US3062521A

US3062521A - Sequence indicating and control system

Info

Publication number: US3062521A
Application number: US96027A
Authority: US
Inventors: Jr Theodore Kraschinsky; Gene C Lutsch
Original assignee: Cutler Hammer Inc
Current assignee: Cutler Hammer Inc
Priority date: 1961-03-15
Filing date: 1961-03-15
Publication date: 1962-11-06
Anticipated expiration: 1979-11-06

Description

Nov. 6, 1962 T. KRASCHINSKY, JR., ETAL SEQUENCE INDICATING AND CONTROL SYSTEM Filed March 15, 1961 o v DUO 2 Sheets-Sheet 1 bVO m w 83 6 is 225 m3 mm s@ maxom 5mm? u x'm aw kn figw X MV I N 35 30 new .3 8 23 Nov. 6, 1962 T. KRASCHINSKY, JR., ETAL SEQUENCE INDICATING AND CONTROL SYSTEM Filed March 15-, 1961 Ll L2 L3 ans sumo VALVE m I :Smv

[smvs FAN SF amowa Ma] 2 Sheets-Sheet 2 [cow mm: VALVE cmv a Mom: Mg]

OPEN

{cmmm' VALVE. cuv z; MOTOR M4] I OPEN I i [51.0mm VALVE aov & MO'TOIL Mal I OPEN I l l United States Patent 3,062,521 SEQUENCE INDICATING AND CONTROL SYSTEM Theodore Kraschinsky, Jr., Milwaukee, and Gene C- Lutsch, Hales Corners, Wis., assignors to Cutler-Hammer, Inc., Milwaukee, Wis, a corporation of Delaware Filed Mar. 15, 1961, Ser. No. 96,027 11 Claims. (Cl. 263-19) This invention relates to sequence indicating and control systems and more particularly to control systems having a plurality of manually operable devices and means for indicating sequences of operation of the manually operable devices.

While not limited thereto, the invention is especially applicable to heating stove changing control systems for blast furnaces for indicating and controlling the sequence in which stove control elements are to be operated for changing the stove from one operating condition to another.

In order to cause the fuel such as coke in a blast furnace to burn at a sufficiently high temperature and to produce sufficient heat to melt the iron ore therein into liquid iron, preheated air is blow into the furnace. This is known as the hot air blast. Because a blast furnace operates continuously, the furnace is provided with a plurality of heating stoves so that while one stove is being used to produce the hot air blast, this being known as the blast condition, the other stoves can be heated by burning gas therein, this being known as the gas condition. When the stove is in its gas condition, combustion air is mixed with heating gas and this mixture is burned in the stove to heat the same. For this purpose, the stove is provided with a gas shutoff valve for controlling admission of gas from a gas main to the stove, a stove fan for mixing combustion air with the gas and .a gas burner valve for controlling admission of the gas and combustion air mixture to a gas burner in the stove. The stove is also provided with a chimney valve for exhausting the products of combustion. When the stove is in its blast condition, cold air is forced through the heated stove to preheat such air and is then forced into the blast furnace. For this purpose, the stove is provided with a cold blast valve for controlling admission of cold air into the stove and a hot blast valve for controlling admission of preheated air from the stove to the blast furnace. The stove is also provided with a mixing chamber and a cold mixer valve having access thereto for mixing some cold air with the preheated air to maintain the hot air blast at the proper temperature. There is also provided a blowoif valve for relieving the pressure within the stove chamber. The aforementioned valves and stove fan must be operated in one sequence to change the stove from its gas condition to its blast condition and must be operated in another sequence to change the stove from its blast condition to its gas condition.

As the aforementioned valves are provided with individual manually-controllable electrical systems for closing and opening the same and the stove fan is provided with a manuallycontrollable electrical system for starting and stopping the same, it has been found desirable to provide sequence indicating and control means for facilitating operation of the manual controls in the proper sequences to change the stove from either operating condition to the other.

An object of the invention is to provide improved sequence indicating and control means.

A more specific object of the invention is to provide an improved arrangement of a plurality of manually-controllable devices together with means indicating sequences of operation thereof.

Another object of the invention is to provide the first device of each such sequence of manually-controllable devices with means indicating the start of each such sequence.

Another object of the invention is to provide such manually-controllable devices with visual indicating means for indicating the progress of operation thereof.

According to the invention, there is provided, for a controllable device having a plurality of control elements each of which has a plurality of operating conditions and which control elements must be operated in diverse sequences to change the controllable device from one operating condition to another and vice versa, an electrical control system for selectively controlling operation of the control elements from one operating condition to another. The control system is provided with an individual manually-controllable switch of the pushbutton type or the like for each operating condition of each control element. To facilitate operation of such switches in the correct sequences, they are arranged on a control panel in an improved arrangement and arrows are provided on the control panel between consecutive pushbuttons of each sequence to indicate the order of operation thereof. Also, the switches are provided with indicia plates to indicate the control functions effectible thereby and the first switch of each sequence is provided with an enlarged indicia plate to indicate the start of each seqnence. And the control system is provided with lamp indicators for lighting the switch actuators to show which switches have been actuated, which control elements have been operated and to show when each succeeding switch may be actuated. The lamps also show the condition of the stove at any given time. Moreover, the switch actuators of each sequence may be of .a distinctive color different from the color of the switch actuators of the other sequence to distinguish the sequences from one another.

The above mentioned and other objects and advantages of the invention and the manner of obtaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment thereof taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a schematic illustration of a heating stove, conduit connections thereto and control elements for controlling fluid flow in the conduits;

FIG. 2 is a schematic illustration of a manual control panel including control devices and sequence start indicators and sequence indicators arranged thereon for controlling the stove of FIG. 1;

FIG. 3 shows an electrical system circuit diagram controllable by the control devices of FIG. 2 for controlling the stove of FIG. 1; and

FIG. 3a shows a cam layout for operating limit switches shown in REG. 3.

