GB2424637A

GB2424637A - A quick hitch coupler with safety mechanism

Info

Publication number: GB2424637A
Application number: GB0606280A
Authority: GB
Inventors: Thomas Francis Sheedy; Thomas Patrick Quinlan
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-03-30
Filing date: 2006-03-29
Publication date: 2006-10-04
Also published as: IES20060247A2; GB0606280D0; IE20060248A1

Abstract

A quick hitch coupler (1) for coupling a bucket (5) or other implement to a dipper arm assembly (4) of an excavator. The quick hitch coupler (1) comprises a pair of side plate members (7) each having first engagement recesses (14) for engaging one of a pair of hitching pins (6) of the bucket (5), and an engagement member (20) pivotally carried on a primary pivot shaft (22) extending between the side plate members (7) is pivotal from a release position by a primary double-acting ram (28) to an engaged position for engaging the other of the hitching pins (6) for securing the bucket (5) to the coupler (1). A latching plate member (35) which is carried on a secondary pivot shaft (36) extending between the side plate members 7 is urged by a compression spring (39) into a latching state for engaging receiver elements (37) of the engagement member (20) for retaining the engagement member (20) in the engaged position in the event of failure of the primary ram (28). A secondary single acting ram (40) urges the latching plate member (35) from the latching state to an unlatched state for permitting pivoting of the engagement member (20) from the engaged position to the release position. The secondary ram (40) and the primary ram (28) are coupled to the same hydraulic supply, however, a restrictor valve is provided for delaying action of the primary ram (28) for urging the engagement member (20) from the engaged to the release position until the secondary ram (40) has urged the latching plate member (35) from the latching state to the unlatched state.

Description

"A quick hitch coupler" The present invention relates to a quick hitch

coupler, and in particular, to a quick hitch coupler for releasably hitching an implement, for example, an excavator bucket, an impact drill, or the like onto a working arm assembly of an earth working machine, for example, a dipper arm assembly of an excavator.

Quick hitch couplers for coupling such implements as excavator buckets, impact drills and the like to a dipper arm assembly of an excavator are known. Typically, such couplers comprise a pair of spaced apart side plate members joined by cross members. Each side plate member is provided with a pair of coupling bores for receiving pivot pins for securing the coupler to a dipper stick and a tipping link of the dipper arm assembly of the excavator. Various different types of engagement means are provided for engaging corresponding spaced apart parallel hitching pins of the implement. Such engagement means typically provide for quick hitching of the coupler to the implement, and also quick release therefrom. Typically, the side plate members of the coupler are provided with a pair of aligned engagement recesses for engaging one of the hitching pins, and a moveable engagement member is provided for engaging the other of the hitching pins. The movable engagement member co-operates with the engagement recesses in the side plate members for facilitating quick engagement of the hitching pins of the implement by the coupler, and quick release of the coupler from the hitching pins of the implement.

However, such quick hitch couplers suffer from a serious disadvantage, in that the moveable engagement member can be inadvertently moved from an engagement position with the implement coupled to the coupler to a release position whereby the implement can be inadvertently released from the coupler. This can result in serious, and indeed, fatal consequences. Various safety mechanisms have been proposed to overcome this problem, however, in general, such safety mechanisms suffer from various disadvantages, in that they militate against quick coupling and quick releasing of the implement to and from the coupler, or they do not always function adequately for preventing inadvertent release of the implement from the coupler. Additionally, many of such safety mechanisms require an operator of the excavator or a helper to manually engage and disengage the safety mechanism for securing the moveable engagement member in the engaged position and for releasing the moveable engagement member from the engaged position. This seriously militates against quick coupling and quick releasing of the implement to and from the coupler, since in the absence of a helper, an excavator operator must leave the cab of the excavator to secure or release the safety mechanism.

There is therefore a need for a quick hitch coupler which overcomes these problems.

The present invention is directed towards providing a quick hitch coupler which addresses at least some of the problems of known quick hitch couplers.

