GB2251311A

GB2251311A - Crack monitoring gauge

Info

Publication number: GB2251311A
Application number: GB9022157A
Authority: GB
Inventors: Roger William Johnson
Original assignee: AVONGARD Ltd; AVONGARD TELLTALE Ltd
Current assignee: AVONGARD Ltd; AVONGARD TELLTALE Ltd
Priority date: 1990-10-11
Filing date: 1990-10-11
Publication date: 1992-07-01
Anticipated expiration: 2010-10-11
Also published as: GB2251311B; GB9022157D0

Abstract

A crack monitoring gauge comprises two plates (10) (12) each having a portion provided with markings and a securing portion (14, 16), whereby the plates can be secured on respective parts of a structure. The portions with the markings are in a mutually sliding overlapping relationship, whereby the relative movement of the markings with respect to each other provides an indication of the relative movement of the parts of the structure. Additionally means (32) for engaging a measuring device e.g. vernier callipers are provided on each plate to allow relative movement to be accurately measured. During mounting the plates are secured together by pins inserted into holes (26) in both plates. <IMAGE>

Description

"CRACK MONITORING GAUGE" The present invention relates to a device for monitoring cracks in buildings.

British Patent No. 1598785 discloses a gauge for the measurement of cracks in buildings, comprising two plates each having a portion provided with markings. At least the first one of these plates has, integral therewith, a securing portion which projects with respect to the portion of that plate which has markings, whereby the plates can be secured one on each side of a crack to be measured with the portions provided with markings in a slidable overlapping relationship. Thus, the movement of the markings with respect to each other provides a direct indication of the movement of the crack.

Where more accurate monitoring of the growth of cracks is required, it is common practice to fix a screw or stud to the wall on opposite sides of the crack. The distance between the studs can then be measured at intervals or when required using either for example, external or internal vernier callipers, the difference between this distance and an initial (datum) measurement providing a highly accurate indication of crack movement.

Accurate measurements may only be needed however from time to time, a visual indication of crack development being adequate for most purposes.

One object of the present invention is to provide a crack monitoring gauge capable of providing both a visual and a highly accurate indication of crack development.

According to one aspect of this invention, a crack monitoring gauge of the kind referred to has on each of the slidably overlapping plates a calliper seat which in the preferred embodiment is in the form of a cylindrical projection or depression, adapted to receive calliper points or fingers.

Important considerations bearing upon the resulting accuracy of a crack monitoring gauge of the kind referred to are firstly the ease with which the gauge can be set and mounted in the zero datum position and the effects of any misalignments and/or prestressing of component parts of the gauge during mounting of the gauge to a wall. The slidably overlapping plates in a conventional gauge are each provided with countersunk holes through which screws are inserted to cooperate with plugs inserted in holes drilled in the wall. It will be understood that in practice there is invariably misalignment between the holes and the plugs so that the slidably overlapping plates of the crack monitoring gauge are rarely mounted in the ideal relative position.

In accordance with another aspect of this invention temporary abutment means are provided to retain the slidably overlapping parts in a predetermined relative position. The temporary abutment means which in a preferred embodiment comprise one or more pegs or the like engaged in holes in both of the parts, can be removed after the gauge has been mounted to the wall bridging the crack, thus leaving the parts free to slide relative to one another.

It will be understood that with the parts of the gauge rigidly tied together along the lines proposed, any misalignment between the securing holes in the gauge parts and the screw fixings will apply strain to the parts of the gauge when the screw fixings are tightened. After release of the temporary abutment means the strain will be relaxed causing an initial displacement of the gauge parts from the zero (datum) position. To avoid this the securing portion of the gauge parts are provided with countersunk slots extending in the direction of relative sliding movement. Thus the gauge can be mounted without applying strain in the direction of movement prior to removal of the temporary abutment means.

It is also preferred to provide a non slip finish on a face of the securing portions of each part intended for contact with the wall. With gauge parts formed from plastics material such as acrylic or preferably polycarbonate material (which is more resilient and durable), a spark finish may be provided on the appropriate faces. In addition to facilitating mounting in so far that the gauge parts can be held without slipping on a smooth wall, such a spark finish provides a good key when as in many instances, the gauge is mounted to the wall by means of an adhesive such as Araldite (RTM).

