WO1999009572A1

WO1999009572A1 - Elastomeric switch responsive to variable pressure

Info

Publication number: WO1999009572A1
Application number: PCT/US1998/017078
Authority: WO
Inventors: Scott L. Ingham; Lary R. Cotten; Joel Shawn Dube
Original assignee: High End Systems, Inc.
Priority date: 1997-08-18
Filing date: 1998-08-18
Publication date: 1999-02-25

Abstract

An electromechanical switch is provided. The switch is responsive to push button force, and therefore comprises a manual actuator which presents a conductive, downward-facing surface. The conductive surface, or conductor, is spaced at an angle relative to a series of printed conductors placed across a plane. Downward force upon the actuator, and therefore upon the conductor, allows contact between the conductor and an incrementally increasing number of printed conductors when an increasing amount of force is applied. The switch can therefore apply power or ground to printed conductors spaced from a power/ground conductor based on the amount for force applied to the conductor. The actuator which retains the conductor is flexible and deforms under pressure to allow the conductor downward facing surface to move from an angular position to a horizontal position consistent with the printed conductors.

Description

Title: ELASTOMERIC SWITCH RESPONSIVE TO VARIABLE PRESSURE

BACKGROUND OF THE INVENTION

1 Field of the Invention

This invention generally relates to a switching device which is sensitive to variable pressure and/or torque for connecting a commensurate, variable number of printed conductors spaced across a printed circuit board ("PCB")

2 Description of Related Art

The operation of an electronic circuit often relies on selective coupling between a pair of conductors Selective couplmg involves periodically shorting the conductors to one another using a switching device, or switch Typical switches are actuated either manually or electronically Electronic switches are often deemed solid state switches and classified as. e g , transistors A manual switch, on the other hand, is actuated by an operator pressing or moving an actuator Accordingly, manual switches are often classified as electromechanical switches

An electromechanical switch generally employs metallic contacts for manually opening and closing an external electrical circuit Commercial electronic switches of this variety are generally packaged in cases designed to securely mount to a panel or PCB containing a plurality of printed conductors A typical switch involves metal contacts insulated from a manual actuator The metal contacts can be periodically moved to make external connections to exposed printed conductors A biasing mechanism may also be provided to accelerate either the "on" or the "off transition There are numerous types of switches generally classified according to their switch action For example, electromechanical switches include push button, toggle, rocker, slide, rotary, etc Of particular interest herein below is the push button switch having momentary action A push button switch can be manufactured to make momentary contact between printed conductors but, when pressure is relieved from the manual actuator, contact is discontinued According to U S. Patent No 4,818,827, rubber or elastomers can be used to effectuate the push-button action, and are generally confined to the manual actuator When pressure is applied to the actuator upper surface, the actuator deforms such that a conductor placed on the lower surface of the actuator contacts a printed conductor upon a PCB When force is removed, the conductor on the actuator and the printed conductor on the PCB separate to disconnect the switch The point, or in proximity to the point, at which pressure is to be delivered may be lighted A lighted push button switch or "LPB" is generally designed for front-panel illumination Thus, the elastomeπc actuator can be selectively translucent to a back-surface illumination caused by, for example, a light emitting diode, neon or mcandescent lamps.

Many modern integrated circuits operate at digital signal levels which can be switched between logic "high" and "low" values. The values can be fed in either parallel or serial format to a detector or decoder whose function is to control various downstream digital or analog signals Depending on the ratio of high and low bits within the parallel or serial bit pattern and the position of those bits m the least significant and most significant position, the decoder will respond by either driving downstream units to a lessor or greater magnitude Used merely as an example, a lessening in the number of digital high values and the position of those values relative to the most significant bit positions may cause a lessening in the drive strength of a motor, lamp intensity, lamp color, lamp focus, zoom, etc

It would therefore be desirable to produce a momentary push button switch which can change the number of high and low value bits within a bit pattern so as to variably control a downstream unit To achieve this result, the desired push button switch must be capable of variably contacting a power or ground supply to an increasing number of printed conductors as the pressure upon the manual actuator is increased The amount of correlation between pressure or force applied and printed conductor contact must be somewhat proportional Moreover, the degree of resolution needed to accurately define a bit pattern based on pressure applied must also be quite high

