US2493608A

US2493608A - Safety device fob furnaces

Info

Publication number: US2493608A
Authority: US
Publication date: 1950-01-03
Anticipated expiration: 1967-01-03

Description

Jan. 3, 1950 A. WILLETT SAFETY DEVICE FOR FURNACES Filed April 27, 1945 $74M N k M f-i 4 4) i Patented Jan. 3, 1950 UNITED STATES PATENT OFFICE SAFETY DEVICE FOR FURNACES Anthony Willett, Cleveland, Ohio Application April 27, 1945, Serial No. 590,633

3 Claims.

This invention relates to safety devices for furnaces, and more particularly to a device for automatically closing the draft door of a furnace or other heating unit when it becomes overheated. These, therefore, are the general objects of the present invention.

Heating plants, particularly hot air furnaces often become overheated due to foregetfulness or neglect to close the draft door. Sometimes the draft door remains open because of a failure in the power supply for an electrical control of the furnace. In either instance the overheating of the furnace is a dangerous condition and may result in loss of the building in which the heating plant is installed. Therefore, one of the objects of the present invention is to provide an improved, eflicient and positive actin safety device which will cause the closing of the draft door whenever the furnace temperature exceeds a predetermined maximum.

Another object of this invention is to provide a safety device which may be manufactured at low cost, readily installed on existing furnace control mechanisms, and which will not effect the operation of an existing control mechanism unless the furnace becomes overheated.

A more specific object of the present invention is to provide a safety device for closing the draft door of a furnace whenever the furnace temperature increases above a predetermined maximum and which device may be readily reset to its normal position without a replacement of any of its component parts, whenever the temperature of the furnace decreases below the danger point.

Other objects and advantages of the inven tion will become more apparent from the following description, reference being had to the accompanying drawings illustrating a preferred embodiment of the invention. The novel features of the invention are summarized in the claims.

In the drawings, Fig. 1 is a more or less diagrammatic illustration of a furnace havin my improved safety device incorporated in the draft control system; Fig. 2 is a plan view of my improved safety device, partially in section to more clearly illustrate the internal construction thereof; Figs. 3 and 4 are sectional views through the device, the planes of the section being indicated by the correspondingly numbered lines on Fig. 2.

Referring now to the drawings in detail, and particularly to Fig. 1, it will be seen that I have illustrated a furnace I!) of the usual construction as being provided with a draft door H,

hinged at I! so as to close under the influence of gravity. The draft door is opened by a flexible unit, such as for instance a chain M. The chain i4 is secured to the draft door, as at I5, and extends upwardly to a sheave l6, and then is looped downwardly around a sheave I1 which is carried by the safety device, thence upwardly, as at Hi, to a suitable control, either manual or automatic, as is well known My improved safety device comprises a housing 20 arranged to be secured to the outer casing IQ of the furnace by suitable screws or bolts passing through openings 2| in the housing. The outer casing l9 of the furnace may be broken away beneath the device or the device may be applied directly to such casing if desired. The sheave I1 is connected to the device by a short chain 24, at the end of which is a ring 25 arranged to be slid onto a lever 26, pivoted as at 21, to the housing 20. This lever is normally held in the position shown in full lines in Fig. 3 by a second lever or beam 28. The lever 28 is pivoted as at 29, to a bracket 30 formed on the housing 20, and is normally locked in the position shown in full lines on Fig. 4 by a spring-pressed latch member 3|. This latch is pivoted, as at 32, to the housing 20, and is normally urged into engagement with the lever 28 by spring 33.

Mounted within the housing 20 is a thermally responsive member 35. As shown, this member comprises .a coiled strip of bi-metallic construction. One end of the strip is clamped to a bracket 36 which projects inwardly from the housing 29 by a clamp 31 which is secured in place by screws 38. The innermost end 40 of the bi-metallic coil passes through a slot 4| in a vertically extending post 42 and is clamped therein by a set screw 43. This post 42 passes upwardly, freely through an opening 44 in the housin 20, and has an arm 46 secured to its upper end. As shown in Figs. 2, 3 and 4, the arm 46 comprises a bent metal strip which is wrapped around the post 42 and clamped thereto by a bolt 41, thus enabling the relative position of the arm on the shaft to be readily adjusted.

