Drilling device and drilling method using such a drilling device

Abstract

There is provided a drilling device for drilling a sheet having conical portions, including a tool-holder plate provided with a plurality of rotary drilling spindles with drill bits oriented according to drilling directions parallel to a mean drilling direction, said drilling spindles being distributed in columns configured to be arranged according to an axial direction and in rows configured to be arranged according to a transverse direction at right angles to the axial direction, the device including at least two rows of spindles and at least two columns of spindles, wherein a center-to-center distance between two spindles of a row is different from a center-to-center distance between two spindles of another row.

Claims

1. A drilling device for drilling a sheet having conical portions, comprising: a tool-holder plate provided with a plurality of rotary drilling spindles with drill bits oriented according to drilling directions parallel to a mean drilling direction, said drilling spindles being distributed in columns configured to be arranged according to an axial direction and in rows configured to be arranged according to a transverse direction at right angles to the axial direction; and at least two rows of spindles and at least two columns of spindles, wherein a center-to-center distance between two spindles of a row is different from a center-to-center distance between two spindles of another row, and wherein G is a nominal center-to-center distance between two spindles of a same row in a matrix configuration of the tool-holder plate and E.sub.i is a maximum inter-patch deviation determined for a row L.sub.i which would result from drillings over a conical portion by a matrix configuration of the tool-holder plate, i is an integer number such that i=1 to n, where n is a number of rows of spindles of the tool-holder plate. and a distance between two spindles of a same row i is given by the relationship: $D=G+F_i=G+\frac{k_1}{\left(m-1\right)}*E_i,$ where m corresponds to a number of columns of spindles of the tool-holder plate and k.sub.1 is a constant.

2. The drilling device according to claim 1, wherein the tool-holder plate has first and last rows of spindles, the first row of spindles configured to be arranged on a side of a tapered part having a smallest radius of the sheet to be drilled and the last row of spindles configured to be arranged on a side of the tapered part having a greatest radius of the sheet to be drilled, the center-to-center distance between two spindles increasing from one row to another row between the first and the last rows of spindles.

3. The drilling device according to claim 1, wherein the constant k.sub.1=0.71.

4. The drilling device according to claim 1, wherein a number of rows of spindles is greater than a number of columns of spindles.

5. The drilling device according to claim 1, wherein a number m of columns of spindles is greater than or equal to three, and in a same row of spindles, intermediate spindles arranged between end spindles are offset according to the axial direction in relation to the end spindles.

6. The drilling device according to claim 5, wherein spindles of a same row are arranged according to a circular arc.

7. The drilling device according to claim 6, wherein the circular arc is defined by two end spindles and a vertex point situated equidistant from the two end spindles, the vertex point being offset by a value c, from the two end spindles in the axial direction, the value c, is given by the relationship:
.sub.i=k.sub.2*(E.sub.iE.sub.i1), where k.sub.2 is a constant and E.sub.0=0.

8. The drilling device according to claim 7, wherein the constant k.sub.2=0.17.

9. A method for drilling a sheet having a conical portion using a drilling device according to claim 1, wherein: a form of the conical portion to be drilled is supplied to computation means, the conical portion to be drilled is divided up into bands according to a transverse direction, and then, for at least one band: the tool-holder plate is positioned to drill holes by contiguous zones along the transverse direction by orienting the tool-holder plate in such a way that a row of spindles having a smallest center-to-center distance between spindles is arranged on a side of the sheet to be drilled having a smallest radius.

10. The method according to claim 9, wherein, when drilling holes according to a pattern in a zone, the tool-holder plate is directed between two hole drilling operations according to regular pitches in the axial direction and/or the transverse direction corresponding to the center-to-center distance between holes according to the axial direction and/or the transverse direction.

11. The method according to claim 9, wherein, when drilling holes according to a pattern in a zone, the tool-holder plate is directed between two hole drilling operations according to regular pitches whose spacing in the axial direction lies within a nominal center-to-center distance tolerances between holes and different from a nominal center-to-center distance between holes in the axial direction so as to configure an extension in the axial direction of the zone to be drilled to correct geometrical defects between bands to be drilled.

