Patent Publication Number: US-2009225032-A1

Title: Overload regulating structure for trackball device

Description:
FIELD OF THE INVENTION 
     The present invention relates to an overload regulating structure for trackball device, and more particularly to an overload regulating structure that protects a trackball device against damaged internal components caused by an overload applied to a trackball. 
     BACKGROUND OF THE INVENTION 
     A trackball device is mainly used with a computer to control the movement of a cursor on a screen and functions similar to the conventional mouse. However, there is another type of trackball device particularly designed for use with a video game machine to control the movement of a cursor thereof. By rotating a trackball, signals are transmitted to control the cursor to move on the screen. 
     A conventional trackball device includes abase, a ball, and a plurality of shafts. The base is provided with a locating recess, in which the ball is rotatably positioned. The shafts are mounted in the base and have a disk each mounted thereon. When the ball is rotated, it brings the shafts and the disks to rotate at the same time, so that movement signals are transmitted to a circuit board for the latter to control the cursor to move on the screen. 
     In the conventional trackball device, the ball is directly positioned in the locating recess in the base. When an operator applies an excessive force to rotate the ball, the ball tends to collide with or rub other internal components to cause undesirable damage and accordingly, errors in transmitting signals. 
     SUMMARY OF THE INVENTION 
     A primary object of the present invention is to provide an overload regulating structure for effectively protecting a ball in a trackball device from an overload, so that the trackball device is not damaged due to collision or rubbing of the ball with other internal components caused by the overload. 
     To achieve the above and other objects, the overload regulating structure for trackball device according to the present invention includes a base, a circuit board, a plurality of shafts, a plurality of bearing sets, a ball, and an overload regulator. The base has an open-topped locating recess formed on a bottom thereof. The plurality of bearing sets are embedded in sidewalls of the base, and the shafts are separately connected at two ends to one of the bearing sets. The overload regulator includes two seats being screwed to one sidewall of the base using fastening elements and having a slide slot each for receiving a spring therein. A bar-shaped supporting element has two ends received in the two slide slots on the overload regulator, such that the springs have one end pressed against the sidewall of the base and the other end pressed against the supporting element. A roller is mounted on and around the supporting element. With the springs in the overload regulator, the supporting element may be elastically moved rearward by the overloaded ball or elastically pushed forward by the springs. 
     In the present invention, the ball is normally three-point supported on and between the plurality of shafts and the roller. When the ball is subject to an overload and gradually sinks to the locating recess, the ball would push against the roller, bringing the supporting element to move rearward along the slide slots, so that the springs in the slide slots are compressed to store energy. And, when the ball has fully sunk into the locating recess, it is restricted from rotating freely. When the overload is released, the springs in the slide slots release the stored energy and elastically push the supporting element forward, so that the roller pushes the ball upward to the originally three-point supported position. 
     With the above arrangements, the ball in the trackball device is effectively protected against overload to avoid damages to the trackball device caused by colliding or rubbing of the overloaded ball with other internal components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein 
         FIG. 1  is a perspective view of an overload regulating structure for trackball device according to a preferred embodiment of the present invention; 
         FIG. 2  is a top view of the overload regulating structure for trackball device shown in  FIG. 1 ; 
         FIG. 3  is a sectional view taken along line  3 - 3  of  FIG. 2 ; and 
         FIG. 4  is a sectional view showing a ball in the trackball device is protected against overload through the overload regulating structure of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Please refer to  FIGS. 1 and 2 , which are exploded perspective and assembled top views, respectively, of an overload regulating structure for trackball device according to a preferred embodiment of the present invention. As shown, the overload regulating structure includes a base  10 , a circuit board  13 , a y-direction bearing set  20 , an x-direction bearing set  21 , a y-direction shaft  22 , an x-direction shaft  23 , a top cover  40 , a ball  50 , and an overload regulator  30 . 
     The base  10  includes an open-topped locating recess  11  formed on a bottom thereof and a plurality of screw holes  14  formed on sidewalls thereof. The x-direction bearing set  21  is embedded in one of the sidewalls of the base  10  corresponding to the x-axis, and the y-direction bearing set  20  is embedded in one of the sidewalls of the base  10  corresponding to the y-axis. The circuit board  13  is attached to an underside of the base  10  for processing control signals sent from the ball  50  when the latter is rotated, and the processed control signals are sent to a screen for moving a cursor thereon. 
     The y-direction shaft  22  is connected at two ends to the y-direction bearing set  20 , and the x-direction shaft  23  is connected at two ends to the x-direction bearing set  21 . Both the y-direction shaft  22  and the x-direction shaft  23  have a disk  24  mounted thereon. 
     Please refer to  FIG. 3 , which is a sectional view taken along line  3 - 3  of  FIG. 2 . The overload regulator  30  has two seats  36  being screwed to a first sidewall  12  of the base  10  with a plurality of fastening elements  33 . The two seats  36  are provided with a slide slot  34  each. A spring  31  is provided in each of the slide slots  34  with one end pressed against the first sidewall  12  of the base  10  and the other end pressed against a supporting element  32 . The supporting element  32  is in the form of a round bar having a roller  35  mounted thereon, and has two ends received in the slide slots  34  on the two seats  36 . With the springs  31  provided in the two slide slots  34 , the roller  35  mounted on the supporting element  32  may be pushed by the ball  50  to elastically move rearward or pushed by the springs  31  to elastically move forward along the slide slots  34 . To assemble the overload regulating structure for trackball device, first position the ball  50  in a space defined between the y-direction shaft  22 , the x-direction shaft  23 , and the roller  35 , so that the ball  50  is three-point supported in the base  10 . Then, attach the top cover  40  and the circuit board  13  to the upper and the lower side of the base  10 , respectively, using fastening elements  33 . 
       FIG. 4  is a sectional view showing the ball  50  in the trackball device is protected against overload through the overload regulating structure of the present invention. As shown, the ball  50  is normally three-point supported between the roller  35 , the y-direction shaft  22 , and the x-direction shaft  23 . 
     When the ball  50  is subject to an overload, the overloaded ball  50  will apply a force on the roller  35 , bringing the supporting element  32  to move rearward and compress the springs  31  into an energy-storing state. Meanwhile, the ball  50  finally sinks into the locating recess  11  under the load constantly applied thereto, and is restricted by the locating recess  11  from rotating freely. That is, the overload regulating structure for trackball device according to the present invention effectively provides the overload protection function by allowing the ball  50  to sink into the locating recess  11  under an overload without causing damages to the external spherical surface of the ball  50  and other components in the trackball device. 
     A user may manipulate the ball  50  to rotate in different directions via a ball opening  41  provided on the top cover  40 . When the ball  50  is rotated, the y-direction shaft  22  and the x-direction shaft  23  are brought by the ball  50  to rotate, and the disks  24  mounted on the two shafts  22 ,  23  in turn transfer movement signals from the rotating ball  50  to the circuit board  13  for processing, so as to control the moving directions of the cursor on the screen.