Abstract: A coupling mechanism includes column-shaped plugs having engagement grooves, cylindrical sockets movable to and from the plugs in the axial direction, slip-proof members which are engaged with the engagement grooves of the plugs to prevent the plugs from slipping out of the sockets and sliding cylinders slidably fitted to the outside of the sockets in the axial direction of the plugs to enable the slip-proof members to engage with the engagement grooves. In operation, first spring members always urge the sliding cylinders in a direction to engage the slip-proof members with the engagement grooves. When cams of cam mechanisms rotates, the sliding cylinders are moved in opposition to the urging of the first spring members, so that the connection between the display units is released.

Abstract: A coupling mechanism includes column-shaped plugs having engagement grooves, cylindrical sockets movable to and from the plugs in the axial direction, slip-proof members which are engaged with the engagement grooves of the plugs to prevent the plugs from slipping out of the sockets and sliding cylinders slidably fitted to the outside of the sockets in the axial direction of the plugs to enable the slip-proof members to engage with the engagement grooves. In operation, first spring members always urge the sliding cylinders in a direction to engage the slip-proof members with the engagement grooves.