Abstract:
An apparatus for conveying a recording medium includes first and second rollers which define a common area through which the recording medium is conveyed. The first and second rollers contact the recording medium in the common area and rotate in concert to convey the recording medium from the common area. A cam leverages the second roller to vary an amount of nonzero force applied to the recording medium in the common area.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to conveying a recording medium and, more particularly, to varying an amount of force applied to the recording medium by conveying rollers. 
     Recording media is conveyed using rollers which “pinch” the media to move it to/from an imaging location. Heretofore, the same amount of pinch force was applied by the rollers to convey media regardless of the thickness (and thus the stiffness) of the media. This can result in poorly formed images since different amounts of force may be required to accurately convey “thin” media (on the order of 0.004 inches thick) than to accurately convey “thick” media (on the order of 0.007 to 0.008 inches thick). 
     SUMMARY OF THE INVENTION 
     In general, in one aspect, the invention features an apparatus which conveys a recording medium. The apparatus includes first and second rollers that define a common area through which the recording medium is conveyed. The first and second rollers contact the recording medium in the common area and rotate in concert to convey the recording medium from the common area. A cam leverages the second roller to vary an amount of nonzero force applied to the recording medium in the common area. 
     Among the advantages of the invention may be one or more of the following. By leveraging the second roller, it is possible to vary the amount of force applied to the recording medium based, for example, on the thickness of the recording medium. Thus, when used with an imaging apparatus, the invention makes it possible to form accurate images on recording media of different thicknesses. 
     This aspect of the invention may include one or more of the following features. The common area is defined by surfaces of the first and second rollers. The cam may be movable into plural positions, each of which leverages the second roller differently to change the amount of force. The apparatus may include a bar arranged in a common mechanical coupling with the second roller. The cam is in contact with the bar and is movable relative to the bar to leverage the second roller. The first roller may be a capstan roller and the second roller may be a pinch roller. 
     The apparatus may include a control mechanism for controlling the cam to leverage the second roller. The control mechanism comprises a first gear connected to the cam, a second gear connected to the first gear by a belt which couples motion of the first gear to the second gear, and a lever which mates to a receptacle in the second gear and which is movable to control motion of the second gear. The second gear may include plural receptacles. The lever is capable of mating to each of these receptacles. The lever controls motion of the second gear to apply a first range of force when mated to a first one of the plural receptacles. The lever controls motion of the second gear to apply a second range of force when mated to a second one of the plural receptacles. The apparatus may include mechanical stops arranged relative to the lever for limiting a range of motion of the lever. 
     The apparatus may include a member which is in a common mechanical coupling with plural pinch rollers (including the second roller) and a bar which couples to the member and which is in contact with the cam. The cam is rotatable relative to the bar to leverage the plural pinch rollers via the bar and the member. The apparatus may include a second cam on an opposite side of the member from the first cam, and a second bar which couples to the member and which is in contact with the second cam. The second cam is rotatable relative to the second bar to leverage the plural pinch rollers via the second bar and the member. 
     The apparatus may include a mounting block which is coupled to the second roller, a member which is coupled to the mounting block, and a bar which is coupled to the member and which is in contact with the cam. The cam is rotatable relative to the bar to leverage the second roller via the bar, the member, and the mounting block. The mounting block may include a spring in contact with the member and the second roller for controlling motion of the second roller during leveraging. The apparatus may be part of a laser imaging system. 
     In general, in another aspect, the invention features an apparatus for conveying a recording medium. The apparatus includes conveying means for conveying the recording medium. The conveying means applies an amount of force to the recording medium during conveying. Changing means changes the amount of force. Among the features that may be included in the invention is a controlling means for controlling the changing means manually. 
     Other features and advantages of the invention will become apparent from the following description and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a laser imaging system. 
     FIG. 2 is a perspective view of a pinch roller assembly, including a mechanism which controls an amount of force applied by pinch rollers in the assembly. 
     FIG. 3A is a sectional view of the pinch roller assembly. 
     FIG. 3B is a sectional view of the controlling cam. 
     FIG. 4 is a perspective view of a mechanism for controlling the amount of applied pinch force. 
     FIG. 5 is a side view of the mechanism of FIG.  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a laser imaging system  10 . Laser imaging system  10  includes media supply  11 , capstan roller  12 , pinch roller  14 , and a laser source  15 . System  10  also include electronics (not shown) for controlling the motion of rollers  12  and  14  and optics (not shown) for controlling scanning of laser beam  18  to form images on medium  16 . 
