WO2008145655A1

WO2008145655A1 - A rotary offset printing press

Info

Publication number: WO2008145655A1
Application number: PCT/EP2008/056492
Authority: WO
Inventors: Darryl Gray
Original assignee: Goss Graphic Systems Limited
Priority date: 2007-06-01
Filing date: 2008-05-27
Publication date: 2008-12-04
Also published as: GB0710547D0

Abstract

A printing press (12) is disclosed. It comprises a print unit (13) and a slitting mechanism (16) associated with the print unit for slitting a web of print medium into a plurality of longitudinal ribbons as the web leaves the print unit. The printing press also comprising a folder (18) spaced from the print unit to receive ribbons cut by the slitting mechanism at the print unit. It also includes means for guiding a web of print medium through the print unit during a web-up procedure prior to initiation of a print run. The guide means is operable to separately guide each ribbon from the print unit to the folder as well as guiding the web through the print unit.

Description

A Rotary Offset Printing Press

Description

The present invention relates to a method and apparatus for conveying a web of printing medium through a rotary web-offset printing press.

A web offset rotary printing press comprises a number of printing units designed to print matter onto separate continuous webs of print medium, such as paper, travelling through each print unit which is fed from a reel stand positioned below or to one side of each print unit. Each print unit comprises at least one pair of cylinder groups or print couples comprising a rotatably mounted plate cylinder, to which one or more printing plates are attached, and a rotatably mounted blanket cylinder. An inking system is associated with each print couple and feeds ink onto the printing plates as the plate cylinders rotate. As the cylindrical surfaces of the plate and blanket cylinders of each print couple are in rolling contact, an inked image is transferred onto the blanket cylinder from the plate cylinder and, form the blanket cylinder to print medium comprising a web of paper passing between the blanket cylinder and an impression cylinder which is a blanket cylinder of another print couple which is arranged on the opposite side of the paper web which runs between them.

The printing units are spaced from each other and are aligned with a folder so that the paper web is fed through each printing unit and then travels in a lateral direction away from the unit and into the folder. The folder collects the webs from each print unit, folds them at least once and cuts them into longitudinal sections.

It is common for the plate and blanket cylinders of newspapers printing presses to be long enough to accommodate a web that is two or three times the width of a newspaper being printed. So called double-width or triple-width print units contribute 8 or 12 broadsheet pages to the newspaper being produced and their use is widespread. A double or triple width web is far too wide to pass over a single former within the folder and so must be slit longitudinally into a number of what are commonly referred to as ribbons. Each ribbon may be the width of a single-width web. The folder is provided with a plurality of formers (two for double width and three for triple width) mounted side-by-side, with the ribbons passing over them to form the longitudinal fold along the centreline of each ribbon.

A slitting mechanism is provided for cutting the web into two or three separate ribbons before it enters the folder, depending on whether the press is a double or triple width press. Without further intervention, the press is inflexible because each printing unit contributes the same number of ribbons to each former and the ribbons from each former, held together by their longitudinal folds, form discrete sections of a newspaper. Therefore, a triple-width press would produce a newspaper divided into three equal sections. In practice, newspaper publishers require flexibility in the number of sections into which a newspaper is divided as well as in the number of pages within each section.

Improved flexibility is achieved by the use of a turner bar module situated after the slitting mechanism so as to laterally shift one or more ribbons so that multiple ribbons can be fed through the same former, thereby enabling sections of different page numbers to be produced. A turner bar module comprises one or more rollers around which a ribbon may be wrapped. If₅ for example, the roller has its longitudinal axis at 45 degrees relative to the direction of travel of the ribbon, the ribbon will be turned through an angle of 90 degrees as a result of being wrapped around it.

