Force sensor with angled coupling

• US 20070040817A1
• Filed: 07/31/2006
• Published: 02/22/2007
• Est. Priority Date: 08/19/2005
• Status: Active Grant

• Current Assignee: Livescribe Incorporated (Anoto Group AB)
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Silverbrook, Kia, Lapstun, Paul, Bertok, Attila, Underwood, Matthew, King, Tobin, Tow, Gregory
• Granted Patent: US 7,928,967 B2
• Time in Patent Office: Days
• US Class Current: 345/179
• CPC Class Codes: B43K 23/12 for pens caps co-operating with retractable nibs B43K5/165
• CPC Class Codes: B43K 23/126 with clips
• CPC Class Codes: B43K 25/022 attached to a pen cap
• CPC Class Codes: B43K 29/00 Combinations of writing implements with other articles
• CPC Class Codes: B43K 29/003 with optical equipment, e.g. magnifier, viewer
• CPC Class Codes: B43K 29/004 with more than one object
• CPC Class Codes: B43K 29/08 with measuring, computing or indicating devices
• CPC Class Codes: B43K 29/093 with calculators
• CPC Class Codes: B43K 29/10 with illuminating devices
• CPC Class Codes: B43K 7/005 Pen barrels
• CPC Class Codes: B43K 7/02 Ink reservoirs; Ink cartridges B43K7/01 takes precedence
• CPC Class Codes: G01L 1/26 Auxiliary measures taken, or devices used, in connection with the measurement of force, e.g. for preventing influence of transverse components of force, for preventing overload
• CPC Class Codes: G01L 5/162 of piezoresistors
• CPC Class Codes: G06F 3/0321 by optically sensing the absolute position with respect to a regularly patterned surface forming a passive digitiser, e.g. pen optically detecting position indicative tags printed on a paper sheet constructional details of pen-shaped pointing devices G06F3/03545, G06F3/03542, G06F3/037
• CPC Class Codes: G06F 3/03545 Pens or stylus

Abstract

A force sensor particularly suited for use in an electronic stylus that senses an applied force on its nib for recording pen strokes and handwriting recognition. The sensor has a load bearing member for receiving an input force to be sensed and associated circuitry for converting the input force into an output signal indicative of the input force. A coupling at least partially transmits the applied force to be the input force acting on the load bearing member. The force transfer coupling transferring the forces so that the applied force and the input force are not co-linear.

Claims

1. A force sensor assembly comprising:

a load bearing member for receiving an input force;

a sensor circuit for converting the input force into a signal indicative of the input force; and

,

a force transfer coupling for receiving an applied force and at least partially transferring it to the load bearing member as the input force;

wherein,

the applied force and the input force are not co-linear.

2. A force sensor assembly according to claim 1 wherein the force transfer coupling is an element configured for elastic deformation in a direction skew to the applied force.

3. A force sensor assembly according to claim 2 wherein the element is a double bowed section that bows outwardly when axially compressed by the applied force.

4. A force sensor assembly according to claim 3 wherein the load bearing member engages one of the bowed sections at its mid point such that the input force is perpendicular to the applied force.

5. A force sensor assembly according to claim 4 wherein the bowed section that does not contact the load bearing member is constrained against lateral displacement in order to stiffen the other bowed section.

6. A force sensor assembly according to claim 5 wherein the bowed sections have an arcuate lateral cross section to reduce contact friction with the load bearing member and the lateral constraint.

7. A force sensor assembly according to claim 3 wherein the load bearing member a rounded protrusion for contacting the bowed section of the force transfer coupling.

8. A force sensor assembly according to claim 1 wherein the force transfer coupling is a hydraulic element that uses the applied force to create hydraulic pressure acting on the load bearing member.

9. A force sensor assembly according to claim 8 wherein the hydraulic pressure acts such that the input force is perpendicular to the applied force.

10. A force sensor assembly according to claim 9 wherein the hydraulic fluid has low viscosity and low shear forces.

11. A force sensor assembly according to claim 10 wherein the hydraulic fluid is silicon gel.

12. A force sensor assembly according to claim 11 wherein the hydraulic fluid is contained in a reservoir at least partially defined by a flexible membrane such that the applied force acts on the hydraulic fluid via the flexible membrane.

13. A force sensor assembly according to claim 12 wherein the hydraulic fluid acts directly on the load bearing member.

14. A force sensor assembly according to claim 1 wherein the circuitry is a piezoresistive bridge circuit.

15. An electronic stylus comprising:

an elongate body;

a nib extending from one end of the elongate body;

a load bearing member for receiving an input force;

a sensor circuit for converting the input force into a signal indicative of the input force; and

,

a force transfer coupling for receiving an applied force caused by contact on the nib, and at least partially transferring it to the load bearing member as the input force;

wherein during use,

the applied force and the input force are not co-linear.

16. An electronic stylus according to claim 15 wherein the nib of the electronic stylus is a ball point writing nib with a tubular ink cartridge extending from the nib toward the load bearing member such that the end of the cartridge opposite the nib transmits the applied force to the hydraulic coupling.

17. An electronic stylus according to claim 15 wherein the output signal from the circuitry support a hand writing recognition facility.

18. An electronic stylus according to claim 15 wherein the circuitry is an integrated circuit (IC) mounted on a PCB (printed circuit board), the plane of the PCB being parallel to the longitudinal axis of the elongate body.

19. An electronic stylus according to claim 15 wherein the load bearing member can move up to 100 microns relative to the elongate body.

20. An electronic stylus according to claim 15 wherein the output signal from the circuitry support a hand writing recognition facility.