US2813175A - Electrical snap switch - Google Patents

Description

Nov. 12, 1957 w. HERING 2,813,175

ELECTRICAL SNAP SWITCH Filed June 7, 1956 4 Sheets-Sheet l jzvrnfor Murnau Halen/q Arr-a nui 1 Nov. 12, 1957 w. HERING 2,813,175

ELECTRICAL SNAP SWITCH Filed June 7, 1956 4 Sheets-Sheet 2 inzien/or I TTURNEY Nov. 12, 1957 w. HERING 2,813,175

ELECTRICAL SNAP SWITCH Filed June 7, 1956 4 Sheets-Sheet 3 .7nvenfar WALT/45A Hennig Nov. 12, 1957 w. HERING ELECTRICAL SNAP SWITCH 4 Sheets-Sheet 4 Filed June 7, 1956 Javea/ar WALTHER. Humm/q l fb. r

. nent deformation coincident to overheating;

States My invention relates to an electrical snap switch of the type including a contact-carrying spring leaf which is prestressed by a longitudinal compression stress and, therefore, tends when brought to an instable central position to snap to one or the other of two end positions.

Snap switches of this kind are particularly adapted for actuation by temperature-responsive elements, such as bimetal strips, for temperature-controlling purposes.

lt is an object of my invention to provide a snap switch of this type in which the flexibility of the spring leaf is localized to a certain section or sections for the purpose of rendering the snapping action more abrupt and reliable.

Other objects of my invention are to so mount the contacts of the snap switch as to effect their separation in transit by arresting one of the contacts at an instant when both contacts while in engagement move with high speed; to provide means protecting the bimetal strip from permaand to provide means applicable where the snap switch serves for ternperature-control purposes for increasing the sensitivity of the snap switch to variations of temperature by imparting additional heat to the temperature-responsive element.

`Further objects of my invention will appear from the detailed description of a number of embodiments following hereinafter with reference to the drawings. It is to be understood, however, that the terms and phrases used in such detailed description have been chosen for the purpose of illustrating the invention rather than that of restricting or limiting the same, the features of novelty for which patent protection is sought being pointed out in the appended claims.

in tr e drawings,

Fig. l is an elevation, partly in section, of a snap switch used to control the temperature of an electric iron, the snap switch being of a type in which the contact carried thereby and the point of engagement of the actuating force with the spring leaf is located in a stilfened central section thereof,

Fig. 2 is a plan View of the snap the adjusting knob being omitted,

Fig. 3 is a more or less diagrammatic elevation of a modified snap switch of a type in which the point of engagement of the actuating force only is located in the stiffened central section of the spring leaf, whereas the contact carried by the spring leaf is spaced from such stiffened section, the neutral position of the spring being shown in full lines, whereas its end positions are shown by dotted lines,

Fig. 4 is a more or less diagrammatic elevation of .a snap switch differing from that shown in Fig. 3 by the provision of abutments for the spring leaf,

Fig. 5 illustrates the same switch shown in Fig. 4 with the spring assuming another position,

Fig. 6 is an illustration similar to that of Figs. 3, 4 and 5 of a snap switch in which the actuating member is rigidly connected with the spring leaf,

Fig. 7 illustrates a snap switch similar to that shown 1n switch shown in Fig. 1,

atent Oiiice 2,813,175 Patented Nov. 12, 1957 Fig. 4 in which the actuating member engages the spring at a point spaced from the stitfened section of the spring,

Fig. 8 is an elevation of a snap switch similar to that shown in Fig. 3 in which the actuating member is formed by a laterally projecting arm,

Fig. 9 is a snap switch similar to that shown in Fig. 6 and differing therefrom in that the stiifened section has the same thickness as the more resilient end sections of the spring leaf,

Fig. 10 illustrates a snap switch similar to that shown in Figs. 6 and 7 in which the contact carried by the support is mounted in a resilient and adjustable manner.

Fig. 11 shows a snap switch including a spring leaf having two spaced stiffened sections,

Fig. 12 shows a snap switch in which the actuating member is formed by a bimetal strip stiifening a central section of the spring leaf,

Fig. 13 is an elevation of a snap switch in which one of the ends of the spring leaf only is rigidly secured to the support, the other end being secured to a bimetal strip,

Fig. 14 illustrates the switch shown in Fig. 13 with the element thereof assuming another position,

Fig. 15 is an elevation of a switch in which one of the contacts is carried by the actuating member and acts on the spring to move same through the instable central position,

Fig. 16 is a cross section through a switch similar to that shown in any one of the Figs. 3, 4 and 5 in which the actuating member comprises a pair of relatively movable elements connected by a spring,

Fig. 17 is a cross section through a switch similar to that of Fig. 16 in which a bimetal strip acting on the actuating member is connected to the support by means of a spring,

Fig. 18 is a plan View of an elongated switch spring leaf in which the more resilient sections are rendered more exible by lateral recesses,

Fig. 19 is a plan view of a switch spring leaf in which the more resilient sections are each rendered more flexible by a plurality of recesses,

Fig. 20 is an elevation of a snap switch in which the central section of the switch spring leaf is stiflened by lateral flanges,

Fig. 2l is a bottom View of the spring leaf shown in Fig. 20, cross sections of the spring leaf being inserted in such figure,

Fig. 22 is an elevation of a Switch similar to that of Fig. 1 and serving the same purpose as the same,

Fig. 23 is a plan View of the switch shown in Fig. 22, and

Fig. 24 is an end view of the switch shown in Fig. 22 viewed from the left.

