Apparatus for Screwing a Threaded Nut Onto a Steel Rod

The invention concerns a device for screwing a threaded nut onto the type of steel rod that is provided on two opposite facing sides with ribs forming a partial exterior thread lying in a helical line, said ribs always extending over only a part of the rod circumference to provide bare or flattened frontal areas from which the ribs slope oppositely to one another, the device consisting of a tubular jacket which at one end has a recess in the form of a nut and which at the other end is provided with means for the receiption of a twisting moment.

In mining, overhead anchors are inserted for securing the layers. For this purpose, the so-called cement anchors are used to a large extent. These are anchors for the manufacture of which cartridges are inserted in rough drilled holes, in which plastic cementing material is stored in closed containers. Thereby, a quick setting cement is available for the anchor in the anchoring area; in the area of the open span length, a slower hardening cement can be provided which serves essentially for corrosion protection. In the borehole containing the cementing cartridge, the tension member of the anchor, preferably a steel rod, is inserted, whereby the chamber of the cartridge opens and the cementing material is admitted into contact with the steel rod on the one hand and the bore hole walls on the other hand. As soon as the quick hardening cement is hardened in the anchoring area, at least one nut is screwed from the end of the threading provided on the rod which is tightened against an adjacent anchor plate on the rock. The anchor is thereby ready for working.

Steel rods which have especial advantages for use as a tensioning member for such an anchor, are those which are provided with hot rolled screw-aligned developed ribs which are arranged on two opposite sides of the rod circumference and which ribs form part of a screw thread (DT-PS No. 1784630). The ribs extend in full height only over about a third of the rod circumference, whereby they form a flattened surface at the sides from which they slope in opposite directions as seen from the sides. The rods have, therefore, special advantages because the threads necessary for screwing in the anchoring body can already be produced in the rolling process so that no further finishing operations are necessary for producing a thread. The partial winding of the formed ribs at the same time work to increase adhesion.

For the application of such a steel rod to a cementing anchor, two sequential operations are required. After the borehole is bored and the cementing cartridge is inserted, the rod is screwed into the cartridge. To do this, a device is necessary which provides for transmitting a twisted motion to the rod. This device is removed after the rod is screwed in. After a certain hardening time for the cement in the anchoring area, the rod is to be tensioned by screwing on a nut. For this purpose, an anchor plate is put on, a nut screwed on and the nut tightened by means of a torque wrench or other suitable tool.

The problem of this invention is to make possible the combination of these two sequential operations to be undertaken, and thus to save the time required for attaching different work tools and to work more economically.

According to the invention, this problem is solved by providing a sleeve, which has a recess at one end to receive the nut for transmitting rotating movement from a suitable tool to the nut and means at the other end for transmitting rotating motion thereto with means for establishing a force locking connection between the steel rod and the sleeve, wherein said connection operates on the flat faces of the rod so as to rotate the rod with the sleeve.

According to the invention, the characteristic of the steel rods mentioned above are utilized so that the ribs extend only over a part of the circumference and that so that they slope oppositely to one another when passing transversely of the bare core cross-section. The rod, which in cross-section has biaxial symmetry but not radial symmetry, can be blocked against rotation with respect to the sleeve by virtue of its structure and the arrangement of the connecting surfaces in the interior of the housing. Thus, the possibility is created, while this blocking is in effect, with the torque moment supplying arrangement in operation and with the threaded nut superposed adjacent the end of the rod, to first screw the steel rod into the bore or into the cementing cartridge and after the hardening time of the cement, with the blocking means released, to screw the nut onto the rod and tighten it with an appropriate twisting moment.

Advantageous embodiments of the apparatus of the invention are set forth in the claims.

The invention will now be further explained in connection with the examples of the embodiments thereof shown in the drawing in which:

FIGS. 1-10 are pairs of longitudinal and cross-sectional views respectively of different forms of the device and

FIG. 11 is a cross-sectional view taken from FIG. 2 but greatly enlarged.

FIG. 1 is the longitudinal view and FIG. 2 is a cross-sectional view taken on line II -- II of FIG. 1 of a first form of the invention. In FIG. 1, a steel anchor plate 2 is positioned on rock 1. A steel rod 3 extends into a bore hole (not completely shown), which rod possesses on opposite sides, hot-rolled ribs 4, which in the normal rod surfaces at the relatively flat transition surfaces 5 slope oppositely to one another. On the rod 3, a nut 6 is screwed which has an interior thread and accordingly can be screwed onto the partial threads of the rod. Through tightening the nut against the anchor plate 2, a tensile force can be introduced in the rod.

On the nut 6, a sleeve 10 is positioned which, at one end, has the opening 11 e.g. with 12 interior edges, corresponding to the outline of the nut 6, and in the other end has an opening 12 in which a lug 7, e.g., a square key, of a work tool 8, can be inserted to operate to transmit twisting moments to the sleeve 10 and to the nut 6.

The sleeve 10 has on its upper, somewhat thickened area 13, a passageway 14 with wedge form inner surfaces 15 sloping slightly towards one another. In the passageway 15, a forked key 16 can be driven in whose two parallel legs 17 form with their inner sides 18, a mating edge for the facing surfaces 5 of the ribs 4 of the rod 3. Thereby, the rod 3 is rotated somewhat by twisting moments until two diametrically opposed facial areas 5 are adjacent to the inner surfaces 18 of key 16. In this state, the twisting moment exerted by the device 8 on the sleeve 10 will be transmitted to the rod 3. After withdrawing the key 16, the rod 3 is free, so that the twisting moment then works on the nut 6 to screw the latter onto the rod 3 and tighten it against the anchor plate 2.

In FIGS. 3, 3A, 4 and 4A, another embodiment of the apparatus of the invention is shown. FIGS. 4 and 4A are cross-sectional views taken on line IV--IV or IVA--IVA of FIG. 3 or 3A, respectively.

The sleeve 20 has the recess 21 at its upper somewhat narrowed end 23, which is again placed on nut 6. In this area of the sleeve there is again a transversely extending passageway 24 in which two opposing transversely shiftable clamping jaws 25 are arranged on opposite sides of the sleeve 20. The clamping jaws 25, with their inner surfaces 25', which face towards the rod 3, form stops for the facing surface 5 of the ribs 4 of the rods 3, while they have inclined surfaces 25" on the outer side which are adjacent to a conical boring 26 of a bushing 27 which is shiftable longitudinally of the sleeve 20. If the bushing 27 of FIG. 3 is shifted upwardly, then the conical sloping surface 26 exerts a radial inward pressure on the clamping jaws 25 which closes them about the flat surface 5 of rod 3 (left hand part of FIG. 3). If the bushing 27 is shifted downward then the clamps, which are prevented from being drawn in by the pegs 28 are free of the rod 3 and the rod does not rotate with the sleeve. For easy servicing, a gripping sleeve 29 can be positioned over the bushing 27, which can be held fast by the hand, for example, to hold the bushing 27 in the blocking state to rotate the rod 3 with the sleeve 20.

A further embodiment of the invention is shown in FIGS. 5 and 6 of which FIG. 6 is a cross-sectional view taken along line VI--VI of FIG. 5.

The sleeve 30 has, at its upper end 33, again a recess 31 for reception of the nut 6. At the lower end is another recess 32 for receiving the square key 7 of the device 8 for exerting the rotating movement. In the cylindrical inner space of sleeve 30, a bushing 34 is arranged having an inner hollow space (at least in its upper area 36) which corresponds to the cross-section of rod 3. The bushing 34 can, thus, when it is pushed onto the rod 3, prevent rod 3 from rotating with respect thereto.

In the lower area of the sleeve 30, cross bores 37 are provided, which pass through the sleeve 20 as well as the bushing 34 and which can be brought into alignment with one another. A cotter 38 is pinned through the borings 37 and makes a rigid connection between the sleeve 30 and the bushing 34. The cotter can consist of a bent steel wire which includes a spring portion 39 which acts as a certain locking mechanism to locate the cotter in a predetermined position with respect to the sleeve 30. If the cotter 38 is withdrawn, then the bushing 34 within the sleeve 38 is freely movable, so that the nut 6 can be screwed onto the rod by means of the sleeve 30.

In FIGS. 7 and 7A, a further modified form of the invention is shown with FIGS. 8 and 8A respectively being cross-sectional views taken on lines VIII--VIII and VIIIA--VIIIA of FIGS. 7 and 7A respectively.

In these modifications the sleeve 40, which again is provided with the recess 41 in the upper portion 43 and with a recess 42 for the square key 7, has a bushing 44 in its upper portion. The bushing 44, which rests on the shoulder 45 and is prevented from falling thereby, has on its outer circumference longitudinal grooves 46 with arcuate-form cross-section. In the transverse boring 47 of the sleeve 40, spheres 48 are situated which are movable radially. By means of an outer bushing 49 which has an area 49' with one internal diameter and an area 49" with a larger internal diameter, the spheres 48 are held within said bushing 49 in one of two positions, in the first of which positions the walls obstruct the sleeve 40 (FIG. 7). By lowering the outer sleeve 47, the spheres 48 have greater play and free the inner bushing 44, so that in this position the rotating force exerted by the square key of device 8 operates only on the nut 6.

A further modified form of the invention is shown in FIGS. 9 and 9A together with FIGS. 10 and 10A, which again are cross-sectional views taken on lines X--X and XA--XA of FIGS. 9 and 9A, respectively.

Also, here the sleeve 50 has, in its upper area, the recess 51 for taking up the nut 6, on the opposite end a recess 52 for taking up the square key 7. In the sleeve 50, a bushing 54 is lengthwise slidably, but not rotatably, arranged. This can, as FIG. 10 shows, have a serrated cross-section which is slidably arranged in corresponding recesses in the sleeve 50. The bushing 54 possesses again, an inner recess 55 which corresponds to that of the rod 3. On the bushing 54, a hand grip 56 is fastened which is movable in the longitudinal slots 57 of the sleeve 50.

In the position shown in FIG. 9, the bushing 54 is in meshing engagement with the rod 3. In this position, the twisting moment will be transmitted to the rod 3. To loosen the connection between the bushing 54 and the rod 3, the bushing is moved downward by the handles 56, thereupon the rod becomes free and the twisting moment is transmitted directly to the nut 6 (FIG. 9A).