US3349352A

US3349352A - Sealed magnetic snap switch

Info

Publication number: US3349352A
Application number: US548321A
Authority: US
Inventors: Harold J Zandt
Original assignee: Individual
Current assignee: Butler Manufacturing Co
Priority date: 1966-05-06
Filing date: 1966-05-06
Publication date: 1967-10-24
Anticipated expiration: 1984-10-24

Description

H. J. ZANDT 3,349,352

SEALED MAGNETIC SNAP SWITCH Original Filed June 12, 1964 INVENTOR.

#42040 zn/var,

BY L

I I fiMw/Mu $514M ATTORNEYS United States PatentO 8 Claims. ((21. 335-154 This application is a substitute of application Ser. No. 374,610, filed June 12, 1964, now forfeited, and relates to electrical switching devices. More particularly, it has to do with snap-acting switches of the type actuated in response to an externally-applied magnetic field.

-There.is in current use a form of switch known as a reed switch. Switches of this general type usually consist of a pair of elongated and overlapping contact members sealed within a non-magnetic non-conductive enclosure. These contact members are usually made partly or entirely of a soft magnetic material having contact elements in the gap between the magnetic members which include coatings of noble contact metal. The contact members are resiliently-mounted within a sealed nonmagnetic envelope and when subjected to a magnetic field strong enough to overcome the inherent resilience of the members are caused to move by mutual attraction to complete an electrical circuit.

Another configuration of this general type of switch is one having a blade-type contact member resilientlymounted in one end of a sealed cylindrical envelope overlapping relationship to two fixed contact members mounted in the opposite end. The suspended end of the resiliently-mounted magnetic contact member is positioned between the two fixed members. The fixed contact members, one being of magnetic material, and the other being of non-magnetic material, appropriately coated with a noble contact material, are arranged so that the suspended end of the resiliently-mounted contact member is biased against the non-magnetic member. When this switch configuration is subjected to a magnetic field strong enough to overcome the inherent resilience of the flexible member, the suspended end is attracted away from the non-magnetic contact member toward the magnetic contact member, interrupting one electrical circuit and completing another circuit. This type of reed switch represents a single-pole doublethrow switch arrangement.

Among the advantages of switches whose contact members are actuated by mutual attraction in response to a magnetic field is the fact that they may be completely sealed in an enclosure to protect the contacts from the contaminating effects of dirt, moisture, explosive atmospheres, and other incidents of an industrial atmosphere. In addition, such an arrangement eliminates the necessity for additional mechanical moving members in the enclosure.

Although the aforementioned switches are suitable for performing a large variety of switching operations, their application is limited primarily by their low current rating due to limited contact fidelity, and because thereris little force available to open the contacts should over-current weld the contacts together. The magnetic contacting surfaces must be in nearly perfect alignment and mate with each other to obtain eflicient magnetic actuation conditions. This involves the necessity of very precise adjustments of alignment during the manufacture of such devices. The contact elements of these devices generally comprise ferromagnetic material, usually iron or iron alloy, plated with high conductivity and corrosionresistant metal, such as gold, or the like. However, such coatings or layers must be very thin, for they also tend to reduce the magnetic eificiency of the switch. Thus,

3,349,352 Patented Oct. 24, 1967 the ferromagnetic portions of the members must be spaced further apart to allow space for the non-magnetic contact coatings.

Another prior art switch configuration of this type utilizes separate contact elements, such as buttons, which are attached to the resiliently-mounted overlapping magnetic contact members. These contact elements are generally postioned relatively close to the overlapping portions of the magnetic contacting members to achieve the maximum space between the contact buttons when the switch is de-energized. The relationship of the contact buttons and magnetic overlap is such as to permit the contact buttons and magnetic overlap elements to engage and yet maintain an absolute minimum space between the members at the magnetic overlap, consequently decreas ing the magnetic efiiciency in accordance with the square of the distance between the elements. By minimizing this space at the magnetic overlap to achieve efficient magnetic performance, the wear allowance of the contact buttons is minimized accordingly, thereby reducing contact life. Although the electrical continuity through the switch is made primarily through the contact buttons, the magnetic and electrical circuits are virtually coincidental.

