US3225168A

US3225168A - Miniature electric switch

Info

Publication number: US3225168A
Application number: US247263A
Authority: US
Inventors: Kenneth D Grimes; William C Dunnington
Original assignee: METAMORA ELECTRONICS CORP
Current assignee: METAMORA ELECTRONICS CORP
Priority date: 1951-01-28
Filing date: 1962-12-26
Publication date: 1965-12-21
Anticipated expiration: 1982-12-21

Description

DSC, 21, 1965 K. D. GRIMES ETAL 3,225,168

MINIATURE ELECTRIC SWITCH iled Dec. ,'26,v 1962 4 Sheets-Sheet 1 NMuNv m M 5 M 5 W M ,fm /W 5%, Ma i M, 4 Z

Dec. 21, 1965 K. D. GRIMES ETAL 3,225,168

MINIATURE ELECTRIC SWITCH 4 Sheets-Sheet 2 Filed Dc. 26, 1962 KRM Xmm Q bww wwkw xwXNNN m NNN Dec. 2l, 1965 K. D. GRIMES ETAL. 3,225,158

MINIATURE ELECTRIC SWITCH Filed Dec. 26, 1962 4 Sheets-Sheet 3 .w @www kv Dec. 21, 1965 K. n. GRIMES ETAL 3,225,168

MINATURE ELECTRIC SWITCH 4 Sheets-Sheet 4 Filed Dec. 26, 1962 United States Patent 3,225,168 MINIATURE ELEQTRIC SWITCH Kenneth D. Grimes and William C. Dunnington, Peoria, Ill., assignors to Metamora Electronics Corporation, Metamora, Ill., a corporation of Illinois Filed Dec. 26, 1962, Ser. No. 247,263 Claims. (Cl. 20G- 159) This application constitutes a continuation-in-part of our copending application Serial Number 153,507, filed November 20, 1961, now abandoned.

The present invention relates to electric switches and more particularly to improved miniature plunger type electric switches.

In the pro-duction line control area and in other areas such as machine tool control, heavy construction vehicle control and aero-space vehicle engine control electrical switches previously known lack the reliability and endurance that is necessary for high speed repeated actuation or for satisfactory performance at lower rates of actuation under adverse environmental conditions such as vibration, for extended periods of use. Usually, micro-switches have been employed for these applications because they are inexpensive and their rapid break-away upon actuation limits the time duration of arcing between the contacts and thus reduces wear. Generally speaking, a microswitch is an over the center, snap action switch having a long, one piece leaf type spring supported at one end. Forwardly of the support, the spring is in close proximity to at least one compression member side blade. Depending on the design of the switch, the depression of a switch actuator snaps, 4the unsupported end of the leaf spring, carrying a movable contact, into or out of engagement with stationary contact members and release of the actuator allows the spring to snap back to its original position. The movable contacts on this type of switch are necessar-ily of small mass to reduce the effect of inertia upon switch actuation and snap back. Such switches have had wide acceptance in slow or moderately fast cycling switching operations, but at relatively high and increasing cycling rates the snap action switch has shown definite inadequacies. Specifically, at high actuation rates, the snap action cannot keep pace with the mechanical actuation of the switch. Also this type of switch is susceptible to fatigue and breakage adjacent the cantilever mount, to contact bounce (electrical chatter), resonance induced failure, and iiutter of the spring and actuation means. These susceptibilities are similarly apparent under service conditions wherein the actuation rate may be low or intermittent lbut the switch must `be reliably operable while subjected to vibration or vibratory cycling during sustained acceleration or deceleration.

It is therefore an object of this invention to provide a miniature electric switch having the capability to keep pace electrically with high mechanical actuation rates.

It is a further object of the present invention to provide miniature electric switch capable of being actuated at very high cycling rates over extended periods of time under adverse environmental conditions with a high degree of reliability and endurance.

It is another object of this invention to provide a plunger type electric switch wherein movable contact motion is essentially rectilinear and self resonance is highly damped.

It is a further object of the present invention to provide a plunger type electric switch capable of high cycling rate wherein the switch plunger and movable contact motion instantaneously follows actuator button motion :both in actuation and relaxation.

Another object of this invention is to provide a miniature electric switch that is substantially free from flutter, chatter contact bounce and self resonance over a wide range of actuating or vibratory cycling rates.

It is an object of the present invention to provide a miniature electric switch having at least one fixed position Contact, a movable contact and means for moving the latter with respect to the former, in which the contacts are completely enclosed within a capsule and a switch actuating button is positioned on the exterior surface of a flexible portion of the capsule.

It is yet another object of the present invention to provide a miniature electric switch having improved heat dissipating means in the form of vented spacers which allow heat to ow from the switch contacts to the switch housing.

It is a further object of this invention to provide a miniature electric switch having massive precision mating contacts.

It is another object of this invention to provide a mniature electric switch so encapsulated as to be operable for long periods of time in a wet, corrosive atmosphere.

These and other objects of this invention are more fully set forth in the following detailed description, reference being made to the attached drawings wherein illustrative embodiments of the present invention are shown.

In the drawings:

FIGURE l is a perspective view of a miniature electric switch embodying characteristics of the invention.

FIGURE 2 is an enlarged sectional view taken along line 2-2 of FIGURE 1 showing parts in elevation.

