referring initially to fig1 - 7 and 13 - 15 of the drawings , in a most preferred embodiment the rodless cylinder rope tensioning apparatus of this invention is generally illustrated by reference numeral 38 . the rodless cylinder rope tensioning apparatus 38 is characterized in a first preferred embodiment by a rodless cylinder 15 , having an elongated barrel 16 with a barrel bore 17 , as illustrated in fig1 . air supply ports 18 are provided in each of the end caps 22 of the barrel 16 and communicate with the barrel bore 17 , as further illustrated in fig1 and 15 . a barrel slot 20 is provided longitudinally in the barrel 16 and communicates with the barrel bore 17 for slidably receiving a piston yoke 26 , which is attached to an internal piston 23 , positioned in the barrel bore 17 by means of a connecting plate 25 , as further illustrated in fig1 . piston seals 24 are fitted to the ends of the piston 23 for sealing the piston 23 in slidable relationship inside the barrel bore 17 of the barrel 16 and the end caps 22 close each end of the barrel 16 , as further illustrated in fig1 . referring again to fig1 , a pair of end cushions 21 are also typically provided in the barrel bore 17 at each end of the barrel 16 to cushion movement of the piston 23 inside the barrel bore 17 with an accompanying sliding movement of the external piston yoke 26 , as hereinafter further described . as further illustrated in fig1 and 8 - 10 , it will be appreciated by those skilled in the art that one or more of the rodless cylinders 15 , which are the primary operating components of the rodless cylinder rope tensioning apparatus 38 , may be horizontally ( fig1 ) or vertically ( fig2 ) oriented , to receive one or more ropes 50 , ( illustrated in phantom ) which are conventionally used in a paper - making machine ( not illustrated ) to carry a paper web ( also not illustrated ) in the paper - making process . accordingly , at least one entry guide roller 47 is typically attached to corresponding rodless cylinder 15 by means of a roller shaft 49 a and shaft bracket 49 b to receive the respective rope ( s ) 50 . furthermore , a yoke sheave 27 is mounted on a corresponding sheave shaft 28 , illustrated in fig8 - 10 and the sheave shaft bearing 29 carrying the sheave shaft 28 is fitted with a yoke slot 30 , for engaging and mounting on the corresponding piston yoke 26 , ( fig1 , 12 , 14 and 15 ) which is slidably mounted on the rodless cylinder 15 as heretofore described . each of the yoke sheaves 27 can therefore slide with the corresponding piston yoke 26 along the length of the rodless cylinder 15 at the barrel slot 20 , for purposes which will be hereinafter described . furthermore , the entry rope segment 51 of the rope or ropes 50 extends around the entry guide roller or rollers 47 as heretofore described and extend 180 degrees around the corresponding yoke sheave 27 , to exit the rodless cylinder rope tensioning apparatus 38 as an exit rope segment 52 , as further illustrated in fig1 and 2 . it will be appreciated by those skilled in the art that under circumstances where a single rope 50 is utilized in the specific paper - making apparatus in question , a single rodless cylinder 15 , with an accompanying entry guide roller 47 and a corresponding slidably - mounted yoke sheave 27 may be utilized to tension the rope 50 , in either the horizontal configuration illustrated in fig1 or the vertical position illustrated in fig2 . alternatively , under circumstances where a pair of ropes 50 is utilized in the paper - making apparatus the ropes 50 may be threaded as indicated in fig1 and 2 around the respective pairs of entry guide rollers 47 and corresponding yoke sheaves 27 for tensioning purposes , as hereinafter further described . referring now to fig4 - 7 of the drawings , in a most preferred embodiment of the invention the respective rodless cylinders 15 are typically installed and mounted in a frame 40 , constructed of longitudinal frame members 41 , cross frame members 42 and a central longitudinal stiffener 43 . mount brackets 44 are also provided on the frame 40 for mounting the frame 40 in a vertical or horizontal position in the rope tensioning apparatus , as deemed necessary . furthermore , roller bearings 49 may be provided on the frame 40 for receiving respective entry guide rollers 47 under circumstances where the entry guide rollers 47 are mounted to the frame 40 and not to the respective rodless cylinders 15 , as illustrated in fig1 and 2 . the rodless cylinder rope tensioning apparatus 38 illustrated in fig4 thus operates in the same manner as the corresponding rodless cylinder rope tensioning apparatus 38 illustrated in fig1 and 2 , either in horizontal or vertical position , wherein the respective ropes 50 are extended through the entry guide rollers 47 as entry rope segments 51 and project from the corresponding yoke