US2568107A - Safety fuel system for heaters - Google Patents

Description

Sept. 18, G. w. ALLEN I SAFETY FUEL SYSTEM FOR HEATERS 3 Sheets-Sheet 1 Filed Sept. 5, 1943 ENEINE CA RB URE TOR SAFETY VAL VE Patented Sept. 18, 1951 SAFETY FUEL SYSTEM FOR HEATERS George W: Allen, Indianapolis, Ind., assignor to Stewart-Warner Corporation, Chicago, Ill., a corporation of Virginia Application September 3, 1948, Serial No. 47,567

(Cl. I5828) 13 Claims.

The present invention relates to safety fuel systems and more particularly to a liquid fuel system for use with heaters, particularly but not necessarily of the small internal combustion type.

One of the objects of the present invention is to provide a simple but inherently safe fuel system for use with heaters or other fuel consuming devices.

Still another object is to provide a fuel system having the above characteristics and in which a quantity of fuel is isolated for starting purposes and this quantity of fuel is supplemented by an additional fuel supply connection to be used only in the event that the fuel consuming device operates promptly.

Still another object is to provide a fuel system having the given characteristics and in which the device functions completely automatically.

Still another object is to provide a fuel system having the above characteristics and which is not sensitive to vibratory forces or to orientation.

Other objects and advantages will become apparent from the following description of several similar embodiments of my invention, the invention being illustrated in the accompanying drawings, in which:

Fig. 1 is a diagrammatic representation of a fuel system in an automotive vehicle which is intended to supply both the vehicle engine and the combustion heater with fuel and which includes the safety device of the present invention;

Fig. 2 is a top view of the principal mechanical safety element used in the system of Fig. 1;

Fig. 3 is a vertical sectional view and may be considered as taken in the direction of the arrows substantially along the line 3-3 of Fig. 2;

Figs. 4 to 7 are electrical diagrams showing alternative circuit arrangements for controlling and operating the heater and safety device of Figs. 1 to 3.

Referring to Fig. 1 of the drawings it will be seen that a fuel tank I which may be considered as the fuel tank of an automobile is connected by a fuel line [2 to a filter i4 and thence to a pump 16 which is connected on its outlet side by a pipe I8 and branch 23 to the vehicle engine carburetor 22. This much of the system may be considered as conventional in an automotive vehicle and is normally present for supplying filtered fuel under pressure from the vehicle tank to the engine carburetor. The pipe It also leads to the safety device indicated generally by the numeral 24 and which comprises one of the principal elements of the present invention. This 2 safety device is connected on its outlet side with a pipe 26 which leads to a magnetic shut-off valve 28 of conventional design and thence to a vehicle heater 30 of the combustion type. This heater may be of the type illustrated and described in copending application filed June 1 1946, for "Heaters and which has been given Serial No. 676,776, now Pat. No. 2,507,081, granted May 9, 1950.

Referring to Figs. 2 and 3 of the drawings the safety device of the present invention includes a base member 32 and a cover member 34, both of which may be formed as sand castings or die castings or the like. These two members are generally cup shaped and circular in outline and are secured together in face to face relation by a plurality of screws 36 spaced around the periphery. The members when together ericlose a space or chamber which is divided by a flexible diaphragm 38. This diaphragm is secured around its edges between the mating faces of the upper and lower members 34 and 32and acts as a gasket to seal the chamber as well as a flexible member for dividing the space within the castings into a lower chamber 40 and an upper chamber 42.

A rivet 46 extends through the center of the diaphragm from the lower surface thereof and passes through a washer 48 above the diaphragm, the stem of the rivet being peened over to fix the rivet in place and form a leak-proof structure. The lower end of this rivet forms a spring seat which bears against the upper end of a coil spring 50, the lower end of which is seated in a socket 52 formed in the base casting 32. This spring is comparatively light in its action but has sufficient force tourge the diaphragm 38 into its uppermost position with the top end of the rivet 46 against the inside surface of the cover member 34. A comparatively light hydraulic pressure in the upper chamber 42 will urge the diaphragm 38 downwardl while compressing the spring until the lower surface of the diaphragm closely follows the contour of the inside surface of the base member 32. The movement of the diaphragm from side to side, therefore, is such that when the diaphragm is in the uppermost position the lower chamber 40 is large while the upper chamber 42 is small. Conversely, when the diaphragm is in the lower position the upper chamber 42 is large while the lower chamber 40 is small.

The upper casting 34 is formed to provide an inlet fitting 54 which is connected to the pipe l8 previously mentioned. Thus, fuel under pressure in the pipe IB is in communication with the upper chamber 42. Similarly, an outlet fitting 56 is formed as a portion of the lower member 32 and communicates by way of a passage 68 with the lower chamber 40. This fitting 56 is connected to the outlet line 26 which leads to the magnetic shut-off valve 28.

