Box beam fabrication process

Abstract

A process is provided for the manufacture of simulated wooden channel, or box, beams. The beams manufactured in accordance with the process of the invention may be composed, for example, entirely of polyurethane plastic; or they may be constructed to consist of a polystyrene or honeycomb paper inner core with a continuous molded thin skin of polyurethane. The channel beam provided in accordance with the process of the invention has a hollow rectangular cross-section, and it has relatively thin side and bottom walls, so as to be light and inexpensive. It may be constructed to exhibit low flame spread and low smoke development. The channel beam fabricated by the process of the invention may be conveniently mounted on the ceiling or walls of a room by use of anchor or support blocks, the blocks being adhesively attached to the ceiling or wall, as the case may be, and the beam being adhesively attached to the anchor block.

Parent Case Text

This is a continuation of application Ser. No. 194,751, filed 11/1/71, now abandoned, and a continuation-in-part of copending application Ser. No. 885,038 which was filed Dec. 15, 1968, and now abandoned.

Description

BACKGROUND OF THE INVENTION

It is well known that the attractiveness of a room may be enhanced by the provision of natural wooden beams, which are mounted either on the ceiling or on the walls of the room, or on both. However, natural wooden beams are heavy and expensive, and they are difficult to mount. Because of this, plastic beams have been devised in the prior art which have all the appearance of natural wooden beams, as to grain and color, but which are less expensive and lighter, and which are more easy to install.

Heretofore, the aforesaid prior art plastic beams have usually been constructed of either a solid cross-section, or to have a shallow internal channel running from one end to the other. Such prior art beams were molded by means of a three-dimensional rubber mold, and a different mold was required for each size of beam. The channel in the prior art beams serves to receive appropriate anchor blocks, the anchor blocks being adhesively attached to the ceiling or wall, and the plastic beam being adhesively attached to the anchor blocks so as to be supported on the ceiling or wall.

The prior art plastic beam of the type discussed above is usually composed of polyurethane foam which is molded in an appropriate three-dimensional rubber mold to exhibit the external grain of a wooden beam and which, apart from the aforesaid shallow channel, is usually solid in cross-section, as mentioned above. As a result, the prior art plastic beam is unduly expensive, and they do not possess particularly favorable flame-retardant or smoke-retardant characteristics.

The improved process of the present invention permits plastic beams to be fabricated with thin bottom and side walls to provide a beam whose side and bottom walls are relatively thin, so that the beam is virtually hollow. Yet the beam constructed by the process of the invention has all the external appearance of a natural wooden beam. Beams may be constructed by the process of the present invention at but a fraction of the cost and weight of the prior art plastic beams, and yet they exhibit all the favorable characteristics thereof.

The process of the invention may also be used to fabricate a continuous thin-skin of polyurethane inner core. The inner core, as mentioned above, may be composed of polystyrene, honeycomb treated paper, or the like. An advantage of the beams of this latter type is that they are much less expensive than beams, composed, for example, completely of polyurethane. Also, the beams of the latter type, and especially when the honeycomb paper core is used, are found to possess much greater flame and smoke retardant properties than plastic beams composed entirely of polyurethane. An added feature with respect to the beams having a polystyrene or honeycomb core with a skin of polyurethane is that they are less susceptible to warpage.

It is well known that polyurethane is a relatively expensive material, and that in order to reduce the overall cost of the simulated beam, the wall should be as thin as possible. When the three-dimensional rubber mold of the prior art is used, it is possible to place a center core section of wood or metal down the length of the beam. However, when the central core section is made large enough in the prior art three-dimensional mold, so as to achieve thinner walls for the beam, a point is reached where actually more polyurethane is required to make the beam. This is because more pressure is required, and thus more polyurethane foam, to overcome the friction involved in forcing the foam up into the restricted cross-section between the center core and the inner surface of the prior art mold.

