ACTIVE VIBRATION DAMPING SYSTEM FOR A PRECISION MOVEMENT SYSTEM

Description

Field of the invention

[0001] The present invention relates to an active anti-vibration system comprising a mounting base for a precision motion system, in particular for a semiconductor processing equipment. The anti-vibration system comprises active bearings for isolating the mounting base from ground vibrations and imparting counteracting forces to the mounting base to compensate for reactions forces generated by the precision motion system when operating. The active anti-vibration system is adapted for easy replacement of an active bearing in case of failure. The invention also relates to a method for disassembling an active bearing from the active anti-vibration system for its replacement.Background of the invention

[0002] Precision motion systems, in particular semiconductor processing equipment such as positioning devices, coordinate measuring machines or robots, comprise active anti-vibration systems, as disclosed in US6021991 or KR20120022572A, for isolating precision motion systems from ground vibrations. Active anti-vibration systems typically comprise several active bearings which are assembled between a granite base onto which the precision motion system can be mounted and a metallic frame that rests on the floor. Active anti-vibration systems therefore ensure the operation of precision motion systems with as little parasitic movement as possible, as a result of which a high positioning or measurement accuracy is obtained.

[0003] Each active bearing comprises linear motors, vertical and horizontal sensors that are connected to electronic controllers to drive each linear motor as a function of the output of vertical and horizontal sensors and as a function of the known movements of the precision motion system to avoid unwanted movements of the granite base and dampen any residual movements. The active bearings support the granite base upwardly using a mechanical spring or an air spring, thereby passively isolating the base from the floor vibrations.

[0004] Active bearings are therefore complex systems that sometimes must be replaced in case of failure. Replacement of any active bearing is however difficult as it implies disassembling the granite base from the metallic frame in order to unscrew the active bearings.Brief summary of the invention

[0005] An aim of the present invention is therefore to provide an active anti-vibration system for a precision motion system, adapted for easy replacement of active bearings in case of failure.

[0006] Another aim of the present invention is to provide a method for disassembling an active bearing from the active anti-vibration system for easy replacement of the active bearing.

[0007] These aims are achieved notably by an active anti-vibration system according to claim 1.

[0008] According to claim 1, each of the first set of fixation elements is in the form of a screw. The upper panel comprises threaded through-holes axially aligned with respective through-holes of the mounting base and receiving a threaded part of respective screws.

[0009] In an embodiment, each through-hole of the mounting base comprises an upper portion having a first diameter and a lower portion having a second diameter smaller than the first diameter to form a shoulder onto which the screw head of a corresponding screw rests to secure the active bearing upper panel to the lower side of the mounting base.

[0010] According to claim 1, each of said second set of fixation elements is in the form of a screw. The lower panel of each active bearing comprises trough-holes and captive screw retainers. Each captive screw retainer comprises a housing lodging a screw engaged with respective through-hole of the lower panel of the active bearing. The housing comprises an upper portion having a central opening axially aligned with the screw head of the screw. The upper side of the supporting frame comprises threaded holes receiving a threaded part of the screw of respective captive screw retainer.

[0011] In an embodiment, the trough-holes of each active bearing lower panel are axially aligned with respective threaded through-holes of each active bearing upper panel.

[0012] In an embodiment, each captive screw retainer further comprises a magnet arranged to hold the screw when said screw is removed from the corresponding threaded hole of the upper side of the supporting frame during the disassembly of the corresponding active bearing for its replacement.