A magnetic by-pass valve 60 is mounted upon the cover member 34. This magnetic valve has a plunger 62 which in the downward position acts to close a valve seat 64 formed as a portion of the cover 34. When the magnetic valve is energized, the plunger 62 is lifted to the position shown in Fig. 3, thereby uncovering the valve seat 64 so as to permit a flow of fuel from the upper chamber 42 by way of a'passage 66 into an annular chamber 68 surrounding the valve members 62 and 64 and thence through the valve seat 64 and into drilled intersecting passages I and 12, the latter of which communicates with the outlet fitting 56. Conveniently, the passages 66, I0 and I2, the annular chamber 68 and the valve seat 64 may all be formed by machining the cover casting 34.

From the above description of the device of Figs. 2 and 3 it will be seen that fuel under pressure may flow into the upper chamber 42 whenever the pumpl6'is operated, that the lower chamber 48 is in communication with the outlet pipe 26 at all times and that whenever the ma netic valve 60 is energized fuel will flow from the upper chamber 42 to the lower chamber 40, in other words, from the inlet fitting 54 to the outlet fitting 56. 'On the other hand, however, when the magnetic valve 60 is de-energized there is no communication between the upper and lower chamber 42 and 40 or between the inlet and outlet fittings 54 and 56.

Fig. 4 illustrates an electrical circuit for use with a heater of the type mentioned when a valve of the above description is included in the fuel circuit. This electricalcircuit may be considered as typical of a group of circuits suitable for this purpose, four of which will be described.

In Fig. 4 the lead indicated by the numeral I4 is connected to the vehicle ignition switch such that this electric lead is energized only when the vehicle ignition switch is in the on position. This lead I4 is also connected to a double pole, single throw heater switch 16 which may be used for placing the heater in and out of operation, provided of course the vehicle ignition switch is in the on position. The lead I4 -is connected to both switch contacts 18 and 80 which respectively co-operate with contacts 82 and 84. One of these contacts, 84 for instance, is connected by lead 86 to a thermostatic overheat switch 88 which'may be of conventional type and which commonly is mounted upon the heater. This switch is simply a thermostatic normally closed switch which opens whenever the temperature of the heater rises sufficiently high to indicate that operation of the heater may become unsafe. The outlet side of this overheat switch is connected to one terminal of the magnetic fuel shut-off valve 28, the other terminal of which is grounded.

It is apparent, therefore, that whenever the vehicle ignition switch is in the on" position and the heater switch I6 is closed, the shut-off fuel valve 28 will be energized and therefore opened, provided of course the temperature of the thermostatic overheat switch 88.

The other output contact, 82 for instance, of I the switch I6 is connected by a lead 90 to a thermostatic igniter switch 92 mounted upon the heater or otherwise so arranged as to be sensitive either to heater temperature or to the air temperature on the output side of the heater. This thermostatic switch is of the single pole, double throw type and is so arranged that when the switch 92 is cold the swinging member 94 thereof will be against an output contact 96 connected by a lead 98 to one terminal of an igniter I00, the opposite terminal of which is grounded. Therefore, if the vehicle ignition switch is closed and if the heater switch I6 is also closed and if the heater is cold, the igniter I00 will be energized. If the heater lights properly, the temperature will rise sufficiently so that after a comparatively short interval of time, as an example, half a minute, the temperature of the igniter switch 92 will rise sufficiently to cause the swinging contact 94 to break the circuit with the output contact 96 and to close a circuit to the other output contact I02 connected by a lead I04 directly to'the vehicle battery.

The lead 90 leading from the contact 82 is also connected by a branch I06 to a combustion air blower motor I08 and a ventilating air blower motor H0 in parallel. The first of these motors when energized supplies air to the heater for combustion purposes while the second motor II8 drives a ventilating air blower which circulates air through the heater and to the space to be heated. This branch lead I06 is also connected to one terminal of the by-pass safety valve 60, the other terminal of which is connected to the swinging member II2 of a single pole, double throw switch II4. Normally this swinging member of the switch H4 is loaded by a spring or otherwise so that it maintains an electrical circuit with an output contact II6 connected by a lead II8 back to contact 96 of the igniter switch 92. The second output contact I28 of the switch I I4 is connected to ground and a push button I22 is provided which when manually actuated urges the switch arm I I2 away from the contact H6 and against the contact I20. It is necessary that this push button I22 be maintained in the depressed position in order to keep the switch in this position. As soon as the button is released the switch snaps back to ,the position shown in Fig. 4.

