Patent Application
20080264405
The invention relates to a fire damper, and more particularly, to a fire damper having a fusible link, and a normally open, thermally insulated rotating louver connected to an external biasing member.
Fire dampers are used to seal an air handling system from a space experiencing a fire, thereby preventing any backflow of oxygen to the space through the ductwork. Sealing the ductwork deprives the fire of oxygen.
Fire dampers may generally comprise louvers, but, such louvers comprise simple metallic sheets. Such construction adversely affects the period of time that the louver, and thereby the fire damper, can resist failure caused by hot gases from a fire.
Representative of the art is U.S. Pat. No. 4,559,867 to VanBecelaere (1985) which discloses a transversely circular fire damper having a butterfly type blade operated by a jack shaft spaced longitudinally of the housing from the blade axle. Linkage including an “over center” stop rotates the blade in one direction by operation of a motor coupled with the shaft. A clutch in the form of a pair of relatively telescoped members secured together with entectic solder is connected with the jack shaft and the motor so that the shaft is released from the motor when the ambient temperature reaches a point high enough to melt the solder. The jack shaft is spring biased in a direction to close the damper blade under such condition.
What is needed is a fire damper having a fusible link, and a normally open, thermally insulated rotating louver connected to an external biasing member. The present invention meets this need.
The primary aspect of the invention is to provide a fire damper having a fusible link, and a normally open, thermally insulated rotating louver connected to an external biasing member.
Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.
The invention comprises a fire damper comprising a housing, a louver member rotationally engaged within the housing, the louver member having a substantially gas tight seal with the housing when the louver member is in a closed position, a biasing member disposed outside of the housing and engaged with the louver member for moving the louver member from an open position and holding the louver member in the closed position, a temperature sensitive member releasably connected to the louver member, the temperature sensitive member for releasing the louver member from the open position at a predetermined temperature, and the louver member further comprising insulation material to control heat transfer through the louver member for a predetermined period of time.
The accompanying drawings, which are incorporated in and form a part of the specification, illustrate preferred embodiments of the present invention, and together with a description, serve to explain the principles of the invention.
a) is a front detail of the louver member.
b) is a side view of the louver member.
Disposed within housing 10 is louver member 20. Louver member 20 is mounted to a shaft 21. Shaft 21 rotates within housing 10. Rotation of shaft 21 allows louver member 20 to pivot between an open position and a closed position.
Member 60 is attached to louver member 20 and is used to connect louver member 20 to temperature sensitive connector 31, see
Louver member 20 is shown in the closed position in
Biasing member 40 is engaged between shaft 21 and housing 10. Biasing member 40 biases louver member 20 toward the closed position as is shown in
Duct portion 200 is a transition piece that is used to connect fire damper 10 to other system ductwork in a building space. Duct portion 200 is connected at end 201 to the housing 10 and at end 202 to a room or HVAC system (not shown). End 201 has a circular form for connecting to the fire damper. End 202 may be rectangular, circular, oval or any other required shape to connect to an HVAC system (not shown), for example thought a room ceiling. Crimps 13 in housing 10 facilitate engagement of housing 10 with end 201.
Disposed between louver member 20 and portion 30 is the temperature sensitive connector 31. Louver member 20 is held in the normally open position by the temperature sensitive connector 31 which is connected to portion 30. Portion 30 is connected to housing 10. Temperature sensitive connector 31 is also known as a fusible link.
Connector 31 is known in the art. Connector 31 is designed to melt at a predetermined temperature, for example approximately 165° F. The range may extend to any known in the art, for example, up to approximately 286° F. The connector 31 is used to hold louver member 20 open during normal operation. However, in the case of a high temperature gas or fire in the room or duct to which the damper is connected, the fusible link melts at the predetermined temperature. When it melts biasing member 40 immediately closes louver member 20 to prevent passage of hot gases through the fire damper.
a) is a front detail of the louver member. Louver member 20 is connected to shaft 21. Louver member 20 comprises a first portion 23 and a second portion 24. First portion 23 and second portion 24 are arranged in parallel to form a sandwich with insulation material 50 disposed between them. Fasteners 22 are used to hold portions 23, 24 together. Fasteners 22 may comprise screws, pins, rivets, or spot welds.
b) is a side view of the louver member. Portions 23 and 24 form parallel layers. Portions 23 and 24 each comprise metal, for example, galvanized steel. Disposed between portion 23 and 24 is insulation material 50. Insulation material 50 is intended to provide a time dependent barrier to high temperatures that are imposed upon louver member 20 during a fire event. The insulation material resists penetration of the high temperatures and combustion gases into the ductwork downstream of the fire damper louver 20. This also prevents backflow of oxygen to a fire burning upstream of the fire damper.
By way of example, the fire damper prevents flow of high temperature gases through the closed fire damper louver member for at least 60 minutes when exposed to a gas temperature of approximately 950° C.
Insulation material 50 comprises either fiberglass, mineral wool, ceramic or other suitable material known in the art. For example, the insulation material may include ceramic fiber material such as Fiberfrax™ from Sohio Carborundum.
The insulation material thickness in the present embodiment is approximately 3 mm, although thicknesses in excess of 7 mm may be used with good results. The thickness of the insulation material may be adjusted depending upon the operational requirements of the fire damper.
The insulation material also acts as a seal 51 between the edge of louver member 20 and the housing 10, thereby preventing hot gas flow around the louver member 20 when in the closed position.
The dimensions provided in this specification are only examples and are not intended to limit the size or range which may be used in the invention.
Although a form of the invention has been described herein, it will be obvious to those skilled in the art that variations may be made in the construction and relation of parts without departing from the spirit and scope of the invention described herein.
