Inspection Checklist for Utility Patent Drawings

Inspection Checklist for Utility Patent Drawings

Use this chapter as a pre-filing checklist for utility patent drawings.
Where helpful, references to other chapters are shown in parentheses—for example:
(see “Figure Standards,” §2 Spacing Between Figures).

1. Media & Source Artwork

1.1 Raster vs. Vector

  • Do you have raster images (scans, JPEG/PNG) of black line drawings?

    • Are all lines smooth, solid, and dark enough? (see “Line Quality Standards,” §2 Character of Lines)
    • Are all characters at least 3.2 mm (⅛", ~12 pt) and clearly readable? (see “Character Size Standards,” §1)
    • If yes to both, the raster image may be used.
      If no, redraw as a clean vector line drawing.

  • Do you have color raster images?

    • Have you converted them to black-and-white?
    • After conversion, are line and text quality still acceptable?
    • If no, redraw as vector line drawings.

1.2 Fills, Photos, and Prototypes

  • Are there any gray, color, or solid-black fills used to show shape instead of lines?
    • Convert them to outline + hatching/shading lines only (no solid fill), unless they are intentional color claims. (see “Line Quality Standards,” §3 Hatching & Shading)
  • Are there any photos or bitmap images that could be shown as line art?
    • Trace or redraw them as vector black line drawings.
  • Are drawings based on rough prototype photos?
    • Have you simplified/idealized parts so they look like clean engineered views, not rough product photos?

2. Sheet Setup: Paper, Margins, and Numbering

2.1 Paper Size & Margins

(see “Page & Margin Standards” chapter)

  • Are all sheets the same size (Letter 8.5"×11" or A4 210×297 mm)?
  • Does every sheet respect the minimum portrait margins (imaginary, not drawn)?
    • Top ≥ 1 in (25 mm)
    • Left ≥ 1 in (25 mm)
    • Right ≥ 0.6 in (15 mm)
    • Bottom ≥ 0.4 in (10 mm)
  • For landscape sheets, are margins applied as if the sheet were in portrait?
    (Top 1 in, bottom 0.6 in, left 0.4 in, right 1 in.)

2.2 Sheet Numbering

  • Are sheets numbered in Arabic numerals using the format:
    sheet_number / total_sheets (e.g., 1/4, 2/4, 3/4, 4/4)?
  • Is the sheet number placed:
    • On the top center, just under the top margin, or
    • In the upper-right of the sight if the center is occupied by a figure?
  • For landscape sheets, is the sheet number:
    • Placed on the right side of the sheet,
    • Oriented as though the sheet were in portrait?

3. Figure Layout, Orientation, and Numbering

(see “Figure Standards” & “Figure Number Standards”)

3.1 Orientation & Spacing

  • Is each figure upright relative to the top of the sheet (portrait or landscape)?
  • On landscape sheets:
    • Are figures and text rotated into landscape, while sheet numbers stay in portrait orientation?
  • Are figures far enough apart so their lines and parts cannot be confused?
  • Are there no construction/projection lines connecting separate figures
    (except for electrical waveforms showing timing)?

3.2 Size and Arrangement

  • Are figures made as large as possible within the margins without crowding?
  • Are figures arranged so:
    • Lower-numbered figures appear on earlier sheets.
    • Figure numbers increase from sheet to sheet (do not restart at FIG. 1).
    • On each sheet, figures generally progress left-to-right, top-to-bottom.

3.3 Figure Numbers & Prior Art Labels

(see “Figure Number Standards”)

  • Are all figures numbered in consecutive Arabic numerals beginning with FIG. 1?
  • Is each figure prefixed with “FIG.” or “Fig.” (e.g., “FIG. 3”)?
  • Does each figure number refer to one specific figure only?
  • If the figure shows prior art, is it labeled “Prior Art” next to or just below the figure number
    (e.g., FIG. 1 — Prior Art)?