FIGURE 3 is a sectional view similar to FIGURE 2 showing a second embodiment of the invention.

FIGURE 4 is a perspective view of another embodiment of the invention. This embodiment is about onethird the size of the one shown in FIGURE l and has an actual size of approximately 2 cm. x 2 cm.

`FIGURE 5 is an enlarged sectional view taken along line 5-5 of FIGURE 4 showing parts in elevation.

FIGURE 6 is an enlarged elevation view of the switch shownin FIGURE 4, a :portion of the housing 'being broken away to expose the interior detail.`

FIGURE 7 is a sectional view similar to FIGURE 5 showing a further embodiment of the invention.

FIGURE 8 is a sectional view similar to IFIGURE 5 showing yet another embodiment of the invention.

FIGURE 9 is an enlarged sectional view of a modcation of the embodiment shown in FIGURE 5 in a housing having a dat mounting surface, mounting holes and an attached actuating arm.

With particular reference to the drawings, a miniature electric switch 10 embodying characteristics of this invention is shown in FIGURE 1. The working parts of the switch 10 are sealed against environmental attack within a cylindrical housing 12. Housing 12 is preferably a length of extruded anodized aluminum alloy tube but can be formed from other corrosion resisting; materials such as stainless steel or nickel alloy tubing or the like to withstand special environmental conditions.

As best shown in FIGURE 2 the components of the switch 10 are coaxially stacked within the cylindrical housing 12 and are held in place by split retainer rings 14 which seat in grooves 16 formed in the inner wall of the housing 12 at each end of the housing 12. The top most member of the component stack as shown in FIGURE 2 is a top end plate 18 which is biased into sealing engagement with ring 14 by an O-ring 20. Immediately below O-ring 20 is positioned an annular resilient diaphragm 22 which surmounts and is secured to a ring-like spacer 24. Diaphragm 22 is preferably formed from a corrosion resistant material such as neoprene.

A second O-ring 26 positioned in underlying engagement with spacer 24 biases the spacer and diaphragm 22 into a sealing relation with the O-ring 20. O-rings 20 and 26 are deformed in the assembly of the switch so that they sealingly engage the interior wall 28 of the housing 12. Below O-ring 26 is positioned an annular insulating bearing 30 having a generally inverted U-shaped cross section wherein the inner leg 32 of the U is longer than the outer leg 34. Within the annular channel defined by the legs of the bearing is secured a massive stationary contact 36. Contact 36 is formed from a metal such as aluminum and has an annular noble metal alloy inlay 38 secured in a groove 40 in the lower surface thereof. Contact 36 does not extend outwardly into engagement with the interior wall 28 of the housing 12 and has a plurality of deep grooves 42 cut in its outer surface which, because they increase the surface area of the contact 36, provide for increased heat dissipation and result in a lower steady state operating temperature for the contact 36 during extended, fast cycling operation, of the switch. The stationary Contact 36 is supported along the outer periphery of its lower surface by an annular spacing ring 44 which is separated from a lower end plate 46 by a sealing O- ring 48. End plate 46 is held in place by the lower split retainer ring 14.

A corrosion resistant actuator button 50 formed from a material such as stainless steel is mounted on and sealed to the resilient diaphragm 22 as by an annular groove 52 which encircles the generally cylindrical button 50 and engages the central hole 54 in the diaphragm. Actuator button 50 projects upwardly through a central hole 55 in the top end plate 18 and is axially slidable with respect to the end plate 18. A shoulder 56 is formed at the bottom of the button 50 and surmounts a plunger 58. The plunger is coaxial with the button 50 and is biased into coacting engagement with the button 50 by a helical spring 60. The spring 60 seats against the lower end plate 46 and is positioned thereon by circumscription of a cylindrical boss 62 formed at the center of the inner surface of lower end plate 46. The spring 60 also encircles a lower portion of the plunger 58 and seats against the bottom surface of an annular shoulder 64 which projects from the plunger. Integrally secured to the plunger 58 closely adjacent the upper extent of shoulder 64 is a massive annular contact 66. An annular noble metal alloy inlay 68 is secured on the upper surface of contact 66 (shown sectioned in FIGURE 2 for clarity). In the rest position shown, the spring 60 urges plunger 58 upward so that the contact inlay 68 on the movable contact 66 abuts the contact inlay 38 on the stationary contact 36. The inner and outer diameters of each of the inlays 3S and 68 are all different from one another to reduce arcing damage at the edges of the inlays. An insulated conductor 70 is secured at one end to the stationary contact 36 and at the other to a screw threaded fastener 72 which extends through the lower end plate 46 and is threaded into a terminal 74. A second conductor 76 is secured by one end to the helical spring 60 which is in electrical contact with the movable contact 66. The other end of conductor 76 is secured to a screw threaded fastener 78 which extends through the lower end plate 46 and is threaded into a terminal 80.

As shown in the FIGURE 2 embodiment of the switch, the contact inlays 38 and 68 are precision machined so that their mating surfaces closely match each other throughout nearly the entire coextension of each. The switch is actuated by depressing the button 50 which distends the diaphragm 22 and moves the plunger 58 and the movable contact 66 carried thereby downwardly thus separating the inlays 38 and 68 and breaking the electrical circuit. The plunger 58 can be moved downwardly until it abuts the upper surface of the cylindrical boss 62. Helical spring 60, which is compressed by the downward travel of the plunger, urges the plunger, movable contact and button upwardly to the rest position shown upon release of the button 50.

