Chain jack

Abstract

Chain jack for the tightening of chains, comprising an upper stopper unit (20) and a lower stopper unit (30) with opposite locking pawls where each can be locked to a through-running chain (12) so that they can be detached, and also several drive units (50; 150) to push the upper and lower stopper units (20,30) mutually towards and away from each other, in which the upper and lower stopper units (20,30) each comprises two pairs of locking pawls (20a,20b;22a,22b and 30a,30b;32a,32b, respectively) which engage with mutually adjoining links (12a, 12b, . . . ) in the chain link (12), is described.

1 .- 19 . (canceled) 
     
     
         20 . A chain jack for tightening of a chain, comprising an upper stopper unit and a lower stopper unit with opposite locking pawls, where each locking pawl is detachable locked to a through-running chain, several drive units pushing the upper and lower stopper units mutually towards and away from each other, wherein
 the chain jack comprises four drive units, one in each corner of the chain jack, providing said mutual movement of the upper and lower stopper units, and   the upper and lower stopper units each comprise two pairs of locking pawls, respectively, which engage with mutually adjoining links in the chain link.   
     
     
         21 . The chain jack according to  claim 20 , wherein each pair of the locking pawls in a stopper unit has a mutual angle of 90° to each other to alternately engage with the underside of two adjoining links in the chain during its travel through the jack. 
     
     
         22 . The chain jack according to  claim 20 , wherein four locking pawls in each stopper unit operate in pairs two by two in the same plane against the chain. 
     
     
         23 . The chain jack according to  claim 20 , wherein each locking pawl in a pair of locking pawls provide respective recesses to push and lock against the underside of respective links in the chain. 
     
     
         24 . The chain jack according to  claim 20 , wherein the lower stopper unit is secured to a foundation, such as a deck of a ship or a platform. 
     
     
         25 . The chain jack according to  claim 20 , wherein the upper stopper unit with its locking pawls are anchored to a top part of the drive units, that is made up of several hydraulic cylinders, and which provide said mutual movement of the upper and lower stopper units. 
     
     
         26 . The chain jack according to  claim 25 , wherein the hydraulic cylinders of the upper stopper unit rest on a seat in a plinth plate of the lower stopper unit. 
     
     
         27 . The chain jack according to the  claim 26 , wherein the upper stopper unit with the hydraulic cylinders are anchored detachably to the plinth plate of the lower stopper unit. 
     
     
         28 . The chain jack according to  claim 20 , wherein two pairs of load cells for continuous monitoring of the tension in the chain are fitted below the lower stopper unit, providing two individual pairs of load cells with full redundancy, with one set in reserve if the other fails. 
     
     
         29 . The chain jack according to  claim 25 , wherein chain tension is calculated according to oil pressure in the hydraulic cylinders. 
     
     
         30 . The chain jack according to  claim 20 , wherein each drive unit to mutually push the upper and lower stopper units towards and away from each other comprises a threaded strut that is driven by an individual electro-motor, and the lower stopper unit is stationary in a frame section while the upper stopper unit is movably upwards or downwards with respective threaded struts when these are rotated by the respective electro-motors. 
     
     
         31 . The chain jack according to  claim 30 , wherein the upper stopper unit is guided upwards and downwards in longitudinally running steering and guiding grooves in the frame section and is screwed upwards and downwards by the threaded struts. 
     
     
         32 . The chain jack according to  claim 30 , wherein a top part and a plinth plate of the frame section define a centrally cross-formed through-run (+) for the chain. 
     
     
         33 . The chain jack according to  claim 30 , wherein each locking pawl is pushed inwards and pulled back with the help of associated electrical actuators, such as linear actuators that function in analogue with hydraulic motors. 
     
     
         34 . The chain jack according to  claim 30 , wherein each threaded strut is coupled to respective electro-motors via an associated planet gear fitted under the electro-motor, and is coupled between the exit shaft from the above-lying electro-motor and the threaded strut from the underside, and wherein the planet gears are adjusting torque moment and revolutions of the motor to what the threaded strut requires. 
     
     
         35 . The chain jack according to  claim 30 , wherein four electro-motors are placed in the top part of the drive units, preferably in each corner of a top part of the frame section to drive the associated four threaded struts that provide said mutual movements of the upper and lower stopper units. 
     
     
         36 . The chain jack according to  claim 20 , wherein each drive unit is a hydraulic pressure cylinder which provide said mutual movements of the upper and lower stopper units. 
     
     
         37 . The chain jack according to  claim 20 , wherein each drive unit is an electrically driven threaded struts which provide said mutual movements of the upper and lower stopper units.