US3033953A - Miniature snap switch - Google Patents

Description

Filed June 15, 1960 fi a 2.

J0 .6' 55 fi-l 10a .54

I N V EN TOR. B05597 E: 5 CHM/E2165 14 r r elvEysQ United States Patent C) This invention relates to a miniature snap switch.

The primary object of this invention is to provide an improved, reliable and simple snap switch of the type utilizing the resilient characteristics of a contact carrying mm for moving the switch to one of two contacting positions.

Prior switch structures of this general character have certain objectionable features. For example, rather complex contact arm structures may be provided, or suspensions for the contact arm may be complex, or the actuating structure may be intricate. One prior art structure utilizes a floating contact arm in which a bowed section is engaged at a stationary fulcrum bracket, and in which the end of the contact arm remote from the contact is movably mounted so as to pass in over center relationship to the fulcrum, thereby achieving snap action. The floating anchor necessitates a complex structure. Thus, since the structure is floating, it must be stabilized against all movement but the desired movement. Since the structure is floating, heat dissipation from the contact to the case is poor. Electrical connection to the contact arm depends upon frictional engagement at knife edges.

Accordingly, the primary object of this invention is to provide a snap switch having a fixed anchor. The shape of the spring arm is itself simplified. It need have no reinforcing or stabilizing flanges. It can be entirely fiat. Since the contact arm has a fixed anchor, heat dissipation is much improved. The electrical connection is secure.

Another object of this invention is to provide a snap switch that uniquely utilizes not only the resilient characteristics of an integral spring tab of the contact arm, but also the resilient characteristics of the arm itself in order to achieve a snap acting switch that is normally maintained in one position.

Another object of this invention is to provide an improved snap switch of this general character in which actuating means positively forces the contact away from its normal contacting position. Accordingly, welding or fusing of the contact at the normal position is prevented. In the floating anchor type of prior art devices, the arm first moves about the contact as a pivot point until the over center relationship is achieved. The mere over center relationship will not be enough to move the contact if there is a slight adherence.

Another object of this invention is to make use of a force multiplying pivoted beam having a portion engaging the contact arm at a place spaced from its anchored end. All of the force of the actuating means is used to move the contact. 7

Another object of this invention is to provide a switch structure of this character that incorporates simple means for changing or controlling the force necessary to move the contact from its normal position to its opposite contacting position. For this purpose, use is made of a simple readily replaceable spring that engages the beam and biases the beam toward released position. The spring may even be removed, if desired, without changing the operation of the switch, except as to force necessary to actuate it.

Another object of this invention is to provide a simple switch in which the fulcrum brackets and other parts are readily and easily assembled with respect to a case and its cover.

t me Patented May 8, 1962 This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of one embodiment of the invention. For this purpose, there is shown a form in the drawings accompanying and forming 'a part of the present specification. This form will now be described in detail, illustrating the general principles of the invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of this invention is best defined by the appended claims.

Referring to the drawings:

FIGURE 1 is an enlarged sectional view of a snap switch structure incorporating the present invention, and showing the parts in assembled relationship;

FIG. 2 is a view similar to FIG. 1, but showing the snap switch in its opposite contacting position;

FIGS. 3 and 4 are sectional views taken along planes indicated by lines 33and 44 of FIG. 1; and

FIG. 5 is a sectional view taken along a plane indicated by line 5-5 of FIG. 2.

In FIG. 1 there is illustrated a generally rectangular case 10 having a central shallow generally rectangular cavity 11 in which switch parts are accommodated. The case it) preferably is molded plastic that has suitable electrical insulation characteristics. The cavity 11 is closed by a cover 9 made of similar material (FIG. 3) that complements the case 19 to form the switch body. A rivet 12 located beyond the cavity ll holds the case 10 and cover 9 together.

Projecting exteriorly from the case 10 are three elongated brackets or strips 13, 14 and .15 forming accessilble terminals of the switch structure. Also projecting eX teriorly of the case It? is a plunger 16 that actuates the switch. The terminal bracket 15 is normally in closed circuit relationship with respect to the terminal bracket 13 and in normally open circuit relationship with respect to the terminal bracket 14. The opposite electrical relationships are the result of inward movement of the plunger 16.

