Worktable assembly for machine tools

Abstract

A worktable assembly (10) for a machine tool (1) includes a support assembly (12), a rotary table (14), a ring gear (20), a plurality of hydrostatic main slides (40), a detection device, a plurality of stops (60), and an electronic management device, wherein the ring gear is provided with an inner surface (20') and an upper surface (20”) and is integral with the worktable (14), the detection device is adapted to detect the lifting force (F1) generated by the main slides (40), and the electronic management device is operatively connected to the main slides (40), the stops (60), and the detection device and is configured to control the stops (60) to generate an opposing force (F2) such that the lifting force (F1) is equal to a predetermined constant rated load (P*), which is greater than the weight of the semi-finished product and less than or equal to the maximum load (Pmax) that the main slides (40) can withstand.

Description

Technical Field

[0001] This invention relates to the field of machine tools, and particularly to the field of large machine tools, such as vertical lathes. Specifically, an object of this invention is to provide a worktable assembly for a machine tool designed to support semi-finished products to be processed. Background Technology

[0002] These machine tools are used to perform machining operations on large semi-finished products, such as shafts for ship engines, fuel tanks for the oil industry, or parts for power plants.

[0003] Due to the critical nature of these components, extremely tight machining tolerances are typically required. Therefore, machine tool manufacturers are constantly researching and developing solutions that can guarantee these tolerances. Summary of the Invention

[0004] The purpose of this invention is to provide a worktable assembly for large machine tools that meets the needs of this field.

[0005] This objective is achieved by a worktable assembly for a machine tool intended to be positioned on a horizontal reference plane, the worktable assembly comprising: - a support assembly including a support member having an annular wall defining an inner compartment; - a worktable supported by the support assembly and rotatable about a vertical axis of rotation; - a primary biasing portion and a secondary biasing portion, the primary biasing portion having a lower surface and the secondary biasing portion having an upper surface, the primary biasing portion and the secondary biasing portion being coupled to the worktable; - a plurality of hydrostatically pressed main slides, the plurality of main slides being fixed to the support assembly and adapted to support the worktable by pressurized fluid, thereby generating a lifting force, each of the main slides being configured to form a primary pressure chamber with the lower surface of the primary biasing portion, the primary pressure chamber having a channel forming a support for the worktable; - A detection device adapted to detect the lifting force generated by the main slider; - A plurality of stops fixed to the support assembly and adapted to push the worktable toward the main slider by pressurized fluid, thereby generating an opposing force, wherein each stop includes a hydrostatic sub-slider, each sub-slider being configured to create a sub-pressure chamber with the upper surface of the sub-biased portion, wherein a channel for pushing the worktable toward the main slider is formed in the sub-pressure chamber; - An electronic management device operatively connected to the main slider, the stops, and the detection device, the electronic management device being configured to control the stops to generate an opposing force such that the lifting force is equal to a predetermined constant rated load, which is greater than the weight of the semi-finished product and less than or equal to the maximum load that the main slider can withstand. Attached Figure Description

[0006] The features and advantages of the workbench assembly according to the invention will become apparent from the following description, which is given by way of non-limiting example with reference to the accompanying drawings, in which:

[0007] - Figure 1 A machine tool according to an embodiment of the present invention is shown;

[0008] - Figure 2 An embodiment according to the present invention is shown. Figure 1 The machine tool's worktable assembly;

[0009] - Figure 3 An embodiment according to the present invention is shown. Figure 2 Support components for the workbench assembly;

[0010] - Figure 4 This is a cross-sectional view of the worktable assembly, which shows the main slider of the worktable assembly;

[0011] - Figure 5 It is a cross-sectional view of the workbench assembly, which shows the stops of the workbench assembly;

[0012] - Figure 6 A stop block of a workbench assembly according to an embodiment of the present invention is shown;

[0013] - Figure 7 yes Figure 6 A cross-sectional view of the stop block, showing the auxiliary slider and piston. Detailed Implementation

[0014] Referring to the attached drawings, the large machine tool as a whole is indicated by reference numeral 1.

[0015] For example, the machine tool is a vertical lathe.

[0016] For the sake of simplicity, vertical lathes will be mentioned below, but the present invention also refers to milling machines or general machining centers.

[0017] In the illustrated embodiment ( Figure 1 In this machine tool 1, the machine tool 1 includes a pair of stands 2, each stand extending substantially along the longitudinal gantry translation axis Y, parallel to each other, and located on a reference plane, such as the ground plane. The machine tool 1 also includes a pair of columns 4, each column extending substantially vertically, parallel to each other, and adapted to move along the gantry translation axis Y upon command.

