FlagploIn 3 2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Control assembly The following statement is a full description of this Invention, including the best method of performing it known to us: 2 Control assembly Field of the Invention The present invention relates to a control assembly. The present invention is particularly suitable for use with appliances which incorporate a water boiler, such espresso 5 machines, however is not limited to such an application. Background of the Invention Many coffee making appliances (such as espresso machines) include a water boiler. When the appliance is used to make a beverage, such as coffee, water is heated or boiled in the water boiler by a heater and pumped from the water boiler to the 10 appropriate component of the apparatus (e.g. a group head filled with coffee grounds or similar). Typically the water boiler also acts as a water reservoir. Water is pumped into the boiler from an external water supply and heated, either continually or on demand, in the boiler. Operation of the heater when there is insufficient water in the boiler can be both 15 damaging to the boiler and appliance and present a safety risk. To minimise the chances of the heater (such as an electric element) operating when insufficient water is present, some water boilers are provided with a control assembly which includes a sensor and control assembly. The sensor senses the water level in the boiler and if it falls below a predetermined level automatically activates a pump to 20 replenish the water in the boiler from the external water supply. While such control assembly's assist in preventing operation of the heater with insufficient water present, they do not serve to prevent this entirely. For example, if the sensor or water pump malfunctions, or the external water supply runs dry, the boiler may also run dry and not be replenished from the external water source.
3 Accordingly, it would be desirable to provide a water boiler with features operative to reduce the likelihood of the heater of the boiler operating when there is insufficient water in the boiler. Reference to any prior art in the specification is not, and should not be taken as, an 5 acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in Australia or any other jurisdiction or that this prior art could reasonably be expected to be ascertained, understood and regarded as relevant by a person skilled in the art, Summary of the Invention 10 In one aspect the present invention provides a control assembly for a boiler including a fluid reservoir, a water inlet controller and a heater, the control assembly including: a first sensor arrangement having a first field of operation and which, if activated, prevents operation of the heater; a second sensor arrangement having a second field of operation and which, if 15 activated, activates the water inlet controller; a third sensor arrangement having a third field of operation and which, if activated, deactivates the water inlet controller; and a float carrying an activator, the float having a range of travel such that as the float moves through its range of travel the actuator passes within the first, second and 20 third fields of operation to, respectively, activate the first second and third sensor arrangements. In a second aspect the present invention provides a control assembly for a boiler including a fluid reservoir, a water inlet controller and a heater, the control assembly including: 4 a first sensor arrangement being a magnetic sensor arrangement and having a first field of operation and which, if activated, prevents operation of the heater; a second sensor arrangement being a magnetic sensor arrangement and having a second field of operation and which, if activated, activates the water inlet controller; 5 a third sensor arrangement being a magnetic sensor arrangement and having a third field of operation and which, if activated, deactivates the water inlet controller; and a float carrying an activator, the actuator being a magnet and the float having a range of travel such that as the float moves through its range of travel the magnet passes within the first, second and third fields of operation to, respectively, activate the 10 first second and third magnetic sensor arrangements. The water reservoir may have a water level which rises and falls as water is pumped into and out of the reservoir, and the float may rise and fall with the water level. The float may be located within the fluid reservoir. The first, second and third sensor arrangements may be vertically aligned, the second 15 sensor arrangement being located above the first sensor arrangement at a predetermined minimum water level, and the third sensor arrangement being located above the second sensor arrangement at a maximum water level. The first second and third sensor arrangements may be located in a cylinder in the water reservoir, and the float may encircle the cylinder and travel up and down the 20 cylinder as the water level in the reservoir rises and falls. The first sensor arrangement and/or the second sensor arrangement and/or the third sensor arrangement may each includes two sensors. The first, second and third sensor arrangements may include Reed switches. The first, second and third sensor arrangements may include Hall effect sensors.
