Image forming apparatus having a drive unit including a torsion spring

An image forming apparatus includes a drive unit disposed inside its housing, a support frame, a protrusion, and a support portion. The drive unit is configured to drive a conveyance unit for conveying a sheet toward an image forming unit. The support frame supports the drive unit. The protrusion has a proximal end and a distal end. The distal end is farther from the support frame than the proximal end is from the support frame. The support portion supports the proximal end of the protrusion. The drive unit further includes a torsion spring including a spiral portion engaged with the protrusion, and a first portion and a second portion each extending from the spiral portion. The first arm is pivotable about a pivot axis and includes a covering portion. The covering portion extends from the first arm and covers the distal end of the protrusion.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application No. 2018-223464 filed on Nov. 29, 2018, the content of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

Aspects of the disclosure relate to an image forming apparatus.

BACKGROUND

Some known image forming apparatus includes a conveyance unit and a drive unit. The conveyance unit conveys a sheet to an image forming unit. The drive unit drives the conveyance unit. Such an image forming apparatus may include, in the drive unit, a gear mechanism including a plurality of gears and a torsion spring that exerts an urging force on one of the gears. The gear mechanism transmits a drive force to the conveyance unit from a drive source.

In the gear mechanism, the gear includes a cam. The gear is configured to be rotated via the cam acted upon by an urging force of the torsion spring.

The torsion spring is attached to a frame of the image forming apparatus with a spiral portion of the torsion spring being engaged with a protrusion of the frame.

SUMMARY

Nevertheless, during assembly of the torsion spring to the frame, the spiral portion of the torsion spring may be disengaged from the protrusion of the frame.

Accordingly, aspects of the disclosure provide an image forming apparatus having a configuration that may reduce or prevent a torsion spring from being disengaged from a protrusion of the image forming apparatus.

According to one or more aspects of the disclosure, an image forming apparatus includes a drive unit, a support frame, a protrusion, and a support portion. The drive unit is disposed inside a housing of the image forming apparatus and configured to drive a conveyance unit for conveying a sheet toward an image forming unit. The support frame supports the drive unit. The protrusion has a proximal end and a distal end. The distal end is farther from the support frame than the proximal end is from the support frame. The support portion supports the proximal end of the protrusion. The drive unit further includes a torsion spring and a first arm. The torsion spring includes a spiral portion engaged with the protrusion, a first portion extending from the spiral portion, and a second portion extending from the spiral portion. The first arm is pivotable about a pivot axis and includes a covering portion. The covering portion extends from the first arm and covers the distal end of the protrusion.

The above structure reduces or prevents the torsion spring from disengaging from the protrusion.

DETAILED DESCRIPTION

Aspects of the disclosure will be described with reference to the accompanying drawings.

Overall Configuration of Image Forming Apparatus

An image forming apparatus1illustrated inFIG. 1is an example of an image forming apparatus.

In the following description, right and left sides of the page ofFIG. 1, a side facing out of the page ofFIG. 1, and a side facing into the page ofFIG. 1are defined respectively as front, rear, left, and right sides of the image forming apparatus1. Upper and lower sides of the page ofFIG. 1are defined respectively as upper and lower sides of the image forming apparatus1.

The image forming apparatus1includes a housing2, a feeder3, an image forming unit5, a discharge unit8, a drive source4, and a drive unit6.

The feeder3includes a feed tray10and a conveyance unit30. The housing2includes a tray accommodating portion2a. The drive unit6is configured to drive the conveyance unit30by a drive force from the drive source4.

The housing2has a substantially rectangular parallelepiped shape. The housing2houses the feeder3, the image forming unit5, the drive source4, and the drive unit6. The tray accommodating portion2ais positioned at a lower portion of the housing2. The tray accommodating portion2ahouses the feed tray10such that the feed tray10is slidable in a front-rear direction. The housing2has a conveyance path P that may extend from the feeder3to the discharge unit8via the image forming unit5.

The feeder3is disposed at a lower portion of the image forming apparatus1. The feeder3is configured to feed a sheet18to the image forming unit5from the feed tray10using the conveyance unit30.

The feed tray10includes a tray body11, a support plate12, and a lifting plate13. The tray body11has a box shape with its upper end open. The support plate12may be a plate-like member. The support plate12is disposed in the tray body11. The support plate12is configured to support from below one or more sheets18loaded in the tray body11.

The support plate12is movable between a lower position and an upper position higher than the lower position. The lifting plate13is disposed below the support plate12in the tray body11. The lifting plate13is configured to contact the support plate12and move the support plate12upward to the upper position from the lower position.

The support plate12has a pivot axis12aat its rear end. The support plate12is supported by the tray body11so as to be pivotable about the pivot axis12a. Pivoting of the support plate12on the pivot axis12aenables the position change of the support plate12between the lower position and the upper position. The lifting plate13has a pivot axis13aat its rear end. The lifting plate13is supported by the tray body11so as to be pivotable about the pivot axis13a. Pivoting of the lifting plate13on the pivot axis13aenables the position change of the support plate12between the lower position and the upper position.

The lifting plate13is configured to be driven by a drive force transmitted from the drive source4via the drive unit6.

The conveyance unit30is configured to separate a single sheet18from one or more sheets18in the feed tray10and convey the separated sheet18toward the image forming unit5. The conveyance unit30includes a feed roller31, a separation roller32, a separation pad33, a conveyance roller pair34, and a registration roller pair35.

The feed roller31is configured to feed one or more sheets18toward the separation roller32from the feed tray10. The separation roller32is disposed downstream from the feed roller31in a sheet conveyance direction. The separation pad33is disposed facing the separation roller32and is urged toward the separation roller32.

The separation roller32is configured to be driven by a drive force transmitted from the drive source4via the drive unit6.

The separation roller32and the separation pad33are configured to cooperate to separate a single sheet18from the one or more sheets18fed by the feed roller31toward the separation roller32. The separation roller32is further configured to convey the separated sheet18toward the conveyance roller pair34along the conveyance path P.

The conveyance roller pair34is configured to apply a conveyance force to a sheet18. The conveyance roller pair34is disposed downstream from the separation roller32and the separation pad33in the sheet conveyance direction. The conveyance roller pair34is configured to further convey, toward the registration roller pair35, along the conveyance path P, a sheet18conveyed by the separation roller32toward the conveyance roller pair34.

The registration roller pair35is disposed downstream from the conveyance roller pair34in the sheet conveyance direction. The registration roller pair35is configured to contact a leading edge of a moving sheet18to temporarily stop the sheet18, thereby correcting skewing of the sheet18. The registration roller pair35is further configured to, after temporarily stopping the sheet18, convey the sheet18toward an image transfer position in the image forming unit5at a specified timing.

The image forming unit5is disposed downstream from the feeder3in the sheet conveyance direction. The image forming unit5is configured to form an image onto a sheet18fed by the feeder3.

The image forming unit5includes a process cartridge50, an exposure device60, and a fixing device70. The process cartridge50is configured to transfer an image onto a sheet18fed by the feeder3. The exposure device60is configured to expose a circumferential surface of a photosensitive drum54of the process cartridge50. The fixing device70is configured to fix an image transferred onto a sheet18by the process cartridge50.

The process cartridge50is disposed above the tray accommodating portion2ain the housing2. The process cartridge50includes a developer storage51, a supply roller52, a developing roller53, the photosensitive drum54, and a transfer roller55.

The exposure device60includes laser diodes, a polygon mirror, a lens, and reflectors. The exposure device60is configured to emit a laser beam toward a circumferential surface of the photosensitive drum54based on image data inputted into the image forming apparatus1to expose the circumferential surface of the photosensitive drum54.

The developer storage51stores toner as a developer. An agitator is configured to agitate toner in the developer storage51to supply toner to the supply roller52from the developer storage51. The supply roller52is configured to further supply toner to the developing roller53.

The developing roller53is in intimate contact with the supply roller52. The developing roller53is configured to carry toner supplied by the supply roller52and positively charged by a slide-contact member. The developing roller53is configured to be applied with a positive developing bias by a bias application device.

The photosensitive drum54is disposed adjacent to the developing roller53. The circumferential surface of the photosensitive drum54is uniformly and positively charged by a charger and is then exposed by the exposure device60. A potential of the exposed portion of the photosensitive drum54becomes lower than a potential of the other portion and thus an electrostatic latent image is formed on the circumferential surface of the photosensitive drum54based on the image data.

Then, the positively charged toner is supplied onto the circumferential surface of the photosensitive drum54having the electrostatic latent image by the developing roller53. The electrostatic latent image is thus visualized to a developer image.

The transfer roller55is disposed facing the photosensitive drum54. The transfer roller55is configured to be applied with a negative transfer bias by the bias application device. In a state where the transfer bias is applied to the circumferential surface of the transfer roller55, the photosensitive drum54having the developer image thereon and the transfer roller55convey a sheet18by pinching the sheet18therebetween (e.g., the transfer position). Thus, a developer image is transferred onto the sheet18from the circumferential surface of the photosensitive drum54.