On the bottom plate of an electric iron a column composed of blocks 31, 32 and 33 interconnected by suitable screws is mounted. Holders 34 and 35 carrying terminal connecting screws are interposed and clamped between such blocks. A spring leaf 36 is interposed and clamped between the block 33 and the holder 35 and extends laterally from the column and carries a substantially horizontally disposed elongated frame 37 of a suitable insulating material, such as ceramic material, for resilient upward and downward movement. The blocks 31, 32 and 33 likewise consist of a suitable insulating material. An elongated switch spring leaf 38 is carried by the frame 37, the ends of the spring leaf being rigidly clamped to the end members of the frame, for instance by rivets 39 and 40, the spring leaf 38 extending across the opening of the frame. A transverse bridge member 41 is carried by the side members of the frame being so disposed as to span the opening of the frame and the spring leaf thereabove. The bridge member is provided with a tapped bore ac commodating an adjusting screw 42 constituting an abutment limiting the deflection of the spring leaf 38.

When the spring leaf 38 is disassembled from the frame 37 and is in relaxed condition, the distance of the holes serving to accommodate the rivets 39 and 40 is somewhat larger than the distance between the rivets 39 and 4t). Therefore, when the spring leaf 33 is fixed to the supporting frame 37 it will be pre-stressed by a longitudinal compression stress producing a tendency of the spring 38 to snap from an instable central position to one or the other of two end positions. For enabling the spring to be so pre-stressed its end section disposed at the left with reference to Fig. l is formed with corrugations. For a purpose which will be described later its central section spaced from the ends of the spring leaf is stiffened so as to be practically non-resilient. Hence, the spring leaf includes two end sections of greater resiliency and a central section therebetween of lesser resiliency. When the spring snaps to its upper end position its stiffened section 43 engages the adjustable stop 4Z. When the spring leaf snaps to its lower position, however, a contact 44 secured to the stiffened section of the spring leaf at the bottom thereof engages a countercontact 45 which is mounted on the support 37, preferably by resilient means. in the embodiment of the present invention illustrated in Fig. l such resilient means is formed by a spring leaf 46 extending beneath the frame 37 and having its left end secured thereto by suitable means not shown, whereas the right end of the spring leaf 46 is provided with a tapped bore engaged by a threaded stem of the contact 45, such threaded stem carrying a counternut 27 for the purpose of adjustment. The contact 45 is located within the opening of the frame 37 beneath the contact 44 carried by the stilfened section of the spring 38. A exible conductor 47 connects the spring leaf 46 with the terminal holder 34. The other terminal holder 35 is electrically connected with the contact 44 through the intermediary of the spring leaf 36 and the spring leaf 38.

Moreover, the frame 37 is provided with a bore accommodating an actuating member in form of a pin 48 which may engage the right hand end of the stiifened section 43 of the snap spring leaf from below and is controlled in dependence on the temperature by a temperature-detecting element. As long as the temperature is below a predetermined limit the spring leaf 38 assumes a position beneath its instable central position and, therefore, urges its contact 44 against the contact 45 whereby the circuit for heating the electric iron is established. When the temperature of the bottom plate 36 of the electric iron exceeds a certain limit, however, the temperature-detecting element will lift the stiffened section 43 at the right hand end thereof. During the initial phases of this lifting operation the longitudinal compression stress set up in the spring leaf 38 and more particularly in the corrugations thereof holds the contact 44 in engagement with the contact 45 while the stiffened section 43 of the leaf is slightly tilted by the ascending pin 48. This tilting motion continues until the spring lleaf passes through its neutral condition and abruptly snaps upwardly away from the Contact 45 and the pin 48 and engages the stop screw 4Z, whereby the contacts 44 and 45 are separated interrupting the circuit heating the electric iron.

In the embodiment of the invention illustrated in Figs. l and 2 the temperature-responsive element is a bimetal strip 49' mounted in a recess 5t? of the bottom plate 30 of the electric iron, such bimetal strip having its left end clamped to the bottom plate 3@ by means of the insulating block 31. On its right end the bimetal strip carries a plate l which projects beyond the bimetal strip and has an insulating lining 52 on which the actuating pin 48 is supported. When the temperature of the electric iron is low the parts assume the position illustrated in Fig. l. As the temperature rises the bimetal strip 49 is exed upwardly so that its top face will become convex 4 whereby the plate 51 will lift the actuating pin 48. A layer 53 of insulating material serves to insulate the spring leaf 46 from the bimetal strip 49.

For the adjustment of the temperature limit at which the snapping action of the switch is effected, the level of the insulating frame 37 may be adjusted. This frame has two lateral projections 54 resting on a pair of parallel arms 55 of a tiltable frame 56 mounted for adjustment about a horizontal axis on the insulating block 33 whereby the pair of arms 55 may be rocked up and down. The frame 56 has a recess 57 through which a vertical threaded spindle 5S extends, such spindle being rotatably mounted in a supporting plate 59 mounted on the insulating block 33. A nut 60 is engaged by the threaded spindle 5t; and slots 6i are provided in the side faces of such nut. These slots are engaged by the opposed edges of the recess 57 of the frame 56. By rotation of the spindle with the aid of a knob 62 ,the nut 6i? may be moved upwardly or downwardly. Such movement causes the nut to rock the frame 56 and the arms 55 thereof. The spring 36 tends to maintain the projections 54 of the frame 37 in engagement with the arms 55. When the bimetal 49 is considerably flexed, however, it may lift the frame 37 causing the projections 54 thereof to be lifted from the arms 55, whereby the bimetal strip is protected from a permanent deformation which, in event of a rigid connection of the frame 37 to the arms 55, would be liable to occur when the knob 62 is adjusted to a low temperature at a time when the bottom plate Sii has a high temperature.

