GB2147967A - Fixing device for use in masonry - Google Patents

Abstract

A device for fixing an item, such as a wooden door or window, to masonry, comprises a screw (10) having a screwed end (11a), a plain shank (12) and a countersunk head (13). The screw (10) has a plastics coating defining a ribbed zone (14) over the screw thread (11a), a plain zone (15), and a plain zone (16) with an annular flange (19). The zones (15, 16) are joined by several tongues (20). in use, the device is driven into aligned holes in the masonry and the item, so that the flange (19) contacts the outer surface of the item and the zone (16) breaks away from the zone (15). When fully driven in, the head (13) of the device is received against the zone (16) in a countersink in the item, whilst the ribs (17) grip the interior of the hole in the masonry and the zone (15) is partly in the masonry and partly in the item. <IMAGE>

Description

SPECIFICATION Fixing device for use in masonry This invention relates to fixing devices for use in masonry.

In Patent Specification No. 1540219 there is disclosed and claimed a fixing device comprising a screwed fastening element which is coated with a layer of plastic material, at least over a threaded end portion thereof, the coating having external ribs extending longitudinally of the device, and the arrangement being such that in use the fastening element with its coating can be driven into a prepared hole in masonry, the size of the hole being smaller than the overall size of the coated screw.

This type of device is very convenient to use since it avoids the laborious task of screwing the screw in, as is necessary with the type of fixing in which a plug is pushed into the hole and the screw is screwed into the plug to expand it. With the arrangement of the above mentioned Patent the ribs become deformed and provide a very secure fixing.

Such fixing devices can be used inter alia to attach various items to walls, such for example as door frames or other structures having significant thickness, so that fairly long screws are needed. With the described fixing devices, the coating may be confined to the threaded end thus avoding the necessity for moulding the plastics material along the whole length, since this is not easily accomplished, by injection moulding or other appropriate process.

When fixing items of substantial thickness, there is therefore a gap surrounding a large part of the length of the shank of the screw and actual security of the item is confined to the engagement of the head of the screw. If the fixing device is fitted in a iess than perfect way, the item may be left loose instead of being securely fixed against the face of the masonry. Alternatively vibration or the weight of the item may allow it to move laterally.

It is the object of this invention to provide a fixing device in which secure fixing of an item to masonry can be well assured.

According to the present invention there is provided a fixing device comprising a screwed fastening element having a threaded end, a plain shank, and a head, the element having a coating of plastics material, the coating defining a first zone, at least over said threaded end, having external ribs extending longitudinally of the device, and a further zone having, at its end nearer to the head of the fastening element, an enlargement, the further zone being moulded in one with the first zone such that the enlargement at its end is initially spaced from the head of the fastening element, the first and further zones of the coating being connected by a severable portion, whereby in use, the further zone can move towards the head of the fastening element as the device is driven into a prepared hole in masonry to secure an item thereto.

According to a further aspect of the invention a method of fixing an item to masonry comprises forming holes in the masonry and in the item, aligning the holes, driving through the item and into the masonry hole a fixing device having a screwed fastening element with a threaded end, a plain shank and a head and a coating of plastics material, the coating defining a first zone. at least over said threaded end, having external ribs extending longitudinally of the device, and a further zone having, at its end nearer to the head of the fastening element, an enlargement the further zone being moulded in one with the first zone such that the enlargement is initially spaced from the head of the fastening element, the first and further zones of the coating being connected by a severable portion, and as the device is driven into the hole in the masonry, the enlargement on the further zone engages on the item to cause this zone to be severed from the remainder of the coating, and finally driving the device into the hole until the head of the fastening element engages the end of the further zone to secure the item to the masonry.

The invention will now be described by way of example with reference to the accompanying drawings in which; Figure 1 is a cross-sectional view of a fixing device constructed in accordance with the invention; Figure 2 is a view showing the fixing device before installation in a hole passing through an item and into masonry; Figure 3 shows the fixing device in partly fitted condition; Figure 4 shows it in a still further partly fitted position; Figure 5 shows the fixing device fully fitted into position, and; Figure 6 is an enlarged scrap view of part of the screw.

Figure 1 shows a fixing device having an elongated screw 10 having a screw threaded end, a plain shank 1 2 and a countersunk type head 1 3. The screw threaded end has a rolled thread. By this process the outside diameter of the screw thread is at least as large, normally larger than that of the plain shank 1 2. The screw thread has a form which includes a major portion 11 a from the extremity of the screw towards the shank of a relatively small pitch, with the apices of the threads reduced from the standard form which would normally be produced by the thread rolling dies. The apices will be formed with somewhat rounded edges. Typically a Whitworth thread form of 1/4 inch nominal size would be suitable.