The fixing device70includes a heat roller71and a pressure roller72. The heat roller71is configured to be rotated by a drive force from the drive source4and generate heat by receiving power from a power source. The pressure roller72is disposed facing the heat roller71. The pressure roller72is configured to rotate following rotation of the heat roller71with intimately contacting the heat roller71. In response to the fixing device70receiving a sheet18having a transferred developer image, the heat roller71and the pressure roller72conveys the sheet18by pinching the sheet18therebetween to fix the developer image onto the sheet18.

The discharge unit8is disposed downstream from the image forming unit5in the sheet conveyance direction. The discharge unit8is configured to discharge a sheet18having an image formed by the image forming unit5to the outside of the housing2. The discharge unit8includes a discharge roller pair81and a discharge tray82. The discharge roller pair81is configured to discharge a sheet18conveyed from the fixing device70to the outside of the housing2. The discharge tray82is defined at the top of the housing2. The discharge tray82is configured to receive and hold one or more sheets18discharged to the outside of the housing2by the discharge roller pair81.

Drive Unit

Hereinafter, the drive unit6will be described in detail.

The drive unit6is configured to receive a drive force from the drive source4and output the drive force selectively to the separation roller32of the conveyance unit30or the lifting plate13of the feed tray10.

As illustrated inFIGS. 2 and 3, the drive unit6includes a switch gear assembly61, a sector gear62, a first arm63, a second arm64, and a torsion spring65.

The housing2includes a support frame21. The support frame21is disposed inside the housing2and at one end portion of the housing2in a right-left direction. The support frame21extends in the front-rear direction and in an up-down direction. The drive unit6is supported by the support unit21. In this example, the support frame21may be disposed inside the housing2and at a left end portion of the housing2.

The switch gear assembly61is supported by the support frame21. The switch gear assembly61includes an input gear611, a first output gear612, and a second output gear613. The input gear611is an example of a force receiving portion configured to receive a drive force. The first output gear612is an example of a first force output portion configured to output the drive force. The second output gear613is an example of a second force output portion configured to output the drive force.

The input gear611, the first output gear612, and the second output gear613are disposed next to each other in the right-left direction. The input gear611, the first output gear612, and the second output gear613are each configured to rotate about a first axis C1extending in the right-left direction.

The input gear611is configured to receive a drive force from the drive source4to rotate in a first direction. In this example, the first direction may be a clockwise direction inFIG. 2.

The switch gear assembly61includes a planetary gear system. More specifically, for example, the switch gear assembly61is configured such that, in a case where the second output gear613is not allowed to rotate while the input gear611receives a drive force, the first output gear612is allowed to rotate. The switch gear assembly61is further configured such that, in a case where the second output gear613is allowed to rotate while the input gear611receives a drive force, the first output gear612is not allowed to rotate. That is, the switch gear assembly61is configured to change its force output state between a state in which the first output gear612outputs a drive force and another state in which the second output gear613outputs a drive force in response to the rotation state of the second output gear613.

In the drive unit6, for example, the first output gear612is connected to the lifting plate13and the second output gear613is connected to the separation roller32. In response to the first output gear612rotating, the drive unit6outputs a drive force to the lifting plate13. In response to the second output gear613rotating, the drive unit6outputs a drive force to the separation roller32.

The sector gear62is supported by the support frame21. The sector gear62is configured to rotate about a second axis C2extending in a direction parallel to the first axis C1. The sector gear62has teeth on a portion of its circumference. That is, the sector gear62has a toothed portion62aand a toothless portion62b.

The sector gear62has one side (e.g., a side facing out of the page inFIG. 2) having a first cam621and the other side (e.g., a side facing into the page inFIG. 2) having a second cam622.

The toothed portion62aof the sector gear62is meshable with teeth of the input gear611. In a state where the toothed portion62afaces and meshes with teeth of the input gear611, the sector gear62receives a drive force from the input gear611to rotate in a second direction. In this example, the second direction may be a counterclockwise direction inFIG. 2.

In a state where the toothless portion62bof the sector gear62faces the input gear611(i.e., in a state where the toothed portion62aof the sector gear62does not mesh with any teeth of the input gear611), the sector gear62might not receive a drive force from the input gear611and is thus not allowed to rotate.

