Segmented Grommet Contour for Low-Force Cable Fastening
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Solution Overview
Problem
Existing fastening devices for electrical cables in motor vehicles are structurally complex and time-consuming to assemble, requiring high insertion forces due to their design, which increases production costs and assembly time.
Innovation Solution
A fastening device featuring a grommet with an irregularly shaped groove contour and deformable plastic material, such as polyurethane, that can be easily sprayed onto the cable, reducing assembly force and play, and a holder with a recess designed to match the grommet's contour for a secure, low-force fit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ring surrounding the edge of the carrier is provided to secure the grommets in the pushed-in position, then the grommets are locked reliably in the recesses, but the overall arrangement becomes structurally complex and assembly time increases
Solution Approach 1:
The patent removes the unnecessary ring component that surrounded the edge of the carrier in prior art. Instead, the grommet's own contour with its engagement surface and irregular groove base provides the locking function directly, eliminating the separate ring structure and simplifying the overall device while maintaining reliable locking.
Solution Approach 2:
The locking function is merged into the grommet itself through its contour design. The engagement surface and irregular groove base are integrated features of the grommet that work together with the recess to provide reliable locking, eliminating the need for separate locking components like the ring in prior art.
2Reliability
If a ring surrounding the edge of the carrier is provided to secure the grommets, then the grommets are locked reliably, but assembly time increases
Solution Approach 1:
The patent eliminates the separate ring component and its associated assembly steps. The grommet's integrated contour design with engagement surface and irregular groove base provides locking functionality without requiring additional assembly operations, thereby reducing assembly time while maintaining reliability.
3Device complexity
If a smooth cylindrical groove base is used in the grommet, then the grommet structure is simple, but high assembly force is required for insertion
Solution Approach 1:
The patent segments the groove base into multiple tooth-like elevations separated by connecting webs instead of using a smooth cylindrical surface. This segmentation creates easily deformable areas between the elevations that can yield during insertion, reducing the peak assembly force required while maintaining structural simplicity.
Solution Approach 2:
The groove base has non-uniform local properties with tooth-like elevations of different heights and connecting webs of varying thicknesses. The connecting webs are designed to be narrower and more easily deformable than the elevations, creating localized deformation zones that reduce insertion force while maintaining overall structural integrity.
4Force
If connecting webs between the elevations are made narrower, then assembly force is reduced, but axial play between the grommet and holder increases
Solution Approach 1:
The groove base is segmented into tooth-like elevations and connecting webs where the connecting webs are narrower and more deformable. This segmentation allows the webs to act as deformation zones during insertion (reducing force) while the elevations maintain structural integrity and prevent excessive axial play after assembly.
Solution Approach 2:
The patent varies the dimensions and properties of different elements in the groove base. The connecting webs have smaller cross-sections and different material properties compared to the elevations, making them more easily deformable during insertion while the elevations provide structural support to limit axial play in the assembled state.
5Ease of manufacture
If PUR plastic material with Shore hardness of 60A to 80A is used for the grommet, then production costs are reduced and processing is simplified, but assembly force may increase due to higher hardness
Solution Approach 1:
The grommet made of PUR plastic has non-uniform local properties through the contour design with tooth-like elevations and connecting webs. The connecting webs are narrower and more easily deformable than the elevations, creating localized deformation zones that reduce insertion force while the overall PUR material provides cost advantages and adequate elasticity for the application.
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
Significantly simplifies the assembly process, reduces production costs, and maintains a tight fit without increasing assembly force, allowing for efficient and cost-effective installation of electrical cables.
Implementation Method 1
The assembly force required for inserting the line with the grommet surrounding it can be kept low, since the segmented surface of the grommet contour is relatively easily deformable even when plastic is used to manufacture the grommet
Implementation Method 2
The elevations at the base of the groove can be deformed much more easily than a smooth cylindrical groove base, which makes it much easier to insert the grommet
Implementation Method 3
The grommet 10 completely encloses the cable and, after assembly, its groove-shaped contour 14 engages in a detachable manner in a recess 16 of a holder 18
Data Source
Figure 1
Figure 2~4
AI summary
A fastening device for a line, in particular for an electric cable (12) in a motor vehicle, is proposed, the fastening device having a bush (10) which can be locked in a holder (18), at least partially surrounds the line, is made of elastically deformable material and is fastened releaseably in a cutout (16) of the holder (18) by means of a contour (14). According to the invention, the surface of a bush (10), which is injection-moulded from plastic, is of segmented design in order to obtain easier deformability of the bush when fitting it into an associated holder (18).