Rotary indexing table

Details Rotary indexing table Rotary indexing table

1999-11-01

2001-04-24

Green, Mary Ann (Department: 3682)

Machine element or mechanism

Rotary member or shaft indexing, e.g., tool or work turret

Locking means

C074S81300L, C074S052000

Reexamination Certificate

active

06220116

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to rotary indexing tables in particular, and may find application in other fields where it is required to accurately drive a working element in rotational manner in a stop and start or reciprocating motion, with a high degree of repeatability. In particular, the present invention finds itself as a rotary indexing table of the sort which is used in many different manufacturing and commercial applications, particularly such as assembly plants employing robotics.
BACKGROUND OF THE INVENTION
Particularly in a robotics application, a rotary indexing table may be employed to move a workpiece between two or more index stations or indexing positions. A typical application might be, for example, a two-position indexing table where, at a first position, a workpiece is loaded and clamped onto the table, and at the second position the workpiece is worked on such as by having another element welded onto it in an accurately positioned manner. The indexing table then returns to the first position, where the first workpiece is removed and a second workpiece is placed on the table. Clearly, such operations are capable of being highly automated, but the automation is contingent upon the workpiece being accurately in place at all times. This requirement, in turn, leads to the necessity for rotary indexing tables to have very high degrees of repeatability as they move from one indexing position to the next.
Indeed, typical robotics used in manufacturing processes may require positioning of a workpiece with an accuracy in the order of tenths of a millimeter.
Still further, indexing tables should be capable of moving from one indexing position to the next quite rapidly. The time taken for moving a workpiece from one indexing position to another is non-productive time. However, the action of moving a workpiece from one station to another, by rotating a rotary indexing table from one indexing position to the next, must not be jerky in any manner. In other words, the motion from one indexing position to the next must require a smooth acceleration and deceleration, but as quickly as possible.
Typically, rotary indexing tables will have only two or three indexing positions, but the present invention contemplates that a rotary indexing table may have more indexing positions, because the precise number of indexing positions is immaterial to the invention.
However, typically a rotary indexing table will have two indexing positions, and the motion of the rotary indexing table is reciprocal. That is, the indexing table will rotate clockwise when moving from the first rotary indexing position to the second rotary indexing position, and counterclockwise when returning from the second indexing position to the first indexing position, or vice versa. Such motion permits the wiring, welding leads, compressed air lines, and the like for any robotics equipment which is mounted on the rotary indexing table to move between the first and second indexing positions without becoming unduly tangled.
Another matter of concern, particularly with indexing tables which employ a reciprocating motion, is the matter of backlash. Typically, as intermeshed gears change the direction of relative rotation one with respect to the other, there will be backlash as the mating sides of the intermeshed gears are replaced by the opposite sides of the respective gear teeth; the clearance between the gear teeth of intermeshed gears being required so as to preclude binding and undue wear. As will be noted hereafter, the problem of backlash is overcome by the present invention.
A further problem with rotary indexing tables is the manner in which they are locked in place as they attain and stop their respective indexing positions. Often times, external brakes are required for those purposes; but there is no necessity for any external braking devices in keeping with the present invention, as will be noted hereafter.
DESCRIPTION OF THE PRIOR ART
HAGEN U.S. Pat. No. 4,377,953, issued Mar. 29, 1983, teaches an indexing apparatus which is intended to move a workpiece from various operating stations in a smooth and jerk-free motion. Suitably arranged cams and cam followers are employed to convert the driving motion into either linear or rotary indexing motion in substantially jerk-free manner, with smooth acceleration and deceleration. This is accomplished by the crank arm having cam followers which control the pivotal movement of a transfer arm which is, in turn, connected to a linearly reciprocal apparatus, or to a reciprocable work supporting surface. However, employment of crank arms having cam followers and acting on cam surfaces typically results in there being substantial looseness or play in the apparatus, so that accurate positioning of a workpiece at differing indexing positions may not be attainable.
GRAMLING U.S. Pat. No. 5,090,267, issued Feb. 25, 1992, teaches an indexing apparatus whose principal concern is to avoid backlash. Here, a pinion is operatively connected to a shaft for rotating an indexing table, and is rotated to a preset angular position by first and second drive gears, each of which are in engagement with the pinion. Those drive gears are worm gears. One of the drive gears is rotated relative to the other gear in a predetermined direction and will rotate the pinion, if necessary, into contact with the other drive gear so as to remove backlash from the apparatus. It is stated that the biassing action comes as a result of a phase shift carried out between the first and second drive gears such that one of the gears is rotated relative to the other drive gear.
U. S. Pat. 5,159,846, issued Nov. 3, 1992 to WARNER teaches an indexing table which employs a stationary gear and two planetary gears mounted opposite each other. There is no looseness between the planetary gears and the stationary gear when the table is in an indexing position, so that no externally induced movement of the indexing table would be allowed at each indexing position. This is attained by having the first side of the gear teeth on one planetary gear being kept in continual contact with the first side of the gear teeth on the main gear, and the second side of the gear teeth on the second gear being kept in continual contact with the second side of the gear teeth on the main gear, when the table is at or near each indexing position. There is no looseness due to gear backlash while the indexing table is at or near each indexing position, and the table may be driven in either of two directions. However, there is looseness when the table is moving from one indexing position to another, and the indexing table requires a complicated double planetary gear arrangement.
OKETANI et al U.S. Pat. No. 5,481,944 issued Jan. 9, 1996 teach an indexing device having an indexing table mounted on a table shaft. There is an indexing gear fixed coaxially to the indexing table. A rotation correction device is provided for stopping the rotation of a worm shaft prior to the indexing operation of the indexing table, and there is a positioning device which operates after the worm shaft has been stopped, to impart a rotational torque to the indexing table. This causes a gear tooth face on the indexing gear to press against a worm tooth face on the worm gear, so that precise positioning of the indexing table occurs.
SOMMER U.S. Pat. No. 5,540,120, issued Jul. 30, 1996, teaches an indexing table which uses an oil shear brake and clutch to provide an accurate and reliable indexing table. This requires a two-speed oil shear drive system for high speed indexing and low speed final positioning. After the oil shear brake stops the table at an approximate final position, the final positioning system rotates and locks the indexing table at the correct position. The driving arrangement calls for a pinion having a very small number of teeth compared to the number of teeth on a main gear affixed to the table; but limit switches stop rotation of the table near each indexing position to permit the final positioning system employing an oil shear brake an

Affiliated with

Also associated with

Rating

Rotary indexing table does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Rotary indexing table, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rotary indexing table will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2508342