US2861143A - Stressed blade snap switch - Google Patents

Description

Nov. 18, 1958 P. D. GROVER 2,8611,143

STRESSED BLADE SNAP SWITCH Filed July 25, 1957 INVENTOR: PHILIP D. GROVER 25 27 ATT YS United States Patent 2,861,143 srnsssnn BLADE SNAP swrrcrr Philip D. Grover, Chicago,,lll., assignor, by mesne asslgnments, to Anderson Controls, Inc., Des Plalnes, lll.,

' a corporation of Illinois Application July 25, 1957, Serial No. 674,060

Claims. (Cl. 200-67) This invention relates to an electric switch, and more especially to a stressed blade snap switch having utility in electric circuits for opening and closing the same.

' A problem of importance that exists in the use of switches to open and close electric circuits, particularly 2,861,143 Patented Nov. is, 1958 "ice of with a concave or dished area adjacent one corner of such opening which defines the center of action of the blade, and having also a corrugation in the base thereof which is in effect projected through the center of action when an actuating force is applied to the blade to effectuate the snap action thereof.

A still further object is to provide a lever means between the actuating button of the switch, and the point at which the blade must be acted upon to snap from an upward to a downward position so that the ratio of pressure required to actuate the snap and the distance through which it must be applied can be varied to suit the particular application. While not necessary to the function of. the switch, as such, the lever has the additional advantage of permitting the actuating force to be applied through the button at a convenient point in the structure. For example, in the embodiment illustrated, the lever is used to permit the applicating force to be applied to the vertical center line of the structure.

Still a further object is to provide a switch of the character described, in which the movable contact wipes over the respective fixed contacts during engagement 1 and disengagement thereof so as to prolong the operating rapid make-and-break action which is substantially independent of the magnitude of the activating force applied and of the rate at which it is applied.

Another object of the invention is to provide a snap switch which has one stable position or normal position, and .has a movable contact which snaps into a transient or unstable position when a suitable actuating force is applied thereto, and which similarly snaps back to the stable position when such actuating force is removed. Y

Still another object is to provide a dependable, longlived switch with the minimum number of simple,,easily fabricated parts, so that manufacturing costs and hence consumer purchase cost is relativelylow.

, Still another object is that of providing a doubleaction switch, commonly known as a single-pole, doublethrow switch-that is, a switch which completes one circuit while interruptinganother, and vice versa; and which (because of the minimization andsimplicity of components) lends itself to miniaturization and subminiaturization, thereby being in keeping with current industrial trends toward economies of space and materials,

A further object of the invention is to provide a snap switch having a stressed blade designed so as to have a center. of action oriented so that an actuating force applied at one predetermined point on the blade remote from such. center of action, is etfective to additionally stress the blade in a manner such that another point thereon also remote from the center of action is snapped from one position to another about an axis extending through the center of action.

Yet a further object is that of providing a switch having a pair of fixed contacts positioned in spaced apart relation, and a stressed blade of generally triangular configuration having a contact-carrying end interposed between the fixed contacts for selective engagement therewith-the blade being fixed at one corner thereof, and being adapted to have an actuating force applied thereto at the remaining corner thereof which is effective to snap the contact-carrying end of the blade from its normal position of engagement with one of the fixed contacts and into engagement with the other; the blade having a generally triangular opening in the center therelife of the switch by keeping the contacts thereof clean,

reducing wear thereon, and reducing the tendency of the contacts to stick or weld together because the theoretically infinitesimal point contact is enlarged to a substantial area. Additional objects and advantages of the invention will become apparent as the specificationdevelops.