For protecting the switch from dust the top of the frame 37 may be closed by a cover 63 indicated by dotted lines.

The spring leaf 46 carrying the contact 45 may be formed as a heating resistance adapted to heat the bimetal strip 49. As a result, the temperature difference existing between the temperature causing the electrical circuit to be closed and the temperature causing the electrical circuit to be interrupted will be reduced. When the parts assume the position shown in Fig. l the heating circuit is closed. When the temperature rises above the cut-off limit the spring leaf 33 snaps upwardly and separates the contacts 44 and 45 and moves to engagement with the stop 42. Now the temperature of the iron drops. ln the initial phases of the drop of temperature the left end of the stiffened section 43 of the spring leaf remains in contact with the stop screw 42, whereas the right end of the stiffened section 43 drops gradually until the spring leaf 38 passes through its neutral condition and snaps downwardly to thereby close contacts 44 and 45 again. Ordinarily the turn-on temperature is somewhat lower than the cut-off temperature. The difference between the two temperature limits is reduced by the above described heating effect exerted by the spring leaf 46 upon the bimetal strip 49.

The stiffening of the spring leaf 38 throughout its central section 43 may be effected in various ways, for instance by increasing the thickness of the spring leaf within this central section by a coextensive metal strip soldered to the spring leaf 38.

The snap switch described adapted to abruptly separate and engage the contacts 44 and 45 to thereby avoid sparking between the contacts and the consequent wear and radio disturbance, excels by its safe operation, its longevity and its ability to operate at comparatively high temperatures which may amount to 240 C. for instance, provided that a heat-resistant spring metal is chosen for the spring leaf 38. Also the snap switch excels by the low mass of its movable elements whereby the impact, wear and noise incidental to its operation are reduced to a minimum. Since the spring leaf 38 is mounted to its support 37 without the use of any pivots, no friction and consequent wear will occur between the spring leaf and the support.

The novel snap switch described including an elongated spring leaf instable in a central position because of a suitable bias and thus tending to snap into one or'the other of its end positions, such spring leaf being rigidly clamped to its support without any pivotal connection therebetween, may be modified in numerous ways.

Thus, Fig. 3 illustrates an embodiment in which the ends of a spring leaf 66 are rigidly clamped in a support 65. A central section 67 of the spring leaf is stitfened again. The non-stitfened end section at the left is corrugated. The spring leaf is pre-stressed by a longitudinal compression bias and, therefore, tends to snap from its instable central position B illustrated in full lines upwardly or downwardly into the positions A or C shown in dotted lines. The spring leaf 66 carries an electrical contact 68 in spaced relationship to the support 65, such contact being adapted to engage a stationary countercontact 69 carried by the support. A suitable actuating member not shown may exert an actuating force k1 or k2 upon the spring leaf at a point spaced from both the support 65 and the contact 68. If it is desired to move the spring leaf from the position A to the position C, the actuating force k1 must be rendered effective to displace the spring leaf. Such displacement will cause the spring leaf to snap into the position C. By then applying the actuating force k2 the spring leaf may be restored to the position B causing it to snap back to the position A.

The snap switch shown in Fig. 3 differs from that shown in Fig. l by the disposition of the contact 68 on the non-stifened, highly resilient corrugated end section of the spring leaf, whereas in Fig. l the contact is mounted on the non-resilient central section of the spring leaf. Moreover, in the snap switch of Fig. 3 the contact is mounted on the top of the spring leaf, whereas in Fig. l it is mounted at the bottom thereof. A further difference resides in that in Fig. 3 the spring leaf is in a stable condition in both end positions A and C tending to remain therein owing to its bias, whereas the spring leaf 38 in Fig. l is in a stable condition in its lower position only. When it assumes its upper position in engagement with the stop 42 then it requires pressure exerted by the actuating pin 48 in order to maintain the spring leaf in such upper position. When the spring leaf is relieved from the pressure exerted by the actuating pin 48 it commences its downward motion. The various phases of this motion are illustrated in Figs. 4 and 5.

In Figs. 4 and 5 the support 37 is indicated diagram- 'matically. The opposite ends of the spring leaf 38 are firmly clamped to the support 37, the central section 43 of the spring leaf being stitfened. The actuating pin 48 exerts the force k3. The stop 42 limits the snapping motion of the spring leaf in upward direction and the contact 45, which for sake of simplicity is shown as being stationary, limits the snapping motion in downward direction. The lowermost position of the spring leaf is indicated in full lines in Fig. 4.

