US2881830A

US2881830A - Electromagnetic control system

Info

Publication number: US2881830A
Application number: US421040A
Authority: US
Inventors: Oscar J Leins
Original assignee: Baso Inc
Current assignee: Baso Inc
Priority date: 1954-04-05
Filing date: 1954-04-05
Publication date: 1959-04-14
Anticipated expiration: 1976-04-14

Description

April 1959 8 6...]. LEINS 2,881,830

v ELECTROMAGNETIC CONTROL SYSTEM Filed April 5, 1954 Fig.5 F3 2 29 h 22 i I 42 46 #43 N 48 5 Jj/ INVENTOR.

Oscar J. Lei ns United States Patent O ELECTROMAGNETIC CONTROL SYSTEM Oscar J. Leins, Milwaukee, Wis., assignor to Base Inc., Milwaukee, Wis., a corporation of Wisconsin Application April 5, 1954, Serial No. 421,040 11 Claims. (Cl. 158-128) This invention relates to improvements in electromagnetic control systems, and more particularly to systems operable on thermoelectric power.

It is a general object of the present invention to provide an improved control system including a control device which eifects one or more of a plurality of control operations in accordance with the magnitude of the power with which said device is energized, for example, in accordance with the output level of a thermoelectric generator supplying power thereto.

A more specific object of the invention is to provide an improved control device of the aforementioned character having coacting relatively movable electromagnet frame and armature members biased toward a retractedposition and movable to an attracted position in magnetic engagement, energization of said electromagnet by an intermediate level of power output of the thermoelectric generator being operable to hold said frame and armature members in attracted position against said bias, and energization of said electromagnet at a higher output level of said generator causing saturation of one of said members and shunting of magnetic flux therefrom, there being a magnetic control member operatively associated with the saturable member and movable between the attracted and retracted positions with respect thereto, said control member being positioned to receive magnetic flux shunted from said saturable member and to be actuated to said attracted position by said flux.

Another object of the invention is to provide an improved control system of the class described which utilizes the heating and cooling periods and the change in the power output of a thermoelectric generator with changes in temperature thereof to provide a time delay separating certain of the operations performed by said system.

Another object of the invention is to provide an improved fuel control system for fluid fuel burning apparatus having a burner and an electric igniter for said burner, the control device for said system including a safety shut-off valve controlled by the coacting electromagnetic frame and armature members and a switch actuated by movement of the control member, said switch affording an interlock between said valve and the electric igniter circuit to effect automatic operation of the igniter on burner outtage, the cooling period of the thermoelectric generator on burner outtage affording a time delay for reignition of said burner and heating of said generator prior to closure of the safety shut-off valve.

Another object of the invention is to provide an improved control apparatus of the character described which is provided with an indicator light in the igniter circuit for indicating operation of the igniter.

Another object of the invention is to provide an improved control apparatus of the aforementioned character which is simple in construction, positive in operation and well adapted for the purposes described.

Other objects and advantages of the invention will become apparent as the description proceeds, reference being had to the accompanying drawing in which:

ice

- and Figure 3 is a view similar to Figure 2 illustrating the parts thereof in reset position.

Referring more particularly to Figure l, the illustrated form of the invention is shown embodied in a fluid fuel burning apparatus having automatic electric ignition means. The numeral 5 indicates an improved electromagnetic control device having a body 6 provided with a transverse partition 7 disposed between a main fuel inlet connection 8 and a main fuel outlet connection 9. The partition 7 is centrally apertured to afford a passage 13, and is provided with a pair of annular valve seats 10 and 11 at opposite ends of said passage. A pilot fuel passage 12 affords communication between the passage 13 and an external pilot fuel connection 14. The control device 5 is interposed in the fuel supply line 15 for a main burner 16, and said supply line may also have interposed therein a suitable thermostatic valve 17. A pilot burner 18 is positioned in coacting relationship with the main burner 16 and is supplied with fuel through a pilot fuel line 19 extending from the connection 14 on the body 6. A thermoelectric generator 20, which may take the form of a thermocouple, is mounted in a position to be subject to the heat of the flame of the pilot burner 18 as shown.