Due to insufiicient clearances, continuity must be made over the magnetic gap. This incidental continuity causes surface erosion and welding at the overlap area, causing premature failure. The electrical continuity through the magnetic gap area becomes considerably more frequent when inductive current loads are interrupted.

The switch configurations aforementioned are further limited to relatively low voltage applications because of the very small electrical clearance between the electrical contact members. These contact members, being in effect solid cantilever beams or blades of soft iron relying on their resilience to provide the movement necessary to make contact with their mating elements, provide an electrical clearance when de-energized of only a few thousands of an inch. This relatively small clearance or space between the overlapping portions of the contact members provides very limited electrical insulation and tends to cause electrical breakdown when relatively high voltages are applied to the device.

Furthermore, difiiculties have been encountered with switches of this type by the accumulation of microscopic particles of iron dust which form on the contact surfaces or are accumulated thereon during switch use, Although the contact surfaces are coated with a noble metal or have contact buttons, these ferromagnetic particles accumulating within the small gap tend to form conductive paths between the contact buttons or undesired magnetic flux paths, or both, causing uncontrolled electrical contin-uity.

A main object of the present invention is to provide a reliable magnetically-actuated sealed switching apparatus which will alleviate the aforementioned shortcomings found in the magnetically-actuated switching devices of the prior art, and which will also be capable of conducting and interrupting relatively large load currents with positive opening and closing operations.

- A further object of the invention is to provide an improved magnetic switch configuration which is suitable for fabrication to produce various contact arrangements, such as single-pole, normally open switching devices, single-pole, normally closed switching devices, and single-pole double-throw switching devices.

A still further object of the invention is to provide an improved magnetically-actuated sealed switching apparatus which lends itself readily to modern manufacturing procedures and which inherently provides the degree of predetermined magnetic as well as electrical values.

A still further object of the invention is to provide an 1 improved magnetically-operated switch device which, al-

though capable of controlling larger currents, may be used in precisely the same combinations as the abovedescribed reed switches of the prior art, namely, may be operated by an externally-applied magnetic field provided by a coil or similar electrically-controlled source of magnetic flux, or by a permanent magnet movable into proximity to the switch.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawing, wherein:

FIGURE 1 is a longitudinal vertical cross-sectional view taken through one form of magnetically-actuated sealed switching apparatus constructed in accordance with the present invention, namely, of the type having contacts which are normally open, the switch being shown in its normal condition.

FIGURE 2 is a perspective view, in separated positions, of the stationary contact member and the movable contact assembly of the switch illustrated in FIGURE 1.

FIGURE 3 is a perspective view, to a somewhat enlarged scale, showing the various components of the movable contact assembly of FIGURE 2 in separated positions.

FIGURE 4 is an enlarged fragmentary perspective view showing the manner in which the free end of the bowed spring element of the main reed member seats in the opposing end edge of the adjacent magnetic armature element of the movable contact assembly of FIGURES 1 to 3.

FIGURE 5 is a longitudinal vertical cross-sectional view, similar to FIGURE 1, showing another form of sealed magnetic switch assembly according to the present invention wherein the contacts are closed under normal conditions.

FIGURE 6 is a longitudinal vertical cross-sectional view taken through still another form of magneticallyoperated switch according to the present invention, this switch being of the single-pole double-throw type.

Referring to the drawing, and more particularly to FIGURES 1 to 4, inclusive, 11 generally designates a typical embodiment of an improved magnetic switch constructed in accordance with the present invention. The switch 11 comprises an elongated, hollow supporting body 12 which may be made of glass, but which can also be made from any other suitable impervious non-magnetic and electrically non-conductive material. Embedded in the opposite ends of the elongated tubular supporting body 12 are

respective terminal members

13 and 14 which may be made, for example, from a magnetic nickel-iron alloy, but can be made of any other suitable material having a coeificient of thermal expansion which closely matches that of the glass envelope 12, permitting a glass to metal seal. Terminal member 14 may be solid, but preferably is a tubular electrode which serves, during the construction of the device, as a means for evacuating the space between the envelope 12 and filling it with any desired type of gas at any desired pressure. This gas may be sealed within the envelope by permanently closing the tube opening in any suitable manner, as by crimping the member 14, as shown at 15, or by welding the tube closed. By thus filling the envelope 12 with an inert gas, the operating life of the switch device 11 is greatly extended.

