GB2151741A - Blind rivet - Google Patents

Abstract

A blind rivet comprises a plastics insert 6 which is drawn by a metal mandrel (not shown) into the tail 11 of a plastics rivet body 5 to expand said tail 11 and thus set the rivet. Subsequent to setting, the mandrel is drawn completely through and out of the set rivet body 5 and insert 6. The insert 6 has one region having an external diameter similar to the internal diameter of the rivet body tail 11, and a larger diameter region for expanding the tail 11. Dimensions and tolerances are specified. <IMAGE>

Description

SPECIFICATION Rivet arrangement This invention relates to rivet arrangements According to one aspect of the present invention, a rivet arrangement comprises a rivet having a tubular tail or resiliently deformable material, and an insert adapted to be urged into and remain within the tail to effect setting the rivet, the insert having two regions of differing external diameter, a first region having a diameter similar to the internal diameter of the rivet tail, and a second region being of a diameter to effect substantial expansion of the tail whereby when the rivet is placed to extend through an aperture in work pieces to be joined, the insert can be urged into the said tail until its first region protrudes into a region of the tail constrained by a work piece, at which stage the second region of the insert has expanded the tail at a desired position to effect rivet setting.

Preferably, both the rivet and the insert are of a resiliently deformable plastics material, for example a nylon or nylon-like material. Additionally, both items are preferably of tubular form. In this case, the rivet and the insert can be mounted in tandem on a headed mandrel for insertion into a blind aperture in the work pieces and withdrawal of the mandrel through the rivet head used to effect setting of the rivet. Unlike some well-known rivet arrangements, the mandrel is preferably totally withdrawn and is not severed to remain partially within the set rivet arrangement. This is possible due to the resilience of the insert and the rivet.

These and other aspects of the invention are disclosed in the exemplary description of one embodiment of the invention with reference to the accompanying drawings in which: Figure 1 is a cross-sectional view of a set rivet arrangement; Figure 2 is a cross-sectional view of an unset rivet assembly, Figure 3 is a cross-sectional view of a rivet plus a table of dimensions suitable for use in a hole formed by Drill Morse No. 11 (0.191" dia.), and Figure 4 is a cross-sectional view of an insert plus a table of dimensions suitable for use with the rivet of Figure 3.

In Figure 1, a rivet arrangement attaches a layer of material 1 to a composite structure comprising a skin 2 bonded to a core material 3. A bonding and sealing agent may also be used to aid attachment.

A blind hole 4 of sufficient depth to allow insertion of a rivet assembly is formed in the work piece 1, 2 and 3. Into this hole is inserted the assembly of Figure 2 comprising a rivet 5 (see Figure 3), an insert 6 (see Figure 4) and a steel mandrel 7, the rivet and the insert being mounted in tandem upon the mandrel as shown.

The rivet 5 has a head region 10 and a tail or shank region 11.

The mandrel has a constant diameter shank 8 which extends through the rivet and the insert when they are undeformed and a head region 9 of enlarged diameter which engages and draws the insert 6 into the tail 11 but effects temporary deformation thereof to exit completely. To set the rivet arrangement, the assembly of Figure 2 is inserted into the blind hole 4 and the mandrel 7 is withdrawn whilst the rivet is held in the position shown. This is effected by a known form of riveting machine, for example a Tucker TT 55 with a slightly modified nose. The modification comprises a counterbore to the tube through which the mandrel is drawn of sufficient diameter to accept the mandrel head 8 as it exits from the rivet 5.

As can be seen, mandrel withdrawal caused the insert 6 to be drawn axially into the rivet tail 11 temporarily and locally causing it to expand until the insert finally achieves the position illustrated in Figure 1 in which its region of diameter M protrudes into the hole formed in the layer 2. This layer is relatively rigid material and therefore stops further axial movement by constraining the tail 11.

The region of the insert of diameter R maintains the rivet tail 11 in a locally expanded condition protruding locally into the core material 3 to both clamp the core material and the two layers 1 and 2 together. The head 9 of the mandrel is allowed to pass through the insert 6 and the rivet 5 at this stage due to the resilience of their material.

The insert shape is of significance in that (a) its external diameter R must pass into the hole 4, (b) its transition shape X between diameters M and R is selected to be smoothly curved to cause rivet tail expansion without splitting, (c) its diameter M and length T are chosen to intrude into that portion of the rivet tail constrained by the relatively rigid material of the layer 2 to give positive permanent rivet deformation and, moreover, to give radial location during the setting process as the insert travels along the rivet.

The mandrel is a standard "off the shelf" item and for the rivet sizes described is referenced AGS 2052-3-25 in the Society of British Aerospace Companies Limited published engineering standards.

The illustrated arrangement is particularly useful for anchoring glass fibre clamping strips (e.g. layer 1) to radomes (items 2 and 3), the clamping strips themselves being utilised to clamp aluminium alloy lightning conductor strips to the radome.

