Abstract:
A liquid crystal display having a supporting base, a display unit and a pre-force mechanism. The supporting base has at least one pivot and at least two sections joined thereby, and the display unit is connected to the supporting base, exerts a first torque on the pivot by the weight of the display unit. The pre-force mechanism is connected to the pivot and exerts a second torque on the pivot. The first torque is opposite to the second torque.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a liquid crystal display, and in particular to a liquid crystal display with a supporting base.  
           [0003]    2. Description of the Related Art  
           [0004]    In FIG. 1, a conventional liquid crystal display on a surface  5  is situated in a stable condition. W is the weight of the display unit  1 , and F is external force used for lifting up the display unit  1 . The force F is directly on the display unit  1  and rotated the first pivot  22  in a counterclockwise direction.  
           [0005]    The liquid crystal display has a display unit  1  and a supporting base  2 . The supporting base  2  has a first section  21 , a first pivot  22 , a second section  23 , a second pivot  24 , a third section  25  and a plate  26 . The first pivot  22  and the second pivot  24  have the same structure, and the first pivot  22  connects the first section  21  and the second section  23 , and the second pivot  24  connects the second section  23  and the third section  25 . The display unit  1  is connected to the third section  25  by the plate  26 . The plate can be integrally formed on the end of third section  25 , and the display unit  1  can be directly mounted on the third section  25 . Thus, the position of the display unit  1  can be adjusted upwardly or downwardly by rotating the second section  23  around the first pivot  22 , and the tilt angle of the display unit  1  can be adjusted by rotating the third section  25  around the second pivot  24 .  
           [0006]    [0006]FIG. 2 is a cross-section of the first pivot  22  of FIG. 1 along its longitudinal direction. The fixed element  211  is a part installed on the first section  21  of the supporting base  2 , and the first section is positioned on the surface  5  motionlessly. The movable element  231  is a part installed on the second section  23  of the supporting base  2 . A bolt  221  passes through the fixed element  211  and the movable element  231  and is secured by a nut  222 . Several washers  224  function as frictional disks between the bolt  221  and the fixed element  211 , as well as between the fixed element  211  and the movable element  231 . The washers  224  are made of soft material, such as rubber, plastic or the like. A U-shaped washer  223  and another washer  224  are disposed between the movable element  231  and the nut  222 . The U-shaped washer  223  is used to keep the washer  224  attaching to the fixed element  211  or the moveable element  231 . The U-shaped washer  223  can be made of rigid, flexible material, such as steel, copper or the like.  
           [0007]    When the nut  222  rotates toward the head  221  H, the U-shaped washer  223  is pushed and moved toward the washer  224  disposed next to the movable element  231 , and the fixed element  211  and the movable element  231  are pressed and pushed to approach each other, bracketed by the deformed washers  224 . These deformed washers  224  provide a frictional force to the fixed element  211  and the movable element  231 , to balance the weight of the display unit  1 .  
           [0008]    Referring again to FIG. 1 and also to FIG. 3, as the liquid crystal display is placed on the surface  5 , the weight W of the display unit  1  exerts a gravity torque T W  by the weight of the display unit  1  on the first pivot  22  in a clockwise direction. In the same time, a static frictional force is generated within the first pivot  22  and exerts a frictional torque T F1  on the first pivot  22  in a counterclockwise direction.  
           [0009]    In the first pivot  22 , frictional torque T F1  is equal to gravity torque T W  (T F1 =T W ), i.e., the display unit  1  is stable. The static frictional force, however, is variable. The amount of the static frictional force is increased when the external force applied on an object increases. When the static frictional force is increased to a critical value, i.e., maximum static frictional force, the object is moving because of the external force, The frictional force becomes a dynamic friction force, and the value of the frictional force decreases and reaches a constant. In this related art, T F1  is a frictional torque generated by the maximum static frictional force within the first pivot  22 .  