According to the invention there is provided a quick hitch coupler for hitching an implement to a working arm assembly of an earth working machine, the quick hitch coupler comprising a coupling means for releasably coupling the coupler to the working arm assembly of the earth working machine, a first engagement means for engaging one of a pair of spaced apart parallel hitching pins on the implement, a second engagement means for engaging the other of the pair of hitching pins, the second engagement means being moveable relative to the first engagement means between an engaged position co-operating with the first engagement means for coupling the implement to the coupler with the respective hitching pins engaged in the first and second engagement means, and a release position for facilitating disengagement of the hitching pins from the first and second engagement means for releasing the implement from the coupler, a primary urging means for urging the second engagement means from the release position to the engaged position, a latching means operable between a latching state for latching the second engagement means in the engaged position and an unlatched state for permitting release of the second engagement means from the engaged position, and a secondary urging means for urging the latching means from the latching state to the unlatched state, the secondary and primary urging means being operably coupled so that operation of the secondary urging means for urging the latching means from the latching state to the unlatched state commences prior to operation of the primary urging means for urging the second engagement means from the engaged position to the release position.

Preferably, the primary urging means is adapted for retaining the second engagement means in the engaged position. Advantageously, the primary urging means is adapted for urging the second engagement means between the engaged position and the release position.

In one embodiment of the invention, the latching means is resiliently urged into the latching state. Preferably, the latching means is springurged into the latching state.

In another embodiment of the invention, a delay means is provided for delaying operation of the primary urging means for urging the second engagement means from the engaged position to the release position until the secondary urging means has urged the latching means from the latching state to the unlatched state.

Preferably, the primary and secondary urging means comprise respective primary and secondary fluid operated rams, th' secondary ram being fluid operated for operating the latching means from the latching state to the unlatched state, and the primary ram being fluid operated for operating the second engagement means from the engaged position to the release position, and the delay means comprises a fluid restrictor for preventing initial operation of the primary ram for urging the second engagement means from the engaged position to the release position until the secondary ram has urged the latching means from the latching state to the unlatched state. Advantageously, the delay means comprises a fluid restrictor valve for acting to initially cushion movement of a piston of the primary ram in a direction corresponding to movement of the second engagement means from the engaged position to the release position.

Preferably, the primary ram is a double acting ram, and the fluid restrictor is located in a fluid port of the double acting ram for cushioning the movement of the piston of the primary ram in the direction corresponding to movement of the second engagement means from the engaged position to the release position.

In one embodiment of the invention, the secondary ram is a single acting ram.

Preferably, the primary and secondary rams are hydraulic rams.

In another embodiment of the invention, a receiver is provided on the second engagement means for engagement with the latching means when the latching means is in the latching state for latching the second engagement means in the engaged position.

In a further embodiment of the invention, the latching means is pivotally mounted, and is pivotal between the latching state and the unlatched state.

Preferably, the second engagement means is pivotally mounted and is pivotal between the engaged and the release positions. Advantageously, the second engagement means terminates in a hook-shaped member for engaging the corresponding hitching pin of the implement.

In one embodiment of the invention, the coupler comprises a pair of spaced apart side plate members, the coupling means for releasably coupling the coupler to the working arm assembly of the earth working machine being formed in the side plate members.

In another embodiment of the invention, the first engagement means comprises a pair of first engagement recesses, one first engagement recess being formed in each side plate member, the first engagement recesses being aligned with each other and defining respective open mouths for accommodating the one of the pair of hitching pins of the implement into the first engagement recesses, the open mouths of the first engagement recesses facing in a direction opposite to the direction of movement of the second engagement means from the release position to the engaged position.

Advantageously, a pair of intermediate plate members extend between the side plate members, the intermediate plate members being located on respective opposite sides of the respective first engagement recesses, and extending from each other at an angle for defining a V-shaped trough extending between the side plate members for engaging the hitching pin when engaged in the first engagement recesses.

In one embodiment of the invention, each side plate member comprises a second engagement recess, the second engagement recesses in the respective side plate members being aligned with each other and co- operating with the second engagement means for retaining the corresponding hitching pin in the quick hitch coupler.

Preferably, the second engagement means is located between the side plate members and is pivotally carried on a primary pivot shaft extending between the side plate members.

Advantageously, the secondary urging means is pivotally carried on the primary pivot shaft. Advantageously, the latching means is located between the side plate members and is pivotally carried on a secondary pivot shaft extending between the side plate members.

Preferably, the primary urging means is located between the side plate members, and advantageously, the secondary urging means is located between the side plate members.

