Patent Publication Number: US-6712291-B2

Title: Spray coating apparatus

Description:
The present invention relates to spraycoating apparatus defined in the preamble of claim 1. 
     Spraycoating apparatus of this kind is known from the European patent document 0 779 105 A1 (U.S. Pat. No. 5,759,271). 
     The invention relates to spraycoating apparatus for liquid coating materials and in particular for coating powders which are pneumatically moved by a flow of compressed air. Such a coating material is sprayed from the front end of a casing through an outlet that illustratively may be the mouth of a material feed duct with or without a transversely deflecting element (baffle or the like), a nozzle or a rotary atomizing element. Preferably the coating material shall be electrostatically charged by electricity of friction and/or by high voltages of more than 1,000 v, for instance using a voltage between 10,000 and 140,00 v to endow said material with improved adhesion to the object to be coated and preferably to be grounded, and in order to reduce dispersion. 
     The objective of the present invention is reduction of the bulk required by the spraycoating apparatus&#39; feed lines, in particular the bulk subtended by a coating-material tube, and simultaneous simplification of assembly and disassembly of this spraycoating apparatus. 
     The goal is attained in the present invention by the features of claim 1. 
     Accordingly the invention relates to spraycoating apparatus containing a casing fitted at its front end with a coating-material discharge element, further with an adapter which is affixed or affixable at its rear end to the casing, and an aperture which is continuous in the longitudinal casing direction, which is characterized in that it comprises a hollow tubular affixation element to affix the adapter to the casing, in that said hollow tubular affixation element may be inserted into the continuous aperture of the adapter in the longitudinal stock direction, in that the hollow tubular affixation element includes an affixation segment to hook up to the casing and a forward-pointing clamping surface allowing clamping the hollow tubular affixation element against the casing, and in that the hollow tubular affixation element exhibits a continuous aperture in the longitudinal stock direction through which the coating-material tube may be plugged in the longitudinal stock direction into the casing. 
     The invention substantially reduces the bul required by the spraycoating apparatus&#39; feed lines, in particular the bulk required to affix an adapter and to radially position the coating-material tube. This design also simplifies assembly and disassembly of the spraycoating apparatus and the time required for such operations, for instance when cleaning or exchanging its parts. 
     The dependent claims disclose further features of the invention. 
    
    
     The invention is elucidated below by illustrative embodiments and in relation to the attached drawings. 
     FIG. 1 is a cutaway longitudinal section of spraycoating apparatus of the invention, 
     FIG. 2 is a sideview of a hollow core screw of spraycoating apparatus of the invention (not to scale), 
     FIG. 3 is a sideview of the spraycoating apparatus of the invention (not to scale), 
     FIG. 4 is a backview of the spraycoating apparatus of FIG. 3 seen in the direction of IV—IV of FIG. 3, devoid of a holding element of FIG.  3  and FIG. 5, 
     FIG. 5 is a longitudinal section of a holding element of FIG. 3, 
     FIG. 6 shows a longitudinal section of a component of FIG. 3, 
     FIG. 7 is a top view on a component of FIG. 3, the holding element being shown in horizontal longitudinal section, 
     FIG. 8 is a sideview of a cable adapter of FIG. 3 (not to scale), and 
     FIG. 9 is a longitudinal section of another embodiment of the spraycoating apparatus of the invention shown on a smaller scale. 
    
    
     Preferably the spraycoating apparatus of the invention is designed to spraycoating powder being pneumatically conveyed in a flow of compressed air. In another embodiment of the invention however, said apparatus may be designed to spray liquid coating material. 
     The spraycoating apparatus shown in the attached drawings contains a casing  2 , a coating-material spray head  6  being affixed or affixable to the front end  4  of said housing and constituting a coating-material feed outlet. An adapter  8  is affixed or affixable to the rear end of the casing in order to connect with at least one element comprises a continuous aperture  12  running in the longitudinal direction of the casing  2  and allowing insertion of a coating-material tube  14  feeding coating material. 
     Illustratively and as shown in FIG. 3, the spray head  6  may contain a nozzle  7  affixed by a coupling nut  9  to the front segment of the casing  2 . 
