US1636191A - Pressure-actuated electric control device - Google Patents

Description

July 19, 1927.

Filed Nov. 9. 1925 /ldnlfllfnfrnnillnlrdflal INVENTOR. )7u @z- ATTORNEYS.

Patented July 19, 19277.

' UNITED STATES PATENTl OFFICE.

IRA E. MCCABE, 0E, CHICAGO, ILLINOIS.

PRESSURE-ACTUATED ELECTRIC CONTROL DEVICE.

' Application led November 9, 1925. Serial No. 67,796.

This invention relates to improvements in electric control ydevices and more particularly to a pressure actuated electrical control device.

In many instances electrically operated devices are employed in the production of heat and in the electric circuit of such a device it is desirable to provide a control for starting and stopping the operation of such a device which control is operated by the temperature created by the operation of the device.

It is an object of this invention to provide a device of this character, and an embodiment of this device is particularly illustrated anddescribed as adapte-d for use in an electrically operated furnace or heat producing device particularly used as a part of an electrically operated liquid fuel burner system for domestic purposes, although this invention contemplates other uses of this control. It is av further object to provide a device of this character which is particularly adaptedh in electrically operated domestic liquidy fuel burner systems tp act as a safety device for such systems.

l/Vhile a preferred form of this invention is illustrated on the accompanying sheet of drawing, yet it is to be understood that minor detail changes may`be made therein without detracting from the scope of the invention.

In the drawings:

Figure 1 is a view in frontelevation ofa preferred form of this device, with the casing cover removed and partly in section.

Figure 2 is a view in end elevation of Figure 1 with parts broken away and with parts in section.

In the embodiment f this invention illustrated, the circuit to the motor is closed or opened by the tiltin movement of the mercury switch 1, whic is shown mounted on a pivoted carrier plate 2, with two terminals adjacent each other and near one end of the tube so that when the tube is tilted in that direction the mercury within the tube will accumulate in that end and close the circuit through said terminals,` and when tilted in the opposite direction the mercury will` flow away from the terminals and break the circuit therethrough. The tilting plate carrying the mercury tube is provided with a counterweight 3 which will normally tilt the tube to the open or circuit-breaking position. The plate 2 carrying the mercury tube is also provided with a depending projection in the form of a pawl 4, adapted to engage' in the teeth of a ratchet wheel 5 carried by a sleeve 6, having a detachable connection with an enclosed fixed shaft 7, whereby the mercury tube switch may be tilted into the @closed position and held against the counterweight by engagement of the pawl with the ratchet and which when the ratchet carrying-sleeve becomes detached will allow the counter weight to cause the ratchet to be rotated by the pa'wl releasing the tilting plate 2 and tilt the switch into the open posltion.

The sleeve 6, carrying the ratchet wheel 5, is of greater inner diameter than the outer diameter of the fixed shaft 7 which it surrounds.y The space between the inner circumference of the sleeve and the outer circumference of the shaft is filled with solder vwhich will normally secure the sleeve `in The shaft 7, is-

.in a cylinder 11 of lavite or other electric insulating material with the disc at one end bearing against the heat transmitting bracket 9, and the other end bearing against a movable block 12, -held in place and movable in the lavite cylinder. Three posts 13 secure the heat transmitting bracket Q to a closure plate 14 beyond the movable block. A sheet' ofv This mica or other electric insulating material f capable of transmitting heat is interposed between the series of gra hite disks andheat transmitting bracket an between the series of graphite disks the movable block. The closure plate 14 supported onl the posts 13 aextending from the heat transmitting bracket is provided with an aperture 15 concentric with the graphite disks 10 'in which aperture is mounted a sleeve 16 having an outstanding flange 17 about its exterior end. l

The interior of the sleeve is screw-threaded and adapted to register with a' similarly screw-threaded Japerture in the movableY block 12. A similarly screw-threaded pivot 18 having a flat head or button 19 is threaded through the sleeve and into the block securing the two together whereby the movement of the block limited by the plate 14 in one direction and by the sleeve flange 17 in the vother direction. The heat transmitting bracket is carried upon and insulated from an outstanding arm 20 of a supporting plate 21 secured to the rear of the instrument casing. Upon this plate 21 below the graphite disks a pressure applying member 22 is pivotally ,mounted having a portion 23 'adapted to contact with the flat head or buta tube 28 leading therefrom to a heat coil or bulb 29 adapted to be' secured within the stack 30 leading from the furnace to the chimney. or otherwise located so that the heat generated in the furnace by the flame from the electrically operated voil burner mechanism will cause an expansible gas or liquid within the bulb 29. tube 28 and Bou'rdon tube 26 to exert and vary the pressure therein causing the Bourdon tube to expand or contract.