SUMMARY OF THE INVENTION

The problems outlined above are in large part solved by an improved elastomenc switch hereof The switch is classified as a push button switch capable of small angles of rotation and, when force is applied to the manual actuator of the switch, the switch contact is made between an increasing number of printed conductors and power (or ground) based on an increasing force applied to the manual actuator Accordingly, the manual actuator is made of any material which has electrical msulative capability and which deforms when subjected to force applied upon the actuator in a direction normal to the printed conductors and/or at an angle across the prmted conductors In the latter instance, the actuator is said to receive a torque which displaces the actuator across the pπnted conductors The amount of deformation is designed to vary based on the amount of downward directed or angled force (henceforth "force ') Thus, the manual actuator can be made of any flexible material having such characteπstics, a suitable material being rubber and/or an elastomer

The present switch is designed to electrically couple an increasmg number of printed conductors The prmted conductors are preferred coupled to a power supply (either V_DD or ground) when force is applied to the actuator To achieve this result, the manual actuator comprises a lower surface spaced above PCB conductors arranged on an upper surface of a PCB (henceforth "prmted conductors") Accordmg to one embodiment, the lower surface of the actuator can be formed at an angle relative to the planar surface of the PCB The angle is preferably between 2° to 15° from the PCB surface, and contains a conductor The conductor compπses a relatively conductive material made of, for example, silicon rubber/elastomer, conductive ink, aluminum, carbon, copper, or any other semi-metallic or metallic substance known to have electrically conductive characteristics In some mstances the conductor upon the actuator is deemed a "pill", however, for simplicity is henceforth referred to as simply a "conductor" The conductor extends along the angled surface a distance which is at least equal to the area occupied by a spaced plurality of prmted conductors The printed conductors are "pπnted" upon the PCB surface using, for example, conventional lithographic techniques The printed conductors are beneficially aligned beneath the conductor One of the printed conductors is a ground or power conductor, denoted so since that conductor is coupled to a ground or power supply The other printed conductors are spaced from each other and from the power/ground conductor. When pressed downward, the conductor upon the actuator will incrementally contact pπnted conductors, beginning with the power/ground conductor. Further mcrease in downward force will couple pπnted conductors spaced incrementally increasing distances from the power/ground conductor. Thus, the actuator is designed to deform so that the downward facing surface of the actuator will transition from an angled surface to a horizontal surface.

The present invention contemplates a switch. The switch mcludes a manual actuator, herem defined as havmg electrically msulative charactenstics and is henceforth referred to as a "dielectric structure". The dielectπc structure is made of a flexible mateπal hav g a first surface and an opposed second surface. The second surface extends from a point near the center of the structure to a perimeter of the structure. A conductor is also provided having opposed surfaces One of the conductor surfaces is connected to the second surface and the other of the conductor opposed surfaces is elevationally lower near the perimeter than at the center. The mechanism m which the surface of the conductor is made elevationally disparate involves two possible alternatives. First, the second surface may extend elevationally lower at the perimeter than at the center, whereby the conductor need only have opposed surfaces which are substantially parallel Second, the second surface may extend at approximately the same elevational level from the center to the perimeter, whereby the opposed surfaces of the conductor thereby extends at an angle relative to one another

The switch may further comprise a flange extending laterally from the perimeter to define a lower flange surface which extends elevationally lower than the conductor A retainer may be fixedly secured over the flange such that the conductor extends a spaced distance above a plurality of printed conductors durmg times when a downward force is absent from the first surface The spaced distance is defined to increase from the perimeter towards the center

The present invention further contemplates a PCB having a plurality of printed conductors arranged partially across an upper surface of the PCB The printed conductors are spaced from each other and from the power/ground conductor According to one embodiment, the power/ground conductor can be made larger m width and length than the remaining prmted conductors The prmted conductors may be arranged withm at least two rows spaced parallel to one another The power/ground conductor extends along a power/ground axis, and each of the printed conductors may extend parallel to that axis withm one of two possible rows Each prmted conductor withm one row is preferably designed to extend along an axis between a respective pair of pπnted conductors withm the other row Accordingly, printed conductors within one row are staggered with respect to those of the other row, and both rows are spaced from the power/ground conductor Downward force upon the actuator causes the conductor mounted on the downward facing surface to contact the power/ground conductor first, followed by the nearest printed conductor within one of the two rows. The next contact resulting from further downward pressure occurs upon the conductor in the other row nearest the power/ground conductor. Thus, incrementally mcreasing force upon the actuator will cause contact to the nearest conductor withm a first row, followed by contact to the nearest conductor on the second row, followed by contact to a more distal conductor in the first row, etc. Staggering the pnnted conductors allows a higher resolution digital output to be formed which results in greater incremental control over servo motors, steppers and/or lamp output, for example. BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent upon readmg the following detailed description and upon reference to the accompanying drawings in which

