Hammer Drill Beat Piece Asymmetric Geometry Rebound Control
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Solution Overview
Problem
In hammer drills, the rebound of the beat piece after engaging with the ram catcher can cause it to disengage from the ram, leading to unintended continued operation and potential damage to the support structure.
Innovation Solution
Designing a beat piece with an eccentric second angled region and shoulder to increase frictional contact upon rebound, preventing the beat piece from disengaging from the ram catcher, and incorporating an air vent to break the air spring when the ram is caught.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the beat piece is designed with a uniform second angled region and shoulder, then the structure is simple and easy to manufacture, but the rebound force causes the beat piece to disengage from the ram catcher
Solution Approach 1:
The patent applies asymmetry by designing the second angled region and second shoulder with non-uniform geometry. Specifically, the second angled region has a first portion and a second portion with different angles relative to the longitudinal axis, and the second shoulder has a first section and a second section with different orientations. This asymmetric design creates increased frictional contact during rebound, preventing the beat piece from disengaging from the ram catcher while maintaining manufacturing feasibility through standard machining operations.
2Reliability
If the ram catcher is designed to stop the ram completely, then the ram remains stationary when the cutting tool is removed, but the rebound force can still cause disengagement
Solution Approach 1:
The patent converts the harmful rebound force into a beneficial frictional contact mechanism. The asymmetric second angled region and second shoulder are specifically designed to engage with the ram catcher during rebound, transforming the potentially damaging rebound motion into a controlled frictional interaction that actually enhances retention. The rebound force, instead of causing disengagement, creates increased surface contact and friction that secures the beat piece to the ram catcher.
3Productivity
If the air spring remains intact when the ram is caught, then the ram can be quickly re-engaged, but the ram continues to reciprocate causing damage
Solution Approach 1:
The patent extracts or removes the air spring from the system when the ram is caught by the ram catcher. The air vent is positioned to allow the air spring to escape or decompress when the ram reaches its forward position and is caught by the catcher. This extraction of the air spring prevents continued reciprocation of the ram, stopping the harmful impacts on the support structure while allowing for quick re-engagement by simply allowing the air spring to re-form.
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
Prevents the beat piece from disengaging from the ram catcher due to rebound force, ensuring the ram remains stationary until intentionally re-engaged, thus preventing damage and maintaining controlled operation.
Implementation Method 1
a piston reciprocatingly driven by a motor via a crank shaft within a spindle, which in turn reciprocatingly drives a ram via an air spring
Implementation Method 2
incorporating an air vent to break the air spring when the ram is caught
Implementation Method 3
Designing a beat piece with an eccentric second angled region and shoulder to increase frictional contact upon rebound
Data Source
Figure 1
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Figure 3
AI summary
A hammer drill comprising; a housing (2); a tool holder 98) mounted on the housing (2) which is capable of holding a cutting tool (12); a motor (48) mounted within the housing (2); and a hammer mechanism comprising: a piston (204) reciprocatingly driven along a longitudinal axis (154) by the motor when the motor is actuated; a ram (152) reciprocatingly driven on the longitudinal axis by the reciprocating piston via an air spring (170); a beat piece (156) supported in an axially slideable manner on the longitudinal axis within a beat piece support structure (150, 210) which, during the normal operation of the hammer mechanism, is repetitively struck by the ram and which transfers the impacts to a cutting tool when held by the tool holder; wherein the beat piece comprises a first impact surface (248) and the beat piece support structure comprises a second impact surface (250), the first and second impact surfaces coming into contact with each other when the beat piece axially slides to its furthest position away from the ram; characterized in that that the shape of the two surfaces relative to each other is arranged so that there is a non uniform amount of contact between the first and second surfaces around the longitudinal axis 154.