Overhead crane

From Wikipedia, the free encyclopedia

1 Uses of Overhead Cranes
2 Selecting an Overhead Crane
3 History
4 External links
- 4.1 Manufacturers

An overhead crane is a type of crane where the hook-and-line mechanism runs along a horizontal beam that runs along two widely separated rails. Often it is in a long factory building and runs along rails along the building's two long walls.

An overhead crane typically consists of three important parts:

The hoist, providing up/down motion to lift items.
The trolley, providing left/right motion for the hoist and load.
The bridge, providing back/forward motion for trolley, hoist, and load.

This is permanently installed in a factory, shop, or warehouse to move items not moveable by humans or forklifts.

[edit] Uses of Overhead Cranes

The most common overhead crane use is in the steel industry. Every step of steel, until it leaves a factory as a finished product, the steel is handled by an overhead crane. Raw materials are poured into a furnace by crane, hot steel is stored for cooling by an overhead crane, the finished coils are lifted and loaded onto trucks and trains by overhead crane, and the fabricator or stamper uses an overhead crane to handle the steel in his factory. The automobile industry uses overhead cranes for handling of raw materials. Smaller workstation cranes handle lighter loads in a work-area, such as CNC mill or saw.

[edit] Selecting an Overhead Crane

It is difficult to select an overhead crane properly. Every crane is different, and none are built alike because no two buildings are alike. Because the industry has undergone massive consolidation in the last few years, it is important to choose a manufacturer that has experience in the market for purposes of safety and availability of spare parts. The Crane Manufacturer's Association of America (CMAA) can provide guidance on selecting a crane manufacturer.

[edit] History

Power Electronics International, Inc. developed the overhead hoist variable speed drive pictured here in 1969.

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Alton Shaw, of the Shaw Crane Company, is credited with the first overhead crane, in 1874. Alliance Machine, now defunct, holds an AISE citation for one of the earliest cranes as well. This crane was in service until approximately 1980, and is now in a museum in Birmingham, Alabama. Over the years important innovations, such as the Weston load brake (which is now rare) and the wire rope hoist (which is still popular), have come and gone. The original hoist contained components mated together in what is now called the built-up style hoist. These built up hoists are used for heavy-duty applications such as steel coil handling and for users desiring long life and better durability. They also provide for easier maintenance. Now many hoists are package hoists, built as one unit in a single housing, generally designed for ten-year life or less.

Notable cranes and dates

1874: Alton Shaw develops the first overhead crane.
1938: Yale introduces the Cable-King hoist.
1944: Shepard-Niles supplies a hoist for lifting atomic bombs for testing in New Mexico.
1969: Power Electronics International, Inc. developed the overhead hoist variable speed drive.
1997: Industry giant P&H files for chapter eleven bankruptcy.
1998: Dearborn Crane supplies two 500-ton capacity overhead cranes to Verson Press of Chicago. The cranes were manufactured by Konecranes America, Inc in Houston, Texas.