Abstract:
A channel letter has a rear surface for mounting against a raceway, wall, or a structure for supporting the signage, and sides defining the figuration of the letter of shape to be depicted. A lighting element is positioned against the rear surface of the enclosure, and a lens is retained to the open front of the enclosure. The lens may be retained by a plurality of retainers to a shoulder recessed within the walls of the enclosure. As a first alternative, the retainers may retain a lens without a shoulder where a sealing edging is fitted around the perimeter of the lens. As a second alternative a lens having dimensions greater than those of the enclosure may be retained across the forward end thereof.

Description:
This is a Continuation-In-Part of our application filed Feb. 1, 1999 and assigned Ser. No. 09/241,644 now U.S. Pat. No. 6,202,333. The present invention relates to channel letters of the type used to create signage and, in particular, to an improved method of manufacturing a channel letter. 
    
    
     BACKGROUND OF THE INVENTION 
     Channel letters are used to provide signage for buildings, shopping malls, and the like where it is desirable that the signage comprise illuminated letters or any other shapes that are easily seen, even at great distances, day or night. Each channel letter consists of an enclosure, usually a metal box, having a rear surface which is positioned against a raceway, or the wall of a building, on which the signage is mounted and a plurality of sides which define the figuration of a letter or number which make up a portion of the sign. A light source, such as a neon tube, is positioned within the walls of the enclosure and attached to the rear surface to provide illumination for the letter. 
     The light sources used in existing channel letters are neon bulbs requiring high voltage power with transformers built into the metal enclosures. To prevent injury to those servicing such channels letters many municipalities require that such letters be inspected to ensure that they are adequately sealed using standards set by Underwriters Laboratories. 
     It is expected that new technology will soon be available for the manufacturers of channel letters. Specifically, low voltage LED type light sources have been developed which provide a very long lasting bright light without requiring the high voltage and transformers needed for neon lighting. It is expected that channel letters employing the new technology will not be required to meet the standards set by Underwriters Laboratories. 
     In addition to the lighting, a channel letter also includes a planar, transparent lens, the outer shape of which corresponds to the figuration of the letter or any other shape defined by the sides of the enclosure. The lens of existing channel letters have a trim cap glued to the outer edges thereof which form a border to the lens. The trim cap also has a lip which, when assembled to the enclosure, is shaped to fit snugly around the forward ends of the walls thereof for retaining the lens to the enclosure and to maintain the water tight seal required by Underwriters Laboratories. Screws are threaded through the lips of the trim cap and into the walls to retain the lens across the forward opening of the enclosure. 
     The manufacture of the lens requires that a planar panel of transparent plastic be cut to the shape of the enclosure and that the trim cap be glued to the outer edges of the lens. The contours of the sides of many letters are curved and the process of shaping and gluing the trim cap around the edges of the lens is labor intensive. It is, therefore, expensive to manufacture existing lenses which fit across the forward ends of the enclosure of a channel letter. 
     It would be desirable to provide a channel letter having a lens which could be manufactured without incurring the labor intensive step of requiring the attachment of a trim cap. It would also be desirable to provide a less expensive method of manufacturing and assembling a lens to the enclosure of a channel letter. 
     SUMMARY OF THE INVENTION 
     Briefly, the present invention is embodied in a channel letter. For the purposes of this description, a channel letter is defined as including a letter of the alphabet, a numeral, an element of punctuation such as a comma, an exclamation point, or any other shape or form intended to constitute a portion of a sign. 
     The channel letter of the present invention has a rear surface for mounting against a raceway, a wall, or any other structure suitable for supporting the signage, and walls defining the figuration of the letter or shape to be depicted. A lighting element, such as a strip of LEDs according to the newly available technology or any other light source, is positioned against the rear surface of the enclosure to provide illumination therefore. 
     In accordance with one embodiment of the invention, to retain the lens to the open front of the enclosure, a shoulder is provided around the inner surface of the sides thereof where the shoulder defines a plane parallel to the outer ends of the sides but is recessed therefrom. A planar transparent lens having an outer edge which is in the shape of the letter and sized to fit within the sides of the enclosure is retained against the shoulder by retaining clamps or by screws extending through the walls of the enclosure with the distal ends thereof projecting in front of the lens. 
