Abstract:
A bionic and posture-correcting backrest for study, including a bracket body disposed at the rear of a desk via a mounting rack. An adjustable element is provided on a frame between the chest/abdomen and the desk edge as well as between the chin and lower part of abdomen (slightly above the thighs). The adjustable element is a fist distance away from the desk edge if a user sits on the chair with the correct sitting position. In this way, the “forward sitting position” and the “backward sitting position” or any sitting position therebetween can be achieved and meanwhile freely switched. The adjustable element ensures an appropriate space being formed between the head, eyes, neck, chest, waist, back, elbows and a desk/chair.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of International Patent Application No. PCT/CN2010/075865 with an international filing date of Aug. 10, 2010, designating the United States, now pending, and further claims priority benefits to Chinese Patent Application No. 200910166756.2 filed Aug. 10, 2009. The contents of all of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference. 
     
    
     CORRESPONDENCE ADDRESS 
       [0002]    Inquiries from the public to applicants or assignees concerning this document should be directed to: MATTHIAS SCHOLL P.C., ATTN.: DR. MATTHIAS SCHOLL ESQ., 14781 MEMORIAL DRIVE, SUITE 1319, HOUSTON, TX 77079. 
       BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The invention relates to a bionic and posture-correcting backrest for study, and more particularly to a bionic and posture-correcting backrest for study for primary school students. 
         [0005]    2. Description of the Related Art 
         [0006]    Nowadays, an increasing number of primary school students and middle school students are suffering from short-sight and hunchback. 
         [0007]    There are many causes for such unhealthy tendency and the results are serious. From the perspective of school hygiene, “forward sitting position” is defined if a person&#39;s upper body gravity is right on or in the front of the ischiatic tuberosity, where the balance is maintained by the back muscles and thighs. “Backward sitting position” is defined if a person&#39;s upper body gravity is behind the ischiatic tuberosity, where the back must be against the backrest. It is apparent that the forward sitting position is likely to cause fatigue while the backward sitting position is not. However, students are fond of using the forward sitting position to study by bending over the desks. From the perspective of the physiology, when your line of sight is perpendicular to the object you are looking at, the image projected onto your retina is the clearest. It is called the “physiological visual angle”. Therefore, the students have to look down for the clearest image. From the perspective of the biology, human bones are made up of hard and fragile inorganic composition and flexible organic composition. The physical properties of bones are hardness and flexibility. The content of different composition and the physical properties of bones vary with age. For example, teenagers&#39; bones are less hard but more flexible and elastic; therefore they are unlikely to be fractured but likely to be deformed. If students do not pay more attention on their sitting position when they study, they would suffer from hunchback, scoliosis or short-sight. Liu Zhiming, the attending physician in Beijing Puren Hospital (previously Beijing No. 4 Hospital), finds out after many years research that if teenagers pay less attention on their sitting position when they study, they are more likely to suffer from fatigue, short-sight and hunchback. An even more serious consequence is that they are at considerably higher risk of contracting cervical spondylosis after growing up. 
         [0008]    However, this unhealthy phenomenon has not been deeply realized. On the one hand, students like to use the forward sitting position to study by bending over the desks, they have not been aware of the function of the backward sitting position. On the other hand, some students partially lay great emphasis on backward sitting position, they have not been aware of the importance of the forward sitting position and not recognized such position can be necessary and corrected. But in fact, if there is no “forward sitting position”, Chinese traditional brush cannot be used properly. The backward sitting position, as a sitting position contrary to the forward sitting position, also has the problem that students study by bending over the desks. In addition, the forward sitting position and the backward sitting position, as two basic positions, can be freely switched. During the switch, there are other optional positions because people cannot sit with only one position. All the positions are contributable to correct sitting, reading, writing, and listening, i.e. a fist distance between chest and edge of desk and a foot from eyes to books. In this way, the fingertip can be an inch from the pen point while the head and body can remain straight. 
         [0009]    To solve the above problems, some measures have been taken but with poor results. With respect to the backrest, related devices have been invented to prevent short-sight and hunchback. They have effects to some extent but still have the following problems. First of all, people cannot move back and forth. As the adjustable support is vertically fixed, people can only sit against the adjustable support. It is only one of the correct forward sitting positions or the backward sitting positions or the combination thereof. Children tend to change their positions from time to time, thus it is difficult to let them stick to only one sitting position. If they sit forwards, the chests and abdomens have no support, if they sit backwards, the adjustable support will block the line of sight. Secondly, the upper part of the body is not completely against the adjustable support (i.e. pectoral plate). The conventional adjustable support is the sternal plate. The lower end of the sternal plate is not connected with the ventral plate and the abdomen is not supported. When students are in study, their waists are likely to bend and their bodies are likely to move downwards. In addition, under normal circumstances, sitting tools do not have backrests, if they have, the backrests are mostly fixed. Even if the backrests are moveable forwards and backwards, they are not fit with the conventional adjustable support, therefore, the external condition for study with the correct sitting position is not achieved. 
       SUMMARY OF THE INVENTION 
       [0010]    In view of the above-described problems, it is one objective of the invention to provide a bionic and posture-correcting backrest for study, which matches with desks and chairs, especially the bionic and posture-correcting desks and chairs. It allows users to maintain the correct “forward sitting position” and the “backward sitting position” or any sitting position therebetween all the time. The sitting position can be easily adjusted and it is unlikely to cause fatigue. 
         [0011]    To achieve the above objective, in accordance with one embodiment of the invention, there is provided a bionic and posture-correcting backrest for study, comprising a bracket body disposed at the rear of the desk via a mounting rack, wherein an adjustable element is provided on a frame which is between the chest/abdomen and the desk edge as well as between the chin and lower part of abdomen (slightly above the thighs); the adjustable element is a fist distance away from the desk edge if a user sits on the chair with the correct sitting position. In this way, the “forward sitting position” and the “backward sitting position” or any sitting position therebetween can be achieved and meanwhile freely switched. The bracket body comprises at least one adjustable tubular pile and a pectoral/ventral plate. The pectoral/ventral plate is moveably connected with an upper adjustable plate. Inside of the adjustable tubular pile is sheathed with a chin adjustment element, which is used to adjust the height of a chin rest. 