An embodiment of, the invention is illustrated in the accompanying drawing, in which- Figure 1 is a perspective view of a snap switch embodying the invention; Figure 2 is a perspective view of the switch illustrated in Figure 1, but with the parts thereof arranged in exploded or spaced relation; Figure 3 is an enlarged perspective view of the stressed blade of the switch; and Figure 4 is a transverse sectional view vided therefor in the cap 12, and through openings 17 and 18 respectively alignable therewith in the base 11. The cap 12 has a depending annular wall with a notch or recess 19 formed therein, and defines an inner compartment. 1 Centrally positioned in the cap 12 is a passage 20 adapted to permit the stem 21 of an actuator button 22 to pass slidably therethrough. 'The actuator 22 has a flanged lower end, as shown at 23, which limits displacement of the actuator upwardly through the passage 20. t

An upper fixed contact 24 is carried by the cap 12 within the compartment thereof, and maybe formed by the enlarged head of a rivet 24a which is employed to mechanically secure an-upper terminal 25 to the cap, and which then electrically connects the contact and terminal. Similarly, the base 11 is provided with a fixed contact 26 which may be the enlarged head of a rivet used to secure the lower terminal 27 to the base, and which will then electrically connect that contact and terminal. Extending upwardly from the base 11 is a tongue 28 dimensioned so as to be received within the recess 19 of the cap. The recess and tongue then function as an'alignment or polarizing means that enables the cap and base to be assembled in only one relative position- I Also extending upwardly from the base 11 are a pair of spaced lands 29 and 30 which define a channel therebetween. These lands are provided, respectively with recesses or grooves 31 and 32 therein having a function that will be described hereinafter. Adjacent the tongue 28 and the land 30 is a boss or mounting plane 33 having a bore or opening 34 extending transversely therethrough which is adapted to receive the shank 35 of a rivet 36, which also extends through an aperture 37 in a blade 38 and functions to anchor the blade on the boss 33. A terminal 39 has an end portion disposed below the opening 34, and is pierced to form an opening in alignment therewith; and such opening also receives the shank 35 of the rivet 36. Thus, the rivet is effective not only to mechanically mount the blade 33, but mechanically secures the lower terminal 39 and electrically connects it to the blade.

The blade 38 is a current conducting element and may be formed from flat metal spring stock, such as Phosphor bronze or beryllium copper tempered to spring hardness. The blade is of generally triangular configuration, and at the apex of such triangle is equipped with an upper contact 40, and a corresponding contact 40a disposed on the opposite side of the blade in alignment with the contact 40. Such lowercontact is adapted to engage and make connection with the fixed contact 26 of the base, while the upper contact 40 is adapted to engage the fixed contact of the cap 12. Extending laterally from the blade 38 is a lug or ear 41 which is adapted to nest between the land 30 and tongue 28, and serves to prevent rotation of the blade about the longitudinal .axis of the rivet 36, which is the only means employed for mounting the blade on the base.

A post or hemispherical-capped conical member 57 is base, and rises at the center point of the base 11 to an elevation equal to that of the mounting plane 33 or thereabouts for engagement with the lower surface of the blade 38 at approximately the center of a dished area 55 therein. This post serves as a universal pivot, or fulcrum to support the blades center of action" when a downward actuating pressure is applied, as will be described in greater detail hereinafter. V

In some instances, it is desirable to employ a lever in v 4 the base, whereupon a circuit is established through theswitch between the terminals 27 and 39. When the aetuator 22 is released, the blade 38 returns to its normal formed integrally with the dielectric material of the association with the actuator 22 for imparting an actuating force to the blade 38. Such a lever is illustrated in Figure 2, and is denoted with the numeral 42. The lever 42 has along the rear edge thereof an arcuate recess 43 and depending legs 44 and 45 adjacent to the ends thereof, which straddle the contact-equipped end of the blade 38 when the switch is assembled. The legs 44 and 45 are receivable, respectively, within the recesses 31 and 32 in the lands, and provide a fulcrum about which the lever pivots to force the arcuate, downwardly turned end 46 thereof into engagement with the corner area 47 of the blade 38 when the actuator 22 is depressed to push the head or flange 23 thereof against the lever in the area denoted 48.

In assembling the switch structure, the terminals 25 and 27 and the corresponding contacts are secured to the cap and base, and the blade 38 and terminal 39 are secured in position on the base by the rivet 36. The lever 42 is then positioned above the blade 38, with the legs 44 and 45 within the recesses 31 and 32, whereupon the arcuate end 46 thereof engages the corner 47 of the blade. The actuator 22 is then pushed upwardly through the opening 20 in the cap, and the cap and base assembled and locked together by the rivets 13 and 14. To use the switch, the terminal 39 is connected to a lead which is to be selectively common to both of the terminals 25 and 27 and to the circuits connected therewith.

