INSPECTOR WITH PRE-AIR CONTROL

Description

[0001] The present invention relates to a spraying apparatus with air atomization and pneumatic drive.

[0002] Spray guns are used to apply liquid, pasty, or powdered media to surfaces, creating a coating. The medium is atomized through a nozzle and directed towards the surface, gradually forming a thickening coating. Examples of media include varnishes, paints, water-based coating systems, adhesives, oils, and release agents, which are fed to the spray gun under pressure. When a media valve opens, the medium exits the nozzle along a longitudinal axis through an orifice.

[0003] Depending on the design of the spray gun, the medium is atomized in different ways. Some spray guns atomize the medium immediately upon exiting due to high media pressure (on the order of several hundred bar overpressure) and the geometry of the media opening, resulting in a spray jet consisting of a finely dispersed, uniformly distributed media mist. No atomizing air is required in this process. This technology is therefore also referred to as "airless." Currently, such spray guns are known to operate with media overpressures of up to 300 bar.

[0004] In air-atomizing spray guns, atomizing air is supplied to the nozzle at high pressure along with the medium. When an air valve is opened, the atomizing air exits the nozzle through air vents and then strikes the medium exiting the medium orifice, atomizing it to form a spray jet consisting of a finely dispersed, uniform mist. The medium pressure is typically significantly lower than in airless atomization, ranging from 1 to 10 bar overpressure. Currently, spray guns operating at medium overpressures of up to 12 bar are known.

[0005] Also included in this category of air-atomizing spray guns are hybrid forms of both techniques, in which "airless" atomization initially occurs due to high media pressures and a small media opening. This atomization is further supported by atomizing air, which exits through air openings in the nozzle and then encounters the already atomized media mist. Currently, such spray guns are known to operate with media overpressures of up to 150 bar.

[0006] Furthermore, spray guns are known that additionally feature a channel arrangement for supplying so-called forming air, which is used to adjust or modify the geometry of the spray jet. The forming air is also referred to as horn air because, in the area of ​​the nozzle, two horns with outlets are usually formed, from which the forming air exits at an acute angle to the longitudinal axis and shapes the spray jet. The forming air is generally supplied separately from the atomizing air and with different parameters (pressure and volume flow).

[0007] Atomizing air and molding air are combined here under the term spray air.

[0008] The term "spraying apparatus" encompasses all applications, from hand-held spray guns to fully automated robotic systems. The coating medium is applied to the surface by, for example, an operator manually guiding the spray gun over the surface to be coated in manual applications, or by a robot fully automatically triggering the spraying process at the designated point in automated applications. DE 38 21 817 A1 and DE 196 54 514 A1 disclose spraying apparatuses from the prior art.

[0009] Air-atomizing spray guns typically also have a pre-air function. For example, reference is made to German patent application DE 808 538 A, which discloses a spray gun in which a media valve and an air valve are arranged coaxially one behind the other, offering advantages in terms of maintenance and servicing. The valves are connected in such a way that they can be adjusted independently of each other. It is therefore particularly possible to adjust the stroke of the media valve relative to that of the air valve so that the air valve opens before the media valve, thereby generating a so-called pre-air supply. This ensures that the exiting medium is atomized uniformly from the outset and that no material build-up occurs at the nozzle, which could lead to an irregular spray pattern.Conversely, at the end of the spraying process, the media valve is closed first for the same reason, with a residual airflow similarly preventing material buildup at the nozzle. The spray gun presented in DE 808 538 A is mechanically operated, meaning that the force to open the valves must be applied manually by means of a trigger lever.

[0010] In addition to mechanically operated spray guns, there are also those operated by pneumatic control. This pneumatic control is used to actuate one or more valves for the medium and / or the spray air, referred to herein as the "pneumatic drive." In manual applications, the pneumatic control facilitates operation because the work of opening the valve(s) is performed by the pneumatic control, and it is essential for automated operation. A hand-operated spray gun with pneumatic control is known, for example, from German patent application DE 20 004 087 U1. An automatically operated spray gun with pneumatic control is known, for example, from German patent application EP 3 100 789 A1.

[0011] The latter combines a coaxial arrangement of the media valve and the air valve with a pneumatic actuator. Here, a drive piston, also acting on the common axis of the media valve and the air valve, moves the valve backward, i.e., away from the nozzle. A first compression spring generates a preload that, in its resting state, presses the piston, along with a closing element of the air valve, into its valve seat. The movement of the drive piston then opens the air valve, initially generating a pre-air supply as long as the media valve remains closed. As the drive piston continues its backward movement, it engages a driver that is fixed to a valve needle of the media valve. A second compression spring applies a preload to the driver, which, in its resting state, presses the valve needle into its valve seat.The drive piston then moves further backwards against the forces of both compression springs, thus also opening the media valve.

[0012] A disadvantage of such an arrangement is that the pressure and volume flow of the pre-air and post-air are lower than those of the injection air, because the air valve opens further along with the media valve during the continued reverse movement of the drive piston. However, it can be desirable to operate with high pre-air and post-air pressures and volume flows, particularly to prevent material build-up at the start and end of the injection molding process.

