Patent Publication Number: US-6901641-B2

Title: Method for manufacturing a valance having a ridge with an accent color

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to coextruded thermoplastics, and, more particularly, to an extrusion having a ridge with an accent color produced by a coextrusion process and to a manufacturing process therefor and, yet more particularly, to the manufacture of such an extrusion for use in a valance. 
     2. Summary of the Background Art 
     A number of patents describe methods for manufacturing elongated plastic members and sheets having flat areas composed of two or more adjacent, differently colored materials by means of a coextrusion process. The location and nature of the juncture of the adjacent materials is a primary concern that is addressed by these patents. In the fabrication of a transparent thermoplastic sheet to be used as the inner layer of laminated safety glass for an automobile windshield, it is desirable to produce a smooth transition between the different colors of material within a relatively wide transition band. For example, U.S. Pat. No. 3,715,420 describes a coextrusion process for forming such a sheet to have a uniform overall thickness and to composed of a clear transparent material except for a band of colored transparent material, to extend along the top of the windshield, and a transition band in which the colored material extends as a wedge shape. Another method for obtaining a smooth transition within a transition band is described in U.S. Pat. No. 4,476,075, which describes such a sheet being formed using two parallel-operating extruders and melt pumps, with the transition band being produced by an injector means including a probe that, by way of a separate bypass conduit and an injection nozzle, injects colored composition in a wedge shape into the die processing the colorless material. 
     In other applications, a sharp transition between adjacent coextruded materials having different colors is needed, so that it is necessary to prevent a pre-solidification creep phenomenon that results in local uncontrollable migration between the materials having different colors, blurring the boundary between to adjacent colors. The prevention of this creep phenomenon is described, for example, in U.S. Pat. No. 4,753,766 as arising from minimizing the pressure within the material where the different colors of material are joined, with the stripes of different colors forming an intermediate layer and being kept separated from each other sufficiently downstream from a feed volume forming a buffer reservoir. In this way, the extrusion pressure is damped or relaxed. The physical properties of a base layer, of an intermediate layer formed by the colored stripes, and of a transparent upper layer are controlled so that these layers weld together simply by contact, without separation or migration of material from one colored stripe to another. Preferably, the stripes forming the intermediate layer are first connected together, are next connected to the upper transparent layer, and are then connected to the base layer. U.S. Pat. No. 6,103,161 describes a process in which this creep phenomenon is prevented by controlling parameters such as the pressure, speed, and flow volume within the melt streams forming each portion of the extruded material. The controls include means for strangling or throttling the flow of each melt stream into the extrusion process. 
     Other patents describe methods for incorporating strips of material to extend along or within extrusions. For example, U.S. Pat. No. 5,772,827 describes a method for forming a trim strip that includes intermediate, spaced-apart sections of a bright or color strip and portions extruded from clear or translucent melt streams. U.S. Pat. No. 5,171,499 describes a method of forming an elongated trim strip by first extruding a strip of thermoplastic material from a die and by pressing the extruded strip and a strip of foil or thin metal between cooperating forming rolls, immediately following the extrusion process, while the extruded strip is still in a plastic state. 
     Valances, or cornices, have been used for many years as decorative coverings for the mechanisms for attachment and movement of window coverings, such as curtains, drapes, shades, and blinds. U.S. Pat. No. 6,094,796 describes a process for extruding an elongated member, for cutting the elongated member into appropriate sections, and for assembling the sections with other elements to form a valance. The process of forming the elongated strip includes the coextrusion of a base material and of a material forming a decorative coating covering the portions of the base material which will be exposed when construction of the valance is completed. 
     What is needed is a method for producing an elongated member having a strip of an accent color extending along a ridge, with the elongated member being used, for example, in the fabrication of a valance. It is particularly desirable that the process for forming the ridge of material be the same as the process used to change the color of the material, and that the process should occur with a minimum level of transfer of visible colored material between the surface of the ridge and adjacent surfaces of the elongated member. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the invention, an elongated member is provided, including a first section composed of an extruded thermoplastic resin having a first color and a second section composed of a thermoplastic resin having a second color, contrasting with the first color. The second section is coextruded with the first section to extend along the first section. The elongated member has an external surface extending along the first and second sections. The external surface includes a corner extending between the first and second sections at each side of the second section. Preferably, the second section extends upward as a ridge between the corners at each side of the second section. For example, the elongated member is used to form the central portion of a valance. 
