Computer graphics processing and selective visual display system – Display peripheral interface input device – Cursor mark position control device
Reexamination Certificate
1999-10-15
2001-02-06
Shalwala, Bipin (Department: 2778)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Cursor mark position control device
C345S163000
Reexamination Certificate
active
06184870
ABSTRACT:
FIELD OF THE INVENTION
This application relates to pointing devices such as electronic mice or trackballs, and particularly relates to the ball cage therein and its components.
BACKGROUND OF THE INVENTION
Electronic mice are well known for their advantages as pointing devices. Basically, an electronic mouse converts the linear movement of the mouse over a surface into digital signals to control the cursor of the computer. One common type of electronic mouse uses an optomechanical interface, whereby the movement of a ball drives at least two shaft encoders. The shaft encoders in turn drive an encoding wheel located between a photosource and a photodetector. The movement of the encoding wheel causes pulses of light to reach the photodetector, which creates a pulse train indicative of movement of the mouse.
To provide accurate correlation between the movement of the mouse and movement of the cursor, the ball in an optomechanical mouse must be supported within fairly close tolerances. In substantial part, these close tolerances are necessary to maintain the ball in constant contact with the shaft encoders. In most such mice, a ball cage is provided to maintain the ball in proper position, and the shaft encoders are integrated into the ball cage. In the past, the ball cage has been a complicated assembly comprising in excess of twenty parts, including multiple parts for the shaft encoders and related mechanical elements, a pressure roller to maintain the ball in contact with the shaft encoders, and the ball cage itself. Also, a traction spring with hooks, which is comparatively difficult to assemble, has been required by many prior designs.
Such complicated assemblies increase manufacturing costs and reduce reliability. In addition, prior art designs typically do not lend themselves to use in automatic assembly. There has therefore been a need for a simple ball cage configuration which provides at least equal accuracy while reducing complexity and part count and permitting automatic assembly.
SUMMARY OF THE INVENTION
The present invention substantially overcomes the limitations of the prior art by providing an integral ball cage having only six parts which is capable of automated assembly. In particular, the shaft encoders are formed integrally, as is the pressure roller, and the integrated shaft encoder and pressure roller simply clip into the remainder of the ball cage. Likewise, the optical elements have been simplified to eliminate the need for a mask by building the mask function into the geometry of the photosensor, thereby also reducing part count. Finally, the pressure roller and its shaft are formed integrally, making assembly much simpler. Additionally, the design has been modified to permit use of an inexpensive, simple, and more easily assembled compression coil spring.
Two embodiments, each an improvement over the prior art, are disclosed. In the first embodiment, the ball cage is mounted on the printed circuit board which supports the logic and the optical elements. In a second embodiment, the ball cage can be integrated into the bottom housing rather than being mounted on the printed circuit board, further simplifying assembly and improving reliability, and also allowing the PCB to be reduced in size.
In either embodiment, the resulting ball cage is, by comparison with the prior art, much simpler to manufacture and assemble, thereby improving both yield and reliability. Importantly, the new ball cage is adapted well to automated assembly techniques.
It is one object of the present invention to provide an improved optomechanical mouse in which the ball cage and remaining elements are capable of automatic assembly.
It is another object of the present invention to provide an optomechanical mouse having a highly integrated ball cage.
It is a further object of the present invention to provide a ball cage having a minimal number of moving parts.
It is a still further object of the present invention to provide an optomechanical mouse having a highly integrated ball cage and optical elements which can be assembled by machine.
These and other objects of the invention will be better understood from the following Detailed Description of the Invention, taken together with the appending drawings.
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Bidiville Marc
Devey Kieran
Karai Denes
Lewis David L.
Logitech Inc.
Shalwala Bipin
Townsend & Townsend and Crew LLP
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