US3079480A - Thermostatic switch - Google Patents

Description

Feb. 26, 1963 R. S. LOVELAND THERMOSTATIC SWITCH Filed Dec. 12, 1960 INVENTOR.

ROGER S. LOVELAN D A 7' TORNE Y ilnited h s tates Patent 3,tl79,4fitl THERMUSTATEC SWHTQH Roger S. Loveland, Torrance, Calih, assignor to Minnespoils-Honeywell Regulator Qompany, Minneapolis, Minn a corporation or Delaware Filed Dee. l2, 196i Ser. No. 75,3il7 Qlalxns. (Cl. 2tl%--l37) This invention relates to a control device for use in a fuel-burning heating system. More particularly, the invention relates to a flame responsive switch which is adapted to control the energization of an igniter for a pilot burner and a safety valve for controlling the flow of fuel to the pilot burner and to a main burner associated therewith.

it is one of the objects of the invention to provide a control device of this kind that is sutliciently small that it may be substituted for a conventional thermocouple unit generally used in heating systems, at the present time.

Another object of the invention is to provide a flame responsive switch of very small size wherein the switching mechanism is completely sealed from the surrounding atmosphere.

Another object of the invention is to provide a small flame sensing unit which is formed of two subassemblies that may be separately assembled and then secured together to form a single unit.

A still further object of the invention is to provide a flame responsive control device that consists of a minimum number of operating parts, but which will be of rugged construction and reliable in operation.

Other objects of the invention will become apparent upon reading the following detailed description of the invention in conjunction with the accompanying drawing wherein:

FIGURE 1 is a vertical sectional view of the invention; and

FIGURE 2 is a cross sectional view of the control device taken along line 22 of FIGURE 1.

The control device is made of two subassemblies, one of which comprises a sleeve 11 having threads 11a at its upper end and terminating at its upper end in an enlarged inner diameter portion 11b and terminating at its lower end in two stepped enlarged diameter portions 110 and 11d.

Threaded into the upper end of the sleeve 11 is a second sleeve 12 having a lower threaded portion 12a and an inwardly flanged portion 1212 at its upper end forming an opening 12c.

Extending coaxially through the tubes 11 and 12 is a metallic rod 13 having a coefiicient of expansion substantially smaller than the coefficient of expansion of the sleeve 12. The upper end of the rod 13 is secured in the opening 120 and to the surrounding flange 12b by means of metal 14 welded or brazed to the rod and to the flange. The lower end of the rod 13 has a discshaped head lea thereon which is located within the enlarged diameter portion lid of the sleeve 11.

A bracket member 15 is of sufiicient width to rest on a step lie and is adapted to be held in this position by means of a staked-over portion llllg of a step 11]". The bracket has a downwardly extending pivot arm 15a providing two shoulders 15b with a projection 15c therebetween. The bracket also has a guide opening 15d through which the rod 13 extends. The bracket also has a downwardly extending positioning arm 15c that nearly reaches the end of the enlarged diameter portion 11d.

Pivotally mounted on the pivot arm 15a is an L-shaped lever 16 having a long arm Me, which is of channel shape in cross section, and a short arm 16:), which is ice substantially fiat except for a downwardly struck pair of pivot points 16c positioned on opposite sides of the rod 13. The arm 16?; has a hole 16d therethrough through which rod 13 extends. The rod 13 is of such length that the upper surface of the head 13a engages the pivot 16c when thearm lab is pivoted on the bracket pivot 15a, with the arm 16:: extending generally parallel to the longitudinal axis of the rod 13.

The arm 16!) also has a rectangular opening 166 which is connected to the opening 16d by a slot 16 The portion 15c of the pivot arm 15a extends into the rectangular opening lee so that an edge of the shoulders 15b bears against the upper surface of the arm 16b.

The lower end of the arm 16a has a hole 16g therethrough. Positioned in the hole 16g is a headed ceramic pin 17 that is held in the hole by a flexible arm 16h struck laterally from the arm 16a. The head of the pin 17 is rounded at 17a to provide a contact arm engaging portion to be presently described.

