In the art of erecting steel beams and columns, there is a need for a device that will allow an operator to release the column or beam from the load line of an erection crane from a position remote from the beam. Such a device will help protect operators from injury when the beam or column is released. It is a general object of the present invention to provide such a device.
Simply stated, the present invention is directed to a crane/load safety shackle for supporting a load on the end of an erection crane load line, and for permitting release of a load from the load line by an operator positioned remotely of the load. An important feature of the crane/load safety shackle in accordance with the invention is that it will prevent release of the load in the event that the load is fully supported by the shackle, which is to say that the load is not fully supported by the ground or by construction. Thus, the safety shackle in accordance with the present invention will help prevent inadvertent release of a load.
The crane/load safety shackle in accordance with the present invention comprises a yoke having a slot that opens along one side edge of the yoke, and a buckle opening or other suitable means for securing the yoke to a crane load line such that the slot opens downwardly. A pin moveably slidably extends laterally across the slot for closing the slot and supporting a load carried by the shackle. A linear actuator and remote control electronics are mounted on the yoke and coupled to the pin for selectively extending the pin across the slot to support the load carried by the shackle, and retracting the pin from the slot so as to release the load. In the event that the load is supported by the pin and thus exerts lateral forces on the pin, the actuator has insufficient power to withdraw the pin from the slot against such lateral forces applied by the load, so that the load will not be inadvertently released.
The actuator in the preferred embodiment of the invention comprises a d.c. linear actuator, and the control electronics includes a rechargeable battery for suppling electrical power to the electronics and the actuator. Electrical power is selectively applied to the actuator by a remote control transmitter responsive to an operator and a receiver within the control electronics wirelessly coupled to the transmitter. The actuator and control electronics are carried within a protective enclosure mounted on one side of the yoke, and a counterbalance extends from the opposing side of the yoke for balancing the yoke with respect to the crane load line.