Machine room，Well and pit of lift

1Machine roomNormally located on top of well (upper-placed machine room), machine room includes traction machine, diverter pulley, control cabinet, overspeed governor and main power control box.1-1Control cabinetLocated near traction machine, control cabinet serves as a trailing device and signal control center,  Originally, control cabinet included contactor, relay, capacitor, resistor, transformer, and rectifier.  With rapid development of computer and electronics as well as wide application of VVVF control technology, optical fiber communication technology, serial communication and network technology in lift, application of big scale integrated circuit makes control cabinet smaller in size, stronger in function and more reliable in operation.  Currently, control cabinet is composed of computer control panel and frequency inverter, to control AC motor in terms of frequency, voltage and speed (VVVF).Power supply of control cabinet is introduced from the main power supply in machine room. Cable leads from the contactor of control cabinet to the motor terminal of traction machine via conduit.  Derived by conduit or channel, lift control signal line enters well then is transmitted by flat or round traveling cable.  Signal exchange control lines are in well, forming lift control loop. It is required that power line and weak signal be separated to prevent weak signal from being interfered with when wiring is made in control cabinet and machine room.1-2Overspeed governorGovernor is installed on the ground of machine room, at the side of machine2WellComposed of well wall, well top and well bottom, well is always located inside the building as moving space for car and counterweight. It is made of concrete, brick or steel so as to bear mechanical strength.2-1Guide railGuide rail: it is used to guide car and counterweight  in vertical direction and restrict their horizontal displacement.Car and counterweight should have at least two rigid steel rails. Guide rails are always made of cold-rolled T-steel, whose anti-pull strength should  range from  370 N/m2 to 520N/m2.  Following conditions should be taken into consideration when guild rails are  designed.When unevenly-distributed load is imposed  on rail;When safety gear is activating;When loading or unloading is under way;Guide rail strength, especially anti-pull strength should be considered when safety gear is activating, while rail deformation should be considered when uneven load is moving on rail.2-1-1Connections between railsUsually each guide rail is 4m to 5m long. When mounted, guide rails are connected to each other and fixed by wedge and wedge groove on both sides.   Its bottom is fixed by connecting board.  Featuring highly processing precision, wedge and groove serve to connect and fix; strength of joint is guaranteed by connecting board and bolts.  After connection is completed, no continual gap should exist in joint and joints should be smooth, if necessary, polished.2-1-2Rail supportRails are connected with well wall by means of rail support which is usually adjustable to ensure specific distance between rails.  Support capacity of rail is related to the distance between rail supports.  For rail with same specifications, the shorter the distance between rail supports is, the larger the support capacity is.  The distance of rail supports is normally 2.5m, which can be decreased or increased according to actual circumstances; however, bending deflection for rails must not exceed maximum allowed value of 6.3mm.2-1-3Rail clipRail supports are connected with rails by means of rail clip, which is classified into floating and mold-cast types.  Floating type can protect rails from deformation caused by the intrinsic energy of rails, which derives from rail expansion and constriction due to temperature change as well as unavoidable precipitation of building.  After the intrinsic energy overcomes friction of boards, rails can extend vertically to reduce deformation and improve lift installation quality.  Mold-cast type is mainly used to fix sensor vane and final limit switch brackets to avoid their displacement.2-2Guide shoePreventing car from wiggling on traction rope or deviating under uneven load, guide shoe is used to make car and counterweight move along rails. If suspension center of car and counterweight is constant, almost no force is applied on guide shoe.  Since load movement always leads to the change of car center, force produced will be reflected on guide shoe, making guide shoe lines worn out with lift moving upwards and downwards.2-2-1Mounting position of guide shoeCar is equipped with four sets of sliding or rolling guide shoes that are located in the overlapping area of the four angles of car frame and rails; to be specific, two sets are fixed on top transoms, while the remaining on safety gear seat.  Counterweight side is equipped with four sets of guide shoes that are located on both sides of top and bottom transoms.2-2-2Types of guide shoeGuide shoe is classified into three types.：Fixed sliding guide shoeElastic sliding guide shoe.Rolling guide shoe2-3Magnetic-isolating or light-isolating plate (sensor vane)Sensor vane is mounted inside leveling area of each landing in well.  When car reaches a certain leveling area, it will insert a sensor of car top, cutting off magnetic (or light) circuit , giving off signal to control cabinet, stopping lift and opening door.2-4Limit switchTo prevent car from continuing running after reaching top or bottom landings, forcing deceleration switch, limit switch and final limit switch to protect though electrical control.2-4-1Forcing deceleration switchForcing deceleration switches are mounted near top and bottom in well.  If lift does not decelerate in normal deceleration point, upper and lower switch will activate, forcing lift to decelerate.2-4-2Limit switchLimit switch is mounted behind forcing deceleration switch.  If the latter fails, lift run beyond top or bottom leveling position, it will activate, forcing lift to stop.2-4-3Final limit switch (terminal limit switch)As the last electrical protection device, final limit switch is classified into mechanical and electrical types; the former is used in cargo lift, while the latter in passenger lift.3PitAt the bottom of well, pit is a circular part below the bottom landing .  In pit there are rail saddle, buffer for car and counterweight, overspeed governor tension device, compensation sheave and emergency switch box.3-1Rail saddleFor traction lift, there is rail saddle in pit to support rails.3-2Overspeed governor tension sheave.Certain tension is required to drive overspeed governor and prevent it from swinging, producing noise, interfering with other parts, to ensure its good function.3-3Compensation sheave or anti-wavering deviceFor lifts with compensation rope, anti-waver device should be mounted in pit. Anti-waver device is used to limit wavering within a specific range, preventing compensation rope from interfering with other parts.For lift with speed of more than 2.5m/s, compensation sheave should be mounted in pit to tension compensation rope.   It is composed of tension sheave, corresponding rails and electrical safety switch preventing precipitation and jumping.  When lift is in normal operation, compensation rope is in vertical floating state, tension compensation rope, rotating instead of jigging. When lift touches bottom or compensation rope breaks, tension sheave will precipitate along corresponding rail on which safety anti-precipitation switch is equipped.  When tension sheave lowers to a specific position, the travel switch will activate, cutting off safety circuit and stopping lift immediately.When lift runs at speed of 3.5m/s or above, in addition to the above mentioned device, a tension anti-jumping device is also needed.  When compensation rope is stationary or slacks to touch upper or lower travel limit switch, this device will activate, cutting off safety circuit and stopping lift immediately.3-4BufferWhatever type a lift is, buffer is needed to protect car.  As the last safety device, buffer will stop lift in pit by absorbing and exhausting lift energy when lift is out of control. Buffer is located between two rails, below bottom transom of car and counterweight.