SIDE ROLLER AND CHAIN WITH SIDE ROLLER BACKGROUND OF THE INVENTION 5 The present invention relates to side rollers that are attached to side sections of an object such as a chain and roll to move the object and to a chain with side rollers including the aforementioned side rollers arranged on side sections of the chain. 10 Conventionally, one such type of chain with side rollers is configured with side rollers that are rotationally attached, with bearings, to roller shafts each covered with a sleeve (see, for example, Japanese Laid-Open Patent Publication No. 15 2014-12596) . The roller shafts are formed integrally with coupling pins of the chain and project outward from outer links. Each side roller is shaped as a cylinder having a closed distal end. In the chain with the side rollers, the basal end surface of each side roller and the outer surface of 20 the outer link are held in slidable contact with each other. A sealing structure is located between the inner circumferential surface of each side roller and the outer circumferential surface of the corresponding sleeve to restrain external foreign matter such as dirt, dust, or rain 25 water from entering the bearing of the side roller through the clearance between the side roller and the outer link. The sealing structure includes two non-contact type labyrinth seals, which are spaced apart in the axial direction 30 of the roller shaft, and a grease seal portion, which is arranged between the two labyrinth seals. The grease seal portion is configured by grease seal layers and felt seal layers, which are arranged alternately in the axial direction. The labyrinth seals provide complicated curves in an entry 35 path of foreign matter to increase the distance of the entry 1 path, thus hampering entry of foreign matter. In the above-described sealing structure, the labyrinth seals are not aimed to block foreign matter. Further, when 5 the chain with side rollers is in operation, the felt seal layers of the grease seal portion slide on the outer circumferential surface of the sleeve. This is likely to form a space between the felt seal layers and the sleeve. As a result, there is a room for improvement with regard to 10 restraint of entry of external foreign matter into the bearing of the side roller. SUMMARY OF THE INVENTION 15 Accordingly, it is an objective of the invention to provide a side roller and a chain with side rollers capable of effectively restraining entry of external foreign matter into a rolling-element bearing. 20 Means for achieving the above objective and advantages thereof will now be discussed. To achieve the foregoing objective and in accordance with one aspect of the present invention, a side roller is provided 25 that includes a roller member, which is rotationally supported, with a rolling-element bearing, by a shaft member projecting from a side section of a movable body. The roller member rolls as the movable body moves. A sealing chamber is formed at a position that is between the roller member and the shaft 30 member and closer to the movable body than the rolling-element bearing is to the movable body. A plurality of first sealing members for sealing, with elastic force, a gap between the roller member and the shaft member are located in the sealing chamber and arranged to be adjacent to one another in an axial 35 direction of the shaft member. The sealing chamber is filled 2 with a first lubricant. In this configuration, the first sealing members are arranged in the sealing chamber. The sealing chamber located 5 between the roller member and the shaft member and is formed at a position closer to the movable body than the rolling chamber is to the movable body. The first sealing members thus seal, with elastic force, the gap between the roller member and the shaft member. This effectively restrains 10 foreign external matter from entering the rolling-element bearing from a side corresponding to the movable body. BRIEF DESCRIPTION OF THE DRAWINGS 15 Fig. 1 is a plan view, with a part cut away, showing a chain with side rollers according to one embodiment; Fig. 2 is an enlarged cross-sectional view showing a main portion of Fig. 1; and Fig. 3 is an enlarged cross-sectional view showing a main 20 portion of a chain with side rollers according to a modification. MODES FOR CARRYING OUT THE INVENTION 25 A chain with side rollers according to one embodiment will now be described with reference to the attached drawings. As shown in Fig. 1, a chain with side rollers 11 includes a chain 12 serving as a movable body and side rollers 14. 30 Each one of the side rollers 14 is arranged rotationally on a corresponding one of shaft members 13, which project from side sections of the chain 12. The side rollers 14 roll and move on non-illustrated rails when the chain 12 moves. 35 The chain 12 includes inner links 16 and outer links 18. 