This circuit operates in the following manner. Assuming that the vehicle ignition switch is in the on" position and that the heater is cold, if the heater switch I6 is closed, current will flow by way of contacts and 84 and by way of the overheat switch 88 to the fuel shut-off valve 28.

It will be assumed for the purpose of providing a starting point in the description that the valve 24 is in the position shown in Fig. 3, that is, the diaphragm 38 is in the uppermost position and the lower chamber 40 is filled with fuel. It should be assumed also that the valve 60 is de-energized and that therefore there is no connection between the upper chamber 42 and the lower chamber 40. Assuming also that the vehicle engine is operating, it will be apparent that the pump I6 will be supplying fuel under pressure. Therefore, fuel flowing into the upper chamber 42 under pressure will urge the diaphragm 38 downwardly, thereby displacing fuel in the lower chamber 40 out through the passageway 58, fitting 56 and pipe 26 to the fuel shut-off valve 28. Since this valve is energized and therefore open, fuel flows to the heater. Inasmuch as the spring 50 is quite soft in its action it will be seen that the fuel pressure flowing outwardly through the pipe 26 is substantially as high as the fuel pressure flowing into the upper chamber 42.

Current also flows through the lead 90 to the switch 92 and inasmuch as this switch is closed, to the contact 96 and then to igniter I00. This igniter which conventionally is of the hot wire type immediately starts heating and will reach ignition temperature in a matter of a few seconds. It will be apparent also that current will be sup plied through the branch I06 to the ventilating air blower motor and to the combustion air blower motor I08. Since, however, both terminals of the by-pass valve 60 are connected to the same side of the circuit, that is, the branch lead I06 connected to one terminal of the by-pass valve is at the same electrical potential as the lead 98 which is connected through the switch II4 to the other terminal of the by-pass valve. this valve of course remains closed. Under these conditions the heater should start operation within a matter of ten seconds or so inasmuch as the igniter will soon be at ignition temperature and since fuel and combustion air are being supplied in appropriate quantities.

If the heater does not start promptly, the thermostatic igniter' switch 92 remains cold and remains in the position shown in Fig. 4. The valve 60 therefore remains de-energized and closed. Thus, as soon as fuel flowing into the upper chamber 42 has displaced the diaphragm downwardly its full distance so as to displace all of the fuel in the chamber 40 to the heater 30, the heater will cease operation since no more fuel can reach the heater. The preferred size of the chamber 40 depends upon the characteristics of the heater and with the heater shown may be such as to provide fuel for approximately two minutes operation. Therefore, if the heater does not start promptly the quantity of fuel isolated for starting purposes in the chamber 40 will become exhausted in about two minutes and the heater will receive no more fuel.

If, on the other hand, the heater does start promptly as it should, then the igniter switch 92 will rise in temperature sufficiently to shift the contact 54 away from the contact 96 and against the contact I02 within less than a minute. This connects the lead 90 to the contact I02 and thence directly to the vehicle battery with the result that the motors I08 and I I0 which drive the combustion air blower and the ventilating air blower no longer depend upon the switch IE or the vehicle ignition switch for energization so long as the igniter switch is hot. Also, since the lead 98 is now disconnected from the switch contact 94 current will flow through the branch I06 through the by-pass valve 60 through the switch H4 and to ground through the igniter I00.

Inasmuch as the lgniter is a low resistance device while the by-pass safety valve 60 has a comparatively high resistance coil, there will be sufficient current flow through the by-pass valve 60 to energize the same and to lift the valve member 62 from the seat 04. The amount of current flowing through this circuit, however, is not enough to raise the temperature of the igniter substantially with the result that the igniter cools.

Inasmuch as the valve 60 has been energized the passage therethrough will be opened, thereby establishing communication between the upper chamber 42 and the lower chamber 40 and between the inlet fitting 54 and the outlet fitting 56. The vehicle fuel pump therefore continues to supply fuel to the heater so as to insure continued operation thereof. Also, inasmuch as communication is now established across the two sides of the diaphragm 38, thereby putting these two sides at substantially the same hydraulic pressure, the spring 50 will urge the diaphragm into the upper position as shown in Fig. 3. The lower chamber 40, therefore, is refilled with fuel in preparation for a new start.

If the heater does not start properly and the fuel within ths chamber 40 becomes exhausted, the operator will know that something is wrong and will either investigate as to the trouble or will take the vehicle to a service station. When the heater has been put in proper functioning order again, depressing the button I22 grounds the terminal II2 with the result that current flows through the by-pass valve 60 so as to energize and open the same, thereby permitting the chamber 40 to refill under the inriuence of the spring 50. It is important to note, however, that if the heater is not in a functioning condition there is no way that the operator will be able to create a dangerous condition inadvertently by causing fuel to continue to flow to the heater since it will require his constant attention in depressing the button I22 every two minutes or so.

