Method for machining a casing of an aircraft turboshaft engine and scraper tool for implementing said method

Abstract

A scraper tool for deburring an edge of an aircraft turboshaft engine casing is arranged to be mounted in a milling device. The scraper tool includes a body including, on a first end, a connection for the milling device and, on a second end, a deburring module including a turning lathe platelet including at least one cutting edge arranged so as to deburr the casing edge. The deburring module includes a guide adapted to contact the edge to be deburred so as to follow the profile of the edge to be deburred without modifying the orientation of the turning lathe platelet.

Claims

1. A scraper tool for deburring an edge of an aircraft turboshaft engine casing, the scraper tool being mountable in a milling device, the scraper tool comprising: a body including, on a first end, a connector to connect to the milling device and, on a second end, a deburring module comprising a turning lathe platelet including at least one cutting edge to deburr the casing edge, said turning lathe platelet being indexable about a first rotation axis; wherein the deburring module comprises a guide to maintain contact with the casing edge to adjust the turning lathe platelet to variations in a height of the casing edge along an axial direction of the casing, said at least one cutting edge being maintained in contact with the casing edge without indexing of the turning lathe platelet about the first rotation axis when the at least one cutting edge is deburring the casing edge, and the deburring module further comprises a connecting pole having a longitudinal axis, the connecting pole and the longitudinal axis thereof extending from the deburring module into the connector, the turning lathe platelet being mounted to the connecting pole, and a plate rotationally mounted about said connecting pole, the guide being arranged on said plate, and the plate having an axis of rotation that is oriented so as to be coincidental with the longitudinal axis of the connecting pole, and the connector inhibits a transfer of rotation of the milling device to the turning lathe platelet when the at least one cutting edge is deburring the casing edge.

2. The scraper tool according to claim 1, wherein the guide comprises at least two parallel rolls that are provided to come simultaneously into contact with the casing edge.

3. The scraper tool according to claim 2, wherein the connecting pole extends between the at least two parallel rolls.

4. The scraper tool according to claim 3 further comprising at least one spring for calibrating a cutting effort of the turning lathe platelet on the casing edge.

5. The scraper tool according to claim 4, wherein the casing comprises an inside portion and an outside portion, and the at least one cutting edge comprises at least two parallel cutting edges to deburr, respectively, the inside portion and the outside portion of the casing edge.

6. The scraper tool according to claim 3, wherein the casing comprises an inside portion and an outside portion, and the at least one cutting edge comprises at least two parallel cutting edges to deburr, respectively, the inside portion and the outside portion of the casing edge.

7. The scraper tool according to claim 3, wherein the connecting pole is spaced equidistant to each of the at least two parallel rolls.

8. The scraper tool according to claim 2 further comprising at least one spring for calibrating a cutting effort of the turning lathe platelet on the casing edge.

9. The scraper tool according to claim 8, wherein the casing comprises an inside portion and an outside portion, and the at least one cutting edge comprises at least two parallel cutting edges to deburr, respectively, the inside portion and the outside portion of the casing edge.

10. The scraper tool according to claim 2, wherein the casing comprises an inside portion and an outside portion, and the at least one cutting edge comprises at least two parallel cutting edges to deburr, respectively, the inside portion and the outside portion of the casing edge.

11. The scraper tool according to claim 1 further comprising at least one spring for calibrating a cutting effort of the turning lathe platelet on the casing edge.

12. The scraper tool according to claim 11, wherein the casing comprises an inside portion and an outside portion, and the at least one cutting edge comprises at least two parallel cutting edges to deburr, respectively, the inside portion and the outside portion of the casing edge.

13. The scraper tool according to claim 1, wherein the casing comprises an inside portion and an outside portion, and the at least one cutting edge comprises at least two parallel cutting edges to deburr, respectively, the inside portion and the outside portion of the casing edge.

14. The scraper tool according to claim 1, wherein the guide includes at least one roll.

15. The scraper tool according to claim 1, wherein the turning lathe platelet is in a diamond shape.

16. The scraper tool according to claim 1 further comprising at least one spring for calibrating a cutting effort of the turning lathe platelet on the casing edge, and the at least one cutting edge comprises at least two parallel cutting edges that extend in opposite directions from the longitudinal axis of the connecting pole.

17. The scraper tool according to claim 1 further comprising at least one spring, wherein the casing includes an irregular radius of curvature at the casing edge, and the at least one spring maintains contact between the turning lathe platelet and the casing edge during deburring of the casing edge.

