Abstract:
An angularly adjustable keyboard support bracket includes a mounting rack attached to a desktop, a movable arm coupled with the mounting rack through a pin, and a bracing rack coupled with another end of the movable arm through another pin for holding a tray. A rotary mechanism is located between the bracing rack and the tray to enable the tray to swivel to the left side and the right side for a selected angle relative to the bracing rack to provide users with a desired operating angle.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a keyboard support bracket structure and particularly to a keyboard support bracket for holding a keyboard and that is movable horizontally and vertically to suit user&#39;s operating position. 
   BACKGROUND OF THE INVENTION 
   Computer has been widely used by individuals and companies nowadays. When the computer is in use, in order to avoid the keyboard from occupying too much desktop space and take into account of ergonomics to prevent users from hand injury caused by taking the same posture for a long period of time during operation, a keyboard support bracket has been developed to suit user&#39;s posture and hand position, and to make adjustment endlessly. 
   There are plenty of keyboard support brackets proposed in the prior art. For instance, U.S. Pat. No. 4,616,798 discloses an adjustable support for CRT keyboard. It has a bracket holding a keyboard and connecting to a parallelogram linkage located underside a desk. Because the parallelogram linkage is fastened to the lower side of the keyboard support bracket, the space between the bottom and the floor is limited. Leg room is not adequate to accommodate leg movements of users. 
   U.S. Pat. No. 5,257,767 discloses an adjustable support mechanism for a keyboard platform. While it addresses the shortcomings of the aforesaid patent and uses a non-parallelogram linkage to increase the leg room, its linkage mechanism is still fastened to the lower side of the keyboard support bracket, and the increased space is limited. 
   U.S. Pat. No. 5,924,664 discloses a keyboard support mechanism which tries to improve the two patents mentioned above. It consists of a mounting bracket, a mounting bracket support in combination with a swivel bracket, a shelf bracket, an upper arm at least one side arm and at least one stopping means. It generates a linkage motion through four pivot points, and the side arm and the stopping means have corresponding connection concave surfaces to generate friction forces to produce locking and positioning effect. However it still has problems remained to be overcome, notably: 
   It still adopts a conventional parallelogram or non-parallelogram linkage with four pivot points linkages to pivotally connect to one another to achieve endless vertical movement. The side arm is extended to form an arched end to produce a friction force on a first side of the stopping means to achieve positioning. As the side arm and the stopping means are made of metal, in terms of applying forces easily and providing frictional forces required for latching, they cannot generate a desirable coordination during the movement. The metal also generates heat and noise under friction. The arched end tends to wear off after used for a long period of time. 
   In addition, according to ergonomics, when the keyboard is under operation, the forearm of users must be in parallel with the back of hands. To make the support bracket to support hands nicely, the support bracket also is preferably in parallel with the forearm. However, all the support brackets in the prior art has the side arm forming a constant angle relative to the floor (generally tilting upwards about 3 degrees, referring to U.S. Pat. No. 5,924,664, item 54). Based on user&#39;s perspective, the forearm inclines downwards gradually from the position adjacent to the desktop to the operation position. If the support bracket does not alter the angle, the support effect of the support bracket to the wrist and forearm diminishes gradually. As a result, it could cause injury to users when operating in such a posture for a long period of time. 
   SUMMARY OF THE INVENTION 
   Therefore the primary object of the invention is to resolve the aforesaid disadvantages and overcome the drawbacks of the prior art. The invention does not adopt conventional fixed pivotal connection for four points axles. Instead, one of the axles is connected movably. The fixed point connection relationship for friction is eliminated. Then other three fixed points axles may be moved endlessly. Thereby wearing of the related elements may be reduced and service life of the product may increase. Noise caused by movements can also be prevented. As there is no restriction of the friction force, the linkage mechanism of the invention enables user&#39;s hand to apply force easily. The keyboard support bracket also is more suitable for people to use. In addition, when the angle of the side arm of the invention increases when it is changed from closing to the highest position of the desktop to the lowest position, the included angle of the holding bracket relative to the desktop must decrease, namely, the support bracket inclines to a selected angle to suit user&#39;s forearm when the side arm is moved downwards. Therefore, user&#39;s forearm may have an effective support whatever operating positions user&#39;s forearm is taking. Thus it can better conform to ergonomics and reduce the risk of injury. 
   In order to achieve the foregoing object, the invention includes a mounting bracket fastening to a desktop, an upper arm pivotally engaged with the mounting bracket through a first axle, a side arm pivotally coupled on two sides of mounting bracket through a second axle, and a holding bracket pivotally engaged with the upper arm through a third axle and pivotally engaged with the side arm through a fourth axle. The fourth axle is movably connected to release the constrained position of the holding bracket, then the first, second and third axles may be moved to perform vertical adjustment endlessly. The keyboard support structure thus made uses a fewer number of elements and may be moved with less effort. 
   The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded view of the present invention. 
       FIG. 2  is a perspective view of the present invention. 
       FIGS. 3A through 3L  are schematic views of the present invention in various adjustment conditions. 
       FIGS. 4A through 4F  are schematic views of the present invention showing the angular relationship between the side arm and the holding bracket. 
       FIG. 5  is a schematic view of the present invention in various swivel adjustment conditions. 
       FIG. 6  is a schematic view of an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Please referring to  FIGS. 1 ,  2 ,  3 A and  5 , the present invention is located under a desktop  101  and may be moved horizontally and vertically relative to the desktop  101  to a desired location for holding a keyboard (not shown in the drawings) at an operating position. The invention includes a mounting bracket  10  fastening to the desktop  101 , an upper arm  20  pivotally engaged with the mounting bracket  10  through a first axle a which runs through pivot holes  11  and  221 , a side arm  30  pivotally coupled on two sides of the mounting bracket  10  through a second axle b which runs through pivot holes  12  and  32 , and a holding bracket  40  pivotally engaged with the upper arm  20  through a third axle c and pivotally engaged with the side arm  30  through a fourth axle d that run through pivot holes  211  and  43 . The first axle a is coupled with an elastic restoring element  80  which provides a biased pressure upwards. 
   The pivot holes  221  and  211  of the upper arm  20  are formed respectively on a front flap  21  and a rear flap  22  that are extended from the front end and the rear end of the upper arm  20  to couple with the first axle a and the third axle c. The front and rear flaps  21  and  22  aim at providing a selected interval between the upper arm  20  and the mounting bracket  10  and the holding bracket  40  to facilitate vertical adjustment and thread the cables of the keyboard. 
   The desktop  101  has a lower side fastening to a track plate  90 . The mounting bracket  10  has a sliding track dock  70  fastened thereon. The sliding track dock  70  has two side flanges  71  each fastens to a sliding rail  72  which may move horizontally on the track plate  90 . The mounting bracket  10  further has a swivel zone  13  which holds a rotary disk  60  between the rotary zone  13  and the sliding track dock  70 . 
   The first, second and third axles a, b and c are pivotally engaged at fixed locations to form a linkage movement. The side arm  30  has an adjusting hole  31  formed on the pivotal connection location for the fourth axle d. The adjusting hole  31  has a transverse width greater than the outer diameter of the fourth axle d. The fourth axle d further is coupled with a sleeve d 1  in the side arm  30  that has an outer diameter greater than the fourth axle d and the height of the adjusting hole  31 . Inside the side arm  30 , there is a brake element  34  which has a brake side  341  facing the holding bracket  40 . The holding bracket  40  has an arched displacement slot  42  corresponding to the adjusting hole  31 . The outer side of the displacement slot  42  forms a harness side  421  corresponding to and capable of in contact with the brake side  341  of the brake element  34 . 
   In addition, the middle portion of the upper arm  20  has a transverse slot  23  relative to the vertical displacement. The transverse slot  23  is coupled with a fifth axle e which runs through pivot holes  33  formed on the side arm  30  and the upper arm  20 . The bottom of the two side arms  30  has a lower arm  50 . The fifth axle e aims at aiding the movement of the upper arm  20  and the side arm  30  to prevent them from skewing or tilting during movement. It also can increase friction force and overall strength of the product. 
   Referring to  FIGS. 3A and 3B , before proceeding vertical displacement adjustment, the sliding rail  72  on the two side flanges  71  of the sliding track  70  is coupled on the track plate  90  to move horizontally relative to the desktop  101  (i.e. the entire keyboard may be moved outwards or inwards through the support bracket to user&#39;s operating position). When the horizontal movement and adjustment is finished, as shown in  FIG. 5 , a leftward or rightward swivel adjustment relative to the sliding track  70  may be made through the rotary disk  60  on the swivel zone  13  of the mounting bracket  10 . Of course, the horizontal adjustment and swivel adjustment may also be done after the vertical adjustment is finished. 
   The vertical adjustment procedures of the invention can be divided as follows:
         1. As shown in  FIGS. 3A and 3B , the side arm  30  is closed to the highest position of the desktop  101 . It is to be noted that the harness side  421  of the holding bracket  40  has its lower section forming a bucking relationship with the brake side  341 . Referring to  FIGS. 3C and 3D , when a force is applied to move the holding bracket  40  upwards, the fourth axle d is pivotally engaged in a movable manner. Thus when the holding bracket  40  is moved upwards, the fourth axle d is moved upwards in the displacement slot  42 , and is moved along an arched adjustment track of the displacement slot  42  and meanwhile the fourth axle d is pushed towards the direction of the holding bracket  40  in the adjusting hole  31  (with the adjusting hole  31  substantially normal to the displacement slot  42 ). With the fourth axle d moved closed to the adjusting hole  31  of the holding bracket  40 , the harness side  421  of the holding bracket  40  is separated from the brake side  341  to release the bucking condition. The corresponding friction force is absent in such a condition.   2. Because the friction force is absent, user can easily move the holding bracket  40 , through the third axle c to move the upper arm  20 , then use the first axle a and the second axle b as fulcrums to move vertically in an endless manner to the middle position as shown in  FIGS. 3E and 3F ; or move to the bottom as shown in  FIGS. 3I and 3J . It is to be noted that the harness side  421  and the adjustment track of the displacement slot  42  have the curvature of the same shape. And the brake side  341  also has a selected concave surface. Thus in the vertical movement, the gap between the harness side  421  and the brake side  341  becomes smaller gradually. Therefore, adjustment range is limited to prevent the harness side  421  from exceeding the adjustment range and resulting in ineffective positioning.   3. After a desired vertical position has been adjusted to suit the user, the force on the holding bracket  40  may be released to move the holding bracket  40  downwards to the horizontal position. The adjustment track of the displacement slot  42  can synchronously push the fourth axle d in the adjusting hole  31  towards the direction of the brake element  34 . Meanwhile, the harness side  421  of the holding bracket  40  is in contact with the brake side  341 . The arched sides generate friction force to press each other and form an anchoring effect. This step is shown in  FIGS. 3G and 3H . When the position of the side arm  30  moves away from the middle portion of the desktop  101 , the harness side  421  of the holding bracket  40  has its middle portion bucking against the brake side  341 . Referring to  FIGS. 3K and 3L , when the side arm  30  is moved away from the lowest position of the desktop  101 , the harness side  421  of the holding bracket  40  has its upper portion bucking against the brake side  341  to form a latching relationship.   4. Referring to  FIG. 6 , the holding bracket  40  includes a holding board  41  to fasten to a holding seat  102 . The holding seat  102 , in addition to holding a keyboard, may also hold other peripheral devices such as a mouse (not shown in the drawing). After having completed the horizontal, swivel and vertical adjustment, the holding seat  102  of the holding bracket  40  is substantially in parallel with the desktop  101  and becomes horizontal to hold the keyboard. Thus it can be adjusted to a desired position to suit user&#39;s sitting posture and hand position.       

   During the operations set forth above, the side arm  30  and the holding bracket  40  have angular alterations relative to the desktop  101 . Details of those angular alterations are depicted below. When the holding bracket  40  is lifted by forces and the harness side  421  is separated from the brake side  341  in a non-contact condition, as the adjustment track of the displacement slot  42  is curved, and if the gap between the harness side  421  and the brake side  341  is w 1  after separated when the side arm  30  is closest to the desktop  101  (referring to  3 D), and the gap is w 2  when the side arm  30  is moved downwards to a medium location from desktop  101  (referring to  FIG. 3F ), and the gap is w 3  when the side arm  30  is moved downwards to a lowest location from desktop  101  (referring to  FIG. 3J ), the relationship of the gaps is w 1 &gt;w 1 &gt;w 3 . Through the bucking arched sides of the brake side  341  and the harness side  421 , the holding bracket  40  may form various inclined angles relative to the desktop  101 . 
