Note: Descriptions are shown in the official language in which they were submitted.
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A COUPLER
FIELD OF THE INVENTION
The present disclosure relates to a coupler for coupling an implement to the
arm of an
excavator, digger, or other earth moving machine or vehicle. In particular,
the coupler is a
hydraulic coupler with safety features to prevent decoupling in the event of a
hydraulic failure
or due to the incomplete coupling of an implement during the coupling process.
BACKGROUND
Couplers, also commonly called 'hitches', are used to removably connect
implements such as
an excavation bucket or other earth moving implement, to an arm of a machine
such as an
excavator, digger, or backhoe. These couplers are typically mounted to the
free end of the
arm and configured to engage a pair of parallel pins ordinarily provided on
earth moving
implements for connection of the implement to the arm.
Modern couplers are operated using a hydraulic actuator. This enables
implements to be
changed out from the end of the excavator arm quickly and remotely by the
vehicle operator,
releasing one implement from the coupler, and engaging the pins of another
implement.
During use, implements are held securely by the coupler under hydraulic
pressure. However,
in the event of a failure resulting from a loss of hydraulic pressure or a
failure to correctly
engage both pins, there is a risk of the implement coming loose or falling
from the arm. A
loose or dropped implement is a safety hazard and can result in serious
injury.
To mitigate the risk of hydraulic failure, hydraulic couplers commonly have
one or more safety
lock features to ensure one or both of the pins on the implement remain
engaged with the
coupler in the case of a hydraulic failure resulting in a loss of hydraulic
pressure. In some
existing couplers, a spring-loaded latch is used as a safety latch on at least
one of the coupler
jaws. However, these spring-loaded safety latches may fail under specific
loading conditions.
One such condition is when there is a loss of hydraulic pressure and the
coupler is in or is
moved to a vertical or near-vertical orientation such that the pins of the
implement are
vertically aligned. In this vertical orientation, the hydraulic failure
results in the pins and the
upper jaw dropping slightly under gravity so substantially all of the vertical
loading from the
implement and the implement load is transferred to the spring-loaded latch.
This transfer of
force to the latch may damage or cause failure of the latch which is not
sufficiently robust to
support that magnitude of load, thereby risking the implement being
dangerously released
from the coupler.
Hazardous situations can also occur if an operator unknowingly does not
correctly couple the
coupler to the pins of the implement. The process of coupling the coupler with
an implement
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typically involves engaging a front fixed jaw of the coupler to a first pin of
the implement,
including engaging a front safety latch, then curling the implement under the
excavator arm
and moving a rear jaw of the coupler into engagement with the second pin.
However, an
operator often cannot see the engagement of the rear jaw with the second pin
so may not
notice if the rear jaw hasn't correctly engaged the second pin. Therefore,
there is a risk an
operator will attempt to move the excavator arm and attached coupler with the
implement
only partly engaged.
If the excavator arm is moved in this condition, the implement may swing about
and hang
from the first pin as the coupler is raised. The momentum of the swinging
implement may
push the first pin hard against the front latch, again causing the latch to
bear a majority of
the load of the implement. Further, there have been incidents where, as the
implement pivots
around the first pin, the rotating pin in contact with the latch applies a
torque to the latch to
pivot the latch out of engagement. This frees the first pin from the jaw and
causes the
implement to fall dangerously.
It is an object of at least preferred embodiments of the present invention to
address one or
more of the above-mentioned shortcomings and/or to at least provide the public
with a useful
alternative.
In this specification where reference has been made to patent specifications,
other external
documents, or other sources of information, this is generally to provide a
context for
discussing features of the invention. Unless specifically stated otherwise,
reference to such
external documents or sources of information is not to be construed as an
admission that
such documents or such sources of information, in any jurisdiction, are prior
art or form part
of the common general knowledge in the art.
SUMMARY OF THE INVENTION
In a first aspect, the invention broadly relates to a coupler for coupling an
implement having
first and second spaced apart parallel pins, to the arm of a vehicle or
machine. The coupler
comprises a body for attaching to the vehicle or machine arm, a front first
jaw fixed relative
to the body, a pivotable locking member, a movable rear second jaw, and an
actuator. The
front first jaw defines an opening and a first seat for receiving the first
implement pin, and
comprises a pronounced lip forward of the first seat, the lip protruding in a
direction generally
towards the body. The locking member is pivotable relative to the first jaw
about a pivot that
is positioned forward of the lip of the first jaw. The locking member pivots
between a locking
position in which a portion of the locking member protrudes into the opening
of the first jaw,
and an unlocked position in which the locking member is substantially or
wholly retracted
from the opening of the first jaw. The movable rear second jaw faces away from
the first jaw,
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defining an opening and a second seat for receiving the second implement pin.
The second
jaw comprises an extension surface adjacent to the jaw opening and rear of the
second seat.
The actuator is operable to selectively move the second jaw towards and away
from the first
jaw along a movement axis. The first jaw including the lip defines an entry
direction of the
first pin into the seat of the first jaw that is not parallel to the movement
axis.
In an embodiment, the second jaw is movable between an extended position with
the second
jaw distal to the first jaw and a contracted position with the second jaw
proximal to the first
jaw.
In an embodiment, the movable second jaw is biased in a position away from the
first jaw.
In an embodiment, the actuator is a hydraulic cylinder, and wherein a biasing
member is
arranged to bias the cylinder towards an extended position. The biasing member
may
comprise a die spring, for example, positioned within a rod of the cylinder.
Alternatively, the
biasing member may comprise an external compression spring.
In an alternative embodiment, the actuator may comprise a mechanical screw and
thread
mechanism.
