Patent Description:
In the field of brewing espresso coffee, the perception of quality is strongly related to the formation of a so-called crema layer, i.e. a thin layer of foam at the top level of the espresso coffee. A requirement in the formation of the crema layer is that the brewing process in which water is forced to flow through a quantity of beverage extract, namely ground coffee beans in order to obtain the espresso coffee takes place at a sufficiently high pressure. For this reason there is utilized a pressure valve a called crema valve, which involves placing a restriction downstream of the brewing chamber, i.e. the chamber where the brewing process takes place during operation. By having such a restriction, it is achieved that the pressure in the brewing chamber is always high enough for creating the crema layer, and that the brewing time is long enough for obtaining good taste. In many practical cases, the restriction is fixed,.

Usually the crema valve being realized in the form of a spring-loaded valve, because this is simply and cheap solution, as is known from the document <CIT>, which discloses a brewing unit having a brewing chamber and a brewing piston which is equipped with a boiling water supply tube, a boiling water distribution chamber and with a boiling water distribution sieve. Piston shaped section on the underside of the carriage supplementing the brewing compartment is equipped with a brew discharge tube, a brew sieve and a brew collection chamber and a crema valve. The crema valve comprises a spring that acting on the ball pressing it towards a ball seat, and which restricts the beverage flow outside the brewing chamber, so it rises the pressure inside the brewing chamber. When the pressure inside the brewing chamber exceeds the appropriate value the crema valve is being opened for letting coffee to flow through the brew discharge tube. Both, the valve spring and the valve ball are placed in the stream of the beverage. A disadvantage of this solution is therefore that the flow is disturbed by the valve ball and the valve spring, and coffee particles can remain on the spring and be difficult to remove. Additionally, some coffee particles remain between the sieve and the crema valve, in a brew collecting chamber, during the brewing process and can be difficult to remove during the automatic cleaning process performed on the machine when the machine starts and stops, because the valve ball opens into a small flushing gap, so these particles are difficult to remove and they can block the sieve, therefore they can lead to a failure of the coffee machine.

The document <CIT> discloses an automatic coffee machine for preparation of beverages comprising a pump, a brewing system with a brewing chamber, a set of valves including a crema valve, an external controller for the valves control, a steam generator, a cleaning system and a coffee line with a coffee spout, and a blow of the steam produced by the steam generator is set to the coffee line and the coffee spout in order to clean and preheat the coffee line and the coffee spout or to the brewing chamber, the coffee line and the coffee spout in order to clean and preheat the brewing chamber, the coffee line and the coffee spout. The invention provides an automatic and efficient system for cleaning and preheating the elements of the coffee machine The cleaning and preheating system of the coffee machine influences the quality of the beverage which leads to increased consumer satisfaction. The crema valve is the spring-loaded valve, which is controlled by the external controller for cleaning and preheating issues, when the steam pressure is not sufficient to open the crema valve. The disadvantage of this solution is that the solution is complicated, requires additional expensive components, which significantly increases the production costs.

It is an object of the invention to provide a brewing unit, especially a brewing unit for the coffee machine to solve the technical problems of the prior art. More concretely, the brewing unit currently used are difficult to clean automatically and/or expensive to manufacture and requires additional expensive such as electronic controllers.

In accordance with the present invention, there is provided a brewing unit for coffee machine comprising: a brewing chamber that is opened for filing ground coffee, a brewing piston that pressure-tightly closes the brewing chamber and moves reciprocally inside it, and can be adjusted between an open position, a brewing position and a cleaning position when it is at its deepest point within the brewing chamber, an inlet port for providing fresh hot water to the brewing chamber, an outlet port for brewed coffee, fluidly communicated with the brewing piston, a pressure valve with a valve chamber, that is placed in the brewing piston downstream of the brewing chamber and upstream of the outlet port, and the brewing piston has a lever, that is pivotally mounted therein and which is coupled with the pressure valve in order to be able to open it, and a lever free end extends outside of the brewing piston and stands transversally to movement of the brewing piston, when the brewing piston reaches the cleaning position the brewing chamber engages and moves the lever.

Advantageously, the pressure valve during a cleaning process of the brewing unit, i.e. when the brewing piston is in the cleaning position can be essentially opened by mechanical coupling the portion of the brewing chamber body with the free end of the lever part of the lever which lifts and holds the valve plunger with which it is coupled, on the predetermined distance to open the pressure valve, and to ensure free flow of the water through the brewing chamber, therefore the cleaning process is more effective. Merely during the cleaning process of the brewing unit, the brewing piston reaches the deepest point of the brewing chamber, in the contrast to other stage of working as the open position and the brewing position. At the brewing position, there is a layer of ground coffee inside the brewing chamber, so the brewing piston can't reach the deepest point at the cleaning position. Therefore only at the cleaning position the mechanical coupling between the brewing chamber body with the free end of the lever is possible. That causes that the solution is reliable and simple to implement in production.

In a preferred embodiment of the invention the pressure valve comprises, a stem and a valve plunger, which are connected together, and also comprises a seat with an opening, a spring pressing the valve plunger toward the seat, acting to close the opening, wherein the stem is provided with a one-way locking mean coupling it with the lever for opening the pressure valve. The positive effect is that the pressure valve works as a fully functional, known spring loaded valve, because the one-way locking mean does not interfere possibility it opening by the pressure of the hot water during for forming the foam.

Advantageously the free end of the stem is guided by a stem guide, that is arranged in the brewing piston, wherein a second end of the stem is connected with the valve plunger. The movement of the stem is supported, what prevents the valve plunger from blocking inside the valve chamber.

In the another preferred embodiment of the invention the valve plunger is moved along side walls of the valve chamber and is provided with a sealing that divides the valve chamber into an upper portion and a lower portion of the valve chamber in a sealing manner, wherein the lower portion of the valve chamber is fluidly communicated with the outlet port, and the upper portion of the valve chamber is fluidly isolated from the outlet port. The positive effect is shortening the flow path of the fluid through the pressure valve and bypassing some of it components, which could disturb fluid flow through the pressure valve, and can destroy the foam and are difficult to clean.

Advantageously a second end of the lever is supported on a support point in the vertical direction of the brewing piston and is arranged on an inner or outer side wall of the brewing piston, that constitutes rotation point for the lever when the free end of the lever is moved by the portion of the brewing chamber body. It provides simple and reliable solution, that is easy to implement in the production. Additionally a second end of the lever can be supported at the support point in the horizontal direction of the brewing piston what prevents from sideways movement of the lever.

In a preferred embodiment of the invention the lever is placed inside the brewing piston, approximately transversely to its side walls, and is in the shape of a board or a rod, and is coupled with the pressure valve by the coupling mean between ends of the lever. The positive effect is that the solution is easy for assembling and reliable due to the small number of cooperating elements.

Advantageously the brewing piston has a body with an outer cylindrical shape, that is closed from the bottom by a bottom wall centrally having the opening, in a front of which a sieve is mounted on the bottom wall with a gap between the sieve and the bottom wall forming a brew collecting chamber, and additionally comprises the brewing chamber having an inner cylindrical shape for receiving the brewing piston, wherein a sealing arranged on the brewing piston provides tight connection for the brewing piston inside the brewing chamber. The positive effect is in that making tools for producing cylindrical parts are cheaper and faster and also a sealing reciprocally cooperating two cylindrical parts are easier and effective than on the other shape.

It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. Other advantages and features of the invention will be apparent from the following description, drawings and claims.

The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself, however, may be best understood by reference to the following detailed description of the invention, which describes an exemplary embodiment of the invention, taken in conjunction with the accompanying drawings, in which:.

A coffee machine, not further depicted here, has a brewing unit <NUM>. The brewing unit <NUM> is only represented in the Figures with the elements essential to the description of the invention.

Referring to the drawings <FIG>, a brewing unit <NUM> for coffee machine in accordance with the preferred embodiment of the present invention comprises a brewing chamber <NUM>, that is opened from above for filing ground coffee, a brewing piston <NUM> that pressure-tightly closes the brewing chamber <NUM>, and moves reciprocally inside it in a slide manner.

The brewing piston <NUM> having a body of cylindrical shape on an outside, and is closed from the bottom side by a bottom wall, having centrally arranged an opening <NUM>, in a front of which, a sieve <NUM> is mounted on the bottom wall, with a gap between the sieve <NUM> and the bottom wall, forming a brew collecting chamber <NUM>.

The brewing chamber <NUM> having a body with a chamber of a cylindrical shape for receiving the brewing piston <NUM>, wherein a sealing <NUM> arranged on the brewing piston <NUM> provides tight connection for the brewing piston <NUM> inside the brewing chamber <NUM>. The brewing piston <NUM> can be adjusted with respect to brewing chamber <NUM> between an open position, i.e. when the brewing piston <NUM> is outside of the brewing chamber <NUM>, as presented in <FIG>. At this position the brewing chamber <NUM> can be fed with ground coffee, and also the coffee grounds can be removed after brewing. Another position of the brewing piston <NUM> is a brewing position (not shown in drawings), i.e. when the brewing piston <NUM> is moved inside, toward the bottom wall of the brewing chamber <NUM>. In that position ground coffee inside the brewing chamber <NUM> is pressed by the brewing piston <NUM>. Another position is a cleaning position, then the brewing chamber <NUM> is empty, and therefore the brewing piston <NUM> reaches the deepest point within the brewing chamber <NUM> as presented in <FIG>.

The brewing unit <NUM> also comprises an inlet port <NUM> for providing fresh hot water to the brewing chamber <NUM>, an outlet port <NUM> fluidly communicated with the brewing piston <NUM> by the opening <NUM>, both are arranged for brewing and cleaning purposes. And additionally comprises a lifting piston <NUM> having series of distribution holes <NUM> for passing hot water flowing from the inlet port <NUM> towards the brewing piston <NUM>, and a lifting piston shaft <NUM>, that is sealed in a bottom of the brewing chamber <NUM> by a sealing <NUM>. The lifting piston shaft <NUM> provides a reciprocal movement back and forth of the lifting piston <NUM>, essentially for removing coffee grounds from the brewing chamber <NUM>, after brewing the coffee.

