Adjustable aligner mechanism

Abstract

An assembly is provided for adjustably aligning sheets of material, particularly sheets of print material fed into a printing apparatus. The assembly includes an alignment section adapted to convey the print material in a direction toward the printing apparatus. The alignment section includes first and second guide members for controlling the position of print material passing through the assembly. Each guide member extends generally parallel to the direction toward the printing apparatus. The assembly also includes a control mechanism for adjustably securing the position of the guide members. The control mechanism includes a first and second shaft extending laterally to the first direction. The first guide member is supported by the first shaft and the second guide member is supported by the second shaft. In this way, rotation of the first shaft selectively translates the first guide member longitudinally along the first shaft without translating the second guide member.

Description

The present application claims priority to provisional patent Application Ser. No. 60/674,138, filed Apr. 22, 2005. This earlier filed provisional application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an adjustable aligner mechanism and more specifically a mechanism for handling and aligning sheets of print material.

Alignment and handling mechanisms are commonly used for manipulating sheets of print material, such as paper, in both commercial and consumer applications. Generally, when print material must be cut, folded, printed onto or otherwise altered, an alignment mechanism is desirable. Also, in order to suit customized or unique projects, an alignment mechanism should be adjustable. Preferably, such adjustments are easily performed by an operator making the overall application more efficient. However, once configured for proper alignment, the apparatus must reliably maintain settings throughout even the largest projects. In particular, printing presses require precision when it comes to the position of the print material relative to the impression stamps, plates, cylinders or other image transfer components.

In a printing application, print material is generally conveyed from a stack and fed individually into a press or printing station. When printing on sheets of paper or envelopes, alignment is often performed while transporting the print material between the stack and the printing station. Each piece is moved along a path while being aligned by guides or rails on two opposed lateral edges. The alignment registers the print material in a position that corresponds with the settings of the print station. In order to accommodate print material of different sizes, it is common to provide an alignment and handling mechanism that allows lateral adjustment of the guides or rails relative to the direction of travel along the path.

Traditionally, any adjustments in alignment guides required removal, repositioning and re-securing of the guides. While adjustable laterally, the guides were often limited in the number of positions available for repositioning. Also, even minor adjustment of the guide positions required tools and was time consuming.

Alternatively, the guide members could slide laterally along a shaft or on a track, providing more flexibility in the number of lateral positions. However, many contemporary alignment mechanisms employing such slide configurations are prone to binding orjamming during adjustment, which can result in undesirable delays.

Additionally, it is common to provide guide and/or handling members that maintain a fixed register for the print material. Often, both edge guides adjust laterally in unison maintaining a common centerline register, while accommodating print material of different sizes. Alternatively, one fixed lateral guide provides a common register, with an adjustable opposite lateral guide accommodating print material of varying width. However, maintaining a fixed register position for the print material (i.e., centerline or one side edge) requires the print station to be adjusted relative to that position. Adjusting the print station position between or during print jobs, can be time consuming.

Accordingly, it would be desirable to provide an alignment mechanism with lateral edge guides or rails that are easily adjustable and are not limited in the number of positions in which they can be secured. Also, it is desirable to provide an adjustment mechanism that does not easily jam or make adjustment difficult. Further, it would be advantageous to provide independently adjustable lateral guides. Such independent adjustment would mean that the print material register position could be easily changed without having to adjust setting in the printing station.

SUMMARY OF THE INVENTION

The present invention provides an adjustable aligner for handling sheet material. The aligner may include independently adjustable first and second guide members for adjusting the position of the sheet material.

The present invention provides an assembly for adjustably aligning a sheet of material. The assembly includes an alignment section adapted to convey the print material in a direction toward the printing apparatus. The alignment section includes a first guide member and a second guide member for controlling the position of print material passing through the assembly. Each guide member extends generally parallel to the direction toward the printing apparatus. The assembly also includes a control mechanism for adjusting the position of the guide members. The control mechanism includes a first and second shaft extending laterally to the first direction. The first guide member is supported by the first shaft and the second guide member is supported by the second shaft. In this way, rotation of the first shaft selectively translates the first guide member longitudinally along the first shaft without translating the second guide member.

