INTRODUCTION

This disclosure generally relates to self-retaining mechanical plugs and compatible sockets.

In manufacturing and assembly environments such as in the automotive industry, a structural assembly such as an automotive cockpit or passenger compartment may include an enclosed compartment made of thin-walled material such as sheet metal or the like. A wall of this compartment may have a hole formed therethrough, which may be used for ventilation, drainage, inspection, tool access or other purposes. In some cases, such a hole may need to be covered up for some time by a plate or cover, and then uncovered at other times. One approach for this is to provide bolts or threaded studs adjacent the hole, either attached on the exterior surface of the wall or fed through from the interior side of the wall. A plate having small holes corresponding to the placement of the bolts or studs may then be placed over the hole in the wall such that the bolts or studs protrude through the small holes, and nuts may be spun onto the bolts or studs, thereby removably fastening the plate against the hole. The plate may optionally have a sampling/monitoring port therethrough, with one end of a hose sealably connected to the port and the other end of the hose sealably connected to a device used for sampling or monitoring the atmosphere or other conditions on the other side of the plate.

This approach involves the use of multiple pieces of hardware, such as bolts or studs, nuts and a plate or cover. Plus, it involves either welding or affixing two or more threaded studs onto the exterior side of the compartment wall where the plate is to be placed, or drilling two or more small holes through the wall and passing bolts through the small holes from the interior side of the compartment and fixing the bolts in place (such as by using low-profile stop nuts).

Furthermore, in automated manufacturing and assembly environments, measures may be put in place to assure that processes have been adequately performed. For example, after certain fasteners and plugs have been installed into an assembly, manual or automated checks may be made to assure that the fasteners and plugs have been installed using the proper torque. A torque gun or torque wrench may be used to apply clockwise and/or counterclockwise torque to the fasteners and plugs, to test whether they do or do not turn using a minimum and/or maximum torque, as the particular case may be.

In some automated environments, testing equipment such as torque guns and torque wrenches may include sensors and other apparatus that generate a signal indicating the amount of torque applied, the amount of torque resistance encountered from the fastener or plug, the magnitude and rotational speed of the fastener or plug turning, and so forth. If a fastener or plug is tested as described above and the fastener or plug fails to meet the expected torque requirements, a signal may trigger an alarm to indicate the need for attention to the failure, and in some cases the signal may also trigger a shut-down of the automated assembly line.

Additionally, once a fastener or plug is installed, it may be difficult to determine by manual testing whether the fastener or plug is adequately installed to the desired torque.

SUMMARY

According to one embodiment, a plug has a longitudinal axis defining forward and rearward axial directions, inward and outward radial directions, and clockwise and counter-clockwise circumferential directions as viewed in the forward direction. The plug includes a plug body having opposed forward and rearward ends wherein the forward end has a generally flat sealing surface facing in the forward direction, and a protuberance extending from the forward end of the plug body generally concentric with the longitudinal axis. The protuberance has a first section contiguous with the plug body, and a second section having a hub portion contiguous with the first section and a plurality of generally evenly spaced arms extending outward from the hub portion. Each arm has a clockwise radial edge, a counter-clockwise radial edge and an underside surface facing the sealing surface of the plug body. A major portion of the underside surface of each arm is generally flat and generally parallel to the sealing surface. A respective rearwardly projecting nub is located on the respective underside surface of each respective arm of the plurality of arms, proximate the clockwise radial edge of each respective arm. Each nub has a ramp on a clockwise side thereof terminating rearwardly in an apex, and a wall on a counter-clockwise side thereof extending generally in the radial and axial directions from the apex to the major portion of the underside surface.

The plug may further include a generally circular elastomeric seal affixed on the sealing surface of the plug body generally concentric with the longitudinal axis. Each arm may have a radial span S from the longitudinal axis to a radial end of each arm, with the elastomeric seal having an inner radius N that is greater than the radial span S of each arm.

At least a portion of the plug body may have an outer circumferential surface adapted for engagement by a wrench and/or a socket, for rotation of the plug about its longitudinal axis. The plug may further include a nipple extending from the rearward end of the plug body, and a through-hole extending through at least the nipple and the plug body, and alternatively through the nipple, the plug body and the protuberance.

Each arm may have a radial end having an arcuate profile as viewed in the axial direction. The nub on each arm may be located proximate a radially distal end of the clockwise radial edge of the arm.

