Patent Application
20230026219
The invention relates to an apparatus for applying viscous material to workpieces, in accordance with the preamble of claim 1.
Such apparatuses are used to apply viscous materials, such as, for example, adhesives, sealants or varnishes to workpieces. In this regard, multiple nozzles having different geometries, mounted on the rotary lance, are often used, into which nozzles a material outlet opens, in each instance. A needle valve is assigned to each material outlet, the valve needle of which closes off or releases the material outlet in question at a valve seat. Cylinders are provided to activate the valve needles, wherein each valve needle is connected with the piston of a cylinder, which is moved by means of applying pressure using a fluid, in particular compressed air. In the case of known apparatuses of the type mentioned initially, the cylinders are arranged next to one another at an equal distance from the valve seats, and the apparatus is controlled in such a manner that always only one of the needle valves opens for material application. In this regard, a need exists for monitoring the switching state of the needle valves, so that it is always recognized when one of the valves is open. Such monitoring can be implemented in a simple manner in the case of apparatuses having only one needle valve, in that a magnet is moved along with the single piston, the position of which magnet is then detected by means of a magnetic sensor of the holding device. However, as soon as the rotary lance has multiple valves such monitoring is almost impossible, since the pistons cannot have a defined position relative to the magnetic sensor, because of the constant rotation of the rotary lance with reference to the holding device. The same thing is the case if the rotary lance has only one needle valve held in it off-center.
It is therefore the task of the invention to further develop an apparatus of the type stated initially, in such a manner that it can be monitored better.
This task is accomplished, according to the invention, by means of an apparatus having the characteristics of claim 1.
Advantageous further developments of the invention are the object of the dependent claims.
The invention is based on the idea of having all the pistons act on a common measuring element by means of the tappets, the position of which element can then be detected by the sensor.
In most cases, in this regard, multiple needle valves are present, the cylinders of which are arranged next to one another, in particular in the sense that their cross-sections do not overlap perpendicular to the axis of rotation, wherein the lower and/or the upper delimitation surfaces of the piston chambers, for example, are arranged in a plane, in each instance. However, it is also possible that the rotary lance has only one needle valve having a cylinder arranged off-center, in particular, with reference to its center longitudinal axis. The measuring element can be structured with rotation symmetry, at least with reference to its parts that act on the sensor, so that its interaction with the sensor of the holding device does not or does not markedly change, even in the event of a rotation of the rotary lance with reference to the holding device. It is furthermore practical if the axis of rotation is a center longitudinal axis of the rotary lance or of the measuring element. The at least one piston is preferably acted on by means of compressed air, and it is practical if it furthermore has a spring impact as a fail-safe function, which forces it into a position in which the valve needle sits on the related valve seat, forming a seal.
The measuring element can be structured in different embodiments. However, it is preferred that it has a permanent magnet, while the sensor is a magnetic sensor. In this regard, it is preferred that the permanent magnet has the shape of a circular ring that encircles the axis of rotation, so that rotation of the rotary lance with reference to the holding device does not bring with it any change in the interaction of the permanent magnet with the magnetic sensor. In particular, the permanent magnet is poled axially, so that its poles follow one another in the axial direction. In order to save expensive magnetic material, it is preferred that the radius of the circular ring is at least 5 times, preferably at least 8 times as great as its thickness, measured in the radial direction. It is practical if the measuring element has a holding plate that can be impacted by the tappets, on which plate the permanent magnet is fastened.
Preferably the rotary lance has a housing composed of non-ferromagnetic material, in which the at least one cylinder and the measuring element are accommodated. Aluminum, in particular, is a possible material for the housing; it barely hinders detection of the permanent magnet by means of the magnetic sensor.
It is practical if the measuring element can be moved away counter to a reset force in the direction of the at least one cylinder, so that the reset force returns the measuring element back to a starting position that corresponds to the information “all needle valves closed” detected by the sensor, after elimination of the impact of one of the tappets. It is practical if the reset force is applied by means of at least one pressure spring that is arranged between the measuring element and a housing ceiling that delimits the housing toward the top. The at least one pressure spring can be configured as a helical spring.
In the case of multiple cylinders arranged next to one another, it is unavoidable that the tappets impact the measuring element off-center, in each instance. In order to prevent tilting of the measuring element in the housing, it is practical if this element is guided by means of at least one guiding pin that extends in the longitudinal direction, wherein each guiding pin extends through the measuring element. In this regard, it is preferred that one guiding pin is arranged centered, so that the axis of rotation extends through it, while further guiding pins can be arranged off-center. Furthermore, it is preferred that at least one of the guiding pins runs through the center of one of the pressure springs. Furthermore, it is practical if it is provided that the cylinders are arranged at equal distances from one another and at equal distances from the axis of rotation, so as to achieve the greatest possible symmetry. If, furthermore, each tappet is connected off-center with the corresponding piston, and is arranged closer to the axis of rotation than to the longitudinal center axis of the piston, a moment exerted on the measuring element by the tappet is reduced, so that the risk of tilting of the measuring element in the housing is further reduced.
According to a preferred exemplary embodiment, each of the pressure springs has a further pressure spring assigned to it that counteracts it with a weaker reset force and presses against the measuring element from the bottom. It is advantageous if the further pressure springs are also configured as helical spring and arranged around the guiding pins. A reset force that forces the measuring element into its starting position then still results from the forces of the reset springs and the further reset springs. However, provision of the further reset springs helps to prevent tilting of the measuring element in the housing.
