IES20011047A2 - A Coupler for Coupling an Accessory to a Dipper Arm - Google Patents

Abstract

The invention concerns a quick hitch coupler for coupling an accessory to a dipper arm of a back acter such as may be used by an earth working apparatus. The quick hitch coupler comprises a body member adapter for coupling to the dipper arm, a fixed engaging means mounted on the body member for engaging a first one of a pair of coupling pins mounted on the accessory, and a moveable engaging means mounted on the body member for engaging a second one of the pair of coupling pins of the accessory. The moveable engaging means is moveable between an engaged state and a disengaged state. In the engaged state, the moveable engaging means engages the second coupling pin while the fixed engaging means engages the first coupling pin for coupling the accessory to the coupler. In the disengaged state, the moveable engaging means disengages the second coupling pin. A latch for retaining the first coupling pin of the accessory engaged in the fixed engaging means is co-operable with the fixed engaging means. The latch is alternately operable in a latched state co-operating with the fixed engaging means for retaining the first coupling pin in the fixed engaging means, and an unlatched state for releasing the first coupling pin from the fixed engaging means. An urging means urges the latched state, and a drive means acting between the moveable engaging means and the latch urges the moveable engaging means between the engaged state and the disengaged state, and urges the latch from the latched state to the unlatched state against the urging action of the urging means when the moveable engaging means is in the disengaged state. <Figure 2>

Description

The present invention relates to a coupler for coupling an accessory to a dipper arm ofa back acter of, for example, earth working apparatus, and in particular, the invention relates to a coupler of the type generally referred to as a quick hitch coupler for coupling an accessory to such a dipper arm.

Quick hitch couplers for coupling an accessory, for example, an excavator bucket, a jack hammer or other such attachment to a dipper arm of a back acter of earth io working apparatus are known. Typically, they comprise a body member which is adapted for coupling to the dipper arm, and a pair of engagement members are provided for releasably engaging a pair of spaced apart coupling pins located on the accessory. One of the engagement members typically is moveable relative to the other between an engaged state with the engagement members co-operating with each other for engaging the coupling pins of the accessory for coupling the accessory to the dipper arm, and a disengaged state for disengaging the coupling pins for releasing the accessory from the dipper arm. Typically, the moveable one of the engagement members is either slideable or pivotally carried in the body member and is moveable between the engaged and disengaged states by a ram, for example, an hydraulic ram, or by a screw drive. Such quick hitch couplers suffer from a number of disadvantages. In particular, where the moveable one of the two engagement members is moveable by an hydraulic ram, should the hydraulic fluid supply to the hydraulic ram fail in general, the moveable one of the engagement members returns to its disengaged state thereby releasing the accessory. This, can have serious consequences, which can result in fatal accidents should the hydraulic IflTCL PlkO llofy.i<. 3I3.L·.

OPEN TO PUBOC INSPECTION UNDER SECTfON 26 ANO RULE 23 IE Ο 110 4 7 supply to the quick hitch coupler fail when the accessory is in an elevated state with a person standing beneath it, in that the accessory could fall on the person, thus leading to fatal injuries.

There is therefore a need for a coupler, and in particular, a quick hitch coupler for coupling an accessory to a dipper arm of a back acter which overcomes this problem.

The present invention is directed towards providing such a quick hitch coupler.

According to the invention there is provided a quick hitch coupler for coupling an accessory to a dipper arm of a back acter, the quick hitch coupler comprising a body member adapted for coupling to the dipper arm, a fixed engaging means mounted on the body member for engaging a first one of a pair of coupling pins mounted on the accessory, a moveable engaging means mounted on the body member for engaging a second one of the pair of coupling pins of the accessory, the moveable engaging means being moveable between an engaged state with the moveable engaging means engaging the second coupling pin while the fixed engaging means engages the first coupling pin for coupling the accessory to the coupler, and a disengaged state for disengaging the second coupling pin, a latch co-operable with the fixed engaging means for retaining the first coupling pin of the accessory engaged in the fixed engaging means the latch being alternately operable in a latched state co-operating with the fixed engaging means for retaining the first coupling pin in the fixed engaging means, and an unlatched state for releasing the first coupling pin from the fixed engaging means, an urging means for urging the ΙΕΟ 1 104? latch into the latched state, and a drive means acting between the moveable engaging means and the latch for urging the moveable engaging means between the engaged state and the disengaged state, and for urging the latch from the latched state to the unlatched state against the urging action of the urging means when the moveable engaging means is in the disengaged state.

