GB2093550A

GB2093550A - Rivet

Info

Publication number: GB2093550A
Application number: GB8138374A
Authority: GB
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 1981-02-23
Filing date: 1981-12-21
Publication date: 1982-09-02
Also published as: CH652458A5; DE3106663A1; NL8200610A; ATA36282A; IT8219336A0; BE892225A; SE8200931L; AT383189B; IT1149500B; FR2500545B1; ES271958U; FR2500545A1; ES271958Y; GB2093550B

Abstract

Rivet sleeve 1 has a succession of annularly-shaped recesses 1d of of saw- tooth configuration which engage with a sharp edged rim 2b of an expansion body to prevent loosening. The rivet is used, for example to fasten insulating material 5 to a wall 6, and the force applied to the stem 2 when the rivet is expanded is sufficient to break the stem at a predetermined breaking point 3. <IMAGE>

Description

SPECIFICATION A blind-rivet-like expansible dowel This invention relates to a blind-rivet-like expansible dowel, more especially for making a fastening to a structured member behind which is a cavity and which is accessible only from its front side, comprising an expansible dowel sleeve which is partially slotted longitudinally in its front region, and an expansion body which can be drawn into said front region and which is connected, by way of a predetermined breaking point, to a draw mandrel, the expansion body having an annular bead which projects radially beyond the periphery of said body.

Blind-rivet-like expansible dowels in which expansion is effected by drawing an expansion body into a dowel sleeve by means of a draw mandrel are used more especially for fairly simple or light fastenings.

If the expansion force or the force applied to the draw mandrel is sufficiently great, the predetermined breaking point disposed between the expansion body and the draw mandrel fractures. The expansion body thus remains in the dowel sleeve, whilst the draw mandrel is removed therefrom.

In order to achieve adequate expansion of the dowel sleeve, the conicity of the expansion body is generally relatively great. However, if the cone angle of the expansion body is greater than the friction angle between the expansion body and the dowel sleeve, self-locking of the expansion body does not occur, so that the expansion body can be forced out of the dowel sleeve again. This danger arises more especially when plastics materials which have a small coefficient of friction are used.

This disadvantage is not even obviated when the expansion body has an annular bead which assists the expansion of the dowel sleeve. In fact, because of the elasticity of resilience of the material of the dowel sleeve, forcing out of the expansion body is promoted.

The problem underlying the invention is to provide an expansible dowel the construction of which is such that release or loosening of the expansion body in the dowel sleeve is prevented.

In accordance with the invention, this is achieved in that the inner surface of the longitudinally-slotted front region of the dowel sleeve has annular recesses for the reception of the annular bead.

The annular recesses provided in the longitudinally-slotted front region of the dowel sleeve, make possible location of the expansion body relative to the dowel sleeve by way of the annular bead.

Non-intentional release of the expansion body from the dowel sleeve is thus prevented. Even extreme streasses, such as for example vibrations, do not result in lossening of the expansion body. The expansion procedure, itself, is not affected by the presence of the recesses.

In order to make possible stepped expansion of the dowel sleeve, with the steps as gradual as possible, it is advantageous for several of said recesses to be arranged consecutively without gaps, in the longitudinal direction along said front region.

The staaes in which the exDansible dowel can be expanded thus correspond to the graduations of the recesses. These can be selected, as required, to be coarse of fine.

In order to achieve progressively increasing expansion upon the drawing of the expansion body into the dowel sleeve, it is advantageous for the inner surface of the dowel sleeve, in the slotted region, to widen towards the front end of the dowel sleeve. This widening can, for example, be conical in configuration. Because the expansion body locks with or locates with the dowel sleeve, the angle of divergence of the inner surface, widening towards the front end of the dowel sleeve, can be selected to be virtually arbitrarily great, without involving risk of loosening of the expansion body.

In order to keep the resistance upon the drawing of the expansion body into the dowel sleeve as low as possible, it is advantageous for the recesses to be of sawtooth configuration, with the longer flanks of the sawtooth profiles directed towards the front end of the dowel sleeve. The annular bead of the expansion body can thus slide over the flanks of the sawtooth profiles. The shorter flanks of the swatooth profiles may extend substantially perpendicularly to the longitudinal axis of the dowel or may be directed towards the rearward end of the dowel sleeve.

For good location of the expansion body with the dowel sleeve it is advantageous for the annular bead to be sharp-edged. For example, in the event of the recesses in the dowel sleeve being designed with sawtooth profiles, the annular bead may be correspondinglytooth-shaped in design. Such coordination of the recesses and the annular bead makes possible delicately stepped locating of the expansion body with the dowel sleeve. A sharpedged annular bead at the expansion body is, however, advantageous also in the case where the recesses in te dowel sleeve lie relatively far apart.

The invention will be described further, by way of example, with reference to the accompanying drawings which reproduce it by way of example, and in which: Figure 1 is a sectional side elevation illustrating the dowel sleeve of a preferred embodiment of the dowel of the invention; Figure 2 is a side elevation showing an expansion body of the dowel of Figure 1; Figure 3 is a fragmentary detail showing the front region of the dowel sleeve of Figure 1, to an enlarged scale; Figure 4 shows a front end view of the dowel sleeve of Figures 1 and 3; Figure 5 is a view comparable with Figure 1, but showing the dowel in its expanded condition and effecting a fastening.

The illustrated preferred embodiment of the blindrivet-like expansible dowel of the invention comprises a dowel sleeve shown in Figure 1 and designated as a whole by the reference numeral 1 on the rearward end of which is a flange la. The front region of the dowel sleeve 1 is formed with longitudinal slots 1b. The dowel sleeve 1 has, in the slotted region, an inner surface lcwhichwidenstowards the front end. This inner surface Ic is formed with annular recesses 1 d.

An expansion body of the dowel is shown in detail in Figure 2 and is designated as a whole by the numeral 2. This body 2 has, at its front end, a conical bead 2a which widens forwardly. The expansion body 2 is connected, by way of a predetermined breaking point 3, to a draw mandrel 4. The expansion body 2 has an annular bead 2b which projects radially beyond the periphery of the bead 2a. The annular bear 2b is sharp-edged.

The front region of the dowel sheet, shown, enlarged in Figure 3, of the dowel sleeve 1, has its inner surfaces widening in the region of the longitudinal slots 1b towards the front end and is formed with the annular recesses id is evident, as already described. The recesses it are of sawtooth configuration. In this connection, the longer flanks la of the sawtooth profiles are each directed towards the front end of the dowel sleeve 1. The shorter flanks lfofthe sawtooth profiles extend approximately perpendicularly to the longitudinal axis of the dowel.

The front view, shown in Figure 4, of the dowel sleeve 1 shows that there are two longitudinal slots 1b. However, three, four or more Ion gitudinal slots ib may alternatively be provided in the dowel sleeve 1.

As shown in Figure 5, expansible dowel may serve, for example for fastening insulating material 5 against a reception surface 6. The flange la of the dowel sleeve 1 abuts against the surface of the insulating material 5 that is to be fastened. The expansion body 2 is drawn to such an extent into the dowel sleeve 1 that is stem becomes torn off at the predetermined breaking point 3. In so doing, the core 2a has brought about expansion of the dowel sleeve 1 form the front end thereof. The sharp-edged annular bead 2b, projecting beyond the cone 2a, has in so doing, entered into engagement with the recesses 1 d, designed in sawtooth form, of the dowel sleeve 1. The expansion body is thus located or locked relative to the dowel sleeve 1 and cannot come loose automatically. Form locking or positive interengagement exists between the dowel sleeve 1 and the reception material 6.

Both the dowel sleeve 1 and the expansion 2 may consist of any desired material, such as metal.

However, production of these parts from plastics material is particularly economical.

Claims

1. A blind-rivet-like expansible dowel, more especially for making a fastening to a structural member behind which is a cavity and which is accessible only from its front side, comprising an expansibie dowel sleeve which is partially slotted longitudinally in its front region, and an expansion body which can be drawn into said front region and which is connected, by way of a predetermined breaking point, to a draw mandral, the expansion body having an annular bead which projects radially beyond the periphery of said body, characterised in that the inner surface of the longitudinally-slotted front region of the dowel sleeve has annular recesses for the reception of the annular bead.

2. An expansible dowel as claimed in claim 1, characteristed in that several of said recesses are arranged consecutively, without gaps, in the longitudinal direction, along said front region.

3. An expansible dowel as claimed in claim 1 or 2, characterised in that the inner surface of the dowel sleeve in the slotted region widens towards the front end of the dowel sleeve.

4. An expansible dowel as claimed in claim 1, 2 or 3, characterised in that the recesses are of sawtooth configuration, with the longer flanks of the sawtooth profiles directed towards the front end of the dowel sleeve.

5. An expansible dowel as claimed in any preceding claim characterised in that the annular bead is sharp edged.

6. An expansible dowel substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.