Eccentric Impact Point in Percussive Tool Prevents Knockback
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Solution Overview
Problem
High-power hammer drills and chisel hammers experience significant 'knockback' due to the percussion piston and firing pin striking when the tool breaks through or is lifted from the surface, leading to inefficient energy dissipation and complex, prone-to-malfunction brake systems, which increase weight and reduce ergonomic handling.
Innovation Solution
An eccentrically arranged contact point outside the impact axis reduces energy dissipation through increased friction, preventing knockback without additional components or complex structures, allowing for a shorter, lighter design with minimal impact on performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If ventilation openings are provided to prevent knockback, then the harmful effect of knocking back is reduced, but the device complexity increases and the length increases
Solution Approach 1:
The invention extracts the harmful knockback effect by providing a free travel path for the percussion piston away from the firing pin, separated by a buffer element. This removes the direct contact that causes knockback without requiring complex brake systems or multiple ventilation openings, thus preventing the harmful effect while maintaining structural simplicity.
Solution Approach 2:
A buffer element is introduced as an intermediary between the percussion piston and the firing pin. This buffer absorbs the impact energy during knockback conditions, preventing direct striking between the piston and firing pin. The intermediary element solves the knockback problem without increasing device complexity or requiring additional braking mechanisms.
2Object-affected harmful factors
If a long free travel is provided to prevent knockback, then the harmful effect of knocking back is reduced, but the length of the device increases
Solution Approach 1:
The free travel path for the percussion piston is nested within the existing guide tube structure. The buffer element is positioned within the guide tube, allowing the piston to move freely during knockback conditions without extending the overall device length. This nesting approach prevents knockback while maintaining a compact device size.
3Loss of energy
If friction is increased to dissipate kinetic energy, then the loss of energy is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The invention converts the harmful knockback energy into beneficial frictional heat dissipation. The buffer element is designed to engage with the guide tube walls during piston movement, creating controlled friction that dissipates the kinetic energy of the percussion piston. This transforms the harmful striking energy into useful friction-based energy dissipation without requiring high manufacturing precision.
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
The solution effectively prevents knockback in high-performance hammer drills and chisel hammers, ensuring reliable function over the service life with a cost-effective, structurally simple design that maintains impulse transmission efficiency.
Implementation Method 1
an air cushion being formed between the drive piston and the percussion piston
Implementation Method 2
a pneumatically driven percussion piston
Implementation Method 3
the kinetic energy of the impact means, the firing pin and also the tool is additionally dissipated by friction in their guides
Data Source
Figure 1~1A
Figure 2
Figure 3
AI summary
The electro-pneumatic hammer mechanism (21) and the motor and transmission unit (14) are accommodated inside a housing (12) with a tool (16) attached to the front (15). The hammer mechanism (21) comprises a piston (23) moved axially inside a cylinder (17). The motion is transferred to a hammer ram (25) hitting the striker (26) slightly off center (27) in order to move the tool (16) by the impact. The distance between the striking axis (22) and the point of impact (27) is selected in a specific relation to the length of the striker (26).