Break-Off Screw Plug Structure for Leak-Safe Hydraulic Removal
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Solution Overview
Problem
Conventional locking screws with internal attacks fail to meet the required tightening and breakaway torques, leading to potential hydraulic fluid leakage and difficulty in removing the screw-in section, especially when designed with a cross slot or weakened stop body.
Innovation Solution
A locking screw with a contact flange featuring an external tool attack and a circumferential inner recess, allowing for a tear-off area formation behind the base when excessive torque is applied, enabling secure loosening with a tool while maintaining closure of the connecting hole to prevent sudden pressure loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a locking screw with internal attack only is used, then the device complexity is reduced, but the tightening torque and breakaway torque requirements cannot be met
Solution Approach 1:
The patent combines both internal attack (recess in mounting flange) and external attack (protrusion on contact flange) into a single screw structure. The external attack protrusion extends through the mounting flange, allowing tool engagement from both sides simultaneously, thereby achieving the required tightening and breakaway torques while maintaining structural integrity
2Strength
If an additional internal engagement is provided by a slot in the stop body, then the tightening torque can be increased, but the stop body is weakened and may break off
Solution Approach 1:
The patent segments the attack mechanisms into two independent parts: external attack through the contact flange protrusion and internal attack through the mounting flange recess. This segmentation allows the stop body to remain intact without slots or weakenings, while still achieving the required torque transmission through the external attack mechanism
3Reliability
If the mounting flange tears off due to excessive torque, then the safety factor is reduced, but the force flow passes through the base causing complete failure
Solution Approach 1:
The patent extracts the force flow path from the base by creating a dedicated tear-off zone in the transition area between the mounting flange and screw-in section. This separation ensures that if the mounting flange fails, the force does not propagate through the base, and the screw-in section remains sealed by the base, preventing catastrophic hydraulic fluid leakage
4Reliability
If the screw-in section cannot be removed after head breakage, then the reliability is improved, but the ease of operation deteriorates due to difficulty in removal
Solution Approach 1:
The patent prepares the screw-in section in advance for potential removal by ensuring the recess with internal attack extends through the entire screw-in section with sufficient engagement length. This preliminary design ensures that even if the mounting flange breaks off, the screw-in section can be easily removed using a tool engaged with the internal attack, preventing the need for destructive removal methods
Data Source
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AI summary
The present invention relates to a screw plug for an outlet opening of fluid-conducting housings, comprising a circular-cylindrical screw-in portion (1) having an external thread (2) and an abutment flange (3) with an enlarged outside diameter compared with the screw-in portion (1) at one end of the screw-in portion (1). The screw-in portion (1) is configured with the abutment flange (3) as a one-piece, single-material plastics injection-moulded part and closed at one end by a base (4). A recess (6) extends, as internal engagement socket for a tool, centrally in the longitudinal direction through the abutment flange (3) and the screw-in portion (1), said recess (6) ending at the base (4) and having a plug-in opening (7), opposite the base (4), for the tool. The abutment flange (3) has, on its outer circumference, an external engagement portion (8) for a tool, wherein, between the external engagement portion (8) and the internal engagement socket (6), an encircling inner recess (12) having a flange opening (14) is arranged. Such a wall formation is present in the transition region between the abutment flange (3) and the screw-in portion (1) that, in order for the abutment flange (3) to break off in the screwed-in state of the screw-in portion (1) and abutment of the abutment flange (3) on account of an increased break-off torque, compared with the permissible tightening torque, on the external engagement portion (8) as seen in the screw-in direction (X), a break-off region is formed in the region at the end of the screw-in portion (1) and behind the base (4) such that the force flow within the screw plug does not run through the base (4) in the event of breaking off. In this case, such a minimum engagement length (L) of the recess (6) for the internal engagement socket is present that detachment of the screw plug is possible by means of a tool inserted into the internal engagement socket (6).