Problem statement:   A mechanical claw ...operable by a piston ....hydraullic 
                     or [and] pully (ordinary brake found in bicycle or two wheelers]

opportunity:  kind of means to clamp or hold objects or lock into a kind of socket
              or hole or ring.

Loose frame work of Design specifications:

              
              a) claws work much similar to the scissor though different in shape
                 and purpose of usage

              b) Deriving from how some rench's used to operate municipal
                 water flow regulators ...kind of a instruments used to measure the
                 guage viz. width

              c) ability to open and close [the opening or mouth]  the claws
                 viz. operate mechanically using a combination of both hydraulic means 
                 and a pully ...say ideally hydraulic means to open the claws ...pully to
                 close the claws or force them to be fastened or closed.

              d) binding the claws with suspension coil that keeps them fastened 
                 ...making it difficult or requiring induction of mechanical forces to
                  open or release the claws ...viz. use of a piston operably by hydraulic
                  or pully to achieve the objective.

              e) A hallow expandable and compressable shaft or pipe (say on the lines of
                 zoom in camera or telescope) ...through which a cable can pass ....assuming
                 the last most shaft or pipe is semi or half cut ... thus a sigma shaped end
                 of the cable passing through the shaft that can plug-in of suspend on to a
                 'i' shaped end locked or sealed atop by a semi or half of the pipe the last
                 of the one's in the expandable shafts or into a apperture (say sensor operated)
                 that globs the cable-end as soon as the cable is inserted.
              

example Usages : ability to attach the engine to a wagon ...railways
                 ability to attach the coach(or car) to another coach(car) ...railways
             

Note: The above problem statement having been encountered in various scenarios
      and detailed in various 'Proof of concepts' as mentioned in 
      
       http://uk.geocities.com/ravivenkatus/projects.pdf
       http://ravishankarkv.tripod.com/projects.pdf
        ....apply appropriate
      'use-case' modeling, rationalize and arrive at a workable and feasible 
       solution both commercially and techinically viable.