IL47674A - Dual-purpose heating element for an electric coffee making machine - Google Patents

Description

nsp luiDO "my »Ο'¾ΜΙ-Π man ηιι n * > a 5? n A DUAL-PURPOSE HEATING ELEMENT FOR AN ELECTRIC COFFEE MAKING MACHINE.

The invention relates to a dual-purpose electric heating unit for a machine making filtered coffee or other beverages, of the type comprising a) an electric hot-plate adapted for placing on it a removable carafe with a preferably flat bottom, b) filter holding means positioned above the mouth of the carafe, c) a water container provided with an opening in its top for filling it with a predetermined quantity of water, and with a water outlet in its bottom portion provided with automatic valve means serving to prevent the return of water and steam into the container, d) water conduit means extending from the water outlet in the container to a point above the filter holding means, a portion of which conduit is provided with electric heating means for heating and partly evaporating the water issuing from the container and to raise it, with the aid of steam bubbles, to the filter holding means .

The majority of the existing coffee making machines are provided with two electric heating elements:- a first element for heating the wate in the conduit controlled by a thermostat which interupts the current as soon as the conduit is empty, and a second element for heating the hot-plate which is continually energised as long as the machine is switched on.

With a viev to dispense vith one of the two electric heating elements it has been proposed to connect a irater conduit in the form of a tube to the underside of a carrier of good thermal conductivity vhich carrier is intimately connected to a hot-plate. A tubular heating body is intimately connected underneath and along the said tube, and temperature limiting means connected to the carrier serve to control the energy input to the heating body.

The drawback of this latter embodiment is that the hot-plate is only indirectly connected to the heating body vhich may lead to overheating of the water tube..

Another drawback is the relatively high cost of tubular heating bodies. Finally, the thickness of this body adds to the total height of the coffee making machine, while additional height is required for its thermal insulation vhich is necessary as protection against damage to table tope etc.

It is, therefore, the object of the present invention to provide a single, flat heating element positioned betveen the water conduit and the hot-plate of a coffee making machine, vith a viev to reduce the total height of the apparatus, and to lover the cost of the machine.

It is a further object t control the temperature of both the conduit and the hot-plate, in order to prevent overheating vhenever the machine is kept in svitched-on state.

The dual-purpose heating unit for a coffee making machine of the kind referred to, having a portion of the vater conduit means passing underneath the said hotplate, comprises :-a) a flat electric resistor covered by electric insulating sheet material on both sides, positioned in a substantially horizontal plane underneath and in proximity of the said hot-plate, b) a flat pad of a heat-resisting material of low heat- conductivity, positioned adjoining the upper insulated surface of the electric resistor, c) an upper heat conductive plate integral with, or heat* oonductively connected to the said hot-plate, and having a flat lower surface in contact vith the upper surface of the said pad, d) a love heat-conductive plate being integral vith, or heat-conductively connected to a po rtion of the said vater conduit means, and having an upper surface in contact vith the lover insulated surface of the electric resistor, e) resilient spring means engaging vith, and connecting the upper heat-conductive plate and the lover heat- conduotive plate respectively, adapted to compress the said electric resistor and the lov heat-conductive pad between their opposed surfaces, f) temperature controlling means adapted to electrically energise and de-energise the electric resistor in response to the temperature of the water conduit means. The heat-conductivity of the pad is so chosen that it restricts the flow of thermal energy through the upper plate to the hot-plate, to a fraction of the flo of thermal energy through the lower plate to the water conduit means* In a preferred embodiment of the invention the water conduit means consist of a metal pipe incorporated in the lower heat-conductive plate.

In the accompanying drawings which illustrate, by way of example, two embodiments of the heater portion of a coffee making machine, Figure 1 is a vertical section through a hot-plate, a water heating and evaporating conduit and an electric heating unit, Figure 2 illustrates, on its right half, a section along A-A of Figure 1 and, on its left half, a section along B-B of Figure 1 , Figure 3 is a section through a dual-purpose heating unit with a U-shaped pipe serving as water conduit means, and Figure 4 is a plan view of the water conduit means shown in Figure 3, seen in the direction of arrows C-C.

