GB2441322A

GB2441322A - Coupler with gravity operated latch

Info

Publication number: GB2441322A
Application number: GB0617394A
Authority: GB
Inventors: Gary Miller; Ronald Keith Miller; Gary Pendleton; Howard Reay
Original assignee: Miller UK Ltd; Tower Street Technologies Ltd
Current assignee: Miller UK Ltd
Priority date: 2006-09-04
Filing date: 2006-09-04
Publication date: 2008-03-05
Anticipated expiration: 2026-09-04
Also published as: GB0617394D0; GB2441322B

Abstract

A coupler 10 for attaching an accessory to an excavator arm of an excavator includes a gravity-operated latch or toggle member 30 for selectively securing and releasing an attachment pin 40 of the accessory in a jaw, groove, hook or slot 24. The member 30 has a jaw-open or jaw-unlocked state (figure 1), and a the jaw-closed or jaw-locked state figures 2 and 4), member 30 at least partially closing jaw 24 when the coupler 10 is in a normal, in-use orientation, due to the influence of gravity on the gravity-operated member (30). Member 30 may move to the jaw open state due to the influence of gravity if the coupler is at least partially inverted. Member 30 may be free to move and allow insertion of pin 40 into jaw 24, but not removal. Member 30 may pivot about a transverse axis of the coupler 10. A second jaw 26 may be provided on the coupler 10.

Description

COUPLER

The present invention relates to a coupler for attaching an accessory to an excavator arm of an excavator and in particular to a coupler comprising a latch for selectively securing and releasing an attachment pin of an accessory in a jaw, groove, hook or slot of the coupler.

Many couplers, either fully automatic or part automatic and part manual, have been developed in the art. See, for example, the couplers disclosed in the following publications: Australian Patent AU557890, German Utility Model DE2OI 19092U, European Patent Applications EP040581 I and EPI3I 8242, GB Patent Applications GB2332417, GB2359062 and 0B2330570, US Patents US5692325 and US6132131, and PCI Publication W099192670. All of these prior art couplers have a first (or top) half that is for attaching the coupler to the excavator, and for most of them, that attachment is to an excavator arm of the excavator. The coupler ofEP0405813, however, is instead for attaching a digger bucket to the front end loader of the excavator. Then, on the other or opposite side of the coupler, there are two attachment pin engaging jaws, grooves, hooks or slots, whereby an accessory having a pair of attachment pins (such as an excavator bucket) can be attached to that coupler via the pair of attachment pins: one of the jaws, grooves, hooks or slots is for engaging a first or front attachment pin of the accessory and the other jaw, groove, hook or slot is for engaging the second or rear attachment pin of the accessory.

Couplers are also known for attaching accessories that have only one attachment pin.

Those couplers have just one jaw, groove, hook or slot. However, the accessory would then have the other jaw, groove, hook or slot for engaging a second attachment pin, which is instead positioned on the coupler.

Many prior art couplers also have an adjustable distance between their two pin engaging jaws, grooves, hooks or slots, whereby accessories from different manufacturers can be accommodated by the coupler (it is commonplace for buckets and other accessories from different manufacturers to have different distances between their pairs of attachment pins, i.e. different pin spacings). For adjusting the distance between the pin engaging jaws, grooves, hooks or slots, most of those prior art couplers rely upon either a screwthread drive system or a hydraulic ram mounted between the two jaws, grooves, hooks or slots. The screwthread or a hydraulic ram may move one or both of the jaws, grooves, hooks or slots relative to a frame of the coupler for achieving that end. It is more normal, however, for just one of them to be moved by the screwthread or hydraulic ram, and that one is most frequently the rear jaw, groove, hook or slot. By moving them relative to each other (usually by moving them away from each other) it is possible to secure the two fixed attachment pins of the accessory within the two jaws, grooves, hooks or slots since the two jaws, grooves, hooks or slot generally face in opposite directions. That securement of an accessory in a coupler can be referred to as a primary securement since it alone will secure an accessory to a coupler.

