GB2193521A - Yieldable post assembly - Google Patents

Abstract

A yieldable post assembly comprises a post support 2 and a post 1 frangibly coupled to the support by means of bolts 5 having a predetermined breaking stress. Thus the coupling will break upon application to the post of a force in excess of a value established by the predetermined breaking stress. The post assembly may alternatively incorporate mountings 13, 14 secured to the end regions of the post and frangibly coupled together by the bolts 5. <IMAGE>

Description

SPECIFICATION Yieldable post assembly and post mounting This invention relates to yieldable posts and especially to yieldable mountings for posts.

Conventional posts, typically road signposts, are constructed from a rigid steel tube having its lower end region buried in the ground and set in concrete. This construction gives a very rigid unyielding post able to withstand substantial impacts before being damaged or broken. However, this strength may result in serious damage to any vehicle contacting the post and, particularly in collisions involving vehicles hitting posts at speed, causes severe injuries to the occupants and drivers of such vehicles.

Once the post has been damaged beyond reasonable repair and it becomes necessary to replace the post, the construction described above means that post replacement is an expensive and time consuming operation.

In addition, where the need for a sign or a post is for limited but recurrent periods, there is a requirement for a permanent installation allowing a post to be erected or removed quickly and cheaply, whilst still providing a yieldable but secure mounting. Currently available temporary road signs, for example, are very susceptible to vandalism thereby reducing their effectiveness and increasing the expense.

According to the present invention there is provided a yieldable post assembly comprising a post support and a post frangibly coupled to the support by means of bolts having a predetermined breaking stress whereby the coupling will break upon application to the post of a force in excess of a value established by the predetermined breaking stress.

The use of a frangible coupling relying on bolts allows the breaking point of the post to be set at a value greatly below that of the body of the post. In accordance with a preferred embodiment of this invention, however, the breaking point can be set very accurately, by reducing the shank of the bolts to a diameter which determines that the coupling will break before significant damage is caused to a vehicie in collision with the post. Damage to the post is minimised in the collision and repair is simply a matter of replacing the bolts and recoupling the post to the support.

According to the present invention there is also provided a frangible mounting assembly for mounting a post to a post support comprising a first mounting for securing to the lower end regions of the post, a second mounting for securing to the post support, and a plurality of bolts having a predetermined breaking stress and adapted to interconnect the first and second mountings, whereby the mountings are frangibly coupled together but will break apart upon application to the post of a force in excess of a value established by the said predetermined stress.

The mounting assembly allows posts to be erected or removed very quickly whilst still providing a yieldable coupling to limit damage and injury. Such a mounting assembly also provides a convenient way of converting a conventional post or a way of re-erecting posts involved in collisions, thereby obviating the need for the expensive replacement of existing posts or foundations.

The preferred embodiments of the present 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 yieldable post assembly according to this invention; Figure 2 is a sectional view of a frangible mounting assembly for securing a post to a support; and Figure 3 is a sectional view of a bolt for use in the frangible couplings of Fig. 1 or 2.

The post assembly shown in Fig. 1 comprises a tubular post 1 and post support 2, for example of steel, the latter being buried in the ground or set in concrete. Desirably circular flanges 3 and 4 are connected respectively to the lower end of the post 1 and to the support 2, for example by welding.

The frangible coupling is completed by means of connecting bolts 5, preferably three in number and spaced equilaterally around the flanges.

The breaking stress of the coupling is determined by the thickness of the bolts 5 and the number of bolts used. It is advantageous to achieve the required breaking stress of each bolt by reducing the diameter of a portion of the shank 10, as shown in Fig. 3. This allows the breaking stress to be set accurately and ensures the bolt will break across the shank 10. In addition, by using large bolts with reduced shanks, the area of the bolt head 9 and nut 23 bearing on the flanges 3 and 4 is kept as large as possible and the stability of the post 1 is improved.

By way of example, a typical arrangement of three bolts arranged equilaterally around the flanges will require each bolt to have a breaking stress of from 100 to 400 kN/m2 to form the frangible coupling. For example, the coupling may comprise a 6 mm diameter bolt with a reduced shank having a breaking stress of about 100 kN/m2. Alternatively, an 8mm diameter bolt should have the shank reduced so as to have a breaking stress of about 380kN/m2.

Smaller bolts may be employed without reducing the shank of the bolt, but these tend to break somewhat unpredictably across the threaded portion of the bolt. Also, reducing the bolt size reduces the diameter of the bolt head and nut and lowers the stability of the post.

The mounting assembly shown in Fig. 2 comprises an upper mounting 13 and a lower mounting 14 each comprising a flange 15 and 16 and a short tube or collar 17 and 18, respectively connected by welding.

The tubes 17 and 18 have inner diameters similar to the outer diameters of the post and support with which they are to be used. Holes 19 are provided in the walls of the tubes.

These enable the mountings 13 and 14 to be secured to the post and support by rivets or, if the holes are threaded, by set screws 21, as seen in Fig. 2. They can also be secured, although less conveniently, by welding.

To erect a post by using the frangible mounting shown in Fig. 2 a support is firstly fixed in the ground, or an existing post cut to a suitable height. The upper and lower mountings 13 and 14 are then fitted over the lower end of the post 1 and the support 2 respectively and secured. The flanges 15 and 16 are then aligned to enable the bolts 5 to be passed through both flanges and then secured using nuts 23.

