You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to an automatic original feeding apparatus mounted on an image forming apparatus such as a printer or a copier.  
           [0003]    2. Description of the Related Art  
           [0004]    There are known image forming apparatuses such as printers and copiers having an automatic original feeding apparatus mounted thereon.  
           [0005]    This automatic original feeding apparatus is openably and closably mounted on the upper surface of the main body of the image forming apparatus on which platen glass is disposed, and is designed to assume a closed position for covering the platen glass and an opened position in which it has been raised upwardly. The automatic original feeding apparatus has its closed position or opened position selected depending on whether an original used for image formation is a sheet-like one or a found one such as a book.  
           [0006]    [0006]FIG. 9 of the accompanying drawings shows a hinge (rotary supporting mechanism)  50  for openably and closably supporting the main body of the automatic original feeding apparatus relative to the main body of the image forming apparatus. The hinge  50  comprises a cam  53  fixed to the main body  1  side of the image forming apparatus, and a hinge frame  51  fixed to the main body  2 A side of the automatic original feeding apparatus, the cam  53  and the hinge frame  51  being rotatably connected together by a rotary shaft  52 . The hinge  50  further comprises a spring (compression spring)  56  interposed between a housing  55  positioned on the hinge frame  51  through a slide shaft  61  and another housing  54  slidably supported by the hinge frame  51 . The housing  54  is urged against the cam  53  by the spring  56  and conversely, the main body  2 A of the automatic original feeding apparatus is biased counter-clockwisely about the rotary shaft  52  by the cam  53  through the spring  56 . The rotational force of the main body  2 A of the automatic original feeding apparatus about the rotary shaft  52  which is attributable to the gravity thereof is offset by this biasing. Therefore, the opening and closing operation of the main body  2 A of the automatic original feeding apparatus becomes light. The spring  56  has its spring length gradually extended to decrease its biasing force by the housing  54  moving after the cam  53  as the main body  2 A of the automatic original feeding apparatus is opened. This corresponds to the fact that the rotational force by the gravity becomes smaller as the opening angle of the main body  2 A of the automatic original feeding apparatus becomes greater. That is, design is made such that at whatever position the main body  2 A of the automatic original feeding apparatus may be opened, the rotational force by the gravity and the rotational force by the spring  56  are substantially offset by each other.  
           [0007]    Also, Japanese Patent Application Laid-Open No. 54-50319 discloses an adjusting mechanism capable of adjusting the compressive force of a spring in accordance with the gravity of an original pressure plate provided on the upper portion of the main body of a copier and capable of being stopped at a predetermined angle for the hinge member of the original pressure plate.  
           [0008]    However, according to the above-described automatic original feeding apparatus  2 , for example, one used in a high-speed image forming apparatus great in the number of developed sheets per unit time is heavy and accordingly, as the spring  56  used in the hinge  51 , use is made of one strong in spring force. Therefore, the unevenness of the spring force becomes great or the spring force is varied by long-period use. There has also been the problem that when the spring force strengthens, the closed position of the automatic original feeding apparatus deviates relative to the main body of the image forming apparatus and the automatic original feeding apparatus becomes incapable of being disposed at a regular position, and when conversely the spring force is too weak, the automatic original feeding apparatus will fall if it is released in its half-opened state.  
           [0009]    Also, the compression spring adjusting mechanism disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 54-50319 has suffered from the problem that when a driver or the like is to be inserted into a groove formed in the rear end of an adjusting screw and be rotated to thereby adjust the compressive forced of the spring, a very great force is required and the working property of the adjusting work is bad. Also, a very great force is applied to the groove formed in the rear end of the adjusting screw, and this has led to the possibility of damaging the adjusting screw.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention has been made in view of the above-noted circumstances and has as its object to provide an automatic original feeding apparatus of which the opening and closing relative to the main body of an image forming apparatus can be done well and in which the adjustment of a biasing force for assisting good opening and closing can be effected simply, and an image forming apparatus provided with the same.  