[0013] Another aspect of the invention relates to a method for disassembling and removing an active bearing from the active bearing compartment of the active anti-vibration system as described above. The method comprises the steps of: a. handling a screwing tool to unscrew and remove the first set of screws from the trough-holes of the mounting base to disconnect the upper panel of an active bearing from the lower side of the mounting base; b. handling the screwing tool with a rod to align the distal end of the rod with one through-hole of the mounting base and to move down the rod through the through-hole, the threaded through-hole of the active bearing upper panel down to the central opening of the housing of one captive screw retainer to engage with the screw head of the screw; c. handling the screwing tool to disengage with the rod the threaded part of the screw from the corresponding threaded hole of the supporting frame to disconnect the active bearing lower panel from the upper side of the supporting frame; d. repeating steps b. and c. for the other screws connecting the active bearing to the upper side of the supporting frame, and e. sliding the active bearing out of the active bearing compartment of the active anti-vibration system. Brief description of the drawings

[0014] The invention will be better understood with the aid of the description of several embodiments given by way of examples and illustrated by the figures, in which: Figure 1 shows a perspective view of the active anti-vibration system comprising several active bearings assembled between a mounting base and a supporting frame that rests on the floor, whereby one active bearing is disassembled from the active anti-vibration system; Figure 2 is a partial cross-sectional view of Figure 1, when a screw is removed from an upper panel of an active bearing to disconnect the active bearing upper panel from the mounting base; Figure 3 is an enlarged view of Figure 2 in the area of the active bearing; Figure 4 is a partial cross-sectional view of Figure 1, when a screw of a captive screw retainer is removed from a lower panel of the active bearing to disconnect the active bearing lower panel from an upper side of the supporting frame; Figure 5 is an enlarged view of Figure 4 in the area of the active bearing; Figure 6 is a perspective view of the captive screw retainer of Figure 4; Figures 7a and 7b are perspective view of a captive screw retainer comprising a flat side according to another embodiment; Figure 8 is a perspective view of a portion of the active bearing lower panel comprising the captive screw retainer of Figure 7; Figure 9 is a cross-sectional view of the portion of the active bearing lower panel of Figure 8 sliding on the upper side of the supporting frame when the active bearing is mounted on or removed from the active anti-vibration system; Figure 10 is a similar view when the active bearing has reached its mounting position before being fixed to the upper side of the supporting frame of the active anti-vibration system, and Figure 11 is a similar view when the active bearing has been fixed to the upper side of the supporting frame of the active anti-vibration system. Detailed description of several embodiments of the invention

[0015] With reference to Figure 1, the active anti-vibration system 10 comprises a mounting base 12 having an upper side 12a onto which a precision motion system, for example a semiconductor processing equipment, can be mounted. The mounting base 12 is preferably in granite and comprises multiple threaded holes for fixing different type of precision motion systems. The mounting base 12 may further comprise a support 16 for installing an optical imaging device, such as a microscope for visual inspection. The active anti-vibration system 10 further comprises a supporting frame 18 resting on the floor, and active bearings 30 mounted into an active bearing compartment 26 between the mounting base 12 and the supporting frame 18. Each active bearing 30 comprises a mechanical spring or an air spring (not shown) to support the mounting base, and passively isolate the base from the floor vibrations.

[0016] Four active bearings 30 are typically mounted on the four corners of the active bearing compartment 26 which is defined by a lower side 12b of the mounting base 12 and an upper side 19 of the supporting frame 18 as shown for example in Figure 2. The active bearing 30 comprises inertial sensors and actuators to provide together a six degrees-of-freedom (DOF) measurement of the motions of the mounting base 12 as well as six-DOF actuation devices. Six-DOF measurement is obtained with six or more inertial sensors shared out among the active bearings. Six-DOF actuation can be realized with six or more actuators shared out among the active bearings. In a preferred embodiment, three active bearings comprise each a horizontal and a vertical actuator, and a horizontal and a vertical inertial sensor, and the fourth active bearing comprises a horizontal and a vertical actuator only.

[0017] The sensors and actuators are built into an active damping multiple-inputs / multiple-outputs (MIMO) control loop that dampens any residual vibrations of the granite base. An active feedforward path is implemented which uses the known motions of the motion system to compute forces and torques to be applied by the actuators to the mounting base to compensate for reaction forces and thus avoid unwanted motions of the base.

