Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B43—WRITING OR DRAWING IMPLEMENTS; BUREAU ACCESSORIES
  • B43K—IMPLEMENTS FOR WRITING OR DRAWING
  • B43K5/00—Pens with ink reservoirs in holders, e.g. fountain-pens
  • B43K5/18—Arrangements for feeding the ink to the nibs
  • B43K5/1818—Mechanical feeding means, e.g. valves; Pumps
  • B43K5/189—Pumps

Definitions

• the present invention relates to a metering device and, in particular, to a metering device for metering a liquid as required and to a writing instrument with such a metering device.
• the electronic writing instrument comprises a writing tip which extends into a capillary space, which is also referred to as a secondary storage space.
• the small-volume secondary reservoir is fluidly connected to a large-volume primary, pressurized ink reservoir through an ink channel, with a reload valve located in the ink channel. If the fluid level in the secondary storage space is too low, the reload valve is actuated to open for a certain time until enough ink has been transported from the primary storage space into the secondary storage space that a sufficient filling level is established there.
• the level in the secondary storage room is measured using a capacitive sensor.
• the capacitive sensor is designed as a cylindrical capacitor, the capacity of which depends on the filling volume of the secondary storage space.
• a resonance circuit is used which measures the change in capacitance digitally by detuning an oscillating circuit.
• this circuit comprises an additional capacitance and a quartz oscillator.
• a counter is used to measure the difference in the vibration frequencies as an indication of the change in capacity.
• Demand-dependent dosing devices form a control system which consists of a storage tank, a buffer reservoir and a pressure control unit.
• the liquid is dispensed from the buffer reservoir. If the pressure in the buffer reservoir drops below a certain threshold due to the dispensing of liquid, the pressure in the buffer reservoir is compensated by the pressure control unit by transferring liquid from the storage tank into the buffer reservoir.
• Such metering devices are vacuum-controlled with respect to the ambient pressure, so that both the buffer reservoir and the storage tank must be closed in a pressure-tight manner with respect to the ambient pressure.
• both the buffer reservoir and the storage tank must be closed in a pressure-tight manner with respect to the ambient pressure.
• the vacuum in the vessel can be reduced, so that the vacuum-controlled delivery of liquid no longer works.
• a further possible reduction of the negative pressure takes place by reducing the ambient pressure.
• Such metering devices require a one-sided connection of the storage tank and buffer reservoir to the ambient air for the purpose of gas entry. This connection can lead to leakage of the stored liquid in the event of a malfunction.
• DE 33 21 301 AI discloses an ink supply system for writing instruments working with liquid ink, which have a large-volume ink space, which is connected via a recharge valve to a small-volume ink supply space adjacent to the writing element.
• the transfer of the ink from the large-volume ink space to the secondary storage space takes place in a sensor-controlled manner as a function of the ink volume present in the secondary ink space.
• a peristaltic pump is used as the reloading valve, which is driven in rotation by an electric motor and can generate the delivery pressure required to deliver the ink to the secondary ink chamber.
• the object of the present invention is to provide a safe metering device for metering a liquid as required.
• Another object of the present invention is to provide a writing device for a liquid writing medium with such a metering device.
• the present invention is based on the knowledge that it must be started from the concept in which the dispensed liquid reaches the dispensing point directly from the buffer volume. Instead, in the metering device according to the invention, the dispensed liquid is supplied via the main liquid channel, which extends directly from the primary container to the dispensing point.
• a secondary container is fluidly coupled to the main liquid channel at a branching point, that is to say arranged in the secondary flow.
• the liquid level in the secondary container is measured by means of a level sensor, which in turn feeds a valve control in order to control a valve provided between the primary container and the branch point in the main liquid channel.
• the secondary container is ventilated and coupled to the main fluid channel in such a way that the main fluid channel preferably fills with the liquid upstream of the secondary container.
• the metering device according to the invention thus uses the fill level in the secondary flow as a control variable, while in the prior art the fill level in the main flow has been used to control the valve. Since the valve in the metering device according to the invention actively prevents the unwanted inflow of liquid from the primary container, ventilation of the primary container can also be provided in addition to aeration of the secondary container. The gas pressures in the primary tank and in the secondary tank can therefore always be at ambient pressure.
• the flow in the main liquid channel is not measured directly in the main flow itself, but rather via the fill level in the secondary container separated from the main flow, which is coupled to the main flow in such a way that the Main stream preferably filled before the secondary stream.
• this can be achieved by capillary dimensioning of the main liquid channel and of the secondary container. If liquid is withdrawn, the level in the secondary container drops and vice versa. With this change, the consumption of liquid can be measured directly and, depending on this, the afterflow can be controlled via the valve.
• An advantage of the present invention is that both the secondary container and the primary container can be designed independently of the ambient pressure and the ambient temperature. The resulting accidents can no longer occur.
