Patent Publication Number: US-2012035758-A1

Title: Device for coating an elongated workpiece

Description:
The invention relates to a device for coating an elongated workpiece with the pre-characterizing features of claim  1  and an associated method as well as an associated system. 
     Complex buildings can be made by a large number of materials, e.g. from wood or timber materials with the help of modern scantling or joinery machines. For example, it is possible to provide complete prefabricated buildings from wood in a construction system of prefabricated components. The elongated components such as boards, beams, slats are automatically processed from a base material, f. i. from solid timber beams. The object is the increase of productivity with the manufacture of prefabricated components. However, it is problematic to protect the prefabricated components with a coating or a glaze. Conventionally, this coating is performed in a painting chamber. In order to reach uniform application of the coating material on all surfaces and recesses of the workpiece, often several painting steps are necessary. However, despite careful application of the coating material such as impregnation, it cannot be avoided that separated recesses, like e.g. halvings and other carpenter-common recesses are not finished. These uncoated parts of the workpiece then form the entrance for moisture as well as for pest, which is to be prevented by the coating. Due to the necessary repeated treating of the surface the application of the coating is one of the most complex processing steps, in particular for the recesses mentioned. 
     An automated application of a coating is shown in DE 42 22 349 C2 by a varnishing line for workpieces, wherein the workpieces are inserted in a painting cab, in order to be painted by a nozzle. The workpieces are fixed on holder frames which are pivotable. The device shown in this reference is mainly suited for the painting of vehicle bodies. Due to the linear extension of elongated workpieces and the complex surfaces the use of the varnishing line of DE 42 22 349 C2 is not practical. DE 11 75 126 shows another mechanism useful for coating of bodies. A paint nozzle is here arranged at a pivotable and nickable boom. The bodies to be painted are directed on a conveyor towards the boom. This system is also not practical for the coating of elongated workpieces with high linear extension, since the complex surface structures can be hardly achieved because of the limited mobility of the boom. Furthermore, the use of the device shown in DE 11 75 126 requires a painting chamber, into which the entire workpiece is introduced. This is also complex due to the linear extension of the joined workpieces. 
     An object of the present invention is to provide a device, a method and a system for coating an elongated workpiece which allows with smallest space requirements an all-round and complete application of a coating on workpieces with complex surface structures. This object is solved by a device according to claim  1 , a method according to claim  10  as well as a system according to claim  13 . Favourable embodiments of the invention are subject-matter of the dependent claims. 
     The device according to the invention for coating an elongated workpiece is suitable in particular for the painting of a joined wooden workpiece having at least one nozzle directed towards the workpiece. The coating material is discharged from this nozzle in the coating operation to be sprayed exactly at the corners or edges of a beam by the adjustability of the nozzle (-s) in several degrees of freedom. The coating is for example a paint, a glaze or other suitable materials to surface coating. The device according to the invention is characterised in that the nozzle is disposed on a holder aligned substantially perpendicular to the workpiece longitudinal axis and being suspended in a frame. Due to this embodiment of the device only a relatively small base is required and can be integrated in a simple and space-saving manner into an existing production system, so that the workpieces to be coated during the painting process are exactly coated or painted, i.e. by the exact alignment on the corner or edge ranges of reamings, incisions or similar recesses of a beam. An elongated workpiece is here a workpiece, which is at least 10× as long as wide, e.g. boards, but no relative compact vehicle bodies. It is favourable that the frame is formed as a fixed portal. This portal does not only serve as holder for the frame, but can also be used as holder for the control and drive elements of the device. These elements, for example a compressor for the pressurization of the coating material or a drive unit for the holder, can be suspended above the holder at the frame, thus being arranged outside of the sphere of the nozzles for the coating material in order to be not contaminated. 