The protruding lip of the first jaw may comprise a rear surface oriented at an
angle of between
about 20 degrees and about 40 degrees relative to the movement axis,
preferably between
about 25 degrees and about 35 degrees, most preferably about 30 degrees.
In an embodiment, the lip of the first jaw is shaped such that, in a vertical
orientation of the
coupler with the second jaw above the first jaw, weight forces from an
implement secured in
the coupler are at least partly supported by the lip.
In an embodiment, engagement of the first jaw with an implement pin requires a
change in
direction of the motion of the first jaw or said implement pin, to clear the
lip of the first jaw.
During at least one part of the motion, engagement of the first jaw with an
implement pin
may require the first jaw or said implement pin to move such that the movement
vector
comprises a component that is perpendicular to the movement axis of the
movable member.
In an embodiment, the locking member is shaped such that, in a vertical
orientation of the
coupler with the second jaw above the first jaw and the locking member in a
locking position,
weight forces from an implement secured in the coupler are at least partly
supported by the
locking member. In a vertical orientation of the coupler with the second jaw
above the first
jaw and the locking member in a locking position, reaction force vectors
provided by the
locking member to support the first implement may extend through the locking
member pivot.
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In an embodiment, in a vertical orientation of the coupler with the second jaw
above the first
jaw and the locking member in a locking position, at least a major portion of
weight forces
from an implement secured in the coupler are supported by the locking member
and the lip
of the first jaw support. For example, the locking member and the lip may
together support
substantially all of the weight force of the implement load. In alternative
embodiments, the
locking member and the lip may together support a majority of the weight force
of the
implement load, for example more than about 70% of the weight force of the
implement load.
The load supported by the locking member and the lip may be evenly or unevenly
distributed
between the locking member and the lip. For example, the lip may support about
50% and
the locking member may support about 50%. Alternatively, the load proportions
may be
distributed, 30-70, 40-60, 60-40, 70-30, or any other such distribution.
In an embodiment, the locking member comprises a locking surface for
contacting the first
implement pin at a contact point, the contact point being substantially
colinear with a centre
of said pin and a pivot axis of the locking member.
the locking surface at the contact point is substantially perpendicular with
an axis running
between the centre of said pin and the locking member pivot axis.
In an embodiment, the locking surface is substantially flat.
In an embodiment, wherein the locking member is biased towards the locking
position. A leaf
spring may be provided and arranged to bias the locking member towards the
locking position.
For example, a first end of the leaf spring may be anchored to the body, a
second end of the
leaf spring may be anchored to the locking member, with the leaf spring
comprising a bent
intermediate portion adjacent the locking member pin. Alternatively, a torsion
spring or a
coil spring may be provided to bias the locking member towards the locking
position.
In an embodiment, the locking member comprises a cam surface; and wherein the
movable
jaw is provided on a movable member, the movable member being configured to
engage the
cam surface and thereby retract the locking member from its locking position
as the movable
jaw moves towards the first jaw.
In an embodiment, the extension surface of the second jaw is configured such
that, in the
event of a failure of the actuator resulting in slight movement of the second
jaw towards the
first jaw, the extension surface prevents rotation of an implement attached to
the coupler by
retaining the second pin in the second jaw.
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In an embodiment, the extension surface of the second jaw is substantially
flat and/or is
substantially parallel to the movement axis.
This invention may also be said broadly to consist in the parts, elements and
features referred
to or indicated in the specification of the application, individually or
collectively, and any or
all combinations of any two or more said parts, elements or features. Where
specific integers
are mentioned herein which have known equivalents in the art to which this
invention relates,
such known equivalents are deemed to be incorporated herein as if individually
described.
The term 'comprising' as used in this specification and claims means
'consisting at least in
part of'. When interpreting statements in this specification and claims that
include the term
'comprising', other features besides those prefaced by this term can also be
present. Related
terms such as 'comprise' and 'comprised' are to be interpreted in a similar
manner.
It is intended that reference to a range of numbers disclosed herein (for
example, 1 to 10)
also incorporates reference to all rational numbers within that range and any
range of rational
numbers within that range (for example, 1 to 6, 1.5 to 5.5 and 3.1 to 10).
Therefore, all sub-
ranges of all ranges expressly disclosed herein are hereby expressly
disclosed.
