US2088556A - Control device - Google Patents

Description

July 27, 1937.

Filed Dec. 27, 19:55

4QNTROL. DEVICE 2 Sheets-Sheet'. 1

FIG. 1

July 27, 1937. E. J. DILLMAN CONTROL DEVICE Filed Dec. 21,' 193s 2 Sheets-Sheet 2 the thrust member Surrounding the member 24 there is a spring seat or abutment member 23 having a circumferential upstanding flange to 1 annular shoulder Ion the member 24, being held thereagainst by swaging a portion of the member 24 over on the head 2l, as at 30. The thrust member 24 is preferably in two parts which are screw-threaded together with the upper part 'or portion 3| terminating adjacent the top wall 2. The spring seat member 29 receives one end of a range determining spring 32, preferably of the helical coil type, which surrounds the upper thrust member portion 3| and which is provided with a cap member 33 which seats on its upper end. The member 33 is preferably of substan tially inverted cup-shaped form, having an aperture through its end wall for passage of the thrust member 24 and having oppositely directed -lateral flange portions 34 projecting from the front and rear ofthe member 33 at its lower edge or rim. The portions 34 have upward facing..

aligned V-grooves or bearing recesses 35 to receive a spring adjustment means, to be described. Through the end wall 5 substantially in. the horizontal plane of the flange portions 34, there is an aperture 36 provided at its inner end with an insert 31, preferably of metal, through which an adjustment means 33 is adjustably screwthreaded. The means 33 preferably comprises a rotatable shaft having circumferential gear teeth 39 external of the wall 5 and having a longitudinal bore 49 opening through the end of the adjustment screw or means 38 into the interior of the casing I. `A bearing plug 4I, preferably of hard metal such as chrome steel, is seated in the inner end of the bore 40 and is provided with an end recess to center one end of a thrust pin 42. Fulcrumed byor plvxoted on a shaft 43 secured at its opposite ends infront and rear casing bosses 44, 45, there is n adjustment levei` 46, preferably substantially U-shaped, with its base or cross member 41 provided with a bearing recess to receive the other end of the thrust pin 42 which provides a universal connection between the shaft 33 and the lever 45. The arms of the lever 46 extend toward the thrust member 24 and preferably terminate above the flange portions 34 such that the lever 46 straddles the cap member 33. The free ends of the arms of the lever 46 are provided with downward directed bearing points 41 which seat in the V-shaped grooves 35. The adjusting screw 38 is preferably provided with a knob or grip member 46 external of the casing I. 'I'he gear teeth 39 are in mesh with the teeth of a dial plate 49 carried by and seating against the outside face of the end wall 5. The plate 49 which is circular is rotatably mounted on a stud 50 molded into the wall 5 and is secured on the LAstud 59 by a headed screw 5I threaded into the stud. The plate 49 is provided along its circumference with suitable indicia to indicate the range of operation of the control device, the indicia cooperating With a pointer or indicating linger 52 clamped to the outside face of. the wall 5 by a screw 53 and overlying the plate 49. 'I'he upper end of the cap member 33 may be provided with a cover 54 of electric insulating material.

Secured to the inside face of the top wall 2 by screws 55 there is a supporting bracket member 53 which overlies the upper end of the thrust member 24 and which is provided with depending,

