BRAKE SYSTEM FOR INDUSTRIAL ROBOTS

Abstract: A brake system for industrial robots, which is adapted to brake a driving mechanism for a support shaft (4) on which an arm is supported so that the arm can be extended and retracted, is capable of stopping the turning of a rod screw (61), so as to create a clearance between a fixing portion of the brake (82), which is adapted to the positioning of a working surface of the arm, and a movable portion (81) of the brake. Accordingly, the replacement of a belt (72) and the inspection of a brake means, such as brake shoe (813), can be easily carried out.

Description: This invention relates to an industrial robot as described for example in US-A-4466770 and especially to a brake apparatus for braking a mechanism that drives 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 (0). 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 6 for moving the support shaft 4 up and down within a predetermined range (Z) to control the height of the first arm 3. Fig. 4 is a longitudinal sectional view of the post 1, in which numeral 7 denotes a drive motor having a motor pulley 71 for rotating a screw rod 61 of the drive mechanism 6 via the motor pulley 71, a belt 72 and a drive pulley 63, whereby a nut 62 threadedly engaged with the screw rod 61 is moved up and down to raise and lower the support shaft 4 and, hence, position the working plane of the arm. A movable brake element 81 is fixedly secured to the lower end of the screw rod 61. Attached to the bottom 11 of the post 1 is a fixed brake element 82 for braking rotation of the screw rod 61 by attracting the movable brake element 81 through use of electromagnetism. In order to prevent the support shaft 4 from being moved out of position by an external force or the like when the drive motor 7 has been stopped to hold the support shaft 4 at a prescribed height, the braking mechanism in the drive mechanism of the aforementioned kind is so adapted that the fixed brake element 82 attracts the movable brake element 81 to brake the rotation of the screw rod 61, thereby positioning the arms 3, 5 in a prescribed working plane. In the above -described industrial robot, exchanging the belt 72 between the motor pulley 71 of drive motor 7 and the drive pulley 63 involves a difficult operation in terms of mounting the new belt, since the movable brake element 81 is fixedly secured to the lower end of the screw rod 61. Moreover, Inspecting the contact surfaces of the movable brake element 81 and fixed brake element 82 is a troublesome operation also since the movable brake element 81 is fixedly secured to the screw rod 61 and the clearance between the two contact surfaces is small. 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 brake apparatus in which belt replacement and brake mechanism inspection can be carried out with ease. According to the present invention there is provided an industrial robot drive mechanism for a robot arm supported on a support shaft which can be extended and retracted to adjust the working plane of the arm, the support shaft being in threaded association with a screw rod rotatable to drive the support shaft as aforesaid, there being a power transfer belt extending between a drive motor for rotatively driving the screw rod and a drive pulley fixed adjacent an end of the screw rod, there also being at the same end of the screw rod a brake for the screw rod comprising a rotatably movable brake element secured to that end of the screw rod, and a fixed brake element secured to base, characterised in that the part of the power transfer belt extending around the drive pulley has free access to the fixed and rotatably movable brake elements, and the rotatably movable brake element is moreover axially movable by being slidably splined onto said end of the screw rod, whereby the belt can be removed from the pulley and then without hinderance can be passed between the fixed and movable brake elements after the movable brake element has been moved axially away from the fixed brake element. With the industrial robot brake apparatus of the present invention, the screw rod and the movable brake element mounted thereon are splined so as to be freely slidable with respect to the fixed brake element. Therefore, when a belt is to be attached or an inspection is to be performed, the movable brake element can easily be moved upward to widen the spacing between the contact surfaces of the movable and fixed brake elements. Brief Description of the Drawings Fig. 1 is a longitudinal sectional view illustrating an embodiment of an industrial robot brake apparatus according to the present invention, Fig. 2 is a perspective view of a portion of the brake apparatus 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 view illustrating the structure of a conventional brake apparatus based on a longitudinal section of a post shown in Fig. 3. An embodiment of the present invention will now be described with reference to the drawings. In the Figures, numeral 61 denotes a screw rod rotated by a drive pulley 63 via a belt 72 and having a spline groove 611 provided in its lower end. A movable brake element 81 having a hub provided with a spline 811 is engaged with the spline groove 611 and is freely slidably fitted on the lower end of the screw rod 61. A portion of the spline groove 611 is provided with an oval-shaped depression 612 extending in the axial direction. The arrangement is such that the movable brake element 81 can be moved up and down a prescribed distance along the spline groove 611 of screw rod 61 by means of a set screw 812 provided in the hub of the movable brake element 81. Numeral 82 denotes a fixed brake element incorporating an electromagnetic coil 821. By passing a current through the electromagnetic coil 821, a brake shoe 813 provided on the lower part of the movable brake element 81 is attracted by the electromagnetic action of the electromagnetic coil 821, whereby rotation of the screw rod 61 is stopped. When no current is flowing through the electromagnetic coil 821, the lower surface of the brake shoe 813 is moved to a prescribed position where it will not contact the upper surface of the fixed brake shoe 82. This is done by the elastic force of a spring, not shown, provided on the hub of the movable brake element 81. The operation of the present embodiment thus constructed will now be described. When the belt is to be exchanged for another or the lower surface of the brake shoe 813 is to be inspected, current is removed from the drive motor 7 and electromagnetic coil 821 to stop the screw shaft 61 from rotating and eliminate the attractive force of the electromagnetic coil 821, thereby freeing the movable brake element 81 for up-and-down motion. Next, the movable brake element 81 is moved upwardly, whereupon the spline 811 provided on the movable brake element 81 moves upwardly owing to the spline groove 611 provided in the screw rod 61. The movable brake element 81 can be moved upwardly until the set screw abuts against the upper portion of the oval-shaped depression 612 of spline groove 611, thereby widening the clearance between the lower surface of the brake shoe 813 and the fixed brake element 82. It is possible to change the belt or to inspect the contact surfaces of the brake shoe 813 and fixed brake element 82 by utilizing the widened clearance. Thus, in the brake apparatus of the invention as described in detail above, the spline groove is provided in the lower end of the screw rod for driving the support shaft of the working arm up and down, the spline engaged with the groove is provided on the central axis of the movable brake element of the brake mechanism, and the movable brake element is capable of being slid up and down. This makes it possible to widen the spacing between the movable brake element and fixed brake element, thereby facilitating belt replacement and inspection of the lower surface of the brake shoe. 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. Thus, in the inventive industrial robot brake apparatus for braking a mechanism that drives a support shaft supporting an arm in a freely extendable manner, the spacing between the movable brake element and fixed brake element can be widened to facilitate belt replacement and inspection of the lower surface of the brake shoe.