In conventional printing presses, the slitting mechanism for cutting the webs into individual ribbons is mounted on, or close to, the folder so that webs, which have travelled up through each print unit and laterally across the press towards the folder, arrive at the first roller in the folder intact. The webs are then slit into ribbons immediately prior to entry of the ribbons into separate formers. Some of the ribbons may pass through a turner bar arrangement between the slitting mechanism and the formers to shift ribbons from one former to another and therefore change the number of broadsheet pages formed over each former. More recently, it has been proposed to provide each print unit with its own associated turner bar module and slitting mechanism so that a web associated with a particular print unit is slit into two or more ribbons, some or all of those ribbons being turned into their required orientation by wrapping them around rollers of the turner bar module immediately after they exit the print unit and before they travel laterally across the press towards the folder. It will be appreciated that, by providing each print unit with its own turner bar module and slitting mechanism, the flexibility of the printing press can be improved because the ribbons can be fed via different routes to the same or different folders. This effectively allows a double width press to function as a single width press for each slit ribbon, thereby offering greater control of lateral and longitudinal ribbon position for improved image alignment of the finished product. However, at the same time the web-up procedure or, more specifically, the pre- preparation of the press prior to initiating a print run in which the print medium is fed along its intended path through the press and across to the folder, is considerably more complicated because each ribbon must be fed along its respective path between each print unit and its designated folder and former within that folder, rather than simply feeding a single web through each print unit all the way to the folder.

The feeding of a web of print medium, such as paper, through the press to the folder is typically achieved by attaching one edge of a triangular shaped drawing member, commonly referred to in the print industry as a "kite", to the leading edge of the print medium on the reel. The kite is made from a material which is stiffer than the print medium but which is sufficiently flexible to enable it to follow the required print medium path through the press to the folder and draw the print medium through the press together with it. The apex of the triangle, remote from the edge, is attached to a strap or rope which is connected to a guiding device forming part of the print press at its opposite end. The guiding device generally comprises a track along which a length of chain is propelled. The strap is attached to the chain via a connecting element so that, as the chain is propelled along the track using drive motors located at intervals along the track, the kite and the web attached to the kite, is pulled through the print unit and across the press to the folder.

Once the web has reached the folder, the kite is detached and the web is then manually fed through the slitting mechanism to cut the web into ribbons. The ribbons are then manually fed around the turner bars and into the required formers in accordance with the appropriate size newspaper that is to be produced. Once all the ribbons have been fed through their respective paths, a print job can be initiated.

It will be appreciated that, when a print unit is provided with its own turner bar module and slitting mechanism, it is not possible to draw the web all the way to the folder using the kite attached to the leading edge of the web, as the web has already been slit into two or three individual ribbons before travelling laterally across the press towards the folder. Therefore, the kite attached to each web must be detached as soon as the web exits its associated print unit and prior to being slit into ribbons so that it can be manually fed through the slitting mechanism, around the turner bars and each ribbon manually taken across to, and fed into, the folder by the press operator. It will be appreciated that this process is very labour intensive and significantly increases press set-up time.

The present invention seeks to overcome or substantially alleviate the problem referred to above and enable relatively quick web-up times even when individual webs are slit into ribbons as they leave their respective print units and before they travel across the press to the folder. More specifically, the present invention seeks to provide a press in which individual ribbons of a web which has been slit by a slitting mechanism associated with a print unit are all guided across to the folder with little or no manual intervention.

According to the invention, there is provided a printing press comprising a print unit and a slitting mechanism associated with the print unit for slitting a web of print medium into a plurality of longitudinal ribbons as the web leaves the print unit, the printing press also comprising a folder spaced from the print unit to receive ribbons cut by the slitting mechanism at the print unit, wherein the printing press include means for guiding a web of print medium through the print unit during a web-up procedure prior to initiation of a print run, said guide means also being operable to separately guide each ribbon from the print unit to the folder.

In a preferred embodiment, the printing press comprises a turner bar module associated with the print unit for changing the relative positions of one or more ribbons, said turner bar module being positioned adjacent to the slitting mechanism such that ribbons are turned by the turner bar module prior to travelling toward the folder spaced from the print unit, said guide means also being operable to separately guide each ribbon from the print unit to the folder through the turner bar module.

The turner bar module comprises at least one roller around which a ribbon may pass to change its direction of travel. A track is associated with said path through the turner bar module and extends around said roller so that a ribbon is guided around said roller as a guide element attached to said ribbon is driven along said track.

In one embodiment, the ribbon approaches the roller in a first direction and leaves the roller in a second direction at right-angles to the first direction, the track having a first section extending parallel to said first direction and, a second section extending parallel to the second direction, wherein the track also has an intermediate section that turns through 90 degrees in a plane parallel to the ribbon such that the guide element is being driven along the track in a direction opposite to said second direction before the track turns out of said plane parallel to said ribbon and around said roller. The turner bar module is preferably configured such that each ribbon may be fed via a different ribbon path through the turner bar module, said guide means being operable to guide each ribbon along its respective path.

