US2715168A - Electric switch - Google Patents

Description

Allg 9, 1955 c. s. MERTLER 2,715,158

ELECTRIC SWITCH Filed Oct. 29, 1952 TTofQA/Eys United States Patent O 'W ELECTRIC SWITCH Charles S. Mertler, Mansfield, Ohio, assignor to Stevens Manufacturing Company, Inc., Lexington, Ohio, a corporation of hio Application October 29, 1952, Serial No. 317,475

21 Claims. (Cl. 200-138) This invention relates to electric switches and, more particularly, to thermostatic switches which operate with a snap action at a predetermined temperature.

An object of the invention is to provide an improved electric switch of the thermal responsive type which does not employ toggle linkages or the like yet operates with a snap action within a narrow temperature differential thereby providing reliable control of an electric circuit or circuits with long contact life and negligible radio and television interference, the switch being capable of carrying substantial current loads although more compact and less expensive to manufacture than conventional switches of comparable current carrying capacity.

Another object of the invention is to provide an improved electric switch wherein the movable contact means is carried by a buckling or over-center spring which is supported only adjacent an edge thereof, the said spring having a convexe-concave curvature between the point of support and the movable Contact means so that the contact means is movable by reversal of the said convexoconcave curvature in response to application of a predetermined force thereto.

A further object of the invention is to provide an im proved electric switch of the type defined in the preceding paragraph wherein the predetermined force for effecting switch actuation is provided by a thermal responsive member as the result of a change in the temperature to which it is subjected.

A still further object of the invention is to provide an improved thermostatic switch of the type defined above in which the thermal responsive member is a bimetallic member, slidably supported adjacent its ends, with a force transmitting member extending from a location between the ends of the bimetallic member to the aforementioned convexo-concave curved portion of the spring member on one side of the latter, a means being provided on the other side of the spring member and engaging the latter to automatically restore it to its initial position when the force exerted by the bimetallic member is reduced below a predetermined value.

Another object of the invention is to provide an electric switch of the type defined above characterized by excellent heat exchange relationship with a body, the temperature of which is to effect switch operation, by virtue of the bimetallic switch operating member having its ends supported in metal-to-metal Contact with the said body while the portion of the bimetallic member intermediate its ends is disposed closely adjacent the said body.

An additional object of the invention is to provide an improved electric switch of the thermal responsive type, as defined above, and in which the contact means on the spring member is movable alternately to and from engagement with two stationary contacts to thereby control two separate electrical circuits.

The invention also has as an object thereof the provision of an improved electric switch of the thermostatic type which is comparatively inexpensive to manufacture,

2,715,158 Patented Aug. 9, 1955 is readily assembled and which may be easily and accurately calibrated for operation in response to predetermined temperature conditions by altering the distance between the spring and birnetallic members without altering the distance between the latter member and the body the temperature of which effects switch operation.

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

Fig. l is an enlarged side View of the presently preferred form of an electric switch constructed in accordance with this invention with certain portions broken away and other portions shown in section to more clearly reveal the construction;

Fig. 2 isa View similar to Fig. 1 but illustrating the movable contact means of the switch in the other of its two positions as the result of flexure of the thermal responsive member;

Fig. 3 is a fragmentary sectional View taken substantially on the line 3 3 of Fig. 1 and illustrating the manner in which an end of the thermal responsive member is supported;

Fig. 4 is a detached plan view of the over-center spring employed in the switch shown in Fig. l; and

Fig. 5 is a detached plan view of a modified form of over-center spring which may be employed in a switch of the type illustrated in Figs. 1-4.

Electric switches embodying the principles of this invention are of the type known as snap acting since the movable contact means thereof are moved from one position to the other relatively rapidly or with a snap action in response to application thereto of a switch operating force. in the presently preferred embodiment, the switch operating force is provided by iiexure or other movement of a thermal responsive member which is subjected to temperature variations although, in its broader aspects, the invention is applicable to switches in which the operating force is supplied by other means.

