US2253553A - Snap-acting device - Google Patents

Description

Aug. 26, 1941. L w. 'BuRcH' SNAP-ACTING DEVICE Filed .July 30, 19:58 2 sheets-sheet 1 'v .7k .q Y Mui r ATTRlY Aug. 26, 1941. L w BURCH I 2,253,553

SNAP-ACTING DEVICE Filed July 30, 1938 2 Sheets-Sheet 2 INVENTOR ATTORNEY Y Patented Aug. H26, 1941 SNAP-ACTING DEVICE y Lyndon W. Burch, Bronxviiie, N. Y., assigner to The Wilcolator Company, a corporation of Del-y aware Application July 30,1938,` Serial No. 222,134

12 clams. (c1. 20o-13s.)

This invention relates to temperature regulators and has particular reference to a novel device'of this character which is reliable and efncient in operation, has a simple, durable and compact construction, and may be manufactured at low cost.

Another feature of the invention resides in the provision of a temperature regulator comprising novel adjustment means for controlling the tem- One feature of the present invention resides in i the provision of a novel temperature regulator comprising a pair of opposed blmetallic members so arranged that lthey bow in opposite directions in response to afchange in temperature, and a flexible strip disposed intermediate the members and operatively connected at one end to adjacent ends thereof. The flexible strip and the bimetallic members are preferably arranged in generally parallel relation and supported on a common mounting, sov that when the members bow in response to a change in temperature their effective.lengths are shortened, with the result that the ilexible strip is compressed endwise. Under this compressive action, the flexible strip bows, whereby the intermediate part thereof moves laterally Aand causes actuation of a valve. a switch, or the like; It will be apparent that by employing two bimetallic members in opposed relation, the tendency for each of them to move the end of the flexible strip laterally when the member bows or straightens, is opposed by the other, so that flexing of the members is effective only in compressing theexible strip endwise or releasing it. Accordingly, the strip is held at all times against any substantial lateral movement relative to the control means.

In the'preferred form of my new device, the nexible strip ,is ybacked intermediate its ends by a stop, which may be part of the valve or switch controlled by the strip, andis so arranged that it is forced against the stop with increased pressure as it is bowed, until the strip assumes a wave-shape of unstable equilibrium. The strip then snaps away from the stop to a bowed form of opposite curvature, thereby operating the switch or other control element with a snap action. The bimetallic members are preferably connected to the snap strip by bending adjacent ends of the .members inwardly over-the correspending e'nd of the strip, so that flexing of the members results in a force transmitted through the bent ends thereof to the strip. With this construction, compression ofthe strip is effected not only by bowing' of the intermediate portions of the bimetallic members and consequent shortening of their effective lengths, but also by the change in the angles of their bent ends which become more acute when the members bow.

perature at which the regulator operates. The adjustment means includes a handle mounted on a frame or casing and operatively connected to a screw threaded in the frame, the screw coaeting with amounting for one end of a flexible strip which actuates a switch, or the like. The flexible 'strip isadapted to be compressed endwise and bowedby a thermo-responsive means engaging the opposite end thereof, and the compression of the strip may be varied independently of the thermo-responsive means by operating the.

handle and thereby turning the screw and ad justing the mounting.

Preferably, the connection 4between the handle and screw may be rendered inoperative so that movement of the handle has no ,eflect on the mounting, and to this endthe screw may be threaded-` through a nut adapted to turn with theA screw and handle but normally held against rotation by releasable locking means, whereby operation of the handle causes the screw to move axially in the nut. When the locking means is released, however, operation of the handle causes the screw and nut to turn together, so that no axial movement 'of the screw isy obtained. This construction is of particular advantage in calibrating the instnnnent, since calibration may be f effected by simply adjusting the screw in the nut until the switch or valve ,is in the desired position at room temperature o'f the thermoresponsive means, then releasingl the lockin means and. adjusting the handle until it is in the position indicating room temperature, and thereafter locking the nut against rotation.v Further operation of the handle willthen move the screw axially in the nut and adjust the mounting, so that the actuating strip operates at the desired temperature.

Still another feature of the invention is in the provision of novel means coaeting with the adjustment means lfor indicating whether the switch or other control element isin its open or its closed position. The indicating means in- -cludes a lamp bulb or other light source mounted inside orbehind the handle,'the latter being 'tranparent or translucent so`that light from the source is visible therethrough.' They light source may be energized by a circuit which includes the adjustment screw, the lflexible strip, and the switch or valve element actuated by the strip.

so that the light source is energized or de-ener@ gized according to the position ofthe actuating strip with respect to its coacting control element. Preferably, the lamp bulb is rotatable with the handle and adjustment screw, and when the actuating strip is used to control a switch, a cam is provided which also rotates with these parts and controls a master switch.