     According to another aspect of the invention, a valance is provided, including an extruded elongated central member and a pair of extruded end members attached to extend form each end of the elongated central member. Each of the end members has a transverse shape similar to a transverse shape of the central elongated member. Each end of the central elongated member is mitered to extend at a 45-degree angle relative to a length of the central elongated member. Each of the end member includes an end mitered to extend at a 45-degree angle relative to a length of the end member, attached to an end of the central elongated member. The central elongated member and each of the end members include an outwardly-curved upper portion, an outwardly-curved lower portion, an intermediate web extending between the upper portion and the lower portion, an upper web extending across the outwardly-curved upper portion to form a closed section, and a lower web extending across the outwardly-curved lower portion to form a closed section. The upper and lower webs facilitate forming the valance from a single elongated extruded member by sawing mitered edges by stiffening the single elongated extruded member to reduce deflection and vibration during the sawing operations. sawing mitered edges by stiffening the single elongated extruded member to reduce deflection and vibration during the sawing operations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a fragmentary exploded view of a valance built in accordance with the invention; 
         FIG. 2  is a transverse cross-sectional view of the valance of  FIG. 1 ; 
         FIG. 3  is a right side elevation of an extrusion die set built in accordance with the invention to form an elongated member used in the manufacture of the valance of  FIG. 1 ; 
         FIG. 4  is a rear elevation of the extrusion die set of  FIG. 3 ; 
         FIG. 5  is a front elevation of the extrusion die set of  FIG. 3 ; 
         FIG. 6  is a transverse cross-sectional view of the extrusion die set of  FIG. 3 , taken as indicated by section lines VI—VI therein to show a die plate forming core and cap portions of the elongated member; 
         FIG. 7  is a transverse cross-sectional view of the extrusion die set of  FIG. 3 , taken as indicated by section lines VII—VII therein to show a die plate forming accent strip portions of the elongated member; 
         FIG. 8  is a longitudinal cross-sectional view of the extrusion die set of  FIG. 3 , taken as indicated by section lines VIII—VIII in  FIG. 5  to show a mandrel forming interior surfaces within the elongated member; 
         FIG. 9  is a longitudinal cross-sectional view of the extrusion die set of  FIG. 3 , taken as indicated by section lines IX—IX in  FIG. 5  to show provisions for inserting melt streams within the die set; 
         FIG. 10  is a fragmentary cross-sectional view of the extrusion die set of  FIG. 3 , taken as indicated by section lines VII—VII therein to show a connection bridge holding a mandrel within the die set in place. 
         FIG. 11  is a fragmentary transverse cross-sectional view of an elongated member formed within the die set of  FIG. 3 , showing an accent strip formed with a minimum acceptable flow of thermoplastic material into the accent strip; and 
         FIG. 12  is a cross-sectional view similar to  FIG. 11 , except that the accent strip is formed with a substantially higher flow of thermoplastic material into the accent strip. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 and 2  are view of a valance  10  built in accordance with the invention, with  FIG. 1  being a fragmentary exploded view thereof, and with  FIG. 2  being a transverse cross-sectional view thereof. Other aspects of the valance  10  described in U.S. Pat. No. 6,094,796, the disclosure of which is incorporated herein by reference. The main structure of the valance  10  includes a central portion  12  and a pair of end portions  14 , all of which are cut from a single elongated extruded member, forming mitered end surfaces  15 . Various features of these portions  12 ,  14 , are formed in the single elongated extruded member during the extrusion process, including a flat web  16 , rear slot surfaces  18 , front slot surfaces  20 , outer slot surfaces  21 , an upper curved portion  22 , and a lower curved portion  24 . At each end surface  15  of the central portion  12 , a leg  25  of an “L”-shaped bracket  26  is slid into place within the rear slot surfaces  18  of the central portion  12 . Another leg  25  of each “L”-shaped bracket  26  is slid into place within the rear slot surfaces  18  of one of the end portions  14 . In this way, the two end portions  14  are attached to the central portion  12 . Alternately, the “L”-shaped brackets  26  are omitted, with legs  27  of small “L”-shaped brackets  28  instead being inserted within the outer slot surfaces  21  of the central portion  12  and the end portions  22 . For example, the larger “L”-shaped brackets  26  are composed of a thermoplastic material, while the small “L”-shaped brackets  28  are composed of metal. 
