GB2600398A

GB2600398A - Liquid heating and dispensing apparatus and method

Info

Publication number: GB2600398A
Application number: GB2016714.4A
Authority: GB
Inventors: Hunt Andrew; Reinier Nijhoff Alex; Wong Francis
Original assignee: Otter Controls Ltd
Current assignee: Otter Controls Ltd
Priority date: 2020-10-21
Filing date: 2020-10-21
Publication date: 2022-05-04
Anticipated expiration: 2040-10-21
Also published as: GB202016714D0; CN114376412A; GB2600398B

Abstract

Dispensing a predetermined volume of liquid at a required temperature by pumping liquid through a flow-through heater 4, e.g. thick-film heater, the heater and pump 2 being controlled by a controller 3. A first volume of hot liquid is dispensed in a first stage followed by a second volume of liquid at a lower temperature in a second stage, the degree of heating being influenced by a temperature sensed 5 at the outlet of the heater during the first dispensation. The heater may be energised for a predetermined time before the pump is energised and the temperature may be sensed a predetermined time after the pump is energised. There may be a stage in which steam is dispensed before initiating the first stage. The dispensing system may be suitable for preparing hot beverages such as coffee and baby or infant milk formula.

Description

Liquid Heating and Dispensing Apparatus and Method Field of the Invention [0001] This present invention relates to an apparatus and method for heating and dispensing liquid.

Background of the Invention

[0002] One type of apparatus for dispensing heated liquid comprises a flow through heater in which liquid is heated as it flows. These may be used for example for continuous or near-instantaneous dispensing of hot or boiling water, for use for example in hot water dispensers or coffee makers.

[0003] One application of such an apparatus is in dispensing water for mixing with baby milk powder to make baby milk. The water is dispensed in two stages: a first quantity of water is heated and dispensed at a high temperature, preferably above 70°C, to sterilize the milk powder, then a second quantity of water is dispensed at a lower temperature, so that the final temperature of the baby milk formula is suitable for feeding, around 38°C.

[0004] An example of a heated liquid dispenser for baby milk is disclosed in WO-A-2014/114935, in which a controller detects the temperature of water upstream of a flow-through heater, calculates how much energy is required to heat a predetermined volume of water from the detected temperature to a desired final temperature, and energises the flow-through heater for a calculated period to deliver that amount of energy to the liquid. After the heater is de-energised, the liquid flowing through the heater removes the residual heat from the heater so that the calculated amount of energy is transferred to the liquid.

[0005] The above example requires a temperature sensor upstream of the flow-through heater, as well as preferably a temperature sensor downstream of the flow-through heater, to detect the residual heat of the heater. This adds to the cost and complexity of the apparatus.

Statements of the Invention

[0006] Aspects of the invention are defined by the accompanying claims.

[0007] Embodiments of the invention relate to an apparatus and method for heating and dispensing a predetermined volume of liquid (e.g. water) using an electrically powered flow-through heater such that the temperature of the dispensed predetermined volume of liquid is at a required temperature. The apparatus comprises a source of liquid, such as a reservoir or mains supply, a pump, a flow-through heater and a controller arranged to control the pump and the flow-through heater.

[0008] A first fraction of the liquid may be dispensed at a high temperature, such as greater 10 than 700, for sterilising material, such as baby milk powder, to which the liquid is added. A second, remaining fraction of the liquid is dispensed at a lower temperature, so as to bring the temperature of the dispensed liquid down to the required temperature.

[0009] The temperature of the dispensed liquid depends on the heater power P, which is a function of the electrical resistance of the heater R and the supply voltage V: p V 2 '1? (1) The resistance R is typically constant over the life of the heater, but varies between heaters due to manufacturing tolerances, typically from +10% to -5% from the nominal value, hence giving a power variation of +5% to -10%. The voltage V depends on the power supply, which at mains voltage varies from the nominal value from +10% to -6% in Europe, giving a power variation of +21% to -11.6%.

[0010] The voltage V can be measured by the controller 3, for example by means of an AC-DC converter. The resistance R is determined during EOL (end-of-line) testing, for example by measuring the current through the heater for a given voltage V, and the value of R is made available to the controller, for example by storing the value in a non-volatile memory within the apparatus.

