Patent Publication Number: US-2009220316-A1

Title: Spreading plug

Description:
The invention relates to a spreading plug with a plug jacket having a plug neck, a plug shank, a plug foot and a continuous spreading means insertion hole. 
     Spreading plugs of this type are known in a broad range of embodiments. Conventionally, the plug jacket is provided in this case with three longitudinal slots which are arranged at the same angular distance and form three spreading elements which spread outward against the wall of the drilled hole when a screw is screwed in. Reliable securing of the plug can be achieved in this way in cleanly drilled cylindrical drilled holes, for example in concrete. In porous brickwork or in hollow blocks or excessively large drilled holes, the extraction resistance is frequently insufficient. In order to be able to achieve support in hollow blocks, spreading plugs are also known which are configured as buckling plugs and in which the screw in the plug foot incises a thread and the plug is axially compressed, as a result of which the jacket segments, which encounter no resistance in the drilled hole, are tied together behind the wall of the hole. 
     DE 75 10 134 U discloses a spreading plug having a cylindrical plug jacket, the plug foot of which has a bevel, and from the rearward end of which a forwardly tapered cavity emanates. The plug jacket has two transverse slots, of which the first emanates from the plug neck and the second is offset rearwardly thereto by 90°. The second transverse slot is closed at the rearward plug end in the region of the plug foot by short projections formed integrally with the circumference. The first transverse slot extends up to at most ⅔ of the length of the plug from the leading plug end. The rearward transverse slot, which is offset by 90° thereto, also extends up to ⅔ of the length of the plug. The receiving bore for a spreading element opens at the rearward end of the plug, the bore tapering forward and overall reaching forward up to two thirds of the total length of the plug. The plug described therein is made of deformable material, preferably of flexible plastics material. Owing to the continuously cylindrical shape of the plug jacket, said plug jacket has difficulty when spreading out adapting to non-uniformities in the shape of the drilled hole along the length thereof, such as inevitably occur for example in hollow perforated bricks. 
     DE 93 12 057 U1 discloses a plastics material plug, preferably for hollow perforated bricks, having a longitudinal bore and at least two spreading parts which are arranged in succession and each separated from one another by transverse slots. The first spreading part is delimited by a sleeve-like head and shank part. The second spreading part is delimited by the shank and foot part. The head and shank part has a longitudinal bore corresponding to the outer diameter of the fastening screw. The longitudinal bore in the foot part is provided with an inner thread adapted to the thread of the fastening screw. The two spreading parts are offset from each other by 90°. In this way, the spread-out legs lie one above the other in the shape of a cross. During tightening of the fastening screw, the legs, which are located in cavities of the hollow perforated brick, of both spreading parts are buckled radially outward and form a thickening in these cavities. For this purpose, it is necessary for the cavities in the direction of the plug bore to have dimensions corresponding approximately to the length of the transverse slots. 
     DE 198 49 821 A1 discloses a plastics material spreading plug with a spreading part which can be secured by screwing in a fastening screw. The plug is provided with a longitudinal bore which is formed on the plug neck by a cylindrical portion which tapers conically toward the plug foot in a plurality of stages. The plug has a first spreading part which directly adjoins the cylindrical part of the bore and is formed by a longitudinal slot which divides the spreading part into two legs. This spreading part is adjoined by a second spreading part. The longitudinal slot of the second spreading part is offset by 90° relative to the longitudinal slot of the first spreading part. The longitudinal slots of the two spreading parts can overlap. Both spreading parts have on their outer surface saw tooth-shaped notches. This produces an outer surface which has good grip and allows the teeth formed by the notches to penetrate the wall of the drilled hole. 
     The invention is based on the object of providing a spreading plug which is universally suitable for a broad range of application purposes, has improved holding values and adapts to the building material as gently as possible. 
     The object set is achieved by the features specified in claim  1 . The arrangement of the slots offset in the circumferential direction and in the axial direction produces different main spreading directions over the length of the plug jacket, as a result of which outstanding securing is achieved even in drilled holes which extend disadvantageously. Whereas in the previously known spreading plugs the spreading effect was limited to a relatively large axial region of the length of the plug, the invention forms two or more axially spaced-apart or overlapping regions which have different main spreading directions and are for their part divided by annular grooves into individual, axially successive spreading portions, allowing more precise and flexible adaptation to the drilled hole. A plurality of regions of this type can be arranged over the length of the plug, although it is generally expedient and sufficient to provide two such regions each having slots extending over the diameter, thus forming two main spreading directions which are positioned at an angle of 90° relative to each other. Such a paired arrangement of slots means that, during spreading, the plug sleeve is spread in four directions uniformly but offset in depth. The pairs of slots thus formed are expediently arranged so as to overlap, i.e. the slots of one pair engage with that region of the jacket that is penetrated by the other pair of slots. This overlapping of the slots, roughly in the center of the shank, produces at this location also parallel spreading which ensures that the plug sleeve issues the spreading force to the securing base absolutely uniformly in this region. This arrangement is also particularly advantageous when the securing base has become cracked when screwing in the screw. Cracks produced in this way then always run toward the drilled hole. 
     In order to prevent co-rotation of the plug, which is merely inserted loosely into a drilled hole, when the spreading screw is screwed in, it is known to provide longitudinal ribs which are arranged fixedly on the outer jacket and dig into the wall of the drilled hole; this is disadvantageous especially when the material surrounding the drilled hole is relatively soft. 
     According to a preferred configuration of the plug, provision is therefore made for the plug jacket to have window slots in which rotary vanes, which at their plug foot-side end are formed integrally with the plug jacket via rotary joints, are radially movably arranged. This provides particularly beneficial securing of the plug in the drilled hole, because the rotary vanes are displaced inward on insertion of the plug into the drilled hole and are driven outward only on insertion of the spreading element and then ensure the anti-rotation function. 
     The formation according to the invention of the plug ensures, even in a relatively long configuration, that the spreading member is guided axially in the insertion hole without drifting laterally. 
     Further advantageous configurations of the invention emerge from the sub-claims. 
    
    
     
       Exemplary embodiments of the invention will be described hereinafter with reference to the drawings, in which: 
         FIG. 1  is a perspective view of a spreading plug according to the invention; 
         FIG. 2  is a side view of the spreading plug according to  FIG. 1 , together with axial views onto the plug neck and plug foot; 
         FIG. 3  is a side view corresponding to  FIG. 2  with the insertion hole indicated by broken lines; 
         FIG. 4  is a section on a larger scale along the line IV-IV according to  FIG. 3 ; 
         FIG. 5  is a section on a larger scale along the line V-V according to  FIG. 3 ; 
         FIG. 6  is a longitudinal section of the spreading plug, cut along the line VI-VI according to  FIG. 2 ; 
         FIG. 7  is a view, rotated about the plug axis through 90° relative to  FIG. 2 , of the spreading plug; 
         FIG. 8  is a vertical section of the plug according to  FIG. 7 ; 
         FIG. 9  is a view of the plug with the screw screwed in in the spread-out state; 
         FIG. 10  shows the plug according to  FIG. 9  rotated about the plug axis through 90°; and 
         FIG. 11  shows the plug according to  FIGS. 9 and 10  in a lightweight vertically perforated brick. 
     
    
    
     The spreading plug according to the invention, which is preferably made of plastics material, has a plug neck  10 , a plug shank  12  and a plug foot  14 . An insertion hole  16 , which has over the shank region and the plug foot a uniform, in the exemplary embodiment square, cross section and merges in the plug neck with an extension  18  forming a spreading pressure-free zone, extends over the entire length of the plug. The plug neck has a closed setting depth stop  20  and a plurality of axial ribs which are arranged at the same angular distance on the outside as a rotary lock, the height of which decreases after the shank. In order to prevent the ribs from becoming torn off and their anti-rotation effect from becoming lost when the plug neck is driven into the drilled hole, an axial slot  24 , which extends over the diameter, ends in the setting depth stop and causes crushing of the plug neck on insertion, so that the function of the rotary lock is maintained, is provided in the plug neck. 
     The plug shank  12  has two first longitudinal slots  26  which are offset by 180°, start at a distance from the slots  24  and end in the shank  12 . Offset by 90° from these first longitudinal slots  26 , the plug jacket has in the shank  12  two further diametrically opposing second longitudinal slots  28  which pass through the plug foot  14  and divide said plug foot into two spreading segments. This achieves a spreading function over the entire length of the plug. The second slots  28  are bridged in the region of transition between the shank and foot by bridging elements  30  which prevent premature spreading. According to the illustrated exemplary embodiment, the longitudinal slots  26  and  28  overlap by a certain distance in the end portion of the shank that faces the plug foot. 
     In the shank portion and in the plug foot portion, the plug jacket is provided with annular grooves  32  of triangular cross section, thus forming annular spreading portions  34  distributing the spreading energy. 
     In this way, the plug is particularly suitable for use in lightweight vertically perforated bricks, such as is shown in  FIG. 11 , as the inner webs of these bricks are relatively thin compared to inner wall bricks. Lightweight vertically perforated bricks are used as heat insulation bricks in outer walls and are distinguished by a low bulk density and a particular hole pattern. The inner webs of these bricks have a wall thickness of from 3 to 6 mm. The hollow chambers are relatively small; the height of the chambers is from 5 to 15 mm longitudinally to the plug axis. The bulk density of bricks of this type is less than 1.0 kg/dm 3 . 
     The distribution of the spreading energy onto the spreading portions  34  acts particularly gently on these inner webs. The continuous adaptation of the spreading portions  34  of the plug to the building material is also apparent from  FIG. 11 . The plug sleeve rests against a large number of individual inner webs. The load bearing performance corresponds roughly to a resiliently embedded beam. The individual spreading portions  34  adapt to the brick. If a spreading portion is located in a cavity, the annular grooves  32  additionally behave like barbs. Via the large number of inner webs, the plug also resists extraction via frictional engagement. 
