US2418765A - Sprinkler unit - Google Patents

Description

April 8, 1947. FREEMAN 2,418,765

SPRINKLER UNIT Filed Jan. 4, 1945 I N VEN TOR.

Patented Apr. 8, 1947 SPRINKLER UNIT Howard G. Freeman, Worcester, Mass., assignor to Rockwood Sprinkler Company of Massachusetts, Worcester, Mass, a corporation of Massachusetts Application January 4, 1945,'Serial No. 571,219

' .6 Claims. 1

The present invention. relates to sprinkler units for fire extinguishing systems.

The usual sprinkler head for use in a sprinkler system uses yokes or arms extending from the base of the head to hold the sealing cap. This form of head is not satisfactory in many cases. For example, for use with a fog generating nozzle of the type shown in my Patent No. 2,302,021, granted November 17, 1942, the arms create a shadow in the fog pattern and also act as collecting surfaces on which the water particles coalesce to form large drops which are highly objectionable in fightng many types of fires. In any case, the standard typeof head is unsightly and this has proved to be a deterrent to the use of sprinkler systems in places where appearance is important.

The object of the present invention is to provide a sprinkler unit in which the cap is tightly sealed. under inactive conditions without the use of obtruding arms or yokes, but in which the sealing mechanism is entirely released from the device under active conditions so that the spray pattern is completely unobstructed. A secondary object is to provide a unit of pleasing appearance.

Various types of sprinkler units, without arms or yokes, have been proposed but, so far as I am aware, none of these has proved satisfactory, either because the required sealing pressure could not be obtained or because the fusible mechanism would not be thrown clear of the unit when the head is called into operation. It will be understood that all parts of the mechanism must remove themselves from the vicinity of the head when the unit is required to operate and this requirement is particularly important in the case of fog generating units where obstruction of the spray might be attend-ed with dangerous results.

With the above and other objects in view as will hereinafter appear, the invention comprises a head having a number of mutually supporting links or struts, each provided with a fusible member, the several struts being mounted in such a manner that release of any one of them results in the release of all. The struts are used to support a holding member engaging with the cap for sealing the head and this member is also constructed to free itself from the unit when the struts are released. The invention also provides a high sealing pressure, while limiting the stresses .on the fusible members to safe values.

tional elevation of the head on line 2--2 of Fig, 1; V

Fig. 3 is a side view of one of the strutsand Fig. 4 is a detailed view illustrating the forces applied to the strut.

The sprinkler head shown in the drawings comprises a base 6 having the usual threaded pipe coupling 8 for attachment to the system. s

The base is provided with a shell or canopy [ll having a cylindrical sidewall l2. The top of the sidewall has a number of bosses l4 extended inwardly for a slight distance. The bosses are uniformly spaced and, in the illustrated form of the invention, are three in number.

A nozzle or spray member I6 is secured within the base. The member I6 is here illustrated as a nozzle having orifices of the type described in my above mentioned patent to produce a fine fog pattern by internally impinging streams of water. The nozzle is normally sealed by a dome-shaped cap or closure l8 which closes against finished portion of the base member surrounding the nozzle l6.

The cap is held in place by a holding member 20 having a number of outwardly extending legs 22. The number of legs may be two or more but preferably the unit is of tripod form, that is, of three legs, for reasons to be hereinafter explained. Sealing pressure is applied to the cap by means of adjustable central screw 24 by which the pressure may be adjusted to the desiredvalua, As shown in Fig. 2 each leg 22 is curved downwardly to conform to the general dome shape of the cap and at its end is provided with an upwardly extending portion 26 having a rounded point.

The holding member 20 is retained in position by means of a number of struts indicated generally at 28. The struts are equal in number to the legs 22 (three in the illustrated device), whereby each is engaged by one of the portions 26 of the holding member. Each strut comprises an areshaped link received within the shell and conforming to the curvature thereof. Near one end each link extends outwardly and i provided with an upward projection 36 toenga-ge under the boss M of the shell. From the projection 30a short portion 32 of the strut extends in one direction to overlie the end of the next adjacent strut, and a longer portion 34 extends in the other direction to underlie the next strut. As indicated in the side view of Fig. 3, the long portion 34 of each strut is recessed at the bottom to receive an upper plate 36, secured thereto by solder 38 to form the fusible part of the assembly. The upper plate 36 slightly overhangs the bottom of the strut and is formed at its end with a bearing point to engage the end of the next adjacent strut. The

points 26 of the tripod engage under the struts at points close to the bosses M. The relations between the length of each strut, its bearing point 30 and its point of connection to the tripod leg, are important and will presently be described in detail. In general, however, it will be noted that because of the sealing force applied to, the. cap I8, the legs of the tripod are stressed upwardly and these stresses are communicated to the individual struts at the points of contact therewith. The struts are mutually supported, that is to say, each strut is held in place not only by the bearing 39 but by the struts adjacent thereto. Therefore, if any strut is released by melting of its fusible portion, all parts of the assembly are without support and are thrown clear of the head. This clearing action is made positive by thespringiness of the arms 22 which are normally under considerable bending stress. It will be noted from Fig. 1 that the arrangement of parts is such that there is no opportunityfor any part to. catch .on any other part and the release is thus reliably accomplished.

' It will be understoodthatthe term upward, "over and under refer to relation of the parts in Fig. 3, which show the positions during assembly. The installed head is usually inverted (or sometimes mounted as shown in Fig. 2).

- In order to describe the necessary dimensional relations for stability of the unit, attention may be directed to theforces acting on a single one of the struts Fig. 4. The point at which the tripod leg engages it isdesignated A, thepoint at which the long portion underlies the next strut is designated B, the point ofengagement of the short portion232 with the adjacent strut at the other end is designatedB, and'thepointof engagement with the boss zl4;is.designated C.

. :Let F=t-he force. at thecenter of the unit. This is the force necessary to hold the head, sealed against any expected pressure and may be of the order of 1,000 pounds.

Let

FA=the force on the strut at the point A Fs=the force on, the strutat each of the points B, B. a=the distance between C and B. b=the perpendicular distance from B tothe line joining C and B. c=component of distance between C and A measured along CB, d=offset between A and measured perpendicular to CB, e=component of distancebetweenB' and C in direction-of'CB.

ThenFAis equal to Fdivided'by the number of armslZ. In this case of a tripod FA=,1/3F. For stability it is necessary that all moments acting on the strut at point C shall be balanced. Considering moments about the axisCB,

from which it follows that there will be no unbalanced forces or moments tending to separate the parts, if

Thejterm a-Ferepresents the total length" of the strut as measured along the line BC. With this relation of dimensions the device has no tendency 4 to come apart, even if dropped or roughly handled.

The foregoing relation is theoretical and is based on a true point contact between parts. Since the actual contact is over a small surface and there is friction at the contact surfaces, the device will be stable even with some deviation from the exact relation. If the deviation is sufficient to overcome the friction forces, the unit cannot be assembled, or if assembled, may come apart upon being jarred.

It is preferable to make the dimension 0 small relative to a+e, that is, the bearing point A is much closer to C than to the remote end of the strut. In the structure shown in the drawings, 0 is less than one-tenth the total length, and d bears the same relation to 2). Thus the force F]; is less than one-tenth the force FA. If th central force F is 1000 lbs., FA is 333 lbs. and Fe at the end of the strut is only about 30 lbs. From reference to Fig. 3 it will be seen that, owing to the sli ht overhang of the point 46 at the end of the strut, the force on the soldered joint is still smaller, namely, in the neighborhood of 5 lbs., which such a joint is well able to withstand over a long inactive period. Nevertheless, upon fusing of the solder there is a sufiicient force to cause the part 36 to spring away from the'main part of the strut. As heretofore stated, when any strut fuses, it removes the support for the other struts, and thus frees'the tripod and sealing cap.

The holding unit 28 may have any number of legs, two or more, radiating at equal angles from the center. With only two legs, however, the stresses on the legs and struts are correspondingly increased. If four or more legs are used, the stresses may be further reduced, but closer tolerances may be required to insure equal division of stresses to the several struts. With three legs, the stresses carried by the individual legs and struts are reduced to satisfactory values for most conditions, and this form has the advantage that, since the three tripod points determine a plane, extreme precision in manufacture is not necessary, and the struts will'be loaded With substantial uniformity even though the parts are constructed with reasonable manufacturing tolerances.

It Will be understood that although the unit is shown as embodied in device having a special type of nozzle, it may be applied to other forms of spray or sprinkler devices. In any case, the height of the sidewall l2 should be small enough to insure it does not interfere with the spray pattern.

Having thus described the invention, I claim:

1. A sprinkler head having a closure, a supporting base, a plurality of struts arranged about the closure in successive overlying and mutually supporting relationship, supporting means on the base overlying and engaging the individual struts, and a'pressure member engaging the closure and having legs underlying and engaging the individual struts, said supporting means retaining the struts in assembled relationship against the pressure exerted thereon by the pressure member,

ing portions underlying and engaging the individual struts, the struts being retained by said points of support against the pressure exerted thereon by the pressure member.

3. A sprinkler head having a closure, a supporting base, a plurality of struts arranged about the closure, the base having bosses overlying the individual struts, the several struts being supported by one another and by said bosses whereby release of any strut removes support for all of the struts, and a pressure member engaging the closure and having ends underlying and engaging the struts, each strut having a portion which is severable at high temperature.

4. A sprinkler head having a closure, a supporting base, a, plurality of struts arranged about the closure in successive overlying and mutually supporting relationship, means on the base for overlying and engaging the individual struts, a pressure member engaging the closure and having legs underlying and engaging the individual struts near one end thereof, each strut having a fusible portion near the end remote from the point of engagement of the pressure member.

5. A sprinkler head having a closure, a supporting base, a plurality of struts arranged about the closure, each strut having a single point of support by the base and the several struts having successive overlying end portions in mutually 6 supporting relationship, a fusible portion near the end of each strut, and a pressure member engaging the closure and underlying and engaging each individual strut near the end remote from the fusible portion and at such a position that moments about the point of support on the 1 base are in substantial balance, the struts being retained by said points of support against the pressure exerted by the pressure member.

f 6. A sprinkler head having a closure, a supporting base, three arc-shaped struts arranged -about the closure, each having a fusible portion near one end, supporting means on the base overlying each strut near the other end, the ends of struts being in overlying relationship, a tripod member having a central portion engaging the closure and legs underlying and engaging the struts near said supporting means, and at such positions that all moments on any strut about said supporting means are in substantial balance.

HOWARD G. FREEMAN.

REFERENCES CITED UNITED STATES PATENTS Name Date Rowley June 2, 1931 Number

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