Patent Publication Number: US-6983987-B2

Title: Tubular metallic simulated bamboo, method for manufacturing and articles fabricated therefrom

Description:
This application claims the benefit of Provisional Application No. 60/379,103, filed on May 10, 2002. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a stock material comprising metallic tubing which realistically simulates bamboo, and to products such as furniture fabricated from such metallic tubing. 
   2. Description of the Prior Art 
   Bamboo and other grasses and woody plants have long been utilized to fabricate furniture and other articles. The appearance of such furniture and other articles is so pleasing as to have inspired many attempts to simulate bamboo and the like when rendered artificially from materials other than those of natural plants. 
   One of the unsolved needs of the furniture and other industries wherein it is desirable to simulate bamboo stalks is realistic rendition of nodes and culms which characterize natural bamboo, while fabricating simulated bamboo from inexpensive yet strong and durable tubular stock material. Many prior art attempts to simulate bamboo depend upon inscribing nodes into tubing or, alternatively, deforming the stock material such that simulated nodes project outwardly from the tubing. Both approaches fail to achieve realistic effect. 
   Casting can realistically simulate bamboo but cast construction, particularly from metals, has undesirable attributes. One is that resultant simulated bamboo product is relatively heavy, being solid rather than hollow, compared to worked tubing. Although hollow castings can be produced, this greatly increases difficulty and expenses of manufacture. Another is that the cost of fabricating suitable dies is extremely expensive. A further problem is that cast metallic simulated bamboo is usually brittle and unsuitable for fabricating furniture, which represents the widest use of simulated bamboo. Brittleness leads to ready breakage and also prevents imparting mild curvature during fabrication to straight sections of simulated bamboo stocks. Although the product could be cast in the final desired configuration, this will likely increase the number of expensive dies required to fabricate a set of related articles of furniture. Still another problem with casting is that cast construction is difficult at best to weld, which may be required when fabricating assembled products such as furniture, in which sections of simulated bamboo stalk intersect. 
   None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. 
   SUMMARY OF THE INVENTION 
   The present invention describes both a stock structural material and also finished consumer products, both of which exhibit construction from simulated bamboo fabricated from thin walled metallic tubing. This construction provides a number of advantages simultaneously. One is the ability to provide strength and durability of construction from metals. Another is the ability to utilize metallic material in stock form, such as extruded or rolled and welded stock. 
   An additional advantage is to avoid casting as a fabrication technique, thereby avoiding inherent disadvantages of casting such as expense and brittleness of the product. 
   A further advantage of the present invention is that it achieves a realistic appearance of natural bamboo stalks. 
   Still another is to provide a constituent material which simulates bamboo while having the strength requisite for fabricating furniture while limiting the overall diameter of simulated bamboo stalk. 
   A further advantage is that the simulated bamboo material may be bent slightly to achieve desired contours without failing, displaying visible distortion such as wrinkling and cracking, or significantly weakening. 
   A still further advantage is to be able to weld abutting sections of simulated bamboo. 
   The invention provides these qualities while realistically simulating bamboo. To this end, the present invention contemplates fabricating simulated bamboo, utilizing thin walled tubing as a stock material and cold working the stock material to exhibit simulated nodes and simulated tapering of culms typical of natural bamboo. The invention may take the form of a stock material simulating bamboo or, alternatively, of an article of manufacture incorporating the stock material simulating bamboo. 
   Accordingly, it is one object of the invention to provide simulated bamboo in the form of thin walled metallic tube stock configured to simulate bamboo. 
   It is another object of the invention to simulate characteristics of natural bamboo such as nodes and curvature of culms. 
   It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes. 
   These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various other objects, features and attendant advantages of the present invention will become more fully appreciated as the same become better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views and wherein: 
       FIG. 1  is a perspective view of a length of a stock elongate structural material simulating bamboo formed according to the present invention. 
       FIG. 2  is a side cross sectional view of the material of  FIG. 1 . 
       FIG. 3  is an enlarged detail view taken along line  3 — 3  of  FIG. 2 . 
       FIG. 4  is a perspective view of an article of furniture utilizing the stock material of  FIG. 1 . 
       FIG. 5  is a diagrammatic and elevational view of apparatus employing dies to form the stock material of  FIG. 1 . 
       FIG. 6  is an enlarged, perspective detail view of a die seen at the left of  FIG. 5 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 and 2  of the drawings show a length of a stock elongate structural material  10  simulating bamboo. The stock material  10  is formed from stock tubing having cylindrical, annular configuration prior to being reformed to take on the nodes and taper of a culm of natural bamboo. The tubing is thin walled and malleable and has been cold worked to be configured to include at least one section, and preferably at least one additional abutting section, each corresponding to a section of a natural stalk of bamboo, where a section will be understood to extend between adjacent nodes. Thin walled signifies that combined thicknesses of the wall of the finished generally tubular or annular stock material simulating bamboo, taken at two diametrically opposing points along the circumference of the finished material, do not exceed one-half of the diameter of the open center of the tube taken along the same line as the two diametrically opposing points. 
