Compliant grooved sealing ring for threadably secured assembly

#This invention relates to a complaint grooved sealing ring for providing a sealed joint between two threadably secured members and more particularly to such a sealing ring whose groove is formed with a V-shape so as to provide high compliance during tightening of the mating parts and then on subsequent relative tilting therebetween the ring can follow their movement without parting therefrom.

#In a threadably secured assembly such as gas cap for closing the filler neck on an automotive vehicle fuel tank, it is common practice to employ a solid elastomeric O-ring to seal their connection. An example of such an arrangement including a torque limiter mechanism is disclosed in U.S. patent application Ser. No. 516,032 assigned to the assignee of this invention. Typically, the O-ring provides satisfactory sealing under the preload determined by the torque limiter mechanism so long as the opposing seats on the cap and filler neck remain parallel which is the normal case. However, it has been found that such a sealing ring configuration is too limited by its inherent compliance characteristics in maintaining sealing should there occur some forced substantial tilting between the cap and filler neck on the occasion of a severe impact providing a large moment on the cap about an axis transverse to that of the cap and neck.

#One well known method of increasing the compliance is to make the O-ring of a softer compound but this is limited by molding defects, swell, compression set and/or long-term heat aging and was found not adequate to the task at handle. It is also known that the actual compression and thus the effective compliance of the O-ring can be further increased by reducing the coefficient of sliding friction between the filler neck sealing surface and the sealing ring which turns with the cap. But even then it was found that the increase in compliance of the conventional solid O-ring could not be made adequate to maintaining sealing in the extreme condition.

#Further objects and advantages of the present invention will be more apparent from the following description and drawing in which:

#FIG. 1 is a view in vertical section of a fuel filler cap assembly having a preferred embodiment of the sealing ring accoring to the present invention installed but at no load.

#FIG. 2 is a view similar to FIG, 1 but with the sealing ring shown under normal load.

#Referring to FIG. 1 there is shown a fuel filler cap assembly 10 for the filler neck 12 of an automotive fuel tank (not shown) whose details but for the compliant grooved sealing ring 14 according to the present invention are disclosed in the afore-indentified U.S. patent application Ser. No. 516,032 which is hereby incorporated by reference. The fuel filler cap assembly 10 comprises a sheet metal cover 16 and skirt 18 which are secured together and contain a torque limiter mechanism 20 by means of which the cap is releasably connected to a plastic closure 22. The closure 22 has an external thread 24 which engages an internal thread 26 formed in the filler neck 12, these engaging threads thus providing the means by which the cap is detachably secured to the neck. The torque limited mechanism 20 operates to drivingly connect the cap 10 to the closure 22 in the closing or tightening direction of cap turning up to a predetermined torque load and thereafter permits the cap to free wheel. Alternatively, the torque limiter operates to provide a positive drive connection between the cap and closure in the opening direction of turning to unthread the closure and thus the cap from the filler neck. For a more detailed understanding of the structure and operation of the fuel filler cap assembly including torque limiter, reference may be made to the afore-indentified U.S. patent application Ser. No. 516,032. The cap assembly may further include a pressure vacuum control valve assembly as disclosed in U.S. Pat. No. 3,937,358 but its structure and operation is not necessary to an understanding of the present invention.

#In such an arrangement the closure 22 is provided with a circumferential radially outwardly facing groove 30 which provides a radially outwardly extending sealing surface or seat 32 opposite a filler neck sealing surface or seat 34 formed by flaring the edge of the open end of the neck. Typically, a solid O-ring of elastomeric material is mounted in a slightly streched condition in the groove 30 on the cap and on threaded engagement of the cap with the filler neck the O-ring is held by the cap and squeezed between the seats 32 and 34 to seal this joint and thereby prevent leakage of any fumes and liquid from the fuel tank.

#According to the present invention and instead of the typical solid O-ring used for sealing, the sealing ring 14 is formed with a radially outwardly facing circumferential V-shape groove 36 that is bisected by a radial plane through the circular centerline of the seal and has a depth substantially greater than half the thickness or diameter of the ring's circular cross-section and has an included acute angle that provides lips 38 and 40 of substantial length extending radially outward between the respective seats 32 and 34 of the cap and neck. The depth and angle of the groove 36 are determined so that when the release torque load is encountered and the sealing ring is thereby squeezed or preloaded between the seats as shown in FIG. 2, the lips are forced toward but do not touch each other at their ends in the normal preload condition with the substantial cross-sectional resistance to axial loading left by the compliant groove taking the squeeze to assure sealing of the small disparities typically found in the filler neck sealing surface. But then on forced substantial tilting of the cap relative to the filler neck which tends to unseat the sealing ring at some circumferential location, the lips at this location remain preloaded to maintain sealing while at the diametrically opposite location the lips are forced together as shown in FIG. 3, the long cantilevered lips with their cross-sections which gradually taper to the end accommodating such tilt while preventing the seal from rolling.