a conveyor embodying features of the invention is depicted in fig1 and 2 . the conveyor 10 comprises an endless conveyor belt 12 advancing in a direction of belt travel 14 . the conveyor belt has a plurality of rollers 16 generally arranged in rows and columns . the belt is driven by a motor 18 coupled to rotating belt - engaging drive elements 20 , such as sprockets , drive drums , or pulleys , mounted on a shaft . articles 22 are supported atop the rollers along an upper carryway portion 24 of the belt . the belt is trained around the drive elements 20 at a downstream end of the conveyor and rotatable idle elements 21 at an upstream end of the conveyor . the belt follows a lower returnway 25 from the drive elements to the idle elements . the belt rollers 16 are preferably generally cylindrical with central bores that receive an axle 26 defining an axis 27 perpendicular to the direction of belt travel . the diameter d of the rollers exceeds the thickness t of the belt . salient portions of the rollers protrude from belt cavities past inner and outer surfaces 28 , 29 of the belt . one example of such a roller belt is the series 400 0 ° angled roller ™ modular plastic conveyor belt manufactured and sold by intralox , l . l . c ., of harahan , la ., u . s . a . other realizations of roller belts include flat belts with rollers and parallel roller chains supporting the opposite ends of axles on which rollers are mounted for rotation . a bearing surface 30 underlies the belt along a portion of the carryway 24 . wearstrips 31 support the belt along its inner surface 28 between the columns of rollers and those portions of the carryway away from the bearing surface . the rollers ride along the bearing surface . because the rollers are arranged in columns , each column rolls along a portion of the bearing surface that constitutes a roller path , or track 23 , extending in the direction of belt travel . the bearing surface provides a number of parallel tracks — one for each column of rollers . as the belt advances along the carryway , the rollers &# 39 ; engagement with the bearing surface causes the rollers to rotate as viewed from above in a direction of rotation 15 parallel to the direction of belt travel . articles 22 atop the rollers are accelerated along the top of the belt in the direction of belt travel at a speed of up to twice the belt speed , depending on how much the rollers slip on the bearing surfaces or on the bottoms of the conveyed articles . the region along the carryway in which the belt rollers engage bearing surfaces is defined as an article - acceleration zone of the conveyor because , in that zone , articles atop the rollers are accelerated forward . the bearing surface 30 shown in fig1 has a generally trapezoidal projection in a plan view . the upstream end 32 of the bearing surface varies , in this example , linearly , across the width of the conveyor . the upstream end is optionally tapered or sloped to provide a gradual entry of the rollers onto the bearing surface and avoid catching . the downstream end 33 of the bearing surface is perpendicular to the direction of belt travel . consequently , the distance d 1 between the upstream and the downstream end at a first side 34 of the conveyor is greater than the distance d 2 at an opposite second side 35 . the belt rollers at the first side 34 of the conveyor are activated over a longer stretch than the rollers at the second side 35 . in this way , articles at the first side of the conveyor are propelled in the direction of roller rotation by the rollers over a longer distance than articles at the second side . one application of the conveyor of fig1 and 2 is shown in fig3 . the conveyor 10 is interposed between an infeed conveyor 36 transporting a pallet layer 38 forward and a centering conveyor 40 oriented perpendicular to the conveying direction 14 of the infeed conveyor 36 and the depalletizing conveyor 10 . ( the infeed conveyor may be jogged to insert a slight delay between the deliveries of consecutive rows of the pallet layer .) when a row 42 of articles reaches the depalletizing conveyor 10 , the row is stripped off the infeed conveyor onto the rollers on the belt 12 . because the rollers at the infeed end 44 of the depalletizing conveyor are outside the article - acceleration zone 46 , they are not rotated as the belt advances . when the articles reach the upstream end 32 of the acceleration zone , they are propelled forward atop the rotating rollers . the angled upstream end of the bearing surface causes the rollers at the first side 34 of the conveyor to rotate at a position farther upstream than the rollers at the second side 35 . this staggered start to the rotation causes the articles at the first side of the conveyor to be accelerated sooner than those at the second side . the row of articles fans out more and more as it advances along the depalletizing conveyor so that the articles closer to the first side exit the downstream end of the belt before the articles toward the second side . the centering conveyor receives the fanned - out articles and centers them as they are conveyed single - file past the first side of the depalletizing conveyor . the centering conveyor may be realized as a roller conveyor or a belt conveyor with the rollers oriented to push articles in the directions indicated by arrows 47 , 47 ′. another depalletizing application is shown in fig4 . this application differs from that of fig3 in that the centering conveyor 40 is in line with the depalletizing conveyor 10 and the upstream end 48 of the acceleration zone 50 is chevron - shaped to cause articles near the centerline of the conveyor to be accelerated earlier the articles at the sides . in this version , two roller belts 52 , 53 are arranged side by side to form the depalletizing conveyor . other bearing surfaces that may be used in the conveyor of fig1 are shown in fig5 a - 5e . the bearing surface of fig5 a is formed on a pan having a stepped upstream end 54 for a longer acceleration stretch along the right side referred to the drawing . the bearing surface of fig5 b has an arcuate upstream end 56 for a slightly different acceleration profile . the bearing surface of fig5 c has an upstream end 58 perpendicular to the direction of belt travel 14 and an angled downstream end 59 . like the other versions of bearing surfaces , this version provides a longer acceleration stretch along the right side . in fig5 d , individual wearstrips 60 , arranged in parallel lanes to align with the columns of rollers in the belt and of varying lengths across the width of the conveyor , provide a bearing surface tracks for the rollers . the bearing surface of fig5 e has angled upstream and downstream ends 62 , 63 to provide an acceleration effect similar to that of the other versions . although the invention has been described in detail with respect to a few preferred versions , other versions are possible . for example , the rollers shown in fig1 - 4 could be roller balls capable of omnidirectional rotation , but rotated by the underlying bearing surface in the direction of belt travel . as another example , a conveyor having an article - acceleration zone that varies in length across the conveyor &# 39 ; s width may be used in applications other than depalletizing ; for example , unscrambling a dense flow of articles . and the article - acceleration direction may be oblique or perpendicular to the direction of belt travel when , for example , belts with rollers arranged to rotate on axes oblique or parallel to the direction of belt travel are used . so , as these few examples suggest , the scope of the claims is not meant to be limited to the exemplary versions used to describe the invention .