WO1994019634A1

WO1994019634A1 - Control circuit for solenoid valve

Info

Publication number: WO1994019634A1
Application number: PCT/US1994/002071
Authority: WO
Inventors: Ivar Schoenmeyr
Original assignee: Aquatec Water Systems, Inc.
Priority date: 1993-02-24
Filing date: 1994-02-24
Publication date: 1994-09-01
Also published as: US5803711A; KR960701327A; US5632468A; JPH08509535A

Abstract

A solenoid valve (10) for a water purification system which opens a first voltage (V1) and is maintained in the opened position by a second voltage (V2) that is lower than the first voltage (V1). The solenoid valve (10) contains a valve (12) which can move between an opened position and a closed position, and a coil (14) which moves the valve (12) to the open position when the voltage (V1) is supplied to the coil (14) and maintains valve (12) in the open position when the second voltage (V2) is supplied to the coil (14). The coil (14) is coupled to a control circuit (18) which initially supplies the first voltage (V1) to the coil (14) when the valve is to be opened, and then reduces the first voltage (V1) to the second (V2) after the valve (12) is in the open position.

Description

CONTROL CIRCUIT FOR SOLENOID VALVE

BACKGROUND OF THE INVENTION

1. FIELD OF THE INVENTION

The present invention relates to a solenoid valve for a water purification system.

2. DESCRIPTION OF RELATED ART

Water purification systems typically include a pump that pumps contaminated water through a filter unit. The filter may contain a reverse osmosis membrane which removes impurities in the water. The water may is then stored within a tank and subsequently removed by the end user. Water purfication systems range in size from large industrial unit to systems that can be installed under the sink of a home.

Residential water purfication units typically have a valve that controls the flow of water between the pump and a municipal water source. To more fully automate the purification unit, the valves may contain solenoids which are controlled by a control circuit. The valves are moved into an open position when the control circuit provides power to the solenoid. Most solenoid operated valves require a relatively large amount of current to move the valves from the closed position to the open position. The large current is typically needed to overcome the fluid backpressure exerted onto the valve. Once the valve is opened, the solenoid does not require the large initial current needed to open the valve. The continual supply of excessive power to the valve, may overheat the solenoid and draw in an unnecessary amount of power. The heat may cause the solenoid to fail, thereby reducing the life and reliability of the valve unit. Additionally, the excessive use of power creates a valve that is costly to operate.

The control circuit of the valve is typically powered by the same transformer that powers the motor of the pump. When the pump is turned on, the motor requires a gradually increasing amount of current to correlate with the increasing speed of the pump unit. In a typical water purification system, the solenoid valve and pump unit are activated simultaneously, so that municipal water is pumped to the filter unit. The transformer must pull in an increasing amount of power during the initial state of the pumpting cycle to accommodate the constant current requirement of the solenoid valve and the ramping current requirement of the pump motor. The transformer must therefore be built to accomodate the current requirements of both devices. It would be desirable to have a solenoid valve which only requires an initial large current to open the valve and then draws a lower amount of current to maintain the valve in the open position. It would also be desirable to have a solenoid valve that has a decreasing current load requirement that matches the increasing load requirement of the pump motor, so that the power provided by the transformer is approximately a constant value during the pumping cycle of the system. SUMMARY OF THE INVENTION

The present invention is a solenoid valve for a water purification system. The solenoid valve contains a fluid valve which can move between an opened position and a closed position, and a coil which moves the valve to the opened position when a first voltage is supplied to the coil and maintains the valve in the open position when a second voltage is supplied to the coil. The coil is coupled to a control circuit which intitially supplies the first voltage to the coil when the valve is to be opened, and then reduces the first voltage to the second voltage after the valve is in the open position.

The valve control circuit may be connected to a tank control circuit, which is coupled to a transformer and a water level sensor within a storage tank. The storage tank is connected to a reverse osmosis membrane that purifies water that is pumped through the system by a pump unit. The tank control circuit is constructed to provide power from the transformer to the pump and solenoid valve when the water within the tank reaches a first level, and terminate power to the pump and valve when the water within the tank rises to a second level. The tank control circuit includes a latching scheme which prevents oscillation of the power switches about the first and second levels of the tank.

The solenoid valve has a gradually decreasing current load which preferably matches a gradually increasing current load of the pump unit, so that the transformer provides an approximately constant level of power during the pumping cycle of the system. Therefore, it is an object of the present invention to provide a solenoid valve which intially opens with a first voltage and is maintianed in the open position by a lower second voltage.

It is also an object of the present invention to provide a water purification system that draws an approximately constant level of power during the pumping cycle.

It is also an object of the present invention to provide a solenoid valve that is energy efficient and does not dissipate a large amount of heat.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, wherein:

Figure 1 is a schematic of a solenoid valve of the present invention;

Figure 2 is a graph showing the output voltage of a valve control circuit as a function of time;

Figure 3 is a schematic of the solenoid valve of Fig. 1 in a water purification system;

Figure 4 is a graph showing the current load requirements of a pump motor and solenoid valve of the water purification system of Fig. 3;

Figure 5 is a schematic of the tank control circuit of Fig. 2;

Figure 6 is a side view of a housing for the solenoid valve.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings more particularly by reference nubmers, Figure 1 shows a circuit for a solenoid valve 10 of the present invention. The solenoid valve 10 typically has a fluid valve 12 coupled to a coil 14. The valve 12 is adapted to move between an open position and a closed position. The valve moves from the closed position to the open position when a voltage is applied to the coil 14. The solenoid valve may also have a spring that biases the valve to the closed position.

The coil 14 is connected to the output pins 16 of a valve control circuit 18 which controls the power supplied to the coil 14. The control circuit 18 also has a pair of input pins 20 that are typically connected to a source of AC power. The AC power is rectified to DC power by rectifier 22.

The control circuit 18 has a pnp transistor 24 that has an emitter El connected to a power supply line 26 and a collector Cl coupled to the coil 14. The emitter El is in parallel with resistor Rl. The collector Cl is coupled to resistor R2. The resistors Rl and R2 are both connected to the base Bl of the transistor 24. The transistor 24 is also in parallel with resistors R3 and R4 which are both connected to the power supply line 26 and the coil 14.

The control circuit 18 may have a first capacitor Cl which is in parallel with the rectifier 22. The circuit also has a second capacitor C2 which is coupled to the base B 1 of the transistor 24. Between the second capacitor C2 and the power supply line 26 is a diode D 1.

In operation the AC voltage source supplies a source voltage Vr to the control circuit 18. The current from the power source initially flows through the pnp transistor 24, which is operating above the saturation point of the device 24. The current flow through the transistor provides a first voltage VI at the coil 14 that is approximately equal to the rectified source voltage Vr. The application of the first voltage VI to the coil 14 moves the fluid valve 12 into the open position. The first voltage VI is typically great enough to overcome any resistive forces on the valve 12. For example, the torque of the coil 14 is typically greater than the fluid back pressure that is exerted on the fluid valve 12. As power is applied to the coil, the second capacitor C2 is drawing current and being charged. The flow of current to the second capacitor C2 maintains the biasing current Bl below the transistion level of the transistor, such that the pnp transistor stays on while the second capacitor C2 is being charged.

As shown in Figure 2, as the second capacitor C2 charges up, more current flows into the base, thereby reducing the current that flows across the transistor 24 and into the coil 14. When the second capacitor C2 becomes completely charged, the capacitor C2 becomes an open circuit to the DC power supplied from the rectifier 22. When the capacitor C2 reaches the fully charged state, the current at the base B 1 reaches a level that turns the transistor off. The rectified source voltage Vr is then applied across the resistors R3 and R4. The resistors R3 and R4 reduce the voltage applied to the coil 14 to a second voltage level V2. The second voltage V2 is large enough to maintain the fluid valve 12 in the open position.

As shown in Figure 3, the solenoid valve 10 may be used in a water purification system. The purification system has a pump 30 which pumps water through a reverse osmosis membrane 32 from an external source of water. The purified water is typically stored in a storage tank 34. The storage tank 34 contains a sensor systems 36 that senses when the water within the storage tank 34 reaches a first predetermined level and a second predetermined level. The sensor system 35 may include floating contacts, pressure transducers or any other means for sensing the level of water within the tank.

The tank sensors 36 are connected to a tank control circuit 38. The tank control circuit 38 is connected to a transformer 40 and a motor 42 that drives the pump 30. The tank control circuit 38 functions as a switch between the transformer 40 and the solenoid valve 10 10 and motor 42 42. The control circuit 38 is constructed so that power is supplied to the motor42 and valve 10 10 when the tank water is at the first level, and power is not supplied to the motor 42 42 and valve 10 10 when the tank water level is at the second level.

In operation, the tank control circuit 38 supplies power to the solenoid valve 10 and motor 42 to open the valve 10 and drive the pump 30, respectively. Water is pumped through the membrane until the water within the storage tank reaches the second predetermined level. The tank control circuit 38 then switches the power to the motor 42 and solenoid valve 10, so that the fluid valve 12 is closed and the pump 30 is stopped.

As shown in Figure 4, the capacitors and resistors of the valve 10 control circuit 38 are typically selected so that the decreasing current requirements of the solenoid valve 10 correspond to the increasing current requirements of the pump 30. This matching current requirement produces a purfication system which draws a relatively constant supply of power through the transformer during a water pumping cycle of the system. Figure 5 shows a preferred embodiment of the tank control circuit 38. The circuit 38 has output pins POl and PO2 connected to the solenoid valve 10 and motor 42, and power input pins PI1 and PI2 connected to the output of the transformer 80. The circuit 38 also has sensor pins SI and Sh that are connected to the sensor system 36 of the storage tank 34.

The control circuit 38 contains a npn transistor 50 which has an emitter E2 connected to a power supply line of the transformer output through resistor Rl l, a collector C2 that is coupled to the gate of triac 52 through diode D3 and resistor R12, and a base B2 that is connected to the power supply line through resistor R13 and diode D2, and also coupled to a first node of the triac 52 through resistors R14 and R15. The circuit 38 also contains a capacitor C3 coupled to the gate of the triac 52.

In operation, when the water within the storage tank falls to the first level, the sense pin SI becomes coupled to the transformer, so that biasing current flows through resistor R13. The biasing current switches the transistor such that current flows from the power supply line, across the transistor and into the gate of triac. The triac is biased so that current can flow through the device 52 and into the motor 42 and solenoid valve 10. The capacitor provide energy to the triac during the negative half cycle of the AC power.

The current from the triac also flows back into the base B2, so that a biasing current is maintained at the transistor even when the sense pin SI becomes decoupled from the transformer and current no longer flows through resistor R13. This latching scheme allows the pump 30 to continue pumping even when the water level rises above the first predetermined level. Such a system prevents power oscillation about the first water level.

Power is supplied to the motor 42 and valve 10 until the water level within the storage tank reaches the second level, at which point the sense pin Sh is coupled to ground. The output of the triac also becomes coupled to ground, which drains the biasing current and turns off the transistor. Turning off the transistor eliminates the biasing current to the triac, which turns the triac off and terminates power to the motor 42 and solenoid.

Figure 6 shows a preferred embodiment of a solenoid valve 10 enclosed by a housing 60 that has a first compartment 62 and a second compartment 64. The first compartment 62 typically contains the valve 10 and coil of the device. The second compartment 64 typically contains the control circuit 38 for the valve 10. The housing has a passage 66 which allows the coil in the first compartment to be connected to the control circuit 38 in the second compartment 64. The compartments are separated by an air channel 68 which is typically of a width so that heat transfer between the compartments is primarily by conduction. The air gap provides an insulative barrier between the compartments, so that the heat dissipation of the coil is not transferred to the control circuit 38.

What is thus provided is a energy efficient solenoid valve 10 which can be used to control the flow of water into the pump 30 of a water purfication system so that a relatively constant supply of power is pulled by the system during a water purification cycle. While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.

Claims

What is claimed is:

1. A solenoid valve, comprising: a valve adapted to move between a opened position and a closed position; coil means for moving said valve from said closed position to said opened position when a first voltage is applied to said coil and maltaining said valve in said opened position when a second voltage is applied to said coil, wherein said first voltage is greater than said second voltage; and, circuit means for initially applying said first voltage to said coil means and then subsequently applying said second voltage.

2. The solenoid valve as recited in claim 1, wherein said circuit means includes; voltage source means for providing said first voltage to said coil means; voltage reduction means for reducing said source voltage to said second voltage; switch means for coupling said voltage reduction means to said voltage source means after said first voltage has been applied to said coil means a predetermined time interval.

3. The solenoid valve as recited in claim 2, wherein said switch means includes a transistor operatively coupled to said voltage reduction means and a capacitor connected to said voltage source means and a base of said transistor.

4. The solenoid valve as recited in claim 3, wherein said voltage source means provides a DC source voltage.

5. The solenoid valve as recited in claim 1, further comprising a housing that has a first compartment substantially separated from a second compartment by an air channel, wherein said first compartment contains said valve and said coil means, and said second compartment contains said circuit means.

6. The solenoid valve as recited in claim 2, wherein said circuit means includes; a DC voltage source; a pnp transistor having a base, an emitter connected to said voltage source and a collector connected said coil means; a resistor circuit connected to said voltage source and said coil means in parallel with said transistor; and, a capacitor connected to said voltage source and said base of said transistor.

7. A water purification system coupled to a source of water, comprising; a reverse osmosis membrane; a pump connected to said reverse osmosis membrane; a solenoid valve connected to said pump and the source of water, said solenoid valve being adapted to move a valve from a closed position to an opened position when a first voltage is supplied to said solenoid valve and maltaining said valve in said opened position when a second voltage is supplied to said solenoid valve, wherein said first voltage is greater than said second voltage; and, valve circuit means for initially applying said first voltage to said coil means and then subsequently applying said second voltage.

