COFFEE BREWING APPARATUS

Abstract

The invention concerns a full automatic coffee machine (100) comprising a coffee extraction unit (10) with: a brewing chamber (1) for receiving coffee powder, an upper piston (2), a lower piston (3) movable inside said brewing chamber (1) between a lowest position and a highest position wherein the lower piston (3) comprises a piston rod (31), which comprises an internal channel (311) extending from a channel inlet (311a) at the lateral wall surface of the rod to a channel outlet (311b) at the bottom wall surface of the rod, and wherein the channel inlet (311a) is designed and positioned on the lateral wall surface of the rod so that said channel inlet (311a) overlaps the bottom wall (11) of the brewing chamber only when the lower piston is in the highest position.

Claims

1. Full automatic coffee machine comprising a coffee extraction unit, said coffee extraction unit comprising: a brewing chamber for receiving roasted and ground coffee powder, said chamber comprising an upper rim, a bottom wall and a water inlet, an upper piston, said upper piston being configured to be movable through the upper rim of the brewing chamber and inside the brewing chamber further to the relative movement of the brewing chamber and the upper piston, and said upper piston comprising a liquid outlet duct, a lower piston movable inside said brewing chamber between: a lowest position wherein the lower piston lies on the bottom wall of the brewing chamber, and a highest position wherein the lower piston is at the upper rim of the brewing chamber, the lower piston comprises a piston rod, said piston rod extending through the bottom wall of the brewing chamber, and the piston rod comprises an internal channel extending from a channel inlet at the lateral wall surface of the rod to a channel outlet at the bottom wall surface of the rod, and the channel inlet is designed and positioned on the lateral wall surface of the rod so that said channel inlet overlaps the bottom wall of the brewing chamber only when the lower piston is in the higher position.

2. Full automatic coffee machine according to claim 1, wherein the machine comprises a waste liquid collector and the channel outlet at the bottom wall surface of the rod is connected to said waste liquid collector.

3. Full automatic coffee machine according to claim 1, wherein the brewing chamber is made movable by a driver.

4. Full automatic coffee machine according to claim 3, wherein: the upper piston is fixed, the rod of the lower piston comprises a free bottom end located outside the brewing chamber and movable with said piston and said chamber, the apparatus comprises a fixed bottom stop wall configured to contact the bottom end of the rod of the lower piston, the movement of the lower piston depends on the movement of the brewing chamber and/or the contact of the free bottom end with the bottom stop wall or the contact of the lower piston with the upper piston.

5. Full automatic coffee machine according to claim 1, wherein the rod and the lower pistons are provided with a friction member to control their movement with respect to the internal walls of the brewing chamber.

6. Full automatic coffee machine according to claim 1, wherein the fixed bottom stop wall comprises a channel configured to connect the channel outlet of the internal channel of the rod with a draining pipe.

7. Full automatic coffee machine according to claim 1, wherein the brewing chamber is fixed and the upper and lower pistons are movable inside and out of the brewing chamber by driving means.

8. Full automatic coffee machine according to claim 1, wherein the apparatus comprises a discharge device for spent coffee

9. Full automatic coffee machine according to claim 1, wherein the apparatus comprises a pressurized hot water fluid system comprising at least a water supply, a water heating device and a water pump wherein said system is connected to the water inlet of the brewing chamber.

10. Method for preparing a coffee beverage with a full automatic coffee apparatus comprising the steps of: ain a dosing position, wherein a lower piston is in a lowest position inside a brewing chamber and an upper piston is at a distance from an upper rim of a chamber and outside the chamber, supplying a dose of roasted and ground coffee powder into the brewing chamber, then bmoving the chamber and the upper piston relatively one to the other to compress the dose of coffee powder, then cintroducing hot water through a water inlet, extracting the coffee powder and dispensing extracted coffee beverage through a beverage outlet of the upper piston, then dmoving the chamber, the upper piston and the lower piston relatively one to the other in order to: position the upper rim of the chamber away from the upper piston, and position the lower piston at the upper rim of the brewing chamber, and discharging the extracted coffee powder from the lower piston, and dispensing residual liquid present at a bottom of the chamber through an internal channel of a rod of the lower piston.

11. Method according to claim 10, wherein said method comprises, after step d), at least one further step e) comprising the step of moving the chamber, the upper piston and the lower piston relatively one to the other in a closed position, wherein the lower piston is in the lowest position and the upper piston closes the chamber.

12. Method according to claim 10, wherein said method comprise at least one further step before step a) is implemented, this step comprising: moving the chamber, the upper piston and the lower piston relatively one to the other in order to: position the upper rim of the chamber away from the upper piston, and position the lower piston at the upper rim of the brewing chamber, and introducing hot water through the water inlet in order to purge a hot water fluid line and dispensing said hot water through the internal channel of the lower piston.

13. Method according to claim 10, wherein said method comprises further steps before step a) is implemented: moving the chamber, the upper piston and the lower piston relatively one to the other in order to: close the chamber with the upper piston, and position the lower piston inside the brewing chamber so that the channel inlet of the internal channel is positioned below the bottom wall of the chamber, and introducing hot water through the water inlet in order to fill at least a part of the internal volume of the brewing chamber defined between the upper piston and the lower piston, then moving the chamber, the upper piston and the lower piston relatively one to the other in order to position the lower piston at the upper rim of the brewing chamber, in order to dispense said volume of hot water through the internal channel of the lower piston, then moving the chamber, the upper piston and the lower piston relatively one to the other to the dosing position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0102] Specific embodiments of the invention are now described further, by way of example, with reference to the following drawings in which:

[0103] FIG. 1A illustrates the hot water fluid system of a coffee extraction unit according to the state of the art,

[0104] FIGS. 2 and 3 illustrate the coffee extraction unit of the full automatic coffee machine according to the present invention in two different operating steps,

[0105] FIGS. 4A and 4B is a view and a cross section of a lower piston according to the invention,

[0106] FIG. 5 illustrates the steps of preparation of a coffee beverage with a coffee extraction unit such as described above,

[0107] FIG. 6 illustrates the hot water fluid system with a coffee extraction unit according to the invention,

[0108] FIGS. 7 and 8 illustrate the steps that can be implemented before the steps of FIG. 5 when no coffee beverage has been prepared for a certain period.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0109] FIG. 1 illustrates the hot water supply line of the coffee extraction unit 10 according to the state of the art WO2016116981. The coffee extraction section corresponds to a bottom-up configuration wherein water is introduced at the bottom of the brewing chamber 1 and coffee beverage is dispensed at the top through line 21. The line comprises successively at least: [0110] a hot water tank 101, [0111] a pump 102 [0112] a flowmeter 103, [0113] a final hot water fluid line 7 connected to the water inlet of the brewing chamber part of the coffee extraction unit 10.

[0114] The water pipe is never drained completely due to the curvature in the machine and is one of the identified cause of the too cold water entering in the brewing unit. This portion of pipe is estimated to contain approximately 2 ml of water.

[0115] In order to evacuate residual liquid retained at the bottom of the brewing chamber 1 after a coffee extraction, a three-way valve 106 is provided in the hot water supply line which enables the draining of residual liquid through the final hot water fluid line 7 down to the three-way valve 106 and then to the drain 8.

[0116] As mentioned in the above section background of the invention, this draining through the final hot water fluid line 7 presents serious drawbacks.

[0117] FIGS. 2 and 3 illustrate schematically the coffee extraction unit 10 of the full automatic coffee machine according to the present invention in two different operating steps.

[0118] In FIG. 2, the coffee extraction unit 10 is represented in a step of coffee extraction or of pre-heating of the chamber, whereas in FIG. 3, the coffee extraction unit 10 is represented in a step of evacuation of coffee cake at the end of the sequence of operations for the preparation of a coffee beverage.

