US2711457A

US2711457A - Fire detector

Info

Publication number: US2711457A
Application number: US335970A
Authority: US
Inventors: Charles W Wise
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-02-09
Filing date: 1953-02-09
Publication date: 1955-06-21
Anticipated expiration: 1972-06-21

Description

June 21, 1955 c, w, w 2,711,457

FIRE DETECTOR Filed Feb. 9, 1953 INVENTOR. CHARLES VV. WISE A T T OHNEYS.

United States Patent 0 The present invention relates generally to fire detecting devices, and more particularly to a novel fire detector especially adapted for use under conditions of extreme vibration.

Modernly, there exists a need for a dependable fire detector which may be used under conditions of extreme vibration, as for example, in the vicinity of an aircraft engine. Although such fire detectors have heretofore been proposed, they generally prove unreliable after being in service for a comparatively short time. Thus, such fire detectors will often indicate a fire where none exists,

or fail to indicate the existence of an actual fire. Either type of false indication can easily result in a disastrous situation. 7

It is a major object of the present invention to provide a novel fire detector which is completely reliable in operation.

It is another object of the present invention to provide a fire detector of extremely simple construction utilizing but few parts, in contradistinction to the heretofore proposed devices of this nature which generally are very complex.

A further object of the present invention is to provide a fire detector which is well adapted to withstand severe vibration over long periods of time without requiring any attention.

Yet another object is to provide a fire detector which is light in weight whereby it is especially suited for use with aircraft.

An additional object of the invention is to provide a fire detector which is readily adjustable to be responsive over a wide temperature range, and yet which is not adversely affected by exposure to extreme conditions of heat or cold.

It is still another object to provide a fire detector which may be manufactured at a low cost.

lt is an additional object of the present invention to provide a fire detector which is both quick-operating and foolproof.

Other objects and advantages of the present invention will become apparent from the following detailed description of a preferred embodiment thereof taken in conjunction with the appended drawings wherein:

Figure 1 is a sectional view taken along the center of a fire detector embodying the present invention;

Figure 2 is a fragmentary sectional view similar to Figure 1, but showing parts of the fire detector in a different position;

Figure 3 is a fragmentary enlarged vertical sectional view taken on lines 3-3 of Figure l; and,

Figure 4 is an electrical wiring diagram showing an electrical circuit which may be utilized in conjunction with the fire detector embodying the present invention.

Referring to the drawings, a preferred form of fire detector embodying the present invention broadly comprises a heat-sensitive case member 10 adapted to expand 12 nested within the case member. The case member 10 includes a contact point, generally designated 14, at one of its ends and the fixed member 12 is likewise formed with a contact point, generally designated 16, disposed adjacent the contact point 14. The opposite ends between the case member and the fixed member are rigidly interconnected as by spot welding 18. With this arrangement, should the fire detector be heated above a predetermined temperature, the case member 10 will expand independently of the fixed member so as to effect engagement of the

contact points

14 and 16, as indicated in Figure 2. These contact points may be included in a suitable electric circuit whereby their engagement will set off an alarm signal. Such an electric circuit is disclosed hereinafter.

The case member 10 will conveniently be of tubular cross section and formed of a material having a comparatively high coefiicient of linear expansion, while the fixed member 12 may likewise be of tubular cross section telescopically disposed within the case member. The fixed member, however, should be formed of a material having a comparatively low coefficient of linear expan sion. The case member and the fixed member should preferably be heat-resistant.

One end of the case member 10 is shown rigidly secured to a plug or spool 20 as by swaging. This spool is coaxially formed with an internally threaded bore 22. The case member and the spool should be electrically insulated from each other. For this purpose the outer surface of the spool is shown coated with a layer of porcelain 23. Although porcelain has proven to be very well adapted for use as an insulating medium, other insulating materials may be utilized for this purpose. The spool bore 22 is shown threadedly engaged with a post generally designated 24, which post extends into the case member 10.

