A dual heater appliance such as a coffee machine Technical field

The invention relates to appliances with a plurality of heating elements. One particular embodiment of the invention relates to coffee machines operable to dispense both coffee and steam. Another particular embodiment of the invention relates to irons with a hot plate and a steam station.

Background

Coffee machines are required and are currently available that produce hot water for producing coffee and also produce steam, for example for a steam wand, which may be used to steam milk. In addition, the coffee machine may be required to dispense hot water.

Recently, there has been an increasing demand from an increasing percentage of the population for coffee machines that produce high quality coffee. This increase in demand has reached the level where many households now have a coffee machine. To satisfy this demand, manufacturers of coffee machines have sought to supply coffee machines that are affordable to many households, but still produce a high quality coffee liquid.

Various types and configurations of coffee makers have been proposed in the past. However, there remains a demand for coffee makers that may be suited to domestic use that produces quality coffee.

Commercial style coffee makers typically have a plurality of dispensers, each supplied with water from a pump for that dispenser and each having their own heating elements. The dispensers may include a plurality of dispensers for dispensing coffee and one or more steam wands for steaming milk. A problem faced by designers and manufacturers of coffee machines destined for domestic use or small-scale commercial use is to obtain a speed and convenience of operation approaching that of the larger commercial style coffee makers. In attempting to achieve this goal, designers and manufacturers face problems in having to limit the size and weight of the coffee machines and face other problems.

It is an object of one embodiment of the present invention to provide a coffee machine that addresses at least one of the aforementioned problems, or at least to provide the public with a useful alternative.

It is an object of another embodiment of the present invention to provide an appliance with a plurality of heating elements that operates in a manner, which with respect to existing methods of operation, represents an improvement or useful alternative.

Summary of the invention

According to a first aspect, the invention broadly resides in a coffee machine including: first and second heater blocks both having a water input and output and a heater for receiving power and converting the power into heat to heat water received by the heater block, wherein the output of the first heater block is connected to a coffee liquid dispenser and the output of the second heater block is connected to a steam dispenser; means to supply water under pressure to the water input of the first and second heater blocks; a power supply circuit for receiving power from a power supply and supplying power to the first and second heater blocks; and a controller for the power supply circuit, the controller controlling the power supply circuit to distribute power available to heat the first and second heater blocks between the heater blocks, wherein the distribution of power is dependent on whether the coffee machine is operating to dispense coffee or steam at the time.

When the coffee machine is dispensing coffee only, the controller may power the first heater block as a first priority and power the second heater block as a second priority, The power available to heat the first and second heater blocks may be a first value and the power used for powering the first heater block may be a second value that is substantially less than the first value. The remaining power may be used to heat the second heater block as required. When the coffee machine is dispensing steam only, the controller may power the second heater block as a first priority and power the second heater block as a second priority. The power available to heat the first and second heater blocks may be

a first value and the power used for powering the second heater block may be a second value that is equal to or substantially equal to the first value.

When the coffee machine is dispensing both coffee and steam, the controller may split power between the first and second heater blocks. The controller may adjust the split of power in response to a detected temperature of the first heater block. The adjustment may maintain the temperature of the first heater block at a required temperature as a priority over maintaining the temperature of the second heater block.

The coffee machine may further include a hot water dispenser connected to the output of the first heater block and a control valve to selectively direct water from the output of the first heater block to the coffee dispenser or the hot water dispenser, wherein the controller operates the control valve to direct water to the coffee dispenser or the hot water dispenser dependent on the operation of an operator interface.

When the coffee machine is dispensing water only, the controller may power the first heater block as a first priority and power the second heater block as a second priority. The power available to heat the first and second heater blocks may be a first value and the power used for powering the first heater block may be a second value that is equal to or substantially equal to the first value.

When the coffee machine is dispensing both water and steam, the controller may split power between the first and second heater blocks. The controller may adjust the split of power in response to a detected temperature of the second heater block. The adjustment may maintain the temperature of the second heater block at a required temperature as a priority over maintaining the temperature of the first heater block.

If both the first heater block and the second heater block are below a minimum operational temperature set for each heater block, the controller may distribute power to both the heater blocks at a set proportion. The controller may prevent operation of the coffee machine until the first and second heater blocks have been heated to at least their respective minimum operational temperatures.