When the force k3 exerted by the actuating member 48 increases it will ex the right hand end section of the spring leaf upwardly moving the central stifened section 43 to the inclined position E indicated by dotted lines. In this position the spring leaf is in its instable conditon. It will be noted that in this first phase of the operation when the spring leaf moves from its lowermost position to the position E, the contacts 44 and 45 in Fig. l will remain closed. As soon as the spring leaf is lifted beyond the position E it will snap abruptly into its upperrnost position F, the stiffened central section 43 being tilted under the effect of the bending stress set up in the spring leaf at 70 causing the left end of the stiffened 'section to swing upwardly. In the position F the spring leaf is kept by the force k3, as illustrated in Fig. 5 in full lines, provided that the force k3 is sufficiently powerful to overcome the effect of the bending stress set up in the spring leaf A38 at 71. As soon as the force k3 .decreases so as tobe overcome by such bending stress,

the stilfened central portion of the spring leaf will rst move into the inclined position indicated in Fig. 5 by dotted lines, such inclined position resulting in a substantially stable condition of the spring leaf. Only upon a further reduction of the actuating force k3 will the snapping action occur whereby the spring leaf will snap into the position H. In this snap switch an actuating force acting in a negative direction, as indicated in Fig. 3 by the arrow k2, is not required. Hence, it will appear that the spring leaf because of the effect of its stiffened central section 43 is capable of assuming two positions in which it is in a substantially stable condition, such positions being the positions indicated in Fig. 4 at E and the position indicated in Fig. 5 at G.

In Fig. 6 I have indicated a snap switch differing from that shown in Fig. 3 and that shown in Figs. 4 and 5 by the fact that the actuating pin 72 does not engage the stitfened section 43 but rather engages the non-stiffened right hand end section being rigidly xed thereto, for instance by a rivet, any pivotal connection being avoided. This offers the advantage that no wear may occur between the spring leaf and the actuating member. The snapping operation is the same as that explained hereinabove with reference to Figs. 4 and 5.

In the embodiment illustrated in Fig. 7 the point of engagement of the actuating member with the spring leaf is located in the non-stiffened, highly resilient right hand end section of the spring leaf just as in the embodiment of Fig. 6. The actuating pin 73, however, acts on the spring leaf without being rigidly connected thereto, the operation being similar to that described hereinabove with reference to Figs. l and 2.

In the embodiment of the snap switch illustrated in Fig. 8 the actuating pin has been replaced by an arm 74 which is riveted to the spring leaf and projects laterally out of the supporting frame 75. The right hand end of this arm may be mounted for pivotal movement about a stationary point. The actuating forces k5 or k6 will act on this arm, such forces setting up bending stresses in the highly resilient right hand end section of the spring leaf 76, such bending stresses initiating the snapping action. The snapping operation occurs in the manner explained with reference to Fig. 3.

This embodiment may be modied by securing the arm 74 to the stiffened section 77 of the spring leaf rather than to the resilient section 76. This modification is particularly well adapted for such cases where the actuation is to be effected by a torsional force. This torsional force is caused to act on the arm 74 about the pivotal axis (not shown) thereof.

In Fig. 9 I have illustrated a snap switch differing from `the embodiments described hereinabove by the fact that the stilfened section has the same thickness as the nonstiffened, highly resilient end sections of the spring leaf. In this embodiment the stiffening of the central sectionl is effected by an increase of its width. Alternatively, the highly resilient end sections rof the spring leaf may have the same width as the stiifened central section, but may be weakened by lateral recesses increasing the flexibility of the end section.

That is illustrated in Fig. 19 showing a spring leaf having a central section 78 of the same thickness as the highly resilient end sections which have their `ends rigidly clamped in the support 79. The flexibility of the end sections may be also increased by lateral recesses where the central section is stiffened in the manner explained hereinabove with reference to Figs. l and 2.

That is illustrated vin Fig. 18 showing a spring leaf 'having a central section reinforced by imposition of a plate 81 rigidly secured to the spring leaf, whereas the end sections 82 are provided with lateral recesses 83 increasing their flexibility.

The actuating pin 84 (Fig. 9) may be rigidly connected to the spring leaf, for instance by being riveted thereto, and may engage either the stiiened central section 78 ora more flexible section. Y Y Theembodim'ent illustrated in Fig. 10 differs from'those described hereinabove with reference to Figs. 3 and 9 by the fact that the countercontact ES is not rigidly mounted on the support 86 but is adjustably and resiliently mounted thereon. For this purpose, the contact 85 is mounted on the end .of a spring leaf 87, the other end of such spring leaf being riveted to the supporting frame 86. The spring leaf 87 engages a setting screw 88 mounted in a tapped bore ofthe supporting frame 86 and serving to adjust the bias of the spring leaf S7. Otherwise this embodiment may be identical with that explained with reference to Figs. 4 and 5.v The adjustability of the bias of the spring leaf 87 aids in assuring that the snapping operation will be effected ina rapid and reliable manner.

In the em-bodiment illustrated in Fig. ll the spring leaf is stiffened throughout a pair of spaced sections 89 and 90. The section intermediate these stiffened 'sections is highly flexible being corrugated as shown at 91. The points where the contact is mounted on the spring leaf and Where the latter is engaged by the acutating member may be chosen -in accordance with `any one of the examples described hereinabove and is not illustrated in Fig. ll.

Y 'In the embodiment of the snap switch illustrated -in Fig. 12 the central section of the lspring leaf 92 is stiifened by 'bimetal strip 93 which is united rigidly with the spring leaf, for instance by soldering. As long as this bimetal stripv 93 assumes a straight shape the spring leaf will remain in its lower position indicated in full lines. When the 'bimetal strip due to a change of temperature is bent upwardly it will set up a bending stress in the spring leaf causing sameto move through its neutral condition and to snap int-o the position indicated by dotted lines. By this snapping effect the switch contacts will be engaged. IIn this embodiment, too, the two limit positions of the spring leaf could be predetermined by stationary and preferably adjustable stops. The bimetal strip 93 thus performs both functions, that of stiffening the central section `of `the spring Ileaf 92 and that of the actuating member.