Rapid movement or snap action of the movable contact means is desirable in switch constructions to prevent contact fluttering or frying and similar defects resulting from relatively slow movement of the movable contact at the instant of contact separation. These difficulties are frequently present in switches operated in response to variations in temperature and are especially pronounced in thermostatic switches of the creep type. Prior efforts to effect a snap action of the movable contact in such switches have, however, generally taken the form of toggle-type linkages or complicated spring constructions which are not only expensive but also require a much wider temperature differential for effecting switch operation so that such switches are less sensitive than the conventional creep type switch. In my co-pending applications, Serial No. 175,696, filed July 25, 1950, and Serial No. 253,777, filed October 30, 1951, I have disclosed and claimed improvement in thermostatic switches of the snap acting type which enable the desired rapid movement of the movable contact means to be eected through the utilization of a single over-center spring member thereby reducing the cost and at the same time providing a more reliable operation with a narrow temperature differential. The switches constructed in accordance with this invention employ the same principle of a single over-center spring member but the spring members are of different form and are embodied in mechanisms of different construction, thereby providing improved operation and further economies in manufacture.

The over-center or buckling spring member or element 10 employed in the presently preferred embodiment of this invention is formed from relatively thin gauge spring metal such as tempered steel, brass, Phosphor bronze, or the like and has a shape iu the nature of a parallelogram with rounded corners so that it is generally elliptical in configuration as viewed in plan, see Fig. 4. Such a member may be stamped from sheet or strip stock and simultaneously with this operation it is apertured adjacent one end,` as indicated at 11, for receiving a mounting post as hereinafter explained. A similar aperture 12 may also be provided adjacent the other end of the member to facilitate securing a contact means thereto. Simultaneously with this stamping, or subsequent thereto, the central portion of the spring is provided with a convexoconcave dished disk portion 13 by stretching the central portion of the spring with respect to the end portions thereof, this operation being performed by means of for it to prefer one of its curved positions over the other of those positions. In addition to the aforementioned curvature, the central portion of the convexe-concave portion 13 of the spring is also preferably provided with a small dimple or depression 14 on one side, and a corresponding projection on the opposite side, as will be apparent from Figs. 1 and 2 for a purpose hereinafter described.

An electric switch, employing a spring member 10 of the type just described, is illustratedin Figs. 1 and 2 as comprising a base member 14 which is provided intermediate its ends with spaced openings 15, 16 and 17 for mounting of the spring member and the stationary contactsy of the switch. Thus as shown in the drawings, the reduced diameter portion 18 of a mounted post 19 extends through the opening 15 in spaced relationship thereto and through an opening in the lower portion of an angularly shaped terminal member 20, the post and terminal member being secured together by peening or otherwise upsetting the outer end of the reduced portion 18. The` lower part of the terminal post 19 likewise hasv a reduced diameter portion extending through a resilient member 21, the aperture 11 of the spring member 1t), and. a washer 22, these parts being secured together by peening or otherwise upsetting the lower end 23' of the lower reduced diameter portion of the terminal post or stud 19.

The resilient member 21 is preferably a spring arm formed of metal or other suitable material and is so disposed that its free end rests upon the raised portion opposite the dimple 14 on the spring member 10 and exerts sutiicient force thereon so that the convexo-concave portion 13 of the springl member 10 is disposed as shown in Fig. l. The resilient member 21, however, is capable of flexing sufciently to allow the curvature of the convexo-concave disk portion 13 of the spring member 10- to be reversed, as hereinafter described, thereby allowing the spring member to move to the other of its positions as indicated in Fig. 2, the member 21 acting to restore the spring member 1t). to its initial position when the force causing reversalL of curvature of the spring member 10 is removed.

The free end of the spring member 1.0 is, provided. with an electric contact means which preferably cornprises oppositely disposed surfaces or buttons 24- and 25- of` silverV or other suitable Contact material secured in any conventional manner to the free end of the spring 10. For example, the surfaces or buttons 24 and 25 may have reduced diameter portions extending into the aforementioned aperture 12 in the spring member. It is not, however, necessary that the spring member be provided with such an aperture since the contact means 24, 2S may be secured to the spring member 10 by spot welding, brazing, or the like.

