Patent Application
20070030112
1. The Field of the Invention
This invention relates to electrical components and more particularly to deflectable resistors which vary in electrical resistance.
2. The Relevant Technology
Potentiometers are standard elements of electrical and electronic circuits. They are widely in use today for a variety of purposes including the measurement of mechanical movement. U.S. Pat. No. 5,157,372 (Langford) and U.S. Pat. No. 5,583,476 (Langford), (which are incorporated herein for all purposes), presented a new device identified as a flexible potentiometer that provided an electrical resistor having a consistent and predictable variable electrical output upon deflection or bending between configurations.
Flexible potentiometers have been sold commercially and, in some configurations, require two side-by-side connecting conductive runs of material proximate each other forming, in effect, a U-shaped device. Such devices, in turn, require a width that can be regarded as excessive or too large, thereby preventing use in selected applications.
In various exemplary embodiments of the present invention, a deflectable resistor is provided. In general, the deflectable resistor comprises a substrate, a first layer of conductive material, a second layer of conductive material, a layer of dielectric material and a third layer of conductive material disposed on the surface of the dielectric layer. The substrate is formed of a deflectable electrical insulating material having a top surface, a first end, a second end, a width and a length between said first end and said second end. In operation, the substrate bends in at least a first direction that is generally in a negative y-direction relative to a longitudinal x-axis extending along the length of the substrate.
A first layer of conductive material has a first end proximate the first end of said substrate, a second end proximate the second end of said substrate, a width and a length between said first end and the second end is disposed on the top surface of the substrate. The first layer of conductive material has a resistance between the first end and the second end of the first layer of conductive material that changes predictably. The resistance is measured when an electrical signal is applied thereto. In general, the change of resistance of the first layer of conductive material reflects the amount of deflection in the first direction.
A second layer of conductive material is deposited on the surface of the substrate and electrically connected to the first end of the first layer of conductive material. The second layer of conductive material is configured to connect the first end of the first layer of conductive material to external electronic componentry.
A first layer of dielectric material is deposited on the top surface of the substrate and over the first layer of conductive material. The dielectric material provides an electrical insulating barrier between the first and second layers of conductive material and a third layer of conductive material disposed on the first layer of dielectric material.
A third layer of conductive material is deposited on the surface of the first layer of dielectric material. The third layer of conductive material is electrically connected to the second end of said first layer of conductive material. The third layer of electrically conductive material also is configured to connect the second end of the first conductive layer to external electronic componentry.
In operation, the bending of the first layer of conductive material between the first configuration and the second configuration opens and widens a number of cracks in the first layer of conductive material. As the cracks open and widen in the first layer of conductive material, the corresponding resistance of the first layer of conductive material also increases in a predictable and measurable manner. Accordingly, the resistance predictably and measurably increases as the amount of bending to a second configuration increases.
In one embodiment, a second layer of dielectric material is deposited on the top surface of the substrate and over the first layer of conductive material, the second layer of conductive material, the first layer of dielectric material and the third layer of conductive material. The dielectric material provides an additional electrical insulating barrier between the deflectable resistor and the atmosphere.
In another embodiment, the substrate has a length with a longitudinal y-axis running along said length. The first direction of bending is in a negative x direction relative to the longitudinal y-axis.
In another preferred arrangement, the substrate is bendable between a first configuration and a second configuration. A layer of electrically conductive ink is deposited on a surface of the substrate. In a preferred configuration, the length and said width of the layer of electrically conductive ink is less than the length and said width of the substrate. The layer of conductive ink has a resistance measured between the first end and the second end of the layer of electrically conductive ink that changes predictably when an electrical signal is applied thereto. The change of resistance of the layer of conductive ink reflects an amount of deflection between the first configuration and the second configuration.
A layer of dielectric material is disposed on the surface of the substrate that contains the layer of electrically conductive ink. The layer of dielectric material disposed over at least the layer of conductive ink. The layer of dielectric material is configured for providing an electrical insulating barrier between the conductive ink and a layer of conductive material disposed on the surface of said layer of dielectric material that is connected to the second end of said layer of electrically conductive ink.
In a preferred configuration, the layer of conductible material comprises a conductor formed of an electrically conductive material, such as a soft conductive metal. In a more preferred configuration, the conductor is made of made of silver or a silver alloy or a carbon or a carbon compound.
In an alternate arrangement, the deflectable resistor further comprises a first connector means coupled to the second layer of electrically conductive ink for interconnection to external electrical components and a second connector means coupled to the third layer of conductive material for interconnection to external electrical components.
In a preferred arrangement, the third layer of conductive material extends from the second end of the layer of electrically conductive ink along the surface of the layer of dielectric material to the first end of said substrate. In a more preferred arrangement, a conductor formed of an electrically conductive material is disposed on the top surface of the substrate. The conductor is electrically connected to the first end of said layer of electrically conductive ink. The layer of dielectric material is disposed over the first and second conductors, thereby providing an electrical insulating barrier between the first conductor, the second conductor and the third conductor. The layer of conductive material and the conductor are configured to receive said electrical signal.
