Rotary Head Machining Unit

Description

Technical field

[0001] The present invention relates to a machining unit with a rotary head carrying at least two pivoting tools, for machining a non-rotating part centered on the axis of rotation of the rotary head, comprising a frame on which is mounted a rotor supported by means of two external bearings, said rotor being provided with an axial conduit and, coupled to rotational drive means, means for axially guiding said non-rotating part, these means being carried by bearings in the rotor and by the fixed support, means for holding and axially moving said non-rotating part, at least two tool supports, mounted in said rotary head so as to pivot about respective axes parallel to the axis of rotation, each support comprising a control lever arranged transversely, pivoting control means, cooperating with said lever and comprising a control element,which is movable in axial translation in the rotor and coupled to a translation control device, and pairs of support members arranged respectively on each control lever and on the corresponding control element, each pair of support members comprising a steering surface and a support surface bearing against the steering surface in a variable position depending on the translation of said control element, said steering surface being located on the tool support and the corresponding support surface being located on the control element, and each steering surface corresponding to a pivoting tool support having the shape of a portion of a helix whose axis coincides with the pivot axis of said support., Prior art

[0002] The machining head of this type described in European Patent No. EP 0 869 858 comprises a tool spindle equipped with two coupled tools, the pair of tools being controlled by a numerical axis. In this same invention, the advancement of the workpiece is achieved by two profiled discs gripping the workpiece, one being driven by the spindle motor and the other carried by a shaft ensuring the clamping of the workpiece.

[0003] In prior art systems, the workpiece is clamped by a collet in the feed system. When the diameter of the workpiece becomes smaller than approximately 1 to 1.5 mm, any resistance due to machining can cause buckling of the workpiece between the collet used for feed and the guide system called bush, knowing that the minimum distance between these two elements must correspond at least to the length of the workpiece. Feeding by rotating disc allows for a short and fixed distance between the feed system and the guide, which allows the machining of workpieces with a diameter of a few tenths of a millimeter.

[0004] Machining small workpieces also requires taking into account the torsion induced by the cutting force: the greater the distance between the feed system, which also ensures rotational stability, and the tool, the lower the torsional rigidity, which can impair machining. Finally, the longer the guidance system, the more expensive it is to produce.

[0005] These considerations have led to current rotary machining heads, using relatively short guides (approx. 100 mm), but whose number of tools is limited to two.

[0006] The solutions currently found to equip such heads with more than two tools all require a lengthwise construction, which makes them inapplicable in the case which concerns us. Statement of the invention

[0007] The present invention proposes a solution to this problem, by making it possible to produce in the same space as current machining heads, heads capable of carrying up to four selectable tools during the machining cycle, without requiring rotation to be stopped.

[0008] This object is achieved by the machining unit having the characteristics of claim 1 according to the invention, characterized in that it comprises a control sleeve mounted coaxially on said spindle, this sleeve being arranged to slide axially and to occupy a first advanced position, a second retracted position, this sleeve carrying at one of its ends a control surface of ellipsoidal shape, arranged to cooperate with the helical guide surfaces and to carry out the plunging of the tools, means for axially moving said control sleeve and a phase shift device arranged to bring said control sleeve into two, three or four predetermined angular positions around its axis.

[0009] According to a preferred embodiment, the means for moving the control sleeve comprise two rods driven by a linear actuator mounted set back from the frame supporting the machining head.

[0010] Preferably, the two rods act on a housing mounted on the control sleeve via two preloaded angular contact ball bearings.

[0011] In a particularly advantageous embodiment, the phase shift system is implemented electronically. It consists of two separate drive motors, one for the rotor and the other for the control sleeve. Each motor is equipped with a system for measuring its angular position. A special feature of the digital control makes it possible to control the two motors so that their rotation is perfectly synchronous, but also so that it is possible during rotation to control an angular offset of one relative to the other. The choice of this solution makes it possible to completely dispense with a complex and expensive mechanical system and greatly simplifies the construction. It is the result of a thorough examination of the technical possibilities, as well as a forecast analysis of the costs of the various versions. Summary description of the drawings

