Careful - Classification searches can miss relevant patents - 2025
June 2025 Patent classification codes, such as CPC and IPC codes, are used by many patent searchers and search systems to find similar patents. There are are good reasons for this - they are widely used and can be useful in some cases.
However, there are good reasons not to rely on them too heavily — they can be highly unreliable and are almost certain to miss key patents.
To show what I mean, I am going to run a case study. In a previous blog we talked about US patent application, 20170063194, filed by Apple for a Electromagnetic Levitator.
Ambercite Ai can quickly provide a similar patents, including a combination of known and unknown (predicted) citations. Running the query below will provide a list of 50 patents (or up to 401 similar patents if you wish):
But for now we might focus on the top 10 of these patents, shown in the list below. 8 out of these 10 patents are known citations, which two are 'unknown' citations, or predicted citations. All refer to magnetically levitated objects.
|
Similar
patents found, in ranked order |
Similarity Rank |
Known Citation |
CPC Classes |
|
US20170063194 Electromagnetic
Levitator, (Priority year 2017) |
Query patent |
Query patent |
F16C32/0444; F16C32/0446; F16C32/0453; F16C32/0457, H02K11/215;
H02K7/09 |
|
US7348691B2 Magnetic
levitation apparatus (2002) |
1 |
Known |
A63H33/26; B60L13/04; F16C32/044; F21V21/096; F21V23/02; H02N15/00;
H02N15/02 |
|
US4585282A Magnetic
levitation system (1983) |
2 |
Known |
F16C32/0451 |
|
US9352665B2 Magnetically
lifted vehicles using hover engines (2013) |
3 |
Known |
A63C17/00; B60L13/04; B60L2220/12; B60L2220/50; H02K5/04;H02K7/09; H02N15/0 |
|
US5168183A Levitation
system with permanent magnets and coils (1991) |
4 |
Known |
F16C32/044; H02N15/00 |
|
US5332987A Large
gap magnetic suspension system with superconducting coils (1992) |
5 |
Known |
H02N15/00 |
|
US8500509B2 Entertainment
device including a remote controlled magnetic mini-craft (2007) |
6 |
Known |
A63H23/14 |
|
US8258663B2 Magnetic
levitation novelty device (2009) |
7 |
Unknown |
H02N15/00 |
|
US9325220B2 Propulsion
and control for a magnetically lifted vehicle (2013) |
8 |
Known |
A63C17/00; A63C17/16; B60L13/04; H02K7/09;H02N15/00 |
|
US7110236B2 Magnetic
suspension system (2002) |
9 |
Unknown |
H02N15/00 |
|
US9245679B1 Wine bottle
floatation device (2014) |
10 |
Known |
A47G2200/10;
A47G23/0241; H02N15/00 |
In the column on the right, we show the listed CPC codes. The CPC codes associated with the query patent are highlighted in blue, allowing us to see where they appear in the most similar patents. Only two of the most similar patents found share any of these CPC codes.
The most common CPC code in these results (marked in pink) is H02N15/00, which refers to holding or levitation devices using magnetic attraction or repulsion, not otherwise provided for. This code is clearly relevant, yet it was not found in the Apple patent application.
Implications
In this case, if a searcher was to rely on the listed CPC codes alone to find similar patents, they would miss similar patents, unless they ran a very broad search.
In this case, the examiner for the Apple 2017 patent application clearly ran a search that went beyond the limitations of these CPC codes, which is why they found these other patents - or at least 8 out of these 10 most similar patents.
Yet, there are patent landscaping systems out there that do propose to find similar patents based on patent classification codes. And there are plenty of patent searches run that use patent classification codes as key limitations.
All which makes us wonder - what relevant patents are being missed by relying on patent classification codes?
The alternative - ambercite ai
Exactly as shown before, Ambercite does not rely on any assumptions regarding patent classification codes when finding similar patents - and instead finds similar patents by applying its AI engine to its database of millions patent citation. Contact us to arrange a demonstration and free trial of just how easy it can be to find prior art and other relevant patents using Ambercite Ai.