     In operation, recording medium  16  is loaded, from media supply  11 , to a common area  17  between the surfaces of capstan roller  12  and pinch roller  14 . Recording medium  16  may be any type of medium; however, photosensitive metal film is used in this embodiment. Rollers  12  and  14  contact recording medium  16  in common area  17  and rotate in concert (in the directions of arrows  19  and  20 ) to convey recording medium  16  away from common area  17  (in the direction of arrow  21 ). While recording medium  16  is being conveyed in this manner, laser beam  18  is scanned over its surface roughly at plane  22 , thereby exposing recording medium  16 . This exposure changes properties of the recording medium  16  which, when further processed, results in the formation of an image at the points of exposure. 
     During conveying, a pinch force (in the direction of arrow  24 ) is provided to recording medium  16  by pinch roller  14 . Pinch roller  14  is leveraged (i.e., moved) relative to capstan roller  12  (which remains substantially immobile) to vary the amount of this pinch force. Mechanisms for controlling the movement of pinch roller  14  are as follows. 
     Referring to FIG. 2, a view of these mechanisms in a pinch roller assembly  25  is shown. Pinch roller assembly  25  includes plural pinch rollers  26   a  to  26   e,  each of which is mechanically coupled to member  27 . When so coupled, pinch rollers  26   a  to  26   e  move in concert with member  27 , thus moving as a single roller, more or less. Pinch rollers  26   a  to  26   e  contact a single capstan roller (not shown in FIG. 2) when the pinch force is applied (via member  27 , see below); however, multiple capstan rollers may also be used. 
     The mechanical coupling to member  27  is the same for all of pinch rollers  26   a  to  26   e;  therefore, it will only be described with respect to pinch roller  26   a.  Pinch roller  26   a  is coupled to mounting blocks  29   a  and  29   b,  which do not interfere with conveying of the recording medium. These mounting blocks have a common design; therefore, only one mounting block  29   a  is described. Mounting block  29   a  includes a hole  30  which receives a shaft  31  of pinch roller  26   a,  thereby allowing pinch roller  26   a  to rotate relative to mounting block  29   a.  Flanges  32   a  and  32   b  on mounting block  29   a  align with sides  34   a  and  34   b,  respectively, on member  27  to align the mounting block to member  27 . Mounting block  29   a  is fixed to member  27  using screws or the like. 
     Internal to mounting block  29   a  is an assembly comprised of a spring  35  and a plunger  36 . Spring  35  is interposed between member  27  and plunger  36 . Plunger  36  contacts spring  35  and shaft  31 , and moves laterally (e.g., “up” and “down”) relative to pinch roller  26   a  as force is applied to pinch roller  26   a.  Spring  35  restricts the motion of plunger  36  (and thus the motion of pinch roller  26   a  ), while still providing pinch roller  26   a  with some freedom of lateral movement relative to the recording medium during the application of a pinch force. 
     As shown in FIG. 2, pinch roller  26   a,  mounting block  29   a,  and member  27  are in a common mechanical coupling with (L-shaped) bar  39   a.  Bar  39   a  is fixed (via screws or the like) to a side  40   a  of member  27 . A similar such bar  39   b  is fixed to an opposite side  40   b  of member  27 . Bars  39   a  and  39   b  operate identically; therefore, only bar  39   a  is described. 
     In contact with the underside  41  of bar  39   a  is cam  42   a  (bar  39   b  contacts a similar cam  42   b ). Cam  42   a  is movable (that is, rotatable) relative to bar  39   a  to leverage bar  39   a  and, in turn, member  27 , mounting blocks  29   a  to  29   f,  and pinch rollers  26   a  to  26   e.  This leverage causes pinch rollers  26   a  to  26   e  to move into closer (that is, tighter) contact with the capstan roller, thereby increasing the amount of pinch force applied to a recording medium between the pinch rollers and the capstan roller. 
