Bonded PTFE radial shaft seal
View Patent ↗A radial shaft seal having a metal casing and a rubber sealing portion attached interior of the metal casing. The rubber sealing portion is bonded to the metal casing during a forming operation. A polytetrafluoroethylene seal is stretched into a conical shape and bonded to the rubber sealing portion while in the stretched state.
1. A radial shaft seal comprising:
a rigid casing;
a rubber sealing portion positioned interior of the rigid casing, the rubber sealing portion bonded to the rigid casing;
a polytetrafluoroethylene seal having an inner diameter, the polytetrafluoroethylene seal being bonded to the rubber sealing portion on an inner surface of the rubber sealing portion; and
the polytetrafluoroethylene seal being stretched into a frusto-conical shape on the inner diameter and wherein the polytetrafluoroethylene seal is bonded to the rubber sealing portion while the polytetrafluoroethylene seal is in the stretched condition and maintained in said stretched condition under tension following bonding.
2. The radial shaft seal of claim 1 wherein the rigid casing includes a radial portion and an axial portion.
3. The radial shaft seal of claim 1 wherein the rubber sealing portion is bonded to the rigid casing at least along an inner surface of the radial portion and may also extend along an outer surface of the axial portion.
4. The radial shaft seal of claim 1 wherein the rubber sealing portion includes an angular portion extending from the inner surface of the radial portion.
5. The radial shaft seal of claim 1 wherein the rubber sealing portion includes a transition from a planar portion bonded to the inner surface of the radial portion to the angular portion, the transition defined by a first recess formed in the rubber sealing portion.
6. The radial shaft seal of claim 1 wherein the angular portion of the rubber sealing portion terminates at a sealing lip.
7. The radial shaft seal of claim 1 wherein the polytetrafluoroethylene seal includes first and second opposing ends spaced along outer and inner surfaces.
8. The radial shaft seal of claim 1 wherein the first end is proximate the sealing lip and the second end is proximate the inner surface of the radial portion of the rigid casing.
9. The radial shaft seal of claim 1 wherein the outer surface of the polytetrafluoroethylene seal is bonded to an inner surface of the angular portion.
10. The radial shaft seal of claim 1 wherein radial portion of the rigid casing includes an arcuate portion that terminates at a first end of the polytetrafluoroethylene seal.
11. The radial shaft seal of claim 1 wherein the polytetrafluoroethylene seal is bonded on its outer surface to the rubber sealing portion and wherein the inner surface of the polytetrafluoroethylene seal is not bonded to the arcuate metal portion.
12. The radial shaft seal of claim 1 wherein the polytetrafluoroethylene seal includes a support portion formed on a first end, the support portion angled into the rubber sealing portion.
13. The radial shaft seal of claim 1 wherein the polytetrafluoroethylene seal includes a support potion formed on a second end, the support portion angled into the rubber sealing portion.
14. The radial shaft seal of claim 1 wherein the polytetrafluoroethylene seal includes support potions formed on the first and second ends, the support portions angled into the rubber sealing portion.
15. The radial shaft seal of claim 1 wherein the polytetrafluoroethylene seal includes hydrodynamic or static sealing grooves formed on the inner surface of the polytetrafluoroethylene seal.
16. The radial shaft seal of claim 1 wherein the first end of the polytetrafluoroethylene seal is positioned proximate the sealing lip of the rubber sealing portion such that the polytetrafluoroethylene seal provides a bridging support to the sealing lip.
17. The radial shaft seal of claim 1 wherein the rubber sealing portion includes a second recess formed opposite the first recess for providing a flex area for the rubber sealing portion.
18. A method of manufacturing a radial shaft seal comprising the steps of:
stretching a polytetrafluoroethylene seal about its inner diameter utilizing a mandrel device,
locating the stretched polytetrafluoroethylene seal in a mold such that the polytetrafluoroethylene seal engages a post surface of the mold;
locating a rigid casing within the mold;
introducing a rubber elastomer into the mold and thereafter molding the rubber under heat and pressure such that the rigid casing and polytetrafluoroethylene seal in a stretched state are bonded to the rubber elastomer.
19. The method of claim 18 wherein the polytetrafluoroethylene seal is stretched from 5 to 120 percent of its original size.