A measurement tool and method of determining the depth of a hole

Abstract

Disclosed is a measurement tool for determining the depth of a hole in a tapered component. The tool comprises: a cylindrical shaft having a first end and a second end, and extending along an axis; a

Description

FIELD OF THE INVENTION [1] The present invention relates to a measurement tool, and to a method of determining the depth of a hole in a component In particular it relates to a method of determining the depth of a hole in a tapered component. BACKGROUND OF THE INVENTION [2] During assembly of complex products, for example an aircraft wing, holes are often provided through components in order to allow for bolts or other such fasteners to be passed through the components to allow it to be fixed to another part of the overall structure. It is important to know the depth of these holes (sometimes referred to as bores) in order to maximise efficiency of the assembly process. For example, the most suitable length fastener can be selected for the depth of the hole in question. [3] In some circumstances, the components through which the holes are provided do not have a uniform thickness. For example, the hole may be formed in a part of a component that tapers. Determining the depth of the hole in a tapered component is not always easy, and imprecise or estimated depths may cause difficulties in the assembly process, for example by the selection of a suboptimal sized fastener. [4] The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved measurement tool and method for determining the depth of a hole in a tapered component. SUMMARY OF THE INVENTION [5] A first aspect of the invention provides a measurement tool for determining the depth of a hole in a tapered component. The tool comprises: a cylindrical shaft having a first end and a second end, and extending along an axis; a first cylindrical section having a diameter greater than that of the shaft; a second cylindrical section having a diameter greater than that of the shaft and also greater than that of the first cylindrical section; the first and second cylindrical sections sharing the same axis as the cylindrical shaft, and being at fixed positions along said cylindrical shaft; a first shoulder being formed at the boundary of the shaft and the first cylindrical section, and a second shoulder being formed at the boundary of the shaft and the second cylindrical section; the first cylindrical section being positioned along the cylindrical shaft at a first distance from the first end of the cylindrical shaft, and the second cylindrical section being positioned along the cylindrical shaft at a second distance from the second end of the cylindrical shaft. [6] The first distance and the second distance may be equal. [7] When in use, the cylindrical shaft may be insertable into a hole in a component to be measured. [8] When in use, each of the first distance and the second distance may be greater than the thickness of a component comprising a hole that is to be measured. [9] When in use, the cylindrical shaft may have a diameter which is slightly smaller than the diameter of a hole in a component such that the cylindrical shaft has a sliding fit in the hole.

[10] According to a second aspect of the invention, there is provided a method of determining the depth of a hole in a tapered component. The method comprises the steps: selecting a measurement tool according to the previous statements, the measurement tool being selected such that the shaft diameter is able to be inserted into the hole with a sliding fit; inserting one end of the shaft into the hole until one of the first or second shoulders abuts with a tapered surface of the component, and the inserted end of the shaft protrudes through the other side of the component; measuring a first distance between the protruding end of the shaft, and the surface of the component through which the shaft protrudes; removing the tool from the hole, and then inserting the other end of the shaft into the hole until the other of the one of the first or second shoulders abuts with the tapered surface of the component, and the inserted end of the shaft protrudes through the other side of the component; measuring a second distance between the protruding end of the shaft, and the surface of the component through which the shaft protrudes; using the first and second measured distances to calculate an angle formed between the abutting shoulder and the tapered surface; then using the calculated angle and one of the first or second measured distances to further calculate the depth of the hole.

[11] The method may further comprise a second step of calculating the depth of the hole using the other of the first or second measured distances and then taking the average of the two calculated depth measurements.

[12] The step of calculating an angle formed between the abutting shoulder and the tapered surface may comprise calculating the step of an equivalent angle.

