Patent Publication Number: US-7708133-B2

Title: Flexible member tensioning

Description:
BACKGROUND 
   Flexible drive members (i.e. “flexible members”), including belts, chains, wires, and cables, are employed in a wide variety of devices to transmit mechanical power. One example of such a device that typically employs at least one flexible member is that of ah inkjet printer, wherein a flexible member can be employed to move and position the print head. 
   A typical flexible member is configured to be coupled, or wrapped at least partially around, one or more pulleys, or rollers, or sprockets, or the like. In order to function properly, at least some tension is generally maintained in the flexible member to prevent various undesirable effects associated with inadequately tensioned flexible members. Such undesirable effects can include slippage of the flexible member relative to the pulleys and the like. 
   Oftentimes, a mechanical power source, such as an electric motor having an output shaft with a pulley attached thereto, is coupled with a flexible member and is employed to drive or circulate the flexible member. In this manner, the mechanical power, and/or motion, produced by such an electric motor can be transmitted by the flexible member to another object or device. 
   Inasmuch as a considerable amount of tension must be maintained in the flexible member in some situations, such as in the case of a smooth or “friction” flexible member, the electric motor output shaft and/or the shaft bearings must be of an adequate size to withstand not only the forces produced by the output power of the motor, but also to withstand the additional forces resulting from the tension in the flexible member. 
   That is, at least in some situations, the force resulting from tension in a flexible member of a given system can have a considerable effect on the required size of the motor for that system. That is, in some systems that employ a tensioned flexible member, the size of a motor employed to drive the flexible member is generally specified front the standpoint of ensuring that the motor bearings and/or motor shaft are not overstressed by the additional forces resulting from the tension in the flexible member. 
   One result of this can be that oversized motors (i.e. motors having excessive power capacity) are utilized in systems employing relatively high-tensioned flexible members simply to ensure that the motor bearings and/or motor shaft are adequate for the forces produced by the tension in the flexible member. This results in inefficient use of motor capacity. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view in which an apparatus in accordance with one embodiment of the present invention is depicted. 
       FIG. 2  is a sectional view taken through the driven roller and the pressure roller of the apparatus depicted in  FIG. 1 . 
       FIG. 3  is another schematic view in which an apparatus in accordance with another embodiment of the present invention is depicted. 
   

   DETAILED DESCRIPTION 
   The present invention, in some embodiments, generally includes apparatus and methods for tensioning flexible member which acts as a drive member in a print head drive system that includes a driven roller that can be configured to be driven by a mechanical power source and that is operationally engaged, or coupled, with the flexible member. The print head drive system can be a portion of an imaging device. Apparatus in accordance with various embodiments of the invention include a pressure roller that is urged into forcible rolling engagement with the driven roller of a print head drive system. The pressure roller can be urged in a direction substantially opposite of the direction of a force imparted on the driven roller as the result of tension in the flexible member. 
   Turning to  FIG. 1 , a schematic view is shown in which an apparatus  100  is depicted in accordance with one embodiment of the present invention. It is understood that only those components essential to the understanding of at least one embodiment of the present invention are shown in the various figures in the interest of clarity. That is, the apparatus  100  can be, for example, a print head drive system. 
   Alternatively, the apparatus. 100  can be, for example, an imaging apparatus of which substantially only the print head drive system thereof is depicted, and in which case at least some conventional components required for the operation of the apparatus as an imaging apparatus have been omitted for clarity. 
   Inasmuch as  FIG. 1  (as well as  FIG. 3  discussed below) is a schematic representation, it is understood that the apparatus depicted thereby can be oriented in a number of possible manners relative to an overall imaging device or other device that incorporates the apparatus depicted in  FIG. 1 . That is, it is understood that  FIG. 1  can be a top view, or a front view, or a side view, depending upon to overall configuration of the device into which the apparatus depicted by  FIG. 1  is incorporated. 
