I. Field of the Invention
The invention relates in general to apparatus for lifting objects into a structure and, more particularly, to a folding, lightweight apparatus that easily can assist in lifting panels or the like into preformed openings of a building under construction.
II. Description of the Prior Art
Modern tall office buildings are generally constructed as a shell with openings for panels and windows or the like. Buildings of this type can reach heights of 70 stories. The shell of the building is constructed with openings. Precast or prefabricated panels are then placed within these openings. These construction panels are of various sizes, shapes and thicknesses. Precast panels are made of reinforced concrete and may have heights as tall as 10 feet and lengths to 20 feet. These thicknesses may vary from 3 to 12 inches. Reinforced concrete panels with dimensions of this order are extremely heavy. Maneuvering of such heavy reinforced concrete panels is therefore difficult. The openings for receiving such a concrete panel may be at or above the 10th story making it necessary to lift panels to the 10th story or higher, and place them within the openings. Ordinarily, cranes are used to lift the panel up to the openings. The cranes may be situated on the ground or as the number of stories of the building increases, it is necessary to position the crane on the top floor of the building as it is being constructed or use a tower crane. A further complication arises in the construction of modern concrete steel buildings in that spandral beams are required. These spandral beams are so constructed that the openings for precast concrete panel may be as much as 3 feet inside the face of the spandral beam. The spandral beam therefore functions as a hindrance to the insertion of the precast concrete panel into the opening of the building. Without going into unnecessary detail, it is well known that the spandrals are required. The spandrals are required to be in place before the precast concrete panels are fit into the opening. Normally, the method of installing a panel of this type in the recessed opening in the building would be to attach lifting rings to the top of the panel. The rings would be attached with suitable bolts and a crane would be hooked to the lifting ring to lift the precast panel to the desired height in the building. Once the panel is lifted in close proximity to the opening it is to be fit into, construction workers will begin attempting to grab the panel and pull the panel into the opening. It is to be appreciated that the panel is large and heavy and the workers must manually pull the panel into the opening. After the panel has been pulled into the opening, it must be secured in place within the opening. The panel may be secured in place by bolting the panel to the structure in the building, welding the panel to the building, or by other suitable means. This procedure has obvious shortcomings. These shortcomings include the amount of time that workers take to fit one panel in place, and also due to the awkwardness of grabbing and fitting the panel in the opening, the possibility of an accident involving the workers.
U.S. Pat. No. 4,671,721 issued to applicants on Jun. 9, 1987, addressed the problems previously outlined above. In this embodiment, an apparatus and method for positioning an object in a building was disclosed. This invention showed that precast panels can be delivered to openings in office buildings in a controlled manner which facilitated placing the panels in the building. The invention had many advantages over the prior art. On the other hand, the invention had a shortcoming in that the apparatus used to lift the panels was of itself extremely bulky and heavy. Although this shortcoming did not necessarily affect the performance of what can be described as "the flying forklift," it did affect its use in construction sites as transportation of the apparatus to and from various sites became a major drawback. Put simply, it would be desirable to have an apparatus that can be transported by a pickup truck as opposed to other more costly methods, and still make installation of precast panels or the like in openings in a building easier and safer than had been in the prior art. Applicants have therefore come up with a new apparatus which fulfills all the desired requirements, as shown in U.S. Pat. No. 4,671,721 and has further advantages in its use and transportation as will become clear from the specification herein.