Patent Publication Number: US-6669468-B2

Title: Candle with polyethersulfone barrier

Description:
FIELD AND BACKGROUND OF THE INVENTION 
     The present invention relates in general to candles, and in particular to a new and useful candle with a heat barrier which is partly or entirely clear or transparent, and a medium outside the barrier which is clear or transparent and which either contains one or more decorative items, or is free of everything but the medium. 
     The clear medium and a wax or wax-like fuel material for burning which is inside the barrier, may be any one of a variety of clear waxes or wax-substitutes such as one of the ester-terminated polyamides (ETPA) disclosed in U.S. Pat. No. 5,998,570 to Pavlin, et al. issued Dec. 7, 1999 or U.S. Pat. No. 5,783,657 to Pavlin, et al. issued Jul. 21, 1998, which are both incorporated here by reference. An example is a product known by the trademark UNICLEAR for an ETPA sold by the owner of these patents. 
     See also U.S. Pat. No. 5,578,089 for another clear candle material which can be used for the present invention. 
     U.S. Pat. No. 6,214,063 teaches candle products with etpabased icons, and is also incorporated here by reference. 
     U.S. Pat. No. 2,354,343 discloses a shield or barrier made of non-flammable metal or plastic material that is opaque of transparent and that is inserted into the body of a large diameter candle. A particular plastic that is disclosed for use in ethyl cellulose and similar compositions. 
     U.S. Pat. No. 3,741,711 discloses a pillar candle having a glass cup supporting a combustible portion of the candle inside a cylinder of insulating material and a second, larger cylinder of glass. The glass cylinder is embedded in an outer body of candle material. The glass cup does not extend the entire depth of the pillar candle. The insulating and glass cylinders are covered by a thin layer of candle material to hide them from view. The rim of the glass cup is visible on the top of the candle. 
     U.S. Pat. No. 5,395,233 teaches a pillar candle having an outer shell of wax, an intermediate cylindrical layer of transparent wax and potpourri and an inner core comprising a combustible candle with a wick. The inner core has a sufficiently large diameter that the intermediate and outer layers do not melt or burn. The candle does not include a barrier. 
     Patents teaching patterns illuminated by candle flames include U.S. Pat. No. 3,773,460 for a clear wax candle having an optical lens. In one embodiment of the candle, a lens insert made of wax is positioned in the candle below the wick which can be used to project an image and diffuse light from the candle flame. When the exposed surfaces of the lens cavity are pigmented, a pattern can be generated which reflects onto the outer surface of the candle. 
     U.S. Pat. No. 589,173 teaches a toy having a pattern cylinder with pattern openings that permit light from a candle burning inside the pattern cylinder to pass through onto spaced screens mounted on an outer frame. Heat rising from the candle is used to turn the pattern cylinder on an axis about the candle, so that the images formed by the pattern openings will move across the screens. The candle is a simple taper candle with a large air space between the candle and the pattern cylinder. The screens are also separated from the pattern cylinder by a gap. 
     A lampshade having a hidden image when the light source it is near is turned off is covered by U.S. Pat. No. 5,975,725. A design or pattern is held between inner and outer layers of the lampshade to hide the design when the shade is not being illuminated. 
     A candle having a non-combusting light source, such as a light bulb, inside the candle for illuminating the candle is taught by U.S. Pat. No. 3,761,702. The bottom of the candle is hollowed out and replaced with a light source. In one embodiment a clear sheath is inserted into the hollow. The sheath is disclosed as possibly having special light distributing or filtering qualities for light emanating from a light source contained therein. 
     A safety night light having a metal shield embedded in a glass container for a candle is disclosed by U.S. Pat. No. 2,315,803. The metal shield can have a pattern such as a mesh or honeycomb or spaced holes which light from the candle flame can pass through. The shield is a layer between the surfaces of the glass holder; the only candle material present is the candle inside the glass holder. 
     U.S. Pat. No. 3,077,981 teaches a candle having a design painted on the outer surface of a container which is illuminated by the candle flame inside the container. A disposable mailing tube for the candle is also provided which may have a similar design to that on the candle container. The mailing tube is discarded before using the candle. 
     Other patents of interest include U.S. Pat. No. 3,744,957 for a candle made of an opaque wax which turns transparent when it melts. A disk with a design is placed just below the top surface of the candle around the wick, so that when the top layer of wax is heated by the candle flame, the disk is revealed. 
     U.S. Pat. No. 6,033,210 discloses a candle with wax core and surrounding gel components in a clear mineral oil gel, has no barrier around the core. 
     A flame-resistant and retardant barrier is needed, that can be easily molded and formed. Plastics are a material which can be easily molded and formed, but which can also combust and produce very toxic by-products. Thermoplastics ordinarily have a low melting point because their structure is not highly cross-linked. In fact, most thermoplastics such as polyethylene and polypropylene are held together by weak dispersion forces causing them to act much like molecular solids (e.g., flexible, low strength, low melting point). Because the tensile strength of a polymer tends to degrade with increasing temperature, a thermoplastic such as polyethylene or polypropylene will melt or flow when heated by a flame. Polyethersulfone (PES) is an ideal material for a barrier because it is a transparent thermoplastic that is easily molded and formed, but also is uniquely and inherently a flame-retardant. 
