subject: The Hercules In The Heavy Industry - Crane [print this page] A crane is a machine that is capable of raising and lowering heavy objects and moving them horizontally. Cranes are distinguished from hoists, which can lift objects but that cannot move them sideways. Cranes are also distinguished from conveyors, that lift and move bulk materials, such as grain and coal, in a continuous process. The word crane is taken from the fact that these machines have a shape similar to that of the tall, long-necked bird of the same name. Human beings have used a wide variety of devices to lift heavy objects since ancient times. One of the earliest versions of the crane to be developed was the shaduf, first used to move water in Egypt about four thousand years ago. The shaduf consists of a long, pivoting beam balanced on a vertical support. A heavy weight is attached to one end of the beam and a bucket to the other. The user pulls the bucket down to the water supply, fills it, then allows the weight to pull the bucket up. The beam is then rotated to the desired position and the bucket is emptied. The shaduf is still used in rural areas of Egypt and India. An important development in crane design occurred during the Middle Ages, when a horizontal arm known as a jib was added to the boom. The jib was attached to the boom in a way which allowed it to pivot, allowing for an increased range of motion. By the sixteenth century, cranes were built with two treadmills, one on each side of a rotating housing containing the boom. Cranes continued to rely on human or animal power until the middle of the nineteenth century, when steam engines were developed. By the end of the nineteenth century, internal combustion engines and electric motors were used to power cranes. By this time, steel rather than wood was used to build most cranes. Manufacturers of cranes are constantly seeking new ways to incorporate new technology into their products. Future cranes will have improved safety and versatility with computers and video screens that will allow operators to move heavy objects with increased accuracy.As the professional manufacturer of complete sets of mining machinery, such as Rotary dryer,Mobile crusher,Clinker rotary kiln, Henan Hongxing is always doing the best in products and service.
