This invention relates to a device for preparing a dose of ground coffee powder ready for infusion.

This device of known type generally comprises a pressing piston and a cup provided with a gripping handle and housing a filter having delimiting walls delimiting an open chamber for collecting the dose of ground coffee powder.

The cup is releasably coupled with a support and receives the pressing piston to close the open chamber delimited by the walls of the filter.

In the closing step, the dose of ground coffee powder contained in the filter is pressed.

After pressing, the cup is uncoupled from the support and coupled with the infusion head of the coffee machine.

Many of these known pressing systems often have the problem of dispersal of the coffee powder outside the cup because for pressing they require the cup to be moved from the zone of collection of the ground coffee to the pressing zone.

For this reason, systems have been proposed that implement in the same position of the cup the function of collecting the ground coffee and the pressing function.

In these systems, to avoid dispersal of the coffee powder, a conveying conduit can be provided for conveying the coffee powder that supplies the filter.

The pressing piston can in this case run inside the conveying conduit and inside the filter.

A critical factor in these known devices is that the pressed dose of ground coffee may detach from the walls of the filter because of the vacuum that is generated in the gap between the piston and the pressed dose of ground coffee powder during the step of disengagement of the pressing piston from the filter and ascent along the conveying conduit.

When this occurs, there is inhomogeneous extraction of the coffee because the infusion water, instead of traversing the pressed dose of ground coffee uniformly, may find preferential paths precisely along the zone where the detachment occurred.

When preferential paths of the infusion water are established, in general also the infusion pressure falls with the inevitable consequence of a further deterioration of the organoleptic properties of the infused coffee.

The technical task addressed by the present invention is accordingly to make a device for preparing a dose of ground coffee powder ready for infusion that enables the decried technical drawbacks of the prior art to be eliminated.

Within the context of this technical task, an object of the invention is to make a device of the aforesaid type that is adapted to optimize the infusion step.

Another object of the invention is to make a device of the aforesaid type adapted to reduce or eliminate dispersal of the ground coffee powder outside the filter holder cup.

Another object of the invention is to make a device of the aforesaid type adapted to simplify and accelerate pressing of the ground coffee present in the filter holder cup.

The above technical task and these and other objects according to the present invention are reached by making a device for preparing a dose of ground coffee powder ready for infusion, comprising a cup provided with a gripping handle and housing a filter containing said dose of ground coffee powder, a coupling support in which said cup is coupled separably, and a pressing piston that is engageable in said filter for pressing said dose of ground coffee powder, characterized in that said pressing piston has anti-detachment means configured to prevent the detachment of said pressed dose of ground coffee powder from the walls of said filter when said pressing piston disengages said filter.

In one preferred embodiment, said anti-detachment means comprises a filtering element that is selectively permeable to the air but not to said ground coffee.

In one preferred embodiment, said filtering element is fitted to the head of said piston.

In one preferred embodiment, said anti-detachment means further comprises air channels that terminate on the head of said pressing piston behind said filtering element.

In one preferred embodiment, said air channels are permanently connected to the outer environment at atmospheric pressure.

In one preferred embodiment, said support has a vertical cylindrical conveying conduit for conveying said dose of ground coffee to said filter.

In one preferred embodiment, said pressing piston has a scraping perimeter gasket for scraping the inner side of said vertical cylindrical conveying conduit.

In one preferred embodiment, said scraping perimeter gasket is configured to form a tight seal with the inner side of said vertical cylindrical conveying conduit and with the inner side of a cylindrical wall of said filter positioned on the axial extension downwards towards the inner side of said vertical cylindrical conveying conduit. In one preferred embodiment, the device comprises a coffee grinder for coffee beans comprising a dispensing slide for dispensing ground coffee having an outlet in said conveying conduit.

In one embodiment, the piston can be movable to engage with and disengage from said filter whilst the cup remains stationary.

In another embodiment, the cup can be movable to engage with and disengage from said piston with said filter whilst the piston remains stationary.

In one embodiment, automatic movement means can be provided for moving said piston or said cup to engage and disengage said piston with said filter.

In another embodiment, manual movement means can be provided for moving said piston or said cup to engage and disengage said piston with said filter.

In one embodiment, the device can be integrated into a coffee machine.

In one embodiment, the device can be integrated into a standalone grinding apparatus.

In one embodiment, the pressing piston acts also as an infusion piston.

Advantageously, owing to the provision of suitable anti-detachment means, the compressed dose of coffee powder adheres perfectly and uniformly to the walls of the filter until the moment in which the infusion takes place. This avoids the risk that preferential paths may be created for the infusion water with the result that the infused coffee has optimal organoleptic properties.

Advantageously, the provision of suitable anti-detachment means makes possible the use of a cup both with a double wall filter, where the risk of detachment is less because a wall of the filter has only one small calibrated hole that prevents the passage of a quantity of air sufficient to promote the detachment, and with a single- wall filter that permits better extraction of the coffee but that, having a plurality of evenly distributed holes, has a greater risk of detachment.

