Abstract:
A prefabricated crown molding strip designed to facilitate one-person installation and composed of plaster that is reinforced by two layers of fiber reinforcement, one of bulk fiberglass intermixed throughout the outer portion of the strip and the ornamentation thereon and a second of a sheet of fiberglass netting generally centrally located as a spine in the strip and substantially coextensive therewith. Two side surfaces of the strip are disposed generally in perpendicular planes for engagement with a wall and a ceiling, and have patterns of longitudinally extending ribs and grooves of predetermined depths for facilitating adhesive mounting of the strip, and also facilitating selective removal of plaster to accommodate irregularities on supporting surfaces. Pre-formed nail holes are molded in preselected nailing locations. Also the method of making crown molding strips in steps providing the above characteristics, in a sequence of pours of plaster in fluid state, the addition of the reinforcing fiber, and formation of the patterns of ribs and grooves.

Description:
FIELD OF THE INVENTION 
     This invention relates to ornamental crown moldings, and relates more particularly to elongated crown molding strips having outer surfaces with decorative ornamentation and side surfaces for engaging supporting walls, usually the ceiling and a vertical wall of a room space. The invention also relates to the method of making such strips, usually of plaster. 
     BACKGROUND OF THE INVENTION 
     It has long been the practice to use crown moldings to cover and decorate the junctures of room walls and ceilings, and to provide ornamentation on the exposed outer sides of the crown moldings as additional room decoration. Current examples of such crown moldings are shown in U.S. Pat. Nos. 5,433,048, 5,662,753 and 5,398,469, and older approaches are shown in U.S. Pat. Nos. 2,981,988, 3,201,910 and 3,481,092. It will be seen in these patents that there are numerous ways to design, manufacture and install crown moldings and a variety of different materials that may be used. As stated in the Loos patent, U.S. Pat. No. 5,662,753, the manufacture of ornamental molding made of plaster has required a relatively high skill level, either to run the molding “in place” on a wall or ceiling, or to cast the molding in elongated strips in stationary molds and then to mount the strips on the supporting room surfaces. It is generally accepted that plaster moldings, whether run-in-place or cast in stationary molds, are the richest looking and generally provide the most elegant appearance, but cost often leads to the use of cheaper substitutes. 
     Loos, for example, proposes the use of a relatively complex substitute for traditional plaster crown moldings, using a special base molding in an attempt to avoid the need for expensive production techniques and highly skilled labor. The other patents cited above provide other approaches for the same general purpose. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention resides in a novel construction for crown moldings that may be composed of plaster or similar molding materials and prefabricated at relatively low cost in elongated strips that are both ligher in weight and stronger in structure than prior plaster crown moldings, and that are specially designed and manufactured for easy installation by a single, unskilled installer. In other words, the crown molding strips of the present invention are particularly well suited for the do-it-yourself market, yet with highly desirable decorative ornamentation of the type previously available only in very expensive moldings. 
     More specifically, the crown molding strip of the present invention has an elongated body that may be composed primarily of conventional plaster, and an outside surface with raised, highly defined ornamentation of any selected design, and two layers in a novel combination of reinforcing fiber that makes it practical to provide the strips in thinner, lighter weight pieces that are not likely to break in shipment or when handled by one person during installation. One layer is bulk fiber, preferably fiberglass in bulk or “wool” form, and is mixed throughout the outer portion of the strip that carries the surface ornamentation. The second layer is a thin sheet of fabric, preferably fiberglass netting, that is approximately the same size as the crown molding strip and embedded in, and substantially coextensive with, the strip, with its edges close to the edges of the strip. This sheet cooperates with the bulk fiber to provide a high degree of strength in a thin, and very light weight, crown molding strip. 
     In addition, the preferred embodiment of the invention has corrugated side surfaces formed by patterns of grooves and ridges for engagement with the room surfaces, facilitating shaping of the side surfaces to accommodate irregularities in the room surfaces. These corrugations also enhance the attachment of the crown moldings with adhesives, providing increased bonding surface area and alleviating the need for precise measurement of the adhesive, and are of predetermined depth to serve as gauges for removal of material to fit bulges in the wall. Pre-formed nail-hole indentations may be provided in the strips at preselected nailing locations, facilitating nailing by a lone installer to secure each strip in place while the adhesive sets. These also may be formed by the installer at the site. 
