Impact Driver Spindle Lubrication for Hammer Seizure Prevention
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Solution Overview
Problem
Impact tools often experience seizure due to an insufficient supply of grease to the sliding surfaces of the spindle and hammer, leading to failure in striking functionality.
Innovation Solution
Incorporating a grease supply path within the spindle and utilizing a pump member that accelerates the flow of grease onto the sliding surfaces through a difference in rotational speed, ensuring a sufficient lubrication during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grease is supplied through a simple through-hole structure, then the device complexity is low, but the grease supply amount is insufficient leading to seizure
Solution Approach 1:
The grease supply path is opened in advance during manufacturing, and grease is preliminarily filled in the hammer case before assembly. This ensures grease is available at the sliding surfaces before operation begins, preventing seizure from the start without requiring complex real-time supply mechanisms.
Solution Approach 2:
The rotational movement of the spindle automatically generates centrifugal force that draws grease from the hammer case through the connection hole and supply path to the sliding surfaces. The system serves itself by using its own motion to distribute lubrication without external pumping or control systems.
2Reliability
If grease is supplied only through gravity or simple diffusion, then the device structure remains simple, but the grease flow speed is insufficient for adequate lubrication
Solution Approach 1:
The system utilizes centrifugal force generated by rotational motion to create a hydraulic-like flow of grease through the supply path. The rotating spindle acts as a centrifugal pump, forcing grease through the connection hole and into the sliding surfaces at sufficient speed and pressure for effective lubrication.
3Reliability
If the hammer case is completely sealed to retain grease, then grease loss is minimized, but grease cannot be supplied to sliding surfaces
Solution Approach 1:
The hammer case is segmented with a dedicated grease supply path and connection hole that create a controlled lubrication circuit. Grease is retained in the hammer case reservoir while a specific portion is channeled through the supply path to the sliding surfaces, achieving both retention and delivery.
Solution Approach 2:
The connection hole and grease supply path act as intermediaries between the grease reservoir in the hammer case and the sliding surfaces. These intermediary structures enable controlled transfer of grease from the sealed case to the lubrication points without compromising overall grease retention.
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 supplies a sufficient amount of grease to the sliding surfaces, preventing seizure and ensuring consistent striking performance.
Implementation Method 1
an accelerator disposed in the spindle, the accelerator being configured to accelerate a flow of the grease onto the sliding surface along the grease supply path in response to rotation of the motor
Data Source
AI summary
An impact driver includes a motor, a spindle, a hammer externally and coaxially mounted on the spindle to receive rotation of the spindle and move relative to the spindle in an axial direction, an anvil in front of the hammer and coaxial with the spindle to be struck by the hammer in a rotation direction, and a hammer case accommodating the spindle, the hammer, and the anvil, allowing a front end of the anvil to protrude frontward from the hammer case, and filled with grease. The spindle includes a grease supply path located in the spindle and open in a sliding surface of the spindle on which the hammer slides to allow grease to be supplied to the sliding surface, and an accelerator in the spindle to accelerate a flow of the grease onto the sliding surface along the grease supply path in response to rotation of the motor.