The slitting mechanism may be configured to slit the web into two ribbons. The guide means preferably comprises a pair of guide elements separately attachable to a leading edge of the web prior to guiding the web through the print unit such that the slitting mechanism slits the web into two ribbons between each guide element to leave one guide element associated with each ribbon.

In another embodiment, the slitting mechanism is configured to slit the web into three ribbons and the guide means comprises three of guide elements separately attachable to a leading edge of the web prior to guiding the web through the print unit such that the slitting mechanism slits the web into three ribbons between guide elements to leave one guide element associated with each ribbon.

Most preferably, the guide means comprises a rigid track associated with each guide element and means movable along each track to which respective guide elements are attachable for driving respective guide elements through the print unit together with die print medium attached thereto.

The guide means is driven along its associated track by a series of motors located at spaced intervals along the length of the track each of which engage the guide means to push it along the track from the reelstand towards the folder.

Each track may advantageously extend from the print unit through the turner bar module to the folder such that, when the web has been slit, each ribbon is guided by its associated guide element through the turner bar module along its respective track to the folder. The track associated with each guide element may extend from the print unit through the turner bar module to the folder via different paths. In one embodiment, the guide means comprises a separate track for every ribbon path through the turner bar module.

In a preferred embodiment, the printing press of the invention comprises control means operable to control the means movable along each track to maintain a substantially constant tension of each ribbon slit from the same web as each ribbon follows a different ribbon path through the turner bar module and from the turner bar module to the folder. The control means may be operable to control the speed of each motor positioned at spaced intervals along the length of the track so as to drive the guide means along the track but to also maintain a constant tension in each ribbon. The drive motors are operable to push said means along the track. Because the motors push the movable means along the track, it is not necessary to pull the leading edge of the web, or ribbons slit from the web, from the folder.

The control means is preferably operable to control the means movable along each track so that the distance travelled by each ribbon fed through different paths in the turner bar module remains substantially the same.

The guide means preferably includes sensors positioned at spaced locations along the length of the track, said sensors being operable to detect the relative positions of the movable means associated with each track and to control the speed of the drive motors associated with each track in dependence on a signal provided by the sensors to vary the relative positions of the movable means of each track.

In one preferred embodiment, the guide elements comprise triangular "kites" and the movable means comprises a chain that travels along said track in response to operation of said drive motors, each kite being attached to a respective chain such that, when the motors drive the chain to push it along the track, a kite and print medium attached thereto is driven through the print unit. The printing press of the invention preferably comprises a plurality of print units each having an associated slitting mechanism and turner bar module for slitting the web into ribbons and for turning one or more ribbons before they pass across the press and into the folder, the ribbons from all the print units meeting prior to entry into the folder.

According to another aspect of the invention, there is provided a method of feeding print medium through a rotary web-offset printing press from a print unit to a folder spaced from the print unit prior to initiating a print job, the method including the step of controlling guide means to guide a web of print medium through a print unit, slitting said web into ribbons as it leaves the print unit and controlling the guide means to separately guide each individual ribbon from the print unit to the folder.

The printing press may include a turner bar module associated with the print unit to turn one or more ribbons after being slit by the slitting mechanism prior to travelling across the printing press to the folder and the method preferably includes the step of controlling the guide means to separately guide each individual ribbon from the print unit to the folder through the turner bar module.

In one embodiment, guide elements are attached to the web and the slitting mechanism slits the web into ribbons between guide elements so that a guide element is associated with each ribbon.

The guide means may comprise a track associated with each guide element and means movable along each track to which respective guide elements are attachable for drawing respective guide elements through the print unit. The method then preferably includes the step of pushing said movable means along its respective track to drive the web through the print unit and the ribbons through the turner bar module and across to the folder. The press of the invention preferably includes control means and the method includes the step of controlling movement of the movable means relative to each other such as to maintain substantially constant tension in the print medium using said control means.

Embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 shows a reel of print medium to which two guide elements have been attached prior to being fed through a print unit of a printing press;

Figure 2 shows a partial view of a track along which a chain is propelled to pull the guide elements and the web through the printing unit;

Figure 3 shows a simplified view of a roller of a turner bar module around which a ribbon extends to change its direction of travel by 90 degrees, together with an associated track for guiding the ribbon around said roller and

Figure 4 is a schematic perspective view of the reelstand, print unit, turner bar assembly and folder which shows the track and web/ribbon path through the press.

