US3423556A - Electrical switch structure including dual arm movable contact - Google Patents

Description

v Jan. 21, 1969 E. n. HARTZLER ETAL. 2

ELECTRICAL SWITCH STRUCTURE INCLUDING DUAL ARM MOVABLE CONTACT Filed May Fl 6. I

FIG.2A

lllll I I lug INVENTOR. EAR/VEST D. HAETZLLQ JACK 5/? fir flrrae/vsr Jan. 21, 1969 E. D. HARTZLER ETAL ELECTRICAL SWITCH STRUCTURE INCLUDING DUAL ARM MOVABLE CONTACT Filed May 9,

Sheet 2 INVENTOR. EIENEST .D. HIQTZLEB TACK J WN BY Arm/ewe Y United States Patent 3 423 556 ELECTRICAL swrrcri STRUCTURE INCLUDING DUAL ARM MOVABLE CONTACT Earnest D. Hartzler, 3141 College, and Jack M. Brown,

2362 Colgate Drive, both of Costa Mesa, Calif. 92626 Filed May 9, 1967, Ser. No. 637,133 U.S. Cl. 200-166 19 Claims Int. Cl. H01l1 3/00; 9/00 ABSTRACT OF THE DISCLOSURE This invention relates to improvement in electrical switch structures and it relates particularly to improvements in biasing arrangements for relays contacts. It is applicable to both conventional and latching relays. The contacts of conventional relays are spring biased to a first switch position and are actuated to another by an electromagnetic means in response to a switching current. Upon interruption the contacts are returned to first position by the bias. Latching relays incorporate means to prevent the contacts from returning to initial position when switching current is interrupted. Instead a positive, opposite force is required to return the contacts. Thus the latching relay may not depend upon spring bias to open contacts. But spring bias is advantageously employed in both kinds of relays because, in addition to causing or aiding contact opening, the spring biasing structure may have additional functions. Thus, it may be used to minimize contact bounce and to provide a wiping action between contacts, and to adjust for dimensional variations in manufacture.

Conceptually, the spring may be associated with either the armature or the movable contact or, in part, with the fixed contact. Also, the spring may be an integral part of one of these elements or it may be a separate member. Each of these arrangements has been employed in the past and each has advantages. But, the various arrangements are not without problems. The combination of the mass of the contractor structure and the resilience in the biasing member makes oscillation possible.

When, as is generally true in practice, the vibrational environment will include a wide range of frequencies and amplitudes, the problem of contactor design is a complex one. The discovery that comprises this invention has provided a reliable and dependable contactor structure that can be mass produced at minimum cost. The structure is arranged so that the movable contactor is biased against movement at one spring rate over a first portion of its travel and at a high spring rate over the remaining portion of travel. Initially the movable contactor acts as a cantilever and then, in conjunction with a fulcrum, as a lever. The multiple spring rate arrangement results in a bias-force-versus-movable-contactor displacement curve which has a low slope for initial dis placement and a higher slope for subsequent displacement. This approximates the force versus displacement curve of simple electromagnetic actuators. Accordingly, in relays employing contacts according to the invention, a simple actuator may be selected which will operate at near capacity throughout its stroke. Stated another way, the contactor Spring rate varies in a way that makes efiicient use of the actuator throughout its stroke thereby permitting use of a minimum capacity actuator.

3,423,556 Patented Jan. 21, 1969 ice The novel features which we consider characteristic of our invention are set forth with particularity in the appended claims. The device itself, however, both as to its organization and mode of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIGURE 1 is a top plan view of the contactor structure embodying the invention;

FIGURE 2 is a cross-sectioned view, taken substantially along line 22 of FIGURE 1;

FIGURE 3 is a cross-sectional view, taken substantially along line 3-3 of FIGURE 1;

FIGURE 4 is a cross-sectional view, taken substantially along line 44 of FIGURE 1; and

FIGURE 5 is a top plan view of an alternative form of contactor structure embodying the invention.

