Abstract:
A mold assembly for press molding plastic material into products under heat and pressure wherein the material is placed on a base mold having at least one or more guide blocks spaced thereabout for accommodation of wedge mold segments each having a surface matched to a portion of the base mold. Each wedge mold segment is arranged to move over an inclined surface of a guide block into compression mated association with material to be molded on the respective portion of the mold base to which it is matched. In operation the wedges are pushed downward by a press and moved laterally over the stationary inclined surfaces of the guide blocks which guide the wedges inwardly in matched pressure relation with the material to be molded on the sides of the base mold. The invention also includes division of the wedge mold segment into an assembly of two parts in which a mold section is backed by an associated wedge member which pushes the mold section into molding position.

Description:
BACKGROUND 
     This invention [deals with molding of] is a mold assembly which, by way of example can mold relatively inextensible thin fiber reinforced plastic sheet material into box or container shaped products in a press in which the plastic sheet material reinforced such as by carbon or glass fibers has little or no stretchability. Usually molding of such boxlike products requires slightly outwardly inclined sidewalls to permit application of vertical pressure to the sidewall layers of material during heat cure. Usual molding of such boxlike products also involves use of metal molds having flared or outwardly inclined walls to permit separation of the product from both male and female mold parts. If the desired thin wall plastic boxlike product is to be made with precise right angular sides, problems arise in molding in that vertical pressure is not applicable to the sides and mold parts are not readily separable from the cured product. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to the present invention, relatively thin high modulus fiber reinforced plastic sheet material can be molded in a press into boxlike products with precisely right angular sides or inwardly angled walls by use of slidably movable, sloping, metal mold wedges. The wedges are pushed downwardly by a press which cause them to slide in a lateral direction over stationary inclined surfaces of metal side guide blocks which guide the wedges at right angles to the pressure toward a male mold. 
     As indicated above the usual female mold with a male mold and die has flaring dimensional requirements to permit closure of the female mold die and removal of the product from about the male mold. Such flaring does not allow application of adequate pressure on the sides of the male mold. In the method and means herein disclosed, however, the female mold is replaced by one or more of what can be termed “wedge molds.” The “wedge molds” are metal segments having one side matched in shape to a portion of the male mold to permit molding of a corresponding portion of product therebetween under heat and pressure. The other side of each wedge mold is inclined and arranged to be moved over a mated inclined surface of a stationary guide inclined downwardly toward the male mold. Each wedge mold is thereby moved transversely or laterally toward the male mold upon application of vertical pressure force against the top of the wedge mold. 
     A series of such stationary guides and associated wedge molds appropriately shaped and spaced about a male mold base can be pressurized from above by a press platen acting against a top plate mold section to cause plastic material placed on the male mold to be encompassed by wedge molds and cured under heat and pressure. In other words, each wedge mold is shaped on its mold side to match a side portion of the male mold while the other side has an inclined slide surface arranged to cause movement of the wedge mold over a cooperatively matching inclined surface of a stationary guide. The guide is positioned to direct movement of its respective wedge mold toward and in side pressure relation with material on the male mold upon application of vertical pressure on the wedge mold. 
     An object of the invention is to provide a method and means for molding relatively inextensible plastic sheet material with vertically applied press force which also translates into transverse molding force by way of a novel mold design incorporating wedge molds capable of making a wide range of difficult shapes. 
     In this regard a number of container shapes can be made using the invention such for example as with inwardly curved walls by using shaping wedges having curved surfaces designed to be pushed into mating curved surfaces of a male mold base. In such arrangements the male mold can also be in segments removable from the boxlike container product after its cured. 
     A feature of the invention is that both its method and means lend themselves to production of container products not only having straight sides but products having curved sidewalls or products with inwardly directed sidewalls using correspondingly shaped mold wedges which mate with matching surfaces on the male mold. 
     Other objects and structural features which are believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention, however, both in organization and the manner of construction, together with further objects and features thereof may be best understood by reference to the following description taken in connection with the accompanying drawings. 