As mentioned above, this invention is applicable to a rotary offset printing press 12 comprising one or more print units 13, a reelstand 14 and a folder. Each print unit 13 has its own associated slitting mechanism 16 for slitting the web into two or three ribbons immediately after it leaves the print unit 13. Each print unit 13 may also have its own associated turner bar module 17 for changing the relative positions of each ribbon once the web has been slit so that all or some of the ribbons can be fed to the same former 18 in the folder spaced laterally away from each print unit 13. Although each web is slit into ribbons as it leaves its associated print unit 13 and although each ribbon may take a separate path from the print unit 13 to the folder through a turner bar module 17, the present invention provides guide means which not only guides the web through the print unit but also guides each discrete ribbon from the print unit 13 across to the folder, even when some or all of the ribbons follow different paths. Referring now to Figure 1 or 4, there is shown a reel 1 of print medium such as paper for use in a double width press in which the web is longitudinally slit into two side-by-side ribbons, along a dashed line indicated by "X" in Figure 1, using a slitting mechanism 16 (see Figure 4) prior to passing one or both of those ribbons through a turner bar module 17 (see Figure 4) to change the relative positions of those ribbons. It will be appreciated that the present invention is also applicable to a triple width press in which the web is slit into three ribbons.

As can be seen from Figure 1, two guide elements or kites 3a,3b are attached to the leading edge 2 of the print medium. Attachment of the kite 3 to the leading edge 2 is achieved by conventional means and so no further detail of this aspect will be described here.

The kites are attached to the leading edge 2 such that there is a centrally located gap between them, generally indicated by reference numeral 4 in Figure 1. It will be appreciated that, when the web is slit into two ribbons, along the dashed line indicated by "X", one guide element or kite 3a,3b becomes associated with one ribbon.

Each kite 3 is triangular in shape and has an apex 4a,4b. A strap or rope 5 extends from each apex 4a,4b and is attached to a chain 10 (only part of which is shown in Figure 2) that extends along a track 8 and follows a path through the print unit that the print medium is to follow so that, when the chain 10 is driven along the track 8 in response to operation of drive motors 25 (see Figure 4) at spaced locations along the length of each track, the chain 10 is pushed along the track 8 and the kite 3a,3b and the web attached thereto is drawn through the print unit. In a double width press, there are two tracks 8 each having a chain 10 or other means movable therealong, one for driving each kite 3a,3b and its associated ribbon formed when the web passes through the slitting mechanism, and the track 8 is illustrated by the lines shown with arrow heads in Figure 4. In a triple width press, there are three tracks 8. The tracks 8 are preferably rigid or fixed in position and follow the same path through the print unit. The tracks 8 also extend beyond the print unit to the folder. However, once the web is slit into ribbons, each ribbon may follow a different path to the folder, especially if one or both ribbons are fed through a turner bar module 17 to change the relative positions of each of those ribbons. Each track 8 therefore also follows a different path so that each web can be guided all the way through the print unit 13 and, from the print unit 13, through the slitting mechanism 16 to form ribbons, each ribbon also being separately guided along its own path from the print unit 13 to the folder through the turner bar module 17.

It will be appreciated that a ribbon may follow a number of different paths through the turner bar module 17 depending on the newspaper being produced. Therefore, the track 8 may split into sections that follow different paths between the slitting mechanism 16 and the turner bar module 17 so as to guide the ribbon through any one of the optional paths through the turner bar module 17 exiting towards the desired former 18 in the folder.

When the web is drawn through the print unit 13, the same force must be applied to each guide element and so the printing press is provided with a controller that determines the relative speed and/or position of the chains in each track 8. If it is determined that one chain is moving faster than the other, the motors 25 driving that chain can either be slowed down or, the motors 25 driving the other chain can be speeded up so that buckling of the web is prevented.

