Patent Grant
7105763
The present invention relates to switches, and more particularly to a wallbox-mountable switch assembly having a pushbutton.
Wall-mountable switch assemblies providing on/off control of an electrical load, such as a lamp, are well known. Known switch assemblies include switch mechanisms actuated by a toggle supported for pivoting movement by a user. Known switch assemblies also include switch mechanisms actuated by pushbuttons supported for reciprocal sliding movement. Inward translation of the pushbutton in response to force applied by a user's finger actuates the switch mechanism. The pushbutton is outwardly biased to provide for return of the switch following release of the applied force.
The switch mechanisms used in known pushbutton switches are varied in their construction. Known pushbutton switches include pen-type switch mechanisms as disclosed in U.S. Pat. No. 4,319,106 to Armitage. It is also known to provide a pushbutton actuated switch with a ratcheting switch mechanism as disclosed in U.S. Pat. No. 3,785,215 to Stefani. It is also known to provide a pushbutton switch in which electrical circuit switching occurs only upon the release stroke of the pushbutton as disclosed in U.S. Pat. No. 3,624,328 to Hansen.
The force required to actuate the switch mechanism of a pushbutton switch will vary through the pushbutton range of movement between the fully-released position and the fully-engaged, hard stop, position. The actuation force will vary because of the resistance developed for outwardly biasing the pushbutton and the resistance presented by the switch mechanism against switching actuation.
The relationship between the pushbutton biasing resistance and the switch mechanism resistance affects user perception regarding quality of construction. Improper distribution between these two resistances can adversely affect tactile feedback presented to a user during the input stroke of the pushbutton. A pushbutton switch presenting an excessively large pushbutton biasing resistance, for example, can diminish tactile perception of transition associated with switching of the switch mechanism. The switching actuation of these switches tends to become masked by the biasing resistance and may feel “mushy” to a user. Conversely, a pushbutton switch having an excessively small pushbutton biasing resistance will create a sudden transition in resistance when the switch mechanism is engaged, which may present a jarring feedback in the nature of an impact with an obstacle.
According to the present invention there is provided a switch assembly for controlling an electrical load including a switch mechanism switchable between first and second alternate fixed electrical states. The switch assembly also includes an actuator assembly having a slidably supported pushbutton and engageable with the switch mechanism to switch the mechanism between the alternate fixed electrical states.
According to one aspect of the invention, the pushbutton of the actuator assembly is received by a pushbutton guide and is outwardly biased by a return member located between the pushbutton and a retainer. Preferably, the pushbutton guide is connected to an actuator mount received by a base housing in which the switch mechanism is mounted. The actuator assembly includes an elongated actuator member received through an opening in the retainer to engage the switch mechanism during inward translation of the pushbutton.
Preferably the return member is a spring having coils and the actuator member is a pin having a shaft portion received through the coils of the return spring. The actuator pin preferably includes a head portion defining a shoulder that contacts an end of the return spring for outwardly biasing the pin. Preferably, the return spring is conical and the opening in the retainer is elongated to permit lateral pivoting of the shaft portion of the pin.
According to one embodiment of the invention, the pushbutton includes a cap portion and a pushbutton carrier. The carrier includes a pedestal portion and a stand portion received within an interior defined by the cap portion. The pedestal portion is dimensioned for sliding receipt between opposite end walls of the pushbutton guide. Preferably, the carrier includes tab projections received within openings in the cap portion to releasably secure the cap portion to the carrier.
According to another aspect of the invention, the switch mechanism includes a switch plate having opposite upper and lower edges. The switch plate preferably includes at least one recess along the lower edge to define supports at opposite ends of the switch plate for supporting the switch plate on a support surface. Preferably, the switch plate holder is supported within a well defined by a switch plate holder.