[0013] Another disadvantage is that, especially in applications with high media pressures, a high preload of the second compression spring is necessary to ensure the media valve closes in its resting state. However, the preload cannot be increased arbitrarily, as it is limited by the force required by the drive piston, which must also overcome the spring force of the first compression spring.

[0014] The present invention is therefore based on the objective of improving a spray apparatus of the type mentioned at the outset in such a way that it ensures precise control of the pre-air and / or the post-air, particularly at high media pressures.

[0015] The problem is solved by a spray apparatus with the features of claim 1.

[0016] The spray apparatus according to the invention with air atomization and pneumatic drive has at least one media valve for controlling at least one media flow through the spray apparatus, at least one air valve for controlling at least one spray air flow through the spray apparatus and at least one first pneumatically actuated drive piston for actuating the at least one air valve and is characterized by at least one second pneumatically actuated drive piston for actuating the at least one media valve.

[0017] In contrast to the applicators discussed above and known from the prior art, the spray apparatus according to the invention has at least two separate drive pistons for independently actuating the air valve on the one hand and the media valve on the other. This offers a number of advantages. The actuation of the air valve on the one hand and the actuation of the media valve on the other can be triggered independently of the stroke, which allows for more variable and precise control of the media flow and the spray air flow. In particular, the air valve can be fully opened before the media valve is activated, so that the complete atomizing airflow is generated right at the beginning of the media exiting the nozzle.In particular, the switching time of the valves can also be reduced, since instead of a single piston stroke actuating both valves sequentially, two separate strokes are available, which, with appropriate piston geometry design, can be made much shorter. The shorter switching time results in higher switching dynamics, meaning that the intervals in which the spray gun is switched on and off can be shortened, which offers advantages in terms of medium and air consumption, coating speed, and application possibilities. And finally, the work or...The force required to overcome the preload of the media valve and the preload of the air valve is distributed between the first and second drive pistons, so that, especially with a high preload for the media valve, the drive pistons and thus the entire housing of the injection unit can be designed to be relatively compact without loss of precision.

[0018] When, as above, the singular terms "the air valve" and "the media valve" are used, this description also refers to a spray gun with multiple media valves for controlling multiple media flows and / or to a spray gun with multiple air valves for controlling multiple spray air flows. Multiple media valves are suitable, for example, for applying a mixture of several components. Multiple air valves are suitable, for example, for separately controlling the atomizing air and molding air flows. Accordingly, "the first pneumatically actuated drive piston" is representative of multiple first pneumatically actuated drive pistons, and "the second pneumatically actuated drive piston" is representative of multiple second pneumatically actuated drive pistons.

[0019] Preferably, the first and second drive pistons are mechanically decoupled.

[0020] The drive pistons are described as "mechanically decoupled" when they are not physically connected to each other, i.e., not by form, material, or frictional connection, such that they can only perform dependent movements due to this connection. According to the invention, the first and second drive pistons move only mediated by the same control air, but otherwise independently of each other. Even if the first and second drive pistons are arranged or movably guided in the same one- or multi-part housing of the injection molding apparatus, the movement of both pistons within the degrees of freedom defined by the piston chambers in the housing is nevertheless independent of each other.

[0021] In a preferred embodiment, the air valve has a first closure element mechanically coupled to the first actuating piston and a corresponding first valve seat. The closure element can be, for example, a disc, a cone, a ball, or a needle. Sealing elements, such as O-rings or the like, can preferably be arranged between the closure element and the valve seat. The sealing elements can optionally be positively connected to the closure element or to the valve seat. The closure element is particularly preferably designed as a valve cone. For the purposes of this feature, "mechanically coupled" refers to a direct or indirect physical connection that transmits a force from the first actuating piston to the closure element, optionally mediated by an intermediary component, such that the movement of the actuating piston necessarily causes a movement of the closure element.

[0022] Particularly preferred is a first preload spring acting on the first drive piston in the opposite direction of its action, wherein the first drive piston is linearly movable back and forth between a rest position and an operating position, and wherein the first preload spring presses the first closing part against the first valve seat via the first drive piston.

[0023] The direction in which the control air moves the piston is called the "direction of action." Opposite this direction of action is the preload direction of the first preload spring. A helical compression spring is particularly preferred as the preload spring. The preload spring can be arranged in a spring housing on the side opposite the piston chamber. The "rest position" refers to the position of the piston in which the spring is least compressed and the piston presses the first sealing element against the first valve seat due to the preload of the first preload spring. In this position, no sprayed air exits the nozzle. The "operating position" refers to the position of the drive piston deflected by the control air, in which the first preload spring is maximally compressed and the air valve is fully open. In this position, the sprayed air exits the nozzle.

[0024] Similarly, the media valve preferably has a second closing element mechanically coupled to the second drive piston and a corresponding second valve seat. The second closing element can also be designed, for example, as a disc, cone, ball, or needle. Sealing elements, such as O-rings or the like, can preferably be arranged between the closing element and the valve seat. These sealing elements can optionally be positively connected to the closing element or to the valve seat. A valve needle is particularly preferred as the closing element.The term "mechanically coupled" is also used in the sense of this feature for a direct or indirect physical connection that transmits a force transmission from the second drive piston to the second locking part, optionally mediated by an intermediate component, so that the movement of the second drive piston necessarily causes a movement of the second locking part.

