Pneumatic Impact Tool Speed Control via Centrifugal Governor
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Solution Overview
Problem
Impact tools with ball-and-cam impact mechanisms often require specific rotational speeds for optimal operation, which existing technologies struggle to control effectively, leading to inefficiencies and potential damage from excessive speed.
Innovation Solution
A pneumatically powered impact tool with a speed controller that regulates the flow of compressed fluid to the motor by adjusting the size of an orifice using a plunger and masses, ensuring the rotational speed remains within optimal limits by overcoming spring bias with centripetal forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a ball-and-cam impact mechanism is used to convert motor torque into rotary blows, then powerful impact force is achieved, but the mechanism requires precise control of rotational speed to prevent damage and maintain optimal operation
Solution Approach 1:
The patent employs a centrifugal governor mechanism that provides automatic feedback control of the motor speed. As the rotor spins faster, centrifugal force pushes masses outward along ramped surfaces, which progressively closes an orifice to restrict compressed fluid flow to the motor. This creates a self-regulating feedback loop where speed increases automatically trigger reduction in fluid flow, maintaining optimal rotational speed for the impact mechanism without external control systems.
2Productivity
If the rotational speed of the motor is increased to improve productivity, then more impacts per minute are achieved, but excessive speed causes damage to the impact mechanism and reduces operational reliability
Solution Approach 1:
The centrifugal governor mechanism is a self-regulating system that automatically controls motor speed without external intervention. The masses and ramped surfaces form a self-actuating mechanism where centrifugal force from the rotor's own rotation directly controls the orifice opening, creating a self-limiting system that prevents excessive speed and protects the impact mechanism from damage.
3Reliability
If a speed controller is added to regulate rotational speed, then operational reliability is improved, but device complexity increases due to additional components
Solution Approach 1:
The patent utilizes the existing compressed fluid system already present in pneumatic impact tools to power the governor mechanism. The same compressed air that drives the motor also acts on the orifice controlled by the governor, eliminating the need for separate hydraulic or pneumatic control systems. This integration reduces overall system complexity while maintaining effective speed control.
Solution Approach 2:
The centrifugal governor acts as a mechanical intermediary between the rotating rotor and the compressed fluid flow. Rather than using complex electronic sensors and control systems, the governor translates rotational speed into mechanical displacement of the orifice through purely mechanical centrifugal force, providing a simple yet effective control interface.
Data Source
AI summary
Illustrative embodiments of impact tools with speed controllers and methods of controlling such impact tools are disclosed. In at least one illustrative embodiment, an impact tool may comprise a ball-and-cam impact mechanism including a hammer and an anvil. The hammer may be configured to rotate about a first axis and to translate along the first axis to impact the anvil to cause rotation of the anvil about the first axis. The impact tool may further comprise a motor and a speed controller. The motor may include a rotor configured to rotate when a flow of compressed fluid is supplied to the rotor to drive rotation of the hammer of the ball-and-cam impact mechanism. The speed controller may be coupled to the rotor and may be configured to throttle the flow of compressed fluid supplied to the rotor based on a rotational speed of the rotor.