Self-centering, self-tightening fastener

A self-centering fastener assembly for releasably applying a load to the recessed surface of a workpiece, said assembly comprising:

• (a) a fastener body having:
• (i) a threaded opening extending therethrough along an axis, the thread having a lead angle,
• (ii) first external tool-engaging means to receive a tool for rotating the fastener body about the axis in either a first direction for applying a load against a workpiece, or in the opposite direction for releasing the load from the workpiece,
• (iii) an axially directed fastener cam face with a plurality of fastener cam elements that extend axially from a base surface and are angularly spaced by a first predetermined angle, each cam element having a sloping surface that slopes away from the base surface at a first rise angle greater than the lead angle and in the same rotational direction, and an abutment surface that slopes toward the base surface, and
• (iv) a skirt extending axially from the fastener cam face by a predetermined length and having means defining a maximum external diameter at a first location spaced from the fastener body and a minimum external diameter at a second location between the fastener body and said first location;
• (b) a first annular locking washer rotatably mounted on the skirt substantially coaxially therewith and having:
• (i) means defining a central opening with a minimum internal diameter greater than the minimum external diameter of the skirt and less than the maximum external diameter of the skirt,
• (ii) a first axially directed washer cam face that faces the fastener cam face and comprises a first base washer surface with a first plurality of washer cam elements extending therefrom and each first cam element comprising a sloping surface that slopes away from the base washer surface along a rise angle substantially equal to the rise angle of the sloping surface of each fastener cam element, the washer cam elements being angularly spaced by angles commensurate with the angles between the fastener cam elements, whereby the sloping surfaces of the first plurality of washer cam elements can fit substantially flush against the sloping surfaces of the fastener cam elements, each washer cam element also comprising an abutment surface sloping toward the base washer surface,
• (iii) a second axially directed washer cam face that comprises a second base washer surface with a second plurality of washer cam elements extending therefrom and angularly spaced by a second predetermined angle and each second cam element comprising a first surface that rises at a second rise angle and in the opposite direction from the sloping surfaces of the first plurality of washer cam elements, and a second surface that slopes toward the second washer base surface;
• (c) a second annular locking washer having:
• (i) means defining a central opening,
• (ii) a third axially directed washer cam face that comprises a third base surface and a third plurality of washer cam elements extending therefrom and each third cam element comprising a first surface and a second surface, each of the first surfaces of the third plurality of washer cam elements slanting at substantially the second rise angle, adjacent ones of the third plurality of washer cam elements being angularly spaced apart by angles commensurate with the second predetermined angle, whereby the first surfaces of the third plurality of washer cam elements can fit substantially flush against the first surfaces of the second plurality of washer cam elements, the second surfaces of each of the third plurality of washer cam elements sloping toward the third base surface, the combined thickness of both of the washers, when the second and third washer cam faces are in surface-to-surface contact with each other, being greater than the axial length of the skirt, the first locking washer being axially movable on the skirt to an axial position in which the abutment surfaces of the washer cam elements engage the abutment surfaces of the fastener cam elements to cooperate therewith to rotate the first locking washer with the fastener body in the first direction, the sloping surfaces on the fastener cam elements wedging against the sloping surfaces on the first washer cam elements to prevent free rotation of the fastener body in the opposite direction, and
• (iii) an annular face generally perpendicular to the axis to engage a workpiece, the annular face having an outer, circumferential border with a diameter at least substantially as great as that of the tool-engaging structure on the fastener body, an inner diameter at least as great as the maximum diameter of the skirt and including a bearing surface comprising a continuous annular spherical zone having a center of curvature lying on said axis, the bearing surface being seatable in the recessed surface of the workpiece;
• (d) means to hold the second washer in face-to-face relationship with respect to the first washer;
• (e) second external tool-engaging means on at least one of the washers to rotate at least that washer about the axis in said opposite direction simultaneously with rotation of the fastener body in said opposite direction, whereby the washers and the fastener body are loosened from the workpiece;
• and
• (f) the means to hold the second washer in face-to-face relationship to the first washer comprises clip means receiving the outer peripheral edges of said washers.

