Detector assembly suited to smoke alarms

A detector assembly (10) powered by mains electricity and an elongate backup battery (76) is disclosed. The assembly includes: a ceiling mountable base (10) having a body defining a downwardly opening socket (24); a detector module (20) having a battery support portion (75) for holding the battery (76) in a vertical orientation, the module (20) receivable by the socket (24); a quick connection means for mechanically and electrically connecting the module (20) to the base (10); and shutter (50) mounted to the base (10). The shutter (50) prevents operation of the quick connection means when no vertical battery (76) is installed within the module (20). The quick connection means comprises co-operable pairs of conductors. The conductor pairs transmit power from the base (10) to the module (20). The pairs of conductors each comprise a stud conductor mounted to the base (10) and a forked conductor mounted to the module (20).

FIELD OF THE INVENTION

The present invention relates to alarm and/or detector assemblies such as smoke alarms and in particular to smoke alarms having a battery back up to a mains electricity power supply.

BACKGROUND TO THE INVENTION

Smoke alarms and carbon monoxide alarms are typically mounted at various locations around a house or other buildings to detect dangerous air quality conditions that may arise as a result of fire and give an alarm signal. Such alarm units must be highly reliable so that the alarm can detect conditions invisible to the human senses when the occupants of the building are asleep. Domestic smoke alarms in the past have typically been powered by a battery that gave about one year of normal operation. No connection to the mains circuit was made. Recent changes to regulations in many countries have mandated the use of fixed wiring to provide mains power combined with battery back up for loss of mains power in smoke alarms.

Most mains power smoke alarms found in Australia, having battery back up systems, use a plug in connector with a small flexible cable (flex) that requires a further termination box for connection usually fixed above the ceiling. This arrangement is not desirable for the installer as he/she is required to fix the terminal connection means to a fixing point as is required by the wiring rules, this usually necessitates entering the roof cavity, plus the extra cost to purchase the junction box.

The small connector plug and separate terminal housing referred to above is used in many countries around the world. The problem with this method of termination is the requirement for a separate terminal connection means plus the plug can get knocked out of its connection when insulation batts or the like are pulled over the smoke alarm. The cable length may also not reach a fixing point for the terminal box. In this case the electrician has to make a fixing point closer to the smoke alarm.

Other smoke alarms in the market have integrated the terminals within their mounting plates, but with the addition of terminals and the conventional layout of components such as the battery position the alarm becomes large and bulky making it less commercially acceptable. Batteries also require replacement annually, hence a simple means is required to allow the battery replacement. The alarm must also prevent the user from connection to the mains circuit without the battery fitted. Many designs for battery removal are available on the market. Most have complicated door mechanism that hide the battery some have complicated switching that allow the user to keep the mains connection but isolate the sense electronics when the battery door is open. In most cases the battery is hidden and is difficult for impaired persons to remove or understand how removal is achieved.

It is an object of the invention to overcome at least some of the problems outlined above.

BRIEF DESCRIPTION OF THE INVENTION

According to a first aspect of the invention there is provided a detector assembly powered by mains electricity and an elongate backup battery, the assembly comprising:

a ceiling mountable base having: a body defining a downwardly opening socket, a mouth within the socket for receiving a portion of the battery, and a means of connecting to the mains electricity;

a detector module having a battery support portion for holding the battery in a vertical orientation, the module receivable by the socket;

a quick connection means for mechanically connecting the detector module to the base;

a quick connection means for electrically connecting the detector module to the base, the electrical connection supplying power from the power supply means to the module; and

a lockout means arranged to prevent operation of at least the mechanical quick connection means when no battery is installed within the detector module.

Preferably the lockout means comprises:

a blocking member pivotally mounted to the module for rotation from a blocking position to a retracted position; and

a biasing means for biasing the blocking member into its blocking position when no battery is installed within the detector module.

Preferably the assembly is for use with a standard nine volt battery having an end face with a pair of projecting spaced apart snap connectors,

wherein the battery support portion comprises a pair of standard upwardly facing snap connectors arranged and constructed to engage the snap connectors of the battery.

Preferably the blocking member comprises an upwardly extending leg joined to a foot, the foot having a battery face engaging portion, the engaging portion located adjacent the snap connectors of the battery support portion,

wherein the engaging portion is displaced and held down by the face of the battery when the battery is installed thereby holding the blocking member into its retracted position.

Preferably the biasing means comprises a spring, for instance, a coil spring.

Preferably the means of connecting to the mains electricity comprises:

at least two terminals for receiving electrical wiring.

Preferably each terminal comprises:

a body defining a cylindrical recess for receiving a mains wire and defining a stud conductor; and

a screw threadably received within a taped hole through the body into the cylindrical recess,

wherein, in use, the screw clamps the wire in place within the cylindrical recess and power is transmitted from the wire into the body and out through the stud to the module.

