Avdel Limited

Avdel Systems Limited

Avdel Systems Limited, a British Company

Advel Limited

William D Bradley

Raymond D Lacey

Michael Woodrow

Zia R Alvi

A breakstem blind rivet comprises a deformable tubular shell 11 of aluminium alloy having a bore 12 inside it. A stem 13 of low-carbon steel is a close fit within the bore, extending along the bore and having a head 14 adjacent the tail end 15 of the shell. The outside of the shell is formed with at least three zones 27, 28, 29 of modified strength spaced apart along its length, these zones being in the form of shallow grooves rolled into the surface. The spacing between each zone 27, 28, 29 and the next progressively decreases as the distance along the shell from the tail end 15 increases. Alternatively the grooves may be formed by a turning process.

Break-stem blind rivet

A blind rivet able to be anchored in material such as softwood, without the need to break through the blind face of the material, comprises a tubular shell and a stem which extends through the shell. The shell has a preformed heat at one end of a shank. An end portion of the shank remote from the head has a thinner wall than the main, next adjacent, portion of the shank, and is thus weakened and made more easily expandible. The stem has a plugging portion having an expander head adjacent the thin-walled end portion of the shell, a breakneck, and a pulling portion which projects from the head end of the shell. The expander head increases in diameter away from the pulling portion, and presents a plurality of longitudinal cutting elements generally towards the weakened end portion of the shell. On gripping the pulling portion and pulling the stem, the cutting elements split the end portion of the shell into a plurality of legs, while the expander head enters into the end portion and forces the legs outwardly. The main part of the shank has a smaller diameter bore than the weakened end portion, and resists entry of the expander head.

Blind rivet

A blind rivet, for anchoring in relatively soft material such as softwood, comprises a tubular shell (14) with a weakened portion (19) at the end remote from the head (18), and a stem (15) with an enlarged head (29) having a smooth underhead curve (32). The weakened portion (19) of the shell has four longitudinal V-section grooves (24) on its inner wall. In addition, the weakened portion (19) has a wall thickness which is less than that of the remainder (22) of the shell, the junction between the two parts presenting an internal annular shoulder (23). When tension is applied to the pulling portion (26) of the stem, the stem head (29) enters the weakened portion (19) and splits it apart along the grooves (24) to form legs which anchor in the soft material. The higher strength of the remainder part (22) of the shell prevents the stem head passing beyond the shoulder (23) before the stem fractures at the breakneck (27).

A threaded fastener for installation in threaded engagement with an initially unthreaded apertured workpiece and which after installation can be removed in the manner of a screw or bolt, has a shank and an enlarged head. At least part of the shank intermediate between its ends has an external screw thread having a sharp crest, and can be radially expanded to cause the thread to embed in the workpiece. A bore extends through the head and the entire shank or at least the threaded port of the shank for receiving means for expanding the shank. An end portion of the shank remote from the head may be unthreaded to avoid splitting of the shank during expansion. The method of installing the fastener involves pulling a tapered mandrel along the bore to expand the shank. The mandrel may have a key-forming head of non-circular cross-section whereby the bore of the fastener can be adopted to receive a key of non-circular cross-section for turning the fastener in the workpiece. The head of the fastener may be deformable towards the workpiece to clamp another member to the workpiece.

Method of installing threaded fastener

A threaded fastener for installation in threaded engagement with an initially unthreaded apertured workpiece and which after installation can be removed in the manner of a screw or bolt, has a shank and an enlarged head. At least part of the shank intermediate between its ends has an external screw thread having a sharp crest, and can be radially expanded to cause the thread to embed in the workpiece. A bore extends through the head and the entire shank or at least the threaded part of the shank for receiving means for expanding the shank. An end portion of the shank remote from the head may be unthreaded to avoid splitting of the shank during expansion. The method of installing the fastener involves pulling a tapered mandrel along the bore to expand the shank. The mandrel may have a key-forming head of non-circular cross-section whereby the bore of the fastener can be adopted to receive a key of non-circular cross-section for turning the fastener in the workpiece. The head of the fastener may be deformable towards the workpiece to clamp another member to the workpiece.

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Welwyn Garden City, United Kingdom

William D Bradley