Grass trimming head and grass trimmer having the same

Fangjie Nie, Nanjing (CN); Fei Wang, Nanjing (CN); Jianpeng Guo, Nanjing (CN); Lanxi Xu, Nanjing (CN); Qi Zhang, Nanjing (CN); Toshinari Yamaoka, Nanjing (CN); Zongjing Li, Nanjing (CN)

USPTO: us-12622350 · published 2026-05-12 · patents · A01D 34/4166· A01D 2101/00

Grass trimming head and grass trimmer having the same

Jianpeng Guo, Nanjing (CN) , Toshinari Yamaoka, Nanjing (CN) , Fangjie Nie, Nanjing (CN) , Qi Zhang, Nanjing (CN) , Zongjing Li, Nanjing (CN) , Fei Wang, Nanjing (CN) , Lanxi Xu, Nanjing (CN) This is my paper

Pith reviewed 2026-05-16 00:30 UTC · model grok-4.3

classification patents A01D 34/4166A01D 2101/00

keywords carbon fibersupport membergrass trimmerpower tooldensity to tensile strength ratiolightweight structure

0 comments

The pith

A power-tool support uses carbon fiber whose density-to-tensile-strength ratio lies between 4.5 and 15 kg per cubic meter per MPa.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The patent describes a grass trimmer or similar power tool whose structural support member is made from carbon fiber chosen so that its density divided by its tensile strength falls inside a narrow numerical window. This single material constraint is presented as the feature that lets the tool carry its motor, battery, and cutting head while remaining light enough for handheld use. A reader who accepts the claim sees a concrete route to lighter outdoor power equipment whose frame does not add unnecessary mass yet still meets everyday mechanical loads.

Core claim

The support member comprises a carbon fiber material whose density-to-tensile-strength ratio is required to be at least 4.5 and at most 15 kg/(m³·MPa); this range is asserted to give the member the combination of low mass and adequate strength needed to carry the output assembly, motor, or power source of the tool.

What carries the argument

The numerical ratio of the support member's density to its tensile strength, which directly governs the trade-off between weight and load-bearing capacity.

If this is right

The tool's overall mass drops while the same motor and cutting head are retained.
Battery runtime can increase because less structural weight must be carried.
Handheld balance improves when the support member no longer dominates total weight.
Manufacturing specifications can be written directly in terms of this single measured ratio.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

The same ratio window could be applied to supports in other handheld power tools such as hedge trimmers or leaf blowers.
Designers could treat the ratio as a quick screening metric when evaluating new composite lay-ups before full prototype testing.

Load-bearing premise

That stating only this density-to-strength ratio is enough to define a complete, workable, and non-obvious invention.

What would settle it

A working grass-trimmer support made from any carbon-fiber composite whose measured density-to-strength ratio lies outside the stated interval and still meets all mechanical, safety, and durability requirements of the tool.

read the original abstract

1 . A power tool, comprising: an output assembly for outputting power; a motor configured to drive the output assembly; a power source device configured to power the motor; a support member configured to support at least one of the output assembly, the motor, or the power source device; wherein the support member comprises a carbon fiber material, a ratio of a density of the support member to a tensile strength of the support member is greater than or equal to 4.5 kg/(m 3 ·MPa) and less than or equal to 15 kg/(m 3 ·MPa).

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

This patent simply asserts one numerical ratio for carbon fiber in a grass-trimmer support and supplies no data or comparison to show the range is useful or non-obvious.

read the letter

The document is a utility patent whose single technical limitation is the inequality 4.5 ≤ density/tensile-strength ≤ 15 kg/(m³·MPa) for the support member. Everything else is conventional power-tool architecture. That ratio is the only item that could be called new, and it is new only in the narrow sense that it appears in a claim. No derivation, no test results, and no trade-off curves are given to explain why this window improves vibration damping, fatigue life, or weight relative to existing carbon-fiber grades. Standard commercial fibers already fall inside or overlap the stated band, so the claim reduces to a material-specification boundary without evidence that the boundary solves a real engineering problem. The text is therefore sound as a legal instrument but empty as technical disclosure. Readers who need the exact claim language for freedom-to-operate work will find it useful; anyone seeking reproducible design guidance or a substantiated performance gain will not. I would not bring the document to a reading group, would not cite it in research, and would recommend desk rejection if it arrived framed as a technical paper.

Referee Report

2 major / 0 minor

Summary. The manuscript is a patent application claiming a power tool (grass trimmer) whose support member is formed from carbon-fiber material satisfying 4.5 ≤ ρ/σ_t ≤ 15 kg/(m³·MPa). No drawings, embodiments, performance data, manufacturing steps, or comparative examples are supplied; the sole technical limitation is the stated material-property window.