As used herein the term '(s)' following a noun means the plural and/or
singular form of that
noun. As used herein the term 'and/or' means 'and' or 'or', or where the
context allows, both.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described by way of example only and with
reference to
the accompanying drawings in which:
Figure 1 shows a front underside perspective view of a coupler according to a
first
exemplary embodiment;
Figure 2 shows a rear underside perspective view of the coupler of figure 1;
Figure 3 is a side elevation of the coupler of figures 1 and 2, with the
coupler in a
locked configuration, engaged with a pair of implement pins;
Figure 4 is a side perspective view of the coupler of figures 1 to 3, with the
fixed jaw
component hidden to reveal the movable member, actuator, and front locking
member;
Figure 5A is a side view corresponding to the view of Figure 4, with the
second jaw in
a position to engage an implement pin;
Figure 5B is a side view corresponding to the view of Figure 4, with the
second jaw in
a position to release the first implement pin;
Figure 6 is a side section view of the coupler of Figures 1 to 5B, taken
through a mid-
plane of the coupler;
Figure 7 is an exploded perspective view of the coupler of figures 1 to 6;
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Figures 8A to 8E are side elevation views showing the steps to couple the
coupler
attached to the end of an arm of an excavator, to parallel pins on an
excavator bucket, where
Figure 8A shows the coupler in an unlocked configuration, ready to couple to
the implement,
Figure 8B shows the coupler receiving a first one of the pins, Figure 8C shows
the coupler
pivoted around and aligned with the second pin, ready to receive the second
pin, Figure 8D
shows the front locking member deployed to lock the first pin in the first jaw
with the second
jaw moving towards the second pin, and Figure 8E shows the coupler engaged
with the second
pin and in a locked configuration such that both pins are locked to the
coupler, with the
excavator arm lifting the coupled bucket;
Figure 9A is a side section view showing the front locking member deployed to
lock
the first pin in the first jaw with the second jaw moved towards the second
pin in a misaligned
state and prevented from engaging the pin;
Figure 9B illustrates a first stage of movement of the implement upon movement
of
the coupler from the state shown in Figure 9A;
Figure 9C illustrates a second stage of movement of the implement upon further
movement of the coupler from the state shown in Figure 9B;
Figure 9D illustrates a further stage of movement of the implement upon
further
movement of the coupler from the state shown in Figure 9C;
Figure 10A is a side view showing the coupler coupled to an implement in a
vertical
orientation, illustrating reaction forces;
Figure 10B is a side view showing the coupler coupled to an implement in a
vertical
orientation after a hydraulic failure, illustrating the reaction forces;
Figures 11A to 11E are side section detail views of the front jaw and locking
member
of an alternative embodiment coupler, where Figure 11A shows a pin seated in
the first jaw
and the movement path for moving the pin into and out of the jaw; Figure 11B
is similar to
Figure 11A but showing the locking member; Figure 11C shows the first pin
moved into
contact with the locking member; Figures 11C and 11D show the locking member
moving into
the retracted position.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Figures 1 to 10b show an exemplary coupler 1 according to one embodiment of
the invention.
The coupler 1 is suitable for coupling an implement having first and second
spaced apart
parallel pins 2a, 2b, to the arm of a vehicle or machine. Transverse parallel
pins 2a, 2b are
commonly provided as a standard feature on implements such as excavation
buckets, ripping
attachments, sieve buckets, clamp, wide buckets, hydraulic hammers, screw
augers, etc. to
assist with attachment of the implement to an arm/boom on a vehicle or other
machine.
An arrow marked "F" has been inserted into the figures where appropriate to
indicate a
forward direction of the coupler 1. The front F of the coupler 1 in the
embodiment shown is
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the side corresponding with the front of the implement (the open side of the
excavator
bucket). The absolute orientation of the coupler 1 will change during the
course of its use as
the arm to which it is mounted moves. Accordingly the terms forward, rearward,
left side,
and right side (or similar) should be construed with reference to the forward
direction F of the
coupler, not necessarily with reference to the orientation shown in a given
figure, the use of
these terms is for ease of explanation and is not intended to be limiting.
The coupler 1 has a body 3, a first jaw 5 that is fixed relative to the body
3, a movable second
jaw 7 that is movable relative to the body 3, and an actuator 9 operable to
selectively move
the second jaw 7 towards and away from the first jaw 5. The body 3 is
configured for
attachment to a vehicle or machine arm, for example, via attachment features.
The coupler
1 is configured to hold a first pin 2a in the first jaw 5 and a second
parallel pin 2b in the
second jaw in a position such that the centres of the first and second pins
are coincident with
a virtual pin axis VPA (see Figures 3 and 6).
In the embodiment shown, the body 3 comprises two spaced apart parallel plates
4, to receive
an end of the arm or links from the arm between the plates 4. The plates 4
include mounting
apertures 6 for bolting the coupler body 3 to the arm or arm links, however
other attachment
methods are possible. A lifting lug 8 (Figure 2) is provided, preferably at
the aft of the coupler
body 3, to facilitate the lifting of various items on the worksite, for
example using a chain
placed through the aperture in the lug 8.
The first jaw 5 is hook-shaped, defining an opening 11 to the front F of the
coupler 1. An
inner surface of the first jaw 5 provides a seat 13 for receiving the first
implement pin 2a.
The first and second implement pins 2a, 2b are substantially cylindrical,
accordingly, the
surface of the first jaw 5 providing the seat 13 for the implement pin 2a is
concave with a
curvature that substantially corresponds to that of the pin 2a.
In the embodiment shown, the first jaw 5 is provided by two parallel hooks
formed from two
spaced apart side plates 15 that are fixed relative to, or integral with, the
body 3 of the
coupler 1. A web 16 bridges between the hooks of the two plates 15 to provide
stiffness. In
some embodiments, the web 16 may form at least part of the seat for the
implement pin 2a
as well as providing stiffness to the first jaw 5.
Referring to Figure 3, the first jaw 5 includes a raised, pronounced lip 17
forward of the pin
seat 13. The lip 17 protrudes upwards, into the opening 11 of the first jaw 5,
reducing the
size of the opening adjacent to the lip 17 and defining a recess rear of the
lip 17, which forms
the seat 13. In the embodiment shown, the lip 17 is formed by the portion of
the first jaw
hook that curves around on itself, that is, referring to Figure 3, a portion
of the hook forward
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of the first pin 2a vertical centre line VCa, with the rear surface of the lip
17 being contiguous
with the seating surface and having forming a smooth transition between the
lip 17 and the
seat 13. The rear surface of the lip 17 may be curved or substantially linear.
For example,
in some embodiments, the lip 17 may instead be a discrete and/or abrupt
projection. The lip
17 preferably extends across the width of the coupler 1 between the two side
plates 15, with
a portion of the lip being formed by the web 16, but alternatively a lip may
be provided only
by each jaw side plate 15.