[0025] In the same way as the first and second drive pistons, the first and second sealing elements are preferably mechanically decoupled. This distinguishes them from the sealing elements of known spray guns, which are physically, or more precisely, positively, connected to each other via the single drive piston and the drive pin that engages with it. The mechanical decoupling of the first and second sealing elements, and thus of the air valve from the media valve, opens up new possibilities for the design of the spray gun. For example, the media valve and the air valve, and therefore the air and media channels and their corresponding connections, can be arranged more freely within and on the spray gun. This allows for a simpler design, even for complex spray guns with atomizer, control, and horn air functions.

[0026] Furthermore, a second preload spring acting on the second drive piston in the opposite direction of action is preferably provided, wherein the second drive piston is linearly movable back and forth between a rest position and an operating position, and wherein the second preload spring, mediated by the intervening second drive piston, presses the second closing part against the second valve seat.

[0027] The analogous definitions of terms "direction of action," "preload direction," "rest position," and "operating position" apply as before. A helical compression spring is again particularly preferred as the preload spring. Here too, the preload spring can be arranged in a spring housing on the side opposite the piston chamber.

[0028] In a preferred embodiment, the first drive piston and the second drive piston are arranged along a common longitudinal axis acting in opposite directions.

[0029] The coaxial design allows for a compact overall construction of the injection molding unit. Alternatively, the first and second drive pistons can be arranged along different longitudinal axes, acting in opposite directions.

[0030] This design allows for a freer design of the drive systems (drive pistons and preload springs) and in particular the relocation of the at least one first pneumatically actuated drive piston, possibly including the first preload spring, or the at least one second pneumatically actuated drive piston, possibly including the second preload spring, into a modular housing part or an adapter of the injection molding apparatus.

[0031] According to the invention, a first piston chamber associated with the first drive piston and a second piston chamber associated with the second drive piston are directly fluidically connected to each other and have a common control air supply.

[0032] As in the prior art, the actuation of the media valve and the actuation of the spray air are controlled by only one control air supply; however, the coupling is pneumatic rather than mechanical. This simplifies the control effort compared to separate drive air supplies for both drive pistons. The timing of the opening and closing of the air valve and the media valve is determined by the dimensions of the pistons, in particular the piston area, and the dimensions of the respective associated preload springs, in particular the spring constant, i.e., the set preloads. The cavity enclosed by the piston area and the housing surrounding the piston, and whose volume changes due to the piston's movement, is referred to as the "piston chamber." The first and second piston chambers are "directly fluidically connected" when the control air supply is...The drive medium must always flow between the first and second piston chambers, and – at least after a certain time – pressure equalization can automatically take place between the first and second piston chambers.

[0033] In a preferred embodiment of the invention, a throttle is arranged in the fluidic connection between the first piston chamber and the second piston chamber.

[0034] A throttle is generally defined as a reduction in the cross-section of the fluidic connection between the first piston chamber and the second piston chamber. This reduction serves to create a pressure drop in order to allow for the targeted control of the air valve and the media valve. For example, this allows the air valve and the media valve to be controlled with a time delay, and one or the other valve to be controlled more slowly.

[0035] Another advantageous embodiment of the invention provides that the first piston chamber and the second piston are formed by a common piston chamber.

[0036] This essentially represents an embodiment in which there is practically no throttle or constriction between the piston chambers, so that the control air flowing into the common piston chamber can act simultaneously and at the same pressure on the first drive piston and the second drive piston. This embodiment also includes injection devices in which the pistons have different cross-sections, and therefore a change in cross-section is necessarily formed between the first and second piston chambers, as long as this change in cross-section is not intended to create a pressure drop.

[0037] Preferably, the first preload spring and the second preload spring are designed such that the first preload spring exerts a lower preload against the first drive piston in its rest position, and the second preload spring exerts a lower preload against the second drive piston in its rest position. Particularly preferably, the first preload spring has a lower spring constant than the second preload spring.

[0038] This ensures, taking into account the dimensioning of the piston area of ​​the first and second drive pistons and taking into account any pressure losses in the air line of the control air between the piston chambers, that the first drive piston is moved first and the air valve opens before the media valve.

[0039] Preferably, a first throttle check valve is positioned upstream of the first piston chamber on the inlet side.

[0040] In other words, the first throttle check valve is positioned upstream of the first piston chamber with respect to the flow direction of the control air entering the piston chambers. The throttle check valve preferably allows the control air to flow into the first piston chamber without restriction and restricts the control air during venting. This creates an asymmetry between the pressure rise and the pressure drop in the first piston chamber, allowing the pre-air and post-air to be adjusted, for example, so that the post-air acts for a longer period than the pre-air.

[0041] If a throttle is arranged in the fluidic connection between the first and second piston chambers, this throttle is preferably formed by a second throttle check valve. The second throttle check valve preferably allows the control air to flow from the first to the second piston chamber at a throttled rate and back from the second to the first piston chamber at an unrestricted rate. In this case, the second throttle check valve serves to slow the pressure rise in the second piston chamber during the inflow of control air, thereby extending the pre-air injection time.

[0042] According to an advantageous embodiment, the spraying apparatus has at least two air valves for controlling a spray air flow through the spraying apparatus, wherein at least two first pneumatically actuated drive pistons are provided for actuating the at least two air valves.

