WO2009127952A1

WO2009127952A1 - Volumetric flow measuring device for coffee machines

Info

Publication number: WO2009127952A1
Application number: PCT/IB2009/005262
Authority: WO
Inventors: Ugo Giovanni Allevi
Original assignee: Prometec
Priority date: 2008-04-15
Filing date: 2009-04-14
Publication date: 2009-10-22
Also published as: ITCR20080008A1

Abstract

Volumetric flow meter for coffee machines comprising a hollow cylindrical structure (10), two tangential couplings (80) for the connection of pipes conveying water respectively into (I) and out of (O) said hollow cylindrical structure (10), an impeller (30) which can be associated with rotational support systems(50), suitable to allow rotation thereof on a plane normal to a pin (40) forming the rotation axis of the impeller (30), electronic means for detecting the revolutions of said impeller (30), wherein said pin (40) is associated with the impeller (30) and comprises two convex ends (41) symmetrical with respect to the rotation plane of this impeller and wherein said rotational support systems (50) are associated with said hollow cylindrical structure (10), are disposed symmetrically with respect to said rotation plane of the impeller and comprise an axial support portion (51) and a radial support portion (52) for said ends (41) of the pin (40).

Description

"VOLUMETRIC FLOW MEASURING DEVICE FOR COFFEE

MACHINES" * * *

DESCRIPTION The invention relates to the sector of measurement instruments for controlling physical parameters.

In particular the invention relates to a volumetric flow measuring device, or flow meter, applicable to coffee machines, from the simplest machines for domestic use to professional machines for bars and restaurants.

Common flow meters operating in low flow rate ranges, for example 40-150 cc/min such as those required for water metering devices in the aforesaid coffee machines, are of the volumetric turbine type. The flow to be quantified is channelled and passes through a hydraulic turbine, also called impeller, with a rotation speed, for example expressed in rpm, proportional to the flow rate. Generally, a kinematic mechanism then causes an indicator on a dial to rotate, so that the quantity of liquid that has passed through can be read; otherwise, using the known Hall effect principle, a fixed sensor detects the revolutions of the impeller, by means of the magnetic field generated by a magnet associated with this impeller.

FR 2 538 103 A1 describes a meter of this type comprising a hollow structure delimited at the bottom by a fixed base and at the top by a removable cap. An impeller, or a bladed wheel, pivotally supported by a pin fixed to the base of the instrument, is housed inside the hollow structure. The liquid, conveyed inside the hollow chamber through a tangential feed duct, strikes the blades of the wheel, which is thus made to rotate, and then flows out through an outlet duct. At least one magnet is positioned on said impeller, which when passing in proximity of a specific fixed sensor associated with the removable cap, generates an impulse for each revolution, or fraction of revolution, completed, which is immediately read by an electronic metering and control unit located on the coffee machine.

These types of instruments have numerous limits and disadvantages which lead to imprecise flow rate metering with substantial error percentages, especially in the range used in coffee machines.

The impeller only has one axial constraint with punctiform support, while it has no specific radial constraint: at low rotation speeds and with low liquid flow rates (typical conditions occurring in the field of coffee machines), it tends to "float" on the pin, being subject to an upward thrust which destabilizes it, and to tilt with respect to the vertical due to the lever arm that is created between the force developed by the jet striking the impeller and this pin. These imbalances cause the impeller to rest axially on the cover and laterally on the pin, generating inconstant mechanical and hydraulic axial and radial frictions. To attempt to overcome these problems some instrument manufacturers have modified the geometry of the hollow structure in which the impeller is housed, inserting radial barriers facing the impeller on the cover; these increase the turbulence of the motion and create a downward thrust of the impeller on the tip of the pin. The barriers thus have the function of pushing the turbine onto the fulcrum, improving only in part, and at high flow rates, the support and constraint system. However, by increasing the turbulence of the motion and exiting from a laminar flow field, there is the risk of disadvantageously modifying the boundary conditions and providing inaccurate flow rate readings, with substantial approximations which compromise the efficiency of the instrument.

Moreover, due to the constraint system of the impeller, volumetric flow meters available on the market can only be installed horizontally on coffee machines: therefore the rotation plane of the turbine, orthogonal to the axis of the pin, must be in horizontal position, excluding installation with different inclination angles.

The object of the invention is to overcome these problems which compromise the efficiency of the measurement instrument.

