GB2262148A

GB2262148A - Mounting of rods in masonry holes

Info

Publication number: GB2262148A
Application number: GB9224759A
Authority: GB
Inventors: Mark Howe
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-12-04
Filing date: 1992-11-26
Publication date: 1993-06-09
Anticipated expiration: 2012-11-26
Also published as: GB2262148B; GB9224759D0

Abstract

A bolt (10) is fixed in a masonry hole by means of an encircling coiled spring (12) which is fixed at its inner end to the bolt (10) and releasably connected at its outer end to the bolt (10), the spring (12) being pre-stressed by tightening its coils to reduce its diameter, and then being fixed in the masonry hole by releasing its outer end to allow it to expand. The spring (12) may be welded or glued or mechanically gripped at its inner end onto a fixed nut (18) (or head) of the bolt (10) and at its outer end onto a movable collar (20) which is released by withdrawal from it of a pin (24). Alternatively, the collar (20) is omitted and the outer end of the spring (12) engages the nut (22), and the pin (24) engages slots in bolt (10) and (nut 22). The material of the spring (12) may be of plastics, and of square-section. <IMAGE>

Description

Fixing device The invention relates to a fixing device primarily intended for use as a masonry fixing device but not necessarily restricted to such use.

Fixing devices at present in use sometimes include some form of screw device which needs to be operated to act on wedging members located in a hole in a wall or floor for example. A particular disadvantage of such fixing devices is that the concentrated loading of wedging devices in certain circumstances is disadvantageous.

According to one aspect of the invention, there is provided a method of making a fixing device in which a cylindrical coiled spring which is prestressed by tightening its coils so that they become of smaller diameter is located on an elongate member with one end of said spring fixed with respect to said elongate member and with its other end releasably connected thereto. The step of locating one end of the spring fixedly with respect to said elongate member may involve a welding operation or fixing of the members with the aid of an adhesive.Alternatively, the step of locating the one end of the spring fixedly with respect to the elongate member and/or the step of making the other end of said spring fast with a slidable collar rotatably mounted on said elongate member may be carried out by frictional engagement with a surface of said elongate member and/or said collar of a diameter larger than the internal diameter of the unstressed spring.

According to another aspect of the invention, a fixing device includes an elongate member; a coiled spring the coils of which encircle said elongate member; means for holding one end of said coiled spring non-rotatably with respect to said elongate member; and means for releasably holding the other end of said spring non-rotatably relative to said elongate member when the spring is in a prestressed condition. The coiled spring will preferably be a close coiled spring.

The means for holding the one end of the coiled spring non-rotatably with respect to the elongate member may comprise a collar fixed on said elongate member; said one end of the spring may be fixed to the collar by mechanical interconnection for example. The means for releasably securing said other end of the coiled spring relative to the elongate member may comprise a collar slidably and rotatably mounted on said elongate member, the collar being fast with said other end of the spring and releasably connected to a part fixed to or formed integrally with said elongate member. The collar may be releasably connected to a part fixed to or formed integrally with said elongate member by means of a pin capable of being displaced longitudinally to release said collar.The slidable collar may be made fast with said other end of the spring by mechanical interconnection or by a weld or may be secured thereto by an adhesive for example.

Alternatively, the means for holding the one end of the coiled spring non-rotatably with respect to the elongate member and/or the means by which the slidable collar is fixed to said other end of the spring may be by frictional engagement with a surface of said member and/or collar of a diameter larger than the internal diameter of the unstressed spring.

In order that the invention may be fully understood and readily carried into effect, the same will now be described, by way of example only, with reference to the accompanying drawings, of which:- Figure 1 is a longitudinal section through a fixing device embodying the invention, a spring part being shown in a captive condition, Figure 2 is a view which shows the device to have been inserted into a hole in a masonry block, but with the spring part still in the captive condition, Figure 3 is a view similar to Figure 2 but showing the device after the spring part has been released to be immovably secured in said block, Figure 4 is a view similar to Figure 1 of a slightly modified form of the device, Figure 5 is an end view of the device, looking in the direction of arrow 5 in Figure 4, and Figure 6 is a longitudinal section through a further modified form of fixing device embodying the invention.

Referring now to Figure 1 of the drawings, the fixing device there illustrated includes an elongate rod member 10; a close coiled spring 12 the coils of which encircle the rod member; means, generally indicated 14, holding one end of said spring non-rotatably with respect to said elongate rod member; and means, generally indicated 16, for releasably securing the other end of said spring relative to said elongate rod member.