3 Each of the inner links 16 has two inner link plates 15, which are faced to each other and spaced apart in the widthwise direction Y. Each of the outer links 18 has a pair of outer link plates 17, which is arranged on the outside in the 5 widthwise direction Y of the corresponding inner link plates 15. The inner link plates 15 and the outer link plates 17 are shaped substantially rectangular plates each extending in the longitudinal direction X, which is perpendicular to the widthwise direction Y. The longitudinal direction X coincides 10 with the direction in which the chain 12 moves when one of the ends of the chain 12 is pulled. Those of the inner link plates 15 and outer link plates 17 facing each other in the widthwise direction Y are arranged 15 parallel with each other. In other words, in the chain 12, each inner link 16 is configured such that the distance between the two inner link plates 15 is the same at the opposite ends of the inner link 16 in the longitudinal direction X. Each outer link 18 is configured such that the 20 distance between the two outer link plates 17 is the same at the opposite ends of the outer link 18 in the longitudinal direction X. That is, the chain 12 is a flat chain. The opposite ends of each inner link plate 15 in the 25 longitudinal direction X each have a circular bushing insertion hole 15a, which extends through the inner link plate 15 in the widthwise direction Y. The widthwise direction Y of the chain 12 corresponds to the thickness direction of each inner link plate 15. A pair of cylindrical bushings 19 is 30 provided between the two inner link plates 15 of each inner link 16, which face each other, to maintain the distance between the inner link plates 15. The opposite ends of each bushing 19 are received in the bushing insertion holes 15a of the inner link plates 15. Each of the bushings 19 is inserted 35 through a cylindrical roller 20 to rotationally support the 4 roller 20. That is, each bushing 19 is loosely inserted through the associated roller 20. The opposite ends of each outer link plate 17 in the 5 longitudinal direction X each have a circular pin insertion hole 17a, which extends through the outer link plate 17 in the widthwise direction Y. A columnar pin 21, which has an outer diameter slightly smaller than the inner diameter of each bushing 19, is inserted through each of the pin insertion 10 holes 17a. The widthwise direction Y of the chain 12 corresponds to the thickness direction of each outer link plate 17. The two outer link plates 17 of each outer link 18 are rotationally coupled to the two inner link plates 15 of the associated inner link 16 using the pin 21 from the outside 15 the inner link 16. In this case, a middle section of each of the pins 21 is inserted through the corresponding one of the bushings 19, which is provided between the two inner link plates 15 of the 20 associated inner link 16. The opposite ends of each pin 21 are received in the corresponding pin insertion holes 17a of the outer link plates 17 of the associated outer link 18. The opposite ends of each pin 21 thus extend through the associated two outer link plates 17. An end of a pair of 25 inner link plates 15 and an end of a corresponding pair of outer link plate 17 adjacent to the inner link plates 15 in the longitudinal direction X are rotationally coupled to each other with the associated pins 21 and bushings 19. The chain 12 of the present embodiment is made of steel. 30 With reference to Figs. 1 and 2, each pin 21 has pin protruding portions 21a, which are formed at the opposite sides in the widthwise direction Y. The pin protruding portions 21a protrude outward in the widthwise direction Y 35 from outer side surfaces 17b of the associated one of the 5 outer link plates 17, which configures side sections of the chain 12. The widthwise direction Y of the chain 12 corresponds to the axial direction of each pin 21. A cylindrical steel shaft member 13 is fixed to and arranged 5 around each pin protruding portion 21a to cover substantially the entire pin protruding portion 21a. Each of the shaft members 13 is formed to have a step such that the diameter of the basal end (the end at the side corresponding to the chain 12) of the shaft member 13 is greater than the diameter of the 10 distal end. Each of the side rollers 14 is rotationally supported by the associated one of the shaft members 13 with two ball bearings 31 each serving as a rolling-element bearing. Each 15 side roller 14 has a cylindrical roller member 32, which rolls when the chain 12 moves in the longitudinal direction X. In the present embodiment, the ball bearings 31 are arranged to be adjacent to each other in the widthwise direction Y. The widthwise direction Y of the chain 12 corresponds to the axial 20 direction of each ball bearing 31. Each ball bearing 31 includes an annular inner ring 33 (an inner race), an annular outer ring 34 (an outer race), and a plurality of balls 35, which are arranged between the inner 25 ring 33 and the outer ring 34. The inner ring 33 is fixed to an outer circumferential surface 13a of the shaft member 13. The outer ring 34 is fixed to an inner circumferential surface 32a of the roller member 32. The balls 35 are aligned in a single row while being spaced apart at regular circumferential 30 intervals and, in this state, held by a non-illustrated holder. In one (the left one as viewed in Fig. 2) of each pair of the ball bearings 31, the inner ring 33 is held in contact with a step portion 13b of the associated shaft member 13 and 35 the outer ring 34 is held in contact with a corner section 6 formed in the inner circumferential surface 32a of the associated roller member 32. In the other one (the right one as viewed in Fig. 2) of the pair of the ball bearings 31, the outer ring 34 is retained by an annular first restriction 5 plate 36, which is engaged with the inner circumferential surface 32a of the roller member 32. The first restriction plate 36 is configured by a C-shaped stopper ring. The inner ring 33 of the ball bearing 31 (located on the 10 right as viewed in Fig. 2) having the outer ring 34 retained by the first restriction plate 36 is retained by a second restriction plate 37. The second restriction plate 37 is configured by an annular washer having a substantially D shaped hole 37a. The distal end of each pin protruding 15 portion 21a having a substantially D-shaped cross section is inserted in the associated one of the holes 37a. A bolt 38 is fastened to an end surface of each pin protruding portion 21a. An annular seat plate 39, which is formed by a flat washer, is arranged between the bolt 38 and the end surface of the pin 20 protruding portion 21a. Each second restriction plate 37 is held in contact with and thus retained by the associated bolt 38 and seat plate 39. As lubricant for the interior of each ball bearing 31, mixture of synthetic resin and grease is employed. 