The plug may be rotatable in the clockwise direction for sealable insertion into a socket formed in a thin-walled part. The socket may include the thin-walled part, defining an aperture therethrough bounded by a rim of the thin-walled part about the aperture. The aperture may have a generally circular or generally regular polygonal perimeter. The socket also includes a plurality of generally evenly spaced tabs of the thin-walled part extending radially inward from the perimeter, wherein the number of tabs is a positive integer multiple of the number of arms. Each tab may have a length L as measured radially from the perimeter to a radial end of the respective tab, each arm may have a radial span S as measured radially from the longitudinal axis to a radial end of the respective arm, and the perimeter may define an inscribed circle inscribed therein having a radius R, wherein R−L<S<R.

According to one embodiment, a mechanical plug has a longitudinal axis defining forward and rearward axial directions, inward and outward radial directions, and clockwise and counter-clockwise circumferential directions as viewed in the forward direction. The plug includes a plug body having opposed forward and rearward ends. The forward end has a generally flat sealing surface facing in the forward direction, and a generally circular elastomeric seal affixed on the sealing surface generally concentric with the longitudinal axis. At least a portion of the plug body has an outer circumferential surface adapted for engagement by a wrench and/or a socket for rotation of the plug about the longitudinal axis. A protuberance extends from the forward end of the plug body generally concentric with the longitudinal axis. The protuberance has a first section contiguous with the plug body, and a second section having a hub portion contiguous with the first section and a plurality of generally evenly spaced arms extending outward from the hub portion. Each arm has a clockwise radial edge, a counter-clockwise radial edge and an underside surface facing the sealing surface of the plug body. A major portion of the underside surface of each arm is generally flat and generally parallel to the sealing surface. A respective rearwardly projecting nub is located on the respective underside surface of each respective arm of the plurality of arms proximate the clockwise radial edge of each respective arm. Each nub has a ramp on a clockwise side thereof terminating rearwardly in an apex, and a wall on a counter-clockwise side thereof extending generally in the radial and axial directions from the apex to the major portion of the underside surface. Each arm may have a radial span S from the longitudinal axis to a radial end of each arm, with the elastomeric seal having an inner radius N that is greater than the radial span S of each arm.

The mechanical plug may also include a nipple extending from the rearward end of the plug body, and a through-hole extending through at least the nipple and the plug body. Alternatively, the through-hole may extend through the nipple, the plug body and the protuberance.

Each arm may have a radial end having an arcuate profile as viewed in the axial direction. The nub on each arm may be located proximate a radially distal end of the clockwise radial edge of the arm.

According to one embodiment, a fastening system includes a plug and a compatible socket. The plug has a longitudinal axis defining forward and rearward axial directions, inward and outward radial directions, and clockwise and counter-clockwise circumferential directions as viewed in the forward direction. The plug includes a plug body having opposed forward and rearward ends, wherein the forward end has a generally flat sealing surface facing in the forward direction. A protuberance extends from the forward end of the plug body generally concentric with the longitudinal axis. The protuberance has a first section contiguous with the plug body, and a second section having a hub portion contiguous with the first section and a plurality of generally evenly spaced arms extending outward from the hub portion. Each arm has a clockwise radial edge, a counter-clockwise radial edge and an underside surface facing the sealing surface of the plug body. A major portion of the underside surface of each arm is generally flat and generally parallel to the sealing surface. A respective rearwardly projecting nub is located on the respective underside surface of each respective arm of the plurality of arms proximate the clockwise radial edge of each respective arm. Each nub has a ramp on a clockwise side thereof terminating rearwardly in an apex, and a wall on a counter-clockwise side thereof extending generally in the radial and axial directions from the apex to the major portion of the underside surface. The socket may be formed in a thin-walled part, and may include an aperture through the thin-walled part bounded by a rim of the thin-walled part thereabout. The aperture has a generally circular or generally regular polygonal perimeter, and a plurality of generally evenly spaced tabs of the thin-walled part extending radially inward from the perimeter. The number of tabs may be a positive integer multiple of the number of arms. The plug may be rotated in the clockwise direction about the longitudinal axis for sealable insertion into the socket. The plug may further include a generally circular elastomeric seal affixed on the sealing surface of the plug body generally concentric with the longitudinal axis, wherein each arm has a radial span S from the longitudinal axis to a radial end of each arm, and the elastomeric seal has an inner radius N that is greater than the radial span S of each arm. The nub on each arm may be located proximate a radially distal end of the clockwise radial edge of the arm. Each tab may have a length L as measured radially from the perimeter to a radial end of the respective tab, each arm may have a radial span S as measured radially from the longitudinal axis to a radial end of the respective arm, and the perimeter may define an inscribed circle inscribed therein having a radius R, wherein R-L<S<R.