Although this embodiment has been described as if the button 50 were positioned at the top of the switch it should be clear that the switch performs equally well when oriented in any other position than the one shown.

4 It should also be realized that the button 50 can be actuated by any outside force such as stimulus from a condition sensing device.

A second embodiment of a miniature electric switch having characteristics of the invention is shown at in FIGURE 3. The working components of the switch 100 are encapsulated within an aluminum alloy tubular housing 102. An upper split retainer ring 104 is seated in a groove 105 in the inner surface of the housing 102 near the upper end thereof. Immediately beneath ring 104 is a resilient disk like neoprene diaphragm 106 having a corrosion resistant button 108 formed from a material such as stainless steel permanently adhered to the upper surface thereof, coaxial with the diaphragm 106. This construction eliminates the upper end plate shown in the embodiment of FIGURE 2 and, as a disk-like, rather than annular, diaphragm is used a more fail safe, better sealing upper end is provided for the switch capsule. This construction, besides compacting the switch design provides less potential traps for fluid which is important when the switch is employed in a wet corrosive environment.

As shown in'FIGURE 3, an annular spacer ring 110 is secured at its top edge to the under surface of the diaphragm 106. An O-ring 112 engages the lower surface of the spacer ring 110 and the housing interior wall providing an added seal and component support means. Beneath the O-ring 112 is an annular insulating bearing 114 having an inverted U shaped cross section similar to bearing 30 and containing a stationary finned contact member 116 having an annular noble metal alloy inlay 118. A second stationary finned contact member 120 contained within an upwardly facing annular insulating bearing 122. A noble metal alloy annular inlay 124 is positioned in the upper surface 126 of the Contact member 120 and the contact members 120 and 116 are axially spaced from one another by an insulated spacer ring 128 `which engages the outer periphery of the lower surface of contact member 116 and the outer periphery of the upper surface of contact member 120.

A lower split retainer ring 130 seated in a groove 132 in the inner surface of the housing 102 near the lower end thereof supports a lower end plate 134. The lower end plate 134 is pressed into intimate engagement with the split retainer ring 130 by an O-ring 136 positioned immediately over the end plate 134 and in sealing engagement with the interior surface of the housing 102. An annular spacer ring 138 overlies the O-ring 136 and is urged thereby into supporting relation with the under'- surface of the stationary contact insulating bearing 122.

An insulated sleeve bearing 140 comprising an upper portion 142 molded from plastic material and a metalic lower portion 144 is bonded to the lower surface of the neoprene diaphragm 106 concentric with the disk-shaped diaphragm and the button 108.

The lower end plate 134 in this embodiment also has a cylindrical boss 146 projecting from the center of its upper surface.

A plunger 148 comprising cylinder of metal such as alluminum having bearing portions 150 and 152 of reduced width projecting coaxially from the upper and lower ends thereof respectively is mounted for longitudinal movement at the center of the switch 100 so as to be coaxial with the bearings 114 and 122 and supported against transverse motion by the bearings 114 and 122. The plunger 148 is supported at the lower end thereof by a helical spring 154 which circumscribes the end plate circular boss 146 and the reduced width portion 152 of the plunger. The plunger 148 is supported at the upper end thereof by sliding engagement of the plunger reduced width portion 150 within the sleeve bearing 140. A helical spring 155 is positioned so as to circumscribe .the reduced width portion 150 and be supported between the lower surface 156 of the sleeve bearing 140 and the shoulder 158 defined by the change in width at the upper end of the plunger 148. In the rest position shown in FIGURE 3 the spring 154 has an assembled deflection which is dependent on the force constant of the spring and the desired applied force necessary to break the engagement of contact 160 with contact 116. Open spaces between the ends of the plunger and the capsule plunger travel and push button overtravel.

Integrally mounted on the plunger 148 midway between the ends there-of is an annular massive contact member 160 having annular fins 162 grooved in the outer periphery thereof. `Contact member 160 has annular noble metal alloy inlays 164 and 165 mounted on the upper and lower surfaces thereof. In the rest position shown, the contact member extends radially in the space between the stationary contact members 120 and 116 `so that the upper inlay 164 on the movable contact member 160 abuts the inlay 118. An insulated conductor 166 is secured to stationary contact member 116 and extends out through a close fitting opening 168 in the lower end plate 134. A second insulated conductor, 170, is secured to the stationary contact member 120 and extends out through another close tting opening 172 in the lower end pla-te 134. A third insulated conductor, 174, is secured to the plunger 148 (shown) or the helical spring 154 (not shown) and likewise extends out of the switch capsule through an opening 176 in the end plate 134. yTo ensure complete sealing of the switch components against environmental attack an epoxy potting compound 178 is poured onto the outside of the lower end plate 134 filling the volume between the end plate and the bottom end of the housing 102.

