Method and apparatus for moving a drum into a nip

Abstract

In a printing apparatus a method and apparatus for applying a loading force to a first roller assembly to move a first roller of the first roller assembly into nip engagement with a second roller of a second roller assembly, the first roller assembly having a first fiducial element for locating the first roller and the second roller assembly having a second fiducial element complementary to the first fiducial element for locating the second roller, the first roller assembly being supported by a hook and pin connection engagement that supports a carriage, which carriage supports the first roller assembly for rotation about an axis external to the first roller. Upon applying of a loading force to the first roller assembly along a line which in a planar diagram of the first roller and load force passes between the center of gravity of the combination of the first roller assembly and the carriage and the first fiducial element to create a moment about the axis so that the carriage and the first roller assembly rotate together toward contact of the first fiducial element with the second fiducial element; and upon continuing to apply the loading force, the first fiducial element and the second fiducial element are moved to nest together with the hook and pin arrangement being clear of engagement.

Description

FIELD OF THE INVENTION

The invention relates to electrostatography and more particularly to a method and apparatus for applying a loading force to a roller used in image transfer.

BACKGROUND OF THE INVENTION

In U.S. Pat. No. 6,075,965, issued Jun. 13, 2000, in the names of Tombs et al (the contents of which are incorporated herein by reference) there is disclosed an electrophotographic reproduction apparatus wherein a series of roller separation image forming stations are arranged so that a receiver sheet may be conveyed from station to station to receive color separation images in transfer so that the images arc superposed onto each other to form a composite multicolor image. In the aforesaid application at each color separation station a compliant intermediate transfer drum or roller (ITR) has an electrically conductive core of, for example, aluminum, a relatively thick (1-20 mm) compliant blanket layer is around the core and a relatively thin (2 micrometers-30 micrometers) hard overcoat layer surrounds the blanket layer. The Youngs modulus of the blanket layer is preferably between 0.1 MPa and 10 MPa, and the blanket layer has a bulk volume electrical resistivity preferably between 10 7 -10 11 ohm-cm. The Young's modulus of the overcoat layer is preferably greater than 100 MPa. The ITR forms a nip under pressure with a photoconductive (PC) drum. An electrical bias is impressed upon the ITR of suitable level and polarity to urge a developed toner image on the PC drum to transfer to the surface of the ITR. A receiver sheet is then moved into a second nip between the ITR and a paper transfer roller (PTR) in a timed or registered condition to receive the image in transfer from the ITR. An electrical bias of appropriate level and polarity is provided to the PTR to urge transfer of the toner image to the receiver sheet.

Heretofore, a PC drum and ITR were urged together by controlling the separation of their respective axes and establishing a predetermined interference in their respective radii of which interference is accommodated by the compliancy in the ITR blanket layer. However, this solution is not desirable because accommodation must be made when the machine is not producing prints to separate the PC drum from the ITR to avoid set forming in the ITR. It is, therefore, an object of the invention to provide an improved method and 15 apparatus for establishing an engagement between a pair of drums or rollers in an image transfer relationship that is relatively stable and insensitive to force changes in a system. While load may vary due to inherent “run-out” in the drums, the run out can be minimized through manufacture of the drums and as described herein force variations otherwise present can be inexpensively reduced.

It is a further object of the invention to provide a method and apparatus for ensuring that the engaged position is very repeatable between disengagement and reengagement.

SUMMARY OF THE INVENTION

In accordance with the first aspect of the invention there is provided in a printing apparatus a method of applying a loading force to a first roller assembly to move a first roller into nip engagement with a second roller of a second roller assembly, the first roller assembly having a first fiducial element for locating the first roller and the second roller assembly having a second fiducial element complementary to the first fiducial element for locating the second roller, the first roller assembly being supported by a hook and pin connection engagement that supports a carnage which carriage supports the first roller assembly for rotation about an axis external to the first roller, the method comprising:

applying a loading force to the first roller assembly along a line which in a planar diagram of the first roller and load force passes between the center of gravity of the combination of the first roller assembly and the carriage and the first fiducial element to create a moment about the axis so that the carnage and the first roller assembly rotate together towards contact of the first fiducial element with the second fiducial element; and

continuing to apply the loading force to cause the first fiducial element and the second fiducial element to nest together with the hook and pin arrangement being clear of engagement.

