GB2054082A

GB2054082A - Pull-type blind-riveting assemblies

Info

Publication number: GB2054082A
Application number: GB8023830A
Authority: GB
Original assignee: Tucker Fasteners Ltd
Current assignee: Tucker Fasteners Ltd
Priority date: 1979-07-20
Filing date: 1980-07-21
Publication date: 1981-02-11
Also published as: DE2929476C2; JPS5620112U; DE2929476A1; JPS6024979Y2; GB2054082B

Abstract

A split-setting pull-type blind- riveting assembly comprising a hollow rivet 10 and a mandrel 16. The underside 26 of the mandrel head 22 is frusto-pyramidal, and there is a flat surface 28 normal to the mandrel stem 18 at least at each corner of the pyramid where it meets the stem 18. Reliable splitting of the rivet shank 14 into uniform petals is thereby achieved. <IMAGE>

Description

SPECIFICATION Pull-type bind-riveting assemblies This invention is concerned with pull-type blind-riveting assemblies comprising a hollow rivet and a mandrel, the mandrel having a head with a pyramidal under-surface which provides radially disposed ridges to cause the tail end of the rivet to split into petals when the mandrel head is pulled into it on setting the rivet. Split-setting blind-riveting assemblies are of two kinds, viz.

those in which the rivet barrel has longitudinal lines of weakness where it will split into petals when a mandrel head is pulled into it and those where the rivet barrel has no such lines of weakness but splitting is induced by radially disposed ridges on the under-surface of the mandrel head. Such ridges are usually provided by the edges of a three, four or five sided pyramidal configuration of such surface, the pyramidal configuration extending substantially from the periphery of a mandrel head to a cylindrical portion of the mandrel stem.

It is potentially more economical to manufacture the latter type of assembly because the process is less complicated than that required to provide lines of weakness along the rivet shank.

However, it is desirable that the effect of the ridges on the under-surface of the mandrel head is to split the rivet shank evenly into the desired number of petals, i.e. four where the under-surface of a mandrel head is part of a square pyramid, and experience has shown that to ensure such a result requires the rivet shank wall to be of uniform thickness within very close limits of the manufacturing tolerance. Where, for example, the rivet bore is eccentric to a small degree outside such tolerance, the shank may split along three lines but not along, or only a short way along, the fourth. The maintenance of the necessary close manufacturing tolerance for the rivet to ensure uniform splitting has proved costly.

It is the object of this invention to provide a split-setting pull-type blind-riveting assembly, the rivet shank of which will split evenly into uniform petals under the influence of a mandrel with radial ridges under its head, and which can be manufactured without observing unduly stringent manufacturing tolerances.

The foregoing object is achieved in accordance with the invention in that the under-surface of the mandrel head meets a cylindrical portion of the stem at a plane normal to the axis of the stem with the result that at least at each corner of the pyramidal surface the mandrel head presents a flat shoulder portion normal to the mandrel stem.

With assemblies in accordance with the invention it has been observed that reliable splitting of the rivet shank into evenly disposed petals has occurred when the bore of the rivet has been eccentric to the outer surface of the shank to an extent outside the stringent manufacturing tolerance that would have ensured such setting with a conventional mandrel in which the pyramidal surface under the head runs down to meet the mandrel stem. Accordingly, a rivet assembly in accordance with the invention is more economical to manufacture than is the case with conventional split-setting blind-riveting assemblies.

An example of a blind-riveting assembly in accordance with the invention is shown in the accompanying drawings in which Figure 1 shows the assembly with a portion of the rivet shank broken away; Figure 2 shows the head end portion of the mandrel of Figure 1 from a direction at 450 to that from which Figure 1 is viewed; Figure 3 is a view of the mandrel of the assembly showing the under-surface of its head, as seen on the line Ill-Ill of Figure 2; and Figure 4 represents a set rivet.

Referring to the drawings, the assembly comprises a hollow aluminium alloy rivet 10 having a head flange 12 and a shank 14 of uniform wall thickness without any longitudinal lines of weakness.

The exemplary assembly also comprises a steel mandrel 1 6 having a cylindrical stem 18 with a neck 20 at which it will break in the course of rivet setting and a head 22. The head 22 has a slightly squared-off near circular periphery 24 with a frusto-pyramidal under-surface 26 which merges with the periphery of the head. The included ansle between opposite sides of the pyramidal undersurface of the mandrel head in the drawings is 80". The difference between the "diagonals" of the head and the minimum "diameter" is about 0.26mm (i.e. 5.5% of a nominal 4.70mm diameter head). The "corners" of the periphery are in alignment with the corners of the pyramidal under-surface.The under-surface 26 of the head meets the stem 1 8 at a plane normal to the axis of the stem with the result that the head presents flat shoulder portions 28 normal to the stem at each corner of the pyramidal surface.

At the plane at which the head meets the stem of the mandrel of an assembly in accordance with the invention, the diameter of the stem may be substantially equal to or less than the distance between the flat sides of the pyramidal undersurface, the shoulder referred to accordingly being either confined to the corners of the head or merging with one another around the stem.

Using a blind-riveting assembly as shown in the drawings to fasten together two plates P, P' (Figure 4), the rivet shank is split by the under-side of the mandrel head uniformly and reliably into four petals 26 which curl over as shown in Figure 4 without resorting to excessiveiy fine tolerances in the manufacture of the rivet.

