EP0044038B1 - Hand-held apparatus for electrostatically flocking objects - Google Patents

Description

The invention relates to a hand-held device for electrostatically flocking objects, in particular for applying short textile fibers to surfaces provided with adhesive.

In the case of electrostatic flocking, short fibers, in particular textile fibers, are applied to any surface to form a velvet-like surface, the connection of flock material to the surface being permanently guaranteed by a previously applied, electrically conductive adhesive.

The adhesive materials can be applied by brushing, spraying, screen printing and the like and, depending on requirements, consist of one- or two-component systems. The flock materials usually consist of viscose, polyamide, polyester or cotton, the length of the individual fibers being approximately in the range from 0.5 mm to 3 mm.

Known flocking devices generally work with direct charging of the flock material to a relatively high voltage, for example above 10 kV, in which case the electrostatically charged fibers of the flock material to the object to be flocked by the electrostatic attraction of the charged particles through the grounded surface of the object to be flocked be transported.

The flock material can be charged, for example, with DC voltage or pulsed high voltage. Known devices that operate on the basis of these charging principles require the supply of a rectified high voltage or pulse voltage, which has been transformed up from the mains voltage, to the flocking device, which requires complex, voluminous and fault-prone power supply units and high-voltage lines that require special safety measures.

GB-A-2 010 126 discloses a hand-held device intended for electrostatic flocking, which has a cup-shaped applicator with a flat high-voltage electrode, which can be coupled to a closed plastic housing. In this approximately cylindrical housing there is arranged a high-voltage generator working on a piezo-electric basis and connected to an actuating lever leading to the outside. Alternatively, a battery-operated oscillator with high-voltage transformer and subsequent rectifier can also be used. In this known device, on the one hand, the housing used is relatively unwieldy, but on the other hand, the structure is also unsatisfactory in electrical terms. The arrangement of the individual components of the high-voltage generator in the housing necessitates cable routing which, with regard to the very high voltages present, can lead to malfunctions and, moreover, result in radio interference which is extremely undesirable. Finally, the operator can be endangered in the event of an interruption in the required grounding line, since in this case high contact voltages can arise due to the use of a plastic housing.

An electrostatic liquid atomizer is known from DE-A-2731 712, in which the respective liquid is supplied to an electrically conductive surface subjected to high voltage for atomization. This electrostatic atomizer has a frame in the form of a plastic tube, which is designed to accommodate a plurality of electrical primary cells. A DC voltage converter is attached to the plastic tube, which converts the battery voltage into a high voltage, and a switch is also attached to this plastic tube. In the area of the atomizer-side end of the plastic tube, a voltage divider is also provided in this tube, and lines lead from this voltage divider to the outside to a field control element in the area of the atomizing nozzle. This field control element, which has the shape of a metal ring, is grounded via an earth line.

The object of the invention is to provide a hand-held device for the electrostatic flocking of objects, which has a compact structure, is not subject to any restrictions with regard to the place of use and ensures simple and, above all, reliable operation.

Starting from a hand-held device of the type defined in the preamble of claim 1, this object is achieved according to the invention in that the rod-shaped plastic housing is connected to a likewise rod-shaped, metallic or metallized housing, that the metallic or metallized housing has a receptacle for batteries provided as a direct current source forms and has an earth connection, and that an oscillator, a transformer and a cascade circuit with protective resistor are arranged in the rod-shaped plastic housing, starting from the DC voltage side as a high-voltage generator.

Through the use of a metallic or metallized housing part serving as a handle for the operator, reliable potential determination is ensured, on the one hand via an earth line and on the other hand via the respective operator, so that even in the event of an interruption of the earth line, there is no danger for the operator consists. Of particular importance in connection with the possible uses of the device is the fact that the occurrence of interference radiation is almost completely excluded, because due to the structure of the Ge the operator is grounded and can therefore no longer act as an antenna and because the individual components of the high-voltage generator are arranged in such a way that short lines can be used on the one hand and the required high voltage is only provided on the cup side. The compact structure of the device according to the invention not only facilitates handling, but also its practical use.

The rod-shaped housing which accommodates the batteries preferably has at least substantially the same diameter as the plastic housing, and it can be coupled thereto, so that a housing part which is known and therefore also inexpensive can be used as a battery-receiving housing.

According to one embodiment of the invention, a switch, in particular a switch, is switched on between the batteries and the high-voltage generator and is held in the wall of the metallic or metallized housing. This switch is not only conveniently accessible for the operator, but it can also be switched off by interfering charges due to its arrangement in the metallic or metallized housing part.

