GB1558904A

GB1558904A - Expansible dowel

Info

Publication number: GB1558904A
Application number: GB31094/77A
Authority: GB
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 1976-08-17
Filing date: 1977-07-25
Publication date: 1980-01-09
Also published as: SE427681B; IT1081156B; DE2637043C2; BE857712A; AU515957B2; DE2637043A1; CA1061144A; AT354706B; CH621390A5; AU2769977A; FR2362299B1; SE7709054L; ATA591877A; FR2362299A1; JPS5324949A; JPS61485B2

Abstract

A straddling dowel (1) has a straddling sleeve (12) and a straddling body (10) which can be drawn into the straddling sleeve (12) by means of an anchoring bar (6). The anchoring bar (6) has a counterbearing (7) for applying a torque. Arranged between the counterbearing (7) and the straddling sleeve (11) are a distance sleeve (14) and a spacer (13) which is flexible in the axial direction. The spacer (13) is arranged between the distance sleeve (14) and the straddling sleeve (12) and has the form of an annular body. As a result of a force which acts in the axial direction and is smaller in relation to the initial deformation force, the spacer (13) can be further deformed in the axial direction. <IMAGE>

Description

(54) EXPANSIBLE DOWEL (71) We, HILTI AKTIENGESELL SCHAFT, a Corporation organised and existing under the laws of the Principality of Liechtenstein, of Schaan, Liechtenstein, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an expansible dowel comprising an expansible sleeve, an expansion body which can be drawn into the expansible sleeve by means of a threaded anchor rod, an abutment arranged on the anchor rod and shaped to enable torque to be applied thereto, and a space piece which is capable of yielding in the axial direction and which abuts, at one end, against that end of the expansible sleeve which is remote from the insertion end, and, at the other end faces the abutment.

A dowel of this kind is anchored in a borehole in receiving material by the expansion body being drawn into the expansible sleeve, the expansible sleeve being supported against or abutting against the abutment. The expansion body can be connected by means of a threaded connection to the anchor rod or it can be designed as part of the anchor rod itself. The anchor rod can have the form of a threaded bolt, in which case the abutment is usually designed as a nut. However, the possibility also exists of using, as the anchor rod, a screw or bolt of which the head forms the abutment, the expansion body connecting, by means of a thread, with the shank thereof.

All of these types of dowel have the advantage that they can be anchored regardless of whether or not the receiving material offers any resistance to axial withdrawing movement of the dowel. However, they have the disadvantage that the abutment is fixed in its axial position as soon as contact.

necessary for the anchorage of the expansible sleeve with the borehole wall has occurred. Where an element or component, for example a profiled beam or the like, is to be fastened to the receiving material, no axially-acting force component remains available, after the dowel has become anchored, to enable the said element or component to be pressed against the receiving material.

An attempt has been made to obviate this disadvantage by providing a plastics sleeve which is arranged between the abutment and the expansible sleeve and which has such a stiffness that, during the anchoring process. it supports the expansible sleeve adequately against the abutment and after a predetermined anchorage value has been achieved is deformable in the axial direction to permit closing-up of the abutment against the receiving material or the part that is to be fastened. However. this solution has not been completely satisfactory, since it is afflicted with further disadvantages. Thus, the relatively high stiffness of the plastics sleeve, which is necessary by reason of the forces to be absorbed during the anchoring process, leads to the fact that substantial forces are necessary for initiating the deformation.

These forces increase with increasing deformation. in such a way that the torque needed to be applied to the abutment is no longer adequate to clamp the part to be fastened, in fully-circumferential manner, against the receiving material. Moreover, such plastics sleeves are not suitable for absorbing transverse forces which act on the part that is to be fastened. Such transverse forces therefore have to be absorbed by the remaining part of the rearward end of the expansible sleeve or by the anchor rod itself, which can lead to overstressing of these elements.

The problem underlying the invention is to provide a dowel which makes possible closing-up of the abutment against the receiving material to an adequate degree and, moreover, is suitably constructed, particularly in the region of the abutment, for the guidance and absorption of transverse forces.

