108 Lesson 1 Railroad Switch(铁道道岔) Introduction
A railroad switch is a mechanical installation enabling trains to be guided from one track to another.
In Figure 1, rail track A divides into two: track B (the straight track) and track C
(the diverging track) . The switch consists
of the pair of linked tapering rails, known as points (switch rails or point blades) lying between the diverging outer rails (the stock rails). These points can be moved laterally into one of two positions so as to determine whether a train coming from A will be led towards B or towards C.2 A train
moving from the A direction towards either B or C is said to be executing a facing-point movement. Unless the switch is locked, a train coming from B or C will be led to A regardless of the position of the points, as the vehicle's wheels will force the points to move. Passage through a switch in this direction is known as a trailing-point movement.
A switch can be described by the direction in which the diverging track leaves the straight track. A right-hand switch has track C to the right of a straight track formed by A and B. A left-hand switch has track C to the left.
A straight track is not always present, however both tracks may curve, one to the left and one to the right or both tracks may curve, with differing radii, in the same direction. The operation of a railroad switch
In Figure 2, the red track is the one travelled during a facing-point movement. The switch mechanism, shown in black, may be operated remotely using an electric motor or lever from a nearby ground frame.
A railroad car's wheels are guided along the tracks by coning of the wheels. Only in extreme cases does it rely on the flanges located on the insides of the wheels. When the wheels reach the switch, the wheels are guided along the route determined by which of the two points is
connected to the track facing the switch. In the
illustration, if the left point is connected, the left wheel will be guided along the rail or' that point, and the train will diverge to the right. If the right point is connected, the right wheel' s flange will be guided along the rail of that point, and the train will continue along the straight track. Only one of the
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points may be connected to the facing track at any time; the two points are mechanically locked together to ensure that this is always the case.
A mechanism is provided to move the points from one position to the other (change the points ) . Historically, this would require a lever to be moved by a human operator, and some switches are still controlled in this way? However, most are now operated by a remotely controlled electric motor or by pneumatic or hydraulic actuation.
In a trailing-point movement, the wheels will force the points to the proper position. This is sometimes known as running through the switch. If the points are rigidly connected to the switch control mechanism, the control mechanism's linkages may be bent, requiring repair before the switch is again usable.For this reason, switches are normally set to the proper position before performing a trailing-point movement. Components Points
The points (switch rails or point blades) are the movable rails which guide the wheels towards either the straight or the diverging track. They are tapered on most switches. In the UK and Commonwealth countries, the term point refers to the entire mechanism, whereas in North America the term refers only to the movable rails. Frog
The frog (common crossing) refers to the crossing point of two rails. This can be assembled out of several appropriately cut and bent pieces of rail or can be a single casting.5 A frog forms part of a railroad switch, and is also used in a level junction (flat crossing) .
On lines with heavy and/or high-speed traffic, a swing-nose crossing is often used. 6 As the name implies, there is a second set of points located at the frog. This effectively eliminates the gap in the rail that normally occurs at the frog, so long as trains are moving in the direction that the switch is aligned to. This use of the word \ rails which recalls the frog of a horse's hoof.
Guard rail (check rail)
A guard rail (check rail) is a short piece of rail placed alongside the main (stock) rail opposite the frog. These exist to ensure that the wheels follow the appropriate flange through the frog and that the train does not derail. Generally, there are two of these for each frog, one by each outer rail. Guard rails are not required with a\ the same purpose. These frogs are for low-speed use and are common in rail yards. Switch motor
A switch motor is an electric or pneumatic mechanism that aligns the points with one of the diverging routes. Point lever
A point lever and accompanying linkages are used to align the points of a switch manually. This lever and its accompanying hardware are usually mounted to a pair of long sleepers that extend from the switch at the points. They are often used in a place of a switch motor. In some places, may be operated from a ground frame.
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Joints
Joints are used where the moving points meet the fixed rails of the switch. They allow the points to hinge easily between their positions.