sheaves 27 , becoming exit rope segments 52 , as illustrated in fig4 . referring again to fig3 and 8 - 10 in a most preferred embodiment of the invention the respective yoke sheaves 27 are mounted on the corresponding piston yokes 26 of the rodless cylinders 15 by means of the respective stepped sheave shafts 28 , which are journalled for rotation in the sheave shaft bearings 29 . in this installation , the yoke slot 30 of each of the sheave shaft bearings 29 is fitted over the corresponding piston yoke 26 , which is slidably mounted on each rodless cylinder 15 , and fasteners such as bolts ( not illustrated ) are extended through the matching bolt openings 33 and 33 a , provided in the sheave shaft bearings 29 and the piston yoke 26 , respectively , to receive corresponding bolts ( not illustrated ) in the installations . each of the yoke sheaves 27 is typically shaped as illustrated in fig3 to accommodate the rope 50 . referring now to fig1 - 20 of the drawings , the rodless cylinder rope tensioning apparatus 38 is operated by means of pneumatic control systems 45 and 45 a which are illustrated schematically in fig1 and 20 , respectively . in the control system embodiment illustrated in fig1 , an air source 39 is pneumatically connected by means of an air flow line 39 a , to a left two - position , two - way push button valve 6 , which is pneumatically connected to a two - position , five - way , double air piloted distributor valve 7 , at a pressure port 9 a , by means of an air signal line 90 b . a right two - position , two - way push button valve 6 a is also connected to the air source 39 by means of an air flow line 39 a and to the distributor valve 7 at a pressure port 9 b , by means of an air signal line 90 c . the air source 39 is also directly pneumatically coupled to the distributor valve 7 by means of an air flow line 39 d . the distributor valve 7 is , in turn , pneumatically connected to the operating end 15 a of a rodless cylinder 15 by means of an air flow line 39 c , and to the non - operating end 15 b of the rodless cylinder 15 , by means of an air flow line 39 b , both at the air supply ports 18 , illustrated in fig1 and 14 . the left push button valve 6 is designed to facilitate threading of the rope 50 onto the entry guide roller 47 and the yoke sheave 27 , while the right push button valve 6 a is designed to facilitate tensioning of the rope 50 on the entry guide roller 47 and the yoke sheave 27 . as illustrated in fig1 , the appropriate controls for the left and right push button valves 6 and 6 a , respectively , may be mounted in a control cabinet 31 , having air line couplings 32 as illustrated in fig1 for coupling to the air lines 39 a and typically including a cabinet lock 31 a , as illustrated in fig1 . a pressure gauge 34 may also be provided in the control cabinet 31 to indicate the pressure of the air source 39 . in operation , and referring again to fig1 of the drawings , the rodless cylinder 15 is operated to move the yoke sheave 27 linearly along the barrel 16 and thread and tension the rope 50 , as follows . for brevity , operation of the pneumatic control system 45 illustrated in fig1 will be described with respect to a single rodless cylinder 15 and rope 50 . initially , referring again to fig1 and 19 , the left push button valve 6 is pressed to slidably adjust the yoke sheave 27 toward the operating end 15 a of the rodless cylinder 15 that will allow for maximum stroke , which will be to the left , nearest the entry guide roller 47 , as illustrated in fig1 and 4 . actuation of the left push button valve 6 facilitates flow of air from the air source 39 through the air flow line 39 a , the left push button valve 6 and air signal line 90 b , generating an air pressure signal at the pressure port 9 a , which opens an air flow port 10 a in the distributor valve 7 . consequently , air flows from the distributor valve 7 through the air flow port 10 a , into the non - operating end 15 b of the rodless cylinder 15 through the air flow line 39 b . as a result , the pressurized air pushes the piston 23 inside the rodless cylinder 15 , and the attached yoke sheave 27 toward the operating end 15 a of the rodless cylinder 15 , until the left push button valve 6 is released . at that time , the air pressure signal at the pressure port 9 a on the distributor valve 7 is terminated and the air flow port 10 a closes , preventing further flow of air into the rodless cylinder 15 from the air source 39 and halting travel of the yoke sheave 27 . the rope 50 is threaded around the entry guide roller 47 and 180 degrees onto the yoke sheave 27 and then spliced to define a continuous loop , in conventional fashion . the right push button valve 6 a is then manipulated , causing the yoke sheave 27 to move in the opposite direction to tension the rope 50 , until the excess slack is removed from the rope 