BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention is related to a liquid crystal display, and particularly to a liquid crystal display with a height adjustable base incorporating with a function of locking the ascending and descending movements of the liquid crystal panel thereof. 
         [0003]    2. Brief Description of the Related Art 
         [0004]    Due to the information technology being developed rapidly, the monitor with screen display is widely applied for showing pictures such as graphical images. The traditional cathode ray tub (CRT), which had been popularly used for a long time, has been largely replaced with the liquid crystal display (LCD), which is light in weight and thin in thickness. 
         [0005]    In order to allow the height or the inclining angle of the liquid crystal panel on the liquid crystal display placed on the desktop being adjustable according to the preference of the user, it is necessary to have an adjustment device on the liquid crystal display for meeting the need of the user from the standpoint of the comfortable operation. 
         [0006]    The conventional height adjustable base on the liquid crystal display offers an upward elastic force with a constant force spring. Because the locating of the height adjustable base is achieved by means of the gravity of the liquid crystal panel balancing with the upward elastic force of the constant force spring, the ascending and descending movements of the height adjustable base work normally only if the liquid crystal display is operated normally. The liquid crystal panel is usually descended to the lowest position with a forward inclining angle 90° before the liquid crystal display is packed for delivering. But, it is very possible that the liquid crystal panel bounces outward suddenly to hurt people at the time of the liquid crystal display being unpacked. Hence, how to avoid the preceding deficiency and secure the safety of the people is a subject worth us to investigate thoroughly. 
       SUMMARY OF THE INVENTION 
       [0007]    Accordingly, an object of the present invention is to provide a liquid crystal display with a height adjustable base, which has a function of locking the ascending and descending movements, such that when the forward inclining angle of the liquid crystal panel is greater than a certain angle, the operation of ascending and descending the liquid crystal panel is capable of being locked during the liquid crystal display being unpacked to prevent the liquid crystal panel from bouncing outward suddenly and to enhance the convenience of the operation. 
         [0008]    In order to achieve the preceding object, a liquid crystal display with a height adjustable base for the panel thereof according to the present invention includes a liquid crystal display and a height adjustable base, and the height adjustable base further includes a base, an inclinable main arm, a panel fixing frame and a lock device. 
         [0009]    Wherein, the inclinable main arm has a pivotal connection with the base and has a slide rail at two opposite lateral sides thereof respectively; the panel fixing frame is mount with the liquid crystal panel has a locating groove and is capable of offering the liquid crystal panel ascending and descending along the rail; and the lock device is disposed between the inclinable main arm and the base and has a locating pin member, which is capable of being pushed to engage with the locating groove, such that the operational function for the ascending and the descending movements of the panel fixing frame on the main arm is locked after the inclinable main arm is rotated to a preset inclining angle with respect to the base. 
         [0010]    In the preferred embodiment of the present invention, the lock device further comprises a pin holding seat assembly, a compression spring, the preceding locating pin member, a movable block member and a linkage. Wherein, the pin holding seat assembly is fastened to the main arm and has a locating pin seat and an axial hole; the locating pin member has a locating pin head, an upper slant and a lower locating jut with the locating pin head penetrating the compression spring and the axial hole to join with the locating pin seat; and the sliding block presses against the upper slant at the time of the movable block member moving upward and downward such that the locating pin member is capable of moving forward and backward due to the movable block member moving upward and downward incorporating with an elastic force of the compression spring. The linkage device is disposed between the base and the movable block member to urge the movable block member to ascend and descend when the main arm rotates to a preset inclining angle with respect to the base. 
         [0011]    In the preferred embodiment of the present invention, the pin holding seat assembly of the lock device has an upper hook; the movable block member has a lower hook; and the linkage device further comprises an extension spring and a flexible line, wherein two ends of the extension spring engage with the upper hook and the lower hook respectively to offer an elastic force for ascending the movable block member; and two end of the flexible line are joined to the base and the movable block member to offer a pull force for descending the movable block member. 
         [0012]    In the preferred embodiment of the present invention, the movable block member of the lock device has an adjustable screw and an end of the flexible line is attached to the adjustable screw for the preset inclining angle, which is obtained at the time of the main arm rotationally inclining forward for locking the ascending and descending movements, being capable of being micro-adjusted. Further, the operation of the ascending and descending movements is locked when the preset inclining angle of the main arm is not less than 5°. 
         [0013]    In the preferred embodiment of the present invention, the base provides a rotational foot pad in the middle of the bottom thereof for the liquid crystal panel being swung rightward and leftward. 
         [0014]    When the liquid crystal display in a state of normal use, the liquid crystal panel is braked with the inclinable connection mechanism and is operated between an inclining forward 5° and an inclining rearward 25°. Meanwhile, the flexible line of the lock device is in a state of tightness such that the movable block member is pulled downward by the flexible line to urge the locating pin member moving outward the locating groove of the panel fixing frame due to the upper slant of the locating pin member being pressed by the movable block member. Hence, the function of ascending and descending the liquid crystal panel is maintained normally. 