         [0012]    In a class of this embodiment, the adjustable element is that the bracket body comprises the pectoral/ventral plate and 1-3 adjustable tubular pile(s) whose inside is sheathed with adjustable tubes. The length of the adjustable element equals to the distance between two points with one from the upper end of the chest to the lower part of the abdomen and the other one from the lower end of the bracket body to the upper side of the thighs, the width of the adjustment element equals to the distance between two points with one at 2.5 cm in the middle of the left and right chest and the other one is the two sides of the chest. The upper end of the adjustable tubular pile is sheathed with a pad cover comprising a reversed pin. Inside of the pad cover is sheathed with a first adjustable tube. The lower end of the first adjustable tube is sheathed with a first adjustable pin, which is larger than the adjustable tube and fits with the adjustable tubular pile. The upper end of the first adjustable tube sheathed with the chin rest. The chin rest comprises a chin pad, a frame cover, a button plate, a spring and a frame base that are sheathed with one another. A button on the button plate extends out of an aperture of the chin pad. A sleeve of the button plate is sheathed on the upper end of a connecting rod. A follow block that is attached to the lower end of the connecting rod is against by the adjustable arm at one side of the upper end of the first adjustable pin. A transverse shaft inside the adjustable groove under the adjustable arm fixes the first adjustable pin to the two walls of one side of the first adjustable tube. The lower end of the adjustable arm is against by a spring of a base plate of the adjustable tubular pile. The lower part of the adjustable arm is in the shape of a “Z” and is sheathed with the pin block, whose one side comprises an inclined recess and whose one end is the pin head. The pin block is disposed in a pin room. On the adjustable tubular pile at one side of the pin head of the first adjustable pin is disposed from top to bottom with the equidistant positional adjustment holes. Inside of the upper end of the first adjustable tube is sheathed with the pad cover for the reversed pin. Inside of the pad cover is sheathed with the second adjustable tube and a second adjustable pin at the lower end. The upper end of the second adjustable tube is covered by the chin rest. The lower end of the second adjustable pin is against by the upper end of the adjustable arm of the first adjustable pin at the other side. When the second and the first adjustable tubes slide to the base plate of the adjustable tubular pile, the pin head of the second adjustable tube, adjacent to one side of the adjustable arm of a second adjustable pin, passes through the first adjustable tube and one aperture of the adjustable tubular pile. When the first adjustable tube is pulled to its limit to the corresponding position of the upper part of the adjustable tubular pile, on the other side, the pin head of the first adjustable pin passes through one aperture of the adjustable tubular pile. On the first adjustable tube of one side of the pin head of the second adjustable pin of the second adjustable tube is disposed with positional adjustment holes from top to bottom. The upper end of the adjustable groove of another adjustable arm is reversely disposed with the spring. The spring  5  is placed on a block that is extended from the wall of the adjustable pin. Another adjustable arm extends downwards with an inclined foot that is sheathed with an inclined aperture of another pin block and a circular pin is used to connect the adjustable tubes as a whole. At the front of the adjustable tubular pile and the pectoral plate is moveably connected with an upper adjustable plate in the transversal direction. The width of the upper adjustable plate equals to the width of the pectoral plate and the length of the upper adjustable plate equals to the distance of the fist (to the desk) plus the part in the mounting bracket. The two sides of the upper adjustable plate are disposed with recesses that fit with a moveable pin of the mounting bracket. The mounting bracket is reversely disposed at the bottom of the desktop. The adjustable plate cover of the mounting bracket comprises an upper plate and a base plate. The top two ends and the front end of the upper plate are each connected with a baffle and disposed with the moveable pins. 
         [0013]    In a class of this embodiment, a reversed button can be sheathed below the chin rest. The chin rest of the adjustable tube comprises a chin pad, another button plate, and lever arms. The chin rest is sheathed at the upper end of the two adjustable tubes. The upper ends of the two lever arms pass through the apertures at the opposite inner sides of the two adjustable tubes to moveably connect with the upper end of the connecting rod, respectively. The apertures at the upper ends of the two lever arms are moveably connected with the transverse shafts on the chin rest. The upturned sides at the lower ends of the two lever arms are inserted into the bottom of a connecting groove, which is reversely disposed in the chin rest and which is on another button plate. Another button plate is hanged on the two lever arms via hanging rods at the front and back of the connecting groove. The chin rest of the adjustable tube comprises a chin pad and another lever arm. The chin rest is sheathed on the upper end of the adjustable tube. The aperture at the upper end of another lever arm is moveably connected with the transverse shaft, which is at the other side of the connecting tube and which is on the adjustable tube. The lower end of another lever arm is at the other side of the adjustable tube to inclinedly extend to the bottom of the chin rest. The upper end of the first adjustable tube is covered by the chin pad and the lower end of the first adjustable tube is sheathed with a first adjustable pin, which is bigger than the first adjustable tube and which fits with the adjustable tubular pile. The two adjustable pins are parallelly connected with each other to form an adjustable pin. The pin head of the adjustable pin can face one side or face both sides. On the pin head of the adjustable pin and on the adjustable tubular pile are disposed with positional adjustment holes from top to bottom. On one side of the pin head, a side button  206  is extended from the adjustable groove of the adjustable tubular pile. The side button comprises an upper button block and a lower button block. The upper button block and the lower button block are respectively at one side of the first adjustable tube to connect with the upper end of the adjustable arm and the lower outer side of the first adjustable pin. One side of the external adjustable tubular pile is connected with the upper/lower ends of an upper circular tube and a lower circular tube that are sheathed with the spring. The upper button block and the lower button block of the two adjustable tubular piles are transversally connected as a whole. 
         [0014]    In a class of this embodiment, the bracket body comprises 1-3 adjustable tubular pile(s), whose inside is sheathed with adjustable tubes and which combines with the pectoral plate. The length of the adjustable element equals to the distance of two points with one from the upper end of the chest to the lower part of the abdomen and the other one is from the lower end of the bracket body to the upper side of the thighs, the width of the adjustment element equals to the distance of two points with one at 2.5 cm in the middle of the left and right chest or the sternal plate is narrow but the ventral plate has the same width as the abdomen. The upper end of the adjustable tubular pile is connected with the chin rest. The other three sides of the adjustable tubular pile form the frame edge. From the middle point of the left and right frame edges extends downwards with a section. An acute angle triangle (the top is the acute angle and the bottom becomes thicker) is formed from the middle point of such section to separate the adjustable column into a rear plate and a front plate. One surface of the rear plate becomes thinner to zero along the rear plate of the adjustable tubular pile while one surface of the front plate becomes thinner along the front plate of the adjustable tubular pile to be the gear head and fit with the positional adjustment gears. The rear side of the front plate of the adjustable column on the gear head passes through the front side and extends with a rectangle button underframe in the transversal direction, which fits with the adjustable groove of the adjustable tubular pile. The button underframe matches with the reversed pin of another button. Another buttons on the two adjustable tubular piles can be transversally connected as a whole. At the connection point between the ventral plate and the sternal plate is moveably connected with an upper adjustable plate. The left and right ends of the upper adjustable plate are disposed with equidistant positional adjustment gears, which fit with the mounting bracket. A bracket position correction element is disposed between the upper adjustable plate and the pectoral plate. The adjustable cover of the mounting bracket comprises a cover plate, a median plate, a base plate, a wheel, a moveable plate, adjustable cover pin blocks, the spring and another handle. On the opposite side of the wheel is respectively disposed with a column. On the one side of the two adjustable cover pin blocks is respectively disposed with the column. The apertures at the two ends of the two moveable plates are moveably connected with wheel and the columns of the two adjustable cover pin blocks. The other side of the adjustable cover pin blocks is against the spring. The above structure fits with the space formed by the median plate and the cover plate. One side of the two adjustable cover pin blocks passes through the median plate and the adjustable groove of the inner side of the baffle with a section. The two adjustable cover pin blocks is extendable along the adjustable groove. The median plate, the baffle and the base plate form a transversal gap. The shaft on the wheel passes through the aperture of the cover plate to connect with another handle. 