[0012] The present invention and its main advantages will appear better in the description of the different embodiments, with reference to the appended drawings, in which: There figure 1 is an axial sectional view of the machining unit according to the invention, showing the various bearings and the internal construction of the tool-holder axes. Figure 2A illustrates the means of axial movement of the control sleeve. The Figure 2B shows a front view of a version with three 120-degree tool holders. The Figure 3A illustrates the construction of one tool-holder axis among three identical ones. The Figures 3B and 3C represent partial views of the control sleeve sliding on the rotor, showing the elements participating in the longitudinal guidance of the sleeve on the rotor. The Figures 4A illustrates the control socket in the rear position. The Figure 4B shows its effect on the referenced tool holder, i.e. a clear position. The Figure 4Cshows in a sectional plane identical to the Figure 4A the control socket in the forward position. The figure 4D shows its effect on the referenced tool holder, i.e. a maximum plunge position in the workpiece. The Figure 5 is a cross-sectional view of the three-tool machining unit according to the invention, which shows the three tool-holder axes returned to the disengaged position by the return springs, when the sleeve is fully retracted. The Figures 6A and 6B illustrate the correspondence between the position of the first tool holder, in maximum plunge, the angular position of the ellipsoidal contact surface on the control sleeve, as well as the pivoting of the lever attached to the tool holder axis. The Figures 7A, 7B And 8A, 8B illustrate the same situation for the second and third tool axes respectively, and The figure 9 illustrates the construction of the electronic phase shift system. Best ways to carry out the invention

[0013] With reference to the figures, the three-tool spindle consists of a rotor 1 carried by a pair of bearings 3, the whole being mounted in a casing 2. The rotational drive is provided by the toothed belt 13 meshing with the toothed pulley 12.

[0014] At the center of the spindle is a non-rotating tube 22 which is supported at one end in the fixed support 23 which also serves as a guide for the control rods 10a, 10b of the Figure 2A , and supported at the other end by a pair of precision bearings 21 housed in the rotor 1. It is inside this tube that the guide bushes 24 are slid, precisely adjusted to the diameter of the part to be machined.

[0015] In this rotor are mounted three tool holder axes 4a, 4b, 4c, all identical. On each end outside the spindle, a hexagon 4g, 4h, 4i allows the mounting of different cutting tool holders 5a, 5b and 5c. Each lever-shaped rear part 4j, 4k, 4l supports the propeller portion 4d, 4e, 4f which will be in contact with the control sleeve.

[0016] Each axle is supported radially by two needle bearings 6a, 6b, 6c and 7a, 7b, 7c; the axial clearance is adjusted with elements 8a, 8b, 8c.

[0017] The axial movement of the control rods 10a, 10b is transmitted to the spool 11. The pair of bearings 9 provides the connection between the non-rotating spool 11 and the rotating control sleeve 14, which slides on the tail of the rotor 1 and rotates with it. This sleeve has its own rotational drive via the belt 16 and the pulley 15. Three pins 17a, 17b, 17c are integral with the pulley 15 and the sleeve 14 and located at 120° to each other ( FIG 3B and 3C ). In the axially retracted position of the control sleeve 14, they open into the radial groove 19 located in the rotor 1; in this position, the angular displacement of the sleeve 14 relative to the rotor 1 is possible, because the pins 17 a, 17 b, 17 c are free in the groove 19.

[0018] In the rotor 1 are also provided three longitudinal grooves 18a, 18b, 18c, machined at 120°. For three angular positions of the sleeve 14, the pins 17a, 17b, 17c will be opposite these grooves; it is then possible to advance the sleeve 14 via the control rods 10a and 10b, and thus to plunge one of the tools. Indeed, by advancing the sleeve 14, the contact point 20 will come into contact with the helix portion 4d or 4e or 4f of the selected tool holder 1, 2, 3, and therefore cause a pivoting of the axis 4a, 4b, 4c and thus cause the selected tool to penetrate into the part to be machined.

[0019] THE Figures 4A to 4D illustrate this functionality for tool holder 2. The Figure 4A shows in section the control sleeve 14 in the retracted position, which corresponds to a position clear of the tip of the tool 2 visible on the Figure 4B . On the Figure 4C , socket 14 is fully advanced, and on the figure 4D, this position of the control sleeve 14 caused the tip of the tool 2 to move beyond the axis of the spindle, and therefore beyond the workpiece to be machined.

[0020] In the chosen construction, on each tool-holder axis 4a, 4b, 4c, a spring 26a, 26b, 26c maintains the contact of the helix portion 4d, 4e, 4f with the point 20 of the sleeve, even in the event of the sleeve moving back.

