Locking device for a quick coupler

A quick coupler for coupling the pin of an attachment to earth working machinery, the coupler comprising a locking device comprising:

• a wedge locking element slidingly retained in the quick coupler and configured to move in a linear direction for coupling the pin of an attachment to said earth working machinery, the wedge locking element including
• a sloping wedge surface, and
• a pin engagement surface projecting from the sloping wedge surface, the pin engagement surface is located at and forming a distal leading part of the wedge locking element, wherein the pin engagement surface is substantially planar and lies in a plane that is substantially in line with the linear direction in which the wedge locking element and pin engagement surface are, in use, moved by a driving force, the pin engagement surface remaining in substantially in line with said linear direction during movement of the wedge locking element,
• wherein in a condition of normal use, the driving force maintaining the wedge locking element in a position whereby the pin is wedge coupled by the sloping wedge surface to the coupler, and
• wherein in a condition of failure of the driving force, the pin engages with said pin engagement surface such that the pin applies-a loading to the wedge locking element normal to the linear direction of movement of the wedge locking element, such that there is no loading acting in the linear direction of movement and the loading does not result in a retracting movement of the wedge locking element,
• the locking device further comprising a clamp device comprising a clamp arm operable to retain the pin with the pin engagement surface in the event of said failure of the driving force, wherein the clamp device is mounted to the wedge locking element via a mount for movement therewith, and
• wherein an angle between the sloping wedge surface and the pin engagement surface is obtuse.