[0043] According to another advantageous embodiment, the spraying apparatus has at least two media valves for controlling a media flow through the spraying apparatus, wherein at least two second pneumatically actuated drive pistons are provided for actuating the at least two media valves.

[0044] Further features and advantages of the invention are explained below with reference to the exemplary embodiments shown in the figures. The figures show: Figure 1: A first embodiment of the spraying apparatus in the rest position in a side sectional view; Figure 2: The first embodiment of the spraying apparatus in an intermediate position in a side sectional view; Figure 3: The first embodiment of the spraying apparatus in the operating position in a side sectional view; Figure 4: A second embodiment of the spraying apparatus in the rest position in a side sectional view; Figure 5: A third embodiment of the spraying apparatus in the rest position in a side sectional view; Figure 6: The third embodiment of the spraying apparatus in the rest position in a top sectional view; Figure 7: The third embodiment of the spraying apparatus in an intermediate position in a side sectional view; Figure 8: The third embodiment of the spraying apparatus in an intermediate position in a top sectional view; and Figure 9: The third embodiment of the spraying apparatus in the operating position in a side sectional view.

[0045] The first embodiment of the spray apparatus according to the invention is described by reference to the Figures 1 to 3 This is explained below. This is an air-atomizing spray gun, where the medium is primarily atomized by means of high media pressure through a small media opening (airless). Secondary air atomization supports the primary airless atomization and improves the spray jet geometry, as explained below.

[0046] Since the Figures 1 to 3 Since sections are in the same plane, lines for the medium or the spray air, specifically for the atomizing air and the molding air, and for the control air, insofar as they lie partially or completely in other planes, are only shown section by section and not at all.

[0047] Orientation and direction terms such as "front," "back," "forward," "backward," or "longitudinal" always refer to the direction in which the medium is discharged. The nozzle, for example, is therefore always "front" in relation to the applicator housing.

[0048] The spray gun 10 comprises a housing 12 extending along a longitudinal axis A. The housing is designed in three parts: a front housing part 14, a rear housing part 16, and a housing cover 18 for closing the rear end of the rear housing part. The three-part design facilitates access to the internal components, simplifying assembly, maintenance, and repair. At the front end of the front housing part 14 is a nozzle 20 through which the medium to be applied exits and is atomized and directed toward the surface to be coated. The nozzle 20 includes a central media opening 22 for the medium. The geometry of the media opening 22, and in particular its cross-sectional area, is dimensioned such that, in conjunction with the medium pressure, the medium is primarily atomized immediately after exiting the media opening.Furthermore, the nozzle has 20 supply channels 24 for atomizing air, which immediately encounters the media mist after primary atomization. The atomizing air supports the atomization and directs the media mist thus generated as a spray jet with a desired geometry towards the object to be coated.

[0049] The spray gun 10 includes an air valve 102 within the housing 12 for controlling the flow of sprayed air. The air valve 102 has a first closure element 106 and a first valve seat 108. The closure element 106 is formed by a conical section whose outer surface rests against the corresponding first valve seat 108, which is designed as an annular bore shoulder in the housing 12 of the spray gun. A first pneumatically actuated drive piston 110 with a piston area 111 is mechanically coupled to the closure element 106 for actuating the air valve. In this case, the coupling is achieved by forming the first closure element 106 together with the first drive piston 110 as a single, integral component. The first drive piston 110 is movably arranged and guided in a cavity in the housing 12 along the longitudinal axis A.

[0050] The spray apparatus 10 further comprises a media valve 112 within the housing 12 for controlling the flow of media. The media valve 112 has a second closing element 116 and a second valve seat 118. The second closing element 116 is formed by a valve needle that extends concentrically along the longitudinal axis to the direction of movement of the first drive piston 110 and through it, and which has a spherical segment-shaped sealing surface (binary) and a sealing ring 120 at its front end, which bears against the corresponding second valve seat 118. As mentioned, the geometry of the media opening 22 is responsible for the primary atomization. The media valve 112 is therefore set back into the interior of the housing relative to the media opening 22 and, thanks to its spherical segment shape, is able to quickly open the maximum cross-section for the media flow.The second valve seat 118 is designed as a conical recess at the inlet opening 124 of a bore 126, through which the medium is directed to the nozzle 14 when the media valve 112 is open. A second pneumatically actuated drive piston 130 with a piston surface 131 is mechanically coupled to the second closure part 116 for actuating the media valve 112. The coupling is effected by a central screw 132, with which the valve needle is positively connected to the second drive piston 130 at its rear end. The second drive piston 130 is also movably arranged and guided in a cavity in the housing 12 along the longitudinal axis A. The first drive piston 110 and the second drive piston 130 are arranged to act in opposite directions along the common longitudinal axis A.

[0051] A common piston chamber 133 is formed between the piston surfaces 111, 131 of the two drive pistons 110 and 130. This chamber simultaneously forms the first piston chamber associated with the first drive piston and the second piston chamber associated with the second drive piston. As a result, the piston chambers are necessarily directly fluidically connected and share a common supply for the control air, symbolized by arrow 134.

