DE10129250A1 - Fluid nozzle for application of broad fluid layer to component surface has spray gap defined by gap walls, one of which is moveable at right angles to the spray gap - Google Patents

Abstract

The nozzle has a housing with two opposite parallel gap walls (14,16) defining a spray gap (28). At least one of the gap walls is moveable at right angles to the level of the spray gap. The moveable wall is supported on a turnable control body, which passes through the gap and has a non-central control surface. The wall is moved by an electric motor, pref. with self-locking reduction gear and piezo actuator.

Description

The invention relates to a liquid dispensing nozzle for Applying a layer of liquid to a workpiece surface according to the preamble of claim 1 and a method of operating such.

It is known that surfaces of workpieces can coat electrostatically, the coating tion material can be powdery or liquid.

When electrostatically coating workpieces with Liquids can be the amount applied vary by changing the applied voltage between Liquid discharge nozzle and workpiece vary or also in that the pressure of the discharge gap supplied Liquid varies. Even if you have workpieces under Use of a liquid having a dispensing gap dispensing nozzle with carrier air support with liquid coated, you can print the order quantity, of the liquid fed to the discharge gap vary.

In some cases it would be beneficial if one too could adjust the size of the dispensing gap.

The present invention is therefore intended to be a liquid keitsabgabedüse according to the preamble of the claim 1 so that the effective width its delivery gap is adjustable.  

This object is achieved by a Liquid dispensing nozzle with those specified in claim 1 Features.

Advantageous developments of the invention are in Unter claims specified.

Claims 2 to 7 give different variants for a part limiting the liquid discharge gap relocatable wall section.

The development of the invention according to claim 8 in terms of servo adjustment of the width of the Dispensing gap is an advantage.

With the development of the invention according to claim 9 is achieved that the width of the discharge gap is very can be easily adjusted electrically, with Use of a self-locking reduction gear additionally an automatic blocking of the gap width in the set size without maintenance guaranteed a supply current to the electric motor is.

The use of a servomotor according to claim 11 is also with regard to simple electrical control the gap width is advantageous, with a piezo actuator especially for very small gaps to the precisely specified Setting the gap width is suitable.

A liquid discharge nozzle according to claim 12 enables it, the flat layer of liquid that comes out of its housing exits, directly at the exit point to conduct an air flow.  

The development of the invention according to claim 13 is Particularly suitable if you are one and the same type of liquid dispensing nozzle optionally for coating use of the top and bottom of workpieces want.

With the development of the invention according to claim 14 it is achieved that the partial air streams, which the from the Dispensing gap liquid layer emerging into individual Tear droplets and the latter to the workpiece surface move with a perpendicular to the liquid delivery plane (Level of the discharge gap) directed movement component hit the sides of the liquid layer. hereby the uniformity of that generated in the dispensing nozzle Droplet curtain influenced favorably.

With the development of the invention according to claim 15 is when the liquid dispensing nozzle at the same time as Electrode of an electrostatic device for application liquid on a workpiece surface is avoided at the ends of the liquid discharge high electrical field peaks occur that lead to a Disturbance of the uniformity of the dispensed liquid layer in the longitudinal direction of the liquid discharge gap would lead.

The method specified in claim 16 enables this Apply particularly thin layers of liquid. To The beginning of a fluid delivery cycle will be the larger Gap worked until a stable layer of liquid is delivered. Then the gap width can be set to the desired one Final size can be reduced. Such a reduction is possible during operation. Would you like the levy splits to this narrow width right from the start  adjust, there would be difficulties in training formation of a homogeneous layer of liquid.

The invention will now be described by way of an embodiment game explained with reference to the drawing.

In this show:

Figure 1 is a transverse section through a strip-shaped liquid discharge nozzle of an electrostatic liquid coating system.

Fig. 2 is a side view of the liquid dispensing nozzle of Figure 1, seen from the right there.

Fig. 3 is a block diagram of a liquid coating line for sheet metal, the two liquid dispensing nozzles according to Figures 1 and 2.

Fig. 4 is an enlarged axial section through one of the piezoelectric actuators, by which, the nozzle of the housing parts of the liquid discharge nozzle of Figures 1 and 2 with respect to the other housing part is displaced together with adjacent portions of the liquid discharge.

