US2643154A - Condition responsive device - Google Patents

Description

ISHED COMBUSTION ESTABL NORMAL START A. WELLMAN Original Filed May 31, 1946 CONDITION RESPONSIVE DEVICE June 23, 1953 Inventor; Albert Wellman.

W J/m His Attorheg,

CRITICAL LOCKOUT PERIOD kl I I rconausnou rms J CYCLE TIME *6 COOLING PERIOD E 36-38 CLOSED f b. x

PERIOD '37CL6ED a HEATING Patented June 23,1953

, CONDITION RESPONSIVE DEVICE Albert Wellman, Schenectady, N. Y., assignor to General Electric Com New York pany, a corporation of Original application May 31, 1946, Serial No. 673,338, now Patent No. 2,550,507, dated April 24, 1951. Divided and this application May 26, 1949, Serial No. 95,435

4 Claims.

This invention relates to condition responsive devices, and more particularly to temperature responsive devices which respond only to the initial changes in a temperature condition.

This application is a division of my copending application Serial No. 673,338 filed May 31, 1946, now Patent 2,550,507, issued April 24, 1951, which is assigned to the same assignee as the present application.

An object of the present invention is to provide an improved regulated air bellows form of temperature responsive device for quickly responding only to the initial changes in a widely variable temperature conditions such as produced upon initiation and termination of combustion of an oil burner.

Another object of the invention is the provision of a temperature responsive device adaptable for operating in conjunction with a timer in controlling both the operation of the timer and the energization of an electroresponsive device so as to meet the essential control and safety requirements encountered in oil burner control or other similar control service.

Further objects and advantages of the invention will become apparent from the following description of the accompanying drawing in which Fig. 1 is a schematic perspective view of a condition responsive timing and sequencing circuit control system embodying the improvements of the present invention in a preferred form suitable for oil burner control service, Fig. 2 is a time-sequence diagram of the various condition responsive, timing, and sequencing control functions provided by the improved control system, and Fig. 3 is a fragmentary view showing schematically therelative positions of the lookout sequence control parts under different conditions of operation. 1

As shown schematically in Fig. 1, the control system in which this invention is embodied is applied to control an oil burner I which may be of a conventional type operated by an electric motor indicated by winding II. Suitable oil pumping mechanism enclosed within the pump casing I2 as well as a combustion air blower within the blower casing I3 are both operated when the driving motor II is energized. As indicated, oil is supplied under pressure through pipe I4 to atomizing nozzle I5 and combustion air is supplied through conduit I6 and air supply tube I! for mixing with the atomized oil to project a combustible mixture into a combustion chamber I8 defined by the wall I9. Under normal burner operating conditions, this combustible mixture is ignited by means of ignition transformer 2i and the high-voltage spark electrodes 22. However, under some abnormal conditions, combustion may not be successfully established during a limited starting period and it then becomes imperative that further operation of the oil burner be stopped. Otherwise a dangerous explosion might occur due to the accumulation of a relatively large amount of unburned atomized oil in the combustion chamber. The present invention provides improved means for aiding'the control system in positively differentiating between the normal establishment of combustion and the failure to establish combustion while the motor I I is initially energized dur-' ing the limited starting period.

Burner motor II is energized from suitable electric supply lines LI, L2, preferably under control of an electro-responsive relay 23 having an operating winding 24 energized from the lowvoltage secondary of a transformer 25. Relay 23 is operated under the control of a timing and sequencing switch mechanism indicated generally by the reference character 26 which is combined in interlocking relation with a preferred form of the improved temperature responsive device of this invention. This device, which is indicated generally by the reference character 21, functions as a combustion responsive device in this case although it is not necessarily limited to such use. A master control switch in the form of a conventional room thermostat 28 or the like is provided for initiating and terminating burner operation to regulate a predetermined condition such as the room temperature.

The timing and sequencing mechanism 26 is provided with a movable thermal timing element 30 having an electric heater 3I supported in heating relation with the thermal element 30 by bracket 32 mounted on a projection 33 from the main supporting base 34. The thermal timing element 30 is shown as of the bimetallic type fixed at its lower end and carrying at its upper end contact plate 35 on which switching contacts 36 are mounted back to back so as to abut with the cooperating switch contacts 3! and 38 for providing a timing energization of the relay 23 in the improved manner described hereinafter.