Fixedly mounted within the body 5 is an electromagnet 21 comprising a generally U-shaped magnetically permeable frame 22, and an energizing coil 23 wound on the legs of said frame. One end of the coil 23 is grounded, as at 24, and the other end of the coil is connected in circuit with an insulated connector 25 having a terminal tip 26 exposed within an external socket 27. A conductor 28, which may be the inner, insulated conductor of a concentric type lead, connects the terminal tip 26 in circuit with one terminal of the thermoelectric generator 20, the other terminal of said generator being grounded as shown, preferably through the outer conductor of the aforementioned concentric lead.

A magnetically permeable armature 29, which may have a portion 46 of reduced cross-section, coacts with the electromagnet 21 and is connected to a valve member 30 by a stem 31 which may be made of non-magnetic material. A coiled compression spring 32 biases the armature 29 away from the pole faces of the magnet frame 22 and thereby biases the valve member 30 toward the annular valve seat 10. The armature 29 and valve member 30 are movable between the reset position shown in Figure 1 and the drop-out or shut-off position shown in Figure 2. In the latter position the valve member 30 shuts off all fuel flow to the main burner 16 and pilot burner 18.

Means is provided for manually resetting the armature 29 and valve 30 from the positions of Figure 2 to the position of Figures 1 and 3. The aforementioned reset means may take the form of a reset stem 33 axially slidably mounted in a suitable sealing type bearing 34 mounted in an end wall of the body 6 as shown. The stem 33 is preferably coaxial with the passage 13 and is provided with an external manually engageable button 35, as well as with an internal flange 36. A flow interruption disk 37 is slidably mounted on the stem 33, and a coiled compression spring 39, having one end abutting the flange 36, biases said disk toward a collar 38 fixed on said stem. A coiled compression spring 40 engages the flange 36 and the partition 7, and biases the stem 33 axially outwardly. On depression of the button 35: and stem 33 to the dot and dash line position of Figure 1,

the inner end of the stem 33 engages the valve member 30 and lifts the latter to the position in which it is disposed in Figures 1 and 3. Simultaneously, the spring 39 biases the flow interrupter disk 37 to its position shown in Figure 3 and also shown in dot and dash lines in Figure 1, i'.e. into sealing engagementwith the annular seat 11, thereby shutting off the fuel flow to the main burner 16 while permitting fuel flow to the pilot burner 18.

The stem 31 is provided with an intermediate flange or bracket 41, and mounted for axial movement on the stem 31 between the flange 41 and the armature 29 is a magnetic control member 42 which, in the illustrated embodiment, comprises a centrally apertured magnetically permeable disk 43 having a coaxial tubular extension 44 provided with an annular flange or bracket 45. The control member 42 is axially movable with respect to the armature 29 and flange 41 between the solid line attracted position shown in Figure 1, wherein the disk 43 is in magnetic engagement with the armature 29, and the; retracted dot and dash line position wherein said control member may rest on the flange 41.

Fixed to the flange 41 is a bracket 47 affording a pivotal mounting for a bell crank lever 48. The lever 48 has

arms

49 and 50, the latter arm carrying a mercury switch -1

havingcontacts

52 and 53. The arm 49 is elongated and is positioned for engagement by the flange 45 of the control member 42 when the latter is moved to its attracted position, suchmovement pivoting the bell crank lever 48 in a clockwise direction against the bias of a coiled tension spring 54 connecting the arm 49 to the bracket 47 asshown. When the bell crank lever 48 is in the solid line position of Figure l, the mercury switch 51 is til-ted so that the circuit between the contacts 52' and 53 is open. When, however, the control member 42 is in its position of Figure 3 and the armature 29 is in; its attracted position as also shown in Figure 3, the spring 54 biases the lever 48' in a counterclockwise direction to its position of Figure 3 wherein the arm 49 thereof engages a fixed lug 65 formed in the interior of the body 6. When the lever 48 is in this position, the mercury switch 51 is tilted to the position shown in Figure 3:, in which the mercury therein completes the circuit between the

