US3542060A - Fluid fuel burner control systems - Google Patents

Description

United States Patent Appl. No. Filed Patented Assignee FLUID FUEL BURNER CONTROL SYSTEMS 4 Claims, 5 Drlwh Figs.

US. Cl. 137/4875, 251/132 Fl6k3l/0Z Fleldolseareh 137/4875, 488, 492, 492.5, 412, 413, 394; 251/129, 132

[ 56] References Cited UNITED STATES PATENTS 1,658,577 2/1928 Smoot l37/487.5UX

1,756,824 4/1930 Hasemann Primary ExaminerM. Cary Nelson Assistant Examiner-R. B. Rothman Attorney-Holman, Glascock, Downing and Seebold ABSTRACT: A fluid fuel burner control system employs an electrically controlled power operated main gas valve for con- Patented Nov. 24, 1970 3,542,060

Sheet 1 0f 3 jlO 44m jZ M- MW ATTORNEYS Patented Nov} 24, 1970 7 Sheet FIGE.

ATTORNEYS Patented Nov. 24, 1970 3,542,060

FIGB.

aw )XM ATTORNEYS burnerat a predetermined pressure.

It h as been customary, in the past, particularly in gas burner systems, to employ pressure governors to control the pressure,

such governors relying upon the pressure energy of the fuel itself-for their operationpwhere it is required to control a large quantity of fuel at a relatively low pressure it has been necessary to utilise extremely large governors to enable the required amount of energy to be obtained from the fuel.

It is also becoming fairly common to utilise power operated valves in fuel burner systems, to enable automatic control to 'be effected.

According to the present invention a fluid fuel burner con-v trol system dispenses with the pressure governor and utilises instead, a pressure-sensitive device on the downstream side of a power operated llow control valve. said pressure-sensitive device being operatively connected to said valve for actuating the latter in such a manner that in use, the pressure downstream of said valve is kept between prescribed limits.

In the accompanying drawings:

FIG. 1 is a diagram showing, by way of example, an entire fuel control system for a gas burner;

FIG. 2 is a sectional view of a power operated flow control valve forming a part of the system;

FIG. 3 is an electrical circuit diagram of the valve shown in FIG. 2;

FIG. 4 is a section showing a pressure switch construction which could be employed in the valve of FIG. 2 instead of the pressure switch construction illustrated therein; and

FIG. 5 is an electrical circuit diagram illustrating the application of the invention to a different type of valve.

Referring firstly to FIG. 1, the burner head is connected via a main gasline to the gas supply 11. Flow of gas through the main gasline is controlled by a manual shutoff valve 12 and an eletrohydraulic safety valve 13. There is also a pilot supply to the burner 10 controlled by a manual shutoff valve 14 a solenoid valve 15 and a pressure governor 16. In addition to the usual automatic controls which control the electrohydraulic valve 13, there is a pressure switch 17 in the main downstream ofthe valve I3'to actuate the latter.

As shown in FIG. 2 the valve 13 incorporates an hydraulic piston and cylinder unit 18 which is supplied with pressurised oil by a pump 19 driven by an electric motor 20. There is a limit switch 21 in the motor circuit to deenergise the latter gasline when the valve 13 is fully open. In addition the valve includes a main solenoid valve 22 which, in use, is normally energised to hold the solenoid valve shut. When it is required to close the main valve 13 the solenoid valve is deenergised and allows pressurised oil in the piston and cylinder unit 18 to be ex hausted rapidly to close it. i

The valve 13-has added to it a further solenoid valve 23 arranged, when not energised, to exhaust the piston and cylinder unit 18 via a restrictor 24. i

The pressure switch 17 shown in FIG. 2 includes two microswitches 25, 26 actuable by a diaphragm 27 and both normally closed when there is no pressure applied to the switch. The arrangement of the switches 25, 26 is such that the switch 25 is opened at a first predetermined pressure (determined by the'adjustment of the spring loading of the pressure switch) whereas the switch 26 is opened at a somewhat higher pressure, the pressure difference between the opening of the two switches being determined by the rate of the spring loading and the amount of lost travel allowed to the diaphragm 27. The switch 25 is connected in series with the limit switch 21 and the motor 20. The switch 26 is connected to the solenoid valve 23.