In another embodiment, the deflectable resistor desirably includes a segmented conductor. The segmented conductor is positioned on the first layer of electrically conductive ink and is formed of an electrically conductive material deposited on the first layer of electrically conductive ink in spaced apart segments. In a more preferred embodiment, the segmented conductor has a plurality of segments each having a width substantially the width of the layer of the electrically conductive ink and a length selected to regulate the resistance of the first layer of electrically conductive ink.
In another preferred configuration, the first configuration of a substrate is a static configuration. Preferably, the static condition of the substrate may be a substantially flat substrate or one where said substrate has at least one bend.
These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.
To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
During a third manufacturing pass, the dielectric layer 3 is positioned over the variable resistance material 6 and a portion of the first conductor 5, leaving a portion of the variable resistance material 6 exposed on the end opposite the first conductor 5. The fourth and possible final manufacturing pass places the second conductor 4 over the exposed portion of the variable resistance material 6 and runs along the surface of dielectric layer 3. The dielectric layer 3 electrically separates the second conductor 4 from both the variable resistance material 6 and the first conductor 5. In an embodiment, a second layer of dielectric material (not shown) is positioned over the variable resistance material 6, the first conductor 5, the second conductor 4, and the first dielectric layer 3. The second layer of dielectric material insulates the deflectable resistor 1 from the atmosphere.
Substrate 12 is formed of a deflectable insulating material. Various types of materials are presently believed to be suitable as the substrate. The substrate may be constructed of various materials including various polymers, such as polyamide, polyimide (Kapton), and polyester (Mylar), which may be thermoplastics. For applications involving multiple bending movements, certain polyimides have been found to be particularly suitable. However, other materials may be suitable in selected applications. For example, the deflectable resistor may be used to measure inelastic deformation so that the substrate itself is inelastically deformable. Preferably, the substrate 12 should be deflectable without causing an electrical discontinuity or open circuit in the conductor means while generally maintaining its electrical insulating characteristics.
The conductible material 14, also referred to herein as a conductor means, may be a two-part epoxy material, a thermoset adhesive, or a thermoplastic, all incorporating conductive material such as graphite or carbon. The variable resistance material may include a carbon ruthenium. To attach to a substrate, the conductible material 14 may include a material which facilitates wetting, gluing, or sticking. The conductible material 14 may include graphite in combination with a binder. The conductible material 14 is preferably of the type which is applied to the substrate in liquid form and which in turn dries to a solid form.
Merely examples, the substrate 12 may be from about 0.005 to about 0.010 inches in thickness (although various other thicknesses may be acceptable); the variable resistive material 14 may be from about 0.0003 to about 0.001 inches in thickness (although various other thicknesses may be acceptable).
Deflectable resistor 10 may be used to measure a degree or angle of deflection. The greater the amount of the deflection, the greater the resistance of conductible material 14. With measurements, a relationship between the degree or angle of deflection of substrate 12 and the resistance of conductible material 14 can be developed and used in software, that is relatively simple to create.
The first top layer of electrically conductive ink 18 has a segmented conductor layer disposed thereon. In the illustrated embodiment, the segmented conductor layer of conductive layer 14 comprises a number of segmented conductors 20, 22, 24 and end segmented conductors 26, 28.
Segmented constant resistance conductive material, although not necessary, may be used in combination with deflectable resistor 10 to reduce the resistance and help linearize changes in resistance. The segmented conductors may be made of silver, silver alloys, or other conductive metals, as well as conductive carbon-based compounds. The segmented conductors may be applied in a liquid form, or applied in a solid form which is pressed onto the variable resistance material. The conductivity of the segmented conductors remains essentially constant upon deflection. Therefore, the segmented conductors provide paths for electrical current that are in parallel with the path provided by the variable resistance material 14. The segmented conductors act as attenuators.
The variable resistance material 14 may be spray painted, rolled, silk screened, or otherwise printed onto the substrate. The variable resistance material may be a solid which is pressed onto the substrate. A conductive substrate may be used. The substrate may be connected to a particular potential, such as ground. A non-conductive coating may be applied to the substrate.
It should be appreciated that while the illustrated embodiment shown in
The layer of dielectric 38 is preferably part number 5018 manufactured by DuPont. In alternative arrangements, Acheson Electrodag Uv1015 works equally as well. In the illustrated embodiment, the dielectric material layer 38 is shown as mirroring the size and shape of substrate 12. As one skilled in the art will appreciate, the dielectric layer 38 may be sized small enough to sufficiently cover the conductive material 18 as well as segments 20, 22, 24, end segment 28 and first conductor 32. The dielectric material layer 38 forms an electrical insulating barrier between the conductive material and any conductive material that may be disposed on the surface 35 of the dielectric material layer 38.