     The novel method of the invention provides for the manufacture of crown molding strips according to the invention, as described in detail in the following detailed description, from which other features and advantages of the invention will become apparent. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary perspective view showing a person installing an ornamental crown molding strip constructed according to the present invention; 
     FIG. 2 is a somewhat enlarged rear perspective view taken from the inner side of the crown molding strip; 
     FIG. 3 is a further enlarged cross-sectional view taken along line  3 — 3  of FIG. 2; 
     FIG. 4 is a perspective view of a production mold for use in the method of the invention, having a cavity into which plaster is being poured in the first pouring step of the method of the invention; 
     FIG. 5 is a perspective view similar to FIG. 4 showing the beginning of a subsequent step of mixing into the first layer a predetermined quantity of bulk fibers; 
     FIG. 6 is a perspective view similar to FIG. 5 after the bulk fibers have been intermixed with the plaster; 
     FIG. 7 is a perspective view similar to FIG. 6 showing the pouring of a second layer of plaster into the mold cavity; 
     FIG. 8 is a perspective view similar to FIG. 7 showing the leveling of the second layer; 
     FIG. 9 is a perspective view similar to FIG. 8 with the further layer leveled and showing the application of a sheet of reinforcing fabric; 
     FIG. 10 is a perspective view similar to FIG. 9 showing the pouring of a further layer of plaster in the mold cavity over the reinforcing fabric; 
     FIG. 11 is a perspective view showing the leveling of the further layer of plaster; 
     FIG. 12 is a perspective view showing the pouring of a fourth layer of plaster into the mold cavity; 
     FIG. 13 is a perspective view showing the leveling of the fourth layer of plaster in the mold; and 
     FIGS. 14 and 15 are perspective views similar to FIG. 13 showing the steps of forming and finishing a pattern of grooves and ridges in the exposed surface of the plaster in the mold. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in the drawings for purposes of illustration, the invention is embodied in an elongated ornamental crown molding strip, indicated generally by the reference number  10  and best seen in FIGS. 1 to  3 . The strip  10  is intended for use as one of a series of such strips mounted end-to-end in a room space, usually to cover and decorate the juncture  11  between an upright wall  12  and a ceiling  13 . 
     For this purpose, the strip  10  comprises generally an elongated body composed primarily of material that can be molded, preferably and traditionally of plaster, and formed with an outer decorative surface  14  for facing into the room and having generally parallel longitudinal edges  15  and  17 . Formed on the outer surface are ornamental patterns, herein shown as raised garland-like designs  18  repeating along the central portion of the outer surface  14 , a patterned cornice decoration  19  in a so-called “dental” design forming an upper border on the outer surface, and raised ridges  20  and  21  (see FIG. 3) extending along the lower edge  17 . 
     The crown molding strip  10  also has two side surfaces, indicated generally at  22  and  23 , for engagement with the ceiling  13  and the wall  12 , the first of these being the top surface above the cornice decoration  19  and-the second being a laterally facing side surface spaced inwardly a preselected distance from the surface  14 . Completing the strip  10  is an inner side  24  extending between the two side surfaces  22  and  23 , herein a relatively short curved surface behind the cornice decoration  19 . It should be understood that various designs may be used, and further that the laterally facing side surface  23  is shorter in many crown moldings, with outer decorative surfaces that are inclined upwardly away from the wall. Examples of such general configurations are shown in the aforesaid patents, but in types of construction that do not incorporate the present invention. 
     It will be evident to those skilled in the art that this general type of strip can be used to create a crown molding extending entirely around a room space, if desired. A plurality of strips  10  are arranged end-to-end along the walls, usually with miter joints (not shown) where two walls meet in a corner of a room, and are secured to the wall and ceiling by suitable fasteners and adhesives. A related application is being filed concurrently with this application for a patent on a preferred method of installation of crown moldings comprising strips of the type shown herein. 
     As previously mentioned, the material that is preferred by many for crown moldings is plaster, which has several advantages over wood and plastics, most notably the capability to be formed with more detailed ornamentation. Important disadvantages, however, have been high cost of time-consuming manufacture and installation by skilled craftsmen, as well as heavy weight and relatively high fragility. The present invention has the objective of making possible, and practical, relatively low cost plaster crown moldings that can be formed with a high degree of detailed ornamentation and, at the same time, being light in weight and durable so as to be installable by a single person, even as a do-it-yourself project. 
