GB2283817A - Latching actuator - Google Patents

Abstract

A latching actuator for operating a radiator valve 1 or a hot air vent comprises a pair of toothed members 22, 23 which move and cooperate within a housing 21 under the control of grooves within the housing and the rod 33 of a piston 32 in a wax-filled chamber 34. The wax may be heated by an element 35 forming part of a control circuit or alternatively the heat may be derived from the ambient air or from the water in the central heating system. The control may communicate with the latching actuator by radio frequency, infra-red or acoustic means. In a further modification a stepped motor and a lead screw am used to operate the actuator. <IMAGE>

Description

LATCHING ACTUATOR This invention relates to a intelligent latching actuator.

Background There is a need to control the use of energy efficiently within buildings to limit the resulting energy cost and also to conserve the consumption of energy reserves for ecological reasons.

A major usage of energy is for space heating within buildings.

This space heating can be powered by various means such as central boilers, heating water or air from fuels such as oil, coal, gas or electric.

Considerable energy is wasted by the inadequate means of control of the distribution of heat energy about a building. For example in wet systems, heat is distributed through out a building by means of radiators which may or may not have temperature regulating valves (TRV's) fitted.

The control of such systems is typified by the feature that the individual radiators are manually set OFF or ON (regulated or non-regulated by TRV's) and controlled by a central time of day programmer and a central or zoned thermostat.

The TRV can only regulate about the manually set target temperature and performs this function continuously until either the boiler switches off or its setting is manually readjusted.

The above control system cannot respond to changing operating requirements of the individual and local heated areas. Therefore if the time and stat are ON then all radiators are ON whether needed or not. Also if different set temperatures are required at different times of the day the standard TRV cannot respond. This can relate to wasted energy in the order of 30 to 40 percent By using a latching valve with an integral intelligent control each radiator can regulate temperature to meet locally set conditions and also respond automatically when the desired control conditions change.( ie when a room is no longer occupied) The obstacle to controlling each radiator individually is the cost of power and control wiring which would be needed through out the building to all radiators and local room stats and proximity detectors.

The cost of this wiring infra-structure is significant on new buildings and is greater still for retro-fitting to older existing building stock.

The principle of this actuator can be applied to the control of hot water radiators or ducted hot air systems but also can be used in any application where a control actuator is required to control a process where the use of cabling and/or energy supplies are restricted.

A separate patent application (Electrical Actuator Control No GB 9311909.7) has been filed relating to an Electrical Actuator Control for implementing such a system for wired and non-wired applications. This document describes in detail the implementation of wireless self powered control circuits so although reference is made to its control functions the detail will not be repeated here.

This invention relates to a complete assembly which can be used on its own without the need for any external electrical connections. However where applications are suited it can also operate with wired connections to power and signal sources.

In both cases means are provided for a actuator that can provide intelligent control and communicating functions and physically activate an actuator mechanism such as a radiator valve to provide total control over the medium being controlled (such as hot water in this case). Means are provided to generate the electrical energy required to operate the actuator to any desired position and also to power the control circuit to perform its logical processing and communicating functions. An important feature that extends the type of actuator that can be controlled in this manner is the latching mechanism that ensures that minimum energy is absorbed in moving from one control position to another and then consuming no energy in maintaining the desired position.

Examples of practical energy requirements of several designs are included in the appendices.

Also detail explanation of the control and thermo electric options are decided in the patent relating to an Electrical Actuator Control.

Essential Technical Features According to the present invention there is provided an actuator that consists of four main parts, namely: 1 The Actuator mechanism which can for example be a spring return water valve shown in Figl as part, which can control the flow of hot water in a radiator.

2 The Latch mechanism which can move to and hold a number of intermediate positions and shown in Figl as part2. It can for example extend a rod to bear upon a valve to maintain a number of positions between fully open to fully closed.

3 The Energising mechanism shown in Figl as part3. This part can be powered from a variety of energy sources and when connected to such a source will extend a rod which bears upon the latch mechanism to cause the latch to move to the next fixed position. Each time the energising part operates it extends and retracts a rod (or rotate) in response to the application of an energy source.