         [0015]    Besides, before the liquid crystal display being packed, the liquid crystal panel is descended to a position first where the locating groove of the panel fixing frame corresponds to the locating pin member of the lock device and then the liquid crystal panel is rotated to incline forward an angle not less than 5° (generally the angle is 90°). Right at this time, the flexible line of the lock device is in a state of looseness such that the movable block member is moved upward with the elastic force of the extension spring and the locating pin member moves forward to engage with the locating groove. Under this circumference, the operations for ascending and descending the liquid crystal panel being locked and incapable of bouncing outward to hurt people during the liquid crystal display being unpacked. 
         [0016]    When the liquid crystal display of the invention is unpacked and taken out, the forward inclining angle of the liquid crystal panel can be adjusted to be less than 5° (or inclining backward) to restore the operational function automatically for ascending and descending the liquid crystal panel smoothly with safety and convenience. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The detail structure, the applied principle, the function and the effectiveness of the present invention can be more fully understood with reference to the following description and accompanying drawings, in which: 
           [0018]      FIG. 1  is a perspective view of a liquid crystal display according to the present invention; 
           [0019]      FIG. 2  is a partial disassembled perspective view of the liquid crystal display shown in  FIG. 1 ; 
           [0020]      FIG. 3  is an exploded perspective view of the height adjustable base shown in  FIG. 2 ; 
           [0021]      FIG. 4  is another perspective view of the height adjustable rotational main shaft shown in  FIG. 3 ; 
           [0022]      FIG. 5  is an exploded perspective view of the height adjustable lock device shown in  FIG. 3 ; and 
           [0023]      FIG. 6  is another perspective view of the height adjustable base shown in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    Referring to  FIGS. 1 to 6 , the preferred embodiment of a liquid crystal display  10  according to the present invention includes a liquid crystal panel  20  and a height adjustable base assembly  30 . The height adjustable base assembly  30  is composed of a base  31 , an inclinable main arm  32 , a panel fixing frame  33 , a lock device  34  and a constant force spring  35 . The base  31  has a plastic cover to embellish the outer look of the liquid crystal panel  20 . The liquid crystal panel  20  is fastened to the panel fixing frame  33  of the height adjustable base  30  with screws. 
         [0025]    Besides, in order to offer the user more flexible applications, the panel fixing frame  33  consists of an ascending-descending seat  331  (See  FIG. 4 ), which is capable of ascending and descending along the inclinable main arm  32 , and a panel rotational seat  332  (See  FIG. 3 ), which is braked with a braking device and rotationally joined to the ascending-descending seat  331 . The liquid crystal panel  20  is fastened to the panel rotational seat  332  with screws for the user being able to turn and adjust the angular position of the liquid crystal panel  20  according to the need of picture displaying. 
         [0026]    Referring to  FIG. 3 , the lower end of the inclinable main arm  32  is rotationally attached to the base  31  with a torsion spring  311  incorporated with the braking device, which is composed of such as a spring washer and an angular positioning plate  312 , at two opposite corners of the lower end of the height adjustable main arm  32 . In this way, the inclinable main arm  32  is capable of being operated to have an inclining angle with respect to the base  31  between a forward inclining angle 90° and a rearward inclining angle 25°. A slide rail  321  is provided at two long lateral sides of the inclinable main arm  32  respectively. It is noted that a reinforcing plate  323 , which is disposed at the inclinable main arm  32  next to the slide rails  321  (See  FIGS. 2 and 6 ) has been removed in  FIG. 3 . Each of the slide rails  321  can be a shape of channel as shown in  FIG. 3  or any other shapes, which are able to provide a function of guidance. A sliding block  333  shown in  FIG. 4  is disposed at two lateral sides of the ascending-descending seat  331  of the panel fixing frame  33  corresponding to the slide rails  321  such that the liquid crystal panel  20  is capable of moving upward and downward along the slide rails  321 . Further, one of the sliding blocks  333  is provided with a locating groove  3331 . 
         [0027]    It can be seen in  FIGS. 3 and 4  that the position of the liquid crystal panel  20  is poised by means of an upward elastic force offered by the constant force spring  35  balancing with the gravity of the liquid crystal panel  20  after the sliding blocks  333  of the panel fixing frame  33  moving along the sliding rails  321  of the inclinable main arm  32 . The constant force spring  35  has a movable end  352  disposed in a constant force spring seat  322  of the inclinable main arm  32  and a stationary end  352  is fastened to the upper end of the ascending-descending seat  331  on the panel fixing frame  33 . In this way, when the panel fixing frame  33  descends, the constant force spring  35  is capable of offering the sufficient upward elastic force for the panel fixing frame  33  to balance with the gravity of the liquid crystal panel  20 . 
         [0028]    In addition, in order to allow the inclining main arm  32  having a preset inclining forward angle such as an angle is not less than 5°, a locating pin member  343  on the lock device  34  is urged to engage with the locating groove  3331  of the panel fixing frame  33  to lock the operation of the inclining main arm  32 . The lock device  34  with the locating pin member  343  is disposed between the inclining main arm  32  and the base  31 . 
