Conduit Boot Bushing Structure to Prevent Rubber Over-Compression
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Solution Overview
Problem
In turbine engine applications, standard torque application to rubber elements in bolt stacks can cause permanent damage due to compressibility and varying hardness levels, particularly when low-hardness rubber is used, leading to over-compression beyond design intent.
Innovation Solution
The integration of a solid material bushing seated in a slot of the rubber flange, which absorbs compressive forces from the fastener, preventing over-torque damage and ensuring a secure sealing interface between the conduit and case.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard torque is applied to rubber elements in a bolt stack, then the sealing interface is secured, but the rubber elements suffer permanent damage due to over-compression
Solution Approach 1:
A rigid bushing is introduced as an intermediary component between the fastener and the rubber flange. The bushing has a land portion that contacts the rubber flange and a slot that receives the fastener. This mediator allows the fastener to apply torque without directly compressing the rubber, thus protecting the rubber from over-compression damage while still enabling the sealing function.
Solution Approach 2:
The invention changes the mechanical parameters of the connection by introducing a rigid bushing with specific geometric features (land portion and slot). The bushing transforms the compression-based connection into a bearing-based connection, where the fastener torque is transferred through the rigid bushing land to the rubber flange without excessive compression, thereby changing the stress distribution and protecting the rubber.
2Reliability
If low-hardness rubber is used in the bolt stack, then the sealing capability is improved, but the rubber becomes more susceptible to over-compression damage
Solution Approach 1:
The rigid bushing serves as a protective intermediary between the fastener and the soft rubber flange. By receiving the fastener in its slot and transferring the load through its land portion, the bushing shields the low-hardness rubber from direct high-compression forces, enabling the use of softer rubber for better sealing without the risk of over-compression damage.
3Device complexity
If the rubber flange is directly attached to the case, then the assembly is simple, but the rubber suffers permanent damage due to compressibility
Solution Approach 1:
The bushing is a simple intermediary component that is integrated into the rubber flange structure. It adds minimal complexity to the assembly while effectively protecting the rubber from over-compression. The bushing with its land and slot configuration provides a straightforward solution that maintains assembly simplicity while preventing rubber damage.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
An assembly (10) for sealing an interface between a conduit (14) and a case (12) includes a boot (16) and a bushing (24; 124; 224). The boot (16; 116; 216) includes a tube (18; 118; 218) and rubber flange (20; 120; 220). The rubber flange (20; 120; 220) extends generally radially outward from the tube (18). The rubber flange (20; 120; 220) includes an opening (22; 122; 222) passing through a portion of the rubber flange (20; 120; 220). The bushing (24; 124; 224) is disposed in the rubber flange (20; 120; 220) and includes a tubular body (28; 128; 228), a channel (30; 130; 230), and a lip (32; 32A, 32B; 132; 232). The tubular body (28; 128; 228) is disposed in the opening (22; 122; 222) of the rubber flange (20; 120; 220). The channel (30; 130; 230) extends through a center of the body (28; 128; 228). The lip (32; 32A, 32B; 132; 232) is generally flat and extends radially outward from the tubular body (28; 128; 228). The lip (32; 32A, 32B; 132; 232) is in contact and engages with the rubber flange (20; 120; 220) so as to compress the rubber flange (20; 120; 220) against the case (12).