4 The Energy Source and Control is shown in Figl as part4. In the simplest application this can be a voltage source provided via wires from a temperature control or control network.

Where cabling is not possible then the energy source can be provided by an integrated thermo-electric power source and control (see ref to patent application on Electrical Actuator Control). Its function is to provide the energy source and control its application to the energiser to meet the requirements of the energising device and latch functionality. Also it will operate the actuator to meet the local room temperature and time setting and any other local demands It will also respond to any other system requirement to ensure the complete building heating specifications and objectives are being met. This for example can involve balancing of water flow and communicating local data to the boiler control to enable it to adjust flow pressure/ temperature parameters.

Example Latching Radiator Valve Fig 1 illustrates a hot water radiator with hot feed and return pipes. The Latching Actuator (Valve) is connected between the feed pipe and the radiator. For a wired installation power and signal cables will be connected to the Latching Actuator With ref to Figl and Fig2 a latching valve is shown as partl.

This can be either a two position ON or OFF device or have intermediate positions between fully OPEN or fully CLOSED.

A three position valve will be described here.

Actuator The construction of the Actuator valve 1, can be as depicted (fig2 partl), for which there are many existing manufacturers and is similar to the mechanism found in popular 'Thermostatic Radiator Valves'. A cast metal body 11, provides two water connections, inlet 12, and outlet 13, and houses plunger 14, which is held open by means of a spring 15. When the plunger is extended the plunger makes a seal with the valve seat 16 and stops flow from inlet to outlet.

The seal is made good by the use of compliant materials attached to parts 14 and 16 at the mating faces Latch The principle of operation of the latch mechanism 2, is similar to that found in a ball point pen where the tip of the pen can be made to extend into the writing position and then retract into the body by the repeated depressing of the push button at the top of the pen. This mechanism differs from the pen example in that there can be more than two positions held by the mechanism.

The latch body 21, houses two mating cogs 22 and 23. The upper cog 22 is the thrust cog and can move up and down within the latch body but is restrained from rotating by mating grooves in the latch body. The lower cog 23, is the latching cog and for part of its travel within the housing is restrained from rotating by another set of grooves in the latch body.

Both cogs have castellated teeth 24, and it is important to note that they are not flat at the tips but inclined at a matching angle (see Fig3).

While both cogs are in their constraining grooves the teeth butt- up in-line with each other and it is through this inclined mating area that the thrust cog forces the latching cog up and down the latch body.

The interaction of the inclined teeth causes a rotation force between the two cogs but neither can rotate while constrained in their respective mating grooves. However the grooves in the body provided for the latching cog are deeper and also open at the 'latch end' of the body (see Fig3).

Thus when the latching cog is pushed past the end of the grooves it rotates over the one set of grooves and moves towards the next set of grooves.The thrust cog is further constrained not to move any further than just sufficient to force the latch cog to trip over the top of the body grooves. At this point the power to the thrust cog is removed and it retracts back into the latch body. With the thrust cog retracted the latch cog under pressure from the valve spring rotates and retracts due to the matching angles forming an incline between the cog teeth and the latch body.

This rotation and retraction continues until the cog hits the stop on the latch body where the cog is forced back into the body by sliding without rotation back into the next groove until it reaches the bottom of the groove. Clearly by fixing the length of these latch body grooves of different lengths the cog can be placed in a number of different mechanical positions.

For this particular example it can be seen that the latch cog has to extend beyond the tip of the latch body grooves before returning to the rest position. When the rest position corresponds to the closed valve position, means will have to be provided to allow this extension. Fig 2 shows how this can be accomplished by the use of a spring 25, fitted between the latch cog-pin 26, and the latch cog 23, and would be rated at the same or greater spring tension of the valve spring 15.

Therefore when the latch pin 26, forces the valve 14 closed, the latch cog 23, still has to extend over the latch body grooves before it can rest in the closed position. Although the pin cannot move any further the cog is free to extend past the body grooves by compressing the spring 25.

Where latching dimensions are small it will be possible to accommodate the extension distance by compression of the valve seat material 16, and dispense with the cog-pin spring 25.

