Positioning table

Abstract: A positioning table includes a pair of direct drive motors (12,13) mounted on a flat surface of a base (11). One of the direct drive motor drives a parallel crank mechanism (28) so as to move a table in one direction (A). The other direct drive motor drives an arm member (37) connected to the table (42) through a rail (43), so as to move the table in the other direction (B) perpendicular to the one direction. Thus, the table can be moved in a common plane into a desired position by driving the pair of direct drive motors.

Description: This invention relates to a positioning table movable in a plane in the directions of the X-axis (the abscissa) and the Y-axis (the ordinate) of the coordinates disposed perpendicular to each other. Description of the Prior Art Positioning tables of the type under consideration have been widely used in an assembling machine, a machine tool, a measuring apparatus, and etc. A typical example of such positioning tables as shown in Fig. 6 comprises an X-table 3 mounted on a bed 1 for sliding movement along a pair of roller guides 2, 2 provided respectively on opposite side portions of the bed 1. A Y-table 5 is mounted on the X-table 3 for sliding movement along a pair of roller guides 4, 4 in a direction perpendicular to the direction of movement of the X-table 3. A motor 6 is fixedly mounted on one end of the bed 1, and another motor 7 is fixedly mounted on one end of the X-table 3. The motor 6 is connected to the X-table 3 by a ball-screw rod (not shown), and the motor 7 is connected to the Y-table 5 by a ball-screw rod 8. Therefore, when the motor 6 is driven, the X-table 3 is moved relative to the bed 1, and when the motor 7 is driven, the Y-table 5 is moved relative to the X-table 3. In the above conventional positioning table, since the driving forces are transmitted to the X- and Y-tables 3 and 5 through the ball-screw rods, positioning accuracies are not satisfactory because of backlashes. Further, the bed 1, the X-table 3 and the Y-table 5 are arranged in a three-layer manner, and the two motors 6 and 7 are projected from the sides of the positioning table. Therefore, the overall construction of the positioning table is rather bulky. It is an object of this invention to provide a positioning table which achieves high positioning accuracies and can make a machine or apparatus, incorporating the positioning table, smaller in size. JP-A-59-081027 discloses a positioning table providing the basis for the prior art portion of claim 1. In this prior construction, the movable table has two pairs of slide members, each respectively engaged with a single movable rail member with the rail members each forming part of a parallel crank mechanism. The present invention, as defined in claim 1, provides a more compact arrangement in which the second rail is secured to the movable table, whereby the drive to that second rail can be achieved by using a single slide member engaged therewith, driven from an arm member secured to the second motor shaft, without need of a second parallel crank mechanism. This permits a very compact, while still accurate, construction. When the first direct drive motor is rotated, the first rail is moved through the parallel crank mechanism to move the table in one direction, for example, in an X-direction along the second rail. When the second direct drive motor is rotated, the third arm member moves the table in the other direction, for example, in a Y-direction along the first rail. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic plan view of a positioning table provided in accordance with the present invention; Fig. 2 is a cross-sectional view of the positioning table, as viewed from the front side; Fig. 3 is a cross-sectional view of a portion of the positioning table; Figs. 4 and 5 are plan views of the positioning table, showing different operative conditions of the positioning table, respectively; and Fig. 6 is a schematic perspective view of a conventional positioning table. DESCRIPTION OF THE PREFERRED EMBODIMENT The invention will now be described with reference to the drawings. Fig. 1 shows a positioning table according to an embodiment of the present invention. This positioning table includes a base 11 of a generally square shape, and a pair of first and second direct drive motors 12 and 13 of an identical size fixedly mounted on an upper surface of the base 11 and disposed substantially on one diagonal line of the square base 11. Rotatable shafts 14 and 15 of the direct drive motors 12 and 13 are directed upwardly. A first arm member 19 has a disk-shaped proximal end portion 16, and two arms 17 and 18 extending radially from the proximal