IIn Fig. 13 I have illustrated a snap switch in which the switch spring leaf 94 has but one of its ends rigidly secured to the supporting frame. A central section of the spring leaf is stiifened by a plate 96 bonded to the spring. The right hand end of the spring leaf 94 is riveted to the free end of a lbimetal strip 97 by a -rivet 101, the other end of the bimetal strip being rigidly `clamped in the support 975 preferably in engagement with the end of the switch spring leaf 94. The spring leaf 94 is pre-stressed by a longitudinal compression bias. When the bimetal strip 97 assumesa certain `temperature it will maintain theV parts in the position illustrated in full lines in Fig. 13. iIn this position the stiffened section 96 of the spring leaf engages ya rigid stop 98 mounted on the 4support 95, whereas the contact 99 mounted on the stidened section of the spring leaf is disengaged from the countercontact 100 mounted on the bimetal strip 97. Upon a chan-ge of the temperature causing the bimetal strip to bend in a manner whereby its right hand end will be lifted, the parts will first move t-o a non-stable position in which the contacts V100 .and 99 are still separated. Upon passage through this non-stable position, the parts will snap into the position Vindicated in Fig. 14 in which the stiffened central section of the spring leaf is .slightly spaced from the stop 98, Whereas the rivet connecting the spring leaf with the bi- 'metal strip 97 engages the frame. In this position the con- , tactsy 99 and 100 engage each other. The stop 98 may be likewise formed by a contact. The snapping operati-on is ,promoted by the bending stress produced -by the rivet joint 101.

A heating coil may be mounted on the bimetal strip 97 and maybe supplied with current under the control by the contacts 99, 100. In this event, the snap switch acts as a "blinker switch which automatically and periodically closes and interrupts the electrical circuit, forV instance for the purpose of controlling blinker lights.

=In the snap. switch illustrated in Fig. l5 the-point ofren-V gagement of the actuating force coincides with the point where the contact is located on the spring leaf, the actu; ating force being inserted on the reinforced section 102 of the spring leaf 104 by a pair of spaced abutrnents 105 and 106 mounted on the endl ofV an actuating member, for instance on the end of a bimetal strip 107'hav-ing its other end rigidly secured to the support 103. In this embodiment, both ends of the switch spring leaf 104 :are firmly. clamped to the support 103. Whereas the abutment 106 is Idirectly attached to the end of the bimetal strip 107, the abutment 105 is carried lby a rigid arm 108 of the bimetal strip. The `abutment 106 may be formed as an electrical contact which cooperates with a countercontact 1,09 mounted on the stiffened section 102 of the spring leaf.

The spring leaf 104 is pre-stressed by a longitudinal compression bias and, for this purpose, is provided with suitable corrugations. This bias produces a tendency of the spring leaf to snap from an instable central position to one or the other of two end positions. In Fig. 15 I have illustrated a condition in which the spring leaf tends to move downwardly and, therefore, engages the abutment 106 with a certain force. Upon a change of the temperature in a manner causing the bimetal strip 107 to rise, the abutment 106 will move the spring leaf 104 through its non-stable position and beyond the same causing the snapping operation to occur whereby the spring leaf moves abruptly upwardly causing its stiifened central section to engage the abutment 105. If desired, the movement on the abutment 106 may be limited by a rigid stop mounted on the frame 103. In this embodiment, too, the bimetal strip 107 may be provided with a heating coil energized by an electric current controlled by the contacts 106 and 109. When the bimetal strip 107 is heated it will rise and move the abutments 105 and 106 upwardly. Then the snap switch shown in Fig. l5 will act as a periodical intermittent interrupter.

In Fig. 16 I have illustrated a cross section through a snap switch in which the actuating pin is riveted to the switch spring leaf. The transverse section through the switch shown in Fig. 16 may be that indicated by the line 16-16 of Fig. 6 or by the line 16-16 of Fig. 9. The actuating pin 84 is riveted to the spring leaf 110. In certain cases it may be desirable in spite of the rigid connection between the actuating pin and the spring leaf to permit the temperature-responsive element to move independently of the spring leaf. Tothis end, the actuating pin 84 is connected with a U-shaped spring leaf 111 to which an actuating pin is attached, the pin 85 being disposed coaxially to the pin 84 and being rigidly secured to the temperature-responsive element 112 which may be constituted by a bimetal strip.

A similar effect may be attained in the switch illustrated in Fig. 17 showing a switch spring leaf 113 which is rigidly connected by the actuating pin 114 with the one end of a bimetal strip 115, the other end of such bimetal strip, however, being not rigidly secured to the support 116 but being secured thereto through the intermediary of an auxiliary spring leaf 117. This auxiliary spring leaf will protect the bimetal strip Vfrom excessive stresses resulting in a permanent deformation which, in the absence of the auxiliary spring, could occur when the bimetal strip tends to bend beyond the limits permitted by the switch spring leaf 113.

In Fig. 20 I have illustrated a snap switch differing from that illustrated in Fig. 3 essentially by the fact that the stiiening of the central section of the spring leaf 118 is effected in another manner. Whereas in the embodiment shown in Fig. 3 a strip or plate is bonded to the central section of the spring leaf to be reinforced, no such strip is provided in the embodiment shown in Fig. 20, the switch spring leaf 118 being simply provided with lateral downwardly bent anges 119 so that the stiened central section has a channel-shaped cross section as indicated in Fig. 2l. Otherwise the snap switch shown in Figs. 20 and 2l is similar to that shown in Fig. 3.y Thus, the spring leaf 113 has both of its opposite ends firmly clamped in the supporting frame 120 in a manner prestressing the spring leaf by a longitudinal compression bias. The contact 122 is mounted on the left highly resilient end section of the spring leaf and cooperates with a stationary contact 121 mounted on the supporting frame 120, such stationary contact acting at the same time as a stop limiting the upward movement of the spring leaf. The actuating member 123 is rigidly secured to the reinforced section of the spring leaf by a rivet or a screw 124.

