US3256405A - Rapid response electrical switch and the like - Google Patents

Description

June 14, 1966 c. A. BODGE ETAL 3,256,405

RAPID RESPONSE ELECTRICAL SWITCH AND THE LIKE Filed May 15 1961 8 Sheets-Sheet 1 Inventors:

CZz'ffard A .fladye June 14, 1966- c. A. BODGE ETAL 8 Sheets-Sheet 2 Filed May 15.

mull] [[Ill 3' Thom as Elivarza,

fnven tons CZzfford A. Bod

June 14, 1966 c. A. BODGE ETAL 3,256,405

RAPID RESPONSE ELECTRICAL SWITCH AND THE LIKE Filed May 15 1961 8 Sheets-Sheet 3 vww Q Nmw m. QN

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Int/enters Clifford A. 5 0d RAPID RESPONSE ELECTRICAL SWITCH AND THE LIKE Filed May 15 1961 8 Sheets-Sheet 4 mmm mk \1 I I 190 /94 Me as fnverz tons: Clifford A. ,Bodye, i Thomas .Eflvans, ua 7 June 14, 1966 c. A. BODGE ETAL 3,256,405

RAPID RESPONSE ELECTRICAL SWITCH AND THE LIKE Filed May 15 1961 8 Sheets-Sheet 5 2/4 a 2 0 f) n 20a 200 /42 //02 2/6 m2 M6 m6 as as Inventors: UZzff0rdA.B0d e, T amas .Eva zs,

June 14, 1966 c. A. BODGE ETAL 3,256,405

RAPID RESPONSE ELECTRICAL SWITCH AND THE LIKE 8 Sheets-Sheet 6 Filed May 15 1.961

[727/672 tors as 84 Cizffard A,,Bodye,

Thomas L. Evans,

June 14, 1966 c. A. BODGE ETAL RAPID RESPONSE ELECTRICAL SWITCH AND THE LIKE Filed May 15 1961 8 Sheets-Sheet 8 F1916.

In ven tors. CZ ifford A ,Bad

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United States Patent RAPID RESPONSE ELECTRICAL SWITCH AND THE LIKE Cliiford A. Badge, Attleboro, and Thomas E. Evans,

Rehoboth, Mass, assignors to Texas Instruments Incorporated, Dallas, Tex., a corporation of Delaware Filed May 15, 1961, Ser. No. 109,933 4 Claims. (Cl. 200-113) The instant invention relates to improved electrical circuit breakers and/or electrical switches having automatic overload current protection. The instant invention is particularly concerned with circuit breakers which are practical for use in low-current applications or in applications where relatively rapid overload response is required.

It has been found that in general, where bimetallic tripping members are employed, many problems have been encountered in providing a circuit breaker which will effectively operate at a low current rating and provide desirous response and protection. The instant invention employs a current-carrying wire-type thermal latch or tripping mechanism which, upon a predetermined overload of current or temperature, is adapted to elongate and actuate or trip the electrical circuit breaker or switch to provide desired response. In operation of electrical switches which are actuated or controlled by a currentcarrying wire tripping mechanism such as, for example, that shown in US. Patent No. 2,943,172, there is many times a time lag or finite time interval between the time that the current-carrying wire mechanism trips the device, and the time that the primary contacts of the electrical switch are separated to open the circuit. During this time lag or interval, overload current is or may still be flowing through the circuit and also through the current-carrying tripping wire. Such current-carrying wires generally have a relatively small cross section and high resistance, and when subjected to such overload currents during the aforementioned time lag or interval, dangers of burnout and deleterious shifts in calibration become critical problems.

It is therefore one object of this invention to provide an electrical switch of the class described, which employs a current-conducting Wire as part of a current overload tripping mechanism and which switch includes means for protecting the current-conducting wire from deleterious overheating and/ or burnout which might result under excessive current conditions.

It is another object or this invention to provide an electrical switch of the class described, which employs a current-conducting wire as part of a current overload tripping mechanism and which switch includes relatively simple and economically constructed means for protecting the current-conducting wire from deleterious overheating and/or burnout which might result under excessive current conditions.

It is another object of the instant invention to provide a new and improved manually operable circuit breaker having automatic overload current protection, and which is adapted to operate at relatively low current values, for example, currents less than five ampcres.

It is another object of the instant invention to provide an electrical switch of the class described, the operation of which is relatively unaffected by ambient temperature conditions or variations.

It is a further object of the instant invention to provide a new and improved latching and tripping mechanism for electrical switches of the class described.

Among the further objects of the instant invention may be noted the provision of an electrical switch which is relatively compact, durable, accurate, reliable in operation; which is versatile and susceptible to varying electrical ratings, including low current ratings; which will pro- Patented June 14, 1966 ice vide an accurate and fast response to predetermine overload current and temperature conditions; and which is economical to assemble and manufacture.

'Other objects will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which some of the various possible embodiments of the invention is illustrated:

FIG. 1 is a top plan view of an electrical switch according to the'instan't invention;

FIG. 2 is an enlarged sectional view of the switch shown in FIG. 1 taken along line 2-2 of FIG. 1, showing the parts in a contacts-closed position;

FIG. 3 is a view similar to FIG. 2, showing the parts in a contacts-open position, with certain parts thereof in phantom;

FIG. 4 is a sectional view taken on line 44 of FIG. 2;

FIGS. 5 and 6 are isometric views respectively of a latch engageable member and an adjusting screw member of the switch shown in FIGS. 1-4.

FIG. 7 -is a sectional view, with certain of the parts shown in phantom for clarity of illustration, taken on line 77 of FIG. 2;

FIG. 8 is an enlarged sectional view taken on line 8-8 of FIG. 7, showing relative and operational movement between the parts;

FIG. 9 is a sectional view taken on line 99 of FIG. 8;

FIG. 10 is a sectional view taken on line 10-10 of FIG. 8;

FIG. 11 is a sectional view taken on line 1111 of FIG. 8;

FIG. 12 is an isometric view of a bell crank latching lever member of the switch shown in FIGS. 1-4;

FIG. 13 is an isometric view of a pair of current-carrying wire trippings members of the latching structure of the switch shown in FIGS. 1-4;

FIG. 14 is an isometric view of a rocker member forming a part of the latching structure of the switch shown in FIGS. 1-4;

FIG. 15 is a view similar to FIG. 2 of the switch, according to another embodiment of this invention;

FIGS. 16 and 17 are views taken respectively on lines 1616 and 1717 of FIG. 15;

FIG. 18 is a view taken on line 1 81 8 of FIG. 17; and

FIG. 19 is a plan view of the member shown in FIG. 18.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

Dimensions of certain of the parts as shown in the drawings have been modified for the purposes of clarity of illustration.