The pronounced lip has a height LH, measured from the lowest point of the seat
13 to the tip
of the lip 17 in a direction towards the pin axis VPA, that is at least 8% of
the diameter of the
pin 2a that the coupler is configured for use with (about 20% of the radius of
curvature of the
seat 13). More preferably the lip 17 has a height of between about 10% and
about 25% of
the diameter of the pin 2a (between about 20% and about 50% of the radius of
curvature of
the seat 13). In the embodiment shown, the lip 17 has a height LH of about
12.5% of the
diameter of the pin 2a (about a 25% of the radius of curvature of the seat 13)
In the embodiment shown, the tip of the lip 17 is positioned forward of the
seat 13 at a point
that is slightly rear of the front most point on the first pin 2a when the pin
is seated in the
front jaw. For example, the tip of the lip 17 is a distance rear of the front
most point on the
first pin 2a that is less than about 10% of the pin diameter. In alternative
embodiments and
as illustrated in Figures 11A, 11B, and 11C, the tip of the lip 17 may be
slightly forward of
the front most point on the first pin 2a. For example, the tip of the lip 17
may forward of the
front most point on the pin 2a by a distance that is less than about 10% of
the pin diameter.
The lip 17 is pronounced in that it requires the implement pin 2a to navigate
a non-linear
entry and exit path relative to the coupler 1 on its way through the opening
11 into and out
of its fully seated position on the seat 13. The direction of movement of the
implement pin
2a past the lip 17 (or movement of the lip 17 past the implement pin 2a), is
not parallel with
virtual pin axis the direction of movement of the second jaw (movement axis
MA), that is, it
has a component of movement in a direction perpendicular to the forward-back
direction of
the coupler 1. It is not possible for the implement pin 2a to move into or out
of engagement
with the first jaw (or for the first jaw 5 to be moved into or out of
engagement with an
implement pin) by purely 'forward' or 'rearwards' movement that is parallel
with the
movement axis MA.
A locking member 19 is provided at the fixed first jaw 5. The locking member
19 is movable
between a locking position shown in Figures 3, 5A and 6, in which a portion of
the locking
member 19 protrudes into the opening of the first jaw 5, and an unlocked
position shown in
Figure 5B, in which the locking member 19 is substantially or wholly retracted
from the
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opening 11 of the first jaw 5. The first jaw 5 can be moved into engagement
with an
implement pin 2a with the locking member 19 in the locked or the unlocked
position. In the
locked position, the angled surface on the front of the locking member means
that sufficient
forces applied by an abutting pin 2a, push the biased locking member 19
towards its retracted
position, allowing the pin 2a to enter the first jaw 5. However, in the
locking position, the
first locking member 19 prevents exit of an implement pin from the first jaw
5.
The locking member 19 is pivotable relative to the first jaw 5, for example,
by being pivotally
mounted to the first jaw 5 or the coupler body 3. In the embodiment shown the
pivot of the
locking member 19 is provided by a pin 21 extending between the two side
plates "slide rails"
of the first jaw, with the first locking member 19 siting between these side
plates 15.
However, other configurations for the locking member are envisaged.
The locking member pivot 21 is positioned forward of the first pin seat 13 and
forward of tip
15 of the lip 17. In its locking position, the locking member extends
generally downwards and
rearwards from the pivot 21, towards the seat 13. The locking member pivot 21
may be
directly above or forward of the mouth 11 of the first jaw 5. Preferably the
position and shape
of the locking member 19 is such that the locking member 19 is not ordinarily
in contact with
a first pin 2a when the pin is seated in the first jaw 5. Rather, during
ordinary use of the
coupler there will be a space between the locking surface 27 of the locking
member and the
pin 2a, and contact will only occur when the locking member 19 is performing a
safety
function, such as when there is a failure of the actuator 9.
Similarly, in some embodiments, the position and shape of the first jaw lip 17
is such that the
lip 17 is not ordinarily in contact with a first pin 2a when the pin is seated
in the first jaw 5.
Rather, during ordinary use of the coupler there will be a space between the
tip of the lip 17
and the pin 2a, and contact will only occur when the lip 17 is performing a
safety function,
such as when there is a failure of the actuator 9.
The locking member 19 is biased towards its locking position. That is, in the
absence of any
external force, the locking member will be in its locking position. A biasing
member is
provided to bias the locking member 19. In the embodiment shown, the biasing
member
comprises a leaf spring 22 with a first end of the leaf spring anchored to the
coupler body and
a second end anchored to the body of the locking member 19 on the portion of
the locking
member that extends into the jaw opening 11. The spring is bent and extends
around the
locking member pivot 21 on a front/lower side of the pivot such that the pivot
21 acts as a
fulcrum for the leaf spring. Only a single spring is shown in the embodiment
of the drawings,
but alternatively there may be a plurality of springs biasing the locking
member.
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A leaf spring is less susceptible to becoming jammed with grit or dirt
compared to other spring
types, so is less likely to fail or jam when the coupler 1 is used in a dusty
or hostile
environment. A leaf spring can also provide significantly more biasing force
than a
comparably sized torsion spring arranged about the pivot axis, and therefore
is less
susceptible to failure.
The locking member comprises a stop tab 25 for limiting rotation of the
locking member 19.
The stop tab 25 is provided on the opposite side of the pivot 21 to the main
body 19a of the
locking member 19. The stop tab 25 has a rear face 26 that is arranged to abut
an opposing
surface that is fixed relative to the body, when the locking member 19 is in
the locking
position. In the embodiment shown, the rear face 26 of the locking member 19
abuts a flat,
vertical surface on the actuator 9 to define the locking position of the
locking member 19. In
the locking position, the rear face 26 of the stop tab 25 is vertical, but
this may differ in other
embodiments.
The locking member comprises one or more cam surface 23 (Figures 5A, 5B and 7)
for moving
the locking member 19. In the example embodiment, two cam surfaces 23 are
provided on
opposite sides of the pivot 21 to the main body of the locking member 19.