In accordance with a second aspect of the invention, there is provided a printing apparatus comprising:

a first roller assembly including a first roller and a carnage for supporting the first roller assembly;

a second roller assembly including a second roller; the first roller assembly having a first fiducial element for locating the first roller and the second roller assembly having a second fiducial element complementary to the first fiducial element for locating the second roller;

a hook and pin connection engagement that supports the carriage which carriage supports the first roller assembly for rotation about an axis external to the first roller;

a loading force applicator that applies a loading force to the first roller assembly along a line which in a planar diagram of the first roller and load force passes between the center of gravity of the combination of the first roller assembly and the carriage and the first fiducial element to create a moment about the axis so that the carriage and the first roller assembly rotate together towards contact of the first fiducial element with the second fiducial element; and

and wherein upon continued application of the loading force causes the first fiducial element and the second fiducial element to nest together with the hook and pin arrangement being clear of engagement.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings in which:

FIG. 1 is a perspective view of an intermediate transfer roller or drum (ITR) assembly in accordance with the invention;

FIG. 2 is a different perspective view of the ITR drum assembly of FIG. 1 as viewed from a different orientation;

FIG. 3 is a front elevational view of the ITR drum assembly of FIG. 1 illustrating a “spider” structure at the front end of the ITR drum assembly and which spider includes various structures for locating the roller as will be described herein;

FIG. 4 is a rear elevational view of the ITR drum assembly of FIG. 1 illustrating the spider structure at the rear end of the spider,

FIG. 5 is a perspective view of a carnage assembly for supporting 20 the ITR drum assembly of FIG. 1 when the ITR drum assembly is in a disengaged position with the PC drum;

FIG. 6 is a different perspective view of the carnage assembly of FIG. 5 ;

FIG. 7 is a perspective view of the carnage assembly of FIG. 5 combined with the ITR of FIG. 1 supported thereon;

FIG. 8 is a front elevational view of the combined carriage assembly and ITR drum assembly of FIG. 7 ;

FIG. 9 is a schematic side elevational view of a mechanism for applying a load to a roller and illustrating the principal of operation of load to a roller in accordance with the method and apparatus of the invention;

FIG. 10 is a perspective view of one of two identical mechanisms in accordance with the invention for applying a constant load force to a roller or drum in accordance with the invention;

FIG. 11 is a view similar to that of FIG. 10 of the load applying 5 mechanism of the invention but showing a portion cut away to illustrate certain elements hidden in the view of FIG. 10 ;

FIG. 12 is a perspective view of the combined ITR carnage assembly of FIG. 7 and additionally illustrating the two load applying mechanisms of FIG. 10 ;

FIG. 13 is a different perspective view of the subject illustrated in FIG. 12 ;

FIG. 14 is a front elevational view of the combined ITR carriage assembly and load applying mechanism and illustrating the load applying mechanism of FIG. 9 in a disengaged position;

FIG. 15 is a front elevational view of the subject matter of FIG. 14 and illustrating a load being applied in accordance with the invention by the load applying mechanism but before seating of the ITR in the engaged position with the PC drum, the view represents a planer diagram of the rollers and a load force;

FIG. 16 is a front elevational view similar to that of FIG. 15 and FIG. 20 illustrating the ITR in the engaged position with the PC drum,

FIG. 17 is a perspective view of a loading tool for loading the ITR drum assembly to or from the reproduction apparatus;

FIG. 18 is a schematic of an alternative device for applying a load to or roller or drum in accordance with the invention; and

FIG. 19 is a second alternative device for applying a load to a roller or drum in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is described below in the environment of an electrophotographic copier and/or printer. However, it will he noted that, although this invention is suitable for use with such machines it can also be used with other types of electrostatographic copiers and/or printers, such as those which employ electrographic writers as well as with other printing apparatus.

