IE20080438A1 - Hydraulic ram for a coupler - Google Patents

Abstract

A hydraulic ram (30) for an excavator coupler (10) for a mini-excavator. The ram (30) comprises a head (38), a hydraulic cylinder (36) , a rod (32) having a piston (34) at its proximal end, the piston (34) being fitted within a bore of the cylinder (36), and a check valve (40) mounted at least partially within the head (38) of the ram (30). Two hinge pins mount the ram (30) within the coupler (10). Further, the rod (32) or piston (34) has a recess or cut-out (95) in its proximal end for accommodating a distal end of the check valve to maintain a full range of travel for the piston (34) within the bore of the cylinder (36). <Fig

Description

The present invention relates to a hydraulic ram for a coupler, and in particular a hydraulic ram for incorporating into small-to-medium size excavator couplers, such as couplers with a capacity of up to 20 tonnes.

Excavator couplers couple accessories to the excavator arm of an excavator. The coupling is usually achieved by a catch within the coupler that engages an attachment bar of the accessory. Known couplers operate that catch manually (e.g. by overcoming a spring force acting against the catch with a removable release bar), mechanically (e.g. by means of a screw-thread drive operating the catch) or hydraulically (e.g. with a hydraulic ram for operating the catch). For manual and hydraulic examples, see GB2330570.

Unfortunately there is a limit as to how small hydraulic rams can be manufactured while still being sufficiently cost effective to incorporate into such couplers, especially when the hydraulic ram is fitted with a check valve. Such check valves are for preventing pressure losses within the hydraulic ram upon a failure of a hydraulic fluid line connected to it, and are typically no smaller than 50mm long, and 20mm diameter, thereby providing the minimum size limitation for the ram as a whole. Thus, hydraulic rams tend not to be provided for the smallest couplers, e.g. couplers for mini-excavators such as couplers categorised with a maximum safe working load of 6 tonnes. Instead, they rely upon manual or mechanical release mechanisms.

It is desired, therefore, to develop a hydraulic ram that can cost-effectively be incorporated into the smaller (i.e. up to 6 tonne) excavator couplers, while still accommodating a check valve within the ram.

According to the present invention, there is provided a hydraulic ram for an excavator coupler comprising: ahead; ' ....... a hydraulic cylinder with a central bore extending away from the head; *980438 a rod having a piston at its proximal end, the piston fitted within the bore of the cylinder with a sliding fit for sliding therein along its longitudinal axis in response to hydraulic forces within the cylinder; and a check valve mounted at least partially within the head of the ram, the check valve having a fluid outlet that is arranged for fluid communication with the central bore; wherein the fluid outlet fluid outlet faces the proximal end of the piston or the rod, and more preferably such that it encompasses the longitudinal axis of the rod. By locating the fluid outlet of the check valve such that it faces the proximal end of the piston or the rod, or such that it encompasses the longitudinal axis of the rod, only a very short length (if any) of fluid pathway is necessary to link that fluid outlet with the central bore of the cylinder. For example, the fluid pathway could simply be an aperture in the endwall of the central bore. Thus, the head can be made smaller than in previously known arrangements.

Preferably the fluid outlet is a single aperture in the check valve. Preferably the longitudinal axis of the rod extends through the centre of the aperture.

In a second arrangement, the fluid outlet may be a ring of apertures. Preferably the longitudinal axis of the rod passes through the centre of that ring.

Preferably the central bore of the cylinder extends to a proximal endwall with a substantially flat portion that defines a proximal end of travel for the piston. Preferably the fluid outlet is located at or within that endwall.

Preferably the fluid outlet is located within a protruding dimple that extends distally from that endwall towards the piston.

To accommodate that dimple, or the distal end of the check valve if the distal end of the check valve instead extends beyond the flat portion and itself defines a dimple, the rod or the proximal end of the piston features a cut-out or recess of a suitable size and/or shape. That cut-out or recess can be sized and/or shaped to match that dimple, or it can be made larger than the dimple. «ΟβΟ*3* Preferably the dimple and cut-out both have an approximately frustoconical shape. Rounded comers or edges, around either or both of the dimple and cut-out, are preferably provided, however, to improve fluid flow characteristics within the cylinder and to remove stress concentration points.