Such primary securement mechanisms are generally reliable since it is most unlikely that either the screwthread or the hydraulic ram will fail. Similarly it is most unlikely that the moveable jaw(s), groove(s), hook(s) or slot(s), or its (their) means of attachment to the frame, will fail since these items are designed with the environment of use in mind (they are usually made as over-engineered items to provide a significant overload buffer).

Despite that, however, it is also common to add failsafe or safety mechanisms for those securement mechanisms to prevent the accessory from decoupling from the coupler in the unlikely event of either the screwthread or the hydraulic ram failing, or in the event of them being accidentally actuated by the user in a manner to decouple the accessory.

Such safety mechanisms have included, at the most simple level, just a cover for the actuation circuit (usually in the cab of the excavator) to prevent accidental access to the actuation switches during use of the accessory. However, for more security, failsafe mechanisms are provided in or on the coupler itself. For example, the coupler of EP 1318242 provides a spring driven hook for the front jaw, which hook defaults to a closed state for securing a front attachment pin within the front jaw of the coupler. That spring driven hook, however, will automatically be retracted by the hydraulic ram that is used to move the coupler's sliding rear jaw as that ram reaches its billy retracted position. US6132131 and US5692325 similarly provide a latching hook for the front jaw that is driven by the rear jaw's hydraulic ram, and as such they have the same problem as EP1318242. GB2330570, on the other hand, provides a gravity operated blocking bar that is designed to fall behind the rear latching hook during normal use, whereby when the coupler is in use, and therefore in a normal, in-use or upright, orientation, the latching hook is prevented from being retracted by the presence of the blocking bar behind the latching hook. However, that blocking bar can be removed from that position either by a second hydraulic ram (i.e. one that is not connected to the latching hook) or simply by inverting the coupler, i.e. by moving the excavator arm and coupler into either the crowd position or to a position curled above the excavator arm (an unusual position).

In that inverted orientation, the blocking bar will fall away from its blocking position to allow the latching hook for the rear attachment pin then to be retracted by the latching hook's own hydraulic ram. A manual safety mechanism is instead taught by GB2359062. It requires a locking pin to be manually slid through apertures in the sides of the frame of the coupler so as to position the locking pin behind the rear latching hook once the rear latching hook has been advanced to its latched position (against the rear attachment pin of the accessory). That locking pin then will prevent inadvertent retraction of the latching hook from its latched position. In one final prior art coupler, as disclosed in GB233241 7, a toggling dual-hook arrangement is provided. The coupler has two moving hooks that are interconnected by a toggling arrangement to ensure that as one hook opens the other hook closes, and vice versa. This prevents both hooks from opening simultaneously.

What is desired, however, is a further, or a supplementary failsafe or securement mechanism for couplers. Preferably the supplementary failsafe or securement mechanism will be able to ensure that an accessory will still be retained upon the coupler until that supplementary failsafe or securement mechanism is released even in the event of a catastrophic failure of the primary securement mechanism, e.g. the hydraulic ram or the screwthread, or even a moveable jaw, groove, hook or slot, or even in the event of an accidental or inadvertant release of that primary securement mechanism by the operator.

The present invention, therefore, provides a coupler for coupling an accessory to an excavator arm of an excavator, the accessory comprising at least one attachment pin for use in the coupling, the coupler comprising a first side for attaching the coupler to an excavator arm of an excavator and the coupler having a second side onto which the accessory will be coupled, the second side comprising a jaw for receiving the attachment pin of the accessory for connecting the accessory to the coupler by the engagement of the jaw with the attachment pin, wherein the jaw comprises a gravity-operated member having a first state -the jaw- open or jaw-unlocked state, and a second state -the jaw-closed or jaw-locked state, the gravity-operated member at least partially closing the jaw of the coupler when it is in its first state, said first state being achieved by the gravity-operated member when the coupler (and, when connected, the accessory) is in a normal, in-use orientation due to the influence of gravity on the gravity-operated member.

