Snap domes as sensor protection

• US 9,389,721 B2
• Filed: 02/09/2012
• Issued: 07/12/2016
• Est. Priority Date: 02/09/2011
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Lackey, Mark
• Primary Examiner(s): Lao, Lun-Yi
• Assistant Examiner(s): KHAN, IBRAHIM A
• Application Number:
  US13/369,808
• Publication Number:
  US 20120200526A1
• Time in Patent Office: 1,615 Days
• Field of Search: 345/173, 345/174, 178 1805- 1807, 36167901-815, 312/7.2, 200/513
• US Class Current: 1/1
• CPC Class Codes: G06F 3/04142 the force sensing means being located peripherally, e.g. disposed at the corners or at the side of a touch sensing plate
• CPC Class Codes: H01H 2215/006 Only mechanical function
• CPC Class Codes: H01H 2215/036 Metallic disc
• CPC Class Codes: H01H 2221/03 Stoppers for on or off position
• CPC Class Codes: H01H 2221/064 Limitation of actuating pressure

Abstract

A protection mechanism for force-based touch sensitive input panels or displays comprising a “snap dome”, e.g., a semi-rigid pliable dome positioned over each sensor for increased overload protection. The snap dome is unidirectionally-resilient to a known point of collapse. It therefore imparts a predetermined resistance to compression over a known range of travel along the z-axis, but is unyielding along the x- and y-axis. As the touch panel is depressed toward the standoff, the snap dome resists compression until it collapses, allowing the touch panel to encounter the standoff. The standoff then imparts dead-stop overload force protection to the sensors. This allows for the placement of mechanical stops (such as stop screws) with a less exacting tolerance. Moreover, the snap domes introduce no x- or y-axis force losses/increases, and do not cause tilting of the touch panel. The touch force remains perfectly perpendicular and accuracy is preserved.

Claims

1. A touch screen assembly for an electronic device having a processor, said touch screen assembly comprising:

an electronic display screen;

a substrate;

a plurality n of differentially-mounted force sensors mounted between said display screen and said substrate and differentially positioned along an x- and y-axis, said force sensors being electrically connected to the processor for registering a force z from a touch of said electronic display screen at any position along said x- and y-axis and for providing an analog differential force signal z; and

a plurality n of differentially-mounted semi-rigid snap-domes each positioned below a respective force sensor and having a central axis that is aligned with a central axis of said respective force sensor, each of said plurality n of snap domes being unidirectionally rigid to a known point of collapse;

a plurality n of caps each interposed between and in contact with a corresponding one of said snap domes and a corresponding one of said force sensors; and

a rigid standoff interposed between said electronic display screen and said substrate for arresting movement of said electronic display screen toward said substrate after the known point of collapse of at least one snap-dome, thereby imparting dead-stop overload force protection to the force sensor.

2. The touch screen assembly for an electronic device according to claim 1, wherein said number n is two (2).

3. The touch screen assembly for an electronic device according to claim 1, wherein said number n is four (4).

4. The touch screen assembly for an electronic device according to claim 1, wherein said snap-domes are unidirectionally-resilient along a z-axis in an x, y, z coordinate system, and impart a predetermined resistance to compression over a known range of travel along the z-axis, but are unyielding along the x- and y-axis.

5. The touch screen assembly for an electronic device according to claim 1, wherein said standoff is a stop screw.

6. The touch screen assembly for an electronic device according to claim 1, further comprising a plurality n of caps each interposed between a corresponding one of said force sensors and a corresponding one of said semi-rigid snap-domes.

7. A protection mechanism for force-based touch sensitive inputs, comprising:

a cap interposed between a snap dome and a force-based sensor, said force-based sensor interposed between said cap and a first opposing surface, said snap dome interposed between said cap and a second opposing surface and having a central axis that is aligned with a central axis of said force-based sensor, said snap dome being formed from a semi-rigid pliable material shaped in a generally concave shape with a symmetric supporting foundation about a bearing surface, said snap dome being unidirectionally rigid to a known point of collapse; and

a rigid standoff having a central axis that is parallel to a central axis of said snap dome for arresting movement of said force-based sensor toward said opposing surface after the known point of collapse of the snap dome, thereby imparting dead-stop overload force protection to the force-based sensor.

8. The protection mechanism according to claim 7, wherein said snap dome comprises a semi-rigid concave annulus defined with a plurality of legs.

9. The protection mechanism according to claim 8, wherein said plurality of legs comprises four equi-angularly-spaced legs.

10. A device for overload protection of a force sensor, comprising:

an individual cap sandwiched between and in contact with said force sensor and a resilient snap dome, said force sensor sandwiched between and in contact with said individual cap and a first opposing surface, said snap dome sandwiched between and in contact with said individual cap and a second opposing surface, said snap dome being formed from a semi-rigid pliable material in a generally concave shape with an apex abutting the individual cap and a symmetric supporting foundation abutting the second opposing surface, said snap dome being unidirectionally rigid to a known point of collapse; and

a rigid standoff offset laterally from said snap dome and said force sensor such that a central axis of said rigid standoff is parallel to a central axis of said resilient snap dome, said rigid standoff imparting dead-stop overload force protection to the force sensor when said snap dome collapses.

11. The device for overload protection of a force sensor according to claim 10, incorporated in a touch screen assembly for an electronic device having a processor, an electronic display screen, a substrate, a plurality of differentially-mounted force sensors mounted between said display screen and said substrate and electrically connected to the processor for registering a force z from a touch of said lens at any position.

12. A touch screen assembly for an electronic device having a processor, said touch screen assembly comprising:

an electronic LCD display screen;

a base substrate parallel to said display screen;

a

circuit board between said LCD display screen and said base substrate, said circuit board containing a number n of force sensors positioned along an x- and y-axis, said force sensor(s) being electrically connected to the processor for registering a force z from a touch of said LCD display screen at any position along said x- and y-axis and for providing an analog force signal z;

a number n of semi-rigid snap-domes each mounted at or near a respective corner of said circuit board and facing said base substrate and having a central axis that is aligned with a central axis of a corresponding one of said force sensors, each of said snap domes being unidirectionally rigid to a known point of collapse;

a number n of caps each sandwiched between and in contact with a corresponding one of said force sensors and a corresponding one of said resilient snap domes; and

one or more rigid standoffs, each standoff being offset from the number n of snap domes, caps, and force sensors, said one or more standoffs imparting dead-stop overload force protection to a force sensor when a corresponding snap dome collapses.

13. The touch screen assembly for an electronic device according to claim 12, wherein said number n is one (1).

14. The touch screen assembly for an electronic device according to claim 12, wherein said number n is four (4).

15. The touch screen assembly for an electronic device according to claim 14, wherein said snap-domes are unidirectionally-resilient along a z-axis in an x, y, z coordinate system, and impart a predetermined resistance to compression over a known range of travel along the z-axis, but are unyielding along the x- and y-axis.

16. The touch screen assembly for an electronic device according to claim 14, wherein at least one standoff is interposed between the display module and the base substrate for prevention of over-compression of said corresponding force sensor(s).

17. The touch screen assembly for an electronic device according to claim 14, wherein the one or more standoffs comprises four corner-mounted standoffs interposed between the display module and the base substrate for prevention of over-compression of said corresponding force sensors.

18. The touch screen assembly for an electronic device according to claim 17, wherein said four corner-mounted standoffs are attached to said base substrate.

19. The touch screen assembly for an electronic device according to claim 18, wherein said four corner-mounted standoffs are posts integrally molded to said base substrate.

20. The touch screen assembly according to claim 18, wherein each force sensor is positioned near or at a respective corner of the circuit board.