US2023940A - Thermostatic device - Google Patents

Description

@@a my E935, D. WSQN 2,023,940

THERMOSTATIC DEVICE Filed OGC. 29, 1934 Ma F7@ 2 30 /l/ [di /J ,Daazd @.5032

Patented Dec. l10, 1935 UNITED STATES PATENT OFFICE Application October 29, 1934, Serial No. 750,556 In Great Britain October 21, 1933 6 Claims.

This invention is for an automatic control device for temperature-indicators, nre-prevention or nre-detection appliances. Among the objects of the invention is to provide a control device which will operate with certainty either by a rise in the atmospheric temperature of an enclosed space (such as a room) above a predetermined maximum, or by iiame, the arrangement being such that the device will operate an alarm or bring into action a sprinkler for fire-extinguishing. medium. A further object of the invention is to simplify the construction of control devices for the above purpose.

According to the invention an automatic control device for electrically operated temperatureindicators, nre-alarms, fire-prevention and like appliances comprises in combination an electric switch device connected in the circuit or circuits of the appliance or appliances to be controlled, inflammable means adapted to hold switch-operating means in the oii position until ignited by flame, and temperature-responsive means adapted to close the said switch at a pre-determined maximum temperature. Conveniently the iniiammable means constitutes part of a substantially dust-proof casing for the electric switch device, or a portion thereof, for the purpose of maintaining the contacts in an operable condition. The temperature-responsive device may be a normal form of bi-metallic strip, but having an elongated arm of cheap material secured to and forming a continuation of the strip and acting as a switch arm wherebyfa small amount of warping of the bi-metallic strip arising from a change in atmospheric temperature may be magnified by the elongated arm to give a sensitive control, and since the bi-metallic strip is a comparatively expensive component the elongation thereof in a cheap material saves in cost of production.

v One preferred construction of automatic control device comprises in combinationv an openwork (e. g. apertured) outer case, an inner case fitting within the said outer case and spaced from the upper part thereof, an insulated baseplate mounted on the upper surface of the inner case, a lai-metallic strip mounted on the baseplate and forming a switch arm, spring means mounted on the base-plate and adapted to operate the said switch arm, and inammable means surrounding the said base-plate holding the spring means inoperative and located between the upper surface of the inner case and the lower surface of the outer case so as to constitute part of a substantially dust-proof casing for the parts mounted on the base-plate. The bi-metallic strip (Cl. ZOO-138) and spring means may be mounted on a common pillar extending through the inner case and the base-plate, and slotted to receive the strip and spring means with a clamping screw threaded in the pillar and adapted to bear on the strip and 5 spring means to hold them in position on the pillar. This arrangement provides a construction which may be readily assembled by unskilled labour, and the bi-metallic strip and spring means are used to key the base-plate and inner case 10 together.

An example of a control device in accordance with the invention will now be described with reference to the accompanying drawing, on which:-

Figure 1 is a sectional view on the line I--I of Figure 3,

Figure 2 is a sectional View on the line II-II oi Figure 3,

'Figure 3 is a sectional view on the line III- III 20 of Figure 1, and

Figure 4 is a developed view of an inflammable means used in connection with the device shown.

Referring to the drawing, I0 is an outer case having apertures II in its walls to permit the passage of heat and ilame into the interior of the device. A metal inner case I2 is tightly fitted into the outer case, and has its edges flared at I3 to retain it in its correct position. A base-plate I4 of insulating material is mounted on the inner case i2, and has passing through it and the top I6 oi the case I2, a slotted-pillar I5. The top I6 of the case I2 is apertured at I1 and I8 and the part of the base-plate I4 in register with the aperture I8 carries pillars I0 supporting contacts 20 which are adjustable to govern the pre-determined temperature at which the device becomes operative. A bi-metallic strip 2l, which is bent into a sinuous form, is positioned in the slottedpillar I5, which also carries a spring-frame 22. A washer 24 is positioned between the bi-metallic strip and spring-frame and the base-plate I4, and a screw 23 serves to clamp the pin I5, bi-metallic strip 2I, spring-frame 22, washer 24, and the base-plate I4 to the inner case I2.

The bi-metallic strip 2| carries contact-making arms 25 which operate in connection with the contacts 20, and' constitute, in combination with said contacts, an electric switch device. By f1tting contact arms of ordinary metal (such as 50 brass) to the bi-metallic strip instead of extending the bi-metallic strip to the contacts 20, the cost of the device is substantially reduced. Further, the length oi the contact arms is such that for a very small movement of the bi-metallic strip a comparatively great movement of the contact arms is obtained.

The bi-metallic strip 2l operates in the well known way to close the contacts 25, 20, when the temperature about the strip reaches a pre-determined degree. The spring-frame 22 is also adapted to close the contacts when a re or ame actually occurs. To this end the spring is normally held in its inoperative position against a stop 2G by an inflammable strip 2l (e. g. of celluloid) which has apertures 28 in its ends which .are threaded over the ends 23 of the springframe, and maintain the said frame in the position shown until the inflammable strip catches fire, whereupon the arms of the frame 22 spring outwards and close the Contact arms 25 on to the contacts 2li.

The inflammable strip 27 surrounds the baseplate Id, and is centered between this base-plate and an annular bead Si) formed on the top of the casing IU and serving to stiffen the latter. This location of the inflammable strip 21 forms a substantially dust-proof casing around the parts carried by the base-plate lll with the exception of a portion of the bi-metallic strip which projects through an aperture 2 'la'. in the inammable strip, so that it is freely acted upon by changes in temperature exterior to the device.

The device shown is adapted for connection in two independent circuits, and for this purpose is provided with terminals 3l which are connected to the slotted pin l5 by the un-perforated portion of the top I6 of the casing i3, and constitute one pole of the device, whilst the pillars I9 are threaded at 32 to receive clamping nuts, and constitute the other pole. It will be seen, therefore, that each of the circuits in which a device is connected has in series with it one of the arms 25, and when this arm makes contact with one of the contacts i9 either by movement of the bi-metallic strip or the spring frame 22, the circuit will be closed, and the alarm or device connected in such circuit will be operated. lA suitable alarm will be a gong, buzzer or an electric lamp, or the device may be arranged to operate a device by which a lire-extinguishing medium is sprinkled onto a fire.

The device shown on the drawing is adapted for mounting on a surface such as a wall, and for this purpose the casing l is flanged at 33, and provided with holes 34 through which screws can be passed.

The device is particularly suitable for use in places where a spark or flash of iiame is liable to occur, and where the temperature does not immediately rise sufficiently to affect the bri-metallic strip. For example, the device can be used in connection with electrical machinery, or adjacent to switches, fuse-boxes or the like, say, in a ships cabin in which case the device can be arranged to operate a main fire-bell and a gong or like alarm located in a room in charge of someone in authority, say in the stewards cabin.

iSuitable switches can be used in connection with the device for shortcircuiting it when desired.

While the invention has been more particularly described as applied to fire alarms and the like it is to be understood that it can be applied to cases where it is desired to give a warning when the temperature of a room or enclosed space (e. g. an incubator or refrigerated store chamber) rises above or falls below a pre-determined limit. Modifications may be made in the invention -Without departing from the scope thereof as herein ascertained. For example, the method of mounting the bi-metallic strip and the springframe on the base-plate can be varied. Instead of clamping these parts together, the slotted pin may be threaded externally and secured to the base-plate by means of a nut. Further, although the device shown is adapted to control two independent circuits it will be appreciated that any number of circuits can be controlled either independently by providing additional contacts in the 10 device, or as a whole by connecting the device in series with a plurality of appliances. Further the inner case I2 may be electrically insulated from the outer case i9, by inserting a piece of insulating material between these two cases.

What is claimed is:-

1. A temperature-sensitive control device for an electric circuit comprising in combination a switch device in the circuit, switch operating means, dust-proof means enclosing the said switch device in a substantially dust-proof manner, inflammable means operatively connected to the said switch operating means to maintain the said means inoperative until the inflammable means is ignited, and a bi-metallic strip located partly within and partly without the said dust-proof means and operatively connected to the said switch device for the operation of the said device at a predetermined temperature, whereby the switch device conducting surfaces are screened from dust and grease and at the same time are operable by either'lame or slow rise in temperature. n

2. A temperature-sensitive control device for an electric circuit comprising in combination an 85 lic strip mounted on the base-plate and forming 40 a switch arm, dust-proof means enclosing the said switch arm in a substantially dust-proof manner, spring means mounted on the baseplate and adapted to operate the said switch arm, and inilammable means surrounding the base-plate and operatively connected to the said spring means to hold the latter inoperative and non-vibratory. f

3. A temperature-sensitive control device for an electric circuit comprising in combination an open-work outer case, an inner case tting Within the said outer case and spaced from the upper part thereof, an insulated base-plate mounted on the upper surface of the inner case, a bi-metallic strip mounted onthe base-plate and form- 55,

in a switch arm, spring means mounted on the base-plate and adapted to operate the said switch arm, and inflammable means surrounding the base-plate and operatively connected to the said spring means to hold the latter inoperative, the said inflammable means being in strip form and located between the upper sur` face of the inner case and the lower surface of the outer case so as to constitute a substantially dustproof casing for the said switch arm.

mounted on the base-plate and adapted to operate the said switch arm, and inflammable means surrounding the base-plate and operatively connected to the said spring means to hold the latter inoperative, the said inflammable means being in stripl form and located between the upper surface of the inner case and the lower surface of the outer case so as to constitute a part of a substantially dustproof casing for the elements mounted on the base-plate.

5. A temperature-sensitive control. device for an electric circuit comprising in combination an apertured outer case, an inner case fitting within the said outer case and spaced on the upper part thereof, an insulated base-plate mounted on the upper surface of the inner case, a slotted pillar, an operative connection between the said slotted pillar and the inner case, a bi-metallic strip operatively connected to the slotted pillar, springs means operatively connected to the slotted pillar, a clamping screw holding the said i bimetal1ic strip and spring means in position in strip form and located between the upper surface of the inner case and the lower surface of the outer case so as to constitute a substantially dust-proof casing for the elements mounted on the base plate.

6. A temperature-sensitive control device for an electric circuit comprising in combination an open-Work outer case, an inner case fitting within the said outer case and spaced from the upper part thereof, an insulated base-plate mounted on the upper surface of the inner case, a bi-metallic strip of sinusoidal form and having an elongated contact arm of cheap material secured to and forming a continuation of the strip mounted on the base-plate and forming a switch arm, spring means mounted on the baseplate and adapted to operate the said switch arm, and inflammable means surrounding the base-plate and operatively connected to the said spring means to` hold the latter inoperative, the said iniiammable means being in strip form and located between the upper surface of the inner case and the lower surface of the outer case so as to constitute a part of a substantially dustproof casing for the elements mounted on the base-plate, and being apertured to permit part of the sinusoidal iii-metallic strip to project beyond the dust-proof casing.

DAVID TYSON.

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