Protective cover for frangible bulb

A cover mountable on a support frame for protecting a frangible item mounted within the frame is disclosed. The cover has first and second cover portions engaging the frame on opposite sides of the item. A hinge connects first ends of the covers together and a releasable fastener connects the other ends. Fingers extend from one or both of the cover portions toward the opposite cover portion and are positioned in spaced relation to the ends of the cover portions. The fingers and the ends of the cover portions define spaces at opposite ends of the cover which receive and engage portions of the support frame. The fingers are in spaced relation to one another and define a space between them for receiving the frangible item. The fingers are sized and spaced so that they transfer any force on the cover to the frame exclusively. The covers have an arcuate shape to provide increased stiffness.

FIELD OF THE INVENTION

This invention relates to a device for protecting frangible items, and especially to frangible glass bulbs used in sprinkler heads of fire suppression systems.

BACKGROUND OF THE INVENTION

Fire suppression systems are used extensively in office buildings, warehouses, factories, hotels, homes and other buildings and structures to provide a reliable and effective means to suppress the spread of fire throughout the building or structure. Such systems may comprise a piping network extending throughout the building. The piping network is connected to a source of fire suppressing fluid, for example, water, and is in fluid communication with sprinkler heads distributed throughout the building which will discharge the fire suppressing fluid in the event of a fire.

Each sprinkler head has a valve which is biased into a normally open position, but is held in a closed position against the biasing force by a frangible glass bulb that contains a heat-sensitive fluid. The bulb is elongate in design and the biasing force places it under compression along its long axis. The bulb is very strong in compression along its long axis but easily breaks when force is applied transverse to this axis. During a fire, the heat-sensitive fluid expands within the bulb and when a predetermined temperature is reached the heat-sensitive fluid applies hydraulic pressure outwardly against the bulb normal to the long axis, causing the bulb to shatter, and thereby allow the valve to open and discharge the fire suppressing fluid.

The bulb is designed to break at the predetermined temperature, and when installed properly is very reliable. However, the bulb must be frangible to operate effectively and is typically made of glass which is susceptible to damage. Damage which can compromise the performance of the bulb may be caused during packing, shipping or installation of the sprinkler head and may comprise a scratch or nick in the bulb caused by a tool or another sprinkler head, as well as a crack or a small hole which allows the heat-sensitive fluid to escape. If such damage is not prevented or at least mitigated, then it is possible that the bulb may fail prematurely at a temperature lower than the predetermined temperature, thus, triggering discharge from the sprinkler head in the absence of a fire condition. This may result in extensive water damage to the building and its contents. More seriously, the damage may prevent the sprinkler head from discharging at all, as may happen if the heat-sensitive fluid is permitted to leak out. This condition will compromise the fire safety of the building and should be avoided. It is, therefore, desirable to protect such frangible items during handling, packing, shipping and installation of the sprinkler heads to ensure that they function properly when the fire suppression system is brought on line.

SUMMARY OF THE INVENTION

The invention concerns a cover for protecting a frangible item mounted within a support frame such as a glass bulb used with a sprinkler head in a fire suppression system. The cover comprises a first cover portion positionable adjacent to the frangible item and having a first end. A second cover portion is also positionable adjacent to the frangible item but opposite to the first cover portion. The second cover portion has a second end, the first and second ends of the cover portions being attached to one another. A first finger projects from the first cover portion toward the second cover portion and is positioned in spaced relation to the first and second ends. A first space is defined between the first finger and the first and second ends for receiving a portion of the support frame, the first finger and the first and second ends of the cover portions engage the support frame for positioning the cover thereon adjacent to the frangible item.

The cover may also comprise a first opposite end positioned on the first cover portion opposite the first end and a second opposite end positioned on the second cover portion opposite the second end. A second finger projects from one of the first and second cover portions toward the other of the first and second cover portions. The second finger is positioned in spaced relation to the first and second opposite ends. A second space is defined between the second finger and the first and second opposite ends for receiving another portion of the support frame. The second finger and the first and second opposite ends of the cover portions engage the support frame for positioning the cover thereon adjacent to the frangible item.

Another embodiment of a cover for protecting a frangible item mounted within a support frame comprises a pair of interengageable cover portions positionable on opposite sides of the frangible item. Each of the cover portions comprises a first end having a latch extending therefrom, a second end having a slot therein and a first finger positioned in spaced relation to one of the first and the second ends. The first finger extends in substantially the same direction as the latch. The cover portions are positionable in engagement one with another by aligning the cover portions and inserting the latches on each one of the cover portions into the slots on each other of the cover portions. A first and a second space are defined between the first fingers and the first and second ends of the cover portions upon their engagement. Each of the spaces receives a respective portion of the support frame. The first fingers and the ends of the cover portions engage the portions of the support frame for positioning the cover thereon adjacent to the frangible item.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1depicts an example of a sprinkler head10, shown in phantom line, used with a fire suppression system to spray a fire suppressing fluid onto a fire. Sprinkler head10includes a support frame12having a collar14from which extend two limbs16and18. Limbs16and18are positioned in spaced relation to one another to define an open space20between them. A valve22is attached to collar14for controlling the flow of fire suppressing fluid onto the fire. A deflector plate24is attached to the ends of limbs16and18in the path of the fluid flow from valve22to deflect and thereby distribute the fluid discharged from the valve over a desired area. A frangible glass bulb26is mounted in space20between the ends of the limbs16and18and the valve22. Bulb26is elongate and, when present, engages the moving member of the valve to keep it in a closed position against a biasing force, usually provided by a spring within the valve (not shown), which normally biases the valve into an open position to permit fluid flow. A heat-sensitive fluid within the bulb expands when heated, and when a predetermined temperature is reached, the internal hydraulic pressure within the bulb breaks it. The bulb collapses, no longer able to restrain the biasing force and the valve opens to allow water to discharge.

A cover28, shown in solid line, is removably mounted on the support frame12surrounding and protecting the glass bulb26exposed in the open space20between limbs16and18. As shown inFIG. 2, cover28comprises first and second cover portions30and32respectively, joined together at their respective ends33aand33bby a hinge34. Cover portions30and32are pivotable about hinge34to facilitate their placement adjacent to bulb26and engagement with support frame12as illustrated inFIG. 1. Hinge34is preferably a flexible “living hinge” made of a thin section of relatively flexible material allowing the cover portions to be pivoted-repeatedly without fatigue failure. Other forms of hinges are also feasible, such as piano hinges, socket and trunnion hinges and the like. Preferably, hinge34is resilient and provides a biasing force which tends to hold the cover portions30and32in a closed position shown in phantom line inFIG. 2.

A fastener36may be positioned between the respective ends35aand35bof cover portions30and32opposite the hinge34. Fastener36releasably attaches ends35aand35bto one another, and preferably comprises a latch38extending from one cover portion (in this example cover portion30) and a slot40in the other cover portion (32) sized and aligned to receive the latch38. Latch38is cantilevered from the cover portion30and has a barbed end42which engages the slot40and prevents inadvertent removal of the latch38from the slot40. However, latch38is flexible and resilient and may be manually deformed so that the barbed end42disengages from slot40to allow the cover portions30and32to be pivoted about hinge34into the open position shown in solid line inFIG. 2for removal of the cover28from or attachment to the sprinkler head10. Other types fasteners could also be used, such as nuts and bolts, hook and loop systems and the like to relesably secure the cover portions30and32one to the other.

As shown inFIG. 3, first and second fingers44and46respectively, are arranged in spaced relation to one another and project from first cover portion30toward second cover portion32. Finger44is positioned in spaced relation to ends33aand33bof the cover portions. The ends33aand33band finger44define a space48between them for receiving the limb16of support frame12when the cover28is positioned on the sprinkler head as shown inFIG. 1. Similarly, finger46is positioned in spaced relation to ends35aand35bof the cover portions. The ends35aand35band finger46define a space50between them for receiving the limb18of support frame12when the cover28is positioned on the sprinkler head as shown inFIG. 1. Although fingers44and46are shown inFIG. 3extending from first cover portion30, it is understood that they could also be positioned on second cover portion32or on both cover portions. Fingers44and46also define a center space52which receives the glass bulb26. Preferably, fingers44and46are sized and spaced relative to respective ends33a,33band35a,35bso that the ends and the fingers will engage the limbs16and18, hold the cover28securely on the support frame12and transfer any impact force on the cover28exclusively to the frame12. To that end, fingers44and46are further sized so that they flank bulb26without contacting it, thereby preventing any side loads from impinging on the bulb when the cover is bumped during handling, packing, shipping or installation of the sprinkler head10.

As shown inFIG. 2, cover28may also have additional fingers54and56offset from fingers44and46. Fingers54and56again extend, in this example, from the first cover portion30toward the second cover portion32, although other variations of finger placement are feasible as described above for fingers44and46. Finger54is positioned in spaced relation to ends33aand33bof the cover portions. The ends33aand33band finger54define a space58between them for receiving the limb16of support frame12when the cover28is positioned on the sprinkler head as shown inFIG. 1. Similarly, finger56is positioned in spaced relation to ends35aand35bof the cover portions. The ends35aand35band finger56define a space60between them for receiving the limb18of support frame12when the cover28is positioned on the sprinkler head as shown inFIG. 1. Fingers54and56also define a center space62which receives the glass bulb26. Similar to fingers44and46, fingers54and56are sized and spaced relative to respective ends33a,33band35a,35bso that the ends and the fingers will engage the limbs16and18, hold the cover28securely on the support frame12and transfer any impact force on the cover28exclusively to the frame12. Fingers54and56are also sized so that they flank bulb26without contacting it, thereby preventing any side loads from impinging on the bulb when the cover is bumped during handling, packing, shipping or installation of the sprinkler head10.

