CA2181246A1 - Pot-shaped permanent filter cartridge - Google Patents
Pot-shaped permanent filter cartridgeInfo
- Publication number
- CA2181246A1 CA2181246A1 CA002181246A CA2181246A CA2181246A1 CA 2181246 A1 CA2181246 A1 CA 2181246A1 CA 002181246 A CA002181246 A CA 002181246A CA 2181246 A CA2181246 A CA 2181246A CA 2181246 A1 CA2181246 A1 CA 2181246A1
- Authority
- CA
- Canada
- Prior art keywords
- filter
- filter element
- base plate
- permanent
- espresso
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- A—HUMAN NECESSITIES
- A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
- A47J—KITCHEN EQUIPMENT; COFFEE MILLS; SPICE MILLS; APPARATUS FOR MAKING BEVERAGES
- A47J31/00—Apparatus for making beverages
- A47J31/06—Filters or strainers for coffee or tea makers ; Holders therefor
- A47J31/0657—Filters or strainers for coffee or tea makers ; Holders therefor for brewing coffee under pressure, e.g. for espresso machines
- A47J31/0663—Filters or strainers for coffee or tea makers ; Holders therefor for brewing coffee under pressure, e.g. for espresso machines to be used with loose coffee
-
- A—HUMAN NECESSITIES
- A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
- A47J—KITCHEN EQUIPMENT; COFFEE MILLS; SPICE MILLS; APPARATUS FOR MAKING BEVERAGES
- A47J31/00—Apparatus for making beverages
- A47J31/44—Parts or details or accessories of beverage-making apparatus
- A47J31/4496—Means to produce beverage with a layer on top, e.g. of cream, foam or froth
Landscapes
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Apparatus For Making Beverages (AREA)
- Control Of Motors That Do Not Use Commutators (AREA)
Abstract
The invention is directed to a cup-shaped permanent filter element (25) for a domestic espresso maker, which receives the espresso grounds in a brewing chamber (28). The cup-shaped permanent filter element (25) has at its bottom a sieve-type filter base plate (1) provided with filter perforations (4), and is insertable into a filter basket holder (15) from which the espresso beverage is allowed to be discharged through the filter perforations (4). The cup-shaped permanent filter element (25) includes a supporting plate (2) mounted downstream of the filter base plate (1) as seen when looking in the direction of flow (A) of the espresso beverage, the supporting plate combining with the filter base plate (1) to form a pressure chamber (8) for the purpose of improving the production of crema. The espresso beverage is required to flow through the pressure chamber (8) before it is allowed to exit on the filter basket holder (15), with the generation of pressure in the pressure chamber (8) being effected by a means (11) mounted on the pressure chamber outlet and operating to increase the flow resistance. The pressure chamber (8) and the permanent filter element (25) are firmly connected with each other mechanically. The means (11) for the generation of pressure is comprised of one or several apertures whose overall cross-section is sufficiently small relative to the overall cross-section of the filter perforations (4) in the filter base plate (1) of the permanent filter element (25) to produce a pressure drop in the aperture(s) (11) sufficient for the production of crema. This results in a one-piece construction of the permanent filter element (25) which affords ease of handling and with which good crema results are obtained.
Description
WO g5/23544 21 8 1246 PCT/EP95/00770 Cup-Sha~ed Permanent Filter Element This invention relates to a cup-shaped permanent filter element for a domestic espresso maker, which receives the espresso grounds in a brewing chamber, has at its bottom a sieve-type filter base plate provided with filter perforations, and is insertable into a filter basket holder from which the espresso beverage is allowed to be discharged through the filter perforations, and with a supporting plate mounted downstream of the filter base plate as seen when looking in the direction of flow of the espresso beverage, the supporting plate combining with the filter base plate to form a pressure chamber for the purpose of improving the production of crema, the espresso bev-erage being required to flow through this pressure chamber be-fore it is allowed to exit on the filter basket holder, with the generation of pressure in the pressure chamber being effected by a means mounted on the pressure chamber outlet and operating to increase the flow resistance.
In particular in espresso makers, cup-shaped permanent fil-ter elements are used which are preferably made of steel and are preferably manufactured by a deep-drawing process. A subsequent operation involves perforating the bottom of the cup by punches entering it, so that filter apertures are obtained. The perfo-rating operation produces burrs which have to be removed in a subsequent gr;n~;ng operation. In this manufacturing process, 2s the filter apertures are very uneven, as a result of which the properties of the respective permanent filter elements may differ, and the espresso produced may greatly vary in its con-sistence. To produce filters with a more accurate and finer structure of the filter perforations, an etching technique known in practice for a long time is also used.
From EP-A-0 459 323, there is further known a cup-shaped permanent filter element for a domestic espresso maker of the 1, l, 2l8l246 type initially referred to. A supporting plate having a central opening is arranged beneath the permanent filter element in the bottom of the filter basket holder which is adapted to be secured to a brewing unit disposed above the perm~nent filter element of the domestic espresso maker (not shown). Secured to the radially outer edge on the upper side of the supporting plate is a ring seal serving as a support for the cup-shaped permanent filter element in the bottom of which the filter per-forations are provided. A pressure chamber is formed between the bottom of the perm~nent filter element and the supporting plate, in which chamber the brew discharged from the brewing chamber of the permanent filter element through the filter per-forations is collected and directed to the opening in the supporting plate.
The outlet of the opening is closed by a resilient`sheet-metal tongue secured laterally on the underside of the support-ing plate and serving as the means for increasing the flow resistance, thus acting as a valve referred to as Ucrema valve".
In operation of the espresso maker, water is then forced under pressure through the espresso coffee grinds held in the brewing chamber and is directed, through the filter perforations in the filter base plate, into the pressure chamber formed between the filter base plate and the supporting plate, whence it reaches the opening. The pressure of the espresso beverage acting in 2s the process on the closing surface of the sheet-metal tongue exerts an opening force on the sheet-metal tongue which, on ex-ceeding the closing force of the sheet-metal tongue, causes the same to be lifted clear of the opening, while the biasing force increases. It is only then that the espresso beverage is allowed to drain through the valve while crema is being pro-duced.
In operation, it is necessary for the bottom, that is, the filter base plate, of the cup-shaped permanent filter element to be firmly urged against the ring seal secured to the supporting plate to form a pressure chamber closed on its sides. However, a pressure-tight seal can be accomplished only when the perma-nent filter element, on latching the filter basket holder onto the brewing unit of an espresso maker, is firmly urged down-wardly by the same, and when in the process the lower peripheral area of the permanent filter element is urged into sealing engagement with the ring seal. On the other hand, it is also necessary for the ring seal to be urged radially outwardly into pressure-tight engagement with the wall of the filter basket holder if it is desired that the espresso beverage be discharged only through the opening of the crema valve, rather than drain-ing past this valve. For this purpose, an additional sealing lip effecting a pressure-tight seal with the cylinder bore of the filter baske~ holder is provided on the radially; outer periphery of the ring seal.
Apart from the plurality of sealing locations which may easily cause leaks in the pressure chamber formed between the filter base plate and the supporting plate, this embodiment of a perm~nent filter element with a downstream pressure chamber is not suitable for use in espresso makers in which the brewing unit is formed by a movable piston sealingly entering the cup-shaped permanent filter element for the formation of a brewing chamber. In such an embodiment, it is not the cup-shaped perma-nent filter element that is urged into sealing engagement withthe stationary brewing unit by means of the filter basket holder, but rather, the brewing unit itself slidingly enters the perm~nent filter element for the formation of a brewing chamber, sealing it in upward direction to provide the brewing chamber.
This means ultimately that the permanent filter element is not exposed to a contact force acting in the direction of flow of the espresso beverage, so that the permanent filter element is not urged downwardly into sealing engagement with the ring seal described in the foregoing either.
In the embodiment of the permanent filter element of EP-A-0 459 323, it is also considered less advantageous that the crema valve is formed by a pressure relief valve that opens from a specified fluid pressure on, in dependence upon the bias of the resilient tongue. Considering, however, that depending on the degree of fineness of the espresso grinds on the one hand and the fluctuating pump pressure on the other hand the pressures occurring on the opening of the crema valve differ - because the pressure decreases on its path from the brewing unit to the opening as hot water penetrates the espresso grinds -, the bias-ing force of the resilient tongue is required to be designed such that the crema valve opens also under the least favorable conditions, that is, when the degree of fineness of the espresso grinds is very high and the pump pressure is relatively low as a result of unavoidable manufacturing variations. This ultimately makes it necessary for the crema valve, that is, the bias of the resilient tongue in dependence upon the cross-sectional area of the opening, to be designed such as to open also in the presence of a relatively low pressure, which is not necessarily conducive to the formation of crema. The formation of crema is reduced still further in that the resilient tongue has to bend up the more, the higher the pressure on the crema valve, which in-creases the area of cross-section of the opening still further which, in consequence, reduces the pressure drop on the crema valve.
