Patent Application
20070246233
All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference
The present invention relates to fire safety devices, and more particularly to thermally actuated sprinklers commonly used in commercial and residential buildings.
Large numbers of thermally-actuated fire sprinklers are installed in structures every year. These sprinklers, generally installed in the structure's ceiling, are connected to a pressurized water supply and are intended to release the water into the room when the temperature in the room indicates that a fire or conflagration is taking place.
Multiple techniques have been used to actuator prior art fire sprinkler heads. Some prior art sprinkler valves bond two components together with alloys that melt at low temperatures. When heated above the melting temperature of the eutectic allow, the bond between the two components is released, and a control valve is permitted to open. This type of actuator is subject to failure as the solder ages and crystallizes, thereby weakening the bond.
A second type of prior art sprinkler valve uses a sealed glass tube nearly filled with a liquid that boils at a low temperature. As ambient temperature increases, the liquid boils, thereby raising the pressure inside the tube. At a high enough temperature the tube ruptures, permitting the sprinkler valve to open. Premature failure may occur, however, if the sprinkler head is subjected to mechanical shock and the tube is cracked.
Yet other prior art sprinkler valves incorporate shape memory components that change shape when a transition temperature is reached to actuate the sprinkler valve. Some such thermally actuated valves are described in U.S. Pat. No. 4,176,719; U.S. Pat. No. 4,549,717; U.S. Pat. No. 4,596,483; U.S. Pat. No. 4,706,758; U.S. Pat. No. 4,848,388; U.S. Pat. No. 5,494,113; U.S. Pat. No. 5,622,225; and U.S. Pat. No. 6,073,700.
False triggering of sprinkler heads can cause damage that is expensive to repair and contributes to the cost of fire insurance. Thermally-actuated fire safety devices must meet strict codes.
The invention relates to a thermally actuated valve assembly with a thermal actuator made at least in part of a shape memory material and methods of operation of such valve assemblies. In one aspect of the invention, the invention provides a thermally actuated valve assembly comprising: a source of pressurized fluid, the source having an outlet; a valve at the outlet; a strut maintaining the valve closed against force applied by the pressurized fluid; and a thermal actuator formed at least in part from shape memory material, the thermal actuator being movable from a first shape permitting the strut to maintain the valve closed and a second shape applying force to move the strut, thereby permitting the pressurized fluid to open the valve. In some embodiments, the strut is collapsible and may be adapted to spring away from the valve when the thermal actuator is in the second shape.
In some embodiments, the strut has first and second support members attached by a hinge. The strut may also have a stay preventing the support members from bending about the hinge until a threshold bending force has been applied to the strut by the thermal actuator.
In some embodiments, the thermal actuator has a heat treated movable member formed at least in part from shape memory material, the movable member having a bent shape and a thermally actuated memory shape that is straighter than the bent shape, the movable member changing from the bent shape to the memory shape at a transition temperature. In some embodiments, the movable member includes a wire which may be longer in the memory shape than in the bent shape. In some embodiments the movable member also includes a contact member adapted to apply force to the strut when the movable member changes from the bent shape to the memory shape.
Another aspect of the invention provides a method of actuating a valve at an outlet of a pressurized fluid source, with the method including the following steps: maintaining a strut at the outlet to maintain the valve in a closed position preventing fluid to flow from the source through the outlet; heating a thermal actuator to a transition temperature; changing the shape of the thermal actuator from a first shape to a second shape in response to applying force to the strut; and moving the strut in response to the force, thereby permitting the pressurized fluid to open the valve.
In some embodiments, the thermal actuator is formed at least in part of shape memory material, the step of changing the shape of the thermal actuator including the step of creating a crystalline phase change in the shape memory material. In some embodiments, the first shape is longer than the second shape, and in some embodiments the second shape is straighter than the first shape.
In some embodiments, the moving step includes the step of collapsing the strut in response to the force and may include the further step of springing the strut away from the valve. In some embodiments, the strut comprises a hinge, and the moving step includes the step of bending the strut about the hinge. The strut may also include a stay resisting bending of the hinge, in which case the moving step includes the step of overcoming the stay's resistance.
In some embodiments, the thermal actuator includes a contact member, with the contact member applying force to the strut when the thermal actuator changes from the first shape to the second shape.
The novel features of the invention are set forth with particularity in the claims that follow. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:
The valve within the sprinkler head 10 is maintained in its closed state by a strut 22, as shown in
Also shown in
Shape memory element 42 may be formed from a wire. Prior to assembly, the wire 42 is heat treated to a length approximating the straight length of strut 22 (i.e., the length shown in
Strut 22 may be fabricated (e.g., by stamping) of a low mass metal or plastic so that is will not be affected by mechanical shock. An adjustment screw may be provided in the diverter hub 32 to adjust the initial compressive force on strut 22. The contact member 44 may be a plastic or glass fulcrum shaped so as to be held between the strut and the shape memory element, and glue or plastic may be placed on the contact member to hold it in place against vibration. A stay, such as a patch of frangible material, may be placed over the hinge such that the frangible material must be fractured before the hinge may be displaced significantly.
In some embodiments, the thermal actuator and strut can be contained in a space of about one inch by one-quarter inch by 1/16 inch, thereby fitting into existing commercial sprinkler heads. Other dimensions of the strut and thermal actuator can be computed as follows: Assuming a contraction of 3% as the shape memory element is heated through its transition temperature, if the strut is 2 cm long and the contact member or fulcrum is 2.5 mm in diameter, the linear movement of the shape memory element and contact member toward the strut can be as much as 2 mm.
This application claims the benefit under 35 U.S.C. § 119 of U.S. Provisional Patent Application No. 60/788,866, filed Apr. 4, 2006, which is incorporated by reference as if fully set forth herein.
| Number | Date | Country | |
|---|---|---|---|
| 60788866 | Apr 2006 | US |
