Abstract:
A carpet seaming iron includes a platen, a heating element conductively coupled to the platen, and a passageway interposed between the platen and handle. The passageway is configured to accommodate a piece of seaming tape over the platen and under the handle of the seaming iron. The handle is designed to protrude between adjacent pieces of carpet that are to be seamed together. The seaming iron may be used to make a seam using a seaming tape having thermal adhesive on an upper side, by heating the seaming tape from below. Advantageously, a seam may be completed without contact between the thermal adhesive of the seaming tape and the platen of the seaming iron.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims priority pursuant to 35 U.S.C. § 119(e) to U.S. Provisional Application No. 60/396,921, filed Jul. 16, 2002, which application is specifically incorporated herein, in its entirety, by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to methods for seaming of carpeting and like materials using thermoplastic adhesive seaming tape, and to tools for activating carpet seaming tape.  
           [0004]    2. Description of Related Art  
           [0005]    In the installation of carpeting materials for the construction trades, it has become a common practice to seam join along abutting edges) adjacent pieces of carpeting together using an adhesive tape that is run along the seam line. The adhesive tape comprises a reinforcement scrim for spanning the seam line together with an adhesive for bonding the scrim to the back layer of the adjoining carpet pieces. Many tapes also include a backing layer of paper or like material to prevent the adhesive from sticking to the floor under the tape.  
           [0006]    Most adhesive tapes employ a thermoplastic, hot-melt adhesive for bonding the scrim to the carpet backing. The adhesive is activated by heating, usually with a heating iron such as generally described in U.S. Pat. No. 4,536,244 (Greci, et al.) FIG. 1 shows an exemplary prior-art carpet seaming iron  20  used for seaming adjoining pieces of carpet  30  together. Prior-art iron  20  has a lower heated platen  22  that is connected to a handle  26  by a blade-like handle support  27 , which is in turn connected to a heat shield  24  that may be mounted to platen  22  and insulated from it by an insulating gasket  23  and other interior insulating materials (not shown). Electric power may be supplied via a cord  28 .  
           [0007]    Seaming iron  20  is operated to direct heat onto the adhesive  40  of adhesive tape  34 . Tape  34  is placed between the floor  32  (which may be covered by a cushioning pad or other covering) and carpet  30 , with the adhesive  40  facing the back of the carpet. Scrim  38  may be in or below adhesive  40 , and a backing paper  36  may be underneath both the scrim and the adhesive.  
           [0008]    To make the seam, an operator gradually moves the iron  20  along tape  34 , melting the adhesive  40 . Shield  24  protects the carpet  30  from being damaged by heat from the platen  22  as the seaming iron is moved underneath the carpet. At the back of the iron (not shown), the operator presses the carpet backing into the molten adhesive, and holds the carpet in place until the adhesive cools.  
           [0009]    The prior-art seaming method as just described is well-proven in practice, but suffers from some limitations. One limitation is that it is relatively difficult to deposit adhesive between the vertical abutting edges  31  of the carpet backing using the method. Bonding of the vertical abutting edges together is desirable, to strengthen the seam, prevent carpet tufts from falling out of the backing, and to bring the centroid of the seam bond closer to the carpet backing, thereby reducing the bulging (“peaking”) of the seam that is sometimes apparent when the carpet is placed into tension transverse to the seam line. A central groove  21  or other channeling feature is sometimes placed in platen  22  to help direct adhesive between edges  31 , but it can be difficult to meter a proper amount of adhesive onto the edges  31  while performing the other tasks required to finish a seam. Adhesive is sometimes placed directly along edges  31  using a separate adhesive spreading tool, but this requires an additional step.  
           [0010]    A further limitation of such prior art methods is that additional effort is required to align the adhesive tape with the carpet seam, because there is no positive alignment between the adhesive tape and the seaming iron. This additional effort may distract the operator from moving the seaming iron at a constant, well-paced speed and from forming a proper bond using the molten adhesive. Also, to compensate for the possibility of misalignment, adhesive tapes may be somewhat wider than is needed for optimal seam strength.  
           [0011]    Yet another limitation of prior art seaming irons is that direct contact between the hot platen  22  and the hot-melt adhesive can lead to undesirable buildup of adhesive on the platen. Such adhesive build-up may cause problems if it is driven into the interior of the iron, such as by failure of gasket  23 . The build-up may also leave undesirable residue on other objects when the seaming iron is set aside after a seam is completed, or may become overheated and generate undesirable smoke or fumes when the iron is idled.  
