Plug for fixing to hollow and to solid building materials

A plug for fixing to hollow and to solid building materials has a plug body having a plurality of longitudinally extending expansible limbs that are expansible by screwing in of an expansion screw, the expansible limbs having a rear end and a leading end, a sleeve-shaped plug end which joins the expansible limbs with one another at the rear end and is formed so that the expansion screw is insertable through the plug end, a sleeve-shaped plug tip which joins the expansible sleeves with one another at the leading end and which is formed so that the expansion screw is screwable into the plug tip, and a stretchable material which joins the expansible limbs with one another circumferentially and which is pierced by several helically arranged slots.

BACKGROUND OF THE INVENTION

The present invention relates to a plug for fixing to hollow and to solid building materials. Hollow building materials shall mean, for example, hollow block bricks or panels behind which there is a cavity. Solid building materials shall mean, for example, concrete or similar structures.

Such plugs are known per se they are normally made of plastic material and in a middle region have longitudinally extending expansible limbs that are separated from one another by slots. The expansible limbs are joined to one another at the rear end by a sleeve-form plug end and at the leading end by a sleeve-form plug tip. An expansion screw can be pushed through the sleeve-form plug end and screwed into the plug tip. To fix the plug in a solid building material, the plug is inserted in a hole drilled in the solid building material and an expansion screw is screwed into the plug. The expansion screw presses the expansible limbs apart, that is, the expansion screw expands the expansible limbs, and consequently anchors the plug in the hole drilled in the solid building material.

In a hollow building material or in a panel, the plug is pushed through a drilled hole so that its sleeve-form plug end is located in the hollow building material. An expansion screw is then pushed through the plug end, guided between the expansible limbs and screwed into the plug tip. Screwing the expansion screw into the plug tip causes the plug tip to move towards the plug end, in so doing expanding the expansible limbs. There are actually two known expansion methods. In the first, the expansible limbs buckle outwards as the plug tip moves closer to the plug end and hence form an interlocking engagement with the hollow building material. The other possible method is that the plug tip twists in relation to the plug end as the expansion screw is screwed in, whereby the expansible limbs are wound round each other and form a knot-like structure that interlocks with the hollow building material.

The disadvantage of the known plugs is that the screw is poorly guided and, as it is screwed in, the expansion screw is able to emerge laterally through the slots between the expansible limbs. A further drawback of the known plugs is their low torsional stiffness, which leads to a resilient twisting of the plug tip in relation to the plug end as the expansion screw is screwed in. When screwing in the expansion screw by hand, the resilient twisting of the plug tip in relation to the plug end causes the plug tip, together with the expansion screw is screwed in. When screwing in the expansion screw by hand, the resilient twisting of the plug tip in relation to the plug end causes the plug tip, together with the expansion screw screwed therein, to turn back again when the user lets go of the screwdriver to re-adjust his grip. This has the result that the expansion screw can be screwed into the plug only poorly by hand.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a plug for fixing to hollow and to solid building materials, which avoids the disadvantages of the prior art.

In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a plug in which expansible limbs are connected to one another circumferentially by a stretchable material that is pierced through by several helically arranged slots.

To render it stretchable, the material can be of thin construction and/or be undulated in the circumferential direction of the plug. In the case of a plug manufactured from plastics material, the stretchable material is preferably integral with the expansible limbs and hence consists of the same plastics material as the remainder of the plug. The stretchable material is in that case preferably of thin construction in the form of a plastic web.

The connection of the expansible limbs circumferentially gives the plug according to the invention the form of a sleeve, which is also closed circumferentially in the region of the expansible limbs. Good guidance of the expansion screw is consequently achieved and the expansion screw, even when subjected to a transverse stress is prevented from emerging laterally from the plug between the expansion limbs.

A further advantage of the connection of the expansible limbs in the circumferential direction is increased torsional stiffness. The increased torsional stiffness has first of all the advantage that the plug tip turns less with the expansion screw as this is screwed in, with the result that the expansion can be screwed better into the plug tip. Furthermore, the increased torsional stiffness has the advantage that the plug tip does not turn back so much when the insertion torque eases, that is, for example, when re-adjusting one's grip on the screwdriver. The expansion screw is therefore easier to screw into the plug, especially when screwing in by hand.

In addition, the plug according to the invention has the advantage that there is less falling off torque after the start of expansion in a hollow building material when screwing in the expansion screw. In the case of the known expansible plugs, the torque diminishes sharply when the expansible limbs have started to buckle outwards or coil around each other when fixing the plug to a hollow building material. This effect is at least reduced by virtue of the increased torsional stiffness of the plug according to the invention, as a consequence of the connection of its expansible limbs circumferentially. The effect of the sharp drop in torque when screwing in the expansion screw is a disadvantage, because the impression is given that the expansion screw or the plug has torn out because of overloading and does not therefore have a firm seating in the hollow building material.

The helically arranged slots in the stretchable material have only a negligible adverse effect on the torsional stiffness, yet promote the formation of an enlargement at the rear side of a hollow building material or a panel such that both limbs bear virtually completely, and with a large bearing surface around the drilled hole, against the rear side of the hollow building material or the panel. In particular in the end phase of the enlargement formation, the slots prevent an uncontrolled tearing of the stretchable material, which in the worst case can lead to complete tearing through of the connection between the two expansible limbs, and possibly to tearing of the plug tip.

In accordance with a further embodiment of the invention, the sleeve-form plug end has a larger diameter than the remaining part of the plug. The purpose of this construction is to achieve good seating of the plug in a hollow or panel-form building material, in which the plug is received essentially only with its sleeve-form plug end in a drilled hole and the remaining part of the plug is located in a cavity.

In accordance with a further embodiment of the invention, on its outer circumference the plug has at least two opposing, longitudinally extending anti-rotation ribs, which are of saw-tooth construction over a part of their length. The anti-rotation ribs absorb the torsional moment occurring as the expansion screw is screwed in and thus prevent co-rotation of the plug. The saw-tooth form construction of the anti-rotation ribs over a part of their length, especially in the region of the expansible limbs, provides discontinuities, which on the one hand, by forming scraper edges, enable the plug to be driven easily into the drilled hole, and on the other hand do not impair the ability of the expansible limbs to twist in order to form the enlargement.

In accordance with a further embodiment of the invention, the sleeve-form plug tip is provided with non-rectilinear, for example, V-shaped, slots, an angle (apex) or peak of the slot preferably pointing towards the leading or to the rear end of the plug. Because of their non-rectilinear formation, the slots have one arm with an inclination in the direction of the lead of the thread of the expansion screw and another arm of opposite inclination. The inclination of the slots in the plug tip can differ from the lead of the thread of the expansion screw, only their direction is the same or opposite. The arms of the non-rectilinear slots, the inclination of which runs in the direction of the lead of the thread of the expansion screw, serve for engagement of the thread turns of the expansion screw, they produce a good adaptation to different screw diameters. The non-rectilinear slots brig about a reliable engagement of expansion screws of small diameter, without the expansion screw tearing out of the plug tip as the expansion screw is tightened. At the same time, the non-rectilinear slots prevent a large increase in torque as an expansion screw of large screw diameter is screwed in.

The arms of the non-rectilinear slots, the inclination of which is directed opposite to the lead of the thread of the expansion screw, cause the plug tip to be axially stretchable, whereby the axial spacing of non-rectilinear slots arranged axially one behind the other on the plug tip changes. Adaptation to different leads of the screw thread of the expansion screw is consequently achieved.

In accordance with a further embodiment of the invention, the plug has a screw channel for the expansion screw, which channel inside the sleeve-form plug tip has a cross-section other than circular. In different directions the screw channel therefore has different transverse dimensions inside the plug tip. This feature also assists adaptation of the plug to different diameters of expansion screw. In a development thereof, the screw channel, inside the plug tip, comprises a flat, for example, slot-shaped, screw channel. The screw channel inside the plug tip can alternatively be in the form of two intersecting slots.

Finally, the plug tip can have two opposing, axially running slots, the base of which slots run spaced from the screw channel. This construction produces a further reduction in insertion torque as the expansion screw is screwed into the plug tip, since the slots improve the stretchability of the plug tip.

The invention is explained in detail below with reference to an exemplary embodiment illustrated in the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A plug for fixing two hollow and two solid building materials is shown in the drawings and identified as a whole with reference numeral10.

The plug10according to the invention shown inFIGS. 1-3is manufactured from plastic material, and is approximately in the form of a sleeve. The plug10has a screw channel12for an expansion screw, not illustrated inFIGS. 1-3. The channel passes axially through the plug10and tapers conically at two points.

In the rear region, the plug10has a sleeve-form plug end14and in the leading region it has a sleeve-form plug tip16. The plug tip16is integrally connected to the plug end14by two oppositely arranged, longitudinally running expansible limbs18. The expansible limbs18define an expansion region20of the plug10. This region extends from the plug end14to the plug tip16. Circumferentially, the expansible limbs18are joined to one another by a stretchable material22, which is interrupted by several helically arranged slots24. The stretchable material22consists of the same plastics material as the remainder of the plug10. The stretchable material22is a component integral with the plug10.