The aforesaid problem is solved with the mold of the present invention, in which the polyurethane is spread over the total area prior to closing the mold. Because of the nature of polyurethane, it is possible to spread the material on the rubber liner used in the mold of the present invention, while the polyurethane is still in a liquid state. However, the polyurethane begins to cure, and its viscosity rises rapidly to the point where the material will not slide down as the sides of the mold of the present invention are raised. Therefore, by use of the mold of the present invention, the amount of polyurethane used may be reduced, and the result is a low density product, rather than a high density product as is the case when the prior art process is used, because the force required to force the foam into the restricted section of the prior art mold.

The capability of the mold of the present invention to make a very thin U-channel polyurethane beam lead to the provision of an inner core composed, as described above, of a less expensive material, such as polystyrene, honeycomb treated paper, or the like. The provision of the inner core added other advantages, in addition to the reduction of cost. For example, the inner core, when composed of polystyrene or honeycomb paper has good temperature stability. This is opposed to polyurethane which has a closed cell, gas-filled structure, and which has a tendency to warp with temperature changes. Polystyrene, for example, is an open cell material, and has no tendency to warp. Also, the use of the paper honeycomb core, composed of treated paper, has the added feature of being an excellent smoke and flame retardant.

Therefore, and as will be described, an improved process is provided which results in reduced tooling cost, since a single flat wooden pattern may be used for providing a liner for use in the mold for all beam sizes, and since the mold itself can be used for all beam sizes. In addition, the resulting product, is less expensive than the prior art simulated beam, and also has the added advantages of greater temperature stability, as well as retarding flame spread or smoke development, in the case of fire.

An important feature of the present invention, therefore, insofar as the first mentioned aspect is concerned, is the provision of a simulated box or channel beam, having an integral monolithic construction, and formed, for example, of a molded foam plastic material such as polyurethane. Another feature of the process of the invention, in its second aspect, as mentioned above, is the provision of a simulated box or channel beam, having a core of appropriate material, and having a thin skin of foam plastic material, such as polyurethane, molded continuously over the core.

In either case, the resulting beams have an external appearance which simulates to a high degree of a wooden beam, insofar as grain and color is concerned. The finished beam may be painted, stained or antiqued, for example, to simulate walnut or mahogany finish, or it may be unfinished. By the process of the invention, an authentic reproduction and simulation of hand-hewed wooden beams may be achieved, simply and inexpensively, complete with grain, random knots, and the like.

The simulated beams constructed in accordance with the process of the invention have advantages over wooden beams, as explained above, in that they are lighter, less expensive and easier to install. Moreover, the simulated plastic beams of the present invention have a high strength, and will not split or rot. Moreover, the beams are not susceptible to termites, or the like, and they may be made to possess more favorable flame and smoke retardant characteristics than wooden beams.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representation of a room in which beams are mounted on the ceiling, and which beams may be constructed in accordance with the process of the present invention;

FIGS. 2A, 2B and 2C illustrate various types of box beams which may be constructed by the process of the invention;

FIGS. 3A and 3B show various types of support or anchor blocks which may be used for mounting the beams on the ceiling or wall of a room;

FIGS. 4A-4E show various components of a mold, and various steps of a process, for the formation of box beams in accordance with the process of the invention in one of its aspects;

FIG. 5 is a perspective representation of a form or mold, in which a rubber liner used in the process of the invention may be made, which liner has embossed in it a desired wood grain;

FIG. 6 is a perspective representation of a rubber liner which may be formed, for example, in the mold of FIG. 5;

FIG. 7 is a perspective representation of a block which is used in the molding process of the invention, and also of a core formed of appropriate material, such as polystyrene or honeycomb paper, and which is fitted over the block in the practice of the process of the invention in another of its aspects;

FIG. 8 is a representation of a mold, similar to the hinged mold shown in FIG. 4, but incorporating additional features, as will be described; and

FIG. 9 is a side elevation of an appropriate clamp which, together with other similar clamps, may be used to hold the walls of the mold in FIG. 8 in an upright position during the molding process.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The room represented in FIG. 1 includes, for example, side walls 10 and 12 and a ceiling 14. A plurality of beams 16 are mounted on the ceiling 14, and these beams extend from one end of the room to the other. As mentioned above, the beams 16 could, if desired, be mounted on the walls of the room. As also mentioned, the beams 16 may be constructed by the process of the present invention.

For example, and as shown in FIG. 2A, the beams 16 may be formed of molded plastic material, such as polyurethane, with the external surface having a wood grain formed therein. The beams of FIG. 2A may be formed completely of polyurethane, as a unitary structure, or else they may be formed to have an appropriate core, with a skin of polyurethane molded continuously around the core. The beams may be stained or painted any desired color, or they may be antiqued, or they may be subjected to any other appropriate external treatment.

In the case of the beams 16 of FIG. 2A, they are joined together by a ship-lap joint, and they are adhesively attached to one another. Decorative heads 18 may be provided, these heads made, for example, to simulate the heads of carriage bolts which are usually used in mounting hand hewn wooden beams. In the representation of FIG. 2B, for example, the beams 16 may be formed with a butt joint, and adhesively attached to one another. In the latter instance, a decorative snap-on antique metal strap 20 may be provided to extend over and cover the butt joint.

Standard single-sized beams may be produced, shipped and stocked, and they may then be attached to one another to be effectively extended to any required length, with the resulting butt joints being covered by the decorative straps 20. Also, the beams may be sawn or otherwise cut, to any desired length.

As mentioned above, the beams 16 of FIGS. 2A and 2B, for example, may conveniently and easily be mounted on the wall or ceiling of the room of FIG. 1. This may be achieved, for example, by the provision of anchor blocks, such as the block 22 of FIG. 3A, and these may be formed of polystyrene or other appropriate material. The anchor blocks 22 are first adhesively attached to the ceiling by any suitable adhesive, and are positioned at spaced intervals across the ceiling along the paths of the individual beams. Then, the surface of the rear channel of each beam may be covered with an adhesive, and the beams pressed into place over the anchor blocks and held until the adhesive dries.

The embodiment shown in FIG. 2C is slightly different from the embodiment of FIGS. 2A and 2B, in that the box beam 16 of the latter embodiment is provided with inwardly extending ridges 16a at its upper edges, the ridges extending from one end of the beam to the other. The beam of FIG. 2C is intended to be mounted, for example, on anchor blocks such as the anchor block 24 of FIG. 3B. This latter type of anchor block has channels formed at its upper edges, and the ridges 16a snap over the channels when the beam 16 of FIG. 2C is mounted. An adhesive may also be used to attach the beam of FIG. 2C to the block 24, however, the engagement of the ridges 16a with the channels on the block provides a firm and positive support for the beam.

The beams of FIG. 2 may be formed by means of a form such as shown in somewhat schematic form in FIGS. 4A-4E. The form, for example, is a three-piece planar form (foreshortened for illustration purposes only) and it may be composed of wood or any other appropriate material. The form of FIG. 4A includes a central elongated member 50 which has a length, for example, corresponding to the desired length of the beams to be formed thereby, and it also comprises a pair of outer elongated side members of the same length as the central member 50. The side members 52 and 54 are longitudinally hinged to the central member 50, and they may be turned up from the position shown in FIG. 4A, for example, to the position formed in FIG. 4E.

As a second step in the process represented in FIG. 4, a mold liner 56 is laid over the wooden form. The mold liner may be composed, for example, of neoprene or other rubber-like material. The liner may be formed, for example, by pouring liquid rubber over a wooden form, such as the form 80 in FIG. 5, so that the surface of the resulting liner, as designated 56 in FIGS. 4B and 6, will take on the grain of the wood which constitutes the bottom of the form. In the form illustrated in FIG. 5, a movable divider strip 84 is provided, which extends the length of the form, so that liners of different widths may be provided, as desired, and so that the same form 80 may serve to produce liners 82 of various widths for various sizes of simulated wooden beams to be formed by the process of the invention.

Rubber liners, such as the liner 82, have been made in the practice of the process of the invention from liquid urethane rubber obtained commercially, for example, from the C.P.R. Division of Upjohn Corporation of Torrance, California. The liquid material is spread over the form 80 at a width determined by the placement of the divider 84, and is allowed to dry at room temperature. The resulting rubber liner 56 is then stripped from the form 80. The mold liner 56 is then placed on the form shown in FIG. 4B with the grain surface facing upwardly.