Because apparatus of the general type described herein are well known, the present description will be directed in particular to elements forming part of, or cooperating more directly with, the present invention. An exemplary image forming reproduction apparatus, as described in Tombs et al, that may include a primary image forming member, for example, a photoconductive drum having a photoconductive surface on which a pigmented marking particle image, or a series of different color marking particles images, is formed. In order to form images, the outer surface of the photoconductive drum is uniformly charged by a primary charger such as a corona charging device or other suitable charger such as roller chargers, brush chargers, etc. The uniformly charged surface is exposed by suitable exposure means, such as, for example, a laser or LED or other electro-optical exposure device, or even an optical exposure device for selectively altering the charge on the surface of the drum to create an electrostatic image corresponding to an image to be reproduced. Electrostatic images are developed by application of pigmented marking particles to the image bearing photoconductive drum by a development station. Marking particle images are transferred to the outer surface of the secondary or intermediate image transfer member, for example, an intermediate transfer drum. The intermediate transfer drum, as noted above, includes a metallic conductive core and compliant layer. The compliant layer is formed of an elastomer such as polyurethane or other materials, which have been doped with sufficient conductive material (such as antistatic particles, ionic conducting materials or electrically conducting dopants) to have a relatively low resistivity. As noted in Tombs et al, a series of color producing modules may be provided, each of which modules includes a primary image forming member such as a photoconductive drum and a respective intermediate transfer member that is associated with that primary image forming member for transferring the toner image from the primary image forming member to the transfer member and then from the transfer member to a receiver sheet which is moved from module to module. The movement of a receiver member, which may be assisted in case of a receiver sheet, by a transport web is such that each color image transfer to the receiver member at the transfer of each module formed with the respective intermediate transfer member is a transfer that is registered with the previous color transfer so that a four-color image formed on the receiver member has the colors in registered superposed relationship. Subsequently, the receiver member may be moved to a fuser station to fix the image to the receiver sheet. Alternatively, fixing of the image to the receiver sheet may be simultaneous with transfer of the image to the receiver sheet.

In U.S. patent application Ser. No. 09/474, 352 there is disclosed an electrophotographic document printer and/or copier in which the photosensitive recording element comprises a photoconductive drum assembly having structure for precisely positioning the various image-processing stations relative to the drum was photoconductive surface. The drum assembly generally comprises a photoconductive drum having axles extending from opposite ends thereof along an intended axis of drum rotation and a pair of drum support members referred to as “spiders” that support the drum for rotation. Each of the drum support members has a centrally located bearing for rotatably supporting a drum axle and a plurality of mechanical fiducials (in the form of rounded buttons or “bullets”) extending in an outward direction relative to the drum's axis of rotation. Each of these fiducials is adapted to engage and mate with a complementary fiducial element preferably in the form of a V-notched block, or the like, associated with one of the image-processing stations (e.g., the primary charger station or development station) as the stations are moved from a standby position substantially spaced from the drum surface towards an operative position closely spaced from or actually touching the drum surface. When the respective fiducials of the drum assembly have engaged and become seated in the V-blocks of the processing stations, the operative elements of the processing stations (e.g., the corona wires of tie primary charging station, or the development brush of the toning station) will have become precisely spaced parallel to, and/or exert substantially uniform pressure on, the drum surface over the entire width of the drum.

In use, the above-described ITR drum assembly is mounted between a pair of parallel and vertically extending plates comprising the front and rear walls of the printer frame. An opening in the front plate (as viewed from the front of the printer) enables the drum assembly, as well as most of the image-processing stations, to enter the region between the plates.

With reference now to FIGS. 1 and 2 , an ITR drum assembly is illustrated. The assembly includes a mounting spider 11 f and 11 r on the front and rear respectively of the drum. Terms used to designate front and rear, respectively, of the drum designate front and rear portions of the machine, wherein the axis of the ITR extends from the front to the rear and a process direction for moving an image receiving member, whether it be a continuous web or a discrete sheet is perpendicular to the axis of the ITR. In order to locate the ITR relative to the PC drum, the ITR spiders, which are rigidly connected and integrated with respective front and rear journal bearings through which the roller shaft 15 extends, include fiducial members :in the form of V-blocks 12 l , 12 r that serve as locators for the ITR drum assembly when mounted in a printer and/or copier machine. Each V-block provides two-point contact with a bullet on the PC drum spider, as will be described below, when the two drums are engaged. Each ITR spider also provides a third point contact for locating the ITR in the form of the ITR spider's stop block 20 13 f , 13 r . The ITR, as noted above, includes the compliant blanket having a relatively hard and thin outer coating for receiving the toner image and transferring the toner image from the PC drum to a receiver member. The rail 16 connects the front and rear spiders by mounting holes in the rail onto two studs extending from each spider. A respective screw 16 bf , 16 bb serves to secure the rail to the spider. The rail includes top and bottom tracks 16 ct , 16 cb which extend front to rear of the machine. The rail 16 includes a cutout 16 a which serves as a detent receiving recess for locking the axial position of the ITR when loaded in the machine. As may be seen in FIG. 2 , the rear spider also features an electrical bias connector in the form of male plugs which extend axially from the rear spider. The male plugs are connected to brushes which electrically engage to the ITR to provide an appropriate electrical bias to the ITR for use in transfer of the toner image. The front and rear spiders are rigidly fixed to the loading rail 16 , but the front spider can slightly expand axially relative to the shaft to allow thermal expansion.

