US 2182856 A
Description (OCR text may contain errors)
De.12, 1939. A, L RIGHE 2,182,856
GOMPRESSION SPRING SUPPORT original Filed'Feb. 2o, 1957 v ,0/5 inch Patented Dec. l2, 1939 UNITED 4STATES PATENT' OFI-lcs amm coiurmissroivl srruNo snrroa'r Arthur Lewis Riche, Freeport, Ill.. alignor. by
meme assignments, to Micro Switch Oorporation, Freeport, lll., a corporation o! Illinois appunti@ rem-uy ze, im. serial No. 126,139
mena omhaso, ma
14 claim'. Vuhu- 11111) The present invention relatesV generally to snap mechanisms formed of thin leaf springs for use in snap switches and the like, and relates more particularly to pivotal supports for thin leaf com` compression member and the notch aiIect appre` ciably the operating characteristics oi' the switch. When a V-shaped notch, such as is illustrated in Figs. 1 and 5 of the McGall patent is used, the compression spring does not pivot freely in the 90 notch under certain circumstances vso that the switch exhibits undesirable operating characteristics such as, for example, a tendency of the mobile contact of the` switch to creep-or move slowly away from the stationary contact instead oi executing a single snap motion from one limit of travel to the other. Objects of the present invention include the provision of an improved support for a thin leaf compression spring in a snap mechanism, the provision of an improved pivotal connection between such a spring and the member that supportsit. and the provision of a snap mechanism of improved construction and operating characteristics.v
These and other objects will become apparent as 3 the description proceeds.
The following description of certain specic I embodiments of my invention serves by way of example to illustrate the manner in which the invention may be used. However, the invention is not limited to the particular details of construction of any such-embodiment or example.
In the drawing:
` Fig. 1 is a sectional elevation of a complete snap switch embodying my present invention;
Fig. 2 is a plan view of the integral spring leaf which includes the thin leaf compression and tension members of the snap mechanism; n
Fig. -3 is a plan view of the support member for the compression leaf spring;
Fig. 4 is a sectional elevational view oi the switch of Fig. 1, taken along the line 4 4 of Fig. 1
and viewed in the direction indicated by thev arrows;
Fig. 5 is an enlarged elevational view of a part vmi or me switch or rig. 1, musmun'g in. setas the,
construction and arrangement ofthe thin` leaf compression spring and its support member;
Fig. 6 is a partial elevational view of an alternative arrangement and construction oi' the thin leaf compression spring and its support member, illus- 5 traurig another embodiment of my invention; and
Fig. 7 is a plan view of the thin leaf compression spring and support member therefor shown in Fig. 6. v
Referring to Figs. 1 to 4 inclusive, the snap 10 switch therein shown is illustrative of the type of switch in which my invention may be used advantageously. It includes an insulating case comprising a base I0 and a cover Il. 'I'he switch lincludes upper and lower stationary contacts or 15 stops I3 and Il respectively which have terminals I5 and Il. The construction which provides insulated supports for the two stationary contact pieces I3 and I I and for connecting them to their terminals 1s and is 1s best iuustrated 1n Fis. 4. 20
A mobile contact I8 is 'carried and supported by a snapv mechanism comprising a system of ten'- Sion and compression leaf springs. 'I'his system of springs includes a thin leaf tension spring 20 which is supported in cantilever fashion by means 25 of a screw 22 to provide an electrical connection between the mobile contact I8 and a terminal 2l -located on the outside of the base I0 of the insulating case. The spring system also includes a pair of thin leaf compression springs 26 which are joined to the tension spring 20 at the mobile con- `tact I8 and plvotally supported intermediate the ends oi' the tension member 20. The compression springs 26 are bowed in compression and bear against a support member 28. 'I'his support mem- 35 ber 28 is cut out in the center'so as to be left U- shaped to clear the tension spring 20 and has'a pair of notches for receiving and pivotally supporting the compression springs 26 as described in more detail hereinafter.