The high-voltage generator housed in the rod-shaped plastic housing comprises an oscillator, which can preferably be connected to the direct current source via a pushbutton switch, a transformer and a cascade circuit with protective resistor. The oscillator, which is supplied, for example, with a DC voltage of 4.5 volts, which can be supplied by three cylindrical batteries connected in series, generates a high-frequency AC voltage in the range from 8 to 50 kHz, which is supplied via a high-voltage transformer, preferably with is equipped with a ferrite rod core, a multistage high-voltage cascade is supplied, at the output of which the required high voltage of, for example, 30 to 100 kV is available.

The high-voltage cascade is preferably constructed from ceramic capacitors in stack form and Si diodes, since in this way an arrangement which is particularly suitable for accommodation in the rod-shaped housing is obtained. In the same way, however, it is possible to construct the cascade circuit from axially parallel, series-connected plastic film capacitors and interposed Si diodes in the form of a grid.

A high-voltage terminating resistor which simultaneously forms the protective resistor limits the short-circuit current to the permissible value.

The high-voltage electrode is arranged on the bottom of the cup-shaped applicator and connected directly to the output of the high-voltage generator via a plug or screw pin, so that the applicator can also be exchanged without problems by loosening this plug or screw connection.

Although the high-voltage electrode can be disk-shaped, plate-shaped or ring-shaped and can be provided with peaks to increase the corona, a rectangular or square plate with ends bent up to form peaks is preferably used as the high-voltage electrode, which covers the bottom of the cup leaving an edge area free .

In the exposed edge area of the cup, several pull holes are preferably provided, by means of which it is possible to noticeably increase the electron wind generated by the electrons emitted by the electrode and to ensure a particularly uniform and vortex-free transport of the flock material.

The draw holes are preferably provided with a fine-mesh cover, in particular made of a fabric.

A cover in the form of a plastic grille lid is also provided for the applicator opening, this plastic grille lid not only preventing the flock material from falling out, but at the same time helping to break up or break up any flock material clumps.

According to a particularly advantageous embodiment of the invention, the applicator consists of at least two nested plastic cups which are fixed relative to one another, the rod-shaped plastic housing containing the high-voltage generator extending through the outer cup bases to the bottom of the cup having the high-voltage electrode and serving to hold the flock material. Two cups are expediently put together to form an applicator, the outer cup, which has a corresponding central opening, being pushed over the cylindrical plastic housing and thus contributing to the stable guidance or mounting of the applicator.

• Fig. 1 eine schematische Längsschnittansicht einer Ausführungsform eines Handbeflockungsgeräts nach der Erfindung,
• Fig. 2 eine schematische Vorderansicht des Applikators des Geräts nach Fig. 1,
• Fig. 3 eine schematische Schnittansicht des im Gerät nach Fig. 1 vorgesehenen Hochspannungstransformators,
• Fig.4 eine schematische Darstellung einer Ausführungsform einer Hochspannungskaskade, wie sie beim Gerät nach Fig. 1 eingesetzt werden kann,
• Fig. eine schematische Darstellung der aus mehreren in einem stabförmigen Gehäuse angeordneten Batterien bestehenden Gleichstromquelle mit erfindungsgemäßem Kontrollkreis, und die
• Fig. 6 und 7 schematische Darstellungen von weiteren Ausführungsformen eines Kontrollkreises nach der Erfindung.

The invention is explained below using an exemplary embodiment with reference to the drawings; shows in the drawing

• 1 is a schematic longitudinal sectional view of an embodiment of a hand flocking device according to the invention,
• 2 shows a schematic front view of the applicator of the device according to FIG. 1,
• 3 shows a schematic sectional view of the high-voltage transformer provided in the device according to FIG. 1,
• 4 shows a schematic illustration of an embodiment of a high-voltage cascade, as can be used in the device according to FIG. 1,
• 1 shows a schematic illustration of the direct current source consisting of a plurality of batteries arranged in a rod-shaped housing, with a control circuit according to the invention, and the
• 6 and 7 are schematic representations of further embodiments of a control circuit according to the invention.

In the hand flocking device shown in FIG. 1, a high-voltage generator, identified by the general reference number 1, is arranged in a rod-shaped or tubular plastic housing 16 and consists of an oscillator 3, a transformer 4 and a high-voltage cascade 5 with a terminating or protective resistor 6. The individual stages of this high-voltage generator 1 are still explained.

The high-voltage generator 1 is supplied from a direct current source which is formed by three cylindrical batteries 13 connected in series, which are arranged in a metal tube 15 which has essentially the same diameter as the plastic tube 16 and is either fixedly or releasably connected to it . At the end, the metal tube 15 can be closed by means of a screw cap, as is customary, for example, with pocket torches. On this metal housing 15, a ground connection 14 is also provided for a line for connection to the object to be flocked. A pushbutton switch 2 is switched on in the electrical connecting lines from the direct current source to the oscillator 3.