Other characteristics of the present invention are defined, further, in the following claims.

Further characteristics and advantages of the invention will more fully emerge from the description of a preferred but not exclusive embodiment of the device for preparing a dose of ground coffee powder ready for infusion according to the invention, illustrated by way of indicative and non-limiting example in the accompanying figures of the drawings, in which: figure 1 shows a coffee machine that incorporates a device in accordance with one embodiment of the invention; figures 2 and 3 show a vertical section of the device with the pressing piston disengaged and engaged in the cup; figure 4 shows a perspective view from below of the sectioned pressing piston; figure 5 shows a perspective view from below of the sectioned pressing piston with the filtering element dismantled; figures 6a, 6b and 6c show a plan and raised side view of the filtering element, and an enlarged detail thereof; figure 7 shows a perspective view of the filtering element; figure 8 shows the filtering element sectioned orthogonally along a diametric plane; and figure 9 shows an enlarged detail of figure 6.

With reference to the figures, a device 2 is illustrated for preparing a dose 100 of ground coffee powder ready for infusion. The device 2 comprises a pressing piston 15 and a cup 3 provided with a gripping handle 13 and housing a filter 4 having delimiting walls 4a, 4b delimiting an open collecting chamber 101 for collecting the dose of ground coffee powder 100.

The bottom wall 4a of the filter 4 has a plurality of uniformly distributed holes through which the coffee infusion passes that then flows to least one dispensing spout 14 of the infused coffee provided at the base of the cup 3.

The side wall 4b of the filter 4 that delimits the opening of the chamber 101 is cylindrical and has the maximum diameter of the filter 4.

The cup 3 is coupled separably with a support 7, in particular with a bayonet coupling system comprising outer fins 11 of the cup 3 that are lockable in suitable guides 12 provided in the support 7 by a roto-translation movement upwards of the cup 3.

The pressing piston 15 is engageable to close the open chamber 101 to press the dose of ground coffee powder 100.

Advantageously, the pressing piston 15 has an anti-detachment means of the pressed dose of ground coffee powder 100 from the walls 4a, 4b of the filter 4 that delimit the chamber 101.

The anti-detachment means, as will be seen better below, is operational when the pressing piston 15 disengages the filter 4.

The anti-detachment means comprises a filtering element 102 that is selectively permeable to the air but not the ground coffee present in the filter 4.

The filtering element 102 is fitted to the head 15a of the pressing piston 15.

The filtering element 102 specifically comprises a slightly convex flat support 102a having a uniform or non uniform distribution of first holes 102b, and a mesh 102c fixed to the flat support 102a and having a uniform or non uniform distribution of second holes 102d of smaller dimension than the first holes 102b.

The flat support 102a has the shape of a disk and is fixed concentrically to the head 15a, which is also circular in shape, of the pressing piston 15.

More precisely, the flat support 102a is housed in a circular recessl5c of joined shape provided on the head 15a of the pressing piston 15.

The depth of the circular recess 15c is equal to the thickness of the flat support 102a, which is thus flush with the outer surface of the head 15a of the pressing piston 15.

The flat support 102a has in turn a concentric circular recess 102f that houses the mesh 102c, which is also flat and circular and has a thickness that is less than the thickness of the flat support 102a.

The depth of the circular recess 102f is equal to the thickness of the mesh 102c that is thus arranged flush with the outer surface of the flat support 102a.

The second holes 102d have a diameter comprised between 0.05 mm and 0.20 mm.

The diameter of the second holes 102 is less than the diameter of the grains of coffee powder that can thus not traverse the mesh 102c.

The first holes 102b have a dimension comprised between 0.8 mm and 3 mm.

The flat support 102a has a thickness comprised between 0.4 mm and 0.6 mm whereas the mesh 102c has a thickness comprised between 0.05 mm and 0.7 mm.

Centrally, the flat support 102a and the mesh 102c have a raised flared hole 102e for fixing the filtering element 102 by a screw 104 to the head 15a of the pressing piston 15.

The filtering element 102 can be made of metal, in particular stainless steel, or also of another material.

For greater dimensional precision, the calibrated holes 102b, 102d present on the filtering element 102 can be made by photo-engraving technique.

In order to assemble the mesh 102c on the support 102a, the outer perimeter edge of the mesh 102c can be welded continuously and the inner perimeter edge of the mesh 102c can be spot welded to the wall of the recess 102f.

Other assembly technologies for assembling the mesh 102c on the support 102a are possible, for example perimeter heading can be performed.

The anti-detachment means also comprises air channels 103 that terminate on the head 15a of the pressing piston 15 behind the filtering element 102.

The air channels 103 can be permanently connected to the outer environment at atmospheric pressure.

Alternatively, the air channels 103 can be closed inside the pressing piston 15.

In the illustrated case, the air channels 103 terminate on the head 15a of the pressing piston 15, in particular at a further drop 15d of the bottom of the recess 15c.

The drop 15d is circular and concentric on the recess 15c and delimits an air chamber 15e precisely behind the filtering element 102.