The next step in the process, and as shown, for example, in FIG. 4C, comprises spreading the foam plastic material over the surface of the mold liner 56. A central block 60 is provided which has a width slightly less than the width of the central member 50, and of the same length. This block may be provided with side stops which extend along its length. As a following step in the process, and as shown in FIG. 4D, the block 60 is placed down over the plastic foam 58 and along the central member 50.

Reinforcing kraft paper for the beam may initially be wrapped around the bottom and sides of the block 60. As an alternative, the block 60 may be covered, for example, by a core of polystyrene, honeycomb paper, or other material, as will be described, before it is placed down in the foam 58. This core, for example, may have a thickness of one-half inch. As explained above, the use of the additional core of polystyrene, honeycomb paper, or the like, greatly reduces the amount of the expensive polyurethane foam needed for the beam, since only a thin skin of the polyurethane is actually formed around the core, and with the grain from the liner 56 being embossed into the external surface of the skin. The resulting beam, using a core of polystyrene, honeycomb paper, or the like, rather than kraft paper, as a reinforcer, has a wall thickness of the order of one-half inch.

Then, as a final step in the process, the side members 52 and 54 are folded up over the sides of the block 60, causing the liner 56 and the layer of foam plastic 58 likewise to be folded up over the sides of the mold. The foam plastic is permitted to set, and the side members 52 and 54 may then be turned down and the central block 60 removed. The liner 56 may then be stripped off and the result is a simulated wooden beam, such as the beam 16 described above.

By means of the process and mold shown in FIG. 4, the fabrication of a thin-walled simulated box beam is achieved, with the desired thin side and bottom walls, and which could not have been obtained by the usual prior art molding process. When the core of polystyrene or honeycomb paper is used, as mentioned above, there is no need to use kraft paper over the block 60 because the polystyrene core itself acts as a release agent on the block.

In the embodiment of the process shown in FIG. 7, for example, a block 60a is used which is similar in some respects to the block 60 of FIG. 4. In accordance with the process in the second aspect, a core 90 formed, for example, of polystyrene or honeycomb paper, and made out of blocks of the core material into the generally rectangular channel-like configuration of the finished beam, is provided. The block 60a is inserted into the core 90, so that the core surrounds the block.

The block 60a is provided with projections at each end, so that the weight of the block is held up from the layer 58 of polyurethane plastic, for example, which, as described above, is spread over the top of the liner 56. In the latter aspect of the process, when the sides of the mold 56 are folded up around the block 60a in a manner similar to that shown in FIG. 4, a thin skin of the polyurethane foam is molded around the external surface of the core 90; the external surface of the skin, as mentioned above, being embossed with the grain of the liner 56.

The core 90 may be formed of blocks of polystyrene plastic obtained, for example, by the Vertex Corporation of Los Angeles, California, or it is preferably formed of honeycomb treated paper blocks obtained, for example, from the Hexcel Corporation of Dublin, California. As mentioned above, when the core 90 is used in the construction of the beam of the invention, a minimum amount of the expensive polyurethane foam is used. Also, the resulting composite beam has been found to have more favorable smoke and flame retardant characteristics than the beams formed completely of polyurethane.

The mold shown in FIG. 8 is generally similar to the mold described above in conjunction with FIG. 4. The mold of FIG. 8 is formed, for example, of an appropriate metal such as aluminum, and includes electrical heating elements (not shown) which serve to raise the temperature of the polyurethane during the curing step of the process to around 120.degree., for a more rapid set than is achieved at room temperature.

The mold shown in FIG. 8 has a bottom 100 which is formed of a plurality of channel members which are bolted together. More or less channel members may be used for any particular beam construction, depending upon the desired width of the beam. The mold also includes side walls 102 and 104 which, like the side walls 52 and 54 of FIG. 4 are hinged to the bottom of the mold so that they may be turned up in the manner described above. Appropriate clamps, such as the clamp 106 of FIG. 9, are provided to clamp the hinge sides in their upright position during the molding process.