Preferably the dimple extends between 1 mm and 20mm from the endwall. Alternatively it may extend by up to 30% of the length of the check valve into the cylinder - it should be appreciated that check valves of different sizes may be provided for differently rated rams, i.e. a 5 tonne ram can have a smaller check valve than a 20 tonne ram.

Most preferably the dimple extends between 5 and 10mm from that endwall, or between 10 ands 20% of the length of the check valve from that endwall.

Preferably the dimple is arranged concentrically relative to both the rod and the cylinder.

Preferably the ram is a double acting ram, i.e. it is powered by hydraulic forces both for forwards and backwards movement, whereby both the ram extension and the ram retraction are hydraulically powered. For that purpose, a fluid line may extend between the distal portion of the cylinder and the distal end of the head. Preferably that fluid line is a tube that runs externally of the cylinder.

Preferably the cylinder is attached to a block at its proximal end, that block defining the head of the ram.

Preferably the head comprises a first bore into which the check valve is mounted. Conventional check valves are usually an elongated component having a series of generally cylindrical sections. Usually they are formed with a series of cylindrical sections of diminishing radiuses that lead towards the fluid outlet at its end. Preferably such a check valve is located within the first bore of the head, with the check valve pointing generally distally, i.e. towards the rod, with the fluid outlet at the distal end of the check valve, i.e. nearest the rod. 11080*3« Preferably the first bore in the head of the ram is drilled into a cast or reamed block via the proximal end of the head.

Preferably the first bore consists of a set of concentric cylindrical bores that match or accommodate a series of cylindrical sections of the check valve.

Control ports are preferably provided in the head to provide a fluid link to that first bore for two hydraulic control lines of the excavator. Such hydraulic control lines are well known in the art for controlling hydraulic rams via the check valve.

Preferably the first control port comprises a second bore that extends substantially perpendicular to the longitudinal axis of the first bore, and the second control port comprises a third bore that extends at an angle of about 45° to that longitudinal axis, the second and third bores separately intersecting the first bore.

Preferably the second and third bores are themselves respectively intersected by two further bores, the fourth and fifth bores. Preferably the fourth and fifth bores are blind bores, i.e. bores that do not extend through to an axial exit.

The second and third bores do not intersect each other. Further, the fourth and fifth bores do not intersect each other.

Preferably the fourth and fifth bores are spaced apart and located either side of the first bore. Preferably they extend parallel to one another. Preferably they extend perpendicularly from the top surface of the head of the ram. Preferably that top surface is angled relative to the longitudinal axis of the ram. Thus, it is preferred that the fourth and fifth bores are not perpendicular to the first bore, since the axis of the first bore is preferably either parallel to, or coaxial with, the longitudinal axis of the rod, the cylinder and the ram.

Preferably the two hydraulic control lines of the excavator are adapted to be connected to the fourth and fifth bores via fittings provided at their open ends. Therefore the open ends of the fourth and fifth bores define hydraulic drive control ports for the ram. t «080431 Preferably the fifth bore is intersected by a sixth bore. The sixth bore forms at least a part of a further fluid link, running from the fifth bore to the distal end of the cylinder for allowing the cylinder to be double acting. That further fluid link preferably includes the tube that runs externally of the cylinder, as is known in the art.

Preferably the sixth bore is a blind bore.

Preferably the fluid link between the sixth bore and the tube additionally comprises a seventh bore that intersects the sixth bore. Preferably that seventh bore completes the fluid link to the tube.

Preferably the seventh bore is perpendicular to the sixth bore.

Preferably the second and sixth bores are spaced apart from each other. Preferably they extend parallel to one another. Preferably they extend perpendicularly to the fourth and fifth bores, respectively.

None of the fourth, the fifth, the sixth and the seventh bores directly intersect the first bore - they are only fluidly linked to the first bore via their intersections with other bores, i.e. the second and third bores. This arrangement provides convoluted fluid passageways within the head of the ram, rather than direct fluid passageways. Those convoluted fluid passageways, however, allow the fluid passageways to be kept away from the lateral areas of the proximal end region of the head, despite the check valve running though the proximal end region of the head. As a result, the head can be still mounted to the frame of the coupler via pivot pins located within those lateral areas, i.e. either side of the check valve, rather than needing to be positioned above or below the check valve.

