Self-Locking Spindle Traction Mechanism With Gear Speed Step-Up
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Solution Overview
Problem
Existing spindle traction mechanisms for surgical applications face challenges in achieving both quick movement and self-locking while maintaining a compact design, as high pitch spindles are not self-locking under axial forces and low pitch spindles require excessive revolutions, leading to undesirably large and heavy designs.
Innovation Solution
A spindle traction mechanism with a gear system that steps up rotational movement, combined with a restraining device providing frictional resistance proportional to the applied load, allowing for a compact spindle design with a diameter less than 20 mm and pitch of 3 mm, ensuring self-locking under high loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a spindle with higher pitch is used to reduce the number of revolutions, then the speed of movement is improved, but the self-locking capability is lost due to insufficient friction forces
Solution Approach 1:
A gear mechanism is introduced as an intermediary between the drive device and the spindle. This gear steps up the rotational speed from the drive device to the spindle, enabling the spindle to complete multiple revolutions per drive revolution. This resolves the contradiction by providing high spindle speed (improving movement speed) while keeping the spindle pitch small (maintaining self-locking capability through sufficient friction forces).
Solution Approach 2:
The invention changes the operational parameters by using a gear ratio greater than 1:1 (specifically 3.5:1 in the embodiment). This parameter change allows the drive device to rotate fewer times while the spindle rotates more times, achieving fast positioning without requiring a large pitch that would compromise self-locking.
2Reliability
If a spindle with lower pitch is used to ensure self-locking, then the self-locking capability is improved, but the number of revolutions required increases making operation laborious
Solution Approach 1:
The gear mechanism acts as a mediator that decouples the relationship between drive revolutions and spindle revolutions. With a gear ratio of 3.5:1, one revolution of the drive device produces 3.5 revolutions of the spindle, allowing the user to operate the mechanism with fewer, easier revolutions while the spindle still completes the necessary rotations for quick positioning.
3Reliability
If the diameter of the spindle is increased to achieve self-locking with higher pitch, then the self-locking capability is improved, but the weight and size of the mechanism increase undesirably
Solution Approach 1:
The invention changes the pitch parameter of the spindle to a smaller value (3 mm pitch) rather than increasing the diameter. This parameter change allows self-locking to be maintained with a compact spindle diameter of less than 20 mm, avoiding the weight and size penalties that would result from using a larger diameter spindle.
4Productivity
If a gear system is introduced to step up speed, then the productivity is improved, but the device complexity increases
Solution Approach 1:
A single gear mechanism is introduced as a compact intermediary between the drive device and spindle. This relatively simple gear system provides a 3.5:1 speed step-up, enabling quick positioning (high productivity) while adding minimal complexity to the overall mechanism. The gear is integrated into the existing spindle structure, minimizing the increase in device complexity.
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 quick and efficient positioning of patient's foot with minimal crank revolutions, maintaining self-locking even under high tensile forces, and achieving a compact and ergonomic design.
Implementation Method 1
a gear that is connected between the drive device and the threaded spindle drive, wherein the gear is configured for stepping up the speed of a rotational movement of the drive device and delivering it to the threaded spindle drive
Implementation Method 2
the restraining device has a friction pair, wherein the friction pair is made up of a first contact surface situated on the housing, and a second contact surface situated on the threaded spindle drive, 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 frictional resistance is present that prevents an automatic relative rotation between the spindle and the spindle nut due to the tensile force
Implementation Method 3
a threaded spindle drive with a) a spindle having an external thread that extends along the longitudinal axis; and b) a spindle nut that is seated on the spindle and that has an internal thread that engages with the external thread
Data Source
AI summary
A self-locking spindle traction mechanism for use in surgical procedures has a longitudinal axis (L). The mechanism may include an operating end, a connecting end for connecting a surgical accessory, and a threaded spindle drive. The spindle drive may include a spindle having an external thread, and a spindle nut that is seated on the spindle and has an internal thread. The mechanism may include a slide that is movable along the longitudinal axis by a relative rotation between the spindle and the spindle nut, a drive device that is situated on the operating end for rotationally driving the threaded spindle drive, and a gear. The gear may be connected between the drive device and the threaded spindle drive, so that the gear is configured for stepping up the speed of a rotational movement of the drive device and delivering it to the threaded spindle drive.