It will be recognized that certain parts in several of the figures of the drawings, have been omitted for the purpose of clarity of illustration.

The embodiment shown in FIGS. 1-14, as particularly described herein, takes the form of an electrical switch or circuit breaker indicated generally by the numeral 20. Circuit breaker 20 includes a casing 22 formed of an electrically insulating material, such as one of the customary molded plastics, and having its upper end open (as viewed in FIG. 2). Casing 22 is formed in two parts, which may be fastened together, for example, by means of screws or rivets, as shown in FIG. 2. The open end of casing 22 is closed by a cover member which may be secured thereto, as by means of screws 26 (as-shown). An insulating piece 96 is disposed between cover member 24 and the open end of casing 22.. Insulating piece 96 is tightly secured between cover member 24 and the open end of easing by screws 26 (see FIG. 2). Switch includes a fixed or stationary contact 28 mounted on exteriorly extending terminal 27, a movable Contact 30, and means carrying the movable contact for pivotal movement about a common axis.

The means which mount the movable contact 30 for movement toward and away from fixed contact 28, the manually operable actuating and resetting means, and the spring members which bias these parts of the switch, are similar to that shown in the circuit breaker construction in U.S. Patent No. 2;813,16 8, issued November 12, 1957 to Mascioli et al., and assigned. to the assignee of the instant invention, and are similar also to that shown in US. Patent No.-2,613,296, granted on October 7, 195 2, to M. 13. Wood. Reference may be had to these patents for specific details of construction and of the cooperative relat-iOnship between parts, such as the latching and actuating members, the contact-carrying members, and manually operable resetting and actuating means, which are shown to the left of line 77 in FIG. 2.

Switch 20 provides a new and improved current overload and tripping mechanism, referred to generally by numeral 100, and shown to the right of line 77 of FIG. 2, which is particularly useful for (though not necessarily limited to) switches of the type shown in the Mascioli et al. and Wood patents, supra.

The means mounting movable contact 30 for pivotal movement includes a contact-carrying arm on member 32 mounted on pivot pin 34. Pivot pin 34 is supported at its ends in a pair of opposed recesses or sockets provided on the interior of a pair of opposed internal walls- 23' and 2-5 of casing 22. Also mounted on pivot pin 34 is a member 36. Member 36. includes a loop 38 deformed therefrom to provide spaced portions 40, on each of which is mounted one end of a respective one of a pair of springs 42. The other ends of each of springs 42 are secured 22, as best seen in FIG. 4. As will be clear from the description to follow, bell crank lever 68 is pivotable to the right, as seen in FIG. 2, in a counterclockwise direction about its pivotal axis to move latching member or abutment 66 out of engagement with latch abutment 64 carried by latch engageable member 62. Until latch bar 66 is moved out of engagement with abutment portion 64 (by means to be described in greater detail below) the parts are in a position to releasably retain the movable contact in electrically conductive engagement with the mating fixed contact 28 in a manner pointed out as follows.

, As shown in FIGS. 2-4, latch engageable member 62 provides a cam surface 76 for co-operation with a roller 78. Member 36 provides a cam surface 80 for cooperation with rollers 82, 82 (as best seen in FIG. 4). Rollers 78, 82 and 82 (see FIG. 4) are respectively mounted in coaxial relationship for rotation about a pin 84, which has its ends fixed in mutually spaced members 86, 86. Members 86, 86 and pin 84 together form a yoke pivotally mounted for movement about pin 88. A link 89 has its opposite ends secured to members 86, 86 to aid and rigidify this yoke. Pin 88 passes in loosely interfitting engagement Within apertures in each of members 86, 86 and insimilar interfitting engagement with an extension 90 of a push button 92. Push button 92 is confined within a hub 93 secured to cover member 24, for substantially rectilinear movement toward and away from the interior of casing 22. Hub 93 is suitably secured in fixed relation to cover member 24 about an aperture in the latter through which button 92 extends. The opposite ends of pin 88 ride in opposed longitudinal recesses 94, 94 provided by Opposed sidewalls 23 and 25 of casing 22, each of which extends to the open end of casto a transversely extending pin 46. Pin 46, like pin 34,

her 36 is resiliently biased away from contact-carrying arm 32 with which it co-operates, by means of a spring 48. Member 50 is mounted on member 32 by means of a rivet 52, which rivet includes a projection 54'which serves as a spring seat for spring 48. Member 36 provides a projection 56 which serves as a spring seat for the other end of spring 48. Member 50 provides a shoulder 58 which co-operates with an opposed shoulder 60 provided by member 36 to limit the extent to which members 36 and 32 are biased away from each other by spring 48. It will be understood that so long as no restraining force is applied to either members 32 or 36, they will pivot in unison about their common axis 34. Since members 32 and 36 are adapted to pivot in unison about their respective common axis 34, when in the absence of a restraint applied to either of the members, springs 42 resiliently bias both members 32 and 36 for movement in a direction to separate contacts 30 and 28.

Switch 20 includes a latch engageable member generally referred to by numeral 62, and best shown in FIG. 5. Member 62 is mounted for pivotal movement about pivot pin 34, and is biased for counterclockwise rotation thereabout (as seen in FIG. 2) by means of a tension spring 72, to bring a projection or abutment 64 fixedly carried thereby into engagement with an opposed projection or abutment 66 fixedly carried by a pivotally mounted bell crank lever 68- which forms part of the latching mechanism to be described in greater detail below.