Referring to FIG. 1, there is shown for exemplary purposes a heating stove H38 in conjunction with which the invention may be employed. The stove is provided on the left-hand side thereof with a heating chamber HC and is provided on the right-hand side thereof with a mixing chamber MC. The heating chamber is provided with well known devices including an open brickwork called checkers which is heated during the gas condition of the stove and through which cold blast air is passed during the blast condition of the stove to preheat the air whereafter the preheated air is forced into a blast furnace. The mixing chamber is provided for the purposes of mix'ng some cold air with the preheated or hot air to maintain the hot air blast at a constant temperature.

For the gas condition, the stove is provided with a gas'shutoff valve GSV, a stove fan SF, a gas burner valve GBV and a chimney valve CHV. For the blast condition, the stove is provided with a cold blast valve CBV, a cold mixer valve CMV and a hot blast valve HBV.

For relieving the stove pressure, that is, for equalizing the pressure inside and outside the stove before the stove is changed to its gas condition, the stove is provided with a blowoff valve BOV. I

Referring to FIG. 3, there is shown an electrical system for controlling the aforementioned valves and stove fan of FIG. 1. The control system of FIG. 3 is provided with a three-phase alternating current power supply source represented by power supply lines L1, L2 and L3 for supplying power to the valve control motors and the fan control motor. The motor control contactors are energized by single-phase power across lines L1 and L2.

As shown in FIG. 3, gas shutolT valve GSV is provided with a three-phase alternating current operating motor M1 having reversing contactors including a gas shutofi opening contactor G80 and a gas shutoif closing cont-actor GSC for controlling reverse energization of the motor to open and close the gas shutoff valve, respectively. Contac-tor GSO is provided with normally open contacts 1, 2 and 3 for energizing motor M1 in the forward direction to open the gas shutoff valve and 21 normally open contact 4 for completing a self-maintaining circuit for the operating coil of such contactor. Contactor GSC is provided with normally open contacts 1, 2 and 3 for energizing motor M1 in the reverse direction to close the gas shutoff valve and a normally open contact 4 for completing a self-maintaining circuit for the operating coil of such contactor. Gas shutoff valve GSV is provided with a limit switch GSLS having a contact 2 for controlling a gas igniter GI and interlocking

contacts

4 and 8 for controlling contactors G80 and GSC, respectively. Igniter GI is of a well known type which ignites the gas for a predetermined self-timed interval in response to energization thereof and resets in response to deenergization thereof as more fully described in D. W. Fath, T. Kraschinsky, Jr. and G. C. Lutsch copending application, Serial No. 95,964 filed March 15, 1961. Limit switch GSLS is also provided with

contacts

3 and 7 for controlling lamps LP} and LPZ mounted within the pushbuttons of switches RG9 and GBZl, respectively, for purposes hereinafter described.

Stove fan SF is provided with a motor M2 similar to motor M1 except that it is unidirectionally energizable for running the stove fan. Stove fan SF and motor M2 are shown schematically as a rectangle to avoid complicating the drawing. The stove fan motor is provided with a main power contactor SFM having contacts also represented by the aforementioned rectangle for connecting power thereto. A lamp LP3 mounted within the pushbutton of switch RG8, is connected in parallel with the operating coil of contactor SFM for purposes hereinafter described. Contactor SFM is also provided with a normally open contact 4 for completing a self-maintaining circuit therefor and for maintaining lamp LP3 energized and a normally closed contact for energizing a lamp LP4 mounted within the pushbutton of switch GBZ, when the stove fan is stopped for purposes hereinafter described.

Gas burner valve GBV, chimney valve CHV, cold blast valve CBV, cold mixer valve CMV, hot blast valve HBV and blowofi valve BOV are provided with operat ing motors M3, M4, M5, M6, M7 and M8, respectively, having reversing contacts similar to motor M1 and each such valve and its associated motor and motor reversing contacts are shown in FIG. 3 schematically as a rectangle to avoid complicating the drawing.

The gas burner valve motor is provided with reversing contactors including a gas burner opening contactor G130 and a gas burner closing contactor GBC having motor reversing contacts like those hereinbefore described in connection with gas shutofi valve GSV for controlling opening and closing of the gas burner valve. Contactor GBO is also provided with a normally open contact 4 and contactor GBC is provided with a normally open contact 4 for completing self-maintaining circuits for the operating coils of the respective contactors. Gas burner valve GBV is provided with a limit switch GBLS having interlocking

contacts

4 and 8 for controlling contactors G and GBC, respectively, and

contacts

3 and 7 for controlling lamps LP5 and LP6 mounted within the pnshbuttons of switches BG7 and G33, respectively.

The chimney valve motor is provided with a chimney opening contactor CH0 and a chimney closing contactor CHC having motor reversing contacts like those hereinbefore described for controlling opening and closing of the chimney valve. Contactors CH0 and CHC are also provided with normally open contacts 4, respectively, for completing self-maintaining circuits for the operating coils of the contactors. Chimney valve CHV is provided with a limit switch CHLS having interlocking

contacts

4 and 8 for controlling contactors CH0 and CHC, respectively, and

contacts

3 and 7 for controlling lamps LP7 and LPS mounted within the pushbutton of switches B66 and 634, respectively.

The cold blast valve motor is provided with cold blast opening and closing contactors CEO and CBC, respectively, having motor reversing contacts like those hereinbefore described for controlling operation of the cold blast valve. Contactors CEO and CBC are also provided with normally open contacts 4, respectively, for completing self-maintaining circuits therefor. Cold blast valve C3! is provided with a limit switch CBLS having interlocking

contacts

4 and 8 for controlling contactors CEO and CBC, respectively and

contacts

3 and 7 for controlling lamps LP% and LPlt mounted within the pushbuttons of switches GBS and BGit, respectively.

