US2634350A - Thermostatic switch - Google Patents

Description

April 7, 1953 c. s. MERTLER' THERMOSTATIC. SWITCH 2 Sl-IEETS-SHEET 1 Filed Feb. 7, 1948 fie. 16

d- I 3Z 150 fie. 4

, INVENTOR. (mazes Silva-mew BY MM, 31 /41 3% p i 1953 c. s. MERTLER 2,634,350

THERMOSTATIC SWITCH Filed Feb. 7, 1948 2 SHEETSSHEET 2 427 IN VEN TOR.

f/mzss .5. Mean 54 Patented Apr. 7, 1953 UNITED STATES PATENT OFFICE 1 4 Claims.

This invention relates to thermostatic electricalswitches and more particularly to improvements in thermostatic switches which are of the type commonly known as semisnap acting.

Thermostatic electrical switches known to the art may be classified in accordance with their operational characteristics as being one of three main types. One of these main types includes those switches which are known as snap acting because they employ springs and/or levers to operate at least one of the electrical contacts with a positive snap action at the instant the thermal responsive member reaches a predetermined temperature. Switches of this type have the advantages of high current carrying capacity, long contact life and absence of circuit disturbances which cause interference with radio reception. However, such switches are relatively expensive to manufacture and possess an inherent wide temperature diiferential between the opening and closing operating temperatures.

A second category of thermostatic electrical switches comprises those which are known as the creep type because the electrical contacts are opened and closed relatively slowly under the sole influence of the bending of the thermal responsive member as the temperature thereof changes. Switches of this type possess the advantages of low cost and relatively small temperature differential but have relatively short contact life and cause considerable radio interference due to the fluttering and consequent frying of the contacts at the instant when they are either opening or closing. Moreover, the current carrying capacity of'thermostatic switches of this type is of a relatively low order since high currents intensify the above mentioned disadvantages.

The third general type of thermostatic switches comprises those known as semisnap acting. Switches of this type are somewhat similar in construction to the creep type but differ in operating principle in that the contacts open with a small snap action. This snap action results from disposing the thermal responsive member so that it is eiiective to exert both a frictional and a motion producing force upon a member which movably supports one of the switch contacts. The frictional force enables the thermal responsive member to store up a certain amount of motion producing energy before any movement of the movable contact supporting member occurs. When the stored energy is sufficient to overcome the frictional force the movable contact is actuated with a small snap action and this mode of operation is effective in both contact opening and closing directions. Switches of this type combine the desirable operating features oi both the creep and snap acting type thermostatic switches while retaining the relatively low cost of the creep type switches but without the undesirable functioning characteristics of the latter.

The principal object of this invention is to provide improved semisnap acting thermostatic switches which are simpler and less expensive to manufacture and which have a greater snap action than prior switches of the same type.

Another object of the invention is to provide improved thermostatic switches each of which employs a thermal responsive member for controlling the movement of a movable contact of the switch, the thermal responsive member comprising two portions extending at substantially right angles to each other and so disposed in the switch as to exert both substantially perpendicular and longitudinal forces upon the member carrying the movable contact, whereby flexing of the thermal responsive member in response to temperature changes does not result in movement or" the movable contact until the flexing has stored sufficient energy in the thermal responsive member to overcome the static friction between the latter and the member carrying the movable contact, whereupon the latter and its contact are moved with a snap action relative to the normally stationary contact.

A furtherobject of the invention is to provide improved thermostatic switches of the type mentioned in the preceding object and in which the two portions of the thermal responsive member are integral parts of a unitary bimetallic strip or bar so that both portions of the thermal responsive member flex in response to a temperature change thereby accentuating the snap action of the movable contact.

A still further object of the invention is to provide an improved thermal responsive member having two integral bimetallic portions extending angularly with respect to each other and so shaped that flexing of the member, in response to temperature changes causes the end of one of said portions to have an increased movement in a direction productive of snap-like action of a movable member actuated thereby.

The invention further resides in certain novel features of construction and combination and arrangements of parts, and further objects and advantages thereof will be apparent to those skilled in the art to which it pertains from the following description of the present preferred aesasso embodiment thereof, and certain modifications thereof, described with reference to the accompanying drawings in which:

Fig. 1 is a top plan view of an improved thermostatic switch constructed in accordance with this invention;

Fig. 2 is a side view, partly in elevation and partly in section, of the switch illustrated in Fig. 1, the view being taken substantially on line 2--2 of Fig. 1;

Fig. 3 is a top plan view of the present preferred. form of a thermostatic switch constructed in accordance with this invention;

Fig. 4 is a side view, partly in elevation and partly in section, of the switch illustrated in Fig. 3, the view being taken substantially on the line 44 of Fig. 3;

Fig. 5 is a detached end elevational view of the thermal responsive member illustrated in Figs. 1 to 4;

Fig. 6 is a side elevational view of a modified form of thermal responsive member suitable for use in thermostatic switches constructed in accordance with this invention;

Fig. 7 is a top plan view of another form of thermostatic switch constructed in accordance with this invention;

Fig. 8 is a side view, partly in elevation and partly in section, of the switch illustrated in Fig. '7, the View being taken substantially on the line 8-8 of Fig. '7;

Fig. 9 is a side view, partly in elevation and partly in section, of a further form of thermostatic switch constructed in accordance with this invention;

Fig. 10 is a detached top plan view of the thermal responsive member employed in the form of switch illustrated in Fig. 9;

Fig. 11 is a top plan view of a still further form of thermostatic switch constructed in accordance with this invention;

Fig. 13.