           [0010]    When the display unit is stable on the surface  5 , the direction of the frictional torque T F1  is opposite to that of the gravity torque T W . When an external force is applied to lift the display unit  1 , the direction of the frictional torque T F1  is changed. When the display unit  1  is successfully lifted, the torque generated by external force F must overcome the sum of the frictional torque T F1  and gravity torque T W . In FIG. 4, T F2  is a torque generated by the external force F in a counterclockwise direction on the first pivot  22 . Thus, torque T F2  must be larger than the sum of frictional torque T F1  and gravity torque T W  (T F1 +T W ). The direction of frictional torque T F1  (clockwise, in FIG. 4) is opposite to the direction of frictional torque T F1  (counterclockwise, in FIG. 3.) because the direction of the maximum static frictional force is changed.  
           [0011]    In general, the nut  222  secured on the bolt  221  is tightly driven, such that the washers  224  can be closely attached on the fixed element  211  and the movable element  231 , and therefore sufficient frictional force is generated therebetween to balance the weight of the display unit  1 . However, the display unit  1  becomes difficult to adjust or position at a predetermined height or angle from the nut  222  on the bolt  221  being over-tightened.  
           [0012]    When the nut  222  is tightly connected to the bolt  221 , the maximum static frictional force within the first pivot  22  is large and the frictional torque T F1  is also very large. Therefore, the torque T F2 , generated by the external force F, used to overcome the frictional torque, is also large.  
           [0013]    If the external force F is too big, the first section will also be lifted to leave the surface  5  when adjusting the position of the display unit  1  as shown in FIG. 5. Therefore, another force N is need to apply on the first section  21  of the supporting base  2  to prevent the first section  21  from leaving the surface  5 . However, it is inconvenient to manually adjust the position or the angle of the display unit  1 .  
         SUMMARY OF THE INVENTION  
         [0014]    Accordingly, an object of the invention is to provide a pre-force mechanism in a pivot of a liquid crystal display, allowing easy lifting of a display unit.  
           [0015]    The invention provides a liquid crystal display having an supporting base, a display unit, and a pre-force mechanism. The supporting base has at least two sections and at least one pivot, the two sections connected by the pivot.  
           [0016]    The display unit is lifted by the supporting base. The display unit is connected to one of the two sections, and exerts a first torque on the pivot by a weight of the display unit. The pre-force mechanism is connected to the pivot and exerts a second torque on the pivot. The second torque and the first torque are in opposite directions. Therefore, the torque generated by external force is substantially reduced, and the display unit can be easily lifted or adjusted.  
           [0017]    A detailed description is given in the following embodiments with reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
         [0019]    [0019]FIG. 1 is a schematic view of a conventional liquid crystal display;  
         [0020]    [0020]FIG. 2 is a cross-section of a first pivot ( 22 ) of the liquid crystal display of FIG. 1 along its longitudinal direction;  
         [0021]    [0021]FIG. 3 is a diagram of the equilibrium of force (torques) on the liquid crystal display in FIG. 1;  
         [0022]    [0022]FIG. 4 is a diagram of the equilibrium of force (torques) on the liquid crystal display in FIG. 1, wherein a display unit ( 1 ) of the liquid crystal display is lifted;  
         [0023]    [0023]FIG. 5 is a schematic view of the liquid crystal display in FIG. 1, wherein the display unit ( 1 ) of the liquid crystal display is lifted;  
         [0024]    [0024]FIG. 6 is a diagram of the equilibrium of force (torques) on a liquid crystal display according to the present invention;  
         [0025]    [0025]FIG. 7 is a diagram of the equilibrium of force (torques) on the liquid crystal display of the present invention, wherein the display unit ( 1 ) of the liquid crystal display is lifted;  
         [0026]    [0026]FIG. 8 is a schematic view of the liquid crystal display according to the present invention;  
         [0027]    [0027]FIG. 9 is a schematic view showing the relationship between a pre-force mechanism ( 3 ) and a first pivot ( 22 ′) of the liquid crystal display in FIG. 8;  
         [0028]    [0028]FIG. 10 is a cross-section of the first pivot ( 22 ′) of the liquid crystal display of FIG. 8 along its longitudinal direction;  