Preferably the first bore, i.e. the bore for receiving the check valve, is arranged coaxially with the longitudinal axis of the rod. 4 lio 8 043β The fluid outlet at the distal end of the check valve preferably is located such that it sits distally beyond the flat portion of the proximal endwall of the bore of the cylinder. In one embodiment, the distal end of the check valve itself defines the above-mentioned dimple. In the preferred construction, however, the distal end of the check valve sits within the dimple in that endwall.

Preferably, that dimple is an integrally formed part of the head.

The cylinder and the head may be formed as two components, which are then welded together. Alternatively they may be formed from a single block of material.

The dimple and the corresponding cut-out in the rod or piston allow the check valve to be mounted longitudinally within the head of a small ram without restricting the range of travel for the rod within the cylinder. In prior art small rams, the check valve was instead arranged transversely. That, however, necessitated a correspondingly wider head for the ram, or a different position for it relative to the pivot pins, i.e. a location above or below the pivot pins. That is because the pivot pins are generally arranged to intersect the longitudinal axis to prevent the generation of bending moments within the ram. Thus, the present invention allows a smaller ram to be made for the smaller couplers.

In the preferred embodiment, the dimple is between 5 and 10mm high. Thus, a length saving of 5-10mm is possible for the head of the ram. However, the available length saving could be greater in other hydraulic ram designs, i.e. rams for medium or large size couplers where the check valve is larger.

In the art it is known to mount hydraulic rams using a single hinge pin that extends through the ram. The check valve, however, prevents such a construction. Thus, preferably the head comprises two transverse bores, each one being for enabling a pivotal mounting of the ram to a body or frame of the excavator coupler via a separate pivot pin. However, where a single hinge point would be strong enough, only a single transverse bore may be provided for accommodating that single hinge pin.

KO 0 0*35 In an alternative arrangement, the one or more hinge pin can be an integral component of the ram, the hinge pin(s) extending from one or both sides of the head of the ram.

Preferably a trunion surrounds one or both of the hinge pins, or one or both of the transverse bores. The or each trunion is for pivotally mounting one or two further components of the coupler onto the ram. The further components will generally be one or two mechanical stops for the catch of the coupler, for example as disclosed in PCT/GB2007/003324, the full content of which is incorporated herein by way of reference.

In the preferred embodiment, where two axially aligned transverse bores are provided, the two transverse bores are positioned on opposite sides of the head with respect to one another. Preferably both bores are blind, i.e. not being through-holes, whereby the bores are separated with respect to one another, i.e. spaced apart along their common axis. A hinge pin is also provided for each bore to mount the ram within the frame of the coupler.

Those two bores are preferably spaced apart along their common axis by a distance that is larger than the largest diameter of the first bore. Further, it is preferred that their common axis passes through both the first bore. Most preferably that common axis perpendicularly intersects the longitudinal axis of the ram, whereby no bending moment is generated within the ram as the ram operates within the coupler.

Preferably the top and bottom extremities of the head of the ram extend upwardly and downwardly, respectively, with respect to longitudinal axis of the rod by no more than 10% of each other, and more preferably by substantially an equal amount, i.e. by no more than 1% of each other.

Similarly, it is preferred that the two sides of the head extend to the left and right with respect to longitudinal axis of the rod by no more than 10% of each other, and more preferably by substantially an equal amount, i.e. by no more than 1% of each other. «Οβ ο 4 38 Preferably the two hydraulic drive control ports are arranged on an upper surface of the head of the ram when the ram is mounted within a coupler.

Preferably the two hydraulic drive control ports are spaced laterally apart, either side of the longitudinal axis of the rod.

The locations of the two hydraulic drive control ports allow the ram to be incorporated into a coupler more easily, especially with regard to smaller couplers, since their locations reduce the length of the hydraulic control lines within the confines of the coupler. Further, they reduce the extent of bending needed for those pipes, i.e. both the length of any bend, and the degree of bending (i.e. they allow a larger minimum radius of curvature for those bends, as compared to situations where the hydraulic drive control ports are positioned either at the sides, or at the proximal end, or at the underneath of, the hydraulic ram.

Preferably all the bores in the head are drilled into a cast or milled block.

The use of two hinge pins for mounting a ram within a coupler is not known in the art. Accordingly a second aspect of the present invention is to provide an excavator coupler comprising a latching means operated by a hydraulic ram, the ram comprising a check valve, the check valve being mounted within a head of the ram, the head of the ram being pivotally mounted with respect to the frame of the coupler by two pivot pins, each pivot pin extending coaxially with respect to one another and transversely with respect to both the ram and the check valve, the common axis of the pivot pins extending through the check valve.