   Still referring to  FIG. 1 , the apparatus  100  can include a chassis  110  on which other components can be operationally supported. For example, a driven roller  120  can be rotatably supported by the chassis  110  as is depicted. The driven roller  120  can be powered, or driven, by a mechanical power source (not shown), such as an electric motor, or the like. That is, although not depicted, a motor or other suitable mechanical power source can be provided so as to be coupled in mechanical power transmitting linkage to the driven roller  120 . 
   The driven roller  120  can have an outer circumferential surface  121  defined thereon, as shown. The driven roller outer circumferential surface  121  can include any of a number of known features, such as flanges, cogs, and the like. That is, the driven roller  120  can be configured in the manner of a cylindrical roller, or pulley. The driven roller  120  can be rotatable about a corresponding axis of rotation  122 . That is, the driven roller  120  is configured to be rotated, or be driven, about the associated axis of rotation  122  as is depicted. 
   The apparatus  100  can also include a driven roller support member  123 . The driven roller support member  123  can be movably supported on the chassis  110 . That is, the driven roller support member  123  can be supported by the chassis  110  such that, on the one hand, the driven roller support member is configured to be movable relative to the chassis, but on the other hand, the driven roller support member is configured to maintain a predetermined orientation of the driven roller relative to the chassis. 
   For example, the driven roller support member  123  can be configured to allow the driven roller axis of rotation  122  to move along a finite, continuous path (not shown), while also preventing any change in alignment of the driven roller axis of rotation. This can be accomplished by way of a number of possible manners. As a specific example, the driven roller support member  123  can be configured in such a manner as to pivot relative to the chassis  110  about an associated pivot point  124 . In this manner, the driven roller axis of rotation  122  can be movable along an arcuate path (not shown) relative to the chassis  110 , while the alignment of the driven roller axis of rotation is held constant. 
   It is to be understood that other configurations of the driven roller support member  123  are possible, although not specifically depicted herein. For example, the rather than being configured to pivot about an associated pivot point  124  that is fixed relative to the chassis  110 , the driven roller support member  123  can be configured in the manner of a device that incorporates a slide mechanism which allows the driven roller axis of rotation  122  to move relative to the chassis  110  along a substantially straight and continuous path (not shown). 
   Regardless of the specific configuration of the driven roller support member  123 , a mechanical power source (not shown) that can be employed to drive the driven roller  120 , as is explained above, can also be supported on the driven roller support member along with the driven roller. Alternatively, such a mechanical power source can be supported by other means. 
   For example, such a mechanical power source can be supported in a substantially fixed position on the chassis  110 , or the like, while the driven roller  120  remains movable relative to the chassis. In the latter situation, a flexible coupling (not shown), or transmission mechanism, can be employed to couple the mechanical power source to the driven roller  120  for mechanical power transmission therebetween while also enabling changes in relative positions with respect to the driven roller and the power source. 
   The apparatus  100  also includes an idler roller  130 . The idler roller  130  can have an outer circumferential surface  131  defined thereon in the manner of the driven roller  120  as is discussed above. That is, the idler roller  130  can generally be configured in a manner substantially similar to that of the driven roller  120  discussed above, although the idler roller is not driven. For example, the idler roller  130  can be configured generally in the manner of typical rollers and/or pulleys. 
   More specifically, the idler roller  130  is supported by the chassis  110  and is configured to be substantially freely rotatable about an associated axis of rotation  132 . The idler roller axis of rotation  132  can be fixed relative to the chassis  110 , as is depicted. However, as is explained below with reference to other embodiments of the present invention, the idler roller axis of rotation  132  can be movable relative to the chassis  110  as in the manner of the driven roller axis of rotation  122  which is discussed above. Moreover, the driven roller axis of rotation  122  can be substantially parallel to the idler roller axis of rotation  132 . 
   The apparatus can further include a carriage  160 . The carriage  160  is movably supported by the chassis  110  and is also configured to traverse back and forth along a given path (not shown) that is substantially fixed relative to the chassis. The carriage  160  can be substantially similar to typical carriages employed in conjunction with conventional imaging apparatus and the like. 