[13] It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[14] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[15] Figures 1A and 1B show perspective views of a measurement tool in two different orientations;

[16] Figure 1C shows a cross section through the measurement tool of Figures 1A and 1B;

[17] Figure 2 is a flow diagram showing the steps of a method of determining the depth of a hole in a tapered component;

[18] Figures 3A, 3B and 3C show cross-sectional views through the measurement tool of Figures 1A, 1B and 1C and a tapered component at different stages of the method of Figure 2;

[19] Figure 4 shows a close up exaggerated schematic view of part of Figure 3C; and

[20] Figure 5 shows a close up exaggerated schematic view of part of Figure 3B. DETAILED DESCRIPTION OF EMBODIMENT(S)

[21] Figures 1A and 1B show perspective views of a measurement tool 1 for determining the depth of a hole in a tapered component in two different orientations. Figure 1 C shows a cross section through the measurement tool of Figures 1A and 1B through the rotational axis X. The measurement tool 1 comprises a cylindrical shaft 2 having a first end 4 and a second end 6. The shaft 2 extends along axis X.

[22] The measurement tool 1 further comprises a first cylindrical section 8 and a second cylindrical section 12, both of which share the same rotational axis X as the shaft. The first cylindrical section 8 has a diameter twice the radius C, and the second cylindrical section 12 has a diameter twice the radius B. Both diameters are larger than the diameter of the shaft 2, and the diameter of the second cylindrical section 12 is larger than the diameter of the first cylindrical section 8.

[23] The differences in the diameters of the first and second cylindrical sections 8, 12 and of the shaft 2 mean that a first shoulder 10 is formed at the boundary of the shaft 2 and the first cylindrical section 8, and a second shoulder 14 is formed at the boundary of the shaft 2 and the second cylindrical section 12.

[24] In the embodiment shown in the figures, the first and second cylindrical sections 8, 12 are at fixed positions along the cylindrical shaft 2, such that the first cylindrical section 8 is positioned along the cylindrical shaft 2 at distance A from the first end 4 of the cylindrical shaft 2, and the second cylindrical section 12 is positioned along the cylindrical shaft 2 at a the same distance A from the second end 6 of the cylindrical shaft 2. Whilst it isn’t necessary for these distances to be the same, it will make subsequent calculations easier. However, in alternative embodiments, the distances between each of the ends and its closest shoulder may be different, so long as they are known to the necessary level of accuracy.

[25] It is important that certain measurements of the tool are known to a high degree of accuracy in order to be able to more accurately use the measurement tool 1 to determine the depth of a hole in a tapered component. In particular, the diameters (and therefore radii) of both the first and second cylindrical sections, and the distances between each end of the shaft and its closest shoulder.

[26] Figure 2 shows a flow diagram outlining the steps of a method 200 of determining the depth of a hole in a tapered component. For example, the tapered component could be an aircraft skin panel. In a first step 201, a measurement tool, such as the measurement tool 1 described above, is selected to be used. The most appropriate measurement tool is selected such that the shaft diameter is able to be inserted into the hole with a sliding fit. The method requires the shaft of the measurement tool to be inserted and removed from the hole being measured, and therefore it is important the fit is snug to ensure an accurate measurement and calculation, but that the tool can also be easily removed.

[27] The second step 202 in the method 200 comprises inserting one end of the shaft into the hole until one of the first or second shoulders abuts with a tapered surface of the component, and the inserted end of the shaft protrudes through the other side of the component.

[28] An example of second step 202 using the measurement tool 1 of Figure 1C is depicted in Figure 3A. In the Figure 3A example a component 20 is shown which has a body 22 which tapers, such that it has a tapered surface 26 and a flat surface 28. A hole 24, which could also be described as a bore, is provided in the body 22 such that it extends through the body from the tapered surface 26 to the flat surface 28. The depth D of this hole is the dimension that is to be determined by this method. The second end 6 of the shaft 2, which is the end closest to the second cylindrical section 12, has been selected to be the end that is inserted into the hole 24, as depicted by arrow E. To insert the measurement tool 1 into the hole 24, the axis X of the shaft 2 is aligned with the axis of the hole 24, and then a transformation E along the axis X is made such that the shaft 2 enters into the hole. This transformation E continues the second shoulder 14 abuts with the tapered surface 26 of the component 20. Once the second shoulder 14 abuts with the tapered surface 26 the inserted end 6 of the shaft 2 will protrude through the other side of the component 20, which can be seen in Figure 3B.

