Measuring device for determining the shortest distance between features in a structure

A measuring device for determining the shortest distance between features in a structure.

This application claims priority to GB Patent Application No. 0918985.3 filed 30 Oct. 2009, the entire contents of which is hereby incorporated by reference.

FIELD OF INVENTION

The present invention relates to a measuring device for determining the shortest distance between features in a structure.

BACKGROUND OF THE INVENTION

During the manufacture of complex structures, such as aircraft, dimension checks are commonly performed on a structure to ensure that it conforms to plan, taking into account manufacturing tolerances. Such dimension checks may be performed using callipers, rules or other devices to take the required measurement from the structure to compare to the corresponding plan. One problem is that such checks may need to be performed in difficult to reach or constricted spaces thus making accurate measurement difficult. For example full sight of the structural elements being measured may not be possible making accurate positioning of a calliper or rule difficult and error prone.

SUMMARY OF THE INVENTION

An embodiment of the invention provides a measuring device for determining the shortest distance between features in a structure, the measuring device comprising:

an elongate body member having a central axis;

a measurement scale provided on the body member parallel to the central axis for providing measurements of distance along the central axis relative to a reference line perpendicular to the central axis;

alignment means arranged for capturing a first feature of a structure so as to centre the first feature on the reference line;

a slide member slidably mounted on the body member for movement along the central axis;

a reference surface provided on the slide member perpendicular to the central axis and arranged for engagement with a surface of a second feature of the structure;

indicator means provided on the slide member and arranged to indicate the distance between the reference line and the reference surface, so that when a first feature is centred by the alignment means on the reference line and the reference surface is engaged with a surface of a second feature, the indicator means indicates on the measurement scale the perpendicular distance between the surface of the second feature and the first feature.

The alignment means may comprise an aperture in the body member arranged to fit to the first feature. The aperture may comprise a pair of surfaces converging towards the reference line, the surfaces being arranged to engage the first feature so as to centre the first feature on the reference line. The surfaces may be orientated at equal angles of convergence to the reference line. The aperture may be arranged to substantially conform to the first feature. The alignment means may comprise a protrusion arranged for capture within the first feature. The protrusion may extend in a direction perpendicular to the central axis and the reference surface. The reference surface and the indicator means may be provided by the same structural element of the slider.

A point reference surface may be provided on the slide member for providing substantially point engagement with a non-linear surface of a third feature of the structure, so that when a first feature is centred by the alignment means on the reference line and the point reference surface is engaged at a given point with a non-linear surface of a third feature, the indicator means indicates the distance on the measuring scale between the point on the non-linear surface of the third feature and the first feature.

The body member may comprise coupling means arranged to couple a rule to the body member and the measurement scale is provided by a rule coupled to the body member using the coupling means. The coupling means may be arranged to enable removal and replacement of the rule. The slide member may comprise resistance means for providing a predetermined degree of resistance to relative movement of the slide member and the body member. The alignment means may be provided by a substantially V-shaped slot in the body member, the body member being cut away behind the V-shaped slot. The rear of the V-shaped slot may form a protrusion arranged for capture within the first feature.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

With reference toFIG. 1, a measuring device101comprises an elongate body member102and a measurement scale103located on the body member102parallel to the long central axis of the body member102. The body member102further comprises alignment means104in the form of a V-shaped aperture formed at one end of the body member102. The alignment means104is arranged to capture a feature105, such as a bolt or rivet, when placed about the feature105. The sides106,107of the alignment means104are arranged to engage and centre the feature105on a notional reference line A perpendicular to the central axis of the body member102. The measurement scale103is arranged to indicate measurements relative to the reference line A. In other words, the measurement scale103is zeroed on the reference line A. In the present embodiment, the sides106,107of the alignment means104are orientated at equal angles relative to the reference line A so that features105of substantially the same cross sectional profile and within a predetermined range of sizes are all automatically centred on the reference line A when captured within the aperture of the alignment means104. For example, a set of features, in the form of rivets, having a range of circular cross-sections, would each be centred automatically on the reference line A.

The measuring device101further comprises a slide member108in the form of a collar mounted around the body member102and arranged to slide along the body member102over the measurement scale103. The slide member108comprises a reference edge109in the form of a lip raised outwardly from the front face of the slide member108adjacent its edge facing the alignment means104. The reference edge109is arranged to provide a reference surface110orientated parallel and perpendicular to the reference line A. The slide member108further comprises indicator means111, which in the present embodiment, is provided by the reference surface110. The indicator means111is arranged to provide an indication of a measurement B on the measurement scale103which is the shortest or perpendicular distance between the reference line A and the reference surface110. Thus, when a first structural feature, such as a rivet, is captured within the alignment means104and the reference surface110is positioned against a linear surface of a second structural feature, such as a girder edge, the indicator means111indicates the perpendicular distance on the measuring scale103between the surface of the second feature and the centre of the first feature.

FIG. 1shows the front face of the measuring device101. With reference toFIG. 2, on the back face of the measuring device101, the slide means108is provided with a further reference means201in the form of a triangular sectioned protrusion extending perpendicularly from the back face of the slide means108. A lead edge202of the reference means201is orientated towards the reference line A and aligned with the indicator means111on the opposite side of the slide means108. The lead edge202is arranged to provide substantially point contact with the surface of a structural feature. In the present embodiment, the reference means201is positioned so as to align the lead edge202with a further reference line C running through the centre of the first structural feature105perpendicular to the reference line A. The position of the reference line C is selected to conform to the actual or average centre of the first feature105. Thus, when a first structural feature, such as a rivet, is captured within the alignment means104and the lead edge202is positioned against a non-linear surface of a third structural feature, such as a curved girder edge, the indicator means111indicates the perpendicular distance on the measuring scale103between the contact point of the lead edge202on the curved surface of the third feature and the centre of the first feature.