With reference to Figures 1 and 2 of the drawing a water heating and evaporating conduit in the shape of a metal pipe 1 integral with a flat plate 2 is in intimate contact, substantially over its entire upper, flat surface with an electric resistor 3 of the known kind serving as a heating element. The resistor is provided on its both sides with thin electrical sheet insulation of known properties permitting the ready transfer of heat energy and is, in addition, partly heat-insulated over its upper surface by a pad 4 of a heat-resistant, resilient material of low heat-conductivity, composed of felted fibres, as e.g. glass wool. The pad 4 adjoins the lower flat surface of an upper metal, heat-rconductive plate 5 which is of substantially the same width as the plate 2; both plates 2 and 4 are forcefully pressed against the interposed resistor 3 and the pad 4 by two U-shaped spring clamps 6 extending along the parallel edges of the two plates and engaging with these plates in longitudinal recesses 7 of triangular cross section.

A flat, thin heater plate 8 is intimately and heat-conductively connected to the top surface of the upper plate 5, so as to obtain sufficient heat energy flow to the heater plate, which in turn heats a glass carafe 9 through its flat bottom. The carafe is kept in its central position on the heater plate by means of a bevelled ring 10 that surrounds the plate and forms part of the coffee maker frame.

Two vertical pipes 11 and 12 provided with 90 -bends at their lower ends are connected to the ends of the pipe 1 and sealed therein by suitable silicone rubber rings 13. One of the vertical pipes, for instance No. 11, extends from the bottom outlet of a water container to the water inlet of pipe 1, and pipe 12 from the outlet of pipe 1 to a point above the filter holder of a standard coffee maker.

A temperature regulating device 14, "thermostat" for short, is attached to the bottom surface of the lower plate 2, adjacent the pipe 1 and is wired to an external lead and to the electric resistor in a manner known pe se. It is adjusted to energise the resistor as long as there is water in the conduit and to interrupt the circuit whenever the plate (2) has reached a temperature a few degrees above boiling point, indicating that no water in liquid state remained in the pipe. As long as the resistor is energised, most of the heat emitted flows through the lover plate to the conduit, heating and evaporating the water, while only a small fraction of the heat flows towards the heater plate through the pad of low heat-conductivity and keeps the heater plate at a temperature considerably belov that of the water conduit. As soon as the current is interrupted the temperature of the conduit gradually drops to a temperature below water boiling point to which the thermostat is set to close the circuit and to re-energise the resistor.

The heat permeability of the pad is designed so as to maintain the heater plate at a suitable temperature of about 40 to 50°C, vhile the temperature of the water conduit is below boiling point. This will ensure that the beverage in the carafe is kept sufficiently hot, while the conduit is not dangerously warm. As long as the coffee making machine is plugged in, the thermostat will alternately energise and de-energise the resistor and will prevent the heater plate to become too hot, even if the carafe has been completely removed.

The embodiment illustrated in Figures 3 and 4 differs from that shown in Figure 1 and 2 in that the upper plate 5 forms an integral part of the heater plate 8, and that the conduit means, on the other hand, are separated from the lower plate. The lower plate 2* is Rectangular and possesses a flat upper surface in contact with a resistor 3; its undereide is shaped to comprise four parallel, thin ribs 15 a, b, c and d projecting out at right angles to the lower surface. The distance between ribs 15a and between 15c and 15d respectively equals that of the external diameter of a metal tube 1 ' to be inserted, and the plate surface between each two thus-spaced ribs at their roots, is semi-cylindrical, also corresponding to the said tube-diameter.

A tube 1 * bent to U-shape is inserted into the space between each pair of ribs, and the ribs, are, after insertion, bent over each tube portion to enclose it tightly, thus retaining the tube in its position and ensuring satisfactory heat transfer from the electric resistor through the plate 2' to the tube and the water contained therein. On the left of the drawing the bent-over ribs are shown in broken lines. The combined heater and upper plate 8* is of substantially identical cross section to the two plates shown in Figures 1 and 2, except for the fact that there is no dividing plane and that the Material is of less thickness than in the previous embodiment. The upper and the lower plate have their surfaces pressed against a resistor 3 and a pad 4 by two longitudinal spring clips 6 engaging with the corresponding edges of the two plates.