The switch mechanism also includes a pivot member supported for pivoting about an axis. The pivot member is adapted for contact with the switch plate adjacent the upper edge of the support plate such that pivoting of the pivot member causes switching movement of the switch plate. The switch mechanism also includes contact elements secured to opposite sides of the switch plate contacting first and second fixed contact surfaces of the switch plate is switched between alternating first and second positions. Preferably, the fixed contact surfaces are defined by an arm extension of the switch plate holder and a contact element carried by a prong extension mounted in the base housing.
The switch mechanism further includes a spring located between the pivot member and the switch plate to apply a contact force between the contact elements and the fixed contact surfaces to maintain the switch plate in one of the alternate positions. Preferably, the switch plate includes recesses along the upper edge in which an end of the spring is received. The recesses preferably extend to a terminal end aligned with centers of the contact elements for substantial alignment between the end of the spring and the contact elements.
According to one embodiment, the pivot member of the switch mechanism includes a body defining a cross section having a substantially V-shaped middle portion and opposite end extensions forming ledges adapted for contact with the actuator assembly during inward translation of the pushbutton.
According to another aspect of the invention, the switch assembly includes a spring damper received within the coils of the switch mechanism spring to limit resonating vibrations in the spring coils following change of relative angular orientation between the pivot member and the switch plate. Preferably, the damper is made from a foam material to limit interference by the damper with axial compression of the spring.
The force applied to the pushbutton will vary during inward traveling of the pushbutton from resistance generated by the return spring of the actuator assembly and from resistance generated by the switch mechanism against switching between the alternate fixed positions. According to one aspect of the invention the input profile will include two segments between a fully released position of the pushbutton and that point at which sufficient force is applied to overcome the resistance generated by the switch mechanism against switching. These profile segments are divided by that point at which resistance is added by the switch mechanism. Preferably, the input profile is substantially linear in each of these segments, with the first segment slope having a value in a range of between approximately 30 percent and 60 percent of the second segment slope.
According to another aspect of the invention, the multiple segment input profile will include two segments between that point at which sufficient force is applied to overcome the switch mechanism resistance to switching and the fully engaged position of the pushbutton. These two segments are divided by that point at which the resistance of the switch mechanism against switching has been removed and further resistance will be generated only by the return spring to the fully engaged position. Preferably, the input profile in these two segments will define a substantially V-shaped profile.
According to another aspect of the invention, the switching assembly provides for limited passage of time before audible and visual feedback occurs following application of sufficient force to overcome the switch mechanism resistance to switching. Preferably, the audible feedback associated with the switching of the switch mechanism will occur within less than approximately 10 milliseconds. Preferably, visual feedback from an electrical load providing visual feedback, such as light from a lamp, will occur within less than approximately 50 milliseconds.
Referring to the drawings, where like numerals identify like elements, there is shown a switch assembly 10 according to the present invention for providing on/off control of an electrical load, such as a ceiling-mounted light or fan or a device powered via plug-in connection to a line source. Referring to
The switch assembly 10 includes a pushbutton 16 supported for inward translation with respect to a pushbutton guide 18 in a sliding manner. As shown in
The pushbutton 16 and pushbutton guide 18 are part of an actuator assembly 24 that provides for switching actuation of a switch mechanism 26 of the switch assembly 10. The actuator assembly 24 actuates the switch mechanism 26 when force is applied to the pushbutton 16 by a user's finger for example. The actuator assembly 24 also provides a biasing force for outward return of the pushbutton 16 following release of the applied force.
The pushbutton guide 18 is connected to an actuator mount 28. The pushbutton guide 18 is preferably formed integrally with the actuator mount 28 from a molded plastic material for example. The actuator mount 28 includes tab projections 30 adjacent opposite ends of the pushbutton guide 18. The tab projections 30 are elongated such that they are capable of flexing with respect to the actuator mount 28 to facilitate a releasable snap connection between the actuator mount 28 and the yoke 14 as shown in FIG. 2.