Fig. 15 is an end elevational view of the thermal responsive member illustrated in Fig. 14 as viewed from the right-hand side of Fig. 14;

Fig. 16 is a side elevational View of yet another form of thermostatic switch constructed in accordance with this invention;

Fig. 17 is a side elevational view, to an enlarged scale, of the novel thermal responsive member employed in the switch illustrated in Fig. 16; and,

Fig. 18 is an end elevational view of the thermal responsive member illustrated in Fig. 17 as viewed from the right-hand side of Fig. 17.

Referring first to Figs. 1 and 2 of the draw- .ings, the improved thermostatic switch illustrated therein comprises an elongated base member 29 preferably formed of metal although other relatively rigid materials such as hard rubber, plastic or the like may be employed. Adjacent one end, the base member 20 is provided with an opening therethrough in which is mounted an internally threaded sleeve 21 the external diameter of the sleeve being less than the opening through the base member. As shown in Fig. 2, this sleeve has an outwardly extending flange 22 adjacent one end, and between this flange and the adjacent face of the base member is positioned a plate or sheet 23 of insulating material. Surrounding the shank of the sleeve 2!, and resting upon the other face of the base member 2%, is an insulating washer 24, and upon the washer 24, and surrounding shank of the sleeve 2!, is positioned a terminal member 25. The outer end of the sleeve 2! is peened over or otherwise deformed into engagement with the terminal member 25 to firmly clamp the parts just mentioned to the base member 28. The terminal member 25 is shown as provided with an outwardly extending lug having a threaded opening 28 therein for receiving a connecting screw to which an electrical conductor may be attached. In place of this construction it will be apparent that the terminal member 25 may be provided with other means for effecting connection to an electrical conductor.

Threaded through the sleeve 2! is the threaded shank of a contact supporting member 27 one end of which extends beyond the flange 22 of sleeve 2! and is provided with an axially extending bore in which is received a reduced cylindrical portion 28 of an electrical contact 29, the latter being formed of silver or other suitable material. In the illustrated construction, the portion 28 of the contact has a force fit within the bore to prevent displacement therefrom but it will be apparent that the contact 29 may be otherwise connected to the end of the member 21. The other end of the member 21, which is opposite to that provided with the contact 29, has a screw-driver slot or is otherwise formed to facilitate engagement of a tool therewith for efiecting threading of the member through the sleeve 2!. Hence, the position of the contact 29 relative to the base 20 may be readily adjusted, the contact being maintained in its adjusted position by means of a lock nut 3i threaded upon the member 27 and cooperating with the end of the sleeve 2|.

A movable contact 32, formed of silver or other suitable material, cooperates with the normally stationary contact 29 and is adapted to be moved with respect thereto by virtue of being mounted on one end of a resilient member 33. The other end of the member 53 is provided with an opening through which extends the shank 34 of a mounting member, generally designated 35. This mounting member 35 has an outwardly extending flange 35 adjacent one end upon which the resilient member 33 rests, the shank 34 of the mounting member also passing through aligned openings in a spacing collar 3'5, an insulating washer 38, a thermal responsive member 39, an insulating washer to and the other end of the insulating plate or strip 23, in the order recited. The portion of the shank 34, above the insulating plate 23, extends through an opening 5] in the base member 20, located adjacent the end of the latter opposite to the end which is provided with the contact 29. The shank 34 also extends beyond the base member 20 and is provided with a terminal member 42 between which and the base member 20 is interposed an in sulating washer 43. The outer end of the shank 35 is peened over or otherwise deformed to firmly clamp the resilient member 33, the thermal responsive member 39, the terminal member 42 and the several insulating spacing washers and/or collars to the base member. The construction just described is such that the thermal responsive member is mounted in vertical alignment between the base and resilient members 33 but spaced and insulated therefrom. The resilient member 33 normally extends substantially parallel with the base member 23 and is electrically connected, through the shank 34 of the mounting means, to the terminal member 42 which preferably is provided with a threaded opening 44 to receive a connecting screw for attaching an electrical conductor thereto.

The thermal responsive member 33 employed in the form of the improved thermostatic switch illustrated in Figs. 1 and 2 comprises a unitary bimetallic strip or bar bent to provide two integral portions, a main portion 39a and an ex= tension 3%, which are disposed at substantially right angles with respect to each other so that the main portion normally extends substantially parallel with the base and the resilient memhere 33 while the extension 39b is directed towards and is substantially perpendicular to the resilient member 33.

As is well known in the art, the thermal responsive member 33 is constructed of two pieces of metal having different coemcients of expansion and welded together so that variations in the temperature of the member causes flexing or bending thereof. In the form of the member shown in Figs. 1 and 2 the metal having the lower coeflicient of expansion is disposed adjacent the resilient member 33 so that an increase in temperature causes the member to flex or bend from the position shown in full lines in Fig. 2 to that indicated in broken lines in the same figure. The switch may, therefore, be employed wherever it is desired to control an electric circuit in accordance with the ambient temperature of the location in which the switch is placed, the I construction being such that the circuit extending from the terminal 25 to the terminal 42 is closed through engagement of contacts 23 and 32 when the temperature is below a certain predetermined value, contact 32 being held in engagement with the contact '29 at such times by the resilient member 33. As the ambient temperature increases the thermal responsive member 39 flexes to engage the resilient member 33 and thus disengages the contact 32 from the contact 29 interrupting the circuit therethrough, the disengagement being eifected with a snap action as hereinafter described. As the ambient temperature drops, the thermal responsive member returns to substantially its initial position thus reclosing the contacts 29 and 32, this movement of the contact 32 likewise being effected with a snap action.