Ideally, the drive means and the urging means co-operate with each other so that the drive means only operates the latch between the latched and the unlatched state when the moveable engaging means has been moved from the engaged to the disengaged state.

In one embodiment of the invention a limit means is provided on the body member for co-operating with the moveable engaging means for defining a disengaged position of the moveable engaging means when the moveable engaging means is in the disengaged state.

In another embodiment of the invention the latch is pivotally mounted on the body member, and is pivotal between the latched and the unlatched states.

Preferably, the drive means is a two part drive means, the respective parts of the drive means being moveable relative to each other for driving the moveable engaging means and the latch, one of the moveable parts of the drive means being connected to the latch, and the other of the moveable parts of the drive means being connected to the moveable engaging means so that on movement of the respective parts relative to each other the moveable engaging means is operated between the ΙΕΟ 1 1047 engaged and the disengaged states, and the latch is operated between the latched and the unlatched state.

Advantageously, both parts of the drive means are moveable relative to the body member.

In one embodiment of the invention the drive means comprises a ram, and one of the parts is formed by a housing of the ram, while the other part is formed by a piston rod of the ram.

Preferably, the moveable engaging means is slideable between the engaged and the disengaged state, and advantageously, is slideable in the body member with rectilinear motion between the engaged and the disengaged states.

In one embodiment of the invention the urging means acts between the latch and the body member, and preferably, the urging means is provided by a spring.

In one embodiment of the invention the urging means comprises a tension spring, and in alternative embodiment of the invention the urging means comprises a compression spring.

In one embodiment of the invention the fixed engaging means comprises a pair of fixed jaws formed by the body member and defining an open mouth for receiving the first coupling pin between the fixed jaws.

IE Ο 1 1 ο 4 7 In another embodiment of the invention the latch co-operates with the fixed jaws for retaining the first coupling pin within the open mouth and between the fixed jaws.

Ideally, a pair of latches are provided at respective opposite sides of the fixed jaws.

In another embodiment of the invention the moveable engaging means defines an open mouth for receiving the second coupling pin therein, and ideally, defines the open mouth with the body member. Ideally, the open mouths defined by the respective moveable and fixed engaging means face in respective opposite directions outwardly away from each other.

Additionally, the invention provides a dipper arm having the quick hitch coupler mounted thereon.

Further the invention provides an accessory mounted to a dipper arm by the quick hitch coupler according to the invention.

Further the invention provides earth working apparatus comprising a dipper arm having the quick hitch coupler according to the invention mounted thereon.

The invention will be more clearly understood from the following description of some embodiments thereof which are given by way of example only with reference to the accompanying drawings in which: Fig. 1 is an outlined perspective view of earth working apparatus according to ΙΕΟ 1 ΙΟ47Ι the invention having a back acter mounted thereto and an excavator bucket hitched to a dipper arm also according to the invention of the back acter by a quick hitch coupler, which is also according to the invention, Fig. 2 is a cut-away side elevational view of the quick hitch coupler of Fig. 1, Fig. 3 is a view similar to Fig. 2 of the quick hitch coupler of Fig. 1 illustrating parts of the quick hitch coupler in a different position to that of Fig. 2, io Fig. 4 is a cut-away perspective view of the quick hitch coupler of Fig. 1, Fig. 5 is another cut-away perspective of the quick hitch coupler of Fig. 1, Fig. 6 is a side elevational view of a portion of the quick hitch coupler of Fig. 1, Fig. 7 is a perspective view of a portion of the quick hitch coupler of Fig. 1, Figs. 8(a) to (c) are side elevational views of portions of the quick hitch 20 coupler illustrating the quick hitch coupler in use, Fig. 9 is-a perspective view substantially similar to Fig. 4 of a quick hitch coupler according to another embodiment of the invention, Fig. 10 is a perspective view of a portion of the quick hitch coupler of Fig. 9, IE ο 1 ι ο 4 7 Ί Fig. 11 is another perspective view of the portion of Fig. 10 illustrated in a different state, Fig. 12 is an exploded perspective view of the portion of Fig. 10, Fig. 13 is a perspective .view of a portion of a coupler according to another embodiment of the invention, and Fig. 14 is an exploded perspective view of the portion of Fig. 13.

