Thermoplastic foam products can be labeled or marked while molding, but if made from non-label molded products, such as foam board and many other products, they present a problem with marking the product with a trade-name, trademark, logo, address, patent notice, etc. Most adhesives, paint and the like will not adhere permanently to the surface of the foam product, usually not at all. While some adhesives have been proposed for adhering labels to polymer foam, these are expensive and can present hazards when the labels are peeled off by young children. Thus, it has been necessary to either foam the polymer against a mold containing the desired marking, in which the formed part often sticks in the small indents or raised places on the mold, or the use of a costly, difficult adhering process like that disclosed in Pub. Pat. Application No. 20030068470, and one or more patents having a similar approach. There is a long felt and very substantial need to mark thermoplastic foam products, and other foam products like cryogenic insulation, etc., in a permanent, durable, relatively inexpensive and attractive manner.
The invention comprises systems and methods for marking, applying one or more of visible letters (in any language including picture words or letters like Kanji, Arabic, and the like), numbers, numerals, symbols, logos, drawings, and other desired images into the surface portion of a meltable and/or thermoplastic materials and products, including polymers, resins, sugars, candies, and low melting point metals having a void or gas pocket content in the surface portion to be marked of at least about 5 or 10 or 15 or 20 or 25 or 30 percent by weight or any percent in between these numbers, and can have 3 percent by volume up to 95 percent by volume or any percent in between these numbers, and products so marked. The marks include grooves, valleys or holes or the like having a depth of at least about 0.01 or 0.02 inch but preferably a greater depth. The depth of the mark often depends to some extent upon the size of the product being marked. Often the void, or gas bubble, content of the material or product to be marked will often exceed about 10 volume percent such as to include any incremental amount of about 5 or 10-99 percent based on the density of the base material, preferably from about 15 to about 90 volume percent and most preferably about 20 to about 90 volume percent. As a further marking step, the grooves, valleys and/or holes can be coated, partially filled, completely filled or slightly over filled to with a material that will set up to form solid material, preferably one that is of a contrasting color and/or at least as flexible as the material or product. Some of these foam items can have densities of 0.01-1 gm/cc and lower, and much higher in other items, particularly metal, glass and ceramics. Typically, polymer foam items have densities higher than 0.1 gm/cc, often in the range of 0.01-2 gm/cc.
The present invention includes methods of marking the above described materials including thermoplastic foam items or products, such as placing a logo, trade-name, trademark, patent notice, or other desired letters, numbers and the like into thermoplastic foam parts while leaving surrounding areas of the surface of the foam in a shape that is not unattractive to consumers and that does not negatively affect the use of the product by bringing an item close to the surface of the material or product, the item being sufficiently hot to melt the material or product surface portion in the vicinity of the item to a depth of at least about 0.03 inch (while the hot item can include many things, those preferred include a hot branding tool, a hot focused flame, a hot wire or rod, a hot energy beam and a hot stream of gas of a desired small diameter). These methods comprise the following different techniques:
1) a method of marking a surface portion of a thermoplastic foam item comprising heating a branding iron having the shape of the desired label comprising shapes comprising letters, numbers, logo(s) and the like with each having specially shaped sides including tapered and/or L shaped, heating at least the contacting ends of said shapes to a temperature significantly higher than the melting point of the thermoplastic foam and applying the hot contact ends of said shapes to a surface of the thermoplastic foam allowing said contact ends to melt into the thermoplastic foam a desired distance and removing said contact ends from said thermoplastic foam a distance to prevent any further deformation of the thermoplastic foam, or
2) a method comprising moving a very hot wire or small rod or other suitable shape while very close to the surface of the foam item, or at times below the surface, in a manner to melt the foam that is close to the very hot wire or rod to form one or more grooves forming the desired marking, or
3) a method comprising moving one or more laser beams of the appropriate type and intensity to melt form one or more grooves in a foam item forming the desired foam item, and
4) optionally, adding paint or a coloring or material of contrasting color to at least a portion of the one or more grooves formed by the methods of 1 and/or 2 and/or 3 above.