The support 7 has a vertical cylindrical conduit 16 for conveying the dose of ground coffee powder 100 to the filter 4.

The pressing piston 15 is positioned inside the vertical cylindrical conveying conduit 16 and has a scraping perimeter gasket 17 for scraping the inner side 16a of the vertical cylindrical conveying conduit 16.

The scraping gasket 17 removes the coffee powder beans that remain attached to the inner side 16a of the vertical cylindrical conveying conduit 16 making the beans fall directly into the filter 4.

The scraping perimeter gasket 17 is configured to form a tight seal with the inner side 16a of the vertical cylindrical conveying conduit 16 and with the inner side of the cylindrical side wall 4b of the filter 4 positioned precisely on the axial downward extension of the inner side 16a of the vertical cylindrical conveying conduit 16.

The conveying conduit 16 and the cylindrical side wall 4b of the chamber 101 are positioned continuously in relation to one another so as not to leave escape paths open for the coffee powder transiting to the filter 4.

Preferably, along the conveying conduit 16, an outlet 10 opens of a dispensing slide 9 of ground coffee connected to a grinder 8.

The device 2, as illustrated, can be incorporated into a coffee machine 1.

Nevertheless, it must be pointed out that, unlike what has been illustrated, the device 2 can also be a structurally and functionally autonomous unit that is completely separate from the coffee machine 1.

The pressing piston 15 can even be specially structured to also act as an infusion piston.

In the solution illustrated, it is the piston 15 that is moved to perform pressing of the dose of ground coffee powder when the cup 3 is coupled with the support 7.

For this purpose, a linear movement mechanism is provided of the pressing piston 15 in the conveying conduit 16.

This mechanism is able to actuate reversibly the pressing piston 15 between a pressing position in which the pressing piston 15 is inside the cup 3 and a rest position in which the pressing piston 15 is above the outlet 10 of the slide 9.

The movement mechanism comprises a rotatable manual control lever 19 and a transmission that transforms rotation of the control lever 19 in a vertical translation of the pressing piston 15.

The pressing force exerted by the piston 15 can be regulated by elastic friction exerted by an elastic clutch that connects the lever 19 to the transmission.

The transmission can comprise specifically a gear formed by a vertical rack 20 that is solidly constrained to the pressing piston 15 and an arc of a cogwheel 21 supported rotationally by a horizontal mechanical axis 22 connected to the control lever 19 and engaging the vertical rack 20.

Naturally, it is possible to provide alternatively a non-manual but automatic or semiautomatic control of the pressing piston.

In order to perform pressing of the dose of ground coffee powder, in other solutions it is possible to provide moving of the cup 3, in particular by moving the support 7 thereof whilst the pressing piston 15 remains stationary.

The device 2 performs a work cycle comprising in sequence a first loading step of loading the dose of coffee powder into the filter 4, a second step of descent of the pressing piston 15, and a third step of lifting the pressing piston 15 above the outlet 10 of the slide 9.

In the first step of the work cycle, the pressing piston 15 is in a raised position above the outlet 10 of the slide 9.

Once the dose of ground coffee has been dispensed to the filter 4 housed in the cup 3 coupled with the support 7, the user can rotate the control lever 19 in the direction that causes vertical downward translation of the pressing piston 15 in the conveying conduit 16.

The pressing piston 15 in the initial step of the descent with the gasket 17 scrapes and cleans the inner side 16a of the conveying conduit 16 and in the final step of the descent engages in the filter 4 and performs pressing of the dose of ground coffee powder present in the filter 4.

Normally, before being able to uncouple the cup 3 from the support 7 and being thus able to couple the cup 3 with the end of the infusion unit of the coffee machine 1 , the pressing piston 15 is returned to the initial position raised above the outlet 10 of the slide 9.

During the ascent of the pressing piston 15, a progressively growing volume opens between the head 15a of the pressing piston 15 and the pressed dose of ground coffee powder present in the filter 4.

During the ascent of the pressing piston 15, the gasket 17 of the pressing piston 15 further creates a tight seal against the cylindrical wall 16a of the conveying conduit 16.

Despite the seal exerted by the gasket 17, in this space of constantly increasing volume no persistent vacuum is created that, if present, could generate significant upward suction force on the pressed dose of ground coffee powder.

In fact, as the volume of said space increases, the decrease of inner pressure is promptly compensated by the inflow of air thereinto drawn through the air channels 103 and the filtering element 102.

The pressed dose of ground coffee powder does not therefore detach from the walls 4a, 4b of the filter 4 and does not promote the formation of preferential paths of the water through the detachment zones during infusion. In practice, with the present invention a device is provided that, without dirtying, enables a dose of ground coffee powder to be loaded and pressed correctly in the filter 4 of the cup 3 ready to be subjected to a correct infusion procedure.

The device thus conceived is susceptible of numerous modifications and variants falling within the scope of the inventive concept; moreover, all the details are replaceable by technically equivalent elements.

In practice, the materials used, as well as the dimensions, can be any according to the needs and the state of the art.