Abstract:
A method of applying a decorative color to a thermoplastic strip suited for use to produce slats for blinds is characterized by the use of a heat sensitive printing paper of the type normally used to color the fabric material from which valances are generally made. By using that type of color transferring medium to color the thermoplastic slats it becomes possible, for instance, to manufacture blind slats having the same color as the fabric valance to be hung decoratively from the window for which the blind is to be installed. There is also disclosed a blind structure for attenuating the flapping noise produced when the slats enter in contact with each other.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to blinds, more particularly, to decorative slats for blinds.  
           [0003]    2. Description of the Prior Art  
           [0004]    It is known to manufacture extruded thermoplastic products, such as blind slats, in a variety of colors. In the case of thermoplastic slats, a film coated with heat transferable colorant is typically used to apply a decorative color onto the slats. This is accomplished by drawing the film under tension into a press where the film is forced against the thermoplastic slat material at an elevated temperature so as to cause the colorant to be transferred from the film to the thermoplastic slat material.  
           [0005]    When color is applied on fabric materials (used to manufacture curtains, valance or the like), a heat sensitive printing paper is used, via a stamping process, rather than the above-mentioned coated film used for thermoplastic blind slats. This difference in color transfer media results in the incapacity of obtaining exactly the same color for the thermoplastic blind and the associated fabric valance. Thus, fabrics have been applied to slats of blinds to ensure color match between the blinds and the valance.  
           [0006]    Therefore, there is a need for a new color transfer process which allows for the production of thermoplastic blind slats having exactly the same color as the associated fabric valance.  
         SUMMARY OF THE INVENTION  
         [0007]    It is therefore an aim of the present invention to provide a novel method of applying a decorative color to a thermoplastic substrate.  
           [0008]    It is also an aim of the present invention to provide such a method which renders possible the production of thermoplastic and fabric products having improved color matching.  
           [0009]    It is a further aim of the present invention to reduce the noise generally produced when a plurality of interconnected blind slats enter in contact with each other.  
           [0010]    Therefore, in accordance with the present invention, there is provided a method of reproducing the color of a given fabric product on a thermoplastic substrate, comprising the steps of: providing a color transfer medium of a same type as the one used for coloring the fabric product, said color transfer medium including a continuous web of heat sensitive printing paper having a colorant thereon corresponding to the color of the fabric product; providing a pair of lamination rollers defining a nip therebetween; advancing a continuous thermoplastic substrate and said continuous web of heat sensitive printing paper through said nip to press said heat sensitive printing paper against a first surface of said thermoplastic substrate at a sufficient elevated temperature to cause transfer of said colorant from said heat sensitive printing paper to said thermoplastic substrate, wherein said web of heat sensitive printing paper supplied to said nip has only a slight tension therein; and separating said thermoplastic substrate from said web of heat sensitive printing paper  
           [0011]    In accordance with a further general aspect of the present invention, there is provided a blind comprising a succession of slats, each said slat comprising a structural strip and a layer of soft material applied at a location thereon to act as a damper to reduce the noise resulting from collisions between adjacent ones of said slats.  
           [0012]    In accordance with a further general aspect of the present invention, there is provided a blind slat comprising a structural base layer, a decorative layer applied on one side of said structural layer, and a pair of lateral lips secured on said decorative layer so as to extend over opposed longitudinal sides thereof. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment thereof, and in which:  
         [0014]    [0014]FIG. 1 is a schematic elevational side view of a thermal transfer printing apparatus used in accordance with a first embodiment of the present invention to produce colored blinds; and  
         [0015]    [0015]FIG. 2 a  is a rear perspective view of a portion of a blind slat manufactured in accordance with a second embodiment of the present invention;  
         [0016]    [0016]FIGS. 2 b  to  2   m  illustrate, in cross-section, various configurations of multi-layered blind slats; and  
         [0017]    [0017]FIG. 3 is a diagram illustrating an embossing process in accordance with an embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    [0018]FIG. 1 illustrates a thermal transfer printing apparatus  10  which can be used to apply a desired color, such as the color of a decorative fabric material, to a thermoplastic product, such as an extruded substrate or strip  12 , made for instance of PVC, used to make window-blind slats.  
         [0019]    It has been found that by using a roll of heat sensitive printing paper  14  of the type used for applying a color to a fabric material rather than using the conventional coated film, it is possible to manufacture blind slats having exactly the same color as the fabric valance, draperies or the like to be hung decoratively from the window in which the blind is to be installed.  
         [0020]    As seen in FIG. 1, the extruded PVC strip  12  is continuously supplied from a die  16  through a nip  18  defined between a pair of power-driven lamination rollers  20  and  22 . The rollers are set so as to exert a pressure of approximately 100 lbs. on the strip  12 ′. The extruded PVC strip  12  is advanced through the apparatus  10  at approximately 30 ft/min and is supplied at about 350° F. The advancing speed of the paper  14  and the strip  12  must be at least equal to 10 ft/min to prevent the paper  14  from burning. It is pointed out that the advancing speed of the strip  12  and of the printing paper  14  could be more than 30 ft/min. The heat sensitive printing paper  14  is wound on a motorized supply spool  24  and is delivered and guided between the lamination rollers  20  and  22  by an appropriate guiding structure schematically illustrated at  26  in FIG. 1. The angle of incidence of the printing paper  14  at the rollers  20  and  22  is preferably about 45 degrees. However, this angle can be comprised in a range from about 20 degrees to about 70 degrees.  