     Where the shoulder supporting the lens is made of rubber or foam, the shoulder may have insufficient rigidity to retain the lens against the elements. Over time, wind, rain, and ice may cause the rubber or foam to yield under the forces applied to the sign by the elements thereby allowing the lens to slide inward or rearward within the walls of the letter. The failure of the foam or rubber will cause the letter to have an unattractive appearance and can result in damage to the lighting fixture within the enclosures or damage to the lens and the wall of the letter. On the other hand, if the fasteners which retain the lens against the shoulder should fail, the lens may fall out of the enclosure altogether. 
     To prevent the failures described above, the invention may also have a first plurality and a second plurality of retainers spaced around the perimeter of the lens to provide support thereto. Each of the first plurality of retainers has a connector portion for connecting to the wall of the channel letter and a retaining portion which is positioned against the outer surface of the lens to retain it within the walls of the channel letter. Each of the second plurality of retains also has a connector portion and a retaining portion. The connecting portion attaches to the wall of the channel letter and the retaining portion provides support to the rear surface of the lens independent of the shoulder. The plurality of second retainers, therefore, prevents damage to the rubber, foam or other material which forms the shoulder. 
     In accordance with a second embodiment of the invention the foam or rubber strip around the inner surface of the letter described with respect to the first embodiment is deleted. In this embodiment the lens is again cut into the shape defined by the enclosure with dimensions that are a little less than the inner dimensions of the enclosure. The lens is held in place within the walls of the enclosure by a first plurality and a second plurality of retainers similar to those described with respect to the first embodiment. To provide a seal between the inner surface of the enclosure walls and the edge of the lens, a U-shaped rubber edging is fitted over the outer edge of the lens before the lens is fitted within the walls of the enclosure. 
     In accordance with a third embodiment of the invention, the lens is cut into the contour defined by the enclosure with the outer dimensions of the lens being a little larger than the outer dimensions of the enclosure such that the edges of the lens overhang beyond the outer edge of the enclosure. A rubber or foam stripping having a constant cross sectional shape is then glued to the inner surface of the enclosure with the forward surface of the rubber or foam projecting a short distance forward of the enclosure to form a seal against the rearward surface of the lens. A plurality of retainers around the perimeter of the lens attach the lens to the walls of the enclosure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better and more complete understanding of the present invention will be had after a reading of the following detailed description taken in conjunction with the drawings wherein: 
     FIG. 1 is a front elevational view of a prior art channel letter; 
     FIG. 2 is an enlarged cross sectional view taken through line  2 — 2  of FIG. 1; 
     FIG. 3 is a front elevational view of a channel letter in accordance with the present invention; 
     FIG. 4 is an enlarged cross sectional view of the channel letter in FIG. 3 taken through line  4 — 4  thereof; 
     FIG. 5 is a fragmentary isometric view of a portion of the enclosure of the channel letter in FIG. 3; 
     FIG. 6 is a fragmentary enlarged cross sectional view of the mounting of the lens in the enclosure of the channel letter shown in FIG. 3; 
     FIG. 7 is a fragmentary enlarged cross sectional view of an alternate mounting of the lens to an enclosure of a channel letter; 
     FIG. 8 is a front elevational view of a channel letter constructed in accordance with a second embodiment of the invention; 
     FIG. 9 is a fragmentary isometric view of an insulating edging attached around a portion of the lens; 
     FIG. 10 is a fragmentary enlarged cross sectional view of both a first and a second retainers used with the second embodiment depicted in FIG. 8; 
     FIG. 11 is a front elevational view of a channel letter constructed in accordance with a third embodiment of the invention; 
     FIG. 12 is a cross sectional view of the channel letter shown in FIG. 11; 
     FIG. 13 is a fragmentary enlarged cross sectional view of a retainer used to retain the lens in accordance with the third embodiment depicted in FIG. 11; and 
     FIG. 14 is a fragmentary enlarged cross sectional view of an alternate retainer used to retain the lens in accordance with the third embodiment depicted in FIG.  11 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 and 2, a channel letter  10  according to the prior art is mounted on a supporting structure  12 . As shown, the channel letter  10  includes a metal enclosure  14  having a rear surface  16  and a plurality of side walls  18 ,  19  which are contoured to define the edges of a letter  10 . The forward edges of the sidewalls  18 ,  19  define a plane and fitted across the forward edges is a transparent lens  22  having a shape corresponding to that defined by the walls  18 ,  19  of the enclosure  14 . Retained to the rear surface  16  of the enclosure  14  is a light source, which extends through the length of the channel letter  10  and illuminates the entire surface of the lens  22 . 
