Abstract:
The invention concerns a sensor arrangement for a coating system for coating workpieces, with at least one sensor for detecting at least one operating quantity of the coating system and for generating a corresponding sensor signal, a transmitter connected to the sensor for transmitting the sensor signal, a receiver for receiving the sensor signal transmitted by the transmitter, and a wireless connection between the transmitter and receiver.

Description:
This is a divisional patent application that claims priority to a patent application Ser. No. 10/653,444 filed on Sep. 2, 2003 now abandoned. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention concerns a sensor arrangement for a coating system according to the preamble of Claim  1  and also a coating system with such a sensor arrangement. 
   2. Relevant Prior Art 
   In modem painting systems, known rotary atomizers are used for which a so-called bell-shaped plate is driven by a compressed-air turbine at high rpm. The bell-shaped plate usually has the form of a truncated cone and expands in the spray direction, with the coating agent to be applied being accelerated in the axial direction and especially in the radial direction in the truncated cone-like bell-shaped plate due to centrifugal forces, so that a conical spray stream is produced at the outer edge of the bell-shaped plate. 
   From DE 43 06 800 A1, it is further known to measure the rpm of the compressed-air turbine. Here, reflective markings are applied onto the turbine wheel of the compressed-air turbine. These markings rotate with the turbine wheel and are detected by a stationary optical sensor by means of optical fibers. For achieving good painting results, the rotary atomizer with the compressed-air turbine is set to a high voltage, while the workpieces to be painted and the optical sensor are electrically grounded. 
   The use of flexible optical fibers for detecting the optical markings on the turbine wheel enables a stationary arrangement of the optical sensor and potential isolation of the sensor relative to the high voltage of the rotary atomizer. 
   A disadvantage of this known sensor arrangement with optical fibers is first the fact that for converting the optical signals transmitted in the optical fibers into an electrical signal, a relatively large number of optoelectrical converters is required. 
   Secondly, for an optical fiber connection, only a relatively small number of separation points is possible, because transmission losses occur at each separation point. For increasing component modularity of modem coating systems, with a corresponding increase in the number of separation points, the known optical fiber technology thus runs into its limitations. 
   Furthermore, optical fibers are relatively sensitive to breaks, which can lead to operational failure of the rpm measurement system for an excess mechanical load on the sensor arrangement. 
   The invention is thus based on the problem of improving the previously described known sensor arrangement to the effect that greater component modularity is possible. The mechanical load capacity should be as large as possible. 
   SUMMARY OF THE INVENTION AND ADVANTAGES 
   The task is solved starting with the known sensor arrangement described in the introduction according to the preamble of Claim  1  by the characterizing features of Claim  1 . 
   The invention includes the general technical teaching of providing a transmitter and a receiver for transmitting the sensor signal, with a wireless connection between the transmitter and the receiver. An advantage of a wireless connection between the transmitter and the receiver is first the unlimited mechanical load capacity of the connection, whereas a connection by means of optical fibers is relatively sensitive to breaks. Secondly, a wireless connection between the transmitter and the receiver advantageously enables arbitrary component modularity, since, in contrast to optical fibers, there are no separation points at the transitions between the individual modules. 
   The use according to the invention of a wireless connection with a transmitter and a receiver advantageously enables an arrangement of the sensor in a moving component of a coating system, whereas the sensor for the known sensor arrangement described in the introduction is stationary and is connected by optical fibers to the moving rotary atomizer. 
   For the sensor arrangement according to the invention, the sensor is preferably formed on a moving part of the coating system, while the receiver is stationary. However, the relative motion between the transmitter and the receiver during the operation of the coating system does not lead to mechanical loading of the connection or to mechanical wear and tear, because the connection between the transmitter and the receiver is wireless. 
   Preferably, the transmitter is a radio transmitter and the receiver is a corresponding radio receiver, with a wireless radio connection between the radio transmitter and the radio receiver. 
   However, as an alternative it is also possible that the transmitter is an optical transmitter and the receiver is an optical receiver, with an optical connection between the optical transmitter and the optical receiver. For example, for transmitting the sensor signals an infrared transmitter is used, whose signal is received by an infrared receiver. 
   Furthermore there is the possibility that the transmitter is an acoustic transmitter and the receiver is a corresponding acoustic receiver. For example, for transmitting the sensor signals an ultrasonic transmitter is used, whose signal is detected by an ultrasonic receiver. 
   In addition, the wireless connection between the transmitter and the receiver enables electric potential isolation, so that the transmitter on one side and the receiver on the other side can be at different electric potentials. This is particularly advantageous for use in an electrostatic coating system with a rotary atomizer, because here the rotary atomizer is typically at a high voltage, while the workpieces to be coated are grounded. Thus, the transmitter can also be at a high voltage for the sensor arrangement according to the invention, while the receiver is at a low voltage or at ground. 
