NZ762637A - Quick hitch - Google Patents

Abstract

A quick hitch assembly for attaching an implement to a boom of a carrier or vehicle, the quick hitch assembly comprises attachment means for attaching the quick hitch assembly to a boom of a carrier or a vehicle, a first recess for receiving a first pin of an implement and a second recess for receiving a second pin of an implement, a latch having a first pin engaging portion, the latch being movable to selectively engage the first pin and to retain the first pin in the first recess, a moving engagement means, the moving engagement means being movable to selectively engage the second pin and to retain the second pin in the second recess, drive means for driving the latch and the moving engagement means to engagement positions to respectively engage the first pin and the second pin, and locking means being operable to prevent unwanted removal of the first pin and the second pin from their respective recesses, the locking means also being operable to allow the first pin and the second pin to move out of their respective recesses to enable removal of the implement from the boom. eiving a second pin of an implement, a latch having a first pin engaging portion, the latch being movable to selectively engage the first pin and to retain the first pin in the first recess, a moving engagement means, the moving engagement means being movable to selectively engage the second pin and to retain the second pin in the second recess, drive means for driving the latch and the moving engagement means to engagement positions to respectively engage the first pin and the second pin, and locking means being operable to prevent unwanted removal of the first pin and the second pin from their respective recesses, the locking means also being operable to allow the first pin and the second pin to move out of their respective recesses to enable removal of the implement from the boom.

Description

TITLE Quick hitch TECHNICAL FIELD The present invention relates to a quick hitch assembly for attaching implements to a boom or arm of a carrier or vehicle.

BACKGROUND ART Implements conventionally fitted to heavy machinery include those suitable for loading, working or carrying loads such as a bucket, dipper bucket, fork lift unit, hydraulic shovel, grader, drill unit, ripper, scarifier, etc. Conventionally, the implements are fitted to the heavy machinery by manually inserting large steel pins through holes in plates formed on the implements and in the operating arms of the machinery. This is a time consuming and tedious process. The operator must also alight from the controls of the vehicle or carrier or employ the services of an assistant to attach the implement.

To rectify this, quick hitch assemblies have been proposed. These assemblies normally enable the connection of the implement to the heavy machinery to be effected automatically by the operator, that is, without the need to alight from the controls of the machinery.

It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

SUMMARY OF INVENTION The present invention is directed to a quick hitch, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.

With the foregoing in view, the present invention in one form, resides broadly in a quick hitch assembly for attaching an implement to a boom of a carrier or vehicle, the quick hitch assembly comprising: - attachment means for attaching the quick hitch assembly to a boom of a carrier or a vehicle, - a first recess for receiving a first pin of an implement and a second recess for receiving a second pin of an implement, - a latch having a first pin engaging portion, the latch being movable to selectively engage the first pin and to retain the first pin in the first recess, - a moving engagement means, the moving engagement means being movable to selectively engage the second pin and to retain the second pin in the second recess, - drive means for driving the latch and the moving engagement means to engagement positions to respectively engage the first pin and the second pin, and - locking means being operable to prevent unwanted removal of the first pin and the second pin from their respective recesses, the locking means also being operable to allow the first pin and the second pin to move out of their respective recesses to enable removal of the implement from the boom.

In one embodiment, the latch comprises a sliding latch. The latch may comprise a tongue. The first pin engaging portion may comprise a hook formed with or attached to the tongue. The hook may comprise a generally U-shaped hook.

In one embodiment, the moving engagement means is rotatable. In one embodiment, the moving engagement means is pivotally mounted to a body or a shell of the quick hitch.

The drive means may comprise a first drive means that drives the latch and a second drive means that drives the moving engagement means. In another embodiment, the drive means comprises a drive means that drives both the latch and the moving engagement means.

In one embodiment, the drive means includes an extendable and retractable cylinder or an extendable and retractable arm. In embodiments where the drive means includes an extendable and retractable cylinder, the cylinder may comprise a hydraulic cylinder or a pneumatic cylinder. As most implements are operated by hydraulic fluid, it is likely that commercial embodiments of such cylinders will comprise hydraulic cylinders.

In one embodiment, a first end of the drive means is mounted to or engages with a body of the moving engagement means and a second end of the hydraulic cylinder is mounted to or engages with the latch. The first end of the drive means may be movable between a forward position and a rear position. The second end may also be movable between a forward position and a rear position.