In accordance with the invention, the problem is solved by the provision of a distance sleeve, having an outside diameter which corresponds substantially to the outside diameter of the expansible sleeve, between the spacer piece and the abutment, the spacer piece being arranged between the expansible sleeve and the distance sleeve and having the form of a ring-like body which, after initial deformation in the axial direction, can be deformed further in said axial direction under a force which acts in the axial direction and which is smaller than the force required for said initial deformation.

The ring-like body, which is deformable in this way, on the one hand serves to support the expansible sleeve relative to the abutment so as to achieve adequate anchorage of the dowel and on the other hand makes possible, adequate closing up of the abutment against the receiving material after achievement of an adequate anchorage value. The initial deformation force accordingly lies above that force which is necessary to achieve this anchorage value, After initiation of the deformation of the ring-like body under action of the initial deformation force, the force necessary for the further deformation of the ring-like body drops to a value which can amount to about one-tenth to one-fifth of the initial deformation force.

In this way only a fraction of the torque applied to the abutment is necessary for the further deformation of the spacer piece. The greater part of the torque is available for the tightening of the element to be fastened against the receiving material. The remaining deformation force of the spacer piece ensures a permanent force connection between the abutment and the expansible sleeve.

The distance sleeve being arranged between the abutment and the spacer piece, shifting of the distance sleeve inwards of the reception bore of the receiving material is possible. Thus, the distance sleeve is fully protected from any external influences.

Moreover. this shifting into the reception bore also has an advantageous aesthetic effect. By use of the spacer piece as proposed in accordance with the invention, an effective guidance is afforded to the part that is to be fastened. Since the expansible sleeve has substantially the same diameter as the distance sleeve. the dowel can simply be inserted through an appropriate opening in the part to be fastened to the receiving material. Moreover, the shear surface of the distance sleeve is added to that of the anchor rod, so that the dowel can absorb considerably higher transverse forces acting on the parts to be fastened to the receiving material.

Preferably the ring-like body is designed as a stepped sleeve which has two different diameter regions of about the same axial length and about the same wall thickness, the smaller outside diameter corresponding substantially to the larger inside diameter.

Such a ring-like body, designed as a stepped sleeve, can be shortened in its axial length by pushing the two different diameter regions the one over the other, so that shorteneing of length arises by deformation.

For initially releasing the conncetion between the two different diameter regions, a specific initial deformation force is necessary, after which the subsequent pushing of the one into the other of the two different diameter regions requires only a force which is smaller than the initial deformation focus.

By appropriate constructional design of the stepped sleeve, the force necessary for the telescoping of the two different diameter regions, the one into the other, can be controlled.

For connection of the two different diameter regions to one another, the stepped sleeve can. for example. be one-piece in design. Further possibilities for the connection of the individual different diameter regions consist in bonding together two tubes of different diameters in a short overlap region thereof, or in connecting the same together by a force fit. In both instances, the stepped sleeve can be axially shortened by telescoping of the individual regions having different diameters. the initial deformation force initiating the commencement of the telescoping.

Plastics material and metal are suitable materials for the stepped sleeve. In the case where the different diameter regions are connected together to form a stepped sleeve by means of adhesive connection or by being a press fit, different materials can be used for the components of the stepped sleeve.

In a further proposal of the invention, the ring-like body may consist of two tubes (e.g.

of sheet metal) which partially overlap in the axial direction, the inner tube having an outside diameter which is substantially smaller than the inside diameter of the outer tube so that there is formed, in the overlap region, a hollow-cylindrical intermediate space into which a rubber layer is vulcanised. This ring-like body can, of course, be shortened by telescoping of the two tubes which are initially offset partially in the axial direction, which is tantamount to the deformation already explained. The result of the initial deformation force is that the bond between the vulcanised-in rubber layer and at least one of the tubes is broken. The elasticity of the rubber layer ensures that, for further telescoping of the tubes, the one into the other, a definite force is necessary, which can be controlled by appropriate choice of the rubber layer and dimensioning of the tubes.

A further possibility consists in designing the ring-like body at least partially from brittle material which disintegrates, upon application of compressive stress thereto, into small pieces. Such a ring-like body is preferably surrounded by a sheath of metal or plastics material. The sheath protects the material of the ring-like body from force peaks which can arise, for example, during transportation or upon knocking the dowel into its borehole. Moreover, the sheathing ensures a positive connection between the expansible sleeve and the distance sleeve, after the ring-like body has disintegrated into small pieces by virtue of a compressive stress which corresponds to the initial deformation force. The sheathing can be deformed axially under a force which is smaller than the initial deformation force.The actual breakage of the ring-like body provides an indication that an adequate anchorage value has been achieved. The same effect can also be achieved with a ring-like body which is designed as a composite body and which combines in it the aforesaid properties.

Ceramics or glass can be used as the material for the ring-like body. The use of ceramics has the advantage that, in accordance with the prinicple of sintered bearings, a corrosion-inhibiting agent, for example on a fat or oil basis, can be incorporated therein.

The invention will be described further, by way of example, with reference to the accompanying drawing in which: Figure I is a sectional side elevation illustrating a practical embodiment of the expansible dowel of the invention in position in a borehole in receiving material and having been tightened to achieve a minimum anchorage value, but with the spacer piece thereof not yet having been deformed; Figure 2 is a view similar to Figure 1, but with the spacer piece deformed; Figure 3 is a sectional elevation illustrating an alternative form of spacer piece usable in the expansible dowel of the invention; and Figures 4 to 6 are views similar to Figure 3 but illustrating three further alternative forms of the spacer piece.

In the example shown in Figures 1 and 2, a part 2, for example a strap, a section beam, or the like, is required to be fastened to receiving material 3 by means of an expansible dowel designated as a whole by the numeral 1. For this purpose, the part 2 has a through bore 4 and the receiving material 3 has a blind bore 5.

The expansible dowel 1 comprises a threaded anchor rod in the form of a screw bolt 6, a head 7 of which serves as an abutment and abuts against a conventional washer 8. Engaged on thread 9 of the screw bolt 6 is an expansion body 10 which can be drawn into an expansible sleeve 11. Upon the expansion body 10 being drawn into the expansible sleeve 11, the latter expands radially outwards and anchors the dowel in the blind bore 5. To facilitate the radial outward expansion of the expansible sleeve 11, the latter is formed with longitudinal slots 12 beginning from the front end.

Towards the head 7 of the screw bolt 6, and linking between the expansible sleeve 11 and a distance sleeve 14 is a spacer piece 13 comprising a ring-like body in the form of a stepped sleeve, for example made of plastics material. The distance sleeve 14 is arranged between the spacer piece 13 and the washer 8.

To achieve the condition shown in Figure 1, the expansible dowel 1 has been introduced through the bore 4 in the part 2 and into the blind hole 5 in the receiving material 3. As a result of application of a torque to the head 7 of the screw bolt 6, the expansion body 10 has been drawn into the expansible sleeve 11 which is supported via the spacer piece 13, by way of the distance sleeve 14 and the washer 8 against the head 7. In this way, the expansible sleeve 11 has been radially expanded, which has led to its anchorage in the blind hole 5 in the receiving material 3. As is apparent from Figure 1, this anchorage has been achieved independently of abutment of the dowel 1 against the part 2 or the receiving material 3.Thus, a slight gap Z still exists between the receiving material 3 and the part 2, this arising as a result of extraneous influences, such as unevenness of the surface of the receiving material 3 or sagging of the part 2.