         [0015]    In a class of this embodiment, the bracket position correction element is disposed with a movable connection between the pectoral plate and the upper adjustable plate. They are connected by bosses that fit with the hinge block of the pectoral plate and the upper adjustable plate. The rear side of the hinge block of the upper adjustable plate is made into a vertical plane and the plane is concave. A long strip-shaped gap is disposed from top to bottom of the two ends of the hinge block of the pectoral plate that corresponds to the hinge block. There is a space at the rear side of an adjustable block between the two strip-shaped gaps. If the adjustable block is too thick, it is appropriate to open a transversal gap at the upper or lower adjustable block of the upper adjustable plate. Because the hinge block is projected backwards, the resilient adjustable block is also projected backwards. The bracket body can be hanged on the upper adjustable plate and is rotatable forwards and backwards. 
         [0016]    In a class of this embodiment, at the front of the lower end of the adjustable column and at two sides of another button are respectively disposed with 1-2 gear head(s), which matches with positional adjustable gear at the front of the adjustable tubular pile. The lower end of the adjustable column is disposed with a bow-shaped leaf spring. A bow point of the bow-shaped leaf spring is against the inner side of the rear wall of the adjustable tubular pile. The adjustable column is the adjustable tube. The lower end of the adjustable tube is disposed with the bow-shaped leaf spring. The bow point of the bow-shaped leaf spring is disposed with another button, which extends out of the adjustable groove at the front of the adjustable tube. The bow points at two sides of another button are respectively disposed with the pin head. The pin head is sheathed with the positional adjustment holes at the front wall of the adjustable tubular pile  25 . Inside of the lower end of the adjustable tube is sheathed with an inner sleeve adjustable pin. The inner sleeve adjustable pin is between pin slices that are moveably connected at the lower end of the adjustable tube and transversally supports the spring. The pin slices have one side relative to the spring respectively disposed with a double button. The two buttons extend out of the left and right adjustable grooves of the adjustable tubular pile. The gear head that is projected from the lower ends (relative sides) of the two pin slices matches with the positional adjustment gear from top to bottom at the inner side of the adjustable groove. 
         [0017]    In a class of this embodiment, inside of the adjustable tubular pile is sheathed with the adjustable column, extending from the chest to the lower part of the abdomen and the upper side of the thighs. The chin pad is at the place where the upper end (end portion) of the adjustable column extends forwards at 90°. The bottom of the upper end of the adjustable column is disposed with another chin adjustment element. The chin adjustment element comprises a cover plate, a front plate of the pectoral plate (equivalent to the median plate), a rear plate of the pectoral plate (equivalent to the base plate), a wheel, moveable plates, the adjustable cover pin blocks, the spring and another handle. The front plate and the rear plate form a vertical gap therebetween. The adjustable cover pin blocks at the left and right of the vertical gap match with the adjustable column having the equidistant positional adjustment gears. The shaft on the wheel extends out of the aperture of the cover plate and is fixed with another handle. The column extending out of the opposite side of the shaft is placed in the aperture at the front of the rear plate via the adjustable groove of the adjustable column In the middle of the front and rear sides of the pectoral plates that are at the left and right sides of the adjustable tubular pile is disposed with a flat gap extending to the left and right sides. At the upper and lower sides of the flat gap are moveably connected with a moveable pectoral plate, respectively. The moveable pectoral plate uses the moveable connecting point as the start point and has the same distance at the left, right and top. Between the moveable pectoral plate and the pectoral plate is covered by a boss. The moveable pectoral plate is moveable by 90° between flat and stand positions. The inner side of the upper end of the adjustable tubular pile is slightly small and is sheathed with the adjustable column for a vertical cap nut. The adjustable column has a small upper section and big lower section and is moveably sheathed with a bolt. The lower end of the bolt is connected with the upper end of an arc-shaped boss. The lower end of the arc-shaped boss is connected with a knob that can be transversally rotated. The lower end of the arc-shaped boss can also be connected with umbrella-shaped gears  94 . The umbrella-shaped gears are sheathed with the umbrella-shaped gears at the two ends of the knob which is rotatable in the vertical direction. The knob is disposed at the two sides or middle of the lower ends of the adjustable tubular piles. 
         [0018]    In a class of this embodiment, on the sternal plate of the bracket body is disposed with a bracket folding element. 
         [0019]    In a class of this embodiment, the bracket folding element is above the upper adjustable plate to horizontally separate the bracket body into upper and lower sections. The intersection point of the two sections is disposed with a hinge. The left and right ends of the pectoral plate are each disposed with a connecting tubular pile. The left/right sides and the three edges of the connecting column in the connecting tubular pile of the sternal plate are the frame edge. The lower side extends upward with a gear head (pin head), which fits with the positional adjustment gear (positional adjustment hole) of the connecting tubular pile. The lower part of the gear head is connected with a handle extending out of a connecting groove. The connecting column is moveable ups and downs. The frame folds to the front or back to form an integral part with the connecting fastener. 
         [0020]    In a class of this embodiment, on the bracket body is disposed with a ventral plate adjustment element. 
         [0021]    In a class of this embodiment, the ventral plate adjustment element shortens the ventral plate. The adjustable tubular piles are disposed at the left and right sides of the ventral plate. At the lower end of the ventral plate is disposed with a lower crossbeam, which aligns to the width of the ventral plate. The upper end of the lower crossbeam is perpendicularly connected with the lower end of the adjustable column in the adjustable tubular pile. The positional adjustment holes and bolts are disposed between the adjustable tubular pile and the lower adjustable column At the front of the lower crossbeam is moveably connected with the lower adjustable plate. The lower end of the ventral plate is disposed with another lower crossbeam. Another lower crossbeam is behind the adjustable tubular pile and is formed by left and right crossbeams. On the side between another lower crossbeam and the adjustable tubular pile is covered by bosses from top to bottom. The upper end of another lower crossbeam is connected with the lower end of the adjustable column of the adjustable tubular pile. The left and right frames of the adjustable column and the top three surfaces form the frame edge; the lower surface extends upwards with a turned gear head. The gear head can be sheathed on the upper or lower equidistant positional adjustment gears of the adjustable tubular pile. At the lower side of the positional adjustment gear is connected with the handle, extending out of the adjustable groove. The connecting column is moveable up and down. 
         [0022]    In a class of this embodiment, at the lower end at the front of the bracket body is moveably connected with a lower adjustable plate. The width of the lower adjustable plate equals to the width of the upper adjustable plate and the length of the lower adjustable plate equals to the distance of the fist (to the desk) plus the element that cooperates with the adjustable base plate (desktop lifting element) and which can adjust the frame to decline forwards and backwards. At the rear of the lower adjustable plate and adjacent to the front of the adjustable tubular pile is disposed with a convex button hole. Between the front end of the lower adjustable plate and the adjustable base plate is disposed with a magnet. 
         [0023]    In a class of this embodiment, the clamp structure is applied for the adjustable plate cover and the adjustable cover. The clamp comprises a mounting bracket follow block, a mounting plate, a connecting plate, fastening bolt, and follow block. The mounting bracket follow block and the mounting plate are connected by the connecting plate. One end of the fastening bolt passes through the mounting plate and is sheathed with the follow block. At the opposite sides of the mounting bracket follow block and the follow block can be sheathed with a rubber padding plate. The clamp is moveable. It divides the connecting plate into upper and lower sections. The lower section, long and narrow, connects one side of the mounting bracket follow block and is disposed with the adjustable groove from top to bottom. The upper section, short and wide, connects one side of the mounting plate and at the overlapped side with the lower section is disposed with a clamp groove from top to bottom, which fits with the connecting plate. A bolt extending out of the lower end of the clamp groove passes through the adjustable groove to engage with a butterfly cap nut. 
