LINEAR GUIDEWAY AND CARRIAGE ASSEMBLY FOR MANIPULATORS

Abstract: A rectilinear guideway and carriage assembly for supporting a robotic arm for up and down movement, comprises an extruded column (1) having guide flanges (6, 7, 8), and a carriage having five pairs (21, 22, 23) of rollers (30, 32) arranged to travel along the guide flanges so that the carriage is guided for movement longitudinally of the column. One roller (32) of each pair is adjustable for the rollers to grip the flanges. A timing belt (40) is secured to the carriage and is trained around a drive pulley at the lower end of the column and an idler pulley (42) at the upper end of the column, pulley (42) being movable to adjust the belt tension. A flexible blind (61) is secured to the carriage for covering the mouth of the channel in which the carriage moves, the blind being guided by lips (10) at the mouth edges. The blind passes around rolls (60) at the ends of the column and includes a stretch extending along the length of the column through a passage (11) defined between the rear wall (2) and a partition wall (5) of the extrusion.

Description: Linear guideway and carriage assembly for manipulators This invention relates to a rectilinear guide- way and carriage assembly for supporting a manipulating device, especially a robotic arm for up and down move¬ ment. • In order to enable accurate control of the spatial position and movement of an implement, such as a gripper carried by a robotic arm it is important that the supporting system should keep to a minimum undesirable relative " displacements between those parts which are arranged to move relative to each other. In the case of a linear guideway and carriage assembly, any displacement of the carriage in a direction other than the longitudinal direction of the guideway is undesirable. The present invention has as its basic objective to provide a linear guideway and carriage assembly which meets with these requirements and which is also economic to manufacture and convenient and reliable in use. In accordance with the invention there is provided a rectilinear guideway and carriage assembly for supporting a robotic arm or the like for up and down movement, comprising an elongate column, and a carriage received on the column and guided thereon for movement in the longitudinal direction of the column, characterised in that the column is an extrusion having first, second and third guide flanges extending continuously therealong, and the carriage comprises a rigid body, a first set of rolling elements mounted on the body and engaging both sides of the first guide flange to restrain the carriage against lateral and tilting movements in a first plane, a second set of rolling elements mounted on the body and engaging both sides of the second guide flange to restrain the carriage against lateral and tilting movements in a second plane transverse to said first plane, and a third set of rolling elements mounted on the body and engaging both sides of the third guide flange for restraining the carriage against turning in a third plane normal to the longitudinal direction of the extrusion. By making the column as an extrusion it can be manufactured at relatively low cost, and by arranging the sets of rolling elements to engage both sides of the guide flanges formed on the extrusion the carriage can be constrained to move longitudinally of the ex¬ trusion without over constraining the system, which would introduce a tendency for the carriage to become jammed on the column due to dimensional variations along the column which are inevitable because of the practical tolerance limitations of the extrusion process. In a preferred embodiment of the invention the extrusion comprises a channel section for receiving the carriage, the guide flanges being provided on the inner end wall and two side walls of the channel, respectively. The first and second flanges are orthogonal to each other and the third flange lies in a plane parallel to that of the second flange, this arrangement of the flanges being optimum for opposing the undesired movements of the carriage relative to the column. The extrusion can conveniently be formed with mounting slots, e.g. of T-shaped cross-section in the rear wall, and with lips adjacent the channel mouth for guiding a flexible blind which can be provided to cover the mouth lips, or other projections may be included for attaching cover panels or the like to the extrusion. At least some of the rolling elements are adjustable on the body for adjusting their engage¬ ment with the guide flanges. In the preferred construct¬ ion the sets of rolling elements comprise pairs of rollers, the r-ol-lers of each pair being arrange to grip one of the guide flanges between them. One roller of each pair is mounted eccentrically on a spindle to enable adjustment relative to