The coupler of the second aspect of the present invention may additionally include any of the features disclosed above with respect to the first aspect of the invention.

The present invention is also directed towards an excavator coupler comprising a ram as defined above with respect to the first aspect of the present invention.

The inventive couplers are preferably for mini-excavators, and thus are preferably rated to a maximum load of between 1 and 6 tonnes.

These and other features of the present invention will now be described, by way of 5 example only, with reference to the accompanying drawings, in which: Figure 1 is a cut-away, side elevation of a coupler incorporating a hydraulic ram of the present invention; Figure 2 is a cut-away, front perspective view of the coupler of Figure 1 attached to a bucket; Figure 3 is a distal, perspective illustration of the various bores within the head of a hydraulic ram; Figure 4 is a proximal, perspective illustration of those bores; Figures 5 to 14 illustrate a preferred design of head for a hydraulic ram of the present invention; Figures 15 to 17 show the head attached to a cylinder to form a hydraulic ram; and Figures 18 to 23 show an alternate embodiment of hydraulic ram, with a different head design.

Referring first of all to Figure 1, there is shown a cut-away side elevation of an excavator coupler 10.

The coupler 10 has a first or upper portion 12, that is adapted to be connected onto an excavator arm of an excavator in a conventional manner. For that purpose it has two pairs of holes 20, although only one of each pair is shown. Those holes allow the coupler to be attached to the excavator arm using a first pair of attachment pins (not shown). »0 8 04 38 fe? '* The coupler also has a front 16 and a rear 18. In normal use the front 16 points towards the cab of an excavator (not shown), whereas the rear 18 points away from the cab.

The coupler 10 also has a second or lower portion 14. The lower portion 14 is for coupling an accessory onto the excavator arm via the coupler 10. Such an accessory might be an excavator bucket 28, as shown in Figure 2.

The lower portion 14 has a pair of jaws 22, 24 for engaging a second pair of attachment pins 52, 54, as provided on the accessory. The rear jaw 22 is a downwardly facing jaw that is usually for engaging a rear attachment pin 54 of the accessory 28. The front jaw 24 is a forward facing jaw usually for engaging a front attachment pin 52 of the accessory 28.

To couple an accessory to the coupler, first the user locates the front attachment pin 52 of the accessory within the front jaw 24. Then he manipulates the coupler to swing the rear attachment pin 54 of the accessory into the rear jaw. Then, to prevent that second pin from swinging out of the rear jaw, a pivoting latching hook, or first latch 26, is swung about its pivot into a latching position that engages the rear attachment pin, as shown in Figure 2. That then secures the accessory firmly onto the coupler 10.

Further details of that coupling procedure (and the decoupling procedure) are provided in PCT/GB2007/003324, the entire contents of which are incorporated herein by way of reference.

Instead of a pivoting latching hook 26, a sliding mechanism for that latch might instead be provided, as known in the art. Further many other different latching arrangements could be substituted for the above described latching arrangement, such as that disclosed in GB2330570.

For the purposes of this invention, the movement of the latching mechanism (here the latch 26) is controlled by a hydraulic ram 30. That ram constitutes the subject matter of the present invention. Thus no further discussion of the operation of the latching mechanism will be provided.

. Ko etui As shown in Figure 1, the hydraulic ram 30 comprises a rod 32 having a piston 34 at its proximal end and a cylinder 36. The piston 34 is fitted within a bore of the cylinder 36 with a sliding fit so that it can slide therein, along the longitudinal axis of the cylinder 36, in response to hydraulic forces within the bore of the cylinder 36.

The wall of the cylinder 36 extends from a head 38 of the ram 30. That head 38 houses a check valve 40 (see Figure 17) and fluid distribution lines.

Referring to Figures 3 and 4, where the ram is shown in phantom, the fluid distribution lines are shown. They are formed by a series of bores that are drilled into the head 38.

Those bores include a first bore 42. That first bore 42 is also shown in Figures 1 and 2.

The first bore 42 is for housing the check valve 40, as shown in Figure 17. In this preferred embodiment, that first bore 42 extends coaxially with respect to the longitudinal axis of the rod 32, whereby the check valve will also extend coaxially with respect to the longitudinal axis of the rod 32.