Further, the firm of M. Schaerer A.G. of Quellenweg 4 - 6, CH-3084 Wabern (canton Bern) in Switzerland manufactures and sells drink ven~; ng machines which are not suitable for domestic use. Among the many drinks offered, these drink vending ma-chines are also capable of dispensing an espresso beverage. In these machines, the machine part serving for the preparation of . `` 2181246 WO g5/23544 PCT/EP95/00770 espresso comprises a cylindrical housing in which an axially movable operating piston is received (in this connection, refer-ence is made to in particular the drink ven~; ng machine of EP-A-0 073 739). The bottom of the housing is formed by a sliding member which, for one purpose, closes during the brewing cycle the brewing chamber formed by the housing and the piston, and for another purpose, releases the outlet opening for ejection of the coffee cake upon termination of the brewing cycle.
While in the drink ven~ing machine of EP-A-0 073 739 an opening is provided laterally on the cylindrical housing at the end of the brewing chamber, which opening receives a filter base plate having filter perforations and, downstream of the filter base plate, a pressure relief valve operating as an outlet valve, the firm of Schaerer also sells a drink ve~ing machine of like construction in which, however, the filter base plate, rather than being received laterally in the cylindrical bore of the housing, is directly received in the sliding member. In this arrangement, a supporting plate combining with the filter base plate to form a pressure chamber is provided downstream of the filter base plate. In the supporting plate, a metal disk is formed incorporating a means increasing the flow resistance, that is, a bore of small diameter. A drink dispenser of this type is not applicable to domestic espresso makers because of its completely different conditions in respect of water pressure, water temperature, quality of the coffee grinds, as well as other handling conditions.
It is an object of the present invention to provide a cup-shaped permanent filter element for a domestic espresso maker which affords ease and economy of manufacture, ease of handling, in particular as regards filling and cleaning, which is suitable for universal use, while yet producing good crema results for an espresso beverage. At the same time, it is desired that the permanent filter element also produce good results in the prepa-ration of a coffee beverage.
According to the present invention, this object is accom-plished with the characterizing features of patent claim 1.
S By mechanically connecting the perm~ne~t filter element with the pressure chamber, a single-piece per~an~nt filter ele-ment results which is removable from the filter basket holder only as a whole, thus preventing components from being lost.
The single-piece construction ensures a perfectly tight seal be-tween the brewing chamber and the pressure chamber downstream thereof, resulting in a durable permanent filter element which, in respect of both function and result, produces good coffee or espresso. The ratio of the overall cross-section of the aper-ture (or apertures) provided at the outlet of the pressure chamber to the overall cross-section of the filter perforations adjoining the pressure chamber is selected so small that at lower water pressures a good coffee (0.5 bar, approximately) or a good French-press coffee (coffee with a small foamy head) (3.5 bar, approximately) is obtained, whereas at higher water pres-sures (10 bar, approximately), good espresso with rich crema results, that is, the higher the pressure, the richer the crema, which is attributable in particular to the increase in velocity in the aperture and the pressure drop occurring therein. A
brewing temperature of about 94 C should be maintained for all types of brew. A further advantage afforded by this invention is that the permanent filter element utilized enables accurately defined filtering operations to be performed which are un-affected by irregularities as, for example, different degrees of fineness to which the coffee or espresso beans are ground, and different degrees of firmness to which the grounds are tamped.
Solely by varying the water pressure is it thus possible with the permanent filter element of the present invention to produce both espresso (high pressure) and good coffee (low pressure).
Conveniently, the discharge location is arranged essentially centrally to the filter base plate. This enables the flow to be directed in a substantially symmetrical pattern.
According to the features of claim 2, the filter base plate S with the supporting plate mount on the collar with particular ease, with a larger collar diameter allowing a large area of the filter base plate and, in consequence, also a large area of the pressure chamber, whereby fluid flow into the pressure chamber is accelerated, whilst on the other hand fluid discharge from the pressure chamber is decelerated (pressure buildup in the pressure chamber).
In particular by injection molding (claim 3), an intimate connection between these parts effecting a tight seal and affording great ease of manufacture can be accomplished, eventu-ally resulting in a perm~n~nt filter element for domestic usewhich is easy to manufacture, simple to clean, and made to last.
To be able to provide a highly complex pattern of receiving channels while at the same time producing the supporting plate as well as its securement to the filter base plate in a single injection-molding operation, the supporting plate is preferably fabricated from a plastic. The filter base plate is made of a thin sheet of high-grade steel provided with filter perforations (claim 4). Alternatively, the filter base plate and the sup-porting plate may also be surrounded by a plastic frame member serving a holding function. This enables the filter base plate and the supporting plate to be manufactured as separate parts, to be joined together by the frame member by means of an injection-molding operation (claim 5).
To ensure an improved and longer lasting attachment of the frame member to the filter base plate, at least one holding opening is provided in the peripheral area of the filter base plate for substantially snugly receiving therein a holdin~ sec-tion of the frame member (claim 6). When the frame member is injection-molded thereon, or when the frame member and the sup-porting plate are injection-molded at the same time, plastic material enters the holding opening during the injection-molding operation, thereby fixedly securing and holding the filter base plate in place. In another embodiment, at least one anchoring opening may be provided in the inner peripheral area of the col-lar for substantially snugly recei~ing therein an anchoring sec-lo tion of the frame member. This also ensures an accurate attach-ment of the frame member to the collar of the cup wall. The collar and the filter base plate can be connected with each other by injection molding in particular when the holding open-ings in the filter base plate and the anchoring openings in the collar are in essentially true alignment to each other. The holding and the anchoring section of the frame member are then equally superposed, jointly positioning the collar and the fil-ter base plate so as to provide an essentially snug fit.
The cup wall and the collar may be integrally made of metal, preferably high-grade steel, with the collar engaging the plastic frame member (claim 7). Thus, the cup wall, the filter base plate and the supporting plate may be connected with each other or also at the same time with the collar in a single in-jection-molding operation, with the cup wall and the collar being deep-drawn in a previous operation.
In a further embodiment, it is also possible that the cup wall, the collar and the frame member are integrally made of plastic (claim 8). In this method, the cup wall need not be manufactured as a separate part, but rather, can be injection molded onto the filter base plate and the supporting plate to-gether with the frame member in a single operation. Such an arrangement is of light weight, affords ease of manufacture, and - 2~81246 is therefore also very inexpensive while yet ensuring sufficient operational reliability.
In order to satisfy the flow conditions at the discharge location, a metal disk comprised of a perforated sheet is in-S serted in the supporting plate (claim 9). The perforated sheetacting as an aperture can be manufactured at very low cost and contributes to substantially improving the formation of crema.
Also, the periphery of the perforated sheet can be easily con-nected with the plastic supporting plate, using the perforated holes in the sheet or any additional slots provided in the sheet as fastening means by injecting plastic material therethrough.
However, it is also possible to mold the aperture(s) directly into the supporting plate fabricated from plastic.
For the formation of good crema, the aperture(s) ~in the lS metal disk must not be larger than 0.6 mmZ, preferably 0.4 mm~
(claim 10).
A particularly advantageous effect on the formation of crema is obtained if the metal disk has a thickness of between 0.2 and 0.6 mm, preferably 0.4 mm (claim 11). If the disk is thicker, the amount of crema produced ~;m;n; shes again according to the invention, because the relative distance of entry to exit on the aperture(s) becomes progressively larger, resulting in a decrease in the abrupt pressure drop.
In a still further embodiment, the filter apertures may be of a triangular cross-section, preferably representing an equi-lateral triangle (claim 12). When looking at the pattern of flow passing through such a triangular aperture, it will be noted that particles located in the corner regions of the aper-ture are required to overcome much higher friction forces than fluid particles located in the center region of the aperture.
In a triangle, this effect is enhanced in particular because the fluid particles are narrowed in the corners from two sides at a _ g _ `- 2181246 relatively acute angle. On passage of the fluid, turbulences set in, producing a particularly fine and creamy foam resulting in a head of excellent crema on the espresso which is very popu-lar with the connoisseur.
S A method of manufacturing fine-mesh perm~n~nt filter ele-ments which has proven to be particularly simple is to make the filter base plate of metal, applying electrolytic metal deposi-tion or punching or etching techniques. The appropriate method may be selected in conformity with the requisite accuracy, en-abling, for example, also the triangular filter apertures to be manufactured with relatively little effort and to rather accu-rate ~;men~ions.
In a further preferred embodiment, the filter apertures may be of a circular cross-section (claim 13) which affords particu-lS lar ease and accuracy of manufacture. In the use of such circu-lar filter apertures, the diameter of the filter apertures on the upper side of the filter base plate may amount to between 100 and 300 ~m, preferably 200 ~m. Within this diameter range, an optimum filter effect is accomplished.
It has proven to be particularly favorable in respect of fluid flow and thus conducive to the formation of the desired crema to configure the metal disk such that the apertures widen in a funnel-shaped configuration in the direction of flow from the upper side of the filter base plate to the underside of the filter base plate. Still further, it is particularly favorable in this configuration to curve the sides of the filter aper-tures in an arcuate shape, thus providing a favorable nozzle-type structure. This avoids at the same time clogging of the filter apertures.
