Patent Publication Number: US-11382426-B2

Title: Bleacher seat with retractable and foldable armrests

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This utility model belongs to the technical field of bleacher seats, and particularly relates to a bleacher seat with retractable and foldable armrests. 
     2. Description of Related Art 
     Nowadays, the vigorous development of social productivity has greatly improved the creature comfort and spiritual pursuit of people and brought more and more large-scale sports matches, concerts, and evening parties, which in turn promote the emergence of derivatives such as movable bleachers and bleacher seats, wherein movable bleacher seats not only need to be designed to be steady and firm, but also should be attractive, durable, and easy to assemble. In general, traditional bleacher seats are integrally formed by plastic through one-time die casting, or are formed by the combination of a non-detachable hard frame and a soft cloth cover, wherein the former ones are easy to clean, but are poor in long-term sitting comfort, and the later ones have better sitting comfort than the former ones, but are difficult to clean after being stained. 
     In view of this, the structure of traditional bleacher seats needs to be improved. 
     BRIEF SUMMARY OF THE INVENTION 
     The objective of this utility model is to overcome the defects of poor long-term sitting comfort and inconvenient cleaning of traditional bleacher seats by providing a bleacher seat with retractable and foldable armrests. The bleacher seat is foldable on the whole, has a cloth cover capable of being disassembled to be cleaned, and adopts retractable armrests and an embedded backrest cloth structure, and the armrests, hooks, and backrest assembly can be folded to facilitate transportation and storage. 
     The following technical solution is adopted by this utility model to fulfill the aforesaid objective: a bleacher seat with retractable and foldable armrests comprises two hook assemblies, a cushion assembly, a backrest assembly, two cushion-backrest connecting assemblies and two armrest assemblies, wherein the two hook assemblies are symmetrically arranged at the front end of the bottom surface of the cushion assembly, the lower ends of the two symmetrical cushion-backrest connecting assemblies are fixedly mounted at the rear ends of the left and right sides of the cushion assembly respectively, and the upper ends of the two cushion-backrest connecting assemblies are symmetrically arranged at and rotatably connected to the lower ends of two sides of the backrest assembly. The two armrest assemblies are arranged symmetrically, the upper end and lower end of each armrest assembly are rotatably connected to a corresponding side of the cushion assembly and a corresponding side of the backrest assembly respectively, and the armrest assemblies are retractable, and a detachable cushion cloth is arranged on the cushion assembly, and a detachable backrest cloth is arranged on the backrest assembly. Armrests of the bleacher seat are retractable and foldable, all components are rotatably connected, and the cushion cloth and backrest cloth are detachable, so that the bleacher can be folded to be stored. 
     Furthermore, each armrest assembly of one structure of this utility model comprises a slotted armrest and a telescopic tube, wherein a long slot is formed in a joint of the slotted armrest and the left side or right side of the backrest assembly, a rivet sequentially penetrates through the long slot, a gasket and the side face of a backrest weld assembly, and the front end of the lower surface of the slotted armrest is rotatably connected to the upper end of the telescopic tube, and the lower end of the telescopic tube is rotatably connected to the left side or right side of the cushion assembly. 
     Furthermore, the telescopic tube comprises a lower vertical armrest tube, an upper vertical armrest tube and a spring fastener, wherein the lower vertical armrest tube and the upper vertical armrest tube are hollow tubes, and the upper vertical armrest tube is disposed around the upper end of the lower vertical armrest tube; a spring fastener fixing hole is formed in the upper end of the lower vertical armrest tube, the U-shaped spring fastener is mounted inside the lower vertical armrest tube, and a spring fastener protrusion is arranged on any side of the upper end of the spring fastener and stretches out of the spring fastener fixing hole. The upper vertical armrest tube has an upper vertical tube hole I and an upper vertical tube hole II which are formed along the same straight line in a length direction and are located at different heights, and is able to slide upwards and downwards, and the spring fastener fixing hole penetrates through the upper vertical tube hole I or the upper vertical tube hole II; and the lower end of the lower vertical armrest tube is rotatably connected to the left side or right side of the cushion assembly. 
     Furthermore, each armrest assembly of a second structure of this utility model comprises a pull-type armrest, a square armrest tube and an upright armrest tube, wherein a long slot is formed in the bottom surface of the pull-type armrest, the square armrest tube slides in the long slot, the lower surface of the front end of the square armrest tube is rotatably connected to the upper end of the upright armrest tube, the rear end of the square armrest tube is rotatably connected to the left side or right side of the backrest assembly; and the lower end of the upright armrest tube is rotatably connected to the left side or right side of the cushion assembly. 
     Furthermore, each armrest assembly of a third structure of this utility model comprises a rear folding armrest piece, a front folding armrest piece, an armrest support tube and a support tube fixing piece, wherein a through hole is formed in the rear end of the rear folding armrest piece, and a rivet penetrates through the through hole to rotatably connect the rear end of the rear folding armrest piece to the left side or right side of the backrest assembly; and a biconcave notch is formed in the front end of the rear folding armrest assembly and allows a biconvex protrusion at the rear end of the front folding armrest piece to be assembled therein through a rivet to rotatably connect the front end of the rear folding armrest assembly to the rear end of the front folding armrest piece. The front end of the front folding armrest piece is rotatably connected to the upper end of the armrest support tube, two through holes are formed in the lower end of the armrest support tube and are located at different heights, a screw penetrates through one through hole to be fixed to the support tube fixing piece, and the armrest support tube is able to rotate around the screw; and an arc groove is formed in the support tube fixing piece, and a short bolt penetrates through the other through hole and the arc groove to be fixed and is able to slide along the arc groove to rotatably connect the lower end of the armrest support tube to the left side or right side of the cushion assembly; and the support tube fixing piece is fixed to the left side or right side of the cushion assembly through a rivet. 
