COUPLER

Abstract

An excavator coupler including a front jaw for receiving a first attachment pin of an accessory and a rear pin receiving area for receiving a second attachment pin of the accessory, a first closure mechanism for the rear pin receiving area, the first closure mechanism including an actuator and a movable second pin engaging surface for selectively securing the second attachment pin in the rear pin receiving area and for pulling the first attachment pin into the front jaw of the coupler, a second closure member for the front jaw for selectively retaining the front attachment pin in the front jaw, and a front latch control component for selectively controlling the second closure member between an open state and a closed state wherein the actuator includes a release member for selectively engaging a release arm on the front latch control component to activate or deactivate the front latch control component.

Claims

1. An excavator coupler comprising: a housing with a top part for attachment to an excavator arm of an excavator, and a bottom part for attachment to an accessory for the excavator, such as an excavator bucket, the bottom part comprising a front jaw open to a front of the coupler for receiving a first attachment pin of an accessory and a rear pin receiving area open to a bottom of the coupler for receiving a second attachment pin of the accessory; the coupler further comprising: a first closure mechanism for the rear pin receiving area, the first closure mechanism comprising an actuator and a movable second pin engaging surface for selectively securing the second attachment pin in the rear pin receiving area and for pulling the first attachment pin into the front jaw of the coupler; a second closure member for the front jaw for selectively retaining the front attachment pin in the front jaw; and a front latch control component for selectively controlling the second closure member between an open state and a closed state; wherein the actuator comprises a release member for selectively engaging a release arm on the front latch control component to activate or deactivate the front latch control component.

2. The coupler of claim 1, wherein the rear pin receiving area is a rear jaw that is open to a bottom of the coupler.

3. The coupler of claim 1, wherein a bottom wall of the front jaw comprises a lip at its free end.

4. The coupler of claim 1, wherein the rear pin receiving area comprises a lip at its free end.

5. The coupler of claim 1, wherein the rear pin receiving area comprises an angled slope leading towards the free end thereof to force the second attachment pin into engagement with the rear pin receiving area when the two attachment pins are clamped onto the coupler by the actuator.

6. The coupler of claim 1, wherein the actuator is a hydraulic ram with a cylinder and piston.

7. The coupler of claim 1, wherein the movable second pin engaging surface is part of a pivoting hook.

8. The coupler of claim 1, wherein the second latching member is pivotally mounted to the housing.

9. The coupler of claim 1, wherein the second latching member is pivotally mounted in the housing to rotate about an axis that is positioned above and in front of a back wall of the front jaw.

10. The coupler of claim 1, wherein the second latching member is sprung into a default latching position.

11. The coupler of claim 1, wherein the second latching member has a range of motion either side of a default latching position between a more closed condition and an open condition.

12. The coupler of claim 1, wherein the second latching member has a more closed condition wherein a release surface of the second latching member moves into a position beyond the reach of the release arm.

13. The coupler of claim 12, wherein when the second latching member is in the more closed condition, the release arm has an end that is located above the second latching member when the release arm is fully engaged by the release member, in which position the release arm prevents opening of the second latching member.

14. The coupler of claim 1, wherein the second latching member is biased into a default latching position by a bi-directional spring that allows bi-directional movements of the second latching member.

15. The coupler of claim 14, wherein the spring is a Rosta-type spring with an inner bar, an outer casing, each with square sections, and elastic members in the corners of the outer casing.

16. An excavator coupler comprising: a housing with a top part for attachment to an excavator arm of an excavator, and a bottom part for attachment to an accessory for the excavator, such as an excavator bucket, the bottom part comprising a front jaw open to a front of the coupler for receiving a first attachment pin of an accessory and a rear pin receiving area open to a bottom of the coupler for receiving a second attachment pin of the accessory; a first latching member for the rear pin receiving area, the first latching member comprising an actuator for moving the first latching member between a latching state a release state; and a second latching member for the front jaw, the second latching member comprising a hub that is mounted for axial rotation about its axis, the hub having a Rosta-type spring to centre it in a default locking position in which a locking arm of the second latching member at least partially extends across a mouth of the front jaw, the Rosta-type spring having an inner bar, an outer casing, each with square sections, and elastic members in the corners of the outer casing.