As mentioned above, the switch illustrated in Figs. 1 and 2 operates with a snap action. This is due to the fact that the flexing or bending of the thermal responsive member 39 results in the free end of the latter moving substantially in an arc intersecting the resilient member 33 so that the thermal responsive member exerts force upon the resilient member in a direction which is substantially perpendicular to that member and also in a direction substantially parallel with the longitudinal extent of the resilient member 33. This will be readily understood from a consideration of Fig. 2 in which it will be seen that the initial movement of the thermostatic member, from the full line position to the broken line position, simply brings the free end of the extension 39b into engagement with the resilient member 33, the extent of this movement being determined by the adjusted position of the contact 29 and the dimensions of the various parts employed in theswitch. A further increase in the ambient temperature causes the thermal responsive member to further flex thus exerting a force upon the resilient member 33 substantially perpendicular thereof as indicated by the arrow A. Simultaneously the end of extension 391), which is now in engagement with the resilient member 33 tends to move longitudinally thereof in the direction indicated by the arrow 13 thereby producing friction between the end of. extension 39b and the surface of the member 33. Due to the well known fact that static friction exceeds sliding friction, the end of the extension 39b is momentarily prevented from further movement so that the contacts 29 and 32 remain in engagement while the further bending or flexing of the thermal responsive member 39 increases the energy stored therein. When this stored energy is sufficient to overcome the static friction, the end of the extension 3% slips over the surface of the resilient member 33 the initial portion of this movement being effected in a relatively short interval due to the energy stored in the thermal responsive member. Consequently, the resilient member 33 and its contact 32 are moved downwardly as shown in Fig. 2 with a snap-like action thus rapidly disengaging the contact 32 from the contact 29.

The snap action just described is greater than that obtained with conventional constructions because the extension 3912 has an appreciable length and since this extension, as well as the main body 33a of the thermal responsive member, is bimetallic it likewise flexes with variations in temperature thereby increasing the extent of longitudinal movement of the end of the extension along the resilient member 33. Consequently, the desired snap action is obtained with a lesser temperature differential than has heretofore been possible or, conversely, a wider contact separation results when an equivalent temperature differential occurs. In view of the fact that friction between two members is proportional to the areas of the surfaces in engagement, the thermal responsive member 39 is of substantial width and the free end of extension 3% is preferably substantially rectangular as indicated in Fig. 5, the corners of this free end being preferably curved slightly, however, so that a slight cooking of the thermal responsive member will not result in a substantiall point contact with the resilient member 33. If less static friction, and hence a smaller degree of snap action is desired, the radius of curvature of the corners of the free end of extension 39b may be increased thereby lessening the area of the bimetal member which contacts the resilient member 33. The degree of snap action may also be varied by altering the pressure exerted by contact 32 upon contact 29 since this will vary the static friction which must be overcome in effecting switch operation. As shown in Fig. 2, the length of the extension 3912 is in the order of one-third the length of the main portion 39a. This relationship of the lengths is not, however, critical and may be varied so long as the extension portion has an appreciable length suflicient to permit flexing thereof.

After the resilient member 33 has been moved, as just described, to separate the contact 32 from contact 29, the parts are held in this position by the thermal responsive member until the ambient temperature drops below a predetermined value.

As the temperature drops the thermal responsive member tends to return to its initial position. 'As before, however, static friction is present between the end of the extension 3% and the resilient member 33 so that movement of the member 33 and contact 32 does not occur as soon as the thermostatic member begins to straighten,

" such movement occurring only after the thermal responsive member has dropped sufiiciently in temperature so that the forces tending to straighten it are sufiicient to overcome this static friction. When this point is reached there is a rapid relative movement of the end of extension 3912 with respect to the resilient member so that the contact 32 reengages contact 29 with a snap action.

The switch construction shown in Figs. 1 and 2 'may be used as a settable thermostatic switch for operation at diiferent temperatures by backing off the nut 3| sufiiciently to permit easy adjustment of the threaded contact supporting member 2?, Normally, however, the switch illustrated in Figs. 1 and 2 is intended for use only at a single predetermined temperature and hence the nut 3| is tightened to prevent movement of contact '29 after the latter has been initially adjusted vided with an opening I2I for receiving the reduced diameter shank of a contact mounting stud I22, which shank also passes through a plate or sheet of insulating material I23 and an insulating washer I23 which are disposed on opposite sides of the base I20 to insulate the stud from the base, it being understood that the shank of the stud has a diameter which is materially less than the diameter of the opening through the base. Resting upon the insulating washer I24, and surrounding the shank of the stud I22, is a terminal member I25 provided with a threaded opening I26 for receiving a screw by which an electrical conductor may be connected to the terminal member. The outer end of the stud I22 is peened over or otherwise deformed, as indicated at I2'I, to rigidly secure the stud and terminal member to the base I20 as shown in Fig. 4. The lower end of the stud I22 is provided with a contact surface I28 which may be a layer of silver or other suitable material secured to the end of the stud in any suitable manner.

Cooperating with the contact I28 is a movable contact I29 of silver or other suitable material which is mounted on the outer end of a resilient member I30. Disposed between the base I23 and the resilient member I33 is a thermal responthe base I20, the members I30 and I3I being separated by a collar I33 and an insulating washer I34, while the thermal responsive member I3I is separated from the base I20 by an insulating washer I35, a collar I36 and a portion of the insulating plate or sheet member I23. One end of the mounting means or stud is provided with an enlarged outwardly extending flange I37 forming a head for engagement with the resilient member I30, the other end of the mounting means extending beyond the base I20 and being provided with a terminal member I38, insulated from the base I20 by an insulating washer I33, this end of the mounting means being peened over to rigidly secure the several parts lust mentioned to the base I20. The terminal member I38 is provided with a threaded opening I33! to receive a screw by which an electrical conductor may be attached to the switch.

