EP0748657B1 - Application head for dispensing and metering a fluid - Google Patents

Description

The invention relates to an application head for metered delivery of flowing media, in particular Hot melt adhesive, cold glue, lubricants, paints or Like., With a housing in which a pivotable, on at least one valve member acting rocker available which is over two sides of one Piezo elements arranged in a rocker joint are driven becomes.

Such an order head is already from the DE-GM 94 05 600.5 of the applicant known. He serves for example to apply hot glue to a made of cardboard, paper, textile, fleece or the like existing substrate. We do the web-shaped Substrate passed the fixed application head. The valve described there has the advantage that the piezoelectric valve actuator is present automatic temperature compensation from only two Piezo elements exist, being through the transmission the movement emanating from the two piezo elements the minor by means of a rocker construction Length increase of each individual piezo element in a relatively large valve lift is converted. Of another becomes a big one with this valve drive Valve force of approx. 3000 N provided, the time for an opening and closing cycle only 0.8 to 0.25 msec. is.

The object of the invention is now to create a new order head, the one has greater throughput and order capacity as well as an even application of glue.

The solution to this problem arises from the Features of claim 1, in particular from the features of the label part, after which the seesaw is bilateral of the rocker joint in each case at least one rocker arm has at least one at each Valve member is arranged.

The solution according to the invention has the basic one Advantage that the design of the valve drive the theoretical order performance as a double rocker is more than doubled, all at the same time Advantages of the aforementioned prior art also for the application head according to the invention be valid.

The fact that in a preferred embodiment the moment an order valve closes, the second application valve inevitably opens in a particularly advantageous manner Pressure fluctuations in the adhesive circulation system as far as possible avoided.

By avoiding pressure fluctuations according to the invention inside the closed hot glue system there is an even circulation of Hot glue inside the circulation channel. This will also prevents the hot glue in the heated part of the application head burns and within the Circulation channel caking, sticking and the like surrender.

Ultimately, this means in summary that during the entire opening cycle of an application valve the hot glue volume flow is steadied, so that the adhesive application has the desired shape.

In an advantageous embodiment of the invention however, the additional valve member serves not to control another order valve, but acts on a valve which is inside a closed circulation system equipped with a pump is arranged for the liquid medium.

This preferred embodiment of the invention has particular advantages if within a Unit of time a larger number of individual substrates, e.g. Cardboard blanks to be coated. It is partly necessary that the gaps between the individual cardboard blanks or between areas coated with glue dots should be bridged. With the preferred Embodiment of the invention is easily possible, the application valve a certain Keep time closed, at the same time as when the order valve closes Hot glue circulation valve a pressure increase in the hot glue system prevented. Reaches the next one now coating area or the next box cut the position of the order valve can do this be opened again, at the same time the Hot melt circulation valve closes. However lies essentially throughout the opening cycle the same pressure at the application valve and thus the hot melt flow rate is also essentially constant.

In a further particularly advantageous embodiment of the invention are the rocker construction driving piezo elements with a Connected online power supply, which in essentially of an accumulator and an associated one Electronics exist, which in the event of a power failure the respective position of the order valve is determined and corrected the closed state. This invention offers particularly preferred embodiment at the same time an automatic leakage protection, as a result it is guaranteed that even in the event of a power failure Order valve is always in the fully closed state located.

Fig. 1 einen vereinfachten Längsschnitt durch einen Auftragskopf und

Fig. 2 ein vereinfachtes Blockschaltbild der Ventilelektronik.

Further advantages of the invention result from the subclaims and from the description of an exemplary embodiment. Show it:

Fig. 1 shows a simplified longitudinal section through an application head and

Fig. 2 is a simplified block diagram of the valve electronics.

In the drawings, an application head is metered Total delivery of hot glue with the reference number Designated 10.

The application head has a housing 11 Housing parts 12 and 13. Between Housing parts 12 and 13 is a thermal separation layer 14 available. In the housing part 12 is a Double rocker valve drive 15, not illustrated electronic components and a electrical supply and control line 16 arranged. The double rocker 15 has two rocker arms 17 at the free ends of each a rod-shaped Valve member 18 is arranged, which by the thermal separation layer 14 into the Housing part 13 protrudes into a valve head 19. In the housing part 13 there is also a heating device 20 and the common feed channel 21 arranged for hot glue. The feed channel 21 is each with hot glue channels 22 with the valve heads 19 connected. Ultimately, is below the hot glue channels 12 to recognize a temperature sensor T. While which contains a valve head 19 an order valve 23, the other valve head 19 serves as a closure valve 24 for a hot glue return line 25, the one Connection to a hot glue pump, not shown manufactures. This hot glue pump is again connected to the feed channel 21 so that a closed Hot glue system is in place.

While the valve members 18 at the free end of the Rocker arms 17 each via a bending cardan B and a screw connection 26 are attached Double rocker 15 itself via a joint 27 with a Base part 28 connected. On both sides above the Joint 27 are also two over joints 29 Piezo elements 30 connected to the double rocker 15. In the articulated connection of double rocker 15 to Base part 28 as well as the piezo elements 30 are cohesive connections. These thin, integral joint connections 27, 29 are created in that the aforementioned Parts together from a single component with the help of the spark erosion process become. So there is between the double rocker 15 and the base part 28 except for a flexible, narrow Material bridge (joint 27) continuous gap 31, which is a relative movement of the double rocker on both sides 15 compared to the base part 28. On the same way are connecting parts 32 which are in turn glued to the piezo elements 30 each over a flexible, narrow material bridge (Joint 29) connected to the double rocker 15, wherein here, too, a narrow one on both sides of the material bridge Gap 31 is present.

