GB2092713A

GB2092713A - Improvements in or Relating to Motor Driven Control Valves

Info

Publication number: GB2092713A
Application number: GB8104147A
Authority: GB
Original assignee: Appliance Components Ltd
Current assignee: Schneider Electric Controls UK Ltd
Priority date: 1981-02-11
Filing date: 1981-02-11
Publication date: 1982-08-18
Also published as: GB2092713B

Abstract

A valve unit 1 has an input port 2 and a valve member 7 movable between two outputs 3, 4. The valve member is normally held against the first output by springs 8. A shaft 5 rotatable by a motor 9 moves the valve member towards the second output 3. Two thermostats 20, 24 sense temperatures at different points (e.g. domestic and radiator water). A triac 33 when triggered by low temperature at the second thermostat supplies the motor with A.C. current to open port 4. Motor driven switches 12, 13 are arranged so that a rectifier 35 supplies D.C. to the motor to lock the valve with both outlets open when both thermostats sense low temperatures. A demagnetizing current via a resistor 37 releases the motor. <IMAGE>

Description

SPECIFICATION Improvements In or Relating to Motor Driven Control Valves The invention relates to a motor-driven multiway control valve. Such valves are particularly suitable for controlling fluid flow through a plurality of circuits and the valves may be of different sizes and used to control various media.

One example of the use of such motor-driven control valves is in the control of hot water and central heating system in which valve means is necessary to control flow of hot water from a boiler into a hot water system and/or a central heating system. It is known to use a three-port spring return valve for this purpose. One port of the valve is the inlet port which receives water from the boiler, and the other two ports are outlet ports to the hot water and radiator circuits.

The spring return valve has a valve member, for example, a vane or a ball type member, that is motor-driven in one direction so that it blocks the hot water supply port. With the supply removed from the motor the spring returns the valve member to its original position where it blocks the radiator supply port. As the member travels between the two outlet ports, switches are operated and the electrical circuit is so arranged that it is possible to stop and hold the member in an intermediate position so that both the supply plots are open.

Normally, operation of the valve is controlled by two thermostats, one being used to sense the temperature of the hot water supply and generally fitted to the hot water storage tank, the other one being used to sense the central heating requirements and generally a room thermostat.

Control circuits for such multiway control valves are known and are operable to switch off the electrical supply to the boiler and/or to the circulating pump when both thermostats are satisfied. However, known circuits do not ensure that the valve is in a position to block the radiator circuit when the boiler and the pump are off.

Accordingly, gravity circulation of the water can transfer the residual heat in the boiler to the first radiator in the circuit.

According to the present invention there is provided a motor driven multiway control valve comprising a valve unit with a valve member movable between at least three predetermined positions, drive means, including an electric motor, coupled to the valve member for driving the valve member between said predetermined positions, said drive means being arranged to normally keep said valve member in a first position. and a control circuit for controlling the supply of electrical power to the motor so as to operate the valve, the control circuit comprising a first control member operable to demand the first position for the valve member, a second control member operable to demand a second position for the valve member and including an electrical switch connected between an electrical supply and the motor by way of a triggerable device, the triggerable device being arranged to be triggered upon operation of said second control member to demand said second position for the valve member to thereby connect the electrical supply to the motor, and means for holding the valve member in a third position when both the first and second control members are demanding different positions for the valve member.

With a control valve of the present invention the valve member is normally held in the first position. Where the control valve is used in a central heating system it is arranged that in the first position of the valve member the radiator circuit is blocked. Furthermore, to move the valve member from this first position it is necessary to supply electrical power to the motor by way of the triggerable device which must be triggered.

Accordingly, it is ensured that gravity circulation of the water cannot occur.

In an embodiment, the valve member is held in its first position by resilient means, such as one or more springs coupled to a driving shaft of the valve member.

Any suitable triggerable device, for example, a relay, may be provided. However, it is preferred that the triggerable device is a triac.

Said means for holding the valve member in the third position preferably comprises rectifying means connectable by way of a first mechanical switch to receive electrical supply by way of said electrical switch.

In an embodiment said electrical switch is an on-off switch having a movable blade connected to an electrical supply line and a switch contact connected to one terminal of said triac. The gate of said triac is connectable to said one terminal thereof by way of a second mechanical switch.

Said first and second mechanical switches, which may be cam-operated switches, are operable by movement of the valve member.