[0052] Furthermore, a first preload spring 136, acting against the direction of action of the first drive piston 110, is arranged in the housing 12. The preload spring 136 is designed as a helical compression spring, which can be arranged in a space-saving manner inside the first drive piston 110. The first drive piston 110 is in Figure 1The figure is shown in a rest position in which the first preload spring 136, mediated via the first drive piston 110, presses the first closing element 106 against the first valve seat 108. Because the first preload spring 136 acts in a backward direction and the first drive piston 110 in a forward direction, it is possible, unlike in the prior art, to simultaneously achieve a large piston area 111 and a large flow cross-section with the air valve 102 open.

[0053] Similarly, a second preload spring 138, acting against the direction of action of the second drive piston 130, is arranged in the housing 12. The preload spring 138 is also designed as a helical compression spring, which can be arranged in a space-saving manner inside the second drive piston 130. The second drive piston 130 is in Figure 1The second preload spring 138 is also shown in a rest position, in which the second preload spring 138, via the second drive piston 130, presses the second closure part 116 against the second valve seat 118. Since the first and second drive pistons 110, 130 act in opposite directions, the preload springs 136, 138 also act in opposite directions. The first preload spring 136 has a lower spring constant than the second preload spring 138. The difference in preload is chosen such that, in the rest position, the first preload spring exerts a lower preload against the first drive piston than the second preload spring exerts against the second drive piston. Since, in the illustrated embodiment, the piston surfaces 111, 131 have only slight size deviations, this ensures that the first drive piston 110 is moved first and the air valve 102 opens before the media valve 112.

[0054] While valves 102 and 112, as previously described, are in Figure 1 With the valves closed, pressurized air (symbolized by arrow 140) and the medium (symbolized by arrows 142) are present in the supply lines upstream of valves 102 and 112. The spraying apparatus 10 is started by pressurizing the common piston chamber 133 with control air 134, which initially drives the first drive piston 110 against the first preload spring 136, thereby opening the coupled air valve 102, as shown in Figure 2Illustrated. In the intermediate position shown here, the first drive piston 110 is already deflected forward by its maximum stroke, so that the air valve 102 is already fully open, while the higher preload of the second preload spring 138 still keeps the media valve 112 completely closed. In the intermediate position, the spray air, symbolized by arrow 144, flows through the spraying apparatus 10 and at this point exits the nozzle 20 as so-called pilot air, symbolized by arrow 146, without any medium. If the pressure of the control air 134 in the piston chamber 133 now increases further, the second drive piston 130 is driven against the second preload spring 138 and the coupled media valve 112 is opened, as shown in Figure 3 illustrated.

[0055] In the operating position shown here, both drive pistons 110 and 130 are deflected forward and backward, respectively, by their maximum stroke, so that the air valve 102 and the media valve 112 are fully open. In this operating position, the spray air, symbolized by arrow 144, and the medium, symbolized by arrows 142, flow through the spraying apparatus 10 and simultaneously exit the nozzle 20, symbolized by arrows 146 and 148, thereby atomizing the medium and directing it toward the object to be coated. When the spraying process is switched off, the media valve 112 and the air valve 102 are closed in reverse order, so that in the intermediate position, residual air escapes from the nozzle, clearing it of any remaining media.

[0056] The second embodiment of the spray apparatus according to the invention is described using the Figure 4explained. Here too, lines for the medium or the spray air, or specifically for the atomizing air, the control air and the molding air, insofar as they lie partially or completely in planes other than the one shown, are only shown in sections or not at all.

[0057] The spray apparatus 30 according to the second embodiment, analogous to the first embodiment, has first and second drive pistons arranged along a common longitudinal axis and acting in opposite directions, each with associated valves and preload springs. It differs from the first embodiment essentially in the dimensions of the components and in a different nozzle geometry. Therefore, the following description will mainly refer to these differences, while otherwise referring to the preceding description of the first embodiment.

[0058] In the case of the spray apparatus 30 according to Figure 4This is an embodiment that operates solely by means of air atomization, i.e., unlike the embodiment shown in Figures 1 to 3, it does not primarily atomize "airless". The spray apparatus 30 includes, in particular at its front end, a nozzle 32, which differs from the nozzle 20 in that the atomizing air exits through an annular opening of an annular feed channel 36, arranged concentrically around the medium opening 34. The channel structure inside the housing 38 is also designed differently.

[0059] Furthermore, nozzle 32 differs from nozzle 20 in its media supply. The medium is supplied through a media connection 39 under a comparatively low overpressure (up to max. 12 bar), which necessitates different cross-sections for the lines inside the housing 38 and a different media valve 212. This media valve 212 is also designed as a needle valve. It has a second closing element 216 in the form of a valve needle and a second corresponding valve seat 218. However, the tip of the valve needle is this time tapered to a point and engages positively in an equally tapered bore without an additional sealing element when the media valve 212 is closed. The sealing surface of the valve seat 218 also opens directly into the central media opening 34, from which the medium emerges without atomization.In this design, the media flow can be adjusted as needed by means of an adjustable end position of the valve needle relative to the valve seat 218. The second pneumatically actuated drive piston 230 is also mechanically coupled to the second closure part 216 for actuating the media valve 212, for example by means of screws.