Preferably the quick connection means comprises at least two co-operable pairs of conductors, in use the conductor pairs transmitting power from the base to the detector module, the pairs of conductors each comprising:

the stud conductor; and

a forked conductor mounted to the module,

wherein the conductors are mutually shaped and constructed so as to provide sufficient mechanical holding strength to support the module against gravity.

Preferably each forked conductor comprises two spaced apart resilient prongs, the prongs biased towards each other to grip the stud.

Preferably the forked conductors are constructed from phosphor bronze.

According to a second aspect of the invention there is provided a detector assembly powered by mains electricity and a backup battery, the assembly comprising:

a ceiling mountable base having: a body defining a downwardly opening socket, and a means of connecting to the mains electricity;

a detector module having a battery support portion, the module receivable by the socket;

a quick connection means for mechanically connecting the detector module to the base;

a quick connection means for electrically connecting the detector module to the base; and

a lockout means having a shutter mounted to the base,

wherein the lockout means prevents operation of at least the mechanical quick connection means when no battery is installed within the detector module.

Preferably the battery support portion is arranged and constructed to hold a battery such that it protrudes upwards to engage the shutter mounted to the base.

Preferably the body of the base defines an mouth for receiving a portion of the battery.

Preferably the body of the base defines an aperture positioned adjacent the mouth, the aperture providing a path through which the mechanical quick connection means can operate.

Preferably the shutter comprises:

a leg having an upper end and a lower end, the upper end connected to an upper end of the mouth; and

a foot connected to the lower end of the leg, the foot having a blocking portion, the blocking portion extending over the aperture so as to block the path through which the quick connection means operates when the shutter is in the closed position.

Preferably the means of connecting to the mains electricity comprises:

at least two terminals for receiving electrical wiring.

Preferably each terminal comprises:

a body defining a cylindrical recess for receiving a mains wire and defining a stud conductor; and

a screw threadably received within a taped hole through the body into the cylindrical recess,

wherein, in use, the screw damps the wire in place within the cylindrical recess and power is transmitted from the wire into the body and out through the stud conductor to the module.

Preferably the quick connection means for mechanically connecting the detector module to the socket and the quick connection means for electrically connecting the detector module to the socket are a single quick connection means.

Preferably the quick connection means comprises at least two co-operable pairs of conductors, in use the conductor pairs transmitting power from the base to the detector module, the pairs of conductors each comprising:

the stud conductor; and

a forked conductor mounted to the module,

wherein the conductors are mutually shaped and constructed so as to provide sufficient mechanical holding strength to support the module against gravity.

Preferably each forked conductor comprises two spaced apart resilient prongs, the prongs biased towards each other to grip the stud.

Preferably the forked conductors are constructed from phosphor bronze.

Preferably the body is shaped to define a post the inside of which forms the mouth.

Preferably the post has a recess for receiving a cable tie to facilitate retention of a mains electrical cable.

Referring toFIG. 1, a low profile smoke detector assembly10according to a first embodiment of the invention is shown. The detector assembly10comprises two main components, a ceiling mountable base20and a plug in detector module70. Referring toFIG. 4, the base20has a body22defining a downwardly opening socket23and a mouth24within the socket23for receiving a portion of a backup battery76.

Referring toFIGS. 2 and 3, it can be seen that the base20is mountable in a ceiling through a circular cut out using mounting arms25. Mounting arms25rotate about mounting screws26. A cover35is mounted about a hinge36to double insulate the terminal area in the roof cavity. The top cover35includes a break out area37for up to three additional cables. Upright portion or post39is provided by body22to enable secure connection of the power supply cable using a cable tie12as is shown inFIGS. 1 and 12. The same post39forms the mouth24for receiving a portion of the battery76.

Referring toFIGS. 10 and 12, it can be seen that the body22of the base20defines an aperture27position adjacent the mouth24. The aperture27provides a path for electrical connection between the detector module70and the base20.

A means of connecting the assembly10to mains electricity is provided by four terminals A E N I (Active, Earth, Neutral, Interconnect). The terminals are arranged in line making wiring easy as is shown inFIGS. 3,9and12. The diameter of the terminals31,32,33and34is preferably five millimeters. Connection of wiring to these terminals is made easy by the fact that the top cover35can flip open180degrees giving dear access to the terminal area as is shown inFIG. 3. Referring toFIG. 13, the construction of each of the terminals31,32,33and34can be seen. For instance, terminal31comprises a body36that defines a cylindrical recess for receiving a mains wire and a screw38threadable received within a tapped hole through the body36into the cylindrical recess. A stud conductor41is also defined by the body36. In use, the screw38clamps the wire in place within the cylindrical recess and power is transmitted from the wire into the body36and out through the stud conductor41to the detector module70.

Referring toFIG. 4, it can be seen that the detector module70has a battery support portion75that holds the battery76in a vertical orientation extending away from and protruding from the body of the detector module70. In other embodiments of the invention the battery may be mounted on its side with one side extending away from the body of the detector module.

