The cab of a boarding bridge for accessing aircraft and ships, which is the part of the machine directly connecting with the aircraft or ship, is attached to the round structure at the central points of the same, both on its upper side (roof) and lower side (floor). This round structure has a circular shape acting as a guide, which aids the cabin to follow said shape during its rotational movement around the aforementioned central points.
Said rotational movement is possible thanks to a system of independent rollers, which are joined to the cab and rest on the circular structure of the floor of the round structure, easing the movement of the cab around it.
Finally, the activation of the described system may be carried out by electrical, mechanical or hydraulic means, being possible to provide the cab with an angular speed following the circular shape of the round structure.
One of the most severe problems which may occur in the described system, may arise if there is a failure in the activating system, in which case, the cab would be completely loose, rotating uncontrollably and being possible for it to impact the fuselage of an aircraft or ship in the vicinity of the cab, or even injuring the operator and users that might be on the boarding bridge in that moment.
There are currently no known systems capable of avoiding this drawback, although the are actuations focused on increasing security in case of breakdown of the actuating means, for example, oversizing those elements susceptible of failure.
Although it is true that these systems reduce the risk of accident, they cannot solve the described problem, as well as a deficient maintenance of the system may reduce considerably or even eliminate the increased security introduced by said designs.
Other designs are known, which being capable of detecting failures of the activating system, use a commercial electromagnetic brake, which coupled to the cab, tries to stop the uncontrolled rotation of the same in case of failure, activating two brake linings of a material made of a ceramic material on the circular rail, acting as a guide in the floor of the round structure. However, this system presents severe drawbacks, as the brake must be of large size, along with the increase of weight and difficult assembly it entails. Furthermore, severe fitting problems with the brake linings have been detected, which requires considerable maintenance as well as an exhaustive control of the system to assure its proper operation, including continuous cleaning of the sliding rail of the brake linings.
It has been shown that the operation of the cabin itself hinders the action of the brake linings as grease is deposited on the rail on which these have to act, decreasing considerably their efficiency, even not being capable of braking the cab.