These and other features of the invention may be better understood by reference to the accompanying drawings illustrating an embodiment of the invention adapted for controlling electric circuits. It will be understood that while the principles of the invention are described specifically hereinafter in connection with an electric regulator, they are not limited to regulators of this type but are applicable to gas and other regulators as well. In the drawings:

Fig. 1 is a front view of one form lof the new regulator;

Fig. 2 is a vertical, longitudinal section through the regulator shown in Fig. 1;

Figs. 3 to 7, inclusive, are sections on the lines 3 3 to 1--1, respectively, in Fig. 2;

Fig. 8 is a plan view of the regulator shown in Fig. 1:

Fig. 9 is a section through part of a slightly modified form of the-regulator;

Fig. 10 is a detail view of a part of the adjustment and indicating means;

Figs. 11 and 12 are detail views of one of the conductors;

Fig. 13 is a schematic view of a circuit for use with the regulator shown in Figs. 1 to 8;

Fig. 14 is a -schematic view of a circuit for use with the regulator shown in Fig. 9;

Fig. 15 is a diagrammatic view of the opposed,

bimetallic members, showing them in diierent operating positions, and

Fig. 16 is a diagrammatic view ofthe flexible strip, showing it in different operating positions.

Referring to the drawings, the regulator shown in Figs. 1 to 8 comprises a casing 20 open at the bottom and made oi' insulating bracket 2| having a leg 2|' which extends into the casing through a slot in the top thereof and lies against the front wall of the casing, the leg being held securely in grooves 22 in the sides of the casing, as shown in Fig. 3. Near its outer end, the bracket carries a thumb screw 23 threaded therein and adapted to clamp the casing to a suitable support.

Mounted inside the casing is a metal bracket 24 having one leg secured to the top of the casing by a binding post 25, the other leg 24 extending downwardly in spaced relation to the front wall of the casing. A contact arm 26 made of spring metal is seated in the casing in atrecess formed in the top thereof above the bracket 24. The front part of the contact arm carries a contact 21 and is offset downwardly from the top of the calsing and disposed in an opening 28 in the bracket 24. A piece of insulating material 29 is interposed between the contact arm 26 and bracket 24.

Below the contact arm 26 is a bus bar 3| secured to the top of the casing by a binding post 32, the bus bar being insulated from the contact arm and bracket 24 by a sheet of insulating material 33. The bus bar extends forwardly in spaced, parallel yrelation to the spring arm and carries near its front end a contact 34 directly below contact 21. The top of the casing is formed with an opening 35 over contact arm 26, and mounted in the opening is a metal bushing 36 which extends downwardly through the contact arm, the bracket 24, the bus bar, andn the material, and a head of the adjustmentscrew is closely fitted.,

' iit into notches 43" insulating members, the top of the bushing being formed with a head which seats on the contact arm. A collar 36' of insulating material surrounds the bushing and serves to insulate the latter from the bracket 24 and bus bar 3|. The bushing is externally threaded and .has a nut 31 screwed on the lower end thereof and clamped against an insulating washer 39 which is interposed between the nut and the bus bar 3|, the nut being held against rotation by a downwardly projecting ear 3| on the bus bar (Figs. 11 and 12) which engages one edge of the nut. A screw 39 is threaded through the bushing and forms at its inner end one contact of a switch.

The other switch contact is designated by the numeral 4| and is carried by a flexible strip of sheet metal 42. The strip 42 is adapted to be compressed endwise and bowed by thermo-responsivemeans comprising two strips of bimetal 43 and 44 arranged in opposed relation with the metal having the higher coefiicient of expansion on the outside. The strips oi.' bimetal are generally parallel, although they are normally bowed youtwardly intermediate their ends, and their front ends are connected to the leg 24' of bracket 24 by integral studs 24" on the sides of the bracket which extend through the bimetallic members and are upset at their ends. A metal strap 45 has its ends secured at the sides of bracket ieg 24 between the latter and the bimetallic strips 43, 44.