The quick hitch may be further provided with a biasing means to bias the latch to a position at which the first pin cannot be removed from the quick hitch. The biasing means may also bias the moving engagement means to a position at which the second pin cannot be removed from the quick hitch. The biasing means may comprise a compression spring.

In one embodiment, the locking means comprises a further latch that is located between the latch and the moving engagement means. When the further latch is in a locking position, the further latch prevents or minimises movement of the latch towards the moving engagement means. Advantageously, the further latch may also prevent motion of the moving engagement means to a position at which neither the front or rear pins can be removed from the quick hitch. In another embodiment, the further latch may function as a stop member that allows a degree of movement of the latch towards the moving engagement member, with the further latch stopping movement of the latch towards the moving engagement member before the latch has moved to a location at which the first pin can be removed from the quick hitch.

In one embodiment, the locking means is integrally formed with the moving engagement means. In another embodiment, the locking means is separate to the moving engagement means. The locking means may comprise a single locking means. The locking means may comprise a first locking means and a second locking means.

The quick hitch may comprise a body or a shell or a chassis. The body or shell or chassis may have opposed side members and one or more cross members joining the side members together. Opposed ears may extend upwardly, with the opposed ears having aligned openings to receive pins that enables a quick hitch to be attached to a boom or an arm of an implement. The opposed openings may be provided with bearings in order to minimise wear.

The body, shell or chassis may have essentially closed sides and a closed top to increase the strength of the quick hitch. In some embodiments, the quick hitch comprises a body shell design that is enclosed on all sides except for the side where the implement engages, to provide greater structural strength and stiffness.

In a second aspect, the present invention provides a quick hitch comprising: - attachment means for attaching the quick hitch assembly to a boom of a carrier or a vehicle, - a first recess for receiving a first pin of an implement and a second recess for receiving a second pin of an implement, - a tongue having a first pin engaging portion, the tongue being movable to selectively engage the first pin and to retain the first pin in the first recess, - a locking latch movably mounted to the quick hitch, the locking latch member including a movable engagement means, the locking latch engagement means being movable to selectively engage the second pin and to retain the second pin in the second recess, - drive means for driving the tongue and the locking latch to engagement positions to respectively engage the first pin and the second pin, and - locking means being operable to prevent unwanted removal of the first pin and the second pin from their respective recesses, the locking means also being operable to allow the first pin and the second pin to move out of their respective recesses to enable removal of the implement from the boom, wherein the locking means includes: a strut or an extension on the rotatable locking latch, the strut or extension extending towards the tongue, plus a hook latch extending away from the tongue towards the front pin. wherein when the tongue is in a position where it engages the first pin and when the movable engagement means is in a position where it engages the second pin, the strut or extension is positioned such that movement of the tongue towards the moving engagement means causes a part of the tongue to come into contact with the strut or extension to thereby prevent further movement of the tongue towards the moving member.

In one embodiment, the locking means includes a strut or an extension on the rotatable locking latch, the strut or extension extending towards the tongue, and a hook latch extending away from the tongue towards the front pin.

In embodiments of the second aspect of the present invention, the driving means may comprise an extendable and retractable arm or an extendable and retractable cylinder or ram.

In one embodiment of the second aspect of the present invention, the movable member includes a slot or recess for receiving a driving means, such operation of the drive means causes motion of the movable member.

In one embodiment of the second aspect of the present invention, the driving means can selectively move the moving member in a forward direction and in a reverse direction. In an embodiment of the second aspect of the present invention, the driving means also drives the tongue along a reciprocating or slidable path.

In a third aspect, the present invention provides a quick hitch comprising: - attachment means for attaching the quick hitch assembly to a boom of a carrier or a vehicle, - a front recess for receiving a front pin of an implement and a rear recess for receiving a rear pin of an implement, - a front pin retainer being selectively movable between a retaining position in which the front pin retainer retains the front pin in the front recess and a retracted position in which the front pin retainer is clear of the front pin in the front recess; - a rear pin retainer being selectively movable between a retaining position in which the rear pin retainer retains the rear pin in the rear recess and a retracted position in which the rear pin retainer allows the rear pin to move out of the rear recess; - actuation means for selectively moving the front pin retainer between the retracted position and the retaining position and selectively moving the rear pin retainer between the retracted position and the retaining position; and -a locking member being operable to prevent unwanted removal of the front pin and the rear pin from their respective recesses, the locking member also being operable to move to an unlocked position to allow the front pin and the rear pin to move out of their respective recesses to enable removal of the implement from the boom, the locking member having at least a part that in a locking position is located between a part of the front pin retainer and a part of the rear pin retainer, wherein when the rear pin retainer is in the retaining position where it retains the rear pin in the rear recess and when the front pin retainer is in the retaining position where it retains the front pin in the front recess, the locking member is positioned such that movement of the rear pin retainer towards the front pin retainer causes a part of the rear pin retainer to come into contact with at least a part of the locking member to thereby prevent further movement of the rear pin retainer towards the front pin retainer.

