DE29703065U1 - Dowel-supported fastening system with expansion bolt to be driven in as a clamping body - Google Patents

Description

For decades, systems based on dowel technology have existed for the installation of fasteners in assembly surfaces and reliably guarantee that the fasteners remain in place once they have been installed, even under tensile loads.

Generally, this is achieved by inserting a deformable auxiliary body, the dowel, into a hole, whose flanks are then expanded by the respective fastening elements such as screws (or nails in the case of nail dowels) in the hole, thus creating a clamping situation that prevents the dowel and fastening element from being pulled out at the same time, e.g. under tensile load.

The use of plastic dowels as elastic, inexpensively manufactured auxiliary bodies to achieve the clamping situation is an effective method, especially when inserting fastening devices into structures made of stone or concrete, and has long been state of the art. A feature of the dowels for this area of application is generally an interior of the dowel that tapers conically towards the dowel tip. When the fastening device, e.g. a screw, is inserted, the conical narrowing creates the displaceable volume for the clamping situation to be achieved. Due to the elasticity of the plastic dowel material, a predefined internal dowel thread is not required; the screw cuts its own thread when inserted.

The interaction of increasing dowel expansion with simultaneously increasing thread structure, i.e. force application area, during the screwing process is the characteristic operating principle when using this dowel configuration.

In practice, however, the process of simultaneously displacing volume and cutting threads often requires a considerable amount of force. The screws with Phillips or single-slot heads that are usually used when expanding plastic dowels using screws are often subject to assembly forces (depending on the respective material structure and the dimensions of the fastening devices) that are so great that they lead to the tool used (screwdriver or cordless screwdriver) being levered out of the screw head when fastening/screwing in.

Applying the necessary assembly force during

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Screwing without levering the corresponding tool out of the screw head is normally not a problem under good access conditions. Good access conditions and thus the possibility of safely applying the required assembly force exist, for example, when fasteners have to be inserted into assembly surfaces at a height that is consistent with the height of the person doing the assembly. Optimal access conditions can be assumed in a range from knee height to shoulder height of an assembly person of assumed average height, i.e. in the range between 30 cm and 160 cm assembly height. At absolute ground level or at assembly heights in the head or overhead area, which may only be accessible with aids such as ladders, the required assembly force can often only be applied with great effort. However, the overhead area of assembly surfaces is the area of application that most often needs to be reached, for example in private homes or business premises (installation of brackets for pictures, shelves, curtain rods, lamps, etc.).

Unfortunately, it is precisely this overhead area, with the need to use aids to reach an elevated standing position, that offers the worst conditions for applying the assembly force. Although aids such as stepladders are known, unsuitable, standing-increasing means such as chairs are often used to insert screws into dowels. The number of resulting accidents is legion, although it must be admitted that even with optimal aids such as a professional stepladder, a satisfactory position for transferring the necessary assembly forces cannot often be guaranteed.

Especially taking into account problematic installation areas when using fasteners based on dowel technology, the task should therefore be to offer a combination of dowel and fastener as a fastening system that, on the one hand, avoids the strenuous process of screwing the fastener into the dowel, but, on the other hand, provides the option of adjusting the positioning of the fastener so that the insertion depth can be freely varied. The freely selectable distance between the installation surface and the outlet of the fastener (e.g. screw head) is a prerequisite for the unrestricted usability of such a fastening system.

This object is achieved according to the invention by the characterizing features of claims 1-10.

The idea is to use a hammer to drive a plastic dowel with a stop ring into a hole previously drilled into the mounting surface in the usual way. However, the expansion of the dowel in the hole is not achieved by a screw that is screwed in, but by an expansion bolt equipped with a separate fastening structure to accommodate fastening devices. This is driven into the plastic dowel, similar to the nail + nail dowel fastening system. Both driving the dowel into the hole in the mounting surface and the subsequent driving in of the expansion bolt to expand the dowel can be carried out without any problems, even in unfavorable assembly areas such as overhead assembly. The force required to expand the dowel in the hole can be easily provided by the hammer hitting the expansion bolt in the form of impulse force. The laborious thread cutting and simultaneous dowel expansion required in the conventional procedure is no longer necessary.

The expansion bolt, which is equipped with a separate internal structure to accommodate fastening devices, can be made of a hard plastic using injection molding technology or of light metal; it is also conceivable to use conventional steel as the bolt material. Its separate internal structure enables all desired fastening devices with a corresponding fastening structure to be inserted/attached using minimal manual force, regardless of the structure ultimately chosen.

Common fastening devices include screws with different head shapes, with hooks or ring ends.

The expansion bolt with its separate internal structure for holding fasteners makes it easier to drive into the dowel that has been previously installed in the usual way thanks to its special design of its surface in the form of V-shaped grooves, because this allows the displacement of the dowel plastic to be controlled. The grooves guarantee the directional stability of the expansion bolt during the driving-in process and create a stable, interlocking connection to the dowel. The groove flanks act like cutting edges and therefore reduce the required driving force. The special shape of the tip of the expansion bolt in the shape of an arrowhead leads to a non-detachable connection between the dowel and the bolt after reaching a position flush with the dowel at the wall exit, thus ensuring that the system remains securely in the mounting surface even under high tensile loads.

One advantage of the invention is that by expanding the dowel with the help of a bolt with a separate internal structure for fastening means, this separate internal structure can be freely selected and its shape is always firmly defined. The resulting, effort-saving assembly of the fastening means also results in significantly faster installation. When assembling shelving systems, for example, with the sometimes numerous necessary fastening points, this is certainly a product improvement that will be gladly accepted.