To activate the `switch 100 the button 108 is depressed by any external mechanism (not shown). Because the spring constant of the lower helical spring 154 is substantially less than that of the upper helical spring 155, the upper spring is forced downwardly only slightly compressed by the sleeve bearing 140. The spring 155, in turn, urges the plunger downwardly compressing the spring 154 and moving `the movable contact 160 away from the stationary contact 116 and into an abutting relationship :with the stationary contact 120. Should the vbutton 108 be depressed a greater distance than the plunger can move before contact inlay 165 abuts contact inlay 124, the spring 155 is compressed thereby taking up the overtravel. When the button 108 is released, springs 154 and 155 return the switch components to the rest position shown. Each of the inlays is precision mated with the one it abuts so that arcing is minimized.

The switch components in the FIGURE 3 embodiment are effectively encapsulated against environmental attack by the cylindrical housing 102, the neoprene diaphragm 106 and the lower end plate 134 surfaced by the potting compound 178. Secondary defense is provided by the O- rings 136 and 112. The actuator button 108 is effectively electrically insulated from the switch contacts by the neoprene diaphragm 106 to which it is secured and by the insulating portion 142 of the sleeve bearing 140.

The embodiments of the miniature electric switch of the invention which are shown in FIGURES 4-9 illustrate preferred constructions of novel and improved construction over those set forth in FIGURES l-3 and in the above mentioned copending application and are set forth to more lucidly show the principles of the invention rather than limit the scope thereof.

Referring to FIGURE 4, a miniature electric switch of the present invention is indicated at 200. The switch components described hereinafter are encapsulated within a cylindrical housing 202 and are all coaxial with one another and with the housing with the exception of

lead Wires

204, 206, and 208. The housing 202 shown has an actual length of about 2 cm. and a diameter of about 2 cm. The housing is preferably formed of anodized aluminum alloy tubing but can also be formed from other materials such as stainless steel or nickel alloy tubing or the like to meet specific environmental and operating re- 6 quirements such as steady state operating 'temperature and resistance to corrosion.

As best shown in FIGURES 5 and 6 the housing 202 is internally grooved near the upper and lower extent of the housing.

Grooves

210 and 212 receive split retaining rings 214 which serve to position the switch components in a stacked relationship Within the switch capsule. Positioned within the housing 202 immediately beneath the upper retaining ring 214 is a flexible, resilient diaphragm 216. The diaphragm 216 is disk shaped and is preferably formed from neoprene but can be constructed from any other plastic material that is resistant to chemical attack and is durably resilient over a wide temperature range. A push button 218 preferably formed from a wear resisting non-corroding material such as stainless steel is permanently bonded to the upper surface of the neoprene diaphragm. Button 218 is the switch actuator which responds to exterior force applied thereon to actuate the switch components located below the diaphragm 216 within the switch capsule as outlined hereinafter. A metallic ring-like spacer 220 is bonded by its upper surface to the lower surface of the diaphragm 216 adjacent the outer periphery of the diaphragm, A sealing compound is applied to the area of coextension 222 between the metallic spacer outer edge and the inner surface of the housing thereby ensuring an anti-environment seal at the push button end of the switch 200. The switch capsule is completed by an end plate 224 preferably injection molded from a plastic insulating material, end plate is positioned immediately above the lower retainer ring 214 and has three small holes therethrough providing exits from the capsule interior for the

lead wires

204, 206 and 208. An adhesive may be applied to the outer periphery of the end plate 224 to provide added sealing for the switch components. The final assembly step comprises flowing an epoxy potting compound into the cup dened by the outer surface of the end plate 224 and the portion of the interior surface of the housing 202 that extends between the groove 212 and the bottom end of the housing. The potting compound 225 seals the lead wire exits and serves as the primary anti-environmental seal for the bottom end of the switch 200.

The switch components positioned within the capsule above described include a push rod 226,. preferable injection molded of plastic material, which is permanently bonded to the lower surface of the diaphragm 216 directly beneath the push button 218. As shown in FIG- URE 5, the push rod is generally cylindrical in shape having a bearing surface 228 and a downwardly directed shoulder 230 thereon. A metallic plunger 232 in the shape of a hollow cylinder having an annular interior boss 234 at the midsection thereof is positioned so as to slidably engage the push rod bearing surface 228. The lower portion of the push rod 226 extends downwardly through circular opening 236 and is slidably supported by the annular boss 234. A helical spring 238 circumscribes a portion of the push rod and extends between the shoulder 230 and the boss 234. A second helical spring 240 extends between the lower surface of the boss 234 and the end plate 224. An integral cylindrical boss 242 formed on the end plate inscribes the spring 240 and secures the spring 240 against transverse motion. The springs 238 and 240 thus support the plunger 232 suspended between the upper and lower ends of the capsule.

An annular contact member, 244 preferably stamped and machined from solid coin silver is precisely positioned and tixedly secured to the plunger 232 as -by silver soldering to the outer surface thereof. This contact member thus moves with the plunger.

An upper insulating bearing 246 is positioned in the housing 202 separated from the metallic spacer 220 by an O-ring 248. Bearing 246 is annular and has an integral downwardly directed lange 250 adjacent the center opening therethrough. An annular stationary contact 252, likewise stamped from solid coin silver is mounted within the bearing 246 so that the mating surface thereof is downwardly directed. A lower stationary contact member 254 identical to contact member 252 is mounted within lan upwardly directed insulating bearing 256. The upper and lower

stationary contact members

252 and 254 are longitudinally spaced from one another by a vented annular insulating spacer 258. A similar insulating spacer 260 separates the lower insulating bearing 256 from the end plate 224.