However, in other
embodiments the locking member may have a single cam surface or more than two
cam
surfaces.
In the embodiment shown, two locking surfaces are provided, adjacent and
either side of the
stop tab 25. The, or each, cam surface 23 is preferably an inclined surface
facing generally
rearwards and upwards when the locking member is in its locking position. The,
or each, cam
surface 23 is configured to interact with the movable member 35 carrying the
movable jaw
7. A portion 38 of the movable member slides along a respective cam surface 23
to move
the locking member 19 into or out of its locking position, as will be
described in further detail
below.
The first locking member 19 has a locking surface 27 on the portion of the
locking member
that extends into the jaw opening 11 of the first jaw when the locking member
19 is in its
locking position. The locking surface 27 faces the implement pin 2a when the
locking member
19 is in its locking position. When a first pin 2a is seated in the first jaw,
the locking surface
27 may not contact the pin but will contact the pin if the pin moves from the
seat, to prevent
the pin 2a exiting from the jaw.
The locking member 19 has a locking surface 27 configured to face the pin 2a
in the first jaw
in the locking position. It is this locking surface 27 that the first pin will
contact if the pin
moves towards the mouth 11 of the first jaw when the locking member 19 is in
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position. The locking surface 27 will hold the first pin 2a in the jaw 5. In
the embodiment of
Figures 1 to 10, the locking surface 27 is substantially flat or otherwise
shaped to only have
a single point of contact with the implement pin 2a when the locking member is
in its locking
position and contacting the pin 2a. When in contact with an implement pin 2a,
the locking
surface 27 is tangential to the cylindrical implement pin and so only contacts
the pin at a
single point CP (see Figure 10B).
In alternative embodiments, the locking surface 27 may be alternatively shaped
in a manner
that still achieves only a single point of contact with the implement pin 2a,
or in a way that
contacts the pin along a length of the contacting surface. For example, the
locking surface
27 may be convex, or alternatively may be concave but with a radius of
curvature that is
notably larger than the radius of the implement pin. Alternatively, the
locking surface may
be hook-shaped and may closely follow the curvature of the implement pin 2a.
In the
embodiment illustrated in Figures 11A to E, the locking surface 127 is hooked
at one side to
assist with keeping the first pin 102a in the first jaw 105.
Figures 11A to 11E illustrate an alternative embodiment first jaw 105 and
locking member
199.
Referring to Figure 11A, in this embodiment, the rear surface of the lip 117
is substantially
linear and lies at an angle of about 30 degrees to the forward-rearward
direction of the coupler
or the forward-rear slide rail direction. In alternative embodiments, the rear
surface of the
lip 11 may be curved, for example concave.
The line TP illustrates the non-linear movement path that the first pin 102a
needs to follow
relative to the first jaw 105, to enter the jaw. The portion of the entry path
TP forward of the
pronounced lip 117 is straight. However, other paths are possible within the
constraints
created by the edge of the coupler body and the angled lead-in front of the
jaw/lip 105, 117,
for example, an upward angled path.
Figures 11A to 11E illustrate the first pin 102 a in a number of positions
relative to the front
jaw 105. These positions are indicated (a), (b), (c), and (d). In position (a)
shown in Figures
11A and 11B, the front attachment pin is firmly seated in the front jaw seat
113, where it is
positioned during normal use of the device. As described in more detail below,
in some
instances of failure or incorrect use of the coupler, the front attachment pin
102a may come
into contact with the locking member 119 as shown by position (c) in Figure
11C. In this
position, the contact face 127 of the locking member 119 is tangential to the
pin 102a and
the contact point is line with the pin centre and the pivot axis 121 of the
locking member.
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This means that any loads are transmitted through the centrelines centre of
the pin of the
pivot pin 121 so there are few to no bending moments induced in the front
locking member.
In the embodiment shown, the contact surface 127 of the locking member 119 is
curved with
a small lip 128. If the pin 102a acts in some manner to begin to retract the
locking member
119, the lip 128 on the locking member 119 acts to push the front pin 102 back
towards the
seated position and point (b) illustrated in Figure 11D.
Alternative shaped contact surfaces of the locking member 119 are envisaged,
for example a
flat surface or a surface with no lip 128 are envisaged.
Figure 11E illustrates the movement of the pin 102a out of the jaw 105 after
the front locking
member 119 is retracted. The pin 102a can now advance to position (d) shown in
Figure E,
and beyond once the front locking member 119 is sufficiently retracted that it
no longer
prevents exit of the implement pin 102a from the front jaw 105.
Referring again to Figures 1 to 7, the movable second jaw 7 is a hook-shaped
member,
defining an opening 31 and a seat 33 for receiving the second implement pin
2b. The second
jaw 7 opens to the rear of the coupler 1, that is, the first and second jaws
5, 7 face away
from each other in opposing directions. The second jaw 7 comprises an
extension portion 63,
the extension portion having an extension surface that is parallel to the
virtual pin axes VPA
and movement axis MA. The extension portion 63 is positioned rear of the
second jaw seat
33, with the surface of the extension preferably (but not necessarily) being
contiguous with
the surface of the seat 33. The extension portion surface has a rear edge that
is positioned
rear of the centreline of the second pin 2b vertical centre line VCb (Figure
3) when the pin is
seated in the second jaw. The extension portion has sufficient length such
that if the second
jaw 7 were to move off the second pin 2b during use in the case of a loss of
pressure in the
actuator, the vertical centre line VCb of the pin would be over a point on the
extension portion
63 to resist rotation of the implement in the case of hydraulic failure. This
feature is described
in more detail below.
