Overhead crane
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[edit] Overview
An overhead crane typically consists of three important parts:
1. The hoist, providing up/down motion to lift items.
2. The trolley, providing left/right motion for the hoist and load.
3. 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 a 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 at least 30 to 50 years experience in the market for purposes of safety and availability of spare parts.
[edit] History
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, and is now only used for heavy-duty applications such as steel coil handling. Now most hoists are package hoists, built as one unit in a single housing.
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.
- 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.