Energiser In this example the energiser is a sealed chamber 31, which houses a piston 32, on the one side of the piston is a substance 34, with a high coefficient of expansion ( E.g. :- solid eg wax, liquid, gas or saturated vapour) where the substance is selected to suit the application ensuring temperature, movement, force and energy available are taken into account.

This substance is heated by means of a resistive heating element 35. On application of electrical power to the heater the medium is heated and expands. This results in a force applied to the piston which moves towards the end of the sealed chamber and in-turn extends the piston rod 33, out of the chamber and so acts upon the thrust cog 22, in the latching mechanism.

Electrical Actuator Control In this example the power is delivered from an external supply which could be a 12volt D.C.

source. The temperature sensing can be by an external thermostat or internally measured by the control circuitry. (A full description of such a control circuit is given in patent application ref No. GB 9311909.7) The control circuit will perform the function of pulsing energy to the energiser to cause the latch to move the valve in the desired position to satisfy the heating control function.

Alternative implementations of the Invention The Latching Actuator can be applied to the control of any fluid, gas or any other substance provided the realisation of the actuator is designed to perform the control action required or trigger a suitable external mechanism.

Actuator The actuator can be realised in the form of any mechanism that can respond to the mechanical input from the latch.

Examples of different forms which the actuator can take are Plunger Valves, Gate Valves, Vents and Flaps or mechanical triggers for other types of control mechanisms ( eg actuator pin can operate an electrical micro switch as a function of another control system or the actuator pin can mechanically operate on a trigger of another separate mechanism.

Latch/Energiser An example of a specific design of the latch has already been described. Clearly there is scope for a variety of alternative design implementations that will give the same functionality detailed earlier.

One alternative design would be to use magnetic rather than mechanical forces to maintain a fixed position of the latch pin.

A multi-position design can be achieved using a stepper motor with a profiled cam on its drive shaft. The motor can be stepped to and held at new detent positions by the interaction of the motor windings and the permanent magnetic poles.

A two position design can be achieved using a magnetic latching solenoid which can be energised to move the latch pin to its extended position where it is held by a permanent magnet until a reversing voltage is applied to the winding to release the magnetic latch and return the latch pin to its retracted position. In these cases the latch pin is acted upon by a return force ( In the example provided by the valve spring 15 ) In the situation where cabling and power supply is not restricted the Latching Actuator functionality can be achieved by electrically latching of the energy source 42, to the energiser by the control circuit 44.Here on receipt of a signal from the temperature sensor 43, indicating that more heat is required then power can be switched and logically latched to the control output and remains there until the temperature sensor confirms that the desired temperature has been reached at which point the electrical latch is released and power is switched off by control circuit 44.

A further alternative implementation of a combined Energiser/Latch is a permanent magnet stepper motor and lead screw. Here the motor shaft is instructed to step by a fixed rotational angle which will be a multiple of the characteristic step angle. Rotation of the shaft which is threaded provides a lead screw mechanism. Since the motor and lead screw will be fixed any threaded part attached to the lead screw will move in a linear direction up and down the lead screw dependent upon whether the lead screw rotates clock wise or counter clock wise. The threaded part can operate directly upon the vent-flap/valve or via the mechanical latch mechanism described earlier. In the latter case the thrust cog would be the threaded part and operate in a linear fashion driven by the step-motor( or other type of motor).

In the case where the moving part on the lead screw is directly attached to the valve plunger or vent flap then the use of a return spring is optional since the reversal of the lead screw will cause the plunger to return under power from the motor and then held latched by the holding force of the permanent magnetic force within the motor which is further assisted by the reduction ratio of the lead screw thread angle.

Features of the latching Actuator relating to a complex control system.

Example with reference to a ducted hot air heating system shown in Fig4. Additional features of this invention will be described by way of example.

Consider a large complex building with an existing serviceable hot air ducted system where heat control per room is via manually operated vents.

This set up generally suffers unacceptably high running cost and poor control due to vents being left open and also putting unnecessary loading factors on the main boiler.