The first cam621is urged in its rotating direction by an urging member. Urging the first cam621by the urging member may enable the sector gear62whose toothless portion62bfaces the input gear611to rotate in the second direction.

The sector gear62is configured to change its state between a rotation restricted state and a rotation allowed state. In the rotation restricted state, the toothless gear62is at standstill with the toothless portion62bfacing the input gear611. In response to the state change of the sector gear62to the rotation allowed state from the rotation restricted state, the sector gear62starts rotating in the second direction by an urging force of the urging member.

The support frame21includes a support shaft211protruding toward the left. The support shaft211has a third axis C3. The third axis C3extends in a direction parallel to the first axis C1. The third axis C3is an example of a pivot axis of each of the first arm63and the second arm64.

As illustrated inFIGS. 4A and 4B, the second arm64includes an engagement portion641, an engagement portion642, a second arm portion643, a guide arm portion644, a support portion645, a protrusion646, and a handle647.

As illustrated inFIG. 3, the engagement portion641has a hollow cylindrical shape. The engagement portion641is rotatably engaged with the support shaft211. The engagement portion642has a hollow cylindrical shape. The engagement portion642is rotatably engaged with the support shaft211. The engagement portion642is positioned farther from the support frame21than the engagement portion641is from the support frame21in the right-left direction. The engagement portion642is one piece with the engagement portion641.

The engagement portion642has a diameter that is smaller than a diameter of the engagement portion641. The second arm64has a stepped portion at a border between the engagement portion641and the engagement portion642. The second arm64is supported by the support shaft211through the engagement of the engagement portions641and642with the support shaft211such that the second arm64is pivotable about the third axis C3.

The second arm portion643extends from the engagement portion641in a direction perpendicular to a direction in which the third axis C3extends (hereinafter, referred to as the third axis C3direction). The second arm portion643includes a second pawl643aprotruding from a distal end of the second arm portion643in a pivot direction of the second arm portion643.

As illustrated inFIG. 2, in a state where the second arm64is supported by the support shaft211, the second arm portion643extends diagonally upward toward the front and the second pawl643apoints substantially upward.

The guide arm portion644extends from the engagement portion641in another direction perpendicular to the third axis C3direction. More specifically, for example, the guide arm portion644extends from the engagement portion641in a direction substantially opposite to the direction in which the second arm portion643extends.

The guide arm portion644has a first wall644a, a second wall644b, and a third wall644c. The first wall644afaces the pivot direction of the second arm64. The second wall644bextends from one of ends of the first wall644ain the third axis C3direction, and faces the third axis C3direction. The third wall644cextends from the other end of the first wall644ain the third axis C3direction, and faces the third axis C3direction. The one end from which the second wall644bextends is farther from the support frame21than the other end of the first wall644ais from the support frame21in the third axis C3direction.

A portion defined by the first wall644a, the second wall644b, and the third wall644cof the guide arm portion644functions as a restriction portion644dthat restricts movement of a first portion652of the torsion spring65. The first wall644ahas an inclined side. The inclined side extends in a direction away from support frame21as the inclined side extends toward the engagement portion641. The inclined side includes a guide portion644econfigured to guide the first portion652of the torsion spring65during attachment of the torsion spring65to the second arm64.

The support portion645may be a plate-like member. The support portion645extends from the engagement portion641in another direction perpendicular to the third axis C3direction. More specifically, for example, the support portion645extends from the engagement portion641in a direction different from the direction in which the second arm portion643extends and the direction in which the guide arm portion644extends. The support portion645is located at one end of the engagement portion641in the third axis C3direction. The one end of the engagement portion641is closer to the support frame21than the other end of the engagement portion641is to the support frame21in the third axis C3direction.

The protrusion646may be a shaft member. The protrusion646protrudes from the support portion645in a direction away from the support frame21with respect to the third axis C3direction. The protrusion646includes a proximal end646aand a distal end646b. The proximal end646ais closer to the support portion645than the distal end646bis to the support portion645. The distal end646bis positioned opposite to the proximal end646a. The protrusion646has a fourth axis C4. The fourth axis C4extends parallel to the third axis C3.

That is, the support portion645supports the proximal end646aof the protrusion646, and the protrusion646is located at the second arm64.

The support portion645is supported by the engagement portion641and the engagement portion641is supported by the support shaft211of the support frame21. Thus, the protrusion646is indirectly supported by the support frame21.

