NEGRINI S.r.l, an Italian manufacturer of a comprehensive range of grabs and buckets for rope machines and crawler mounted cranes, unveiled recently one of its latest innovations, the electro-hydraulic clamshell grab.
NEGRINI, active in the market since 1967, supports their clients by analyzing the job that needs to be done and, if needed, adjusts the standard design of grabs and buckets to enhance their performance for the specific operation.
The company has just released a special study for the electro-hydraulic clamshell grab, analyzing in detail the main product features.
According to the study, the traditional construction of the clamshell includes 90° welded plates; in this case the material pastes easily on the walls, the insertion of a profiled plate inclined at 45° greatly strengthens the structure and creates two 45° corners facilitating the sliding of the material.
The bucket may also be provided with valves of different shape, “standard” valves, valve with opening windows to reduce load capacity, “Anti-dust” or “Containing” valves to reduce the loss of material.
It is possible to apply metal or rubber roofings to reduce loss of dust, protecting the environment. Change of the bucket’s characteristics is also possible by replacing the valves, mounting large valves for moving light materials, or smaller (but heavy and robust) valves for hard and compact materials.
The timing of the valves is obtained via innovative hydraulics, which does not use teeth or rods eliminating wear, breakage and maintenance. This is obtained by the equal oil distribution to jacks through a innovative hydraulic circuit; the jacks receive the same amount of oil on both opening and closing, obtaining a correct movement of the valves without using mechanical parts.
Further, the company outlines that all jacks have a retarding device to prevent the collision between the “end-run” lines during valve opening. Pistons are protected from shocks, hydraulic hoses are wired inside the structure. The total protection of pistons and hydraulic hoses prevents accidents such as the bucket exiting from the ship hold.
Also interesting to note is that the hydraulic unit is independent and can be easily removed, tested or controlled comfortably “on the ground” in one-hour time, without unplugging electrical or mechanical parts but only 4 hydraulic couplings to the bucket.
The buckets can be fitted with standard hydraulic units (with solenoid valves) or with reverse motor, in the latter type the opening and closing of the bucket will be controlled by the reverse rotation of the motor.