The output of the high-voltage generator is connected to a high-voltage electrode 7, which is arranged on the bottom of a cup-shaped applicator 8. The connection is expediently made via a plug-socket arrangement 25, 26, so that a convenient separation of applicator and high-voltage generator is possible at any time and, accordingly, different applicators can be used in a simple manner.

The applicator 8 consists of two nested plastic cups 22, 23, wherein the outer cup 22 can be closed with a cover 9 designed as a grid, so that a receiving space for the flock material 10 is defined.

The inner cup 23, the height of which is significantly less than the height of the outer cup 22, is firmly connected to the latter, for example at an adhesive area 24.

The rod-shaped plastic housing 16 extends through the bottom of the outer container 24. In this way, the applicator 8 is guided and securely held with respect to the rod-shaped housing 16.

Both at the bottom of the inner cup 23 and at the bottom of the outer cup 22 there are several, preferably uniformly distributed draw holes 11, which are covered by a fine-mesh grid 12. The draw holes 11 of the inner cup 23 lie in the edge area between the electrode 7 and the cup side wall and in the radial direction outside the draw holes 11 of the outer cup 22.

The applicator 8 and also the rod-shaped housing 16, in which the high-voltage generator 1 is located, can consist of PE material.

For flocking, the applicator 8 is filled approximately halfway with flock material 10 and guided at a distance of approximately 10 to 20 cm to the flocking object 27 which is provided with electrically conductive adhesive and contacted with an earth line. When the high voltage is switched on, the flock particles become negative, e.g. B. charged to about 30-100 kV and fly supported by the developing electron wind to the grounded object 27. The particles align themselves like arrows and penetrate into the adhesive due to their kinetic energy, where they are permanently anchored when the adhesive hardens.

FIG. 2 shows the applicator 8 according to FIG. 1 consisting of two nested cups 22, 23 in a front view. It can be seen that the high-voltage electrode 7 is essentially square, the bent corners forming peaks which lead to an increase in the corona. In the corner areas of the applicator, which in this case has a rectangular or square cross section, the draw holes 11 are provided, which are covered with a fine-mesh grid 12.

The correspondingly offset draw holes 11 of the outer cup 22 are indicated by dashed lines.

Instead of an applicator that is rectangular or square in cross section, an applicator that is circular in cross section can also be used, with no differences in terms of function.

3 shows an embodiment of a transformer which can be used in high-voltage generator 1 and which consists of a ferrite rod 17, on which the primary winding consisting of relatively few turns and, if appropriate, a feedback winding are attached and fixed, for example, by means of a double-sided adhesive tape. The secondary winding 19 is accommodated in a bobbin core 18 provided with chambers and has a relatively high number of turns. The number of turns of the secondary winding is expediently in the range from 5000 to 10,000 turns.

The output voltage of the transformer is fed to a high-voltage cascade, as shown for example in FIG. 4. This cascade circuit is preferably also rod-shaped and constructed from capacitors 20 and diodes 21. The capacitors can be designed as ceramic capacitors or plastic film capacitors.

A Cernet-based resistor is preferably used as the high-voltage terminating resistor 6, which also consists of a protective resistor chain in the form of several resistors can be formed and limits the short-circuit current in the necessary manner.

Fig. 5 shows a rod-shaped, metal or at least metallized housing 15, which serves to hold batteries 13 and is fixed or detachably connected in the manner already described with a plastic tube which carries a cup-shaped applicator. The rod-shaped housing 15 can be closed by means of a screw cap, as is customary, for example, in the case of rod flashlights. One pole of the batteries 13 is connected to the housing via a spring 28. The other pole 29 of the batteries 13 is guided to a contact of a switch 2 which, when actuated, ie. H. closed switch is connected to the line 31 leading to the high voltage generator. In practice, switch 2 is formed by the "ON" button on the flocking device.

A control circuit, which is formed by a light-emitting diode 30, a zener diode 33 and a limiting resistor 34, is connected between the line 31 leading to the high-voltage generator and the negative pole of the direct current source. This control circuit is accordingly on the one hand electrically connected to the switch or push button contact 32 and on the other hand to the housing 15.

The Zener voltage of the Zener diode 33 is selected in accordance with the lower limit voltage of the battery 13, i. H. that the light-emitting diode 30 can perform a double function in that it ensures charge control and switch-on control at the same time. In one exemplary embodiment shown, both functions can be checked when the button 2 is actuated, but if two separate switches or buttons or contacts to be connected in succession are used, it is also possible to switch the two functions separately and thus carry out the switch-on control separately from the charge control .

In the embodiment variant shown in FIG. 6, at least one diode 35 is used instead of a zener diode. Since a voltage level of 0.7 V is assigned to a diode, several diodes 35 'may have to be connected in series.