A base housing 32 receives the actuator mount 28 to define an interior for the switch assembly 10. As shown in
Referring to FIG. 2 and the exploded view of
The actuator assembly 24 also includes a pushbutton return spring 52 located between the pushbutton carrier 34 and a retainer 54 to outwardly bias the pushbutton 16. The retainer 54 is secured to the actuator mount 28 to provide a reaction surface for compression of the pushbutton return spring 52 during inward translation of the pushbutton 16. The compression of pushbutton return spring 52 provides for outward return of the pushbutton 16 following removal of actuating force from the pushbutton. Elongated tabs 56 extending from the end walls 50 of pushbutton guide 18 are received by a plate portion 58 of retainer 54 for releasable connection between the retainer 54 and the pushbutton guide 18. The retainer 54 also includes an upstanding sidewall portion 60 such that the retainer 54 defines a tray-like construction. The pushbutton return spring 52 is conical in shape and is received within a bell-shaped receptacle 62 connected to the pedestal portion 36 of the pushbutton carrier 34, preferably integrally as part of a plastic molding process. A lower end 66 of pushbutton return spring 52 is received in a recessed portion 64 of the retainer plate portion 58.
The actuator assembly 24 also includes a pin 68, preferably made from a plastic material. The pin 68 includes a shaft portion 70 having a tapered end and a head portion 72 defining an annular shoulder adjacent the shaft portion. The shaft portion 70 of pin 68 is received through an upper end 74 of the return spring 52 such that the head portion 72 contacts the upper end 74 of pushbutton return spring 52. When force is applied to the pushbutton 16, by a user's finger for example, the pin 68 is driven through an opening 76 in the recessed portion 64 of retainer 54 compressing the pushbutton return spring 52. The opening 76 in the retainer 54 forms an elongated slot, which allows the shaft portion 70 of pin 68 to pivot laterally with respect to the retainer 54. As described in greater detail below, the provision of such freedom allows the pin shaft 70 to actuate the switch mechanism 26 of the switch assembly 10.
The switch mechanism 26 of switch assembly 10 defines alternate first and second fixed electrical positions, respectively shown in
The switch mechanism 26 includes a switch plate 88 supported by a switch plate holder 90 received by the base housing 32. The switch plate 88 is received by a well portion 92 defined at a lower end of the plate holder 90. The switch plate 88 and the plate holder 90 are preferably made from cartridge brass. The plate holder 90 includes an arm extension 94 connected to the well portion 92. The arm extension 94 is located adjacent one end of the well portion 92 for contact with a conductive contact element 96 secured to a first side of the switch plate 88 with the switch mechanism 26 in the first fixed position of FIG. 6. Preferably, the plate holder 90 is coated with a thin coating of silver to limit wearing damage of contact surfaces. The switch plate 90 also includes an elongated prong extension 98 connected to the well portion 92 opposite the arm extension 94.
The switch mechanism 26 also includes a traveler terminal 100 received by the base housing 32. A contact support prong 102 carrying an electrical contact element 104 extends from traveler terminal 100. The contact element 104 contacts a contact element 106 secured to a second side of the switch plate 88 when the switch plate is in the second fixed position shown in FIG. 5.
The switch mechanism 26 shown in the figures is a single-pole switch. The first switch position of
The switch assembly may include a circuit board (not shown) electrically connected to the above-described path, through the prong 98 of plate holder 90 for example, to receive electrical current when the switch mechanism is in the closed-circuit condition of FIG. 5. The present invention is not limited to the single-pole switch shown in the figures. The switch mechanism could be modified, for example, to include a second traveler terminal opposite traveler terminal 100 and supporting an electrical contact element. Such a modified switch mechanism provides for a three-way switch having two closed-contact positions.