With the features of patent claim 14, a system of channels results in the pressure chamber through which the espresso bev-erage is routed to the means increasing the flow resistance, that is, the aperture. As the espresso beverage is passed through the filter perforations in the filter base plate, fluid is not directed into the channel in the area where the filter perforations abuttingly engage the end of the receiving chan-nels, but rather, only at those locations where the receivingc~nnels directly comml~n;cate with the filter perforations. For one purpose, this results in an increased pressure at the fil-ter, and for another purpose, the fluid is collected in the re-ceiving channels, mixed and ch~nneled to the aperture, resulting in improved crema.
Two embodiments of the present invention will be described in the following with reference to the accompanying drawings. In the drawings, FIG. l is a full sectional view of a first cup-shaped per-m~nent filter element illustrating a first embodiment of thepresent invention, indicating the supporting surface and the metal disk providing the aperture at the outlet of the pressure chamber;
FIG. 2 is a top plan view of a cup bottom of FIG. l (the filter apertures having been omitted for the sake of clarity);
FIG. 3 is a view of a filter base plate for the permanent filter element illustrated in FIG. l, showing a first variant of holding openings;
FIG. 4 is a side view of the filter base plate of FIG. 3;
2s FIG. 5 is an enlarged view of the fragment V of FIG. 4;
FIG. 6 is an enlarged view of a metal disk for the perma-nent filter element of FIG. l;
FIG. 7 is an enlarged view of a connection between the fil-ter base plate and the cup wall;
FIG. 8a is a view of a second variant of anchoring open-ings;
FIG. 8b is a view of a third variant of anchoring openings;
and FIG. 9 is a partial sectional view of a second cup-shaped permanent filter element illustrating a second embodiment of the present invention, showing a perforated sheet as metal disk whose apertures form the outlet of the pressure chamber.
The embodiment of a permanent filter element 25 of the in-vention as illustrated in FIGS. 1, 2 and 9 essentially comprises a relatively thin, circular filter base plate 1, a supporting plate 2 arranged beneath the filter base plate 1 and carrying it, an annular plastic frame member 3 surrolln~;ng the filter base plate 1 and the supporting plate 2, and a cup wall 17 attached to the plastic frame member 3. The filter base plate 1 is of a substantially plane configuration including a multiplic-ity of filter perforations 4 (about 240) ext~n~;ng essentially in the direction of flow A, as becomes particularly apparent from FIGS. 1, 5 and 9. Advantageously, the filter perforations 4 widen in the flow direction A in a funnel-shaped configuration from the upper side 5 of the filter base plate 1 to the under-side 6 of the filter base plate 1. The sides 7 of the filter perforations 4 are curved in an arcuate configuration.
The filter perforations 4 are spaced essentially uniformly apart in the filter base plate 1. As FIG. 3 shows, a columnar or serial arrangement is found preferable. The filter perfora-tions 4 may be of a circular cross-section. It will be under-stood, however, that any other shape, such as triangles, quadrangles, etc. may also be used. Purther, the filter base plate 1 is preferably made of precious metal, such as stainless steel, enabling it to be manufactured also by electroly~ic metal deposition, punching or etching processes.
.- 2181246 WO 95~23544 PCT/EP95/00770 According to the FIGS. 1, 2, 7 and 9, the supporting plate 2 is preferably fabricated from a plastic, having on its inner bottom 26 a pressure chamber 8 with labyrinth- or me~n~er-shaped receiving channels 30 the main portion of which is co~prised of s coaxially arranged, circular-ring-shaped channel sections inter-connected by openings 9 exten~i ng through lands 10 separating the individual channel sections. The pressure chamber 8 is formed by the filter base plate 1, the supporting plate 2, and the plastic frame member 3 with collar 18 connecting these parts 1, 2. The open pressure chamber 8 is a space admitting fluid only through the filter base plate 1 and discharging it only through the aperture 11. The chamber serves to collect the espresso beverage entering through the filter base plate whence it is conveyed onwards to the central aperture 11.
In the center of the supporting plate 2, a means 11 in the form of one or several apertures is provided increasing the flow resistance. In FIGS. 1 and 2, the aperture 11 is a single bore with a cross-section of 0.6 mm located in a metal disk 12 which in turn has the plastic supporting plate 2 injection molded around it. The bore 11 is drilled or eroded for greater accu-racy of the area of cross-section and for the obt~;nment of sharp edges in the transition area to the end surfaces 31, 32, which ensures the formation of good crema. As becomes apparent in particular from FIG. 6, the metal disk 12 includes for im-proved anchoring an annular collar 13 mounted on the outerperiphery and surrounded by the material of the supporting plate 2. This secures the metal disk 12 in place in both an axial and a radial direction.
In FIG. 9, the metal disk 12 is comprised of a thin perfo-rated sheet having one or several apertures 11, preferably 3 to6 apertures, with an overall cross-sectional area of 0.6 mm .
The sheet thickness is between 0.2 and 0.4 mm, approximately.
The perforated sheet 12 has its periphery 33 equally injection-`- . 21 81 246 molded with the plastic supporting plate 2 as the latter was molded. Adjoining the perforated sheet 12 on the supporting plate 2 in the direction of flow A is an annular collar 34 with a discharge port 35. In contrast to FIG. 1, the collar 18 of 5 FIG. 9 has a substantially smaller passageway 36, so that the collar 18 provides a better support for the supporting plate 2.
According to FIG. 2, the receiving ch~nnel sections 14 ad-joining the metal disk 12 extend essentially radially to the axis of the aperture 11 in order to thus accomplish an improved chAnneling of the beverage to the central aperture 11. The re-ceiving channel 30 has essentially a width of between 2.5 and 5 mm, while the lands 10 bolln~;ng the receiving channel 30 at least in sections are essentially of a width of between 1.5 and 3 mm, preferably 2 mm. This results in a maximum possible area lS of the receiving ch~nnel 30 beneath a maximum possible area of the filter base plate 1, while yet the lands 10 are still stable. The depth of the receiving channel 30 is essentially between 0.6 and 1 mm, preferably 0.8 mm. The diameter of the aperture 11 at the discharge location is between 0.4 and 1 mm, preferably 0.6 mm. The filter perforations 4 have a diameter of between 0.1 and 0.3 mm, preferably 0.2 mm. Because the aperture 11 is substantially larger than the individual filter perfora-tions 4, clogging of the permanent filter element 25 is avoided.
In the embodiments illustrated in FIGS. 1 and 9, the filter 2s base plate 1 and the supporting plate 2 are of a circular configuration and are surrounded by a common plastic frame mem-ber 3. This has the advantage that the filter base plate 1 and the supporting plate 2 which are manufactured as separate parts can be joined in a further operation in an injection mold by means of the frame member 3. The supporting plate 2 being manu-factured separately, receiving channels 30 of any desired con-figuration may be provided in the inner bottom 26 thereof which is subsequently arranged so as to be close to the filter base WO g5/23544 PCT/EP95/00770 plate 1. It is, however, also possible to provide between both parts 2, 3 just a shallow pressure chamber 8 without any ch~nnels 30.
In the espresso maker, the permanent filter element 25 bears against an annular collar 44, shown only schematically in FIG. 1, of a filter basket holder 15 having an outlet 16 arranged beneath the aperture 11.
The embodiments shown in FIGS. 1 and 9 comprise a cup wall 17 having at its lower peripheral area the circumferential col-lar 18 extend;ng in the direction of the cup axis 27. Thecollar 18 engages within the plastic frame member 3, thereby en-abling the cup wall 17 to be attached to the filter base plate 1 and the supporting plate 2 by injection-molding the frame member 3 in a single operation. To this end, the frame member~ 3 and the supporting plate 2 have a common passageway 36 serving as a centering location to ensure a precise fit and positive engage-ment. The cup wall 17 and the collar 18 may be made of metal, preferably high-grade steel. However, an embodiment not shown may also be contemplated in which the cup wall 17, the collar 18 and the frame member 3 are integrally fabricated from a plastic.
The components identified may then be injection-molded to the filter base plate 1 and the supporting plate 2 in a single oper-ation.
As can be seen in particular from FIGS. 1, 7 and 9, holding openings 19 are disposed in the peripheral area of the filter base plate 1 for snugly receiving therein the holding sections 20 of the frame member 3. The holding openings 19 and anchoring openings 21 arranged in the collar 18 are provided in the form of a circumferential ring of holes in the peripheral area of the filter base plate 1 and, respectively, the peripheral inner area of the collar 18. As becomes apparent from FIGS. 1 and 7, the holding openings 19 in the filter base plate 1 and the anchoring openings 21 in the collar 18 are at least in part in essentially true alignment to each other. Even in the event that only some of the holding openings 19 and anchoring openings 21 are super-posed due to a non-uniform pitch, this will be sufficient to ensure a good fastening of the filter base plate 1 and the collar 18 in the frame member 3. To establish a tight seal be-tween the filter base plate 1, the supporting plate 2 and the collar 18 for the formation of the pressure chamber 8, the plas-tic frame member 3 encompasses with its outer section 23 the radially outer periphery of the filter base plate 1, resting sealingly against the upper side 38 of the collar 18.