The brackets v1.3 and 14 are identically formed, and are disposed symmetrically about a median plane extending along the long dimension of the case, or horizontally as viewed in FIG. 1. One of the brackets 13 occupies the upper right hand corner of the cavity 11, and the other of the brackets 14 occupies the lower right hand corner of the cavity. These bracket portions within the cavity respectively mount identical contacts 17 and 18 in spaced opposed relationship.

Each contact has a stem 19 that passes through an aperture 20 in the corresponding bracket. The end of the stem 19 is riveted over, as at 2.1, to secure it it firmly.

The brackets 13 and 14 are held in place relative to the housing by virtue of a fitted relationship to the case 10 and the cover 9. The central portion of each bracket fits into a corresponding slot or recess 22. The recesses 22 extend through the right hand wall lilb of the casing 10, form the case surface 23- abutted by the cover 9 (FIG. 3) to a place short of the bottom or inner wall 10a of the case. The brackets each have a necked down portion 24 forming shoulders 25. whereby the brackets inter.- lit the case 10 and cover 9. Thus the bracket 14, for example slidably enters the corresponding case recess 22 by transverse movement via the opening at the case surface 22. The shoulders 25 at the inner side of the bracket 14 (FIG. 4) engage the case wall 10b beyond the bottom of the recess 22, and adjacent the inner case wall 10a. An interlock is thus formed. The shoulders 25 at the outer or upper side of the bracket 14 form a recess receiving a peripheral rim 26 of the cover 9. The bracket 13 similarly cooperates with the case lit and cover 9.

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- v The brackets 13- and '14 also have outwardly turned and completes the confinement ofthe bracket terminus.

' A contact button 34, connected to the terminal bracket 15, in'a manner to be hereinafter described, is movable between the contacts 17 and 18 in order to accomplish the switching functions. The bracket 15 has an inter bows to a point where it is aligned with the fulcrum notch In order to hex the arm 41 and thus to move the contact button 34 from the normal position illustrated in FIG. 1, a beam 56 is provided that is preferably molded of plastic material. The beam 50 is pivoted on a pin 51 (FIG. 4) indie case cavity'll that projects outwardly from the bottom wall Illa of the case 19 from'a place just below the center of the upper wall 19c of theca'se' f The-pin 51 has mediate ofiset portion35 accommodated in a groove 36 inthe lower'wall of the case 10. The oifset portion 35 is necked down, as at 37 (FIG. 4), so that shoulders38f interlock the case 'lll and the riin26 of the cover 9 as the contact brackets 13 and 14 do; 7 i

The inner portion of the bracket 15 beyond the oifset 35 projects toward the lower left hand corner of the caserece ss 11. The inner terminus 39 of the bracket 35 fits a groove 46 formed in the left hand wall 10c of the case. 10. A companion groove (not shown) of the cover 9 receives the outwardly projecting corner of the bracket terminus 39; The contact bracket 35 is accordingly held in position. a Y

' The contact button 34 is mounted upon the endof an arm 41 made of thin beryllium copper or other'resilient flexible material having electrical conductive properties'. The arm 41 is generally of rectangular outline, as shown in FIG. 3. The center of the spring arm 41 has a cutout 42 that is rectangular except for a cantilever tab 43; located at the end adjacent the contact button 34. The other end of the arm 41 is riveted to the terminus 39 of the'terminal bracket '35. For this purpose, a rivet44 is provided that passes through registering apertures 45 and 46 of the bracket 15 and the spring arm 41 A protective washer 47 is interposed between the spring arm 41 and the corresponding head of the rivet 44. Electrical connection between the button 34 andthe bracket 15 is thus established. V Struck upwardly from the contact bracket 35 (see also FIG. 4) is a. fulcrum .bar 48. The fulcrum bar 48 provides a V-notch 49 that opens toward the'tab 43 and the contact button 34. It receives the free end of the tab 43, and is so placed that the tab. is substantially bowed whatever'may be the position of the arm 41. As. shown in FIGS. 3 and 4 the fulcrum bar 48 is of a width small enough to provide clearance with respect to the edges of the arm aperture 41.'

