Smoke and fire detector

• US 4,845,474 A
• Filed: 08/01/1986
• Issued: 07/04/1989
• Est. Priority Date: 08/01/1986
• Status: Expired due to Fees

• Current Assignee: Huafeng Electronics, Inc.
• Original Assignee: Pioneer Manufacturing Company Limited (Pioneer Corporation)
• Inventors: Brooks, Stanley J., Moore, Prentice G.
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Queen, Tyrone
• Application Number:
  US06/892,668
• Time in Patent Office: 1,068 Days
• Field of Search: 340/629, 340/628, 340/630, 340/384 R, 340/384 E, 361/331, 250/381, 250/382, 250/384
• US Class Current: 340/629
• CPC Class Codes: G08B 17/11 using an ionisation chamber for detecting smoke or gas
• CPC Class Codes: G08B 17/113 Constructional details
• CPC Class Codes: H05K 1/02 Details
• CPC Class Codes: H05K 3/3468 Applying molten solder

Abstract

An ionization smoke and fire detector comprises a molded plastic housing that includes a nodal ring for supporting a vibrating plate that is part of an alarm. The alarm may be driven by piezoelectricity or by an electromechanical device. If the detector is battery powered, a portion of the housing is cut out to permit removal and insertion of a battery holder that makes contact automatically upon insertion to supply electric power to the electronic circuit of the smoke detector. One electrode of a reference chamber for the smoke detector is formed by wave-soldering an open metallized area on the printed-circuit board. Contact with the movable element of the alarm and with a high-impedance input in an integrated circuit are made through springs that are not soldered or welded. The outside of the smoke and fire detector is formed in part by a smoke-chamber cover which makes various electrical contacts with the printed-circuit board at electrical conductors that are bent around the edge of the board and wave-soldered. The smoke and fire detector is assembled without screws and all electrical connections among components are made without welding, hand soldering, or any soldering beyond wave soldering of a printed-circuit board.

Claims

1. In a smoke and fire detector having a housing, a source of ionizing radiation, a smoke chamber, a reference resistance, means for comparing the electrical conductivity of ionized components in the smoke chamber with the electrical conductivity of the reference resistance, and means for sounding an alarm when the difference between the electrical conductivities exceeds a predetermined amount, the improvement comprising:

a nodal ring that is molded into the housing;

a piezoelectric transducer formed by depositing piezoelectric material onto a metal disc and disposed on the nodal ring at a mode of oscillation of the transducer to form a part of the means for sounding an alarm;

a sound-emission aperture formed as a part of the housing and coupled acoustically to the transducer, whereby the means for sounding an alarm is thereby made an integral part of the housing; and

a retainer that is adapted to snap into engagement with the housing to secure the transducer in physical contact with the nodal ring, the retainer further including a plurality of guides, each adapted to support a spring to make electrical contact with the transducer.

2. In a smoke and fire detector having a housing, a source of ionizing radiation, a smoke chamber, a reference resistance, means for comparing the electrical conductivity of ionized components in the smoke chamber with the electrical conductivity of the reference resistance, and means for sounding an alarm when the difference between the electrical conductivities exceeds a predetermined amount, the improvement comprising:

a reference ion chamber that is the reference resistence, the reference ionization chamber including a reference ionization source and an electrode formed as a conducting region on a printed circuit board; and

an insulator adapted to snap into the printed-circuit board and to engage a source plate that forms an electrode of the reference ion chamber and also provides support for the reference ionization source and the source of ionizing radiation on opposite sides of the source plate.

3. In a smoke and fire detector having a housing, a source of ionizing radiation, a smoke chamber, a reference chamber, means for comparing the electrical conductivity of ionized components in the smoke chamber with the electrical conductivity of ionized components in the reference chamber, and means for sounding an alarm when the difference between the electrical conductivities exceeds a predetermined amount, the improvement comprising:

a printed-circuit board that contains electric components including the means for comparing electrical conductivity, the printed-circuit board further including a plurality of electrical conductors disposed to make electrical contact, each with one of a plurality of springs;

a battery holder that forms part of the housing, the battery holder including means for effecting an electrical connection between a battery and the printed-circuit board to supply electrical energy to operate the smoke and fire detector, the battery holder disposed in the housing to allow removal and replacement of the battery holder without detaching the smoke detector from a mounting and without allowing access to the source of ionization radiation, the smoke chamber, the reference resistance, the means for comparing electrical conductivity, or the means for sounding an alarm, the battery holder further including means for effecting electrical connections of the battery holder;