• Another advantage of the present invention is that by a suitable choice of the surface properties within the secondary container and the adjacent channels, there is the possibility of designing the capillary forces so that the metering device, if it is not intended to dispense any liquid, does not leak automatically, or the secondary volume does not overflow when there is an increase in pressure in the main liquid channel.
• the secondary container can be ventilated and can be dimensioned so that the capillary pressure in the secondary container decreases with increasing fill level. In preferred exemplary embodiments of the present invention, this can be achieved by increasing the cross section over the filling path. For such a disproportionate increase in volume over the filling path in the secondary container, a clear filling or emptying direction can be pronounced in the secondary container, particularly in the case of capillary systems.
• FIG. 1 shows a schematic diagram of the dosing device according to the invention
• FIG. 2a shows a coupling of the secondary container to the main liquid channel according to an embodiment of the invention
• FIG. 2b shows a coupling of the secondary container to the main liquid channel according to a further exemplary embodiment of the present invention
• FIG. 2c shows a coupling of the secondary container to the main liquid channel according to a further exemplary embodiment of the present invention
• FIGS. 3a to 3c show a conventional, hydrostatic filler, which is not controlled electronically.
• the filler comprises a filler housing 70 in which there is a filler cartridge 72 which is attached to a plastic component 74.
• the ink is finally discharged through a spring 76 to create a stroke 78.
• a conventional filler can generally be viewed as a complex microdosing system.
• a property of this system is that all essential fluidic functions are integrated in the only inexpensive plastic component 74.
• the fluidic system then shows weaknesses when so-called accidents occur, for example the change in the ambient temperature and the change in the external air pressure, as they occur e.g. B. can occur inside a starting aircraft.
• FIG. 3b in which the fluidic concept of the conventional filler is shown.
• the cartridge 72 which has both a vent 80 and which has an ink duct 82 as an outlet, which is coupled to a plurality of compensation chambers 84, which are usually located under the spring 76 of a fountain pen.
• the ink cartridge 72 To release ink, the ink cartridge 72 must be ventilated. If an unimpeded air inlet were provided for this purpose, the entire ink present in the ink cartridge would be dispensed via the spring due to the hydrostatic pressure. A regular levy, as required for writing, would then not be possible.
• the ventilation 80 of the ink cartridge 72 is in the form of a short capillary channel wetted by ink.
• This channel only opens when a negative pressure is built up in the ink cartridge, which corresponds to the capillary pressure of the ink in the ink conductor 82.
• the negative pressure in the ink cartridge draws the ink out of the channel and air can flow in from outside. The process ends when the inflowing air has released the negative pressure in the cartridge.
• the ink wets the short capillary channel 80 again and closes it.
• the portion of the volume of ink that is not used for writing must be stored in the equalization chambers 84, which form a buffer or a secondary volume.
• the intermediate storage is a capillary storage below the spring 76 in Form of plane-parallel plates, which are referred to as compensation chambers. This memory stores the excess amount of ink and releases it back onto the paper during the further writing process. If the buffer is empty, the ink required for writing is removed from the cartridge 72. This increases the negative pressure, and when the critical value is undershot, the short capillary channel 80 opens again and the cycle begins again.
• a disadvantage of this conventional system is the limited accident tolerance. Another disadvantage is that the reliable function of the system depends heavily on the coordination of the capillary pressures effective in the ventilation 80 and the secondary volume 84. These, in turn, are a function of the surface properties of the materials used and are therefore heavily dependent on the manufacturing parameters and contamination of the surfaces.
• the dosing device comprises a primary container for storing liquid 12.
• the primary container 10 thus contains the liquid 12 and a gas volume 14.
• the primary container is connected to a main liquid channel 16 which extends from an outlet of the primary container via a valve 18 and a branch point 20 to a delivery point 22, which in the case of using the metering device according to the invention is connected to a pen 24 in a fountain pen.
• a secondary container 26 is connected to the branching point 20 and communicates with the ambient atmosphere via a ventilation 28.
• the liquid level in the secondary container 26 is measured by means of a level sensor 30, which feeds its measurement signals to a valve control 32, which can open and close the valve 18.
• valve 18 is controlled by the sensor 30 and the valve control 32.
• the sensor is located in the secondary container below the nib 24 and monitors the fill level of the secondary container 26.
• the secondary container is via a fluidic T-piece, which through the branch point 20 is shown schematically in Fig. 1, coupled to the main liquid channel between the valve 18 and the nib 24.
• the T-piece 20 is designed capillary so that the front part of the spring, ie the tip of the spring with the grain, fills up in front of the secondary container during the first filling.
• the secondary container is implemented in the form of a capillary gap, the spacing of which increases in a preferred exemplary embodiment (which is discussed in greater detail in FIG. 2c). This ensures that the effective capillary pressure decreases with increasing filling when the volume is filled in a defined manner.
• ink When writing, ink is dispensed from the main liquid channel via the dispensing point 22 and the pen 24. This ink comes from the secondary tank when the valve is assumed to be closed. However, the ink is not dispensed directly from the secondary container, but from the main liquid channel, since the secondary container only via the main liquid channel and not directly communicated with the delivery point itself. If the ink volume in the secondary container empties below a defined point, the valve 18 is opened again and ink flows into the buffer volume in the secondary container. When the level in the secondary tank has reached an upper limit again, the valve is closed.
