the present invention is now described in its embodiments referring to the accompanying fig1 through 12 . it should be appreciated to note here that in these figs ., the same numbers and symbols are used for members equivalent with those used in the conventional bicycle front derailleur . referring now to fig1 through 3 , there is illustrated an embodiment of the present invention . in this embodiment , a bicycle front derailleur 31 is configured in the same way as a conventional bicycle front derailleur , with a base member 4 fixed near a hanger rack at a lower portion of a seat pipe 2 by a mounting band 3 . this base member 4 is linked , via a shift link mechanism 5 comprising a pantograph mechanism 5a , to a movable member 6 . the pantograph mechanism 5a is formed by pivotally connecting the base member 4 to respective upper ends of inner and outer link members 15 , 16 with respective pins 17 , 18 , while connecting respective lower ends of the inner and outer link members 15 , 16 to the movable member 6 with respective pins 19 , 20 . the pins 17 , 18 which connect the base member 4 to the inner and outer link members 15 , 16 , and the pins 19 , 20 which connect the movable member 6 to the inner and outer link members 15 , 16 represent vertices of the parallelogram . thus , when the inner and outer link members 15 , 16 are pivoted against the base member 4 , the movable member 6 is moved laterally of a bicycle while the movable member &# 39 ; s orientation is kept unchanged . this parallelogram pantograph mechanism 5a is constantly urged by a coil spring 21 mounted around the pin 19 which connects the inner link member 15 to the movable member 6 so that the movable member 6 has a tendency to move inward laterally of the bicycle ( the direction indicated by the arrow q .) above the outer link member 16 , there is extended an operating arm 22 which is connected to an inner wire t1 of a control cable t , while an outer sheath t2 of the control cable t is fixed to the base member 4 . to perform speed shift operation , the inner cable t1 is pulled against the outer sheath t2 . the movable member 6 includes inner and outer guide plates 7 , 8 opposed to each other with a predetermined spacing and generally in parallel to a sprocket ( not shown ). the movable member according to the present embodiment is made of a thin plate by punching and pressing methods , and as shown in fig1 through 3 , is formed integrally with the inner and outer guide plates 7 , 8 . the movable member 6 according to the present embodiment has a connecting portion 23 at its upper portion that lies over the inner and outer guide plates 7 , 8 . this connecting portion 23 is formed with a pair of upright linking portions 24 made by a bending method for connecting to the outer link member 16 , one of the pair being formed at a front end of the connecting portion 23 , and the other of the pair being formed at a rear end thereof . there is another linking portion 25 formed integrally with the inner guide plate 7 by bending a portion of the inner guide plate inward laterally of the bicycle . the pins 19 , 20 are respectively inserted through the linking portions 24 , 25 to connect the movable member 6 to the inner and outer link member 15 , 16 . the movable member 6 according to the present embodiment which includes the inner and outer guide plates 7 , 8 has a chain entering edge 14 which includes portions left as punched , where catch preventive means 26a , 26b are provided for the chain c not to be caught by the chain entering edge 14 . the catch preventive means 26a , 26b according to the present embodiment are formed , as shown in fig1 through 3 , by offsetting the chain entering edge 14 of the movable member away from a guide space a through which the chain runs . more specifically , upper portions of respective chain entering edges of the inner and outer guide plates 7 , 8 are bent away from the guide space a : the upper portion of the chain entering edge of the inner guide plate 7 is bent inward laterally of the bicycle whereas the upper portion of the chain entering edge of the outer guide plate 8 is bent outward laterally thereof . the provision of the catch preventive means 26a , 26b has avoids a situation such as shown by phantom lines in fig3 wherein the chain c is caught by the chain entering edge 14 of the inner and outer guide plates 7 , 8 when the chain c is wildly oscillated vertically during a rugged downhill riding to hit or contact the chain entering edge 14 of the movable member 6 . this also avoids a situation where the chain c is driven with part of the chain c stuck in the front derailleur 31 , and thus , eliminates risk of damage to the front derailleur 31 , resulting in highly improved safety of a bicycle in downhill riding for instance . another advantage of this particular catch preventive means 26a , 26b is that it includes a slanted face 9a located adjacent to the chain entering edge and inclined toward the guide space a through which the chain c runs . this slanted face 9a guides the chain c back to the guide space a even if the chain c hits the inner or outer guide plates 7 , 8 or an upper portion of the movable member 6 . in other words the slanted face 9a also protects the chain c from hitting or contacting the chain entering edge 14 and from being damaged . fig4 through 9 show modifications of the catch preventive means 26 according to the present invention . fig4 through 6 shows cross - sectional views of the catch preventive