A further advantage of the invention is that the defined bolt structure is suitable for receiving a cover that can cover both the bolt itself and the dowel surrounding it in the area of the wall exit. This cover, as a separate, attachable part, can be made in white, for example, the color often used indoors, and thus ensure an aesthetically acceptable presentation of fastening openings that would otherwise previously be visible. Covers made of high-quality materials, e.g. chrome colors, in conjunction with appropriately selected, high-quality fastening materials (chrome-plated decorative screws) would also be a possible offer that would certainly be appreciated by some groups of buyers.

The process of removing a no longer required fastening point in the mounting surface with a fastening system equipped with the invention is carried out in such a way that the stop ring of the dowel is removed with a cutting knife and the expansion bolt, which is still slightly above the wall level, is completely driven into the wall. The hole in the mounting surface is thus already filled and can easily be filled or wallpapered over. Complete removal of a fastening system according to the invention according to the appended claims can otherwise only be carried out by drilling out of the mounting surface due to the irreversible connection between the dowel and the expansion bolt.

The new design of the dowel-supported fastening system is explained in more detail below in an example using the drawings.

Drawing 1 shows: The individual components

of the fastening system and its position in an application example.

Drawing 2: The deformation process of the

Dowel during the driving process of the expansion bolt

Drawing 3: Fasteners in various - 6 -

Drawing 4 Drawing 5

eid-like shape of the head area, in addition to purely functional shapes also examples of decorative designs, all based on screw threads.

Fasteners with different shape of the head area, based on a locking technology using a spring-loaded ball

Fasteners with different head shapes based on a key/lock technique and a disused and filled-over representation of the fastening system.

Drawing 1 shows a new fastening system, consisting of the dowel (1) with a reduced diameter front area (6) which is designed to accommodate the expansion bolt (2), whereby the arrow-shaped tip (5) of the expansion bolt forms a connection with the dowel front area (6) which cannot be separated.

The surface of the expansion bolt is formed from V-shaped grooves (7) which have a direction-stabilizing effect and reduce the impact force during the driving-in process. Recesses on the surface of the expansion bolt in the area of the wall exit enable a cover element (9) to be attached, whereby the dowel and expansion bolt are covered and a hole enables unrestricted access for fastening devices using the separate fastening structure (3).

Drawing 2 shows an impact process in various positions, whereby it is clear that the front, reduced diameter dowel area in the hole (4) allows sufficient movement space for elastic expansion during penetration of the expansion bolt (5). Drawings 3-4 and 5 show possible fastening means, whereby in drawing 4, an embodiment of the fastening system similar to a combination of key and lock, the solution for covering the fastening means is shown using an eccentric cam as a second shaft expansion volume (10) of the fastening means shaft. Finally, drawing 5 shows a disused, filled fastening system representation.

Claims (9)

s£hujSzärfcpkj>che ]** j 1. Fastening system based on dowel technology for the introduction of fastening elements into mounting surfaces, characterized in that that the expansion of the anchor (l) in the bore (4i_of the mounting surface is carried out by an expansion bolt (2) with an integrated, separate fastening structure (3) for fastening means. 2. Fastening system according to claim 1, characterized in that the fixation of the expansion bolt (2) in the dowel (1) is ensured when hammered in by means of two additional fixation methods, which are subject to different operating principles and act in spatially separated dowel areas. a) Frictional fixing using the pressure build-up achieved when the expansion bolt (2) is driven into the dowel (l) (dowel deformation/expansion) b) Position fixation of the expansion bolt (2) in the form of a permanent, permanent connection with the dowel (l) after reaching a position flush with the dowel at the wall exit, achieved by an arrowhead-shaped design of the front part (5) of the expansion bolt, the entry of which into the corresponding dowel front area (6) takes place in the form of a movement that is no longer reversible. 3. Fastening system according to claim 1 and 2, characterized in that the front area of the dowel (6) is designed with a reduced diameter compared to the external diameter of the dowel body in order to ensure an elastically springing movement within the bore (4) of the mounting surface when the arrowhead front part (5) of the expansion bolt (2) penetrates. 4. Fastening system according to claims 1-3, characterized in that the surface of the expansion bolt (2) is constructed in the form of V-shaped longitudinal grooves (7) which act like cutting edges to stabilize the direction and reduce the impact force when the dowel plastic is displaced during the driving-in process of the bolt. 5. Fastening system according to claims 1-4, characterized in that groove-shaped recesses^) are provided on the surface of the expansion bolt (2) in the area of the wall exit, for receiving a cover element (9) of the dowel (1) and the expansion bolt (2) which is provided with a bore for the passage of the respective fastening means. 6. Fastening system according to claims 1-5, characterized in that the separate fastening structure (3) for fastening means is designed in the form of a fine thread (internal thread). 7. Fastening system according to claims 1-5, characterized in that the separate fastening structure of the expansion bolt is designed in the form of a DIN/metric thread (internal thread) 8. Fastening system according to claims 1-5, characterized in that the separate fastening structure of the expansion bolt is designed in the form of stepped notches for receiving a spring-loaded ball lock (fastener-supported). 9. Fastening system according to claims 1-5, characterized in that the separate fastening structure of the expansion bolt is designed in the form of stepped notches for receiving an expansion volume projecting beyond the fastener shaft, whereby this fastening structure works in the manner of a key-lock combination, with an additional integrated clamping device in the form of a second shaft expansion volume (10) based on eccentric technology.