Patent Publication Number: US-5831543-A

Title: Fire alarm glass cover frame

Description:
BACKGROUND OF THE INVENTION 
     The field of the invention is safety devices and the invention relates more particularly to fire alarm switches. Fire alarm switches can provide a temptation for vandals to surreptitiously pull the fire alarm switch while walking by. It has been found that this sort of vandalism can be greatly reduced by providing a sheet of breakable glass over the switch. In this way the breaking of the glass creates a very distinctive sound which would call attention to a potential vandal. As the result, alarm switches with glass covers are rarely pulled by vandals. 
     One problem with such switches, however, is that when the glass is broken for the purpose of sounding a fire alarm, the user needs to reach into the alarm box and pull out the fire alarm switch lever. Occasionally the broken shards of glass resulting from the breaking of the glass cover are held up in such a way by the bottom of the cover so that the user is cut while attempting to sound the alarm. 
     BRIEF DESCRIPTION OF THE INVENTION 
     It is an object of the present invention to provide an alarm box which has a reduced tendency to cut a user. 
     The present invention is for a frame for supporting a sheet of glass over a fire alarm signal switch mounted on a wall. The frame is of the type where the sheet of glass must be broken to reach the fire alarm signal switch. The frame has an inner frame member which is held against the wall and the inner frame member has four arms extending outwardly from the wall to four glass supporting tabs. The inner frame member includes means for attachment of a cover member. A cover member is attached to the inner frame member and has a top wall, a first and a second side wall and a face with a glass exposing opening having an inner surface. The cover member has an inwardly directed glass supporting ledge at the bottom of the face and the bottom of the cover member is generally open. A sheet of glass is held against the inner surface of the face of the cover member by said four glass supporting tabs. The sheet of glass is shaped so that it about extends to the top wall, first and second side walls and the glass supporting ledge. When the glass is broken into shards the shards will fall downwardly out of the generally open bottom and not be held where they might cut the operator of the fire alarm switch. Preferably the inwardly glass supporting ledge extends from the first side wall to the second side wall. Also preferably the glass supporting ledge extends inwardly a slightly greater distance than the thickness of the glass so that no sharp edges of the glass are exposed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of the frame for supporting a sheet of glass of the present invention. 
     FIG. 2 is an enlarged cross-sectional view of the bottom of the cover member and of the sheet of glass of FIG. 1. 
     FIG. 3 is a perspective view partially cut away of the cover member and frame of FIG. 1. 
     FIG. 4 is a cross-sectional side view of the frame of FIG. 1 mounted on a wall. 
     FIG. 5 is a front view thereof. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The frame for supporting a sheet of glass is shown in exploded perspective view in FIG. 1 and indicated generally by reference character 10. Frame 10 has an inner frame member 11 which has a back wall 12 which is screwed or otherwise affixed to a building wall indicated by reference character 13 in FIG. 4. Inner frame member 11 has four outwardly extending arms 14, 15, 16, and 17 which in turn have glass supporting tabs 18, 19, 20, and 21. 
     A sheet of glass 22 is sandwiched between the inner frame member 11 and cover member 23. Cover member 23 has a top wall 24, a first side wall 25, a second side wall 26 and a face 27. Face 27 has a glass exposing opening 28 in it so that it is largely open. The bottom of cover member 23 is almost entirely open except that there is an inwardly directed glass supporting ledge 29 shown in FIG. 2 which holds the bottom of the glass sheet 22. 
     The assembled frame member 11 and cover member 23 are shown in perspective view partly broken away in FIG. 3 where it can be seen that the bottom area 30 is generally open and only the inwardly directed glass supporting ledge 29 and a small reinforcing flange 31 extend at all into the generally open area 30. 
     As shown in FIG. 4 a fire alarm signal switch 32 is surrounded by cover member 23. The sheet of glass 22 has been broken by a hammer held adjacent the assembly and the broken shards of glass are indicated by reference character 33 which have fallen downwardly through the open bottom 30 of cover member 23. Thus, when the user reaches in to pull down the switch 34 shown in FIG. 5, the user will not be cut by shards of broken glass which formerly have been supported on the bottom of the cover member after breaking. 
     Preferably the sheet of glass 22 has a thickness less than the length of the inwardly directed glass supporting ledge 29 as shown in FIG. 2. In this way no sharp edge of the glass is exposed 21 reaching inside of the bottom of the cover member 23. Preferably ledge 29 extends from the first side wall 25 to the second side wall 26 so that no portion of the glass edge is exposed. This is shown in phantom view in FIG. 5. 
     The present embodiments of this invention are thus to be considered in all respects as illustrative and not restrictive; the scope of the invention being indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.