Fig 1 is a top view m partial breakaway of an elastomenc switch mounted upon a PCB contammg a set of prmted conductors exposed withm a staggered configuration,

Fig 2 is a cross-sectional, exploded view along plane 2-2 of Fig 1, showing angled-placement of a conductor, or an angled-surface of a conductor, configured upon a downward- facing surface of a flexible structure,

Fig 3 is a cross-sectional view along plane 2-2 of the conductor contactmg a first set of pπnted conductors when undergomg a first downward force,

Fig 4 is a cross-sectional view along plane 2-2 of the conductor contactmg a second set of pπnted conductors when undergoing a second downward force greater than the first downward force

Fig 5 is a top plan view of the conductor capable of being forced upon the printed conductors at an angle to allow slight lateral movement withm the plane formed by the PCB surface, and

Fig 6 is a cross-sectional view along plane 6-6 of Figs 1 and 5, showing the manual actuator and associated conductor undergoing torque about a central axis, and applied upon a select set of prmted conductors as m Fig 5

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Turning now to the drawings, Fig 1 illustrates, in partial breakaway, an elastomenc switch 10 mounted upon a circuit 12 containing prmted conductors Circuit 12 may, accordmg to one embodiment, be a PCB The printed conductors may extend partially across the PCB and be partially exposed According to a preferred embodiment, the printed conductors on the upper surface are exposed in a staggered configuration Partial removal of the elastomenc switch and the retainer member of the switch allows visual exposure of prmted conductors 14 arranged on the upper surface of PCB 12 Switch 10 comprises a manual actuator 16 which extends above a retamer 18 Only the upper surfaces of actuator 16 and retainer 18 are shown in the top plan view of Fig 1 Actuator 16 is made of a flexible, dielectric material Around the perimeter of actuator 16 is a flexible flange mateπal The flange material (not shown) is secured to PCB 12 by retamer 18 Accordmgly, the flange mateπal is fixedly interposed between PCB 12 and retainer 18 Various means described herein below will illustrate mechanisms used to retain actuator 16 in position above one or more sets of staggered pπnted conductors 14

Turning now to Fig 2, a cross-sectional view along plane 2-2 of Fig 1 is shown The cross-sectional view is also shown as an exploded view depictmg flange 20 and connected actuator secured between retamer 18 and PCB 12 Flange 20 extends via a small connecting membrane 22 about the penphery of actuator 16 Membrane 22 is made of flexible material similar to that used to form flange 20 and actuator 16 Flange 20 can be made of dissimilar material from membrane 20 and actuator 16, if desired Regardless of its composition, or dimension, flange 20 may accommodate at least one aperture preferably near its corners to accommodate a threaded screw 24 mounted on the downward facing surface of flange 18 Screw 24 accommodates threads on its outer surface which rotatably tension mto corresponding threads on the inner surface of aperture 26 shown in PCB 12 Thus, the elastomenc switch 10 can be assembled by tensionmg screw 24 into aperture 26 or, in the alternative, tensionmg a nut upon screw 24 after screw 24 is placed entirely through PCB 12 via a through-hole aperture (not shown)

Once secured, actuator 16 extends upward above retainer 18 to expose a first surface 30 Opposite first surface 30 is a second surface 32 Second surface 32 can be formed according to two different embodiments For example, second surface 32a can be formed at an angle relative to a horizontal surface This allows a conductor 34 having parallel-spaced opposing surfaces to configure a downward facing surface of a conductor at an angle Alternatively, the second surface 32b can be arranged along a horizontal plane (shown as a dotted line) To produce an angled downward facing surface of conductor 34, conductor 34 must be shaped having opposed surfaces which are aπanged at an angle relative to one another, if conductor 34 is mounted to second surface 32b Regardless of the configuration of second surface 32 and conductor 34, the intent is to produce a downward facing surface of a conductor which is arranged at an angle relative to a horizontal plane

Importantly, the downward facing surface near the perimeter of actuator 16 is elevationally lower than the downward facing surface near the center of actuator 16

