US 3388747 A
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June 18, 1968 R. M. HODNETT 3,388,747
FUSIBLE APPARATUS FOR PROTECTING AUTOMATIC SPRINKLERS Filed April 8, 1966 INVENTOR. ROBERT M. HODNETT ATTORNEY United States Patent 3,388,747 FUSKBLE APPARATUS FOR PROTECTING AUTOMATIC SPRINKLERS Robert M. Hodnett, Providence, R.I., assignor to Grinnell Corporation, Providence, R.I., a corporation of Delaware Filed Apr. 8, 1966, Ser. No. 541,275 1 Claim. (Cl. 169-39) ABSTRACT OF THE DISCLOSURE For an upright fire protection sprinkler head installed in a clean room a fusible solder cover which encloses the sprinkler and has its open end fric.ionally engaged on a base, which forms with this base exterior surfaces relatively free of crevices and therefore easily wiped off during periodic cleanings and which melts before the sprinkler head is actuated by the heat from a fire.
In recent years, as a result of increased requirements for exacting precision, the assembling of complex components, such as are used in the space program and pharmaceutical houses, has been carried out in superclean and sterile rooms, often referred to as clean rooms.
To maintain a superclean atmosphere requires frequent, periodic, sterilization by wiping all of the surfaces in the room. To date most of the owners of such rooms have waived the placing of fire protection systems containing automatic sprinklers in the rooms because the heads contain so many irregular and varied surfaces and crevices that to clean the large number of heads normally required in such a room is an onerous and costly job.
In my copending application S.N. 529,731, filed Feb. 24, 1966, I have described a means by which an automatic sprinkler system containing pendent sprinklers may be made highly suitable for use in clean rooms. Such pendent sprinkler systems are the type that are prevalent in a majority of clean rooms. Occasionally, however, a clean room may be located in a building in such a manner that the only suitable automatic sprinkler protection which may be desired or obtained is one utilizing upright sprinkler heads. Generally, such a system cannot be concealed and therefore the clean room operator, in addition to cleaning the sprinklers, must put up with the added burden of cleaning the exposed piping of such a system. Under normal circumstances the heads would be considerably more difiicult to clean than the piping. However, by placing suitable smooth caps over the heads this tedious cleaning procedure can be greatly simlified. The present invention makes it possible to cover each head with such a cap; one that will fuse and be removed, so as not to interfere with the proper actuation of the sprinkler in the event of a fire.
Unlike the construction used to protect pendent sprinklers the present invention cannot rely on the force of gravity alone to remove any molten solder from the operative area of the sprinkler. Thus, to prevent any clogging of the sprinkler or its deflector I have utilized the novel structure hereafter described. In addition, this novel structure will also overcome the problems relating to the prior art devices as described in my aforementioned copending application S.N. 529,731.
Other advantages of the invention will become apparent by reference to the following description and accompanying drawing which describe and show, for illustrative purposes only, a preferred embodiment of the invention.
In the drawing:
FIG. 1 is a side elevation view, partly in section, illustrating a typical upright sprinkler installation with my improved base plate and protective cap combination;
FIG. 2 is a perspective view of the combination of FIG. 1 with a portion cut away for clarity of details;
FIG. 3 is an exploded perspective view of the combination of FIG. 2.
Referring now in greater detail to the drawing, 10 generally indicates a fusible automatic sprinkler mounted on an exposed water pipe 12. The mounting is accomplished normally by placing a T-fitting 14 in the pipe 12. Each sprinkler head has a threaded butt portion 16 which extends into the threaded opening 18 in the fitting 14.
About the butt portion 16 is a substantially flat circular base plate 20 which has an outstanding peripheral ledge 22 extending about the outer circumference 21 of-the plate. For reasons which will be explained hereafterthe outer circumference 21 is shown to be threaded. Through the center of the plate is a threaded hole 23 for engaging the threaded butt portion 16.
Each sprinkler 10 is provided with a thermally responsive element and a closure construction 25 and 26 respectively, also, a deflector 15 to properly disperse the discharge water emanating from the sprinkler. The sprinkler 10 illustrated herein is sold under the name Duraspeed. However, other types of sprinklers may be used.
A protective closed cuplike cap 30 is placed over the sprinkler 10 and plate '20 with the rim portion 32 of the cap resting on the ledge 22. A rubber or rubber-like gasket ring 34 is preferably interposed between the rim portion 32 and the threaded circumference 21 of the plate to hold the cap in place by frictional engagement. The circumference is threaded to give increased frictional holding power and thus prevent loss of the gasket ring should the cap 30 be removed. This increased frictional holding power can also be achieved by knurling or similar scoring. In fact, under some circumstances it may be desirable to eliminate the gasket ring and construct the plate and cap so that the cap is held in direct frictional engagement with the circumference 21. This would be particularly true where the sprinkler and cap combination would be located in an atmosphere of constant high ambient temperature which might tend to make a gasket ring dry and brittle.
The protective cap 30 is composed of a fusible solder preferably cast to a uniform thickness. The outer surface of the cap is normally polished to a smooth finish to enhance its appearance and the ease with which it can be wiped clean.
Each entire sprinkler combination is assembled by first fastening the pipe 12 into a suitable fitting 14, making sure that the threaded opening 18 in the fitting is preferably oriented upwardly. The butt portion 16 of the sprinkler is then threaded through the opening 23 in plate 20 and into the threaded opening 18. It should be noted that the illustrated plate 20 contains a central depression 27 adjacent the hole 23. This is to provide sufiicient clearance for a wrench so that a good purchase will be obtained on the base of the sprinkler when tightening it into the fitting 14.
The plate 20 is then threaded downwardly into engagement with the top of the fitting 14.
At this time the gasket 34 is placed over the plate 20 to rest on ledge 22. and firmly engage the threaded circumference 21. The cap 30 is then placed over the gasket 34 so that the two are in frictional engagement, and the rim 32 rests on ledge 22.
As has been stated, the cap is composed of cast solder of a generally uniform thickness. A thickness of A has been found suitable. Unlike the cap described in my aforementioned copending application it has been found preferably in the present instance to use a solder which has a melting point lower than the rating of the sprinkler head which it covers. For example, a solder cap suitable for use with a F. or a F. rated head is A solder containing: Bismuth-44.47%; lead22.6%; tin-8.3%; cadmium-5.3%; and indium-19.1% would have a 117 melting point. Naturally, a higher rated head could use a cap having a higher melting point solder. One reason for this distinction is that an upright sprinkler with its cap will have more exposed surface and be subject to a greater heat soaking action because of the opportunity available to the heat to surround the upright construction. Thus, the sprinkler within the cap will generally be subject to a similar heat buildup at the same rate as the cap. If the protected sprinkler were rated at a temperature lower than the cap it is likely that the sprinkler would go off before the cap melted under most fire conditions. This is not normally true of the pendent sprinkler construction as is brought out in my copending application referred to above.
In operation, when subjected to heat from a fire the cap will melt at a predetermined temperature. Generally this melting action will be in the form of a general collapse of the solder about the sprinkler. Normally, as the temperature continues to rise most of the molten solder will run 01? the deflector 15 and plate 20'. It is to be expected, however, that some solder may remain on these parts. Ultimately, when the temperature reaches a sufficiently high point the closure construction 25, 26 will be actuated, opening the sprinkler to water flow. Should any solder be located so that it would obstruct the normal Water pattern the water will sweep this solder out of its path and be dispersed as the sprinkler design requires. After a fire the entire cap and :plate combination is replaced when the sprinkler is replaced.
Occasionally, either in the course of cleaning or merely by carrying a large object nearby, the cap 30 may be knocked loose from its engagement with gasket 34 and ledge 22. Replacement is simple; merely requiring that the cap be placed into engagement with ledge 22 and frictional engagement with gasket 34.
It is thus clearly seen that the present construction assures that under the influence of a fire the proper sequence of cap removal and sprinkler actuation to extinguish the fire will occur. This permits the use of sprinklers where they normally would not be used.
The present disclosure has been made by way of example and it is understood that changes in details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as claimed below.
It is intended that suchterms of reference as upper, lower, downwardly, etc., in the claims below are intended merely as terms to relate portions of the claimed combination with one another and not as terms of limitation as to the orientation of the combination.
1. A combination comprising:
(I) a substantially horizontal water supply pipe,
(II) a'fire extinguishing sprinkler which:
(A) has abutt portion joined to said pipe,
(B) extends upwardly from said pi e,
(C) has a predetermined temperature rating for actuation,
(III) a base plate which:
(A) is between said pipe and said sprinkler,
(B) has a first portion of its periphery provided with friction amplifying means,
' (C) has a second portion of its periphery provided with a circumferential flange which:
(1) is adjacent said first portion, (2) projects outward beyond said friction amplifying means, (IV) a fusible cap which:
(A) is substantially cylindrical,
(B) has a substantially uniform thickness,
(C) has a closed upper end,
(D) has an open lower end which:
(1) embraces said friction amplifying means, (2) rests on said flange,
(E) is composed of a solder which has a melting temperature less than said predetermined temperature rating.
References Cited UNITED STATES PATENTS 1,230,469 6/1917 Esty 16937 1,432,386 10/1922 Curney 169--37 2,531,790 11/1950 Rowley 16938 2,890,758 6/1959 Pfalzgrafi et al. 169--37 3,130,790- 4/1964 Hodgman 169-40 3,178,879 4/1965 Nardin 277187 X ALLEN N. KNOWLES, Primary Examiner.
M. HENSON WOOD, ]R., Examiner. M. MAR, Assistant Examiner.