The means 14 for holding the one end of the spring non-rotatably with respect to the elongate rod member are constituted by a collar 18 to which the endmost coil of the spring is welded, the collar 18 being itself welded to the end of the rod member.

The means 16 for releasably securing the other end of the spring relative to the elongate rod member are constituted by a collar 20 slidably and rotatably mounted on said rod member, said other end of the spring having been welded to the collar 20.

In Figure 1, the collar 20 is shown to be releasably connected to a nut element 22 by means of a pin 24 which extends through aligned holes in the two parts, said nut element engaging a screwthreaded length of the rod member 10. As shown, the pin 24 has a laterally projecting head portion. In the condition in which it is shown in Figure 1, the spring is under load, that is to say it has been wound up so that it has increased in length and has simultaneously been reduced somewhat in diameter. It has increased in length because, being a close coiled spring, its coils have been caused to ride over each other as winding has taken place.

Referring now to Figure 2, this shows the fixing device, in the condition in which it is illustrated in Figure 1, to have been inserted into a hole in a block of masonry. As shown, the device has been inserted into the hole until the laterally projecting head portion of the pin 24 has contacted the face of the masonry block; in this position of the device its inner end is spaced from the bottom of the hole.

In Figure 3 there is illustrated the action required to activate the device so that it becomes fixed in the hole in the masonry block. As shown, the protruding screwthreaded end length of the eldngate rod member has been struck by a hammer to displace the device inwardly. This has caused the pin 24 to be withdrawn from the collar 20, the latter then being free to rotate together with the end of the spring to which it is welded.

The release of the collar has thus allowed the spring to unwind so that it has simultaneously become shorter in length and of increased diameter.

As the spring has unwound, its coils have engaged the cylindrical surfaces of the hole. Any tendency for the device to be withdrawn from the hole increases the tendency for the coils of the spring to unwind further and their external surfaces are caused to dig into the cylindrical surfaces of the hole. The screwthreaded end length of the elongate rod member can therefore be used as part of a clamping arrangement against the exposed face of the masonry block for a variety of purposes.

It will be understood that all the coils of the coil spring will take a substantially equal share in resisting the extraction of the fixing device from the hole in which it has been fixed. Since there is virtually no limit to the length of coil spring which can be used, it will be understood that this is a very significant feature of the device. It can be used, for example, in materials such as breeze block which are not suitable for sustaining concentrated heavy loads. The fact that the load is distributed along the length of the spring will compensate for this drawback of breeze block materials.

The fixing device will also be ideally suitable for fitment in timber and other materials prone to changing their shape and size due to changes in temperature and/or humidity. Any change of shape or size of the hole in which the device is fitted will generally be at least partly taken up by further unwinding or by resilient deformation of the spring coils.

Referring now to Figures 4 and 5, the fixing device there illustrated is basically similar to that described above except that the opposite ends of the coil spring 12 are not welded to the parts of the device to which they are connected. As shown, in this case, one end of the spring is turned through a right angle and engages a slot 26 in the head 28 of a bolt 30 which constitutes the elongate member. The other end of the spring is turned through a right angle and engages a slot 32 in a nut 34 engaging a screwthreaded length of said bolt. (Opposite end portions of the spring encircle respective sleeve portions 36,38 but these have the sole purpose of locating said end portions substantially concentrically on the bolt. In its free condition, the ends of said spring encircle said sleeve portions with a certain amount of radial clearance).The dimensions across corners of both the bolt head and nut are somewhat less than the outside diameter of the spring in its free condition.

A further point of difference is that the pin 24 which is provided to maintain the coil spring in its stressed condition is located in a longitudinal slot in the screwthreaded end length of the bolt and in a complementary slot in the nut 34.

The diameter of the spring wire in this case is substantially the same as (and certainly no greater than) the pitch of the single start thread of the screwthread of the bolt, and the spring and screwthread are both of the same "hand".

It will be understood that in this case, from a free condition of the spring (at which point it has been connected to the nut 34), it has been possible to extend the spring, that is to stress it, by turning the nut to retract it away from the bolt head. In doing this, as in the previous embodiment, the outside diameter of the spring will be reduced sufficiently for the device to be inserted as a close sliding fit into a hole in which it is to be secured. During this prestressing operation there is no tendency for the nut to pull away from the end of the spring because the coils of the spring ride over each other to follow the nut, the endmost coil moving at the same or substantially the same rate of travel as that of the nut.