Referring to the drawings and initially to Fig. 1 there is illustrated earth working apparatus according to the invention indicated generally by the reference numeral 1. The apparatus 1 comprises a main housing 2 which is carried on a main chassis 3, which in turn is carried on ground engaging tracks 4. The main housing 2 is mounted on a sub-housing 5 which is rotatably carried on the main chassis 3 about a vertically extending axis, so that the sub-housing 5 and the main housing 2 are rotatable through 360° relative to the main chassis 3. This aspect of such earth working apparatus will be well known to those skilled in the art. A back acter arm 8 is mounted on the sub-chassis 5 and comprises a boom 9 which is pivotally connected to the sub-chassis 5 and extends upwardly therefrom. A dipper arm 10 is pivotally carried on the boom 9 for in turn pivotally carrying an accessory, which in this embodiment of the invention is an earth moving bucket 12. A quick hitch coupler according to the invention and indicated generally by the reference numeral 14 releasably hitches the bucket 12 to the dipper arm 10. The quick hitch coupler 14 is IE Ο 110 4 7 described in detail below. A pair of boom operating rams 15 acting between the subchassis 5 and the boom 9 operate the boom 9 for raising and lowering the boom 9 about its pivot connection to the sub-chassis 5. A dipper arm operating ram 16 acting between the boom 9 and the dipper arm 10 pivots the dipper arm 16 relative to the boom 9. The operation of a boom and dipper arm of such earth working apparatus will be well known to those skilled in the art, and it is not intended to describe this aspect of the invention further. A cab 17 located in the main housing 2 accommodates an operator of the apparatus 1.

A pivotally mounted connecting linkage 18 is pivotally connected by a pair of pivot pins 19 to the dipper arm 10 towards the distal end thereof. An accessory operating ram 20 acting between the dipper arm 10 and the connecting linkage 18 is provided for pivoting the connecting linkage 18 for in turn pivoting the bucket 12 relative to the dipper arm 10. A pair of mounting linkages 22 extending from the connecting linkage 18 are provided for connecting the bucket 12 to the connecting linkage 18. The mounting linkages 22 terminate in bushed bores (not shown) for engaging a first connector pin 25 for connecting the quick hitch coupler 14 to the mounting linkage 22. A bushed bore (not shown) extending through the dipper arm 10 at the distal end thereof accommodates a second connector pin 28 also for pivotally connecting the quick hitch coupler 14 to the dipper arm 10.

A pair of coupling pins, namely, a first coupling pin 30 and a second coupling pin 31 are provided on the bucket 12, or indeed, any other accessory to be connected to the dipper arm 10 for engagement with the quick hitch coupler 14 as will be described below.

IE Ο Π Ο 4 7 Referring now in particular to Figs. 2 to 8, the quick hitch coupler 14 according to one embodiment of the invention comprises a body member 35 formed by a pair of spaced apart side plates 36 of steel and a transversely extending connector plate 37 also of steel extending between the adjoining side plates 36. The side plates 36 each comprise a main side plate 36a and reinforcing side plates 36b and 36c welded together, however, for convenience the combination of the main and reinforcing side plates 36a, 36b and 36c are referred to as the side plates 36. A pair of connector members 38 and 39 of steel plate extend between the side plates 36 at opposite io ends of the connector plate 37 for reinforcing the body member 35. The connector plate 37 and the connector members 38 and 39 are welded to the side plates 36.

A connecting means for connecting the quick hitch coupler 14 to the dipper arm 10 and the mounting linkages 22 comprises a pair of bushed bores 40 and 41 which extend through the respective side plates 36. The bushed bores 40 in the side plates 36 are aligned with each other for in turn aligning with the bushed bores in the mounting linkages 22 for engagement with the first connector pin 25. The bushed bores 41 in the respective side plates 36 are aligned with each other for in turn alignment with the bushed bore through the dipper arm 10 for engagement with the second connector pin 28. In this way the quick hitch coupler 14 is connected to the dipper arm 10 and the mounting linkages 22, and is thus pivotal about the second connector pin 28 by the mounting linkages 22 under the action of the accessory operating ram 20 for in turn pivoting the bucket 12.