A second subassembly 18 comprising a cylinder 19 having an enlarged diameter portion 19a at its upper end and a reduced diameter portion 1% atits lower end. The 19a portion of the cylinder 19 has an inside diameter slightly larger than the outside diameter of the portion 11d of the tube 10.

Positioned in the cylinder 19, against the reduced di ameter portion 19b, is a ceramic plug 2% through which extends a fixed contact bar 21 having an arc resisting contact plate 21a thereon. The outer end of the contact bar 21 is connected to a lead wire 22; which extends outwardly from the lower end or" the reduced diamete portion 1%.

A second contact bar 23 extends through the ceramic block in opposed and spaced relationship with respect to the contact bar 21 and is connected at its outer end to a lead wire 24 which, likewise, extends outwardly from the lower end of the reduced diameter portion 19b. A lead wire 24 is connected to the outer end of bar 23.

A movable contact supporting bar 25 also extends through the ceramic block 25 and is connected at its outer end to a lead wire 26 which, likewise, extends beyond the lower end of the reduced diameter portion 1%. Contact bar 25 has a transversely extending arm 25a struck from the intermediate portion thereof and has a laterally offset upper end portion 2512 which is located substantially centrally of the cylinder 19 and in spaced relationship with the upper ends of the fixed contact arms 21 and 23. The end of the transversely extending arm 25a lies substantially in line with the bar 23 and the portion 25b of bar 25. f

Secured to the portion 251), by means of a hollow rivet 27 extending through an opening in the portion 25b, is a flexible contact arm 28. The contact arm 28 carries a contact button 29 at its lower end, which is positioned between the fixed contacts 21 and 23 for selective engagement therewith. The contact arm 28 also has a longitudinal slot 28a therein. A generally U-shaped spring member 30 is positioned in the slot. One leg of the spring 30' bears against the lower end of the slot 28a while the other side of the spring 38 has an upwardly extending arm 36a which engages in a notch in the arm 25a. The notch 25b is located slightly to the right of the contact arm 28 so that the spring 30 normally biases the contact arm and the contact button 29 toward and against contact plate 21a on thefixed contact 21.

The contact button 29 is adapted to be moved into engagement with the fixed contact 23 by movement of the abutment member 17 on the lever 16 counterclockwise or to the right to engage the contact arm 23 between the rivet 27 and the arm 25a. Movement of the contact blade to the right of the notch 25b will cause the spring a) 30 to snap the button 29 from engagement with the plate 21a and into engagement with the fixed contact 23. Return movement of the lever 16 under the inherent bias of the contact blade 28 will permit the spring 30 to snap thecontact button back into engagement with plate 21a.

To aid in the assembly of the two subassemblies 1t) and 18 and to help hold the upper end of bar 25 in its properly assembled relationship, is a block 31 of electricallyinsulating material, such as ceramic material, that is securedto portion 2512 by means of the same tubular rivet 27 that secures the upper end of flexible contact blade 28 to the bar 25. The block has a recess 31a to permit the head. of the rivet 27 to be spaced from the wall of the cylinder 19 and has a longitudinally extending groove 31b which receives the lower end of the position ing arm He in the subassembly It is thus seen that inserting the positioning arm in the slot 31b when assembling the two subassemblies, it is impossible to improperly position the abutment member 17 with respect to the flexible contact blade or arm- 28. His also to be noted thatthe block 31-has-a pair of spaced ribs 310 (one of which is shown in the drawing) which straddle the sides of the portions 25b and the sides of the contact blade 28 andrthe sides of. the washer between the contact blade 28 andrthe lefthand head portionof the-rivet 27, sotha-t all -of theassociated parts are held in a fixed assembled relationship, with nodanger of them-being moved out of this relationship, byv operation of the control device.

The control piont at which the contact button 29 is moved zfrom one fixed contact to anotheris calibrated by screw threading the sleeve 12into and outof the sleeve ILuntil the contactbutton 17 actuates the switch at a predetermined: temperature surrounding the. sleeve 12.