The first bore 42 is formed from a plurality of concentric cylindrical sections of diminishing radiuses, from the proximal end of the head towards the distal end of the head. The diameter of each cylindrical section is reduced down to the next cylindrical section by a taper, i.e. a frostoconical portion, as clearly shown in Figures 3 and 6.

Extending transversely from a side of that first bore 42 is a second bore 44. As shown in Figure 6 and Figure 7, that second bore 44 extends out to a first side wall 46 of the head 38, and it is perpendicular to both the axis of the first bore and the side wall 46. It is drilled into the head via that side wall 46.

The outermost opening of that second bore 44 comprises a larger diameter bore for providing a location for a closing plug (not shown) for closing the bore 44 at the side wall 46. As shown in Figure 7 (and Figure 22 for the second embodiment), that larger diameter bore takes a nick out of a stepped flange into which a hinge pin will be placed Κθ·Μ3» upon mounting the ram within the coupler (as explained below). That illustrates the degree of longitudinal compaction provided for the head.

The point at which the second bore 44 intersects the first bore 42 defines a first opening 58 (see Figure 4) in the side of the first bore 42.

A second opening 59 (see Figure 13) is provided in the opposite side of the first bore 42. That second opening 59, however, is proximally spaced along the axis of the first bore 42 relative to the first opening 58. That second opening 59 is formed by a third bore 60. That third bore 60 is drilled into the head via a second side wall 50 of the head 38 at approximately a 45° angle with respect to that second side wall 50. That second side wall is parallel to the first side wall 46. Thus the third bore 60 intersects the first bore 42 also at approximately a 45° angle - as shown it intersects one of the cylindrical sections, line the first opening.

Like the second bore 44, the third bore 60 also features a larger diameter bore 62 at its opening (at the second side wall 50) for providing a location for a closing plug (not shown) for closing the bore 60 at the side wall 50.

Since this third bore is drilled at an angle of 45°, to facilitate that drilling, a spot face 64 is formed into that opposite side wall 50 at an angle of 45°. Thus there is a suitably flat surface for the drilling of at third bore 60 perpendicular to a surface of the head.

That spot face 64 may be provided by a reaming operation carried out on the head 38.

Fourth and fifth bores 66, 68 are also provided. They are spaced apart on opposite sides of the first bore 42 and extend parallel to one another. They also are provided with larger diameter bores at their openings. However, instead of fitting plugs into them, those larger diameter bores accommodate connection means for connecting the bores to hydraulic control lines (not shown) of the excavator, such as those known in the art, in order to allow the check valve 40, and the ram 30, to be controlled.

The fourth and fifth bores 66,68 do not directly intersect the first bore 42. Instead, the fourth bore 66 perpendicularly intersects the second bore 44 and the fifth bore 68 perpendicularly intersects the third bore 60. Thus, a fluidic connection is provided between the fourth bores 66 and the first opening 58 via the second bore, and between the fifth bore 68, 68 and the second opening 59 via the third bore 60. Those hydraulic control lines can thus control the operation of the ram 30 via the check valve 40 in a known manner - the two openings 58, 59 are appropriately positioned along the check valve for allowing such control of the ram.

The fourth bore 66 is shorter than the fifth bore 68 - whereas the fourth bore 66 only extends to, or slightly beyond the second bore 44, the fifth bore 68 extends well beyond the third bore 60, although not all the way through the head. By means of that longer length, it is intersected by a sixth bore 74. That sixth bore 74, like the second bore 44, is drilled into the first side wall 46 of the head. However, whereas the second bore 44 intersects the first bore 42, the sixth bore 74 is positioned lower down, i.e. below the first bore 42, and it extends beyond the first bore 42 up to and through the fifth bore 68.

Indeed, it extends beyond the fifth bore 68, although it does not extend all the way through the head 38.

At the opening of the sixth bore, another larger diameter bore 78 is provided for a closing plug (not shown), again for closing the bore 74 at the side wall 46.

The sixth bore 74 runs below but parallel to the second bore, although it is slightly distal thereto in view of the slight angle off perpendicular, relative to the longitudinal axis, of the fourth and fifth bores 66, 68, whereby the sixth bore 74 intersects the fifth bore relatively centrally.

The fourth and fifth bores 66, 68 have the slight angle off perpendicular, relative to the longitudinal axis, in view of them being drilled perpendicularly into the top surface of the head, which top surface is tapered (referring to Figure 8, that angle is approximately 15°.