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

In the drawings there is shown a header 10 for a conventional relay which in this embodiment comprises a double pole double throw switch. A shield can, not shown, fits over the header and is secured to it by any suitable means as by welding or soldering. The contacts shown in FIGURE 1 are inside the can when the can and header are assembled. The can also contains an electromagnetic actuating mechanism, not shown, which is attached to the header by tabs which fit in notches 12 and 14 at the sides of the header. The actuating mechanism includes an armature extending almost to header 10 where it terminates in a contact engaging portion which may comprise a glass bead. The glass head is disposed in the plane of movement of the contactor structure when the relay is asse1n bled and two such beads 16 and 18 are represented by dashed line circles in FIGURE 1.

The header 10, in the embodiment shown, carries eight posts which extend through and are secured to it. The posts are all electrically insulated from the header and are numbered 21, 22, 23, 24, 25, 26, 27 and 28, respectively. They are arranged in two, parallel rows and the posts of one row are directly opposite the posts of the other. The posts terminate in terminals on the underside of the header. That portion of the posts 22 and 27 which extends above the header 10 are intended to serve as terminals to which the leads of an electromagnetic actuator coil will be fastened when the relay is assembled. Posts 21, 23 and 25 are arranged as corners of a triangle and serve as the electrical connectors to and the mounting structures for one of the relay switches. Posts 26, 28 and 24 serve as the electrical connectors and the mounting structures for the other switch. The normally closed stationary contacts are fixed to posts 21 and 28 at the opposite ends of their respective rows of posts. The normally open stationary contact of each switch is directly opposite the normally closed contact and in the other row, The normally open and normally closed contact structures are generally U-shaped conductors extending clockwise and counterclockwise respectively from their post mountings terminating in contacts disposed generally opposite one another on planes between the rows of posts and outboard from them. The movable contactors are relatively elongated structures extending from that post one post removed from the post holding its respectively associated normally closed Contact. The movable contactor structures extend between their respective normally open and normally closed contacts to a point beyond the latter and even with the former. Thus, the normally open and normally closed contacts are not directly opposite one another. The normally open contact extends farther outboard into the plane of movement of the respectively associated one of glass beads 16 and 18.

Normally closed contact member 29 is secured by welding, or by a high melting point solder as shown, to post 21. The contact comprises a strip of metal having a rectangular cross section and bent into the form of a U. One arm of the U is bent inwardly and wrapped around post 21. The lower part 32 of the U extends toward post 22. The other arm of the U extends past post 21, clearing it by a small distance, to a point midway between post 21 and the plane of movement of bead 16. The extreme upper end of that arm of the U is bent outwardly so that the outside, upper corner 30 of the arm forms a knife edge contact for engaging the movable contactor.

The U shape of the normally closed contact member 29 gives it some resilience but it is formed of relatively heavy material so that it will yield substantially less than will the normally open contact structure 33. The latter is made of thinner material. It is U-shaped with the bottom of the U extending toward post 26. One arm 35 is bent inwardly and wrapped around post to which it is sweated with high melting point solder. The other arm 36 extends past post 25 and the normally closed contact 30 to the normally open contact 34. The latter is formed integrally with arm 36 and ha a compound curve. Thus, it is bowed in both the longitudinal and transverse directions so that its mid-area extends slightly in the direction of head 16. Motion of the normally open contact 34 in a direction to move arm 36 closer to post 25 is opposed by a damper spring 37. This member comprises a strip of spring material bent through a large radius into an angle somewhat less than a right angle. It is assembled with member 33 so that one leg 38 bears against the portion of arm that is wrapped around post 25. The other leg extends through a hole, not shown, in arm 35 near the bottom of the -U of member 33. At the juncture of its legs, the damper spring bears against leg 36 of member 33. During assembly the spring is placed in position and its leg is drawn through the hole in arm 35 until the spring has the desired tension. Thereupon the leg is crimped over as shown at 39 whereby the damper spring is trapped in place.

