According to Judge Rader in Frankâ€™s Casing Crew & Rental Tools, Inc. v. Weatherford Intâ€™l, Inc. (Fed. Cir., November 30, 2004)
The primary difference between structural equivalents under Â§ 112, Â¶ 6 and the doctrine of equivalents is a question of timing. Al-Site Corp. v. VSI Intâ€™l, Inc., 174 F.3d 1308, 1321 n.2 (Fed. Cir. 1999). As this court has explained, "[a] proposed equivalent must have arisen at a definite period in time, i.e., either before or after [patent filing]. If before, a Â§ 112, Â¶ 6 structural equivalents analysis applies and any analysis for equivalent structure under the doctrine of equivalents collapses into the Â§ 112, Â¶ 6 analysis. If after, a non-textual infringement analysis proceeds under the doctrine of equivalents." Id. In this case the proposed equivalent â€“ a lifting mechanism without a lift plate â€“ was in use before filing of the patent, therefore this court need not conduct a separate analysis under the doctrine of equivalents. See, e.g., Kemco Sales, 208 F.3d at 1364 ("Because the 'way' and 'result' prongs are the same under both the 35 U.S.C. section 112, paragraph 6 and the doctrine of equivalents tests, a structure failing the 35 U.S.C. section 112, paragraph 6 test under either or both prongs must fail the doctrine of equivalents test for the same reason(s).").