COFFEE MACHINE

The present invention relates to a system for removal of deposits from a heat exchanger, particularly a heat exchanger for a coffee machine.

More specifically, the invention concerns a system of the above kind permitting removal of limestone deposits from heat exchanger, through which usually passes water, in a simple way both under a functional and structural point of view.

It is known that when fresh water, from a natural supply or from a well, is heated, as it occurs in coffee machines, decomposition of calcium and magnesium bicarbonates brings to formation of carbonates, which are insoluble into the water, precipitating in a microcrystalline form, depositing on walls of the container where water heats.

Thus, the so called "limestone deposit" is formed, crusting the espresso coffee machine heat exchanger, diminishing the efficiency of thermal apparatuses directly or indirectly heating water, up to even arriving to fully clog the water passage.

Deposit is mainly due to calcium carbonate, since usually it is calcium the largest metallic element within fresh water. Crystallographic study made by X-ray refractometry and the morphologic study obtained by scanning electronic microscopy permitted discovering that higher amount of crystals formed by boiling of fresh water are comprised of aragonite, very thin crystals, beam or ray acicular comprising fibrous aggregates, firmly interweaved each other. This particular structure permits "making" solid, compact and well adhering structures, on the wall of containers having every shape. Only a chemical attack by acids (that cannot be made on metallic structures of standard implants) permits eliminating it. Micro- photography has shown that crystallized calcite (trigonal system) is present, even if in small amounts, along with aragonite (rhombic system), according to the basic rhomboedric structure. The latter structure, inserting among the aragonite needles, weakens the texture. Crystal nature is confirmed by RX spectrum (energy dispersion). If one can produce a higher number of rhombohedric calcite crystals, deposit, lacking compactness and mechanical resistance, detaches from the walls and, dragged by water current, outflows from taps under a earthy and dusty form leaving implant walls where water is heated clean.

As already said, problem of limestone deposit on the surface of a heat exchanger by sedimentation at the high temperature of calcium carbonate tends permanently obstructing calibrated ducts of espresso coffee machine heater.

When machine is used, increasing limestone deposit, water flow is gradually reduced, as well as pressure of the same, obtaining an always worse coffee quality, up to the full clogging of water passage. Different solutions have been suggested during the years in order to try to obviate the above mentioned problem.

A first solution is the one described in the Italian Patent n°

1309828, filed on April 13, 1999 in the name of Giovanni Spinelli, and concerning an "Innovation in capsule coffee machines". Solution suggested provides eliminating limestone by a rotatory motion of accelerator (22) within heat exchanger (23).

A second solution is the one suggested in the Italian Patent Application n° RM2005A000464, filed on September 9, 2005 in the name of Edilizia Web S.r.l. and Gerardo Palmieri. An evolution of the solution of the above '828 Italian Patent is described in this patent application, wherein limestone is eliminated by translation of the heater with respect to heat exchanger.

However, the Applicant has found that absolutely satisfying and better results with respect to the known solutions are obtained realizing a system permitting obtaining breaking of crystals by a uniform mechanical action of heater on the heat exchanger surface.

In fact, it is known that crystals will sediment only on the warmest part, ad this phenomenon in a coffee machine, being the heat exchanger the warmest part, since it builds in the electric resistance, occurs on said heat exchanger.

In other words, heat exchanger acts as protection against limestone for heater channels, leaving them fully free from crystals.

Heater acts as "crystal breaker" of the heat exchanger each time a coffee is prepared, so as to keep it always clean. It is therefore specific object of the present invention a system for removal of deposits from a heat exchanger, particularly a heat exchanger for a coffee machine, said machine comprising a heating element, said heating element being provided with helicoidal channels for passage of water, said system being characterized in that it further provides means for introducing water under pressure within said heating element, through a first end of the heating element, and buckling elastic means, between the second end of said heating element and the inner wall of the heat exchanger, a discharge circular channel being provided on said heating element, and on said heat exchanger being provided a passage or hole for discharge of the liquid from inside the channel of the heating element, said elastic means normally keeping the heating element in a position displaced within the heat exchanger toward the end where water enters within the same, water pressure causing the axial displacement of the heating element prevailing against the force of said elastic means, until bringing said discharge circular channel in correspondence of the discharge passage or hole of the heat exchanger, the system further providing that, once released the water pressure force, elastic means bring the heating element back in its rest position, making an action of removal of the limestone deposits accumulated along the heating element.

Preferably, according to the invention, said elastic means are comprised of a spring.

Particularly, said elastic means can be adjusted by the user. Still according to the invention, water under pressure is supplied by a pump, preferably at a pressure of about 15 bar.

Always according to the invention, clearance between said heating element and heat exchanger is about 15 mm.

The invention further relates to a method for removal of limestone deposit within a heat exchanger of a coffee machine, said heat exchanger providing inside a heating element axially movable within the heat exchange, and elastic means opposing to the motion of the heating element within the heat exchanger, said method comprising the steps of:

- introducing water under pressure within the channel of the heating element, causing a longitudinal displacement within the heat exchanger, prevailing on the resistance of said elastic means keeping said heating element normally displaced toward the inlet of pressure water; - removing the pressure on the heating element, determining crashing of limestone deposits within the heating element; - eliminating crashed limestone deposit during the following stroke of the heating element, along with the infusion water.

The present invention will be now described, for illustrative but not limitative purposes, according to its preferred embodiments, with particular reference to the figure of the enclosed drawings, wherein: figure 1 shows a scheme of the system according to the invention in a first position; figure 2 shows heater of the system of figure 1 ; figures 3 and 4 are vertical section views of heater of figure 2; and figure 5 shows a scheme of the system according to the invention in a second position.

Observing figures of the enclosed drawings, it can be observed that system according to the invention comprises a monoblock 1 , made up of food brass, or heat exchanger, suitably machined to house a brass movable ogive 2, or heater, by a screw inner working to realise channels 3 calibrated for passage and heating of water in order to obtain an infusion/expression of ground coffee.

Said exchanger 1 is provided with a hole 4, within which a heater 2 slides with a piston-like motion, in view of clearance of about 15 mm between hole 4 and heater 2.

In correspondence of the final part of heater 2, a calibrated spring 5 is provided, innerly abutting on exchanger 1 , maintaining heater 2 in the initial position. Said spring 5 advances only when a pump (not shown) for extracting coffee is activated, e.g. by a 15 bar pressure, equivalent to a force of about 15 kg/cm ² .

Thus, calibrated spring 5 is compressed displacing forward heater 2.

In the final part of heater 2 a circular discharge 6 is provided, facing on underlying hole 7 that in this embodiment has a diameter of 3.5 mm, and through which water under pressure will freely pass for extracting coffee.

Once terminated coffee extraction, and thus when pump is switched off, heater will go back to a rest state thanks to the action of the spring 5, which is no more subjected to the inlet liquid thrust. This tangential motion of about 15 mm of heater 2 with respect to exchanger 1, by abrasion, causes breaking of crystals that have created by water residuals during previous coffee extraction.

Thus, disgregation of crystalline structures, such as calcium carbonate, is obtained.

Disgregated crystal are ejected during the following coffee expression by the pump, under a pressure of about 15 bar toward capsule (not shown), acting also as a filter, keeping disgregated limestone formations, and thus not "polluting" coffee poured within the cup. The present invention has been described for illustrative but not limitative purposes, according to its preferred embodiments, but it is to be understood that modifications and/or changes can be introduced by those skilled in the art without departing from the relevant scope as defined in the enclosed claims.