The arm 46 is so adjusted relative to the latch 3i and the bi-metallic member that when the furnace becomes heated to a predetermined degree the action of the bi-metallic member will cause the arm 46 to swing in a clockwise direction (Fig. 2) and swing the latch from the fullline position shown in Fig. 4 to the dotted line position therein shown. -Whereupon, the weight of the draft door, through the flexible member or chain l4, will rock the

arms

28 and 26 about their respective pivots to the dotted line positions shown in Figs. 3 and 4, thus freeing the ring 25 from the member 26 and increasing the effective length of the chain [4, thus permitting the draft door to drop to a closed position.

From the foregoing description, it will be seen that I have provided an extremely simple device which is positive in its action .and which will insure the closing of the draft door whenever the temperature of the furnace exceeds a predetermined maximum. Likewise, it will be noted that in my improved construction, the latch mechanism, if reengaged while the temperature of the furnace exceeds the predetermined maximum will immediately be forced outof-engagebracket. andextending across said support, a second bracket secured to and extending upward from said support, a lever having one end pivoted to said last named bracket and extending substantially at right angles to and across said arm at a point remote from the pivot thereof ment by the action of the bi-metallic member;

Likewise, it will be noted that when the furnace temperature drops below the danger point, the latch mechanism may be reset to its normal position without requiring the replacement of any parts thereof, and thus may be used over and over again. a

I claim:

1. In a trip release mechanism, a support, an arm pivoted to said support and extending thereacross, a second arm pivoted. to said support and extending across said first'named arm at a point remote from the pivot thereof to prevent movement of the first named arm away from said support, a ring slidably embracing said first named arm intermediate the pivot thereof and the second named arm, a releasable latch engaging said second named arm to prevent movement thereof away from said first named arm, resilient means to retain said latch in latching engagement with said second named arm, and movable means to trip said latch and permit the release of said ring.

2. In a trip release mechanism, a support, an arm pivoted at one end to said support and extending thereacross, a lever having one end pivoted to said support and extending across and substantially at right angles to and across said arm at a point remote from. the pivot thereof to prevent movement of said arm away from said support, a ring slidablyembracing said arm intermediate the pivot thereof and said lever whereby the sliding movement, of said ring is restricted by engagement with said lever, a pivoted latch overlaying the other end of said lever, resilient means to retain said latch in latching engagement with said lever, means movable to engage and swing said latch away from said lever to permit release of said ring consequent upon upward tensicning of said ring, said means being movable to a position out of engagement with said latch, said lever and arm being free to swing toward said support under the influence of gravity in the absence of upward tension applied to said ring and unattended by the release of said ring, whereby consequent upon the release of said latch by engagement therewith of said means unattended by tensioning of said to prevent movement of the arm away from said support, a ring slidably embracing said arm intermediate the pivot thereof and said lever whereby movement of said ring along said first named arm is restricted by said first named bracket and said lever, a pivoted latch overlaying the other end of said lever, resilient means to retain said. latch in latching engagement with said lever, and thermally responsive means carried by said support. and operative to engage and swing said latch away from said arm to permit release of said ring consequent upon upward tensioning of said ring and to move out of .engagement' with said latch, said arm and lever each being free to swing toward said support under the influence of gravity in the absence of upward tension applied to said ring without releasing said ring, whereby following upon the release of said latch by said thermally responsive means unattended by the application of tension to said ring the latch will return to its latching position and prevent release of said ring consequent upon a subsequent application of a tensioning force thereto unattended by a latch engaging movement of the thermally responsive means.

ANTHONY WILLETT.

- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS