(12) United States Patent
`Miller
`
`US006422805B1
`US 6,422,805 B1
`Jul. 23, 2002
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`(54) QUICK COUPLER FOR BUCKET
`EXCAVATORS
`
`76
`
`I
`nventor:
`
`G yM'll 42W
`hD'
`r1ve,
`entWort
`1 er,
`ar
`UsWorth, Washington Tyne and Wear
`NE27 1PX (GB)
`
`* N'
`ot1ce:
`
`Sbj
`yd'l'
`h
`fh'
`u ect to an 1sc a1mer, t e term 0 t is
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/337,447
`(22) Filed:
`Jun. 21, 1999
`(30)
`Foreign Application Priority Data
`
`Sep. s, 1998
`
`(GB) ........................................... .. 9819598
`
`(51) Int. Cl.7 ................................................. .. E02F 3/32
`(52) US. Cl. ........................................ .. 414/723; 37/468
`(58) Field of Search ......................... .. 414/723; 37/468;
`403/320, 321, 325; 172/272_275
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,871,292 A 10/1989 Milanowski
`4,929,143 A * 5/1990 Dohnalik .............. .. 172/272 X
`
`5,244,047 A * 9/1993 Eudy . . . . . . . . .
`. . . . . .. 172/275
`5,332,353 A * 7/1994 Arnold ................. .. 172/275 X
`5,549,440 A * 8/1996 Cholakon et al. ......... .. 414/723
`5,692,325 A 12/1997 KuZutani
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`EP
`FR
`FR
`GB
`W0
`
`1/1991
`0 405 813 A2
`0 578 447 A1 12/1994
`2 701 047 A1
`5/1994
`2 760 029 A1
`2/1997
`2205299 A 12/1988
`WO 95/33895
`12/1995
`
`* cited by examiner
`
`Primary Examiner—Donald W. Underwood
`(74) Attorney, Agent, or Firm—Stephen B. Salai, Esq.;
`Brian B. ShaW, Esq.; Harter, Secrest & Emery LLP
`
`(57)
`
`ABSTRACT
`
`A coupler for connecting a dipper arm of an excavator to a
`bucket Without the need for the operator of the excavator to
`leave the cab of the excavator, the coupler having means for
`connecting it to the end of the dipper arm, and means,
`including a latching hook for connecting it to one of a
`plurality of different buckets and Wherein locking means is
`provided to prevent inadvertent unlatching of the latching
`hook, said locking means being operable from the cab. The
`locking means may be gravity operated and include resil
`iently deformable means thereon to prevent unlatching When
`the coupler is inverted. Alternatively, it may be spring
`operated in Which case, further means is provided to move
`the locking means against the bias of the spring. Preferably,
`the hook has a special internal pro?le so that When it is
`supporting the Weight of a bucket, it Will tend to move to a
`latching position, not to an unlatching position.
`
`EP
`
`0 122 547 A1 10/1984
`
`4 Claims, 12 Drawing Sheets
`
`Page 1 of 19
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`CATERPILLAR EXHIBIT 1004
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`U.S. Patent
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`Jul. 23, 2002
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`Sheet 1 0f 12
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`US 6,422,805 B1
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`F?
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`mmw
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`FIG. 2
`(Prior art)
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`FIG. 3
`(Prior art)
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`US 6,422,805 B1
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`1
`QUICK COUPLER FOR BUCKET
`EXCAVATORS
`
`This invention relates to a quick coupler for bucket
`excavators.
`Hydraulically operated mechanical excavators have a
`dipper arm on the end of Which are tWo mounting points by
`means of Which an excavating bucket is pivotally attached to
`the end of the arm, and pivoted relative to the arm, respec
`tively. Until relatively recently, if the operator Wished to
`change the bucket, eg to a larger one, this had to be done
`manually. This involved the operator leaving the cab of the
`excavator, removing tWo pivot pins by means of Which the
`bucket is connected to the dipper arm, getting back into the
`cab to lift the dipper arm clear of the bucket, aligning the
`dipper arm With the neW bucket (and aligning the pivot
`apertures), de-mounting from the cab again, and locating the
`pivot pins in the aligned apertures, and securing them in
`place (e. g. With circlips, locking pins or bolts or the like) and
`then getting back into the cab to use the excavator.
`Sometimes, the operator Would have considerable dif?culty
`in removing or re-inserting the pivot pins, due to slight
`misalignment of the pivot apertures, and Would have to use
`a heavy hammer for this purpose.
`More recently, this time consuming exercise has been
`largely dispensed With, With the introduction of quick cou
`plers Which are located betWeen the dipper arm and the
`bucket. The couplers can either be of the hydraulic type or
`of the mechanical type and are effectively permanently ?tted
`to the tWo pivot apertures of the dipper arm and the bucket
`pivoting link, respectively. These couplers incorporate a
`generally horiZontally and rearWardly extending hook-like
`aperture or jaW adapted to engage With one of the pivot pins
`on the bucket (both of Which are left ?tted to the bucket), and
`a generally doWnWardly extending aperture or jaW adapted
`to locate over the other pivot pin on the bucket, With Which
`doWnWardly extending aperture a moveable latching hook is
`associated.
`In the manual version of the coupler, this latching hook
`is biased by a coil spring to its latching position, and is
`moved aWay from its latching position by a release handle
`or lever rod Which is removably locatable in an aperture in
`the nose of the latching hook.
`In the hydraulic version, a double acting hydraulic piston
`and cylinder device moves the latching hook betWeen its
`respective positions, and check valves are located Within the
`piston and cylinder device to prevent inadvertent movement
`of the piston in the event of hydraulic failure.
`HoWever, in both the manual and hydraulic versions, a
`safety pin has to be provided Which must be located by the
`excavator operator in specially provided apertures in the
`coupler, to lock the latching hook in its latching position.
`This means that in both of these versions, the digger operator
`still has to leave his cab to secure in position the safety pin;
`this is inconvenient and time consuming.
`In FR 2760029 and FR 2701047, couplers With hydrau
`lically operated latching hooks are disclosed. HoWever,
`these couplers are not provided With latch locking devices
`Which can be operated from Within the cab of the excavator.
`It is an object of the present invention to provide a fully
`automatic coupler for an excavator bucket Which can be
`operated by the excavator operator from his cab and be
`locked in its latching position Without the operator having to
`leave the cab.
`According to the present invention, We provide a coupler
`to enable an excavator operator to couple an excavator
`bucket to a dipper arm of an excavator Without leaving his
`
`10
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`35
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`cab, the coupler comprising tWo spaced side plates each
`having four ?xed pin location points, the coupler being
`mountable in use betWeen the bucket and the dipper arm and
`comprising a ?rst aperture and a second aperture de?ning
`tWo of said points and connectable respectively, in use, to the
`dipper arm of the excavator and a bucket piston and cylinder
`device, by suitable pins, a ?rst open-ended hooklike aperture
`de?ning a third of said points and for engagement With a ?rst
`pivot pin provided on an excavator bucket, and a pivoting
`latching hook co-operating With a second open-ended aper
`ture de?ning said fourth point and for latching engagement
`With a second pivot pin provided on the bucket once the ?rst
`hook-like aperture has been engaged With the ?rst pivot pin,
`in use, poWer operated means for moving the latching hook
`betWeen latching and unlatched positions and operable by
`the operator from the cab, and blocking means adjustably
`supported on the body of the coupler and moveable from
`Within the cab of the excavator independantly from the
`latching hook from and into a blocking position in Which it
`prevents the latching hook from being disengaged from the
`second pivot pin on the bucket.
`In one preferred construction, the blocking means is
`moveable under its oWn Weight by the force of gravity into
`a latch blocking position in Which it prevents the latching
`hook from being disengaged from the second pivot pin on
`the bucket, and resiliently deformable means is provided on
`the blocking means Which, in use, Will engage an abutment
`When the coupler is inverted by rotation in one sense (With
`the result that the blocking means Will tend under its oWn
`Weight to move aWay from its blocking position) such
`engagement resulting in the resiliently deformable means
`biasing the blocking means into its latch blocking position.
`In this construction, by inverting the coupler, the block
`ing means Will move, under its oWn Weight, to a fully
`croWded position in Which it no longer blocks the latching
`hook.