   The sensor can be, e.g., a pressure sensor, which measures a pressure quantity of the coating system, such as the pressure of a medium (air, coating agent, solvent) of the coating system. Here, a few pressure quantities to be measured, which are named only as examples, include the drive air pressure, the steering air pressure, the solvent pressure, the paint pressure, and the line pressure. 
   In one variant of the invention, the sensor detects the position, the regulating speed, and/or the state of a component of the coating system. 
   For example, the sensor can be a smart-pig sensor, which detects the position, speed, and/or a characteristic of a smart pig. Here, the smart-pig sensor can output a signal when the smart pig has passed a certain line section or when the smart pig is located in the line section. 
   Furthermore, in the scope of the invention, there is the possibility that the sensor detects the position of a nozzle needle of the coating system, with the needle preferably being the main needle of a rotary atomizer. 
   The sensor can further detect the position of a cylinder of a piston dosing device or a piston pump of a coating system. 
   In addition, there is also the possibility that the sensor is a rotational quantity sensor, which detects the rpm, the rotational angle, and/or the direction of rotation of a turbine wheel of a rotary atomizer. 
   Finally, the sensor can also detect the position and/or the regulating speed of one or more shafts of a painting robot of the coating system. 
   In addition to the previously described sensor arrangement, the invention also includes a complete coating system with such a sensor arrangement. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other advantageous refinements of the invention are characterized in the subordinate claims or are described in more detail in the following together with the description of the preferred embodiments of the invention with reference to the figures. Shown are: 
       FIG. 1  shows a side view of a turbine wheel of a compressed-air turbine for driving a rotary atomizer with a sensor arrangement according to the invention, 
       FIG. 2  shows a piggable line with a sensor arrangement for detecting the smart-pig position, and also 
       FIG. 3  shows a rotary atomizer with a sensor arrangement according to the invention for pressure measurement. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The side view in  FIG. 1  shows an essentially conventional turbine wheel  1 , which can be used in a rotary atomizer turbine, which is known, e.g., from DE 43 06 800 C2. For the constructional configuration of the rotary atomizer turbine and the complete rotary atomizer, for simplification, refer to DE 43 06 800 C2, whose content is taken into account completely by the present description. 
   The turbine wheel  1  has a bell shaped-plate shaft  2 , wherein in  FIG. 1  a bell-shaped plate can be mounted on the left side of the bell shaped-plate shaft  2 . Furthermore, the turbine wheel  1  has a circular disk-shaped armature  3 , with numerous turbine blades  4  distributed around the circumference on the bell shaped-plate end surface of the armature  3 . During the operation of the rotary atomizer, the turbine blades  4  are driven by so-called drive air, which has been known for a long time. 
   On the end surface of the armature  3  facing away from the bell-shaped plate, there is an optical marking, which enables both a determination of the rotational velocity of the turbine wheel  1  and also a determination of the rotational direction of the turbine wheel  1 . The optical marking consists of several circle-segment coatings, which are applied to the end surface  5  distributed over the periphery. 
   On the side of the armature  3  facing away from the bell-shaped plate there is an optical sensor  6 , which detects the different reflective capacities of the optical markings and the otherwise matte end surface  5  and transmits a corresponding electrical signal to a transmitter  7 . 
   The transmitter  7  emits a radio signal by means of an antenna  8 . This signal is received over an antenna  9  by a receiver  10 , wherein the antennas  8 ,  9  are shown here only schematically. The receiver  10  then outputs a corresponding electrical signal, from which an evaluation unit can determine the rpm and direction of rotation of the turbine wheel  1 . 
   Here, the transmitter  7  is arranged in the rotary atomizer, which can be moved by a painting robot. In addition, the transmitter  7  with the sensor  6  and the antenna  8  are at a high voltage during the operation of the rotary atomizer, so that no electrical isolation of the receiver  7 , the sensor  6 , or the antenna  8  is required relative to the rotary atomizer. 
   In contrast, the receiver  10  is arranged stationary in the cabin wall of a painting cabin and is therefore exposed only to minimal mechanical loads during operation. In addition, the receiver  10  is grounded, with the wireless connection between the transmitter  7  and the receiver  10  providing potential isolation. 
     FIG. 2  shows another embodiment of a sensor arrangement according to the invention, which is used to determine the position of a smart pig  11  in a piggable line  12 . Here, the smart pig  11  has a permanent magnet  13 , which controls a magnetic field sensor  14 , with the magnetic field sensor  14  being arranged on the outside of the line  12 . 
   When the smart pig  11  is located at the position shown in  FIG. 2 , the magnetic field sensor  14  generates an electric signal based on the permanent magnet  13 . This signal is transmitted to a transmitter  15 . The transmitter  15  then emits a corresponding radio signal over an antenna  16 , wherein the radio signal is received by a receiver  17  over an antenna  18 . The receiver  17  then transmits a corresponding electrical signal to an evaluation unit. For simplification, the evaluation unit is not shown. 
