US3061016A

US3061016A - Fusible link

Info

Publication number: US3061016A
Application number: US859413A
Authority: US
Inventors: Jr Willis K Hodgman
Original assignee: HODGMAN Manufacturing CO Inc
Current assignee: HODGMAN Manufacturing CO Inc
Priority date: 1959-12-14
Filing date: 1959-12-14
Publication date: 1962-10-30
Anticipated expiration: 1979-10-30

Description

Oct. 30, 1962 w, HQDGMAN, JR 3,061,016

FUSIBLE LINK Filed Dec. 14. 1959 IIIIIIJIIIIII I \\\\W||Ill la is .lllll 7/1. W

FIG. 2

' INVENTOR.

YWILLIS K.HODGMAN JR.

611-14. 5W v M ATTORNEYS United States Patent 3,961,016 FUSIBLE LINK Willis K. Hodgman, Jr., Taunton, Mass, assignor to Hodgman Manufacturing Co., Inc., Taunton, Mass., a corporation of Massachusetts Filed Dec. 14, 1959, Ser. No. 859,413 1 Claim. (Cl. 169-42) This invention relates to improvements in fusible links used in automatic sprinklers for extinguishing fires, or in other devices wherein it is desirable to hold certain parts of the mechanism to which they are applied in assembled condition until a predetermined degree of temperature exists in the vicinity of the apparatus and melts the solder uniting the parts of the links.

The objects of the invention are to provide a fusible link of superior efliciency as to both its holding and releasing functions.

I attain these objects, in a fusible link of the three piece type embodying the principle of the invention, by employing two opposed plates having relatively shoal transverse channels, substantially rectangular in cross section, which provide a chamber between the plates which is occupied by a fulcrum-block located half and half in each of the plates. The sides of the channels are made with the edges bevelled or rounded and may have rounded fillets where they join the bottoms of the channels. These radii are sufliciently small so that a straight portion is left on both sides of the channels, these straight portions being substantially perpendicular to the common plane of the opposed plates. The fulcrum-block is substantially rectangular in cross-section and also has bevelled or rounded edges, the radii of which do not have a common meeting point.

In order that the principle of the invention may be readily understood, I have disclosed a single type or embodiment thereof in the accompanying drawing, in which:

FIG. 1 is a side elevation of my link;

FIG. 2, a vertical section on line 22 of FIG. 1; and

FIG. 3 is a magnified view of the central portion of FIG. 2.

Similar numerals refer to similar parts throughout the several views.

My fusible link, as shown in the drawing, is of the three piece type and consists of

duplicate plates

4 and 5, a fulcrum-block 6 and a fusible solder which melts at a predetermined degree of heat. The solder is applied between the opposed surfaces of the parts of the link in the usual manner but is not shown in the drawing.

Each of the plates is provided, near its outer end, with an aperture 7 to receive one of the parts to be held in assembled condition, shown in the drawing as the end of one of the levers 8 or 9 (shown in FIG. 2, only) of a usual type of automatic sprinkler (not shown).

The inside face of each plate about midway of its length is provided with a transverse channel 10, of an approximately rectangular cross section with the flat parts of its sides perpendicular or nearly perpendicular to the face of the plate. The edges of these channels are bevelled or rounded as shown at 4a and a and may have rounded fillets where the sides join the bottom of the channel. In the drawings, these latter corners are shown, however, as perpendicular.

The fulcrum-block 6 is of slightly less width over all than the width of each channel 10 thus being free to tilt and pry the

plates

4 and 5 apart when the solder melts, and has rounded corner edges as shown at 6a. The thickness of the fulcrum-block is twice the depth of each channel so it is normally located half and half in the channels. The rounded or bevelled edges 6a of the fulcrumblock are relatively short and leave opposed flat surfaces, indicated at 11 in FIG. 3, bearing against each other at definitely predetermined distances from the plane of the flat abuting inner surfaces of the link plates. The object of this construction is to provide a definite turning moment or tilting to the fulcrum-block since the bearing surfaces of the fulcrum-block edges make contact with the adjacent sides of the channels in the link plates on opposite sides of the plane of the inside surfaces of the link plates.

