Sign with changeable character plates

Claim 1

A sign for displaying at least one horizontal row of character plates in a manner such that the character plates can be installed, removed and replaced by authorized persons, said sign comprising: a sign backing member having at least one face; at least two channel members secured on the backing member, one above the other so the channel members proceed horizontally across said face parallel to one another and terminating adjacent the opposite sides of said backing member; the lower channel member having means defining an upwardly opening groove extending therealong, said groove having means defIning a lip along the upper extent thereof, said lip being spaced from said face of the backing member by a distance at least equal to the thickness of a character plate adjacent the lower edge of the character plate; the upper channel member having means defining a downwardly opening groove extending therealong, said groove having means defining a lip along the lower extent thereof, said lip being spaced from said face of the backing member by a distance at least equal to the thickness of a character plate adjacent the upper edge of the character plate; means defining a longitudinally extending ledge within said downwardly opening groove intermediate the height of that groove, said ledge partly constricting said downwardly opening groove but leaving a gap between itself and said face of the backing member at least equal in thickness to the thickness of a character plate adjacent the upper edge of the character plate; said ledge thereby defining a compartment thereabove within said downwardly opening groove; the distance between the upper and lower channel members being such that a character plate cannot be frontally installed and removed unless the upper edge thereof is permitted to temporarily pass said ledge and enter said compartment so the lower edge of the character plate can clear said lip of the upwardly opening groove; and a flexible locking strip longitudinally, slidably received in said compartment, said locking strip being thicker than said gap, and said locking strip, when disposed within said compartment obstructing the compartment sufficiently to prevent character plate upper edges from passing said ledge and entering said compartment to an extent sufficient to permit the lower edges of the character plates to clear said lip of the upwardly opening groove, so that character plates may neither be frontally installed nor frontally removed when the locking strip is disposed within the compartment.