Preferably, space58is substantially aligned with space48, space60is substantially aligned with space50and space62is substantially aligned with space52. The fingers may have different lengths to accommodate any variation in dimensions of the limbs16and18.

Preferably, as shown inFIG. 3, the cover portions30and32have outwardly facing surfaces64and66that are arcuate in shape. This increases the stiffness of the cover28and thus reduces the magnitude of cover deflection when forces impinge on it to provide additional protection to the bulb26.

FIG. 4shows another embodiment68of a cover according to the invention. Cover68comprises two separate cover portions70and72which are attached to one another at their respective ends74a,74band76a,76bby fasteners78. Preferably, the fasteners78comprise latches38and receiving slots40as described above because they facilitate rapid manual engagement and disengagement of the cover portions70and72. Other types fasteners could also be used however, such as nuts and bolts, hook and loop systems and the like.

Preferably, cover portion72is a mirror image of cover portion70, each having a latch38at one end, a slot40at an opposite end, and a finger identified as80aor80b, which extends toward the opposite cover portion when the cover68is mounted on the support frame12. Such a configuration allows each cover portion70and72to be substantially identical to one another, thus saving on capital costs, such as molds, associated with manufacture.

As best shown inFIG. 5, finger80aextends from cover portion70and is positioned in spaced relation to the ends74aand74bof the cover portions70and72. Together finger80aand ends74aand74bdefine a space82for receiving limb16of support frame12. Similarly, finger80band ends76aand76bof cover portions70and72define a space84for receiving limb18of support frame12. Fingers80aand80bare positioned in spaced relation to one another and also define a center space86which receives the glass bulb26when the cover portions70and72are positioned on the support frame12. Preferably, fingers80aand80bare sized and spaced relative to respective ends74a,74band76a,76bso that the ends and the fingers will engage the limbs16and18, hold the cover28securely on the support frame12and transfer any impact force on the cover28exclusively to the frame12. To that end, fingers80aand80bare further sized so that they flank bulb26without contacting it, thereby preventing any side loads from impinging on the bulb when the cover is bumped during handling, packing, shipping or installation of the sprinkler head10.

As shown inFIG. 4, cover68may also have additional fingers88aand88boffset from fingers80aand80b. Fingers88aand88bagain extend, in this example, respectively from each cover portion70and72, although other variations of finger placement are feasible. Finger88ais positioned in spaced relation to ends74aand74bof the cover portions. The ends74aand74band finger88adefine a space90between them for receiving the limb16of support frame12when the cover68is positioned on the sprinkler head. Similarly, finger88bis positioned in spaced relation to ends76aand76bof the cover portions. The ends76aand76band finger88bdefine a space92between them for receiving the limb18of support frame12when the cover68is positioned on the sprinkler head. Fingers88aand88balso define a center space94which receives the glass bulb26. Similar to fingers80aand80b, fingers88aand88bare sized and spaced relative to respective ends74a,74band76a,76bso that the ends and the fingers will engage the limbs16and18, hold the cover28securely on the support frame12and transfer any impact force on the cover68exclusively to the frame12. Fingers88aand88bare also sized so that they flank bulb26without contacting it, thereby preventing any side loads from impinging on the bulb when the cover is bumped during handling, packing, shipping or installation of the sprinkler head10.

Preferably, space90is substantially aligned with space82, space92is substantially aligned with space84and space94is substantially aligned with space86. The fingers may have different lengths to accommodate any variation in dimensions of the limbs16and18.

Again, as best shown inFIG. 5, the cover portions70and72have respective arcuate outer surfaces96and98to increase stiffness of the cover68and reduce cover deflection to provide additional protection to the bulb26.

Covers according to the invention are preferably made of polymers such as polypropylene, polyethylene, and nylon in an injection molding process. These plastics are preferred because they result in a tough, resilient cover which maintains its flexibility and structural integrity over a wide temperature range.

Use of covers as described herein will provide increased protection to frangible bulbs used in sprinkler heads thus providing a greater degree of fire safety by increasing the likelihood that properly functioning sprinkler heads are installed in fire suppression systems. The covers will also help reduce costs as fewer bulbs will be damaged during handling, packing, shipping and installation and require replacement.