a smoke chamber cover that forms an exterior bound to the smoke chamber, the smoke-chamber cover having an exterior cross-section that is substantially equal in area and shape to an interior cross-section of the housing, the smoke-chamber cover sized to extend to and around the printed-circuit board to provide radio-frequency shielding for the smoke chamber and the reference chamber; and

a plurality of openings in the housing and a plurality of openings in the smoke-chamber cover that are aligned to permit substantially equal access from all directions in a plane perpendicular to an axis of symmetry of the housing, the openings in the housing and the openings in the smoke-chamber cover disposed in cooperative engagement to serve as a screen to keep insects for entering the smoke chamber and also to imnpede air flow into the smoke chamber.

4. In a smoke and fire detector having a housing, a source of ionizing radiation, a smoke chamber, a reference chamber, means for comparing the electrical conductivity of ionized components in the smoke chamber with the electrical conductivity of ionized components in the reference chamber, and means for sounding an alarm when the difference between the electrical conductivities exceeds a predetermined amount, the improvement comprising:

a printed-circuit board that contains electric components including the means for comparing electrical conductivity;

a smoke-chamber cover that forms an exterior bound to the smoke chamber, the smoke-chamber cover having an exterior cross-section that is substantially equal in area and shape to an interior cross-section of the housing, the smoke-chamber cover sized to extend to and around the printed-circuit board to provide radio-frequency shielding for the smoke chamber and the reference chamber;

a first strip that is attached as a cantilever to the housing to form a first movable element that is substantially flush with a surface of the housing;

a first tab that is attached to the smoke-chamber cover to form a second movable element that is substantially flush with a surface of the smoke-chamber cover, the first strip and the first tab disposed so that when the first strip is pressed from outside the smoke and fire detector the first tab is caused to move into electrical contact with a first conductor on the printed-circuit board to test the operation of the smoke and fire detector;

a second strip that is attached as a cantilever to the housing to form a third movable element that is substantially flush with a surface of the housing;

a second tab that is attached to the smoke-chamber cover to form a fourth movable element that is substantially flush with a surface of the smoke-chamber cover, the second strip and the second tab disposed so that when the second strip is pressed from outside the smoke and fire detector the second tab is caused to move into electrical contact with a second conductor on the printed-circuit board to test the operation of the smoke and fire detector and then silence an alarm from the smoke and fire detector for a predetermined time;

a capacitor having a first terminal and a second terminal, the first terminal connected to a source of electrical voltage; and

a diode having a cathode connected to the second terminal of the capacitor and to the second conductor on the printed-circuit board, the diode having an anode connected to the means for comparing electrical conductivity whereby when the second tab is caused to move into electrical contact with the conductor on the printed-circuit board, the cathode of the diode is grounded to sound an alarm and the capacitor is charged, and when the second tab is released from electrical contact the charged capacitor applies a voltage that silences the smoke and fire detector until the capacitor discharges.

5. In a smoke and fire detector having a housing, a source of ionizing radiation, a smoke chamber a reference chamber, means for comparing electrical conductivity of ionized components in the smoke chamber with electrical conductivity of ionized components in the reference chamber, and means for sounding an alarm when the difference between the electrical conductivities exceeds a predetermined amount, the improvement comprising;

a printed-circuit board that contains electric components including the means for comparing electrical conductivity;

a smoke-chamber cover that forms an exterior bound to the smoke chamber, the smoke-chamber cover having an exterior cross-section that is substantially equal in area and shape to an interior-cross section of the housing, the smoke-chamber cover sized to extend to and around the printed-circuit board to provide radio-frequency shielding for the smoke chamber and reference chamber; and

a battery holder that forms part of the housing, the battery holder including means for effecting an electrical connection between a battery and the printed-circuit board to supply electrical energy to operate the smoke and fire detector.

6. The apparatus of claim 5 wherein the battery holder is further disposed in the housing to allow removal and replacement of the battery without detaching the smoke and fire detector from a mounting.

7. The apparatus of claim 6 wherein the battery holder comprises in addition means for effecting electrical connections with the smoke and fire detector automatically upon replacement of the battery holder.