In another example, the protrusion646may be directly supported by the support frame21. In such a case, for example, the proximal end646aof the protrusion646may be directly supported by the support frame21, and the protrusion646may protrude from the support frame21such that the distal end646bis positioned farther from the support frame21than the proximal end646ais from the support frame21. In this case, the support frame21may serve as the support portion of the protrusion646.

The handle647includes a first contactable portion647aand a second contactable portion647b. The first contactable portion647aand the second contactable portion647beach extend from the engagement portion641in a direction away from the support frame21with respect to the third axis C3direction.

The first contactable portion647aand the second contactable portion647bare located around the engagement portion642and spaced from the engagement portion642. A distal end (which may be farther from the support frame21than a proximal end is from the support frame21) of the first contactable portion647ais located at substantially the same level as a distal end (which may be farther from the support frame21than a proximal end is from the support frame21) of the second contactable portion647b.

The first contactable portion647aand the second contactable portion647bare positioned at respective phases different from the second arm portion643, the guide arm644, and the support portion645around the third axis C3. The first contactable portion647aand the second contactable portion647bare located opposite to each other with respect to the engagement portion642.

As illustrated inFIG. 5, the torsion spring65includes a spiral portion651, the first portion652, and a second portion653. The spiral portion651is engageable with the protrusion646of the second arm64and may be engaged with the protrusion646. The first portion652and the second portion653each extend from the spiral portion651. The spiral portion651has a cylindrical shape having a hollow core and the fourth axis C4. The first portion652and the second portion653of the torsion spring65each extend in respective directions perpendicular to the fourth axis C4. The first portion652and the second portion653extend in the respective directions opposite to each other when the torsion spring65is in its natural state.

The torsion spring65may be supported by the protrusion646through engagement of the spiral portion651with the protrusion646such that the torsion spring65is rotatable about the fourth axis C4.

As illustrated inFIGS. 6A and 6B, the first arm63includes an engagement portion631, a first arm portion632, a guide portion633, a covering portion634, a first position restriction portion635aand a second position restriction portion635b.

As illustrated inFIG. 3, the engagement portion631has a hollow cylindrical shape. The engagement portion631is rotatably engaged with the engagement portion642of the second arm64. The first arm63is supported by the second arm64through the engagement of the engagement portion631with the engagement portion642of the second arm64such that the first arm63is pivotable about the third axis C3. The first arm63and the second arm64are pivotable about a common axis (e.g., the third axis C3).

The first contactable portion647aand the second contactable portion647bof the handle647are located around the engagement portion631of the first arm63engaged with the engagement portion642of the second engagement portion642. That is, the first contactable portion647aand the second contactable portion647bof the handle647each extend to a respective position in the third axis C3direction such that the first contactable portion647aand the second contactable portion647beach overlap the engagement portion631of the first arm63when viewed in the direction perpendicular to the third axis C3direction. The third axis C3direction may be a protruding direction in which the protrusion646protrudes.

In a state where the first arm63is supported by the second arm64, the second arm64is disposed closer to the proximal end646aof the protrusion646than the first arm63is to the proximal end646ain the third axis C3direction. More specifically, in that state, the second arm portion643of the second arm64is located closer to the proximal end646aof the protrusion646than the first arm portion632of the first arm63is to the proximal end646ain the third axis C3direction.

The first arm portion632extends from the engagement portion631in a direction perpendicular to the third axis C3direction. The first arm portion632includes a first pawl632aprotruding from a distal end of the first arm portion632in a pivot direction of the first arm portion632. As illustrated inFIG. 2, in a state where the first arm portion632is supported by the second arm64, the first arm portion632diagonally extends upward toward the rear and the first pawl632apoints substantially upward. The first pawl632ais meshable with the second output gear613.

The first arm portion632further has a first guide surface632bat an end face on an opposite side to the side toward which the first pawl632aof the first arm portion632protrudes. The first guide surface632bfaces the pivot direction of the first arm portion632. The first arm portion632further includes a second portion633ahaving a second guide surface and a third portion633bhaving a third guide surface. The second portion633aand the third portion633beach extend from the first guide surface632bin a direction opposite to the protruding direction of the first pawl632a.

The second portion633aand the third portion633bare spaced from each other by a specified gap in the third axis C3direction. In addition, the second portion633aand the third portion633bare located at respective different positions in a direction in which the first arm portion632extends. A portion defined by the first surface632b, the second guide surface of the second portion633a, and the third guide surface of the third portion633bfunctions as the guide portion633configured to guide movement of the second portion653of the torsion spring65.