           [0012]    It is desirable, therefore, to provide a seaming iron and method that overcomes the limitations of the prior art.  
         SUMMARY OF THE INVENTION  
         [0013]    The present invention provides a carpet seaming iron that prevents direct contact between the adhesive of an adhesive tape and the iron platen, provides for positive alignment between the adhesive tape and the seam line, and facilitates placement of molten adhesive on the abutting vertical edges of the seam. The iron is relatively inexpensive to build and operate, and easy to use. Proper use of the iron according to the method of the invention may eliminate adhesive build-up on the seaming iron, allow for perfect alignment of the seaming tape with the seam, and conveniently ensure that adhesive will be placed in optimal locations in the seam.  
           [0014]    The seaming iron according to the invention comprises a heated platen that is placed underneath the adhesive tape; not on top of it as with prior-art seaming irons. The seaming iron further comprises a bridge that connects the platen to a handle. A passageway is defined between the bridge and the platen, through which the adhesive tape may pass through and be disposed over the heated platen. The platen is designed to heat the adhesive through the backing of the tape, so no adhesive need contact the hot platen. Sidewalls of the bridge, or other guide features, may be used to direct the adhesive tape over the platen and along the seam line. A handle may be attached to the bridge by a blade-like support that permits the seaming iron to easily pass between abutting pieces of carpet. An insulating layer may be placed under the platen to protect the floor from the heat of the platen.  
           [0015]    To use the new seaming iron, it may be drawn along the seam between abutting edges of the carpet in a manner similar to prior-art seaming irons. The adhesive tape is threaded between the bridge and the platen, and passes over the top of the platen, thereby melting the adhesive on the tape. The carpet passes over the bridge and may be pressed down into the adhesive near the rear of the platen. The rear, trailing end of the platen may be maintained at a relatively cool temperature compared to the forward section of the platen, so as to not overheat the carpet backing. In the alternative, the carpet may be pressed into the adhesive after the tape has cleared the trailing edge of the platen.  
           [0016]    In an embodiment of the invention, the upper surface of the heated platen is crowned or contoured so as to bring the abutting carpet pieces together through a layer of molten adhesive as the seaming iron is drawn forward. The contour of the platen may be configured so that an optimal amount of adhesive is deposited between the vertical abutting edges of the carpet during this process. The platen may further be tapered to a thin trailing edge, to guide the seamed carpet back onto the floor.  
           [0017]    A more complete understanding of the carpet seaming iron and method will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the preferred embodiment. Reference will be made to the appended sheets of drawings which will first be described briefly. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    In general, the drawings are intended to illustrate the concepts of the invention in a schematic fashion. It should be appreciated that the drawings do not reflect or limit actual physical embodiments with respect to engineering and design details. The drawing scale is generally arbitrary. Particularly with respect to FIGS.  1 - 3  and  9 - 12 , the vertical drawing scale has been exaggerated somewhat to better illustrate the concepts of the invention. One of ordinary skill in the design of carpet seaming tools will understand appropriate sizes for components of seaming irons according to the invention, without needing to review scaled drawings.  
         [0019]    [0019]FIG. 1 is a front elevation view of a prior-art seaming iron during seaming of carpeting materials.  
         [0020]    [0020]FIG. 2 is a front elevation view of an exemplary seaming iron according to the invention during seaming of carpeting materials.  
         [0021]    [0021]FIG. 3 is a side view of an exemplary seaming iron according to the invention during seaming of carpeting materials.  
         [0022]    [0022]FIG. 4 is a perspective view of an exemplary heating platen for use with a seaming iron according to the invention.  
         [0023]    [0023]FIG. 5 is a rear elevation view of an exemplary seaming iron according to the invention.  
         [0024]    [0024]FIG. 6 is a front elevation of an exemplary heating platen with a crown having zero curvature.  
         [0025]    [0025]FIG. 7 is a front elevation an exemplary heating platen with a crown having negative curvature.  
         [0026]    [0026]FIG. 8 is a side elevation an exemplary heating platen, showing a taper from the leading edge to the trailing edge.  
         [0027]    [0027]FIG. 9 is a side elevation view of an exemplary seaming iron with a crowned heating platen during seaming of carpeting materials.  
         [0028]    FIGS.  10 - 12  are cross-sectional views taken at the successive sections  11 - 12  of FIG. 9, respectively, showing operation of a method for applying adhesive to edges of carpet backing using a crowned iron.  
