The invention relates generally to a coupler for a hitch such as a quick hitch for a three point hitch or a Euroframe assembly of a work machine such as a tractor, a wheeled loader or the like, and more particularly, to a coupler having a latching mechanism for a holding bar of a work element such as an implement or the like, wherein the coupling mechanism is locked clearance-free by an additional, hydraulically operated wedge that locks between the holding bar and a base plate. BACKGROUND OF THE INVENTION

Quick hitches for three point hitches and Euroframe attachments of work machines such as tractors for agriculture, construction and earth moving are well known in the art. Usually they are equipped with releasably holding pins or bars, that latch into recesses or bores by horizontally shifting -wether mechanically spring loaded or hydraulically driven, one- or double-sided.

However, these mechanisms and its siblings inherit the disadvantage of mechanical wear and tear, which regularly results in a growing clearance between the movement of the hitch and the implement and thus between the tractor and the implement, thereby making it difficult to exactly position and move the implement, e.g. lifting forks into the lifting recesses of pallets or containers if not, even more delicately, positioning an exchange part or motor into correct position for mounting it.

The here disclosed invention therefore is to fix this problem of exact positioning at whatever age of the equipment and its state of wear and tear. PRIOR ART

There had been in fact quite a few attempts to solve that problem, as in

EP197026 with a triangular counter frame, locked against the triangular coupling frame, or US 5.732.488 with an elongated shaft, more hook elements and a ram with a link pin moved within, or GB 2471720 with more fixed or pivoted hooks (although there not for three point hitches, but for couplings to excavator buckets) . However, although alleviating the problem by less scuffing, these measures hitherto did not quite solve the problem of precise positioning with older equipment. PROBLEM TO BE SOLVED

Therefore it is the task of the here disclosed invention to find fixtures, that are free from float as well as remotely lockable and detachable for quick hitches and exchange frame systems on tractors and wheel loaders.

INVENTIVE STEP

The inventive step therefore is to quit the paradigma of locking the attachment device by bolts pushed into receptacles, or to use latches or other form-closed fixtures, but to secure the locking bars to the hooks of the holding device by hy- draulically jamming a wedge between a locking bar and the hook or holder, thus resulting in a quick lock-and-release mechanism that may be operated by remote control with hydraulic switches from the driver's position.

SUMMARY OF THE INVENTION

What is disclosed in a first embodiment is a hitch coupler for a three point hitch attachment of a work machine, such as a tractor or the like, which has both self-latching and self-locking capabilities and overcomes one or more of the problems and disadvantages set forth above and which is not only simpler in construction and complexity, but provides a hitherto unknown ease of handling in combination with exactitude and perfection of handling critical manipulations with implements.

In another embodiment the implement is attached to the front of the work machine which may be a tractor or wheeled loader by an implement holder, commonly a Euroframe.

The attachment is here fixed the same way with a fixed bar on it, that is inserted through an opening in the implement holder and locked to its crossbar with similar hydraulic wedges, that can as well be operated from the hydraulic steering box inside the vehicle. CLOSER DESCRIPTION ALONG TO THE DRAWINGS

Fig. 1 is a simplified side view of a representative work machine 1 , which is a tractor including a three point hitch 2 on a rear end thereof, a lifting mechanism 3 for it and an implement 4 (broken lines).

On its front side a big hydraulic lifting system 5 is working on a standard frame connector 6 , to which a work implement-attachment 7 (broken lines) is hooked on, to that a shovel, lifting fork or similar (not shown) may be fixed.

It is well to be seen, that the agricultural implemen4, as well as the front work implement attachment 6 are hooked on by lifting the hitch 2 respectively the implement attachment 6 by engaging it into the hooks .

Fig. 2 shows Prior Art: The standard locking device for a Euroframe attachment 10, using a toggle lever 11 , displacing two locking bars 12, 13 outwardly though passage holes 14, 15 into recesses 16, 17 within the frame attachment.

Fig 3 explains the new system for quick hitches: Instead of moved locking bars, two fixed bars 14, 15 on the implement attachment are moved into the implement holder's hooks and blocked by hydraulically moved wedges 16 and 17.

Fig. 4 demonstrates the system on an Euronorm exchange frame, where a bar 18 from the implement, that is moved into the implement holder 7 is fixed to it by hydraulically moved wedges 19 and 20, which are jammed into the space between the bar 18 and the implement holder's frame bar 21.

It is understood, that these wedges allow no clearance, which makes a perfect placement of the implement possible, e.g. for a lifting fork, that needs to be inserted into exactly matching recesses.