GB2275979A - Anchorage for screws in plasterboard - Google Patents

Abstract

An anchorage for a screw in plasterboard 12 comprises a body 18 with a thread 34 formed thereon, a flange 20 at one end of the body and a drilling tip 30 having a diameter which is greater than the diameter of the end 24 of the body to which it is attached, so that debris from drilling can be accommodated. The tip 30 is connected by a neck 28 to the end 24, and there is a hole 36 in the neck for debris. The anchorage tapes from flange 20 to the end 24, and is made of plastics. The flange 20 has an annular recess 40 so that rapture occurs on overtightening. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO ANCHORAGES The present invention concerns improvements in or relating to anchorages, especially but not exclusively anchorages for fixing screws for use in plasterboard walls, partitions, etc.

There are presently available many differring designs of anchorages for fitment into holes pre-drilled into plaster-faced brick walls, the anchorages then receiving a screw by which a fitment can be attached to the wall. Such anchorages are not generally suitable for use in plasterboard walls as a result of the relative thinness of the plasterboard sheet and its delicate nature, this resulting from the friable nature of the plaster forming the main component of the wall which, itself, is sandwiched between two fibrous, for example, paper, sheets.

Attempts have been made in the past to provide anchorages for plasterboard walls. Once such attempt has taken the form of an assembly which is passed through a pre-drilled hole in the wall in a collapsed condition and, as the fixing screw is tightened relative to the anchor, a portion of the assembly projecting beyond the inner face of the wall is caused the expand to prevent expulsion of the anchor in the inwards to outwards direction. These arrangements have been relatively costly to manufacture and difficult to operate.

More recently atte.mpts have been made to provide a single piece anchorage comprising a cylindrical plastics material body provided on its outer surface with a deep flighted thread and at its leading end with a wall penetrating member, for example a drill tip. Anchorages of this design have been presented to the wall and, while applying a force thereto in the direction of the wall, have been rotated so that the leading end of the anchorage creates a hole through the wall, ultimately to accommodate the body portion of the anchorage which is drawn into the hole by the deep flighted thread when the anchorage penetrates a sufficient distance into the wall to enable the thread to engage the plasterboard, the thread thereafter fixing the anchorage by its body portion in the plasterboard so that a central bore in the body portion can receive a fixing screw.

Whereas these more recent attempts have proved to be more successful than the original attempts they are not always wholly successful as they depend for their strength, to a large measure, on the penetration of the screw thread into the plasterboard. As a result of the relatively crude drilling arrangement at the leading end of the anchorage and the fact that for it to successfully operate it must have a force directed along the longitudinal axis of the anchorage applied thereto, the drilling head often bursts through the delicate plasterboard when it is drilled as little a half way through the board. Thus, the inner face of the board does not have a neat circular hole drilled therethrough and often the burst hole formed by the penetrating drill is of a diameter greater than the external diameter of the thread.

It will be readily apparent that the thread on the inner face of the plasterboard will have nothing against which to grip consequently the efficiency of the anchorage will be much reduced. In certain instances the resistance provided by that part of the plasterboard surviving intact on the outer side of the burst is so little that when the anchorage is tightened up, rather than forming a rigid fix with the plasterboard, the application of torque thereto ruptures the remaining plasterboard.

It is an object of the present invention to obviate this and other disadvantages.

According to the present invention there is provided an anchorage comprising a body portion having a thread extending therefrom, a flange at one end of the body portion and a drilling member at the other end of the body portion, the drilling member having an outer diameter greater than the outer diameter at the end of the body portion to which the drilling member is attached.

Preferably the anchorage is manufactured as a single component by injection moulding from a glass-filled plastics material.

Preferably the external diameter of the flange is greater than the external diameter of the thread on the body portion.

Preferably the drill member is a drilling point of substantially conical shape and a neck of diameter less than the maximum diameter of the drilling point which connects the point to the body member. The drilling point has two substantially diametrically opposed drilling faces formed thereon by removing diametrically opposed segments from the cone.

Preferably the external diameter of the body member decreases gradually from the flange towards the drilling point.