In one embodiment of the invention, the coupling means for releasably coupling the coupler to the working arm assembly of the earth working machine comprises two pairs of aligned spaced apart bores, one of each pair of spaced apart bores being formed in one of the side plate members, and the other of each pair of spaced apart bores being formed in the other of the side plate members, and the respective pairs of bores being aligned with each other for engaging corresponding pivot pins coupleable with the working arm assembly.

Preferably, the second engagement means is moveable into two engaged positions for accommodating implements with hitching pins of different spacing between the hitching pins, and the latching means is operable for latching the second engagement means in either one of the engaged positions.

In another embodiment of the invention, the quick hitch coupler is adapted for coupling to a dipper arm assembly of an excavator.

The advantages of the invention are many. A particularly important advantage of the invention is that the latching means provides a safety mechanism for retaining the second engagement means in the engaged position even in the event of failure of the primary urging means, and furthermore, the latching means is operable from within the cab of an earth working machine and thereby the provision of the latching means does not impede or militate against the quick hitching and quick releasing actions of the quick hitch coupler. Furthermore, when the latching means is resiliently urged into the latching state, the latching means is operated and urged into the latching state entirely independently of the motive means which operates the primary urging means, thereby providing a further additional factor of safety.

The invention will be more clearly understood from the following description of a preferred embodiment thereof which is given by way of example only with reference to the accompanying drawings in which: Fig. 1 is a side elevational view of a quick hitch coupler according to the invention, Fig. 2 is a plan view of the quick hitch coupler of Fig. 1, Fig. 3 is a side elevational view of the quick hitch coupler of Fig. 1 illustrated in use, Fig. 4 is a side elevational view of the coupler of Fig. I with a portion of the quick hitch coupler removed, Fig. 5 is a view similar to Fig. 4 of the quick hitch coupler of Fig. I with another portion of the quick hitch coupler removed, Fig. 6 is a view similar to Fig. 4 illustrating a portion of the quick hitch coupler in a different state, Fig. 7 is a view similar to Fig. 4 of the quick hitch coupler of Fig. I illustrating the quick hitch coupler in a different state, Fig. 8 is a view similar to Fig. 7 of the quick hitch coupler of Fig. I with a portion of the quick hitch coupler removed, Fig. 9 is a view similar to Fig. 4 of the quick hitch coupler of Fig. I illustrating a portion of the quick hitch coupler in a different state, Fig. 10 is a view similar to Fig. 9 of the quick hitch coupler of Fig. 1 with another portion of the quick hitch coupler removed, and Fig. 11 is a circuit diagram of an hydraulic circuit of the quick hitch coupler of Fig. 1.

Referring to the drawings there is illustrated a quick hitch coupler according to the invention indicated generally by the reference numeral 1 for hitching an implement, for example, an excavator bucket, an impact drill or the like to a dipper stick 2 and a tipping link 3 of a dipper arm assembly 4 of an earth working machine, namely, an excavator (not shown). The quick hitch coupler I is remotely operable from within the cab of the excavator for both hitching an implement to and releasing the implement from the dipper arm assembly 4, as will be described below. Such dipper arm assemblies of excavators will be well known to those skilled in the art. A portion of an excavator bucket 5 is illustrated in Fig. 3 in broken lines coupled to the dipper arm assembly 4 by the quick hitch coupler 1, and the bucket 5 comprises a pair of parallel spaced apart hitching pins 6 for engagement by the quick hitch coupler I for coupling the excavator bucket 5 to the dipper arm assembly 4. An implement to be coupled to the dipper arm assembly 4 will also be provided with a similar pair of spaced apart hitching pins 6 as will be understood by those skilled in the art.

The quick hitch coupler I comprises a pair of spaced apart side plate members 7 joined by a pair of intermediate plate members 8 and an end plate member 9. The side plate members 7 each comprise an outer plate member 7a, an inner plate member 7b and a spacer plate member 7c located between the outer and inner plate members 7a and 7b, respectively. The outer, inner and spacer plate members 7a, 7b and 7c, as well as the intermediate plate members 8 and the end plate members 9 are all of steel plate material welded together. A coupling means for coupling the coupler I to the dipper arm assembly 4 is provided by two pairs of aligned coupling bores 10 and 11, one of each of the coupling bores 10 and 11 of the respective pairs of coupling bores being provided in each side plate member 7. The coupling bores 10 and 11 receive corresponding pivot pins 12 and 13, respectively, for pivotally coupling the coupler I to the dipper arm assembly 4. The pivot pin 12 engages the coupling bores 10 for pivotally coupling the coupler 1 to the dipper stick 2, while the pivot pin 13 engages the coupling bores 11 for coupling the coupler I to the tipping link 3 of the dipper arm assembly 4. The coupling of a quick hitch coupler to the dipper arm assembly of an excavator will be understood by those skilled in the art.

