GB2072782A

GB2072782A - Expansible dowel

Info

Publication number: GB2072782A
Application number: GB8102475A
Authority: GB
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 1980-03-31
Filing date: 1981-01-27
Publication date: 1981-10-07
Also published as: IT1134986B; YU36281A; NL8100920A; GB2072782B; FI804072L; DE3012498A1; JPS56143812A; FI804072A7; AU6682381A; SE8101095L; ES264921Y; BE888155A; ATA76181A; FR2479367A1; IT8119070A0; ES264921U; CA1168483A

Abstract

To enable the dowel to be anchored satisfactorily in boreholes having a relatively wide range of diameters it comprises an expansion element 3 composed of a sleeve 3b, which abuts a shoulder on expansion bolt 1, and radially resilient lamellae or tongues 3a which connect with the end of the sleeve 3b remote from head 1a of the bolt 1 and extend at an angle preferably of 15 DEG relative to the axis of the bolt 1. Expansion of the element 3 is achieved by drawing a frusto-conical expansion body 4 into the element 3 by rotating the bolt 1. <IMAGE>

Description

SPECIFICATION Expansible dowel The invention relates to an expansible dowel comprising an anchor bolt which has an abutment in the rearward region, an expansion body which widens conically forwardly, and an expansion element which is radially expansible as a result of the expansion body being drawn into said expansion element by means of the anchor bolt.

Known expansible dowels of this kind usually have a sleeve-shaped expansion element. For locating it against rotating and for retaining the dowel in the borehole, the sleeve-shaped expansion element is usually provided, on its periphery, with prominences. However, these expansible dowels require the diameter of the borehole to be very accurate. If the borehole diameter is too large, the prominences do not come into contact with the borehole wall.

Drawing-in of the expansion body, into the expansion element, is then not possible.

The problem underlying the invention is to provide an expansible dowel which is capable of being anchored satisfactorily in boreholes of a relatively wide range of diameters.

In accordance with the invention, this is achieved in that the expansion element comprises lamellae or tongues which are arranged around the entire periphery or circumference of the expansion body, and the lamellae each have a radially-resilient free end which extends at an acute angle with respect to the longitudinal axis of the dowel and is directed at the abutment.

In such an arrangement, the radially-resilient lamellae can adapt to the diameter of the borehole within a fairly large range. Since the free ends of the lamellae are directed towards the abutment, only a relatively small resistance arises therefrom upon the insertion of the dowel into a borehole. On the other hand, when the dowel, expanded within a borehole is loaded in a direction tending to draw it out of the borehole, the lamellae serve the practical function of barbs resisting the withdrawal.

The lamellae can be arranged separately around the anchor bolt. From the point of view of production technology it is, however, advantageous if the lamellae are connected to a sleeve. Then, the sleeve holds the lamellae together without restricting their function.

Connection of the lamellae to the sleeve can be effected in different ways. One possibility is, for example, for the lamellae to be connected to the sleeve by spot welding. Further connection possibilities are bonding, rivetting or soldering.

For simple production of the lamellae, it is advantageous if the free ends of the lamellae are each connected, by way of a fold, integrally with the sleeve. The sleeve and the lamellae can thus be produced together, for example in a single punching operation. Then, basically two different possibilities exist for the connections of the lamellae to the sleeve. If the lamellae are arranged to connect at the rearward end of the sleeve, then the lamellae are bent outwardly merely by an acute angle. If, on the other hand, the lamellae are arranged to connect at the front end of the sleeve, these have to be bent rearwardly by an obtuse angle. Basically, thus, both kinds are possible.

In order to meet the requirement that the dowel should be usable for a fairly large diameter range, the lamellae must project outwardly to an adequate extent. It is therefore advantageous that the lamellae form, in their non-sprung-in state, relative to the longitudinal axis of the dowel, an angle of 5 to 30, preferably 1 5 degrees.

The invention will be described further, by way of example, with reference to the accompanying drawing, in which: Fig. 1 is a part-sectional side view illustrating a first embodiment of the expansible dowel in accordance with the invention, in the nonexpanded state; Fig. 2 is a development of the expansion element of the expansible dowel of Fig. 1; Fig. 3 is a part sectional side view illustrating the expansible dowel of Fig. 1 in position in a borehole and anchored therein; and Fig. 4 is a view similar to Fig. 1, but showing a second embodiment of the dowel in accordance with the invention.

The expansible dowel illustrated in Fig. 1 comprises an anchor bolt which is designated as a whole by the numeral 1. The rearward end of the anchor bolt 1 is in the form of a hexagonal head 1 a which serves as an abutment. Adjacent the abutment 1 a, a washer 2 is arranged on the shank of the anchor bolt 1. The front end of the anchor bolt 1 is formed with a thread 1 b. Arranged on the thread 1 b is an expansion element which is designated as a whole by 3. This expansion element 3 comprises radially-resilient lamellae 3a and a sleeve 3b connected thereto. A frustoconical expansion body 4, screwed onto the thread 1 b, upon tightening of the expansible dowel by means of the abutment 1 a, is drawn into the expansion element 3. The outwardlyprojecting lamellae 3a serve to prevent loss of the washer 2 when the dowel is not in use.In their non-sprung-in state, the lamellae 3a extend at an angle a relative to the longitudinal axis of the expansible dowel. The angle a amounts to between 5 and 30 degrees, but is preferably about 1 5 degrees.

The development, evident from Fig. 2, of the expansion element 3 shows that the lamellae 3a are connected to one another by way of the sleeve 3b, with slits 3c present between the individual lamellae 3a. The free ends of the lamellae 3a are bent over about the fold lines 3d shown in dotdash lines.

For the purposes of illustration, Fig. 3 shows the expansible dowel inserted into a borehole 5. It will be understood that in practice the dowel will normally serve to secure a component (e.g. a bracket or fitment) against receiving material, but such a component has been omitted from the drawing for the sake of clarity. By tightening the anchor bolt 1 by means of the abutment 1 a the expansion body 4 has been drawn into the expansion element 3, with the result that the expansion element 3 has been expanded radially to anchor the entire dowel in place in the borehole 5. Upon the anchor bolt 1 being loaded in a direction such as to tend to withdraw it from the borehole 5, this has the effect of causing further expansion and tightening of the dowel in the borehole 5 by reason of the relative arrangement of the expansion body 4 and the expansion element 3.The lamellae 3a also serve, during the tightening, to prevent the expansion element 3 from rotating.

Fig. 4 shows a further version of the expansible dowel in accordance with the invention. This comprises an anchor bolt which is designated as a whole by the numeral 6 and a washer 7, as well as an expansion element which is designated as a whole by the numeral 8. The anchor bolt 6 is provided, at its front end, with an expansion cone 6a. The rearward end of the anchor bolt 6 is formed with a thread 6b. The expansion element 8 comprises lamellae 8a and a sleeve Bb. The lamellae 8a are arranged at the rearward end of the sleeve 8b and connected thereto by way of a fold 8c. In contrast to the version shown in Figs. 1 to 3, the bend angle of the lamellae 8a is only slight. At the rearward end of the anchor bclt 6, a hexagonal nut 9 is screwed onto the thread 6b to serve as an abutment. Upon tightening the hexagonal nut 9, the expansion cone 6a is drawn into the sleeve Bb, as a result of which the latter is expanded radially. The lamellae 8a of the expansion element 8 serve to retain the dowel against fall-out forces and prevent rotation of the element 8 during expansion of the dowel.

Claims

1. An expansible dowel comprising an anchor bolt which has an abutment in the rearward region, an expansion body which widens conically forwardly, and an expansion element which is radially expansible by the expansion body being drawn into said expansion element by means of the anchor bolt, characterised in that the expansion element comprises lamellae which are arranged around the entire periphery of the expansion body, and the lamellae each have a radially-resilient free end which extends at an acute angle with respect to the longitudinal axis of the dowel and is directed towards the abutment.

2. An expansible dowel as claimed in claim 1, characterised in that the lamellae are connected to a sleeve.

3. An expansible dowel as claimed in claim 2, characterised in that the free end of each of the lamellae is connected, by way of a fold, integrally with the sleeve.

4. An expansible dowel as claimed in claim 1, 2 or 3, characterised in that, in their non-sprung-in state, the lamellae extend at an angle a of 5 to 30 degrees, preferably 1 5 degrees relative to the longitudinal axis of the dowel.

.5. An expansible dowel substantially as hereinbefore described with reference to and as illustrated in Figs. 1 to 3 or in Fig. 4 of the accompanying drawing.