5) a method comprising heating a thermoplastic coloring material to produce a hot liquid having a temperature that will cause a thermoplastic foam to collapse beneath an applied stream of the hot liquid placed on a surface of the thermoplastic foam item, applying a stream of said hot liquid to the surface of the thermoplastic foam item in a desired pattern, allowing said applied stream to recede into the foam while leaving the immediate surrounding foam relatively unaffected to the eyes of an observer thus leaving a pattern of contrasting color in the thermoplastic foam item. Optionally, the thermoplastic coloring material can be of a composition that it will expand slightly following application such that when cooled and solidified it will be even more tightly attached to the thermoplastic foam item. The stream can be applied by mounting a heated pot containing the hot liquid and having an outlet with a controllable valve, etc. onto an XYZ positioner and programming the movement of said pot and the opening and closing of said controllable valve to apply the hot liquid in the desired pattern.
6) an optional step comprising using an X Y positioner, or an X Y Z positioner to move the various apparatus used to practice the methods set out in the methods of methods 1-5 set out above and programming said positioner and said apparatus with on and off control and optionally other control to melt a desired pattern onto and into the surface portion of a thermoplastic foam item to one or more desired depths. Optionally, the pattern can then be at least partially filled with a material of contrasting color, optionally an elastomer material and optionally a material that will expand some during curing to even more firmly grip the interior of the pattern. Also optionally, materials of different colors can be applied to different parts of said pattern in the same manner and with the same optional features.
The invention also includes systems, combinations of apparatus used in the methods described above including one or more of the following:
1) a branding iron having tapered sides on one or more sides of patterns to form the desired label, mark, or having an inverted T shaped continuous or discontinuous branding iron that when it melts the foam directly under the brand will form a desired grooved pattern, a device to heat the branding iron quickly to the desired temperature desired for branding and a mechanism for moving the branding iron first to the heating device, then to the proper position for forming the one or more grooved pattern(s) and then back to the heating device,
2) an X-Y positioning device or an X-Y-Z positioning device holding a tube, a gas source and the tube connected to a gas source, the tube being heated to a temperature sufficient to melt thermoplastic foams, a heater for heating the gas while moving through the tube and a programmable device for guiding the X Y positioning device or X Y Z positioning device to locate an end of the tube close to the surface of the thermoplastic foam and to move the tube in a path and at a rate for producing a desired grooved label,
3) an X Y positioning device or an X Y Z positioning device holding a wire or rod that can be heated, preferably with electrical resistance, to a temperature sufficient to melt thermoplastic foams, an apparatus for heating the wire or rod and a programmable device for guiding the X Y positioning device or X Y Z positioning device to locate an end of the wire or rod close to the surface of the thermoplastic foam and to move the tube in a path and at a rate for producing a desired grooved label,
4) an X Y positioning device or an X Y Z positioning device holding a flame source and a flame having a temperature sufficient to melt TPPFP including thermoplastic foams and a programmable device for guiding the X Y positioning device or X Y Z positioning device to locate an end of the tube close to the surface of the thermoplastic foam and to move the tube in a path and at a rate for producing a desired grooved label,
5) an X Y positioning device or an X Y Z positioning device holding a laser and directing a laser beam of a temperature sufficient to melt a thermoplastic foam, and a programmable device for guiding the X Y positioning device or X Y Z positioning device to move the laser beam in a path, at the desired intensity or percentage of the laser's power, and at a rate for producing a desired grooved label,
6) an X Y positioning device or an X Y Z positioning device holding a container of coloring or colored material and for activating and deactivating an orifice in or on the container to release a small stream of the contents and a programmable device for guiding the X Y positioning device or X Y Z positioning device to move the container in a path and at a rate, while activating and deactivating the orifice for producing a desired color in the grooved label, alone or in combination with any of (1) through (5) above, and
7) an X Y positioning device or an X Y Z positioning device holding a container of hot, molten coloring or colored material and a mechanical or hydraulic activating and deactivating device on an orifice in or on the container to release a small stream of the contents, a heater for keeping the container hot, the temperature of said material being sufficient to melt a groove in a thermoplastic foam a desired depth, and a programmable device for guiding the X Y positioning device or X Y Z positioning device to move the container in a path and at a rate, while activating and deactivating the orifice for producing a desired pattern in the thermoplastic foam item. The size of the stream, the temperature of the stream and the heat capacity and coefficient of thermal conductivity of the material in the stream determine the width and depth of the marking, alone or in combination with any of (1) through (5) above, and