The contact means, formed by the contact surfaces or buttons 24 and 25 on the spring member 1t), is adapted to alternately engage one or the other of two stationary contacts thereby enabling the switch to control two separate electrical circuits. Thus, as shown in the drawings, the opening 16 through the base member 14 is substantially aligned with the contact means 24, 25 and receives the reduced diameter portion 26 of a contact supporting member or post 27. The upper end of this reduced diameter portion 26 extends through the lower leg of an angular terminal bracket or member 28, the post 27 being secured to the terminal member 28 by peening or otherwise upsetting the outer end of the reduced diameter portion 26 of the` post. The member or post 27 may have its lower surface provided with a suitable contact material 29, such as silver or the like, for cooperation with the contact member or button 24. The second stationary contact is provided by a contact arm or member 30 which extends in spaced relationship with respect to the contact member or post 27 and in alignment with the latter and with the movable contact means 24, 25. This contact arm or member, the surface of which may be provided with silver or other suitable material, is secured to the lower end of a terminal post 31 by suitable means. For example, as shown, a reduced diameter portion of the post extends through an opening in the contact arm with the outer end of this reduced diameter portion peened, over or otherwise upset, a washer preferably being provided between the member 30 and the upset end of post 31 as will be readily understood. The upper end of the terminal post or member 31 is likewise of reduced diameter, as indicated at 32, and extends through the opening 17 at the base member 14, the terminal member or post 31 being secured to a terminal bracket 33 in a manner similar to that in which brackets 20 and 28 are secured.

The base member 14 is here shown as formed of metal or other conductive material and consequently the openings such as 15, 16 and 17 for the terminal members are of larger diameter than the portions of the terminal members extending therethrough. For the same reason, sheets of insulating material, such as 34 and 35, are provided on either surface of the base member 14 extending between the latter and the enlarged portions of the terminal posts and between the base and the legs of the terminal brackets to thereby insulate the terminals from the base and from each other as will be readily apparent from the drawings. ln place of employing such sheets of insulating material it will be evident that separate insulating washers may be employed or, if desired, the base member 14 may in some instances itself be formed of insulated material, in which event the insulating plates or sheets 34 and 35 need not be provided and the openings 15, 16 and 17 through the base member may be made of substantially the same diameter as the portions of the terminal posts extending therethrough.

The means for operating the switch by effecting reversal of the curvature of the spring member 1t) is preferably a thermal responsive member, a portion of which moves in response to a change in temperature. In the illustrated form, this thermal responsive member is shown as an elongated bimetallic strip or member 36, the ends of which are slidably supported in a manner such that the member is in good heat exchange relationship with respect to a. body whose temperature is to effect. switch operation. As shown, the bimetallic member 36l is substantially rectangular and has its ends bifurcated, as

will be seen from Fig. 3, thereby providing spaced projecting ears or portions such as 37 and 38 at each end of the member. The pair of ears or projections 37 and 38 at one end of the member 36 straddle a reduced diameter portion of a supporting post or member 39 and the ears or projections at the other end of member 36 straddle a corresponding reduced diameter portion on a supporting member or post 40, the ears or projections 37 each being provided with a raised boss or projection such as 41 which slidably rest upon a planar surface shoulder of the corresponding supporting post or member. The projections or bosses 41 may be formed by indenting the opposite sides of the ears 37, 38 by means of a suitable die or may be otherwise provided, the purpose of these projections being to provide a relatively small area of contact between the ends of the bimetallic member and its supports so that both ends of the bimetallic member are free to partake of sliding movement relative to their supports in response to changes of temperature.

Intermediate its ends, the bimetallic member 36 is provided with a recess or dimple 42 which, in the assembled form of the switch, is in alignment with the recess or dimple 14 of the spring member 10. Received in these two recesses and supported thereby is a motion transmitting member or pin 43 which is preferably formed of ceramic or other electric insulating material. Alternatively, the lower end of the force transmitting member or pin 43 may be rigidly secured to the bimetallic member 36 in which event the recess or dimple 14 may be omitted from the spring member 10.

The supporting members 39 and 40 for the bimetallic member 36 are adjustable relative to the base 14 to thereby adjust the position of the bimetallic member 36 relative to the spring and correspondingly adjust the switch operation. For this purpose, the supporting members 39 and 40 are externally threaded and are screwed into threaded openings extending through the base member 14. it will be apparent therefore that by adjusting the positions of the posts 39 and 40 the amount of force required to cause reversal of curvature of the spring member 10, from the position shown in Fig. 1 to the position shown in Fig. 2, may be readily predetermined thereby Calibrating the switch for operation at the corresponding temperature. After the switch has thus been calibrated, the adjustment may be maintained without change by placing a drop of solder or the like 44, between the supporting posts 39 and 40 and the base 14.