Once the web has been slit into two or more ribbons, the same control aspect is required to maintain a substantially constant tension in each ribbon and to control the distance travelled by each ribbon through the press. If each ribbon follows a different path through the turner bar module 17, the friction applied by one or more rollers of the turner bar module to one ribbon may be different to the factional force applied to the other ribbon which may not have been wrapped around any, or as many, rollers of the turner bar module. Furthermore, the chains used to drive the ribbons may have different degrees of free play or slack in them which needs to be compensated. Therefore, the controller monitors the relative positions of each ribbon as it travels from the print unit through the turner bar module 17 and across to the folder and speeds up or slows down one chain relative to the other chain to compensate for, for example, increased friction applied to one ribbon by the rollers of the turner bar module 17, thereby preventing buckling or ripping of the web or ribbons or, slack in the chains.

Monitoring of the relative position of the chain can be carried out by positioning sensors 20 (see Figure 4) at different locations along the length of the track along which the chain is driven. One option is to use an optical sensor 11 (see Figure 2) so that, as the chain 10 or a point in the chain passes the sensor 11, its position is determined which is then fed back as an optical signal to the controller. One such sensor and a partial length of track 8 along which the chain is driven is shown in Figure 2. If these sensors 11, 20 are located at the same relative positions along the length of each track 8, the relative positions of each chain 10 can be determined. If it is found that one chain or guide element is ahead of the other, the motors 25 driving one of the chains 10 can be slowed down or speeded up to bring them back into line so that the ribbons all arrive together at the folder and each have the same tension.

Referring to Figures 3 and 4, it will be appreciated that the turner bar module 17 may comprise a series of rollers 6 and that one or more ribbons may pass over these rollers to alter their direction of travel. One such roller 6 for turning a ribbon 7 through an angle of 90 degrees is shown in more detail in Figure 3. A track 8, along which a guide element is drawn to feed a ribbon through the turner bar module 17 and around the roller 6 is also shown. As shown in Figure 3, the ribbon 7 approaches the roller 6, which has its axis at 45 degrees to the direction of travel of the ribbon 7, in a first direction (indicated by arrow "F" in Figure 3) and leaves the roller 6 in a second direction (indicated by arrow "S" in Figure 3) at right-angles to the first direction F. To enable the ribbon to be fed around the roller 7, the track 8 has a first section 8A which extends parallel to said first direction F and, a second section 8B which extends parallel to the second direction S. The track 8 also has an intermediate section 8C that turns through 90 degrees in a plane parallel to the ribbon 7 such that the guide element is being drawn along the track in a direction (indicated by "O" in Figure 3) which opposite to said second direction S before the track 8 turns out of said plane parallel to said ribbon 7 and around said roller 6 (in a direction "D" in Figure 3). The initial turn of the track 8 in section 8c in the plane of the ribbon 7 means that, once the track turns around the roller, the relationship between the chain and the ribbon edge is maintained.

The aforementioned description relates to the preferred embodiments only and it will be appreciated that modifications may be made that still fall within the scope of the appended claims.

Claims

1. A printing press comprising a print unit and a slitting mechanism associated with the print unit for slitting a web of print medium into a plurality of longitudinal ribbons as the web leaves the print unit, the printing press also comprising a folder spaced from the print unit to receive ribbons cut by the slitting mechanism at the print unit, wherein the printing press includes means for guiding a web of print medium through the print unit during a web-up procedure prior to initiation of a print run, said guide means also being operable to separately guide each ribbon from the print unit to the folder.

2. A printing press according to claim 1, comprising a turner bar module associated with the print unit for changing the relative positions of one or more ribbons, said turner bar module being positioned adjacent to the slitting mechanism such that ribbons are turned by the turner bar module prior to travelling toward the folder spaced from the print unit, said guide means also being operable to separately guide each ribbon from the print unit to the folder through the turner bar module.

3. A printing press according to claim 2, wherein the turner bar module is configured such that each ribbon may be fed via a different ribbon path through the turner bar module, said guide means being operable to guide each ribbon along its respective path.

4. A printing press according to claim 2 or claim 3, wherein the slitting mechanism is configured to slit the web into two ribbons and the guide means comprises a pair of guide elements separately attachable to a leading edge of the web prior to guiding the web through the print unit such that the slitting mechanism slits the web into two ribbons between each guide element to leave one guide element associated with each ribbon.

5. A printing press according to claim 2 or claim 3, wherein the slitting mechanism is configured to slit the web into three ribbons and the guide means comprises three guide elements separately attachable to a leading edge of the web prior to guiding the web through the print unit such that the slitting mechanism slits the web into three ribbons between guide elements to leave one guide element associated with each ribbon.

