DETAILED DESCRIPTION OF THE INVENTION The door alarm system of the invention is for a door 1 (FIGS.
1 to 4) rotatably mounted in a door frame 2 (FIGS.
1 to 3).
The door alarm system of the invention comprises an alarm 3 (FIGS.
1, 6 and 7) of any suitable type, which alarm may be audible, visible, or a combination of both.
A door switch 4 (FIGS.
1 to 7) is mounted on the door 1 and has a switch arm coupled to the door frame.
The door switch 4 is open when the door 1 is closed and is moved to closed position when the door is opened at least approximately 35.
degree.
.
The door switch 4 comprises an electric conductor 5 stationarily affixed to the door 1 via a support 6 in a housing 7 (FIGS.
4 and 5).
A switch arm 8 is pivotally mounted on the support 6 on the door in the housing 7, as shown in FIGS.
2 to 5.
The switch arm 8 has an electric conductor 9 (FIGS.
4 and 5) which is maintained in spaced relation with the conductor 5 of the support 6, so that it is maintained out of electrical contact with the conductor 5, when the switch arm is in its position shown in FIGS.
2 and 5.
The electric contact 9 of the switch arm 8 is moved into electrical contact with the contact 5, thereby closing an electrical circuit between them, when said switch arm is in its position shown in FIG.
3 and by broken lines in FIG.
4.
In the non-contacting position, the switch arm 8 is substantially parallel to the surface of the door 1, whereas in the contacting position, said switch arm is at an angle with said surface of said door.
A mechanical linkage 10 of any suitable type such as, for example, a bead chain, extends from the switch arm 8 to the door frame 2, as shown in FIGS.
1 to 3, and couples the switch arm to the door frame in a manner whereby when the door is closed, the switch arm is out of electrical contact with the electric conductor 5 and when the door is opened beyond approximately 35.
degree.
, the linkage causes the switch arm to move into electrical contact with the electric conductor 5.
This is accomplished by a spring 11 (FIGS
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