Rail Screw Tightening Machine Using Reaction Torque Feedback
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Solution Overview
Problem
Existing screwing machines for tightening or loosening rail fitting screws face complexities in construction, mechanical damage susceptibility, and inaccuracies due to wear and inertia in torque limitation methods, particularly with servo screwdrivers and hydraulic drives.
Innovation Solution
A screwing machine with a motor that uses a measuring means to record the reaction moment between the motor and the machine frame, allowing for precise torque control through a load cell and controller, eliminating the need for complex assemblies and reducing mechanical stress, and enabling accurate torque limitation by using a hydraulic or electric motor with direct torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a servo screwdriver with integrated torque measuring shaft is used, then torque measurement capability is achieved, but the spindle length increases and construction complexity increases
Solution Approach 1:
The torque measurement function is extracted from the spindle and relocated to the motor. A measuring means is arranged between the motor and the machine frame to record the reaction moment of the motor, separating the measurement function from the drive shaft assembly and simplifying the overall construction.
Solution Approach 2:
The reaction moment of the motor serves as an intermediary parameter to indirectly measure the torque applied to the screw. By measuring the reaction moment acting from the motor on the machine frame, the torque can be determined with high accuracy without requiring direct measurement in the spindle.
2Measurement precision
If a servo screwdriver with integrated torque measuring shaft is used, then torque measurement capability is achieved, but the system becomes susceptible to mechanical damage
Solution Approach 1:
The torque measurement function is extracted from the mechanically vulnerable spindle and relocated to the motor, which is a more robust component. The measuring means records the reaction moment of the motor, protecting the measurement system from mechanical damage while maintaining measurement capability.
3Ease of operation
If a mechanical friction clutch is used for torque limitation, then torque control is achieved, but inaccuracies occur due to wear and inertia
Solution Approach 1:
The mechanical friction clutch system is replaced with a motor control system that uses measured reaction moment data. The controller is supplied with measurement values proportional to the reaction moment and controls the motor depending on these values, eliminating wear and inertia errors associated with mechanical clutches.
Solution Approach 2:
The system implements feedback control by supplying the controller with measurement values proportional to the reaction moment and using these values to control the motor. This closed-loop control ensures accurate torque limitation without the inaccuracies inherent in mechanical friction-based systems.
4Power
If a hydraulic drive system is used for torque application, then high torque with small frame size is achieved, but inaccuracies occur due to temperature and viscosity dependency
Solution Approach 1:
The hydraulic system incorporates feedback control where the controller receives measurement values proportional to the reaction moment and adjusts motor control accordingly. This compensates for temperature and viscosity variations in the hydraulic fluid, maintaining accurate torque limitation while preserving the high torque density advantage.
5Force
If transmission means such as clutches or gears are used between motor and screw head, then torque transmission is achieved, but damping and elastic effects reduce accuracy
Solution Approach 1:
The torque measurement function is extracted from the transmission path and placed at the motor. By measuring the reaction moment directly at the motor, the system avoids the damping and elastic effects that would otherwise interfere with torque measurement accuracy in the transmission components.
Solution Approach 2:
The system segments the torque transmission path by placing the measurement means at the motor rather than in the transmission components. This separation allows accurate measurement of the source torque without being affected by losses or deformations in the transmission means.
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 provides a simple, robust, and accurate method for torque control, ensuring precise rotation speed limitation and reducing maintenance needs, while maintaining high torque application with a compact design, suitable for demanding conditions like track construction.
Implementation Method 1
the measuring means comprises a load cell for measuring a force acting on the motor
Data Source
AI summary
A screwing machine tightens or releases rail fixing screws. The screwing machine contains a machine frame which can be rolled on a track, handles for moving the screwing machine, a motor for applying a torque to a screw head, and a device for transmitting a torque. A measuring device is provided opposite the machine frame in order to detect a reaction torque of the motor. The motor is actuated in order to limit the torque depending on the reaction torque. The reaction torque is used as a reference variable. The reaction torque is applied to the machine frame by the motor and is ascertainable with a high degree of precision by a simple measuring device. In this manner, a simple and robust design and a precise rotational speed limiting function are implemented.