US1518979A - Thermostatic circuit closer - Google Patents

Description

Deg, 9,, 1924.

N. H. FREEMAN THERMOSTATIC CIRCUIT CLOSER Filed Sept. 2, 1921 Patented Dec. 9, 1924.-

UNITED STATES PATENT OFFICE.

NAT HARRIS FREEMAN, OF HOLBORN, LONDON, ENGLAND.

THERMOSTATIC CIRCUIT CLOSER.

Application filed September 2, 1921.

To all whom it may concern Be it known that I, NAT HARRIS FREEMAN, a citizen of the United States of America, residing at Holborn, London, England, have invented certain new and useful Improvements in Thermostatic Circuit Closers, of which the following is a specification.

This invention relates to thermostatic cir cuit closers which are particularly adapted for use with furnace chambers and other apparatus, such as fire-alarms, and has for one of its objects to provide an improved construction which shall be less liable to derangement during working than those known heretofore. Another object of the invention is to extend the range of temperature which can be controlled by such devices.

The thermostatic circuit closer according to the present invention is of the type which comprises a holder for fluid (hereinafter termed a gas holder) which holder is intended to be placed in the chamber whereof the temperature is to be controlled, and a conduit extending from d holder to one surface of a movable opera mg -member, such as a column of mercury, which member is exposed at another surface to atmospheric pressure, and is movable under the pressure ofsaid fluid into and out of operative position to close and open an electric circuit. Such a circuit closer is described in the specification of my United States specification Serial No. 442,195, and the present invention may conveniently,though not essentially, be used in conjunction with the features of that specification.

- According to the primary feature of the present invention there is provided a thermostatic circuit closer of the type above described which is characterized by the provision of an automatic pressure-operated valve which is distinct from said movable member and is arranged to control communications between the interior of said holder and the exterior thereof. Conveniently the valve is arranged to operate either to admit fluid to the holder or to release fluid from the holder according to the variations in the relative pressure in the interior and at the exterior thereof. By the provision of such a valve, safety valve action can be secured whereby derangement of the a paratus in abnormal circumstances may e prevented. This safety valve action is more fully described hereinafter.

Serial No. 498,163.

According to another feature of the invention a temperature controlling device is provided which, instead of operating to close the circuit at a constant temperature of the fluid in the holder, is arranged to provide for a series of predetermined temperatures each higher than the preceding one. In this case the valve is combined with adjusting means whereby it can be set to open momentarily, during the cyles of temperature changes in the normal working of the device, at some instant in the increase of temperature (namely the expansion) of the fluid in the holder between that instant in a cycle at which the temperature is such that the movable operating member first reaches operative position and that instant at which the temperature reaches its maximum for such cycle (namely the instant of maximum expansion of the fluid in the holder).

The invention also comprises the provision of a temperature controlling device which is arranged to provide for a series of predetermined temperatures each lower than the preceding one. For this purpose the valve is combined with adjusting means whereby it can beset to open momentarily, during the cycles of temperature changes in the normal working of the device, at some instant in the decrease of temperature (namely the contraction) of the fluid in the holder between that instant in a cycle at which the temperature is such that the pressures inside and outside of the holder are equal, and that instant at which the temperature reaches its minimum for such cycle (namely the instant of maximum contraction of the fluid in the holder).

Preferably the valve is combined with adjusting means whereby it can be set to open at abnormal increase and abnormal decrease in pressure in the holder, and also momentarily, during normal working of the device, at either of the instants specified in the two preceding paragraphs.

For a more complete understanding of the invention there will now be described, by

way of example only and with reference to the accompanying drawings, certain constructional forms of thermostatic circuit closers accordin to the invention. It is to be understo however, that the invention is not limited to the precise details set forth.

In these drawings Figure 1 is an elevation, partly in section,

(lit

showing more or less diagrammatically one form of the present .invention as applied to an apparatus of the kind described in the aforesaid prior patent specification.

Figure 2 is a detail view of a modification of part thereof.

Figure 3 is a similar view of another modification, and

Figure 4 a view on a larger scale of a further modification.

Like reference numerals indicate like parts throughout the drawings.

In the construction illustrated the valve takes the form of a liquid seal to the open end of the conduit which communicates with the holder 11 for fluid, and preferably the volumetric capacity of the conduit 10 is such that there can be drawn into it, andv it will contain, a sulficient quantity of the sealing liquid 12 to expose the. open end of the conduit to atmosphere. The holder 11 may take the form of a gas bulb which is to be' inserted in the chamber whereof the temperature is to be controlled, and is shown as connected by a tube 13 to a column of mercury 14 contained in an angularly adjustable tube 19 which communicates with the tube 13 by a conduit as described in the aforesaid prior patent specification. The mercury co-operates with an adjustable contact 21, as described in the said prior specification, to open and close an'electri'c circuit including the mercury column 14, the contact-wire 21, the supports carrying the same and the wires 22 and 23 connected to these supports. Opening from the tube 13 there is shown a branch tube 15 which communicates with the conduit 10. The sealing liquid is received in a container 16 and the position of the latter can be adjusted by the screw 17 to immerse the open end of the tube 10 more or less below the surface of the sealing liquid 12. Included in the branch 15 there may be one or more enlargements 18 to receive sealing liquid sucked into the tube 10 and thus prevent the said liquid from reaching the main conduit 13.