Normally, the apex of the warped blade 38 is angled upwardly from the horizontal mounting plane 33 so that the upper contact 40 thereof engages the fixed contact can'ied by the cap 12. Thus, a circuit is established through the switch between the terminals 25 and 39. When the actuator button 22 is depressed, the vertex of the blade 38 snaps downwardly to bring the lower contact thereof into engagement with the fixed contact 26 of upper position to break connection with the terminal 27 and its contact, and reestablish connection with the upper terminal 25 and its contact.

Having in mind the description heretofore set forth, it is believed that an elaboration of the construction and function of the blade 38 will be readily understood, and such a description will now be developed. In addition to the features of the blade 38 which have already been described, it is noted that the blade has a base leg 49 connecting the side members 52 and 53 of the blade, which are integral at the apex or contact-equipped end 51 thereof. The blade is stressed or distorted from its original planar form by shortening base leg 39, by bending a wave or corrugation therein. This pulls members 52 and 53 inward slightly, causing a stressed, dishing effect. At the same time, the lower right hand corner or wing 47 is bent upwardly to give it bias to help the blade return to its normal position.

Material is removed from the blade to form an enlarged central opening 54 generally conforming to the configuration of the blade, so as to permit the blade to be stressed without making the stresses therein of too great a magnitude. The blade 38 has a center of action" that comes generally within the area bounded by the circle 55. This center of action" may be defined as being located on the vertical center line of an abstract segment of a sphere embraced by the distorted surfaces of the stressed blade.

Such segmental sphere may also be thought of as a dished construction of concave character (considered along the upper surface of the blade 38). As the dished area is snapped from a concave to a convex configuration, it can be seen that the apex of the blade, on an extension of the dished area, must also be snapped downwardly. Conversely, when the dished area changes from convex to concave form, the apex snaps back to its initial position. In order to assure a reliable return of the blade after the actuating force has been removed therefrom, it is desirable to deform or coin the blade slightly within the area of the circle 55 to accentuate the concavity or dishing thereof and, in addition, to bend the corner formed by members 43 and 59 upwardly. The numeral 56 denotes such coined area of the blade. This coining augments the up-bias of portion 47 to help insure snapping back to the normal concave configuration.

As stated before, the blade 38 is fixed at the aperture 37 therethrough, and the actuating force is applied downwardly against the corner 47. In order to better describe the action which occurs in the blade when such actuating force is applied thereto, an analogy may be made to the action which occurs in a fairly stitf pieceof paper which is held at the corners of one of the short sides thereof. Initially, the paper sheet bends downwardly at one end thereof due to the action of gravity if an effort is made to hold it in a horizontal plane. If, however, when the paper is so bent, the grasped corners of the short sides thereof are drawn slightly together, the paper forms a trough or concave depression in the center. If the paper is relatively stiff as one edge is lifted relative to the other, this corrugation or "kink" will travel from the pinched or inwardly drawn end to the opposite end thereof, thereby causing the downwardly turned end of the paper to straighten out. In other words, such downwardly turned end snaps upwardly.

Now considering the blade 38-if the corner 47 thereof is pressed downwardly relative to the fixed area surrounding hole 37, the kink or corrugation 50 tends to travel outwardly and along the legs 52 and 53 of the blade until it envelopes the area at the center of action within the circle 55 causing this dished area to snap from a concave form to a convex form, whereupon the end portion 51 of the blade which was angled upwardly snaps to a downward angle, causing the lower contact thereof to engage the contact 26 of the base. The sides 52 and 53 of the triangular blade may then be considered as extensions of the dished area 56 through whichthe actuating force is applied on on@ side (that is, the leg 53), and the increasing reaction force is induced on the opposite side (leg 52) thereof, to snap the dished area inside-out.

In order to effectively utilize this snap action of the blade 38, the fixed contacts provided respectively by' the base 11 and cap '12 are arranged to limit the throw or movement of the apex 51 and therefore, the spacing therebetween is less than the full possible travel of the blade. This assures a good contact pressure between the movable contacts and the fixed contacts. It will be appreciated that the throw of the apex 51 can be increased or diminished by changing its distance relation to the center of action.

With the foregoing snapaction of the blade in mind,

it can now be seen that the post 57 plays an important part in the eflectiveness of the action. With the blade 38 supported at 37, and the apex contact 40 in pressurized conjunction with fixed contact 24, it can be seen that any downward pressure on any unsupported part of the blade (as at 47) will have a tendency to decrease the pressure between the contacts prior to inducing a snap. This is an undesirable condition, for not only is the current-carrying capacity of a given set of contacts dependent upon the pressure therebetween, but also because it makes the correct alignment of components in the switch assembly rather critical to adjust if the contact is not to be broken before the snap is induced.

However, if the post 57 is placed under the center of action as shown, it acts as a fulcrum so that any pressure applied downwardly on the blade in an area behind the fulcrum (47, for example) is reversed in direction at points beyond the fulcrum. In efiect then, we have a means of increasing the pressure on the contact points, as downward pressure is applied, instead of lessening it, until the violent deformation or snap is induced.

At the time of the snap, the concave upper surface of the blade becomes convex, as previously explained,

to its normal position when such actuating force is reand the center of action point tends to lift clear of post 57. In switch constructions other than the one illustrated, where the actuating button was not located in the center, directly above the center of action, it can be seen that it would be advantageous to have a similar post extending downwardly to the top side of the center of action of the blade, so that the same advantages would accrue on the opposite cycle and with the other fixed contact 26.

Further advantages inherent in the structure of this invention are that thesupport means and actuating force applications are not essentially linear in location along the lateral axis of the blade 38, and therefore permit wide adaptation of housing or supporting means. Further, the construction described gives a positive, nonsensitive location for the application of the actuating force rather than an abstract sensitive point" which is difficult to locate. Moreover, as the snap action of the blade initiates at a non-critical point (that is, the corner 47) distant from the movable contact, there is considerable latitude in arranging the functional components of the switch to accommodate special requirement applications.

A prime advantage inherent in the structure of this invention is that the movable contact 40 remains in pressurized conjunction with the fixed contact 24 regardless of how slowly the actuating pressure may be applied, until the rapid concave-to-convex snap occurs to suddenly disengage contact 40 from contact 24, and to suddenly engage contact 40a with contact 26. Consequently, the pressure between the contacts is maintained, and there is no minimization of the current-carrying capacity thereof until the movable contact is snapped from engagement therewith. The same result is achieved in reverse, when the actuating force is removed from the blade 38.

While in the foregoing specification an embodiment of the invention has been described and set forth in considerable detail for providing an adequate disclosure thereof, it will be apparent that those skilled in the art may make changes therein without departing from the spirit and scope of the invention.

I claim:

1. In a stressed blade snap switch structure, a casing provided with a pair of fixed contacts oriented in spaced apart relation, a spring blade of triangular configuration having an enlarged opening therein defining a base leg and side legs extending from the corners of the base leg and merging to form an apex, a pair of contacts carried by said blade at the apex for engagement with the respective fixed contacts, the base leg of said blade being shortened intermediate the connecting ends of the side legs and also having a preformed concave area intermediate said blade contacts and the adjacent end of the blade opening, means for anchoring the blade within the casing adjacent one of said base corners with said apex contacts interposed between said casing contacts, and other means on the casing for applying an actuating force against said blade other base corner, said blade having a normal position within said casing whereby one of said blade contacts normally are in engagement with one of said fixed casing contacts, the forces of stress within said blade being efiective to snap the apex thereof into transient position when an actuating force is applied to said other means to engage the other said blade contact with the other of said fixed contacts and to return the blade moved from said other means.