     In the direction of the first longitudinal slots  26 , window slots  36 , which are widened with spacing and extend into the plug foot, adjoin on the side of the plug foot. Rotary vanes  38  in the plug foot  14  are formed integrally with the plug foot-side end of these window slots via rotary joints  40 . These rotary vanes are able to move freely in the window slots  36  and form, spread outward, a rotary vane lock. 
     The surface of the plug jacket offers maximum frictional area as resistance to extraction. At the same time, the profiles allow the plug jacket to adapt optimally to unevenness as a result of the spreading segments which are able to move relative to one another. 
     In order to avoid at the ends of the slots notch effects in the plastics material, roundings  42  were provided at the prominent slot ends, allowing tension peaks owing to the spreading and deformation effects to be broken down. 
     The rotary vanes  38 , which are arranged on the plug foot so as to be able to pivot laterally, can, on introduction of the plug into the drilled hole, fold inward into the insertion hole  16  through the window slots  36 . When the spreading element is screwed into the insertion hole, the rotary vanes are pressed outward against the wall of the drilled hole and prevent co-rotation of the plug. The rotary vane locks can reach with their barb-like ends through existing drilled hole projections and thus generate additional support even in hollow blocks. This leads to optimum adaptation to the building material. The insertion hole  16  forming the spreading channel is optimized in such a way as to allow a broad range of spreading elements, such as clamping plate screws and wood screws, to be screwed in in such a way as to produce a beneficial spreading effect. At the same time, the torque required for screwing in the screw does not rise in such a way as to cause excessive torsional stressing of the screw. Instead of screws, the spreading elements can also be secured in the drilled hole while being spread out by striking elements such as nails. 
     The arrangement, offset in the circumference, of the overlapping spreading slots  26  and  28  causes, as may be seen from  FIGS. 9 and 10 , spreading-out in a plurality of circumferentially offset directions. The spreading parts, which are offset from one another by 90°, are stressed, when the spreading element is screwed in, in two main spreading directions which are offset from each other by 90°. The elements are arranged in such a way that the energy which occurs and provides the resistance to extraction of the plug sleeve distributes the effect of the force around the plug, i.e. the spreading force is transmitted into the securing base uniformly in all directions in a gentle manner. Two axially overlapping pairs of spreading slots  26 ,  28 , which are offset in the circumferential direction by in each case 90°, are provided in the illustrated exemplary embodiment. However, it should also be reserved for the invention to arrange groups of offset slots consisting of three or more slots, for example in each case three first slots, at an angular distance of 120° and to offset them at an angle of 60° relative to second individual slots. According to the exemplary embodiment, the slots extend in the axial direction. For the invention, it should however be reserved to arrange the slots so as to extend obliquely or helically in a corresponding offset arrangement; this can result in further optimization during screwing-in and spreading. 
     According to the exemplary embodiment, the rotary vanes are arranged in the plug foot in an articulated manner. It is however also conceivable to place said rotary vanes further into the shank region. The important thing in this case is that these rotary vanes can swivel within their windows inwardly into the insertion channel in order then to be pressed outward against the wall of the drilled hole when the screw is screwed in. 
     Thus, within the scope of the present invention, still further alterations, modifications or design changes can be brought about without departing from the scope of the invention.