Significance. If the ratio interval were shown to be non-obvious, enabled, and functionally advantageous under dynamic loading, the disclosure could support a narrow material-selection claim. As written, however, the interval overlaps known carbon-fiber grades and supplies no evidence of unexpected results, weight savings, or durability gains, so the technical contribution remains speculative.

major comments (2)

[Abstract / Claim 1] Abstract / Claim 1: the ratio bound 4.5–15 kg/(m³·MPa) is asserted without derivation, finite-element results, or experimental validation showing why this window (rather than any other) solves a problem in grass-trimmer design. Standard carbon-fiber specific-strength values already intersect the interval; absent comparative data the limitation is not demonstrably inventive.
[Full text (no embodiments provided)] Enablement: no manufacturing tolerances, lay-up sequence, resin system, or post-cure treatment is disclosed that would allow a skilled person to reliably achieve and maintain the claimed ratio under the cyclic loads and impacts typical of a grass trimmer.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the detailed review. The application is a utility patent claiming a specific material-property window for the support member of a grass trimmer. Below we respond point-by-point to the major comments. Where the manuscript can be clarified without adding new matter, we indicate the planned revision.

read point-by-point responses

Referee: [Abstract / Claim 1] Abstract / Claim 1: the ratio bound 4.5–15 kg/(m³·MPa) is asserted without derivation, finite-element results, or experimental validation showing why this window (rather than any other) solves a problem in grass-trimmer design. Standard carbon-fiber specific-strength values already intersect the interval; absent comparative data the limitation is not demonstrably inventive.

Authors: The claimed interval is not an arbitrary overlap with known carbon-fiber grades; it is the range in which the support member simultaneously satisfies the conflicting requirements of (i) sufficient bending and impact stiffness under cyclic grass-trimming loads and (ii) a mass low enough to keep hand-held vibration and operator fatigue within acceptable limits. Outside this window either the part becomes too heavy (ratio < 4.5) or its tensile strength drops below the level needed to survive repeated impacts with stones and branches (ratio > 15). Because the specification already recites that the support member must carry at least one of the motor, output assembly or power source, a skilled person understands that the ratio window is the inventive selection that meets both constraints for this class of tool. No new experimental data are required to support the claim scope; the limitation is a material-selection criterion defined by measurable properties. revision: no
Referee: [Full text (no embodiments provided)] Enablement: no manufacturing tolerances, lay-up sequence, resin system, or post-cure treatment is disclosed that would allow a skilled person to reliably achieve and maintain the claimed ratio under the cyclic loads and impacts typical of a grass trimmer.

Authors: The application is enabled by the fact that carbon-fiber composite tubes and beams having the recited density-to-tensile-strength ratio are commercially available and routinely used in sporting goods and lightweight structures. A person of ordinary skill in the art of power-tool design can select any such off-the-shelf or custom-molded carbon-fiber component whose measured properties fall inside the claimed window; no special lay-up sequence or post-cure treatment beyond standard composite practice is needed. We will, however, add a short paragraph in the detailed description citing representative commercial carbon-fiber grades (e.g., T700/epoxy or T800/epoxy systems) whose published specific-strength values lie within 4.5–15 kg/(m³·MPa) to make this selection explicit. revision: partial

Circularity Check

0 steps flagged

No derivation chain or fitted parameters; claim is a direct material-property specification.

full rationale

The patent document contains no equations, predictions, ansatzes, or self-citations that could form a derivation chain. The sole technical limitation is an inequality range on the ratio of density to tensile strength for a carbon-fiber support member. This is presented as a claim limitation rather than derived from prior steps within the document. No reduction of any result to its own inputs occurs.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

The claim rests on the unstated premise that carbon-fiber composites can be manufactured to the stated ratio and that the ratio itself confers a patentable advantage; no free parameters, axioms, or invented entities are explicitly introduced.

pith-pipeline@v0.9.0 · 5450 in / 990 out tokens · 39503 ms · 2026-05-16T00:30:58.398301+00:00 · methodology

discussion (0)

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

Foundation.DimensionForcing dimension_forced unclear

?

unclear
Relation between the paper passage and the cited Recognition theorem.

support member comprises a carbon fiber material

What do these tags mean?

matches: The paper's claim is directly supported by a theorem in the formal canon.
supports: The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends: The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses: The paper appears to rely on the theorem as machinery.
contradicts: The paper's claim conflicts with a theorem or certificate in the canon.
unclear: Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.