   A print head  170  can be included in the apparatus  100  and can be supported on the carriage  160 , whereby the print head is movable relative to the chassis  110  along with the carriage. The print head  170  is configured to selectively eject ink droplets  171  in a given direction while the carriage is moving relative to the chassis. It is understood that, inasmuch as  FIG. 1  (as well as  FIG. 3  discussed below) is a schematic drawing, the depiction therein of the ink droplets  171  is intended solely to provide assistance in recognition of the print head  170  as a print head. That is, it is understood that the orientation of the ink droplets  171 , and/or the path thereof, relative to the apparatus is not intended to limit the print head  170  to any specific configuration and/or orientation relative to the apparatus and/or to any other device into which the apparatus can be incorporated. 
   The print head  170  can be configured in the manner of typical print heads employed in conjunction with conventional imaging apparatus. Thus, the print head  170  together with various other components of the apparatus  100 , in addition to various components which may not be specifically described and/or depicted herein, can form an image on a sheet of imaging media (not shown), wherein such an image is made up of the ink droplets  171 . Such a process of forming an image from ink droplets  171  projected from the print head  170  can be performed while the print head is traversed back and forth while supported on the carriage  160 . 
   As is also depicted in  FIG. 1 , a guide  180  can be included in the apparatus  100 . The guide  180  can be supported on the chassis  110 , wherein the guide movably supports the carriage  160 , as shown. The guide  180  can include one or more rails or rods  181  on which the carriage  160  is slidably supported. The rails or rods  181  are aligned along a path (not shown) on which the carriage is configured to traverse relative to the chassis  110 . The rails or rods  181  can be supported by one or more support brackets  182  that are in turn supported on the chassis  110 . 
   The apparatus  100  also includes a flexible member  150 . The flexible member  150  is configured to transmit mechanical power as is explained in greater detail below. The flexible member  150  can have any of a number of specific forms including those of a smooth friction belt, or a toothed, or cogged, synchronous belt, or a chain, or a cable, or a wire, for example. Regardless of the specific configuration of the flexible member  150 , the flexible member is operationally engaged, or coupled, with the driven roller  120 , the idler roller  130 , and the carriage  160 . 
   That is, the flexible member  150  is wrapped at least partially about both the driven roller  120  and the idler roller  130  such that at least some tension exists in the flexible member. The term “tension” as used herein is defined as the force within the flexible member when the flexible member is at rest, or static, wherein such force is the result of the relative positions of two or more pulleys or the like with which the flexible member is coupled. That is, the term “tension” is defined herein does not necessarily include stress and/or force within the flexible member that is the result of mechanical power transmission. 
   Still referring to  FIG. 1 , the flexible member  150  can be in contact with the driven roller circumferential surface  121  as well as the idler roller circumferential surface  131 . It can be appreciated that the specific configuration, or type, of flexible member  150  can be a factor in the desired amount of tension in the flexible member. For example, smooth friction belts, regardless of the cross-sectional shape thereof (e.g., flat, round, “V”-shaped), as well as wires and cables, can generally require significantly more tension than synchronous belts (also known as “toothed belts” or “cogged belts”) or chains. 
   Regardless of the specific type or configuration of the flexible member  150 , the manner of operational engagement of the flexible member with the driven roller  120 , the idler roller  130 , and the carriage  160 , is such that a powered rotation of the driven roller  120  can result in circulation of the flexible member  150  about both the driven roller and the idler roller  130 . As is mentioned above, the flexible member  150  is also operationally engaged, or coupled, with the carriage  160  in a manner whereby circulation of the flexible member about the driven roller  120  and about the idler roller  130  results in movement of the carriage relative to the chassis  110 . 
   Thus, more specifically, the manner of the operational engagement, or coupling, of the driven roller  120 , the idler roller  130 , the flexible member  150 , and the carriage  160 , is such that a given amount of mechanical power transmitted to the driven roller from a mechanical power source (not shown) results in rotation of the driven roller, which in turn results in rotation of the idler roller and circulation of the flexible member about the driven roller and the idler roller, which in turn results in movement of the carriage  160  relative to the chassis  110 . 
