referring to fig1 and 2 , the foldable frame of the present invention comprises a first tube 11 , a second tube 12 , a rectangular tube 21 and at least one base part 30 , wherein the second tube 12 is connected to a first end of the rectangular tube 21 and a second end of the rectangular tube 21 is pivotably connected to an extension portion 31 of the at least one base part 30 by a pin 32 . therefore , the first tube 11 is pivotable about the pin 32 to form the single - point folding unit 50 . an outer tube 40 is movable between the second tube 12 and the rectangular tube 21 , and a securing bolt 41 secures the outer tube 40 when the outer tube 40 is moved to a desired position . referring to fig3 and 4 , which show the two - point folding unit 60 of the present invention and includes a first tube 11 a , a second tube 12 a , a rectangular tube 21 a and two base parts 30 a , 30 b . the first and second tubes 11 a , 12 a are pivotably or fixedly connected to the two base parts 30 a , 30 b by two pins 32 a , so that the first and second tubes 11 a , 12 a are pivotable about the two pins 32 a to form the two - point folding unit 60 . an outer tube 40 a is movable between the second tube 12 a and the rectangular tube 21 a , an inner diameter of the outer tube 40 a is the same length as the length of two rod 91 , 92 connected to the rectangular tube 21 a vertically . the outer tube 40 a can be connected to the first and second tubes 11 a , 12 a and is reinforced when connected between the first and second tubes 11 a , 12 a . the rectangular tube 21 a is rotatable so as to change the folding direction . fig5 to 7 show a stretcher which comprises two two - point folding units 60 , four single - point folding units 50 , two links 70 and a fabric sheet 71 . the two two - point folding units 60 form the two side rails of the stretcher and the two links 70 are connected between the two side rails . the fabric sheet 71 is mounted to the two side rails and the two links 70 . the four single - point folding units 50 are connected to two respective undersides of the two side rails to function as four legs of the stretcher . the two - point folding unit 60 includes a first tube 11 a , a second tube 12 a , a rectangular tube 21 a and two base parts 30 a , 30 b . the first and second tubes 11 a , 12 a are pivotably or fixedly connected to the two base parts 30 a , 30 b by two pins 32 a , so that the first and second tubes 11 a , 12 a are pivotable about the two pins 32 a to form the two - point folding unit 60 . the rectangular tube 21 a has two ends thereof pivotably connected to two respective extension portions 31 a , 31 b of the two base parts 30 a , 30 b by two pins 32 a as shown in fig3 and 4 . an outer tube 40 a is movable between the second tube 12 a and the rectangular tube 21 a . the single folding unit 50 as shown in fig1 and 2 comprises a first tube 11 , a second tube 12 , a rectangular tube 21 and at least one base part 30 , wherein the second tube 12 is connected to a first end of the rectangular tube 21 and a second end of the rectangular tube 21 is pivotably connected to an extension portion 31 of the at least one base part 30 by a pin 32 . therefore , the first tube 11 is pivotable about the pin 32 to form the single - point folding unit 50 . an outer tube 40 is movable between the second tube 12 and the rectangular tube 21 , and a securing bolt 41 secures the outer tube 40 when the outer tube 40 is moved to a desired position . fig8 and 9 show a recliner using the foldable frame of the present invention and the recliner comprises four two - point folding units 60 , four single - point folding units 50 and a pad 72 . the four two - point folding units 60 form a rectangular frame and the pad 72 is mounted onto the rectangular frame . the four single - point folding units 50 are connected to an underside of the rectangular frame . the two - point folding unit 60 as shown in fig3 and 4 includes a first tube 11 a , a second tube 12 a , a rectangular tube 21 a and two base parts 30 a , 30 b . the first and second tubes 11 a , 12 a are pivotably or fixedly connected to the two base parts 30 a , 30 b by two pins 32 a , so that the first and second tubes 11 a , 12 a are pivotable about the two pins 32 a to form the two - point folding unit 60 . the rectangular tube 21 a has two ends thereof pivotably connected to two respective extension portions 31 a , 31 b of the two base parts 30 a , 30 b by two pins 32 a as shown in fig3 and 4 . an outer tube 40 a is movable between the second tube 12 a and the rectangular tube 21 a . the single folding unit 50 as shown in fig1 and 2 comprises a first tube 11 , a second tube 12 , a rectangular tube 21 and at least one base part 30 , wherein the second tube 12 is connected to a first end of the rectangular tube 21 and a second end of the rectangular tube 21 is pivotably connected to an extension portion 31 of the at least one base part 30 by a pin 32 . therefore , the first tube 11 is pivotable about the pin 32 to form the single - point folding unit 50 . an outer tube 40 is movable between the second tube 12 and the rectangular tube 21 , and a securing bolt 41 secures the outer tube 40 when the outer tube 40 is moved to a desired position . fig1 and 11 show the desk using the foldable frame of the present invention and comprises at least four two - point folding units 60 , at least four single - point folding units 50 and a desk top 73 . the at least four two - point folding units 60 form a rectangular frame and the desk top 73 is mounted onto the rectangular frame . the at least four single - point folding units 50 are connected to an underside of the rectangular frame so as to form the four legs of the desk . the two - point folding unit 60 as shown in fig3 and 4 includes a first tube 11 a , a second tube 12 a , a rectangular tube 21 a and two base parts 30 a , 30 b . the first and second tubes 11 a , 12 a are pivotably or fixedly connected to the two base parts 30 a , 30 b by two pins 32 a , so that the first and second tubes 11 a , 12 a are pivotable about the two pins 32 a to form the two - point folding unit 60 . the rectangular tube 21 a has two ends thereof pivotably connected to two respective extension portions 31 a , 31 b of the two base parts 30 a , 30 b by two pins 32 a as shown in fig3 and 4 . an outer tube 40 a is movable between the second tube 12 a and the rectangular tube 21 a . the single folding unit 50 as shown in fig1 and 2 comprises a first tube 11 , a second tube 12 , a rectangular tube 21 and at least one base part 30 , wherein the second tube 12 is connected to a first end of the rectangular tube 21 and a second end of the rectangular tube 21 is pivotably connected to an extension portion 31 of the at least one base part 30 by a pin 32 . therefore , the first tube 11 is pivotable about the pin 32 to form the single - point folding unit 50 . an outer tube 40 is movable between the second tube 12 and the rectangular tube 21 , and a securing bolt 41 secures the outer tube 40 when the outer tube 40 is moved to a desired position . fig1 and 13 show that the foldable frame is used on a foldable bicycle and includes at least two two - point folding units 60 , wherein the two - point folding unit 60 as shown in fig3 and 4 includes a first tube 11 a , a second tube 12 a , a rectangular tube 21 a and two base parts 30 a , 30 b . the first and second tubes 11 a , 12 a are pivotably or fixedly connected to the two base parts 30 a , 30 b by two pins 32 a , so that the first and second tubes 11 a , 12 a are pivotable about the two pins 32 a to forth the two - point folding unit 60 . the rectangular tube 21 a has two ends thereof pivotably connected to two respective extension portions 31 a , 31 b of the two base parts 30 a , 30 b by two pins 32 a as shown in fig3 and 4 . an outer tube 40 a is movable between the second tube 12 a and the rectangular tube 21 a . fig1 and 15 show that the foldable frame is used on a crutch and comprises at least one two - point folding unit 60 . the two - point folding unit 60 as shown in fig3 and 4 includes a first tube 11 a , a second tube 12 a , a rectangular tube 21 a and two base parts 30 a , 30 b . the first and second tubes 11 a , 12 a are pivotably or fixedly connected to the two base parts 30 a , 30 b by two pins 32 a , so that the first and second tubes 11 a , 12 a are pivotable about the two pins 32 a to form the two - point folding unit 60 . the rectangular tube 21 a has two ends thereof pivotably connected to two respective extension portions 31 a , 31 b of the two base parts 30 a , 30 b by two pins 32 a as shown in fig3 and 4 . an outer tube 40 a is movable between the second tube 12 a and the rectangular tube 21 a . it is noted that the each of the first and second tubes 11 , 11 a , 12 , 12 a and the outer tubes 40 , 40 a has a collar mounted to each end 93 thereof so as to avoid the user being injured by the sharp edges and reinforce the structural strength of the tubes . the outer tubes 40 , 40 a can be different shapes such as oval tubes , elongate tubes , and triangular tubes . fig1 a and 16 b show that the rectangular tube 21 includes three walls and an open side , or the rectangular tube 21 includes two flanges extending inward from two parallel sides walls of the rectangular tube 21 . fig1 shows that the base part 30 , 30 a is connected to the connector 80 first and the connector 80 is connected to the first tube 11 , 11 a . while we have shown and described the embodiment in accordance with the present invention , it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention .
a foldable frame includes two tubes , a rectangular tube and two base parts . the two tubes are pivotably or fixedly connected to the base parts . two ends of the rectangular tube are connected to two respective extension portions of the two base parts by two pins so that the two tubes are pivotable about the two pins . the frame can also be structured as one tube directly connected to the rectangular tube and the other tube is pivotably connected to the base part . the extension of the base part is pivotably connected of the rectangular tube by a pin to form single - point folding feature . an outer tube is rotatably movable between one of the tubes and the rectangular tube , the outer tube hides the rectangular tube when the two tubes are arranged linearly .