in fig1 the rotary printing installation comprises several printing units 1 . at the left hand side , two supply rollers 2 for web - shaped material to be printed are located in a change over device 3 by means of which , when one roller is running out of material , it is possible to change over to the other roller to so ensure continuous operation of the installation . at the right hand side , there are also depicted some of the conventional processing installations such as a drying apparatus 4 and a roller system 5 for cooling the web 6 . so far , the device generally conforms to the present state of the art . as seen at the right hand side of fig1 before a winding roller receiving station 31 , there are provided so - called sample taking means 7 which constitutes the main subject of the present invention . the noted means 7 are provided for obtaining a temporarily stopped length of the web a ( see fig2 ) for a web 6 and are formed by a combination of a first loop system or accumulator 8 for taking up a certain length of the supplied web 6 , a rotatable drum 11 with a supporting surface 9 provided for the web 6 , and a second accumulator device 18 . this drum 11 with supporting surface 9 cooperates with means 10 for temporarily retaining web 6 , cutting the same twice , and for rejoining the web ends so cut with the aid of means 16 . as is best seen in fig3 - 7 , the drum 11 is positioned with its center line 12 transverse to the direction of travel f of the web , such that the supporting surface 9 passes closely to means 10 . the means 10 comprises two fixed suction bars 13 and 14 located on the side of web 6 opposite from the drum 11 . within drum 11 and adjacent to a slit in the drum , a third suction bar 15 is provided which is rotatable jointly with the drum and furthermore a so - called glueing bar 16 likewise rotatable jointly with the drum but also capable of a reciprocal motion in radial direction , for a purpose to be described hereafter . between the fixed suction bars 13 and 14 there is provided a cutting member 17 which serves to cut web 6 . the second accumulator device 18 ( see fig2 ) comprises two fixed guide rollers 19 and a third linearly displaceable turning roller 20 rotatably attached to the piston rod 21 of a cylinder 22 . the first section of the accumulator 8 is shown in fig2 and consists of several fixed rollers 23 and displaceable rollers 24 , the latter being mounted on a so - called disk block 25 . this block 25 is coupled to a disk block 26 that forms part of the second section of the accumulator 8 serving to receive web material and releasing same , during the time the web 6 is clamped against rollers 19 and 29 , causing a portion a of the web to be temporarily stopped . this second section again comprises several displaceable rollers 27 cooperating with several fixed guide rollers 23 and 28 . the coupled disk blocks 25 and 26 are capable of displacement between the positions b and c . it is apparent from fig2 that the printed web 6 passes through the first accumulator section with the rollers 23 and 24 in a number of loops , whereupon the web travels via rollers 19 and 20 of the second accumulator device 18 . thereafter , the web 6 travels past the fixed suction bars 13 and 14 and over a fixed guide roller 29 , and subsequently toward the second section of the first accumulator device 8 with the rollers 28 , 23 and 27 . herefrom the web 6 is discharged toward the winding station 31 ( see fig1 ) via the last guide roller 30 . finally , it may be noted that drum 11 is provided with a drive 32 , one roller 19 and roller 29 cooperating with a brake device 33 . the operation of the sample taking means 7 will now be explained with reference to fig2 - 7 . when it is decided to sample a web , the web - supporting surface 9 , i . e ., drum 11 , is moved from the rest position ( fig3 ) at which the glueing bar 16 has been provided with an adhesive strip 34 , to the start position for sampling ( fig4 ). suction bar 15 then faces the fixed suction bar 13 , web 6 being positioned therebetween . thereupon , the brake device 33 is activated and the coupled disk blocks 25 and 26 are set in motion and gradually move from position b toward position c thus permitting temporary storage of the incoming web from the previous stations 1 , 4 and 5 in the first section of the first accumulator device 8 and at the same time allowing uninterrupted delivery of the web to the receiving winding station 31 . the speed v 1 of the incoming web and the speed v 2 of the outgoing web from the first accumulator device remain equal to each other ( v 1 = v 2 ) due to the coupled motion of the two disk blocks 25 and 26 of the first and second section , each having the same number of web loops . the speed v 3 at which the coupled disk blocks 25 and 26 move downward is then equal to the time available to take a sample out of the stopped web portion a between the rollers 19 and 29 is determined by the length d of the path between the upper position b and lower position c of the coupled disk blocks 25 and 26 and is equal to d / v 3 . the actual sample taking then preceeds as follows . after activation of the brake device 33 , which stops web portion a , web portion 6 &# 39 ; is drawn by suction against the upper suction bar 15 ( see fig4 ). thereupon , cutting member 17 is actuated and web 6 is cut through in the area confined between the suction bars 13 and 14 . subsequently , lower portion bar 13 is then deactivated and the drum 11 is rotated over an angle such that , a useful length , e . g ., one or several printed repeats of the web 6 , is wound on the drum ( see fig5 ), the length of the web being supplied by the downward movement of roller 20 of the second accumulator device 18 . the speed of displacement v 4 of the roller 20 then amounts to half the circumferential speed of the drum 11 . after this first angular rotation of drum 11 , the drum is stopped and the web portion 6 &# 34 ;, the front part of which is positioned along the periphery of drum 11 ( see fig5 ), is drawn by suction against the reactivated bar 13 . thereupon , cutting member 17 is actuated for the second time and web 6 is cut again . subsequently , drum 11 is further rotated ( fig6 ), the glueing bar 16 then being located directly opposite the center of the cutting member 17 . the bar 16 with the adhesive strip 34 provided thereon , then moves radially outwardly and the adhesive strip is subsequently pressed against the free end of the web portion 6 &# 39 ; retained by bar 14 , and upon the end of web portion 6 &# 34 ; retained by bar 13 , thus joining together web portions 6 &# 39 ; and 6 &# 34 ;, however , without the cut - off portion position upon drum 11 . after termination of the vacuum in suction bars 13 and 14 and release of the brake device 33 , the temporary stoppage of the web portion a is terminated , thereby permitting the first and second accumulator devices 8 and 18 to travel back to their original position . after removing the sample from the drum 11 by terminating the vacuum of suction bar 15 , the drum is rotated to the position depicted in fig7 and the suction bar 16 is provided with a new glueing strip in preparation for the next sampling operation . as is apparent from the above , the device according to the invention enables continuous operation of a rotary printing installation while still allowing a sample to be taken and inspected without the conventional cutting and folding apparatus being required which , due to its complexity , frequently gives rise to disturbances and , in addition , greatly limits the maximum printing speed and thus also the operational capacity of the installation .