4. Special View Types

4.1 Sectional Views

(see “Figure Standards,” §11 Sectional Views)

  • Where internal structure must be shown, are sectional views provided?
  • On the corresponding general view:
    • Is there a broken cutting plane line?
    • Are arrows at each end showing the direction of sight?
    • Is the section figure number written next to the arrows (e.g., “2” or “2–2”)?
  • In each sectional view:
    • Are cut surfaces hatched (e.g., at ~45°)?
    • Are adjacent parts distinguished by changes in hatch angle/spacing?

4.2 Partial Views & Tiled Figures

(see “Figure Standards,” §9 Partial Views)

  • If a figure is too large for one sheet, is it split into partial views?
  • For mechanical views:
    • Are partial figures arranged so sheets can be tiled without ambiguity (side-by-side, top-to-bottom, or grid)?
    • Are dot–dot–dash (phantom) lines used along broken edges?
    • Are all partial sheets labeled with the same base figure number plus letter suffixes (e.g., FIG. 3A, FIG. 3B)?
  • For flowcharts/diagrams:
    • Are connector circles with letters (A, B, C…) used to show continuation?
    • Are matching connectors used on the continuation sheet?

4.3 Shortened (Broken) Figures

(see “Figure Standards,” §10 Shortened Figures)

  • For very long objects, are they shortened instead of squeezed into tiny scale?
  • Are breaks shown with standard break symbols (zig-zag / phantom) and no essential detail removed?

4.4 Exploded Views & Brackets

(see “Figure Standards,” §8 Exploded Views)

  • Where assembly relationships are important, are exploded views provided?
  • Are parts separated enough to show how they fit?
  • Are projection lines used as needed to indicate alignment?
  • If the figure has disconnected components:
    • Are brackets used to “embrace” all parts that belong to the same figure, even when not exploded?

4.5 Enlarged Views

  • Are enlarged views provided for small or complex areas?
  • In the general view:
    • Is the enlarged region surrounded by a dashed circle or boundary?
    • Does the circle carry a reference indicating the enlarged figure number?
  • In the enlarged figure:
    • Is the same circle/boundary shown around the enlarged area?

4.6 Moving Parts & Motion Arrows

(see “Figure Standards,” §12 Moving Parts)

  • For mechanisms with moving parts:
    • Are arrows used to show directions of motion (linear and rotational)?
    • If multiple arrows appear, are they distinguished with different reference numbers?
    • Are phantom lines or additional figures used appropriately to show alternate positions?

5. Reference Numbers & Lead Lines

(see “Reference Number Standards” & “Lead Line Standards”)

5.1 Reference Numbers

  • Does every part mentioned in the specification have a reference number in the drawings?
  • Does every numbered part in the drawings appear in the written description?
  • Is each part given one unique number (same number for same part in all figures)?
  • Are identical, interchangeable parts given the same number only when not distinguished in text?
  • Are letters used only for:
    • non-tangible elements (e.g., airflow A) or
    • standard electronics notation (R1, C2, etc.)?
  • Are all characters (numbers & letters):
    • in a simple, non-ornate font (no script or decorative styles)?
    • at least 3.2 mm (⅛", ~11 pt) high, except subscripts/superscripts?

5.2 Placement of Reference Numbers

  • Are numbers placed close to the part they identify, but not overlapping it?
  • Are they positioned far enough from other parts to avoid ambiguity?
  • Are they preferably outside the figure where possible to reduce clutter?
  • Are they never drawn over any object or hatch lines?
    (White background or hatch gaps are used where numbers lie on cross-sections.)

5.3 Lead Lines & Underlines

  • Does every reference number connect to its feature via a lead line or underline?
  • Are lead lines:
    • straight or smoothly curved
    • clearly pointing to the part, with the end touching the object
    • not crossing or overlapping other lead lines whenever possible
    • positioned at a distinct angle from nearby shape edges to avoid confusion?
  • If a part appears in multiple figures, are separate lead lines and numbers used in each figure (no single number with two lead lines connecting figures)?
  • Where numbers lie directly on a surface or section, is a simple underline used instead of a lead line, with hatching interrupted to leave room—used sparingly?