     It is favourable, if the holder for the nozzle is adjustable in transverse and/or height direction. Due to this adjustability the device can be adapted to the dimensions of the workpieces to be painted or coated together with the recesses therein. Further, the holder is formed as a linear guide aligned to the workpiece longitudinal axis. It is conceivable that several mounting plates are provided at the sides of the frame such that the transferred workpiece can be coated in one cycle. 
     It is recommendable, that the holder is formed as rotatable collar or rotating assembly and the nozzle is arranged at the periphery of the collar. It is also favourable, if the nozzle is formed adjustable in horizontal, vertical and/or radial direction and has at least three degrees of freedom. The arrangement of an adjustable nozzle at a rotatable collar enables that even complex structures (openings, recesses, chamfers etc.) of workpieces passing through the device are coated or painted in a single operation. 
     In order to further improve the adjustment of the nozzle in radial direction, it is advantageous that a curve rail is provided to deviating the nozzle movement from a rotation into a largely linear respectively radial movement. Due to this adjustable radial movement of the nozzle it is ensured that the nozzles always keep the equal distance to the workpiece surface in response to the workpiece geometry. Thus, uniform application of the material is ensured on the surface of complicated or inclined recesses etc. Such a control in the respective space axis (and/or around it) is advantageous if only partial ranges of the workpiece, e.g. the faces of the rafters are painted/glazed, which exceed latter from the roof framing over the masonry. For instance it is possible to paint the inclined surface of the rafter intensively at the foot end. 
     It is favourable, that the rotation of the collar is carried out by a crank stroke transmission engaging at the collar periphery and/or a belt drive. For example, the stroke transmission accomplishes the movement into a circumferential direction of the collar, whereas the return movement is carried out by a belt drive. Of course, it is possible to accomplish the rotation of the collar (e.g. over +/−90°) only via a crank slot or a belt drive. In addition, a rotation of the collar is carried out up to 360°. By rotation of the collar around 360° the arrangement of a single nozzle at the collar periphery is sufficient in order to reach all surface portions of the workpiece. However, if two or more nozzles are arranged at the collar periphery, it is sufficient to have a rotatability of the collar around 180° or only 90°, in order to accomplish a full surface application for coating on the workpiece surface. With that arrangement of more than two nozzles an acceleration of the painting process is achieved. Thus, a further reduction of the cycle times can be realized. 
     Pretty often the joined workpieces have inclined faces, whose coating/finishing is difficult. In order to provide a satisfactory coating of these faces, it is favourable that the holder is formed pivotable towards the workpiece longitudinal axis. By pivoting the holder towards the faces or other inclined surfaces of the workpiece an optimum coating of the workpiece can be performed. Thus, manual rework of the front faces or other inclined surfaces of the workpiece can be avoided and productivity can be further increased. 
     In order to apply various coating materials, f. i. multi colour paints or coating agents with different chemical properties by the same device, it is possible to arrange several nozzles next to each other at the holder. A multiplicity of holders that are hung up in series at the device is preferred. Thus, a shut down of the entire system can be avoided on failure of one nozzle. 
     The inventive process for coating a workpiece, and here in particular for painting a wooden workpiece from a scantling or joinery system covers the subsequent steps: 
     First, at least one record stored in a memory is selected. The record include information on workpiece geometry. As next step transfer of the record into control commands for the movement of the above described device for coating of the workpiece is carried out. It is favourable that the information from the record are additionally transferred into control commands for the nozzle adjustment and/or movement, e.g. the pivoting of the holder. 
     Exact data on the workpiece geometry are of particular importance mainly with the operation of an automatic scantling or joinery system. Thus, it is advantageous that the record is passed on the memory device with information on the workpiece geometry (e.g. length, depth, slope of a reaming) from the control of the upstream scantling or joinery system. The invention process thus enables a fully automated and continuous working progress of the delivery of the unprocessed workpiece blanks over the scantling system up to the coating and shipping the coating operation. 