In one embodiment, when the locking member is in the locking position, movement of the rear pin retainer towards the front pin retainer causes part of the rear pin retainer to come into contact with the locking member which, in turn, transmits a force to the front pin retainer to thereby more tightly retain the front pin.

In one embodiment, the front pin retainer may comprise a rotatable member having a hook portion, the rotatable member being pivotally mounted to the quick hitch. The locking member may be integrally formed with the rotating member and the at least a part of the locking member may comprise a strut or arm of the rotatable member. The rear pin retainer may comprise a sliding tongue that can reciprocally move forwardly and rearwardly in the quick hitch. The sliding tongue may have a portion that comes into contact with the locking member when the sliding tongue and the front pin retainer are in the retaining positions.

The actuation means may comprise a driving means, such as a hydraulic ram or hydraulic cylinder. A biasing means, such as a spring, may also be provided to bias the front pin retainer and the rear pin retainer to the retaining positions in the event of hydraulic failure.

In another embodiment, the locking member may be provided as a separate component to the front pin retainer and the rear pin retainer. For example, the locking member may comprise a rotating locking latch that is pivotally connected to the quick hitch, the locking member being moved to the locking position when the front pin retainer and the rear pin retainer are moved to the retaining positions, the locking member being moved out of the locked position when it is desired to move the front pin retainer and the rear pin retainer to the retracted positions at which the implement pins can be removed from the quick hitch. In this embodiment, the locking means may be moved by a locking pin drive means. The locking pin drive means may comprise hydraulic fluid, a hydraulic ram or hydraulic cylinder, a small motor, a stepper motor, or the like.

Other features of this aspect of the present invention may be as described with reference to the first aspect of the invention and the second aspect of the invention.

Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention.

The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

BRIEF DESCRIPTION OF DRAWINGS Various embodiments of the invention will be described with reference to the following drawings, in which: Figure 1 shows a side view of the shell or chassis of a quick hitch in accordance with an embodiment of the present invention; Figure 2 shows a side view of a rotatable locking latch member, a sliding tongue and spring and stop member that are mounted to the chassis shown in figure 1; Figure 3 shows a side view of a hydraulic ram that may be used in conjunction with the embodiment shown in figures 1 and 2 to drive the components of the quick hitch; Figure 4 shows a cross sectional side view taken through a centre section of the quick hitch that has been assembled from the components shown in figures 1 to 3; Figure 5 shows a cross sectional side view taken at the shell wall/chassis wall of the quick hitch in accordance with the embodiment shown in the drawings; Figure 6 shows a front sectional side view taken at tongue guide keys 2.1 shown in figure 5; Figure 7 shows a front sectional view taken at ram guide slots 2.2 shown in figure 5; Figures 8A to 8E show schematic cross sectional views of the quick hitch shown in figures 1 to 7, with some detail removed, showing the sequence of actions that occur in order to lock the front pin and the rear pin of an implement in place; and Figures 9A to 9E show schematic cross sectional views of the quick hitch shown in figures 1 to 7, with some detail removed, showing the sequence of actions that occur in order to unlock and remove the front pin and the rear pin of an implement from the quick hitch.

DESCRIPTION OF EMBODIMENTS It will be appreciated that the drawings have been provided for the purposes of describing preferred embodiment of the present invention. Therefore, it will be understood that the present invention should not be considered to be limited solely to the features as shown in the attached drawings.

The quick hitch 10 shown in figures 1 to 7 comprises a chassis having side plates 12, 14 and a top plate 16 that connects the side plates 12, 14. Other cross members (not numbered in figures 6 and 7) may also be present to form a strong and stiff chassis. The quick hitch also includes upstanding ears 18, 20. Ears 18, 20 have opposed openings 22, 24. Opposed openings 22 and opposed openings 24 can receive pins that attach the quick hitch 10 to a boom or arm of an implement, such as a front end loader, a digger, an excavator, or the like.

Turning to figure 1, which shows part of the chassis, the side plate 12 has a second recess 26 formed in a lower surface thereof and a first recess 28 formed in a front part thereof.

