GB1601214A - Fixing devices for use in masonry - Google Patents

Description

(54) FIXING DEVICES FOR USE IN MASONRY (71) We, HOLDFAST FIXINGS LIMITED, formerly known as LUNWEB (PRoDucrS) LIMITED, a British Company of PO Box No. 2, Mandeville Road, Aylesbury, Buckinghamshire, do hereby declare the invention for which we pray that a Patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to devices for fixing in masonry. A screw threaded fastening element, such as a screw is provided and means which, in use, encloses the fastening element and which provides packing between the fastening element and the hole in the - masonry to hold the fastening element securely in the hole.

There are many such devices available and in most, the menas. in the form of a plug, is generally tubular and is first inserted into a prepared hole in the masonry.

The fastening element is then inserted into the interior of the plug, by screwing it in, and as this takes place, the plug expands to grip the wall of the hole so that the fastening element is securely fixed in the masonry.

It has been proposed, however, to form a plug around the fastening element such as by moulding and the assembly is then inserted into the hole and hammered in.

This has substantial advantages in ease and speed of fixing and is very secure. However, this arrangement has certain manufacturing drawbacks.

The object of this invention is to provide a device for use in masonry comprises a plug, for use in combination with a screw threaded fastening element, said plug including at least two integral relatively movable moulded members, portions of screw threads being formed in said members respectively, said members defining, when placed together in a position of use, a cavity with screw threads corresponding with those of the fastening element with which the device is to be used, and ribs formed on the external surfaces of the members, said ribs being distortable, without said ribs undergoing flexing to provide a secure fit in a hole having a diameter slightly smaller than the outer diameter of said plug and ribs.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a perspective view of a fixing device in accordance with the invention and Figure 2 is a cross-sectional view showing three devices in different conditions.

The device is intended for securing in masonry and may be used for attaching fixtures, such as the member 10 shown in Figure 2, to the masonry which is indicated at 11. The masonry may be a high density brick or concrete wall and the member 10 may be part of shelving or a cupboard or other structure.

Referring to Figure 1 there is shown a fixing device comprising a plug and a fastening element. The fastening element is in the form of a conventional wood or self tapping screw 12 having a countersunk slotted head 13. The plug is a plastics moulding and may be made from nylon, polyurethane, polypropane or other mouldable plastics material. Conveniently, the plug is formed by injection moulding.

The plug has two elongated members in the form of semi-circular section arms. In the internal surface of each arm, screw threads 16 are formed and when the two arms are placed in a position of use so that they lie in edge to edge contact, there is defined a cavity with continuous screw threads. The screw threads are of a pitch to match and co-operate with the screw threads of the screw 12. The two arms 14, 15 are connected by an integral spigot 17 by integral hinge portions. This spigot in this example, is a short cylindrical portion.

This forms an end for the cavity defined as aforesaid, between the arms 14, 15 and it is hollow so as to receive the pointed end of the screw 12. The spigot 17 is closed ended so that the point of the screw bears on the flat or domed internal end portion of the spigot.

The arms and spigot are moulded with the arms substantially lengthwise aligned or coplanar with one another and the spigot between their adjacent ends. This arrangement is shown in Figure 1.

On the external surface of each of the arms 14, 15 are ribs 18 which extend lengthwise of the plug. These ribs of which the example has four, are equally spaced around the external surfaces of the arms and extend over the full length of the plug except for the spigot 17.

The length of the plug corresponds with the threaded length of the screw 12 when the latter is engaging within the spigot 17.

Thus, when the two arms are drawn together, as will be described, they encompass the whole of the threaded portion of the screw 12.

Referring to Figure 2 the uppermost portion of the illustration shows the fixing device including the screw with the plug surrounding the screw and engaged in a hole 19 in the member 10. This hole is countersunk to receive the head 13 of the screw and has a diameter beyond the countersink of a diameter equal to or slightly larger than the overall diameter of the plug including its ribs 18. The spigot 17 is shown in position within the entrance of the drilling 20 formed in the masonry 11. This drilling 20 has a diameter slightly less than the overall diameter of the plug, including the ribs 18. If the hole in 10 is too small to accept the plug, it is merely necessary to remove the screw from the plug and after passing the screw through the hole, the plug is repositioned on the protruding end of the screw, at the side of the member 10 to be presented to the masonry 11.This is more applicable in a hard material such as metal than in a softer material such as timber. 21 illustrates a hammer used to drive the screw 12 and the plug into the drilling 20 in the masonry. When the screw and plug are driven fully home they take up the position shown in the centre view in Figure 2. The countersunk head 13 of the screw is shown occupying the corresponding countersunk in the hole in the member 10.

The lower illustration in Figure 2 shows a similar fastening device in which, however, the shank of the screw has a long plain portion 22 between the screw thread and the head. The plug extends only over the threaded portion of the screw and is exactly the same size as that used for the screws in the other two illustrations of Figure 2.

It will be seen therefore that the plug may be used with screws of different lengths but of the same diameter and having the same thread form.

Before the screw and plug are placed in the position shown in the upper illustration of Figure 2, it is necessary to insert the screw into the plug in the condition in which the two arms lie closely surrounding the screw, as illustrated in Figure 1 and in the upper illustration of Figure 2. To accomplish such insertion of the screw, the screw is merely laid against one arm, with its screw threads engaged therein. The other arm is folded over and engaged on the screw threads. The close engagement causes the arms to grip the screw and the assembly can therefore be handled without significant risk of separation.

In an alternative construction more than two arms are provided. However, when assembled, all the arms come together to define the screw threaded cavity.