A first engagement means is provided by a pair of aligned first engagement recesses 14 formed in the respective side plate members 7 for engaging one of the hitching pins 6 of the bucket 5 or other implement to be coupled to the dipper arm assembly 4. The first engagement recesses 14 are provided by parallel-sided slots 15 which define respective open mouths 16 for accommodating the one of the hitching pins 6 into the slots 15. The slots 15 terminate in radiused ends 17 of radius corresponding to substantially half the diameter of the hitching pins 6 for snugly seating the hitching pin 6 in the slots 15. Additionally, the intermediate plate members 8 extend between the side plate members 7 at an angle to each other to define a V-shaped trough 19 extending between the side plate members 7 which also acts as the first engagement means for engaging the corresponding hitching pin 6. The intermediate plate members 8 extend tangentially to the radiused ends 17 of the slots 15 of the first engagement recesses 14 for minimising wear in the first engagement recesses 14 and for positively and snugly locating the corresponding hitching pin 6 in the first engagement recesses 14.

A second engagement means comprising a movable engagement member 20 for engaging the other one of the hitching pins 6 is located between the side plate members 7 and is pivotally carried on a primary pivot shaft 22 extending between the side plate members 7. The engagement member 20 is pivotal on the primary pivot shaft 22 between two engaged positions, one of which is illustrated in Figs. 7 and 8, co-operating with the first engagement recesses 14 for coupling and securing the bucket 5 to the coupler I with the respective hitching pins 6 engaged in the first engagement recesses 14 and theengagement member 20, and a release position illustrated in FIgs. 4, 5 and 6 for permitting disengagement of the hitching pins 6 from the coupler 1. The second engaged position is not illustrated but is described below.

The engagement member 20 comprises a pair of spaced apart engagement plate members 23 of steel plate material joined by a pair of reinforcing plate members 24 also of steel plate material and welded to the engagement plate members 23.

Primary bores 25 extending through the engagement plate members 23 pivotally engage the primary pivot shaft 22 for facilitating pivoting of the engagement member between the engaged and the release positions. The engagement plate members 23 terminate in hook shaped portions 26 for engaging the corresponding hitching pin 6 of the bucket 5.

A primary urging means, in this embodiment of the invention, a primary double- acting hydraulic ram 28 is located between the side plate members 7 for urging the engagement member 20 between the engaged and release positions. A cylinder 29 of the primary ram 28 is pivotally carried on a carrier shaft 30 which extends between and is secured to the side plate members 7. A pivot coupling shaft 32 extends between and pivotally engages the engagement plate members 23 of the engagement member 20, and couples a piston rod 33 of the primary ram 28 to the engagement member 20. The primary ram 28 is adapted for retaining the engagement member 20 in the engaged position while appropriately powered with hydraulic fluid until the flow of hydraulic fluid is reversed for operating the primary ram 28 for urging the engagement member 20 into the release position.

A pair of aligned second engagement recesses 34 formed in the side plate members 7 co-operate with the engagement member 20 for positively retaining the corresponding hitching pin 6 captive in the coupler 1. The first engagement recesses 14 are located in the side plate members 7 so that the open mouth 16 of Is the first engagement recesses 14 extend in a direction away from the direction of pivotal movement of the engagement member 20 from the release position to the engaged position so that as the engagement member 20 is urged from the release position to the engaged position in the direction of the arrow A, see Fig. 6, the hitching p'ns 6 of the bucket 5 are securely and tightly engaged by the co-operating action of the engagement member 20 and the first engagement recesses 14.

A latching means comprising a latching plate member 35 located within the side plate members 7 is carried on a secondary pivot shaft 36 extending between and pivotal in the side plate members 7 between a latching state illustrated in Figs. 7 and 8 for latching and retaining the engagement member 20 in the engaged position in the event of hydraulic fluid failure to the primary ram 28, and an unlatched state illustrated in Figs. 4, 5, 9 and 10 for permitting pivoting of the engagement member from the engaged to the release position. The latching plate member 35 is of steel plate material and is welded to the secondary pivot shaft 36 and extends radially therefrom, and when in the latching state engages either pair of two pairs of abutment faces 38a and 38b of a pair of receiver elements 37 which extend from the respective engagement plate members 23 of the engagement member 20 for retaining the engagement member 20 in either one of the two engaged positions.