The strap extends rearwardly from the bracket leg and is formed intermediate its ends with a ilat, vertical surface forming a mounting or seat for the front end of the flexible strip 42. The latter is bifurcated at its front end, as shown at 42', and the bifurcations extend through slots 45 formed in strap 45 at each side of the Hat seat. whereby the flexible strip 42 is held by the strap 45 in a plane transverse to the faces of the bimetallic members. From the bracket leg 24', the bimetallic members 43 and 44 extend rearwardly and terminate in end portions 43' and 44', respectively, which are bent inwardly and then forwardly. The ends of the members are slotted and and 44", respectively, in the the rear end of flexible strip 42.

'Ihe mounting for the ilexible Astrip 42 is adjustable by means comprising a square headed screw 41 extending rearwardly through an enlarged opening in bracket leg 24 and adapted to engage the flat seat of strap 45. A nut 48 is threaded on the end of screw 41 and is held against the rear face of bracket leg 24 by a locking screw 49 which is threaded through the bracket leg with its head engaging the rear face of the nut. The locking screw 49 is normally tightened against nut 48 to prevent rotation of the latter, so that when adjustment screw 41 is rotated, it moves axially in the nut, whereby the mounting for strip 42 may be adjusted. However, when locking screw 49 is loosened. rotation of adiustment screw 41 permits lthe nut 48 to turn with it, so that there is no adjustment of the mounting.

The adjustment screw 41 is rotatable by a member 50 made of insulating material and provided with a square, central bore 5B' in which the A metal collar 52 closely surrounds the front end of member 50 and is formed at its rear with a flange seated against a shoulder on the member 50 and with a pair of prongs 52 extending into recesses in the member. The collar 52 extends forwardly tlgough a metal sleeve 53 tted in aligned openings in the bracket leg. 2| and the 50 and adjustment screw 41. Rotation oi collar 52 is effected by means of a handle 54 formed with a central bore 54 and iltted tightly on the front end of the collar, the handle being held on the collar by a detent 52" on the collar which engages in a suitable recess in the handle. The handle 54 is made of a translucent or a transparent material and is provided on its front face with an indicating arrow 54' cooperating with temperature graduations 5 5 marked on the front wail of the casing or on a suitable-dial, not shown.

'I 'he position oi' switch 38, 4| may be indicated by means comprising an incandescent lamp bulb 51 located in the collar 52 and the central bore of the handle. Intermediate its ends, the collar 52 is formed with circumferentially spaced ears 58 which are struck inwardly from the cylindrical surface of the collar and extend rearwardly, as shown particularly in Figs. 4 and 10. The base of the lamp bulbis clamped between the ears 58 and has a pin 51' which yengages -in a notch formed in the rear end of one oi the ears (Fig. 2), and the lamp bulb may be removed from the collar by vpressing it inwardly to release the pin 51 from the notch in the-ear, and then rotating the bulb and withdrawing it from the iront end of the collar. A metal eyelet 58 extends through the front end of the rotatable member 50 be` tween the bore 56' and the interior of collar 52, and the front end of the eyelet is normally urged against the base contact of the lamp bulb by a coil spring 60 lseated in bore 50'. between the rear end of the eyelet and the head of adjustment screw 41. A

The rotatable member 50 is adapted to actuate the contacts 21, 34, and to this endit is formed with a cam 62 (Fig. 5) adapted toengage an extension 26 ofcontact arm 26. The extension`26' is curved transversely, as shown in Fig. 5, and

engages one side of cam 82 when the handle is in its oif position, whereby the contact arm 26 is elevated so as to disengage contacts 21 and 34. When the handle is turned in a clockwisedirection from its 01T position, the top of cam 62 rides Y under the extension 26 so as to elevate it further and then allow it to snap downwardly and engage contacts 21 and 34. Rotation of the handie 54 isilmited by a ilnger 63 on the rotatable member 50, adapted to engage a stop 64 formed on the inside of'the casing.

The ilexible strip 42 is of such a form and is so positioned that it is normally bowed slightly against the contact screw 38, whereby the strip assumes a wave-shape, as shown in exaggerated form in Fig. 16. When the temperature rises, the

bimetallic members bow and cause their intermediate parts to move outwardly and assume a more pronounced bow-shape, and at the same timethe bent ends of the members move inwardly at a more acute angle with respect to the intermediate parts of the members as shown diagrammatically in Fig. 15. 'The exible strip 42 is thus compressed not only by the tendency for the bimetallic members to shorten their eiective lengths incident to bowing thereof, but also by the change in the angle of the bent ends of the members. As the strip 42 is compressed endwise, it is forced against screw 39 with greater pressure so that its wave-form becomes more pronounced, until it attains a condition of un-` stable equilibrium. Thereupon, it moves away` from contact screw 38 with a snap action to the bowed form shown by the dotted line in Fig. 16.