With reference now to FIGS. 3 and 4 , the elements of the front and rear spiders, respectively, are more visible there being further identified on each spider the spider push plate 18 f , 18 r , respectively, which are each a rigid ledge-like surface on the spider upon which a force may be impressed.

Reference will now be had with regard to FIGS. 5 and 6 which illustrate the ITR carriage 20 . The ITR carriage supports the ITR drum assembly when the ITR drum and PC drum are not engaged. The ITR carriage 20 includes the front-to-rear extending carriage plate 21 . The plate 21 supports two rows of guide rollers comprising five top and four bottom V-guide rollers 22 t , 22 b , respectively. A pin 23 f , 23 r each supports a hook 24 f , 24 r , respectively, that is rigidly connected to the carriage plate 21 . The hooks extend perpendicular to the plate 21 and away from the ITR drum. The hooks receive the pins, and, effectively, the hooks hang from the pins 23 f , 23 r which mount into the frame. A detent leaf spring 25 is supported on carriage plate 21 at a position to enter a detent recess in the form of latch cutout 16 a when the ITR drum assembly is moved axially a fixed extent. A front leaf spring 26 is mounted on the front hook. This leaf spring engages the frame and biases ITR carriage 20 rearwardly. The back of the carriage plate 21 has mounted thereto a stop rotation bracket 29 that includes a roller bearing 29 a . The roller bearing engages a surface on a thumb screw with lock nut 28 that is connected to the frame. Since the ITR carriage is free to pivot about the pins 23 f , 23 r and pivots due to gravity, the thumb screw 28 provides, through rotation thereof, an adjustable stop position for controlling the amount of pivoting permitted when the ITR is not engaged with the PC drum. As will be noted below, this adjustability of the ITR drum assembly allows for adjustments that facilitate loading and unloading of the ITR drum assembly. A bracket at the rear of the carriage plate supports a pair of high voltage bias connectors (female) 27 for receiving the male electrical bias connectors 17 when connected, and power is applied, thus establishing an electrical bias to the supportive core of the ITR which is electrically isolated from the spiders. The bracket 27 a has hook 24 r formed thereon. With reference now to FIGS. 7 and 8 , there is shown a combination 30 of ITR carriage 20 and ITR drum assembly 10 . The drum assembly 10 is mounted by axially moving the assembly into the machine, as will be described below, with the top and bottom rails 16 ct , 16 cb engaged, respectively, by the respective V-guide rollers 22 t , 22 b . As may be seen in FIG. 8 , the center of gravity of the combination 30 is such that there is a tendency of the combination 30 , which is supported by hooks 24 f , 24 r , to rotate counterclockwise about pins 23 f , 23 r until the roller bearing 29 engages the thumbwheel 28 . The position of the thumbwheel is adjusted to a position that allows full disengagement of the ITR and PC and also orients the ITR carriage to match the orientation of the ITR loading tool carriage to be described below.