     Further, it is favourable that the record is read out from a central memory device with information on workpiece geometry after identification of the individual workpiece. Here it is recommendable that the workpiece has identification means, f. i. a machine-readable code. For example this code can be mounted on the workpiece in form of a bar code after processing in the scantling system or in each other upstream processing station to be then detected by corresponding readers at the device for coating the workpiece. 
     On automatic processing of the workpiece and an automated coating it is important to consider the alignment of the workpiece with the control of the movements of the holder. Thus, it is favourably on start of the coating operation to detect the exact alignment of the workpiece as well as a corresponding adaptation of the movement to approach at this alignment. The system for coating of a workpiece, in particular from a upstream scantling or joinery system includes a loading system for the workpiece to the above described device for coating the workpiece, a removal device for the coated workpiece, a controller for the movement of the loader, of the device for coating of the workpiece and/or of the removal device, a memory device for records with information on the workpiece geometry as well as a device for transferring the records to the controller. The system includes data for movement of the loader, of the device for coating the workpiece and/or of the removal device relative to the workpiece geometry. With the system the subsequent exemplary represented operation is performed. 
     A wooden workpiece processed on a scantling or joinery system is handed over by the loader to the device for coating the workpiece. As loading systems all types are suitable, f. i. linear conveyer systems or transport vehicles without driver. By the use of corresponding loading systems it is possible, to set up the components of the system at different locations. The workpiece transported to the device for coating the workpiece is now passed through the device and thus coated with the coating material. When passing the workpiece through the coating device a control of the device movement is carried out, i.e. the movement of the holder as well as the nozzles according to the workpiece geometry. The records with information on the workpiece geometry are selected before starting the coating operation from memory means and passed on to the controller. Compiling the records can be made by computer aided manufacture software (CAD/CAM programmes). After the coating process the coated workpiece is further transported by the removal device. For this removal the mentioned linear motion devices are suitable; however, the use of transport vehicles or transport systems is also possible, which can include drying means, for example fans or lamps to ensure the hardening or drying of the coating material during the transport. The removal device can transport the workpieces to a subsequent packaging or shipping station. In order to reach an optimum coating of all surfaces of the workpiece, it is favourable, that the system has an additional device for rotation or alignment of the workpiece. This system can be arranged upstream of the coating device. Such a rotation or adjustment device can effect an optimum feeding of the workpiece to the coating device. 
     If the rotation or adjustment device is arranged downstream, it can be used for optimum alignment of the workpiece for drying of the coated workpiece. Of course, it is also possible to arrange a rotation or adjustment device on both sides of the device for coating the workpiece. The records with information on the workpiece geometry are selected from the upstream scantling or joinery system and are passed to the memory of the system. The memory communicates with the device for the transfer of the records to the controller, that accomplishes the movements of the loader as well as of the coating device in accordance with the workpiece geometry. 
     It is favourable to implement the memory as central data memory of the system. In order to verify the information on the workpiece geometry recovered from the records, the system preferably has an additional detector for the geometry of the workpiece or its alignment. 
    
    
     
       Other advantages, features and characteristics of the invention result from the subsequent description of preferred, but not restrictive embodiments of the invention on the basis the schematic figures. They show in: 
         FIG. 1  a preferred embodiment of the device for coating a workpiece; 
         FIG. 2  another preferred embodiment of the device; 
         FIG. 3  a system, that comprises the device in side view; and 
         FIG. 4  a preferred embodiment of the system in plan view. 
