Ladder: Wikis

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From Wikipedia, the free encyclopedia

A ladder

A ladder is a vertical or inclined set of rungs or steps. There are two types: rigid ladders that can be leaned against a vertical surface such as a wall, and rope ladders that are hung from the top. The vertical members of a rigid ladder are called stringers (US) or stiles (UK). Rigid ladders are usually portable, but some types are permanently fixed to buildings.

Contents

Variations

Sketch of double extension ladder
Photo of a dog and pawl on an extension ladder
Sketch of Cat Ladder (UK terminology) an aid when working on steep roofs.

Rigid ladders are available in many forms, such as:

  • Fixed ladder, Two side members joined by several rungs; affixed to structure with no moving parts
  • Extension ladder or Telescopic ladder, fixed ladder divided into two or more lengths for more convenient storage; the lengths can be slid together for storage or slid apart to maximize the length of the ladder; a pulley system may be fitted so that the ladder can be easily extended by an operator on the ground then locked in place using the dogs and pawls
  • Step ladder, hinged in the middle to form an inverted V, with stays to keep the two halves at a fixed angle
  • Folding ladder, A ladder in the step ladder style with one or more (usually no more than three) one-way hinges. Ideal for use on uneven ground (i.e. stairs), as a trestle or when fully extended a Fixed ladder. Some variations feature a central one-way hinge with extensible locking legs
  • Platform steps, step ladder with small horizontal platform at the top
  • Orchard ladder, three legged step ladder with third leg made so that it can be inserted between tree branches for fruit picking
  • Roof ladder, rigid ladder with large hook at the top to grip the ridge of a pitched roof
  • Cat ladder (US chicken ladder), lightweight ladder frame used on steep roofs to prevents workers from sliding
  • Hook ladder or pompier ladder, rigid ladder with a hook at the top to grip a windowsill; used by firefighters
  • Turntable ladder, extension ladder fitted to rotating platform on top of a fire truck
  • Bridge ladder, ladder laid horizontally to act as passage between two points separated by a drop.
  • Vertically rising ladder, a ladder designed to climb high points and facilitate suspending there.

Rigid ladders were originally made of wood,but in the 20th century tubular aluminum became more common because of its lighter weight. Ladders with fiberglass stiles are used for working on or near overhead electrical wires, because fiberglass is an electrical insulator.[1]

Safety

For safety, a rigid ladder should be leaned at an angle of about fifteen degrees to the vertical. In other words, the distance from the foot of the ladder to the wall should be about one quarter of the height of the top of the ladder. At steeper angles, the ladder is at risk of toppling backwards when the climber leans away from it. At shallower angles, the ladder may lose its grip on the ground. Ladder stabilizers are available that increase the ladder's grip on the ground.

A ladder standoff, or stay, is a device fitted to the top of a ladder to hold it away from the wall. This enables the ladder to clear overhanging obstacles, such as the eaves of a roof, and increases the safe working height for a given length of ladder.

  • Rope ladders are used where storage space is extremely limited, weight must be kept to a minimum, or in instances where the object to be climbed is too curved to use a rigid ladder. They may have rigid or flexible rungs. Climbing a rope ladder requires more skill than climbing a rigid ladder, because the ladder tends to swing like a pendulum. Steel and aluminum rope ladders as sometimes used in vertical caving.
  • Dissipative ladders are portable ladders built to ESD (Electrostatic Discharge) standard. Electrostatic Discharge is a natural occurrence in which electricity is passed through our body, or other conductor, and discharges onto some object. For example, the shock we feel when we touch a doorknob is an ESD. This natural occurrence is becoming a very hot topic in the field of electronics assembly due to the costly damage ESDs can cause to sensitive electronic equipment. Dissipative ladders are ladders with controlled electric resistance: the resistance slows the transfer of charge from one point to another, offering increased protection during ESD events: ≥105 and < 1012 Ω / square ([e.g.][1])
  • Pool ladders. A ladder is also used on the side of a boat, to climb into it from the water, and in a swimming pool. Swimming pool ladders are usually made from plastic steps with special grip and metal bars on the sides to support the steps and as handrails for the user.
  • Assault ladders. These are designed to be used by units which may need to board or assault vessels or buildings. They can be used when a full sized ladder is not required or when working in confined spaces. Suited for covert operations such as sniper placement, and vessel boardings. It was developed and designed for tubular assaults including buses and trains and for first story breaching.[2] Its extra wide design gives the user greater stability, but still can fold away to be stored. It is available in standard aluminum or non-reflective black finish in 6 and 8 foot lengths.