50 . actuation of the right push button valve 6 a facilitates flow of air from the air source 39 and air flow line 39 a , through the right push button valve 6 a and air signal line 90 c , generating an air pressure signal at the pressure port 9 b , which opens an air flow port 10 b in the distributor valve 7 . consequently , air flows from the distributor valve 7 through the air flow port 10 b , and into the operating end 15 a of the rodless cylinder 15 through the air flow line 39 c . the resulting air pressure exerted on the piston 23 relocates the yoke sheave 27 toward the right on the rodless cylinder 15 , thereby exerting tension on the rope 50 . the right push button valve 6 a remains in this “ run ” mode during running of the rope 50 through the paper - making machine ( not illustrated ) and the yoke sheave 27 , as well as the corresponding entry guide roller 47 in the apparatus . referring now to fig1 and 20 of the drawings , the illustrated alternative pneumatic control system 45 a is designed to include additional equipment for augmenting tension on the rope 50 , as well as a safety feature for protecting the rodless cylinder 15 during operation of the rodless cylinder rope tensioning apparatus 38 . accordingly , the pneumatic control system 45 a illustrated in the schematic of fig2 includes an adjustable pressure regulator with automatic water drain 1 , which is pneumatically coupled to the air source 39 by means of an air flow line 39 a . the adjustable pressure regulator with automatic water drain 1 further includes a pressure gauge 34 , typically mounted in the control cabinet 31 ( fig1 ), a water sump ( not illustrated ) and a sump drain ( also not illustrated ), for removing water from the air applied to the adjustable pressure regulator with automatic water drain 1 from the air source 39 . the left push button valve 6 , which facilitates initial threading of a rope 50 on the entry guide roller 47 and yoke sheave 27 of the rodless cylinder 15 as heretofore described with respect to fig1 , is pneumatically coupled to the adjustable pressure regulator with automatic water drain 1 by means of air flow lines 39 b , as well as to the distributor valve 7 at a pressure port 9 a , by means of an air signal line 90 b . the distributor valve 7 is , in turn , pneumatically connected by means of air flow lines 39 e and 39 f at an air flow port 10 b , to the operating end 15 a of the rodless cylinder 15 for controlling flow of air under pressure from the adjustable pressure regulator with automatic water drain 1 , into the rodless cylinder 15 , as further heretofore described . the distributor valve 7 is also pneumatically coupled by means of air flow lines 39 i and 39 g at an air flow port 10 a , to the non - operating end 15 b of the rodless cylinder 15 through an air piloted check valve 12 . the right push button valve 6 a , which facilitates tensioning of the rope 50 , is pneumatically connected to the adjustable pressure regulator with automatic water drain 1 by means of air flow lines 39 b , and an air flow line 39 h , extending from pneumatic communication with the right push button valve 6 a , terminates at the air piloted check valve 12 . an air signal line 90 c is pneumatically coupled to the air flow line 39 h and terminates in pneumatic communication with the distributor valve 7 at a pressure port 9 b , for purposes hereinafter further described . a two - position , three - way lever valve 3 , which controls “ run ” and “ paper thread ” system operation , is also pneumatically coupled by means of air flow lines 39 b to the adjustable pressure regulator with automatic water drain 1 and by means of an air signal line 90 a , to a two - position , three - way air piloted flow valve 5 at a pressure port 9 c . an adjustable pressure regulator 4 which regulates the “ paper thread ” air pressure in the system , is pneumatically connected to the adjustable pressure regulator with automatic water drain 1 by means of air flow lines 39 b , and to the flow valve 5 by means of an air flow line 39 c , at an air entry port 11 . the flow valve 5 is also connected to the adjustable pressure regulator with automatic water drain 1 by means of air flow lines 39 b , and to the distributor valve 7 by means of an air flow line 39 d . the flow valve 5 serves to direct air from the adjustable pressure regulator with automatic water drain 1 to the operating end 15 a of the rodless cylinder 15 , by operation of the right push button valve 6 a , as hereinafter further described . the flow valve 5 also directs air from the adjustable pressure regulator 4 to the operating end 15 a of the rodless cylinder 15 by operation of the lever valve 3 , to augment the air pressure entering the operating end 15 a of the rodless cylinder 15 and further tension the rope 50 in “ paper thread ” operation , as hereinafter further described . an