Whenthe device is thus calibrated, sealing cement 32 maybe inserted :around the threads of the sleeve 12; and within the enlarged diameter portion 11b of the sleeve 11, to. lock the members 11. and 12m this calibrated position..-

While. the two subassemblies-are indicated as: being securedtogether in their assembled relationship. by means of. an annular weld between the two, around the upper end; of the .enlarged diameter portion19a, it is obvious that: the portion 19a could be-shaped in the same manner as the upper end of the sleeve 11 for the admission of sealing cement, such as that shown at 32. between the memb erslZ-and 11b.

'Iheflame sensingunit is; shown greatly magnified in the drawing, the actual physical size thereof being; approximatelythreeinches-in length from the upper end of rod 13 to thelower end of the cylinder portion 19b. The unit is adapted to be substituted for a thermocouple of aconventional pilotburner thermoelectric generator (not shown) by removing the thermocouple from the generators supporting bracket and inserting the unit of this invention in its place. The means'for holding the-flame sensing unit'in thebracket of the generator consists ofa tubularnut 34 swivelly mounted oathe-reduced diameter portion 19b of; the cylinder 19. A b.evelled shoulder portion 340 is adapted to-b ear against; a similar bevelled shoulder l9gcbetween the portions 19 and19b of thesubassembly 18 A threaded sleeve portion 34b is adapted to,- screw'thread into a threaded socket of the thermoelectric generator bracket to tightly clamp the flame sensing unit in the bracket.

The lead, wires 22, 24 and 26 are securely held'in the cylinder portion 1% by cement 35 extending all around these lead wires and by having a portion of the cylinder 19* crimped into the lead wires as at 19d.

Operation Assumingthat the control device of this invention is installed in a heating system with the device substituted for the conventional thermocouple, the elements of the control device are, shown in the position they would assume withno pilot burnerflame playing onthe tube12.

Under these conditions the inherent bias of the leaf spring 28 is forcing the contact moving lever 16 clockwise or to the left as viewed in the drawing so that the contact button 29 is bearing against the fixed contact 21. Since the lead line 22 is connected to an igniter for the pilot burner, the turning on of the electrical supply to the heating system would cause the igniter to become energized and, if gas is turned on at this time, the pilot burner will become ignited. After a few seconds of the flame playing on the tube 12, the tube 12 will be lengthened to cause the head 13a ofthe rod 13 to move upwardly and rock the lever 16 about the pivot arm 15a. The movement of the arm 16 counterclockwise will cause the switch blade 28 to be moved to the right as viewed in the drawing to snap the button 29 from fixed contact 21 into engagement with fixed contact 23. Since lead line 24, connected to 23, connected to a safety valve controlling the flow of gas to the pilot burner as well as the main burner, the safety valve will be energized so as to. hold. the valve open when the manually operable means for operating the gas valve has been released, in the. conventional manner. The line 26 is obviously connected to a power sourceto supply the current to either the igniter or the safety valve, depending upon the position 5 of the switch arm 1 28.

Should there be aflamefailure at the pilot burner, the tube 12 will cool downcausing the switch 28 to again snap over to engage the igniter contact and thereby cause reignition-of the pilotgas.

As it is, obvious that various minor changes may be madein, the. design of thiscontrol device without departing from the spirit of the invention thereof, it is to be understood that thescope of the invention is to be determined from the appended, claims.