8) a laser emitting tube arranged with an X-Y positioning device, or an X-Y-Z positioning device directing the laser beam of an intensity and duration sufficient to melt or deform a thermoplastic or meltable foam, and a programmable device for guiding the X-Y or X-Y-Z positioning device to move the laser beam in a path, at the desired intensity or percentage of the laser's power, and at a rate for producing the desired marked, grooved mark or label,
9) one or more lasers with or without one or more Z positioners, i.e. for moving up and down, for the laser(s) with one or more mirrors, preferably one or more movable mirrors, to change the laser beam(s) and to rapidly direct them to produce the desired mark in a more rapid manner than that produced by system (8) just above,
10) an ink jet printer, or equivalent printer, in combination with the laser systems of either (8) or (9) above such that following the laser(s) making the desired mark, the printer then afterwards prints a contrasting color into all or part(s) the mark,
11) an ink jet printer, laser printer or any known (at the time of use) and suitable printer, in combination with the laser systems of either (8) or (9) such that the ink jet printer first prints the mark, or part(s) of the mark onto the foam product, followed by the laser(s) melting the ink alone or the ink and foam just below the mark, both locking the ink mark into the foam,
12) a device (many are known) to move a particle dispenser to lay a thin layer of particles of contrasting material (color, texture, or the like) on the surface of the foam product covering at least a part of the mark and a laser system described in (8) or (9) above to heat at least the particles in at least a portion of the mark to cause the particles to either melt or to melt the foam just below the particles such as to lock the particle melt or particles into the foam, optionally forming the rest of the mark in the area(s) of the desired mark not covered with said particles.
Finally, the invention includes the marked products made by the methods and systems described above.
The marked products, systems and methods disclosed herein have marks made by melting one or more grooves or holes or other shaped depressions in TPPTP products or products made from meltable foam materials. One or more of the systems and methods results in a product in which a hot melt, preferably of a contrasting color to the foam product, forms the grooves or holes and at least partially fills the groove(s) and/or hole(s). While often the foam product will be a resin or polymer, the foam product can also be inorganic materials like foamed glass, foamed metal, foamed alloy and foamed ceramic items including foamed hydraulic set items like foamed cement, foamed plaster of Paris, foamed concrete and similar foamed items. Some of the thermoplastic and meltable polymer foam items include items made using polyethylene, polypropylene, polystyrene, polyurethane, elastomers, urea formaldehyde, polycarbonate, ABS, PPO, PVOH, PVC, nylon, acrylic, polyester, and other meltable organic foam materials.
Other embodiments involve painting or at least partially filling the one or more holes and/or grooves with a material, preferably of a contrasting color to the foam product, that dries or sets up to form a flexible material bonded to or locked in to said hole(s) and/or groove(s). The depth of the grooves, holes, or other shaped depressions are really a matter of choice to provide the desired visibility, but typically can vary from just enough to easily see the mark to from about 0.03 (0.76 mm) to as deep as desired, usually less than 0.5 (12.7 mm) inch and often less than 0.3 inch (7.6 mm), however, the one or more hole(s) and/or groove(s) can penetrate the entire thickness of the foam product when desired, and should be deep enough that one can readily see the mark.
Herein, when a range of number values is disclosed it is to be understood by those of ordinary skill in the appropriate art(s) that each numerical value in between the upper limit and the lower limit of the range is also disclosed, to at least 0.01 of a full number. Thus in a range of 1 to 10, this includes 2.04 to 10, 3.06 to 8 or 8.50, and so on. The addition of a new limitation in a claim previously stating from 2 to 7 changing it to from 3-7 or 4-6 would not introduce new matter whether those new ranges were specifically disclosed in the specification or not because of this explanation of the meaning of a disclosed broader range, such as 1-10. This meaning of a range is in keeping with the requirement in 35 USC 112 that the disclosure be concise.
Further, when the word “about” is used herein it is meant that the amount or condition it modifies can vary some beyond that stated so long as the advantages of the invention are realized. Practically, there is rarely the time or resources available to very precisely determine the limits of all the parameters of one's invention because to do so would require an effort far greater than can be justified at the time the invention is being developed to a commercial reality. The skilled artisan understands this and expects that the disclosed results of the invention might extend, at least somewhat, beyond one or more of the limits disclosed. Later, having the benefit of the inventors' disclosure and understanding the inventive concept and embodiments disclosed including the best mode known to the inventor, the inventor and others can, without inventive effort, explore beyond the limits disclosed to determine if the invention is realized beyond those limits and, when embodiments are found to be without any unexpected characteristics, those embodiments are within the meaning of the term “about” as used herein. It is not difficult for the artisan or others to determine whether such an embodiment is either as expected or, because of either a break in the continuity of results or one or more features that are significantly better than reported by the inventor, is surprising and thus an unobvious teaching leading to a further advance in the art.