FIGS. 8a and 8b further show a variant of anchoring open-ings 21 which are, however, readily applicable to the holding openings 19 of the filter base plate 1. The anchoring openings 21 are of an open configuration in the direction of the inner periphery of the collar 18. Correspondingly, the holding open-ings 19 would then be of an open configuration in the direction of the periphery of the filter base plate 1. This configuration improves the anchoring of the collar 18 and the filter base plate 1 in the plastic frame member 3 still further. The hold-ing and anchoring openings 19 and 21, respectively, may have a preferred length in the range from 2 to 4 mm, their distance to the periphery and to each other being in the range from 1.5 to 2 mm. The width of the slots 39 of FIG . 8b may be preferably in the range from 1 to 1.5 mm.
In FIG . 9, a handle 43 (illustrated only in part) is pro-vided on the upper rim of the annular collar 37 to improve manipulation of the permanent filter element 25.
The mode of operation of the present invention will be briefly explained in the following.
According to the first embodiment of FIG . 1, upon insertion of the perm~ne~t filter element 25 of the invention into the re-2~81246 ceptacle 45 (shown only in part), the underside of the annular collar 37 rests against a suitably configured annular collar 44 of the filter basket holder 15, thus bearing against it. The bottom 46 of the filter basket holder 15 is thus spaced from the S supporting plate 2 by a small distance. As a rule, the filter basket holder 15 is provided with a handle (not shown) for better manipulation. In the permanent filter elements illus-trated in FIGS. 1 to 9, the filter basket holder 15 is pivotally mounted on the housing of an espresso maker.
After the brewing chamber 28 of the permanent filter ele-ment 25 is filled with coffee grinds (not shown), which may be done either with the permanent filter element 25 removed or with the permanent filter element 25 inserted in the filter basket holder 15, filter basket holder 15 and permanent filter element lS 25 are jointly moved into an operating position on the espresso maker. By means of an actuating device provided in the espresso maker, the piston 40 then travels into the brewing chamber 28, so that the ring seal 41 attached to the piston is in sealing engagement with the cup wall 17. The brewing chamber 28 is thus closed, and hot water under pressure may be injected into the brewing chamber 28 through the feed conduit 47 (shown in broken lines). In this connection, it is noted that the feed conduit 47 is connected to a water heater and a pressure pump (not shown). Hot water fed under pressure into the brewing chamber 28 mixes with the coffee grounds, extracting therefrom the aroma and flavors necessary for a coffee or espresso beverage. In the process, a pressure drop occurs in the direction of flow A down to the filter base plate 1, because the co~fee bed presents a certain resistance to the hot water flow. As the espresso beverage passes through the filter base plate 1, the fine filter perforations 4 provided therein retain the espresso grounds in the brewing chamber 28. After passing through the filter perforations 4, the espresso beverage enters the pressure cham-~ 2~81246 ber 8 provided between the supporting plate 2 and the filter base plate 1, whence it is delivered to the aperture 11 while being still under pressure. As the espresso beverage flows through the aperture 11, its flow velocity increases, while at the same time an abrupt pressure drop occurs from the pressure chamber 8 to the outside 48, causing to a certain degree foaming of the espresso beverage resulting in crema being produced.
After being discharged through the aperture 11, the espresso beverage and its crema components flow through the outlet 16 provided in the bottom 46 of the filter basket holder 15, whence it may collect in an espresso cup placed beneath the outlet 16 or some other container (not shown). As the espresso beverage flows through the pressure chamber 8, this chamber serves to maintain the espresso beverage under pressure, because the amount of espresso allowed to enter the pressure chamber 8 through the filter perforations 4 is greater than the amount that can be discharged through the aperture 11.
In the perm~nPnt filter element 25 of FIG. 9, a thin perfo-rated sheet provided with a number of apertures 11 is substi-tuted for the metal disk 12 in which the aperture 11 of FIG. 1 is formed. The sum of the overall cross-sections of the aper-tures 11 of FIG. 9 corresponds approximately to the-cross-section of the single aperture 11 of FIG. 1. The perforated sheet 12 contributes to enhancing the formation of crema still 2~ further because, as a result of the relatively thin metal film 12, the espresso beverage experiences a high velocity and a high pressure drop in a m;n;mllm of time. It is preciselY these prop-erties which, according to the invention, increase the amount of crema produced. With the brewing chamber 28 filled with espresso grinds to a normal level using a normal degree of fine-ness and tamping, particularly good crema values result by main-t~; n; ng a water temperature of about 94 C, a pump pressure of about 10 bar, and an overall cross-sectional area of the aper-~ 21 81246 ~O g5/23544 PCT/EP95/00770 ture or apertures 11 of about 0.4 to 0.6 mm2. Upon completion of the brewing cycle, the piston 40 is retracted from the brew-ing chamber 28 in upward direction, and the filter basket holder 15 with the permanent filter element 25 can be removed or swung out of the espresso maker. Then the permanent filter element 25 is ready for removal from the filter basket holder 15 by means of the handle 43 for cle~n; ng purposes. In an embodiment in which the perm~ent filter element 25 is held in its receptacle 45 with a light press-fit, it may remain seated in the filter basket holder 15, so that it is cleaned together with the filter basket holder which in this event is advantageously provided with a handle (not shown).
As appears from FIGS. 1 and 9, receiving channels 30 are formed in the p~essure chamber 8 enabling the espresso beverage to be channeled to the central aperture 11 provided in the per~nent filter element 25. At the same time, the receiving channels 30 serve the function of supporting the filter base plate 1 which is thus largely prevented from being deflected in operation. In FIG . 9, adjoining the perforated sheet 12 in the direction of flow A is the discharge port 35 which is part of the supporting plate 2 and of a diameter which is a multiple of the overall cross-section of the apertures 11 to allow the espresso beverage to flow out freely without further blocking its movement. As shown in FIG. 1, the brew delivered through the discharge port 35 is then directed to the outlet 16 provided in the filter basket holder 15 which, as a rule, is comprised of two adjacent spouts. This enables two cups to be filled with espresso at the same time. The compact construction of the per-manent filter element 25 of the present invention affords ease of handling while producing good crema.
In particular in espresso makers, cup-shaped permanent fil-ter elements are used which are preferably made of steel and are preferably manufactured by a deep-drawing process. A subsequent operation involves perforating the bottom of the cup by punches entering it, so that filter apertures are obtained. The perfo-rating operation produces burrs which have to be removed in a subsequent gr;n~;ng operation. In this manufacturing process, 2s the filter apertures are very uneven, as a result of which the properties of the respective permanent filter elements may differ, and the espresso produced may greatly vary in its con-sistence. To produce filters with a more accurate and finer structure of the filter perforations, an etching technique known in practice for a long time is also used.
From EP-A-0 459 323, there is further known a cup-shaped permanent filter element for a domestic espresso maker of the 1, l, 2l8l246 type initially referred to. A supporting plate having a central opening is arranged beneath the permanent filter element in the bottom of the filter basket holder which is adapted to be secured to a brewing unit disposed above the perm~nent filter element of the domestic espresso maker (not shown). Secured to the radially outer edge on the upper side of the supporting plate is a ring seal serving as a support for the cup-shaped permanent filter element in the bottom of which the filter per-forations are provided. A pressure chamber is formed between the bottom of the perm~nent filter element and the supporting plate, in which chamber the brew discharged from the brewing chamber of the permanent filter element through the filter per-forations is collected and directed to the opening in the supporting plate.
The outlet of the opening is closed by a resilient`sheet-metal tongue secured laterally on the underside of the support-ing plate and serving as the means for increasing the flow resistance, thus acting as a valve referred to as Ucrema valve".
In operation of the espresso maker, water is then forced under pressure through the espresso coffee grinds held in the brewing chamber and is directed, through the filter perforations in the filter base plate, into the pressure chamber formed between the filter base plate and the supporting plate, whence it reaches the opening. The pressure of the espresso beverage acting in 2s the process on the closing surface of the sheet-metal tongue exerts an opening force on the sheet-metal tongue which, on ex-ceeding the closing force of the sheet-metal tongue, causes the same to be lifted clear of the opening, while the biasing force increases. It is only then that the espresso beverage is allowed to drain through the valve while crema is being pro-duced.
In operation, it is necessary for the bottom, that is, the filter base plate, of the cup-shaped permanent filter element to be firmly urged against the ring seal secured to the supporting plate to form a pressure chamber closed on its sides. However, a pressure-tight seal can be accomplished only when the perma-nent filter element, on latching the filter basket holder onto the brewing unit of an espresso maker, is firmly urged down-wardly by the same, and when in the process the lower peripheral area of the permanent filter element is urged into sealing engagement with the ring seal. On the other hand, it is also necessary for the ring seal to be urged radially outwardly into pressure-tight engagement with the wall of the filter basket holder if it is desired that the espresso beverage be discharged only through the opening of the crema valve, rather than drain-ing past this valve. For this purpose, an additional sealing lip effecting a pressure-tight seal with the cylinder bore of the filter baske~ holder is provided on the radially; outer periphery of the ring seal.
Apart from the plurality of sealing locations which may easily cause leaks in the pressure chamber formed between the filter base plate and the supporting plate, this embodiment of a perm~nent filter element with a downstream pressure chamber is not suitable for use in espresso makers in which the brewing unit is formed by a movable piston sealingly entering the cup-shaped permanent filter element for the formation of a brewing chamber. In such an embodiment, it is not the cup-shaped perma-nent filter element that is urged into sealing engagement withthe stationary brewing unit by means of the filter basket holder, but rather, the brewing unit itself slidingly enters the perm~nent filter element for the formation of a brewing chamber, sealing it in upward direction to provide the brewing chamber.
This means ultimately that the permanent filter element is not exposed to a contact force acting in the direction of flow of the espresso beverage, so that the permanent filter element is not urged downwardly into sealing engagement with the ring seal described in the foregoing either.
In the embodiment of the permanent filter element of EP-A-0 459 323, it is also considered less advantageous that the crema valve is formed by a pressure relief valve that opens from a specified fluid pressure on, in dependence upon the bias of the resilient tongue. Considering, however, that depending on the degree of fineness of the espresso grinds on the one hand and the fluctuating pump pressure on the other hand the pressures occurring on the opening of the crema valve differ - because the pressure decreases on its path from the brewing unit to the opening as hot water penetrates the espresso grinds -, the bias-ing force of the resilient tongue is required to be designed such that the crema valve opens also under the least favorable conditions, that is, when the degree of fineness of the espresso grinds is very high and the pump pressure is relatively low as a result of unavoidable manufacturing variations. This ultimately makes it necessary for the crema valve, that is, the bias of the resilient tongue in dependence upon the cross-sectional area of the opening, to be designed such as to open also in the presence of a relatively low pressure, which is not necessarily conducive to the formation of crema. The formation of crema is reduced still further in that the resilient tongue has to bend up the more, the higher the pressure on the crema valve, which in-creases the area of cross-section of the opening still further which, in consequence, reduces the pressure drop on the crema valve.
Further, the firm of M. Schaerer A.G. of Quellenweg 4 - 6, CH-3084 Wabern (canton Bern) in Switzerland manufactures and sells drink ven~; ng machines which are not suitable for domestic use. Among the many drinks offered, these drink vending ma-chines are also capable of dispensing an espresso beverage. In these machines, the machine part serving for the preparation of . `` 2181246 WO g5/23544 PCT/EP95/00770 espresso comprises a cylindrical housing in which an axially movable operating piston is received (in this connection, refer-ence is made to in particular the drink ven~; ng machine of EP-A-0 073 739). The bottom of the housing is formed by a sliding member which, for one purpose, closes during the brewing cycle the brewing chamber formed by the housing and the piston, and for another purpose, releases the outlet opening for ejection of the coffee cake upon termination of the brewing cycle.
While in the drink ven~ing machine of EP-A-0 073 739 an opening is provided laterally on the cylindrical housing at the end of the brewing chamber, which opening receives a filter base plate having filter perforations and, downstream of the filter base plate, a pressure relief valve operating as an outlet valve, the firm of Schaerer also sells a drink ve~ing machine of like construction in which, however, the filter base plate, rather than being received laterally in the cylindrical bore of the housing, is directly received in the sliding member. In this arrangement, a supporting plate combining with the filter base plate to form a pressure chamber is provided downstream of the filter base plate. In the supporting plate, a metal disk is formed incorporating a means increasing the flow resistance, that is, a bore of small diameter. A drink dispenser of this type is not applicable to domestic espresso makers because of its completely different conditions in respect of water pressure, water temperature, quality of the coffee grinds, as well as other handling conditions.
It is an object of the present invention to provide a cup-shaped permanent filter element for a domestic espresso maker which affords ease and economy of manufacture, ease of handling, in particular as regards filling and cleaning, which is suitable for universal use, while yet producing good crema results for an espresso beverage. At the same time, it is desired that the permanent filter element also produce good results in the prepa-ration of a coffee beverage.
According to the present invention, this object is accom-plished with the characterizing features of patent claim 1.
S By mechanically connecting the perm~ne~t filter element with the pressure chamber, a single-piece per~an~nt filter ele-ment results which is removable from the filter basket holder only as a whole, thus preventing components from being lost.
The single-piece construction ensures a perfectly tight seal be-tween the brewing chamber and the pressure chamber downstream thereof, resulting in a durable permanent filter element which, in respect of both function and result, produces good coffee or espresso. The ratio of the overall cross-section of the aper-ture (or apertures) provided at the outlet of the pressure chamber to the overall cross-section of the filter perforations adjoining the pressure chamber is selected so small that at lower water pressures a good coffee (0.5 bar, approximately) or a good French-press coffee (coffee with a small foamy head) (3.5 bar, approximately) is obtained, whereas at higher water pres-sures (10 bar, approximately), good espresso with rich crema results, that is, the higher the pressure, the richer the crema, which is attributable in particular to the increase in velocity in the aperture and the pressure drop occurring therein. A
brewing temperature of about 94 C should be maintained for all types of brew. A further advantage afforded by this invention is that the permanent filter element utilized enables accurately defined filtering operations to be performed which are un-affected by irregularities as, for example, different degrees of fineness to which the coffee or espresso beans are ground, and different degrees of firmness to which the grounds are tamped.
Solely by varying the water pressure is it thus possible with the permanent filter element of the present invention to produce both espresso (high pressure) and good coffee (low pressure).
Conveniently, the discharge location is arranged essentially centrally to the filter base plate. This enables the flow to be directed in a substantially symmetrical pattern.
According to the features of claim 2, the filter base plate S with the supporting plate mount on the collar with particular ease, with a larger collar diameter allowing a large area of the filter base plate and, in consequence, also a large area of the pressure chamber, whereby fluid flow into the pressure chamber is accelerated, whilst on the other hand fluid discharge from the pressure chamber is decelerated (pressure buildup in the pressure chamber).
In particular by injection molding (claim 3), an intimate connection between these parts effecting a tight seal and affording great ease of manufacture can be accomplished, eventu-ally resulting in a perm~n~nt filter element for domestic usewhich is easy to manufacture, simple to clean, and made to last.
To be able to provide a highly complex pattern of receiving channels while at the same time producing the supporting plate as well as its securement to the filter base plate in a single injection-molding operation, the supporting plate is preferably fabricated from a plastic. The filter base plate is made of a thin sheet of high-grade steel provided with filter perforations (claim 4). Alternatively, the filter base plate and the sup-porting plate may also be surrounded by a plastic frame member serving a holding function. This enables the filter base plate and the supporting plate to be manufactured as separate parts, to be joined together by the frame member by means of an injection-molding operation (claim 5).
To ensure an improved and longer lasting attachment of the frame member to the filter base plate, at least one holding opening is provided in the peripheral area of the filter base plate for substantially snugly receiving therein a holdin~ sec-tion of the frame member (claim 6). When the frame member is injection-molded thereon, or when the frame member and the sup-porting plate are injection-molded at the same time, plastic material enters the holding opening during the injection-molding operation, thereby fixedly securing and holding the filter base plate in place. In another embodiment, at least one anchoring opening may be provided in the inner peripheral area of the col-lar for substantially snugly recei~ing therein an anchoring sec-lo tion of the frame member. This also ensures an accurate attach-ment of the frame member to the collar of the cup wall. The collar and the filter base plate can be connected with each other by injection molding in particular when the holding open-ings in the filter base plate and the anchoring openings in the collar are in essentially true alignment to each other. The holding and the anchoring section of the frame member are then equally superposed, jointly positioning the collar and the fil-ter base plate so as to provide an essentially snug fit.
The cup wall and the collar may be integrally made of metal, preferably high-grade steel, with the collar engaging the plastic frame member (claim 7). Thus, the cup wall, the filter base plate and the supporting plate may be connected with each other or also at the same time with the collar in a single in-jection-molding operation, with the cup wall and the collar being deep-drawn in a previous operation.
In a further embodiment, it is also possible that the cup wall, the collar and the frame member are integrally made of plastic (claim 8). In this method, the cup wall need not be manufactured as a separate part, but rather, can be injection molded onto the filter base plate and the supporting plate to-gether with the frame member in a single operation. Such an arrangement is of light weight, affords ease of manufacture, and - 2~81246 is therefore also very inexpensive while yet ensuring sufficient operational reliability.
In order to satisfy the flow conditions at the discharge location, a metal disk comprised of a perforated sheet is in-S serted in the supporting plate (claim 9). The perforated sheetacting as an aperture can be manufactured at very low cost and contributes to substantially improving the formation of crema.
Also, the periphery of the perforated sheet can be easily con-nected with the plastic supporting plate, using the perforated holes in the sheet or any additional slots provided in the sheet as fastening means by injecting plastic material therethrough.
However, it is also possible to mold the aperture(s) directly into the supporting plate fabricated from plastic.
For the formation of good crema, the aperture(s) ~in the lS metal disk must not be larger than 0.6 mmZ, preferably 0.4 mm~
(claim 10).
A particularly advantageous effect on the formation of crema is obtained if the metal disk has a thickness of between 0.2 and 0.6 mm, preferably 0.4 mm (claim 11). If the disk is thicker, the amount of crema produced ~;m;n; shes again according to the invention, because the relative distance of entry to exit on the aperture(s) becomes progressively larger, resulting in a decrease in the abrupt pressure drop.
In a still further embodiment, the filter apertures may be of a triangular cross-section, preferably representing an equi-lateral triangle (claim 12). When looking at the pattern of flow passing through such a triangular aperture, it will be noted that particles located in the corner regions of the aper-ture are required to overcome much higher friction forces than fluid particles located in the center region of the aperture.
In a triangle, this effect is enhanced in particular because the fluid particles are narrowed in the corners from two sides at a _ g _ `- 2181246 relatively acute angle. On passage of the fluid, turbulences set in, producing a particularly fine and creamy foam resulting in a head of excellent crema on the espresso which is very popu-lar with the connoisseur.
S A method of manufacturing fine-mesh perm~n~nt filter ele-ments which has proven to be particularly simple is to make the filter base plate of metal, applying electrolytic metal deposi-tion or punching or etching techniques. The appropriate method may be selected in conformity with the requisite accuracy, en-abling, for example, also the triangular filter apertures to be manufactured with relatively little effort and to rather accu-rate ~;men~ions.
In a further preferred embodiment, the filter apertures may be of a circular cross-section (claim 13) which affords particu-lS lar ease and accuracy of manufacture. In the use of such circu-lar filter apertures, the diameter of the filter apertures on the upper side of the filter base plate may amount to between 100 and 300 ~m, preferably 200 ~m. Within this diameter range, an optimum filter effect is accomplished.
It has proven to be particularly favorable in respect of fluid flow and thus conducive to the formation of the desired crema to configure the metal disk such that the apertures widen in a funnel-shaped configuration in the direction of flow from the upper side of the filter base plate to the underside of the filter base plate. Still further, it is particularly favorable in this configuration to curve the sides of the filter aper-tures in an arcuate shape, thus providing a favorable nozzle-type structure. This avoids at the same time clogging of the filter apertures.
With the features of patent claim 14, a system of channels results in the pressure chamber through which the espresso bev-erage is routed to the means increasing the flow resistance, that is, the aperture. As the espresso beverage is passed through the filter perforations in the filter base plate, fluid is not directed into the channel in the area where the filter perforations abuttingly engage the end of the receiving chan-nels, but rather, only at those locations where the receivingc~nnels directly comml~n;cate with the filter perforations. For one purpose, this results in an increased pressure at the fil-ter, and for another purpose, the fluid is collected in the re-ceiving channels, mixed and ch~nneled to the aperture, resulting in improved crema.
Two embodiments of the present invention will be described in the following with reference to the accompanying drawings. In the drawings, FIG. l is a full sectional view of a first cup-shaped per-m~nent filter element illustrating a first embodiment of thepresent invention, indicating the supporting surface and the metal disk providing the aperture at the outlet of the pressure chamber;
FIG. 2 is a top plan view of a cup bottom of FIG. l (the filter apertures having been omitted for the sake of clarity);
FIG. 3 is a view of a filter base plate for the permanent filter element illustrated in FIG. l, showing a first variant of holding openings;
FIG. 4 is a side view of the filter base plate of FIG. 3;
2s FIG. 5 is an enlarged view of the fragment V of FIG. 4;
FIG. 6 is an enlarged view of a metal disk for the perma-nent filter element of FIG. l;
FIG. 7 is an enlarged view of a connection between the fil-ter base plate and the cup wall;
FIG. 8a is a view of a second variant of anchoring open-ings;
FIG. 8b is a view of a third variant of anchoring openings;
and FIG. 9 is a partial sectional view of a second cup-shaped permanent filter element illustrating a second embodiment of the present invention, showing a perforated sheet as metal disk whose apertures form the outlet of the pressure chamber.
The embodiment of a permanent filter element 25 of the in-vention as illustrated in FIGS. 1, 2 and 9 essentially comprises a relatively thin, circular filter base plate 1, a supporting plate 2 arranged beneath the filter base plate 1 and carrying it, an annular plastic frame member 3 surrolln~;ng the filter base plate 1 and the supporting plate 2, and a cup wall 17 attached to the plastic frame member 3. The filter base plate 1 is of a substantially plane configuration including a multiplic-ity of filter perforations 4 (about 240) ext~n~;ng essentially in the direction of flow A, as becomes particularly apparent from FIGS. 1, 5 and 9. Advantageously, the filter perforations 4 widen in the flow direction A in a funnel-shaped configuration from the upper side 5 of the filter base plate 1 to the under-side 6 of the filter base plate 1. The sides 7 of the filter perforations 4 are curved in an arcuate configuration.
The filter perforations 4 are spaced essentially uniformly apart in the filter base plate 1. As FIG. 3 shows, a columnar or serial arrangement is found preferable. The filter perfora-tions 4 may be of a circular cross-section. It will be under-stood, however, that any other shape, such as triangles, quadrangles, etc. may also be used. Purther, the filter base plate 1 is preferably made of precious metal, such as stainless steel, enabling it to be manufactured also by electroly~ic metal deposition, punching or etching processes.
.- 2181246 WO 95~23544 PCT/EP95/00770 According to the FIGS. 1, 2, 7 and 9, the supporting plate 2 is preferably fabricated from a plastic, having on its inner bottom 26 a pressure chamber 8 with labyrinth- or me~n~er-shaped receiving channels 30 the main portion of which is co~prised of s coaxially arranged, circular-ring-shaped channel sections inter-connected by openings 9 exten~i ng through lands 10 separating the individual channel sections. The pressure chamber 8 is formed by the filter base plate 1, the supporting plate 2, and the plastic frame member 3 with collar 18 connecting these parts 1, 2. The open pressure chamber 8 is a space admitting fluid only through the filter base plate 1 and discharging it only through the aperture 11. The chamber serves to collect the espresso beverage entering through the filter base plate whence it is conveyed onwards to the central aperture 11.
In the center of the supporting plate 2, a means 11 in the form of one or several apertures is provided increasing the flow resistance. In FIGS. 1 and 2, the aperture 11 is a single bore with a cross-section of 0.6 mm located in a metal disk 12 which in turn has the plastic supporting plate 2 injection molded around it. The bore 11 is drilled or eroded for greater accu-racy of the area of cross-section and for the obt~;nment of sharp edges in the transition area to the end surfaces 31, 32, which ensures the formation of good crema. As becomes apparent in particular from FIG. 6, the metal disk 12 includes for im-proved anchoring an annular collar 13 mounted on the outerperiphery and surrounded by the material of the supporting plate 2. This secures the metal disk 12 in place in both an axial and a radial direction.
In FIG. 9, the metal disk 12 is comprised of a thin perfo-rated sheet having one or several apertures 11, preferably 3 to6 apertures, with an overall cross-sectional area of 0.6 mm .
The sheet thickness is between 0.2 and 0.4 mm, approximately.
The perforated sheet 12 has its periphery 33 equally injection-`- . 21 81 246 molded with the plastic supporting plate 2 as the latter was molded. Adjoining the perforated sheet 12 on the supporting plate 2 in the direction of flow A is an annular collar 34 with a discharge port 35. In contrast to FIG. 1, the collar 18 of 5 FIG. 9 has a substantially smaller passageway 36, so that the collar 18 provides a better support for the supporting plate 2.
According to FIG. 2, the receiving ch~nnel sections 14 ad-joining the metal disk 12 extend essentially radially to the axis of the aperture 11 in order to thus accomplish an improved chAnneling of the beverage to the central aperture 11. The re-ceiving channel 30 has essentially a width of between 2.5 and 5 mm, while the lands 10 bolln~;ng the receiving channel 30 at least in sections are essentially of a width of between 1.5 and 3 mm, preferably 2 mm. This results in a maximum possible area lS of the receiving ch~nnel 30 beneath a maximum possible area of the filter base plate 1, while yet the lands 10 are still stable. The depth of the receiving channel 30 is essentially between 0.6 and 1 mm, preferably 0.8 mm. The diameter of the aperture 11 at the discharge location is between 0.4 and 1 mm, preferably 0.6 mm. The filter perforations 4 have a diameter of between 0.1 and 0.3 mm, preferably 0.2 mm. Because the aperture 11 is substantially larger than the individual filter perfora-tions 4, clogging of the permanent filter element 25 is avoided.
In the embodiments illustrated in FIGS. 1 and 9, the filter 2s base plate 1 and the supporting plate 2 are of a circular configuration and are surrounded by a common plastic frame mem-ber 3. This has the advantage that the filter base plate 1 and the supporting plate 2 which are manufactured as separate parts can be joined in a further operation in an injection mold by means of the frame member 3. The supporting plate 2 being manu-factured separately, receiving channels 30 of any desired con-figuration may be provided in the inner bottom 26 thereof which is subsequently arranged so as to be close to the filter base WO g5/23544 PCT/EP95/00770 plate 1. It is, however, also possible to provide between both parts 2, 3 just a shallow pressure chamber 8 without any ch~nnels 30.
