GB2028950A

GB2028950A - Anchoring Assemblies

Info

Publication number: GB2028950A
Application number: GB7929622A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-08-30
Filing date: 1979-08-24
Publication date: 1980-03-12
Also published as: IT1122525B; BR7905255A; DK358579A; GR64883B; ES245226Y; NL184973B; NL7904626A; NL184973C; BE878449A; FR2438190A1; ES245226U; DK148666C; ATA412779A; JPS5533991A; HU177614B; DK148666B; JPS6019808U; AT365750B; GB2028950B; SE7905536L

Abstract

This invention relates to an anchoring assembly comprising an expansible fixing plug 1 and a fastening screw 5 provided with rounded thread crests, the assembly being especially suitable for fixing building components to masonry. The fixing plug 1 preferably consists of plastics material and has longitudinal slots 10 and fins 12. The rounded thread crests avoid deep penetration into the plug material and consequently do not tend to weaken the plug, as with conventional threads. The screw core diameter corresponds to the plug hole diameter, and the outer diameters of the screw thread and the plug correspond, prior to expansion of the plug by the screw. <IMAGE>

Description

SPECIFICATION Improvements in and Relating to Fastening Equipment This invention relates to a fastening set or equipment comprising an expansible fixing plug and a fastening screw and which is especially suitable for anchoring in concrete building components, wherein the expansible fixing plug consists of plastics material and has a longitudinal bore or slit for screwing in and bracing the fastening screw.

Expansible fixing plugs of plastics material are generally anchored by screwing in wood screws which, as is known, have a screw thread with a pointed profile. When screwed in, the thread crests penetrate very deeply into the plug material and consequently weaken the cross-section of the fixing plug. Further, although a portion of the plug material is displaced towards the outer wall by the flank of the thread, the greater part is displaced in the longitudinal direction of the plug, so that the plug is stretched. The form of the thread of fastening screws used in conjunction with plastics expansible fixing plugs is therefore not suitable for achieving optimal anchoring values.

The problem underlying the invention is to provide a fastening set with which optimal anchoring values can be obtained.

This is achieved in accordance with the invention in that the fastening screw has a rounded thread and at the tip of the screw the end of this thread is tapered.

The construction according to the invention improves the strength of the screw as firstly, the notch effect caused by the sharp-edged cuts of the thread is eliminated and secondly, the movement of fibre in the fastening screw is improved by the rounded thread. The combined effect of the expansible fixing plug and the rounded thread achieves a very much stronger radial displacement of the fixing plug material towards the wall of the drilled hole, which produces a considerably stronger wedging, and thus a considerably stronger anchorage of the plug in the drilled hole. As the rounded crests of the thread also do not penetrate so deeply into the fixing plug material, the cross-section of the fixing plug is not weakened.The crests of the thread press instead into the plug material over a large surface area, and curve the outside surface of the plug outwards to correspond with the pitch of the thread. This produces a wave-like distribution of the expansion force with increased tensional forces in the region of the thread crests.

Consequently, the screw tends to be drawn or pulled into the drilled hole, the head of the fastening screw being held directly against the face of a component to be secured and, in the case of a fixing plug that is inserted more deeply, against the mouth of the hole drilled in the masonry, so that bending stresses are almost completely eliminated. As a result of this design the fixing plug material is especially strongly braced and wedged in the thread, so that unusually- high holding forces are achieved.

Advantageously, the central region of the expansible fixing plug, can have slits, which are closed towards the ends of the plug, and fins, which run along one longitudinal edge of each of the slits and correspond in length thereto. This construction enables the fixing plug to be anchored also in soft building materials, for the slits allow the central region of the fixing plug to expand. Further, the fins, which bite into the wall of the drilled hole and also strengthen the bracing of the fixing plug in the drilled hole, prevent the plug being turned with the screw.

Because of the yielding property of the softer building material, the plug material is pressed in the radial direction into the wall of the drilled hole also in the region of the thread crests, producing a positive attachment in addition to the bracing and wedging.

Advantageously, the fixing plug may have an elongated neck. When fastening door or window frames this elongated neck engages in the article to be fastened and protects the shaft of the fastening screw against corrosion. Further, the elongated neck also provides a good support for absorbing bending forces.

The present invention also provides fastening equipment comprising an expansible fixing plug and a fastening screw, the plug having a longitudinal opening for receiving the screw, and the screw having a portion provided with a thread for expanding the plug into engagement with the wall of a hole, wherein, in axial plane section, each crest of the thread is a curved line.

Fastening equipment constructed in accordance with the present invention will now be described, by way of example only, with reference to the accompanying drawing the single figure of which shows the equipment anchored in position in a bore in masonry.

Referring to the accompanying drawing the fastening equipment comprises a fixing plug 1 and a fastening screw 5.

The plug 1 is arranged to be placed in a drilled hole 4 formed in masonry-such as a wall 2and the screw 5 is then screwed into the plug 1 to hold against the wall 2, a building component, for example a facing plate 3, the plate being held between the face of the wall and a head 6 of the screw.

The diameter of the hole 4 in the masonry corresponds to the outer diameter of the fastening screw 2. As shown in the drawing, the screw has a threaded portion the major portion of which has a substantially cylindrical core of constant diameter, only the tip of the screw being provided with a core which is not of constant diameter, and is substantially conical in form. The depth of thread over the core portion of constant diameter is also constant so that the outer diameter of the screw over that portion is constant in diameter.