adjustable safety regulator 2 is pneumatically coupled to the adjustable pressure regulator with automatic water drain 1 by means of air flow lines 39 b , and to a two - position , three - way air piloted safety valve 5 b by means of an air flow line 39 c . an air flow line 39 g pneumatically connects the safety valve 5 b to the non - operating end 15 b of the rodless cylinder 15 . the adjustable safety regulator 2 is designed to maintain air pressure in the “ dead ” or non - operating side of the rodless cylinder 15 during “ paper thread ” and “ run ” operations of the rodless cylinder 15 . the air piloted check valve 12 is provided in the air flow line 39 i to prevent backflow of air from the rodless cylinder 15 or adjustable safety regulator 2 to the distributor valve 7 . a two - position , three - way , air piloted actuation valve 5 a is pneumatically connected to the distributor valve 7 by means of the air flow line 39 e and an air signal line 90 e , and to the safety valve 5 b at a pressure port 9 e , by means of the air signal line 90 e . the actuation valve 5 a is further pneumatically connected to the air flow line 39 h , by means of an air signal line 90 d . the actuation valve 5 a facilitates opening of the safety valve 5 b during operation of the right push button valve 6 a , and flow of air under pressure from the adjustable safety regulator 2 to the non - operating end 15 b of the rodless cylinder 15 , in the “ running ” and “ paper threading ” operations of the rodless cylinder 15 , as hereinafter further described . accordingly , referring again to fig2 of the drawings , in operation , the yoke sheave 27 is initially slidably adjusted on the rodless cylinder 15 toward the non - operating end 15 a thereof , to the point of minimum rope stretch , as heretofore described with respect to the pneumatic control system 45 illustrated in fig1 . the left push button valve 6 is utilized for this purpose and , when activated , air under pressure set by the adjustable pressure regulator with automatic water drain 1 , flows through air flow lines 39 b , the left push button valve 6 and air signal line 90 b , to generate an air pressure signal at the pressure port 9 a on the distributor valve 7 . the air pressure signal opens the air flow port 10 a in the distributor valve 7 , which now allows a flow of air under pressure set by the adjustable pressure regulator with automatic water drain 1 , through air flow lines 39 b , the flow valve 5 , the air flow line 39 d , air flow port 10 a of the distributor valve 7 , air flow line 39 i , air piloted check valve 12 , air flow line 39 g and finally , into the non - operating end 15 b of the rodless cylinder 15 . the pressurized . air pushes the internal piston 23 and attached yoke sheave 27 toward the operating end 15 a of the rodless cylinder 15 , until the left push button valve 6 is released . at that time the left push button valve 6 closes and causes the air flow port 10 a in the distributor valve 7 to close , by terminating the air pressure signal at the pressure port 9 a . as a result , the flow of air into the non - operating end 15 b of the rodless cylinder 15 is terminated , halting leftward travel of the yoke sheave 27 on the rodless cylinder 15 . the rope 50 is then extended through the entry guide roller 47 and 180 degrees around the yoke sheave 27 and spliced , taking out maximum slack in the splicing operation . after splicing is completed and the rope 50 is in the proper position in the paper - making machine ( not illustrated ) and in the rodless cylinder rope tensioning apparatus 38 , the right push button valve 6 a is pressed to locate the yoke sheave 27 toward the right on the rodless cylinder 15 and remove the balance of the slack in the rope 50 , as heretofore described with respect to fig1 . this action maintains tension on the rope 50 during the “ run ” operation of the rodless cylinder 15 . after activation of the right push button valve 6 a , air under pressure from the adjustable pressure regulator with automatic water drain 1 flows through air flow lines 39 b and the opened , right push button valve 6 a , the air flow line 39 h , and the air signal line 90 c to generate an air pressure signal at the pressure port 9 b , which opens the air flow port 10 b in the distributor valve 7 . air then flows under pressure set by the adjustable pressure regulator with automatic water drain 1 , through air flow lines 39 b , flow valve 5 , air flow line 39 d , air flow port 10 b in the distributor valve 7 , the air flow lines 39 e and 39 f and finally , into the operating end 15 a of the rodless cylinder 15 , to locate the internal piston 23 and yoke sheave 27 toward the non - operating end 15 b of the rodless cylinder 15 . although the rope 50 is now in the “ run ” configuration , additional tension must normally be exerted on the rope 50 in order to begin