[0060] The third embodiment of the spray apparatus according to the invention is described using the Figures 5 to 9 explained. These show sections in two mutually perpendicular planes. And here too, lines for the medium or the spray air, or specifically for the atomizing air, the control air and the molding air, insofar as they lie partially or completely in other planes, are only shown in sections or not at all.

[0061] The spray gun 40 comprises a housing 42 extending along a longitudinal axis A. The housing is made up of four parts and includes a front housing part 44, a rear housing part 46, an adapter 47 connected laterally to the front and rear housing parts 44 and 46 with respect to the longitudinal axis A, and a housing cover 48 for closing the rear end of the rear housing part 46. At the front end of the front housing part 44 is a nozzle 50 through which the medium to be applied emerges and is atomized and directed towards the surface to be coated. The nozzle 50 includes a central opening 52 for the medium.Furthermore, the nozzle 50 has an annular opening of an annular feed channel 54, arranged concentrically around the media opening 52. The atomizing air exits from this channel, atomizing the exiting medium and directing the resulting media mist as a spray jet towards the object to be coated. Additionally, separate forming air channels (not shown) are provided, which open into two horns 56 that are mirror images of each other with respect to the longitudinal axis A. The forming air exits the horn openings 58 at an acute angle to the longitudinal axis, strikes the spray jet, and shapes it. This spray gun 40 is a so-called robotic sprayer with air atomization and separate forming air for automated application.

[0062] The spray gun 40 includes an air valve 302 for controlling a spray air flow 340, which is arranged in the adapter 47 of the housing 42. The air valve 302 has a first closure part 306 and a first valve seat 308. The closure part 306 is formed by a conical section, the outer surface of which rests against the corresponding first valve seat 308, which is designed as an annular bore shoulder in the adapter 47 of the spray gun. A first pneumatically actuated drive piston 310 with a first piston surface 311 is mechanically coupled to the closure part 306 for actuating the air valve. In this case, the coupling is achieved by the fact that the first closure part 306 and the first drive piston 310 are formed as a single component. The first drive piston 310 is arranged and guided in a cavity in the adapter 47 so as to be movable back and forth perpendicular to the longitudinal axis A.The first drive piston 310 is assigned a first piston chamber 313, which forms a variable part of the cavity limited by the first piston surface 311.

[0063] The spray gun 40 further comprises a media valve 312 within the housing 42 for controlling a media flow 342. This media valve 312 is also designed as a needle valve extending along the longitudinal axis A. It has a second closing element 316 in the form of a valve needle and a second corresponding valve seat 318. Similar to the second example, the tip of the valve needle is conically tapered and engages positively in the second valve seat 318, which is formed by an equally conically pointed bore, without an additional sealing element when the media valve 312 is closed. The sealing surface of the valve seat 318 opens directly into the central media opening 52. A second pneumatically actuated drive piston 330 with a second piston surface 331 is mechanically coupled to the second closing element 316 for actuating the media valve 312.The coupling is achieved by a central screw 332, with which the valve needle is positively connected at its rear end to the second drive piston 330. The second drive piston 330 is movably arranged and guided in a cavity in the rear housing part 46 of the housing 42 along the longitudinal axis A. A second piston chamber 333 is associated with the second drive piston 330, forming a variable portion of the cavity bounded by the piston surface 331.

[0064] In contrast to the first example, the first drive piston 310 and the second drive piston 330 are not arranged coaxially. Nevertheless, the first piston chamber 313 associated with the first drive piston 310 and the second piston chamber 333 associated with the second drive piston 330 are directly connected fluidically to each other and to a common control air supply 352 via a connecting line 350, also referred to herein as the fluidic connection. A throttle in the form of the connecting line 350 itself is arranged in the fluidic connection 350 between the first piston chamber 313 and the second piston chamber 333. Because this throttle represents a reduction in cross-section compared to the cross-sections of the piston chambers 313 and 333, it causes a pressure drop along its length, so that the pressure in the second piston chamber 333 builds up more slowly than in the first piston chamber 313.Instead of the cross-sectional reduction, a second throttle check valve can also be provided at this point.

[0065] Furthermore, a first preload spring 336, acting against the direction of action of the first drive piston 310, is arranged in the adapter 47 of the housing 42. The preload spring 336 is designed as a helical compression spring, which can be arranged in a space-saving manner inside the first drive piston 310. The first drive piston 310 is in Figure 6 The figure shows the first preload spring 336 pressing the first closing element 306 against the first valve seat 308 via the first drive piston 310. Here too, the first preload spring 336 and the first drive piston 310 act in opposite directions, thus simultaneously enabling a large piston area 311 and a large flow cross-section when the air valve 302 is open.

[0066] Similarly, a second preload spring 338, acting against the direction of action of the second drive piston 330, is arranged in the housing part 46 of the housing 42. The preload spring 338 is also designed as a helical compression spring, which can be arranged in a space-saving manner inside the second drive piston 330. The second drive piston 330 is in Figure 5 also shown in a rest position, in which the second preload spring 338, mediated via the second drive piston 330, presses the second closing part 316 against the second valve seat 318.

