SHAFT SUPPORTING MECHANISM FOR INDUSTRIAL ROBOTS

Abstract: A shaft supporting machanism for industrial robots, in which an arm is supported on an extensible and retractable suport shaft (4) in the interior of a hollow post (1) and which is capable of setting a working surface of the arm variably, is provided with a plurality of sets of linear support guides (16) opposed to each other around a driving means for the sup­ port shaft (4). Accordingly, the support shaft (4) is held on the post (1) in a vertically stable and balanced state even when an external force of inclining the support shaft (4) is applied thereto during a vertical movement thereof and an operation of the arm.

Description: This invention relates to an industrial robot shaft supporting mechanism for supporting, internally of a post, a support shaft supporting an arm in a freely extendable manner. A variety of industrial robots have recently come into wide use in various fields. Fig. 3 is a side view illustrating one example of a horizontal articulated industrial robot installed on a floor and provided with a swiveling post. In Fig. 3, numeral 1 denotes the post supported on a base 2 and capable of being swiveled within a predetermined rotational range (ϑ). Provided within the base 2 is a swiveling mechanism 21 for swiveling the post 1. Numeral 3 denotes a first arm (working arm) supported at the upper portion of the post 1 by a support shaft 4. A second arm 5 capable of being swiveled in the horizontal direction is attached to the distal end of the first arm 3, and the distal end of the second arm 5 is provided with a wrist 51. Provided in the post 1 is a drive mechanism 11 for moving the support shaft 4 up and down within a predetermined range (Z) to control the height of the first arm 3. Though the details are not shown, the drive mechanism 11 drives the support shaft 4 up and down by e.g. a rack-and-pinion combination or a screw rod-nut combination, thereby controlling the height of the first arm (working arm). A guide for linear support is provided between the support shaft 4 and the inner wall of the post 1 so that the support shaft 4 will move linearly with respect to the post 1 when it is driven up and down by the drive mechanism 11. Fig. 4 is a sectional view taken along line A-A' of Fig. 3 and illustrating an example of the drive mechanism 11. The support shaft 4, which is driven by the drive mechanism 11 consisting of a combination of a screw rod 6 and nut 41, possesses a sliding contact portion 42 at which the support shaft slides on the side faces of a linear support guide 14 provided on a supporting plate 13, thereby forming a guide mechanism. The arrangement is such that the support shaft 4 moves in the vertical direction. In the above-described shaft supporting mechanism of support shaft 4, the shaft moves linearly while the sliding contact portion 42 thereof is in contact with three faces of the linear support guide 14, and the working plane of the arm moves up and down in parallel with the longitudinal direction of the post 1. However, the guide 14 and sliding contact portion 42 tend to separate from each other in response to a force acting in the direction of the arrow shown in Fig. 4. For example, if the reaction force of a load acting upon the second arm 5 is in the direction of the arrow, the support shaft 4 will no longer be supported stably. The present invention has been devised in view of the foregoing problems of the prior art and its object is to provide an industrial robot shaft supporting mechanism capable of supporting the shaft of a working arm and of moving the shaft linearly in the vertical direction while maintaining a stable balance. EP-A-0122146 discloses some aspects of a known robot shaft supporting mechanism providing vertical movement, while JP-U-60-17977 discloses a mechanism according to the precharacterising part of the attached claim 1. According to the present invention there is provided an industrial robot comprising a vertically movable support member inside a hollow post for moving a load carrying element up and down, a drive mechanism for driving the support member up and down, and guide means for guiding the support member in its up and down movement within the hollow post, the guide means comprising a plurality of guide seats attached to the movable support member and a fixed linear support means engaging said guide seats, wherein said load carrying element is an arm extending laterally away from said support member, and the movable support member is a shaft which extends upwardly from the hollow post with the arm arranged at the top thereof so that the arm is arranged to be pushed upwardly by the movable support member so that the working plane of the arm can be variably set, characterised in that said guide seats are arranged symmetrically about said drive mechanism and said fixed linear support means comprise a plurality of linear support guides engaging securely within openings of said guide seats even when a lateral force is applied to the support member, the linear support guides being attached to opposing inner wall portions of the hollow post to increase its rigidity, and the hollow post being longitudinally separable into two portions one of which has the linear support guides attached thereto. In accordance with the industrial robot shaft supporting mechanism of the invention, a plurality of linear support guide mechanisms are provided to oppose one another with the drive mechanism at the center. As a result, the support shaft is held in the post stably and balanced in the vertical direction even if an external force attempting to tilt the support shaft is applied during up-and-down movement of the support shaft or operation of the working arm. Furthermore, the linear support guides also function as post reinforcing members at the inner wall portion of the post. Brief Description of the Drawings Fig. 1 is a longitudinal sectional view illustrating an embodiment of an industrial robot shaft supporting mechanism according to the present invention, Fig. 2 is a transverse sectional view taken along line B-B' of Fig. 1, Fig. 3 is a side view illustrating an example of a common horizontal articulated-type industrial robot, and Fig. 4 is a sectional view, taken along line A-A' of Fig. 3, illustrating an example of the conventional shaft supporting mechanism. An embodiment of the present invention will now be described with reference to the drawings. In Figs. 1 and 2, portions similar to those shown in Figs. 3 and 4 are designated by like reference characters and a description thereof is omitted. Numeral 7 denotes a drive motor for supplying a driving force that drives the support shaft 4 up and down by the drive mechanism composed of the combination of the screw rod 6 and nut 41. Fitted on a shaft 71 of the drive motor 7 is a motor pulley 72, which is attached to a partitioning wall 15 of post 1 via a bearing 73. The screw rod 6 is attached to the partitioning wall 15 via a bearing 61 and is freely rotatable so as to be rotated by driving a belt 74 stretched between a drive pulley 62 provided on the screw shaft 6 and the motor pulley 72. The lower end portion of the screw rod 6 is provided with a brake mechanism 63 actuated by electromagnetic action to stop the screw rod 6 from rotating. The nut 41, which is threadedly engaged with the screw rod 6, is attached to a nut holder 43 provided on the support shaft 4, as shown in Fig. 2. Two guide seats 44 are attached to both side faces of the nut holder 43. The guide seats 44, each of which has an opening 44a and a back face 44b, are attached to the nut holder with their openings 44a facing outward and their back faces 44b facing each other about the screw rod 6 as center. Guide rails 16 serving as linear support guides each have a groove in two opposite side faces thereof, each guide rail therefore having a cross section similar to that of a railroad rail. The arrangement is such that the opening 44a of each guide seat 44 is engaged with the grooves of the corresponding guide rail 16, so that the guide seat may be moved linearly along the guide rail 16. Each guide seat 44 engages with the corresponding guide rail 16 and slides smoothly on the side surface of the guide rail 44. The guide rails 16 are attached in opposing relation to the inner wall of the hollow, cylindrically shaped post 1, and the support shift 4, which has the nut holder 43 whose two sides are provided with the guide seats 44 engaged with the guide rails 16, is arranged within the post 1. Accordingly, the support shaft 4 moves linearly up and down, while being guided by the guide seats 44 having the respective openings 44a engaged with the guide rails 16, along these guide rails attached in opposing relation to the inner wall of the post 1 in such a manner that the rigidity of the post 1 is increased. In the present embodiment, the post 1 can be separated into two halves longitudinally by removing locking bolts 17, thus making it possible to install components within the post and to adjust them. The operation of the present embodiment constructed as set forth above will now be described. When current is passed through the drive motor 7 to rotate the same, the motor pulley 72 rotates, thereby rotating the drive pulley 62 via the belt 74 to turn the screw rod 6. Owing to rotation of the screw rod 6, the support shaft 4 provided with the nut 41 threadedly engaged with the screw rod is acted upon by a force that moves the support shaft up or down, and the guide seats 44 travel linearly longitudinally of the post 1 under the guidance of the guide rails 16. Since the guide seats 44 and guide rails 16 flanking the screw rod 6 are provided at positions symmetrical with respect to the nut holder 43, the up-and-down movement of the support shaft 4 is balanced and stable. Since the guide rails 16 are provided in opposed relation on the inner wall of the post 1 having the hollow, cylindrical structure in the present embodiment, the post is provided with additional rigidity. In the shaft support mechanism of the present invention as described in detail hereinabove, plural sets of linear support guide rails and guide seats are provided in opposing relation about a drive mechanism for up-and-down movement and serve as a mechanism for supporting a shaft, which moves the working arm of an industrial robot vertically up and down. As a result, vertical support of the support shaft is achieved stably with excellent balance even if an external force attempting to tilt the support shaft is applied during up-and-down movement of the support shaft or operation of the working arm. Further, the guide mechanism has left-right symmetry with respect to the screw shaft for drive. This has the advantage of simplifying the arrangement inside the post. In addition, the provision of the guide rails on the inner wall of the post raises the rigidity of the post and makes it possible to obtain a more compact arrangement. Though the present invention has been described based on an embodiment thereof, the invention can be modified in various ways without departing from the scope of the claims. By applying the invention to an industrial robot in which an arm is supported by a freely extendable support shaft inside a hollow post and the working plane of the arm is variably set, vertical support of the support shaft can be achieved stably with excellent balance even if an external force attempting to tilt the support shaft is applied during up-and-down movement of the support shaft or operation of the working arm.

Claims: An industrial robot comprising a vertically movable support member (4) inside a hollow post (1) for moving a load carrying element (3) up and down, a drive mechanism (6,41) for driving the support member (4) up and down, and guide means (16,44) for guiding the support member (4) in its up and down movement within the hollow post (1), the guide means (16,44) comprising a plurality of guide seats (44) attached to the movable support member (4) and a fixed linear support means (16) engaging said guide seats (44), wherein said load carrying element (3) is an arm extending laterally away from said support member (4), and the movable support member (4) is a shaft which extends upwardly from the hollow post (1) with the arm (3) arranged at the top thereof so that the arm (3) is arranged to be pushed upwardly by the movable support member (4) so that the working plane of the arm (3) can be variably set, characterised in that said guide seats (44) are arranged symmetrically about said drive mechanism (6,41) and said fixed linear support means comprise a plurality of linear support guides (16) engaging securely within openings (44a) of said guide seats (44) even when a lateral force is applied to the support member (4), the linear support guides (16) being attached to opposing inner wall portions of the hollow post (1) to increase its rigidity, and the hollow post (1) being longitudinally separable into two portions one of which has the linear support guides (16) attached thereto. An industrial robot according to claim 1, wherein said linear support guides (16) are rails each of which has grooves in opposed side surfaces thereof which are engaged by projections on the guide seats (44). An industrial robot according to any preceding claim, wherein the drive mechanism (6,41) and the guide means (16,44) are arranged together at one side of the movable support shaft (4). An industrial robot according to claim 3, wherein said arm (3) extends laterally away from the support shaft (3) at the same side thereof at which are arranged the drive mechanism (6,41) and the guide means (16,44).

Inventors: NIHEI, RYO, TORII, NOBUTOSHI
Applicants: FANUC LTD.
Application year: 1986
Main classification: B25J19
IPC codes: B25J19, B25J9, B23Q1, B25J18