17. The coupler of claim 16, the first latching member being a first closure mechanism comprising a movable second pin engaging surface for selectivity securing the second attachment pin in the rear pin receiving area and for pulling the first attachment pin into the front jaw of the coupler; the second latching member being a second closure member for selectively retaining the front attachment pin in the front jaw; and the coupler further comprises a front latch control component for selectively controlling the second closure member between an open state and a closed state; wherein the actuator comprises a release member for selectively engaging a release arm on the front latch control components to activate or deactivate the front latch control component.

18. The coupler of claim 16, wherein an axle of the second latching member is rotationally fixed relative to the second latching member, and it forms the inner bar of the Rosta-type spring, the outer casing of the Rosta-type spring being rotationally fixed relative to the housing of the coupler.

19. The coupler of claim 16, wherein the outer casing of the Rosta-type spring is rotationally fixed relative to the second latching member, and an axle of the second latching member is rotationally fixed relative to the housing of the coupler.

20. The coupler of claim 16, wherein the outer casing is a single piece construction.

21-32. (canceled)

Description

[0101] These and other features of the present invention will now be described in further detail, purely by way of example, with reference to the accompanying drawings in which:

[0102] FIG. 1 schematically shows internal workings of an example of a coupler in accordance with the present invention in an accessory latching condition, with two attachment pins of an accessory secured within the two jaws of the coupler;

[0103] FIG. 2 schematically shows internal workings of the coupler of FIG. 1 in an accessory release condition, with a first attachment pin of the accessory in, but free to be removed from, the front jaw of the coupler, and the second attachment pin ready to be moved into, or having been removed from, the rear jaw of the coupler;

[0104] FIG. 3 schematically shows internal workings of the coupler of FIG. 1 in an improper release condition, with a first attachment pin of the accessory locked within the front jaw of the coupler, and the second attachment pin ready to be moved into, or having been removed from, the rear jaw of the coupler;

[0105] FIGS. 4 and 5 show a hydraulic cylinder for a coupler according to a further aspect of the present invention;

[0106] FIGS. 6 and 7 show a different hydraulic cylinder for a coupler according to the further aspect of the present invention;

[0107] FIGS. 8 and 9 show another different hydraulic cylinder for a coupler according to the further aspect of the present invention;

[0108] FIGS. 10 and 11 show an alternative arrangement for a hydraulic cylinder for a coupler according to a third aspect of the present invention;

[0109] FIG. 12 shows a detail of a preferred form for the spring member of a latch of the front jaw of the coupler—a Rosta-type spring;

[0110] FIGS. 13 to 15 illustrate the operation of a Rosta type spring; and

[0111] FIG. 16 shows an example centre pin for the Rosta type spring of the coupler.

[0112] Referring first of all to FIG. 1, there is shown a schematic view of a coupler 10 in accordance with the present invention. The coupler 10 comprises a main housing 88 having a top part 12 and a bottom part 18. In this preferred style of coupler, the top part has a pair of attachment holes 44 for attaching the coupler 10 to an excavator arm of an excavator, as is well known in the art.

[0113] The bottom part 18 instead has two jaws 22, 26 with a first jaw 22 being positioned to be open to the front 24 of the coupler whereas the second jaw 26 is open to the bottom 28 of the coupler 10. The second jaw is commonly referred to as the horseshoe, although it can have different shapes, including a narrower opening, a wider opening or a single side—for a more variable accessory capacity, as this is a rear pin receiving area and a rear attachment pin 134 may be at a wider or narrower spacing from a front attachment pin 122 of the accessory, dependent upon the size or manufacturer of the accessory. Any given accessory, however, will generally have a fixed pin spacing, whereby a coupler can be sized to accommodate a range of accessory sizes, or just a few accessories of a given pin arrangement, if the rear jaw is narrower.

[0114] The illustrated rear jaw 26 is wider than it is deep, to offer a wide range of accessory compatibilities, whereas the first or front jaw 22 is deeper than it is wide to offer a deeper securement of the first attachment pin 122 therein.

[0115] As illustrated, the rear jaw is preferred to be at least 2× the depth (i.e. height) of the jaw 26 at its deepest part.

[0116] The coupler 10 also includes a first latching member 30, a second latching member 74 and a hydraulic ram or cylinder 40. The hydraulic ram or cylinder 40 is commonly referred to as the actuator. Other forms of actuator, such as pneumatic or screw-drive actuators, can instead be used.