The side plates 36 define corresponding pairs of fixed jaws 45 and 46 for forming a ΙΕΟ 1104 7 ίο fixed engaging means for engaging the first coupling pin 30 of the bucket 12. The jaws 45 and 46 define an open mouth 47 which faces outwardly of the quick hitch coupler 14 for receiving the first coupling pin 30.

A pair of latches 50 are pivotally mounted, one on each side plate 36. The latches 50 are pivotal between a latched state illustrated in Fig. 3 co-operating with the fixed jaws 45 and 46 for extending across the open mouth 47 defined by the jaws 45 and 46 for retaining the first coupling pin 30 within the jaws 45 and 46, and an unlatched state illustrated in Fig. 2 for releasing the first coupling pin 30 from the fixed jaws 45 and 46 through the open mouth 47. The latches 50 are pivotally carried on pivot pins 52 which extend from the corresponding side plates 36 and are urged into the latched state by a pair of tension springs 53 acting between the respective latches 50 and the connector member 38. The operation of the latches 50 is described in detail below.

A moveable engaging means provided by a moveable engagement member 58 is slideably carried in the body member 35, and is slideable between an engaged state illustrated in Fig. 3 for engaging the second coupling pin 31 of the bucket 12, and a disengaged state illustrated in Fig. 2 for disengaging the second coupling pin 31 for releasing the bucket 12 from the coupler 14. Guide tracks 59 mounted on the respective side plates 36 slideably engage corresponding guide grooves 60 on respective opposite sides of the engagement member 58 for guiding the engagement member 58 between the engaged and disengaged states with rectilinear motion. A jaw 62 extending from the engagement member 58 defines ΙΕΟ 11Ο*7 with adjacent edges 63 of the respective side plates 36 an open mouth 64 for accommodating the second coupling pin 31 into and between the jaw 62 and the edges 63 of the side plates 36. The open mouth 58 faces outwardly of the coupler 14 in a direction opposite to the direction in which the open mouth 47 defined by the fixed jaws 45 and 46 faces. Accordingly, when the moveable engagement member 58 is in the engaged state the first and second coupling pins 30 and 31 are securely engaged between the fixed jaws 45 and 46 and the engagement member 58 respectively. io An abutment means comprising respective abutment members 65 extend from the side plates 36 defining the spacing between coupling pins 30 and 31 of an accessory which can be accommodated by the coupler 1.

A limit means, namely, a pair of limit members 66 extend inwardly from the side plates 36 for defining a disengaged position of the engagement member 58 when the engagement member 58 is in the disengaged state, and for preventing further movement of the engagement member 58 in a direction from the engaged state to the disengaged state when the moveable engagement member 58 is in the engaged position.

A drive means comprising an hydraulically operated double acting ram 70 acts between the moveable engagement member 58 and the latch 50 for urging the engagement member 58 between the engaged and disengaged states, and for moving the latches 50 between the latched and the unlatched states. The ram 70 comprises a ram housing 71 and a piston rod 74 extending from the ram housing 71.

A pair of trunions 72 extending transversely from one end of the ram housing 71 slideably engage corresponding longitudinally extending guide grooves (not shown in this embodiment of the invention, but described in the embodiment of the invention which is described with reference to Figs. 13 and 14) in the side plates 36 for facilitating longitudinal movement of the trunions 72, and in turn the ram housing 71 in the body member 35. The piston rod 74 is connected to the engagement member 58 for urging the engagement member 58 between the respective engaged and disengaged positions. The trunions 72 also engage corresponding slots 73 in the latches 50 for urging the latches 50 from the latched to the unlatched state against the action of the springs 53 after the engagement member 58 has been urged by the ram 70 from the engaged to the disengaged state. Accordingly, the ram 70 co-operates between the engagement member 58 and the latches 50 for respectively operating the engagement member 58 and the latches 50.