The heater is placed out of operation either by opening the heater switch 16 or by turning the vehicle ignition switch to the off position. As soon as this is done the shut-off valve 28 is de-energized, thereby interrupting the supply of fuel to the heater. Since the heater is hot and since some fuel still remains therein, the circuit is so arranged that the combustion air blower motor I08 and the ventilating air blower motor IIO receive energy directly from the battery by way of lead I94 and contacts I02 and 94. The combustion air blower motor and the ventilating air blower motor therefore continue in operation until all of the fuel has been burned away and until the heater has cooled sufficiently to shift the thermostatic igniter switch 92 to the starting position, that is, with contact 94 against cohtact 96, after which both blower motors are deenergized.

This device has very substantial advantages over the commonly used arrangement wherein fuel is supplied to a heater and interrupted subsequently if the heater does not start. One of these advantages is that most systems of the conventional nature depend upon the characteristics of a time delay relay in order to time the starting period. These time delay relays are conventionally of the type wherein a bimetallic member is heated by an electric resistance heater such that after the temperature of the bimetallic member has been raised to a certain predetermined point the switch will shift so as to interrupt the fuel supply to the heater.

These switches have several disadvantages, particularly in automotive vehicles. One of the most serious of these is that the voltage fluctuations in an automotive vehicle electrical system are considerable with the result that the electric energy the resistance heater receives may vary so greatly under different conditions as to make it extremely difiicult and expensive to provide a time delay switch which will have a sumciently long period of delay under high voltage conditions and a sufficiently short period of delay under low voltage conditions. Inother words, it is expensive to provide a switch designed to operate in two minutes under high voltage conditions and which will also operate under low voltage conditions, since under the latter condi- 7 tions the heat loss of the thermostat may balance the heat gain at a temperature below that at which the switch is designed to operate.

The present system, however, overcomes this and other disadvantages because it does not attempt to provide a time limit during which a heater is supplied with fuel for starting purposes, but rather isolates and provides only a certain predetermined quantity of fuel which is used for this purpose. It is also apparent that the device is not sensitive to vibratory forces or to orientation since the diaphragm 38 has extremely low mass and therefore produces only low forces as compared to the hydraulic pressure acting upon the two sides thereof.

The circuit of Fig. 5 which accomplishes generally the same result as the circuit of l' ig. 4 includes the electric lead I24 which, as in the previous instance, is connected to the vehicle ignition switch so that this lead is energized whenever the iginition is in the on position. This lead is connected through a single pole, single throw heater switch I26 and a thermostatic overheat switch I28 to the fuel shut-off valve 28. The output side of the heater switch is also connected through a branch lead I30 to one of the fixed contacts I32 of a double pole, double throw switch I34 preferably of the snap action type. The two movable contacts I36 and I38 of this switch are connected together by a lead I40 also connected tcrthe combustion air blower motor I08. the other side of which is grounded.

The switch I34 is of the thermostatic type and is associated with the heater in the same manner as igniter switch 92 in the previous embodiment. The contacts of this switch are so arranged that when the switch is cold one of the movable contacts is associated with the previously referred to fixed contact I32 while the other movable contact I30 is in engagement with fixed contact I42 connected to the igniter I00, the other side of which is grounded. When the temperature of the thermostatic switch I34 has been raised sufiiciently to indicate that the heater is in operation the movable contacts I36 and I38 snap into engagement with the fixed contacts I44 and I46, respectively. Of these, the contact I44 is connected directly to the vehicle battery and also to one side of a normally open reset switch I48, the other contact of which is connected to the other fixed contact I 46 of switch I34 and also to the ventilating air blower motor H and the by-pass safety valve 60.

The reset switch I48 may be considered as essentially similar to the reset switch II4 excepting that it is a normally open single pole, single throw switch spring loaded to the open position instead of being a double throw switch.

- The circuit of Fig. operates in the following manner. Assuming that the heater is cold and that the lower chamber 40 of the valve in Figs. 2 and 3 is filled with fuel, if now the vehicle ignition switch is shifted to the on" position and the heater switch I26 is closed, current will flow through the thermostatic overheat switch I28 to the shut-off valve 28, thereby opening the same so as to permit fuel to flow to the heater from the chamber 40. Simultaneously current flows through the branch lead I to the contact I32 and thence by way of contacts I36 and I38 to contact I42 and to the igniter I00. Also it energizes the combustion air blower motor I08 through lead I 40. Inasmuch as the igniter quickly heats to ignition temperature under these conditions and since combustion air and fuel are ill being supplied, the heater will normally start after a brief interval.