[0119] The coffee extraction unit 10 comprises a brewing chamber 1 for receiving a dose of coffee powder, usually roasted and ground coffee. Preferably, the brewing chamber 1 is a cylinder with an open top extending from a bottom wall 11 to un upper rim along an axis XX substantially vertical. The chamber 1 comprises a water inlet 13 to which a hot water fluid line is connected. The water inlet 13 is preferably positioned close to the bottom of the chamber such as inside the lower part of the lateral wall as illustrated in FIG. 2 or optionally in the bottom wall.

[0120] The coffee extraction unit 10 comprises driving means 6 to move vertically the chamber 1 up and down For example, the chamber 1 can be mounted on a worm drive by motor means. Rotation of the worm causes vertical translation of the chamber.

[0121] The coffee extraction unit 10 comprises an upper piston 2. This upper piston 2 presents a lower end portion presenting a cylindrical design and having a diameter substantially equal to the diameter of the chamber so that the upper piston is able to pass through the upper rim 12 of the chamber and inside the brewing chamber further to the movement of the brewing chamber upwardly in direction of the upper piston. Accordingly, the upper piston enables the closure of the brewing chamber during the coffee extraction (FIG. 2) and the compression of a dose of roasted and ground coffee powder introduced inside the brewing chamber. Coffee powder can be introduced inside the chamber by means of a chute (not illustrated) guiding the dose of power in direction of the open top of the chamber.

[0122] In addition the upper piston 2 comprises a liquid outlet duct 21 extending from the bottom surface of the upper piston and connected to a coffee beverage dispensing line.

[0123] The coffee extraction unit 10 comprises a lower piston with a head 32 comprising water outlets 34 configured for distributing water introduced through the water inlet 11 in the bottom surface of compressed coffee positioned above the head of the lower piston (FIG. 2). This head acts as water supplier. A water distributor (not illustrated) is positioned above to distribute water through the coffee powder.

[0124] This type of piston for bottom-up extraction where water is introduced by the bottom created a large dead volume at the bottom of the chamber and prevents the evacuation of all. It has been observed that up to 3 ml of water remain trapped at the bottom of the brewing chamber.

[0125] The head is disc-shaped and has a diameter substantially equal to the inner diameter of the chamber cylinder. The lower piston 3 comprises a rod 31 fixed to the bottom of the disc-shaped head 32 and that extends downwards. The piston 3 is assembled to the chamber with the rod 31 extending through an opening in the bottom wall of the chamber.

[0126] The rod 31 of the lower piston is free from guiding means, retaining means spring wherein the lower piston is co-axially movable with the brewing chamber and within said brewing chamber.

[0127] Usually a mesh filter (not illustrated) is placed at the upper surface of the head of the lower piston to retain coffee particles.

[0128] The lower piston 3 is movable inside the brewing chamber 1 between two end positions [0129] a lowest position wherein the lower piston lies on the bottom wall 11 of the brewing chamber (FIG. 2) and [0130] a higher position wherein the lower piston is at the upper rim 12 of the brewing chamber (FIG. 3).

[0131] The coffee extraction unit 10 comprises a discharge device 4 to sweep away a coffee cake that has been extracted (FIG. 3). It is positioned slightly above the upper rim of the brewing chamber. Coffee cake that has been swept away is stored in a cake receiving section.

[0132] In the present illustrated embodiment, the upper piston 2 is fixed. The lower piston 3 is co-axially movable: [0133] with the brewing chamber 1, which means that when the chamber 1 moves, it takes the lower piston simultaneously with it, and [0134] within the brewing chamber 1, which means that the lower piston can be moved at different positions inside the brewing chamber. The movement of the lower piston 3 inside the brewing chamber is driven by the contact of the disc-shaped member 32 of the piston rod against the upper piston 2 when the brewing chamber moves upwards and by the contact of the bottom end 312 of the piston rod of the lower piston against a bottom stop wall 5 when the brewing chamber moves downwards. When the lower piston 3 is stopped in its course upwardly by the upper piston 2, the continuous upwards movement of the chamber enables the relative movement of the piston 3 inside the chamber, the same happens with the bottom stop wall during the downwards movement of the chamber.

