Tool holder comprising plurality of spindles for holding tools and numerically controlled machine tool comprising such tool holder

Abstract

The invention relates to a tool holder (10) comprising a body (11) extending along an axis A-A, which body comprises, at one end thereof, a base (12) for fastening to a numerically controlled machine tool (20) and, at the other end, a rotatably movable head (13) comprising at least two spindles (14, 14 ', 14' ') for holding a tool, 14 ', 14' ') each intended to receive a cutting tool (15, 15', 15 '') in an engaged manner, the spindles occupying, depending on the angular position of the head (13), a working position in which they are intended to perform a machining operation on a workpiece held in position in the clamp (21) or a standby position in which they are withdrawn from the workpiece, each spindle being configured to be controlled independently of the other spindles, therefore, the cutting tool carried by the main shaft is fixed or driven to rotate regardless of the position occupied by the main shaft.

Description

Technical Field

[0001] The invention relates to the field of numerically controlled machine tools for machining parts, preferably micromechanical parts, and to the field of devices for such machine tools.

[0002] More particularly, the present invention relates to a tool holder including a plurality of spindles for holding tools and a numerically controlled machine tool including the tool holder. Background Art

[0003] CNC machine tools are used to mass produce parts, particularly by machining in accordance with instructions from a computer program. These machines include a tool mounted on a spindle for holding the tool, and are usually equipped with a tool changer for changing the tool held by the spindle to adapt it to the machining operation to be performed on a part held in place in a fixture.

[0004] When changing a tool, the machine tool is no longer productive, which means that the machining operation is interrupted. Therefore, the goal is to minimize the tool change time. For this purpose, tool changers have been developed to work as much as possible within the shielding time and minimize the machine tool downtime to increase its productivity.

[0005] For example, a multi-axis tool holder is known that comprises a head on which several spindles are arranged, one of which is in operation and the others are in a resting state. Specifically, the working spindle is coupled to a drive mechanism via a coupling system. Thus, between two machining operations, the tool can be changed by disengaging the working spindle (i.e. the spindle carrying the tool to be changed), rotating the head so as to present the next spindle and coupling this spindle to the drive mechanism.

[0006] However, this solution is not entirely satisfactory, since, although the tool change time is reduced, it is not completely eliminated. In fact, between each tool change, with this type of multi-axis tool holder, it is necessary to brake the tool to be changed before the tool change is carried out and to accelerate the next tool after it has been coupled to the drive until it reaches its machining speed. These multi-axis tool holders also require a certain amount of time to disengage the tool to be changed, rotate the head and position the next tool so that it is aligned with the coupling system and then couple it. This solution is also particularly complex and expensive due to the coupling system.

[0007] There are also multi-axis tool holders that solve the problem of spindle acceleration and braking, in which all tools are driven to rotate synchronously. Therefore, when changing a tool, the next tool is already driven at its processing speed and can start processing the part. However, these multi-axis tool holders require a lot of energy to rotate all the tools at the same time. In addition, due to the motion transmission power chain, the maximum speed of the tools they carry is relatively limited.

[0008] In general, the prior art multi-axis tool holders are bulky, whether the tools they carry are rotated individually or simultaneously, which creates a large moment of inertia and increases the risk of collision between the fixture and the tools carried by the tool holder.

[0009] Besides the above mentioned disadvantages, these solutions are not suitable for machining micromechanical parts. Summary of the invention

[0010] The present invention solves the above mentioned drawbacks by providing a solution which allows to completely shield the tool change time, in particular by shielding the tool acceleration and deceleration phases.Another object achieved by the present invention is to maximize the compactness of the machine tool and reduce the moving masses.

[0011] To this end, the invention relates to a tool holder comprising a body extending along an axis AA, the body comprising at one end a base for fastening to a numerically controlled machine tool and at the other end a head movable in rotation. The head comprises at least two spindles for holding the tools, each spindle being intended to receive a cutting tool in engagement. Depending on the angular position of the head, the spindles occupy either a working position, in which they are intended to carry out a machining operation on a workpiece held in position in a fixture, or a standby position, in which they are withdrawn from the workpiece. Each spindle is configured to be controlled independently of the others so as to immobilize or drive the cutting tool it carries in rotation, regardless of the position it occupies.