To prevent a broken post from rolling into the path of other vehicles following an impact, the post 1 and support 2 may be flexibly connected, for example by a hawser 25 having a first loop 26 passing around the tube 17 or the foot of the post and a second loop 27 passing around the tube 18 or the support.

Claims (16)

1. A yieldable post comprising a post support and a post frangibly coupled to the support by means of bolts having a predetermined breaking stress whereby the coupling will break upon application to the post of a force in excess of a value established by the predetermined breaking stress.

2. An assembly according to claim 1 wherein the bolts have a portion of the shank of reduced diameter which determines the breaking stress of the bolt.

3. An assembly according to claim 1 or 2 wherein the frangible coupling comprises a first mounting secured to the lower end region of the post and a second mounting secured to the post support;

4. An assembly ,according to claim 1, 2 or 3 wherein the frangible coupling comprises an upper flange connected to the lower end of the post and a lower flange connected to the post support, each bolt passing through both flanges.

5. A frangible mounting assembly for mounting a post to a post support comprising a first mounting for securing to the lower end regions of the post, a second mounting for securing to the post support, and a plurality of bolts having a predetermined breaking stress and adapted to interconnect the first and second mountings, whereby the mountings are frangibly coupled together but will break apart upon application to the post of a force in excess of a value established by the said predetermined stress.

6. An assembly according to claim 5 wherein the bolts have a portion of the shank of reduced diameter which predetermines their breaking stress.

7. An assembly according to any of claims 3 to 6 wherein the means for securing the first and/or second mounting comprises a tube or tubes adapted to engage the respective end regions of the post or post support.

8. An assembly according to claim 7 wherein the means for securing the first or second mountings comprises a collar for receiving internally the post or post support.

9. A mounting assembly according to any of claims 5 to 8 wherein the first or second mountings further comprise a flange through which each bolt will pass.

10. An assembly according to any preceding claim wherein the bolts each have shank portion of reduced diameter providing a breaking stress of from 100 to 400 kN/m2.

11. An assembly according to claim 9 wherein the bolts are 6mm bolts with a breaking stress of about 100kN/m2.

12. An assembly according to claim 9 wherein the bolts are 8mm bolts with a breaking stress of about 380 kN/m2.

13. An assembly according to any preceding claim wherein the post is coupled to the post support by means of three bolts equispaced around the post.

14. An assembly according to any preceding claim comprising a flexible connection between the post and the post support, the connection comprising a first loop to extend around the post and a second loop to extend around the post support.

15. An assembly substantially as herein before described with reference to Fig. 1 of the accompanying drawings.

16. An assembly substantially as hereinbefore described with reference to Fig. 2 of the accompanying drawings.

16. An assembly substantially as herein before described with reference to Fig. 2 of the accompanying drawings.

CLAIMS Amendments to the claims have been filed, and have the following effect: Claims 1-16 above have been deleted or textually amended.

New or textually amended claims have been filed as follows:

1. A yieldable post assembly comprising a post support and a post frangibly coupled to the support by means of bolts having a predetermined breaking stress whereby the coupling will break upon application to the post of a force in excess of a value established by the predetermined breaking stress.

2. An assembly according to claim 1 wherein the bolts have a portion of the shank of reduced diameter which determines the breaking stress of the bolt.

3. An assembly according to claim 1 or 2 wherein the frangible coupling comprises a first mounting secured to the lower end region of the post and a second mounting secured to the post support.

4. An assembly according to claim 1, 2 or 3 wherein the frangible coupling comprises an upper flange connected to the lower end of the post and a lower flange connected to the post support, each bolt passing through both flanges.

5. A frangible mounting assembly for mounting a post to a post support comprising a first mounting for securing to the lower end regions of the post, a second mounting for securing to the post support, and a plurality of bolts having a predetermined breaking stress and adapted to interconnect the first and second mountings, whereby the mountings are frangibly coupled together but will break apart upon application to the post of a force in excess of a value established by the said predetermined stress.

6. An assembly according to claim 5 wherein the bolts have a portion of the shank of reduced diameter which predetermines their breaking stress.

7. An assembly according to any of claims 3 to 6 wherein the means for securing the first and/or second mounting comprises a tube or tubes adapted to engage the respective end regions of the post or post support.

8. An assembly according to claim 7 wherein the means for securing the first and/or second mountings comprises a collar for receiving internally the post or post support.

9. A mounting assembly according to any of claims 5 to 8 wherein the first and/or second mountings further comprise a flange through which each bolt will pass.

10. An assembly according to any preceding claim wherein the bolts each have a shank portion of reduced diameter providing a breaking stress of from 100 to 400 kN/m2.

11. An assembly according to claim 10 wherein the bolts are 6mm bolts with a breaking stress of about 100 kN/m2.

12. An assembly according to claim 10 wherein the bolts are 8mm bolts with a breaking stress of about 380 kN/m2.

13. An assembly according to any preceding claim wherein the post is coupled to the post support by means of three bolts equispaced around the post.

14. An assembly according to any preceding claim comprising a flexible connection between the post and the post support, the connection comprising a first loop to extend around the post and a second loop to extend around the post support.

15. An assembly substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawings.