Trackball device

The trackball device comprises cylindrical first and second supports. First and second code wheels are respectively coupled to the supports and are rotatable therewith. First and second reader means are respectively associated with the first and second code wheels for generating control signals. A ball is seated on the supports. The second support, both of the reader means, the second code wheel and the ball all lie on the same side of the first support.

BACKGROUND OF THE INVENTION 
The present invention relates to a cursor position control device of the 
type commonly referred to as a trackball device. Such devices are used, 
for example, to control the movement of a cursor of a video display as in 
a video game. 
Trackball devices include a housing having a circular opening therein and a 
plurality of rotatable supports, at least two of which are respectively 
rotatable about perpendicular axes. A ball is loosely seated on the 
supports, with a portion of the ball projecting through the opening so 
that the user can manually rotate the ball. The rotatable supports 
respectively respond to corresponding components of rotational movement of 
the ball. The supports are respectively connected to reader means which 
produce signals indicative of the speed and direction of rotation of the 
supports. The two perpendicular supports respectively correspond to the x 
and y directions of the movement of the cursor so that speed and direction 
of movement of the cursor in the x and y directions correspond 
respectively to the speed and direction of rotation of the associated 
supports. 
In prior trackball devices, the components thereof have been arranged so as 
to necessitate a large housing. Furthermore, prior trackball devices have 
not completely solved the problem of friction in the rotation of the 
supports while still addressing the problem of rattling and poor shock and 
impact resistance. 
SUMMARY OF THE INVENTION 
It is therefore an important object of this invention to provide a 
trackball device with a compact configuration of the supports and the 
reader means for efficient use of space and materials. 
It is another object of this invention to provide a trackball device which 
exhibits improved shock and impact resistance and smooth operation, while 
still providing reduced friction in the rotation of the supports and the 
trackball. 
These and other objects of the invention are attained by providing a 
trackball position control device comprising a housing having a circular 
opening therein, a generally cylindrical first support mounted for 
rotation in the housing and having a first axis of rotation, a generally 
cylindrical second support mounted for rotation in the housing and having 
a second axis of rotation, first and second code wheels respectively 
coupled to the supports and rotatable therewith, first and second reader 
means respectively associated with the first and second code wheels for 
generating control signals, a ball seated on the supports and having a 
portion projecting through the opening for manual rotation by the user, 
the second support and both of the reader means and the second code wheel 
and the ball all lying on the same side of the first axis, and a plurality 
of mounting means each including a bearing and bias means, the plurality 
of mounting means being constructed and arranged to allow movement of the 
first and second supports in directions toward and away from the plane of 
the opening and preventing movement of each support in directions parallel 
to the plane of the opening, the first and second supports each being 
carried between a pair of associated mounting means, the first and second 
supports having journals at the ends thereof respectively engaging the 
bearing surfaces associated therewith, the configuration of the journals 
and the bearing surfaces being such as to cause each journal to make 
substantially point contact with its associated bearing surface, the bias 
means being carried in the mounting means and resiliently urging each 
bearing surface and the associated support carried therebetween toward the 
plane of the opening. 
The invention consists of certain novel features and a combination of parts 
hereinafter fully described, illustrated in the accompanying drawings, and 
particularly pointed out in the appended claims, it being understood that 
various changes in the details may be made without departing from the 
spirit, or sacrificing any of the advantages of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIGS. 1 and 2 of the drawings, there is illustrated a 
trackball device generally designated by the numeral 10. The trackball 
device 10 is mounted in a housing defined in part by a top wall 12 and a 
bottom wall 14. Such housing may incorporate other devices, so that space 
is at a premium. In the top wall 12 is an opening 16. 
The trackball device 10 comprises a ball 18 protruding through the opening 
16. The trackball device 10 further comprises one-piece, plastic shafts 20 
and 30 which are oriented such that their axes are perpendicular to each 
other. The shaft 20 includes a support portion 22, a connecting portion 24 
and an attachment portion 26. The support portion 22 is a larger diameter 
cylinder that supports the ball 18. A code wheel 28 is attached to the 
attachment portion 26 and is rotatable therewith. The connecting portion 
24 is a smaller diameter cylinder located between the support portion 22 
and the attachment portion 26. The support portion 22, the connecting 
portion 24 and the attachment portion 26 are coaxial. The shaft 20 is 
rotatably supported by a pair of mounting structures which will be 
described hereinafter. 
The shaft 30 includes a support portion 32, a connecting portion 34, and an 
attachment portion 36. The support portion 32 is a larger diameter 
cylinder that supports the ball 18. A code wheel 38 is attached to the 
attachment portion 36 and is rotatable therewith. The connecting portion 
34 is a smaller diameter cylinder located between the second support 
portion 32 and the second attachment portion 36. The support portion 32, 
the connecting portion 34 and the attachment portion 36 are coaxial. The 
shaft 30 is rotatably supported by a pair of mounting structures as will 
be described hereinafter. 
The trackball device 10 further includes a ball support 40 which includes a 
pillow block 41 into which is journaled a short, cylindrical shaft 42 
which carries an idler wheel 43. 
The code wheel 28 is associated with a reader means 45. The reader means 45 
includes a printed circuit board 47, which is mounted in a pair of 
upstanding channels 46. The circuit board 47 has electrical components 
thereon connected to an associated source of electric power and control 
circuit (not shown). The reader means 45 also includes a U-shaped housing 
48 having legs 49 and 50. 
