Equipment for applying viscous materials to workpieces

Abstract

The invention relates to a device for applying a viscous material to a workpiece, comprising a rotary spray gun which is rotatably arranged in a holding device about a rotation axis extending in the longitudinal direction, the rotary spray gun having at least one material outlet, wherein a needle valve is assigned to each material outlet, by means of a valve needle extending in the longitudinal direction of the needle valve, the corresponding material outlet can be closed at a valve seat, and a cylinder is assigned to each valve needle, in the piston chamber of which a piston can be moved by pressure loading with a fluid, and the valve needle is fixedly connected to the piston. According to the invention, each piston is connected to a tappet, which tappet is led out of the relevant piston chamber in a sealed manner on the upper side facing away from the at least one valve seat, the rotary spray gun has a measuring element which can be loaded by the tappet and can be moved in the longitudinal direction, and the holding device has a sensor for determining the position of the measuring element.

Description

Technical Field

[0001] The present invention relates to an apparatus for applying a viscous material to a workpiece. Background Art

[0002] Such a device is used to apply viscous materials, such as adhesives, sealing materials or paints, to a workpiece. Here, a plurality of nozzles of different geometric structures mounted on a rotary spray gun are often used, each of which has a material outlet leading to the nozzle. Each material outlet is equipped with a needle valve, the valve of which is locked or released for the relevant material outlet on the valve seat. In order to operate the valve needle, a cylinder is set, wherein each valve needle is connected to a piston of a cylinder, and the piston moves by pressure loading through a fluid, especially compressed air. In the known device of the type described at the beginning, each cylinder is arranged side by side at the same distance relative to the valve seat, and the device is controlled so that only one needle valve among the needle valves is always opened for material application. There is a need to monitor the switching state of the needle valve so as to always identify the opening of one of the valves. Such monitoring can be realized in a simple way in a device including only one needle valve, so that a magnet is moved together with a single piston, and the position of the magnet is then detected by a magnetic sensor of a retaining device. However, such monitoring is almost impossible if the rotary spray gun has multiple valves, because the piston cannot assume a defined position relative to the magnetic sensor due to the permanent rotation of the rotary spray gun relative to the holding device. The same is true when the rotary spray gun has only a needle valve eccentrically received therein. Summary of the invention

[0003] It is therefore an object of the present invention to further develop a device of the type mentioned in the introduction in such a way that it can be better monitored.

[0004] This object is achieved according to the invention by a device having the features of the invention.

[0005] The invention is based on the idea that all pistons can act by means of a tappet on a common measuring element, the position of which can then be detected by a sensor. Typically, there are a plurality of needle valves whose cylinders are arranged side by side, in particular in the sense that their cross sections perpendicular to the axis of rotation do not overlap, wherein, for example, the lower and / or upper limiting surfaces of the piston chambers are each arranged in one plane. However, it is also possible for the rotary spray gun to have only one needle valve, which comprises a cylinder that is arranged, in particular, eccentrically with respect to the central longitudinal axis.

[0006] The measuring element can be designed rotationally symmetrically at least with respect to its parts acting on the sensor, so that its interaction with the sensor of the holding device does not change or does not change significantly when the rotary spray gun is twisted relative to the holding device. The rotation axis is also preferably the central longitudinal axis of the rotary spray gun or the measuring element. The at least one piston is preferably acted upon by compressed air and, as a fail-safe function, also expediently has a spring load that pushes the piston into a position in which the valve needle rests sealingly on the associated valve seat.

[0007] The measuring element can be implemented in different designs. However, preferably, the measuring element has a permanent magnet and the sensor is a magnetic sensor. Preferably, the permanent magnet has the shape of a ring, which surrounds the axis of rotation, so that the rotation of the rotary spray gun with respect to the holding device does not bring about a change in the interaction between the permanent magnet and the magnetic sensor. In particular, the permanent magnet is axially polarized, so that its poles are consecutive in the axial direction. In order to save expensive magnetic material, it is preferred that the radius of the ring is at least 5 times, preferably at least 8 times, its thickness measured in the radial direction. Suitably, the measuring element has a retaining plate that can be loaded by a tappet, and the permanent magnet is fastened to the retaining plate.