end portion 16 and spaced an angle of substantially 90° from each other. The proximal end portion 16 of the first arm member 19 is fixedly mounted on the rotatable shaft 14 of the first direct drive motor 12. The first arm member 19 is disposed in parallel relation to the base 11. Like the first arm member 19, a second arm member 23 has a disk-shaped proximal end portion 20, and two arms 21 and 22 extending radially from the proximal end portion 20 and spaced an angle of substantially 90° from each other. The proximal end portion 20 of the second arm member 23 is angularly movably mounted on a support shaft 24 fixedly mounted on the base 11 in perpendicular relation thereto. The second arm member 23 is disposed in parallel relation to the base 11. A straight line, passing through the center O1 of the proximal end portion 16 of the first arm member 19 and the center O2 of the proximal end portion 20 of the second arm member 23, is substantially parallel to one side 11a of the base 11. The height of the support shaft 24 is smaller than the height of the first direct drive motor 12. Upwardly-directed pins 25 and 26 are provided respectively on the distal end portion of the arm 17 of the first arm member 19 and the distal end portion of the arm 21 of the second arm member 23. The distance between the center O1 of angular movement of the proximal end portion 16 and the center (axis) O3 of the pin 25 is equal to the distance between the center O2 of angular movement of the proximal end portion 20 and the centre (axis) 04 of the pin 26. The pin 26 is provided on an upper end of a boss 27 formed integrally on the distal end portion of the arm 21. The two pins 25 and 26 are angularly movably fitted respectively in two pin-receiving holes 29 and 30 formed in a first rail 28. The distance between the centre 01 and the centre 02 is equal to the distance between the centre 03 and the centre 04. The first and second arm members 19 and 23 cooperate with the first rail 28 to form a parallel crank mechanism. As shown in Figure 1, the pivotal connection at the hole 30 between the distal end of the arm 21 of the second arm member 23 and the rail 28 is at a location intermediate a pair of first and second slide members 34 and 35. Opposite ends of an elongate connecting plate 31 are pivotally connected respectively to the distal end of the arm 18 of the first arm member 19 and the distal end of the arm 22 of the second arm member 23 by pins 32 and 33. The connecting plate 31 serves to reinforce the parallel crank mechanism. The distance between the centre 01 and the centre 05 of the pin 32 as well as the distance between the centre 02 and the centre 06 of the pin 33 is equal to the distance between the centres 01 and 03 as well as the distance between the centres 02 and 04. The distance between the centres 05 and 06 is equal to the distance between the centres 03 and 04. The first and second slide members 34 and 35 are of a channel-shaped cross-section and are slidably fitted on the first rail 28. A third arm member 38 has a disk-shaped proximal end portion 36, and a short arm 37 extending radially from the proximal end portion 36. The proximal end portion 36 is fixedly mounted on the rotatable shaft 15 of the second direct drive motor 13. The third arm member 38 is disposed in parallel relation to the base 11. A pin-receiving hole 39 is formed in the distal end of the arm 37 of the third arm member 38, and a pin 41 formed on a lower surface of a third slide member 40 of a channel-shaped cross-section is angularly movably received in the pin-receiving hole 39. A second rail 43 is fixedly secured to a reverse or lower surface of a table 42, the second rail 43 extending in a direction perpendicular to the first rail 28. The third slide member 40 is fitted on the second rail 43 from the lower side thereof so as to slide therealong. The first and second slide members 34 and 35 are also fixedly secured to the reverse surface of the table 42. The operation of the above positioning table will now be described. In the condition shown in Fig. 1, when the first direct drive motor 12 is rotated or angularly moved through an angle of 45° in a clockwise direction (Fig. 1), the parallel crank mechanism, comprising the first and second arm members 19 and 23 and the first rail 28, is angularly moved 45° in a clockwise direction to move the first rail 28 in a parallel manner so as to move the table 42 in a direction A (i.e., X-direction) through the first and second slide members 34 and 35. At this time, since the movement of the table 42 in a Y-direction is prevented by the third arm member 38 through the second rail 43 and the third slide member 40, the second rail 43 