[0018] Each active bearing 30 further comprises an upper panel 32 mounted against the lower side 12b of the mounting base 12, and a lower panel 36 mounted against the upper side 19 of the supporting frame 18.

[0019] With reference to Figure 3, the mounting base 12 of the active anti-vibration system 10 comprises through-holes 13 extending from the upper side 12a to the lower side 12b of the mounting base 12. Each through-hole 13 of the mounting base 12 comprises an upper portion having a first diameter d1 and a lower portion having a second diameter d2 smaller than the first diameter d1 to form a shoulder 14. A first set of fixation elements 15 are arranged into the through-holes 13 to fix the upper panel 32 of each active bearing 30 against the lower side 12b of the mounting base 12. The fixation elements 15 are preferably screws 15 comprising a screw head 15a resting on the shoulder 14 and a threaded part 15b extending through the lower portion of the second diameter d2, wherein a distal portion of the threaded part 15b is screwed into a corresponding threaded through-hole 34 of the upper panel 32 of the active bearing 30.

[0020] A second set of fixation elements are arranged into through-holes 37 of the lower panel 36 of each active bearing 30 to fix the active bearing lower panel 36 to the upper side 19 of the supporting frame 18. In an advantageous embodiment, the second set of fixation elements are in the form of three or more captive screw retainers 40.

[0021] With reference to Figures 6 to 11, each captive screw retainer 40 comprises a housing 42 which may be obtained for example by an additive manufacturing process. The housing is typically in plastic and is adapted to house a screw 48 engaged with respective through-hole 37 of the active bearing lower panel 36. The housing 42 comprises an upper portion 44 having a funnel shape with a central opening 45 aligned with the screw head 48a of the screw 48 as shown in Figures 9 to 11. The upper side 19 of the supporting frame 18 comprises threaded holes 20 into which are screwed a threaded part 48b of the screw 48 of respective captive screw retainer 40.

[0022] Each captive screw retainer 40 further comprises a magnet 47 arranged in the housing 42 to hold the screw 48 within the captive screw retainer when the screw is removed from the corresponding threaded hole 20 of the upper side 19 of the supporting frame 18 during the disassembly of the corresponding active bearing 30 for its replacement.

[0023] The housing 42 of the captive screw retainer 40 may be fixed to the active bearing lower panel 36 with different fixation means. In the illustrated embodiment, the housing 42 is screwed onto the active bearing lower panel 36. In this respect, the housing 42 comprises two lateral openings 50 comprising each a through-hole 52 extending through the mounting base of the housing for accommodating a screw 49 ensuring the connection with the active bearing lower panel 36 as shown in Figures 9 to 11. In a non-illustrated embodiment, the housing of the captive screw retainers may simply be glued onto the active bearing lower panel.

[0024] In case the captive screw retainers 40 need to be placed very near the edge of the upper side surface of the supporting frame 18 or mechanical parts in the active bearing limit the space available, the housing 42 can be cut along a vertical plane to have flat side 46 as shown for example in Figure 7a.

[0025] The trough-holes 37 of the active bearing lower panel 36 are axially aligned with respective threaded through-holes 34 of active bearing upper panel 32 for easy replacement of any active bearing in case of failure as described subsequently.

[0026] Referring to Figures 2 and 3, which show an operation to remove a faulty active bearing 30 from the active anti-vibration system for its replacement, a screwing tool is used to remove the first set of screws 15 connecting the active bearing upper panel 32 to the lower side 12a of the mounting base 12. For this operation a screwdriver or a torque wrench 100, such as a ratchet wrench 100, may be used. In the latter case, a rod 102a with a distal end configured to engage the screw head 15a of the screws 15 is used together with the wrench 100 for unscrewing the threaded part 15b of the screws from respective threaded through-hole 34 of the active bearing upper panel 34. The distal end of the rod 102a is magnetized to lift the screws 15 out of the trough-holes 13 of the mounting base 12.