     Referring further to FIG. 2, in accordance with the prior art, the lens  22  is retained to the side walls  18 ,  19  of the enclosure  14  by a trim cap  24 , a plastic border member which is glued to the outer edges of the lens  22 . The trim cap  24  has a rearwardly extending lip  26  that fits over the forward edges of the side walls  18 ,  19  and the trim cap  24  and the lens  22  are retained to the enclosure member  14  by a plurality of screws  28 . 
     The manufacture of a channel letter  10  in accordance with the prior art requires the construction of the enclosure  14 , the manufacture of a light fixture  23  and the lens  22 . Manufacture of the lens  22  requires cutting a transparent acrylic material into the shape of the channel letter  10  and attaching the trim cap  24  around the edges thereof. The gluing of the trim cap  24  to the edges of the lens  22 , however, must be carefully undertaken and is a time consuming, labor intensive process which adds significantly to the cost of the channel letter  10 . The trim cap  24  is intended to meet the sealing standards set by Underwriters Laboratories, but such standards may not be needed for channel letters which employ the new LED technology. It would, therefore, be desirable to provide a less expensive method of attaching a lens  22  to the enclosure of the channel letter  10 . 
     Referring to FIGS. 3,  4 ,  5 , and  6 , a channel letter  32  in accordance with a first embodiment of the present invention is attached to a supporting structure  34  and includes a metal enclosure  36  having a rear surface  38  and a plurality of side walls  40 ,  41  according to the prior art. Fitted within the enclosure  36  is a suitable light source  42 . Extending around the inner surface  46 ,  47  of the side walls  40 ,  41  and spaced a short distance from the forward edges  48 ,  49  thereof are shoulders  50 ,  51  and the forward surfaces  52 ,  53  of the shoulders define a plane. It should be appreciated that the least expensive method should be employed to provide the shoulders  50 ,  51  along the inner surfaces  46 ,  47 . Rubber stripping, foam stripping, or any other suitable flexible material can be easily glued to the inner surface of the walls  40 ,  41  as shown to form the shoulders  50 ,  51 . 
     The lens  54  for the channel letter  32  is cut from a planar panel of transparent acrylic with the outer edges  56  thereof having dimensions small enough to fit within the walls  40 ,  41  of the letter  32  and against the forward surfaces  52 ,  53  of the shoulders  50 ,  51 . Extending around the perimeter of the lens  54  is a first plurality of retainers for retaining the lens  54  against the shoulder  50 ,  51 . As shown in FIG.  4 . the retainers may be simple screws  59  extending through the walls of the enclosure with the distal ends of the screws  59  forming a barrier for retaining the lens  54 . As shown in FIG. 6, as an alternative to the screws  59 , retainers  60  formed from aluminum, of any other suitable material, having a mounting portion  62  for attachment to the inner surface of the wall  40  by a screw  64  extending through the wall  40 , may be used. The retainers  60  have a planar retaining portion  66  which forms a 90° angle with the mounting portion  62 , ans has a rear surface which abuts the forward surface of the lens  54  to retain the lens  54  within the walls of the enclosure and against the shoulders  50 ,  51 . 
     In addition to the first plurality of retainers  59 ,  60 , a plurality of second retainers  68  also extend around the perimeter of the lens  54  to provide support of the inner surface of the lens  54 . As shown, each of the second retainers  68  has a mounting portion  70  which is attached by a screw  79  extending through a portion of the wall  40  and into the mounting portion  70 . A formed arm  74  extends from the mounting portion  70 , around the rubber of foam body of the shoulder  50 , and to a retaining portion  76 . The retaining portion has a surface which contacts the rear surface of the lens  54  when the lens  54  is pressed against the shoulder  50 . The second retainers  68  provide support to the lens  54  and thereby prevent damage to the foam or rubber which make up the shoulders  50 ,  51 . 