     Since the central portion  12  and the end portions  14  are formed from a single elongated extruded member, their transverse shapes (i.e. the shapes shown in a transverse cross-sectional view, such as  FIG. 2 , are similar. In the example of  FIGS. 1 and 2 , the elongated extruded member used to form the central portion  12  and the end portions  14  is symmetrical, so this elongated member, having been cut to an appropriate length with end surfaces perpendicular to its length, is placed in the sawing apparatus described in U.S. Pat. No. 6,094,796 to saw the mitered surfaces  15  forming the end portions  14  from opposite ends of the elongated extruded member, with the remaining portion of the elongated extruded member forming the central portion  12 . On the other hand, if the elongated extruded member is not symmetrical (for example, if the upper curved portion  22  and the lower curved portion  24  are of different sizes), the portion of the elongated extruded member remaining after the end portions  22  are removed has mitered surfaces slanted in the wrong direction, so it is necessary to apply the additional operations described in U.S. Pat. No. 6,094,796, removing scrap portions of this remaining portion of the elongated extruded member to form the central portion  12 . 
     In accordance with a preferred version of the present invention, the curved portions  22 ,  24  each form part of a closed structure including a web  29 , which therefore has a stiffness minimizing flexure and vibration during the sawing process used to form mitered edges  15 . 
     Additionally in accordance with a preferred version of the present invention, the central portion  12  and the end portions  14  include a pair of accent strips  30 , extending outwardly as ridges composed of a thermoplastic material having a color that is visibly different from the adjacent visible surfaces of the portions  12 ,  14 . Preferably, the valance  10  also includes a trim strip  31 , formed at corners  32  as also described in U.S. Pat. No. 6,094,796, and installed within the front slot surfaces  20  of the central portion  12  and the end portions  14 . The accent strips  30  and the trim strop  31  may be of a common color contrasting with the color of remaining visible portions of the central portion  12  and end portions  14 , or accent strips  30  may be of a different color, such as gold. 
     A number of attachment brackets  34  are also installed within the rear slot surfaces  18  of the central portion  12  to attach the valance  10  to a structural surface. Each attachment bracket  34  is installed by pivoting in the direction of arrow  36  to place the attachment tabs  38  of the bracket  34  within the rear slot surfaces  18 . Apertures  40  within the attachment bracket  34  are then used to attach the bracket  34  to a headrail (not shown), for example, of a vertical blind assembly extending behind the valance  10  or, by means of additional mounting brackets (also not shown) to a wall extending behind the valance  10 . 
       FIGS. 3-9  show a die set  46  used to form, by coextrusion, the elongated extruded member subsequently used to form the central portion  12  and end portions  14  of the valance  10 .  FIG. 3  is a right elevation of the die set  46 , which includes an adapter block  48  for attachment to an extruder (not shown), which is understood to be a device well known to those skilled in the art for providing a stream of thermoplastic melt at a temperature and pressure sufficient for passage through the opening of an extrusion die. The dies set  46  also includes a transition plate  50 , a first structure forming plate  52 , an accent strip forming plate  54 , and a final die forming plate  56 .  FIGS. 4 and 5  are rear and front end views of the die set  46 , respectively.  FIGS. 6 and 7  are transverse cross-sectional views thereof, with  FIG. 6  being taken as indicated by section lines VI—VI in  FIG. 3  to show a an internal structure of the first structure forming plate  52 , and with  FIG. 7  being taken as indicated by section lines VII—VII in  FIG. 3  to show an internal structure of the accent strip forming plate  54 .  FIGS. 8 and 9  are longitudinal cross-sectional views of the die set  46 , with  FIG. 8  being taken as indicated by section lines VIII—VIII in  FIG. 5  to show a mandrel  57  forming interior surfaces within the elongated extruded member, and with  FIG. 9  being taken as indicated by section lines IX—IX in  FIG. 5  to show a first channel  58  through which a primary stream of thermoplastic melt is introduced into the die set  46 , a second channel  60  through which a stream of thermoplastic melt is introduced to form a cap layer extending along surfaces that will be visible in the valance  10 , and a third channel  62 , through which a stream of thermoplastic melt is introduced to form the accent strips  30  in the valance  10 . 