The Loading Mechanism

Description will now be had with reference to FIG. 9 , which is a schematic illustration of a mechanism or loading device 100 for applying a fixed load upon the ITR drum either directly or through a mechanical advantage, via a load lever arm 112 . The spring, which is the source of the load force, can be designed to operate in tension or compression but will be described herein operating in compression as the preferred embodiment. In FIG. 9 a mount 101 on the frame is provided for pivotally supporting a double-acting pneumatic cylinder 102 . The mount 101 is connected to the housing of the cylinder 102 by a pivotable connection pin 101 a . The cylinder may, alternatively, be hydraulic fluid instead of air and, thus, generally a fluid acting cylinder. The cylinder need not be double acting but may have a return spring or rely upon the load spring to cause it to return when air is not applied to establish load. The air inputs to the double-acting cylinder are indicated as 102 t , 102 b . The cylinder drives a cylinder rod 103 and bracket 104 downwardly against a stop 106 that is rigidly held by the frame. By providing for the engagement of the bracket 104 with the stop 106 , any minor variations in pressure in the air cylinder are isolated from the compression spring 105 , as long as the pressure in the cylinder is sufficient to retain the engagement of the bracket 104 with the frame stop 106 . The spring 105 is supported in a spring cup 107 that has a threaded center hole on the bottom thereof. A threaded stud 108 is fixed at one end to pivoting cup mounting bracket 110 and is threaded into the threaded centerhole at the bottom of the spring cup 107 . The spring cup is rotated about the threaded stud to adjust the spring force of the spring to a predetermined force level determined previously to generate the loading force at the needle bearing 113 when the spring force is multiplied by the mechanical advantage of the lever arm. A locking nut 109 restrains the spring cup from moving relative to the threaded stud 108 . The cup-mounting bracket is pivotably connected to the load lever arm 112 which is itself pivotably supported at 111 to the frame of the machine. The needle bearing 113 is located at the remote end of the arm 112 and engages a surface 114 of the spider to transmit to the spider on roller 115 any force with appropriate mechanical advantage that is applied by the spring 105 . In addition to providing a mechanical advantage, the use of a lever 112 also allows for positioning of the load applying mechanism at a location so that access to the ITR from the front of the machine is not hampered by this mechanism. The location shown would position the loading mechanism between adjacent ITR drums, it being understood that no conflict with the receiver sheet path is provided, since these load-applying mechanisms are outboard (front and rear) of the receiver sheet path. It is preferred to use two identical load-applying mechanisms, one engaging each spider. A retaining spring 116 is connected between the spring cup and the cylinder rod end bracket, and a spring alignment stud is in the center of the spring 105 to ensure alignment of the spring 105 .

In FIG. 10 the elements illustrated for the load applying mechanism 200 are substantially similar to that described with reference to the schematic of FIG. 9 , except that corresponding parts have 100 added to them. It can be seen that cylinder 202 is mounted on a pivotable bracket 201 that pivots about pivot pin 201 a.

FIG. 11 is a view of the load applying mechanism 200 but showing certain parts cut away to illustrate details of the spring cup 107 b and the threaded stud 208 .

FIGS. 12 and 13 are different perspective views of the combined ITR drum assembly 10 , the ITR carriage 20 and the front and rear load applying mechanisms 200 f , 200 r showing their combination. The load lever arms are each mounted to the frame using screws 221 .

Motion of ITR Drum Engagement

With reference now to FIG. 14 , the ITR combination comprising the combined ITR drum assembly 10 , the ITR carriage 20 and the load applying mechanisms 200 f , 200 r are present (only 200 f being shown), and the surface of the ITR 14 is supported out of engagement with the surface 301 of a PC drum and spider assembly 300 . The ITR combination is supported at the hooks 24 f , 24 r by frame pins 23 f , 23 r and, in this disengaged position, the center of gravity of the ITR combination is such as to cause pivoting of the combination about the frame pins 23 f , 23 r until the roller bearing 29 a engages the thumb screw 28 . In FIGS. 14 , 15 , and 16 , various key points are identified with an ‘E’ for engaged or a ‘C’ for clearance. In FIG. 14 the engaged point E 1 represents, respectively, the engagement of the hooks 24 f , 24 r with the frame pins 23 f , 23 r , which pins now support the ITR combination. The engaged point E 2 represents the engagement of the roller bearing 29 a with the thumb screw 28 . The clearance point C 3 represents a clearance between the spider stop blocks 13 f , 13 r and a respective stop pin 13 s fixed to the frame at the front and rear. The clearance point C 4 shows a clearance between the needle bearing 213 and the spider push plate 18 f (similar clearance provided at the rear spider). The clearance point CS shows a clearance between a bullet on the PC spider (which spider is rigidly connected to the PC drum but allows the drum to rotate), and the V-block 12 f , 12 r (front-to-rear have similar clearance).