The resulting tendency of the link plates to be thrown apart when the solder melts is in the ratio of between the limit-s 5 to l and 10 to 1. That is, if a pressure equal to 1 unit is imposed on the assembled unsoldered link to hold the plates together, it takes a longitudinal pull applied at the apertures 7 of from 5 to 10 units to rock the fulcrum-block thereby throwing the link plates apart.

When the link is assembled the channels in the plates overlap and the fulcrum-block is mounted in that portion of the chamber formed by the overlapped portions of the channels. The fulcrum-block 6, it will be noted, is symmetrical with respect to a plane extending midway the thickness of the block. Hence the fulcrum-block may be placed in position with either edge up or down and with either longer face against the bottom of either channel. The fulcrum-block is thus reversible both edgewise and endwise. This is of material advantage in assuring the correct assembly of the link because it is impossible by reason of this symmetrical form of the fulcrum-block to place it in the wrong position.

In addition, it will be noted that the radii of the

corner edges

4a and 5a of the channels 10 are easily controlled to close tolerances and that their contour permits long wear for stamping dies employed in fabricating them. Thus, since it is the distance from the plane of abutment between the

plates

4 and 5 to the point of contact with the fulcrum-block 6 which determines the wedging apart leverage of the link, and since this distance is determined by these radii, this exact control feature adds to the desirability of using this construction set forth herein. The

edges

4a and 5a need not be round but can be bevelled or faired and I shall use the term truncated in the claim to define any such equivalents generically.

It will also be noted that rounding the corner edges 6a of the fulcrum-block 6, permits a free tilting of the block 6 which would otherwise be hindered by friction, surface tension and/ or a suction effect of the liquid solder if the corner edges 6a were sharp.

With the link assembled and the parts soldered together, the longitudinal pull applied at apertures 7 is taken mostly by the fulcrum-block thereby producing a link of great holding power until the solder is melted or fused by heat. When this takes place, the fulcrum-block tilts and insures the immediate separation of the plates so that the link falls apart at once.

Having thus described one illustrative embodiment of my invention, I desire it to be understood that although specific terms are employed, they are used in a generic and descriptive sense and not for purposes of limitation, the scope of the invention being set forth in the following claim.

I claim:

In a fusible link having identical link plates disposed in assembled condition in face to face relationship and sealed together by a fusible material; a substantially rectangular transverse channel formed in each said plate, said channels being opposed to each other when said plates are in assembled condition; each said channel having a top wall and a bottom wall, each said wall being normal to the face of said plate, and a side wall parallel to said face of said plate joining said top wall and said bottom wall; said substantially rectangular transverse channels being provided with rounded edges formed at the juncture of said top wall and said bottom wall with the said face of said plate, said rounded edges extending only a slight distance along the adjacent surfaces; and further including a fulcrum block normally residing Within said opposed channels, said fulcrum block being substantially rectangular in cross-section and having a substantially fiat top face, a substantially flat bottom face, a first side face, and a second side face, said top and said bottom faces being parallel to each other and said first and said second side faces being parallel to each other; said fulcrum block further having rounded edges and being of substantially the same width as the combined width of said channels to abut said sides of said channels at said first and said second side faces of said fulcrum block and further having a vertical dimension such that said top wall of one of said channels abuts said substantially fiat top of said fulcrum block and said bottom Wall of said other of said channels abuts said substantially fiat bottom of said fulcrum block, said points of abutment being in each instance inwardly in said chanme] from said rounded edge thereof and inwardly on said fulcrum block from said rounded edge thereof, whereby when said fusible link is in assembled condition and a force is exerted on said link plates along the center line of the plane of said abutting faces thereof to draw said plates apart, said force will be exerted upon said fulcrum block through said link plates at portions of said top and of said bottom of said fulcrum block spaced off center on opposite sides of the center line of said fulcrum block to impart a turning moment to said fulcrum block to cause instant separation of said link plates upon melting of said fusible material.

References Cited in the file of this patent UNITED STATES PATENTS 725,495 Shaw et a1 Apr. 14, 1903 1,155,339 Cook Oct. 5, 1915 1,308,075 Hopkins July 1, 1919 1,356,919 Hopkins Oct. 26, 1920 1,452,522 Nacy Apr. 24, 1923 1,520,750 Hodgman Dec. 30, 1924 1,539,311 Hodgman May 26, 1925