If, as would usually be the case, the wall plug and the fastening screw are chosen to have the same or approximately the same outer diameter the time-saving "push-through" fastening process can be used. According to this method a bore having a diameter corresponding to the outer plug diameter is drilled both in the building component to be mounted and in the masonry in a single operation. The plug can then be introduced into the masonry bore through the bore in the component, without removing the positioned component, and subsequently can be expanded in the masonry bore by means of the fastening screw.

The plug is preferably made from plastic material and is injection-molded. The plug has a tubular body which is open ended and is provided with a longitudinally extending bore 9.

When the plug has been inserted into the masonry hole the fastening screw is turned so that the screw passes into and along the bore 9 of the plug. In relatively hard masonry the thread digs into (but does not break the surface of) the body of the plug and at the same time the plug material is compressed and wedged between the thread and the wall of the masonry hole.

The plug can also, however, be used in soft masonry because it is provided with at least two longitudinally extending slots 10 the ends of each slot lying between the ends of the body of the plug, that is to say neither of the slots opens into the ends of the plug body. Consequently when the plug is inserted into the masonry hole in soft masonry, and the screw is inserted into the plug, the intermediate region of the plug body formed with the slot expands outwardly so that a bulblike bulge is formed which prevents the fastening screw and the plug being withdrawn from the masonry hole.

A longitudinally extending fin 12 is provided along one edge of each slot. Each fin is of triangular cross-section. Further, proceeding around the circumference of the plug for example in a clock-wise direction, the fins are arranged on the same side of its respective slot, that is to say each fin is arranged upstream of its slot.

The fins have two main purposes. First, when the plug is used in soft masonry materials they tend to stop the plug rotating when the fastening screw is inserted into the plug. The triangular form of the slot is particularly useful in preventing this rotational movement. Secondly, when the plug is used in hard masonry material as the plug is inserted into the bore the fins will flex and effectively close the slot. Again, in this case, the triangular form of the fin serves to facilitate the flexing of the fins into the slot.

For fastening door or window frames the plug has an elongated neck portion 13 which is arranged to engage in a bore in the frame. The screw has a threadless portion 14 which is arranged to engage in the elongated neck 13 of the plug. The diameter of the threadless portion 14 of the screw is equal to the outer diameter of the threaded portion of the screw less the thickness of the elongated neck portion 13 of the plug.

As will be evident from the drawings, in axial plane section each crest-that is to say, that part of the surface of the thread connecting adjacent flanks-of the thread 7 of the screw, is a curved line. This results in the thread having a rounded form which can be continued down the flanks and into the root of the thread. This construction of the screw thread facilitates the entry of the screw into the plug whilst resulting in an anchorage which has very high resistance to withdrawal.

As the core diameter of the threaded portion of the screw corresponds to the inner diameter of the longitudinal bore in the plug, when the screw is screwed into the plug, the thread digs into the plug material and that material is simultaneously compressed and wedged between the thread flanks, crests and roots and the wall of the hole in the masonry.

Generally the space between the screw thread and the wall of the hole is filled with the material of the plug when the screw is screwed right home.

Unlike conventional screw threads which have a substantially triangular crest the curved crest of the illustrated thread ensures that it does not penetrate into the material of the plug when it is screwed into the plug, but rather that it effects a greater radial expansion of the plug-forming wave-like crests 11-which produces a considerably stronger wedging of the plug between the wall of the drilled hole in the masonry and the screw and thus a considerably stronger anchorage of the plug in that drilled hole.

To reduce resistance to turning of the screw in the plug the leading end portion 8 of the screw is tapered.

Claims

1. Fastening equipment comprising an expansible fixing plug and a fastening screw, the plug having a longitudinal opening for receiving the screw, and the screw having a portion provided with a thread for expanding the plug into engagement with the wall of a hole, wherein, in axial plane section, each crest of the thread is a curved line.

2. Fastening equipment as claimed in claim 1, wherein in axial plane section, each crest and its adjacent flanks is a curved line.

3. Fastening equipment as claimed in claim 1 or claim 2, wherein, in axial plane section, each root of the thread is a curved line.

4. Fastening equipment as claimed in any one of claims 1 to 3, in which the diameter of the core of the said portion of the screw corresponds to the diameter of the longitudinal opening of the fixing plug.

5. Fastening equipment as claimed in any one of claims 1 to 4, in which the outer diameter of the said portion of the screw corresponds to the outer diameter of the fixing plug.

6. Fastening equipment as claimed in any one of claims 1 to 5, in which the plug has at least two longitudinally extending slots, the end of each slot lying between the ends of the plug, and at least two longitudinally extending fins, a respective fin being provided along a longitudinal edge of each slot.

7. Fastening equipment as claimed in any one of claims 1 to 6, in which the fixing plug has a length such that when the said portion of the screw is engaged in the plug, another portion of the plug surrounds a threadless portion of the screw.

8. Fastening equipment as claimed in any one of claims 1 to 7, in which the leading end portion of the screw is tapered, the thread extending into that portion.

9. Fastening equipment comprising an expansible fixing plug and a fastening screw and which is especially suitable for anchoring in masonry, the plug being made of plastic material and having a longitudinal bore or slot for receiving the fastening screw, wherein the fastening screw has a rounded thread and, at the tip of the screw, the end of the thread is tapered.

10. Fastening equipment substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.