'I'he operating plunger 21 carried by the cover l I isadaptedto bear against the thin leaf tension spring 20 at a point near the cantilever support of the spring to deect and stress the spring. The
switch normally assumes the position shown in 45 Fig. 1, with the mobile contact I8 lying against the upper stationary contact or stop I8. When the plunger 21 isdepressed it deiiects the tension spring 20 downward near its cantileversupport -22 and causes the center line of tension of the 50 '-me'mber 20 to curve downward and move below the continues to move, propelled by the spring action of tension and compression members 2l and 26,
until contact I3 comes into engagement with the lower contact or stop l4-. Thus mobile contact I3 5 moves from one stationary contact to the other with a snap action. When the pressure is released from the plunger 21, the tension spring 2l tends to recover its former unstressed condition and in so doing bends upward near its point of cantilever support, snapping contact Il back to its original position in abutment with the upper stationary contact or stop I3.
The particular embodiment which I have selected for illustration in Figs. 1 to 4 inclusive has approximately the dimensions indicated on Fig. 1. Thus the tension member is approximately 11% inches long; the distance between the ends of the bowed compression leaf springs 26 is approximately 2%2 of an inch; and the moving contact I8 when it snaps' from one stationary contact to thev other travels a distance of .015 of an inch, or approximately V64 of an inch.
The compression leaf springs 26 and the tension leaf spring 20 are dierent parts of a single leaf of spring tempered beryllium copper 81/2 thousandths of an inch thick v(0.0085 inch), the mobile contact I8 consisting of a strip of silver folded over the connected ends of the tension and compression springs. The stationary contacts i3 and i4 also are of silver.
The U-shaped member 28 provides two lateral supports for the compression leaf springs 26 while permitting the central tension spring 20 to deflect through, and to opposite sides of, the
Fig 5 provides an enlarged View of the supporting connection between the support member 28 and the compression leaf spring 26. The support member 28 has a milled slot or notch 30 in its end, said slot having three planar faces 32, 34 and 36. Faces 32 and 34 meet to form a ninety degree dihedral angle having its vertex line at the corner 33, and faces 34 and 36 meet to form another ninety degree dihedral angle having a vertex line at the corner 35. Faces 32 and 36 are parallel. 'Ihis notch 30 is cut at the proper angle in the end of the support member 28 to bring face 36 substantially parallel with the bowed face of the leaf spring 25 at its left end as viewed in Figs. 1 and 5, that is at the end at which it engages the support member 28.
The left or pivot end of spring 26 has its lower left corner lying firmly and squarely in the dhedral angle between the faces 34 and 36 of the notch 30, which angle has the vertex line 35. This lower left corner of the spring 26 is the dihedral corner formed by the meeting of the end face of thespring 26.with the tension face or convex bowed face thereof. Since spring 26 is a compression member its convex bowed face is stressed in tension while its concave bowed face is stressed in compression.
For purposes of reference in the present description, the position of the switch in Fig. 1 is assumed to be horizontal. Accordingly, the position at which the curve of the bowed portion of Ithe. compression spring 26 meets the mobile contact I8 in Fig. 1 is approximately four to six de- 70 grecs above the position at which the left end of the compression spring 26 engages the support member 2.8. The direction of the thrust exerted by the compression leaf spring 26 on the support member 28 is towards the left and approximately u along the line between the two ends 0I the G0111- axis of the pivotal support of the compression pression spring 26. that is to the left and dropping four to six degrees below the horizontal. This line of thrust is indicated approximately by the line 40 in Fig. 5.
The compression spring 26 is of such a length that when bowed and assembled in the switch as shown in Fig. 1, it makes an Yangle of approximately 21 to 22 degrees with the horizontal at the point at which it engages the support member 28. The exact angle depends in part upon which of the two stationary contacts I3 and Il the mobile contact II is lying in engagement with. Accordingly the slot 30 is cut in the support member 23 at an angle of 22 degrees with the horizontal. The thrust of the compression spring 26 against the support member 28 is borne by the faces 34 and 36 of the notch 30, the compression spring 26 seating its dihedral angle `formed by its end face 3l and tension face 36 in the dihedral angle having the vertex line 35. The height of the notch 30, or the distance between its faces 32 and 36 is only great enough to provide sufficient clearance between the concave bowed face of the spring 26 and the face 32 of the notch 30 for operation of the switch.
The left or pivot end of the compression spring 26 is accurately 'and sharply squared oil. In constructing the complete spring leaf shown in Fig. 2 which includes both the tension spring member 20 and the two compression spring members 26, the leaf first is blanked out and then mounted in a jig where the left or pivot ends of the compression members 26 are dressed by hand with a ilne ille to ensure that the ends be perfectly square and smooth and that the corner between the end face and the convex or tension face of each compression spring 26 be clean and sharp.