Which of the two pairs of abutment faces 38a and 38b the latching plate member 35 engages will depend on the angle through which the engagement member 20 pivots from the release position to the engaged position, which in turn will be dependent on the spacing between the hitching pins 6 of the bucket 5 or other implement. For widely spaced hitching pins 6, the latching plate member 35 engages the pair of abutment faces 38b, and for more closely spaced hitching pins 6, the latching plate member 35 engages the pair of abutment faces 38a. A compression spring 39 acting between the end plate member 9 and the latching plate member 35 urges the latching plate member 35 into the latching state, A secondary urging means comprising a secondary single acting hydraulic ram 40 is pivotally carried on the primary pivot shaft 22 and is pivotally coupled to the latching plate member 35 for urging the latching plate member 35 from the latching state to the unlatched state. The secondary ram 40 comprises a cylinder 41 which is carried in a pivot housing 43 which is pivotally carried on the primary pivot shaft 22 between the engagement plate members 23 of the engagement member 20. A piston rod 44 extending from the cylinder 41 of the secondary ram 40 is pivotally secured by a pivot pin 45 to a pivot mounting bracket 46 rigidly extending from the latching plate member 35. The secondary ram 40 is operated by an hydraulic fluid supply for urging the latching plate member 35 from the latching state to the unlatched state, and a return spring (not shown) located within the cylinder 41 of the secondary ram retracts the piston rod 44 into the cylinder 41 when the hydraulic supply is removed from the secondary ram 40.

The primary ram 28 and the secondary ram 40 are operably coupled by the hydraulic supply so that the secondary ram 40 is operated for urging the latching plate member 35 from the latching state to the unlatched state prior to operation of the primary ram 28 for urging the engagement member 20 from the engaged position to the release position.

Referring in particular to Fig. 11 an hydraulic circuit through which the primary and secondary rams 28 and 40 are coupled to the hydraulic system of the exavator (not shown) is illustrated, so that the primary and secondary rams 28 and 40 are operable from within a cab of the excavator. The primary ram 28 comprises hydraulic ports 53 and 54 which alternatively act as flow and return ports, depending on whether a piston 55 in the cylinder 29 of the primary ram 28 is to be urged for extending or retracting the piston rod 33. The secondary ram 40 is provided with a single hydraulic port 56 which acts as a flow and return port for operating a piston 57 in the cylinder 41 of the secondary ram 40 for extending or permitting retraction of the piston rod 44 of the secondary ram 40. The piston 57 of the secondary ram 40 is operated for extending the piston rod 44 when it is desired to urge the latching plate member 35 from the latching state to the unlatched state, and the piston 55 of the primary ram 28 is operated for retracting the piston rod 33 of the primary ram 28 for urging the engagement member 20 into the release position. A spool valve 59 of the hydraulic system of the excavator supplies hydraulic fluid to the primary and secondary rams 28 and 40 under the control of control valves in the cab of the excavator. The hydraulic port 56 of the secondary ram 40 is coupled to the hydraulic port 53 of the primary ram 28, so that when the spool valve 59 is operated for delivering hydraulic fluid to the primary ram 28 for operating the primary ram 28 to urge the engagement member 20 from the engaged position to the release position the secondary ram 40 is operated for urging the latching plate member 35 from the latching state to the unlatched state.

A delay means comprising a restrictor valve 58 is located in the hydraulic port 54 of the primary ram 28 for restricting return of hydraulic fluid from the cylinder 29 through the hydraulic port 54 thereby cushioning movement of the piston 55 when hydraulic fluid is simultaneously applied to the hydraulic port 53 of the primary ram 28 and to the hydraulic port 56 of the secondary ram 40 so that initial movement of the piston 55 of the primary ram 28 is retarded when hydraulic fluid is initially supplied to the hydraulic port 53 thereof, thereby permitting the piston 57 of the secondary ram 40 to extend the piston rod 44 of the secondary ram 40 for pivoting the latching plate member 35 from the latching state to the unlatched state prior to commencement of retraction of the piston rod 33. of the primary ram 28 for urging the engagement member 20 from the engaged position to the release position.

