Sealed Ball Screw Drive Unit for Clean High-Dynamics Molding
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Solution Overview
Problem
Existing drive units for molding machines, particularly those with a rotatable spindle and non-rotatable nut, face limitations in dynamics and loadability, and often suffer from lubrication issues that lead to soiling of the surrounding area.
Innovation Solution
A drive unit design featuring a rotatably mounted spindle with an oil-tight seal, allowing for improved lubrication and cooling within an enclosed space, reducing inertia and enhancing dynamics while eliminating external soiling, and incorporating a gear unit for efficient power transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a ball screw with rotatable spindle and non-rotatable nut is used, then the inertia is reduced and dynamics are improved, but lubrication becomes problematic leading to soiling of the surrounding area
Solution Approach 1:
A seal ring is introduced as an intermediary element between the spindle and the surrounding environment. This seal ring prevents lubricant from escaping and contaminants from entering, thereby eliminating soiling while maintaining the beneficial low-inertia design with rotatable spindle and non-rotatable nut.
Solution Approach 2:
The harmful function of lubricant leakage is extracted and isolated by positioning the seal ring at the protrusion of the spindle. This separates the lubrication function from the harmful soiling effect, allowing the ball screw to operate with proper lubrication without contaminating the surrounding area.
2Force
If the drive power is increased to improve loadability, then the force capacity increases, but the inertia also increases reducing dynamics
Solution Approach 1:
The conventional design is inverted by making the spindle rotatable and the nut non-rotatable, rather than the traditional approach. This inversion transfers the rotational mass to the spindle which can be more efficiently driven, while the nut only translates linearly, reducing overall system inertia and improving dynamics while maintaining high loadability.
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 achieves higher dynamics and loadability with reduced inertia, ensuring sufficient lubrication and cooling, and allows for retrofitting in molding machines, enhancing the performance and efficiency of the drive unit.
Implementation Method 1
The oil-tight seal allows a sufficient lubrication of the ball screw, without having to accept soiling of the surrounding area
Implementation Method 2
an oil pan is arranged in the oil-tight space, in which the spindle is at least partly located. In addition to a sufficient lubrication of the ball screw, this also allows a cooling through the oil pan. Similarly, a gear train and/or the bearing of the spindle can also be cooled and lubricated in this way
Data Source
AI summary
A drive unit for driving at least one component of a molding machine, includes a first support, a spindle, a drive for rotating the spindle, a second support, a nut, at least one rod arranged on the second support, and an oil-tight seal. The spindle, the second support, and the nut are arranged along the spindle inside the oil-tight space in each movement position of the second support and the nut.