HYDRAULIC LIFTS - FLUID DEVICE

MECHANICAL TIPS AND STUDY MATERIAL
Hydraulic lift

It is a hydraulic device which is capable or transporting goods or passenger through small distance or from one floor to another in a building. These are mainly of two types



  • Direct acting hydraulic lift
  • Suspended hydraulic lifts

Direct acting lifts



It is very simple in construction. It consists of a vertical hollow cylinder. A ram which can slide is fitted inside the cylinder. The ram has a cage fitted on its top end. This cage is nothing but the platform on which goods can be placed or people can stand. A liquid under pressure can be forced form bottom which strikes the ram. As such the ram moves in upward direction and reaches the desired height. If the cage is to be moved in downward direction, the liquid under pressure is allowed to move out of cylinder. This allows the ram to move down and hence cage comes down.




  • Suspended hydraulic lift

It is has slight alterations but the principle of working is similar to direct acting hydraulic lift. As shown in figure, it has cage suspended by the wire or rope. As discussed earlier, cage is the platform on  which people stand or goods are kept.

There are two pulley blocks ( fixed and movable ) out of which ram is connected to movable block. A wire or rope connects the pulley, passes over guide pulley to the cage.

Operation

When liquid under high pressure is injected into the cylinder, it strikes the ram and it is forced to move left. The movable pulley connected to it also moves left side. This increases tension in the wire and the cage is lifted upwards to desired height. When it is to be lowered, the pressurized liquid is forced out of cylinder and ram along with the pulley move right and the tension in strings is reduced. Hence the cage comes downwards.
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