As best shown in FIG. 5, latch engageable member 62 provides an aperture or eye 70 for attachment of one end of tension spring 72, the other end of spring 72 being Supported by pin 74. Pin 74 is mounted in a pair of opposed recesses formed in walls 23 and 25 of casing ing 22, as best seen in FIGS. 2 and 4. Button 92 also includes a transversely extending pin 95, the opposite ends of which also ride in opposed recesses 94, 94.

Latching mechanism 100 Latching mechanism or assembly 100 includes a frame member 102, having a pair of sidewalls 104 and 106, as best seen in FIGS. 7 and 9. Frame member 102 further includes a transversely extending wall 108 which connects and maybe integrally formed with sidewalls 104 and 106. Wall 108 includes an extension 110 which is electrically connected and secured to an exteriorly extending electrical terminal 112, disposed and received within a recess 114 formed in casing 22. Portion 110 may be secured to terminal 112, as by welding, to firmly secure the parts together. Latching subassembly advantageou'sly can be mass produced as a separate subassembly unit and can be mounted as a unit within casing 22 by 'slidably inserting terminal 112 within a slot 114 provided by each half of the casing 22. Latching unit 100 further includes latching member 68 (best shown in FIG.- 12) which mounts latch abutment 66, as by means of rivets 67, as shown. Member 68 takes the form of a bell crank lever having a long leg 116 and a pair of relatively short legs 118 and 120 which may be formed integrally with leg 116. Legs 118 and 120 co-operate with leg 116 to provide a pair of opposed spaced notches 122 and 124. Disposed within notches 122 and 124 is a pin 126, as best seen in FIGS. 8 and 12. Pin 126 is fixed or securedto bell crank member 68, as by welding. The free ends of pin 126 are disposed for rotation (in concert with bell crank 68) in sleeve or bearing members 128 and 130 which are mounted in sidewalls 104 and 106 of frame 102, as shown. Bearing or trunnion members 128 and 130 are formed of an electrically insulating material, such as, for example, a ceramic, and

are received within suitable apertures provided by sidewalls 104 and 106 of frame 102. Bell crank lever 68 is thus adapted to pivot with pin 126 in bearing members 128 and 130 to move abutment member 66 into and out of position for engagement by projection or abutment 64 of latch engageable member 62. Bell crank lever 68 is electrically connected with electrical contact 30 by means of a pigtail 132, which electrically connects leg 116 and contact-carrying member 32. Contact-carrying member 32 provides a struck-out projection 134 formed integrally therewith, to which one end of pigtail 132 is electrically connected, as clearly shown. Bell crank lever 68 is urged for pivotal movement in a counterclockwise direction (as seen in FIG. 8) by spring 136, as best seen in FIGS. 2, 3 and 8. Spring 136 is received within, and one end thereof is seated in, an aperture 138 provided by casing 22. The other end of spring 136 is disposed about a spring seat projection 140, provided by leg 116 of bell crank lever 68, as best seen in FIG. 7.

Latching mechanism 100 further includes a pair of electrically conductive wires, which may be referred to as hot wires, 142 and 144, as best seen in FIGS. 8 and 13. Hot- wire elements 142 and 144 are formed of materials having a relatively high electrical resistance. By way of example, the materials forming hot wires 142 and 144 can be a nickel-chrome alloy, such as that sold under the trademark Nichrome," which is an alloy con sisting essentially of 15 %16% chromium, 59%62% nickel, about 24% iron, and 0.1% carbon. It is preferred that hot wires 142 and 144 be of substantially rectangular cross section, as illustrated, but it is to be understood that they may take other forms (e.g., circular, elliptical or other polygonal cross-sectional shapes) within the practice of the instant invention. Each of hot wires 142 and 144 are respectively provided with a layer of- electrical insulation 146, 147, disposed thereabout throughout substantially the entire length of the hot wires, as best seen in FIG. 13. Hot wires 142 and 144 are electrically connected together by means of a pigtail 148, as best seen in FIGS. 8 and 13. Ends 150 and 152 respectively of hot wires 142 and 144 are mounted on a rocker arm generally referred to by numeral 154, which is best shown in FIG. 14. Rocker arm 154 includes a pair of spaced, substantially parallel leg portions 156 and 158, which are interconnected and may be formed integrally with portion 160. Rocker arm 154, may be formed, for example, by stamping. Each of legs 156 and 158 is respectively provided with a pair of opposed spaced and registering notches 162, 164 and 166, 168. vLegs 156 and 158 are respectively provided with opposed and aligned registering apertures 170 and 172, which are disposed respectively intermediate notches 162, 164 and 166, 168, as shown. Rocker member 154 is mounted on frame 102 for pivotal movement about pin 174. The free ends of pin 174 are disposed within sleeves 176 and 178 which are in turn respectively mounted and received within suitably formed apertures provided in sidewalls 104 and 106 of frame member 102, as best seen in- FIGS.

.8-10. Trunnion or bearing members 176 and 178 are or may be substantially identical to members 128 and 130 described above. Each of sleeve members 128, 130 and 176, 178 serve a dual function of providing a bearing for their respective pins and also serve as spacers to maintain their respective parts in predetermined spaced assembled relation. Ends 150 and 152 of hot wires 142 and 144 are advantageously pivotally mounted on rocker arm 154, as will be described in greater detail below. Ends 150 and 152 are each respectively provided with a connector plate or bracket 180, 182, which bracket members are substantially identical. Connector plates or brackets 180 and 182 are respectively electrically connected and secured to ends 150 and 152, respectively of hot wires 142 and 144, as by riveting, or preferably, as by welding, as at 181 and 151, respectively. Brackets 180 includes a pair of transversely extending fingers or projections 184, 186 and member 182 includes a pair of similar fingers 188, 190. Fingers or projections 184, 186 and 188, 190 respectively extend transversely and substantially perpendicular to the longitudinal axes of hot wires 142, 144. Fingers 184, 186 and 188, 190 are respectively receivable within opposed, aligned pairs of notches 162, 168 and 164, 166 to pivotally secure ends and 152, respectively of hot wires 142 and 144 to the rocker arm 154. Each of fingers 184, 186; 188, 190 is provided with a rounded upper surface 192, which is received adjacent the apex of each of notches 162, 168; 164, 166 of rocker arm 154 to facilitate pivotal movement therein and provide advantages to be described below. It is to be noted that hot wire 142 is somewhat longer than hot wire 144. Each of members and 182 respectively provide a bent-over lip portion 194 and 196 to which end of pigtail 148 are electrically connected, as by welding.

