In industry and construction, it is necessary that heavy loads can be safely lifted and transported by a lifting means, such as a crane. In this regard, a primary safety issue relates to the inadvertent release of the load during operation.
It is known in the prior art for rigid mechanical connections, such as nut and bolt assemblies, to be utilized to connect loads to lifting means during operation. The use of rigid mechanical connections is advantageous, as such connections are inexpensive to purchase, are relatively light-weight, and are not susceptible to the accidental release of the load during operation. However, rigid mechanical connections are inconvenient, in that workers are required to mechanically connect and disconnect the lifting means to and from each load, which can be time-consuming and difficult, especially at high altitudes. This situation is compounded by worker safety legislation enacted in many jurisdictions which prohibits workers from working at elevated positions without a fall arrest system. In some jurisdictions, this legislation can require that another crane or manlift be used for workers to disconnect the rigging, which is at all times an expensive proposition, and, in some applications, a very awkward solution, depending upon the site conditions.
Lifting devices of the general type comprising a body member, adapted to operatively receive a lifting lug rigidly attached to a load and having a throughpassage extending therethrough adapted to receive a lift pin, which lift pin operatively rigidly connects the lifting lug to the body member, are known in the prior art. In known devices of this general type, when the body member is connected to a lifting means and is in receipt of the lifting lug, and a pull line is attached to the lift pin, such known lifting devices are capable of conveniently engaging loads for the lifting and transporting of same by the sliding insertion of the lift pin into the throughpassage, and for disengaging same by a distant operator by operative application of tensile force upon the pull line, thereby effecting sliding withdrawal of the lift pin from within the throughpassage. Additionally, known safety devices comprise a safety pin, insertable into a bore in the lift pin such that the lift pin can not be withdrawn from the throughpassage without first extracting the safety pin from the bore. One such known lifting device of this general type is a device previously manufactured and made available to the public by John T. Hepburn, Limited, of Toronto, Ontario, Canada, in or about 1992 (hereinafter, the "Hepburn device").
Such known lifting devices maintain the economy and relatively low weight of rigid mechanical connections. However, the Hepburn device suffers in that rotation of the lift pin in the throughpassage may occur, such that tensile forces applied upon the pull line may not be directed to extract the safety pin from the bore, resulting in an inability to remotely disconnect the load. Additionally, the Hepburn device suffers from unreliability with respect to the issue of accidental release of the load, which unreliability is related to the fact that the single pull line utilized in the Hepburn device is attached to the safety pin and to the lift pin, and that undesirable tensile force may be applied upon the pull line by same becoming snagged, thereby simultaneously disengaging the safety pin and the lift pin, with inadvertent release of the load. Needless to say, this can have disastrous consequences to workers and other ground personnel.
The problem of the Hepburn device relating to rotation of the lift pin in the throughpassage, namely, the inability to remotely disconnect the load upon said rotation, was addressed in a device manufactured and made available to the public by Canron Inc., of Toronto, Ontario, Canada, in or about 1995 (hereinafter, the "Canron device"). The Canron device differs from the Hepburn device, inter alia, in that the safety pin for arresting withdrawal of the lift pin from within the throughpassage is upwardly inserted into the bore in the lift pin, to a locked position, and is arrested from falling out of the bore by a spring-loaded ball bearing. The Canron device resolves, to a limited extent, the problem caused by rotation of the lift pin in the throughpassage. However, the Canron device does not resolve the problem of undesirable load release caused by inadvertent application of tensile force upon the pull line.