Fire alarm glass cover frame

A frame for supporting a sheet of glass over a fire alarm signal switch mounted on a wall. The frame is of the type which holds the glass over the switch so that the alarm signal can only be operated by breaking the glass. The frame has a cover member with an open bottom so that when the glass is broken to operate the alarm the resulting shards of glass fall through the open bottom of the cover member so that they do not injure the operator.

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.

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.