When the heater has been in operation for a matter of a half minute or so the thermostatic switch I34 will heat sufllciently to shift the contacts I36 and I38 from contacts I32 and I42 to contacts I44 and I46. Since contact I44 is connected directly to the battery it will be seen that when this switch shifts, the combustion air blower will be energized directly from the battery rather than through the heater switch I26 and that the ventilating air blower motor H0 and the by-pass safety valve will be energized by way of contacts I44, I36, I38 and I46 in that order.

Since the by-pass safety valve 60 has now been energized and opened, the heater continues to receive fuel and the diaphragm moves upwardly so as to refill the chamber 40.

In the event that the heater does not start, the fuel within the chamber 40 becomes exhausted in about two minutes or so. After the heater has been repaired pushing the reset button of the switch I48 opens the by-pass safety valve .and permits the lower chamber 40 to be refilled.

It will be seen that the circuit of Fig. 5 operates in a manner essentially similar to that of Fig. 4, excepting that it uses somewhat different although standard switch components and has the advantage of keeping the ventilating air blower motor out of operation until combustion has become well established in the heater. In other words, the ventilating air blower motor is turned on at the same time that the igniter is de-energized. The advantage of this is that no cold ventilating air is circulated during the warm-up period of the heater; As in the previous example, placing the heater out of operation by opening either the heater switch or the engine ignition switch de-energizes only the fuel shut-off valve 28, thereby permitting the ventilating air blower motor and the combustion air blower motor to continue in operation until all remaining fuel has been burned and the heater has been cooled.

The circuit of Fig. 6 is similar to that of Fig. 4 excepting that a relay is used to handle the heavier currents required by the igniter and the blower motor. In this circuit the main lead I50 extending from the vehicle ignition switch is connected to the heater switch I52 and thence by way of lead I54 and branch lead I56 through the single pole, single throw normally closed thermostatic overheat switch I58 to the fuel shut-off valve 28. Lead I54 is also connected to the coil I60 of a relay I62, the other side of the coil being grounded. Thus, when the heater switch is closed and when the vehicle ignition switch is in the on" position the fuel valve 28 is energized and opened and the coil I60 of the relay I62 is energized. This relay is of the normally open single pole, single throw type and has contacts I64 which are closed when the coil I60 is energized. One of the contacts I64 is connected directly to the vehicle battery while the other is connected to ground through a blower motor I66. Although a single blower motor is shown it will be assumed that it will supply both ventilating and combustion air to the heater. If desired, two motors wired in parallel may be used in the manner illustrated in Fig. 4.

The contact I64 connected to the blower motor I66 is also connected by a lead I68 to the swinging member I10 of a thermostatic igniter switch I12. This switch is of the single pole, double throw type and is so arranged that the swing ing contact 0 is in engagement with a contact I14 connected to the igniter I when the igniter switch is cold whereas the swinging contact I engages contact I16 connected by a lead I18 directly to the battery when the igniter switch is hot.

The lead I68 is also connected by a branch I80 to one end of the coil of the by-pass safety valve 60, the other end of whichis connected to the swinging contact member I82 of a reset switch I84. This switch is of the single pole,

double throw spring loaded type, in other words. the type shown in Fig. 4. and is arranged so that the contact I82 is normally spring loaded into engagement with a fixed contact I86 connected by a branch I88 to the fixed contact I14 of the thermostatic igniter switch I12. The other fixed contact I90 of the reset switch is connected to ground and engages the swinging contact I82 only when the reset button I92 is pushed and held.

When this circuit is used, closure of the vehicle ignition switch and the heater switch I52 supplies electrical energy through the overheat switch I58 to the fuel shut-off valve 28, thus opening the connection between valve chamber and the heater. Simultaneously relay coil I60 is energized, thereby causing relay contacts I64 to close so that energy is supplied directly from the battery by way of switch contacts I64 to the blower motor I66and by way of switch I12 to the igniter I00. The by-pass safety valve 60 is not energized, however, since both ends of its coil are connected to points in the circuit at the same potential. In other words, the by-pass safety valve is connected across contacts I10 and I14 which are closed.

After the heater starts, the igniter switch I12 shifts to bring contact I10 against contact I16. This causes electrical energy to be supplied from the battery by way of lead I18 to contacts I16 and I10 and thence to the blower motor I66, so that the blower motor is no longer directly under influence of the relay I62. Also, current will now fiow by way of the lead I18, contacts I16 and I10, lead I68, branch I80 through the coil of the valve 60 and thence through contacts I82 and I86 and lead I88 to ground through the igniter I00. Thus, the by-pass valve is opened so as to permit a continuing supply of fuel to the heater and to permit the chamber 40 to refill.