     Referring to  FIGS. 4 and 9 , the adapter block  48  includes a face  63  having four threaded holes  66  for attachment to the extruder (not shown), a cylindrical portion  68  for engaging the output structure of the extruder, and an opening  70  forming a portion of the channel  58  receiving a primary flow of thermoplastic melt from the extruder. The opening  70  extends from a round input aperture  72  to a generally rectangular output aperture  74  at the front surface  76  of the adapter block  48 . The transition plate  50  includes an opening  78  extending as a portion of the channel  58  between an input aperture  80 , coextensive with the output aperture  74  of the adapter block  48 , and an output aperture  82 , which is somewhat larger than the input aperture  80 . 
     Referring to  FIGS. 6 and 9 , the first structure forming plate  52  includes an opening  84  through which the primary flow of thermoplastic melt from channel  58  is forced to form the core of the elongated extruded member. This opening  84  has the general shape of the elongated extruded member, lacking the ridges to be formed as accent strips  30 , and being somewhat larger than the elongated extruded member to compensate for shrinkage during cooling from an extrusion temperature. 
     The first structure forming plate  52  also includes the second channel  60 , through which a stream of thermoplastic melt is introduced to form a cap layer extending along surfaces that will be visible in the valance  10 . The second channel  60  includes an input section  86  extending downward from internal threads  88  provided for connection to a second extruder (not shown) providing a source of this thermoplastic melt, an intermediate section  90  extending forward from the input section  86  and a pair of distribution channels  92  extending outward and downward from the intermediate section  90  toward the structure forming opening  84 . Each of the distribution channels  92  is bifurcated to form a pair of channels  94  extending along sides of a distribution surface  96 , which is offset in the direction of arrow  98  from the front surface  100 , which is held against an adjacent rear surface  102  of the second structure forming plate  54 . In this way, a narrow space is formed, allowing the thermoplastic melt from the second channel  60  to flow to the surfaces of the structure being extruded opposite the direction of arrow  98  through the structure forming opening  64  that are exposed to the distribution surface  96 . These surfaces of the structure include the surfaces that will be visible within the valance  10  to be constructed using the structure. 
     Referring to  FIGS. 7 and 9 , the second structure forming pate  54  includes a opening  104  through which the flow of thermoplastic material from the opening  84  of the first structure forming plate  52  and the cap of thermoplastic material formed over a portion of this structure from the flow of thermoplastic melt driven through channel  60 . The opening within the opening  104  adjacent the areas of the thermoplastic material where this cap is formed may be enlarged to provide for the thickness of this cap. Like the opening  84 , the opening  104  does not include provisions for the ridge shape of the accent strips  30 . 
     The second structure forming plate  54  also includes the third channel  62 , through which a stream of thermoplastic melt is introduced to form the accent strips  30 . The third channel  62  includes an input section  106  extending downward from internal threads  108  provided for connection provided to a third extruder (not shown) providing a source of this thermoplastic melt, an intermediate section  110  extending forward from the input section  106  and a pair of distribution channels  112  extending outward and downward from the intermediate section  110  toward the locations where the accent strips  30  are to be formed along the melt structure being driven through the opening  104 . 
     Referring additionally to  FIG. 5 , a pair of screws  113 , engagin threaded holes  114  within the final die forming plate  56  and extending into cavities  115  within the second structure forming plate  54 , are turned to balance the flow of thermoplastic melt within the two distribution channels  112 . Each of the screws  113  forms a variable restriction within the corresponding distribution channel  112 , with the screws  113  being separately adjustable to balance the flow of thermoplastic melt forming the two accent strips  30 . The final die forming plate  56  additionally includes an opening  116 , which is similar in shape to the opening  104  within the second structure forming plate  54  except that recessed areas  117  are included in the opening  114  to form the ridge-shaped structure of the accent strips  30 . The various structures within the die set  46  are held together by a number of bolts  118  extending through holes in the plates,  50 ,  52 ,  54 , and  56  to engage threaded holes  120  within the adapter block  48 . 
