In the field of robotics a need has been recognized for mechanism which will automatically sense process disruptions as, for example, excessive forces and inadvertent physical contacts with the end of the arm tooling of robots and interrupt the process. It has likewise been determined that there is a need for protecting not only the robot but the tooling from damage if a disruption occurs in a process.
Many such devices have been developed. One such device is known as a "breakaway" joint. This type of joint is interposed between the tooling and the robot arm and physically breaks if an overload force greater than a predetermined amount is applied between the robot and the tooling. Such joints are difficult to replace and are not always reliable in protecting the robot and/or the tooling from damage. In most cases, such breakaway joints may only be used once and must be discarded and replaced with a new one.
Another type of protective device is known as a "snapaway" joint. When the robot or the tooling encounters a disruption, such as striking a misplaced part, the device actually snaps out of place displacing the tooling or allowing it to yield from contact with whatever it struck. For the most part, these devices embody releasable springs which yield when a predetermined load is placed upon them. Subsequently, they snap back after the disruption has been corrected. Many such devices use ball detent mechanisms. The range of such devices is limited by the strength of the springs employed, which is relatively low, and their ability to return to their original set position.
While the above described mechanisms are designed to unlock the rigid connection between the robot arm and its tooling, few, if any, are equipped to either shut down the process completely to prevent further spoilage of workpieces or to allow the robot to be reset with minimal downtime.
Consequently, a need exists for an overload protective device which will prevent or minimize damage to the workpiece or tooling upon the detection of a disruption and which will allow the process to be restarted in a minimal amount of time while retaining a high degree of tooling repeatability. Such a device should be adjustable to account for a wide range of loads and should be universally adaptable to tooling of various kinds.