the other roller of that pair. The first and second sets of rolling elements each consist of two pairs of rollers spaced apart along the respective guide flange, and the third set of rolling elements consists of a single pair of rollers. This configuration of rollers ensures that the guide system is not over constrained and it can accommodate the dimensional variations of the extruded column. The above and other features of the invention will be understood from the following detailed des¬ cription of the preferred embodiment, reference being made to the accompanying drawings, in which: Figure 1 is a cross-section through the column extrusion; Figure 2 is a perspective view showing schematically the column and the carriage; Figure 3 is a rear view of the carriage; Figure 4 is an end view of the carriage, shown partly in section, and with the column shown in phantom line; Figure 5 is a partly cut-away rear view of the ends of the guideway and carriage assembly; Figure 6 is a longitudinal section through the assembly; Figure 7 is a longitudinal section through an upper end portion of the assembly; Figure 8 is a transverse section through the assembly taken along the line Vlll'-Vlll of Figure 10; Figure 9 is a schematic front view of a medial portion of the assembly; and Figure 10 is a longitudinal section of the assembly portion shown in Figure 9- The rectilinear guideway and carriage assembly illustrated in the drawings is designed for supporting a robotic arm which is carried on the carriage of the assembly. The assembly may be mounted on a stationary base for up and down movement of the carriage in a predetermined location, or may be mounted as part of a mobile robot. The guideway is formed by a column 1 consisting of a length of extruded metal or rigid plastics. As may be seen clearly from Figure 1 , the extrusion in¬ cludes a rear wall 2, opposed side walls 3, 4, and a partition wall 5 defining with the side walls a channel for receiving the carriage. Projecting into the channel from the inner end wall 5 and the two side walls 3j 4 are first, second and third guide flanges 6, 7, 8 which extend continuously along the column. The second and third flanges 7, 8 lie in the same plane which is perpendicular to the plane of the first guide flange 6. The extrusion includes also slots 9 of T-shaped section in the rear wall 2, which slots may be used for mounting the column or for attaching other com¬ ponents to the column. In-turned lips 10 at the mouth of the channel define slots for guiding a flexible blind (described in more detail below), and a longitudin¬ al passage 11 is defined between the partition wall 5 and rear wall 2 for a stretch of the blind to pass through. Out-turned lips 12 at the mouth of the channel define slots which may be used for attaching casing panels to the column. Protruding from the partition wall 5 and parallel to the guide flange 6 is a lip 13 which defines with the flange 6 a shallow groove for receiving a ribbon cable, as described more fully below. It should be noted that the partition wall 5, in addition to defining the passage 11, imparts torsional stiffness to the extrusion. The carriage, depicted schematically in Figure 2, comprises a substantially rigid chassis or body 20 including a main platform extending between opposed sides. The platform carries two pairs 21 of rollers 30, 32 spaced apart along the carriage, the rollers of each pair being arranged to grip between them the flange 6. Similarly, two pairs 22 of rollers 30,32* are carried on one side of the carriage, the rollers of these two pairs being arranged to grip between them the guide flange 7 - A single pair 23 of rollers 30, 32 is carried on the other side of the carriage and the rollers of this pair grip the guide flange 8. Thus, the flanges 6-8 serve as tracks for the three sets of rollers 21-23, respectively. Furthermore, the rollers cooperate with the guide flanges so that the first set of rollers 21 restrains the carriage against rotating or moving laterally in the XZ plane; the second set of rollers 22 restrains the carriage against rotating or moving backwards and forwards in the YZ plane; and the third set of rollers 23 restrain the carriage against rotating in the XY plane about the flange 7 • Thus, the carriage is guided for rectilinear movement in ' the longit.udinal direction Z of the column extrusion, but the system" is not over constrained and will accommodate tolerance variations along the length of the extrusion. Referring now to Figures 3 and 4, each roller 30, 3 consists of a precision bearing fitted with a plastic tyre 33- One roller 30 of each pair is mounted on a spindle 34 having an axis which is fixed with respect to the body 20, and the other larger roller 32 of each pair is carried on an eccentric end of a spindle 35- The end of the spindle opposite the roller