In Figs. 22, 23 and 24 1 have shown a switch which serves the same purpose as that illustrated in Figs. 1 and 2 differing therefrom mainly by its simplified and more compact structure. A base plate 110' is secured to the outwardly extending llanges of an inverted U-shaped frame member 111 provided in its upper horizontal portion with a bore accommodating a vertical shaft 112', the lower end face of such shaft resting on the base plate 110' and being provided with a stud 113' journalled in a bore of the base plate 110'. A horizontal pin 114' extends past the shaft 112' through the Vertical sections of the frame member 111' and is mounted therein. Spaced vertical ears 116 of a supporting member 117' are pivotally mounted on the pin 114'. The supporting member 117' is connected by a helical traction spring 118 with the upper portion of the frame member 111. The spring 11S' keeps a downwardly projecting arm 119' of the supporting member 117' in engagement with a cam 120' secured to the shaft 112. The latter has a knob (not shown) permitting to turn the cam and to thereby adjust the angular position of the supporting member 117. The supporting member 117' has a horizontal arm 121' having its upper and lower face lined by mica sheets 122 and 123'. A terminal sheet metal plate 124 is imposed on the mica sheet 122 and projects laterally, as shown in Fig. 23, for connection thereto of an electrical conductor 125. A supporting member 126 is secured to the plate 124 and extends substantially parallel to the arm 121'. The downwardly turned end of the member 126 carries an adjusting screw 127. A switch spring leaf 128 has one end rmly clamped between the plate 124 and the frame member 126 and has its other end bent upwardly and rearwardly and firmly fixed to the top of the frame member 126, as indicated at 130. It will be noted that the bent section of the spring leaf 128 is slightly spaced from the downwardly bent end of the supporting member 126 and the head of the adjusting screw 127. A resilient sheet metal member 131 which is likewise iixed to the supporting member 126 extends between the head of the adjusting screw 127 and the bent portion of the spring leaf 128 bearing against the latter at 132. The adjusting screw 127 is tightened thereby causing the sheet metal member 131 to prestress the spring leaf 128 by a longitudinal compression stress producing a tendency of the spring leaf to snap from an instable central position to one or the other of two end positions. When the parts assume the position shown in Fig. 22 the spring leaf 128 assumes a position lower than its neutral position and, therefore, tends to move downwardly thus keeping a contact 133 secured to it between its ends in engagement with a countercontact 134 disposed beneath the Contact 133 and carried by a spring leaf 135 which underlies the mica sheet 123 and is clamped thereagainst by another mica sheet 136.

An electrical heating element 137 formed by a resilient strip of a suitable conductive material has one end connected to the spring leaf 135 beneath the contact 134 to be in conductive connection therewith and has its other end electrically connected to a terminal metal sheet 138 that is clamped between the mica sheet 10 136 and another mica sheet 139. A washer 140 underlies the mica sheet 139 and a rivet extends through the superimposed elements 126, 128, 124', 122', 121', 123', 135, 136, 138, 139 and 140 thus holding the same firmly together in stepped condition. Two spaced sections of the spring leaf 128 are stitfened by sheet metal plates mounted thereon. One such section indicated at 141 is disposed between the terminal sheet 124' and the contact 133 and spaced therefrom. The section 141 is stitened by a sheet metal strip folded around the spring leaf 128 and soldered thereto. The other section of the spring leaf 128 that is stiffened is indicated at 142. It overlies the contact 133 being conductively connected therewith and extends close to the point 132 and has a hole for the passage therethrough of a stop screw 149 which will be described later. It is likewise reinforced by a sheet metal strip folded around the spring leaf 128 and soldered thereto. This reinforcing sheet metal strip forms a depending resilient bent tongue 143 adapted to be engaged by an actuating member 144 consisting of a block of insulating material fixed to the end of a horizontal arm 145, which, in its turn, is fixed by a rivet 146 to the free end of a bimetal strip 147. The other end of the bimetal strip underlies the base plate and is clamped by the same against the base plate 30 (Fig. 1) of the electric iron and is thus firmly held in contact therewith. When the temperature of the base plate 30 of the electric iron rises, the bimetal strip 147 bends upwardly lifting the actuating member 144 and causing it to engage the tongue 143 to thereby lift the spring leaf 128 towards and through its neutral position. As a result, the spring leaf 128 snaps upwardly into Contact with a stop screw 148 carried by the supporting arm 126. During the initial phase of the upward motion of contact 133 the bias spring leaf will lift the contact 134 keeping the same in engagement with the Contact 133. When both contacts have reached a comparatively high velocity and shortly before the spring leaf 128 will arrive in contact with the stop 148, the end of the spring leaf 135 will be arrested by engagement with the lower end of the adjustable screw 149 carried by the supporting arm 126. At the instant when this arrest occurs contact 133 continues its upward motion at high speed thus ensuring a particularly quick separation of the contacts 133 and 134 whereby any sparking will be avoided. The end of the spring leaf 13S is lined with a mica plate 150 for the purpose of electrical insulation of the stop screw 149.