[0011] The temperature of the dispensed liquid also depends on the flow rate of the pump, which is dependent on the supply voltage to the pump; this can be constant or variable.

The flow rate varies between pumps but is typically constant over the life of each pump for a given supply voltage. The flow rate for the given supply voltage can be measured during EOL testing and made available to the controller. Alternatively, the apparatus may include a flow meter for detecting the flow rate and providing this as an input to the controller, although this adds to the cost of the apparatus.

[0012] The temperature of the dispensed liquid also depends on the inlet water temperature, which may vary between 5°C and 30°C. Although the inlet temperature could be monitored using a temperature sensor upstream of the heater, the inventors of the present invention have realised that it is only necessary to monitor the temperature downstream of the heater. In particular the downstream temperature, as measured a predetermined time after the pump is started and the heater is powered on, is indicative of the upstream temperature of the liquid, provided that the flow rate and heating power are accounted for. Furthermore, the amount of liquid already dispensed and the energy provided to the heater are also known at that time, and the remaining amount of liquid to be dispensed and energy required to achieve the required temperature of the dispensed liquid may then be calculated.

[0013] Preferably, the heater is pre-heated before the pump is started such that liquid already contained within the flow-through heater is heated.

100141 Preferably, the heater is a thick film flow-through heater, for example as disclosed in GB-A-2580948, comprising a thick film heating element and a channel plate fixed to the heating element so as to form a channel for heating fluid. This type of flow-through heater has a low thermal mass such that the liquid is heated quickly up to temperature when the heater is energised, and has low residual heat.

Brief Description of the Drawings

[0015] There now follows, by way of example only, a detailed description of preferred embodiments of the present invention, with reference to the figures identified below.

[0016] Fig. 1 is a schematic diagram of the main components of a liquid heating and 5 dispensing apparatus in an embodiment of the invention.

[0017] Fig. 2 is a flow diagram of a method of operation of the liquid heating and dispensing apparatus in the embodiment.

[0018] Fig. 3 is one example of a graph of outlet temperature of the flow-through heater as a function of time elapsed after energisation of the pump, for different values of inlet 10 temperature.

[0019] Fig. 4 is another example of a graph of outlet temperature of the flow-through heater as a function of time elapsed after energisation of the pump, for different values of inlet temperature and different levels of heater power.

[0020] Fig. 5 is another example of a graph of outlet temperature of the flow-through 15 heater as a function of time elapsed after energisation of the pump, for different values of inlet temperature and different levels of heater power.

[0021] Fig. 6 is a perspective view of one example of the flow-through heater in the embodiment.

Detailed Description of the Embodiments

[0022] As shown in Figure 1, liquid heating and dispensing apparatus 10 in an embodiment of the invention comprises a liquid flow path comprising a liquid supply 1, such as a reservoir or mains supply, a pump 2 for pumping liquid through the flow path, a flow-through heater 4 for heating liquid and an outlet 6, such as a dispensing nozzle or spout, through which the heated liquid is dispensed, for example into a receptacle 7 such as a baby milk bottle. A temperature sensor 5 is positioned between the flow-through heater 4 and the outlet 6, for sensing the temperature of liquid flowing from the outlet of the flow-through heater 4.

[0023] A controller 3, such as an electronic processor, receives an output of the temperature sensor 5 and controls energisation of the pump 2 and the flow-through heater 4, as described below. User input to the controller 3, and optionally a display of the operational state of the apparatus 10 is provided by a user interface (UI) 8, such as a touchscreen and/or push buttons.

[0024] Preferably, the flow-through heater 4 is powered by AC mains power. The heating power P of the flow-through heater 4 may be constant for a given supply voltage V, and switchable on and off by the controller 3. Alternatively, the heating power P may be variable by the controller 3, for example by selectively switching each of a plurality of heating tracks arranged in parallel, or by controlling the voltage supplied to the heater 4.

[0025] The pump 2 is preferably supplied by a DC voltage derived from the AC mains power, for example using an AC to DC converter. The DC voltage may be constant so as to give a constant flow rate, or variable by the controller 3 so as to vary the flow rate.

[0026] The apparatus may be operated to dispense a predetermined volume of liquid in two stages: at a first stage, a first fraction of the predetermined volume of liquid may be dispensed at a high temperature, such as greater than 70°C, for sterilising material, such as baby milk powder, in the receptacle 7. In the second stage, a second, remaining fraction of the predetermined volume of liquid is dispensed at a lower temperature, so as to bring the temperature of the dispensed liquid in the receptacle 7 down to the required temperature; in the case of baby milk formula, this may be a suitable feeding temperature such as around 38°C.

[0027] One example of a method of operation of the apparatus is shown in Fig. 2. At step Si, the user selects via Ul 8 a volume of liquid VL to be dispensed, for example between 120 ml and 330 ml. This volume may be varied in incremental steps, or the user may select one of a plurality of options corresponding to the volumes of different standard sizes of baby bottle. The user may select the required temperature of the dispensed liquid, or this may be pre-set and not variable by the user. The user then starts the dispensing operation, for example by selecting a 'start' option.

100281 At step S2 the controller 3 measures the supply voltage V as supplied to the flow-through heater 4. The resistance R of the flow-through heater 4 is known, for example it is stored in a non-volatile memory of the controller 3. The controller 3 thereby calculates or determines the power P provided by the flow-through heater 4.

[0029] The first stage of dispensing then begins. At step 53, the controller 3 energises the flow-through heater 4, so that the temperature of the flow-through heater 4 and any liquid already held within the flow-through heater 4 begins to rise. At step 54, the controller 3 waits for a predetermined time to, such as 3 seconds, before energising the pump 2 so that the liquid begins to flow through the flow path. Preferably, the pump 2 is operated at a constant rate at this stage.

[0030] At step S6, the controller 3 measures the outlet temperature as sensed by the temperature sensor 5 at one or more predetermined times. Examples of the measured outlet temperature as a function of time after energisation of the pump 2 are shown in Figs. 3 and 4, where the different lines represent the variation of outlet temperature over time for different inlet temperatures. Fig. 3 shows lines for different inlet temperatures and the same value of heating power P, while Figs. 4 and 5 show examples of lines for different inlet temperatures Ti, T2 and different values of heating power P1, P2. Fig. 5 shows an example where lines for Ti, P1 and T2, P2 cross at time 1s, so that it is necessary to sense the temperature at more than one time to distinguish the two lines.

[0031] Hence, if the heating power P is known, the inlet temperature can be deduced from a single outlet temperature measurement at a predetermined time after energisation of the pump. If the heating power P is not known, then a plurality of outlet temperature measurements at different times may be needed in order to deduce the heating power P and the inlet temperature. Hence, the controller 3 deduces the inlet temperature of the liquid from the measured outlet temperature, for example at a predetermined time after pump 2 has been energised or at intervals over a predetermined period. The controller 3 may deduce the inlet temperature from the one or more measurements of the outlet temperature, for example by using a predefined function and/or a lookup table stored in non-volatile memory.

[0032] At step 57, the controller 3 determines the energy E required to heat the predetermined volume of liquid so that it is at the required temperature when dispensed, given the inlet temperature as determined above, the controller 3 determines the amount of energy E0 already provided, from the length of time to for which the heater 4 has been energised, multiplied by the calculated heating power P. The controller 3 then determines the remaining energy requirement E-E0 such that the selected volume of liquid VL to be dispensed, including the volume of liquid already dispensed, will be at the required temperature in the receptacle 7.

[0033] The controller 3 also determines how much liquid VLo has already been dispensed 10 during the first stage, from the known flow rate of the pump 2 and the time (t1-to) for which the pump 2 has been energised.

[0034] For the remaining volume of liquid VLi to be dispensed during the first stage, the dispensing temperature must be sufficiently high, e.g. at least 70°C, to sterilise the contents of the receptacle 7. Preferably, a predetermined minimum volume of liquid must be dispensed at this high temperature, for example a predetermined fraction of the total volume of liquid to be dispensed; for example, for a total volume of 120 ml, 25 ml may be dispensed at the first stage and 95 ml at the second stage. This may be so that the material in the receptacle, such as baby milk powder, is raised above a required sterilising temperature.

[0035] At step 58, the controller 3 determines the remaining energising time for the heater 4 and/or the pump 2 during the first stage. The remaining energising time for the pump 2 may be determined so that a predetermined fraction of the required volume of liquid is dispensed during the first stage. The remaining energising time for the heater 4 may be determined such that the remaining heating energy requirement E-E0 is provided during the first stage, if this is possible for the known heating power P and for a time not greater than the energising time of the pump 2 for the first stage; otherwise, the proportion of the remaining heating energy requirement E-E0 is provided during the first stage, and the controller 3 calculates the remaining proportion of the heating energy requirement E-E0 to be provided in the second stage.

[0036] At step S9, the controller 3 de-energises the pump 2 andthe heater 4 when their respective remaining energising times have lapsed, and the first stage is complete.

[0037] At step S10, the controller 3 determines that the second stage of dispensing is to start. The user may be required to initialise the second stage via the Ul 8, for example to 5 allow the user to stir the contents of the receptacle 7 and/or to add material such as baby milk powder if this has not already been added. Alternatively, the controller 3 may start the second stage after a predetermined period of time has elapsed after the end of the first stage. Alternatively, the second stage may follow continuously from the first stage, with the second stage differing from the first stage in that the temperature of the dispensed liquid is 10 lower.

[0038] At step 511, the controller 3 energises the pump 2 for a duration required to dispense the remaining volume of water VL2, such that: VL = VLo + VLi + VL2 [0039] At step S12, the controller 3 energises the heater 4 for a duration such that the required remaining proportion of the heating energy requirement is applied to the liquid. In the case where the heating power P is variable, the heating duration may be fixed and the heating power P selected such that the required remaining heating energy is applied. In some cases, the required amount of heating energy may already have been applied in the first stage, so that no further heating is required in the second stage.

[0040] At step 513, the second stage is complete and the pump 2 is de-energised. The heater 4 may already have been de-energised during the second stage.

[0041] The required energisation times and/or heating power P for the heater during the first and second stages may be calculated by the controller 3 based on the constraints outlined above and/or may be determined from a lookup table. The values in the lookup table may be set during EOL testing, based for example on the determined flow rate of the pump 2 and resistance R of the heater 4.

[0042] The controller 3 need not calculate or determine a value of the inlet temperature T. Instead, the controller 3 may determine one or more adjustments to the energisation times of the pump 2 and/or the heater 4 based on the detected outlet temperature(s) at predetermined times during the first stage, as discussed above. In other words, the outputs of the controller 3 may be determined directly from the detected input(s) without the need to determine an intermediate value representing a variable such as the inlet temperature T. [0043] The controller 3 may have a 'self-learning function such that the values in the lookup table are adjusted after an initial running of the appliance, for example by checking the outlet temperature at intervals during the first stage of dispensing, which may be performed during a set-up operation performed by the user.

[0044] The pump 2 may be operated at a constant flow rate during the first and second 10 stages, or the flow rate may be varied by the controller 3 during either or both of the first and second stages, for example in order to control the outlet temperature while the heater 4 is energised.

[0045] Fig. 6 shows an example of a flow-through heater 4 suitable for use in the above embodiment, having an inlet 21, an outlet 22 and the temperature sensor 5 arranged to sense the temperature of the outlet 22. A liquid channel between the inlet 21 and the outlet 22 is defined between a planar thick-film heating element 23 and a channel plate 24, such that liquid flowing through the channel is heated by the heating element 23. The heating element 23 and channel plate 24 have a low thermal mass, giving a fast heating response and low residual heat.

[0046] Another advantage of the thick-film heater 4 is that it is able to dispense water at or above 100°C e.g. as steam, which can also be used to sterilise the receptacle 7. Hence, in some embodiments, the heater 4 and pump 2 may be energised before the first stage so as to deliver steam at the outlet 6.