Switch contact 31 is resiliently carried by a spring strip 40 mounted on the arm M which in turn is movably mounted by the flexible strip 42 that extends from the support 13 so that the position of contact 31 and arm 4i may be adjusted by means of the adjusting screw 44. The arm 4| is formed of magnetic material and is movable into magnetic attractive relation with the permanent magnet 46 that is carried by the switch plate 35, being suitably secured thereto as by screw 45. Thus a releasable holding means is provided by magnet 46 and arm 4| for maintaining contact 31 in resilient abutment with contact 36 during a predetermined movement of the switch plate 35 by the thermal element 33 due to the heating thereof until arm 4I engages the extension 41 of adjustable stop 48 to release arm 4| from magnet 46. Thus the adjustment of stop 48 by adjusting screw 49 regulates the heating period of thermal element 30.

Switch contact 38 is carried by a flexible strip 55 extending from the base 34 to position contact 38 so as to engage with contact 36 during the predetermined heating of the thermal element 30. To eliminate difliculties due to chattering of room thermostat 28, the switch plate 55 also may carry contact into abutting engagement with contact 52 carried by the fiexible strip 53 extending from the base so as to shunt the room thermostat 28 for a limited interval during the starting of burner ID.

The temperature responsive device 21 in the improved form shown comprises an expansible air-filled bellows 55 mounted on a connection basec55 and interconnected through tube 51 with a temperature sensitive air bulb 58 disposed so as toLbe heated to expand the air inside the bulb upon establishment of. combustion in the combustion chamber 18. An operating arm 59 is pivotally mounted on the pin '55 to engage with and be operated by the finger 5| extending from the closed end of the bellows 55. The pivoted arm 59 is operably connected with the switching interlock member 62 that is movably mounted by means of bracket 55 and the resilient mounting spring 65 extending from a fixed support 55 having a motion limit stop 65.

As explained more in detail hereinafter, the

interlocking member 62 is provided with a projecting finger 69 for cooperating with the extension it of switch plate 35, an interlocking finger ll for cooperating with the bent-over eX- tension l2 of the fiexible strip 53 and an adjustably mounted interlocking finger 13 for cooperating with the extension 14 of the movable magnetic arm 4!. Also, interlocking member 52 carries a finger for engaging with arm it to separate the normally closed switch contacts ii and thereby open the primary circuit of the ig.

nition transformer 2| after combustion is established.

An improved automatic air pressure control valve mechanism 80 is provided for regulating the air pressure to which the bellows 55 is subjected both before heatingof the bulb 58 in response to combustion and also during the heat-,

ing of bulb 58. As shown,a conventional form of pneumatic tire valve 8! is mountedcinside the tube 82 that communicates through passage 83 formed in base 55 with the interior of bellows 55. The opening and closing of the tire valve 8! is automatically controlled by means of a lever 85 pivotally mounted on pin 85 and carrying the adjusting screw 86 into and out of engagement with the tire valve stem 81.

The improved pressure control operates as follows: When the bulb 58 is cooling, bellows 55 contracts due to the decreased internal air pressure below atmospheric and a suitable spring 88. moves lever 55 to carry the head of adjustable screw 89 into engagement with the forked end of the pressure control lever 84 so as to engage adjustable screw 86 with valve stem 81 and thereby open the tire valve 31. As a result, the air pressure inside bellows 55 becomes equalized with the outside air pressure and bellows 55 then can expand sufficiently to reclose tire valve 85. In this way a predetermined equalized pressure is always provided inside the bellows 55 when bulb 53 is cooled.

When bulb 58 is heated, the resulting increase of internal air pressure causes bellows 55 to ex pand relatively quickly until the knob 95 on lever 55 engages adjusting screw 91 and tilts lever 84 to press adjusting screw 85 against tively small increase or decrease of the temperature of bulb 58 to effect reverse operations of interlocking member 52. This in turn enables a very quick andpositive response of bellows 55 to the establishment or termination .of combustion to be obtained.