The cold mixer valve motor is provided with cold mixer opening and closing contactors CMO and CMC, respectively, having motor reversing contacts like those hereinbefore described for controlling operation of the cold mixer valve. Contactors CMO and CMC are also provided with normally open contacts 4, respectively, for completing self-maintaining circuits therefor. Cold mixer valve CMV is provided with a limit switch CMLS having interlocking

contacts

4 and 8 for controlling contactors CMO and CMC, respectively, and

contacts

3 and 7 for controlling lamps LPll and LP'lZ mounted within the pushbuttons of switches G86 and B62, respectively.

The hot blast valve motor is provided with hot blast opening and closing contactors HBO and HBC, respectively, having motor reversing contacts like those hereinbefore described for controlling operation of the hot blast valve. Contactors HBO and HBC are also provided with normally open contacts 4, respectively, for completing self-maintaining circuits therefor. Hot blast valve HBV is provided with a limit switch HBLS having interlocking

contacts

4 and 8 for controlling contactors HBO and HBC, respectively, and contacts '3 and 7 for controlling lamps LP13 and LP14 mounted within the pushbuttons of switches G87 and B63, respectively.

The blowotf valve motor is provided with blowotf opening and closing contactors B00 and BOC, respectively, having motor reversing contacts like those hereinbefore described for controlling operation of the blowoif valve. Contactors B00 and BOC are also provided with normally open contacts 4, respectively, for completing self-maintaining circuits therefor. Blowofi valve BOV is provided with a limit switch BOLS having interlocking

contacts

4 and 8 for controlling contactors B00 and BOC, respectively, and

contacts

3 and 7 for controlling lamps LP15 and LP16 mounted within the pushbuttons of switches BG4 and BGS, respectively.

Referring to FIG. 3, the aforementioned reversing control contactors of the plurality of valve motors are provided with individual open and close control manually operable switches such as pushbutton switches or the like and the stove fan motor contactor is provided with individual start and stop control manually operable switches such as pushbutton switches or the like, that is,

pushbutton swtiches 6131 through G137 and BG1 through As will be apparent by reference to FIG. 2, these pushbutton switches have been given reference characters indicative of their control functions and their sequence of operation. Thus, the two letters of each such reference character GB and BG are indicative of the operating sequences gas to blast and blast to gas, respectively, whereas the suflix numeral in each such reference character indicates the order of operation of the corresponding pushbutton switch in the respective sequence.

The lamp under the Open pushbutton of each valve such as lamp LPl, for example, when energized, indicates that the associated valve is open or in transition and the lamp under the Close pushbutton of each valve such as lamp LP2, for example, when energized, indicates that the associated valve is closed or in transition. Lamp LP3 under the pushbutton of Start switch BGS indicates that the stove fan is running and lamp LP3 under the pushbutton of Stop switch GBZ indicates that the stove fan has been stopped.

FIG. 3a shows a cam layout development for operating the contacts of the limit switches of the stove control valves. The left-hand end of the layout is indicative of the fully open condition of each valve and the right-hand end of the layout is indicative of the fully closed condition of each valve. The horizontal areas represent operating cams or the like for the respective limit switch contacts. The shaded portions indicate the closed conditions of the respective contacts and the unshaded areas indicate the open conditions of the respective contacts. In FIG. 3a, there are also shown at the lefthand side contact 2 of limit switch GSLS and

contacts

4, 3, 3 and 7 of each of limit switches GSLS, GBLS, CHLS, CBLS, CMLS, HBLS and BOLS in the positions that they assume when the respective valves are fully open. These same limit switch contacts are shown at the right-hand side of FIG. 3a in the positions that they assume when the respective valves are fully closed.

Referring to FIG. 2, there is shown a control panel for the system of FIG. 3. On this panel, the Open pushbutton switch for each valve is arranged above the Close pushbutton switch therefor in a vertical column. In a similar manner, the Start pushbutton switch for the stove fan is arranged above the Stop pushbutton switch therefor in a vertical column. Above each such vertical column there is provided an indicia plate identifying the stove fan and the particular valve which the vertically arranged pushbutton switches control. The valve opening control pushbutton switches and the stove fan start control pushbutton switch are preferably arranged in a first horizontal row and the valve closing control pushbutton switches and the stove fan stop control pushbutton switch are preferably arranged in a second lower horizontal row although other arrangements thereof are possible.

The vertical columns or subgroups of pushbutton switches are preferably arranged on the control panel in consecutive order from left to right corresponding to the order in which the associated control elements such as valves and stove fan must be operated for one of the operating sequences involved. In the example chosen, the pairs of vertically arranged pushbutton switches are arranged in consecutive order from left to right corresponding to the gas to blast sequence of operation thereof and the blowoif valve control pair of switches is positioned at the right-hand end thereof. However, it will be apparent that the pairs of vertically arranged pushbutton switches could alternatively be arranged in consecutive order in either direction correspending to the gas to blast or the blast to gas sequence of operation thereof or different switches of each pair could be arranged in the respective horizontal rows.

The pushbutton of the first switch of each sequence, such as the pushbutton of switch G81 and BG1, is provided with an enlarged indicia plate to indicate the start of each sequence whereas the remaining pushbuttons are provided with smaller indicia plates. Each of these indicia plates is provided with indicia indicative of the function performed by the corresponding pushbutton switch such as Close, Open, Start and Stop. In addition, each enlarged indicia plate is provided with indicia indicative of the sequence of operation initiated from the respective switch such as Gas to Blast and Blast to Gas.

The control panel is provided with stripes or metal strips or the like extending between the switches or be tween the indicia plates of the pushbutton switches in each sequence. These strips are provided with arrows, each such arrow pointing to the next pushbutton in the sequence, to indicate the order in which the pushbuttons of each sequence must be pressed to change the stove from one operating condition to the other.

To further distinguish the pushbuttons of the sequences from one another, they preferably are given different colors. For example, the pushbuttons of the gas to blast sequence may be green as indicated by the diagonal lines thereon whereas the pushbuttons of the blast to gas sequence may be white.

Operation The operation of the system of FIG. 3 will now be described.