The tension in the tension springs 53 is sufficiently strong for retaining the latches 50 in the latched state unless they are positively urged from the latched state by the ram 70. Accordingly, the ram 70 co-operates with the tension springs 53 and the limit members 66 for controlling operation of the latch 50. Thus, when the engagement member 58 is in the engaged position engaging the second coupling pin 31 of the bucket 12, and the fixed jaws 45 and 46 are engaging the first coupling pin 30, and the piston rod 74 is extended from the ram housing 71, thereby retaining the engagement members 58 in the engaged position and the latches 50 in the latched position. In order to release the bucket 12 from the coupler 14, the ram 70 is initially operated for retracting the piston rod 74 into the ram housing 71. Because of the strong tension in the tension spring 53 the initial retraction of the piston rod 74 ΙΕΟ 1 1047' into the ram housing 71 urges the engagement member 58 from the engaged to the disengaged position until it abuts the limit member 66. At that stage further movement of the engagement member 58 is no longer possible, and thus further retraction of the piston rod 74 into the ram housing 71 causes the latches 50 to be pivoted from the latched to the unlatched state, thus permitting disengagement of the first coupling pin 30 through the open mouth 47. For so long as the piston rod 74 is fully retracted within the ram housing 71, the engagement member 58 is held in the disengaged state and the latches 50 are held in the unlatched state. Initial movement of the piston rod 74 outwardly of the ram housing 71 causes the latches 50 to be urged from the unlatched to the latched state by the tension springs 53.

Once the latches 50 are in the latched state, further outward movement of the piston rod 74 from the ram housing 71 causes the engagement member 58 to be urged from the disengaged position to the engaged state.

Accordingly, in use the quick hitch coupler 14 is initially connected to the mounting linkages 22 and the dipper arm 10 by the first and second connector pins 25 and 28, respectively. The ram 70 is appropriately connected to an hydraulic fluid supply of the apparatus 1 for operating the ram 70. With the piston rod 74 of the ram 70 in the fully retracted state, in other words, with the piston rod 74 fully retracted within the ram housing 71 the dipper arm 10 is operated for aligning the coupler 14 with the bucket 12 or other accessory to be attached to the dipper arm 10. With the ram 70 in the fully retracted state, and thus the moveable engagement member 58 in the disengaged state and the latches 50 in the unlatched state the coupler 14 is initially hitched to the first coupling pin 30 by engaging the first coupling pin 30 in the open mouth 47 defined by the fixed jaws 45 and 46. The coupler 14 is then pivoted ΙΕΟ ι 104 7 around the second connector pin 28 and the first coupling pin 30 until the open mouth 64 defined between the engagement member 58 and the edges 63 of the side . plates 36 is aligned with the second coupling pin 31. The ram 70 is then operated for urging the piston rod 74 outwardly of the ram housing 71. Initial movement of the piston rod 74 out of the ram housing 71 causes the latches 50 to be urged under the action of the tension springs 53 from the unlatched to the latched state thereby engaging around and retaining the first coupling pin 30 in the open mouth 47.

Further outward movement of the piston rod 74 urges the moveable engagement member 58 into engagement with the second coupling pin 31 until the first coupling io pin 30 is tightly engaged within the fixed jaws 45 and 46 and the second coupling pin 31 is tightly engaged by the jaw 62 of the engagement member 58. The bucket 12 is thus securely engaged on the coupler 14 and is operated by the dipper arm 10 in conventional fashion.

Removal of the bucket 12 from the coupler 14 is the reverse of engagement.

Initially, the moveable engagement member 58 is urged from the engaged to the disengaged state by initial retraction of the piston rod 74 into the ram housing 71.

Once the engagement member 58 abuts the limit member 66 further movement of the engagement member 58 is prevented and thus further retraction of the piston rod 74 into the ram housing 71 causes the latches 50 to be urged from the latched to the unlatched state. The coupler 14 can then be disengaged from the bucket 12.

If during operation of the apparatus 1 the hydraulic fluid supply to the ram 70 should fail, under the weight of the bucket 12 the coupling pin 31 bearing on the moveable engagement member 58 will in general urge the moveable engagement member 58 ΙΕΟ I 1047 into the disengaged position abutting the limit member 66. This will allow the second pivot pin to disengage the coupler 14. However, the tension in the tension springs 53 is such as to continue retaining the latches 50 in the unlatched state, thereby preventing disengagement of the first coupling pin 30 from between the fixed jaws 45 and 46. Thus, even in the event of failure of the hydraulic fluid supply to the ram 70 there is no danger of the bucket 12 becoming detached from the coupler 14. The coupler 14 may comprise a safety check valve to prevent loss of hydraulic fluid from the ram 70 in the event of failure of the hydraulic fluid supply. However, even where such·a safety check valve is provided, it is possible for the check valve and/or the io hydraulic ram to be damaged, or suffer seal failure, and thus, the latches 50 retain the bucket or other accessory attached to the coupler, and in turn to the dipper arm in the event of such failure.