A switch constructed as here illustrated and described is characterized by havirg an excellent heat exchange relationship with a body Whose temperature is to effect the switch operation since the supporting posts or members 39 and 4l) may be placed in engagement with that body which is here designated as B. The switch may be maintained in engagement with such a body by any suitable means. In the illustrated embodiment, this retention of the switch is effected by making the members or posts 39 and 40 tubular and passing mounting screws, such as 45, 46, therethrough with the lower ends of the screws threaded into tapped openings 47 in the body B. By this construction the bimetallic member 36 of the switch is maintained in lirm metal-to-metal contact with the body B, whose temperature is to effect the switch operation, this contact being from the surface of the body through the supporting members or posts 39 and 40 to the ends of the bimetallic member where they rest upon the planar surfaces of the supporting members or posts. Moreover, the unsupported length of bimetallic member is closely adjacent the body B so that the heat radiating therefrom, or moving therefrom by convection, is directly incident upon and effects operation of the bimetallic member.

It will also be apparent that, by the illustratcd construction, adjustment of the switch through the aforementioned adjustment of posts 39 and 40 relative to the base member 14 does not alter the relationship of the bimetallic member 36 with respect to the body B so that the member 36 remains at-the same distance from the body B regardless of the adjustment of the switch strueture. Hence, the adjustment or calibration of the switch operation is not complicated by a variation in the response of the bimetallic member for each different position of the latter relative to the spring member 19.

The illustrated switch is designed to move the contact means 24, 25 from the position shown in Fig. l to the position shown in Fig. 2 upon a predetermined elevation of temperature. Therefore, the position of the switch shown in Fig. l can be said to comprise the cold position of the switch. In this position, the contact 24 is in engagement with the contact surface 29 and consequently a circuit connected with the terminal members 20 and 28 will be closed through the spring member 10 and contacts 24 and Z9, while a circuit through the contact member 3i) will be open. When the temperature of the body B is elevated to a value corresponding to the operating point of the switch, the bimetallic member 36 will have flexed or curved to a position substantially as shown in Fig. 2, this movement being unrestrained since the ends of the member 36 are slidably supported. The movement of the central portion of the bimetallic member is transmitted through the member or pin 43 to the central portion of the spring 10, thereby causing the convexoconcave portion 13 to reverse its curvature and snap through center to a position substantially as shown in Fig. 2, the spring arm 21 yielding suiciently to permit this movement. Since the spring member 10 is supported at only one end thereof, the other end, which carries the contact means 24, 25, will also move with a snap action from the position shown in Fig. 1 to the position as shown in Fig. 2 so that the contact 2S new engages the Contact 30, while the contact 24 is moved from engagement with the contact 29. Therefore, the circuit through the spring member 10 to the contact 29 is now broken, while a circuit is established through the spring member 10 to the contact arm 30.

When the temperature of the body B drops below the predetermined value which caused the ilexure of the bimetallic member 36 to the position shown in Fig. 2, the bimetallic member will straighten to substantially its position as shown in Fig. 1, this movement being unrestrained since, as noted above, the ends of the bimetallic member are slidably supported. As the member 36 returns to its initial position the force exerted thereby through the force transmitting member or pin 43 is reduced until it is less than the force exerted by the spring arm 21 and at this time the latter causes the convexoconcave portion 13 of the spring 10 to again reverse its curvature and return to the position as shown in Fig. 1. This results in movement of the contact 25 from engagement with the contact arm 30 and the contact 24 is again engaged with the contact 29, the movement of the contacts 24, 25 being eiected with a snap action.

It will now be apparent that a switch of the type here illustrated and described provides a snap acting movement of the movable contact means with a minimum of movable parts. Moreover, the parts of the switch may be easily assembled and the assembled switch accurately calibrated to provide reliable contact operation in response to a relatively narrow temperature differential. Furthermore, by employing a construction in which the ,bimetallic member is substantially unrestrained the reliability of operation is improved since erratic operations, such as are likely to occur in switches where the bimetallic member is at least in part rigidly mounted, are eliminated.