[0018] The machine tool 1 also includes a crossbar 6, which extends substantially laterally and is supported by two columns 4 that can be translated; in particular, the crossbar 6 can be translated along a vertical crossbar translation axis W perpendicular to the reference plane upon command.

[0019] The machine tool 1 also includes a head 8 that is movably supported by a crossbar 6; in particular, the head 8 can be translated along a transverse head translation axis X on command, which is orthogonal to or parallel to the crossbar translation axis W or to the reference plane.

[0020] The machine tool 1 also includes a spindle (not shown) that carries a tool for machining and is supported translationally by a head 8; in particular, the spindle can be translated along a vertical spindle translation axis Z perpendicular to a reference plane upon command.

[0021] In order to support the semi-finished product to be turned (or milled) and to rotate it about the axis of rotation C, the machine tool 1 also includes a worktable assembly 10, which is usually arranged between the frames 2.

[0022] In the illustrated embodiments ( Figure 2 and Figure 3 The worktable assembly 10 includes a fixed, basin-shaped support assembly 12 and a circular worktable 14 typically supported by the support assembly 12, which is rotatable about a rotation axis C.

[0023] The worktable assembly 10 also includes at least one electric motor 16 operatively connected to the worktable 14 via a kinematic chain, which rotatably actuates the worktable 14.

[0024] For example, each motor 16 is located on a reference plane, has a horizontal axis and is adjacent to the rotary table 14, and the kinematic chain includes a bevel gear redirection device 18 to achieve rotation about a vertical axis.

[0025] The worktable 14 is also equipped with a toothed ring gear 20. Figure 4 The ring gear is operatively connected to the motor 16, for example, via the redirection device 18, so as to be driven to rotate.

[0026] For example, the workbench 14 includes an upper portion 14a that carries a circular upper surface 14' for supporting a semi-finished product and a lower portion 14b that extends axially downward from the upper portion 14a. The upper portion 14a has a first maximum diameter D1, while the lower portion 14b has a second maximum diameter D2; the first maximum diameter D1 is greater than the second maximum diameter D2, so that the workbench has a stepped configuration.

[0027] Preferably, the ring gear 20 is coaxially fixed to the lower portion 14b of the worktable 14.

[0028] According to an embodiment, the support assembly 12 includes an annular wall 21, a bottom 23 (which closes the annular wall 21 from below), and a ring 22 in the form of a circular ring gear, which is coaxial with the rotation axis C and located at the upper end of the annular wall 21, circumferentially defining an opening toward the inner compartment 25 of the support assembly. The outer periphery of the upper portion 14a of the worktable 14 is superimposed on the ring 22.

[0029] The labyrinthine device 30 operates between the ring 22 and the outer region of the upper portion 14a to achieve a seal between the rotary table 14 and the fixed support assembly 12.

[0030] The worktable assembly 10 also includes a plurality of hydrostatic sliders 40 for supporting the worktable 14 by pressurized fluid, which can provide a bottom-up lifting force F1 that tends to lift the worktable 14 relative to the support assembly 12, thereby disengaging the worktable from contact with the support assembly and allowing rotation with low friction.

[0031] Preferably, the hydrostatic slider 40 is located below the ring gear 20 to cooperate with the lower surface 20' of the ring gear 20 to form a pressure chamber 40' or a channel (meatus).

[0032] According to a preferred embodiment, each hydrostatic slider 40 has an inner bag 42 for forming an inner channel and an outer bag 44 located radially outside the inner bag 42 for forming an outer channel.

[0033] Preferably, the workbench assembly 10 further includes: a first hydraulic pump and a first circuit connected to the first hydraulic pump for supplying pressurized fluid to the inner pockets 42 of all hydrostatic sliders 40; and a second hydraulic pump and a second circuit connected to the second hydraulic pump for supplying pressurized fluid to the outer pockets 44 of all hydrostatic sliders 40.

[0034] The worktable assembly 10 also includes a detection device adapted to detect the lifting force F1 generated by the main slider 40; for example, the detection device includes at least one pressure sensor (not shown) for detecting the fluid pressure operating in the main pressure chamber 40'; preferably, the worktable assembly includes a first pressure sensor operating along a first loop and a second pressure sensor operating along a second loop.

[0035] In a preferred embodiment, a plurality of pressure sensors are provided that detect pressure in only a few main sliders. The detected pressure values ​​are interpolated to estimate the pressure values ​​also on other sliders, and thereby the lifting force F1 is calculated.

[0036] Fluid escaping from the main chamber 40' of the main slider 40 is preferably collected by gravity on the bottom 23 of the support assembly 12 and returned by the pumping device 50 to the hydrodynamic unit, which pressurizes the hydrostatic slider supply circuit.