     A hollow screw  16  is used to affix the adapter  8  to the casing  2 . The hollow core screw  16 , hereafter called “hollow screw”, can be inserted in the longitudinal direction of the casing  2  through the continuous aperture  12  of the adapter  8  and together with the wall of said aperture  12  preferably shall constitute a sliding seat. The hollow screw  16  comprises an axial, continuous duct  19  in the longitudinal direction of the casing  2  to receive the coating-material tube  14 . The hollow screw  16  is preferably fitted with an outside thread  18  preferably situated at its front end to screw into a complementary thread  20  in the casing  2 , and it further comprises a forward-pointing clamping surface  22  of a bolt head  24  allowing to clamp the adapter  8  against the casing  2 . In this design the forward-pointing clamping surface  22  will be clamped against a rearward pointing end face  26  or a rearward-pointing cross-sectional surface of the adapter  8 . The coating-material tube  14  and the hollow screw  16  exhibit a central longitudinal axis  15 . 
     The wall of the continuous duct  19  of the hollow screw  16  rests against the coating-material tube  14 , preferably along its entire circumference, and together with it constitutes a sliding seat. 
     Preferably the casing  2  is integral and made of plastic. In another embodiment mode, it may also consist of several parts and/or of another, electrically conducting or preferably electrically insulating material. 
     The thread  20  of the casing  2  used to affix the hollow screw  16  preferably is constituted by the very casing  2 . In another embodiment mode, a threaded element also may be anchored in this casing  2 . 
     Preferably the adapter  8  is a metallic and integral element in order it be electrically conducting and serve as an electrical conductor which is optionally grounded. In another embodiment said adapter may be made of an electrically insulating material, for instance plastic. 
     The hollow screw  16  defines the radial position of the coating-material tube  14  relative to the adapter  8  and thereby also relative to the casing  2  and it radially supports said coating-material tube  14 . Preferably the two elements shall abut each other directly radially with so little play that preferably they shall be radially jitter-free. 
     Another tubular hollow affixation element than the hollow screw  16  also may be used. The thread  18  may be replaced by another hollow tubular affixation element  18  of a different geometry that can be hooked up to an appropriate affixation element of the casing  2  (said element being part of the casing or inserted into it or affixed to it). Illustratively either the hollow affixation element  16  or the casing  2  may be designed as a male connector and the other one as the matching female connector. Preferably the affixation segment of the hollow affixation element shall be the male part and the affixing element of the casing shall be the hookup element. One of said two elements may comprise a pawl or another locking element which shall engage a stop surface running transversely to the coating-material tube. For instance one of the two said elements may be fitted with a cross-pin which may be inserted into an L-shaped groove constituted in the other element and thereupon be rotatable in the manner of a bayonet lock. 
     In all embodiments, the connection between the hollow affixation element  16  (preferably hollow screw  16 ) and the casing can be unlatched and released in order to separate the hollow affixation element again from the casing  2  and hence also removing said element from the adapter  8  for the purpose of separating all three parts from each other for instance for cleaning and/or exchanging them with other elements. 
     In what follows the hollow, tubular affixation element  16  is called according to the shown embodiment mode “hollow screw  16 ” and represents all other embodiments of such a hollow, tubular affixation element as well. In the shown and preferred embodiment, the coating-material tube  14  preferably is designed to be affixed to the hollow affixation element  16  or hollow screw  16  and in the process can be locked in place axially. This affixation is detachable in order that the coating-material tube  14  may be removed and cleaned or exchanged. Preferably the affixation is implemented by an inside thread  27  (or outside thread) at the rear end or at the head  24  of the hollow screw  16  and a meshing outside thread  28  (or inside thread) constituted at the coating-material tube  14  or, corresponding to FIG. 1, to a hose adapter  30  receiving the rear end of the coating-material tube  14 , said rear end then being clamped toward a forward-pointing transverse surface  31 . However, instead of the connection of threads  27 ,  28 , the coating-material tube  14  also may be connected with the hollow screw  16  by a locking male/female connection or another quick-connect means for instance in the manner of a bayonet lock. 
     The coating-material tube  14  and the hose adapter  30  preferably are made of an electrically insulating material, in particular plastic. 
     Opposite its front tube-receiving segment  32 , the hose adapter  30  is fitted with a rearward-pointing female segment  34  receiving a coating-material hose, and with a terminal segment which projects rearward from there and comprises forward slots dividing it into fingers  36  that, using a tightening ring  40 , can be clamped on the hose. 
     The outside circumference of the adapter  8  at its front end differs from that of the casing  2  and according to the embodiment illustratively is less than the circumference of the rear end of the casing  2 . However different ratios of these circumferences also are admissible. A junction element  42  comprises a front end  44  matching the periphery of the casing  2  and a rear end  46  matching the periphery of the adapter  8 . The junction element  42  may be axially clamped in place by the hollow screw  16  between a forward pointing transverse surface  48  of the adapter  8  and a rearward pointing end face  50  of the casing  2 . The forward pointing transverse surface  48  is constituted by an annular rib  52  which furthermore constitutes a rearward pointing transverse surface  54 . 