[0067] The first preload spring 336 has a lower spring constant than the second preload spring 338. The first preload spring 336 and the second preload spring 338 are designed such that the first preload spring 336, in its rest position, exerts a lower preload against the first drive piston 310 than the second preload spring 338, in its rest position, exerts a lower preload against the second drive piston 330, by such an amount that, taking into account the size difference between the first and second piston areas 311, 331 and, if applicable, taking into account a pressure loss via the connecting line 350, the first drive piston 310 is moved first and the air valve 302 opens before the media valve 312.

[0068] In contrast to all previous examples, the adapter 47 of the housing 42 also includes a second air valve 362 for the separate control of a molding air flow. The second air valve 362 is shown in the view of the Figure 6The second air valve 362 is constructed in a mirror-symmetrical manner to the air valve 302. Accordingly, the second air valve 362 has a further first closure part 366 and a further first valve seat 368. The closure part 366 is formed by a conical section whose outer surface rests against the corresponding valve seat 368, which is designed as an annular bore shoulder in the adapter 47 of the injection unit 40. Accordingly, a further first pneumatically actuated drive piston 370 with a piston surface 371 for actuating the second air valve 362 is mechanically coupled to the closure part 366. The coupling is achieved, as in the case of the first drive piston 310 with the air valve 302, by the closure part 366 being formed together with the first drive piston 370 as a single component.The first drive piston 370 is arranged and guided in a cavity in the adapter 47, also perpendicular to the longitudinal axis A and in the opposite direction to the first drive piston 310, so that it can move back and forth. The first drive piston 370 is assigned the same first piston chamber 313 as the first drive piston 310.

[0069] Similarly, a further first preload spring 376 is arranged acting on the first drive piston 370 in the opposite direction to its action. The preload spring 376 is designed as a helical compression spring, which can be arranged inside the first drive piston 370 in a space-saving manner. The first drive piston 370 is in Figure 6The first drive piston 310 is shown in a rest position, in which the preload spring 376, mediated via the first drive piston 370, presses the closure element 366 against the valve seat 368. Here, too, the preload spring 376 and the first drive piston 370 act in opposite directions, thereby simultaneously achieving a large piston area 371 and a large flow cross-section when the second air valve 362 is open. With the same piston area 371 and a shared first piston chamber 313, the preload spring 376 is designed in the same way as the preload spring 336, so that the first drive piston 370 moves simultaneously with the first drive piston 310 and before the second drive piston 330, thus opening the second air valve 362 simultaneously with the air valve 302 and before the media valve 312.

[0070] On the inlet side, i.e., between the first piston chamber 313 and the control air supply 352, a first throttle check valve 378 is also located upstream of the first piston chamber 313 in the adapter 47. The first throttle check valve 378 allows the control air to flow into the first piston chamber 313 without restriction, but restricts the control air during venting, so that a back pressure builds up in the first piston chamber during venting. This results in an asymmetry between the pressure rise and the pressure drop.

[0071] While valves 302, 312 and 362, as previously described, are in Figure 5 and Figure 6With the valves closed, atomizing air (symbolized by arrow 340) and forming air (symbolized by arrow 341) are present in the supply lines upstream of valves 302 and 312, while the medium (symbolized by arrow 342) is under pressure. The injection molding apparatus 40 is started by pressurizing the piston chambers 313 and 333 with control air 334. This initially drives the first drive pistons 310 and 370 against their respective preload springs 336 and 376, thereby opening the air valves 302 and 362, as shown in the Figures 7 and 8Illustrated. In the intermediate position shown here, the first drive pistons 310, 370 are each already deflected by their maximum stroke, so that the air valves 302, 362 are fully open, while the higher preload of the second preload spring 338, in combination with any pressure drop in the connecting line 350, still keeps the media valve 312 completely closed. In the intermediate position, the atomizing air, symbolized by arrow 340, and the molding air, symbolized by arrow 341, flow through the injection unit 40 and at this point exit the nozzle 50 as so-called pilot air without any medium. If the pressure of the control air 334 in the piston chamber 333 now increases further, the second drive piston 330 is driven against the second preload spring 338 and the coupled media valve 312 is opened, as in Figure 9illustrated. In the operating position shown here, all three drive pistons 310, 330, and 370 are deflected to the side or rearward by their maximum stroke, so that the air valves 302, 362, and the media valve 312 are fully open. In the operating position, the atomizing air, symbolized by the arrows 340, and the molding air (not in Figure 9(shown) and the medium, symbolized by arrows 142, pass through the spray gun 40 and simultaneously exit the nozzle 50, thereby atomizing the medium and propelling it with the set spray pattern towards the object to be coated. When the spraying process is switched off, the media valve 312 and the air valves 302, 362 are closed in reverse order, so that in the intermediate position, after-air consisting of atomizing air and forming air exits the nozzle, blowing it free of any media residue. Due to the aforementioned asymmetry between the pressure rise and the pressure drop in the first piston chamber 313, the after-air time is extended.