New Words and Expressions Railroad switch 铁路道岔
Diverge 分开；偏离；分歧：分道扬镳 taper (使)一端逐渐变细 Point blades尖轨 Stock rails 基本轨
trailing 拖尾的，曳尾的，被拖动的，蔓延的 passage 通过，经过
lateral 侧面的，从旁边的，至侧面的 execute 处决，执行，实现；使生效 right-hand switch 右开道岔
left-hand switch 左开道岔 ·
radii 半径
Flange (机械等的)凸缘， (火车的)轮缘 ， Illustration n． 插图，图表，图案，例证，实例，·说明，图解，图示 Electric motor 电机
Pneumatic 充气的，由压缩空气操作[推动]的，风动的 Hydraulic adj． 液力的，液压的 Actuation n．刺激，冲动 Trailing direction背向
Linkage n． 连接；结合：联系；联动装置 guardrail(check rail) 护轨
align 使结盟，使成一行，使成一线 Manually adv． 用手地
hinge 用铰链连接(某物)，给(某物)装上铰链 derail 出轨
Regardless Of不管，不顾 So long as只要
Derive from 由??起源 Out Of 由?．”制成 Be used to 过去习惯于 divide into 分成；分为 whether．．。or 或者??或者
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Notes to the Text
1.A railroad switch is a mechanical installation enabling trains to be guided from one track to another．
译文：铁路道岔是一个使火车由一个股道转入另一个股道的连接设备。 ，， “enabling”引导的部分是现在分词作定语，后置，修饰“a mechanical installation\， 如：The farmers working here are very busy．
2.These points can be moved laterally into one of two positions so as to determine whether a train Coming from A will be led towards B or towards C． ·
译文：这两个尖轨能从侧面移动到两个位置中的任何一个，从而确定火车是轨道A驶向 轨道B，还是由轨道A驶向轨道C。
3.A mechanism is provided to move the points from one position to the other(change the points)． Historically，this would require a lever to be moved by a human operator，and some switches are Still controlled in this way．
译文：为使尖轨从一个位置移到另一个位置而设置了一种机械装置。但历史上，则是由人使 用一个操作手柄来移动尖轨，如今仍有一些道岔是采用这种方法。
4.If the points are rigidly connected to the switch control mechanism，the control mechanism's Linkages may be bent，requiting repair before the switch is again usable．
译文：如果尖轨与道岔控制装置紧密地连接在一起，那么控制装置的连接部分会弯曲变形， 在道岔再次使用之前需要维修。
5.The frog(common crossing)refers to the crossing point of two rails．This can be assembled out of Several appropriately cut and bent pieces of rail or can be a single casting．
译文：辙叉(公共主叉部分)是指两轨交叉的部分。辙叉可以由几段经过适当切割和弯曲的 钢轨组装而成，也可以是一个单个的铸件。 “out of'’在这里表示“由??制成”。 如：She made a hat out of bits of old material．她用旧的零碎材料做了一顶帽子。 6.On lines with heavy and／or high-speed traffic，a swingnose crossing is often used． 译文：在重载或者高速运输线路上，经常使用活动心轨道岔。 ，，
“a swingnose crossing是指“The crossing has flexibly moving point and splice rails\。 Exercises to the Text
I Translate the following terms into Chinese．
(1)railroad switch (2)the straight track (3)the diverging track
(4)switch rails or point blades(5)a facing-point movement(6)a trailing-point movement (7)right-hand switch (8)left-hand switch (9)guard rail(checkrail) (10)frog(common crossing)(11)switch motor ，
ⅡDecide whether each of the following statements is true or false according to the text． (1)From the text we know the point blades can be moved laterally into one of two positions so as To determine whether a train coming from A will be led to wards B or towards C． ( )
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(2) A train moving from the A direction towards either B or C is said to be executing a trailing -point movement in Figure 1. ( )
(3) A right-hand switch has track C to the fight of a straight track formed by A and B. ( ) (4) From the text we can conclude that some switches are still require a lever to change the points by a human operator today. ( )
III Answer the following questions according to the text.
( 1 ) What's the function of the joints ?
(2) Where are points lever and its accompanying hardware usually mounted ?
(3) Is the check rail a short piece of rail placed alongside the main rail opposite the frog ? (4) Which does a railroad switch consist of? IV Translate the following passage into Chinese.
Classification
The divergence and length of a switch is determined by the angle of the frog (the point in the
switch where two rails cross) and the curvature of the switch blades. The length and placement of the other components are determined from this using established formulas and standards. This divergence is measured as the number of units of length for a single unit of separation. In North America this is generally referred to as a switch's \one unit apart at a distance of twelve units from the center of the frog. In the United Kingdom points and crossings using chaired bullhead rail would be referred to using a letter and number combination. The letter would define the length (and hence the radius) of the switch blades and the number would define the angle of the crossing (frog) . Thus an A7 turnout would be very short and likely only t0be found in dockyards etc. whereas a El2 would be found as a fairly high speed turnout on a mainline.
Lesson 2 D-C Track Circuits(直流轨道电路)
Introduction
A track circuit is a track clear detection device consisting of an electrical circuit fed through t~ running rails of a section of track. Each section is electrically isolated from o~ers. It is not only u~ to detect the presence or absence of a train on a railroad track, but also used to inform signalmen a~ control relevant signals.
The track circuit is fundamental to most of signaling systems. There are many different arrangements of the track circuit used today, but they are alike in their basic principle of operation. Fundaments of D-C track circuits
The simplest form of track circuit is an insulated section of track with a relay on one end a~ with a battery, or some other source of energy on the other end.
Figure 3 shows an elementary track Circuit. It consists of the following: