Patent Publication Number: US-2005126478-A1

Title: Applicator and method for in-mold coating

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application is a divisional of U.S. application Ser. No. 10/115,360, filed Apr. 3, 2002 and entitled “Applicator and Method for In-Mold Coating.” 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an improved nozzle for use with in-mold coating processes.  
      2. Background Art  
      In-mold coating processes are used in a number of applications to spray, or otherwise apply, coatings onto the working surfaces of molds used in molding operations. One common application of in-mold coating can be found in the processes used for manufacturing the soft interior paneling of automotive vehicles, like the soft interior paneling of an instrument panel dashboard  10 , shown in cross-section in  FIG. 1 . Instrument panel  10  can be manufactured by a skin making process or a foam-in-the-mold process that each include spraying a mold, like mold  12  shown in  FIG. 2 , with a coating such as a one or two component waterborne acrylic, or a one component or two component urethane, or other material. The material hardens to form a relatively thin covering  14 , generally 0.80 to 1.20 millimeters, which is used as a finished coating for a final color and gloss for appearance and UV-resistance to sunlight. In the case of skin making, skin  14  is removed from mold  12  for application to foam material  16  at another location. The foam-in-the-mold process is similar to the skin making process, except foam material  16  is applied to the skin  14  by a foam injection device (not shown) while the skin is in mold  12 , instead of at a different location like the skin making process.  
      Referring to  FIG. 1 , the skin  14  includes a curvilinear or arcuate rim portion  18  extending along the outer periphery of skin  14  for gripping foam material  16 . To form curvilinear rim portion  18 , or other edges and flats that bend away from the outer surface of the skin and roll back over towards the center of the skin, an undercut mold portion  20  is needed within mold  12 , as shown in  FIG. 2 . The undercut mold portion  20  is a difficult-to-reach area for applying the coating. In the past, a collinear applicator  22  has been used to apply the coating to form skin  14 . For example, the collinear applicator  22  is mounted to a robot  24  and moved around working surfaces  13  to spray coating onto mold  12 . As shown in  FIG. 3 , mold opening  26  somewhat prevents direct viewing of undercut portion  20  from outside of mold  12 . Accordingly, those areas in mold  12  which are not directly viewable from outside mold  12 , like undercut portion  20 , are difficult for collinear applicator  22  to squarely spray with the coating. Thus, such areas are considered difficult-to-reach areas of mold  12 .  
      As it is difficult for collinear applicator  22  to reach the difficult-to-reach areas, additional measures are required to manufacture skin  14  with collinear applicator  22 . For example, since collinear applicator  22  cannot squarely spray undercut portion  20  (in order to squarely spray a surface, the surface must be within a width of a fan spray pattern of the applicator), the methods which use collinear applicator  22  must either coat the uncoated areas in a secondary operation, which usually consists of a human operator using a spray gun, or coat around the uncoated areas with excessive amounts of coating material so that the material can run down the sides of mold  12  to the difficult-to-reach surfaces. It is expensive, however, to have operators coat the uncoated portions in a secondary operation, and it is similarly expensive to apply excess material to the mold. Moreover, the excess coating can cause additional problems in bi-color applications in which it is desirable to have one portion of the skin coated with a first color and another portion of the skin coated with a second different color, as the running of coating material from one color into the other color can discolor the appearance of the skin.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide an improved applicator and method for coating difficult-to-reach in-mold portions of a mold cavity in one coating operation and without requiring excessive amounts of coating.  
      In accordance with one aspect of this invention, an in-mold applicator for spraying a coating on difficult-to-reach surfaces of a mold is disclosed. The in-mold applicator includes a spray head and body portion at an oblique angle to each other. The body portion and spray head have outer dimensions that are sufficiently small in combination with the oblique angle to enhance the spraying of the coating onto the difficult-to-reach surfaces of the mold.  
      In accordance with another aspect of the present invention, an in-mold applicator is disclosed for spraying a coating on a first difficult-to-reach undercut surfaces of a mold. The in-mold applicator includes a body portion and a spray head extending at an oblique angle with respect to the body portion. The body portion and spray head have outer dimensions that are sufficiently small in combination with the oblique angle to enhance the spraying of the coating to the undercut surface. Furthermore, each of the spray head and the body portion have a central passageway for delivering a liquid medium and an outer passageway surrounding the central passageway for delivering a gaseous medium. The applicator still further includes a liquid medium head joining the central passageways in liquid medium flow relationship proximate the oblique angle. In addition, the applicator includes a closable and operable liquid medium valve within the liquid medium head for selectively controlling a sufficient flow of liquid medium through the liquid medium head for atomization with the delivered gaseous medium.  
      In accordance with still another aspect of the present invention, a method is disclosed for spraying a coating on a mold having a first difficult-to-reach undercut surface which is not directly visible from an external view of the mold. The method includes spraying a first atomized fluid onto the mold including the undercut surfaces from an applicator having a body portion and a spray head extending at an oblique angle with respect to the body portion. The body portion and the spray head having a configuration that is sufficiently small in combination with the oblique angle such that the spray head is positional within the mold in a head-on position sufficient to squarely spray the atomized fluid onto the mold and the first undercut surface. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a fragmentary cross-sectional view of a instrument panel dashboard covering;  
       FIG. 2  is a schematic cross-sectional view of a prior art mold and collinear applicator used for molding the instrument panel shown in  FIG. 1 ;  
       FIG. 3  is an elevational view of the mold shown in  FIG. 2 , showing the portions of the mold that are directly viewable from outside the mold;  
       FIG. 4  is a cross-sectional view of the prior art mold of  FIG. 1  and an applicator, according to the invention, attached to a robot adaptor;  
       FIG. 5  is a perspective view of the applicator and robot adaptor in accordance with the present invention;  
       FIG. 6  is a cross-sectional view of the applicator of  FIG. 5 , wherein the applicator includes a spray head and a body portion at an oblique angle to each other, and the spray head includes a spray cap;  
       FIG. 7  is an end view of the spray head shown without the spray cap;  
       FIG. 8  is an enlarged fragmentary sectional view of the spray cap shown in  FIG. 5 ;  
       FIG. 9  is an end view of the spray cap;  
       FIG. 10  illustrates a fan spray profile provided by the spray cap; and  
       FIG. 11  is a flowchart depicting an improved method for spraying a coating on a mold according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       FIG. 4  shows an improved applicator device or applicator, according to the invention, for applying a coating to mold  12 . The applicator of the invention is hereinafter referred to with reference numeral  30 , and can be used in any number of applications in which it is desirable to spray a coating onto a mold. One area of interest is in processes used to manufacture soft interior components for automotive vehicles, like the skin making process and foam-in-the-mold process used to manufacture instrument panel  10  shown in cross-section in  FIG. 1 . As described above, instrument panel  10  can be manufactured by spraying mold  12  with a coating such as polyurethane, polyvinylchloride, or other material to form a relatively thin covering type skin  14  that forms a covering panel for covering a soft foam material  16 .  
      In either the skin making process or the foam-in-the-mold process, the applicator  30  may deliver either waterborne or solvent-borne, one component or two component, coatings for providing “Class A” surface color matches. The coatings may be delivered, for example, at 300 cubic centimeters per minute with a variable fan width from 38 to 102 millimeters at a distance of 102 millimeters from the surface being coated. In addition, the applicator  30  may be capable of delivering 50 cubic centimeters per minute of mold release agents, either waterborne or solvent-borne, with the same fan width viscosities of 22 to 30 seconds using a number 3 Zahn cup.  
      In general, the molding processes broadly includes a first step of spraying a mold release onto a mold, a second step of applying a skin forming material to the mold, after the mold release has had time to evaporated, or flash, its volatile elements, and a third optional step of injecting a foam material into the mold, after the skin forming material has had time to evaporated, or flash. (Flash is a term of art which references the time required for the volatile elements used to liquify the skin forming material to evaporate, typically the volatile element is water but it could also be any other soluble additive.) The novel interaction of applicator  30  with these broad steps is described below in greater detail.  
      Common in-mold applications require skin  14  to have a curvilinear rim portion  18  extending along a portion of the outer periphery of skin  14  for gripping foam material  16 . To form curvilinear rim portion  18 , or other similar edges and flats which, for example, bend away from an outer surface of the skin  14  and extend inwardly, an undercut mold portion, like undercut portion  20  shown in  FIG. 4 , is needed within mold  12 . While the undercut portion  20  is shown as a curvilinear portion, the undercut portion  20  may be any difficult-to-reach portion of mold  12 , like a straight edge or aperture.  
      As shown in  FIG. 3 , mold opening  26  substantially prevents direct viewing of undercut portion  20  from outside of mold  12 . Accordingly, those areas in mold  12  which are not directly viewable from outside mold  12 , like undercut portion  20 , are difficult for line of sight devices to reach. Accordingly, those areas within mold  12  which are not directly viewable through mold opening  26  by an external viewer are referred to as difficult-to-reach areas of mold  12 , like undercut portion  20 .  
      Referring to  FIG. 5 , the invention is directed to an improved apparatus and process for coating difficult-to-reach surfaces of mold  12 . As such, in the following detailed description, it becomes apparent that the applicator  30  turns the once difficult-to-reach surfaces into easy-to-reach surfaces. Applicator  30  can reach undercut surface  20 , because it is relatively small and includes a spray head  32  and a body portion  34  that are at an oblique angle alpha to each other. While spray head  32  may have any suitable dimension or configuration, in one embodiment the dimensions for the diameter of spray head  32  are in the range of 0.500 inch to 1.500 inches. In the embodiment of  FIG. 6 , spray head  32  has a diameter of 0.500 inches. In addition, while the length of spray head  32  may be any have any suitable dimension or configuration, in one embodiment the dimensions for the length of spray head  32  are in the range of 0.750 to 1.500 inches. In the embodiment shown in  FIG. 6 , the dimension for the length of spray head  32  is 1.000 inches. Furthermore, while body portion  34  may have any suitable dimension or configuration, in one embodiment the dimensions for the diameter of body portion  34  is in the range of 0.250 to 0.750 inches. In the embodiment of  FIG. 6  the dimension of the diameter of body portion  34  is 0.500 inches. In addition, while the length of body portion  34  may have nay suitable dimension or configuration, in one embodiment the dimensions for the length of body portion  34  are in the range of 4 to 18.000 inches. In the embodiment of  FIG. 5 , the dimension of the length of body portion  34  is 10.000 inches. The oblique angle alpha is greater than 0 degrees and less than 180 degrees. In one embodiment, the oblique angle alpha is in the range of 120 to 150 degrees. In the embodiment shown in  FIG. 5 , the angle alpha is approximately 135 degrees. Accordingly, the dimensioning of applicator  30  is sufficiently small for coating difficult-to-reach undercut surfaces  20  within mold  12 .  
      As shown in  FIG. 4 , applicator  30  can position itself within mold  12  for applying a coating squarely to undercut portion  20 . With spray head  32  at an angle, spray head  32  can direct a spray fan pattern  35  into difficult-to-reach undercut surfaces  20  of mold  12 . In one embodiment, spray head  32  is positional to squarely spray the coating onto mold  12  by having at least a portion of the width of spray head fan pattern  35  in-line with undercut portion  20  to strike undercut portion  20  in a head-on manner.  
      Applicator  30  also includes an adaptor  36  to operatively interconnect body portion  34  to a robot  38 . While adaptor  36  may have any suitable dimension or configuration, in one embodiment the dimensions for the breadth squared adaptor  36  are in the range of 0.500 inch to 3.00 inches in width. In the embodiment of  FIG. 5 , adaptor  36  has a breadth of 2 inches. In addition, the length of adaptor  36  may be any have any suitable dimension or configuration, but in one embodiment the dimensions for the length of adaptor  36  are in the range of 2.000 to 6.000 inches. In the embodiment shown in  FIG. 5 , the dimension for the length of adaptor  36  is 4.000 inches. The robot  38  positions applicator  30  in and around mold  12  to apply the coating thereupon. Adaptor  36  can be configured to work with any type of robot, including multi-axis robots, such as 6-axis and 7-axis robots that are commonly used for in-mold coating applications. Furthermore, applicator  36  and includes three valves  39 ,  40 , and  41 , described below in greater detail.  
      The angled spray head  32  allows applicator  30  to coat difficult-to-reach surfaces in molding applications without having to apply excess coating material, and/or without requiring a manual, secondary operation. Consequently, the applicator  30  minimizes the amount of coating material required. Furthermore, use of the applicator  30  allows designers and manufacturers to produce complex parts having numerous complex surfaces and features once thought to be too expensive to manufacture because of all the secondary operations required to coat corresponding undercut surfaces, or other difficult-to-reach surfaces, of a mold.  
      Referring to  FIG. 5 , body portion  34  and adaptor  36  work in combination with the spray head  32  to enhance the ability of applicator  30  to perform unique movements. To begin with, spray head  32 , body portion  34 , and adaptor  36  are threadably interconnected. For example, there are situations in which the mold  12  can have first and second undercut surfaces, where the second undercut surface is more difficult-to-reach for a first spray head  32  used to coat the first difficult-to-reach surface. Accordingly, a second spray head  32 , having either a different spray pattern or a different oblique angle, can be threaded to the body portion  34 , either by hand or with machine movement, for coating the second difficult-to-reach undercut portion. Consequently, time is saved when swapping spray heads, and the ability to coat multiple difficult-to-reach surfaces improves design flexibility. Likewise, when multiple color coatings are desired, the body portion  34 , and thereby the spray head  32  attached thereto, can be threadably removed from the adaptor  36  and exchanged for another body portion  34  so that the color from the first body portion does not infect the second body portion. Again, these components may be removed and exchanged manually or automatically. For example, a robotic system including a shunt action robotic arm can be used to exchange various components for others located nearby for coating one mold, or a number of molds passing thereby.  
      The particular elements for achieving the foregoing results will now be described in greater detail. Referring to  FIG. 6 , spray head  32  and a segment of body portion  34  are shown with greater detail. As shown, spray head  32  is secured to body portion  34  by threadably interconnecting first spray head threads  42  with first body threads  43 .  
      Body portion  34  generally refers to a number of components, including outer tube  44 , inner tube  46 , liquid medium needle valve  48 , and liquid medium head or tip  50 . The configuration shown is one of the many arrangements which may be used in combination with the teachings of this invention, and is not in any way intended to limit the scope of this invention. As shown, outer tube  44  generally surrounds inner tube  46  and liquid medium tip  50 . The liquid medium tip  50  and inner tube  46  connect with each other to surround liquid medium needle valve  48 . This arrangement forms a passageway between outer tube  44  and inner tube  46 , referred to as outer body passageway  47 , and another passageway between inner tube  46  and liquid medium needle valve  48 , referred to as central body passageway  49 .  
      Spray head  32  generally refers to a number of components, including spray head angled body portion  54 , spray cap  56 , and spray cap lock  57 . As shown in  FIG. 7 , spray head angled body portion  54  includes a center aperture  58 , a number of outer apertures  60 , and a spray cap cavity  62 . As shown in  FIG. 8 , the apertures  58  and  60  define a central spray head passageway  64  and a plurality of outer spray head passageways  66 .  
      When spray head  32  is secured to body portion  34 , central body passageway  49  is joined with central spray head passageway  64 , and outer body passageway  47  is joined with the plurality of outer spray head passageways  66 . As described above, adaptor  36  includes three valves  39 ,  40 , and  41 . The valves  39 ,  40  and  41  deliver fluid from robot  38  to applicator  30 . Referring to  FIG. 5 , one valve, such as valve  39 , delivers a gaseous medium to outer body passageway  47 , and thereby, to the plurality of outer spray head passageways  66 . A second valve, such as valve  40 , delivers a liquid medium to central body passageway  49 , for delivery through liquid medium tip  50  and into central spray head passageway  64 . The liquid flow through liquid medium tip  50  is regulated by a third valve, such as valve  41 , which delivers a gas from an outside source for controlling an actuating device (not show, but located in adaptor  36 ) for causing reciprocating action of liquid medium needle valve  48 . The needle valve  48  is closable to shut-off the flow of liquid to spray head central passageway  64  and selectively operable to control the flow of liquid to spray head central passageway  64 . Uniquely, both a liquid and gas are deliverable to spray head  32  for spraying a coating on mold  12  with only three valves, whereby the necessity of using a fourth valve for controlling the spraying of the atomized fluid is eliminated by controlling the spraying of the atomized fluid by controlling only the liquid flow and atomization gas flow.  
      Referring to  FIG. 8 , an enlarged view of spray cap  56  allows for better description of the atomization process for spray head  32 . Spray cap  56  inserts into spray cap cavity  62 , and is secured to spray head angled body portion  54  by spray cap lock  57 , which is threadably secured to an second spray head threaded portion  72 . Spray cap  56  includes two angled, or curved, apertures  74  and  75 , shown also in the end view of  FIG. 9 , for mixing the gaseous medium from the plurality of outer spray head passageways  66  with the liquid medium expelling through central cap aperture  76  from central spray head passageway  64 . The liquid and gas collide with one another and atomize in cap opening  78  to form spray fan pattern  35 . The pressures of each of the fluids and the angle of angled apertures  74  and  75  in combination determine spray fan angle  0  and spray fan profile  80 . Profile  80  is shown in greater detail in  FIG. 10 . In one embodiment, spray fan angle θ is 45 degrees. In another embodiment spray fan angle θ may be in the range of 30 to 60 degrees. In the embodiment of  FIG. 8 , spray fan angle θ is 90 degrees. Spray fan profile  80  is ellipsoid, but it may be circular or any other suitable configuration. Advantageously, spray cap  56 , like body portion  34  and spray head  32 , can be removed and replaced into spray head angled body portion  54  by hand or machine operation.  
       FIG. 11  illustrates operation of an in-mold method for spraying a coating on difficult-to-reach surfaces of mold  12  for manufacturing a skin or a foam-in-the mold covering. At step  90 , applicator  30  is configured with an oblique angle interconnecting spray head  32  and body portion  34 . At step  92 , applicator  30  is positioned within mold  12 , for either a skin molding or foam-in-the-mold process at a location for the applicator  30  to squarely spray a coating on difficult-to-reach surface  20 . At step  94 , a first coating, such as a mold release agent, is sprayed onto mold  12 , including the difficult-to-reach surface  20 . At step  96 , the mold release agent supplied in step  94  is allowed to flash for a predetermined period of time. At step  98 , a second coating is applied to the mold  12 . The second coating may be any suitable material, such as an acrylic or polyurethane. At step  100 , the material sprayed in step  98  is allowed to flash for a predetermined period of time. Optionally, at step  102 , a foam material is injected into mold  12  by a foam injecting device (not shown). Finally, at step  104  the skin or foam-in-the-mold covering is removed from mold  12 .  
      While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.