It is desirable to minimize the hydraulic and mechanical frictions which can be generated by the impeller rubbing on the pin and on the closing cover. The effectiveness of flow measurement instruments is evaluated by constructing a graph which places the flow rate of the fluid in relation with the measurement deviation % of the ratio between flow rate and rpm (gain). Designing an instrument with high precision means attempting to obtain a curve as close as possible to a straight line, eliminating, reducing or in any case evening out any load losses and frictions, which on the graph are shown as peaks and drops in the curve. In substance, this means preventing the impeller from becoming laterally unbalanced on the pin or from floating thereon.

A further object is to allow use of the instrument on any type of coffee machine, making it universal, practical, with limited overall dimensions and easy to install, but also to allow orientation thereof in space, so that it can be installed with any inclination and rotation.

These objects are achieved with a volumetric flow meter for coffee machines comprising:

- a hollow cylindrical structure;

- two tangential couplings for the connection of pipes conveying water respectively into and out of said hollow cylindrical structure; - an impeller which can be associated with rotational support systems, suitable to allow rotation thereof on a plane normal to a pin forming the rotation axis of the impeller;

- electronic means for detecting the revolutions of said impeller, characterized in that:

- said pin is associated with the impeller and comprises two convex ends symmetrical with respect to the rotation plane of this impeller;

- said rotational support systems are associated with said hollow cylindrical structure, are disposed symmetrically with respect to said rotation plane of the impeller and comprise an axial support portion and a radial support portion for said ends of the pin. Advantageously, the pin is a through pin and is made of metal, for example hardened steel, stainless steel, synthetic metal, etc.. According to a preferred embodiment, said electronic detection means comprise at least one Hall effect sensor which detects the passage of at least one magnet installed on the impeller and sends electrical pulses which allow the number of revolutions of the impeller to be counted. A further external electronic component receives the signal from the sensor and closes a solenoid valve arranged on the water supply duct when a predetermined volume has passed through.

Advantageously, the through pin of the turbine, associated with these types of axial and radial supports, ensures a rotation with almost null mechanical friction values, for any flow rate value. Due to the materials selected and the surface finishes used for these components, i.e. gemstone bearings, for example ruby, for the supports and hard metal, for example Zirconium Oxide, for the pin, the spaces between impeller and body have been reduced, thus improving the precision of the quantity of volume displaced for each revolution. The inner walls of the hollow cylindrical structure have also been subjected to polishing and lapping treatments which considerably decrease any hydraulic friction, evening out the rotation.

The configuration of the pin and of the supports not only ensures more accurate measurement, but it also makes it possible to produce an entire instrument which is perfectly symmetrical with respect to the rotation plane of the impeller: the magnets for measuring the revolutions are through magnets: the hollow cylindrical structure can be closed with two identical covers; the electronic control unit can be associated with both covers and rotated in its seat; it is possible to invert the direction in which the flow rotates and the relative position of the connectors for the feed and outlet pipes by inverting during installation the positions of the electronic control unit with the other closing cover.

Advantageously, these embodiments allow the instrument to be oriented in space as desired, adapting to all installation situations. Even more advantageously, it is possible to pre-calibrate the instrument positioning, inside the connector of the feed pipe, an appropriate nozzle selected according to operating requirements and thus establishing the operating ranges for the outlet flow rate.

Two nuts can also be applied to the two pipe couplings for direct fixing of the instrument to the coffee machine, allowing direct fastening to the sheet metal of the machine, reducing overall dimensions to a minimum and eliminating unsightly and inconvenient locking systems.

These and other advantages of the invention will be more apparent in the text below, in which a preferred embodiment is described by way of non limiting example and with the aid of the figures, wherein:

Figure 1 shows an axonometric view of the invention;

Figure 2 shows a sectional axonometric view, with particular attention to the internal components;

Figure 3 shows an axial section of the invention, in a direction orthogonal to the rotation plane of the impeller;

Figure 4 shows a top view of the instrument, partly sectional at the fluid feed coupling;

Figures 5 and 6 show exploded axonometric views of all the components of the invention and of the impeller; Figure 7 shows a partly sectional view of a closing cover of the cylindrical structure and of the axial and radial supports associated therewith.

