Abstract:
A robot wrist for a painting robot has several wrist sections that can be rotated relative to one another, an internal conduit that passes through the wrist sections, a flexible hose carried in the internal conduit and having a hose drive operating on the hose to achieve positive rotation of the hose in the internal conduit corresponding to the rotation of the wrist sections.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of Provisional Patent Application Ser. No. 60/720,578 filed on Sep. 26, 2005. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates in general to robots, and more particularly to a multi axis wrist for a painting robot and a method of operating the same.  
       BACKGROUND OF THE INVENTION  
       [0003]     In modem paint facilities, multi-axis painting robots are used which carry application equipment, as for example a rotary atomizer, by means of a three-axis robot wrist. The hoses needed to operate the application equipment for paint, drive air, shaping air, and the like, are carried through an internal conduit in the robot wrist to the application equipment.  
         [0004]     The disadvantage of routing the paint hose through the robot wrist is that the paint hose may become deformed when the robot wrist moves, which may preclude cleaning the paint hose inside the robot wrist using a device, such as a go-devil. To minimize paint losses during color changes it would be desirable if the paint hose can be cleaned along its entire length up to the application equipment using the go-devil, or similar device, including those portions of the hose located inside the highly mobile robot wrist.  
       SUMMARY OF THE INVENTION  
       [0005]     The ability of the paint hose to be cleaned with a go-devil, or similar device, may be hampered by torsional loads which arise from movement of the robot wrist, wherein a clean bend in the paint hose is less disruptive and therefore does not preclude cleaning with the go-devil, or similar device. The present invention provides a robot wrist in which the hoses passing through the robot wrist are essentially loaded in flexion when the robot wrist moves, whereas only negligible torsion loads are imposed on the hoses. This is advantageous in that the ability to clean the hoses routed through the robot wrist using a go-devil, or similar device, will be only minimally, if at all, affected by movement of the robot wrist.  
         [0006]     The robot wrist in accordance with the present invention may include three rotatable wrist sections. Application equipment can be installed rotatably on a connecting flange on the kinematic output side of the robot wrist. The robot wrist has three axes (i.e. three degrees) of freedom. It shall be understood, however, that the present invention is not limited to robot wrists having three axes of freedom, but may also include robot wrists with a greater or smaller number of rotational axes.  
         [0007]     An internal conduit passing through the entire robot wrist is positioned within the wrist sections through which the hoses supplying the application equipment carried by the robot wrist are routed. The internal conduit can consist, for example, of a duct which is not sealed off with respect to the robot wrist for locating the hoses for operating the application equipment. When the wrist moves, however, there may be undesirable contact between the hoses and the inner wall of the robot wrist. Preferably, the internal conduit passing through the robot wrist has a protective sleeve which forms the inside lining of the internal conduit and thus prevents damage to, or excessive wear of, the hoses being carried through the robot wrist when the wrist moves. In addition, a protective sleeve of this type can consist of an electrically insulating material to insulate the electrically charged paint in the paint hose from the surrounding components. The protective sleeve preferably has an insulating capacity of at least 50 kV.  
         [0008]     In accordance with the invention, the hoses for operating the application equipment do not run haphazardly inside the internal conduit. Instead, the robot wrist of the present invention has a hose drive which positively rotates the hose or hoses in the internal conduit in accordance with the rotation of the wrist sections to prevent, or at least minimize, imposing undesirable torsional loads on the hoses. With movement of the robot wrist and an associated rotation of the individual wrist sections relative to each other, the hose being guided is positively rotated on one side or on both sides by the hose drive to prevent, or at least minimize, the torsional load.  
         [0009]     The hose drive allows rotation of the hose being carried through the robot wrist independent of the drive of the individual wrist sections. The hose drive can thus rotate the hose relative to one or more wrist sections.  
         [0010]     The hose drive may also operate on the hose both at the kinematic input-side wrist section and at the kinematic output-side wrist section. Preferably, the hose drive rotates the hose passing through the internal conduit at the kinematic input-side wrist section and at the kinematic output-side wrist section independently of each other. Accordingly, it may be possible that the hose in the kinematic input-side wrist section is rotated more or less than in the kinematic output-side wrist section.  
         [0011]     The hose drive may also act on the hose only at the kinematic input-side wrist section, while the hose in the kinematic output-side wrist section is secured to prevent rotation. This may be simpler from a construction standpoint because the hose drive does not need to operate through the entire robot wrist up to the kinematic output-side wrist section.  
         [0012]     The rotation of the hose preferably takes place relative to the particular wrist section or to the internal conduit, with the rotation preferably taking place with respect to the center axis of the internal conduit. However, it is possible that the hose being carried through the robot wrist is rotated with respect to its own longitudinal axis.  
         [0013]     The hose being carried through the robot wrist may be positioned by a guide plate in the kinematic input-side wrist section and/or in the kinematic output-side wrist section and/or in a wrist section located there between. The robot wrist of the present invention may include a guide plate for locating the hose or hoses preferably in both the kinematic input-side wrist section and in the kinematic output-side wrist section, whereas there is no guide plate in the wrist section located between those two sections. A guide plate of this type advantageously allows the hose or hoses being carried to be guided in the radial direction and in the peripheral direction relative to the longitudinal axes of the internal conduit, whereby the individual hoses are kept in position. In addition, carrying several hoses in one guide plate allows synchronous angular rotation of the hoses relative to the longitudinal axis of the internal conduit.  
         [0014]     In instances where it may be desirable to have the hose secured to prevent rotation in the kinematic output-side wrist section, this can be achieved by mounting the guide plate securely in the kinematic output-side wrist section to prevent rotation.  
         [0015]     In instances where it may be desirable to have a hose drive acting on both sides, the guide plate is preferably mounted rotatably in the kinematic input-side wrist section and in the kinematic output-side wrist section.  
         [0016]     The hose drive preferably acts on the guide plate and preferably rotates it with respect to the longitudinal axis of the internal conduit.  
         [0017]     It should be understood that the invention is not restricted to the previously described robot wrist as a single component, but may also include a complete robot, particularly a painting robot having a robot wrist of the type in accordance with the invention.  
         [0018]     The present invention may also be used in connection with a painting robot.  
         [0019]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating a preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     The present invention will become more fully understood for the detailed description and accompanying drawings, wherein:  
         [0021]      FIG. 1  is a side elevational view of a painting robot having a robot wrist in accordance with the present invention;  
         [0022]      FIG. 2A  is a side elevational view of the robot wrist showing a drive mechanism for operating an output section of the robot wrist;  
         [0023]      FIG. 2B  is a side elevational view of the robot wrist showing a drive mechanism for operating an intermediate section of the robot wrist;  
         [0024]      FIG. 2C  is a side elevational view of the robot wrist showing a drive mechanism for operating an input section of the robot wrist;  
         [0025]      FIG. 2D  is a side elevational view of the robot wrist showing the positioning of hoses within the robot wrist; and  
         [0026]      FIG. 3  is an axial front elevation of a guide plate of the robot wrist. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]      FIG. 1  shows a painting robot  1  in accordance with the invention, which can be used, for example, for painting automobile body parts.  
         [0028]     The painting robot  1  is attached by a foot  2  to a base  3 , where the foot  2  of the painting robot  1  carries a pedestal  4  which is rotatable relative to the foot  2  about a first axis A 1 . The drive for the pedestal  4  may be provided by an electric motor, or any other suitable drive device.  
         [0029]     Painting robot  1  further includes a robot arm  5  that is rotatable about a second axis A 2  relative to the pedestal  4 , where the drive for the robot arm  5  may be similarly provided by an electric motor, or any other suitable drive device.  
         [0030]     Painting robot  1  may also include a robot arm  6  that is rotatable about a third axis A 3  relative to the robot arm  5 , where the drive for the robot arm  6  is similarly provided by an electric motor.  
         [0031]     A robot wrist  7 , in accordance with the present invention, as illustrated in  FIGS. 2A-2D , is attached to a distal end of robot arm  6 .  
         [0032]     The robot wrist  7  may carry a rotary atomizer  8  which drives a bell cup  9  for applying a coating medium to the automobile body parts.  
         [0033]     The robot wrist  7  has a connecting flange  10  on the kinematic input-side that is rigidly and securely attached to prevent rotation relative to the distal end of robot arm  6 .  
         [0034]     On the side opposite the connecting flange  10 , robot wrist  7  has a rotatable connecting flange  11 , to which the rotary atomizer  8  is rotatably attached.  