The movable contact element 40 comprises a pair of arms which are connected to one another at one end and extend together side by side. Their opposite ends are biased toward one another but are held substantially parallel by a fulcrum element between them. In the preferred form shown in the drawing, the contact element is formed from a strip of metal bent around a small radius near its midpoint into a U shape the bottom of which is designated by the numeral 41 in FIGURE 1. The contact element is held by a mounting member 42 so that the ends of its arms 44 and 46 extend just past the plane of motion of bead 16 between the fixed contacts 30 and 34. The centerline of the radius about which contact element 40 is bent at 41 is parallel to the posts and knife edge 30 whereby arms 44 and 46 are movable toward one of the fixed contacts and away from the other. Mounting member 42 is T-shaped. The stem of the T is bent midway along its length so as to contact post 23 along two surfaces about 60 degrees of arc apart. The angle is not at all critical. The stem is bent only to provide two bearing surfaces instead of one to facilitate orientation parallel with header 10 and the soldering of support 42 to post 23. The arms of the T are bent and crimped around arm 44 of movable contact 40 at a point adjacent the bottom 41 of the U it forms.

Arms 44 and 46 operate as cantilever springs cantilevering, in response to pressure near their outer ends, about the connection to mounting member 42 in the case of arm 44 and about its connection to mounting member 42 and the work hardened bottom 41 of the U in the case of arm 46. Means are provided in the invention for converting the cantilever action of the movable contactor structure into a lever action during the contact sealing phase of switch action. Advantageously this means comprises the double arm construction employed in movable contact member 40 and a fulcrum disposed between them coupled with arrangement of the switch actuator and the normally open contact such that the actuator engages one movable contactor arm and the normally open contact engages the other. In the embodiment selected for illustration the fulcrum is formed as a nib 48 extruded from the side of arm 44 toward arm 46. The contactor is bent at 41 to bias arms 44 and 46 into engagement with one another whereby arm 46 is urged against nib 48. During assembly supporting member 42 is soldered to post 23 so that arm 44 is biased firmly against normally closed contact 30 as shown in FIGURE 1.

The other switch has the same construction. Its normally open contact structure 50 and damping spring 51 are attached to post 24 and correspond to contact member 33 and spring 37. Normally closed contact element 52 secured to post 28 corresponds to the normally closed contact element 29. The movable contactor assembly 54 secured to post 26 corresponds to contactor 4t and supporting member 42.

A single electromagnetic actuator, not shown, operates to move the glass beads 16 and 18 which engage and move the movable contactors. In the relay which FIG- URE 1 depicts, the beads 16 and 18 occupy the same position relative to the elements of their respectively associated switches. However, in the interest of clarity they are shown at different stages of the switch actuating cycle. Bead 18 is shown in the position it occupies when the relay is de-energized. Bead 16 is shown at that point of movement, after energization of the relay, at which it just engages the movable contactor 40 and before the normally closed circuit is opened. Comparison of the bead positions shows that the beads move in a plane at right angles to the movable contactor. Continuing its motion head 16 will force arm 44 out of engagement with normally open contact 30. The nib 48 bears against arm 46 so both arms are cantilevered from their point of attachment to supporting member 42.

The arms 44 and 46 move together away from normally closed contact 30 toward contact 34. When arm 46 engages contact 34 the latter yields until the compression in contact member 33 and the tension in the damping spring 37 is equal to the stress in the movable contact arms. Continued movement of the head 16 toward contact 34 squeezes the outer ends of arms 44 and 46 toward one another. Thus, the arms act as levers tending to rotate about the fulcrum 48. The arms 44 and 46 are strained along with the normally open contact structure 33. The requisite sealing pressure between the contacts arm 46 and contact 34, is achieved with less movement of contact member 33 because some of the strain appears in the movable contactor arms. The result is that less inertia is imparted to member 33 and contact bounce is minimized.

The movement of bead 16 is unopposed at first as it moves from a position corresponding to that occupied by bead 18 to the position in which it is shown in FIG- URE 1. Beginning at that point head movement is opposed by arms 44 and 46 acting as long cantilevers. When arm 46 engages contact 34 the movement of the bead is opposed by the arms 44 and 46 and the normally open contact structure 33 and its damping spring 37. Finally, when the contact structure 33 and spring 37 have experienced substantial strain, bead movement is opposed by these elements and by arms 44 and 46 acting as levers. At this stage of operation bead movement ceases and the contacts are sealed closed. The force in opposition to the bead and the electromagnetic actuator of which it forms a part is increased in stages approximating the force of the actuator so the latter is not accelerated unduly. The head is permitted to complete its stroke and the contacts wipe (because they rotate about dilferent radii) and are sealed with minimum acceleration and motion of the normally open contact.

