"TEST TOOL FOR CHECKING THE PROFILE OF A STRUCTURAL COMPONENT AND METHOD FOR TESTING THE CONFORMITY OF A PROFILE OF A STRUCTURAL COMPONENT TO A SPECIFIC TOLERANCE"

Cross-Reference to Related Applications

This Patent Application claims priority from Italian Patent Application No. 102021000012104 filed on May 11, 2021, the entire disclosure of which is incorporated herein by reference.

Technical Field of the Invention

The present invention relates to a test tool for checking the profile of a structural component, in particular a structural component made of composite material for aeronautical use.

The present invention also relates to a method for testing the conformity of a profile of a structural component, in particular a structural component made of composite material for aeronautical use, to a specific tolerance, more precisely to a dimensional twisting tolerance .

State of the Art

Structural components used in the aeronautical field, e.g. airplane fuselages and parts thereof made of composite materials, are known.

Structural components used in the naval or automotive fields, which are also made of composite materials, are also known.

Structural components of the above type, used in the aeronautical, naval or automotive fields, are also known to be made of materials other than composite 2 materials, for example light metal alloys or plastics.

As is known, especially in the aeronautical or aerospace field, structural components made of composite materials are preferred as they guarantee adequate strength and at the same time allow the desired weight limits not to be exceeded.

Therefore, the need for realizing structural components made of composite materials in order to reduce the overall weight of the airplanes has arisen. The use of composite material in fact allows to reduce the overall weight of the airplanes and to obtain at the same time very strong structures.

In the most common solutions, the composite material used consists of untreated fibre material, e.g. carbon fibre, which is generally pre-impregnated with fluid resin according to a well-known process (e.g. by means of the method known as "Resin Transfer Moulding" or RTM).

In particular, each layer made of composite material normally consists of a thermosetting (resin) matrix prepreg reinforced with fibres of various kinds such as carbon fibres, aramid fibres, glass fibres, etc.

In order to produce the structural component, a plurality of layers of said untreated composite material are laminated together. Depending on the shape to be given to the component, the aforesaid lamination takes place by means of a suitably shaped forming tool.

The laminated component is then subjected to a known treatment process by applying high pressure and temperature so as to treat the composite material and to compact the aforesaid layers together.

The need to check whether the structural components 3 produced, whether they are made of composite material or light alloy, are "within tolerance", i.e. the need to check whether the profile of these structural components is in conformity (or in compliance) with a specific tolerance is known.

For example, especially in the case of structural components made of composite materials having an elongated shape along a longitudinal axis, the need to check the conformity of their profile to a dimensional twisting tolerance along the longitudinal axis itself is known.

For this purpose, test systems or tools for checking the profile of a structural component (aeronautical, aerospace, naval or automotive, made of composite material or of light alloy or plastics) are known, which essentially comprise a base defining a support surface for the structural component, and a plurality of weights (or light weights) each having a weight that is well determined and known to the operator.

In use, in order to check whether the profile of a structural component is "within tolerance" of twisting, the operator places the structural component on the base, then he places a plurality of weights at control points arranged at respective distinct positions of the structural component, where these points are spaced from one another with a predetermined and standardized distance.

In particular, for each control point, the operator places as many weights as required to push the structural component completely onto the support surface, i.e. so that one rest surface of the component 4 matches by contact with the support surface.

Therefore, the operator applies, for each control point, a certain control force.

At this point, the operator determines the total weight, i.e. the control force applied, at each point and compares it with a predetermined and standardized threshold value.

If the control force required to completely push the component at a control point is greater than the threshold value, the component is to be discarded, as its profile is not in conformity with the twist tolerance.

Otherwise, the structural component passes the test.

Although functionally sound, the test tools and the relative test methods of the type described above are susceptible to further improvements. In particular, a need felt in the sector to increase the effectiveness and the simplicity of known test tools, to increase the flexibility thereof in terms of application and to minimise the test errors attributable to the operator.

Subject and Summary of the Invention

Aim of the present invention is to realize a test tool for checking the profile of a structural component which is highly reliable and of limited cost, and which enables at least some of the needs specified above and connected to the test tools of the known type to be met.