l the wire 68,'another wire 10 leads to one side of When the temperature decreases, the bimetallic members 43 and 44 ilex to the full line positions shown in Fig. 15, thereby gradually releasing the endwise compression of strip 42. As soon as the compression in the latter is released sufilcientiy, the tendency for the strip to assume its initial position asserts itself, and the strip then snaps back against the contact screw 39 to the full line position shown in Fig. 16. v

The temperature at which the bimetallic members43 and 44 operate the snap strip 42 may be adjusted by turning handle 54 and thereby rotat'ing adjustment screw 41 through collar 52 and the insulating member 50. When the handle is turned in a clockwise direction, the, adjustment member 41 is screwed inwardly in nut 48 so as to increase the initial compression in flexible strip 42, whereby the latter will snap away from contact screw 38 at a lower temperature. Conlversely, when the handle is turned in a counterclockwise direction, the screw 41 is moved away from strip 42 so as to decrease the initial compression therein, whereby a higher temperature is required to flex the bimetallic members sufciently to operate the ilexible strip and open the contacts.

It will be apparent that a conducting path is traceable from binding post 25 through bracket 24 to ilexible strip 42 by way of the parallel paths consisting of the nut 48 and adjustment screw, the strap 45, and the bimetallic members 43 and 44. From the contact 4| .on ilexiblestrip 42, the conducting path continues through screw 39, bushing 36, contact arm 26, contacts 21 and 34, bus bar 3|, to the other binding post 32. The conducting path described may be broken by turning handle 54 to its off position, wherein contacts 21, 34 are separated by cam 62, or as' a ro'ult of the bowing-of flexible strip 42 away from screw 36. A conducting path is also traceable from binding post 32 through bus bar 3|, contacts 3K4 and 21, contact arm 26, screw 38, ilexible strip 42, adjustment screw 41, coil spring 60, eyelet 59, lamp 51, collar 52, sleeve 53, and bracket 2l which may be clamped to a lsuitable groundI from the positive terminal thereof to the binding post 32, and another wire 68 leading from the negative terminal to a ground connection 68, preferably the metal frame' of the vehicle to which the clamp 2| is likewise connected. From the electric motor 1| which operates the heater,

and the other side of the motor is connected i through a wire 12 to binding post 25.

When the handle 54 is in its oi position (Fig. 5), the contacts 21 and 34 are separated so that the conducting path from the positive side of the battery to the motor 1| is broken. In this position of the handle, the conducting path from the positive side of the battery to the lamp 51 is likewise broken by contacts 21, y34. When the handle is turned in a clockwise direction from its on' position, it permits contacts 21, 34 to close and also screws the adjustment member 41 toward the iiexible strip 42. 'Upon closing oi contacts 21, 34, a circuit is established which is traceable from the positive side of the battery through wire 61, binding post 32, bus bar 3|, contacts 34 and 21, contact arm 26, screw 39, flexible strip 42, bracket 24, binding post 25, wire 12, motor 1|, wires 10 and 69, to the negative side of the battery, whereby the motor is energized and the heater started in operation. Simultaneously, another circuit is established which is traceable from the positive side of the battery through binding post 32 and ilexible strip 42, adjustment screw 41, lamp 51, bracket 2|, the frame of the vehicle, ground connection 59, wire 6I, to the negative side of the battery. The

-lamp 51 is thus energized and light rays there-A from pass through the handle 54 so as to inform the operator that the heater is functioning. Thereafter,` the handle 54 is set to the desired temperature indicated by the graduations 55.

As the temperature rises, due to operation of the heater, the bimetallic members 43 and 44 bow and gradually increase the compression of strip 42 and ilnally cause the latter to snap away from contact screw 39 at the temperature for which the handle is set. Thereupon, the conducting path from the positive side of the battery to the motor 1| is broken by the contacts 39, 4I and the heater is stopped. Also, the conducting path from the positive side of the battery to the lamp 51 is broken by these contacts, so that the lamp is de-energized, thus indicating to the operator that the heater is no longer in operation. As the temperature decreases, the bixnetallic members 43 and 44 gradually release the compression in strip 42 and finally permit the latter to against contact once more energized and the lamp 51 illuminated. The heater may be shut oil at any time by turning the handle 54 in a counterclockwise direction to its ofi position, thereby opening the contacts 21, 34 and breaking the circuits through the motor and indicating lamp.