Fig. 5 illustrates a somewhat different embodiment of a spring member which may be employed in a switch of tially diametrically opposite the aperture 49, is a contact portion or button t) which is secured to the member 48 in any suitable manner. The spring member 48 has a convexo-concave curvature, provided as described for the portion 13 of the member l0, and hence constitutes an over-center or buckling spring. The entire member 48 may be curved to the convexoconcave curvature or, if desired, the member may have a substantially planar portion adjacent the edge with the central portion having the aforementioned curvature.

The spring member 48 is adapted to be employed in a switch constructed in the manner illustrated in Figs. l and 2 by substituting the member 48 for the member l0 now shown therein, the member 48 having a dimple or de pression 5l centrally of the lower surface thereof for reception of the force transmitting member or pin 43. Alternatively, as described above, the lower end of the force transmitting member or pin 43 may be rigidly secured to the thermal responsive member 36 in which event the central depression 5l may be omitted from the spring member 48. A switch employing the spring member 48 operates in the same manner as does the switch employing the spring member It?.

Although the switches of this invention have been specifically described and illustrated as being of the type adapted to control two separate circuits it will be apparent that a similar construction may also be used to control but a single circuit, When so utilized the contact and the associated terminal member 33 may be omitted but some abutment means should preferably be provided in the position now occupied by contact 30 to prevent excess movement of the spring member. It will also be apparent that, although the switch has been described as operating upon an elevation of temperature, it can also be so constructed as to operate upon a lowering of the temperature. In addition, it will be evident that many advantages of the switch construction here shown and described can be achieved when the switch operating member is of different shape than that shown or even is a means other than a thermal responsive device. That is to say, in some instances the bimetallic member 36 may be omitted and the pin 43 extended to act as a push button or for operation by other means. These and other changes in the switch construction are all considered as coming within the ambit of this invention and hence the latter is not to be construed as limited to the exact details illustrated and described except as may be required by the spirit and scope of the subjoined claims.

Having thus described the invention, I claim:

1. An electric switch comprising an over-center spring having a disk portion provided with a convexo-concave curvature adapted to be reversed upon the application of a predetermined force thereto, means supporting said spring at a location adjacent the circumference of the disk portion thereof, contact means connected with said spring adjacent the circumference of the disk portion thereof and diametrically opposite said supporting means location and free to move from one to the other of two positions upon reversal of curvature of said disk portion of said spring, a stationary contact adapted to be engaged by said contact means in one position of said spring, switch operating means including a portion engaging said spring at substantially the center of said disk portion and on one side thereof and adapted to effect reversal of the direction of curvature of said disk portion thereby rapidly moving said contact means from one to the other of its two positions, and means engaging the other side of said disk portion of said spring substantially at the center thereof and applying a restoring force thereto for return of said Spring and Contact means to their initial positions.

2. An electric switch comprising an over-center spring having a disk portion provided with a convexo-concave curvature adapted to be reversed lupon application of a predetermined force thereto, means supporting said spring at a single location adjacent the circumference of said disk portion thereof, contact means connected with said spring adjacent the circumference of said disk portion and diametrically opposite said supporting means location and free to move from one to the other of two positions upon reversal of curvature of said disk portion of said spring, a stationary contact adapted to be engaged by said contact means in one position of said spring, thermal responsive means having a portion adapted to move relative to said spring in response to changes in temperature and exert force on one side of said disk portion of said spring to effect reversal of the direction of curvature thereof thereby rapidly moving said contact means from one to the other of its two positions, and means engaging the other side of said disk portion of said spring and applying a restoring force thereto for return of said spring and contact means to their initial positions when the force exerted by said thermal responsive means is reduced below a predetermined value.

3. An electric switch as defined in claim 2 and further comprising threaded means cooperating with the said thermal responsive means and the supporting means for said spring to bodily move one relative to the other to thereby adjust the operation of the switch.

