Retractable Drive Shaft With Slip Coupling for Repeatable Strap Tensioning
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Solution Overview
Problem
Existing drive formations face challenges in being easily accessible, avoiding overtightening, ensuring consistent torque delivery, and protecting against external damage, particularly in narrow spaces like packaging lids for securing loads to pallets.
Innovation Solution
A drive formation with a torque limiter that retracts upon slip, featuring a shaft movable between extended and retracted positions, a grip, torque transmission, locking element, and a slip coupling between coupling halves, allowing the shaft to return to a sheltered position upon torque overload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the drive formation is built into a narrow space to fit a thin object, then the system can be integrated into compact packaging lids, but the drive formation becomes difficult to access and operate manually
Solution Approach 1:
The drive formation is designed to dynamically change its position between retracted and extended states. The handle can be manually extended from the housing for operation, then automatically retracts after torque limiter slip, providing both compact integration and ease of operation.
Solution Approach 2:
The handle is nested within the housing when not in use, with the proximal end of the shaft placed outside the housing for access. This nesting arrangement allows the drive formation to fit into thin packaging lids while remaining manually accessible during operation.
2Ease of operation
If the drive formation is designed for manual operation in narrow spaces, then it becomes accessible, but it may deliver inconsistent torque and cause overtightening
Solution Approach 1:
The torque limiter provides mechanical feedback by slipping at a predetermined torque threshold. This slip event triggers the automatic retraction mechanism, giving the operator tactile and visual feedback that the correct torque has been applied, ensuring consistent and reliable torque delivery.
Solution Approach 2:
The drive formation is self-regulating through the torque limiter mechanism. Once the predetermined torque is reached, the system automatically limits further torque application and triggers retraction, eliminating the need for operator judgment and ensuring consistent torque delivery across multiple operations.
3Ease of operation
If the handle remains in the extended position after use, then it is easily accessible for repeated operations, but it becomes vulnerable to external damage
Solution Approach 1:
The handle dynamically transitions from an extended operational position to a retracted protected position. After torque limiter slip, the handle automatically retracts into the housing, protecting it from external damage during shipping and handling while remaining accessible when needed.
Solution Approach 2:
The housing provides protective cushioning for the handle when not in use. The retracted position places the handle within the protective enclosure of the housing, shielding it from external damage during storage and transport between operations.
4Force
If the drive formation delivers high torque to tighten straps, then it secures loads effectively, but it may overtighten and damage the system
Solution Approach 1:
The torque limiter provides mechanical feedback by slipping at a predetermined torque threshold. This slip event triggers the automatic retraction mechanism, giving the operator tactile and visual feedback that the correct torque has been applied, ensuring consistent and reliable torque delivery.
Solution Approach 2:
The torque limiter converts the potentially harmful effect of excessive torque into a beneficial safety feature. By designedly failing at a predetermined torque level, it prevents overtightening damage while ensuring sufficient tension for effective load securing.
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 easy access, consistent torque delivery, and protection from damage by retracting the grip into a sheltered position, preventing component breakage and ensuring repeatable tensioning results.
Implementation Method 1
a first spring element, configured for favouring the shaft in the retracted position
Implementation Method 2
the torque limiter comprises a slip coupling between a first coupling half and a second coupling half; wherein slip of the torque limiter causes translation of the second coupling half relative to the first coupling half in a direction along the axis of the shaft
Data Source
Figure 1a
Figure 1b
Figure 2a
AI summary
The invention provides in a drive formation, comprising: - a housing; - a shaft, wherein the shaft is axially movable between a retracted position and an extended position; - a grip; - a torque transmission; - a first spring element; - a locking element; - a torque limiter, wherein the torque limiter comprises a slip coupling between a first coupling half and a second coupling half; wherein the first coupling half is rotationally fixed to the grip; wherein the second coupling half is rotationally fixed to the shaft; wherein slip of the torque limiter causes translation of the second coupling half relative to the first coupling half in a direction along the axis of the shaft; and, wherein the second coupling half is configured to, upon axial movement, unlock the locking element. The invention provides further in a tensioning system for a strap comprising such a drive formation.