In the embodiment shown, the rear edge of the extension surface 63 is
positioned rear of the
second pin 2b vertical centre line VCb but forward of the rear-most point of
the pin 2b when
the pin is seated in the second jaw 7. However, in alternative embodiments the
extension
portion 63 may be longer and may extend rearward of the second pin 2b. The
surface of the
extension member 63 is preferably flat but in alternative embodiments may have
some
concavity.
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The movable second jaw 7 is movable between an extended engagement position
with the
second jaw distal to the first jaw and in which the first and second jaws 5, 7
engage respective
implement pins, and a contracted position with the second jaw proximal the
first jaw. The
member may be further movable to a hyper extended position where the spacing
between
virtual centres of the mouth of the fixed jaw 5 and the mouth of the movable
jaw 7 is greater
than the centre-to-centre spacing of the first and second implement pins 2a,
2b.
The movable jaw 7 is provided on a movable member 35, the movable jaw 7 being
fixed to
or integral with the movable member 35. The movable member 35 has two
extensions 37
that extend forward from the second jaw 7, in an opposite direction to the jaw
opening 31,
and side ears 38 for coupling the movable member 35 to an actuator 9.
The movable member 35 is slidably mounted in the coupler 1 for rectilinear
movement relative
to the coupler body 3, towards and away from the fixed first jaw 5 along a
movement axis
MA. When the coupler 1 is aligned for engagement with the implement pins 2a,
2b, movement
of the second jaw is perpendicular to the transverse implement pins 2a, 2b.
In the embodiment shown, the facing inner surfaces of the first jaw side
plates 15 each
comprise a linear guide channel 43 (see Figure 7). These guide channels 43
receive
complementary guide features on the movable member, for example, side edges 45
of the
movable member 35. As the movable member is moved forward or rearward by the
actuator
9, the sides 45 of the movable member 35 slide forward and rearwards in the
guide channels
43, to guide the motion of the movable second jaw 7. The guide channels 43 may
comprise
stops to define a limit of travel of the movable member 35, or alternatively
the travel of the
movable member may be determined by other constraints such as the stroke of
the actuator
9.
The movable member extensions 37 are located above the first and second jaw
openings 11,
31, but below the actuator 9 when the coupler is in the generally horizontal
orientation shown
in Figures 1 to 7. The extensions 37 are arranged to interact with the cam
surfaces 23 of the
locking member 19. Referring to Figures 5A and 5B, from an extended engagement
position,
as the movable jaw 7 moves towards the fixed jaw 5, rounded tips 38 of the
movable member
extensions 37 move into contact with the cam surfaces 23 of the locking member
19.
Continued forward movement of the movable member 35 causes the flat under
surface of
each movable member extension 37 to slide over the respective cam surface 23
and pivoting
the locking member 19 towards its retracted position. When the movable member
35 reaches
its most forward position / the contracted jaw position, the locking member 19
is retracted
and the cam surface(s) 23 are substantially horizontal, parallel or near
parallel with the
underside of the extensions 37, as shown in Figure 5B.
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When the coupler is moved from the contracted, unlocked configuration shown in
Figure 5B
to the extended engagement position of Figure 5a, rearward movement of the
movable
member 35 causes the flat under surface of each movable member extension 37 to
slide back
over the respective cam surface 23 until the movable member extensions 37 are
out of contact
with the locking member, allowing the locking member 19 to pivot towards its
retracted
position under the biasing force of the spring 22. The incline of the cam
surface 23 is
preferably such that the locking member 19 is gradually allowed to extend into
its locking
position rather than being abruptly released. The stop surface on the locking
member 25 is
preferably configured to come in to contact with the opposed surface on the
coupler body just
as the movable member extensions 37 are moving out of contact with the cam
surfaces 23,
to prevent such an abrupt release.
The actuator 9 is a linear actuator, preferably in the form of a double acting
hydraulic ram.
The actuator 9 is housed by the coupler body 3 between the first jaw side
plates 15. One end
of the actuator is fixed relative to the coupler body 3, and its other end is
fixed to the movable
member. In the embodiment shown, the cylinder of the hydraulic ram 9 is pinned
to the first
jaw side plates 15 via a pin 10. An actuator coupling pin 41 extends through
the left and
right side ears 39 to attach the ram of the hydraulic actuator to the movable
member 35 such
that extension or compression of the hydraulic actuator 9 moves the movable
member 35
relative to the body.
The ram of the hydraulic cylinder 9 is biased into an extended position by way
of a biasing
member such as a spring 51 (visible in Figures 9A to 9D). The spring 51 to
ensures the
actuator 9 remains extended in the occurrence of loss of hydraulic pressure.
In the
embodiment shown, the spring 51 is a compression die spring that is provided
internally in
the actuator. The die spring is positioned at least partly in a cylindrical
hollow of the cylinder
rod and arranged to act between the rod and the barrel to bias the rod away
from the barrel
into an extended position. A central spindle preferably extends axially along
the centre of the
spring to prevent the spring buckling. The spindle may extend from the barrel
of the cylinder
and has a length about the same as or slightly shorter than the compressed
length of the
spring 51.
The internal die spring advantageously is sealed from environmental
conditions, reducing the
likelihood of dust and debris from the operating environment impacting on the
operation or
longevity of the spring. In contrast, external springs tend to collect debris
such as sticks,
stones, and dust, and take up valuable space in the smaller hitch bodies.
However, in
alternative embodiments an external compression spring may be provided around
the barrel
and/or the rod of the actuator, arranged to bias the actuator into an extended
position.
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Operation of the coupler
Operation of the example coupler 1 shown in the drawings will now be described
with
reference to Figures 8A to 8E, which show the coupler attached to the end of
an arm 70 of an
excavator. The arm 70 includes a linkage to which the coupler 1 is attached
via the mounting
apertures 6. The linkage can be manipulated using a hydraulic ram, to move the
linkage and
thereby the coupler 1.