If further torque is applied to the screw bolt 6 after achieving the predetermined anchorage value, the spacer piece 13, designed as a stepped sleeve is shortened in its axial length after overcoming an initial deformation force. This makes it possible for the distance sleeve 14 to close up against the expansible sleeve 11, so that the head 7 is supported for the most part only by way of the washer 8 against the part 2. The torque continuing to act on the head 7 presses the part 2 against the receiving material 3, as is shown in Figure 2, only a fraction of the force produced by the torque being necessary for effecting further deformation, i.e.

length curtailment by telescoping of the different diameter regions of the spacer piece 13. As soon as the part 2 abuts snugly against the receiving material 3, further torque acting on the head 7 causes further drawing of the expansion body 10 into the expansible sleeve 11, in which case the resultant force is absorbed principally by the part 2.

Figure 3 illustrates an alternative form of spacer piece, which can be used in the place of the spacer piece 13, of Figures 1 and 2 and is designed as a ring-like body 16 having a sheathing 17, the ring-like body consisting of a material which, after the initial deformation force has been exceeded, disintegrates into small parts, such as glass, ceramics or the like.

The alternative form of spacer piece shown in Figure 4 comprises two sheet metal tubes 18, 19 of different diameters, which are arranged partly overlapping, with the one projecting into the other. In the hollowcylindrical gap between the tubes 18, 19 is a vulcanised rubber layer 20. Upon the initial deformation force being exceeded. the bond of the rubber layer 20 to the outer tube 18 and/or the inner tube 19 is broken, so that the two tubes can be telescoped into one another in the axial direction.

The alternative spacer pieces shown in Figures 5 and 6 are designed, similarly to the spacer piece of Figures 1 and 2. as comprising stepped sleeves and are designated as a whole by the numerals 21 (Figure 5) and 22 (Figure 6). In contrast to the one-piece design of the spacer piece 13 of Figure 1. the tubes 21, 22 consist of individual diameter regions or sections 23. 24 (Figure 5) and 25, 26 (Figure 6). The individual diameter regions 23. 24, 25, 26 of the tubes 21. 22 are connected together by an adhesive connection or by being a press fit.This connection is releasable after the initial deformation force has been exceeded. so that the axial length of the tubes 21, 22 can be shortened along with telescoping into one another of the different diameter regions 23, 24. 25, 26.

The regions 23. 24, connected together in the aforesaid manner, of the tube 21 in the embodiment of Figure 5 consist, for example, of plastics material. The regions 25. 26 of the tube 22 of Figure 6 consist, for example, of metal. The connection of the individual different diameter regions or tubes can be chosen at will taking account of the materials. involved. it being possible to make use of combinations. for example of bonding and press fitting. are possible for achieving this connection.

WHAT WE CLAIM IS: 1. An expansible dowel comprising an expansible sleeve. an expansion body which can be drawn into the expansible sleeve by means of a threaded anchor rod, an abutment arranged on the anchor rod and shaped to enable torque to be applied thereto, and a spacer piece which is capable of yielding in the axial direction and which abuts, at one end, against that end of the expansible sleeve which is remote from the insertion end, and at the other end faces the abutment, characterised by the provision, between the spacer piece and the abutment, of a distance sleeve having an outside diameter corresponding substantially to the outside diameter of the expansible sleeve, the spacer piece being arranged between the expansible sleeve and the distance sleeve and having the form of a ring-like body which, after initial deformation in the axial direction, can be further deformed in said axial direction under a force which acts in the axial direction and which is smaller than the force required for said initial deformation.

2. An expansible dowel as claimed in Claim 1, characterised in that the ring-like body is designed as a stepped yieldable sleeve having two different diameter regions, of which the smaller outside diameter corresponds substantially to the larger inside diameter.

3. An expansible dowel as claimed in Claim 2, characterised in that the stepped yieldable sleeve is of one-piece form.

4. An expansible dowel as claimed in Claim 2, characterised in that the individual different diameter regions of the stepped yieldable sleeve are connected together by an adhesive connection.

5. An expansible dowel as claimed in Claim 2, characterised in that the individual different diameter regions of the stepped yieldable sleeve are connected together via a press fit.

6. An expansible dowel as claimed in any of Claims 2 to 5, characterised in that the stepped yieldable sleeve is of plastics material.

7. An expansible dowel as claimed in any of Claims 2 to 5, characterised in that the stepped yieldable sleeve is of metal.

8. An expansible dowel as claimed in Claim 1, characterised in that the ring-like body consists of two tubes which partially overlap in the axial direction and which provide, in the overlap region, a hollowcylindrical gap. a rubber layer being arranged in this hollow-cylindrical gap.

9. An expansible dowel as claimed in Claim 1, characterised in that the ring-like body consists at least partially of a brittle material which disintegrates into small pieces upon application of compressive stress thereto.

10. An expansible dowel as claimed in Claim 9, characterised in that the ring-like body has a sheathing of metal or plastics material.

11. An expansible dowel as claimed in Claim 9 or 10, characterised in that the material of the ring-like body is glass.

12. An expansible dowel as claimed in

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. torque acting on the head 7 causes further drawing of the expansion body 10 into the expansible sleeve 11, in which case the resultant force is absorbed principally by the part 2. Figure 3 illustrates an alternative form of spacer piece, which can be used in the place of the spacer piece 13, of Figures 1 and 2 and is designed as a ring-like body 16 having a sheathing 17, the ring-like body consisting of a material which, after the initial deformation force has been exceeded, disintegrates into small parts, such as glass, ceramics or the like. The alternative form of spacer piece shown in Figure 4 comprises two sheet metal tubes 18, 19 of different diameters, which are arranged partly overlapping, with the one projecting into the other. In the hollowcylindrical gap between the tubes 18, 19 is a vulcanised rubber layer 20. Upon the initial deformation force being exceeded. the bond of the rubber layer 20 to the outer tube 18 and/or the inner tube 19 is broken, so that the two tubes can be telescoped into one another in the axial direction. The alternative spacer pieces shown in Figures 5 and 6 are designed, similarly to the spacer piece of Figures 1 and 2. as comprising stepped sleeves and are designated as a whole by the numerals 21 (Figure 5) and 22 (Figure 6). In contrast to the one-piece design of the spacer piece 13 of Figure 1. the tubes 21, 22 consist of individual diameter regions or sections 23. 24 (Figure 5) and 25, 26 (Figure 6). The individual diameter regions 23. 24, 25, 26 of the tubes 21. 22 are connected together by an adhesive connection or by being a press fit.This connection is releasable after the initial deformation force has been exceeded. so that the axial length of the tubes 21, 22 can be shortened along with telescoping into one another of the different diameter regions 23, 24. 25, 26. The regions 23. 24, connected together in the aforesaid manner, of the tube 21 in the embodiment of Figure 5 consist, for example, of plastics material. The regions 25. 26 of the tube 22 of Figure 6 consist, for example, of metal. The connection of the individual different diameter regions or tubes can be chosen at will taking account of the materials. involved. it being possible to make use of combinations. for example of bonding and press fitting. are possible for achieving this connection. WHAT WE CLAIM IS:

1. An expansible dowel comprising an expansible sleeve. an expansion body which can be drawn into the expansible sleeve by means of a threaded anchor rod, an abutment arranged on the anchor rod and shaped to enable torque to be applied thereto, and a spacer piece which is capable of yielding in the axial direction and which abuts, at one end, against that end of the expansible sleeve which is remote from the insertion end, and at the other end faces the abutment, characterised by the provision, between the spacer piece and the abutment, of a distance sleeve having an outside diameter corresponding substantially to the outside diameter of the expansible sleeve, the spacer piece being arranged between the expansible sleeve and the distance sleeve and having the form of a ring-like body which, after initial deformation in the axial direction, can be further deformed in said axial direction under a force which acts in the axial direction and which is smaller than the force required for said initial deformation.

12. An expansible dowel as claimed in

Claim 9 or 10, characterised in that the material of the ring-like body is ceramics.

13. An expansible dowel as claimed in Claim 12, characterised in that corrosion protective agents are admixed with the ceramics.

14. An expansible dowel substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2, in Figure 3, in Figure 4, in Figure 5 or in Figure 6 of the accompanying drawings.