As before, in order to carry out the process of the invention in its latter aspect, the rubber liner 56 is placed over the mold of FIG. 8 with the hinged sides 102 and 104 in their turned-down open position. Then, the layer 58 of polyurethane foam is spread over the liner 56, as was the case in the process described in conjunction with FIG. 4. The core 90 of FIG. 7 is then plaed around the block 60a and the block and core are set down over the base 100 of the mold of FIG. 8. The projecting ends of the block 60a support the block up from the polyurethane plastic on the base of the mold, so that the plastic only supports the relatively light weight of the core 90. The sides 102 and 104 are then turned up and clamped by clamps, such as the clamp 106 of FIG. 9, and the mold is heated by the aforesaid electrical heating elements, to set the thin polyurethane layer 58, and to cause it to form a thin skin around the core.

The invention provides, therefore, an improved process whereby plastic box beams may be produced having thin side and bottom walls, and which are relatively light and inexpensive, and which use a minimum amount of plastic material in their construction. Different sized beams may be constructed, merely by using different sized blocks 60 or 60a, and by making the width of the central strip 50 of FIG. 4 adjustable, as described in conjunction with FIG. 8. As described in FIG. 8, the width of the central strip is made adjustable by providing separate channels which may be inserted or removed, depending upon the width desired of the resulting beam.

An important feature of the present invention, as described above, is that a single wooden pattern may be used to manufacture a full range of beam sizes, for example, from 2 inches .times. 4 inches to 12 inches .times. 24 inches; and a single rubber liner may, likewise, be used to produce many beam sizes. This is in contradistinction to the prior art which required a separate mold and wooden pattern for each different width beam produced.

While particular embodiments of the process of the invention have been shown and described, modifications may be made. It is intended to cover all such modifications in the following claims.

Claims

What is claimed is:

1. A process for forming a plurality of beams, each beam being defined by a bottom and a pair of spaced and parallel sidewalls, the process comprising:

a. providing a form having a central elongated base member and an elongated side member hinged to each longitudinal side of the base member;

b. providing a reusable, flat, flexible rubber-like mold liner having a grain surface simulating a wood grain;

c. placing the liner flat on a surface of the form to cover the base member and the side members with the grain surface of the liner facing upwardly;

d. spreading a layer of uncured polyurethane foam plastic over the grain surface of the mold liner while the liner is flat;

e. placing an elongated block over the layer of plastic on the base member in coextensive relationship with the base member;

f. thereafter turning the side members up relative to the base member towards the elongated block to cause the liner and layer of plastic to be folded against the block;

g. permitting the plastic to set;

h. thereafter removing the liner from the set plastic; and

i. thereafter repeating steps (c) through (h) by using the liner previously removed from the set plastic.

2. The process defined in claim 1, and which includes first placing a channel-shaped member over the bottom and sides of said elongated block to constitute a core for the beam.

3. The process defined in claim 2, in which said core is formed of polystyrene plastic material.

4. The process defined in claim 2, in which said core is formed of honeycomb paper material.

5. The process defined in claim 1, in which said central elongated base member is formed of a plurality of adjacent strips releasably attached to one another.

6. The process defined in claim 1, and which includes the steps of forming said liner by spreading liquid rubber-like material over a wooden form, the form having a removable central elongated divider for determining the width of said liner.

7. A method for forming a lightweight beam having a textured exterior surface comprising the steps of forming a thin, deformable and reusable rubber-like liner having a textured side by providing a wooden form, spreading a fluid rubber-like material over a face of the form, curing the material to form a liner and removing the liner from the form; spreading a relatively thin layer of uncured polyurethane foam plastic on the textured side of the liner; placing an elongated block having upright, longitudinal surfaces lengthwise over the liner length, thereafter folding the liner longitudinally to contact the layer with the block surface, supporting the liner in such position, expanding and curing the plastic within a closed space defined by the liner and block while the liner is supported in such position to form the beam with a textured surface complementary to the textured surface of the liner, thereafter removing the liner from the article, and reusing the same liner for forming another beam from uncured polyurethane foam in accordance with the steps and in the same sequence of steps as are set forth above.