PUSH BUTTON SWITCHES

Abstract: A reciprocable push button switch achieves sequential switching (ON/OFF or ON/ON) through a simple coil spring (28) and pivoted contact lever (26). A push button (14) of the switch has depending abutment means (14e, 14f) which coop­ erate with camming means (40, 42) inside the switch case (10) to swing the contact lever (26) from side-to-side as it pivots about a first axis (32) between its limit positions. The cam­ ming means (40, 42) contribute to an additional swinging mo­ tion about a second axis (35) to locate the ends (26a, 26d) of the lever (26) alternately in a position for operation by the abutment means (14e, 14f). The resulting compound contact lever action is achieved with a straight line push button mo­ ton.

Description: Field of Invention This invention relates generally to push button electric switches of the type having a button adapted to be pushed to achieve alternate switch conditions in sequence in order to energize either two different circuits from the same switch, or to achieve a simple ON/OFF function. Background of Invention It is amongst the aims of the invention to provide a push button switch having a small number of component parts within the switch housing to reduce assembly and production costs. US Patent No. 4,408,106 discloses a push button switch which includes, in addition to a spring, a staple or strut element for camming the movable contact element in order to achieve the desired motion of the latter against the force of the single spring. General Description of the Invention The invention provides a push button switch having a movable contact element resiliently connected to a push button to urge the element to either one of two limit positions characterised in that abutment means on the push button are arranged for abutting said movable contact element on either side of a first pivot axis and in that means are provided for swinging the element about a second axis angled with respect to the first axis during a final stage of element movement so that one end of the element is moved sideways to not engage the abutment means at a subsequent push button operation and the other end is moved to engage the abutment means at that subsequent operation. The push button switch may include a switch housing having a generally rectangular shape with a top opening for slidably receiving a push button, and with a bottom wall in which are provided at least a centre fixed contact and one additional fixed contact connected to the centre contact through the movable contact element, suitably in the form of a lever. The movable contact lever may have a raised land provided well above its pivot point and a spring may be provided between this land and the underside of the push button. One end portion, and preferably both end portions of the movable contact lever define abutment surfaces for selective engagement with depending abutment means provided in the push button itself. One or the other of these depending abutment means engages one or the other of the abutment surfaces on the contact lever to move the lever from one of its limit positions toward the other limit position as a result of initial downward push button movement. The lever may be pivotally mounted on the centre fixed contact for pivotal movement on the transverse first pivot axis arranged at a slight angle with respect to the horizontal floor or bottom wall of the switch housing. The centre fixed contact may be in the shape of a yoke for so receiving the movable contact lever, and notches may be provided on opposite sides of the movable lever for supporting the lever for pivotal motion on the centre contact. One of these notches is preferably wider than the other to allow limited swinging or shifting movement of the contact lever in addition to such pivotal motion on said first axis. One end portion of the lever is adapted to engage one of two fixed contacts provided on either side of the centre contact in the bottom wall of the housing. Finally, camming means is provided in the switch housing for engaging one of the lever end portions as the lever end portion moves into one of its two limit positions so as to achieve a shifting of the lever, at least slightly, on a secondary pivot axis provided at right angles to the transverse primary pivot axis. This compound lever action provides clearance for the depending abutment means on the push button during upward return movement. Drawings Figure 1 is a vertical cross sectional view showing one condition for a push button switch according to the invention with the movable contact lever in one of its two limit positions; Figure 2 is a vertical sectional view similar to Figure 1, but illustrating the movable contact lever in an alternative or second limit position; Figure 3 is a horizontal sectional view taken generally on the line 3-3 of Figure 1, illustrating the movable contact lever in solid and phantom line in different angular positions: Figure 4 is a vertical sectional view taken at right angles to the sectional views of Figures 1 and 2 and illustrating the push button after it has been depressed partly into the switch housing: Figure 5 is a sectional view similar to Figure 4 on line 5-5 of Figure 2 but illustrating the push button in a fully depressed condition; Figure 6 is a sectional view taken generally on the line 6-6 of Figure 1 and illustrates the relationship