         [0035]     Three wrist sections  12 - 14  are located between the kinematic input-side connecting flange  10  and the kinematic output-side connecting flange  11 , where the wrist sections  12 - 14  are rotatable relative to each other and with respect to the two connecting flanges  10 ,  11 .  
         [0036]     Wrist section  12  is rotatable about a fourth axis A 4  relative to kinematic input-side connecting flange  10 . Wrist section  13  located between wrist section  12  and wrist section  14  is rotatable about a fifth axis A 5  relative to the wrist section  12 . Wrist section  14  is further rotatable relative to the wrist section  13 , but the rotation of wrist section  14  relative to wrist section  13  is positively coupled to the rotation of wrist section  12  relative to wrist section  13 . Further, wrist section  14  is rotatable about a sixth axis A 6  relative to the connecting flange  11 .  
         [0037]     The rotation of wrist section  12  about the fourth axis A 4  relative to connecting flange  10  is described with reference to  FIG. 2C , where, for the sake of clarity, only those components are shown which effect this rotation. Rotation is achieved by a drive shaft  15 , depicted schematically, which drives a similarly schematically depicted external gear  16 , wherein external gear  16  engages an annulus gear  17  which is connected non-rotatably to the wrist section  12 . Rotation of the drive shaft  15  results in rotation of the external gear  16 , where this rotation is transferred via the coupling between the external gear  16  and the annulus gear  17  to the wrist section  12 .  
         [0038]     The rotation of centrally located wrist section  13  about the fifth axis AS relative to wrist section  12  is described with reference to  FIG. 2B , where, for the sake of clarity, only those components are shown which are required for this rotation. For this rotation, robot wrist  7  has a drive shaft  18  which rotates an external gear  19 , where the external gear  19  engages an external gear  20  and rotates same. External gear  20  has a helical gear  21  at its kinematic output end which engages a corresponding helical gear  22 , wherein helical gear  22  is connected non-rotatably to wrist section  13  located between wrist sections  12  and  14 . Rotation of drive shaft  18 , via external gear  19 , external gear  20 , helical gear  21 , and helical gear  22 , results in rotation of wrist section  13  relative to the wrist section  12 , wherein the rotation about axis A 4  can be controlled independently of the rotation around axis AS.  
         [0039]     Wrist section  13  carries an additional helical gear  23  that engages a helical gear  24 , which is connected non-rotatably to wrist section  14 , so that the rotation between wrist section  14  and wrist section  13  is positively coupled to the rotation between wrist section  13  and wrist section  12 .  
         [0040]     The rotation of drive flange  11  relative to wrist section  14  about axis A 6  is described with reference to  FIG. 2A . For this rotation, robot wrist  7  has an additional drive shaft  25  which carries an external gear  26 , which in turn engages an external gear  27  and rotates same. At its kinematic output end, external gear  27  has a helical gear  28  that engages a corresponding helical gear  29  on wrist section  13 . Wrist section  13  further includes a helical gear  30  that is non-rotatably coupled to helical gear  29 . Helical gear  30  on wrist section  13  in turn engages a helical gear  31  on wrist section  14 . Connecting flange  11  has a helical gear  33  which engages a helical gear  32 . The rotation of drive shaft  25  is thus transferred via external gears  26 ,  27  and helical gears  28 - 33  to the connecting flange  11 .  
         [0041]     With reference also to  FIG. 2D , robot wrist  7  has an internal conduit  34  that consists of a flexible protective sleeve with an electrical insulating capacity of 100 kV. The internal conduit  34  serves to carry several hoses  35 ,  36  for operating rotary atomizer  8 .  
         [0042]     The hoses  35 ,  36  are connected non-rotatably to the kinematic output-side connecting flange  11 , whereas hoses  35 ,  36  are carried in the kinematic input-side connecting flange  10  in a rotatably mounted guide plate  37 , wherein guide plate  37  is also shown in  FIG. 3 .  
         [0043]     Guide plate  37  has external teeth  38  on its circumferential surface, which engage the teeth of an external gear  39 . External gear  39  can be rotated by a drive shaft  40 . Guide plate  37  serves to dispose the hoses  35 ,  36  in the radial direction and in the circumferential direction inside the internal conduit  34 . Guide plate  37  is rotatable via drive shaft  40 , external gear  39 , and external teeth  38 , where rotation takes place such that the hoses  35 ,  36  are subject to minimal torsional loading when the robot wrist moves.  
         [0044]     The detailed description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.