This invention concerns a tie rod assembly.

Tie rods are currently used in civil engineering in general, and more especially in mines, quarries and buildings for provisional or final anchorage or support of structures. Tie rods are also used for the maintenance of sheet piling, the anchorage of sloping walls or trenches, the stabilisation of foundations subject to heavy, off-centre loads, the stabilisation of cladding of foundation ditches, and the local consolidation of walls.

Each tie rod generally comprises a bar made of steel, which can be fixed in a drilled hole recessed in the ground or a wall either by sealing material eg poured cement or resin, or by means of a mechanical expansion system. To achieve good adherence with the poured material, the bar can have one or more ribs projecting or indented.

The free end of the bar, which protrudes from the hole and passes through a structure to be anchored to the wall, generally receives a head capable of supporting

the structure on the wall, called the "tie rod head".

EP 0,348,060A and GB 2,127,512A disclose couplers for joining bars or wires embedded in structural concrete.

The bars used with current tie rod heads have the disadvantage of requiring threading at one or both ends to receive the tie rod head. The threading provided on the bar may reduce the section (and therefore strength) of the bar locally which is therefore non-uniform in strength. Threading the bars is also costly and requires the modified bars to be transported and handled, which delays completion of the work.

This invention seeks to remedy these disadvantages by providing a tie rod head which can be adapted to a bar without substantial modification of the bar being necessary.

According to the present invention there is provided a tie rod assembly comprising a tie rod head having a sleeve for receiving a tie rod and means for securing the tie rod therein so as to prevent relative axial movement of the tie rod head and the tie rod, said means comprising a screw-threaded locking member extending through a correspondingly screw-threaded aperture in a side wall of the sleeve, a tie rod having one end anchored in a wall and having a second end extending from said wall, and a construction element, the sleeve of the tie rod head being disposed over the tie rod and being secured thereto, the construction element being disposed between the tie rod head and the wall and being held against the wall by the tie rod head.

The screw-threaded locking member can be tightened in

the aperture to bear against the tie rod inside the sleeve, thereby preventing relative axial movement.

The securing means can comprise a combination of resin and a screw-threaded locking member as taught in GB 2,127,512A.

In a preferred embodiment the securing means comprises at least one screw-threaded locking member and aperture, and a roughened or serrated area inside the sleeve (eg on the inner surface or protruding therefrom) against which the tie rod is clamped by the screw-threaded locking member. Optionally the aperture for the screw-threaded locking member is located opposite the roughened area.

The assembly can be adapted to different types of tie rod. Clamping is obtained whatever the type of bar, with or without ribs and even with or without threading.

The tensile strength of the tie rod head is preferably greater than that of the tie rod with which it is to be used.

To ensure better fixing of the tie rod head on the bar, the screw-threaded locking member preferably has a pointed end. It is advantageous to choose a screw- threaded locking member made from steel with a hardness greater than that of the bar. Thus, on tightening the member penetrates the bar and a more secure attachment is made.

The locking of the tie rod head to the tie rod can be gauged by applying a desired torque to the screw- threaded locking member using a torque wrench.

The use of a torque wrench can be advantageously replaced by the use of self-shearing screws-threaded locking member. The shearing of the head of these members occurs the moment the desired torque is obtained. Suitable self-shearing screw-threaded locking members and a suitable form of sleeve are disclosed in EP 0,348,060A.

As to the roughened or serrated area inside the sleeve, there are several ways of forming this. The roughened area can be formed by a radial projection inside the sleeve advantageously formed by another screw-threaded locking member. Alternatively a serrated saddle can be disposed inside the sleeve. The roughened area can also be obtained by direct serration or scoring of the inner surface of the sleeve.

Advantageously, the external surface of the sleeve is threaded at the end facing the wall and co-operates with an internally-threaded ring which extends beyond the said end of the sleeve and which upon rotation relative to the sleeve can move axially along the sleeve. The function of the ring is to eliminate play. The ring can first be screwed onto the end of the tie rod, the tie rod head is fixed in place on the tie rod, and the ring is then rotated such that it abuts the wall face. Relative rotation of the ring and sleeve causes relative axial movement to allow or to take up play-

To adapt to the variable slopes of bars fixed in the wall, the element fixed to the wall can have a shape that complements that of the end of the sleeve, allowing pivotal movement of the tie rod around the abutment between the sleeve and the element.

According to the present invention there is also provided a method for securing an element, sura as a plate, on a tie rod anchored in a wall, characrsrised by the steps of disposing the element over the tie rod such that it abuts the wall, providing a tie rod head having a sleeve for receiving a tie rod and means for securing the tie rod therein so as to prevent relative axial movement of the tie rod head and the tie rod 3, said means comprising a screw-threaded locking member and a correspondingly screw-threaded aperture extending through a side wall of the sleeve, disposing the sleeve of the tie rod head over the tie rod such that the tie rod head abuts the element, and securing the tie rod head to the tie rod such that the element is held against the wall by the tie rod head.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which:

Fig. 1 is a longitudinal section view of a tie rod head fixed to a bar anchored in a wall;

Fig. 2 is a transverse section view on line II-II of Fig. 1;

Figs. 3 and 4 are section views similar to that of Fig. 2 of variants of the sleeve; and

Figs. 5 and 6 are longitudinal section views of two other embodiments of a tie rod assembly in accordance with the invention.

Figure 1 represents a wall 1 in which a bar 2 (tie rod) has been anchored. The bar 2 has been placed in a hole made in wall 1, then sealed with mortar. Wall 1 is

covered with a layer of concrete 3 which must be anchored to this wall 1. A plate 4 is disposed on the extending end of the bar 2 and a tie rod head 5 holds the plate 4 firmly against the layer of concrete 3.

The tie rod head 5 has a sleeve 6 and screws 7. The sleeve 6 is a cylindrical tube, with an inner diameter greater than the outer diameter of bar 2. Its overall strength is greater than that of bar 2.

In the examples shown in Figs. 1 and 2, the sleeve 6 has four radial threaded apertures 8, all four extending through the sleeve 6 and being aligned in a line parallel with the axis of sleeve 6. The apertures are drilled at 90° to the longitudinal axis of the sleeve.

In other embodiments, fewer or more than four apertures are provided, and they may be provided at angles other than 90°.

Opposite these threaded apertures 8, on the inner surface of the sleeve 6, one (Fig. 2) or two (Fig. 2a) serrated saddles 9 each with a toothed surface is disposed eg by welding. Each serrated saddle 9 can extend all along the sleeve 6, although it suffices to provide discrete areas of serration or saddles opposite the apertures. In other embodiments the saddle can be serrated on both faces.

Four screws 7 with threading co-operating with the threads on apertures 8 are screwed into the apertures 8. They are made from steel with a hardness greater than that of tie rod 2.

The head 5 is disposed on the free end of bar 2 in

contact with plate 4 which itself is held tight against the cement layer 3. Locking is achieved by the screws 7 which, upon being screwed into the apertures 8, penetrate bar 2.

The screws 7 can be self-shearing. Thus, when the desired torque is obtained, the heads of such screws shear off. This allows visual control of the locking of screws 7.

Fig. 3 shows a variant of tie rod head 5. Here, the four aligned threaded apertures 8 are replaced by eight threaded apertures, four being made on a line parallel with the axis of sleeve 6, the other four being on another line parallel with this. These two lines and the serrated saddle 9 are circumferentially spaced at regular intervals on the sleeve 6 and are thus, in this embodiment, separated by an angle of about 120°.

Fig. 4 shows a second variant. In relation to tie rod head 5 of Fig. 3, the serrated saddle 9 with a toothed surface is replaced by screws 7a, the tips of which protrude inside sleeve 6. These tips form a gripping means inside the sleeve 6 and allow locking of tie rod head 5 on bar 2.

All these variants, and of course others not described here, can co-operate with a ring 11 for eliminating play (Fig. 5) . In this embodiment, the end a of sleeve 6 located on the side of wall 1 is threaded on its external surface. Before tie rod head 5 is fixed on bar 2, the threaded ring 11 is screwed onto the threaded end of sleeve 6. The tie rod head is then fixed onto bar 2 as previously described, such that the ring 11 abuts against plate 4.

If, after locking the sleeve 6 to the bar 2, play occurs between ring 11 and plate 4 or between the plate 4 and the layer of concrete 3, the play can be taken up by turning ring 11.

The ring 11 or any other separate mechanism for taking up play is optional, since the tie rod head can simply be held firmly against the element, eg the plate, and attached when the rod is firmly anchored in the wall. Alternatively, where the rod is anchored by means of a resinous setting compound, inherent elasticity in the setting compound before setting can be used to take up play. For example, the tie rod can be embedded in the compound and pulled out slightly, and thereafter the tie rod head can be attached to it before the resinous setting compound is set and some elasticity is retained. Before final setting of the compound, the tie rod is then pulled back into the aperture by the compound thereby pulling the tie rod head against the element and taking up play.

Fig. 6 shows another variant which can be fitted to bars 2 which protrude from the wall at an angle which is not perpendicular to the surface of the layer of concrete 3. The end of sleeve 6 opposite wall 1 has a convex shaped end, and plate 4 fixed on wall 1 presents a concave shape which is complementary to that of the end of the sleeve 6. This allows some pivotal movement of the tie rod head relative to the plate 4.

Modifications and improvements may be incorporated without departing from the scope of the invention. For example, instead of being welded to the sleeve on a serrated saddle the toothed surface can be directly incorporated in the sleeve by inner shaping such as knurling, threading or any other procedure for making a

toothed or roughened surface.

Any other provision relating to screws and roughness could be suitable. The number of serrated saddles with a toothed surface not limited to 1, but could be more, eg 2 or 3.