The approx. 200 0.1 mm thick ceramic Pieces 30 assembled and glued together lie on the groundbreaking of the double rocker 15 End at a compliant, with not shown Screws attached cover plate 33.

The piezo elements 30 are on both sides of a vertical, through the joint 27 running axis x each articulated at a distance d with the double rocker 15 connected. This results in connection with the resilient mounting of the piezo elements 30 automatic temperature compensation through the cover plate 33.

If the piezo elements 30 now alternate expand under tension, the Double rocker 15 times clockwise or counterclockwise Clockwise torque through which a rocker arm 17 and the each associated valve member 18 upwards and a rocker arm 17 is moved down. Through this Double rocker arrangement can in the embodiment alternately the application valve 23 and the closure valve 24 are opened, in which case the opposite each other valve is closed. Through the resulting prevention of pressure peaks results during the opening cycle of the application valve 23 a relatively continuous outflow of hot glue, which ensures a clean application of glue to the Substrate is guaranteed.

The control and regulation of the two piezo elements 30 is done by special valve electronics 34, which is essentially shown in Fig. 1 Housing part 12 is arranged. The one Block circuit diagram shown in Fig. 2 valve electronics 34 enables alternating on the one hand Voltage application to the two piezo elements 30 and on the other hand a special energy saving and thus also operation with low heat losses of the application head 10.

Especially for the purpose of reduced The valve electronics 34 have an energy consumption so-called charge pump arrangement 35, which is basically shown in FIG. 2. The Charge pump arrangement 35 has an intermediate store 36 and several power field effect transistors 37, with the intermediate storage 36 as well as the power field effect transistors 37 each are connected to both piezo elements 30. The intermediate store 36 contains a coil 38 and a capacitor 39. The energy saving is at Operation of the piezo elements 30 by the so-called Push-pull arrangement of the piezo elements 30 usable Reloading principle achieved.

Basically, this reloading principle means that each stored in a piezo element 30 Energy (charge) "in portions" in each other piezo element 30 is transformed. Basically this takes place within the charge pump arrangement 35 in that on the one hand the charge of a Piezo element 30 is temporarily stored in the buffer 36 and that on the other hand the power field effect transistors 37 step by step targeted switching of different networks stored energy on the other piezo element 30 transform. The timing of the Reloading processes and the respective switching status of the Power field effect transistors 37 is by a programmable controller 40 determines. On the programmable Controller 40, however, operates one more Control circuit 41, which constantly the target-actual value comparison the state of tension of the individual Piezo elements 30 queries.

Through this reloading principle it is possible that the energy present in a piezo element 30 fed back the primary circuit and then back to Excitation of the other piezo element 30 used can be.

However, because of these electronic processes a small part of the energy is converted into heat and moreover, a larger part of the electrical Energy is converted into mechanical energy however constantly the need for this Energy deficit must be compensated. this happens by using the switching regulator 43 and the internal Power supply 42 provided energy.

In addition, the valve electronics 34 a clock generator 44 and a status display 45 on, however, arranged outside of the application head 10 are. While the clock generator 44 - like that Name says - the beat for the expiring electronic Processes, the status display is concerned 45 around an optical display for the operator.

The valve electronics 34 also have one Temperature controller 46 on, the valve temperature on that specified on a setpoint potentiometer 47 Temperature regulates. This means that an above the heating cartridge 20 arranged, not shown Temperature sensor constantly measures the valve temperature. Only if this temperature with that on the setpoint potentiometer 47 existing temperature matches and thus the working temperature is reached, the valve released by programmable controller 40.

So in the event of a power failure the double rocker trained valve actuator 15 not in a Middle layer goes and thus hot glue from the application valve 23 can flow out, is the valve electronics 34 ultimately with an online power supply 48 provided, which essentially consists of an accumulator and electronics that determined the respective state of the order valve and ensures complete closure.

Claims (6)

1. Applicator head for metering out flowing media, in particular hot-melt adhesives, cold-setting glue, lubricants, paints or the like, comprising a housing (11) in which a swivel-mounted rocker (15) acting on at least one valve member (18) is provided and is driven by means of two piezoelectric elements (30) arranged on either side of a rocker joint (27), characterised in that the rocker (15) is provided on either side of the rocker joint (27) with at least one rocker arm (17) on each of which at least one valve member (18) is arranged.
2. Applicator head according to claim 1, characterised in that the valves are opened and closed in opposite directions.
3. Applicator head according to claim 1, characterised in that each valve member (18) acts on an applicator valve (23).
4. Applicator head according to claim 1 or claim 2, characterised in that one valve member (18) acts on an applicator valve (23) and one valve member (18) acts on a valve (24) arranged within a closed circulation system for the liquid medium provided with a pump.
5. Applicator head according to one of claims 1 to 4, characterised in that the two valves (23, 24) have a joint feed channel (21) for the medium.
6. Applicator head according to one of the preceding claims, characterised in that the piezoelectric elements (30) are connected to an on-line power supply (48) consisting essentially of an accumulator and associated electronics which, in the event of a power failure, determine the respective position of the applicator valve (23) and correct the closed state.

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