contacts

52 and 53. On drop-out of the armature 29, however, the bracket 47 moves downwardly with the armature 29 and stem 33, and engage ment of the arm 49 with the lug 65 during such move ment pivots the bellcrank lever 48 in a clockwise direction against the bias of the spring 54. This, of'course, tilts the mercury switch to the circuit-interruptingposition shown in Figure 2.

The. mercury switch 51 controls thepower circuit to an electric igniter'55positioned in coacting relationshipwiththe pilot burner 18 as shown in Figure l". The igniter 55 is connected in series circuit relation with the mercury switch contacts 52" and 53, an indicator light 56 and a sourceof energizing current, for example the secondary winding 57 ofa step-down transformer 58, the primary winding 59 of which is connected to analternating currentline. More specifically, a conductor 60' connects the switch contact 52 in circuit with one terminal oftheigniter 5'5, and a conductor 61 connects the contact 53 in. circuit with oneterminal of theindicatorl-ight 56. The other terminal of the indicator light- 56 is connected in circuit withone terminal of the transformer winding; 57' by' a conductor 62, and the other terminal of the winding 5-7'i'sconnected in circuit with the other terminal of'the igniter. 55- by aconductor 63. As shown, the indicator light 56'- may be mounted on thecontrol device 5, and may be enclosed within a transparent bubble 64 of glass or other suitable material.

To place the improved control apparatusinto operation. from the shut-down condition shown in Figure 2, the

reset; button 35 is depressed toopen the valve 30and' reset the armature 29 to. the electromagnet 21, while at the same time the flow interrupter disk sealsagainst the seat 11to prevent fuel flow to the main burner 16 while permitting fuel to flow to the pilot burner 18 all as shown in Figure 3. As the stem 31 is lifted during the resetting operation, the bell crank lever 48 pivots in a counterclockwise direction under the bias of the spring 54 so that when the armature 29 is in the attracted position shown in Figure 3, the bell crank lever 48 assumes the circuitmaking position shown in said figure, thereby completing the circuit. to the igniter and rendering the latter operative while at the same time causing illumination of the indicator light 56.

Operation of the igniter causes ignition of the fuel being emitted from the pilot burner 18', and. the resulting fiame heats the thermocouple 20. The power generated by the couple 20 energizes the electromagnet coil 23 and causes the latter to generate magnetic flux flow in the frame 22 and armature 29. As the temperature of the couple 20 comes up to a predetermined level less than the normal operating temperature thereof, the power output of said couple comes up to a predetermined level less than the full power available therefrom. Energization of the coil 23 by this intermediate level of power from the couple 20 causes said coil to produce sufficient flux to hold the armature 29 to the magnet frame 22 against the bias of the spring 32. As the temperature of the couple 20 continues to rise and approaches its normal operating temperature, its output correspondingly increases. Energization of the coil 23 by this higher power output level causes said coil to produce .a flux density above that necessary to saturate the reduced portion 46 of the armature 29; As a result, flux is shunted from the armature- 29' and links the portion 43 of the control member 42".

The shunted flux lifts the control member 42 from the retracted position of Figure 3' to the attracted position thereof in contact. with the armature 29 shown in Figure 1'. This lifting. movement pivots the bell" crank lever 48 in a. clockwise direction. and tilts the mercury switch to the circuit-interrupting position shown in Figure 1. As a result, the indicator light 56 and the igniter 55 are deenergized', and extinguishment of the light 56 indicates to the operator that the reset button 35' may be released. Release of the button 35 causes retraction of the flow interrupter disk 37 to the solid line position, of Figure 1 and permits fuel flow to the main. burner 16. Thereafter, fuel flow to the main burner may be. under the control of the thermostatic valve 17. It is apparent that since, the power output of the couple 20. varies with. the temperature thereof, the heating period required to bring said generator up to normal operating temperatures provides. a substantial time lag' between the initial subjection of said. couple to the heat of the pilot burner flame and thernovement of the control member 42 into engagement with the armature for interruption of the. igniter circuit.

