Patent ID: 7001137

Claim:
In a combination including a lifting arm, an implement holder coupled to the lifting arm for movement about a first horizontal transverse axis, mounted to the implement holder by a connecting arrangement including an elongate locking bar carried by said implement holder and extending along a second horizontal transverse axis that is generally parallel to said first horizontal transverse axis, said locking bar being mounted for movement in a first direction along said second horizontal transverse axis between a locking position wherein it penetrates aligned openings respectively provided in said implement holder and said implement, and an unlocking position, wherein it is withdrawn from those of the aligned openings which are in said implement, said locking bar including a stop surface and being movable about said second horizontal transverse axis to an arrested position wherein said stop surface engages said implement holder and prevents said locking bar from moving back to said locking position, a hydraulic lock control cylinder coupled to said locking bar and being selectively pressurized for moving said locking bar from said locking position to said unlocking position, and an implement control cylinder coupled between said lifting arm and said implement holder for adjusting said implement relative to said lifting arm, the improvement comprising: a coupling arrangement establishing a one-way connection between said hydraulic lock control cylinder and said locking bar so that movement of said locking bar in said first direction occurs only during extension of said hydraulic lock control cylinder and so that said locking bar may be moved relative to said coupling arrangement to and from said arrested position; a biasing member located for yieldably retaining said hydraulic lock control cylinder in a collapsed state; said hydraulic lock control cylinder being a single-acting cylinder and being selectively pressurized for effecting extension of said cylinder for moving said locking bar from said locking position to said unlocking position, whereby said lock control cylinder may be depressurized when said locking bar is in said arrested position, with said biasing member acting to return said lock control cylinder to said collapsed state.