The conditions of the stove control valves and the stove fan when the stove is in its gas condition and also when the stove is in its blast condition are as follows:

Let it be assumed that three-phase alternating current power is connected to lines L1, L2 and L3. Let it also be assumed that the stove is initially in its gas condition. The contacts of the valve limit switches are shown in FIG. 3 in the positions that they assume when the stove is in its gas condition. However, the contactors in FIG. 3 are shown in their normal deenergized condition.

In the gas condition of the stove, as shown in the above table, the gas shutoff valve is open. Therefore, as shown in FIGS. 3 and 3a, contact 2 of limit switch GSLS is closed. Igniter IG has performed its gas igniting cycle and has timed out. Lamp LPl is energized through closed contact 3 of limit switch GSLS to light the pushbutton of switch BG9 to indicate that the gas shutoff valve is open. Also, lamps LPS and LP7 are energized through contacts 3 of limit switches GBLS and CHLS, respectively, to light the pushbuttons of switches B67 and BG6 to indicate that the gas burner valve and the chimney valve are open. Moreover, lamps LP10, LP12, LP14 and LP16 are energized through contacts 7 of limit switches CBLS, CMLS, HBLS and BOLS, respectively, as shown in FIGS. 3 and 3a, to light the pushbuttons of switches BG1, B62, B63 and BG5 to indicate that the cold blast valve, the cold mixer valve, the hot blast valve and the blowoff valve are closed. In FIG. 3, contactor SFM is energized whereby stove fan SF is on or running.

As a result, contact 4 of contactor SFM is closed to maintain contactor SFM energized following reopening of Start switch BGS and lamp LP3 is maintained energized in parallel with the operating coil of contactor SFM in a circuit extending through Stop switch GB2 and contact 4 of contactor SFM across lines L1 and L2. Lamp LP3 lights the pushbutton of stove fan Start switch BG8 to indicate that the stove fan is on. Contact 5 of contactor SFM is open so that lamp LP4 is deenergized.

Gas to Blast To change the stove from its gas condition toits blast condition, the stove control elements, that is the valves and fan, must be controlled or operated in a predetermined order. The gas shutoff valve must be closed before the stove fan is stopped to prevent flow of pressurized gas into the combustion air line. The stove fan must be stopped before the gas burner valve is closed because, if these elements were controlled in the reserve order, there would be no place for the combustion air to be blown by the fan. The gas burner valve must be closed before the chimney valve is closed in order to continue exhausting of the combustion products as long as the gas is burning. The gas shutoff valve, the gas burner valve and the chimney valve must be closed and the stove fan must be stopped before the cold blast valve, the cold mixer valve and the hot blast valve are opened. The reasons for this are apparent because the hot air blast must be confined to the hot blast line leading to the blast furnace and should not enter the gas or combustion air lines or be exhausted through the chimney. Also, the cold blast and cold mixer valves must be opened before the hot blast valve is opened. The reason for this is that the stove must be pressurized before the hot bast valve is opened to prevent reverse flow from the pressurized blast furnace into the stove. Therefore, the required order of operation of the stove control elements is as follows:

(1) Close gas shutofi GSV (2) Stop stove fan SF (3) Close gas burner valve GBV (4) Close chimney valve CHV (5) Open cold blast valve CBV (6) Open cold mixer valve CMV (7) Open hot blast valve HBV To change the stove from its gas condition to its blast condition, the pushbuttons of gas to blast control switches GBl through GB7 are pressed in the order shown in FIG. 2. Pressing the pushbutton of switch 6131 causes energization of contactor GSC whereupon the latter closes its contacts 1, 2 and 3 to connect power supply lines L1, L2 and L3 to motor M and closes its contact 4 to complete a self-maintaining circuit therefor in shunt of pushbutton switch GB]. whereafter the latter may be released to allow it to reopen. Motor M1 operates in a first direction to close gas shutoff valve GSV. When the gas shutoff valve starts to close, contact 2 of limit switch GSLS opens and

contacts

4 and 7 thereof close as shown in FIG. 3a. Contact 2 of limit switch GSLS interrupts energization of gas igniter 16 to cause the latter to reset its timing mechanism and contact 4 thereof closes a point in the circuit of contactor 650. Contact 7 of limit switch GSLS energizes lamp LP2 to light the pushbutton of switch GB thereby to indicate that this pushbutton has been pressed. When the gas shutoff valve is fully closed,

contacts

3 and 8 of limit switch GSLS open as shown in FIG. 3a. Contact 8 of limit switch GSLS interrupts energization of contactor GSC to stop motor M1 by reopening its contacts 1, 2 and 3 and to interrupt its self-maintaining circuit by reopening its contact 4. Contact 3 of limit switch GSLS interrupts energization of lamps LPl to extinguish the light from the pushbutton of switch B69. Extinguishing of the light from the pushbutton of switch B69 with the lamp in the pushbutton of switch GBl remaining lighted indicates to the operator that the gas shutoff valve is fully closed and that the next pushbutton in the sequence may be pressed.

Pressing the pushbutton of switch GB2 interrupts energization of contactor SFM to stop the stove fan and to deenergize lamp LP3. Lamp LP3 extinguishes the light from the pushbutton of switch BGS. Contactor SFM also opens its contact 4 to interrupt the self-maintaining circuit of its operating coil whereafter the pushbutton of switch GBZ may be released to allow it to reopen and closes its contact 5 to energize lamp LP4. Lamp LP4 lights the pushbutton of switch GB2 to indicate that this pushbutton has been pressed to stop the stove fan and that the next pushbutton in the sequence may be pressed.

