Machine element or mechanism – Control lever and linkage systems – Multiple controlling elements for single controlled element
Reexamination Certificate
1999-02-03
2001-03-06
Herrmann, Allan D. (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Multiple controlling elements for single controlled element
C074S490060, C248S651000, C901S029000
Reexamination Certificate
active
06196081
ABSTRACT:
TECHNICAL FIELD
The invention relates to devices for manufacturing and machining, particularly devices that include a movable platform for positioning a tool in space.
BACKGROUND OF THE INVENTION
High precision automated manufacturing, such as computer aided manufacturing (CAM), requires that the position of a tool be precisely known in space. However, most machine tools today fail to provide the necessary precision, in part due to their limited range of movement, high cost, inability to recognize their own work space to plan complex motion activity, and unrealistically high expectations of technical expertise available for the users of CAM software. To overcome these problems, engineers have developed mechanical movement systems that include a movable platform that is mounted with substantial freedom in translation and rotation by means of a plurality of legs the length and angular orientation of which are controllably adjustable. Through coordinated control of the effective length of the legs, the platform can be precisely moved through space. A tool can be mounted on to the platform and carried thereby to a precisely selected position and orientation. One such system is described in U.S. Pat. No. 5,575,597 entitled Mechanical Manipulator, the teachings of which are herein incorporated. As shown therein, one such movable platform system has three pairs of supportive legs coupled to a platform at triangularly spaced-apart locations by means of three universal joints each of which couples to one end of each of the two legs of the respective pair, and the two legs of each pair extend from their respective universal joint in divergent directions to spaced-apart locations in a mounting where each leg is drivingly engaged by a motor for moving the leg in its own longitudinal direction, thereby changing the effective length of the leg. Six such motors are mounted at spaced-apart locations in the mounting in a manner such as to accommodate the pivotal movements of the legs that will accompany their effective length variations.
Each pair of legs thus defines a triangle of support for the platform with the apex of the triangle coupled to the platform by means of the universal joint, the base of the triangle defined by the separation between the mounted motors which drive the respective legs, and the effective lengths of the legs being independently adjustable by operation of the motors. With the platform supported by three such support triangles and the effective lengths of all six legs independently adjustable, the position and orientation of the platform becomes infinitely adjustable within the limits of accommodation of the universal joints and the motor-mountings. Thus the tool mounted to the platform can be positioned with high precision and moved with a great range of freedom.
Although these movable structures can work well, the supportive leg assemblies are generally quite complex, costly and difficult to manufacture. Moreover, the complexity of the legs, typically including inter-locking members, are subject to problematic thermal expansion, that can change the length of the extension arm and therefore interfere with the accurate placement of the point on the platform. In addition, these structures have limits within which the platform may be positioned and oriented. To achieve rotational orientation about an axis perpendicular to their platforms, these systems generally require that the platform carry an additional rotational stage with an additional motor or other actuator.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the invention to provide systems and methods that provide improved platform systems which are facile to manufacture, which can have reduced thermal expansion and which can achieve greater ranges of positioning and orientation.
The systems and methods described herein include hexapod systems, Stewart platform systems and other mechanical movement systems, in which a set of independently moveable trucks support legs that couple to a working surface capable of holding a machine tool or other end-effector, and preferably wherein the trucks travel across a reference surface, such as around the circumference of a circle or along some other pre-defined geometrical pattern or track. For example, as described herein, the systems include Stewart platform machines that have six supportive legs each of which connects to a truck that can travel independently along a track. By coordinating the movement of these six trucks, the working surface can be moved in three dimensional space and can be oriented about three axes, providing control of roll, pitch and yaw. It will be apparent to one of ordinary skill in the art that although the illustrated embodiments comprise a track system upon which a set of six trucks travel independently, any system capable of allowing the trucks to move independently for selectively positioning and orienting a platform within space will be understood to fall within the scope of the invention described herein.
Accordingly, the systems described herein provides for the positioning and orientation of a working surface by the coordinated movement of supportive legs. This movement may be in one, two or three dimensions, and is not confined to movement effective to alter the effective length of the legs. This system may be further combined with a system for altering the effective length of some or all of the legs, such that positioning and orientation of the working surface is achieved by coordinated movement of the position of the legs in addition to the coordinated control over the effective length of some or all of the legs.
Certain illustrative embodiments are provided herein for purposes of describing the systems and methods of the invention. The embodiments depicted are merely illustrative and are not to be understood as exhaustive or limiting in any way. Like reference numerals refer to like elements.
REFERENCES:
patent: 4536690 (1985-08-01), Belsterling et al.
patent: 4790053 (1988-12-01), Godbecker
patent: 5378282 (1995-01-01), Pollard
patent: 5575597 (1996-11-01), Bailey et al.
patent: 0 263 627 A1 (1988-04-01), None
patent: 0 668 130 A1 (1995-08-01), None
patent: 602 289 (1936-03-01), None
patent: 197 01 820 A1 (1997-08-01), None
patent: WO 97/22436 (1997-06-01), None
Atwood Pierce
Caseiro Chris A.
Herrmann Allan D.
Hexel Corporation
Kelly Edward J.
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