[0012] Since the spindles are independently servo controlled, it is possible to accelerate and decelerate the spindles within the masking time. Thus, the present invention allows tool changes to be made within the dead time, which is reduced to the duration of only the head rotation until the next tool makes contact with the workpiece. Due to the features of the present invention, the tool change time (total tool change time) is estimated to be in the range of a few tenths of a second.

[0013] The invention also has the advantage of being adaptable to any existing machine tool.

[0014] Furthermore, due to the invention, the spindle can reach relatively high rotational speeds, for example in the range of 60,000 to 80,000 revolutions per minute.

[0015] In a specific embodiment, the present invention may further include one or more of the following features, which may be considered alone or in any technically feasible combination.

[0016] In a particular embodiment, the axis of rotation of the head coincides with axis AA.

[0017] In a particular embodiment, the base is configured such that axis AA forms an angle between 35 degrees and 55 degrees relative to the vertical axis.

[0018] These features help to maximize the compactness of the device.

[0019] In a particular embodiment, these main axes are distributed around the axis of rotation of the head, preferably evenly distributed, and each main axis is arranged so that its axis BB, BB' and BB" form an angle between 35 degrees and 55 degrees relative to the axis AA, and their axes BB, BB' and BB" do not intersect.

[0020] On the one hand, this feature makes it easier to clean the tool when it is at rest, to avoid or limit the risk of collision with the fixture; on the other hand, it enables all spindles to maintain the same working position, thus helping to ensure that machining tolerances are met.

[0021] In a particular embodiment, these main axes are arranged relative to each other so that the projections of their longitudinal axes BB, BB' and BB" in a plane P orthogonal to the axis AA form a regular n-gon centered on the axis AA, where n is the number of main axes.

[0022] In a particular embodiment, the main shafts are arranged such that their longitudinal axes BB, BB' and BB" are spaced apart from the axis AA by a distance greater than the radius of the main shaft.

[0023] This feature also helps to clear the tool at rest to avoid or limit the risk of collision with the fixture.

[0024] In a specific embodiment, each spindle includes its own motor for rotating or stationary the cutting tool it carries.

[0025] This feature allows reducing the energy consumption of the tool holder, since the spindles not performing a machining operation do not rotate about their respective longitudinal axes.

[0026] In a particular embodiment, at least one spindle is adapted to assume at least two different working positions, each working position being defined by a predetermined angular position of the head of the tool holder.

[0027] In a particular embodiment, at least one spindle is adapted to continuously occupy a working position when the head of the tool holder rotates. This arrangement also involves a continuous movement of the clamp.

[0028] According to another object, the present invention relates to a CNC machine tool preferably used for machining micromechanical parts, comprising at least one tool holder as described above, which is directly fastened to the frame or a carrier capable of translational movement in a vertical plane through a base, so that the axis AA forms an angle between 35 degrees and 55 degrees relative to the vertical axis, and the machine tool also includes a clamp for holding the part to be machined in place.

[0029] In a specific embodiment, the machine tool comprises two tool holders arranged on both sides of the fixture.

[0030] In a particular embodiment, the machine tool comprises a protective wall for preventing chips and cutting fluid from splashing, the body of the or each tool holder being engaged in a corresponding opening of the protective wall in a fluid-tight manner.

[0031] Yet another aspect of the present invention relates to a method for replacing a tool of a machine tool as described above, wherein:

[0032] a first cutting tool engaged in the spindle in the working position performs a first machining phase, a second cutting tool engaged in the spindle in the standby position is intended for performing a second machining phase and is blocked from rotating;

[0033] - before the end of the first machining phase, the second cutting tool rotates about its axis BB' until it reaches the rotational speed characteristic of the second machining phase;

[0034] - Once the first machining phase is completed, the head is pivoted about the axis AA so as to drive the spindle carrying the second cutting tool into a working position so that the second cutting tool can start the second machining phase, and to drive the spindle carrying the first cutting tool into a standby position, preventing the first cutting tool from rotating once the spindle carrying the first cutting tool reaches its standby position. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Other characteristics and advantages of the present invention will become apparent on reading the following detailed description given as non-limiting examples with reference to the accompanying drawings, in which:

[0036] - Figure 1 A perspective view showing a multi-spindle tool post according to a preferred embodiment of the present invention;

[0037] - Figure 2 The longitudinal axis of the tool holder body is shown. Figure 1 A view of the tool holder;

[0038] - Figure 3 Shows Figure 1 A side view of a tool holder;

[0039] - Figure 4 A perspective view of two tool holders arranged on either side of a workpiece fixture is shown.