     Referring to FIG. 3, a cut-away view of assembly  25  taken along line  3 A- 3 A (FIG. 2) is shown. Cam  42   a  has a radius which varies relative to its center shaft  50 . This center shaft is rotatable and fixed (to side plate  51 , described below), meaning that center shaft  50  is laterally immobile relative to bar  39   a  but can rotate about its own axis (arrow  52 ). As center shaft  50  and thus cam  42   a  rotates, variations in the radius of cam  42   a  will cause bar  39   a  to move upwards (arrow  54 ) or downwards (arrow  55 ), depending upon which radius of cam  42   a  comes into contact with bar  39   a.  As bar  39   a  moves, so does member  27 , mounting block  29   a,  and pinch roller  26   a,  thereby affecting the amount of pinch force applied to medium  56  by pinch roller  26   a  and capstan roller  57 . 
     For example, if cam  42   a  is rotated to a position where radius  59  is in contact with bar  39   a  (as shown), a low (nonzero) pinch force will result (for use, e.g., with thin recording media) since radius  59  is relatively small. If cam  42   a  is rotated to a position where radius  60  is in contact with bar  39   a,  a higher (nonzero) pinch force will result (for use, e.g., with thick recording media) since radius  60  is relatively large. Cam  42   a  is also provided with a “media loading” radius  61 . This radius is small relative to the remainder of cam  42   a  and, when cam  42   a  is rotated to a position where this radius  61  is in contact with bar  39   a,  a gap (or zero pinch force) will be produced between rollers  26   a  and  57 . This gap is used to load new media to common area  62  between rollers  26   a  and  57 . 
     Referring now to FIG. 4, a control mechanism  64  is shown for controlling cam  42   a  (cam  42   a  itself is not visible in FIG. 4) to leverage pinch rollers  26   a  to  26   e.  Control mechanism  64  is connected to side plate  51 , which is interposed between assembly  25  (FIG. 2) and electro-mechanical devices (not shown) for controlling the rotation of capstan roller  57  (the pinch rollers are passive in that they rotate when capstan roller  57  rotates). 
     Control mechanism  64  includes a master gear  65  and a slave gear  66 , which are mounted to shafts  67  and  69 , respectively, on side plate  51 . Shaft  67  is fixed. Master gear  65  rotates around shaft  67  and slave gear  66  rotates shaft  69  to rotate the cam. Slave gear  66  is mounted on the center shaft (shaft  69 ) of the cam, which protrudes from side plate  51 . A belt  70  connects master gear  65  to slave gear  66 , and thus couples the motion (rotation) of master gear  65  to slave gear  66 . Belt  70  may include teeth (not shown) which mate to corresponding teeth (also not shown) on master gear  65  and slave gear  66 . In operation, rotating master gear  65  causes slave gear  66  to rotate which, in turn, causes the cam to rotate (since slave gear  66  is coupled to the center shaft of the cam). 
     A lever  71  is provided for controlling rotation of master gear  65  manually (and thus for changing the amount of pinching force). Receptacles  72  and  74  (e.g., holes) are provided on an outer portion  75  of master gear  65  for receiving lever  71 . When mated to one of these receptacles, lever  71  is used to control rotation of master gear  65 . 
     As shown in FIGS. 4 and 5, mechanical stops  76   a  and  76   b  are arranged relative to lever  71  for limiting the range of rotation of the lever (and thus of master gear  65 , slave gear  66 , and the cam). Mechanical stops  76   a  and  76   b  and receptacles  72  and  74  are arranged so that, when lever  71  is mated to receptacle  74 , cam  42   a  can be rotated between radius  60  (high pinch force) and radius  61  (media load) (FIG.  3 ); and, when lever  71  is mated to receptacle  72 , cam  42   a  can be rotated between radius  59  (low pinch force) and radius  61 . Thus, by moving lever  71  from one receptacle to another, it is possible to change, and/or control, the amount of the pinch force manually. 
     Other embodiments not described herein are also included within the scope of the following claims. For example, more than two receptacles may be provided on outer portion  75  of master gear  65 . These additional receptacles would provide additional pinch force variations. Lever  71  could be mated to outer portion  75  differently. For example, lever  71  could be mated to a track on outer portion  75  which includes plural slots (similar to a manual gear shift). The lever could be moved along the track into (or out of) these slots to vary the amount of applied force. Such a configuration eliminates the need to remove lever  71  to reset the amount of force. Also, additional radii could be provided on the cam, again to provide further pinch force variations. The invention could be incorporated into a variety of different types of imaging systems using any type of recording medium, and is not limited to the specific configurations set forth above.