In the event that the heater does not start, the fuel will be exhausted as in the previous examples and similarly also the fuel chamber 40 may be refilled by pushing and holding the reset button I92. Similarly, also, the blower motor will continue in operation after the heater switch or the ignition switch has been opened since opening of this latter portion of the circuit only deenergizes the fuel valve 28, the blower motor continuing to receive energy until the igniter switch cools.

The circuit of Fig. 7 uses a relay much like the circuit of Fig. 6 to accomplish much the same results as the circuit of Fig. 5. In this arrangement a double pole, double throw relay I94 has one end of its coil I96 connected by a lead I98 directly to the vehicle battery. The other end of the coil I96 is connected by way of a lead 200 to the swinging contact 202 of a single pole, double throw reset switch of the push button type such as is used in the circuits of Fig. 4 and Fig. 6.

The contact 204 with which contact 202 normally is in engagement is connected through a normally open single pole, single throw thermostatic igniter switch 206 to ground. This igniter switch is open when cold and closes whenever the temperature of the heater rises sufliciently to indicate that efflcient combustion is taking place. The normally open contact 208 of the push button reset switch is-connected to ground. It is apparent, therefore, that the relay coil I96 is energized only after the igniter switch 2.06 has closed following a period of heater operation.

The moving contacts 2I0 andp2l2 of relay I94 are normally in engagement with fixed contacts H4 and 216 respectively. (if these, contact 2I4 is connected by a lead 2 I8 to one side of a normally open single pole, single throw heater switch 220, the other end of which is connected to lead 222 leading to the vehicle ignition switch. Lead 2I8 is also connected by way of a branch 224 to one side of a normally closed single pole, single throw thermostatic overheat switch 226, the other terminal of which is connectedto ground through the fuel shut-off valve 28.

The moving contacts 2I0 and 2.I2 of the relay I94 are connected together and are also connected by a lead 228 to the combustion air blower motor I08, the other terminal of which is grounded. The other normally closed contact'2l6 of relay I94 is connected to ground by way of theigniter I00. 0f the normally open contacts of the relay I94, one, indicated by the numeral 230, is connected to the"'lead I98 extending directly to the battery while the other of these contacts, 232, is connected to the by-pass safety valve 60 and the ventilating air, blower motor H0 in parallel.

When the ignition switch and heater switch 220 are closed, energy is supplied through lead 224 and switch 226 to the fuel shut-off valve 28 so as to connect the fuel chamber 40 to the heater, thereby permitting fuel to be supplied to the heater from the chamber. Simultaneously, energy is supplied through branch lead 2I8 and contacts 2I4 and 2I0 to lead 228, thereby energizing the combustion air blower motor. Also. since contacts 2I2 and 2I6 are in engagement, the igniter is energized.

After the heater has been in operation for a brief interval the igniter switch 206 closes, thereby energizing the relay coil I96 by way of battery lead I98, relay coil I96, lead 200, switch contacts 202 and 204, and switch 206 and thence to ground. Energization of the relay coil I96 shifts contacts 2I0 and M2 into engagement with contacts 230 and 232 respectively. Since contact 230 is connected directly to the vehicle battery, it will be seen that the combustion air blower motor I08 now receives energy independently of the heater switch 220. Also, the igniter will be tie-energized and current will fiow from the battery lead I98 through contacts 230 and 2I0 to contact 2 I2 and thence by way of contact 232 to the by-pass safety valve and the ventilating air blower motor.

If the heater does not start promptly and the fuel in the chamber 40 becomes exhausted it may be replenished by manually holding the reset push button of the switch 202 which energizes the relay I96 independently of the igniter switch 206. This circuit operates much in the manner of the circuit of Fig. 5 in that although both the combustion air blower motor and the ventilating air blower motor remain energized after the heater has been turned off until all remaining fuel has been burned and the heater has been cooled sufficiently to cause operation of the igniter switch 206, the ventilating air blower motor does not come into operation during the starting cycle until the heater is hot. In other words, cold ventilating air is not circulated during the warm-up period.

If it is desired to use a system of this type with in several modifications thereof it is contemi plated that still other modifications may be made without departing from the spirit of my invention. It is understood, therefore, that the invention is to be measured by the scope of the following claims.

