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Patent CN106427302B

Updated October 23, 2026

Smart Pencil Cap That Checks the Point with a Camera

Blunt pencils make thick, smudgy lines, and nobody notices until the drawing or the test sheet is already spoiled. This pencil cap checks for you. A small camera sits in the closed end, looking straight at the point. Slide the pencil in, press the button, and a sensor confirms the pencil is there, the camera takes a picture, and a controller measures the width of the lead. If it is wider than the chosen limit - 0.5 mm or 0.7 mm - the cap reminds you to sharpen with a sound, light or vibration. A small screen shows the point inside a ring gauge, and an alarm can warn when the pencil is missing from the cap.

  • China invention patent - lapsed
  • No filings outside China
  • Smart stationery
  • Molded cap, camera module, small display
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Smart Pencil Cap That Checks the Point with a Camera - patent drawing

📷

Camera in the cap

A tiny image sensor in the closed end looks straight at the pencil point.

📏

Measures the point

The controller reads the lead width from the picture and compares it with a 0.5 or 0.7 mm limit.

🔔

Sharpen reminder

Sound, light or vibration when the point is too blunt; a screen shows it inside a ring gauge.

🚨

Missing-pencil alarm

An optional alarm goes off when the sensor finds no pencil in the cap.

🔥 Popularity – views

Bring this product to market

  1. ✓ Patent vetted China-only family and legal status checked
  2. 2 Product brief · now How it works, uses and options written up
  3. 3 Prototype First samples for buyers to review
  4. 4 Pilot run Small first batch for launch customers
  5. 5 Volume production Repeat orders at scale

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The problem

Pencils wear down gradually, so people rarely notice when the point has become too thick - until the handwriting is fuzzy, a technical drawing has uneven lines, or a bubble on an answer sheet is badly filled. The patent names exactly this: people are busy, forget to sharpen, and the work suffers. A pencil cap is already on most pencils in a school bag; it is the obvious place for a check.

The solution

The patent turns the cap into a small measuring device:

  1. The cap body (111) is a hollow tube with an open end (1112) for the pencil and a closed end (1114).
  2. An image unit (113) - a tiny camera - sits at the center of the closed end, right where the point arrives.
  3. A sensor (114) near the open end detects whether a pencil is inside.
  4. When the check button (115) is pressed, the controller (112) confirms a pencil is present, triggers the camera and reads the diameter of the lead at the point from the picture.
  5. If the diameter is larger than the set value, a reminder unit (116) signals by sound, light or vibration.
  6. Preset buttons (117) select the limit - 0.5 mm or 0.7 mm in the patent. A display (119) shows the point with a ring gauge (1192) of that size, and an alarm unit (118) can sound when no pencil is in the cap.
Smart Pencil Cap That Checks the Point with a Camera - Patent drawing - pencil with smart cap
Patent figure 1 - the pencil (100): cap (110) on the barrel (120), with display (119), check button (115), reminder light (116), preset buttons (117) and alarm (118).

Who it is for

  • Stationery and school-supply brands looking for a “smart” item with a simple, visible function.
  • STEM and educational-toy companies - a cap that shows children how a camera and a controller measure something real.
  • Art and drafting suppliers serving people who need a consistent line width.
  • Gift and promotional suppliers wanting an unusual tech gadget for students.

How it works

The main parts

Smart Pencil Cap That Checks the Point with a Camera - Patent drawing - inside the cap
Patent figure 2 - front view of the cap: hollow body (111), open end (1112), closed end (1114), camera (113), controller (112), sensors (114) and the buttons on top.
No.PartWhat it does
111Cap bodyHollow tube; open end (1112) for the pencil, closed end (1114).
113Image unitCamera at the closed end, aimed at the point.
114SensorDetects whether a pencil is in the cap.
112ControllerTriggers the camera, measures the lead width, compares it with the limit.
115Check buttonStarts a measurement.
116Reminder unitSound, light or vibration when the point is too blunt.
117Preset buttonsChoose the limit, e.g. 0.5 mm or 0.7 mm.
118Alarm unitWarns when no pencil is detected.
119, 1192Display and ring gaugeShow the point inside a ring of the chosen size.