I. claim:

1. A control device comprising a temperature responsive actuator having a tube housing, a rod within said tube and having an end that moveswith temperature change, a1bracket securedin-said tube housing, a lever pivoted on said bracket, said lever having a free end extending lengthwiseiof said tube housing and having an electrically insulating abutment means thereon, said end of said rod being operably associated with said lever, a switch subassembly cylinder. connected to said tube housing at one of its ends and having an intermediate portion into which said free end of the lever extends and a small diameter portion at its other end, a sealing plug of electrically insulating material in said cylinder at said small diameter portion, a fixed contact arm extending through said plug, a movable-contact supporting bracket positioned within said intermediate portion and having one end extending through and beyond said plug for supporting said bracket within said cylinder, means in said intermediate portion disengageably connected to said bracket in said tube housing for holding said lever and said flexible contact arm in operable positions, and a flexible contact arm secured to the inner end of said supporting bracket, the other end of said flexible contact arm being positioned to .engage said fixed contact arm so that said abutment means is able to actuate said flexible contact arm to and from said fixed contact arm.

2. In a control device, the combination comprising a rod and tube actuator, a head on said rod and located within said tube, an apertured bracket surrounding said rod. and secured to said tube intermediate its ends, an L-shaped lever having an aperture in the short arm thereof and being pivoted on said bracket, said rod extending through said aperture, said pivot arm extending partially through said second aperture, said L-shaped lever having its long arm extending beyond the open end of said tube andhaving .an electrically insulating abutment means thereon; aswitch subassembly cylinder having an end into which said tube extends and having an intermediate portion into which said long arm extends and a small diameter portion at its other end, a sealing plug of electrically insulating material in said cylinder at said small diameter portion, a pair of fixed contact arms extending through said plug and having their inner and outer ends in spaced and opposed relationship, a movable-contact supporting bracket positioned within said intermediate portion and having one end extending through and beyond said plug for supporting said bracket wi'hin said cylinder, said bracket having an offset inner end, and a flexible contact arm and an insulator secured to said oilset inner end, the other end of said contact arm being positioned between said fixed contact arms, said insulator being positioned to space said inner end from the wall of said cylinder and to hold said subassemblies so that said abutment means is able to actuate said contact arm between said fixed contacts upon expansion and contraction of said tube.

3. A control device comprising a tube having a closed end and an open outwardly stepped end, a rod connected to said closed end at one of its ends and having a second end with a head thereon located within and spaced from the walls of said open outwardly stepped end of said tube, an apertured bracket surrounding said rod and secured non-rotatably to a step in said open outwardly stepped end, said bracket having a pivot arm and a positioning arm extending toward said open end, an L-shaped lever having a first aperture and a second aperture in the short arm thereof, said rod extending through said first aperture and said pivot arm extending partially through said second aperture, said short arm having laterally struck pivot ribs thereon engaging said head, the outer end of the long arm of said L-shaped lever extending beyond the open end of said tube and having an electrically insulating abutment means thereon, a switch subassembly cylinder having an end into which said open outwardly sepped end extends and an intermediate portion into which said long arm extends and a small diameter portion at its other end, a sealing plug of electrically insulating material in said cylinder at said small diameter portion at its other end, a sealing plug of electrically insulating material in said cylinder at said small diameter portion, a pair of fixed contact arms extending through said plug and having their inner and outer ends in spaced and opposed relationship, a movable-contact supporting bracket positioned within said intermediate portion and having one end extending through and beyond said plug for supporting said bracket Within said cylinder, said bracket having an inner end, and a flexible contact arm and a grooved insulator secured to said inner end, the other end of said contact arm being positioned between said fixed contact arms, said insulator being positioned to space said inner end from the wall of said cylinder and to receive said positioning arm in its groove during assembly and to hold said subassemblies so that said abutment means is able to actuate said flexible contact arm between said fixed contacts upon expansion and contraction of said tube.