The upper ends 198 and 246 respectively of hot wires 144 and 142 are each respectively provided with a connecting bracket or plate 200, 248 which are identical to each other, and similar to plates 180 and 182, as best seen in FIG. 13. Connector plates or brackets 200 and 248 are respectively electrically connected and secured to hot wires 144 and 142, as by riveting or welding respectively, as at 218 and 254. Each of connecting plates or brackets 200 and 248, respectively, include a pair of projecting fingers 202, 204 and 250, 252 which extend transversely and substantially perpendicular too the longitudinal axes of hot wires 144 and 142. Each of fingers 202 and 204 are adapted to be received within a pair of spaced, opposed and aligned notches 206 and 208 respectively provided by arms 118 and 120 of bell crank lever 68 (as best seen in FIGS. 9 and 12). The lower edge surfaces of fingers 202 and 204 are rounded, as at 210, to facilitate pivoting of fingers 202 and 204 within their respective'notches 206 and 208 in a manner similar to that described above for rounded portion 192 of fingers 184, 186; 188,190.

Each of connector brackets 200 and 248 further include bent-over portions 212 and 249 to which pigtails 214 and 251 are respectively electrically connected, as by welding. The other end of pigtail 214 is electrically connected to leg 116 of ball crank lever 68, as at 216, as best seen in FIGS. 7 and 8.

Sidewalls 104 and 106 of frame 102 respectively provide a pair of opposed, spaced notches 222 and 224 which co-operate with wall108 to form a pair of opposed, aligned registering open-ended slots. Latching assembly 100 further includes a thermally responsive plate generally referred to by numeral 226. Thermally responsive mounting plate 226 may be formed of a conventional thermostatic multilayered material, for example, a bimetallic material having a high expansion component 228 and a low expansion component 230, as shown, the high and low expansion components being respectively indicated in the drawings by HES and LES.

As best seen in FIGS. 2 and 4, bimetallic mounting plate 226 is mounted and fixedly secured, as by welding, to a transversely extending pin 232, the ends of which project beyond the ends of bimetallic member 226. Bimetallic member 226 is thus adapted to rotate in concert or in unison with pin 232. The free ends of pin 232 are respectivelly received within open-ended slots 222 and 224 provided by frame 102, as described above, to pivotally mount bimetallic mounting plate 226 with respect to frame 102.

Referring now to FIG. 4, bimetallic mounting member 226 is provided with a keyhole shaped slot 240 which comprises a narrow slotted section 242 adjacent one end thereof, and a relatively wide slotted section 244 adjacent the other end thereof. Connecting plate 248 pivotally mounts end 246 of hot wire 142 on bimetal mounting plate 226. Connecting plate 248 may be pivotally secured to bimetal mounting plate 226 simply by inserting connecting bracket 248 through keyhole shaped slot 240, with fingers 250 and 252 disposed lengthwise of the slot, and then rotating the bracket 248 about its narrower shank portion 256, the width of which is slightly less than the width of the wide keyhole portion section 244 of the keyhole slot 240. After insertion and rotation of bracket member 248, the bracket fingers 250 and 252 are disposed in engagement with the upper surface of bimetal mounting member 226 adjacent the edges of the wide slot portion 244, as best seen in FIG. 4. Each of fingers 250 and 252 are provided with rounded, lower surface portions 258 (as best seen in FIG. 12) to facilitate pivotal movement thereof about the adjacent upper surface portion of bimetal member 226.

Referring now to FIG. 8, it can be seen that rotation of hell crank lever 68 in a counterclockwise direction (to disengage abutting latch portion 66 from abutting finger 64 of latch engageable member 62) under the biasing force of spring 136 is normally resisted by hot wires 142 and 144. End 198 of hot wire 144, which is pivotally connected to arms 118 and 120 of the bell crank to the right of the pivotal axis through pin 126 (as seen in FIG. 8) tends to resist counterclockwise rotation of member 68. Rotation of the rocker arm 154 is normally prevented by means of its pivotal connection to each of hot wires 142 and 144, and by means of the pivotal connection of end 246 of hot wire 142 to mounting plate 226. The tension in hot wires 142 and 144 is so calibrated or adjusted (by means to be described below) that the hot wires normally tend to resist rotation of leg 116 of bell crank 68, and tend to retain leg 116 and abutment 66 carried thereby, in a position for engagement by abutment 64 of latch engageable member 62, to permit movement of contact 30 into engagement with fixed contact 28, and to releasably maintain the same in a contactsclosed position.

Sidewalls .104 and 106 of frame 102 each respectively include a projecting or extending wall portion 270 and 272, as best seen in FIGS. 4, 7 and 8. Pigtail 251 is electrically connected to projecting wall portion 272 as by welding at 271, as best seen in FIGS. 7 and 8, to electrically connect hot wire 142 to frame 102. Opposed projecting walls 270 and 272 respectively provide a pair of opposed, spaced, aligned and registering open-ended slots 274 and 276. Each of aligned, open-ended slots or notches 274 and 276 receive a respective one of a pair of projections 280 and 282 provided by a plate 284. Projections 280 and 282 interfit with and are seated respectively in slots 274 and 276 to seat and mount plate 284, as best seen in FIG. 7. Plate 284 is provided with a bore or aperture 286 in which is disposed a calibrating or adjusting screw member 290 having a threaded portion 292. As best seen in FIG. 6, calibrating member 290 includes a headed portion 294. Headed portion 294 includes a narrow width portion 296 having a width which is slightly less than that of the narrow slot portion 242 of keyhole shaped slot 248. Adjusting screw 290 is secured to mounting and calibration plate 226 by first inserting the head 294 of the screw into the wide portion 244 of keyhole shaped slot 240, and then sliding the narrow width portion 296 into the narrow slot portion 242. Narrow width portion 296 co-operates with the sidewalls of narrow slot portion 242 to inhibit or limit relative rotation between the adjusting screw and the bimetallic plate. The free threaded end of screw 290 is threadedly engaged with a nut 298, which. thereby maintains headed-over flange portion 294 in engagement with the underside of the mounting and calibrating plate 226 (as best seen in FIGS. 7 and 8).