The novel spacers 258 and 268 are preferably injection molded from plastic material and have radially extending vents 262 formed therein which increase in cross section from the inner edge of a spacer to the outer edge as is best illustrated in FIGURE 6. Heat generated in the contacts during switch operation is conducted through the vents to the housing 282 so that the switch operates at a low steady state temperature even during fast cycling operation this greatly lessening the prospect of heat damage to the switch components and thereby lengthening the useful life of the switch.

Contact members

244, 252 and 254 are each massive when `compared to those of conventional switches. The massiveness results in less mating surface erosion and the coin silver composition provides better he-at dissipation. As is seen clearly in FIGURE 5, the mating surfaces of the

contact members

244, 252 and 254 .are olfset from one another to prevent pitting and burning at the thin edges of the contacts. The mating surfaces are precision formed to close tolerances so Ithat each surface engages its mate over a very substantial portion of the coextensive Iarea of each.

Insulated

lead wires

204, 206 and 298 are secured to upper stationary contact 252, lower stationary contact 254, and the helical spring 24@ or plunger 232 respectively and extend through the end plate 224 as discussed above. A notch 264 is formed in each vented

spacer

258 and 260 to allow passage of wire 204 therethrough. A plate 266 identifying the electrical leads is adhered to the exposed surface of the potting compound.

The helical spring 240 biases the movable contact member upwardly into engagement with the upper stationary contact 252. An electrical `circuit is thus established through the loop comprising the lead wire 204, lthe stationary contact 252, the movable contact 244, the plunger 232 and/or the spring 240 and the lead wire 208. An `external force acting downwardly on the push button 218 rst compresses the helical spring 238 until the load ybuilt up therein slightly exceeds the assembled load of the spring 240 and the plunger begins to move downwardly thus breaking the engagement of the

contact members

244 and 252. The applied force necessary to produce this movement is herein referred to as the break force, and the concurrent movement of the push button is referred to as the pretravel to break.

As the push button 218 is depressed further, a further compression of the spring 238 urges the Contact member 244 into engagement with the lower stationary contact member 254. An electrical circuit is thereby closed through the loop comprising the lead wire 266, the lower stationary contact 254, the movable contact 244, the plunger 232 and the lea-d 288. The applied force necessary to produce the travel of the plunger to this point is refered to as the make force, and the travel of the push button is referred to as the pretravel to make. The latter is equal Ito the sum of the plunger travel and the compression of spring 238.

The external force acting on Ithe push button 218 proceeds against the helical spring 238, the helical spring 240 and the small spring force inherent in the neoprene diaphram 216 until the movable contact member 244 engages the lower stationary contact member 254. Thereafter any additional force applied to the push button produces no furthe-r compression of the spring 240. The over travel of the push button beyond its travel to make is accommodated by the spring 238 and the diaphragm until the lower surface of the push rod 226 abuts the cylindrical boss 242 providing a positive stop. An alternative stop is provided when the upper shoulder 268 on the push rod 226 abuts the upper insulating bearing 246. Upon release of the externally applied force, the helical spring 240 returns the mov-able contact member 244 to the rest position shown in FIGURES 5 and 6.

A second embodiment of the improved miniature electric switch 206A is shown in FIGURE 7. A majority of the components thereof are identical to those shown in the FIGURES 5 and 6 embodiment and are therefore designated by like numerals. In this embodiment the push rod 226 has been replaced by a shorter push rod 226A which extends downwardly into the circular opening 236A in the plunger 232A but not beyond (as shown in rest position). The plunger 232A has lan inner annular boss 234A more nearly at the midpoint of the plunger. The helical spring 238A is somewhat shorter than .the helical spring 238 and the helical spring 240A is longer than the helical spring 248 and engages the shoulder 268 of a movable spring guide 278 which is positioned within the plunger 232A immediately below the boss 234A.

The helical spring 240A. biases the movable contact 244 into engagement with lthe upper stationary contact 252. An external force applied to the push button in this embodiment is transmitted directly to the helical spring 240A through the push rod 226A and the guide 278 offsetting he biasing force and bringing

contact members

244 and 252 to the point of disengagement. As the push button is depressed further, each of the springs 240A and 238A is compressed. Energy stored in the spring 238A which is compressed to a measured degree at the rest position shown, serves to actuate the plunger 232A and the movlable contact member y244 secured thereto and to assist the externally applied force in deflecting spring 240A thereby engaging the movable Contact member 244 with the lower stationary Contact member 254. IOver travel of the push button 218 beyond this engagement is accommodated by both of the

helical spring

238A and 248. Upon removal of the actuating force from the button, the helical spring 240A restores the switch components to the rest position shown.

The embodiment shown in FIGURE 7 differs in operational characteristics from the one shown in FIGURES 5 and 6 in that it requires less pretravel to break by virtue of the direct application of force to the helical spring 240A and less pretravel to make because the sole function of the helical spring 238A, to the point of over travel accommodation, is to store and release suiicient energy to move Ithe mass of the plunger 232A and its associated contact 244 through the short vertical distance from break to make In this embodiment, therefore, fewer ounce inches are required to break and make and the embodiment is appropriately referred to as a low energy switch.

