A multi-degree-of-freedom positioning mechanism

Abstract: A positioning mechanism having a plurality of degrees of freedom, comprising at least a guide shaft (2a,2b) and first and second movable members (3a,3b) movably mounted on the guide shaft, drive means (4) being connected with the first and second movable members to allow the first and second movable members to travel on the guide shaft individually; the ends of a pair of foldably joined equally long links (5a,5b) pivotally rotatably engaged with the first and second movable members through first and second couplings (6a,6b); and one edge of a table pivotally rotatably engaged with the joint between the mating links of the pair, whereby displaceably to support the table.

Description: The present invention relates to a multi-degree-of-freedom positioning mechanism according to the preamble of claim 1 which can be applied to precision measuring instruments, precision machine tools, precision assembling apparatuses, etc. In the past, machine tools and manipulators of robots have been designed on the existing principle that a cantilever structure was the best. In recent years however, a new structure has emerged which destroys that existing principle. Products utilising the new structure have begun to be marketed. The new structure is called a parallel mechanism, and has a plurality of links connected in parallel between an end effector (called a table in this specification) and a base. These links are either a telescopic type or of folding type. This structure is generally said to provide high precision, high rigidity and high speed, compared to the previous cantilever structure (see Nikkei Mechanical). On the other hand, however, the calculation of the table position and orientation or attitude control is complicated. Also it is complicated and expensive to manufacture the required software. In addition, telescopic type links are narrow in travelling range, and folding type links have problems in view of precision and dynamics. In GB-A-2295601, on which is based the preamble of claim 1, there is described a machine tool or robot having a travelling plate for attachment to a tool and a plurality of guide rods attached at one end via a first set of joints to the travelling plate and radially extending out therefrom. The guide rods are each attached at their other ends via a second set of joints to a slide table movable longitudinally with respect to the guide rods. Actuators for moving the slide tables are provided. In EP-A-0494564 there is described apparatus having a moving platform rotatably mounted in a set of joints connecting at one end to the platform and at each of their other ends to a linear jack-type actuator. The joints include a parallelogram-shaped frame constructed so that the linear movement of the jacks is parallel to the axis of rotation of the platform. The present invention is proposed to mitigate or overcome the disadvantages of the prior art. The object of the present invention is to provide a multi-degree-of-freedom positioning mechanism simplified in mechanism, larger in travelling range and easy in orientation or attitude control. To solve the above problem, according to the present invention there is provided a multi-degree-of-freedom positioning mechanism of the type having a table movably engaged to one end of one or more link, with a moving member movably engaged to the other end of the or each link, the or respectively each moving member being mounted on a draft shaft, with drive means for moving the or each moving member along its respective drive shaft so as to cause displacement of the supported table, characterised in that the positioning mechanism comprises: a first and a second moving member mounted on the or each guide shaft; drive means being connected to the or each of the first and second moving members so as to allow each of them to individually travel on the or respectively each guide shaft; a pair of jointedly coupled links of equal length provided for the or each guide shaft, one edge of the table being pivotally rotatably engaged at the joint of the coupled end of the or each pair of links and the other ends of the or each pair of links being pivotally rotatably engaged with the or respectively each first and second moving members through respective first and second couplings. The positioning mechanism of the present invention can comprise first and second guide shafts with first and second moving members movably mounted on each of the first and second guide shafts; drive means being connected with each first and second moving member. The ends of two pairs of jointedly coupled equally long links may then be pivotally rotatably engaged with each of the respective first and second moving members, through respective first and second couplings and two opposite edges of the table may be pivotally rotatably engaged with the two joints between the two pairs of coupled links. Furthermore, the positioning mechanism of the present invention can comprise first, second and third guide shafts with first and second moving members movably mounted on each of the first, second and third guide shafts. The ends of three pairs of jointedly coupled equally long links may then be engaged with the respective first and second moving members through respective first and second couplings and three edges of a table may be pivotally rotatably engaged with the three joints of the coupled pairs of links. Each of the links in any given pair may take the form of a one-part link spanning from one end of the link to the other. Alternatively each link may comprise one or more parts. A pair of links could, for example, comprise a first pair of equally long link elements, which may be mutually pivotally connected to each other at a point intermediate of their ends at which they cross over each other, each of the first pair of link elements being engaged at one end with one of the movable