         [0029]    [0029]FIG. 11 is a schematic view of the liquid crystal display of FIG. 8, wherein a pre-force (P) generated by the pre-force mechanism ( 3 ) is applied in the liquid crystal display;  
         [0030]    [0030]FIG. 12 is a partial view of the liquid crystal display of FIG. 8, wherein a wear liner ( 35 ) is disposed between a second section ( 23 ) of a supporting base ( 2 ) and a rod ( 33 ) of the pre-force mechanism ( 3 );  
         [0031]    [0031]FIG. 13A-13 B are two schematic views of the liquid crystal of FIG. 8, wherein the second section ( 23 ) of the supporting base ( 2 ) in FIG. 13A is in an initial state, and the second section ( 23 ) of the supporting base ( 2 ) in FIG. 13B is in a raised condition when the display unit ( 1 ) is lifted and the second section ( 23 ) of the supporting base ( 2 ) rotates about an axis (A) of the first pivot ( 22 ′);  
         [0032]    [0032]FIG. 13C is a simulation diagram of deployment of the second section ( 23 ) of the supporting base ( 2 ), wherein a distance from point (A) to point (C) represents the state of the second section ( 23 ) of the supporting base ( 2 ) in FIG. 13A, and a distance from point (A) to point (C′) represents the state of the second section ( 23 ) of the supporting base ( 2 ) in FIG. 13B; and  
         [0033]    [0033]FIG. 14 is a schematic view of an exemplary rod ( 33 ′) of the pre-force mechanism ( 3 ). 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]    As shown in FIG. 6, when the liquid crystal display is situated in a stable condition, the present invention provides a pre-force mechanism  3  (as FIG. 8) to generate a second torque T P  in a pivot of a liquid crystal display (LCD) in advance, such that the second torque T P  is formed to overcome a first torque T W  generated by the weight of the display unit  1 . The direction of the first torque T W  is opposite to that of the second torque T p . In addition, a third torque is exerted on the pivot of the LCD because of the frictional force within the pivot. When the LCD is situated in the stable condition, the first torque T W  generated by the weight of the display unit  1  is larger than the second torque T P  formed by the pre-force mechanism  3  and the third torque T F3  formed by the frictional force, that is, T W ≧T F3 +T P . Because of the second torque T P , the third torque T F3 , the frictional torque for balancing the weight of the display unit  1 , can be reduced. That is to say, the frictional torque T F3  in FIG. 6 is smaller than the frictional torque T F1  in FIG. 4.  
         [0035]    When an external force F is applied to lift the display unit  1 , the fourth torque T F4  is the torque generated by the external force F on the first pivot  22  in a counterclockwise direction. In addition, the direction of the frictional force within the pivot is changed.  
         [0036]    The expression of the equilibrium formula of the state in FIG. 7 is written as T F4 +T P =T F3 +T W . When the display unit  1  is lifted because of the external force F, the torque T F4  generated by external force F needs to overcome the first torque T W  generated by the weight of the display unit  1  and the frictional torque T F1 . However, the second torque T P  is exerted on the pivot in advance. Therefore, the torque TF 4  can be reduced and the external force F can also be reduced. That is to say, the display unit  1  can be lifted or adjusted without additional force N on the first section  21  as shown in FIG. 5.  
         [0037]    It can be seen that frictional torque T F3  as the LCD is positioned in the stable status as shown in FIG. 6 is effectively reduced and the torque T F4  generated by external force F is reduced commensurately.  
         [0038]    In FIG. 8, a liquid crystal display D of the present invention has a display unit  1 , a supporting base  2 ′ and a pre-force mechanism  3 . The supporting base  2 ′ has a first section  21 , a first pivot  22 ′, a second section  23 , a second pivot  24 , a third section  25  and a plate  26 . The first pivot  22 ′ and the second pivot  24  have the same structure, and the first pivot  22 ′ connects the first section  21  and the second section  23 , and the second pivot  24  connects the second section  23  and the third section  25 . The display unit  1  is connected to the third section  25  by the plate  26 . In another embodiment, the plate can be integrally formed on the end of third section  25 , and the display unit  1  can be directly mounted on the third section  25 . Thus, the position of the display unit  1  can be adjusted upwardly or downwardly by rotating the second section  23  around the first pivot  22 ′, and the tilt angle of the display unit  1  can be adjusted by rotating the third section  25  around the second pivot  24 .  