Designated at 16 is a first contact spring arm which is secured to the reduced flattened inner end portion 17 of terminal element 13, as by a rivet 18, overlying the fiattened portion 17 and being provided at its free end with a depending contact pad or button 19 of suitable conductive material and of proper cross-sectional area from making and breaking the rated circuit current for which the switch is designed. As shown in FIGURE 1, the spring arm 16 is mounted so that it can flex upwardly, the upward flexure thereof being limited by an indentation 20 formed in the top wall of the envelope 12. The spring arm 16 is made of relatively thin resilient metal having suitable electrical conductivity. The contact element 19 may be suitably fastened to the bottom surface of the free end portion of the spring arm 16, or alternatively, may be made integral with said spring arm.

Designated generally at 21 is a movable contact assembly which is secured to the inner end of the tubular terminal element 14. The movable contact assembly 21 comprises an elongated flexible leaf spring member 22 having attached to its inner end a contact button 23 formed of silver or any other suitable contact material. The inner end portion of the tubular electrode 14 is provided with the reduced flat lug element 24 having an arcuately-conc'ave end edge 25 against which is rotatablyengaged the arcuately-curvedconvex end edge '26 of a moving or floating armature element 27 of magnetic material. Designated at 28 is a supporting arm of non-magnetic material having the upwardly-offset end portion 29 which underlies the right end portion 30 of the leaf spring member 22, as viewed in FIGURES 1 and 3, and is secured therewith to the flattened inner end portion 24 of the tubular terminal member 14. Secured on the end portion of arm 28 opposite member 29 is an armature element 32 of magnetic material which is provided with the upwardly-offset end portion 33 which underlies the inner end portion of the floating armature member 27, the leaf spring member 22 being formed with an elongated longitudinally-extending aperture 35 and the overlapping inner end portions of the

armature elements

27 and 32 being normally disposed respectively above and below said aperture adjacent the intermediate portion thereof.

The right end edge of the aperture 35 includes the spring arm 37 which underlies and resiliently-supports the floating armature member 27 and biases said armature upwardly toward a non-magnetic stop arm 38 secured to the inner end lug 24 of terminal member 14.

As shown in FIGURE '3, the stop arm 38 has an apertured end lug 39 which is fastened to the top surface of the apertured lug 24 of terminal member 14 and likewise to the end portion 30 of leaf spring member 32 and the apertured end portion 29 of arm 28 by a common rivet 40. As will be readily apparent, the stop arm 38 has an abutment edge 41 which is engaged by the top surface of the floating armature member 27 to limit the upward movement of said floating armature element. The arm 38 is downwardly-concave in shape, and its attaching lug 39 is spaced sufliciently from the attaching lug 29 of ,arm 28 by the thickness of the supporting lug 24 of terminal member 14 to allow ample clearance for rotation of the floating armature element 27, with the edge 26 pivoted against the edge 25, to assure opening and closing of the switch contact elements during the operation of the switch.