Preferably the two different states of the gravity-operated member are two different positions of the gravity-operated member. However, the gravity-operated member might instead simply remain in a constant normal position, instead switching between a rotatable or free state and a non-rotatable or more restricted state depending upon the orientation of the coupler.

The present invention, with its gravity-operated member, therefore has a jaw that can be selectively opened or closed (or unlocked and locked) dependent upon the orientation of the coupler since gravity will open or unlock the member in one orientation and will close or lock the member (with the jaw at least partially closed by the member) in other orientations.

It should be noted that the terms "jaw" should be interpreted to encompass similar pin receiving members such as grooves, hooks or slots, or other similar terms that are to be found in the art. For example, a hook can form a jaw, a groove or a slot, and similarly a groove is in essence just a slot, in view of that, and also for the sake of convenience, the single term "jaw" is used hereinafter.

Preferably, in a first orientation (e.g. the normal, in-use orientation) the member will fall under the influence of gravity into its closed position. However, upon reorienting the coupler, for example to an inverted position, the member will fall under the influence of gravity from that closed position into its open position. Instead of simply falling between two positions, however, the member may roll, slide or pivot between those positions.

Alternatively, it might remain stationary, instead either being locked or unlocked from a particular closed position dependent upon the orientation (or path of motion between orientations) of the coupler.

When open (or unlocked), an attachment pin within the jaw can be removed from the jaw. Similarly, an attachment pin can be inserted into the jaw. However, when closed, be that either completely or partially, or when locked, an attachment pin within the jaw camiot be removed from the jaw since the locked or closed member will block its path out of the jaw. It might be possible, however, dependent upon the chosen configuration of the locking/closing mechanism, to insert an attachment pin into the jaw even when the gravity-operated member is either closing the jaw or locking the jaw closed.

Preferably, the gravity-operated member is mounted onto the second side of the coupler either directly to the jaw, or onto a frame of the coupler, which frame carries the jaw.

Preferably the gravity-operated member is a pivotal member, mounted to the coupler about a pivot axis, the pivoting of the member moving it between its open and closed (or locked and unlocked) positions.

Preferably the first side is a top side of the coupler, the second side is a bottom side of the coupler, and the coupler also comprises a frame having two sideplates extending generally between the top and bottom sides of the coupler. Preferably the pivot axis runs perpendicular to those sideplates, i.e. in a transverse direction of the coupler. The axis might, however, extend in a longitudinal direction of the coupler (the above-mentioned pin-spacing is measured in the longitudinal direction of the coupler, whereas the attachment pins of an accessory extend in the transverse direction of the coupler).

The member might comprise two pivoting axes, the first running in the transverse direction of the coupler and the second running in the longitudinal direction of the coupler. This allows the member to pivot in more than one direction. Even more pivoting directions can be achieved with a ball and socket joint. However, instead of pivoting, the member may slide or roll between its open and closedllocked and unlocked positions.

Preferably an accessory for coupling to the coupler comprises two attachment pins, the coupler thereby needing two jaws. One or more gravity-operated member as defined above may be provided for each or either jaw. However, preferably only one jaw has a gravity-operated member, and most preferably it will just be the front jaw -usually the jaw without a hydraulically or mechanically driven latching hook or latching plate.

Preferably the other jaw (the rear jaw) points downwards and has a hydraulically or mechanically driven latching hook or latching plate, which, together with the first jaw, (which usually points forwards) provides a primary coupling mechanism for coupling the accessory to the coupler in a fixed orientation relative to the coupler. The gravity-operated member is then preferably just a secondary securing mechanism (as a secondary securing mechanism, the gravity-operated member does not serve to couple the accessory to the coupler in a fixed orientation relative to the coupler, but instead merely serves to attach or tether the accessory to the coupler simply by retaining the attachment pin within the first jaw when the member is in its closed or locked position).