     Furthermore, the cushion assembly comprises an n-shaped cushion tube weld assembly, the cushion cloth, two square tube sleeves and a rear tube, wherein the front side, left side, and right side of the cushion cloth are detachably connected to three edges of the n-shaped cushion tube weld assembly respectively, and the rear end of the cushion cloth is wound around an outer circle of the rear tube through a rear cushion cloth tube sleeve. The front ends of the square tube sleeves are mounted at the rear ends of the left and right sides of the cushion tube weld assembly; mounting holes for mounting the rear tube are formed in the sides, facing each other, of the two square tube sleeves, and the two square tube sleeves are respectively mounted at the two ends of the rear tube via the mounting holes; and through holes are formed in the square tube sleeves, and self-tapping screws sequentially penetrate through the through holes of the square tube sleeves and the end face of the rear tube to be fixed; and the two hook assemblies are respectively mounted on the inner surfaces of front portions of the left and right sides of the cushion tube weld assembly. 
     Furthermore, the cushion assembly further comprises a front cushion cloth pressing piece and two side cushion cloth pressing pieces, wherein the cushion tube weld assembly comprises a horizontal square tube, two side square tubes, two hook holders and two side cloth-pulling tubes. The two side square tubes are symmetrically welded to the two ends of the horizontal square tube to form an n shape, and the two arched side cloth-pulling tubes are respectively welded to the upper ends of the two side square tubes; and the two hook holders are respectively welded to the sides, close to the horizontal square tube, of the two side square tubes, and the hook assemblies are mounted on the hook holders; side cushion cloth rims on the left and right sides of the cushion cloth are wound around the two side cloth-pulling tubes, are pressed against the side cloth-pulling tubes by means of the side cushion cloth pressing pieces, and are fixed with pressing piece screws; and a front cushion cloth rim on the front side of the cushion cloth is wound around the horizontal square tube, is pressed against the horizontal square tube by means of the front cushion cloth pressing piece, and is fixed with a pressing piece screw. 
     Furthermore, the backrest assembly comprises two cloth embedding strips, the backrest cloth, the backrest weld assembly and four slotted tube plugs, wherein the backrest weld assembly is an n-shaped structure formed by welding two vertical backrest rods and a horizontal backrest tube, circular slots are formed in sides, towards a human body, of the two vertical backrest rods, cylindrical sleeves allowing the cloth embedding strips to be inserted therein are arranged on the left and right sides of the backrest cloth, and the cylindrical sleeves having the cloth embedding strips inserted therein are embedded in the circular slots; and the four slotted tube plugs seal open ends of the two vertical backrest rods. 
     Furthermore, each cushion-backrest connecting assembly comprises an outer cushion-backrest connecting piece and a cushion-backrest big-hole connecting piece, wherein the outer cushion-backrest connecting piece is riveted to the outer sides of the rear ends of the side square tubes of the cushion tube weld assembly, and the lower ends of the vertical backrest rods of the cushion-backrest weld assembly are rotatably connected to the outer cushion-backrest connecting piece and the cushion-backrest big-hole connecting piece. 
     Furthermore, each hook assembly comprises a fixing screw, a plastic sheath, a metal hook and a self-locking nut, wherein the plastic sheath wraps around the metal hook, and the fixing screw sequentially penetrates through a through hole in the corresponding hook holder  38  of the cushion assembly, a through hole in the plastic sheath and a through hole in the metal hook to be locked with the self-locking nut. 
