Tractor Drawbar Coupling Assembly for Tool-Free Position Changes
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Solution Overview
Problem
The existing coupling arrangement for agricultural tractors requires high effort to move the pull rod between different coupling positions due to the direct application of vertical forces on screw connections, making it difficult to change positions without a workshop visit.
Innovation Solution
A coupling arrangement with a pull rod that can be moved longitudinally and locked into different positions using a threadless securing bolt and support cheeks, which directs vertical forces into the coupling carrier plate, reducing the effort required for actuation and allowing manual adjustment without tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If screw connections (hexagon bolts) are used to secure the drawbar to the coupling carrier plate, then the vertical forces during attachment operation can be transmitted directly to the coupling carrier plate, but the tightening torques required become correspondingly high, making it difficult to move the drawbar between coupling positions without a workshop visit
Solution Approach 1:
The drawbar is divided into two rod sections (first rod section and second rod section) that can be independently positioned and secured. The first rod section is mounted in a bracket on the differential housing, while the second rod section is guided in support cheeks of the coupling carrier plate. This segmentation allows each section to be optimized for its specific function, with the second rod section's guidance system handling the securing mechanism separately from the force transmission path.
Solution Approach 2:
The guidance system formed by the two support cheeks (upper and lower support cheeks) acts as an intermediary between the vertical forces during attachment operation and the actuating forces required to lock the drawbar. By guiding the second rod section longitudinally within these support cheeks, the system separates the force transmission function from the locking function, allowing the locking bolt to operate independently without bearing the full vertical loads.
2Reliability
If high tightening torques are required for the screw connection, then reliable securing is achieved, but the locking mechanism becomes complex and requires tools for operation
Solution Approach 1:
The traditional threaded screw connection is replaced with a threadless securing bolt system. The locking bolt (82, 84) is a simple cylindrical element without threads that passes through positioning openings and is secured by a collar resting against the coupling carrier plate and a free end secured by a cotter pin. This substitution eliminates the need for high tightening torques and complex threading mechanisms, allowing for simple manual operation with basic tools or even tool-free adjustment.
3Strength
If the drawbar is secured with threaded hexagon bolts requiring high tightening torques, then secure attachment is achieved, but the time required to change coupling positions increases significantly
Solution Approach 1:
The positioning openings (86, 88, 90, 92, 94, 96, 98, 100) are pre-formed in both the coupling carrier plate and the second rod section, with multiple openings positioned at intervals corresponding to different coupling positions. The locking bolt is designed in advance with a collar and free end configuration that enables quick insertion and removal. This preliminary preparation of the locking mechanism and positioning features allows for rapid coupling position changes without requiring time-consuming tightening operations.
Data Source
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AI summary
A coupling assembly (10) for an agricultural tractor (12) comprises a drawbar (16) with a first rod section (22) which is longitudinally displaceable in a holder (26) for mounting on a lower surface (38) of a differential housing (40) of the agricultural tractor (12), and a second rod section (24) opposite the first rod section (22), which is longitudinally displaceable within adjacent upper and lower support flanges (42, 44) of a coupling carrier plate (50) intended for rear mounting on the agricultural tractor (12). The drawbar (16) can be moved longitudinally into several coupling positions (18, 20) and locked therein relative to the coupling carrier plate (50) by means of at least one locking element (78).