One final bore, the seventh bore 80, is also provided in the head 38 of the ram 30. That seventh bore 80 is drilled perpendicular to the distal surface 82 of the head 38. It intersects the extension of the sixth bore 74 beyond the fifth bore 68. It provides a final section of a secondary fluid link within the head 38 for the hydraulic control line connected, in use, to the fifth bore 68. That secondary fluid link connects the hydraulic control line to a tube 84 that runs outside the cylinder for linking hydraulic fluid in the distal end of the cylinder 32 to the head. Such tubes 84 are known in the art. They enabling the ram to be dual acting, i.e. a ram with powerpd retraction as well as powered * extension.

The fluid distribution lines of the first embodiment of ram, as described above, are similarly provided in the second embodiment of hydraulic ram, as shown in Figures 18 to 23. Thus they will not be described again in relation to that second embodiment.

A main difference between the first and second embodiments of hydraulic ram is in the provision of trunions 48. Trunions 48 are provided on the head 38 of the first embodiment, whereas they are not provided on the second embodiment.

A mechanical stop 56 is pivotally mounted upon the trunions. The purpose of the mechanical stop is discussed in PCT/GB2007/003324. One half of the mechanical stop 56 is shown in Figure 2. For the purposes of the present invention, however, no further discussion of that mechanical stop is required.

Instead of the mechanical stop 56, a blocking bar might be provided on the trunions, also with a pivotal mounting. See GB2330570. Again, for the purposes of the present invention, no further discussion of that blocking bar is required.

There are a pair of trunions 48 since there may be two mechanical stops or blocking bars. Alternatively the mechanical stop or blocking bar may take the form of a bifurcated element, with respective ends of the fork engaging the respective trunions 48.

If the coupler’s mechanical stop or blocking bar is only requiring one pivotal mounting position, however, only a single trunion might be provided, i.e. on just one side of the ram. «080438 In the second embodiment, no trunions are provided. This ram will thus be used for applications where a mechanical stop or blocking bar is not needed to be mounted onto the ram 3, such as where no such mechanical stop or blocking bar is provided for the coupler, or where the mechanical stop or blocking bar is mounted elsewhere within the coupler, such as directly onto the ram’s hinge pins (not shown), or onto some other element of the coupler.

The hinge pins for pivotally mounting the ram within the frame of the coupler extend from stepped flanges 94 that extend beyond the side walls 46, 50 of the head 38. Such hinge pins are not illustrated, but they would be located within a pair of axially aligned transverse bores 86 provided either through the trunions 48, as shown in Figure 7, or directly into the stepped flanges as shown in Figure 20.

To provide sufficient strength for the head around those transverse bores 86 for withstanding the loadings applied thereto by the hydraulic ram in use, the stepped flange 94 is more greatly stepped in the second embodiment than in the first embodiment. This is appropriate since no trunions 48 are provided in that embodiment for providing sufficient depth in the sidewalls for receiving the hinge pins in a sufficiently secure manner. For example, in order to provide sufficient inherent strength for securing the hinge pins in a manner to withstand the loadings applied thereto by the hydraulic ram in use, the depth of the bores 86 for the hinge pins should preferably be greater than the diameter of the pins. Further, they should also be uncompromised by the surrounding bores within the head.

In the first embodiment of Figures 6 and 8, the depth of the transverse bores is approximately 27mm.

Where the width of the ram already provides adequate depth of material for the formation of appropriate transverse bores 86, the stepped flanges could be omitted entirely. The use of stepped flanges 94, however, allow unnecessary material to be removed from the head, which reduces the overall weight of the ram.

The first bore 42 in both illustrated embodiments is coaxially aligned with the rod 32. Further, the axes of the transverse bores 86 intersect the longitudinal axis of the rod in order to avoid bending moment generation during use of the ram. Thus those transverse bores 86 only extend partway through the head 38, i.e. from the outermost surfaces of the stepped flanges 96, or the trunions 48, towards, but not into, the first bore 42. As such the transverse bores 86 are blind bores in that they stop short of that first bore 42. As a result, a single hinge pin, as commonly used in the art, is not used. Instead, two hinge pins are used for pivotably mounting the head 38 of the ram 30 to the frame of the coupler.

