Abstract:
A liquid crystal display with a height adjustable base assembly includes a base, a 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 of the main arm and has a lock rod. A plumbing stop block is pivotally connected to the main arm to correspond to the lock rod. When the main arm rotates a preset inclining angular position with respect to the base, the plumbing stop block is urged to rotate by the gravity thereof for the lock rod being pushed to engage with the locating groove of the plumbing stop groove such that the operation of lifting 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.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     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. 
     2. Brief Description of the Related Art 
     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. 
     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. 
     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 upward and downward movements of the height adjustable base work normally only if the liquid crystal display is operated normally. The liquid crystal panel usually moves downward 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 
     Accordingly, an object of the present invention is to provide a liquid crystal display with a height adjustable base, which has a function for locking ascending and descending movements, such that when the liquid crystal panel inclines forward an angular displacement greater than a certain angle, the operation of the liquid crystal panel being lifted and moving down can be locked for facilitating the liquid crystal display being unpacked and preventing the liquid crystal panel from bouncing outward suddenly and to enhance the convenience of the operation. 
     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, a main arm, a panel fixing frame and a plumbing stop block. 
     Wherein, the 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 to slide upward or downward along the rail, and is positioned with the upward elastic force of the panel fixing frame balancing with the gravity of the liquid crystal panel; a lock rod is disposed on the panel fixing frame, and the plumbing stop block is pivotally connected to the main arm at a position corresponding to the lock rod and has a locating groove for engaging with the lock rod, which is urged to enter the locating groove with the plumbing stop block rotating due to the gravity itself, when the main arm rotates to incline a preset angle such that the operation for lifting the main arm is locked by the panel fixing frame. 
     In the preferred embodiment of the present invention, the plumbing stop block of the height adjustable base assembly further comprises an upper block pivotally connecting with the main arm with an upper groove seat at the upper block and a lower block at the lower block corresponding to the upper groove seat for forming the locating groove. 
     In the preferred embodiment of the present invention, the height adjustable base assembly further comprises a rail seat and a connecting rod device, wherein the rail seat is attached to said main arm corresponding to the plumbing stop block for a connecting rod rail being formed between the rail seat and the main arm, and the connecting rod device is disposed on the connecting rod rail for the rotational inclining movement of the main arm being converted to a reciprocal movement along the connecting rod rail to press against or depart from the plumbing stop block for preventing the function for locking the movement from ineffectiveness at the time of the plumbing stop block rotating along with the angular position of the liquid display being rotated. 
     In the preferred embodiment of the present invention, the connecting rod device of the height adjustable base assembly further comprises a stop lever, a compression spring and a flexible line, wherein the stop lever has a lever head and a lever body connecting with the lever head, the lever body is disposed in the connecting rod rail to move upward or downward along the connecting rod rail for the lever head pressing against or departing from the plumbing stop block; the compression spring is disposed to surround the lever body between the lever head and the rail seat to offer the push force of the reciprocal movement; and the flexible line with two ends thereof is attached to the base and the lever body, respectively for offering the pull force of the reciprocal movement. 
     In the preferred embodiment of the present invention, the lever head of the height adjustable base assembly has a slant to press against the plumbing stop block for resisting the plumbing stop block from moving rotationally. 
     In the preferred embodiment of the present invention, the connecting rod device of the height adjustable base assembly further comprises a flexible line guide rail for the flexible line moving reciprocally along the flexible line guide rail and offering the flexible line being attached to the base at a position flexible. 
     In the preferred embodiment of the present invention, the preset angular displacement of the main arm with respect to the base is less than 30° for the operation of locking the upward and downward movements works well. 
     In the preferred embodiment of the present invention, the plumbing stop block of the height adjustable base is pierced with a stop pin and secured with a C-shaped retaining ring for being pivotally connected to the main arm, and the upward elastic force for pushing the panel fixing frame is offered with the constant force spring on the main arm. 
     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, due to the angular displacement of the plumbing stop block, there is a distance between the plumbing stop block and the lock rod such that the lock rod is incapable of entering the locating groove of the plumbing stop block and the normal operation of the upward and downward movements works well. 