Fig. 5 is a view similar to Figure 1, in which a modified liquid discharge nozzle is shown with an adjustable width of the discharge gap. and

Fig. 6 to 8 Similar to Figs. 1 and 5 view further modified liquid exhaust nozzle.

1 and 2, a liquid dispensing nozzle is designated by 10 in total. It comprises a total of 12 designated stretched housing, which is composed of two housing parts 14 , 16 .

The housing part 14 carries, below the bevel 26, four guide rods 17 at its corners, which are guided in sliding play through guide openings 18 of the housing part 16 . In this way, the housing part 16 can be displaced with respect to the housing part 14 in a parallel orientation.

Between the two housing parts 14 , 16 , a sealing part 20 is arranged, which is shown in the drawing for purposes of explanation with a greatly increased thickness.

In practice, the sealing part 20 has a thickness of approximately 10 to a few 100 μm in the stress-free state. It is cut out of a plastic film or an elastomeric material. The sealing part 20 has an essentially U-shaped edge contour with a lower base section 22 and lateral legs 24 .

Behind or in front of the drawing plane marked in fig. 1 the faces of the housing part 14 is a bridge portion 100 attached, which carries at its corners four motors Piezo-Aktua 102nd Roughly speaking, these work in such a way that they work with their driven parts on the housing part 16 which can be displaced on the guide rods 17 and can press this more or less strongly against the housing part 14 by compressing the sealing part 20 .

As can be seen from FIG. 4, each of the piezo actuators 102 has a housing 104 with a fastening flange 106 which is screwed onto the outside of the housing part 16 . Inside is a stack 108 of piezoelectric disks, each of which is closed at the ends by an insulating part 110 or 112 . The disk stack 108 extends with play through an opening 114 which is formed in the bridge part 100 .

If an electrical high voltage is applied to the disk stack 108 , the effective total length of the disk stack changes depending on the voltage applied. Since the end of the disk stack 108 on the right in FIG. 4 is supported on the bottom of the cup-shaped housing 104 , the insulating disk 110 moves to the left depending on the magnitude of the voltage applied and correspondingly presses the housing part 16 in the direction of the housing part 14 , whereby the Sealing part 20 is compressed.

In this way, a delivery gap 28 can be reduced to a size of approximately 5 μm to approximately 50 to 80 μm, starting from the initial thicknesses of the sealing part 20 specified above.

As can be seen from the drawing, the housing parts 14 and 16 each have an essentially rectangular cross section, bevels 26 being provided at the upper outer corners. The top of the liquid dispensing nozzle 10 thus has essentially the shape of a saddle roof with a broken tip.

The liquid discharge gap 28 is delimited by the two housing parts 14 and 16 and by the U-shaped sealing part 20 , which is connected via internal channels 30 of the housing parts 14 , 16 to a liquid feed valve 32 and in the manner described above the high voltage applied to the piezo actuator 102 is adjustable. The liquid feed valve is an electromagnetic valve capable of high switching frequencies, as it is e.g. B. is used for fuel injection in internal combustion engines. An electromagnet 34 of the liquid feed valve 32 is connected to a control line 36 , and via a valve body 38 of the liquid feed valve 32 , the channels 30 and thus the liquid discharge gap 28 can be connected to a liquid feed line 40 .

Flat depressions 42 are provided in the bevels 26 , which in practice can have a depth of fractions of a mm to one mm. The indentations 42 run freely into the upper boundary surface of the housing parts 14 , 16 . About the recesses 42 baffles 44 are attached, for. B. screwed by screws 46 . The guide surfaces 44 extend completely over the depressions 42 up to their upper end.

The depressions 42 are connected via internal channels 48 of the housing parts 14 , 16 to an air feed opening 50 of the housing part 14 .

Inside the housing parts 14 , 16 , two bores 52 , 54 extending in the longitudinal direction are provided. From this, the upper bore receives a resistor chain 56 , which together forms a protective resistor in the order of magnitude of 100 MOhm, via which the housing parts 14 , 16 are connected to the one terminal of a high-voltage source. The lower bore 54 receives a heating resistor 58 , which is coupled to the housing part 14 or 16 under consideration via a thermal coupling mass 60 .

In the housing parts 14 , 16 temperature sensors 62 are also embedded in order to continuously determine the actual temperature of the housing 12 and to regulate the housing temperature to a predetermined value via the current loading of the heating resistors 58 .