         [0024]    Advantages of the invention are summarized below: 1. the effect is significant and immediate. Bionic principle is adopted in the invention. The ventral plate and the upper adjustable plate are added. The pectoral plate and the upper adjustable plate are moveably connected to allow the chest and abdomen to lean forwards or backwards. The mounting bracket is used to adjust the distance between the chest and abdomen to the desk edge. The chin adjustment element is improved. It can be freely adjusted and hold the chin. The chin adjustment element is suitable for any desk and chair. If the bionic and posture-correcting backrest is equipped with such chin adjustment element, a reasonable space will be formed between the head, eyes, neck, chest, abdomen, waist, back, buttocks, elbows, legs, feet and the desk and chair. Users will always be at the correct “forward sitting position” or “backward sitting position” or any position in between. The problem that students study by bending over the desks is solved. In addition, the position can be changed at will and students will not easily fatigue. It saves large amount of time for teaching and study, and 2. The bionic and posture-correcting backrest for study provided by the invention is easy to be used, stored and carried. Users are only required to press buttons or turn the handle to use the bionic and posture-correcting backrest. It is only necessary to tighten the bolts when clamps or movable clamps are used. The bracket body is disposed with the ventral plate adjustment element, which can be used on different desks. The bracket body folding element functions to fold the bracket body. Furthermore, the clamps or moveable clamps can connect the adjustable plate cover with the bracket body. The above elements or structure make it convenient for users to carry the bionic and posture-correcting backrest. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The invention is explained in further detail below with reference to the embodiments and attached drawings. 
           [0026]      FIG. 1  is a front view of a bracket body in accordance with a first embodiment of the invention (the moveably connected upper adjustable plate and the lower adjustable plate are horizontally disposed); 
           [0027]      FIG. 2  is a front view of the bracket body of  FIG. 1  in accordance with another embodiment of the invention; 
           [0028]      FIG. 3  is a front view of the bracket body of  FIG. 1  in accordance with another embodiment of the invention; 
           [0029]      FIG. 4  is a front view of a chin adjustment element of  FIG. 1 , which is drawn to its maximum limit; 
           [0030]      FIG. 5  is a front view of the chin adjustment element of  FIG. 2 , which is drawn to its maximum limit; 
           [0031]      FIG. 6  is a front view of the chin adjustment element of  FIG. 3 , which is drawn to its maximum limit; 
           [0032]      FIG. 7  is a front view of the bracket body of  FIG. 1  in accordance with another embodiment of the invention; 
           [0033]      FIG. 8  is a rear view of the bracket body of  FIG. 7 ; 
           [0034]      FIG. 9  is a front view of the bracket body of  FIG. 2  in accordance with another embodiment of the invention; 
           [0035]      FIG. 10  is a front view of the bracket body of  FIG. 3  in accordance with another embodiment of the invention; 
           [0036]      FIG. 11  is a vertically sectional front view of an adjustable tubular pile internally sheathed with an adjustable tube and an adjustable pin of  FIGS. 1-10 ; 
           [0037]      FIG. 12  is a side schematic diagram of the adjustable tubular pile of  FIG. 11 ; 
           [0038]      FIG. 13  is an exploded front view of a chin rest of  FIGS. 1-10 ; 
           [0039]      FIG. 14  is an exploded front view of another chin rest of  FIG. 13 ; 
           [0040]      FIG. 15  is a side view of the bracket body of  FIG. 1  after being collapsed; 
           [0041]      FIG. 16  is a vertically sectional front view of another adjustable pin of  FIG. 11 ; 
           [0042]      FIG. 17  is a side view of the frame mounted on a desk of  FIG. 1 ; 
           [0043]      FIG. 18  is a top view of an upper adjustable plate of the invention; 
           [0044]      FIG. 19  is a top view of another upper adjustment plate of  FIG. 18 ; 
           [0045]      FIG. 20  is a side view of a chin pad of the invention; 
           [0046]      FIG. 21  is a front view of the chin pad of the invention; 
           [0047]      FIG. 22  is a top view of another chin pad of the invention; 
           [0048]      FIG. 23  is a rear view of an adjustable plate cover of the invention; 
           [0049]      FIG. 24  is a top view of the adjustable plate cover of  FIG. 23 ; 
           [0050]      FIG. 25  is a rear view of the adjustable plate cover of  FIG. 23  in accordance with another embodiment of the invention; 
           [0051]      FIG. 26  is a top view of the adjustable plate cover of  FIG. 25 ; 
           [0052]      FIG. 27  is a vertically sectional front view of another double-post chin rest of the invention; 
           [0053]      FIG. 28  is a vertically sectional front view of another single-post chin rest of the invention; 
           [0054]      FIG. 29  is a vertically sectional front view of another adjustable tubular pile internally sheathed with an adjustable tube and the adjustable pin of  FIG. 11 ; 
           [0055]      FIG. 30  is a side schematic diagram of the adjustable tubular pile of  FIG. 29 ; 
           [0056]      FIG. 31  is a vertically sectional front view of another embodiment of  FIG. 29 ; 
           [0057]      FIG. 32  is a side view of the adjustable tubular pile of  FIG. 31 ; 
           [0058]      FIG. 33  is a front view of the bracket body in accordance with embodiment  2  of the invention (the moveably connected upper adjustable plate and the lower adjustable plate are horizontally disposed); 
           [0059]      FIG. 34  is a front view of the bracket body of  FIG. 33  in accordance with another embodiment of the invention; 
           [0060]      FIG. 35  is a front view of the bracket body of  FIG. 33  in accordance with another embodiment of the invention; 
           [0061]      FIG. 36  is a front view of the declined upper adjustable plate of  FIG. 35 . 
