Fast response sprinkler head

A fast response sprinkler head. The sprinkler head includes a frame having a base portion connected to a source of water under pressure and a pair of arms extended outwardly from the base and are connected at a junction. A cap normally encloses the outlet in the base and a lever assembly, which extends between the junction and the cap, holds the cap in the closed position. The lever assembly includes a pair of lever members, with one of the lever members being biased in a direction away from the other lever member. A fusible link assembly interconnects the lever members and includes a pair of thin metal sheets that are joined together by a layer of fusible metal or solder. Each sheet is formed with a recess in one side edge and the recesses face each other to define an opening which receives the lever member. The corners of each sheet are bent generally normal to the sheet to provide fins or tabs. The fins increase the rate of heat transfer to the fusible metal to cause rapid release of the lever assembly to open the outlet.

BACKGROUND OF THE INVENTION 
Automatic sprinkler heads, as used in commercial and industrial buidings, 
include a cast metal frame having a base that defines an outlet connected 
to the water piping system. The frame also includes a pair of arms that 
extend outwardly from the base and are connected together at a junction. 
The outlet in the base is normally enclosed by a cap, which is held in the 
closed position by a lever assembly, that extends between the cap and the 
junction. The lever assembly includes a pair of lever members, with one of 
the lever members being normally biased in a direction away from the 
other. 
In the conventional sprinkler head, a fusible link, including a fusible 
element or metal, retains the lever assembly in position to close off the 
outlet. On exposur to an elevated temperature, the fusible metal will 
melt, releasing the link and the lever assembly to open the outlet to the 
water line. 
The primary use in the past of automatic sprinkler systems has been for 
property protection in commercial and industrial applications, such as 
warehouses, stores, buildings and the like. With the recent increased use 
of sprinkler systems in hospitals, hotels, nursing homes and residences, 
where the prime object is to save human life as opposed to property 
protection, there is a demand for a faster response sprinkler head, 
meaning one that will release more quickly when exposed to elevated 
temperatures. 
U.S. Pat. No. 4,273,195, discloses a fast response sprinkler head, in which 
the fusible link that retains the lever assembly in the engaged position 
includes a pair of their copper sheets connected by a layer of solder. 
Each sheet has an opening to receive one of the lever members. The major 
portion of the fusible link of the aforementioned patent is located 
between the lever members in a location where the lever members tend to 
shield the central portion of the link. Because of this, a side edge of 
each sheet is formed with an angular wing which is disposed at an acute 
angle to the sheet and is designed to direct heated air onto the central 
portion of the fusible link. 
SUMMARY OF THE INVENTION 
The invention is directed to an improved fast response sprinkler head. In 
accordance with the invention, the fusible link assembly includes a pair 
of thin metal sheets, preferably formed of copper, which are joined 
together by a layer of fusible metal or solder. Each sheet has a generally 
C-shaped configuration with a recess along one edge. The sheets are 
positioned so that the recesses face each other and define an opening 
which receives the lever members of the lever assembly. The corners of 
each sheet are bent generally normal to the sheet to provide tabs or fins 
which increase the frontal area exposed to the heat of combustion, thereby 
increasing the rate of heat transfer to the fusible link and achieving a 
faster response time. 
By positioning the metal sheets of the fusible link assembly at an angle to 
the horizontal, a further increase in the surface area exposed to the 
upward flow of heated gas can be obtained. 
The sprinkler head of the invention has a very fast response achieved by 
the orientation of the fusible link assembly and the incorporation of bent 
tabs or fins. 
Other objects and advantages will appear in the course of the following 
description.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
The drawings illustrate an improved fast response sprinkler head which 
includes a cast metal frame 1 having a base portion 2 that includes a 
threaded outlet 3 which is adapted to be connected to a water piping 
system. Frame 1 also includes a pair of generally curved arms 4 which 
extend downwardly from base 2 and are connected at a juncture 5. 
Outlet 3 is normally enclosed by a cap 6 which is held in the closed 
position by a lever assembly 7. Lever assembly 7 is composed of a first 
lever member or strut 8 and a second lever member or spring 9. 
As best shown in FIG. 2, one end of strut 8 is engaged with a groove 10 
formed in cap 6, while the other end of strut 8 is in contact with the end 
12 of spring 9. As illustrated in FIG. 2, the tip of a projection 13 on 
juncture 5, is engaged with a groove in end 12 of spring 9 while the end 
of the strut 8 is engaged with a second groove in the end 12 of lever 
member 9 at a location which is offset from the tip of projection 13. Due 
to the offset position of the grooves in end 12, spring 9 will be biased 
outwardly away from strut 8, as shown in FIG. 2. 
A deflector 14 is mounted on the outer end of frame 1 and serves to deflect 
the water emerging from outlet 3 in the desired spray pattern., 
In accordance with the invention a fusible link assembly 15 maintains the 
lever members 8 and 9 in position to retain cap 6 in the closed condition. 
Assembly 15 is composed of a pair of sheets 16 and 17, preferably formed 
of copper or other metal having a high coefficient of thermal 
conductivity. Sheets 16 and 17 are in lapping relation and are joined 
together by a layer of a fusible metal or solder 18. 
As best shown in FIG. 3, sheet 16 is generally square in shape and one side 
edge is formed with a recess 19. The corners of sheet 16 are bent upwardly 
to form generally triangular tabs or fins 20, which are non-parallel and 
are located generally normal to the sheet 16 itself. 
Similarly, sheet 17 is also square in shape and one side edge is provided 
with a recess 21. Recesses 19 and 21 face each other and define an opening 
22, which receives the lever members 8 and 9, as shown in FIG. 4. 
The corners of sheet 17 are bent downwardly to form non-parallel tabs or 
fins 23, which are normal to sheet 17 and extend in the opposite direction 
from the tabs 20. When assembled, fins 20 on sheet 16 are aligned with 
corresponding fins 23 on sheet 17 to provide generally square flanges or 
surfaces that extend normal to sheets 16 and 17, as best shown in FIGS. 1 
and 2. As shown in the drawings, fins 20 and 23 each lie in a single 
plane. 
To provide increased resistance to shear force, the sheets 16 and 17 are 
provided with mating dimples or projections 25. As shown in FIG. 3, the 
fusible material or solder 18 extends along the entire interface between 
the sheets 16 and 17, including the mating dimples 25, so that the fusible 
metal will be subjected to tension stress, as opposed to shear stress. 
To prevent longitudinal movement of the lever members 8 and 9 relative to 
the sheets 16 and 17, the sheets are provided with prongs 26 at the base 
of the respective recesses 19 and 21 and the prongs, as shown in FIG. 4, 
are disposed in holes 27 in the respective lever members 8 and 9. 
The fins 20 and 23 are not intended to direct heated air across sheets 16 
and 17, but instead function to provide increased frontal area for 
exposure to the flowing heat of combustion to thereby increase the rate of 
heat transfer to the fusible metal 18. A further improvement in the rate 
of heat transfer can be achieved by positioning the sheets 16 and 17 at an 
angle of 10.degree. to 30.degree. with respect to the horizontal, as shown 
in FIG. 2. 
When the sprinkler head is exposed to the heat of combustion, the heat will 
flow upwardly along the lower sheet 17, as well as across the exposed fins 
20 and 23. Thus, the increased surface area provided by fins 20 and 23 
substantially improves the rate of heat transfer to the fusible metal 18, 
with the result that a faster response time is achieved. 
In the construction of the invention, the strut 8 and spring 9 are in close 
proximity within opening 22 and as a result the fusible metal layer 18 is 
located outwardly of the opening 22 in a position where the strut and 
spring will not shield the fusible layer from the flow of the heat of 
combustion. 
Various modes of carrying out the invention are contemplated as being 
within the scope of the following claims particularly pointing out and 
distinctly claiming the subject matter which is regarded as the invention.