     A widely accepted test to determine flammability of plastics used in products is found in Underwriter Laboratories UL-94 standard. A material is only considered flame-retardant if it meets the UL flammability standards, in which a product satisfying the V-0 standard is considered to have the highest flame resistance. ASTM standard 3801-96 and ISO standard 1210-1991 are similar standards having similar tests and equivalent ratings. 
     The UL-94 standard includes horizontal and vertical burn tests which can be used to rate the flammability of plastics. The vertical burn test is considered more stringent and a plastic can receive one of several ratings, depending on its flammability. 
     A rating of V-0 from the UL-94 vertical burn test indicates that combustion of the product stops within ten seconds after two applications of ten seconds each of a flame to a test bar of the plastic material, and the material must not produce any flaming drips. The V-0 rating is considered one of the best ratings of non-flammability for a plastic. 
     The UL-94 vertical burn test is performed by suspending a ½ inch wide by 5 inch long test rod of the plastic material over a cotton pad. A burner flame is applied to the lower end of the test rod for ten seconds, following which combustion of the rod, if any is observed until it stops. The burner flame is applied to the test rod for a second period of ten seconds. Observations of the test rod following application of the flame determine the rating the material will receive. In addition to the requirements noted above, the specimen must not begin glowing or flaming combustion after application of the burner flame. The rating for the material is based on the thickness of the test rod used. That is, a ¼ inch thick test rod which achieves a V-0 rating qualifies the material of the test rod used in products in ¼ or greater thicknesses. The thinner the test rod, the less combustible the material. 
     Polyethersulfone is one such material which has a V-0 rating for the UL-94 vertical burn test at a thickness of 0.8 mm, or about {fraction (1/32)} inches. Polyethersulfone is commonly used for electrical applications such as wire insulation, connectors, molded interconnects and housings for starters. Polyethersulfone is also known for use in other applications as well where heat resistance is desired. However, while the combustion characteristics of polyethersulfone are known, PES is not known for use in applications involving open flames. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a pillar or jar candle having a flame barrier that is at least partly clear and which fits around a core of the candle and having a wick therein so that the core material can be burned. The barrier and core candle are surrounded by an outer solid body of clear candle material, for example, of wax or UNICLEAR material. The barrier is made of polyethersulfone so as not to be combustible and prevents the outer body, as well as anything embedded in the outer body, from burning. Thus, the pillar candle has the outer appearance of a candle, but will not burn and change shape or design. In likewise fashion, the jar candle of the invention, that is a candle contained in a glass or other contained, may include decorative features which are protected from the heat of the burning wick, and which may even be advantageously illuminated by light from the candle flame. 
     The barrier material, when entirely clear, appears essentially invisible inside the outer candle body when the fuel inside the barrier is also clear. Though many plastics are ideal because of their transparent qualities, they must also be resilient to the effect of temperature created by a candle flame. The material used for the barrier is selected for a melt point that is higher than the temperature of heat generated by the flame of the core candle. In particular, the preferred material for the barrier is polyethersulfone, which is a thermoplastic polymer that softens at about 215° C. and melts at about 230° C. PES is capable of withstanding temperatures much higher than most typical thermoplastics such as polyethylene and polypropylene. A very favorable feature of polyethersulfone is that it is intumescent. That is, when PES is heated, such as by a candle flame, it begins to swell and form a heat shield. PES is substantially non-combustible, having a UL-94 standard vertical test burn rating of V-0 for very thin sections. 
     PES is a favorable material for several other reasons. The shape of the barrier may be varied to control the burn of the core candle. The barrier may taper toward the bottom, for example, rather than being a straight-sided cylinder or have another cross-sectional shape. 
     Another object of the present invention is to provide a pillar or jar candle having a flame barrier having a design painted or otherwise included onto one of the barrier surfaces and surrounded by a relatively clear outer candle shell. A paper or other translucent wrapping around the outer shell acts like a screen for receiving a projected image from the barrier pattern by light from the inner core as the candle burns. Light from the flame is projected through the unpainted or clear portions of the barrier onto the paper wrapping on the outer shell. 
     The barrier is preferably a clear plastic material which permits light to pass through. The design which is projected onto the paper screen is formed by painted opaque portions of ink or paint preferably on the outer surface of the barrier (away from the flame) and unpainted clear portions. UNICLEAR ETPA is a preferred material for the outer shell since light from the flame can pass through the clear unpainted portions of the barrier and through the shell while the opaque portions block the light. As the candle burns down, more light or more of the design will be apparent. If the inner core candle is transparent or translucent as well, the design is projected by light from the flame passing through the inner core to the barrier even before the core burns down. 
     The candle of the invention does not have any air gaps between layers; each layer is in direct contact with the adjacent layer. The invention takes advantage of the transparent properties of the candle materials used to project the image from the barrier between the inner core candle and outer shell. 
     As noted, a preferred barrier is made of PES. In an alternate embodiment, the design is painted onto the inner surface of the barrier as a negative image. The inner core candle is placed or poured inside the painted barrier and then surrounded by a pour of UNICLEAR ETPA. An opaque wax can be used to cover the top edges of the layers to give the appearance of a conventional pillar candle. The outside is then covered with the paper or other wrap that has been treated with a fire retardant coating and glued in place. The wrap may be applied directly to the rigid outer surface of the pillar candle of the invention, or onto or inside a glass or other clear container for the jar candle of the invention. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a perspective view of a first embodiment of the invention; 
     FIG. 2 is a fragmentary, top plan view of the first embodiment; 
     FIG. 3 is a view similar to FIG. 2 but of a second embodiment of the invention; 
     FIG. 4 is a view similar to FIG. 1 of a third embodiment of the invention; 
     FIG. 5 is a view similar to FIG. 1 of a fourth embodiment of the invention; 
     FIG. 6 is a view similar to FIG. 1 of a fifth embodiment of the invention; 
     FIG. 7 is a top plan view of the fifth embodiment; 
     FIG. 8 is a side sectional view of a sixth embodiment of the invention; 
     FIG. 9 is a view similar to FIG. 1 of a seventh embodiment of the invention; and 
     FIG. 10 is a side sectional view similar to FIG. 8 but of a seventh embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings in which like reference numerals are used to refer to the same or functionally similar elements, the invention embodied therein in FIG. 1, is a candle  10  comprising a core of solid fuel that can be burned by a flame  14  on a wick  16  in the fuel. The wick is of know type and gauge for burning the fuel of core  12 . The wick extends into the core and up out of the top of the core for burning the fuel. 
     A flame resistant and heat resistant barrier  18  is provided around the core. The barrier is at least partly, but preferably all transparent for passing light from the flame  14 , out from the center of the candle. The barrier is preferably heat resistant plastic and about 0.01 to 0.5 inches thick. A clear, rigid, outer shell  20  of shell material about ½ inch thick from barrier to its outer surface, is placed around the barrier for passing light from the flame to an outer surface  22  of the shell. 
     The candle  10  of FIG.  1  and FIG. 2, includes an opaque pattern  24  on the inner surface of barrier  18  for modifying light from the flame  14  for projecting an image of the pattern and a translucent wrap  26 , e.g. of paper, at the outer surface  22  of the shell receives the projected image of the pattern at  28 . As illustrated in FIG. 2, the shell may itself be contained in an outer container  30 , e.g. of glass, onto which wrap  28  is glued, to from a jar candle, or as illustrated in FIG. 3, the shell  20  may be free standing with wrap  26  glued to the outer surface of the shell directly, and from a pillar candle. 
     FIG. 4 shows another embodiment of the invention where a pattern  25  is formed, e.g. of black paint or ink on the inner surface if barrier  18 , and projects image  29  to the outer surface of the shell. Although both the core  12  an shell  20  may be clear, or the core may be translucent or opaque, a thin translucent or opaque layer of wax  32  may be applied over both to hide the top edge of barrier  18  and to make the candle look more like a common pillar candle. Top layer  32  also confines and reflects the light more effectively and thus intensifies the projected image  29 , which, in any case, moves and shiners in an animated manner due to the normal flickering of flame  14 . 
     FIG. 5 shows a candle according to the invention, which includes at least one decorative item such as a silk flower  34  or pieces of well-know brands of wrapped candy  36  or unwrapped candle  38 , in the shell  20 , which are visible through the transparent material or medium of the shell and protected from the heat of the flame by the barrier  18 . The light from a flame on wick  16  also illuminated and animated the decorative items in a novel and entertaining way according to the invention. Although only a few items  34 ,  36  and  38  are shown, and these may be real items, or simulated versions of these items, the invention is meant to include at least one item in shell  20  or as many items as can be fit in the volume of shell  20 . Non-limiting examples of the real items are candies, silk flowers or parts thereof, real flowers, berries or other botanicals or other small decorative items that fit in medium shell  20 . Non-limiting examples of the simulated items may be cast from UNICLEAR, wax or other moldable, injectable or castable material. 
     FIGS. 6 and 7 illustrate an example of the invention which comprises a barrier  18  filled with UNICLEAR-based gel  12  and a wick  16  for burning the gel, a clear UNICLEAR-based solid medium  20  abound the barrier, and real jellybeans of different colors  40 , packed and substantially filling the shell  20 . The shell medium may only be present in the voids between adjacent jellybeans. The shell and encased jellybeans are held within an outer glass wall or jar  42 . A few jellybeans  44  are encased in an upper layer of the core material  12  so that it looks as though the jar  42  is a candy jar filled with jellybeans. Jellybeans  42  can also hid or obscure the top edge of the barrier  18  to further enhance the illusion of a jar of candy. The jellybeans  40 , 42  may be replaced with cast imitation jellybeans or any other real or simulated decorative items. The decorative items may also be mixed and of different types. For example, the jellybeans or items  42  at the top of core  12  may be a burnable wax or gel material, so as not to hamper burning by the wick  16 , with real jellybeans or other decorative items  40  outside the barrier. 