Usually the holder 11 will contain air and bubles of air will pass between the holder 11 and atmosphere via the tube 10. Other gases or liquids may, however, be employed provided that the sealing liquid is suitably chosen to correspond and that a correspondlng atmosphere is provided between which and the holder 1'1 the bubbles may pass. Any suitable liquid may be used for the seal but it should be such as not to evaporate quickly nor to affect adversely the fluid in the holder.

Safety val 0e a0ti0n.-For a simple safety valve action the apparatus should be so set that on the circuit being closed no bubbles will pass into or out of the holder 11. Should, however, the air in the holder expand excessively the tendency, if the safety valve were not present, would be for the mercury to be blown out of its tube 19. Instead of this occurring, however, the excess pressure of air is got rid of by allowing bu bles of air to pass out through the sealing liquid 12. The mercury, therefore, will not be unduly displaced from itscorrect operative position. If, on the other hand, the air in the holder should unduly contract the tendency, in the absence of the safety-valve, would be for the mercury to be sucked back into the tube 13, whence it would be very difficult to displace it again. But instead of this happening the sealing liquid 12 is sucked up into or toward the enlargements 1'8 whence it is easily displaced later.

Temperature in0rease.'It will be appre ciated that the mercury does not immediately discontinue its outward movement at the instant that it touches the contact 21, but due partly perhaps to a little momentum which it has ac uired, but mainly to the expansion of t e air in the holder 11 'and the adjacent tubes, it moves along the contact and thus causes the point of the latter to be immersed to a greater or lesser extent.

For some purposes, for example pottery work, it is desirable that instead of the tem perature in the chamber under control being maintained constant, it should be caused to increase gradually and under control at a predetermined rate. For this purpose the apparatus should be so set by adjusting the height of the level of the sealing liquid 12 in relation to the open end of the tube 10 that at some instant between that at which the mercury first touches the contact 21 and the instant of maximum expansion, a bubble of air is released from the tube 10. After the bubble is released there will naturally be less air in the holder 11 and its tubes than before, and for any given temperature the.

. 10 than before, to an extent governed ,by its specific gravity. If, however, heat is continued to be supplied, the air in the holder 11 and its tubes will ultimately reach such a temperature as to cause it to attain a pressure and volume sufiicient to cause the mercury to reach and pass beyond the contact 21 and also release another bubble. Since a smaller quantity of air is in question, however, than at first, the temperature required to effect this will be higher than before, and thus instead of the apparatus securing a constant temperature it will 0 crate to secure a governed but continuous y increasing temperature. The rate of increase will depend upon the size of the bubble released, and this can be governed by varying the specific gravity of the sealing liquid 12, or by varying the aperture through which the bubble is released, say by perforated concentric sleeves upon the tube 10, or other means.

Insetting the apparatus, care should be taken that it is not so arranged that a bubble is released suiflciently early during the expansion of the air to prevent the mercury from reaching the contact 21. If this occurs at the first expansion of the air, it will in all probability occur during succeeding expansions, with the result that the mercury will never reach the contact and thus the supply of heat will never be automatically shut oil'. In other words such a setting of the valve cuts out of operation entirely the temperature controlling device.

Temperature decrease-To cause the temperature to decrease gradually and under control at a predetermined rate, the apparatus should be so set that at some instant between that at which the pressures inside and outside the holder 11' are equal and the instant of maximum contraction, a bubble of air is admitted from atmosphere to the holder. The operation is the converse of that hereinbefore described in connection with securing temperature increase.

Any suitable bubble-forming device may be employed. The tube has a plain open end in the construction shown in Figure 1. In the construction shown in Figure 2 a slit 24 is provided for formin the bubble, while in the construction shown in Figure 3 the tube 10 has a bell mouth. In the construction shown in Figure 4, the tube 10 has a slit 2% the operative opening of which is controlled by a sleeve 26 which is perforated at 27. The sleeve 26 can be rotated upon the tube 10 to shut ofl' more or less of the length of the slit 24 as desired. The sleeve 26 may conveniently be held in place by splaying the end of the tube 10 after the sleeve has been placed in position.