           [0062]      FIG. 37  is a front view of the upturned upper adjustable plate of  FIG. 36 ; 
           [0063]      FIG. 38  is a rear view of the bracket body of  FIG. 35 ; 
           [0064]      FIG. 39  is a vertically sectional side view of the adjustable tubular pile internally sheathed with an adjustable column of  FIG. 35 ; 
           [0065]      FIG. 40  is a top view of a button of  FIG. 39 ; 
           [0066]      FIG. 41  is a sectional side view of the button of  FIG. 39 ; 
           [0067]      FIG. 42  is a front view of the adjustable column of  FIG. 39 ; 
           [0068]      FIG. 43  is a vertically sectional side view of the adjustable column of  FIG. 39  in accordance with another embodiment of the invention; 
           [0069]      FIG. 44  is a vertically sectional side view of the adjustable column of  FIG. 39  in accordance with another embodiment of the invention; 
           [0070]      FIG. 45  is a front view of the adjustable tubular pile of  FIGS. 39 ,  43  and  44 ; 
           [0071]      FIG. 46  is a vertically sectional side view of the adjustable tubular pile internally sheathed with the adjustable column of  FIGS. 33-35  in accordance with another embodiment of the invention; 
           [0072]      FIG. 47  is a front view of the adjustable tubular pile of  FIG. 46 ; 
           [0073]      FIG. 48  is a vertical sectional view of another adjustable column of  FIGS. 46-47 ; 
           [0074]      FIG. 49  is a structural representation of the upside of an adjustable collar of the invention; 
           [0075]      FIG. 50  is a structural representation of the rear side of the adjustable collar of  FIG. 49 ; 
           [0076]      FIG. 51  is a top view of a median plate of the adjustable collar of  FIG. 49 ; 
           [0077]      FIG. 52  is a bottom view of a cover plate of the adjustable collar of  FIG. 49 ; 
           [0078]      FIG. 53  is a top view of an adjustable collar locking block and a spring of  FIG. 51 ; 
           [0079]      FIG. 54  is a front view of the adjustable column of  FIG. 35  in accordance with another embodiment of the invention; 
           [0080]      FIG. 55  is a vertically sectional front view of a chin adjustment element of  FIG. 54 ; 
           [0081]      FIG. 56  is a vertically sectional rear view of the chin adjustment element of  FIG. 54 ; 
           [0082]      FIG. 57  is a front view of an unfolded moveable pectoral plate of another bracket body of  FIG. 54 ; 
           [0083]      FIG. 58  is a front view of the collapsed moveable pectoral plate of the bracket body of  FIG. 57 ; 
           [0084]      FIG. 59  is a front view of the bracket body of  FIG. 33  in accordance with another embodiment of the invention; 
           [0085]      FIG. 60  is a front view of the bracket body of  FIG. 35  in accordance with another embodiment of the invention; 
           [0086]      FIG. 61  is a vertically sectional front view of the chin adjustment element of  FIG. 60 ; 
           [0087]      FIG. 62  is a vertical sectional view of the chin adjustment element of  FIG. 59 ; 
           [0088]      FIG. 63  is a side view of a clamp of the invention; 
           [0089]      FIG. 64  is a side view of a moveable clamp of the invention; and 
           [0090]      FIG. 65  is a rear view of the moveable clamp of  FIG. 64 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0091]      FIGS. 1-32  show a first embodiment of the invention. The frame comprises a bracket body and a mounting bracket  41 . As shown in  FIGS. 1-10 , the bracket body comprises 1-2 adjustable tubular pile (s)  25  and a pectoral/sternal plate  29 . The length of the bracket body equals to the distance from the upper end of the chest to the lower part of the abdomen (slightly above the thighs) and the width of the bracket body is 2.5 cm from the left/right chest to the two sides of the chest. The upper end of the bracket body is defined from the upper end of the chest to any point of the desk edge (where the chest and abdomen meet) while the lower end of the bracket body is defined from the desk edge to the lower part of the abdomen (bottom of the desk) and to any point above the thighs. The width is 2.5 cm from the left/right chest to any point between the two sides of the chest. As shown in  FIGS. 9 and 10 , a sternal plate  30  is narrow and a ventral plate  31  is wide. As shown in  FIG. 1 , the upper end of the bracket body is parallel to the upper end of the chest and the adjustable tubular pile  25  is disposed on the sternal plate  30 . As shown in  FIG. 2 , the upper end of the bracket body is between the upper and lower parts of the chest and the adjustable tubular pile  25  is disposed from the upper end to the lower end of the sternal plate  30 . As shown in  FIGS. 1-2 , inside of the adjustable tubular pile  25  is only disposed with a first adjustable tube  24 . As shown in  FIG. 3 , the upper end of the bracket body is at the connection point between the chest and the abdomen, the adjustable tubular pile  25  is disposed on the ventral plate  31  from top to bottom, and inside of the adjustable tubular pile  25  is disposed with the first adjustable tube  24  and a second adjustable tube  124 . The  FIGS. 7-10  show the similar structure as the  FIGS. 1-3 , the difference is that the adjustable tubular pile  25  has a single column and no ventral plate adjustment element. As shown in  FIGS. 2-3 ,  5 - 6  and  9 - 10 , two sides of the adjustable tubular pile  25  of the sternal plate  30  can be omitted. Certainly, the bracket body may also be in the shape of a frame, which is formed by two or three adjustable tubular piles  25  that are transversely connected by connecting plates or connecting tubes therebetween. As shown in  FIGS. 1-10 , the bracket body is provided with a chin adjustment element. The chin adjustment element is at the upper end of the adjustable tubular pile  25  and is sheathed with a pad cover  32  for a reversed pin  87 . Inside of the pad cover  32  is sheathed with the first adjustable tube  24 . Inside of the lower end of the first adjustable tube  24  is sheathed with a first adjustable pin  27  (“adjustable pin  27 ”), which is slightly bigger than the first adjustable tube  24  and which fits with the adjustable tubular pile  25 . The adjustable pin  27  comprises an adjustable arm  12 , an adjustable groove  13 , a pin block  20 , and a pin head  17  that is between the adjustable tubular piles  25 , positional adjustment holes  22  and a spring  5 . As shown in  FIG. 13 , the upper end of the first adjustable tube  24  is covered by a chin rest  1 . The chin rest  1  comprises a chin pad  2 , a frame cover  3 , a button plate  4 , the spring  5  and a frame base  7  that are sheathed with one another. A button  6  on the button plate  4  extends out of an aperture  8  that is at one side of the chin pad  2  on the frame cover  3 . As shown in  FIG. 14 , the button  6  extends out of the aperture  8  that is under the chin pad  2  supported on the frame cover  3 . As shown in  FIGS. 11-14 , a sleeve  9  of the button plate  4  is sheathed on the upper end of a connecting rod  10 . A follow block  11  that is attached to the lower end of the connecting rod  10  is against by the adjustable arm  12  at one side of the upper end of the first adjustable pin  27 . A transverse shaft  14  inside the adjustable groove  13  under the adjustable arm  12  fixes the first adjustable pin  27  to the two walls of one side of the first adjustable tube  24 . The lower end of the adjustable arm  12  is against by a base plate  78  of the adjustable tubular pile. The lower part of the adjustable arm  12  is in the shape of a “Z” and is sheathed with the pin block  20 , whose one side comprises an inclined recess  16  and whose one end is the pin head  17  (gear head  18 ). The pin block  20  is disposed in a pin room  21 . On the adjustable tubular pile  25  at one side of the pin head  17  of the first