[0040] It should be noted that for the sake of clarity, the drawings are not necessarily drawn to scale. DETAILED DESCRIPTION

[0041] Figure 1A tool holder 10 for machining parts, preferably micromechanical parts, is shown. The tool holder 10 comprises a body 11 extending along a longitudinal axis indicated by the "axis AA", in an embodiment of the invention, the body 11 comprises a base 12 at one end thereof and a head 13 at the other end, the base 12 being intended to be fastened to a numerically controlled machine tool 20, the head 13 being rotatably movable about an axis coinciding with the axis AA. The head 13 has at least two spindles 14, 14' or 14" for holding tools, each spindle being intended to receive a cutting tool 15, 15' or 15". Depending on the angular position of the head 13, each spindle 14, 14' and 14" occupies a working position, in which it is used to perform a machining operation on a workpiece held in place in a fixture 21, or a standby position, in which it is withdrawn from the workpiece.

[0042] It should be noted that the tool holder 10 can be driven in translation, for example when the base 12 is fastened to a carrier (not shown) of the machine tool 20 that can move along at least one translational degree of freedom, the carrier preferably moves along three translational degrees of freedom in reference XYZ directions.

[0043] Alternatively, the tool holder 10 may be stationary, such as where the base 12 is secured directly to the frame 22 of the machine tool 20 .

[0044] Advantageously, the spindles 14, 14' and 14" are configured to be controlled independently of one another so as to rotate or hold stationary the cutting tools 15, 15' or 15" they carry. This feature is particularly advantageous when changing the tools. Preferably, the spindles 14, 14' and 14" are motorized spindles, also called "electric spindles", and each spindle comprises its own motor for rotating or holding stationary the cutting tools 15, 15' or 15" it carries.

[0045] In particular, in order to replace the first cutting tool 15 for performing the first machining phase with the second cutting tool 15' for performing the second machining phase, the second cutting tool 15' is rotated before the first machining phase ends until it reaches a rotation speed specific to the second machining phase.

[0046] The first cutting tool 15 engages in the spindle 14 in a working position and the second cutting tool 15 ′ engages in the spindle 14 ′ in a standby position.

[0047] Once the first machining phase has been completed, the head 13 is pivoted so as to drive the spindle 14 in the working position to the standby position and the spindle 14' in the standby position to the working position. Since the second cutting tool 15' has reached its machining speed when the spindle 14' in which it is engaged is in the standby position, the second machining phase begins immediately. The spindle 14 carrying the first cutting tool 15 is now in the standby position, the first cutting tool 15 being immobile.

[0048] Therefore, since the second cutting tool 15' rotates and the first cutting tool 15 stops rotating during the hidden time, the cutting tools are changed with the dead time reduced to only the duration of the head rotation.

[0049] Each spindle 14, 14' and 14" extends along a longitudinal axis indicated by "axis BB", "axis BB'" and "axis BB"", respectively, which also form their axes of rotation. Figure 1 and Figure 3 In the figures, this axis is only shown on the spindle 14 in the working position. As shown in these figures, in the working position, the spindle 14 is oriented so that its axis BB is parallel to the vertical axis. However, in another working position, the spindle 14 can also be oriented so that its axis BB is parallel to the horizontal axis. The spindle 14 can also occupy a dynamic working position, that is, the head 13 can rotate during the machining operation. In this case, the clamp 21 can be moved and moved according to instructions related to the machining program, and / or the tool holder 10 can be moved via its base 12 and moved according to instructions related to the machining program.