threading the paper web ( not illustrated ) through the paper machine on the rope 50 . accordingly , the right push button valve 6 a remains activated and the lever valve 3 is manipulated from the “ run ” position to the “ paper thread ” position to increase the rope tension . air under pressure from the adjustable pressure regulator with automatic water drain 1 then flows through the opened lever valve 3 and air signal line 90 a , and the resulting air pressure signal at the pressure port 9 c on the flow valve 5 opens the air entry port 11 in the flow valve 5 , which action facilitates a flow of air under pressure set by the adjustable pressure regulator 4 , through the air flow line 39 c and into the flow valve 5 . there , air under pressure from the adjustable pressure regulator 4 joins air under pressure from the adjustable pressure regulator 1 and the combined air pressure flows through the air flow line 39 d and air flow port 10 b in the distributor valve 7 , and into the operating end 15 a of the rodless cylinder 15 through air flow lines 39 e and 39 f . the combined pressure of the air from the two regulators are thus additive in the flow valve 5 , resulting in an increased air pressure at the operational end 15 a of the rodless cylinder 15 , to facilitate a tighter stretching or tensioning of the rope 50 than is achieved by the air flowing from the adjustable pressure regulator with automatic water drain 1 , alone . accordingly , the rope 50 is now operating at maximum tension in the “ paper thread ” operation to facilitate loading of a paper web ( not illustrated ) on the rope 50 and threading the paper web through the paper machine ( not illustrated ) in conventional fashion . referring again to fig2 of the drawings , it will be appreciated by those skilled in the art that the adjustable safety regulator 2 is designed to protect the rodless cylinder 15 and other components of the system from inadvertent damage should the rope 50 suddenly break . during the “ running ” and “ paper threading ” operations of the rodless cylinder 15 by operation of the right push button valve 6 a or operation of both that valve and the lever valve 3 , respectively , the yoke sheave 27 is slidably relocated from the left to the right on the rodless cylinder 15 , as described above , thereby exerting tension on the rope 50 . simultaneously , air under pressure set by the adjustable pressure regulator with automatic water drain 1 , flows from the right push button valve 6 a and air flow line 39 h , as heretofore described , and then through the air signal line 90 d , generating an air pressure signal at the pressure port 9 d , which signal opens the normally closed actuation valve 5 a . because the air signal line 90 c , by operation of the right push button valve 6 a , generates an air signal at the pressure port 9 b which opens the air flow port 10 b in the distributor valve 7 , to allow flow of air into the operating end 15 a of the rodless cylinder 15 , as heretofore described , air also flows from the distributor valve 7 through the air signal line 90 e and the now open actuation valve 5 a , thus generating an air pressure signal at the pressure port 9 e , which signal opens the normally closed safety valve 5 b . consequently , air under pressure from the adjustable safety regulator 2 flows through the air flow line 39 c , safety valve 5 b , air flow line 39 g and into the non - operating end 15 b of the rodless cylinder 15 . the resulting air pressure maintained in the “ dead ” side of the rodless cylinder 15 serves to cushion the piston 23 in the rodless cylinder 15 and prevent the piston 23 from slamming into the non - operating end 15 b of the rodless cylinder 15 , due to the tension exerted by the rope 50 , should the rope 50 inadvertently break . it will be appreciated by those skilled in the art that the above explanation of the operation of the pneumatic control system 45 is directed to the single rope 50 threaded through a single entry guide roller 47 and corresponding yoke sheave 27 . however , in many operations , two such rodless cylinder rope tensioning apparatus 38 will be necessary , thus necessitating a second pneumatic control system 45 which is identical to the pneumatic control system 45 illustrated in fig1 . hence , referring to fig1 , a pair of left push button valves 6 and a pair of right push button valves 6 a would be utilized for that purpose and all of the other components illustrated in fig1 would be duplicated , with the exception of the adjustable pressure regulator with automatic water drain 1 . while the preferred embodiments of the invention have been described above , it will be recognized and understood that various modifications may be made in the invention and the appended claims are intended to cover all such modifications which may fall within the scope and spirit of the invention .