The provision of the ribs 18 on the exterior of the plug enables varying clearances in different holes to be taken up. As the fixing device enters the hole in the member 10 and passes into the drilling 20 in the masonry 11, the ribs become flattened to a greater or lesser degree, dependent upon the clearance between the hole and said drilling and the cylindrical external surface of the plug between the ribs 18 thereon. The ribs tend to become wider and shallower but do not tear away. This provides a very tight interference fit which has very high strength and security. The extent of interference is to some extent dependent upon the nature of the masonry material.

The screw may be removed with the aid of an ordinary screwdriver engaged in the slot in the head. The plug remains in place and has an undamaged screw thread which may again be used if the screw is to be reinserted. Other forms of fastening device may be used with different head forms as appropriate for the tasks which they have to perform.

WHAT WE CLAIM IS: 1. A fixing device for use in masonry comprising a plug for use in a combination with a screw threaded fastening element, said plug including at least two integral relatively movable moulded members, portions of screw threads being formed in said members respectively, said members defining, when placed together in a position of use, a cavity with screw threads corresponding with those of the fastening element with which the device is to be used, and ribs formed on the external surfaces of the members, said ribs extending longitudinally of said members, said ribs being distortable, without said ribs undergoing flexing to provide a secure fit in a hole having a diameter slightly smaller than the outer diameter of said plug and ribs.

2. A fixing device as claimed in claim 1 in which the moulded members are generally part circular section arms with respective interior screw threaded portions.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. the arms substantially lengthwise aligned or coplanar with one another and the spigot between their adjacent ends. This arrangement is shown in Figure 1. On the external surface of each of the arms 14, 15 are ribs 18 which extend lengthwise of the plug. These ribs of which the example has four, are equally spaced around the external surfaces of the arms and extend over the full length of the plug except for the spigot 17. The length of the plug corresponds with the threaded length of the screw 12 when the latter is engaging within the spigot 17. Thus, when the two arms are drawn together, as will be described, they encompass the whole of the threaded portion of the screw 12. Referring to Figure 2 the uppermost portion of the illustration shows the fixing device including the screw with the plug surrounding the screw and engaged in a hole 19 in the member 10. This hole is countersunk to receive the head 13 of the screw and has a diameter beyond the countersink of a diameter equal to or slightly larger than the overall diameter of the plug including its ribs 18. The spigot 17 is shown in position within the entrance of the drilling 20 formed in the masonry 11. This drilling 20 has a diameter slightly less than the overall diameter of the plug, including the ribs 18. If the hole in 10 is too small to accept the plug, it is merely necessary to remove the screw from the plug and after passing the screw through the hole, the plug is repositioned on the protruding end of the screw, at the side of the member 10 to be presented to the masonry 11.This is more applicable in a hard material such as metal than in a softer material such as timber. 21 illustrates a hammer used to drive the screw 12 and the plug into the drilling 20 in the masonry. When the screw and plug are driven fully home they take up the position shown in the centre view in Figure 2. The countersunk head 13 of the screw is shown occupying the corresponding countersunk in the hole in the member 10. The lower illustration in Figure 2 shows a similar fastening device in which, however, the shank of the screw has a long plain portion 22 between the screw thread and the head. The plug extends only over the threaded portion of the screw and is exactly the same size as that used for the screws in the other two illustrations of Figure 2. It will be seen therefore that the plug may be used with screws of different lengths but of the same diameter and having the same thread form. Before the screw and plug are placed in the position shown in the upper illustration of Figure 2, it is necessary to insert the screw into the plug in the condition in which the two arms lie closely surrounding the screw, as illustrated in Figure 1 and in the upper illustration of Figure 2. To accomplish such insertion of the screw, the screw is merely laid against one arm, with its screw threads engaged therein. The other arm is folded over and engaged on the screw threads. The close engagement causes the arms to grip the screw and the assembly can therefore be handled without significant risk of separation. In an alternative construction more than two arms are provided. However, when assembled, all the arms come together to define the screw threaded cavity. The provision of the ribs 18 on the exterior of the plug enables varying clearances in different holes to be taken up. As the fixing device enters the hole in the member 10 and passes into the drilling 20 in the masonry 11, the ribs become flattened to a greater or lesser degree, dependent upon the clearance between the hole and said drilling and the cylindrical external surface of the plug between the ribs 18 thereon. The ribs tend to become wider and shallower but do not tear away. This provides a very tight interference fit which has very high strength and security. The extent of interference is to some extent dependent upon the nature of the masonry material. The screw may be removed with the aid of an ordinary screwdriver engaged in the slot in the head. The plug remains in place and has an undamaged screw thread which may again be used if the screw is to be reinserted. Other forms of fastening device may be used with different head forms as appropriate for the tasks which they have to perform. WHAT WE CLAIM IS:

1. A fixing device for use in masonry comprising a plug for use in a combination with a screw threaded fastening element, said plug including at least two integral relatively movable moulded members, portions of screw threads being formed in said members respectively, said members defining, when placed together in a position of use, a cavity with screw threads corresponding with those of the fastening element with which the device is to be used, and ribs formed on the external surfaces of the members, said ribs extending longitudinally of said members, said ribs being distortable, without said ribs undergoing flexing to provide a secure fit in a hole having a diameter slightly smaller than the outer diameter of said plug and ribs.

2. A fixing device as claimed in claim 1 in which the moulded members are generally part circular section arms with respective interior screw threaded portions.

3. A fixing device as claimed in either

claim 1 or claim 2 in which the arms are moulded in generally coplanar configuration vith an integral spigot connecting them.

4. A fixing device substantially as hereinbefore described with reference to and as shown in the accompanying drawings.