One-Piece Gear Housing for Fast Hammer Impact Unit Assembly

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Solution Overview

Problem

The assembly process for a pneumatic impact mechanism in drill or chisel hammers is cumbersome due to misalignment of components and requires tight manufacturing tolerances, making it difficult to assemble efficiently.

Innovation Solution

A one-piece gearbox housing with a cylindrical section and console section is used, allowing for pre-assembly of the impact mechanism unit, which includes a guide tube and eccentric unit, and is designed to accommodate drive transmission elements, enabling easy insertion and attachment into the gearbox housing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the guide tube and eccentric unit are assembled separately with tight tolerances, then the alignment precision is improved, but the assembly complexity increases

Engineering Contradiction:
Improvealignment precisionVSAvoidassembly complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent combines the guide tube and eccentric unit into a single integrated component with built-in alignment features. The guide tube includes an integrated eccentric unit where the eccentric pin and connecting rod eye are pre-aligned as one piece, eliminating the need for separate assembly and complex tolerance control during assembly.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The alignment of the eccentric pin and connecting rod eye axes is performed in advance during the manufacturing of the integrated guide tube, rather than during final assembly. This preliminary alignment ensures precision without requiring complex assembly procedures or tight tolerances on multiple separate components.

Inventive Principle:
Principle #10Preliminary action

2Ease of manufacture

If multiple components are assembled step-by-step, then the manufacturing flexibility is improved, but the assembly time increases

Engineering Contradiction:
Improvemanufacturing flexibilityVSAvoidassembly time
Core Design Contradiction:
Ease of manufactureVSLoss of time

Solution Approach 1:

The guide tube and eccentric unit are merged into a single integrated component that can be manufactured as one piece or pre-assembled as a unit. This integration allows the entire impact mechanism to be inserted into the gearbox housing in a single operation, dramatically reducing assembly time from multiple steps to one step.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent segments the impact mechanism into a self-contained integrated unit (guide tube with eccentric unit) that can be manufactured independently and then installed as a complete module. This modular segmentation maintains manufacturing flexibility while enabling quick installation.

Inventive Principle:
Principle #1Segmentation

3Ease of operation

If the housing is separated into multiple parts, then the ease of assembly is improved, but the structural strength decreases

Engineering Contradiction:
Improveease of assemblyVSAvoidhousing strength
Core Design Contradiction:
Ease of operationVSStrength

Solution Approach 1:

The gearbox housing is designed as a single integrated piece that combines the cylindrical section for the guide tube and the console section for mounting the eccentric unit. This integration eliminates weak points at flange connections and maintains continuous load paths, preserving structural strength while still allowing easy access for assembly.

Inventive Principle:
Principle #5Merging (Combining)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design simplifies assembly, reduces component count, eliminates the need for a conventional flange, and allows for a lightweight construction by eliminating separation of the housing load path, facilitating quick and secure attachment.

Implementation Method 1

pneumatic impact mechanism with a free piston movable along a striking axis

Methodology Applied
Scientific EffectPneumatic pressure: Pressure Gradient

Implementation Method 2

exciter piston arranged linearly alternating in a guide tube by means of an eccentric unit with connecting rod

Methodology Applied
Scientific EffectEccentric mechanism: Eccentric

Data Source

PatentEP4650110A1Striking mechanism arrangement with a gear housing for receiving a striking unit
Publication Date: 2025.11.19 HILTI AG
  • EP4650110A1 patent drawingFigure 1
  • EP4650110A1 patent drawingFigure 2~3
  • EP4650110A1 patent drawingFigure 4~5

AI summary

Impact mechanism arrangement for a drill or chisel hammer with a gearbox housing (1) for receiving a pneumatic impact mechanism unit (2), comprising an exciter piston (8) arranged linearly alternating in a guide tube (5) by means of an eccentric unit (6) with connecting rod (7), wherein the one-piece gearbox housing (1) consists of a cylinder section (14) for accommodating the guide tube (5) and a console section (15) adjoining it in the longitudinal direction for mounting the eccentric unit (6), wherein a mounting surface (16) of the console section (15) provided for this purpose is arranged radially spaced from the central axis (Xz) of the cylinder section (14).