[0135] The rod 31 of the lower piston 3 comprises an internal channel 311 extending from a channel inlet 311a at the lateral wall surface of the rod to a channel outlet 311b at the bottom wall surface of the rod. This channel provides a fluid communication from the channel inlet 311a down to channel outlet 311b.

[0136] The channel inlet 311a is designed in size and shape and positioned on the lateral wall surface of the rod so that, when the lower piston 3 is in its higher position (FIG. 3), then the channel inlet 311a crosses and faces the edge of the hole of the brewing chamber in which the rod is engaged, forming a liquid outlet. Consequently, in this higher position, any waste liquid present in the chamber is able to flow through the channel inlet 311a and down the channel 311 to the channel outlet 311b. In place of being evacuated through the water inlet 11, waste liquid is evacuated through the rod of the piston eliminating the problems of contamination of the water supply.

[0137] The bottom stop wall 5 comprises a channel 51 that cooperates with the channel outlet 311b of the rod connected to a tube to conduct waste liquid to a collector of waste liquid, such as drip tray.

[0138] The channel inlet 311a is designed in size and shape and positioned on the lateral wall surface of the rod so that, when the lower piston 3 is in the other operating position like coffee dosing, brewing, pre-heating, then the channel inlet 311a is positioned below the bottom wall 11 of the brewing chamber. Consequently, in the other positions (like the position illustrated in FIG. 2), no liquid is able to blow through the channel inlet 311a.

[0139] FIG. 4A is a perspective view of such a lower piston 3. The disc-shaped head 32 comprises multiple water outlets 34 to distribute water through the surface of compressed coffee placed above. Usually a circular seal is positioned in the circumferential notch 33 to provide tightness during extraction.

[0140] FIG. 4B is vertical cross section of the rod of the piston: it makes apparent that the rod 311 is empty which provides a channel 311 for waste liquid.

[0141] FIG. 5 illustrates the different steps of the method for preparing a coffee beverage with a full automatic coffee apparatus comprising a coffee extraction unit such as described above.

[0142] Step a) corresponds to a dosing operation where the chamber is in position O) wherein the lower piston 3 is in the lowest position inside the brewing chamber and the upper piston 2 is at a distance from the upper rim 12 of the chamber. In this position a dose of roasted and ground coffee powder can be introduced through the top of the brewing chamber.

[0143] In step b) the brewing chamber 1 and the upper piston 2 are moved one relatively to the other to compress the dose of coffee powder.

[0144] In step c), hot water is introduced in the brewing chamber through the water inlet 71, it is distributed by the head of the lower piston through the compressed coffee powder. Coffee powder is extracted and the extracted coffee beverage 91 is dispensed through the beverage outlet inside the upper piston.

[0145] Then in step d), the brewing chamber 1 is moved downwardly which has the effect of withdrawing the upper piston 2 from the chamber. During the downwards movement of the chamber, the bottom end of the rod of the lower piston is stopped by the stop wall and, as a result, the lower piston 3 is moved upwardly inside the chamber up to the upper rim of the chamber. As illustrated, when the lower piston 3 is in its upper position in the chamber, the coffee cake 92 is positioned above the upper rim of the chamber and can be swept away.

[0146] Simultaneously the inlet 311a of the internal channel of the rod 31 creates an outlet for waste liquid 72 present in the chamber. This liquid 72 is evacuated through the rod and emerges from the outlet 311b.