     Compared with the prior art, this utility model has the following beneficial effects: the bleacher seat is simple in structure, attractive, elegant, firm and durable. The whole bleacher seat is foldable, thus occupying a small space when carried and transported, and being more suitable for mass transportation, application, and more convenient to use. The structures of slotted tube sliding armrests are conducive to autonomous adjustment by users and conform to an ergonomic sitting posture, and the cushion cloth and the backrest cloth can be easily disassembled to be cleaned and can be used repeatedly. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is an unfolded axonometric diagram of a bleacher seat with slotted pipe sliding armrests; 
         FIG. 2 a    is schematic diagram of the bleacher seat with slotted pipe sliding armrests, in an unfolded state; 
         FIG. 2 b    is a schematic diagram of the bleacher seat in a folded and stored state; 
         FIG. 3 a    is a schematic diagram of the bleacher seat with slotted pipe sliding armrests in the state where a folded backrest faces upwards; 
         FIG. 3 b    is a schematic diagram of the bleacher seat with slotted pipe sliding armrests in the state where a folded cushion faces upwards; 
         FIG. 4  is a schematic diagram of a backrest assembly of the bleacher seat with slotted pipe sliding armrests; 
         FIG. 5  is a partially exploded view of a cushion assembly of the bleacher seat with slotted pipe sliding armrests; 
         FIG. 6  is an exploded view of a sliding armrest assembly of the bleacher seat with slotted pipe sliding armrests; 
         FIG. 7 a    is a schematic diagram of a vertical tube, in an unfolded state, of a sliding armrest; 
         FIG. 7 b    is a schematic diagram of the vertical tube, in a folded state, of the sliding armrest; 
         FIG. 7 c    is a schematic diagram of the armrest vertical tube in a locked state when the bleacher seat is unfolded; 
         FIG. 7 d    is a schematic diagram of the armrest vertical tube in a locked state when the bleacher seat is folded; 
         FIG. 8 a    is a perspective view of a bleacher seat with pull-type armrests, in an unfolded state; 
         FIG. 8 b    is a perspective view of the bleacher seat with pull-type armrests, in a folded state; 
         FIG. 9  is a turning perspective view of the bleacher seat with pull-type armrests; 
         FIG. 10  is an exploded view of a pull-type armrest; 
         FIG. 11 a    is a schematic diagram of a pull-type armrest assembly in an unfolded state; 
         FIG. 11 b    is a schematic diagram of the pull-type armrest in a retracted and folded state; 
         FIG. 11 c    is another schematic diagram of the pull-type armrest in the retracted and folded state; 
         FIG. 12  is a half sectional view of the pull-type armrest; 
         FIG. 13 a    is a perspective view of a bleacher seat with folding armrests, in an unfolded state; 
         FIG. 13 b    is a perspective view of the bleacher seat with folding armrests, in a folded state; 
         FIG. 14  is a turning perspective view of the bleacher seat with folding armrests; 
         FIG. 15 a    is an exploded view of a folding armrest; 
         FIG. 15 b    is a structural diagram of a support tube fixing piece; 
         FIG. 16 a    is a schematic diagram of a folding armrest assembly in an unfolded state; 
         FIG. 16 b    is a schematic diagram of the folding armrest in a retracted and folded state; 
         FIG. 17 a    is a vertical view of a square tube-rope cushion cloth in a collapsed state; 
         FIG. 17 b    is a side view of the square tube-rope cushion cloth in the collapsed state. 
     
    
    
     In the figures:  1 , hook assembly;  2 , cushion assembly;  3 , cushion cloth;  4 , armrest assembly;  5 , backrest cloth;  6 , backrest assembly;  7 , cushion-backrest connecting assembly;  8 , lower vertical armrest tube;  9 , upper vertical armrest tube;  10 , slotted armrest;  11 , backrest weld assembly;  12 , spring fastener protrusion;  13 , horizontal backrest tube;  14 , front cushion cloth pressing piece;  15 , pressing piece screw;  16 , fastening screw;  17 , side cushion cloth pressing piece;  18 , cloth embedding strip;  19 , slotted tube plug;  20 , circuit slot;  21 , side cushion cloth rim;  22 , front cushion cloth rim;  23 , rear cushion cloth tube sleeve;  24 , rivet;  25 , self-tapping screw;  26 , outer cushion-backrest connecting piece;  27 , square tube sleeve;  28 , cushion-backrest big-hole connecting piece;  29 , semicircular notch;  30 , rear tube;  31 , side cloth-pulling tube;  32 , rubber pad;  33 , horizontal square tube;  34 , fixing screw;  35 , plastic sheath;  36 , metal hook;  37 , self-locking nut;  38 , hook holder;  39 , gasket;  40 , long slot;  41 , U-shaped fork;  42 , spring fastener;  43 , small gasket;  44 , big gasket;  45 , upper vertical tube hole II;  46 , upper vertical tube hole I;  47 , lower vertical tube spring fastener fixing hole;  48 , pull-type armrest assembly;  49 , long slot;  50 , pull-type armrest;  51 , square armrest tube;  52 , tube plug;  53 , nut;  54 , shim plate;  55 , U-shaped armrest piece;  56 , screw;  57 , upright armrest tube;  58 , internal hexagonal screw;  59 , upright armrest tube gasket;  60 , folding armrest assembly;  61 , square tube-rope cushion cloth;  62 , rope;  63 , rear folding armrest piece;  64 , biconcave notch;  65 , biconvex protrusion;  66 , front folding armrest piece;  67 , big notch;  68 , circular armrest connecting head;  69 , armrest support tube;  70 , support tube fixing piece;  71 , arc groove;  72 , short bolt;  73 , semicircular ring matching base;  74 , metal ring through hole;  75 , rim. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The technical solution of the invention is further described and explained below with reference to specific embodiments to be understood more clearly. Those skilled in the art can easily appreciate other advantages and effects of the invention by referring to the contents in the specification. This utility model can also be implemented or applied in other different forms, and various modifications or transformations can be made to the details in the specification on the basis of different viewpoints and different applications without departing from the spirit of this utility model. 
     Embodiment 1 
     This embodiment provides a bleacher seat with retractable and foldable armrests, which primarily consists of two hook assemblies  1 , a cushion assembly  2 , a backrest assembly  6 , two cushion-backrest connecting assemblies  7 , and two armrest assemblies  4  (as shown in  FIG. 1 ). The bleacher seat has an unfolded state and a folded state (as shown in  FIG. 2 a    and  FIG. 2 b   , and  FIG. 3 a    and  FIG. 3 b   ), wherein in  FIG. 2 a   , sliding armrests and a backrest of the bleacher seat are unfolded to be in a service condition; in  FIG. 2 b   , the sliding armrests of the bleacher seat are retracted and folded; in  FIG. 3 a   , the backrest assembly  6  of the bleacher seat faces upwards; and in  FIG. 3 b   , the cushion assembly  2  and the hook assemblies  1  face upwards. 
     Particularly, the two hook assemblies  1  are symmetrically arranged at the front end of the bottom surface of the cushion assembly  2 , the lower ends of the two symmetrical cushion-backrest connecting assemblies  7  are fixedly mounted at the rear ends of the left and right sides of the cushion assembly  2  respectively, and the upper ends of the two cushion-backrest connecting assemblies  7  are symmetrically arranged at and rotatably connected to the lower ends of two sides of the backrest assembly  6 . The two armrest assemblies  4  are arranged symmetrically, the upper end and lower end of each armrest assembly  4  are rotatably connected to a corresponding side of the cushion assembly  2  and a corresponding side of the backrest assembly  6  respectively, and the armrest assemblies  4  are retractable; and a detachable cushion cloth  3  is arranged on the cushion assembly  2 , and a detachable backrest cloth  5  is arranged on the backrest assembly  6 . 
     In this embodiment, each armrest assembly  4  (shown in  FIG. 6 ) primarily comprises a slotted armrest  10 , a telescopic tube consisting of an upper vertical armrest tube  9 , a lower vertical armrest tube  8  and a spring fastener  42 , three rivets  24 , a gasket  39 , a small gasket  43 , and a big gasket  44 , wherein a long slot  40  is formed in a joint of the slotted armrest  10  and a backrest weld assembly  11  on the left side or right side of the backrest assembly  6 , and one rivet  24  sequentially penetrates through the long slot  40 , the gasket  39 , and the side face of the backrest weld assembly  11 ; and the front end of the lower surface of the slotted armrest  10  is rotatably connected to the upper end of the telescopic tube, the lower end of the telescopic tube is rotatably connected to the left side or right side of the cushion assembly  2 , particularly, a U-shaped fork  41  (U-shaped joint) is arranged on the side, towards the ground, of the slotted armrest  10 , and the upper vertical armrest tube  9  penetrates through a concave part of the U-shaped fork  41  and is rotatably connected to the U-shaped fork  41  through another rivet  24 . 
     The lower vertical armrest tube  8  and the upper vertical armrest tube  9  of the telescopic tube of the armrest assembly  4  are hollow tubular structures, and the upper vertical armrest tube  9  is disposed around the upper end of the lower vertical armrest tube  8 ; a spring fastener fixing hole  47  is formed in the upper end of the lower vertical armrest tube  8 , the U-shaped spring fastener  42  is mounted inside the lower vertical armrest tube  8  and is made of a leaf spring, and under the elastic effect, a spring fastener protrusion  12  which is arranged on any side of the upper end of the spring fastener  42  stretches out of the spring fastener fixing hole  47  to be exposed to the outer circumferential face of the lower vertical armrest tube  8 ; an upper vertical tube hole I  46  and an upper vertical tube hole II  45  are formed in the upper vertical armrest tube  9  along the same straight line in a length direction and are spaced from each other by a certain distance, the upper vertical armrest tube  9  is able to slide upwards or downwards, and the spring fastener fixing hole  47  penetrates through the upper vertical tube hole I  46  or the upper vertical tube hole II  45 ; and the lower end of the lower vertical armrest tube  8  is rotatably connected to the left side or right side of the cushion assembly  2 . A through hole is formed in the lower end of the lower vertical armrest tube  8 , the rivet  24  penetrates through the through hole to be rotatably connected to the outer side of the cushion assembly  2  (to be specific, a side cloth-pulling tube  31 ), and the small gasket  43  and the big gasket  44  are mounted between the lower vertical armrest tube  8  and the side cloth-pulling tube  31  of the cushion assembly  2  to fulfill a buffer effect, and the rivet  24  sequentially penetrates through the lower end of the lower vertical armrest tube  8 , the big gasket  44 , and the small gasket  43  to be connected to the left side or right side of the cushion assembly  2 . The surfaces of the big cushion  44  and the small cushion  43  can be designed in shapes matched with contact surfaces, for example, the surface, in contact with the lower vertical armrest tube  8 , of the big gasket  44  can be designed as an arc surface matched with the outer surface of the lower vertical armrest tube  8 . 
     In this embodiment, the cushion assembly  2  (shown in  FIG. 5 ) primarily consists of a cushion tube weld assembly, the cushion cloth  3 , two square tube sleeves  27 , a front cushion cloth pressing piece  14 , two side cushion cloth pressing pieces  17 , nine pressing piece screws  15 , a rear tube  30 , two self-tapping screws  25 , six fastening screws  16 , and two rubber pads  32 , wherein the cushion tube weld assembly is n-shaped, the front side, the left side, and the right side of the cushion cloth  3  are detachably connected to three edges of the n-shaped cushion tube weld assembly respectively, and the rear end of the cushion cloth  3  is wound around the outer circle of the rear tube  30  by means of a rear cushion cloth tube sleeve  23 . The two square tube sleeves  27  are respectively disposed around the rear open ends of left and right side square tubes of the cushion tube weld assembly; mounting holes for mounting the rear tube  30  are formed in sides facing each other (inner sides) of the two square tube sleeves  27 , and the two square tube sleeves  27  are respectively mounted at the two ends of the rear tube  30  via the mounting holes; through holes are formed in sides backing onto each other (outer sides) of the two square tube sleeves  27 , the self-tapping screws  25  sequentially penetrate through the through holes of the square tube sleeves  27  and one end face of the rear tube  30  to fulfill fixation, and threads are tapped on the two end faces of the rear tube  30  for connection and fastening; and the two hook assemblies  2  are respectively mounted on the inner surfaces of front portions of the left and right sides of the cushion tube weld assembly. The self-tapping screws  25  are preferably internal hexagonal self-taping screws. Particularly, the cushion tube weld assembly comprises a horizontal square tube  33 , two side square tubes, two hook holders  38 , and two side cloth-pulling tubes  31 , wherein the two side square tubes are symmetrically welded to the two ends of the horizontal square tube  33  to form an n shape, the two arched side cloth-pulling tubes  31  are respectively welded to the upper ends of the two side square tubes, the two hook holders  38  are respectively welded to the sides, close to the horizontal square tube  33 , of the two side square tubes, and the hook assemblies  1  are detachably mounted on the hook holders  38 ; side cushion cloth rims  21  on the left and right sides of the cushion cloth  3  are respectively wound around the two side cloth-pulling tubes  31 , are pressed against the side cloth-pulling tubes  31  by means of the side cushion cloth pressing pieces  17 , and are fixed with the corresponding pressing piece screws  15 ; and the front side of the cushion cloth  3  is wound around the horizontal square tube  33  by means of a front cushion cloth rim  22 , is pressed against the horizontal square tube  33  by means of the front cushion cloth pressing piece  22 , and is fixed with the corresponding pressing piece screws  15 . The two rubber pads  32  are respectively arranged on the left side and the right side and are fixedly mounted on the sides, towards the ground, of the left and right side square tubes of the cushion tube weld assembly through the fastening screws  16 . 
     In this embodiment, the backrest assembly  6  (shown in  FIG. 4 ) primarily consists of two cloth embedding strips  18 , the backrest cloth  5 , a backrest weld assembly  11 , and four slotted tube plugs  19 , wherein the backrest weld assembly  11  is an n-shaped structure formed by welding two vertical backrest rods and a horizontal backrest tube  13 , the two vertical backrest tubes are profiles, circular slots  20  are formed in the sides, towards the back of a human body, of the two vertical backrest rods, the left and right sides, connected to the vertical backrest rods, of the backrest cloth  5  are designed as cylindrical sleeves, outer circles of the cylindrical sleeves on the two sides of the backrest cloth  5  are slightly smaller than inner circles of the circular slots  20  in the vertical backrest rods, the cloth embedding strips  18  are inserted into the cylindrical sleeves and are then embedded into the circular slots  20  to be mounted and fixed, and a large flat surface of the backrest cloth  5  is located between the two vertical backrest rods of the backrest assembly  6  and is elastically tensioned slightly; and the four slotted tube plugs  19  are used to seal and close the open ends of the two vertical profiles of the backrest assembly  6 . 
     In this embodiment, the two cushion-backrest connecting assemblies  7  (shown in  FIG. 5 ) are used to fixedly connect the backrest assembly  6  to the cushion assembly  2 . Each cushion-backrest connecting assembly  7  primarily consists of an outer cushion-backrest connecting piece  26 , a cushion-backrest big-hole connecting piece  28 , and three rivets  24  used for connection and fixation, wherein the outer cushion-backrest connecting piece  26  is fixedly mounted on the outer sides of the rear ends of the side square tubes of the cushion tube weld assembly, the cushion-backrest big-hole connecting piece  28  is fixed to the inner sides of the left and right side square tubes of the cushion tube weld assembly, and the lower ends of the vertical backrest rods of the backrest weld assembly  11  are rotatably connected to the outer cushion-backrest connecting piece  26  and the cushion-backrest big-hole connecting piece  28 . A semicircular notch  29  is designed in the cushion-backrest big-hole connecting piece  28  to avoid interference with the outer circle of the rear tube  30 . 
     In this embodiment, the two hook assemblies  2  are respectively mounted on the hook holders  38 , close to the horizontal square tube  33 , at the front ends of the two side square tubes of the cushion assembly  2  and are located below the cushion cloth  3 . Each hook assembly  1  consists of a fixing screw  34 , a plastic sheath  35 , a meal hook  36  and a self-locking nut  37 , wherein as shown in  FIG. 5 , the plastic sheath  35  sleeves and wraps around the metal hook  36 , the fixing screw  34  sequentially penetrates through a through hole in the hook holder  38 , a through hole in the plastic sheath  35 , and a through hole in the metal hook  36  and is locked with the self-locking nut  37 . After the metal hook  36  is wrapped in the plastic sheath  35 , the plastic sheath  35  can rotate by 90° to be folded and be parallel to the cushion cloth  3  as shown in  FIG. 3 a    from being perpendicular to the cushion cloth  3  of the cushion assembly  2 . When the hook assemblies  1  need to be folded, the metal hooks  36  wrapped with the plastic sheaths  35  are rotated to be hidden below the cushion cloth  3  and be parallel to the cushion cloth  3 . When the hook assemblies  1  need to be unfolded, the metal hooks  36  wrapped with the plastic sheaths  35  are rotated by 90° to be perpendicular to the cushion cloth  3 . 