     Besides, when the liquid crystal display being packed, the liquid crystal panel is rotated to incline forward an angle not less than 30° (generally the angle is 90°). Right at this time, the plumbing stop block has rotated already and plumbed to a position below the lock rod when the liquid crystal panel is moved toward the base such that the lock rod can engage with the locating groove of the plumbing stop block to lock the operation of the upward and downward movements for avoiding the liquid crystal panel bouncing outward to hurt people at the time of unpacking the liquid crystal display. 
     After the liquid crystal display of the invention is unpacked and taken out and the forward inclining angle of the liquid crystal panel is adjusted to less than 30° (or inclining backward), the liquid crystal panel can be pressed downward lightly and the plumbing stop block rotates to the original position to depart from the lock rod a distance due to the gravity thereof such that the function for ascending and descending the liquid crystal panel can be resumed automatically with safety and convenience. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a perspective view of a liquid crystal display according to the present invention; 
         FIG. 2  is a partial disassembled perspective view of the liquid crystal display shown in  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of the height adjustable base shown in  FIG. 2 ; 
         FIG. 4  is another perspective view of the height adjustable rotational main shaft shown in  FIG. 3 ; 
         FIG. 5  is an exploded perspective view of the stop block shown in  FIG. 3 ; 
         FIG. 6  is another perspective view of the linkage device shown in  FIG. 3 ; 
         FIG. 7  is a perspective view of the plumbing stop block in the another embodiment of the present invention; and 
         FIG. 8A to 8I  are plan views illustrating the operation of locking the height adjustable base assembly of a liquid crystal display according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 to 6 , a liquid crystal display  10  in a preferred embodiment 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 , a main arm  32 , a panel fixing frame  33 , a constant force spring  34 , a plumbing stop block  36 , a rail seat  323  and a connecting rod device  35 . Although it is shown in the figures that the rail seat  323  is fastened to the main arm  32 , alternatively, the rail seat  323  can be made integrally with the main arm  32 . Besides, the base  31  can be provided with a plastic cover for enhancing the good outer look thereof and a reinforcing plate for reinforcing the strength thereof (not shown). The liquid crystal panel  20  is fastened to the panel fixing frame  33  of the height adjustable base  30  with screws. 
     In order to offer the user more flexible applications, the panel fixing frame  33  consists of a lifted seat  331 , which is capable of moving upward and downward along the main arm  32 , and a panel rotational seat  332 , which is braked with a braking device and pivotally joined to the lifted seat  331 . The liquid crystal panel  20  can be 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  depending on the picture shown on the liquid crystal panel  20 . 
     Referring to  FIG. 3 , the main arm  32  at two opposite corners of the lower end thereof is disposed with a torsion spring  311  respectively incorporated with the braking device, which is composed of such as a spring washer and an angular positioning plate  312 . In this way, the 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°. Two long lateral sides of the main arm  32  are provided with a slide rail  321  respectively. The slide rail  321  is composed of a stationary member and a movable member, and the stationary member has steel balls for the movable member capable of moving along the steel balls. The lifted seat  331  provides two lateral walls  3312  to be fastened to the movable member of the respective slide rail  321  for the liquid crystal panel  20  being lifted along the slide rails  321 . Besides, the lifted seat  331  has a lock rod  3311  (see  FIG. 4 ) to lock the operation of lifting. 
     It can be seen in  FIGS. 3 and 4  that the liquid crystal panel  20  can be positioned with an upward elastic force offered by the constant force spring  34  balancing with the gravity of the liquid crystal panel  20  after being lifted to a certain height. The movable end  341  of the constant force spring  34  is received in a constant force spring seat  322  of the main arm  32  and the stationary end  342  of the constant force spring  34  is fastened to the upper end of the lifted seat  331  on the panel fixing frame  33  such that a sufficient upward elastic force can be offered to balance with the gravity of the liquid crystal panel  20  when the panel fixing frame  33  moves downward. 
     In addition, in order to lock the lifting operation of the panel fixing frame  33  with respect to the main arm  32  after the main arm  21  rotating a preset inclining forward angle such as an angle is not less than 5° relative to the base  31 , the plumbing stop block  36 , which is disposed at the lift-locking rod  3311 , rotates in accordance with the gravity at the time of the main arm  32  inclining rotationally to urge the lock rod  3311  to enter the locating groove  365  provided in the plumbing stop block  36  (see  FIGS. 8B and 8D ). In this way, the operation of moving the panel fixing frame  33  with respect to the main arm  32  is locked. The detail principle for locking the lifting operation of the panel fixing frame  33  with respect to the main arm  32  will be recited hereinafter. 