55 operative. Because of the cooling period of the couple 20, there is a substantial time lag. between the drop-out of the control. member 42 and point at: which the power output level' of the couple 2.0 drops to. the.- pointiat which energizationofthe coil 23 thereby is no longer sufficient to hold. the armature 29 in attracted position. This time lag is of sufficient length sothat the burner 1 8 can nor .maliy-be ignited wellbefore the armature 29 drops out and closes the valve member 30.

When the power output of the couple drops I If the pilot burner 18 is reignited bythis operation, the generator 20 is' reheated to its normal operating temperature, and during this heating, the control member 42 is again actuated to its attracted position, thereby again interrupting the igniter circuit. If, however, the operation of the igniter 55 does not reignite the pilot burner 18, the generator 20 continues to cool, and after a predetermined time delay, eifects drop-out of the armature 29 to the position of Figure 2. As pointed out previously, such armature movement shuts off all fuel flow to the main and pilot burners, and simultaneously pivots the bell crank lever 48 and mercury switch 51 to circuit-interrupting position, thereby shutting off the igniter and the indicator bulb 56. The apparatus remains shut down until the reset button 35 is subsequently depressed to start a new operational cycle.

The specific illustrations and corresponding description are used for the purpose of disclosure only and are not intended to impose unnecessary limitations on the claims, or to confine the patented invention to a particular use. Various changes and modifications may be made without departing from the spirit of the invention, and all of such changes are contemplated as may come within the scope of the claims.

What is claimed as the invention is:

1. In electromagnetic control apparatus having a fluid fuel burner, thermoelectric generator means subject to the heat of the flame of said burner, and an electric igniter for said burneri a magnetically permeable electromagnet frame member, a magnetically permeable armature member, one of said members being fixed and the other being movable, said movable member having an attracted position in magnetic engagement with said fixed member and a retracted position separated from said fixed member; means biasing the movable member to said retracted position; energizing coil means for said electromagnet frame member connected in circuit with said thermoelectric generator means for establishing, when energized by said generator means, magnetic flux flow through said electromagnet frame and armature members, energization of said coil means by a predetermined amount of power less than the full power available from said generator means producing sufiicient flux flow to hold the movable member attracted to the fixed member against said bias, whereas energization of said coil means by a larger amount of power from said generating means produces a flux density above that required to saturate one of said magnetic members, whereby magnetic flux is shunted from said saturated member; a magnetic control member biasd to a retracted position with respect to said saturable member and movable to an attracted position with respect thereto, said control member being positioned to receive the flux shunted from said saturable member and to be actuated by said flux to said attracted position against said bias; and a switch actuated by said control member and having contacts in circuit with said igniter for controlling the operation of the latter, said switch completing the igniter circuit to effect operation of said igniter when the control member is in retracted position, and interrupting the igniter circuit to render the igniter inoperative when the control member is in attracted position.

2 In electromagnetic control apparatus having a fluid fuel burner, thermoelectric generator means subject to the heat of the flame of said burner, and an electric igniter for said burner: a magnetically permeable electromagnet frame member, a magnetically permeable armature member, one of said members being fixed and the other being movable, said movable member having an attracted position in magnetic engagement with said fixed member and a retracted position separated from said fixed member; means biasing the movable member to said retracted position; energizing coil means for said electromagnet frame member connected in circuit with said thermoelectric generator means for establishing, when energized by said generator means, magnetic flux flow through said electromagnetic frame and armature mem bers, energization of said coil means by a predetermined amount of power less than the full power available from said generator means producing suflicient flux flow to hold the movable member attracted to the fixed member against said bias, whereas energization of said coil means by a larger amount of power from said generating means produces a flux density above that required to saturate one of said magnetic members, whereby magnetic flux is shunted from said saturated member; a magnetic control member biased to a retracted position with respect to said saturable member and movable to an attracted position with respect thereto, said control member being positioned to receive the flux shunted from said saturable member and to be actuated by said flux to said attracted position against said bias; a switch actuated by said control member and having contacts in circuit with said igniter for controlling the operation of the latter, said switch completing the igniter circuit to effect operation of said igniter when the control member is in retracted position, and interrupting the igniter circuit to render the igniter inoperative when the control member is in attracted position; and means including connections between said switch and said movable member for effecting actuation of said switch and interruption of said igniter circuit on movement of said movable member to retracted position.

3. In electromagnetic control apparatus having a fluid fuel burner, thermoelectric generator means subject to the heat of the flame of said burner, and an electric igniter for said burner: a magnetically permeable electromagnet frame member, a magnetically permeable armature member, one of said members being fixed and the other being movable, said movable member having an attracted position in magnetic engagement with said fixed member and a retracted position separated from said fixed member; means biasing the movable member to said retracted position; energizing coil means for said electromagnet frame member connected in circuit with said thermoelectric generator means for establishing, when energized by said generator means, magnetic flux flow through said electromagnet frame and armature members, energization of said coil means by a predetermined amount of power less than the full power available from said generator means producing suflicient flux flow to hold the movable member attracted to the fixed member against said bias, whereas energization of said coil means by a larger amount of power from said generating means produces a flux density above that required to saturate one of said magnetic members, whereby magnetic flux is shunted from said saturated member; a magnetic control member biased to a retracted position with respect to said saturable member and movable to an attracted position with respect thereteo, said control member being positioned to receive the flux shunted from said saturable member and to be actuated by said flux to said attracted position against said bias; a switch actuated by said control member and having contacts in circuit with said igniter for controlling the operation of the latter, said switch completing the igniter circuit to effect operation of said igniter when the control member is in retracted position, and interrupting the igniter circuit to render the igniter inoperative when the control member is in attracted postion; and a fuel shut-off valve connected to said movable member for actuation thereby to open and closed positions on movement of said movable member to attracted and retracted positions respectively.

4. In electromagnetic control apparatus having a fluid fuel burner, thermoelectric generator means subject to the heat of the flame of said burner, and an electric igniter for said burner: a magnetically permeable electromagnet frame member, a magnetically permeable arma ture member, one of said members being fixed and the other being movable, said movable member having an attract ed position in magnetic engagement with said fixed member and a retracted position separated from said fixed member; means biasing the movable member to said retracted position; energizing coil means for said electromagnet frame member connected in circuit with said thermoelectric generator means for establishing, when energized by said generator means, magnetic flux flow through said electromagnet frame and armature members, energization of said coil means by a predetermined amount of power less than the full power available from said generator means producing suificient flux flow to hold the movable member attracted to the fixed member against said bias, whereas energization of said coil means by a larger amount of power from said generating means produces a flux density above that required to saturate one of said magnetic members, whereby magnetic flux is shunted from said saturated member; a magnetic control member biased to a retracted position with respect to said saturable member and movable to an attracted position with respect thereto, said control member being positioned to receive the flux shunted from said saturable member and to be actuated by said flux to said attracted position against said bias; a switch actuated by said control member and having contacts in circuit with said igniter for controlling the operation of the latter, said switch completing the igniter circuit to effect operation of said igniter when the control member is in retracted position, and interrupting the igniter circuit to render the igniter inoperative when the control member is in attracted position; a fuel shut-01f valve connected to said movable member for actuation thereby to open and closed positions on movement of said movable member to attracted and retracted positions respectively; and means including connections between said switch and movable member for effecting actuation of said switch and interruption of said igniter circuit on movement of said mov able member to retracted position.