2. The switch structure of claim 1 in which the base leg of said blade is foreshortened by a corrugation.

3. In a stressed blade snap switch structure, a casing provided with a pair of fixed contacts oriented in spaced apart relation, a spring blade of triangular configuration having an enlarged opening therein defining a base leg and side legs extending from the corners of the base leg and merging to form an apex, a pair of contacts carried by said blade at the apex for engagement with the respective fixed contacts, the base leg of'said blade being shortened by a corrugation formed therein intermediate the connecting ends of the side legs and also having a preformed concave area intermediate said blade contacts.

and the adjacent end of the blade opening, means for anchoring the blade within the casing adjacent one of said base corners with said apex contacts interposed between said casing contacts, other means on the casing for applying an actuating force against said blade other base corner, an outwardly-extending ear on said blade, and wall portions on said casing contacting said ear for constraining said blade against rotation, said blade having'anormal position within said casing whereby one of said blade contacts normally are in engagement with one of said fixed casing contacts, the forces of stress within said blade being effective to snap the apex thereof into transient position when an actuating force is applied to said other means to engage the other said blade contact with the other of said fixed contacts and to return the blade to its normal position when such actuating force is removed from said other means.

4. In a snap switch structure of the character described, a generally triangular spring blade provided with an enlarged central opening therein having a generally triangular configuration conforming to that of the blade and defining a base leg and side legs extending therefrom and merging to define an apex, said base leg having the ends thereof drawn toward each other to define a centrally disposed corrugation stressing said blade, a casing, means fixedly securing said blade adjacent one base corner thereof at said base leg to said casing, means for applying an actuating force to the other base corner of said blade adjacent said base leg, a contact carried by said blade adjacent the apex thereof, a preformed concave area in said blade between said contact and the central opening, and a fixed contact carried by said casing for engagement with the aforementioned contact, said blade being operative to snap the contact-equipped end thereof from its normal position to an alternate position when an actuating force of sufiicient magnitude is applied thereto and to return the contact-equipped end thereof to its normal position with a snap action when such actuating force is removed therefrom.

5. In a stressed blade snap switch structure, a casing provided with a pair of fixed contacts oriented in spaced apart relation, a spring blade of triangular configuration having an enlarged opening therein defining a base leg and side legs extending from the corners of the base leg and merging to form an apex, a pair of contacts carried by said blade at the apex for engagement with the respective fixed contacts, the base leg of said blade being shortened by a corrugation formed therein intermediate the connecting ends of the side legs and also having a preformed concave area intermediate said blade contacts and the adjacent end of the blade opening, means for anchoring the blade within the casing adjacent one of said base corners with said apex contacts interposed between said casing contacts, a lever fulcrumed within said casing for pivotal movement and having an end thereof engageable with said blade other base corner, and an actuator button slidably extending through said casing and being engageable with said lever for pivoting the same about the fulcrum thereof to push said end of lever into engagement with said blade, said blade having a normal position within said casing whereby one of said blade contacts normally are in engagement with one of said fixed casing contacts, the forces of stress within said blade being efiective to snap the apex thereof into transient position when an actuating force is applied to said actuator button to engage the other said blade contact with the other of said fixed contacts and to return 40 the blade to its normal position when such actuating force is removed from said actuator button.

6. The switch structure of claim 4 in which said blade at the apex thereof is equipped with a pair of contacts one on each side thereof, and in which said casing is provided with a pair of fixed contacts for selective engagement with the contacts carried by said blade.

7. The switch structure of claim 6 in which said pair of fixed contacts are spaced apart by a distance less than the throw of said blade so as to limit the movement of the contact-equipped end thereof and thereby assure a good electrical connection between the respective fixed contacts and contacts carried by said blade.

8. In a snap switch structure, alcasing, a blade of generally triangular configuration fixedly secured adjacent a corner thereof to said casing and equipped at its apex with a contact, said blade having a dished area centrally disposed therein defining a center of action, level means engageable with said blade at said center of action to define a fulcrum therefor, means for applying an actuating force to the remaining corner of said blade of a magnitude that tends to invert said dished area and thereby snap the contact-equipped apex thereof into an alternate position, said blade returning to its initial position when said actuating force is removed, and a fixed contact carried by said casing for engagement with the content carried by said blade when in one of its positions.

9. The snap switch structure of claim 8 in which said lever means engages the normally convex side of said dished area.

10. The snap switch structure of claim 9 in which said lever means comprises a post.

References Cited in the file of this patent UNITED STATES PATENTS 2,202,681 Allen May 28, 1940 2,513,053 Roswell June 27, 1950, 2,624,819 Spina et a1. Jan. 6, 1953 2,777,032 Burch Jan. 8, 1957

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