     By adoption of the plastic sheaths  35 , the abrasion between the metal hooks  36  and a bleacher where the bleacher seat is assembled is reduced. The square tubes and circular tubes in this embodiment can be replaced with tubes of other cross-section shapes. 
     As shown in  FIG. 4 , the backrest cloth  5  of the bleacher seat in this embodiment is assembled or disassembled to be cleaned as follows: when the backrest cloth  5  of the bleacher seat is assembled, the backrest weld assembly  11  is fixed, then the cloth embedding strips  18  penetrate through the inner circles of the cylindrical sleeves of the backrest cloth  5  to be combined with the backrest cloth  5  and then stretch into the inner circles of the circular slots  20  in the backrest weld assembly  11  until the large flat surface of the backrest cloth  5  is located between the two vertical backrest rods of the backrest weld assembly  11  and is elastically tensioned slightly, and finally, the slotted tube plugs  19  are assembled. The backrest cloth  5  can be disassembled to be cleaned by performing the operations reversely. 
     As shown in  FIG. 7 a    to  FIG. 7 d   , the vertical tubes of the armrest assemblies  4  in this embodiment are unfolded or folded as follows: when the bleacher seat is in the unfolded state, the spring fastener protrusions  12 , which are hidden in inner holes of the lower vertical armrest tubes  8  and located in the spring fastener fixing holes  47 , of the spring fasteners  42  are exactly clamped in the upper vertical tube holes I  46  of the upper vertical armrest tubes  9 , so that the upper vertical armrest tubes  9  are disposed around the lower vertical armrest tubes  8  and are locked and connected to the lower vertical armrest tubes  8  under the effect of the spring fastener protrusions  12  of the spring fasteners  42 ; and at this moment, the rivets  24  on the slotted armrests  10  are connected to the tail ends of the long slots  40 . When the vertical tubes are to be folded, the spring fastener protrusions  12  of the spring fasteners  42  are pressed by hand into inner holes of the upper vertical armrest tubes  9 , and then the upper vertical armrest tubes  9  are slid along the outer circles of the lower vertical armrest tubes  8  to be retracted; and when the spring fastener protrusions  12  are exactly clamped in the upper vertical holes II  45 , the slotted armrests  10  slide under the restriction of the rivets  24  and the long slots  40  to drive the backrest assembly  6  to be folded and to be locked. When the bleacher seat needs to be unfolded, the spring fastener protrusions  12  are pressed by hand into the inner holes of the upper vertical armrest tubes  9 , and the upper vertical armrest tubes  9  are slid along the outer circles of the lower vertical armrest tubes  8 ; and when the spring fastener protrusions  12  are exactly clamped in the upper vertical tube holes I  46 , the bleacher seat is unfolded and locked. To facilitate manual folding and unfolding of the bleacher seat, the spring fastener  42  may be disposed in the vertical armrest tube on one side. 
     As shown in  FIG. 3 a    and  FIG. 3 b   , the bleacher seat in this embodiment is folded as follows: first of all, the metal hooks  36  and plastic sheaths  35  of the hook assemblies  1  are rotated together by 90° to be parallel to the cushion cloth  3  and be located below the cushion cloth  3 ; and then the spring fastener protrusions  12  are pressed by hand to enable the upper vertical armrest tubes  9  to slide around the lower vertical armrest tubes  8 , so that the slotted armrests  10  and the backrest assembly  6  are driven to move around the rotation points of the cushion-backrest connecting assemblies  7  towards the cushion assembly  2 . In this way, the hook assemblies  1 , the cushion assembly  2 , the backrest assembly  6 , and the armrest assemblies  4  are folded on one plane layer by layer to facilitate storage and transportation of the bleacher seat. 
     As shown in  FIG. 1 ,  FIG. 2A , and  FIG. 2 b   , the bleacher seat in this embodiment is unfolded as follows: first of all, the spring fastener protrusions  12  are pressed by hand to enable the upper vertical armrest tubes  9  to slide along the outer circles of the lower vertical armrest tubes  8 , and at this moment, the slotted armrests  10  and the backrest assembly  6  are driven to rotate away from the cushion assembly  2  around the rotation points of the cushion-backrest connecting assemblies  7 . When the spring fastener protrusions  12  are exactly clamped in the upper vertical tube holes I  46 , the bleacher seat is unfolded and locked. 
     Embodiment 2 
     Different from Embodiment 1, this embodiment provides an armrest assembly of another structure, which particularly refers to a pull-type armrest assembly  48  (as shown in  FIG. 8 a   ,  FIG. 8B , and  FIG. 9 ). The pull-type armrest assembly  48  primarily consists of a pull-type armrest  50 , a square armrest tube  51 , a tube plug  52 , two nuts  53 , a shim plate  54 , a U-shaped armrest piece  55 , two screws  56 , an upright armrest tube  57 , an internal hexagonal screw  58 , an upright armrest tube gasket  59 , two rivets  24 , and a self-locking nut  37 , wherein the pull-type armrest  50 , the square armrest tube  51 , and the upright armrest tube  57  are key components, a long slot  49  is formed in the bottom surface of the pull-type armrest  50 , the square armrest tube  51  slides in the long slot  49 , the lower surface of the front end of the square armrest tube  51  is rotatably connected to the upper end of the upright armrest tube  57 , and the lower end of the upright armrest tube  57  is rotatably connected to the left side or right side of the cushion assembly  2 . 
