Prior art

An analysis of the prior art cited during the prosecution of US patent 6,434,212 and in subsequent post-grant challenges reveals several key references. The most relevant art is that which was successfully used in the inter partes review (IPR) proceedings to invalidate claim 6.

I. Prior Art Cited in Successful IPR Challenges

The following references were central to the PTAB's decision to invalidate claim 6 of the '212 patent for obviousness. While they did not anticipate the claims under 35 U.S.C. § 102 (as no single reference contained every element), their combined teachings were found to have rendered the invention in claim 6 obvious.

1. US Patent 5,891,042 ("Sham")

• Full Citation: US 5,891,042, "Fitness monitoring device having an electronic pedometer and a wireless heart rate monitor," issued to Acumen, Inc.
• Publication/Filing Date: Filed Sep 9, 1997; Published Apr 6, 1999. This qualifies as prior art.
• Brief Description: The Sham patent describes an integrated fitness monitoring device worn on the wrist. It includes a pedometer for step counting, a wireless receiver to get heart rate data from a separate chest-strap transmitter, and a processor. It calculates distance by multiplying the step count by a user-entered, fixed stride length.
• Relevance to Claims: Sham was the primary reference used against claim 6 in IPR2017-02012.
  • Claim 1, 2, 5 (Exercise monitoring device with strap, step counter, heart rate monitor): Sham discloses a wrist-strapped device that integrates a step counter and a heart rate monitor receiver. However, it critically fails to teach a stride length that varies according to the rate at which steps are counted. Instead, it uses a fixed stride length. Therefore, Sham does not anticipate claims 1, 2, or 5.
  • Claim 6 (Pedometer with transmitter/receiver and data processor): The PTAB found that Sham taught most elements of claim 6: a step counter, a transmitter (for the heart rate portion), a receiver (on the wrist), and a data processor that calculates distance. The key missing element was a processor programmed to "derive an actual stride length from a range of stride lengths calculated from a range of corresponding stride rates."

2. US Patent 5,976,083 ("Livingstone")

• Full Citation: US 5,976,083, "Portable aerobic fitness monitor for walking and running," issued to Living Systems, Inc.
• Publication/Filing Date: Filed Jul 30, 1997; Published Nov 2, 1999. This qualifies as prior art.
• Brief Description: Livingstone discloses a portable fitness monitor that calculates distance traveled with improved accuracy. It explicitly teaches that a person's stride length changes with their speed or cadence (stride rate). It describes a method where the device stores a lookup table or uses a formula to correlate different stride rates with different stride lengths to calculate distance more accurately than a device using a single, fixed stride length.
• Relevance to Claims: Livingstone was the secondary reference that, when combined with Sham, rendered claim 6 obvious.
  • Claim 1, 2, 5, 6 (Variable stride length based on rate): Livingstone provides the central inventive concept of the '212 patent: varying the stride length based on the stride rate. It teaches calculating a "cadence-dependent stride length" to determine total distance. The PTAB found that it would have been obvious to a person of ordinary skill in the art to implement Livingstone's cadence-dependent stride length calculation into the hardware system described by Sham. This combination supplied the missing element needed to invalidate claim 6. Livingstone by itself does not anticipate the specific hardware configuration of a separate transmitter/receiver claimed in claim 6, nor the specific "plurality of calibration samples" required by claims 2 and 5.

II. Other Key Prior Art Cited by Examiner or in Patent Background

These references were considered during the original examination or were discussed by the inventor in the patent text as representing the state of the art at the time.

1. US Patent 4,371,945 ("Karr")

• Full Citation: US 4,371,945, "Electronic pedometer," issued to Lawrence Joseph Karr.
• Publication/Filing Date: Filed Dec 1, 1980; Published Feb 1, 1983. This qualifies as prior art.
• Brief Description: Karr describes an electronic pedometer that aims for high accuracy by measuring the length of each individual stride. It uses an ultrasonic transmitter on one leg and a receiver on the other to measure the distance between the legs for each step. This stride data is then sent via a VHF transmitter to a wrist-mounted display.
• Relevance to Claims: Karr was cited in the IPRs and is discussed in the '212 patent's background section.
  • Claim 6 (Pedometer with transmitter/receiver): Karr discloses the system architecture of a body-worn sensor (ultrasonic modules) wirelessly transmitting data to a wrist-mounted receiver and display. This teaches the general system structure of claim 6.
  • Claim 1, 2, 5, 6 (Variable stride length): Karr teaches a variable stride length, but it does so through direct, real-time physical measurement of each stride. It does not teach calculating or deriving a variable stride length based on the rate of steps or from a set of calibration samples. The '212 patent's method of using stride rate as a proxy for stride length is a different technical approach. Therefore, Karr does not anticipate the claims.

2. US Patent 4,771,394 ("Puma")

• Full Citation: US 4,771,394, "Computer shoe system and shoe for use therewith," issued to Puma AG.
• Publication/Filing Date: Filed Feb 3, 1986; Published Sep 13, 1988. This qualifies as prior art.
• Brief Description: The Puma patent describes a "computer shoe" with a heel-mounted sensor. It calculates distance based on footstrike counts and time. The patent acknowledges the relationship between stride length and foot speed and requires a complex calibration process involving at least 15 test runs over a known distance to build a data model.
• Relevance to Claims: This is discussed in the '212 patent's background.
  • Claim 1, 2, 5, 6 (Variable stride length based on rate): Like Livingstone, the Puma patent teaches the core concept that stride length is not fixed and varies with speed. It discloses a method of calculating distance as a "function of stride time," which is conceptually similar to stride rate. However, its implementation in a shoe and its requirement for extensive, user-entered calibration data differ from the specific methods claimed in the '212 patent, particularly the use of a "plurality of calibration samples" to derive a range as claimed in claims 2 and 5. It does not anticipate the claims but shows the general concept was known in the art.