The above described arrangement for the head 38, both with respect to the transverse bores 86 for the hinge pins, and the fluid passageways within the head for the control of the ram, allows a more compact head 38 to be provided than was previously achievable. That in tum results in a smaller ram, especially since no additional bulk needs to be added above or below the check valve for allowing a hinge pin to extend all the way through the body of the ram 30.

The size of the head in the first illustrated embodiment, i.e. Figures 6 and 8, is as follows: The width of the head, from side wall 46 to sidewall 50: 65mm.

The width of the head, between the ends of the trunions 48: 95mm.

The length of the head, from its proximal most part 96 to the distal most part 98 of the dimple 88 (see Figure 6): 52mm.

The height of the head, from the top 97 of Figure 8 to the bottom 99 of Figure 8: 60mm.

The size of the head in the second illustrated embodiment, i.e. Figures 19 and 20, is as follows: The width of the head, from side wall 46 to sidewall 50: 65mm.

The width of the head, between the ends of the stepped flanges 94: 83mm.

The length of the head, from its proximal most part 96 to the distal most part 98 of the dimple 88 (See Figure 19): 57mm. «080438 v The height of the head, from the top 97 of Figure 8 to the bottom 99 of Figure 8: 57mm.

Different sizes, however, may of course be used.

Referring again to Figures 6 and 7, a first embodiment of dimple 88 is illustrated. The dimple 88 extends distally of a flat portion 90 provided on the distal surface of the head. The distance it extends is approximately 5mm.

The flat portion 90 forms an end limit for the retraction travel of the piston 34 within the bore of the cylinder 36, as shown in Figure 17. This is also shown for the second embodiment in Figure 19. In that second embodiment, the dimple 88 extends further approximately 10mm from the flat portion 90.

For accommodating the dimple 88, a cut-out or recess 95 (see Figures 1 and 2) is provided in the proximal end of the rod 32. That recess allows the rod 32 to travel over the top of the dimple 88 to allow the proximal end of the piston 34 to engage the flat portion 90. Thus the range of travel of the piston 34 is not shortened by the presence of the dimple 88.

In the illustrated embodiments, the dimple 88 has a generally frostoconical shape, although with rounded edges. The recess 95 has a corresponding shape for accommodating that dimple 88. However, other shapes for accommodating the dimple can be provided. Similarly, the dimple can take different forms.

The first bore 42 for accommodating the check valve 40 extends into the dimple 88 and terminates with a final cylindrical section 92 (see Figure 19). That final cylindrical section 92 provides a fluid pathway from the fluid outlet of the check valve 40 into the proximal space between the piston 34, or recess 95 in the rod 32, and the flat portion 90 of the head 38. As a result, the piston 34 can be driven outwards relative to the bore of the cylinder 36 by hydraulic fluid entering that proximal space via the check valve.

Since the distal end of the check valve 40 extends at least partially into the dimple 88, the length of that final cylindrical section 92 is shorter than the height of the dimple 88.

IS08 0438 In an alternative design, the fluid outlet of the check valve 40 could be located flush with, or extending beyond, the end of the dimple. Then no such final cylindrical section 92 would need to be provided for that purpose - the hydraulic fluid would enter the proximal space directly from the fluid outlet of the check valve 40.

The above dimple, or where the distal end of the check valve forms the dimple, just the recess in the end of the rod 32, further allows a reduction in the size of the head of the hydraulic ram compared to prior art designs, whereby the overall size of the hydraulic ram can be minimised without reducing the range of travel available to the piston 34. Thus the desired smaller rams can be fabricated for incorporation into smaller couplers.

The present invention has been described above purely by way of example. Modifications in detail, however, may be made to the invention as defined in the claims appended hereto. *089*3«

Claims (25)

1. A hydraulic ram for an excavator coupler comprising: a head; a hydraulic cylinder with a central bore extending away from the head; a rod having a piston at its proximal end, the piston fitted within the bore of the cylinder with a sliding fit for sliding therein along its longitudinal axis in response to hydraulic forces within the cylinder; and a check valve mounted at least partially within the head of the ram, the check valve having a fluid outlet that is arranged for fluid communication with the central bore; wherein the fluid outlet the proximal end of the piston or the rod.

2. The ram of claim 1, wherein the fluid outlet encompasses the longitudinal axis of the rod.

3. The ram of claim 2, wherein the fluid outlet is a single aperture in the check valve and the longitudinal axis of the rod extends through the centre of the aperture.