The coffee machine may further include a flow controller for the means to supply water under pressure and adjust the flow rate of water supplied to the first and/or second heater blocks. The flow controller may adjust the flow rate in response to a detected temperature of the first and/or second heater blocks. In addition or

alternatively, the flow controller may adjust the flow rate dependent on whether the coffee machine is dispensing coffee only, steam only or both coffee and steam. In an embodiment where the coffee machine also dispenses water, the flow controller may adjust the flow rate dependent on whether the coffee machine is dispensing water only or water and steam.

According to a second aspect, the invention broadly resides in a method of manufacturing a coffee machine, the method including: providing in a housing first and second heater blocks having respective outputs to dispensers; providing in the housing a first water pump located in a fluid path between a water supply connection and the first heater block and providing in the housing a second water pump connected between the water supply connection and the second heater block; providing in the housing a power supply that is operable to controllably power both the first heater block and the second heater block and supply power to the first and second water pumps; providing a controller for the power supply and the first and second water pumps, wherein the controller operates to provide different levels of power to the first and second heater blocks dependent on the mode of operation of the coffee machine. The provided controller may also adjust the speed of operation of the first and second water pumps dependent on the mode of operation of the coffee machine. The method may further comprise providing temperature sensors for the first and second heater blocks and the provided controller may also or instead adjust the speed of operation of the first and second water pumps dependent on signals from the first and second heater blocks.

The method may further include connecting the first heater block to a dispenser of coffee and the second heater block to a dispenser of steam.

The method may further include connecting the output of the first heater block to an input of a control valve having two outputs, one connected to a dispenser of hot water and the other connected to the dispenser of coffee.

According to a third aspect of the invention, there is provided an electric appliance including a first heating element and a second heating element, a power

supply circuit for receiving power from a power supply and supplying power to the first and second heating elements, and a controller for controlling supply of power to the first and second heating elements, wherein the controller controlling the power supply circuit to distribute power available to heat the first and second heating elements between the heating elements, wherein the distribution of power is dependent on the mode of operation of the electric appliance and wherein heating of the first heating element is given priority over heating of the second heating element in at least one mode of operation of the electric appliance.

The electric appliance may be a coffee machine and the first heating element may be used to heat water for a coffee liquid dispense and the second heating element used to heat water for steam.

The electric appliance may be a steam iron and the first heating element may be used to heat a hot plate of the iron and the second heating element used to heat water for steam. Further aspects of the present invention, which should be considered in all its novel aspects, will come apparent from the following description, given by way of preferred embodiments as presently contemplated and with reference to the accompanying drawings.

Brief description of the drawings Figure 1 : shows a block diagram of a coffee machine according to one embodiment of the present invention.

Figure 2: shows a block diagram of a control circuit for the coffee machine represented in Figure 1.

Figure 3 : shows a flow chart of a control process for supplying power to the heating blocks of the coffee machine represented in Figures 1 and 2.

Figure 4: shows a flow chart of an embodiment of a control process for distributing power to the heating blocks of the coffee machine represented in Figures 1 and 2.

Figure 5: shows a block diagram of an alternative control circuit.

Detailed description

One application of the present invention is to a coffee machine that includes a plurality of heating elements. Another possible application is to a steam iron, which includes a heating element to heat a hot plate (i.e. the surface of the iron that is pressed against clothing during use) and another heating element to produce steam.

Coffee machine

Referring to Figure 1, a block diagram of a coffee machine 1 is shown. The coffee machine 1 includes a water tank 2, which acts as a water supply to a coffee pump 3 and a steam pump 4. Alternative water supplies may be used if required, including a line to a mains pressure water supply system, or a combination of a mains supply with a tank. The coffee pump 3 and steam pump 4 respectively pump water at pressure to a coffee heater block 5 and a steam heater block 6. In an alternative embodiment, a single pump may be provided between the water tank 3 or other water source and coffee heater block 5 and a steam heater block 6, with an appropriate valve arrangement downstream of that pump to direct the water to the appropriate heater block.

The coffee heater block 5 is connected to a first valve 7, which directs water received from the coffee heater block 5 to one of a group head/handle 9, a hot water dispenser 10 or a drip tray 12. The steam heater block 6 is connected to a second valve 8, which directs water or vapour from the steam heater block 6 to either a steam wand 11 or the drip tray 12.

Figure 2 shows a block diagram of circuitry 100 for the coffee machine 1. The circuitry 100 controls the operation of the coffee pump 3, steam pump 4, coffee heater block 5, steam heater block 6, first valve 7 and the second valve 8. In the embodiment shown, the circuitry 100 includes five inputs 20 - 24:

• a coffee user control 20, which is a button or other device that indicates that the user requires the coffee machine 1 to pump water through the group head/handle 9;

• a steam wand user control 21, which may be a dial, button, mechanical valve or other device that when operated by the user indicates a requirement for the coffee machine 1 to supply steam to the steam wand 11 ;

• a water dispenser user control 22, which indicates that the user requires hot water to be supplied to the hot water dispenser 10;

• a coffee heater block temperature sensor 23, which provides a feedback circuit to allow control over the temperature of the coffee heater block 5; and • a steam heater block temperature sensor 24 allows feedback control of the temperature of the steam heater block 6.