Second recess 26 has opposed shoulders 30, 32 and a central wall 34 extending between the shoulder 30 and the shoulder 32. The second recess 26 is sized so that it is larger than a rear pin PR. This enables some room for misalignment when the quick hitch 10 is moved to position the rear pin PR into the second recess 26.

The first recess 28, which is a front recess for the quick hitch, has a lower wall 36 and an upper wall 38. The first recess 28 is formed as a generally U-shaped recess having a reasonable depth to it. The first recess 28 is sized so that it can receive a front pin PF of an implement to be attached to the quick hitch.

The sidewall 12 has a key 2.1 formed in it. Key 2.1 is in the form of a slot machined into or cast into the sidewall 12. A ram slot 2.2 is formed in a front part of the sidewall or, in the embodiment shown in figure 1, ram slot is formed in a plate 40 welded to or otherwise attached to the side plate 12. It will be appreciated that figure 1 shows the inside wall of side plate 12. The side plate 12 is also provided with a hole 42 for mounting the rotatable locking latch member thereto (to be explained in more detail hereunder). Side plate 12 is also provided with holes 44, 46, which enable stop member 7 to be mounted thereto, as described hereunder. The other side plate 14 is similarly arranged with an inner wall that faces side plate 12 having similar features as shown for side plate 12 in figure 1.

Figure 2 shows the tongue 3, rotating locking latch member 5, spring 6 and stop member 7. The tongue 3 is slidably mounted in slot 2.1. Rotating locking latch member 5 is pivotally mounted to the hole 42 by use of appropriate pivot pin. Stop member 7 is mounted by appropriate mounting pins that extend through openings 48, 49 in stop member 7 and through openings 44, 46 in sidewall 12. A similar stop member is mounted to sidewall 14. The stop member 7 is positioned in the assembled quick hitch such that the end 7A positioned just to the right of the entrance to ram slot 2.2 that is shown in figure 1.

Biasing spring 6, which is a compression spring, has a first end 50 that contacts an inner end 51 of tongue 3. The second end 52 of biasing spring 6 is restrained by a ring 54 mounted to a hydraulic ram 4 (see figure 3). Hydraulic ram 4 comprises a cylinder 56 and the piston 58. Cylinder 56 has a trunnion 57 at one end thereof. Piston 58 has a clevis 59 at another end thereof. It will be appreciated that trunnion pins are omitted from trunnions 57 and 59 for clarity. The hydraulic ram 4 is a two-way ram that can be driven to extend and driven to retract.

The construction of such rams will be well understood by person skilled in the art. As will be appreciated, the left-hand end of biasing spring 6 extends around the outer periphery of cylinder 56 to the right of ring 54.

The tongue 3 comprises a tongue body 60 having a U-shaped hook 61 extending from a lower part of one end of the tongue body 60. A housing or bore 62 receives a clevis pin of the clevis 59 of the hydraulic ram 4. The tongue 3 includes an extension arm 63 extending forwardly from an upper part of the tongue body 60.

The rotating locking latch member 5 has a hook portion 64 formed therein. An opening 65 receives a pivot pin that enables the rotating member 5 to be pivotally mounted through hole 42 in the side plate 12. A slot 66 is formed in the rotating member 5. The slot 66 can receive a trunnion pin of the trunnion 57 of the cylinder 56 of the hydraulic ram 4. As shown in figure 2, the stop 66 has a bottom that is circumferentially spaced from the opening 65, and therefore the bottom of the slot 66 is circumferentially spaced from the rotating axis or pivot axis of the rotating member 5. The rotating locking latch member 5 also includes a strut 67 extending rearwardly. The strut 67 may also be described as an extension arm.

The assembled ram 4, tongue 3, biasing spring 6 and rotating locking latch member 5 is shown in figure 4. In the assembled quick hitch, the trunnion pin associated with trunnion 57 of cylinder 56 of hydraulic ram 4 is positioned such that it is located within slot 66 of rotating locking latch member 5. The respective ends of the trunnion pin are also positioned in slot 2.2.

Due to the location of stop member 7, the trunnion pin associated with trunnion 57 of the hydraulic cylinder 56 can move between the left-hand end 2.2A of the slot 2.2 and the end 7A of the stop member 7, which effectively means that the trunnion pin of the hydraulic cylinder 56 is constrained to move only within slot 2.2. The tongue 3 has a surface 68 that can come into contact with surface 7B of stop member 7 when the tongue 3 is moved to its left-hand most location. Similarly, the trunnion pin associated with trunnion 59 of piston 58 of hydraulic ram 4 has movement that is constrained by the length of key 2.1, as the clevis pin of clevis 59 is mounted in bore 62 and the tongue 3 has movement that is limited by key 2.1.