According to the invention, this aim is achieved by a test tool as claimed in claim 1.

A further aim of the present invention is to provide a method for testing the conformity of a profile of a structural component to a specific tolerance which 5 is highly reliable and of limited cost, and which enables at least some of the needs specified above and connected to the test tools of the known type to be met.

According to the invention, this aim is achieved by a method for testing as claimed in claim 7.

Brief Description of the Drawings

For a better understanding of the present invention, a preferred non-limiting embodiment is described below, purely by way of example and with the aid of the attached drawings, wherein:

Figure 1 is a perspective view, with parts removed for clarity's sake, of a test tool realized according to the present invention;

- Figure 2 is a perspective view, on an enlarged scale and with parts removed for clarity's sake, of a detail of the test tool of Figure 1; and

- Figures 3, 4 and 5 are partially sectioned side views, on an enlarged scale and with parts removed for clarity's sake of a component of the test tool of Figure 1.

Detailed Description of Preferred Embodiments of the

Invention

With reference to the accompanying Figures, 1 denotes as a whole a test tool for checking (or testing or verifying) the profile of a structural component 2, in particular a component 2 made of composite material for aeronautical use, to which the present description will refer explicitly without thereby losing generality.

In fact, the test tool 1 according to the present invention can also be used to check the profile of structural components made of other materials, for example light alloys or polymeric or plastic materials, 6 and which can be used in other fields, for example in the naval, aerospace or automotive fields.

Furthermore, in the present description, "check of the profile" is understood to mean a check of conformity of the profile of the component 2 to a specific tolerance, in particular a twisting tolerance with respect to a longitudinal axis of component 2 itself, without thereby losing generality.

In the example described, the component 2 is defined by a longitudinal element having an elongated shape along a longitudinal axis X and made of composite material.

In particular, the composite material used consists of untreated fibre material, e.g. carbon fibre, which is pre-impregnated with fluid resin according to a process that is known and not described in detail (e.g. by means of the method known as "Resin Transfer Moulding" or RTM).

More specifically, each layer of composite material constituting component 2 consists of a thermosetting (resin) matrix prepreg reinforced with fibres of various kinds such as carbon fibres, aramid fibres, glass fibres, etc.

After lamination, the layers are subjected to a treatment process that is known and not described in detail, by applying high pressure and temperature, so as to treat the composite material and to compact the aforesaid layers together.

Figure 3 shows component 2 under twisting conditions. In particular, the twist extent shown in that Figure is exaggerated for the purposes of understanding the present invention. 7

As can be seen in Figures 1 and 2, the test tool 1 comprises a base 3 defining a support surface 4 for the component 2.

In one embodiment, the support surface 4 is substantially horizontal.

In an alternative embodiment, the support surface 4 is inclined with respect to a horizontal plane by an angle other than 0°, e.g. it is vertical. This configuration is possible thanks to the particular conformation of the test tool 1, which will be shown below.

In the preferred non-limiting example described herein, the base 3 comprises a series of support bodies 5 protruding from the base 3 and having respective rest surfaces for the component 2.

In detail, each support body 5 is defined by an upright protruding vertically from the base 3, the rest surface thereof is an upper surface.

Consequently, the support surface 4 is defined by the set of rest surfaces of all support bodies 5 on which the component 2 to be tested rests.

The test tool 1 further comprises a plurality of force application devices 6 arranged in respective distinct positions along the base 3 at a predetermined distance from one another and each configured to apply, at the respective position, a control force to the component 2 supported by the base 3.

According to this preferred embodiment, each force application device is defined by a lever clamp 6 which can be switched between an open position and a closed position.

Conveniently, each clamp 6 is arranged at a 8 respective support body 5, in particular it is fixed to said support body 5 by means of a bracket 7.

In more detail, each clamp 6 includes a fixed frame 8 mounted on the bracket 7. Therefore, the clamps 6 are mounted to the base 3 by means of the respective frames 8.

Each pair of clamp 6 - support body 5 defines, according to the invention, a control point of the test tool 1, at which it is checked, in use, whether the profile of the component 2 is "within tolerance", i.e. whether it is in conformity with the aforesaid twist tolerance.

Suitably, the control points are spaced from one another by said predetermined distance, which is preferably standardized within said specific tolerance.

Each clamp 6 further comprises an actuation member, in particular a lever mechanism 10, and a tip 11, and is arrangeable, by means of the lever mechanism 10, between:

- an open position, (Figure 3), in which the tip 11 is at a non-zero distance from the support surface 4 and from the structural component 2 resting on it, in use; and

- a closed position (Figures 4 and 5), in which the tip 11 is pressed against the component 2 to apply the aforesaid control force thereon and thus push it completely in abutment against the support surface 4 to check the conformity of the profile to the aforesaid specific tolerance, in particular the twist tolerance.

In other words, each clamp 6 is moved to the closed position to hold the component 2 and press it, thereby and at the relative control point, against the support 9 surface 4 of the base 3 and thus "crush" or "flatten" it against the support surface 4, through the tip 11.

In more detail, the tip 11, pushed by the lever mechanism 10 of the clamp 6, presses the component 2 against the base 3 with a certain control force that is predetermined and standardized within the aforesaid tolerance, as explained below.

According to this non-limiting example, the lever mechanism 10 comprises: a lever 12 manually operable or automatically operable by control of a control unit (not shown) and pivoted to the frame 8; and

- a movable bracket 13 pivoted to the frame 8 and to the lever 12 (at two different points) and carrying the tip 11 according to a manner described below.

In use, the lever 12 is pivotally rotatable (downwards in Figure 3) to cause a pivoted rotation of the bracket 13 (again downwards in Figure 3) with respect to the frame 8, so as to bring the tip 11, initially spaced from the component 2 (Figure 3), to press against the component 2 (Figures 4 and 5).

According to one aspect of the present invention, as seen in Figures 4 and 5, each clamp 6 further comprises:

- a spring member 14 operatively coupled to the tip 11 and compressible by means of the aforesaid pressing of the tip 11 against the component 2; and

- an indicator element 15 carried by the spring member 14, in particular integrally coupled to the spring member 14, having an external surface 16 with at least one distinctive surface feature 17 and movable by compression of the spring member 14 to render the 10 distinctive surface feature 17 detectable or undetectable according to the extent of the control force applied, in use, to the component 2 by means of said pressing of the tip 11.

In particular, the spring member 14 is compressible (by pressing the tip 11 against the component 2 arranged on the support surface 4 and, therefore, by closing the clamp 6) to move the indicator element 15 so that the distinctive surface feature 17 is detectable when the applied control force is lower than a predetermined threshold value, in particular standardized within the aforesaid specific (twist) tolerance, and so that this distinctive surface feature 17 is undetectable when the control force is higher than the threshold value.

In the example described, the spring member 14 is defined by a helical spring. In particular a cylindrical helical spring.

In an alternative embodiment, the spring member 14 could be defined by a pneumatic spring, a hydraulic spring, a magnetic spring, an electromagnetic spring or any other type of elastic means suitable for the purpose.

As is known, the spring member 14 has its own elastic constant which will determine a certain recall force. In practice, this recall force acts on the tip 11 when it is pressed against the component 2 to flatten it against the support surface 4.

Therefore, the recall force defines the control force applied to the component 2 by means of each clamp 6.

Advantageously, it is therefore sufficient to change the spring member 14 in one or more clamps 6 to 11 vary the control force.

As shown in Figures 3, 4 and 5, each clamp 6 comprises:

- a first cup-shaped body 18 having a longitudinal axis Y and carrying axially the spring member 14; and

- a second cup-shaped body defining the indicator element 15, movable with respect to the first cup-shaped body 18, coaxially engaging the latter in a sliding manner and internally receiving the spring member 14 in coaxial coupling.

In detail, the first cup-shaped body 18 is carried by the bracket 13, in particular rigidly, so that a pivoted rotation of the bracket 13 with respect to the frame 8 corresponds to an identical pivoted rotation of the first cup-shaped body 18 with respect to the frame 8. In more detail, the first cup-shaped body 18 has a single axial opening and, on the axially opposite side, an axial wall coupled to the bracket 13 and to which a first end of the spring member 14 is fixed, which at least in an uncompressed condition protrudes from the single opening.

Similarly, the second cup-shaped body or indicator element 15 (it should be noted that these terminologies indicate the same element) is arranged coaxial to the axis Y and has a single axial opening and, on the axially opposite side, an axial wall to which a second end of the spring member 14 is fixed.

In light of the foregoing, the second cup-shaped body 15 axially engages the first cup-shaped body 18 through the single opening of the latter and so that the axial walls of the first cup-shaped body 18 and of the second cup-shaped body 15 are facing one another and 12

"connected" one another by the spring member 14.

Accordingly, the second cup-shaped body 15 is progressively insertable inside the first cup-shaped body 18 by means of the aforesaid compression of the spring member 14, so that the first cup-shaped body 18 covers a portion of said external surface 16 the axial extension thereof depends on the extent of said control force applied, in use, to the component 2 by means of said pressing of the tip 11 (against the component 2 itself resting on the support surface 4).

More specifically, the second cup-shaped body 15, i.e., the indicator element 15, has a first axial end portion 15a, to which the spring member 14 is internally (and axially) coupled and the tip 11 is externally (and axially) fixed, and a second axial end portion 15b with respect to the tip 11.

Advantageously, the distinctive surface feature 17 is placed at the distal portion 15b for axially entering into the first cup-shaped body 18 by the aforesaid compression of the spring member 14 when said control force is higher than the aforesaid predetermined threshold value.

In other words, the distinctive surface feature 17 is placed on the external surface 16 of the indicator element 15, i.e. of the second cup-shaped body 15, so that an excessive compression of the cup-shaped member 14, derived from a control force the extent of which is higher than the predetermined and standardized threshold value, causes the distinctive surface feature 17 to enter into the first cup-shaped body 18, which thereby renders it undetectable.

For example, Figure 4 shows an operating condition 13 in which the control force applied by a clamp 6 on the component 2 to push it completely against the base 3 and "flatten" it against the support surface 4 is lower than the threshold value. In this case, the distinctive surface feature 17 is detectable.

On the contrary, in the operating condition shown in Figure 5, this control force is higher than the threshold value and the excessive compression of the spring member 14, caused by the excessive twisting of the component 2, causes the distinctive surface feature 17 to enter into the first cup-shaped body 18, thus rendering it undetectable.

According to the preferred, non-limiting embodiment described and shown herein, the distinctive surface feature 17 is detectable optically.

In particular, the distinctive surface feature 17 is defined by a chromatic variation with respect to the remaining part of the external surface 16.

In particular, the external surface 16 of the indicator element 15 has a first zone of a certain colour, for example red, and a second zone of another colour, for example green. For example, the end portion 15a is red coloured, while the distal portion 15b is green coloured.

In this case, the green portion, i.e. the entire distal portion 15b, defines the distinctive surface feature 17. So if, after the closure of the clamp 6 and the consequent compression of the spring member 14 caused by the pressing of the tip 11 against the component 2 to flatten it against the support surface 4, the green portion remains detectable optically, then the control force is lower than the threshold value, and the 14 component 2 is within tolerance. If, on the other hand, the green portion completely enters into and is covered by the first cup-shaped body 18, the control force is higher than the threshold value, and the component 2 is to be discarded.

Conveniently, the first cup-shaped body 18 is made of an optically opaque material.

In this way, the detection of the distinctive feature 17 can be carried out optically by an operator, who can therefore easily check whether, once the relative clamp 6 has been placed in the closed position, the control force at that control point is lower or higher than the predetermined and standardized threshold value and, thus, determine whether the profile of the component 2 is in conformity with the tolerance of twisting or not.

According to an alternative embodiment not shown, the distinctive surface feature 17 is defined by a portion of the external surface 16 having a surface machining distinct from the remaining part of the external surface 16 itself.

For example, the distal portion 15b could be knurled and the end portion 15a smooth.