     The junction element  42  matches the contour and size of the circumference of the rear end of the casing  2  to the contour and size of the circumference of the adapter  8 . 
     In another (omitted) embodiment mode, the shape and size of the front end of the adapter  8  matches the shape and size of the rear end  10  of the casing  2 , whereby a junction element  42  is no longer required. In this design too the adapter  8  may comprise a rearward pointing transverse surface  54  of a similar rearward-pointing stop surface cooperating with a support that shall be described further below. 
     Preferably a longitudinal groove and a longitudinal rib are constituted in either of the adapter  8  and the junction element  42  in order to rotationally position the two parts relative to each other. 
     A seal  56  is mounted between the adjacent end faces on one hand of the rear end of the casing  2  and on the other hand of the front end of the junction element  42 . Preferably this seal shall be an elastic disk or plate in order that it may also rest in sealing manner against other elements corresponding to FIG.  1 . The sealing plate  56  is axially clamped by the hollow screw  16  between rearward pointing surfaces of the casing  2  and a partition  58  behind a high-voltage generator  60 , both situated in the casing  2 , on one hand, and on the other hand forward pointing surfaces of the adapter  8  and of the junction element  42 , so that all said components be mutually sealed. The sealing plate  56  is fitted with feedthroughs for lines or ducts, for instance with a borehole  62  to be used for an electrical connection, which shall be described further below, to the high-voltage generator  60 , furthermore a borehole  64  for the hollow screw  16  and boreholes for one or more compressed-air paths (or none). 
     Preferably at least one compressed-air duct  66  runs longitudinally and continuously through the casing  2 , for instance one each on each side next the coating-material tube  14  as schematically shown in FIG.  3 . The rear end of each compressed-air duct  66  is axially opposite the front end of each compressed-gas borehole  68  running longitudinally through the adapter  8  and is fitted at its rear end with a thread  70  cooperating with an adapter nipple  72  of an omitted compressed-gas hose or with a closing screw  73 . The mutually opposite ends communicate—as regards flow—through a borehole constituted in the sealing plate  56 . In the embodiment of FIGS. 1,  3  and  4 , there are two compressed-gas boreholes  68  in the adapter  8  and they are configured one on each side of the hollow screw  16  and the coating-material tube  14 . Two compressed-gas ducts  66  are constituted in the casing  2 . One compressed-gas flowpath  66 ,  68  illustratively supplies compressed air or another gas which flows over one or more high-voltage electrodes  74  which are configured beyond, at or in the front end of, the casing  2 , and which receive high voltage from the high-voltage generator  60  to electrostatically charge the coating material. The other compressed-gas flowpath  66 ,  68  may serve to feed compressed air or another gas for other purposes, for instance for atomizing, shaping or otherwise controlling the flow of coating material. 
     As shown in FIG. 1, part of the adapter  8  is designed as a socket  80  receiving and affixing a cable adapter  82  of an electric power cable  84 . The socket  80  runs in the longitudinal direction of the casing  2  parallel to the feedthrough  12  receiving the hollow screw  16 . 
     Preferably the socket  80  shall be a feedthrough constituted in the adapter  8  and assuming the function of the female receiving the cable adapter  82  acting as the male. 
     The cable adapter  82  is fitted at its front end with at least one electrically conducting terminal  86 ,  87  to contact at least one electrically conducting terminal  88 ,  89  configured at the rear end of the casing  2  in the partition  58  to assure low-voltage application by the cable  84  to the high-voltage generator  60 . 
     The cable adapter  82  preferably comprises an electrically conducting case which on one hand is connected to an electric grounding wire in the cable  84  and on the other hand makes electrical contact inside the socket  80  with the adapter  8 . 
     In another, omitted embodiment, the high-voltage generator  60  is mounted not inside the casing  2 , but externally to it. In that design the cable  84  is not a low-voltage cable, but a high-voltage one, which transmits the high voltage from an external high-voltage generator  60  into the casing  2  and within same to the minimum of one high-voltage electrode  74 . 
     At least one (two or more in other embodiment modes) locking protrusion  90  is constituted at the cable adapter  82  and a locking path  92  is constituted at the adapter  8 , said path  92  comprising a path segment  94  that runs in the longitudinal direction of the socket  80 , that is open toward the rear and that is adjoined transversely by a peripheral path segment  96  fitted with a forward-pointing locking surface  98  behind which the locking protrusion  90  inserted into the longitudinal path segment  94  may be rotated by turning the cable adapter  82  relative to the adapter  8 . 
     In another embodiment—also omitted—the locking protrusion  90  is constituted at the adapter  8  and the locking path  92  is constituted at the cable adapter  82 . In an embodiment variation, other locking elements are provided between the cable adaptor  82  and the adapter  8 , for instance pawls, clamping elements or threads. 
     The rear segment  108  of the adapter  8  projecting rearward from the junction element  42  and comprising the locking path  92  is designed as an affixation zone for affixation to a support  110 . The support  110  comprises a tubular affixation segment  112  that may be plugged onto the affixation segment  108  of the adapter  8  and that constitutes thereon a jitter-free socket. 
     The rearward pointing transverse surface  54  of the adapter  8  acts as a stop for the support  110  of which it defines the position on the adapter  8 . 
     As shown in FIGS. 3 and 6, the support  110  in its tubular affixation segment  112  may be fitted with an L-shaped clearance  113  constituted by a longitudinal clearance  114  running forward from the rear end of the support  110  and by a circumferential zone  116  which adjoins said longitudinal clearance  114  at its front end, said elements  114  and  116  being mountable on the adapter  8  while congruent with the L-shaped locking path  92  of the cable adapter  82 . In this manner the locking protrusion  90  of the cable adapter  82  may simultaneously and optionally function as a locking protrusion to axially lock the support  110  on the adapter  8 . 
     However, in addition or instead, the support  110  as shown in FIGS. 3,  4 ,  5 ,  6  and  7 , may be secured in position axially and/or circumferentially on the adapter  8  using a resilient pawl  120 , for instance a pawl head  122  on a resilient strip  124  and affixed to one of the two components, namely the adapter  8  or the support  110 , and able to engage a transverse aperture  126  constituted at the respectively other of the two components, namely adapter  8  or support  110 . As regards the shown preferred embodiment, the transverse aperture  126  has been fitted into the support  110  and the pawl  120  is mounted in radially resilient manner on the adapter  8 . The pawl  120  automatically engages the transverse aperture  126  once the support  110  being mounted on the adapter element  108  has reached its axial and circumferential end positions. The transverse aperture  126  runs transversely to the longitudinal direction of the feedthrough aperture  12  receiving the hollow screw  16 . The resilient strip  124  runs inside a longitudinal groove of the adapter  8 . 
     As shown in FIG. 7, the transverse aperture  126  constitutes a rearward pointing locking surface  128  entered by the pawl  120 . Unintended removal of the support  110  from the adapter  8  is prevented thereby. To remove the pawl  120  from the locking surface  128 , it must be manually forced away transversely and thus out of the transverse aperture  126 . 
     The support  110  may be amounted to a rest means, for instance a jack or a robot arm or a grip. For this purpose and for the embodiment of FIGS. 3 and 5, the support  110  is fitted with at least one threaded borehole  129  running transversely to the hollow screw  16 . 
     FIG. 3 furthermore shows a system to drain charged particles, namely excess electric charges, in particular ions, from the high-voltage electrode  74 , where such charges do not contribute to electrostatically charging the coating material either because it is already saturated with electrical charges or because the charged particles are so far from this coating material that they cannot charge it. This drain system contains for instance a ring  130  with a plurality of drain electrodes  132  which are electrically connected by an electrically conducting bar  134  and an electrical contact pin  136 , for instance a screw, inside the junction element  42  to the adapter  8 . The adapter  8  may be grounded through the cable adapter  82  and the cable  84 . 
     As shown by FIG. 9, the support  110 , which is limited to the length of the adapter  8 , may be replaced by a tubular support element  110 - 2  made optionally of an electrically insulating but preferably an electrically conducting material which is designed at its front end in the same manner as the support  110  of FIG. 3 but is devoid of a threaded borehole  129 . The coating-material tube  14  and further all other lines supplying material and/or power run through the support element  110 - 2 , in particular the cable  84  and compressed-gas lines for the various compressed gases, for instance compressed air, illustratively being moved through the compressed-air ducts  66  in the casing  2  (FIG.  3 ). A second adapter  8  (of the same or of a different design as the first adapter  8 ) is present at the rear end  142  of the tubular support element  110 - 2  and allows longitudinally passing the coating-material tube  14  inside a second hollow screw  16  and connecting a further electrical cable  84  with a cable adapter  82 . Also compressed-air ducts  68  may be contained in the second adapter  8  in the manner described above in relation to the other Figures.