[0008] Preferably, the rotary spray gun has a housing made of a non-ferromagnetic material, in which the at least one cylinder and the measuring element are accommodated. Aluminum is particularly suitable as a material for the housing, which hardly hinders the detection of the permanent magnet by means of the magnetic sensor.

[0009] The measuring element can be moved against a restoring force in a direction away from the at least one cylinder, so that the restoring force resets the measuring element again into an initial position after removal of the load via one of the tappets, which initial position corresponds to the information "all needle valves closed" detected by the sensor. The restoring force is expediently applied by at least one compression spring, which is arranged between the measuring element and a housing cover delimiting the housing upwards. The at least one compression spring can be designed as a helical spring.

[0010] In the case of a plurality of cylinder bodies arranged side by side, it is inevitable that the tappets load the measuring elements eccentrically in each case. In order to prevent the measuring elements from tilting in the housing, the measuring elements are preferably guided by means of at least one guide pin extending in the longitudinal direction, wherein each guide pin extends through the measuring element. It is preferred that the guide pins are arranged centrally so that the axis of rotation extends through the guide pins, while the other guide pins can be arranged eccentrically. It is also preferred that at least one of the guide pins extends centrally through one of the compression springs. It is also expedient to provide that the cylinder bodies are arranged at the same distance from each other and at the same distance relative to the axis of rotation in order to achieve the greatest possible symmetry. If, in addition, each tappet is eccentrically connected to the corresponding piston and is arranged closer to the axis of rotation than the central longitudinal axis of the piston, the torque applied by the tappet to the measuring element is reduced, thereby further reducing the risk of tilting the measuring element in the housing.

[0011] According to a preferred embodiment, each of the compression springs is provided with an additional compression spring which opposes the compression spring with a weaker restoring force and which presses the measuring element from below. The additional compression spring can also advantageously be designed as a helical spring and arranged around the guide pin. The force of the restoring spring and the additional restoring spring then always still results in a restoring force which pushes the measuring element into its initial position. However, the provision of the additional restoring spring helps to prevent the measuring element from tilting in the housing. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention will now be explained in more detail with reference to the exemplary embodiments schematically depicted in the accompanying drawings. In the drawings:

[0013] Figure 1 A perspective view showing an apparatus for applying a viscous material, and

[0014] Figure 2a , 2b Shown in accordance with Figure 1 A cross-sectional side view and a perspective view of a portion of the device. DETAILED DESCRIPTION

[0015] The device 10 shown in the drawings is used to apply a viscous material to a workpiece, in this embodiment, a paint. However, other uses are also conceivable, such as applying adhesives, sealing materials, sound-insulating materials or heat-conducting glues. The coating device 10 has a holding device 12, which is designed to be mounted on a robot arm. A rotary spray gun 14 is mounted in the holding device 12, which can rotate about the holding device 12 around a rotation axis extending in the longitudinal direction 16. The rotary spray gun 14 has three material outlets 18 at its lower end, at which the viscous material for application to the workpiece can be discharged from the housing 20 of the rotary spray gun 14 made of aluminum, and at which a coating nozzle is usually mounted respectively. Three needle valves 22 are accommodated in the housing 20, wherein each needle valve 22 is assigned to one of the material outlets 18. The valve needle 24 of the needle valve 22 closes one of the material outlets 18 at the valve seat or releases the material outlet 18 by lifting it from the valve seat. Each of the needle valves is equipped with a double-acting pneumatic cylinder 26, in whose piston chamber 28 a piston 30 can be moved back and forth in the longitudinal direction 16, to which the associated valve needle 24, which also extends in the longitudinal direction 16, is fixedly connected. The movement of the piston 30, which is acted upon by compressed air, thus causes a movement of the valve needle 24 and an opening or closing of the associated material outlet 18 at the valve seat. A locking spring 32, which is arranged in the piston chamber 28 and is designed as a helical spring, presses the corresponding piston 30 downward and the valve needle 24 onto the associated valve seat, so that the material outlet 18 is always closed when the compressed air fails.

