GB2257455A

GB2257455A - Jointing device.

Info

Publication number: GB2257455A
Application number: GB9113869A
Authority: GB
Inventors: Michael John Harborow; David Wooster
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-06-27
Filing date: 1991-06-27
Publication date: 1993-01-13
Also published as: GB9113869D0

Abstract

A snap action releasable jointing device has a first shaft 2 with a resilient ball 10 at one end thereof and a second shaft 6 with a socket 12 formed in its core. The socket 12 has a diameter which is substantially the same as that of the ball 10, but the opening 16 to the socket 12 has a lesser diameter. The shafts 2 and 6 may be jointed by forcing the resilient ball 10 into the socket 12 under compression. Preferably the ball is hollow and has slots to enhance its compressibility. The jointing devices of the invention are of use in mounting traffic signposts. <IMAGE>

Description

TITLE Jointing Device DESCRIPTION Technical Field The invention relates to a jointing device, and particularly to a releasable jointing device with snap action, suitable, for example, for holding together sections of a signpost.

Background Art Traffic, such as motor cars, taxiing aircraft and vehicles of all types, is most commonly directed by signs mounted on signposts. The signposts usually consist of a single section or a number of sections which are fastened together. The posts are rigidly fixed, for instance, to the ground. In the unfortunate event that a vehicle collides with the post, the post will not yield, that is absorb impact forces or break, without opposition or reaction, and as a result damage may be caused not only to the post but also to the colliding vehicle. Damage may be reduced by minimising the breaking strength of the post, although the post may then be liable to breaking unnecessarily, and a broken post still has to be replaced.

The Invention The invention provides a releasable jointing device with snap action, having first and second shafts, a resilient ball at an end of the first shaft, and a socket in the core of the second shaft, which first and second shafts are jointed by forcing the ball into the socket through a socket opening having a smaller diameter than the diameter of the ball. The difference between the diameter of the opening and the diameter of the ball determines the force required to release the joint.

The invention can be used for jointing the sections of a signpost. The sign may be mounted on a single vertical post, or may be mounted on a number of vertical posts and supported by further inclined posts.

Each of the shafts is fastened to one of the sections, the shaft preferably being housed in the central hollow core of the post. The joint acts as a focal breaking point in the structure of the post. The joint is strong enough to hold the post sections together, and to ensure that the post can withstand the stresses of everyday effects, such-as wind buffeting, but the joint will release and the sections will break apart when the post is subjected to the force of a colliding vehicle. The yielding of the post minimises damage to the colliding vehicle, and enables the post to be erected immediately following the breakage.

The device is preferably injection moulded from plastics material. The ball may be moulded with a collapsible core so as to be hollow in the finished device.

The ball preferably has a number of slots which enhance the ball's compressibility and flexibility.

A locking mechanism may be provided in order to prevent the shafts rotating relative to one another.

The invention further provides a signpost incorporating a releasable jointing device with snap action.

The Drawings Figure 1 is a perspective view of a releasable locking device according to the invention; Figure 2 is a cross sectional view along the line II - II shown in Figure 1; Figure 3 depicts the result of a collision between a motor car and a signpost incorporating a jointing device according to the invention.

Best Mode With reference to Figures 1 and 2, a releasable locking device has a first shaft 2 and a second shaft 6. Integral with a stub shaft 24 at one end 4 of the first shaft 2 is a ball 10 having a hollow interior 18. Cut through the wall of the ball- 10 are slots (two of which are shown) 20a and 20b. The second shaft 6 has a core 8, and in the core 8 there is a spherical socket 12. The core 8 also has a spacing portion 14 which extends between an end 22 of the shaft 6 and an opening 16 to the socket 12.

The first and second shafts 2 and 6 are jointed by forcing the ball 10 into the socket 12. The ball 10 and the socket 12 have substantially the same diameter, but the diameter of the opening 16 is less than the diameter of the ball 10, the socket 12 having a volume in excess of half the volume of a complete sphere.

The ball 10 and the socket 12 can be locked together by snap action. The ball lo, in being made of plastics material, is resilient and therefore compressible. The compressibility of the ball lo is assisted by the slots 20a and 20b which provide increased flexibility for the wall of the ball 10. The ball 10 is compressed as it is forced through the opening 16 until the centre of the ball 10 passes the opening 16, at which point the ball 10 is able to expand to its original volume, thereby locking the ball 10 in the socket 12 and jointing the first and second shafts 2 and 6 together.

The joint can be released by pulling or levering the first and second shafts 2,6 apart. Applying a force which has a component perpendicular to the common axis of the shafts 2,6, produces a moment, with the region at which the shaft ends 4 and 22 meet acting as the pivot point. The resultant force of the moment acts along the common axis of the shafts 2,6 and tends to separate the shafts 2,6. The shafts 2,6 will separate when the resultant force is sufficient to produce the degree of compression of the ball 10 required to enable the ball 10 to pass through the opening 16. The diameter of the opening 16 therefore determines the force that must be exerted in order to release the joint.

With further reference to Figure 3, a signpost 26 has three tubular sectons 261,262 and 263. The sections 261,262 and 263 are jointed together using the device described with reference to Figures 1 and 2. The shafts 2 and 6 of each of the devices are housed inside the tubular sections 261,262 and 263. The vehicle 28 has collided with the signpost 26. The force of the colliding vehicle, which is exerted perpendicularly to the common axis of the joint shafts 2,6, produces a moment with a resultant force acting along the common axis of the shafts 2,6 and of sufficient magnitude to separate the shafts 2,6. The separation of the shafts 2,6 causes the signpost sections 261,262 to break apart. The diameter of the opening 16 has been determined so that the sections 261,262 will break apart without substantially reacting to or opposing the force of the colliding vehicle, and consequently the damage to the vehicle is minimised. The signpost can be erected again following the collision by jointing the sections 261, 262 back together.

Claims

1. A snap action releasable jointing device comprising first and second shafts, a resilient ball at the end of the first shaft, and a socket in the core of the second shaft, wherein the first and second shafts are jointed by forcing the ball into the socket through a socket opening having a smaller diameter than the diameter of the ball.

2. A device according to claim 1 in which the ball is a hollow ball.

3. A device according to claim 1 or claim 2 in which the ball is provided with one or more slots to enhance its compressibility and flexibility.

4. A device according to any preceding claim, further comprising a locking mechanism suitable to prevent rotation of the shafts relative to one another.

5. A signpost incorporating a device according to any preceding claim.