Referring now to Figs. 9 to 12, there is illustrated a quick hitch coupler according to another embodiment of the invention indicated generally by the reference numeral 80. The quick hitch coupler 80 is substantially similar to the quick hitch coupler 14, and similar components are identified by the same reference numerals. The main difference between the quick hitch coupler 80 and the quick hitch coupler 14 is that the ram 70 of the quick hitch coupler 1 is replaced in the quick hitch coupler 80 by a manually operated screw drive mechanism which is indicated generally by the reference numeral 81. The screw drive mechanism 81 comprises an outer housing sleeve 82 which is trunion mounted in the body member 35 by a pair of trunions 72 similar to the trunions 72 of the quick hitch coupler 1. The trunions 72 of the quick hitch coupler 80 are similarly slideable in corresponding guide grooves (not shown) in the side plates 36. A shaft 84 which is connected to the moveable engagement ΙΕ ο 11 Ο 4 τ member 58 in similar fashion as the piston rod 74 is connected to the engagement member 58 in the coupler 14 terminates in a threaded end 85 which engages a correspondingly internally threaded intermediate sleeve 86. The intermediate sleeve 86 is rotatably mounted within the housing sleeve 82 for in turn urging the shaft 84 inwardly and outwardly of the housing sleeve 82 for in turn urging the moveable engagement member 58 between the engaged and the disengaged position, and similarly for urging the latches 50 between the latched and the unlatched states against the actions of the springs 53 in similar fashion to that as already described with reference to the coupler 14. A threaded ferrule 89 engages internal threads 90 at an end 91 of the housing sleeve 82 for retaining the intermediate sleeve 86 within the housing sleeve 82. A bore 92 extending through the ferrule 89 slideably accommodates the shaft 84 through the ferrule 89. An end 93 of the housing sleeve 82 is closed by an end cap (not shown), and four compression disc springs 94 located in the housing sleeve 82 act between the end cap (not shown) of the housing sleeve 82 and the intermediate sleeve 86 for urging the intermediate sleeve 86 against the ferrule 89, and also for urging the internal threads of the intermediate sleeve 86 against the threads of the threaded end 85 of the shaft 84 for effectively securing the shaft 84 and the intermediate sleeve 86 in a desired relative position.

An end cap 95 closes one end 96 of the intermediate sleeve 86, and a keyed opening provided by a square opening 97 is engageable by a T-bar key 98 through a bore 99 in the shaft 84 for rotating the intermediate sleeve 86 for in turn urging the shaft 84 inwardly and outwardly of the housing sleeve 82 for urging the moveable engagement member 58 between the engaged and disengaged states, and for urging the latches 50 between the latched and the unlatched states against the springs 53.

IE 0110 4 t An opening 100 in the connector member 39 accommodates the key 98 into the bore 99 in the shaft 84 for in turn engaging the square opening 97 in the end cap 95 of the intermediate sleeve 86. Accordingly, in this embodiment of the invention the moveable engagement member is moveable between the engaged and the disengaged positions and the latches 50 are moved between the latched and the unlatched states manually by manual operation of the screw drive mechanism 81 by the key 98.

Otherwise, the coupler 80 and its operation is similar to that of the coupfer 14.

Referring now to Figs. 13 and 14, there is illustrated an hydraulic ram 70 and a portion of the trunion mounting 72 for mounting the ram 70 to the side plates 36 of a coupler (not shown) according to another embodiment of the invention. The coupler according to this embodiment of the invention is identicaf to that of Figs. 2 to 8, with the exception that the trunion mountings 72 of the ram 70 slideably engage longitudinally extending guide grooves 110 which in this embodiment of the invention are formed in carrier plates 112, which are in turn welded to the side plates 36. A transversely extending entry slot 111 is provided to each guide groove 110 for facilitating entry of the corresponding trunion 72 into the guide groove 110. The advantage of providing the entry slots 111 to the guide grooves 110 is that they facilitate ease of assembly of the ram 70 into the coupler. The trunions 72 are initially entered into the entry slots 111 as illustrated in Fig. 14. The ram 70 is then pivoted through 90° so that the trunions 72 align with the guide grooves 110, and the piston rod 74 is then secured to the moveable engagement member 58.