para1leispaced, side members 51 which lie parallel to and are spaced from the front and rear walls of the casing I. Positioned between the members 51 there is an operating lever 59 which is journaled adjacent one end for pivoted movement in a substantially vertical plane on a bearing shaft 59 secured in and extending between the side members 51. The lever 53 preferably has depending side flanges 6U jointed by longitudinally spaced cross members 6I, 62. Intermediate the members 6I, 62 the flanges 60 are provided with upwardly open recess portions 63, for a purpose to be described. Positioned between the horizontal portion of the bracket 56 and the lever cross member 6I there is a light spring 54 which is held under compression therebetween and which normally tends to rotate the lever 5l in a clockwise direction about its shaft or pivot pin 59 when facing Figs. 3 and 4. The spring 64 is positioned substantially at the end of the lever 53 adjacent wall 5 .and seats at its lower end on an extension projecting horizontally from the lever 53. The other end portion of the lever 53 which extends toward the end wall 4 is provided 'with a. transverse `portion 66 serving as an armature. Secured to the underface of the cross member 62 by a rivet or the like 61, there is a resilient contact carrying blade E8 which extends substantially to the free end of the lever adjacent wall 4 4and terminates beneath the armature 65. The armature 66 is provided with a vertical aperture B9 to receive the reduced neck portion of a contact member 10 which is rigidly secured to the free end of the blade 63. The contact member 10 is cooperable with an adjustable contact member 1I which projects downward into the casing through the top wall 2 and which is adjustably screw-threaded in a sleeve member 12 secured in an aperture 13 in the top wall 2. The sleeve member 12, which is of metal, is secured to onevend of a current conducting member 14 such as a copper strip which'is sealed within and extends longitudinally through the walls of the casing I. The metal strip 14 preferably leads longitudinally through the top wall 2 to the rear wall 6 `and thence longitudinally downward through the same to a point adjacent the bottom wall 3 where it is connected to a binding post or terminal 15 positioned inside of or wit-hin the casing I. The sealing of the strip or member 14 in the casing wall serves to conserve space, to prevent interference with the mechanism which might occur with an external lead wire, and to efficiently insulate the conductor from the parts of the mechanism.-` The armature 66 cooperates with a magnet 16, preferably of the U-shaped permanent type, which is carried by the end wall 4 adjacent and substantially parallel to the top wall 2 and which extends from wall 4 toward the end wall 5 with its poles or arms 11 positioned on opposite sides of the contact members 1I), 1I and vertically between the top wall 2 and the lever 53. The magnet 13 is rigidly secured by a nut and bolt 18 or the like to the horizontal leaf 'of a hinge member 19 which has its other or vertical leaf -rigidly securedto the inside face of the end wall 4 by screws or the like 80. The

y hinge member 19 is preferably of resilient sheet Justment screw 8| acts through a push rod 83 or electric insulating material having its opposite ends 'in engagement with the screw 8| and the head of the bolt 18, the resilience of the hinge 19 which acts through the magnet 16 serving to hold the rod 83 in position and the magnet in adjusted position. The screw 8| is operable by means oi a knob or'inger grip 84 having a depending, annular flange 85 -which travels in an annular groove or recess 86 formed in the top face of the-wall 2. 'I'he groove 86 is provided with an abutment 81 having oppositely directed races cooperable with the oppositely directed faces on a depending stop finger 88 on the flange 85 to limit the rotation of the screw 8|. The knob 84 is preferably provided with dial markings 84a cooperable with a pointer 84b preferably formed integral with the top wall 2 to indicate the position of the magnet 16./

Positioned between the lever iianges 63 and intermediate the lever cross members 6|, 62, there isa lever member 89, preferably of electric insulating material, which lies substantially parallel to and -in the plane of the lever 58. 'I'he lever member 89 is journaled for substantially vertical pivotal movement, parallel to the plane of movement of lever 58, on bearing pins or trunnions 90 which are secured in the bracket side members 51 and which project through the ilange recesses 63 and above the ilanges 60 into bearing sockets 9| formed in the side faces of the lever member 99. One end 92 of the lever member 89 extends into overlying, engageable relation with an abutment member 93, preferably a pin or rod rigid with the lever 58 and extending transversely between and secured at its opposite ends in the flanges 60. The abutment member 93 is preferably positioned between and substantially in the plane of the fulcrums for the lever 58 and the lever member 89. The lever member 89 is provided with a vertical aperture 94 therethrough substantially centrally thereof which is preferably rectangular and re'- ceives the upper end portion of the thrust member 24. The thrust member is pivotally secured in the aperture 95 by a pin 95 which extends horizontally through ythe lever member 89 and the upper end portion 3| of the thrust member, the aperture 94 being of sufficient cross-sectional area to permit rocking of the lever member on the end of the thrust member. The lever 58 is electrically connected by a lead wire 96 to a metal insert 91 embedded and sealed within the rear Wall 6, the insert being connected to a binding post 89 adjacent the binding post 15. The end wall 4 is preferably provided with an aperture 99 for the passage of lead wires into the casing and which are to be connected to the binding posts 15 and 98.