Claims: An industrial robot drive mechanism for a robot arm (3) supported on a support shaft (4) which can be extended and retracted to adjust the working plane of the arm (3), the support shaft (4) being in threaded association with a screw rod (61) rotatable to drive the support shaft (4) as aforesaid, there being a power transfer belt (72) extending between a drive motor (7) for rotatively driving the screw rod (61) and a drive pulley (63) fixed adjacent an end of the screw rod (61), there also being at the same end of the screw rod (61) a brake for the screw rod (61) comprising a rotatably movable brake element (81) secured to that end of the screw rod (61), and a fixed brake element (82) secured to a base (11), characterised in that the part of the power transfer belt (72) extending around the drive pulley (63) has free access to the fixed and rotatably movable brake elements (82,81), and the rotatably movable brake element (81) is moreover axially movable by being slidably splined onto said end of the screw rod (61), whereby the belt (72) can be removed from the pulley (63) and then without hinderance can be passed between the fixed and movable brake elements (82,81) after the movable brake element (81) has been moved axially away from the fixed brake element (82). An industrial robot drive mechanism according to claim 1, wherein said robot arm (3) is part of a horizontal articulated robot arm structure (3,5). An industrial robot drive mechanism according to claim 1 or 2, wherein a lower end portion of said screw rod (61) is provided with a spline groove (611), a spline (811) is formed in a shaft hole of the movable brake element (81) fitted onto said lower end portion, and the screw rod (61) and movable brake element (81) are joined by being spline-fitted so that the latter is freely slidable up and down. An industrial robot drive mechanism according to any preceding claim, wherein the movable and fixed brake elements (81,82) cooperate electromagnetically. An industrial robot drive mechanism according to any preceding claim, wherein a splined end portion of the screw rod (61) is provided with a depression (612) extending in the axial direction to cooperate with an internal projection from the movable brake element (81) thereby to define a prescribed distance of axial movement for the movable brake element (81) on the screw rod (61). An industrial robot drive mechanism according to claim 5, wherein said internal projection is provided by a set screw (812) provided in a hub of the movable brake element (81).

Inventors: NIHEI, RYO, TORII, NOBUTOSHI
Applicants: FANUC LTD.
Application year: 1986
Main classification: B25J19
IPC codes: F16D65, B25J19, B25J17, F16D55