Abstract:
A method of manufacturing loading plane border frame tubes for chairs utilizes continuous roll-forming processes to roll a base material to form loading plane border frame tubes for use on chairs. The processes include: transport a steel sheet to a roller leveler for flattening; then roll the steel sheet through a first roller calender, a second roller calender, a third roller calender, and a fourth roller calender to form a semi-finished tube; send the semi-finished tube to a high frequency generator for welding and soldering at high temperature; trim the semi-finished tube in a trimming machine; and roll the semi-finished tube through a fifth roller calender to form a finished tube of a selected shape for making border frames of loading planes of the chairs.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a method of manufacturing loading plane border frame tubes for chairs and particularly a method that utilizes continuous roll-forming processes to roll a base material to form loading plane border frame tubes for use on chairs.  
           [0002]    Many leisured chairs now available on the market have small sizes and light weights, and are easy to carry and store. Their prices are also relatively inexpensive. Hence they are widely accepted by consumers. Whereas they still have problems when in use.  
           [0003]    Most leisured chairs have a loading section to support human body. The loading section generally has a loading border frame formed by a round steel tube and a seat pad made of a selected fabric or leather. The fabric or leather is stitched at the rims to form a coupling section. During assembly, the steel tube is directly inserted into the coupling section. Or the coupling section of the fabric or leather may be connected to the border frame by springs. When used for supporting people for a period of time, the stitching of the fabrics or leather could be frayed and ruptured, or the springs connecting the fabrics (or leather) and loading border frame could have elastic fatigue, or the round steel tube will result in deformation. It could become risky to users when using.  
           [0004]    The loading border frame of conventional leisured chairs may also be made of light wood to couple with the fabric or leather coupling section. Or the fabric or leather may be stitched directly to the wooden border frame by means of staple guns. When used for supporting people for a period of time, the stitching of the fabrics or leather could be frayed and ruptured. The stapled portions also tend to rupture, or the wooden frame broken. It also incurs safety concerns to users.  
         SUMMARY OF THE INVENTION  
         [0005]    The primary object of the invention is to resolve the foregoing disadvantages. The invention aims to provide a continuous roll-forming processes to roll a base material to form loading plane border frame tubes for use in chairs. When in use, the rims of the loading plane (such as loading planes made by weaving or braiding fabrics, leather, plastic sheets) are fastened to an insert element which may be directly wedged into the frame tube so that the loading plane won&#39;t be ruptured when supporting the weight of people.  
           [0006]    Another object of the invention is to provide formed tubes that are simple and easy to assemble to save processes and time.  
           [0007]    A further object of the invention is to provide formed tubes with selected cross sections to complement the supporting power of the loading plane so that deformation or rupture is less likely incur to the loading plane  
           [0008]    To attain the foregoing objects, the method for manufacturing the tubes of the invention includes to flatten and smooth steel sheets through a roller leveler, then the steel sheets are formed to semi-finished tubes by roll-forming processes through a first, a second, a third and a fourth roller calender. The semi-finished tubes then are conveyed to a high frequency generator for welding and soldering at high temperature, then are delivered to a trimming machine for finishing, and finally are transported to a fifth roller calender to proceed final roll-forming to become finished tubes for use in loading planes of chairs.  
           [0009]    The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1A is a schematic view of a first manufacturing process for making a first tube embodiment of the invention.  
         [0011]    [0011]FIG. 1B is a first schematic end view of a semi-finished first tube embodiment.  
         [0012]    [0012]FIG. 2A is a schematic view of a second manufacturing process for making a first tube embodiment of the invention.  
         [0013]    [0013]FIG. 2B is a second schematic end view of a semi-finished first tube embodiment.  
         [0014]    [0014]FIG. 3 is a schematic view of a third manufacturing process for making a first tube embodiment of the invention.  
         [0015]    [0015]FIG. 4A is a schematic view of a fourth manufacturing process for making a first tube of the invention.  
         [0016]    [0016]FIG. 4B is a third schematic end view of a semi-finished first tube of the invention.  
         [0017]    [0017]FIG. 5 is a schematic view of a fourth manufacturing process for making a first tube embodiment of the invention.  
         [0018]    [0018]FIG. 6A is a schematic view of a first manufacturing process for making a second tube embodiment of the invention.  
         [0019]    [0019]FIG. 6B is a first schematic end view of a semi-finished second tube embodiment.  
         [0020]    [0020]FIG. 7A is a schematic view of a second manufacturing process for making a second tube of the invention.  