25 A disk-shaped cap 40 is fitted in the distal portion of the inner circumferential surface of each roller member 32 with the outer circumferential surface of the cap 40 sealed by an 0 ring 41. Each of the caps 40 is retained in the 30 associated one of the roller members 32 by an annular third restriction plate 42, which is engaged with the inner circumferential surface 32a of the roller member 32. Each of the third restriction plates 42 is configured by a stopper ring. 35 7 An annular sealing chamber 43 is formed at a position that is between the roller member 32 and the shaft member 13 and is adjacent to the ball bearings 31 on the side corresponding to the chain 12. That position is closer to the 5 chain 12 than the ball bearings 31 is to the chain 12. Each of the sealing chambers 43 is defined by the associated roller member 32, shaft member 13, and ball bearings 31. Each sealing chamber 43 receives a plurality of annular oil seals 44 each serving as a first sealing member, which are arranged 10 adjacently in the widthwise direction Y, which is the axial direction of the shaft member 13. In the present embodiment, two oil seals 44 are provided in each sealing chamber 43. A slight clearance of approximately 1 mm, for example, is 15 formed between each adjacent pair of the oil seals 44 in the widthwise direction Y. The oil seals 44 press, with elastic force, the associated roller member 32 and shaft member 13 in the radial direction of the oil seals 44. That is, each of the oil seals 44 seals, with elastic force, the gap between 20 the roller member 32 and the shaft member 13. Each sealing chamber 43 is filled with lubricant such as grease. The lubricant lubricates the oil seals 44. An annular 0 ring 45 serving as a second sealing member 25 is arranged at a position that is between the associated roller member 32 and shaft member 13 and closer to the chain 12 than the associated sealing chamber 43 is to the chain 12, thus sealing, with elastic force, the gap between the roller member 32 and the shaft member 13. Each of the 0 rings 45 is 30 arranged in a first recess 46, which is formed in the inner circumferential surface 32a of the associated one of the roller members 32. In each roller member 32, the surface facing the outer 35 side surface 17b of the associated outer link plate 17, which 8 configures the side section of the chain 12, configures a facing surface 32b. An annular V ring 47 serving as a third sealing member is arranged radially outward of each shaft member 13 and between the outer side surface 17b of the 5 associated outer link plate 17 and the facing surface 32b of the associated roller member 32, thus sealing, with elastic force, the gap between the outer side surface 17b and the facing surface 32b. Each of the V rings 47 is arranged in a second recess 48, which is formed in the facing surface 32b of 10 the associated one of the roller members 32. Operation of the chain with side rollers 11 in an environment having a large amount of foreign matter such as dust (for example, coal or cement) will hereafter be described. 15 The chain with side rollers 11 operates with the side rollers 14 rolling and moving on non-illustrated rails when the chain 12 moves. At this time, foreign matter such as dust enters the clearance between the outer side surface 17b of the 20 associated outer link plate 17 and the facing surface 32b of the associated roller member 32 through an inlet, which is the outermost section in the radial direction of each shaft member 13. After having entered through the inlet, the foreign matter is blocked by the V ring 47, which is located in the 25 vicinity of the inlet. However, since the V ring 47 slides on the outer side surface 17b, the foreign matter gradually proceeds past the V ring 47 through between the V ring 47 and the outer side surface 17b of the outer link plate 17 and thus moves into the side roller 14. 30 After having moved into the side roller 14 past the V ring 47, the foreign matter is blocked by the 0 ring 45. However, since the 0 ring 45 slides on the shaft member 13, the foreign matter gradually proceeds past the 0 ring 45 35 through the gap between the 0 ring 45 and the outer 9 circumferential surface 13a of the shaft member 13 and thus moves toward the interior of the side roller 14. While moving toward the interior of the side roller 14 past the 0 ring 45, the foreign matter moves into the sealing chamber 43. 