members and pivotally engaged at their other ends with one end of a second pair of equally long link elements, which second pair of link elements are jointedly coupled at their other ends, with the table being engaged at the joint of the second pair of link elements. In the above embodiments of the present invention, each of the second couplings can be provided with a rotation arrester in which an arbour is rotatably mounted in a bracket provided on the second moving member, with both the ends of the arbour protruding from the bracket, and has its one end rotatably engaged with the end of the link, to prevent the rotation of the arbour around itself. Since the positions of the joints between the pairs of coupled links can be easily detected from the positions of the respective first and second moving members on the respective guide shafts, table position and orientation or attitude control can be easily calculated. Furthermore, when a pair of links and the table are located to form a straight line (dead point), stopping the pivotal rotation of the pair of links around its guide shaft and operating another pair of links allows the table to progress from the dead point in a desired direction. Therefore the travelling range of the table increases by that. Moreover, if the table is pivotally rotatably supported by three pairs of links engaged with respective moving members on first, second and third guide shafts, further more delicate table orientation control can be carried out. If the links used comprise pairs of equally long link elements crossed over each other and mutually pivotally rotatably connected at an intermediate point which are pivotally engaged with pairs of jointedly coupled equally long link elements supporting the table, the displaceable range of the table can be further expanded. For a better understanding of the present invention and to show how the same may be put into effect, reference will now be made, for the purposes of illustration only, to the accompanying drawings in which: Figure 1 is a side view of a first embodiment of a multi-degree-of-freedom positioning mechanism of the present invention; Figure 2 is a plan view of the positioning mechanism of Figure 1; Figure 3 is a schematic side view illustrating the function of the couplings of the positioning mechanism of Figure 1; Figure 4 is a series of schematic views illustrating the degrees of freedom of couplings used in a positioning mechanism of the present invention; Figure 5 is a pair of schematic views illustrating the action states of a rotation arrester used in a positioning mechanism of the present invention; Figure 6 is a side view illustrating an action of the positioning mechanism of Figure 1; Figure 7 is a side view illustrating a further action of the positioning mechanism of Figure 1; Figure 8 is a side view illustrating a further action of the positioning mechanism of Figure 1; Figure 9 is a side view of a second embodiment of a multi-degree-of-freedom positioning mechanism of the present invention; Figure 10 is a side view for explaining the function of the positioning mechanism of Figure 9; Figure 11 is a plan view of the positioning mechanism of Figure 10; Figure 12 is a side view for explaining the actions of the positioning mechanism of Figure 10; Figure 13 is a side view of a third embodiment of a multi-degree-of-freedom positioning mechanism of the present invention; Figure 14 is a side view of the positioning mechanism shown of Figure 13; Figure 15 is a further side view of the positioning mechanism of Figure 13; Figure 16 is a perspective view illustrating a coupling used in the present invention having two degrees of freedom; Figure 17 is a side view illustrating an example of the pivotal rotation preventing means in the mechanism of the first embodiment; Figure 18 is a side view illustrating an example of the pivotal rotation preventing means in the mechanism of the second embodiment; Figure 19 is a sectional view illustrating a coupling having three degrees of freedom; and Figure 20 is a sectional view of the coupling of Figure 19, after some motion has taken place. Figures 1, 2 and 6 show the basic configuration of a first embodiment of a multi-degree-of-freedom positioning mechanism 1 of the present invention. The positioning mechanism 1 is composed of first and second guide shafts 2a and 2b parallel to each other. First and second sliding members 3a and 3b are slidably mounted on each of the first and second guide shafts 2a and 2b, and drive means 4 are connected with the respective first and second sliding members 3a and 3b. In this configuration, the drives 4 are selectively controlled to allow the respective first and second sliding members 3a and 3b to properly slide on the first and second guide shafts 2a and 2b. The configuration and selective control actions of the drives will be described later. The respective first and second sliding members 3a and 3b on both the first and second guide shafts 2a and 2b are each engaged with the ends of a pair of foldably jointed, that is jointedly coupled, equally long links 5a and 5b, respectively through first and second couplings 6a and 6b, in order that the two pairs of links can pivotally rotate in a direction along the first guide shaft 2a and in a direction transverse to the first guide shaft 2a. At the joints between the coupled links 5a and 5b of the two pairs, a table 7 is biaxially pivotally rotatably supported through third couplings 16 (the detail of which will be described later). The drives 4 on each of the guide shafts 2a and 2b consist of a pair of parallel threaded shafts 8a and 8b provided with a predetermined distance kept between them respectively on each of the first and second guide shafts 2a and 2b, and motors 9a and 9b installed at the ends of the threaded shafts 8a and 8b. The threaded shafts 8a and 8b are threadedly engaged with internally threaded members 10a and 10b respectively and