GB2159595A

GB2159595A - Blind rivets

Info

Publication number: GB2159595A
Application number: GB08504126A
Authority: GB
Inventors: George Siebol
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-05-30
Filing date: 1985-02-18
Publication date: 1985-12-04
Also published as: GB2159595B; FR2565303B1; DE3519231A1; IT8547696A1; GB8504126D0; IT1182207B; IT8547696A0; FR2565303A1; JPS60256612A

Abstract

A tubular blind rivet assembly includes a rivet (10) having an enlarged head (24) and a shank (12) and a locking pin (39) having a flared skirt (42) for clamping workpieces (16, 18) together and expanding the blind end of the rivet (10). Spaced apart locking rings (80) are provided on the locking pin for locking the rivet (10) and workpieces (16, 18) together. The spaced rings (80) to enable the rivet (10) to be used with differing thicknesses of workpieces (16, 18) and the leading faces (83) of these are inclined at 45 DEG -75 DEG to the axis of the pin. The flared skirt (42) is elbow-shaped in cross-section with an annular ridge (46) and is formed in the region of the breakneck (96). The trailing faces (87) are inclined at 75 DEG -90 DEG to the axis of the pin (39). <IMAGE>

Description

SPECIFICATION Rivet assembly This invention relates to rivets. In particular, it relates to blind rivets which can be installed and fastened to a workpiece when access can be gained to only one side of the workpiece.

It is well known in the art to provide rivets which can be installed in a workpiece from the front side of the workpiece, even though the installer has no access to the back or blind side. Various types of such rivets have been designed to operate in a variety of ways. One design is described in US-A-3,073,205. This specification describes a rivet assembly consisting of a tubular rivet and a locking pin.

The locking pin is inserted through the shank end of the rivet and extends outwardly through the head. The outwardly extending end is adapted to be gripped with a pulling device, while the other end of the locking pin is enlarged slightly larger than the inside diameter of the tubular rivet. The assembly is positioned through a hole in a workpiece or workpieces, so that the head is on the outside and the other end extends beyond the blind side of the workpiece. When the outwardly extending end of the locking pin is pulled by a pulling device, it forces the enlarged portion on the blind side of the locking pin to wedge inside the tubular shank of the rivet, thus expanding the rivet on the blind side of the workpiece. When the blind end of the rivet has been expanded to a size larger than the hole in the workpiece the rivet is then fixed permanently in position.

A more advanced rivet having an increased shear strength is shown in GB-A-2124317 and the present invention is concerned with detailed improvements in this rivet.

According to a first aspect of this invention such a rivet assembly comprises an elongate rivet having a head and a shank having a common axial bore, the head being larger than the opening in the workpiece and the shank being arranged for axial insertion through the opening so that when the head is engaged with the one side of the workpiece, the end of the shank remote from the head protrudes through the opening beyond the other side of the workpiece, and, an elongate, integrally formed locking pin having an elongate pulling section at one end, a generally cylindrical body at the other end, and an elongate neck between them, a weakened portion being provided at the join between the neck and the body so that when the locking pin is subjected to excessive axial tension it fractures at this weakened portion, the body having a plurality of integrally formed locking rings extending around its circumference and lying in a plane transverse to its axis with circumferentially extending grooves on the side of each locking ring remote from the pulling section, and a hollow skirt flared radially outwards and downwards away from the pulling section, the skirt being joined at its base to the body adjacent the joint with the neck and surrounding and being spaced apart from the neck to provide an annular space between the skirt and neck, the pulling section and neck being arranged to fit through the bore in the rivet with the pulling section extending out of the bore through the rivet head whilst the body of the pin extends beyond the bore opening on the other end of the shank, the plurality of locking rings being spaced between the neck joint and the other end of the body, each of the locking rings having an outside diameter greater than the diameter of the bore of the shank, and at least one of the locking rings having its face adjacent the pulling section sloping away from the pulling section at an angle between substantially 75 and substantially 45 from the axis of the body.

According to a second aspect of this invention such a rivet assembly comprises an elongate rivet having a head and a shank having a common axial bore, the head being larger than the opening in the workpiece and the shank being arranged for axial insertion through the opening so that when the head is engaged with the one side of the workpiece, the other end of the shank remote from the head protrudes through the opening beyond the other side of the workpiece, and an elongate, integrally formed locking pin having an elongate pulling section at one end, a generally cylindrical body at the other end, and an elongate neck between them, a weakened portion being provided at the join between the neck and the body so that when the locking pin is subjected to excessive axial tension, it fractures at the weakened portion, the body having a plurality of integrally formed locking rings extending around its circumference and lying in a plane transverse to its axis and a hollow flared skirt having a base portion joined to the body adjacent the joint with the neck, an open end portion opposite the base portion and surrounding a portion of the neck adjacent its joint with the body and an enlarged diameter portion having a larger diameter than the base and open end portions, the flared skirt having an elbow-shaped cross section and being spaced from the neck to provide an annular space between the skirt and the neck, the pulling section and the neck being arranged to fit through the bore in the rivet with the pulling section extending out of the bore through the rivet head when the body of the pin extends beyond the bore opening on the other end of the shank.

Such rivet assemblies are suitable for fastening together a workpiece, such as two metal sheets, when access is only available to one side (referred to herein as the "front side"). In a particular example of assembly the rivet has an enlarged head, a tubular shank, a bore extending through the shank and head, and a locking pin for locking the rivet to the workpieces. The locking pin has a relatively narrow cylindrical neck, small enough to fit within the bore of the rivet, and a slightly larger cylindrical body integrally formed and axially aligned with the neck. A flared skirt is provided at the intersection of the neck and body, the skirt being connected to the body and extending outwardly surrounding a portion of the neck, with an annular recess terminating in a breakneck groove between the skirt and the neck.The skirt tapers from a relatively narrow tip, small enough to enter the rivet bore, to an annular ridge intermediate the join of the skirt and body of the locking pin, the ridge having a diameter greater than the diameters of the bore and of the adjacent portion of the body.

The body of the pin is also equipped with an integrally formed series of ductile locking rings separated by annular grooves or channels running circumferentially around the body, the rings having diameters greater than the diameter of the body, and the channels having diameters no greater, and preferably smaller, than the diameter of the body. When the pin is pulled into the rivet shank, the annular ridge on the flared skirt effects an expansion of the tip of the shank and rolls it outwardly, simultaneously clamping it tightly against the blind side of the inner workpiece.

As the body of the pin is pulled into the shank, the ductile locking rings are also drawn into the shank and are collapsed into the adjacent channels, the extent of collapsing and deformation depending upon the thickness of the workpieces being riveted.

The wall of the flared skirt is elbow-shaped in cross section, being of narrowest cross section at the bend where the elbow extends outwardly to form the annular ridge. The end portion of the neck is enlarged in diameter near the connection with the body inside the flared skirt. When the neck of the pin is drawn through the rivet, the portion of the flared skirt between the elbow and the body of the pin flares outwardly, locking the pin to the rivet, while the remainder of the skirt beyond the elbow folds inwardly towards the axis of the bore through the rivet head.

Particular examples of rivet assemblies in accordance with this invention will now be described with reference to the accompanying drawings; in which: Figure 1 is a perspective view, Figures 2 to 6 are all partial fragmentary cross sections through the rivet assembly with the assembly inserted in openings in a pair of workpieces and showing the fastening operation of the assembly; Figure 7 is a partial fragmentary cross section of the flared skirt and adjacent portions of the neck and body of the locking pin; Figure 8 is similar to Figure 6, showing the rivet installed in thinner workpieces; and, Figure 9 shows an alternative form for the locking rings.

Figure 1 shows a rivet assembly 10 consisting of a blind rivet 1 2 and a locking pin 14.

Figures 2 to 6 show the sequential steps of using the rivet assembly 10 to rivet together a front workpiece 16 and a rear workpiece 18.

Typically, the workpieces consist of a pair of metal sheets of aluminium steel, or the like.

Aligned, circular apertures 20 and 22 are provided in the sheets. The apertures are sufficiently large to admit all of the rivet assembly, except the head 24. Preferably, the outside diameter of the tubular shank 26 is just slightly smaller than the apertures 20 and 22, so that the rivet can fit easily within the apertures and yet expand to completely and snugly fill the apertures when the riveting process is complete.

The locking pin 14 includes a pulling section 30 which is provided with a series of lands 32 and grooves 34, as shown in Figure 1. The pulling section 30 is integrally connected to cylindrical neck 36, which is sized to fit within the bore 38 of tubular shank 26.

The cylindrical neck is, in turn, integrally connected to the body 40 of the locking pin.

The body 40, like the cylindrical neck, is generally a solid metallic cylinder; however, the diameter along most of the body may be varied, and it initially is slightly larger than the inside diameter of the bore 38. It is wire drawn to a smaller diameter as it is pulled inside the bore 38, simultaneously producing a desired interference fit between the tubular shank 26 and the walls of apertures 20 and 22 by expanding the walls of the shank radially outwards. The body is also equipped with a flared skirt 42, which tapers from a tubular tip 44 to an annular ridge 46 and then tapers inwardly to outwardly join the body adjacent the juncture of the cylindrical neck with the body.

The tubular shank 26 of the rivet is equipped with an expandable point 50 at its blind end. The expandable point is also provided with a counterbore 52 on the inside of the point. The counterbore is sized to permit entry of the tip of the flared skirt, as shown in Figures 2 and 3.

To install a rivet in the workpieces, the rivet assembly is positioned in the apertures 20 and 22 of the workpieces, as shown in Figure 2. A riveting tool 60 engages the lands 32 and grooves 34 of pulling section 30 of the locking pin and urges a die 66 against the front surface 68 of the rivet. The tool 60 thus can pull the locking pin inwardly through the bore 38 of the tubular shank 26 of the rivet, while the head of the rivet is held securely against the inner surface 70 of the front workpiece 16.

As the locking pin is drawn into the interior of bore 38, as shown in Figures 2 and 3, the flared skirt 42 is drawn and compressed into expandable point 50 of the tubular shank 26.

Since the flared skirt tapers from a relatively narrow tip 44 to an enlarged annular ridge 46, it rolls the walls of the tubular shank radially outwardly compressing the two workpieces to close the gap 72 (exaggerated in Figure 2) and compressing the two workpieces together (as shown in Figure 3), while simultaneously locking them together by creating the expanded hip 74 on the tubular shank.

In the preferred embodiment of the invention, the annular ridge 46 is slightly larger than the diameter of body 40, so that in the initial stage of drawing the pin inside the shank, shown in Figure 3, an annular space 75 is provided between the shank and the body of the locking pin. Thus, the only frictional drag exerted against drawing the pin is believed to be that exerted between the tapering outer surface of the flared skirt and the inner wall of the shank.

As the riveting tool 60 draws the locking pin 14 further through the bore of the rivet, as shown in Figure 4, the annular ridge of the flared skirt is compressed as the skirt is straightened out, and the skirt and body 40 of the locking pin expand the walls of the tubular shank against the walls of the apertures 20 and 22, thus rigidly fixing the rivet in position.

The body of the shank also is provided with a series of ductile locking rings 80 separated by grooves or channels 82. The volume of metal in each locking ring extending radially outwardly from the body of the locking pin corresponds to the volume of the adjacent channel or groove inward of the ring. Thus, as the locking pin is drawn still further into the tubular shank, as shown in Figure 5 and Figure 6, the ductile locking rings are deformed and compressed into the channels behind them. Simultaneously with the deformation of each locking ring, the radius of the hip 74 of the tubular shank 26 is reduced and the hip is compressed more tightly against the blind side surface 84 of the rear workpiece 1 8. This increases the tensile strength in thin workpieces to levels comparable to thicker workpieces.

As shown in Figures 2 and 3, the front face 83 of each locking ring slopes rearwardly away from the body of the pin. Preferably, the angle of slope is between about 15 and 45 from the horizontal, and more preferably about 25 to about 35 . A circumferential line of weakness 85 is provided at the front intersection of each or at least the front locking ring with the body of the pin. The line of weakness constitutes a reduced diameter portion which permits the locking ring to be deformed and rotate rearwardly, as shown in Figures 4 and 8, without being sheared off as it is drawn into the rivet.

The rear surface 87 of the locking rings is normally horizontal, i.e., perpendicular with respect to the axis of the locking pin. However, an alternative form is shown in Figure 9 wherein the rear face 87 is angled slightly forward. This design allows for the selection of materials that give the best results for each contemplated use. For example, in contrast to this invention, other rivet and pin assemblies often use very soft sleeve materials and rely upon the expansion of the sleeve by compressing the sleeve axially from the ends.

Applicant's design permits the use of hard sleeve materials with much greater shear and tensile strengths. To upset or roll back the sleeve, or expand it outwardly, for securing to the workpiece, it may be desirable to use locking rings as shown in Figure 9, since these rings will not deform as readily as the type shown in Figures 2 to 6. It is contemplated that the back angle of the back face 87, as shown in Figure 9, should be less than about 15 forward of the horizontal, and preferably in the range from about two to eight degrees, depending on the ductility of the ring and the hardness of the sleeve to be expanded.

Figure 5 also shows the initiation of flaring of the flared skirt 42 as it is compressed against the die 66. The head 24 of the rivet 1 2 is provided with an internal annular recess or countersink 86 whose volume is sufficient to accommodate the volume of metal in the flared skirt 42. When the flared skirt is fully flared and expanded, as shown in Figure 6, it essentially completely fills the void space in annular recess 86. At the same position at which the flared skirt is completely compressed linearly and fully expanded radially into the recess, one or more of the locking rings 80 are wedged into the expandable point 50 of the tubular shank beyond the inner shoulder 94 of the counterbore 52.

Axial movement of the pin relative to the rivet is thus blocked. Thereafter, as the riveting tool 60 attempts to pull the locking pin still further into the tubular shank, and further movement is blocked by the abutment of the face 67 of die 66 against skirt 42, the pulling section and cylindrical neck of the locking pin are broken off from the body 40 at the breakneck groove 96, which is located at the base of the flared skirt and the juncture of the cylindrical neck and body of the locking pin. The breakneck groove consists of a groove around the circumference of the locking pin to ensure that fracture or rupture of the metal will occur along a relatively uniform plane, so that the surface 98 of the ruptured portion will be relatively smooth, as shown in Figure 6.

After the neck is severed from the body, the riveting tool and the neck are removed, leaving the finished rivet head exposed on the front side of the workpiece.

Figure 8 shows a riveted pair of substantially thinner workpieces than those shown in Figures 2 to 6. As can be seen, the installed rivet is capable of providing the same type of bonding as is provided with thicker workpieces. This is achieved due to the plurality of ductile locking rings 80a, 80b, and 80c and adjacent channels 82 spaced along a substantial length of the blind end of the locking pin.

As seen in Figure 8, only the first locking ring 80a is deformed substantially by entry into the portion of the tubular shank that is within the aperture of the inner workpiece. The use of the same rivet assembly on thicker workpieces will provide equally satisfactory results up to the point where the last locking ring 80c is adjacent the shoulder 74. Thus, the rivet assembly provides a substantial degree of flexibility for use with different thicknesses of workpieces than has been previously achievable with such devices. Furthermore, although the embodiments in the drawings show only three locking rings, it is also contemplated to use four or even more such rings for maximum flexibility of use of the devices.

Figure 8 also shows an alternative method for securing the locking pin to the rivet head by simply using a washer 90 over the neck of the pin. The washer thus effectively performs the function of the die face 67 (as shown in Figure 21).

Figure 7 shows an enlarged fragmentary cross section of a particularly preferred embodiment showing the relationship of the flared skirt and adjacent portions of the neck and body of the locking pin. As shown, the flared skirt 42 has an elbow 100 intermediate the tip of the flared skirt and the junction of the flared skirt with the body 40 of the pin.

The elbow is positioned adjacent an expanded section 102 of the neck 36 of the locking pin, directly forward of breakneck 96. The tapered expanded portion 102 is of sufficient diameter relative to the bore of the rivet 1 2 as to ensure that the elbow 100 does not completely straighten out when the annular ridge 46 is compressed as it is drawn through the bore of the rivet (see Figure 4). This ensures that upon final drawing and severing of the neck from the body, as shown in Figures 5 and 6, the flared skirt will, upon compression, be returned to its elbow configuration, with the tip folding inwardly to fill the cavity of countersink 86. Also, the expanded portion 102 of the neck ensures that the flared skirt will fold outwardly from its junction with the body 40 of the pin to engage with and lock with the head 24 of the rivet, as shown in Figures 5 and 6. By providing a weakened elbow portion having a wall thickness thinner than that of the rest of the flared skirt, it is possible to use extra thick portions of the skirt at the bottom where the skirt connects to the body and still readily flare the skirt for locking to the rivet head. This permits the use of assemblies having greatly improved shear strengths, due to enhanced thicknesses of pin material virtually throughout the rivet bore.

Claims

1. A rivet assembly for fastening through an opening in a workpiece from the one side without access to the other side comprising an elongate rivet having a head and a shank having a common axial bore, the head being larger than the opening in the workpiece and the shank being arranged for axial insertion through the opening so that when the head is engaged with the one side of the workpiece, the end of the shank remote from the head protrudes through the opening beyond the other side of the workpiece, and, an elongate, integrally formed locking pin having an elongate pulling section at one end, a generally cylindrical body at the other end, and an elongate neck between them, a weakened portion being provided at the join between the neck and the body so that when the locking pin is subjected to excessive axial tension it fractures at this weakened portion, the body having a plurality of integrally formed locking rings extending around its circumference and lying in a plane transverse to its axis with circumferentially extending grooves on the side of each locking ring remote from the pulling section, and a hollow skirt flared radially outwards and downwards away from the pulling section, the skirt being joined at its base to the body adjacent the joint with the neck and surrounding and being spaced apart from the neck to provide an annular space between the skirt and neck, the pulling section and neck being arranged to fit through the bore in the rivet with the pulling section extending out of the bore through the rivet head whilst the body of the pin extends beyond the bore opening on the other end of the shank, the plurality of locking rings being spaced between the neck joint and the other end of the body, each of the locking rings having an outside diameter greater than the diameter of the bore of the shank, and at least one of the locking rings having its face adjacent the pulling section sloping away from the pulling section at an angle between substantially 75 and substantially 45 from the axis of the body.

2. A rivet assembly for fastening through an opening in a workpiece from one side without access to the other side comprising an elongate rivet having a head and a shank having a common axial bore, the head being larger than the opening in the workpiece and the shank being arranged for axial insertion through the opening so that when the head is engaged with the one side of the workpiece, the other end of the shank remote from the head protrudes through the opening beyond the other side of the workpiece, and an elongate, integrally formed locking pin having an elongate pulling section at one end, a generally cylindrical body at the other end, and an elongate neck between them, a weakened portion being provided at the join between the neck and the body so that when the locking pin is subjected to excessive axial tension, it fractures at the weakened portion, the body having a plurality of integrally formed locking rings extending around its circumference and lying in a plane transverse to its axis and a hollow flared skirt having a base portion joined to the body adjacent the joint with the neck, an open end portion opposite the base portion and surrounding a portion of the neck adjacent its joint with the body and an enlarged diameter portion having a larger diameter than the base and open end portions, the flared skirt having an elbow-shaped cross section and being spaced from the neck to provide an annular space between the skirt and the neck, the pulling section and the neck being arranged to fit through the bore in the rivet with the pulling section extending out of the bore through the rivet head when the body of the pin extends beyond the bore opening on the other end of the shank.

3. A rivet assembly according to claim 2, wherein at least one of the locking rings has its face adjacent the pulling section sloping away from the pulling section at an angle between substantially 75 and 45 from the axis of the body.

4. A rivet assembly according to claim 2 or 3, wherein the enlarged diameter portion defines an annular ridge, the ridge and the tubular shank being sufficiently deformable that when the locking pin is drawn into the shank by pulling the pulling section of the pin axially beyond the front side of the workpiece, the other end of the shank is progressively rolled and flared radially outwards to a size larger than the opening in the workpiece so that the workpiece is clamped between the rivet head and the flared shank, and the ridge on the locking pin is progressively compressed and drawn to a size sufficiently small to fit within the shank in the region of the workpiece.

5. A rivet assembly according to claim 2, 3 or 4, wherein the wall thickness of the enlarged diameter portion of the flared skirt is less than the wall thickness of the base portion and the open end portion of the flared skirt.

6. A rivet assembly according to claim 2, 3, 4 or 5, wherein the front of the rivet head is provided with a counterbore about the bore, the counterbore having a volume sufficient to contain the volume of material in the flared skirt, in use the flared skirt being compressed into the counterbore to form a circumferential rim, and wherein the portion of the neck of the locking pin adjacent the weakened portion and inside the enlarged diameter portion of the flared skirt has a larger diameter than the rest of the neck.

7. A rivet assembly according to any one of the preceding claims, wherein the outside diameter of each locking ring is less than the original outside diameter of the flared skirt before use.

8. A rivet assembly according to any one of the preceding claims, wherein each locking ring is sufficiently deformable that when the locking pin is drawn into the shank, the ring is progressively drawn and compressed to a size to fit within the shank with the displaced material being accommodated in the spaces between adjacent rings.

9. A rivet assembly according to any one of the preceding claims, wherein at least one of the locking rings has its face remote from the pulling section which slopes forwardly away from the pulling section of the locking pin at an angle between substantially 75 and 90' to the axis of the body.

10. A rivet assembly according to claim 9, wherein the face remote from the pulling section slopes at an angle between substantially 88 and substantially 82 from the axis of the body.

11. A rivet assembly substantially as described with reference to the accompanying drawings.