         [0029]    Referring to  FIG. 5  again, the lock device  34  of the height adjustable base assembly  30  includes a pin holding seat assembly  341 , a compression spring  342 , the locating pin member  343 , a movable block member  344  and a linkage device  345 . The linkage device  345  is capable of transferring a rotational movement to a reciprocating movement. The linkage device  345  shown in  FIG. 5  consists of an extension spring  3451  and a flexible line  3452 . The material of the flexible line  3452  is a cord or wire with flexibility such as a plastic cord, a nylon cord, a steel wire or a metal chain. It is noted that the strength of the flexible line at least has to overcome the elastic force of the extension spring  3451  but no excessive extension or, even more, no breakage is allowed. The flexible line  3452  employed in the preferred embodiment is the KEVLAR® fiber cord made by DU PONT company. 
         [0030]    It can be seen in  FIG. 5  that the pin holding seat assembly  341  is fastened to a lateral side of the inclinable main arm  32  with screws passing through a hole  3411 . The pin holding seat assembly  341  further includes a locating pin seat  3412 , an axial hole  3413  and an upper hook  3414 . The locating pin member  343  has a locating pin  3431 , an upper slant  3432  and a locating jut  3433 . The locating pin  3431  pierces the compression spring  342  and the axial hole  3413  and is secured to the locating pin seat  3412 . 
         [0031]    The movable block member  344  has a sliding groove  3441  and a lower hook  3443 . The sliding groove  3441  receives the locating jut  3433  of the locating pin member  343 . When the movable block member  344  ascends or descends, the locating pin member  343  is operated to move forward or backward by means of the upper surface of the sliding groove  3441  pressing against the upper slant  3432  of the locating pin member  343  incorporating with the elastic force of the compression spring  342 . Both ends of the extension spring  3451  engage with the upper hook  3414  and the lower hook  3443  respectively. An end of the flexible line  3452  is tied to the angular positioning plate  312  on the base  31  (See  FIG. 3 ) and another end of the flexible line  3452  is joined to the movable block member  344  via an adjustable screw  3444  and a reinforcing plate  3445 . In this way, the operation of locking the inclinable main arm  32  with a micro-adjustment of a preset inclining angle can be achieved with turning the adjustable screw  3444 . Of course, persons who is skillful in the art understand that the end of the flexible line  3452  tying to the angular positioning plate  312  can be tied to any one place on the base  31  as long as the place corresponds to the other end of the flexible line  3452  for the liquid crystal panel  20  being capable of inclining pivotally to meet the need of tightness or looseness. 
         [0032]    The principle of operation for the lock device  34  of the liquid crystal panel  20  is in that the liquid crystal panel  20  is braked with the torsion spring  311  incorporating with the braking device such as the spring washer and the angular positioning plate  312  and is rotationally operated between a range of inclining forward 5° and inclining rearward 25° in a normal state. Meanwhile, the flexible line  3452  of the lock device  34  is in a state of tightness such that the movable block member  344  is pulled downward by the flexible line  3452  to urge the locating pin member  343  moving outward the locating groove  3331  of the panel fixing frame  33  due to the upper slant  3432  of the locating pin member  343  being pressed by the movable block member  344 . Hence, the function of ascending and descending the liquid crystal panel  20  can be operated normally. 
         [0033]    Furthermore, before the liquid crystal display  10  being packed, the liquid crystal panel  20  is descended to a position where the locating groove  3331  of the panel fixing frame  33  corresponds to the locating pin member  343  of the lock device  34  first and then the liquid crystal panel  20  is rotated to incline forward an angle not less than 5° (generally the angle is 90°). Right at this time, the flexible line  3452  of the lock device  34  is in a state of looseness such that the movable block member  344  moves upward due to the elastic force of the extension spring  3451  and the locating pin member  343  moving forward to engage with the locating groove  3331 . Under this circumference, the operation for ascending and descending the liquid crystal panel  20  is locked and incapable of bouncing outward to hurt people during unpacking the liquid crystal display. 
         [0034]    Referring to  FIG. 6  again, the base  31  of the height adjustable base assembly  30  is provided with a pivotal foot pad  36  at the middle of the bottom of the base  31  for the liquid crystal panel  20  being able to be angularly swung rightward or leftward for enhancing the use of the liquid crystal display. 
         [0035]    While the invention has been described with referencing to a preferred embodiment thereof, it is to be understood that modifications or variations may be easily made without departing from the spirit of this invention, which is defined by the appended claims.
A liquid crystal display with a height adjustable base assembly includes a base, an inclinable main arm, which is provided with a pivotal connection with the base and has slide rails, a panel fixing frame, which is capable of ascending and descending along the slide rails and has a locating groove, and a lock device, which is disposed between the main arm and the base and provides a locating pin member. When the main arm rotates a preset inclining angle relative to the base, the locating pin member is pushed to engage with the locating groove such that the operation of ascending and descending the panel fixing frame with respect to the main arm is locked. Hence, the liquid crystal panel bouncing outward suddenly during unpacked is avoided to secure the safety with convenient operations.