Patent Application
20060238291
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. Even though potentiometers are presently available, for example U.S. Pat. No. 5,157,372 (Langford) and U.S. Pat. No. 5,583,476 (Langford), which are incorporated herein for all purposes, no bi-directional deflectable resistor is known to applicant that produces a consistent and predictable variable electrical output upon deflection or bending between configurations occurring in opposite directions from a static configuration.
The use of electrically conductive inks in association with electrical or electronic circuitry is also known. For example, U.S. Pat. No. 4,649,748 (Fulks, et al.) discloses the use of a conductive ink which is pressure sensitive to produce electrical switching signals for a keyboard. However, as stated previously, no bi-directional flexible or deflectable resistor is known which uses electrically conductive or resistive ink.
In various exemplary embodiments of the present invention, a bi-directional deflectable resistor is provided. In general, the deflectable resistor comprises a substrate, a first layer of conductive material and a second layer of conductive material. The substrate has a top surface and a bottom surface and a first configuration. In operation, the substrate bends from a first configuration to a second configuration in a direction that is generally downward and away from relative to said top surface. The substrate also bends from a first configuration to a third configuration in a direction that is generally upward and away from relative to said bottom surface and opposite to said direction upward and away from relative to said top surface.
The first layer of conductive material is disposed on said top surface of the substrate. The first layer of conductive material has a resistance that changes predictably when the resistor is bent from the first configuration and an electrical signal is applied thereto. In general, the change of resistance of the first layer of conductive material reflects the amount of deflection between the first configuration and the second configuration. The second layer of conductive material is disposed on the bottom surface of the substrate. The second layer of conductive material has a resistance that also changes predictably when the resistor is bent from the first configuration and an electrical signal is applied thereto. The change of resistance of the second layer of conductive material reflects the amount of deflection between said first configuration and the third configuration.
In operation, the bending of the first layer of conductive material between the first configuration and the second configuration causes a number of micro-cracks that are added during the manufacturing process to open up and separate in the first layer of conductive material. As the amount of bending to the second configuration increases, the size of the micro-cracks (i.e., the distance between the conductive materials) in the first layer of conductive material increases and the resistance, therefore, also increases. Similarly, the bending of said second layer of conductive material between the first configuration and the third configuration causes a number of micro-cracks that are added during the manufacturing process to open up and separate in said second layer of conductive material. As the amount of bending to the third configuration increases, the size of the micro-cracks in the second layer of conductive material increases and the resistance, therefore, also increases.
In another embodiment, the substrate has a top surface and a bottom surface. The substrate bends in a first direction downward and away from relative to said top surface and in a second direction upward and away from relative to said bottom surface and opposite said first direction. A first layer of electrically conductive ink is disposed on said top surface of said substrate. The first layer of resistive ink has a resistance that changes predictably when the resistor bends in the first direction and an electrical signal is applied thereto. The change of resistance of the first layer of resistive ink reflects the amount of deflection in the first direction. A second layer of resistive ink is disposed on the bottom surface of the substrate. The second layer of electrically conductive ink has a resistance that changes predictably when the resistor bends in the second direction and an electrical signal is applied thereto. The change of resistance of the second layer of electrically conductive ink reflects the amount of deflection in the second direction.
In still another embodiment, the substrate has a length with a longitudinal y-axis running along said length. The first direction of bending is in a positive x-direction relative to the longitudinal y-axis and the second direction of bending is in a negative x-direction relative to the longitudinal y-axis.
In another embodiment, the deflectable resistor desirably includes a first and second segmented conductor. The first segmented conductor is positioned on a 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. The second segmented conductor is positioned on a second layer of electrically conductive ink and is formed of an electrically conductive material deposited on the second layer of electrically conductive ink in spaced apart segments.
In yet another embodiment, 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.
In still another embodiment, a first connector means is coupled to a first layer of conductive material for interconnection to external electrical components and a second connector means is coupled to a second layer of conductive material for interconnection to external electrical components.
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:
The bottom surface 50, shown in
Substrate 12 is formed of a deflectable insulating material. Various types of phenolic resin materials are presently believed to be suitable as the substrate. The substrate may also 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, a phenolic resin has 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 19, 21 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 19, 21 may include a material which facilitates wetting, gluing, or sticking. The conductible material 19, 21 may include graphite in combination with a binder. The conductible material 19, 21 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 0.003 to about 0.007 inches in thickness (although various other thicknesses may be acceptable); the variable resistive material 19, 21 may be from about 0.0006 to about 0.0011 inches in thickness (although various other thicknesses may be acceptable).
Bi-directional 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 19, 21. With measurements, a relationship between the degree or angle of deflection of substrate 12 and the resistance of conductible material 19, 21 can be developed and used in software that is relatively simple to create.
The first top layer of electrically conductive ink 11 and a second top layer of electrically conductive ink 31 are interconnected by segmented conductor runs 36, 38. In this manner, the resistance of conductive layer 19 and conductive layer 21 are connected and can be measured together. To facilitate the measurement of the resistance of conductive layer 19 and conductive layer 21, segmented conductor run 40 is electrically connected to the end segmented conductor 20 and segmented conductor run 42 is electrically connected to the end segmented conductor 22. Segmented conductor runs 40, 42 would be electrically connected to a suitable connector means for interconnection to external electrical components.
