GB2289538A

GB2289538A - A device for indicating at a distance,relative movement of adjacent elements of a structure

Info

Publication number: GB2289538A
Application number: GB9409126A
Authority: GB
Inventors: Robin Arthur Warren Elsey
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-05-09
Filing date: 1994-05-09
Publication date: 1995-11-22
Also published as: GB9409126D0

Abstract

A device for visually indicating movement between adjacent members of a structure can be viewed at a distance using low to medium powered binoculars to check if predetermined movement maxima have been exceeded. When one or more of these maxima are exceeded one or more previously hidden indicators (b) come into view. By using different mountings, movement due to either tensile, compressive or shear forces can be monitored. The device employs a mechanism using two thin spring elements which are kept in alignment prior and during fixing, by two pins or buttons (k). Once fixed these alignment devices are removed. One spring element constitutes an indicator plate (a), and the other a trigger plate (d) having a trigger edge (e) cut to preset distances from a datum line (j). Each indicator (b) is connected to a flexible member (c). To set the device, a spring (g) which is part of plate (a) is moved to a position where plate (d) is interposed between spring (g) and plate (c). Element (b) is hidden behind plate (a) and latched down by a tab. In operation, upon relative movement of the respective structure elements, the trigger edge (e) reaches spring (g) which is released to strike element (b) which is then free to travel to a visible position. <IMAGE>

Description

A DEVICE FOR INDICATING AT A DISTANCE, RELATIVE MOVEMENT OF ADJACENT ELEMENTS OF A STRUCTURE The invention here described relates to a range of devices which enable relative movement in a plane parallel to the surface of the device and between adjacent structural elements, to be visually monitored from a distance and by a method which reduces the risk of observer error. Intrinsic to the device is the ability to record if transient maxima as well as sustained movement have exceeded pre-set increments at which indication is required.

It is known that visual fiducial devices exist which are able to give a quantifiable indication of relative movement in any direction between two adjacent structural members as in a crack or join. These devices require close scrutiny in a manner which avoids parallax error.

It is also known that devices exist based on electronic transducers which can be read from a distance. These devices are generally more expensive than both the subject of this invention or the device previously described. In addition transducer based indicators usually require wire connection which is vulnerable to damage. Movement transducers combined with radio transmission are known to be possible but would be expensive and vulnerable to radio interference.

The invention which is the subject of this application and shown in fig. 1 and figs 2a and 2b comprise two major mechanism components fabricated from thin spring quality metal. The indicator plate a) comprises one or more indicator elements b) individually connected to the indicator plate by means of a flexible member c). Each indicator element is capable of being obscured from view until the predetermined movement maxima for that particular indicator element has been exceeded.

In fig. 1 three indicating elements are shown but with only the lower element in the movement indication position.

The second major mechanism component is the trigger plate d) which is basically rectangular and having a trigger edge e) cut or otherwise formed to pre set distance(s) from a datum line drawn between the centres of the register holes or slots j). Register pins or buttons k) retain correct alignment between the two major components and prevent accidental firing of the device before and during installation.

Following installation by adhesive bonding or other forms of fixing between the mounting plates m) and the structual elements being monitored, the pins or buttons k) are removed, allowing the two major mechanism components to move relative to each other in response to the relative movement of the structural elements being monitored.

The device shown in fig. 1 indicates separating movement only. This separating movement is generally caused by tensile forces. The device shown in fig. 1 is designed to tolerate but not indicate movement in other directions which might be caused by compressive or shear forces.

Further embodiments of this invention allow for devices using similar indicating and triggering components fixed to alternative mountings enabling movement due to either compressive or shear forces to be similarly monitored. It is envisioned that to meet some requirements, a single device using the principles described can be fabricated to indicate four directions of movement in a plane parallel to the surface of the device.

A typical example of a suitable triggering mechanism which when fired, allows the obscured indicator disc(s) to become visible at a distance, is shown in figs. 2a and 2b.

To set the device, the beam spring g) which is part of the indicator plate a) is deflected from its unflexed position to a new position where the trigger plate d) can be interposed between the afore mentioned beam spring g) and the top surface of the indicator plate a) To complete the setting procedure the indicator element b) is deflected so that it is hidden behind the indicator plate a) and latched behind the down turned tab h) which is formed at such an angle as to prevent accidental firing due to vibration or other external influence.

In operation when the edge e) of the trigger plate reaches the end of the beam spring g) (due to relative movement of the structure elements to which the device is fixed), the beam spring g) is released to strike the indicator element b) and release it from its retained position. The indicator element b) is then free to travel in an arcuate manner to its unflexed position where it becomes visible as in fig. 2b.

The device allows for the indicating element to be brightly coloured to contrast with the remainder of the indicator plate a) which can be coloured dull black. Alternative finishes for the indicating element are envisioned to enable sensing with a laser or microwave beam.

Claims

1. A structural movement indicator mechanism comprising two spring elements.

2. A structural movement indicator as claimed in 1) with one or more indicating elements visible at a distance and angle by the use of low to medium powered binoculars or telescope, such as to minimise the use of inspection scaffolding, ladders, cherry pickers or hoists.

3. A structural movement indicator as described in 1) and 2) and providing indication of transient movement maxima in excess of those specified.

4. A structural movement indicator designed to provide indication at a distance in harsh environments including under water and which has a memory so that if rendered inoperable by ice, will indicate the presence of movement as soon as the ice is melted either with the application of heat or by an increase in ambient temperature.

5. A structural movement indicator as described capable of being monitored using laser illumination in the visible or infra red parts of the spectrum or by microwave radiation.