Patent Publication Number: US-11392055-B2

Title: Developing cartridge including movable cam having first and second inclined surfaces

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a by-pass continuation application of International Application No. PCT/JP2020/005469 filed on Feb. 13, 2020 which claims priority from Japanese Patent Application No. 2019-063301 filed Mar. 28, 2019. The entire contents of the earlier applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a developing cartridge. 
     BACKGROUND 
     Conventionally, there have been known electro-photographic type image-forming apparatuses such as laser printers and LED printers. Such a conventional image-forming apparatus includes a developing cartridge. The developing cartridge includes a developing roller for supplying developing agent. One of such conventional image-forming apparatuses is disclosed in a prior art. The image-forming apparatus described therein includes a drum cartridge including a photosensitive drum. The developing cartridge is attachable to the drum cartridge. Upon attachment of the developing cartridge to the drum cartridge, the photosensitive drum and the developing roller contact with each other. 
     SUMMARY 
     The image-forming apparatus according to the above prior art is switchable between a state where the developing roller and the photosensitive drum are in contact with each other and a state where the developing roller and the photosensitive drum are in separation from each other. In the image-forming apparatus according to the above prior art, components for moving the developing cartridge to separate the developing roller from the photosensitive drum are provided at each side of a drum unit. The components at each side must receive a driving force from a main body of the image-forming apparatus. 
     In view of the foregoing, it is an object of the present disclosure to provide a developing cartridge capable of providing separation between the developing roller and photosensitive drum by a driving force transmitted from only one side without necessitating application of driving force to both sides. 
     In order to attain the above and other objects, according to an aspect, the present disclosure provides a developing cartridge including a casing, a developing roller, and a first cam. The casing is configured to accommodate therein developing agent. The developing roller is rotatable about a developing-roller axis extending in a first direction and is contactable with a photosensitive drum. The developing roller has a peripheral surface a portion of which is exposed to an outside of the casing in a second direction and another portion of the peripheral surface opposite the exposed portion in the second direction is positioned inside the casing. The first cam is positioned at an outer surface of one end portion of the casing in the second direction. The first cam is movable in a third direction relative to the casing and the developing roller between a first position and a second position closer to the developing roller than the first position is to the developing roller in the third direction. The first cam has a first inclined surface and a second inclined surface. The first inclined surface is configured to receive a pressing force directing from one end portion of the casing in the first direction toward another end portion of the casing in the first direction. A distance in the second direction between the second inclined surface and the casing varies as the second inclined surface extends away from the developing roller in the third direction. The first cam is movable between the first position and the second position in response to application of the pressing force to the first inclined surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The particular features and advantages of the embodiment(s) as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which: 
         FIG. 1  is a schematic diagram of an image-forming apparatus; 
         FIG. 2  is a perspective view of a developing cartridge according to one embodiment; 
         FIG. 3  is a view illustrating a drum cartridge to which the developing cartridge is attached as viewed from another side thereof in a third direction; 
         FIG. 4  is a perspective view of a first pressure contact portion which is a part of the drum cartridge; 
         FIG. 5  is a perspective view of a second pressure contact portion which is a part of the drum cartridge; 
         FIG. 6  is an exploded perspective view of the developing cartridge according to the embodiment; 
         FIG. 7  is a perspective view illustrating the developing cartridge according to the embodiment and a photosensitive drum in a contacting state; 
         FIG. 8  is a view of the developing cartridge according to the embodiment and the photosensitive drum in the contacting state as viewed from one side thereof in a second direction; 
         FIG. 9  is a view of the developing cartridge according to the embodiment and the photosensitive drum in the contacting state as viewed from one side thereof in a first direction; 
         FIG. 10  is a perspective view of the developing cartridge according to the embodiment and the photosensitive drum in a separated state; 
         FIG. 11  is a view of the developing cartridge according to the embodiment and the photosensitive drum in the separated state as viewed from one side thereof in the second direction; and 
         FIG. 12  is a view illustrating the developing cartridge according to the embodiment and the photosensitive drum in the separated state as viewed from one side thereof in the first direction. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, one embodiment of the disclosure will be described with reference to accompanying drawings. 
     In the following description, a direction in which a rotational axis (developing-roller axis) of a developing roller extends will be called as a “first direction.” On a peripheral surface of the developing roller, a portion exposed to outside of a casing and a portion accommodated within the casing will be assumed to be arranged side by side in a “second direction.” Here, the first direction and the second direction cross each other, preferably orthogonal to each other. Further, a direction crossing both the first and second directions (preferably, orthogonal to the first and second directions) will be called as a “third direction.” 
     &lt;1. Overall Configuration of Image-Forming Apparatus&gt; 
       FIG. 1  is a schematic diagram of an image-forming apparatus  100 . The image-forming apparatus  100  is an electrophotographic-type printer, such as a laser printer and an LED printer. As illustrated in  FIG. 1 , the image-forming apparatus  100  includes four developing cartridges  1  according to the present embodiment, a drum cartridge  2 , and a main body portion  9 . 
     &lt;1-1. Overall Configuration of Main Body Portion&gt; 
     Hereinafter, an overall configuration of the main body portion  9  will be described. As illustrated in  FIG. 1 , the main body portion  9  includes a main-body frame  101 , a transfer belt (not illustrated), and a controller  102 . 
     The main-body frame  101  is a generally rectangular parallelepiped and has an internal space therein. The drum cartridge  2  with the developing cartridges  1  attached thereto can be accommodated in the internal space of the main-body frame  101 . Further, in the main-body frame  101 , four chargers (not illustrated), four light sources (not illustrated), the transfer belt, and the controller  102  are provided. 