Opposite the resilient tongue element '37 the end edge of aperture 35 is formed with ,another resilient tongue element 44 whose end edge is pivotally-engaged in a generally V-shaped groove 45 formed in the inner end edge of the floating armature member 27, as is clearly shown in FIGURE 4. The resilient tongue 44 is normally bowed upwardly and is placed under tension by its pivotal engagement with the grooved end of armature element 27, providing a biasing action which urges the armature element '27 upwardly against the edge 41 of a stop arm '38 and which consequently exerts a downward biasing force on the inner end portion of leaf spring 22, biasing the contact button 23 downwardly into engagement with an indentation 48 formed in the bottom wall of the tubular envelope 12. As shown in FIGURE 1, the contact button 23 is thus biased to an open-circuit position relative to the opposing contact element 19 carried by arm 16. When the floating armature member 27 is urged downwardly toward the upwardly-ofiset end portion 33 of the bottom garmature member 32 by a magnetic field, the downward movement of the pivoted edge of finger 44 flexes the leaf spring member 22 past a dead-center configuration, causing the free end portion of member 22 carrying contact button 23 to snap upwardly and to cause the button 23 to rapidly engage the bottom surface of the contact element 19 on arm 16. This provides rapid closure of the switch with snap action. When the magnetic field is removed, whereby armature element 27 is free to move away from the cooperating magnetic armature portion 33 by the biasing force of resilient finger 37, the pivoted edge of finger 44 is moved upwardly past the dead-center configuration of the leaf spring member 22, causing said leaf spring member to rapidly assume its normal configuration, namely, that shown in FIGURE 1, wherein the bottom of button 23 engages the indentation 48.

Armature member 32 is preferably secured to the nonmagnetic arm 28 in a permanent manner, for example, by .a Weld. Similarly, the flat lug member 24, which is preferably of magnetic material, is secured to the inner end of the tubular terminal member 14 in a permanent manner, for example, by means of a weld.

The elongated reed member 22 is preferably made of relatively thin non-magnetic conductive material, such as copper or an alloy thereof, and serves not only as a snapacting leaf spring element to cooperate with floating armature member 27 to provide toggle action, but also serves to provide a current-conducting path from the contact button member 23 to the terminal member 14. The

center tongue elements

44 and 37 serve as the control means for regulating the movement of the floating armature element 27. In the normal position of the switch, shown in FIG- URE 1, the finger 37 acts as a resilient support for the armature element 27, opposing the downward force exerted thereon by the bowed resilient arm 44. The spring arm 37 thus serves as a means to maintain a small air gap between the overlapping inner end portions of the

armature members

32 and 27. It will be seen from FIGURES 1 and 2 that the spring 37 terminates short of the inner end of the floating armature member 27 and also short of the transverse edge 49 of the upwardly-offset stationary armature element 33 so as not to interfere with the air gap between element 33 and the overlying end portion of arma ture 27 which overlaps it.

It will be noted that the armature 27 automatically aligns itself longitudinally under the biasing force exerted thereon by the arcuately-curved spring arm 44 because of the arcuate seat 25 provided therefor on stationary element 24 which receives the convexly-curved end edge 26 of the floating armature element 27. The arcuate seat 25 permits any necessary self-adjustment of the armature 27 to properly align its inner end portion with the cooperating stationary armature element 33, providing a substantially articulated joint with respect to its supporting bearing member 24 and allowing free movement of the floating armature element 27 except as restrained by the cooperation therewith of the

resilient finger elements

44 and 37. As above-mentioned, the resilient finger member 37 provides a cushioned limiting action with respect to downward movement of the armature element 27 under the spring force exerted thereon by the bowed finger 44,

whereas the resistance of the finger 37 is overcome responsive to the application of a magnetic field to the switch, causing the armature element 27 to be magnetically attracted toward the stationary armature element 33, moving the recessed edge 45 thereof downwardly past the deadcenter position of the leaf spring member 22, causing said leaf spring member to snap in the manner above-described and move button 23 suddenly into engagement with contact member 19.

When the device is subjected to an adequate magnetic field, as above-described, so as to bring the contacts into engagement, the resilient contact arm 16, having substantial resilience, is displaced from the top surface of portion 17, as viewed in FIGURE 1, and is elevated until further upward movement thereof is prevented by its engagement with indentation 20.

During the displacement of arm 16, the accelerated contact button 23 is retarded before converging with the surface of indentation 20, resulting in a cushioning elfect reducing contact bounce. This displacement also achieves a desirable sliding action between the contacts.

Consequently, in its return movement, the contact arm 16 acquires a certain momentum before colliding with its normal supporting surface of portion 17. The impact between these members, in effect, hammers the contacts apart. This hammering action on contact separation, along with the sliding action on contact engagement, provides a means of breaking the bond of welds which incidentally occur and insures increased contact fidelity.

As above-mentioned, the self-aligning feature provided by the arcuate seat 25 which receives the convex arcuate edge 26 of floating armature element 27 provides a substantial amount of manufacturing tolerance latitude while assuring dependable and repetitive performance of the switch and also increasing the magnetic efiiciency thereof so that a minimum amount of magnetic energy is required to actuate the device.

As above-described, the snap action of the reed member 22 is caused by the movement of the grooved end 45 of armature 27 past the dead-center position of the reed member 22, namely, by the movement of said grooved end past the plane of the reed member. The snap action of the reed member 22 achieves the desired quick-make and quick-break contact action to minimize electrical arcing at the contacts. Also, electrical arcing across the magnetic gap is prevented inasmuch as the magnetic actuating mechanism is isolated from the electrical contacts of the device.

It will be further noted that by locating the contact button 23 at the end of the reed member 22, its movement is multiplied with respect to the movement of the grooved end 45 of armature element 27. This factor permits maintaining a relatively small magnetic gap, whereby to achieve a high degree of magnetic efiiciency, while permitting a relatively large electrical gap between the contact button 23 and the cooperating contact element 19 under open-circuit conditions, without interfering with the ability of the switch to handle relatively high load currents.

It will be further noted that since the magnetic actuating mechanism is integral with the contact assembly, adjustment of the magnetic elements may be made, with regard to magnetic actuation values and contact performance, prior to sealing the assembly within the envelope 12.

It will be noted that the support member 28 is provided at its bottom surface with an abutment lug 50 which bears against the bottom wall of the envelope 12, supporting the member 23 and increasing its resistance to vibration.

Referring now to FIGURE 5, the magnetic switch therein illustrated is similar to that shown in FIGURES l to 4, except that the switch is arranged as a normally closed switch which opens responsive to the application of a magnetic field to the spaced

armature elements

27 and 32. In the arrangement of FIGURE 5 the spring arm 16 is secured to the bottom surface of the lug 17 with the bottom surface of the inner end of the spring arm bearing normally against the indentation 48, and being urged thereagainst by the contact button 23 which normally engages same under the biasing force exerted thereon by the arcuately-bowed finger 44. The configuration and arrangement of the movable contact assembly 21 is the same as described previously and as illustrated in FIGURES 1 to 4, except that the switch is biased normally to a closed position. When a magnetic field is applied to the switch, whereby to cause floating armature member 27 to move toward fixed armature element 33,

the reed member 22 snaps in the manner above-described,

rapidly disengaging contact button 23 from contact element 19.

, FIGURE 6 illustrates a magnetic switch according to this invention in the form of a double-throw, single-pole switch. The switch, designated generally at 11 has elongated supporting envelope 12' in one end of which is secured the tubular electrode 14 and a movable contact assembly 21, similar to that above-described in connection with FIGURES 1 to 5. Embedded in the opposite end of the envelope 12' are

respective terminals

13 and 13, the terminal 13 being provided with a contact arm 16 having a contact element 19 on the bottom surface of its free end, as in the form of the invention illustrated in FIG- URES 1 to 4. The terminal member 13' is rovided at its inner end with a contact configuration similar to that illustrated in FIGURE 5, including a resilient contact arm 16 provided with a contact element 19 on the top surface of its inner end. The contact element 19 is normally engaged by the contact button 23 on the inner end of the flexible reed member 22 of the movable contact assembly 21. Thus, the terminal member 14 is normally electricallyconnected to the terminal elements 13', but in response to the application of a magnetic field to the switch, as in the case of the previously-described embodiments of the invention, the floating armature 27 is urged toward the magnetic stationary armature element 33, causing the reed member 22 to snap. This disengages the contact button 23 from the bottom contact 19' and moves said button rapidly into engagement with the upper contact element 19, thus disconnecting terminal member 14 from terminal member 13 and connecting said terminal member 14 to terminal member 13. When the magnetic field is removed the parts snap back to their normal positions shown in FIGURE 6.