It will be observed that the new regulator is simple and compact in construction and has only a few moving parts. By arranging the bimetallic members 43 and 44 in opposed relation, the tendency for each of them to move the notched end of strip 42 laterally is opposed equally by the other, so that the resultant of the forces exerted 39 at all times. Since the contact 4| is snapped by the exible strip into and out of engagement with contact screw 39, arcing between the contacts is prevented. The contact screw 39 may be readily adjusted in bushing 35 to obtain the desired snap action of the iiexible strip 42. Calibration of the device may be effected easily by adjusting the handle 54 until the adjustment screw 41 maintains strip 42 under the desired amount ol' compression at room temperature, then loosening the locking screw 49 and turning the handle to the position indicating room temperature, and then tightening the locking screw 43.

In the illustrated embodiment of the invention, the screw 41 serves not only as anadjustment means for controlling the operating temperature of the snap strip 42,- but also as part of the conducting path leading through the insulating member III to the indicating lamp 51. The member 53, in tum, serves not only to transmit rotation snap back to its initial position screw 39, whereby the motor 1| is of the handle to adjustment screw 41 and to house the conductors between the lamp base and the adjustment screw, but also to control the cut-olf switch composed of contacts 21 and 34 and to limit the rotation of the handle by coaction with stop 64. In addition, the bracket 2| performs the dual function of clamping the regulator to a suitable mounting on the vehicle and providing a return path for the current which energizes the indicator 51.

In some instances, it may be desired to cause the motor 1| to rotate slowly when the flexible strip snaps away from contact screw 39, and to this end, the modied form of the regulator shown in Fig. 9 may be employed with the circuit shown diagrammatically in Fig. 14. The regulator shown in Fig. 9 is similar to that shown in Figs. 1 to 8, except that a headless screw 12 is threaded in the bushing 36 in place of contact screw 39, the screw 12 forming an adjustable, xed contact coasting with the movable contact 4| on the ilexible strip. A headed screw or bind ing post 13 is threaded in the top of the bushing with the end of the screw terminating in spaced relation to the top of screw 12. The screw 13 extends through a metal washer 14 and has a wire connector 15 clamped between the Washer and the top of the casing over the opening 35. A lug 16 formed on the casing prevents accidental bridging of the wire connector 14 and bracket 2|.

The wiring shown in Fig. 14 is similar to that shown in Fig. 13, except that a resistor 11 is connected between the binding post 13 and binding post 25. Accordingly, when flexible strip 42 is in its normal position in contact with screw 12, the motor 1I is energized through contacts 4I and 12 which short circuit the resistor. However, when the strip 42 snaps away from contact screw 12, the motor obtains suilicient current through the resistor 11 to cause it to rotate slowly until the contacts 4| and 12 are again closed,

whereupon the motor is brought up to full speed.

It will be apparent that by forming the bimetallic members 43 and 44 with their high expanding elements on the inside, instead of the outside, the members will bow and break the circuit in response to a decrease in temperature 'and Willcause the circuit to close upon a rise in temperature. With the bimetallic members so arranged, the regulator may be used for controlling cooling appliances, such as refrigerators and air conditioning apparatus. Also, the regulator may be adapted to control selectively either a heating appliance or a, cooling appliance by employing a second contact screw. (not shown) similar to the screw 39 but on the opposite side of the flexible strip 42 and associating with one of the contact screws a circuit for controlling a heater and with the other contact screw a circuit for controlling a cooling appliance. One or the other of the control circuits may then be rendered effective, as desired, by means of a twoway switch operable to complete a circuit through one or the other of the contact screws. Thus,

when a heater is to be controlled. the circuit through the upper contact screw 39 would be effective, and when a cooling appliance is to be controlled the two-way switch would be thrown over to render the circuit through the lower contact screw effective.

I claim:

1. A temperature regulator comprising a pair of opposed bimetallic members adapted to flex in opposite directions in response to a change in temperature and having adjacent ends. a Ilexing the compression of the strip and ible strip disposed between the members with one end of the strip operatively connected to said adjacent ends of the members, said members being operable conjointly on said end of the strip to move the same toward the opposite end of the strip, means for mounting said strip and members, adjustment means for compressing the strip endwise relative to said members, and control means coacting with the strip intermediate its ends.

2. In a temperature regulator, the combination of a pair of bimetallic strips arranged in opposed relation and adapted to flex in opposite directions when heated, adjacent ends of the strips being bent inwardly and back towardv the opposite ends of the strips, a exible strip intermediate the bimetallic strips and generally parallel thereto and operatively connected at one end to said bent ends thereof, and means mounting the opposite ends of said strips.