[0117] The first latching member 30 is for latching the second attachment pin 134 in the rear jaw 26, whereas the second latching member 74 is for latching the first attachment pin 122 in the first jaw 22. The hydraulic cylinder 40, hydraulic lines for which are conventional in the art but not shown, is for powering the movement of the first latching member 30, which in this embodiment pivots within the coupler housing 88 around an axle 118 between a latched condition, such as that shown in FIG. 1, in which the first latching member 30 secures the second attachment pin, to a release condition, in which the latching member 30 is pulled away from that second attachment pin to open the rear jaw, as shown in FIGS. 2 and 3. In this embodiment this is achieved by rotating the latching member 30 in a direction such that the bottom part moves towards the front of the coupler 10.

[0118] The coupler also includes a pivot pin 98 for the second latching member 74 for pivotally mounting the second latching member 74 above and in front of the seating position for the first attachment pin 122. The second latching member thus likewise has a fixed axis relative to the coupler housing 88.

[0119] A piston pin 102 is also provided, extending between opposing side walls of the coupler, generally parallel to the two attachment pins 122, 134, for pivotally mounting a distal end of the piston 104 of the hydraulic cylinder 40 in the coupler housing 88. The head 112 of the cylinder 40 is then pivotally attached to the first latching member 30 by one or more pins 114, whereupon the hydraulic cylinder can move the first latching member—in this case a latching hook. In an alternative embodiment, the cylinder and piston may be reversed so that the head 112 of the cylinder 40 is fixed to the housing 88 and the distal end of the piston 104 is instead mounted on the first latching member 30.

[0120] The actuator, and in this example the cylinder 40, has a front latch actuating member 36 extending in a forward direction therefrom. That front latch actuating member 36 is provided for interaction with the second latching member 74—in this embodiment indirectly. In this embodiment, this is achieved by the free end of the front latch actuating member 36 engaging a release arm 152, which in turn interacts with the second latching member 74. For this purpose there is a flange 80 provided on the second latching member 74, which flange has a release surface 82 that can be contacted by the release arm 152 when the second latching member is in any position between a default latching position, as per FIG. 1, and an open condition, as per FIG. 2, continual movement of the front latch actuating member 36 in a forward direction 38 relative to the housing 88, after contact with the release arm 152, causing such contact between the release arm 152 and the release surface 82 to occur and then a resultant movement of the second latching member 74 from its default latching position to the open condition due to the bias of the release arm 152 on the release surface of the second latching member 74.

[0121] The second latching member can also move from the default latching position of FIG. 1 in an opposite direction towards a more closed condition, as per FIG. 3. In that more closed condition, where the free end at the bottom thereof moves forwards, the release surface 82 moves into a position beyond the reach of the release arm 152 (wherein below its line of movement), whereby the release arm 152 can no longer interact with the release surface 82 of the flange to move the second latching member 74 to the open condition. Instead, upon the continued movement of the front latch actuating member 36 into the position in which it would have opened the second latching member 74, the release arm 152 now instead puts its eng at a position that lies over the flange 80, the reverse side 136 of which flange being now a latch retention surface 136. The front latch actuating member 36 thus instead moves the release arm 152 into a condition in which it locks the second latching member 74 in a position below the open condition, such as its default latching or more closed condition—the release arm will be prevented from rotating or moving further upwards, thus providing the locking function, either by a stop on the housing, or as shown by a second arm 52 on the pivotal component 50 that has the release arm 152 that instead would be stopped from such further rotation.

[0122] In order to default the second latching member 74 into its default latching position, it is provided with a spring to provide a biasing force there into. This will be a bi-directional spring to allow the bi-directional movements of the second latching member—to either the more latched condition or the open condition.

[0123] In this embodiment the second latching member is pivotally mounted about its axle 98. The spring biases the second latching member 74 such that it defaults under the forces of the spring into the default latching position in which it partially extends across the mouth 58 of the front jaw 22. The spring in this preferred embodiment is a Rosta-type spring. However a conventional coil spring could likewise be provided to serve that purpose, for example by being connected to the housing at one end and to a flange of the second latching member 74 at the other. The Rosta-type spring, however, provides a compact solution. It will be described in greater detail below with reference to FIGS. 12 to 16.

[0124] A free end 32 of the second latching member 74 is arranged so that should the first attachment pin 122 be attempted to be removed from its seat at the back 34 of the front jaw 22, it will eventually engage the second latching member, upon which the second latching member 74 will tend to be rotated into (or towards) the more closed condition of FIG. 3.

