US2227291A - Safety system responsive to temperature and fluid flow - Google Patents

Description

Dec. 31, 1940. R A wn- 2,227,291

SAFETY SYSTEM RESPONSIVE TO TEMPERATURE AND FLUID FLOW Filed May 26, 1938 Patented Dec. 31, 1940 PATENT OFFICE SAFETY SYSTEM RESPONSIVE T TEM- PERATURE AND FLUID FLOW Robert A.. Wittmann, Chicago, Ill., assignor to Chicago By-Products Corporation, a corporation of Illinois Application May 26, 1938, Serial No. 210,144

4 Claims.

My invention relates, generally, to safety sys tems for gas burners of the type disclosed in my Patent No. 2,185,490, and it has particular relation to systems of this nature in which controls are provided that are responsive to both temperature and fluid flow.

In devices for the automatic fuel control to heating apparatus employing a fan or blower to force or draw air over the heating sections or heat transfer surface, it is desirable and often necessary to be assured that the air is passing over the heating surfaces before the main burner is put into operation. At the same time itis also necessary to be assured that fuel cannot be fed 5 to the main burner unless the pilot flame or other ignition means is either burning or in satisfactory operative condition.

An important object of my invention is to provide for checking as to whether or not the pilot 20 is burning at each time that there is a demand or call for heat.

Another important object of my invention is to prevent the main burner of a heating system from going into operation unless air is passing 25 over the heating or heat transfer sections to which heat is applied from the flame of the main burner.

A further object of my invention is to provide a simple form of safety pilot system employing principally a strip of metal and thereby eliminating the usual moving parts that are complicated by linkages and leverages, electric contacts, bleed valves, and other sources of likely causes of trouble.

Still another object of my invention is to provide a safety pilot control system which, when the pilot burner is lighted, will go into operation in a predetermined time, preferably in about thirty seconds, so as to give the operator ample 40 time to move away from the furnace before the main humer is lighted and which will shut down or cause to shut down the main burner quickly in case that the pilot burner is extinguished. Samples of my control system capable of effect- 45 ing the foregoing objects have been operated successfully and consistently for shutting down 1 the main burner within approximately three seconds after the exting uishment of the pilot burner, even with-the main burner on.

A further object of my invention is to provide a safety pilot system which does not require any adjustments, thereby eliminating tampering by unauthorized or inexperienced persons.

Other objects of my invention will, in part, be 66 obvious and in part appear hereinafter.

Accordingly, my invention is disclosed in the embodiment thereof shown in the accompanying drawing and it comprises the features of construction, combination of parts, and arrangement of elements which will be exemplified in the con- 5 struction hereinafter set forth and the scope of the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of my invention reference may 10 be had to the following detailed description taken in conjunction with the accompanying drawing in which the single figure illustrates a concrete embodiment of my invention.

Referring now particularly to the drawing, it will be observed that the reference character In designates, generally, a gas heated hot air furnace. The furnace in may be a conventional coal fired hot air furnace with its grates removed and a main gas burner H installed, as is the practice in changing from burning coal to gas.

A fan i2 is located in the cold air return i3 for drawing in cold air and forcing it over the heating surface it of the furnace Ill and out through the hot air pipes IS. The fan I2 is driven by a suitable motor it which may be connected by means of conductors l1 and I8 to the energized conductors i9 and 20. For example, the conductors l9 and 20 may be connected to a source of 110 volt alternating current. A switch 2| is provided in conductor I8 for controlling the operation of the motor It as desired.

The main gas burner H in the fire box of furnace Ill, may be connected by a pipe 25 to a gas supply main 26 through a shut-off valve shown, generally, at 21. The shut-off valve 21 comprises a valve port 28 which may be closed by a valve body 29 that is operated by an electromagnet 30. For purposes of illustration the valve body 29 is shown as being lifted off of the valve port 28. It will be understood, however, that when the eiectromagnet 30 is deenergized, the valve body 29 will drop and close the valve port 28, thereby preventing the flow of gas through the shut-off valve 21.

With a view to lighting the main gas burner II a pilot burner 3| is provided that is connected by a suitable pipe 32 to the supply main 26. It will be understood that, under normal operating conditions, the pilot burner 3| is lighted continually.

The electromagnetsli may be energized from the energized conductors Hand 20. One terminal of electromagnet 30 is directly connected to the energized conductor 20 through a conductor 33. The other terminal is indirectly connected to the energized conductor l9 through a conductor 34, containing in series a mercury control switch 35, and conductor l8 through switch 2|. Thus the electromagnet 30 can not be energized until both the mercury control switch 35 and switch 2| are closed.