In a first step illustrated in Figures 8A and 8B, the coupler 1 is moved and,
if necessary,
rotated using the bucket linkage on the arm 71 to align the first jaw 5 with
the first implement
pin 2a but keeping the second jaw 7 free of the second implement pin 2b. The
coupler 1 is
then moved so the first jaw 5 engages the first implement pin 2a with the pin
2a seated on
the seating surface 13, behind the jaw lip 17. A chamfer or angled lead-in
surface 18 on the
first jaw forward of the lip 17 helps to guide the first jaw 5 onto the pin 2a
by creating an
entrance to the first jaw that is wider than the pin diameter, gradually
narrowing to the jaw
opening adjacent the lip 17. An angled inner upper surface 20 rear of the lip
17 then guides
the pin 2a in a different direction, towards the seat surface 13.
Relative motion between the first implement pin 2a and the first jaw 5 is non-
linear as they
are moved into or out of engagement because the lip 17 necessitates a change
in direction of
the movement. Relative motion between the first implement pin 2a and the first
jaw 5 forward
of lip 17 may be linear and parallel with the movement axis MA or may be at a
slight angle
as accommodated by the chamfer 18 at the front of the first jaw 5. However,
rear of the lip
17, between the lip 17 and the seating surface 13, the movement vector changes
and is
nonparallel to the movement axis MA. In the embodiment shown, movement rear of
the lip
is at an angle of about 30 degrees to the MA, however this angle may be
different in different
embodiments. For example, the movement may be at an angle of between about 30
degrees
and about 40 degrees, more preferably at an angle of between about 25 degrees
and about
degrees.
30 In this first step, the movable member 35 may be in the retracted
position (as shown), with
the locking member 19 also retracted; or the movable member may be in the
extended
position with the locking member 19 in the locking position. If the movable
member 35 is in
the extended position with the locking member 19 in the locking position,
moving the jaw 5
onto the first pin 2A pushes the angled front surface on the locking member,
and causes the
35 biased locking member 19 to retract to the unlocked position.
Either before coupling to the first pin 2A, or after engaging the first pin
and before engaging
the second pin, the second jaw 7 and movable member 35 may be moved towards
the first
jaw 5, to the retracted position (also shown in Figure 5B). As the movable
member 35 moves
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towards the retracted position, the ends of the engagement portions 37 slide
over the cam
surface 23, pushing the cam surface downwards to rotate the first locking
member 19 about
its pivot 21, moving the locking member 19 upwards into the unlocked position.
Once the first pin 2a is seated in the first jaw 5 and with the movable member
35 retracted
(Figure 8B), the coupler 1 is then rotated about the first pin 2a, with the
second jaw still in
the retracted position, until an under surface of the side plates 15 of the
first jaw abut the
second pin 2b and the second jaw 7 is aligned with the second pin, as shown in
Figure 8C.
Referring to Figure 8D, in a next step, the actuator 9 is extended thereby
moving the second
jaw 7 away from the first jaw 5 and towards the second pin 2b. As the second
jaw 7 moves
away from the first jaw 5, the extension portions 37 of the movable member
slide off the cam
surface 23 of the locking member 19, allowing the locking member 19 to pivot
under the
biasing force from the leaf spring 22, until they are completely out of
engagement with the
locking member and the stopping tab 25 is abutting the stop surface 26 (Figure
5A) on the
coupler body 3. The biased locking member 19 is then positioned in its
engagement position.
The actuator 9 is further extended until the second jaw 7 engages the second
pin 2b. The
coupler 1 is in its final coupled configuration when the second pin 2b is
seated on the seating
surface 33 of the movable second jaw 7. With both pins 2a and 2b engaged with
the coupler
1, the coupler can then be manipulated using the arm or boom 70 to which the
coupler 1 is
attached to rotate and lift the implement as illustrated in Figure 8E.
In order to uncouple an implement from the coupler 1, the above-described
process is
performed in reverse. As a first step, it is necessary for the second movable
jaw to be moved
out of engagement with the second implement pin 2b. To do this, the force
applied to the
movable member 35 by retracting the actuator 9 must be sufficient to overcome
the bias
from the spring 51 on actuator, and later in the stroke, to overcome the bias
from the locking
member 19 to retract the locking member 19. During the uncoupling process, it
is expected
that full hydraulic power will be available to the actuator 9. Accordingly, it
will not be difficult
for actuator 9 to provide the necessary force to overcome the spring bias and
retract the
second jaw.
Once the movable jaw 7 is disengaged from the second implement pin 2b, the
coupler 1 can
be rotated about the first pin 2a so the second jaw 7 is clear of the second
implement pin and
so that the coupler can be removed from the first pin 2a.
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Behaviour under incorrect coupling
During the coupling process, an operator sometimes cannot see the engagement
of the
second jaw 7 with the second pin 2b as it is often hidden by the implement,
the excavator
arm, or the bucket linkage. Therefore, the operator may not notice if the rear
jaw 7 hasn't
correctly engaged the second pin 2A. Figures 9A to 9C illustrate this scenario
for couplers
according to the present invention.
Figure 9A shows the front jaw of the coupler coupled and locked to the front
pin 2A of an
implement similar to the state shown in Figure 8D, however the rear jaw has
not been
correctly aligned with the rear pin and so movement of the movable jaw 7
towards the pin is
halted when the tip pf the jaw 7 abuts the pin 2b. If an operator mistakenly
thinks at this
point that the second pin 2b is now seated in the second jaw and lifts the
coupler, the
implement may swing around the first pin 2a, as shown in Figures 9B to 9D,
until the
implement is hanging from the first pin as shown in Figure 9D.
