Methods and apparatus for capacitively detecting key motion and finger presence on a magnetic keyboard key

• US 9,406,453 B2
• Filed: 01/03/2014
• Issued: 08/02/2016
• Est. Priority Date: 01/04/2013
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Bolender, Robert J., Reynolds, Joseph Kurth
• Primary Examiner(s): Nguyen, Vincent Q
• Application Number:
  US14/146,811
• Publication Number:
  US 20140190811A1
• Time in Patent Office: 942 Days
• Field of Search: 324660-662
• US Class Current: 1/1
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G06F 3/0202 Constructional details or processes of manufacture of the input device
• CPC Class Codes: H01H 13/7065 characterised by the mechanism between keys and layered keyboards
• CPC Class Codes: H01H 2217/01 Off centre actuation
• CPC Class Codes: H01H 2221/04 magnetic
• CPC Class Codes: H01H 3/122 with enlarged actuating area, e.g. of the elongated bar-type; Stabilising means therefor
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 17/98 having a plurality of control members, e.g. keyboard
• CPC Class Codes: H03K 2217/96079 using a single or more light guides

Abstract

Devices and methods for capacitively sensing key cap position during the initial and latter stages of a keystroke. A key assembly includes a stationary key guide magnet, a movable key cap magnet, and a transmitter/receiver electrode pair. One or both of the electrodes underlies the key cap. The capacitance change between the electrodes during a keystroke includes the capacitance change between the key cap and the electrode pair, and the change in capacitance between the key cap and the key guide. Key cap position may thus be accurately detected throughout the entire keystroke.

Claims

1. A keyboard comprising a plurality of key assemblies, wherein each of at least a subset of the key assemblies comprises:

a key guide having a first conductive portion;

a key cap having a second conductive portion;

a transmitter electrode; and

a receiver electrode disposed underneath the second conductive portion;

wherein the first and second conductive portions cooperate magnetically to return the key cap to a nominal position following a keystroke; and

wherein the first transmitter electrode and first receiver electrode form a variable capacitance in response to the keystroke.

2. The keyboard of claim 1, wherein the transmitter electrode is disposed beneath the key guide.

3. The keyboard of claim 1, wherein the transmitter electrode, the receiver electrode, and the first and second conductive portions are configured to form:

a first capacitance between the receiver electrode and the second conductive portion;

a second capacitance between the first and second conductive portions; and

a third capacitance between the transmitter electrode and the first conductive portion;

wherein the variable capacitance comprises the first, second, and third capacitances.

4. The keyboard of claim 1, wherein the transmitter electrode is disposed beneath the key cap, and wherein the first conductive portion is configured to be maintained at a substantially constant electrical potential.

5. The keyboard of claim 1, wherein at least one of the first and second conductive portions comprises a magnet.

6. The keyboard of claim 1, wherein each of the subset of key assemblies further comprises a planar-translation-effecting (PTE) mechanism configured to impart planar, vertical, and lateral motion to the key cap when pressed by a user.