   Where a series of abutting sections are provided, they may be fabricated from a single piece of tubing of desired length. Sections of culms of natural bamboo are characterized in that each has enlarged nodes separating adjacent sections, and in that each section is progressively, increasingly tapered from the minimum diameter of the section, usually at the middle, towards the maximum diameter located near each node. Both this characteristic taper and also joint structure of each node, which joint structure includes a defined crease where abutting sections meet, are reproduced in the present invention, using tubular stock material as a raw material. This was heretofore an unrealized goal in commercial production of simulated bamboo products. 
   The tubular stock material is both sufficiently malleable as to accept cold working to reproduce realistic node and culm characteristics, and also sufficiently rigid to provide structural members for furniture. Examples of preferred stock tubular material include rolled ferrous metallic stock, such as steel, and extruded aluminum material. Aluminum material will be understood to encompass aluminum and its alloys. However, other malleable, strong materials such as other metals and alloys, polyvinyl chloride, and other plastics could be utilized if desired. 
   The simulated section  12  is tapered to simulate the taper of a culm of natural bamboo. To this end, the simulated section  12  has a portion of a first node  14  at the proximal end  16  of the simulated section  12  and a portion of a second node  17  at the distal end  18  of the simulated section  12 . As seen in  FIGS. 1 and 2 , the simulated section  12  is visibly tapered progressively along its length. The center  20  of the simulated section  12  has no taper, where taper is meant to signify curvature of the outer surface  22  of the simulated section  12  from a point  24  of minimum outer diameter towards the center  20  to a point  26  of maximum outer diameter taken at a node  14  or  17  of the simulated section  12 . Of course, the simulated section  12  could be modified if desired so that there is always some taper therealong. The simulated section  12  will be understood to be typical of a repeating series of identical or similar sections. The stock material  10  may include any number of sections of the type typified by the simulated section  12 , and is not necessarily limited to similar, repeating lengths. 
   Minimum and maximum outer diameters of other sections may be identical to those of the simulated section  12 , although this represents a departure from natural bamboo. In natural bamboo, maximum and minimum outer diameters of each section generally become progressively smaller from the base of the stalk to the tip of the stalk. For purposes of fabricating articles from simulated bamboo, lengths of simulated bamboo are used wherein such decrease in dimensions is not discernible to casual observation. Similarly, length of each one of a series of sections formed in a length of stock material according to the present invention may vary in a manner not found in nature. 
   The nature of the tapering of section  12  will now be described, with reference to  FIG. 3 . The taper of the outer surface  22  of the simulated section  12  is curved and further is of variable radius. That is, the curve may be, for example, parabolic rather than being sinusoidal. The slope progressively increases when considered starting from the proximal end  16  and proceeding towards the center  20  when the simulated section  12  is horizontally oriented as depicted in  FIGS. 1  and  2 . Horizontal orientation signifies that the longitudinal axis  21 , which is located along the hollow center of that section of structural material  10  including the simulated section  12 . Slope characteristics are seen in  FIG. 3  by comparing projection lines A, B, and C, which touch the surface  22  tangentially, slopes of lines A, B, and C deviating increasingly from the horizontal. Slope of lines C, D, and E then progressively decreases when considered starting from the proximal end  16  and proceeding towards the center  20 . 
   The slope described above characterizes the proximal end  16 . The distal end  18  is essentially a mirror image of the proximal end  16 , and thus need not be shown to the scale and level of detail of  FIG. 3 . In summary, at the distal end  18 , the slope progressively increases in magnitude, or deviation from the horizontal, then decreases when considered starting from a point located between the center  20  and the distal end  18 , and proceeding to the distal end  18  (best seen in  FIG. 2 ). 
   The simulated nodes  14  and  17  are disposed between and separate the simulated section  12  and additional sections essentially similar to the simulated section  12 . The simulated nodes  14  and  17  are formed at abutting tapered portions of the simulated section  12  and any adjacent section where each section has the greatest diameter. The simulated  14  and  17  are each depressed into the stock material  10  such that the interior surface  28  is inwardly displaced, as indicated for the simulated node  14  by an inward bulge  30  in  FIG. 2 . 
   Referring now to  FIG. 4 , an article of manufacture, including an article of furniture such as a chair  40 , is fabricated using lengths of stock material  10  as elongate structural members, each of which is connected to at least one other elongate structural member formed from the stock material  10 . The chair  40  is further shown in our co-pending Design Patent Number D465,668, entitled Simulated Bamboo and Wicker Chair. The chair  40  has four vertical load bearing structural members  42 ,  44 ,  46 , and  48 . Two of the structural members  42  and  48  are connected by a generally horizontal armrest  50 . Two of the structural members  44  and  46  are similarly connected by a generally horizontal armrest  52 . A load bearing member such as a seat  54  is supported by the structural members  42 ,  44 ,  46 , and  48 . A seatback  56  has two horizontal members  58  and  60 , each of which is fixed to two of the structural members  46  and  48 . A horizontal cross brace  62  connects two of the structural members  46  and  48  at the top thereof. The seat  54  is supported by attachment of the peripheral frame members  64 ,  66 ,  68 , and  70  to the vertical members  42 ,  44 ,  46 , and  48 . 
