Shaft Cooler Inside-Out Cooling for Spindle Thermal Expansion
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Solution Overview
Problem
Existing shaft cooling systems for tool motor spindles inadequately reduce shaft growth due to insufficient cooling, leading to suboptimal measurement accuracy in workpiece dimensional checking.
Innovation Solution
The cooling medium is fed into the rotating shaft through cooling bores in the static lance from the inside outwards, utilizing a symmetrical and eccentric cooling circuit design with forward-flow and return bores, and lip-seals to enhance sealing and reduce leakage, leveraging centrifugal force for efficient medium transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If external cooling or convection gap cooling is used, then some heat removal is achieved, but shaft growth is insufficiently reduced
Solution Approach 1:
Instead of cooling the shaft from the outside (external cooling) or through convection gaps, the patent inverts the approach by feeding cooling medium through bores from the inside outwards. The cooling medium is introduced into the hollow interior of the shaft and exits through the shaft's outer surface, directly cooling the shaft material from within. This internal cooling approach more effectively reduces shaft temperature and thermal expansion, thereby improving measurement accuracy.
2Temperature
If cooling medium is fed from outside inwards, then cooling is provided, but sealing and leakage control become problematic
Solution Approach 1:
The patent inverts the conventional cooling medium feeding direction. Instead of introducing cooling medium from the outside and having it flow inwards (which creates sealing challenges at the rotating interface), the cooling medium is fed from the inside outwards through bores in the shaft. This eliminates the need for complex sealing at the cooling medium introduction point, as the lance remains stationary and sealed at its base, while the cooled shaft rotates freely.
3Productivity
If high rotational speeds are used, then productivity increases, but bearing friction and heat generation increase
Solution Approach 1:
The patent implements continuous cooling of the shaft through constantly flowing cooling medium through the shaft bores. This continuous cooling action counteracts the continuous heat generation from bearing friction during high-speed rotation. The cooling medium flows continuously through the shaft, absorbing heat at all times, which allows the spindle to maintain high rotational speeds without excessive temperature rise in the bearings and shaft.
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
This approach minimizes shaft growth, ensuring high measurement accuracy and improved machining quality by maintaining a stable temperature, allowing for precise 3-D probing and extending the service life of the motor spindle through reduced thermal expansion and bearing rigidity.
Implementation Method 1
leveraging centrifugal force for efficient medium transfer
Implementation Method 2
feeding of the cooling medium into the static lance is effected via cooling bores, from the inside outwards into the rotating shaft
Data Source
AI summary
A shaft cooler (1) for a tool motor spindle (2), which has a rotating shaft (3), a static lance (4), and at least one coolant loop (7), which comprises a coolant inlet (5) and a coolant outlet (6), said shaft cooler being implemented such that the flow of the coolant from the static lance (4) into the rotating shaft (3) is performed via a flow path that includes radially-extending cooling holes (31) to cause the coolant to flow from a radially inside location to a radially outside location.