According to a further alternative embodiment, the distinctive surface feature 17 is automatically detectable by an optical sensor.

For example, in such a case the distinctive surface feature 17 could be defined by a zone covered by a coating that is sensitive to ultraviolet or infrared rays and, therefore, automatically detectable by an optical sensor.

According to another alternative embodiment, the 15 distinctive surface feature 17 could be defined by a magnetic zone detectable by an inductive or electromagnetic sensor.

Thus, in such cases, the degree of automation of the process could be increased and, consequently, the possibility of operator error decreased or eliminated altogether .

Furthermore, as mentioned above, the lever mechanism 10 could be operated automatically by control of a control unit, further increasing the degree of automation of the component check process 2.

Advantageously, each clamp 6 comprises an adjusting element 20 operatively coupled to the spring member 14 and operable to adjust the spring member 14 so as to vary a preload thereof when the clamp 6 is arranged in the closed position.

More specifically, the adjusting element comprises an adjusting screw 20 coupled to the first cup-shaped body 18, in particular rigidly fixed to the axial wall of the latter, and operable to adjust a distance of the first cup-shaped body 18 from the base 3 with respect to the axis Y, when the respective clamp 6 is arranged in the closed position.

In more detail, the adjusting screw 20 is coupled to the bracket 13 by means of two nuts 21 and is operable by means of a knob 22, or automatically by means of a special actuator controllable by a control unit, to rotate the screw on itself and cause an axial displacement of the first cup-shaped body 18 relatively to the bracket 13.

Alternatively, the bracket 13 has a threaded hole in which the screw 20 is inserted and coupled. 16

In practice, the adjusting screw 20 is arranged coaxial to the axis Y and is operable to control the distance of the tip 11 from the support surface 4 measured when the clamp 6 is in the closed position.

This results in a variation of the preload of the spring member 14 when the tip 11 is pressed against the component 2 and, therefore, in a test tool 1 that is adjustable and adaptable to components 2 of different thickness.

Thanks to the test tool 1 described above, it is therefore possible to implement a simple and effective method for testing the conformity of the profile of a structural component 2, in particular made of composite material, in which the method comprises the steps of: a) arranging the structural component 2 on a support surface 4; b) applying a control force on a plurality of points spaced at a predetermined distance of the component 2 arranged on the support surface 4 so as to push it completely against the support surface 4 to check the conformity of said profile to said specific tolerance; c) compressing the spring member 14 for each of said points by means of step b) of applying; d) moving, by means of step c) of compressing, the indicator element 15 carried by the spring member 14, for each spring member 14, and having an external surface 16 with at least one distinctive surface feature 17; e) detecting the distinctive surface feature 17 for each of said control points; and f) determining, for each of said control points, 17 whether the control force is lower or higher than a threshold value on the basis of said step e) of detecting.

From an examination of the characteristics of the test tool 1 and the method realized according to the present invention, the advantages that they allow to obtain are evident.

In particular, thanks to the configuration described above, the effectiveness and simplicity of known test tools for checking the conformity of the profile of a structural component 2 to a specific (twist) tolerance has been improved.

The flexibility of these test tools has also been increased: it is in fact sufficient to replace the spring member 14 to modify the control force to be applied, since this modifies the elastic constant of the spring and, therefore, the return force applied by it, by reaction, to the component 2, which defines the control force.

In addition, the adaptability of the system is improved, since, unlike known test tools which use weights to apply the force, the clamps 6 can also apply the force in a horizontal or otherwise inclined direction, i.e. with a vertical or otherwise non horizontal support surface 4, since the spring member 14 is not affected by the force of gravity.

In addition, possible errors in placing and identifying control points by the operator are eliminated, as the clamp 6 are placed at a fixed distance from one another, established by the standard.

In addition, it is no longer necessary to have a plurality of weights of different dimensions and/or 18 weights, which can be easily lost.

Finally, since the clamps 6 can be controlled automatically and the distinctive surface feature 17 can be detected automatically, the degree of automation of the check process is increased.

It is clear that modifications and variations can be made to test tool 1 and to the method for testing described and shown herein without departing from the scope of protection defined by the claims.