When working through confined openings in walls such as those in storage tanks, or other large containers or rooms it is difficult and often dangerous for men to enter and leave through the opening. This is particularly true if the floor of the container or room is sloped or otherwise uneven or is located a distance below the opening. Under these circumstances it is important to be able to secure the men as they enter and leave the opening and also as they are working within the container or room. When moving equipment or materials through an opening of this type the difficulties are similar to those of handling the men.
In Olson et al, U.S. Pat. No. 5,147,013 Sep. 15, 1992 an apparatus is shown which mounts on a projection at the opening in a side wall of a storage tank. The apparatus has a plurality of arms which are arranged to be mounted on the interior of the tank at the opening for raising and lowering men and materials within the tank. The arms however block a portion of the opening from the inside and cannot be moved away from the opening without completely removing the apparatus from the tank. Furthermore the apparatus is configured to mount a hoist and a fall arresting device only and is not designed to mount different kinds of appliances at the opening.
An apparatus for mounting an appliance at an opening in a wall is needed which allows men and materials to be safely raised and lowered within the opening, can be moved away from the opening without completely removing the apparatus from the tank, and which can be used to mount a variety or different appliances for use through the opening.