Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B47/00—Constructional features of components specially designed for boring or drilling machines; Accessories therefor
  • B23B47/34—Arrangements for removing chips out of the holes made; Chip- breaking arrangements attached to the tool
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B2220/00—Details of turning, boring or drilling processes
  • B23B2220/36—Turning, boring or drilling at high speeds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B2260/00—Details of constructional elements
  • B23B2260/008—Bearings

Definitions

• the present invention relates to a high speed spindle with forced mechanical vibration assistance.
• the Applicant has developed numerous vibratory drilling solutions in which a cutting tool is subjected during its rotation to axial oscillations.
• one or more of the track (s) has (s) a corrugated surface.
• the bearings are typically formed by balls, the maintenance of the angular position of which relative to each other during rotation is provided by a rotating cage.
• the frequency of the axial oscillations depends on the speed of rotation and the number of undulations seen by the bearings during their rotation.
• the speed of rotation of the tool depends on its cutting speed and its diameter.
• the frequency of the axial oscillations cannot exceed a threshold, which is of the order of approximately 300 Hz, under penalty of generating excessive mechanical forces, in particular due to the inertia of the moving parts.
• the speed of rotation of known vibratory drilling spindles based on a mechanical transformation of the rotational movement into axial vibratory movement, is thus generally limited to 10,000 rpm.
• DE102005002460 presents a drilling tool, comprising an oscillating unit incorporating a “thrust ball” type bearing comprising a single ball rolling between a first and a second ring.
• a “thrust ball” type bearing comprising a single ball rolling between a first and a second ring.
• a calibration spring produces a forward force that keeps the bearing in compression.
• US3088342 describes an oscillating drilling tool comprising a bearing of the “thrust ball” type comprising a single ball.
• the oscillating movement is obtained with a split ring which, taking into account its arrangement and the projection printed on the ball, generates an oscillating movement which has a significant discontinuity. Consequently, such a device cannot operate at high rotational speeds due to mechanical wear and the vibrations generated.
• a housing a drive shaft of a cutting tool, rotatably mounted inside the housing with a possibility of axial displacement relative to the housing, a single ball, interposed axially between a fixed bearing ring relative to the housing and a rolling ring movable with the shaft, one of these rings defining an inclined rolling surface not perpendicular to the axis of rotation of the shaft, such that the rotation of the ball generates an axial oscillation of the tree.
• the use in the invention of a single ball to generate the axial oscillating movement of the shaft makes it possible to maintain the frequency of the axial oscillations at a value compatible with the inertia of the parts to be moved, including for speeds of rotation greater than 10,000 rpm.
• the absence of a rotating cage with the ball reduces heating of the bearing at high rotation speeds.
• the invention allows, if desired, to achieve a compact vibratory drilling spindle, which can replace a conventional spindle without further modification of the machine tool.
• the ball is partially engaged in an annular groove formed on the shaft. This reduces the distance from the axis of its center of gravity and therefore the unbalance associated with its rotation, as well as the bending moment exerted by the ball on the shaft.
• the fixed bearing race is the one which defines the inclined bearing surface.
• the inclined rolling surface is advantageously flat, which makes it possible to produce it very easily with great precision and a good surface condition, which is advantageous for minimizing the friction between the ball and the rolling rings.
• Such an inclined running surface does not have a projection.
• the absence of jerk limits the generation of vibrations and mechanical wear.
• the axial cutting forces are at least partially taken up on the fixed rolling ring relative to the housing.
• the ball is ceramic, which makes it possible to optimize the resistance / density ratio.
• the ball is located at the rear of the spindle. This limits the effect of the bending moment on the guiding quality of the shaft at the tool.
• the spindle preferably comprises two trains of two ball bearings, respectively at the front and at the rear of the spindle. These bearings are preferably angular contact, and flanged.
• the ball is preferably disposed behind the rear axle.
• the bearings are preferably kept centered with a possibility of axial displacement by elastic blades with oriented deformation, of generally annular shape.