8. The system as recited in claim 7, further comprising a motor operatively connected to said pump and a transformer that supplies a transmformer voltage to said motor and said valve circuit means.

9. The system as recited in claim 7, further comprising a storage tank connected to said reverse osmosis membrane, and sensor means for sensor when water within said storage tank reaches a first predetermined level and a second predetermined level.

10. The system as recited in claim 9, further comprising tank circuit means for supplying a source voltage to said solenid valve when water reaches said first predetermined level within said storage tank and terminating said source voltage voltage when the water reaches said second predetermined level within said storage tank.

11. The system as recited in claim 10, wherein said tank circuit means includes latching means for supplying said source voltage when the water reaches said first predetermined level until the water reaches said second predetermined level, and terminating said source voltage when the reaches said second determined level until the water falls to said first predetermined level.

12. The solenoid valve as recited in claim 7, wherein said circuit means includes; voltage source means for providing said first voltage to said coil means; voltage reduction means for reducing said source voltage to said second voltage; switch means for coupling said voltage reduction means to said voltage source means after said first voltage has been applied to said coil means a predetermined time interval.

13. The system as recited in claim 10, wherein said tank circuit means includes; a first level contact that is coupled to said tank circuit means when water within said storage tank is at said first predetermined level; a second level contact that is coupled to said tank circuit means when water within said storage tank is at said second predetermined level; a transistor having a base coupled to a transformer power line and said first and second level contacts, an emitter connected to said transformer power line and ground, and a collector; and, a triac having a first node connected to said transformer power line and a second node connected to said valve circuit means and said motor, said triac further having a gate connected to said collector of said transistor.

14. The solenoid valve as recited in claim 13, wherein said switch means includes a transistor operatively coupled to said voltage reduction means and a capacitor connected to said voltage source means and a base of said transistor.

15. The solenoid valve as recited in claim 14, wherein said voltage source means provides a DC source voltage.

16. The solenoid valve as recited in claim 7, further comprising a housing that has a first compartment substantially separated from a second compartment by an air channel, wherein said first compartment contains said valve and said coil means, and said second compartment contains said circuit means.

17. The solenoid valve as recited in claim 13, wherein said circuit means includes; a DC voltage source; a pnp transistor having a base, an emitter connected to said voltage source and a collector connected said coil means; a resistor circuit connected to said voltage source and said coil means in parallel with said transistor; and, a capacitor connected to said voltage source and said base of said transistor.

18. A water purification system coupled to a source of water, comprising; a storage tank; sensor means operatively connected to said storage tank for sensing when water reaches a first predetermined level and a second predetermined level within said storage tank; a reverse osmosis membrane connected to said storage tank; a pump connected to said reverse osmosis membrane; a motor operatively connected to said pump; a transformer connected to said motor; a solenoid valve connected to said pump and the source of water, said solenoid valve being adapted to move a valve from a closed position to an opened position when a first voltage is supplied to said solenoid valve and maintaining said valve in said opened position when a second voltage is supplied to said solenoid valve, wherein said first voltage is greater than said second voltage; valve circuit means for initially applying said first voltage to said coil means and then subsequently applying said second voltage; tank circuit means for providing said motor and said valve circuit means a source voltage when the water within said storage tank reaches said first predetermined level within said storage tank and terminating said source voltage when the water reaches said second predetermined level within said storage tank.

19. The solenoid valve as recited in claim 18, wherein said circuit means includes; voltage source means for providing said first voltage to said coil means; voltage reduction means for reducing said source voltage to said second voltage; switch means for coupling said voltage reduction means to said voltage source means after said first voltage has been applied to said coil means a predetermined time interval.

20. The solenoid valve as recited in claim 19, wherein said circuit means includes; a DC voltage source; a pnp transistor having a base, an emitter connected to said voltage source and a collector connected said coil means; a resistor circuit connected to said voltage source and said coil means in parallel with said transistor; and, a capacitor connected to said voltage source and said base of said transistor.

21. The system as recited in claim 20, wherein said tank circuit means includes; a first level contact that is coupled to said tank circuit means when water within said storage tank is at said first predetermined level; a second level contact that is coupled to said tank circuit means when water within said storage tank is at said second predetermined level; a transistor having a base coupled to a transformer power line and said first and second level contacts, an emitter connected to said transformer power line and ground, and a collector; and, a triac having a first node connected to said transformer power line and a second node connected to said valve circuit means and said motor, said triac further having a gate connected to said collector of said transistor.

22. A solenoid valve, comprising: a housing having a first compartment substantially separated from a second compartment by an air channel; a solenoid valve within said first compartment; and, circuit means for controlling said solenoid valve within said second compartment.