18. The scraper tool according to claim 1, wherein the at least one cutting edge is disposed at a cutting angle relative to the casing edge to machine a burr of the casing edge; and the cutting angle of the at least one cutting edge is maintained when the guide is in contact with the casing edge.

19. The scraper tool according to claim 18, wherein said turning lathe platelet is linearly translatable with respect to the body along an axial direction that extends between the first end and the second end, and the deburring module further comprises a limiter for limiting a stroke of the turning lathe platelet along the axial direction.

20. A scraper tool for deburring an edge of an aircraft turboshaft engine casing, the scraper tool being mountable in a milling device, the scraper tool comprising: a body including, on a first end, a connector to connect to the milling device and, on a second end, a deburring module comprising a turning lathe platelet including at least one cutting edge to deburr the casing edge, said turning lathe platelet having a diamond shape and being indexable about a first rotation axis; wherein the deburring module comprises a guide to maintain contact with the casing edge to adjust the turning lathe platelet to variations in a height of the casing edge along an axial direction of the casing, the turning lathe platelet not undergoing indexing about said first rotation when the at least one cutting edge is deburring the casing edge, and the deburring module further comprises a connecting pole having a longitudinal axis, the connecting pole and the longitudinal axis thereof extending from the deburring module into the connector, the turning lathe platelet being mounted to the connecting pole, and a plate rotationally mounted about said connecting pole, the guide being arranged on said plate, and the plate having an axis of rotation that is oriented so as to be coincidental with the longitudinal axis of the connecting pole, and the connector inhibits a transfer of rotation of the milling device to the turning lathe platelet when the at least one cutting edge is deburring the casing edge.

Description

(1) The invention will be better understood with the help of the following description of the invention referring to the accompanying drawings, wherein:

(2) FIG. 1 is a part sectional view of an outside ferrule of an aircraft turboshaft engine exhaust casing extending along an axis W (already commented);

(3) FIG. 2 is perspective view of an exhaust casing and a milling device according to the state of the art upon a milling operation for the axial length of the exhaust casing (already commented);

(4) FIG. 3 is a perspective view of a scraper tool according to a first embodiment of the invention so as to deburr an edge of the exhaust casing;

(5) FIG. 4 is an end view of the scraper tool of FIG. 3;

(6) FIG. 5 is a schematic view of the scraper tool of FIG. 3, a sectional plan V-V being shown;

(7) FIG. 6 is a schematic sectional view according to the section plan V-V of the scraper tool of FIG. 5;

(8) FIG. 7 is a perspective view of the deburring step for the outside upstream edge of the exhaust casing;

(9) FIG. 8 is a perspective view of the deburring step for the inside upstream edge of the exhaust casing;

(10) FIG. 9 is a perspective view of the deburring step for the outside downstream edge of the exhaust casing;

(11) FIG. 10 is a perspective view of the inside downstream edge of the exhaust casing; and

(12) FIG. 11 is a schematic section of a scraper tool according to a second embodiment.

(13) The invention will be presented now as an example for an exhaust casing of an aircraft turboshaft engine, but it goes without saying that the invention applies to any exhaust casing, preferably a circumferential casing built by making several casing sectors integral.

(14) As shown on FIGS. 1 and 2, an exhaust casing 1 of an aircraft turboshaft engine is a metal part with a cylindrical shape axially extending along an axis W and comprising an upstream edge BM and a downstream edge BV. In such example, the exhaust casing 1 is circumferential and is built by making several casing sectors 10 integral. It results therefrom, on one side, that the axial dimension of the exhaust casing 1, i.e. the size along the axis W, is not constant at the casing circumference and, on the other side, that the profile of the edges of the exhaust casing 1 is not regular.

(15) In order to correct the axial dimension of the casing 1, a machining step is carried out on one of the upstream and/or downstream edges so that the distance from the upstream edge to the downstream edge is substantially constant for the circumference of the casing 1. According to the invention, referring to FIG. 2, the axial length of the casing 1 is corrected through a milling device 3 comprising a milling tool 31 for coming in contact with the upstream BM and/or downstream BV edges of the exhaust casing 1. Further on, the exhaust casing 1 and the milling device 3 are shown on FIG. 2 in an orthogonal referential system (X, Y, Z).

(16) Upon milling, the exhaust casing 1 is put in a lying position within a chassis 2, also called machining center, so that the axis W thereof vertically extends along the vertical direction Z. The chassis 2 is here arranged around the axis W thereof so as to present the whole circumference of the edges BM, BV of the exhaust casing 1 before the milling tool 31 of the milling device 1. The rotation speed of the exhaust casing 1 is weak of the order of 1 cm/sec so as to renew the portion of the edge to be deburred by the milling tool without generating horizontal efforts therefor. Such speed is known from the man skilled in the art by the expression milling rotation speed. The milling tool 31 comprises here a milling cutter being driven at a high speed of about 30 m/min; such milling tool is known from the man skilled in the art.

