Abstract:
A tubular strip for leisure chair is made of a specific pliable polyvinyl chloride (PVC) material by way of injection molding, so that the tubular strip has a reduced wall thickness with a plurality of spaced reinforcing ribs integrally molded on an outer surface of the tubular strip to provide a common force-bearing structure.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a tubular strip for leisure chair, and more particularly to a tubular strip that is molded using largely reduced quantity of polyvinyl chloride (PVC) material while provides sufficient structural strength required for use on a leisure chair.  
       BACKGROUND OF THE INVENTION  
       [0002]     Due to its wide applications, polyvinyl chloride (PVC) material has become one of the most important raw materials in current plastic industry. PVC is also appreciated for it low price, good workability, and noncombustible property. Plasticizer and fillers may be added for PVC material to have different hardness and be used in making products such as plastic tubes, pipes, hoses and the like.  
         [0003]     In recent years, the demand for PVC in the world constantly increases, and is as high as 25 million metric tons in 1999. The demand for PVC keeps growing at a rate approximate to 4.5% each year. Among others, PVC demand in Asian countries has the highest annual rate of growth of 8%.  
         [0004]     Calcium carbide process is currently a major way for producing PVC though it disadvantageously consumes high energy and possibly results in environment pollution. In recent years, the shortage of coal in the international market due to the high demand for PVC in Asia, and the current policy of restricted supply of power in China, one of the largest PVC production centers in the world, have caused further reduction in productivity of PVC produced by the calcium carbide process, as well as constant rise in PVC price in Far East. In view that the shortage of coal in the international market and the restricted power supply policy in China will continue, it is expected the market demand and the price for PVC would still keep rising at least in the near future.  
         [0005]     The largely increased PVC price in turn results in increased manufacturing cost in firms that use PVC as a major material in their products. For example, as illustrated in  FIG. 1 , a deck chair  10  typically includes a seat  11 , a back  12 , and a footrest  13 , a large part of these areas are usually formed using a plurality of tubular strips  14  parallelly and continuously arranged and stretched over frames of the deck chair  10 . The tubular strips  14  are then firmly set in place on the deck chair  10  by welding at predetermined positions to form welded seams  15 .  
         [0006]      FIGS. 2 and 3  are perspective and cross-sectional views, respectively, of the conventional tubular strip  14 . For the tubular strip  14  to have required structural strength for bearing a force applied thereon, the tubular strip  14  must have a specific wall thickness T. Each deck chair  10  would require at least several decades of tubular strips  14 , each being in the length no less than one meter. Therefore, a significantly large quantity of PVC material is required for producing one such deck chair. Under this condition, the recently constantly increased PVC price inevitably becomes a heavy burden of the manufacturers of such deck chair with PVC strip seat, back and footrest.  
       SUMMARY OF THE INVENTION  
       [0007]     A primary object of the present invention is to provide a tubular strip that provides a structural strength required for forming the seat, the back, and the footrest of a leisure chair but can be made with largely reduced quantity of PVC material to effectively reduce the manufacturing cost of such leisure chair.  
         [0008]     Another object of the present invention is to provide an improved tubular strip for leisure chair; so that the seat, the back, and the footrest of the leisure chair formed using the tubular strip of the present invention have good air ventilation for comfortable contact with a user&#39;s skin.  
         [0009]     To achieve the above and other objects, the tubular strip for leisure chair according to the present invention is made of a predetermined pliable polyvinyl chloride (PVC) material by way of injection molding, so that the tubular strip has a reduced wall thickness with a plurality of spaced reinforcing ribs integrally molded on an outer surface of the tubular strip to provide a common force-bearing structure. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein  
         [0011]      FIG. 1  is a perspective view of a deck chair with its back, seat, and footrest formed with tubular strips;  
         [0012]      FIG. 2  is a fragmentary perspective view of a conventional tubular strip used in the deck chair of  FIG. 1 ;  
         [0013]      FIG. 3  is a cross-sectional view of  FIG. 2 ;  
         [0014]      FIG. 4  is a fragmentary perspective view of an externally ribbed tubular strip for leisure chair according to a preferred embodiment of the present invention;  
         [0015]      FIG. 5  is a cross-sectional view of  FIG. 4 ; and  
         [0016]      FIG. 6  is a fragmentary cross-sectional view of a plurality of tubular strips of the present invention in a parallelly positioned and tightly stretched state. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]     Please refer to  FIGS. 4 and 5  that are fragmentary perspective and cross-sectional views, respectively, of a tubular strip  20  according to a preferred embodiment of the present invention for use on a leisure chair.  
         [0018]     The tubular strip  20  is in the form of a hollow tube made of a specific pliable PVC material, and has a wall thickness Ti that is significantly reduced as compared to the wall thickness T of the conventional tubular strip  14  shown in  FIGS. 2 and 3 . In the illustrated embodiment, the wall thickness T 1  of the tubular strip  20  for leisure chair is about one third (⅓) to one half (½) of the wall thickness T of the conventional tubular strip  14 .  
         [0019]     The tubular strip  20  of the present invention is characterized by a plurality of axially extended reinforcing ribs  22  circumferentially spaced on an outer surface of the tubular strip  20 . Though not necessary, the reinforcing ribs  22  in the illustrated embodiment are angularly arranged on the outer surface of the tubular strip  20  at equidistance. For example, the reinforcing ribs  22  may be spaced from one another by  45  degrees on the tubular strip  20 . However, it is understood the present invention is not limited to the above design. That is, for the sake of saving material, the reinforcing ribs  22  on the outer surface of the tubular strip  20  may be in the number and at angular positions determined according to actual need in forming differently designed leisure chairs.  
         [0020]     Please refer to  FIG. 6 . When a plurality of tubular strips  20  of the present invention are parallelly positioned and tightly stretched over the leisure chair to form the back, the seat, and the footrest, the tubular strips  20  subject to the stretch have each a hollow elliptic cross section that provides relatively larger force-bearing surface area. The parallelly positioned and tightly stretched tubular strips  20  are then welded at predetermined positions to firmly fix on frames of the leisure chair. When the tubular strips  20  that are welded together and firmly fixed to the frames of the leisure chair are subjected to a force, it is the outer surfaces of the tubular strips  20  and the spaced reinforcing ribs  22  provided thereon that together provides the tubular strips  20  with sufficient structural strength to bear the force applied thereto.  
         [0021]     The tubular strip for leisure chair according to the present invention can be advantageously mass-produced using PVC material by way of injection molding and in procedures exactly the same as the existing ones with slightly modified molds.  
         [0022]     Since the tubular strip  20  of the present invention has largely reduced wall thickness and sufficient structural strength, it enables the leisure chair that uses the tubular strips  20  to cover most areas of the back, the seat, and the footrest of the leisure chair to be manufactured with largely reduced quantity of PVC material and accordingly, at effectively lowered manufacturing cost without being affected by the constantly rising price in the international PVC cash market. Moreover, with the reinforcing ribs  22 , the outer surface of the tubular strip  20  provides better air ventilation for forming a more comfortable leisure chair.  
         [0023]     The present invention has been described with a preferred embodiment thereof and it is understood that many changes and modifications in the described embodiment can be carried out without departing from the scope and the spirit of the invention that is to be limited only by the appended claims.