[0050] In a preferred embodiment of the present invention, as shown in the figure, the tool holder 10 includes three spindles 14, 14' and 14". In the figure, the distribution of the spindles 14, 14' and 14" on the head 13 of the tool holder 10 is specifically shown. Figure 2 In the embodiment of the present invention, the main axes 14, 14' and 14" are evenly distributed around the rotation axis of the head 13, that is, in the embodiment of the present invention, the main axes 14, 14' and 14" are evenly distributed around the axis AA. The main axes 14, 14' and 14" are arranged relative to each other so that the projections of their axes BB, BB' and BB" in the plane P orthogonal to the axis AA form a regular n-gon centered on the axis AA, where n is the number of main axes. Figure 2 In the example shown, the longitudinal axes of the main shafts 14 , 14 ′ and 14 ″ form an equilateral triangle.

[0051] Furthermore, in a preferred embodiment of the invention, the spindles 14, 14' and 14" are arranged so that their axes BB, BB' and BB" are spaced apart from the axis AA at a distance greater than the radius of the spindle 14, 14' or 14", for example corresponding at least to the diameter of the spindle 14, 14' or 14". This arrangement allows maximizing the clearance between the cutting tool 15' or 15" and the spindle 14' and 14" in the standby position, thereby avoiding the risk of these cutting tools 15' and 15" colliding with the fixture 21 or the workpiece. It should be noted that, in general, the greater the number of spindles included in the head, the greater the distance between the axis AA and the axes BB, BB' and BB" of the spindles.

[0052] In addition, especially if Figure 3 As shown, the tool holder 10 is configured so that, due to the structure of the base 12, the axis AA forms an angle of between 35 and 55 degrees, preferably 45 degrees, with respect to the vertical axis. Therefore, the spindles 14, 14' and 14" are arranged on the head 13 so that their axes BB, BB' and BB" are inclined at an angle of between 35 and 55 degrees, preferably 45 degrees, with respect to the axis AA, so that, in their working position, they are parallel to the vertical axis, as previously described.

[0053] In general, it can be inferred from the foregoing and the drawings that the main shafts 14, 14' and 14" are arranged symmetrically to each other about the axis AA and that the axes BB, BB' and BB" of the main shafts 14, 14' and 14" do not intersect each other.

[0054] Furthermore, the specific arrangement of the spindles 14, 14' and 14" relative to the head 13 of the tool holder 10 makes it possible to reduce force cycles. In practice, the spindles 14, 14' and 14" are fastened as close as possible to a connecting element, formed, for example, by a ball bearing, which enables the head 13 to pivot relative to the body 11 of the tool holder 10.

[0055] In addition, the machine tool 20 may include two tool holders 10, which are arranged on both sides of the fixture 21, such as Figure 4 As shown in the figure, due to the presence of two tool holders 10, two machining operations can be performed on the same workpiece at the same time. Advantageously, in the working position, the axis of rotation of the spindle 14 of each tool holder 10 may coincide.

[0056] The fixture 21 may take the form of a table designed to hold a workpiece in place and having varying degrees of translational and rotational mobility.

[0057] like Figure 4As shown, the machine tool 20 may have a protective wall 23 to prevent chips and cutting fluid from splashing. In particular, the protective wall 23 is arranged in a liquid-tight manner around the body 11 of the tool holder 10 or each tool holder 10, and for this purpose includes an opening through which the body 11 engages. The opening may include an oil scraper seal arranged against the body 11 at its periphery. In addition, the protective wall 23 may advantageously include a corrugated portion. The oil scraper seal and the corrugated portion allow liquid tightness to be maintained during movement of the tool holder in the three directions XYZ.

[0058] The protection wall 23 is fastened to the machine frame 22 of the machine tool 20 via its periphery.

[0059] Furthermore, each protective wall 23 advantageously extends in a plane orthogonal to the axis AA, ie in a plane inclined relative to the horizontal axis, which allows facilitating the flow of cutting fluid and chips. This arrangement also makes it easier for the operator to access the fixture 21 and the spindle 14, 14' or 14".

[0060] More generally, it should be noted that the embodiments and manufacturing methods considered above have been described as non-limiting examples and that other variants are therefore conceivable.

