FI91014B - Method for fastening a cotter bolt in a hole by striking it, as well as cotter bolts and wedge body combination for application of the method - Google Patents

Description

91014

The present invention relates to a method in which an anchor portion consisting of a bolt or sleeve spaced at one end into two or more straight tongues is anchored, an anchor portion consisting of a bolt or sling a hole made in another material, the wall of which, on the outside of the tongues, makes it possible, by means of vibration, to widen the anchor housing wider than the diameter of the hole for the wedge bolts. The invention also relates to a method in which the tongues 15 of the anchor part are penetrated into a hole made in metal or other load-bearing material, in the wall of which it is possible to form an anchor housing wider than the hole diameter on the wedge, into which the wedge bolt can be anchored only by impact anchoring device.

The 0-0 position in Figure 1 shows a traditional wedge bolt known for centuries. In the past, wedge bolts were used to strengthen m.m. the walls of castles and fortresses, connecting with them the stones of the walls. As you know, the results were almost insignificant, as straight iron pins would have driven the same thing. Due to the infrequent strikes of the hammer and the latch of the anchoring means available at that time, the straight tongues of the wedge bolt shown in Fig. 1 do not penetrate the hole wall and do not open the grooves forming the anchorage. penetrates the gaps between the wedge surfaces and the hole wall. The wedge bolt stops there without forming a single anchor piece and without opening the anchor slot at all. The wedge bolt thus anchored cannot be loaded with even a small traction load, as it is completely 2 loose. If the tongues of a traditional wedge bolt are forcibly attempted to penetrate the wall of the hole with strong blows, then the wedge bolt acts as a splitting means to break even the strongest structure. This was en-5’s first attempt to anchor wedge bolts.

When the above-mentioned conventional wedge bolt is attached to a hole made in stone, concrete, brick or other similar material with a rock drilling machine, picking rod or other simultaneously impacting and vibrating anchoring device, the tongues of the wedge bolt can widen the inside the hole wall as shown in positions 1-1 to 4-4. The tongues become more and more inclined inwards as they penetrate deeper into the hole and at the same time are constantly detached from the wall of the anchorage they have already widened. Thus, no bending forces can be applied to them in the direction of the wedge surfaces, but the tongues remain straight throughout the anchoring and expand the space required by the tongues 1-1 to 4-4 of the wedge bolt tongues in Fig. 1 by vibration. The tabs only touch the wedge surfaces and the wall of the finished 25 anchorages at their very right tip in all tab positions. Due to the vibration used in the fastening, even the tip of the tabs does not come into tight contact.

However, if the wedge engages between the tongues, e.g. in the gaps between the wedge body and the tongues filled by the fine powder detached from the wall, no pressure-resistant wedge forces holding the wedge body 91014 3 are generated. Thus, in this case too, the wedge bolt remains loose in the anchor housing.

This is another fastening method by which wedge bolt-type straight-tongue fastening devices have been attempted to anchor the borehole without success.

The anchoring event quite generally shown in the wedge bolt drawings, in which conventional wedge bolts are anchored to form a tight and uniform anchor body formed together by a wedge body and tongues and an anchor socket corresponding in size and shape to the resulting anchor body, does not correspond to reality. For the tight tongues of a conventional wedge bolt formed by a wedge body and tongues taken together and closely matched to an anchor body exactly like 15 of these anchors, the straight tongues of a conventional wedge bolt cannot penetrate because its tongues cannot expand the metal. Penetration is prevented because the tongues form an angle against the wedge surfaces, and at no point do the tongues bend in the direction of the wedge surfaces.

U.S. Pat. 4,073,212, the wedge piece of the wedge bolt shown in Figures 9-20 is attached to the bolt-25 portion after anchoring so that it cannot slide out between the tabs. The fastening device thus formed slides outwards under the effect of the tensile load in the anchor housing which is too wide and anchors at the tip part of the anchor surface of the tongues to the tip part of the anchor housing, so that it is possible to load the device somewhat.

FI pat. 58 388 The tip of the tongues of the conventional wedge bolt shown in Figures 1-2 is formed with an outwardly bent edge acting as a blocking blade which pivots outwards from the outside of the tongue so much that the space it opens during anchoring is such that the straight tongues are free to pivot freely. . This fastening device only anchors when the fastening device has slid in the anchor colony 4 so much that the anchor surfaces of the tongues and the anchor-colony press against each other and the edges of the tongue tip bend behind the wedge body and lock it in place. Low load possible.