Said first control member preferably comprises a two-way switch having a movable blade connected to the electrical supply line. A first contact of the two-way switch is connected to said first mechanical switch and a second contact of the two-way switch is connected to said second mechanical switch.

Preferably said first and second control members comprise thermostat switches.

The present invention also extends to a central heating and hot water system incorporating a motor driven valve as defined above, the valve being arranged to control supply of hot water from a boiler to a hot water system and to a central heating system.

Preferably, the control circuit is also arranged to control operation of a boiler and/or water circulating pump provided in said system.

One embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which the single Figure shows schematically a control system for a multiway valve for use in a central heating and hot water system.

The valve 1 has an input port 2 which is connected to the hot water supply from the boiler (not shown). Port 3 is an output port connected to a domestic hot water system (not shown), and port 4 is an output port connected to the radiators of a central heating system (not shown). In the drawing, the front of the valve 1 is cut open to show the ports. The valve 1 has a valve member in the form of a ball 7 connected to a driving shaft 5 which passes through a gland 6 in the valve casing. The gland 6 seals the interior of the valve casing, which is full of water, from the rest of the mechanism. The shaft 5 is spring loaded by the springs 8 so that the ball 7 normally blocks the port 4 leading to the central heating system.A unidirectional electric motor 9 which includes a gearbox, is coupled to the shaft 5 by a pinion 10 and a quadrant 11 so that when the motor 9 is operated, the ball 7 is moved across the valve to block port 3 leading to the hot water system.

On the driving shaft 5 are mounted two cams 12 and 13 which operate two snap action changeover switches 14 and 15 respectively.

The two cams 12, 13 are so arranged on the shaft 5 that the switch 14 is closed on contact 16 and open on contact 17, and the switch 15 is closed on contact 18 and open on contact 19 when the shaft is in the spring return position and the ball 7 blocks ports 4. This situation is illustrated in the Figure.

When the motor 9 drives the ball 7 across the valve 1 to block port 3, the switch 14 will changeover at 45% of the travel of the ball 7 across the valve ciosing contact 1 7 and opening contact 1 6.

The switch 1 5 will operate at 55% of the travel of the ball 7 closing contact 1 9 and opening contact 1 8. As the shaft 5 is returned under the operation of the springs 8, the switches 14 and 15 will return to their original position as shown in the drawing as the 55% and 45% position of the cams is reached.

The hot water supply system includes a thermostat 20 which can be mounted on the hot water storage tank to sense the temperature of the hot water. When the water temperature is above the desired value, a movable blade 21 of the thermostat 20 is made on contact 22, and when the water temperature is below the desired value the movable blade 21 is made on contact 23, the thermostat 20 acting as a changeover switch. The central heating has a room thermostat 24 to sense the room temperature.

When the room temperature is above the desired value, a movable blade 25 is not connected to contact 26 and when the room temperature is below the desired value, the movable blade 25 contacts the contact 26, the thermostat 24 acting as an ON-OFF switch.

The live and neutral of the electrical supply are connected to terminals 27 and 28 respectively.

Terminal 27 is connected directly to the movable blade 25 of thermostat 24 and also to the movable blade 21 of thermostat 20. Terminal 28 is connected directly to terminal 30 of the unidirectional motor 9 and also to terminal 31 of a control box 29 which is provided to control the operation of the boiler and/or circulating pump (neither of which are shown). Details of the control box 29 are not shown as they are of known type. The boiler and/or pump will operate subject to local and override controls when the mains supply is connected to the control box 29.

A terminal 32 of the motor 9 can be supplied with mains voltage via a triac 33 which has a gate resistor 34 connected to the centre contact of switch 14, or by a half wave rectified signal via a diode 35 and dropping resistor 36. This half wave rectified signal acts as a brake on the motor.

When the half wave rectified signal is applied to the motor will stop immediately and cannot be easily moved while the signal is maintained. One disadvantage of applying a half wave rectified signal to the motor, is that when it is removed, a permanent residual magnetism may be retained by the motor which can hold the motor in its locked position. To overcome this, a resistor 37 is provided which allows a low level A.C. current to flow through the motor to remove the residual magnetism.