Preferably, the gravity-operated member is not hook-shaped. The member instead is preferably a blocking bar, a blocking toggle or a blocking wedge.

By the term "gravity-operated", it is intended that no spring or hydraulic member, or any other mechanical, hydraulic, magnetic or electrical biasing influence, is to be used, in normal use, to move the member from its closed or locked position into its open or unlocked position. Instead, simply gravity is to be relied upon for that purpose, whereby the coupler has to be at least partially inverted in order to release the gravity-operated member. Such inversion of the coupler should not occur during the normal use of the coupler with an accessory attached thereto.

Similarly it is desired just to rely upon gravity to return the member to its closed or locked position. However, it is possible to provide a gravity-operated member that has a biasing member, such a spring, for assisting in ensuring that the gravity-operated member will fall, move into or assume its closed or locked state when the coupler is in its normal, in-use orientation. In such an embodiment, gravity would still be relied upon to overcome that biasing force in order for the member to assume its open or unlocked state.

Preferably, the gravity-operated member is arranged such that it will be in its locked or closed state for most normal, in-use orientations and rotations of the coupler. Those normal, in-use orientations will usually range from a level orientation (i.e. where the two attachment pins are level) to perhaps at least 45 from that level orientation in a first or digging curl direction (i.e. moving towards the crowd position) and from the level orientation to perhaps at least 135 from that level orientation in an opposite curl direction -the emptying curl direction (i.e. up and over the excavator arm). Therefore the preferred embodiment of the present invention will keep its gravity-operated member in a locked or closed position through a range of angles of curl perhaps in excess of 1800.

In a more preferred embodiment, the member will only move to its open position in response to specific re-orientations of the coupler, such as a full inversion of the coupler (i.e. into a position curled up and above the excavator arm, which may be a rotation of more than 170 in the emptying curl direction from the level orientation), or in response to lesser rotation, e.g. 60 or more in the digging curl direction (i.e. into or towards the crowd position). Adjusting the position of the pivot point of the member relative to the centre of gravity of the member provides for different angle ranges in that regard where the pivot axis runs transverse across the coupler, e.g. between sideplates of the coupler.

Further, undesired rotations for the member can be avoided, or rotation limits can be provided, by pivot stops.

It should also be noted that the former of the two decoupling positions (i.e. a position curled up and above the excavator arm) is the less desirable position for the coupler during a decoupling of the accessory from the coupler. That is because it positions the coupler at a significantly more elevated position than that achieved in the crowd position. As a result, such a position would never be used in practice. It should also be noted that such a position serves no useful purpose, and thus is an unlikely position for an operator to put the coupler into.

It is also preferred that a decoupling of the accessory from the coupler is not an automatic result of (at least partially) inverting the coupler. With the preferred embodiment of the present invention, there is also a primary coupling mechanism, with the gravity operated member providing just a secondary securement function, for example of being an automatic tether. As a result, the mere reorientation of the coupler into a position that moves the gravity-operated member into an open or unlocked position will not actually decouple the accessory from the coupler. The primary coupling mechanism would also need to be disengaged or retracted before that could happen.

It should also be noted that when a coupler is in a fully inverted orientation (i.e. up above the excavator arm, and rotated by more than I 700 from the level orientation), the weight of the accessory will be bearing directly down onto the coupler. The weight of the accessory, therefore, should keep the accessory on the coupler.

The accessory also cannot be released while the weight of the accessory is forcing the attachment pin to press into the back of the jaw. That, therefore, is a preferred state for the coupler at the time of decoupling. That state is achieved for example by reorienting the coupler into the crowd position. Then, to withdraw the attachment pin from the jaw in that orientation, the weight of the accessory will be rested on the floor or the like, preferably in a stable manner (e.g. on a flat bottom surface of the accessory or on a stand for the accessory), and then the weight of the accessory on the ground is used to keep the accessory stationary while the jaw is disengaged from the attachment pin of the accessory by manipulation of the excavator arm and the coupler relative to that accessory in an appropriate manner (after disengagement of any primary coupling mechanism).