(17) In such example, the upstream edge BM and the downstream edge BV are both machined, thereby leading to a machined material deposit in the vicinity of the upstream BM and downstream BV edges, as well on the inside surface and the outside surface of the exhaust casing 1, such material deposit being known from the man skilled in the art under the meaning burr. In order to eliminate such burrs, it is necessary to machine the outside BM1 and inside BM2 portions of the upstream edge BM as well as the outside BV1 portions and inside BV 2 portions of the downstream edge BV. For sake of simplicity, the burrs will designate further on the inside upstream burr BM2, the outside upstream burr BM 1, the inside downstream burr BV2 and the outside downstream burr BV 1.

(18) According to the invention, the burrs will be eliminated with the help of a scraper tool 4 mounted on the milling device 3, thereby machining the burrs by turning (and not by milling).

(19) Upon a milling operation, the material removal results from the combination of two movements: the rotation of the cutting tool, on the one side, and the advance of the part to be machined on the other side. On the contrary, upon a turning operation, the cutting movement consists in one single movement: either the part to be machined is stationary and the cutting tool is mobile, or the part to be machined is mobile and the cutting tool is stationary.

(20) Scraper Tool 4

(21) The scraper tool 4 will be first of all presented. The use thereof in the machining method according to the invention will be detailed later on.

(22) Referring to FIG. 3, the scraper tool 4 comprises a body 6 longitudinally extending along the direction U, that includes, on a first end, means 5 for connection with a milling device 3 and, on a second end, a deburring module 7 being arranged to machine the burrs.

(23) Connecting Means 5

(24) The connecting means 5 are present in such example under the shape of a tapered connection (known from the man skilled in the art under the designation taper 540) adapted to be connected with the milling device 3 like a conventional milling tool. In other words, the scraper tool 4 according to the invention is adapted to be connected with the milling device 3 instead of the milling tool 31. Such connections means 5 are traditionally adapted to enable the transmission of a milling speed set point from the milling device 3 to the milling tool so that the milling cutter of the milling tool is driven at such milling speed. As for an example, if the milling speed set point is of 5000 revolutions/min for the milling device 3, such set point is transmitted by the tapered connection of the milling tool so that the milling cutter thereof rotates at 5000 revolutions/min.

(25) According to the invention, the connecting means 5 are arranged to impose a nil milling speed, since the scraper tool 4 is not a milling tool, but a turning tool that, by nature, implements a machining step while staying stationary. Thus, differently from the traditional connecting means, the connecting means 5 according to the invention inhibit the milling set points from the milling tool 3.

(26) Deburring Module 7

(27) In this example, in reference to FIGS. 3 to 6, the deburring module 7 comprises a connecting pole 72 extending along the direction U, on which a plane plate 71 is rotationally mounted, here with a polygonal shape, extending perpendicularly to the direction U.

(28) A turning lathe platelet is mounted on a first end of the connection pole 72. The platelet 9 comprises four cutting edges C1-C4 arranged to deburr the inside upstream burr BM2, the outside upstream burr BM1, the inside downstream burr BV2 and the outside downstream burr BV1. As shown schematically on FIG. 6, the turning lathe platelet shows a diamond shape, the edges C1 and C3 as well as the edges C2 and C4 are parallel between them. In the mounted position, the cutting edges C1-C4 partially project from the connection pole 72 as shown on FIG. 4. The turning lathe platelet is here made of aluminum, but it goes without saying that other materials could also be appropriate.

(29) As represented on FIGS. 5 and 6, a second end of the connecting pole 72 extends within the longitudinal body 6 of the scraper tool 4. The longitudinal body 6 comprises limiting means for the stroke of the connecting pole 72 along the direction U having in such example the shape of a front abutment 61 and a rear abutment 62 being integral with the body 6.

(30) Moreover, to apply a calibrated effort on the edge to be deburred, spring means are arranged around the second end of the connecting pole 72 as shown on FIG. 6. The spring means are positioned on either side of a stop ring 73 being integral with the second end of the connection pole 72.

(31) According to a first embodiment of the invention, four damping rods 63, 63 are mounted in the body 6, two first damping rods 63 being mounted on one portion of the stop ring 73, two second damping rods 63 being mounted on another portion of said stop ring 73 as shown on FIG. 6. Each first damping rod 63 is here positioned so as to be in a longitudinal alignment with a second damping rod 63 so as to apply the effort distributed on the stop ring 73.

(32) A damping rod 63, 63 extends longitudinally and comprises a first rectilinear member 631 and a second rectilinear member 632 being connected by a spring 633. In such example, the spring 633 is mounted outside the rectilinear members 632, 633 so as to enable the longitudinal guiding thereof. As shown on FIG. 6, the second rectilinear member 632 is mounted in a abutment on a face of the stop ring 73, whereas the first end 631 is integrally mounted with one of the abutments 61, 62. Preferably, each damping rod 63 comprises adjustment means 64 being arranged to parameterize the constraint of the spring 633 of the damping rod 63. As shown on FIGS. 4 to 6, such adjustment means 64 as formed by one end of the first member 631 of the damping rod 63 projecting from the body 6 of the tool. Quite advantageously, by screwing or unscrewing the projecting end, the axial length of the first member 631 of the damping rod 63 is controlled in the body 6 and the compression length of the spring 633 of the damping rod 63 is then parameterized, thereby modifying the constraint being applied. Thus, for the four damping rods 63, 63, four adjusting means 64 of an easy access and handle are available so as to parameterize with precision the force of the springs 633 on the connecting pole 72 and thus, the cutting force of the tool 4.

(33) As for an example, when the turning lathe platelet 9 is abutted on an inside edge of the exhaust casing 1, the spring means enable to calibrate the bearing force for deburring. In order to push the turning lathe platelet 9 on the inside edge, an effort is exerted on the scraper tool 4 towards the outside of the exhaust casing 1. In other words, the body 6 is driven outside, whereas the connecting pole 72 (being integral with the turning lathe platelet 9) is stationary due to the contact with the edge of the casing 1. It results therefrom a relative movement of the connecting pole 72 with respect to the body 6, thereby increasing the length of the portion of the connecting pole 72 projecting outside the body 6. In this example, the first damping rods 63 limit the movement of the connecting pole 72 by applying an opposite force on the stop ring 73 so as to limit the length of the portion of the connecting pole 72 projecting outside the body 6.

(34) In other words, the first damping rods 63 fulfill a damping function in order to balance the effort applied to the connecting pole 72 and thus the effort applied by the turning lathe platelet 9 on the inside edge. The cutting edge of the turning lathe platelet 9 contacting the edge can thus remove the burr optimally, i.e. without machining said edge in an excessive or insufficient way. An excess machining presents this advantage to exceed the machining tolerance range, thereby requiring an alteration by welding, an insufficient machining having this advantage that a reduced burr remains, but that can still cause injuries for the operators. In the set of the damping rods 63, 63, two damping rods are used for machining while pushing and two other are used for machining while drawing. The springs of the damping rods are selected with respect to the hardness of the material to be machined.

(35) Furthermore, this allows an edge to be deburred, the curvature radius of which varies and is not regular. This is most advantageous for a casing formed from sectors. In this example, the damping rods 63, 63 and the abutments 61, 62 enable a stroke of the connecting pole 72 of about 10 mm so as to overcome the circularity variations of about 1.5 mm for an average exhaust casing.

(36) According to another embodiment of the stroke limitation means for the connecting pole 72 along the direction U, in reference to FIG. 11, the spring means take the shape of a first spring 163 and a second sprint 164 mounted on either side of the stop ring 73 being integral with the second end of the connecting pole 72. Referring to FIG. 11, the first spring 163 is mounted around the connecting pole 72 in the body 6 between a front abutment 161 and the stop ring 73, a second spring 164 being mounted around the connecting pole 72 in the body 6 between the stop ring 73 and a rear abutment 162. Such means are simple to be implemented and manufactured. In order to calibrate the cutting force, it is advantageously possible to control the position of the abutments 161, 162 and thus to modify the constraint of the springs 163, 164.

(37) Guiding Means 8

(38) In order to position the turning lathe platelet 9 at the height of the burr, the deburring module 7 further comprises guiding means 8 arranged to follow the profile of the edge portion to be deburred by guiding the deburring module 7.

(39) Referring to FIGS. 3 to 6, the guiding means 8 take in this example the shape of two rotating cylindrical rolls 81, 82 extending from the plate 71 and the orientation axes B1, B2 extend perpendicularly to the plan defined by said plate 71. In other words, the axes B1, B2 of the rotating rolls 81, 82 are parallel between them and extend along the axis U. Each roll 81, 82 comprises here an inside core being integral with the plate 71 and an outside sheath rotationally mounted on said inside core.

(40) As shown on FIG. 4, the connecting pole 72 extends between the two rolls 81, 82, in this example, at the same distance from the rolls 81, 82. When the rolls 81, 82 abut on a transverse portion of the edge of the exhaust casing 1, i.e. in a vertical abutment along the direction Z, the deburring height is defined with precision to position the turning lathe platelet 9 being integral with the connecting pole 72. The turning lathe platelet 9 is at the good cutting height to machine the burr located between the two rolls 81, 82, i.e. the edge portion being deburred.

(41) As and when the exhaust casing 1 rotates around the axis W thereof, the profile of the curvilinear edge portion located between the two rolls 81, 82 varies. Only the outside sheath of the rolls 81, 82 is driven into rotation, thereby avoiding the driving of the inside core of the rolls 81, 82 as well as the plate 71 of the deburring module 7. It results therefrom a movement of the plate 71 that leads to a vertical movement of the connecting pole 72 without modifying the orientation of the turning lathe platelet 9.

(42) The invention will be now presented, in reference to FIGS. 7 to 10, during the deburring operation for the outside upstream burr BM1 (FIG. 7), the inside upstream burr BM2 (FIG. 8) the outside downstream burr BV1 (FIG. 9) and the inside downstream burr BV2 (FIG. 10).

(43) Implementation Of The Machining

(44) According to the invention, after height setting of the exhaust casing 1 at the right height, while the latter is still in a lying position in the chassis 2, the deburring operation is started by substituting to the milling tool 31 of the milling device 3 the above mentioned scraper tool 4.

(45) The scraper tool 4, which is not a milling tool, does not include any rotating portion for machining, but only a turning lathe platelet 9. In a very advantageous way, the rotation of the chassis 2 is not modified between the milling operation and the deburring operation, thereby advantageously enabling to machine the exhaust casing 1 by turning, the casing 1 being driven into rotation around the axis W at the milling rotation speed, while the scraper tool 4 stays stationary.

(46) As for an example, referring to FIG. 7, the milling device 3 positions the scraper tool 4 on the upstream edge BM in order to machine the outside burr BM1 of the exhaust casing 1. To do so, the cutting edged C1 of the scraper tool 4 is positioned, at least partially, outside the exhaust casing 1 and is abutted on the outside portion of the upstream edge BM1, the springs 63, 64 calibrating the bearing force of the cutting edge C1. Referring to FIG. 7, the turning lathe platelet 9 extends obliquely with respect to the vertical direction Z and is directed inside the exhaust casing 1 upwards.

(47) The rolls 81, 82 are in a vertical abutment along the axis Z on the upstream edge BM so as to follow the profile of said edge BM1 upon the rotation of the exhaust casing 1. As the profile evolves, the height of the rolls 81, 82 along the direction Z is modified, thereby modifying the cutting height of the cutting edge C1.

(48) The upstream outside burr is literally scraped by the cutting edge C1 during the rotation of the exhaust casing 1, which corresponds to a machining by turning. The outside upstream edge BM1 is smooth after deburring, thereby making the manipulation of the exhaust casing 1 easier.

(49) In order to deburr the inside upstream edge BM2 as shown on FIG. 8, the deburring module 7 is rotated within a half revolution around the axis U so that the cutting edge C3 is in contact with the inside upstream edge BM2. Referring to FIG. 8, the turning lathe platelet 9 extends obliquely with respect to the vertical direction Z and is directed outside the exhaust casing 1 upwards.

(50) On a way being similar to the deburring of the outside upstream edge BM1, the deburring by the cutting edge C3 enables to make the inside upstream edge BM2 smooth, thereby making the manipulation of the exhaust casing 1 easier. Moreover, as the inside and outside burrs of a same edge have been removed, it is easy to mount a flange on said edge.

(51) As regards the downstream edge BV, the milling device 3 enables to tilt the scraper tool 4 downwards so as to reach the inside and outside portions of the downstream edge BV as represented on FIGS. 9 and 10, the cutting edges C1, C3 machining respectively the outside downstream edge BV1 and the inside downstream edge BV2.

(52) Once the four burrs being removed, the exhaust casing 1 is removed from the chassis 2 so as to mount for example flanges on said edges.

(53) Thanks to the machining method according to the invention, it is possible to carry out the height setting and deburring operations by means of a same milling device while only changing the machining tool. Moreover, such operations do not require to remove the exhaust casing 1 from the chassis 2, thereby allowing to connect said operations and thus to shorten the overall duration of the machining method for the exhaust casing 1. Furthermore, the injury risk for an operator is eliminated due to the fact that all the operations are carried out by the milling device with no manipulation of the exhaust casing 1 by an operator.