FIG. 3is a cross-sectional side view in the direction D of the measuring device101ofFIG. 1showing the reference surface110and lead edge202of the alignment means201both aligned with the indicator edge111for indicating measurements relative to the reference line A.FIG. 4is a cross-sectional end view in the direction E of the measuring device101ofFIG. 1showing the body member102captured within the slide means108. In addition, the reference surface110parallel and perpendicular to the reference line A and the off-centre lead edge202of the alignment means201are also shown.

With reference toFIG. 5, the measuring device101is shown in use in a section of a first aircraft wing panel501. The first aircraft wing panel501comprises a wing cover502to which a linear stringer503has been fixed using rivets504. The linear stringer503comprises a linear edge505and, in the present example, the shortest distance between the linear stringer edge505and the centre of the rivet504is monitored to ensure that the first wing panel501is within predetermined manufacturing tolerances. In order to measure the shortest distance between the linear stringer edge505and the centre of a rivet504, the alignment means104is placed about the rivet504and the slide means108moved to bring the reference surface110into contact with the linear stringer edge505. With the alignment means104and slide means108biased into these positions by the operator, the rivet504is centred on the reference line A and the reference surface110held against the linear stringer edge505. Thus the indicator means111is positioned over the measuring scale103so as to indicate the shortest distance between the centre of the rivet504and the linear stringer edge505.

With reference toFIG. 6, the measuring device101is shown in use in a section of a second aircraft wing panel601. The second aircraft wing panel601comprises a wing cover602to which a curved stringer603has been fixed using rivets604. The curved stringer603comprises a curved edge605and, in the present example, the shortest distance between the curved stringer edge605and the centre of the rivet604is monitored to ensure that the second wing panel601is within predetermined manufacturing tolerances. In order to measure the shortest distance between the curved stringer edge605and the centre of a rivet604, the alignment means104is placed around the rivet604and the slide means108moved to bring the lead edge202of the alignment means201into contact with the curved stringer edge605. With the alignment means104and slide means108biased into these positions by the operator, the rivet604is centred on the reference line A and the lead edge202is held against the curved stringer edge605. Furthermore, the biasing of the alignment means104and slide means108enables the lead edge202to slide along the curved stringer edge605towards its closest position to the centre of the rivet604. Thus the indicator means111is positioned over the measuring scale103so as to indicate the shortest distance between the centre of the rivet604and the curved stringer edge605.

As will be understood by those skilled in the art, the alignment means may be adapted from the V-shaped slot described above so as to be self-centering on other, non-circular profiles. For example, the sides of the alignment means may be arranged at different angles and one or both of them may be convex or concave. The alignment means may be provided by an open or closed aperture arranged to substantially conform to the cross-section of a given structural feature. The alignment means may be provided by a set of protrusions arranged to act together to capture a given structural feature.

In another embodiment, the alignment means is arranged itself to be captured within a structure feature. For example, the alignment means is provided by a triangular protrusion from one side of the body member arranged itself to be captured within a structural feature in the form of a hole. In a further embodiment, the triangular protrusion is provided adjacent the triangular aperture, described above with reference toFIG. 1, and similarly aligned on the line A. The triangular protrusion adjacent the triangular aperture together thus form and angled arm arranged on one side to capture and centre a structural feature, such as a rivet, and on the other side to be captured and thus centre on a structural feature, such as a hole. Such an arrangement also provides an alignment means capable of operating on structural features in constricted spaces. As will be understood by those skilled in the art, the body member or alignment means may be formed or adapted so as to fit within any applicable constricted space such as the space between two structural features so as to enable a measurement to be based on one of the structural features. For example, as shown inFIGS. 5 & 6, the body member or alignment means are formed or adapted so as to fit between two rivets.

As will be understood by those skilled in the art, the lead edge of the reference means may be provided by any suitable structure for providing substantially point contact with the surface of a curved structural feature and also capable of sliding along the curved surface to the point at which the shortest distance between the two relevant features may be measured.

In another embodiment, measuring scales are provided on both sides of the body member. In a further embodiment, the body member is provided with fixing means for fixing a measuring scale, such as a rule, to the body member. The fixing means may be arranged to allow the rule to be permanently or removably fixed to the body member. The fixing means may be arranged to accept a range of one or more commonly available or standard sized rules. Such fixing means may be provided on both sides of the body member.

In another embodiment, the slide means may be provided with means for providing a predetermined resistance to its sliding movement on the body member so that, once a measurement has been taken from a structure, the measuring device is transportable while the taken measurement is maintained. For example, a spring may be provided between the slide means and the body member to bias the slide means and body member into contact with each other and thus provide the required resistance. Alternatively a ratchet or threaded arrangement may be employed to perform a comparable function.

As will be understood by those skilled in the art, the body member and slide means may be formed from any suitable material. For example, the body member may be formed from aluminium and the slider from clear polycarbonate so as not to obscure the measuring scale. The measuring scale may be applied directly to the body member by etching or a suitable printing process. The measuring scale may be provided as a printed label attached directly to the body member.

In another embodiment, the indicator means is provided by separate means from the reference surface thus enabling the indicator means to be positioned elsewhere on the slide means. For example, where the slide means is transparent, the indicator means may be provided by an etched or printed line on the body of the slide means over the measuring scale.

Embodiments of the invention provide a measuring device having alignment means arranged to automatically and repeatably centre on a given structural feature. The alignment means may be arranged to centre on a predetermined range of structural features. The positive location of the measuring device on structural features enables the measuring device to be used for measuring structural elements that may be obscured from direct view or positioned within constricted spaces. The measurements taken by the measuring device may be transported from measuring site. The measuring device is of a relatively simple and inexpensive construction.