Design patent applicants often choose to utilize 3D drawing software to produce drawings in their design patent applications. In such drawings, the surface shape or curvature of the rounded corners of the article embodying the design are usually represented by tangent lines, even though they are absent from the physical article. Since there is a risk that tangent lines may be interpreted as claimed ornamental features, which can be different from what the applicant intends to claim, this raises the crucial issue of how to represent tangent lines in design patent applications. This is not explicitly stipulated in Taiwan’s patent-related regulations or patent examination guidelines. Neither is there an established practice in Taiwan regarding how to interpret the scope of patent protection represented by tangent lines.

It is noteworthy that in the 2020 design patent litigation case involving Simplehuman, LLC and iTouchless Housewares & Products, Inc., the US Court interpreted the tangent lines in the plaintiff’s design patent as ornamental lines. Since practices in Taiwan are prone to being influenced by US rulings, there remains a risk of tangent lines being interpreted as ornamental lines when filing design patent applications in Taiwan, despite the absence of relevant case law. To mitigate such risk, applicants may consider adopting the following drafting techniques for tangent lines in the drawings:

1. Omitting tangent lines in the views.
2. Changing tangent lines to long dashed lines and adding shading lines near the object’s surface contour where appropriate to illustrate surface contour (For instance, TW D229175, TW D230449).
3. Changing tangent lines in the views to dash-dot-dot lines (For instance, TW D229280, D229196).
4. Representing tangent lines with stippling shading (For instance, TW D205987, US D1015782).
5. Similarly representing tangent lines with solid lines but using the solid lines with lighter line weight to differentiate tangent lines from claimed lines (For instance, TW D228190, US D0984109).

Among the above five drafting techniques for showing tangent lines, the 2nd technique (using long dashed lines and shading lines) and the 3rd technique (dash-dot-dot lines) are more ideal as they can distinguish tangent lines from the claimed lines more clearly.

In contrast, the 5th technique (modifying the line weight of the solid lines representing tangent lines to be lighter line weight) is less ideal because the discrepancy in line weights is not sufficiently distinctive. Moreover, when the drawings are scaled down to two-thirds their original size, the lines may become too thin, leading to broken or disappearing lines, resulting in unclear views.

Applicants are reminded that, in addition to adopting the above drafting techniques for tangent lines when providing views, it is critical to make a statement in the design description within the specification that the tangent lines are not ornamental features and form no part of the claimed design. This will ensure the scope of the claim is clear to the examiner.