The brewing unit <NUM> is provided with a lever <NUM>, that is pivotally mounted inside the brewing piston <NUM> and extends transversally to its axis. The lever <NUM> is in the shape of a rod. A lever free end <NUM> extends outside of the brewing piston <NUM>, and stands transversally to movement of the brewing piston <NUM>, and a second end of the lever <NUM> is supported in the vertical and horizontal direction on a support point <NUM>. The support point <NUM> is arranged on an inner side wall of the brewing piston <NUM>.

The brewing unit <NUM> also comprises a pressure valve <NUM>, that is essentially responsible for forming thin layer of foam at the top level of the espresso coffee and quality of the beverage. The pressure valve <NUM> is implemented in the brewing piston <NUM>, downstream of the brewing chamber <NUM>, and located upstream of the outlet port <NUM>. The pressure valve <NUM> is a spring-loaded valve that comprises a cylindrical valve chamber <NUM>, which extends along the axis of the brewing piston <NUM>, and comprises a valve plunger <NUM>, with a stem <NUM> placed inside the valve chamber <NUM>, and also a spring <NUM> which is applied on the stem <NUM>, and that acting on the valve plunger <NUM>, pressing it towards a seat <NUM> for closing the opening <NUM>, and which restricts the beverage flow outside the brewing chamber <NUM>, so it rises the pressure inside the brewing chamber <NUM>, therefore creates conditions for the formation of foam. The stem <NUM> is provided with a one-way locking mean <NUM> coupling it with the lever <NUM> in the middle of the ends of the lever <NUM>. A free end of the stem <NUM> is guided by a stem guide <NUM>, that is arranged in the brewing piston <NUM>, wherein a second end of the stem <NUM> is connected with the valve plunger <NUM>. The valve plunger <NUM> is moved along the axis of the valve chamber <NUM> and is provided with a sealing <NUM>, that divides the valve chamber <NUM> into an upper portion and a lower portion of the valve chamber in a sealing manner. The lower portion of the valve chamber <NUM> is fluidly communicated with the outlet port <NUM>, and the upper portion of the valve chamber <NUM> is fluidly isolated from the outlet port <NUM>, therefore the flow path of the fluid has been shortened and the stem <NUM> and the spring <NUM> have been bypassed. When the brewing piston <NUM> is in the cleaning position, namely reaches the deepest point inside the brewing chamber <NUM>, a portion of the body of the brewing chamber <NUM> engages the lever free and <NUM>, and moves the lever <NUM>, which lifts the valve plunger <NUM> and the opening <NUM> is opened for cleaning the brewing unit <NUM>, as it is presented in <FIG>. In other positions of the brewing piston <NUM>, the lever free end <NUM> is not pressed, therefore only at the cleaning position the mechanical coupling between the body of the brewing chamber <NUM> with the free end <NUM> of the lever <NUM> is possible.

Advantageously, during a cleaning process of the brewing unit, i.e. when the brewing piston is in the cleaning position, the pressure valve can be essentially opened by mechanical coupling the portion of the brewing chamber body with the free end of the lever which lifts and holds the valve plunger with which it is coupled, on the predetermined distance to open the pressure valve, to ensure free flow of the water through the brewing chamber therefore the cleaning process is more effective. Additionally bypassing some of the pressing valve components, has a positive effect on the smooth fluid flow through the pressure valve for forming the layer of foam at the top level of the espresso coffee. The brewing unit has been described in conjunction with a coffee machine comprising such brewing unit. The described brewing unit having a pressure valve, that can be mechanically opened in a proper operational mode can also be employed with the same advantages for brewing units of other beverage preparation machines, in which a brewing chamber and a brewing piston, moved relative to one another, are used.

Claim 1:
A brewing unit (<NUM>) for coffee machine comprising: a brewing chamber (<NUM>) that is opened for filing ground coffee, a brewing piston (<NUM>) that pressure-tightly closes the brewing chamber (<NUM>) and moves reciprocally inside it, and can be adjusted between an open position, a brewing position and a cleaning position when it is at its deepest point within the brewing chamber (<NUM>), an inlet port (<NUM>) for providing fresh hot water to the brewing chamber (<NUM>), an outlet port (<NUM>) for brewed coffee, fluidly communicated with the brewing piston (<NUM>), a pressure valve (<NUM>) with a valve chamber (<NUM>), that is placed in the brewing piston (<NUM>) downstream of the brewing chamber (<NUM>) and upstream of the outlet port (<NUM>), characterized in that the brewing piston (<NUM>) has a lever (<NUM>) that is pivotally mounted therein and which is coupled with the pressure valve (<NUM>) in order to be able to open it, and in that a lever free end (<NUM>) extends outside of the brewing piston (<NUM>) and stands transversally to movement of the brewing piston (<NUM>), when the brewing piston (<NUM>) reaches the cleaning position, the brewing chamber (<NUM>) engages and moves the lever (<NUM>).