The present invention further provides an assembly including a frame and an alignment mechanism for controlling the position of print material. The frame includes a first side member, a second side member opposed to the first side member, and a central member disposed between the first and second side members. The alignment mechanism includes a first guide member supported on a first shaft. Rotation of the first shaft causes the first guide member to translate. The first shaft extends between the first side member and the central member. The alignment mechanism also includes a second guide member supported on a second shaft. Rotation of the second shaft causes the second guide member to translate. The second shaft extends between the second side member and the central member. The alignment mechanism further includes a control mechanism with an one actuator linked to at least one of the first and second shafts such that activation of the actuator causes the first shaft to rotate independent of the second shaft.

The present invention also provides an assembly for adjustably aligning a sheet of material. The assembly includes first and second guides for controlling the position of the sheet. The first and second guides are laterally movable independent of each other. The first guide includes a first carriage operatively connected to a first drive and a second carriage is operatively connected to a second drive. The first and second drives are operatively linked together such that operation of one of the first and second drives causes operation of the other of the first and second drives, thereby causing lateral translation of the first and second carriages and the first guide. Additionally, The second guide preferably includes a third carriage operatively connected to a third drive and a forth carriage connected to forth drive. The third and forth drives are operatively linked together such that operation of one of the third and forth drives causes operation of the other of the third and forth drives, thereby causing lateral translation of the third and forth carriages and the second guide.

These and other objectives, features, and advantages of this invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a printing machine having an aligner of the present invention.

FIG. 2 is a top perspective view of the aligner of the present invention.

FIG. 3 is a top perspective view of the aligner with the top paper guides removed and part of a rail in section.

FIG. 4 is a top perspective view of the aligner with the support rails and pusher chain mechanism removed.

FIG. 5 is a top plan view of the aligner of FIG. 4.

FIG. 6 is a cross-sectional view taken along line A-A of FIG. 5.

FIG. 7 is a side elevation view of the aligner of FIG. 4.

FIG. 8 is a top exploded perspective view of a support rail of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a device for aligning and handling sheets of material conveyed from a stack and loaded into an adjacent material handling apparatus. The invention has particular application to print material handling. Sheets of material can include paper, fabric, polymers or other known substrates. Also, traditional sheets of paper, envelopes, card stock, tags or other printable material could be manipulated using the present invention.

Referring to FIG. 1, the printing machine 10 may preferably include a feeder 12 in which printable material 13 such as envelopes or sheets of paper may be stored and fed into the printing process. Adjacent the feeder 12 is an aligner 14 which receives the material from the feeder 12 and guides, aligns and transports it to a printing unit 16. The printable material exits the printing unit 16 to an output table 17. In the printing unit, an image may be formed on the material. The printing unit may be in a form of an offset printer; however, any known printing process may be employed. The feeder and printing unit may be of a type well known in the art.

The aligner 14 of the present invention permits a high degree of adjustability, thereby permitting a user to accurately position the printable material as it is carried into the printing unit. As shown in FIG. 2, in the preferred embodiment, the aligner 14 includes a frame 18 that supports a first pair of carriages 22 and a second pair of carriages 24. The carriages in each pair are aligned with each other along the direction of printable material travel T. Supported on each of the carriage pairs 22 and 24 are elongate support rails 26 and 28 that extend in the direction of the travel of the printable material 13 of the type shown in FIG. 2 and are well known in the art. As shown in FIG. 3, the support rails have an upper surface 26a and 28a upon which printable material 13 may be slidingly supported along the lengths of the rails. The support surfaces 26a and 28a have a lateral extent that supports the sides of the printable material as it travels along the aligner 14.

Referring to FIGS. 3 and 4, the first pair of carriages 22 and the second pair of carriages 24 also each cooperate with first and second pusher mechanisms 27a and 27b. The first pusher mechanism 27a includes sprockets 20a and 20b, which are supported on shafts 29a and 29b respectively. A pusher chain 30 is operably connected to sprockets 20a and 20b and extends between the first pair of carriages 22. The sprockets 20a and 20b allow pusher chain 30 to travel along a linear path over the length of the aligner 14. Carriages 22a and 22b include extended forks 22c and 22d, respectively. The forks 22c and 22d are placed in the circumferential grooves 23a (not shown) and 23b adjacent sprockets 20a and 20b respectively. Translation of the carriages results in the corresponding movement of the sprockets connected thereto along shafts 29a and 29b.

Second pusher mechanism 27b is similar to the first pusher mechanism and includes sprockets 24a and 24b, which are supported on shafts 29a and 29b respectively. A pusher chain 31 is operably connected to sprockets 21a and 21b and extends between the second pair of carriages 24. The sprockets 21a and 21b allow pusher chain 31 to travel along a linear path over the length of the aligner 14. Carriages 24a and 24b included extended forks 24c and 24d, respectively. The forks 24c and 24d are placed in the circumferential grooves 25a (not shown) and 25b adjacent sprockets 21a and 21b, respectively. Translation of the carriages results in the corresponding movement of the sprockets connected thereto along shafts 29a and 29b.

Each of the sprockets 20a, 20b, 21a and 21b, are preferably operably connected to their respective shafts 29a and 29b in a manner that permits the sprockets to translate along the shafts. However, the sprockets are rotationally fixed to at least one of the shafts, such that rotation of the shaft results in rotation of the sprockets and the attached pusher chains. Such a connection may be achieved by having the sprockets keyed to the shaft with the shaft having a longitudinally extending slot. Alternatively, only one of the paired sprockets linked by a pusher chain 20a, 20b and 21a, 21b needs to be keyed to its respective shaft. Thus, only sprockets 20a and 21a or sprockets 20b and 21b, would drive the pusher chain.

Attached to pusher chains 30 and 31 are a plurality of pushers 32 (which includes a base structure not shown in FIG. 3) spaced along their lengths. The pushers include an extending portion 34 that may engage the trailing edge of the printable material 13 and move the material along rails 26 and 28, upon rotation of the pusher chains 30 and 31. Such pushers and chain mechanisms may be of a type well known in the art for transporting sheet-like material such as that disclosed in U.S. Pat. No. 5,964,461, incorporated herein by reference. The first and second pair of carriages 22 and 24 may each include a pusher chain support to help prevent sagging of the chain as it extends between the sprockets. The pushers ride in a longitudinally extending slot 35 created between support rails 26 and 28 and inner guides 26b and 28b. The inner guides 26b and 28b are attached to the first and second pair of carriages, respectively, and assist in supporting the printable material.

In order to further assist in guiding the printable material 13, the first and second rails 26 and 28 each include an elongate edge guide 36 and 38. The edge guides are positioned adjacent the outer edges of the printable material and guide the material during its travel along the length of the support rails. These edge guides may each have a vertical containment wall 36a and 38a providing a surface along which the edge of the printable material may travel toward the printing unit along a directed course. Referring additionally to FIG. 8, edge guide 38 preferably has a flange 41c extending perpendicularly from the bottom of wall 38a. Edge guide 36 has a similar flange. There is preferably no gap between the upstanding walls and the flange in order to prevent an edge of the printable material from becoming jammed. This is preferably achieved by forming each edge guides as a unitary integral piece.

Edge guides 36 and 38 are each adjustably connected to one of the support rails. Preferably, support rails 26 and 28 include a plurality of laterally spaced elongate channels 41 formed therein, and the edge guides are fastened to the support rails with threaded fasteners 41a. Depending on the width of the printable material the edge guide on each support rail may be moved into a different channel 41. The movement of the edge guides provides a user with a great deal of flexibility when aligning the printable material. For example, a printing plate of printing unit 16 may be used to print an image on one size material, and by adjusting the edge guides a different size printable material may be printed with the image without changing the printing plate.

Each support rail 26 and 28 may have printable material supporting surfaces 41b being of the same elevation. Printable material 13 slides on surfaces 41b as it travels along the aligner 14. Printing material supporting surfaces formed by edge guide flanges 41c are preferably positioned below surfaces 41b of rails 26 and 28 when connected in a channel 41 to prevent jamming of printing material 13.

As shown in FIG. 2, the first and second pair of carriages may also support top paper guides 40, which hold the printable material 13 down on the support rails as it travels along the aligner 14. In addition as shown in FIG. 3, frame 18 may include a center support 39 located between the first and second rails. Center support 39 may extend along a length of the aligner and have a lateral extent. Center support 39 supports the printable material along a length between its ends in order to assist the transportation of the material along the aligner 14.

The position of the support rails 26 and 28 and edge guides 36 and 38 determine the position of the printable material as it is fed into the printing unit 16. The present invention provides for independent adjustability of the support rails 26 and 28, thereby permitting the printable material to be properly position. As the sheet of printable material is fed into the printing unit 16 from the aligner 14, it is very important that the material be properly aligned such that the image is printed on the material at the correct position. Failure to properly align a piece of material may result in the printing to be of unacceptable quality.