The free endof the Bourdon tube 26 is pivotally connected by an operating link to the pressure applying member 22, preferably with an adjustable connection thereto, such as the slot illustrated, so that upon the expansion of the Bourdon tube pressure will be applied to the series of .graphite disks, the amount of pr ssure and the time of application of the p1" sure being regulated by the distance between the head or button '19 upon the shaftand the sleeveflange 17 by the screwing or unscrewmg of the threaded portion of the shaft 18 into the movable block 12.

It is preferable to construct the operating link of two parts having a slidable fric` tional engagement with the other, such as by providing one part 31 with a reduced Aportion 32 adapted to be received and slide within a recessed portion 33 of the other member 34 having said recessed portion cut out on one side adapted to receive a spring pressed clamping member 35 to bear with adjustable tension upon the reduced portion of the other member sliding within the recess, whereby an outward movement of the free end of the Bourdon tube, as the Bourdon tube expands, will be transmitted through the operating link to cause the pressure applyingmember 22 to move about its pivot and apply pressure upon the shaft 18 and thence through the movable block 12 to compress the graphite disks 10 and when further movement of the shaft is limited by the flange 17 on the sleeve engaging the plate 11 and extension 22 stopping on lower limiting post 25,v further movement of the tree end oi the Bourdon tube will cause the reduced end portion 32 of the operatinglink' continued inward movement of the free end thereof the reduced portion of one member of the operating link will be caused to over-- come the frictional engagement with the clamp and slide within the recess of the other member, whereby expansion of the Bourdon tube at any -time will immediately apply pressure to the graphite disks. l

The pawl 4, normally engaging the ratchet wheel 5 is so constructed that a pressure against the pawl in the direction of the back of the casing -will cause it to disengage from the ratchet and thereby allow the counterweight 3 to tilt the mercury tube into the open position and break the circuit.l therethrough. A pawl releasing means is provided in this dev ice which will break the circuit as the expansion of the Bourdon tube reaches its danger limit and this-means comprises an arm 36 pivoted at one end to the free end of the Bourdon tube which passes. over the horizontal portion of thepawl 4 when engaging the ratchet wheel and is provided with an angular depending portion 37 adapted ,as the Bourdon tube approaches its danger limit, to engage and depress the pawl .4 to release it from the ratchet 5 and allow the counterweight to break the circuit. The free end of the pawlreleasing member 36 is provided with an irregular slot 38 adapted to slide over a pin 39 to support the varm 36 with the depending portion thereof out of contact with the pawl during the normal operation of the Bourdon tube, but from the shape of the slot 38 adapted to present the depending portion`37 first into line and then into engagement with the pawl 4 as the Bourdon tube approaches the danger limit.

`The instrument casing is provided with three binding posts the upper binding post 40 being connected to a lead 41 from the commercial source of current and to one terminal of the mercury tube switch. The other terminal of the mercury-tube switch is connected to the middle binding post 42 which in turn is connected by a lead 43'to one of the outermost graphite disks 10 of the series. The other outermost graphite disk of the series is connected by a lead 44 to the lowermost binding post 45 which in turn is connectedto one plple ofthe electric motor M for operating t e burner mecha# .nism and the other pole of the motor isv connected to the other lead 46 of the commercial current.

In the electrical. art it is recognized that a series of graphite disks such as shown and described will transmit electricity and generate-heat in 'proportion to t-he ,amount of pressure applied to the end of such series. of disks, the greater the pressure, the greater the conductivity or ease with which the current passes through t-he series, as increasing the pressure upon the series of disks decreases the electrical resistance therethrough and the heat generated by the resistance varies in direct proportion thereto. By a proper adjust-ment of the relation between the movable plate 12 and the screw-threaded shaft 18 an amount of pressure can be normally applied to the series of graphite disks to generate heat sufficient to melt the solder normally securing the ratchetwheel 5 in fixed relation to the fixed shaft 7 and by providing a proper number of graphite disks Asuliicient pressure may be applied thereto by normal movement of the member 22 upon expansion of the Bourdon tube 26 to allow the current to pass through the disks without generating suflicient heat to` melt the solder. The instrument is so adjusted that with the switch in closed posit-ion, as shown iugFigure 1, and the circuit through the motor closed, the current will pass through the mercury tube 1, and thence through the series of graphite disks lOwhich are so adjusted that a continuation of the passage of current will generate sufficient heat to melt the solder and release the switch to be operated by the counterweight 3 to break the circuit. The parts are also adjusted so that as soon as themotor starts the oil burner *mechanism operating, the flame therefrom or the heat arising from the fire box acting upon the bulb or coil 29 will cause an expansion of the Bourdon tube 26- thus applying pressure through the link and pressure applying member to t-he series of graphite disks reducing the generation of heatherein and the parts are further adjusted so that the normal expansion of the Bourdon tube under these conditions will cause the flange 17 upon the sleeve to engage the plate 14 when the current passes freely through the compressed graphite disks without generating suiiicient heat to melt the solder. A.

further expansion ofthe Bourdon tube will be accommodated by the frictional engagement of the two sections 31 and 34 of the connecting link without further movement of the pressure applying member. Upon the failure of the burner iiame .from any cause the contraction of the Bourdon tube Will immediately release the pressure from the graphite disks thereby immediately increasing the heat generated therein to melt the solder and release the switch toy assume the open position. If from any cause the amount of pressure within the Bourdon tube approaches its danger limit, the sliding member 37 will engage the pawl and release it from the ratchet and allow the counterweight to break the circuit.

From the above description it is seen that this device includes a double safety device both of which depend upon the operation of the oil burner mechanism. The first safety device is operated by the commercial source of current passing therethrough causing the circuit to be broken in case the burner flame fails to ignite or becomes extinguished for any reason. The second safety devicer will operate if the burner mechanism produces excessive pressure within the' Bourdon tube causing it to expand and approach this danger limit to release lthe pawl and allow the counterweight to throw the switch to break the electric circuit. i

I claim:

1. In a pressure actuated electric control, an electric switch,means normally acting to hold the switch in open position, detachable means for holding the switch in closed position, an operating member therefor in circuit `with the switch and operable by variations in current passing therethrough to release said switch holding means, an expansible and contractable member, means actuated thereby to cause variations in the current passing through the operating member of the switch holding means, and additional means operable thereby to mechanically detach said switch holding means. y

2. In a pressure actuated electric control,

an electric switch, means normally acting to hold the switch in open position, detachable means for holding the switch in closed position releasable mechanically and upon the application of heat, an electric heat generating, means in circuit lwith said switch, an expansible and contractable member,

means .actuated thereby adapted to produce variations in the heat generated by the electrio means to hold or release the detachable means, an additionalmeans actuated at Yal predetermined expansion thereof to operate said mechanical releasing means.

3. In a pressure actuated electric control, an electric switch, means normally acting to hold the switch in open position, detachable lill) means for holding the switch in closed position releasable mechanically and independently upon application of heat, pressure controlled electric heat generating means in circuit `with the switch, an expansin ble and contractable member, meansfassociated with said member and said heat generating means for transmitting pressure upon expansion and contraction of said member to said heat generating means for controlling generation of heat thereby, and independent means operable at a predetermined expansion of said member to release said switch holding means.

4. In a pressure actuated electric control, an electric switch, means` normally acting to hold the switch in open position, detachable means holding the switch in closed position releasable mechanically and independently upon the application of heat, pressure controlled electric heat generating means in circuit with the switch, an expansible and contractable member, means operable upon the expansion and contraction of said member to transmit Variations in pressure to said .electric heat generating means to vary the degree of heat generated thereby and at predetermined expansion of said expansible and'contractable means to reduce the amount of heat generated by said electric means, and at a predetern'iined greater expansion to mechanically release said switch holding means.

5. In a pressure actuated electric control, an electric switch, means normally acting' to hold the switch in open position, detachable means for holding the switch in closed position, said means adapted to release the switch by mechanical operation and additionally bythe application of heat, pressur controlled electric heat generating means in circuit with the switch adapted to release said detachable switch holding means, a pressure actuated expansible and contractable member, means for applying pressure therefrom to said pressure control electric heat generating means, a connection between said means and said expansible and contractable member normally allowing said electric means to generate sufficient degree of heat to detach said switch and upon expansion of said expansible and contractablel member to apply pressure t0 said electric heat generating means to reduce the degree of heat therebelow, and means operable upon abnormal expansion of said expansible and contractable member to operate said mechanical means to release said switch holding means.

lRA E. MCCABE.

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