Back box with mounting posts projecting from recessed portions in sidewalls

A weatherproof back box for receiving a fire alarm notification or other fire alarm device includes a back wall and sidewalls that project from the back wall and define a mouth. The sidewalls further include recessed portions that extend from the back wall toward the mouth, and end prior to the mouth. The back box further includes mounting posts, which are preferably less than 50% of the depth of the back box, that project from the recessed portions into the mouth. Additionally, these mounting posts receive fasteners for securing the fire alarm notification device in the mouth of the back box.

BACKGROUND OF THE INVENTION

Fire alarm notification devices (e.g., speakers, horns, bells, chimes, and flashing lights/strobes) are often mounted in weatherproof back boxes (back boxes). These back boxes provide protection from wet, humid, and/or outdoor environments. In general, a back box is an enclosure designed to receive a fire alarm notification device or other device of a fire alarm system such as a smoke or fire detector or a pull station, to list a few examples. The back boxes provide a volumetric region in which wires of the fire alarm devices are connected to interconnect wiring (e.g., power and/or communication) of the fire alarm system.

FIG. 1illustrates an example of a back box10, which was manufactured via injection molding. In the illustrated example, the back box10includes a back wall10-band sidewalls10-s1,10-s2,10-s3,10-s4, which project from the back wall10-b. The sidewalls10-s1to10-s4define a mouth10-m, which receives the fire alarm device. In the illustrated example, alignment tabs18ato18dare positioned on the sidewalls to align the fire alarm device in the mouth of the back box10. The back box10further includes mounting posts (or bosses)12aand12b. These mounting posts12a,12bproject from the back wall10-bto the mouth10-mof the back box10. The mounting posts further include fastener receiving holes14aand14bfor screws that secure the fire alarm device to the back box10. The illustrated example further includes sidewall fastener receiving holes22aand22b, which receive additional fasteners for securing the fire alarm notification device to the back box10.

Additionally, the back box10often includes other features. Installation tabs20a,20b, which include fastener receiving holes21a,21b, are used to attach the back box to a surface such as a vertical wall or ceiling. In the illustrated example, the back wall10-band sidewalls10-s1to10-s4include “punch outs” (or knock outs)16ato16dfor connecting conduits to the back box10. A gasket26sits on a gasket surface24to provide a seal between the fire alarm device and the back box10.

SUMMARY OF THE INVENTION

There are, however, some problems when manufacturing conventional back boxes via injection molding. For example, the mounting posts12a,12b, which extend from the back wall10-bto the mouth10-mof the back box10, are typically formed with long core pins that are part of the injection molding tool or mold. These pins are fragile and may break in the molding process. Additionally, the mounting posts12a,12boften necessitate longer cooling times due to associated plastic wall thicknesses and poor cooling along the length of the posts and mounting posts may occasionally warp or develop irregular surface conditions which can impair the ejection of the back box from the tool or mold.

The present invention is directed to a back box, which includes one or more recessed portions in sidewalls of the back box. One or more mounting posts project from the recessed portions into a mouth of the back box. Typically, the mounting posts each have a length that is less than 50% of the depth of the back box. By reducing the length of the mounting posts, the injection molding no longer requires long and thus fragile core pins. As a result, the mold or tool is more mechanically robust and thus less susceptible to breakage. Also, the shorter mounting posts can be cooled more quickly, which improves mold cycle times.

In general, according to one aspect, the invention features a back box for a fire alarm device, such as a fire alarm notification device. The back box includes a back wall and one or more sidewalls projecting from the back wall and defining a mouth for receiving the fire alarm device. The one or more sidewalls further include one or more recessed portions. Additionally, the back box also comprises one or more mounting posts projecting from the recessed portions into the mouth. These one or more mounting posts receive fasteners for securing the fire alarm device in the mouth.

Preferably, the mounting posts project from surfaces of the recessed portions. Additionally, the one or more recessed portions extend from the back wall toward the mouth, and end prior to the mouth.

In a preferred embodiment, the one or more mounting posts each have a length that is less than 50% of the depth of the back box.

Typically, the one or more mounting posts maintain uniform wall thicknesses throughout the length of the one or more mounting posts.

In embodiments, the back box includes device alignment tabs projecting from the one or more sidewalls of the back box to align the fire alarm device within the mouth of the back box.

In a typical implementation, the back box includes one or more installation tabs, which include fastener receiving holes for mounting the back box to surfaces.

In general, according to yet another aspect, the invention features a back box for a fire alarm device. The back box comprises a back wall and one or more sidewalls projecting from the back wall and defining a mouth for receiving the fire alarm device. The back box further includes one or more mounting posts projecting from the sidewalls into the mouth. Additionally, the one or more mounting posts receives fasteners for securing the fire alarm notification device in the mouth.

In general, according to yet another aspect, the invention features a back box for a fire alarm notification device that includes a back wall and one or more sidewalls projecting from the back wall and defining a mouth for receiving the fire alarm notification device. The back box further including one or more mounting posts projecting into the mouth. Additionally, the one or more mounting posts each have a length that is less than 50% of the depth of the back box.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 2 and 3are perspective views that illustrate a back box100, which has been constructed according to the principles of the present invention.