The aligner 14 of the present invention permits both first 26 and second 28 rails to be independently adjusted in a direction perpendicular to the direction of material travel T. Such independent adjustment allows an operator of the printing machine 10 to effectively adjust the center of the printable material 13 relative to the printing unit 16. In this way, a sheet of printable material 13 can also be run through printing unit 16 more than once in different positions. Thus, with an additional pass through the aligner 14, an image could be transferred to more than one position on a single sheet without having to adjust the printing unit 16. Generally, the independent adjustment provides an operator accurate and selective positioning of the sheet of printable material 13 relative to an image transfer element disposed in the printing unit 16.

Referring to FIGS. 3-7, in order to achieve independent support rail adjustment, the present invention includes a first adjustment mechanism 42 and a second adjustment mechanism 44. Actuation of the first adjustment mechanism 42 causes lateral movement of the first pair of carriages 22 along with the first support rail 26, inner guide 26b, edge guide 36 and pusher chain 30. Actuation of the second adjustment mechanism 44 results in lateral movement the second pair of carriages 24, second support rail 28, inner guide 28b, edge guide 38, and pusher chain 31 attached thereto. In the preferred embodiment, movement of the first adjustment mechanism 42 does not move the second pair of carriages 24. Likewise, actuation of the second adjustment mechanism 44 does not move the first pair of carriages 22.

The first adjustment mechanism 42 includes a first shaft 46 having a threaded portion 48. The first shaft 46 is rotatably supported at one end on center frame member 50 by a bearing 49. The other end of first shaft 46 is rotatably supported on first frame end member 52 by a bearing 47. A portion of the first shaft 46 extends beyond the first frame member 52 and attaches to a sprocket 54. One of the first pair of carriages 22a includes a central opening extending there through aligned with the first shaft 46. A portion of the central opening has female threads 75 which threadedly engaged threaded portion 48 of the first shaft 46. Rotation of the first shaft 46 results in the carriage 22a moving in a lateral direction L perpendicular to the direction of material travel T.

The other carriage of the first carriage pair 22b is supported on a second shaft 57 which is similar to first shaft 46. Second shaft 57 includes a threaded portion 59, which engages internal threads 75 formed on a central opening extending through carriage 22b. One end of the second shaft 57 is rotatably supported in center frame member 50 by a bearing. The other end of second shaft 57 extends through the frame first end member 52 and is rotatably supported by a bearing held in the frame first end member 52. The portion of second shaft 57 extending through the first frame end member 52 includes two sprockets 51 and 53 secured thereto. Rotation of second shaft 57 result in carriage 22b translating in the direction L perpendicular to the motion of the transported printed material.

Since the first support rail 26 is attached to carriages 22a and 22b, it is preferred that the carriages translate in a lateral direction simultaneously. This is preferably achieved by having the first 46 and second 57 shafts rotate simultaneously. In the preferred embodiment, the first and second shafts are operably linked. Simultaneous movement is initiated by the rotation by a user of a first actuation device in the form of a first handle 55. First handle 55 is attached to a post 56 that is rotatably secured in the frame first end member 52. Attached to post 56 is a sprocket 58. A first chain 60 extends between sprocket 58 and sprocket 51. A second chain 62 extends between sprocket 53, secured to second shaft 57 and sprocket 54, which is attached to the end of first shaft 46. Therefore, rotation of first handle 55 causes both the first and second shafts 46 and 57 to rotate simultaneously. This rotation will result in linear movement of the first pair of carriages 22 and the first support rail 26 attached thereto. The pusher chain 30 with pushers 32 secured to sprockets 20a and 20b will also move.

The position of the second support rail 28 is adjusted in a manner similar as that of the first rail 26 by way of the second adjustment mechanism 44. The second pair of carriages 24 is supported on third and forth shafts 72 and 74 that extend from frame center 50 and to and through a frame second end member 76. The third and fourth shafts are preferably rotatably supported by bearings secured to the frame center 50 and frame second end member 76. Third shaft 72 and first shaft 46 are longitudinally aligned, and adjoin the center frame member 50 at generally the same position. These shafts thus rotate on a common axis, but rotate independently of each other. Similarly, the second 57 and forth 74 shafts are longitudinally aligned sharing a common rotational axis, and adjoin at the center frame member 50 at generally the same position. However, these shafts also rotate independently of each other. The third and forth shafts included threaded portions 72a and 74a, respectively. The second pair of carriage members 24a and 24b includes an opening extending there through, and the openings include internally threaded portions 77 that cooperate with the threaded portions 72a and 74a of the third and fourth shafts. Therefore, when the shafts 72 and 74 rotate the carriages 24a and 24b translate in the lateral direction L. Third shaft 72 may include two sprockets 84 and 86 on the end extending through the frame second end member 76. Fourth shaft 74 may include a single sprocket 88 on its end extending through the frame second end member 76.

In the preferred embodiment, the third and fourth shafts are operably linked so that the carriages 24a and 24b move together. Carriages 24a and 24b preferably move simultaneously upon operation by a user of a second actuation device. In the preferred embodiment, second actuation device includes a handle shaft 78 extending from the first end member 52 through the center frame member 50 and through the second frame end member 76. The handle shaft 78 may be rotatably supported on the frame first and second end members by bearings. A second handle 80 may be attached to the end of the handle shaft 78 in order to permit a user to turn shaft 78. Accordingly, both the first 55 and second 80 handles are disposed on the same side of the frame 18 facilitating ease of use by an operator. The end of the handle shaft 78 extending through the frame second end wall includes a sprocket 82. A chain 89 extends between the sprocket 82 and sprocket 86 secured to third shaft. A chain 91 then is attached and extends between third shaft sprocket 84 and fourth shaft sprocket 88. Therefore, rotation of second handle 80 causes the second pair of carriage members, along with the components connected thereto, to translate in the direction L perpendicular to the direction of printable material movement through the aligner.

In addition to the first, second, third, and fourth shafts, in a preferred embodiment in order to provide structural rigidity to the frame, fixed shafts 90 and 92 may be employed running between the first frame end member 52 and second frame end member 76 and extending through openings in the frame center member 50.

In the preferred embodiment, the first and second adjustment device includes chains and sprockets. However, it is within the contemplation of the invention that belts and pulleys and/or other types of mechanical linkages may be employed in order to connect the various shafts. Also, while manual actuators in the form of handles 55 and 80 are shown, it is further contemplated that motorized or automated actuators be integrated into the assembly.

In operation, in order to adjust the aligner 14, an operator would first set the position of one of the support rails. For example, an operator may rotate the first handle 55 which would cause sprocket 58 to turn. Due to the linkage of chain 60, second shaft 57 would rotate along with sprockets 51 and 53. Chain 62 connecting sprocket 53 to sprocket 54 would cause first shaft 46 to turn. Accordingly, both of the first pair of carriages 22a and 22b would translate laterally moving support rail 26, and associated components. Movement of the first pair of carriages 22 can be controlled from side to side by selectively changing the direction of rotation of the handle 55. With the position of support rail 26 set, the operator may then rotated handle 80 to turn handle shaft 78 and the sprocket 82 attached thereto. The linkage created by chain 89 will rotate sprocket 86 and the third shaft 72 secured thereto. Such rotation rotates sprocket 84, which through the linkage to sprocket 88 created by chain 91, turns fourth shaft 74. Therefore, second pair of carriages 24a and 24b move laterally together along with the support rail 28, and associated components, to their desired position. An operator may also adjust the edge guides 36 and 38 into the appropriate channel 41 to accommodate the width of the printable material. This edge guide adjustment may be done either before or after the adjustment of the support rails.

Although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention.

Claims

1. An assembly for adjustably aligning print material fed into a printing apparatus, said assembly comprising:

an alignment section adapted to convey said print material in a first direction toward the printing apparatus, said alignment section including a first guide member and a second guide member for controlling the position of print material passing through said assembly, said first and second guide members extending generally parallel to said first direction; and

a control mechanism for adjusting the position of said guide members, said control mechanism including a first and second shaft extending laterally to said first direction, said first guide member supported by said first shaft, said second guide member supported by said second shaft, whereby rotation of said first shaft selectively translates said first guide member longitudinally along said first shaft without translating said second guide member.

2. The assembly as defined by claim 1, wherein rotation of said second shaft selectively translates said second guide member longitudinally along said second shaft without translating said first guide member.

3. The assembly as defined by claim 1, wherein said control mechanism further includes a third and forth shaft extending laterally to said first direction, said first guide member further supported by said third shaft and said second guide member further supported by said forth shaft.

