Variable Groove Annular Seal for Hammer Drill Piston Wear
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Solution Overview
Problem
The annular seal in manually operated hammer drills experiences rapid wear due to reciprocating motion, leading to reduced sealing effectiveness and performance when the hammer mode is deactivated, causing overheating and damage.
Innovation Solution
The radial groove and annular seal are designed to move parallel to the axis of rotation, with a variable groove depth that adjusts to minimize friction when the piston is stationary, and increases contact pressure when the piston is moving, allowing the annular seal to assume positions that reduce wear and enhance sealing during hammer mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the annular seal is sealed tightly against the cylinder to increase sealing effectiveness, then the sealing effect is improved, but friction and wear on the annular seal increase significantly
Solution Approach 1:
The patent makes the groove depth variable along the axial direction, allowing the annular seal to dynamically adjust its position and contact pressure with the cylinder. The groove depth transitions from a first value at one end to a second value at the other end, enabling the seal to assume positions that optimize the balance between sealing effectiveness and friction reduction.
Solution Approach 2:
The patent changes the geometric parameter of the groove depth along the axial direction, creating a gradient structure. This parameter variation allows the annular seal to experience different contact pressures at different positions, enabling optimization of both sealing performance and friction characteristics.
2Reliability
If the annular seal is pressed harder against the cylinder to improve sealing, then the sealing effect is improved, but the friction forces increase and cause rapid wear
Solution Approach 1:
The variable groove depth creates a dynamic system where the annular seal can shift its position along the axial direction. This dynamic capability allows the seal to assume positions with optimal contact pressure, balancing sealing effectiveness with wear reduction over time.
Solution Approach 2:
The groove depth is not uniform but varies locally along the axial direction. This local variation in groove depth creates different contact pressure zones, allowing the seal to have high contact pressure where sealing is critical and lower contact pressure where friction reduction is prioritized.
3Power
If the piston executes reciprocating movements to create pressure pulses for hammering action, then hammer drilling performance is improved, but the annular seal experiences rapid wear due to the reciprocating motion
Solution Approach 1:
The variable groove depth structure allows the annular seal to dynamically adjust its position during reciprocating movements. The seal can assume positions that reduce friction and wear while still maintaining the necessary sealing effect for effective hammering action.
Solution Approach 2:
The gradient in groove depth creates varying contact pressure conditions that accommodate the reciprocating motion. This parameter variation helps reduce wear on the annular seal while maintaining the pressure pulse generation necessary for hammer drilling performance.
4Adaptability or versatility
If the hammer mode is deactivated and the piston stops moving, then drilling without percussive action is enabled, but the annular seal may overheat and be damaged due to sustained contact pressure
Solution Approach 1:
The variable groove depth enables the annular seal to shift to positions with reduced contact pressure when hammer mode is deactivated. This dynamic position adjustment allows the seal to 'float' or experience minimal friction during sustained drilling operations, preventing overheating and damage.
Solution Approach 2:
The gradient structure of the groove depth creates zones of varying contact pressure. When hammer mode is off, the annular seal can assume positions in the groove where contact pressure is minimized, reducing friction-generated heat and preventing thermal damage during extended drilling operations.
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 design reduces wear on the annular seal, maintains effective sealing during hammer mode, and minimizes friction when the hammer action is deactivated, improving the overall performance and longevity of the hammer drill.
Implementation Method 1
the sealing effect between the piston and the cylinder depends on the contact pressure exerted on the cylinder by the annular seal. The greater this radial pressing force, the greater the effective frictional forces as well.
Data Source
AI summary
A manually operated hammer drill (1) includes a spindle (3) that drives a chuck (5) in a rotary manner about an axis of rotation (6) in a drilling mode, and includes a pneumatic hammer mechanism (4), that hammers against a tool inserted in the chuck (5) in a hammer mode. The hammer mechanism (4) has a piston (10) which performs reciprocating movements (12) parallel to the axis of rotation (6) in a cylinder (11) conformed inside the spindle (3) when hammer mode is activated. The piston (10) has at least one radial groove (21) in which an annular seal (22) is arranged.