A thermostat 14 is attached to the plate 2' and electrically wired to the resistor as before, all other parts being similar or identical with those depicted in Figures 1 and 2.

The main advantage of this embodiment is the possibility to use one continuous pipe as a donduit between the water container and the filter holder, needing no leak-prone connections inbetween. Another advantage is the unification of the heater plate with the upper plate, doing away with their heat conductive jointing as in the previous embodiment.

Only two embodiments of the dual-purpose heating unit have been described and illustrated in the foregoing, but modifications and alterations may be carried out by a person skilled in the art without departing from the spirit of the invention and the scope of the appended claims.

It is, for instance proposed to provide two parallel pipes (1) on the underside of a heat-conductive lower plate (2) and to connect the adjoining ends of the two pipes by a U-shaped tube or the like. This arrangement would serve to double the length of the heatable conduit, almost without additional cost.

The flat pad (4) not only serves as a heat-insulation against possible overheating of the hot-plate, but fulfills the important function of pressing the flat resistor firmly against the lower heat-conductive plate, thus ensuring intimate contact and maximum heat transfer between the two surfaces.

The heat-conductive plates 5, 2 and 2' are advantageously produced by extrusion of aluminum alloys or the like heat-conductive and non-corrosive materials, the extruded bars being cut to measure in accordance with size and length requirements.

The dual-purpose heating unit is not limited to its application to coffee making machines, but may be employed in all cases where two different temperatures are required for different portions of an appliance.

Claims (7)

1. C L A I M S t- 1 · In a machine for making filtered coffee or other beverages, of the kind having a portion of the water conduit means positioned underneath a hot-plate, a dual-purpose heating unit which comprises: a flat electric resistor covered by electric insulating sheet material on both sides, positioned in a substantially horizontal plane underneath and in proximity of the said hot-plate, a flat pad of a heat-resisting material of low heat-conductivity, positioned adjoining the upper insulated surface of the electric resistor, an upper heat-conductive plate integral with, or heat-conductively connected to the said hot-plate, and having a flat lower surface in contact with the upper surface of the said pad, a lower heat-conductive plate being integral with, or heat-conductively connected to a portion of the said water conduit means, and having an upper surface in contact with the lower insulated surface of the electric resistor, resilient spring means engaging with, and connecting the upper heat-conductive plate and the lower heat-conductive plate respectively, adapted to compress the said electric resistor and the low heat-conductive pad between their opposed surfaces, temperature controlling means adapted to electrically energise and de-energise the electric resistor in response to the temperature of the water conduit means .

2. In a machine for making filtered coffee as in Claim 1 , water conduit means in the shape of at least one metallic tube intimately and heat-conductively connected to the lower heat-conductive body.

3. In a machine for making filtered coffee as in Claims 1 and 2, a lower heat-conductive body comprising an upper flat surface contacting the installed electric resistor and downwardly projecting portions integral with its lower portion, adapted to clamp between them the tube-shaped water conduit means*

4. In a machine for making filtered coffee as in @laim 1 , a lower heat-conductive body having a flat upper surface and at least one substantially horizontal bore extending along and underneath the said surface serving, as water conduit means, this bore or bores having an inlet end and an outlet end adapted for connecting pipe means thereto.

5. In a machine for making filtered coffee as claimed in any of the preceding claims, a lower heat-conductive, metallic body consisting of an extruded portion cut to measure at its both ends.

6. In a machine for making filtered coffee as claimed in any of the preceding claims, an upper heat-conduet i body and a lower heat-conductive body each provided with corresponding projections adapted. to engage with resilient spring means in the shape of spring clips.

7. In a machine for making filtered coffee as in Claim 1 temperature controlling means in the form of a thermostat attached to the water conduit means and adjusted to energise the electric resistor, as long as there is water in liquid form in the conduit means and the temperature of the conduit means is below a predetermined value. The Applicant . GLUCKS AN