A quick connection means for mechanically and electrically connecting the detector module70to the base20is provided. The quick connection means comprises at least two cooperable pairs of conductors, in use the conductor pairs transmitting power from the base20to the detector module70. The pairs of conductors are most clearly shown inFIGS. 12 and 13. They are mutually shaped and constructed so as to provide sufficient mechanical holding strength to support the module against gravity.

In another embodiment of the invention, quick connection means for mechanical connection and for electrical connection may be separate.

More specifically, each of the cooperable pairs of conductors comprises a stud conductor, such as the stud conductor41shown inFIG. 13, and a forked conductor, such as a conductor91shown in the same Figure. Forked conductor91has a pair of spaced apart resilient prongs91′ that are biased towards each other and are disposed on opposite sides of the stud41thereby gripping the stud41. The slot formed between each pair of prongs ensures that contact with the corresponding stud is achieved in spite of height differences arising from manufacturing tolerance variations.

The lockout means is arranged to prevent operation of the above described connection means when no battery is installed within the detector module70. The lockout means includes a shutter50mounted to the base20as shown inFIGS. 5,10and11. The construction of the shutter is best seen inFIG. 10.FIG. 10shows that the shutter includes a leg54having an upper end56connected to an upper end29of the mouth24. A foot53is connected to the lower end58of the leg54. The foot53has a blocking portion, the blocking portion extending over the aperture27so as to block the path through which the quick connection means operates when the shutter is in its dosed position as shown inFIG. 10. In this position, cut outs52are not aligned with the row of terminal studs41,42,43and44and therefore the central forked conductors92and93are mechanically blocked from engaging the studs42and43.

The shutter50is shaped and positioned such that when a battery76is installed in the detector module70, as is shown inFIG. 4, the battery76will displace it as the detector module70is inserted up into the base20. This is best seen in the cutaway view ofFIG. 12. The upper part of the battery76engages the leg54of the shutter50before the top of the forked conductor92reaches the cut out area52. The cut out area52is in the position shown inFIG. 11by the time the forked conductor92is about to pass through towards the terminal stud42.

It can be seen that electrical connection between the detector module70and the ceiling mountable base20is made via linear connection rather than by a plug in terminal or a rotating connection as is commonly used in other smoke detector systems.

The printed circuit board80housed within the detector module70is shown inFIGS. 6,7,8and9. Referring toFIG. 8, a sensor82is shown. In this embodiment of the invention the sensor82is a smoke sensor. However, in other applications, a carbon monoxide or other type of detector may be fitted. A horn84is provided to produce a loud warning signal. Conventional red and green LEDs85and86are provided together with light pipes105and106(light pipes shown inFIGS. 4 and 6). A push-to-test button102is provided as shown inFIGS. 6 and 7.

FIG. 9shows how the battery76simply engages battery contacts81. The terminals31,32,33and34, although shown inFIG. 9for clarity of illustration, are in fact located within the ceiling mountable base20. ThusFIG. 9shows how the terminal31,32,33and34engage with the contact tabs91,92,93and94when the detector module70is installed with a battery76within the ceiling mountable base20.

A second embodiment of the invention is shown inFIGS. 14 and 15. This embodiment of the invention is similar to the first embodiment of the invention described above except for the lockout means. Referring toFIGS. 14 and 15, it can be seen that the lockout means for the second embodiment of the invention comprises a blocking member120pivotably mounted to the module70for rotation from a blocking position to a retracted position. The blocking member is shown in its blocking position inFIG. 14and its retracted position inFIG. 15. The lockout means also comprises a biasing means in the form of a spring128positioned within recess28for biasing the blocking member120into its blocking position when no batteries are installed within the detector module as shownFIG. 14. The spring128is dearly shown inFIG. 15, but has been omitted fromFIG. 14for clarity.

With this embodiment of the invention, the battery contact81of the first embodiment of the invention has been replaced with standard snap connectors181as shown inFIG. 14. These snap connectors engage with the standard projecting spaced apart snap connectors mounted on the end face of a standard knife or battery.

Referring again toFIG. 14, the blocking member120comprises an upwardly extending leg122joined to a foot124, the foot having a battery face engaging portion126located adjacent snap connectors181of the battery support portion. Referring toFIG. 15it can be seen that the engaging portion126is displaced and held down by the face77of the battery76when the battery76is installed, thereby holding the blocking member120into its retracted position. In this retracted position, the leg122of the blocking member120is adjacent and parallel to the battery76allowing it to enter the mouth within the base20.

It can be seen that the above described detector assemblies10both provide a compact low profile smoke detector that is easy to install by an electrical contractor.

While the present invention has been described in terms of a preferred embodiment in order to facilitate better understanding of the invention, it should be appreciated that various modifications can be made without departing from the principals of the invention. Therefore, the invention should be understood to include all such modifications within its scope.