GB2134713A - Energy regulating switch - Google Patents

Abstract

An energy regulating switch has a pair of contacts (2, 3) in series with a load (1). A bi-metallic strip (4) is operably associated with the contact 3. A cam (8) and a cam follower (7) are arranged to position the contact 2. First and second electrical heaters (5, 6) are arranged to heat the bi-metallic strip (4) with the first heater (5) connected in series with the contacts (2, 3) and in parallel with the load (1). A cam (11), a cam follower (12) and contacts (13, 14) are provided for connecting the second heater (6) in parallel with the first heater (5). A spindle (9) carries the cams (8, 11) and when rotated in a first direction from a datum position, the heater (6) is connected in parallel with the heater (5) whereas when rotated in the opposite direction from the datum position, the heater (6) is disconnected. Rotation of the spindle (9) in either direction from its datum position causes the cam (8) to move the contact 2 in the same direction in relation to the bi-metallic strip (4) and contact 3. <IMAGE>

Description

SPECIFICATION Energy regulators This invention relates to energy regulators controlling the input of electrical energy to a device such as a hot plate consuming electrical energy. It is conventional to provide an energy regulator employing a bi-metallic strip with an associated electrically energised heater. In one known construction the electrical heater of the bimetallic strip is connected in parallel with the load and an electrical switch is connected in series with the parallel circuit of the load and the heater of the bi-metallic strip. The bi-metallic strip is associated with the switch contacts of that electrical switch and its position relative to the switch contacts can be varied to change the temperature of the bimetallic strip at which the switch contacts are opened.

In use, the regulator operates in the manner that on initial energisation, both the load and the heater of the bi-metallic strip are energised until the bi-metallic strip is sufficiently deformed to open the switch contacts. The load and the heater are then de-energised until the bi-metallitic strip has sufficiently recovered its initial shape to allow the contacts to close when the cycle starts again.

The load is therefore energised in a pulsating manner, the porportion of time during which the load is energised being dependent on the position of the bi-metallic strip in relation to the contacts.

A common load for an energy regulator is a cooking element of an electrical cooker and for this purpose it is desirable not only to be able to set the regulator so that energy is supplied to the load for over 50% of the time that the load is in use but also to provide a relative position of the bimetallic strip and the switch contacts such that the load is energised for less than 10% of the time.

In practice, it is difficult to provide an energy regulator capable of providing energy to a load over most or all of the time and also capable of providing energy to a load for less than 10% of the time.

It is an object of this invention to provide an energy regulator in which the stated problem is alleviated.

According to this invention there is provided an energy regulator for controlling the supply of electrical energy to an electrical load comprising a pair of switch contacts, a bi-metallic strip operably associated with the switch contacts, positioning means for positioning the bi-metallic strip in relation to the switch contacts, electrical heater means associated with the bi-metallic strip and connected so as to be energised when the load is energised, said heater means being operable in first and second modes in the first of which the heat output is higher than that when the heater means is operated in the second mode, control means for setting the heater means to its first or second mode, and an actuating member coupled to both the positioning means and the control means, the arrangement being that when the actuating member is moved in a first direction from a datum position, the control means sets the heater means to its first mode and when the actuating member is moved in the opposite direction from its datum position, the control means sets the heater means to its second mode, movement of the actuating member in either direction from the datum position causing the positioning means to move the switch contacts in relation to the bi-metallic strip in the same direction.

In one embodiment of the invention, the heater means comprises first and second electrical heaters of which the first heater is arranged to be energised whenever the load is energised, the control means being arranged to connect the second electrical heater so that it is energised when the load is energised in said first mode alone.

In one arrangement, the first electrical heater is connected in series with the switch contacts and, in use in parallel with a load, and the control means is arranged to connect the second heater in parallel with the first heater only in the second mode.

In another arrangement, said first and second electrical heaters are connected in series with each other and, in use, in series with a load, said control means being arranged to short the second heater in said second mode.

In yet another embodiment of the invention, said electrical heater means comprises an electrical heater in series with impedance means and said control means is arranged to connect said impedance means in series with said heater means only in said first mode.

Preferably, the positioning means is so arranged that movement of the actuating member in the first direction from the datum position causes movement of the switch contacts relative to the bi-metallic strip through a distance greater than that caused by movement of the actuating member through a corresponding angle or distance in the opposite direction from the datum position.

Preferably, the control means comprises a cam and a further pair of switch contacts.

Preferably, the positioning means comprises a further cam.

Preferably the actuating member comprises a spindle to which the cams are secured and a manual operable users handle dial secured to the spindle.

An embodiment of this invention will now be described by way of example only, with reference to the accompanying drawings, which is a schematic diagram of an energy regulator in accordance with this invention.

Referring to the drawing, a hot plate element 1 is connected in series with switch contacts 2 and 3 of an energy regulator. The energy regulator comprises a bi-metallic strip 4, mechanically coupled to the switch contact 3 and warmed by.

heaters 5 and 6. Each of the heaters 5 and 6 comprises a thick film printed onto a substrate, for example, as disclosed in our Patent Specification No. 1 201 537. The movable contact 2 is secured to a cam follower 7 which co-operates with a cam 8. Cam 8 is mounted on a cam spindle 9 which also carries cam 10 of an indexing mechanism and a further cam 11. A cam follower 12 co-operates with the cam 11 and is carried by a movable contact 1 3 which co-operates with a fixed contact 14. Corresponding ends of the heaters 5 and 6 are connected to the bi-metallic strip 4 which in turn is electrically connected to the junction between the hot plate element 1 and the movable contact 2.The other end of the heater 5 is connected to the terminal of the hot plate element 1 remote from the movable contact 2 so that the hot plate element 1 and the heater 5 are in parallel. The end of the heater 6 remote from that connected to the bi-metallic strip 4 is connected to the fixed contact 14 so that when contacts 1 3 and 14 are engaged heater 6 is in parallel with heater 5 whereas when they do not engage, heater 6 is disconnected from the circuit.