means 26 provided on the inner guide plate 7 whereas fig7 through 9 show cross - sectional views of the catch preventive means 26 provided on the outer guide plate 8 . each of the views corresponds to the cross section shown in fig3 . catch preventive means 26c , 26d shown respectively in fig4 and 7 are provided by forming chamfered portions 27 to make slanted faces 9a on the chain entering edges of the inner and outer guide plates 7 , 8 . preferably , these chamfered portions 27 should be made by removing at least a half of a thickness of the respective guide plates . the provision of the chamfered portions 27 has practically the same effect as offsetting of the chain entering edge away from the guide space a . thus , the provision of the catch preventive means 26c , 26d avoids the situation wherein the chain c is caught by the chain entering edge 14 of the inner and outer guide plates 7 , 8 when the chain c is wildly oscillated vertically during a rugged downhill riding to hit or contact the chain entering edge 14 of the inner and outer guide plates 7 , 8 . catch preventive means 26e , 26f shown respectively in fig5 and 8 are provided by forming projections 28 to prevent the chain c from contacting or hitting the chain entering edge 14 of the inner and outer guide plates 7 , 8 . as shown in fig5 and 8 , the projections 28 have an arcuate shape so that they do not catch the chain c . the provision of the projections 28 has practically narrowed the guide space a . thus , the provision of the catch preventive means 26e , 26f prevents the chain c from contacting or hitting the chain entering edge 14 even if the chain c contacts or hits the inside face of the guide plates 7 , 8 . hence the chain c is effectively protected from being caught by the chain entering edge 14 . catch preventive means 26g , 26h shown respectively in fig6 and 9 are provided by forming stepped portions with transitive slant faces 9a to the guide space a . the provision of the catch preventive means 26g , 26h prevents the chain c from contacting or hitting the chain entering edge 14 with substantially the same function as achieved in the first embodiment described hereinabove . fig1 through 12 show another embodiment of the present invention . in this embodiment , the catch preventive means 26 is provided not only on both of the guide plates 7 , 8 but also on the connecting portion 23 which connects the inner and outer guide plates 7 , 8 opposingly at a predetermined spacing . as shown in fig1 through 12 , the movable member 6a according to this embodiment includes a generally u shaped connecting member 30 which has linking portions 24 integrally formed therewith for connecting to the outer link member 16 . this connecting member 30 is made separately from the inner and outer guide plates 7 , 8 , and is welded to the connecting portion 23 which connects the inner and outer guide plates 7 , 8 in a bridge - like manner . respective portions of the chain entering edge 14 of the inner and outer guide plate 7 , 8 and the connecting portion 23 is bent away from the guide space a to form a catch preventive means 26i . the provision of the catch preventive means 26i avoids a situation wherein the chain c is caught by the chain entering edge 14 of the inner and outer guide plates 7 , 8 when the chain c is wildly oscillated vertically to hit or contact the chain entering edge 14 of the movable member 6 . the provision of the catch preventive means 26i also eliminates a situation in which the chain c is driven with part of the chain c stuck in the front derailleur 31 , and thus , eliminates risk of damage to the front derailleur 31 , with highly improved riding safety . further , since the catch preventive means 26i is also provided on the chain entering edge 14 of the connecting portion 23 which locates above the chain c , it is now possible to guide the chain c back to its normal running position even if the chain c contacts or hits the connecting portion 23 , preventing effectively a case where the chain c is caught or damaged by the edge of the connecting portion 23 . the present invention being thus described , it is obvious that the same may be varied in many other ways , and the scope of the present invention should not be limited or confined to those described in the embodiments hereinabove . for instance , the catch preventive means 26a , 26b provided respectively on the opposed inner and outer guide plates 7 , 8 in the embodiment shown in fig1 through 3 may not always be provided in a pair , but instead , one of the inner and outer guide plates may be provided with the catch preventive means 26 as required . likewise , in the embodiment shown in fig1 through 12 , the inner and outer guide plate 7 , 8 and the connecting portion 23 which connects the inner and outer guide plate 7 , 8 are provided with the catch preventive means 26i extending continuously over their edges , but this catch preventive means may not be continuous and may be provided partially to cover portions of their edges . still further , the cross - sectional shape of the catch preventive means 26 shown in fig1 through 13 is not limited to those described in the embodiments , but other shapes of the catch preventive means such as the ones shown in fig4 through 9 may of course be used . the embodiments uses a pantograph link mechanism for the shift link mechanism 5 , but the present invention is also applicable to bicycle front derailleurs which use different types of the shift link mechanism .