4. A control device comprising a tube having a closed end and an open outwardly stepped end, a rod connected to said closed end at one of its ends and having a second end with a head thereon located within and spaced from the walls of said open outwardly stepped end of said tube, an apertured bracket surrounding said rod and secured non-rotatably to a step in said open outwardly stepped end, said bracket having a pivot arm and a positioning arm extending toward said open end, an L-shaped lever having a first aperture and second aperture in the short arm thereof, said rod extending through said s cond aperture, said short arm having laterally struck pivot thereon engaging said head, the outer end of the long arm of said L-shaped lever extending beyond the open end of said tube and having an electrically insulating abutment means thereon, a switch subassembly cylinder having an enlarge diameter portion at one of its ends into which said stepped open end extends and an intermediate portion into which said long arm extends and a small diameter portion at its ot er end, a sealing plug of electrically insulating material in said cylinder at said small diameter portion, a pair of fixed contact arms extending through said plug and having their inner and outer ends in spaced and opposed relationship, a movable-contact supporting bracket positioned within said intermediate portion and having one end thereof extending through and beyond said plug for supporting the bracket within said intermediate portion, said supporting bracket having an offset inner end, and a flexible contact arm and a grooved insulator secured to said oiiset inner end, the other end of said contact arm being positioned between said fixed contact arms and said insulator being positioned to space said offset inner end from the wall of said cylinder and to receive said positioning arm in its groove during assembly and to hold said subassemblies so that said abutment means is able to actuate said contact arm between said fixed contacts upon expansion and contraction of said tube.

5. A control device comprising a temperature responsive actuator having a tube housing, a rod within said tube and having an end that moves with temperature change, a bracket mounted in said tube housing, a lever pivoted on said bratket, said lever having a free end extending lengthwise of said tube housing and having an electrically insulating abutment means thereon, said end of said rod being operably associated with said lever, a switch subassembly cylinder connected to said tube housing at one of its ends and having an intermediate portion into which said free end of the lever extends, electrically insulating material in said cylinder at the other end thereof, a fixed contact arm extending through said material, a movable contact supporting bracket positioned within said intermediate portion and having one end extending through and beyond said material for supporting said bracket within said cylinder, separable team in said tube housing and cylinder and between said bracket and contact supporting bracket for holding them in proper alignment, and a flexible contact arm secured to the inner end of said movable contact supporting bracket, the other end of said flexible contact arm being positioned to engage said fixed contact arm so that said abutment means is able to actuate said flexible contact arm to and from said fixed contact arm.

References Cited in the file of this patent UNITED STATES PATENTS 2,793,270 Burch et al May 21, 1957 2,911,514 Haller Nov. 3, 1959 2,924,700 Huffman Feb. 9, 1960

Claims (1)

1. A CONTROL DEVICE COMPRISING A TEMPERATURE RESPONSIVE ACTUATOR HAVING A TUBE HOUSING, A ROD WITHIN SAID TUBE AND HAVING AN END THAT MOVES WITH TEMPERATURE CHANGE, A BRACKET SECURED IN SAID TUBE HOUSING, A LEVER PIVOTED ON SAID BRACKET, SAID LEVER HAVING A FREE END EXTENDING LENGTHWISE OF SAID TUBE HOUSING AND HAVING AN ELECTRICALLY INSULATING ABUTMENT MEANS THEREON, SAID END OF SAID ROD BEING OPERABLY ASSOCIATED WITH SAID LEVER, A SWITCH SUBASSEMBLY CYLINDER CONNECTED TO SAID TUBE HOUSING AT ONE OF ITS ENDS AND HAVING AN INTERMEDIATE PORTION INTO WHICH SAID FREE END OF THE LEVER EXTENDS AND A SMALL DIAMETER PORTION AT ITS OTHER END, A SEALING PLUG OF ELECTRICALLY INSULATING MATERIAL IN SAID CYLINDER AT A SAID SMALL DIAMETER PORTION, A FIXED CONTACT ARM EXTENDING THROUGH SAID PLUG, A MOVABLE-CONTACT SUPPORTING BRACKET POSITIONED WITHIN SAID INTERMEDIATE PORTION AND HAVING ONE END EXTENDING THROUGH AND BEYOND SAID PLUG FOR SUPPORTING SAID BRACKET WITHIN SAID CYLINDER, MEANS IN SAID INTERMEDIATE PORTION DISENGAGEABLY CONNECTED TO SAID BRACKET IN SAID TUBE HOUSING FOR HOLDING SAID LEVER AND SAID FLEXIBLE CON-

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