[0037] For example, the worktable assembly 10 includes twelve main sliders that are equidistant from each other at an angle.

[0038] Furthermore, according to the invention, the worktable assembly 10 includes a plurality of stops 60 adapted to be operated by pressurized fluid on the worktable 14 to provide a counterforce F2 from top to bottom, opposite to the lifting force F1.

[0039] Preferably, the stop 60 is disposed above the ring gear 20 to cooperate with the upper surface 20'' of the ring gear 20 to form a secondary pressure chamber 60' or channel.

[0040] According to other embodiments of the invention, the main slider 40 operates on the lower surface 120' of the main bias portion 120 integral with the worktable 14, and the stop 60 and its secondary slider 70 operate on the upper surface 220' of the secondary bias portion 220 integral with the worktable 14.

[0041] According to a preferred embodiment, each stop 60 includes a body 62 intended to be fixed to the support assembly 12, within which at least one piston chamber 64 is obtained, which can be fed pressurized fluid via a control circuit 66.

[0042] The stop block 60 also includes a sealing sliding piston 68 in the piston chamber 64, preferably a double-acting piston along the actuation direction K.

[0043] The stop block 60 also includes a hydrostatic secondary slider 70, which can be biased by the piston 68 to push the upper surface 20'' of the ring gear 20 upward, thereby forming a secondary pressure chamber 60'.

[0044] The auxiliary slider 70 is preferably movable relative to the piston 68 along the actuation direction K. In other words, with the piston 68 fixed, the slider 70 can move along the driving direction K to change the height of the corresponding auxiliary pressure chamber 60'.

[0045] For this purpose, the auxiliary slider 70 engages with the piston 68 by at least one flat-head screw (not shown) that is housed in the piston housing 72 and the slider housing 74 with clearance and aligned along the actuation direction K.

[0046] Fluid escaping from the secondary pressure chamber 60' of the secondary slider 70 is preferably collected by gravity and returned to the fluid power unit via the pumping device 50.

[0047] According to an embodiment, the piston can be actuated by, for example, an electrically powered universal piston actuator.

[0048] We will assume that the main slider 40 of the worktable assembly 10 can support the maximum load Pmax, the worktable 14 has a weight Ptav, and the semi-finished product to be processed has a weight Psem.

[0049] In the step of setting up the worktable assembly 10, the worktable 14 is positioned on the support assembly 12, and the main slider 40 is actuated until the worktable 14 is lifted. Based on the pressure value detected by the pressure sensor, the weight Ptav of the worktable can be determined, which constitutes the tare weight of the system.

[0050] When the semi-finished product is placed on the worktable 12, the pressure of the fluid operating on the main slider 40 increases; the weight Psem of the semi-finished product can be determined based on the value measured by the pressure sensor.

[0051] Therefore, the total load on the worktable 14 is Ptot = Ptav + Psem.

[0052] Under the specified rated load P (where Ptot < P) ≤ Pmax, i.e., greater than the total load but less than or equal to the maximum load that the main slider can withstand, preferably equal to the maximum load (P After Pmax is reached, pressurized fluid is supplied to stop 70, which operates with thrust on the corresponding piston 68 to obtain an additional load equal to the opposing force F2 = Pmax. -Ptot, meaning the opposing force is equal to the difference between the rated load and the total load pressing on the worktable.

[0053] Therefore, the main sliders 40 are subjected to a load equal to the rated load P. It operates under conditions of load and load supplied by pressurized fluid to generate a lifting force equal to the rated load, i.e., F1 = P. .

[0054] Under the same load applied to the slide, the height of the main pressure chamber 40' is constant. This means that the upper surface 14' of the worktable 14 is at a constant height relative to the tool carried by the machine head 6, even when the weight of the semi-finished product changes.

[0055] The weight of the semi-finished product changes because different semi-finished products with different weights are processed at different times, or because the weight changes due to chip separation during the processing of the intended semi-finished product.

[0056] In other words, the worktable assembly 10 includes an electronic management device operatively connected to the main slide 40, the stop 60, and the detection device. This electronic management device is configured to control the stop 60 to generate a counterforce F2, such that the lifting force F2 is equal to a predetermined constant rated load P. .

[0057] Furthermore, the loads on the main slider are equal, and the stiffness of the main slider is constant. In fact, it is well known that the stiffness of a hydrostatic slider is not linear, but varies with the load on the slider itself. On the other hand, this invention makes it possible to maintain constant stiffness, and, taking into account the proportional relationship between weight load and stiffness, maintain it in fact equal to the maximum stiffness.

[0058] As mentioned above, all of these factors enable the use of worktable sets to ensure reduced machining tolerances, as needed in the field.

[0059] Obviously, those skilled in the art can modify the machine tool described above, and all modifications are included within the scope of protection defined in the appended claims in order to meet possible needs.

Claims

1. A worktable assembly (10) for a machine tool (1), the machine tool being positioned on a horizontal reference plane, the worktable assembly comprising: - Support assembly (12), the support assembly includes a support member (13), the support member includes an annular wall (21) defining the inner compartment (25); - Workbench (14), which is supported by the support assembly (12) and is rotatable about a vertical axis of rotation (C); - A main bias portion and a secondary bias portion, wherein the main bias portion is provided with a lower surface and the secondary bias portion is provided with an upper surface, and the main bias portion and the secondary bias portion are combined with the worktable (14); - A plurality of main slides (40) under static pressure, the plurality of said main slides being fixed to said support assembly (12) and adapted to support said worktable (14) by pressurized fluid, thereby generating lifting force (F1), each of said main slides (40) being configured to form a main pressure chamber (40') with the lower surface of said main bias portion, wherein a channel for supporting said worktable (14) is formed in said main pressure chamber; - A detection device adapted to detect the lifting force (F1) generated by the main slider (40). - Multiple stops (60), the multiple stops being fixed to the support assembly (12), adapted to push the worktable (14) toward the main slider (40) by pressurized fluid, thus generating an opposing force (F2), wherein each of the stops (60) includes a hydrostatic sub-slider (70), each of the sub-slider (70) being configured to create a sub-pressure chamber (60') with the upper surface of the sub-biased portion, wherein a channel is formed in the sub-pressure chamber to push the worktable (14) toward the main slider (40); - An electronic management device, operatively connected to the main slider (40), the stop (60), and the detection device, is configured to control the stop (60) to generate a counterforce (F2) such that the lifting force (F1) is equal to a predetermined constant rated load (P). The rated load is greater than the weight of the semi-finished product and less than or equal to the maximum load (Pmax) that the main slider (40) can withstand.

2. The workbench assembly (10) according to claim 1, comprising: - At least one electric motor (16) adapted to rotate the worktable (14); - A ring gear (20) engages with the worktable (14) and is operatively connected to the motor (16). - wherein the ring gear (20) forms the main bias portion (120), and the lower surface (20') of the ring gear (20) forms the lower surface (120') of the main bias portion (120).

3. The workbench assembly (10) according to claim 1 or 2, comprising: - At least one electric motor (16) adapted to rotate the worktable (14); - A ring gear (20) engages with the worktable (14) and is operatively connected to the motor (16). - wherein the ring gear (20) forms the secondary bias portion (220), and the upper surface of the ring gear (20) forms the upper surface of the secondary bias portion (220).

4. The workbench assembly (10) according to claim 1 or 2, wherein each of the stops (60) further comprises a body (62) and a piston (68) having at least one piston chamber (64) within the body, the piston sliding in the piston chamber (64) to bias the corresponding sub-slider (70) toward the upper surface of the sub-biasing portion.

5. The worktable assembly according to claim 4, wherein the secondary slider (70) floats relative to the piston (68) along the actuation direction (K).

6. The worktable assembly according to claim 5, wherein the secondary slider (70) engages with the piston (68) by at least one flat-head screw aligned along the actuation direction (K), the at least one flat-head screw being received in a gapped manner in the piston seat (72) and the slider seat (74).

7. The worktable assembly according to claim 1 or 2, wherein the detection device includes at least one pressure sensor configured to detect the pressure of a fluid operating on the main slider (40).

8. A machine tool (1) comprising a worktable assembly (10) according to any one of the preceding claims.

9. The machine tool according to claim 8, including a vertical axis lathe, milling machine or machining center.

10. A method for managing a machine tool (1) according to claim 8 or 9, comprising the following steps: - The predetermined semi-finished product is supported on the worktable (14) of the worktable group (10) of the machine tool (1) by the main slide block (40) fed with hydrostatic pressure by fluid with a predetermined pressure, so that a lifting force (F1) is generated on the worktable (14), and the main slide block forms a channel; - Detect the lifting force (F1); -Limited rated load (P) The rated load is greater than the lifting force (F1) and less than or equal to the maximum load (Pmax) that the main slider (40) can withstand. - Define the opposing force (F2), which is equal to the rated load (P). The difference between F2 and the maximum load (Pmax) (F2=Pmax-P) ); - Actuate the multiple stops (60) of the worktable assembly (10) to press the worktable (14) with the opposite force (F2) that is opposite to the lifting force (F1).

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