[0147] In a last step e), the chamber 1, the upper piston 2 and the lower piston 3 are moved relatively one to the other in order to close the chamber with the result of keeping the chamber warm for the preparation of the next coffee beverage.

[0148] FIG. 6 illustrates schematically the hot water fluid system with a coffee extraction unit 10 according to the invention. The line comprises successively at least: [0149] a cold water tank 101, [0150] a flowmeter 103, [0151] a pump 102 [0152] a heater 104, [0153] a valve 105, [0154] a final hot water fluid line 7 connected to the water inlet of the brewing chamber part of the coffee extraction unit 10.

[0155] Waste liquid retained at the bottom of the brewing chamber 1 after a coffee extraction is evacuated through the rod of the lower piston directly to a collector of waste liquid. The inlet of the discharge channel created in the rod of the lower piston acts as a passive valve that opens automatically when the lower piston is in its higher position inside the brewing chamber. All water in the dead volume can be drained out towards a waste liquid collector like the drip tray.

[0156] This passive valve enables the implementation of steps of improving the preparation of the first coffee beverages prepared after a long period during which no coffee beverage has been prepared with the consequence that the brewing chamber and the water retained in the water supply line are cold.

[0157] In particular, when no coffee has been prepared for a certain time, certain additional steps can be implemented for the first new prepared coffee. This certain time can be for example 15 minutes, but it may be possible for the operator to define this period in a setting menu of the machine since machines can differ in their environment (hot or cold) and construction.

[0158] FIG. 7 illustrates an additional step a.sub.0) that can be implemented before preparing a new coffee in order to improve the temperature of supplied water if no coffee has been prepared for a certain period.

[0159] Starting from the illustrated dosing position O) wherein the lower piston 2 is in the lowest position inside the brewing chamber and the upper piston 3 is at a distance from the upper rim 12 of the chamber, the chamber 1, the upper piston 2 and the lower piston 3 are moved one relatively to the other in order to: [0160] position the upper rim 12 of the chamber away from the upper piston 2, and [0161] position the lower piston 3 at the upper rim 12 of the brewing chamber.

[0162] Then hot water 71 is introduced through the water inlet 1 in order to purge the hot water fluid line 7. Since the inlet 311a of the internal channel of the rod 31 creates an outlet for liquid present in the chamber, introduced water 71 is evacuated immediately through the rod and emerges from the outlet 311b. As result, cold water retained in the water supply line is removed before a new coffee beverage is prepared.

[0163] Then, the coffee preparation can start as illustrated by the steps of FIG. 5 after positioning the different elements of the brewing chamber in the dosing position.

[0164] When no beverage is prepared during a certain time, the control unit of the coffee machine can be configured to automatically move the brewing unit 1 to the position illustrated in step a.sub.0) of FIG. 7 in order to be ready to purge cold water from the water supply line 7 when a coffee will be ordered.

[0165] FIG. 8 illustrates other additional steps that can implemented before preparing a new coffee in order to improve the temperature of supplied water if no coffee has been prepared for a certain period. These steps can be implemented after step a.sub.0) or independently; it may depend on the location of the coffee machine and in particular on the external environmental conditions.

[0166] Starting from the illustrated dosing position O) wherein the lower piston 3 is in the lowest position inside the brewing chamber and the upper piston 2 is at a distance from the upper rim 12 of the chamber, in a step a.sub.1) the chamber 1, the upper piston 2 and the lower piston 3 are moved one relatively to the other in order to: [0167] close the chamber 1 with the upper piston 2, and [0168] position the lower piston 3 inside the brewing chamber 1 so that the channel inlet 311a) of the internal channel is positioned below the bottom wall 11 of the chamber. In these positions of the different elements of the unit 10, the brewing chamber is closed and no liquid can drain from the bottom.

[0169] Then hot water is introduced through the water inlet 13 inside the internal volume of the brewing chamber defines by the upper and lower pistons in order to fill at least a part of the internal volume of the brewing chamber defined between the upper piston 2 and the lower piston 3.