adjustable pin  27  is disposed from top to bottom with the positional adjustment holes  22  (positional adjustment gears  23  in the inner side) at equal intervals. As shown in  FIGS. 3 ,  6  and  10 , inside of the upper end of the first adjustable tube  24  is sheathed with the pad cover  32  for the reversed pin  87 . Inside of the pad cover  32  is sheathed with the second adjustable tube  124  and a second adjustable pin at the lower end. The upper end of the second adjustable tube  124  is covered by the chin rest  1 . The lower end of the second adjustable pin is against by the upper end of the adjustable arm  12  of the first adjustable pin  27  at the other side. When the second and the first adjustable tubes  124 ,  24  slide to the base plate  78  of the adjustable tubular pile, the pin head of the second adjustable tube  124 , adjacent to one side of the adjustable arm  12  of a second adjustable pin, passes through the first adjustable tube  24  and one aperture of the adjustable tubular pile  25 . When the first adjustable tube  24  is pulled to its limit to the corresponding position of the upper part of the adjustable tubular pile  25 , on the other side, the pin head  17  of the first adjustable pin  27  passes through one aperture of the adjustable tubular pile  25 . On the first adjustable tube  24  of one side of the pin head  17  of the second adjustable pin of the second adjustable tube  124  is disposed with positional adjustment holes  22  from top to bottom. As shown in  FIGS. 4-6 , the first and the second adjustable tubes  24 ,  124  are moveable with the button  6  and the pin head  17  is extendable and retractable. In addition, as shown in  FIG. 16 , the upper end of the adjustable groove  13  of another adjustable arm  112  is reversely disposed with the spring  5 . The spring  5  is placed on a block  61  that is extended from the wall of the adjustable pin. Another adjustable arm  112  extends downwards with an inclined foot that is sheathed with an inclined aperture of another pin block  120  and a circular pin is used to connect the adjustable tubes  24 . As shown in  FIGS. 1-10  and  17 - 19 , at the front of the adjustable tubular pile  25  and the pectoral/sternal plate  29  is moveably connected with an upper adjustable plate  34  in the transversal direction. The width of the upper adjustable plate  34  equals to the width of the pectoral/sternal plate  29  and the length of the upper adjustable plate equals to the distance of the fist (to the desk) plus the part in the mounting bracket  41 . The two sides of the upper adjustable plate are disposed with recesses that are fit with a moveable pin  95  of the mounting bracket  41 . The top of the upper adjustable plate is provided with adjustable scales  57 . As shown in  FIG. 17  and  FIGS. 23-24 , the mounting bracket  41  is reversely disposed at the bottom of the desktop  88  (top and bottom of the mounting plate  38 ). The adjustable plate cover of the mounting bracket  41  comprises an upper plate  85  and a base plate  84 . The top two ends and the front end of the upper plate  85  are each connected with a baffle  79 . At the opposite sides transverse to the inner sides of the two baffles are disposed with the moveable pin  95 . The moveable pin  95  is smaller than the pin mouth. Inside of the moveable pin is disposed with an adjustable plate cover pin head  217  (a round sphere or the front end is the round sphere and the rear end is connected with a round column) The rear side of the adjustable plate cover pin head  217  is against the spring  5 . As shown in  FIGS. 25-26 , inside of the upper plate  85  of the moveable pin  95  is disposed with arc-shaped leaf springs  51 . On the upper adjustable plate  34  is disposed with recesses that fit with the arc-shaped leaf springs  51 . Furthermore, the base plate  84  may also be one of the top/bottom surfaces of the desktop  88  or the mounting plate. The gap between the pectoral/sternal plate  29  may be in the shape of a honeycomb. 
         [0092]    As shown in  FIGS. 1 and 4 , a handle  15  can be disposed between the adjustable tubular pile  25  and the other elements. The handle may be made with a ventilation function. The pectoral/sternal plate  29  can be made according to the shape of the chest and abdomen. The chin pad  2  is connected with the frame cover  3  (engage with each other, magnetically attract each other or stick together). 
         [0093]    As shown in  FIGS. 1 ,  4  and  7 - 8 , the chin adjustment element of the pectoral/sternal plate  29  is on the sternal plate  30 , on which a bracket folding element is disposed. The bracket folding element is slightly above the upper adjustable plate  34  to horizontally separate the bracket body into upper and lower sections. The intersection point of the two sections is disposed with a hinge  59 . The left and right ends of the pectoral/sternal plate  29  are each disposed with a connecting tubular pile  62 . As shown in  FIGS. 42 and 45 , the left/right sides and the three edges of the connecting column in the connecting tubular pile  62  of the sternal plate  30  are the frame edge. The lower side extends upward with a gear head (pin head), which fits with the positional adjustment gear (positional adjustment hole) of the connecting tubular pile  62 . The lower part of the gear head is connected with a handle  65  extending out of a connecting groove  66 . The connecting column is moveable up and down. The connecting tubular pile  62  and the connecting column can be replaced by a connecting fastener  68  that is disposed at two sides of front/back surface of the pectoral/sternal plate  29 , or a concave clamp that is covered on left/right ends of the sternal plate  30 , or upper and lower grooves that fit with front/back surface of the ventral plate. As shown in  FIG. 15 , the frame folds to the front or back to form an integral part with the connecting fastener  68  (magnet). 
         [0094]    As shown in  FIGS. 1-10  and  FIG. 17 , at the lower end (slightly at the upper part) at the front of the ventral plate  31  is moveably connected with a lower adjustable plate  35 . The width of the lower adjustable plate  35  equals to the width of the upper adjustable plate  34  and the length of the lower adjustable plate  35  equals to the distance of the fist (to the desk) plus the element that cooperates with the adjustable base plate  86  (desktop lifting element) and which can adjust the frame to decline forwards and backwards. Furthermore, the lower adjustable plate  35  may be in the shape of a trapezoid or a triangle. Similar to the  FIG. 36 , at the rear of the lower adjustable plate  35  and adjacent to the front of the adjustable tubular pile  25  is disposed with a convex button hole  54 . Certainly, it is possible for the moveable seat of the lower adjustable plate  35  to be made more convex so as to fold the lower adjustable plate  35  vertically upwards to the button  6 . Between the lower adjustable plate  35  and the adjustable base plate  86  (desk base plate) is disposed with a magnet (bolt, positional adjustment holes and adjustable grooves). 
         [0095]    As shown in  FIGS. 1-6 ,  17  and  33 - 35 , a ventral plate adjustment element is disposed on the frame. The ventral plate adjustment element shortens the ventral plate  31 . The adjustable tubular piles  25  are disposed at the left and right sides of the ventral plate  31 . At the lower end of the ventral plate  31  is disposed with a lower crossbeam  40 , which is align to the width of the ventral plate  31 . The upper end of the lower crossbeam  40  is perpendicularly connected with the lower end of the adjustable column in the adjustable tubular pile  25 . The positional adjustment holes  22  (adjustable grooves) and bolts are disposed between the adjustable tubular pile  25  and the lower adjustable column. At the front of the lower crossbeam  40  is moveably connected with the lower adjustable plate  35 . 