[0021] However, in the maximum retracted position of the sleeve 14, a boss 25a, 25b, 25c on the rotor 1 serves as a stop for each tool-holder axis 4a, 4b, 4c according to the Figure 5. It thus limits the angular movement of the axes during the maximum retraction of the sleeve 14. In this axial position of the sleeve 14, there is no longer any contact between the propeller portions 4d, 4e, 4f and the contact point 20 of the sleeve 14. This position also brings the pins 17a, 17b, 17c into a position corresponding to the groove 19. These two conditions make it possible for the sleeve 14 to rotate freely relative to the rotor 1, without risk of damaging the contact point 20 or the propellers 4d, 4e, 4f.

[0022] In summary, in the retracted position, the sleeve 14 can be rotated freely relative to the rotor 1. After having angularly positioned the sleeve 14 in such a way that the three pins 17a, 17b, 17c are located opposite the longitudinal grooves 18a, 18b, 18c, which corresponds to three possibilities all spaced 120° apart, it is possible to advance the sleeve 14 and therefore to plunge the selected tool.

[0023] In fact, each of these three angular positions allows, by axially moving the sleeve 14, the point 20 to be brought into contact with the helix portion 4d or 4e or 4f of one of the three different tool holders. It thus makes it possible to plunge the chosen tool so that the tool selection is therefore carried out.

[0024] THE Figures 6A and 6B illustrate the case of the first tool-holder axis whose tip is completely immersed. To do this, the contact point 20 was brought opposite the helix portion 4d of axis no. 1 and the sleeve 14 pushed forward. We see on the Figure 6B that the lever 4j is well detached from the stop 25a. On the other hand, we see that the other two axes are themselves resting on their respective stops 25b and 25c.

[0025] THE Figures 7A and 7B , respectively 8A and 8B illustrate the cases of the second and third tool holders, with the tool tip in a position analogous to that of the Figure 6A . We can clearly note on the Figures 7B And 8B the different angular positions of the contact point 20 in each case and the fact that only the controlled axis is detached from its stop.

[0026] When the pins are engaged in the grooves 18a, b, c, the phase shift is no longer possible, the pins 17a, 17b, 17c then serving as longitudinal guidance.

[0027] In the electronic phase shift system, each of the belts 13 and 16 is driven by a separate motor, 27 respectively 29, each carrying a toothed pulley 28, respectively. 30. The motor / spindle transmission ratio should preferably be an integer; in a particular case, the ratio chosen is equal to 1. Each motor has an electronic encoder measuring its angular position and providing a reference index once per revolution. The electronic control system (CNC) makes it possible to drive the two spindle elements in a perfectly synchronous manner, the motor 29 matching its angular position at all times to that of the motor 27. It also has instructions making it possible to command the motor 29 to shift its angular position by a defined value relative to that of the motor 27, and this while the spindle is working, that is to say with the two motors rotating.

[0028] This feature thus makes it possible, during the rotation of the spindle, to freely choose to work with one of the three tool holders 4a or 4b or 4c.

[0029] It would allow the creation of a spindle with two or four tool holders instead of three, because there is no limit to the number of programmable positions.

[0030] The advantages provided by the machining unit according to the invention compared to the system of the prior art are as follows: The determining point is the particular arrangement of the main bearings 3. It brings great advantages in terms of rigidity and load capacity. It also makes it possible to have a specific lubrication point for the bearings 3, which guarantees absolute control of the quantity of lubricant supplied, and therefore of the temperature and operating conditions of the spindle.

[0031] It also allows for easy replacement of the bearings 21 of the barrel support tube 22, bearings which are most exposed to chips and machining forces.

[0032] It allows for easy and complete replacement of this central part receiving the guide bush. This results in the possibility of using different types of guide bush on the same spindle; the prior art system, but also commercially available, adjustable guide bushes used on standard turning machines with rotating bar. It is also an opening towards any future development in workpiece guidance systems.

[0033] This arrangement finally makes it possible to simply bring cutting oil through the guide barrel to the tools, without having to pass through the curtain formed by the rotating tools passing in front of the jet.

[0034] The above features can be applied without further ado to the production of a spindle with two controlled tools according to the prior art. They constitute a significant technological leap in themselves.

[0035] But these modifications also make it possible to produce a spindle using a controlled angular offset system of the tool control sleeve relative to the spindle, during rotation. It is thus possible to produce short spindles with two, three or even four tools, a limit set by the use of a pivoting tool holder system.

[0036] The solution described is that of three tools; the version with two tools by controlled angular offset does not provide any significant advantage over the classic solution. With three tools, the gain is much more interesting, while maintaining a layout not too tight compared to the version with four tools. There is more freedom in the shapes of the tool holders and also more space for chip evacuation.

Claims

1. Rotary head machining unit that carries at least two pivoting tools to machine a non-rotary part centered on the rotational axis of the rotary head, including a frame (2) on which a rotor (1) is mounted, carried by two external bearings (3), said rotor (1) having an axial channel and, coupled to rotational drive means (12) and (15), axial guiding means for said non-rotary part (22) and (24), these means being carried by bearings (21) in rotor (1) and by fixed support (23), means for holding and moving said non-rotary part axially, at least two tool holders (4a-4c) mounted in said rotary head in order to pivot about respective axes parallel to the rotational axis, each holder comprising a control lever (4j-4l) arranged transversally, pivoting control means cooperating with said lever and comprising a control element (14) that is movable in axial translation in the rotor and coupled to a translation control device, and pairs of pusher elements arranged respectively on each control lever and on the corresponding control element, each pair of pusher elements comprising a guiding surface (4d-4f) and a pushing surface (20) resting against the guiding surface in a position that varies according to the translation of said control element (14), said guiding surface (4d-4f) being located on the tool holder and the corresponding pushing surface (20) being located on the control element (14), and every guiding surface corresponding to a pivoting tool holder having the shape of a helix portion whose axis coincides with the pivoting axis of said holder, characterized in that it comprises a control bush (14) mounted coaxially on said spindle, said bush (14) being arranged to slide axially and to be in a first advanced position, in a second retracted position, said control bush (14) carrying at one of its ends a control surface with an ellipsoidal shape (20) arranged to cooperate with helical guiding surfaces (4d-4f) and to make the tools plunge, means for moving said control bush (14) axially and a phase shift device arranged to bring said control bush (14) in two, three or four predetermined angular positions about its axis.

2. Rotary head machining unit according to claim 1, characterized in that the phase shift system is made of two separate drive motors (27) and (29), one for rotor (1) by means of pulley (28), belt (13) and pulley (12), the other for bush (14) by means of pulley (30), belt (16) and pulley (15), each motor being equipped with a system to measure its angular position.

3. Rotary head machining unit according to claims 1 and 2, characterized in that it includes numerical control means that allow controlling both motors in order to ensure a perfectly synchronous rotation, but it also allows commanding any angular phase shift of one with respect to the other during the rotation.

4. Machining unit according to claims 1 and 2, characterized in that it includes means that allow a complete change of central section (22) and (21) receiving axial guiding means (24), thus allowing the easy replacement of bearings (21) and the possible adaptation of other guiding systems for the part to be machined, without having to modify the spindle itself.

5. Machining unit according to the preceding claims, characterized in that three tool holder axes (4a, 4b, 4c) are mounted in the rotor, all being identical, wherein a hexagon (4g, 4h, 4i) located on each end outside of the spindle allows mounting various cutting tool carriers (5a, 5b, 5c).

6. Rotary head machining unit according to claim 1, wherein every lever-shaped rear section (4j, 4k, 4l) carries helix portion (4d, 4e, 4f) that will be in contact with control bush (14).

7. Rotary head machining unit according to the preceding claims, characterized in that every axis is supported radially by two needle bearings (6a, 6b, 6c) and (7a, 7b, 7c); the axial play being adjusted with elements (8a, 8b, 8c).

8. Rotary head machining unit according to the preceding claims, characterized in that the axial movement of control rods (10a, 10b) is transmitted to spool (11) and in that the pair of bearings (9) connects non-rotary spool (11) and rotary control bush (14), which slides on the shank of rotor (1) and turns with it.

9. Rotary head machining unit according to claim 8, characterized in that rotary control bush (14) has its own rotational drive by means of belt (16) and pulley (15) and in that three pins (17a, 17b, 17c) are integral with pulley (15) and bush (14) and located at 120° from each other.

10. Rotary head machining unit according to claim 1, characterized in that the means for moving control bush (14) comprise two rods (10a and 10b) driven by a linear actuator mounted in a set back manner in relation to the frame carrying the machining head.

11. Rotary head machining unit according to claim 10, characterized in that said two rods act on a box (12) mounted on control bush (14) by means of two preloaded angular contact ball bearings (9).