`Alternatively, a spring may be provided permanently to
`bias the blocking means into its blocking position, and
`means is provided to move the blocking means against the
`bias of the spring, so that it no longer blocks the latching
`hook. In one arrangement, said means is provided by a Wire
`and pulley arrangement, the Wire of Which Will tighten When
`the coupler is inverted, ie on full curl of the bucket, to move
`the blocking means out of its blocking position.
`In an alternative construction, a small hydraulic cylinder
`could be provided to move the blocking means out of its
`blocking position, against the bias of the spring.
`Preferably, the latching hook is operated by means of a
`double acting piston and cylinder device, one end of Which
`is pivotally connected about a ?rst pivot axis to the coupler,
`and the other end of Which is pivotally connected to the
`latching hook.
`In one construction, the blocking means comprises a
`bifurcated blocking bar, the tWo limbs of Which are pivotally
`supported on the coupler, preferably on the said ?rst pivot
`axis, and the opposite end of Which bears against a face on
`the rear of the latching hook.
`In another construction, the blocking means may com
`prise a single blocking bar pivotally supported at one end
`region on the coupler, preferably on the ?rst pivot axis and
`adapted to bear at its opposite end against a face on the rear
`of the hook.
`Preferably, the face is stepped so that the coupler can be
`used With different siZed bucket pivot pin distances (knoWn
`as pin spread).
`Preferably, the resiliently deformable means comprises
`an upstanding resiliently deformable arm on the blocking
`
`Page 14 of 19
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`US 6,422,805 B1
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`3
`bar Which Will bear against an abutment on the dipper arm
`When the coupler is inverted, eg when a bucket operating
`cylinder is retracted to pivot the bucket.
`Preferably, a protection plate is ?tted over the latching
`hook and blocking means, through Which plate the resil
`iently deformable arm projects, the plate being provided to
`ensure that excavated material does not interfere With the
`operation of the blocking means. The plate may be Welded
`or bolted in position. Hydraulic hoses for the double acting
`piston and cylinder device for operating the latching hook
`preferably pass through one or more apertures in the plate,
`but alternatively the plate may carry tWo hydraulic hose
`couplings and on the inner side of the plate, the couplings are
`permanently connected by suitable hoses to the said piston
`and cylinder device. This alloWs further hoses leading from
`the main pressure system on the excavator to be connected
`and disconnected easily to the coupler.
`The spring for biasing the blocking means into its
`blocking position (if provided) may be located betWeen the
`protection plate and the blocking means.
`Although the piston and cylinder device for the latching
`hook is provided With a check valve and the blocking means
`is provided, it is important that maximum provision is made
`to ensure that a bucket cannot accidentally become discon
`nected from the coupler, and preferably therefore, the latch
`ing hook is designed so that it Will not rotate to a release
`position When under load, or When there is a hydraulic
`failure in the piston and cylinder device controlling the
`hook, and When the blocking means has failed.
`In the knoWn coupler, the hook has a pro?le Which is
`such that, under the above conditions, and the hook is
`carrying the Weight of the bucket, the forces acting on the
`pin are such that there is a moment about the pivot support
`ing the hook Which Will cause the hook to rotate to its
`unlatched position, thus releasing the bucket.
`In the present invention, We preferably provide a hook
`Which has a pro?le such that under the above conditions, and
`When the hook is carrying the Weight of the bucket, and there
`Would otherWise be a tendency for the hook to rotate to a
`release position, the pin Will move along the internal con
`cave surface of the hook, from a ?rst position tending to
`unlatch the hook to one putting no unlatching force on the
`hook and thereafter to one tending to move the hook to a
`latching position.
`For this purpose, the free end of the hook preferably has
`an upturned, extended nose, the inner face of Which is
`concave and Which is preferably connected to the normal
`concave internal surface of the hook by an internal planar
`portion.
