicators that include a tent lamp1602, heat lamp1604, petrol level speaker1606and motor1608.

While the invention has been described in connection with its preferred embodiments, it should be recognized that changes and modifications may be made therein without departing from the scope of the appended claims.