       FIG. 10  is a fragmentary cross-sectional view taken as indicated by section lines VII—VII in  FIG. 3  to show a connection bridge  122  holding the mandrel  57  in place within the second structure forming plate  54 . Several such connection bridges  122  are spaced around the mandrel  57 . Referring additionally to  FIG. 8 , a pair of mandrels  57 , while being supported by bridges  122  within the second structure forming plate  54 , extends additionally within the first structure forming plate  60  and the final die forming plate  56 . Thermoplastic material flowing opposite the direction of arrow  98  through the opening between the mandrel  57  and adjacent surfaces of the opening  104  is separated by the bridges  122  to be rejoined after flowing past the bridges  122 . 
       FIGS. 11 and 12  are fragmentary transverse cross-sectional views of the elongated extruded member  124  formed within the die set  46 , showing allowable variations in the formation of the accent strips  30 . The elongated extruded member  124  includes a core layer  126  formed of thermoplastic material driven into the die set  46  through the first channel  58 , a cap layer  128  formed of thermoplastic material driven through the second channel  60 , and the accent strip  30 , formed of thermoplastic material driven through the third channel  62 . For example, the core layer  126 , the cap layer  128 , and the accent strip  30  are each composed of a polyvinyl chloride resin, with the materials forming the cap layer  128  and the accent strip  30  including additives to achieve a particular, repeatable color of the material and to protect the material from damage or discoloration by ultraviolet light. The cap layer  128  and the accent strip  30  have different coloration additives to produce different colors. The use of the cap layer  128  in this way allows the use of a less expensive thermoplastic material, not requiring stabilization for exposure to ultraviolet light, and not requiring accurate color control, for the core layer  126  forming a substantial part of the elongated extruded member  124 . 
     As described in the prior art, previous attempts to produce coextruded strips of materials having different colors have been troubled by difficulties in controlling the appearance of the edges of the strips. These difficulties result from the mixing of materials at the edges of the strip, so that the appearance of these edges is blurred, and from variations in the width of the strips or in the straightness of their edges due to changes in the rate at which material forming the edges flows through the extrusion die. 
     In accordance with the present invention, the visible effects of such difficulties are alleviated by the shape of the accent strip  30  being formed as an outward-extending ridge, with corners  130  being formed in the exterior shape of the elongated extruded member  124  at the location of the external color change occurring between the accent strip  30  and the adjacent cap layer  128 . Referring again to  FIGS. 5 and 7 , these corners  130  are formed by corners  132  within the second structure forming plate  54  adjacent the ends of distribution channels  112  and by similar corners at the edges of recessed areas  117  within the opening  116  of the final die forming plate  56 . 
     In the example of  FIG. 11 , thermoplastic material has been flowed to form the accent strip  30  at a rate sufficient to form the strip and to close a gap between the accent strip  30  and the underlying cap layer  128 , resulting in a satisfactory version of the accent strip  30 . In the example of  FIG. 12 , thermoplastic material has been flowed to form the accent strip  30  at a substantially greater rate, causing the accent strip to bulge into the underlying thermoplastic material  128 , which is still soft when the accent strip  30  is formed. Since the external appearance of the elongated member  124  is the same as shown in  FIGS. 11 and 12 , these FIGS. both show acceptable versions of the elongated member  124 . The additional material forming the accent strip  30  in  FIG. 12  extends into a bulge that is formed opposing the pressure of the material forming the cap layer  128  and the core layer  126 , since it is more difficult for this material forming the accent strip  30  to flow around the corners  130 , while additionally opposing the pressure of the other material. Furthermore, a mixing of the materials at the interface between the accent strip  30  and the underlying cap strip  128  does not blur the external appearance of the change in colors. 
     While the process of forming an accent strip as an outward-extending ridge has been explained as a part of a process for manufacturing a valance assembly having two such strips, it is understood that this process can be used, within the scope of the invention, to produce other types of elongated members with one or more accent strips of this type. 
     While the invention has been described with some degree of particularity, it is understood that this description has been given only by way of example, and that many changes can be made without departing from the spirit and scope of the invention.