   To provide aesthetic benefits of simulation of bamboo, the members  42 ,  44 ,  46 ,  48 ,  50 ,  52 , and  62  are made from the stock material  10 . An advantage of the nature of the stock material  10  is that lengths of the stock material  10  can tolerate some bending, as seen by examining the structural members  42  and  48 , among others, and still maintain the characteristic curvature of each section of simulated bamboo. The effect of simulated bamboo can be combined with other thematically related visual features. For example, the seat  54  and the seatback  56  are formed from real or simulated wicker construction. Real or simulated rattan is another example of thematically related material. Also, simulated bamboo members may be combined in the frame structure with members that do not simulate bamboo. 
   It should be noted that the entire length of every structural member of the chair  40  need not be worked to simulate bamboo. For example, concealed portions of the structural members  46  and  48  may retain their original stock configuration. Such construction saves cost of producing the chair  40  while still presenting a dominant impression of bamboo construction. The concealed structural members  58 ,  60 ,  64 ,  66 ,  68 , and  70  also need not be worked to simulate bamboo. 
   Both lengths of stock material corresponding to the stock material  10  and also articles utilizing the stock material in fabrication may utilize alternative embodiments of the invention wherein a length of the stock material  10  may include the novel characteristics set forth above in combination with other configurations. For example, lengths of the stock material  10  may be configured according to the invention along only part of the entire length thereof. The remaining length may be of the original cross sectional configuration or, alternatively, may be formed to have another configuration. The remaining length may be ornamented utilizing a different decorative scheme, or may be unornamented. In the example of the embodiment of  FIG. 4 , only visible portions of the members  42 ,  44 ,  46 ,  48 ,  50 ,  52 , and  62  need include a series of abutting sections, each of which is tapered to simulate taper of a culm of natural bamboo in order to present the visual effect of bamboo framed furniture. 
   The simulated stock material  10  thus described is formed from cylindrical, annular tubing by cold working. It is thought that the best way of imparting the described characteristics to tubing is accomplished by using dies. The preferred method is to place a plurality of complementing dies around a tube, urge the dies inwardly such that they converge in complementing contact with the tube, and to urge the tube outwardly against the dies. The tube may be urged outwardly by compressing the tube axially, causing the tube to “buckle” outwardly in a near plastic deformation. This arrangement is shown diagrammatically in  FIG. 5 , with the dies  80 ,  82 ,  84 , and  86  shown in a position drawn away from the tube  88 . The dies  80 ,  82 ,  84 , and  86  are held in a rotatable spindle (not shown) such that they rotate at the same rate as the tube  88 , which is secured in a suitable chuck (not shown) or the like. There is no relative rotation between the dies  80 ,  82 ,  84 , and  86  and the tube  88 . 
   The dies  80 ,  82 ,  84 , and  86  are urged inwardly towards the tube  88 , as indicated by arrow in  FIG. 5 . Centrifugal force simultaneously urges the wall of the tube  88  outwardly against the dies  80 ,  82 ,  84 , and  86 . Additionally, this method enables the dies such as die  80  (see  FIG. 6 ) to bear a female die face  90  which includes features  92  rendered as a negative of a simulated node. Because the tube  88  is under compressive axial forces, the tube  88  will deform (“buckle”) outwardly to fill the void between the dies  80 ,  82 ,  84 , and  86  and the tube  88 , causing the tube  88  to take the inverse shape of the die(s)  80 ,  82 ,  84 , and  86  and the tube  88 . The surfaces of die face  90  towards the ends  94  and  96  are cylindrical and conform to the outer surface of the tube  88 . This enables nodes to be formed in the tube  88  at periodic, selectable intervals. Minor variations in distances between adjacent nodes will not be discernible. 
   A length of stock material  10  is formed by repeating the operation for forming nodes, with relative positions of the dies  80 ,  82 ,  84 , and  86  and the tube  88  being adjusted to suit. It would be possible to fabricate dies (not shown), including more than one node, so that more than one section of simulated bamboo is formed in every forming operation. However, the apparatus and method described above will result in minimal capital outlay for dies, and also confer ability to form only one section on the tube  88 . Also, this may be desirable in articles wherein only a short section of a structural member simulating bamboo is revealed. 
   Other methods may be employed to form the stock material  10 . For example, dies (not shown) extending the full length of a tube which is to be reconfigured to simulate bamboo may be utilized. Where full length dies are utilized, tubing may be urged outwardly by means other than rotation and/or axial compression, such as by applying internal fluid pressure, an example being hydroforming. Alternatively, specially formed rollers may be employed in a rolling method. Die forming, rolling, and other techniques may be combined if desired. 
   It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.