Patent Application
20080190044
These inventions improve the design of the current grid structure. The use, safety, and assembly of safe aerial platforms is likewise improved. The present invention is used to allow personnel safe access to high reach areas for mechanical tasks and maintenance operations, such as changing the position of theatrical lights, servicing air conditioning ducts, etc.
The wire rope tension grid has been in use for decades. It is usually installed in performing art centers, black box theaters, and in locations were it is difficult, impossible, or impractical to get a ladder or man lift in an area for maintenance. Through both the use and construction of many wire rope tension grid systems, InterAmerica Stage, Inc. has made various improvements to the structures. Currently we will be releasing a new line of improved wire rope tension grids. These grids will feature both the improvements that have been made over time by our firm and new improvements that have been developed and tested by our engineering staff.
Safety is one of the major reasons the wire rope tension grid is used. It minimizes the risk of falling while performing high reach operations using ladders or lifts. The other major benefit to the wire rope tension grid is that light can pass through without casting shadows on surfaces below it. This is particularly useful in the entertainment industry, where lighting of props, the focus of sound, and special effects placement are of the utmost importance in a performance.
Modularity: A wire rope tension grid is installed as a modular item, able to be removed for service and transported easily for erection. The connections to the modular attachments have been improved. Through bolts connect hanger points to the grid. This provides a hard connection as opposed to a floating clamped connection. This is a further improvement over the pieces in the past that are non-modular, being welded to their respective support hangers.
Reducing the lateral stress on the wire rope within the wire rope tension grid was a major priority. Rolled edges and chamfered through holes have aided in this regard. Even the position of the hole itself has been reconsidered, and positioned accordingly. The cable is supported over the frame support tube increasing the area of impact and lessening the stress at any particular point in the cable. This allows for a horizontal load to be applied to the wire rope.
Structural strength of the frame has likewise been improved by adding support tabs that do not interfere with the location of the wire rope. These help distribute the vertical and torsion loads that are exerted on the frame while it is in use.
The bottom portion of the hanger connections were further improved, providing streamlined outer perimeter and corner connections for safe handling and aesthetics.
The top of the hanger mounting plates are sized to allow for a flush walking surface.
A lighting pipe outrigger system has been developed applying lighting fixtures or light bars outboard from principal wire rope tension grid suspension points.
Originally, a spacer on the wire rope was used to assist in the swaging of a copper stop sleeve on the wire. With the use of a new purpose built hydraulic swaging tool this is no longer necessary.
Through bolts within the frame allow for a rigid connection to adjacent wire tension grid panels. This helps to prevent the frame from bowing under stresses applied by taught wire rope.
In an instance where a wire rope tension grid system is required to have the wire rope non-perpendicular and non-parallel to the frame a new way of distributing the wires had to be realized. A wire rope turn pin was added to the frame so that the wire rope can be weaved in the same way that the regular rectangular tension grids. The wire rope turn pin decreases the stress on the cable. Elliptical slots on frame for the cables further lessen pinch points.
Holes are predrilled into the angle at increments of 2″ center. These holes are 5/32″ in diameter. Holes are also predrilled into specific points on the tubing for modular through holes and for hanger plate bolts.
The angle is welded onto the tubing making the basic frame structure. This basic frame is reinforced by supports welded above the locations of the through holes used for modular attachments.
Frame is often powder coated or painted, often flat black, so that is not visually intrusive to the general public.
The wire rope is then weaved into the frame by hand. The ends of the wire rope are inserted into the 5/32″ holes. A copper stop sleeve is slid over the ends of the cable. A modified torque wrench is used to apply an accurate amount of tension within the wire as the copper stop sleeve is swaged onto the cable. This is done on both sides of the cable resulting in an evenly distributed amount of tension along the entire wire rope tension grid.
The hanger assembly is comprised of mild steel tubing, often 1.5″ schedule 40. The upper hanger plate is welded onto the steel tube. Holes are drilled in locations that correspond to the predrilled holes in the frame's tubing. The upper portion of the entire assembly varies per application and structure. Please see
The lower portion of the hanger plate assembly is a steel plate that is drilled to correspond to the bolt holes for the frame and the upper plate of the hanger assembly. These parts are often painted or powder coated, often flat black, so that is not visually intrusive to the general public and so that it matches the frame.
The entire assembly is erected on site and is bolted together using grade 5, ½″×13″ Carbon Zinc Plated Hex Head Bolt, with a ½ Carbon Zinc Plated Nylok nut, and flat ½ washers.
The pipe clamps are measured out to fit the support hangers. Likewise, the outrigger pipe is sized to fit common lighting fixtures with ease.
All of the parts of the wire rope tension grid system are design for modular installation, easy and safe use, and simple maintenance.