     The main-body frame  101  is a generally rectangular parallelepiped and defines an internal space therein. The drum cartridge  2  with the developing cartridges  1  attached thereto is configured to be accommodated in the internal space of the main-body frame  101 . In the main-body frame  101 , four chargers (not illustrated), four light sources (not illustrated), the transfer belt, and the controller  102  are also positioned. 
     The transfer belt is an endless belt for conveying printing sheets. In a state where the drum cartridge  2  to which the developing cartridges  1  are attached is positioned in the internal space of the main-body frame  101 , the transfer belt is positioned opposite to developing rollers  30  with respect to photosensitive drums  21 . The transfer belt has an outer peripheral surface contactable with outer peripheral surfaces of the respective photosensitive drums  21 . 
     The controller  102  includes a processor such as a CPU, and a main-body memory. The main-body memory is a readable and writable storage medium, such as a Flash ROM and EEPROM. The main-body memory is configured to store computer programs for controlling operations performed in the image-forming apparatus  100 . The processor is configured to execute various processing according to the computer programs stored in the main-body memory. That is, the processor is configured to execute various printing processing and other processing associated therewith to be performed in the image-forming apparatus  100 . 
     &lt;1-2. Overall Configurations of Developing Cartridges&gt; 
     An overall structure of each developing cartridge  1  will be described next.  FIG. 2  is a perspective view of the developing cartridge  1  according to the embodiment. 
     As illustrated in  FIGS. 1 and 3 , the developing cartridges  1  are attachable to and detachable from a frame  200  of the drum cartridge  2 . As illustrated in  FIG. 2 , each developing cartridge  1  includes a casing  10  configured to store therein developing agent. The casing  10  includes a container portion  10 A, and a lid portion  10 B. The container portion  10 A defines an internal space therein. The lid portion  10 B is flat plate shaped. The lid portion  10 B is positioned at one end portion of the casing  10  in the second direction. The lid portion  10 B has a third outer surface  13  described later. The lid portion  10 B covers an opening portion positioned at one end portion of the container portion  10 A in the second direction. The container portion  10 A has one end portion in the third direction where an opening  10 C is formed. A developing roller  30  (described later) is positioned at the opening  10 C. 
     The casing  10  has one end portion in the first direction which has a first outer surface  11 . The casing  10  has another end portion in the first direction which has a second outer surface  12 . The casing  10  also has the third outer surface  13  and a fourth outer surface  14  ( FIG. 9 ) spaced away from each other in the second direction. The third outer surface  13  is positioned at one end portion of the casing  10  in the second direction. The fourth outer surface  14  is positioned at another end portion of the casing  10  in the second direction. 
     The four developing cartridges  1  accommodate therein toner of different colors (for example, cyan, magenta, yellow and black), respectively. However, the four developing cartridges  1  may accommodate therein toner of an identical color. 
     Each developing cartridge  1  includes one developing roller  30 . The developing roller  30  is cylindrical in shape. The developing roller  30  is rotatable about a rotational axis (developing-roller axis) extending in the first direction. The developing roller  30  is supported by the casing  10  so as to be rotatable about the developing-roller axis. 
     The developing roller  30  includes a developing-roller body  31  and a developing-roller shaft  32 . The developing-roller body  31  is hollow cylindrical in shape and extends in the first direction. The developing-roller body  31  is made from an elastic material, such as rubber. The developing-roller shaft  32  is a solid cylindrical member penetrating through the developing-roller body  31  in the first direction. The developing-roller shaft  32  is made from meal or electrically conductive resin. The developing-roller body  31  is fixed to the developing-roller shaft  32  without relative rotation therebetween. That is, the developing-roller body  31  is rotatable together with the developing-roller shaft  32  about the developing-roller axis. A part of an outer peripheral surface of the developing-roller body  31  in the second direction is exposed to the outside of the casing  10  through the opening  10 C. A remaining part in the second direction of the outer peripheral surface of the developing-roller body  31  is positioned inside the casing  10 . 
     The developing-roller shaft  32  has one end portion in the first direction. A developing-roller gear (not illustrated) is attached to the one end portion of the developing-roller shaft  32  in the first direction. The developing-roller gear is positioned at the first outer surface  11 . The developing-roller gear is fixed to the one end portion of the developing-roller shaft  32  without relative rotation therebetween. Hence, a rotation of the developing-roller gear causes a rotation of the developing-roller shaft  32 , so that the developing-roller body  31  is rotatable together with the developing-roller shaft  32 . 
     Incidentally, the developing-roller shaft  32  may not extend through the developing-roller body  31  in the first direction. For example, the developing-roller shaft  32  may be configured of two shafts extending outward in the first direction respectively from both ends of the developing-roller body  31  in the first direction. 
     As illustrated in  FIG. 2 , each developing cartridge  1  also includes a gear portion  40 . The gear portion  40  is positioned at the first outer surface  11  of the casing  10 . The gear portion  40  includes the developing-roller gear described above, a coupling  41 , and a gear cover  43 . 