the internally threaded members 10a and 10b can be moved on the threaded shafts 8a and 8b by rotation of the threaded shafts 8a and 8b driven by the motors 9a and 9b. The internally threaded members 10a and 10b are integrally attached to the sides of the first and second sliding members 3a and 3b respectively. So, if the motor 9a is selected and actuated, for example, to rotate the threaded shaft 8a only, the internally threaded member 10 threadedly engaged with it is moved along the threaded shaft 8a, to slide the first sliding member 3a only along the first guide shaft 2a (or the first guide shaft 2b). On the other hand, if the motor 9b is selected and actuated to rotate the threaded shaft 8b, the internally threaded member 10b threadedly engaged with it is moved along the threaded shaft 8b, to slide the second sliding member 3b along the first guide shaft 2a (or the second guide shaft 2b). Furthermore, if both the motors 9a and 9b are selected and actuated to rotate both the threaded shafts 8a and 8b, both the internally threaded members 10a and 10b threadedly engaged with them are moved along the threaded shafts 8a and 8b, to slide both the first and second sliding members 3a and 3b along the first guide shaft 2a (or the second guide shaft 2b). As described above, in the drives 4, if the threaded shafts 8a and/or 8b to be rotated by the motors 9a and/or 9b is selected, either the first or second sliding member 3a or 3b only can be slid along the first guide shaft 2a (or the second guide shaft 2b), or both the first and second sliding members 3a and 3b can be simultaneously slid along the first guide shaft 2a (or the second guide shaft 2b). When both the first and second sliding members 3a and 3b are simultaneously slid along the first guide shaft 2a (or the second guide shaft 2b), the first and second sliding members 3a and 3b can be slid in the same direction or reverse directions at respectively set proper speeds for respectively set proper distances. Moreover, the threaded progressions directions on the threaded shafts 8a and 8b can be the same by adopting either right handed thread or left handed thread for both of them, or either the threaded shaft 8a or 8b can be of right handed thread, while the other can be of left handed thread. In any case,, the progression directions of the first and second sliding members 3a and 3b can be controlled by the directions of the threaded shafts 8a and 8b rotated by the motors 9a and 9b. In the first and second couplings 6a and 6b, arbors 12a and 12b are rotatably installed in brackets 11a and 11b mounted on the first and second sliding members 3a and 3b, in such a way that the grooved heads 12h of the arbors 12a and 12b are protruded. The ends of the links 5a and 5b are rotatably fitted in the grooved or forked heads 12h of the arbors 12a and 12b. Therefore, the respective links 5a and 5b can rotate around two axes orthogonal to each other, and so the first and second couplings 6a and 6b assure two degrees of freedom while they connect the links 5a and 5b with the first and second sliding members 3a and 3b. Furthermore, each of the second couplings 6b is provided with a rotation arrester 13 to prevent the rotation of the arbor 12b around itself. The rotation arrester 13 consists of a disc 14 installed at the end on the side opposite to the grooved head 12h, of the arbor 12b protruded from the bracket 11b, and a clamp 15 for grasping the disc 14 on both sides of the disc 14, to prevent the rotation of the disc 14, thereby preventing the rotation of the arbor 12b. Each of the third couplings 16 connecting the joints of the respectively coupled links 5a and 5b to the table 7 can pivotally rotate in the direction along the first guide shaft 2a (or the second guide shaft 2b)and in a direction transverse the first guide shaft 2a (or the second guide shaft 2b). Figure 16 shows an example of the third coupling 16 on the first guide shaft 2a, which consists of a grooved or forked member 100 on the table 7 side and a link coupling member 101 pivotally rotatably fitted in the groove of the grooved member 100, and the link coupling member 101 is protruded transversely from the joint between the links 5a and 5b and can rotate around the same axis as that of the pivot between the coupled links 5a and 5b. That is, since the third coupling 16 can rotate around two axes orthogonal to each other, it assures two degrees of freedom while it connects the joint of the links 5a and 5b with the table 7. Figure 3 schematically shows a first embodiment of the multi-degree-of-freedom mechanism 1. As described above, since the first, second and third couplings 6a, 6b and 16 can rotate around two axes orthogonal to each other respectively, they assure two degrees of freedom. This configuration is symbolised in Figure 3. An explanation of the respective symbols used in the drawings including those referred to later are shown in Figures 4 and 5. As shown in Figure 3, the second couplings 6b at the second sliding members 3b on the first and second guide shafts 2a and 2b are provided with the rotation arresters 13. So, the symbols as illustrated are used. In each of the rotation arresters 13, the clamp 15 is actuated to grasp the disc 14, for preventing the rotation of the arbor 12b around itself, and the rotation-arrested state is expressed by blacking out the symbol of the clamp 15 as shown in Figure 5. On the other hand, when the rotation arrester 13 is not actuated, the arbor 12b is in a rotatable state which is expressed by keeping the symbol of the clamp 15 open. In the above configuration, if the motors 9a and 9b as components of the drives 4 are started and controlled selectively, considering the respective rotation angles and directions, to rotate either or both of the respective threaded shafts 8a and 8b, the respective first and/or second sliding members 3a and/or 3b are slid, as intended, together with the respective internally