In the illustrated example, the back box100include a back wall100-band four sidewalls100-s1to100-s4, which project from the back wall100-bto form a generally rectilinear open box. These sidewalls define a mouth100-mof the back box100that receives a fire alarm notification device, or more generally a fire alarm device. Some examples of fire alarm notification devices include speakers, horns, bells, chimes, and flashing lights/strobes. Fire alarm device is a broader class that includes fire alarm notification devices and further includes fire detection devices (e.g., smoke detectors) and other devices such as pull stations.

The back wall and sidewalls define a volumetric region in which wires of the fire alarm notification devices are able to be connected to wiring (e.g., power and/or communication) of an interconnect of a fire alarm system.

While the illustrated example is directed to a back box with four sidewalls for a fire alarm notification device, it will be understood by those skilled in the art that back boxes could be manufactured in different sizes, shapes, and with different numbers of sidewalls to accommodate different fire alarm notification devices and fire detection devices (e.g., smoke detectors and temperature sensors).

In a preferred embodiment, the sidewalls100-s1to100-s4include recessed portions101ato101d, which extend from the back wall100-btoward the mouth100-mand end prior to the mouth100-m. These recessed portions can help reduce the amount of material (e.g., plastic) required to make the back box100. Additionally, surfaces102ato102dare formed.

Mounting posts104ato104dproject from the surfaces102ato102dinto the mouth100-mof the back box100. The mounting posts104ato104dinclude fastener receiving holes105ato105dthat receive fasteners for securing the fire alarm notification device in the mouth100-m. Preferably, the mounting posts104-ato104-deach have a length that is less than 50% of the depth ‘D’ of the back box100, and the length is preferably less than 20% of the depth ‘D’ of the back box. In one current embodiment, the mounting posts104a-dare approximately ⅜ inches (or about 1 centimeter) in length. However, in a typical implementation, the size and shape of the mounting posts are based on the size and shape of the back box and the size of the fasteners required to install a fire alarm notification device in the back box. In any event, the shorten posts result in less fragile mold pins used in their manufacture.

Generally, the mounting posts104ato104dmaintain uniform wall thicknesses throughout the length of the mounting posts104ato104d. This provides more even cooling of the back box immediately after injection molding, less chance of warping, and water lines can be run into all required areas of the back box100to further facilitate cooling.

In alternative embodiments, the recessed portions101ato101dand mounting posts104ato104dmay be located along the sidewalls100-s1to100-s4, rather than at the corners, to provide compatibility with fire alarm notification devices fire detection devices that require mounting posts in different locations of the back box.

Typically, the back box100includes installation tabs108a,108bfor installing the back box to surfaces (e.g., walls or ceilings). These tabs108a,108bgenerally have fastener receiving holes109a,109bthat are designed to accept fasteners such as screws for affixing the back box100to the surfaces.

In the illustrated example, the sidewalls100-s1to100-s4and the back wall100-binclude “punch outs” (or knock outs)106ato106e. These punch outs106ato106eprovide access to the volumetric region of the back box for conduits, which carry alarm system interconnect wiring (e.g., power and/or communication wires). Typically, the conduit is sealed against the back box to prevent moisture, dirt, and/or other contaminants from entering the back box.

In a current implementation, the back box100is fabricated from plastic via an injection molding. Alternatively, other manufacturing techniques (e.g., casting, or stamping) could be used to fabricate the back boxes. Likewise, other materials such as aluminum, stainless steel, or alloys may be used in the manufacture of the back boxes.

FIG. 4further illustrates the recessed portions101c,101din sidewall100-s3of the back box100. Moreover, this figure illustrates how the recessed portions101c,101dextend from the back wall toward the mouth and end prior to the mouth of the back box100. Additionally, punch out106dand installation tabs108a,108bof the back box100are also further illustrated.

FIG. 5is another view that illustrates the recessed portions101a,101bin sidewall100-s1of the back box100and how the recessed portions101a,101bextend from the back wall toward the mouth and end prior to the mouth.

FIG. 6is a schematic view that illustrates an example of a fire alarm system that includes back boxes100-1to100-3installed on an exterior of a building50.

In general, a fire alarm system includes fire detection devices, fire alarm notification devices, and a control panel. The fire detection devices (not shown) such as smoke detectors or temperature sensors are located throughout a building to detect indicators of fire. In response to indicators of fire being detected by the fire detection devices, the control panel receives a signal that one or more fire detection devices have been triggered and activates audio and/or visible alarms of the fire alarm notification devices.

In the illustrated example, the back boxes100-1to100-3are installed on an exterior (or unfinished) wall of a building50. Some examples of buildings include hospitals, warehouses, retail establishments, malls, schools, or casinos, and/or gymnasiums to list a few examples. Conduit52, which carries alarm system interconnect wiring, connects the back boxes100-1to100-3to each other and to a control panel54. Typically, the control panel54is located within the interior building50.