Another embodiment of the improved miniature electric switch is shown in FIGURE 8. It is a two contact normally closed switch having many parts in common with the switches shown in FIGURES 5-7. In the instant switch, 200B, however, the lower stationary contact member is replaced by a vented spacer 272 and the lower insulating bearing 256B is inverted. Omitted are the upper helical spring and the third lead out wire. In this embodiment a shorter push rod 226B is spaced from the diaphragm 216 so that a pretravel to break is provided. Plunger 232B is shorter than the one shown in earlier embodiments. This embodiment of the switch is particularly useful in the canning industry in conjunction with a so called dud detector to detect and separate cans that have been poorly sealed. For this use the normally closed

contacts

244 and 252 are held open by external means engaging the switch push button 218. When a dud is detected by the external means, the button 212 is released, the contacts are closed by the spring 240B and a mechanism connected to the switch operates to eject the dud from the production line. The switches of the invention are adapted for use on the wet side of canning production lines and in similar environments where the atmosphere is hot and humid, in that the switch components are all protectively encapsulated.

FIGURE 9 shows a further embodiment of the switch employing the components similar to those of FIGURE in another housing. The housing of FIGURE 5 has been replaced by a massive block-like housing 274 having a cylindrical opening 276 formed therethrough and counter bored so as to dene an annular shoulder 278. The opening receives the stacked components of the switch and the diaphragm seats against the annular shoulder 278. A recess 280 formed in the lower portion of the housing receives an insulating terminal block 282 having three conductive inserts 284 molded therewith to which the contact leads 204, 206 and 208 are connected The terminal block 282 abuts the end plate 224 and serves to retain the stacked arrangement of the switch components. Terminal block 282 is secured to the housing 274 by means of an epoxy potting compound as at 286. A well 288 forme-d in the top of the housing 274 adjacent the switch components receives the base portion of a lever 290 which is pivotable with respect to the housing 274 by means of a roll pin 292 which passes through the lever base and the housing. The forward portion of the lever extends over the switch and a projection 294 formed on the lower surface of the lever 290 engages the button 218. The projection 294 is biased into light pressing engagement of the button by a helical spring 296 positioned in the well 288. A bearing 298 is positioned at the outer end of the lever 290 to engage the external switch actuating means. Because the button 218 is lightly pressed by the lever 290 even at the rest position shown, very little pretravel exists in this embodiment and the switch is extremely sensitive in response to actuation pressure. This embodiment, then, is a plunger type micro switch having the advantages of a snap action micro switch, but not possessing the disadvantages thereof as described hereinabove.

IMPROVEMENTS advantages presented by contacts inlayed with dissimilar materials.

(2) The higher heat conductivity of coin silver over aluminum obviates the necessity of machining cooling `tins on the contacts, while providing faster heat dissipa- Ition.

(3) The vented insulating spacers allow outward ow of heat generated at the contacts to the housing and thus fallow higher switch actuation rates at lower steady state contact temperatures.

(4) The reciprocating plunger member is recessed at each end to receive the helical spring members, thereby allowing a reduction in the overall switch length.

The smaller, lighter structures embodying this invention have been vigorously tested and have given an excellent account of their performance in certain areas where other previously available switches are not suitable. The present switch is specially adapted to use where reliable performance, and endurance at a variety of actuation rates ranging from low to very high rates in a corrosive environment is important. The switch of the invention is not a snap action switch and therefore is not hampered by the inability of the contact members to keep up with the mechanical actuation rate.

1 O rri-:srs

In an endurance test at 780 mechanical cycles per minute the switch of the invention as shown in FIGURES 5 and 6 was operated to more than 160,000,000 cycles before mechanical failure. In a parallel test, an overcenter, snap-action switch failed mechanically at approximately 6,000,000 cycles. The long, leaf-type spring of the snap-action switch experienced metal fatigue and resulting breakage adjacent the cantilever mount.

Actuation up to 900 cycles per minute of a switch of the invention as shown in FIGURES 5 and 6 when monitored on an oscilloscope showed positive break and make of the contacts with no misses and no contact bounce.

Tests to 3200 actuations per minute, with an actuator shaped to apply sinusoidal travel to the push button clean square waves with no contact bounce up to 1800 actuations per minute and only instantaneous bounce from there to 3200 cycles pei minute. A switch of the invention was actuated at 3200 cycles per minute to approximately 100,000,000 cycles prior to mechanical failure. In contrast, a conventional snap actuation switch tested in a like manner showed utter and contact chatter in the 500 to 1000 actuations per minute range and the normally open contacts failed to show engagement after a short run. In vibration tests, switches of the invention showed no major resonance and no electrical chatter when subjected to cycling from 500 to 3000 and back to 500 cycles per second at accelerations from 5 to 50 gs.

SUMMARY It is clear that the novel construction of the present switch results in superior electrical performance. The mechanical heart of the miniature electric switch comprises a reciprocable contact carrying plunger suspended between dissimilar helical springs with stops in the form of xed contacts the terminate movable contact travel, one end of the mass elastic system terminating in a fixed end plate and the other in a flexible, actuator engaged diaphragm, and wherein vented spacers are provided to dissipate heat generated in the contacts during actuation to the switch capsule.