Checking a pencil

  1. Cap the pencil.
  2. Choose the limit with a preset button (0.5 mm or 0.7 mm).
  3. Press the check button - the sensor confirms the pencil, the camera takes a picture.
  4. Read the result - the screen shows the point inside the ring; if it is wider, the cap beeps, lights or vibrates.
  5. Sharpen and check again.
Smart Pencil Cap That Checks the Point with a Camera - Patent drawing - top view of the cap
Patent figure 3 - top view: display (119) with ring gauge (1192), check button (115), reminder (116), preset buttons for 0.5 mm and 0.7 mm (117) and alarm (118).

The electronics

Smart Pencil Cap That Checks the Point with a Camera - Patent drawing - block diagram
Patent figure 4 - block diagram: preset buttons (117), check button (115), sensor (114) and camera (113) feed the controller (112), which drives the alarm (118), reminder (116) and display (119).

The patent describes the functions, not specific chips. In a modern product, a low-cost camera module and a small microcontroller can do the measurement; the patent also suggests a lanyard hook on the closed end and a ring inside the open end so the pencil does not fall out.

Applications

Exam preparation and standardized tests

Students checking pencils before tests that use pencil answer sheets.

Technical drawing and drafting classes

Students and draftspeople who need a consistent line width.

Sketching and fine art

Artists who keep several pencils at specific points.

STEM classrooms and coding kits

An open-source version of the cap as a project: camera, measurement, feedback.

Novelty gifts for students

A “smart” back-to-school gift that does something visible.

Where it is less suitable

  • Mechanical pencils - their lead width is fixed by the lead, so a sharpen reminder is not needed.
  • Very low price points - a camera and electronics cost far more than a plain cap; this is a premium or educational item.

Frequently asked questions

How does the cap know the pencil is blunt?

A camera in the closed end photographs the point, and the controller measures the width of the lead at the tip from the picture. If it is wider than the chosen limit, the cap gives a reminder.

Which limits can be set?

The patent describes preset buttons with 0.5 mm and 0.7 mm. Other values - for example for soft art pencils - can be added in design.

How accurate is it?

The patent gives no accuracy figures. Accuracy depends on the camera, the lighting inside the cap and calibration, and is measured on prototypes with real pencils.

Does it need a screen?

No. The patent includes a display with a ring gauge as a preferred option; a simpler version can use only a light, a beeper or vibration.

How is it powered?

The patent does not specify. A small rechargeable battery with USB-C, or a coin cell with a child-resistant compartment, are both possible.

Can it be sold as a STEM kit?

Yes - the camera, sensor and controller make a clear teaching project. We can supply an assembled cap or a kit version with documented code.

Can this design be made and sold in the US?

The patent was filed only in China and has lapsed, so it does not restrict the design in the US or in China. Smart writing tools may be covered by other patents - see Patent & Production - so we recommend a freedom-to-operate check before volume production.

Are you affiliated with the patent owner?

No. IP2M is an independent design and manufacturing service working from the public patent document.

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Helpful details to include:

  • Your company and sales channel (stationery, education, STEM kits, gifts, Amazon…)
  • Target users (students, artists, classrooms) and age range
  • Features - screen or no screen, feedback type, presets
  • Power source and battery life
  • Estimated quantity and target price
  • Timeline - when you would like samples and the first shipment

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Patent CN106427302B: bibliographic data, legal status, family, a plain-language reading of the claims, plus customization, US compliance points and how a manufacturing project runs.

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This page is based on the public patent document CN106427302B, assigned to Nanjing Lianhan Machinery Co., Ltd. (current owner; originally filed by Yancheng City Experimental Primary School). IP2M is an independent manufacturing service and is not affiliated with, endorsed by or licensed by the patent owner. Images marked as concept renderings are illustrations, not photos of an existing product. Patent status information is provided for reference only and is not legal advice; confirm freedom to operate for your market before production. Full disclaimer.