Machine Tool Clamping Device with Integrated Force Accumulator
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Solution Overview
Problem
Existing clamping devices for machine tools face inaccuracies in measuring clamping force due to undefined spindle nut positioning between spring assemblies with different spring characteristics, leading to errors and frictional forces, making precise distance-dependent measurement impossible without complex controls.
Innovation Solution
Integration of the movement converter and energy accumulator as a functional unit in a separate tubular jacket piece with rotatably supported spindle nut, using a displacement sensor to measure the adjustment path, and adjustable spring assemblies clamped between stop rings and covers to maintain constant preload, allowing for precise clamping force measurement with one displacement sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the spindle nut is clamped between two spring assemblies with different spring characteristics, then the clamping device can maintain force, but measurement precision deteriorates due to encoding errors and friction
Solution Approach 1:
The clamping device is divided into functionally independent segments: the spindle nut assembly for clamping force application and the spring assembly for force maintenance. This segmentation allows each component to perform its specific function without interfering with measurement accuracy, resolving the contradiction between reliable force maintenance and precise measurement.
Solution Approach 2:
The spring assembly is extracted from the measurement path. By positioning the spring assembly separately from the spindle nut and sensors, the system eliminates the interference of spring forces and friction on the measurement process, while the spring assembly continues to maintain clamping force independently.
2Measurement precision
If two sensors are used to measure encoder difference between spindle nut and pull rod, then clamping force can be determined, but device complexity increases
Solution Approach 1:
The spring assembly and its associated measurement challenges are extracted from the measurement path. This allows the use of a single displacement sensor to measure only the relevant parameter (spindle nut position) without needing to compensate for spring force variations or friction, thereby reducing device complexity while maintaining measurement accuracy.
Solution Approach 2:
A magnetic coupling mechanism acts as an intermediary to transmit rotational position information from the spindle nut to the displacement sensor without mechanical contact. This eliminates friction and wear in the measurement path while maintaining accurate position feedback, simplifying the overall system.
3Ease of manufacture
If spring assemblies are inserted in displaceable bushings with undefined positioning, then assembly is simple, but measurement accuracy deteriorates due to undefined axial positions
Solution Approach 1:
The spring assembly is extracted from the measurement path and positioned in a separate location within the housing. This extraction eliminates the problem of undefined axial positioning affecting measurement accuracy, while the spring assembly remains freely displaceable to maintain its force maintenance function.
Solution Approach 2:
The mechanical connection between the spring assembly and the measurement system is replaced with a magnetic coupling mechanism. This substitution eliminates the need for precise mechanical positioning and alignment, allowing simple assembly while maintaining accurate measurement through non-contact sensing.
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
Enables precise clamping force measurement in all operating positions with reduced construction effort, maintaining constant preload and operational reliability, and allowing versatile applications with high service life and low energy consumption.
Implementation Method 1
the energy store (41) acting on the pull rod (7, 7') being formed from pretensioned spring assemblies (42, 43)
Implementation Method 2
the adjustment path of the casing piece (52) or of the spindle nut (32) of the movement converter (31) is measured and evaluated using a displacement sensor
Data Source
AI summary
The clamping device (1) has motion converter (31) and force accumulator (41) that are integrated as functional unit (51) in housing (21). A tie rod (7) is connected to portions (53,54) of casting element (52). A spindle nut (32) of motion converter is rotatably supported by projecting lug (38). The spring assemblies of the force accumulator are arranged on the sides of the portions of the casing element, and are movable between stop rings. A circular trained cover (61) is clamped to the casting element and motion converter is mounted in housing by tie rod.