In order to provide for adjustment of the switch for operation at different temperatures, the base member I20 intermediate its ends is provided with a central opening surrounded by an integral, upstanding boss or sleeve I40 which is internally threaded and threadingly receives the threaded shank of an adjusting member Ill. The lower end of the adjusting member MI is preferably provided with a button I42 of insulating material and the sleeve or boss I40, together with the adjusting member I3I, are preferably so located that the button I42 engages the thermal responsive member substantially intermediate the ends of its horizontal portion I 3Ia. The member It! may be actuated by means of a knob or the like, not shown, provided thereon, the extent of adjustment being limited by providing the member It! with a radially extending projection I33 which is adapted to abut a projection I03 extending upwardly from the boss :53 and preferably formed integrally therewith. It will be readily understood that by rotating the member It! the thermal responsive member I3I may be deflected to bring the free end of its extension portion I3Ib to any desired position relative to the resilient contact carrying member I30 thereby selecting the operating temperature for the switch.

The thermal responsive member I3I, shown in Figs. 3 and 4, is identical with that shown in Figs. 1 and 2 and operates in the same manner to effect opening and closing of the contact I23 with respect to the contact l28, the contact 29 being moved by a snap action as was previously described for the contact 32. In the present construction, however, the insulator button I42 on the adjustment member I3I forms an abutment for the main body portion I3Ia of the thermal responsive member thus limiting the extent this portion can flex in an upward direction as viewed in Fig. 4 and thereby determining the temperature at which contact separation occurs.

The thermal responsive members illustrated in Figs. 1 to 4 are each formed from a bimetallic strip or bar bent to provide two portions extending at substantially right angles to each other the radius of curvature at the bend being relatively small. This radius of curvature, may, however, be increased without altering the operations of the switches. Thus, Fig. 6 illustrates a bimetallic member which may be employed in the switches illustrated in the Figs. 1 to 4 and will operate in the same manner as the bimetal lic members illustrated therein. This thermal responsive member, designated generally I50, is constructed of a bimetallic strip or bar, one end of which is provided with an opening I5I therethrough for receiving a mounting means such as the shank 34 or I32 of the mounting members illustrated in Figs. 2 and 4. The other end of the member I50 is bent on a relatively large radius to provide an extension l50b which is disposed at substantially right angles to the main body portion l5lla. This thermal responsive member will operate in the switches shown in the Figs. 1 to 4, to eiiect the previously mentioned snap action of the movable contact, by lessening the radius of curvature of the extension Gb as the temperature of the thermal responsive member rises, the operation being otherwise the same as that previously described for the thermal responsive members 39 and Hi.

Figs. '7 and 8 illustrate still another form of thermostatic switch constructed in accordance with this invention, this form of switch being substantially like that illustrated in Figs. 3 and 4 but diirering therefrom primarily in the type of thermal responsive member employed. As illustrated, this form of switch comprises a base 220 adjacent one end of which is mounted a relatively stationary contact 221 provided on the lower end of a stud 222, the stud being connected to a terminal member 223 and insulating members 224 and 225 being provided on either side of the base 223 in the same manner as are the corresponding parts shown in Fig. 4. Cooperating with the stationary contact 22| is a movable contact 226 mounted adjacent one end of a resilient member 221. The other end of the resilient member 221 is mounted in vertical spaced alignment with the base and a thermal responsive member 228 by a headed mounting member or stud 229 the shank of which passes, in order, through openings in the resilient member 221, spacing collar 230, insulating washer 23I, thermal responsive member 228, insulating washer 232, insulating member 224, the base 220, insulating washer 233 and terminal member 234. The end of the mounting member or stud 229 is peened over above the terminal member to rigidly mount the assembly just described upon the base 22!] thereby providing an electrical connection between the terminal 234 and resilient member 221 while insulating the mounting member and the thermal responsive member from the base and from each other. If desired, the insulating washer 232 may be replaced by a suitable spacer if greater separation is desired between the base and thermal responsive member 228.

The base 220 is also provided with an opening therethrough surrounded by an upstanding boss or sleeve 235 which is internally threaded to receive the threaded shank of an adjusting member 236, the lower end of the latter being provided with an insulating button 231 for engagement with the main body portion 228a. of the thermal responsive member to thereby adjust the switch for operation at different predetermined temperatures. As before, the adjusting member 236 is preferably provided with a radially extending projection 238 for cooperation with an upstanding axial projection on the sleeve or boss 235 and thereby limit the extent of rotative movement of the adjusting member 233.

'In the form of switch illustrated in Figs. 7 and 8 the thermal responsive member 228 is shown as constructed of a main body portion 228a formed from a bimetallic strip or bar which preferably tapers somewhat from its mounted endtowards it forward or free end. This forward or free end of the main body portion 228a provided with a projection or pin 2281) which ell 10 extends at substantially right angles from the main body portion 228a and is connected therewith so as to constitute an extension of the thermal responsive member.

The operation of a switch thus constructed is substantially similar to that of the switches previously described and hence need not be further set forth in detail, it being sumcient to note that snap action is again provided by the static friction developed between the end of extension 2281) and the resilient member 221 when the bimetallic main body portion 228a flexes in response to variations in temperature. In the instant construction, however, the extension 2281) is not bimetallic and hence does not itself flex. Therefore, the extent of longitudinal movement of the end of this extension along the resilient member 221 is less than in the case of the bimetallic extensions of the previously described thermal responsive members and hence the snap action and/or extent of contact separation is lessened.

Figs. 9 and 10 show still another form of thermostatic switch constructed in accordance with this invention and which is in a large part constructed substantially like the switches described with reference to Figs. 3 to 8. That is to say, the switch comprises a base member 320 on which a stationary contact 321 is mounted and connected with a terminal member 322, the contact and terminal members being insulated from the base by insulating washers or members 323 and 324 as in the forms illustrated in Figs. 4 and 8.

Cooperating with the contact 321 is a movable contact 325 mounted on one end of a resilient member 323. The other end of this resilient member is rigidly mounted upon the base 320 by a headed mounting means or stud 321, the shank of which passes through an opening in the resilient member 323 and through an opening in the base 320 as in the previously described constructions. As before, the mounting means or stud 321 supports and engages a terminal member 328, the latter being insulated from the base by an insulating washer 329, an electrical connection being provided by the terminal member 328 through the mounting member 321 to the resilient member 326 and thence to the contact 325.

A thermal responsive member 330 is disposed between the base 323 and the resilient member 326. This thermal responsive member is formed from a bimetallic strip or bar one end of which is bent at substantially right angles to the main body portion 333a thereby providing an extension 3301: directed towards the resilient member 323. The other end of the thermal responsive member is provided with a substantially arcuate opening 33f, the member having oppositely disposed integral ears 332 and 333 extending radially inwardly of this opening. These ears 332 and 333 are received in cooperating recesses provided adjacent the upper surface of a spacing collar 333 which is mounted upon th mounting member or stud 321, a space being provided between the spacing collar and the arcuate opening in the bimetal member as clearly shown in Fig. 10. Hence, the thermal responsive member 333 is hingedly connected to the base member through the agency of the ears 332, 333, collar 33-1 and mounting member 321, the ears 332, 333 being retained within their recesses by a superimposed collar member 335 provided upon the mounting member 321 between the collar 334 andthe insulating member 324. This form of thermostatic switch also employs an adjusting means comprising a threaded member 335 which is threadedly received in a boss or sleeve 33? surrounding an opening extendin through the base 328. The end or the adjusting mean is provided, as in the previously described construction, with an insulating button 333 for engagement with the thermal responsive member 333, the extent of adjustment being limited by abutment members carried upon the adjusting member and the boss or sleeve, respectively.

The form of switch illustrated in Figs. 9 and 10 operates in the same manner as that illustrated in Figs. 3 and 4 and, hence need not be further described. In the instant form of switch, however, adjustment or" the thermal responsive member 338, to effect switch operation at a preselected temperature, does not involve any bending of the thermal responsive member adjacent its mounting so that no stresses are introduced therein by varying the setting at which the switch will operate. This makes for longer life and at the same time avoids introducing stresses which might affect accurate operation of the switch. Th movable contact 325 is, nevertheless, actuated with a snap action in this type of construction since the insulating button 338 provides an abutment limiting the extent that the portion 333a of the thermal responsive member can move in an upward direction, as viewed in Fig. 9, so that flexing of this main body portion and of the extension 3331) are effective, as in the previously described construction, to actuate contact 325 with a snap action.

Each of the switches heretofore described is so constructed that increase in temperature effects contact separation, the contacts being normally held in engagement by the biasing action of the resilient member which carries the movable contact. The basic principles of this invention may, however, be embodied in a switch in which the movabl contact is so mounted as to be biased away from engagement with a stationary contact, the contact being held in engagement by a thermal responsive member in its cold position and allowed to open with a semisnap action under the control of the thermal responsive member when the temperature of the latter rises above a p e mined value. Such a switch is illustrated in Figs; 11 and 12.

The switch illustrated in Figs. 11 and 12 comprises a base 420 having an opening therethrough for receiving a threaded portion of a mounting stud 421 which forms a common mounting means for the various elements of the switch. This is effected by providing the base 420 with an integral sleeve 422 which rigidly interconnects the various parts of the switch, the stud 42! passin therethrough and thereby connecting the switch elements to a supporting surface 45!]. The base 423 rests upon the surface 453 and adjacent to this base the sleeve 422 is provided a thermal responsive member 423, an insulating sleeve 424 being provided between the shank of the sleeve 422 and the -open ing through the thermal responsive member, and insulating washers 425 and 423 bein provided on opposite sides of the thermal responsive member to insulate the latter from the sleeve. One of the contacts 42'! of the switch is mounted upon the outer end of a resilient arm or member 428- the inner end of which is disposed about the insulating sleeve '424'and is spaced from the insulating washer 426, and hence from the thermal responsive member 423, by a spacing collar 429. A terminal member 430 also surrounds a portion of th insulating sleeve 424 and rests upon the adjacent end of the resilient arm 423 thereby providing electrical contact between these members, the outer end of the terminal member 436 being provided with suitable means for connecting an electrical conductor thereto.

The second contact 43! is mounted on the outer end of a resilient switch arm or member 432 the inner end of which is supported invertical spaced relationship with respect to the resilient member 428 by an insulating washer 433 and a terminal member 434, the resilient arm 432 and the terminal member 434 being insulated from the shank of th sleeve 422 by an insulating sleeve 435. The resilient arm 432 and terminal member 433 being in contact with each other thereby provide a path for electrical current from contact 43! through the resilient member 432 and to a conductor attached to the outer end of the terminal member 434.