Preferably the flange has a recess formed in its outer face to form a ridge of weakness in the material of the anchorage at a diameter which is substantially equal to the external diameter of the body member at its connection to the flange.

Preferably a screw receiving passage is formed through the body member.

Preferably the body member has a recess for engaging a driving tool at its flanged end. Preferably the passage through the body member is blind and terminates at the end of the body member. Alternatively the passage terminates in a secondary passage leading from the main passage, said secondary passage being of smaller diameter than the main passage.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings, in which Fig. 1 shows a side elevation of an anchorage for use in a plasterboard wall; and Figs. 2 and 3 shows respectivelly end elevations from opposite ends thereof.

The anchorage of the present invention is intended to be fitted in a plasterboard wall 10 which comprises a core 12 of friable plaster sandwiched between outer paper skins 14.

The anchorage 16 is manufactured as a single component by injection moulding from a glass-filled plastics material. Consequently the anchorage, when compared to the plaster 12 of the plasterboard is relatively hard.

The anchorage comprises a substantially circular cross-section body portion 18 provided at its, in use, outer end with a relatively thin flange 20 of increased diameter. The diameter of the body portion decreases in the direction away from the flange 20, that is, it is inwardly converging. An inwardly converging passage 22 is formed along the axis of the body portion terminating at or near its inner end 24, the passage being intended to receive a fixing screw, the length of which is carefully chosen such that when it is screwed up against the item to be supported on the wall by the screw and anchorage assembly, the point of the screw does not extend to the end 24 of the body member.

A cruciform recess 26 is formed in the outer end of the anchorage and is intended to receive a driving tool, for example a screwdriver, by which the anchorage can be rotated relative to the wall 10.

A neck portion 28-.extending from the inner end 24 of the body portion connects the body portion 18 with a conical drilling tip 30, the maximum base diameter of which is greater than the external diameter of the body portion at its inner end 24. Two substantially quadrant sections 32 are removed from the drilling tip to provide drilling faces 34 so that when the anchorage is presented to an unbroken wall 10 and rotated relative to the wall by a driving member, for example a screwdriver, while force is applied to the anchorage along its longitudinal axis towards the wall, the drilling tip will cut a circular hole through the wall in a manner to be described in greater detail below.

Formed on the outer surface of the body portion there is a relatively deep flighted screw thread 34 commencing from the inner end 24 and terminating close to the flange 20. The external diameter of the thread 34 is greater than the greatest diameter of the drill tip 30 but less than the greatest diameter of the flange 20 and it will be realised that as the anchorage proceeds through the wall the thread 34 will engage the wall and, due to the respective heardnesses of the material of the anchorage and the plaster of the wall, will cause the anchorage to be screw threaded into the wall with the body portion lying within the circular cross-section passage pre-formed by the drill tip 30.

It has been realised that the anchoring efficiency of the anchorage can be considerably reduced if a neat circular hole is not formed through the wall. For example, if the pressure applied to the plasterboard causes its inner face to burst as illustrated, for example, in the phantom lines B in Fig. 1, there will be a relatively small area of plaster for engagement by the screw thread 34.

The present invention provides an anchorage which is specifically designed in an attempt to obviate or mitigate this problem.

It will be noticed that a radial through passage 36 is provided in the neck 28. Additionally the neck has a reduced diameter thereby providing a recess behind the drill tip. Furthermore the maximum diameter of the drill tip is greater than the outside diameter of the body portion 18 at least at its inner end 24.

When the drill tip is first presented to the wall any plaster which it removes in forming the hole 38 therethrough will fall away from the anchorage and the wall and it is only when the drill assembly comprising the drill tip and neck portion has penetrated into the wall that this discharge of drilled material will reduce . .

or cease. At this stage the start of the thread 34 will engage and penetrate into the plaster 12 of the wall and as the anchorage continues to move into the wall the drill tip 30 will drill a circular hole ahead of it, the debris from the hole being accommodated in the through passage 36, the recess formed by the reduced diameter of the neck and the oversized drilled hole 38 behind the tip. As a result there will be a minimum build up of additional pressure on the inner face 14 of the wall so that the tendancy for the drill to burst the wall before it has fully penetrated is considerably minimised and the drill tip will drill a neat cylindrical hole through the wall, thereby obviating the disadvantage referred to above.