IEO ι 104 7 18 Additionally, as well as the fixed jaws 45 and 46 being formed in the side plates 36, the fixed jaws 45 and 46 are also formed in the carrier plate 112. Bores 113 in the carrier plate 112 pivotally carry the pivot pins 52, which in this embodiment of the invention extend from the latches 50 for pivotally carrying the latches 50.

Otherwise, the coupler according to this embodiment of the invention and its operation is similar to that of the coupler of Figs. 2 to 8.

While the couplers have been described as being provided with a pair of latches, any suitable number of latches may be provided, and indeed, in many cases a single latch may be sufficient.

It is also envisaged that other suitable moveable and fixed engaging means may be provided, and while it is advantageous that the open mouths defined by the respective engagement means face outwardly in directions opposite to each other, this is not essential, in certain cases, the open mouths of the moveable and fixed engaging means may face each other, or may face in the same direction parallel to each other.

While the drive means have been described as being provided by an hydraulic ram and by a screw drive mechanism, any other suitable drive means may be provided, for example, a pneumatic ram, or indeed, in certain cases, a linear drive, for example, a power driven liner screw drive mechanism may be provided.

While the urging means for urging means for urging the latches into the unlatched ΙΕ η 11 η 4 Τ state have been described as being tension springs, any other suitable urging means may be provided, for example, compression springs or spring, a leaf spring or springs, a torsion spring, and indeed, a single tension spring may be sufficient.

The invention is not limited to the embodiment hereinbefore described which may be varied in construction and detail.

Claims (8)

Claims

1. A quick hitch coupler for coupling an accessory to a dipper arm of a back acter, the quick hitch coupler comprising a body member adapted for coupling to the dipper arm, a fixed engaging means mounted on the body member for engaging a first one of a pair of coupling pins mounted on the accessory, a moveable engaging means mounted on the body member for engaging a second one of the pair of coupling pins of the accessory, the moveable engaging means being moveable between an engaged state with the moveable engaging means engaging the second coupling pin while the fixed engaging means engages the first coupling pin for coupling the accessory to the coupler, and a disengaged state for disengaging the second coupling pin, a latch co-operable with the fixed engaging means for retaining the first coupling pin of the accessory engaged in the fixed engaging means the latch being alternately operable in a latched state co-operating with the fixed engaging means for retaining the first coupling pin in the fixed engaging means, and an unlatched state for releasing the first coupling pin from the fixed engaging means, an urging means for urging the latch into the latched state, and a drive means acting between the moveable engaging means and the latch for urging the moveable engaging means between the engaged state and the disengaged state, and for urging the latch from the latched state to the unlatched state against the urging action of the urging means when the moveable engaging means is in the disengaged state.

2. A quick hitch coupler according to claim 1 wherein the drive means and the urging means co-operate with each other so that the drive means only operates the latch between the latched and the unlatched state when the moveable engaging means has been moved from the engaged to the disengaged state.

3. A quick hitch coupler according to claim 1 or claim 2 further comprising a limit means provided on the body member for co-operating with the moveable engaging means for defining a disengaged position of the moveable engaging means when the moveable engaging means is in the disengaged state; and/or lEu 1 184 7. wherein the latch is pivotally mounted on the body member, and is pivotal between the latched and the unlatched states.

4. A quick hitch coupler according to any preceding claim wherein the drive

5. Means is a two part drive means, the respective parts of the drive means being moveable relative to each other for driving the moveable engaging means and the latch, one of the moveable parts of the drive means being connected to the latch, and the other of the moveable parts of the drive means being connected to the moveable engaging means so that on movement of the respective parts relative to

6. 10 each other the moveable engaging means is operated between the engaged and the disengaged states, and the latch is operated between the latched and the unlatched state. 5. A quick hitch coupler according to any preceding claim wherein the fixed engaging

7. 15 means comprises a pair of fixed jaws formed by the body member and defining an open mouth for receiving the first coupling pin between the fixed jaws, and wherein the latch co-operates with the fixed jaws for retaining the first coupling pin within the open mouth and between the fixed jaws; and/or the moveable engaging means defines an open mouth for receiving the second

8. 20 coupling pin therein, and optionally further wherein the open mouths defined by the respective moveable and fixed engaging means face in respective opposite directions outwardly away from each other.