• the valve can be controlled by means of a two-point controller, which monitors the minimum or maximum fill level of the secondary container.
• the primary container can be ventilated or be under pressure. According to the invention, however, in view of the high load on the valve 18 when the primary container is under pressure, a vented primary container is preferred. It should be noted that with the primary reservoir under pressure, a relatively strong valve is necessary in order to be able to withstand the pressure of the reservoir. This can lead to increased costs of the entire system.
• FIG. 2a shows an enlarged view of a writing tip 40 which has the writing pen 24 which has a grain 42 at its front tip.
• the main liquid channel 16 which ends below the nib at the delivery point 22.
• the junction point 20, which is also referred to as a fluidic T-piece, is also located within the writing tip.
• the secondary container which in the embodiment shown in FIG. 2a is formed by a secondary liquid channel 26a and a storage area 26b.
• the fill level sensor 30 is located within the storage area of the secondary container 26 and measures the fill level in the storage area 26 b of the secondary container 26.
• the secondary container 26 is coupled to the ambient atmosphere via an elongated meandering channel 28a and an opening 28b of the channel.
• the long meandering ventilation channel 28a provides sure that the evaporation rate of the liquid in the secondary container 26 is minimized.
• the channel has the smallest possible cross-section and that the opening of the channel, which is designated by reference numeral 28b, is non-wetting towards the surroundings.
• a capillary negative pressure is generated which is greater in the main flow than in the secondary container 26. This is realized by a capillary gap in the secondary container 26 which is larger than the main flow.
• FIG 2b shows an alternative embodiment of a writing tip 40 ', in which the secondary container 26 is located directly below the writing pen 24.
• This embodiment has the advantage that the hole usually present in the nib can be used as ventilation 28 of the secondary container 26.
• the preferred filling of the main fluid channel 16 is again ensured by a capillary negative pressure in that the capillary gap of the main flow is made larger than the capillary gap in the secondary flow, that is to say the capillary gap which is formed by the secondary liquid channel 26a and the storage area 26b.
• 2c shows a further possibility of designing the writing tip 40 ′′, the secondary container in the exemplary embodiment shown in FIG. 2c being dimensioned in such a way that its volume increases disproportionately in the filling direction, which is due to the non-parallel arrangement of the fill level sensor 30 with the writing pen 24 is reached. A decreasing capillary pressure in the secondary container 26 is thus achieved with an increasing fill level.
• 2c also shows a section of the electronics belonging to the valve control 32, which can be connected to the fill level sensor 30 by means of bond wires 34, for example.
• the surface of the secondary container and the surface of the main fluid channel should be wetting, so that the liquid, that is to say the ink in the example of the writing instrument, does not automatically leak out without a customer.
• the opening of the secondary container to the environment should be non-wetting to minimize the rate of evaporation.
• the embodiment shown in FIG. 2a has the advantage over the vents shown in FIGS. 2b and 2c that a long channel with a small cross section is provided.
• the embodiment shown in FIGS. 2b and 2c is easy to implement, since the opening does not have to be provided, especially since the hole usually present in the nib 24 can be used.
• a capacitive fill level sensor which has an electrode arrangement, a passivation layer which is arranged on the electrode arrangement and has a contact electrode.
• the contact electrode is in electrically conductive contact with the electrically conductive ink, so that the electrically conductive ink as a capacitor electrode, the electrode arrangement as another capacitor electrode, and the region of the passivation layer which is wetted by the electrically conductive liquid as a dielectric a measuring capacitor acts, the capacity of which depends on the degree of wetting of the passivation layer by the electrically conductive liquid. Because of the use of the liquid to be measured as an electrical conductor and thus as a capacitor plate, such a sensor is distinguished by a high sensitivity and by a very low dependence on the liquid to be measured.
• Suitable materials for the design of the main fluid channel and the secondary container are polypropylene (PP), polycarbonate (PC) or LCP. These materials are not wetting per se, but can be activated and stained well to have wetting surface properties. ABS should also be mentioned in particular for the wetting materials.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Pens And Brushes (AREA)
• Coating Apparatus (AREA)
• Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
• Telephone Function (AREA)
• Ink Jet (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=7662080

Family Applications (1)

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Family Cites Families (9)

• 2000
  • 2000-11-03 DE DE10054599A patent/DE10054599C1/de not_active Revoked
• 2001
  • 2001-10-31 US US10/415,971 patent/US7093994B2/en not_active Expired - Fee Related
  • 2001-10-31 DE DE50104993T patent/DE50104993D1/de not_active Expired - Fee Related
  • 2001-10-31 AT AT01982455T patent/ATE285906T1/de not_active IP Right Cessation
  • 2001-10-31 WO PCT/EP2001/012647 patent/WO2002036361A1/fr not_active Ceased
  • 2001-10-31 EP EP01982455A patent/EP1333994B1/fr not_active Expired - Lifetime
  • 2001-10-31 ES ES01982455T patent/ES2233704T3/es not_active Expired - Lifetime
  • 2001-10-31 AU AU2002214037A patent/AU2002214037A1/en not_active Abandoned

Non-Patent Citations (1)

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