         [0021]    As represented in broken lines in FIG. 3, the guiding structure  26  is preferably adjustable for allowing the angle of incidence of the printing paper  14  to be varied as required or desired.  
         [0022]    As opposed to conventional coated film used to apply a decorative color to an extruded thermoplastic product, it has been found that there must be virtually zero tension in the heat sensitive paper  14  between the supply spool  24  and the lamination rollers  20  and  22  (i.e. upstream of the nip  18 ) in order to effectively and efficiently color the extruded PVC strip  12 . This can be accomplished, for instance, by driving and continuously adjusting the unwinding speed of the supply spool  24  so as to compensate the pulling action exerted by the lamination rollers  20  and  22  on the heat sensitive paper  14 . Before being installed in the apparatus  10 , the paper  14  is precisely cut so as to have a width which is slightly greater than that of the PVC strip  12 . For instance, if the strip  12  has a 3½″ width, the width of the paper  14  would be 4″. This ensures proper application of the paper  14  onto the strip  12 .  
         [0023]    The heat sensitive paper  14 , which is at the ambient temperature, is advanced through the apparatus  10  at the same speed as that of the extruded PVC strip  12 . At the nip  18 , the heat sensitive paper  14  is pressed against a top surface of the extruded PVC strip  12  at a sufficiently elevated temperature to cause the colorant present on the paper  14  to migrate to the extruded PVC strip  12 . The lamination rollers  20  and  22  are maintained between approximately 275° F. and 350° F. during the color transfer process.  
         [0024]    At their exit from, i.e. downstream of, the nip  18 , the colored extruded PVC strip  12  and the heat sensitive printing paper  14  are separated. A take-up spool  28  is thus provided downstream of the lamination rollers  20  and  22  to receive the continuous web of used printing paper  14 . In FIG. 1, a slight tension is induced in the paper  14  between the lamination rollers  20  and  22  and the take-up spool  28 .  
         [0025]    As seen in FIG. 3, it is contemplated to provide a second roll of printing paper  14 ′ upstream of the lamination rollers  20  and  22  and underneath a strip  12 ′ to provide for the coloration of the under surface thereof. It is understood that a second guiding structure  26 ′ and a second take up spool  28 ′ would also be provided. This arrangement would allow a decorative color to be simultaneously applied on both sides of the extruded strip  12 ′. Obviously, the roll of printing papers  14  and  14 ′ could be of a different colors, if desired.  
         [0026]    [0026]FIG. 2 a  illustrates a transversally curved blind slat  30  formed of a substantially rigid PVC structural strip  32  having a front surface lined with a coextensive decorative flexible or resilient PVC strip  34 . The structural strip  32  and the resilient PVC strip  34  are preferably co-extruded. The opposed longitudinal sides of the resilient PVC strip  34  are folded over against the opposed longitudinal sides of a rear surface  36  of the structural strip  32  to act as dampers to reduce the noise resulting from collisions between the slats  30  of a blind.  
         [0027]    The blind slat  30  is typically formed by a co-extrusion process and the strips  32  and  34  are assembled together in a unitary structure by a fusion process.  
         [0028]    [0028]FIGS. 2 b  to  2   m  illustrate various other configurations of the resilient or soft layer of PVC material  34  and of the rigid PVC structural strip  32  to also provide a noise dampening effect.  
         [0029]    As shown in FIGS. 2 b  to  2   e,  the structural strip  32  can have a flat central portion  33  merging into two longitudinally extending rounded side portions  35 . The flexible layer  34  can extend over one side of the central flat portion  33  and about ¼, ½, ¾ or even over the full circumference of the rounded side portions  35 . Alternatively, as illustrated in FIG. 2 i,  the structural strip  32  can be completely surrounded or covered by the soft or flexible layer  34 .  
         [0030]    The dampers could alternatively be formed through a triple extrusion process wherein in addition to the structural strip  32  and to an overlying decorative layer  37 , a pair of narrow resilient PVC strips or clear lateral lips  39  are extruded along the opposed longitudinal side edges of the blind slat  30 , for instance, on the decorative strip  37 , as illustrated in FIG. 2 g.  The triple extrusion can be done either with two subsequent dies or all with one triple extrusion die.  
         [0031]    In addition to providing noise attenuation, the narrow resilient strips  39  provide the impression that the decorative strip  37  is held within a channel formed on a front surface of the slat  30 , thereby reproducing the look of a channeled blind slat of the type having an elongated strip of fabric material held on front side thereof. To this end, the decorative layer is preferably textured to better emulate the appearance of a fabric tissue. As will be explained hereinbelow, such a textural effect can be provided by embossing or engraving a desired pattern on the decorative strip  37  and the structural strip  32 .  
         [0032]    It is noted that the opaqueness of the dampening lips or resilient strips  39  can be modified to obtain different levels of translucency.  
         [0033]    Alternatively, as illustrated in FIG. 2 f , one side of the structural strip  32  can be co-extruded so as to be completely covered with a soft layer of material  41  which can, in turn, be covered by a decorative layer  37 ′.  
         [0034]    As shown in FIG. 2 h,  the soft lateral lips  39  can be directly co-extruded along the sides of the hard structural strip  32 .  
         [0035]    As shown in FIGS. 2 j  and  2   k,  the soft translucent lips  39  can be extruded so as to have an L-shaped cross-section in order to cover the lateral edges of the flexible PVC decorative layer  37  and of the rigid structural strips  32  (see FIG. 2 k ) or, alternatively, only the lateral edges of the decorative layer  37  (see FIG. 2 j ).  
         [0036]    As shown in FIGS. 2 l  and  2   m  all or some of the edges of the soft lips  39  can be rounded to vary the noise attenuation characteristics thereof.  
         [0037]    In summary, the slats  30  can be made substantially silent by three different methods: 1) one side thereof may be co-extruded with a material so as to be completely covered by a softer material, 2) a small section on each of the slat (approximately ¼ inch) may be co-extruded with a soft material, or 3) a co-extruded rigid structural core can be covered by a co-extruded soft covering layer all over the surface of the slat.  
         [0038]    As discussed hereinbefore, the noise dampening effect can be obtained with different configuration of the soft lips  39 . The soft lips  39  can be partially co-extruded either on the top soft layer, top and middle layers or wrapped around the edges of the slat.  
         [0039]    As seen in FIG. 3, once the color has been transferred onto the strip  12 ′, the latter is directed in a continuous way to one of first and second embossing stations  40  and  40 ′.  
         [0040]    The first embossing station  40  includes a first heater  42  for heating the strip  12 ′ from above before the same is pressed between a top embossing roller  44  and a bottom roller  46 . Cooling of the strip  12 ′ after the color transferring process requires re-heating of the strip  12 ′ for subsequent embossing. The heater  42  allows to soften the top surface of the PVC strip  12 ′ in preparation for the subsequent top embossing operation. The embossing or textured roller  44  is provided on its circumference with a given embossing pattern to emboss or engrave the top surface of the strip  12 ′ as it passes between the rollers  44  and  46 . The pressure between the rollers  44  and  46  can vary from about 50 lbs. to 1000 lbs. The bottom roller  46  is preferably made of hypalon and the embossing roller  44  of steel.  
         [0041]    A second heater  48  is provided downstream of the rollers  44  and  46  for heating the strip from below before the same is pressed between a top hard rubber roller  50  and a bottom embossing roller  52 . The bottom embossing roller  52  is provided on its circumference with an embossing pattern to emboss or engrave the undersurface of the strip  12 ′ after the same has been heated to an appropriate temperature by the heater  48 . According to a preferred embodiment of the present invention, the heaters  42  and  48  each consist of an infra red heater. However, it is understood that other types of heaters could be used as well.  
         [0042]    It is noted that the embossing rollers  44  and  52  may be water or air cooled.  
         [0043]    The resulting embossed strip  12 ′ is then directed to a cooling station (not shown) for stabilization before being cut and packaged.  
         [0044]    It has been found that the definition of the embossed patterns on opposed sides of the strip  12 ′ can be improved by prolonging the contact of the strip  12 ′ with the embossing rollers. As illustrated with respected to the embossing station  40 ′, this is achieved by adding appropriate guiding structures  54   a  and  54   b  immediately downstream of the embossing rollers  44 ′ and  52 ′. Apart from the guiding structures  54   a  and  54   b,  the embossing station  40 ′ is similar to the embossing station  40  and, thus, the duplicate description thereof will be omitted for brevity.  
         [0045]    The guiding structures  54   a  and  54   b  are arranged to cause an inverse wrap around cycle about the embossing rollers  44 ′ and  52 ′. More particularly, the guiding structure  54   a  is arranged to deviate the strip  12 ′ about 80 degrees so that the same is maintained in contact with about ¼ of the circumference of the top embossing roller  44 ′. Likewise, the guiding structure  54   b  is arranged to deviate the strip  12 ′ about 80 degrees so as to maintain the strip  12 ′ in contact with about ¼ of the circumference of the bottom embossing roller  52 ′.  
         [0046]    By prolonging the contact between the strip  12 ′ and the embossing rollers  44 ′ and  52 ′, the definition of the pattern engraved on the opposed surfaces of the strip  12 ′ is improved.  
         [0047]    It is also understood that the strip  12 ′ can be embossed on a single side thereof instead of being embossed on both sides thereof.  
         [0048]    When the strip  12 ′ is embossed on a single side, the lamination rollers  20  and  22  are preferably respectively made of silicon and steel. When the PVC strip  12 ′ is embossed on both sides thereof, the lamination rollers  20  and  22  are preferably both made of silicone.