• the latter preferably have on their outer circumference fixing lugs fixed relative to the housing and, between them, bearing retaining lugs, the flexibility of the portions of the blades extending between the fixing lugs and the retaining lugs. bearings allowing axial movement of the bearings during axial oscillations of the shaft.
• the use of the blades provides an elegant solution to the problem of ensuring radial rigidity while allowing the axial displacement necessary for the shaft to oscillate axially.
• the blades have significant stiffness in the radial direction, but their low thickness allows them to flex to follow the axial displacement of the bearings.
• the slats can be superimposed to gain radial stiffness, while retaining axial flexibility.
• the bearings can be mounted on bearings indexed in rotation relative to the blades, preferably by pins passing through the blades, the bearings having sectors projecting on their end edge, against which the blades rest, the blades being in contact with the blades. outer rings of the bearings by their retaining tabs. These sectors make it possible to immobilize the retaining tabs of the blades relative to the bearings while maintaining an axial play between the immobilized zones to allow the portions of the blades extending between them to flex in order to allow the axial displacement of the bearings relative to the housing. during axial oscillations of the shaft.
• Flat springs may be present to press the leaves against the outer races of the bearings. These flat springs can be omitted, with the exception of the one or those which may serve as an elastic member to apply the axial preload of the shaft, as explained below.
• the spindle comprises an elastic return member which ensures the return of the shaft to the rear, during the rotation of the ball.
• This axial preload of the shaft towards the rear is advantageously provided by at least one flat spring.
• the spindle can thus comprise at least one flat spring, or even a single flat spring, which exerts a return force towards the rear.
• This flat spring can be located on the front or back of the spindle. The placement at the rear avoids introducing a compressive force over a long rotor length.
• the return force towards the rear of such an elastic member is advantageously maximum when the cutting forces are harmful and relieved when the cutting forces are greater than 0.
• the spindle thus comprises a main tubular spacer, fixed relative to the casing, and fixed positioning rings arranged on either side of G main spacer, the blades having their fixing lugs clamped between G main spacer and the rings. positioning.
• the spindle preferably comprises bearing end rings on either side of the bearings, in which the aforementioned pins are engaged, the flat spring (s) being applied to one end of these end rings, the other end resting against a fixed surface relative to the casing.
• the housing is preferably closed at the rear by an end piece against which rests the bearing ring defining the inclined bearing surface.
• the spindle comprises a peripheral rolling ring, coaxial with the shaft, to take up the centrifugal forces of the ball.
• the absorption of centrifugal forces is particularly advantageous for making holes with rotation speeds greater than 10,000 rpm.
• the dbiiie / dtrajectory ratio is preferably between 1 ⁇ 4 and 1 ⁇ 2, where dbuie denotes the diameter of the ball and d trajectoi ⁇ that of the point of contact of the ball on the inclined rolling surface.
• the subject of the invention is also a machining method, in particular drilling, in which the shaft of a spindle according to the invention is driven at a speed of rotation of at least 10,000 rpm, for example comprised between 15,000 and 30,000 rpm, in particular of the order of 15,000 to 20,000 rpm.
• the subject of the invention is also a machining method, in particular of drilling, in which the shaft of a spindle according to the invention oscillates axially with a vibratory frequency of between 0.4 and 0.6 axial oscillations per revolution. , in particular about 0.5.
• the spindle can undergo a forward movement during the rotation of the shaft, in a conventional manner.
• Figure 1 shows schematically, in perspective, an example of a spindle according to the invention
• Figure 2 is a longitudinal section of the spindle of Figure 1
• FIG. 3 Figure 3 shows in more detail the rear of the spindle
• FIG 4 Figure 4 shows in more detail the front of the spindle
• Figure 5 shows in isolation, in perspective, an elastic blade
• Figure 6 shows in isolation, in perspective, a bearing end ring
• Figure 7 shows in isolation, in perspective, a bearing
• Figure 8 shows, in axial section, the ring with inclined rolling surface
• Figure 9 shows in longitudinal section an alternative embodiment of the spindle.
• the spindle 1 according to the invention, shown in Figures 1 to 4 in particular, comprises a casing 10, preferably metallic, of generally cylindrical shape of revolution about a longitudinal axis X.
• the housing 10 is mounted in a guide and advance mechanism (not shown), known per se, of the machine tool.
• a support 11 fixed to the casing allows said mechanism to axially displace the spindle 1 by the distance necessary for carrying out the drilling.
