Hammer Drill Boss Sleeve Isolation for Stable Drill Mode
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Solution Overview
Problem
Existing hammer drills experience unexpected impacting motions in the drill mode due to friction between the intermediate shaft and impact transmission member, despite the clutch member being disengaged.
Innovation Solution
The hammer drill design includes a cantilevered impact transmission member supported by a bearing, which is rotatably mounted externally to the intermediate shaft, and a clutch member that can be slidably engaged or disengaged to prevent unintended reciprocating motions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the impact transmission member is directly mounted on the intermediate shaft, then the structure is simple and compact, but unexpected impacting motion occurs due to friction between the intermediate shaft and impact transmission member in drill mode
Solution Approach 1:
The patent introduces a bearing as an intermediary component between the intermediate shaft and the impact transmission member. This bearing serves as a mediator that separates the two rotating components, preventing direct frictional contact while allowing both to rotate independently. The bearing enables the impact transmission member to be mounted on the intermediate shaft structure while eliminating the harmful friction that causes unexpected impacting motion in drill mode.
2Ease of operation
If the clutch member is disengaged from the impact transmission member in drill mode, then the impact transmission member should not rotate, but friction causes it to rotate unexpectedly
Solution Approach 1:
The bearing acts as a physical intermediary that decouples the rotational motion transmission between the intermediate shaft and impact transmission member. Even when the clutch member is disengaged, the bearing prevents frictional contact that would otherwise cause the impact transmission member to rotate unexpectedly, ensuring pure drill mode operation.
Solution Approach 2:
The patent segments the rotational motion transmission path by introducing the bearing as a separate component. This segmentation allows the intermediate shaft and impact transmission member to rotate independently without frictional coupling, enabling clear distinction between different operation modes when the clutch member is engaged or disengaged.
3Ease of manufacture
If the impact transmission member is in contact with the intermediate shaft, then mounting is simplified, but component wear increases due to continuous friction
Solution Approach 1:
The bearing serves as a mediator that eliminates direct frictional contact between the intermediate shaft and impact transmission member. This intermediary component prevents wear and extends the service life of both rotating parts while maintaining the simplified mounting structure where the impact transmission member is still mounted on the intermediate shaft assembly.
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 configuration effectively suppresses unexpected impacting motions in the drill mode by preventing friction between the intermediate shaft and impact transmission member, ensuring smooth operation and reducing component wear.
Implementation Method 1
the impact transmission member is rotatably supported not to be in contact with the intermediate shaft by the housing via a bearing
Data Source
AI summary
A hammer drill includes a boss sleeve rotatably and externally mounted to an intermediate shaft separately from the intermediate shaft. The boss sleeve includes a rod coupled to a rear end of a piston cylinder via a swash bearing. The boss sleeve is configured to rotate to convert a rotation of the intermediate shaft into a reciprocating motion in a front-rear direction of the rod and transmit the reciprocating motion to the piston cylinder. The hammer drill includes a second clutch disposed at the intermediate shaft. By performing a switch operation of a slide position of the second clutch, a hammer mode in which the second clutch is engaged with the boss sleeve to reciprocate the piston cylinder back and forth and another operation mode are selectable. The boss sleeve is rotatably cantilevered not to be in contact with the intermediate shaft by an inner housing via a bearing.