The dataset identifies a small cluster of repeat filers, including established component manufacturers such as those behind the strongest co-assignee pairing of 17 shared filings. No single assignee shows growth in the latest tracked year, so leadership in this field is better described as an existing position held over time rather than one currently expanding. A full assignee ranking with family counts is the right next step for identifying the specific companies to watch in your sub-area.

No. Filing volume peaked at 11 records in 2017 and returned to that same level at the 2022 midpoint, which reads as a plateau rather than growth. Because publication lags filing by roughly 18 months, the most recent one or two years in the trend will always look lower than they eventually turn out to be, but the multi-year flatness predates that lag effect. Practically, this suggests a mature category where new entrants face an already-staked claim landscape.

F16D, the clutches-and-brakes classification, covers 626 of the 644 records in this search, making torque transmission the dominant framing even for patents that also address alignment or vibration. Motor vehicle and steering applications (B62D, 72 records) and vibration damping (F16F, 40 records) are meaningfully smaller but still active branches. Dedicated shaft-and-coupling classification F16C, by contrast, holds only 24 records, which is a useful signal that most inventors file coupling improvements as brake/clutch mechanisms rather than as standalone coupling devices.

The clearest gaps sit in the branches with IPC counts well below the F16D core: optical alignment measurement under G01B11, vibration isolation in pump-drive couplings (F04D and F04B), and torsional damping specific to combustion-engine coupling interfaces (F02B). These branches appear in the search scope but carry a fraction of the filings that F16D does, which points to claim space that has not been heavily contested. A first claim there would typically need to combine a specific coupling geometry with a measurement or damping function drawn from the adjacent, less-crowded classification.

US4795402A, assigned to Hackforth GmbH & Co. KG, claims a resilient shaft coupling built from two coaxial coupling rings with meshing radial cams or dogs that form chambers holding radially pre-loaded resilient members. Anyone designing a coupling that uses that specific cam-and-dog geometry with pre-loaded resilient inserts in the chambers between cams is likely to sit close to its claim scope, even decades after grant, because it remains one of the most-cited records in this corpus. Designs that achieve torsional compliance through a different mechanism — for example, laminated discs, elastomeric sleeves without the cam structure, or bellows-type flexures — sit further from this claim and are a reasonable design-around direction.