The position of nib 48 is adjusted to provide the desired force-distance characteristic. Advantageously, as shown, it is located between the support for arm 44 and the point at which it engages normally closed contact 30. When the electromagnetic actuator is released the bias in arms 44 and 46 return them to the position shown. In that position arm 46 bears against nib 48 which serves as the fulcrum for arm 44 acting as a lever. The distance from contact 30 to nib 48 is much less than the distance from the nib to the supporting member 42. Thus, the purchase is great and the relative motion between arm 44 and contact 30 is small. None-the-less, there is a wiping and sealing movement when they come together.

An alternative form of contactor structure is shown in FIGURE 5. The movable contacts 60 and 62 differ from the corresponding structures 40 and 54 of FIGURE 1 in that portions of the contactor arms 85 and 86 have reduced cross-sectional area enabling actuation with a lesser force. In addition, the inner and outer ends of the arms of movable contacts 60 and 62 have increased crosssectional area for greater strength at the inner end and greater heat dissipation, or increased current capacity, at the outer end of the arms in the region of engagement with the fixed contacts.

The contactor assembly shown in FIGURE 5 is suitable for incorporation into a double pole-double throw magnetically latched relay. It comprises eight connector posts designated 63. 64, 65. 66. 67, 68, 69 and 70, respectively, which are mounted on and insulated from a header 80 by insulators 71, 72, 73, 74, 75, 76, 77 and 78. Two additional connectors are provided in the form of wires 81 and 82 which extend through the header 80 via insulators 83 and 84. The movable contact structure 62 comprises a pair of arms 85 and 86 which are connected together at one end and extend together side-by-side. Their outer ends are biased toward one another but are held substantially parallel by a fulcrum element 87 between them. Like contacts 40 and 54 of FIGURE 1, arms 85 and 86 are formed from a strip and are bent on a small radius into a U-shape. A mounting member 88 soldered to post 68 is clamped over arm 85 at its inner end, at the bottom of the U.

Prior to assembly with the actuating mechanism, the arms 85 and 86 extend between stationary contacts 90 and 92 secured to posts 70 and 66, respectively, without touching either of them. However, once the contact assembly is assembled with the actuating mechanism the movable contact engages one stationary contact or the other. The actuating mechanism comprises an armature, two coils one connected to wires 81 and 82 and the other connected to posts 64 and 69, and at least one permanent magnet. These elements are not shown. The actuating mechanism also includes two pairs of arms the lower portions of which are shown. They extend from the armature down into the plane of the contact assembly where their ends terminate in glass beads. Thus arms 93 and 94 terminate in beads 95 and 96 which straddle the outer end of movable contact 62. In FIGURE 5 the head 96, hearing against arm 86 of contact 62, applies force about fulcrum 87 to hold arm 85 against the contact engaging portion 97 of stationary contact 90. The bead 96 is so held by a permanent magnet in the actuating mechanism until the armature is rotated electromagnetically to move beads 95 and 96 to the left in FIGURE 5. Then head 95 will bear against arm 85 and will push arm 86 into engagement with the contact engaging portion 98 of stationary contact 92. A permanent magnet in the actuating mechanism will keep it thus engaged until the switch is again actuated. Movable contact 60, connected to post 65, and stationary contacts 99 and 100, connected to posts 63 and 67, are similarily controlled by glass beads 101 and 102 which are connected to the same actuating mechanism.

It is apparent then that it is not essential in the latching relay that the movable contact exhibit a bias tending to break engagement with the stationary contact. In the construction shown in FIGURE 5 the contactor arms have reduced cross-sectional area in the region between the bracket 88 and the fulcrum. The latter is secured or formed on one arm toward the bracket but near the point of engagement with the stationary contacts. Thus the contactor arms exhibit little tendency to oppose movement of the movable contact from one stationary contact to the other. Moreover the thinner section permits easier relative movement of the outer ends of arms and 86 about fulcrum 87. Thus this construction permits overtravel of the glass beads (and the other elements of the actuating mechanism) by increased relative movement of the outer ends of the movable contact arms thereby minimizing the need for resilience in the stationary contact. Accordingly, the problem of resonance may be solved in part by the use of a heavier fixed contact. The damper springs of FIGURE 1 can be omitted in many applications and if, as shown, the other ends of the movable contact are also made heavier a greater current can be switched.