[0072] As the examples show, the invention provides a high-performance spraying apparatus whose drive is efficient and less prone to wear due to reduced stress on the individual components. At the same time, the spraying apparatus requires fewer components compared to the prior art. It is therefore advantageous overall in terms of both service life and maintenance. Reference sign

[0073] 10 Spray gun 12 Housing 14 Front housing part 16 Rear housing part 18 Housing cover 20 Nozzle 22 Media opening 24 Feed channel 30 Spray gun 32 Nozzle 34 Media opening 36 Feed channel 38 Housing 39 Media connection 40 Spray gun 42 Housing 44 Front housing part 46 Rear housing part 47 Adapter 48 Housing cover 50 Nozzle 52 Media opening 54 Feed channel 56 Horn 58 Horn opening 102 Air valve 106 First sealing part 108 First valve seat 110 First drive piston 111 Piston surface 112 Media valve 116 Second sealing part 118 Second valve seat 120 Sealing ring 124 Inlet opening 126 Bore 130 Second drive piston 131 Piston surface 132 Screw 133 Piston chamber 134 Arrow: Control air 136 First preload spring 138 Second preload spring 140 Arrow: Spray air 142 Arrow: Medium 144 Arrow: Spray air 146 Arrow: Spray air 148 Arrow: Medium 212 Media valve 216 Second sealing part 218 Second valve seat 230 Second drive piston 302 Air valve 306 First sealing part 308 First valve seat 310 First drive piston 311 First piston surface 312 Media valve 313 First piston chamber 316 Second sealing part 318 Second valve seat 330 Second drive piston 331 Second piston surface 332 Screw 333 Second piston chamber 334 Control air 336 First preload spring 338 Second preload spring 340 Spray air flow 342 Media flow 350 Connecting line 352 Control air supply 362 Second air valve 366 Second first sealing part 368 Second first valve seat 370 Second first drive piston 371 Piston surface 376 Second first preload spring 378 Throttle check valve

Claims

1. Spraying apparatus (10, 30, 40) with air atomisation and pneumatic drive, comprising: at least one air valve (102, 302, 362) for controlling a spray air flow through the spraying apparatus (10, 30, 40), at least one media valve (112, 212, 312) for controlling a media flow through the spraying apparatus (10, 30, 40), at least one first pneumatically actuated drive piston (110, 310, 370) for actuating the at least one air valve (102, 302, 362) and at least one second pneumatically actuated drive piston (130, 230, 330) for actuating the at least one media valve (112, 212, 312), characterised in that a first piston chamber associated with the at least one first drive piston and a second piston chamber associated with the at least one second drive piston are directly fluidly connected to each other, so that the control air can always flow between the first and second piston chambers and pressure equalisation between the first piston chamber and the second piston chamber can take place automatically, and have a common control air supply.

2. Spraying apparatus (10, 30, 40) according to claim 1, characterised in that the at least one first and the at least one second drive piston are mechanically decoupled.

3. Spraying apparatus (10, 30, 40) according to one of the preceding claims, characterised in that the air valve has a first closure member, preferably a valve cone, mechanically coupled to the at least one first drive piston, and a valve seat.

4. Spraying apparatus (10, 30, 40) according to claim 3, characterised by a first preload spring acting on the at least one first drive piston against its direction of action, wherein the at least one first drive piston is linearly movable back and forth between a rest position and an operating position and wherein the first preload spring presses the first closure member against the first valve seat via the at least one first drive piston.

5. Spraying apparatus (10, 30, 40) according to one of the preceding claims, characterised in that the media valve has a second closure member, preferably a valve needle, mechanically coupled to the at least one second drive piston, and a second valve seat.

6. Spraying apparatus (10, 30, 40) according to claim 5, characterised by a second preload spring acting on the at least one second drive piston against its direction of action, wherein the at least one second drive piston is linearly movable back and forth between a rest position and an operating position, and wherein the second preload spring presses the second closure member against the second valve seat via the at least one second drive piston.

7. Spraying apparatus (10, 30, 40) according to claim 1, characterised in that a restrictor is arranged in the fluid connection between the first piston chamber and the second piston chamber.

8. Spraying apparatus (10, 30, 40) according to claim 7, characterised in that the restrictor is formed by a second throttle check valve.

9. Spraying apparatus (10, 30, 40) according to claim 1, characterised in that the at least one first drive piston and the at least one second drive piston are arranged to act in opposite directions along a common longitudinal axis and that the first piston chamber and the second piston chamber are formed by a common piston chamber.

10. Spraying apparatus (10, 30, 40) according to claims 4 and 6, characterised in that the first preload spring and the second preload spring are designed such that the first preload spring presses, in the rest position, against the at least one first drive piston with a lower preload than the second preload spring presses, in the rest position, against the at least one second drive piston.

11. Spraying apparatus (10, 30, 40) according to claim 10, characterised in that the first preload spring has a lower spring constant than the second preload spring.

12. Spraying apparatus (10, 30, 40) according to claim 1, characterised in that a first throttle check valve (378) is arranged upstream of the first piston chamber (313) on the inlet side.

13. Spraying apparatus (10, 30, 40) according to one of the preceding claims, characterised by at least two air valves (302, 362) for controlling a spray air flow through the spraying apparatus (40), wherein at least two first pneumatically actuated drive pistons (310, 370) are provided for actuating the at least two air valves (302, 362).

14. Spraying apparatus (10, 30, 40) according to one of the preceding claims, characterised by at least two media valves (112, 212, 312) for controlling a media flow through the spraying apparatus (40), wherein at least two second pneumatically actuated drive pistons (130, 230, 330) are provided for actuating the at least two media valves (112, 212, 312).