           [0011]    The present invention for achieving the above object is an automatic original feeding apparatus mounted on the main body of an image forming apparatus for conveying an original to a predetermined position in the main body of the image forming apparatus, characterized by the provision of an automatic original feeding apparatus main body and rotary supporting means for openably and closably mounting the automatic original feeding apparatus main body relative to the main body of the image forming apparatus, the rotary supporting means including an opening and closing mechanism interposed between the main body of the image forming apparatus and the automatic original feeding apparatus main body and permitting the rotating operation of the automatic original feeding apparatus main body relative to the main body of the image forming apparatus, and a plurality of biasing members for biasing the automatic original feeding apparatus main body so as to offset the rotational force by the gravity thereof, at least one of the biasing members having an adjusting mechanism for adjusting the biasing force thereof.  
           [0012]    Also, the present invention is the above-described automatic original feeding apparatus characterized in that the opening and closing mechanism has an immovable member fixed to the main body side of the image forming apparatus, a movable member fixed to the automatic original feeding apparatus main body side, and a rotary shaft for rotatably connecting the movable member to the immovable member.  
           [0013]    Also, the present invention is the above-described automatic original feeding apparatus characterized in that the biasing members are interposed between the immovable member and the movable member.  
           [0014]    Further, the present invention is an image forming apparatus provided with automatic original feeding means for conveying an original to a predetermined location in the main body of the image forming apparatus, reading means for reading the image information of the original conveyed to the predetermined location, and image forming means for forming an image on a sheet material on the basis of the image information read by the reading means, characterized in that the automatic original feeding means is the above-described automatic original feeding apparatus. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a longitudinal cross-sectional view schematically showing the construction of the main body of an image forming apparatus.  
         [0016]    [0016]FIG. 2 is a longitudinal cross-sectional view schematically showing the construction of the main body of an automatic original feeding apparatus.  
         [0017]    [0017]FIG. 3 is a top plan view of the image forming apparatus.  
         [0018]    [0018]FIG. 4 is a partly broken-away left side view of an automatic original feeding apparatus in Embodiment 1 in its closed state.  
         [0019]    [0019]FIG. 5 is a partly broken-away left side view of the automatic original feeding apparatus in Embodiment 1 in its opened state.  
         [0020]    [0020]FIG. 6 is a longitudinal cross-sectional view of a hinge when an automatic original feeding apparatus in a reference example is in its closed state.  
         [0021]    [0021]FIG. 7 is a longitudinal cross-sectional view of a hinge when the automatic original feeding apparatus in Embodiment 1 is in its opened state.  
         [0022]    [0022]FIG. 8 is a longitudinal cross-sectional view of a hinge when an automatic original feeding apparatus in Embodiment 2 is in its opened state.  
         [0023]    [0023]FIG. 9 is a longitudinal cross-sectional view of a hinge when an automatic original feeding apparatus according to the prior art is in its closed state. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    Some embodiments of the present invention will hereinafter be described with referenced to the drawings.  
         [0025]    An image forming apparatus according to the present invention is provided with the main body of the image forming apparatus and an automatic original feeding apparatus. The main body of the image forming apparatus, the automatic original feeding apparatus and the opening and closing mechanism of the automatic original feeding apparatus which is the characteristic portion of the present invention will hereinafter be described in the named order.  
         [0026]    [0026]FIG. 1 shows an example of the main body  1  of the image forming apparatus (hereinafter simply referred to as the main body of the apparatus). FIG. 1 is a longitudinal cross-sectional view of the main body  1  of the apparatus along the conveying direction of a sheet material P.  
         [0027]    As shown in FIG. 1, the main body  1  of the apparatus is provided with an image forming portion  11 , a feeding and conveying portion  12  and a fixing portion  13 .  
         [0028]    The image forming portion  11  has a photosensitive drum  11   a  as an image bearing member, and a primary charger (charging means)  11   b , an exposing device (exposing means)  11   c , a developing device (developing means) lid, a transfer separation charger (transfer separating means)  11   e  and a cleaner (cleaning means)  11   f  disposed substantially in succession along the direction of rotation (clockwise direction in FIG. 1) of the photosensitive drum  11   a.    