`Several preferred embodiments of coupler according to
`the present invention are noW described by Way of example
`With reference to the accompanying draWings, in Which:
`FIGS. 1 to 3 are schematic side elevations shoWing hoW
`a coupler is used to connect an excavator bucket to a dipper
`arm of an excavator,
`FIG. 4 is a partly schematic side elevation With parts
`broken aWay, shoWing details of a manual prior art coupler,
`FIG. 5 is a vieW similar to FIG. 4 of a hydraulically
`operated prior art coupler,
`FIG. 6 is a perspective vieW With parts broken aWay
`shoWing a ?rst embodiment of coupler according to the
`invention,
`FIG. 7 is a vieW similar to FIG. 6 shoWing a second
`embodiment of coupler according to the invention,
`FIG. 8 is a further perspective vieW With parts cut aWay
`shoWing tWo further preferred features of the invention,
`FIG. 9 is a scrap vieW shoWing a coupler latching hook
`according to a preferred feature of the invention,
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`10
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`FIG. 10 is a vieW similar to FIG. 9, but shoWing the hook
`With the bucket pin in a slightly different position,
`FIG. 11 is an enlarged vieW shoWing the hook and pin in
`its FIG. 10 position,
`FIG. 12 shoWs schematically six different relative orien
`tations of an excavator dipper arm, coupler and excavator
`bucket, and
`FIG. 13 is a vieW similar to FIGS. 6—8, but shoWing the
`coupler in a different position, and shoWing tWo possible
`alternative constructions.
`Referring to FIGS. 1 to 5 of the draWings, an excavator
`bucket is shoWn at 1, and the distal end of an excavator
`dipper arm is shoWn at 3. In accordance With standard
`practice, the dipper arm 3 supports a bucket piston and
`cylinder device 4 for controlling the bucket 1 via tWo pivot
`links 6‘, the bucket I normally being connected directly to
`the dipper arm 3 by means of a ?rst pivot pin 7 carried by
`the bucket and engaging directly Within a mounting point or
`pivot aperture in an end region of the dipper arm 3 and a
`second pivot pin 9 engaging directly Within a mounting
`point or pivot aperture 5‘ in an end region of one of the links
`6‘ (this arrangement is not shoWn).
`More recently, hoWever, a coupler II has been used to
`enable the semi-automatic connection of the bucket 1 to the
`dipper arm 3 and as illustrated, the coupler has tWo mount
`ing points thereon by means of Which it is connected to the
`mounting points 5 and 5‘ on the dipper arm 3 and on the link
`6‘ respectively, by suitable connecting pins 12. The coupler
`11 is provided in a loWer region thereof With a ?rst generally
`horiZontally and rearWardly extending aperture or jaW 13
`and a second generally doWnWardly extending aperture or
`jaW 15. By rearWardly extending, We mean opening
`outWardly, in use, from the coupler toWards the operator of
`an excavator on Which the dipper arm 3 and coupler 11 are
`?tted and by doWnWardly extending We mean, in use,
`extending or opening outWards generally doWnWards
`toWards the ground. In order to connect the bucket I to the
`dipper arm, the excavator operator manoeuvres the dipper
`arm to the position shoWn in FIG. 1 and then moves the
`dipper arm doWnWardly and rearWardly so as to engage the
`?rst aperture or jaW 13 With the ?rst pivot pin 7, Which is
`virtually permanently ?tted to the bucket 1; he then operates
`the bucket-controlling piston and cylinder device 4 so as to
`sWing the pivot links 6‘ doWnWardly, as represented by t he
`arroW A in FIG. 2, so as to move the second aperture or jaW
`15 into engagement With the second pivot pin 9, Which is
`also virtually permanently secured to the bucket 1. The
`coupler is then latched in position so that the jaW 15 is
`clamped around the pin 9 and the bucket can be used for
`digging as illustrated in FIG. 3.
`In FIG. 4, a manual prior art coupler is disclosed Which
`is provided With a latching hook 17, pivotally supported on
`the body of the coupler about a pivot 18 and biased to a
`latching position (in Which it maintains the pivot pin 9 in the
`aperture 15) by means of a coil spring 16. In order to move
`the hook 17 against the bias of the spring 16, eg to release
`the pivot pin 9 from the aperture 15 and thus to drop a bucket
`1, a bar or release handle. 14 has to be inserted into an
`aperture 10 in a nose portion of the hook 17 so that When
`doWnWard pressure is applied to the end of the bar, the hook
`17 Will pivot about its pivot 18 accordingly.