The five inputs 20-24 are connected to a control circuit 25, including a controller 26 and a pulse width modulation (PWM) controller 27. The control circuit 25 may be formed by any suitable computational devices, for example a microcontroller including or connected to a dedicated PWM controller. The controller 26 receives input signals from the input devices 20-24 and provides control signals to the output devices 28-32. In addition, alternative methods of control to PWM control may be used, including proportional integral derivative (PID) control or using a thermostat. Other alternatives will be apparent to a person skilled in the relevant arts. The output devices 28-32 are:

• a coffee pump drive 28, which receives a control signal from the controller 26 and operates within a range of speeds dependent on the received control signal;

• a steam pump drive 29, which controls the speed of the steam pump 4; • a coffee heater block heater 30, which receives current from a power supply

(not shown) under the control of the PWM controller 27;

• a steam heater block heater 31 for the steam heater block 6; and

• valve actuators 32 for the first valve 7 and the second valve 8,

For example, if the coffee heater block 5 overheats, as detected by the coffee heater block temperature sensor 23, then the controller 26 may operate the first valve 7 to direct water from the coffee heater block 5 to the drip tray 12 and cause the coffee pump 3 to pump water to the coffee heater block 5 until it has reached the required operating temperature.

Figure 3 shows a flow diagram of an example control process for the coffee machine 1 as implemented by the circuitry 100, in particular the control circuit 25.

The process commences at step 50, with the coffee machine 1 being powered on. Following this, the coffee machine 1 warms up the coffee hear block 5 and the steam heater block 6. The PWM controller 27 may split and/or distribute the available power between the coffee heater block heater 30 and the steam heater block heater 31. For. example, 40% of the available power may be provided to the coffee heater block heater 30 and 60% to the steam heater block heater 31. If for example, the coffee heater block 5 needs to be heated to a temperature of approximately 92 degrees Celsius and the steam heater block 6 heated to a temperature of approximately 165 degrees Celsius, then the uneven splitting of power between the blocks may result in the blocks reaching the required temperature at approximately the same time. The splitting of power may be achieved by splitting a proportion of the available power to each heater block so that power is constantly fed to each heater block, or alternatively may be achieved by switching the available power between the heater blocks so that each block is cycled on and off with a duty cycle dependent on its share of the available power.

The controller 26 detects when the coffee heater block 5 and steam heater block 6 have reached the operating temperature by receiving a signal from the coffee heater block temperature sensor 23 and steam heater block temperature sensor 24. If one of the heater blocks reaches the operating temperature before the other, the controller 26 may cause the PWM controller 27 to redistribute supply of current to the heater block it to reach operating temperature, for example by sending 100% of the available power to that heater block.

Once the coffee heater block 5 and the steam heater block 6 have been heated to their respective operating temperatures, or a time-out period expires, as determined in decision step 52, the process proceeds to step 53 in which the controller 26 determines whether the coffee or water is on. This is indicated by a signal received from the coffee user control 20 or the water dispenser user control 22.

In the exemplary coffee machine 1 described, the hot water dispenser 10 and group head/handle 9 operate from the same heater block and the coffee machine 1 allows only one to be operated at a time. In an alternative embodiment a further heater block may be provided to allow independent operation of the group head/handle 9 and

the hot water dispenser 10. This alternative embodiment may require additional power when coffee, water and steam are provided simultaneously.

If it is determined that coffee or water is required, the process proceeds to step 54 and the controller 26 determines whether steam is also required, as indicated by a signal received from the steam wand user control 21. If steam is not required, the controller 26 causes the PWM controller 27 to fully power the coffee heater block heater 30 (step 55).

Step 55 may involve providing less than the total available power to the coffee heater block heater 30. This may provide improved control characteristics for the coffee heater block 5, particularly if there is a lag between the actual temperature of the coffee heater block 5 and detection of the temperature by the coffee heater block temperature sensor 23. For example, if an available power supply for both heater blocks is 2,300 Watts (which result from a 2,400 Watt supply to the coffee machine 1, less about 100 Watts to drive the pumps, control circuit and other devices), the PWM controller 27 may supply approximately 1 ,200 Watts to the coffee heater block heater 30 when increasing the temperature of the coffee heater block 5, which may reduce overshoot of the target temperature than if 2,400 Watts was used.