     FIG. 7 depicts a second configuration for a plurality of retainers to retain the lens  54  to the enclosure  36 . In this configuration a retainer  80  has an elongate mounting portion  82  which is retained along the inner surface  46  of the wall  40  by a screw  84  extending through the wall  40 . Positioned perpendicular to the mounting portion  82  is a retaining portion  83  having a forward surface against which the lens  54  is positioned. In this configuration the retaining portion  83  is positioned against the foam or rubber shoulder  50 , deforming and compressing the forward surface  52  thereof. The foam or rubber is deformed only in the immediate proximity of the retainers  80 , and except for the portion of the shoulder  50  deformed by the  80 , the foam or rubber will seal against the inner surface of the lens  54 . In the embodiment depicted, the retaining portion  83  is positioned at the rearward end of the mounting portion  82  and the retaining screw  84  are paced from the retaining portion distance such that the distal end of the screw  84  will retain the lens  54  against the retaining portion  83 . 
     Referring to FIGS. 8 to  10 , in a second embodiment of the invention, a lens  87  of a channel letter  86  is retained within the walls  88 - 93  of an enclosure  94  by a first and a second plurality of spaced retainers without employing the shoulders  50 ,  51  of the first embodiment. In this embodiment a U-shaped rubberized edging  96  is fitted around the outer edge of the lens  87  so that the back of the edging  96  will abut the inner surfaces of the walls  88 - 93  to seal the lens  87  against the walls  88 - 93 . The first plurality of retainers  97  are spaced around the perimeter of the channel letter and have mounting positions  98  which extend, along the inner surface of the walls  88 - 93  and retaining portions  99  oriented perpendicular to the mounting position  98 . The retainers  97  are positioned on the walls  88 - 93  such that the retaining portions  99  thereof define a plane recessed a short distance from the ends  100  of the walls  88 - 93 . The rearward surface of the lens  87  is positioned across the retainer portions  99  of the retainers  96  and are held in place by an associated screws  101 . 
     A second plurality of angular shaped retainers  102  retain the lens  87  within the forward end of the enclosure  94 . Each of the second plurality of retainers  102  has a mounting portion  103  secured to the inner surface of the wall  88 - 93  by a screw  104  and a perpendicularly extending retaining portion  106  abutting the forward surface of the lens  87 . 
     Referring to FIGS. 11 to  13 , in a third embodiment of the invention a channel letter  110  includes an enclosure  112  having a back  114  and a plurality of walls  116  to  123  which define the shape of the letter  110 . Across the forward ends of the walls  116 - 123  of the enclosure  112  is an acrylic lens  126  having an outer edge  128  in the shape of the letter  110  but having outer dimensions that are a little larger than the outer dimensions defined by the walls  116 - 123 . The outer edge  128  of the lens overhangs beyond the walls  116 - 123 , and is retained in place by a plurality of retainers  130  spaced around the walls  116 - 123  of the enclosure  112 . A strip  131  of foam or rubber is glued around the inner surface of the enclosure  112  with the forward surface of the strip  131  extending forward of the forward ends of the walls  116 - 123  a short distance, perhaps ⅛ th inch to form a seal between the enclosure and the lens  126 . 
     Referring to FIG. 13, in the preferred configuration, each retainer  130  has a planer attachment portion  132  for receiving a sheet metal screw  134  for attachment to one of the walls, of which wall  118  is representative of all the walls  116 - 123 . A hooked shaped retaining portion  136  extends around the outer edge  128  of the lens  126 . A cap  138  similar to the rubberized edging  96  described with respect to the second embodiment may be fitted around the outer edge  128  of the lens  126  prior to assembling the retainers  130  to block light rays from radiating out the ends of the lens  126 . 
     Referring to FIG. 14, in which an alternate embodiment of a retainer  140  is depicted, the retainer  140  has a planar mounting portion  142  for receiving a screw  144  for attachment to the wall  118  of the enclosure, and a perpendicularly extending attachment portion  146  having a planar surface which is glued to the rearward surface of the lens  126 . 
     The lens of all the embodiments of the present invention can be manufactured and attached to their associated enclosures less expensively than can the presently available lenses. Once assembled, the lenses of the present invention can be adequately sealed against the walls of the enclosure to protect the light source, and will present an attractive appearance. 
     While several embodiments of the present invention have been disclosed, it will be appreciated that many modifications or variations may be made without departing from the true spirit and scope of the invention. It is, therefore, the intent of the pending claims to cover all such variations and modifications which fall within the true spirit and scope of the invention.