         [0029]    [0029]FIG. 13 is a flow diagram showing exemplary steps of a method according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0030]    The present invention provides a novel carpet seaming iron, and method of using it, that overcomes the limitations of the prior art. In the detailed description that follows, like element numerals are used to identify like elements that appear in one or more of the drawings.  
         [0031]    Referring to FIGS. 2 and 3, an exemplary seaming iron  50  is shown relative to pieces of carpet  30  that are to be seamed together with adhesive tape  34 . The various elements of iron  50  are shown in a generally schematic, simplified fashion, and the particular shapes depicted are not intended to limit the inventive concept of the iron. Rather, FIGS. 2 and 3 are intended to depict an exemplary overall arrangement and combination of elements of a seaming iron, based on which one of ordinary skill could develop various different engineering designs for the manufacture of irons. In like manner, a seaming iron according to the invention may be constructed using any of the well-known materials currently used for seaming irons, or any other suitable materials. Suitable materials, components, and devices for a particular seaming iron will be evident to one of ordinary skill, without needing information more detailed than the general information provided herein.  
         [0032]    Similarly to a conventional iron, seaming iron  50  is placed under the carpet  30  and over the floor material  32 , with a blade-like handle support  62  supporting the handle  60  between the abutting edges  31  of the carpet. The similarity ends there, however, because seaming iron  50  is not placed on top of adhesive tape  34 . Instead, tape  34  is threaded through passageway  58  formed between bridge  56  and platen  52 , and over the top surface of the platen. Platen  52  is heated, such as by an electric current that may be supplied through cord  64 . Insulator  54  may cover the bottom surface of platen  52 , to protect floor  32  from the platen heat. It may be advantageous to include an air gap (not shown) between platen  52  and insulator  54 . Handle  60  may be a plastic or other non-conductive piece for gripping by an operator and for housing wiring, controls, indicators, and the like.  
         [0033]    The iron  50  is operated by pushing it forward between the abutting edges  31  of carpet  30 . Prior to beginning the seam, a length of adhesive tape  34  is laid out under edges  31 , and the tape  34  is threaded through the passageway  58  at one end. In FIG. 2, the forward or leading end of the iron is indicated by the numeral  72 , and the trailing end is indicated by  74 . The platen is heated to above the melting point of the adhesive on tape  34 , and thus, the adhesive is heated from below as it passes over platen  52 .  
         [0034]    In an embodiment of the invention, the platen is configured so that the tape adhesive is substantially melted as it passes through passageway  58 . It may be necessary to make passageway  58  somewhat longer, such as by making bridge  56  extend further back towards the trailing end  74 , to ensure complete melting. In this embodiment, the section of the platen behind the bridge (i.e., between the bridge and the trailing edge  74 ) may be maintained at a relatively cool temperature. The temperature in this zone may be warm enough to maintain the adhesive in a softened state, but not so warm so as to damage the carpet backing. In the alternative, essentially all of platen may be maintained at a temperature that is high enough to melt the adhesive after the tape has passed over the entire length of the platen. In such case, the carpet may be held away from the platen until near trailing edge  74 , as shown in FIG. 3. An insulating support or supports (not shown) may be mounted on or over platen  52  to hold it away from carpet  30 . The carpet passes over bridge  56 , which also serves to protect it from the hot platen.  
         [0035]    Sidewalls  66  of bridge  56  may be used to align tape  34  with passageway  58 . Likewise, bridge  56  is aligned relative to the seam by the blade-like handle support  62 . Hence, alignment of tape  34  with the seam is ensured. In lieu of sidewalls  66 , any suitable alignment tabs, channels, rollers, or like elements, may be provided in bridge  56  and/or platen  52 , for alignment of tape  34 .  
         [0036]    It may be desirable to make the length of the bridge adjustable to accommodate different types of adhesive tape or carpet. For example, when working with a carpet that is especially heat-sensitive, it may be desirable to make the bridge longer. Such adjustability may be provided by a telescoping-type of mechanism, by additional panels that may be attached to, or removed from, the top of the iron platen as desired, by a movable bridge, or by any other suitable method. A movable bridge is one that can be moved backwards or forwards along the length of the platen, and locked in a desired position. By moving the bridge back towards the trailing edge, contact between the carpet and the platen may be delayed. Conversely, when a movable bridge is in a more forward position, contact time with the platen may be increased, and an “excess” portion of the bridge may overhang the leading edge of the platen.  