threaded members 10a and/or 10b on the first and/or second guide shafts 2a and/or 2b, to change the respective relative positional relations between the first and second sliding members 3a and 3b, and their absolute locations on the first and/or second guide shafts 2a and/or 2b. Such actions of the first and second sliding members 3a and 3b can displace the ends of the respective links 5a and 5b through the respective first and second couplings 6a and 6b, as intended, in the direction along the first and second guide shafts 2a and 2b and in a direction transverse to the first and second guide shafts 2a and 2b. These displaced links 5a and 5b displace the table 7 connected through the third couplings 16 at the joint of the respectively coupled links 5a and 5b, as intended, in a direction along the first and second guide shafts 2a and 2b and in a direction transverse to the first and second guide shafts 2a and 2b. Thus, multi-degree-of-freedom positioning can be executed. The action of the first type of multi-degree-of-freedom positioning mechanism described above is described below in more detail. At first, the drives 4 are controlled to slide the respective first and second sliding members 3a and 3b, while the respective relative positions between the respective first and second sliding members 3a and 3b on the first and second guide shafts 2a and 2b are kept constant. This control can be effected by controlling the two pairs of the motors 9a and 9b on the first and second guide shafts 2a and 2b, to turn the two pairs of threaded shafts 8a and 8b, i.e. all the threaded shafts 8a and 8b, by the same number of revolutions. Needless to say, the respective motors 9a and 9b are rotated in the directions to make the respective threaded shafts 8a and 8b progress in the same direction. If the respective first and second sliding members 3a and 3b are slid on the first and second guide shafts 2a and 2b, while the respective relative positions between the first and second sliding members 3a and 3b are kept constant, the third couplings 16 located at the joints between the respectively coupled links 5a and 5b are moved along the first and second guide shafts 2a and 2b, while the heights of the third couplings 16 are kept constant. Therefore, the table 7 is displaced in the axial direction (X direction in Figure 1) of the first and second guide shafts 2a and 2b, while the initial orientation and supported height of the table 7 are kept constant. In another case, the drives 4 are controlled to slide the respective first and second sliding members 3a and 3b on both the first and second guide shafts 2a and 2b at the same speed for the same distance along the first and second guide shafts 2a and 2b, in such a way that the respective first and second members 3a and 3b may become closer to each other or farther away from each other. In this case, the third couplings 16 located at the joints of the coupled links 5a and 5b are moved vertically only, without being moved along the first and second guide shafts 2a and 2b. That is, if the respective first and second sliding members 3a and 3b are slid to become closer to each other at the same speed, the angles formed by the coupled links 5a and 5b at their joints become gradually smaller, to gradually raise the positions of the joints. On the other hand, if the respective first and second sliding members 3a and 3b are slid to become farther away from each other at the same speed, the angles formed by the coupled links 5a and 5b at their joints become gradually larger, to gradually lower the positions of the joints. Therefore, this control action causes the table 7 to be raised or lowered vertically (Y direction in Figure 1), i.e. adjusted in height, while its supported state is kept constant. In a further other case, in the state of Figure 3, the rotation arrester 13 of the second coupling 6b at the second sliding member 3b on the second guide shaft 2b is actuated to let the clamp 15 grasp the disc 14 for preventing the rotation of the arbor 12 around itself, and in this state, the drives 4 are started to slide the first and second sliding members 3a and 3b on the first guide shaft 2a only, in such a way that the first and second sliding members 3a and 3b may become farther away from each other. In this case, only the third coupling 16 connected with the links 5a and 5b on the first guide shaft 2a descends, while the third coupling 16 connected with the links 5a and 5b on the second guide shaft 2b keeps its height. As described above, since the arbor 12b supporting the coupled links 5a and 5b on the second guide shaft 2b is prevented from being rotated around itself, the third coupling 16 at the joint between these coupled links 5a and 5b is kept stationary at its height and at its location on the second guide shaft 2b. Therefore, the table 7 is pivotally rotated to gradually descend with the third coupling 16 at the joint between the coupled links 5a and 5b on the second guide shaft 2b as a pivot, as the third coupling 16 connected with the links 5a and 5b on the first guide shaft 2a descends. That is, since the arbor 12b supporting the links 5a and 5b on the first guide shaft 2a is not prevented from being rotated around itself, the links 5a and 5b on the first guide shaft 2a are pivotally rotated around the axis of the arbor 12b installed along the first guide shaft 2a, i.e. rotated in the direction transverse the first guide shaft 2a. In this action, the table 7 can be lowered and inclined to an angle equal to the inclination angle of the links 5a and 5b. This state is shown in Figure 6. In the state of Figure 6, if the drives 4 are started to slide the first and second sliding members 3a and 3b on the first guide shaft 2a only at the same speed, in such a way that the first and second sliding members 3a and 3b may become closer to each other, the third coupling 16 connected with the links 5a and 5b on the first guide shaft 