Claims

1. A tool holder (10) comprising a body (11) extending along an axis AA, said body (11) comprising a base (12) at one end and a rotatably movable head (13) at the other end, said base (12) being intended to be fastened to a numerically controlled machine tool (20), said head (13) comprising at least two spindles (14, 14', 14") for holding the tools, each spindle being intended to receive a cutting tool (15, 15', 15") in engagement, said tool holder (10) being characterized in that these The spindles (14, 14', 14") occupy a working position or a standby position, depending on the angular position of the head (13), in which the spindles are used to perform machining operations on a workpiece held in position in a fixture (21), and in which the spindles are withdrawn from the workpiece, each spindle (14, 14', 14") being configured to be controlled independently of the other spindles so that the cutting tool (15, 15', 15") carried by the spindle is either stationary or driven in rotation, regardless of the position occupied by the spindle.

2. The tool holder (10) according to claim 1, characterized in that: The axis of rotation of the head (13) coincides with the axis AA.

3. The tool holder (10) according to claim 2, characterized in that: The base (12) is configured such that the axis AA forms an angle between 35 and 55 degrees relative to a vertical axis.

4. The tool holder (10) according to any one of claims 1 to 3, characterized in that: The main shafts (14, 14', 14") are distributed around the rotation axis of the head (13), and each main shaft (14, 14', 14") is arranged so that the axes BB, BB' and BB" of the main shafts form an angle between 35 degrees and 55 degrees relative to the axis AA, and the axes BB, BB' and BB" of the main shafts do not intersect each other.

5. The tool holder (10) according to claim 4, characterized in that: The main axes (14, 14', 14") are arranged relative to each other so that the projections of their axes BB, BB' and BB" in a plane P orthogonal to the axis AA form a regular n-gon centered on the axis AA, where n is the number of the main axes (14, 14', 14").

6. The tool holder (10) according to any one of claims 1 to 5, characterized in that The main shafts (14, 14', 14") are arranged so that their axes BB, BB' and BB" are spaced from the axis AA at a distance greater than the radius of the main shaft (14, 14', 14").

7. The tool holder (10) according to any one of claims 1 to 6, characterized in that Each spindle (14, 14', 14") comprises its own motor for rotating or stationary the cutting tool (15, 15', 15") carried by each spindle.

8. The tool holder (10) according to any one of claims 1 to 7, characterized in that At least one spindle (14, 14', 14") is suitable for assuming at least two different working positions, each working position being defined by a predetermined angular position of the head (13) of the tool holder (10).

9. The tool holder (10) according to any one of claims 1 to 7, characterized in that At least one spindle (14, 14', 14") is suitable for continuously occupying a working position during the rotation of the head (13) of the tool holder (10).

10. A numerically controlled machine tool (20) for preferably machining micromechanical workpieces, characterized in that: The CNC machine tool (20) comprises at least one tool holder (10) according to any one of claims 1 to 9, wherein the tool holder (10) is directly fastened to a frame (22) or a carrier capable of translational movement in three directions XYZ through the base (12), so that the axis AA forms an angle between 35 degrees and 55 degrees relative to the vertical axis, and the CNC machine tool also comprises a fixture (21) for holding a workpiece to be processed in place.

11. The numerically controlled machine tool (20) according to claim 10, characterized in that: The numerically controlled machine tool (20) comprises two tool rests (10) arranged on both sides of the fixture (21).

12. The numerically controlled machine tool (20) according to claim 10 or 11, characterized in that: The numerically controlled machine tool (20) comprises a protective wall (23) for preventing chips and cutting fluid from splashing, and the body (11) of the tool holder (10) is engaged in a corresponding opening of the protective wall (23) in a liquid-tight manner.

13. A method for replacing a tool of a numerically controlled machine tool (20) according to any one of claims 10 to 12, wherein: - a first cutting tool (15) engaged in the spindle (14) in the working position performs a first machining phase, and a second cutting tool (15') engaged in the spindle (14') in the standby position is intended for performing a second machining phase and is blocked from rotating; - before the end of the first machining phase, rotating the second cutting tool (15') about its axis BB' until a rotation speed characteristic of the second machining phase is reached; - Once the first machining phase is completed, the head is pivoted about the axis AA so as to drive the spindle (14') carrying the second cutting tool (15') into the working position so that the second cutting tool (15') starts the second machining phase, and the spindle (14) carrying the first cutting tool (15) is driven into the standby position, and once the spindle (14) carrying the first cutting tool (15) reaches its standby position, the first cutting tool (15) is prevented from rotating.

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