         [0037]    In an embodiment of the invention, the platen is an essentially flat, rectangular piece, such as shown in FIGS. 2 and 3. In other embodiments, the platen may be provided with a crowned or contoured upper surface, as shown in FIG. 4. Of course, other surfaces of the platen, such as the lower surface or side surfaces, may be contoured for various reasons, but the invention does not concern such details. Rather, it is the contouring of the upper surface that represents an especially innovative variation of the invention, because of the significant and surprising benefits provided thereby.  
         [0038]    As shown in FIG. 4, one suitable crowned configuration for a crowned platen  70  comprises an upper surface  71  with a convex curvature at a leading edge  72 , tapering to a relatively flat and thin trailing edge  74 . Side edges  76  may have a uniform height as shown, or in the alternative, may be tapered so as to be thinner towards the trailing edge, or blended entirely with the upper surface  71 . Side edges  76  may provide flat surfaces, or other mounting surfaces, for mounting the platen to a suitable bridge and/or connecting electrical wiring. For example, and not by way of limitation, side edges  76  may be provided with mounting holes  78  for threaded fasteners or the like, and/or pins  80  for making electrical connections. Platen  70  may be attached to a bridge  56  and handle  60  of an iron  88 , as shown in FIG. 5. In the alternative, the platen may be provided with wing-like projecting tabs to which a bridge may be attached, or a bridge may be fastened to the top of the platen near its side edges, or to the bottom of the platen. In lieu of a bolted connection, the platen may be attached to the bridge using a hinging connector in opposition to a latch, or by any other suitable connector. A hinged connector provides the advantage of allowing the bridge assembly to be opened for placement of the tape, or for cleaning. An insulating layer  54  may be provided under platen  70 , optionally separated from platen  70  by an air gap (not shown).  
         [0039]    Instead of a convex curvature, the upper surface of a crowned platen  82  may be raised, yet have zero curvature, as shown in FIG. 6. It may even be suitable to provide a crowned platen  84  with a negative, convex curvature, as shown in FIG. 7. Whatever the curvature of the platen upper surface, it is preferable for the platen to be tapered from a relatively thick section towards its leading edge  72  to a relatively thin section towards its trailing edge  74 , as shown in FIG. 8. The thickest portion of platen  70  may be at the leading edge  72 , as shown. In the alternative, the thickest (i.e., highest point of the crown) may be located at a position somewhat behind the leading edge, if desired. It is believed preferable for the platen to taper to its thinnest at the trailing edge  74 , but the invention is not limited thereby. For making symmetrical seams, the platen should be essentially symmetrical across its side edges with the highest part of its crown along an longitudinal central axis along the length of upper surface  71 .  
         [0040]    A side view of an exemplary iron  88  with a crowned platen  70  during a seaming operation is shown in FIG. 9. Seaming iron  88  may be compared to iron  50 , having a flat platen  52 , shown in FIG. 3. With reference to FIG. 9, tape  34  is threaded between a bridge  56  and the platen  70  of iron  88 . Tape  34  is bowed upwards and outwards by platen  70 , following the contour of its upper surface. Carpet  30  passes over bridge  56  and contacts the adhesive tape  34  at a position behind bridge  56  where the crowned upper surface of the platen is at or near its maximum height, indicated as section  10  of FIG. 9. Carpet  30  may remain in contact with adhesive tape  34 , which, in turn, remains in contact with platen  70 , from the point of first contact to the trailing edge  74 . By the time the carpet reaches the trailing edge, it may be bonded to tape  34  and require no further setting. In the alternative, the adhesive may remain melted or softened at the trailing edge, and pressure may be maintained to hold the carpet and tape in position while the adhesive cools and hardens. In either case, it should be appreciated that platen  70  is preferably configured so as to not be excessively hot rearward of the point of first contact between the adhesive tape and the carpet, both to avoid damaging the carpet  30  and perhaps also to permit an operator to manipulate the carpet in this area.  
         [0041]    The operation and benefits of crowned iron  88  are more apparent from inspection of FIGS.  10 - 12 , which show a sequence of cross-sectional views taken as sections  11 - 12  of FIG. 9, respectively. The sequence of views demonstrates how the crowned platen  70  may be used to efficiently create a seam with an optimal edge weld. At section  10 , carpet  30  first contacts adhesive  40  of tape  34 . Platen  70  may be relatively thick at this section, thereby presenting a curved upper surface that, consistent with elementary principles of geometry, is substantially longer than a straight line between the side edges. Because of this curvature of the platen&#39;s upper surface, a gap  96  is present between the opposing pieces of carpet  30 , through which adhesive  40  is exposed.  
