GB2141369A

GB2141369A - Rivetting

Info

Publication number: GB2141369A
Application number: GB08316254A
Authority: GB
Inventors: Charles Spencer King; Ian Gordon Campbell
Original assignee: BL Technology Ltd
Current assignee: BL Technology Ltd
Priority date: 1983-06-15
Filing date: 1983-06-15
Publication date: 1984-12-19
Also published as: EP0129358A2; GB8316254D0; EP0129358A3; GB2141369B

Abstract

A rivetting system incorporates a fixed base 11, a punch 14 and a flat anvil 12 having substantial inertia and movable on base 11. A hollow rivet is driven by punch 14 through sheet 15 and into sheet 16, A piercing edge of the rivet cuts through sheet 15 and penetrates substantially into sheet 16 while supported by the flat anvil. A protruding portion 23 develops in sheet 16. When the anvil 12 retracts to base 11 an increased rivetting force causes protruding portion 23 to flow radially outward, expanding the end of the rivet and thus setting it. <IMAGE>

Description

1 GB 2 141 369 A 1

SPECIFICATION

Rivetting and rivets The invention relates to rivetting apparatus, a 70 method of rivetting and to rivets. The invention is particularly but not exclusively concerned with a rivetting system for rivetting sheets in which a rivet with a preformed head is used and in which on the opposite side of the workpiece from the head the rivet is substantially flush with the surface of the workpiece.

According to a first aspect of the invention a method of rivetting comprises supporting a Work piece on an anvil, driving the shank of a hollow shanked rivet into the workpiece from one side, causing the rivet to deform the workpiece by produc ing a projection of workpiece material on the other side of the workpiece and thus displacing the anvil, and subsequently deforming the rivet radially out ward by further compression of the workpiece between the punch and the anvil, causing the projection and with it part of the rivet to flow radially outward as the projection is compressed axially to set the rivet.

Preferably the length of the rivet shank is selected in relation to the workpiece thickness such that the shank does not penetrate completely through the workpiece. Preferably the rivet punches out a disc from an upper sheet of the workpiece and this disc is held captive within the hollow shank of the rivet.

Preferably the rivet has a piercing edge around its outer periphery at its end remote from the head and a deformable portion of narrowed wall thickness behind the piercing edge, the arrangement being such that the rivet enters axially into the workpiece and its deformable portion is then expanded radially outward.

According to a second aspect of the invention there is provided a rivet comprising a head, a hollow shank having a piercing edge around its outer periphery at its end remote from the head and a deformable portion of narrowed wall thickness be hind the piercing edge.

According to a third aspect of the invention there is provided rivetting apparatus comprising a base, an anvil supported with respectto the base and movable towards and awayfrom the base, a punch arranged to drive a rivet into a workpiece to be rivetted while the workpiece is supported on the anvil, subsequently to drive the anvil into positive engagement with the base by means of a protruding portion formed on the workpiece by the rivet and then to cause the rivet and workpiece to be de- formed by axial loading between the punch and the positively supported anvil. Preferably the anvil has a flat surface for engagement by the workpiece.

An embodiment of the invention will now be described with reference to the accompanying draw- ings in which:- Figure 1 is a diagrammatic representation of rivetting apparatus, a rivet and a workpiece atthe commencement of the rivetting operation; and Figures 2 and 3 correspond to Figure 1 but show 130 an intermediate position during the rivetting operation and the final position with a completed rivetted joint.

Referring to Figure 1, the apparatus comprises a fixed base 11 on which is supported an anvil 12 with a flat upper surface. The anvil has a substantial mass to provide it with inertia and is supported in such a way that it is movable along the rivetting axis, in this case vertically, with respect to the base 11. In this example, a belville spring 13 is provided between the base 11 and anvil 12 both to provide some resistance to movement of the anvil towards the base and to allow the anvil to recover its original position as shown in Figure 1 after a rivetting operation. The belville spring 13 is shown merely as a diagrammatic representation of a means for controlling movement of the anvil 12. As an alternative, which may be preferable, the movement of the anvil 12 with respect to the base 11 may be controlled hydraulically.

The apparatus also incorporates a vertically movable punch 14 which is powered to be moved down vertically towards the base 11 by means not shown in order to effect a rivetting operation.

The apparatus is shown in Figure 1 with a workpiece consisting of two sheets 15 and 16 which are to be rivetted together. A rivet 17 is also shown supported on the punch 14. Figure 1 shows the punch 14 in a position where it has just begun to drive the rivet 17 into the sheet 16 but prior to rivetting the punch would be retracted upwardly from the position shown to allow a clearance for insertion of sheets 15 and 16. The rivet 17 should be of a material which is harderthan the sheets 15 and 16. For example, sheets 15 and 16 may be of unhardened metal such as mild steel and rivet 17 could be made of a harder material but with sufficient ductility to enable the rivet to be set. Alternatively, the sheets 15 and 16 could be fibre- board panels intended as interior trim for a motor vehicle while rivet 17 is of a ductile metal.

The rivet 17 has a countersunk circular head 18 and a hollow tubular shank 19. Shank 19 has in this example an upper portion 20 with a relatively thick wall and a lower portion 25 with a relatively narrow wall thickness to form a deformable portion which can be set as the rivet is loaded axially. At its lower end, the rivet terminates in an annular piercing edge 21 which is tapered to a knife edge to facilitate entry of the rivet into a sheet 15 or 16. For some applications the stepped wall thickness and the knife edge may not be necessary.

The nature of the rivetting operation can be seen by comparing Figures 2 and 3 with Figure 1. As punch 14 is lowered towards the base 11 and anvil 12, its piercing edge cuts into the sheets 15 and 16. During this operation, the inertia associated with the mass of anvil 12 and the force of spring 13 hold the anvil clear of the base 11 until after the rivet has passed completely through the sheet 15 and penetrated substantially into the lower sheet 16 as shown in Figure 2. At this stage the rivet head 18 comes into contact with sheet 15. During this part of the rivetting operation a disc 22 is cut from the upper sheet 15 and is forced up into the narrower part of the tubular 2 GB 2 141 369 A 2 shank so that it becomes firmly retained. The rivet also causes the lower surface of the workpiece to be displaced axially downward to form a protruding portion 23. During further movement of the punch 14 the anvil is driven downward towards the base 11 until the anvil reaches the position shown in Figure 3 in which it is supported directly and positively against further movement by the base 11. This is illustrated in Figure 3 by a complete flattening of the beiville spring 13 but other forms of positive stop may be provided. Further downward movement of the punch 14 against the positively fixed anvil 12 causes the protruding portion 19 of the rivet to be deformed outward as illustrated at 24 in Figure 3.

During this deformation, the rivet is expanded outward by the outward flow of the workpiece as the protruding portion is flattened. Further movement of the punch 14 causes the rivet head 18 to be at least partially embedded in the upper sheet 15 as illus- trated in Figure 3. This completes the rivetting operation apart from retraction of the punch 14 and removal of the rivetted workpiece. In the completed rivetted joint, a substantially flush lower surface results at the side of the joint where the rivet has been set. Also, depending on the nature of the materials employed and the impact applied to the punch, a substantially flush surface can be provided on the head side of the rivet.

Claims

1. A method of rivetting comprising supporting a workpiece on an anvil, driving the shank of a hollow shanked rivet into the workpiece from one side, causing the rivet to deform the workpiece by producing a projection of workpiece material on the other side of the workpiece and thus displacing the anvil, and subsequently deforming the rivet radially outward by further compression of the workpiece between the punch and the anvil, causing the projection and with it part of the rivet to flow radially outward as the projection is compressed axially to set the rivet.

2. A method as claimed in claim 1 wherein the length of the rivet shank is selected in relation to the workpiece thickness such that the shank does not penetrate completely through the workpiece.

3. A method as claimed in claim 1 orclaim 2 wherein the rivet punches out a disc from an upper sheet of the workpiece and this disc is held captive within the hollow shank of the rivet.

4. A method as claimed in any preceding claim wherein the rivet has a piercing edge around its outer periphery at its end remote from the head and a deformable portion of narrowed wall thickness behind the piercing edge, the arrangement being such that the rivet enters axially into the workpiece and its cleformable portion is then expanded radially outward.

5. A rivet comprising ahead, a hollow shank having a piercing edge around its outer periphery at its end remote from the head and a deformable portion of narrowed wall thickness behind the piercing edge.

6. Rivetting apparatus comprising a base, an anvil supported with respectto the base and movable towards and away from the base, a punch arranged to drive a rivet into the workpiece to be rivetted while the workpiece is supported on the anvil, subsequently to drive the anvil into positive engagement with the base by means of a protruding portion formed on the workpiece by the rivet and then to cause the rivet and workpiece to be deformed by axial loading between the punch and the positively supported anvil.

7. Rivetting apparatus as claimed in claim 6 wherein the anvil has a flat surface for engagement by the workpiece.

8. A method of rivetting substantially as de- scribed with reference to and as illustrated by the accompanying drawings.

9. A rivet substantially as described with reference to and as illustrated by the accompanying drawings.

10. Rivetting apparatus substantially as described with reference to and as illustrated by the accompanying drawings.

Printed in the U K for HMSO, D8B18935,10184,7102. Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.

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