    
    
     THE DRAWINGS 
     FIG. 1 is an illustration of a container product having straight right angular sides extending from a base surface which according to the present invention can be made of sheet material having very little or no extensibility such as of high tensile strength glass fiber reinforced plastic sheet material; 
     FIG. 2 is a schematic illustration of a mold for making the product of FIG. 1 wherein a male mold section has fiber reinforced plastic material placed thereover and wedge type mold sections placed thereabout for application of lateral pressure thereon which upon application of heat results in cure of the plastic material into the desired product; 
     FIG. 3 is an exploded perspective view of the mold assembly of FIG. 2 for making the product of FIG. 1 showing the plastic material for the container lying over the male mold and the three mold wedges spaced above the guides which provide inclined surfaces over which the mold wedges slide; 
     FIG. 4 is a perspective view of the assembled mold components of FIG. 3; 
     FIG. 5 is a perspective view of a circular container made according to the present invention; 
     FIG. 6 is somewhat schematic perspective view of mold components for making the circular container in FIG. 5; and 
     FIG. 7 is a schematic view of mold components for making a container shown with vertically curved sides produced according to the principles of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 is illustrative of one type of container moldable according to the concepts of the present invention in which the container  10  shown in down side up position is open sided and has two opposing sides  11  and  12  and a backside  13  and a top  14  which during molding is at the top but actually is the bottom of the container. The method of producing the container is unique in that only vertical pressure is applied by a press to the mold to produce the container with vertical sides. That is, whereas the press pressure is only in one direction, mold pressures are applied to the material of the container transversely to the direction of such pressure by uniquely designing the mold assembly with wedge mold segments which move laterally responsive to the vertical pressure applied by a press. 
     The container  10  is molded by a mold assembly mounted in a press such as is partially shown in FIG. 2 in which a press platen  21  driven by a press shaft  20  applies pressure to a plate-like top mold segment  22 . The top mold  22  is arranged to apply force to the upper surface of each of three wedge molds, namely the two opposing wedge molds  27  and  28  on opposite sides of a male mold  24  and the backside wedge mold  29 . Whereas the platen  21  of the press can be used to apply pressure directly to the assembly, in the assembly of FIG. 2 a separate top plate mold  22  provides some flexibility in design such as were the bottom of the container design calls for different thicknesses across its length and width. 
     The wedge mold segments are shown in a raised condition to illustrate more clearly how the components fit together and how the mold segments operate in relation to each other. The two wedge molds  27  and  28  operate cooperatively with the stationary guides  25  and  26  respectively, on opposite sides of the male mold  24 . Each of the stationary guides has an angular surface over which its respective wedge mold is slid in wedged or relation toward the mold base or male mold  24 . 
     By way of example, the left wedge mold  27 , is provided with an inverted angular surface  37  which functions cooperatively with a matching angular surface  35  on the stationary guide  25  to guide the wedge mold toward the male mold  24 . In this respect the wedge mold  27  has an opposite mold surface  31  arranged to press against the material to be molded on the male mold base  24  namely the side  11  of the open container side  10 . That is the wedge mold  27  is moved downwardly by force applied to the top mold segment  22  by the press platen  21 . The wedge mold  27  thereupon slides on its angular surface  37  over the reverse matching angular surface  35  of the guide  25  to press the mold  27  into compression relation with the material forming the side  11  between the wedge mold surface  31  and the side of the male mold base  24  which it matches. 
     Correspondingly, the wedge mold  28  is pressed down by the mold top  22  to slide over an angular surface  36  of the stationary guide  26  toward the side of the male mold  24  to compress the side material of  12  of the container  10 . In this respect the wedge mold  28  has a mold surface  32  which matches the side of the male mold on which the material forming the side  12  of the container is disposed. The side  38  opposite to the mold surface  32  is inclined complementary to the surface  36  so that as pressure is applied to the wedge mold  28  from above, transverse pressure is applied toward the material to be molded on the mold  24  in forming the side  12  of the container  10 . 
     Similarly the backside  13  of the container is molded by the mold surface  33  the wedge mold  29  moved over an inclined stationary guide on the backside of the male mold, not here shown. 
     Upon application of pressure to the top mold segment  22  and correspondingly to the three wedge molds  27 ,  28  and  29  in unison, pressure is exerted against the material on the male mold  24 . Pressure applied to the male mold  24  in the direction of the open side of the container  10  being formed is met by a bracing bar  30  located on the side of the male mold where the open side of the container  10  is located. 
     FIG. 3 which is an exploded view of the components discussed in FIG. 2 illustrates more clearly in perspective the location of the wedge molds  27 ,  28  and  29  relative to the male mold  24  and their respective side stationary guides  25 ,  26  and the back stationary guide  34 . The wedge mold  27  slides on its surface  37  over the angular guide surface  35  of the stationary guide  25  until the mold surface  31  presses against the material on the male mold  24 . Correspondingly, the wedge mold  28  slides on its wedge surface  38  over the angular guide surface  36  of stationary guide  26  until its mold surface  32  presses against the material being molded on the male mold  24 . In similar manner the wedge mold  29  slides on its inclined surface  41  over the angular guide surface  39  of the stationary guide  34  until its mold surface  33  presses against the material at the back side of the male mold  24 . 