[0170] Then hot water 71 is kept inside the brewing chamber with the effect of pre-heating the chamber. A small volume of hot water presenting a temperature comprised between 80 and 95 C. can be kept in the chamber during a time sufficient to pre-heat the chamber as if a coffee had been prepared recently. For example, 25 ml of water at 80-95 C. kept for 15 seconds inside a plastic coffee espresso chamber of a diameter 45 mm were sufficient to pre-heat said chamber for the preparation of a first coffee.

[0171] After this pause, in a step a.sub.2), the chamber 1, the upper piston 2 and the lower piston 3 are moved one to the other in order to position the lower piston 3 at the upper rim 12 of the brewing chamber, in order to dispense the volume of hot water through the internal channel 311 of the lower piston. Then, in this position, hot water is introduced through the water inlet 13 in order to purge the hot water fluid line 7 and this hot water is immediately evacuated through the internal channel 311 of the lower piston.

[0172] Then, in a step a.sub.3), the chamber 1, the upper piston 2 and the lower piston 3 are moved one relatively to the other to the dosing position O), before a coffee preparation starts, as illustrated in FIG. 5.

[0173] The effect of heating the chamber with hot water and purging the hot water supply line from stagnating water improves drastically the preparation of the first cups of coffee after the machine is cold and has not dispensed coffee for a certain time.

[0174] The time of preparation of the first coffee with the sequence of pre-warming the chamber increases the time of preparation by less than 20 seconds. The first coffee presents the same organoleptic properties as following coffees prepared from the warm chamber.

[0175] The present invention presents the advantage of enabling the upgrade of existing machines by simply replacing the lower piston of the chamber by a new piston and adapting the software of the control unit of the machine commanding the movement of the brewing chamber and the dispensing of water. This upgrade does not increase the machine cost and can be implementable easily.

[0176] Another advantage is that new full automatic coffee machines can be produced with a simple one-way valve in place of the three-way valve in the hot water supply line which reduces the costs of production. Moreover, the invention prevents residual water to flow back to this one-way valve with the risk of clogging or bad sealing of this valve after a certain time.

[0177] Another advantage is that the removal of waste liquid from the chamber through the rod of the piston does not create a discharge of a splashing volume of coffee beverage generated in the prepared cup as observed during the opening of a three-way valve according to prior arts (due to drop of pressure). The drainage of the chamber is not perceived by the coffee consumer.

[0178] Although the invention has been described with reference to the above illustrated embodiments, it will be appreciated that the invention as claimed is not limited in any way by these illustrated embodiments.

[0179] Variations and modifications may be made without departing from the scope of the invention as defined in the claims. Furthermore, where known equivalents exist to specific features, such equivalents are incorporated as if specifically referred in this specification.

[0180] As used in this specification, the words comprises, comprising, and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean including, but not limited to.

LIST OF REFERENCES IN THE DRAWINGS

[0181] coffee extraction unit 10 [0182] brewing chamber 1 [0183] bottom wall 11 [0184] upper rim 12 [0185] water inlet 13 [0186] upper piston 2 [0187] outlet duct 21 [0188] lower piston 3 [0189] piston rod 31 [0190] internal channel 311 [0191] inlet 311a [0192] outlet 311b [0193] head 32 [0194] friction means 33 [0195] water outlets 34 [0196] discharge device 4 [0197] bottom stop wall 5 [0198] channel 51 [0199] driving means 6 [0200] hot water fluid line 7 [0201] water 71 [0202] residual liquid 72 [0203] liquid collector 8 [0204] roasted and ground coffee 9 [0205] coffee beverage 91 [0206] coffee cake 92 [0207] coffee machine 100 [0208] water tank 101 [0209] pump 102 [0210] flow meter 103 [0211] heater 104 [0212] valve 105 [0213] three-way valve 106