1.  Field of the Invention
The present invention relates to visual display units for use in vehicles, such as automobiles and aircraft.  More specifically, the present monitor is adapted to be mounted in a headrest of a vehicle seat. 
2.  Description of the Related Art
Monitors for displaying visual images have been commonplace aboard commercial aircraft and motor coaches for quite some time.  For example, U.S. Pat.  No.  5,267,775 to Nguyen, and U.S. Pat.  No.  5,507,556 to Dixon disclose monitors that are adapted to be mounted in a seat back of an aircraft seat.  Neither of these monitors is adapted for use in an automobile. 
Disadvantageously, each of these monitors pivots automatically with the seat back.  A viewer cannot adjust a viewing angle of either monitor independently of a recline angle of the seat back.  This limitation prevents a viewer from adjusting the monitor to minimize glare.  In an automobile a position and orientation of the vehicle relative to the sun is constantly changing.  The movement creates glare at certain times, and viewers prefer to be able to adjust the screen to eliminate the glare.  Thus, any monitor for use in an automobile is preferably adjustable so that viewers can minimize glare. 
The Nguyen monitor pivots about a lower edge, and pivots into the seat back when a passenger reclines the seat back.  Thus, the Nguyen monitor occupies a relatively large depth of the seat back.  This configuration is not suitable for use in an automobile headrest, where space is very limited. 
The Dixon monitor pivots about an axis located in the upper half of the housing.  The axis is spaced downward and inward from the upper outer edge of the monitor (see FIGS.  3-5).  The Dixon monitor pivots away from the seat back when a passenger reclines the seat back.  However, because of the location of the pivot axis, an upper rear edge of the Dixon monitor moves toward the seat back when the monitor pivots.  Like the Nguyen monitor, this configuration occupies a relatively large depth of the seat back and is not well-adapted for use in an automobile headrest, where space is very limited.  Further, when the seat of Dixon is in a reclined position, and the monitor is in a position such that a lower edge thereof protrudes from the seat back, tension in a cable within the seat back holds the monitor in position.  Thus, if a passenger strikes the monitor in this position, he or she could be injured because the monitor will not retract into the seat back.  This configuration is also not appropriate for use in an automobile headrest, where during emergency braking passengers are frequently thrown forward. 
Monitors have recently become more popular in private passenger vehicles where space is more limited than in aircraft and motor coaches.  For example, U.S. Pat.  No.  5,842,715 to Jones, and U.S. Pat.  No.  6,250,976 to Chu disclose monitors that are adapted to be mounted in a head rest of an automobile seat.  The Jones and Chu monitors are adapted to be mounted in an automobile headrest.  However, neither of these monitors is adjustable independently of the headrest. 
Unfortunately, none of these patents teaches a monitor that is adapted to be mounted within an automobile headrest, and is independently adjustable by a viewer to provide an optimum viewing angle and to reduce glare. 
Several monitors for use in private passenger vehicles include a plastic housing that is mounted to the vehicle headrest.  The housing is glued into a cavity within the headrest, and the screen structure is securable within the housing using a variety of different attachment methods.  For example, the housing may include tabs that snap into slots on the screen structure.  Unfortunately, the connections between these screen structures and their respective housings are not very sturdy.  Furthermore, the glued connections between the housings and their respective headrests are not very sturdy.  Thus, during a vehicle collision, the screen structures tend to detach from their housings, and the housings tend to detach from their headrests.  The loose screen structures and housings drifting about the passenger compartment pose a threat to the passenger's safety.