In the espresso maker, the permanent filter element 25 bears against an annular collar 44, shown only schematically in FIG. 1, of a filter basket holder 15 having an outlet 16 arranged beneath the aperture 11.
The embodiments shown in FIGS. 1 and 9 comprise a cup wall 17 having at its lower peripheral area the circumferential col-lar 18 extend;ng in the direction of the cup axis 27. Thecollar 18 engages within the plastic frame member 3, thereby en-abling the cup wall 17 to be attached to the filter base plate 1 and the supporting plate 2 by injection-molding the frame member 3 in a single operation. To this end, the frame member~ 3 and the supporting plate 2 have a common passageway 36 serving as a centering location to ensure a precise fit and positive engage-ment. The cup wall 17 and the collar 18 may be made of metal, preferably high-grade steel. However, an embodiment not shown may also be contemplated in which the cup wall 17, the collar 18 and the frame member 3 are integrally fabricated from a plastic.
The components identified may then be injection-molded to the filter base plate 1 and the supporting plate 2 in a single oper-ation.
As can be seen in particular from FIGS. 1, 7 and 9, holding openings 19 are disposed in the peripheral area of the filter base plate 1 for snugly receiving therein the holding sections 20 of the frame member 3. The holding openings 19 and anchoring openings 21 arranged in the collar 18 are provided in the form of a circumferential ring of holes in the peripheral area of the filter base plate 1 and, respectively, the peripheral inner area of the collar 18. As becomes apparent from FIGS. 1 and 7, the holding openings 19 in the filter base plate 1 and the anchoring openings 21 in the collar 18 are at least in part in essentially true alignment to each other. Even in the event that only some of the holding openings 19 and anchoring openings 21 are super-posed due to a non-uniform pitch, this will be sufficient to ensure a good fastening of the filter base plate 1 and the collar 18 in the frame member 3. To establish a tight seal be-tween the filter base plate 1, the supporting plate 2 and the collar 18 for the formation of the pressure chamber 8, the plas-tic frame member 3 encompasses with its outer section 23 the radially outer periphery of the filter base plate 1, resting sealingly against the upper side 38 of the collar 18.
FIGS. 8a and 8b further show a variant of anchoring open-ings 21 which are, however, readily applicable to the holding openings 19 of the filter base plate 1. The anchoring openings 21 are of an open configuration in the direction of the inner periphery of the collar 18. Correspondingly, the holding open-ings 19 would then be of an open configuration in the direction of the periphery of the filter base plate 1. This configuration improves the anchoring of the collar 18 and the filter base plate 1 in the plastic frame member 3 still further. The hold-ing and anchoring openings 19 and 21, respectively, may have a preferred length in the range from 2 to 4 mm, their distance to the periphery and to each other being in the range from 1.5 to 2 mm. The width of the slots 39 of FIG . 8b may be preferably in the range from 1 to 1.5 mm.
In FIG . 9, a handle 43 (illustrated only in part) is pro-vided on the upper rim of the annular collar 37 to improve manipulation of the permanent filter element 25.
The mode of operation of the present invention will be briefly explained in the following.
According to the first embodiment of FIG . 1, upon insertion of the perm~ne~t filter element 25 of the invention into the re-2~81246 ceptacle 45 (shown only in part), the underside of the annular collar 37 rests against a suitably configured annular collar 44 of the filter basket holder 15, thus bearing against it. The bottom 46 of the filter basket holder 15 is thus spaced from the S supporting plate 2 by a small distance. As a rule, the filter basket holder 15 is provided with a handle (not shown) for better manipulation. In the permanent filter elements illus-trated in FIGS. 1 to 9, the filter basket holder 15 is pivotally mounted on the housing of an espresso maker.
After the brewing chamber 28 of the permanent filter ele-ment 25 is filled with coffee grinds (not shown), which may be done either with the permanent filter element 25 removed or with the permanent filter element 25 inserted in the filter basket holder 15, filter basket holder 15 and permanent filter element lS 25 are jointly moved into an operating position on the espresso maker. By means of an actuating device provided in the espresso maker, the piston 40 then travels into the brewing chamber 28, so that the ring seal 41 attached to the piston is in sealing engagement with the cup wall 17. The brewing chamber 28 is thus closed, and hot water under pressure may be injected into the brewing chamber 28 through the feed conduit 47 (shown in broken lines). In this connection, it is noted that the feed conduit 47 is connected to a water heater and a pressure pump (not shown). Hot water fed under pressure into the brewing chamber 28 mixes with the coffee grounds, extracting therefrom the aroma and flavors necessary for a coffee or espresso beverage. In the process, a pressure drop occurs in the direction of flow A down to the filter base plate 1, because the co~fee bed presents a certain resistance to the hot water flow. As the espresso beverage passes through the filter base plate 1, the fine filter perforations 4 provided therein retain the espresso grounds in the brewing chamber 28. After passing through the filter perforations 4, the espresso beverage enters the pressure cham-~ 2~81246 ber 8 provided between the supporting plate 2 and the filter base plate 1, whence it is delivered to the aperture 11 while being still under pressure. As the espresso beverage flows through the aperture 11, its flow velocity increases, while at the same time an abrupt pressure drop occurs from the pressure chamber 8 to the outside 48, causing to a certain degree foaming of the espresso beverage resulting in crema being produced.
After being discharged through the aperture 11, the espresso beverage and its crema components flow through the outlet 16 provided in the bottom 46 of the filter basket holder 15, whence it may collect in an espresso cup placed beneath the outlet 16 or some other container (not shown). As the espresso beverage flows through the pressure chamber 8, this chamber serves to maintain the espresso beverage under pressure, because the amount of espresso allowed to enter the pressure chamber 8 through the filter perforations 4 is greater than the amount that can be discharged through the aperture 11.
In the perm~nPnt filter element 25 of FIG. 9, a thin perfo-rated sheet provided with a number of apertures 11 is substi-tuted for the metal disk 12 in which the aperture 11 of FIG. 1 is formed. The sum of the overall cross-sections of the aper-tures 11 of FIG. 9 corresponds approximately to the-cross-section of the single aperture 11 of FIG. 1. The perforated sheet 12 contributes to enhancing the formation of crema still 2~ further because, as a result of the relatively thin metal film 12, the espresso beverage experiences a high velocity and a high pressure drop in a m;n;mllm of time. It is preciselY these prop-erties which, according to the invention, increase the amount of crema produced. With the brewing chamber 28 filled with espresso grinds to a normal level using a normal degree of fine-ness and tamping, particularly good crema values result by main-t~; n; ng a water temperature of about 94 C, a pump pressure of about 10 bar, and an overall cross-sectional area of the aper-~ 21 81246 ~O g5/23544 PCT/EP95/00770 ture or apertures 11 of about 0.4 to 0.6 mm2. Upon completion of the brewing cycle, the piston 40 is retracted from the brew-ing chamber 28 in upward direction, and the filter basket holder 15 with the permanent filter element 25 can be removed or swung out of the espresso maker. Then the permanent filter element 25 is ready for removal from the filter basket holder 15 by means of the handle 43 for cle~n; ng purposes. In an embodiment in which the perm~ent filter element 25 is held in its receptacle 45 with a light press-fit, it may remain seated in the filter basket holder 15, so that it is cleaned together with the filter basket holder which in this event is advantageously provided with a handle (not shown).
As appears from FIGS. 1 and 9, receiving channels 30 are formed in the p~essure chamber 8 enabling the espresso beverage to be channeled to the central aperture 11 provided in the per~nent filter element 25. At the same time, the receiving channels 30 serve the function of supporting the filter base plate 1 which is thus largely prevented from being deflected in operation. In FIG . 9, adjoining the perforated sheet 12 in the direction of flow A is the discharge port 35 which is part of the supporting plate 2 and of a diameter which is a multiple of the overall cross-section of the apertures 11 to allow the espresso beverage to flow out freely without further blocking its movement. As shown in FIG. 1, the brew delivered through the discharge port 35 is then directed to the outlet 16 provided in the filter basket holder 15 which, as a rule, is comprised of two adjacent spouts. This enables two cups to be filled with espresso at the same time. The compact construction of the per-manent filter element 25 of the present invention affords ease of handling while producing good crema.
Claims (14)
1. A cup-shaped permanent filter element (25) for a domestic espresso maker, which receives the espresso grounds in a brewing chamber (28), has at its bottom a sieve-type filter base plate (1) provided with filter perforations (4), and is in-sertable into a filter basket holder (15) from which the espresso beverage is allowed to be discharged through the filter perforations (4), and with a supporting plate (2) mounted down-stream of the filter base plate (1) as seen when looking in the direction of flow (A) of the espresso beverage, the supporting plate (2) combining with the filter base plate (1) to form a pressure chamber (8) for the purpose of improving the production of crema, the espresso beverage being required to flow through the pressure chamber before it is allowed to exit on the filter basket holder (15), with the generation of pressure in the pres-sure chamber (8) being effected by a means (11) mounted on the pressure chamber outlet and operating to increase the flow resistance, c h a r a c t e r i z e d i n t h a t the pressure chamber (8) and the permanent filter element (25) are firmly connected with each other mechanically, and that the means (11) for the generation of pressure is comprised of one or several apertures whose overall cross-section is sufficiently small relative to the overall cross-section of the filter perforations (4) in the filter base plate (1) of the permanent filter element (25) to produce a pressure drop in the aperture(s) (11) suffi-cient for the production of crema.