     The coupling  41  is a rotary member configured to receive a driving force supplied from a power source in the image-forming apparatus  100 . The coupling  41  is rotatable about a rotational axis extending in the first direction. The coupling  41  has a fixing hole  411  recessed inward in the first direction. Upon attachment of the drum cartridge  2  to the main body portion  9  with the developing cartridges  1  attached to the drum cartridge  2 , a transmission shaft (not shown) of the main body portion  9  is configured to be inserted in the fixing hole  411 . The transmission shaft and the coupling  41  are thus connected each other without relative rotation therebetween. Accordingly, rotation of the transmission shaft causes rotation of the coupling  41 . In accordance with the rotation of the coupling  41 , the developing-roller gear rotates together with the developing roller  30 . The rotation of the coupling  41  also causes rotations of a supply roller (not illustrated) and an agitator (not illustrated). 
     A handle  38  for being gripped by a user is positioned at an outer surface of another end portion of the casing  10  at the other side in the third direction. 
     &lt;1-3. Overall Configuration of Drum Cartridge&gt; 
     Next, an overall configuration of the drum cartridge  2  will be described next.  FIG. 3  is a view of the drum cartridge  2  to which the developing cartridges  1  are attached as viewed from the other side thereof in the third direction. As illustrated in  FIGS. 1 and 3 , the drum cartridge  2  includes four of the photosensitive drums  21 , and the frame  200 . 
     Each of the four photosensitive drums  21  depicted in  FIG. 1  has a cylindrical-shaped outer peripheral surface centered on a drum axis, which is a rotational axis extending in the first direction. The outer peripheral surface is a surface coated with photosensitive material. Each of the four photosensitive drums  21  is rotatable about the drum axis. 
     The frame  200  is a frame supporting the four photosensitive drums  21 . The frame  200  holds the four photosensitive drums  21  such that the photosensitive drums  21  are spaced away from one another in the second direction. The frame  200  includes a pair of side frames  201 ,  202  opposite each other in the first direction. The side frame  202  is positioned further in the first direction toward the other side than the side frame  201 . The photosensitive drums  21  are rotatably supported by the side frames  201  and  202 . 
     For performing a printing process in the image-forming apparatus  100 , the controller  102  drives a motor (not illustrated) so that the photosensitive drums  21  and the developing rollers  30  can rotate by a driving force transmitted from the motor through the transmission shaft and the coupling  41 . Further, the controller  102  supplies power to the chargers (not illustrated) to charge the outer peripheral surfaces of the respective photosensitive drums  21 . The controller  102  further causes the light sources (not illustrated) to emit light onto the outer peripheral surfaces of the respective photosensitive drums  21 . In this way, an electrostatic latent image corresponding to a printing image is formed on the outer peripheral surface of each photosensitive drum  21 . The toner accommodated in each developing cartridge  1  is then supplied through the corresponding developing roller  30  to the electrostatic latent image formed on the corresponding photosensitive drum  21 . Thus, the electrostatic latent image becomes a visible toner image on the outer peripheral surface of each photosensitive drum  21 . 
     Then, a printing sheet is conveyed between each photosensitive drum  21  and the transfer belt, whereby the toner image is transferred from the outer peripheral surface of each photosensitive drum  21  onto the printing sheet. The printing sheet carrying the toner image is then conveyed to a fixing unit (not illustrated) where the toner image is thermally fixed to the printing sheet. Image printing on the printing sheet is performed in this way. 
     In the image-forming apparatus  100 , it may be preferable that the developing rollers  30  be separated from the corresponding photosensitive drums  21 , for example, in order to change colors for printing or during a standby period. For this purpose, the image-forming apparatus  100  of the present embodiment provides a contacting state and a separated state. The contacting state denotes a state where the developing rollers  30  and the photosensitive drums  21  are in contact with each other in a state where the developing cartridges  1  are attached to the drum cartridge  2 . The separated state denotes a state where the developing rollers  30  and the photosensitive drums  21  are separated from each other in the state where the developing cartridges  1  are attached to the drum cartridge  2 . 
     To this effect, as components for realizing the contact and the separation, each developing cartridge  1  includes a first cam  61 , a second cam  62 , a first resilient member  63 , a second resilient member  64 , a first guide shaft  65 , a second guide shaft  66 , and a connection bar  67 . Further, as components for realizing the contact and the separation, the drum cartridge  2  includes a first pressure contact portion  26  and a second pressure contact portion  27 . As components for realizing the contact and the separation, the main body portion  9  includes four drive shafts  103 . 
     &lt;2. Components in Drum Cartridge for Contact and Separation&gt; 
     Hereinafter, components of the drum cartridge  2  for performing the contact and the separation between the developing rollers  30  and the photosensitive drums  21  will be described with reference to  FIGS. 3 through 5 .  FIG. 4  is an enlarged perspective view of the first pressure contact portion  26 .  FIG. 5  is an enlarged perspective view of the second pressure contact portion  27 . 
     As illustrated in  FIG. 3 , in the state where the developing cartridges  1  are attached to the drum cartridge  2 , the first outer surface  11  of each developing cartridge  1  faces an inner surface of the first side frame  201  in the first direction. Also, in the state where the developing cartridges  1  are attached to the drum cartridge  2 , the second outer surface  12  of each developing cartridge  1  faces an inner surface of the second side frame  202  in the first direction. 
     As illustrated in an enlarged view in  FIG. 3 , the first side frame  201  includes four of the first pressure contact portions  26 . That is, each first pressure contact portion  26  is positioned at one end portion of the frame  200  in the first direction. As illustrated in  FIG. 4 , each first pressure contact portion  26  has a first pressure contact surface  260  which is a flat surface slanting with respect to the second and third directions. 