A self-centering fastener assembly for releasably applying a load to the recessed surface of a workpiece, said assembly comprising:

• (a) a fastener body having:
• (i) a threaded opening extending therethrough along an axis, the thread having a lead angle,
• (ii) first external tool-engaging means to receive a tool for rotating the fastener body about the axis in either a first direction for applying a load against a workpiece, or in the opposite direction for releasing the load from the workpiece,
• (iii) an axially directed fastener cam face with a plurality of fastener cam elements that extend axially from a base surface and are angularly spaced by a first predetermined angle, each cam element having a sloping surface that slopes away from the base surface at a first rise angle greater than the lead angle and in the same rotational direction, and an abutment surface that slopes toward the base surface, and
• (iv) a skirt extending axially from the fastener cam face by a predetermined length and having means defining a maximum external diameter at a first location spaced from the fastener body and a minimum external diameter at a second location between the fastener body and said first location;
• (b) a first annular locking washer rotatably mounted on the skirt substantially coaxially therewith and having:
• (i) means defining a central opening with a minimum internal diameter greater than the minimum external diameter of the skirt and less than the maximum external diameter of the skirt,
• (ii) a first axially directed washer cam face that faces the fastener cam face and comprises a first base washer surface with a first plurality of washer cam elements extending therefrom and each first cam element comprising a sloping surface that slopes away from the base washer surface along a rise angle substantially equal to the rise angle of the sloping surface of each fastener cam element, the washer cam elements being angularly spaced by angles commensurate with the angles between the fastener cam elements, whereby the sloping surfaces of the first plurality of washer cam elements can fit substantially flush against the sloping surfaces of the fastener cam elements, each washer cam element also comprising an abutment surface sloping toward the base washer surface,
• (iii) a second axially directed washer cam face that comprises a second base washer surface with a second plurality of washer cam elements extending therefrom and angularly spaced by a second predetermined angle and each second cam element comprising a first surface that rises at a second rise angle and in the opposite direction from the sloping surfaces of the first plurality of washer cam elements, and a second surface that slopes toward the second washer base surface;
• (c) a second annular locking washer having:
• (i) means defining a central opening,
• (ii) a third axially directed washer cam face that comprises a third base surface and a third plurality of washer cam elements extending therefrom and each third cam element comprising a first surface and a second surface, each of the first surfaces of the third plurality of washer cam elements slanting at substantially the second rise angle, adjacent ones of the third plurality of washer cam elements being angularly spaced apart by angles commensurate with the second predetermined angle, whereby the first surfaces of the third plurality of washer cam elements can fit substantially flush against the first surfaces of the second plurality of washer cam elements, the second surfaces of each of the third plurality of washer cam elements sloping toward the third base surface, the combined thickness of both of the washers, when the second and third washer cam faces are in surface-to-surface contact with each other, being greater than the axial length of the skirt, the first locking washer being axially movable on the skirt to an axial position in which the abutment surfaces of the washer cam elements engage the abutment surfaces of the fastener cam elements to cooperate therewith to rotate the first locking washer with the fastener body in the first direction, the sloping surfaces on the fastener cam elements wedging against the sloping surfaces on the first washer cam elements to prevent free rotation of the fastener body in the opposite direction, and
• (iii) an annular face generally perpendicular to the axis to engage a workpiece, the annular face having an outer, circumferential border with a diameter at least substantially as great as that of the tool-engaging structure on the fastener body, an inner diameter at least as great as the maximum diameter of the skirt and including a bearing surface comprising a continuous annular spherical zone having a center of curvature lying on said axis, the bearing surface being seatable in the recessed surface of the workpiece;
• (d) means to hold the second washer in face-to-face relationship with respect to the first washer;
• (e) second external tool-engaging means on at least one of the washers to rotate at least that washer about the axis in said opposite direction simultaneously with rotation of the fastener body in said opposite direction, whereby the washers and the fastener body are loosened from the workpiece;
• and
• (f) the means to hold the second washer in face-to-face relationship to the first washer comprises a clip means that at least partially encircles both washers and includes means extending over the edges of both washers.