Pressing the pushbutton of switch GB3 causes energization of contactor GBC to effect closure of the gas burner valve. Contactor GBC also closes its contact 4 to maintain energization of its operating coil whereafter switch G133 may be released to allow it to reopen. When the gas burner valve starts to close,

contacts

4 and 7 of limit switch GBLS close as shown in FIG. 3a. Contact 4 of limit switch GBLS closes a point in the circuit of contactor GBO and contact 7 thereof energizes lamp LP6 to light the pushbutton of switch G133 thereby to indicate that this pushbutton has been pressed. When the gas burner valve is fully closed,

contacts

3 and 8 of limit switch GBLS open as shown in FIG. 30. Contact 8 of limit switch GBLS interrupts energization of contactor CBC to stop the gas burner valve. Opening of contact 3 of limit switch GBLS causes the light in the pushbutton of switch BG7 to be extinguished by deenergization of lamp LPS to indicate to the operator that the gas burner valve is fully closed and that the next pushbutton in the sequence may be pressed.

Pressing the pushbutton of switch GB4 causes energization of contactor CHC to effect closure of the chimney valve. Contactor CHC also closes its contact 4 to maintain energization of its operating coil whereafter switch GB4 may be released to allow it to reopen. When the chimney valve starts to close,

contacts

4 and 7 of limit switch CHLS close as shown in FIG. 3a. Contact 4 of limit switch CHLS closes a point in the circuit of contactor CH0 and contact 7 thereof energizes lamp LPS to light the pushbutton of switch G34- thereby to indicate that this pushbutton has been pressed. When the chimney valve is fully closed,

contacts

3 and 8 of limit switch CHLS open as shown in FIG. 3a. Contact 8 of limit switch CHLS interrupts energization of contactor CHC to stop the chimney valve. Opening of contact 3 of limit switch CHLS causes the light within the pushbutton of switch BG6 to be extinguished by deenergization of lamp LPll to indicate to the operator that the chimney valve is fully closed and that the next pushbutton in the sequence may be pressed.

All of the stove valves are now closed to completely close the stove and the stove fan has been stopped. The stove is now ready to be placed in its blast condition by pressing the remaining three pushbuttons in the sequence shown in FIG. 2. That is, the cold blast valve, the cold mixer valve and the hot blast valve may now be opened in that order to place the stove in its blast condition.

Pressing the pushbutton of switch G35 causes energization of contactor CBO to cause opening of the cold blast valve. Contactor CBO also closes its contact 4 to maintain energization of its operating coil whereafter switch GBS may be released to allow it to reopen. When the cold blast valve starts to open,

contacts

3 and 8 of limit switch CBLS close as shown in PEG. 30. Contact 8 of limit switch CBLS closes a point in the circuit of contactor CBC and contact 3 thereof energizes lamp LP9 to light the pushbutton of switch GB5 thereby to indicate that this pushbutton has been pressed. When the cold blast valve is fully open,

contacts

4 and 7 of limit switch CBLS open as shown in FIG. 3a. Contact 4 of limit switch CBLS interrupts energization of contactor CEO to stop the cold blast valve. Contact 7 of limit switch CBLS interrupts energization of lamp LPN) to extinguish the light in the pushbutton of switch BGl to indicate to the operator that the cold blast valve is fully open and that the next pushbutton in the sequence may be pressed.

Pressing the pushbutton of switch GB6 causes energization of contactor CMO to cause opening of the cold mixer valve. Contactor CMO also closes its contact 4 to maintain energization of its operating coil whereafter switch 9 GB6 may be released to allow it to be opened. When the cold mixer valve starts to open,

contacts

3 and 8 of limit switch CMLS close as shown in FIG. 3a. Contact 8 of limit switch CMLS closes a point in the circuit of contactor CMC and contact 3 thereof energizes lamp LPlll to light the pushbutton of switch GB6 thereby to indicate that this pushbutton has been pressed. When the cold mixer valve is fully

open contacts

4 and 7 of limit switch CMLS open as shown in FIG. 3a. Contact 4 of limit switch CMLS interrupts energization of contactor CMO to stop the cold mixer valve. Contact 7 of limit switch CMLS interrupts energization of lamp LP12 to extinguish the light in the pushbutton of switch BG2 to indicate to the operator that the cod mixer is fully open and that the next pushbutton in the sequence may be pressed.

Pressing the pushbutton of switch GB7 causes energization of contactor HBO to cause opening of the hot blast valve. Contactor HBO also closes its contact 4 to maintain energization of its operating coil whereafter switch GB7 may be released to allow it to be opened. When the hot blast valve startes to open,

contacts

3 and 8 of limit switch HBLS close as shown in FIG. 3a. Contact 8 of limit switch HBLS closes a point in the circuit of contactor HBC and contact 3 thereof energizes lamp LP13 to light the pushbutton of switch GB7 thereby to indicate that this pushbutton has been pressed. When the hot blast valve is fully open,

contacts

4 and 7 of limit switch HBLS open as shown in FIG. 30. Contact 4 of limit switch HBLS interrupts energization of contactor HBO to stop the hot blast valve. Contact 7 of limit switch HBLS interrupts energization of lamp LP14 to extinguish the light in the pushbutton of switch BG3 to indicate to the operator that the hot blast valve is fully open and that the sequence of operation has been completed.

Blast to Gas To change the stove from its blast condition to its gas condition, it i necessary to control or operate the aforementioned gas to blast stove control elements and an additional stove control element in a predetermined order which is different from the order in which the elements are operated when the stove is changed from its gas condition to its blast condition. The sequence in which the pushbuttons are pressed to actuate the stove control elements when the stove is changed from its blast condition to its gas condition is shown in FIG. 2. In this sequence of operation, a blowotf valve must be opened and reclosed at an intermediate point in the sequence to relieve the pressure in the stove before heating of the stove can be initiated. The cold blast and cold mixer valves must be closed before the hot blast valve is closed because, if these valves were closed in the reverse order, there would be no place for the hot air blast to be blown. The hot blast valve must be closed before the blowoff valve is opened and reclosed in order to equalize the pressures inside and outside of the stove and to prevent repressurizing the stove. The chimney valve must be opened before the gas burner valve is opened in order to vent the stove preparatory to the ignition of the gas. The gas burner valve must be opened before the stove fan is started in order to enable the combustion air to be blown into the stove and vented through the chimney. And the stove fan must be started before the gas shutoff valve is opened in order to prevent pressurized gas from flowing into the combustion air line. Moreover, the cold blast valve, the cold mixer valve and the hot blast valve must be closed and the pressure within the stove must be relieved before the chimney valve, the gas burner valve and the gas shutoff valve are opened and the stove fan is started in order to prevent air blast from the stove from being forced into the gas line, the combustion air line or out through the chimney. Therefore, the required blast valve.