The covering portion634may have a plate-like shape. The covering portion634extends outward from the engagement portion631in a radial direction of the engagement portion631. More specifically, for example, the covering portion634may have a substantially fan shape. A width of the covering portion634may increase as the covering portion634extends outward in the radial direction of the engagement portion631. The covering portion634is located at one end of the engagement portion631in the third axis C3direction. The one end of the engagement portion631is farther from the support frame21than the other end of the engagement portion631in the third axis C3direction is from the support frame21.

The covering portion634is positioned farther from the support frame21than the distal end646bof the protrusion646is from the support frame21in the third axis C3direction. In other words, the covering portion634is spaced from the distal end646bof the protrusion646by a particular dimension smaller than a dimension of the spiral portion651of the torsion spring65in the third axis C3. The covering portion634covers the distal end646bof the protrusion646. The covering portion634is an example of a covering portion covering the distal end646bof the protrusion646.

The first arm portion632includes the first position restriction portion635aat a surface thereof facing the pivot direction of the first arm63and facing the first contactable portion647aof the second arm64. The first position restriction portion635ais contactable with the first contactable portion647a. The covering portion634includes the second position restriction portion635bat a surface thereof facing the pivot direction of the first arm63and facing the second contactable portion647bof the second arm64. The second position restriction portion635bis contactable with the second contactable portion647b.

As illustrated inFIGS. 7A and 7B, the first arm63, the second arm64, the torsion spring65are assembled such that the engagement portion631of the first arm63is engaged with the engagement portion642of the second arm64and the torsion spring65is positioned between the first arm63and the second arm64.

In such an assembled state, the first portion652of the torsion spring65is engaged with the restriction portion644dof the second arm64and the second portion653of the torsion spring65is engaged with the guide portion633of the first arm63. The first arm63and the second arm64are thus urged by the torsion spring65such that the first arm63pivots in an approaching direction in which the first pawl632amoves toward the second pawl643aand the second arm64pivots in an approaching direction in which the second pawl643amoves toward the first pawl643a.

In response to the first arm63and the second arm64pivoting in their respective approaching directions by an urging force of the torsion spring65, the first position restriction portion635aof the first arm63and the first contactable portion647aof the second arm64contact with each other, thereby restricting the first arm63and the second arm64from further rotating in their respective approaching directions.

The position of the first arm63relative to the second arm64in a state where the first position restriction portion635aand the first contactable portion647acontact with each other may refer to a first position (refer toFIG. 7A). That is, the first arm63is configured to be held in the first position by the first position restriction portion635a. When the first arm63is located at the first position, the first contactable portion647acontacts the first position restriction portion635a. In a state where the first position restriction portion635acontacts the first contactable portion647a, the first arm63and the second arm64form an angle θ1therebetween.

In response to the first arm63and the second arm64pivoting in their respective separating directions against the urging force of the torsion spring65, the second position restriction portion635bof the first arm63and the second contactable portion647aof the second arm64contact with each other, thereby restricting the first arm63and the second arm64from further rotating in their respective separating directions. When the first arm63pivots in the separating direction, the first pawl632amoves in a direction away from the second pawl643a. When the second arm64pivots in the separating direction, the second pawl643amoves in a direction away from the first pawl632a.

The position of the first arm63relative to the second arm64in a state where the second position restriction portion635band the second contactable portion647bcontact with each other may refer to a second position (refer toFIG. 7B). That is, the first arm63is configured to be held in the second position by the second position restriction portion635b. When the first arm63is located at the second position, the second contactable portion647bcontacts the second position restriction portion635b.

In a state where the second position restriction portion635bcontacts the second contactable portion647b, the first arm63and the second arm64form an angle θ2therebetween. The angle θ2is larger than the angle θ1.

As described above, the first arm63is rotatable between the first position and the second position. When the first arm63is located at the first position, the covering portion634covers the distal end646bof the protrusion646. When the first arm63is located at the second position, the covering portion634also covers the distal end646bof the protrusion646. Further, when the first arm63is located at any position between the first position and the second position, the covering portion634covers the distal end646bof the protrusion646.

As described above, the covering portion634covers the distal end646bof the protrusion646at all times. Consequently, once the first arm63, the second arm64, the torsion spring65are assembled, the covering portion634may reduce or prevent the torsion spring65engaged with the protrusion646from disengaging therefrom via the distal end646b.

That is, the covering portion634covers the distal end646bof the protrusion646to reduce or prevent the torsion spring65from disengaging from the protrusion646.