[0016] The device 10 is controlled so that only one material outlet 18 is always open. In order to monitor whether one of the material outlets 18 is open or whether all the material outlets 18 are closed, the holding device 12 has a fixedly mounted magnetic sensor 34. The magnetic sensor detects the position of a measuring element 36 that can be moved in the housing 20 of the rotary spray gun 14. The measuring element 36 has a holding plate 38 that can be moved back and forth in the housing 20 in the longitudinal direction 16 and an annular permanent magnet 40 that is fixedly connected to the holding plate 38. The holding plate 38 is guided on a central guide pin 42 and on three outer guide pins 44, wherein each of the guide pins 42, 44 extends through an opening in the holding plate 38. Around each of the guide pins 42, 44, a compression spring 48, 50 is arranged, which is supported on the housing cover 46 at the top and on the holding plate 38 at the bottom, and which presses the measuring element 36 downward. This is a central compression spring 48 arranged around the central guide pin 42 and three outer compression springs 50 arranged around one of the outer guide pins 44. Each piston 30 is fixedly connected to a tappet 52, which is led out of the upper side of the associated piston chamber 28 facing away from the valve seat and toward the measuring element 36 in a sealing manner and rests on the retaining plate 38. If one of the material outlets 18 is opened by lifting the associated piston 30, the tappet 52 connected to this piston 30 presses the measuring element 36 upwards, so that the magnetic sensor 34 can detect the movement of the permanent magnet 40. The magnetic sensor 34 then generates a "valve open" signal. If the material outlet 18 is closed again by lowering the associated piston 30, the pressure springs 48, 50 cause the measuring element 36 to be lowered, which is detected by the magnetic sensor 34, which generates a "valve closed" signal.

[0017] The cylinders 26 are arranged side by side in the sense that the cross sections of the cylinders, which are made perpendicular to the longitudinal direction 16, do not overlap. The loading of the measuring element 36 by means of the tappet 52 can therefore be carried out non-centrally, i.e. centrally on the retaining plate 38. In order to avoid a tilting of the measuring element 36 in the housing 20, the tappet 52 is arranged eccentrically on the piston 30 and is offset as far as possible in the direction of the center of the retaining plate 38 or in the direction of the central longitudinal axis of the rotary spray gun 14. In addition, a weaker additional compression spring 48', 50' is arranged opposite each of the compression springs 48, 50, which presses against the retaining plate 38 from below. The dimensions of the compression springs 48, 50 and the additional compression springs 48', 50' are determined here so that each pair, which includes one of the compression springs 48, 50 and the opposing additional compression spring 48', 50', exerts a force on the retaining plate 38 in total, which is directed downward, i.e. in the direction of the cylinders 26.

[0018] In the exemplary embodiment shown, the rotary spray gun 14 has three needle valves 22 . It goes without saying that the rotary spray gun 14 can be equipped with two or more than three needle valves 22 .

[0019] In summary the following can be determined:

[0020] The invention relates to a device for applying a viscous material to a workpiece, the device comprising a rotary spray gun 14 arranged rotatably about a rotation axis extending in a longitudinal direction 16 in a holding device 12, the rotary spray gun having at least one material outlet 18, wherein a needle valve 22 is associated with each material outlet 18, by means of a valve needle 24 of the needle valve extending in the longitudinal direction 16, the corresponding material outlet 18 can be closed at a valve seat, and a cylinder 26 is associated with each valve needle 24, in a piston chamber 28 of which a piston 30 can be moved by pressure application by means of a fluid, the valve needle 24 being fixedly connected to the piston. According to the invention, a tappet 52 is associated with each piston 30, which tappet is led out of the associated piston chamber 28 in a sealed manner on an upper side facing away from the at least one valve seat, the rotary spray gun 14 has a measuring element 36 that can be applied by means of the tappet 52 and can be moved in the longitudinal direction 16, and the holding device 12 has a sensor 34 for determining the position of the measuring element 36.