         [0029]    Such an image forming portion  11  uniformly charges the surface of the photosensitive drum by the primary charger  11   b , and effects exposure conforming to image information by the exposing device  11   c  to thereby form an electrostatic latent image. Further, it causes a toner to adhere to the electrostatic latent image by the developing device  11   d  to thereby develop the electrostatic latent image as a toner image, and thereafter transfers the toner image onto the sheet material P (e.g. paper) by the transfer separation charger lie, and separates this sheet material P from the surface of the photosensitive drum. On the other hand, the surface of the photosensitive drum  11   a  after the transfer of the toner image has any residual toner thereon removed by the cleaner  11   f  and is used for the next image formation.  
         [0030]    The whole of the image forming portion  11  forms a toner image on the surface of the sheet material P in conformity with the image information.  
         [0031]    The feeding and conveying portion  12  has, substantially in succession from the upstream side with respect to the conveying direction of the sheet material P, a feed deck  12   a , feed cassettes  12   b , feed rollers  12   c , conveying rollers  12   d , conveyance guide  12   e , registration rollers  12   f , a conveying belt  12   g , discharge rollers  12   h  and a re-conveying mechanism  12   i.    
         [0032]    Such a feeding and conveying portion  12  feeds the sheet materials P stacked on the feed deck  12   a  or contained in the feed cassettes  12   b  one by one by the feed roller  12   c , and conveys the sheep material P to the registration rollers  12   f  along the conveyance guide  12   e  by the conveying rollers  12   d . The registration rollers  12   f  once stops the sheet material P conveyed thereto, and thereafter supplies it to the photosensitive drum  11   a  in timed relationship with the toner image on the photosensitive drum  11   a . The conveying belt  12   g  conveys the sheet material P after the transfer of the toner image thereto the fixing portion  13 , and the discharge rollers  12   b  discharge the sheet material P after fixing to an option sorter  14 . When image formation is to be effected again on the sheet material P after the fixing of the toner image, the sheet material P after the fixing of the toner image may be again sent to the image forming portion  11  by the re-conveying mechanism  12   i.    
         [0033]    The fixing portion  13  has a fixing roller  13   a  containing a heater therein, and a pressure roller  13   b  brought into pressure contact therewith from below it.  
         [0034]    Such a fixing portion  13  beats and pressurizes the sheet material P conveyed thereto with an unfixed toner image borne on its surface while nipping and conveying the sheet material P by the fixing nip portion N between the fixing roller  13   a  and the pressure roller  13   b , to thereby fix the toner image on the surface of the sheet material P.  
         [0035]    The main body  1  of the apparatus has been described above.  
         [0036]    The main body  1  of the apparatus of the above-described construction has platen glass  1   a  provided on the upper surface thereof, and is designed to form a toner image on the basis of the image information of an original S placed on the platen glass  1   a . There are two methods of placing the original S on the platen glass  1   a  at this time: one is a method of automatically placing the original by the automatic original feeding apparatus  3 , and the other is a method of opening the automatic original feeding apparatus  3  to thereby enable a user to manually place the original. For example, when the original S is a book or one found as by pasting or staple, the automatic original feeding apparatus  2  cannot be used and therefore, like the latter, design is made such that the user manually places the original.  
         [0037]    The automatic original feeding apparatus  2  will now be described with reference to FIG. 2. FIG. 2 is a longitudinal cross-sectional view along the conveying direction of the original S. The automatic original feeding apparatus  2  in the present embodiment is provided with an automatic original feeding apparatus main body  2 A and a hinge (rotary supporting means)  50 . In the following description, however, the automatic original feeding apparatus main body  2 A will also be called the automatic original feeding apparatus  2  as long as it is not particularly necessary to distinguish between the two.  
         [0038]    As shown in FIG. 2, the automatic original feeding apparatus  2  has a sheet feeding and stacking stand  21 , a shutter  22 , a sheet feeding roller  23 , a separating roller  24 , a separating belt  25 , conveying roller  26 , registration rollers  27 , a conveying belt  30  passed over a conveying drive roller  28  and a conveying driven roller  29 , a train of pressing runners  31 ,  32 ,  33 ,  34 , a sheet discharging flapper  35 , a sheet discharging intermediate roller  36  and sheet discharging rollers  37  disposed substantially in succession from the upstream side along the conveying direction of the original S. The scanner  1   c , the platen glass  1   a  and the sheet discharge tray  1   b  of the main body  1  side of the apparatus are disposed below the above-mentioned conveying drive roller  28 , conveying belt  30  and sheet discharging rollers  37 , respectively.  