10 order of operation of the stove control elements is as follows:

To change the stove from its blast condition back to its gas condition, the pushbuttons of blast to gas switches BS1 through BGQ are pressed in the order shown in FIG. 2. Pressing the pushbutton of switch B61 causes energizatio-n of contactor CBC to effect closing of the cold blast valve. Contactor CBC also closes its contacts 4 to complete a self-maintaining circuit for its operating coil whereafter switch B61 may be released to allow it to reopen. When the cold blast valve start to close,

contacts

4 and 7 of limit switch CBLS close as shown in FIG. 3a. Contact 4 of limit switch CBLS closes a point in the circuit of contactor CEO and contact '7 thereof energizes lamp LPN) to light the pushbutton of switch RG1 to indicate that this pushbutton has been pressed. When the cold blast valve is fully closed

contacts

3 and 8 of limit switch CBLS open as shown in PEG. 3a. Contact 8 of limit switch CBLS interrupts energization of contactor CBC to stop the cold blast valve. Contact 3 of limit switch CBLS interrupts energization of lamp LP9 to extinguish the light in the pushbutton of switch GBS to indicate to the operator that the cold blast is fully closed and that the next pushbutton in this sequence may be pressed.

Pressing the pushbutton of switch BGZ causes energization of contactor CMC to cause the cold mixer valve to be closed. Contactor CMC also closes its contacts 4 to complete a self-maintaining circuit for its operating coil in shunt of pushbutton switch BGZ whereafter the pushbutton switch may be released to allow it to reopen. When the cold mixer valve starts to close,

contacts

4 and 7 of limit switch CMLS close as shown in FIG. 3a. Contact 4 of limit switch CMLS closes a point in the circuit of contactor CMO and contact 7 thereof energizes lamp LP12 to light the pushbutton of switch B62 to indicate that this pushbutton has been pressed. When the cold mixer valve is fully closed

contacts

3 and 8 of limit switch CMLS open as shown in FIG. 3w. Contact 8 of limit switch CMLS interrupts energization of contactor CMC thereby to stop the cold mixer valve. Contact 3 of limit switch CMLS interrupts energization of lamp LPll to extinguish the light in the pushbutton of switch 6B6 to indicate to the operator that the cold mixer valve is fully closed and that the next pushbutton in this sequence may be pressed.

Pressing the pushbutton of switch BGS causes energization of contactor HBC to cause the hot blast valve to be closed. Contactor HBC also closes its contact 4 to complete a self-maintaining circuit for its operating coil in shunt of switch B63 whereafter the latte may be released to allow it to reopen. When the hot blast valve starts to close,

contacts

4 and 7 of the limit switch HBLS close as shown in FIG. 3a. Contact 4 of limit switch HBLS closes a point in the circuit of contactor HBO and contact 7 thereof energizes lamp LP14 to light the pushbutton of switch BS3 thereby to indicate that this pushbutton has been pressed. When the hot blast valve is fully closed

contacts

3 and 8 of limit switch HBLS open as shown in FIG. 3a. Contact 8 of limit switch HBLS intermpts energization of contactor HBC to stop the hot Contact 3 of limit switch HBLS interrupts energization of lamp LP13 to extinguish the light in the pushbutton of switch GB7 to indicate to the operator that the hot blast valve is fully closed and that the next push button in this sequence may be pressed.

All of the stove control valves are now closed to completely close the stove and the next step is to relieve the pressure within the stove chamber before reheating of the stove can be initiated. This is done by opening and reclosing blowofi valve BOV. Pressing the pushbutton of switch BGi causes energization of contactor BOO to cause the blowo-ff valve to be opened. Contactor 1300 also closes its contact 4 to complete a self-maintaining circuit in shunt of switch BSA? for its operating coil Whereafter switch B64 may be released to allow it to reopen. When the blowoff valve starts to open,

contacts

3 and 8 of limit switch BOLS close as shown in FIG. 3a. Contact 3 of limit switch BOLS closes a point in the circuit of contactor BOC and contact 3 thereof energizes lamp LPES to light the pushbutton of switch BG4 thereby to indicate that this pushbutton has been pressed. When the blowoff valve is fully open,

contacts

4 and 7 of limit switch BOLS open as shown in FIG. 3a. tact 4- of limit switch BOLS interrupts energization of contactor BOO to stop the blowoff valve. Contact 7 of limit switch BOLS interrupts energization of lamp LPl to extinguish the light in the pushbutton of switch BGS to indicate to the operator that the blowoff valve is fully open.

With the blowoff valve fully open, the pressures inside and outside the stove are equalized whereafter the blowoff valve may be reclosed. Pressing the pushbutton of switch BG5 causes energization of contactor BOC to close the blowofi valve. Contactor BOC also closes its contact 4 to complete a self-maintaining circuit for its operating coil in shunt of switch BS5 whereafter the latter may be released to allow it to reopen. When the blowoif valve starts to close,

contacts

4 and 7 of limit switch BOLS close as shown in FIG. 3a. Contact 4 of limit switch BOLS closes a point in the circuit of contactor B00 and contact 7 thereof energizes lamp LP16 to light the pushbutton of switch B65 thereby to indicate that this pushbutton has been pressed. When the blowofi valve is fully closed,

contacts

3 and 8 of limit switch BOLS open as shown in FIG. 3a. Contact 8 of limit switch BOLS interrupts energization of contacts BOC to stop the blowotf valve. Contact 3 of limit switch BOLS interrupts energization of lamp LP to extinguish the light in the pushbutton of switch BG4- to indicate to the operator that the blowoff valve is fully closed and that the next pushbutton in the sequence may be pressed.