Fig 2 illustrates a circuit, preferablv a PCB 12, containing numerous conductors printed upon one or more layers of PCB 12 Conductors 14 are shown extending from an upper surface of PCB 12 However, it is recognized that the conductors extend downward through vias to layers of conductors arranged withm PCB 12 Accordingly, pnnted conductors 14 may comprise terminating ends of one or more conductors withm PCB 12 The terminating ends extend upward and are exposed a spaced distance from conductor 34, absent pressure upon actuator 16 According to one example, prmted conductors 14 are formed by depositing a layer across the entire upper surface of PCB 12 and into through-hole vias extending to conductive layers therebelow After deposition, select regions of the conductive laver are removed, leaving "printed" regions of retained conductors 14

Turning now to Fig 3, a cross-sectional view along plane 2-2 is shown after assembling the switch and deforming actuator 16 via downward pressure Being flexible, actuator 16 responds to, e g , finger pressure 38, as shown Absent finger pressure, a space exists between conductor 34 and printed conductors 14 due to the elevationally lower surface of flange 20 relative to conductor 34 Thus, Fig 3 illustrates a first force amount 40 which causes a reduction in the angle of the downward facing surface of conductor 34 In other words, conductor 34 can, to some extent, flex along the mterface with actuator 16, whereby contact is made to a power/ground conductor 42, followed by the printed conductor 14 nearest power/ground conductor 42 First force 40 is shown to cause coupling between conductor 42 and conductors 14a and 14b Contact to conductor 14c, however, has not yet been initiated Accordmgly, Fig 3 illustrates a fine-lme resolution of contact between conductors 14a and 14b to a power or ground supply, but not conductor 14c Accordingly, switch 10 is shown suitable for high resolution digital output of a particular binary bit pattern of high and low values The amount or quantity of pπnted conductors coupled to conductor 42 dictates the quantity and/or intensity of the resulting outcome Accordmgly, printed conductors 14 provide connection to a controller which actuates one or more downstream circuits and/or devices which can variably respond to the number of printed conductors being shorted to conductor 42.

Fig. 4 illustrates further application of force and, specifically, a second force amount 44. Second force 44 is greater than first force 40 (shown in Fig. 3) to allow contact to additional printed conductors 14d through 14f. The additional contact areas caused by flattening more of the downward facing surface 32 and, correspondingly, flattening of the downward facing surface of conductor 34. Second force 44 can vary at incremental amounts to incrementally contact conductors 14 in a sequence beginning with power/ground conductor 42 and ending with conductor 14g, 14h, etc., depending on the number of parallel spaced conductors 14. Turning now to Fig. 5, a top plan view of the relationship between conductor 34 and conductors 42 and

14 is shown. Initially, conductor 34 is aligned a spaced distance above the printed conductors 14/42. In addition to a downward force, the manual actuate upon which conductor 34 resides can also undergo rotational torque and be slightly displaced in a lateral direction as shown by reference numeral 34a. Lateral displacement involves moving the pliable actuator and, specifically, applying tensile and compressive lateral stresses to connecting member 22. to cause conductor 34 movement. A proper selection of lateral movement and downward movement may allow only certain conductors 14 to be coupled via conductor 34. For example, lateral movement to position 34b may couple only a subset of the entire plurality of conductors 14. That subset will vary depending upon the amount of angular force being applied, as shown in Figs. 5 and 6 in combination.

An example of angular (i.e., torque) movement is shown in Fig. 6 in more detail. When force is applied at an angle, rather than perpendicular, relative to the PCB surface, conductor 34 will "tilt" in response to the angular force. A membrane at one end of actuator 30 will be pulled with tension while the membrane on the opposing side of the actuator will slightly fold. Conductor 34, tilted at an angle between 2 and 15°, will contact only a subset of the entire plurality of printed conductors 14. For example, only one row of two (or more) rows of printed conductors 14 will be contacted. In the example shown in reference to Figs. 5 and 6, only printed conductors 14a - 14i will be contacted.

Figs. 5 and 6 illustrate a preferred arrangement of staggered conductors set forth in two rows of conductors. The rows may be spaced from one another a parallel distance, wherein a conductor of one row extends along an axis between a pair of conductors in the other row. The two-row arrangement allows a high resolution switching of digital outputs for more accurate control of devices responsive to the digital pattern produced therefrom. Of course, more than two rows may be used if additional resolution is desired.

It will be appreciated to those skilled in the art having the benefit of this disclosure that this invention is believed applicable to any push button electromechanical switch involved in, for example, controlling a lighting fixture (i.e., the intensity level, color and movement thereof) through a digital outcome from a variably responsive switch. It is also to be understood that the form of the invention shown and described is to be taken as exemplary, presently preferred embodiments. Various modifications may be made to each and every component provided, however, the conductor arranged on the downward facing surface of the actuator contacts an increasing number of printed conductors during receipt of an increasing downward force. It is therefore intended that the following claims be interpreted to embrace all such modifications and changes and, accordingly, the specification and drawings are to be regarded in an illustrative rather a restrictive sense. It is noted, according to one example, that rotational force may be applied to the manual actuator as well as the conductor attached thereto. The rotational torque causes a leading and trailing edge of respective conductors at a opposing sides of the manual actuator to contact a subset of printed conductors beneath those respective conductors. The rotational movement is therefore believed to, in part, cause movement along the horizontal plane of the PCB as well as a tilt toward the PCB.

Claims

WHAT IS CLAIMED:

1. A switch, comprising:

a flexible, insulative structure having a first surface and an opposed second surface extending from a point near a center of the structure to a perimeter of the structure; and

a conductor having opposed surfaces, one of which is connected to the second surface and the other of which is elevationally lower near the perimeter than at the center.

2. The switch as recited in claim 1. wherein said second surface extends elevationally lower at the perimeter than at the center, and wherein the opposed surfaces of the conductor are substantially parallel.

3. The switch as recited in claim 1. wherein said second surface extends at approximately the same elevational level from the center to the pe╧Çmeter, and wherein the opposed surfaces extend along a respective pair of axes which intersect at an acute angle.

4. The switch as recited in claim 1. wherein said first surface is adapted to receive a force directed at a perpendicular angle toward the second surface.

5. The switch as recited in claim 1 , wherein said first surface is adapted to receive a force directed at an acute angle toward the second surface.

6. The switch as recited in claim 1. further comprising:

a flange extending laterally from the perimeter to define a lower flange surface which extends elevationally lower than the conductor; and

a retainer for fixedly securing the flange such that the conductor extends a spaced distance above a plurality of printed conductors during times when a downward force is absent from the first surface.

7. The switch as recited in claim 6, wherein said spaced distance increases from the perimeter toward the center.

8. The switch as recited in claim 6, wherein said pluraUty of printed conductors are spaced from each other across a substantially planar printed circuit board.

9. The switch as recited in claim 6, wherein said conductor contacts a first set of printed conductors during times when a first force amount is present upon the first surface.

10. The switch as recited in claim 8, wherein said conductor contacts a second set of printed conductors greater than the first set of printed conductors during times when a second force amount greater than the first force amount is present upon the first surface.

11. The switch as recited in claim 6. wherein said pluraUty of printed conductors are spaced from each other within at least two spaced rows, and wherein the printed conductors within one row each extend along an axis between a respective pair of printed conductors within the other row.

12. The switch as recited in claim 11, wherein said conductor contacts a printed conductor within one of the two spaced rows before contacting a printed conductor within the other of the two spaced rows during incremental increases in a force amount present upon the first surface.

13. A method for incrementally contacting printed conductors to a power supply, comprising:

providing a conductor having a downward facing surface arranged at an angle relative to a horizontal plane;

providing a plurality of spaced, upward facing printed conductors arranged across the horizontal plane a spaced distance from the downward facing surface;

applying incrementally increasing downward force to the conductor for removing the angle at incrementaUy increasing distances across the downward facing surface and for contacting an incrementaUy increasing number of printed conductors with the conductor in the area in which the angle is removed.

14. The method as recited in claim 13. wherein said applying comprises asserting the downward force at an angle substantially perpendicular to the horizontal plane.

15. The method as recited in claim 13, wherein said applying comprises asserting the downward force at an acute angle relative to the horizontal plane.

16. The method as recited in claim 13, wherein said applying comprises moving said conductor within the horizontal plane while incrementally increasing the downward force.

17. The method as recited in claim 13, wherein said printed conductors comprise a first and a second set of printed conductors arranged within a first row and a second row, respectively, placed a parallel distance apart.

18. The method as recited in claim 16, wherein said applying comprises incrementaUy contacting a printed conductor within the first row before contacting a printed conductor within the second row.

19. The method as recited in claim 13, wherein one of said printed conductors embodies said power supply, and wherein said applying comprises contacting the conductor between the power supply and an incrementally increasing number of printed conductors.

20. The method as recited in claim 13, wherein said power supply comprises a ground or a voltage source.