At the junction with the plain shank there is however a portion of different thread form at 11 b. this is of coarser form, that is having a greater pitch. Typically a Whitworth thread form of larger nominal size, such as 1/2 inch would be suitable. The coarser form portion llb is rolled simultaneously with the main portion 11 a thread. Thread rolling is carried out using die blocks moved transversely. The blocks chosen are, over both the major and further portions 11 a, 1 b for a screw thread larger than conventional for the initial diameter of bar. Preferably the conventional screw threading for a self tapping screw is used. Furthermore the screw threaded portion of the screw has a pointed end.

The head of the screw is of countersink type and includes a socket to accept a cruciform screwdriver. However other head forms can be used as necessary.

Surrounding the screw is a coating of a plastics materials which whilst stiff is yet soft enough to be distorted in a controlled manner. Preferably a synthetic resin plastics material may be used but other appropriate materials including metals may be used. Nylon, polyurethane, polypropylene, or other plastics material may be used. Preferably nylon of the kind usually referred to as high impact nylon is used.

The coating includes three distinct zones 14, 15 and 16. The zone 14 extends over the screw threaded portion 11 of the screw and has four longitudinal external ribs 1 7. At its end this zone has a rounded end projection 1 8 which serves as a lead in as will be described.

The second zone 1 5 is plain cylindrical and has the same outside diameter as that portion of the zone 14 between the ribs 1 7 thereon.

The further zone 1 6 is cylindrical over most of its length but at its end nearer to the head 1 3 of the screw 10 there is an enlargement in the form of an annular flange 1 9. This flange is of. countersink form and if desired this end of the zone 1 6 may have an internal countersink corresponding with the external countersink on the flange 1 9 though this feature is not illustrated.

Connecting the second and further zones 1 5 and 1 6 is a severable portion 20 which as shown in Figure 2 is in the form of a series of tapered tongues the narrower ends of which can break away to allow the second and further zones 1 5 and 1 6 to be separated thus allowing the further zone 1 6 to slide on the plain shank 1 2 of the screw.

Figure 2 shows the fixing device ready for securing an item to a masonry wall. The item which may be for example a door or window frame is in this example made of wood and has a substantial thickness. It is identified at 21 in the drawing. The masonry wall is identified at 22. As shown aligned holes are formed in the item 21 and in the masonry 22.

Preferably the hole in the item 21 has its outer end countersunk as shown. The diameter of the holes in the item 21 and in the masonry 22 are equal to or preferably slightly larger than the diameter of the plain zones 1 5 and 1 6 of the coating of the fixing device but smaller than the overall diameter of the ribbed zone 1 4. A lead into the hole is provided by the projection 1 8 at the end of the first zone 14. The ribs 1 7 on the first zone 1 4 are able to cut through the timber of the item 21 without becoming distorted and this tends to make four grooves in the timber which however will to some extend recover depending upon the hardness and type of the timber.

The fixing device is inserted by applying a suitable tool to the headed end of the screw 10 and driving this by means of hammer blows through the hole in the item 21 and into the hole in the masonry 22. As the fixing device enters the hole in the masonry the ribs become flattened to a greater or lesser degree depending upon the clearance between the hole and the cylindrical surface of the zone 1 4 of the coating. Rib flattening is not accompanied by tearing away of the ribs but instead they widen and form a significant grip in the hole. The extent of interference and the distortion of the ribs is dependent to some extent on the nature of the masonry material into which the fixing device is being driven.

Figure 3 shows the partially inserted device and illustrates how all the zones 14, 1 5 and 1 6 are held together during this part of the operation.

However when the enlargement 1 9 on the further zone 1 6 comes into contact with the outside of the item 21 resistance is offered to the further penetration of the further zone 1 6 into the timber. The severable portion 20 now breaks away so that the first and second zones of the device continue to be driven in towards the bottom of the hole in the masonry 22 but the further zone 1 6 remains behind and slides along the screw 10 as the latter is driven further in.

Figure 5 shows the condition when the screw is driven fully in. The first and second zones are down at the bottom of the hole and the screw head is in contact with the enlargement 19 on the further zone 16. Both the enlargement flange 1 9 and the head 1 3 of the screw can be driven into the countersink in the timber so that the outside of the screw head is flush with the surface of the timber.