FIG. 7 shows that a lamp 36 can also be used instead of a light-emitting diode 30, as has been shown in FIGS. 5 and 6. It is indicated in FIG. 7 that the solutions already described above with zener diode 33 and at least one diode 35 can also be implemented in connection with such a lamp 36.

All of the solution variants shown according to the invention are characterized by simplicity and operational reliability and can be implemented in practice with minimal effort.

Claims (17)

1. Hand-held apparatus for electrostatically flocking objects, in particular for applying short textile fibres to surfaces covered with adhesive, the apparatus comprising an applicator (8) of beaker-like shape for accommodating the flock material, a high voltage electrode (7) arranged in the beaker (23) and a high voltage generator (1), wherein the high voltage generator is arranged in a plastic housing (16), which simultaneously serves as the carrier for the applicator, and is fed from a d. c. source (13), and wherein the plastic housing (16) is bar-shaped and serves to accommodate a high voltage transformer (4) fed by an oscillator (3), characterised in that the bar-shaped plastic housing (16) is connected with a likewise bar-shaped metallic or metallised housing (15); in that the metallic or metallised housing (15) forms a receptacle for batteries (13) provided as the d. c. source and has an earth connection (14); and in that, starting from the d. c. side, an oscillator (3), a transformer (4) and a cascade circuit (5) with a protective resistor (6) are arranged as the high voltage generator (1) in the bar-shaped plastic housing (6).

2. Hand-held apparatus in accordance with claim 1, characterised in that the bar-shaped housing (15) is made with at least substantially the same diameter as the plastic housing (16) and can be coupled therewith.

3. Hand-held apparatus in accordance with claim 2, characterised in that a switch, in particular a push button switch (2) is inserted between the batteries (13) and the high voltage generator (1) and is mounted in the wall of the metallic or metallised housing (15).

4. Hand-held apparatus in accordance with one or more of the preceding claims, characterised in that the high voltage electrode (7) arranged in the beaker-like applicator (18) has projecting points and is connected via a plug pin or a threaded pin (25) with the output of the high voltage generator (1).

5. Hand-held device in accordance with claim 4, characterised in that the high voltage electrode (7) consists of a rectangular plate with upwardly turned corners for the formation of points.

6. Hand-held apparatus in accordance with one or more of the preceding claims, characterised in that several draft holes (11) are provided in the base of the beaker-like applicator (8).

7. Hand-held apparatus in accordance with claim 6, characterised in that the draft holes (11) are provided with a fine meshed cover (12) which in particular consists of a fabric.

8. Hand-held apparatus in accordance with one or more of the preceding claims, characterised in that the applicator (8) consists of at least two plastic beakers (22, 23) which are plugged into one another and fixed relative to one another, wherein the bar-like plastic housing (6) containing the high voltage generator (1) extends through the base of the outer beaker up to the base of the beaker (23) which has the high voltage electrode (7) and serves to receive the flock material (10).

9. Hand-held apparatus in accordance with claim 8, characterised in that the bases of the beakers (22, 23), which are inserted into each other are spaced apart by a distance in the range from 5 to 80 mm.

10. Hand-held apparatus in accordance with claim 8 or claim 9, characterised in that draft holes (11) are provided in all the bases of the beakers which are plugged inside one another and are in particular displaced relative to one another.

11. Hand-held apparatus in accordance with claim 1, characterised in that the oscillator (3) which can be connected to the d. c. voltage of for example 4.5 volts operates in the high frequency range of approximately 8 to 50 kHz.

12. Hand-held apparatus in accordance with claim 1, characterised in that the transformer (4) has a cylindrical ferrite-rod core (17) on which the primary winding (28) which has few turns is arranged, whereas the secondary winding (19) is accommodated in chambers (18) of a cylindrical synthetic carrier.

13. Hand-held apparatus in accordance with claim 1, characterised in that the transformer is constructed as a pot transformer or toroidal core transformer.

14. Hand-held apparatus in accordance with claim 1, characterised in that the cascade circuit (5) is built up from a stack of ceramic capacitors (20) with Si-diodes (21

15. Hand-held apparatus in accordance with claim 1, characterised in that the cascade circuit (5) is built up from synthetic foil capacitors which are arranged with their axis parallel and connected in series, and from Si-diodes which lie in gridlike form between the synthetic foil capacitors.

16. Hand-held apparatus in accordance with claim 1, characterised in that the protective resistor (6) which forms the high voltage termination resistor consists of a cermet base resistor.

17. Hand-held apparatus in accordance with one or more of the preceding claims, characterised in that the components of the high voltage generator (1) are potted in the plastic tube (16) in void-fee manner with a material for insulating against high voltages.

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