Summarizing, the double arm construction of the movable contact presents several advantages over prior single arm contactors in providing, in one biasing arrangement, an overtravel mechanism, contact wiping, minimization of resonant vibration and bounce, and, for conventional relays, contact opening bias. In addition the dual arm construction permits greater deflection for a given total cross-sectional area and deflection force. Accordingly, in the invention the movable contactor may have larger cross-sectional area and greater current carrying capacity for a given actuating force. These qualities are enhanced as described by making the outer end of the movable contact arms relatively larger than the cross-sectional area of an intermediate section and, while described in connection with the latching relay, this feature is applicable as well to conventional relays.

It is observed that there is no switch position to which the movable contact of a latching relays returns upon deenergization of the relay actuating coils. Thus the latching relay has no normally closed contact. Either of its fixed or stationary contacts can be considered to be normally open and they are sometimes referred to as normally open contacts.

Although we have shown and described a certain embodiment of our invention, we are fully aware that many modifications thereof are possible. Our invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

We claim:

1. An electric switch comprising a stationary contact, a movable contact, and an actuator movable toward and away from said stationary contact, said movable contact comprising a pair of arms having one end fixed and extending together to a position between said stationary contact and said actuator, said arms having bias tending to urge them together at said position and means comprising a fulcrum between said arms at a point between said position and said fixed end holding said arms separated at said position.

2. The invention defined in claim 1 in which said arms have reduced cross-sectional area in the region between said fulcrum and said fixed end.

3. The invention defined in claim 1 in which said stationary contact is resiliently mounted and movable as an incident to pressure on an arc smaller in radius than the arc of movement of said movable contact.

4. The invention defined in claim 1, in which said stationary contact is normally open and which further comprises a normally closed contact disposed in the arc of movement of said movable contact on the side opposite said normally open contact and normally in engagement with one are of said movable contact on the side of said fulcrum away from the fixed end of said arm.

5. An electric switch comprising, an insulating header, at least three posts mounted in said header as corners of a triangle, a normally closed contact structure mounted on a first one of said posts and having its normally closed contact on the side of said first post toward a second one of said posts, a normally open contact structure mounted on said second post and having its normally open contact on the side of said second post toward said first post, a movable contact structure mounted on said third post and comprising a pair of arms and a fulcrum element between them, said arms extending between said normally closed and said normally open contact and movable in an are so that one arm can engage said normally closed contact and so the other arm can engage the normally open contact, said fulcrum element being located at a point between said third post and the points at which said arms can engage said contacts, and means for moving said movable contact structure through said arc.

6. The invention defined in claim 5 in which said movable contact structure comprises a U-shaped element and a mounting structure secured to the lower end of said U-shaped element and to said third post, the arms of said U-shaped element being biased toward one another and held substantially parallel by said fulcrum element.

7. The invention defined in claim 5 in which said fulcrum has the form of a nib fixed relative to one of said arms.

8. The invention defined in claim 5 in which said normally open cont-act structure is resilient and said normally open contact yields to pressure by movement in an arc having a smaller radius than said are of movement of said movable contact structure whereby a wiping and sealing action is provided on switch closure.

9. An electric switch comprising a movable contact structure movable through an arc and having a double armed portion in which a pair of arms arranged side by side are spaced apart and afford resilient opposition to force urging them together, a stationary contact disposed in the plane of said are in position for engagement with one arm of said movable contact structure, and means engageable with the other arm for forcing movement of said movable contact structure through said are and into engagement with said stationary contact, in which said means comprises a fulcrum disposed between said arms at a point between the center of said arc and the point of engagement of said movable contact structure and said stationary contact.

10. The invention defined in claim 9 in which said arms have reduced cross-sectional area in a region between said center and said fulcrum.

References Cited UNITED STATES PATENTS 3,042,773 7/1962 Keller et a1 335125 3,152,237 10/1964 Richert et al 335l25 3,260,829 7/1966 Auer. 3,337,707 8/1967 Iuptner et al. 2,813,165 11/1957 Seidel et al.

ROBERT K. SCHAEFER, Primary Examiner.

H. O. JONES, Assistant Examiner.

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