The conductor |1, connecting one terminal of the motor 5 to the energized conductor 20, contains in series a thermostatic switch 40. This thermostatic switch 40 may be any one of several different types and might be located in a position to be responsive to the temperature of a room heated by the furnace I0. When the room gets to a predetermined temperature the contact at 4| will open and the motor i6 driving the fan l2 will be turned off. It is also seen that when the room cools sufficiently the contact at 4| will be closed and the fan I2 started, thereby again forcing air through the furnace ill to heat the room.

When the fan |2 is stopped and not forcing air over the heating surface H the main burner II should be turned off for two reasons. First, if air is not passing over the heating surface l4 when the main burner II is heating it, it may become overheated and may be seriously damaged by the high temperature to which it will be raised. Secondly, when the fan i2 is not running, the rooms heated by furnace II) are warm enough and the heat from the main burner II is not needed.

With a view to causing the main burner H to be put in operation only when the fan I! is running, a control mechanism shown, generally, at 42 is provided. The control mechanism 42 operates the mercury control switch 35 which has been shown to be connected in series relationship with electromagnet 30. This mercury control switch 35 may be of the type having a pool of mercury 43 which is moved from one end to the other of the switch in accordance with tilting thereof. The control switch 35 is mounted for operation on a suitable operating member or shaft 44.

The control mechanism 42, besides controlling the operation of the main gas burner II, also performs the safety measure of not allowing the shut-off valve 21 to open unless the pilot 3| is burning. It is seen that this is very important, as it would be extremely dangerous to have gas escaping unignited through the main burner II.

In order to operate the switch 35 in accordance with whether or not the pilot 3| is burning, an arm 45 is provided extending downwardly from shaft 44 and having at its lower end a permanent magnet 46, having a horseshoe shape. Cooperating with the permanent magnet 46 is a member 41 of Curie point metal, in the shape of an angle. The vertical leg of member 41 is arranged to bridge between the ends of the permanent magnet 46 and the horizontal leg is positioned in thermally conductive relation to the flame of the pilot burner 28. When this flame is absent, the temperature of the member 41 is below the Curie point and possesses magnetic properties. When the pilot burner 3| is lighted and the member 41 is heated above its Curie point, it loses its magnetic properties to such an extent that it functions as if it were made of non-magnetic material.

When the pilot burner 3| is not lighted, the member 41 of Curie point metal possesses magnetic properties. Since the member 41 is stationarily mounted, the permanent magnet 46 is attracted and held in contact with the member 41 and, since the permanent magnet 46 is mechanically connected to the shaft 44 carrying the switch 35, the latter is held in the position illustrated in the drawing, which is the open circuit position. As long as the pilot burner 3| remains unlighted, the permanent magnet 46 will hold itself in engagement with the member 41 of Curie point metal and thereby will hold the switch 36. controlling the electromagnet 36, in the open position. When the pilot burner 3| is lighted, the member 41 of Curie point metal will be heated and will lose its magnetic properties and the permanent magnet 46 will no longer cling to it. However, the rotating force due to the weight of the permanent magnet 46 is so counterbalanced by the adjustable weight 43, that when the member 41 is heated and therefore the permanent magnet 46 is not attracted to it, the shaft 44 will rotate slightly so that permanent magnet 46 no longer engages member 41. It will, however, not rotate suiiiciently to tilt the switch 36 enough to close it. This may be called the intermediate position of the permanent magnet 46. As the result, switch 35 will still remain in the open position until some outside force is applied to the shaft 44 for rotating it sufllciently to close it.

This outside force is supplied by the draft from the fan I2. For this purpose the shaft 44 has extending upwardly therefrom an arm 46 which carries at its upper end a sail member 60. As illustrated, the sail member 60 is positioned in the path of the air from fan II. This blast of air from the fan I! is sufficient to cause the sail member 50 to move and rotate the shaft 44 for operating the control switch 35 to the closed position, provided that the pilot burner 3| is lighted and the permanent magnet 46 is not attracted to the member 41 of Curie point metal.