It will be seen that the portion of the post 24 dis posed within the case member is of reduced diameter at that part of its length remote from the spool 20. One end of this reduced-in-diameter portion 26 of the post is formed with external threads 28 adapted to receive a nut 30. The opposite end of this reduced-in-diameter portion 26 defines a shoulder 32. A washer 34 formed of an electric current conducting material is slidably disposed on the reduced-indiameter portion 26 for axial movement therealong. This washer is shown biased against the shoulder 32 by means of a helical compression spring 36 interposed between the washer and the nut 30.

A washer 38 formed of an insulated material is carried by the post 24 adjacent the outer end of the spool 20 in order to electrically insulate the end of the case when exposed to a source of heat and a fixed member member from the post. A metallic spacer or washer 40 is shown disposed adjacent the insulated washer 38 and an adjustment nut 42 is threadedly mounted by the post adjacent this latter washer. With this arrangement, axial adjustment of the post relative to the spool 20 may be readily effected. The side of the washer 34 proximate the spool 20 is seen to constitute the contact point 14 of the case member 10. The contact point 16 of the fixed member may conveniently be defined by one side of a radially inwardly extending fiange 44 integrally formed at one end of the fixed member.

In operation, at such time as the fire detector is heated above a predetermined temperature, the case member 10 will expand independently of the fixed member 12 because of the difference in their coefiicients of linear expansion. Since these members are rigidly interconnected by the spot weld 18 the case member must expand in a direction away from the post 24, or to the right in the drawings. Such movement causes the right side of the contact point 16 to be concurrently moved toward,

Patented June 21, 1955 and to finally engage, the left side of the washer 34, as shown in Figure 2. This engagement is adapted to see oif a warning alarm signal in a manner to be set forth hereinafter.

The temperature at which the contact points 14 and 16- are to be caused to be engaged may be be readily varied by axial adjustment of the post 24 relative to the spool 20. Thus, if it is desired that the fire detector provide a warning at a higher temperature, the post may be rotated so as to effect its movement to the right in the drawings. If on the other hand, the fire detector is to be set to function at a lower temperature, the post is rotated so as to effect its movement in the opposite direction.

it should be especially noted that engagement of the washer 34 with the flange 44 cannot in any way damage the device. This is true inasmuch as upon such engagement further movement of the case member to the left will permit the washer 34 to be forced along the reduced-in-diameter portion 26 of the post against the yielding compressive force of the spring 36.

In order to provide a maximum rate of response for the present device, the fixed member 12 may be insulated from the case member, as by means of a thin coating of porcelain 45 disposed upon the outer surface of the fixed member. Although porcelain is well-suited for this purpose, other insulating mediums may also be utilized. With this arrangement, the fixed member is prevented from absorbing as much heat as the case member. hence any heat applied to the case member will be quickly absorbed and dissipated. Accordingly, the fire detector of the present invention may have an extremely rapid response rate.

In assembling the preferred form of fire detector disclosed herein it is anticipated that the case member, fixed member, and the spool initially be arranged as shown in the drawings. Thereafter, the post and contact assembly including the washer 34, spring 36 and nut 30 may be installed in the spool 20 through the right side of the device by means of the opening 49. Rotation of the post 24 relative to the spool bore 22 may conveniently be accomplished by means of a wrench (not shown) which may be removably inserted into the device through the opening 49. If the nut 30 is rigidly secured to the post as by a pin 51, this wrench may engage the nut 36 so as to elfect rotation of the post 24 relative to the spool 20. In this manner adjustment of. the distance separating the contact washer 34 and the flange 44 may be closely controlled. The opening 49 may be sealed by means of a closure disk 50 which is adapted to be soldered or brazed in place after being pressed into the opening.

Referring now to Figure 4, the preferred form of electrical diagram utilizes a warning lamp a first lead 56 connecting the case member 19 with a grounded or negative connection 53 and a second lead 60 connecting the post 24 with one terminal of the lamp 54. The second lead may be secured to the post 24 by a nut 55. Although the case member is shown grounded by lead 56, it will be apparent that it may be grounded directly. The opposite lamp terminal is shown connected to the positive pole 63 of a source of electric current by a third lead 64. With this arrangement, the contact points 14 and 16 of the detector will normally be separated, and hence no current will be permitted to flow between the ground 58 and the lamp 54. At such time, however, as these contact points are engaged, electric current will fiow from the ground connection 53 to the case member and then by means of the spot weldings 1S and the solder or brazing used to secure the closure 50, to the fixed member 12. From the fixed member 12 the electric current will then pass through the post 24 by means of the washer 34 and the flange 44. From the post 24 the current will pass through lead 69 to the lamp 54 so as to cause it to be illuminated. This wiring circuit permits the use of light-in-weight components in the fire detector, as well as the use of wire leads having a small current-carrying capacity.

Although there has been shown and described what is at present believed to be the preferred embodiment of the present invention, it will be apparent to those skilled in the art that various modifications and changes may be made thereto without departing from the spirit of the invention and the scope of the following claims.

I claim:

l. A fire detector, comprising: a heat-sensitive case member adapted to expand when exposed to a source of heat; a mounting element secured to one end of said case member and electrically insulated therefrom; a post mounted by said mounting element and extending into said case member; a contact point formed on said post; a fixed member nested within said case member and rigidly connected thereto at a location spaced from said mounting element; and, a second contact point formed on said fixed member adjacent said first contact point, said case member having a higher coefiicient of linear expansion than said fixed member whereby said case member is ex pandable independently of said fixed member in order that engagement of said contact points will be eifected when said fire detector is heated above a predetermined temperature.

2. A fire detector comprising: a heat-sensitive case member adapted to expand when exposed to a source of heat; a mounting element secured to one end of said case member and electrically insulated therefrom, said mounting element being formed with a threaded bore; an externally threaded post engaged with said bore and extending into said case member; a contact point formed on said post; a fixed member nested within said case member and rigidly connected thereto at a location spaced from said mounting element; and, a second contact point formed on said fixed member adjacent said first contact point, said case member having a higher coefiicient of linear expansion than said fixed member whereby said case member is expandable independently of said fixed member in order that engagement of said contact points will be effected when said fire detector is heated above a predetermined temperature.

3. A fire detector, comprising: a heat-sensitive case member adapted to expand when exposed to a source of heat; a mounting element secured to one end of said case member and electrically insulated therefrom, said mounting element being formed with a threaded bore; an externally threaded post engaged with. said bore and extending into said case member, the portion of said post disposed within said case member being formed with a portion of reduced cross-sectional area defining a shoulder; a washer having a contact point slidably mounted upon the reduced in cross-sectional area portion of said post; spring means carried by said post biasing said washer against said shoulder; a fixed member nested within said case member and rigidly connected thereto at a location spaced from said mounting element; and, a second contact point formed on said fixed member adjacent said first contact point, said case member having a higher coefiicient of linear expansion than said fixed member whereby said case member is expandable independently of said fixed member in order that engagement of said contact points will be elfected when said fire detector is heated above a predetermined temperature.

4. A fire detector, comprising: a heat-sensitive tubular case member adapted to expand when exposed to a source of heat; a spool secured to one end of said case member and electrically insulated therefrom, said spool being formed with a threaded here; an externally threaded post engaged with said bore and extending into said one end of said case member; nutmeans carried by said post for effecting axial adjustment thereof relative to said case mem her; a contact point formed on the portion of said post disposed within said case member; a tubular fixed member telescopically disposed within said case member; means rigidly interconnecting the opposite end of said case member to said fixed member; and, a second contact point formed on said fixed member adjacent said first contact point, said case member having a higher coefficient of linear expansion than said fixed member whereby said case member is expandable independently of said fixed member in order that engagement of said contact points will be effected when said fire detector is heated above a predetermined temperature.