4. The assembly as defined by claim 3, wherein said control mechanism further includes a first linkage for rotating said first and third shafts in unison.

5. The assembly as defined by claim 1, wherein said first and second guide members each include a print material support surface and a containment wall for limiting lateral movement of said print material, said containment wall extending vertically from said support surface.

6. The assembly as defined by claim 5, wherein said containment wall is removeably attached to said support surface and said support surface includes more than one attachment location for said containment wall.

7. The assembly as defined by claim 1, further comprising:

at least one pusher mechanism for moving said print material, said pusher mechanism is linked to said first guide member and adapted to translate generally laterally to said first direction in unison with said first guide member.

8. The assembly as defined by claim 1, wherein said control mechanism includes a first and second adjustment handle, said first adjustment handle linked to said first guide member and said second adjustment handle linked to said second guide member.

9. The assembly as defined by claim 8, wherein said first and second adjustment handles are both disposed on the same side of the assembly.

10. The assembly as defined by claim 1, wherein said first and second shafts are adapted to rotate on a common axis.

11. An assembly for adjustably aligning a sheet of material comprising:

a frame including a first side member, a second side member opposed to said first side member, and a central member disposed between said first and second side members; and

a first alignment mechanism for controlling the position of the sheet including,

i) a first guide member supported on a first shaft, whereby rotation of said first shaft causes said first guide member to translate, said first shaft extending between said first side member and said central member,

ii) a second guide member supported on a second shaft, whereby rotation of said second shaft causes said second guide member to translate, said second shaft extending between said second side member and said central member, and

iii) a control mechanism linked to at least one of said first and second shafts, said control mechanism including a first actuator whereby activation of said first actuator causes said first shaft to rotate independent of said second shaft.

12. The assembly as defined by claim 11, wherein said control mechanism includes a second actuator whereby activation of said second actuator causes said second shaft to rotate independent of said first shaft.

13. The assembly as defined by claim 11, wherein said first guide member is further supported by a third shaft and said second guide member is further supported by a forth shaft.

14. The assembly as defined by claim 13, wherein said control mechanism further includes a first linkage for rotating said first and third shafts in unison.

15. The assembly as defined by claim 11, wherein said first and second guide members each include a print material support surface and a containment wall for limiting lateral movement of said print material, said containment wall extending vertically from said support surface.

16. The assembly as defined by claim 15, wherein said containment wall is removeably attached to said support surface and said support surface includes more than one attachment location for said containment wall.

17. The assembly as defined by claim 11, further comprising:

at least one pusher mechanism for moving said print material, said pusher mechanism linked to said first guide member and adapted to translate generally in unison with said first guide member.

18. The assembly as defined by claim 11, wherein said control mechanism includes a first and second adjustment handle, said first adjustment handle linked to said first guide member and said second adjustment handle linked to said second guide member.

19. The assembly as defined by claim 18, wherein said first and second adjustment handles are both disposed on the same side of the assembly.

20. The assembly as defined by claim 11, wherein said first and second shafts rotate about a common axis.

21. An assembly for adjustably aligning a sheet of material comprising:

a first and second guide for controlling the position of said sheet, said first and second guides laterally movable independent of each other, said first guide including a first carriage operatively connected to a first drive and a second carriage operatively connected to a second drive, the first and second drives being operatively linked together such that operation of one of said first and second drives causes operation of the other of said first and second drives, thereby causing lateral translation of the first and second carriages and the first guide.

22. The assembly as defined by claim 21, wherein said second guide includes a third carriage operatively connected to a third drive and a forth carriage connected to forth drive, the third and forth drives being operatively linked together such that operation of one of said third and forth drives causes operation of the other of said third and forth drives, thereby causing lateral translation of the third and forth carriages and the second guide.

23. The assembly as defined by claim 21, wherein at least one of said first and second drives includes a threaded shaft whereby rotation of said shaft causes said lateral translation of said first guide.

24. The assembly as defined by claim 21, wherein a mechanical linkage operatively links said first and second drives.

25. The assembly as defined by claim 24, wherein said mechanical linkage includes a chain cooperating with at least one sprocket member.

26. The assembly as defined by claim 24, wherein said mechanical linkage is driven by an actuator for controlling the lateral position of said first guide.

27. The assembly as defined by claim 26, wherein said actuator includes at least one manually operable device.