         [0096]    As an improvement shown in  FIGS. 27-32 , a reversed button  106  can be sheathed below the chin rest  1 . The chin rest  1  of the adjustable tube  24  comprises a chin pad  2 , another button plate  104  and lever arms  28 . The chin rest  1  is sheathed at the upper end of the two adjustable tubes  24 . The upper ends of the two lever arms  28  pass through the apertures at the opposite inner sides of the two adjustable tubes  24  to moveably connect with the upper end of the connecting rod  10 , respectively. The apertures at the upper ends (slightly at the lower position) of the two lever arms  28  are moveably connected with the transverse shafts  14  on the chin rest  1 . The upturned sides at the lower ends of the two lever arms  28  are inserted to the bottom of a connecting groove  66 , which is reversely disposed in the chin rest  1  and which is on another button plate  104 . Another button plate  104  is hanged on the two lever arms  28  via hanging rods  43  at the front and back of the connecting groove  66 . As shown in  FIG. 28 , the chin rest  1  of the adjustable tube  24  comprises a chin pad  2  and another lever arm  128 . The chin rest  1  is sheathed on the upper end of the adjustable tube  24 . The aperture at the upper end (slightly at the lower position) of another lever arm  128  is moveably connected with the transverse shaft  14 , which is at the other side of the connecting tube and which is on the adjustable tube  24 . The lower end of another lever arm  128  is at the other side of the adjustable tube  24  to inclinedly extend to the bottom of the chin rest  1 . As shown in  FIGS. 29-30 , the side button  206  is disposed at the lateral side of the adjustable tube  24 . The upper end of the first adjustable tube  24  is covered by the chin pad  2  and the lower end of the first adjustable tube is sheathed with a first adjustable pin  27 , which is bigger than the first adjustable tube  24  and which fits with the adjustable tubular pile  25 . As shown in  FIGS. 31-32 , the two adjustable pins  27  are parallelly connected with each other to form an adjustable pin  227 . The pin head  17  (gear head  18 ) of the adjustable pin  227  can face one side or face both sides. As shown in  FIGS. 29-32 , on the pin head  17  of the adjustable pin  227  and on the adjustable tubular pile  25  are disposed with positional adjustment holes  22  (positional adjustment gears  23  in the inner side) from top to bottom. On the lateral side (opposite side) of the pin head  17 , a side button  206  is extended from the adjustable groove  13  of the adjustable tubular pile  25 . The side button  206  comprises an upper button block  44  and a lower button block  45 . The upper button block  44  is at one side of the first adjustable tube  24  to connect with the upper end of the adjustable arm  12 . One side of the external adjustable tubular pile  25  is connected with an upper circular tube  47 . The lower button block  45  that is at one side of the adjustable tubular pile  25  is connected with the outer side (slightly at the lower position) of the first adjustable pin  27 . One side of the external adjustable tubular pile  25  is connected with a lower circular tube  48  that is covered by the upper circular tube  47 . The upper circular tube  47  and the lower circular tube  48  are sheathed with a spring  5 . The bottom of the button block  44  on the upper circular tube  47  and the lower circular tube  48  is against the upper side of the first adjustable pin  27 , the pin head  17  can be contracted within the first adjustable pin  27 . The lower and upper ends of the upper circular tube  47  and the lower circular tube  48  are respectively connected with the upper or lower side of the lower button block  45  and the upper button block  44 . The first adjustable tube  24  is movable up and down. The upper button block  44  and the lower button block  45  of the two adjustable tubular piles  25  can be transversally connected as a whole. 
         [0097]      FIGS. 33-62  show a second embodiment of the invention. The adjustable tubular pile  25  is sheathed with an adjustable column  49 . The upper end of the adjustable column  49  is sheathed with the chin rest  1 . As shown in  FIG. 42 , the left and right sides of the lower portion of the adjustable column  49  and the lower three sides form a frame edge  64 . From the middle point of the left and right frame edges  64  extends downwards with a section. As shown in  FIG. 39 , an acute angle triangle (the top is the acute angle and the bottom becomes thicker) is formed from the middle point of such section to separate the adjustable column  49  into a rear plate and a front plate. One surface of the rear plate becomes thinner along the rear plate of the adjustable tubular pile  25  while one surface of the front plate becomes thinner along the front plate of the adjustable tubular pile  25  to be the gear head  18  (pin head  17 ) and fit with the positional adjustment gears  23  (positional adjustment hole  22 ). The rear side of the front plate of the adjustable column  49  on the gear head  18  passes through the front side and extends with a rectangle button underframe  89  in the transversal direction, which fits with the adjustable groove  13  of the adjustable tubular pile  25 . The button underframe  89  matches with the reversed pin  87  of another button  306  as shown in  FIGS. 40-41 . Certainly, the rear plate of the adjustable column  49  may be in the shape of an arc. As shown in  FIGS. 33-34 , another buttons  306  on the two adjustable tubular piles  25  can be transversally connected as a whole. As shown in  FIGS. 35-37 , the upper adjustable plate  34  is moveably connected with the front side of the adjustable tubular pile  25 . The left and right ends of the upper adjustable plate  34  are disposed with equidistant positional adjustment gears  23 , which fit with the mounting bracket  41 . A convex button hole  54  is disposed at the front side of the adjustable tubular pile  25 . As shown in  FIGS. 36-37 , the pectoral/sternal plate  29  is moveably connected with the upper adjustable plate  34  by bosses  67  that fit with the hinge block  60 . A bracket position correction element is disposed between the upper adjustable plate  34  and the pectoral/sternal plate  29 . The rear side of the hinge block  60  of the upper adjustable plate  34  is made to be a vertical rectangle surface as the position correction element. The rectangle surface (circle or ellipse) is concave. A strip-shaped gap  37  is disposed from top to bottom of the two ends of the hinge block  60  of the pectoral/sternal plate  29  that corresponds to the hinge block  60 . There is a space at the rear side of an adjustable block  71  between the two strip-shaped gaps  37 . If the adjustable block  71  is too thick, it is appropriate to open a transversal gap at the upper or lower adjustable block  71  of the upper adjustable plate  34 . Because the hinge block  60  is projected backwards, the resilient adjustable block  71  is also projected backwards. The bracket body can be hanged on the upper adjustable plate  34  and is rotable forwards and backwards. As shown in  FIGS. 35-38 , the lower end of the ventral plate  31  is disposed with another lower crossbeam  140 . Another lower crossbeam  140  is behind the adjustable tubular pile  25  and is formed by left and right crossbeams. On the side between another lower crossbeam  140  and the adjustable tubular pile  25  is covered by bosses from top to bottom. The upper end of another lower crossbeam  140  is connected with the lower end of the adjustable column of the adjustable tubular pile  25 . Similar to  FIG. 42 , the left and right frames of the adjustable column and the top three surfaces form the frame edge, the lower surface extends upwards with a turned gear head (pin head). The gear head can be sheathed on the upper or lower equidistant positional adjustment gears of the adjustable tubular pile  25 . At the lower side of the positional adjustment gear is connected with the handle  65 , extending out of the adjustable groove  13 . The adjustable column is moveable up and down. As shown in  FIGS. 49-53 , the adjustable cover of the mounting bracket comprises a cover plate  82 , a median plate  83 , a base plate  84 , a wheel  72 , a moveable plate  98 , adjustable cover pin blocks  220 , the spring  5  and another handle  165 . On the opposite side of the wheel  72  is respectively disposed with a column  73 . On the one side of the two adjustable cover pin blocks  220  is respectively disposed with the column  73 . The apertures at the two ends of the two moveable plates  98  are moveably connected with wheel  72  and the columns  73  of the two adjustable cover pin blocks  220 . The other side of the adjustable cover pin blocks  220  is against the spring  5 . The above structure fits with the space formed by the median plate  83  and the cover plate  82 . One side of the two adjustable cover pin blocks  220  passes through the median plate  83  and the adjustable groove  13  of the inner side of the baffle  79  with a section. The two adjustable cover pin blocks  220  is extendable along the adjustable groove  13 . The median plate  83 , the baffle  79  and the base plate  84  form a transversal gap  137 , which can be adjusted to fit with the adjustable cover pin blocks  220 . The width between the upper adjustable plate  34  and the desk edge can be adjusted via the transversal gap  137 . The width fits with the adjustable cover pin block  220  and there is an equidistant positional adjustment gear  23  at the two sides. The base plate  84  can be directly the top or bottom of the desktop  88  (the mounting plate). The shaft  74  on the wheel  72  passes through the aperture of the cover plate  82  to connect with another handle  165 . 