3'. In a temperature regulator, the combination of a pair of bimetallic strips arranged in opposed relation and adapted to flex in opposite directions when heated, adjacent ends of the strips being bent inwardly and back toward the opposite endsA o f the strips, a flexible strip in termediate the bimetallic strips and generally parallel thereto and having notches in one end thereof, said bent ends of the bimetallic strips being tted inthe notches, and means for mounting the opposite ends of said strips.v

4. In a temperature regulator, the combination of a supporting member, a flexible strap mounted at its ends on the supporting member, a pair of bimetallic members mounted at one end on the supporting member adjacent the ends of the strap, said bimetallic members being opposed and operable to flex in opposition directions when heated, and a flexible strip seated at one end on the strap intermediate its ends'and operatively connected at its opposite end to the free ends of the bimetallic members.

5. In a temperature regulator, the combination of -a supporting member, a exible strap mounted at its ends on the supporting member, a pair of bimetallic members mounted at one end on the supporting member, said bimetallic members being opposed and operable to ex in opposite directions when heated, a flexible strip seated at one end on the strap intermediate its ends and operatively connected at its opposite end to the free ends of the bimetallic members, and adjustment means engaging the strap intermediate its ends and operable to vary the position of the Iintermediate part of the strap relative to the supporting member. 4

6. In` a temperature regulator, the combination of a supporting member, a flexible strap mounted at its ends on the member and having a. substantially at seat intermediate its ends and slots adjacent the seat, a iiexlble strip bifurcated at one end and mounted on said seat With the bifurcations disposed in the slots, and a pair of bimetallic members mounted at one end on the supporting member and operatively connectedito the free end of the strip, said members being opposed and operable to flex in opposite directions when heated. f

7. In a. temperature regulator comprising a flexible strip and thermo-responsive means for compressing the strip endwise and bowing it, the combination of adjustment means for varyincluding a nut, an adjustment screw threaded in the nut and operatively connected to one end of the strip, said screw and nut being rotatable together, and locking means cooperating with the nut for securing the same against rotation.

8. A temperature regulator comprising a pair of opposed bimetallic members adapted to flex in opposite directions when heated, a flexible strip intermediate the members and operatively connected at one end to adjacent ends of the mem-y bers, means for mounting the strip and members, said members being operable to compress the strip, a fixed contact coacting with the strip intermediate its end, a pair of contacts connected to the fixed contact, a handle for adjusting the compression in the strip, and means responsive to operation of the handle for actuating one of said pair of contacts.

9. In a regulator, the combination of a metallic supporting member, thermo-responsive control means carried by the supporting member and including a movable contact, a current conducting path connecting said contact and supporting member, a pair of contact arms on the supporting member and insulated Ifrom the member and from each other, a pair of cooperating contacts carried by said arms, a metal bushing connected to one of the arms, a screw threaded through the bushing andcoacting with said first contact, and wire terminals connected 4to the other arm and the supporting member.

10. In a regulator, the combination of a. metallic supporting member, thermo-responsive control means carried by the supporting. member and including a movable contact, a current conducting path connecting said contact and supporting member, a pair of contact arms on the supporting member and insulated from the member and from each other, a pair of cooperating contacts carried by said arms, a metal bushing connected to one of the arms, a headless screw threaded in the bushing and coacting with said first contact, a binding' post threaded in the bushing over said iirstv screw, and wire terminals connected to the other arm and the supporting member.

11. In a temperature regulator comprising a thermo-responsive control means and a temperature adjustment handle for adjusting the control means to different temperature settings, the combination of an operative connection between the handle and the control means including a nut, an adjustment screw threaded in the nut and operatively connected to the control means, said screw and nut being rotatable together, and locking means cooperating with the nut for securing the same against'rotation, said locking f means being releasable to permit rotation of the screw and nut as a unit to calibrate the regulator.

12. A thermo-responsive regulator comprising a bimetallic member, a llexible, bowed strip adjacent and generally parallel to said member, the

strip and member being operatively connected at one end, means for mounting rthe other ends of the member and strip, the bimetallic member being operable to compress the strip endwise to increase the bowing of the strip, temperature adjustment means at said second end of the strip adjacent the mounting means and operable to vary the position of said second end relative to the corresponding adjacent end of the bimetallic member, and control means coacting with the strip intermediate vits ends.

LYNDON W.BURCH.

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