Although several embodiments of the invention have been set forth for illustration it should be real-ized that many modifications in the embodiments are possible without departing from the principles of the invention and therefore the invention should be limited only by the scope and spirit of the following claims.

What is claimed is:

`1. An electric switch comprising a capsule, the capsule including a housing formed from heat conductive material and having a cylindrical opening formed therethrough, a rigid material sealingly closing one end of the opening and a resilient disk-like diaphragm sealingly closing the opposite end of the opening; movable switch components mutualy coaxially positioned within the capsule at the longitudinal axis of the capsule, the movable switch components comprising a plunger, an annular washer-like contact member secured to the plunger intermediate the ends thereof so as to circumscribe the plunger, and an upper and a lower helical spring supporting the plunger between the resilient and rigid ends of the capsule respectively; and stationary switch components mutually coaxially positioned within the capules closely adjacent the inner periphery thereof, the stationary switch components comprising an upper annular contact member positioned above the movable contact member and a lower annular contact member positioned beneath the movable contact member, the lower spring biasing the plunger upwardly whereby the contact member mounted thereon abuts the upper stationary contact member in the rest position of the switch, the switch being actuatable by a downwardly directed force on the resilient end `of the capsule which moves the plunger downwardly compressing the lower spring thereby moving the contact mounted on the plunger out of engagement with the upper stationary contact member and into engagement with the lower stationary contact member the stationary contact members being separated from the ends of the capsule by a plurality of annular spacing members `and separated from one another a distance greater than the thickness of the movable contact by an annular spacer formed from an instulating material and having circumferentially spaced radially extending -serration-like vents formed in the upper and lower surfaces thereof through which heat generated at the contact member surfaces during repeated switch actuation ows to the switch capsule and is dissipated.

2. An electric switch as set forth in claim 1 wherein the plunger has the general shape of a hollow cylinder having an inwardly extending annular boss integrally formed therein, a major portion of said upper and lower helical springs being positioned within the plunger respectively abutting the upper and lower surface of said boss.

3. An electric switch as set forth in claim 1 wherein an insulating push rod is interposed between the upper helical spring and the resilient diaphragm.

4. An electric switch as set forth in claim 1 wherein the serration like vents increase in cross sectional area as they extend radially.

5. An electric switch comprising a capsule, the capsule including a housing formed from a heat conductive material and having a cylindrical opening formedl therethrough, a rigid material sealingly closing one end of the opening and a resilient, disk like diaphragm sealingly closing the opposite end of the opening; movable switch components mutually coaxially positioned within the capsule at the longitudinal axis of the capsule, the movable switch components comprising a plunger, an annular washer-like contact member secured tot the plunger intermediate the ends thereof so as to circumscribe the plunger, an insulating push rod interposed between the plunger and the resilient diaphragm of the capsule and a helical spring interposed between the plunger and the rigid end of vthe capsule; and stationary switch cornponents, mutually coaxially positioned within the capsule closely adjacent the inner periphery thereof, the stationary switch components comprising an annular contact member positioned intermediate the ends of the capsule, the plunger mounted contact member being movable into and out of engagement with the stationary Contact member by intermittent depression of the resilient diaphragm the stationary contact member being secured in position by a plurality of stacked annular spacing members at least one of which having radially extending vent means formed therein through which heat generated at the surfaces of the contact members during repeated switch actuation flows to the switch capsule. and is dissipated.

6. An electric switch as set -forth in claim 5 wherein said vent means comprise radially extending serrations formed in the upper and lower surfaces of the annular spacing member.

7. An electric switch as set forth in claim 5 wherein the insulating pushrod is spaced a short distance below the under surface of the resilient diaphragm thereby providing a pretravel for the diaphragm.

8. A miniature electric switch comprising a housing having a cylindrical opening formed therethrough, a disklike end plate sealingly closing one end of the housing, an annular end plate secured to the opposite end of the housing, an annular resilient diaphragm secured within the housing and spaced subjacently to the annular end plate, a switch actuator button projecting through the diaphragm opening, thereby sealingly closing the opening and being supported by the diaphragm, said button projecting upwardly through the annular end plate opening andI being slidably received therein; mutually coaxial movable switch components within the housing, the movable switch components comprising la helical spring mounted adjacent the disk-like end plate, and elongated plunger supported between the actuator button and the helical spring, and a massive annular contact member fixedly secured on the plunger intermediate the ends thereof so as to circumscribe the plunger; and mutually coaxial stationary switch components positioned in the housing adjacent the inner periphery thereof, the stationary switch components comprising a massive annular contact member circum- Scribing the plunger intermediate the ends thereof adjacent the plunger mounted contact member, an insulating bearing interposed between the inner periphery of the stationary contact member and the plunger, heat dissipating means comprising a plurality of spaced fins formed in the outer periphery of the stationary contact member, and a plurality of spacing members supporting the stationary contact in position intermediate the disk-like end plate and the annular end plate; whereby an outside force acting downwardly on the actuato-r button, moves the button and therefore the plunger and the movable contact downwardly against the yforce of the helical spring.