If the water is on all available power, in this example 2,300 Watts, may be provided to the coffee heater block heater 30, to allow increased speed and heating. Often there are less stringent requirements for the temperature for water supplied to the hot water dispenser 10 in comparison to those for the group head/handle 9, which may allow increased tolerance to overshoot.

Different power levels to the coffee heater block heater 30 may be used if required. The selection of the appropriate power level to supply to the coffee block heater supply circuit 30 may depend on the lag in the control system. A smaller lag may allow a higher amount of power to be supplied to the coffee heater block heater 30.

If in decision step 54 the controller 26 determines that the steam wand user control 21 is on, the process proceeds instead to step 56 and the control circuit 25 distributes power between the coffee heater block heater 30 and the steam heater block heater 31. This process is described in more detail herein below in relation to Figure 4.

The process then proceeds to step 57 and the controller 26 controls the speed of operation of the coffee pump 3 and the speed of the steam pump 4, dependent on the temperature of the coffee heater block 5 and the steam heater block 6, as detected by the coffee heater block temperature sensor 23 and the steam heater block temperature sensor 24 respectively. For example, if one of the blocks drops below a required temperature, the respective pump may be slowed down to reduce the flow of water into that heater block. Similarly, the pump speed may be increased as the temperature of the heater block increases.

Returning to step 53, if the controller 26 determines that neither coffee nor water is required, the process proceeds to step 58 and the controller 26 determines whether steam is required. If not, the process cycles around steps 53 and 58 and the control circuit 25 maintains the temperature of the coffee heater block 5 and the steam heater block 6 at their respective required holding temperatures in a process similar to step 51. The holding temperatures may be the same as the operating temperatures, or may be less to conserve some power while still reducing any delay before reaching the operating temperature.

If it is determined at step 58 that steam is required, the control circuit 25 supplies full available power to the steam heater block heater to 31 (step 59). Taking the previously described example, this would result in 2,300 Watts being provided to the steam heater block heater 31. The control circuit 25 then also controls the speed of operation of the steam pump 4 as required to maintain the temperature of the steam heater block 6 (step 57).

Switching between fully powering the heater blocks and distributing power between the heater blocks may provide increased speed of operation and may also provide improved steam generation than if power was permanently distributed between the heater blocks. Providing the ability to power the coffee heater block heater 30 at two levels may provide increased control for coffee dispensing and increased speed for water dispensing. The ability to distribute power to the coffee heater block 5 and steam heater block 6 may have the further advantage of allowing both to be operated simultaneously. This may be achieved by providing a lower flow rate of steam at the steam wand 11, as controlled by a reduced pump speed of the steam pump 4.

Figure 4 shows the flow diagram of a process that may be performed at step 56 in the process shown in Figure 3. When the controller determines that coffee or water is required simultaneously with steam (as determined in steps 53 and 54 in the process shown in Figure 3), the control circuit 25 initially splits the available power between the coffee heater block heater 30 and the steam heater block heater 31 , for example in a proportion of 40% to the coffee heater block heater 30 and 60% to the steam heater block heater 31 (step 56A). This may represent the default arrangement when cycling around steps 53 and 58.

The process then proceeds to step 56B and the control circuit 25 determines if coffee is required and the temperature of the coffee heater block 5 is low. If yes, the control circuit 25 ensues that the coffee heater block 5 is fully powered and only the remaining power is supplied to the steam heater block 6. For example, if the available power to the both heater blocks is 2,300 Watts the power to the coffee heater block 5 maybe increased from about 920 Watts, being 40% of 2,300 Watts to about 1,200 Watts.

In alternative embodiments, there may be no change in the power supplied to the coffee heater block heater 30, which may be powered at a constant level. In other alternative embodiments, the control mechanism may be linear or provide more than two levels, so that the lower the temperature drops away from the required operating temperature, the more power is supplied to the coffee heater block heater 30.

If the coffee is not on and/or the temperature of the coffee heater block 5 is not low, the process proceeds from step 56B to step 56D and the control circuit 25 determines whether the water is on and the temperature of the steam heater block 6 is low. If yes, the process proceeds to step 56E and full power is provided to the steam heater block heater 31 , at least temporarily to assist in fast heating of the steam heater block 6, at the detriment of some cooling of the coffee heater block 5. This process therefore results in a higher priority given to steam generation than to hot water generation.