To increase the pressure exerted radially by the plastics coating around the screw threaded portions, the screw may be rotated a short way and this causes the plastics material to tend to move along the thread slopes, but in particular the zone around the coarser thread portion 11 b. Very tight fixing in masonry is therefore achieved. Other enlargements may be substituted for the coarser thread form of the portion 11 b, such as an annular plain ridge or separate radially spaced formations.

It will be seen that in the final position the second zone 1 5 of the coating of the device is partly in the masonry and partly in the timber.

This provides a secure support for the timber on the masonry preventing any lateral movement resulting from the gap around the shank of the screw. However this feature may be omitted by shortening the coating by omitting the second zone 1 5 and connecting the further zone 1 6 directly to the first zone 14.

Any form of enlargement suitable for carrying out the desired function may replace the flange 1 9 on the further zone 1 6.

Any form of screw head may be used as desired.

Claims (11)

1. A fixing device comprising a screwed fastening element having a threaded end, a plain shank, and a head, the element having a coating of plastics material, the coating defining a first zone, at least over said threaded end, having external ribs extending longitudinally of the device, and a further zone having, at its end nearer to the head of the fastening element, an enlargement, the further zone being moulded in one with the first zone such that the enlargement at its end is initially spaced from the head of the fastening element, the first and further zones of the coating being connected by a severable portion, whereby in use, the further zone can move towards the head of the fastening element as the device is driven into a prepared hole in masonry to secure an item thereto.

2. A device as claimed in claim 1, wherein the threaded end has a rolled thread, the outer diameter of the thread being at least as large as the diameter of the plain shank.

3. A device as claimed in claim 2, wherein diameter of the thread is larger than that of the plain shank, the screw thread including a major portion extending from the extremity of the screw towards the shank and of a relatively small pitch, and a portion of greater pitch at the junction with the plain shank.

4. A device as claimed in any one of claims 1 to 3, wherein said further zone is cylindrical except at its head and has the same outer diameter as the first zone between said ribs.

5. A device as claimed in claim 4, wherein the severable portion is formed by a series of tapered tongues which can break away at their narrower ends to allow separation of the zones.

6. A device as claimed in any one of claims 1 to 5, wherein the enlargement at the end of said further zone is an annular flange of countersink form.

7. A device as claimed in claim 6, wherein the annular flange has an internal countersink to receive a countersink part of said head, in use.

8. A device as claimed in any one of claims 4 to 7, wherein said first zone has a first part which includes said ribs and a second, cylindrical part, the outer diameter of which is the same as that of said further zone, to which it is joined by said severable portion.

9. A method of fixing an item to masonry comprising forming holes in the masonry and in the item, aligning the holes, driving through the item and into the masonry hole a fixing device having a screwed fastening element with a threaded end, a plain shank and a head and a coating of plastics material, the coating defining a first zone, at least over said threaded end, having external ribs extending longitudinally of the device, and a further zone having, at its end nearer to the head of the fastening element, an enlargement, the further zone being moulded in one with the first zone such that the enlargement is initially spaced from the head of the fastening element, the first and further zones of the coating being connected by a severable portion, and as the device is driven into the hole in the masonry, the enlargement on the further zone engages on the item to cause this zone to be severed from the remainder of the coating, and finally driving the device into the hole until the head of the fastening element engages the end of the further zone to secure the item to the masonry.

10. A method as claimed in claim 9, wherein the aligned holes are each formed with a diameter smaller than the external diameter of said first zone at said ribs.

11. A method as claimed in claim 9 or claim 10, comprising formng the outer end of the hole in the item with a countersink into which the enlargement and the head of the fixing device, in the form of countersinks, are received, so that the outside of the head is flush with an outer surface of the item when the fixing device is fully driven in.

1 2. A method as claimed in any one of claims 9 to 11, wherein the first zone has a first part which includes said ribs and a second, cylindrical part of the same diameter as said further zone, to which it is joined by said severable portion, said second part, in the fully driven in condition of the fixing device, being partly received in the masonry and partly in said item.

1 3. A method as claimed in any one of claims 9 to 12, wherein the screwed fastening element is rotated to increase the pressure exerted radially by said coating of plastics material around said threads.

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

1 5. A method of fixing an item to masonry substantially as hereinbefore described with reference to and as shown in the accompanying drawings.