I believe that the dlniculty encountered with prior switches having compression springs or the like supported in notches, wherein those switches would fail to snap properly so that their mobile contacts could be controlled to move slowly between their stops, was due in part to a limited and only partially secure wedging of the end of the compression spring in the notch of the support member. Either a frictionless pivot connection permitting free turning of the spring in its support, or a secure grip on the spring preventing any turning at all in the support, should enable the switch to execute a reliable snap motion. But an insecure grip or a pivot with considerable friction may hold the compression spring from turning in its support only until the contact begins to move and then may permit the spring to turn so as to release the stress and thereby dissipate the energy that should have driven the contact.
Certain prior attempts to prevent thin leaf compression springs of snap mechanism from wedging in V notch supports have resulted in the thin leaf compression springs exhibiting a tendency to twist or warp about their longitudinal cordsV out of their properly oriented positions so that the springs could not pivot easily on the support members. This restraint upon the pivoting of the compression springs of a switch tended to prevent the switch from executing a snap motion and caused the mobile contacts to creep, or move slowly, between the stationary contacts. A common result of sluggish or faulty action of a switch of this type is that the contacts separate a suillcient distance to impair good electrical contact'between them but they do not separate far enough to interrupt the resulting Til t n 52,189,850 arc between the. switch contacts and the un-l.
extinguished arc quickly destroys the switch conf tactsr In my construction shown in Fig. 5, the slot 36 in the support member 28 has a width which is just enough greater than the thickness of spring 26 to aii'ord freedom for the necessary movement of the compression spring 26 in the snap over action. The movement of the spring in the slot is slight and the required clearance is small so that the spring is substantially restrained from twisting about its longitudinal cord. In addition, the force reactions between the leaf spring 26 and the faces 34 and 36 of the notch 30 tend to seat the dihedral corner of the spring firmly in the dihedral angle formedl by those faces and thereby further restrains twisting of the spring 26. The end face of the spring 26 abuts squarely against the bottom of the slot and frictionaily engages the face 34 thereof over the entire end face of the compressionv spring 26y itself. This firm engagement between the end of the compression spring 26 and the support member 28 eliminates any tendency for the springs 26 to shift laterally out of place. v
Fig. 6 illustrates another embodiment of my invention which consists in 'an alternative construction for the compression spring' support member and the manner of its engagement with the pivot end of thecompression leaf spring.
In Fig. 6, reference numeral 46 indicates a bowed compression leaf spring identical with I the compression leaf spring 26 of Figs. 1 to 5 inclusive, and reference numeral 48 indicates a support member for the compression spring46. 'I'he support member 48 differs from the support member 28 of Figs. 1 and 5 principally in the configuration of the notch for receiving the end part, is identical with the switch shown in Figs.
1 to 5 inclusive.
The support `member 48 ycontainsa groove 50 for receiving the left or pivot end of the compression leaf spring 46, which groove has three planar.
faces 52, 54 and 56, all of which appearas lines in the elevational view of Fig. 6.. Faces 52 and 54 meet to form a concave dihedral angle of 135 degrees having a vertex line 53, and faces 54 and 56 meet to form a concave dihedral angle of 135 degrees having a vertex line 55., The central face 54 makes an angle of y 15 degrees with the vertical and its normal makes an angle of 15 degrees with the horizontal. The dihedral corner of the compression leaf. spring 46 which is formed by the meeting of the end face 6i thereof with the convex bowed face thereof,` which corner has the vertex line 63, lies in the dihedral angle between the faces 54 and 56, so that the two vertex lines 55 and 63 substantially coincide. The line of thrust of the compression spring 46 is directed from an angle of approximately four to six degrees above the horizontal and consequently approximately bisects the dihedral angle between the faces 54 and 56 of the notch 50.