The first position restriction portion635acauses the first arm63to stop at the first position such that, when the first arm63is located at the first position, the covering portion634covers the distal end646bof the protrusion646. The first position restriction portion635afurther causes the first arm63to stop at the second position such that, when the first arm63is located at the second position, the covering portion634covers the distal end646bof the protrusion646.

Such a configuration may enable the covering portion634to cover the distal end646bof the protrusion646at all times when the first arm63pivots between the first position and the second position. The effect of the covering portion634that reduces or prevents disengagement of the torsion spring65may be thus achieved not only when the torsion spring65is assembled to the first arm63and the second arm64but also when the drive unit6is driven.

The protrusion646that may be engaged with the torsion spring65is located at the second arm64that may be disposed adjacent to the first arm63. Such a configuration may thus enable the torsion spring65and the covering portion634to be disposed adjacent to each other. Consequently, as compared with a case where the first arm63and the second arm64are disposed far from each other, the covering portion634may have a smaller size, thereby enabling a size reduction of the drive unit6.

Procedure for Assembling First Arm, Second Arm, and Torsion Spring

Hereinafter, a procedure for assembling the first arm63, the second arm64, and the torsion spring65will be described.

As illustrated inFIG. 8A, the second arm64is oriented such that the distal end646bof the protrusion646is located above the proximal end646aof the protrusion646. Then, the spiral portion651of the torsion spring65is placed around the protrusion646from the distal end646b. More specifically, for example, the torsion spring65is placed around the protrusion646such that the first portion652of the torsion spring65is located on the second arm portion643side relative to the protrusion646and the second portion653of the torsion spring65is located on the guide arm portion644side relative to the protrusion646.

Thereafter, as illustrated inFIG. 8B, the engagement portion631of the first arm63is engaged with the engagement portion642of the second arm64. More specifically, for example, the first arm63is engaged with the second arm64such that the first arm portion632is located on the guide arm portion644side relative to the engagement portion642.

Then, as illustrated inFIG. 8C, the first portion652of the torsion spring65is turned toward the guide arm portion644(e.g., clockwise inFIG. 8C). In response to the turn of the first portion652of the torsion spring65, the second portion653of the torsion spring65moves correspondingly and is thus engaged with the guide portion633of the first arm portion632. After the second portion653of the torsion spring65is engaged with the guide portion633, a further clockwise movement of the second portion653is restricted and a future movement of the second portion653is guided by the guide portion633. In response to a further clockwise turn of the first portion652of the torsion spring65after the second portion653of the torsion spring65is engaged with the guide portion633, the torsion spring65generates an urging force acting in a direction opposite to the turning direction of the torsion spring65.

Thereafter, as illustrated inFIG. 8D, the first portion652of the torsion spring65is further turned clockwise to be engaged with the restriction portion644dof the guide arm portion644of the second arm64. In such a state, although the first portion652of the torsion spring65is urged in the direction opposite to the turning direction of the torsion spring65by the urging force of the torsion spring65, the engagement of the first portion652with the restriction portion644drestricts the movement of the first portion652of the torsion spring65in the urging direction relative to the second arm64.

In a state where the first portion652of the torsion spring65is engaged with the restriction portion644dof the second arm64and the second portion653of the torsion spring65is engaged with the guide portion633of the first arm63, the first arm63and the second arm64are urged by the torsion spring65such that the first arm63pivots in its approaching direction in which the first pawl632amoves toward the second pawl643aand the second arm64pivots in its approaching direction in which the second pawl643amoves toward the first pawl632a.

In the step of engaging the first portion652of the torsion spring65with the restriction portion644d, the guide portion644emay facilitate the engaging step. More specifically, for example, the first portion652is turned toward the restriction portion644dwith contacting the guide portion664eof the second arm64. By doing so, the first portion652is guided downward along the inclined guide portion644eand may be thus engaged with the restriction portion644dreadily.

After the first arm63, the second arm64, and the torsion spring65are assembled into a unit, the unit is assembled to the support frame21. More specifically, for example, the engagement portion641of the second arm64is engaged with the support shaft211of the support frame21to assemble the unit into the support frame21.

In the step of assembling the unit to the support frame21, a working robot may hold the handle647of the second arm64from above to pick up the unit.

In the unit, the second arm64is positioned below the first arm63and the torsion spring65. Thus, if the second arm64does not include the handle647, it may be difficult for the working robot to pick up the second arm64.

