Geometrical instruments – Gauge – Collocating
Patent
1996-04-18
1998-11-17
Gutierrez, Diego F. F.
Geometrical instruments
Gauge
Collocating
33520, 901 45, G01B 525
Patent
active
058360832
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a remote elastic center machine which is mounted on a robot or an exclusive assembling machine. More particularly it provides means for actively or passively changing the position of the elastic center existing along the central axial direction of the machine body, so that one machine may perform assembling work of fitting parts of various specifications without changing tools or the like.
BACKGROUND OF THE INVENTION
A remote elastic center machine, or a remote compliance center device (hereinafter referred to as an RCC device) performs smooth assembling by appropriately absorbing relative lateral and angular positioning errors of assembly parts when a robot or an exclusive assembly machine assembles precision parts such as cylindrical shafts, pins, and semiconductor chips. The RCC device prevents the robot or the exclusive assembling machine from excessive load so as to eliminate damage of parts to the maximum extent during assembling. As a result, the RCC device enhances the quality and productivity of products.
The RCC device has a special point known as a compliance center at a specific distance in the central axial direction of a main body from the origin of the coordinate frame provided in the main body. The location of this point depends on the physical properties, focal angle, and mounting radius (a radial distance from the center) of elastic elements which connect an upper structure and a lower structure of the main body.
The conventional RCC device had a simple structure in which a compliance center is fixed at one point. Therefore, when parts of various specifications are assembled, multiple RCC devices must be used in order that the specifications of parts and RCC devices corresponded one by one.
FIGS. 1 to 4 briefly illustrate a conventional RCC device. In the device, a plurality of elastic elements 30 (provided radially at specified angle intervals) are fixed between an upper structure 10 and a lower structure 20. The upper structure 10 is fixed to a robot or an exclusive assembling machine 40. On the lower side of the lower structure 20, a gripper 50 is provided so as to grip a part A to be assembled.
FIG. 1 shows a state in which the focus F where extension lines of the central axes of the slant elastic elements 30 intersect is set in a long distance from the upper structure 10. FIG. 2 shows a state in which the focus F is set in a short distance therefrom. In other words, the focal angle .theta. of the elastic element 30 in FIG. 1 is large, while that in FIG. 2 is smaller. In such cases, generally, the compliance center X is present on the central axial line between the upper structure 10 and the focus F. Such a position is determined by the modulus of elasticity, focal angle .theta. and mounting radius r of the elastic element 30.
The compliance center X of the RCC device is a special position at which a horizontal external force passing this position gives an assembly part a translation (horizontal) motion, and a pure moment about this position provides the assembly part with only a rotary motion around the position.
When the compliance center X of the RCC device exists in the front end portion of the part held by the gripper 50, if there is a relative position error between assembly parts as shown in FIG. 3, the horizontal component of the reaction R by contact of the front end portion of the part on the gripper 50 with the other part passes near the compliance center X, and therefore the part is moved horizontally as shown in FIG. 4, and resulting in smooth assembling. The RCC device is a device for applying such a compliance center X in the assembling work of precision parts.
On the other hand, in the RCC device, the position of the focus F changes depending on the focal angle .theta. of the elastic element 30, and accordingly the position of the compliance center X changes, and hence parts to be assembled vary in specification depending on the center position S. What is shown in FIG. 1 is suitable for assembling long assembl
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Gutierrez Diego F. F.
Hirshfeld Andrew
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