What I claim as my invention and desire to secure by Letters Patent is 1. A thermostatic circuit closer comprising a holder for fluid adapted to be placed in. a chamber, the temperature of which is to be controlled, an electrical circuit-closing device comprising a movable column of electrically conducting material controlled by the pressure of the fluid in said holder, and an automatic pressure-operated valve distinct from said movablecolumn and arranged to control communication between the interior of said holder and the exterior thereof. n I

2. A thermostatic circuit closer comprising a holder for fluid, adapted to be placed in a chamber, the temperature of which is to be controlled, and an electrical circuit-closing device comprising a movable column of electrically conducting material controlled by the pressure of the fluid in said holder, and an automatlc valve distinct from said device comprising a tubular container carrying a movable column of electrically conducting material, a conduit connecting the lower end of sald container with said holder,

and an automatic valve which is distinct from said movable column, is operated by pressure in said holder and is arranged to control communication between the interior of said conduit and the atmosphere.

4. A thermostatic circuit closer comprising a holder for fluid adapted to be placed in a chamber, the temperature of which is to be controlled, an electrical circuit-closing device comprising a movable column of electrically conducting material controlled by the pressure of the fluid in said holder, an automatic valve operated by the fluid pressure in the holder and arranged to control communication between the interior and the exterior of said holder, and means for adjusting said valve to permit the same to open momentarily owing to increase of pressure on it due to increase of temperature of the fluid in the holder at some instant between that instant in a cycle of temperature changes at which the temperature is such that the movable column first reaches operative position and that instant at which the temperature reaches its maximum for such cycle.

5. A thermostatic circuit closer comprising a holder for fluid adapted to be'placed in a chamber, the temperature'of which is to be controlled, an electrical circuit-closing device comprising a movable column of an electrically conducting material controlled by the pressure of the fluid in said holder, an automatic valve operated by the fluid pressure in the holder and arranged to control communication between the interior and the exterior of said holder, and means for adjusting said valve to permit the same to open momentarily owing to decrease of pres sure on it due to decrease of temperature of the fluid in the holder, at some instant between that instant in a cycle of temperature changes at which the temperature is such that the pressures inside and outside of the holder are equal, and that instant at which the temperature reaches its minimum for such cycle, namely, the instant of maximum contraction of the fluid in the holder.

6. A thermostatic circuit closer comprising a holder for fluid adapted to be placed in imum and minimum pressures.

7. A thermostatic circuit closer comprising a holder for fluid adapted to be placed in a chamber, the temperature of which is to be controlled, and an electrical circuit- ,closing device comprising a movable column of electrically conducting material controlled by the pressure of the fluid in said holder and an automatic valve operated by the fluid pressure in said holder and arranged to control communication between the interior and the exterior of said holder, said valve distinct from said movable column and taking the form of a liquid seal at the open end of a'conduit communicating with said holder.

8. A thermostatic circuit closer comprising a holder for fluid adapted to be placed in a chamber, the temperature of which is .to be controlled, an electrical circuit-closing device comprising a tubular container carrying a movable column of electrically conducting material, and a conduit connecting the lower end of said container with said holder, a valve conduit opening into the aforesaid conduit, and a liquid seal distinct vfrom said movable column for the open end of'said valve conduit.

9. A thermostatic circuit closer comprisring "a holder for fluid adapted to be placed in a chamber, the temperature of which is to be controlled, an electrical circuit-closing devlce comprising a tubular container carrying a movable column of electrically conducting material, a conduit connecting the lower endof said container with said holder, a valve conduit opening into the aforesaid conduit, and a liquid seal for the open end of said valve conduit, the 0 en end of said valve conduit having a bubb e-forming slit.

10. A thermostatic circuit closer comprising a holder for fluid, adapted to be placed in a chamber, the temperature of which is to be controlled, an electrical circuit-closing device comprising a tubular container and a movable column of electrically conducting material therein, a conduit connecting the lower end of said container with said holder, a valve conduit opening at one end into the aforesaid conduit and having a bubble-forming slit at its other end, a liquid seal for the slit end of said valve conduit, and means for adjusting the operative area of said slit.

11. A thermostatic circuit closer comprising a holder for fluid adapted to be placed in a chamber, the temperature of which is to be controlled, an electrical circuit-closing device comprising a movable column of electrically conducting material controlled by the pressure of the fluid in said holder, an automatic valve operated by the pressure in said holder and arranged to control communication between the interior of the holder and the atmosphere, a valve conduit in open communication at one end with said holder, and a liquid seal for the other end of said valve conduit, said liquid-sealed conduit comprising a chamber of such volumet ric capacity that it can contain a sufficient quantity of the sealing liquidrto expose the open end of the valve conduit to atmosphere and thereby connect the said holder with atmosphere.

Intestimony whereof I aflix my signature.

NAT HARRIS FREEMAN

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