The first method comprises using a branding tool, such as that shown in photos labeled
The branding tools can be heated to a temperature that will melt or at least melt the foam product being marked by any suitable manner such as with a torch, hot air, electrical resistance, etc. Another way to heat the branding tool is to set it, letters, numbers etc. against a hot surface of a hot plate 62 as shown in
A modification of the method just described is to add another step of either painting a portion or all of the interior surface(s) of the marking(s) in the TPPFP, or partially or completely filling or over filling them with a liquid or paste or caulk of a desired color that will set up to form a durable contrasting material, preferably a flexible material, making the marking more readily seen and more impressive. Some examples of suitable materials are commercial latex paints, silicon rubber, caulking products, caulking material for concrete, especially for swimming pools and walks, etc. surrounding swimming pools. Due to some unevenness of the surfaces of the groove(s) the paint or filling material will be locked into the groove(s). The groove filling material can be made more colorful if desired by blending in one or more appropriate pigments or colorants that will not interfere with the setting up and/or durability of the groove filling material. An example of a TPPFP, foam board, partly marked by this technique is shown in
The vessel 1 shown in
The marking tool shown in
Just a few of suitable filler materials for partially, fully or over-filling the grooves, holes, etc. in the TPPFP products to give further contrast and enhancement of the mark include latex paints, flexible paints, preferably quick drying, Quickcrete® polyurethane Self-Leveling Sealant and acrylic Self-Leveling Sealant, and Quickcrete® mortar repair, concrete repair products, siliconized acrylic colored caulks called Bonsai manufactured by Color Fast Tile and Grout Caulk, WEATHERMASTER SEALANT (polyether and available in many colors, ASi 502 Silicone Sealant RTV Translucent Colors, Sikaflex 1a construction sealant manufactured by Sika Mexicana, SA, in Mexico, flexible waxes and thermoplastics of various types including the type used to make the grooves while also filling them, but heated to a temperature that will not significantly further melt the foam surface inside of the grooves. Many other filler materials can be used that are similar to these materials and also substantially different, but preferably are materials that will have a significant degree of flexibility upon drying, setting up and aging so as not to break up or chip easily with age and use.
Many of the marks made and shown in the figures identified above were made by hand and thus are not optimum in shape and uniformity, but can be made so with the marking tools or hot liquid application and the painting and/or groove filling devices moved with a programmed X-Y or X-Y-Z positioning machine and with the temperature of the branding tools and the hot liquid controlled within an optimum range, all of which is within the ordinary skill of the art and will depend upon the type of TPPFP being marked and the type of groove filling material.
Any of the branding tools, hot wires or rods or other hot melting tools including lasers, flames, hot gas tubes and other marking, painting or filling tools disclosed herein can be used to form the most precise marks by either mounting them on X-Y or X-Y-Z positioners or by keeping them in place and moving the TPPFP product with an X-Y or X-Y-Z positioner programmed to provide the desired mark. Some suppliers of X-Y and/or X-Y-Z positioners include Newmark Systems, Inc. of Rancho Santa Margarita, Calif., Zaber Technologies, Inc. of Vancouver, BC, Canada and HIS Engineering 360 website. It is well known how to set up such equipment and controlling programs to produce the desired mark. It is also within the ordinary skill of the art to determine the best temperature for the marking tools, the speed of movement of the tools, the positioning of the marking tools with respect to the surface of the TPPFP products, the depth of the mark to achieve the desired appearance, the appropriate painting materials or grove filling materials to achieve the desired appearance of the marks.