U.S. Pat. 4,073,212 and FI Pat. Due to the outward sliding of the fastening devices shown in Fig. 58388 in the too wide anchor housing, the anchor area of this type of fastening devices easily becomes too small, so that they cannot be loaded with the full load otherwise allowed for the device, but only with a partial load.

The present invention relates to a method based mainly on the realization that the tongues of the anchor part of the fastening device 15 must be bent inwardly curved already at the stage of anchoring when the tip of the outer side acting as an anchor surface of the tongues penetrates the hole wall. For only in this way do the bent tongues 20 penetrate merely into the wall of the hole parallel to the tip-and-wedge surfaces. The tongues are bent to the position shown above, either by means of projections formed as an extension of the tip of the tongues, which act as bending means, or the tongues have already been bent into this position in advance. At the final stage of anchoring, pushed by an inwardly sloping surface near the bottom of the hole, the protrusions shown above lock the wedge body between the tabs.

30 The fastening devices are thus provided with a tight and uniform anchor body formed by the wedge body and the tongues, with an anchorage housing corresponding in size and shape, when the anchoring takes place in a hole made in stone, concrete, brick or other material. with the edge of the tongue tip acting as a blade, it is possible to widen the grooves forming a tight anchor-colony, as well as to the metal, hard I! 91014 5 in a hole made of plastic or other material, the wall of which can be shaped in advance by turning, milling, pressing or other suitable method to form an anchor housing corresponding to the resulting tight anchor piece 5.

Since the anchoring method according to the invention provides the fastening devices with a tight and uniform anchor body formed by a wedge body and tongues and an anchorage housing corresponding to its size and shape, the anchor forces holding the fastening devices are mainly generated against the operation of the wedge. The tensile load on the fastening devices causes the anchor pressure on the anchor surfaces such that the component forces of the tensile load holding the anchor pressure 15 and the frictional forces generated by this anchor pressure between the anchor surfaces correspond to the respective tensile load. Thus, the forces holding the anchored fasteners are generated by the pressure exerted on the anchor surfaces of the tensile load, increase as the tensile load increases, decrease as the tensile load decreases, and the fasteners remain attached until the strength of the fasteners or structure is exceeded. The forces caused by the anchor piece consisting of wedge-shaped anchor surfaces and the stresses applied to their structure can be calculated by a calculation method corresponding to the wedge formula. The force groups corresponding to the anchor pressure and the force groups caused by the friction acting between the anchor surfaces, as well as the force groups holding or pushing the wedge piece between the tongues 30, are obtained separately, so that the fastening devices can be designed on the basis of reliable load data. Thus, the area of the anchor surfaces can be defined so that the anchor pressure does not exceed the allowable pressure 35 even with the maximum load of the fastening device, and it can be determined when there is a need to lock the wedge piece between the tongues.

6

The characteristic features of the anchoring method according to the invention are defined in the claims and the accompanying drawings.

5 The method is described in more detail below:

Figures 2-7 and 8-10 show two examples of fastening devices according to the invention with different structures and their operation during anchoring. Both fastening devices can be anchored in a hole made of both a rock-type and a metal-type material, by forming a suitable protrusion as a bending means for the tongues, which, if necessary, also acts as a locking means for the wedge body.

15

The fastening device shown in Fig. 2 consists of an anchor part 1 fixedly formed at the end of the rod part and a separate wedge piece 4.

Figure 3 is a cross-sectional view of the fastening device 20 shown in Figure 2 at the tabs 2.

Figures 4, 5 and 6 show the anchoring event of the fastening device shown in Figure 2 in three different steps. Figure 7 is a cross-sectional view of the anchor piece of the pre-anchored fastening device shown in Figure 6.

25 Since the fastening device shown in Fig. 2 is intended to be anchored in stone, concrete, brick, etc. in the hole made in the corresponding material, the protrusion 3 acting as a bending means of the tongues 2 is made so that an edge 30 11 is formed in the tip of the tongues 2 as a punching blade when anchoring the fastening device described above, the fastening shocks are applied to the rod end using a rod end protection device.

Figure 8 shows a fastening device consisting of a wedge body 4 formed at the end of a rod-35 part and a separate sleeve-like anchor part 1 sliding along the rod part 4 against the wedge body 4.

Figure 9 is a cross-sectional view of the fastener shown in Figure 8;

II

91014 7 at the tabs 2 of the anchor part 1 of the device.

Figure 10 is a cross-sectional view of the anchor piece of the pre-anchored fastening device shown in Figure 8.

When the fastening device shown in Fig. 8 is anchored to a metal-5 line, a hard plastic, etc. a protrusion 3 acting as a bending means for the tongues 2 is made as shown in Fig. 8 without an edge 11 acting as a perforating blade. When anchoring this fastening device, the fastening strokes are directed to the anchor part 1 by means of a tubular tube.

If the tongues 2 of the anchor part 1 of the fastening devices are already bent inwards during the manufacturing step of the fastening devices 15 so that the tip part of the tongues 2 turns parallel to the wedge surfaces 6 of the wedge body 4 at the beginning of the anchoring, the projections 3 are not required. However, they can also act as a locking means for the wedge body 4 in the final case of the anchoring 20.

The placement of the edge 11 acting as a grooving blade at the junction of the tip of the protrusion 3 and the tongue 2 Fig. 2 is advantageous in that the grooves 10 25 forming the anchor housing only have to be opened up to the thickest point of the wedge body 4. When the stiffness of the protrusions 3 is to be considered sufficiently high, the thickness of the tabs 2 must be determined to correspond to the maximum height of the edge 11 and the thickness of the base portion of the protrusion 3 in Fig. 2. The thickness of the tabs 2 can be thinned by moving the edge 11 toward the tip. by thinly thinning the projections 3 between the edge 11 and the tip of the tongue 2. In that case, it is necessary to open the grooves 10 35 forming the anchor housing unnecessarily at all the tongues 2 of the anchor body 1 by the displacement of the edge 11 past the thickest point of the wedge body 4.

Either of the above-mentioned projections 3, Figures 2 and 8 8, can act as a locking means between the wedge body 4 at the end of the anchoring process. The surfaces 12 forcing the projections 3 to bend inwards are shaped into the wall of the hole, e.g. with a suitably shaped drill or 5 milling cutter. They can also be formed from a shaped surface, e.g. a steel plate, which is fastened to the leg of the wedge body 4. Then ordinary drills can be used to drill the holes.

The slits separating the tongues 2 of the anchor part 1 are made so wide that there is enough space for the tongues 2 to bend inwards when the tip part of the tongues 2 turns parallel to the wedge surfaces Fig. 5. The wedge body 4 has a much steeper tip part 7 and a wedge 6 are shaped so that their wedge angle is greatest at the beginning of the wedge surface 6 and gradually decreases towards the thickest part of the wedge body 4 Figures 2 and 8. The wedge body 4 thus shaped causes the outer side tip 9 of the tongues 2 to press against the hole wall only. a little deeper into the hole. By using the largest possible wedge angle at the beginning of the wedge surfaces 6, the difference in the length of the anchor surfaces due to the difference in the diameter of the holes made by the nearly worn and new drill 25 is minimized.

The wedge body 4 is provided with a tip portion 5, Figures 2 and 8, which expands slightly towards the tip, into which the slightly inwardly tensioned protrusions 3 of the tongues 2 grip and hold the wedge body 4 Figure 2 or the anchor part 1 Figure 8 firmly in place when inserting the fastening device. The same tip part 5 acts as a topper at the end of the anchoring, which prevents the anchor part 1 from penetrating too deeply into the hole Fig. 6 at the end of the anchoring.

The anchoring of the fastening devices according to the method takes place as follows:

