Handheld Tool Handle Core with Connecting Channels
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Solution Overview
Problem
Existing hand tool handles face challenges in achieving optimal ergonomics, force transmission, and wear resistance while also allowing for the production of complex designs and graphics, with current methods being complex and requiring high manufacturing accuracy.
Innovation Solution
A hand tool design featuring a handle core made of a first plastic material with a second plastic material area that forms the outer surface, allowing for improved force transmission and ergonomic design, and enabling the production of graphic symbols and numbers without separate injection openings, using a connecting channel to simplify the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a soft plastic grip pad is injection-molded onto a hard plastic grip core, then ergonomics and friction for applying torsional moment are improved, but the manufacturing process becomes complex requiring multiple injection steps and separate injection openings
Solution Approach 1:
The patent combines the grip core and grip pad into a single integrated handle body made of semi-crystalline plastic material. The ergonomic finger engagement areas are formed directly during the main injection molding process without requiring separate injection steps or additional components, thus merging the structural and ergonomic functions into one manufacturing operation.
Solution Approach 2:
The semi-crystalline plastic material serves multiple functions simultaneously: it provides the rigid structural core for force transmission, creates the outer surface for ergonomic grip, and forms the visual design elements including graphic symbols and numbers. This multi-functional material eliminates the need for separate materials and injection steps for each function.
2Adaptability or versatility
If graphic symbols and numbers are produced using separate injection openings, then visual differentiation and design complexity are improved, but the manufacturing process becomes more complex and requires higher manufacturing accuracy
Solution Approach 1:
The graphic symbols, numbers, and design elements are incorporated into the mold cavity structure before the injection molding process begins. These features are pre-formed as part of the mold design, allowing them to be automatically replicated during the standard injection process without requiring separate injection openings or additional precision alignment steps.
3Strength
If a two-component handle with hard plastic core and soft plastic pad is used, then wear resistance and force transmission are improved, but the handle stiffness decreases radially outwards reducing overall rigidity
Solution Approach 1:
The patent applies local quality by creating ergonomic finger engagement areas with enhanced friction characteristics directly on the handle body surface through injection molding. These localized soft-touch zones provide improved grip without compromising the overall structural integrity and radial stiffness of the handle, as the ergonomic features are surface-level modifications rather than core structural changes.
Data Source
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AI summary
The invention relates to a hand tool (1), in particular a screwdriver. The hand tool (1) has a shaft (3) and a handle (5) into which the shaft (3) is embedded in a form-fitting and/or material-locking manner. According to the invention, the handle (5) has a handle core (22) made of a first plastic material (6), in particular a hard plastic. The handle core (22) forms an internal gap with the shaft (3). The handle core (22) has at least one radially oriented connecting channel which connects an internal longitudinal recess of the handle core (22) with the outer surface of the handle core (22). The handle core (22), with the shaft (3) inserted therein, is placed in a mold into which a second plastic material (7), which is preferably softer than the first plastic material (6), is then injected.The second plastic material (7) passes from the space via the at least one connecting channel to the outside of the handle core (22), where it can form on the one hand grip padding (35) and on the other hand partial outer surface, by means of which the formation of a graphic symbol (20) or numbers (21) on the outer surface of the handle (5) is possible.