Hydraulic Actuator Monitoring Patents: Leaders & White Space 2026
- Filing has plateaued, not grown. activity peaked at 15 families in 2022 and the run rate since has not exceeded that level, despite the field's obvious relevance to predictive maintenance.
- China is the dominant receiving office by a wide margin. 52 of 108 families were filed there, roughly three times the next largest office (United States, 17), which matters for freedom-to-operate screening.
- The most-cited prior art is leakage detection hardware, not software. the top-cited records are physical seal-test rigs and cylinder-leakage detectors, not the diagnostic algorithms that later filings build on.
Filing growth compares 2021 (4 records) with 2024 (11) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 108 records in scope (CR5), not by the ranked leaders only.
What this landscape covers
Hydraulic actuator condition monitoring sits at the intersection of fluid-power hardware and industrial diagnostics: sensing leakage, seal wear and pressure anomalies in hydraulic cylinders, servo-hydraulic actuators, and related fluid-pressure systems, then feeding that signal into predictive-maintenance logic. The dataset covers 108 patent families published between 2015 and mid-2026, filtered to records whose title or abstract names condition monitoring, leakage detection, predictive maintenance or seal wear monitoring, and whose classification sits in fluid-pressure actuator control or testing/diagnostic art.
Because publication lags filing by roughly 18 months, the 2025 and 2026 counts in any trend line are undercounts of true filing activity, not evidence that inventors have stopped filing.
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Filing trend and technology composition
Two views of the same 108 families: how filing volume moved year over year, and which classification codes the claims actually sit in.
Filings plateaued after 2022
Filings ran at 12 in 2017 and reached a peak of 15 in 2022; the years since have not broken above that peak, and the flat-to-declining midpoint reading suggests the field is not currently in a growth phase — though the most recent year or two will always look artificially low due to publication lag.
F15B dominates; testing and adjacent domains are thin
F15B (fluid-pressure actuators & systems) covers 104 of 108 records, confirming this is fundamentally actuator-hardware art. G01M (testing/structure balance) appears in 25 records as the main diagnostic-method overlap. Wind turbines (F03D), load-handling vehicles (B60P), filtration (B01D), pumps (F04B), seals/gaskets (F16J) and materials testing (G01N) each appear in single digits — these are the application domains where hydraulic condition-monitoring claims have barely been extended.
Shares are the percentage of the 108 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Hydraulic Actuator Condition Monitoring with Eureka
This page is one run against one query. Ask Eureka your own question about hydraulic actuator condition monitoring and every answer comes back with the patent numbers behind it.
Try EurekaMost-cited prior art and a representative filing
US20200300277A1 — Fluid leakage detection system (KYB Corporation, 2020)
The system detects leakage of working oil in a hydraulic cylinder via a measurement unit, and a controller that distinguishes a genuine leak signal from two failure modes of the measurement unit itself: battery depletion and communication abnormality in the unit's first communication part. The diagnostic logic is built around ruling out sensor-side faults before attributing a missing signal to actual leakage.Filed by KYB Corporation, published 2020-09-24.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | CN106194900A | 一种液压往复密封动态性能检测装置及设计 | 31 |
| 2 | WO2013152807A1 | Bushing wear sensing device | 15 |
| 3 | CN105697460A | 一种高精度液压缸内泄漏检测装置 | 13 |
| 4 | CN107725535A | 一种挖掘机液压缸泄漏检测方法和装置 | 12 |
| 5 | CN104006029A | 具有漏油检测结构的液压缸 | 11 |
| 6 | WO2018153524A1 | Method and arrangement to detect an oil leakage between sections of a hydraulic cylinder | 9 |
| 7 | US20220243746A1 | Hydraulic cylinder monitoring | 8 |
| 8 | CN106884830A | 摆动式液压缸叶片密封磨损状态的监测装置及监测方法 | 7 |
| 9 | JP2017120116A | Hydraulic cylinder device including oil leakage detection mechanism | 7 |
| 10 | US20170211600A1 | System and method for heatlh monitoring of servo-hydraulic actuators | 7 |
Citation counts favour older records within the searched corpus; treat this as a measure of influence on later filings, not of current commercial relevance.
Patent titles are shown in the language they were filed in, not translated, so that each record stays verifiable against the original filing — a translated title will not match in Eureka or in any national register. Each row carries its publication number; clicking a row searches Eureka by that number.
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Browse MCP servers →What the numbers say about the field
Three readings of the same dataset: where activity is concentrated, where it isn't, and what that split implies for filing strategy.
China is the primary filing venue
Nearly half of all families in this dataset were filed at China's receiving office, roughly three times the volume of the United States (17) and EPO (14) combined with Japan and WIPO trailing further behind. A freedom-to-operate review that skips Chinese filings is reviewing a minority of the art.