Hot wires 142 and 144 are adapted to elongate, upon an increase in temperature thereof, which could be caused, for example, by an overload current flowing therethrough. Hot wires 142 and 144, when so elongated by a predetermined amount, will permit leg 116 of bell crank lever 68 to rotate in a counterclockwise direction under the bias of spring 136 and move to the dashed-line position, as shown in FIG. 8, to disengage abutment latch member 66 from finger 64 to permit release and opening of contacts 30 and 28, in a manner to be described more fully below. Bimetallic mounting member 226 advantageously provides a simple and economical means for ambient compensation. Bimetal plate 226 is adapted to flex upwardly to the dashed-line position, as shown in FIG. 8, upon an increase in ambient temperature, to move end 246 of hot wire 142 upwardly. Movement of end 246 upwardly, as seen in FIG. 8, results in tensioning hot wire 142, pivoting rocker arm 154 in a counterclockwise direction, which in turn further tensions hot wire 144 to compensate for any elongation which may have taken place due to an increase in ambient temperature, which thus avoids undesirable and deleterious calibration shifts or nuisance tripouts. The bimetal mounting plate 226 is thus effective to maintain the tension in the hot wires 142 and 144 substantially constant irrespective of the ambient temperature, and thereby avoids undesirable and deleterious calibration shifts and inadvertent and nuisance tripouts of the switch which might otherwise occur on an increase of the ambient temperature in absence of thermally responsive mounting plate 226.

Bimetallic mounting plate 226, in addition to rendering the operation of switch 20 relatively insensitive to ambient temperatures, also serves the function of a calibrating means for the switch. Calibration of the switch 20 may be efiFected by suitable rotation of nut 298 about threaded shank portion 292. It will be clear that, upon appropriate rotation of nut member 298 about threaded shank portion 292 (as best seen in FIG. 8) that bimetallic member 226 will pivot either in a clockwise direction to increase tension on the hot wires 142 and 144, or bimetallic plate 226 will pivot in a counterclockwise direction (aided by the spring force exerted by spring 136) to reduce the tension on hot wires 142 and 144. It will be clear that varying the tension in the hot wires 142 and 144 will be effective to vary the the operating characteristics of the latching mechanism, and consequently, the

operating characteristics of the switch.

Latching assembly .100 further includes a layer of insulation 300 disposed against the interior side of lower wall portion 110 of wall 108 intermediate wall 110, and the pigtail 148, as best seen in FIG. '8. Another layer of electrical insulation 302 is provided intermediate pigtail 214 and bimetallic calibration and ambient compensating mounting plate 226, as best seen in FIG. 8.

The operation of circuit breaker 20 thus far described, is as follows: with the parts in the contacts-open position shown in FIG. 3, arm 36 is resiliently biased away from contact-carrying member 32 to the extent permitted by the engagement of the respective shoulders 58 and 60 of these members. Also, member 36 and contact-carrying member 32 are biased upwardly (as seen in FIG. 3) for rotation about pivot 34 in a clockwise direction under the influence of springs 42, and latch engageable member 62 is resiliently biased upwardly, as viewed in FIG. 3, for movement in a counterclockwise direction about pivot 34, under the influence of spring 72.

It will be noted that with the parts in the position of FIG. 3, the force exerted by spring 48 is greater than the force exerted by springs 42, and that the combined force exerted by springs 42 is greater than the force exerted by spring 72. The result is that, upon depression of push button 92, rollers 82 ride along cam surface provided by member 36, whereby roller 78 moves against cam surface 76 provided by latch engageable member 62, thereby to swing the latch engageable member 62 in a clockwise direction about the axis of pin 34 until projection 64 moves into engagement with abutment 66 provided by bell crank latch member 68. Thereafter, roller 78 moves along cam surface 76 thereby to move rollers 82, 82 against cam surface 80- and corner 81 provided by member 36, causing member 36, along with member 32, to pivot in a counterclockwise direction about the axis of pin 34. Members 36 and 32 pivot in unison with each other until movable contact 38 comes into engagement with fixed contact 28. At this point, lost motion of member 36 with separated from each other.

cuiting conditions. "loads of comparatively high magnitudes, hot wires 142 9 respect to member 32 ensues, whereby member 32 remains stationary while member 36 continues to move to the position shown in FIG. 2, at which the respective shoulders 58 and 60 provided respectively by members 32 and 36 are It will be noted .that with the parts in the position shown in FIG. 2, wedging'means or rollers 78 and 82 have moved into an overcenter position with respect to the latch engageable member 62 and memto terminal 112.

It will be recognized that by wedging the parts into overcenter relationship with the structure as described above, the circuit breaker inherently possesses high shock and vibration resistance.

1 The electrically conductive path between the terminals 27 and 112 will remain intact until the latched condition described above is disrupted in any one of several ways.

First, push button 92 may be manually and forciblyretracted from the wedging overcenter relationship shown .in FIG. 2, whereby the parts will quickly return under the influence of the respective springs to the position shown in FIG. 3.

Alternatively, the parts are movable from the position shown in FIG. 2 to that shown in FIG. 3, upon movement of the abutment 66 carried by bell crank latch lever 68 away from engagement with projection 64 carried by latch engageable member 62. As noted above, leg 116 of bell crank latch member 68 is movable to the right and pivotable about pin 126 in a counterclockwise direction, as viewed in FIG. 3, upon the occurrence of a predeterminedcurrent overload. Such current overload will heat hot wires 142 and 144, and the resultant elongation thereof will permit arms 1118 and 120 of bell crank lever 68 and also leg 116 of bell crank lever 68, to pivot in a counterclockwise direction about the axis of pin 126 under the bias and influence of spring 136. Elongation of hot wires 142 and 144 and consequent tripping of the switch 20 will result upon the occurrence of predetermined moderate current overload, and also with those of comparatively high magnitudes, such as might be occasioned by short cir- Upon the occasion of current overand 144 will rapidly elongate and effect rapid and substantial movement of leg 116 of bell crank lever 68 to Y quickly move abutment 66 out of engagement with abutment 64 of latch engageable member 62.