When the engagement member 20 is in the release position, the latching plate member 35 is resiliently urged by the compression spring 39 towards the engagement member 20, and abuts camming surfaces 60 on the receiver elements 37 of the engagement plate members 23. When the engagement member 20 is being urged by the primary ram 28 from the release position to the engaged position the camming surfaces 60 of the receiver elements 37 act on the latching plate member 35 for urging the latching plate member 35 towards the unlatched state against the compression spring 39 until the abutment faces 38a of the receiver elements 37 have cleared the latching plate member 35, at which stage the latching member 35 is urged under the action of the compression spring 39 into engagement with the receiver elements 37 for engaging the abutment faces 38a or 38b of the receiver elements 37, depending on the spacing between the hitching pins 6 of the bucket 5 or other implement.

A lug 61 rigidly extending from the secondary pivot shaft 36 is provided for facilitating manual operation of the latching plate member 35 from the latching state to the unlatched state. A bore 62 extending through the end plate member 9 accommodates a push rod 63, see Fig. 8, for engagement with the lug 61 for manually urging the latching plate member 35 from the latching state to the unlatched state in the event of failure of the secondary ram 40 for releasing the engagement member 20 from the engaged position.

In use, the quick hitch coupler 1 is secured to the dipper arm assembly 4 by engaging the pivot pin 12 through the coupling bores 10 in the side plate members 7 with a corresponding coupling bore (not shown) in the dipper stick 2, and by engaging the pivot pin 13 through the coupling bores 11 in the side plate members 7 with a corresponding coupling bore (not shown) in the tipping link 3. The primary ram 28 and the secondary ram 40 are coupled to the spool valve 59 of the hydraulic system of the excavator. With the quick hitch coupler I coupled to the dipper arm assemb'y 4 and the hydraulic system of the excavator, the quick hitch coupler is ready for use. With the primary ram 28 retracted and the engagement member 20 in the release position, the coupler I is manoeuvred by the dipper arm assembly 4 for initially engaging one of the hitching pins 6 of the bucket 5 or other implement in the first engagement recesses 14. The coupler 1 is then further manoeuvred by the dipper arm assembly 4 so that the other hitching pin 6 is located between the hook- shaped portions 26 of the engagement member 20 and the second engagement recesses 34. With the quick hitch coupler I so located, the primary ram 28 is operated for urging the engagement member 20 from the release position to the engaged position, so that the corresponding hitching pin 6 is positively located and held captive between the hook-shaped portions 26 of the engagement member 20 and the second engagement recesses 34. As the engagement member 20 is being urged from the release to the engagedposition, the camming surfaces 60 act on the latching plate member 35 for urging the latching plate member 35 against the action of the compression spring 39 towards the unlatched position.

Once the engagement member 20 is in the engaged position, and the abutment faces 38b and/or 38a of the receiver elements 37 are clear of the latching plate member 35, the latching plate member 35 is urged under the action of the compression spring 39 into the latching position for engaging the receiver elements 37 so that the latching plate member 35 is in abutting engagement with the appropriate pair of abutment faces 38 of the receiver elements 37. The action of the latching plate member 35 on the appropriate pair of abutment faces 38a or 38b of the receiver elements 37 latches and retains the engagement member 20 in the engaged position and prevents pivoting of the engagement member 20 even in the event of an hydraulic fluid failure to the primary ram 28.

However, for so long as the primary ram 28 remains powered hydraulically with the piston rod 33 thereof extended, the primary ram 28 retains the engagement member in the engaged position. However, should the primary ram 28 lose hydraulic power, the latching plate member 35 continues to retain the engagement member 20 in the engaged position, thereby avoiding any danger of the bucket 5 or other implement becoming inadvertently disengaged from the quick hitch coupler 1.

When it is desired to release the bucket 5 or implement from the quick hitch coupler 1, the hydraulic supply to the primary and secondary rams 28 and 40 is operated for extending the piston rod 44 from the secondary ram 40 for urging the latching plate member 35 into the unlatched state, and then for retracting the piston rod 33 of the primary ram 28 for urging the engagement member 20 into the release position. The restrictor valve 58 cushions the retracting action of the piston rod 33 into the primary ram 28, thereby retarding retraction of the piston rod 33 into the primary ram 28 until the secondary ram 40 has been operated for urging the latching plate member 35 into the unlatched state. At that stage, the piston rod 33 of the primary ram 28 has just commenced retraction into the primary ram 28, thereby urging the engagement member 20 into the disengaged position without interference from the latching plate member 35 which is now in the unlatched state.

Once the engagement member 20 is in the released state, the dipper arm assembly 4 is operated for disengaging the quick hitch coupler I from the hitching pins 6 of the bucket 5 or other implement.

The piston rod 44 of the secondary ram 40 remains in the extended state holding the latching plate member 35 in the unlatched state for so long as the hydraulic supply is applied to the port 56 thereof. Once the hydraulic power supply is switched over for operating the primary ram 28 for urging the engagement member 20 from the release position to the engaged position, the piston rod 44 of the secondary ram 40 is retracted into the secondary ram 40 under the action of its own return spring (not shown) and the action of the compression spring 39 which urges the latching plate member 35 towards the latching state, and into engagement with the camming surfaces 60 of the engagement member 20. As the engagement member 20 is again urged into the engaged position, the camming surfaces 60 of the engagement member 20 urge the latching plate member 35 towards the unlatched position until the pair of abutment faces 38a of the receiver elements 37 clear the latching plate member 35, at which stage the latching plate member 35 is urged by the action of the compression spring 39 again into engagement with the pair of abutment faces 38a of the receiver elements 37. If the hitching pins 6 of the bucket 5 or other implement are more widely spaced apart, the engagement member 20 continues to pivot until the pair of abutment faces 38b are engaged by the latching plate member 35.

While the latching plate member 35 has been described as being urgable from the latching state to the unlatched state by a single acting secondary ram 40, in certain cases, it is envisaged that the secondary ram may be provided as a double acting ram, and in which case, the compression spring 39 may be dispensed with, although, in general, it is envisaged that the secondary urging means will be provided as a single acting ram, which is believed to be safer than a double acting ram. However, it is also envisaged that the secondary urging means may be provided by any other suitable means besides a secondary ram, for example, by a solenoid operated rod or an electrically powered linear motor, both of which could be remotely operated from within the cab.