5 After having moved into the sealing chamber 43, the foreign matter is blocked by the two oil seals 44. In this case, the two oil seals 44 are arranged adjacent to each other in the widthwise direction Y in the sealing chamber 43, which 10 is filled with lubricant. The foreign matter, which has moved into the sealing chamber 43, is thus blocked in two steps. That is, even after the foreign matter, which has moved into the sealing chamber 43, proceeds past one (the left one as viewed in Fig. 2) of the two oil seals 44, the other one (the 15 right one as viewed in Fig. 2) of the two oil seals 44 blocks the foreign matter. In this case, the foreign matter moving into each sealing chamber 43 causes the sealing performance of the one (the left 20 one as viewed in Fig. 2) of the associated two oil seals 44 that is spaced from the ball bearings 31 to be decreased earlier than the sealing performance of the oil seal 44 located closer to the ball bearings 31. However, even with the decreased sealing performance, the oil seal 44 spaced from 25 the ball bearings 31 (the left oil seal 44 as viewed in Fig. 2) reduces the amount of foreign matter moving toward the oil seal 44 located closer to the ball bearings 31 (the right oil seal 44 as viewed in Fig. 2) . That is, even after the sealing performance is decreased by foreign matter, each of the oil 30 seals 44 restrains downstream movement of foreign matter in the foreign matter entry path. This effectively restrains entry of foreign matter into the ball bearings 31 after foreign matter has moved into the sealing chamber 43. 35 As has been described, the V ring 47, the 0 ring 45, and 10 the two oil seals 44, which are contact-type sealing members using elastic force, are arranged sequentially in the foreign matter entry path from the exterior of each side roller 14 to the associated ball bearings 31 in the side roller 14. The 5 contact-type sealing members using elastic force exhibit highly improved sealing performance compared to conventional non-contact type labyrinth seals and felt seals. As a result, entry of foreign matter into the ball bearings 31 is effectively restrained. 10 The above described embodiment achieves the following advantages. (1) Each sealing chamber 43 is filled with the first 15 lubricant and accommodates two oil seals 44 (the first sealing members), which seals, with elastic force, the gap between the associated roller member 32 and shaft member 13. The two oil seals 44 are located adjacent to each other in the widthwise direction Y. The oil seals 44 thus block foreign matter that 20 has moved into the sealing chamber 43 in two steps. Entry of external foreign matter from the side corresponding to the chain 12 into the ball bearings 31 is thus effectively restrained. 25 (2) A clearance is formed between the two oil seals 44 in each sealing chamber 43. As a result, the first lubricant in the sealing chamber 43 is provided also in the clearance between the oil seals 44. The oil seals 44 are thus effectively lubricated. This reduces sliding resistance of 30 each oil seal 44 with respect to the outer circumferential surface 13a of the associated shaft member 13, thus prolonging the wear life of the oil seals 44. Additionally, the clearance between the two oil seals 44 restrains interference between the oil seals 44. 35 11 (3) An 0 ring 45 serving as a second sealing member is arranged at a position that is between each roller member 32 and the associated shaft member 13 and closer to the chain 12 than the associated sealing chamber 43 is to the chain 12. 5 This improves sealing performance against foreign matter moving into the ball bearings 31. (4) A V ring 47 is arranged at a position radially outward of each shaft member 13 and between the outer side 10 surface 17b of the associated outer link plate 17 and the facing surface 32b of the associated roller member 32. That is, the V ring 47 is arranged in the vicinity of the inlet through which foreign matter moves into the side roller 14. Entry of foreign matter is thus effectively restrained at an 15 early stage. (5) Mixture of synthetic resin and grease is employed as the second lubricant for the ball bearings 31. This improves wear resistance of each ball bearing 31. 20 Modifications The above illustrated embodiment may be modified as follows. 25 As shown in Fig. 3, three oil seals 50 may be arranged in each sealing chamber 43. In this case, each one of the oil seals 50 is arranged to have a slight clearance with respect to an adjacent one of the oil seals 50. Additionally, at least one of the three oil seals 50 may be replaced by an 0 30 ring. Four or more sealing members may be arranged in each sealing chamber 43. In this case, at least one of the sealing members may be configured by an 0 ring or an oil seal. 35 Alternatively, one (some) of the four or more oil seals may be 12 configured by an 0 ring (0 rings) and the rest of the oil seals may be configured by an oil seal (oil seals). At least one of the two oil seals 44, which are arranged 5 in each sealing chamber 43, may be replaced by an 0 ring. The V rings 47 may be omitted. The 0 rings 45 may be omitted. 10 A clearance does not necessarily have to be formed between the two oil seals 44 in each sealing chamber 43. That is, the oil seals 44 may be held in contact with each other. 15 The lubricant for the ball bearings 31 does not necessarily have to be the mixture of synthetic resin and grease. One of each pair of ball bearings 31 may be omitted. 20 A roller bearing may be used as a rolling-element bearing instead of each ball bearing 31. The movable body may be a transport tray or a case. 25 The chain 12 may be an offset type chain, in which the distance between each pair of link plates is varied between the opposite ends in the longitudinal direction. 30 The chain 12 may be formed of plastic. 13