The first bottom layer of electrically conductive ink 51 and the second bottom layer of electrically conductive ink 61 are interconnected by segmented conductor runs 72, 74. In this manner, the resistance of conductive layer 51 and conductive layer 61 are connected and can be measured together. To facilitate the measurement of the resistance of conductive layer 51 and conductive layer 61, segmented conductor run 76 is electrically connected to the end segmented conductor 58 and segmented conductor run 78 is electrically connected to the end segmented conductor 56. Segmented conductor runs 76, 78 would be electrically connected to a suitable connector means for interconnection to external electrical components.
Segmented constant resistance conductive material, although not necessary, may be used in combination with bi-directional 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 19, 21. The segmented conductors act as attenuators and reduce the overall resistance of the conductive material. It is also believed but not proven that the segmented conductors may help to make the resistance versus load curve of a flexible potentiometer more linear. The segmented conductors may also help make the resistance at a particular deflection configuration more consistently repetitive.
The variable resistance material 19, 21 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 the while illustrated embodiment illustrated in
Referring now to
In operation, when first length 81 deflects in the first direction, the resistance of the first top layer of conductive material 82 predictably changes. The measurement of the change of resistance of the first top layer of conductive material reflects the amount of deflection. Similarly, when the second length 83 deflects in the second direction, the resistance of the second bottom layer of conductive material (not shown) predictably changes. The measurement of the change of resistance of the second bottom layer of conductive material (not shown) reflects the amount of deflection. This operation will be described in greater detail hereinafter.
Continuing with the operation of deflectable resistor 10, 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 10 is bent, the change can then be measured upon application of suitable electrical signals.
The top view of a portion of a deflectable resistor of
The bottom view of a portion of a deflectable resistor of
Referring to
The conductor means 114, 152 of
As illustrated in
As illustrated in
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 0.007 millimeters to about 0.015 millimeters and preferably about 0.011 millimeters. Each segment 116, 118, 120, 122 has a length selected to regulate the electrical resistivity of the bi-directional deflective resistor as discussed hereinafter.
In
As the bi-directional deflectable resistor is deflected or bent, it is believed that micro-cracks added during manufacturing to the conductive ink which contains graphite, separate and widen. That is, the dried conductive ink 114, 152 has a granular or crystalline-type structure with micro-cracks that separate or open up upon deflection. As the conductive ink 114, 152 bends, the space between the micro-cracks increases, thereby changing the electrical resistance in a predictable manner. As the resistor is bent, the change can be measured upon application of suitable electrical signals.
The segmented conductor 116, 118, 120 is positioned along the conductive ink 114 on top surface 112 and segmented conductor 154, 158, 160 is positioned along the conductive ink 152 on bottom surface 150 in pre-selected lengths to control or regulate the resistivity of the deflected conductive ink 114, 152 and in turn ensure that upon repetitive deflections, the variation of the resistance between configurations A, B and D is consistent throughout the life of the substrate. For example, if the width is the same as the width of the conductor means 114, 152, a length of about 3 to about 5 millimeters with spacing from about 1 to about 2 millimeters has been found suitable for a deflectable resistor 10 similar to that of
The segmented conductor 116, 118, 120, 154, 158, 160 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 116, 118, 120, 154, 158, 160 retains its electrical conductivity upon deflection.
With the segmented conductor 116, 118, 120 affixed or adhered to the conductor means 114 and segmented conductor 154, 158, 160 affixed or adhered to the conductor means 152, 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.
Bi-directional deflectable resistor 10 generates a substantial change in resistance when deflected in both a first direction from a generally straight position and in a second direction that is in an opposite direction from a generally straight 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 y-axis extends the length of deflectable resistor 10 and the x-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 y-axis, and hence the top and bottom surface of deflectable resistor 10, in either a positive x-direction or a negative x-direction. In the illustrated example, deflection degrees B and C are in a positive x-direction, generally upward and away from relative to the top surface, and deflection degrees D and E are in a negative x-direction, generally downward and away from relative to the bottom surface and opposite the positive x-direction, both the positive x-direction and the negative x-direction being relative to the imaginary longitudinal y-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 substantially greater than resistance RA. At deflection degree D, the level of resistance RD is predictable and repeatable. At deflection degree E, deflectable resistor 10 has a resistance RE, which is substantially greater than resistance RD and is predictable and repeatable. Accordingly, as the deflection changes from degree E to degree D, there is a predictable and repeatable decrease in resistance.
Continuing with the
The bottom surface of substrate 203 has a first bottom segmented conductor 215 positioned on the second layer of conductive ink 202 and a second bottom segmented conductor 220 electrically connected to the first layer of conductive ink 202 and printed on the top surface of substrate 203. First bottom segmented conductor 205 and second bottom segmented conductor 210 are configured to be connectable to a connector for measuring the resistance of the second layer of conductive ink 210.
As shown in
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.