Claims

Claims 1. A quick hitch coupler for hitching an implement to a working arm

assembly of an earth working machine, the quick hitch coupler comprising a coupling means for releasably coupling the coupler to the working arm assembly of the earth working machine, a first engagement means for engaging one of a pair of spaced apart parallel hitching pins on the implement, a second engagement means for engaging the other of the pair of hitching pins, the second engagement means being moveable relative to the first engagement means between an engaged position co-operating with the first engagement means for coupling the implement to the coupler with the respective hitching pins engaged in the first and second engagement means, and a release position for facilitating disengagement of the hitching pins from the first and second engagement means for releasing the implement from the coupler, a primary urging means for urging the second engagement means from the release position to the engaged position, a latching means operable between a latching state for latching the second engagement means in the engaged position and an unlatched state for permitting release of the second engagement means from the engaged position, and a secondary urging means for urging the latching means from the latching state to the unlatched state, the secondary and primary urging means being operably coupled so that operation of the secondary urging means for urging the latching means from the latching state to the unlatched state commences prior to operation of the primary urging means for urging the second engagement means from the engaged position to the release position.
2. A quick hitch coupler as claimed in Claim I in which the primary urging means is adapted for retaining the second engagement means in the engaged position.
3. A quick hitch coupler as claimed in Claim I or 2 in which the primary urging means is adapted for urging the second engagement means between the engaged position and the release position.
4. A quick hitch coupler as claimed in any preceding claim in which the latching means is resiliently urged into the latching state.
5. A quick hitch coupler as claimed in Claim 4 in which the latching means is spring-urged into the latching state.
6. A quick hitch coupler as claimed in any preceding claim in which a delay means is provided for delaying operation of the primary urging means for urging the second engagement means from the engaged position to the release position until the secondary urging means has urged the latching means from the latching state to the unlatched state.
7. A quick hitch coupler as claimed in Claim 7 in which the primary and secondary urging means comprise respective primary and secondary fluid operated rams, the secondary ram being fluid operated for operating the latching means from the latching state to the unlatched state, and the primary ram being fluid operated for operating the second engagement means from the engaged position to the release position, and the delay means comprises a fluid restrictor for preventing initial operation of the primary ram for urging the second engagement means from the engaged position to the release position until the secondary ram has urged the latching means from the latching state to the unlatched state.
8. A quick hitch coupler as claimed in Claim 7 in which the delay means comprises a fluid restrictor valve for acting to initially cushion movement of a piston of the primary ram in a direction corresponding to movement of the second engagement means from the engaged position to the release position.
9. A quick hitch coupler as claimed in Claims 7 or 8 in which the primary ram is a double acting ram, and the fluid restrictor is located in a fluid port of the double acting ram for cushioning the movement of the piston of the primary ram in the direction corresponding to movement of the second engagement means from the engaged position to the release position.
10. A quick hitch coupler as claimed in any of Claims 7 to 9 in which the secondary ram is a single acting ram.
11. A quick hitch coupler as claimed in any of Claims 7 to 10 in which the primary and secondary rams are hydraulic rams.
12. A quick hitch coupler as claimed in any preceding claim in which a receiver is provided on the second engagement means for engagement with the latching means when the latching means is in the latching state for latching the second engagement means in the engaged position.
13. A quick hitch coupler as claimed in any preceding claim in which the latching means is pivotally mounted, and is pivotal between the latching state and the unlatched state.
14. A quick hitch coupler as claimed in any preceding claim in which the second engagement means is pivotally mounted and is pivotal between the engaged and the release positions.
15. A quick hitch coupler as claimed in any preceding claim in which the second engagement means terminates in a hook-shaped member for engaging the corresponding hitching pin of the implement.
16. A quick hitch coupler as claimed in any preceding claim in which the coupler comprises a pair of spaced apart side plate members, the coupling means for releasably coupling the coupler to the working arm assembly of the earth working machine being formed in the side plate members.
17. A quick hitch coupler as claimed in Claim 16 in which the first engagement means comprises a pair of first engagement recesses, one first engagement recess being formed in each side plate member, the first engagement recesses being aligned with each other and defining respective open mouths for accommodating the one of the pair of hitching pins of the implement into the first engagement recesses, the open mouths of the first engagement recesses facing in a direction opposite to the direction of movement of the second engagement means from the release position to the engaged position.
18. A quick hitch coupler as claimed in Claim 17 in which a pair of intermediate plate members extend between the side plate members, the intermediate plate members being located on respective opposite sides of the respective first engagement recesses, and extending from each other at an angle for defining a V- shaped trough extending between the side plate members for engaging the hitching pin when engaged in the first engagement recesses.
19. A quick hitch coupler as claimed in any of Claims 16 to 18 in which each side plate member comprises a second engagement recess, the second engagement recesses in the respective side plate members being aligned with each other and co- operating with the second engagement means for retaining the corresponding hitching pin in the quick hitch coupler.
20. A quick hitch coupler as claimed in any of Claims 16 to 19 in which the second engagement means is located between the side plate members and is pivotally carried on a primary pivot shaft extending between the side plate members.
21. A quick hitch coupler as claimed in any of Claims 16 to 20 in which the secondary urging means is pivotally carried on the primary pivot shaft.
22. A quick hitch coupler as claimed in any of Claims 16 to 21 in which the latching means is located between the side plate members and is pivotally carried on a secondary pivot shaft extending between the side plate members.
23. A quick hitch coupler as claimed in any of Claims 16 to 22 in which the primary urging means is located between the side plate members.
24. A quick hitch coupler as claimed in any of Claims 16 to 23 in which the secondary urging means is located between the side plate members.
25. A quick hitch coupler as claimed in any of Claims 16 to 24 in which the coupling means for releasably coupling the coupler to the working arm assembly of the earth working machine comprises two pairs of aligned spaced apart bores, one of each pair of spaced apart bores being formed in one of the side plate members, and the other of each pair of spaced apart bores being formed in the other of the side plate members, and the respective pairs of bores being aligned with each other for engaging corresponding pivot pins couplable with the working arm assembly.
26. A quick hitch coupler as claimed in any preceding claim in which the second engagement means is moveable into two engaged positions for accommodating implements with hitching pins of different spacing between the hitching pins, and the latching means is operable for latching the second engagement means in either one of the engaged positions.
27. A quick hitch coupler as claimed in any preceding claim in which the quick hitch coupler is adapted for coupling to a dipper arm assembly of an excavator.
28. A quick hitch coupler substantially as described herein with reference to and as illustrated in the accompanying drawings.