The cost of installing electrically powered vents require both power and signal cables. The cost and disturbance caused to the building due to cable installation and commissioning is high and often a reason for not proceeding with energy saving schemes.

It is in addressing these practical problems that brought about the current invention. The ideal solution to the above problem is to replace the manually operated vents throughout the building with automatic vents that have the following features: Vent Actuator to open and close vent to move vent and hold in intermediate position to be electrically powered to maintain all fixed control positions without consuming power Power Source to be powered by thermo electricity from the heat gradient from the hot ducting and ambient air peak load requirements to be supplied from rechargeable storage device such as a Nickel Cadmium battery Control Circuit to respond to control instructions from remote locations to communicate with remote control devices communication to be via radio frequency Cabling No power or signal cables.

Energiser/Actuator The vent actuator can be built using a solenoid together with the mechanical latch (fig3), to provide the means to move the vent flap between ON, OFF and intermediate control positions Alternatively if only ON and OFF positions are required then a magnetically latching solenoid could be used without the need for the mechanical latch.

In both cases the actuator will only draw electrical power to make a transition from one control position to another and draw no power to hold the latched position. In the case of the magnetically latched solenoid the control circuit needs to apply a demagnetising current to un-latch the solenoid.

Power source The solenoid can be powered from a rechargeable battery cell which will satisfy the momentary pull-in current of the solenoid. The energy consumed by the solenoid during the short period of activation is replaced by the low level charging current from the thermoelectric generator during the longer period when the actuator is latched. A positive energy balance is achieved by ensuring that more energy is returned to the battery cell while the actuator vent flap is latched than is consumed by moving the actuator from one fixed position to the next. Typically a vent flap will be repositioned in a matter of seconds where as the time between activation can typically be 15 minutes to an hour.

The storage cell also has to supply power to the control circuit and meet the intermittent loading placed by the radio frequency communication to and from other latching activators or control devices such as programmers and thermostats. In the case of ducted systems the source of heat being absorbed from the metal ducting is available whether the vent flap is open or closed.

Clearly when the main boiler switches OFF for any prolonged period the storage device (battery) must maintain functionally of the latching actuator and ensure that the vent flap is positioned to an acceptable default position prior to the onset of battery discharged. An important function of the control circuit is to communicate to the system the status of actuator position and other parameters at all times and particularly prior to shut down.

Once the main boiler is reactivated the thermo electric generator will start recharging the energy storage device (battery) and once the circuit has sufficient charge to resume control functions the local latching valve can be advised of all relevant system parameters that were not locally stored and the vent flap can be moved to the new control position when required. It is clearly illustrated the importance of the non power consuming latch in applications where the energy balance is marginal.

Generalised Features Actuator Any device that can be set to a number of states and each state represents or performs a control function Examples water valve vent flap Latch Device that will physically maintain a mechanical position with or without consuming electrical power. Implementation can be mechanical, electrical or magnetic.

Examples Mechanical latch (thrust and latch cog) described in Fig3 Magnetic solenoid permanent magnet stepper motor Energiser Any device that can respond to the application of energy to cause movement of a shaft (thrust pin or latch pin or actuator direct) Examples Thermo expansion valve solenoid Motor and cam or lead screw with linear thrust pin Energy Source and Control Energy source can be remote or local Energy source can be any voltage or current source Energy source can be a heat source The control can be remote or local or both.

Communication to and from the control to other control devices can be via transmission over the following communicating media.

wires fibre optic infra red radio frequency Temperature sensing can be from remote devices or internally sensed.

General Applications of the Latching Actuator It is possible to apply the latching actuator to control another control mechanism or system.

For example in the case of a Thermostatic Radiator Valve the latching valve can act upon such a device to replace the manual setting mechanism to provide automatic end target temperature values about which the TRV will compensate for change in ambient temperatures. With reference to Fig2 part3, the thermo-expansion device would be designed to respond to ambient temperatures in addition to the heat generated by the internal heater element so that when the latch pin is positioned to an intermediate position between open and closed then movement of the thrust pin due to changes in ambient temperature are superimposed onto the position of the valve.This provides the facility of self powered temperature regulation (about an automatically set and latched target temperature setting) direct from the ambient heat source in addition to self powered control (from heated medium ie hot water or air) for fully ON/OFF and new target set temperatures APPENDIX A Energy balance for different types of actuator Example using a PP3 Nickel Cadmium battery cell recharged by a thermo electric generator In all cases the return spring pressure is lKg/mm and max spring compression of 3mm Total force to over come spring pressure is 3*1=3Kg (30Newtons) Thermo electric generators capable of converting heat energy flow can be obtained from Marlow Industries U.K. An output at 2% conversion efficiency can be obtained from a temperature gradient of 40degrees centigrade. Eg A 12 Watt rated device part No.MI1064 can produce 12*0.02=0.24Watts of charging power.

Thermo expansion generator Electrically heated thermo expansion valve Suitable device: Thermohydraulic motor ABN supplied by Danfoss Randall Ltd U.K.

Consumes 3Watts to heat the expansion fluid Opens in typically 2minutes Typical Energy consumed to open valve against a spring return water valve of 1KG per mm.

Energy = 3Watts * 2minutes = 6 Watt-minutes.

For duty cycle of two activations of the latch per hour requires to replace the 6watt-minutes of energy in a period of 30-2=28minutes.

This relates to an average charging power of 6 watt-min/28min= 0.22Watts.

Solenoid Suitable device: TDS-12M Supplied by Lucas Industries U.K.

Power required to provide 5.8Kg pull-in force is 30Watts Time to pull-in circa lsecond Energy consumed is 30*1/60=0.5 Watt-minutes.

Average charging power to replace activation energy is 0.5/30=0.017Watts Stepper Motor Stepper motor with a 10 to 1 increase in motor torque by use of lead screw attached to motor shaft.

Suitable device: Permanent Magnet step motor type 82910 0 supplied by Crouzet Ltd U.K.

Power require to produce 3Kg linear force via 10:1 ratio lead screw is 5Watts.

Time to move shaft through 3mm against return spring is typically 5seconds Energy consumed in activating latch is 5*5/60=0.42watt-minutes Average charging power required to replace energy consumed is 0.42/30=0.014Watts

Claims (13)

1. Claims 1 A Latching Actuator (as shown in Figl) is a self contained device which has the means for energy conversion and storage which under intelligent control can be applied to an Energiser and Latch mechanism which provides the means to convert a controlled amount of energy into physical mechanical movement of an Actuator, the position or state of which can be maintained in a stable condition without using any further energy.
2. 2 A latching Actuator as claimed in 1 provides the means to latch the actuator in two or more positions or intermediate positional states.
3. 3 A latching Actuator as claimed in 1 and any preceding claim whereby the actuator can control the flow of any liquid, gas or any other substance.
4. 4 A latching Actuator as claimed in 1 and any preceding claim whereby the Energy is derived from the local ambient air or water temperature.
5. 5 A latching Actuator as claimed in 1 and any preceding claim whereby the energy is derived from the temperature of the substance being controlled.
6. 6 A latching Actuator as claimed in 1 and any preceding claim whereby the power source and con -trol are supplied by external means and connected to the Latching Actuator by means of wires.
7. 7 A latching Actuator as claimed in 1 and any preceding claim whereby the control provides the means to communicate to other Latching Actuators or other external devices by means of Radio frequency, InfraRed, Acoustic methods of wireless communication.
8. 8 A latching Actuator as claimed in 1 and any preceding claim whereby the control function pro -vides the means to operate radiator or hot air vents to regulate a heating or cooling system where the Latching actuator implements the function of a hot air vent or radiator valve actuator.
9. 9 A latching Actuator as claimed in 1 and any preceding claim whereby the control function provides the means to optimise the performance of the boiler or other energy source that powers the heating or cooling system in which the Latching Actuators provide the means of control of the heating or cooling medium (eg a radiator valve for hot water in radiator systems).
10. 10 A latching Actuator substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.
11. 11 A latching Actuator substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.
12. 12 A latching Actuator substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.
13. 13 A latching Actuator substantially as hereinbefore described with reference to the accompanying drawings in Appendix B,C and D.