The person fixing the anchorage will realise that it is in its optimum design position when the flange abuts or just penetrates the outer coating 14 of the wall such that the flange lies flush with the wall. The anchorage can then be used to accept a screw, for example, a wood screw, in its passage 22, the wood screw, as described above, having its length carefully chosen such that when it is in its final position its tip does not project beyond the inner end 24 of the body portion.

As described above the passage 22 terminates at or near this inner end so t.hat the screw could not penetrate. Furthermore, owing to the converging nature of the passage 22 as the screw tip approached the end of the passage the force thereon signals to the operative that the correct position has been reached. If the operative misguidedly applies greater torque to the screw the combination of the abutment of the screw tip with the end of the passage and the circumferentially applied force on the screw experienced due to the converging passage will result in the anchorage turning further relative to the wall and the flange 20 rupturing from the body portion or collapsing as a result of a circular recess 40 formed therein, the diameter of said recess being substantially equal to the external diameter of the body portion at the flanged end 20.

Various modifications can be made without departing from the scope of the invention, for example, the drill tip can have any convenient shape provided that it drills a neat hole and allows for removal of the drilled material. To accommodate drilled material as the anchorage is penetrating the wall the neck portion can be extended or its diameter reduced to provide greater accommodation for said drilled material.

Additionally the transverse passage 36 can be of different size or shape and in certain instances the through passage 22 can extend into the transverse passage 36 the extension.having a diameter less than the minimum diameter of the passage 22 and certainly less than that which would allow the screw nail to pass therethrough. In a further modification the passage 22 can extend into the through 36. In this modification the fixing screw may penetrate beyond the end 24 of the body portion but will be prevented from further penetration when its tip contacts the base of the drill tip 30.

In another modification the anchorage can be moulded from any suitable alternative material, with or without glass or other filling, for example high quality polyamide.

The thread 34 can be a multi-start thread and have any convenient pitch. The cruciform recess 26 can be replaced by a slotted recess, a hexagonal recess or any other suitable shaped recess capable of receiving a driving tool.

Claims (13)

1. An anchorage comprising a body portion having a thread extending therefrom, a flange at one end of the body portion and a drilling member at the other end of the body portion, the drilling member having can outer diameter greater than the outer diameter at the end of the body portion to which the drilling member is attached.

2. An anchorage as claimed in Claim 1, manufactured as a single component by injection moulding from a glass-filled plastics material.

3. An anchorage as claimed in Claim 1 or Claim 2, in which the external diameter of the flange is greater than the external diameter of the thread on the body portion.

4. An anchorage as claimed in any of Claims 1 to 3, in which the drill member is a drilling point of substantially conical shape and a neck of diameter less than the diameter of the drilling point which connects the point of the body member.

5. An anchorage as claims in Claim 4, in which the drilling point has two substantially diametrically opposed drilling faces formed thereon by removing diametrically opposed segments from the cone.

6. An anchorage as claimed in any one of the preceeding claims, in which the external diameter of the body member decreases gradually from the flange towards the drilling point.

7. An anchorage is claimed in any one of the preceeding claims, in which the flange has a recess formed in its outer face to form a ridge of weakness in the material of the anchorage at a diameter which is substantially equal to the external diameter of the body member at its connection to the flange.

8. An anchorage is claimed in any one of the preceeding claims, in which a screw receiving passage is formed through the body member.

9. An anchorage is claimed in any one of the preceeding claims, in which the body member has a recess for engaging a driving tool at its flanged end.

10. An anchorage as claimed in Claim 8 or Claim 9, in which the passage through the body member is blind and terminates at the end of the body member.

11. An anchorage as claimed in Claim 8 or Claim 9, in which the passage terminates in a secondary passage leading from the main passage, said secondary passage being of smaller diameter than the main passage.

12. An anchorage substantially as herein before described with reference to the accompanying drawings.

13. Any novel subject matter or combination including novel subject matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.