[29] In the next step 203, a first distance between the protruding end of the shaft, and the surface of the component through which the shaft protrudes is measured. Figure 3B shows this step in the previous example described in Figure 3A. Here it can be seen that the shoulder 14 is in contact with the tapered surface 26 of the component 20, but due to the taper, an angle 0 is formed between the tapered surface 26 and the shoulder 14. The measurement of step 203 measures the distance H1 between the second end 6 and the surface 28 shown in Figure 3B. This measurement can be done in any of a number of ways which will be well known by a skilled person. For example callipers may be used to measure the distance H1.

[30] The next step 204 of the method 200 of Figure 2 comprises removing the tool from the hole, and then inserting the other end of the shaft into the hole until the other of the one of the first or second shoulders abuts with the tapered surface of the component, and the inserted end of the shaft protrudes through the other side of the component. In the examples being followed in Figure 3A-3C, this would mean removing the measurement tool 1 from the hole, and rotating it by 180°, then inserting first end 4 into the hole 24 and continuing to insert the tool until the first shoulder 10 comes into contact with the tapered surface 26. This configuration is shown in Figure 3C.

[31] The next step 205 is similar to earlier step 203, and comprises measuring a second distance between the protruding end of the shaft, and the surface of the component through which the shaft protrudes. Figure 3C shows this step in the worked example of Figures 3A-3C. Here it can be seen that the shoulder 10 is in contact with the tapered surface 26 of the component 20. And similarly to the previous configuration shown in Figure 3B, the same angle 0 is formed between the tapered surface 26 and the shoulder 10. The measurement of step 205 measures the distance H2 between the first end 4 and the surface 28 shown in Figure 3C. Similarly to the measurement in step 203, this measurement can be done in any of a number of ways which will be well known by a skilled person. For example callipers may be used to measure the distance H2.

[32] Step 206 of the method 200 of Figure 2 comprises using the first and second measured distances H1 and H2 to calculate the angle 9 formed between the abutting shoulders 10,14 and the tapered surface 26. This step is actually carried out by calculating an angle that is equivalent to the angle 9. Figure 4 shows a zoomed in exaggerated schematic view of part of Figure 3C, and more clearly explains how this calculation is made. In Figure 4 we are attempting to calculate angle 9 which we can see is equal to angle a (a = 0). We are able to determine the lengths marked as F and G in Figure 4. Length F is the difference between the radii B and C, therefore: F = B — C

[33] Length G is equivalent to the difference between the amounts the shaft is able to protrude from the surface when the first shoulder 10 abuts the tapered surface 26 compared with when the second shoulder 14 abuts the tapered surface 26, therefore: G = H2 — Hl

[34] Now, trigonometry states that: Opposite Adjacent therefore we can determine that: _ G Tana = — F and -if G\ 0 = a = Tan — \ F J

[35] The next step 207 of the method 200 of Figure 2 comprises then using the calculated angle 9 and one of the first or second measured distances H1 or H2 to further calculate the depth of the hole. Figure 5 shows a zoomed in exaggerated schematic view of part of Figure 3B, and more clearly explains how this calculation is made. In Figure 5 it can easily be seen that: D=J — K and that: J = A - Hl

[36] So the length K must be determined, which again can be done using trigonometry: T an Q = ^-B therefore: K = Tan 0 x B

[37] As such the depth D of the hole 24 in the component 20 can be calculated.

[38] The method 200 shown in Figure 2 shows a further step 208 which is as a dotted arrow and box. Step 208 isn’t mandatory, but is an optional step which may be taken to check the previous calculation, or to provide an averaged value for the depth D of the hole 24 in case of any differences due to tolerances of the measurement tool 1 or the component 1. Step 208 comprises calculating the depth of the hole using the other of the first or second measured distances to that which was previously used in the previous calculation of step 207, and then taking the average of the two calculated depth measurements.

[39] It will be appreciated that in this further step 208, it will be required to use the correct radius dimension as well. So, for example, instead of using the dimensions when the second shoulder 14 abuts the tapered surface as shown in Figure 5, other dimensions will be used for when the first shoulder 10 abuts the tapered surface (using radius C). As such, following the the equations to be used will be: K' = Tan 9 x C where A = H2 + D + K'.