• the spindle 1 comprises a shaft 20 which is intended to carry at the front a tool such as a drill (not shown) and which is coupled at the rear to a pulley 21 allowing it to be driven in rotation.
• the drill has for example a diameter less than or equal to 2.5mm.
• the speed of rotation of the shaft 20 is for example between 10,000 and 20,000 revolutions per minute.
• the invention is not limited to a particular tool, or to making a hole. In particular, it can be useful for carrying out formwork such as milling, counterboring, etc.
• the shaft 20 is guided in rotation about the X axis relative to the housing 10 by front 30 and rear 40 undercarriages.
• the front bearing set 30 comprises two angular contact ball bearings 31, the contact angle of which is for example 15 °, each comprising an inner ring 32, in contact with the shaft 20, balls 33, an outer ring 34 and flanges 35.
• the bearings 31 bear against one another and are engaged in a front bearing 50.
• the rear bearing set 40 has a similar embodiment, with two angular contact ball bearings 41, the contact angle of which is for example 15 °, each comprising an inner ring 42, in contact with the shaft 20, of the balls. 43, an outer ring 44 and flanges 45.
• the bearings 41 bear against each other and are engaged in a rear bearing 51.
• the inner ring 42 of the rearmost bearing bears axially against a shoulder 23 of the shaft 20, as can be seen in FIG. 3 in particular.
• a tubular inner spacer 24 is mounted on the shaft 20 between the front 30 and rear 40 undercarriages, and bears at its ends against the inner rings 32 and 42 of the corresponding bearings.
• a locking ring 70 is fixed on the shaft 20 at the front and comes to immobilize and axially preload on the shaft the inner rings 32 of the bearings 31, G inner spacer 24 and the inner rings 42 of the 4L bearings
• the ring 70 is attached to the shaft in the example illustrated using three needle set screws 71 which make it possible to correct a runout, if necessary.
• An O-ring seal 72 is housed in a groove 73 of shaft 20 and applies to locking ring 70.
• the casing 10 is closed at the front by a front nut 90, screwed into it, and at the rear by a rear closing part 95, which can be held in various ways on the casing 10, for example at the rear. using a nut 96, as shown in Figure 2.
• the front nut 90 has a flange 190 facing forward, which forms a baffle 192 with a flange 191 facing the rear of the locking ring 70.
• An inner ring 195 is mounted on shaft 20 at the rear, and has a forward facing flange 196, which forms a baffle 198 with a flange 197 of closure piece 95.
• Baffles 192 and 198 form a non-contact sealing system at the front and rear of spindle 1 while providing clearance for frictionless rotation and translation between rotating and stationary facing parts.
• An O-ring 199 is housed in a groove 27 of shaft 20 and is applied to the facing surface of inner ring 195.
• a succession of spacers is arranged in the casing 10 in contact with its inner surface, being immobilized between the front nut 90 and the rear closing part 95, namely, from the front to the rear:
• a ring forming a spacer front 91, a front bearing spacer ring 92, a main tubular spacer 93 and a rear bearing spacer ring 94.
• Each stack 100, 101, 102 or 103 comprises, in the example considered, at least two blades 110, for example five, one of which has been shown in isolation in Figure 5.
• Each blade 110 has a generally annular shape, and comprises fixing lugs 111, distributed regularly around its periphery, three in number in the example considered, which are directed radially outwards and which come to bear by their radially edge. exterior against the interior surface of the housing 10.
• the height of the brackets 111 is slightly greater than the thickness of the bearing spacers 92 and 94.
• the arcuate portions 112 connecting the fixing lugs 111 bear other lugs 113 at mid-length, which are directed radially inward.
• These tabs 113 each have a radial slot 114 which opens, at one end, on the radially inner free edge of the tabs 113 and, at the opposite end, in a circular hole 115 formed on the arcuate portion 112.
• the front bearing 50 is disposed between two bearing end rings 121 and 122. Pins 130 are engaged in bores 140 and 141 in correspondence of these end rings 121 and 122 and of the front bearing 50, to hold the rings. 121 and 122 in a predetermined angular orientation relative to the front bearing 50.
• pins 130 pass through the blades 110 through the holes 115.
• the slots 114 facilitate the establishment of the pins 130.
• the stacks 100 and 101 are held angularly in a predefined position relative to the bearing 50 and the rings of. end 121 and 122.
• the bearing 50 and the rings 121 and 122 have on their opposite faces projecting sectors 143, as can be seen in FIGS. 6 and 7, the angular extent of which corresponds substantially to that of the tabs 113, and which come to grip between them these.
• the rear bearing 51 is likewise disposed between bearing end rings 120 and 121, and pins 130 angularly immobilize the blades 110 disposed between them, as for the front bearing 50.
• This assembly allows a certain freedom of movement in the axial direction of the undercarriages 30 and 40, while keeping them centered due to the stiffness of the blades 110 in the radial direction, as will be detailed below.
• the main spacer 93 is formed with a shoulder 171 at each of its ends, set back from an end portion 172 surrounding the corresponding end ring 121 or 122.
• a flat spring 170 is mounted inside each end portion 172 and interposes axially between the shoulder 171 and this end ring 121 or 122.
• two superimposed flat springs 170 are mounted around the locking ring 70 and interposed axially between the front nut 90 and the end ring 121, as can be seen in Figure 2.
• the closure piece 95 is formed with a shoulder 176 and an end portion 177 forward thereof, which extends around the adjacent end ring 122.
• a flat spring 170 is mounted inside the end portion 177 and interposes axially between the closure part 95 and the adjacent end ring 122.
• the flat springs 170 ensure the clamping of the elastic leaves around the front and rear bearings by the end rings 121 and 122, via the support of the tabs 113 on the outer rings of the bearings.
• the spindle 1 comprises a mechanism for generating axial oscillations of the shaft 20 during its rotation.
• This mechanism comprises a single ball 200 which rolls between a rotating bearing ring 201, mounted on and rotating with the shaft 20, and a fixed bearing ring 202, carried by the closure part 95.
• a peripheral rolling ring 203 is inserted into the closure piece 95, after the shoulder 176, and extends around the path followed by the ball 200 as it rotates. This peripheral ring 203 makes it possible to take up the centrifugal forces during the rotation of the ball 200.
• the rotating ring 201 is held against a shoulder 28 of the shaft 20, which borders an annular groove 29, the concavity of which substantially follows the path followed by the ball 200.
• the rolling ring 202 has a rear face 230, which is flat and perpendicular to its axis, and a front face 231 which is flat and extends obliquely, as can be seen in FIG. 8, the normal to this face forming a angle g with the axis of the rolling ring 202, which is a few degrees, for example of the order of 0.3 ° in the example considered.
• the running surface 231 does not have a projection.
• the ball 200 performs a periodic and sinusoidal axial displacement which is due to the inclination of the front face 231.
• the ball 200 is only in contact, during its rotation at speed. high, with the fixed bearing ring 202, the rotating bearing ring 201 and the peripheral bearing ring 203. Due to the use of a single ball, the bearing of the latter induces stresses of deflection on the shaft, which however remains controlled and of acceptable amplitude due to the relatively small distance separating the ball 200 from the spindle axis 20.
• the ball 200 is ceramic. Its diameter is preferably greater than or equal to 5 mm, which makes it possible to reduce the Hertz pressures at the level of the contacts. Its diameter is for example 6mm.
• pin 1 The operation of pin 1 is as follows.
• the shaft 20 is rotated by the pulley 21, for example by a belt.
• the ball 200 rolls between the bearing rings 201 and 202, and in doing so moves the shaft 20 forward against the preload associated with the presence of an additional flat spring 170 at the front.
• the movement of the shaft 20 is possible due to the presence of the blades 110, the arcuate portions 112 of which can bend due to the play provided opposite them by the presence of the sectors 143. This bending allows the front bearings 50 and rear 51 to move axially to follow the oscillations imposed by the movement of the ball 200.
• the axial travel of the shaft 20 during the oscillatory movement is for example between 0.02 mm and 0.15 mm.
• the spindle shaft oscillates with a vibratory frequency between 0.4 and 0.6 oscillations per revolution, for example about 0.5.
• the invention is not limited to the example which has just been described.
• the rear closing part 95 is retained in the casing by an elastic ring 300 mounted in a corresponding groove of the casing 10, which reduces the axial and radial size of the casing.
• the flat springs can be omitted, with the exception of the one used to constitute the axial preload of the shaft.
• the flat spring serving to ensure the axial preload of the shaft can be arranged at the rear, that is to say where in Figure 2 is the flat spring 170 between the rear shoulder 171 and the ring 121 adjacent to the bearing 41 radially inside the bearing 51.

Applications Claiming Priority (2)

Publications (1)

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ID=71094538

Family Applications (1)

Country Status (7)

Family Cites Families (5)

• 2020
  • 2020-04-07 FR FR2003470A patent/FR3108863B1/fr active Active
• 2021
  • 2021-04-01 CA CA3174649A patent/CA3174649A1/fr active Pending
  • 2021-04-01 JP JP2022561454A patent/JP2023521369A/ja active Pending
  • 2021-04-01 CN CN202180025108.4A patent/CN115427177A/zh active Pending
  • 2021-04-01 WO PCT/EP2021/058763 patent/WO2021204709A1/fr unknown
  • 2021-04-01 US US17/916,281 patent/US20230150038A1/en active Pending
  • 2021-04-01 EP EP21716728.7A patent/EP4132735A1/de active Pending

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