5. In electromagnetic control apparatus having a fluid fuel burner, thermoelectric generator means Subject to the heat of the flame of said burner, and electric ignition means for said burner: electromagnetic safety shut-ofi means in circuit with said generator means and having a reset position in which said safety shut-off means is held when energized by a predetermined first power output value less than the full power output of said generator means and having a drop-out position toward which it is biased and to which it is moved when power less than said first output value is supplied thereto; a magnetic control member operatively associated with said electromagnetic safety shut-off means, said control member having a first position toward which it is biased and having a second position to which it is moved when said safety shut-off means is in reset position and is energized by power from said generaor means of a second predetermined higher output value, said control member being released for movement to said first position under said bias whenever power of less than said second output value is supplied to said safety shut-off means; and a switch actuated by said control member and having contacts in the power circuit of said ignition means for opening said circuit to render the ignition means inoperative when said control member is in said second position and closing said circuit to render the ignition means operative when the control member is in said first position, wherefore on outtage of said burner and cooling of said generator means the power output of said generator means drops below said second value thereby moving the control member to said first position, closing said igniter circuit, and effecting operation of said ignition means, the cooling period necessary for the output of said generator to drop from said second to said first output value providing a time delay for reignition of said burner and reheating of said generator means before the output of said generator means reaches said first value and said safety shut-off means drops out.

6. In electromagnetic control apparatus having a fluid fuel burner, thermoelectric generator means subject to the heat of the flame of said burner, and electric igniter means for said burner; A magnetically permeable elec tromagnet frame member, a magnetically permeable armature member, one of said members being fixed and the other being movable, said movable member having an at tracted position in magnetic engagement with said fixed member and a retracted position separated from said fixed member; means biasing the movable member to said retracted position; energizing coil means for said electromagnet frame member to which said thermoelectric generator means is connected for energization of said coil means and establishment of magnetic flux flow through said electromagnet frame and armature members, said generator having a normal operating temperature, heating of said generator means to a predetermined first temperature less than said normal operating temperature afiording a power output causing said coil means to produce. sufficient flux to flow in said members to hold the movable member attracted to the fixed member against said bias, whereas heating of said generator means to a predetermined second temperature higher than said first temperature affords a power output causing said coil means to produce a flux density above that required to saturate one of said members, whereby magnetic flux is shunted from said saturated member; a magnetic control member biased to a retracted position and movable to an attracted position with respect to said saturable member, said control member being positioned to receive the flux shunted from the saturable member and to be actuated by said flux to said attracted position against said bias; and a switch actuated by said control member and having contacts in the power circuit of said ignition means for opening said circuit to render the ignition means inoperative when said control member is in said attracted position and closing said circuit to render the ignition means operative when the control member is in said retracted position, wherefore on outtage of said burner cooling of said generator means to below said second temperature effects movement of said control member to its retracted position, closing of the ignition circuit, and operation of said ignition means, the cooling period necessary for said gen erator means to drop from said second temperature to said first temperature affording a time delay for reignition of said burner and reheating of the generator means be fore said ignition means reaches said first temperature and said movable member drops out to its retracted position.

7. An electromagnetic control device, comprising: means including a first and a second magnetic member, one of said members being fixed and the other being movable, said movable member being biased toward a retracted position separated from said fixed member and being movable to an attracted position in magnetic engagement with said fixed member providing a low reluctance flux path, means tending to establish magnetic flux flow through said first and second members at a first level sufficient to hold said movable member in attracted position when moved thereto against said bias and through the same path through said members at a predetermined higher density level, said movable member having a portion having a cross-sectional area of a size permitting flux flow therethrough at said first density level and saturable by flux flow therethrough at less than said predetermined higher density level, wherefore on flux flow through said flux path at said higher density level flux is shunted from said movable member adjacent the saturable portion thereof, and a magnetic control member movable to attracted and retracted positions with respect to said movable member and positioned to be linked by said shunted flux and to be actuated thereby from said retracted to said attracted position.