Thus, in use, when the pressure switch is connected to a supply of electrical energy the motor 20 and both of the sole noid valve 22 and 23 are energised. Thus the valve 13 is opened until the pressure on the downstream side of said valve is sufficient to open the switch 25. The motor 20 is then enable the spring loading of valve 13 to deenergised to check opening ofthe valve 13. Should the fuel pressurerise above the pressure required to open switch 26 the solenoid valve 23 will be opened and the valve 13 will therefore slowly close until the fuel pressure falls below the value required for the switch 26 to be closed. The valve 13 still operates, in the normal way, in the automatic control of the burner and shut down thereofin the event of electrical failure.

In the arrangement shown the pressure switch 17 is mounted on the valve body and actually forms a part of the valve. It will be appreciated, however, that a separate pressure switch 17 divorced from the valve 13 maybe employed, if convenient. It will thus be appreciated that a relatively simple and inexpensive arrangem'enthas been provided for controllingthe' pressure at which the gas is supplied to the burner; without using a bulky and expensive pressure governor as utilised in present practice. The invention merely requires the addition of the solenoid valve 23 to the existing valve 13 and the addition to the control system of the pressure switch 17. Both of these items are extremely small and of relatively low cost as compared with the large pressure governor which would otherwise have been required.

The pressure switch construction 116 shown in FIG. 4 is of more sophisticated design than that shown in FIG. 2. In FIG. 2 the switches 25, 26 are operated directly by the diaphragm or a plate lying against the diaphragm. In the arrangement of FIG. 4, however, the switches 124, are actuated by a fork 127 connected by a stern 128 to the diaphragm 126. The switches are movably supported by pillar 129 and an adjusting lmechanism I30, 131 is provided for adjusting each switch relative to the fork. This enables the difference between the pressure at which the two switches are actuated to be adjusted without necessitating dismantling ofthe entire switch. There is also an adjustment screw 132 for varying the spring loading of the diaphragm 126 as before.

In the alternative embodiment of the invention, to which FIG. 5 refers, the valve has a purely electrical drive. There is a reversible electric motor 210 with forward drive terminal 210A, reverse drive'terminal 2108, and common neutral terminal 210C for driving the closure member of the valve towards and away from its seat. The motor in fact, drives the input member of an electromagnetic clutch 211 which in turn drives a pinion 226 engaging a rack 227. This rack 227 is coupled tov the closure member, which is strongly spring loaded l pading towards its fully open position. The clutch 211 is energ ised by closing ofa main switch 228 whenever it is desired to have the valve open and deenergised by opening of switch 228 for rapid shutdown. The pressure switch arrangement has a normally closed switch 224 and a normally open switch 225 which closes at a pressure higher than that at which switch 224 opens. Switch 224 is connected in series with the switch 228 and a limit switch 220 (corresponding to the limit switch 21 of FIG. 3) to the forwarddrive terminal 210A of the motor and switch 225 is connected in series with switch 228 to the to rise until the pressure is high enough toopen switch 224."

Drive of the motor then stops. Should the pressure rise above a prescribed limit switch 225 will be closed and the motor will be driven in reverse direction, thereby applying slow closing movement to the closure member of the valve. On opening of switch 228 the clutch 211 is deenergised so that the valve is shut off rapidly by the action ofits spring loading.

In either of the examples described the closure member is preferably so shaped that the downstream pressure varies gradually over the whole range of movement of the closure member. This enables fine pressure control to be effected.

Iclaim:

towards its seat, to drive the closure member against its spring l. A fuel flow control system for a fluid fuel burner comprispower means when the pressure downstream of the valve is below a first predetermined value and for actuating said means actuable to cause slow closing movement when the pressure is higher than a second predetermined ,value,

whereby in use, the pressure downstream of the valve iskept between said predetermined values.

2. A system as claimed in claim 1 in-which the pressure-sensitive device comprises a member movable against spring loading by fluid pressure, and a pair of switches aetuable by said member at pressures corresponding to said predetermined values.

3. A system as claimed in claim 2 in which the power means comprises an electrically driven pump and a piston and cylinder unit movable by liquid displaced by said pump and in which the means actuable to cause slow closing movement comprises a slow release solenoid valve to allow fluid to be displaced from said pistonand cylinder unit, the switchesbeing respectively connected to the motor and the solenoid valve, the release means being a further solenoid valve.

4. A system as claimed in claim 2 in which said valve incorporates a reversible electric motor', said power means comprising a forward drive circuit of. said motor and said means for causing slow closing movement comprising a reverse drive circuit of said motor, the switches being connected respectively in said forward and reverse drive circuits. and said release motor to the closure member.

means comprises an electromagnetic clutch connecting the

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