Figures 8A to 8E show the movement of the various components that result in an implement becoming connected to the quick hitch 10. In figure 8A, the implement pins PF and PR are loaded into the front recess 28 and rear recess 26, respectively. Typically, the boom will be operated to move the quick hitch 10 forwardly so that the front pin PF enters into front recess 28 and the quick hitch is then pivoted by the boom and arm to locate the rear pin PR in the rear recess 26. In the position shown in figure 8A, the hydraulic ram 4 his fully retracted so that the rotating locking latch member 5 and the tongue 3 are in the retracted positions.

In figure 8B, the ram 4 is operated to move the tongue 3 towards rear pin PR. In this location, the U-shaped hook 61 of the tongue 3 comes into contact with the rear pin PR. In figure 8C, the hydraulic ram 4 is further extended, which causes the trunnion pin 57A of the cylinder 56 to move towards the left. Trunnion pin 57A is positioned in slot 66 of the rotating locking latch member 5. This causes the rotating locking latch member 5 to rotate in an anticlockwise direction. As a result, the hook 64 closes in on the front pin PF. This also causes the strut or extension arm 67 to rotate upwardly and towards the extension arm 63 of the tongue 3.

In figure 8D, the ram 4 is further extended such that trunnion pin 57A comes into contact with the end 2.2A of slot 2.2. This represents the furthest leftwards travel of the hydraulic cylinder 56 of the hydraulic ram 4. In this position, the hook 64 is fully closed on the front pin PF and the strut or extension arm 67 is located essentially in the same region as the extension arm 63 of the tongue the 3, with the respective ends of strut or extension arm 67 and arm 63 facing each other. In figure 8E, the hydraulic ram 4 continues to extend. As the trunnion pin 57A has hit its leftmost point of travel, the piston 58 of hydraulic ram 4 extends further to the right, which pushes the tongue 3 further to the right and moves the tongue 3 to the position as shown in figure 8E. In this position, the hook 61 of the tongue 3 fully engages the rear pin PR of the implement. Further, although the extension arm 63 of the tongue 3 and the rear extension arm or strut 67 of the rotating member are aligned with each other, there is a slight space between them.

The extension arm 67 acts as a locking arm in the quick hitch. As will be appreciated from figures 8 D and 8E, once the front pin and rear pin are retained by the respective hooks 64 and 61, if excessive force is applied to the rear pin, the rear pin could overcome a hydraulic ram 4 if it was in a failed condition and move from the position shown in figure 8E to the position shown in figure 8D. As can be seen in figure 8D, the tongue 3 moves forwardly until the end of extension arm 63 comes into contact with the strut or extension arm 67. As the trunnion pin 57A is fully locked in place at its leftmost position of travel, engagement between the extension arm 63 of tongue 3 and the strut 67 of rotating locking latch member 5 prevents further movement of the tongue 3 towards the left side of figure 8D. Further, the extension arm 63 of tongue 3 applies a force moment about the pivot pin that holds the rotating locking latch member 5 to the quick hitch. As a result, the front hook 64 clamps even more tightly onto the front pin.

Figures 9A to 9E show disengagement of the implement pins from the quick hitch.

Figure 9A, which is essentially identical to figure 8E, shows the hydraulic ram 4 holding the rear pin PR out to its fullest extent. In order to disengage the pins from the quick hitch, the hydraulic ram 4 is retracted so that tongue 3 moves back to contact rotating locking latch member 5 (see figure 9B). In particular, in figure 9D, the extension arm 63 of the tongue 3 contacts the strut 67 of the rotating locking latch member 5. Similarly, if hydraulic pressure in the hydraulic ram 4 fails, the tongue 3 can move only as far as shown in figure 8D. As a result, the rear pin PR cannot escape through the gap G. Further, front pin PF is firmly held in place by the hook portion 64 of the rotating locking latch member 5. Effectively, the locking means holds the pins of the implement in position in the event of hydraulic failure.