[0125] As known in the art, the second latching member may have flanges or surfaces thereon which interact with stop surfaces 46 on the coupler housing 88 to restrict rotational movement of this second latching member 74 so that it will allow degrees of rotation of perhaps no more than 40 to 90°. In this embodiment it is about 60° between fully blocking and fully open—fully open bringing the lowest edge of the second latching member substantially parallel to the upper wall 42 of the front jaw, and the more closed condition having that surface instead at about 60° from that upper wall 42. Its default rest position, however, may be a chosen angle between 20° and 50° from the fully open position. As shown, it is about 30 degrees. As for the more closed position, this might be between 30 and 70 degrees.

[0126] As shown in FIGS. 1 to 3, the second latching member is provided with a curved free end surface 32, which surface is engaged by the first attachment pin 122 when the second latching member 74 is being moved from its default position into the more closed position. That curved surface can serve to reduce or remove the requirement of one of the stops 46—by partially cupping the attachment pin, a condition can be achieved where there is a two-point contact between the attachment pin and the free end surface 32, or such that the cup starts to jam against the attachment pin as the cup provides a varying interface angle with the pin. In that jammed condition, further downward rotation of the second latching member 74 would be prevented. This would generally occur if the coupler and accessory was inverted such that the pin sits against and is loaded upon the upper wall 42 of the front jaw. That thus provides a secure blocking of the exit of the first attachment pin 122 out of the front jaw.

[0127] In FIG. 3, however, the coupler is not inverted and thus the first attachment pin 122 sits on a lower part of the front jaw 22. In that lower part, this embodiment has a recess 48, sized to accommodate a part of the attachment pin 122—preferably with at least a two-point contact. This recess terminates at or before a lip 126 near the free end of that lower part of the jaw 22. This recess and lip will work with the second latching member's free end 32 to contain the first attachment pin within the recess because the cupped portion pushes the pin 122 down into that recess 124 if the first pin continues to press against the latching member and the lip.

[0128] The cupped portion 128 pushing that attachment pin 122 into the recess 124 is shown in FIG. 3. With this arrangement, the pin 122 cannot exit the front jaw 22, and the lip caries much of the force from the pin.

[0129] In addition to the cupped portion 128, the second latching member 74 comprises a body for housing the axle 98 and the Rosta-type spring as discussed below, with the body featuring the first flange for providing the release surface 82 and a second flange for providing a latching bar of the front jaw. In this embodiment the latching bar extends generally radially from the body with respect to the axle 98. The first flange 80 likewise extends generally radially from that body. Between them they provide a groove or recess 84 therebetween. In use, the release arm 152 will enter into that groove or recess 84 when lifting the second latching member 74 into the open condition as shown in FIG. 2, but will fall out of that groove or recess 84 when the cylinder 40 extends its piston 104 to move the first latching member rearwardly. It thus can then instead pass over the original flange 80 when the latching bar is instead first moved by the first attachment pin of the accessory into its more closed condition. As the release arm 152 passes over the original flange 80, the release arm moves into a position over the top of that original flange 80 for instead selectively engaging with the latch retention surface on the reverse side 136 of the original flange 80 in the event that the second latching member 74 was attempted to be re-opened again, until such a time that the actuator once again re-extends the piston 104 out from the cylinder 40 (which then returns the release arm 152 to a position rearward of that original flange 80.

[0130] As for the cupped portion 128, it is formed by a rearward edge of a further flange 84, extending at the sides of, but between, the original flange 80, with the release surface, and the second flange with the latching bar and free end 32.

[0131] As for the actuating member 36 on the cylinder 40, it comprises a forward facing finger. To the side of that finger is a protrusion 86, which protrusion 86 has a forward face that contacts the release arm 52. This allows the release arm 152 to be spaced to the side of the cylinder 40, as the protrusion extends sideways too.

[0132] In this embodiment the release arm 152 is part of a pivotal component 50, which pivotal component 50 is mounted on the same axis as the piston pin 102. For this purpose, the same axle pin 102 may be used. The pivotal component 50 has the release arm 152 extending substantially radially outward therefrom and has circumferentially spaced therefrom a second arm 52. Between the release arm 52 and the second arm 52 is a further recess or groove within which the protrusion 86 will fit during engagement of the release arm 152 with the release surface 82 and during positioning of the release arm 152 above the first flange 80, as shown in FIG. 3. Upon extension of the piston 104 out of the cylinder 40, however, the protrusion 86 exits that further groove or recess, thus allowing free rotation of the pivotal component 50.