2. The permanent filter element as claimed in claim 1, c h a r a c t e r i z e d i n t h a t the permanent filter element (25) is formed by a cylindrical cup wall (17) providing the brewing chamber (28), that the lower peripheral area of the cup wall (17) includes a circumferential collar (18) extending in the direction of the cup axis (27), and that the filter base plate (1) and the supporting plate (2) are both supported upon the collar (18) and secured to it, that is, to the cup wall (17).
3. The permanent filter element as claimed in claim 2, c h a r a c t e r i z e d i n t h a t the filter base plate (1) and the supporting plate (2) are secured to the collar (18) by injection molding.
4. The permanent filter element as claimed in claim 3, c h a r a c t e r i z e d i n t h a t the supporting plate (2) is fabricated from a plastic, and the filter base plate (1) is made of a thin sheet of high-grade steel.
5. The permanent filter element as claimed in claim 3, c h a r a c t e r i z e d i n t h a t the filter base plate (1) and the supporting plate (2) are surrounded by a plastic frame member (3) serving a holding function, which establishes the firm and tight connection with the collar (18) and is injection-molded onto the parts (2, 3).
6. The permanent filter element as claimed in claim 4 or claim 5, c h a r a c t e r i z e d i n t h a t at least one holding opening (19) is provided in the peripheral area of the filter base plate (1) for substantially snugly receiving therein a holding section (20) of the frame member (3).
7. The permanent filter element as claimed in claim 1, c h a r a c t e r i z e d i n t h a t the cup wall (17) and the collar (18) are made of metal, preferably of high-grade steel, with the collar (18) engaging the plastic frame member (3).
8. The permanent filter element as claimed in claim 1, c h a r a c t e r i z e d i n t h a t the cup wall (17), the collar (18) and the frame member (3) are integrally made of plastic.
9. The permanent filter element as claimed in claim 1, c h a r a c t e r i z e d i n t h a t a metal disk (12) is inserted in the supporting plate (2), and that the metal disk (12) is a perforated sheet.
10. The permanent filter element as claimed in claim 1 or claim 9, c h a r a c t e r i z e d i n t h a t the sum of the area of the aperture or apertures (11) is not greater than 0.6 mm, preferably 0.4 mm.
11. The permanent filter element as claimed in claim 10, c h a r a c t e r i z e d i n t h a t the perforated sheet has a thickness of between 0.2 and 0.6 mm, preferably 0.4 mm.
12. The permanent filter element as claimed in claim 9, c h a r a c t e r i z e d i n t h a t the aperture or apertures (11) is or are of a triangular cross-section, prefer-ably representing an equilateral triangle.
13. The permanent filter element as claimed in claim 9, c h a r a c t e r i z e d i n t h a t the aperture or apertures (11) is or are of a circular cross-section.
14. The permanent filter element as claimed in claim 1, c h a r a c t e r i z e d i n t h a t essentially along the underside (6) of the filter base plate (1) there is arranged at least one labyrinth- or meander-shaped receiving channel (30) for receiving and conveying the filtered fluid to the common means (11) operating to increase the flow resistance.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE9403616U DE9403616U1 (en) | 1994-03-03 | 1994-03-03 | Pot-shaped permanent filter insert |
| DEU.M.G9403616.0 | 1994-03-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2181246A1 true CA2181246A1 (en) | 1995-09-08 |
Family
ID=6905450
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002181246A Abandoned CA2181246A1 (en) | 1994-03-03 | 1995-03-02 | Pot-shaped permanent filter cartridge |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0749283B1 (en) |
| AT (1) | ATE165719T1 (en) |
| CA (1) | CA2181246A1 (en) |
| DE (2) | DE9403616U1 (en) |
| WO (1) | WO1995023544A1 (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7383763B2 (en) | 1997-09-30 | 2008-06-10 | Sara Lee/De N.V. | Assembly for use in a coffee machine for preparing coffee |
| CN102482030A (en) * | 2009-06-17 | 2012-05-30 | 莎莉／De有限公司 | System, method and capsule for preparing a beverage |
| US9161652B2 (en) | 2009-06-17 | 2015-10-20 | Koninklijke Douwe Egberts B.V. | Capsule and system for preparing a beverage comprising soluble substance |
| US10709285B2 (en) | 2016-03-17 | 2020-07-14 | De'longhi Appliances Srl | Double-walled filter for coffee machine with improved dispensing |
| IT201900012573A1 (en) * | 2019-07-22 | 2021-01-22 | De Longhi Appliances Srl | FILTER FOR FILTER CUP OF A COFFEE MACHINE |
| US11134806B2 (en) | 2016-03-17 | 2021-10-05 | De'longhi Appliances Srl | Disassemblable double-walled filter for coffee machine with tightening element |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2805726B1 (en) * | 2000-03-02 | 2002-05-03 | Seb Sa | FILTER HOLDER FOR COFFEE MAKER OF EXPRESSO TYPE |
| FR2833825B1 (en) | 2001-12-24 | 2004-07-02 | Carasso Bossert S A | COFFEE FILTER HOLDER |
| US20030226449A1 (en) | 2001-12-24 | 2003-12-11 | Philippe Carasso | Coffee Filter holder |
| FR2838947B1 (en) | 2002-04-25 | 2004-08-13 | Carasso Bossert S A | COFFEE FILTER HOLDER |
| FR2837370B1 (en) | 2002-03-19 | 2005-02-18 | Carasso Bossert S A | FILTER HOLDER AND FILTER FOR COFFEE MACHINE |
| DE102009049158A1 (en) * | 2009-10-12 | 2011-04-21 | Niro-Plan Ag | Filter for the preparation of liquid foods from a beverage substrate and method for the production of a filter |
| ITUA20161785A1 (en) * | 2016-03-17 | 2017-09-17 | De Longhi Appliances Srl | DOUBLE WALL FILTER FOR COFFEE MACHINE´ |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0124473A1 (en) * | 1983-01-06 | 1984-11-07 | Isor AG | Automatic espresso coffee machine |
| IT1243337B (en) * | 1990-07-13 | 1994-06-10 | Rancilio Macchine Caffe | ESPRESSO COFFEE MACHINE |
-
1994
- 1994-03-03 DE DE9403616U patent/DE9403616U1/en not_active Expired - Lifetime
-
1995
- 1995-03-02 DE DE59502115T patent/DE59502115D1/en not_active Expired - Fee Related
- 1995-03-02 CA CA002181246A patent/CA2181246A1/en not_active Abandoned
- 1995-03-02 WO PCT/EP1995/000770 patent/WO1995023544A1/en active IP Right Grant
- 1995-03-02 AT AT95910545T patent/ATE165719T1/en not_active IP Right Cessation
- 1995-03-02 EP EP95910545A patent/EP0749283B1/en not_active Expired - Lifetime
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7383763B2 (en) | 1997-09-30 | 2008-06-10 | Sara Lee/De N.V. | Assembly for use in a coffee machine for preparing coffee |
| CN102482030A (en) * | 2009-06-17 | 2012-05-30 | 莎莉／De有限公司 | System, method and capsule for preparing a beverage |
| CN102482030B (en) * | 2009-06-17 | 2014-11-26 | 皇家戴维艾格伯茨有限公司 | System, method and capsule for preparing a beverage |
| US9161652B2 (en) | 2009-06-17 | 2015-10-20 | Koninklijke Douwe Egberts B.V. | Capsule and system for preparing a beverage comprising soluble substance |
| US9604776B2 (en) | 2009-06-17 | 2017-03-28 | Koninklijke Douwe Egberts B.V. | System, method and capsule for preparing a beverage |
| US10709285B2 (en) | 2016-03-17 | 2020-07-14 | De'longhi Appliances Srl | Double-walled filter for coffee machine with improved dispensing |
| US11134806B2 (en) | 2016-03-17 | 2021-10-05 | De'longhi Appliances Srl | Disassemblable double-walled filter for coffee machine with tightening element |
| IT201900012573A1 (en) * | 2019-07-22 | 2021-01-22 | De Longhi Appliances Srl | FILTER FOR FILTER CUP OF A COFFEE MACHINE |
| EP3769648A1 (en) * | 2019-07-22 | 2021-01-27 | De'Longhi Appliances S.r.l. | Filter for a filter holder cup of a coffee machine |
Also Published As
| Publication number | Publication date |
|---|---|
| ATE165719T1 (en) | 1998-05-15 |
| DE9403616U1 (en) | 1995-07-06 |
| EP0749283B1 (en) | 1998-05-06 |
| WO1995023544A1 (en) | 1995-09-08 |
| DE59502115D1 (en) | 1998-06-10 |
| EP0749283A1 (en) | 1996-12-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |