APPARATUS, SYSTEM AND METHOD FOR POWER MEASUREMENT AT A CRANK AXLE AND CRANK ARM

• US 20140165744A1
• Filed: 08/27/2013
• Published: 06/19/2014
• Est. Priority Date: 01/23/2012
• Status: Active Grant

• Current Assignee: Foundation Fitness LLC
• Original Assignee: Foundation Fitness LLC
• Inventors: Lull, Andrew P., Warner, Patrick A.
• Granted Patent: US 9,921,118 B2
• Time in Patent Office: Days
• US Class Current: 73/862.338
• CPC Class Codes: A63B 2022/0611 Particular details or arrangement of cranks
• CPC Class Codes: A63B 2220/54 Torque
• CPC Class Codes: A63B 2220/833 Sensors arranged on the exercise apparatus or sports implement
• CPC Class Codes: A63B 2225/50 Wireless data transmission, e.g. by radio transmitters or telemetry
• CPC Class Codes: A63B 24/0087 Electric or electronic controls for exercising apparatus of groups A63B21/00 - A63B23/00, e.g. controlling load
• CPC Class Codes: B62J 45/41 characterised by the type of sensor
• CPC Class Codes: B62J 45/411 Torque sensors
• CPC Class Codes: B62J 45/421 at the pedal crank
• CPC Class Codes: B62M 3/00 Construction of cranks operated by hand or foot
• CPC Class Codes: G01L 3/242 by measuring and simultaneously multiplying torque and velocity

Abstract

A power measurement assembly mounted within an axle. In a specific example, the axle is a spindle that is interconnects the cranks of a bicycle, exercise, bicycle, or other fitness equipment. The power measurement assembly may include strain gauges connected with an appropriate circuit (e.g., Wheatstone bridge) that provides an output of the force on the axle by a rider pedaling the crank. In the case of an axle, the strain gauges measure the torsion due to the applied torque on the crank. The value is converted to a power value by a processor and that value is then wirelessly transmitted for display. The processor and/or the transmitter may be mounted within the axle. A separate power measurement assembly may be mounted on one of the cranks, which may include its own processor and transmitter or may take advantage of the processor and transmitter within the axle.

Claims

19. A power measurement device comprising:

a crank axle defining a hollow inner portion supporting at least one strain gauge, the hollow inner portion further including a first circuit connected to the strain gauge and configured to provide a first output proportional to a force applied to the crank axle, the first circuit coupled with a processor configured to receive the first output from the first circuit and calculate a first force value, the inner portion further comprising a wireless transmitter in operable communication with the processor, the wireless transmitter configured to transmit information representative of the first force value.

1. A power measurement assembly comprising:

a crank axle;

a first strain gauge mounted on an inner portion of the crank axle; and

a first circuit connected to the strain gauge and configured to provide a first output proportional to a force applied to the crank axle.

2. The power measurement assembly of claim 1 further comprising a first crank arm coupled with the crank axle, the first output proportional to a force applied to the first crank arm.

3. The power measurement assembly of claim 1 wherein the first strain gauge includes at least two strain gauges.

4. The power measurement assembly of claim 3 wherein the at least two strain gauges comprise four strain gauges and wherein the first circuit comprise a wheatstone bridge circuit.

5. The power measurement assembly of claim 1 wherein the axle defines a hollow inner portion and wherein the first circuit is mounted within the hollow inner portion, and further comprising a processor first configured to receive the first output from the first circuit and calculate a first force value.

6. The power measurement assembly of claim 5 further comprising a wireless transmitter in operable communication with the first processor, the wireless transmitter mounted within the hollow inner portion, the wireless transmitter configured to transmit information representative of the first force value.

7. The power measurement assembly of claim 1 wherein the crank axle is configured to coupled with a first crank arm, the first output being proportional to a force applied to the first crank arm when the crank arm, and further comprising:

a second crank arm coupled with the crank axle, the second crank arm including at least two strain gauges, the at least two strain gauges coupled with a second circuit configured to provide a second output proportional to a second force applied to the second crank.

8. The power measurement assembly of claim 7 wherein the axle defines a hollow inner portion and wherein the first circuit and the second circuit are mounted within the hollow inner portion, the first processor configured to receive the first output from the first circuit and the second output from the second circuit, the first processor configured to calculate a first force value representative of a first force applied to the first crank and a second force value representative of a second force applied to the second crank.

9. The power measurement assembly of claim 8 further comprising a wireless transmitter in operable communication with the first processor, the wireless transmitter mounted within the hollow inner portion, the wireless transmitter configured to transmit information representative of the first force value and the second force value.

10. The power measurement assembly of claim 6 further comprising a wireless receiver operably coupled with a second processor, the second processor configured to receive a value indicative of the revolutions of at least the first crank arm and calculate a power value based on the revolutions of the crank arm and the first force value.

11. The power measurement assembly of claim 7 further comprising a housing mounted on the second crank arm and including a second circuit connected to the at least two strain gauges and configured to provide an output to a third processor proportional to a second force applied to the second crank arm, the second processor configured to calculate a second force value;

and

the housing further including a second wireless transmitter configured to receive the second force value and transmit information representative of the second force value.

12. The power measurement assembly of claim 7 wherein:

the second crank arm defines a longitudinal line wherein a first strain gauge is positioned on a first side of the line and a second strain gauge is positioned on a second side of the line equidistant from the first strain gauge, the at least first and second strain gauges being substantially parallel and on a common wall of the second crank arm.

13. The power measurement assembly of claim 12 wherein the longitudinal line is a centerline, and wherein the common wall is an inside wall of the crank arm.

14. The power measurement assembly of claim 13 further comprising:

the second crank arm further including a pedal aperture and bottom bracket aperture, the longitudinal centerline extending between the pedal aperture and the bottom bracket aperture, the at least two strain gauges including four strain gauges with a third strain gauge positioned adjacent the first strain gauge and on the same side of the centerline, and with a fourth strain gauge positioned adjacent the second strain gauge and on the same side of the centerline, the circuit being a second Wheatstone bridge circuit including the first strain gauge, the second strain gauge, the third strain gauge and the fourth strain gauge.

15. The power measurement assembly of claim 10 further comprising at least one of a reed switch, an accelerometer, and optical sensor coupled with the second processor to produce a value indicative of crank revolutions used by the second processor to determine the power value.

16. The power measurement assembly of claim 10 further comprising an element providing a value indicative of temperature, the value used to provide a temperature compensated power value.

17. The power assembly of claim 10 further comprising a display processor and associated display that are configured to receive the power value from the second processor, the power value being an instantaneous value that is averaged by the display processor.

18. The power measurement assembly of claim 17 further comprising a thermistor in communication with the second processor, the second processor further configured to adjust the power value to compensate for temperature effects, and wherein the display shows a temperature compensated and doubled power value.

20. The power measurement device of claim 19 wherein:

the at least one strain gauge comprises four strain gauges; and

the circuit comprises a Wheatstone bridge circuit.

21. The power measurement device of claim 20 wherein the hollow inner portion defines an inner wall and wherein the four strain gauges are affixed to the inner wall.

22. The power measurement device of claim 21 wherein the hollow inner portion of the axle defines a longitudinal line and a first and second strain gauge of the at least four strain gauges are mounted at about a 45 degree angle relative to the longitudinal line and a third and fourth strain gauge of the at least four strain gauges are offset about 90 degrees from the first and the second strain gauges.

23. The power measurement device of claim 19 wherein the crank axle is coupleable to a first crank and a second crank.

24. The power measurement device of claim 19 wherein the processor calculates a power value.

23-1. The power measurement device of claim 19 wherein the transmitter transmits a face value for translation into a power value.