The laser unit was a fixed CO2 laser tube that emitted a laser beam that was reflected through a series of mirrors, some of which were movable to allow transmission of the laser beam to the desired location relative to the surface of the product being marked. The mirror through which the beam ultimately passed before contacting the surface of the foam product to be rastered, marked, engraved or labeled was moved horizontally and longitudinally in the same manner similar to an inkjet printer head in a common office inkjet printer. The beam was focused through a lens such that the beam contacted the foam board surface on or below said surface at the desired depth of the groove(s) of the mark, indentation or void. The desired “Z” (vertical) axis positioning was achieved by adjusting the level on which the foam board was placed relative to the mirror/lens unit focusing the laser beam through the lens, or adjusting the height of the mirror/lens unit focusing the laser beam through the lens, or adjusting the height of the mirror/lens unit relative to the surface of the foam board such as by mounting the laser on an X-Y-Z positioner. This can, in another embodiment, involve an X-Y positioner coordinating with movement of what is commonly referred to as a “Z” table (the surface on which the foam board product is mounted).
The pattern, design or indicia imparted to the foam board product was created in a commonly available illustration/design/photo manipulation software program, such as Adobe Illustrator, Adobe Photoshop, Corel Draw, etc. The desired art was then saved as a bitmapped or vector based image depending upon the nature of the image. Alternatively, said desired mark can be simply scanned from a hard copy (printed) image and the file saved as a bitmapped file in a format such as JPEG of BMP. Vector based images permit both rastering, engraving as well as vectoring (cutting) laser functions, whereas bit-mapped based imaged permit only laser rastering. Vector based images are also fully-scaleable without a decrease in detail—unlike bit-mapped images which do not enlarge without a decrease in resolution. The saved art file is then sent to the laser in the same manner as art to be printed on a piece of paper would be sent. The ability to send files to rastered, marked or vector cut by the laser is an increasingly common feature found on commercially available lasers such as the H-Series 20×12 CO2 laser made by Full Spectrum Lasers (FSL) of Las Vegas, Nev. Other suitable commercially available CO2 lasers, such as those made by FSL, Boss Laser of Sanford, Fla., Epilog and Universal are also suitable.
Once the relative height or distance between the focusing lens and foam product surface has been set, the placement of the foam product in relation to the X and Y axes of the laser unit must be confirmed. This is accomplished by establishing and verifying that the start point on the foam product corresponds to the starting point where the laser will first contact the foam product. The depth of the groove(s), hole(s), indent(s) or void(s) to be created with the laser melting the foam can be determined by the following factors:
a) varying the percentage of the laser tube's total power or intensity. The minimum strength recommended is a 30 watt CO2 laser tube. Stronger laser tubes can be used, but depending on the type of foam being marked, the power may need to be “dialed down” to avoid burning completely through the foam or the first pass, or “dialed up” to obtain the desired depth of the mark.
b) The number of passes the laser head makes over the area of the product being marked.
c) The speed of movement that the laser head or laser beam makes over the area being marked. How fast or slow the laser beam is moved over the area being marked will determine the duration that the laser beam is focused on any given area, thus how long it is subject to the melting action of the beam.
d) Whether the area being marked is rastered, engraved, vectored, or a combination of both.
Some experimentation may be required to arrive at an optimal combination of the factors listed above to achieve the desired mark(s). The nature of the foam of the product, its density, the melting point of the foam material, nature of the art being used for the mark in the foam and strength of the laser will all impact the speed of the marking process and the mark's final appearance. Varying these factors can result in extremely subtle marking with grooves or indentations of less than 0.01 mm deep to complete vaporization of the foam material resulting in holes or channels extending from the top of the foam surface straight through to the bottom, depending upon the thickness of the product, or as deep as desired within reason. By varying the factors listed above, the edges inside the grooves, channels and/or indentations created by the laser beam can be made smooth and the foam itself annealed creating a smooth, even finish if so desired.
Because the laser beam often vaporizes part of the foam material it is important to vent the fumes created by the process out of the work area, or preferably capture them in an activated carbon filter, to prevent the operator and others from breathing in potentially hazardous fumes. Commercial lasers provide a small jet of compressed air to be blown onto the area being hit by the laser to prevent fires and blow away any debris. It is important for safety and health to be sure that this air stream is fully functioning while the laser is working. Since the air stream is generally not varied, it is considered a constant in determining the correct mix of variables that produce the desired groove(s), indentation(s) and/or void(s) created by the laser. Also, standard safety precautions are recommended such as wearing appropriate eye protection, not operating the laser with the safety shield up, and never leaving the laser unattended while operating. For best practice the laser operator should have a CO2 fire extinguisher in good order on hand in the event of a fire.
