Door alarm with infrared and capacitive sensors

• US 4,804,945 A
• Filed: 10/29/1987
• Issued: 02/14/1989
• Est. Priority Date: 10/29/1987
• Status: Expired due to Fees

• Current Assignee: Terrance Millet
• Original Assignee: Terrance Millet
• Inventors: Millet, Terrance
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US07/114,044
• Time in Patent Office: 474 Days
• Field of Search: 340/541, 340/562, 340/563, 340/567, 340/521, 340/693
• US Class Current: 340/541
• CPC Class Codes: G08B 13/06 by tampering with fastening
• CPC Class Codes: G08B 13/19 using infrared-radiation detection systems G08B13/194 takes precedence
• CPC Class Codes: G08B 13/26 by proximity of an intruder causing variation in capacitance or inductance of a circuit

Abstract

An alarm system for providing separate discrete signals corresponding with the approach of an individual to a door and the touching of the door knob by the individual utilizes a combination of infrared sensors and a capacitive discharge sensor. The infrared sensors are mounted on a circular ring on the face of the door knob. The sensors are angled in different directions to detect individuals approaching from various directions. The door knob is composed of a metallic material and acts as an antenna of a capacitive discharge proximity sensor. The door knob is insulated by a sleeve from the rest of the door and latch structure. Approach of an individual is detected by the infrared sensors which activates a first alarm signal. When the individual reaches for and touches the door knob, a second different alarm is activated.

Claims

1. A door alarm for providing two separate discrete signals indicating approach of an individual to a door and touching of the door knob by the individual, comprising:

a metallic door knob on said door;

a shaft connected to said door knob and a latch mechanism on said door;

insulating means for electrically insulating said door knob and said shaft from said door and said latch mechanism;

a key lock cylinder extending through a front face of said door knob;

a circular mounting ring on said front face of said door knob surrounding said key lock cylinder;

four infrared sensors spaced circumferentially at ninety degree intervals around said mounting ring;

first control means connected to said infrared sensors;

audible alarm means activated by said control means in response to approach of an individual to said door to provide a first signal;

a capacitive discharge sensor connected to said metallic door knob;

second control means connected to said capacitive discharge sensor; and

means connected to said second control means for providing a second signal in response to touching of said door knob by an individual.

2. A door alarm, comprising:

door knob means;

infrared sensor means on said door knob means for detecting approach of an individual remote from said door knob; and

alarm means connected to said infrared sensor means activated by said approach of an individual.

3. A door alarm, comprising:

door knob means;

sensor means on said door knob means for detecting approach of an individual remote from said door knob;

said sensor means comprising at least one infrared sensor and a capacitive discharge sensor; and

alarm means connected to said sensor means activated by said approach of an individual.

4. The door alarm of claim 3, further comprising a circular mounting ring on a front face of said door knob means;

and

a plurality of infrared sensors circumferentially spaced around said ring.

5. The door alarm of claim 4, wherein said plurality of infrared sensors are each angled in a different direction to detect individuals approaching from various directions.

6. The door alarm of claim 3, wherein said door knob means is formed from a metallic material and is an antenna of said capacitive discharge sensor.

7. The door alarm of claim 6, wherein said door knob means includes a shaft;

and

insulating means on said shaft for electrically insulating said door knob means and said shaft from a door.