Filing volume rose to 71 records in 2018 and then declined steadily, reaching 9 at the 2022 midpoint. This pattern typically appears when the dominant mechanical approaches in a field — here, film cooling hole shapes, impingement cavity layouts and serpentine internal passages — have already been claimed by the major assignees, leaving later filers with less open space to patent around. It does not necessarily mean the underlying engineering work has stopped; it means the patenting of new geometric variations has slowed. Readers should also factor in the roughly 18-month publication lag, which understates filing activity in the last one to two years of any dataset.

The assignee ranking in this dataset is led by established turbine OEMs including General Electric, United Technologies, Rolls-Royce, Florida Turbine Technologies, Mitsubishi Heavy Industries and Alstom Technology, alongside research partners such as Penn State Research Foundation. Notably, recent-year momentum data shows all of these leading assignees recorded zero filings in the most recent year covered, consistent with the broader decline in filing volume across the field rather than any single company withdrawing. A full ranking table with family counts is rendered separately on this page.

Film cooling ejects a thin layer of coolant air through small holes onto the external surface of the blade, forming a protective film between the hot gas path and the metal. Impingement cooling instead directs coolant jets internally against the inside wall of the blade cavity to remove heat directly through convective transfer, often used near the leading edge where thermal loads are highest. Many patented designs, including the representative record on this page, combine both mechanisms in a single serpentine circuit — impingement cooling the leading edge cavity first, with spent air then discharged through film cooling holes downstream.

The core mechanical design space, covered by IPC class F01D, holds 1,135 of the 1,210 records in this dataset, making hole geometry and internal passage layout heavily contested. By contrast, manufacturing-adjacent classes such as B23K (welding and brazing), B23P (metalworking) and B22C (foundry moulding) each carry only 16 to 27 records, suggesting the methods used to produce cooling passages — brazing joints, casting internal surfaces, additive lattice structures — are comparatively under-claimed relative to the geometry itself. This is a reasonable starting point for a design-around or a novel process claim, though it warrants its own targeted prior art search.

US8016564B1, assigned to Florida Turbine Technologies and granted in 2011, claims a turbine rotor blade using a low-flow 3-pass serpentine circuit that combines leading-edge impingement cooling with downstream film cooling on the pressure and suction side walls. It does not block all turbine blade cooling designs; it specifically covers this particular serpentine routing and the sequence of impingement-then-film-discharge for the leading edge and forward mid-chord region. Designs using different passage counts, different cooling sequences, or cooling mechanisms outside this specific serpentine architecture would need a separate freedom-to-operate assessment against this and the other most-cited records in the field.