Abstract:
A method of making a part includes introducing expandable material into a cavity of a mold containing a substrate, the mold including at least one projection extending into the cavity. The method further includes retracting the at least one projection to allow the expandable material to expand in the cavity, such that the expandable material forms an expanded material layer on the substrate.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to a method and apparatus for making a part having a substrate and an expanded material layer attached to the substrate.  
         [0003]     2. Background Art  
         [0004]     An arm rest for use with a motor vehicle may include a substrate and an expanded foam layer attached to the substrate. A prior method of making such an arm rest includes injecting foamable plastic material and a blowing agent into a pressurized mold cavity having the substrate positioned therein, in order to form the foam layer on the substrate. The mold cavity is pressurized in order to form a suitable appearance surface on the foam layer. Because the mold cavity is pressurized, however, expansion of the plastic material is restricted. As a result, the softness of the foam layer is limited.  
       SUMMARY OF THE INVENTION  
       [0005]     Under the invention, a method of making a part is provided. The method includes introducing expandable material into a cavity of a mold containing a substrate, the mold including at least one projection extending into the cavity. The method further includes retracting the at least one projection to allow the expandable material to expand in the cavity, such that the expandable material forms an expanded material layer on the substrate.  
         [0006]     Further under the invention, an apparatus for making a part includes a mold having a cavity configured to receive a substrate having an aperture. The mold includes a moveable projection that is configured to extend through the aperture of the substrate and into the cavity. The apparatus further includes an expandable material introduction device for introducing expandable material into the cavity. Moreover, the mold is configured to retract the projection after the expandable material has been introduced into the cavity, to thereby provide space for expansion of the expandable material.  
         [0007]     While exemplary embodiments in accordance with the invention are illustrated and disclosed, such disclosure should not be construed to limit the claims. It is anticipated that various modifications and alternative designs may be made without departing from the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a schematic cross-sectional view of a part according to the invention, wherein the part includes a substrate and an expanded material layer attached to the substrate;  
         [0009]      FIG. 2  is a schematic cross-sectional view of a mold for making the substrate, wherein the mold includes first and second mold portions that define a first mold cavity;  
         [0010]      FIG. 3  is a schematic cross-sectional view of the mold showing a third mold section engaged with the first mold section to define a second mold cavity, and further showing projections of the mold extending into the second mold cavity;  
         [0011]      FIG. 4  is a schematic cross-sectional view of the first and third mold sections and showing expandable material injected into the second mold cavity; and  
         [0012]      FIG. 5  is a schematic cross-sectional view of the first and third mold sections and showing the projections retracted out of the second mold cavity. 
     
    
     DETAILED DESCRIPTION  
       [0013]      FIG. 1  shows a part  10  according to the invention for use with a motor vehicle (not shown). For example, the part  10  may be an interior trim part, such as an arm rest, console, instrument panel, door panel, etc. As shown in  FIG. 1 , the part  10  includes a substrate  12  having multiple apertures  14  extending therethrough, and an expanded material layer  16  attached to the substrate  12 .  
         [0014]     The substrate  12  may be configured to support the expanded material layer  16 , and may be made of any suitable material. For example, the substrate  12  may be made of injection molded or compression molded plastic, such as non-expanded polypropylene, polyethylene terephthalate, urethane, or acrylonitrile butadiene styrene.  
         [0015]     The expanded material layer  16  may be formed such that a substantial portion or all of the expanded material layer  16  has a relatively low density. Moreover, the expanded material layer  16  may be formed as a resilient layer that is configured to provide a soft feel to the part  10 . The expanded material layer  16  may also define an appearance surface or “A” surface  18  of the part  10 . Furthermore, the expanded material layer  16  may be made of any suitable material, such as expanded polypropylene, polyethylene, polycarbonate, polyvinyl chloride, or thermoplastic elastomer.  
         [0016]     Referring to  FIGS. 2-5 , an exemplary method of making the part  10  will now be described in detail. First, the substrate  12  may be made in any suitable manner. Referring to  FIG. 2  for example, one or more first material introduction devices  19  may inject or otherwise introduce plastic material into a first mold cavity  20  of a mold  22 . In the embodiment shown in  FIG. 2 , the mold  22  includes first and second mold portions  24  and  26 , respectively, that cooperate to define the first mold cavity  20 . The second mold portion  26  also has multiple projections  27 , such as cylindrical projections, for forming the apertures  14  in the substrate  12 . The mold  22  further includes multiple projections  28 , such as cylindrical pins, that are moveable with respect to the first mold portion  24 .  
         [0017]     After the substrate  12  has been molded, the mold  22  may be opened, such as by moving the second mold portion  26  with respect to the first mold portion  24 . Next, referring to  FIG. 3 , a third mold portion  30  may be brought into contact with the first mold portion  24  to define a second mold cavity  32 . The projections  28  may also be raised or otherwise moved so that the projections  28  extend into the second mold cavity  32 . For example, the projections  28  may be raised by a slide member  34  that supports the projections  28 .  
         [0018]     A pressure source  36  may also be used to supply any suitable fluid, such as air, nitrogen, or other inert gas, to the second mold cavity  32  in order to pressurize the second mold cavity  32 . While the second mold cavity  32  may be pressurized to any suitable pressure, in one embodiment, the second cavity  32  is pressurized to a pressure in the range of 50 to 2000 pounds per square inch.  
         [0019]     Referring to  FIG. 4 , the method then involves introducing expandable material into the second mold cavity  32 . For example, one or more second material introduction devices  38  may be used to inject or otherwise introduce a mixture of expandable plastic material and a blowing agent into the second mold cavity  32 . Suitable blowing agents are available from PolyOne Corporation of Cleveland, Ohio, and A. Schulman Inc. of Akron, Ohio, for example.  
         [0020]     After the second mold cavity  32  has been sufficiently filled, the pressure may be reduced in the second mold cavity  32  and the projections  28  may be retracted, as shown in  FIG. 5 , thereby providing additional space for expansion of the expandable material. For example, after the mold cavity  32  has been filled greater than approximately 90%, one or more vent passages (not shown) may be used to vent fluid introduced by the pressure source  36 . The expandable material may then expand to form the expanded material layer  16 .  
         [0021]     With such a process, the expanded material layer  16  may be formed with a low density main portion  40 , such as a low density foam portion, and a more dense skin portion  42  that defines the “A” surface  18  of the part  10 . For example, the main portion  40  may have a specific gravity in the range of 0.4 to 1.2, and the skin portion  42  may have a specific gravity in the range of 0.8 to 1.5. Thus, if the expanded material layer  16  is formed as a resilient layer, the expanded material layer  16  may provide a soft feel for the part  10 , while also providing a high quality “A” surface  18 .  
         [0022]     More specifically, by pressurizing the second mold cavity  32  during introduction of the expandable material, expansion of gas bubbles may be inhibited until after sufficient formation of the skin portion  42 . As a result, surface imperfections, such as bubbles or other surface splay, on the “A” surface  18  may be minimized or eliminated.  
         [0023]     The above method may also be modified in any suitable manner. For example, the projections  28  of the mold  22  may be used to form the apertures  14  of the substrate  12 . As another example, the substrate  12  may be formed in a separate mold (not shown). Next, the substrate  12  may be transferred to the first mold portion  24 , and the method may then continue as described above in detail.  
         [0024]     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.