In the illustrated example, the dielectric material layer 38 has an aperture 36 cut into one end of the layer proximate the second end 19 of the layer of conductive material 18. The aperture 36 allows for an electrical connection between end segment 40 and end connection 26 of second conductor 30. The second conductor extends along the surface 35 of the dielectric material layer 38 from the end segment 40 to the end of the dielectric material layer 38, which, in the illustrated example, aligns with the first end 13 of the substrate 12. In operation, the resistance of conductive material 18 is measured between first conductor 32 and second conductor 30 by applying an electrical signal thereto.
Referring now to
Continuing with the operation of deflectable resistor 50, micro-cracks (not shown) are added to the variable resistance material during the manufacturing process. It is believed but not known that as a deflectable resistor (of some or all compositions), is deflected or bent, the distance between the micro-cracks of the variable resistance material separates or widens. That is, in some or all compositions, dried variable resistance material has micro-cracks in a granular or crystalline-type structure which widens and separates upon deflection. As the variable resistance material deflects, the number of cracks and the space between them is believed to increase, thereby changing the electrical resistance in a predictable manner. When the resistor 50 is bent, the change in resistance between the first configuration 52 and the second configuration 54 can be measured upon application of suitable electrical signals to first conductor 60 and second conductor 62.
The top view of a portion of a deflectable resistor of
Referring to
The conductor means 104 of
As illustrated in
Continuing with
It may also be noted that the segmented conductor is adhered to the conductive ink and in turn has a thickness which is from about 0.01 millimeters to about 0.02 millimeters and preferably about 0.015 millimeters. Each segment 106, 108, 110 has a length selected to regulate the electrical resistivity of the deflective resistor as discussed hereinafter.
Although illustrated as suspended above substrate 100, in operation, the dielectric layer 112 shown in
The layer of dielectric 112 in turn has a thickness which is here illustrated substantially larger than the actual thickness. That is, the thickness of the layer of dielectric material 112 is illustrated disproportionate to the actual thickness of the substrate 100 and of the actual layer of the dielectric 112. In particular the thickness of the layer of dielectric material 112 is from about 0.01 millimeters to 0.02 millimeters.
In
The dried conductive ink 104 has a granular or crystalline-type structure which cracks or breaks upon deflection. As the conductive ink 104 bends, the number of cracks and the space between the cracks is believed to increase, thereby changing the electrical resistance in a predictable manner. The change can be measured upon application of suitable electrical signals.
The segmented conductor 106, 108, 110 is positioned along the conductive ink 104 on top surface in pre-selected lengths to control or regulate the resistivity of the deflected conductive ink 104 and in turn ensure that upon repetitive deflections, the variation of the resistance between configurations A and B is consistent throughout the life of the substrate. More particularly, the length and width of the segments 106, 108, 110 as well as the spaces between the segments are empirically selected to ensure a useful resistance range. For example, a sensor is needed that measures 10 cm in length, however, the resting or flat resistance is twice the desired amount. Then, conductors 106, 108 and 110 are configured as such to reduce the surface area of conductive ink, and therefore the resting or flat resistance, by half.
The segmented conductor 106, 108, 110 has been successfully formed of silver. It is also believed formable from conductive silver alloys, and other conductive metals, as well as carbon-based compounds. The segmented conductor 106, 108, 110 retains its electrical conductivity upon deflection.
With the segmented conductor 106, 108, 110 affixed or adhered to the conductor means 104, the resistance may still vary somewhat over time, but the degree of variance is either within acceptable tolerances or otherwise measurable from time to time so that adjustments can be made to accommodate for the drift in resistance over time.
Deflectable resistor 10 a substantial change in resistance when deflected in a first direction from a straight or static position. For example,
Generally speaking, position A is a static position that is substantially flat or straight relative to an imaginary x-y axis, where the longitudinal x-axis extends the length of deflectable resistor 10 and the y-axis extends upward and downward relative to the top and bottom surface of deflectable resistor 10. Accordingly, the deflection of deflectable resistor 10 moves in a direction relative to this longitudinal x-axis, and hence the top and bottom surface of deflectable resistor 10, in either a positive y-direction or a negative y-direction. In the illustrated example, deflection degrees B and C are in a negative y-direction and deflection degree D is in a positive y-direction relative to the imaginary longitudinal x-axis extending along the length of the substrate of deflectable resistor 10.
At deflection degree A, which is straight, deflectable resistor 10 has a resistance RA. At deflection degree B, deflectable resistor 10 has a resistance RB, which is substantially greater than resistance RA. At deflection degree B, the level of resistance RB is predictable and repeatable. At deflection degree C, deflectable resistor 10 has a resistance RC, which is substantially greater than resistance RB and is predictable and repeatable. Accordingly, as the deflection changes from degree C to degree B, there is a predictable and repeatable decrease in resistance. At deflection degree D, deflectable resistor 10 has a resistance RD, which is insufficiently different than resistance RA. At deflection degree D, since the resistance RD remains virtually unchanged from RA.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