8. An electromagnetic control device, comprising: means including a fixed eletctromagnet frame member and an armature member biased toward a retracted nosition separated from said frame member and movable to an attracted position in magnetic engagement with said frame member providing a low reluctance flux path, means including an energizing coil for said electromagnet frame tending to establish magnetic flux fiow through said electromagnet frame and armature members at a first level suflicient to hold said movable member in attracted position when moved thereto against said bias and through the same path through said members at a predetermined higher density level, said armature member having a portion having a cross-sectional area of a size permitting flux flow therethrough at said first density level and saturable by fiux flow therethrough at less than said predetermined higher density level, wherefore on fiux flow through said flux path at said higher density level flux is shunted from said armature member ad jacent the saturable portion thereof, and a magnetic control member movable to attracted and retracted positions with respect to said armature member and positioned to be linked by said shunted flux and to be actuated thereby from said retracted to said attracted position.

9. An electromagnetic control device, comprising: means including a first magnetic member and a second magnetic member biased toward separated relation and relatively movable to attracted relation with respect to said first member to provide therewith when in attracted relation a low reluctance flux path, means tending to establish magnetic flux flow through said flux path at a first level sufiicient to hold said magnetic members in attracted relation when moved thereto against said bias and through the same path at a predetermined higher density level, said low reluctance flux path means including a portion having a cross-sectional area of a size permitting flux flow therethrough at said first density level and saturable by flux flow therethrough at less than said predetermined higher density level, wherefore on flux flow through said flux path means at said higher density level flux is shunted from said flux path adjacent said saturable portion, a magnetic control member positioned to be linked by said shunted flux and to be actuated thereby from a first to a second controlling position, a circuit to be controlled, and a circuit controlling device having contacts in said circuit actuated from a first to a second controlling position by movement of said control member from its said first to its said second controlling position.

10. An electromagnetic control device, comprising: means including a first magnetic member and a second magnetic member biased toward separated relation and relatively movable to attracted relation with respect to said first member to provide therewith when in attracted relation a low reluctance flux path, a first control mem ber connected to said movable magnetic member for actuation from one to another controlling position by movement of said movable member to attracted and retracted relations respectively, means tending to establish magnetic flux flow through said flux path at a first level sufiicient to hold said movable member in attracted relation when moved thereto against said bias and through the same path at a predetermined higher density level, said low reluctance flux path means including a portion having a cross-sectional area of a size permitting flux flow therethrough at said first density level and saturable by flux flow therethrough at less than said predetermined higher density level, wherefore on fiux flow through said flux path means at said higher density level flux is shunted from said fiux path adjacent said saturable portion, a magnetic second control member positioned to be linked by said shunted flux and to be actuated thereby from a first to a second controlling position, a circuit to be controlled, and a circuit controlling device having contacts in said circuit actuated from a first to a second controlling position by movement of said control member from its said first to its said second controlling position.

11. An electromagnetic control device, comprising: means including a first magnetic member and a second magnetic member biased toward separated relation and relatively movable to attracted relation with respect to said first member to provide therewith when in attracted relation a low reluctance flux path, means tending to establish magnetic flux flow through said flux path at a first level sutficient to hold said magnetic members in attracted relation when moved thereto against said bias and through the same path at a predetermined higher density level, said low reluctance flux paths means including a portion having a cross-sectional area of a size permitting flux flow therethrough at said first density level and saturable by flux flow therethrough at less than said predetermined higher density level, wherefore on flux flow through said flux path means at said higher density level flux is shuntedfrom said flux path adjacent said saturable portion, a magnetic control member positioned to be linked by said shunted flux and to be actuated thereby from a first to a second controlling position, a circuit to be controlled, a circuit controlling device having contacts in said circuit actuated from a first to a second controlling position by movement of said control member from its said first to its said second controlling position, and means including connections between said circuit controlling device and one of said magnetic members for efiecting actuation of said contacts to said second controlling position by movement of said movable members to separated relation.

References Cited in the file of this patent UNITED STATES PATENTS 2,292,478 Ray Aug. 11, 1942