[40] Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

[41] In an alternative embodiment, the first and second cylindrical sections may not be adjacent. In the embodiments described above the cylindrical sections are adjacent and abutting as this makes the tool smaller and easier to manufacture. It can be, for example, easily milled from a single cylindrical piece of material. However, alternative embodiments may have separation between the first and second cylindrical sections. This may be beneficial if the tool is required to have a longer “reach” in order to be insertable into harder to reach holes that need to be measured. In this instance it may be desirable for the shaft to have an extended central part between the cylindrical sections.

[42] The method described above was described such that end 6 is inserted into the hole 24 first, but it will be understood that the tool could be used by inserting end 4 first.

[43] The measurement tool 1 described above has the two exposed shaft portions as being of equal length A, however it will be understood that the same length is not necessarily required. As long as the exact dimensions are known, and used correctly during the calculations, the shaft lengths at each end do not necessarily need to be the same. However having the shafts of equal length does make the calculations easier, and makes it less likely that human errors are made in the subsequent calculations.

[44] The above embodiments are to be understood as illustrative examples of the invention. Equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

[45] It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments.

[46] It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

[47] It should be noted that throughout this specification, “or” should be interpreted as “and / or”.

[48] Although the invention has been described above mainly in the context of assembly of a fixed-wing aircraft application, it may also be advantageously applied to various other applications, including but not limited to applications on vehicles such as helicopters, drones, trains, automobiles and spacecraft.

Claims

1. A measurement tool for determining the depth of a hole in a tapered component, the tool comprising:a cylindrical shaft having a first end and a second end, and extending along an axis;a first cylindrical section having a diameter greater than that of the shaft;a second cylindrical section having a diameter greater than that of the shaft and also greater than that of the first cylindrical section;the first and second cylindrical sections sharing the same axis as the cylindrical shaft, and being at fixed positions along said cylindrical shaft;a first shoulder being formed at the boundary of the shaft and the first cylindrical section, and a second shoulder being formed at the boundary of the shaft and the second cylindrical section;the first cylindrical section being positioned along the cylindrical shaft at a first distance from the first end of the cylindrical shaft, and the second cylindrical section being positioned along the cylindrical shaft at a second distance from the second end of the cylindrical shaft.

2. A measurement tool as claimed in claim 1, wherein the first distance and the second distance are equal.

3. A measurement tool as claimed in claim 1 or claim 2, wherein, when in use, the cylindrical shaft is insertable into a hole in a component to be measured.

4. A measurement tool as claimed in any of the preceding claims, wherein, when in use, each of the first distance and the second distance are greater than the thickness of a component comprising a hole that is to be measured.

5. A measurement tool as claimed in any of the preceding claims, wherein, when in use, the cylindrical shaft has a diameter which is slightly smaller than the diameter of a hole in a component such that the cylindrical shaft has a sliding fit in the hole.

6. A method of determining the depth of a hole in a tapered component, the method comprising the steps:selecting a measurement tool according to any of claims 1 to 5, the measurement tool being selected such that the shaft diameter is able to be inserted into the hole with a sliding fit;inserting one end of the shaft into the hole until one of the first or second shoulders abuts with a tapered surface of the component, and the inserted end of the shaft protrudes through the other side of the component;measuring a first distance between the protruding end of the shaft, and the surface of the component through which the shaft protrudes;removing the tool from the hole, and then inserting the other end of the shaft into the hole until the other of the one of the first or second shoulders abuts with the tapered surface of the component, and the inserted end of the shaft protrudes through the other side of the component;measuring a second distance between the protruding end of the shaft, and the surface of the component through which the shaft protrudes;using the first and second measured distances to calculate an angle formed between the abutting shoulder and the tapered surface;then using the calculated angle and one of the first or second measured distances to further calculate the depth of the hole.

7. A method of determining the depth of a hole in a tapered component as claimed in claim 6, wherein the method further comprises a second step of calculating the depth of the hole using the other of the first or second measured distances and then taking the average of the two calculated depth measurements.

8. A method of determining the depth of a hole in a tapered component as claimed in claim 6, wherein the step of calculating an angle formed between the abutting shoulder and the tapered surface comprises calculating the step of an equivalent angle.

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