12. A drilling device for drilling a sheet having conical portions, comprising a tool-holder plate provided with a plurality of rotary drilling spindles with drill bits oriented according to drilling directions parallel to a mean drilling direction, said drilling spindles being distributed in columns configured to be arranged according to an axial direction and in rows configured to be arranged according to a transverse direction at right angles to the axial direction, the device comprising at least two rows of spindles and at least two columns of spindles, wherein a center-to-center distance between two spindles of a row is different from a center-to-center distance between two spindles of another row, and wherein G is a nominal center-to-center distance between two spindles of a same row in a matrix configuration of the tool-holder plate and E.sub.i is a maximum inter-patch deviation determined for a row L.sub.i which would result from drillings over a conical portion by a matrix configuration of the tool-holder plate, i is an integer number such that i=1 to n, where n is a number of rows of spindles of the tool-holder plate, and a distance between two spindles of a same row i is given by the relationship: $D=G+F_i=G+\frac{k_1}{\left(m-1\right)}*E_i,$ where m corresponds to a number of columns of spindles of the tool-holder plate and k.sub.1 is a constant.

Description

(1) Other advantages and features will emerge on reading the description of the following figures, given by way of nonlimiting example.

(2) FIG. 1A is a perspective view of a drilling device facing a sheet to be drilled,

(3) FIG. 1B shows an example of an elementary rectangular pattern for drilling holes in an acoustic sheet,

(4) FIG. 2, according to a front view, an example of a drilling device according to the prior art comprising a matrix distribution of drilling spindles,

(5) FIG. 3 schematically shows a hole drilling pattern produced by a single spindle,

(6) FIG. 4 shows an example of a hole drilling pattern produced by a tool-holder plate comprising 33 spindles according to a matrix arrangement on a planar acoustic sheet,

(7) FIG. 5 shows an example of a hole drilling pattern produced by a tool-holder plate comprising 33 spindles according to a matrix arrangement on a conical acoustic sheet,

(8) FIG. 6 shows a diagram making it possible to determine inter-patch defects,

(9) FIG. 7 shows an example according to a schematic front view of a tool-holder plate according to a first embodiment,

(10) FIG. 8 shows a schematic view in cross section of FIG. 7 according to a central cutting plane PII,

(11) FIG. 9 shows an example according to a schematic front view of a tool-holder plate according to a second embodiment,

(12) FIG. 10 shows a simplified diagram for positioning the central spindles offset in relation to the transverse direction,

(13) FIG. 11 shows an example of sheet portion to be drilled according to a first conventional version with a constant extension according to the axial direction of the patches,

(14) FIG. 12 shows an example of sheet portion to be drilled according to a second version making it possible to adapt the extension according to the axial direction of the patches,

(15) FIGS. 13A and 13B show, according to schematic views, simplified examples of drilling patterns according to the axial direction, namely a first conventional version and a second version making it possible to adapt the axial extension of the patches,

(16) FIGS. 14 and 15 are perspective views of two automated digital carriers on which the drilling device according to the invention can be borne.

(17) In all the figures, the same references apply to the same elements.

(18) For certain specific production aspects, reference can be made to the published patent EP 2 783 777 in the name of the Applicant.

(19) In some figures, a reference is indicated in order to better understand the orientation of the elements in relation to one another.

(20) In the present explanation, the axial direction Z (from bottom to top in the figures), also called station axis which denotes the direction intended to be parallel to the axis of rotation of the engine of the turbojet engine when the sheet to be drilled is mounted on a nacelle with the turbojet engine.

(21) The transverse direction R (also called radial direction) is at right angles (or perpendicular) to the axial direction Z. Since an engine nacelle is of generally cylindrical/tapered form, the transverse direction is therefore at right angles to the axis of the engine of the turbojet engine and at right angles to the axial direction Z.

(22) The embodiments described are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Single features of different embodiments can also be combined to provide other embodiments.

(23) Moreover, in the present explanation, the elements have to be indexed. For example, an element may bear a reference number followed by two indices. It therefore relates to identical elements positioned for example at different points. Thus, a spindle may be referenced by the numeral 3 and the spindle 3a1 means a spindle 3 of row a and column 1.

(24) Referring to FIG. 6 and, naturally, assuming that the planes of the sheet 12 to be drilled are supplied in numerical form to make it possible to design the tool-holder plate 2 in CAD (computed-assisted design) for the drilling device 1.

(25) It is assumed in the context of the present explanation that the sheet 12 as shown in FIG. 1A has a tapered form whose small radius is located at the bottom (seen on the figures page) and the large radius is located at the top (a small diagram of the sheet 12 appears at the top of FIG. 6).

(26) For a more complex sheet 12, consideration is given to designing different tool-holder plates 2 for different zones of the sheet 12 to be able to address, in each zone, the drilling accuracy requirements while having, to the greatest possible extent, the greatest number of spindles 3 in order to drill the greatest possible number of holes in one go.

(27) FIG. 6 shows a diagram making it possible to determine inter-patch defects which would result from the use of a tool-holder plate 2 provided with spindles 3 in matrix as explained in relation to FIGS. 1A to 5. The outlines of the patches Pa and Pb delimit the zones to be drilled ideally, and the outlines of the patches Pa and Pb delimit the zones drilled by a tool-holder plate 2 having a strictly matrix distribution of the spindles 3.

(28) In FIG. 6, the outline of a patch PA has been shown by a square drawn with an alternating line and single dots and the outline of a patch PB has been embodied by a square drawn with an alternating line and double dots.

(29) It is thus possible to determine, for each line L.sub.1 to L.sub.3 an inter-patch defect Ei (i=1, 2 or 3 and corresponding to the index of the line of squares), A being the nominal center-to-center distance between holes.

(30) To reduce the inter-patch defects, as well as the intra-patch defects, the idea of the invention consists in spreading, for each line L.sub.i, the defect according to the transverse direction R while remaining within the center-to-center distance tolerances between holes given by the manufacturer of the nacelle that has to be equipped with a drilled sheet 12.

(31) Thus, FIG. 7 shows an example according to a schematic front view of a tool-holder plate 2 according to a first embodiment and FIG. 8 shows a schematic view in cross section of FIG. 7 according to a central cutting plane PII.

(32) This example is very similar to the tool-holder plate of FIGS. 1A and 2 and differs therefrom by the precise positioning of the spindles 3a1 to 3c3, which is no longer a matrix. Indeed, the center-to-center distance between two spindles 3 of a row a, b or c in the transverse direction is different from the center-to-center distance between two spindles 3 of another row, for example b, c, or a, in the transverse direction R.

(33) To show these differences, FIG. 7 is simplified compared to FIG. 2 and shows a little less detail to focus on these differences of positioning of the spindles 3 of a row in relation to another row.

(34) Thus, the drilling device 1 for drilling a sheet 12 having conical portions comprises a tool-holder plate 2 provided with a plurality of rotary drilling spindles 3a1 to 3c3 with drill bits 4a1 to 4a3 oriented according to drilling directions parallel to a mean drilling direction M-M.

(35) The drilling spindles 3 being distributed on the one hand in columns indexed in the present exemplary embodiment from 1 to 3 and intended to be arranged according to an axial direction Z and on the other hand in rows indexed a, b and c intended to be arranged according to a transverse direction R, at right angles to the axial direction.

(36) The number of rows is at least two, but can for example reach five or seven rows of spindles 3.

(37) The number of columns is at least two, but can for example reach three or five rows of spindles 3.

(38) The tool-holder plate 2 has a first and a last rows of spindles 3. The first row of spindles 3 is intended to be arranged on the side of the tapered part having the smallest radius of the sheet 12 to be drilled and the last row of spindles 3 is intended to be arranged on the side of the tapered part having the greatest diameter of the sheet 12 to be drilled. The center-to-center distance between two spindles increases from one to the adjacent next row between the first and last rows of spindles 3. According to the embodiment of FIG. 7, the first row of spindles 3 corresponds to the row bearing the spindles 3c1 to 3c3 and the last row of spindles 3 corresponds to the row bearing the spindles 3a1 to 3a3.

(39) If G is the nominal center-to-center distance between two spindles 3 of a same row in a matrix configuration of the tool-holder plate 2 (which would be adapted for a planar sheet and in which G is a multiple of the center-to-center distance between the center-to-center distance between holes) and E.sub.i is a maximum inter-patch deviation determined for the row i and resulting from drillings over a conical portion by a matrix configuration, i being an integer number i=1 to n, where n is the number of rows of spindles of the tool-holder plate, the center-to-center distance between two spindles 3 for a tool-holder plate 2 according to the invention as shown in FIG. 7 is given by the relationship:

(40) $D=G+F_i=G+\frac{k_1}{\left(m-1\right)}*E_i$ in which m corresponds to the number of columns of spindles 3 of the tool-holder plate 2 and k.sub.i is a strictly positive constant, notably k.sub.i=0.71.