`In the hydraulic type of prior art coupler Which is
`illustrated in FIG. 5, the latching hook 17 is moved betWeen
`its illustrated latching position and a release position by
`means of a double-acting hydraulic piston and cylinder
`device 19, the piston of Which is pivotally connected to the
`hook at 20 and the cylinder of Which is pivotally connected
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`US 6,422,805 B1
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`5
`to the body of the coupler at 22. A suitable check valve (not
`shown) is provided Within the piston and cylinder device 19
`in case there should be a failure in the hydraulic supply to
`the piston and cylinder device 19. HoWever, in case this
`check valve should fail, or in the case of the manual coupler
`shoWn in FIG. 4, in case the spring 16 should fail, a safety
`pin 23 is alWays provided. This safety pin 23 bridges
`betWeen the body or tWo side plates of the coupler 1 and a
`rear face of the latching hook 17 so as to hold the latching
`hook 17 in a latching position and prevent the bucket pivot
`9 from being released from the aperture 15. The disadvan
`tage With this arrangement is that every time the safety pin
`23 has to be inserted or removed, the excavator operator has
`to dismount from the cab of the excavator. This is time
`consuming and inconvenient for the excavator operator and
`as a result, the operator often never ?ts the safety pin 23.
`In accordance With the present invention, automatically
`operating blocking means is provided to overcome this
`problem. In the ?rst embodiment of coupler as shoWn in
`FIG. 6, Wherein parts of the coupler have been broken aWay
`for the sake of clarity, the safety pin of the prior art
`construction shoWn in FIG. 5 is dispensed With and replaced
`With a blocking means shoWn generally at 25. The blocking
`means is in the form of a bifurcated blocking bar With tWo
`rearWardly extending limbs 26 Which are pivotally sup
`ported on the pivot 22 by means of Which the piston and
`cylinder device 19 is connected to the coupler 11, and a
`forWard end 24 of Which engages Within a recess on a rear
`face of the latching hook 17. The blocking means 25 moves
`into blocking engagement With the rear face of the latching
`hook 17 under its oWn Weight due to the force of gravity,
`causing it to pivot anticlockWise about the pivotal connec
`tion 22 under normal operating conditions of the coupler and
`excavator bucket. HoWever, in the event of the bucket
`operating piston and cylinder device 4 being retracted so as
`to lift the bucket so as to pivot it clockWise about the
`mounting point 5 on the dipper arm 3, there Will be a
`tendency for the blocking means 25 to become inoperative
`due to its oWn Weight and accordingly, the blocking means
`25 is provided on its rearmost end With resiliently deform
`able means 27 Which is then activated to bias the forWard
`end 24 of the blocking means into engagement With the rear
`face of the latching hook 17. This Will hold the hook in its
`latching position to prevent inadvertent displacement of the
`second bucket pivot pin 9 from the aperture 15. In the
`preferred arrangement, the resiliently deformable means 27
`is in the form of an upstanding leaf-spring 28, a free end
`portion of Which Will abut against an abutment on the dipper
`arm 3, thus producing a suitable reaction force to hold the
`blocking means 25 in engagement With the rear face of the
`hook 17.
`In the alternative preferred embodiment shoWn in FIG. 7,
`the bifurcated blocking bar With its tWo limbs 26 is replaced
`by a single blocking bar 37, Which is pivotally connected to
`the pivot connection 22, as in the previous embodiment.
`LikeWise, as in the previous embodiment, this single block
`ing bar 37 has an upstanding leaf-spring 28 connected
`thereto Which operates as previously described. In the
`embodiment of FIG. 7, a forWard end portion 35 of the
`blocking bar engages Within a recess 33 in a rear face of the
`latching hook 17 to hold the latching hook 17 in its latching
`position but in other respects, the single blocking bar 37 acts
`in the same Way, under its oWn Weight, as in the previous
`embodiment.
`In a preferred arrangement of the embodiment shoWn in
`FIG. 8, a series of steps or recesses 41 are provided on a rear
`face of the latching hook 17 With Which a modi?ed forward
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`end portion 31 of the blocking means 25 engage. As Will be
`apparent from FIG. 8, the bucket pivot pin 9 shoWn therein
`is of a normal siZe, but by providing the series of steps on
`the rear face of the latching hook 17, larger siZes of bucket
`pin 9, or different-sized bucket pin pivot centres (knoWn as
`pin spread) can be accommodated.