With the present invention, therefore, the decoupling of an accessory from the coupler involves specific deliberate reorientation and manipulations, which acts would not be carried out during normal excavation operations. As a result, the accessory cannot be decoupled from the coupler accidentally. Thus the present invention will provide remarkable reassurances to an excavator operator.

The present invention also provides a method of coupling an accessory onto a coupler that is attached to an excavator arm of an excavator.

The present invention also provides a method of uncoupling an accessory from a coupler that is attached to an excavator arm of an excavator.

The present invention will now be described purely by way of example with reference to the accompanying drawings in which: Figure 1 shows a part sectional side elevational view of a coupler illustrating a first embodiment of the present invention; Figure 2 shows the same part sectional/side elevational view of the coupler of the first embodiment of the present invention, but in which the member is in its second, jaw-closed position; Figure 3 shows a front elevation view of the coupler of Figures 1 and 2 with the member in its jaw-closed position; Figure 4 is a detail side view of the gravity-operated member of Figures 1, 2 and 3; Figure 5 is a front perspective view of a second embodiment of the present invention; Figure 6 is a schematic view of the second embodiment showing an attachment pin of an accessory passing the member; and Figure 7 is a front elevation view of the second embodiment with the member in its jaw-closed position.

Referring now to Figure 1, a first embodiment of the present invention is shown. The coupler 10 comprises a top side 12, a bottom side 14, a front 16 and a rear 18. The coupler also comprises sideplates 20 (see Figure 3).

in the top side 12, two holes 22 are provided for attachment of the coupler 10 to an excavator arm of an excavator in a conventional manner, i.e. with two attachment pins (not shown).

In the bottom side 14, a front jaw 24 and a rear jaw 26 are provided for receiving two further attachment pins (not shown), this time of an accessory (also not shown) for attachment of the accessory to the coupler 10 again in a generally conventional manner.

Indeed, for this embodiment, a primary coupling mechanism (not shown) for that purpose can consist of a pivoting latching hook and hydraulic cylinder as disclosed in GB2359062. However, for simplicity, those features have not been shown in the drawings. For completeness, however, the disclosures of GB2359062 are incorporated herein by way of reference, and as such, a full discussion of the primary coupling mechanism is not required herein. The drawings do, however, show three apertures 28 that pass through both of the sideplates 20 of the coupler 10 which are for receiving a locking pin (through just one pair of them) for locking the latching hook in its latched position, as disclosed in GB2359062.

The present invention, however, has an additional feature that is not disclosed in GB2359062. That is the gravity-operated member 30, as most clearly shown in Figure 4. That gravity-operated member 30 is a toggle in an upper wall 32 of the front jaw 24.

The jaw is otherwise of a generally conventional configuration, having a moulded lower wall (of a pointed type, with a pointed front 33) and the upper wall, with the opening 31 for the jaw 24 being defined therebetween.

The toggle is mounted within a hole 34 in the upper wall 32 and is mounted for rotation about a pivot axis, as defined by a peg or bolt 36 that passes through the hole 34 in a transverse direction (i.e. transverse to the sideplates 20 of the coupler 10). The head 35 and nut 37 of the bolt are shown in Figure 3.

The toggle may pivot about the bolt 36 between an open position, as shown in Figure 1, in which the toggle sits fully within the hole 34, and a closed position, as shown in Figures 2 to 4, in which part of the toggle still sits within the hole 34, but in which a second end or nose 38 of the toggle extends out of the hole 34 to partially close the opening 31 of the jaw 24.