5 The heater may be an electric heating element. The water inlet controller may be selected from a group including a pump and a valve, The control assembly may further include a boiler controller, and when activated the first sensor may send a first signal to the boiler controller $ causing the boiler controller to prevent operation of the heater, when activated the second sensor may send a second signal to the boiler controller causing the boiler controller to activate the water inlet controller, and when activated the third sensor may send a third signal to the boiler controller causing the boiler controller to deactivate the water inlet controller. 10 The present invention also extends to an espresso machine or other appliance including a control assembly as described above. Brief description of the drawings An embodiment of the invention will be described with reference to the accompanying drawings In which: 15 Figure 1 provides a perspective view of a boiler including a control assembly in accordance with an embodiment of the invention; Figure 2 provides a plan view of the boiler of figure 1; Figure 3 provides a cross-sectional view of the boiler of figure 1 along line IlIl - ill of figure 2: 20 Figure 4 provides a cross-sectional view of the boiler of figure 1 along line IV - IV of figure 2; and 6 Figure 5 provides a functional block diagram of the boiler controller of the boiler of figure 1. Detailed description of the embodiments Figures 1 to 4 provide various views of a boiler 100 including a control assembly 102 in 5 accordance with an embodiment of the invention. The boiler 100 includes a base 104 and wall 106 which, together, define a water reservoir 108. The boiler 100 also includes a cover 110 (which has been omitted from figure 1 for clarity) which supports the various components of the boiler 100, 10 The components of the boiler include: * the control assembly 102 S a heater 112 * a water inlet pipe 114 S a water outlet pipe 116 15 * steam outlet pipe 118 * a pressure relief elbow 120 * an earth terminal 122 The heater 112 in this embodiment is an electric heater and includes a positive terminal 124 and a negative terminal 126 which are connected to a heater coil 128 located in the 20 water reservoir 108. Each of the positive terminal 124, negative terminal 126 and earth terminal 122 are connected to a power source (not shown) which heats the coil 128.
7 The heater 112 is connected to, and operated by, a boiler controller 502 (discussed In further detail in relation to figure 5). The water inlet pipe 114 is connected to an external water source (not shown) and a water inlet controller 504 (depicted in figure 5). The water inlet controller 504 controls 5 the flow of water into the reservoir 108 and is also connected to and operated by the boiler controller 502. The external water source may, for example, be a tap, in which case the water inlet controller is a valve operable to allow/prevent flow of water into the reservoir 108. As an alternative example the external water source may be a water container that can be 10 easily filled by a user, in which case the water inlet controller may be a pump operable to pump water from the container into the reservoir 108. The water outlet pipe 116 is connected to an outlet pump 506 (depicted in figure 5) which is connected to and controlled by the boiler controller 502. When heated water is required by the appliance with which the boiler 100 is being used (e.g. an espresso 15 maker), the controller 502 operates the outlet pump 506 to pump heated water out of the reservoir 108. The control assembly 102 includes a shaft 130 and a float 132. The float 132 encircles the shaft 130 sufficiently loosely to allow the float 132 to travel up and down the shaft 130 as the water level in the reservoir 108 rises and falls. The shaft 130 is provided with 20 a bottom stop 142 and a top stop 144 which limit the travel of the float 132. The shaft 130 houses first second and third sensing arrangements, 134, 136, and 138, each of which is connected to the boiler controller 502. The float 132 carries an actuator 140 capable of activating the sensing arrangements 134, 138 and 138. In the present embodiment each sensing arrangement 134, 136 and 138 includes a pair 25 of magnetic sensors such as Reed switches or Hall Effect sensors, and the actuator 140 carried by the float 132 is a magnet. By providing a pair of sensors for each sensing 8 arrangement 134, 136 and 138 rather than a single sensor the reliability of the control assembly 102 is increased. Each sensing arrangement 134, 136 and 138 is placed at a pre-determined position in the column and has a field of operation - i.e. a field inside which the sensing S arrangement can sense the actuator 140. As the water level in the reservoir 108 rises and falls the float 132 (and therefore actuator 140) travels up and down the shaft 130 in which the sensing arrangements 134, 136 and 138 are housed. As the float 132 and magnet 140 pass a particular sensing arrangement that sensing arrangement is activated and an appropriate signal (as described further below) sent to the boiler 10 controller 602. While the present embodiment has been described with each sensing arrangement including a pair of sensors, it would of course be possible to use a single sensor for each arrangement. Further, while magnetic sensors activated by a magnet have been described alternative sensing arrangements (such as inductive sensors activated by an 16 electric field or mechanical sensors triggered by a mechanical activation means) could also be used. Further, while the sensing arrangements have been described as being housed in a column, the arrangements could equally be provided elsewhere in the boiler 100 (e.g. carried by the wall 106 of the boiler 100). In this case movement of the float 132 could 20 (for example) be constrained by a channel or similar in fluid communication with the reservoir 108. Referring to figure 5, a logical view of the boiler control system 500 is provided. The boiler control system 500 includes a boiler controller 502 which is connected to: * the heater 112 26 the water inlet controller 504 * the water outlet pump 606 9 * the first sensing arrangement 134 * the second sensing arrangement 136 * the third sensing arrangement 138 The boiler controller 502 may be programmed to operate the heater 112 and water 5 outlet pump according to the type of appliance with which the boiler 100 Is to be used. The boiler controller 502 may be one and the same as the controller for the appliance or, alternatively, may receive control signals from an appliance controller to operate the various components of the boiler 100. The boiler controller 502 may be implemented in a microcontroller or, alternatively, using analog electronics. 