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Lever frame
Mechanical railway signalling installations rely on lever frames for their operation to interlock the signals, track locks and points to allow the safe operation of trains in the area the signals control. Usually located in the signal box, the levers are operated either by the signalman or the pointsman.[citation needed]
The world's largest lever frame is believed to have been in the Spencer Street No.1 signal box in Melbourne, Australia, which had 191 levers, but was decommissioned in 2008.[citation needed] The largest, currently operational, lever frame is located at Severn Bridge Junction in Shrewsbury, England, and has 180 levers; although most of them have now been taken out of use.
The lever frame is located in the signal box, which can be a building at ground level or a tower, separated from or connected to an existing station building. Early lever frames were also built as ground frames next to the track, without any form of shelter and were usually operated by traincrew and not permanently staffed. Especially in England, lever frames with the pivot underneath the floor of the signal box were common. This design's relatively short lever angle is a major disadvantage, as it requires more force to move the lever. Therefore, later, especially in Germany, lever frames with pivots inside the signaller's room were used, that allow for a lever angle of approximately 180°.
By the movement of individual levers (or sometimes cranks), signals, points, track locks, level crossing gates or barriers and sometimes navigable movable bridges over waterways are operated via wires and rods. The signaller chooses the correct combination of points, facing point locks and signals to operate, which will control the movement of each train through their area of control. The lever frame contains interlocking designed to ensure that the levers cannot be operated to create a conflicting train movement. Each interlocking installation is individual and unique to the location controlled. The interlocking may be achieved mechanically or by electric lever locks, or (more usually) a combination of both.[citation needed]
A mechanical lever frame is designed to harness mechanical advantage to operate switch points, signals or both under the protection of the interlocking logic. The levers are connected to field appliances via solid pipes or taut wires such that the full travel of the lever will reliably cause full travel in the appliance. Each lever is engaged with the interlocking logic such that movement of the lever is only possible when all necessary conditions are met. The interlocking may be mechanical, electric (via solenoids) or both with the apparatus being mounted horizontally behind the lever frame or vertically below it.
To assist the operator in determining their functions, each lever in a frame will generally be uniquely labelled, one common method being to number the levers in order from left to right. A lever's identification may be painted on its side or engraved on a badge or plate fitted either to the lever or behind it. This may be accompanied by a description of the lever's function. Usually, a large track diagram is positioned within easy view of the operator, which clearly shows each lever number adjacent to symbols representing the items of equipment that they operate. Levers are commonly coloured according to the type of equipment they control, the code of colours varying between different railway administrations. For example, in British practice, the following code generally applies: a red lever controls a stop signal or shunt signal, a yellow lever controls a distant signal, a black lever controls a set of points, a blue lever controls a facing point lock, and a white lever is spare. Brown levers are used to lock level crossing gates. Lever handles are usually of polished, unpainted steel, and signalmen operate them with a cloth to prevent rusting from the sweat on their hands. In Germany, signal levers are red, whilst levers for points and track locks are usually blue, and route lock levers are green. Also, individual numbers and letters are used to indicate each individual item a lever operates in Germany as well.
Some mechanical frames were combined with a set of electric levers or switches to more efficiently work electrically powered signals or other non-mechanically operated devices.[citation needed] Typically the switch points would be left under mechanical operation as the other devices used comparatively little electrical power and could be run off of batteries or a low capacity railroad-operated power system.[citation needed]
A power operated interlocking frame uses some form of power assist to operate switches, signals and other interlocking appliances in the field. The power can come from hydraulic, pneumatic or electric sources with direct acting or low voltage electric control.
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Lever frame AI simulator
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Lever frame
Mechanical railway signalling installations rely on lever frames for their operation to interlock the signals, track locks and points to allow the safe operation of trains in the area the signals control. Usually located in the signal box, the levers are operated either by the signalman or the pointsman.[citation needed]
The world's largest lever frame is believed to have been in the Spencer Street No.1 signal box in Melbourne, Australia, which had 191 levers, but was decommissioned in 2008.[citation needed] The largest, currently operational, lever frame is located at Severn Bridge Junction in Shrewsbury, England, and has 180 levers; although most of them have now been taken out of use.
The lever frame is located in the signal box, which can be a building at ground level or a tower, separated from or connected to an existing station building. Early lever frames were also built as ground frames next to the track, without any form of shelter and were usually operated by traincrew and not permanently staffed. Especially in England, lever frames with the pivot underneath the floor of the signal box were common. This design's relatively short lever angle is a major disadvantage, as it requires more force to move the lever. Therefore, later, especially in Germany, lever frames with pivots inside the signaller's room were used, that allow for a lever angle of approximately 180°.
By the movement of individual levers (or sometimes cranks), signals, points, track locks, level crossing gates or barriers and sometimes navigable movable bridges over waterways are operated via wires and rods. The signaller chooses the correct combination of points, facing point locks and signals to operate, which will control the movement of each train through their area of control. The lever frame contains interlocking designed to ensure that the levers cannot be operated to create a conflicting train movement. Each interlocking installation is individual and unique to the location controlled. The interlocking may be achieved mechanically or by electric lever locks, or (more usually) a combination of both.[citation needed]
A mechanical lever frame is designed to harness mechanical advantage to operate switch points, signals or both under the protection of the interlocking logic. The levers are connected to field appliances via solid pipes or taut wires such that the full travel of the lever will reliably cause full travel in the appliance. Each lever is engaged with the interlocking logic such that movement of the lever is only possible when all necessary conditions are met. The interlocking may be mechanical, electric (via solenoids) or both with the apparatus being mounted horizontally behind the lever frame or vertically below it.
To assist the operator in determining their functions, each lever in a frame will generally be uniquely labelled, one common method being to number the levers in order from left to right. A lever's identification may be painted on its side or engraved on a badge or plate fitted either to the lever or behind it. This may be accompanied by a description of the lever's function. Usually, a large track diagram is positioned within easy view of the operator, which clearly shows each lever number adjacent to symbols representing the items of equipment that they operate. Levers are commonly coloured according to the type of equipment they control, the code of colours varying between different railway administrations. For example, in British practice, the following code generally applies: a red lever controls a stop signal or shunt signal, a yellow lever controls a distant signal, a black lever controls a set of points, a blue lever controls a facing point lock, and a white lever is spare. Brown levers are used to lock level crossing gates. Lever handles are usually of polished, unpainted steel, and signalmen operate them with a cloth to prevent rusting from the sweat on their hands. In Germany, signal levers are red, whilst levers for points and track locks are usually blue, and route lock levers are green. Also, individual numbers and letters are used to indicate each individual item a lever operates in Germany as well.
Some mechanical frames were combined with a set of electric levers or switches to more efficiently work electrically powered signals or other non-mechanically operated devices.[citation needed] Typically the switch points would be left under mechanical operation as the other devices used comparatively little electrical power and could be run off of batteries or a low capacity railroad-operated power system.[citation needed]
A power operated interlocking frame uses some form of power assist to operate switches, signals and other interlocking appliances in the field. The power can come from hydraulic, pneumatic or electric sources with direct acting or low voltage electric control.