`From the foregoing, it Will be appreciated that the gravity
`operated blocking means 25 Whether it be the embodiment
`shoWn in FIG. 6 or the embodiment shoWn in FIG. 7, or that
`shoWn in FIG. 8, alloWs an excavator operator to change
`buckets Without leaving his cab. This is because the latching
`hook 17 is hydraulically actuated by means of the piston and
`cylinder device 19, Which itself is provided With check
`valves to prevent movement of the piston therein in the event
`of hydraulic failure. HoWever, even if there is a hydraulic
`failure and, the check valves also fail, then the blocking
`means 25 Will still prevent the latching hook 17 moving to
`an unlatched position.
`When the excavator operator Wishes to change a bucket,
`it is necessary for the operator fully to extend the piston and
`cylinder device 4 for the bucket to rotate the coupler
`anticlockWise (as seen in the draWings) so as to move the
`bucket into a ?lly inverted position, Wherein it is tucked
`beneath the dipper arm 3 (sometimes knoWn as the croWd
`position) in Which position the coupler 11 Will be inverted
`and the blocking means 25 Will then sWing under its oWn
`Weight due to the forces of gravity to an unblocking position.
`This Will then alloW the operator to retract fully the piston
`of the piston and cylinder device 19, thus moving the
`latching hook 17 to an unlatched position. When the bucket
`is in this position, its Weight Will be supported largely
`completely on the back of the bucket 1 and the operator can
`then by retracting the main bucket operating piston and
`cylinder device 4, roll the coupler 11 to a generally vertical
`position, thus alloWing the second bucket pin 9 to sWing out
`of the second aperture or jaW 15 (Which is noW generally
`rearWardly extending) Whereupon, on further retraction of
`the piston and cylinder device 4, the coupler 11 Will be
`moved back to its normal position, thus alloWing the ?rst
`pivot pin 7 to slide out of the rearWardly facing ?rst aperture
`13. This effectively disconnects the bucket from the coupler
`and alloWs the operator then to ?t a different bucket to the
`dipper arm. These various different relative positions of
`dipper arm, coupler and excavator bucket are illustrated in
`the six different vieWs comprising FIG. 12 of the draWings.
`Because of the provision of the gravity operated blocking
`means 25, it is important to ensure that excavated material
`does not interfere With its satisfactory operation.
`Accordingly, We prefer to ?t a protection plate 47 betWeen
`the tWo side plates of the coupler 11, Which completely
`overlies the blocking means 25 and the double acting
`hydraulic piston and cylinder device 19, as shoWn in FIG. 8.
`This plate 47 is preferably Welded in position and
`accordingly, has an aperture therein through Which the
`resiliently deformable leaf-spring 28 projects. Furthermore,
`tWo hydraulic hose connectors are ?tted to the plate, as
`shoWn at 55, to Which hydraulic hoses 47 for the piston and
`cylinder device 19 are connected. On the upper exposed face
`of the plate, the connectors 55 are provided With ?ttings to
`receive connectors from further hydraulic hoses (not
`shoWn), Which are secured to the dipper arm 3 and lead to
`the main pressure system on the excavator. Although the
`presence of the protection plate 47 prevents the ingress of
`excavated material to the interior of the coupler, the provi
`sion of the hydraulic connectors 55 still alloWs the coupling
`11 to be disconnected from the dipper arm if required and
`When various parts of the coupler become Worn, these can all
`
`Page 16 of 19
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`

`US 6,422,805 B1
`
`7
`simply be removed by dropping them downwardly from the
`coupler as shoWn in FIG. 8, since all the various pivot
`connections are easily removable from the coupler.
`In spite of the various safety features described above, all
`enabling bucket exchange to be carried out from the cab of
`the excavator, there is still a slight risk that the latching hook
`17 may sWing to its unlatching position, thus alloWing the
`bucket to be dropped from the dipper arm if there is a
`hydraulic failure, and the check valve in the piston and
`cylinder device 19 fail, and the gravity operated blocking
`means 25 fails for some reason or another. Accordingly, We
`prefer to provide a modi?ed latching hook Which, under
`normal conditions, cannot sWing to an unlatched position,
`due to the Weight of the bucket pivot 9 thereon. This
`modi?ed latch hook is shoWn in FIGS. 9, 10 and 11.