6. A printing press according to claim 4 or claim 5, wherein the guide means comprises a track associated with each guide element and means movable along each track to which respective guide elements are attachable for drawing respective guide elements through the print unit together with the print medium attached thereto.

7. A printing press according to claim 6, wherein each track extends from the print unit through the turner bar module to the folder such that, when the web has been slit, each ribbon is guided by its associated guide element through the turner bar module along its respective track to the folder.

8. A printing press according to claim 6 or 7, comprising separate drive motors located at spaced locations along the length of the track, said motors being operable to drive said means moveable along the track.

9. A printing press according to claim 7 or claim 8, wherein the turner bar module comprises a roller around which a ribbon may pass to change its direction of travel, wherein a track extends around said roller so that a ribbon is guided around said roller as a guide element attached to said ribbon is drawn along said track.

10. A printing press according to claim 9, wherein the ribbon approaches the roller in a first direction and leaves the roller in a second direction at right-angles to the first direction, the track having a first section extending parallel to said first direction and, a second section extending parallel to the second direction, wherein the track also has an intermediate section that turns through 90 degrees in a plane parallel to the ribbon such that the guide element is being drawn along the track in a direction opposite to said second direction before the track turns out of said plane parallel to said ribbon and around said roller.

11. A printing press according to any of claims 8 to 10, wherein the track associated with each guide element extends from the printing unit through the turner bar module to the folder via a different path.

12. A printing press according to any of claims 8 to 11, wherein the guide means comprises a separate track for every ribbon path through the turner bar module.

13. A printing press according to any of claims 8 to 12, comprising control means operable to control the means movable along each track to maintain a substantially constant tension in each ribbon slit from the same web as each ribbon follows a different ribbon path through the turner bar module and from the turner bar module to the folder.

14. A printing press according to claim 13, wherein said control means are operable to control the means movable along each track so that the distance travelled by each ribbon fed through different paths in the turner bar module remains substantially the same.

15. A printing press according to any of claims 8 to 14, wherein the guide means includes sensors positioned at spaced locations along the length of the track, said sensors being operable to detect the relative positions of the movable means associated with each track and to control the speed of the drive motors associated with each track in dependence on a signal provided by the sensors to vary the relative positions of the movable means of each track.

16. A printing press according to claim 15, wherein the guide elements comprise triangular "kites" and the movable means comprises a chain that travels along said track in response to operation of said drive motors, each kite being attached to a respective chain such that, when the chain is driven along the track, a kite and print medium attached thereto is driven through the print unit.

17. A printing press according to any preceding claim, comprising a plurality of print units each having an associated slitting mechanism and turner bar module for slitting the web into ribbons and for turning one or more ribbons before they pass across the press and into the folder, the ribbons from all the print units meeting prior to entry into the folder.

18. A method of feeding print medium through a rotary web-offset printing press from a print unit to a folder spaced from the print unit prior to initiating a print job, the method including the step of controlling guide means to guide a web print medium through a print unit, slitting said web into ribbons as it leaves the print unit and controlling the guide means to separately guide each individual ribbon from the print unit to the folder.

19. A method according to claim 18, wherein the printing press includes a turner bar module associated with the print unit to turn one or more ribbons after being slit by the slitting mechanism prior to travelling across the print press to the folder, wherein the method includes the step of controlling the guide means to separately guide each individual ribbon from the print unit to the folder through the turner bar module.

20. A method according to claim 19, wherein guide elements are attached to the web and the slitting mechanism slits the web into ribbons between guide elements so that a guide element is associated with each ribbon.

21. A method according to claim 20, wherein the guide means comprises a track associated with each guide element and means movable along each track to which respective guide elements are attachable for drawing respective guide elements through the print unit, the method including the step of driving said movable means along its respective track to push the web through the print unit and the ribbons through the turner bar module and across to the folder.

22. A method according to claim 21, wherein the press includes control means and the method includes the step of controlling movement of the movable means relative to each other such as to maintain substantially constant tension in the print medium.

23. A method according to claim 21, wherein the press includes a plurality of motors associated with, and spaced at intervals along, each track and the method includes operating said motors to drive the movable means along said track.