     To these ends, the present invention, as illustrated by the preferred embodiment disclosed herein, resides in an elongated and relatively thin (for plaster) crown molding strip  10  that has two layers  27  and  28  (FIG. 3) of reinforcing fiber that are combined in a novel manner to produce a lighter, more durable strip, and in which the side surfaces  22  and  23  are finished with a pattern of ribs and grooves that contribute significantly to the simplification of the installation process. One reinforcing layer  27  is bulk fiber, preferably fiberglass, that is intermixed throughout the outer portion of the strip  10 , and the second layer  28  is a thin sheet of fabric, preferably fiberglass netting, that is embedded in the strip and substantially coextensive with the strip (see FIGS.  9  and  10 ). The bulk fiberglass provides both durability of the outer portion and surface of the strip and overall structural strength, and the fabric forms a generally central, strengthening spine for the strip. Optionally, additional small sheets of reinforcing fabric can be placed in selected areas, such as near each end in the strip along the surface  24 . Together, these reinforcements impart sufficient strength to permit substantial reduction in thickness and weight of the strip, when cast of plaster, to as low as eight to fourteen millimeters, the preferred overall thickness (apart from ornamentation) being ten to eleven millimeters for optimum characteriestics. 
     As shown most clearly in FIG. 3, the bulk fiberglass  27  is intermixed in the outer layer of the strip  10  to a depth of approximately one-third to one-half of the thickness of the body, and into the raised ornamentation  18  to  21  as well, and the fabric  28  is centrally located, herein just to the outside of the center. The ends  30  (FIG. 9) of the fabric reinforcement  28  are close to the ends  29  of the strip  10 , and the longitudinal edges  30   a  of the fabric are spaced a short distance from the edge  17  and side surface  22 , as shown in FIG.  3 . 
     The side surfaces  22  and  23  of the strip  10  are disposed generally in imaginary reference planes spaced ninety degrees apart, for substantially flat engagement with the wall  12  and the ceiling  13  as shown in FIG.  1 . The illustrative molding strip has a narrow upper side surface  22  and a much wider vertical side surface  23 , connected by a short arcuate inside surface  24 . The pattern of ribs and grooves in each side surface is seen most clearly in FIG. 3, and herein runs longitudinally of the strip and covers virtually the full width and length of the strip. The preferred configuration is a regular wavy or corrugated pattern, but with different preselected depths of grooves  31  and  32 . and with ribs  33  that lie on the same plane. In the illustrative embodiment, every fourth groove  32 , from the right, is approximately double tie depth of the intervening grooves. In the illustrative strip  10 , the shallow grooves  31  are about two millimeters deep and the deep grooves  32  are about four millimeters deep. It is to be noted that the fabric reinforcement  29  is spaced substantially more than four millimeters from the inner side edge  23 . In view of its narrow width, the upper side edge  22  has only two shallow grooves  31 . 
     These ribs and grooves serve several important purposes in the installation of the crown molding. First, when a bead (not shown) of fluid adhesive is applied wave-like to the surface that will engage the wall  12  or ceiling  13 , the grooves  31 ,  32  provide spaces for receiving excess adhesive and confining it against the strip  10 , thus reducing the tendency of the adhesive to leak away from the strip. Flats at  34 ,  35  and  37 , along the margins of the side surfaces  22  and  23  tend to seal against the wall and the ceiling. In addition, improved holding by the adhesive results from the increased surface area covered by the adhesive, and also by the increased thickness of the layer of adhesive in the grooves. 
     Another important function of the ribs and grooves during installation is facilitating the removal of plaster in selected areas of the side surfaces  22  and  23  to fit over low spots (not shown) in the ceiling  13  or bulges (not shown) in the wall  12  in the area to be covered by the crown molding. Using a hand tool such as a rasp (not shown), the installer can shave away part of the plaster of the ribs  33 , to a selected depth that can be roughly gauged by reference to the known depth of the grooves  31  and  32 . Grooved plaster is very easily shaped in this way to fit properly against the supporting surface. 
     An optional feature of the molded strip  10  is the provision of pre-formed nail holes  38  in selected nailing locations along the strip. These facilitate the starting of nails, which can be fairly difficult to do for one person holding a strip in place against the ceiling. The primary purpose of the nails, of course, is to hold the strip in place until the adhesive sets, and thereafter to reinforce the adhesive. The nail holes also can be formed by the installer at the work site, using a drill or other suitable tool. 