9. An electric switch comprising a capsule formed from a heat conductive material and having a cylindrical opening formed therethrough, a rigid material sealingly closing one end of the opening and a resilient disk-like diaphragm sealingly closing the opposite end of the opening; movable switch components mutually coaxially positioned at the longitudinal axis of the opening, the movable switch components comprising a plunger, an annular washer-like contact member secured to the plunger intermediate the ends thereof so as to circumscribe the plunger, and upper and lower resilient means supporting the plunger between the resilient and rigid ends of the capsule respectively; and -stationary switch components mutually coaxially positioned within the capsule opening centrally thereof, the stationary switch components comprising an upper annular contact member positioned above the movable contact member and a lower annular contact member positioned beneath the movable contact member, the lower resilient means biasing the plunger upwardly whereby the contact member mounted thereon abuts the upper stationary contact member in the rest position of the switch, the stationary contact members being separated from the ends of the capsule by a plurality of annular spacing members, and separated from one another a distance greater than the thickness of the movable contact member by an annular spacer formed from an insulating material, the switch being actuable by a downwardly directed force on the exterior of the resilient end of the capsule which deforms the diaphragm moving the plunger downwardly and compressing the lower spring, thereby moving the Contact member mounted on the plunger out of engagement with the upper stationary contact member and into engagement with the lower stationary contact member, the upper resilient means being relatively stiffer than the lower resilient means whereby the upper resilient means transmits the downwardly directed force and remains substantially less deflected so long as no greater force is placed on the resilient diaphragm than that necessary to move the plunger mounted contact member just into engagement with the lower stationary contact member.

10. An electric switch as set forth in claim 9 wherein the annular spacers between each stationary contact and an end of the capsule are ported whereby heat generated at the Contact surfaces during repeated switch actuation is transmitted from the stationary contact members to the housing and dissipated therethrough.

No references cited.

KATHLEEN H. CLAFFY, Pm'mary Examiner.

ROBERT K. SCHAEFER, Examiner.

Claims

1. AN ELECTRIC SWITCH COMPRISING A CAPSULE, THE CAPSULE INCLUDING A HOUSING FORMED FROM HEAT CONDUCTIVE MATERIAL AND HAVING A CYLINDRICAL OPENING FORMED THERETHROUGH, A RIGID MATERIAL SEALINGLY CLOSING ONE END OF THE OPENING AND A RESILIENT DISK-LIKE DIAPHRAGM SEALINGLY CLOSING THE OPPOSITE END OF THE OPENING; MOVABLE SWITCH COMPONENTS MUTUALLY COAXIALLY POSITIONED WITHIN THE CAPSULE AT THE LONGITUDINAL AXIS OF TH CAPSULE, THE MOVABLE SWITCH COMPONENTS COMPRISING A PLUNGER, AN ANNULAR WASHER-LIKE CONTACT MEMBER SECURED TO THE PLUNGER INTERMEDIATE THE ENDS THEREOF SO AS TO CIRCUMSCRIBE THE PLUNGER, AND AN UPPER AND A LOWER HELICAL SPRING SUPPORTING THE PLUNGER BETWEEN THE RESILIENT AND RIGID ENDS OF THE CAPSULE RESPECTIVELY; AND STATIONARY SWITCH COMPONENTS MUTUALLY COAXIALLY POSITIONED WITHIN THE CAPSULES CLOSELY ADJACENT THE INNER PERIPHERY THEREOF, THE STATIONARY SWITCH COMPONENTS COMPRISING AN UPPER ANNULAR CONTACT MEMBER POSITIONED ABOVE THE MOVABLE CONTACT MEMBER AND A LOWER ANNULAR CONTACT MEMBER POSITIONED BENEATH THE MOVABLE CONTACT MEMBER, THE LOWER SPRING BIASING THE PLUNGER UPWARDLY WHEREBY THE CONTACT MEMBER MOUNTED THEREON ABUTS THE UPPER STATIONARY CONTACT MEMBER IN THE REST POSITION OF THE SWITCH, THE SWITCH BEING ACTUATABLE BY A DOWNWARDLY DIRECTED FORCE ON THE RESILIENT END OF THE CAPSULE WHICH MOVES THE PLUNGER DOWNWARDLY COMPRESSING THE LOWER SPRING THEREBY MOVING THE CONTACT MOUNTED ON THE PLUNGER OUT OF ENGAGEMENT WITH THE UPPER STATIONARY CONTACT MEMBER AND INTO ENGAGEMENT WITH TTHE LOWER STATIONARY CONTACT MEMBER THE STATIONARY CONTACT MEMBERS BEING SEPARATED FROM THE ENDS OF THE CAPSULE BY A PLURALITY OF ANNULAR SPACING MEMBERS AND SEPARATED FROM ONE ANOTHER A DISTANCE GREATER THAN THE THICKNESS OF THE MOVABLE CONTACT BY AN ANNULAR SPACER FORMED FROM AN INSTULATING MATERIAL AND HAVING CIRCUMFERENTIALLY SPACED RADIALLY EXTENDING SERRATION-LIKE VENTS FORMED IN THE UPPER AND LOWER SURFACES THEREOF THROUGH WHICH HEAT GENERATED AT THE CONTACT MEMBER SURFACES DURING REPEATED SWITCH ACTUATION FLOWS TO THE SWITCH CAPSULE AND IS DISSIPATED.