     As illustrated in another enlarged view in  FIG. 3 , the second side frame  202  includes four of the second pressure contact portions  27 . That is, each second pressure contact portion  27  is positioned at another end portion of the frame  200  at the other side in the first direction. As illustrated in  FIG. 5 , each second pressure contact portion  27  has a second pressure contact surface  270  which is a flat surface slanting with respect to the second and third directions. 
     The first pressure contact portion  26  and the corresponding second pressure contact portion  27  are positioned to be spaced away from each other in the first direction. As described later, the first cam  61  of each developing cartridge  1  is contactable with the first pressure contact surface  260  of the corresponding first pressure contact portion  26 , and the second cam  62  of each developing cartridge  1  is contactable with the second pressure contact surface  270  of the corresponding second pressure contact portion  270 . 
     &lt;3. Components in Main Body Portion for Contact and Separation&gt; 
     Next, components of the main body portion  9  for realizing the contact and separation between the developing rollers  30  and the photosensitive drums  21  will be described. 
     The main body portion  9  includes four drive shafts  103  (see  FIGS. 9 and 12 ) as a component for performing the contact and the separation. Each drive shaft  103  is a solid cylinder or solid prismatic column extending in the first direction. The drive shaft  103  is movable in the first direction between an advanced position and a retracted position upon receiving a driving force from a power source of the main body portion  9 . 
     &lt;4. Components in Developing Cartridge for Contact and Separation&gt; 
     Next, components of each developing cartridge  1  for realizing the contact and the separation between the developing roller  30  and the corresponding photosensitive drum  21  will be described with reference to  FIGS. 2 and 6 .  FIG. 6  is an exploded perspective view of the developing cartridge  1 . 
     As the components for the contact and separation, the developing cartridge  1  includes the first cam  61 , the second cam  62 , the first resilient member  63 , the second resilient member  64 , the first guide shaft  65 , the second guide shaft  66 , and the connection bar  67 . 
     As illustrated in  FIGS. 2 and 6 , the first cam  61  is positioned at the first outer surface  11  of the casing  10 . Further, the first cam  61  is positioned at the third outer surface  13  of the casing  10 . The first cam  61  has a first inclined surface  61   a , a second inclined surface  61   b , a first surface  61   e  (see  FIGS. 6, 9 ), a second surface  61   d , a first through-hole  61   c , and a first recess  61   f  (see  FIG. 9 ). As described later in detail, the first cam  61  is movable in the third direction relative to the casing  10  and the developing roller  30  between a first position ( FIG. 9 ) and a second position ( FIG. 12 ). The second position is closer to the developing roller  30  in the third direction than the first position is to the developing roller  30 . 
     The first inclined surface  61   a  is a flat surface sloping with respect to the first direction and the third direction. The first inclined surface  61   a  is parallel to the second direction. Specifically, the first inclined surface  61   a  is sloped to be distant from the first outer surface  11  in the first direction as extending toward the developing roller  30  in the third direction. 
     The second inclined surface  61   b  is a flat surface sloping with respect to the second direction and the third direction. The second inclined surface  61   b  is parallel to the first direction. Specifically, the second inclined surface  61   b  is sloped to extend toward the third outer surface  13  in the second direction as approaching the developing roller  30  in the third direction. That is, a distance between the second inclined surface  61   b  and the casing  10  in the second direction increases as the second inclined surface  61   b  extends away from the developing roller  30  in the third direction. 
     The first inclined surface  61   a  and the second inclined surface  61   b  are different surfaces of the first cam  61 . The first inclined surface  61   a  is generally trapezoidal in shape as viewed from one side thereof in the first direction. The trapezoidal shape has a short side at one side thereof in the third direction and a long side at the other side thereof in the third direction. The second inclined surface  61   b  is generally trapezoidal in shape as viewed from one side thereof in the second direction. The trapezoidal shape has a long side at the one side in the third direction and a short side at the other side in the third direction. The first inclined surface  61   a  has a hypotenuse at the one side in the second direction that is connected to a hypotenuse of the second inclined surface  61   b  at the one side in the first direction. 
     The first cam  61  also has the first surface  61   e  and the second surface  61   d . The first surface  61   e  and the second surface  61   d  are perpendicular to the third direction. The first surface  61   e  is at one end portion of the first cam  61  at the one side in the third direction. The second surface  61   d  is at another end portion of the first cam  61  at the other side in the third direction. 
     The first through-hole  61   c  extends in the third direction throughout the first cam  61 . The first through-hole  61   c  has a circular cross-section. The first through-hole  61   c  has an end at the other side in the third direction that is open at the second surface  61   d  of the first cam  61 . 
     The first recess  61   f  is recessed at the first surface  61   e  in the third direction toward the other side (toward the second surface  61   d ). The first recess  61   f  has a cross-sectional area greater than a cross-sectional area of the first through-hole  61   c . The first through-hole  61   c  has one end in the third direction (at the one side) that is connected to an inner space of the first recess  61   f.    
     The first resilient member  63  is a coil spring extending in the third direction. The first resilient member  63  is expandable and shrinkable in the third direction. The first resilient member  63  has one end portion seated on a bottom of the first recess  61   f  (see  FIG. 9 ). That is, the one end portion of the first resilient member  63  is accommodated in the inner space of the first recess  61   f . The first resilient member  63  has another end portion connected to a first seat member  43   a  (see  FIG. 9 ). The first seat member  43   a  protrudes toward the one side (outward) in the second direction from a side wall of the gear cover  43  positioned at one side thereof in the second direction. The first seat member  43   a  has a first flat surface perpendicular to the third direction. The other end portion of the first resilient member  63  is seated on the first flat surface of the first seat member  43   a . The first resilient member  63  is interposed between the bottom of the first recess  61   f  and the first flat surface of the first seat member  43   a  such that the first resilient member  63  is compressed in the third direction to have a smaller length than a natural length thereof. 
     The first guide shaft  65  extends in the third direction, and has a solid cylindrical shape or solid prismatic columnar shape. The first guide shaft  65  is positioned at the third outer surface  13  of the casing  10 . The first guide shaft  65  is positioned inside the first resilient member  63 . The first guide shaft  65  has one end connected to the first flat surface of the first seat member  43   a . The first guide shaft  65  is inserted in the first through-hole  61   c . Hence, the first guide shaft  65  extends throughout the first cam  61  in the third direction. 
     The first guide shaft  65  has another end in the third direction connected to a second seat member  43   b  (see  FIG. 6 ). The second seat member  43   b  protrudes toward the one side (outward) in the second direction from the side wall of the gear cover  43  positioned at one side thereof in the second direction. The second seat member  43   b  is positioned further in the third direction toward the other side than the first seat member  43   a . The second seat member  43   b  has a second flat surface perpendicular to the third direction. The other end of the first guide shaft  65  in the third direction is seated on the second flat surface of the second seat member  43   b.    
     The one end of the first guide shaft  65  is fixed to the first flat surface of the first seat member  43   a  by a fastener of a well-known configuration, such as a screw and a pin. The other end of the first guide shaft  65  is fixed to the second flat surface of the second seat member  43   b  by a fastener of a well-known configuration, such as a screw and a pin. That is, each end of the first guide shaft  65  in the third direction is supported by the casing  10  through the gear cover  43 . The first cam  61  is movable in the third direction along the first guide shaft  65 . The first resilient member  63  urges the first cam  61  in the third direction toward the other side (from the one end portion toward the other end portion in the third direction of the casing  10 ). Hence, the first cam  61  is urged by an urging force of the first resilient member  63  toward the first position ( FIG. 9 ) from the second position ( FIG. 12 ). 
     As illustrated in  FIGS. 2 and 6 , the second cam  62  is positioned at the first outer surface  11  of the casing  10 . Further, the second cam  62  is positioned at the third outer surface  13  of the casing  10 . The second cam  62  has a third inclined surface  62   a , a third surface  62   d , a fourth surface  62   b , a second through-hole  62   c , and a second recess (not illustrated). As described later in detail, the second cam  62  is movable in the third direction relative to the casing  10  and the developing roller  30  between a third position ( FIG. 8 ) and a fourth position ( FIG. 11 ). The fourth position is closer to the developing roller  30  in the third direction than the third position is to the developing roller  30 . The second cam  62  is movable from the third position to the fourth position in accordance with the movement of the first cam  61  from the first position to the second position. 
     The third inclined surface  62   a  is a flat surface sloping with respect to the second direction and the third direction. The third inclined surface  62   a  is parallel to the first direction. Specifically, the third inclined surface  62   a  is sloped to extend toward the third outer surface  13  in the second direction as approaching toward the developing roller  30  in the third direction. That is, a distance between the third inclined surface  62   a  and the casing  10  in the second direction increases as the third inclined surface  62   a  extends away from the developing roller  30  in the third direction. 
     The third inclined surface  62   a  is generally trapezoidal in shape as viewed in the second direction from the one side toward the other side. The trapezoidal shape has a long side at the one side in the third direction and a short side at the other side in the third direction. The second cam  62  has the third surface  62   d  and the fourth surface  62   b . The third surface  62   d  and the fourth surface  62   b  are perpendicular to the third direction. The third surface  62   d  is at one end of the second cam  62  in the third direction. The fourth surface  62   b  is positioned further in the third direction toward the other side than the second cam  62  in the second cam  62 . 
     The second through-hole  62   c  extends in the third direction throughout the second cam  62 . The second through-hole  62   c  has a circular cross-section. The second through-hole  62   c  has an end at the other side in the third direction that is open at the fourth surface  62   b  of the second cam  62 . 
     The second recess (not illustrated) is recessed at the third surface  62   d  in the third direction toward the other side (toward the fourth surface  62   b ). The second recess has a cross-sectional area greater than a cross-sectional area of the second through-hole  62   c . The second through-hole  62   c  has one end at the one side in the third direction that is connected to an inner space of the second recess. 
     The second resilient member  64  is a coil spring extending in the third direction. The second resilient member  64  is expandable and shrinkable in the third direction. The second resilient member  64  has one end portion seated on a bottom of the second recess. That is, the one end portion of the second resilient member  64  is accommodated in the inner space of the second recess. The second resilient member  64  has another end portion connected to a third seat member  10 D ( FIG. 6 ). The third seat member  10 D protrudes from the third outer surface  13  of the casing  10  toward the one side (outward) in the third direction. The third seat member  10 D has a third flat surface perpendicular to the third direction. The other end portion of the second resilient member  64  in the third direction is seated on the third flat surface of the third seat member  10 D. The second resilient member  64  is interposed between the bottom of the second recess and the third flat surface of the third seat member  10 D, such that the second resilient member  64  is compressed in the third direction to have a smaller length than a natural length thereof. 
     The second guide shaft  66  extends in the third direction, and has a solid cylindrical shape or solid prismatic columnar shape. The second guide shaft  66  is positioned at the third outer surface  13  of the casing  10 . The second guide shaft  66  is positioned inside the second resilient member  64 . The second guide shaft  66  has one end connected to the third flat surface of the third seat member  10 D. The second guide shaft  66  is inserted in the second through-hole  62   c . Hence, the second guide shaft  66  extends throughout the second cam  62  in the third direction. 
     The second cam  62  has another end connected to a fourth seat member  10 E ( FIG. 6 ). The fourth seat member  10 E protrudes from the third outer surface  13  of the casing  10  toward the one side in the second direction. The fourth seat member  10 E is positioned further in the third direction toward the other side than the third seat member  10 D. The fourth seat member  10 E has a fourth flat surface perpendicular to the third direction. The other end of the second guide shaft  66  in the third direction is seated on the fourth flat surface of the fourth seat member  10 E. 
     The one end of the second guide shaft  66  is fixed to the third flat surface of the third seat member  10 D by a fastener of a well-known configuration, such as a screw and a pin. The other end of the second guide shaft  66  is fixed to the fourth flat surface of the fourth seat member  10 E by a fastener of a well-known configuration, such as a screw and a pin. Hence, each end of the second guide shaft  66  in the third direction is supported by the casing  10 . The second cam  62  is movable in the third direction along the second guide shaft  66 . The second resilient member  64  urges the second cam  62  in the third direction toward the other side (from the one end portion to the other end portion of the casing  10  in the third direction). Hence, the second cam  62  is urged by an urging force of the second resilient member  64  toward the third position from the fourth position. 
     The connection bar  67  extends in the first direction and has a solid prismatic columnar shape or solid cylindrical shape. The connection bar  67  is positioned between the first cam  61  and the second cam  62  in the first direction. The connection bar  67  connects the first cam  61  to the second cam  62 . Specifically, the first cam  61  is connected to one end portion of the connection bar  67  at the one side in the first direction. The second cam  62  is connected to another end portion of the connection bar  67  at the other side in the first direction. Hence, the second cam  62  is movable in the third direction in interlocking relation to the first cam  61 . 
     &lt;5. Movement of Each Component at the Time of Switching Between Contact and Separation&gt; 
     Hereinafter, how each component operates for realizing switching between the contact and the separation will be described with reference to  FIGS. 7 through 12 . 
       FIG. 7  is a perspective view illustrating the developing cartridge  1  and the photosensitive drum  21  in the contacting state.  FIG. 8  is a view of the developing cartridge  1  and the photosensitive drum  21  in the contacting state as viewed from one side thereof in the second direction.  FIG. 9  is a view of the developing cartridge  1  and the photosensitive drum  21  in the contacting state as viewed from one side thereof in the first direction.  FIG. 10  is a perspective view of the developing cartridge  1  and the photosensitive drum  21  in the separated state.  FIG. 11  is a view of the developing cartridge  1  and the photosensitive drum  21  in the separated state as viewed from one side thereof in the second direction.  FIG. 12  is a view illustrating the developing cartridge  1  and the photosensitive drum  21  in the separated state as viewed from one side thereof in the first direction. 
     In the image-forming apparatus  100 , in a case where the drive shaft  103  is driven or moved toward the other side in the first direction to the advanced position, the first inclined surface  61   a  of the corresponding first cam  61  is pressed by the drive shaft  103 . That is, the first inclined surface  61   a  of the first cam  61  receives a pressing force F directing from the one end portion toward the other end portion of the casing  10  in the first direction. 
     The pressing force F applied to the first inclined surface  61   a  from the drive shaft  103  is converted into a force directing in the third direction by contact of the drive shaft  103  with the first inclined surface  61   a . The first cam  61  is thus pressed toward the one side in the third direction. As the pressing force F pressing the first cam  61  toward the one side in the third direction is greater than the urging force of the first resilient member  63 , the first cam  61  at the first position is caused to move in the third direction toward the one side to be at the second position. 
     In the meantime, the second inclined surface  61   b  is in contact with the first pressure contact surface  260  of the first pressure contact portion  26 . In accordance with the movement of the first cam  61 , a contacting position between the second inclined surface  61   b  and the first pressure contact surface  260  is shifted over the second inclined surface  61   b  from a position close to the first surface  61   e  to a position close to the second surface  61   d . As a result, a distance between the first pressure contact surface  260  of the first pressure contact portion  26  and the casing  10  in the second direction is gradually increased. Since the second inclined surface  61   b  is pressed by the first pressure contact surface  260  of the first pressure contact portion  26 , the casing  10  and the developing roller  30  move together with the first cam  61  in the second direction to separate the developing roller  30  from the corresponding photosensitive drum  21 . 
     According to another aspect, because of the contact between the second inclined surface  61   b  and the first pressure contact surface  260  of the first pressure contact portion  26 , the force moving the first cam  61  toward the one side in the third direction is converted into the force pressing the first cam  61  in the second direction toward the other side. As a result, the casing  10  and the developing roller  30  move together with the first cam  61  in the second direction toward the other side, thereby separating the developing roller  30  from the photosensitive drum  21 . 
     Thereafter, in a case where the drive shaft  103  is retracted in the first direction toward the one side (from the other end portion to the one end portion of the casing  10  in the first direction), the first cam  61  moves toward the other side in the third direction by the urging force of the first resilient member  63 . Hence, the first cam  61  moves from the second position to the first position. 
