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Invalidating a welding machine patent

Invalidating A Welding Machine Patent

An attorney in a law firm, approached us with this patent, the first step was understanding the technology discussed. Attorney had shared list of references which he was aware of as he had already performed search from others as well.

It was a challenge to find a good reference list shared by client has almost every type of reference.

Overview of Patent

The patent for invalidation was related to the field of welding machines, particularly a reversible welding mask i.e. welding mask was rotated 180-degrees for welding, welding mask had clips to hold free ends of stator. Machine further had a cleaning device installed in lower section.

Search Methodology

Initially the patent was thoroughly studied and file wrapper was analyzed. File wrapper analysis gave clear understanding of the grounds on which the patent was granted. The keywords and their synonyms were extracted.

We began with the search to find prior art in the field of stator free end welding machines. The preliminary search was performed on the patent databases like ORBIT, ESPACENET, GOOGLE PATENTS, FPO and PATENTSCOPE. The IPC/CPC classes related to the particular field were also analyzed to perform class related search. The assignee/inventor search & citation analysis of the related and relevant references was also performed.

Challenges Faced During Search

During the search, we found relevant prior arts related to this field but

  • Few were already known to the client as he had already shared the list of known references with us.

  • Few disclosed welding workpiece holders but, failed to disclose us of a rotatable welding mask,

  • Few disclosed workpiece holder with rotatable mask, but had different workpiece loading and unloading position along with restricted rotation of workpiece.

  • Few references disclosed movable workpiece holder which can be moved up, down and forward, backward.

In the case of non-patent literature searching, the identified results were only related to the welding mask, but were not having clips and were not reversible.

We decided to broaden the search and focused on using combination of classes only as it had helped me earlier to find good relevant reference.

Game Changer

While analyzing the references patents and research papers, we recognized that the most of references were specifically of Korean & China jurisdiction. It was an indication to us that these countries are actively working on this technology on a big scale. Then, we started broad searching on the native databases Korean, Chinese, Japanese (KIPRIS & CNIPA).

Search was now directed to finding a welding machine used for holding and welding any type of workpiece, and workpiece can be rotated 180-degrees either for welding or for cleaning.

  • This strategy worked, we found Korean patents disclosing welding machines having reversible (180-degrees rotatable) welding masks and used clips to hold a workpiece.

  • We also found a good reference which disclosed installation of cleaning device in lower section of machine, but it was a separate unit which was installed after welding for washing. This reference provided teaching that cleaning device can be installed in lower section of welding machine.

We also performed broad non-patent literature search and found some companies making welding positioners.

We searched for demonstration videos, technical white papers, datasheets, of products manufactured by identified assignees and are published prior to the priority date.

We found one company video on YouTube and was uploaded before priority date of patent. Video disclosed a 180-degree rotatable workpiece holding and welding bench. For further analysis, product broachers, data sheets were analyzed. This company video and its data sheets were very useful as it disclosed a 180-degree rotatable workpiece holding and welding bench which was the novelty of the patent to be invalidated.


Claim charts were prepared for identified prior arts with the proper searcher comments and summaries for each prior art. Along with relevant Chaim charts relevant text mapping were also provided for additional references which when combined provided teachings to make such a machine.