The 'top wall 2 is provided with a mounting boss |00 which overlies the bracket 56. Rigidly secured upon the boss |00 nated generally I0 provided with a thrust member |02 which engages the upper end of the thrust member 2t.4 The means |0| comprises asubstantially inverted, cup-shaped container |03 having a lateral flange |04 which seats upon the boss |00 and is rigidly secured thereto by screws or the like |05. Within the container |03 there is a movable wall, preferably in the form of an expansiblecollapsible, metal bellows |06 having a head |01 secured and hermetically sealed to one end of the bellows. The other end ofthe bellows |06 is secured and hermetically sealed to an annular member |08 provided with a circumferential flange which seats against a downward facing, annular shoulder formed inthe inside face of the side wall vthrust member |02.

there is a power means desig-I of the container |03. The member |00 @preferably hermetically sealed to the container |03 by solder or the like, as at |09. The bellows head |01 is preferably substantially cup-shaped so that it extends into the bellows and is provided with a central aperture in which the thrust member |02 is rigidly secured and sealed. The thrust member |02 is preferably provided with a conical end portion which seats in a substantially conical recess formed in the top end of the thrust member portion 3| to prevent lateral displacement of the engaged ends of the thrust members relative to each other and to permit angular movement of the thrust members relative lever member 89 oscillates about its fulcrum. 'I'he end wall of the container |03 is provided with a fitting I0 having a longitudinally extending bore therethrough which opens into the expansible chamber ||2 formed within the container by the expansible wall. The fitting ||0 is preferably provided with a recess ||3 surrounding the inner end of the borel A helical coil spring 4 is seated at one end in the recess ||3 and at its other endengages the head |01, being held under compression therebetween and surrounding the The force exerted by spring 4 is preferably substantially equal to the force of spring 25h, each of the springs preferably bein the bore 'I'he stop |5 is preferably formed by the head of a end of the thrust member |02. 'I'he top wall 2 and the bracket 56 are provided with aligned apertures ||1 for the passage of the thrust member |02 into the interior of the casing l The operation of my control device will be described as employed in controllingthe operation of the burner of a heating apparatus wherein it is desired to maintain a predetermined difference of pressures between a certain pressure in the supply line and a relatively lower pressure in the return line to the heating apparatus. However, the control device' is not limited to this application which is merely illustrative of one of its nuses as it is obvious that it may be employed in other apparatus wherein it is desired to control an operating means in response to a differential between two pressures or two temperatures corresponding to the pressures. The terminal posts 15and 98 will be connected to the control means for the burner, of the heating apparatus by suitable lead wires which enter the casing through the opening 99. The fittings 25 and ||0 will be *connected by suitable pressure transmitting conduits to the supply and return lines respectively of the heating apparatus. Assuming iirst for illustration of operation that the absolute fiuid'pressure in chamber ||2 is constant, so that the force exerted by the wall |01 and through the thrust member |02 against movement of thrust member 24 by power means |2 is constant, then the force required to be exerted by the power means I2 to break circuit at the contacts 10, 1| will be equal to the resisting force of spring 32 plus the resisting force of power means |0| acting through thrust member 02 and increased by the magnetic attraction of magnet 16 for armature 66 transmitted to thrust member 24 through lever 68 and lever member 89. When the pressure of the uid in the supply line and transmitted `to the chamber 2-1 exerts through head 2| a force on to each other as the screw or the like secured in the members 1I and 18, blade 88. lever 58, lead wire of the opposing forces exerted by spring 82 and power means I8I the forces exerted by 4springs 4|I4 and 25" being equal and opposite, then the the abutment pin 88. Further movement of lever member 88 is now opposed by the attractive force o! magnet 18 for armature 88 acting through 1ever Il, so that the force exerted by power means I2 must increase in order to break circuit.` The initial movement of lever 58 by the increased force o! power means I2 which will overcome the magnetic force will not however break contact due to the spring blade 88 which holds the contacto 18, 1| in engagement until the lever 58 is in motion, so that engagement between contacts 18, 1I will be broken quickly as the lost motion is taken up between blade 88 and the moving lever 58. Breaking of contact at 18, 1I will actuate the burner control means to stop the burner and the further increase of pressure in the supply line and the chamber 21. As the pressure in the chamber 21` decreases due to the stopping of the burner, the algebraic sum o! the forces of the power means |82 and spring 32 acting on the thrust member 24 will movef the same downward and rotate the lever member 88 counter-clockwise o! Fig. 4 on its pivot pins 88. As the lever end 82,moves upward, the light coil spring 84, which ,only exerts suillcient force to lift the freely moving lever 58,v will rock the lever 58 clockwise of Fig. 4 about its fulcrum 58, maintaining the abutment member 88 in engagement with lever end 82, until the armature 88 comes into the active field of the magnet 18 when the magnet poles 11 will attract the armature 88 and acting with the spring 32 will close the contacts 18, 1I with a quick movement. Further increase in the force tendingto turn lever member 88 counter-clockwise of Fig. 4 will merely result in the lever end 82 moving away from and out .oi contact with the abutment member 88 so that the continued downward movement of the thrust member 24 will be unopposed by the lever 58. This provision for lost motion between the thrust member 24'and the lever 58 permits of the utilization o! light weight moving parts which increases the emciency of operation of the instrument.- The annular downward facing shoulder on contact 18 cooperates with armature 86 to prevent engagement of the armature with the magnet poles and to maintain a slight air gap thereby enhancing the operation of the instrument. Closing ofcontacts 18, 1I establishes the following circuit through the instrument: from the terminal 15 through the lad member 14, contact 88 and connecting link-81 to the terminal 88, which places the burner in operation to again increase the pressure in the supply line and the chamber 21. From the foregoing, it will be apparent that the range of operation of the instrument, that is, the pressure at which contact will be made, the force of power means |8I remaining constant, is determined by the range adjusting spring 82. Rotation of' the knob 48 will act through screw-threaded shaft 88, pin 42, lever 48 and cap member 88 to regulate thetension ofsprlng 82 against the movable wall 2|. As the torce exerted by spring 82 isincreased, the greater or higher the pressure will be in chamber 21 gagement of contacts 18 vand 1I.

`thrust member 24 equal to, the algebraic sum at which the contacts 18, 1I will be engaged. The differential operation of the instrument, that is, the pressure at which contact will be broken relative to the pressure at which contact is made, still assuming the force of power means I8I to be constant, is determined by the position, when the contacts are in engagement, of the magnet poles 11 relative to the armature 88. As shown, the i instrument is set for its Widest differential oi" operation, the magnet poles 11 being separated from the armature 88 by only a minute air gap. To decrease the differential between` the pressures at which contact will be made and broken, vthe knobv 84 is rotated to permit retraction of the member 88 so that the resilient force of the hinge l member 18 can move the magnet upward thereby increasing the air gap between poles 11 and armature 88. The greater the air gap, the narrower'or closer will be the differential of operation thereby requiring a less increase in the force of power means I2 after engagement between lever member 88 andi ver 58 in order to overcome the attractive force of he magnet and break circuit between the contacts.

With the parts in the position shown, if the pressure in the return line and the chamber II2 should now increase, the thrust member |82 would force the thrust member 24 downward causing the lever end 82 to lift away'from the lever abutment 83 resulting in lost motion, the contacts 18, 1I remaining )in engagement. If, however, the pressure in chamber II2 decreased relative to the pressure in chamber 21 so as to exert a relatively less force onthrust member 24 through the thrust member |82, then when the the relatively increased force of power means I 8| l acting through thrust member |02 plus the force of spring 82 became equal to and overbalanced the force of power means I2 on thrust member 24, the thrust member 24 would move downward relieving the resistance to movement of lever 58 and permitting engagement of contacts 18, 1I under theiorce of spring 84. i

Itiwill be apparent from the foregoing description that I have provided an instrument in which the range of operation is determined by the force of spring 82, so that when the algebraic sum oi. the forces exerted by the opposed power means I2 and I8I becomes lessl than the force exerted by spring 82, the circuit will be made by en The dierential operation of the instrument as determined by the setting 'of magnet 18 will remain constant relative to the differential force .determined by spring 82 and exerted by power means I2 and I`8 I, sothat breaking of circuit by disengagement of contacts 18 and 1I is at a constant increase o!` pressure for any given setting of the magnet 18. It will also be'apparent that the operation oi?v the instrument can be readily reversed by merely changing the position of-the fulcrum pins 88 to thefopposite side oi. the thrust member, i. e. the left side facing Fig. 4, so that upward movement of thrust member 24 will `cause counter-clockwise rotation of lever member 89, facing Fig. 4. With the lever fulcrum so repositioned, the attractive force of magnet llwill oppose the spring 32 so that the algebraic sum of the forces exerted by power means I2 and IUI must be less in order t0 break circuit than the algebraic sum of the `forces of power means I2 .and IOI .at which circuit will be made.

` Although I have shown the control device as provided with fittings 25 and H0 for connection to sources of iiuid pressure or to pressure conveying conduits, it will be apparent that the fittings may without invention be provided with bulb elements charged with a suitable expansible liquidl such that the control device will operate by a diierential between the pressures in the chambers 21 and I I2 created by the temperatures to which the bulb elements are subjected.

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

1. A device of the character described, comprising a supporting casing, a lever fulcrumed at one end portion thereof in said casing and having side ilanges with an aperture between said iianges, control means operable by said lever, a second 1ever fulcrumed in said casing and positioned in said aperture between said flanges, an abutment member carried by said :first-named lever and positioned between said iianges intermediate the fulcrums for said levers, said abutment member be-l ing positioned beneath one end portion of said second-named lever for engagement thereby, power means carried by said casing, and a thrust member operatively connecting said power means to said second-named lever.

2. A device of the character described, comprising a supporting casing, a lever fulcrumed at one end portion thereof in said casing and having sidev flanges with an aperture between said anges, control means operable by said lever, a second lever fulcrumed in said casing and positioned in said aperture between-said flanges, an abutment member carried by said first-named lever intermediate the fulcrums -for said levers and said power means to said second-named lever,

and a spring acting on said first-named lever and normally urging said abutment member toward said one end portion of said second-named lever.

3. A device of the character described, comprising a hollow supporting casing, a bracket member secured to the inside top wall 0i"k said casing and having depending side members, a lever positioned between said side members, said side members having bearing means pivotally supporting said lever, a contact member secured in and projecting inward from the top wall of said casing, a contact member resiliently carried by said lever and ccoperable with said first-named contact member, a second lever pivotally supported by said side members and having its fulcrum spaced from the fulcrum of said first-named ley ver; an abutment member on said first-named 1eland the topwall of a contact member secured in and projecting inward from the top wall oi' said casing, a contact member resiliently carried by said lever and ccoperable with said rst-named contact member, a second lever pivotally supported in' said casing and carried by said side members, an abutment member on said ilrst-named lever engageable by said second-named lever whereby said second-named lever is` operable to transmit motion to said rst-named lever, power means, a thrust member operatively connecting said power means and said second-named lever, a range determining spring resisting operation of said thrust member by said power means, said firstnamed lever having an armature, a magnet having its poles positioned between said armature said casing and on opposite sides of said contact, members, a resilient hinge vmember rigidly secured to the inside wall of said casing, means clamping said magnet to said hinge member, and adjustment means carried by said casing and ccoperable `with said magnet to regulate the position of said magnet relative to said armature whereby to adjustthe differential operation of the device.

5. A device of the character described, comprising a supporting member, a lever pivotally carried by said supporting member, control means operable by said lever, an abutment member on said lever, a second lever pivotally carried by said supporting member and engageable with said abutment member, said abutment member being positioned between the fulcrums for said levers, said second-named lever havingv an aperture therethrough, power means carried by said supporting member, a thrust member having one end portion engaging said power means and having "its other end portion extending into said aperture, and means in said aperture pivotally lever to said thrust said lever, a second lever pivotally carried by said l supporting member and engageable 4with said abutment member, said abutment member being positioned between the fulcrums for said levers, said second-named lever having an aperture therethrough, power means carried by said supporting member, a thrust member having one end portion engaging said power means and having its other end portion extending` into said aperture, means in said aperture pivotally connecting said second-named lever to said thrust member, a second power means carried by said supporting member, and a thrust member operable by said second-named power means and engaging said other end portion of said inst-named thrust member whereby to oppose operation of said first-named ,thrust member by said rst-named power means.

7. An electric switch comprising cooperable contact members, a lever for actuating one of said members, power means for moving said lever, a spring resisting said power means, a lever for l members having bearing means pivotaily suppo ing said lever,

regulating the resisting force of said spring, a v

8. An electric switch comprising cooperable contact members, a lever for actuating one of said members, power means, a thrust rod for transmitting movement from said power means to said lever, a helical coil spring surrounding said rod and resisting operation oi said rod by said power means, an `aperturedY cap member receiving said springand surrounding said spring and said rod and acting to hold said spring under compression, said cap member having cppositely positioned bearing means intermediate the ends of said spring, a spring regulating lever straddling said spring and engaging said bearing means, and means to actuate said regulating lever.

9. An electric switch comprising cooperable contact members, a lever for actuating one of said contact members, a thrust rod engaging said lever, opposed power means responsive to a fluid characteristic and engaging the ends of said rod, a spring interposed between said power means and acting with one of said power meansto oppose' operation of the other of said power means, a

-regulating lever having a fulcrum support and cooperable with said spring, and an adjustment screw acting through said regulating lever to hold said spring under compression.

10. A device of the character described,.com prising a control means, a lever for actuating said controlmeans, power means responsive to a iiuid characteristic for'moving said lever, said lever having an armature,V a magnet cooperable with said armature, resilient mounting means for said magnet acting to move said magnet relative to said armature, and anadjustable abutment member opposing movement of said magnet by said mounting means and acting to hold said mag'- net against movement by said mounting means.

11. A device of the character described, comprising a supporting casing, a lever fulcrumed in said casing and having an amature, control means operable by said lever, said lever Ahaving an opening intermediate its fulcrum and said armature, a second lever having a iulcrum and positioned in said opening and engageable with said first-named lever between the iulcrums of said levers so that pivotal movement of said second-named lever in one direction pivots said ilrst-named lever in the opposite direction, power means, a thrust member operable byl said power means and engaging said second-named lever, and a permanent magnet having a pole side face in substantially parallel and close proximity to said amature. Y Y

12. A device o! the character described, comprising a supporting casing, a lever fulcrumed in said casing and having an armature, control meansA operable by said lever, said lever having an opening intermediate its iulcrum and said armature, a second lever having a fulcrum and positioned in lsaid opening and engageable with said first-named lever between the fulcrums of said levers so that pivotal movement oi' said second-named lever in one direction pivots said iirstnamed lever in the opposite direction, power means, a thrust member operable by said power means and extending into said opening, means pivotally securing saidthrust member to said second-named lever, and a magnet cooperable with said armature.

13. A device ofthe character described, comprising a supporting casing having a top wall, a lever fulcrumed in .said casing and lying substantially parallel to and adjacent said wall, said lever having an armature adjacent one end, a

magnet in said casing and positioned substantially parallel to and between said wall and said armatura-control means operable by said lever,-

means pivotally` supporting said magnet, and ad- :lustable means to move said magnet about its pivotal support relative to said armature.

