US2363696A

US2363696A - Control system

Info

Publication number: US2363696A
Application number: US429725A
Authority: US
Inventors: Philip S Russel
Original assignee: Detroit Lubricator Co
Current assignee: Detroit Lubricator Co
Priority date: 1942-02-06
Filing date: 1942-02-06
Publication date: 1944-11-28
Anticipated expiration: 1961-11-28

Description

P. s. Russn-zl..4

CONTROL SYSTEM Nov. 28, 1944.

Fld Feb. 6, 1942 NVEVNTOR ink; ATTORNEY FIG-2 Patented Nov. 28,1944

CONTROL SYSTEM Philip S. Russel, Detroit, Mich., aasignor to Detroit Lubricator Company, Detroit, Mich., a corporation of Michigan 4 Applioation February s, 1942, serial No. 429,125 9 claims. (cl. 12e-11o)V I'his invention relates generally to control systems and is particularly adapted among other uses for use in a forced draft heating apparatus.

One object of this invention is to provide means for preventing theoverheating of a heat generating apparatus.

^ Another object is to provide such a means which is responsive to the flow of air over the heat generating apparatus.

Another object is to provide means to shut down the heat generating apparatus' upon failure of the fan means for supplying the medium to be heated. 4

Another object is to provide means to reduce to a predetermined minimum the rateof combustionof the fuel inthe heat generating'apparatus upon failure of the fan means for supplying the medium to Ybe heated.

Other objects will-be apparent from a reading l of the specification.

'I'he invention consists in the new and novel construction of and ,combination of parts, to be more fully described hereinafter and the novelty of which will be particularly pointed out and distinctly claimed.

In the-accompanying drawing to be taken as a part of this speciilcation, there is fully and clearly illustrated a preferred embodiment of the invention in which drawing:

Figure 1 is a schematic yview of a heating system embodying the invention.

Fig. 2 is a schematic view of a modified heat-A the' inlet opening n. rositionedlongiiudlnelly 'ofthe chimney I6 and extending upward from above the burner I8 toward the upper end of the chimney I6 is a tubular heat exchange member I9 which is preferably circular in cross-section and which may be made ofcast iron. The prod- .ucts of combustion from the burner I8 pass upchimney I8. At its lower end portion, the plenum chamber I5 has the outlets 2 through which the heated air from the plenum chamber I5 is discharged to the room, 3. The outlets 2 may be covered with grills if desired but which are not shown for convenience. Liquid fuel for the burner I3 is supplied from a constant level gravity feed control unit 22 through a conduit 23. The control unit 22 is supplied from a source of supply through a conduit (not shown). The rate of inilowto the control unit 22 is controlled by a suitable float conti-oued valve (not showrll vto maintain the level ofthe liquid within the unit 22 substantially at the line LL. The outflow of the liquid fuel from the unit 22 is controlled by means of a reciprocally `movable valve member 24 which cooperates with an youtlet 25 opening into theconduit 23.

The valve member 24 is urged toward open pov sition by a helical coil spring 26 positioned conl' and which is rigid with the unit 22. The upper the duct 5V the return air passes into 'a horizontal duct 1 formed intermediate the ceiling 8 and a duct cover 9 joining a pairof adjacent'ceiling .loists I0. A fan inlet duct4 I I conducts the return or cool air from the duct 'I to the inlet VI2 of a pressure type fan unit I3. The fan unit I3 has its outlet I4 opening into and for discharge of centric with and surrounding the member 24. The spring 26 rests at its lowerend on a member 21 through which the valve member extends end of the spring 28 abuts a radially extending circumferential collar 28 which is suitably held to the member 24. A bimetallic'power element 23 has'one portion held by means `of a support 30 to a member rigid with the unit 22 and has a movable lip portion 3| 'abutting an upwardly facing shoulder 32 of the valve member 24. When the element 29 i's at ambient temperature, the lip portion 3l exerts a sui'iicient downward force on I the member 24 to hold' it against the upward air into the upper end portion of a plenum chamber I5 of the chimney furnace I. The furnace I comprises a chimney I3 which may be1 of `briclr and which has at its lower end portion am force of the spring 28 and in a closed position with the outlet 25. Closing movement of the lvalve member 24 by the element 29 is limited, however, by a. low fire stop member 33 which is screw-threadedly `secured to a portion ofthe unit 22 and which has a flanged head portion against which the lip portion 3l abuts. Opening Il positioned within the chimney It adiacent movement of thevalve member'u is limited byV gagement. The resistance unit l has one end ,thereof connected by a lead wire 52' to the contact member 41 so that the unit 56 is placed in series circuit with and controlled by the

contact members

46 and 41. The other end of the unit 50 is connectedby means of a lead wire 53 to l one end of a resistance unit 54 which is in heat able with an insulating button 4I secured to the arm 38. Upon upward or valve opening movement of the valvemember 24, the lever member- 39 is rocked about its fulcrum 46 in a counterclockwise direction to move the movable contact member 31 into engagement with theilrst contact member 36 to complete an electric circuit between

lead wires

42 and 43.

