Impact Driver Bit Holder Sleeve for Smooth Insertion and Durability
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Solution Overview
Problem
Existing tool-holding apparatuses in electric work machines, such as impact drivers, face issues with durability due to stress concentration at narrowed portions and difficulty in inserting bits when the bit sleeve is axially positioned incorrectly, leading to potential blockage and reduced efficiency.
Innovation Solution
A tool-holding apparatus with movable engaging members and biasing members that allow the bit sleeve to transition between blocking and permitting positions, ensuring smooth bit insertion regardless of the bit sleeve's axial position, and a projection that contacts the rotational-output shaft to enhance durability by reducing stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the tool holder narrows at the front end to restrict radial movement, then radial stability is improved, but cracks form in the narrowed portion under impact loads
Solution Approach 1:
The tool holder is divided into a narrowed portion (for radial stability) and a reinforced portion (for crack resistance). The reinforced portion with increased wall thickness is positioned axially adjacent to the narrowed portion, creating a segmented structure that addresses both requirements independently.
Solution Approach 2:
The wall thickness of the tool holder is not uniform but varies locally. The reinforced portion has a greater wall thickness than the narrowed portion, concentrating material where impact stresses occur while maintaining the narrowed geometry where radial stability is needed.
2Ease of operation
If the bit sleeve is moved axially forward to improve bit insertion, then ease of operation is improved, but the inner-circumferential surface blocks ball movement
Solution Approach 1:
The bit sleeve is designed to be movable in the axial direction, transitioning between a first position (where the inner-circumferential surface blocks ball movement) and a second position (where it permits ball movement). This dynamic positioning allows the system to adapt to different operational requirements.
Solution Approach 2:
The bit sleeve is moved axially forward to the second position before bit insertion occurs. This preliminary action creates space for the balls to move outward and engage the bit, ensuring smooth insertion regardless of the sleeve's initial axial position.
3Force
If the engaging members are biased to engage the tool accessory, then holding force is improved, but insertion difficulty increases when sleeve is mispositioned
Solution Approach 1:
The system uses dynamic positioning of the bit sleeve to control when the biased engaging members engage the tool accessory. When the sleeve is in the second (forward) position, the balls can move outward despite the biasing force, allowing easy insertion. Once inserted, the biasing force maintains strong holding force.
Data Source
AI summary
A tool-holding apparatus (70) includes an engaging member (71) for engaging a tool accessory (B) and being movably supported in axial and radial directions in a rotational-output shaft (26) having an insertion hole (81) for holding the tool accessory (B). A first biasing member (72) biases the engaging member towards engagement with the engaging member. A bit sleeve (73) is movable in the axial direction along an outer-circumferential surface of the rotational-output shaft between a blocking position at which radial outward movement of the engaging member is blocked and a permitting position at which radial outward movement of the engaging member is permitted. A second biasing member (74) biases the bit sleeve toward the blocking position. A positioning part (75) is fixed on the outer-circumferential surface of the rotational-output shaft and stops the bit sleeve at the blocking position. The bit sleeve has a projection (88), which is disposed on the forward side of the first biasing member, extends inward in the radial direction, and slidably contacts the rotational-output shaft.