The liquid dispensing nozzle 10 described above operates as follows:
For the coating, the voltage difference mentioned above between the workpiece surface and the liquid discharge nozzle 10 is applied to the liquid discharge nozzle 10 . Then, the air supply port is pressurized to 50 bar with air of 0.2 to 1.5, so that from the free ends of the recesses 42 fine sharp air curtains 64, exit 66th

The liquid feed valve 32 is struck with a liquid under a pressure of 0.1 to 0.8 bar.

When the liquid feed valve 32 is controlled open, the air exiting from the dispensing column sharp separate air curtains at the liquid discharge from the gap-forming advanced and at the gap end of a meniscus of liquid from individual droplets. As the nozzle moves away, the air relaxes and slows down and forms a droplet layer 68 together with the droplets.

The droplet layer 68 is thus moved both under the influence of the electrostatic field and in particular with the aid of the thin and sharp air curtains 64 , 66 against the underside of a workpiece 70 , which is shown as a sheet in FIG. 3 and there to the right on the liquid dispensing nozzle 10 is moved past. The droplets are deposited on the workpiece surface and grow together into a coherent layer of liquid.

If one wishes on the workpiece 70 coated and uncoated subareas which are sharply separated from one another, the channels 30 can additionally be connected via a liquid relief valve 72 to a pressurized liquid return line 74 . The liquid relief valve 72 is preferably constructed the same as the liquid feed valve 32 and also includes an actuating electromagnet 76 which is activated via a control line 77 .

Where sharp transitions between coated and uncoated areas of a workpiece are less important, the liquid relief valve 72 can also be omitted.

Fig. 3 shows a system with which both the top and the bottom schematically shows a workpiece 70 can be coated. To move the workpiece 70 , a conveyor tongs 78 is provided which is moved by a drive (not shown in more detail) and which engages at one end of the workpiece 70 and at the same time serves to place the workpiece at ground potential.

Above and below the conveying plane of the workpiece 70 , two identical liquid dispensing nozzles 10 are seen before, each of which has the structure shown in FIGS . 1 and 2 with respect to the fluid guide mirror image structure.

The liquid feed lines 40 of the two liquid discharge nozzles are connected via a pressure regulator 80 to the outlet of a liquid feed pump 82 which draws in from a reservoir 84 . This contains a volume of liquid 86 to be applied. The liquid can in particular be a drawing oil, as it is applied in whole or in part to metal sheets before they are deformed in a press.

The liquid return lines 74 are connected to the inlet of a suction pump 88 , the feed inlet of which feeds back into the reservoir 84 .

The air feed openings 50 of the two liquid discharge nozzles 10 are connected to the outlet of a blower 92 via a pressure regulator 90 . To control the air flow to the liquid discharge nozzles 10 is an Luft-Speiseven valve 94 , which is also designed as a solenoid valve.

To control the various solenoid valves, to control the heating housing 12 by means of the heating resistors 58 , to control the high voltage applied to the piezo actuator 102 (and thus to control the width of the discharge gap) and to apply high voltage to the housing 12 is a control unit, designated overall by 96 provided which controls the dispensing amounts of the liquid and the liquid pattern on the workpiece surfaces.

If a liquid dispensing nozzle 10 is used alone, the corners of the ridge line are rounded, as shown at 98, to avoid high field peaks that could affect the uniformity of the liquid layer 68 . Where liquid nozzles are juxtaposed to form a longer nozzle unit, the ridges remain, as indicated at 100.

In a modification of the exemplary embodiment described above, a plurality of liquid discharge nozzles 10 can be provided successively above and below the workpiece in a liquid coating system for metal sheets perpendicular to the drawing plane, whereby the liquid discharge through these different nozzles can be selected differently in order to different parts of the To coat or leave the workpiece surface free.

The housing 12 consisted of metal in the exemplary embodiment described above. It goes without saying that it is also possible to manufacture only the section of the housing 12 which is directly adjacent to the liquid discharge gap 28 , the outer housing regions, on the other hand, from isolating the plastic material. In any case, the housing of the valves 32 and 74 are preferably also produced from such a valve, so that their actuating magnets 34 and 76 are only at a low potential.

It also goes without saying that the liquid discharge gap 28 can also be sealed by a sealing part 20 which is designed differently in detail, insofar as only the peripheral seal of the discharge gap in FIG. 1 downwards and to the sides of the liquid discharge nozzle 10 is ensured.