All of the stove control valves are again closed to completely close the stove. The pressure within the stove chamber, if any, has been relieved and the remaining pushbuttons in the sequence may now be pressed in their proper order as shown in FIG. 2 to initiate reheating of the stove. Pressing the pushbutton of switch BG6 causes energization of contactor CHO to cause the chimney valve to be opened. Contactor CHO also closes its contact to complete a self-maintaining circuit for its operating coil in shunt of switch BGo whereafter the latter may be released to allow it to reopen. When the chimney valve starts to 01.511,

contacts

3 and 8 of limit switch CHLS close as shown in FIG. 3a. Contact 8 of limit switch CHLS closes a point in the circuit of contactor CBC and contact 3 thereof energizes lamp LP7 to light the pushbutton of switch 866 thereby to indicate that this pushbutton has been pressed. When the chimney valve is fully open;

contacts

4 and 7 of limit switch CHLS open as shown in FIG. 3a. Contact 4 of limit switch CHLS interrupts energization of contactor CHO to stop the chimney valve. Contact 7 of limit switch CHLS interrupts energization of lamp LP8 to extinguish the light in the pushbutton of switch G134 to indicate to the operator that the chimney valve is fully open and that the next pushbutton in this sequence may be pressed.

Pressing the pushbutton of switch RG7 causes energization of contactor GBO to cause the gas burner valve to Conbe opened. Contactor GBO also closes its contact 4 to complete a self-maintaining circuit for its operating coil in shunt of switch BG7 whereafter the latter may be released to allow it to reopen. When the gas burner valve starts to open, contacts 3 and S of limit switch GBLS close as shown in FIG. 3a. Contact 8 of limit switch GBLS closes a point in the circuit of contactor GBC and contact 3 thereof energizes lamp LPS to light the pushbutton of switch BG7 thereby to indicate that this pushbutton has been pressed. When the gas burner valve is fully open,

contacts

4 and 7 of limit switch GBLS open as shown in FlG. 3a. Contact 4 of limit switch GBLS interrupts energization of contactor GBO thereby to stop the gas burner valve. Contact 7 of limit switch GBLS interrupts energization of lamp LP6 to extinguish the light in the pushbutton of switch GBS to indicate to the operator that the gas burner valve is fully open and that the next pushbutton in this sequence may be pressed.

Pressing the pushbutton of Start switch BGS causes energization of contactor SFM to start the stove fan running. The circuit of the operating coil of contactor SFM may be traced from line L1 through Stop switch G32 and Start switch BGS to line L2. Contactor SFM also closes its contact 4 to complete a self-maintaining circuit for its operating coil in shunt of switch BGS whereafter the latter may be released to allow it to reopen. Contact 4 of contactor SFM also completes a maintaining circuit through Stop switch 682 for lamp LP3 thereby to light the pushbutton of switch B68 to indicate that this pushbutton has been pressed. Contactor SFM also opens its contact 5 to interrupt energization of lamp LP4. This causes the light in the pushbutton of switch (3B2 to be extinguished to indicate to the operator that the next pushbutton in the sequence may be pressed.

Pressing the pushbutton of switch 3G9 causes energization of contactor GSO through contact 4 of limit switch GSLS across lines Li and L2. Contactor GSO closes its contacts 1, 2 and 3 to energize motor M1 in the forward direction and thereby to cause gas shutoff valve GSV to be opened. Contactor 650 also closes its contact 4 to complete a self-maintaining circuit for its operating coil in shunt of switch BG9 whereafter the latter may be released to allow it to reopen. When the gas shutoff valve starts to open, contact 8 of limit switch GSLS closes in the circuit of contactor GSC and contact 3 of limit switch GSLS closes to energize lamp LPl. Lamp LPl lights the pushbutton of switch B69 to indicate that this pushbutton has been pressed. When the gas shutoff valve is fully open, contact 2 of limit switch GSLS closes and

contacts

4 and 7 thereof open. Contact 4 of limit switch GSLS interrupts energization of contactor GSO whereupon the latter opens its contacts 1, 2 and 3 to deenergize motor M1 and to stop gas shutoif valve GSV. Contactor GSO also opens its contact 4 to interrupt its self-maintaining circuit. Contact 2 of limit switch GSLS energizes gas igniter GI whereupon the latter operates for a predetermined self-timed interval to ignite the gas at the burner. Contact 7 of limit switch GSLS interrupts energization of lamp LPZ to extinguish the light in the pushbutton of switch GB thereby to indicate to the operator that the gas shutofi valve is fully open and that the blast to gas sequence has been completed.

While the apparatus hereinbefore described is effectively adapted to fulfill the objects stated, it is to be understood that we do not intend to confine our invention to the preferred embodiment of sequence indicating and control system disclosed, inasmuch as it is susceptible of various modifications without departing from the scope of the appended claims.

We claim:

1. In a system for controlling a controllable device 13 wherein the latter is of a type having a plurality of diverse operating conditions and is provided with a multiplicity of control elements predetermined ones of which must be operated according to first and second diverse sequences to change the controllable device from a first one of its operating conditions to another operating condition and vice versa, and each said control element having first and second diverse operating conditions; in combination, electroresponsive control means for the control elements of the controllable device, said means comprising a multiplicity of manually-operable switches, there being a pair of such switches associated with each said control element, means in said electroresponsive control means responsive to operation of the first switch of each said pair thereof for establishing the respective control element in its first operating condition, means in said electroresponsive control means responsive to operation of the second switch of each said pair thereof for establishing the respective control element in its second operating condition, a control panel having said switches mounted thereon in an arrangement whereby the two switches of each said pair thereof are spaced apart in a first direction, said pairs of switches are spaced apart on said panel in a second direction, and predetermined pairs of said switches are arranged on said panel in consecutive order corresponding to said first sequence of operation of the control elements respectively associated therewith, and means on said control panel for indicating the respective sequences in which switches of said pairs are to be operated corresponding to the diverse sequences of operation of said control elements.