     While reference has been made, throughout this description, to aspects of the steps that make up the method of making the crown molding strip  10 , a step-by-step explanation now will be given with reference to FIGS. 4 through 15 of the drawings. First, an open-sided mold cavity  40  is provided in a generally flat mold  41  having one side  42  that is shaped to form the grooved side surface  22  of the strip  10 , a generally flat bottom wall  43  (FIG. 4) formed with indentations  44  for forming the garland ornamentation  18 , and a second side  45  that forms the strip&#39;s lower edge  17 . The illustrative cavity  40  is at least ten to eleven millimeters deep, for molding of strips  10  of that thickness, and has detailed shapes for molding all of the details of the strip  10 , other than the inwardly facing portions. The length of the strip may be varied, but a length of six and one-half feet is preferred, for ease of shipment and also for ease in handling during installation. 
     Into this mold cavity  40 , a preselected quantity of plaster  47  is poured in fluid state from a container  48 , the amount being sufficient to fill the indentations  44  and cover the bottom wall  43  to the first preselected depth, herein about two millimeters. At this point, a preselected quantity of bulk reinforcing fiber  27 , preferably bulk fiberglass or fiberglass “wool”, is placed in the mold and then intermixed with the plaster of the first pour. These steps are shown in FIGS. 5 and 6, the latter showing the plaster  47  generally leveled with the bulk fiber  27  mixed in. 
     Next, a second pour  49  (FIG. 7) of plaster in fluid state is made from a container  48 , this time with a preselected amount sufficient to form an intermediate layer of plaster on top of the first layer that will form the outer portion of the strip  10 . The preferred thickness of this layer is approximately two to three millimeters, bringing the mold cavity  40  to about one-half full. Preferably this layer  49  is leveled to a fairly even exposed surface by drawing a template  50  over the exposed surface as indicated by the arrow  51 . The template has shaping portions  52  and  53  which begin forming the shape of the inner side of the strip  10 , as shown. 
     The fabric reinforcement  28  now is applied to the leveled surface of the layer  49  (see FIG.  9 ). The preferred fabric is a sheet of fiberglass netting with a fairly large mesh size, on the order of three-sixteenths of an inch, so as to be easily spread and pressed into the surface of the plaster, with the edges  30   a ,  30  of the fabric close to the sides and ends of the mold. 
     With the fabric netting  28  in place, a further pour  54  of fluid plaster is made from a container  48  (FIG.  10 ), this time with a preselected quantity sufficient to bring the thickness of the illustrative strip  10  to six to seven millimeters. This plaster is levelled in the mold cavity  40  as shown in FIG. 11, with a shaping template  55  having shaping portions  57  and  58  for the inner side, and moved in the direction of the arrow  59 . This is an opportune time for applying additional small pieces of fabric netting (not shown) near the ends of the strip, for example, a four-inch wide piece embedded about one inch from each end, and lying in the curved part of the strip. Another pour  60  preferably is made to complete the filling of the cavity  40  (see FIG.  12 ), usually with an excess of plaster that is scraped off in the last leveling step with a template  61 , moved in the direction of the arrow  62  in FIG.  13 . 
     The finishing of the exposed surface of the plaster in the mold, to form the side surface  23  and the inside  24  of the strip  10 , should be delayed until just before the plaster hardens. This preferably is done in two or more passes over the surface, the first shown in FIG. 14 with a detailing template  63  that forms the ribs  33  and grooves  31 ,  32  while finishing the surface. A second finishing pass is shown in FIG. 15, to smooth the finish of the exposed plaster. After completion, the plaster is allowed to set before removal from the mold. The mold is of the reusable type, and a production line of multiple molds for each casting worker or team is the usual practice in mass-production of such strips. 
     From the foregoing, it will be apparent that the present invention makes possible the production of crown molding strips  10  from traditional plaster in a manner that provides a relatively lightweight and strong strip that can be mass-produced at low cost and can be installed with relative ease by a single unskilled installer. It also will be evident that, while one currently preferred embodiment has been illustrated and described, various modifications and changes may be made by those skilled in the art without departing from the spirit and scope of the invention.