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Telescoping Bridge Cranes

In some manufacturing situations, the project engineer will find that a bridge crane is the right solution for a material-handling problem, except that at one position in the layout, the bridge (the moving rail in a bridge-and-runway crane) has to reach out to a neighbouring zone and then be withdrawn. 

Using a Telescoping Monorail

In this example, the bridge of the crane “telescopes” out beyond the rest of the crane to reach a point in a robot cell. However, the bridge has to be withdrawn from the robot cell to avoid a collision when the robot starts working. In this case, there is no runway; the arrangement is then called a telescoping monorail

A worker using a telescoping monorail with a bridge crane

Addressing Material Handling Challenges with Telescoping Bridge Cranes 

There are various reasons to arrange a bridge to reach out into an area and then withdraw. Some examples include:  

  • Another crane may need to pass through the same space 
  • A transfer may pass by 
  • A manufacturer may have food-grade bins that open only when there is no hoist above
  • And more.

In the below example, a “ski-bar” activates a limit switch which verifies that the telescoping bridge crane has actually been withdrawn from the robot cell, enabling the robot to begin work.   

A ski bar on a telescoping bridge crane

Engineering Challenges in Designing Telescoping Bridge Cranes 

Supporting the Telescoping Bridge 

One of the challenges to the designer is to ensure that the trolleys supporting the telescoping bridge are not overloaded by the cantilevered load.  Here we can see that the leading trolley experiences an exaggerated load, far exceeding the load on the hoist, while the trailing trolley experiences an upward loading.  Not all trolleys are designed for upward loads, however, G-Rail trolleys are designed to be ready to take both downward and upward loads. Also, the header (or the runway, in the more usual case) has to take an unusually large load.    

Illustration of trolleys supporting a telescoping bridge crane

Managing Softstop Impacts 

Another factor that has to be taken into consideration is the constant bumping of the telescoping bridge against the stops (“softstops”) of the bridge.  No matter how careful the operator is, in any fast-paced production environment, the telescoping bridge slams into the softstops routinely.  If the softstop is made of a durable, harder material, then the impact will transfer to the bridge, and then to the runways or to the frame. It is best that a softer material, or hydraulic shock absorbers, be used.   

The Telescoping Bridge Crane in Action

Mixing Machines with Dual Direction Extension 

In the following photo, a telescoping bridge can actually extend in both directions, reaching out into 2 zones.  A brake keeps the telescoping bridge centered in normal use.  In this case, mixing machines had to enter the zones on either side of the crane, bringing about the need for the bridge to reach out and then withdraw.   

A dual direction extension on a telescoping bridge crane

I-Beam Telescoping and Frame Integration

In this sketch, G-Rail enclosed-track is not actually used; instead 2 I-beams are arranged to telescope out together and then withdraw. The frame of the crane becomes the runways.   

Illustration of l-beams arranged to telescope

G-Rail Telescoping Bridge and KBK Bridge Cranes

In this application, a G-Rail telescoping bridge is supported by two trolleys riding on a KBK bridge crane.  The G-Rail bridge has to withdraw out of an area where a transfer will pass by.  

A G-Rail telescoping bridge crane riding on a KBK bridge crane
A bridge crane using a telescoping bridge

Designing Telescoping Bridge Cranes for your Operation

Find out more about how a telescoping bridge crane could benefit your operation. Our engineers will help by designing a customized solution tailored to your needs.