Swim fin

Abstract

A swim fin that changes down kick force is revealed. The swim fin worn over the foot to aid movement through the water includes a footpocket and a flat fin blade. The flat fin blade extends from the front part of the footpocket and has an upper blade surface and a lower blade surface. At least one blade surface is disposed with two fin ribs arranged symmetrically. By being embedded with heavy objects inside the fin rib, the weight of the swim fin is increased so as to increase the force of the swim fin acted on the water by kicking. This favors down kick of legs and the propelling force of kick is increased so that the user is allowed to move faster in the water with the swim fin.

1 . A swim fin comprising:
 a footpocket worn over feet of users; and   a flat fin blade extending from front part of the footpocket and having an upper blade surface as well as a lower blade surface while at least one blade surface is disposed with two fin ribs arranged symmetrically and the two fin ribs are mounted with slots for loading heavy objects;   wherein when the slot on the fin rib of the blade surface is loaded with heavy objects, weight of the swim fin is increased so as to increase kick down force of the swim fin.   
   
   
       2 . The device as claimed in  claim 1 , wherein two fin ribs are arranged correspondingly on left and right sides of the upper blade surface and the lower blade surface of the flat fin blade. 
   
   
       3 . The device as claimed in  claim 1 , wherein the heavy object is lead block. 
   
   
       4 . The device as claimed in  claim 1 , wherein the heavy objects include a plurality of blocks with certain weight and a certain number of the blocks are put into the slot of the fin rib. 
   
   
       5 . The device as claimed in  claim 1 , wherein the heavy object is integrated into the fin rib. 
   
   
       6 . The device as claimed in  claim 1 , wherein the footpocket is a single footpocket for both feet so as to form a mono-fin type swim fin. 
   
   
       7 . The device as claimed in  claim 1 , wherein the footpocket is a footpocket for each foot so as to form a bio-fin type swim fin. 
   
   
       8 . The device as claimed in  claim 1 , wherein a tail line is disposed on a front end of the lower blade surface and a plurality of cutting lines with intervals is disposed on the lower blade surface, corresponding to the tail line. 
   
   
       9 . The device as claimed in  claim 8 , wherein the cutting line on the lower blade surface is a structure with a step height. 
   
   
       10 . The device as claimed in  claim 8 , wherein the structure with the step height of the cutting line on the lower blade surface is a steplike or slot-like structure. 
   
   
       11 . The device as claimed in  claim 8 , wherein the cutting line on the lower blade surface is streamlined that looks like a tail fluke of whales. 
   
   
       12 . The device as claimed in  claim 8 , wherein the plurality of cutting lines are arranged apart at an equal distance. 
   
   
       13 . The device as claimed in  claim 8 , wherein the plurality of cutting lines are spaced at an unequal distance.