One embodiment of this invention will now be described by way of example with reference to the accompanying drawings, in which Figure 1 is a plan view of a crack monitoring gauge according to the present invention, and Figure 2 is a cross-section taken on line AA in Figure 1 As will be seen from Figures 1 and 2, the gauge consists of two plate-like parts 10,12 basically similar in shape and each having a securing portions 14,16. The securing portions 14,16 are stepped in opposite directions so that arms 18 and 20 can be overlapped as shown in Figure 2 to permit relative sliding movement of gauge plates 22,24 at the ends of the arms. This substantially rectangular central part of the gauge has markings to indicate the extent of relative movement in mutually perpendicular directions.The upper surface of the lower plate 22 is marked with a grid over a white background and a lower surface of the upper plate 24 is marked with perpendicularly intersecting cursor lines. In the datum position the cursor lines are congruent with the axis of the grid. To retain the two plates 22,24 in this position prior to mounting on a wall, pegs 26 are fitted through holes in each of the plates.

Each securing portion 14,16 is formed with parallel countersunk slots 28 through which screws can be inserted to cooperate with plugs inserted in holes drilled in the wall. The underside of the slots are also countersunk to enable attachment of an adaptor such as described in my co-pending U.K Patent application No.

9016444.3 whereby the gauge can be adapted to extend around internal or external corners. It will be understood that these slots 28 avoid any pre-stressing of the plates as the screws are tightened. The underside of each securing portion 14,16 intended for contact with the wall has a spark finish 30 or other non-slip surface. In addition to preventing the gauge from slipping while marking the wall in preparation for drilling, the spark finish serves to provide a good key if an adhesive such as Araldite (RTM) is to be used as well as or instead of screw fixings.

Metal inserts 32 are fitted in recesses 34 formed in laterally projecting tabs 36 on the securing portions, these inserts having central holes 38 to provide seats for the fingers of a vernier calliper. When it is required to take highly accurate measurements of the growth of a crack, vernier callipers are used to take an initial reading of the distance between the centres 38 of the calliper seats 32, this being an initial (datum) reading. The growth of the crack is indicated by subtracting this distance from subsequent readings which can be logged to provide a record of the growth of the crack.

The above described crack monitoring gauge can thus provide both a visual indication of the growth of the crack sufficiently accurate for most purposes and a highly accurate record of crack growth.

Claims

1. A crack monitoring gauge comprising two plates each having a portion provided with markings and a securing portion, whereby the plates can be secured on respective portions of a structure, the portions with the markings being in a mutually sliding overlapping relationship, whereby the relative movement of the markings with respect to each other provides an indication of the relative movement of the structure portions in which one or each plate is provided with engagement means for engaging a measuring device whereby relative movement of the structure portions can be accurately measured.

2. A crack monitoring gauge according to claim 1 in which the engagement means comprises at least one recess or projection.

3. A crack monitoring gauge according to claim 2 in which the engagement means comprises a recess defined by each plate.

4. A crack monitoring gauge according to claim 1 or 2 in which the recess(s) and/or the projection(s) are formed by the securing portions of the plates.

5. A crack monitoring gauge according to any one of claims 2 to 4 in which the or each recess is adapted to receive means for receiving the measurement device.

6. A crack monitoring gauge according to claim 5 in which the said means is an insert adapted to receive the measuring device.

7. A crack monitoring gauge according to any preceding claim in which the measuring device is an internal or external caliper.

8. A crack monitoring gauge comprising a crack monitoring gauge comprising two plates each having a portion provided with markings and a securing portion, whereby the plates can be secured on respective portions of a structure, the portions with the markings being in a mutually sliding overlapping relationship, whereby the relative movement of the markings with respect to each other provides an indication of the relative movement of the building portions in which a temporary abutment means are provided to retain the slidably overlapping parts in a predetermined relative position when securing the gauge to a structure.

9. A crack monitoring gauge according to claim 8 in which the temporary abutment means comprise at least one peg adapted to engage a recess in one or more portions of the gauge.

10. A crack monitoring gauge according to claim 9 in which the pegs can be removed after the gauge has been mounted to the structure.

11. A crack monitoring gauge according to any preceding claim.

12. A crack monitoring gauge substantially as described herein and with reference to the accompanying drawings.