The bowed cantilever tab, being of resilient material resists increased bowing, and thus tends to move the contact button 43 asv far away from the fulcrum notch 49 as possible, and in either convenient direction from a position a maximum stress or rninimum distance.

In the position shown in FIG. 1 the contact button 34is urged by the action of the spring tab 43 into e n' gagement with the contact 17. The contact 34 in this position is spaced from the position of minimum distance or maximum stressrbecause a straight line forming the anchored end of the arm 41, about which the arm position with snap action derived from the energy stored in the arm l'andthetab 43. This position ofmaximum combinedstress may be reached when the arm 41 itself a knurled head 52 embedded and thereby anchored in the bottom walllflkz of the case 14?. raised circular land 53 surrounding the pin 51 is formed on the inner side of the case bottom wall lila. The outer end of the pin 51 is received in a recess54 formed in the cover 9. Thisrecess 54 extends inwardly from a raised circular land 55. for-med on the inside of the cover 9. The beam 53 has an apertured hub 56 that is journalled upon the pin 51.

The dimension of the hub 56 corresponds to the distance between the lands 53' and '55." Hence, the lands hold'the beam 50 suitably in centered relationship in the cavity formed between the case and cover;

The beam extends from the pin 51 along the upper left corner of the case cavity 11'. Intermediate the length of the beam 50, a depending projection 58 is integrally formed that has a relatively sharp knife-edge surface 57 engagea-ble with the sides of the spring arm '41 on opposite sides of the cutout 42fand behind the fulcrum bar 48'.

' As the beam 50' is moved angularly downwardly about the pin 51 asan axis, the arm 41iscaused to flex or how until the'arm 41 snapsto the opposite contacting position as above described. r

' The plunger 16 is used to operate the beam 50. For this purpose, the plunger'16 which may also be molded of plastic material, is guidingly accommodated in a through aperture Gil in the top wall 10c of the body. The lower end of the plunger ld'h'as ahead fil 'engageable with the free endof the beamfilll By virtue of the relative placement of the plunger 16 and the edge 57, the force -applied to the plunger 16- is multiplied as his ultimately applied to the arm 41'. i Al-l'iof the force is thus efiectively and directly used in moving the cdntact button 34 away fr'om' the contact 191. Hence,any tendency for the contacts to stick is directly overcome; i

When the arm 41' flexes prior to snap movement away from the contacting position of FIG. 1; it assumes a slightly arced or bowed configuration; This means a shortening of the length of the arm 41, and hence a desirable wiping action between the contact button 34 and the contact 17. To produce wiping action at the opposite contact 18; the end of the arm may be bent downwardly so thatupon engagement 'of the button with the contact 18, the end tends to straighten out.

When the force applied to the plunger 16 is released, the induced fiexure of the spring arm 41 is removed and it passes upwardly of the fulcrum point 49. At that point, the bowed tab 43 dominates, so that it, with'the residual force or stress of the arm 41freturns: the arm 41 to the position illustrated in FIG. 1. 'When the arm 41 is itself unliexed, there is one and only one stable contacting position, and as illustrated in FIG. 1. The reason for this is that the parts are so located that mere movement of v the contact button 34 to the contacting position of "FIG. Z

V will not carry the arm 41beyond center with respect to the V-notch 42' The arm 41 must be flexed before this occurs. Hence, the switch normally returns to a distinct PO OH- .e a

The force necessary critically to move the switch is dependent upon the spring characteristics of the arm 41 and the, tab 43. In orderto introduce an additional bias force that must be overcome before the switch'is critically moved, a C-spring 62 is provided. The. spring62 has a central curved part at 63 that embraces the hub'portion 56013 the beam 50. one end of the C-spring 62 engages beneath the beam 50, and the opposite end is anchored in an inverted L-shaped'groove 64' to which configuration 5 the C-spring generally conforms. Accordingly, the spring biases the beam in a direction away from engagement with the contact arm 41.

