Cover with improved vibrational characteristics for an electronic device
A cover or housing member for an electronic device comprises a central region and a perimeter region surrounding the central region. The central region comprises an elevated pattern of radial ribs and elliptical elevations elevated above a generally planar lower surface, such that the cover has multiple vibrational modes of natural resonance in which a maximum deflection of the cover occurs in a first mode at a central point of the cover.
1. A cover for attachment to an electronic device, the cover comprising:
a central region comprising an elevated pattern of radial ribs and elliptical elevations elevated above a generally planar lower surface of a cover exterior, such that the cover has multiple vibrational modes of natural resonance in which a maximum deflection of the cover occurs in a first mode at a central point of the cover; and
a perimeter region surrounding the central region, wherein the first mode has a lower frequency of natural resonance of vibration than other modes, among the multiple vibrational modes.
2. The cover according to claim 1 wherein the cover has a second mode of natural resonance in which the maximum deflection occurs at two deflection points along a longitudinal axis of the cover and spaced approximately equidistant from the central point of the cover.
3. The cover according to claim 2 wherein the first mode has a lower frequency of natural resonance than that of the second mode.
4. The cover according to claim 1 wherein the cover has a third mode of natural resonance in which the maximum deflection occurs at two deflection points along a transverse axis of the cover and spaced approximately equidistant from the central point of the cover.
5. The cover according to claim 4 wherein the first mode has a lower frequency of natural resonance than that of the third mode.
6. The cover according to claim 1 wherein the elevated pattern is formed by stamping a generally planar sheet metal with or against a die.
7. The cover according to claim 1 wherein the central region is generally rectangular.
8. The cover according to claim 1 wherein the perimeter region has a step and a mating flange for mating with the electronic device.
9. The cover according to claim 8 wherein the edge of the perimeter region terminates in a lip extending in an opposite direction from the elevated pattern.
10. The cover according to claim 1 wherein the radial ribs and elliptical elevations are within a range of approximately 1 millimeter to approximately 3 millimeters above the generally planar lower surface.
11. An electronic device comprising:
a housing having at least one open side;
a circuit board secured within the housing;
a cover for mating with the open side and spaced apart from the circuit board by a clearance distance, the cover comprising:
a central region comprising an elevated pattern of radial ribs and elliptical elevations elevated above a generally planar lower surface of a cover exterior, such that the cover has multiple vibrational modes of natural resonance in which a maximum deflection of the cover occurs in a first mode at a central point of the cover and wherein the maximum deflection is less than the clearance distance; and
a perimeter region surrounding the central region, wherein the first mode has a lower frequency of natural resonance of vibration than other modes, among the multiple vibrational modes.
12. The electronic device according to claim 11 wherein the cover has a second mode of natural resonance in which the maximum deflection occurs at two deflection points along a longitudinal axis of the cover and spaced approximately equidistant from the central point of the cover.
13. The electronic device according to claim 12 wherein the first mode has a lower frequency of natural resonance than that of the second mode.
14. The electronic device according to claim 11 wherein the cover has a third mode of natural resonance in which the maximum deflection occurs at two deflection points along a transverse axis of the cover and spaced approximately equidistant from the central point of the cover.
15. The electronic device according to claim 14 wherein the first mode has a lower frequency of natural resonance than that of the third mode.
16. The electronic device according to claim 11 wherein the elevated pattern is formed by stamping a generally planar sheet metal with or against a die.
17. The electronic device according to claim 11 wherein the central region is generally rectangular.
18. The electronic device according to claim 11 wherein the perimeter region has a step and a mating flange for mating with the electronic device.
19. The electronic device according to claim 18 wherein the edge of the perimeter region terminates in a lip extending in an opposite direction from the elevated pattern.
20. The electronic device according to claim 11 wherein the radial ribs and elliptical elevations are within a range of approximately 1 millimeter to approximately 3 millimeters above the generally planar lower surface.