The sealing part 20 also does not need to perform the function of a deformable spacer. Instead, you can work in the mutually facing inner boundary surfaces of the two housing parts 14 , 16 very shallow depressions and accomplish the circumferential sealing of the discharge gap by a round cord seal, which are inserted in smaller than semi-circular sealing grooves with a U-shaped shape, which surround the very shallow depressions just mentioned.

In the above described embodiment of a liquid discharge nozzle 10 of the liquid discharge gap 28 air curtains were provided on both sides. It goes without saying that for some applications it is also possible to use a single air curtain.

In the coating system described above, the amount of liquid dispensed and thus the thickness of the liquid layer applied to the workpiece surfaces can be controlled via the following parameters: size of the high voltage applied to the piezo actuators 102 , the pressure set by the pressure regulator 80 , and the level in the liquid dispensing nozzle 10 through the heating resistors 58 set temperature, strength of the electrostatic field, size of the relative speed between workpiece 70 and liquid discharge nozzles 10 .

Fig. 5 shows a simplified liquid discharge nozzle 10 , which is formed without components for the production of curtains 64 , 66 , as well as the liquid discharge nozzle according to Fig. 6 to 8. It is understood that these liquid discharge nozzles can equally be provided with slots for air discharge , Similar to the exemplary embodiment from FIGS. 1 to 4.

In FIG. 5 (and the following FIGS. 6 to 8) components of the liquid dispensing nozzle, which functionally correspond to components already described above, are again provided with the same reference numerals and are not described again in detail below.

In the exemplary embodiment according to FIG. 5, the housing part 16 has a groove 116 , which springs back from the surface to the center of the nozzle, slightly below its roof surface 26 and which defines a bending section 118 of the housing part 16 .

The sections below the bending section 118 of the two housing parts 14 , 16 are connected by four thread screws 120 , which can be provided approximately at the locations where the guide rods 18 were in the embodiment according to FIGS. 1 to 4.

At the lying above the bending section 118 from section 122 of the housing part 16 engages a pressure roller 124 , the ends of which support shaft ends 126 which are arranged eccentrically with respect to the axis of the pressure roller 124 by a small distance. The shaft ends 126 are mounted in bearing brackets 128 , which are supported by a fixed frame part 130 .

The pressure roller 24 is driven by an electric gear motor 132 , as shown by a dashed drive connection.

It can be seen that by exciting the geared motor 132 the section 122 of the housing part 116 can be pressed against the housing part 114 , so that the end of the discharge gap 28 narrows accordingly.

In a modification of the embodiment of Fig. 5 can be, as indicated by dashed lines, a socket member 134 attach the upper end of portion 122 in the area of the top surface 26 with a curved end face. This can be attacked by the curved end of a threaded spindle 136 , which runs in a frame-fixed threaded plate 134 and is adjusted by a geared motor 132 , which is only indicated schematically. Also in this way you can adjust the width of the discharge gap 28 under electrical control.

In the embodiment of FIG. 6 are in tabs 140 out at the top end of the housing part 16 are formed, stored stub shaft 142 of a roller 144 which extends over the entire length of the discharge gap 28th The shaft ends 142 of the roller 144 are arranged slightly eccentrically with respect to the circumferential surface of the roller 144 and are connected to an electric geared motor 132 for drive purposes like that.

It can be seen that by exciting the geared motor 132 in one direction or the other, the size of the discharge gap 28 can be adjusted directly at the outlet opening.

In the embodiment of Fig. 7 of the housing portions 16 is provided in each case a substantially semi-cylindrical recess 146 in the upper ends. The two recesses 146 together define a cylindrical receiving space for a control cylinder 148 , which is provided on the end faces with stub shafts 150 , which are again connected to a geared motor 132 for drive purposes.

The control cylinder 148 has a flat control surface 152 which, in an angular position of the control cylinder 148, provides a smooth continuation of the inner boundary surface of a (in FIG. 7, the left) housing part.

It can be seen that by exciting the geared motor 132, the control surface 152 can be tilted so that throttling of the liquid in the discharge gap 28 can be set. If the Steuerzylin 148 is rotated heavily, the dispensing gap can be closed completely.

Is similar to the exemplary Example according to Fig. 8, the one according to Fig. 7, the control cylinder is formed 148 hollow and its interior is (z. B. a formed in the end portion slot is not reproduced voltage in the drawing) with a liquid - Feed line 36 in connection.

A plurality of control openings 154 are formed in the peripheral wall of the control cylinder 148 , which follow one another at regular axial distances.

It can be seen that the output quantity can be adjusted again by turning the control cylinder 148 by means of the gear motor 132 .

In the exemplary embodiments described above, this was done moving the behind the dispensing gap through the sharp Air curtains created droplets to the workpiece surface under the combined effect of air curtains and of the electric field. In a modification of the one described above benen embodiments you can post that the force acting on the droplets, the force on the applied electrostatic field is due omit and traceable to the air curtains Increase the contribution accordingly by the pressure of the Air discharge gaps air supplied increased accordingly becomes.

Claims (16)

1. Liquid dispensing nozzle for applying a liquid layer over a wide area to a workpiece surface with a housing ( 14 , 16 ) 1 which has two mutually opposite parallel slit walls ( 14 , 16 ) which together open a dispensing gap ( 14 , 16 ) opening into a boundary surface of the housing ( 14 , 16 ) 28 ), characterized in that at least one ( 16 ) of the diaphragm walls ( 14 , 16 ) can be moved at least in one section with a movement component perpendicular to the plane of the discharge gap ( 28 ). 2. Liquid dispensing nozzle according to claim 1, characterized in that the movable wall section is carried by a movable component ( 144 ; 148 ). 3. Liquid discharge nozzle according to claim 2, characterized in that the movable component is a rotatably mounted control body ( 144 ; 148 ). 4. A liquid discharge nozzle according to claim 3, characterized in that the control body ( 148 ) passes through the delivery gap ( 28 ) and has an eccentric control surface ( 152 ; 154 ). 5. Liquid dispensing nozzle according to claim 3, characterized in that the control body ( 144 ) rotatably mounted on the housing ( 14 , 16 ) ( 140 , 142 ) and that its peripheral surface is not concentric with the bearing axis and in any angular position of the control body from the other diaphragm wall ( 14 ) is removed. 6. A liquid dispensing nozzle according to claim 1, characterized in that the movable wall section ( 122 ) is carried by a bending section ( 118 ). 7. Liquid dispensing nozzle according to claim 1, characterized in that the two slot walls ( 14 , 16 ) are spaced apart by an elastically flexible spacer ( 20 ). 8. Liquid dispensing nozzle according to one of claims 1 to 7, characterized by an actuator ( 100 ; 132 ) which works on the movable wall section. 9. Liquid dispensing nozzle according to claim 8, characterized in that the servomotor has an electric motor ( 132 ), preferably an electric motor with a self-locking reduction gear. 10. Liquid discharge nozzle according to claim 8, characterized characterized in that the servomotor is a linear actuator is driven. 11. Liquid discharge nozzle according to claim 11, characterized in that the servomotor comprises a Piezoaktua gate ( 102 ). 12. Liquid discharge nozzle according to one of claims 1 to 11, characterized in that the housing ( 10 ) in the vicinity of the liquid discharge gap ( 28 ) is provided with at least one air discharge gap ( 42 , 44 ), which at least in its end portion in Liquid delivery direction seen to the liquid discharge gap ( 28 ) is parallel and seen perpendicular to the liquid flow direction has a parallel to the liquid ice discharge gap extension component. 13. A liquid discharge nozzle according to claim 12, characterized in that the air discharge gaps ( 42 , 44 ) to the central plane of the liquid discharge gap ( 28 ) are symmetrical. 14. Liquid discharge nozzle according to claim 12 or 13, characterized in that the liquid discharge gap ( 28 ) containing the boundary surface of the Ge housing ( 20 ) is substantially roof-shaped ( 26 ) and the air discharge gap ( 42 , 44 ) recesses ( 42 ) in the Have roof surfaces ( 26 ) and guide elements covering the latter, in particular guide plates ( 44 ). 15. Liquid dispensing nozzle according to one of claims 12 to 14, characterized in that the liquid-dispensing gap ( 28 ) containing the limiting surface of the housing is rounded at its ends ( 98 ). 16. Method of operating a liquid dispensing nozzle according to one of claims 1 to 15, characterized records that the location of the movable wall section at the beginning of a delivery cycle at a first interval from the opposite diaphragm wall and after a specified period of time to one second distance from the opposite diaphragm wall is set that is smaller than the first distance.