Patent ID: 7753599

Claim:
An accessory to be detachably attached to an apparatus-side detachably attaching portion of an apparatus, the accessory comprising: an accessory-side apparatus detachably attaching portion to be attached to the apparatus-side detachably attaching portion, the accessory-side apparatus detachably attaching portion including an attachment/detachment surface, an internally threaded portion open on the attachment/detachment surface, and an externally threaded member to be rotatably engaged with the internally threaded portion, wherein the externally threaded member is positioned either in a retraction position by rotation of the externally threaded member in one direction or in an extension position by rotation of the externally threaded member in an other direction opposite to the one direction, the retraction position being a position wherein a lead end portion of the externally threaded portion of the externally threaded member is retracted into the internally threaded portion and the externally threaded portion is exposed on the attachment/detachment surface, and the extension position being a position wherein the lead end portion of the externally threaded member is extended from the attachment/detachment surface, wherein the accessory-side apparatus detachably attaching portion further includes a central wall portion and two extending wall portions, the central wall portion including the internally threaded portion and extending along the axial direction of the internally threaded portion, the two extending wall portions respectively extending along a lateral direction at a same thickness from two sides of end portions of the central wall portion in the extension direction, wherein the attachment/detachment surface includes an end face of the central wall portion wherein the internally threaded portion is open and one-side faces of the two extending wall portions in a thickness direction, wherein other-side faces of the extending wall portions in the thickness direction are used as engagement faces extending in parallel to one another in an opposite direction of the attachment/detachment surface, and wherein ends of the two extending wall portions in extension directions are respectively used as guide surfaces extending perpendicular to the attachment/detachment surface and parallel to one another.