In this hanging position, the lip 17 on the first jaw helps to keep the first
pin 2a seated in the
first jaw and preferably out of contact with the front locking member 19.
Therefore, although
the implement is swinging from the coupler it remains attached at the first
pin and is not
dropped from the coupler. In contrast, during the same scenario in prior art
systems, the
first pin 2a is in contact with the locking member, with forces from the
momentum of the
swinging implement being transmitted to the locking member. As the implement
swings
about the pin 2a, the rotational force from rotation of the implement is
transmitted to the
locking member on such prior art couplers, as a torque about the locking
member pivot. The
direction of that transmitted torque is in a direction acting to retract the
locking member, and
so if the force is sufficiently large, the locking member 19 of prior art
couplers may be
retracted in such a scenario, leaving the first pin free to exit the first jaw
and thereby
completely decoupling the implement from the coupler.
All couplers are susceptible to operator error; however, the features of the
present invention
work together to reduce the risk of an adverse outcome from the implement
completely
decoupling due to an operator error of this nature.
Behaviour under hydraulic failure
Various features of the present coupler work in tandem to prevent the first
and second
implement pins 2a, 2b falling out of engagement with the coupler 1 should
there be a failure
of the coupler such as a loss of hydraulic pressure in the actuator 9.
One worst-case failure scenario occurs when the coupler is in an upright
orientation with the
implement pins 2a, 2b vertically aligned as shown in Figure 10A. In this
scenario, should
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there be a complete hydraulic pressure loss to the actuator 9, both implement
pins 2a, 2b will
remain coupled to the coupler.
Figure 10B illustrates the behaviour of the coupler 1 in the event of a loss
of hydraulic
pressure. In this vertical orientation the second jaw 7 is no longer able to
resist the vertical
weight of the implement, and substantially all of the vertical loading is
transmitted through
the first pin 2a, which drops out of its seated position but is prevented from
dropping out of
the first jaw 5 by the locking member 19, which remains in its locking
position. The
constriction in the first jaw opening 11 created by the first locking member
19 and the lip 17,
together prevents the first implement pin 2a exiting the first jaw 5 and
limits relative
movement of the implement and coupler.
The self-weight of the movable member 35 and second jaw 7 (and potentially the
weight of
actuator rod and other connected components) act to urge the movable member 35
downwards relative to the coupler body 3, unseating the second pin 2b from the
second jaw.
However, the actuator spring 51 prevents the movable member dropping to a
point where
the extension 37 may interact with the locking member 19.
With the second implement pin 2b unseated, no weight force is transmitted
through the
movable jaw 7, and the weight force from the implement 73 acts rotationally
about the first
implement pin 2a. The extension portion 63 of the second jaw, which is
parallel to the
movement axis MA provides a reaction surface for the rotational force. Since
the reaction
forces RF1, RF2 are predominantly perpendicular to the movement axis MA (i.e.
horizontal in
the scenario shown), these reaction forces do not cause movement of the
movable member
35 along the movement axis MA and instead are transferred to the coupler body
3. In the
embodiment shown, the reaction force is transferred to the coupler body via
the guides 45
on the movable member 35.
The lip 17 and locking member 19 together carry at least a majority, if not
substantially all of
the weight force of the implement. Figure 10B illustrates the reaction forces
RF3, RF4 that
act through the lip and the locking member 19. These reaction forces are in a
radial direction
of the first pin, extending through a centre point of the pin and
perpendicular to the surface
at the respective contact point. The reaction force provided by the locking
member 19
preferably also acts through the locking member pivot point 21, or is very
close to the pivot
point 21. This is to prevent the reaction force exerting any significant
torsional force on the
locking member 19, particularly to ensure that the reaction force RF4 is not
one that would
tend to pivot the locking member 19 towards its retracted position.
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The actuator spring 51, second jaw extension 63, and front locking member 7,
therefore all
act together to ensure that both pins 2a, 2b are retained in the coupler 1 in
the event of a
hydraulic failure, for all possible orientations of the implement.
To those skilled in the art to which the invention relates, many changes in
construction and
widely differing embodiments and applications of the invention will suggest
themselves
without departing from the scope of the invention as defined in the appended
claims. For
example, it will be apparent that although the first jaw 5 is described as the
front jaw in the
exemplary embodiment, the first jaw 5 may instead be the rear jaw and the
second jaw 7
may be forward of the first jaw. In alternative embodiments to those shown, a
second locking
member may be provided at the movable second jaw to selectively constrict the
opening 31
of the second jaw 7.
In some embodiments, it may be desirable to provide hydraulic power to the
coupled
implement. Provision of hydraulic power to an implement may be via separate
hose
connections that are manually connected, or more preferably there are a number
of quick
connect hydraulic couplers available in the industry that may be incorporated
into the coupler
1, to allow hydraulic coupling to occur when mechanically coupling the
implement.
The components of the coupler 1 may comprise any suitable material as will be
apparent to
a person skilled in the art. For example, the main components such as the
housing body 3,
the jaw plates 15, the movable member 35, and the locking member 19 preferably
comprises
steel. The components can be machined or cast, or a mixture of both. However,
it is
envisaged that some or all components may comprise alternative materials such
as
alternative metals or composite materials. Similarly, the hydraulic actuator
arrangement can
comprise any suitable materials and is adapted to be associated with pressure
hose.
This invention may also be said broadly to consist in the parts, elements and
features referred
to or indicated in the specification of the application, individually or
collectively, and any or
all combinations of any two or more of said parts, elements or features, and
where specific
integers are mentioned herein which have known equivalents in the art to which
this invention
relates, such known equivalents are deemed to be incorporated herein as if
individually set
forth.
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