     
    
    
       FIG. 1  shows a device  10  for coating a workpiece  20 , wherein a holder  11  for at least one nozzle  14  is arranged in a fixed frame  17  to be aligned to the workpiece  20  to be coated. The holder  11  has a rotating assembly  12 , at which periphery  13  multiple nozzles  14  are arranged, from which the coating material  15  discharges. In the embodiment of  FIG. 1  the rotating assembly  12  is rotatable around 90°. While the rotation of the rotating assembly  12  the coating material  15  discharges from the nozzles  14  and adheres to the surfaces  22  of the workpiece  20 , while it is passed through the device  10 . In the embodiment of the  FIG. 1  the rotating assembly  12  is formed as circular element. However, another form is conceivable, for example two opposite U- or L-rails, at which the nozzles  14  are arranged. Further, it is possible to construct the rotating assembly  12  in a segmented manner. Thus, the device  10  with a segmented rotating assembly  12  allows adaptation of the size of the inlet opening  21  to most cross sections of the workpiece  20 . 
     The nozzles  14  are arranged at the periphery of the rotating assembly  12  and are adjustable in horizontal, vertical and/or radial direction. Due to these adjustability of the nozzles  14  all surfaces  22  of the workpiece  20  can be coated on rotation of the rotating assembly  12 , even if this there are rough structures, cuts or steps without using several coating operations. Horizontal and vertical movement of the nozzles  14  is performed via joints  19 , whereas the displacement in radial direction is carried out via a curve rail  23 . This curve rail  23  transmits the rotational movement of the nozzles  14  to a largely linear or radial movement in accordance with the workpiece geometry and ensures an almost equal distance of the nozzles  14  to the surface  22  of the workpiece  20 . Thus, an uniform application of the coating material  15  is performed. The nozzle  14  can also spray into a pocket  20 ′ at the left side surface of the beam  20 . By swivelling of the nozzle  14  (either at the joint  19  and/or by the rotating assembly  12 ) around a few degrees of angle (e.g. over +/−20°) in the plane of the drawing also the upper and lower sides of the recess or pocket  20 ′ (a purlin mount) can be sprayed as well. 
     The frame  11  in the embodiment of the  FIG. 1  is adjustable in height and transversely. In order to accomplish this vertical adjustment, the device  10  has an electric motor  24 , that is suspended at the frame  11  and operates the adjusting member  26  for the vertical adjustment via a drive belt  25 . Likewise, that electric motor  24  drives a crank stroke transmission  27 , which engages at the periphery  13  of the rotating assembly  12  to drive the rotating assembly  12  around the longitudinal axis. Further, the device  10  has an additional motor  30  for pivoting and/or transverse movement of the holder  11 . By pivoting the holder  11  towards the workpiece longitudinal axis it is possible to coat inclined faces  31  of the workpiece  20  (e.g. foot end of rafters). 
     In the embodiment of  FIG. 1  the rotating assembly  12  rotates around 90°. Due to several nozzles  14  at the periphery  13  of the rotating assembly  12  it is possible to perform a coating of all surfaces  22  of the workpiece  20  in one operation. If only two nozzles  14  are provided at the periphery  13  of the rotating assembly  12 , a rotation of the rotating assembly  12  will be around 180°, in order to coat all surfaces  22  of the workpiece  20 . If only one nozzle  14  is provided at the periphery  13 , a corresponding coating effect requires a rotation of the rotating assembly  12  up to 360°. 
     In the shown embodiment the workpiece  20  is supported on a conveyor  29  for transport through the fixed coating device  10 . 
       FIG. 2  shows a device  10  for coating a workpiece comparable with the device  10  of  FIG. 1 . Instead of a crank stroke  27  for the rotation of the rotating assembly  12 , the device  10  in  FIG. 2  has a belt drive  28  for the rotating assembly  12 . Here again, a rotation of the rotating assembly  12  around only 90° is provided, as the plurality of nozzles  14  at the periphery  13  of the rotating assembly  12  achieve a coating of all surfaces  22  of the workpiece  20  already by a rotation around 90°. 
