This invention relates to cable pushing machines. More specifically, it relates to a machine for wrapping cable together prior to installation and subsequently pushing it into a conduit or duct.
The installation of electrical or other cables often involves feeding a number of cables together through a length of underground duct or conduit. For example, power cables, such as secondary cables are typically bundled in three""sxe2x80x94two hots and a neutral. In this way, a primary high voltage cable is brought into a transformer. The voltage is stepped down and/or split into phases, and sent out of the transformer as low voltage, high amperage supply lines. Power supply to homes also involves a plurality of power cables and generally involves significant distances that the three secondary cables must travel in an underground duct between the transformer and the service entrance. It is not unusual for one transformer to feed a number of homes, for example, 2 to 4 homes. Pulling the cables in place through the duct involves transporting and setting up heavy equipment at each final destination. If cables are pushed through the underground duct, the cable reel and pusher are set up only once at the transformer, and the cable is pushed to each of the service locations, saving considerable time and money.
Because the cables are fairly heavy, and the distances the cables must travel in the underground ducts possibly significant, the pushing force necessary may rise to several hundred pounds. Depending on the free clearance for the cable inside the duct, the cables have a tendency to buckle, which induces them to deflect laterally against the duct wall, thus resisting further movement. It has been found that if the cables are wrapped prior to installation, their resistance to buckling improves significantly, thus allowing higher pushing forces to be applied.
One solution would be to have cable suppliers parallel and pre-wrap cables prior to winding them on the master reel. The problem with this is that it is expensive, time consuming and unwieldy. Also, the winding media must be sufficiently flexible so as to allow the cables to bend on the reel and recover when uncoiled.
These problems are solved by the present invention, which provides for the wrapping of cables together at the point of installation. On-site wrapping has several advantages. First, a number of cables can be wrapped together, which provides more resistance to buckling. This means that larger axial forces can be applied to the cables, and thus, they can be pushed greater distances. Second, the cables may be unrolled and straightened prior to wrapping. This results in a straighter and stiffer product. Third, a wider variety of winding media may be used because the media is not wound on the cable reels along with the cables. Fourth, installation of the cables is faster because the cables deflect within the duct less often. As on-site wrapping requires less employee-hours to deal with deflected cables that become jammed in the duct, it is also less expensive.
Thus, a portable cable wrapping and pushing machine are provided to allow the user to wrap cables at the point of installation. A method of wrapping and installing cables is also provided.
This invention includes a machine for wrapping a plurality of cables together before installation that includes a cable pushing machine and a platform upstream of the cable pushing machine. The platform is provided with an opening through which the cables may pass. The machine also includes a mount for the platform that allows the platform to rotate about the opening, a coil of winding media mounted on the platform, and a drive mechanism for rotating the platform so that the winding media may wrap the cables as they move through the opening in the platform.
A method of installing a plurality of cables in a duct is also provided. The method comprises gathering a plurality of cables together, feeding the plurality of cables through an opening in a platform, then feeding a winding media gathered on the platform onto the plurality of cables. The winding media is rotated around the plurality of cables, while the cables are propelled along a path through the opening in the platform. In this way, the winding media is wrapped in a spiral around the plurality of cables. Finally, the cables are fed into the duct.