1. A rivet arrangement comprises a rivet having a tubular tail of resiliently deformable material, and an insert adapted be urged into and remain within the tail to effect setting the rivet, the insert having two regions of differing external diameter, a first region having a diameter similar to the internal diameter of the rivet tail, and a second region being of a diameter to effect substantial expansion of the tail whereby when the rivet is placed to extend through an aperture in work pieces to be joined, the insert can be urged into the said tail until its first region protrudes into a region of the tail constrained by a work piece, at which stage the second region of the insert has expanded the tail at a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Rivet arrangement This invention relates to rivet arrangements According to one aspect of the present invention, a rivet arrangement comprises a rivet having a tubular tail or resiliently deformable material, and an insert adapted to be urged into and remain within the tail to effect setting the rivet, the insert having two regions of differing external diameter, a first region having a diameter similar to the internal diameter of the rivet tail, and a second region being of a diameter to effect substantial expansion of the tail whereby when the rivet is placed to extend through an aperture in work pieces to be joined, the insert can be urged into the said tail until its first region protrudes into a region of the tail constrained by a work piece, at which stage the second region of the insert has expanded the tail at a desired position to effect rivet setting. Preferably, both the rivet and the insert are of a resiliently deformable plastics material, for example a nylon or nylon-like material. Additionally, both items are preferably of tubular form. In this case, the rivet and the insert can be mounted in tandem on a headed mandrel for insertion into a blind aperture in the work pieces and withdrawal of the mandrel through the rivet head used to effect setting of the rivet. Unlike some well-known rivet arrangements, the mandrel is preferably totally withdrawn and is not severed to remain partially within the set rivet arrangement. This is possible due to the resilience of the insert and the rivet. These and other aspects of the invention are disclosed in the exemplary description of one embodiment of the invention with reference to the accompanying drawings in which: Figure 1 is a cross-sectional view of a set rivet arrangement; Figure 2 is a cross-sectional view of an unset rivet assembly, Figure 3 is a cross-sectional view of a rivet plus a table of dimensions suitable for use in a hole formed by Drill Morse No. 11 (0.191" dia.), and Figure 4 is a cross-sectional view of an insert plus a table of dimensions suitable for use with the rivet of Figure 3. In Figure 1, a rivet arrangement attaches a layer of material 1 to a composite structure comprising a skin 2 bonded to a core material 3. A bonding and sealing agent may also be used to aid attachment. A blind hole 4 of sufficient depth to allow insertion of a rivet assembly is formed in the work piece 1, 2 and 3. Into this hole is inserted the assembly of Figure 2 comprising a rivet 5 (see Figure 3), an insert 6 (see Figure 4) and a steel mandrel 7, the rivet and the insert being mounted in tandem upon the mandrel as shown. The rivet 5 has a head region 10 and a tail or shank region 11. The mandrel has a constant diameter shank 8 which extends through the rivet and the insert when they are undeformed and a head region 9 of enlarged diameter which engages and draws the insert 6 into the tail 11 but effects temporary deformation thereof to exit completely. To set the rivet arrangement, the assembly of Figure 2 is inserted into the blind hole 4 and the mandrel 7 is withdrawn whilst the rivet is held in the position shown. This is effected by a known form of riveting machine, for example a Tucker TT 55 with a slightly modified nose. The modification comprises a counterbore to the tube through which the mandrel is drawn of sufficient diameter to accept the mandrel head 8 as it exits from the rivet 5. As can be seen, mandrel withdrawal caused the insert 6 to be drawn axially into the rivet tail 11 temporarily and locally causing it to expand until the insert finally achieves the position illustrated in Figure 1 in which its region of diameter M protrudes into the hole formed in the layer 2. This layer is relatively rigid material and therefore stops further axial movement by constraining the tail 11. The region of the insert of diameter R maintains the rivet tail 11 in a locally expanded condition protruding locally into the core material 3 to both clamp the core material and the two layers 1 and 2 together. The head 9 of the mandrel is allowed to pass through the insert 6 and the rivet 5 at this stage due to the resilience of their material. The insert shape is of significance in that (a) its external diameter R must pass into the hole 4, (b) its transition shape X between diameters M and R is selected to be smoothly curved to cause rivet tail expansion without splitting, (c) its diameter M and length T are chosen to intrude into that portion of the rivet tail constrained by the relatively rigid material of the layer 2 to give positive permanent rivet deformation and, moreover, to give radial location during the setting process as the insert travels along the rivet. The mandrel is a standard "off the shelf" item and for the rivet sizes described is referenced AGS 2052-3-25 in the Society of British Aerospace Companies Limited published engineering standards. The illustrated arrangement is particularly useful for anchoring glass fibre clamping strips (e.g. layer 1) to radomes (items 2 and 3), the clamping strips themselves being utilised to clamp aluminium alloy lightning conductor strips to the radome. CLAIMS

1. A rivet arrangement comprises a rivet having a tubular tail of resiliently deformable material, and an insert adapted be urged into and remain within the tail to effect setting the rivet, the insert having two regions of differing external diameter, a first region having a diameter similar to the internal diameter of the rivet tail, and a second region being of a diameter to effect substantial expansion of the tail whereby when the rivet is placed to extend through an aperture in work pieces to be joined, the insert can be urged into the said tail until its first region protrudes into a region of the tail constrained by a work piece, at which stage the second region of the insert has expanded the tail at a desired position to effect rivet setting.

2. A rivet arrangement according to Claim 1 wherein both the rivet and the insert are of a resiliently deformable plastics material.

3. A rivet arrangement according to Claim 2 wherein the insert has a transition region between its first and second regions of different external diameter, shaped to prevent splitting of the tubular tail of the rivet by having an annular concave curvature portion blending with the first region, an annular convex curvature portion blending with the second region, the concave and convex portions themselves blending with one another.

4. A rivet assembly suitable for blind rivetting comprising a mandrel and the rivet arrangement of Claim 3, the mandrel having a shank portion and a head portion, the two components of the rivet arrangement being mounted in tandem upon the mandrel shank with the insert lying adjacent the mandrel head, and the shank protruding through both components, the rivet having a portion of reduced internal diameter to lightly grip the shank of the mandrel.

5. A rivet arrangement substantially as described with reference to the Figures.