     Here, the frame  200  of the drum cartridge  2  includes a pressure mechanism (not illustrated) for pressing the casing  10  of each developing cartridge  1  toward the corresponding photosensitive drum  21 . Since the pressure mechanism moves the developing cartridge  1  in the second direction toward the one side in this state, the contacting state between the developing roller  30  and the corresponding photosensitive drum  21  is restored. In this way, the state of image forming apparatus  100  is switchable between the contacting state ( FIGS. 7 through 9 ) and the separated state ( FIGS. 10 through 12 ). 
     In accordance with the movement of the first cam  61  between the first position and the second position, the second cam  62  also moves between the third position and the fourth position through the connection bar  67 . By the movement of the second cam  62 , the third inclined surface  62   a  is pressed by the second pressure contact surface  270  of the second pressure contact portion  27 , so that the casing  10  and the developing roller  30  move in the second direction together with the second cam  62 . In this way, both end portions of the casing  10  in the first direction are respectively pressed by the first pressure contact portion  26  and the second pressure contact portion  27 , which are components of the drum cartridge  2 , to move the casing  10  in the second direction toward the other side. Accordingly, this structure can reduce a likelihood that the casing  10  may be slanted with respect to the first direction at the time of switching between the contacting state and the separated state. 
     Incidentally, as illustrated in  FIG. 9 , in the attached state of the developing cartridge  1  to the drum cartridge  2  and the first cam  61  is at the first position, the second inclined surface  61   b  is in contact with the first pressure contact surface  260  of the first pressure contact portion  26  which is part of the drum cartridge  2 . On the other hand, as illustrated in  FIG. 12 , in the attached state of the developing cartridge  1  to the drum cartridge  2  and the first cam  61  is at the second position, the second inclined surface  61   b  is separated from the first pressure contact surface  260  of the first pressure contact portion  26 . In accordance with the movement of the first cam  61  from the first position to the second position, the second inclined surface  61   b  is gradually pressed by the first pressure contact surface  260  in the second direction toward the other side. The first cam  61  is accordingly moved, together with the casing  10  and the developing roller  30 , to be separated away from the corresponding photosensitive drum  21  in the second direction. 
     As illustrated in  FIGS. 7 and 9 , the developing roller  30  is in contact with the corresponding photosensitive drum  21  when the first cam  61  is at the first position. At this time, the first resilient member  63  has a first length L 1  in the third direction; and the first cam  61  and the developing roller  30  define a first distance D 1  therebetween in the third direction. 
     As illustrated in  FIGS. 10 and 12 , the developing roller  30  is separated from the photosensitive drum  21  when the first cam  61  is at the second position. At this time, the first resilient member  63  has a second length L 2  in the third direction smaller than the first length L 1 ; and the first cam  61  and the developing roller  30  define a second distance D 2  therebetween in the third direction smaller than the first distance D 1 . 
     Similarly, in the attached state of the developing cartridge  1  to the drum cartridge  2  and the second cam  62  is at the third position, the third inclined surface  62   a  is in contact with the second pressure contact surface  270  of the second pressure contact portion  27  which is part of the drum cartridge  2 . At this time, the developing roller  30  is in contact with the corresponding photosensitive drum  21 . On the other hand, in the attached state of the developing cartridge  1  to the drum cartridge  2  and the second cam  62  is at the fourth position, the third inclined surface  62   a  is separated from the second pressure contact surface  270  of the second pressure contact portion  27 . At this time, the developing roller  30  is in separation from the photosensitive drum  21 . 
     &lt;6. Summary&gt; 
     As described above, the developing cartridge  1  according to the embodiment includes the casing  10 , the developing roller  30 , and the first cam  61 . The first cam  61  has the first inclined surface  61   a , and the second inclined surface  61   b . In the developing cartridge  1 , the first cam  61  is movable between the first position and the second position in response to the application of the pressing force F to the first inclined surface  61   a . During the movement of the first cam  61  between the first position and the second position, the second inclined surface  61   b  is pressed by the first pressure contact surface  260  which is a part of the drum cartridge  2 . Hence, the developing roller  30  can be separated from the corresponding photosensitive drum  21 . 
     As such, in the developing cartridge  1  according to the embodiment, separation of the developing roller  30  from the corresponding photosensitive drum  21  can be performed by the driving force applied only to the one side in the first direction of the developing cartridge  1 . Application of driving force to both sides in the first direction of the developing cartridge  1  is unnecessary. 
     Further, in the developing cartridge  1  according to the embodiment, the first inclined surface  61   a  is inclined with respect to the first direction. The pressing force F applied to the first inclined surface  61   a  is converted to the force directing in the third direction by the inclination of the first inclined surface  61   a . As a result, the first cam  61  can move in the third direction between the first position and the second position. 
     Further, in the developing cartridge  1  according to the embodiment, the second inclined surface  61   b  is inclined with respect to the second direction and the third direction. Hence, the pressing force F for moving the first cam  61  from the first position to the second position is converted into pressing force of the first pressure contact surface  260  which is the part of the drum cartridge  2  for moving the second inclined surface  61   b  in the second direction. As a result, the casing  10  and the developing roller  30  can move in the second direction, thereby separating the developing roller  30  from the corresponding photosensitive drum  21 . 
     Further, the developing cartridge  1  according to the embodiment includes the first resilient member  63 . Hence, the first cam  61  can be returned to the first position by the urging force of the first resilient member  63 , after the first cam  61  moves from the first position to the second position by the pressing force F applied to the second inclined surface  61   b  of the first cam  61  from the first pressure contact surface  260  which is the part of the drum cartridge  2 . Further, the second inclined surface  61   b  can easily move along the first pressure contact surface  260 . 