That toggle is mounted off-centre relative to the bolt 36, whereby it is balanced so that in a normal orientation of the coupler 10, i.e. in an in-use orientation in which the front and rear jaws 24, 26 (and therefore also any attachment pins held therein) are generally level to each other, the toggle's centre of gravity will cause it to rotate under the influence of

II

gravity into that latter closed position in which the nose 38 descends into the front jaw so as to partially close the opening 31 of the front jaw 24.

By having this arrangement, in normal use an attachment pin 40 within that front jaw 24 will only be able to be removed from the front jaw 24 through the opening 31 of the jaw 24 if the toggle was to rotate out of its way. That is because attachment pins 40 have a size corresponding generally to the height of the front jaw 24. However, further rotation of that toggle is not possible due to the configuration of the toggle, the bolt 36 and the hole 34. The toggle in its closed position has a wall 48 that bears against a front wall member 42 of the hole 34 (see Figure 4). Further, preferably that front wall member 42, the bolt 36 and the toggle are all reinforced, toughened or hardened as well, whereby they should be able to resist even a significant attempt to force an attachment pin 40 out of the jaw.

Referring now to Figure 4, specific details of the preferred arrangement for the toggle, the hole 34, the bolt 36 and the front wall member 42 will now be described.

The toggle preferably comprises at its first end two perpendicular walls 44, 48 that tangentially extend from a curved section 46. There is also a third wall 49 that extends parallel to and perpendicular to the two other walls 44, 48, respectively. Further, that first end has an aperture therein through which the bolt 36 passes for pivotally mounting the toggle within the hole 34 of the front jaw 24. The aperture is between the two parallel walls 48, 49 and runs parallel to all three walls 44, 48, 49.

The hole 34 in the upper wall 32 of the front jaw 24 has a flat bottom 51 and the inside surface of the front wall member 42 extends perpendicular to that flat bottom 51. That inside surface also is flat.

The bolt 36 is arranged through the hole 34 of the first jaw 24 in a position that is spaced from, yet parallel to, both the flat bottom 51 and the inside surface of the front wall member 42. The distance of the bolt 36 from the inside surface is slightly greater than the radius of the curved section 46 of the toggle. The distance of the bolt 36 from the flat bottom is greater than its distance from the inside surface.

The aperture in the toggle is arranged concentrically to the curved section 46 of the toggle. As a result, the toggle will be free to rotate within the hole 34 through a full 9 0 range of angles, i.e. between its open and closed positions. In the open position, the first of the two perpendicular walls 44, 48 will bear against the front wall 42 to provide a first rotation limitation for the toggle. In the closed position, the second of the two perpendicular walls 44, 48 will bear against the front wall 42 to provide a second rotation limitation for the toggle. Changing the angle between these two perpendicular walls 44, 48 will therefore change the available range of angles of rotation for the toggle.

In addition, the toggle comprises a second end 38 -the end that extends out of the hole 34 when the gravity-operated member 30 is in its closed position. That end 38 comprises a curved wall 50 that will face towards an attachment pin 40 within the front jaw 24 when the member 30 is in its closed position. That curved surface, although optional, provides an increased area of surface contact between the attachment pin 40 and the toggle in the event of an attempt to remove the attachment pin 40 from the front jaw 24 through the opening of the jaw 24 when the member 30 is in its closed position. As a result, forces are less concentrated on the toggle.

No biasing member is provided for the toggle, whereby it relies purely upon gravity for its orientation. However, as a result it is free to rotate within that 90 range if it is acted upon by an external force. Accordingly, although the toggle will prevent the withdrawal of an attachment pin 40 from the front jaw 24, the toggle will rotate to allow an attachment pin 40 to be inserted into the jaw 24 (as shown in Figure 1).

By positioning the aperture for the bolt 36 in the first end of the toggle, the centre of gravity of the toggle is arranged towards the second end of the toggle relative to its pivot axis. Thus the gravity-operated member 30, which is mounted in the upper wall 32 of the front jaw 24 (which upper wall 32 extends generally parallel to the longitudinal axis of the coupler 10) will default to a closed position whenever the coupler is level (e.g. as shown in Figure 2). However, the toggle can be opened by rotating the coupler clockwise (as seen in the drawings) through an angle of about 90 , i.e. into the crowd position.

Referring now to Figure 5, 6 and 7, an alternative embodiment of the present invention is disclosed in which an alternative gravity-operated member 30 is provided. Instead of the coupler having a primary coupling mechanism in

accordance with GB2359062, the coupler of this embodiment features a primary coupling mechanism involving a latching hook 54 and a blocking bar 52 for that latching hook 54, similar to that disclosed in GB2330570, the disclosures of which are incorporated herein by way of reference. Yet further, the front jaw is formed from two sideplates 53, rather than having the moulded, pointed, configuration of the first embodiment. Both configurations, however, are generally conventional and interchangeable.

In accordance with this alternative embodiment, the gravity-operated member 30 features a flap member that has a first pivot axis 36 that extends in a generally longitudinal direction of the coupler 10. Therefore, to allow it to rotate out of the opening of the jaw 24 from its locked position (as shown in Figure 5), the coupler 10 needs to be inverted to a greater degree than the first embodiment -it must be almost completely inverted in order for gravity to cause it to rotate about its pivot axis into its open position. Additionally, however, the flap member has a second pivot axis 56 -a hinge axis. That second pivot axis 56 can be free swinging between a straight and folded position or it may be spring biased to keep it closed even when the coupler is inverted.

The hinge, however, will have a rotation stop (not shown) as known in the art of hinges, to prevent it from swinging in the opposite direction to that shown in Figure 6, whereby an attachment pin can be inserted into the jaw, but by means of which the attachment pin cannot be removed from the jaw without inverting the coupler. Thus the hinged flap can also provide a similar function to the toggle of the first embodiment.

The present invention has been described above purely by way of example. It should be noted, however, that modifications in detail can been made within the scope of the invention as defined in the claims appended hereto.

Claims

CLAIMS

I. A coupler for coupling an accessory to an excavator arm of an excavator, the accessory comprising at least one attachment pin for use in the coupling, the coupler comprising a first side for attaching the coupler to an excavator arm of an excavator and the coupler having a second side onto which an accessory would be coupled, the second side comprising a jaw for receiving the attachment pin of the accessory for connecting the accessory to the coupler by the engagement of the jaw with the attachment pin, wherein the jaw further comprises a gravity-operated member having a first state -the jaw-open or jaw-unlocked state, and a second state -the jaw-closed or jaw-locked state, the gravity-operated member at least partially closing the jaw of the coupler when it is in its first state, said first state being achieved by the gravity-operated member when the coupler is in a normal, in-use orientation due to the influence of gravity on the gravity-operated member.

2. The coupler of claim 1, wherein in a first orientation of the coupler, the member will fall, or will have fallen, under the influence of gravity into a closed position, but upon reorienting the coupler to an alternative orientation, the member will fall, or will have fallen, under the influence of gravity from that closed position into an open position.

3. The coupler of claim 1 or claim 2, wherein in the closed or locked state, the jaw's opening is only partially closed by the member.

4. The coupler of claim I or claim 2, wherein in the closed or locked state, the jaw's opening is fully closed by the member.

5. The coupler of any one of the preceding claims, wherein in the normal, in-use orientation, an attachment pin can still be inserted into the jaw by virtue of the gravity-operated member being free to move in a direction for allowing that insertion, but the member not allowing an attachment pin to be removed from the jaw past the member.

6. The coupler of any one of the preceding claims, wherein the gravity-operated member is a pivotal member, mounted to the coupler about a pivot axis, the pivoting of the member moving it between open and closed positions.

7. The coupler of claim 6, wherein the pivot axis runs in a transverse direction of the coupler.

8. The coupler of any one of the preceding claims, wherein the first side is a top side of the coupler, the second side is a bottom side of the coupler, and the coupler comprises a frame having two sideplates, extending generally between the top and bottom sides of the coupler.