The code wheel 28 is a thin disk with a plurality of generally rectangular 
apertures 29 therethrough equiangularly spaced therearound adjacent to the 
periphery thereof. The code wheel 28 is dimensioned so that the apertured 
portion thereof projects into the U-shaped housing 48. The housing 48 
carries a transducer of standard construction. Specifically in the leg 49 
is an LED light source and in the leg 50 is a photodetector. In operation, 
light from the LED passes through the apertures 29 in the code wheel 28 to 
the photodetector to provide a series of pulse signals as the code wheel 
28 rotates. 
The code wheel 38, having apertures 39, is similarly associated with a 
reader means 51. The reader means 51 includes a printed circuit board 53 
which is mounted in a pair of upstanding channels 52. The reader means 
also includes a U-shaped housing 54 having legs 55 and 56. The reader 
means 51 and the code wheel 38 function the same as the reader means 45 
and the code wheel 28 described above. 
In use, the first support portion 22, the second support portion 32 and the 
idler wheel 43 support the ball 18. The ball 18 is dimensioned so that a 
portion thereof projects through the opening 16. The protruding portion of 
the ball 18 is rotated manually in the usual manner by the user. The free 
seating of the ball 18 allows for rotation in any direction. Upon rotation 
of the ball 18, the support portions 22 and 32 and the idler wheel 43 will 
be rotated in response to a component of rotational movement of the ball 
18. The rotation of the support portions 22 and 32 causes a resultant 
rotation of the respective code wheels 28 and 38. The rotation of the code 
wheels 28 and 38 produces code signals registered in the respective reader 
means 45,51 which controls movement of a cursor or other element in an xy 
plane. The speed and direction of movement in the x or y directions are 
proportional to the speed and direction of rotation of the corresponding 
one of the support portions 22 or 32. 
Referring now to FIG. 5, there is shown a mounting structure 60a. The 
mounting structure 60a includes a housing 61 having a bearing slot 64 and 
a groove 66. Positioned in each bearing slot 64 is a bearing disk 62 
having a bearing surface 63. Positioned in the groove 66 is a bias means 
or spring 65. The spring 65 contacts the bearing disk 62 urging the 
bearing disk 62 towards the top wall 12 of the trackball device 10. 
As shown in FIG. 1, the shaft 30 is rotatably mounted between the mounting 
structure 60a and a mounting structure 60b. The mounting structure 60b is 
identical to the mounting structure 60a shown in FIG. 5. 
Referring now to FIG. 4, the details of the mounting of the shaft 30 will 
be described. At the distal end of the support portion 32 is a large 
journal 67. At the distal end of the attachment portion 36 is a small 
journal 68. The large journal 67 and the small journal 68 each engage a 
bearing surface 63 with point contact for minimal friction upon rotation. 
The shaft 20 is mounted between a mounting structure 60c and a mounting 
structure 60d. Each of the structures 60c and 60d is identical to the 
structure 60a shown in FIG. 5. The shaft 20 is mounted in the same manner 
as the shaft 30 shown in FIG. 4, with the journals 67 and 68 engaging the 
respective bearing surface 63 in each mounting structure 60c and 60d. The 
only difference is that the connecting portion 24 is longer than the 
connecting portion 34 shown in FIG. 4, for reasons to be explained. 
The point contact between the journals 67 and 68 and the respective bearing 
surfaces 63 allows for rotation of the ball 18 with a minimal amount of 
frictional resistance. Shock and impact resistance are greatly increased 
by the bearing disks 62 being urged upward in the bearing slots 64 by the 
respective springs 65. Downward force on the ball 18 causes a downward 
motion of the ball 18, the shafts 20 and 30, and the respective bearing 
disks 62. The springs 65 operate to create an opposite force on the disks 
62, the shafts 20,30 and the ball 18, thereby reducing shock and impact on 
the entire device 10. The excessive downward movement of the ball 18 is 
prevented by stop blocks 70 and 71. The stop block 70 engages the support 
portion 22 and the stop block 71 engages the support portion 32 when an 
effort is made to depress the ball 18 too far. At rest, the springs 65 
cause the ball 18 to rest against the perimeter of the opening 16. 
An important aspect of the present invention is the compact configuration 
of the trackball device 10. The compact configuration is accomplished in 
part by the connecting portion 24 being longer than the connecting portion 
34. This allows the the mounting structure 60b to be positioned adjacent 
the connecting portion 24, between the code wheel 28 and the larger 
diameter of the support portion 22 with the axis of the shaft 30 
perpendicular to the axis of the shaft 20. 
The reader means 51 lies on the opposite side of the shaft 30 from the ball 
18 with the printed circuit board 53 lying parallel to the axis of the 
shaft 30 and the code wheel 38 extending between the legs 55 and 56 of the 
U-shaped housing 54. The reader means 45 lies between the second reader 
means 51 and the axis of the shaft 20 adjacent the mounting structure 60c. 
The printed circuit board 47 lies parallel to the axis of the shaft 20 
with the code wheel 28 extending between the legs 49 and 50 of the 
U-shaped housing 48. The compact configuration of the above components 
allows for significant savings of space and materials over prior art 
trackball devices. 
From the foregoing, it can be seen that there is provided an improved 
trackball device with a more compact configuration for savings of space 
and materials. Also, provided is an improved trackball device which has 
minimal friction upon rotation of the ball while still reducing rattling 
and increasing shock and impact resistance.