4. An electric switch comprising an over-center spring having a convexe-concave disk portion adapted to reverse its curvature upon application of a predetermined force thereto, means supporting said spring at a single location adjacent the circumference of said disk portion, contact means connected with said spring adjacent the circumference of said disk portion and diametrically opposite to the location of the supporting means and free to move from one to the other of two positions upon reversal of curvature of said disk portion, a stationary contact adapted to be engaged by said contact means in one position of said spring, a bi-metallic member adapted to move relative to said spring in response to changes in temperature and exert force on one side of the disk portion thereof to effect reversal of the direction of curvature of said disk portion thereby rapidly moving said contact means from one to the other of its two positions, and means engaging the other side of said disk portion and applying a restoring force thereto for return of said spring and contact means to their initial positions when lthe force exerted by said bimetallic member is reduced below a predetermined value.

5. A thermostatic switch comprising a base member, a normally stationary contact supported on said base member, a spring member having a convexo-concave disk portion intermediate its ends adapted to snap through center when a force is applied thereto, electric contact means supported on said spring member adjacent the circumference of said disk portion, means supporting the said spring member upon said base member in a position such that the said contact means is movable to and from engagement with the first-mentioned contact in response to reversal of curvature of said convexo-concave disk portion, means including a thermal responsive member supported for movement in response to a change of temperature and having a portion in continuous engagement with said spring member substantially centrally of said convexo-concave disk portion on one side thereof, and resilient means on the other side of said spring member engaging the disk portion and acting to restore said spring member to its initial position when the force exerted by said thermal responsive member is reduced below a predetermined value.

6. A thermostatic switch as defined in claim 5 wherein the said resilient means is a spring arm having one end secured to said base member and the other end engaging substantially the center of said convexo-concave disk portion of said spring member.

7. A thermostatic switch comprising a base member, a normally stationary contact supported on said base member, a spring member having a convexo-concave disk portion adapted to snap through center when a force is applied thereto, electric contact means supported on said spring member adjacent the circumference of said disk portion, supporting means mounted upon said base member and connected to said spring member at a location substantially diametrically opposite said contact means in a manner such that the said contact means is movable to and from engagement with the first-mentioned contact in response to reversal of curvature of said disk portion, means including a thermal responsive member supported for movement in response to a change of temperature and having a portion in continuous engagement with said spring member substantially centrally of said convexoconcave disk portion on one side thereof, resilient means on the other side of said spring member engaging substantially the center of said disk portion and acting to restore said spring member to its initial position when the force exerted by said thermal responsive member is reduced below a predetermined value, and means to change the position of said base member relative to said thermal responsive member to thereby adjust the operation of the switch.

8. A thermostatic switch comprising a base member, a normally stationary contact supported on said base member, a metallic spring member having a convexoconcave disk portion intermediate its ends adapted to snap through center when a force is applied thereto, electric contact means supported on said spring member adjacent one end of the latter, means supporting the other end of said spring member upon said base member in a position such that the said contact means is movable to and from engagement with the first-mentioned contact in response to reversal of curvature of said convexoconcave disk portion, a thermal responsive member supported for movement in response to a change of temperature, a motion transmitting connection between said thermal responsive member and said spring member substantially centrally of said convexo-concave disk portion on one side thereof, and resilient means on the other side of said spring member engaging substantially the center of said disk portion and acting to restore said spring member to its initial position when the force exerted by said thermal responsive member is reduced below a predetermined value.

9. A thermostatic switch as defined in claim 8 and further comprising a second normally stationary contact, and means supporting the said second contact on said base member adjacent said contact means on the spring member in a position such that the said contact means engages the said second contact member when the spring member moves the contact means from engagement with the first-mentioned contact.

10. A thermostatic switch comprising a base member, a normally stationary contact supported on said base member, a metallic spring member having a convexoconcave disk portion intermediate its ends adapted to snap through center when a force is applied thereto, electric contact means supported on said spring member adjacent one end of the latter, means supporting the other end of said spring member upon said base member in a position such that the said Contact means is movable to and from engagement with the stationary contact in response to reversal of curvature of said conveXo-concave disk portion, a bimetallic member supported in spaced relationship to said spring member, a motion transmitting connection between said bimetallic member and said spring member substantially centrally of said convexoconcave disk portion on one side thereof, and resilient means on the other side of said spring member engaging substantially the center of said disk portion and acting to restore said spring member to its initial position when the force exerted by said thermal responsive member is reduced below a predetermined value.

l1. A thermostatic switch as defined in claim l0 and further comprising means to alter the distance between said base member and said bimetallic member to thereby adjust the operation of the switch.

12. An electric switch comprising an over-center spring having a convexe-concave disk portion adapted to be reversed upon the application of a predetermined force thereto, means supporting said spring at only a single location adjacent the circumference of said disk portion, contact means connected with said spring adjacent the circumference of said disk portion and diametrically opposite said single location and free to move, a first stationary contact normally engaged by said contact means, a second stationary contact electrically insulated and spaced from the said first stationary contact and adapted to be engaged by the said contact means when the latter is moved from engagement with the said first stationary contact, thermal responsive means having a portion adapted to move relative to said spring in response to changes in temperature, motion transmitting means extending between the said portion and said spring at a location on one side thereof and exerting force on substantially the center of the disk portion when the said portion of the thermal responsive means moves to effect reversal of the direction of curvature of the disk portion of the spring thereby rapidly moving said contact means from engagement with said first stationary contact and into engagement with said second stationary contact, means engaging the other side of said spring member substantially centrally of the disk portion and acting to restore said spring member and contact means to their initial positions when the force exerted by the thermal responsive member is reduced below a predetermined value, and separate terminal members connected respectively with said first and second contacts and with said contact means whereby the switch is adapted for connection in two separate electrical circuits for control thereof.

13. A thermostatic switch comprising a base member, a 'first contact mounted on said base member, a second contact supported on said base member in spaced alignment with said first contact, an over-center spring member with a convexo-concave disk portion intermediate its ends adapted to snap through center when a force is applied thereto, electric contact means supported on said spring member adjacent the circumference of the disk portion, means adjacent the circumference of the disk portion and supporting the said spring member upon said base member in a position such that the said contact means on the spring member is disposed between said first and second contacts for alternate movement from engagement with one and into engagement with the other of said contacts in response to reversal in the curvature of said conveXo-concave dislf` portion of said spring means, a bimetallic member, a force transmitting member extending between said bimetallic member and the said convexe-concave disk portion of said spring member at one side thereof to effect movement of the latter in response to iiexure of the bimetallic member as the result of a change of temperature thereby moving the said contact means from engagement with one of the stationary contacts and into engagement with the other of the stationary contacts, and means engaging the said convexoconcave disk portion of said spring member on the other side thereof and acting thereon to restore said spring member and the contact means thereon to their initial positions when the exure of the said bimetallic member is reduced below a predetermined value.

i4. A thermostatic switch comprising a base member, a rst contact mounted on said base member, a second contact supported on said base member in spaced alignment with said first contact, a metallic spring member of generally elliptical shape with a convexo-concave disk portion intermediate its ends adapted to reverse its direction of curvature when a force is applied thereto, electric contact means supported on said spring member adjacent one end thereof, means supporting the other end of said spring member upon said base member in a position such that the said Contact means is disposed between said first and second contacts for alternate movement from engagement with one and into engagement with the other of said contacts in response to a reversal in the curvature of said convexo-concave disk portion of said spring means, a bimetallic member, a force transmitting member carried by said bimetallic member intermediate its ends and engaging the said convexe-concave disk portion of said spring member on one side thereof to effect movement thereof in response to exure of the bimetallic member as the result of a change of temperature thereby moving the said Contact means from engagement with one of the stationary contacts and into engagement with the other of the stationary contacts, and resilient means engaging the said conVexo-concave disk portion of said spring member on the other side thereof and acting thereon to restore said spring member and the contact means thereon to their initial positions when the ilexure of the said bimetallic member is reduced below a predetermined value.