With reference now to FIG. 15 , it will be noted that the load applying mechanism has ban activated to cause air under pressure to enter the cylinder and commence engagement (E 4 ) of the needle bearings 213 (front and rear) with the spider push plates 18 f , 18 r . A load line 6 (which is perpendicular to the spider push plate) illustrates the direction of the applied force by the needle bearing that the load line passes between the center of gravity CG of the ITR drum assembly 10 with ITR carriage 20 and the engagement ES of the PC bullets 305 (front-to-rear) with the V-blocks 12 f , 12 r on the ITR's spiders. The load creates a moment (arrow A) around engagement point E 1 so that the ITR combination rotates about E 1 . As soon as the PC spider bullets contact the respective IT spider V-blocks at the upper right edge illustrated, the ITR assembly translates up, riding on the bullet (arrow B) until the bullet nests in the vertex of the “V”. The two hooks 24 f , 24 r now no longer engage the frame pins 23 f , 23 r indicated by clearance C 1 in FIG. 16 . When the bullet rests in the V-block, the applied force of the loading mechanism creates a moment (arrow C) around the PC bullet and the ITR combination now starts to pivot around the PC bullet until the ITR spider stop blocks 13 f , 13 r hit the respective stop bearings 13 s.

In FIG. 16 , there is shown the fully engaged portion of the ITR 14 with the surface 301 of the PC drum. The ITR is located by the ITR spider V 15 block at the PC bullet (ES) and the ITR spider stop blocks 13 l , 13 r engage the respective front and rear frame stop bearings 13 s (E 3 ). The ITR carriage hooks 24 f , 24 r clear one of the respective frame pins 23 f , 23 r (C 1 ), and there is clearance between the carriage stop rotation bracket roller bearing 29 a and the thumb screw 28 that is secured to the frame.

In order to insure proper nip width of the ITR-PC nip, the ITR spider V-blocks are radially adjustable and adjusted and locked in position during factory setup and/or during service. There is an overconstraint condition because of establishment of six points of engagement of the two spiders. This provides extra rigidity to the ITR drum assembly when engaged.

ITR Loading/Unloading

The use of the ITR carriage facilitates loading and unloading of the ITR drum assembly 10 in the reproduction apparatus. With reference now to FIG. 17 , a loading tool 400 comprises front and rear rectangular frames 404 f , 404 r , 30 respectively, each formed of four right angle stock pieces. For similar stock pieces 404 s connect the front and rear frames. The rear frame has mounting holes 505 r , 505 l formed therein. An ITR loading tool carriage 403 is fixed in the tool 400 and oriented and fixed at an angle identical with that to which the ITR carriage supports the ITR drum assembly 10 when the load applying mechanism does not apply its load. When loading or unloading of the ITR arm assembly 10 is to take place, the tool 400 is mounted to the locating studs (not shown) on the reproduction apparatus or machine frame by mounting the rear frame holes 505 r , 505 l onto the locating studs 506 r , 506 l . For unloading, the ITR drum assembly 10 is pulled axially forwardly from the machine, and the ITR rails 16 ct , 16 cb become engaged with the upper and lower V-guide rollers 405 t , 405 b , respectively, supported on the ITR loading tool carriage 403 because there has been kept an alignment of the ITR carriage in the machine at an identical angle to that of the loading tool carriage through adjustment of the position of the thumb screw 28 . Once the ITR drum assembly 10 is completely supported by the loading/unloading tool, the tool may be lifted off the frame studs 506 r , 506 l that support same and moved to carry the ITR drum assembly 10 to a location, such as a bench where it is more convenient to remove the assembly 10 from the tool and place the assembly 10 in a suitable supporting structure. Loading of an ITR drum assembly 10 is by a reverse operation wherein the assembly is placed in the tool 400 with the rail 16 of the assembly 10 supported by the ITR loading tool carriage 403 . The tool 400 is then mounted on the frame loading studs 506 r , 506 l and the ITR drum assembly is moved axially into the machine until the rail 16 engages the ITR carriage V-guide rollers and with further rearward movement of the ITR drum assembly 10 , the male electrical bias connectors engage the female connectors on the carriage and with still further rearward movement of the ITR drum assembly the detent leaf spring 25 enters the latch cutout 16 a to lock the ITR drum assembly 10 in the machine.