10 For example, if the boiler 100 is installed in an espresso machine 600 (as shown in figure 6), a user will typically be able to select an operation mode by which a cup of coffee is made. For this operation the boiler controller 502 may be configured (or an appliance controller configured to send control signals to the boiler controller 502) to heat water in the reservoir 108 to a particular temperature and then pump a certain 15 amount of that water to a water outlet (such as a group head filled with coffee grounds or similar). In addition to controlling ordinary operation of the appliance in which the boiler 100 is used, the boiler controller 502 operates to automatically control the water inlet controller 504 and the heater 112 in accordance with signals received from the first, second and 20 third sensing arrangements 134, 136, and 138. As discussed above, as the water level in the reservoir 108 rises and falls, so to does the float 132, thereby activating the first second and third sensing arrangements 134, 136 and 138 (depending on the water level and height of the float 132). If there is no or very little water in the reservoir 108 the heater 112 should not be 25 activated, No or very little water in the reservoir 108 may be a result of a faulty or broken water inlet controller 504 (i.e. a fault or broken pump or valve), or of the external 10 water source (e.g. tap or water container) having no water. Operating the heater 112 with little or no water is not only a waste of electricity, but may present a safety risk, When there is no or very little water in the reservoir 108 the actuator 140 in the float 132 will lie within the field of operation of the lowermost first sensing arrangement 134 and 5 trigger the first sensing arrangement 134. When the first sensing arrangement 134 is triggered a first control signal is sent to the boiler controller 502, on receipt of which the boiler controller 502 sets a flag to prevent operation of the heater 112. This flag overrides any other signal the boiler controller 502 may receive requesting operation of the heater 112. 10 Noting that a signal will only be sent to the boiler controller 502 by the first sensing arrangement 134 if there is insufficient water in the reservoir 108, the boiler controller may also be configured to attempt activation of the water inlet controller 504 on receipt of the first control signal, The boiler 502 may also begin a countdown timer and if the second control signal (described below) is not received within this time the boiler 15 controller 502 may be programmed to interpret this as an indication that the water inlet controller 504 is indeed faulty or broken, desist in attempting to activate the water inlet controller 504 (and, if desired, shut down all other operations of the appliance with which the boiler 100 is being used). On receipt of the first control signal the boiler controller 502 may also provide an 20 indication (via an appliance display panel or similar) that a fault has occurred and the water reservoir 108 is empty. The second sensing arrangement 136 is positioned within the shaft 130 at a minimum water level height - i.e. the lowest water level at which the heater 112 should be operated. During operation of the boiler 100 or appliance, the float 132 may carry the 25 actuator 140 into the field of operation of the second sensing arrangement 136. This will occur either as water is introduced into the reservoir and the float 132 rises away from the first sensing arrangement 134 and towards the second sensing arrangement 136, or as water is pumped out of the reservoir 108 (via the outlet pump 606) and the float 132 II falls away from the third sensing arrangement 138 and towards the second sensing arrangement 136. When the actuator 140 triggers the second sensing arrangement 136 a second control signal is sent to the boiler controller 502. On receipt of the second control signal the 5 boiler controller activates the water inlet controller 504. If the flag preventing operation of the heater 112 has been set by the boiler controller (indicating that there has previously been a delay or fault in filling the reservoir 108) receipt of the second control signal will also cause this flag to be removed and any timer cancelled, thereby allowing regular operation of the heater 112 by the boiler controller 502 or apparatus controller, If 10 a fault message had been displayed by the boiler controller 502 this will be hidden on receipt of the second control signal. The third sensing arrangement 138 is positioned within the shaft 130 at a maximum water level height - i.e. a height at which the reservoir 108 is full. If the float 132 carries the actuator 140 into the field of operation of the third sensing arrangement 138 the third 15 sensing arrangement sends a third control signal to the boiler controller 502. On receipt of the third control signal the boiler controller 502 will deactivate the water inlet controller 504, thus preventing overfilling of the reservoir 108, As will be appreciated, in "normal" operation of the boiler 100 the water level in the reservoir 108 (and hence the float 132 and actuator 140) will travel only between the 20 second and third sensing arrangements 136 and 138. As water is pumped out of the reservoir 108 the water level will drop until the second sensing arrangement 136 is triggered, at which point the water inlet controller 504 will be activated and the reservoir 108 replenished to the maximum water level (at which point the water Inlet controller 504 is deactivated). 25 The first sensing arrangement 134 will only be triggered in the event that there is insufficient water in the reservoir. This may be due to a fault with the water inlet controller 504, with the external water source, or merely due to the boiler 100 being new or not having being used for some time.
12 While the boiler 100 of the present invention has, above, been described for use with an espresso maker or similar, it will of course be appreciated that the boiler 100 may alternatively be used with other appliances which require heated or boiling water to be delivered on demand. 5 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.