Operation With the various parts in their respective positions shown in Fig. 1, the oil burner I0 is started'into operation upon closure of the master control switch 28. This first closes a time delay heating circuit extending from the secondary of transformer 25 through relay winding 2 conductor I55, master switch 23, conductor Illi, switch plate 35, abutting contacts 35 and 31, strip 40, arm 4i, strip 42, support 43, conductor I52,- heater 3| and conductors I53 and I04 to the opposite terminal of the transformer winding. Due to the current limiting action of electric heater 3!, the resulting limited energization of relay winding 24 is below the pickup value and hence is inefiective to 'cause response to the relay'to close contact 23. However, heater 3| begins to heat thermal timing element 35 to produce movement of the upper end thereof to the left as indicated by the arrow H. Magnet 45 holds plate 4| in attractive relation therewith so as to maintain contacts 36, '3! in abutment during a predetermined heating period of element 50. As indicated in Fig. 2, this heating period extends from the initial starting time To when master switch 28 closes its contacts to time T2 when contact 31 becomes separated from contact 35 due to engagement of 'arm li with the extension ll of the ad-- justable stop 45. During this heating period, thermal element 35 carries plate 35 to abut contact 36 with ccntacttt at a time indicated in Fig. 2 as Tl. Thus, during a relatively short interval between time Ti and time T2, contact 36 is maintained in abutment with both contacts 3'! and 38.

Upon abutment of contact 35 with contact 38 at time Tl, a parallel circuit is closed shunting the electric heater 3!. This parallel circuit extends from contact 56 through contact 58, strip With resistor 555 thus connected in parallel or shunt with the electric heater 3 I, the relay winding 24 now becomes sufficiently energized to pick up and effect operation of relay contact 23 from its normally opened position in which it is shown to) the closed position to start operation of burner Upon closure of relay 25 the oil burner operating motor l l is energized from supply line I through conductor I57, relay 23, conductor i58, the energizing winding of motor I i and conductor E55 and the usual'saiety limit switches i it. Also the closure of relay 25 energizes the ignition transformer 2i, the circuit extending through conductor HI, normally closed ignition control switch contacts ll, conductor N2, the primary ignition transformer 2|, and conductors H3 and I09 and limit switch H0. With both motor I and ignition transformer 2| thus energized upon closure of relay 23 at time T in the diagram of Fig. 2, the subsequent operation of oil burner II] should successfully establish combustion within a limited time thereafter. During this limited time contacts 52 and 52 by-pass the master switch 28 to insure against the difficulties that might result from chattering of the room thermostat contacts.

Let us assume that combustion is initially established at time E, as shown in diagram of Fig. 2, during the cooling period of thermal element 30. At this time relay 23 is maintained effectively energized entirely by the shunt circuit including resistor 105 since thermal element 30 has previously moved contact plate 35 in the direction of the arrow sufficiently to pull arm 4|, through the agency of magnet 46, into engagement with adjustable stop 41 and thereby release the arm from the magnetic attraction of magnet 46. Thereupon arm 4| and strip 46 are biased by resilient strip 42 to move to the right until extension 14 engages with the sloping cam surface 13a of the adjustably mounted cam 13 so as to carry arm 4| entirely out of attractive relation with magnet 46 and contact 31 out of abutment with contact 36 and thereby open the circuit through electric heater 3| and thus terminate the heating period and initiate the cooling period a of thermal element 30 at time T2.

With combustion established at time E as assumed, the bulb 58 will quickly become heated to expand bellows 55 and thereby relatively quickly operate interlocking member 62 upwardly so as to move arm 4| to the left due to the camming action of the sloping surface 73a on extension '14 and thus return arm 4] into the position indicated by the dotted lines in Fig. 3 to be attracted by magnet 45 when the latter returns to its normal starting position as shown in Fig. 3. The further upward movement of member 63 also will position finger 66 in the path of extension 10, finger 1| in the path of the projection 72 and engage finger 75 with the arm '36 to separate contact ll and thereby deenergize the ignition transformer 2|. Thus as thermal element 36 continues to cool, finger ll engages with extension 72 to separate contacts 55, 52 and thereby remove the by-pass circuit around the master control thermostat 28. Shortly thereafter, projection engages the finger 69 so as to block further movement of plate 35 to the right even though thermal element 36 continues to cool. Consequently, contact 36 is maintained in abutment with contact 38 by the blocking engagement of finger 59 with extension 10 in response to establishment and maintenance of combustion during the cooling period of thermal element 30.

