fig1 is a partially sectional plan view of a principal portion of a chain according to the present invention and fig2 is an enlarged sectional view of the principal portion shown in fig1 . a roller chain 10 with seal is provided with a pair of inner plates 12 , 12 into which are press - fitted both ends of a bushing 15 and a pair of outer plates 13 , 13 through which are inserted both end portions of a connection pin 11 , the connection pin 11 being inserted rotatably through the bushing 15 . both end faces 11a , 11a of the connection pin 11 are caulked to form expanded portions so as to prevent dislodgment of the outer plates 13 , 13 from the connection pin . between the paired inner plates 12 , 12 , a roller 16 is rotatably fitted on the outer periphery of the bushing 15 . an elastic seal 14 is held on each outer plate 13 , which is opposed to the associated inner plate on the connection pin 11 , so as to cover the outer plate . an annular sealing projection 14a is formed on an opposed surface 13a of the outer plate 13 opposed to the inner plate . the annular sealing projection 14a is abutted against an opposed surface 12a of the inner plate 12 opposed to the outer plate in a surrounding relation to the connection pin 11 . the annular sealing projection 14a functions to prevent a lubricant such as grease or lubricating oil sealed between the outer peripheral surface of the connection pin 11 and the inner peripheral surface of the bushing 15 from leaking out from between the opposed surfaces of the inner plate 12 and the outer plate 13 and also functions to prevent a foreign matter such as dust from getting in between the outer peripheral surface of the connection pin and the inner peripheral surface of the bushing through the opposed surfaces . as is seen from fig2 the elastic seal 14 is held on the outer plate 13 so as to cover the outer plate . more specifically , the elastic seal 14 covers the opposed surface 13a of the outer plate 13 and further covers an outside surface 13b of the outer plate beyond the peripheral edge of the outer plate . therefore , even in the event of peeling of the opposed surface 13a of the outer plate and the elastic seal 14 from each other , the elastic seal does not fall off the outer plate 13 but keeps a predetermined sealing position thereof . there are various plate covering forms of the elastic seal , typical of which are shown in fig3 to 6 with respect to the outer plate . however , these are also true of the inner plate and no limitation is made to the illustrated examples . in fig3 ( a ) and 3 ( b ), the elastic seal 14 is held so as to cover the whole surface of the outer plate 13 whose peripheral edge contour is indicated with a dotted line . in the same fig3 ( a ) and 3 ( b ) are enlarged views of the opposed surface 13a and the outside surface 13b , respectively . in fig4 the elastic seal 14 is held on the outer plate 13 by forming a folded - back portion 14b on the outside surface 13b of the outer plate along the peripheral edge of the same plate . the opposed surface 13a of the outer plate 13 is the same as in fig3 ( a ). fig5 is a sectional side view of the outer plate 13 , in which the elastic seal 14 does not have a peripheral edge folded - back portion on the outside surface 13b of the outer plate , but it is held by covering the peripheral edge of the outer plate . further , in fig6 independent elastic seals 14 are held on the opposed surface 13a of the outer plate so as to cover the surrounding portions of connection pins respectively . the annular sealing projection 14a may be a double ring projection for enhancing the sealability . further , the projecting end of the annular sealing projection 14a may be abutted against an end face of the bushing 15 , or it may be abutted directly against the opposed surface 12a of the inner plate , whereby the space between the outer periphery of the connection pin and the inner peripheral surface of the annular sealing projection is increased and hence the amount of the lubricant held between the connection pin and the bushing is increased . referring now to fig7 there is illustrated another embodiment of the present invention , in which an elastic seal 14 is held so as to cover the whole surface of each inner plate 12 , an annular sealing projection 14a is formed on the elastic seal 14 on the side of an opposed surface 12a of the inner plate opposed to an outer plate 13 , the annular sealing projection 14a being abutted against an opposed surface 13a of the outer plate 13 opposed to the inner plate 12 , and a buffer projection 14c for preventing the generation of a collision noise between a roller 16 and the inner plate caused by axial free play of the roller 16 is formed on the elastic seal 14 on the side of an inside surface 12b of the inner plate 12 , the roller 16 being rotatably fitted on a bushing 15 . since an elastic seal having an annular sealing projection is held on one of inner and outer plates of the chain so as to cover the one plate , the elastic seal does not fall off the plate and can keep a predetermined position thereof even in a bending motion of the chain . thus , there is no fear of damage or destruction of the elastic seal caused by peristaltic movements of the seal and hence the sealability of the seal is not deteriorated . besides , the resistance at the time of bending of the chain caused by peristaltic movements of the elastic seal is removed and therefore it is possible to improve the transmission efficiency . moreover , when the inner plate is covered with the elastic seal , it is possible to form a buffer projection on the inside surface of the inner plate to buffer the collision of a roller with the inner plate caused by an axial free play of the roller , whereby not only the elastic seal is prevented from falling off the plate but also the collision of an end face of the roller with the inside surface of the inner plate is prevented and hence it is possible to prevent the generation of noise based on such collision . further , since the plate peripheral edge is covered with the elastic seal , the generation of collision noise between the plate and a chain guide rail is prevented when the chain is used as a conveyance chain . besides , the wear of the plate caused by a sliding contact of the plate with the guide rail can be prevented .