In order to continue removal of the implement from the quick hitch, the hydraulic ram 4 retracts further. As the biasing spring 6 has compressed somewhat, this further retraction of the hydraulic ram 4 causes the rotating locking latch member 5 to rotate in a clockwise direction, as shown in figure 9C. Further retraction causes the strut 67 of rotating member 5 to rotate further in a clockwise direction until it moves out of alignment with the extension arm 63 of the tongue 3. This then allows the tongue 32 to move towards the rotating locking latch member 5 with continued retraction of the hydraulic ram 4, as shown in figure 9D. Retraction of the tongue 7 continues until the tongue 3 hits the end 7B of stop 7. Continued retraction of the ram causes further clockwise rotation of the rotating locking latch member 5 until the hook portion 64 has rotated out of the way of front pin PF, as shown in figure 9E. Hydraulic ram 4 continues to retract until the trunnion pin 57A contacts the end 7A of the stop 7. At this stage, the implement pins PR and PF have been freed and the quick hitch can be removed from the implement.

In the embodiment shown in the attached drawings, the rotating locking latch member 5 comprises both the front pin retainer and the locking member. The front pin retainer and the locking member are formed as a single component that is pivotally mounted in the quick hitch by a single pivot pin. In other embodiments, the front pin retainer may be formed as a first component and the locking member may be formed as a separate member.

In preferred embodiments of the present invention, in the case of failure of the hydraulic ram, locking means restrain both the front pin and the tongue that engages with the rear pin. The front pin is restrained firstly by the hook. Further even without this hook it is still restrained from being able to travel far enough to allow the front pin to be released from its hook portion. Further, the rear tongue can only move by a small amount if there is hydraulic failure and the rear pin cannot pass through the gap between the rear side of the recess and the sliding tongue hook. As a result, both implement pins are restrained with double redundancy against release and they are also restrained against swing of the implement.

The remaining description in this specification relates to preferred embodiments of the present invention.

In preferred embodiments, the front pin lock is a simple hook pulling in line with the acting force on a trailing pivot pin attached to the body shell. Therefore, no sideway forces from the front pin can be created on this lock to release it, so it cannot be released other than by independent external disengagement.

The rear pin lock acts on its restraining tongue which, in turn, is resisted by the over- centre strut of the locking latch/rotating member. This over centre strut can only try to move up when forced from the rear pin tongue due to the rear pin trying to push it out of the way. This locking strut is restrained from moving up by the tongue and the tongue in turn is also restrained from moving up as it is keyed to the body. Thus, as the locking strut cannot rotate up and out of the way of the rear pin restraining tongue when the rear pin restraining tongue pushes on it. The locking strut bears the forces acting on it as a strut in compression back to the pivot pin and from this pivot back to the body. This pivot pin is also a common pivot pin shared with the front pin latch, which reduces parts. The over centre toggle action of this rear locking strut (being strut 67 in the drawings) means that the more load the rear pin applies to it in an effort to escape, the more the strut will lock up tighter to resist. Therefore, the locking latched strut cannot be released by pin forces acting on it. It can only be released by independent forcible external disengagement which comes from the trunnion of the main hydraulic ram when it is fully retracted.

In preferred embodiments, a single part combines for both the front latch hook/front pin retainer and the rear latch strut (strut 67) for locking both front and rear implement pins in a single combined locking latch. Further, this combined locking latch also pivots about a single pivot pin. Finally, as the combined front and rear latches are one common pivoting part, both functions are engaged and disengaged using a common actuator in the form of the moving trunnion, on the single hydraulic ram. Accordingly, the number of parts required is minimised in such preferred embodiments.

As a further advantage, each of the two pin locks are capable of resisting forces acting them up to the full force capacity that the implement can exert on each pin locking mechanism and without any additional restraint required to be provided from the primary hydraulic ram that is part of the quick hitch. The pin retaining means not only retain the pins against the above machine forces when transmitted through the pins, but also when these machine forces applied directly to the retaining means from the reactions from external objects in the material being dug that may directly act on the tongue as the retaining means. Without this locking latch rear strut retaining means, forces applied directly to the tongue could push the tongue away from the rear pin allowing disengagement of the rear pin.

In preferred embodiments, only a single driving means actuator is required. A single spring can automatically engage both pin retainers via the common double latch. Disengagement is done using the single primary hydraulic ram by the controlled retraction in the release direction of the ram. Retraction is completed after the release travel hits the respective tongue travel stops, which allows the hydraulic ram to provide additional independent travel needed to compress the engagement spring and force the two locks into the release positions.

The spring working on the trunnion actuating main hydraulic ram ensures the default position of the ram is with the rear trunnion up against the stop so that the ram pushes against it to extend for normal operation. This is also the default position under normal hydraulic operation during digging. The trunnion in this spring-loaded default position also means both the front hook and the rear strut of the double latch (rotating member) are in their pin locking positions. In the case of the rear tongue locking latch strut/rear pin retainer, it sits up in the position to catch the sliding tongue at its minimum pin centres position. If the tongue is forward of this due to longer pin centres. Should the hydraulic ram fail the tongue can only slide back to these minimum pin centre at which point the double lock rear strut is up in the default position to catch the tongue and restrict rear pin movements so the rear pin cannot pass through the gap between the sliding tongue hook in the rear stop on the shell.

The trunnion actuating hydraulic ram moving in retraction can only change the spring-loaded default condition when release travel is completed up to the travel stops for the implement pins. This in turn allows the hydraulic ram to provide the additional independent travel needed to compress the engagement spring and thus allows the trunnions to move forward from their normal end stops to allow the trunnions to force the pivoting double lock latch into the release positions for both front and rear locks. In this position, the implement can be either released from or loaded into the hitch.

Actuation of the pin latch is by a slot profile in the pivoting double latch locking component has the additional feature of having a rolling action on the motion between the driving trunnion of the ram and the slot of the locking latch to minimise sliding and wear. This is similar motion to that as used by gear teeth in contact with each other.

Preferred embodiments of the present invention have a body shell design that is enclosed on all sides except for the side where the implement engages. This provides greater structural strength and stiffness. A top hook-up plate connection can be provided to the lower implement-hook plates. This provides this connection from the lower front pin to the overhanging top front pin hook up plates without a stressed notch close to the main force path along the line joining the upper and lower front pins, as viewed from the vertical plane parallel to the hitch ram axis. Elimination of this stress connection notch provides a design with the fatigue resistance advantage over designs that commonly have such a notch close to the line of maximum force between upper and lower front pins.

The sliding tongue is designed with a spring recess capable of accommodating the length of the fully compressed spring. The tongue has holes to fit pins to restrain spring inside the tongue as one unit for assembly purposes. Further, the restraint ring for the spring is located on a small lip on the hydraulic ram so the main spring ring is separate from the ram, so it can be held behind the spring retaining pins. This allows the ram to pass between the above spring retaining pins, allowing the pins to be fitted and removed with the assistance of the ram to compress the spring. The purpose of these pins for restrain spring in the sliding tongue as one unit is to freely allow assembly and disassembly without having to fight against any springs.

These pins to retain the spring are only used to facilitate easy maintenance and are removed for normal operation.

The sliding tongue for the rear pin is designed to minimise digging radius and maximise digging force. The sliding tongue for the rear pin design eliminates leveraged digging forces perpendicular to the digging motion for all components except for the body shell of the hitch.

In the present specification and claims (if any), the word ‘comprising’ and its derivatives including ‘comprises’ and ‘comprise’ include each of the stated integers but does not exclude the inclusion of one or more further integers.

Reference throughout this specification to ‘one embodiment’ or ‘an embodiment’ means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases ‘in one embodiment’ or ‘in an embodiment’ in various places throughout this specification are not necessarily all referring to the same embodiment.

Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.

Claims (13)

1. CLAIMS 1. A quick hitch assembly for attaching an implement to a boom of a carrier or vehicle, the quick hitch assembly comprising: - attachment means for attaching the quick hitch assembly to a boom of a carrier or a vehicle, - a first recess for receiving a first pin of an implement and a second recess for receiving a second pin of an implement, - a latch having a first pin engaging portion, the latch being movable to selectively engage the first pin and to retain the first pin in the first recess, - a moving engagement means, the moving engagement means being movable to selectively engage the second pin and to retain the second pin in the second recess, - drive means for driving the latch and the moving engagement means to engagement positions to respectively engage the first pin and the second pin, and - locking means being operable to prevent unwanted removal of the first pin and the second pin from their respective recesses, the locking means also being operable to allow the first pin and the second pin to move out of their respective recesses to enable removal of the implement from the boom.
2. 2. A quick hitch assembly as claimed in claim 1 wherein the latch comprises a sliding latch.
3. 3. A quick hitch assemblyas claimed in claim 2 wherein the latch comprises a tongue and the first pin engaging portion comprise a hook formed with or attached to the tongue.
4. 4. A quick hitch assembly as claimed in claim 3 wherein the hook comprises a generally U- shaped hook.
5. 5. A quick hitch assembly as claimed in any one of the preceding claims wherein the moving engagement means is rotatable.
6. 6. A quick hitch assembly as claimed in claim 5 wherein the moving engagement means is pivotally mounted to a body or a shell of the quick hitch.
7. 7. A quick hitch assembly as claimed in any one of the preceding claims wherein the drive means comprises a first drive means that drives the latch and a second drive means that drives the moving engagement means, or the drive means comprises a drive means that drives both the latch and the moving engagement means.
8. 8. A quick hitch assembly as claimed in any one of the preceding claims wherein the drive means includes an extendable and retractable cylinder or an extendable and retractable arm.
9. 9. A quick hitch assembly as claimed in any one of the preceding claims wherein a first end of the drive means is mounted to or engages with a body of the moving engagement means and a second end of the hydraulic cylinder is mounted to or engages with the latch, the first end of the drive means binge movable between a forward position and a rear position and the second end being movable between a forward position and a rear position.
10. 10. A quick hitch assembly as claimed in any one of the preceding claims wherein the quick hitch is further provided with a biasing means to bias the latch to a position at which the first pin cannot be removed from the quick hitch.
11. 11. A quick hitch assembly as claimed in claim 10 wherein the biasing means also biases the moving engagement means to a position at which the second pin cannot be removed from the quick hitch.
12. 12. A quick hitch assembly as claimed in any one of the preceding claims wherein the locking means comprises a further latch that is located between the latch and the moving engagement means, wherein when the further latch is in a locking position, the further latch prevents or minimises movement of the latch towards the moving engagement means and/or the further latch also prevents motion of the moving engagement means to a position at which neither the front or rear pins can be removed from the quick hitch.
13. 13. A quick hitch assembly as claimed in claim 12 wherein the further latch functions as a stop member that allows a degree of movement of the latch towards the moving engagement member, with the further latch stopping movement of the latch towards the moving engagement member before the latch has moved to a location at which the first pin can be removed from the quick hitch. 15. A quick hitch comprising: - attachment means for attaching the quick hitch assembly to a boom of a carrier or a vehicle, - a first recess for receiving a first pin of an implement and a second recess for receiving a second pin of an implement, - a tongue having a first pin engaging portion, the tongue being movable to selectively engage the first pin and to retain the first pin in the first recess, - a locking latch movably mounted to the quick hitch, the locking latch member including a movable engagement means, the locking latch engagement means being movable to selectively engage the second pin and to retain the second pin in the second recess, - drive means for driving the tongue and the locking latch to engagement positions to respectively engage the first pin and the second pin, and - locking means being operable to prevent unwanted removal of the first pin and the second pin from their respective recesses, the locking means also being operable to allow the first pin and the second pin to move out of their respective recesses to enable removal of the implement from the boom, wherein the locking means includes: a strut or an extension on the rotatable locking latch, the strut or extension extending towards the tongue, plus a hook latch extending away from the tongue towards the front pin. wherein when the tongue is in a position where it engages the first pin and when the movable engagement means is in a position where it engages the second pin, the strut or extension is positioned such that movement of the tongue towards the moving engagement means causes a part of the tongue to come into contact with the strut or extension to thereby prevent further movement of the tongue towards the moving member. 16. A quick hitch comprising: - attachment means for attaching the quick hitch assembly to a boom of a carrier or a vehicle, - a front recess for receiving a front pin of an implement and a rear recess for receiving a rear pin of an implement, - a front pin retainer being selectively movable between a retaining position in which the front pin retainer retains the front pin in the front recess and a retracted position in which the front pin retainer is clear of the front pin in the front recess; - a rear pin retainer being selectively movable between a retaining position in which the rear pin retainer retains the rear pin in the rear recess and a retracted position in which the rear pin retainer allows the rear pin to move out of the rear recess; - actuation means for selectively moving the front pin retainer between the retracted position and the retaining position and selectively moving the rear pin retainer between the retracted position and the retaining position; and -a locking member being operable to prevent unwanted removal of the front pin and the rear pin from their respective recesses, the locking member also being operable to move to an unlocked position to allow the front pin and the rear pin to move out of their respective recesses to enable removal of the implement from the boom, the locking member having at least a part that in a locking position is located between a part of the front pin retainer and a part of the rear pin retainer, wherein when the rear pin retainer is in the retaining position where it retains the rear pin in the rear recess and when the front pin retainer is in the retaining position where it retains the front pin in the front recess, the locking member is positioned such that movement of the rear pin retainer towards the front pin retainer causes a part of the rear pin retainer to come into contact with at least a part of the locking member to thereby prevent further movement of the rear pin retainer towards the front pin retainer.