Positioned within the outlet I4 of the fan unit I3 and in the path of the air stream is a control unit or switch 44 comprisinga pivoted current conducting lever arm 45 having 'at one end a contact member 46 cooperable upon movement of the arm 45 to engage and disengage a second contact 'member 41 to control an electric circuit. 'I'he y for heating the bimetallic member 48. The resistance unit 50 is so chosen relative to the ilow output of the fan unit I3 that with the fan unit I3 operating normally, the air flow over the resistance unit 56' and bimetallic member'48 will maintain .at al1 times the temperature of the member 48-below the temperature at which the free end or end of the member 48 which is in engagement, with the perpendicular portion of the arm 45 will move beyond the end of the perpendicular portion to allow the spring 49 to rotate the arm 45 counter-clockwise to'part the

contact members

46 and 41. Should, however, the output of the fan unit I3 be reduced to or be.. low a predetermined minimum flowfor any reason such as failure of the driving motor or the blocking of the inlet or outlet of the air circulating system, the resistance unit 50 will supply suillcient heat to raise the temperature of the bimetallic member 48 so that the free end thereof will be ilexed or warped suiilciently to pass below the end of the perpendicularly extending portion of the arm 45 to release the arm for counter-clockwise movement bythe spring y4i! so that the contact member 46 is moved out of engagement with the contact member 41. Upon this counter-clockwise movement ofthe arm 45,

the spring 49 will maintain the

contact members

46 and 41 out of engagement until the arm 45 is manually moved in a clockwise direction by' a manually operable push button, or thrust member 5I. When this manual ,movement is imparted and the bimetallic member 48 has cooled suillciently,I the member 48 will move upward toward the position shown and upon release of the push button 5I the member 49 will again engage exchange relation with and acts to heat the bimetallic element 29 so that the lip portion 3| thereof will be moved to position the valve member 24 for increased liquid flow through the outlet 25.

The lead wire 43 is connected to one terminal of the moto'r (not shown) for driving the fan unit I3. The other terminal is connected by a. lead wire 55 which along with the lead wires 42 provides the source of electrical energy supply. A transformer 56 has a primary coil 51 connected by means of

lead wires

58 and 59 to the

lead wires

42 and 55 for energization thereof. One end of a secondary coil 60 of the transformer 56 is connected by a lead wire 6I to a bimetallic blade 62 of a room thermostat diagrammatically shown at 63. The blade 62 carries a contact member 64 which is moved by and at a predetermined minimum temperature of the blade 62 to engage -a fixed contact member 65. A lead wire connects the contact member 65 to the movable arm 45 of the ow sensitive control unit or switch 44. As stated hereinbefore the electrical circuit through the unit 44 is through the arm 45,

contact members

46 and 41, lead wire 52 and unit 56 to the lead wire 53. `'I'he lead wire 53 is connected to one end of the resistance unit 54 and the other end of the unit 54 is connected by a lead wire 61 to the other side' of the secondary coil 66 from that connected to the lead wire 6 I.

The operation of the invention asI shown in Fig. 1 is as follows: Electrical energy is supplied to, the primary coil 51 of the transformer 56 through the

lead wires

42, 58 and 55, 59. In the position of the elements as shown in the drawing, the temperature of the room 3 is above the predetermined desired temperature and the

contact members

64 and 65. are in a separated position. It should be noted that the room thermostat 63 is positioned in the room 3 or in any other space in which the temperature is to be controlled. The

contact members

64 and 65 being separated, the resistance units 50 and 54 are deenergized and the element 29 is at ambient temperature and therefore the lip portion 3l is in engagement with the low fire stop member 33 and holding the valve member 24 in a position to permit only pilot ilow of fuel to the burner I8. Since the valve member 24 is being held in pilot fire poV f ward the right moving the contact member 64 the perpendicularly extending portion of the arm l into engagement with the contact member 65 to complete the secondary circuit of the transformer 56. Electric current will then ilow from the secondary coil 60 through lead wire 6I, blade 62,

the bimetallic member 48 and bimetallic power element 23 respectively. -The relative heating efeach other and to the member 46 and element 23 that the lip portion 3I will have been moved to l allow the valve member 24 to be moved suiliciently toward open position to causethe lever member 33 to close switch 35 to start the fan unit I3 prior to the member-48 reaching the predetermined plenum chamber I5 where itis heated by the heat exchange member I9. The air then flows from the plenum chamber I back to the room 3 through the outlet 2. unit I 3 to the plenu chamber l5 cools the unit 50 and bimetallic member 48 and. prevents the temperature ofthe member 48 from reachingthe predetermined temperature at which the arm 45 is released to part the