(41) In the design of the tool-holder plate 2, care is taken to ensure that the term

(42) $\left|\frac{k_1}{\left(m-1\right)}*E_i\right|\frac{\mathrm{IT}}{2}$
with IT being the tolerance interval given by the client.

(43) FIG. 8 is a view in transverse cross section of the drilling device according to the plane PII-PII.

(44) The drilling device 1 further comprises controlled individual displacement means 5a to 5c, controlled by control means 6 for axially displacing, in relation to the tool-holder plate 2, each of the rotary drilling spindles 3a1 to 3c3 according to their respective drilling directions parallel to M-M.

(45) To automatically control the controlled individual displacement means 5a to 5c, the control means 6 comprise computation means 60 which are linked to acquisition means formed so as to be capable of memorizing a digital image of the form of the surface S of the sheet 12 to be drilled, and to position acquisition means capable of memorizing the position of the sheet 12 to be drilled in a predetermined reference frame R.

(46) To ensure the displacement of the tool-holder plate 2 in relation to the sheet to be drilled during the drilling cycle, the tool-holder plate 2 is mounted on a cartesian carrier 11 with five or six axes (FIG. 14) or, as an alternative, on a polar carrier 11 with five or six axes (FIG. 15). The cartesian II and polar 11 carriers are both programmable numerically-controlled machines.

(47) FIG. 9 shows a second embodiment whereby the number of rows of spindles 3 is greater than the number of columns of spindles 3. The drawing is again simplified and the spindles 3 are, as in the other figures, represented by a broken line circle. Indeed, the tool-holder plate 2 here has three columns and seven rows of spindles 3.

(48) FIG. 10 shows yet another embodiment which differs from that of FIG. 7 by the fact that the spindles 3a2, 3b2 and 3c2, called intermediate spindles, are no longer aligned with the spindles 3 of the adjacent columns, that is to say end spindles 3a1, 3b1 and 3c1 on the one hand and 3a3, 3b3 and 3c3 on the other hand, but offset according to the axial direction Z.

(49) More specifically for a tool-holder plate 2 having a number m of columns of spindles 3 greater than or equal to three and in a same row of spindles formed by end spindles and intermediate spindles arranged between the end spindles, the intermediate spindles are offset according to the axial direction Z in relation to the end spindles.

(50) The spindles 3 of a same row are arranged according to a circular arc which can be defined on the one hand by the two end spindles, here for example 3c1 and 3c3, 3b1 and 3b3 or even 3a1 and 3a3 and, on the other hand, by the vertex point of the circular arc which is situated equidistant from the end spindles and offset by a value .sub.i from the end spindles in the axial direction.

(51) In the present exemplary embodiment, the vertex point of the circular arc coincides with the axis of the intermediate spindles, here 3a2, 3b2 and 3c2 respectively, and also with the position of the drill bits 4a2, 4b2 and 4c2.

(52) The offset value .sub.i is given by the relationship:
.sub.i=k.sub.2*(E.sub.iE.sub.i1),

(53) in which k.sub.2 is a constant, in particular k.sub.2=0.17 and E.sub.0=0.

(54) In the case where the tool-holder plate 2 for example comprises four spindles 3, no spindle 3 of a same row is located at the vertex but there are two intermediate spindles 3 which are positioned on the duly defined circular arc and are offset by the same deviation from the line linking the two end spindles 3.

(55) To produce holes in a sheet 12 having a conical portion using a drilling device 1 as defined above, the procedure is as follows.

(56) In a first step, the form of the conical portion to be drilled is supplied to computation means 60.

(57) To establish a drilling plan, the conical portion to be drilled is divided up into bands according to the axial direction Z.

(58) FIG. 11 shows an example of such a band BND which has a form thinned at the center and wider at the ends. This issue arises in particular for sheets having variations in relation to a strict symmetry of revolution. In effect, the nacelles and thus the acoustic sheets 12 are close to a symmetry of revolution, but not exactly. More generally, airplane nacelle parts are of revolution with constant section or of revolution with non-constant section. Furthermore, within these parts, specific zones can be encountered which are of random form (notably the edges of the parts) and which are not of revolution but which belong to a global part having an axis of revolution.

(59) FIG. 11 also shows various patches PA, PB, PC, PD and PE arranged contiguously.

(60) Then, the tool-holder plate 2 is positioned to drill holes by successive patches in the band BND according to patterns by contiguous zones along the transverse direction R.

(61) In FIG. 11, the holes are produced by orienting the tool-holder plate 2 in such a manner that the central plane P1 of the columns of spindles 3 is parallel to the axial direction Z of the sheet 12 to be drilled, the row of spindles L.sub.1 having the smallest center-to-center distance between spindles 3 is arranged on the side of the smallest radius of the tapered part.

(62) After having finished a band, the tool-holder plate 2 is displaced according to the axial direction Z to place it in position for the next band and to recommence the drilling operations.

(63) Then, the method is stopped when the zones to be treated are provided with holes.

(64) FIG. 11 and FIG. 13A show an example of sheet portion to be drilled according to a first conventional version with an axial extension of the patches that is constant.

(65) As can be seen in FIG. 13A, the example relates to a tool-holder plate 2 with n rows of spindles 3, here n=3.

(66) For simplification purposes, it can be considered that the tool-holder plate 2 is identical to that of FIG. 7 for example, but only the spindles 3a1, 3b1 and 3c1 are represented.

(67) B is the nominal center-to-center distance between two holes shown by a cross and i1 is the nominal center-to-center distance between the spindles 3 which is a multiple of B (i1=j*B, with j a natural number>1, typically j lies between 4 and 10), in the present case i1=4*B. Conventionally, it is possible to choose the pitch of displacement of the tool-holder plate 2 in the axial direction Z to be equal to the nominal center-to-center distance B between two holes. In this case, the axial extension of the patches PA to PE is constant and equal to the number of spindles 3 in a column minus a pitch, that is to say, in the present case with m spindles 3 per row:
H.sub.PA=m*i1B=(m*j1)*B.

(68) As can be seen in FIG. 11 in the band, the central patch PC is well placed while PA and PE show a not-inconsiderable deviation .sub.B with the band limit L.sub.B, which leads to inter-band defects which can appear on sheets 12 which follow a symmetry of quasi-revolution. To remedy these inter-band defects, the applicant had the idea that the extension in the axial direction of the patches can be modified within certain limits as shown in FIGS. 12 and 14B.

(69) FIG. 14B is similar to that of FIG. 14A and differs only by the drilling pitches in the axial direction.

(70) Thus, when producing holes for a given patch, it is possible to choose a regular pitch of displacement different from the center-to-center distance between holes, that is to say a pitch B.sub.1B (see FIG. 138B).

(71) In this case:
H.sub.PA=m*i1B.sub.2 with B.sub.2=i1j*B.sub.1

(72) The only additional condition for B.sub.2 is that B.sub.2 must be within the limit of the center-to-center distance tolerances between holes.

(73) In FIG. 13B for example, by choosing B.sub.1>B, the center-to-center distance between the last hole produced by the first spindle 3c1 and the first hole produced by the spindle 3b1 is equal to B.sub.2<B. However, it will be noted that the axial extension of the patch of FIG. 13B is greater than that of FIG. 13A.

(74) Thus, it will be understood that it is possible to adjust the axial extension of the patches and reduce, even eliminate, the inter-band defects.

(75) The concept behind this adaptation of the axial extension is similar to that for the design of the tool-holder plate 2 to reduce or even eliminate the defects linked to the conical form of the sheet 12, that is to say to spread or distribute, for each column, the defect according to the axial direction while remaining within the center-to-center distance tolerances given by the manufacturer of the sheet 12 to be drilled.

(76) According to an embodiment, the method making it possible to adapt the axial extension of the patches can be implemented independently also for a tool-holder plate 2 with matrix-wise distribution of spindles 3. A patent protection could be sought independently for this method.

(77) FIG. 12 is similar to FIG. 11 except that the axial extension according to Z of the various patches PA, PB, PC, PD and PE arranged contiguously is no longer constant and is adapted to the band limits L.sub.B to reduce .sub.B as much as possible while remaining within the limits L.sub.B.

(78) As can be seen in FIG. 12, the inter-band limits L.sub.B can be better observed for the set of patches PA to PE.

(79) It will be understood that, through the features of the invention, it is possible to better observe the specifications for the sheets 12 having portions that are in particular conical. This then makes it possible to contribute to a better efficiency of the acoustic sheet surrounding the turbojet engine and to further reduce the noise emitted thereby.

(80) There is also a gain in efficiency because it is possible to increase the number of spindles 3 for a tool-holder plate 2 and reduce the time needed for drilling.