With reference now to FIG. 18 , a first alternative loading mechanism embodiment is shown schematically wherein part numbers similar to that of FIG. 9 are identified with a prime. The operation of the embodiment of FIG. 18 is similar to that of FIG. 9 , except that no mechanical advantage is achieved, and the placement of the cylinder towards the front of the machine so as to engage a surface at the front of the ITR drum assembly to which load is to be applied is such that the apparatus provides some restrictions to access at the front of the machine. In both the apparatus of FIG. 9 and the other embodiments using air, some pneumatic source or system and control therefore is provided for controlling injection and exhaustion of air to and from the air cylinder. Overall, control may be overseen by a computer containing a logic and control unit that is programmed in response to machine cycle operation to determine when the ITR drum is to be engaged and held in engagement under pressure with the PC drum and when load is to be removed to allow movement of the ITR drum assembly to its disengaged position.

With reference now to FIG. 19 , a second alternative loading mechanism embodiment is shown schematically wherein an alternative driver mechanism 102 ″ is substituted for the air cylinder driver 102 of FIG. 9 , the mechanism 102 ″ being in the form of a cam being rotated by a motor M under control of the LCU. When a loading force is needed, the cam 102 ″ is rotated by motor M so that its high point drives the end bracket 102 ″ against frame stop 106 ″. The other structures, shown in this figure, are similar to that of FIG. 9 but identified with a double (″).

Still other alternatives include providing of a fixed stop location represented by the adjustable thumbscrew 28 . An adjustable positioning could then be provided for in the loading tool carriage. However, for a machine with multiple image forming modules and thus multiple FIR drum assemblies and FIR carriages, it is preferred to have the adjustable thumb screw stop be provided for the machine's ITR carriages.

In the embodiments of FIGS. 18 and 19 movement of the threaded stud 108 ′, 108 ″ is preferably constrained by suitable structure so that movement is limited to back and forth movement in the vertical direction shown and lateral movement is blocked.

In the various embodiments, the loading force is of a sufficient extent to ensure proper engagement of the bullets with V-blocks, and the spider stop blocks with frame stop bearings. The summation of the forces on the ITR should not overcome this proper engagement. The location of the load line 6 between the center of gravity CG (as diagrammed in FIG. 15 ) and the V-block fiducial insures that the bullet will enter the V-groove as a rotational movement is established about E 1 (the carriage hooks on their respective frame pins). The loading force should not be so large that it deforms the bullet. In still another alternative, the bullet could be on the ITR and the V-block on the PC drum. There may be a need with such modification to change location of the hook engagement E 1 .

The invention has been described with regard to an ITR moving to engage a PC drum, but it is also contemplated that the moveable drum need not be an ITR but could be a photoconductor or other drum in a printing apparatus providing movement or load application in accordance with the teachings herein. The invention has been described in detail with particular reference to preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