[0133] That pivotal component 50 could alternatively be sprung biased into a default condition with the release arm 152 positioned out of the groove or recess 84 of the second latching member, which in this embodiment is a downwardly hanging position.

[0134] Preferably the release arm 152 has a lip for engaging the release surface.

[0135] The second arm, by being behind the protrusion 86 when the protrusion is engaging the release arm 152, will serve to prevent over rotation of the pivotal component 50 upon inversion of the coupler, or during opening of the second latching member when the release arm has been moved to the position above the second latching member by the actuating member 36 or protrusion 84.

[0136] Referring next to FIG. 3, the front attachment pin 122 has moved forwards from the back 34 of the front jaw 22. Further, the piston 104 has retracted further into the cylinder, whereby the latching hook 30 has released the rear attachment pin. In this situation the accessory is still secured onto the coupler by the front jaw, whereby it won't fall off the coupler. As this situation is undesireable, FIGS. 4 to 11 illustrate further optional features of this coupler designed to avoid this situation. They are discussed further below.

[0137] In the coupler of FIGS. 1 to 3, the maximum retraction of the piston 104 into the cylinder 40 pulls the first latching member clear of the rear jaw 26, as shown in FIG. 2. Alternative embodiments may only allow it to pull less far, perhaps with the length of the piston or cylinder being longer, or the coupler shorter. In preferred embodiments, the front jaw's latching mechanism still functions as described. In such embodiments, the first latching member will still partially close the opening of the rear jaw even when fully retracted. However, it should pull far enough forwards to release the second attachment pin of any accessory intended to be used with the coupler. Such an arrangement is typically compatible with fewer accessories.

[0138] Referring next to FIGS. 13 to 16, the Rosta-type spring is further described.

[0139] The axle 98 of the second latching member is provided with a square section 54 along a part of its length. As shown in FIG. 16, this is a part that is distal of a flanged end 56. Proximal of the square section, i.e. closer to the flanged end, is a round section having a diameter approximately equal to the diagonal length of the square section 54, which round section ends at the flanged end.

[0140] The flanged end has flattened side portions such that it can be turned with a tool. It will fit in a recess in the sidewall of the coupler, or in a bushing there within, such that the pin will rotate relative to the housing.

[0141] The distal end 60 of the axle 98 is instead provided with a stub with a circular diameter smaller than the square width of the square section 54 so that the axle 98 can be inserted through the rest of the Rosta spring components with the square section 54 being an operable part within the Rosta spring, as discussed below. The distal end 60 will pass through the other side of the housing such that the axle entends through both sides of the housing.

[0142] The distal end 60 has a groove near its free end for a circlip for holding the axle at the other side of the housing—shown here within a bushing 64. The axle is this fixed between the two sides of the housing 88.

[0143] Mounted upon the square section is the second latching member 74, with a bifurcated body form, from which the flange 80 and the latching arm with the free end 32 extend. They two ends of the biforcated body form respectively have a round hole at one end and a square hole at the other, such that the round hole sits on the round section part of the axle, proximal to the square section of the axle, and the square section on the square section of the axle. The axles is thus rotatably fixed to the body form.

[0144] Between the two ends, however, is a square outer frame 64 and a square inner frame 66 of the Rosta-type spring. Between the two frames are four rubber inserts 68, each one in a respective corner of the outer frame 64.

[0145] The outer frame is rotated 45° relative to the inner frame such that the corner gaps internal of the outer frame and external of the inner frame can be mostly filled with the rubber inserts 68. The rubber inserts 68, by being in the corner gaps between the frames, then compress against the flat sides of the inner square frame and against the corner or two side intersecting walls of the outer frame to provide a default 45° position for the inner frame relative to the outer frame. That in turn provides the required default latching condition for the second latching member as the inner square frame is a tight fit on the square section of the axle.

[0146] Angles other than 45 may be provided by having differently shaped rubber inserts.

[0147] Due to the non-infinite compressibility of the inserts, the Rosta-type spring will allow rotations, without breaking the Rosta-type spring, or angles up to perhaps between 20-38 degrees either side of the default position. Preferably the range of movements is up to 30 degrees either side of centre.

[0148] Instead of 30°, other angles are possible, dependent upon the amount of tortion desired to open the jaw—the deformable members provide additional resistance to torque, the more the inside rotates relative to the outside.