With a view to describing the operation of my safety system responsive to temperature and fluid flow, assume that the pilot burner 3| is lighted, the main burner II is out, and that the fan I2 is stopped. Under these conditions the permanent magnet 46 will not be attracted to the member 41 and under the effect of gravity it will move to the intermediate position not touching the member 41. As there is no draft of air from the fan l2 the control switch 35 will be in the open position, thereby, causing the electromagnet 30 to be deenergized. Now if the room in which the thermostatic switch 46 is positioned cools sufficiently, the contact at 4| will be closed on the action of the thermostatic switch 4|! and the fan l2 will be started. When the fan I! starts the sail member 50 will be acted on by the draft set up and thereby cause the control switch 36 to'close. When the control switch 35 closes the electromagnet 30 will become energized and gas will flow to the main gas burner II and will be lighted by the pilot burner 3|. After the room is heated sufficiently, the thermostatic switch 46 will open the contact at 4| and cause the fan If to stop. When the fan I! stops there will no longer be a draft against the sail member 50 and consequently the control switch 35 will open, thereby deenergizing the electromagnet 30 and shutting off the gas supply to the main gas burner II.

It will be seen, from the description of the operation given above, that if the pilot burner 3| should go out for some reason and the fan I! should be started by the closing of the contact at 4|, the switch 36 would not be closed as the permanent magnet 46 would cling to the member 41 and as a result no gas would flow to the main burner I. But, since the air forced through furnace ID by the fan I2 is not heated the thermostatic switch 40 will not open the contact at 4| and the fan l2 will continue running indefinitely. In order to prevent an occurrence of this nature, a bell or other alarm 55 may be connected to the conductor I I by the conductor 56 as shown. The other terminal is connected to conductor i8 by the conductor 51 through the switch 58. As shown, one contact member of the switch 58 is carried on a projection of the downwardly projecting member. The switch 55 is so set up that it will not be closed unless the permanent magnet 46 is clinging to the member 41 or Curie point metal as shown in the drawing. Now, it will be seen that if the pilot burner 3| should go out the switch 58 will close and the bell 55 will give warning of the condition.

It is to be understood that the alarm 55 and the corresponding contacts 58 may optionally be omitted. In that event, the movable system including magnet 46 need not shift to the intermediate position heretofore described. That is to say, when the Curie point material 41 loses its magnetic properties the magnet 46 need not move away, even though no attraction between the parts 55 and 1 exists. When this attraction ceases, the draft acting on the sail is free to shift the movable system to the desired position of closing the switch 35 or performing any other desired operation. Thus, when the alarm is not incorporated, the permanent magnet 45 may engage the member 41 at all times except when it is forced away by a draft acting against the sail member 50.

Since certain further changes may be made in the foregoing construction and different embodiments of the invention made without departing from the scope thereof, it is intended that all matter shown in the accompanying drawing or described hereinbefore shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. Safety control means responsive to temperature and fluid flow comprising, in combination, a control switch, magnetic means operatively connected to said control switch, a body of Curie point material, and sail means operatively connected to said control switch, said magnetic means being attracted to said body of Curie point material when said body is below its Curie point, there being substantially no attraction between said magnetic means and said body of Curie point material when said body is at a temperature above its Curie point.

2. Control means responsive to temperature and fluid flow comprising, in combination, a control switch, relatively movable cooperating magnetic means and Curie point metal means, one of said means being'operatively connected to said control switch for controlling its operation according to whether the temperature of said Curie point metal means is above or below its Curie point, and fluid flow responsive means also operatively connected to said control switch and adapted to control its operation in accordance with change in fluid flow.

3. Control means responsive to temperature and fluid flow comprising, in combination, a rockable member, switch means operated from one position" to another by said rockable member, relatively movable cooperating magnetic means and Curie point metal means, one of said means being operatively connected to said rockable member for moving it from one position to another according to whether the temperature of said Curie point metal means is above or below its Curie point, and fluid flow responsive means also operatively connected to said rockable member for moving it from one position to another in accordance with change in fluid flow, said switch means being operable from one position to another only under predetermined conditions of both temperature and fluid flow.

4. Control means responsive to temperature and fluid flow comprising, in combination, switch means carried on a rockable shaft, a permanent magnet carried by said shaft, a body of Curie point metal in cooperative relation to said magnet for controlling the position of said shaft according to whether the temperature of said Cin'ie point metal is above or below its Curie point, and a sail carried by said shaft for controlling its position in accordance with change in fluid flow, said switch means being operable from one position to another only under predetermined conditions of bothtemperature and fluid flow.

ROBERT A. WI'I'IMANN.

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