Threaded Spindle Drive With Bearing Rollers for Low-Friction Pressing

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Solution Overview

Problem

Existing power tools with hydraulically driven linear actuators are complex, large, heavy, inefficient, and require long working cycles, while threaded spindle drives lead to high friction losses, making them costly to minimize.

Innovation Solution

A power tool design featuring a threaded spindle drive with an inner and outer threaded spindle part connected via bearing rollers with radially encircling channels, reducing friction and allowing for efficient torque transmission with low rolling friction, and incorporating a telescopic shaft device and eccentric transmission for torque adaptation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If a hydraulically driven linear actuator is used, then high pressing forces can be generated, but the device becomes complex, large, heavy, and requires long working cycles

Engineering Contradiction:

Improvepressing forceVSAvoidstructural complexity

Core Design Contradiction:

ForceVSDevice complexity

Solution Approach 1:

The patent extracts the hydraulic system from the power tool, eliminating the hydraulic pump, fluid reservoir, and associated control mechanisms. Instead, it uses a direct electric motor driving a threaded spindle mechanism to generate linear motion and pressing force, thereby dramatically simplifying the overall device structure while maintaining high force capability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the hydraulic mechanical system with an electromechanical system consisting of an electric motor and threaded spindle drive. This substitution eliminates the need for hydraulic fluid, seals, and complex pressure control mechanisms, resulting in a simpler, more compact design with faster response times

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If a threaded spindle drive is used to eliminate hydraulics, then device complexity is reduced, but friction losses increase

Engineering Contradiction:

Improvestructural complexityVSAvoidfriction losses

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent employs spherical or cylindrical bearing rollers in the threaded spindle mechanism to replace traditional sliding contacts. These curved rolling surfaces significantly reduce friction losses compared to linear sliding interfaces, thereby improving energy efficiency while maintaining the simplified electromechanical structure

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The patent optimizes the thread geometry and bearing roller dimensions to minimize friction. By carefully selecting thread pitch, angle, and roller radius, the design achieves low friction coefficients that reduce energy losses while maintaining high force transmission capability

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If bearing rollers with complex helical threads are used to reduce friction, then friction losses decrease, but manufacturing cost and structural complexity increase

Engineering Contradiction:

Improvefriction lossesVSAvoidmanufacturing cost

Core Design Contradiction:

Loss of energyVSEase of manufacture

Solution Approach 1:

The patent divides the bearing roller into distinct functional segments: a simple cylindrical or spherical body with radially encircling channels, separate from the threaded spindle components. This segmentation allows the bearing roller to be manufactured as a simple, inexpensive part using standard machining or forming processes, while the threading is provided on the spindle parts themselves

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of providing helical threads on the bearing roller itself, the patent inverts the approach by providing the threading on the spindle parts and using simple bearing rollers with radially encircling channels. This inversion dramatically simplifies bearing roller manufacturing while achieving the same friction reduction effect through the rolling contact geometry

Inventive Principle:

Principle #13The other way round (Inversion)

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 design results in a power tool with high load-bearing capacity, low friction losses, and improved efficiency, making it cost-effective and suitable for mobile applications like pipe presses and crimping devices.

Implementation Method 1

The bearing roller can roll on the internal thread and on the external thread. The bearing roller thus forms a roller bearing, which can exhibit particularly low rolling friction in relation to sliding friction

Methodology Applied

Scientific EffectRolling friction: Friction

Data Source

PatentUS12257676B2Power tool with threaded spindle drive

Publication Date: 2025.03.25 HILTI AG

AI summary

A power tool is provided comprising a drive, an output shaft, a threaded spindle drive and a linear actuator, wherein torque generated by the drive is transmissible via the output shaft, and the threaded spindle drive connected to the output shaft, to the linear actuator. the threaded spindle drive has an inner threaded spindle part with an external thread and an outer threaded spindle part with an internal thread, wherein the internal thread interacts with the external thread via at least one bearing roller, and the at least one bearing roller has at least one radially encircling channel by which the bearing roller engages in each case into the external thread and into the internal thread.