Upon such disengagement between abutments 64 and 66, latch engageable member 62 will first pivot in a clockwise direction (as seen in FIG. 3) since the combined force exerted by springs 42 added to the force exerted by spring 48 is of a much greater magnitude than that of the force exerted by spring 72. In this manner, the parts i are unlatched and member 36 moves upwardly, as viewed in FIG. 2, thereby moving roller 78 against latch engageable member -62, causing the latter to pivot in a clockwise direction against the bias of spring 72. The combined effect of springs 42, 42 and spring 48 is to snap the shoulder 60 provided by member 36 against the adjacent fixed contact with which it co-operates, may be more effectively broken. Continued movement of members 36 and 32 brings the parts back to the contacts-open position shown in FIG. 3. Meanwhile, the initial counterclockwise movement of latch engageable member 62 about the axis of pin 34 in combination with the effect of spring 72 and roller 78, results in movement of this member whereby slots 71 and 73 provided by member 62 ride along pin 34. Latch engageable member 62 and push button 92 then return to the position shown in FIG. 3 under the influence of spring 72. From the above, it will be noted that circuit breaker 20 is trip free of push button 92, and that upon the occurrence of a fault or current overload in the circuit to which the circuit breaker is connected, contacts 28 and 30 will be opened, even though push button 92 may be held in a depressed position; and that so long as such a fault exists, depression of the push button will be ineffective to close the contacts.

Shunting contact arrangement As pointed out above, current traverses both of the hot wire elements in circuit breaker 20. Upon the occurrence of current overloads of a comparatively large magnitude (for example, of the nature of many times the rated current) there is a danger that the hot wire elements 142 and 144 may suffer burnout or be otherwise permanently damaged by these large currents during the relatively short time interval between disengagement of latch abutment member 66 and abutment 64, and the opening of contacts 30 and 28 to open the circuit. The instant invention advantageously provides a simple and inexpensive means to obviate this danger. Such means takes the form of a shunting arrangement which includes a pair of shunting contacts 352 and 354, as best seen in FIGS. 2 and 8. Shunting contact 352 is electrically connected to and carried by leg 116 of bell crank lever 68 for movement therewith, as best seen in FIGS. 3, 8 and 12. Stationary shunting contact 354 is mounted on and electrically connected to frame '102, as best seen in FIGS. 7 and 9. Leg 116 of bell crank 68 is provided with a layer of electrical insulation 360 adjacent fixed'shunting contact 352, as best seen in FIGS. 3 and 8.

Referring now to FIG. 8, the dashed-line position of the latch engageable member 62 illustrated therein corresponds to the contacts-open position shown in FIG. 3. The position of latch engageable member 62, as shown in solid lines in FIG. 7, wherein abutment 64 is in engagement with the latchabutment 66, corresponds to the contacts-closed position shown in FIG. 2. Leg 116, in moving from the solid to the dashed line position shown in FIG. '8, upon the occurrence of a predetermined current overload, is effective not only to disengage the latch abutment 66 and abutment '64 to effect opening of contacts 30 and 28, but also is effective to quickly move shunting contact 352 from the solid to the dashed line position to effect a closing of the shunting contacts 352 and 354 to immediately shunt the current out of the hot wire elements 142 and 144, and thereby advantageously avoiddanger of burnout or permanent damage to the hot wires 142 and 144 which might result from such excessive current overloads. The protection afforded by shunting contacts 352 and 354 permits using relatively high resistance hot wires of relatively low thermal mass, which affords fast response on current overloads.

When shunting contacts 352 and 354 are closed during the relatively short time interval after disengagement of latch abutment 66 and abutment 64, and prior to opening of contacts 30 and 28, current will flow in the following manner: through terminal 27, to fixed contact 28, to movable contact 30, to contact arm 32, through extension 134 of contact arm 32, through pigtail 132, to leg 116 of hell crank 68, to movable shunting contact 352, to fixed shunting contact 354, to frame 102, to wall portion 110 of frame 102, to terminal 112. contacts 352 and 354 are operable only during the interval between disengagement of the latch abutment 66 and abutment 64 and the opening of contacts 30 and 28 to open or de-energize the circuit, which contacts 30 and 28 7 control. It should be understood that the short time interval, as referred to herein, includes the time required for contacts 30-and 28 to open after abutments 64 and 66 It is to be noted that the shunting are disengaged, as well as the time required for dissipation of 'any arcing that may take place after contacts 30 and 28 are opened. As hot wires 142 and 144 cool and contract, contacts 352 and 354 will separate. It is also to be noted that leg 116 of bell crank lever 68 can disengage abutment 66 from abutment 64 without moving far enough in a counterclockwise direction to close shunting contacts 352 and 354, for example, with a slow rate of rise condition. The shunting contacts advantageously operate only on high surges of current and not during slow rate of temperature rise conditions. Thus, the danger of inadvertently shorting the current out of the hot wire sensing elements, for example, upon an increase in ambient temperature, is advantageously averted.

The pivotal connection between the ends of the hot wires and the rocker arm 154, legs 118 and 120 of bell crank lever 68, and mounting plate 226, uniquely and advantageously avoids undesirable overstress ing and possible calibration shifts and rupture which might otherwise result with other types of connections, e.g.,-a welded arrangement. Thus, upon elongation and rotation of parts, the ends of the hot wires pivot about their respective connections and maintain substantially all of the stress in the hot wires in the form of tensile stress which is exerted axially of the hot wires. This advantageously avoids creation of moments and bending stresses of the hot wires about their respective connections.

Ambient compensation may also be achieved by replacing the polymetallic thermostatic type mounting plate 226 with a monolayered mounting plate, and forming frame 102 and the monolayered mounting plate of a material or materials having substantially the'same cefiicient of thermal expansion as that of hot wires 142 and 144. Ambient compensation could also be achieved by making plate 280 of a thermostatic material, such as bimetal, in which case mounting plate 226 could be formed of monometal or a single layered material.

Embodiment of FIGS. 15-19 In FIGS. 15-19 is shown a second embodiment of this invention, in which like numerals designate parts like those shown in the FIG. 1 embodiment, further verbal description in which respect is unnecessary. The operation of circuit breaker 4001s substantially similar to that described above for circuit breaker 20. The point of departure in the FIG. 15 embodiment is in the latching mechanism assembly unit, which in this form of the invention, is generally referred to by numeral 401. Unit 401 includes a frame member 402, which comprises a pair of sidewalls 404 and 406 and a transversely extending wall 408 which connects and may be integrally formed with sidewalls 404 and 406. Wall 408 includes an extension 410 which is electrically connected and secured to exteriorly extending terminal 112. Frame 402 also includes an upper wall portion 411 extending transversely of and preferably formed integrally with wall 408, as shown. Latching unit 401 further includes a latching member 468 in the form of a bell crank lever having a long leg 416 and a short leg 418. Leg 416 mounts abutment member 66, which abutment member 66 is identical to that of circuit breaker 20, and serves the same function.

Latching mechanism 401 includes a single, continuous electrically conductive hot wire doubled into a U-shape to form two legs or portions 442 and 444. The bight portion between legs 442 and 444 of the hot wire is disposed about a rocker arm generally referred to by numeral 453, which is best seen in FIGS. 18 and 19. Rocker arm 453 includes a pair of spaced, substantially parallel leg portions 456 and 458. Rocker arm 453 is mounted on frame 402 for pivotal movement about pin 174, substantially in the manner described above for the pivotal mounting of rocker member 154. As best seen in FIGS. 18 and 19, rocker arm 453 provides a pair of spaced notches 455 and 457 which receive hot wire por- . tions 442 and 444 therein ,to inhibit relative lateral movement between the hot wire and the rocker arm 453. Leg 418 provides an aperture 419 and an open-ended slot 421, as best seen in FIG. 16. Free end 443 of leg portion 442 of the hot wire is disposed in slot 421 and is electrically connected and fixedly secured to leg 418, as by welding, as best seen in FIG. 16. Upper portion 411 provides an open-ended slot 413, as best seen in FIGS. 15 and 16. The free end 445 of leg 444 of the hot wire extends through aperture 419 in leg 418, through the slot 413, and

is electrically connected and fixedly secured to the upper surface of wall portion 411 of frame 402, as by welding, as best seen in FIGS. 16 and 17. Leg 416 of bell crank 468 is electrically connected to extending portion 134 of contact arm 32 by means of pigtail 132, in the manner described above for circuit breaker 20.

Bell crank member 468 is fixedly connected to a pin 126, as by welding, as best seen in FIGS. 15 and 17. The free ends of pin'126 are disposed for rotation (in concert with bell crank 468) in sleeves or bearing members 128 and 130 which are mounted in sidewalls 404 and 406 of frame 402, in the manner described above for circuit breaker 20. Bell crank lever 468 is thus adapted to pivot with pin 126 to move abutment member 66 into and out of position for engagement by abutment member 64, in

the manner described above for circuit breaker 20. Spring 136 engages projection 140 on leg 416 to resiliently urge bell crank lever 468 for pivotal movement in a counterclockwise direction, as seen in FIG. 15.

Latching subassembly 100 further includes a calibration arrangement wherein upper wall section 411 of frame 402 serves as a calibrating means, in a manner somewhat similar to mounting plate 226 of circuit breaker 20. Frame 402 includes a pair of projecting or extending wall portions 470 and 472 (similar to wall portions 270 and 272 of circuit breaker 20) as best seen in FIG. 17. Opposed projecting wall portions 470 and 472 respectively provide a pair of spaced, opposed, aligned and registering open-ended slots 474 and 476, as best seen in FIGS. 16 and 17. Each of aligned open-ended slots or notches 474 and 476 receive a respective one of a pair of projections 480 and 482 provided by a plate 484. Plate 484 provides a bore or aperture 486 in which is disposed a calibrating or adjusting screw member 490 having a threaded portion 492. As best seen in FIG. 17, the calibrating member includes a headed portion 494 which is identical to headed portion 294 of calibrating member 290, as best seen in FIG. 6. Headed portion 494 includes a narrow width just slightly less than that of the slot 413 in member 411,

which inhibits relative rotation between portion 411 and the adjusting screw. Adjusting screw 490 is secured to the calibrating portion 411 by first inserting the head 494 of the screw into the slot portion 413, and then disposing the threaded portion 492 into aperture 496 of plate 484.

The threaded end portion 492 is then threadedly engaged with a nut 498 which maintains headed over flange portion 494 in engagement with the underside of the calibrating portion 411, as best seen in FIG. 17.

Calibration of switch 400 may be effected by suitable rotation of nut 498 about shank portion 492, in the manner described above for adjusting screw 292 of switch 20. It will be clear that upon appropriate rotation of the nut 498 about the threaded portion 492, that portion 411 will be moved upwardly, as seen in FIG. 15, pivoting about its bight or connecting bent portion with wall 408 of frame 402. It is to be noted that when portion 411 is moved upwardly, its joint with wall 408 is deformed and stressed, tending to resiliently urge portion 411 for movement downwardly, as seen in FIG. 15, which downward movement is resisted by engagement of portion 411 with headed-over portion 494 of the adjusting screw 490. Upward movement of portion 411, as seen in FIG. 15, serves to increase the tension in the hot wire legs 442 and 444 to vary the operating characteristics of the latching mechanism and consequently the operating characteristics of the switch 400.

Latching mechanism 401 further includes a shunting contact arrangement similar to that of circuit breaker 20 and includes a pair of shunting contacts 452 and 454 which may be identical to shunting contacts 352 and 354 of switch 20. Stationary shunting contact 454 is mounted on and electrically connected to frame member 402, as best seen in FIG. 17, and movable shunting contact 452 is electrically connected to and mounted on bell crank 468 for movementtherewith, in the manner described above for shunting contact 354 and bell crank member 368 of switch 20.