The stretchable material22is in the form of a thin web22, which joins the expansible limbs18circumferentially with one another (compare the cross-section I—I of the expansion region20in FIG.4). The thin web22has an undulation in the circumferential direction. The thin web22is stretchable in the circumferential direction of the plug10both by virtue of its undulation and by virtue of its thin construction and the stretchability of the plastics material of which it consists. The helically arranged slots24promote the formation of an enlargement by the expansible limbs, illustrated inFIG. 6, when mounting the plug10in a panel, but at the same time prevent the thin web22from tearing.

Starting from the plug end14, two opposing anti-rotation ribs28running in the lengthwise direction of the plug are arranged on the outer circumference of the plug10, and extend beyond the expansion region20as far as the plug tip16. The anti-rotation ribs28are of saw-tooth construction over a part of their length, the perpendicular front edge30facing towards the plug tip16.

The sleeve-form plug tip16is provided with non-rectilinear slots32, the peak or angle34of which is directed forwards. The slots32are arranged at two oppositely located places on the plug tip16and several (three) slots32are arranged spaced axially from one another on the plug tip16. The non-rectilinear slots32have arms36,38, one arm36being inclined in the direction of a lead of the thread of the expansion screw, not shown inFIGS. 1-3. The other arm38is inclined in the opposite direction. The inclination of the arms36need not correspond to the lead of the thread of the expansion screw, the inclination runs only in the same direction.

In the region of the plug end14, the screw channel12has approximately a circular cross-section, it narrows in the expansion region20(FIG. 4) and in the plug tip16is in the form of a slot (FIG.5). This enables the screw channel12to adapt well to expansion screws of different diameter. The two opposing, axially extending slots39in the region of the plug tip16serve the same purpose, their slot base running spaced from the screw channel12.

The function of the plug10according to the invention is explained below with reference to FIGS.6and7:FIG. 6shows the fixing of an article40to a panel-form building material42. The plug10is inserted in a hole drilled in the panel-form building material42. Because of the relatively large transverse dimension of the plug end14, the plug end14widens the drilled hole and in so doing compacts the building material surrounding the plug end14. The anti-rotation ribs28form abutment surfaces, which prevent the plug from turning with an expansion screw44as this is screwed in.

After insertion of the plug10, the article40to be fixed, in which a hole has been drilled, is held against the panel-form building material and the expansion screw44is pushed through the article40and screwed into the plug10. A screw thread46of the expansion screw44cuts into the plug tip16and the screw thread46engages in the arms36of the non-rectilinear slots32that are inclined in the same direction as the screw thread46of the expansion screw44. The arms38of the non-rectilinear slots32that are inclined in the opposite direction enable the plug tip16to stretch axially, so that the axial spacing of the slots32from one another adapts to a lead of the screw thread46. In combination with the flat, slot-form screw channel12in the plug tip16, the effect of the non-rectilinear slots32is that the plug tip16adapts well to a diameter of the particular expansion screw being used and to lead of its screw thread46.

During screwing in and tightening, the expansion screw44draws the plug tip16towards the plug end14, the spacing between the plug tip16and the plug end14being reduced. During that process, the expansible limbs18wind around one another to form a knot-like structure, so that the expansible limbs18of the plug10engage positively behind the panel-form building material42, producing a good anchorage of the plug10even on a low-stretch panel-form building material42, such as plasterboard.

FIG. 7illustrates the anchoring of an article40to a solid building material48, such as concrete, for example. Here, the expansible plug10is inserted in a manner known per se into a hole50drilled in the solid building material, the article40is offered up and the expansion screw44is pushed through the article40and screwed into the plug10. The expansion screw44presses the expansible limbs18apart and consequently anchors the expansible plug10in the drilled hole50. Pressing the expansible limbs18apart, that is, expansion thereof, is not hampered by the thin webs22connecting the expansible limbs18circumferentially, since these are thin and have an undulation and are therefore stretchable circumferentially. The thin webs22, which join the expansible limbs18in the expansion region20to form a kind of sleeve, prevent the expansion screw44from being able to emerge laterally from the screw channel12between the expansible limbs18as it is being screwed in.

While the invention has been illustrated and described as embodied in a plug for fixing to hollow and to solid building materials, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.