In this example, the second arm64includes the handle647extending from the second arm64to the particular position in the protruding direction of the protrusion646such that the handle647overlaps the first arm63when viewed in the direction perpendicular to the third axis C3direction. Such a configuration may thus enable the working robot to hold the handle647of the second arm64and pick up the unit readily without dropping. In particular, the handle647includes the first contactable portion647aand the second contactable portion647blocated opposite to each other relative to the engagement portion642. Such a configuration may thus enable the working robot to pick up the unit further readily. In addition, the handle647may enable a human operator to also hold and lift the unit readily.

The first contactable portion647aof the handle647causes the first arm63to stop at the first position by contacting the first position restriction portion635awhen the first arm63is located at the first position. The second contactable portion647bof the handle647causes the first arm63to stop at the second position by contacting the second position restriction portion635bwhen the first arm63is located at the second position.

As described above, each of the first contactable portion647aand the second contactable portion647bof the handle647may be used for holding the second arm64and for causing the first arm63to stop at the first position or at the second position.

Operation of Drive Unit

Hereinafter, operation of the drive unit6will be described in detail.

As illustrated inFIG. 2, in a state where the toothless portion62bof the sector gear62faces the input gear611and the sector gear62is not allowed to rotate, the sector gear62might not rotate even if the input gear611is driven to be rotated. The second arm64is urged by the urging member in a direction in which the second arm64pivots about the third axis C3such that the second pawl643amoves toward the second cam622of the sector gear62. In such a state, the first arm63is located at the first position.

The second cam622is configured to, in response to the sector gear62rotating, pivot the second arm64about the third axis C3. The first arm63is configured to, in response to the second arm64being pivoted by the second cam622, move between an engaged position and a disengaged position. When the first arm63is located at the engaged position, the first pawl632ais in engagement with a tooth of the second output gear613. When the first arm63is located at the disengaged position, the first pawl632ais not in engagement with any tooth of the second output gear613.

In a state where the toothless portion62band the input gear611face each other, the second arm64is oriented such that the second pawl643ais located relatively close to the second axis C2and the first arm63is located at the disengaged position where the first pawl632ais not in engagement with any tooth of the second output gear613.

In the state illustrated inFIG. 2, the second output gear613is not in engagement with the first pawl632aof the first arm63and is thus allowed to rotate. Consequently, in response to the input gear611starting rotating in such a state, the second output gear613rotates to output a drive force and the first output gear612is not allowed to rotate.

In response to changing of the state of the sector gear62to allow the sector gear62to rotate from the state illustrated inFIG. 2, the sector gear62starts rotating in the second direction by the urging member to cause the toothed portion62aof the sector gear62to mesh with teeth of the input gear611.

Thereafter, the sector gear62is rotated by a drive force transmitted from the input gear611. As illustrated inFIG. 9, in response to the input gear611rotating the sector gear62, the second arm64pivots in a direction in which the second pawl643amoves away from the second axis C2. The first arm63pivots to the engaged position in accordance with the rotation of the second arm64and thus the first pawl632aof the first arm63comes into engagement with a tooth of the second output gear613.

In the state illustrated inFIG. 9, the second output gear613is in engagement with the first pawl632a. Thus, the second output gear613is not to be allowed to rotate while the first output gear612is allowed to rotate, thereby enabling the first output gear612to output a drive force. In such a state, the first arm63is located at the first position and the first contactable portion647aand the first position restriction portion635aare in contact with each other.

In response to the input gear611further rotating from the state illustrated inFIG. 9, the second cam622causes the second arm64to further pivot in the direction in which the second pawl643amoves away from the second axis C2. In such a state, the first arm63is not allowed to rotate by the engagement of the first pawl632aand the second output gear613. The second arm64thus pivots relative to the first arm63.

In response to the second arm64pivoting relative to the first arm63, as illustrated inFIG. 10, the first arm63pivots to the second position and the second contactable portion647band the second position restriction portion635bcome into contact with each other. During the state change from the state ofFIG. 9to the state ofFIG. 10, the first arm63is urged toward the second output gear613by the urging force of the torsion spring65.

As described above, the first arm63and the second arm64are configured to drive the switch gear assembly61of the drive unit6to change the destination to which a drive force is transmitted. In addition, the first arm63includes the covering portion634. The first arm63may thus also serve as a stopper for the torsion spring65.

In this example, the second arm64is configured to contact the second cam622and the first arm63is configured to engage the second output gear613. Nevertheless, in another example, the first arm63may be configured to contact the second cam622and the second arm64may be configured to engage the second output gear613.