         [0021]    [0021]FIG. 7B is a second schematic end view of a semi-finished second tube of the invention.  
         [0022]    [0022]FIG. 8 is a schematic view of a third manufacturing process for making a second tube embodiment of the invention.  
         [0023]    [0023]FIG. 9A is a schematic view of a fourth manufacturing process for making a second tube embodiment of the invention.  
         [0024]    [0024]FIG. 9B is a third schematic end view of a semi-finished second tube embodiment.  
         [0025]    [0025]FIG. 10A is a schematic view of a fifth manufacturing process for making a second tube embodiment of the invention.  
         [0026]    [0026]FIG. 10B is a schematic end view of a finished second tube embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]    The method of manufacturing loading plane border frame tubes for chairs according to the invention includes a front stage process  10 , a middle stage process  30  and a rear stage process  40  for roll-forming a metal sheet  20  to tubes for use as loading plane border frame on chairs.  
         [0028]    Referring to FIG. 1A, in the front stage process  10  a metal sheet  20  is prepared and setup as the base material for the tube. The steel sheet  20  is transported to a roller leveler  1  which has a plurality of rollers  11  to flatten and smooth the surfaces of the steel sheet  20  to ensure the quality of the finished tubes.  
         [0029]    After the steel sheet  20  is flattened by the roller leveler  1 , it is conveyed to a first roller calender  3  and is rolled between a first upper roller  31  and a first lower roller  32 . The first upper roller  31  and the first lower roller  32  have respectively a first concave surface  311  and a first convex surface  321  to roll and form the steel sheet  20  to become a semi-finished steel sheet as shown in FIG. 1B. The cross section of the semi-finished steel sheet  20  has a bulged section  2  and two flat sections  21  at two sides.  
         [0030]    After completing the rolling process set forth above, the semi-finished steel sheet  20  is transported to a second roller calender  4  (as shown in FIG. 2A). There is a second guide plate  41  inserting into the bulged section  2 , and two second flank rollers  42 ,  42 ′ are provided at two sides of the second guide plate  41  to roll the bulged section  2  of the steel sheet  20  from two sides on the junctures of the bulged section  2  and the flat sections  21  against the second guide plate  41 . The resulting semi-finished steel sheet  20  will have a narrower opening  22 . There is a second forming roller  43  located above the second guide plate  41 . The second forming roller  43  has a second concave surface  431  rolling on an arched surface  23  formed on the top of the bulged section  2 . The resulting semi-finished steel sheet  20  has a cross section as shown in FIG. 2B.  
         [0031]    After completing the front stage process  10  set forth above, the semi-finished steel sheet  20  is transported to a third roller calender  5  of the middle stage process  30  as shown in FIG. 3. The third roller calender  5  has a third guide plate  51  which may be inserted into the bulged section  2 , and two third flank rollers  52 ,  52 ′ located at two sides of the third guide plate  51  for rolling the flat sections  21  at two sides of the bulged section  2  to deform the flat sections such that they become curving upwards to the center of the bulged section  2 . There are a third upper forming roller  53  and a third lower forming roller  54  which have respectively a third concave surface  531  and a third convex surface  541  to roll the bulged section  2 . The third lower roller  54  further has two concave surfaces  542  located at two sides of the third convex surface  541  to deform the flat sections  21  of the semi-finished steel sheet  20  and makes them curving further towards the center of the bulged section  2 .  
         [0032]    After finishing roll-forming in the third roller calender  5 , the semi-finished steel sheet  20  is conveyed to a fourth roller calender  6  (as shown in FIG. 4A). There are a fourth upper forming roller  61  and a fourth lower forming roller  62 , and two sets of fourth flank rollers  63 ,  63 ′ to roll and further deform the semi-finished steel sheet  20  at two ends (to make the two free ends adjacent to each other) above the bulged section  2  (as shown in FIG. 4B). After finishing roll-forming in the fourth roller calender  6 , the semi-finished steel sheet  20  is welded and soldered by a high frequency generator  7 , and then is trimmed by a trimming machine  8 .  
         [0033]    After completing the middle stage process  30  set forth above, the semi-finished steel sheet  20  is transported to a fifth roller calender  9  of the rear stage process  40 . The fifth roller calender  9  has two feeding rollers  91 ,  91 ′ (as shown in FIG. 5) to move and carry the semi-finished steel sheet  20 . There is a fifth upper forming roller  92  which has a fifth concave surface  921  to roll and form the two ends of the flat sections  21  to become an arched or flat surface. There is also a fifth lower forming roller  93  which has two concave surfaces  931 ,  931 ′ to roll and form the junctures of the flat sections  21  and the bulged section  2  to become arched or flat surfaces. Then there are transport rollers  94 ,  94 ′ located at the rear end of the fifth roller calender  9  to move and discharge the formed tubes to complete the manufacturing of the border frame tubes of the loading plane for chairs.  
         [0034]    In the foregoing processes, different forms of tubes can be made by changing the surface profiles of the roller calenders. The following depicts another tube embodiment of the invention.  
         [0035]    Referring to FIG. 6A, in the front stage process  10  a metal sheet  20  is setup as the base material for the tube. The steel sheet  20  is transported to the roller leveler  1  which has a plurality of rollers  11  to flatten and smooth the surfaces of the steel sheet  20  to ensure the quality of the finished tubes.  
         [0036]    After the steel sheet  20  is flattened by the roller leveler  1 , it is conveyed to a first roller calender  3 A and is rolled between a first upper roller  31 A and a first lower roller  32 A. The first upper roller  31 A and the first lower roller  32 A have respectively a first upper corrugated surface  311 A and a first lower corrugated surface  321 A to roll and form the steel sheet  20  to become a semi-finished steel sheet as shown in FIG. 6B. The cross section of the semi-finished steel sheet  20  has a corrugated section  2 A and two flat sections  21 A at two sides.  
         [0037]    After completing the rolling process set forth above, the semi-finished steel sheet  20  is transported to a second roller calender  4 A (as shown in FIG. 7A). The second roller calender  4 A has a second upper forming roller  41 A and a second lower forming roller  42 A which have respectively a second upper corrugated surface  411 A and a second lower corrugated surface  421 A rolling on the semi-finished steel sheet  20  to make the two flat sections  21 A tilted upwards (as shown in FIG. 7B).  
         [0038]    After completing the front stage process  10  set forth above, the semi-finished steel sheet  20  is transported to a third roller calender  5 A of the middle stage process  30  as shown in FIG. 8. The third roller calender  5 A has two sets of first flank rollers  51 A,  52 A and two sets of second flank rollers  51 A,  52 A located behind the first flank rollers  51 A,  52 A, and a third lower forming roller  55 A located below the second flank rollers  53 A,  54 A. The rollers  51 A,  52 A,  53 A,  54 A and  55 A have respectively a concave surface  511 A,  521 A,  531 A,  541 A and  551 A to roll and form the two flat sections  21 A to tilt upwards in a curvy fashion. There is a third upper forming roller  56 A which has a concave surface  561 A to roll and form the two flat sections  21 A until two ends of the two flat sections  21  adjacent to each other in the center.  
         [0039]    After finishing roll-forming in the third roller calender  5 , the semi-finished steel sheet  20  is conveyed to a fourth roller calender  6 A (as shown in FIG. 9A). The fourth roller calender  6 A has two sets of fourth flank rollers  61 A,  62 A which have respectively a fourth concave surface  611 A and  621 A to roll and further deform the two flat sections  21  of the semi-finished steel sheet  20  to become as curvy as desired (as shown in FIG. 9B).  
         [0040]    After finishing roll-forming in the fourth roller calender  6 A, the two ends of the two flat sections  21  are welded and soldered by a high frequency generator  7 , and then the semi-finished steel sheet  20  is trimmed by a trimming machine  8 .  
         [0041]    After completing the middle stage process  30  set forth above, the semi-finished steel sheet  20  is transported to a fifth roller calender  9 A of the rear stage process  40 . The fifth roller calender  9 A has a fifth upper forming roller  91 A and a fifth lower forming roller  92 A to roll and flatten the semi-finished steel sheet  20  to a desired shape. Then there are two sets of fifth flank rollers  93 A and  94 A to roll and form the side walls of the semi-finished steel sheet  20  to a curved shape desired. Thus complete the production of the tubes for border frame of loading plane for chairs (as shown in FIG. 10B).  
         [0042]    The tubes manufactured by the processes set forth above can be used to make loading plane border frames of chairs. When in use, first, measure the size of the loading plane, then cut the tube based on the border frame required for supporting the loading plane. The cut tube is then formed and shaped to become the border frame. The loading plane may be directly inserted into the tube to form the loading plane of the chair.  
         [0043]    Furthermore, after the tube is formed, the cross section of the tube can complement the loading plane to support the weight of people. It is less likely to deform and can effectively prevent the loading plane from rupturing.