The temperature at which the snapping action occurs depends on the altitude of the tongue 143 above the base plate 30 of the electric iron and may be adjusted within wide limits by rotation of the shaft 112'.

The stops 148 and 149 are so adjusted that the contacts 133 and 134 will be separated a distance suflicient to ensure the interruption of any arc that may form. Moreover, this adjustment and that of the adjusting screw 127 must be effected in such a manner as to ensure that the spring 128 when engaging the stop 148 will descend as soon as the tongue 143 is relieved from pressure by the actuating member 144. As a result, the contacts 133 and 134 will re-engage as soon as the temperature drops beneath a certain limit. If desired, however, the adjustment of the stops 14S and 149 and the adjustment of the screw 127 may be so eected that the spring leaf 128 will remain in its upper position in engagement with the stop 148 even after the tongue 143 is relieved from pressure by the actuating member 144. With this adjustment the novel snap switch illustrated in Figs. 22 to 24 may be used for the purpose of cutting olf the current from an electrical apparatus should the latter be heated to an excessive temperature. With that adjustment it will be necessary for a re-engagement of the contacts 133 and 134 to depress the spring leaf 128 manually, for instance by a temporary lowering of contact 148 or otherwise.

The electric circuit controlled by the snap switch extends through the conductor 125, the terminal sheet 124';

11 theaswitch, spring-f leaf 128, the contact 133, thecontact lLtlie-heating element 137, the terminalsheet 138, and thewire 1.51,; Y

The resilient tongiiefllV limits the reactionary force actingon, the actuatorV 144 thereby preventingv permanent, deformation of the, bimetal strip 147 should the same-be heated beyondthe cut-off temperature.

The stiffeningy of thev sections 141 and 142 of the springL leaf 128 maybe effected in the manner described hereinabove with reference to Figs. 18, 19, 2O and 2l, thatl is to say by an increase of the width or by ateral tianges; rather than by'a separate and additional metal sheet e While the invention has been described in connection with :njnnmber of preferred embodiments thereof, it will be understoodthatit is capable ofV further modification, and, this application is intended to cover any variations, uses,4 or; adaptations ofthe invention following, in generalthe.principles of the invention and including such departures from the present disclosure as come within lrnowrn or; customary practice in the art to which the inyentionrpertains, and as fall withinthe scope of the invention orV the-limitsof the appended claims.

What l claim is: Y -Y *1., A snap switch comprising a support, a switch spring leaf having. lat least one central section of greater width andz consequent stiffness than the adjoining end sections ofjjsaid spring. leaf, means for rigidly securing said end sectionof*4 saidv spring leaf to saidsupport and for prestressing said spring leaf by a longitudinal compression stresslproducing` a tendency of said spring leaf to snap from,Y an` instable central position to one or the other of two end positions, a rst contact carried by said spring leaf in spaced relationship to saidV support, a second contact` mounted for engagement by said first contact in one ofA said, end positions, abimetal element, means for mounting one. end of said bimetal element in fixed condition, an actuating member mounted on the other end of said bimetali element for movement relative to said support in response to changes of temperature, said actuating member being so disposed relative toV said spring leaf as to move same through said instable central position when the temperature` increases beyond a predetermined limit.

2A. A snap switch comprising a support, an elongated switchy spring leaf, means for rigidly securing the opposite ends of said spring leaf to said support and for prestressing said spring leaf by a longitudinal compression stress. producing a tendency of said spring leaf to snap from an instable central position to one or the other of two end positions, a first contact carried by said spring leaf between its ends, a second contact cooperatively coordinated to said first contact, resilient means movably supporting said second contact and tending to maintain same in engagement with said first contact, an actuating member mounted for relative movement with respect to said support for acting on said spring leaf to cause movement of same away from said second contact through said instable central position, a iirst stop carried byfsaid support for arresting said second contact prior to the termination of said movement, and. a second stop coordinated to said spring leaf to limit said movement, saidv stops being so disposed relative to each other as to permit said first contact to travel in the course of said movement through a longer distance than said second Contact.

3. A snap switch as claimed in claim 2 in which said second stop is carried by said support.

4.. A snap switch as claimed in claim 2 further cornprising meansy for adjusting said support towards and away from said actuating member.

5. A snap switch as claimed in claim 2 further comprising` a frame, means for movably mounting said support thereon, an adjusting cam rotatably mounted in said frame for engagement with said support, a spring connected; to Said. slipped t0, hold; Same, in engagement with said cam, and a bimetal strip havingr one endV fixed to said fratrieA andthe other end carrying said actuating, member. Y

Y k6. A snap switch comprising aV frame, a support pivoted thereto for adjustment about an axis, an adjusting cam rotatably mounted in such frame in engagement with said support, said support having an arm extending substantially radially with respect to said axis, an elongated switch spring leaf substantially coextei'isive with said arm having its ends fixed thereto, the end of said spring leaf remote from said axis being bent over the end of said4 arm inspaced relationship thereto, adjustable means secured to the end of said arm and engaging the bend of said leaf to set up a longitudinal compression stress therein producing a tendency of said spring leaf to snap from an instable central position to one or the other of two end positions, a first contact carried by said spring leaf between its ends, a second contact cooperatively col ordinated to said first contact, resilient means` fixed to said support and movably supporting said second contact and tending to maintain same in engagement with said first contact, an actuating member mounted for relative movement with respect to said support for acting on said spring leaf to cause movement of same away from said second contact through said instable central position, a first stop carried by said support for arresting said second contact prior to the termination of said movement, and a second stop coordinated to said spring leaf tovlimit said movement, said stops being so disposed relative to each other as to permit said first contact to travel in the course of said movement through a longer distance than said second Contact.

