Abstract:
A female mold for plastic sanitaryware manufacture has an open top to promote improved air escape from the mold as resinous backing resin fills the mold in order to reduce the number of gas inclusions within the backing material after it is cured. The female mold also provides thermal insulation for the curing backing material to permit better curing and to reduce the potential for delamination in the finished product. A production fixture is equipped with a gas impermeable lid for selective contact with the female mold, after the air has been expelled from the mold, in order to control undesirable styrene emissions.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to plastic molding apparatus and, more particularly, to a female mold structure for use in manufacturing items of plastic sanitaryware, and the like.  
         BACKGROUND OF THE INVENTION  
         [0002]    The advantages of plastic sanitaryware, e.g., lavatories, bathtubs, shower stalls, and shower trays, in contrast with the ceramic and enamel-on-cast iron or enamel-on-steel units that characterized the prior art are well known. Illustratively, plastic sanitaryware is much lighter than corresponding pieces of ceramic or enamel ware. Consequently, less labor and effort is needed to install plastic ware fixtures either as replacements in existing bathrooms or in new construction. Further in this regard, although an item of plastic sanitaryware is considerably lighter than an enamel or ceramic counterpart, plastic sanitaryware, when properly made with a heavy backing material for the plastic surface structure, or shell, has a “solid feel” to it; that is, a stable and sound response to application of body pressures. In this manner, well made plastic sanitaryware is able to overcome the flimsy and “cheap” reputation that some plastic sanitaryware units constructed without a suitably heavy backing structure acquired because of the unsupported and undamped resilient response of these less sturdy units to body weight application.  
           [0003]    There are a number of other advantages inherent in the use of plastic sanitaryware in contrast, particularly, with enamel fixtures. For example, if during construction, a heavy weight, such as a hammer or other tool, is dropped on an enamel ware unit, the enamel will almost always chip or crack, requiring a costly replacement of the entire fixture. Dropping the same heavy weight on a plastic fixture, however, might not mar the fixture or, even if marring does occur, the marred surface can be repaired by buffing to restore the surface to an undamaged condition.  
           [0004]    Manufacturing suitable plastic sanitaryware, however, has led to several difficult production problems. Illustratively, a typical item of plastic sanitaryware is manufactured by first forming an acrylic plastic shell in the general shape of the final product. The non-finish side of the acrylic shell is suitably activated in order to bond with a resin that is manually sprayed or brushed onto the non-finish side. The foregoing procedure is slow, involves a considerable amount of manual labor and produces products that vary widely in quality.  
           [0005]    The resin, moreover, often spills out from the non-finish side of the acrylic shell to which it is applied. The waste in material and extra labor required to trim off the spilled resin from the finished piece is quite clear. Premature cooling of the setting resin creates further difficulties. For example, if a thermosetting resin cools too quickly, the resulting product will be of poor quality and subject to delamination or other undesirable consequences.  
           [0006]    In those instances in which an acrylic shell has been lodged in a female mold, it had been customary to close or to put a perforated lid on the otherwise open back of the mold. As a result, the acrylic shell is seated in one side of the female mold and the side of the mold that is opposite to the shell is obstructed by a solid or a perforated lid. Flowing a backing resin into the void space within the female mold, however, leads to air entrapment within the resinous backing material in spite of the perforations in some of the lids that have been used with these older female molds. Air trapped within the female mold&#39;s void space can not be expelled completely from the mold as the resin flows into the female mold. Thus, the trapped air often forms bubbles within the backing material when the resin cures, or become hardened. This hardening of the resin and bubble formation is aggravated by a premature heat loss from the curing resin. Had the heat of the curing resin been conserved, not only would a better resinous backing material be produced, but also the curing resin would have remained fluid long enough to enable more air to escape, thereby at least reducing bubble formation.  
           [0007]    As a result there is a need for an improved female mold structure that will conserve the heat within a curing backing resin to produce a better product and a structure that will permit air to escape more readily from the mold as the resin flowing into the mold displaces the air within the mold void space.  
           [0008]    There is a further and more subtle need that a female mold structure should satisfy. Curing resins produce environmentally undesirable styrene emissions. These emissions must be controlled in order to establish an environmentally acceptable manufacturing process.  
         SUMMARY OF THE INVENTION  
         [0009]    These and other needs that have characterized the prior art are satisfied to a large extent through the practice of the invention. For example, a salient feature of a female mold that embodies principles of the invention is the addition of thermal insulation to the female mold structure. This insulation arrests the escape of heat from the thermosetting resin within the mold. In this manner, the mold promotes better curing for the resin, thereby producing a consistently superior product that is less subject to defects, such as delamination, than prior art mold structures.  