         [0039]    The pre-force mechanism  3  has an annular stopper  31 , a resilient element  32  and a rod  33 . The stopper  31  is disposed in the hollow second section  23  and rotates around the first pivot  22 ′ when the second section  23  rotates around the first pivot  22 ′. The stopper  31  has an orifice  311  penetrated by the rod  33 . In the present embodiment, the resilient element  32  is a spring.  
         [0040]    In FIG. 9, the rod  33  has a first end  331 , a second end  332  and a middle portion  333  located between the first end  331  and the second end  332 . The second end  332  is thinner than the middle portion  333  so that the spring  32  is disposed on the middle portion  333  of the rod  33  and confined and pressed between the stopper  31  and the second end  332 . Both the rod  33  and the spring  32  are disposed in the second section  23 . The first end  331  of the rod  33  is hooked at an opening  212  of the first pivot  22 ′ (See FIG. 10), such that the rod  33  is coupled to the fixed element  211 ′ and the rod  33  rotates around the first pivot  22 ′.  
         [0041]    [0041]FIG. 10 is a cross-section of the first pivot  22 ′ of FIG. 8 along its longitudinal direction. The fixed element  211 ′ is a part installed on the first section  21  of the supporting base  2 , and the first section  21  is positioned on the surface  5  motionlessly. A through hole  212  is formed on the fixed element  211 ′. The movable element  231  is a part installed on the second section  23  of the supporting base  2 . A bolt  221  passes through the fixed element  211 ′ and the movable element  231 , and is secured by a nut  222 . Several washers  224  function as frictional disks are positioned between the bolt  221  and the fixed element  211 ′, and between the fixed element  211 ′ and the movable element  231 . The washers  224  are made of soft material, such as rubber, plastic or the like. A U-shaped washer  223  and another washer  224  are disposed between the movable element  231  and the nut  222 . The U-shaped washer  223  is used to keep the washer  224  attaching to the fixed element  211  or the moveable element  231 . The U-shaped washer  223  can be made of rigid, flexible material, such as steel, copper or the like.  
         [0042]    When the nut  222  rotates toward the head  221 H, the washer  223  is pushed and moved toward the washer  224  next to the movable element  231 . The fixed element  211 ′ and the movable element  231  are then pressed and pushed to approach each other, bracketed by the deformed washers  224 . These deformed washers  224  provide frictional force on the fixed element  211 ′ and the movable element  231 , such that the frictional force is applied to balance the weight of the display unit  1 .  
         [0043]    Referring to FIG. 11 and also FIG. 8, the spring  32  confined between the stopper  31  and the second end  332  is compressed so as to generate a force P, pushing the opening  212  of the first pivot  22 ′ through the rod  33 . That is to say, the spring  32  is a pre-stressed element and generates the force P to rotate the second section  23  around the first pivot  22 ′ in a counterclockwise direction, i.e., the pre-torque T P  in FIG. 6 is provided by the force P acting on the fixed element  211 ′. The pre-torque T P  is applied to overcome first torque T W  generated by the weight W of the display unit  1  and the reduced frictional torque T F3  in FIG. 7, such that the display unit  1  is easily lifted or adjusted without additional force on the first section  21 .  
         [0044]    When the display unit  1  is lifted or adjusted, i.e., the second section  23  rotates about the first pivot  22 ′, in a counterclockwise or clockwise direction, the second end  332  of the rod  33  is moved within the second section  23 , as demonstrated by the formulas in the following description.  