   In the following discussion, in order to facilitate explanation of the related positions, the lowering of the horizontal line of the desktop  101  is shown by an imaginative broken line, and the angles are the included angles relative to the desktop  101 , not the variations of included angle of the holding bracket  40  relative to the side arm  30 . First, refer to the variations of the gap between the holding bracket  40  and the side arm  30  discussed previously. Referring to  FIG. 4A , the holding bracket  40  may have a preset inclined angle è 1  (about 3 degrees), the included angle of the side arm  30  relative to the desktop  101  is è 7 . The angles è 1  and è 7  indicate that the side arm  30  is closed to the highest position of the desktop  101  as shown in  FIG. 3A . When the holding bracket  40  is lifted to a position as shown in  FIG. 3C , the angular variations are shown in  FIG. 4B , with the inclined angle of the holding bracket  40  relative to the desktop  101  increased to è 2  (about 10 degrees). In this condition, the position of the side arm  30  does not change, thus the angle relative to the desktop  101  is è 8 =è 7 . 
   When the holding bracket  40  is moved vertically downwards to a middle position as shown in  FIG. 3E , the included angle è 9  between the side arm  30  and the desktop  101  increases as shown in  FIG. 4C . As the force applied on the holding bracket  40  is not yet released, the angle è 3  relative to the desktop  101  remains unchanged, i.e. è 3 =è 2 . 
   When the force applied on the holding bracket  40  is released as shown in  FIG. 3G , and the holding bracket  40  is anchored at the middle position, the included angle of the side arm  30  relative to desktop  101  remains unchanged, i.e. è 10 =è 9 . But due the gap is eliminated, the included angle of the holding bracket  40  relative to the desktop  101  decreases slightly to become è 4  which is smaller than è 3  (about 7 degrees), But è 4  is still greater than è 1 . Namely, the included angle of the holding bracket  40  relative to the desktop  101  is greater than the inclined angle. 
   Referring to  FIG. 3L , when the holding bracket  40  is moved vertically to the lowest position without releasing the force, the included angle è 11  between the side arm  30  and the desktop  101  is maximum. Due to the force on the holding bracket  40  is not yet released, its angle relative to the desktop  101  e 5  remains unchanged, i.e. è 5 =è 3 =è 2 . 
   Referring to  FIG. 3K , when the force on the holding bracket  40  is released and the holding bracket  40  is moved to the lowest position, the relative included angle between side arm  30  and the desktop  101  remains unchanged, i.e. è 12 =è 11 . But due to the gap has been eliminated, the included angle of the holding bracket  40  relative to the desktop  101  decreases, i.e. è 5 &lt;è 6  (about 9 degrees). However, è 6  is still greater than è 4  and è 1 . Namely, the inclined angle of the holding bracket  40  relative to the desktop  101  has changed to the maximum. 
   Based on previous discussions, the angular relationship can be summed up as follows: the included angle relative to the desktop  101  is è 1  when the holding bracket  40  is located at the highest position, è 4  when the holding bracket  40  is located at the middle position, and è 6  when the holding bracket  40  is located at the lowest position, and è 6 &gt;è 4 &gt;è 1 . Thus the inclined angle of holding bracket  40  increases as the operation position of the holding bracket  40  lowers. Therefore it conforms to ergonomics and enables the forearms of users to form the same inclination (relative to the vertical angle of human body), thereby to get effective support and can prevent injury that might otherwise happen when operating at the same posture for a long period of time. 
   In summary, compared with U.S. Pat. No. 5,924,664, the invention offers features and advantages as follows:
         1. The invention permits vertical adjustment after the frictional anchoring between the harness side  421  and the brake side  341  has been released. During adjustment, there is no limitation of friction forces, thus adjustment may be made with less efforts, and no metal friction sound occurs, and noise may be prevented.   2. In the invention, the anchor fulcrum is located between the holding bracket  40  and the side arm  30 , and the frictional force borne by the brake element  34  is merely the weight of the holding bracket  40  and the keyboard. It requires a smaller frictional force. Thus the invention can achieve an effective anchoring at every position when doing the endless adjustment. By contrast, the stopping means in U.S. Pat. No. 5,924,664 has to bear the weight of the side arm  30 , upper arm  20 , lower arm  50 , holding bracket  40  and keyboard. The moment of force is greater, and required frictional force also is greater, and damage is prone to occur.   3. The angle of the holding bracket  40  relative to the desktop  101  is not constant. The inclined angle of the holding bracket  40  changes as the angle of the side arm  30  increases. Thus it better conforms to ergonomics.