The present invention relates to a packer as defined in the preamble of claim 1 and to an injection method as defined in the preamble of claim 9. In concrete structures, such as bridges, sup¬ porting walls, foundations, pillars, girders and vari¬ ous underground tunnels, cracks appear when the tensi¬ on exceeds the tensile strength of the concrete. Such cracks significantly reduce the strength and service life of the structure. The formation of cracks is mostly due to factors resulting from faulty design, over-stressing, movement of structures, excessive con¬ struction joints or defective work. Such cracks, gene¬ rally less than one millimetre wide, extending over a large area and reaching the reinforcement, reduce the service life of the structure as the reinforcement un¬ dergoes faster corrosion, and lead to a reduced strength of the structure. Especially cracks appearing in rock often lead to significant water damage as a- ter flows through them into constructions.

Generally it is assumed that a cracked struc¬ ture can be restored to its original strength by the injection method. Injection is generally performed by pumping injection material into the crack through a packer using pressure generated by means of a manual or mechanical injection device, the crack being packed with the mixture solidifying in it. The mixture is introduced using disposable connectors, which are pla¬ ced in holes made around or in the crack so that they remain in position while a liquid mixture is being pumped into the crack. A suitable injection pressure and the distances between injection points are deter¬ mined via a preliminary test carried out prior to the operation. A known device currently used in the procedu¬ re described above is a packer comprising a rubber se¬ al around a plug placed in the hole. The rubber seal

is pressed into the hole by means of a tightening sleeve placed at the outer end of the plug, said slee¬ ve being provided with a thread. When the sleeve is screwed onto the plug, it causes the seal to be pressed against the interior surface of the hole. The inner end of the plug is provided with a check valve, formed by a ball and a spring, designed to prevent the mass forced into the crack from flowing back through the plug. After use, the tightening element can be de- tached from the rest of the packer, so it can be used several times.

Patent specification CH 644662 and patent applications WO 84/01601 and FI 821905 present packers which, in respect of both structure and operation, substantially correspond to the one described above.

The worst problem with prior-art packers is that they have a complicated construction and are the¬ refore expensive. The task of connecting the fixing tube to the packer and especially detaching it from it, often in difficult working conditions, signifi¬ cantly retards the injection job. Depending on the job, as many as thousands of packers are needed, so their use should be as quick and simple as possible; being used in large quantities, they involve signifi- cant additional costs if they are expensive.

The object of the present invention is to eliminate the drawbacks referred to above. A specific object of the invention is to produce a new type of packer which, both in respect of construction and use, is as simple as possible and reliably seals and closes the hole in all possible pressure conditions.

As for the features characteristic of the in¬ vention, reference is made to the claims.

The packer of the invention comprises a packer body designed to be inserted into a hole dril¬ led in a structure to be mended, said packer body ha¬ ving a part with a conical outer surface, a seal being

provided around the packer body. Moreover, the packer comprises a fixing tube which, when the packer is in the hole, protrudes out of the hole, and in the packer body a check valve which, with respect to the fixing tube, is located on the opposite side of the seal and opens into the hole, said check valve communicating with the outer end of the fixing tube via a hole going through the packer body and the fixing tube.

According to the invention, the packer body and the fixing tube are implemented as a single, con¬ tinuous integral body, preferably fabricated from plastic by the injection moulding technique. Further¬ more, according to the invention, the seal is as simple as possible in construction, in other words, it consists of an elastic tube of constant circular cross-section which can slide between and around the fixing tube and the conical part of the packer body, in other words, the seal is a straight piece of elas¬ tic tube. The outer end of the fixing tube is prefera¬ bly provided with a draw stop, such as a lobe, set- off, indentation or other irregularity or relief of surface allowing the packer to be gripped firmly with a suitable tool so that it can be vigorously pulled outward from the hole while the seal is being held in place in the hole. Preferably the outer end of the fi¬ xing tube is so shaped that the nozzle of the injecti¬ on device can be tightly connected to the packer wit¬ hout a separate injection cock or grease nipple. The inner end of the conical packer body of the packer, i.e. the body end pointing toward the check valve, is preferably provided with a limit stop, such as an annular collar, which forms a stopper that hits the stationary seal when the packer is being pul- led outwards from the hole. Thus, the limit stop pre¬ vents the packer from being pulled out too far. The flange receives the counterpressure generated in the

course of the injection work and utilizes this pressu¬ re to squeeze the packer more tightly in the bore ho¬ le.

The valve at the inner end of the body is formed by a transverse aperture in the body, the packer body being provided with a longitudinal hole extending from its outer end towards the inner end down to this transverse aperture, and by an elastic sheath placed on the outlet or outlets of the trans- verse aperture. Due to its elasticity, this sheath blocks the outlet or outlets in normal conditions, thus acting as a check valve during injection. The elastic sheath preferably also consists of a straight piece of elastic tube. In the injection procedure of the invention, the above-described packer according to the invention is used. In the procedure, the unitary integral body formed by the fixing tube and the packer body is in¬ serted, with a grip by the fixing tube, into a hole drilled in the structure to be repaired. The integral body is tightened in the hole by holding the seal around it immovable in the hole and pulling at the fi¬ xing tube by its outer end, causing the seal to be squeezed between the interior surface of the hole and the conical part of the packer. After this, packing material can be pumped through the packer into the ho¬ le. Either immediately thereupon or later after the injected mass has settled down, the part of the fixing tube remaining outside the hole is broken off e.g. by simply applying a transverse blow to the base of the fixing tube, whereupon the hole can be patched up.

The packer and injection method of the inven¬ tion have significant advantages as compared with pri¬ or art. The invention is very simple in construction, only consisting of a body piece, which can be fabrica¬ ted in a simple manner e.g. by the injection moulding technique, and two tubular sheaths of elastic material

placed around it. Thus, the packer is very cheap to manufacture. Moreover, the packer is easy to use and it can be mounted in place using a suitable tool with one hand and only a small effort. In addition, the packer can be easily broken off from the hole, leaving the pressure in the structure, so the hole can be cap¬ ped even in connection with the same operation.

In the following, the invention is described in detail by the aid of the attached drawings, in which

Fig. 1 presents a packer as provided by the invention, partially sectioned,

Fig. 2 shows how the packer of Fig. 1 is in¬ serted into a hole, and Fig. 3 shows the packer of Fig. 1, mounted in a hole and ready for use.

A packer according to the invention as shown in Fig. 1 comprises an elongated packer body 1 having a relatively pointed inner end 3 and a tubular fixing tube 13 forming a straight and seamless extension of the packer body and provided with an outer end 4 ha¬ ving a round shape resembling a grease nipple. Inside the packer body and fixing tube there is a longitudi¬ nal hole 5 extending from the outer end 4 to a point close to the inner end 3 of the packer body, opening to the exterior surface of the packer body via a transverse aperture 11.

Disposed around the transverse aperture 11 is an elastic rubber sheath, covering the outlets of the aperture 11. Thus, the transverse aperture 11 and the sheath 12 form a check valve that permits outward flow from the hole 5 through the aperture 11 and out from under the sheath 12 while preventing reverse flow back into the hole 5. The packer body 1 comprises a conical part 8 of circular cross-section, extending from the valve towards the outer end of the packer body and tapering

towards the outer end and the fixing tube. After the conical part there is a fixing tube 13 of uniform thickness, ending at a shoulder or draw stop 9. The conical part 8 thus widens towards the inner end 3 of the packer body 1, ending before the valve at an ex¬ pansion of the packer body, a ring-like collar forming a limiter 10. A ring-shaped collar is also formed in the packer body 1 on the side facing towards the check valve 6, so that the pressure prevailing in the hole is applied to this collar, pressing the packer body outwards and tightening the packer in a manner to be described later on. Fitted around the straight fixing tube 13 and the conical part 8 is a seal 7 made of elastic and flexible material, e.g. a piece of rubber hose, which is of a size that allows it to slide on both the straight part and the conical part between the draw stop 9 and the limiter 10. The length of the seal 7 is substantially shorter than the lengths of the fixing tube 13 and the conical part 8 together. Referring to Fig. 2 and 3, the packer presen¬ ted in Fig. 1 is used as follows. A hole 2 has been drilled in the structure to be treated. In concrete structures, the mouth of the hole is generally more or less ragged. The packer is inserted into the hole with the seal 7 substantially in the area of the straight fixing tube 13. The packer is inserted to a depth such that the seal 7 lies completely in the undamaged hole area, somewhat sunk in from the mouth of the hole. Next, a pressure is applied to the upper edge of the seal 7 in the direction of arrows A to hold it in po¬ sition while at the same time gripping the draw stop 9 at the outer end 4 and drawing it straight outwards as indicated by arrow B. The packer is preferably mounted using a special mounting tool by means of which the seal can be held in position and a pull exerted on the draw stop at the same time. When this is done, the co¬ nical part 8 of the packer body 1 is thrust into the

seal 7, pressing the seal against the interior surface of the hole. The pulling action B is continued until the limiter 10 hits the lower edge of the seal 7. In this way, the seal has been squeezed very tightly bet- ween the conical surface 8 and the interior surface of the hole 2, whereupon it is possible, in a manner known in itself, to attach a hose or connector to the outer end 4 of the packer body 1 to inject suitable packing material into the hole 2 while the check valve 6 prevents the mass from flowing back into the hole 5. The conical shape of the body ensures that the packer cannot be pushed out of the hole by the counterpressu- re generated in the hole and the crack, because the pressure is applied to the body 1 and especially to the flange 10, which is pressed against the seal 7, thus squeezing it more tightly in the hole.

The packer is preferably fabricated from a suitable plastic material e.g. by the injection moul¬ ding technique, and the part of the packer remaining above the seal 7 can easily be broken off from the ho¬ le 2 and the hole can be capped using suitable materi¬ al. According to the tests carried out, the packer of the invention is fully pressure-proof, having a pres¬ sure resistance of at least 250 bar, yet it performs perfectly in low-pressure injection as well, which may involve the use of pressures below 10 bar.

The invention has been described above by presenting an example by the aid of the attached dra¬ wings, but different embodiments of the invention are possible within the framework of the inventive idea defined by the claims.