         [0045]    To reduce the frictional resistance of moving the second end  332  and eliminate noise generated by the friction, a wear liner  35  can be disposed between the second end  332  of the rod  33  and the second section  23  of the supporting base  3 ′, i.e., the wear liner  35  can be disposed on the outside of the second end  332  of the rod  33  or on the inner wall of the second section  23  of the supporting base  3 ′.  
         [0046]    In FIGS. 13A and 13B, A is a center of the first pivot  22 ′, Bp is the location of the opening  212 , and Cp is the center of the stopper  31 . When the second section  23  rotates around the first pivot  22 ′, the center of the stopper  31  is moved from point Cp to point C′.  
         [0047]    [0047]FIG. 13C is a resultant diagram of FIGS. 13A and 13B together. Distance “{overscore (ApBp)}” measured from points Ap to Bp is a constant whenever the second section  23  rotates around the first pivot  22 ′, and “{overscore (ApBp)}” is defined as “r” ({overscore (ApBp)}=r). With respect to point Ap, distance “{overscore (ApCp)}” measured from points Ap to Cp, and distance “{overscore (ApC′)}” measured from points Ap to C′ are also constant and have the same value, and therefore, “{overscore (ApCp)}” and “{overscore (ApC′)}” are defined as “R” ({overscore (ApCp)}={overscore (ApC′)}=R). In addition, the distance between points Bp and Cp is “d”, and the distance between points Bp and C′is “d′”.  
         [0048]    Based on Cosine equation, a geometric formula for the triangle ΔApBpC is expressed as follows:  
           d   2   =r   2   +R   2 −2 rR  cos θ l    (1)  
         [0049]    Another geometric formula for the triangle ΔApBpC′ is expressed as follows:  
           d′   2   =r   2   +R   2 −2 rR  cos θ h    (2)  
         [0050]    By subtracting (2) from (1) to get a formula (3) as follows:  
           d   2   −d′   2 =2 rR (cos θ h −cos θ l )   (3)  
         [0051]    In FIG. 13C, θ h  is an angle between edge {overscore (ApBp)} and {overscore (ApC′)}, and θ l  is an angle between edge {overscore (ApBp)} and {overscore (ApCp)}, θ h  is small than θ l , and thus cos θ h  exceeds cos θ l .  
         θ h &lt;θ l            cos θ h &gt;cos θ h −cos θ l &gt;0   (4)  
         [0052]    Putting (4) into (3) results in formula (5) as follows:  
                       d   2     -     d   ′2       =                2                   rR        (       cos                   θ   h       -     cos                   θ   l         )         &gt;   0     ⇒                     d   2     -     d   ′2       =                  (     d   +     d   ′       )          (     d   -     d   ′       )       &gt;   0     ⇒                            d   -     d   ′       &gt;   0                   (   5   )                               
 
         [0053]    In formula (5), it is understood that the distance between the opening  212  and the stopper  31  decreases when the second section  23  rotates around the first pivot  22 ′ in a counterclockwise direction, as the distance between the stopper  31  and the second end  332  increases. Thus, the second end  332  of the rod  33  is moved within the second section  23  whenever the second section  23  rotates about the first pivot  22 ′.  
         [0054]    Referring to FIG. 14, a different pre-force mechanism is provided. The rod  33 ′ is a variant of the rod  33  in FIG. 9. The rod  33 ′ differs from the rod  33  in that the resilient element (spring) is integrally formed on the rod  33 ′. A resilient portion  32 ′ is integrally formed on the second end  332 ′ of the rod  33 ′ and encloses the rod  33 ′. When the rod  33 ′ is properly disposed in the second section  23  of the supporting base  2 ′, the spring  32 ′ is confined between the stopper  31  and the second end  332  and compressed, such that the force (as the same force P in FIG. 11) is generated by the compressed spring  32 ′ pushing the opening  212  of the first pivot  22 ′ through the rod  33 ′. Thus, the pre-torque T P  overcomes gravity torque T W  generated by the display unit  1 , such that display unit  1  can be easily lifted or adjusted without additional force on the first section  21 .  
         [0055]    While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to enclose various modifications and equivalent arrangements included within the spirit and scope of the appended claims.