     FIG. 8 illustrates a variation of the embodiment of FIGS. 6 and 7, where the outer glass container  43  is even more like a candy jar by including a neck  46  that can be closed by a top or lid (not shown). 
     FIG. 9 illustrates the fact that the outer container  48  when it is present, or the shape of the outer surface of the shell  50 , either with or without the paper of other screen materiel for the projector or hidden image version of the invention, can be any cross-sectional shape, i.e. square, pyramid-shaped, oval, rectangular, star-shapes, etc. FIG. 10 illustrates an embodiment of the invention which has a shell of container with an outer shape  52  that is spheroid or ovoid in elevation and in section, with images  54  on or in barrier  18  that case a projected image onto an outer surface or surface material of the container or shell. To this end, the outer surface  52  can be frosted or otherwise treated to hold a projected image, or may be coated or carrier a layer of translucent material that can hold the image. The vertically varying shape  52  has the further advantage of enlarging and/or reshaping the projected image from barrier  18 , that is projected by light from the flame  14  of wick  16 , burning the core fuel material  12 . 
     In each of the embodiments described, the barrier  18  is preferably made from polyethersulfone (PES). The barrier  18  is between 0.01 and 0.5 inches thick, and preferably between 0.03125 inches and 0.1 inches thick. The following illustrates the flame resistance of PES barriers  18  used in the invention. 
     Test 1 
     Thirty-five candles were provided. Seventeen candles contained a BAYER MAKROLON polycarbonate resin heat shield and a wick that was glued midway between the center position and the edge of the shield. Three candles also contained the BAYER MAKROLON polycarbonate resin heat shield, and a wick that was glued ⅛″ off the center position. Fifteen candles contained a BP AMOCO RADEL polyethersulfone resin heat shield, and a wick that was glued midway between the center position and the edge of the shield. 
     All thirty-five candles were placed on metal shelves and tipped to a 15° angle using wood wedges. The candles were positioned such that the wick of the candle was near the highest position of the candle while the candle was tipped, facilitating for direct flame impingement on the heat shield while the candle burned. The candles were burned for 12 hours per day and monitored twice per day, once at six hours and once toward the end of the testing period. 
     Of the thirty-five candles, the seventeen candles having polycarbonate resin heat shields with the wick glued midway were all deformed in some fashion and became charred by the end of the testing. Four candles in this set had also experienced a flashover, two of which melted the UNICLEAR wax such that it flowed under the barrier and flooded the interior of the candle. All four of these candles caught on fire. Eleven candles with a polycarbonate resin heat shield heated the UNICLEAR wax on the other side of the barrier such that it became molten and flowed under the barrier, thereby flooding the candle. 
     The three candles having a polycarbonate resin heat shield with a glued wick ⅛″ off the center position, were similarly deformed and charred. All three of these candles heated the UNICLEAR EPTA on the opposite side of the barrier such that it became molten and flowed under the barrier, flooding the candle. 
     Thirteen candles having a PES heat shield showed some evidence of charring, but only at the end of the test. 
     Candles with a polycarbonate resin heat shield had shown significantly more deformation and charring than the candles with a PES heat shield. 
     Making the Candle 
     To manufacture candles of the invention, various methods can be used. 
     Method 1: Inside a candle mold, place flame barrier insert  18  around a preformed candle. Place icons or items on side of the insert away from candle. Over-pour preformed candle, insert and icons with appropriate candle making material to form finished product. 
     Method 2: Fill flame barrier insert with appropriate candle making material and allow to cool (optional—processing can continue while cooling/solidification occurs under proper system design). Place this combination inside of a candle mold, adding icons to the side of the barrier away from the candle making material Over-pour insert/candle making material and icons with appropriate candle making material (same as or different from original material) to form finished product. 
     Method 3: Using a pre-selected container, such as a jar, place flame barrier insert into jar. Place a preformed candle within insert. Place icons on side of insert away from the preformed candle. Over-pour preformed candle, insert and icons with appropriate candle making material. 
     Method 4: Using a pre-selected container, such as a jar, place flame barrier insert into jar. Fill flame barrier insert with appropriate candle making material and allow to cool/solidify (optional—processing can continue while cooling/solidification occurs under proper system design). Place icons on side of insert away from the candle material. Over-pour insert/candle material and icons with appropriate candle making material (same as or different from original material) to form finished product. 
     Compositions 
     Examples of the compositions for the core and shell, and, where wax-like material is used to cast the simulated decorative items or “icons” as they are sometimes called, the composition for the icons, are as follows. 
     
       
         
           
               
            
               
                   
               
               
                 CORE AND SHELL 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Preferred % 
                 Permitted 
               
               
                   
                 Ingredient 
                 by Weight 
                 Range (wt %) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 UNICLEAR 80 ETPA 
                 31.25 
                 18-65 
               
               
                   
                 Mineral Oil #7 
                 37.25 
                 20-75 
               
               
                   
                 Capric/Caprylic 
                 25.00 
                  0-35 
               
               
                   
                 Triglyceride 
                 2.00 
                 0-7 
               
               
                   
                 Myristic Acid 
                 2.00 
                 0-7 
               
               
                   
                 Hexylene Glycol 
                 2.50 
                  0-12 
               
               
                   
                 Fragrance 
                 0 
                 0 
               
               
                   
                 Pigment 
                 0.01 
                 0-1 
               
               
                   
                 Dye 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 ICONS 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Preferred % 
                 Permitted 
               
               
                   
                 Ingredient 
                 by Weight 
                 Range (wt %) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 UNICLEAR 80 ETPA 
                 52.75 
                 18-65 
               
               
                   
                 Mineral Oil #7 
                 44.74 
                 35-82 
               
               
                   
                 Capric/Caprylic 
                 0.00 
                 0 
               
               
                   
                 Triglyceride 
                 0.00 
                 0 
               
               
                   
                 Myristic Acid 
                 0.00 
                 0 
               
               
                   
                 Hexylene Glycol 
                 2.50 
                  0.1-12.0 
               
               
                   
                 Fragrance 
                 0.01 
                 0-1 
               
               
                   
                 Pigment 
                 0.00 
                 0 
               
               
                   
                 Dye 
               
               
                   
                   
               
            
           
         
       
     
     General Considerations 
     Barrier  18  and the various embodiments of the present invention serve several purposes. The barrier  18  prevents the naked flame from coming into contact with the various icons or decorative items placed around the candle and beyond the barrier. In this capacity, the barrier  18  serves as a safety device. The barrier  18  sets the patterns for the burning properties of the candle. This means, that the candle will burn in a manner that is controlled by the diameter and the design of the core fuel in the barrier  18 . In most cases, this would be a straight down burn varying in diameter by the diameter of the barrier. The flame barrier also serves to preserve the aesthetic properties of the candle. This is achieved because the flame, which is restricted to the barrier area, does not consume the total candle. As a result at the end of the useful life of the candle, the consumer still has a decorative display item which is substantially the same in appearance as it was when it was first purchased. 
     While polyethersulfone is a preferred material for the barrier  18 , other plastics having similar combustion properties may be used as well. 
     The plastic material of the barrier should soften at a temperature of about 215° C. and melt at about 230° C. These tolerances can be controlled by selection and design of the polymer and can be achieved by those having ordinary skill in the field of plastics. The plastic must not readily support combustion, however, and should be invisible or nearly invisible when cased between the core and shell. The plastic should be intumescent and have a UL94 flammability rating of V-0. As noted above, manufacturing can be by extrusion or molding. 
     While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.