With reference to Figure 1 , the invention comprises externally a hollow cylindrical structure 10 made of stainless steel, delimited laterally by an annular body 15, at the bottom and at the top by two covers 20 and 21 , also made of stainless steel, identical, suitable to form a perfectly symmetrical casing. A control unit 70, with electronic detection and electrical connection means 72, is associated with the top cover 20, but without distinction can be positioned on the bottom cover 21 , and the perfectly circular shape of the control unit 70 allows it to rotate by 360° in both seats. A threaded seat 75 allows fixing of a micro-connector for electrical connection of the instrument. Disposed along the annular body 15 are two tangential couplings 80 for connection of the pipes (not shown) conveying the water required to prepare the coffee: a coupling I will receive the duct for feed of the liquid to be metered, the other coupling O will be used to deliver only the quantity of fluid measured by the instrument. The pipes can be made of metal, copper, iron, plastic, PE or RILSAN. Also associated with said couplings are threaded portions 82 and nuts 81 and 83, which can be used respectively for fixing the instrument directly to the structure of the coffee machine and for direct fixing to the pipes.

Figures 2 and 3 instead show a cutaway section and a cross section of the instrument to allow all the inner components to be viewed. All the surfaces of the chamber are mirror polished, both to offer less resistance to the flow of water, but also for hygiene purposes. Positioned in the cylindrical chamber is an impeller 30 installed on a pin 40, which passes through it along its rotation axis. Both ends 41 of said pin 40 are enclosed by support systems 50 made of gemstones, hard and with lapped and mirror polished surfaces. These support systems comprise cylindrical portions 52 disposed parallel to the rotation axis and therefore acting radially with respect to the pin, and portions 51 disposed horizontally with respect to said axis and therefore acting axially. Said portions 52 and 51 are made of sintered ruby and are commonly known technically as bearing and counter bearing respectively.

In diametrically opposite positions, on the impeller 30, two magnets 60, also through magnets, are arranged, positioned with the poles N, S inverted, with the passive function of revolution counters. According to the variant shown in the figure, the detection electronic control unit 70, electrically connected through the connectors 72, is positioned on the top cover 20. Said control unit comprises at least one sensor 73 of known type, using the Hall effect principle which, detecting the passage of the two magnets 60 is capable of reading the revolutions of the turbine 30 activated by the feed water flow rate and of emitting electrical signals. After counting the predetermined revolutions, an electronic control unit installed in the coffee machine (not shown) activates a solenoid valve (not shown) located along the feed duct I, interrupting the flow of water and concluding the measurement process. Operation is indicated by a LED 77, positioned on a support surface 74 of the electronic components, again associated with the control unit 70, closed by a cover 76 made at least partly of translucent material and therefore backlit during delivery and measurement. Inside the control unit 70 the electronic components are embedded in a transparent insulating resin for electrical protection reasons.

Also positioned inside the feed duct I is a nozzle 90, easily removable and replaceable, provided with a hole 91 which, according to the diameter selected, allows pre-calibration of the instrument.

The two metal covers 20 and 21 , identical and symmetrical, are caulked onto the annular body 15 interposing two gaskets 22 made of food grade silicone, to ensure the quality and duration of the watertight seal and of operation without the need for maintenance.

The identity of the two covers 21 and 22 allows them to receive, without distinction, the control unit 70 or a simple cap 71 with the same shape.

In Figure 3, which shows a sectional view of the instrument along a plane transverse to the rotation plane of the impeller 30, the symmetry of each component with respect to the rotation plane is evident: the two ends 41 of the pin 40 made of hard metal, with reduced diameter and convex tip; the supports 50 with the ruby bearings; the covers 20 and 21.

Figure 4 shows a top view of the instrument, partly sectional, along a horizontal plane, at the feed pipe coupling I. It is pointed out that the nozzle 90 simply screws into this coupling and is therefore easy to replace, if the feed flow rates require to be modified. Both couplings I- O 80, "IN" and "OUT", are integrated with a system 79, 81 , 82, 83 to clamp the instrument to the machine and the pipes to these couplings, which allows easy and precise installation.

The part of the couplings 80 connected to the annular body 15 has a square section and has the function of allowing gripping and prevent rotation during operations to install and connect the instrument and the pipes.

Figures 5 and 6 identify all the components of the instrument separately: the electronic control unit 70 and the cap 71 , the covers with the gaskets 20, 21 and 22, the impeller 30, the two through magnets 60 and the pin 40 with the reduced convex ends 41, the annular body 15 with the two lateral couplings 80 for the pipes I-O, the moving nozzle 90, the nuts 81 and 83 and the ferrules 79, for installation and direct connection, through hydraulic seal of bi-conical mechanical type, of the feed and delivery pipes.

Figure 7 shows a detail of the support 50 of the pin 40 according to a preferred embodiment; the convex end of the axis is literally enclosed by a hollow ruby cylinder 52, the bearing, surmounted by a disc 51 in the same material, the counter bearing. As will be apparent to the skilled man, the invention has been described referring by way of example to a volumetric flow meter applicable to coffee machines, but it can be used more in general on any machine or automatic or semi-automatic beverage dispenser, always achieving the advantages specified above.

Claims

1) Volumetric flow meter for coffee machines comprising:

- a hollow cylindrical structure (10);

- two tangential couplings (80) for the connection of pipes conveying water respectively into (I) and out of (O) said hollow cylindrical structure (10);

- an impeller (30) which can be associated with rotational support systems (50), suitable to allow rotation thereof on a plane normal to a pin (40) forming the rotation axis of the impeller (30);

- electronic means for detecting the revolutions of said impeller (30); characterized in that:

- said pin (40) is associated with the impeller (30) and comprises two convex ends (41) symmetrical with respect to the rotation plane of this impeller;

- said rotational support systems (50) are associated with said hollow cylindrical structure (10), are disposed symmetrically with respect to said rotation plane of the impeller and comprise an axial support portion (51) and a radial support portion (52) for said ends (41) of the pin (40).

2) Volumetric flow meter for coffee machines as claimed in claim 1 , characterized in that said radial (52) and axial (51) support portions are of the type with bearing and counter-bearing.

3) Volumetric flow meter for coffee machines as claimed in claim 2, characterized in that said rotational support systems (50) with bearing (52) and counter bearing (51) comprise mirror polished gemstones.

4) Volumetric flow meter for coffee machines as claimed in claim 3, characterized in that said gemstones (51 , 52) comprise rubies.

5) Volumetric flow meter for coffee machines as claimed in claim 1 , characterized in that said hollow cylindrical structure (10) comprises two covers (20, 21) disposed to close said structure (10) at the top and at the bottom.

6) Volumetric flow meter for coffee machines as claimed in claim 1 , characterized in that said electronic means for detecting the revolutions of said impeller (30) comprise at least one fixed Hall effect sensor (73), which detects the passage of magnetic means (60) associated with said impeller (30) and emits electrical pulses.

7) Volumetric flow meter for coffee machines as claimed in claim 6, characterized in that said magnetic means (60) comprise two through magnets, i.e. installed on the impeller (30) so as to pass therethrough parallel to its rotation axis.

8) Volumetric flow meter for coffee machines as claimed in claim 6, characterized in that said electronic means which detect the passage of magnets (60) are contained in a control unit (70) which can be associated either with the top cover (20), or with the bottom cover (21).

9) Volumetric flow meter for coffee machines as claimed in claim 8, characterized in that said electronic control unit (70) is free to rotate by 360° in the seat present in one of the covers (20, 21).

10) Volumetric flow meter for coffee machines as claimed in claim 8, characterized in that the electronic control unit (70) comprises a LED, protected by a translucent cover (76), suitable to supply an operating signal.

11) Volumetric flow meter for coffee machines as claimed in claim 1 , characterized in that a removable and interchangeable nozzle (90) is arranged inside the coupling (80) of the feed pipe (I).

12) Volumetric flow meter for coffee machines as claimed in claim 1 , characterized in that the couplings for the pipes (I, O) comprise a threaded portion (82) and components (79-81-83) for fixing directly to the structure of the machine and direct coupling of the hydraulic pipes.

13) Volumetric flow meter for coffee machines as claimed in claim 1 , characterized in that the hollow cylindrical structure (10) comprises an annular body (15) on which the covers (20, 21) are fixed, with interposition of a gasket in food grade silicone (22).

14) Volumetric flow meter for coffee machines as claimed in one or more of the preceding claims, characterized in that all the components are symmetrical or can be symmetrically associated with the hollow cylindrical structure (10) with respect to the plane of the impeller (30).

15) Coffee machine characterized in that it comprises a volumetric flow meter as claimed in at least one of the previous claims.