GB2293047A - Energy regulator - Google Patents

Abstract

An energy regulator comprises a bimetallic actuator 10 heated by a heater 22 having a variable resistance. The heater may be a ceramic substrate heater having a positive temperature coefficient of resistance, so that as the temperature of the heater increases, its resistance decreases. This limits the heating effect of the heater at high settings of the regulator while increasing its heating effect at lower settings. Alternatively, the heater may have discrete resistance tracks which can be selectively switched in or out. <IMAGE>

Description

Energy Regulators The present invention relates to energy regulators for controlling the supply of electrical energy to electrical loads such as cooker hot plates or grills.

Typically, energy regulators comprise a snap-acting microswitch having a set of switch contacts arrangeable in the electrical supply circuit to the electrical load, an actuating member, for example a snap-acting switch contact arm, operatively associated with a bimetallic actuator for operating the switch contacts, and electrically energisable heating means associated with the bimetallic actuator. In such constructions, electrical power is initially supplied to the load and to the heating means which may be connected either in parallel or in series with the load. The heating means heats the bimetallic actuator, causing it to deform to the point where it causes snap-movement of the contact arm to open the switch contacts and interrupt the power supply to both the load and the heating means.The bimetallic actuator then cools and deforms in the opposite direction to the point where the contact arm undergoes reverse snap-action to close the contacts once more, whereupon the cycle recommences. Thus such regulators operate on the principle of supplying power to the load over a proportion of an operating cycle, the proportion being determined, typically, by the initial position of a free end of the bimetallic actuatorwhich actuates the contact arm, such initial position being set stable by control means coupled in use to a user actuated control member. An energy regulator of this type is disclosed, for example, our International Patent Application No. WO 93/26067.

In practice, there are certain restrictions on operating cycle times. They should not be too short, or the regulator may not meet radio interference requirements. Similarly they should not be too long, for example over 2 minutes, or an undesirable impression may be given to a user, for example when simmering milk.

If the cycle is too long, then the milk may boil furiously for a short time and then stop. Rather it is better to have a shorter cycle time, which results in less heat being produced in the heating element in each cycle, so that the thermal capacity of the system can more closely imitate a steady heating effect, such as obtained on a gas cooker. To do this, however, when on a low setting, the bimetallic actuator should be heated quickly so as to switch off the supply after a relatively short time say after 4 seconds, typically about 3% of the total cycle time. This in turn requires a relatively high wattage heater, for example a 10W heater.

However, if such a heater is employed when the regulator is used on a higher setting, this is too much, since it may cause the switch to cycle too quickly, thereby giving problems with radio interference, or may even cause the whole regulator to overheat leading to damage or loss of calibration, which is undesirable.

There is thus a need to have a different heating effect for the bimetallic actuator at different settings of the regulator. In one known arrangement, a diode is connected in the supply to the heater. When the regulator is in a low setting, the diode is bypassed so as to pass a full a.c. current through the heater, but in higher settings, the diode is switched on to rectify the supply to the heater, thereby reducing the heating effect therein. This, however, is a very expensive system. In a further proposal, a high wattage heater is used, and a switch inserted in the supply to the heater which is then switched off in the maximum setting of the control, to prevent overheating. In such a condition, power is supplied continuously by the regulator, since the bimetallic actuator does not deflect. Again however, this is expensive since it requires the provision of an additional switch.

From a first aspect the invention provides an energy regulator comprising a bimetallic actuator and a heater, preferably a ceramic substrate heater, mounted thereon, said heater having contact means for engagement with an electrical contact provided on a power supply member; and means for selectively engaging and disengaging said heater contact means and said electrical contact.

Thus, according to the invention the heater itself forms part of a switch mechanism, thereby obviating the need for a further, separate switch.

Preferably the power supply member is movable to effect the engagement and disengagement. The movement of the power supply member may be effected most simply by cam means provided on the control member of the regulator, and a cam follower operatively coupled to the power supply member.

In one arrangement, the power supply member contact may simply be lifted on and off a heater terminal.

Preferably, however, the power supply member contact is mounted so as to be slidably movable relative to the heater, whereby engagement and disengagement is effected by a sliding movement. This type of construction is particularly suitable for energy regulators such as those described in our aforementioned Wa 93/26027, where the contact is resiliently biased onto a ceramic substrate heater terminal so as to retain the heater on the bimetallic actuator, and where it would not, accordingly, be possible to lift the contact from the heater. Thus in a particularly preferred embodiment, the power supply member is an arm having a contact provided at one end and preferably having its other end coupled to, or forming, a terminal member. The arm may be provided with a cam follower for engaging a cam formed in a peripheral portion of the control member of the regulator.

The provision of a sliding power supply contact also has advantages in that it facilitates the provision of a further important feature of the invention. Whilst in simple embodiments of the embodiment, the heater may simply be switched off at the maximum power setting of the regulator to prevent it overheating by disconnecting the contact and terminal, it is, however, advantageous to provide some heating effect in the heater at higher settings. This is because, if the heater is turned off at the maximum setting of the regulator and the user turns the regulator from a high setting to a low setting, power will still be supplied by the regulator for some time while the heater heats the bimetallic actuator (which initially will be in its unheated position) sufficiently so as to deflect to open the main switch contacts of the regulator.If, however the heater is energised to a reduced level, for example to provide 2W at the maximum setting, the bimetallic actuator will be deflected from its unheated condition, whereby when the regulator is turned down, the power will, if the regulator is turned down low enough, be turned off immediately. This is particularly important with ceramic hobs where the heating means is visible.

Preferably, therefore, the heating means has a variable resistance whereby a lower heating effect on the bimetallic actuator may be obtained at the maximum or higher settings of the regulator. For example in the case of a ceramic substrate heater the substrate may be provided with a number of discrete heating tracks, electrically connected together. In one embodiment, the heating means comprises a plurality of heating tracks arranged electrically in parallel, and having respective adjacent terminals. For example there may be two tracks, one say of lOW and the other say of 4W. More preferably, however, the heater tracks are arranged electrically in series with one another.This is preferred because it might be possible with a parallel arrangement, without perfect register between the contacts and the heating track terminals, to have both tracks energised at once, giving an even higher power output from the heater which clearly would be desirable.

In such a series arrangement, the power supply contact and the terminals are preferably arranged so that as the contact moves from one terminal to the next, it will make with the next terminal before it breaks from the one terminal. This avoids the need for perfect register to obtain switching, and also avoids the possibility that no heating track is energised, whereby the bimetallic actuator would return to its rest position and the regulator would go fully on.

Such an arrangement can be obtained by making the contact of such a size that it can bridge the gap between adjacent terminals.

In a series arrangement, it would be possible to have all the heating tracks in positions where they efficiently convey heat to the bimetallic actuator, with them being sequentially switched in and out to vary the heating effect. However it is preferred to arrange a main heating track in a position in which it is in good thermal contact with the actuator, and reduce the heating effect of that track by switching in the other tracks which are arranged in a position where their heating effect on the actuator is less, thereby reducing the current flowing through the main track and thus reducing its heating effect.

From a further broad aspect, therefore, there is provided an energy regulator comprising a bimetallic actuator and a heater arranged in good thermal contact therewith, with resistor means selectively arrangeable in series with said heater to reduce the heating effect of said heater.

Thus in the arrangement described in WO 93/26067 where the heater is mounted in contact with a pivot formed on the actuator, the main track may be positioned directly over the contact region and the other tracks arranged spaced away from this region.

As discussed above, the heater employed in the invention is preferably a ceramic substrate heater.

Such heaters comprise an insulating ceramic substrate onto which is printed a thermal resist heating track and on which are deposited terminals for connection to an electrical supply. The ceramic is abrasive, and will lead to wearing down of the contact on the power supply member as it slides across the substrate between terminals. This in turn could lead to unwanted tracking from terminal to terminal, or to an 'off' position.

This is reduced in a preferred embodiment by printing a fused vitreous coating onto the substrate between and around the terminals and over which the contact will move, thereby reducing abrasion and improve the life of the regulator.

Further, the terminals provided are normally a 6:1 silver/palladium alloy, which is relatively soft. As such, the terminal can be eroded by the movement of the power supply contact thereover leading to further tracking or, in the worst case, complete erosion of the terminal leading to loss of the electrical contact to the power contact. This can be improved by, for example increasing the percentage of palladium in the heater terminal, for example to above 4:1.

While in the arrangements described above, the heater has a series of discrete resistance tracks, it would also be possible to employ heaters with, for example, a continuously variable resistance. Thus, a potentiometer type substrate heater, or even a PTC (positive temperature coefficient) heater could be used allowing the power output of the heater to match the requirements of the regulator. It will be appreciated that in these cases, switch means on the heater itself will not necessarily be required, and from a further broad aspect, therefore the invention provides an energy regulator comprising a bimetallic actuator and a heater associated therewith said heater having a variable resistance, whereby the heating effect thereof or of part thereof can be varied.

A PTC heater is particularly preferred. Such heaters employ a material having a positive temperature coefficient of resistance (PTCR) which means that as the temperature of the heater rises, its electrical resistance falls, and accordingly the heating effect of the heater (which is inversely proportional to the resistance) falls.

In an energy regulator, the temperature of the heater will be low at low regulator settings, since the heater will be activated only for relatively short periods, that is the heater will be activated for a short proportion of the regulator's operating cycle.

However, when the regulator is set at higher settings, the heater operates for a greater portion of the cycle time and its temperature will, therefore, rise. The variation in heater temperature may be as much as 3000C, from a minimum of 50"C in the lowest regulator setting to say 3500C in the highest setting. If, however, a heater is used with a PTCR, as the temperature of the heater rises, its resistance will fall thereby reducing its heating effect and thus its temperature rise.

Preferably the heater has a PTCR of at least 2000 x 10-6 OC-l, for example between 3000 and 4000 x 10-6 oC-1.

The particular value of coefficient can, of course, be chosen to give the desired operating conditions.

Assuming a PTCR of 4000 x 10-6 0C-1, a temperature rise or 300"C would cause a rise in resistance by a factor of 300 x 4000 x 10-6 = 1.2, i.e. to 2.2 times the original resistance. Thus a heater which in its initial ambient condition produces a heating effect of 10W reduces to one of about 4.5W at the higher temperature.

In this way, therefore, the heating effect of the heater can be varied without the need for switching or for moving parts.

In practice, the maximum heating effect of the heater may be chosen so as to be equivalent to that of a standard heater thereby limiting the upper temperature of the regulator. This means that at lower regulator settings, where the heater will not be so hot, the power output is significantly increased, giving a quicker heating time at lower settings, which is advantageous, as explained above.

Preferably the heater is a substrate heater, most preferably a ceramic substrate heater, with a resistive track of a material having a PTCR. The material or 'ink' of known properties may be laid down on the substrate in, for example, a serpentine pattern and trimmed to give the desired initial resistance.

In the arrangements described above, the heating effect of the heater is varied as the control member of the regulator is moved from a 'low' power setting of the regulator to a 'high setting, the heating effect being reduced at the higher setting to prevent overheating of the regulator at the high setting.

It will be apparent, however, that by changing the heating effect of the heater, in normal operation, the bimetallic actuator will take longer or less time to heat up and thus take a longer or shorter time to switch power on and off to the load being controlled by the regulator. Thus, the whole operating characteristic of the regulator can be changed by varying the heating effect. One problem with electric cookers, on which energy regulators are most commonly used, is that in low settings, it is often difficult to obtain a satisfactory control in the lowest power settings, due to conflicting operating requirements of the wattage of the bimetallic actuator's heater, as discussed above. It would be desirable therefore if a finer range of control could be provided in low power settings of the regulator.

In accordance with a yet further aspect of the invention, therefore, there is provided an energy regulator comprising a bimetallic actuator, heating means associated with said actuator, and a control member for setting the output of the regulator, wherein the regulator has two ranges of operation controlled by said control member, and wherein means are provided so as to produce a first heating effect from said heating means in a first range of operation and to produce a second heating effect therefrom in a second range of operation.

Thus in accordance with this aspect of the invention, a regulator may, in one mode of operation allow the control of for example a cooker element, over a complete heating range, ie. from 0 to 100t power. In this condition, the heating means should produce a relatively low wattage, to allow satisfactory operation over this complete range. In another mode of operation, however, by increasing the heating effect of the heating means, a separate control output can be obtained over a restricted range, say 0 to 30% power. Thus a user would have the option of choosing between a 'full power' or 'reduced power' range of operation.

The change in heating effect between the different modes of operation could be obtained using switchable heaters, such as those described above. Alternatively there could be entirely separate heaters mounted on or associated with the bimetallic actuator with suitable switching means. Whereas in the arrangements described earlier, the switching between heaters occurs towards the upper end of a single power operating range, in this aspect of the invention, the switching occurs between operating ranges. (Of course there could, if appropriate, be further switching within the individual ranges.) Alternatively, the heating effect could be varied by varying the heating current through the heater. An externally switched device, for example a shunt resistor, could therefore be provided.

The switching between heaters could be effected, as above, by cam means provided on the control member.

Normally in an energy regulator, a full range of operation is covered by substantially full rotation of the control member in one direction from 0 to say 3300.

However, a dual range of operation could be obtained by turning the control member through 1700 on either side at an 'off' position, for example 0 to 1700 clockwise, for full power range operation and 0 to 1700 anti-clockwise for the reduced power range.

This however has the disadvantage of reducing the accuracy of setting, since there is only half the normally available range of movement available.

Accordingly, a substantially full range of movement for both operating ranges can be obtained using a lost motion mechanism of the type generally described in our co-pending application No. EP 94303403.3 (EP-A-624890), in which the mechanism is used to control a split output of the regulator. One possible arrangement would be that when the control member of the regulator is initially rotated from the 'off' position, the regulator operates in the full power range. If, however, the control member were first rotated back beyond the 'off', the mechanism switches the heater to the higher wattage, so that when turned back past the 'off' position, it operates in the reduced power range.Turning the control member beyond the end of the lower power range would then switch the low wattage heater back in, so that as it was rotated back to the 'off' position, the regulator would operate in the full power range.

As stated above, the invention is particularly applicable to energy regulators using ceramic substrate heaters. The invention also extends, therefore, to ceramic substrate heaters per se having means to provide a variable heating effect. This heating effect may be variable in a continuous or a stepwise manner, as described above, with a plurality of heating tracks which may selectively be switched in or out of the electrical circuit, or by heaters with a PTCR.

Some preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a prior art energy regulator as described in WO 93/26027; Figs. 2a and 2b show part of an energy regulator in accordance with the invention; Fig. 3 shows a heater as used in the arrangement of Fig. 2; Fig. 4 shows schematically a further arrangement in accordance with the invention; Fig. 5 shows a heater mounted on a bimetallic actuator; Figs. 6a and 6b show a modification of the system of Fig. 2 to provide a dual output regulator; Fig. 7 shows graphically, a dual output as obtainable from an energy regulator in accordance with the invention; and Fig. 8 shows a heater for use with the invention.

With reference to Fig. 1, an energy regulator 2 (shown with its lid removed) comprises a snap-acting microswitch 4 having a contact arm 6 pivotally mounted on the free end of a bimetallic actuator 10. A snap acting "C" spring 12 is released from the contact arm 6 and engages in a fulcrum provided in an output tab 14.

A movable contact 16 is mounted on the free end of the contact arm 6, and a fixed contact 18 is provided on the upper face of an input tab 20.

An electrical circuit to a load such as a first section of a cooker grill element, not shown, is established through the input tab 20, the contacts 16,18, the spring 12, and the output tab 14.

A ceramic substrate heater 22 is mounted on the root end of the bimetallic actuator 10, and when energised, causes the actuator 10 to deflect, to open the contacts 16,18 with a snap-action after a predetermined deflection. The electrical supply to the heater 22 is made via the input tab 20, the contacts 16, 18, the contact arm 6, the bimetallic actuator 10, a tongue 24 released therefrom, and a resilient power supply member 26 connected to a neutral tab 28. Thus when the contacts 16,18 open the load and the heater are de-energised, allowing the actuator 10 to cool and deflect in the other direction, to close the contact once again.

The actuator 10 forms one arm of a bimetallic member 30, the other arm 32 of which acts as an ambient temperature compensator in a manner well known in the art. It is provided with a cam follower 34 which engages in a cam track 36 formed in a cam member 37 having a cam body 38.

The cam member 37 is of plastics and attached to, or formed with, a control member or spindle 40, to the top end of which may be attached a knob, not shown. As the spindle 40 is rotated, the cam track 36 is rotated, with the follower 34 moving up and down accordingly. As it does so, the free end 8 of the actuator 10 is also moved up or down, so changing the amount of deflection necessary to open or close the switch contacts 16,18.

Thus the operating point of the regulator is set by the angular position of the spindle.

The heater 22 is provided with a resistive heating track 42 having end terminals 44,46. The terminal 44 engages electrically with the tongue 24 while the terminal 46 engages with the power supply member 46.

The bimetallic actuator 10 is formed with a raised pivot 48 on which the heater is mounted, the resilient power supply member 46 acting both to supply power to the heater 22 but also to push the heater 22 into contact with the actuator 10. This form of mounting is more fully discussed in our co-pending application GB 9409529.6.

Figs. 2 and 3 show a modification of the above regulator in accordance with the invention. Only those parts of the regulator needed to explain the invention are shown, for simplicity.

With reference to Fig. 3, a ceramic substrate heater 100, which is mounted in the same manner as the heater 22 in Fig. 1 comprises two printed heating tracks 101,102 arranged electrically in parallel and shown schematically as resistors in Fig. 3. Heater track 101 runs between a terminal pad 103 and a common terminal 104, while track 102 runs between a terminal pad 105 and the common terminal 104.

Methods of construction of ceramic substrate heaters are well known in the art and need not be elucidated here.

Heater track 101 has a resistance of 15 KQ while track 102 has a higher resistance of 38 KQ. At a voltage of 240 V, this gives a heating effect of about 1.5W in track 102 and about 4W in track 101.

In use, common terminal 104 engages with the tongue 24 of the bimetallic actuator 10, and as can be seen from Figs. 2A and 2B, terminals 103 and 105 are engaged, selectively, by the end of a power supply member or arm 106, which is in the form of a strip extending from a neutral tab 108. The arm 106 may be provided with a separate contact mounted on its end for making contact with the terminals 103,105 or, more simply the end portion 109 of the strip itself, suitably formed and if necessary silver plated, may form the contact.

The power supply member 106 is provided with a cam follower 110 for engagement with a cam surface 112 provided on a circumference of the control member 114 of the regulator.

As well as being biased down into contact with the heater 100, the arm 106 is also biased into engagement with the cam surface 112. The cam surface 112 is uniform over approximately 300 but has a depression 116 in a position corresponding to the maximum power setting "9" of the regulator. (Nominal power settings of the regulator are indicated schematically on the control member.) In Fig. 2A, the control member of the regulator is in its 'off' condition, limited by interengaging detents 118,120 on the regulator housing and control member respectively. In this condition, the cam follower 110 of the arm 106 is in the high portion of the cam surface 112 and its contact portion 109 is engaging the terminal 103.Thus once the regulator is switched on, the bimetallic actuator will be heated by the relatively low resistance track 101, giving a high wattage heating effect (about 4W). This heating will be maintained over substantially the whole rotational range of the control member 114 until it reaches a maximum power setting "9"), at which point the cam follower 110 engages in the depression 116, so switching the contact portion 109 of the arm into contact with terminal 105 of the high resistance track 102, whereby the heating effect is reduced to about 1.5W, thereby avoiding problems with over-heating of the regulator which might otherwise occur. If different heating effects are desired in other parts of the operating range, further heater tracks may be provided, and the cam profile 112 modified to give the desired switching between them.

Fig. 4 shows, schematically, a modified system in which heater tracks 200,202,204 are arranged electrically in series on the substrate 206. In this embodiment, three tracks are provided, although that number can be varied to give desired operating conditions. A terminal 208 is provided for engagement with tongue 24 in the actuator 10 while three further terminals 210,212,214 are provided as shown. The power supply terminal is moved across the terminals from the 'low' power setting shown in solid lines to the high power setting in dotted lines, so as to switch in sequentially the tracks 202 and 204.

Heating track 200 is provided on a part 'A' of the substrate 206 which directly contacts the bimetallic actuator 220. This is shown schematically in Fig. 5 which shows the heater mounted on an actuator of the type described in WO 93/26067. Thus there is good heat transfer between the track 200 and the actuator 220.

The resistance of the track 200 may be chosen such that in the condition shown in solid lines in Fig. 4 its heating effect is about 10W (R20o - 5.7 Kin). The resistance of tracks 202 and 204 are chosen so as to reduce such that the heating effect of track 200 is reduced to about 4W when track 202 is switched in, and to about 2W when track 204 is also switched in.

The power supply member 216 is substantially as described earlier, being deflected through a cam follower, by a cam surface 218 of the control member switchably modified from that shown in Fig. 2 to give the desired deflection as the control member is rotated.

Clearly this embodiment could be simplified by having only two heater tracks rated to give the desired heating effect.

It will be noted from the position in the solid lines in Fig. 4 that the contact portion of the arm 216 is sufficiently broad to bridge the gap between the respective pairs of adjacent terminals 210,212;212,214.

This means that contact will be made with the next terminal before contact is broken with the previous one.

This will avoid situations in which the heaters are disconnected altogether, leading to the regulator going fully "on".

With reference now to Figs. 6 and 7, a dual output range regulator will be described. This regulator is generally similar to that of Fig. 2, having the same form of parallel track heater 300, and a similar power supply arm 302. The main difference with the earlier embodiment is the cam profile 304 provided on the control member 306. In this case, the profile has a depression 308 extending for approximately 1700 around the control member. This will allow the regulator to operate in two distinct power ranges, one a 'full' power range and the other a 'reduced' power range.

As can be seen from Fig. 6a, which shows the regulator in the 'off' position, if the control member is turned clockwise for up to 1700, the contact portion 310 of the power supply arm remains in contact with terminal 312 of a low resistance relatively high wattage track 314. This corresponds to a 'reduced power' mode of operation of the regulator, as shown by line 350 in Fig. 7. The control member (or in practice a knob attached to it) will indicate a complete range of settings 1 to 9 for this reduced output range (as shown schematically in Fig. 6a), but at the '9' setting, the actual output of the regulator is only about 30t of maximum (i.e. the regulator supplies power for only say 30% of total cycle). The heater power, and main control cam surface for the regulator (formed in an other surface of the control member) can be chosen to give the desired operating characteristics as this range.

When, however the control member 306 is turned anti-clockwise from the 'off' position, the cam follower 316 of the power supply arm 302 drops into the depression 308 to move the contact 310 into contact with the terminal 318 of a high resistance, low wattage track 320. This is shown in Fig. Sb. This will allow the regulator to operate over its full output range, as indicated by line 352 in Fig. 7, in which the power setting '9' corresponds to 100t output. Again the heater wattage and main cam profile are chosen to give the desired operating characteristic.

With such an arrangement, improved control in the lower output range can be obtained, as is evident from Fig. 7.

Turning now to Fig. 8, a ceramic substrate heater 400 is provided with a heater track 402 of a material having a PTCR, for example in the region of 3000 to 4000 x 10-6 OC-l, extending between two contact pads 404,406.

The track 402 is printed onto the substrate in known manner with a serpentine configuration and fired.

Typically the ink used may have a resistance of 50Q/ square unit area and the track have a nominal resistance of 2kQ as fired. After firing, the resistance may be trimmed to the desired figure eg. about 5kn by selectively cutting through one of the bridges 408,410 extending from the contact pad 404, for example by laser, and also cutting down the centre of the thick track portion 412 to a desired distance. This increases the resistance to enable an exact resistance to be achieved without local hot spots. The contact pads 404, 406 are then applied and the over glaze 414 then applied and fired.

The heater 400 may then be installed in the regulator as shown in Fig. 1, and its resistance automatically changes as it heats under different regulator settings. As described earlier, as the temperature of the heater increases, its resistance increases, and thus its heating effect decreases, thereby reducing the heating effect at higher regulator settings. As an example, if a heater having a PTCR of 4000 x 10.6 OC-l is used with a resistance giving an initial heating effect of about 10W at room temperature, when the temperature of the heater is raised by say 300 , the restance of the heater increases by a factor of about 1.2 to a total of 2.2 times its original value, thereby reducing the heating effect by the same factor, that is to about 4.5W.