[0047] The heater 4 preferably includes a thermal cut-out to prevent over-heating; this 25 may comprise an overheat sensor such as the E-FAST sensing technology as described in WO-A-2008/150172 Al.

Alternative embodiments [0048] The above specific embodiment is described for use in preparing baby milk, but may be used for the preparation of other drinks or foods (e.g. instant noodles), where a predetermined volume of liquid and/or final temperature is required.

[0049] Although the above description refers to two stages, distinguished by the temperature of dispensing being higher at the first stage, each of these stages may be considered as comprising a plurality of sub-stages; for example, the period of the first stage during which the outlet temperature is measured may be considered as a preliminary stage.

[0050] In some embodiments, individual features as described above may be combined or omitted. On reading the above description, the skilled person may contemplate alternative embodiments which nevertheless fall within the scope of the accompanying claims.

Claims

Claims 1. Liquid heating and dispensing apparatus, comprising a flow-through heater, a pump for pumping liquid through the flow-through heater and a controller arranged to control the operation of the pump and the flow-through heater such that: a) a volume of liquid to be dispensed and a required temperature of the dispensed liquid are determined; b) during a first stage, the pump and the flow-through heater are energised so as to dispense a first volume of liquid heated at or above a first temperature; and c) during a second stage, at least the pump and optionally the flow-through heater are energised so as to dispense a second volume of liquid at a second temperature lower than the first temperature, wherein the controller is arranged to sense an outlet temperature of the flow-through heater during the first stage and to control the energisation of the flow-through heater during the first and/or second stage in response to the outlet temperature sensed during the first stage, such that the predetermined volume of liquid is dispensed at the required temperature.
2. Apparatus of claim 1, wherein during the first stage the heater is energised for a predetermined time before the pump is energised.
3. Apparatus of claim 1 or claim 2, wherein during the first stage the outlet temperature is sensed a predetermined time after the pump is energised.
4. Apparatus of any preceding claim, wherein the supply voltage of the heater is variable and is sensed by the controller, and wherein the energisation of the flow-through heater is controlled during the first and/or second stage in response to the sensed supply voltage.
5. Apparatus according to any preceding claim, including a user interface for selecting the volume of liquid to be dispensed and/or the required temperature of the dispensed liquid.
6. Apparatus of any preceding claim, wherein the heater comprises a thick film flow-through heater.
7. Apparatus of claim 6, wherein the controller is arranged to energise the pump and the heater before the first stage, so as to dispense steam.
8. Apparatus according to any preceding claim, including an outlet temperature sensor arranged to sense the liquid temperature at an outlet of the heater.
9. Liquid heating and dispensing apparatus, comprising a flow-through heater, a pump for pumping liquid through the flow-through heater and a controller arranged to control the operation of the pump and the flow-through heater such that: a) a volume of liquid to be dispensed and a required temperature of the dispensed liquid are determined; b) during a first stage, the pump and the flow-through heater are energised so as to dispense a first volume of liquid heated at or above a first temperature; and c) during a second stage, at least the pump and optionally the flow-through heater are energised so as to dispense a second volume of liquid at a second temperature lower than the first temperature, wherein the controller is arranged to control the energisation of the flow-through heater during the first and/or second stage, such that the predetermined volume of liquid is dispensed at the required temperature; and wherein the heater comprises a thick film flow-through heater.
10. A method of heating and dispensing a liquid using a flow-through heater and a pump for pumping liquid through the flow-through heater, the method comprising: a) determining a volume of liquid to be dispensed and a required temperature of the dispensed liquid; b) during a first stage, energising the pump and the flow-through heater so as to dispense a first volume of liquid heated at or above a first temperature; and 1 3 c) during a second stage, energising at least the pump and optionally the flow-through heater so as to dispense a second volume of liquid at a second temperature lower than the first temperature, wherein an outlet temperature of the heater is sensed during the first stage and the energisation of the flow-through heater is controlled during the first and/or second stage in response to the outlet temperature sensed during the first stage, such that the predetermined volume of liquid is dispensed at the required temperature.