The steam heater block heater 31 may be fully powered until the coffee heater block temperature sensor 23 indicates that the coffee heater block 5 has fallen to a certain "switch-on" temperature, which may be slightly less than the normal temperature when power would be supplied to the coffee heater block 5 for supplying

water. Alternatively, the "switch-on" temperature may be the same for when only water is being dispensed and for when both water and steam are being dispensed, but this temperature may be less than the "switch-on" temperature for the coffee heater block 5 when coffee is being dispensed. In an alternative embodiment where linear control is provided or the power can be stepped up and down at more than two levels, the power to the steam heater block heater 31 may be increased and the power to the coffee heater block heater 30 reduced.

In one embodiment of a coffee machine 1 that has an available power supply of 2,400 Watts, requires 100 Watts for operations other than the heater blocks, and currently has all heater blocks at the required operating temperatures, the PWM controller 27 may supply power to the heating blocks 5, 6 as shown in Table 1.

Table 1

If one of the heater blocks falls below a required operating temperature in hot water and steam mode or in coffee and steam mode, then the power distribution may be varied to allow faster compensation. The coffee heater block 5 may be given priority when the coffee machine 1 is in coffee and steam mode and the steam heater block 6 may be given priority when the coffee machine 1 is in hot water and steam mode. Steam iron

Referring to Figure 5, a simplified circuit diagram of a steam iron 200 in accordance with an embodiment of the invention is shown. The steam iron 200 may

include user controls of hot plate temperature control 70, for setting the temperature of the hot plate and a steam control 71 for controlling the amount of steam produced. Both of these may be a dial, turned to the required setting by the user. The steam iron may also include a steam blast control 72, for providing a short blast of additional steam. The steam iron 200 also includes a power and switching circuit 73, which receives power from a power supply (VCC) and switches it between a hot plate heater 74 and a steam station heater 75.

The power supply and switching circuit 73 receives temperature signals for the hot plate from the hot plate sensor 76 and temperature signals for the steam station from the steam station sensor 77. The temperature signals may be from a thermistor, thermocouple, thermostat, pressure switch or other suitable device.

The hot plate heater 73 is given 'priority' over the steam station heater during most operations. Under this priority arrangement, all available power is directed to the hot plate heater 74 when it is required to bring the hot plate up to a required temperature, which depends on the setting of the hot plate temperature control 70. When the hot plate heater 74 is not in use, in other words the hot plate sensor 76 indicates that the hot plate is at its set point (allowing for any hysteresis cycle built into the power supply and switching circuit), then power is made available to the steam station heater 75 whenever it is needed. This priority arrangement may optionally be reversed whenever the steam blast control 72 is operated. By reversing this arrangement a prolonged supply of steam may be available than if the steam iron did not reverse the priority arrangement.

Two possible control methodologies which involve reversing the priorities of the heater blocks dependent on operation of the steam blast control 72, are represented in Table 2. In Table 2 T _H is the current hot plate temperature, Ts is a the set point temperature dependent on the hot plate temperature control 70, and Tc is a control temperature below Ts. In this arrangement, Tc is used to avoid overshoot of the set point when the hot plate heater 74 is heating the hot plate. When the temperature reaches Tc, heating is either stopped or slowed (depending on the selected control methodology), which allows for any time lag in the system. Again, the table assumes an available power supply to the heating elements of 2300 Watts.

Table 2

Alternative control methods

In addition to the control methods for the coffee machine and steam iron described herein above, further alternative methods may be used.

For example, the heaters may be each assigned a priority, with the highest priority heater taking 100% of the available power whenever required. The next highest priority heater than takes 100% of the available power when required and if not already being supplied to the highest priority heater. This continues for any third priority heater. For example, in the coffee machine 100, using this simplified arrangement, the coffee heater block 5 may be given priority over the steam heater block 6 and the control make independent of operation of the user controls. In the steam iron 200, the hot plate heater 74 may have priority over the steam station heater 75.

In another embodiment where the supply of power to the priority heater is proportionally controlled, as the priority heater approaches its set point, the power

supplied to that heater may be progressively reduced. For example, in one embodiment, the control system may be a first order system.

If a lower priority heater requires power during the time when power to the priority heater is reduced, then the power reduction to the priority heater is matched by a power increase to the lower priority heater.

It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention. Where in the foregoing description reference has been made to features or components having known equivalents, then those equivalents are hereby incorporated herein as if individually set forth.

Those skilled in the relevant arts will appreciate that modifications and reference may be to the embodiments described herein without departing from the scope of the invention.