The laser made grooves making the logo mark shown in
The method utilizing a laser produced the markings shown in
1) In the case of the text “GOZUNDA™” as shown in
2) In creating both the laser engraved foam surface shown in
3) The Full Spectrum Laser H-Series 20×12 laser comes with Retina Engrave® software, which allows a COREL DRAW® file to be sent to the H-Series laser simply by choosing the laser as an output “printer”. Once the “Full Spectrum Engineering Driver” is chosen as the filed output device, the following settings must be put in place:
a) Landscape orientation layout.
b) Under “Preferences” tab on the right
The following is a brief list of considerations common to imparting an image using laser rastering, marking:
a) The pattern, design or indicia, logo, etc. to be imparted to the foam may be created not only in Adobe Photoshop®, but also in a commonly available illustration/design/photo manipulation software programs such as Adobe Illustrator,® Corel Draw®, etc. Alternatively, said pattern, design or indicia can be simply scanned from a hard copy (printed) image and the file saved as a bit-mapped file in a format such as JPEG of BMP, and then imported into COREL DRAW® to be translated into vector based files.
b) Vector based images permit both rastering (engraving, marking, etc.) as well as vectoring (cutting) laser functions, whereas bit-mapped based imaged permit only laser rastering. Vector based images are also fully-scaleable without a decrease in detail, unlike bit-mapped images which do not enlarge without a decrease in resolution.
c) The ability to send files to be rastered or vector cut by the laser directly is an increasingly common feature found on commercially available lasers such as the H-Series 20×12 CO2 laser made by Full Spectrum Lasers® (FSL) of Las Vegas, Nev. Other suitable commercially available CO2 lasers, such as those made by FSL, Boss Laser® of Sanford, Fla., Epilog® and Universal®.
d) The laser unit consists of a fixed CO2 laser tube that emits a laser beam that is reflected through a series of mirrors, some of which are moveable to allow transmission of the laser beam to the desired location relative to the surface being processed. The mirror through which the beam ultimately passes before contacting the surface to be rastered or cut is moved horizontally and longitudinally in the same manner similar to an inkjet printer head in a common office inkjet printer. The beam is focused through a lens such that the beam contacts the foam surface on or below said surface at the desired depth of the groove, indentation or void. The unit that holds the last mirror, the lens and the opening of the low-pressure air hose is called the laser head unit. The optimal distance between the laser head unit and the surface to be worked on is set using a set focal length reference tool, which comes with the laser.
The laser made grooves making the logo mark shown in
Instead of mounting one or more lasers on an X-Y or X-Y-Z positioner to move the laser(s) to form the mark it is also known to avoid an X-Y positioner and in some instances either the Z positioner and instead use one or more mirrors, usually movable in ways including the angle of reflector, by rotation or movement in the X, Y, and/or Z direction, to direct one or more laser beams to make the mark in a much faster manner than using an X-Y positioner. These systems are well known and are mentioned and/or cited and/or described in U.S. Pat. Nos. 5,786,594, 6,313,433, 6,423,925, 7,060,934, 8,101,883, 8,294,062, and 8,599,898, and also U.S. Published Application No. 20150183231, the disclosures of which, including the prior art and the patents cited therein, are hereby incorporated herein by reference. At least some of these systems are available from Universal Laser Systems® Inc. of Scottsdale, Ariz.
Different embodiments employing the concept and teachings of the invention will be apparent and obvious to those of ordinary skill in this art and these embodiments are likewise intended to be within the scope of the claims. Just one example of this is to use a robot or other positioning device to position the various systems disclosed above in the manner or similar manner described to achieve the disclosed results. The inventor does not intend to abandon any disclosed inventions that are reasonably disclosed, but do not appear to be literally claimed below, but rather intends those embodiments to be included in the broad claims either literally or as equivalents to the embodiments that are literally included.
This application claims the benefit of the filing date of Provisional Patent Application No. 62/386,997 filed on Dec. 17, 2015. The present invention includes labeled or marked thermoplastic foam items, systems and methods for marking thermoplastic foam items, including polymer and resin foams, inorganic foams like glass and ceramic and metal foam products, with special grooves forming letters, numbers, logos, symbols, and other desired images, including optionally filling some or all of the grooves with a contrasting material.
Number | Date | Country | |
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62386997 | Dec 2015 | US |