Referring to
The switch mechanism 26 includes a spring 114 located between the pivot member 78 and the switch plate 88. Located in this manner, the spring 114 reacts against the pivot member 78 and applies force to the switch plate 88 for maintaining the switch plate 88 in one of the alternate fixed positions of
As shown in
The recesses 122, 124 defining support legs 126 limit the surface contact area that would otherwise exist between the lower edge 120 of switch plate 88 and the well portion 92 of plate holder 90. As shown in
Referring again to
Referring to
Application of force to the pushbutton 16, as shown in
The downwardly extending legs 108 of pivot member 78 contact the switch plate 88 adjacent its upper edge 112 as the pivot member 78 is pivoted. This contact results in switching movement of the switch plate 88 from its second closed contact position shown in
The orientation of the pivot member 78, switched to the first switch position of
Electrical resistance at the contact elements 96, 106 is inversely proportional to the contact force applied at the contact elements 96, 106. Increasing the contact force applied to switch plate 88, however, increases the resistance to switching movement thereby undesirably increasing the actuator force that must be applied to pushbutton 16. The above-described optimized pressure provided by the knifed-edge switch plate support legs 126 facilitates switching actuation of the switch plate 88 thereby providing for switching actuation at a lower actuator force for a given contact force applied by spring 114.
Efficient switch actuation at reduced actuator force is further promoted by the above-described torque-limiting alignment between the spring 114 and the contact elements 96, 106. As a non-limiting example, a switch assembly adapted for use in a standard toggle-type opening as shown in the figures and having the capability of switching 15 amps, 120-277V, developed a contact force of approximately 0.10 pounds. The switch mechanism of the assembly, however was switchable between its alternate fixed positions in response to an actuation force of approximately 0.8 pounds or less applied to the pushbutton 16.
As discussed above, the spring 114 applies force to switch plate 88 to maintain the switch plate 88 in one of the alternate fixed positions of
As described above, the over-center spring 114 will deflect lengthwise during switching actuation because of the change in relative angular orientation between the switch plate 88 and pivot member 78. The change in the lengthwise configuration of the over-center spring 114 will occur rapidly along with the corresponding snap movement of the switch plate 88, described above. This rapid change in the spring configuration causes resonating vibration of the coils of spring 114, which translates into a ringing noise. Ringing noises generated by the over-center spring 114 would create an undesirable perception of lack of quality in the construction of the switch assembly 10. The switch assembly 10 of the present invention includes a spring damper 136 received within the coils of the contact spring 114, as shown in
The switching movement of the switch plate 88 was further controlled by optimizing the dimensions of the switch plate and the respective location of the arm 94 of switch plate holder 90 and the prong 102 of traveler terminal 100. Referring to
Reduction in the contact distance, dce, and the plate pivoting angle, θs, reduces the distance over which the contact elements 96, 106 will be moved between the alternate switch positions. Reduction in the movement distance results in reduction in the acceleration time for the contact elements 96, 106 and a corresponding reduction in maximum velocity for the contact elements. This desirably limits momentum generated during the switching movement, thereby desirably limiting the above-described contact bouncing and the associated damage.
It should be understood that the above-described optimization of the switch plate pivot angle, θs, and contact distance, dce, represents a trade-off between the benefits provided for the switch plate 88 and efficiencies regarding the pivoting movement of the pivot member 78. The reduction of θs and dce should not be so large as to significantly impair the operation of the pivot member 78.
The actuation force applied to the pushbutton 16 is identified in
As shown, the pushbutton travel between the fully-released and fully-engaged positions includes four segments. In each of the four travel segments, the force that must be applied to the actuator pushbutton varies in response to changes in the resistance generated by the actuator assembly 24 and the switch mechanism 26. In the first travel segment, the actuation force will increase as the pushbutton return spring 52 is compressed and when the pin 68 contacts the pivot member 78. As shown in the input force profile of
In the second travel segment, the required actuator force will increase faster than it did in the first travel segment because of the combined resistance by the actuator assembly 24 and switch mechanism 26. Throughout much of the second segment, the relationship between the actuator force and travel distance will vary in a substantially linear manner. This relationship is shown and identified in
In the third travel segment, the actuation force reduces from F2 to F3, which corresponds to the resisting force generated by the actuator assembly 24 alone. The pushbutton travel distance at this point is identified as d3. In the fourth travel segment, the actuator force again increases in response to further compression of the pushbutton return spring 52. The fourth travel segment ends at distance d4 at the fully-engaged, hard stop, position for the pushbutton 16 shown in FIG. 6.
As described above, factors such as ringing noises associated with a switch assembly affect a user's perception of quality. The amount of force required to actuate the switch mechanism may also affect a user's perception. It was found that the particular relationship between the varying actuator force and the pushbutton travel in the above-described profile travel segments also has a large effect on perceived quality for a given switch assembly.
The relationship between the first and second slopes s1 and s2, associated with the first and second travel segments for example, can have a dramatic effect on perceived quality. Two switch assemblies having the same actuation force and distance values, F2 and d2, may nevertheless be perceived as varying in quality of construction depending on the relationship between the slopes s1 and s2. If s1 is too large, the tactile perception of transition between the first and second travel segments may become masked. This provides a switch that may feel “mushy” to a user. Conversely, a pushbutton switch having an excessively small value for s1 will present a sudden transition to a user in the nature of impact with an obstacle.
The above-described construction of the switch assembly 10 provides for the desirable force/travel relationship shown in FIG. 8. The relationship between the slopes s1 and s2 is preferably as follows:
0.30 (approx.)≦s1/s2≦0.60 (approx.)
It is also desirable, irrespective of the particular relationship between the slopes s1 and s2, that the travel distance, d2, required to achieve switching actuation not be excessively large. In the above-described 15 Amp, 120-277V switch assembly adapted for use in a standard toggle-type faceplate, the actuator force, F2, was approximately 0.8 pounds. It is preferable that the associated travel distance, d2, be approximately 0.120 inches or less.
Referring again to
(d3−d2)/d3≦0.15 (approx.) 1.
0.10 (approx.)≦(d4−d3)/d4≦0.30 (approx.) 2
0.10 (approx.)≦(F2−F3)/F2≦0.30 (approx.) 3
As described previously, noises such as ringing of the spring 114 may detrimentally affect perceptions regarding the quality of the switch assembly construction. A certain amount of audible feedback associated with the snapping movement of the switch plate 88 as it is moved between its alternate positions, however, is desirable. The audible feedback associated with the switch plate movement should occur shortly after the point shown at which F2 of
Visual feedback may also affect perceptions of quality. It is desirable that visual indication of power supply to an electrical load, such as light from a lamp, occur shortly after the F2 point of FIG. 8. Preferably the visual feedback occurs within approximately 50 milliseconds after the F2 point of
The present invention is not limited to the particular construction shown and may have application to switches having application to switches having pushbuttons of various dimensions and switches having varying switching capabilities.
The foregoing describes the invention in terms of embodiments foreseen by the inventor for which an enabling description was available, notwithstanding that insubstantial modifications of the invention, not presently foreseen, may nonetheless represent equivalents thereto.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2044065 | Douglas | Jun 1936 | A |
| 2095180 | Douglas | Oct 1937 | A |
| 2469337 | Kohl | May 1949 | A |
| 3046377 | Fraser | Jul 1962 | A |
| 3183333 | Golbeck | May 1965 | A |
| 3624328 | Hansen | Nov 1971 | A |
| 3785215 | Stefani | Jan 1974 | A |
| 3882295 | Madland | May 1975 | A |
| 4300026 | Bull | Nov 1981 | A |
| 4319106 | Armitage | Mar 1982 | A |
| 4757164 | Bauer et al. | Jul 1988 | A |
| 4803362 | Butts | Feb 1989 | A |
| 5860514 | Beattie | Jan 1999 | A |
| Number | Date | Country |
|---|---|---|
| 2298176 | Aug 1976 | FR |
| Number | Date | Country | |
|---|---|---|---|
| 20050077163 A1 | Apr 2005 | US |
