Warning device for indicating locked position of door

Claim 1

The combination with a door-locking mechanism having a member movable between door-locked and door-unlocked positions, of a door-attachment warning device for indicating locked position of a door comprising: a. a tubular housing disposed in an opening formed in the door, a light bulb mounted in this housing in a position so that its light will be seen from the exterior of the door when the bulb is illuminated; b. a mounting plate secured to an inner face of the door, an electrical circuit connecting the bulb to a source of electricity, a switch supported from the mounting plate, the switch being coupled into the electrical circuit and including a pushbutton operable for closing and opening the circuit; c. a swingable arm engaging with the pushbutton for closing and opening the switch when the arm is moved in one direction or the other, respectively; d. the arm engaging with said member of the locking mechanism, and said member moving the arm on one direction to close the switch and thereby illuminate the bulb when said member is moved into door-locking position; e. and the arm being movable in the other direction to open the switch and thereby extinguish the light of the bulb when said member is moved into door-locked position; f. said member of the locking mechanism being provided by a plunger mounted for axial movement in an inner door knob, the mechanism being locked when said plunger is depressed and unlocked when said plunger is extended relative to the knob; g. the arm having one end thereof abutting an outer end of the plunger so that the arm will swing into a position to close the switch when the plunger is depressed, and the arm being swingable into a position to open the switch when the plunger is extended.