   As a specific example, the flexible member  150  can be fixedly connected to the carriage  160 , whereby circulation of the flexible member about the driven roller  120  and the idler roller  130  causes movement of the carriage. However, it is to be understood that other means of engagement of the flexible member  150  with the carriage  160  may be employed, wherein the flexible member is not fixedly connected to the carriage, yet movement thereof is caused as the result of circulation of the flexible member about the driven roller  120  and the idler roller  130 . 
   It is to be understood further that the specific circulatory path of the flexible member  150  can be varied. That is, the flexible member  150  can have any of a number of various types and/or shapes of circulatory paths, as long as the flexible member is operationally engaged, or coupled, with the driven roller  120 , the idler roller  130 , and the carriage  160 , such that driven rotation of the driven roller results in movement of the carriage relative to the chassis  110 . 
   With further reference to  FIG. 1 , it is seen that the apparatus  100  includes a pressure roller  140 . The pressure roller  140  is supported by the chassis  110 , and is configured to be substantially freely rotatable relative to the chassis about an associated axis of rotation  142 . Furthermore, the pressure roller  140  can have an associated circumferential surface  141  defined thereon in the manner of the driven roller  120  as is discussed above. 
   As is further seen, the pressure roller  140  is configured to be in forcible rolling engagement with the driven roller  120 . More specifically, the pressure roller  140  can be forced against the driven roller  120  in a manner wherein the driven roller axis of rotation  122  and the pressure roller axis of rotation  142  are substantially parallel to one another. Furthermore, inasmuch as the pressure roller  140  is in forcible rolling engagement with the driven roller  120 , the pressure roller circumferential surface  141  can be in forcible contact with the driven roller circumferential surface  121 . 
   Moreover, a pressure roller support member  143  can be included in the apparatus  100 , and can be employed to movably support the pressure roller  140 . That is, the apparatus  100  can include the pressure roller support member  143  which can be movably supported by the chassis  110  in the manner of the driven roller support member  123  as is described above. For example, the pressure roller support member  143  can be configured to pivot substantially freely about an associated pivot point  144 . In turn, the pressure roller  140  can be supported by the pressure roller support member  143  while also being substantially freely rotatable relative thereto. 
   A biasing member  190  can also be included in the apparatus  100 . The biasing member  190  is configured to urge the pressure roller  140  into forcible rolling engagement with the driven roller. Furthermore, the biasing member  190  can be configured to urge the pressure roller  140  in a direction away from the idler roller  130 . The biasing member  190  can be connected to the pressure roller support member  143  in the manner depicted. That is, the biasing member  190  can be connected between the chassis  110  and the pressure roller support member  143 , whereby the biasing member urges the pressure roller support member, along with the pressure roller  140 , in a given direction relative to the chassis. 
   It is to be understood that the biasing member  190  can have different specific configurations and/or can include different specific components, including that of a mechanical spring, as is specifically depicted in  FIG. 1 . As yet further examples, the biasing member  190  can be substantially in the form of a selectively controllable actuator such as a pneumatically powered actuator, or a hydraulically powered actuator, or an electrically powered actuator. Moreover, a conventional controller (not shown) and associated actuator power source can be included and employed to control the amount of force produced by such a selectively controllable actuator, and thus the tension in the flexible member  150  can be controlled automatically. 
   Thus, with continued reference to  FIG. 1 , the idler roller axis of rotation  132  can have a fixed position relative to the chassis  110 . Conversely, both the driven roller axis of rotation  122  and the pressure roller axis of rotation  142  can be movable relative to the chassis  110  by way of the driven roller support member  123  and the pressure roller support member  143 , respectively. In other words, both the driven roller  120  and the pressure roller  140  can be moved away from the idler roller  130 , while the location of the idler roller remains substantially fixed relative to the chassis  110 . 
   Thus, the flexible member  150  can be wrapped about the driven roller  120  (i.e. coupled therewith) and the idler roller  130  as is shown, while the respective locations of the driven roller and of the pressure roller  140  are movable relative to the location of the idler roller. As is mentioned above, the flexible member  150  can also be connected to the carriage  160  is such a manner that the flexible member is substantially in the form of an endless loop that is stretched, or tensioned, between the driven roller  120  and the idler roller  130 . 