Historical usage

Ladders are ancient tools and technology. A ladder is depicted in a Mesolithic rock painting that is at least 10,000 years old, depicted in a cave in Valencia, Spain. Bee Wilson (2004: p.5) references the rock painting which shows two naked humans carrying baskets or bags that are employing a long wobbly ladder, which appears to be made out of some kind of grass, to reach a wild honeybee nest to harvest honey. Modern ladders are believed to have been conceived by Hebrews and Egyptians.

See also

References

  1. ^ "Preventing Worker Deaths and Injuries from Contacting Overhead Power Lines with Metal Ladders". National Institute of Occupational Safety and Health. Workplace Solutions, Publication No. 2007-155, September 2007.
  2. ^ Foldable Quikstep Ladder website
  • Wilson, Bee (2004). The Hive: The Story Of The Honeybee. London, Great Britain: John Murray (Publishers). ISBN 0 7195 6598 7

External links

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1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

LADDER, (0. Eng. hlaeder; of Teutonic origin, cf. Dutch leer, Ger. Leiter; the ultimate origin is in the root seen in "lean," Gr. icXI aE), a set of steps or "rungs" between two supports to enable one to get up and down; usually made of wood and sometimes of metal or rope. Ladders are generally movable, and differ from a staircase also in having only treads and no "risers." The term "Jacob's ladder," taken from the dream of Jacob in the Bible, is applied to a rope ladder with wooden steps used at sea to go aloft, and to a common garden plant of the genus Polemonium on account of the ladder-like formation of the leaves. The flower known in England as Solomon's seal is in some countries called the "ladder of heaven."


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Bible wiki

Up to date as of January 23, 2010

From BibleWiki

occurs only once, in the account of Jacob's vision (Gen 28:12).

This entry includes text from Easton's Bible Dictionary, 1897.

what mentions this? (please help by turning references to this page into wiki links)


Simple English

]] A ladder is a tool which is made for people to climb up or down. Ladders have two vertical supports that go along the whole length of the ladder. Between these supports are the horizontal rungs. The rung is what the climber can put his foot on. The climber can use his hands to hold on to the rungs above him, or to the supports at the side.

Ladders can be made of metal, wood or even rope. There are different types of ladders.

Some ladders are made in one piece. They can be carried around and made to lean against something such as the wall of a house. There should be a good distance between the bottom of the ladder and the wall so that the ladder is not too vertical, otherwise the ladder might fall backwards and the climber would fall off. Sometimes these ladders are extension ladders. Extension ladders are made in two or more sections so that the ladder can fold up to make it easier to carry about and to store. To open up the ladder, each section slides up almost to the top of the next section.

Step ladders are useful in the home or the garden to reach things that are not too high, e.g. ceilings or the tops of hedges. They have two parts which are joined together by a hinge, so that they are shaped like an upside down V. There is usually a platform at the top to stand on, but this can be dangerous unless great care is taken that the ladder will not wobble or fall down.

Some ladders are vertical (they go straight up or down). These are fixed onto something. Examples are: ladders in a swimming pool for climbing in and out of the water, small ladders to climb up to a top bunk bed, ladders at the side of a big boat or at the side of a canal lock or of any other high or low construction where workmen may need to get up or down to do repairs.

[[File:|left|thumb|250px|A fire engine with a turntable ladder in Tokyo.]] Fire engines always have ladders. They often have a turntable ladder which makes it possible for the ladder to be facing in any direction.

Rope ladders can be folded away easily. They may be used for climbing trees or for rock climbing or in caves.

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