Haptic button with SMA
Broadly speaking, embodiments of the present techniques provide haptic button assemblies in which the haptic button has a low profile while still providing a satisfying tactile response or sensation to a user. Advantageously, the haptic button assemblies may have a profile that, for example, enables the assembly to be incorporated into the free space along an edge of a portable computing device. The haptic assemblies may, for example, be arranged to move the button perpendicularly with respect to the edge of the device.
1. A haptic button assembly comprising:
a housing comprising a cavity;
a button provided within the cavity and moveable along a first axis within the cavity;
at least one intermediate moveable element provided within the cavity in contact with the button and moveable in a plane defined by the first axis and a second axis, the second axis being perpendicular to the first axis, and arranged to drive movement of the button along the first axis, wherein the at least one intermediate moveable element is in indirect contact with the button, and the assembly comprises a first bearing provided between the intermediate moveable element and the button and arranged to move the button along the first axis when the intermediate moveable element moves, wherein the first bearing comprises at least one ramp and at least one ball bearing arranged to roll along the at least one ramp; and
at least one shape memory alloy (SMA) actuator wire coupled to the at least one intermediate moveable element and arranged to, on contraction, laterally move the intermediate moveable element in the plane, thereby driving movement of the button along the first axis and providing a haptic effect.
2. The haptic button assembly as claimed in claim 1 comprising a plurality of SMA actuator wires.
3. The haptic button assembly as claimed in claim 2 , wherein all of the plurality of SMA actuator wires are arranged to move the intermediate moveable element in a first direction in the plane.
4. The haptic button assembly as claimed in claim 1 , wherein each SMA actuator wire is coupled to the at least one intermediate moveable element via a coupling element, wherein the coupling element is a crimp connector.
5. The haptic button assembly as claimed in claim 1 further comprising a resilient biasing element coupled to the intermediate moveable element and arranged to oppose the movement of the intermediate moveable element caused by contraction of the at least one SMA actuator wire.
6. The haptic button assembly as claimed in claim 1 , wherein the at least one ramp is a localised ramp provided on a surface of the button and/or the intermediate moveable element.
7. The haptic button assembly as claimed in claim 1 further comprising a third bearing provided between the button and one or more side walls of the cavity and arranged to constrain movement of the button along the second axis.
8. The haptic button assembly as claimed in claim 1 further comprising a bearing provided between the intermediate moveable element and a base of the cavity and arranged to bear movement of the intermediate moveable element along the second axis.
9. The haptic button assembly as claimed in claim 1 further comprising a sealing mechanism.
10. The haptic button assembly as claimed in claim 1 , wherein the button and the housing are integrally formed.
11. The haptic button assembly as claimed in claim 10 wherein the button comprises at least one free edge.
12. The haptic button assembly as claimed in claim 1 further comprising:
a sensor to detect a button press; and
control circuitry coupled to the sensor and the at least one SMA actuator wire and arranged to:
receive data from the sensor indicating that the button has been pressed; and
send a signal to drive the at least one SMA actuator wire.