slides relative to the third slide member 40 in the direction A, and at the same time the first arm 28 slides relative to the first and second slide members 34 and 35. This condition is shown in Fig. 4. Namely, the table 42 is moved from the position of Fig. 1 only in the direction A. In this condition, when the second direct drive motor 13 is rotated or angularly moved by 45° in a counterclockwise direction, the third arm 38 angularly moves the third slide member 40 through 45° in the same direction, so that the second rail 43 is moved in a direction B (i.e., Y-direction) through the third slide member 40. At this time, since the movement of the table 42 in the X-direction is prevented by the first and second slide members 34 and 35 engaging the first rail 28, the table 42 is moved only in the direction B. This condition is shown in Fig. 5. In an actual machine or apparatus to which the above positioning table is applied, it is preferred that stepping motors of a high resolution be used as the first and second direct drive motors 12 and 13 so as to simultaneously effect the X-direction and Y-direction positionings instantaneously. As described above, in the positioning table according to the present invention, the two direct drive motors are mounted on the common flat surface, and one of the two motors drives the parallel crank mechanism to move the table in one direction. The other direct drive motor drives the third arm member connected to the table through the second rail, so as to move the table in the other direction perpendicular to the one direction. Therefore, high positioning accuracies can be achieved, and a high-speed positioning control can be attained, and the machine or apparatus incorporating the positioning table can be made smaller in size.

Claims: A positioning table comprising: a base (11); a pair of first and second motors (12,13) fixedly mounted on said base (11) and having respective rotatable shafts (14,15) directed upwardly; a first arm member (19) fixedly mounted at its proximal end on said rotatable shaft (14) of said first motor (12); a second arm member (23) angularly movably mounted at its proximal end on said base (11); a first rail (28) to which distal ends of said first and second arm members (19,23) are pivotally connected, said first rail (28) cooperating with said first and second arm members (19,23) to form a parallel crank mechanism; a pair of first and second slide members (34,35) mounted on said first rail (28) for sliding movement therealong; a third arm member (38) fixedly mounted at its proximal end on said rotatable shaft (15) of said second direct drive motor (13); a second rail (43) with a third slide member (40) mounted for sliding movement therealong; and a table (42) having an undersurface to which said first and second slide members (34,35) are fixedly secured in such a manner that the direction of movement of said first and second slide members (34,35) along said first rail (28) is perpendicular to said second rail (43), characterised in that said motors are direct drive motors (12,13), in that the lower surface of third slide member (40) is pivotally mounted on a distal end of the third arm member (38), and in that the second rail (43) is fixedly secured to the undersurface of the table (42). A positioning table according to claim 1, wherein the distal end of one of the first and second arm members (19,23) is pivotally connected to the first rail (28) at a location between said first and second slide members (34,35). A positioning table according to claim 1 or 2, in which each of said first and second arm members (19,23) has a proximal end portion at its axis of rotation, and a pair of arms (17,18;21,22) extending in a common plane from said proximal end portion and spaced a predetermined angle from each other, one (17;21) of said two arms being pivotally connected at its distal end to said first rail (28), said parallel crank mechanism further comprising an elongated connecting plate (31) disposed parallel to said first rail (28), and the other (18;22) of said two arms (17,18; 21,22) of each of said first and second arm members (19,23) being pivotally connected at its distal end to said connecting plate (31). A positioning table according to claim 1, 2 or 3, in which each of said first and second slide members (34,35) has a channel-shaped cross-section and is slidably fitted on said first rail (28), said third slide member (40) having a channel-shaped cross-section and being slidably fitted on said second rail (43).

Inventors: KATO HEIZABURO, KATO, HEIZABURO
Applicants: SANKYO MFG, SANKYO MANUFACTURING COMPANY, LTD.
Application year: 1990
Main classification: B23Q1
IPC codes: B23Q1