         [0042]    By way of example, tubular heating element  94  is shown embedded in platen  70 , but it should be appreciated that any manner of heating plating  70  may be provided. For example, a relatively flat foil element heat may be used as an alternative to a tubular heater. Different temperature zones may also be provided along the length of the platen, by changing the spacing of heating elements along the length of the heater, using a heating element with different power dissipation in different zones, or by any other suitable method. In particular, as described above, it may be desirable to provide a lower temperature zone towards the trailing edge of the iron. For example, it may be preferable to not heat platen  70  near or behind section  10 , in which case element  94 , or other heating elements, should be omitted towards the trailing edge. Heating in the region would then rely on conduction of heat from a forward section of the iron.  
         [0043]    At section  11 , platen  70  is thinner than at section  10  because of the platen&#39;s rearward taper. The edge-to-edge length of the platen&#39;s upper surface is accordingly less than at section  10 , as shown in FIG. 11. Gap  96  is therefore smaller than at section  10 , as the opposing carpet pieces converge towards the center of platen  70 . As the carpet pieces converge, they scrape a portion of the exposed adhesive  40  towards the center of the platen, creating a bulge  90 . This converging of the carpet pieces continues as the carpet travels down the rearward taper of the platen, building the adhesive bulge between the carpet pieces.  
         [0044]    At section  12 , platen  70  is essentially flat and the carpet pieces have fully converged. The adhesive bulge is now configured to become an adhesive weld between the opposing vertical carpet edges  31 , as shown in FIG. 12. The adhesive may be cooled and hardened in this position to create a seam with an optimal edge weld  92 . It should be appreciated that an optimal weld  92  will most likely not actually extend through the entire thickness of the carpet  30 , as shown in FIG. 12. Instead, an optimal weld will most likely extend through and perhaps slightly beyond the carpet backing only, leaving the carpet tufts essentially free of adhesive. The weld  92  is depicted as shown in FIG. 12 merely for illustrative simplicity.  
         [0045]    In summary therefore and with reference to FIG. 13, the present invention provides a method  100  for seaming a carpet using a heated platen that underlies a hot-melt adhesive tape. Method  100  comprises the following steps. At step  102 , a length of adhesive tape is placed under abutting edges of carpet to be seamed and on top of a floor. The adhesive tape comprises a layer of hot-melt adhesive over a backing layer, and is oriented with its adhesive layer facing the lower surface of the carpet. At step  104 , a heated platen is placed between the floor and the seaming tape. The seaming tape may be threaded over the platen through a bridge, or a bridge may be opened up to allow placement of the tape over the platen. The platen is heated to a temperature sufficiently high to melt the tape&#39;s adhesive layer through the backing layer. At step  106 , the carpet backing is wetted with the melted adhesive layer of the tape. At optional step  108 , the opposing carpet pieces are moved towards each other through the layer of melted adhesive, thereby collecting adhesive between the opposing pieces of carpet, until the carpet pieces abut one another and adhesive wets the opposing vertical edges of the carpet backing. At step  110 , the adhesive is cooled and hardened with the adhesive tape held in place against the carpet to complete the seam. At step  114 , the platen is moved forward to the next section of seam, while drawing the adhesive tape over the heated platen. Steps  104 - 114  may be repeated in sequence, until the seam is completed as determined at step  112 .  
         [0046]    Having thus described a preferred embodiment of a carpet seaming iron and method, it should be apparent to those skilled in the art that certain advantages of the within system have been achieved. It should also be appreciated that various modifications, adaptations, and alternative embodiments thereof may be made within the scope and spirit of the present invention. For example, applications for seaming carpets have been illustrated, but it should be apparent that the inventive concepts described above would be equally applicable to seaming other sheet materials. In addition, various refinements may be made to the embodiments described herein, including but not limited to: making the bridge of the iron longer, so as to cover a more substantial portion of the platen; constructing the platen to have at least two zones, a hotter forward zone for melting adhesive and a cooler trailing zone for acting as a seaming mandrel on which the carpet is placed; providing rollers or other guide features to guide the adhesive tape through the iron; providing electronic controls for the iron; and controlling the platen temperature using one or more temperature sensors for detecting the temperature of the upper surface of the platen or of the molten adhesive. The invention is defined by the following claims.