[0149] The provision of the inner frame is non essential as the axle can instead provide that function directly. However, assembly is easier when the Rosta-type spring is preformed with the inner and outer frames with the square hole in the inner frame for receiving the axle.

[0150] To hold the square outer frame in a fixed orientation relative to the coupler's housing 88, that square frame 64 will be located in a recess of the housing 88, or otherwise fixed thereto.

[0151] The structure of the Rosta-type spring allows a certain degree of rotation of the inner frame relative to the outer frame—typically up to 30° either way by compressing the rubber elements, as shown in FIG. 15. The second latching member 74 can thus rotate through the illustrated 30 degrees either way.

[0152] Instead of the outer frame being a square tube, it could be formed as three sides attached to a flat face of housing 88.

[0153] As illustrated, the Rosta-type arrangement of the bi-directional spring allows rotation of the inner square frame relative to the outer square frame by compression and shearing of the rubber elements, which compression and shearing creates a return biasing force to return the square section to its original or default condition. In the present invention, this original condition is the default latching condition as shown in FIG. 1.

[0154] Referring next to FIGS. 4 to 11, various methods of providing a bias for the cylinder/piston is shown—arranged to bias the piston into an extended position relative to the cylinder.

[0155] In FIGS. 4 to 9, a sprung driver or biasing mechanism is provided internal of the piston 104. Various solutions for that are illustrated. A first solution is shown in FIGS. 4 and 5, wherein a pneumatic back-up piston is provided internal of the actuator's piston 104, wherein the end of the actuator's piston 104 that is internal of the cylinder 40 has a bore 70 drilled therein for receiving a pneumatic gas spring or piston 72. The pneumatic gas spring or piston comprises a casing 76 and a rod 78, which rod 78 can extend between an extended condition as shown in FIG. 5 and a contracted condition as shown in FIG. 4.

[0156] Although a pneumatic piston is illustrated, other forms of sprung driver or biasing mechanism can be used, such as a coil spring, or a compressive material spring, such as a rubber spring. Preferably it achieves a return force upon compression of the component or material device shape within it, be that a coil spring or a compressive gas, fluid or solid. Preferred is a pneumatic piston with the movable rod.

[0157] In the contracted condition of FIG. 4, the rod 78 has been contracted into the void 90 as shown in black in FIGS. 4 and 5, thus compressing the gas therein and creating a biasing force to counter the compression of the piston 104 into the cylinder 40.

[0158] In this embodiment, to allow for a shorter gas spring 72, the void 90 extends into the head 112 of the cylinder 40.

[0159] The void 90 contains air or gas under pressure to provide the pneumatic spring force. As such, the contracted condition of FIG. 4 has a higher pressure at the void 90 than the expanded condition of FIG. 5. Likewise the free-space in the bore, between the rod 78 and the walls of the bore can contain air or gas under pressure, also with the compression being higher when the rod is contracted into the casing 76. FIG. 5 is thus the default condition for the rod 78, whereby the actuator is biased by the gas spring to default to an extended condition, i.e. with the piston 104 extended out of the cylinder 40, thus helping to prevent release of an accessory in the event of a failure of the cylinder 40 as the extended condition locks the attachment pins of the accessory in the jaws of the coupler.

[0160] In this first embodiment, the casing 76 is attached to the head 112 of the cylinder 40. Therefore, it will slide within the bore 70 of the piston 104. A seal 92 is provided at the distal end of the piston 104 to seal between the casing 76 and the bore 70 of the piston 104. This prevents the hydraulic fluid of the cylinder 40 entering the space between the casing 76 and the piston 104, during normal use of the actuator. It also prevents that hydraulic fluid entering the free space between rod 78 and the bore 70. This avoids a locking out of the gas spring (as hydraulic fluid is non-compressible). Likewise it prevents the air or gas in the free space of the bore, around the rod, from entering the hydraulic fluid, thus preventing softening of the hydraulic forces of the actuator (as entrained air in hydraulic fluid makes the hydraulic fluid part-compressible).