Ambient compensation may be providedfor circuit breaker 400 by a number of means. For example, ambient compensation may be achieved by forming plate member 484 of a thermostatic, polymetallic material, such as a thermostatic bimetal. Ambient compensation can also be achieved by forming frame 402 of a material or materials having substantially the same coefficient of thermal expansion as that of the hot wire element.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above methods without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense, and it is also intended that the appended claims shall cover all such equivalent variations as come within the true spirit and scope of the invention.

We claim:

1. An electrical switch comprising a casing; first and second electrical terminals mounted in said casing and extending exteriorly thereof for connection to an external circuit; a first electrical contact electrically connected to said first terminal; a movable electrical contact electrically connected with said second terminal and disposed within said casing for movement into and out of engagement with said first contact; means resiliently urging said movable contact for movement in a contacts-opening direction; releasable latch means for holding said movable contact in engagement with said first contact against the urging of said resilient means, said releasable latch means being engageable with a detent to maintain said contact in a latched contacts-closed position; an overload responsive tripping mechanism for disengaging said latch means from said detent to permit said movable contact to move to a contacts-open position under the bias of said resilient means, said tripping mechanism comprising a frame member; said frame member being electrically connected with said second terminal; a bell crank lever pivoted to said frame member, said detent being carried by one leg of said bell crank lever; spring means urging said bell crank lever for pivotal movement in a direction to move said detent out of engagement with said latch means; first and second current-conducting wire portions electrically connected together; a composite thermostatic plate member mounted on said frame member; adjusting means operatively connected with said thermostatic plate member for calibrating said switch; one end of said first current-conducting wire portion being connected 'with said thermostatic plate member and the other end thereof being con nected to a first portion of a rocker arm; one end of said second wire portion being connected to a second portion of said rocker arm and the other end thereof being connected to the other leg of said bell crank lever; said rocker arm being pivotally mounted on said frame intermediate said first and second portions thereof, said first wire portion being electrically connected to one of said contacts and said second wire portion being electrically connected to said frame member; said current-conducting wire portions being tensioned by said spring means and normally retaining and positioning said lever and detent for engagement with said latch means; and said currentconducting wires being operative upon a predetermined increase in temperature thereof to elongate and permit said lever to move said detent out of engagement with said latch means.

2. The electrical switch as set forth in claim 1 and wherein the connections between the respective ends of said first and second wire portions to said thermostatic plate member, rocker arm and said other leg of said bell crank lever are pivotal connections.

3. The electrical switch as set forth in claim 1 and wherein said adjusting means comprises a rotatable threaded member having a portion engageable with said composite thermally responsive plate member for moving the latter relative to said frame member to vary the tension in said current-conducting wire portions and thereby effect calibration of said switch.

4. The electrical switch as set forth in claim 1 and wherein said frame, adjusting means and current-conducting wire portions are formed of material having substantially the same coefficient of thermal expansion thereby providing for ambient compensation.

References Cited by the Examiner UNITED STATES PATENTS 2,096,608 10/ 1937 Combi 200-1 16 2,320,117 5/1943 Ayers 200113 2,656,437 10/ 1953 Allen 200116 2,689,239 9/1954 Bell 200122 2,943,172 6/ 1960 Ingwersen 200116 3,021,404 2/1962 Wood 2001 16 3,046,371 7/1962 Jencks 20088 3,097,279 7/ 1963 Whinery 200122 3,134,873 5/1964 Malone et a1 200116 3,142,737 7/ 1964 Brackett 200116 3,158,715 11/1964 Ingwersen 200116 ROBERT MACON, Acting Primary Examiner. BENARD A. GILHEANY, Examiner.

A. M. LESNIAK, M. GINSBURG,

Assistant Examiners.

Claims (1)

1. AN ELECTRICAL SWITCH COMPRISING A CASING; FIRST AND SECOND ELECTRICAL TERMINALS MOUNTED IN SAID CASING AND EXTENDING EXTERIORLY THEREOF FOR CONNECTION TO AN EXTERNAL CIRCUIT; A FIRST ELECTRICAL CONTACT ELECTRICALLY CONNECTED TO SAID FIRST TERMINAL; A MOVABLE ELECTRICAL CONTACT ELECTRICALLY CONNECTED WITH SAID SECOND TERMINAL AND DISPOSED WITHIN SAID CASING FOR MOVEMENT INTO AND OUT OF ENGAGEMENT WITH SAID FIRST CONTACT; MEANS RESILIENTLY URGING SAID MOVABLE CONTACT FOR MOVEMENT IN A CONTACTS-OPENING DIRECTION; RELEASABLE LATCH MEANS FOR HOLDING SAID MOVABLE CONTACT IN ENGAGEMENT WITH SAID FIRST CONTACT AGAINST THE URGING OF SAID RESILIENT MEANS, SAID RELEASABLE LATCH MEANS BEING ENGAGEABLE WITH A DETENT TO MAINTAIN SAID CONTACT IN A LATCHED CONTACTS-CLOSED POSITION; AN OVERLOAD RESPONSIVE TRIPPING MECHANISM FOR DISENGAGING SAID LATCH MEANS FROM SAID DETENT TO PERMIT SAID MOVABLE CONTACT TO MOVE TO A CONTACTS-OPEN POSITION UNDER THE BIAS OF SAID RESILIENT MEANS, SAID TRIPPING MECHANISM COMPRISING A FRAME MEMBER; SAID FRAME MEMBER BEING ELECTRICALLY CONNECTED WITH SAID SECOND TERMINAL; A BELL CRANK LEVER PIVOTED TO SAID FRAME MEMBER, SAID DETENT BEING CARRIED BY ONE LEG OF SAID BELL CRANK LEVER; SPRING MEANS URGING SAID BELL CRANK LEVER FOR PIVOTAL MOVEMENT IN A DIRECTION TO MOVE SAID DETENT OUT OF ENGAGEMENT WITH SAID LATCH MEANS; FIRST AND SECOND CURRENT-CONDUCTING WIRE PORTIONS ELECTRICALLY CONNECTED TOGETHER; A COMPOSITE THERMOSTATIC PLATE MEMBER

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