           [0010]    A further salient feature of the invention is embodied in the manner in which air is allowed to escape from the female mold as that mold is being filled with curing resin. Thus, a pair of acrylic shells, vacuum molded in the shape of a sanitaryware fixture is mounted in a production fixture with the non-finished side of the pair of shells each facing respective female molds. The two female molds, moreover, are both mounted on a movable stage, each of these molds being in vertical alignment with a respective one of the molded acrylic shells. These female molds are provided with vertical sides and an open top.  
           [0011]    A set of pneumatic cylinders control the vertical movement of the stage to selectively lower the female molds into position around their associated shells.  
           [0012]    When the female molds are lowered into position relative to the respective shells they form liquid-tight seals between the acrylic flange surrounding each of the shells and the corresponding contacting edge of the sides that form the mold. A catalyzed resin is pumped into each of the female molds in order to bond to the non-finished sides of the acrylic shells. The catalyzed resin, being a thermosetting substance, generates heat while curing and, as the resin is being pumped or poured into the individual female molds, displaces the air in these molds, the air escaping to the atmosphere through the open tops of the molds.  
           [0013]    As the resin is curing, and after the air within the molds has been fully displaced, a pair of lids, mounted on the production frame by means of pneumatic cylinders, are pressed downwardly to bear against the upper edges of the respective female molds. These lids, when positioned on their molds, form an essentially gas-tight seal with the respective molds. This seal prevents environmentally undesirable styrene fumes from the curing resin from escaping into the atmosphere, which is a significant improvement over prior art processes.  
           [0014]    Thus, there is provided in accordance with the invention an improved female mold and method for using that mold to produce quality sanitaryware in contrast with that which has characterized the prior art, the scope of the invention, however, is limited only through the claims appended hereto. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0015]    [0015]FIG. 1 is a perspective view of a typical vacuum formed sanitaryware shell for use in connection with the invention;  
         [0016]    [0016]FIG. 2 is a perspective view of a female mold for use with the shell shown in FIG. 1, embodying features of the invention;  
         [0017]    [0017]FIG. 3 is a perspective view of a production fixture for use with the shell and mold shown in FIGS. 1 and 2 that illustrate further salient features of the invention;  
         [0018]    [0018]FIG. 4 is a full section view of a portion of a female mold for use in accordance with the invention; and  
         [0019]    [0019]FIG. 5 is a full side elevation in full section of a portion of a sanitaryware item made through the apparatus shown in FIGS. 1 through 5. 
     
    
     DETAILED DESCRIPTION  
       [0020]    For a more complete appreciation of the invention, attention is invited to FIG. 1 which shows an acrylic shell  10  in which two lavatory shells  11 ,  12  have been vacuum molded. The shell  10  has two primary surfaces, a finished side  18  (FIG. 5) that will constitute the exposed surface of the lavatory shells  11 ,  12  in the completed sanitaryware fixture. Illustrated in FIG. 1 of the drawing, however, are unfinished surfaces  13 ,  14  of the respective lavatory shells  11 ,  12  that are opposite to the finished surface of which only the finished surface  18  (FIG. 5) is shown in the drawing. Each of the lavatory shells  11 ,  12  (FIG. 1), moreover, is provided with individual drain holes  15 ,  16 , respectively, for the purpose of enabling waste water to drain from the fixtures, when these fixtures are completed and installed.  
         [0021]    The two lavatory shells  11 ,  12  are joined together by means of a web  17  that facilitates handling of the acrylic shell  10  because as joined at the web  17 , both of the lavatory shells  11 ,  12  can be processed as a single unit until final finishing and trimming, as described subsequently in more complete detail.  
         [0022]    The acrylic shell  10  also has a peripheral flange  20  that rests on a horizontally disposed base  21  for a production fixture  22  (FIG. 3).  
         [0023]    Turning now to FIG. 2, two female molds  23 ,  24  are shown on a vertically movable stage  25 . The stage  25  has apertures  26 ,  27  that are aligned with corresponding openings  30 ,  31  in the respective molds  23 ,  24 . Mold wall or walls  32 ,  33 , generally perpendicular to the plane of the stage  25  have inner surfaces  34 ,  35  that define the dimensions of the perimeters of the respective openings  30 ,  31 . These dimensions are adequate to encompass the lavatory shells  11 ,  12  (FIG. 1) within the confines of the respective inner surfaces  34 ,  35  (FIG. 2) of the female molds  23 ,  24  and to provide gaps between the unfinished surfaces  13 ,  14  of the lavatory shells  11 ,  12  and the inner surfaces  34 ,  35  of the female molds  23 ,  24  to enable a suitably thick layer of resinous backing material  19  (FIG. 5) to form between the unfinished surfaces  13 ,  14  of the lavatory shells  11 ,  12  and the inner surfaces  34 ,  35  of the female molds  23 ,  24 .  
         [0024]    To prepare a female mold, wood  36  (FIG. 4), preferably balsa wood, is applied to the outside of the male mold  37 , the thickness of the wood  36  establishing a predetermined gap between the male mold and the inner surfaces  34 ,  35  (FIG. 2) of the female molds  23 ,  24  that are under construction. This gap is equal to the desired thickness of the resinous backing material  19  (FIG. 5).  
         [0025]    Primer  40  (FIG. 4) is sprayed on exposed surface of the wood. The primed wood then is sanded to 150 grit with wax and polyvinyl alcohol (PVA)  41  being applied subsequently to the primed and sanded wooden surface.  
         [0026]    In accordance with a feature of the invention, a tooling lubricant, preferably Gelcoat  42 , is sprayed onto the prepared wax  41  on the sanded and waxed surface of the wood  36  mounted on the male mold  37 . The Gelcoat  42  is sprayed to a desired thickness and dried to the touch before a mixture of polyester resin and fiberglass  43  is sprayed into place on the Gelcoat  42 . Finally, balsa wood  44  is placed and sprayed with an adhesive  45  to the cured, exposed surface of the polyester resin and fiberglass mixture  43 .  
         [0027]    The cured and layered structure of polyester resin and fiberglass  43  to which the balsa wood  44  is joined through the adhesive  45 , then is ground and demolded. A gasket  46  (FIG. 2), moreover, is glued to the perimeters of the respective female molds  23 ,  24 , the dimensions of the gasket  46  being essentially the same as the corresponding dimensions of the web  17  (FIG. 1) and peripheral flange  20  of the acrylic shell  10 .  
         [0028]    To complete the female mold structure, a layer of Teflon, nickel plate, ceramic finish or stainless steel (not shown in the drawing) is secured to the inner surface  34  (FIG. 4) of the illustrative mold wall  32  (FIG. 2).  
         [0029]    The female molds  23 ,  24  (FIG. 3), treated in the foregoing manner, are waxed and then mounted on the vertically movable stage  25  in the production fixture  22 . In this way, the female molds  23 ,  24  conserve heat generated through exothermic reactions in the catalyzed resin  19  (FIG. 5) that is deposited within the mold walls  32 ,  33  (FIG. 2) for adherence to the unfinished surfaces  13 ,  14  of the lavatory shells  11 ,  12 . Thus, the layered structure of the mold wall  32  shown in FIG. 4, a layered combination of Teflon, nickel plate or stainless steel, the resin and fiberglass mixture  43 , completely covered with the layer of balsa wood  44  and the adhesive  45  provide an improved, more effective thermal insulation that enables the catalyzed and curing resin  19  (FIG. 5) within the female molds  23 ,  24  (FIG. 3) to harden in a manner that promotes better adherence between the unfinished surfaces  13 ,  14  of the lavatory shells  11 ,  12  and the cured resin  19  (FIG. 5). Finished product quality is improved and occurrences of delamination between the cured resin and the unfinished surfaces  13 ,  14  of the lavatory shells  11 ,  12  is significantly reduced.  
         [0030]    As mentioned above, and best shown in FIG. 3, the peripheral flange  20  of the acrylic shell  10  is mounted horizontally on a stationary base  21  that is joined, at longitudinal ends  47 ,  50  to respective, fixed vertical supports  51 ,  52 . The tops of the vertical supports  51 ,  52 , moreover, are joined to a horizontal support  53 .  
         [0031]    Four actuators, or pneumatic cylinders  54 ,  55 ,  56 ,  57  are secured to the upper surface of the horizontal support  53  to enable respective piston rods  60 ,  61 ,  62 ,  63  to protrude vertically through the horizontal support  53  for individual and selective vertical movement. Each of the pneumatic cylinders  54 ,  55 ,  56 ,  57  has a respective control element  64 ,  65 ,  66 ,  67  connected to a control panel  70  that is secured to the outer surface of the vertical support  51 . The control panel enables the piston rods  60  and  63  to be moved simultaneously and through the same distances in vertically upward and downward directions, as illustrated by means of arrows  71 ,  72 . The pneumatic cylinders  55 ,  56 , however, and in accordance with another salient feature of the invention, are each separately operable through the control panel  70  to move individually in the directions of the arrows  71 ,  72  as described subsequently, in more complete detail.  
         [0032]    To complete the description of the production fixture  22 , it should be noted that the free ends of the piston rods  60 ,  63  are connected to the movable stage  25  for selective vertical movement in the directions of the arrows  71 ,  72  under the control of the respective pneumatic cylinders  54 ,  57  with which the piston rods  60 ,  63  are associated. As described above, the gasket  46  is mounted, in fluid-tight relation, on the movable stage  25 , the mold walls in the female molds  23 ,  24  being aligned with the individual openings  30 ,  31  (FIG. 2) in the movable stage  25 .  
         [0033]    Two flat, horizontally arranged lids  73 ,  74 , spaced below the horizontal support  53  are connected, individually, to piston rods  61 ,  62 , respectively. In accordance with the invention, the lids  73 ,  74  are separately movable in the vertical directions of the arrows  71 ,  72  under control from the panel  70 . The range of motion for the lids  73 ,  74  is defined by the gap between the inner and lower surface of the horizontal support  53  and corresponding top edges  75 ,  76  of the female molds  23 ,  24 .  
         [0034]    In operation, the unfinished surfaces  13 ,  14  of the lavatory shells  11 ,  12  are activated by automatically or otherwise spraying a barrier coat  28  (FIG. 5) on the unfinished surfaces  13 ,  14 . Illustratively, a typical barrier coat  28  can have the following composition:  
                                                                                   Acrylic Barrier Coat            Resin Mix       Product   Weight per   Weight Per   %       Component   Supplier   Code   U.S. Gallon   Recipe (lbs.)   Recipe                    Resin   Hydrex   33348-15   10.5   237.5   59.26%       Filler   Performance Minerals   SPT   N/A   100   24.95%           Dancing Bear Minerals   PDT-325   N/A       Gelcoat   Neste   WG-2X1984   10.8   35   8.73%           Interplastics   W-663B-IUU       Pigment   American Colors   PC-47173   19.9   19   4.74%       Cabosil   Composite One   20913   N/A   3   0.75%       Catalyst   Norac   925    8.0   5.92278   1.48%       6% Cobalt   Composite One   23820-MG    7.0   0.352   0.09%                  
 
         [0035]    For the purpose of this illustrative example, about five to seven pounds of barrier coat material should be sprayed on each of the lavatory shells  11 ,  12  in order to properly bond the barrier coat not only to the unfinished surfaces  13 ,  14  of the lavatory shells  11 ,  12  but also to bond the barrier coat to the subsequently applied catalyzed resin and fiberglass mixture  19  (FIG. 5) that constitutes the backing material for the finished product.  
         [0036]    The pneumatic cylinders  54 ,  57  are activated to draw the stage  25  upward until the stage  25  reaches about two-thirds of the height of the vertical supports  51 ,  52  from the bottom of these supports  51 ,  52 .  
         [0037]    The female molds  23 ,  24  are cleaned and waxed with TR 214 mold release wax. Then, the female molds  23 ,  24  are placed on the vertically movable stage  25  in alignment with respective openings  30 ,  31  (FIG. 2) in the stage  25 . The gasket  46  (FIG. 3), moreover, forms a fluid-tight seal between the stage  25  and the female molds  23 ,  24 . The pneumatic cylinders  54 ,  57  next are activated to lower the stage  25  downwardly in the direction of the arrow  72  to permit the stage  25  to settle firmly on the peripheral flange  20 , establishing a fluid-tight seal with the flange  20 .  
         [0038]    Because the openings  30 ,  31  in the stage  25  also are aligned with corresponding lavatory shells  11 ,  12 , the shells  11 ,  12  are nested within their associated female molds  23 ,  24  with a clearance between the mold walls  32 ,  33  and the opposite unfinished surfaces  12 ,  13  of the lavatory shells  11 ,  12  to accommodate a predetermined thickness of the backing material  19  (FIG. 5).  
         [0039]    A typical resin mix for the backing  19  on the lavatory shells  11 ,  12  is:  
                                                                                   Resin Mix            Resin Mix       Product   Weight per   Weight Per   %       Component   Supplier   Code   U.S. Gallon   Recipe (lbs.)   Recipe                    Resin   Reichhold   33348-15   1.8   19   35.31%           Reichhold   32144-08           Interplastics   COR44-201-034       Filler   Performance Minerals   SPT   N/A   33.5   62.25%           Dancing Bear Minerals   PDT-325   N/A       Pigment   American Colors   PC-47173   10.7    0.15625   0.29%       Glass   Owens Corning   360-RR   N/A   0.5   0.93%       Catalyst   NORAC   925   8.0   0.66   1.23%           NORAC   9H           Reichhold   46771                  
 
         [0040]    This catalyzed resin mixture is poured either manually or through an automated delivery system into the female molds  23 ,  24  to fill the volume between the barrier coat on the lavatory shells  11 ,  12  and the corresponding mold walls  32 ,  33 . A vibrator  80  attached to the fame  21  agitate the mold and shell structure as the backing resin is pouring into the molds. The vibrations fill the cavity in the mold more swiftly and promote escape of trapped air. The vibrator  80  can be applied to the molding apparatus and resin at any suitable place beside that shown on FIG. 3.  
         [0041]    Other salient features of the invention are characterized not only by the open tops to the female molds  23 ,  24 , but also by the fluid-tight seals between the gasket  46  on the female molds  23 ,  24  and the stage  25  with the peripheral flange  20 . Thus, as the catalyzed resin  19  (FIG. 5) is flowing into the respective female molds  23 ,  24  (FIG. 3), the air within the molds  23 ,  24  is displaced by the resin, the air so displaced being ejected from the female molds  23 ,  24  through the open tops of these molds that are defined by the mold walls  32 ,  33 . In this manner, air does not become trapped within the backing resin  19  (FIG. 5) to form quality-degrading bubbles and void spaces in the hardened resin. Because the heat from the exothermic curing of the resin  19  is conserved by the structure of the molds  23 ,  24  (FIGS. 3 and 4), the curing resin also maintains a degree of fluidity for a period somewhat longer than that which has characterized the prior art, thereby permitting the escape of even more air displaced by or entrained within the resin.  
         [0042]    The tight seals that are established between the female molds  23 ,  24  and the peripheral flange  20  also reflect a further improvement that characterizes the invention. By establishing fluid-tight sealing, the catalyzed resin  19  (FIG. 5) within the female molds  23 ,  24  does not leak beyond the confines of the seals. In this way, expensive resin is not wasted and the labor that heretofore had been required to trim this excess resin from the finished product is no longer required.  
         [0043]    With the aid of the thermally insulated female molds  23 ,  24 , the curing resin within the molds reaches a temperature of 150° F. to 200° F. and, after a setting time of approximately twenty to thirty minutes, the resin is 95% cured.  
         [0044]    The curing resin  19  in the female molds  23 ,  24  emits environmentally unacceptable styrene fumes. To prevent the dispersion of these fumes into the atmosphere, after suitable volumes of the resinous backing material  19  have been deposited in the molds  23 ,  24  and air, entrained within the resin  19  has been allowed to escape in the manner described above, the pneumatic cylinders  55 ,  56  are activated to lower the respective lids  73 ,  74  in the direction of the arrow  72 , onto the top edges  75 ,  76 , of the female molds  23 ,  24  to establish therewith an air tight relation. Styrene fumes emanating from the curing resin  19  within the molds  23 ,  24  are thus trapped within the void space (not shown in the drawing) between the resin  19 , the exposed mold walls  32 ,  33  and the respective lids  73 ,  74 . The styrene fumes, so trapped, can be off-gassed through a vacuum system (also not shown in the drawing) and stored safely for later, suitable disposal.  
         [0045]    After off-gassing is complete, the pneumatic cylinders  55 ,  56  are once more energized to retract the lids  73 ,  74  in the upward direction of the arrow  71 , clear of the molds  23 ,  24 , as shown in FIG. 3.  
         [0046]    Upon curing in the foregoing manner, the pneumatic cylinders  54 ,  57  are activated to draw the female molds  23 ,  24  upwardly in the direction of the arrow  71  to demold the lavatory shells  11 ,  12  and their associated cured resin backing  19  (FIG. 5) The stage  25  (FIG. 3) is drawn upwardly in the direction of the arrow  71  until a vertical clearance of 8 inches to 10 inches is established between the stage  25  and the demolded lavatory shells  11 ,  12  with their respective cured resin backings.  
         [0047]    The lavatories then are removed from the production fixture  22  for drilling and trimming, as necessary, the approximate weight of a finished lavatory being about 56 pounds.  
         [0048]    Thus, there is provided in accordance with the principles of the invention an improved method and production apparatus for manufacturing plastic sanitaryware from which bubbles and air inclusions within the backing material are markedly reduced and better curing and attendant improved bonding is attained between the backing material and the shell, while suppressing the emission of environmentally undesirable styrene fumes.