In this way, the change in resistance required to give a lower heating effect at higher temperatures can be effected without the need for separating switching means.

Claims (29)

Claims

1. An energy regulator comprising a bimetallic actuator and a heater associated therewith said heater having a variable resistance, whereby the heating effect thereof or of part thereof can be varied.

2. An energy regulator as claimed in claim 1 wherein said heater has a positive temperature coefficient of resistance (PTCR).

3. An energy regulator as claimed in claim 2 wherein said heater is a substrate heater printed with a material having a PTCR.

4. An energy regulator as claimed in claim 1, 2 or 3 wherein said heater is mounted on said bimetallic actuator.

5. An energy regulator comprising a bimetallic actuator and a heater, mounted thereon, said heater having contact means for engagement with an electrical contact provided on a power supply member; and means for selectively engaging and disengaging said heater contact means and said electrical contact.

6. An energy regulator as claimed in claim 5 wherein the power supply member is movable to effect the engagement and disengagement.

7. An energy regulator as claimed in claim 6 wherein movement of the power supply member is effected by cam means provided on the control member of the regulator, and a cam follower operatively coupled to the power supply member.

8. An energy regulator as claimed in claim 6 or 7 wherein the power supply member contact is lifted on and off a heater terminal.

9. An energy regulator as claimed in claim 6 or 7 wherein the power supply member contact is mounted so as to be slidably movable relative to the heater, whereby engagement and disengagement is effected by a sliding movement.

10. An energy regulator as claimed in claims 5 to 9 wherein the heating means has a variable resistance whereby a lower heating effect on the bimetallic actuator may be obtained at the maximum or higher settings of the regulator.

11. An energy regulator as claimed in claim 10 wherein the heater is provided with a plurality of discrete heating tracks.

12. An energy regulator as claimed in claim 11 wherein said tracks are electrically in series with each other.

13. An energy regulator as claimed in claim 10 or 11 wherein the power supply contact and the terminals are arranged so that as the contact moves from one terminal to the next, it will make with the next terminal before it breaks from the one terminal.

14. An energy regulator as claimed in claim 11, 12 or 13 wherein a main heating track is arranged in a position in good thermal contact with the actuator and another heating track is arranged in a position where its heating effect is less.

15. An energy regulator comprising a bimetallic actuator and a heater arranged in good thermal contact therewith, with resistor means selectively arrangeable in series with said heater to reduce the heating effect of said heater.

16. An energy regulator as claimed in any of claims 5 to 15 wherein said heater is a ceramic substrate heater.

17. An energy regulator as claimed in claim 16 wherein a fused vitreous coating is printed onto the substrate between and around the terminals, and over which the contact will move.

18. An energy regulator as claimed in claim 16 or 17 wherein the terminals are of a silver/palladium alloy in which the ratio of palladium to silver is about 4:1.

19. An energy regulator as claimed in claim 1 wherein said heater has a continuously variable resistance.

20. An energy regulator comprising a bimetallic actuator, heating means associated with said actuator, and a control member for setting the output of the regulator, wherein the regulator has two ranges of operation controlled by said control member, and wherein means are provided so as to produce a first heating effect from said heating means in a first range of operation and to produce a second heating effect therefrom in a second range of operation.

21. An energy regulator as claimed in claim 20 wherein the heating effect is varied by switching heater elements in or out.

22. An energy regulator as claimed in claim 20 or 21 comprising heaters mounted on or associated with the bimetallic actuator with suitable switching means.

23. An energy regulator as claimed in claim 20 wherein the heater effect is varied by varying the heating current through the heater.

24. An energy regulator as claimed in claim 23 wherein the current is varied by an externally switched device.

25. An energy regulator as claimed in claim 20 to 24 wherein switching between heaters is effected by cam means provided on the control member.

26. A ceramic substrate heater having means to provide a variable heating effect.

27. A heater as claimed in claim 26 having a PTCR.

28. An energy regulator substantially as hereinbefore described with reference to the accompanying drawings.

29. A heater substantially as hereinbefore described with reference to the accompanying drawings.