A rigid arm 435 is mounted in vertical alignment with respect to the thermal resp nsive member 423 and resilient members 428 and 432 by having its inner end apertured and positioned about the sleeve 422, the arm 436 being spaced from the resilient member 432 and insulated therefrom by a spacing collar 43! and an insulating washer 438. The thermal responsive member 433, resilient members 428, 432 and the arm 436 are rigidly held together by spinning or otherwise deformin the end of the sleeve 422 into engagement with the upper surface of the arm 436, as shown in Fig. 12, so that the entire switch assembly may be readily attached to or removed from a supporting surface, such as 450, by means of the threaded stud 42 I.

The arm 436 is provided with an opening therethrough, adjacent its free end, and surrounding this opening is an upstanding boss or sleeve 439 internally threaded to receive the threaded end of an adjusting screw 440. The lower end of the adjusting screw is provided with an abutment button 44i of insulating material which is adapted to engage the resilient arm 432 intermediate its ends to thereby effect adjustment of the switch operation. The adjusting member 440 is provided with a radially outwardly extending projection 44! adapted to abut an upwardly extending projection 442, which may be formed as as integral part of the arm 436, thereby providing means for limiting the amount of adjustment of the switch. While the contact 43l is shown as mounted upon a resilient arm or member 432 this resiliency is provided primarily for ease in eflecting adjustment of the switch and it will be understood that for any adjusted position the contact 43I is substantially stationary.

The resilient arm 428 biases the movable contact 421 in a direction to eifect disengagement of the latter from the relatively stationary contact 43! but the contacts are held in engagement, at

all temperatures below a predetermined value, by

tension 423b, extending substantially perpendicular to the arm or member 428. This form of thermal responsive member is, therefore, generally similar to that shown in Figs. 1 through 4 but diifers therefrom in that the metal having the lower coefiicient of expansion is disposed on the outer side of the thermal responsive member in the form thereof shown in Fig. 12. Hence, when the ambient temperature is below a predetermined value, the thermal responsive member occupies the position indicated in full lines so that the contacts 12? and 531 are in engagement thus completing the electrical circuit therethrough. Upon an increase in the ambient temperature, however, the thermal responsive member flexes or bends to the position shown in broken lines in Fig. 12 thereby effecting disengagement of the contact 421 from contact 43! and interrupting the electrical circuit therethrough. Operation of the contact 421 to and from engagement with contact 431 is, as in the previously described embodiments of the switch, effected with a snap action due to the peculiar construction of the switch by virtue of which the outer end of extension 123b exerts both perpendicular and longitudinal forces upon the resilient member 428. As mentioned in detail above, this results in creating friction between the end of extension 423i) and the resilient member 428 which prevents movement of the end of the extension over the resilient member, and hence prevents movement of the resilient member and its contact, until sufficient energy has been stored in the thermal responsive member to overcome the static friction whereupon actuation of the contact 42; is effected with a snap action.

Fig. 13 illustrates yet another form of thermostatic switch constructed in accordance with this invention, this form of switch being substantially like that illustrated in Figs. 3 and 4 but differing therefrom primarily in the type of thermal responsive member employed. As illustrated, this form of switch comprises a base 52 3, adjacent one end of which is mounted a relatively stationary contact 52 I, provided on the lower end of a stud 522, the stud being connected to a terminal member 523 and insulating members 524 and 525 being provided on either side of the base 523 in the same manner as are the corresponding parts shown in Fig. 4. Cooperating with the stationary contact 52l is a movable contact 526 mounted adjacent one end of a resilient member 52'! which normally biases the contact 526 into engagement with the contact 52 l. The other end of the resilient member 521 is mounted in vertical spaced alignment with the base and a thermal responsive member 528 by a headed mounting member or stud 529 the shank of which passes in order through openings in the resilient member 521, spacing collar 53!], insulating washer 53 l, thermal responsive member 528, insulating washer 532, spacing collar 533, insulating member 524, the base 520, insulating washer 534 and terminal member 535. The end of the mounting member or stud 529 is peened over above the terminal member 535 to rigidly mount the assembly, just described, upon the base 520 thereby providing an electrical connection between the terminal 535 and resilient member 521 while insulating the mounting member and the thermal responsive member from the base and from each other.

The base 523 is also provided with an opening therethrough surrounded by an upstanding boss or sleeve 533 which is internally threaded to receive the threaded shank of an adjusting member 531, the lower end of the latter being provided with an insulating button 538 for engagement with the main body portion 528a of the thermal responsive member to thereby adjust the switch for operation at different predetermined temperatures. As before, the adjusting member 531 is preferably provided with a radially extending projection 539 for cooperation with an upstanding axial projection on the sleeve or boss 536 to thereby limit the extent of rotary movement of the adjusting member 531.

The thermal responsive member 528, which is shown per se to an enlarged scale in Figs. 14 and 15, is formed of a bimetallic strip or bar, the metal having the higher coefiicient of expansion being disposed on that side of the member which is adjacent the insulating button 538. One end of the main body portion 528a is provided with an opening therethrough to receive the shank of the stud or mounting means 529. The other end of the main body portion is bent to a substantially inverted J-configuration, as shown in Figs. 13 and 14, thereby providing an extension or leg 52% which extends substantially at right angles with respect to the main body portion 523.

