AU2005220176A1 - An improved rivet assembly - Google Patents

Description

Regulation 3.2 -1-

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT

APPLICANT:

NUMBER:

FILING DATE: Loi Tran Pty. Limited 2004905717 4/10/2004 Invention Title: AN IMPROVED RIVET ASSEMBLY The following statement is a full description of this invention, including the best method of performing it known to me/us: -2-

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AN IMPROVED RIVET ASSEMBLY

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Technical area INO This invention relates to the area of fastening elements and in particular, to improvements made to a self-drilling rivet which is adapted to join sheet metal Sor fasten sheet metal to a framework.

1 Background to the invention For many years rivets have been widely used as a means of connecting two materials such as sheet metal together. Previous adaptions include the so-called pop-rivet in which the rivet is provided with a flange and a stem, whereby the stem is adapted to receive a mandrel therethrough. The combination of the mandrel and the rivet is inserted into a hole formed in the workpieces and a fastening tool is then brought into contact with the flange of the rivet, with the shank of the mandrel being drawn by the fastening tool to deform the stem of the rivet. When the mandrel has ben completely drawn, the mandrel, separates from the stem, leaving the workpieces fastened between the flange and the deformed portion of the rivet.

The disadvantage with this process is that holes must be drilled or punched in the workpieces prior to the rivet being set which requires two separate pieces of machinery and operations. Consequently, there may be a small interval between the two pieces, and upon setting of the rivet, the two pieces will shift towards each other in a manner which compromises the rivetted connection. Further, there is the expense of a worker having to insert the rivet in two steps.

Y:\SPECOLoi Tran Self Drilling Rivet CAP 031005.wpd 4/10/05 I, -3-

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0: ti nojc ftepeetivnio ooecm rsbtnilyaeirt Outline of the invention It is an object of the present invention to overcome or substantially ameliorate the disadvantages of the prior art by providing an improved rivet assembly which N eradicates the need for separate tools and provides an efficient means for 0rivetting.

The invention provides a rivet assembly having a rivet having a body comprising a stem and a head and a mandrel having a self-drilling tip passing through the body, the arrangement being such that the mandrel and its tip can be rotated to drill a hole at least the diameter of the rivet stem through the members to be connected and once drilling is complete, the stem can pass through the hole and the mandrel can be drawn outwardly, causing the stem to deform, the mandrel breaking from the rivet when the rivet is in place.

It is preferred that the head is at the outer end of the stem, the head portion being of a diameter larger than the diameter of the hole formed by the drill tip.

It is also preferred that the self-drilling tip of the mandrel is formed to have a point which can initiate the drilling action, cutter surfaces adjacent the point and flights to clear swarf cut by the cutter surfaces.

The self drilling tip is formed separately from the mandrel and connected thereto and can be of a harder metal than the mandrel so that there is the benefit of Y:\SPECLoi Tran Self Drilling Rivet CAP 031005.wpd 4/10/05

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-4- I easily forming the required holes by the drill tip and yet permitting the mandrel O to break away when the rivet has been fully set.

The outer end of the mandrel is formed to be positively held during rotation and O may be hexagonal for ready connection to the chuck of the insertion machine.A 0rivet assembly as claimed in any preceding claim wherein the mandrel and drill

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N' tip can rotate relative to the rivet stem.

In Description of an Embodiment of the Invention In order that the invention may be more readily understood we will describe by way of the attached drawings, a non limiting example being a specific embodiment thereof.

In these drawings: Fig 1 Shows the rivet assembly of the invention prior to piercing the material it is to hold but with the mandrel of the rivet in an insertion tool; and Fig 2 shows the rivet of Fig when in its final position.

In this embodiment, the rivet has provided a head portion 61 and an annular body portion 60 which extends outwardly from the bottom of the head portion.

The rivet can be made of any material however, it is preferred that it be made of a non-corrosive metal, often aluminium, steel or brass. The annular body portion includes an inner surface 62 and an outer surface 63. The outer surface of Y:\SPEC\Loi Tran Self Drilling Rivet CAP 031005.wpd 4/10/05 c the annular portion will normally be cylindrical but it could be of any other o suitable shape provided that deformation properties and requirements of the rivet are met.

IND The inner surface 62 is complimentary to the shape and size of the outer surface of a connecting portion of the mandrel. In this way, the annular portion 60 of (1 the rivet can be passed over the mandrel and a connection between the annular 0 portion of the rivet and the connecting portion of the mandrel can be maintained.

In a preferred embodiment, the annular body portion of the rivet defines a bore which extends therethrough which enables a mandrel to be passed therethrough. The annular body portion of the rivet may be provided with a deformation portion which, upon deformation thereof, will form a closure head.

The head portion 61 of the rivet may be disc-shaped or any other suitable shape so long as it enables the head portion to act as a setting head for the rivet. In a preferred embodiment of the invention the head portion is disc-shaped and concave with the outer edge of the head portion being smooth such that, it is adapted to be used with any rivetting tool without the need for a particular nosepiece to be used.

In order to drive the rivet, the mandrel is provided having a shank at one end and a drilling tip 51 at the opposite end. The drilling tip 51 is a standard self-drilling tip similar to that used with screws which, enables a clean hole to be cut through the pieces of sheet material to be connected without causing damage to the material around the hole.

Y:\SPECLoi Tran Self Drilling Rivet CAP 031005.wpd 4/10/05 S-6cl In a preferred form, the tip has two facets which meet at a point and the sides of C.) o these are formed to provide cutting surfaces 57 whereby, once penetration has started a conical incursion into the upper sheet of metal is formed. There can be cut out portions 56 which are designed to carry the swarf away from the INO cutting tip.

c In practice, the mandrel is made from a single length of material but, if required, Sthe drill tip can be formed separately, normally of a harder material than the mandrel, and connected to the mandrel by welding or the like.

The head of the mandrel is shaped such that it is adapted to be received by a nosepiece which is attached to a standard drill for driving a rivet. This may be a cylindrical portion which is a continuation of the main portion of the mandrel or it could be hexagonally shaped such that, it can be fitted directly into a rivetting apparatus and be secured in place via a chuck connection or another other suitable means of connection.

The mandrel may also have, above the drill tip, a weakened portion 52 at which the portion of the mandrel held in the insertion tool with break before any other part.

In practice, a first metal member is placed on top of a second metal member, wherein at least a portion of a underside of the first member is in overlapping contact with a upper side of the second member. Using a rivetting apparatus in a rotating mode, the drill tip of the mandrel is rotated and forms a hole through the members to permit the rivet body 60 to pass therethrough until the head 61 of the rivet is in abutment with the first member. At this time the drill tip of the Y:\SPECoi &Tran Self Drilling Rivet CAP 031005.wpd 4/10/05 n-7c mandrel and the body of the rivet has has passed through the first and second o members in the overlapping region.

After the rivet has reached this state, the rivetting apparatus draws the mandrel rearwardly, and this causes the part of the annular portion 63 which passes through the sheets to be deformed radially outwardly away from the central axis Sof the rivet and thus the rivet is secured between the sheets by the head on one Sside and the deformed portion of the body on the other.

The deformation of the annular body occurs up until a point of maximal tension, at which time the rivet comes free from the mandrel and "pops" at the weakened section 52. The drill bit end of the mandrel has been drawn into the rivet body a short distance. The remainder of the mandrel is then removed from within the rivet body and can be discarded.

As described, the rivet body is free to have the mandrel rotate therein but, If required, it is possible that the mandrel and the rivet body are interconnected so they both rotate whilst the hole is being drilled but can move axially one relative to the other when the body is compressed.

While we have described herein particular embodiments of the improved rivet assembly, it is envisaged that other embodiments of the invention will exhibit any number of and combination of the features previously described, and it is to be understood that variations and modifications in this can be made without departing from the spirit and scope thereof.

The claims defining the invention are as follows: Y:\SPECULoi &Tran Self Drilling Rivet CAP 031005.wpd 4/10/05

Claims (7)

1. 2. A rivet assembly as claimed in claim 1 wherein the head is at the outer end of the stem, the head portion being of a diameter larger than the diameter of the hole formed by the drill tip.
2. 3. A rivet assembly as claimed in claim 1 or claim 2 wherein the self-drilling tip of the mandrel is formed to have a point which can initiate the drilling action, cutter surfaces adjacent the point and flights to clear swarf cut by the cutter surfaces.
3. 4. A rivet assembly as claimed in claim 3 wherein the self-drilling tip is made integral with the remainder of the mandrel. A rivet assembly as claimed in claim 3 wherein the self-drilling tip is made of a metal different to that of the remainder of the mandrel.
4. 6. A rivet assembly as claimed in claim 5 wherein the self drilling tip is formed separately from the mandrel and connected thereto. Y:\SPEC\Loi Tran Self Drilling Rivet CAP 031005.wpd 4/10/05 s, -9- c- 7. A rivet assembly as claimed in any preceding claim wherein the outer end o of the mandrel is formed to be positively held during rotation.
5. 8. A rivet assembly as claimed in claim 7 wherein the outer end of the IO mandrel is hexagonally shaped for ready connection to a chuck. C( 9. A rivet assembly as claimed in any preceding claim wherein the mandrel Shas a point of weakness at which is shears when the rivet is set. A rivet assembly as claimed in any preceding claim wherein the mandrel and drill tip can rotate relative to the rivet body.
6. 11. A rivet assembly as claimed in any one of claims 1 to 9 wherein the rivet body is caused to rotate with the mandrel and drill tip.
7. 12. A rivet assembly substantially as hereinbefore described with reference to the accompanying drawings. DATED this 4 day of October, 2005 Loi Tran Pty. Limited By Its Patent Attorneys A TATLOCK ASSOCIATES Y:\SPEC\Loi Tran Self Drilling Rivet CAP 031005.wpd