[0161] Referring next to FIGS. 6 and 7, an alternative arrangement is provided, albeit with similar benefits. In this second version, the pneumatic gas spring is reversed such that the casing 76 is instead mounted in the bore of the piston 104 and the rod 78 is instead attached to the head 112 of the cylinder 40. With this arrangement, a protective sleeve 94 is provided, into which the casing 76 can slide as the rod 78 contracts into the casing 76, as shown in FIG. 6. A seal is again provided at the end face of the piston 104 to prevent hydraulic fluid from entering the bore, and the air or gas of the bore from entering the hydraulic fluid. However, a further seal 110 is provided at the end of the protective sleeve 94 for sealing against the casing 76. This allows the space around the casing to switch between a single free space and two closed spaces, and it further provides support for the casing as the rod compresses into the casing, thus resisting buckling of the rod/casing.

[0162] In an alternative arrangement, the protective sleeve 94 is made longer such that the casing 76 is always nosed into the protective sleeve 94, such that the space around the casing is always separate to the space around the rod.

[0163] A benefit from the provision of the protective sleeves 94 is that there is an additional radius to the gas spring arrangement, whereby the protective sleeve provides additional bending stiffness, and thus buckle resistance to the gas spring. Previously the rod could be subject to buckling, especially where it enters the casing.

[0164] Referring then to FIGS. 8 and 9, a third integrated gas spring is illustrated wherein the casing 76 is again internal to the piston 104. However, the rod is instead wider, and the protective sleeve is not present. Yet further, the rod 78 now terminates against the head of the cylinder, rather than being attached into it.

[0165] Rather than providing a casing 76 in a bore of the piston, as shown, it would instead be possible to have the rod in a bore of the piston, whereby the piston itself provides the function of the casing. The casing would thus effectively be defunct, or considered integrated with the piston.

[0166] In this third illustrated embodiment, the pressurised void 90 is connected with a tube 96 near the pivotally mounted end of the piston 104, with a threaded stop or cork 100 closing a side vent 106 for that tube 96. With this arrangement, the pressure of the air or gas in the pressurised void 90 can be re-compressed or recharged in the event of pressure loss. It can also be flushed if needed.

[0167] Such a recharge port could likewise be provided for the embodiment of FIGS. 6 and 7.

[0168] The head could likewise comprise a recharging vent for accessing the void 90 in the embodiment of FIGS. 4 and 5.

[0169] Referring finally to FIGS. 10 and 11, an alternative arrangement is shown wherein the gas spring is instead mounted external and to a side of the cylinder 40, in a side structure 120. The side structure can be specifically for the gas spring, or it can be part of a moulding around the cylinder from which the actuating member 36 extends.

[0170] The side structure 120 has a cavity therein containing the gas spring as shown. There is again a protective sleeve 94, but this time it is merely to provide protection for the rod 78 as by being external of the piston, it would otherwise be subject to exposure of the working environment of the coupler. It is no longer exposed to the hydraulics in the cylinder.

[0171] In this arrangement, the gas spring 72 can operate to drive the rod 78 and the protective sleeve 94 between a contracted position of FIG. 10 and an extended position of FIG. 11, the extended configuration being the default configuration.

[0172] The end of the rod or protective sleeve 94 can be attached to a further flange 124 extending radially from the piston pin 102, which further flange 124 can have a pivotal connection 116 to the rod 78 or protective sleeve 94. By being pivotal, the rod can rotate with the piston as the pivotal latching hook moves. Alternatively the further flange will rotate relative to the piston pin 102. For a sliding latch, the connection might instead be fixed, rather than pivotal, as the actuator would not have a need to pivot.

[0173] Usually the external gas spring will be located below the cylinder. This has two benefits. Firstly, as space is limited to the sides of the cylinder, putting it below the cylinder does not further fill the side spaces. Secondly, by being below the cylinder, it will not be as exposed to the external elements during use of an accessory (once an accessory is attached to the coupler) as the accessory will close the bottom of the coupler.

[0174] With these gas sprung mechanisms inside or outside the piston of the cylinder 40, the cylinder 40 and the piston 104 will default into a condition such that the first latching hook is in a latching condition in the event of a failure of the hydraulics system of the cylinder 40, or the cylinder itself, albeit not with the usual retention force of the hydraulics. Nevertheless, it will allow an operator to maintain safe retention of an accessory, after noticing a relaxation of the securement of the accessory, for long enough for him to lower the accessory to the floor.

[0175] The present invention therefore enables an accessory attached to the coupler to be releasable only by following a proper procedure, as per FIG. 2—it cannot be released from the coupler in the event of an improper use of the coupler.

[0176] These and other features of the present invention have been described above purely by way of example. Modifications in detail may be made to the invention within the scope of the claims appended hereto.