     In addition to the electric motor  24  that effects the rotation and vertical adjustment of the holder  11 , the device  10  illustrated in  FIG. 2  has an motor  30  for pivoting of the holder  11 . With this pivoting of the holder  11  (out of the vertical direction) towards the workpiece longitudinal axis it is possible to coat inclined faces  31  of the workpiece  20 . Each of the arranged nozzles  14  of the rotating assembly  12  has an own supply for the coating material  15 . Thus, it is possible with a single holder  11  and a sufficient number of nozzles  14  to apply various coating materials  15  via the same holder  11  and in a single operation. In response of the information from the controller the application of the coating material  15  can also follow successively, so that parts of the workpiece  20  are coated with a first coating material  15 , while other portions are applied with a second, third etc. coating material  15 . 
       FIG. 3  schematically shows a system  40 , which includes a device  10  for coating a workpiece  20 , as described. The system  40  in the embodiment of the  FIG. 3  has a loader  50  to supply bar-like workpieces  20  to the downstream device  10  for coating. Upstream of the device  10  the system  40  has an alignment device  60  that guarantees an aligned feeding of the workpiece  20  to the device  10 . Upstream of the feeder  50 , a scantling or joinery system (not shown in  FIG. 3 ) is arranged for milling and/or cutting recesses  70  in the workpiece  20 . From the scantling system the data and/or the records with information on the workpiece geometry (location of the recesses, their depth etc.) are passed to the controller  16  at the device  10  such that on the basis of the provided information a control of the motion of the device  10  and/or the alignment of the nozzles  14  can take place (here arranged at covers  18 ). 
     Due to this control is it possible to reach all recesses  70  in the workpiece  20  uniformly in a single operation with the coating material  15 . After passing the device  10  the workpiece  20  is taken by the removal device  80  for transport of the workpiece  20 , e.g. by a role conveyor  81  with lamps  82  for drying of the coated surfaces  22 . After the drying process on the removal device  80  the workpiece  20  can be passed to downstream working, packaging or transportation stations (not shown). 
     In  FIG. 4  the system  40  of  FIG. 3  is shown in plan view. In difference to  FIG. 3 , the loader  50  of the system  40  is fed in a manual method, i.e. the joined workpieces  20  are transported to the system  40  and subsequent placed on the loader  50  by an operator  90 . The system  40  in the embodiment of  FIG. 4  has detecting means (not shown) for a code mounted at the workpieces  20 , such that the workpiece  20  is uniquely identified. After identification of the workpiece  20  the associated record with geometrical information is used for the control of the device  10  for the coating, i.e. selected from a central memory and processed for the control of the device  10  in the controller unit  16 . After supply of the workpiece  20  to the device  10  the coating process begins together with proper alignment of the workpiece  20  as checked by corresponding detecting means (not shown). If the workpiece  20  is not properly aligned, the system  40  shown in  FIG. 4  has an additional alignment device  60  for the workpiece  20 , to align it to the corresponding set points. The loader  50  leads the workpiece  20  through the device  10  up to the removal device  80  downstream of the device  10 . In the embodiment a multiplicity of linear movers  92  are aligned vertical to the feed direction of the workpiece  20  and pass the workpiece  20  to a transport cart  93 , which is here furnished with lamps  82 . After a complete filling of the transport cart  93  it moves automatically to the packaging station (in  FIG. 4  not shown) and an empty transport cart  93  is advanced to the system  40 . 
     REFERENCE SYMBOL LIST 
     
         
           10 =device 
           11 =holder 
           12 =rotating assembly 
           13 =periphery 
           14 =nozzle 
           15 =coating material 
           16 =controller 
           17 =frame 
           18 =cover 
           19 =joint 
           20 =workpiece 
           21 =opening 
           22 =surface 
           23 =curve rail 
           24 =electric motor 
           25 =drive belt 
           26 =adjusting member 
           27 =crank stroke transmission 
           28 =belt drive 
           29 =conveyor 
           30 =motor 
           40 =system 
           50 =loader 
           60 =alignment device 
           70 =recesses 
           80 =removal device 
           81 =role conveyor 
           82 =lamp 
           90 =operator 
           92 =linear movers 
           93 =transport cart