is screw threaded and is equipped with a locking nut 36 for clamping the spindle 35 in its adjusted position. Thus, to adjust the pair of rollers to grip the flange 6, 7 or 8 along which the rollers run, the nut 36 is slackened, the spindle 35 is rotated, e.g. by a screw driver engaged with a slot in the end of the spindle, to adjust the separation between the two rollers 30, 32, and the nut 36 is then retightened. It will be noted that all of the nuts 36 are accessible from the front of the carriage through the mouth of the column so that the adjustments can be carried out without dismantling the assembly. Provided on the carriage 20 are bosses 38 which serve as attachment points for the opposite ends of timing belt 40 which is used to drive the carriage up and down on thecolumn. The belt 40 is trained around a driving pulley 41 (Fig- 5) located at the lower end of the column, and a further idler pulley 4 mounted at the upper end of the column. The pulley 41 is driven by an electric motor 43 and gear box 44 which are mounted on the side of the column by a bracket 45- The pulley 42 is movable longitudinally of the column for adjusting the tension in the belt 40. Thus, the pulley 4 is mounted on a shaft carried by a block 46 supported on the column by a bracket 47- The shaft passes through a slot 48 in the side wall of the column and is adjustable along the slot to adjust the belt tension by turning a screw 49 which is threadedly engaged with the block 46 and the head of which is supported by a block 50 fixed on the bracket 47• Clamping screws 51 are provided for fixing the the block 46 securely in position once the tension has been adjusted. The brackets 45, 47 also serve to mount pairs of rolls 60 at the top and .bottom of the column, which rolls serve to guide a flexible blind 6l which covers the mouth of the extrusion channel above and below the carriage. At either end the carriage body 20 has hook-like projections 62 for attaching the ends of the blind 6l, as clearly seen in Figure 7« The blind extends upwardly from the top of the carriage to the rolls 60 at the top of the column, and the blind passes around these rolls and then downwardly through the passage 11 of the extrusion to the lower end where it passes around the lower rolls 60 before extending upwardly again to the carriage. A spring i 63 is inserted between the blind and the attachment hooks on the bottom end of the carriage so that the blirfd is held under light tension. At the front of the column where the blind 60 covers the channel mouth the edges of the blind run in the guide slots formed by the lips 10 of the extrusion. A ribbon cable 65 is used for supplying electric power and control signals to the robotic arm which is mounted on the carriage. The cable enters the column through an opening 70 (Fig. 8) provided in the side wall 3 of the extrusion at a position mid-way along its length. The opening 70 opens. into, the passage 11, and a slot 71 * made in the partition- wall 5 between the flange 6 and the lip 13 allows the cable 65 to pass into the extrusion channel from the passage 11. The length of cable received in the channel is sufficient to enable travel of the carriage over the full column height. Between the slot 71 and the carriage the cable is supported by a spring metal strip 72 which is fastened by one end to the partition wall 5 at a position above the slot 71, and has its other end fixed to the carriage by a screw 74 * The strip 72 and cable 65 thereby follow a U-shaped path, the relative lengths of the limbs of the U depending on the carriage position, and over the rear limb of the U the cable being held in the groove between the flange 6 and lip 13 so that there is no risk of the carriage being snagged by the cable as it is driven up and down. To the end of the cable 65 is connected a connector 78 which plugs into an electronic distribution board 80 supported on the front of the carriage body 20 by bosses 8l and posts 82. The board 80 takes the power and control signals from connector 78 and distributes them to connectors 84 (Fig 3)« The column and carriage are adapted to enable the drive motor 43 to be mounted either to the left or to the right of the base on which the assembly is mounted. From Figure 6 it can be seen that the mounting arrangements for the brackets 45, 47 and the parts supported on them are the same at either end of the column thus enabling the column to be inverted. The carriage is symmetrical with respect to its mid-plane A-A (Fig. 3) so that it is substantially unaffected by the column inversion, although the distribution boards 8θ does need to be repositioned on the mounting bosses 83- The facility to invert the guideway and carriage so that the motor may project either to the left or to the right is advantageous where a robot is to be equipped with left and right arms.

