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See wikt:excavator for other meanings.
A typical modern excavator:
a CAT 325C, fitted with quick hitch and tilting bucket
An old excavator under the Northwest (now Terex) name at the Pageant of Steam grounds

Excavators are heavy equipment consisting of a boom, bucket and cab on a rotating platform (known as the "house"). The house sits atop an undercarriage with tracks or wheels. All movement and functions of the excavator are accomplished through the use of hydraulic fluid, be it with rams or motors. Their design is a natural progression from the steam shovel.

Contents

Usage

Excavator demolishing a house. Note the hydraulic thumb
Link-Belt excavator trenching.
Close up of Knuckle Boom.

Excavators are used in many ways:

Configurations

Excavators come in a wide variety of sizes. The smaller ones are called mini or compact excavators. Caterpillar's smallest mini-excavator weighs 3549 lb (1610 kg) and has 19 hp; their largest model weighs 187,360 lb (84,980 kg) and has 513 hp. The largest excavator available is the Terex RH 340, it weighs in excess of 1,210,000 lb (550,000 kg), has 3000 hp and has a bucket size of nearly 9000 gallons (34.0 ).

Engines in excavators drive Hydraulic pumps; there are usually 3 pumps: the two Main pumps are for supplying oil at high pressure (up to 5000 psi) for the rams, slew motor, track motors, and accessories, and the third is a lower pressure (700 psi) pump for Pilot Control, this circuit used for the control of the spool valves, this allows for a reduced effort required when operating the controls.

The two main sections of an excavator are the undercarriage and the house. The undercarriage includes the blade (if fitted), tracks, track frame, and final drives, which have a hydraulic motor and gearing providing the drive to the individual tracks, and the house includes the operator cab, counterweight, engine, fuel and hydraulic oil tanks. The house attaches to the Undercarriage by way of a center pin, allowing the machine to slew 360° unhindered.

The main boom attaches to the house, it can be one of 3 different configurations, Most are Mono Booms, these have no movement apart from straight up and down, some others have a Knuckle Boom which can also move left and right in line with the machine, the other option is a hinge at the base of the boom allowing it to hydraulically pivot up to 180° independent to the house, however this is generally available only to compact excavators.

Attached to the end of the Boom is the Stick (or dipper arm), the stick provides the digging force required to pull the bucket through the ground, the stick length is optional depending whether reach (longer stick) or break-out power (shorter stick) is required. On the end of the stick is usually a bucket. A wide, large capacity (Mud) bucket with a straight cutting edge is used for cleanup and leveling or where the material to be dug is soft, and teeth are not required. A general purpose (GP) bucket is generally smaller, stronger, and has hardened side cutters and teeth used to break through hard ground and rocks. Buckets have numerous shapes and sizes for various applications. There are also many other attachments which are available to be attached to the excavator for boring, ripping, crushing, cutting, lifting, etc.

Prior to the 1990s, all excavators had a long, or conventional counterweight that hung off the rear of the machine to provide more digging force and lifting capacity. This became a nuisance when working in confined areas. In 1993 Yanmar launched the world's first Zero Tail Swing excavator,[1] which allows the counterweight to stay inside the width of the tracks as it slews, thus being safer and more user friendly when used in a confined space. This type of machine is now widely used throughout the world.

Excavator attachments

In recent years, hydraulic excavator capabilities have expanded far beyond excavation tasks with buckets. With the advent of hydraulic powered attachments such as a breaker, a grapple or an auger, the excavator is frequently used in many applications other than excavation. Many excavators feature a quick coupler for simplified attachment mounting, increasing the machine's utilization on the jobsite. Excavators are usually employed together with loaders and bulldozers. Most wheeled, compact and some medium sized (11 to 18 tonne) excavators have a backfill (or dozer) blade. This is a horizontal bulldozer-like blade attached to the undercarriage and is used for leveling & pushing removed material back into a hole.

Terminology

Excavators are also called diggers and 360-degree excavators, sometimes abbreviated simply to a 360. Tracked excavators are sometimes called trackhoes by analogy to the backhoe. Even though the 'back' in backhoe refers to the action of the bucket (which pulls "back" toward the machine) and not the location of the shovel, excavators are also occasionally referred to as fronthoes or even just "hoes". In North America, digging excavators are sometimes referred to as "hi-hoes" and often simply as "shovels".

In the UK, wheeled excavators are sometimes known as 'Rubber ducks'.[2]

In Japan, the alias Yumbo (ユンボ Yunbo?) is a more popular name for excavators. In 1954 after the patent right was obtained from Italy, the French company SICAM produced an excavator model Yumbo S25 . SICAM licensed this technology to many companies, such as Drott in United States, Priestman in UK, and Mitsubishi in Japan and other countries in the early 1960s.[3] The first excavator from Mitsubishi using this technology was named Yumbo Y35 which was aimed for the international market in 1961. Since then, Yumbo has become the popular name and de facto standard in Japan because of its use in Classified ads even though this is not the formal name there.

The excavating technology of Mars rovers

NASA’s Phoenix Mars Lander’s solar panel and the lander’s Robotic Arm with a sample in the scoop (June 10, 2008)

The Phoenix spacecraft has a robotic excavating arm, controlled by an on-board computer system or the terrestrial command center, and equipped with a bucket, a drill, a camera and other sensors. Because of the extreme climatic conditions of Mars there were several malfunctioning problems with Phoenix's "excavator".

Gallery

Notable manufacturers

See also

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Types of excavator

Other

Notes and references

  1. ^ http://www.yanmar.com/construction/products/excavators/
  2. ^ http://www.heservices.co.uk/plant/komatsupw130.php
  3. ^ Book title:Giant Earthmovers/An Illustrated History, [1] ISBN 0-7603-0369-X, 9780760303696, MBI Publishing Company, page 201

External links


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