Safety ceiling vent

A ceiling vent to reduce the temperature in a room that is subject to becoming uncomfortably hot. The vent contains two concentric tubes, one movable and the other stationary. The movable tube is attached to a damper plate so that when the movable tube is lowered, the vent opens. Attached to the stationary tube is a plastic fuse pin in a metal sleeve that engages a notch in the stepped upper portion of the movable tube. There is a spring attached at one end to the metal sleeve and at the other end to the damper plate. When the vent is opened, the spring is stretched. Should there be a fire in the room being vented, hot air rising through the vent would cause the plastic fuse pin to soften or melt, which would cause the plastic fuse pin to disengage from a notch and allow the spring to resume its rest position and close the vent.

BACKGROUND OF THE INVENTION
 This invention relates to a ceiling vent for releasing heat from a room to
 reduce the temperature in the room to thereby enhance comfort and reduce
 the load on energy-consuming air-conditioning units. The vent has a safety
 feature that causes it to close when the temperature in the vent becomes
 hot enough to indicate a fire or when it is subject to a shock indicative
 of an explosion. The vent can be used in any room that becomes
 uncomfortably hot, especially rooms with sun exposure and kitchen with
 heating-releasing appliances such as refrigerators, stoves, and ovens.
 SUMMARY OF THE INVENTION
 The invention comprises a duct pipe that extends through a hole in the
 ceiling of a room. There is a damper plate that is in contact with the
 ceiling when the vent is closed. The damper plate would contact a tube
 called the lower guide. The top of the lower guide is a series of stepped
 notches. The vent contains another tube, the upper guide, concentric with
 the lower guide. Attached to the upper guide is a metal sleeve
 encompassing part of a plastic fuse pin. When the vent is closed, the fuse
 pin engages the lowest notch of the lower guide. The two concentric tubes
 contain a spring. A hook attached to the upper end of the spring loops
 around the metal sleeve. A second hook at the bottom of the spring engages
 a retaining screw that is attached to the bottom lower guide. To lower the
 damper plate and open the vent, the second hook is lowered and rotated
 until the fuse pin engages the notch on the lower guide that results in
 the desired opening of the vent. The fuse pin is made of a plastic with a
 relatively low melting point. The fuse pin would melt when air with
 temperatures characteristic of a fire in the room being ventilated passes
 through the vent. Melting of the fuse pin would cause it to disengage the
 notch on the lower guide, which results in the damper plate closing. Shock
 from an explosion could cause the damper plate to slide up the lower guide
 to close the vent a short time before heat from the explosion would cause
 the fuse pin to melt.
 A ceiling vent helps to cool a room using the property that warmer air is
 less dense than cooler air and consequently tends to rise and escape
 through the vent. It is a simple, inexpensive way to provide some cooling
 to enhance comfort or reduce the load on air conditioning units. However,
 building codes provide that if a room has a ceiling vent, that vent should
 close in the event of a fire to close a pathway for the fire to another
 area. Thus it is one object of this invention to provide a ceiling vent
 that will close in the event of a fire. An explosion may lead to the
 spread of fire. Thus, it is another object of this invention to provide a
 ceiling vent that will close in event of an explosion.

DETAILED DESCRIPTION OF THE INVENTION
 With reference to the drawings, the invention contains a duct pipe 7 that
 would be inserted in a hole in a ceiling. In the preferred embodiment, the
 duct pipe would be galvanized metal and cylindrical in shape. Its lower
 end would be secured to the bottom of the ceiling 20 by use of a retaining
 ring and flashing 12, and it would be secured to the top of the ceiling by
 means of spring clips 11 that press against the top of the ceiling. At the
 top of the vent, a metal bar 6, called the upper hanger, is attached to
 the duct pipe. Attached to the upper hanger by means of screws or rivets
 14 is a tube called the upper guide 5. Attached to the upper guide and
 passing through it horizontally is a metal sleeve 30. Placed within the
 metal sleeve and extending beyond it is a plastic fuse pin 8. The plastic
 fuse pin is made of a plastic material that will melt when air with a
 temperature indicating a fire in the room being ventilated passes through
 the vent. High Impact Polystyrene (H.I.P.S.) is an appropriate material
 for the fuse pin. Its maximum working use temperature is 74.degree. C.
 (165.degree. F.). Its soft temperature is in the range of 85.degree. C. to
 93.degree. C. (185-200.degree. F.) and its total melt temperature is
 121.degree. C. (250.degree. F.).
 Concentric with the upper guide 5 and with a slightly larger diameter is a
 second tube, the lower guide 15. The upper part of the lower guide is a
 series of stepped notches 34. A spring 9 is contained within the lower
 guide 15 and the upper guide 5. Attached to the top of the spring is an
 upper spring hook 36 that loops around the metal sleeve 30. Attached to
 the top of a retaining plug 2 is a lower spring hook 10, which loops
 around the bottom of the spring 9. Also in contact with the retaining plug
 is the inner surface of the lower guide 4. Attached to the bottom of the
 retaining plug is a hook 3. The vent also contains a damper plate 1, part
 of which contacts the bottom of the ceiling when closed and which is in
 contact with the outer surface of the lower guide 15 and the retaining
 plug 2. The vent may also have a horizontal stability bar 13 attached to
 the duct pipe 7 and containing a hole to allow passage of the lower guide.
 The fuse pin 8 engages the lowest notch of the lower guide when the spring
 is at rest and the damper is closed. The vent is opened or closed as
 described below. When the vent is closed, it can be opened by lowering and
 rotating hook 3. This causes the damper plate 1 and the lower guide 15 to
 be lowered and rotated. When the lower guide is lowered certain discrete
 distances, the fuse pin will engage a higher notch in the lower guide and
 the opening of the damper plate can be maintained. Four stepped notches on
 the lower guide will support three open positions and the closed position
 of the damper plated.
 Because the height of the plastic fuse pin 8 is not changed when the lower
 guide 4 is lowered, the position of the top of the spring 9 is not
 changed. However, the bottom of the spring is lowered when the lower guide
 is lowered; this puts the spring under tension. However, the spring cannot
 return to its rest position because the fuse pin engages a notch in the
 lower guide and prevents the lower guide from rising. To close the vent or
 to reduce the size of the opening through which air enters the vent, the
 hook is rotated and raised until the fuse pin engages the desired notch.
 If there is fire in a room being ventilated, the temperature of the air
 passing through the vent will increase until the temperature is sufficient
 to cause the fuse pin 8 to melt. When the fuse pin melts, it will
 disengage from the notch. The upper spring hook 36 is still hooked over
 the metal sleeve 30 to fix the elevation of the top of the spring.
 However, because nothing is engaged with a higher notch to keep the spring
 under tension, the spring will tend to resume its rest position. As the
 height of the top of the spring is fixed, the bottom of the spring will
 rise when it resumes its rest position causing the retaining plug 2, lower
 guide 15, and damper plate 1 to rise. When the spring has reached it rest
 position, the damper plate will have closed by contacting the bottom of
 the ceiling.
 The damper plate is not attached to the lower guide, but rather rests on a
 ledge 82 of the retaining plug 2. If there is an explosion in the room
 being ventilated, the resulting shock wave could raise the damper plate 1
 to slide up the lower guide and thereby close the vent. This mechanism
 could cause the vent to close before heat from the explosion would cause
 the fuse pin to melt.