Interval Sandwich Handle Injection Molding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing handle designs for tools, particularly screwdrivers, face issues with transmitting torsional moments effectively while ensuring user comfort and adaptability to different hand sizes, as they often suffer from material separation under heavy loads, leading to discomfort and injury.
Innovation Solution
A method for producing handles using an 'interval sandwich injection molding process' where a hard plastic handle core is inserted into a mold, followed by sequential injection of two materials, with the outer layer hardening first against the mold walls and the inner layer forming later, creating a cohesive and structurally enhanced handle with ribs or webs for increased torsional stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a soft plastic handle cover is mounted on a hard plastic handle core, then the grip comfort is improved, but the handle cover lifts off from the handle core under heavy loads
Solution Approach 1:
The patent applies preliminary action by creating mechanical interlocking features (protrusions and recesses) between the handle core and handle cover before the bonding process. These pre-formed structural elements ensure that the components are mechanically locked together, preventing the handle cover from lifting off under heavy loads while maintaining grip comfort.
Solution Approach 2:
The patent uses composite materials by combining hard plastic for the handle core and soft plastic for the handle cover. This composite construction allows the handle core to provide structural strength and torque transmission, while the soft handle cover provides grip comfort, resolving the contradiction between comfort and reliability.
2Ease of operation
If a soft plastic handle cover is used, then the grip comfort is improved, but the handle cannot transmit high torsional moments effectively
Solution Approach 1:
The patent segments the handle into two functional parts: a hard plastic handle core that transmits torsional moments and a soft plastic handle cover that provides grip comfort. This segmentation allows each component to optimize its specific function, with the hard core handling torque transmission and the soft cover handling user comfort.
Solution Approach 2:
By using composite materials with different mechanical properties (hard plastic and soft plastic), the patent creates a handle where the hard plastic core maintains structural integrity for torsional moment transmission, while the soft plastic cover enhances grip comfort without compromising the overall strength.
3Adaptability or versatility
If successive layers of plastic materials are formed using transfer presses with multiple injection heads, then multi-layer handles can be produced, but the manufacturing process becomes complex
Solution Approach 1:
The patent merges multiple injection molding operations into a single integrated process. Instead of using transfer presses with multiple injection heads, the invention uses a single injection mold with a two-shot injection system that sequentially injects different plastic materials in one continuous operation, simplifying the manufacturing process while maintaining multi-layer structure capability.
Solution Approach 2:
The patent applies parameter changes by controlling the injection sequence, material temperatures, and pressure parameters in a two-shot injection process. This allows different plastic materials to be sequentially injected and properly bonded without requiring complex transfer press equipment, reducing device complexity while achieving multi-layer handle production.
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 method allows for the production of handles that effectively transmit torsional moments while providing comfort and adaptability to various hand sizes, reducing the risk of material separation and enhancing ergonomic properties.
Implementation Method 1
a first material is injected into the mold cavity and is displaced by a second material injected under or through the first material
Implementation Method 2
The amount of the first material is dimensioned such that when the injection of the first material has ended, the mold cavity is not completely filled and partial volumes of the mold cavity still remain free
Implementation Method 3
a first material is injected into the mold cavity and is displaced by a second material injected under or through the first material
Implementation Method 4
the partial flows of the second material also push the first material in front of them in the circumferential direction
Implementation Method 5
The surface of the material streams cools down as they flow to such an extent that in the area where the partial streams meet, the cooled surface is no longer broken through by the hot material inside the stream
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a handle for a tool, for example a hammer, a screwdriver, a ladle, pliers, a knife or similar. According to the invention, said handle (1) is produced according to the interval-sandwich method for encasing, in a simple manner, the handle core (6) with a handle core covering (9), a soft layer (10) and an external layer (11). The handle core covering (9) and the outer layer (11) are made of a first material, whereas the soft layer (10) is made of a softer, second material.