15. A thermostatic switch comprising a base member, a first contact mounted on said base member, a second contact supported on said base member in alignment with said hrst contact and spaced from the latter and from said base member, a metallic spring member having a convcxo-concave disk portion adapted to be reversed when a force is applied thereto, electric contact means supported on said spring member adjacent the circumference of said disk portion, mounting means upon said base member engaging said spring member at a single location adjacent the circumference of said disk portion and spaced diametrically from said contact means to support said spring member in a position such that the said contact means thereon is disposed between said first and second contacts for alternate movement from engagement with one contact and into engagement with the other conact in response to a reversal in the curvature of said disk portion of said spring member, a bimetallic member, means connected to said base member and providing a support on which said bimetallic member rests in spaced f.

relationship to said spring member and in a position for intimate heat exchange relationship with a body whose temperature is to be controlled, a force transmitting member carried by said bimetallic member and engaging the said disk portion of said spring member on one side thereof to effect movement thereof in response to flexure of the bimetallic member as the result of a change of temperature thereby moving the said contact means from engagement with one of the stationary contacts and into engagement with the other of the stationary contacts, and resilient means engaging the said disk portion of said spring member on the other side thereof and acting thereon to restore said spring member and the Contact means thereon to their initial positions when the exure of the said bimetallic member is reduced below a predetermined value.

16. A thermostatic switch as defined in claim l5 wherein the support for the bimetallic member comprises means adjustably connected with said base member and having a surface on which said bimetallic member is slidably supported.

17. A thermostatic switch as defined in claim l5 wherein the said resilient means acting to restore said spring member is a spring arm secured at one end to said base member and having the other end in engagement with the said disk portion of said spring member.

1S. A thermostatic switch as defined in claim 15 wherein the said force transmitting member is a pin, the ends of which are supported in recesses in said disk portion of said spring member and bimetallic member.

19. A thermostatic switch comprising a base member, a iirst contact mounted on said base member, a second contact supported on said base member in alignment with said first contact and spaced from the latter and from said base member, a metallic spring member of generally elliptical shape with a convexe-concave disk portion i11- termediate its ends adapted to reverse its direction of curvature when a force is applied thereto, electric contact means supported on said spring member adjacent one end thereof, means supporting the other end of said spring member upon said base member in a position such that the said contact means on the spring member is disposed between said rst and second contacts for alternate movement from engagement with one and into engagement with the other in response to a reversal in the curvature of said convexo-concave disk portion of said spring member, an elongated bimetallic member slidably supported adjacent its opposite ends and adapted to be mounted in metal-to-metal contact with a body whose temperature is to be controlled, a force transmitting member carried by said bimetallic member intermediate its ends and engaging the said convexe-concave disk portion of said spring member on one side thereof to effect movement thereof in response to flexure of the bimetallic member as the result of a change of temperature thereby moving the said contact means from engagement with one of the stationary contacts and into engagement with the other of the stationary contacts, and resilient means engaging the said convexo-concave disk portion of said spring member on the other side thereof and applying a restoring force thereto for automatic return of said spring member and the contact means thereon to their initial positions when the exure of the said bimetallic member is reduced below a predetermined value.

20. A thermostatic switch comprising a base member, an electrical contact supported by said base member, a metallic spring member having a convexo-concave portion adapted to reverse its direction of curvature when a force is applied thereto, electric contact means supported on said spring member adjacent a free edge thereof and in operative relationship with respect to said rst mentioned electric contact, means spaced from said electric contact means and adjacent the free edge of said spring member for supporting said spring member in a position such that the said Contact means thereon will move alternately into engagement with or disengagement from said first mentioned contact in response to a reversal in the curvature of said convexo-concave portion of said spring member, spaced adjustable supporting members carried by said base member and extending from the side thereof on which are located the first mentioned contact and said spring supporting means, an elongated bimetallic member supported at its opposite ends by said spaced adjustable supporting means carried by said base whereby adjustment of said means will vary the relationship between said bimetallic member and said spring member, and a. force transmitting member carried by said bimetallic member intermediate its ends and engaging the said convexo-concave portion of said spring member on the other side thereof and applying a force thereto in the opposite direction for automatic return of said convexo-concave portion to its initial position when the flexure of said bimetallic member is reduced below a predetermined value.

21. A thermostatic switch as defined in claim 2O and wherein said spaced adjustable supporting means include posts having externally threaded portions screwed into threaded openings in said base member and spaced from said threaded portion and being provided with circumferential recesses while said bimetallic member has its opposite ends of fork-shaped configuration extending into said recesses and embracing said posts whereby adjustment of said posts varies the spacing relationship between said base member and said bimetallic member.

References Cited in the le of this patent UNTTED STATES PATENTS

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