1 . A pull-type blind-riveting assembly comprising a hollow rivet and a mandrel, the mandrel having a head with a pyramidal undersurface which provides radial ridges to cause the taii end of the rivet to split into petals when the mandrel head is pulled into it on setting the rivet,

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Pull-type bind-riveting assemblies This invention is concerned with pull-type blind-riveting assemblies comprising a hollow rivet and a mandrel, the mandrel having a head with a pyramidal under-surface which provides radially disposed ridges to cause the tail end of the rivet to split into petals when the mandrel head is pulled into it on setting the rivet. Split-setting blind-riveting assemblies are of two kinds, viz. those in which the rivet barrel has longitudinal lines of weakness where it will split into petals when a mandrel head is pulled into it and those where the rivet barrel has no such lines of weakness but splitting is induced by radially disposed ridges on the under-surface of the mandrel head. Such ridges are usually provided by the edges of a three, four or five sided pyramidal configuration of such surface, the pyramidal configuration extending substantially from the periphery of a mandrel head to a cylindrical portion of the mandrel stem. It is potentially more economical to manufacture the latter type of assembly because the process is less complicated than that required to provide lines of weakness along the rivet shank. However, it is desirable that the effect of the ridges on the under-surface of the mandrel head is to split the rivet shank evenly into the desired number of petals, i.e. four where the under-surface of a mandrel head is part of a square pyramid, and experience has shown that to ensure such a result requires the rivet shank wall to be of uniform thickness within very close limits of the manufacturing tolerance. Where, for example, the rivet bore is eccentric to a small degree outside such tolerance, the shank may split along three lines but not along, or only a short way along, the fourth. The maintenance of the necessary close manufacturing tolerance for the rivet to ensure uniform splitting has proved costly. It is the object of this invention to provide a split-setting pull-type blind-riveting assembly, the rivet shank of which will split evenly into uniform petals under the influence of a mandrel with radial ridges under its head, and which can be manufactured without observing unduly stringent manufacturing tolerances. The foregoing object is achieved in accordance with the invention in that the under-surface of the mandrel head meets a cylindrical portion of the stem at a plane normal to the axis of the stem with the result that at least at each corner of the pyramidal surface the mandrel head presents a flat shoulder portion normal to the mandrel stem. With assemblies in accordance with the invention it has been observed that reliable splitting of the rivet shank into evenly disposed petals has occurred when the bore of the rivet has been eccentric to the outer surface of the shank to an extent outside the stringent manufacturing tolerance that would have ensured such setting with a conventional mandrel in which the pyramidal surface under the head runs down to meet the mandrel stem. Accordingly, a rivet assembly in accordance with the invention is more economical to manufacture than is the case with conventional split-setting blind-riveting assemblies. An example of a blind-riveting assembly in accordance with the invention is shown in the accompanying drawings in which Figure 1 shows the assembly with a portion of the rivet shank broken away; Figure 2 shows the head end portion of the mandrel of Figure 1 from a direction at 450 to that from which Figure 1 is viewed; Figure 3 is a view of the mandrel of the assembly showing the under-surface of its head, as seen on the line Ill-Ill of Figure 2; and Figure 4 represents a set rivet. Referring to the drawings, the assembly comprises a hollow aluminium alloy rivet 10 having a head flange 12 and a shank 14 of uniform wall thickness without any longitudinal lines of weakness. The exemplary assembly also comprises a steel mandrel 1 6 having a cylindrical stem 18 with a neck 20 at which it will break in the course of rivet setting and a head 22. The head 22 has a slightly squared-off near circular periphery 24 with a frusto-pyramidal under-surface 26 which merges with the periphery of the head. The included ansle between opposite sides of the pyramidal undersurface of the mandrel head in the drawings is 80". The difference between the "diagonals" of the head and the minimum "diameter" is about 0.26mm (i.e. 5.5% of a nominal 4.70mm diameter head). The "corners" of the periphery are in alignment with the corners of the pyramidal under-surface.The under-surface 26 of the head meets the stem 1 8 at a plane normal to the axis of the stem with the result that the head presents flat shoulder portions 28 normal to the stem at each corner of the pyramidal surface. At the plane at which the head meets the stem of the mandrel of an assembly in accordance with the invention, the diameter of the stem may be substantially equal to or less than the distance between the flat sides of the pyramidal undersurface, the shoulder referred to accordingly being either confined to the corners of the head or merging with one another around the stem. Using a blind-riveting assembly as shown in the drawings to fasten together two plates P, P' (Figure 4), the rivet shank is split by the under-side of the mandrel head uniformly and reliably into four petals 26 which curl over as shown in Figure 4 without resorting to excessiveiy fine tolerances in the manufacture of the rivet. CLAIMS

1 . A pull-type blind-riveting assembly comprising a hollow rivet and a mandrel, the mandrel having a head with a pyramidal undersurface which provides radial ridges to cause the taii end of the rivet to split into petals when the mandrel head is pulled into it on setting the rivet, the under-surface of the mandrel head meeting a cylindrical portion of the stem at a plane normal to the axis of the stem with the result that at least at each corner of the pyramidal surface the mandrel head presents a flat shoulder portion normal to the mandrel stem.

2. An assembly according to claim 1 the mandrel of which has a square pyramidal surface under its head.

3. An assembly according to claim 2 in which the diameter of the mandrel stem adjacent the head is substantially equal to the distance between the flat sides of the pyramidal undersurface.

4. An assembly according to claim 3 the periphery of the mandrel head of which is a slightly squared-off circle with its corners in alignment with the corners of the pyramidal under-surface.

5. A split-setting pull-type blind-riveting assembly substantially as hereinbefore described with reference to the accompanying drawings.