14. A device of the character described, comprising a supporting casing having a wall with an aperture therethrough, a lever iulcrumed' in said casing and lying substantially parallel to said wall, said lever having an armature adjacent substantially parallel to and between said wall and said armature, control means operable by said lever, means carried by and projecting from a wall of said casing and pivotally supporting said magnet, means cooperable with said firstnamed wall for pivotally moving said magnet relative to said armature, power means responsive to a fluid characteristic and mounted on said iirstnamed wall external of said casing, and a thrust member extending through said aperture and operable to transmit movement from said power means to said lever.

15. A device of the character described, comprising a supporting casing having a top wall, a lever fulcrumed in said casing substantially parailel to and adjacent said top wall, said lever having a contact member and an armature, a contact member carried by and projecting from said wall and cooperable with said mst-named contact member, amagnet cooperable with said armature and positioned between said top wail and said armature, power means responsive to a iluid characteristic and supported externally by said casing, a thrust rod transverse to said lever and helical coil spring surrounding said rod and hav-` ing one end abutting said rod, an abutment member engaging the other end of said spring, a regulating lever engaging said abutment member and positioned substantially parallel to said firstnamed lever, an adjustment screw transverse -to said rod and adiustably screw-threaded through a wall of said casing, and a thrust pin interposed between said screw and said regulating lever and serving as a universal connecting means therebetween. i

16. A device oi' the character described comprising a supporting member, a pair of levers pivotally carried by said supporting member, one or saidle'vers having an abutment member for engaging the other of said levers, said abutment member being disposed between the fulcrums of said levers whereby pivotal movement of one of said levers in one direction pivots the other of said levers in the opposite direction, a control means operable bysaid levers, a power means carried by said supportingmember, and a thrust member operable by said power means for transmitting movement to said levers to actuate said control device.

17. In a control device, a supporting member. a pivotal switch arm carried by said supporting member and having an abutment member, a pivotal lever carried by said supporting member and arranged to engagesaid abutment member when pivoted in Vone direction to move said switch arm to open circuit position, said abutment member being located between the pivot points Vof said switchfarm and said lever so that said switch arm will be pivoted by said lever in an opposite direction thereto, a power means, a thrust rod operable by said power means and having pivotal conone end, a magnet in said casing and positioned .arm toward nection with said pivotal lever, a second power means operable to move said thrust rod and oppose .said rst-named power means, said pivotal lever being pivoted upon movement of said thrust rod by said second-named power means without transmitting such movement to said switch arm, and spring means operable to move said switch closed circuit position upon a predetermined movement ofsaid thrust member by said second-named power means.

18. A device of the character described, comprising a supporting structure, a lever pivotally supported by said structure and having an armature,V control means operable by said lever, a

leaf spring secured at one end to said structure. a magnet carried by said spring and cooperable with said armature, and means to flex said spring to adjust the position of said magnet relative tosaid armature.

19. A device of the character described, comprising a casing having a top wall and a bottom wall, a power means carried by said bottom wall, a thrust member operable by said power means and extending toward said top wall, a substantially straight lever pivotlly supported adjacent one end wall of said casing and extending transverse to said thrust -member toward the opposite end wall of said casing, means operatively confree end portion of said lever dening an armature, a magnet extending from adjacent said opposite end wall toward said lever and havingone end positioned between said armature and said top wall, means under tension supporting said magnet and urging said magnet in one direction relative to said armature, and means cooperable with said tensionedsupporting means for adjusting and opposing movement of said magnet rela- 'tive to said a1-mature.

20. A control device comprising a supporting means, a lever pivotally supported by said supporting means, said lever having an aperture therethrough, control means operable V`by said lever, a second lever, said second-named lever being positioned'in the aperture vof said lrst-A named lever and being arranged to pivot in one direction to pivot said first-named lever in the opposite direction, said second-named lever being arranged to pivot in another direction without transmission of movement to said rst-named lever, and means for pivoting said second-named lever.

EARN'EST J. DILLMAN.

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