The operation of the switch thus constructed is substantially similar to that of the switches previously described and hence need not be further set forth in detail, it being sufiicient to note that snap action is again provided by the static friction developed between the end of the extension 528i) and the resilient member 527 when the member 528 flexes in response to variations in temperature. In the instant construction, however, this snap action is enhanced over that provided by the thermal responsive members illustrated in the other forms of switches. Ihis is due to the fact that, since the entire thermal responsive member is formed from a unitary bimetallic strip or bar, it flexes throughout its entire length in response to changes in temperature. That is to say, the main body portion 528a and the leg or extension 5281) both flex in response to changes in ambient temperature and, in addition, the curved portion of the member has its radius of curvature altered by flexing thereof thus increasing the movement of the end of the extension 5253b in a direction which exerts longitudinal force upon the resilient member or arm 52?. Consequently, the substantially longitudinal movement of the free end of the thermal responsive member with respect to the resilient member is considerably increased and, since it is this movement which produces the snap action, it will be apparent that a thermal responsive member of this configuration is highly desirable where a relatively large snap action is desired. It will be apparent that the curved portion of the thermal responsive member here illustrated may be altered from that shown in Figs. 13 and 14, if desired. For example, the radius of curvature may be greater or smaller than that indicated in the drawings. Furthermore, this extension portion may be substantially U-shaped rather than substantially J-shaped, if desired, in which event the main body portion 528a would then be located more closely adjacent the resilient member 521 in a switch constructed substantially as shown in Fig. 13, the collar 539 then being replaced by one having a lesser thickness.

Fig. 16 illustrates still another form of thermostatic switch constructed in accordance with this invention. This form of switch comprises a base 629 which may be constructed of any suitable material but is here shown as formed of an insulating material such as porcelain or the like. It

ass-43cc will be readily understood, however, that a metal base may be employed together with suitable insulating washers as in the prior forms of switches. Adjacent one end of the base cze is mounted a relatively stationary contact 62! provided on the lower end of a stud 622, the shank of the stud passing through an opening in the base member 628 and an opening in a terminal member 623 and the latter member, as well as the contact, being secured in place upon the base by deformation of the end of the stud as in the previous forms of the switches illustrated. Adjacent its head, the stud 622 is provided with a thermal responsive member, generally designated 62d, one end of which is provided with an enlarged opening through which the shank of the stud 622 passes with a clearance. An insulating washer 625 is provided between the thermal responsive member and the head of the stud 622, and a similar insulating washer B26 is provided between the other side of the thermal responsive member and a spacing collar 62'! which provides the desired spacing between the thermal responsive member and the base.

The thermal responsive member 624, illustrated in Figs. 16, 17 and 18, comprises a main body portion 624a and an integral extension 6262), the said extension including a portion extending adjacent the said main portion and united thereto by a substantially U-shaped curved portion 6240, the free end 624d of the extension being bent at an angle with respect to the main portion so as to be disposed at substantially right angles with respect to the main portion and directed away from the latter, see Figs. 16 and 17. This thermal responsive member is integrally formed of bimetallic material and is adapted to flex, when subjected to variations in ambient temperature, in a manner such that the free end 624d of the extension 62 3?) moves relative to the main portion 822a in a direction having components extending both substantially perpendicular to and sub-stantially parallel with the main portion as in the previously described forms of thermal responsive elements. In a thermal responsive member having the present configuration, however, the latter component is increased.

The free end 62% of the thermal responsive member is disposed adjacent a contact supporting member 628, one end of which is provided with a contact 629 movable to and from engagement with the contact 52 I. This movable mounting is effected in the instant embodiment by forming the supporting member 628 from flexible or resilient material such as thin metal, or the like, and. supporting the end thereof, which is opposite to that provided with the contact era, in a manner such that the contact 629 is biased into engagement with contact 62!. The illustrated mounting for the movable contact supporting arm 628 is similar to that in the previously described forms of switches and comprises a headed stud 638 which passes serially through the contact supporting arm 628, a spacing collar 63L base 62% and a terminal member 532, the outer end of the stud being peened or otherwise deformed to rigidly secure together the parts just mentioned.

In order to effect adjustment of the operation of a switch of the type just described, a means is provided for adjusting the position of the main portion 624a of the thermal responsive member relative to the base and to the movable contact supporting arm 628. This adjusting means may take any desired form but is here illustrated as being similar to those previously described with respect to Figs.'3, 4, 8, 9, 12 and 13. That is to say, the base 626 is provided with a suitable aperture through which extends a threaded adjusting shaft 333, theouter end of which may be provided with a knob or other means for effecting rotation thereof. The shaft 633 has a threaded engagement with a sleeve-like member 634 which surrounds the aperture through the base and is connected with the latter in any suitable manner. Adjustment of the shaft or screw 533 is limited by providing a radially extending projection 635 thereon which is adapted to abut an axially extending projection 63B upon the sleeve 634. The lower end of the adjusting screw or shaft 633 is provided with an abutment member or button 53! which may be formed of insulating material if so desired. This abutment member or button engages the main portion of the thermal responsive member 62d relatively close to its mounted end so that the freely flexing portion of the thermal responsive member represents a majority of the entire length of the member.

The operation of this form of switch is substantially similar to the operations of the previously described switches, since flexing of the thermal responsive member, in response to variations in temperature, cause the outer end 624a of the extension 6242) to engage the movable contact supporting arm 628 and exert forces thereon in directions both substantially perpendicular and longitudinal with respect thereto. As in the prior forms of switches, the longitudinal force creates friction between the free end of the thermal responsive member and the movable contact supporting arm and hence no movement of said movable contact arm occurs until sumcient energy has been stored in the thermal responsive member, by the flexing thereof, to overcome the static friction between it and the movable contact arm at which time the latter is moved with a snap action. The peculiar configuration of this form of thermal responsive member, which for purposes of brevity may be referred to as substantially hairpin shaped with one leg thereof shorter than the other, increases the amount of longi tudinal movement of the free end thereof so that greater snap action may be achieved with thev same temperature diiferential or equivalent snap action may be achieved with a smaller temperature difierential.