   Here, numerous sensors can be provided within the line system. These sensors transmit their signals to a central receiver, so that the evaluation unit can detect the positions of all smart pigs. 
   The cross-sectional view shown in  FIG. 3  shows a rotary atomizer  19 , which essentially has a conventional configuration, so that as a supplement to the following description, one may reference the cited state of the art. 
   For assembling the rotary atomizer  19 , this has on its mounting-side end surface an attachment flange  20  with an attachment pin  21 , which enables mechanical attachment to a robot arm of a painting robot. 
   A conventional, truncated cone-like bell-shaped plate  22  is attached to the rotary atomizer  19 . The bell-shaped plate is shown here only with dashed lines and is driven during operation of the rotary atomizer  19  by a compressed-air turbine  23  with a high rpm. The rotation of the bell-shaped plate  22  leads to the situation where the coating medium fed into the interior of the bell-shaped plate  22  is accelerated in the axial direction and particularly in the radial direction and is sprayed at an outer edge of the bell-shaped plate. 
   Here, the drive of the compressed-air turbine  23  is realized by compressed air, which is fed by the painting robot over the attachment flange  20 , wherein the supply of drive air is not shown here for simplification. 
   Furthermore, for shaping the spray stream output by the bell-shaped plate  22 , a so-called steering air ring  24  is provided, which is arranged in the bell shaped-plate side end surface of a housing  25  of the rotary atomizer  19 . In the steering air ring  24  there are several steering air nozzles  26 ,  27 , which are directed in the axial direction and by means of which, during operation of the rotary atomizer  19 , a steering air current can be blown outwards onto the conical surface shell of the bell-shaped plate  22 . Depending on the amount and velocity of the steering air blown from the steering air nozzles  26 ,  27 , the spray stream is formed and the desired spray width is set. 
   Here, the supply of steering air for the two steering air nozzles  26 ,  27  is realized by corresponding flange openings  28 ,  29 , which are arranged in the attachment flange  20  of the rotary atomizer  19 . The position of the flange openings  28 ,  29  within the end surface of the attachment flange  20  is set by the position of the corresponding attachments to the associated attachment flange of the painting robot. 
   The outer steering air nozzle  26  is supplied by a steering air line  30 , which is led along the outside of the compressed-air turbine  23  between the housing  25  and the compressed-air turbine  23 . Here, the flange opening  28  first opens into an axial needle hole  31 , which then transitions into a radial needle hole  32 , with the radial needle hole  32  finally opening at the outside of a valve housing  33  into an intermediate space between the housing  25  and the valve housing  33 . The steering air is then fed past the compressed-air turbine  23  into an air space  34 . From this location, the steering air is finally led by needle holes  35  into the steering air ring  24  to the steering air nozzle  26 . 
   In contrast, the supply of steering air for the steering air nozzle  27  is realized by a steering air line  36 , which starts in the axial direction from the flange opening  29  in the attachment flange  20  and passes through the valve housing  33  without kinks. In addition, the steering air line  36  also goes in the axial direction through a bearing unit  37  of the compressed-air turbine  23 . Here, the radial distance of the steering air line  36  from the axis of rotation of the bell-shaped plate  22  is greater than the outer diameter of the turbine wheel not shown for simplification, so that the steering air line  36  runs on the outside of the turbine wheel. The steering air line  36  then opens on the bell shaped-plate side into another air space  38 , which is arranged between an essentially cylindrical section  39  of the compressed-air turbine  23  and a cover  40  surrounding this turbine. 
   In the surface shell of the section  39 , several holes  41  are located, which open in the bell shaped-plate end surface of the compressed-air turbine  23  and finally supply the steering air nozzles  27 . The holes  41  in the section  39  of the compressed-air turbine  23  consist of a needle hole running in the radial direction starting from the surface shell of the section  39  and a needle hole running in the axial direction starting from the bell shaped plate-side end surface of the section  39 , which enables simple assembly. 
   Here, a pressure sensor  42  with an integrated radio transmitter opens in the steering air line  36  near the attachment flange  20 , wherein the pressure sensor  42  measures the steering air pressure and transmits a corresponding radio signal by the radio transmitter. 
   This radio signal is received by a receiver  43  by means of an antenna  44  and is forwarded to an evaluation unit, wherein the evaluation unit is not shown for simplification. 
   The invention is not limited to the previously described preferred embodiments. Instead, a plurality of variants and modifications are conceivable, which also use the concept of the invention and therefore fall within the scope of protection. 
   The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than limitation. 
   Obviously, many modifications and variations of the present invention are possible in light of the above teachings it is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for convenience and not to be in any way limiting, the invention may be practiced otherwise than as specifically described.