In use of the fixing device the spring is of course released in the same way as that of the device illustrated in Figures 2 and 3, that is to say by the withdrawal of the pin 24, the nut 34 then being free to rotate together with the end of the spring to which it is connected.

Referring now to Figure 6, the fixing device there illustrated is basically similar to those described above except that the coil spring 12 is made of material of square cross section. In addition, in this case (although it should be noted that the earlier described embodiments could have been made in this way also) the step of fixedly locating one end of the spring with respect to the elongate member 10 and the step of fixedly locating the other end of said spring on the collar 20 have been carried out using the frictional clutch operation of the spring or member concerned, that is - to say, the ability of the spring to be "threaded" onto the member in a direction tending to unwind the spring coils. As shown, in this case the elongate member 10 has a portion 40 adjacent an integral root portion 11 and the collar 20 has a reduced diameter portion 42.The ends of the spring are an interference fit on the respective portions 40 and 42, the arrangement being such that the spring ends have been able to be "threaded" thereon in a direction tending to unwind the spring coils. It will be understood that the subsequent step of pre-winding the spring in order to reduce its diameter between the end portions will have the effect of wedging even more firmly those coils which surround the respective portions 40 and 42.

Various other modifications may be made. For example, it is not essential that the coil spring be made from round or square section wire and in fact it may well be advantageous to make the spring of wire of other non-circular section so that the coils will better dig into the walls of the hole in which the device is being secured. It is not essential that the spring be made of metal; it could for example be made of a tough synthetic plastics material and in this case in particular the ends of the spring may be fixedly located on the collars 18 and 20 (of the embodiment illustrated in Figure 1) by means of a suitable adhesive. Even if the spring is made of metal it may be secured to said collars 18 and 20 by means of a suitable adhesive, for example that available under the trade mark ARALDITE, preferably being first screwthreaded onto said collars in the manner illustrated in Figure 4.

Claims

CLAIMS:

1. A method of making a fixing device, in which a cylindrically coiled spring which is prestressed by tightening its coils so that they become of smaller diameter, is located on an elongate member with one end of said spring fixed with respect to said elongate member and with its other end releasably connected thereto.

2. A method according to claim 1 of making a fixing device, the method including the step of locating one end of the spring fixedly with respect to said elongate member by a welding operation or fixing of the members with the aid of an adhesive.

3. A method according to claim 1 of making a fixing device, the method including the step of locating the one end of the spring fixedly with respect to the elongate member and/or the step of making the other end of said spring fast with a slidable collar rotatably mounted on said elongate member, by frictional engagement with a surface of said elongate member and/or said collar of a diameter larger than the internal diameter of the unstressed spring.

4. A fixing device including an elongate member; a coiled spring the coils of which encircle said elongate member; means for holding one end of said coiled spring non-rotatably with respect to said elongate member; and means for releasably holding the other end of said spring non-rotatably relative to said elongate member when the spring is in a prestressed condition.

5. A fixing device according to claim 4, in which the coiled spring is a close coiled spring.

6. A fixing device according to either one of claims 4 and 5, in which the means for holding the one end of the coiled spring non-rotatably with respect to the elongate member comprise a collar fixed on said elongate member.

7. A fixing device according to claim 6, in which the one end of the spring is fixed to the collar by mechanical interconnection.

8. A fixing device according to any one of claims 4 to 7, in which the means for releasably securing said other end of the coiled spring relative to the elongate member comprise a collar slidably and rotatably mounted on said elongate member, the collar being fast with said other end of the spring and releasably connected to a part fixed to or formed integrally with said elongate member.

9. A fixing device according to claim 8, in which the collar is releasably connected to a part fixed to or formed integrally with said elongate member by means of a pin capable of being displaced longitudinally to release said collar.

10. A fixing device according to either one of claims 8 and 9, in which the slidable collar is fixed to said other end of the spring by mechanical interconnection or by a weld or is secured by an adhesive.

11. A fixing device according to any one of claims 6 to 9, in which the means for holding the one end of the coiled spring non-rotatably with respect to the elongate member and/or the means by which the slidable collar is fixed to said other end of the spring is by frictional engagement with a surface of said elongate member and/or said collar of a diameter larger than the internal diameter of the unstressed spring.

12. A method of making a fixing device, substantially as hereinbefore described.

13. A fixing device constructed, arranged and adapted to be used substantially as hereinbefore described with reference to and as illustrated by Figures 1 to 3 or Figures 4 and 5 or Figure 6 of the accompanying drawings.