   Such tensioning, or stressing, of the flexible member  150  can be the result of the pressure roller  140  being forcibly urged against the driven roller  120  in rolling engagement therewith by way of the biasing member  190 . That is, the biasing member  190  is configured to produce a force that can be applied to urge the pressure roller  140  against the driven roller  120  so as to move the driven roller away from the idler roller  130 , to thus provide tensioning of the flexible member  150 . 
   Moreover, such a force provided by the biasing member  190  can be set and/or adjusted so as to provide a predetermined level of tension in the flexible member  150 . For example, a level of tension can be determined such that the driven roller  120  can be selectively rotated by application of mechanical power thereto as described above without significant slippage of the flexible member  150  relative to the driven roller. This can result in an associated selective circulation of the flexible member  150  about the driven roller  120  and the idler roller  130 , which in turn can result in selective movement of the carriage  160 , and thus the print head  170 , for production of an image or the like. 
   It is seen from a study of  FIG. 1  that the driven roller  120  can be of a diameter that is substantially the same as a diameter of the idler roller  130 . That is, the driven roller  120  and the idler roller  130  can be substantially of the same overall diameter. Furthermore, as is also seen from a study of  FIG. 1 , the pressure roller  140  can be of a diameter that is smaller than that of the driven roller  120 . However, it is understood that other relative roller sizes can be employed in the alternative. 
   In the example depicted, the driven roller  120  and the idler roller  130  can be substantially the same diameter, and the pressure roller  140  can be of a diameter that is smaller than the diameters of both the driven roller and the idler roller. This can allow the pressure roller  140  to be located substantially between the driven roller  120  and the idler roller  130 , wherein the driven roller axis  122 , the idler roller axis  132 , and the pressure roller axis  142 , are substantially aligned with one another, and wherein the pressure roller does not come into contact with the flexible member  150 . 
   Moving now to  FIG. 2 , a sectional view is shown in which a portion of the apparatus  100  is depicted. Specifically, the sectional view shown in  FIG. 2  is taken through the driven roller axis  122  and the pressure roller axis  142 . As is seen from a study of  FIG. 2 , a driven roller axle pin  125 , or the like, can be employed to rotatably support the driven roller  120  on the driven roller support member  123 . Likewise, a pressure roller axle pin  145 , or the like, can be employed to rotatably support the pressure roller  140  on the pressure roller support member  143 . 
   The flexible member  150  is depicted as being as being at least partially wrapped about, or coupled with, the driven roller  120 . As is further seen, a pair of flanges,  126  can be defined on the driven roller circumferential surface  121 . The flanges  126  can serve to maintain alignment of the flexible member  150  relative to the driven roller  120 . Moreover, the flexible member  150  can be nested between the pair of flanges  126  as is also shown. It is to be understood that the idler roller (shown in  FIG. 1 ) can have defined thereon flanges similar to the driven roller flanges  121 . 
   The pressure roller  140  can have defined thereon a pilot ridge  146 . More specifically, the pilot ridge  146  can be in the form of a raised portion of the pressure roller circumferential surface  141 . The pilot ridge  146  can be configured to substantially nested between the driven roller flanges  126 , while the pressure roller circumferential surface  141  is in forcible rolling engagement, or contact, with the driven roller circumferential surface  121 , as is seen from a study of  FIG. 2 . As can be appreciated, such nesting of the pilot ridge  146  between the flanges  126  can serve to maintain alignment of the driven roller  120  relative to the pressure roller  140 . 
   As is yet further seen from a study of  FIG. 2 , and as is mentioned above, the driven roller axis  122  and the pressure roller axis  142  can be substantially parallel to one another. Moreover, both the driven roller support member  123  and the pressure roller support member  143  can be configured movably support the driven roller  120  and the pressure roller  140 , respectively, such that the driven roller axis  122  and the pressure roller axis  142  remain substantially parallel to one another and remain in a substantially normal orientation relative to at least a portion of the chassis  110 . 
   Turning now to  FIG. 3 , a top view is shown in which an apparatus  200  is depicted in accordance with another embodiment of the present invention. The apparatus  200  can be, for example, a print head drive system. Alternatively, the apparatus  200  can be an imaging apparatus of which substantially only the print drive system thereof is depicted. From a study of  FIGS. 1 and 3 , it is seen that the apparatus  200  can be substantially similar to the apparatus  100 , except for minor differences that are made apparent in the discussion below. 
   More specifically, as is seen from a study of  FIGS. 1 and 3 , the apparatus  200  can include substantially all of the components of the apparatus  100 , except for the pressure roller support element  143 . That is, with regard to the apparatus  200 , an idler roller support member  133  can be included therein while the pressure roller support element  143  of the apparatus  100  can be omitted. In other words, the apparatus  100  can include all of the components of the apparatus  200  except for the idler roller support member  133 , while the apparatus  200  can include all of the components of the apparatus  100  except for the pressure roller support member  143 . 
   Still referring to  FIGS. 1 and 3 , another difference between the apparatus  100  and the apparatus  200  is that the biasing member  190  of the apparatus  100  can be operatively connected to the pressure roller support element  143 , while the biasing member of the apparatus  200  can be operatively connected to the idler roller support element  133 . 
   Moreover, with regard to the apparatus  100 , the pressure roller axis  142  can be movable relative to the chassis  110 , while the idler roller axis  132  can be fixed relative to the chassis. Conversely, with regard to the apparatus  200 , the pressure roller axis  142  can be fixed relative to the chassis  110 , while the idler roller axis  132  can be movable relative to the chassis. It is further noted that with regard to both the apparatus  100  and the apparatus  200 , the pressure roller axis  122  can be movable relative to the chassis  110 . 
   Focusing now on  FIG. 3 , a more detailed examination of the apparatus  200  reveals that the idler roller  130  can be rotatably supported by the idler roller support member  133 . The idler roller support member  133  can, in turn, be movably supported by the chassis  110  such that the idler roller axis  132  is movable relative to the chassis along a given continuous path (not shown). The idler roller support member  133  can be configured in any of a number of possible manners so as to render the idler roller axis  132  movable relative to the chassis  110 . 
   For example, the idler roller support member  133  can be movably supported by the chassis  110  so as to be capable of pivoting about an associated pivot point  134 . In this manner, the idler roller axis  132  can be movable relative to the chassis  110  along an arcuate path of movement (not shown). Alternatively, the idler roller support member  133  can be configured in the manner of a slide device (not shown) so as to enable the idler roller axis  132  to move relative to the chassis  110  along a substantially straight path of movement (not shown). 
   Regardless of the specific configuration of the idler roller support member  133 , the idler roller support member can be configured in a manner such that the idler roller axis  132  is maintained in a substantially constant orientation. That is, for example, the idler roller support member  133  can be configured in a manner such that the idler roller axis  132  is maintained in substantially parallel, alignment with the pressure roller axis  142 , and/or with the driven roller axis  122 . 
   As is mentioned briefly above, the biasing member  190  can be operatively connected with the idler roller support member  133 . More specifically, the biasing member  190  can be operatively connected between the idler roller support member  133  and the chassis  110  as is depicted in  FIG. 3 . In this manner, the biasing member.  190  can exert a force against the idler roller support member  133  such that the idler roller  130  is urged away from the pressure roller  140 . 
   As is also mentioned briefly above, the pressure roller  140  can be rotatably supported on the chassis  110  in a manner such that the pressure roller is rotatable about the pressure roller axis  142 , and wherein the pressure roller axis is substantially fixed relative to the chassis. Furthermore, the driven roller  120  can be rotatably supported by the driven roller support member  123  in a manner such that the driven roller axis  122  is movable relative to the chassis  110  as is described above with respect to the apparatus  100  shown in  FIG. 1 . 
   As is further seen with reference to  FIG. 3 , the flexible member  150  can be at least partially wrapped about, or coupled with, both the driven roller  120  and the idler roller  140 , while the pressure roller  140  is urged into forcible rolling engagement with the driven roller. More specifically, with the pressure roller  140  being rotatably supported by the chassis  110  such that the location of the driven roller axis  122  is fixed relative to the chassis, and with the pressure roller axis  142  being located substantially between and in line with the driven roller axis and the idler roller axis  132 , it can be appreciated that application of a force provided by the biasing member  190  to urge the idler roller support member  133 , and thus the idler roller  130 , away from the pressure roller can cause the flexible member  150  to pull the driven roller  120  against the pressure roller to thus tension the flexible member. 
   With reference now to both  FIGS. 1 and 3 , it is seen that, on the one hand in regard to the apparatus  100 , the biasing member  190  can be employed to urge the pressure roller  140  into forcible rolling engagement with the driven roller  120  to thereby urge the driven roller in a direction away from the idler roller  130 , the location of which remains fixed relative to the chassis. 
   On the other hand in regard to the apparatus  200 , the biasing member  190  can be employed to urge the idler roller  130  away from the pressure roller  140 , the location of which remains fixed relative to the chassis  110 , wherein the driven roller  120  is drawn into forcible rolling engagement with the pressure roller. However, in regard to both the apparatus  100  and the apparatus  200 , the flexible member  150  can be tensioned by a force provided by the biasing member  190 . 
   Thus, inasmuch as it is understood that the driven roller  120  can include various components such as bearings (not shown), shafts (not shown), and the like which are typically associated with conventional rollers and/or pulleys, it can be appreciated from the above discussion with reference to the accompanying figures that the use of the pressure roller  140  in the manner described herein can result in significantly lower levels of stress and strain in such bearings, shafts, and other components that can be associated with the driven roller and/or a mechanical power source (not shown). 
   That is, conventional driven rollers and/or mechanical power sources, in addition to being subjected to stress and strain as the result of torque applied thereto by way of the application of mechanical power, can also be subjected to bending stress and/or shear stress as the result of tension in the flexible member. The combination of such stresses from both the application of mechanical power and tension in the flexible member can have a significant impact on the strength requirements of the various components associated with the driven roller and/or mechanical power source. 
   However, as can be appreciated from the above discussion, the use of the pressure roller  140  as described herein can reduce such strength requirements to a considerable degree because, in accordance with the various embodiments of the present invention, the tensioning force applied to the flexible member  150  by the biasing member  190  can be transferred through the driven roller  120  and to the pressure roller  140  by way of the respective circumferential surfaces  121  and  141  rather than through various shafts and or bearings typically associated with the operation of conventional driven rollers and/or mechanical power sources. Thus, such shafts and/or bearings, in accordance with one or more embodiments of the present invention, can be subjected substantially only to stresses imposed by the application of mechanical power for operational rotation of the driven roller. 
   In accordance with yet another embodiment of the present invention, a method of tensioning a flexible member in an imaging device can include providing a, chassis, a driven roller supported by the chassis, an idler roller supported by the chassis, and a pressure roller. The driven roller and the idler roller are engaged, or coupled, with the flexible member as in the manner described above with regard to the apparatus  100  and  200 . Furthermore, the driven roller is movably supported by the chassis as in the manner described above. 
   Also in accordance with the method, the pressure roller is urged into forcible rolling engagement with the driven roller in facilitation of tensioning of the flexible member. That is, as is described above with regard to the apparatus  100  and  200 , the pressure roller and the driven roller can be forced against one another in rolling engagement therewith, wherein such forcible rolling engagement results in tensioning of the flexible member. 
   In accordance with the method, the forcible engagement of the driven roller and the pressure roller can be accomplished by holding the idler roller in a fixed location while moving the pressure roller into forcible rolling engagement with the driven roller. Alternatively, the forcible engagement of the driven roller and the pressure roller can be accomplished by holding the pressure roller in a fixed location while forcibly moving the idler roller in a direction away from the pressure roller, whereby the driven roller is pulled by the flexible member into forcible rolling engagement with the pressure roller. 
   While the above invention has been described in language more or less specific as to structural and methodical features, it is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.