Inasmuch as the central cord of the compression leaf spring 46 lies at an angle of approximately 21 to 22 degrees with the horizontal at the end at which the spring engages the support member 48, theend face 6I of the compression leaf spring 46.1ies atan angle of 6 or I degrees with the central face 54 of the. notch in the end of the support member 48.- And inasmuch as the motion of the compression leaf. spring 46 when degrees, the compression spring 43 always will. .I
engage the support member 43 onl'yat, the di hedral corner ofthe spring which has the vertex line 63. 4Inasmuch as-the vdirection of the thrust exerted by the compression spring 46 upon the support member 48 is directed approximately along the bisector of the dihedral angle inl which the corner of the compression spring rests, this i thrust maintains the dihedral corner of the spring firmly seated' in the apex of the angle. Referring to Fig. 7, the notches 56 in the en of the supportymember 48 do not'extend the full width of the piece. 'I'he notches are closed by `means of projections 60 at the outer lateral ends of the notches. These projections 60 serve to prevent movements of the compression leaf' springs 4 6 in the notches 50 longitudinally' with respect to the notches, that is laterally with respect to the leaf springs themselves.
As in the construction of Fig. 5, the notch 50 of Fig. 6 provides insumcient clearance to permit any considerable twisting of the compression spring members 4,6 about their longitudinal axes.
And furthermore the tendency of the spring 46 25 surfaced and accurately shaped notch.
It will be readily apparent to those skilled in the art that the embodiments of my present in vention, herein shown and described are by way of illustration and example only, and that those embodiments are capable of numerous variations and modifications. Dimensions and structural details, where given, are included only to make Vthe description of the particular embodiment complete and explicit. The-invention is not limited to such details. Therefore I do not intend to be limited yto "the specific form, size and construction shown in the foregoing particularembodiments butY rather I wish to be limited only by the scope of the appended claims. For example my improved support for a thin leaf spring need not be-employed in a switch in which a tension spring is flexed to operate the switch.' The invention also may be used in switches operated differently, as by moving the member that supports either the compression springer the tension spring or by moving the contacts between which the mobile contact snaps.
1. In 'combinationin a spring vsnap mechanism of the class described, a bowed thin leaf spring and a support therefor, the support -for said thin leaf spring including means providing a. notch in the form of a dihedral angle, said spring having a dihedral corner of substantially 90 formed by the meeting of the tension face of said leaf spring with a face substantially perpendicular to the longitudinal chord of the spring, said dihedral -corner of said thin'leaf spring being seated in said dihedral angle of said support, so that the vertices of saidangles ofv the spring and the support coincide.
2. In combination in a snap mechanism of the class described, a compression member consistting of a bowed leaf spring having one end thereofY squared-oi! and having smoother faces and sharper corners than are formed by ordinary class` described, a compression member consisting of abowed leaf spring having one end thereof squared-off, and a support for said end of the bowed leaf spring, said support providing a notch in the form .of a dihedral Yangle whose vvertex line substantially coincides with the f vertex line of that dihedral corner of the bowed spring which is formed by the meeting of the end face of said end of the spring with the convex bowed face of the spring. I
4. In combination in a, snap mechanismof the class described, a compression member consisting. of a bowed leaf spring having one end there.- of squared off and having smoother faces and sharper corners than are formed by ordinary shearing tools, and a vsupport for said end of Vthe b'owed leaf spring, said support providing a notch in the form yof a dihedral angle which engages only that dihedral corner of the bowed spring which is formed by the meeting of the end face of said end of the spring with the convex bowed face of'said spring, the vertices of s aid dihedral angles of said spring andsupport coinciding.
5. In combination in a snap mechanism of the class described, a tension member mounted at one end and free to move at the other end, a stop for limiting the motion of the free end of the tension member, a compression member consisting of a bowed leaf spring fastened at the first end thereof to the free end of the tension member, the second end of said leaf spring being squared of! and having smoother faces and sharper corners than are formed by ordinary shearing tools, a supportfor said second end of the bowed leaf spring intermediate the ends of said tension member, said support providing a notch in the form of a dihedral angle containing the dihedral corner of the bowed spring formed by the meeting of the end face of said second end of the spring with the convex bowed face of the spring and an obstruction for limiting displacement of said spring in said dihedral angle in the direction of the vertex line of said angle, the vertices of said dihedral angles f said spring and support coinciding.
6. In combination in a spring snap mechanism of the class described, a compressionmember consisting of a bowed leaf spring having one end thereof squared-0E, and a support for said `end of the bowed leaf spring, said support providing a dihedral angle of substantially ninety degrees, the end face of said end of the spring and the convex bowed. face of the spring lying substantially hat against the two faces of said dihedral angle and the sharp corner of said spring laying in the apex of said dihedral angle.
7. In combination in a spring snap mechanism of the class described, a tension member mounted at one end and free to move at the other end, a stop for limiting the motion of the free end of the tension member, a compression member consisting of a bowed leaf spring fastened at one end thereof to the free end of the` tension member, the other end of said leaf spring constituting a pivot end, said pivot end being squared ofi', and a support for the pivot end of the bowed leaf spring intermediate the ends of said tension member, said support having a aisae'se 1 L s'e'cting plane extends therefrom approximately in the direction of said-stop, said concave dihedral angle containing'that dihedral corner of the bowed spring which is formed by the meetingoftheendfaeeofthepivotendofthespring with the convex bowed face of said'sprlng, said leaf springv beingbowed to such an extent that said concave dihedral angle engages substantially only said dihedral corner.
8. The combination of'claim 'I wherein there is included an obstructionv ending said notch at a position anking said spring to limit lateral displacement of said spring in said notch.
9. In combination in a spring snap mechanism of the class described, a compression member consisting of a bowed leaf spring having one end thereof squared olf, a support for said end of the bowed leaf spring-said support having a notchhaving three planar faces forming first and second dihedral angles, said nrst dihedral angle being approximately two radians, the corner between the end face and the convex bowed face of said leaf spring at said end thereof lying in'the first dihedral angle of said support, the corner between the end face and the concave bowed face of the leaf spring at said end thereof being adjacent to the vertex of the second dihedral angle, the end face` of the leaf spring lying at an angle of approximately one-tenth radian to that face of the notch which contains the vertices of both said first and second dihedral angles, said second dihedral angle being at least approximately one and one half radians and sumciently great that its faces avoid engagement with said corner of the leaf spring between the end face thereof and the concave bowed face thereof, the reaction 'of said leaf spring against said. support consisting of a thrust directed toward the vertex of the first dihedral angle and in a direction that approximately bisects said rst dihedral angle.
10. The combination of claim 9 wherein there is included an obstruction ending said notch at a position flanking said leaf spring for preventing displacement of said spring in said'notch laterally of said spring.
11. In combination in an apparatus of the class described, a tension member operatively mounted at one end thereof with the other en d free to move, a stopV for limiting 'the motion of said free end, a pair of parallel compression members adjacent and. on opposite sides of said tension member consisting of bowed leaf springs each having one end connected to the free end of said tension member with its other end constituting a pivot end, each of said leaf springs having the end face at its pivot end forming a dihedral corner of substantially ninety degrees with the convex bowed face of the spring, each of said leaf springs having the vertex line of said dihedral corner substantially coinciding with the corresponding vertex line of the other leaf spring, means for supporting the pivot end of each of said leaf springs intermediate the ends of said tension member, said means including a member having a notch with two planar faces forming a .concave dihedral angle of approximately two radians and having a vertex line substantially parallel to the corresponding vertex line of the support of the other leaf spring, and substantially parallel to the' vertex lines of the dihedral corners of said leaf springs, said dihedral corner of each spring lying in said diaisasse hedral angle of its support, the pivot end face of the leaf spring lying at an angle of approximately one-tenth -radian to the face of the notch adjacent it, the reaction of said spring against said support consisting of a thrust directed towards the vertex line of the dihedral angle of said support in adirection that approximately bisects said dihedral angle, and means for manipulating the foregoing elements to cause the line of tension of said tension member to cross the extended vertex lines of said dihedral angles.
12. In combination in asnap mechanism of the class described, a compression member consisting of a bowed leaf spring having one end thereof squared oi, a support for said end of said bowed leaf spring, said support providing a concave dihedral angle containing thedihedral corner of the bowed spring formed by the meeting of the end face of said end of the spring with the convex bowed face of the spring, and an obstruction in said dihedral anglefor limiting the displacement oi' said spring in said dihedral angle in the direction of the vertex line of said angle.
13. In combination in a spring snap mechanism of the class described, a thin leaf compression member and a support therefor, the support for said compression member including means 'for providing a notch in the form of a dihedral angle; said compression member having a. dihedral corner having an angle less than the angle of the notch so that it cannot ll the notch, the vertex lines of said dihedral-angles of said notch and compression member coinciding, said t member is squared 01T so that said dihedral corner of said compression member engaging said support is substantially 90.
ARTHUR LEWIS RIGHE.