         [0098]    As an improvement to the bracket body shown in  FIGS. 43-45 , at the front of the lower end of the adjustable column  49  and at two sides of another button  306  are respectively disposed with 1-2 gear head (s)  18  (pin head  17 ), which matches with the front wall of the adjustable tubular pile  25  or the positional adjustment gears  23  (positional adjustment holes  22 ) from top to bottom at the inner side of the adjustable groove  13 . The lower end (slightly at the upper position where it is relatively thinner) of the adjustable column  49  is disposed with the bow-shaped leaf spring  51 . A bow point  52  of the bow-shaped leaf spring  51  is against the inner side of the rear wall of the adjustable tubular pile  25 . As shown in  FIGS. 46-47 , the adjustable column  49  is the adjustable tube  24 . The lower end (slightly at the upper position) of the adjustable tube  24  is disposed with the bow-shaped leaf spring  51 . The bow point  52  of the bow-shaped leaf spring  51  is disposed with another button  306 , which extends out of the adjustable groove  13  at the front of the adjustable tube  24 . The bow points  52  at two sides of another button  306  are respectively disposed with the pin head  17  (gear head). The pin head is sheathed with the positional adjustment holes  22  (positional adjustment gear) from top to bottom at the front wall of the adjustable tubular pile  25 . As shown in  FIG. 48 , inside of the lower end of the adjustable tube  24  is sheathed with an inner sleeve adjustable pin  327 . The inner sleeve adjustable pin  327  is between pin slices  56  that are moveably connected at the lower end of the adjustable tube  24  and transversally supports the spring  5 . The pin slices  56  have one side (slightly at the lower position) relative to the spring  5  disposed with two buttons  406 . The two buttons extend out of the left and right adjustable grooves  13  of the adjustable tubular pile  25 . The gear head  18  that is projected from the lower ends (relative sides) of the two pin slices  56  matches with the positional adjustment gear  23  from top to bottom at the inner side of the adjustable groove  13 . 
         [0099]    As an improvement to the bracket body shown in  FIGS. 54-56 , inside of the adjustable tubular pile  25  is sheathed with the adjustable column  49 , extending from the chest to the thighs (slightly above the thighs). The chin pad  2  is at the place where the upper end (end portion) of the adjustable column  49  extends forwards by 90° . The bottom of the upper end of the adjustable column  49  is disposed with another chin adjustment element. Similar to  FIGS. 49-53 , the chin adjustment element comprises a cover plate  82 , a front plate  76  of the pectoral plate (equivalent to the median plate  83 ), a rear plate  77  of the pectoral plate (equivalent to the base plate  84 ), a wheel  72 , moveable plates  98 , the adjustable cover pin blocks  220 , the spring  5  and another handle  165 . The front plate  76  and the rear plate  77  form a vertical gap  237  therebetween. The adjustable cover pin blocks  220  at the left and right of the vertical gap  237  match with the adjustable column  49  having the equidistant positional adjustment gears  23 . The shaft on the wheel  72  extends out of the aperture of the cover plate  82  and is fixed with another handle  165 . The column extending out of the opposite side of the shaft is placed in the aperture at the front of the rear plate  77  via the adjustable groove  13  of the adjustable column  49 . The adjustable column  49  is moveable up and down in the vertical gap  237 . 
         [0100]    As an improvement to the bracket body shown in  FIGS. 57-58 , in the middle of the front and rear sides of the pectoral/sternal plate  29  that are at the left and right sides of the adjustable tubular pile  25  is disposed with a flat gap extending to the left and right sides. At the upper and lower sides of the flat gap are moveably connected with a moveable pectoral plate  58 , respectively. The moveable pectoral plate uses the moveable connecting point as the start point and has the same distance at the left, right and top. Between the moveable pectoral plate  58  and the pectoral/sternal plate  29  is covered by a boss. The moveable pectoral plate  58  is moveable by 90° between flat and stand positions. 
         [0101]    As an improvement to the bracket body, as shown in  FIGS. 59-61 , the inner side of the upper end of the adjustable tubular pile  25  is slightly small and is sheathed with the adjustable column  49  for a vertical cap nut  91 . The adjustable column  49  has a small upper section and big lower section and is moveably sheathed with a bolt  33 . The lower end of the bolt  33  is connected with the upper end of an arc-shaped boss  167 . The lower end of the arc-shaped boss  167  is connected with a knob  93  that can be transversally rotated. As shown in  FIGS. 59 and 62 , the lower end of the arc-shaped boss  167  can also be connected with umbrella-shaped gears  94 . The umbrella-shaped gears  94  are sheathed with the umbrella-shaped gears  94  at the two ends of the knob  93  which is rotatable in the vertical direction. The knob  93  is disposed at the sides or middle of the lower ends of the adjustable tubular piles  25 . The knob  93  is moveably connected with the bolt  33  and the adjustable column  49  can rise and descend. As shown in  FIGS. 60-61 , the arc-shaped boss  167  may be convex or concave or in other shapes as long as the arc-shaped boss  167  and the adjustable tubular piles  25  can rotate. 
         [0102]    The mounting bracket  41  can be improved to be the clamp. As shown in  FIG. 63 , the clamp comprises a mounting bracket follow block  99 , a mounting plate  38 , a connecting plate  81 , fastening bolt  75  and follow block  80 . The mounting bracket follow block  99  and the mounting plate  38  are connected by the connecting plate  81 . One end of the fastening bolt  75  passes through the mounting plate  38  and is sheathed with the follow block  80 . At the opposite sides of the mounting bracket follow block  99  and the follow block  80  can be sheathed with a rubber padding plate. As shown in  FIGS. 64-65 , the moveable clamp divides the connecting plate  81  into upper and lower sections. The lower section, long and narrow, connects one side of the mounting bracket follow block  99  and is disposed with the adjustable groove  13  from top to bottom. The upper section, short and wide, connects one side of the mounting plate  38  and at the overlapped side with the lower section is disposed with a clamp groove  97  from top to bottom, which fits with the connecting plate  81 . A bolt  33  extending out of the lower end of the clamp groove  97  passes through the adjustable groove  13  to engage with a butterfly cap nut  92 . 
         [0103]    The above frame can be covered with soft a cover pad at the rear of the pectoral/sternal plate  29 . The cover pad extends from the rear, left and right sides of the frame cover  3  or the crossbeam  39  or the pectoral/sternal plate  29  to the front side of the pectoral/sternal plate  29 . In addition, the cover pad and the pectoral/sternal plate  29  can also be electrified for warm. The bionic and posture-correcting backrest for study provided by the invention can be made of plastics, metal or both. 
         [0104]    The foregoing descriptions of the embodiments and their accompanying drawings of the invention are intended to illustrate and not to limit this invention. Various changes and modifications may be made to the embodiments without departing from the spirit of the invention. For example, the upper and lower adjustable plates and the frame can be connected by means of a folding structure as used in the washing machines&#39; covers (little swan). Spring structure or scale structure (for small-bore rifles) or push-pull structure (for cutters) can be used for the chin adjustment element. The mats or its connecting structure used in shopping trolleys (Walmart) can be used for the upper and lower adjustable plates. Furthermore, the existing structures can be left out or exchanged. For example, the chin adjustment element can be left out with only the pectoral/sternal plate. The chin adjustment element, the bracket folding element, the pectoral plate adjustment element and the upper/lower adjustable plates can be exchanged. In summary, people who are skilled in the related art can easily make any changes and modifications, but all changes and modifications made without departing from the invention in its broader aspects are deemed to be within the applied scope of the invention.