2. The invention defined in claim 1, wherein said indicating means comprise directional indicators on said panel in the spaces between consecutive switches of each group of sequentially operable switches for indicating the order of operation of the switches in each such group.

3. The invention defined in claim 2, wherein said directional indicators comprise strips mounted on said control panel extending between consecutive switches of each said group thereof, arrows on said strips, and each said arrow pointing to the next switch in each sequence to be operated.

4. The invention defined in claim 1, together with means for the first switch of each said sequentially operable group thereof indicative of the change in operating condition of the controllable device efiectible by the switches of the corresponding group and being also effective to readily distinguish said first switch of each said group from the other switches therein.

5. The invention defined in claim 1, together with an indicia carrying member for each switch of each said sequentially operable group thereof for indicating the operational control effectible on the corresponding control element thereby, and the indicia carrying member for the first switch of each said group thereof being substantially larger than those for the other switches of the corresponding group to readily distinguish said first switch from said other switches.

6. The invention defined in claim 1, together with visual indicator means for said switches and means effective when the switches of either said sequence thereof are successively operated and being responsive to operation of each said control element corresponding thereto to one of its operating conditions for operating said visual indicator means whereby to indicate which switches of the sequence thereof have been operated and for also indicating whether each preceding control element operation in the sequence has been completed so as to advise the operator that the next switch in the sequence may be operated.

7. The invention defined in claim 1, together with means integral with said switches for readily distinguishing the switches operable in one of said sequence from the switches operable in the other of said sequences.

8. In a control system for operating a controllable device wherein said controllable device is of the type having a plurality of operating conditions and is provided with a plurality of control elements which must be operated in a first sequence to change the controllable device from a first operating condition to a second operating condition and which control elements must be operated in a second sequence to change the controllable device from said second operating condition back to said first operating condition; and each said control element having a first operating position and a second operating position, in combination; control means for each of said control elements, each said control means comprising a first manually operable switch for controlling the associated control means to operate the corresponding control element from its first operating position to its second operating position, and a second manually operable switch for controlling the associated control means to operate the corresponding control element from its second operating position to its first operating position; a control panel; means mounting said switches on said control panel in vertical columns and horizontal rows wherein said first and second switches of each said control means are in a vertical column, the first switches of all said control means are in a first row, the second switches of all said control means are in a second row, and said vertical columns of switches are arranged in consecutive order corresponding to said first sequence of operation thereof; indicia members on said panel for the first switches of said sequencies; and arrows on said panel pointing to each consecutive switch in each sequence for indicating the order in which the switches in each sequence thereof are to be operated.

9. In a system having a multiplicity of manually actuatable switches, a pair of said switches being controllably associated with each one of a corresponding multiplicity of control elements, means responsive to actuation of a first switch of each said pair thereof for causing the respectively associated control element to assume a first operating condition, means responsive to actuation of a second switch of each said pair thereof for causing the respectively associated control element to assume a second operating condition, said control elements being adapted to control a device which is alternately settable into different operating conditions and the setting of which device into the respective operating conditions requires that said control elements be controlled to assume predetermined operating conditions in diverse sequences, the improvement including sequence indicating and control means for facilitating manual actuation of the switches of different groups thereof in correct sequences corresponding to the diverse sequences in which said control elements must be controlled comprising a control panel having said pairs of switches mounted thereon in spaced apart relation, directional indicators mounted on said panel and extending between the switches of the first one of said groups thereof for indicating the sequential order in which these switches must be operated to set said device in a first operating condition, similar directional indicators mounted on said panel and extending between the switches of the second one of said groups thereof for indicating the sequential order in which these switches must be operated to set said device in a second operating condition, and enlarged indicia plates mounted on the first switches of the respective sequentially operable groups thereof for indicating the starts of the respective sequences.

10. In a hot blast stove control system having a plurality of stove control valves, a stove fan and a multiplicity of manually actuatable switches, a pair of said switches being controllably associated with each one of said plurality of stove control valves and with said stove fan, control means responsive to actuation of first switches of said pairs thereof for opening the respectively associated stove control valves and for starting the respectively associated stove fan, control means responsive to actuation of second switches of said pairs thereof for clos- 15 ing the respectively associated stove control valves and for stopping the respectively associated stove fan, said stove control valves and said stove fan being adapted to control a hot blast stove which is alternately settable into a gas condition wherein the stove is being heated and into a blast condition wherein air is forced through the stove to heat such air, the changing of said stove from its gas condition to its blast condition requiring actuation of a first group of said switches in a predetermined sequence, and the changing of said stove from its blast condition back to its gas condition requiring actuation of a second group of said switches in a predetermined sequence, the improvement including sequence indicating and control means for indicating to the operator the sequences of operation of the respective groups of switches comprising a control panel having said pairs of switches mounted thereon in spaced apart relation, strips on the face of said panel extending between the switches of each of said first group and said second group thereof, pointers on said strips oriented so that the pointers point from each preceding switch to the next switch in each sequentially operable group thereof to indicate to the operator the successive order in which the switches in each group must be operated, an indicia plate for each switch indieating the operational control efiectible on the corresponding valve or fan by actuation of such switch, and the indicia plates for the first switches in the two groups thereof being substantially larger than the indicia plates on the other switches to indicate the start of the respective sequences.

11. The invention defined in claim 10, wherein said switches comprise pushbutton actuators, indicator lamps mounted within said actuators, and control means responsive to operation of said stove control valves and said stove fan for operating said lamps for indicating which pushbuttons in a sequence have been pressed and for also indicating when each valve and fan operation has been completed to indicate to the operator that the next pushbutton in the sequence may be pressed.

References Cited in the file of this patent UNITED STATES PATENTS 2,399,530 York et a1 Apr. 30, 1946 2,601,979 Rice et al. July 1, 1952 2,694,755 Schuman et al. Nov. 16, 1954 2,931,635 Braun et al Apr. 5, 1960 2,977,428 Showalter Mar. 28, 1961