Under assumed conditions, when combustion is once successfully established and maintained during the cooling period of thermal element 36, the burner motor I I is thereafter operated under the joint control of the temperature responsive device 21, master control switch 28 and relay 23. Thus, in case for any reason combustion should fail after time T3, the control system insures an automatic restart of the burner in the following manner: Upon the initial cooling of bulb 58 bellows 55 relatively quickly responds to move interlocking member 62 downwardly and thus disengage finger 69 from extension 16 and thereby free plate 35 for snap-action movement to reengage contact 36 with contact 3! due to the resilient biasing action provided by the cooling of thermal element 36. Such reengagement of contacts 36 and 31 after termination of combustion'is obtained solely due to the fact that when finger 69 disengages extension 16 to release plate 35 for snap-action movement, the cam surface 13a of.

interlocking finger 13 still engages extension 14 of arm 4| as indicated by the dotted lines in Fig. 3 and thus holds arm 4| in a position to again be attracted and thereby held by magnet 46 and consequently maintain contact 31 in engagement with contact 36. Upon the release of plate 35, contact 36 disengages contact 38 and thereby opens the maintaining circuit through resistor N15 for relay 23. As a result relay 23 returns to its open position and deenergizes burner motor Upon the snap action reengagement of contacts 36 and 31 just described, the electric heater 3| again is energized and thermal element 36 again is heated to restart burner operation in precisely the same timed cycle as described above. Furthermore, exactly the same automatic restart operation is obtained in case of voltage failure of the power supply lines Ll, L2, whenever the power failure is of sufficient duration to produce a response of the combustion responsive device 21 to slow down or stop the burner operation and thereby cool bulb 58.

In case a normal burner operation has continued sufficiently to satisfy the demands of the master control thermostat 28, the opening of the thermostat contacts will deenergize relay 23 and thus stop further burner operation at time Tzr shown in Fig. 2. In this case, contact 36 is returned into engagement with contact 31 and magnet 46 into attractive relation with arm 4| in exactly the same manner as previously described. Thus the control system is ready to restart the burner whenever the master switch 28 again recloses its contacts.

Let us now assume that due to some fault of the burner l0, combustion is not successfully established during the cooling time of thermal element 3!). In this case interlocking member 62 will remain in its initial position during the entire starting cycle time since bulb 58 is not heated and bellows 55 is not expanded. Hence, the ad- I justable interlock stop 13 is maintained in its initial lockout position shown in full lines in Fig. 3 to engage with extension 74 without exerting any camming action thereon that would tend to return arm 4| into attractive relation with magnet 46. Consequently arm 4| when released at time T2 moves in accordance with its bias provided by resilient strip 42 as adjusted by screw 44 to a lookout position that is out of attractive rela tion with magnet 46 when thermal element 33 has cooled as shown by the dot-dash lines of Fig. 3. Thus, when element 36 has cooled extension 10 will engage with the flat end of interlocking member 62 but arm 4| will not be magnetically attracted or held by magnet 46 and thus contact 31 will not abut contact 36. In this way the control system is automatically locked out when combustion is not successfully established by a predetermined time L that is before the end of thecooling time T3.

To restart burner operation after such an automatic lockout and after the burner fault producing the lockout has been corrected, the manual push button H5 is operated to engage the extension I I6 with arm 4| to move this arm into magnetic attractive relation with magnet 46. At the same time extension ||1 engages with strip 50 so as to move contact 38 out of the range of movement of contact 36. Only a momentary operation of the reset button H is required. since arm ll will at once beheld by magnet it and push button 1 l5 may then be returned to its initial position by spring I [8 to restore the whole control again to its normal operating condition. While the invention has been illustrated and described in a preferred form adaptable for use with the improved control system and thermal timer of my copending application Serial No. 673,338, it will be readily apparent that this improved temperature responsive device may also be used in other'control systems and with other timers. Furthermore, modifications of the temperature responsive device itself will occur to those skilled in the art. Therefore, it should be understood that I intend to cover by the appended claims all modifications which fall within the true spirit and scope of the invention.

7 What I claim as new and desire to secure by Letters Patent of the United States is:

l. A temperature responsive device comprising a first pivotally mounted reversely movable control lever having operating means including an air pressure responsive bellows provided with a temperature sensitive bulb for varying the pressure within said bellows responsively to heating and cooling of said bulb, means including a normally closed valveconnected with said bellows for venting air. into and out of said bellows to regulate the movement of said control lever, and

means including a pivotally mounted valve oper ating lever connected to open said valve and having one operating connection with said control lever for opening said valve responsive to movement of said control lever in one direction to equalize th pressure within and without said bellows thereby to limit the movement of said control lever insaid one direction when said bulb is cooled, said valve operating lever having another operating connection with said control lever for opening said valve responsive to movement of said control lever in the opposite direction to regulate the pressure within said bellows thereby to limit the movement of said control lever in said opposite direction when said bulb is heated.

2. A temperature responsive actuating device comprising air pressure responsive bellows, a temperature responsive bulb connected to said bellows for varying the pressure therein, a normally closed valve connecting said bellows to the atmosphere for venting air into said bellows when the pressure therein is below atmospheric pressure and for venting air therefrom when the pressure therein is above atmospheric pressure, a pivotally mounted actuating lever operatively connected to said bellows for movement in a first direction responsiv to expansion of said bellows and in the other direction responsive to contraction of said bellows, and a second pivotally mounted lever connected to said valve for opening the same responsive to movement thereof, said actuating lever having a first connection with said second lever arranged to move the same .to open said valve responsive to movement of said actuating lever in its first direction, said actuating lever having a second connection with said second lever arranged to move the same to also open said valve responsive to movement of said actuating lever in its other direction whereby expansion and contraction of said bellows is limited thereby to limit movement of said actuating lever.

3. A temperature responsive actuating device comprising air pressure responsive bellows, a

d temperatur responsive bulb connected to said bellows for varying the pressur therein, a normally closed valve connecting said bellows to the atmosphere for venting air into said bellows when the pressure therein is below atmospheric pressure and for venting air therefrom when the pressur therein is above atmospheric pressure, a mounting member, an actuating member pivotally mounted on said mounting member and operatively connected to said bellows for movement in a first direction responsive to expansion I or said bellows and in the other direction responsive to traction of said bellows, and a second lever pivotally mounted on said mounting member and connected to said valve for opening the same responsive to movement thereof, said actuating lever having a first connection with said second lever arranged to move the same to open said valve responsive to movement of said actuating lever in its first direction, said actuating lever having a second connection with said second lever arranged to'move the same to also open said valve responsive to movement of said actuating lever in its other direction whereby expansion and contraction of said bellows is limited thereby to limit movement of said actuating lever.

1-. A control device comprising an air pressure responsive bellows having a conduit connection to a source of varying air pressure, a mounting member, a control lever pivoted at one end to said mounting member and operatively engaged at an intermediate point thereon with said bellows for movement in a first direction responsive to expansion of said bellows and in the other direction responsive to contraction of said bellows, a biasing spring connected to the opposite end of said control lever and arranged to oppose expansion of said bellows, a normally closed valve connecting said conduit to the atmosphere for venting air into said bellows when the pressure therein is below atmospheric and out of said bellows when the pressure therein is above atmospheric, and a second lever positioned adjacent the portion of said control lever adjoining said opposite end thereof and in substantial parallel relation therewith, said second lever being pivoted intermediate its ends to said mounting member and having a connection at one end thereof with said valve for opening the same responsive to movement thereof, said control lever having an operative connection with the other end of said second lever adjacent the point at. which the first lever engages said bellows for moving said second lever responsive to said control lever moving in its first direction, said control lever having a loose connection between said opposite end thereof and said one end of said second lever for moving the same responsive to said control lever moving in its other direction whereby expansion and contraction of said bellows is limited thereby to limit movement of said control lever.

ALBERT l/VELL'MAN.

Number Name Date 1,884,286 Schroeder Oct. 25, 1932 2,346,284 Baak Apr. 11, 1944 FOREIGN PATENTS Number Country Date 280,536 Great Britain Mar. 22, 1928

Images