contact members

46 and 41 to deenergize the units 5U and 54. The unit 54 will continue 4to heat the element 2 so that the portion 3I will move upward at least a suilicient amount to enable the spring 26 to move the valve member 24 4into engagementwith the high re stop member 34. Subsequent movement of the lever member 39 after the contact member 31 has engaged the contact member 36 is allowed due to the resilient mounting of the member 36 and will cause a sliding and wiping action between the two contact members 36v and 31 to insure a good electrical contact therebetween.l The units 50 and 54 remain energized and the element 29 remains heated while the member 48 normally remains below its predetermined critical temperabe moved out of engagement with the contact member 55 thereby. deenergizing the secondary 45 circuit of the ,transformer 56. The unit 5U and i member 48 then cool to ambient temperature without any useful result, but cooling of the unit 54 and element 29 moves the valve member 24 to pilot fire position and opens the switch 35 to stop operation of tlie fan unit |03. The system then remains in the conditionshownuntil the temperature about the thermostat 63 falls starting a subsequent operation of the system.

Should, however, the airl flow of the fan unit I3 be reduced below a predetermined minimum for any reasons during a period of operation,

l the heater unit 50 will act to heat the member 48 at least to the predetermined critical temperature so that the free end portion thereof will move downward beyond the end of the per, pendicularly extending portion'of the arm 45 thereby allowing the arm 4 5 to be. moved by the spring 49 to part the

contact members

46 and 41. Parting of the

members

46 and 41 deenergizes the secondary circuit of thetransformer 56 causing the unit 54 to be deenergized k and the element 23 to cool and move the valvel member 24 to pilot iire position. The predetermined minimum ilow at which the heat vunit 50 actuatesthe switch 44 is' preferably chosen so that air flows at or above this minimum flow4 are sumcient to prevent overheating of the furnace or generating apparatus I. It follows therefore that at allair ows below the predetermined he air flowing from the minimum now the switch 44 acts to prevent an undesired operation wherein the apparatus would the apparatus. l

In Figure 2 of the drawing amodified syste is shown in4 which like parts are designated by likeV numerals. "In this' system a conventional type furnace Vor heating apparatus Il'L is used and has a combustionlchamber 16 formed by a tubular heat exchange member 1I. The lower end of the member 1I is closed by a pot type burner y I8* and the upper end is closed by an end wall 1,2. The products of combustion are exhausted to the chimney I6EL through a flue pipe 13 opening into the chamber 10 adjacent the wall 12. The burner I8'i is enclosed by a shell 14 having an inlet for admitting air for combustion to the burner I6. A shell 16 encasesvthe combustion member 1Iand is spaced therefrom to provide a plenum chamber I5l wherein air is heated by the member 1I The plenum chamber Iiia has an inlet opening I4* adjacent :its lower end portion for flow of air thereto and an outlet opening 2e adjacent its top end portion for iiow of air to a space or room 2l.

The operation of the system is identical to that of Figure 1 and the difference being that the air is'l forced upward through the plenum chamber I5u in the conventional manner rather than downward as inFig. 1 and-the furnace Ial isaconventional type. v

It may now be seen that there is provided by this invention a new and novel control system for forced convection heating systems in which the b'urner is controlled Vby the convection air ilow through the furnaceor vheating apparatus and in the event the flow of air over the furnace falls below a predetermined minimum the burner is rendered ineilective to provide more than a predetermined minimum heat output.

What is claimed and is desired to be secured by Letters Patent 'of the United States is:

' 1. In a, heating system, a heat generating means having a plenum chamber in heat exchange re-A lationshipwith said heat generating means,

means for supplying air to be heated to said chamber, an electric switch, bimetallic means positionedin the path of the air supplied by said air supplying means and operatively connected to and for holding said switch in closed position, said bimetallic means being operable at a temperature above a predetermined temperature to cause said switch to move to an open posiftion, means positioned in heat exchange rela- '55 tion with said bimetallic means and operable to supply heat at a substantially predetermined rate, said rate being `so related to the ow of said supplied air that said bimetallic means is maintained` below said predetermined temperature for normal flows of said supplied air and so related to the flow of said supplied air that saidbimetallic means is heated-to said predetermined temperature at subnormalilows of said supplied a'ir, electrical means connected to, said switch and operable to increase the rate of heat being supplied by said heat generating means to said chamber, said switch when in said open -position acting to render ineiective said electrical means.

2. In an oil burning system, a pot type oil burner, valve means for controlling the flow of oil to said burner, means for limiting movement of said valve means toward minimum ow position to provide for a pilot llame in said burn- V` er. electrically actuated means for moving said be injured due to overheating by shutting down actuated by said heater.

vvalvemeans toward a maximum ilow position to increase the flow of oil to said burner, a heat exchange surface heated by said burner, a casing surrounding at least .a portion of said surface and cooperable therewith to form a flow passagewayfor fluid ow, fan means for propelling air and having an outlet, an electric motor for driving said fan means, means connecting said fan means outlet to said passageway, switch means operated upon movement of said valve means by said moving means for energizing said electric motor, a bimetallic member positioned in the ilow path of at least a portion of the fluid flow caused by said propelling means, electric heating means positioned in heat exchange relation, with and operable to heat said bimetallic member, switch means operatively connected to said bimetallic member and operable to be moved to open circuit position thereby, and an electrical circuit connecting said electrically actuated moving means and said last-named switch means, said heating means being so interrelated be heated and actuated by said electrically operated means, a heat actuated switch means controlling the circuit of said electric'allyioperated means' and positioned in the inlet path of the fluid medium to said transfer means, heater means positioned in heat exchange relation with said switch means, said heater means being operable to raise the temperature of said switch -means above a predetermined temperature when the rate of flow of the fluid medium is below ai predetermined minimum flow rate, the heat output of said heater means being so related to the output of said fluid supplying means that at all rates of uid flow above said predetermined minimum rate the uid will cool said switch means below said predetermined temperature, and means for simultaneously energizing said electrically operated means and said heater means, said heater means having a rate of increase in temperature upon energization thereof so related to the4 ratel of actuation of said electrically operated means that said uid supplying means Ywill 'be actuated by said electrically operated means to cool said` switch means prior to said plenum chamber, electrically operable means controlling-said combustion controlling means, a switch controlling said ian and closed by 'said electrically operable means, athermostatic switch controlling the circuit of said electrically operable means, and an electric heater for heating said thermostatic switch to open said circuit, said thermostatic switch eing positioned to be cooled by the flow of air to be heated and resulting from operation of said fan so that said electric heater will be ineffective to open said thermostatic switch. y

6. In a heating system, a furnace having an oil burner and a plenum chamber heated thereby, an electrically operable valve controlling the supply of fuel to said burner and movable toward open position upon energization, a fan 4for supplying air to said chamber, a switch controlling said fan and closed upon energization of said valve, a thermostatic switch controlling the. circuit of said valve and positioned tobe cooled by air flow created by said fan, and aneletric heater for heating said thermostatic switch to open said circuit upon failure of said fan, said heater being in circuit with said thermostatic switch.

7. A heating apparatus comprising an'air heating chamber and a combustion chamber separated by a heat transfer wall; a fuel burner in said combustion chamber for heating said wall, means controlling the rate of combustion of fuel in said burner, electrically operable means controlling said controlling means and operable when energized to increase the rate of com bustion,- an electrically driven fan for supplying air to b'e heat-ed to said heating chamber, a thermostatic switch controlling the circuit of said electrically operable means and positioned to be cooled by air flow to said heating chamber resulting from operation of said fanand an electric heater in circuit with said electrically operable means and operable to heat said thermostatic switch, said heater actuating said thermostatic switch upon failure of said fan to cool the same thereby to prevent increase' in the rate of combustion.

8; A heating apparatus comprising an air heating means having a heat exchange wall separating a combustion chamber from an air heating space, a fuel burner in said chamber for heating said wall, means controlling the rate of combustion of fuel in said combustion chamber, electrically operable means controlling said controlling means and operable when energized to increase the rate of combustion, an electrically driven fan for supplying air to be heated to said heating space, an electric switch controlling the circuit of said fan and closed upon energization of said switch means reaching said predetermined temperature.

4. In a heating system, a, heat exchanger, a fan for supplying to said exchanger air to be heated, electrically operable means for controlling the heating of said exchangena thermostatic switch controlling the circuit of said electrically operable means, and an electric heater for heating said switch to open said circuit, said switch being positioned to be cooled by air flow created by operation of said fan so that said switch will not 5. In a heating system, la, furnace having a plenum chamber and a combustion chamber separated by a heat transfer walljmeans controlling combustion in said furnace combustion chamber, a fan for supplying, air to be heated to said 9. A heating apparatus comprising an air heating means having a heat exchange wall separatingr a combustion chamber fromv an air heating space,I a fuel burner in said chamber for heating said wall, meansl controlling the rate of combustion of fuel in said combustion chamber, an electrically driven fan for supplying air to be heated to said heating space, a thermostatic switch posiaseaeoe i u 5 controlling said fan and closed by operation of said electrically operable means, an electric heater in circuit with vsaid thermostatic switch and said electrically operable means and operable to heat said thermostatic switch to break the cir-1v cuit of said electrically operable means, and a switch controlling the circuit of said heater and said electrically operable means, saidheater actuating said thermostatic switch to prevent increase in the rate of combustion upon failure of said fan to cool said thermostatic switch.

PHILIP S. RUSSEL.