                            Parts List
6                           load line
10                          ITR drum assembly
11f, 11r                    spider front/rear
12f, 12r                    V-block front/rear
13f, 13r                    spider stop block
13s                         frame stop bearing
14                          ITR with blanket
15                          ITR shaft
16                          ITR rail
16a                         latch cutout
16bf, 16bb, 16ct, 16cb      screws front/back rail tracks
                            top/bottom
17                          electrical bias connectors -
                            male
18f, 18r                    spider push plate front/rear
20                          ITR carriage
21                          carriage plate
22t, 22b                    V-guide rollers top/bottom
23f, 23r                    frame pin front/rear
24f, 24r                    carriage hook
25                          detent leaf spring
26                          front leaf spring
27                          high voltage bias connectors female
27a                         bracket
28                          thumb screw with lock nut
29                          stop rotation bracket with roller bearing
29a                         roller bearing
30                          combination of ITR carriage 20 and IT
                            drum assembly 10
100, 100′, 100″, 200f, 200r (front/rear load applying mechanism
                            schematic drawing/detailed drawing)
101, 201                    mount for cylinder
101a, 201a                  pivot pin for cylinder mount
102, 102′, 202              double-acting pneumatic
                            cylinder
102t, 102b, 102t′, 102b′,   input-output to pneumatic cylinder
202t, 202b
103, 103′, 203              cylinder rod
104, 104′, 204              cylinder rod end bracket
105, 105′, 205              compression spring
106, 106′, 206              hard stop on frame
107, 107′, 207              spring cup with threaded center hole on the
                            bottom
108, 108′, 208              threaded stud
109, 109′, 209              locking nut
110, 210                    stud mount for load lever arm
112, 212                    load lever arm
113, 113′, 213              needle bearing
114, 114′                   nominal position of engaged
                            spider
115, 115′                   ITR drum and spiders
116, 116′, 216              cup retaining spring
117, 117′                   spring alignment stud
221                         load lever arm mounting
                            screws
300                         PC drum and spider assembly
301                         surface of the PC drum
305                         bullet
400                         ITR drum loading/unloading tool
403                         ITR loading tool carriage
404f, 404r                  frame elements
405t, 405b                  V-guide rollers top/bottom
505r, 5051                  mounting holes at rear of frame
506r, 5061                  loading studs on front frame
Engagement Points
E1                          pivot of carriage assembly Hook
E2                          carriage assembly stop
E3                          spider stop block
E4                          load applying to spider
E5                          PC bullet - spider V-block
Clearance Points
C1                          pivot of carriage assembly Hook
C2                          carriage assembly stop
C3                          spider stop block
C4                          load applying to spider
C5                          PC bullet - spider V-block
CG                          center of gravity of ITR drum
                            assembly and ITR carriage

Claims

1. A method for applying a loading force to a first roller assembly in a printing apparatus to move a first roller into nip engagement with a second roller of a second roller assembly, wherein the first roller has a first fiducial element and the second roller has a second fiducial element that is complementary to the first fiducial element, and the first roller being supported by a carriage for rotation about an axis external to the first roller comprising the steps of:placing the first roller assembly in a first position wherein the first roller is supported by the carriage through a plurality of relatively moveable elements such that the first roller and the second roller are out of nip engagement; moving the first roller into nip engagement with the second roller by applying a loading force to the first roller assembly to create a moment about the axis causing the first roller assembly to rotate into contact between the first fiducial element with the second fiducial element; and applying the loading force to move the first roller assembly into a second position wherein the first fiducial element and the second fiducial element nest together and the plurality of relatively moveable elements are in a second position wherein the first roller is in nip engagement with the second roller and the first roller is not supported by the carriage through the plurality of relatively moveable elements.

2. The method of claim 1 wherein the step of moving further comprises applying the loading force along a line which passes between the center of gravity of the combination of the first roller assembly and the carriage and the first fiducial element.

3. The method of claim 2 wherein the step of moving further comprises applying the loading force in perpendicular to a central axis of rotation of the first roller through the center of gravity of the combination of the first roller assembly and the carriage and the first fiducial element.

4. The method of claim 1 wherein the placing step further comprises the plurality of relatively moveable elements are a pair of relatively moveable elements.

5. The method of claim 4 wherein the placing step further comprises the pair of relatively moveable elements being a hook and pin arrangement.

6. A printing apparatus comprising:a first roller assembly including a first roller having a first fiducial element; a carriage for supporting the fist roller assembly; a second roller assembly including a second roller, the second roller assembly having a second fiducial element complementary to the first fiducial element for locating the first roller in nip engagement with the second roller; a plurality of relatively moveable elements supporting the carriage in a first position and allowing for rotation about an axis external to the first roller; a loading force applicator that applies a loading force to the first roller assembly to create a moment about the axis rotating the carriage and the first roller assembly such that the first fiducial element contacts the second fiducial element; and a second position of the relatively moveable elements resulting from the loading force when the first fiducial element and the second fiducial element nest together and wherein the plurality of relatively moveable elements are not supporting the first roller.

7. The apparatus of claim 6, wherein the plurality of relatively moveable elements further comprises a pair of relatively moveable elements.

8. The apparatus of claim 7 wherein the pair of relatively moveable elements further comprises a hook and pin connection arrangement.

9. The apparatus of claim 7, wherein the loading force applicator applies the loading force such that the loading force passes the center of gravity of the combination of the first roller assembly and the carriage and the first fiducial element.

10. The apparatus of claim 7, further comprising the loading force applicator applying the loading force such that it is perpendicular to an axis of rotation for the first roller.