A user's handle dial 1 5 is coupled to the spindle 9.

In conventional manner indexing mechanism cam 10 has notches 1 6 with which a spring loaded ball 17 is engageable. The spindle 9 is shown in its datum position in which a lobe 18 on the cam 8 maintains the switch contacts 2 and 3 separated so that this is an off position.

Rotation of the spindle 9 in either direction from the datum position shown brings the cam follower 7 out of engagement with the lobe 1 8 so that the contacts 2 and 3 close and the energy regulator is brought to its on condition. The shape of the cam 11 is such that rotation of the spindle in the anticlockwise direction causes the contacts 1 3 and 14 to remain open so that only heater 5 is effective and under this condition the energy regulator acts as a conventional regulator. Thus, rotation through approximately 1 6or angular degrees in the anticlockwise direction provides output percentages from about 15% through to about 60% and then fully on. This corresponds to the designations of the dial 1 5 from "OFF", "MEDIUM", "BOiL" to "FULL".

However, during rotation of the spindle 9 in the clockwise direction, the contacts 1 3 and 1 4 are closed so that both heaters 5 and 6 are operative.

As a result a relatively large amounts of energy is outputted from the heaters 5 and 6 to the bi metallic strip 4 and the percentage output of the energy regulator falls. For this reason clockwise rotation of the users handle dial 1 5 through say 1 60O will provide output percentages from say 3% to 30% corresponding to the designations on the users handle dial 1 5 of "LOW", "SIMMER", to "MEDIUM".

The positioning of the notches 1 6 on the index cam 10 corrspond to "OFF", "MEDIUM SIMMER" and "FULL".

In the illustrated embodiment, the heaters 5 and 6 are connected in parallel with the hot plate element 1. In an alternative embodiment, heaters 5 and 6 are connected in series with each other and with the load with only the heater 5 being in the circuit when the spindle 9 is rotated in the anti-clockwise direction whereas both heaters 5 and 6 are in circuit when the spindle 9 is rotated in a clockwise direction. For this purpose, the electrical contacts 1 3 and 14 operated by the cam 11 are arranged to short-circuit the electrical heater 6 when the cam is rotated in the anticlockwise direction. Alternatively, the contacts 1 3 and 14 are replaced by a changeover switch arranged to connect the heater 6 into the circuit only on rotation of the spindle 9 in the anticlockwise direction.

In yet another embodiment, heaters 5 and 6 are replaced by a single heater connected in series with an impedance in the form of a resistance or a diode. This combined circuit of one heater and a resistance or a diode is connected either in series with the hot plate elemnt 1 or in parallel thereto.

The resistance or the diode constituting the impedance is connected in parallel with the switch operated by the cam 11 and for this purpose the contacts 13 and 14 could be used. When the switch contacts are open a reduced rate of heating will be generated by the single heater and when the switch contacts are closed a relatively high rate of heating will be generated by the single heater which is of course arranged to heat the bimetallic strip 4. It is of course arranged that the higher rate is applied when the spindle is rotated in the clockwise direction from the datum position.

The switch operated by the cam 11, instead of being arranged to short out the resistance or the diode could be replaced by a switch having a changeover function.

Claims (9)

1. An energy regulator for controlling the supply of electrical energy to an electrical load comprising a pair of switch contacts, a bi-metallic strip operably associated with the switch contacts, positioning means for positioning the bimetallic strip in relation to the switch contacts, electrical heater means associated with the bimetallic strip and connected so as to be energised when the load is energised, said heater means being operable in first and second modes in the first of which the heat output is higher than that when the heater means is operated in the second mode, control means for setting the heater means to its first or second mode, and an actuating member coupled to both the positioning means and the control means, the arrangement being that when the actuating member is moved in a first direction from a datum position, the control means sets the heater means to its first mode and when the actuating member is moved in the opposite direction from its datum position, the control means sets the heater means to its second mode, movement of the actuating member in either direction from the datum position causing the positioning means to move the switch contacts in relation to the bi-metallic strip in the same direction.

2. An energy regulator according to claim 1, wherein the heater means comprises first and second electrical heaters of which the first heater is arranged to be energised whenever the load is energised, the control means being arranged to connect the second electrical heater so that it is energised when the load is energised in said first mode alone.

3. An energy regulator according to claim 2, wherein the first electrical heater is connected in series with the switch contacts and, in use in parallel with a load, and the control means is arranged to connect the second heater in parallel with the first heater only in the second mode.

4. An energy regulator according to claim 2, wherein said first and second electrical heaters are connected in series with each other and, in use, in series with a load, said control means being arranged to short the second heater in said second mode.

5. An energy regulator according to claim 1, wherein said electrical heater means comprises an electrical heater in series with impedance means and said control means is arranged to connect said impedance means in series with said heater means only in said first mode.

6. An energy regulator according to any preceding claim, wherein the positioning means is so arranged that movement of the actuating member in the first direction from the datum position causes movement of the switch contacts relative to the bi-metallic strip through a distance greater than that caused by movement of the actuating member through a corresponding angle or distance in the opposite direction from the datum position.

7. An energy regulator according to any preceding claim, wherein the control means comprises a cam and a further pair of switch contacts.

8. An energy regulator according to claim 7, wherein the positioning means comprises a further cam.

9. An energy regulator according to claim 9, wherein the actuating member comprises a spindle to which the cams are secured and manual operable users handle dial secured to the spindle.

1 0. An energy regulator substantially as hereinbefore described with reference to the accompanying drawing.