[0027] Once the screws 15 are removed from the mounting base 12, the wrench 100 is used with another rod 102b which is specifically designed to unscrew the screw head 48a of respective captive screw retainer 40 of the active bearing lower panel 36 from the upper side 12a of the mounting base 12. The length of this rod 102b is therefore significantly longer than the rod 102a used for removing the first set of screws 15. The outer diameter of this rod 102b is also smaller than both the lower portion d2 of the trough-holes 13 and the threaded through-hole 34 of the active bearing upper panel 32.

[0028] The wrench 100 can thus be handled to introduce the rod 102b into each through-hole 13 and to move its distal end downwardly though the corresponding threaded through-hole 34 of the active bearing upper panel 34 down to respective captive screw retainer 40. The funnel-shaped upper portion 44 of the housing 42 of respective screw retainer 40 guides the distal end of the rod 102b into the central opening 45 such that the distal end of the rod 102b engages with the screw head 48a of respective captive screw retainer 40.

[0029] The wrench 100 is then handled for unscrewing the threaded part 48b of the screws from respective threaded hole 20 of upper side 19 of the supporting frame 18 of the anti-vibration system 10. As soon as the threaded part 48b of these screws are disengaged from the supporting frame upper side and the rod 102b is disengaged from the screw head 48a, the magnet 47 of the captive screw retainer 40 attracts and hold the screws 48 such that the end of the threaded part 48b is inside respective through-hole 37 of the active baring lower panel 36 and distant from the upper side 19 as shown in Figure 9. When all captive screws 48 have been released, the active bearing 30 can thus be slid along the upper side 19 out of the active bearing compartment 26 without scrapping the upper side surface of the supporting frame 18. A screw jack 17 can be used to temporarily slightly increase the height of the active bearing compartment 26 to facilitate the sliding of the active bearing 30 out of the active bearing compartment and into said compartment.

[0030] Before mounting a new active bearing 30, the magnet 47 of each captive screw retainers 40 mounted on the active bearing lower panel 36 hold respective screws in the same position shown in Figure 9. The new active bearing 30 can thus be placed inside the active bearing compartment 26 of the anti-vibration system 10 and slid on the upper side surface of the supporting frame in its mounting position, whereby the threaded through-holes 34 of the active bearing upper panel 32 and the through-hole 37 of the active bearing lower panel 36 are axially aligned with the respective through-holes 13 extending from the upper side 12a to the lower side 12b of the mounting base.

[0031] With reference to Figure 4, the ratchet wrench 100 is then handled in a similar way as for disengaging the screws from respective threaded hole 20 of upper side 19 of the supporting frame 18 of the anti-vibration system as explained above. This time, the ratchet wrench 100 is handled to fix the active bearing lower panel against the supporting frame by screwing the threaded part of screws in the respective threaded holes 20 of the upper side of the supporting frame as shown in Figure 10 and 11.

[0032] The screws 15 are then positioned in the respective through-holes 13 of the mounting base 12 and screwed, by the ratchet wrench 100 with the extension 102a into respective threaded through-holes 34 of the active bearing upper panel 32.Reference list

[0033] Active anti-vibration system 10 Mounting base 12 Upper side 12a Lower side 12b Through-holes 13 Upper portion of a first diameter d1 Lower portion of a second diameter d2 Shoulder 14 Fixation element 15 (e.g. screw) Screw head 15a Threaded part 15b Support 16 Screw jack 17 Supporting frame 18 Upper side 19 Threaded hole 20 Active bearing compartment 26 Active bearings 30 Upper panel 32 Threaded through-hole 34 Lower panel 36 Through-hole 37 Captive screw retainer 40 Housing 42 Upper portion 44 Central opening 45 Flat side 46 Magnet 47 Screw 48 Screw head 48a Threaded part 48b Fixation means 49 (e.g. screw) Lateral openings 50 Through-hole 52 Tool 100 (e.g. ratchet wrench, screwdriver) First rod 102a Second rod 102b

