Abstract:
A position sensor for determining the relative physical location of a movable item via a combination of a sensor and an indicator plate affixed to an actuator device.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to entertainment systems and more specifically to retractable display assemblies integrated into entertainment systems utilized on transportation vehicles. 
   Today&#39;s world involves numerous situations in which one is required to endure trips of varying distance and time for both pleasure and work reasons. To accomplish these travels a wide assortment of personal and commercial vehicles including automobiles, buses, ships, trains and aircraft are relied upon on a daily basis. For those individuals not operating the respective vehicle, the duration of the trip provides a captive situation which is often addressed by access to wireless broadcast information, such as television, or viewing pre-recorded information stored on the vehicle for playback during the trip. Such systems are often referred to as on-board entertainment system or mobile entertainment systems. With advances in electronics in recent years, with respect to size, cost and ruggedness, such on-board entertainment system entertainment systems are commonly found in numerous vehicles. 
   One drawback to the present day utilization of on-board entertainment system entertainment systems, is the maintenance associated with the display or monitor stowage and deployment. In order to provide maximum viewing access, the physical location of the display or monitor often subjects the device to excessive stress, both planar and rotational, when deployed. Additionally, the operating environment of such entertainment systems is often characterized by high vibration and deliberate, but uninformed attempts to deploy or retract the display. 
   During normal deployment and operation, certain conditions may arise that result in system operator desire to retract and stow the display assembly. Although the display assembly can be deployed manually, a typical on-board entertainment system on a large passenger vehicle, such as an aircraft, may utilize a large number of individual displays. A preferred method of deployment and storage is the minimization of user manipulation of display assembly location. Accordingly, a sensor assembly that is lightweight, low-cost, accurate and rugged that allows for the repetitive deployment and storage of the display assembly would be advantageous. 
   SUMMARY OF INVENTION 
   The present invention comprises a position sensor for determination of relative location of an item that is physically manipulated from a first location to one or more alternate locations in a controlled manner. In a preferred embodiment the position sensor comprised a indicator disk affixed to an actuator or moveable element, said indicator disk incorporating a “step” created by a region of varied diameter and a receive/transmit device contiguous to the path of movement of the step portion of said indicator disk. As the indicator disk travels contemporaneously with the controlled movement of the physically adjustable item, movement of a step region through the sensor channel creates a control signal, which may be coupled with intentional delay time, and subsequently triggering a signal to disable the actuator. 
   It is an object of the present invention to provide a device for controlling physical adjustment of a movable device. 
   It is an advantage of the present invention to provide an on-board entertainment system that incorporates a controlled display assembly deployment mechanism of varying position. 
   It is a feature of the present invention to utilize an indicator plate in combination with a step region relative to the deployed assembly location. 
   These and other objects, features, and advantages are disclosed in the specification, figures, and claims of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagrammatic view of the passenger compartment of a vehicle, which includes an on-board entertainment system having a deployed display. 
       FIG. 2  is a perspective view of one embodiment of an on-board entertainment system display retract assembly incorporating the features of the present invention. 
       FIG. 3  is a perspective of one embodiment of the sensor and indicator plate of the present invention. 
   

   DETAILED DESCRIPTION 
   Referring now to the drawings wherein like numerals refer to like matter throughout,  FIG. 1  shows the display  100  of an entertainment/information system in the passenger portion of a vehicle  105 , which incorporates the teachings of the present invention. The display is depicted in a deployed or extended position from its stowed location in cavity  115  of the ceiling panel  117  of the vehicle  105 . Although not shown, the display assembly is coupled to additional components of the entertainment system for receiving power and content signals. 
     FIG. 2  depicts a perspective view of one embodiment of a display assembly  300  that incorporates the teachings of the present invention. The display assembly is comprised of an elongated lever arm  305  that is pivotally affixed, at a first distal region of said elongated lever arm to an actuator device  310 . The actuator device, may be of any type consistent with the preferred design parameters, such as a linear or rotary motor. The display assembly further comprises an engagement arm  315 , said engagement arm rigidly affixed to a display assembly  300  such that a defined portion of the engagement arm  317 , extends beyond the perimeter of the edge of the display housing  320 . As depicted a pivot pin  320  is utilized to accomplish the coupling of the lever arm  305  to the actuator  310 , however it is understood that any type of common fastener device, including but not limited to rivets, screws, bolts, clips, adhesives or even an integrated clip mechanism, will equally satisfy the coupling task and accomplish the advantages of the present invention. An indicator plate or disk  330  is mechanically coupled to one end of the actuator  310  and rotates through a sensor or optical switch  335  that is generally “U” shaped, thereby providing a channel through which the indicator plate  330  travels during actuator movement. The sensor is electrically coupled to additional controller means (not shown) via cable  340  for transmission of a signal indicative of indicator wheel position. 
     FIG. 3  is a perspective view of one embodiment of a sensor and indicator plate of the present invention. As shown, the sensor assembly  400  is comprised of a sensor device  405 , an indicator plate  410  and cabling  415 . The indicator plate is generally circular shaped having a primary radius of R and includes a step region defined by an increased radius of the disk R plus V, where V is a value that alters the radius R, either by increasing the radius over a given arc  420  of the indicator plate (as shown) or by decreasing the radius, resulting in a pronounced step or difference at the point on the edge of the indicator plate where V is maximized. The step dimension may be of varying size per design preference, a range of one eighth of an inch to three eight&#39;s of an inch would be consistent with an indicator plate having a two-inch diameter, exclusive of the varied diameter region. The region of increase diameter is defined by a prescribed arc of varying degrees, typically between one hundred twenty and forty degrees. It should also be noted that multiple step regions may be included on a given indicator plate. In the preferred embodiment of the present invention the arc having the displaced diameter comprised ninety degrees and yielded a “step” of approximately one quarter of an inch. 
   The sensor  405  includes a signal modulator, such as an LED or alternate source disposed upon a first vertical wall comprising one segment of the “U” and detector complementary located along a second vertical wall, such that in the absence of an obstruction in the channel formed by the first and second wall, the detector will be sensitive to the modulated signal. The channel formed by the sensor accommodates the indicator plate  410  in a contact-less fashion thereby allowing rotation of the indicator plate. Upon the passage of the step region, the detector senses the signal from the opposite sensor wall and generates a pulse signal provided to the actuator controller, to terminate further actuator movement. The signal to terminate additional motion may be additionally and varied delayed to comport with desired deployment control signals for associated final display assembly deployed condition. 
   In operation the operator of the on-board entertainment system enables, instantaneously or via delayed program, the movement of the display assembly at a predetermined time. For example, for short duration prior to takeoff, or after attainment of a certain altitude. The actuator device receives a command to relocate the current position of the display assembly to a second position from the on-board entertainment system control unit. In response to such command an enabling signal is conveyed to the actuator device. Simultaneous thereto, the sensor assembly modulator is provided a signal from the control unit to allow rotation until receipt of a cancellation signal that is triggered by the movement of the step region of the indicator plate through the sensor. In this manner the display assembly can be fully retracted, extended or adjusted within a predetermined increment consistent with the indicator plate movement step location with respect to the actuator/lever relationship. 
   In one embodiment of the present invention, the indicator plate is comprised of a flat aluminum disk approximately two inches in diameter and 0.02 inches in thickness. The disk is mounted on the extended shaft of a rotary actuator motor and has a receive-transmit infrared sensor along the edge of each primary face of the indicator plate, such that as the disk rotates, the portion of the perimeter edge that contains the step indicia passes through the detection region of the sensor. As the disk rotates on an axis that is parallel to the beam between the sensor the transmit beam is blocked or obstructed via the solid portion of the indicator plate. As the step region of the disk passes through the sensor the received pulses from the transmit region of the sensor are detected and monitored via signals provided from the sensor to the control unit. Upon attainment of such pulses, plus any additional latency desired by the operator and incorporated into the retract/deployment system, the actuator receives a signal to discontinue additional movement. It should be noted that alternative sensors, including mechanical, piezoelectric, or other optical sensors could readily be utilized by one of ordinary skill in the art, wishing to practice the present invention. 
   It is understood that, while the detailed drawings, specific examples, and particular values given describe preferred exemplary embodiments of the present invention, they are for the purpose of illustration only. The apparatus and method of the present invention is not limited to the precise details of the conditions disclosed. Accordingly, changes may be made to the details disclosed without departing from the spirit of the invention the scope of which should be determined by the following claims.