4. The ram of any one of the preceding claims, wherein the central bore of the cylinder extends to a proximal endwall with a substantially flat portion that defines a proximal end of travel for the piston and the fluid outlet is located at or within a protruding dimple that extends distally from that endwall towards the piston.

5. The ram of any one of the preceding claims, wherein the rod or the proximal end of the piston features a cut-out or recess of a suitable size and/or shape, and in a suitable position, to accommodate a dimple extending from a distal surface of the head containing the distal end of the check valve, or alternatively the distal end of the check valve directly, where it extends itself from a distal surface of the head.

6. The ram of claim 5, wherein the dimple, or the distal end of the check valve, extends between 1 mm and 20mm from a distal surface of the head. iioeous

7. The ram of claim 6, wherein the dimple, or the distal end of the check valve, extends between 5 mm and 10mm from a distal surface of the head.

8. The ram of any one of the preceding claims, wherein two control ports are provided in the head to provide two fluid links to the check valve for two hydraulic control lines of the excavator.

9. The ram of claim 8, wherein the two control ports enter the head at openings in an upper surface of the head, the openings being spaced laterally apart, either side of the longitudinal axis of the rod.

10. The ram of claim 8 or claim 9, wherein the head comprises a first bore into which the check valve is mounted, and the check valve points generally distally, i.e. towards the rod or piston, with the fluid outlet at the distal end of the check valve.

11. The ram of claim 10, wherein the first control port comprises a second bore that extends substantially perpendicular to the longitudinal axis of the first bore, and the second control port comprises a third bore that extends at an angle of about 45° to that longitudinal axis, the second and third bores separately intersecting the first bore.

12. The ram of claim 11, wherein the second and third bores are themselves respectively intersected by two further bores, the fourth and fifth bores, and where neither the second and third bores, nor the fourth and fifth bores, intersect one another.

13. The ram of claim 12, wherein the fifth bore is intersected by a sixth bore, which in tum is intersected by a seventh bore, the seventh bore being linked to a tube that runs externally of the cylinder to a distal portion of the cylinder.

14. The ram of any one of the preceding claims, wherein the head comprises two axially aligned transverse bores, each one being for enabling a pivotal mounting of the ram to a body or frame of the excavator coupler via a separate pivot pin. HO 8 043®

15. The ram of claim 14, wherein the transverse bores are provided on opposite sides of the head and they are separated with respect to one another by a distance that is larger than the largest diameter of check valve, their common axis passing through the check valve.

16. The ram of any one of the preceding claims, wherein a trunion is provided on one or both sides of the head, onto which a mechanical stop or blocking bar can be pivotally mounted.

17. The ram of claim 16, when dependent upon claim 14 or claim 15, wherein the transverse bores are formed within two opposed trunions.

18. The ram of any one of the preceding claims, wherein the check valve is mounted within the head coaxially with respect to the longitudinal axis of the rod.

19. An excavator coupler comprising a latching means operated by a hydraulic ram, the ram comprising a check valve, the check valve being mounted within a head of the ram, the head of the ram being pivotally mounted with respect to the frame of the coupler by two separate pivot pins, each pivot pin extending coaxially with respect to one another and transversely with respect to both the ram and the check valve, the common axis of the pivot pins extending through the check valve.

20. The coupler of claim 19, wherein the ram is in accordance with any one of claim 1 to 18.

21. An excavator coupler comprising a ram according to any one of claims 1 to 18.

22. A mini-excavators rated to a maximum load of between 1 and 6 tonnes, comprising an excavator arm, the excavator arm having a coupler on the free end thereof, the coupler comprising a hydraulic ram having a check valve mounted within its head. Koβ0438

23. The mini-excavator of claim 22, wherein the coupler is in accordance with any one of claims 19 to 21.

24. A hydraulic ram substantially as hereinbefore described with reference to Figures 5 3 to 17.

25. A hydraulic ram substantially as hereinbefore described with reference to Figures 18 to 23. *080436 1/10 FIG. 1 FIG.2 FIG. 3 2/10 p llo Ο 0438 3/10 8 04 38 4/10 FIG.5 5/10 «Ο 8 0*38 FIG. 9 6/10 FIG. 12 FIG. 13 7/10 FIG. 16 84' 8/10 043® 9/10 HO 8 04 38 10/10 FIG. 22 46 94 FIG. 23