Self-Locking Spindle Traction Mechanism for Faster Surgical Adjustment
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Solution Overview
Problem
Existing pull spindle units for surgical applications face challenges in being both self-locking and compact, as low pitch spindles require many revolutions for movement, while higher pitch spindles are not self-locking due to insufficient friction, and increasing spindle diameter makes the unit heavy and bulky.
Innovation Solution
A self-locking pull spindle unit with a high-speed gearbox and an additional locking device, featuring a trapezoidal spindle with a diameter of 12mm and 3mm pitch, and a planetary gear that translates one revolution of the drive device into 3.5 revolutions of the spindle drive, ensuring quick movement and self-locking under high loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spindle with a low pitch is used to achieve self-locking, then the pull spindle is self-locking, but a high number of spindle revolutions are required to travel the required distance
Solution Approach 1:
A locking device is introduced as an intermediary mechanism between the spindle and the external environment. This locking device includes a locking surface that contacts a counter-locking surface, creating a friction-based locking mechanism that works independently of the spindle pitch, thereby enabling self-locking without requiring low-pitch threads that would slow down adjustment
2Productivity
If a spindle with a larger pitch is used to reduce the number of revolutions, then the adjustment speed increases, but the pull spindle is no longer self-locking due to insufficient frictional forces
Solution Approach 1:
The locking device serves as a mediator that transfers and maintains the locking function separately from the pitch-dependent thread friction. By using a dedicated locking mechanism with sufficient frictional contact, the system achieves self-locking capability independent of the spindle pitch, allowing high-pitch spindles to be used for faster adjustment
3Reliability
If the spindle diameter is increased to achieve self-locking with a larger pitch, then the self-locking capability is maintained, but the pull spindle unit becomes heavy and bulky
Solution Approach 1:
The locking device acts as an intermediary that provides the necessary frictional locking force without requiring an increased spindle diameter. The locking mechanism with its contact surfaces generates sufficient friction to maintain self-locking, allowing the use of smaller-diameter, lighter spindles while preserving the self-locking function
4Reliability
If the spindle diameter is increased to maintain self-locking, then the self-locking capability is improved, but the pull spindle unit becomes oversized for the loads involved
Solution Approach 1:
The locking device is introduced as a separate intermediary component that handles the self-locking function independently of the spindle dimensions. This allows the spindle to be sized appropriately for the load requirements without being oversized for self-locking purposes, as the locking device provides the necessary frictional resistance
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 enables quick and efficient positioning of a patient's foot with fewer crank revolutions while maintaining self-locking, even under high loads, and allows for a compact design without the need for oversized spindles.
Implementation Method 1
the locking device has a friction pair, the friction pair consisting of a first contact surface located on the housing and a second contact surface located on the threaded spindle drive and opposite the first contact surface, wherein, when a tensile force is exerted on the connecting end along the longitudinal axis, the second contact surface is supported on the first contact surface in such a way that a frictional resistance exists which prevents automatic relative rotation between the spindle and the spindle nut
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
Self-locking spindle traction mechanism (16) for use in surgical interventions, with a longitudinal axis (L), comprising: - an operating end (11); - a connecting end for connecting a surgical accessory; - a threaded spindle drive (17) with a) a spindle (32) having an external thread; and b) a spindle nut (31), which is seated on the spindle (32) and has an internal thread which engages with the external thread; - a slide (22), which can be moved along the longitudinal axis by a relative rotation between the spindle and the spindle nut; - a driving device (20), which is located at the operating and (11) and is intended for rotationally driving the threaded spindle drive; and - a gear mechanism (30), which is arranged between the driving device (20) and the threaded spindle drive (17), wherein the gear mechanism is designed for stepping up the speed of the rotational movement of the driving device (20) and delivering it to the threaded spindle drive (17).