Electric Clamping Spindle with Spring Re-Tightening After STO
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Solution Overview
Problem
Existing electrically operated clamping devices cannot re-tighten a workpiece after a Safe-Torque-Off signal is applied, as the motor's power is no longer available, and mechanical elasticity is insufficient for this purpose.
Innovation Solution
A clamping device with an electric motor, power transmission means, and an energy storage device, featuring a bearing sleeve and a high-pitch threaded spindle, allows the electric motor to drive the clamping element, and the energy storage device provides a restoring force to re-tighten the clamping element even after the Safe-Torque-Off signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an electric motor is used to operate the clamping device, then the clamping force can be precisely controlled, but the motor power becomes unavailable after Safe-Torque-Off signal preventing re-tightening
Solution Approach 1:
The energy storage device is pre-loaded with potential energy before the clamping operation. When the motor loses power after Safe-Torque-Off, the pre-stored energy automatically activates to drive the threaded spindle and re-tighten the clamping element, ensuring continuous clamping force without requiring additional motor power.
Solution Approach 2:
The energy storage device creates a mechanical copy of the motor's clamping action. Instead of relying on the motor itself to re-tighten, the stored mechanical energy in the spring assembly replicates the tightening function through the threaded spindle mechanism, providing redundancy when the motor is unavailable.
2Reliability
If hydraulic accumulators are used to provide retightening force, then continuous clamping is possible, but the device complexity and system requirements increase
Solution Approach 1:
The invention extracts the energy storage function from the hydraulic system and implements it using a simple mechanical spring assembly. This eliminates the need for complex hydraulic accumulators, pressure vessels, and fluid management systems while achieving the same re-tightening effect through purely mechanical means.
Solution Approach 2:
The patent replaces the hydraulic mechanical system with a simpler mechanical spring system. The spring assembly directly stores and releases mechanical energy through the threaded spindle, substituting the complex hydraulic pressure generation and transmission system with a straightforward mechanical elastic energy storage and release mechanism.
3Reliability
If the restoring force of the energy storage device is greater than the propulsive force, then re-tightening is enabled, but the motor must overcome higher initial resistance
Solution Approach 1:
The system dynamically transitions between two states: during initial clamping, the motor overcomes the pre-loaded spring force to advance the threaded spindle; after clamping, the spring force reverses to maintain tension and enable automatic re-tightening. The high-pitch thread design allows the motor to quickly overcome the initial resistance and then the system transitions to passive spring-maintained clamping.
Solution Approach 2:
The threaded spindle uses a high-pitch thread design that changes the mechanical advantage parameter. This allows the motor to generate sufficient force to overcome the pre-loaded spring during the brief clamping phase, while the same high-pitch design enables the spring to generate adequate re-tightening force through the same mechanical leverage in the reverse direction.
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 the clamping device to maintain clamping force on the workpiece even after the Safe-Torque-Off signal, ensuring continuous operation without the need for motor power.
Implementation Method 1
a power storage device for pre-tensioning the at least one clamping or gripping element... wherein the restoring force of the power storage device is greater than a propulsive force required for driving the clamping or gripping element
Implementation Method 2
a threaded spindle guided in a threaded sleeve... by means of a threaded spindle guided in a threaded sleeve
Implementation Method 3
the drive shaft has a bearing sleeve between the electric motor and the power transmission means, relative to which the electric motor is axially displaceable
Data Source
Figure 1
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Figure 4~5
AI summary
With electrically operated clamping or gripping devices, such as vises, it is necessary to de-energize them after clamping the workpiece to prevent overheating. Machining, for example with a robot, can only begin once a safe torque-off signal is present. However, during such machining, the workpiece can loosen due to vibrations because the de-energized electric motor can no longer re-tighten. This can lead to damage to the workpiece and, in the worst case, injuries to the operator. The present invention therefore proposes a solution to enable re-tightening from a power storage device. This is achieved by extending the motor's drive shaft via a threaded spindle, thereby pre-tensioning the power storage device. Particularly when using a high-helix threaded spindle, this can enable effective re-tightening of the clamping or gripping device.