Display unit with radiation sensitive control

Claim 2

A display unit comprising: a box formed with a window; support means inside the box for supporting a strip of film frames to be individually displayed while spanning across the window; said support means including a pair of spools on which the film strip is received for movement frame by frame past the window; a film drive for moving the film strip longitudinally past the window; a timer; sensing means responsive to the registration of each frame with the window for stopping the film drive and starting the timer; a source of illumination disposed behind the strip of film frames and operative to illuminate the registered film frame while the film drive is stopped; means controlled by the timer for restarting the film drive and extinguishing the source of illumination after a predetermined display time of the registered frame in the window; and, means for sensing when the final frame has been displayed in either direction of movement of the film strip and for controlling the film drive to obtain reversal of the direction of movement imparted to the film strip following the display of the final frame; said means for sensing when the final frame has been displayed including: a dark area marked on an each of the film strip adjacent each end of the film strip, the edge of the film strip between the dark areas being transparent; and, a photoelectric cell disposed adjacent each spool to detect a respective one of the dark areas, each photoelectric cell being normally illuminated by a beam of light, the illumination being interrupted when the corresponding dark area passes over the photoelectric cell, whereby the cell produces an electric pulse indicating that the end of the film strip has been reached in a respective direction.

Claim 3

A display unit as claimed in claim 1, wherein each photo-electric cell is connected to the input of a Schmitt trigger circuit the output of which is connected to a relay having a contact operative to effect reversal of the direction of rotation of a drive motor when the photo-electric cell produces a pulse indicating that the end of the film strip has been reached.

Claim 4

A display unit as claimed in claim 1, wherein the drive for the film strip comprises an electric motor arranged to run in either direction, a differential unit through which the drive motor drives both the spools, and a one-way retarder through which each spool is driven by the differential unit, each such retarder providing resistance to rotation in the direction of rotation applying when the film strip is being unwound from that spool.

Claim 5

A display unit as claimed in claim 1, wherein the drive for the film strip comprises an electric motor for driving each spool independently, such motors being arranged to run in opposite directions and each motor being connected to drive its respective spool through a one-way clutch and a one-way retarder which provides resistance to rotation in the direction applying when the strip is being unwound from the respective spool.

Claim 6

A display unit as claimed in claim 1, wherein the sensing means which responds to the registration of each frame of the film strip with the window is a photo-electric cell.

Claim 7

A display unit as claimed in claim 5, wherein a transparent marginal portion of an edge of the film strip is provided with a number of dark marks, one for each frame of the strip, which are so positioned that they come opposite the photo-electric cell when the associated frame registers with the window, the photo-electric cell being Normally illuminated through the marginal portion of the film strip by a beam of light whereby the photo-electric cell provides an electric pulse each time a frame is displayed in the window.

Claim 8

A display unit as claimed in claim 6, wherein the photo-electric cell is connected to the input of a Schmitt trigger circuit the output of which is connected via the timer to a relay having contacts operative to stop the operation of the drive and to energize the source of illumination disposed behind the film strip when the photo-electric cell provides a pulse indicating that a frame is displayed in the window, the relay being de-energized by the timer after a predetermined display time of the frame in the window so that the drive is again set in operation and the source of illumination is extinguished.

Claim 9

A display unit comprising: a box formed with a window defining a viewing area in one side thereof; support means mounted inside said box for receiving an elongated strip of image frames to be individually displayed in said viewing area; drive means operatively connected to said support means for moving said strip longitudinally past said window; a timer; sensing means disposed along one edge of said strip end responsive to the registration of each image frame with said window for deenergizing said drive means and energizing said timer; a source of illumination for projecting light toward said window and through an image frame in registration with said window; said source of illumination being energized in response to the deenergization of said drive means; braking means operative in response to said sensing means for applying a braking force to one of said strip and said drive means when the registration of an image frame with said window is sensed; means operative in response to said timer for restarting said drive means and extinguishing said source of illumination after a predetermined display time of an image frame; a dark area carried by the other edge of said strip of image frames adjacent each end of said strip, the edge of said strip between said dark areas being transparent; first and second light sources spaced along the length of said strip adjacent said other edge of said film strip outside said viewing area defined by said window and on one side of said film strip; first and second light responsive cells each disposed adjacent a respective one of said light sources on the other side of said strip so that said cells are normally illuminated by light from said associated light sources, the illumination being interrupted when one of said dark areas on said strip passes between one of said light sources and its associated cell; means for generating an electrical signal responsively to the interruption of the illumination of said cell to indicate that an end of said strip has been reached; and, means for reversing the direction of said drive means in response to said electrical signal.

Claim 10

A display unit comprising: a box formed with a window defining a viewing area in one side thereof; support means mounted inside said box for receiving an elongated strip of image frames to be individually displayed in said viewing area; drive means operatively connected to said support means for moving said strip longitudinally past said window; a timer; sensing means disposed along one edge of said strip end responsive to the registration of each image frame with said window for deenergizing said drive means and energizing said timer; a source of illumination for projecting light toward said window and through an image frame in registration with said window; said source of illumination being energized in response to the deenergization of said drive means; braking means operative in response to said sensing means for applying a braking force to one of said strip and said drive means when the registration of an image frame with said window is sensed; means operative in response to said timer for restarting said drive means and extinguishing said source of illumination after a predetermined display time of an image frame; a dark area carried by the other edge of said strip of image frames adjacent each end of said strip, the edge of said strip between said dark areas being transparent; first and second light sources spaced along the length of said strip adjacent said other edge of said film strip outside said viewing area defined by said window and on one side of said film strip; first and second light responsive cells each disposed adjacent a respective one of said light sources on the other side of said strip so that said cells are normally illuminated by light from said associated light sources, the illumination being interrupted when one of said dark areas on said strip passes between one of said light sources and its associated cell; means for generating an electrical signal responsively to the interruption of the illumination of said cell to indicate that an end of said strip has been reached; and, means for reversing the direction of said drive means in response to said electrical signal.

Claim 11

The display unit as claimed in claim 8, wherein the drive for the strip of image frames comprises an electric motor arranged to run in either direction, a differential unit through which the electric motor drives both of the spools, and a one-way retarder through which each spool is driven by the differential unit, each retarder providing resistance to rotation in the direction of rotation applying when the strip is being unwound from that spool.