I claim:

1. A fuel safety device comprising a flexible diaphragm, means enclosing one side of said diaphragm to form a chamber with said diaphragm forming one wall thereof, means enclosing the other side of said diaphragm to form a second' chamber with said diaphragm forming one wall thereof so that when said diaphragm is displaced in one direction, said first chamber is enlarged in volume while the volume of the second chamber is reduced and when said diaphragm is displaced in the opposite direction the volume of the first chamber is reduced while the volume of the second chamber is enlarged, means forming a fuel supply connection to said first chamber, means forming a fuel outlet connection from said second chamber, resilient means for urging said diaphragm in the direction for reducing the volume of said first chamber, means providing an outlet connection for said first chamber in direct communication with the outlet to said second chamber, and valve means for controlling the flow through the outlet connection for said first chamber.

2. A fuel safety device comprising a movable member, means enclosing one side of said movable member to form a chamber with said movable member forming one wall thereof, means enclosing the other side of said movable member to form a second chamber with said movable member forming one wall thereof so that when said movable member is displaced in one direction said first chamber is enlarged in volume while the volume of the second chamber is reduced and when said movable member is displaced in the opposite direction the volume'of the first chamber is reduced while the volume of the second chamber is enlarged, means forming a fuel supply connection to said first chamber, means forming a fuel outlet connection from said second chamber, resilient means tending to move said movable member in the direction for reducing the volume of said first chamber, means providing an outlet connection for said first chamber in direct communication with the outlet to said second chamber, and valve means for controlling the flow through the outlet connection for said first chamber.

3. A fuel safety system for use with a combustion heater comprising, a flame detector switch responsive to combustion in the heater, a flexible diaphragm, means enclosing one side of said diaphragm to form a chamber with said diaphragm forming one wall thereof, means enclosing the other side of said diaphragm to form a second chamber with said diaphragm forming one wall thereof so that when said diaphragm is displaced in one direction said first chamber is enlarged in volume while the volume of the second chamber is reduced and when said diaphragm is displaced in the opposite direction the volume of the first chamber is reduced while the volume of the second chamber is enlarged, means for supplying fuel under pressure to said first chamber, means forming a connection from said second chamber to the heater, resilient means for urging said diaphragm in the direction for reducing the volume of said first chamber, means providing a fluid connection between said chambers, a normally closed magnetic valve arranged for controlling the fiow through said last connection, and electric circuit means including said flame detector switch adapted for opening said valve when said flame detector responds to combustion in said heater.

4. A fuel safety system for use with a combustion heater comprising, a flame detector switch responsive to combustion in the heater, a movable member, means enclosing one side of said movable member to form a chamber with said movable member forming one wall thereof, means enclosing the other side of said movable member to form a second chamber with said movable member forming one wall thereof so that when said movable member is displaced in one direction said first chamber is enlarged in volume while the volume of the second chamber is reduced and when said movable member is displaced in the opposite direction the volume of the first chamber is reduced while the volume of the second chamber is enlarged, means for supplying fuel under pressure to said first chamber, means forming a connection from said second chamber to the heater, resilient means for urging said movable means in the direction for reducing the volume of said first chamber, means providing a fluid connection between said chambers, a normally closed magnetic valve arranged for controlling the fiow through said last connection, and electric circuit means including said flame detector switch adapted for opening said valve when said flame detector responds to combustion in said heater.

5. A fuel safety device comprising, means providing a first expansible chamber, means providing a second expansible chamber, both of said means being arranged so that collapse of one of said chambers causes expansion of the other of said chambers, resilient means for expanding the second of said chambers, means forming a fluid fuel supply connection to said first chamber, means forming a fuel outlet connection from said second chamber, means providing an outlet connection for said first chamber in direct communication with the outlet to said second chamber, and valve means for controlling the flow through the outlet for said first chamber.

6. A fuel safety system for use with a combustion heater comprising, a flame detector switch responsive to combustion in the heater, means providing a first expansible chamber, means providing a second expansible chamber, both of said means being arranged so that collapse of one of said chambers causes expansion of the other of said chambers, means normally expanding the second of said chambers, means for supplying fluid fuel under pressure to said first chamber, means forming a fuel outlet connection from said second chamber to said heater, means providing a fluid connection between said chambers, a normally closed magnetic valve arranged for controlling the flow through the last said connection, and electric circuit means including saidfiame detector switch adapted for openingsaid valve when said flame detector re-' providing a first expansible chamber, means pro-- viding a second expansible chamber, both of said means being arranged so that collapse of one of said chambers causes expansion of the, other of said chambers, means normally expanding the second of said chambers, means for supplying fluid fuel under pressure to said first chamber, means forming a fuel outlet connection from said second chamber to said heater, means providing a fluid connection between said chambers, a normally closed magnetic valve arranged for controlling the flow through the last said connection. electric circuit means including said flame detector switch adapted for opening said valve when said flame-detector responds to combustion in said heater, a normally closed magnetic valve arranged in said fuel outlet connection, and an electric circuit for opening the last said valve to permit operation of said heater.

