Patent Number: 051903334
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to mechanical linkages for positioning an end effector such as a gripper. 2. Discussion of Background An "end effector" is a tool or device designed for a particular function and operated from the end of a deploying or positioning handle. End effectors include gripping devices of all sorts, whether designed to grip one or more tools that perform an operation on a workpiece or to grip the workpiece itself and to move it or simply hold it while a second operation takes place with another tool. Frequently, end effectors are designed so that they can be operated not only in line with a handle but also at an angle with respect to the handle. If the end effector can not be fixed at the particular angle needed, or if the angle varies from one operation to the next, the end effector and the handle may be interconnected by mechanical or electro-mechanical linkages so that the end effector can be positioned or rotated or turned as desired while the handle remains fixed. A linkage is composed of one or more links interconnected so as to cooperate with each other in the achievement of some motion of an end effector. There are many examples of linkages that will allow flexibility in the coupling of the end effector to the handle, from robotic arms and servo-mechanical manipulators to socket wrenches. In particular, see Shackleford's gripper mechanism described in U.S. Pat. No. 4,243,257 and Greer, et al.'s material handling manipulator described in U.S. Pat. No. 2,765,930. Shackleford's device has an air cylinder that moves one of two links, the links pivotally interconnected, so that jaws operated from the links open and close. Greer's device is also a gripper, opening and closing by the manipulation of a hand grip separated from the gripper by a flexible hose so that the gripping operation can take place at large angles with respect to the hand grip. In particular, there are linkage mechanisms that invert an object. See the mechanisms of Kitamura, et al. in U.S. Pat. No. 3,773,189, Misawa in U.S. Pat. No. 3,734,556, Youmans in U.S. Pat. No. 2,861,699, and Couser in U.S. Pat. No. 2,807,373. However, all of these rotate the object to invert it. It is sometimes necessary to grip an object from the end and turn it 180.degree. or more and hold it. There is a need for a mechanical linkage that deploys a gripper or other end effector and inverts it for application to a workpiece, especially a linkage that is compact so that it performs the inverting in a minimum of space. SUMMARY OF THE INVENTION According to its major aspects and broadly stated, the present invention is a mechanical linkage for use with an end effector, such as a gripper. The linkage comprises a frame with a first axis and means for rotating the end effector about a second axis that is perpendicular to the first axis and translating the end effector, so that the end effector is inverted from its original position and moved laterally. In particular, the linkage includes a frame with an actuator such as an air cylinder attached to it that slides a shaft or rod between a first position, when the end effector is hanging vertically, and a second position, when the end effector has been inverted and translated. There is a stationary bracket also on the frame, next to the air cylinder. One end of the first of three links that make up the heart of the linkage is pivotally attached to the rod. The other end of the first link is attached to about the middle of the second link. One end of the second link is attached to the side of the end effector and the other to a stopping bracket. The stopping bracket, attached to said frame, has two faces, perpendicular to each other, that engage the sides of the second link to stop its rotation. The third link is attached at one end to a stationary bracket mounted to the frame. The other end of the third link is attached to the end of the end effector. The first link, moved by the rod of the air cylinder, causes the second link to rotate about an axis perpendicular to the axis of the frame. The stopping bracket limits the rotation at both extremes of motion, corresponding to the first and second positions of the end effector. The third link helps to control the end effector which would otherwise be attached, pivotally, to only the second link of the linkage. The third link prevents the end effector from pivoting about the end of the second link when moving or when stationary. The configuration and cooperation of the linkage is a major feature of the present invention because it not only inverts an end effector but it does so in a very compact package. The links, frame and end effector can fit through a small hole and then invert and translate the end effector laterally. Another feature of the present invention is that it operates on one actuator, such as an air cylinder. The links and brackets are configured so that the shaft of the single cylinder will cause the inversion and translation, yet control and precisely position the end effector. The advantage of this feature is that it minimizes power requirements and reduces the number of air hoses and wires required. This advantage is especially important since the end effector will likely have its own air cylinder or other actuator and may well have more than one. Still another feature of the present invention is the fact that the inversion and translation are accomplished with three, simple, mechanical links and one air cylinder. Mechanical linkages can withstand stresses and strains that other types of motion producing systems cannot; they are rugged and relatively impervious to electro-magnetic noise, impact, heat, cold, radiation, and chemical attack. Other features and advantages of the present invention will be apparent to those skilled in the art from a careful reading of the Detailed Description of a Preferred Embodiment presented below and accompanied by the drawings.