In the following, the invention will be explained in greater detail using an exemplary embodiment shown schematically in the drawing. The figures show:
The apparatus 10 shown in the drawing serves for applying viscous material to workpieces, in the present exemplary embodiment for applying varnish. However, other uses are also conceivable, such as, for example, the application of adhesives, sealants, insulation material or heat-conducting paste. The application apparatus 10 has a holding device 12, which is intended to be mounted on a robot arm. A rotary lance 14 is mounted in the holding device 12, which lance can rotate about an axis of rotation with reference to the holding device 12, which axis extends in a longitudinal direction 16. At its lower end, the rotary lance 14 has three material outlets 18, from which viscous material can exit to be applied to a workpiece, from a housing 20 of the rotary lance 14 that is produced from aluminum, and at which outlets an application nozzle is generally mounted, in each instance. 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 needles 24 of the needle valves 22 each close off one of the material outlets 18 at a valve seat, or release the material outlet 18 by means of lifting off from the valve seat. Each of the needle valves has a dual-action pneumatic cylinder 26 assigned to it, in the piston chamber 28 of which a piston 30 can be displaced back and forth in the longitudinal direction 16, with which piston the valve needle 24 in question, which also extends in the longitudinal direction 16, is firmly connected. A movement of the piston 30 by means of applying compressed air thereby results in a movement of the valve needle 24 and in opening or closing of the material outlet 18 in question at the valve seat. A closing spring 32, arranged in the piston chamber 28 and configured as a helical spring, presses the corresponding piston 30 downward and the valve needle 24 onto the related valve seat, so that the material outlets 18 are always closed when the compressed air is not in effect.
The apparatus 10 is controlled in such a manner that only one material outlet 18 is always open at a time. 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 magnetic sensor 34 that is fixed in place. This sensor detects the position of a measuring element 36 that can move in the housing 20 of the rotary lance 14. The measuring element 36 has a holding plate 38 that can be displaced back and forth in the housing 20, in the longitudinal direction 16, and a ring-shaped permanent magnet 40 that is firmly connected with the holding plate 38. The holding plate 38 is guided on a central guiding pin 42 as well as on three outer guiding pins 44, wherein each of the guiding pins 42, 44 extends through an opening in the holding plate 38. A pressure spring 48, 50 supported at the top on a housing ceiling 46 and at the bottom on the holding plate 38 is arranged around each of the guiding pins 42, 44, which spring presses the measuring element 36 downward. In this regard, this involves a central pressure spring 48 arranged around the central guiding pin 42 and three outer pressure springs 50, each arranged around one of the outer guiding pins 44. A tappet 52 is firmly connected with each of the pistons 30, which tappet is passed out from the top of the piston chamber 28 in question, which top faces away from the valve seats and faces the measuring element, and the tappet lies against the holding plate 38. If one of the material outlets 18 is opened by means of raising the piston 30 in question, the tappet 52 connected with this piston 30 presses the measuring element 46 upward, 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 means of lowering the piston 30 in question, the pressure springs 48, 50 bring about lowering of the measuring element 36, which is detected by the magnetic sensor 34, which generates a “valves closed” signal.
The cylinders 26 are arranged next to one another in the sense that their cross-sections, which are made perpendicular to the longitudinal direction 16, do not overlap. Impacting of the measuring element 36 by means of the tappets 52 therefore cannot take place centrally, in other words in the center of the holding plate 38. In order to prevent tilting of the measuring element 36 in the housing 20, the tappets 52 are arranged off-center on the piston 30 and offset as far as possible in the direction toward the center of the holding plate 38 or in the direction of the center longitudinal axis of the rotary lance 14. Furthermore, a further, weaker pressure spring 48′, 50′ lies opposite each of the pressure springs 48, 50, the former pressing against the holding plate 38 from below. In this regard, the pressure springs 48, 50 and the further pressure springs 48′, 50′ are dimensioned in such a manner that each pair, consisting of one of the pressure springs 48, 50 and the opposite further pressure spring 48′, 50′, exerts a force on the holding plate 38, in total, that is directed downward, in other words in the direction toward the cylinders 26.
In the exemplary embodiment shown, the rotary lance 14 has three needle valves 22. It is obviously understood that the rotary lance 14 can be equipped with one, two or more than three needle valves 32.
In summary, the following should be stated:
The invention relates to an apparatus 10 for applying viscous material to workpieces, having a rotary lance 14 arranged to rotate about an axis of rotation that runs in a longitudinal direction 16, in a holding device 12, which lance has at least one material outlet 18, wherein a needle valve 22 is assigned to each material outlet 18, by means of the valve needle 24 of which, extending in the longitudinal direction 16, the corresponding material outlet 18 can be closed off at a valve seat, and wherein a cylinder 26 is assigned to each valve needle 24, in the piston chamber 28 of which cylinder a piston 30 can be moved by means of a fluid, by applying pressure, with which piston the valve needle 24 is firmly connected. According to the invention, it is provided that a tappet 52 is connected with each piston 30, which tappet is passed out of the piston chamber 28 in question, in a sealed-off manner, on the top that faces away from the at least one valve seat, that the rotary lance 14 has a measuring element 36 that can be impacted by means of the tappets 52 and displaced in the longitudinal direction 16, and that the holding device 12 has a sensor 34 for determining the position of the measuring element 36.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 102 871.7 | Feb 2020 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/052329 | 2/1/2021 | WO |