9. The coupler of any one of the preceding claims, wherein the gravity-operated member is fitted to a front jaw of the coupler, which jaw points in a generally longitudinal direction of the coupler.

10. The coupler of any one of the preceding claims, wherein the jaw has no hydraulically or mechanically driven latching hook or latching plate.

11. The coupler of any one of the preceding claims, wherein the coupler has a second jaw, the first jaw being for the first attachment pin of the accessory and the second jaw being for a second attachment pin of the accessory.

12. The coupler of claim 11, wherein the second jaw has a hydraulically or mechanically driven latching hook or latching plate, which, together with the first jaw, provides a primary coupling mechanism for coupling an accessory to the coupler in a fixed orientation relative to the coupler.

13. The coupler of any one of the preceding claims, wherein the gravity-operated member provides a secondary securing mechanism for securing an accessory to the coupler, the gravity-operated member not serving to couple an accessory to the coupler in a fixed orientation relative to the coupler, but instead merely serving to attach or tether the accessory to the coupler simply by retaining an attachment pin of the accessory within the first jaw of the coupler when the gravity-operated member is in its closed or locked state.

14. The coupler of any one of the preceding claims, wherein the gravity-operated member has a biasing member for assisting in ensuring that the gravity-operated member adopts a closed or locked state when the coupler is in its normal, in-use orientation, but which biasing force will be overcome by gravity by the weight of at least an element of the gravity-operated member for putting the member into its open or unlocked state when the coupler is at least partially inverted to a sufficient degree.

15. The coupler of any one of the preceding claims, wherein the gravity-operated member is a rotatable member, having rotation limits defined by one or more pivot stops.

16. The coupler of claim 15, wherein the pivot stop is an inside surface of a front wall member of a hole provided in a upper wall of the jaw, the rotatable gravity-operated member comprising a toggle mounted for rotation within that hole, the toggle having two walls that extend from a curved portion, the two walls bearing against that inside surface at the two allowable extremes of rotation of that rotatable member, the toggle fitting within that hole in a first allowable extreme of rotation -the open state, and part of the toggle extending out of the hole in the second extreme of rotation -the closed state.

17. Preferably the two walls are perpendicular to each other, whereby the toggle can rotate through 90 .

18. A coupler substantially as hereinbefore described with reference to Figures 1 to 4.

19. A coupler substantially as hereinbefore described with reference to Figures 5 to 7.

20. A method of releasing an accessory from a coupler, the accessory comprising at least one attachment pin engaged in a jaw of the coupler and the coupler being attached to an excavator arm of an excavator, wherein the jaw further comprises a gravity-operated member having a first state -the jaw-open or jaw-unlocked state, and a second state -the jaw-closed or jaw-locked state, the gravity-operated member at least partially closing the jaw of the coupler when the coupler is in a normal, in use orientation such as a level orientation due to the influence of gravity on the gravity-operated member, and moving to an open or unlocked state due to the influence of gravity on the gravity-operated member when moved to an at least part inverted orientation that is at least 45 from a level orientation, comprising the steps of orienting the coupler and accessory to that at least partially inverted orientation to open or unlock the gravity-operated member, and then, to withdraw the attachment pin from the jaw in that orientation, while the weight of the accessory is resting either on the floor or on a stand, using the weight of the accessory on the ground or on the stand to keep the accessory stationary while disengaging the jaw, with its unlocked or open gravity-operated member, from the attachment pin of the accessory by manipulation of the excavator arm and its attached coupler relative to that accessory.

21. The method of claim 20, wherein the step of orienting the coupler and accessory to that at least partially inverted orientation involves moving them and the excavator arm towards the crowd position.

22. A method of releasing an accessory from a coupler substantially as hereinbefore described with reference to the accompanying drawings.