Lifiting and Unloading of Machine Tools

Lifiting and Unloading of Machine Tools

Lifiting and Unloading of Machine Tools -Assume that a lorry with a machine tool stands at the door of factory.

Rope Blocks

Weston Block

Worm Block

The machine tool is to be lifted vertically and then is to be transported to the site of foundation. The general purpose medium employed for obtaining the vertical movement of a suspended load is the pulley block.

For the light loads a set of rope blocks is adequate. Medium loads up to about 1 ton may be lifted with a set of differential chain blocks.

For heavier loads (1-5.tons) a more robust unit employing a worm and wheel should be employed.

If the use of blocks is likely to occur often, motor driven units may be installed.

For the suspension of loads and in some cases of the blocks, an assortment of slings will be necessary. These may be of rope or chain mace up in various lengths from about 1.5 meter upwards. Chain slings may have a ring at each end, or a ring at one end and a hook at the other.

Collar Sling

Double Sling

Endiess Sling

There should be a girder from which the pulley blocks may be suspended for raising the load. A cantilever beam projecting from the building wall will serve the same purpose.

Girder Across Opening

Built Out Cantilever

If a beam is not available and a lift is the only means of dealing with the situation, some form of transportable equipment must be employed. Examples of such are

(a) The gantry
(b) The derrick and
(c) The J-legs (shear legs).

(i) The gantry consists of a steel frame surmounted by a supporting beam. The lifting tackle is suspended from the beam and used to hoist the load.

(b) The derrick consists of a thick, stiff post held up with guy ropes. When the derrick is erected its foot should be sunk into the ground the prevent slipping and it is held in a slightly sloping position by guy ropes. Before the pole is erected, unless a ladder is available, the block for lifting the load should be attached.

Gantry

Derrick

Shear Legs

This may be effected by wrapping a chain sling round the derrick and slipping the chain through the end ring so that load on the free end tends to tighten the grip round the pole. The derrick is useful when there is plenty of headroom and space round about.

(c) When the (soft) floor condition or the space available prohibits the employment of a derrick, a set of 3-legs may be erected. To take the weight of the machine tool, it must be slung by slings. The slings should support the load through portions of the machine well able to withstand the weight and the arrangement should be such that the line of pull will pass approximately through the centre of gravity of the body to prevent tilting.

At the same time the points of application of the support should be well spaced apart towards the machine extremities also to avoid slipping. Thick sacking is advisable between the sling and the point where it may contact sharp comers on the load. This protects a rope sling against cutting and the machine surface from abrasion by a chain sling.

A ramp can be used to unload machine tools from a relatively low vehicle. The ramp should be secured at its ends against slipping. If the ramp is steep, a rope round the machine attached through a set of rope blocks to some fixed point enables it to be lowered gently and. is a safeguard against its getting out of control.

Pinch bars are used to obtain small lifts of machines for the purpose of inserting rollers and packings under them. Pinch bars are used for propelling the machine along with or rollers. When held up on a pinch bar a machine may be given a small horizontal movement by oscillating the end of the bar side ways.

Use of Pinch Bars

Pinch bars are used for propelling the machine along with OD rollers. When held up on a pinch bar a machine may be given a Pinch bars are made from medium carbon steel about 1 meter to 1.25 meter long, 25 mm to 30 mm diameter or square, forged to an edge at one end and set to an angle. Thin steel wedges are useful for driving under the edges of a machine base to obtain a slight initial lift for the insertion of the end of a pinch bar.

When moving over uneven ground, up slopes etc., steel or wood skids may assist in reducing friction. Lifting jacks are valuable when lifts of more than a few centimeters are necessary and when conditions do not allow of any other form of lifting. A good jack may lift upto 200 tons with about 18 cm of lift.

Where the transportation of machines is likely to occur frequently a flush top, low loading platform track is a very useful piece of equipment. The machine may be raised on pulley blocks and placed on the truck or raised on jacks and the truck inserted underneath. Some trucks permit one end to be lowered to the floor so that the machine may be barred on to the platform.