         [0039]    The conveyance of the original S and the reading of image information by the automatic original feeding apparatus  2  of such a construction will hereinafter be described.  
         [0040]    The originals S are set on the sheet feeding and stacking stand  21  of the automatic original feeding apparatus  2 . The feeding and conveyance of the originals S are started by an image formation starting signal from the main body  1  of the apparatus. The shutter  22  is first lowered relative to the originals S on the original stacking stand  21  rammed against the shutter  22  and positioned thereby and opens an original conveying path. Thereafter, the sheet feeding roller  23  is lowered onto the originals S, and thereafter is clockwisely rotated to thereby convey the originals S leftwardly as viewed in FIG. 2, and the originals S are separated one by one by the separating roller  24  and the separating belt  25 . The original S separated into one is further conveyed by the conveying rollers  26 , and the leading end of the original arrives at the nip between the registration rollers  27  being stationary. Since the registration rollers  27  are stationary, the original S cannot have its leading end moved forwardly of the nip and has its trailing end pushed and therefore, a loop is formed intermediately thereof. Thereby, the original S is aligned in a direction orthogonal to the conveying direction with its leading end at the registration rollers  27 . That is, the original S, even if it is being skew-fed by sheet feeding, separation, etc., has its skew feeding corrected. After the formation of a predetermined loop, the registration rollers  27  start to be rotated and the conveyance of the original S is continued.  
         [0041]    Also, the conveying belt  30  is resiliently stretched between the conveying drive roller  28  and the conveying driven roller  29  by a spring member or the like. The train of belt pressing runners  31 ,  32 ,  33 ,  34  for pressing the conveying belt  30  against the platen glass  1   a  of the main body  1  side of the apparatus to thereby create a conveying force between themselves and the platen glass are disposed between the conveying drive roller  28  and the conveying driven roller  29  and inside the conveying belt  30 , and a belt pressing roller (not shown) for pressing the conveying belt  30  against the platen glass  1   a  uniformly in the widthwise direction thereof is disposed in a direction perpendicular to the conveying direction of the original.  
         [0042]    At the registration rollers  27 , the original S is conveyed between the conveying belt  30  and the platen glass  1   a  and is stopped at a predetermined position (reading position) on the platen glass  1   a . After the original S has been stopped, the scanner  1   c  is moved rightwardly as viewed in FIG. 2 while applying light to the original S, and receives the reflected light thereof to thereby read the image information of the original S.  
         [0043]    Thereafter, the original S having had its image information read passes from on the platen glass  1   a  to the sheet discharging flapper  35  and passes the sheet discharging intermediate roller  36  and the sheet discharging rollers  37  and is discharged onto the sheet discharge tray  1   b.    
         [0044]    What has been described above is the flow of the conveyance of the original S and the flow of the reading of the image information by the automatic original feeding apparatus  2 .  
         [0045]    The feature of the present embodiment will now be described with reference to FIGS.  3  to  6 . FIG. 3 is a top plan view of the main body  1  of the apparatus and the automatic original feeding apparatus  2  disposed so as to cover the upper surface thereof. In the following description, the “lower side”, the “upper side”, the “left side” and the “right side” in FIG. 3 will be described as the “front side”, the “rear side (back side)”, the “left side” and the “right side”, respectively. The automatic original feeding apparatus  2  in FIG. 3 is partly sectioned in order to show the attached states of the hinges (rotary supporting means)  40  and  50 . The hinges  40  and  50  are attached to the right side and the left side, respectively, on the rear side (back side) of the main body  1  of the apparatus in spaced apart relationship with each other.  
         [0046]    [0046]FIG. 4 is a left side view of the automatic original feeding apparatus  2  and shows the state of the hinge  50  when the automatic original feeding apparatus  2  has assumed a closed position relative to the main body  1  of the apparatus, that is, when the automatic original feeding apparatus  2  has assumed a prone posture so as to cover the upper surface of the main body  1  of the apparatus. On the other hand, FIG. 5 shows the state of the hinge  50  when the automatic original feeding apparatus  2  has assumed an opened position relative to the main body  1  of the apparatus, that is, when the automatic original feeding apparatus  2  has assumed an upright posture relative to the main body  1  of the apparatus. The automatic original feeding apparatus  2  is adapted to be stopped stably by the operational effect of the present embodiment which will be described later without being supported by the user&#39;s hand when it has assumed the closed position as well as when it has assumed the upright position.  
       REFERENCE EXAMPLE  
       [0047]    [0047]FIG. 6 shows a longitudinal cross-sectional view of the hinge  50  in the state of FIG. 4. The hinge  50  will be described as a reference example with reference to FIG. 6. The hinge  50  is rotary supporting means for openably and closably mounting the automatic original feeding apparatus  2  with respect to the main body  1  of the image forming apparatus. The hinge  50  is fixed (fastened) to the automatic original feeding apparatus  2  by a mounting plate  60  constituting a portion of a hinge frame  51 . The hinge  50  is divided into a member (movable member) effecting rotative movement with the automatic original feeding apparatus  2  like the hinge frame  51 , and members (immovable members) fixed to the main body  1  of the apparatus and immovable like a core stand  59  and a cam  53 . The movable member and the immovable members are pivotally (rotatably) connected together by a rotary shaft  52 . A spring (compression spring)  56  as a biasing member which is a construction in the above-described movable member is disposed between independent housings  54  and  55 . The spring  56  acts to widen the space between these housings  54  and  55 , and one housing  55  has its moved position regulated by a sliding shaft  61 , a sliding stand  62  and an adjusting screw (adjusting mechanism)  63 . The sliding stand  62  is moved in the directions of arrow (rightward and leftward directions) in FIG. 6 by adjusting (fastening or loosening) the adjusting screw  63 , and the sliding shaft  61  follows the movement of the sliding stand and therefore, the spring length of the spring  56  can be changed to thereby change the spring force (biasing force) thereof. The other housing  54  is movable until it abuts against the cam  53 . The pressure contact force between the housing  54  and the cam  53  offsets the gravity of the automatic original feeding apparatus  2  and mitigates the operational load with which the user opens or closes the automatic original feeding apparatus. That is, the automatic original feeding apparatus  2  is set such that the gravity thereof acts clockwisely about the rotary shaft  52 , whereas the spring force acts counter-clockwisely by the cam  53  and the spring  56  and the spring force at this time substantially offsets the gravity.  
         [0048]    In the aforedescribed hinge  50 , the adjusting screw  53  for adjusting the acting force thereof can be adjusted from the outside of the hinge  50  by a simple tool or the like. Thereby, the hinge  50  is assembled as a unit and further, after it is connected to the automatic original feeding apparatus  2 , the spring force in the hinge  50 , i.e., the operating force when the automatic original feeding apparatus is opened or closed, is adjustable, and is adjustable even when the operating feeling of the hinge  50  changes after the user has used the apparatus for a long period and therefore, the spring force can be made to become a suitable operating force. While in the foregoing, one hinge  50  only has been described, the other hinge  40  may be of a construction similar to that of one hinge  50  or of a construction having not the adjusting mechanism such as the spring  56 .  
         [0049]    &lt;Embodiment 1&gt; 
         [0050]    While in the above-described reference example, an adjusting mechanism for varying the operating force of the above-described spring is provided for the spring  56  in a hinge  50 , in the present embodiment, two kinds of springs  56  and  57  are juxtaposed in the hinge  50 , and this will now be described with reference to FIG. 7.  
         [0051]    Of the springs  56  and  57  acting on the opening-closing force of the automatic original feeding apparatus  2 , one spring  56  is disposed between the housings  54  and  55 . The housing  55  has its other end regulated by a fixed shaft  71 . The other housing  54  is movable until it abuts against the cam  53 , and the spring  56  acts with a spring force corresponding to a change in the contact resulting from the opening and closing of the automatic original feeding apparatus  2 . The spring  57  has its one end regulated by an adjusting stand  72  and has its other end regulated by the housing  54 . What makes the housing  54  abut against the cam  53  and act is the same as the aforedescribed spring  56 , but the adjusting stand  72  which is one end of the spring  57  is movable for adjustment in the directions of arrow (the rightward and leftward directions) by an adjusting screw to thereby make the acting force of the spring  57  adjustable.  
         [0052]    Usually, the spring provided with an adjusting mechanism is set to a weaker spring force to improve the adjusting work property than the spring not provided with an adjusting mechanism.  
         [0053]    Also, the adjusting screw  73  is operable from the outside of the hinge  50  by a simple tool or the like, whereby the hinge  50  is assembled as a unit and further, after it is connected to the automatic original feeding apparatus  2 , the spring force in this hinge  50 , i.e., the operating force with which the automatic original feeding apparatus is opened or closed, is adjustable, and even if the operating feeling of the hinge  50  changes after the user has used the apparatus for a long period, the operating force is adjustable and can therefore be rendered into a suitable operating force. In addition, in the present embodiment, the adjustment of the adjusting screw  73  can be effected with a smaller force than in the case of the aforedescribed reference example.  
         [0054]    &lt;Embodiment 2&gt; 
         [0055]    This embodiment will hereinafter be described with reference to FIG. 8. In FIG. 8, a hinge  50  is fastened to the automatic original feeding apparatus  2  by a mounting plate  60  provided on a hinge frame  51 , and is divided into a portion (movable portion) effecting rotative movement with the automatic original feeding apparatus  2  and portions (immovable portions) connected to the image forming apparatus and immovable like a core stand  59  and a cam  53 .  
         [0056]    The movable portion and the immovable portions are rotatable connected together by a rotary shaft  52 . As regards the construction in the above-described movable portion, a spring  56  is disposed between independent housings  54  and  55 , and a spring  56  acts to widen the space between these housings  54  and  55 , and one housing  55  has its position regulated by a fixed shaft  71 . The other housing  54  is movable until it abuts against the cam  53 . A housing fixing stand  65  is engaged with the housing  54  and a portion thereof protrudes outwardly of the hinge  50 .  
         [0057]    An adjusting spring  66  is hooked to this protruding portion and contributes to a force which makes the housing  54  abut against the cam  53 . The other end of this adjusting spring  66  is designed to be hooked to the spring hooking portion of a sliding plate  67 . This sliding plate  67  is movable in the directions of arrow (rightward and leftward directions) by a simple tool such as a driver, and by adjusting this sliding plate  67 , it is possible to vary the amount of displacement of the adjusting spring  66  to thereby adjust the spring force. Thereby, the hinge  50  is assembled as a unit and further, after it is connected to the automatic original feeding apparatus  2 , the spring force in the hinge  50 , i.e., the operating force with which the automatic original feeding apparatus is opened or closed, is adjustable, and even if the operating feeling of the hinge  50  changes after the user has used the apparatus for a long period, the operating force is adjustable and can therefore be rendered into a suitable operating force.  
         [0058]    As described above, according to the present invention, provision is made of an adjusting mechanism capable of adjusting the biasing force of a biasing member for biasing the automatic original feeding apparatus main body so as to offset the rotational force by the gravity thereof, whereby even when the biasing force of the biasing member becomes uneven or is changed by the long-period use of the apparatus, the biasing force can be set to a suitable magnitude by the adjusting mechanism and therefore, the opening and closing of the automatic original feeding apparatus main body relative to the main body of the image forming apparatus can be effected well.  
         [0059]    Also, the biasing force which biases the automatic original feeding apparatus main body so as to offset the rotational force by the gravity thereof is set in parallel in a plurality of biasing members, whereby the adjustment can be effected with a small force.

Summary:
An object of the present invention is to provide an automatic original feeding apparatus mounted on the main body of an image forming apparatus for conveying an original to a predetermined location in the main body of the image forming apparatus, which has an automatic original feeding apparatus main body, and rotary supporting device for operably and closably mounting the automatic original feeding apparatus main body with respect to the main body of the image forming apparatus, wherein the rotary supporting device includes an opening and closing mechanism interposed between the main body of the image forming apparatus and the automatic original feeding apparatus main body and permitting the rotating operation of the automatic original feeding apparatus main body relative to the main body of the image forming apparatus, and a plurality of biasing members for biasing the automatic original feeding apparatus main body so as to offset the rotational force by the gravity thereof, and wherein at least one of the biasing members having an adjusting mechanism for adjusting a biasing force.