Claims: Claims 1. A rectilinear guideway and carriage assembly for supporting a robotic arm or the like for up and down movement, comprising an elongate column (1), and a carriage received on the column and guided thereon for movement in the longitudinal direction (Z) of the column, characterised in that the column is an extrusion (1) having first, second and third guide flanges (6,7*8) extending continously therealong, and the carriage comprises a rigid body (20), a first set (21) of rolling elements (30,32) mounted on th.e body and engaging both sides of the first guide flange (6) to restrain the carriage against lateral and tilting movements in a first plane (XZ), a second set (22) of rolling elements (30,32) mounted on the body and engaging both sides of the second guide flange (7) - to restrain the carriage against lateral and tilting movements in a second plane (YZ) transverse to the first plane (XZ), and a third set (23) of rolling elements (30,32) mounted on the body and engaging both sides of the third guide flange for restraining the carriage against turning in a plane (XY) normal to the longitudinal direction (Z) of the column (1). 2. An assembly according to claim 1, wherein the first and second guide flanges (6 and 7) lie in orthogonal planes, and the third guide flange (8) lies in a plane parallel to the plane of the second guide flange (7). 3- An assembly according to claim 1 or 2, wherein the extrusion defines a channel, the carriage is positioned in the channel, and the first second and third guide flanges (6, 7, 8) ' project into the channel from the inner end wall (5) and the opposed side walls (3*4) of the channel, respectively. 4. An assembly according to claim 1,2 or 3, wherein at least some of the rolling elements (32) are movable on the carriage body (20) for adjusting the sets of rolling elements to grip the guide flanges (6,7*8). 5 An assembly according to claim 1,2 or 3* wherein the sets of rolling elements comprise rollers (30,32) arranged in pairs (21,22,23), the two rollers of each pair gripping between them one of the guide flanges (6,7,8). 6. An assembly according to claim 5* wherein the first set of rolling elements comprises two pair.s (21) of rollers spaced apart along the first guide flange (6), the second set of rolling elements comprises two pairs (22) of rollers .(30, 32) spaced apart along the second guide flange, and the- third set of rolling elements comprises a single pair (23) of rollers. 7. An assembly according to claim 6, wherein one roller (32) of each pair (21,22,23) is adjustably mounted on the body (20) to enable adjustment of the pair of rollers to grip the respective guide flange (6,7,8). 8. An assembly according to claim 7, wherein said one roller (32) of each pair has adjustment means (36) accessible to permit adjustment of said roller (32) while the carriage is mounted on the column. 9 An assembly according to claim 7 or 8, ' wherein said one roller (32) of each pair is mounted eccentrically on a spindle (35)* the spindle being rotatable relative to the body (21) for adjusting the roller ( 32 ) . 10 An assembly according to any one of the preceding claims, wherein the body (20) and the rolling elements (30,32) mounted thereon are so arranged that the carriage is symmetrical with respect to a transverse mid-plane (A-A). 11. An assembly according to any one of the preceding- claims, wherein a belt (40) is secured to the carriage for driving the carriage along the column, the belt being trained around a driving pulley (41) mounted at one end of the column, and an idler pulley (42) at the other end of the pulley. 12. An assembly according to claim 11, wherein the idler pulley (42) is movable on the column by adjusting means (49) for adjusting the tension in the belt. 13- An assembly according to claim 3, or any one of claims 4 to 12 when appended to claim 3, wherein the extrusion comprises opposed side walls interconnected by a rear wall (2) and by a partition wall (5)* the partition wall constituting the inner end wall of the channel and defining with the rear wall a longitudinal passage ( 11 ) . 14• An assembly according to claim 13* wherein a flexible blind (61) is connected to the carriage and covers the mouth of the channel above and below the carriage, the blind including a return stretch extending along the column through said passage (11). 15. An assembly according to claim 14, where rollers (60) are mounted at the ends of the column for guiding the blind between the channel mouth and the passage (11). 16. An assembly according to claim 14 or 15* wherein the extrusion includes lips (10) on the side walls (3,4)* at the channel mouth for guiding the edges of the blind (6l) therealong. 17. An assembly according to claim 14 * 15 or 16, wherein the carriage body (20) has attachment points (62) at the ends thereof for attaching the ends of the blind (6θ) to the carriage. 18. An assembly according to any one of the preceding claims, wherein an electric cable (65) is connected to the carriage, the cable passing through a hole (70,71) provided in the extrusion approximately half way along the column. 19. An assembly according to claim 18, wherein a resiliently flexible strip (72) has one end secured to the column and the other end thereof secured to the carriage, the strip being arranged to guide the electric cable (65) between the entry hole (72) and the carriage. 20. An assembly according to any one of the preceding claims, wherein the extrusion includes one or more external recesses (9) and/or projections (12) for securing additional components to the column.

Inventors: LUXFORD GEOFFREY, POWER JOHN, LUXFORD, GEOFFREY, POWER, JOHN
Applicants: UNIVERSAL MACHINE INTELLIGENCE, UNIVERSAL MACHINE INTELLIGENCE LTD
Application year: 1986
Main classification: B25J9
IPC codes: B25J9, B25J18