While a number of different embodiments of switches, constructed in accordance with this invention, have been illustrated and described in detail it will be readily apparent that various modifications may be made therein by those;

skilled in the art. For example, While the insulating member between the base and the normally stationary contact, in each of the switches illustrated in Figs. 1 through 9, has been shown as a strip or plate of material extending substantially the length of the base and also serving to insulate the latter from the mounting means for the thermal responsive member and the movable contact, it will be apparent that separate insulating washers may be employed for this purpose or the base itself may be formed of insulating material so that separate insulating washers or members are not necessary as is shown in Fig. 16. Furthermore, while various arrangements of spacing collars and insulating washers have been illustrated for effecting the desired spacing and/ or insulation of the various elements of the switches it will be apparent that the thicknesses of these insulating washers and/or collars may be varied as desired and the separate collars and insulating washers may be replaced by insulating collars of suitable size.

In each of the forms of the switches disclosed in the drawings the thermal responsive members have been indicated as electrically insulated from the contacts of the switch. This is to prevent electrical current from flowing through the thermal responsive member which current might result in altering the operation thereof due to the heating effect produced thereby. In some instances, however, it is desirable that this heating efiect be provided in a thermostatic switch and this may be readily effected, in accordance with the constructions here illustrated and described, by simply omitting the insulation between certain of the parts as will be readily apparent to one skilled in the art.

While each of the forms of switches disclosed in the drawings have been so constructed that the contacts thereof are normally in engagement for temperatures below a predetermined value, and are separated at temperatures equal to or above a predetermined value, it will be readily apparent that the principles of this invention may be readily incorporated in switch constructions operating in the reverse manner. That is, the switches may be so made that the contacts are normally in open position below a predetermined temperature and are operated into engagement at temperatures canal to or above predetermined temperatures. Moreover, while the thermal responsive members have been here indicated as employed for operating electrical switches it will be apparent that similarly constructed elements may be advantageously employed in thermal responsive devices other than electrical switches. These, as well as other changes and adaptations are contemplated as included within the breadth of the present invention which is intended to be limited only by the breadth and scope or the appended claims.

Having thus described my invention, I claim:

1. A thermostatic switch comprising a rigid base member, an electrical contact rigidly mounted upon and insulated from said base member, an elongated resilient member, an elon ated bimetallic member, a common means mounting one end of each of said resilient and bimetallic members upon said base member in superposed alignment with the bimetallic member between said base and resilient members, means cooperating with said mounting means to vertically space said resilient and bimetallic members from each other and from said base member, an electrical contact carried by the other end of said resilient member for engagement with the first mentioned contact, the said bimetallic member including a main portion extending substantially parallel with said resilient member and an integral extension of length sufficient to provide for appreciable flexing thereof disposed at substantially right angles to said main portion and directed towards said resilient member so that flexing of said bimetallic member in response to variations of temperature causes the outer end of said extension to exert both substantially perpendicular and longitudinal forces on the resilient member with the said longitudlnal force producing friction between said ex tension and said resilient member such that flexing of the bimetallic member is prevented from causing movemnt of said resilient member until the said flexing has stored sufiicient energy in the bimetallic member to overcome the static friction whereupon the resilient member and its contact are moved with a snap action relative to the first mentioned contact, and means adjustably mounted on said base member and engaging the main portion of said bimetallic member intermediate its ends to provide an adjustable abutment for the latter thereby regulating the operation of said switch.

2. The combination as defined in claim 1 and in which the means for mounting said bimetallic member comprises a hinged connection between said bimetallic member and the said mounting means.

3. The combination as defined in claim 2 and in which the said hinged connection includes a pair of diametrically extending ears upon said himetallic member received in cooperating recesses in a portion or" the mounting means.

A thermostatic switch comprising a base member, a first electrical contact mounted on said base member, a second electrical contact, an elongated resilient member supporting said second contact on said base member for movement in opposite directions relative to said first contact and normally biasing said second contact for movement in one of said directions, a unitary elongated bimetallic member having two integral portions extending in directions at substantially right angles to each other, means supporting said bimetallic member intermediate said base and resilient member with one of said portions extending substantiall parallel with said resilient member in superposed alignment therewith and with the other of said portions directed towards and adapted to engage said resilient member, the length of said other portion of the bimetallic member being in the order of one-third the length of said one portion thereof, and adjustable means mounted on said base and adapted to engage said one portion of the bimetallic member intermediate its ends, whereby variations in temperature cause both of said portions of the bimetallic member to flex thereby exerting both substantially perpendicular and longitudinal forces upon said resilient member with the said longitudinal force producing friction between the end of said other portion of the bimetallic member and the adjacent surface of the resilient member so that flexing or" the bimetallic member is prevented from causing movement of the resilient member until the said bimetallic member has stored sufiicient energy therein by flexing of both of the said portions thereof to overcome the static friction whereupon the said bimetallic member moves said resilient member and the said second contaicjt relative to the said first contact with a snap ac ion.

CHARLES S. MERTLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,970,224 Cole Aug. 14, 1934 2,020,538 Dennison Nov. 12, 1935 2,103,181 Richmond Dec. 21, 1937 2,109,848 Olds Mar. 1, 1938 2,158,850 Campbell May 16, 1939 2,200,557 Kuhn et al May 14, 1940 2,267,387 Winborne Dec. 23, 1941 2,298,928 Clark et a1 Oct. 13, 1942 2,317,033 Dafforn Apr. 20, 1943 2,409,420 Clark Oct. 15, 1946 2,476,083 Clark July 12, 1949

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