Segmented Broach Assembly for Coated Replaceable Teeth
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Solution Overview
Problem
Existing broach manufacturing techniques that use glued hard-metal teeth prevent the application of PVD or CVD coatings due to heat-induced adhesive failure, leading to shorter tool service life and premature broach discarding.
Innovation Solution
Securing hard-metal toothed sheet segments to a sheet-holder using a mechanical dovetail coupling and a softer metal dolly with tightening screws and anchor pins, allowing for coating processes and segment replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hard-metal teeth are secured to the sheet-holder by means of gluing, then the manufacturing process is simple, but the broach cannot be subjected to PVD or CVD coating processes due to heat-induced adhesive failure
Solution Approach 1:
The broach is divided into modular segments (toothed sheets) that can be independently secured to the sheet-holder. This segmentation allows the teeth to be mechanically attached rather than glued, enabling them to withstand the high temperatures of PVD/CVD coating processes while maintaining the ability to replace individual segments if needed.
Solution Approach 2:
The patent replaces the chemical bonding method (gluing) with a mechanical fastening system consisting of screws and anchor pins. This mechanical substitution eliminates the adhesive layer that would fail under coating process temperatures, allowing the broach to undergo PVD or CVD coating while maintaining structural integrity.
2Ease of manufacture
If the entire broach is discarded when teeth deteriorate, then manufacturing simplicity is maintained, but resource waste increases and service life is reduced
Solution Approach 1:
The broach is designed as a modular system where the toothed sheets are separate segments that can be independently replaced. When teeth deteriorate, only the affected segments need to be removed and replaced, rather than discarding the entire broach. This significantly reduces material waste and extends the overall service life of the tool.
Solution Approach 2:
The patent enables selective replacement of worn toothed sheets while retaining the sheet-holder and other intact components. This partial replacement strategy recovers and reuses the majority of the broach structure, minimizing material loss and reducing the frequency of complete broach replacements.
3Strength
If tightening screws are used to secure the toothed sheet, then mechanical fastening is achieved, but the screws may loosen due to strains and stresses during broaching
Solution Approach 1:
The anchor pins are pre-positioned in the sheet-holder to provide immediate mechanical constraint in the direction perpendicular to the screw axes. This preliminary mechanical action prevents the tightening screws from loosening under the strains and stresses generated during broaching operations, ensuring sustained fastening reliability.
Solution Approach 2:
The anchor pins act as intermediary elements that work in conjunction with the tightening screws. While the screws provide the primary clamping force, the anchor pins serve as a secondary mechanical constraint that prevents screw backout, creating a redundant fastening system that enhances overall reliability under dynamic loading conditions.
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
The invention relates to a broach for a broaching machine, which comprises a toothed sheet (4) with hard-metal teeth, formed by one or more segments arranged in longitudinal correlation and a sheet-holding support (3) in which the toothed sheet (4) is placed; characterized in that the sheet-holding support (3) has a recess (3.1) into which a base (4.1) of the toothed sheet (4) with matching configuration fits, in order to establish mechanical coupling between the two, and in that the sheet-holding support (3) includes tightening means (6) for securing the toothed sheet (4) in position in the sheet-holder (3).