     FIG. 4 illustrates how the exploded space components of FIG. 3 appear when the mold is closed with the top  22  pressed downwardly on the wedge molds and into compression with the material on the male mold  24 . The material on the mold is compressed and heated at a temperature, for example, at 350 degrees Fahrenheit, to a effect a cure of the product whereupon the top is lifted and the wedge molds removed to permit removal of the container. Since as illustrated the sides  11 ,  12  and  13  are at right angles to the top  14  of the container it can be lifted from the male mold without mold block. The molded material, by way of example may be high modulus glass fibers or carbon fibers in roving form woven into a fabric saturated with a polyester resin or an epoxy resin which upon cure becomes a rigid product. The material when in its uncured condition can be placed on the male mold in sections preparatory to molding by first placing one or more lengths of the flexible uncured material about the sides of the male mold and covering the top of the male mold with a layer of the material cut to size to match the top. Extra material can be provided at the edges where necessary to effect a merger abutting edges of the material parts upon cure. 
     FIG. 5 illustrates another container shape, namely a round container  50  which can be made according to the present invention having a circular top  51  and a wall  52  at right angles thereto. 
     FIG. 6 shows the mold component assembly by which the container  50  of FIG. 5 can be made according to the present invention. The container material mounted on the male mold is surrounded by mold segments  57 ,  58 ,  59  and  60  having laterally curved mold surfaces  47 ,  48 ,  49  and  46  respectively. The mold segments under the force of a press can be arranged to be moved over the inclined guide surfaces of stationary guides  55 ,  56 ,  53  and  54  respectively. 
     Each of the mold segments, however, can be also divided into an assembly of two parts in which a mold section is backed by an associated wedge member. In this arrangement each mold section is shaped to be placed in matched relation adjacent to the material on the male mold and then pushed laterally against the material by its associated wedge member under the downward action of a press. In this regard the mold sections of segments  57 ,  58 ,  59 , and  60  have wedge slide surfaces inclined oppositely to the inclined surfaces of the stationary guides  55 ,  56 ,  53  and  54  respectively. Each of the associated wedge members  67 ,  68 ,  69  and  66  with complementary wedging surfaces are arranged to be pressed downward between its respective mold sections and guides by a press which causes their respective mold segments to move laterally into compression communication with the base material being molded on the male mold. 
     Still another product form which can be produced by the invention is shown schematically in FIG. 7 in which a three dimensional rigid product  70  having generally vertical inward curved walls  71  and  72  can be produced by wedge mold segments  77  and  78 , respectively, having correspondingly curved mold surfaces. The wedge mold segments  77  and  78  under pressure of a press can be arranged to slide over the inclined surfaces of the stationary guides  75  and  76  to compress the material which form the curved walls  71  and  72 . 
     As a variation, the mold segments, as in the embodiment of FIG. 6, can be divided into two parts with each mold segment being divided into a mold section and an associated wedge member. More specifically the mold sections  77  and  78  have associated wedge members  81  and  88  which are arranged to be moved over the inclined surfaces of their respectively associated guides  75  and  76  as well as to press against the complementary back angled surfaces of the mold sections. The mold sections  77  and  78  are thus moved into compression molding relation with the material for forming the curved walls  71  and  72  as the wedge members  81  and  88  are pressed downward by a press platen. The press platen not shown also presses against the top of the material on the male mold. The platen may be arranged to heat the mold assembly or the mold assembly can be internally heated such as from the male mold for cure of the material under both heat and pressure. Since the cured product in a sense will lock about the male mold  74 , making it difficult or impossible to remove a rigid product, the male mold is divided into segments A, B, and C which can be readily removed one by one to free the cured product. The central segment C can be tapered on two sides with largest dimension on the open side of the product to facilitate its removal from the center of the male mold, whereafter the side segments A and B can also be readily removed from the product. 
     If the product is one having rigid inwardly curved walls on four sides the male mold can be divided into five segments with a central tapered segment removable like a plug to permit removal of the remaining segments from a rigid product or by dividing the male mold into four segments with the central segment being divided into two parts with an angular parting plane. 
     In view of the foregoing it will be understood that many variations of the concept of the invention herein disclosed can be effected within the broad scope of the principles embodied therein. Thus while particular embodiments of the invention have been shown and described, it is intended by the appended claims to cover all modification which fall within the true spirit and scope of the invention.