2a ascends. So, the table 7 is displaced in reverse to the above mentioned action, to return to the state of Figure 3. If the same action is continued further still after the table 7 has returned to the state of Figure 3, the table 7 is rotated to gradually ascend, with the third coupling 16 at the joint between the coupled links 5a and 5b on the second guide shaft 2b acting as a pivot, as the third coupling 16 connected with the links 5a and 5b on the first guide shaft 2a ascends. In the above action, the arbor 12b for the second sliding member 3b on the second guide shaft 2b is prevented from being rotated around itself. It is evident that even if only the rotation arrester 13 of the second coupling 6b at the second sliding member 3b on the first guide shaft 2a is actuated to let the clamp 15 grasp the disc 14 for preventing the rotation of the arbor 12b around itself, the same actions as described above can occur. In this case, the third coupling 16 connected with the links 5a and 5b on the first guide shaft 2a acts as the pivot of the table 7. In the first embodiment of the multi-degree-of-freedom positioning mechanism, the following action can be effected in addition to the basic actions described above. In the state of Figure 6, the rotation arrester 13 of the second coupling 6b at the second sliding member 3b on the first guide shaft 2a is actuated to let the clamp 15 grasp the disc 14, for arresting the rotation of the arbor 12b around itself, while the rotation arrester 13 of the second coupling 6b at the second sliding member 3b on the second guide shaft 2b side is released from its actuated state, to allow the arbor 12b to be rotated around itself. In this state, if the drives 4 are started to slide the first and second sliding members 3a and 3b on the second guide shaft 2b at the same speed in an action similar to the above, in such a way that the first and second sliding members 3a and 3b may become closer to each other, the third coupling 16 connected with the links 5a and 5b on the second guide shaft 2b ascends. So, the table 7 is pivotally rotated to ascend and to be steep in inclination, with the third coupling 16 at the joint between the coupled links 5a and 5b on the first guide shaft 2a acting as a pivot. Finally, the table 7 exceeds an inclination angle of 90 degrees, to the extreme end of a proper stroke (full travel or excursion) where the parts threaten to interfere with each other, as shown in Figure 7. On the other hand, in the state of 6, the rotation arrester 13 of the second coupling 6b at the second sliding member 3b on the first guide shaft 2a is actuated to let the clamp 15 grasp the disc 14, for arresting the rotation of the arbor 12b around itself, and the rotation arrester 13 of the second coupling 6b at the second sliding member 3b on the second guide shaft 2b side is released from its actuated state, to allow the arbor 12b to be rotated around itself. In this state, if the drives 4 are started to slide the first and second sliding members 3a and 3b on the second guide shaft 2b at the same speed in an action similar to the above, in such a way that the first and second sliding members 3a and 3b may become farther away from each other, the third coupling 16 connected with the links 5a and 5b on the second guide shaft 2b descends. So, the table 7 is pivotally rotated to descend and to be gentle in inclination, with the third coupling 16 at the joint between the coupled links 5a and 5b on the first guide shaft 2a acting as a pivot. Thus, the table 7 becomes horizontal again as shown in Fig. 8. However, it is to be noted that even though the table 7 is horizontal, it is lower in height compared with the state of Figure 3, and is displaced in a direction transverse the first and second guide shafts 2a and 2b. The above action can be effected even if the second sliding member 3b with the arbor 12a prevented from being rotated is on the second guide shaft 2b side. Figure 9 shows the basic configuration of a second embodiment of the multi-degree-of-freedom positioning mechanism 1 of the present invention. The second embodiment has substantially the same components as those of the first embodiment except that the components corresponding to the links 5a and 5b are different. The same components in the second embodiment are given the same symbols as those in the drawings referred to in the above description, to avoid double description. In the multi-degree-of-freedom positioning mechanism 20 of the second embodiment, the respective first and second sliding members 3a and 3b slidably mounted on the first and second guide shafts 2a and 2b are each engaged through first and second couplings 6a and 6b, with the end of one of a pair of equally long link elements 21a and 21b. The link elements are mutually pivotally rotatably connected at an intermediate point where they are crossed over. The other ends of the pairs of link elements 21a and 21b are engaged with the ends of a respectively corresponding pair of foldably joined equally long link elements 5a and 5b as used in the first embodiment which are mutually pivotally rotatably connected. Furthermore, through the biaxially rotatable third couplings at the joints between the respectively coupled links 5a and 5b, the table 7 is supported. To express briefly, the second embodiment uses pantograph type links instead of one-piece foldably joined links 5a and 5D formed like isosceles triangles. In this example, a pantograph consists of respectively coupled links 5a and 5b and links 21a and 21b. In the second embodiment the selectively controllable drives 4 are provided for the respective first and second sliding members 3a and 3b, and the rotation arresters 13 are provided for the second couplings 6b at the second sliding members 3b on the first and second guide shafts 2a and 2b. The multi-degree-of-freedom mechanism 20 of the second embodiment can perform all the actions of the first