     Particularly, the long slot  49  is formed in the side, towards the ground, of the pull-type armrest  50  (as shown in  FIG. 9  and  FIG. 12 ) and has a square inner cavity (as shown in  FIG. 12 ) allowing the outer square surface of the square armrest tube  51  to be inserted therein. The square armrest tube  51  is of a hollow square tube structure and has two through holes close to the lower portion of the pull-type armrest  50 , and the distance between the through holes is equal to the distance between two through holes formed in the U-shaped armrest piece  55 . The two nuts  53  are arranged in the hollow inner cavity of the square armrest tube  51 , the shim plate  54  is located below the two through holes of the square armrest tube  51  and is of a rectangular structure, the width of the shim plate  54  is slightly smaller than that of the long slot  49 , the two ends, in the length direction, of the shim plate  54  are in semi-arc shapes, the distance between the two semi-arcs of the shim plate  54  is slightly smaller than the distance between the two through holes in the U-shaped armrest piece  55 , and the mounting position of the shim plate  54  in the width direction is limited within the width range of the long slot  49 , so that the shim plate  49  is able to move in the length direction of the long slot  49 . The U-shaped armrest piece  55  is located below the shim plate  54  and has an opening facing downwards and a flat bottom formed with the two through holes. The screws  56  penetrate through the through holes in the U-shaped armrest piece  55 , then penetrate through the long slot  49  of the pull-type armrest  50  to lean against the semi-arcs of the shim plate  54 , and finally stretch out of the through holes in the square armrest tube  51  to be assembled and combined with the nuts  53 . The opening of the U-shaped armrest piece  55  is connected to one end of the upright armrest tube  57  through one rivet  24 , and the other end of the upright armrest tube  57  is rotatably connected to the corresponding side cloth-pulling tube  31  through the internal hexagonal screw  58 , the upright armrest tube gasket  59  and the self-locking nut  37 . The end, away from the pull-type armrest  50 , of the square armrest tube  51  is rotatably connected to the backrest weld assembly  11  through the other rivet  24  and the gasket  39 . The tube plug  52  is mounted at an opening of the end, connected to the backrest weld assembly  11 , of the square armrest tube  51 . 
     As shown in  FIG. 11 a    to  FIG. 11 c   , the pull-type armrest assembly  48  is unfolded or folded as follows: when the bleacher seat is in the folded state, the upright armrest tube  57  rotates around the corresponding rivet  24  to be approximately parallel to the side cloth-pulling tube  31 , and the square armrest tube  51  connected to the upright armrest tube  57  through the U-shaped armrest piece  55 , and the pull-type armrest that can be pulled to move are also approximately in parallel; at this moment, the pull-type armrest  50  can move in the length direction of the square armrest tube  51 ; and generally, in the folded state, the length is minimized after the square armrest tube  51  is inserted into the pull-type armrest  50  (as shown in  FIG. 11 b    and  FIG. 11 c   ). When the bleacher seat needs to be unfolded, the pull-type armrest  50  is pulled to move outwards along the square armrest tube  51  and is then lifted, and at this moment, the square armrest tube  51  and the upright armrest tube  57  are mechanically driven to move accordingly; and when the backrest assembly  6  is completely unfolded, an angle (allowing users to sit on the bleacher seat comfortably) is formed between the upright armrest tube  57  and the square armrest tube  51  (as shown in  FIG. 11 a   ). In this way, the pull-type armrest assembly and the bleacher seat are completely unfolded. The bleacher seat can be unfolded by performing the operations reversely. 
     Embodiment 3 
     Different from Embodiment 1 or 2, this embodiment provides an armrest assembly of another structure, which particularly refers to a folding armrest assembly  60 . The folding armrest assembly  60  primarily consists of a rear folding armrest piece  63 , a front folding armrest piece  66 , a circular armrest connecting head  68 , an armrest support tube  69 , a support tube fixing piece  70 , a short bolt  72 , and five rivets  24  (as shown in  FIG. 15 a    and  FIG. 15 b   ). 
