Rotary Hammer Anvil Deceleration via O-Ring Friction
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Solution Overview
Problem
Rotary hammers face challenges in effectively decelerating the anvil during transitions from hammer-drill mode to idle mode, leading to transient movement and inefficiency.
Innovation Solution
Incorporation of a retainer with an O-ring that compresses to impart frictional force on the anvil, preventing further reciprocation of the striker and reducing anvil movement by decelerating it through frictional force when transitioning to idle mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the striker is allowed to reciprocate freely within the piston, then hammering function is achieved, but transient movement and instability occur during mode transition to idle
Solution Approach 1:
The retainer acts as an intermediary component between the striker and the piston. During idle mode, the retainer selectively secures the striker in an idle position, preventing unwanted reciprocation. During hammer-drill mode, the retainer releases the striker to allow free reciprocation for hammering. This intermediary mechanism resolves the contradiction by providing controlled restraint that enables both stable idle operation and effective hammering function.
2Productivity
If the anvil is allowed to move freely during mode transition, then operational flexibility is maintained, but transient movement reduces efficiency
Solution Approach 1:
The O-ring is pre-positioned around the outer peripheral surface of the anvil before mode transition occurs. When the striker assumes the idle position, the O-ring is compressed preliminarily to create frictional force on the anvil's outer peripheral surface. This preliminary frictional action decelerates the anvil before complete stopping, reducing transient movement and improving operational efficiency during the transition to idle mode.
3Reliability
If frictional force is applied to decelerate the anvil, then transient movement is reduced, but additional components increase device complexity
Solution Approach 1:
The O-ring serves as a flexible element that provides frictional force through its elastic deformation. When compressed between the retainer and the spindle, the O-ring contacts the outer peripheral surface of the anvil and creates sufficient friction to decelerate it. This flexible film approach achieves reliable anvil deceleration without complex mechanical braking systems, maintaining relatively simple device architecture while improving reliability.
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 solution effectively reduces transient movement of the anvil upon mode transition, enhancing operational efficiency and stability by ensuring smooth deceleration and 'parking' of the anvil, thereby improving the rotary hammer's performance.
Implementation Method 1
The compressed O-ring imparts a frictional force on the outer peripheral surface of the anvil to decelerate the anvil
Data Source
AI summary
A rotary hammer includes a motor, a spindle coupled to the motor for receiving torque from the motor, a piston at least partially received within the spindle for reciprocation therein, a striker received within the spindle for reciprocation in response to reciprocation of the piston, and an anvil received within the spindle and positioned between the striker and a tool bit. The rotary hammer also includes a retainer received within the spindle for selectively securing the striker in an idle position in which it is inhibited from reciprocating within the spindle, and an O-ring positioned between the retainer and the spindle. The O-ring is disposed around an outer peripheral surface of the anvil. The O-ring is compressible in response to the striker assuming the idle position. The compressed O-ring imparts a frictional force on the outer peripheral surface of the anvil to decelerate the anvil.