embodiment described above. In addition, the pantograph type links can elongate the strokes or range of their movement in a direction orthogonal to the direction in which the first and second sliding members 3a and 3b are slid to become closer to each other or farther away from each other, compared to the isosceles triangular links of the first embodiment. Therefore, in the second type compared with the first type, the table 7 can be displaced in a wider range and can be applied to a wider range of applications. As can be seen from the above actions, in the multi-degree-of-freedom positioning mechanisms of the first and second embodiments, the position and orientation of the table 7 can be known in reference to the locations of the respective first and second sliding members 3a and 3b of the first and second guide shafts 2a and 2b. So, if the drives 4 are actuated while detecting the locations of the respective first and second sliding members 3a and 3b, the table 7 can be set in a desired position and orientation. It is to be noted here that the description of the multi-degree-of-freedom mechanisms 1 and 20 of the first and second embodiments based on Figures 1 through 9 does not refer to any means for preventing the rotation of the table 7 around the axis of the third couplings 16, i.e., as described above, around the axis in a direction transverse the first and second guide shafts 2a and 2b. In Figures 1 through 9, for the sake of convenience and to clearly describe the essential actions of the multi-degree-of-freedom mechanisms 1 and 20 of the first and second embodiments, the table 7 is supported by one each of the third couplings 16 on each of both the linearly arranged sides, and no means for preventing the pivotal rotation of the table 7 caused by any load on the table 7 is illustrated. An example of the pivotal rotation preventing means is described below. Figure 17 shows an example of the pivotal rotation preventing means for the multi-degree-of-freedom positioning mechanism 1 of the first embodiment. In this means, an arbor 12a' is additionally installed on the first sliding member 3a, and a third coupling 16' is also additionally installed for the table 7. And between the additionally installed arbor 12a' and third coupling 16', another link 5a' is connected along the link 5a to form a parallel link mechanism. It is evident that this configuration can prevent the pivotal rotation of the table 7 around the axis of the third coupling 16, i.e. around the axis perpendicular to the paper surface. Figure 18 shows an example of the pivotal rotation preventing means for the multi-degree-of-freedom positioning mechanism 20 of the second embodiment. In this means, as in the means for the first embodiment described above, an arbor 12a' is additionally installed on the first sliding member 3a, and a third coupling 16' is additionally installed for the table 7. Links 5b' and 21a' respectively parallel to the links 5b and 21a are connected between the head of the arbor 12a' and the third coupling 16', and holding links 110a and 110b are connected between the joint between the links 5b and 21a and the joint between the links 5b' and 21a', and between the crossing point of the blinks 21a and 21b cross-connected at an intermediate point of link 21a. It is also evident that this configuration can prevent the pivotal rotation of the table 7 around the axis of the third coupling 16, i.e. around the axis perpendicular to the paper surface, by analogy with the pivotal rotation preventing means for the first embodiment described above. Though not illustrated, even if the support point of the table 7 by either of the third couplings 16, i.e. the location of the axis acting as the pivot of the rotation to be prevented on either of the first and second guide shafts 2a and 2b is changed in relation with that on the other guide shaft 2a or 2b, the pivotal rotation of the table 7 can be prevented. Dislocating either of the points where the third couplings 16 are installed to the table 7 can also be used as the pivotal rotation means. When such a pivotal rotation preventing means is used, not only the third couplings 16 of two degrees of freedom but also the third couplings 16 of three degrees of freedom described later can be used. Figures 10 through 13 show the basic configuration of an example embodying the multi-degree-of-freedom positioning mechanism 30 of a third embodiment. The multi-degree-of-freedom positioning mechanism 30 has the first and second guide shafts 2a and 2b arranged in parallel to each other, and components connected with them, as in the first embodiment described before. So, the same components as those used in the first embodiment are given the same symbols, to avoid double description. The third embodiment is different from the first type, in that sixth couplings 33 of three degrees of freedom are used instead of the third couplings 16 of two degrees of freedom, and that the sixth couplings 33 on the first and second guide grooves 2a and 2b are installed near an edge of the table 7. The increment in the degree of freedom of the couplings of three degrees of freedom allows the pivotal rotation of the table 7 in the horizontal direction. Figures 19 and 20 show an example of the sixth coupling 33 of three degrees of freedom. The sixth coupling 33 consists of a first member 203 with a spherical body 202 provided at the tip of rod 201, a second member 205 with a spherical concavity 204 larger than the outer diameter of the spherical body 202, and a third member 207 holding a plurality of spheres or balls 206 to fill the clearance formed when the spherical body 202 of the first member 203 is fitted in the spherical concavity 204 of the second member 205. In this configuration, the first member 203 and the second member 205 can rotate around three axes orthogonal to each other. For example, the rod 201 of the first member 203 is used as the axis at the joint between the coupled links 5a and 5b, and the second member 205 is fixed to the table 7 (or vice versa), to constitute the coupling 33 of three degrees of freedom. Now back to the description of the entire configuration of the third embodiment in addition to the above mentioned first and second guide shafts 2a and 2b, a third guide shaft 31 is provided to be orthogonal to them. On the third guide shaft 31, fourth and fifth sliding members 31a and 31b are slidable installed. These fourth and fifth sliding members 31a and 31b can be respectively independently slid, or slid simultaneously in the same direction for the same distance, or slid simultaneously in different directions to be closer to each other or to be farther away from each other for the same distance along the third guide shaft 31, like the first and second sliding members 3a and 3b, by the selective control action of drives similar to the drives 4 of the first and second embodiments, though the drives for the fourth and fifth sliding members 31a and 31b are not illustrated. On the fourth and fifth sliding members 31a and 31b, a pair of foldably joined equally long links 5a and 5b are installed through the fourth and fifth couplings 32a and 32b of two degrees of freedom, like the links 5a and 5b installed through the first and second couplings 6a and 6b on the first and second sliding members 3a and 3b. At the joint between these coupled links 5a and 5b, the table 7 is supported through the sixth couplings 33 of three in degrees of freedom, as configured for the first and second sliding members 3a and 3b. The point where the sixth coupling 33 on the third guide shaft 31 is connected with the table 7 is at the edge opposite to the edge, near which the sixth couplings 33 on the first and second guide shafts 2a and 2b support the table 7. Thus, a three-point support structure is formed, and the pivotal rotation axes around which the table 7 can be vertically pivotally rotated by these sixth couplings 33 are orthogonal to each other. According to the third embodiment, since the table 7 can be pivotally rotated around the three axes orthogonal to each other respectively at the points where the table 7 is connected with the sixth couplings 33, the following actions can be effected in addition to the actions described above for the first and second types. At first, in a state where the table 7 is supported horizontally as shown in Figure 10, if the fourth and fifth sliding members 31a and 31b only are controlled to lower the sixth coupling 33 on the third guide shaft 31, the table 7 is pivotally rotated to descend and incline with the axis across the pair of sixth couplings 33 on the first and second guide shafts 2a and 2b as a pivot. On the contrary, if the sixth coupling 33 on the third guide shaft 31 is raised, the table 7 is pivotally rotated to ascend and incline with the axis across the pair of sixth couplings 33 on the first and second guide shafts 2a and 2b acting as a pivot. In these actions, the links 5a and 5b on the third guide shaft 31 are pivotally rotated around a virtual axis in parallel to the guide shaft 31. Contrary to the above, in a state where the table 7 is supported horizontally, even if the respective first and second sliding members 3a and 3b of the first and second guide shafts 2a and 2b are controlled to raise or lower their sixth couplings 33 while the fourth and fifth sliding members 31a and 31b are kept at their locations, the table can be inclined in the same directions as stated above. The mechanism of the third embodiment can perform not only these actions, but also actions caused by combining the actions of the first embodiment and the above mentioned actions effected by the components on the third guide shaft 3. For example, if the distance between the first and second sliding member 3a and 3b on the first guide shaft 2a is elongated while the fourth and fifth sliding members 31a and 31b on the third guide shaft 331 are fixed, the sixth coupling 33 between the table 7 and the joint between the coupled links 5a and 5b on the first guide shaft 2a descends, displacing the table 7 with the position of the sixth coupling 33 as the lowest point. In this case, if the rotation arrester 13 of the second coupling 6b at the second sliding member 3b on the first guide shaft 2a is actuated to arrest the rotation of the arbor 12b around itself, and the first and second sliding members 3a and 3b on the second guide shaft 2b are slid, then the sixth coupling 33 between the table 7 and the joint between the coupled links 5a and 5b on the second guide shaft 2b also descends, tilting the table 7 in such a way that the edge of the table 7 near the sixth couplings 33 between the table 7 and the joints between the respective coupled links 5a and 5b on the first and second guide shafts 2a and 2b becomes the lowest position, as shown in Figure 12. As described above, the table 7 is supported at three points, both sides at one edge of the table 7 by the sixth couplings 33 at the joints between the respective coupled links 5a and 5b engaged with the respective first and second sliding members 3a and 3b on the first and second guide shafts 2a and 2b, and at the centre at the other edge of the table 7 by the sixth coupling 33 at the joint between the coupled links 5a and 5b engaged with the fourth and fifth sliding, members 31a and 31b on the third guide shaft 31. So, the table 7 can be displaced delicately by properly sliding the respective first and second sliding members 3a and 3b and the fourth and fifth sliding members 31a and 31b. The locations of the sixth couplings 33 at which the table 7 is supported can be obtained in reference to the locations of the respective first and second sliding members 3a and 3b of the first and second guide shafts 2a and 2b and of the fourth and fifth sliding members 31a and 31b on the third guide shaft 31. So, if the drives are actuated while detecting the locations of the respective first and second sliding members 3a and 3b and the fourth and fifth sliding members 31a and 31b, the table 7 can be set in a desired position and orientation. As described above, in the multi-degree-of-freedom positioning mechanism 30 of the third embodiment, the table 7 can be displaced in the longitudinal (X) direction, transverse (Y) direction, and vertical (Z) direction, and furthermore can be rotated around the Z axis in the drawing. Furthermore, the table 7 in the horizontal state (XY plane) can be tilted in the longitudinal (X) direction and in the transverse (Y) direction. Thus, the table has six degrees of freedom to allow control in position and orientation. Figures 13 through 15 show the basic configuration of an example embodying a fourth embodiment of the multi-degree-of-freedom positioning mechanism 1 of the present invention. The relation of the fourth embodiment to the third embodiment corresponds to the relation of the second embodiment to the first embodiment, and to the links 5a and 5b of the third embodiment. Since the other components are substantially the same, those components are given the same symbols as those used for the third embodiment described above, to avoid double description. The multi-degree-of-freedom positioning mechanism 40 of the fourth type uses so-called pantograph type links as in the second embodiment, instead of the foldably joined links 5a and 5b formed like isosceles triangles used in the third embodiment. Also in this case, a pantograph consists of the respectively coupled links 5a and 5b and links 21a and 21b. Figures 13 through 15 for the mechanism 40 of the fourth embodiment show drives 4 similar to those described for the first and second embodiment. The multi-degree-of-freedom positioning mechanism 40 of the fourth embodiment as described above can perform all the actions of the third embodiment described before. In addition, as described for the mechanism of the second embodiment, the pantograph type links can elongate the strokes in, i.e. range of, their movement in the direction orthogonal to the direction in which the first and second sliding members 3a and 3b and the fourth and fifth sliding members 31a and 31b are slid to become closer to each other or farther away from each other. Therefore, in the fourth embodiment compared with the third embodiment, the table 7 can be displaced in a wider range and can be applied to a wider range of applications. As described above, the table can be displaced in multi-degree of freedom, and the position and orientation of the table can be determined by the locations of the sliding members on the guide shafts. That is, since the present invention allows the position and orientation of the table to be easily derived from the positions of sliding members on guide shafts, orientation control is easy. Furthermore, the mechanism is simple, and the range of table displacement can be expanded to cater for a wider range of applications.

Claims: A multi-degree-of-freedom positioning mechanism of the type having a table (7) movably engaged to one end of one or more link (5a,5b,21a,21b), with a moving member (3a,3b,31a,31b) movably engaged to the other end of the or each link (5a,5b,21a,21b), the or respectively each moving member (3a,3b,31a,31b) being mounted on a guide shaft (2a,2b,31), with drive means (4) for moving the or each moving member (3a,3b,31a,31b) along its respective guide shaft (2a,2b,31) so as to cause displacement of the supported table (7), characterised in that the positioning mechanism (1;20;30;40) comprises: a first (3a;31a) and a second (3b;31b) moving member mounted on the or each guide shaft (2a;2b;31); drive means (4) being connected to the or each of the first (3a;31a) and second (3b;31b) moving members so as to allow each of them to individually travel on the or respectively each guide shaft (2a;2b;31); a pair of jointedly coupled links (5a,5b;21a,21b) of equal length provided for the or each guide shaft (2a;2b;31), one edge of the table (7) being pivotally rotatably engaged at the joint of the coupled end of the or each pair of links (5a,5b;21a,21b) and the other ends of the or each pair of links (5a,5b;21a,21b) being pivotally rotatably engaged with the or respectively each first (3a;31a) and second (3b;31b) moving members through respective first (6a) and second (6b) couplings. A positioning mechanism according to Claim 1, wherein two guide shafts (2a,2b) are provided. A positioning mechanism according to Claim 2, wherein two opposite edges of the table are engaged with the joints of the two pairs of coupled links. A positioning mechanism according to Claim 1, wherein three guide shafts (2a,2b,31) are provided. A positioning mechanism according to any preceding claim, wherein the or each pair of links comprises a first pair of equally long link elements (21a,21b), which are pivotally connected to each other at a point intermediate of their ends at which they are crossed, and pivotally rotatably engaged at one end with the first and second moving members respectively and at their other ends with one end respectively of a second pair of equally long link elements (5a,5b), which second pair of equally long link elements (5a,5b) are jointedly coupled at their other ends, with the table being engaged at the joint of the second pair of link elements (5a,5b). A positioning mechanism according to any preceding claim, wherein the or each of the second couplings is provided with a rotation arrester in which an arbor is rotatably mounted in a bracket provided on the second moving member, with both the ends of the arbor protruding from the bracket, and has its one end rotatably engaged with the end of the link, to prevent the rotation of the arbor around itself.

Inventors: HIROSE KAZUYA, HIROSE, KAZUYA
Applicants: HIHAISUTO SEIKO CO LTD
Application year: 1996
Main classification: B25J9
IPC codes: B25J9, F16H21, F16H25