Claims

1. A device for applying a viscous material to a workpiece, comprising a rotary spray gun (14) arranged in a holding device (12) so as to be rotatable about a rotation axis extending in a longitudinal direction (16), the rotary spray gun having at least one material discharge opening (18), wherein: A needle valve (22) is provided for each material outlet (18), by means of which a valve needle (24) extending in the longitudinal direction (16) of the needle valve can close the corresponding material outlet (18) at the valve seat, and a cylinder (26) is provided for each valve needle (24), in which a piston (30) can be moved by pressure applied by a fluid in a piston chamber (28) of the cylinder, the valve needle (24) being fixedly connected to the piston, characterized in that each piston (30) is connected to a tappet (52), which is led out of the relevant piston chamber (28) in a sealed manner on the upper side facing away from the at least one valve seat, the rotary spray gun (14) having a measuring element (36) movable in the longitudinal direction (16) which can be loaded by means of the tappet (52), and the holding device (12) having a sensor (34) for determining the position of the measuring element (36).

2. The device according to claim 1, characterized in that The rotary spray gun (14) has at least two material outlet openings (18).

3. The device according to claim 1 or 2, characterized in that The measuring element (36) has a permanent magnet (40), and the sensor (34) is a magnetic sensor.

4. The device according to claim 3, characterized in that The permanent magnet (40) has the shape of a circular ring which surrounds the axis of rotation.

5. The device according to claim 4, characterized in that The ring is axially polarized.

6. The device according to claim 4, characterized in that The radius of the ring is at least 5 times its thickness measured in the radial direction.

7. The device according to claim 6, characterized in that The radius of the ring is at least 8 times its thickness measured in the radial direction.

8. The device according to claim 3, characterized in that The measuring element (36) has a holding plate (38) which can be acted upon by a tappet (52) and to which a permanent magnet (40) is fastened.

9. The device according to claim 1 or 2, characterized in that The rotary spray gun (14) has a housing (20) made of a non-ferromagnetic material, in which the at least one cylinder (26) and the measuring element (36) are accommodated.

10. The device according to claim 1 or 2, characterized in that The measuring element (36) is movable in a direction away from the at least one cylinder (26) against a restoring force.

11. The device according to claim 9, characterized in that The measuring element (36) is movable in a direction away from the at least one cylinder (26) against a restoring force.

12. The device according to claim 11, characterized in that The restoring force is applied by at least one compression spring (48, 50) which is arranged between the measuring element (36) and a housing cover (46) which delimits the housing (20) upwards.

13. The device according to claim 12, characterized in that Each of the compression springs (48, 50) is associated with a further compression spring (48', 50') which opposes it with a weaker restoring force and which presses the measuring element (36) from below.

14. The device according to claim 1 or 2, characterized in that The measuring element (36) is guided by means of at least one guide pin (42, 44) extending in the longitudinal direction, wherein each guide pin (42, 44) extends through the measuring element (36).

15. The device according to claim 12, characterized in that The measuring element (36) is guided by means of at least one guide pin (42, 44) extending in the longitudinal direction, wherein each guide pin (42, 44) extends through the measuring element (36).

16. The device according to claim 13, characterized in that The measuring element (36) is guided by means of at least one guide pin (42, 44) extending in the longitudinal direction, wherein each guide pin (42, 44) extends through the measuring element (36).

17. The device according to claim 15, characterized in that At least one of the guide pins (42, 44) extends centrally through one of the compression springs (48, 50), wherein the particular one of the compression springs (48, 50) is designed as a helical spring.

18. The device according to claim 16, characterized in that At least one of the guide pins (42, 44) extends centrally through one of the compression springs (48, 50) and through another of the other compression springs (48', 50'), wherein the relevant one compression spring (48, 50) or the one other compression spring (48', 50') is designed as a helical spring.

19. The device according to claim 2, characterized in that The cylinders (26) are arranged at the same distance from each other and at the same distance relative to the axis of rotation.

20. The device according to claim 1 or 2, characterized in that Each tappet (52) is eccentrically connected to the corresponding piston (30) and is arranged closer to the rotation axis than the central longitudinal axis of the piston (30).

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