`Normally, With a latch hook such as shoWn in FIG. 7 or
`FIGS. 4 and 5, the Weight of the bucket on the hook, Which
`is transferred to the hook through the bucket pin 9, Will cause
`the hook to sWing anticlockWise, due to the reaction force
`R1, acting on the inner concave face of the hook, causing an
`anticlockWise moment represented by the arroW M, shoWn
`in FIG. 9. HoWever, as is shoWn in FIG. 9, the preferred
`hook of the invention instead of simply having an internal
`pro?le such as shoWn schematically in FIGS. 4 and 5, is
`provided not only With a ?rst concave portion 56 and a
`planar portion 57, both of Which are generally of knoWn
`construction, but also With a second concave portion 61, by
`virtue of the presence of a nose portion 63 on the free end
`portion of the hook 17. As can be seen from FIG. 9, When
`the bucket pin 9 is bearing doWn upon the ?rst concave
`portion 56 of the hook, there Will be reaction forces gener
`ated such that the moment acting on the hook 17 about its
`support pivot 18 is anticlockwise. HoWever, as the coupler
`is tipped during operation, so that there is a tendency for the
`bucket 9 to move off the ?rst concave surface 56 and onto
`the planar surface 57, reaction forces R1 and R2 Will be
`generated, the tWo components of Which, When combined,
`Will eventually produce a composite force component Which
`moves from the dotted line position 62, shoWn in FIG. 9, in
`the direction of the arroW B. Eventually, as the pin 9 slides
`doWn the surface 57, the dotted line 62 Will sWing through
`the centre line of the pivot 18, Whereupon there is no
`moment acting on the hook 17, about the pivot 18.
`Subsequently, the Whole Weight of the bucket pin 9 is
`supported on the second concave surface 61 on the interior
`of the nose portion 63 of the pin, Whereupon the reaction
`force R2 disappears and the Whole Weight of the bucket is
`transferred to the bucket pin 92 to produce a reaction force
`R3, as shoWn in FIG. 10, Which Will result in a clockWise
`moment acting on the latching hook 17 about its support
`pivot 18, as represented by the arroW N. When this occurs,
`Which is at the time When the pin 19 Would appear to be at
`a position in Which it Was thought it Would cause the latching
`hook 17 to move to its unlatched position, the Weight of the
`bucket on the latching hook 17 in fact causes the latching
`hook not to move to an unlatching position, but to tend to
`move clockWise about its support pivot 18 to its latching
`position. This effectively means that if none of the safety
`systems previously described is correctly operating, it
`becomes impossible for the Weight of the bucket to cause the
`latching hook to move to an unlatching position, because the
`shape of the internal surface of the neWly provided tip
`portion 63 of the hook results in the moment N acting on the
`latching hook 17, alWays to move the latching hook 17
`toWards a latching position.
`With the construction shoWn in FIGS. 9, 10 and 11, it is
`only possible to disconnect a bucket from the coupler in the
`
`5
`
`15
`
`25
`
`35
`
`45
`
`55
`
`65
`
`8
`manner previously described and illustrated in the various
`vieWs of FIG. 12. In FIG. 12(1), the bucket piston and
`cylinder device 4 (not shoWn in this vieW) is fully retracted
`and the resiliently deformable leaf-spring 28 bears against
`an abutment on the dipper arm 3, and thus ensures that the
`blocking bar is kept in position against the hook 17. In FIG.
`12(2), the bucket piston and cylinder device 4 has been
`partially extended and the blocking bar25 is kept in the
`correct position by gravity. FIG. 12(3) shoWs the position
`that the coupler 11 takes up after the bucket piston and
`cylinder device has been further extended and, When in this
`position, the blocking bar25 remains in its blocking position
`due to gravity. FIG. 12(4) shoWs the position taken by the
`coupler 11 When the bucket (not shoWn) is in the fully
`croWded position, ie the coupler is inverted. In this
`position, the blocking bar 25 Will sWing under gravity to an
`open position to alloW the hook 17 to be retracted by
`operation of the piston and cylinder device 19. FIG. 12(5)
`shoWs the coupler 11 after it has been rolled to a position to
`alloW the bucket pin 9 to sWing clear of the coupler, Whereas
`FIG. 12(6) shoWs hoW the bucket can then be removed by
`rolling the coupler 11 clockWise relative to its FIG. 12(5)
`position.
`In other