While certain specific embodiments of an improved snap-acting magnetic switch have been disclosed in the foregoing description, it will be undertsood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore, it is intended that no limitations be placed on the invention except as defined by the scope of the appended claims.

What is claimed is:

1. A snap-acting magnetic switch comprising a hollow elongated support, terminal members secured in each end of the support, a first contact element secured to one of the terminal members inside said support, a flexible. conductive non-magnetic reed member secured to the other said first contact element, said reed member being proterminal member inside said support and extending toward vided at its free end with a second contact element engageable with said first contact element, a first magnetic armature element fixedly-mounted in said support subjacent said reed member, a second magnetic armature element pivotally-mounted in said support above said reed member, said armature elements having overlapping spaced inner end portions, and a bowed resilient longitudinal tongue element on the reed member pivotally-engaged with the inner end portion of said second magnetic armature element and cooperating therewith to exert biasing force on the free end of the reed member.

2. The switch according to claim 1, wherein said reed member is provided at its free end with a second contact element engageable with said first contact element, and wherein said second magnetic armature element is movable toward said first magnetic armature element responsive to a magnetic field whereby to cause fiexure of said reed member. 7

3. ThesWitch according to claim 2, wherein the inner end of the second armature element is provided with a groove pivotally-receiving the end of said tongue element.

4. A snap-acting magnetic switch comprising an elongated support, respective terminal members at opposite ends of the support, a first contact element secured to one. of the terminal members, a flexible conductive reed member secured to the other terminal member and having a free end portion extending adjacent said first contact element, said free end portion being provided with a second contact element conductively-engageable with said first contact element, a fixed magnetic armature mounted below the intermediate portion of said reed member, abutment means adjacent said other terminal member, a movable magnetic armature engaging said abutment means and overlapping said fixed magnetic armature, toggle spring means extending between the free end portion of the reed member and the movable magnetic armature and exerting endwise biasing force on the movable armature, and means limiting upward movement of said movable armature, said movable armature being movable downwardly towardsaid fixed magnetic armature in response to a magnetic field to flex the reed member past a dead-center configuration and to thereby produce rapid movement of said second contact element relative to said first contact element.

5. The switch according to claim 4 which includes in addition a resilient tongue element on the reed member which extends from the end portion of the reed member, the end edge of the resilient tongue element being pivotally-received in a recess formed in the end of the movable armature and exerting endwise biasing force on the movable armature.

6. The switch according to claim 5 which includes in addition means limiting upward movement of said movable armature.

7. The switch according to claim 4, wherein said abutment means is formed with an arcuate concave seat, and wherein said movable armature is formed with an arcuate convex end edge which is received in and engages said concave seat.

8. The switch according to claim 4, wherein one of said terminal members comprises a metal tube adapted to be employed for filling the hollow support with inert gas and to, be subsequently sealed.

References Cited UNITED STATES PATENTS 7/1956 McClain 335-188 4/1959 Curzon 335-188

Claims

1. A SNAP-ACTING MAGNETIC SWITCH COMPRISING A HOLLOW ELONGATED SUPPORT, TERMINAL MEMBERS SECURED IN EACH END OF THE SUPPORT, A FIRST CONTACT ELEMENT SECURED TO ONE OF THE TERMINAL MEMBERS INSIDE SAID SUPPORT, A FLEXIBLE CONDUCTIVE NON-MAGNETIC REED MEMBER SECURED TO THE OTHER SAID FIRST CONTACT ELEMENT, SAID REED MEMBER BEING PROTERMINAL MEMBER INSIDE SAID SUPPORT AND EXTENDING TOWARD VIDED AT ITS FREE END WITH A SECOND CONTACT ELEMENT ENGAGEABLE WITH SAID FIRST CONTACT ELEMENT, A FIRST MAGNETIC ARMATURE ELEMENT FIXEDLY-MOUNTED IN SAID SUPPORT SUBJACENT SAID REED MEMBER, A SECOND MAGNETIC ARMATURE ELEMENT PIVOTALLY-MOUNTED IN SAID SUPPORT ABOVE SAID REED