5.4 Arrows

  • Are arrows used correctly to:
    • designate a group of parts with a single number,
    • indicate the cutting plane and direction for sectional views,
    • or show movement?
  • Where multiple arrows appear, are they given distinct reference numbers to avoid confusion?

6. Line Quality, Types, and Hatching

(see “Line Quality Standards”)

6.1 Line Quality

  • Are all drawings in black lines (no gray anti-aliasing or colored lines)?
  • Are all lines:
    • Dense and dark enough to survive photocopying and reduction?
    • Uniform in thickness along their length (except intentional thick vs. thin line use)?
    • Smooth, not jagged, with no feathered or pixelated edges?
    • Unbroken, with no random gaps?

6.2 Line Types

  • Are allowed line types used correctly:
    • Solid for visible edges and shading lines
    • Dashed for hidden edges
    • Phantom (dash–dot–dot–dash) for parts not claimed or for continuation edges
    • Dash–dot–dash projection lines (e.g., in exploded views) when needed?
  • Are broken line styles used consistently across all figures?

6.3 Hatching & Shading

  • Are hatch lines thin, evenly spaced, and at a consistent angle (typically ~45°)?
  • Are adjacent parts in section distinguished by:
    • different hatch angles, or
    • different spacing/offsets?
  • Are there no large solid black areas except bar graphs or explicit color-claim graphics?

7. Prohibited Elements

(see “Prohibited Elements” chapter)

  • No scale notes such as “Actual Size” or “Scale 1:2.”
  • No morally offensive or irrelevant images.
  • No trademarks/service marks (e.g., logos) unless proprietary rights are established.
  • No centerlines drawn solely to show axes of circles (rarely enforced but best avoided).
  • No circles or brackets surrounding reference numerals.
  • No descriptive phrases like “ON/OFF SWITCH” or “SERATED SURFACE” outside of allowed contexts:
    • Flowcharts
    • Block diagrams
    • Tables and graphs where labels are indispensable.
  • No copyrighted artwork used without ownership/permission.
  • No lines connecting separate figures, except between electrical waveforms to show timing.

8. Quality-Control Questions (Final Review)

Use these questions for a final QC pass or to instruct an assistant:

  • Are all figures aligned and evenly spaced, with consistent margins and layout?
  • Are figure numbers, sheet numbers, labels, and line types consistent across pages?
  • Are all text elements:
    • the approved simple font (e.g., Arial-like, non-ornate)?
    • at or above minimum size?
    • black only, with no color or gray?
  • Do reference numbers and text fit within shapes or areas without touching borders?
  • Are line breaks, spacing, and alignment clean and readable?
  • Are lead lines:
    • clearly distinguishable from object edges,
    • not crossing each other unnecessarily,
    • not shared between separate figures?

Special Cases

  • Dimensions are omitted unless critical to understanding or distinguishing from prior art.
  • Exploded views:
    • Use brackets and/or projection lines correctly.
  • Long objects:
    • Properly shortened with break symbols, or split into partial views if needed.
  • Sectional views:
    • Have cutting plane indicators, arrows, and varying hatching where appropriate.
  • Enlarged views:
    • Have clear callouts and matching figure numbers.
  • Special content types (if present) all comply with line, text, and numbering rules:
    • electronic schematics
    • block diagrams & flowcharts
    • graphs & waveforms
    • chemical formulas
    • tables
    • screenshots / GUI figures
    • mixed symbolic + physical drawings

By running each drawing set through this checklist—and cross-referencing the detailed rules in the other chapters—you can systematically catch most USPTO drawing defects before filing and keep your utility figures consistent, clear, and examination-ready.