The G-spring 52, can be omitted or replaced by another of slightly ditferent spring characteristics. Accordingly, various specifications as to bias forces can readily be met. Holes 65 and 66 at opposite corners of the case serve as a means whereby the switch may be connected to a support or an external actuating arm (not shown).

The inventor claims:

1. In a snap switch. a supporting case having a cavity; an arm in the case cavity made of flexible resilient material, and having a contact at one end; means anchoring the other end of the arm to the case; said arm having an integrally formed spring tab having an unattached end extending generally toward the anchored end of the arm; means connected to the case forming a fulcrum receiving the end of said spring tab; abutment means on opposite sides of said contact and defining opposite limits of movement therefor; at least one of said abutment means being a contact; the arm being so located that when acted upon only by the stress of said spring tab, it exclusively engages one of said abutment means; and releasable means for flexing the arm until the combined stress in the arm and said spring tab moves the arm with snap action toward said other abutment means, comprising a beam pivoted at one end in the cavity and having a part located on the same side of the arm as said one abutment means, said part being opposed to an intermediate portion of said arm, said beam being movable so as to cause the part to engage the arm to flex the arm away from said one abutment means and toward the other abutment means, an actuator guided by the case having one end opposite the beam on the side thereof remote from said arm for engagement therewith at a place spaced from its pivoted end, said actuator having its other end projecting extetiorly of the case for access thereto, said case having provisions for limiting outward movement of said actuator, and biasing means urging the beam against the said one end of said actuator whereby the said actuator forms a stop for movement of the beam in a direction away from said arm.

2. The combination as set forth in claim 1 in which said a beam part is located between the plunger and the pivoted end of the beam to provide a force multiplication.

3. The combination as set'forth in claim 1 in which said beam biasing means comprises a replaceable spring extending about said one end of said beam and having one end engaging the beam to position it in spaced relationship with respect to said arm, and having its other end confined by a slot in the case.

4. In a miniature snap switch: a case having a cavity therein; a cover for the case; a pair of contact brackets fitting the case, and each projecting in spaced relationship through one wall of the case into the cavity; opposed contacts mounted on the inner ends of the contact brackets; a third bracket fitting the case and having an inner end located to one side of the opposed contacts; a spring arm anchored to the inner end of said third bracket, and projecting between the opposed contacts; a contact button mounted on the arm for engagement with said contacts upon opposite movement of said arm; said arm having a central cutout portion forming a spring tab extending in a direction toward the anchored end of said arm; said third bracket having an integrally formed fulcrum bar providing a notch engaged by the free end of said spring tab; said anchored end being so located that the spring tab causes the arm, in the absence of external forces, to engage one of said contacts to the exclusion of the other; a pivot pin extending across the cavity and on the same side of the arm as said one contact; a beam having one end pivotally mounted on said pin, said beam extending in snpenimposed relationship along the arm, said beam having a part opposed to and engageable with said arm at the area of the cutout adjacent the fulcrum bar for flexing the arm in a direction tending to increase the flexure of said spring tab until the combined stress of the arm and the tab snaps the arm so that the button engages the opposite contact; an actuating plunger guided by the case having one end engaging the beam on the side thereof remote from said arm and having its other end accessible exteriorly of the case; said case having means forming a limit to the out-V ward movement of the plunger; and a replaceable substantially right-angled spring extending about the said beam and said one end of said beam, said spring having one end oriented between the beam and the arm and engaging the beam to urge it against the said one end of said plunger, whereby the said plunger forms a stop limiting movement of the beam away from said arm, said spring having its other endprovided witha retaining projection receivedin a slot of the case; said spring normally spacing the beam part from said am and imposing a bias force on said beam that must be overcome before the said arm is moved to engage the said opposite contact.

References Cited in the file of this patent UNITED STATES PATENTS 2,354,027 Kaminky July 18, 1944 2,417,169 Kaminky Mar. 11, 1947 2,486,033 Kaminky Oct. 25, 1949 2,627,754 Millard Feb. 10, 1953 2,701,475 Readeker Feb. 8, 1955 2,743,331 Lauder Apr. 24, 1956 2,818,734 Howe Jan. 7, 1958

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