between a primary and secondary axis about which a movable contact lever of the switch pivots or swings respectively; Figure 7 is a detailed view of a raised land defined by the movable contact lever for receiving the lower end of a return spring; and Figure 8 is a schematic view of one end of the movable contact lever and a fixed contact associated with it, the arrows illustrating contact closing and contact opening movement. Description with Reference to the Drawings The push button switch of Figures 1 to 7 comprises a generally rectangular switch housing 10, which housing may be molded of one piece plastic construction or may be formed with an open bottom and fitted with a separately molded bottom wall 12 as shown. The switch housing includes integrally connected end and side walls as indicated generally at 10a, 10b and 10c in Figures 1 and 2. These four end and side walls are depicted in horizontal section in Figure 3. The bottom, side and end walls of the switch housing cooperate to define an upwardly open switch cavity, and this cavity has a top opening 10e which is also generally rectangular and may be slightly smaller in size than the switch cavity itself in order to slidably receive a vertically movable push button 14. The switch housing 10 may include integrally formed resilient wings (not shown) or may include other devices for mounting of the switch housing in a generally rectangular panel opening or the like. When so mounted an outer bezel portion 10f of the switch housing will be all that is visible to the observer. Figure 4 shows in solid lines the push button 14 in an intermediate position, that is between the normal extended position illustrated in Figures 1 and 2 and a fully depressed position best shown in solid lines in Figure 5 but also visible in Figure 4 in phantom lines. It will be apparent that the push button 14 has a generally rectangular configuration with a peripherally extending inner portion 14a that serves to limit the upper position for the push button relative to the switch case 10. The depressed condition may be limited by a stop surface 10g best shown in Figures 4 and 5 as engaging a portion 14b of the push button for this purpose. The push button 14 also includes two depending leg portions 14c and 14d, which leg portions define abutment means adapted to engage selected surface portions of a contact lever 26 to be described. One abutment means so provided on depending leg 14c is illustrated at 14e in Figures 4 and 5. The other such abutment means provided in spaced relationship to the first mentioned abutment means is illustrated at 14f in Figure 2. Still with reference to the push button 14, and for a purpose to be described hereinafter, each depending leg 14c and 14d also includes a ramp surface 14g which is designed to assure that the movable contact lever 26 will be properly positioned after actuation of the push button 14 and more particularly during return movement of the push button 14 relative to the movable contact lever 26. The push button 14 includes a spring locating nub 14h and a coil spring 28 is provided between the push button 24 and a raised land 26a defined by upstanding tang 26b integrally formed in the movable contact lever 26. This spring 28 serves to bias the push button 14 toward its normal, upper position as illustrated in Figures 1 and 2, and also serves to engage the raised land portion 26a of the movable contact lever so as to urge the lever into either one of its two limit positions as illustrated in Figures 1 and 2 depending upon orientation of that lever. Figures 1 and 2 show stable positions for the contact lever 26, positions which will be altered only when the tang 26b has moved through the vertical plane defined by the centre fixed contact 30. Several fixed contacts are provided in the bottom wall 12 of the switch case housing 10 and these include the centre fixed contact 30 having its upper end portion defining two mutually angled pivot axes for the contact lever 26 as shown in Figure 6. More particularly, the upper end 30a of centre fixed contact 30 defines a primary pivot axis 32 for the contact lever 26 and this axis is preferably inclined at least slightly with respect to the horizontal or with respect to the bottom wall 12 of the switch housing. A second axis 35 is angularly related to the first or primary axis 32 and is more particularly oriented generally perpendicular thereto so as to define an axis for swinging or shifting movement of the movable contact lever as suggested generally in Figure 3. This shifting or swinging movement of the movable contact lever 26 about the generally vertical axis 35 permits a compound motion for the contact lever 26 as suggested by the successive positions for this movable contact lever 26 in Figures 4 and 5. Turning next to a more detailed description of the movable contact lever, Figure 3 shows the lever 26 in plan view with the upstanding tang 26b oriented at right angles to the plane of the lever itself. This tang is stamped from the initially flat lever as shown by the opending 26e. The end portions of the lever define upturned tabs 26f and 26g or abutment surfaces that are engaged by the abutment means, 14e and 14f respectively, on the push button to achieve a desired sequence or cycle of compound lever action to be described. Still with reference to the lever 26, Figure 3 also shows the lever with laterally opposed notches 26h and 26j receiving raised portions of the centre fixed contact 30. One such notch 26h is larger than the other notch 26j so that the lever can swing or shift between the solid and phantom line positions depicted in Figure 3 about the secondary axis 35. The movable contact element C, C can be seen to move horizontally relative to the upper ends 34c and 36c of the fixed contacts 34 and 36 in a manner to be described. The lever is shown in Figure 1 in a first position wherein one end portion 26c has a contact engaging an upper end 34c of a fixed contact 34 provided for this purpose in the bottom wall 12 of the housing. Figure 2 illustrates a contact on the opposite or second end portion 26d of the contact lever 26 engaging the upper end of a second fixed contact 36 in a second limit position. It will be apparent that the push button switch shown in the drawings is an ON/OFF type. Alternatively an ON/OFF push button switch can also be provided simply by omitting one of the two fixed contacts 34, 36 and substituting a plastic abutment surface defined for this purpose in the bottom wall 12 of the switch housing. As shown, the opposite end portions 26c and 26d of the contact lever 26 are provided with precious metal contacts as illustrated at C, C in Figures 1 and 2. Further, the upper ends 34c and 36c of the fixed contacts 34 and 36 also are made of a precious metal. Figures 1 and 2 illustrate the opposed limit positions of pivotal movement for the contact lever 26 and it will be apparent that the lower end of coil spring 28 engages the raised land portion 26a of the contact lever 26 in those limit positions at locations spaced to either side of the fixed centre contact 30. The coil spring 28 moves through a dead-centre position. More particularly, the pivot axis 32 defined by the fixed centre contact 30 is fixed in the switch housing, but the lower end of spring 28 moves to one side or the other of this axis to exert a force or moment on lever 26 tending to hold the lever in one or the other of its two limit positions. This is due to the raised land 26a being provided well above the flat underside of the contact lever which engages the upper end 30a defining pivot axis 32. Thus, the spring 28 serves to hold the movable contact lever 26 in either one of the two positions shown in Figures 1 and 2 as a result of this geometry. In order to achieve the desired switching action of the movable contact lever from the position of Figure 1 to that of Figure 2 and vice versa, push button 14 is depressed as suggested in Figures 4 and 5 from the normal or raised position of Figures 1 and 2 through intermediate positions and to a depressed condition such as that shown in Figure 5. With particular reference to Figure 4, assuming that the lever 26 had tab 26f uppermost as shown in Figure 2 and in the attitude shown in phantom lines in Figure 3, engagement between depending abutment means 14e on the depending leg 14c of the push button and tab 26f serves to pivot the contact lever 26 through the series of positions illustrated in Figures 4 and 5. Once the push button 14 has been fully depressed, as suggested in the phantom line position of Figure 4 and in the solid line position of Figure 5, further movement of the contact lever as necessary to achieve contact between the contact elements C and 36c is achieved as a result of spring force from the spring 28, the spring 28 having moved through dead-centre during the preliminary movement about axis 32. The movable contact lever 26 will ultimately reach the limit position shown in phantom lines in Figure 5. During this final movement the lever 26 will tend to swing about the secondary axis 35 as a result of the force provided from spring 28 and as a result of the cooperative action of fixed camming means 40 provided for this purpose in the bottom wall 12 of the switch housing with the tab 26f. Such camming means 40 comprises an integrally formed post having a canted upper end as shown in Figure 4. A similar camming means 42 is provided at the other side of the wall 12 (Figure 1) for cooperation with the tab 26g. The camming means 40 will achieve a swinging or shifting movement of the movable contact lever 26 from whatever position it has assumed, a result of downward movement of the push button, to a position as shown in solid lines in Figure 3 (that is swung about the secondary generally upright axis 35 defined by the fixed centre contact and in a counterclockwise direction relative to the axis 35). The other tab 26g is hence brought to its uppermost position in the attitude shown in solid lines in Figure 3. On release of the push button 14, the spring 28 will urge it upwards. The inclined upper slope of the abutment 14f will momentarily deflect the inclined lower face of the tab 26g when passing it to then occupy the position illustrated in Figure 1. The deflection may result in a brief tipping or sideways motion of the lever 26. The shifting or swinging movement of the movable contact lever 26 allows for return movement of the push button 14 and of the depending legs without causing any corresponding pivotal movement of the contact lever 26 on its primary pivot axis. Thus, the contact lever 26 will reach one of its two limit positions and will remain there as the push button 14 returns after it has been released by the user and moves upwardly as a result of the spring 28. The spring 28 not only serves to maintain the movable contact lever 26 in whatever position it had assumed on full depression, but as pressure is released on the push button itself the spring urges the lever to one or the other of its limit positions whichever limit position it is then closer to. Upon depressing the push button once again (that is after it has returned to its upper position) the sequence will be repeated, and the downwardly moving abutment means 14f on the other leg of the push button will engage the opposite tab 26g of the lever 26 to cause motion of the lever to the other limit position in a manner analogous to that described previously. The compound action of the movable contact lever 26 can be described with reference to Figure 8 as follows. This view shows movable lever contact C e separated from fixed contact C f in one of the two limit positions for the switch (refer to Figures 1 and 2). Pushing the push button down caused downward movement of the contact C e in Figure 8, and also the shifting movement suggested by the line of arrows labeled d in Figure 8. After the push button is allowed to return to its normal position these contacts C e and C f remain closed until the push button is again depressed to open these contacts. The line of the arrows labeled U in Figure 8 suggests the path of movement for the movable contact C e as it moves back to the position shown in Figure 8. A hysteresis effect is achieved whereby the lever follows a compound motion about the two angularly relates axes 32 and 35 as the switch is successively cycled to provide two different switch conditions in response to the same up and down motion for the push button itself. After the spring 28 has moved through a dead-centre attitude, the spring 28 will urge that part of the lever 28 which is lowered not merely downwards but also translationally because the primary axis 32 is tilted, thus completing the compound lever movement. The construction is relatively simple, no strut or staple elements need be used. Inclined camming surfaces on the movable element may also be avoided. The exterior switch components may be made of few molded components. The movable contact element need not be latched in its limit position and successive identical strokes of the push button 14 with fixed abutment shoulders (14e, 14f) results in a to and fro movement of a symmetric lever 26 at successive push-button operations.

Claims: A push button switch having a movable contact element (26) resiliently connected to a push button (14) to urge the element to either one of two limit positions characterised in that abutment means (14e, 14f) on the push button (14) are arranged for abutting said movable contact element (26) on either side of a first pivot axis (32) and in that means (28, 40, 42) are provided for swinging the element (26) about a second axis (35) angled with respect to the first axis (32) during a final stage of element movement so that one end (26c or 26d) of the element is moved sideways to not engage the abutment means at a subsequent push button operation and the other end (26d or 26c) is moved to engage the abutment means at that subsequent operation. Push button switch according to claim 1 further characterised in that the pivotable contact element (26) includes a raised land (26a) above the pivot axis (32) for engaging a spring (28) interposed between the land (26a) and the push-button (14) for urging the push button to its rest position and the element (26) to either one of its two limit positions after the abutment means (14e, 14f) have moved the element (26) through its dead-centre position. Push button switch according to claim 1 or claim 2 further characterised in that a central fixed contact (30) defines the first pivot axis (32), the arrangement being such as to allow also limited swinging movement about the second axis (35) preferably substantially perpendicular to the first axis and preferably substantially parallel to the direction of push button movement. Push button switch according to claim 2 or claim 3 in which the fixed contact (30) has a recess with an upstanding shoulder for defining the second axis (35) and a lower edge inclined so that the spring (28) urges the lowermost end (26c or 26d) of the element (26) sideways to pass the abutment means. Push button switch according to any of the preceding claims further characterised in that the swinging means (28, 40, 42) include camming means (40, 42) for the respective ends of the element (26) to swing the element (26) about the second axis (35) under push button or resilient bias. Push button switch according to claim 5 further characterised In that the camming means (40, 42) are arranged to swing the element (26) initially under push button bias and the swinging movement is completed under resilient bias. Push button switch according to any of the preceding claims further characterised in that the element (26) is associated with fixed contacts (34, 36) at either one or both elements ends. Push button switch according to any of the preceding claims further characterised in that the element ends (26c, 26d) include upturned tabs (26f, 26g) and the abutment means (14e, 14f) have inclined upper surfaces (14g) for faciliting their mutual passing movement upon push button return.

Inventors: SORENSON, RICHARD W.
Applicants: CARLINGSWITCH, INC.
Application year: 1985
Main classification: H01H13
IPC codes: H01H13