Alarm buzzer

Abstract

An alarm buzzer comprising an electromagnet, a yoke on which said electromagnet is mounted while maintaining insulation from the housing, an armature which is held with a plate spring on said yoke and is attracted by said electromagnet, a vibratory plate which contacts said armature, and a housing which incorporates the above components, wherein the bobbin of said electromagnet is made of an insulating material and consists of a hollow cylinder which receives an iron core in it and is wrapped with coil on its outer periphery, first flange provided on one end of said hollow cylinder, second flange provided on the other end of the hollow cylinder and at least one hollow projection provided on said second flange in the direction parting from said first flange, said yoke is provided with at least one hole into which said hollow projection of the bobbin is inserted, and the bobbin and the yoke are fixed to the housing of the alarm buzzer by a fixture which is inserted into the hollow projection of the bobbin inserted into said hole of the yoke.

What we claim is: 
     
       1. An alarm buzzer comprising an electromagnet, a yoke on which said electromagnet is mounted while maintaining insulation from a housing, an armature which is held with a plate spring on said yoke and is attracted by said electromagnet, a vibratory plate which contacts said armature, and a housing which incorporates the above components wherein a bobbin of said electromagnet is made of an insulating material and consists of a hollow cylinder which receives an iron core in it and is wrapped with coil on its outer periphery, first flange provided on one end of said hollow cylinder, second flange provided on the other end of the hollow cylinder and at least one hollow projection provided on said second flange in a direction parting from said first flange, said yoke is provided with at least one hole into which said hollow projections of the bobbin is inserted, and the bobbin and the yoke are fixed to the housing of the alarm buzzer by a fixture which is inserted into the hollow projection of the bobbin inserted into said hole of the yoke. 
     
     
       2. An alarm buzzer as claimed in claim 1, wherein said fixture is a rivet. 
     
     
       3. An alarm buzzer as claimed in claim 1, wherein more than two hollow projections are provided and said fixture is inserted into at least one hollow projection and a terminal into the other hollow projection, one end of said terminal being projected outside the housing from the hollow projection. 
     
     
       4. An alarm buzzer as claimed in claim 1, wherein a part of the yoke is cut and raised in the same direction as said hollow projection, the tip end of the raised part being inserted into a hole provided in the bottom of the housing as is kept insulated and being projected outside the housing. 
     
     
       5. An alarm buzzer as claimed in claim 3, wherein a part of the yoke is cut and raised in the same direction as said hollow projection, the tip end of the raised part being inserted into a hole provided in the bottom of the housing as is kept insulated and being projected outside the housing. 
     
     
       6. An alarm buzzer as claimed in claim 5, wherein said bobbin is made of a thermoplastic resin, an uneven part is provided at a part of said terminal located inside said hollow projection of the bobbin and said hollow projection which is melted by a heat generated when soldering the coil to the terminal engages with said uneven part of the terminal, thereby the terminal is fixed to the hollow projection. 
     
     
       7. An alarm buzzer as claimed in claim 5, wherein a lug terminal is fixed with said fixture on the outer surface of the bottom of said housing. 
     
     
       8. An alarm buzzer as claimed in claim 7, wherein the projections are provided on the outer surface of the bottom of the housing and on the terminals for temporarily securing the alarm buzzer before soldering it to the printed circuit board. 
     
     
       9. An alarm buzzer as claimed in claim 7, wherein a projection is provided on each terminal in order to insert and fix the terminal of the alarm buzzer into the holding fixture fixed on the printed circuit board. .Iadd. 10. An improved horn for generating an audible signal, comprising a housing formed of electrically conductive material having walls the margins of which define an opening; an electro-magnetic coil within said housing and having a pair of terminals connected to opposite sides of a winding thereof and extending exteriorly of said housing; a diaphragm of electrically conductive material positioned on said housing in electrical contact therewith over said opening and closing said housing; a striker member of magnetically permeable and electrically conductive material; and means for mounting said striker in said housing between said diaphragm and said coil in operative association with said coil for movement away from and strikingly against said diaphragm to generate noise, said means normally resiliently urging said striker toward and into electrical contact with said diaphragm, electrically insulating said striker from direct electrical contact with said housing, and including a terminal extended exteriorly of said housing and electrically connected with said striker. .Iaddend..Iadd. 11. An improved horn as in claim 10, a cover, said housing having an outwardly extending lip about said opening, said diaphragm and cover resting on said lip, said housing and cover having interengaging portions securing said cover to said housing with said diaphragm therebetween. .Iaddend. .Iadd. 12. An improved horn as in claim 11, said cover having conical-frustrum shaped walls and a poart therethrough for the passage of noise generated by said horn. .Iaddend..Iadd. 13. An improved horn as set forth in claim 10, said coil having a pair of magnetic poles, said striker being mounted between said diaphragm and one of said poles, means providing a magnetically permeable path for magnetic flux at the other of said poles to a position closely spaced from said one pole to provide a relatively high density expanding field of magnetic flux thereat to attract said striker away from said diaphragm and toward said one pole when said coil is energized. .Iaddend..Iadd. 14. An improved horn as in claim 10, said means for mounting said striker including a bracket of electrically conductive material mounted in said housing, electric insulator means between said bracket and said housing, and a spring of electrically conductive material extended between said bracket and said striker and normally urging said striker into electrical contact with said diaphragm, said terminal electrically connected with said striker being electrically connected with said bracket. .Iaddend. .Iadd. 15. An improved horn as in claim 14, said coil having a pair of magnetic poles and being mounted on said bracket, said striker being between one of said poles and said diaphragm, the other of said poles being magnetically linked with said bracket and said bracket having portions providing a magnetically permeable path for magnetic flux at said other pole to a position closely spaced from said one pole to provide a relatively high density expanding field of magnetic flux thereat to attract said striker away from said diaphragm and toward said one pole when said coil is energized. .Iaddend..Iadd. 16. An improved horn as in claim 15, a first electrical contact mounted on said diaphragm and electrically connected therewith, and a second electrical contact electrically connected with said spring and mounted for movement with said striker, said spring normally urging said second contact into electrical engagement with said first contact. .Iaddend..Iadd. 17. An improved horn as in claim 14, said coil including a bobbin of electrically insulating material, said bobbin being mounted on said bracket and said bobbin, bracket, insulator means and housing having aligned passages, said bobbin having a shoulder formed around said passage therein and extending into said bracket passage, and fastener means extended through said passages and between said bobbin and housing to mount said bobbin, bracket and insulator means in said housing, said bobbin shoulder electrically insulating said fastener from said bracket whereby said bracket is maintained electrically insulated from said housing. .Iaddend.