When, for example, the anchor part 1 of the fastening devices li 91014 9 shown in Figs. presses against the wall of the hole, when the anchor part 1 penetrates only slightly deeper into the hole Fig. 4. As the anchor part 1 protrudes a little deeper into the hole, the wedge surfaces 4 push the protrusions 3 10 further outwards and the tip part 9 of the anchor surfaces 8 slides along the hole wall 9 the effect of penetrating the outer surface of the anchor surface 8 into the wall of the hole Figures 3 and 9. As it slides along the hole wall 15, the tip portion 9 of the anchor surfaces 8 acts as a fulcrum as the wedge surfaces 6 now push the tip of the lever arm projections 3 outward and force the tabs 2 to gradually bend inwardly. Figure 5, as the gaps between the tabs 2 are so wide that the tabs turn freely parallel to the wedge surfaces 6, the tabs 2 not touching each other. When the anchor part 1 has penetrated so deep into the hole that the thickness of the tongues 2 corresponds to the gap between the hole wall and the wedge surface 6, the tongues 2 are bent inwardly curved by the projections 3 acting as lever arms that the tip part of the tongues 2 turns parallel to the wedge surfaces 6 or the tongues 2 have already been bent in advance, e.g. during the manufacturing step of the fastening devices, to the position shown above 30, whereby the tongues 2 are in each case ready to penetrate only the tip above and parallel to the wedge surfaces 6 into the hole wall. When anchoring takes place in stone, concrete, brick, etc. the grooves 10 forming the anchorage in the hole made in the corresponding material 35 are opened in the wall of the hole by an edge 11 acting as a rutting blade connected to the projection 3, Fig. 2.

While the anchoring takes place in a hole made of metal, hard plastic 10 or the like, the resulting anchor body corresponding in size and shape is formed in the hole wall in advance, e.g. by turning, milling or the like in the fastening manufacturing stage. As the anchor part 1 protrudes further deeper into the hole, the tongues 2 penetrate the entire length of the anchor piece with the tip first and following the shape of the wedge surfaces 6 inside the hole wall and either open 10 of the projections the grooves or tongues 2 forming already penetrate into the anchorage 15 formed in the wall of the hole (metal or the like) in advance, guided by the protrusion 3 acting as a lever arm, Fig. 8. Thus, in both cases, the tongues 2 and the wedge body 4 of the anchor part 1 together form a tight and uniform anchor body based on the wedge-shaped anchor surfaces 8 and an anchorage of corresponding size and shape, so that the fastening devices anchor the wedge-shaped anchor surfaces 8 to the tensile load. When the anchor part 1 has been pushed so deep into the hole that the projections 3 acting as bending means of the tongues 2 or merely as locking means of the wedge-25 body 4 meet the inwardly inclined surface 12 formed near the bottom of the hole, the projections 3 act as locking means of the wedge body 4, 1 protruding a little deeper into the hole, the projections 3 30 bend sharply inwards, the wedge surface 12 pushing the tip 3 of them inwards and thus locking the wedge piece 4 between them so that a strong vibration does not cause the wedge piece 4 to slide out between the tabs 2. After the anchor part 1 has penetrated so deeply into the hole that the tip of the tongues 2 protrudes into the thickest part of the wedge piece 4, the tip part 5 of the wedge piece 4 stops the penetration of the anchor part 1 exactly to the right point.

91014 11

Since the average wedge angle 6 of the wedge body 4 of the fastening devices used in the method is generally relatively small, and while the friction between the inner surfaces of the tongues 2 and the wedge surfaces 6 may be weak, the frictional forces holding the wedge body 4 between the tongues 2 may remain very small. wedge body 4 between the tongues 2 for ejection forces. The wedge piece 4 of the fastening devices to be anchored in this way must therefore be locked between the tongues 2.

This method provides the fastening devices with a tight and uniform anchor body consisting of wedge-shaped anchor pins formed by the tongues of the anchor part and the wedge body and an anchor socket corresponding in size and shape to the anchor body thus formed. The anchor surfaces of the fastening devices are the outer sides of the tongues with a length that touches the entire wall of the anchorage. Due to the tensile load on the fastening devices, the anchor surfaces of the anchor piece and the anchor seat of the same shape press tightly against each other, whereby the anchor forces holding the fastening devices, as well as the anchor forces , that the component forces against the tensile load holding the forces corresponding to this anchor pressure and the frictional forces 30 generated between the anchor surfaces of the same anchor pressure together correspond in magnitude to the respective tensile load.

Since the anchor forces 35 generated by the friction on the anchor surfaces do not cause forces tending to split the structure, it is preferable to provide the anchor surfaces of the fastening devices with rough lathe, suitable teeth, knuckles or other similar anti-slip means. The method is the same as for the non-slip anchoring of the prestressing steels by concrete soldering 5 before the actual stressing. By increasing the friction between the anchor surfaces, the fastening devices to be anchored in this way can also be designed in such a way that the forces corresponding to the anchor pressure generated by the tensile load in the anchor surfaces, which tends to split the structure, remain significantly less than the tensile load. Although the anchor pressure generally increases as the wedge angle of the anchor surfaces of the wedge-shaped anchor body decreases, by increasing the friction between the anchor surfaces, this anchor pressure-increasing effect is reduced to almost no sign. Thus, even a small angle can be used as the wedge angle of the anchor surfaces.

For example, when a fastening device is used with an average wedge angle of the anchor surfaces of 6 ° and the friction between the anchor surfaces corresponds to the coefficient of friction u = 0.40 between the stone and the smooth steel, the forces corresponding to the anchor surfaces are twice as high as the tensile load. 79% of the forces are generated by friction and 21% by anchor pressure.

By increasing the friction between the anchor surfaces by roughening them so that the friction between the anchor surfaces corresponds to a coefficient of friction u = 0.90, the forces corresponding to the anchor pressure are equal to the tensile load and 89.5% of the forces holding the device are generated by friction and 10.5% by anchor pressure.

When the friction between the anchor surfaces of the above fastening devices corresponds to a coefficient of friction u = 1.40, the forces corresponding to the anchor pressure together are only 2/3 of the tensile load and the forces holding the device generated by 93% friction and 7% anchor pressure and when the coefficient of friction u = 1.90 the forces corresponding to the anchor pressure are only 1/2 of the tensile load and 95% of the forces holding the device are generated by friction and 5% by the anchor pressure 11 13 91014.

By using a smaller angle as the wedge angle of the anchor surfaces, the length dimension of the anchor surfaces and at the same time the anchor surface area can be increased without increasing the depth of penetration of the tongues 5 into the wall of the hole. At the same time, the functionality of the fastening devices is facilitated during anchoring; the tabs have to bend only slightly when turning parallel to the wedge surfaces and the fastening strokes are effectively directed at the tabs as they penetrate the tip 10 above inside the wall of the hole. By dividing the anchor part into several tongues, in addition to the increase in the anchor area, the number of anchor forces acting on the structure is correspondingly smaller, distributed in different directions to the structure, and thus the stresses on the structure are reduced.

The anchoring method according to the invention makes it possible to design and manufacture fastening devices which can be anchored on a wedge-shaped anchor piece, which are significantly more reliable than the current corresponding devices, which are suitable for various current and, above all, new fastening needs made possible by the present invention. The fastening devices can be anchored to very different materials, such as, for example, a hole made of stone, concrete or brick, or to various metals, hard plastics, even a ready-made anchor colony shaped into wood. In this way, it is possible to anchor fasteners or fastening bolts, concrete or rock grips, rock reinforcement bolts and various even strong drawbars used in construction or other production for various fastening needs. Since all the anchor forces of the fastening devices to be anchored in this way can be determined by calculation so that the permissible stresses of the device and the structure are not exceeded even with the maximum permissible load of the fastening device, this method can be used to anchor fastening devices such as prestressing steels. The fastening devices which can be anchored by the method according to the invention and which receive sufficiently large forces can even be used for the support ropes of drawbars and suspension bridges, etc. anchoring when they 5 can be attached deep enough to intact rock.

The fastening devices can be designed to fit into the hole of a nearly worn-out drill and the anchor surfaces can be dimensioned so that the required anchor surface area is provided even when the devices are anchored to a hole made by a new drill; the anchor area of the device increases only slightly as a result of drill wear. In this way, the drills used for drilling holes can be used to the end.

Depending on the size of the devices and the number of devices to be fastened at a time, a hammer, a sledgehammer or a suitably sized, preferably sparse-grained picking or drilling machine is used as the percussion means for anchoring the fastening devices. The so-called so-called rock reinforcement bolts can also be used for anchoring. rockbolting machine. A suitable piling hammer is used to anchor the large drawbars and drawbars. Thanks to the simple structure of the fastening devices, they can be manufactured economically on cutting or press machines. The making of the blank of the anchor part of the fastening devices divided into several tongues 25, its division by cutting into the tongues and their final shaping can advantageously be carried out, e.g. with suitable pressing tools. If necessary, very high-grade steel can also be used for the manufacture of fastening devices, since properly shaped tongues function properly in the anchoring phase, regardless of whether they are made of soft and flexible or hard but flexible high-tensile steel. Steel grades can also be used in the manufacture of fasteners, the strength properties of which can be improved by suitable heat treatments.

Claims (6)

A method in which on one side an anchor part (1) having two or more uniformly thick tips (2), and on the other side a wedge piece (4) with wedge surfaces (6) corresponding to the number of tips (2) forming an attachment stage arrangement by merging, anchored in a heel made either of stone, concrete, brick or other similar, in whose wall it is possible to extend with an edge of the tips (2) 10 (11) an anchoring recess with larger diameter than the heel or in a shark made of metal, plastic or other similar material, in whose wall it is already possible, in advance, for example, in the manufacturing stage of the fastener, to form an anchor depression of greater diameter than the heel, the fastener being anchored in both cases say, that the tips (2), through blows or bumps guided by the wedge piece (4) supported in the bottom of the heel, are either forced to penetrate the wall of the heel or to be expanded in a finished anchor joint. lowering, wherein the tips (2) and the wedge piece (4) together form an anchor part larger than the diameter of the heel and at the same time the tips (2) read the wedge piece (4) between them characterized in that in that phase of the anchorage, when the anchor part (1) has penetrated so deep into the heel that the thickness of the tips (2) corresponds to the gap between the wall of the heel and the surface of the wedge (6) (figure 5), the tips (2) have been bent into a bend either in the beginning by means of a ledge (3) of the anchorage or already in advance at the manufacturing stage of the fasteners 30 in such a way that while the tips (2) branch, their ends are pivoted parallel to the wedge surfaces (6), so that the tips (2) throughout the length forming the anchor part penetrate into the the wall of the heel with the end first and the shape of the wedge surfaces (6) and where either with the edge (11) on the end of the tips (2) open dents (10) which form the anchor depression and which in size and shape correspond to the cross-section of the tips (2) or penetrates with the end first into hazards (10) already pre-drilled into the walls of the heel and forms an anchor depression, such that the tips (2) of the anchor part (1) and the wedge piece (4) together form a compact and uniform anchor part which is based on wedge-shaped anchor surfaces (8) and an anchor depression corresponding in size and shape to the anchor part, so that the fastening device in the wedge-shaped anchor surfaces (8) develops as a result of the forces of the tensile load and also forces the inwardly swinging surface formed in the bottom of the neck. (12) the ledges (3) at the end of the anchoring stage 10 to be swung inwardly and read the wedge piece (4) between the tips (2). 2. Fastening device for carrying out a method known by the Finnish patent no. 58388 (explanation pages 3 and 15) and according to claim 1, characterized in that as a extension on the end part of the tips (2) a ledge (3) has been formed. which at the beginning of the anchorage stage acts as a lever and bends the tips (2) in a beak mesh and at the end of the anchorage stage acts as a reading device between the tips (2) of the wedge piece (4) and that in the end portion of the wedge piece (4) has formed an end (7) that is steeper than the wedge surfaces (6) and which immediately at the beginning of the anchoring stage forces the end (9) on the outside of the tips (2) to be pressed against the wall of the heel when the fastener is only slightly penetrated into the heel. 3. Fastening device according to claim 2 for applying the method according to claim 1, characterized in that the ledge (2) of the tips (2) is thinned out towards the end of the ledge (3) so that when the tips (2) at the beginning of the anchoring stage branch press leaking from the wedge piece (4), the end of the edge of the tips (2) first touches the walls of the heel. 35 4. Fastening device according to any one of claims 2, 3 or 4, characterized in that the end of the wedge piece (4) is provided with a locking member (5) which extends towards the end and so on the ledges (3) on the anchorage tensions of the anchor part (1). gripping and retaining the wedge piece (4) or anchor portion (1) firmly in place when the fastener is placed in the tail. 5 5. Fastening device according to any of claims 2, 3 or 4, characterized in that the locking part (5) is so long that it stops the anchor part (1) from penetrating before the junction point (13) of the tips (2) falls within the wedge angle at which the inclination at the end of the wedge surfaces (6). 6. Fastening device according to any one of claims 2, 3 or 4, characterized in that the gaps between the tips (2) of the anchor part (1) are εέ wide, that the tips (2) can be bent freely so that they are parallel to the wedge piece (4). wedge surfaces (6), without the splitting section (15) of the tips (4) touching each other. li