Claims

1. Active anti-vibration system (10) comprising a mounting base (12) having an upper side (12a) onto which a motion system can be mounted, a supporting frame (18) resting on the floor, and active bearings (30) mounted into an active bearing compartment (26) defined by a lower side (12b) of the mounting base (12) and an upper side (19) of the supporting frame (18), each active bearing (30) comprising actuators for imparting counteracting forces to the mounting base (12) to compensate for reactions forces generated by the motion system, when mounted onto the mounting base (12) and operating, to avoid unwanted movements of the mounting base (12) and dampen any residual movements, each active bearing (30) further comprising an upper panel (32) mounted against the lower side (12a) of the mounting base (12) and comprising threaded through-holes (34), a lower panel (36) mounted against the upper side (19) of the supporting frame (18), and a first set of screws (48) securing the active bearing lower panel (36) to the upper side (19) of the supporting frame (18), wherein the mounting base (12) comprises through-holes (13) extending from the upper side (12a) to the lower side (12b) of the mounting base (12) and axially aligned with the through-holes (13) of the upper panel (32) of respective bearing member (30), and a second set of screws (15) comprising a threaded part (15b) screwed into respective through-holes (18) to secure the active bearing upper panel (32) to the lower side (12b) of the mounting base (12) and characterized in that the lower panel (36) of each active bearing (30) comprises trough-holes (37) and captive screw retainers (40), each captive screw retainer comprising a housing (42) lodging a screw (48) of said first set of screws, said screw being engaged with respective through-hole (37) of the lower panel (36) of the active bearing, the housing (42) comprising an upper portion (44) having a central opening (45) axially aligned with the screw head (48a) of the screw (48), the upper side (19) of the supporting frame (18) comprising threaded holes (20) receiving a threaded part (48b) of the screw (48) of respective captive screw retainer (40).

2. Active anti-vibration system (10) according to the preceding claim, wherein each through-hole (13) of the mounting base (12) comprises an upper portion having a first diameter (d1) and a lower portion having a second diameter (d2) smaller than the first diameter (d1) to form a shoulder (14) onto which the screw head (15a) of a corresponding screw (15) rests to secure the active bearing upper panel (32) to the lower side (12b) of the mounting base (12).

3. Active anti-vibration system (10) according to any preceding claim, wherein the trough-holes (37) of each active bearing lower panel (36) are axially aligned with respective threaded through-holes (34) of each active bearing upper panel (32).

4. Active anti-vibration system (10) according to any preceding claim, wherein each captive screw retainer (40) further comprises a magnet (47) arranged to hold the screw (48) when said screw is removed from the corresponding threaded hole (20) of the upper side (19) of the supporting frame (18) during the disassembly of the corresponding active bearing (30) for its replacement.

5. Method for disassembling and removing an active bearing (30) from the active bearing compartment (26) of the active anti-vibration system (10) according to any preceding claim, the method comprising the steps of: a. handling a screwing tool (100) to unscrew and remove the first set of screws (15) from the trough-holes (13) of the mounting base (12) to disconnect the upper panel (32) of an active bearing (30) from the lower side (12a) of the mounting base (12); b. handling the screwing tool (100) with a rod (102b) to align the distal end of the rod (102b) with one through-hole (13) of the mounting base (12) and to move down the rod (102b) through the through-hole (13), the threaded through-hole (34) of the active bearing upper panel (32) down to the central opening (45) of the housing (42) of one captive screw retainer (40) to engage with the screw head (48a) of the screw (48), c. handling the screwing tool (100) to disengage with the rod (102b) the threaded part (48b) of the screw (48) from the corresponding threaded hole (20) of the supporting frame (19) to disconnect the active bearing lower panel (32) from the upper side (19) of the supporting frame (18), d. repeating steps b. and c. for the other screws (48) connecting the active bearing (30) to said upper side (19) of the supporting frame (18), and e. sliding the active bearing (30) out of the active bearing compartment (26) of the active anti-vibration system (10).