No assignee is currently accelerating
Every tracked assignee in the recent-year momentum data shows zero filings in the latest year, including large industrial names. That is consistent with the overall plateau after 2022 rather than any single company retreating from the space.
Influence sits with hardware, not algorithms
The most-cited records describe physical test rigs and leakage-detection hardware for hydraulic seals and cylinders, not the diagnostic software layer. Later filers appear to have built their monitoring logic on top of these mechanical sensing concepts rather than displacing them.
This is a field of solo filers
Only two co-assignee pairings appear across 108 families, both involving the same corporate-individual grouping. Cross-company joint filing is essentially absent, which is unusual for a diagnostics niche this technically narrow.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to hydraulic actuator condition monitoring, with the prior art for and against each one.
Who is filing, and where the claim space is still open
Filing is spread across industrial vehicle, aerospace and academic assignees with no single company commanding a majority share, and recent momentum has cooled across the board.
The leaderboard has gone quiet
Every one of the assignees with tracked recent-year momentum — including KYB, Siemens Gamesa and Wagner-linked entities — shows zero filings in the most recent year, one (Heil Co) with a reported -100% year-on-year change. That is a plateau signal across the leaderboard, not a single company's retreat.
A mix of OEMs, academic and cross-border filers
The assignee set spans industrial vehicle and construction-equipment makers, an aerospace name, wind-energy filers, and university research groups, alongside Japanese and German industrial names. That breadth suggests the underlying sensing techniques are being adapted independently across several end markets rather than converging on one dominant applicant.
Almost no joint filing
With just two co-assignee pairs identified across the entire dataset, and both tied to the same corporate-individual relationship, this is not a field where companies are pooling IP through joint applications. Most participants are filing solo.
| Assignee | Recent year | YoY |
|---|---|---|
| Haiwo Holdings Co., Ltd. | 0 | — |
| Primetals Technologies Germany GmbH | 0 | — |
| KYB Corporation | 0 | — |
| Siemens Gamesa Renewable Energy | 0 | — |
| WAGNER VERMOGENSVERWALTUNGS GMBH & CO KG | 0 | — |
| HEIL CO | 0 | -100% |
| Wuhan University of Technology | 0 | — |
| Sintokogio, Ltd. | 0 | — |
Where to take this
The dataset points to a field with an occupied hardware core and thinner claims at its edges. Two directions follow from that.
Screen the adjacent IPC branches before filing
F03D, B60P, B01D, F04B, F16J and G01N each show only a handful of overlapping records. Before assuming an application domain is open, run a targeted search inside that specific subclass rather than relying on the F15B core count.
Explore white space in EurekaTreat China filings as first-order prior art
With roughly half of all families filed in China, any competitive or FTO review that starts and ends with US/EPO literature is working from an incomplete picture of what's already claimed.
Run a China-inclusive search in EurekaCommon questions about this landscape
It covers technology for sensing the operating state of hydraulic cylinders, servo-hydraulic actuators and related fluid-pressure systems — most commonly leakage detection, seal wear monitoring, and pressure or flow anomaly diagnostics that feed into predictive-maintenance decisions. In classification terms this dataset sits primarily in F15B (fluid-pressure actuators and systems) with a strong secondary presence in G01M (testing and structure balance). It excludes general hydraulic system design that has no diagnostic or monitoring element.
Filing is spread across industrial vehicle and construction equipment makers, aerospace firms, wind-energy companies, and university research groups, with no single assignee holding a commanding share of the 108 families tracked here. Notably, every tracked assignee shows zero filings in the most recent year, which points to a broadly cooled filing environment rather than one leader pulling ahead. A full ranking by family count is the more reliable way to assess relative position than any single company's recent activity.
Filing peaked at 15 families in 2022 and has not exceeded that level since, with the flat-to-declining trend continuing through the most recent complete years. That said, publication typically lags actual filing by around 18 months, so the last one to two years in any count will understate real activity. The honest read is a plateau rather than clear growth or clear decline.
52 of the 108 families in this dataset were filed at China's receiving office, roughly three times the volume filed in the United States and more than the US and EPO combined against the rest. This likely reflects both the concentration of hydraulic equipment manufacturing in China and strong domestic patenting incentives for incremental diagnostic hardware. Anyone doing freedom-to-operate work in this space should treat Chinese-language filings as core prior art, not a supplementary search.
The patent, assigned to KYB Corporation, covers a fluid leakage detection system that distinguishes an actual oil leak in a hydraulic cylinder from two failure modes of its own measurement unit — battery depletion and a communication fault in the unit's first communication part. The narrow scope is that specific fault-discrimination logic, not leakage detection generally. Designs that use different means of ruling out sensor-side faults, or that don't attempt that discrimination at all, sit outside its claim scope, though a detailed claim chart is needed to confirm this for any specific product.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.