7. A snap switch comprising a support, an elongated switch spring leaf having stiened sections spaced from each other and from the ends of said spring leaf, means for rigidly securing said ends of said spring leaf to said support and for pre-stressing said spring leaf by a longitudinal compression stress producing a tendency of said spring leaf to snap from an instable position to one or the other of two end positions, a first contact carried by one of said stiffened sections of said spring leaf, a second contact mounted for engagement by said first contact in one of said end positions, and an actuating member movable relative to said support for acting on said stiffened sections of said spring leaf to move same through said instable central position.

S. A snap switch comprising a support, a switch spring leaf having at least one section of less iiexibility than the adjoining sections of said spring leaf, means for rigid/ly securing said adjoining sections of said spring leaf to said support and for pre-stressing said spring leaf by a longitudinal compression stress producing a tendency of saidV spring leaf to snap from an instable central posi- Ytion to one or the other of two end positions, a first con.- tact carried by said spring ieaf in spaced relationship to said support, a second contact mounted for engagement by said first contact in one of said end positions, a bimetal element, means for mounting one end of said bimetal element in fixed condition, an actuating member mounted on the other end of said bimetal element for movement relative to said support in response to changes of temperature, said actuating member being so disposed relative to said spring leaf as to engage said section of less exibility to thereby move said leaf through said instable central position when the temperature increases beyond a predetermined limit, and an electrical heating element electrically disposed in series with at least one of said contacts and mounted adjacent to said bimetal element.

9. A snapl switch comprising a support, a switch spring leaf having at least one central section of greater width than the adjoiningendsections of said spring leafmeans for rigidly securing said end sections to said support and for pre-stressing saidV spring leaf by a longitudinal cornpression'L stress producing .a tendency Of saidY spring leaf to snap from an instable central position to one or the other of two end positions, a first Contact carried by said spring leaf in spaced relationship to said support, a second contact mounted for engagement by said first contact in one of said end positions, a bimetal element, means for mounting one end of said bimetal element in ixed condition, an actuating member mounted on the other end of said bimetal element for movement relative to said support in response to changes of temperature, said actuating member being so disposed relative to said spring leaf as to engage said central section to thereby move said spring leaf through said instable central position when the temperature increases beyond a predetermined limit.

10. A snap switch comprising a support, a switch spring leaf having at least one central section having lateral anges reducing the flexibility of said central section compared with that of the adjoining sections of said spring leaf, means for rigidly securing said adjoining section of said spring leaf to said support and for pre-stressing said spring leaf by a longitudinal compression stress producing a tendency of said spring leaf to snap from an instable central position to one or the other of two end positions, a first contact carried by said spring leaf in spaced relationship to said support, a second contact mounted for engagement by said first contact in one of said end positions, a bimetal element, means for mounting one end of said bimetal element in xed condition, an actuating member mounted on the other end of said bimetal element for movement relative to said support in response to changes of temperature, said actuating member being so disposed relative to said spring leaf as to engage said central section and move said spring leaf through said instable central positions when the temperature increases beyond a predetermined limit.

11. A snap switch comprising a support, a switch spring leaf, means for rigidly securing said spring leaf to said support and for pre-stressing said spring leaf by a longitudinal compression stress producing a tendency of said spring leaf to snap from an instable central position to one or the other of two end positions, a first contact carried by said spring leaf in spaced relationship to said support, a second contact mounted for engagement by said first contact in one of said end positions, a bimetal element, means for mounting one end of said bimetal element in fixed condition, an actuating member mounted on the other end of said bimetal element for movement relative to said support in response to changes of temperature, said actuating member being so disposed relative to said spring leaf as to move same through said instable central position when the temperature increases beyond a predetermined limit, adjustable holding means constituting a seat for said support, and resilient means tending to keep said support seated on said holding means but affording freedom for said support to be lifted from said holding means by said actuating member through the intermediary of said spring leaf.

l2. A snap switch comprising a support, an elongated switch spring leaf, means for rigidly securing the opposite ends of said spring leaf to said support and for prestressing said spring leaf by a longitudinal compression stress producing a tendency of said spring leaf to snap from an instable central position to one or the other of two end positions, a first contact carried by said spring leaf between its ends, a second contact cooperatively coordinated to said first contact, temperature-responsive means coordinated to said second contact and adapted to cause same to engage said first Contact imparting movement to the latter and to said spring leaf through said instable central position, a stop, and means for movably mounting said stop and said second contact for common displacement in the path of said spring leaf on opposite sides thereof to limit said movement thereof.

13. A snap switch comprising a support, a bimetal strip having one end rigidly secured to said support, the other free end being movable under the influence of a change of temperature, a switch spring leaf having one end rigidly secured to said support and the other end rigidly secured to the free end of said bimetal strip and being in prestressed condition by a longitudinal compression stress producing a tendency of said spring leaf to snap from an instable central position to one or the other of two end positions, a first contact carried by said spring leaf between its ends, and a second contact mounted on said bimetal strip for engagement with said first Contact in one of said end positions.

References Cited in the file of this patent UNITED STATES PATENTS 2,133,309 Schmidinger Oct. 18, 1938 2,191,670 Kuhn et al. Feb. 27, 1940 2,394,121 Ulanet Feb. 5, 1946 2,440,025 Singleton Apr. 20, 1948

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