     The rear folding armrest piece  63 , the front folding armrest piece  66 , the armrest support tube  69 , and the support tube fixing piece  70  are key components; a through hole is formed in the rear end of the rear folding armrest piece  63 , and one rivet  24  penetrates through the through hole to rotatably connect the rear end of the rear folding armrest piece  63  to the backrest weld assembly  11 . The front end of the rear folding armrest piece  63  is formed with a biconcave notch  64 , which allows a biconvex protrusion  65  at the rear end of the front folding armrest piece  66  to be assembled therein to rotatably connect the front end of the rear folding armrest piece  63  to the rear end of the front folding armrest piece  66 . The front end of the front folding armrest piece  66  is rotatably connected to the upper end of the armrest support tube  69 , two through holes are formed in the lower end of the armrest support tube  69  and are located at different heights, the internal hexagonal screw  58  penetrates through one through hole to be fixed to the support tube fixing piece  70 , and the armrest support tube  69  is able to rotate with respect to the internal hexagonal screw  58 ; an arc groove  71  is formed in the support tube fixing piece  70 , and the short bolt  72  penetrates through the other through hole and the arc groove  71  to be fixed and is able to slide along the arc groove  71  to rotatably connect the lower end of the armrest support tube  60  to the left side or right side of the cushion assembly  2 ; and the support tube fixing piece  70  is fixed to the left side or right side of the cushion assembly  2  through one rivet  24 . Particularly, one end of the rear folding armrest piece  63  is formed with one through hole and is rotatably connected to the backrest weld assembly  11  through one rivet  24 , the other end of the rear folding armrest piece  63  is formed with the biconcave notch  64  and is rotatably connected to the front folding armrest piece  66  after the biconvex protrusion  65  on the front folding armrest piece  66  is assembled in the biconcave notch  64  through one rivet  24 , a big notch  67  is formed in the end, away from the biconvex protrusion  65 , of the front folding armrest piece  66 , the whole circular armrest connecting head  68  is of a flat tube structure, the lower end of the circular armrest connecting head  68  is of an oblate structure, the end of the flat tube structure of the circular armrest connecting head  68  is located in a concave part of the big notch  67 , and the armrest support tube  69  has an end inserted into an inner cavity of the circular armrest connecting head  68  and is rotatably connected to the circular armrest connecting head  68  and the big notch  67  of the front folding armrest piece  66  through one rivet  24 . Two through holes are formed in the other end of the armrest support tube  69 , wherein one through hole is located on the flat tube of the armrest support tube  69 , is fixed to the support tube fixing piece  70  through the internal hexagonal screw  58 , and is locked with the self-locking nut  37 , and the armrest support tube  69  is able to rotate with respect to the internal hexagonal screw  58 ; and the other through hole is located at the center of the oblate structure of the circular armrest connecting head  68 , and the short bolt  72  penetrates through the through hole to be located in the arc groove  71  of the support tube fixing piece  70  and is able to slide along the arc groove  71  through the self-locking nut  37  to fulfill fastening and connection. The support tube fixing piece  70  is a special-shaped disk part, a semicircular matching base  73  matched with the outer surface of the side cloth-pulling tube is arranged on the side, connected to the side cloth-pulling tube  31 , of the support tube fixing piece  70 , and the support tube fixing piece  70  is fixedly mounted on the outer sides of the left and right side square tubes of the cushion tube weld assembly through rivets  24  (as shown in  FIG. 14 ). 
     As shown in  FIG. 16 , the folding armrest assembly  60  is unfolded or folded as follows: when the bleacher seat is in the folded state (as shown in  FIG. 14 ), the rear folding armrest piece  63  is rotated and folded around the biconcave notch  64  connected to the biconvex protrusion through the rivet  24  until the angle between the rear folding armrest piece  63  and the front folding armrest piece  66  is minimized and the rear folding armrest piece  63  and the front folding armrest piece  66  form a whole, then the front folding armrest piece  66  is rotated around the circular armrest connecting head  68  until the angle between the front folding armrest piece  66  and the armrest support tube  69  is minimized and the front folding armrest piece  66  and the armrest support tube  69  form a whole, then the armrest support tube  69  is rotated to enable the short bolt  72  thereof to slide along the arc groove  71  of the support tube fixing piece  70  to reach the notch in the farthest end, and at this moment, the armrest support tube  69  is approximately located at the same horizontal position as the left and right side square tubes of the cushion tube weld assembly. Meanwhile, the backrest assembly  6  is driven to move towards the cushion assembly  2  until the angle between the backrest assembly  6  and the cushion assembly  2  is minimized. The bleacher seat can be unfolded by performing the operations reversely. 
     Embodiment 4 
     Different from the above embodiments, this embodiment provides a cushion cloth of another structure, which particularly refers to a square tube-rope cushion cloth  61  (as shown in  FIG. 14 ,  FIG. 17 a    and  FIG. 17 b   ). The square tube-rope cushion cloth  61  is mounted on the cushion tube weld assembly of the cushion assembly  2  and wraps around the cushion tube weld assembly, wherein the left and right sides of the square tube-rope cushion cloth  61  wrap the side cloth-pulling tubes  31 , the front and back sides of the square tube-rope cushion cloth  61  wrap the horizontal square tube  33  and the rear tube  30  of the cushion tube weld assembly, and thickened rims  75  are arranged on the four sides of the square tube-rope cushion cloth  61 , different numbers of metal ring through holes  74  are formed in the edges of the front and back rims  75  and in the edges of the left and right rims  75 , and a rope  62  penetrates through the metal ring through holes  75  and is tied in a way similar to shoelaces to fulfill fixation and connection. 
     The aforementioned embodiments are only preferred ones of this utility model, and are not intended to limit the protection scope of this utility mode, and all transformations and improvements made by those skilled in the art according to the design concept of this utility model should also fall within the protection scope of this utility model. More particularly, various transformations and improvements can be made to the constituent parts and/or the layout of the subject matter within the scope of the drawings and claims of this application