     Referring to  FIG. 5 , the plumbing stop block  36  includes an upper block  361 , a lower block  362  and a block pin  363 . The upper block  361  has an upper through hole  3612  and the lower block  362  has two lower through holes  3622 ,  3623  corresponding to the upper through hole  3612 . The main arm  32  has two locating holes  324 ,  425 . The block pin  363  passes through the first locating hole  324 , the first lower through hole  3622 , the upper through hole  3612 , the second lower through hole  3622 , and the second locating hole  325 . Then, a C-shaped retaining ring  364  engages with the tail end of the block pin  363 . In this way, the plumbing stop block  36  can be pivotally attached to the main arm  32 . Hence, when the main arm  32  rotationally inclines with respect to the base  31 , the plumbing stop block  36  is capable of rotating corresponding to the gravity thereof to urge the lock rod  3311  to engage with the locating groove part  365  of the plumbing stop block  36 . 
     Wherein, the upper block  361  has an upper grooved seat  3611  and the lower block  362  has a lower grooved seat  3621  corresponding to the upper grooved seat  3611  such that the locating groove part  365  is formed when the upper grooved seat  3611  fits with the lower grooved seat  3621 . The actuation of the pluming stop block  36  for the lock rod  3311  for engaging with the locating groove part  365  and performing the operation of locking is described in detail hereinafter with  FIGS. 8A to 81 . 
     Referring to  FIGS. 8A to 8D , when the main arm  32  rotationally inclines to 90° with respect to the base  31 , the upper block  361  and the lower block  362  rotate with respect to the block pin  363  due to the gravity thereof to droop the locating groove part  365  below the position of the lift-locking rod  3311  as shown in  FIGS. 8A and 8B . Right at the time, the user can push the liquid crystal panel  20  toward the base  31  to move the lock rod  3311  to enter the locating grooved part  365  as shown in  FIGS. 8C and 8D  such that the operation of upward and downward movements of the liquid crystal panel  20  with respect to the main arm  32  is locked. 
     Referring to  FIGS. 8E to 8I , when the main arm  32  is rotated to the original normal inclining position with respect to the base  31 , the lock rod  3311  presses against the upper block  361  of the plumbing stop block  36  such that the upper block  361  is incapable of restoring to the original plumbing position in time in accordance with the change of gravity. Furthermore, the lower block  362  of the plumbing stop block  36  is resisted with a lateral projection  3613  of the upper block  361  (see  FIG. 5 ) and incapable of restoring to the original plumbing position with the change of the gravity such that the operation for locking lift of the liquid crystal display  10  is still in a state of not being unlocked yet. 
     In order to unlock the operation of lifting the liquid crystal display  10  for the liquid crystal panel  20  being able to restore the function of upward and downward movements, simply presses the liquid crystal panel  20  downward lightly to allow the lock rod  3311  to move away the upper block  361  with pressing against the plumbing stop block  36 . In this way, the upper block  361  and the lower block  362  can rotate due to the gravity as shown in  FIGS. 8G to 8I  such that the lock rod  3311  disengages from the locating groove part  365  to restore the function of upward and downward movements of the liquid crystal panel  20  with respect to the main arm  32 . 
     As the foregoing, the operation for lifting the liquid crystal display  10  being locked or unlocked is achieved by means of the change of the position of the lock rod  3311  relative to the plumbing stop block  36  under a condition of normal use. Nevertheless, the plumbing stop block  36 , which is pivotally attached to the main arm  32 , works normally depending on the direction of the gravity thereof changing correctly. If the liquid crystal display  10  is in a state of abnormal use, it is very likely that a problem of angular position of the liquid crystal display  10  results in the function of the upward and downward movements being unlocked unexpectedly. 
     For instance, in case of the state of locking as shown in  FIGS. 8C and 8D , the liquid crystal display  10  is rotated 180° to allow the directions of both the liquid crystal panel  20  and the base  31  are inverted to each other such that the plumbing stop block  36 , which is pivotally connected to the main arm  32 , probably rotates and leads to the lock rod  3311  departing from the locating groove  365  due to the direction of the gravity of the plumbing stop block  36  changing. Under this circumstance, the operation of locking the lift for the liquid crystal display  10  is unlocked unexpectedly. 
     In order to prevent the operation of locking the upward and downward movements of the liquid crystal display  10  from being unlocked unexpectedly, the height adjustable base assembly  30  further provides the rail seat  323 , which has been mentioned previously and illustrated in  FIG. 3 , at the main arm  32  and a connecting rod device  35 , which includes a stop lever  351 , a compression spring  352 , a flexible line  353  and a guide rail  354  as shown in  FIGS. 3 and 6 . Of course, as persons familiar to the art know, the rail seat  323  and the connecting rod device  35  can be arranged to change the rotational movement of the main arm  32  with respect to the base  31  to a reciprocal movement with any linkages instead. 
     It can be seen in  FIGS. 3 and 6  that the rail seat  323  is attached to the main arm  32  such that a connecting rod rail  3231  between the rail seat  323  and the main arm  32  is formed corresponding to the plumbing stop block  36 . The lever body  3512  of the stop lever  351  is disposed in the connecting rod rail  3231  and move upward or downward along the connecting rod rail  3231 . Further, the plumbing stop block  36  is prohibited from rotating when a lever head  3511  of the lever body  3512  pressing against the plumbing stop block  36 , and is allowed to rotate when the lever head  3511  departs from the plumbing stop block  36 . In order to enhance the effect of pressing against the plumbing stop block  36 , the lever head  3511  is provided with a slant  3513 . 
     An end of the flexible line  353  is tied to the lower end of the lever body  3512  of the stop lever  351  and another end of the flexible line  353  is tied to an orientation locating plate  312  shown in  FIG. 3  after passing through the guide rail  354  such that the flexible line  353  in association with the compression spring  352 , which is disposed to surround the lever body  3512  between the lever head  3511  and the rail seat  323 , to offer a push force and a pull force of the reciprocal movement of the stop lever  351  respectively. 
     Wherein, the flexible line  353  can be such as a steel wire, metal chain, plastic cord or a nylon cord with a strength at least overcoming the elastic force of the compression spring  352  and without being excessively extended or broken. The flexible line  353  employed in the preferred embodiment is a KEVLAR® fiber cord made by DuPont Co. The guide rail  354  is used for an end of the flexible line  353  being guided to tie with the orientation locating plate  312  of the base  31 . The guide rail  354  can be omitted if the flexible line  353  is designed to tie to the base  31  directly. 
     When the liquid crystal display  10  is operated normally, the inclining angle of the main arm  32  with respect to the base  31  usually is less than 30°. Because the flexible line  353  is in a state of being tightly pulled, the lever body  3512  of the stop lever  351  is pulled downward to depart the lever head  3511  departs from the plumbing stop block  36  for maintaining the normal operation of locking the lift of the liquid crystal display  10 . 
     In addition, when the main arm  32  is rotated and taken up for rotating an inclining angle greater than 30°, the flexible line  353  is in a state of being released and an end thereof presses against the compression spring  352  on the rail seat  323 . Under this circumstance, another end of the flexible line  353  pushes the lever head  3511  to result in the slant  3513  at the lever head  3511  presses against the plumbing stop block  36  for preventing the function of locking the liquid crystal display  10  from being unlocked unexpectedly. 
     Referring to  FIG. 7 , although the height adjustable base assembly  30  has a block pin  363 , a C-shaped retaining ring  364  and a plumbing stop block  36  containing the upper block  361  and the lower block  362  accompanying the lock rod  3311  on the lifted seat  331  of the panel fixing frame  33  to perform the function for locking the lift of the liquid crystal display  10 , persons familiar to the art should know that the plumbing stop block  66  with a locating groove  665 , a stop block pin  663  and a C-shaped retaining ring  664  shown in  FIG. 7  being used instead of the plumbing stop block  36  for matching with the lock rod  3311  on the lifted seat  331  of the panel fixing frame  33  can perform the function for locking the lift of the liquid crystal display  10  as well. Alternatively, other types of plumbing stop block, which has the upper and lower block as the plumbing stop block  36  does with a little difference from the plumbing stop block  36  in configuration, structure and relative position, work as well if the locating groove is provided corresponding to the lock rod  3311 . 
     While the invention has been described with referencing to the preferred embodiments 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.