5. A fire detector, comprising: a heat-sensitive tubular case member adapted to expand when exposed to a source of heat; a spool secured to one end of said case member and electrically insulated therefrom, said spool being formed with a threaded bore; an externally threaded post engaged with said bore and extending into said one end of said case member, the portion of said post disposed within said case member being of reduced diameter for part of its length so as to define a shoulder; a washer slidably mounted upon the reduced in diameter portion of said post; spring means carried by said post for biasing said washer against said shoulder; nut means carried by said post for effecting axial adjustment thereof relative to said case member; a tubular fixed member telescopically disposed within said case member, said fixed member having one of its ends formed with a radially inwardly extending flange disposed adjacent said contact washer, and having its other end rigidly fixed to the other end of said case member, said case member having a higher coetficient of linear expansion than said fixed member whereby said case member is expandable independently of said fixed member in order that engagement of said washer and said flange will be effected when said fire detector is heated above a predetermined temperature.

6. A fire detector, comprising: a heat-sensitive tubuo lar case member adapted to expand when exposed to a source of heat; a spool secured to one end of said case member and electrically insulated therefrom by a porcelain coating, said spool being coaxially formed with a threaded bore; an externally threaded post engaged with said bore and extending into said one end of said case member, the portion of said post disposed within said case member being of reduced diameter at that part of its length remote from said spool so as to define a shoulder; an electrically conductive washer slidably mounted upon the reduced in diameter portion of said post; a helical compression spring coaxially disposed upon said post for biasing said washer against said shoulder; an insulated washer carried by said post adjacent the outer end of said spool; nut means engaged with said post adjacent said insulated washer for effecting axial adjustment of said post relative to said case member; a tubular fixed member telescopically disposed within said case member, said fixed member having one of its ends formed with a radially inwardly extending flange disposed adjacent said electrically conductive washer, and having its other end rigidly fixed to the other end of said case member, said case member having a higher coefiicient of linear expansion than said fixed member whereby said case member is expandable independently of said fixed member in order that engage ment of said electrically conductive Washer and said flange will be effected when said fire detector is heated above a predetermined temperature.

7. A fire detector, comprising: a heat-sensitive case member adapted to expand when exposed to a source of heat; a mounting element secured to one end of said case member and electrically insulated therefrom, said mounting element being formed with a threaded bore; an ex-. ternally threaded post engaged with said bore and extending into said case member; a contact point formed on said post; a fixed member nested within said case member and rigidly connected thereto at a location spaced from said mounting element; heat insulation means interposed between said case member and said fixed member; and, a second contact point formed on said fixed member adjacent said first contact point, said case member having a higher coefficient of linear expansion than said fixed member whereby said case member is expandable independently of said fixed member in order that engagement of said contact points will be effected when said fire detector is heated above a predetermined temperature.

8. A fire detector, comprising: a heat-sensitive tubular case member adapted to expand when exposed to a source of heat; a spool secured to one end of said case member and electrically insulated therefrom by a porcelain coating, said spool being coaxially formed with a threaded bore; an externally threaded post engaged with said bore and extending into said one end of said case member, the portion of said post disposed within said case member being of reduced diameter at that part of its length remote from said spool so as to define a shoulder; an electrically conductive Washer slidably mounted upon the reduced in diameter portion of said post; a helical compression spring coaxially disposed upon said post for biasing said washer against said shoulder; an insulated washer carried by said post adjacent the outer end of said spool; nut means engaged with said post adjacent said insulated washer for effecting axial adjustment of said post relative to said case member; a tubular fixed member telescopically disposed within said case member, said fixed member having one of its ends formed with a radially inwardly extending flange disposed adjacent said electrically conductive washer, and having its other end rigidly fixed to the other end of said case member, said case member also being coated with porcelain on its outer surface, said case member having a higher coefiicient of linear expansion than said fixed member whereby said case member is expandable independently of said fixed member in order that engagement of said electrically conductive washer and said flange will be efiected when said fire detector is heated above a predetermined temperature.

References Cited in the file of this patent UNITED STATES PATENTS 1,111,652 Fryling Sept. 22, 1914 1,935,762 Appelberg Nov. 21, 1933 FOREIGN PATENTS 615,974 France Oct. 23, 1926