     Further, in the developing cartridge  1  according to the embodiment, the first resilient member  63  is a coil spring. The first cam  61  is allowed to move between the first position and the second position in accordance with expansion and shrinkage of the coil spring. 
     Further, in the developing cartridge  1  according to the embodiment, the first cam  61  has the first recess  61   f . The one end portion of the first resilient member  63  is positioned at the bottom portion of the first recess  61   f . Since the one end portion of the first resilient member  63  is accommodated in the first recess  61   f , a larger stroke of expansion/shrinkage of the first resilient member  63  can be obtained than otherwise. 
     Further, the developing cartridge  1  according to the embodiment includes the first guide shaft  65 . The first cam  61  is movable in the third direction along the first guide shaft  65 . Hence, movement of the first cam  61  in the third direction between the first position and the second position can be realized at high accuracy. 
     Further, in the developing cartridge  1  according to the embodiment, the first guide shaft  65  is positioned inside the first resilient member  63 . Hence, deflection of the first resilient member  63  in a direction crossing the third direction can be restrained. As a result, accurate operations of the first cam  61  can be attained. 
     Further, in the developing cartridge  1  according to the embodiment, the first guide shaft  65  extends throughout the first cam  61  in the third direction. Hence, space saving layout of the first guide shaft  65  and the first cam  61  can be attained. Further, the first cam  61  can move in the third direction at high accuracy because the movement of the first cam  61  is guided by the first guide shaft  65 . 
     Further, the main body portion  9  which can accommodate the drum cartridge  2  includes the drive shafts  103 . The first cam  61  moves from the first position to the second position in accordance with the application of the pressing force F to the first inclined surface  61   a  from the corresponding drive shaft  103 . Hence, the developing roller  30  can be separated from the photosensitive drum  21  by the driving force applied from the main body portion  9 . 
     Further, the developing cartridge  1  according to the embodiment includes the second cam  62 . The second cam  62  has the third inclined surface  62   a . The third inclined surface  62   a  is pressed by the second pressure contact surface  270  which is a part of the drum cartridge  2  during movement of the third inclined surface  62   a  between the third position and the fourth position. Because the second inclined surface  61   b  and the third inclined surface  62   a  are positioned at the one end portion and the other end portion of the casing  10  in the first direction, respectively, the one end portion and the other end portion in the first direction of the casing  10  can be pressed by the first pressure contact surface  260  and the second pressure contact surface  270 , respectively, which are parts of the drum cartridge  2 . As a result, the developing roller  30  can be securely separated from the corresponding photosensitive drum  21 . 
     Further, in the developing cartridge  1  according to the embodiment, the third inclined surface  62   a  is inclined with respect to the second direction and the third direction. Therefore, the force for moving the second cam  62  from the third position to the fourth position is converted into the force applying from the second pressure contact surface  270  (the part of the drum cartridge  2 ) for moving the third inclined surface  62   a  in the second direction. As a result, the casing  10  and the developing roller  30  can be moved in the second direction, thereby separating the developing roller  30  from the corresponding photosensitive drum  21 . 
     Further, the developing cartridge  1  according to the embodiment includes the connection bar  67  for connecting the first cam  61  and the second cam  62  together. Hence, interlocking movement of the first cam  61  and the second cam  62  can be attained. Accordingly, inclined posture of the developing cartridge  1  with respect to the first direction can be restrained in the state where the developing cartridge  1  is separated from the corresponding photosensitive drum  21 . 
     &lt;7. Modifications&gt; 
     While the description has been made in detail with reference to the above embodiment, it would be apparent to those skilled in the art that many modifications and variations may be made therein without departing from the scope of the disclosure. 
     For example, in the above-described embodiment, the first guide shaft  65  is inserted in the first through-hole  61   c  of the first cam  61 . Instead, the first cam may have a groove extending throughout a length thereof in the third direction, and the first guide shaft may be inserted in the groove. 
     In the above-described embodiment, the pressure contact portions  26  and  27  have the pressure contact surfaces  260 ,  270 , respectively, which have inclined flat surfaces. Instead, the pressure contact portions may be cylindrical members rotatable about rotation axes extending in the first direction. 
     In the above-described embodiment, the first resilient member  63  and the second resilient member  64  are compression coil springs. Instead, the first resilient member and the second resilient member may be tension coil springs. In the latter case, one end portion of the first resilient member may be connected to the second surface  61   d  of the first cam  61 , and another end portion of the first resilient member may be connected to the second flat surface of the second seat member  43   b . Further, one end portion of the second resilient member may be connected to the fourth surface  62   b  of the second cam  62 , and another end portion of the second resilient member may be connected to the fourth flat surface of the fourth seat member  10 E. 
     In the above-described embodiment, the developing roller  30  is in contact with the photosensitive drum  21  when the first cam  61  is at the first position, and the developing roller  30  is separated from the photosensitive drum  21  when the first cam  61  is at the second position. Alternatively, the developing roller  30  may be in contact with the photosensitive drum  21  when the first cam  61  is at the second position, and the developing roller  30  may be separated from the photosensitive drum  21  when the first cam  61  is at the first position. In the latter case, the second inclined surface  61   b  of the first cam and the third inclined surface  62   a  of the second cam  62  may be sloped to approach the casing  10  in the second direction as extending away from the developing roller  30  in the third direction. 
     Note that the detailed configuration of the developing cartridge  1  may be different from that described above and illustrated in the drawings. Further, each component in the above-described embodiment and modifications may be suitably combined together as long as no technical conflicts is incurred.