The operation of the circuit is as follows. When both the thermostats 20 and 24 are satisfied t:1ey are in the position shown in the drawings and there is no circuit from the live terminal 27 to the contacts 26 and 23. The motor 9 is therefore unenergised and the springs 8 return the valve 1 so that port 4 to the central heating radiators is blocked as shown. Switches 14 and 1 5 all be on contacts 1 6 and 1 8 respectively, and the only live contact 17 which is connected to terminal 27 via the blade of thermostat 20 and contact 22, is open. There is therefore no circut to the control box 29 and the boiler and/or pump will be off.

If the hot water thermostat 20 calls for heat, the blade 21 of the thermostat moves across from contact 22 to contact 23, this will directly energise the control box 29 starting the boiler and/or pump. The circuit is from the live terminal 27 via the blade 21 of thermostat 20 and contact 23 to terminal 38 of the control box 29, and then via terminal 31 to the neutral terminal 28. The only other circuit is via the ciemagnetising resistor 37 and the motor 9, but the resistor 37 limits the current to such a low value that it will not drive the motor, therefore, port 4 remains blocked and all the circulation of the boiler water is via port 3 of valve 1 to satisfy the hot water system. When this satisfies the thermostat 20, the blade will return to contact 22, opening contact 23 and turning off the-boiler and/or pump.

If the room thermostat 24 calls for heat, the blade 25 will connect onto contact 26. This will start the motor 9, the circuit being from the live terminal 27 via the blade 25 and contact 26 through the triac 33 to the motor terminal 32, then via motor terminal 30 to the neutral terminal 28. The triac 33 will be conductive because its gate terminal 39 is energised via the gate dropping resistor 34 and contact 1 6 of switch 14.

When the ball 7 has travelled 45% of its movement, switch 14 will operate opening contact 1 6 and making contact 17. The gate circuit of the triac 33 is now via the dropping resistor 34 and the contact 1 7 of switch 14, which is connected to the live terminal 27 via contact 22 of thermostat 20, so the motor 9 will continue to run. When the ball 7 has travelled 55% of its movement across the valve, switch 1 5 will operate to connect the supply to contact 1 9 which will energise terminal 38 of the control box 29 and start the boiler and/or pump.When the ball 7 reaches the end of its travel it blocks the port 3 to the hot water system and all the circulation of the boiler water is via port 4 of valve 1 to satisfy the central heating system, When this satisfies the thermostat 24, the blade 25 will open the circuit to contact 26 removing the power from both the motor 9 and the control box 29. This will turn off the boiler and/or pump and the springs will return the motor to the start position so that the ball 7 blocks the port 4 which will stop gravity circulation to the radiators.

If both thermostats 24 and 20 should call for heat, the blades of the thermostats will connect the live terminal 27 to both contacts 26 and 23.

The circuit through contact 23 will energise the control box 29 so that the boiler and/or circulating pump will start. The circuit through contact 26 will energise the motor 9 via the triac 33 which is conductive at its gate is supplied via contact 1 6 of switch 14 and the gate resistor 34. When the ball 7 has moved 45% of its travel, switch 14 will operate breaking the circuit to the gate of the triac at contact 16; in this case the contact 1 7 is not connected to the supply as the blade 21 of thermostat 20 is not on contact 22. Therefore, the triac 33 will become non-conductive and the motor 9 will receive a supply from contact 26 via contact 18 of switch 15, diode 35 and resistor 36.As this supply is half wave rectified A.C. the motor will lock in this position and the circulation of the boiler water will be via both port 3 and port 4 to both the hot water system and the central heating.

Should the room thermostat 24 now be satisfied, contact 26 will open removing the supply to the motor which was via contact 18, diode 35 and resistor 36. There is, however, a circuit to the motor via contact 23 of thermostat 20 and resistor 37 which is a very small A.C.

current that will remove any residual magnetism from the motor caused by the half wave rectified A.C. so that the motor will return to its start condition blocking port 4 and we are in the normal condition for only the hot water thermostat calling for heat.

If, when both thermostats were made the hot water thermostat 20 became satisfied, first the blade 21 would open circuit contact 23 and make circuit on contact 22. This would reconnect the supply to the gate of the triac 33 via the contact 1 7 of switch 14 and resistor 34, and the motor will start to drive. When the ball 7 reaches 55% of its travel, switch 1 5 will operate making the circuit to contact 1 9 which will re-establish the supply to the control box 29 which was previously via contact 23 of thermostat 20, the motor will continue to drive until port 3 is blocked and we are in the normal condition for only the room thermostat calling for heat.

If, from this position where only the room thermostat 24 is calling for heat the hot water thermostat 20 also calls for heat, the blade 21 breaks the supply to contact 22 and makes it on 23. As the supply to the gate of the triac was via contact 22 and contact 17, the triac will become non-conductive removing the supply to the motor, and the springs 8 will start to return the valve to its original position. When it reaches the 55% position switch 1 5 will operate, breaking the circuit to contact 1 9 which does not matter as the circuit to control box 29 has been re-established via contact 23 and making on contact 18 which gives a half wave rectified supply to the motor 9 via diode 25 and resistor 36 which locks the motor in this position.We are now in the normal condition for both thermostats calling for heat and the boiler water can circulate through both the hot water system and the central heating system.

There are known circuits similar to the one described above which do not include the triac or other triggered device. In all these known circuits when the hot water thermostat is satisfied and the room thermostat calls for heat and is then satisfied, the boiler is turned off, the hot water port blocked and the central heating port is opened. With the circuit of invention, in such conditions the hot water port is open and the central heatimg port is closed. This is important as it prevents gravity circulation.

It will be appreciated from the above that when the boiler and pump are off, the radiator circuit is blocked such that gravity circulation of water to the radiator circuit is not possible. Furthermore, if one or both thermostats call for heat, the boiler and/or circulating pump circuit is energised. If only the hot water thermostat calls for heat, the valve member remains in or moves to the position where the radiator port is blocked. If only the room thermostat calls for heat, the valve member is driven to a position where the hot water port is blocked. If both thermostats are calling for heat, the valve member moves to the mid position so that both output ports are open.

Claims

1. A motor driven multiway control valve comprising a valve unit with a valve member movable between at least three predetermined positions, drive means, including an electric motor, coupled to the valve member for driving the valve member between said predetermined positions, said drive means being arranged to normally keep said valve member in a first position and a control circuit for controlling the supply of electrical power to the motor so as to operate the valve, the control circuit comprising a first control member operable to demand the first position for the valve member, a second control member operable to demand a second position for the valve member and including an electrical switch connected between an electrical supply and the motor by way of a triggerable device, the triggerable device being arranged to be triggered upon operation of said second control member to demand said second position for the valve member to thereby connect the electrical supply to the motor, and means for holding the valve member in a third position when both the first and second control members are demanding different positions for the valve member.

2. A motor driven multiway control valve as claimed in Claim 1 wherein the valve member is held in its first position by resilient means.

3. A motor driven multiway control valve as claimed in Claim 2, wherein said resilient means comprises one or more springs coupled to a driving shaft of the valve member.

4. A motor driven multiway control valve as claimed in any preceding claim, wherein the triggerable device is a relay.

5. A motor driven multiway control valve as claimed in any of Claims 1 to 3, wherein the triggerable device is a triac.

6. A motor driven multiway control valve as claimed in any preceding claim, wherein said means for holding the valve member in the third position comprises rectifying means connectable by way of a first mechanical switch to receive electrical supply by way of said electrical switch.

7. A motor driven multiway control valve as claimed in Claim 6, wherein said electrical switch is an on-off switch having a movable blade connected to an electrical supply line and a switch contact connected to one terminal of said triggerable device.

8. A motor driven multiway control valve as claimed in Claim 7, wherein the trigger of said triggerable device is connectable to said one terminal thereof by way of a second mechanical switch.

9. A motor driven multiway control valve as claimed in Claim 8, wherein said first and second mechanical switches are operable by movement of the valve member.

1 0. A motor driven multiway control valve as claimed in Claim 9, wherein said first and second mechanical switches are cam-operated switches.

11. A motor driven multiway control valve as claimed in Claim 9 or Claim 10, wherein said first control member comprises a two-way switch having a movable blade connected to the electrical supply line, a first contact of the twoway switch being connected to said first mechanical switch and a second contact of the two-way switch being connected to said second mechanical switch.

12. A motor driven multiway control valve as claimed in any preceding claim, wherein said first and second control members comprise thermostat switches.

13. A central heating and hot water system incorporating a motor driven multiway control valve as claimed in any preceding claim, the valve being arranged to control supply of hot water from a boiler to a hot water system and to a central heating system.

14. A central heating and hot water system as claimed in Claim 13, wherein said control circuit is also arranged to control operation of the boiler and/or of a water circulating pump provided in said system.

1 5. A motor driven multiway control valve substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.