Cap with injected sealant

Abstract

A cap for forming a sealed cavity around an end of a fastener is disclosed having a cap body with an annular base terminating at an inner cap rim which surrounds an opening into a central cavity and lies in an inner cap plane around a majority of a circumference of the annular base. A skirt provides an annular pocket between the skirt and the annular base. The skirt has a first part which is integrally formed with the cap body from a first material and terminates at an edge, and a second part which is formed from a second material and extends from the edge of the first part of the skirt to a skirt rim which lies in or below the inner cap plane around a majority of a circumference of the skirt.

The invention claimed is: 
     
       1. A cap for forming a sealed cavity around an end of a fastener, the cap comprising:
 a. a cap body with an annular base terminating at an inner cap rim which surrounds an opening into a central cavity and lies in an inner cap plane around a majority of a circumference of the annular base; 
 b. a skirt providing an annular pocket between the skirt and the annular base, wherein the skirt has a first part which is integrally formed with the cap body from a first material and terminates at an edge, and a second part which is formed from a second material and extends from the edge of the first part of the skirt to a skirt rim, wherein the skirt extends to or through the inner cap plane around a majority of a circumference of the skirt, the first material has a first elastic modulus, and the second material has a second elastic modulus which is lower than the first elastic modulus; and 
 c. an inlet hole in the skirt, wherein the inlet hole is in fluid communication with the annular pocket to permit a flow of sealing material through the skirt via the inlet hole into the annular pocket. 
 
     
     
       2. The cap of  claim 1  wherein the skirt forms a continuous annular wall with no holes through the annular skirt in fluid communication with the annular pocket other than the inlet hole. 
     
     
       3. The cap of  claim 1  wherein the second part of the skirt has a length between the edge of the first part and the skirt rim which varies around the circumference of the skirt. 
     
     
       4. The cap of  claim 3  wherein the length of the second part of the skirt increases around the circumference of the skirt away from the inlet hole. 
     
     
       5. The cap of  claim 4  wherein the length of the second part of the skirt reaches a maximum opposite the inlet hole. 
     
     
       6. The cap of  claim 1  wherein the second part of the skirt is attached to the edge of the first part of the skirt by a joint comprising a male part received in an annular groove which runs round the circumference of the skirt. 
     
     
       7. The cap of  claim 1  wherein the skirt rim lies in the inner cap plane around a full circumference of the skirt. 
     
     
       8. The cap of  claim 1  wherein the skirt extends through the inner cap plane around a majority of a circumference of the skirt so that there is an offset between the skirt rim and the inner cap plane. 
     
     
       9. The cap of  claim 1  wherein at least part of the skirt extends away from the cap body at an acute angle to the annular base. 
     
     
       10. The cap of  claim 1  wherein the skirt comprises a tubular projection which projects outwardly from the skirt and leads to the inlet hole. 
     
     
       11. The cap of  claim 1  wherein the inlet hole is in the first part of the skirt. 
     
     
       12. The cap of  claim 1  wherein the second material is an elastomer. 
     
     
       13. A method of manufacturing the cap of  claim 1 , the method comprising co-bonding the first part of the skirt and the second part of the skirt. 
     
     
       14. A joint comprising: a structure; an end of a fastener protruding from the structure; and a cap according to  claim 1  forming a sealed cavity around the end of the fastener, the cap comprising a cured sealing material in the annular pocket which secures the cap to the structure. 
     
     
       15. The joint of  claim 14  wherein the skirt rim contacts the structure. 
     
     
       16. The joint of  claim 14  wherein the inner cap rim contacts the structure. 
     
     
       17. A method of assembling the joint of  claim 14 , the method comprising: fitting the cap over the end of the fastener; and injecting sealing material through the skirt via the inlet hole into the annular pocket. 
     
     
       18. The method of  claim 17  wherein the second part of the skirt flexes as the sealing material is injected so that the skirt rim lifts up to form a gap between the skirt rim and the structure which enables air to escape the annular pocket by flowing through the gap. 
     
     
       19. A cap for forming a sealed cavity around an end of a fastener, the cap comprising:
 a. a cap body with an annular base terminating at an inner cap rim which surrounds an opening into a central cavity and lies in an inner cap plane around a majority of a circumference of the annular base; 
 b. a skirt providing an annular pocket between the skirt and the annular base, wherein the skirt extends from the cap body to a skirt rim forming an annular opening into the annular pocket, and the skirt extends through the inner cap plane around a majority of a circumference of the skirt so that there is an offset between the skirt rim and the inner cap plane; and 
 c. an inlet hole in the skirt, wherein the inlet hole is in fluid communication with the annular pocket to permit a flow of sealing material through the skirt via the inlet hole into the annular pocket. 
 
     
     
       20. A method of assembling a joint with the cap of  claim 19 , the joint comprising a structure, and an end of a fastener protruding from the structure, the method comprising:
 fitting the cap over the end of the fastener; and 
 injecting sealing material through the skirt via the inlet hole into the annular pocket, wherein prior to fitting the cap over the end of the fastener the skirt extends through the inner cap plane around a majority of a circumference of the skirt so that there is an offset between the skirt rim and the inner cap plane, and when the cap is fitted over the end of the fastener the skirt rim contacts the structure before the inner cap rim contacts the structure and then the skirt flexes to enable the inner cap rim to contact the structure.