8. A fuel safety system for use with a fluid fuel burning combustion heater comprising, a source of fluid fuel under pressure, fluid motor means including means defining a collapsible chamber for isolating a predetermined quantity of fuel, hydraulic means for collapsing said chamber to feed the fuel isolated thereby to said heater, resilient means normally tending to expand said chamber, a first conduit forming means for conveying fuel from said chamber to said heater, a second conduit forming means through which said hydraulic means is subjected to the hydraulic pressure of the fuel at said source connecting said source of fuel to said hydraulic means, a third conduit forming means for subjecting the interior of said isolating chamber to the hydraulic pressure of the fuel at said source to neutralize the effect in said hydraulic means of the pressure of the fuel at the source, and a valve for closing communication through said third conduit forming means.

9. In a device of the class described the combination comprising means forming a hollow casing having internal walls defining a closed space, means forming a flexible wall in said casing dividing said closed space into first and second fluidtight chambers, means biasing said flexible wall to a predetermined position when balanced hydraulic pressures are exerted on opposite sides thereof, means forming an inlet to the first chamber for delivering fluid under pressure thereto from an external source, means forming an out let connection in direct communication with both chambers, and valve means in said outlet connection to close communication between the said first chamber and outlet connection.

10. In a device of the class described the combination comprising means forming a hollow casing having internal walls defining a closed space, flexible means cooperating with the walls of said casing to define fluid-tight chambers increasing or decreasing in volume in accordance with movements of said flexible means, biasing means to move said flexible means to a position at which said chambers have a predetermined volume, means forming an inlet connection for delivering fluid under pressure to said first chamber from an external source, means forming an outlet for conveying fluid from said device to the exterior, passageway forming means connecting said two chambers to each other for equalizing the pressure,. therein and to said outlet, and valve means to control flow of fluid between said chambers independently of the control of flow from the second chamber to the outlet.

11;; In a device of the class described the combination comprising means forming a hollow casing having internal walls defining a closed space, flexible means cooperating with the walls of said casing to define fluid-tight chambers increasing or decreasing in volume in accordance with movements of said flexible means, means for biasing said flexible means to a position at which said chambers have a predetermined volume,,means forming an inlet connection for delivering fluid under pressure to said first chamber from an external source, means forming a passageway between said chambers for equalizing the pressure of the fluid therein, means forming an outlet connection for conveying fluid from said second chamber to the exterior of said device, and a valve to close communication through the passageway between said first and second chambers.

12. A fuel safety system for use with a fluid fuel burning heater comprising, a flame detector switch responsive to combustion in the heater, means providing first and second expansible chambers arranged so that collapse'of one of said chambers causes expansion of the other of said chambers, biasing means to collapse said first chamber, means for supplying fluid fuel under pressure to said first chamber, means forming a fuel outlet connection from said second chamber to said heater, means providing a fluid connection between said chambers, a normally closed magnetically operated valve arranged for controlling the flow through the last said connection, electric circuit means including said flame detector switch adapted for opening said valve when said flame detector responds to combustion in said heater, power operated combustion and ventilating air supply means and circuits for energizing said power operated air supply means including a circuit independent of said flame detector switch for energizing said air supply means" before said flame detector switch responds to combustion, and a circuit including said flame detector switch for energizing said air supply means when said flame detector responds to combustion in said heater.

13. A fuel safety system for use with a fluid fuel burning heater comprising, a flame detector switch movable from one position to another in response to combustion in the heater, means providing first and second expansible chambers arranged so that collapse of one of said chambers causes expansion of the other of said chambers, biasing means to collapse said first chamber, means for supplying fluid fuel under pressure to said first chamber, means forming a fuel outlet connection from said second chamber to said heater, means providing a fluid'connection between said chambers, a normally closed magnetically operated valve arranged for controlling the flow through the last said connection, electric circuit means including said flame detector switch adapted for opening said valve when said flame detector responds to combustion in said heater, independent combustion and ventilating air supply means, independent circuit means connected to said flame detector switch for connecting said combustion and ventilating air supply means to a source of electric current including a circuit to connect said combustion air supply'means to said source of current at both positions of said flame detector switch, and a circuitito connect said van- 3 15 tilatlng air supply means to a source of current when said flame detector switch responds to combustion in said heater.

. GEORGE W. ALLEN.

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

UNITED STATES PATENTS Name Date 941,587 Putnam NOV. 30, 1909 Number Number

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